SDI: setting the record straight
Adelman, K.L.
1985-01-01
After a few introductory remarks, Mr. Adelman first discusses Soviet propaganda against SDI. He then poses and answers questions regarding the following: SDI and the ABM Treaty; SDI and US arms control objectives; and the ethics of SDI. The final portion of the address reviews US nonproliferation efforts.
Internet Access to National Library of Medicine SDI Search Results
Michael Watson; Kerri Ann Christopher; Robert T. Wood
1997-01-01
The results of selective dissemination of information (SDI) searches are typically printed offline and mailed to the library for distribution. Postprocessing this material-sorting the printouts, gathering and recording statistics, and actually delivering itnrequires substantial effort by staff. With the recent introduction of Internet access to SDI search results at the National Library of Medicine (NLM), the library at Louisiana State
Garthoff, R.L.
1987-09-01
The role, if any, of ballistic missile defense is not an issue that can be decided by any individual nation. Even a dedicated US or Soviet unilateral military-technological drive toward a defense of the nation against ballistic missiles could not succeed. The very dynamics of the arms competition, manifesting itself in reciprocal measures and counter-measures, would preclude attaining an effective defense of either country. And in the extreme case, a perceived impending mortal threat could provoke direct military interference in any attempt to deploy such a system. The security and the fate of the two superpowers - and of the world - are ineluctably bound together. The problems of deterrence, defense, and survival are shared, and any solution must also be shared. The author attempts here to recast the problem and suggest a possible solution to both American and Soviet readers. The analytical approach is new, and so is the policy course recommended on the basis of the analysis. It does not correspond to the present positions of either the US or the Soviet Union, and debate and further consideration in both countries are, of course, required. It is, in short, an interim prescription for a common course of action that could be accepted by both the US and the Soviet Union while the leadership of both countries in the years ahead decide on further resolution of this mutual security dilemma.
Lee, S.
2011-05-05
The Savannah River Remediation (SRR) Organization requested that Savannah River National Laboratory (SRNL) develop a Computational Fluid Dynamics (CFD) method to mix and blend the miscible contents of the blend tanks to ensure the contents are properly blended before they are transferred from the blend tank; such as, Tank 50H, to the Salt Waste Processing Facility (SWPF) feed tank. The work described here consists of two modeling areas. They are the mixing modeling analysis during miscible liquid blending operation, and the flow pattern analysis during transfer operation of the blended liquid. The transient CFD governing equations consisting of three momentum equations, one mass balance, two turbulence transport equations for kinetic energy and dissipation rate, and one species transport were solved by an iterative technique until the species concentrations of tank fluid were in equilibrium. The steady-state flow solutions for the entire tank fluid were used for flow pattern analysis, for velocity scaling analysis, and the initial conditions for transient blending calculations. A series of the modeling calculations were performed to estimate the blending times for various jet flow conditions, and to investigate the impact of the cooling coils on the blending time of the tank contents. The modeling results were benchmarked against the pilot scale test results. All of the flow and mixing models were performed with the nozzles installed at the mid-elevation, and parallel to the tank wall. From the CFD modeling calculations, the main results are summarized as follows: (1) The benchmark analyses for the CFD flow velocity and blending models demonstrate their consistency with Engineering Development Laboratory (EDL) and literature test results in terms of local velocity measurements and experimental observations. Thus, an application of the established criterion to SRS full scale tank will provide a better, physically-based estimate of the required mixing time, and elevation of transfer pump for minimum sludge disturbance. (2) An empirical equation for a tank with no cooling coils agrees reasonably with the current modeling results for the dual jet. (3) From the sensitivity study of the cooling coils, it was found that the tank mixing time for the coiled tank was about two times longer than that of the tank fluid with no coils under the 1/10th scale, while the coiled tank required only 50% longer than the one without coils under the full scale Tank 50H. In addition, the time difference is reduced when the pumping U{sub o}d{sub o} value is increased for a given tank. (4) The blending time for T-shape dual jet pump is about 20% longer than that of 15{sup o} upward V-shape pump under the 1/10th pilot-scale tank, while the time difference between the two pumps is about 12% for the full-scale Tank 50H. These results are consistent with the literature information. (5) A transfer pump with a solid-plate suction screen operating at 130 gpm can be located 9.5 inches above settled sludge for 2 in screen height in a 85 ft waste tank without disturbing any sludge. Detailed results are summarized in Table 13. Final pump performance calculations were made by using the established CW pump design, and operating conditions to satisfy the two requirements of minimum sludge disturbance, and adequate blending of tank contents. The final calculation results show that the blending times for the coiled and uncoiled tanks coupled with the CW pump design are 159 and 83 minutes, respectively. All the results are provided in Table 16.
NASP and SDI Spearhead CFD Developments
NASA Technical Reports Server (NTRS)
Mehta, Unmeel B.
1992-01-01
The National Aerospace Plane (NASP) program's purpose, as stated by the National Space Council, is to "develop and demonstrate hypersonic technologies with the ultimate goal of single stage to orbit." The council has also directed that "performance of the experimental flight vehicle will be constrained to the minimum necessary to meet the highest priority research, as opposed to operational objectives .... The program will be conducted in such a way as to minimize technical and cost uncertainty associated with the experimental vehicle." The purpose of the Strategic Defense Initiative (SDI), as defined by President Bush, is "...protection from limited ballistic missile strikes, whatever their source." Computational fluid dynamics (CFD) plays a vital role in both endeavors.
The economic common sense of SDI
1990-01-01
The present development history and current status evaluation of the economic viability of SDI technologies suggests that much of the exaggeration of SDI costs has been due to an effort of the part of the program's opponents to consider only the most exotic, and commensurately expensive, options for orbital missile defense. It is noted that, by contrast, extraordinary advancements in
The Evaluation of SISMAKOM (Computerized SDI Project).
ERIC Educational Resources Information Center
University of Science, Penang (Malaysia).
A survey of 88 users of SISMAKOM, a computerized selective dissemination of information (SDI) and document delivery service provided by the Universiti Sains Malaysia and four other Malaysian universities, was conducted in August 1982 in order to collect data about SISMAKOM and to assess the value of a computerized SDI service in a developing…
Statistics as a dynamical attractor
Michail Zak
2012-08-30
It is demonstrated that any statistics can be represented by an attractor of the solution to a corresponding systen of ODE coupled with its Liouville equation. Such a non-Newtonian representation allows one to reduce foundations of statistics to better established foundations of ODE. In addition to that, evolution to the attractor reveals possible micro-mechanisms driving random events to the final distribution of the corresponding statistical law. Special attention is concentrated upon the power law and its dynamical interpretation: it is demonstrated that the underlying dynamics supports a " violent reputation" of the power law statistics.
The economic common sense of SDI
Graham, D.O. (High Frontier, Inc., Arlington, VA (USA))
1990-01-01
The present development history and current status evaluation of the economic viability of SDI technologies suggests that much of the exaggeration of SDI costs has been due to an effort of the part of the program's opponents to consider only the most exotic, and commensurately expensive, options for orbital missile defense. It is noted that, by contrast, extraordinary advancements in microelectronics have made possible the creation of 20-100 lb devices which detect hostile missile launches, calculate the paths of enemy missiles and warheads through space, and fly to pinpoint accuracy to intercept targets and destroy them by means of high-speed collision. This 'Brilliant Pebbles' scheme has reduced the cost of an effective SDI system to below 25 billion.
CRITICAL MANAGEMENT ISSUES WHEN USING SDI IN HUMID AREAS
Technology Transfer Automated Retrieval System (TEKTRAN)
The use of subsurface drip irrigation (SDI) is increasing throughout the United States. Proper SDI system management that includes water management, system maintenance and chemigation is imperative to the successful implementation of SDI. Improper or inadequate management of any system can result ...
Surface drip irrigation (SDI): Status of the technology in 2010
Technology Transfer Automated Retrieval System (TEKTRAN)
Subsurface drip irrigation (SDI), although a much smaller fraction of the microirrigated land area than surface drip irrigation, is growing at a much faster rate and is the subject of considerable research and educational efforts in the United States. This paper will discuss the growth in SDI, highl...
Investigating strategies to improve crop germination when using SDI
Technology Transfer Automated Retrieval System (TEKTRAN)
As the nation's population increases and available irrigation water decreases, new technologies are being developed to maintain or increase production on fewer acres. One of these advancements has been the use of subsurface drip irrigation (SDI) on field crops. Research has shown that SDI is the m...
Air Force Satellite Control Network and SDI development
NASA Astrophysics Data System (ADS)
Bleier, T.
The Air Force Satellite Control Network (AFSCN) represents a military, worldwide network of control centers and remote tracking sites (RTS). A relatively large and growing constellation of DOD satellites is supported. The near term and long term plans for the AFSCN are discussed, taking into account also the impact of the Space Defense Initiative (SDI) on the AFSCN. It is pointed out that the SDI adds a new dimension to the support provided by the AFSCN to the DOD satellites, because some SDI scenarios being considered include many more satellite platforms, each containing multiple kinetic energy weapons. Space-ground link sites are discussed along with AFSCN control sites, and communication between RTS and control centers. Attention is given to changing roles and responsibilities, the Satellite Test Center (STC) as an excellent site for the R and D phase of SDI development, and an operational concept for a highly proliferated weapons platforms architecture, and goals of developing more survivable satellite systems.
Artificial intelligence applications in space and SDI: A survey
NASA Technical Reports Server (NTRS)
Fiala, Harvey E.
1988-01-01
The purpose of this paper is to survey existing and planned Artificial Intelligence (AI) applications to show that they are sufficiently advanced for 32 percent of all space applications and SDI (Space Defense Initiative) software to be AI-based software. To best define the needs that AI can fill in space and SDI programs, this paper enumerates primary areas of research and lists generic application areas. Current and planned NASA and military space projects in AI will be reviewed. This review will be largely in the selected area of expert systems. Finally, direct applications of AI to SDI will be treated. The conclusion covers the importance of AI to space and SDI applications, and conversely, their importance to AI.
Statistical Prediction and Molecular Dynamics Simulation
Cooke, Ben; Schmidler, Scott C.
2008-01-01
We describe a statistical approach to the validation and improvement of molecular dynamics simulations of macromolecules. We emphasize the use of molecular dynamics simulations to calculate thermodynamic quantities that may be compared to experimental measurements, and the use of a common set of energetic parameters across multiple distinct molecules. We briefly review relevant results from the theory of stochastic processes and discuss the monitoring of convergence to equilibrium, the obtaining of confidence intervals for summary statistics corresponding to measured quantities, and an approach to validation and improvement of simulations based on out-of-sample prediction. We apply these methods to replica exchange molecular dynamics simulations of a set of eight helical peptides under the AMBER potential using implicit solvent. We evaluate the ability of these simulations to quantitatively reproduce experimental helicity measurements obtained by circular dichroism. In addition, we introduce notions of statistical predictive estimation for force-field parameter refinement. We perform a sensitivity analysis to identify key parameters of the potential, and introduce Bayesian updating of these parameters. We demonstrate the effect of parameter updating applied to the internal dielectric constant parameter on the out-of-sample prediction accuracy as measured by cross-validation. PMID:18676654
UNL Researchers Studying SDI Technology Near Clay Center
Nebraska-Lincoln, University of
UNL Researchers Studying SDI Technology Near Clay Center By Steve Ress University of Nebraska researchers have been burying plastic drip irrigation tubing in fields near Clay Center to get a better idea a previously dryland, 33-acre cornfield at UNL's South Central Agricultural Laboratory near Clay Center . Drip
Ames Selective Dissemination of Information (SDI) System Operating Manual.
ERIC Educational Resources Information Center
Anderson, Lloyd E.; Wegner, Waldo W.
The Ames Selective Dissemination of Information (SDI) System is an attempt to efficiently place rapidly increasing amounts of information into the hands of scientists and engineers who can exploit it. It is a computerized current awareness system designed to increase researchers' literature searching capabilities by bringing to their attention…
1 of 3 DOE Response to EPA Question SDI(HCR)-1 on the SDI Planned Change Notice
the planned SDI heater tests on the lower portion of the WIPP exhaust shaft. Background: Convectively of the exhaust shaft, potentially altering shaft geometry and disrupt or reduce the operational lives of the shaft. We would expect the area of greatest impact, if there were to be any, to be at the base
Soviet military on SDI (Strategic Defense Initiative). Professional paper
Fitzgerald, M.C.
1987-08-01
Numerous Western analysts have suggested that all American assessments of SDI should proceed not only from a consideration of American intentions, but also from the outlook of Soviet perceptions. Since 23 March 1983, the prevailing tone of Soviet military writings on SDI has been overwhelmingly negative. Myron Hedlin has concluded that this harsh reaction to a U.S. initiative still years from realization suggests both a strong concern about the ultimate impact of these plans on the strategic balance, and a perceived opportunity for scoring propaganda points. Indeed, the present review of Soviet writings since President Reagan's so-called Star Wars speech has yielded both objective Soviet concerns and regressions to psychological warfare. This, in turn, has necessitated a careful effort to separate rhetoric from more official assessments of SDI. While there has long been dispute in the West over the validity of Soviet statements, they have time and again been subsequently confirmed in Soviet hardware, exercises, and operational behavior. Some Western analysts will nonetheless contend that the Soviet statements under examination in this study are merely a commodity for export.
A statistical description of neural ensemble dynamics.
Long, John D; Carmena, Jose M
2011-01-01
The growing use of multi-channel neural recording techniques in behaving animals has produced rich datasets that hold immense potential for advancing our understanding of how the brain mediates behavior. One limitation of these techniques is they do not provide important information about the underlying anatomical connections among the recorded neurons within an ensemble. Inferring these connections is often intractable because the set of possible interactions grows exponentially with ensemble size. This is a fundamental challenge one confronts when interpreting these data. Unfortunately, the combination of expert knowledge and ensemble data is often insufficient for selecting a unique model of these interactions. Our approach shifts away from modeling the network diagram of the ensemble toward analyzing changes in the dynamics of the ensemble as they relate to behavior. Our contribution consists of adapting techniques from signal processing and Bayesian statistics to track the dynamics of ensemble data on time-scales comparable with behavior. We employ a Bayesian estimator to weigh prior information against the available ensemble data, and use an adaptive quantization technique to aggregate poorly estimated regions of the ensemble data space. Importantly, our method is capable of detecting changes in both the magnitude and structure of correlations among neurons missed by firing rate metrics. We show that this method is scalable across a wide range of time-scales and ensemble sizes. Lastly, the performance of this method on both simulated and real ensemble data is used to demonstrate its utility. PMID:22319486
Dynamic Statistical Graphics in the CAVE Virtual Reality Environment
Symanzik, Jürgen
Dynamic Statistical Graphics in the CAVE Virtual Reality Environment Jurgen Symanzik, Dianne Cook: symanzik@iastate.edu Abstract The CAVE is a high end immersive virtual reality environment that allows 3 Introduction This paper contains work related to dynamic statistical graphics DSG and the CAVE virtual reality
Statistical Mechanics of Recurrent Neural Networks II Dynamics
Coolen, ACC "Ton"
CHAPTER 15 Statistical Mechanics of Recurrent Neural Networks II ± Dynamics A.C.C. COOLEN none- quilibrium statistical mechanical techniques, is the sequel of [1], which was devoted to solving networks and their properties. Equilibrium statistical mechanical techniques can provide much detailed quan
SDI APPROACH IN THE IMPROVED USE OF GEOSPATIAL DATA IN GOVERNMENT
Zainal A. MAJEED; Fuziah ABU HANIFAH; Hazri HASSAN
Geospatial data and GIS technology are increasingly fitting and rightfully used as widespread tools because of the capability to improve development and planning of a nation. Spatial Data Infrastructure (SDI) is a notion within the idea of making geospatial data be shared and accessed using the advanced geo-information technologies. Many nations around the world are developing national SDI to help
Subsurface drip irrigation (SDI) research at USDA-ARS in Bushland, TX
Technology Transfer Automated Retrieval System (TEKTRAN)
Producers in the Texas High Plains have recently adopted subsurface drip irrigation (SDI) at unprecedented rates in response to drought, declining water resources from the Ogallala Aquifer, and increasing energy costs to pump groundwater. However, SDI has much greater capital and maintenance require...
ERIC Educational Resources Information Center
Scheffler, F. L.; March, J. F.
The Aerospace Materials Information Center (AMIC) Selective Dissemination of Information (SDI) program was evaluated by an interview technique after one year of operation. The data base for the SDI consists of the periodic document index records input to the AMIC system. The users are 63 engineers, scientists, and technical administrators at the…
Multichannel scaler for general statistical analysis of dynamic light scattering
Sprik, Rudolf
Multichannel scaler for general statistical analysis of dynamic light scattering Rudolf Sprika of the multichannel scaler is demonstrated in dynamic light scattering experiments. The recorded traces are analyzed the fluctuation of the intensity I(t). An example is dynamic light scattering DLS also called photon correlation
Dynamaps: Dynamic Queries on a Health Statistics Atlas
Golbeck, Jennifer
of detail data. Printed maps and atlases are used but access to detail is lost since all values are splitDynamaps: Dynamic Queries on a Health Statistics Atlas Catherine Plaisant and Vinit Jain Human) 4052768 Email: plaisant@cs.umd.edu KEYWORDS: Animation, map, statistics, graphic, query
Nonequilibrium statistical-mechanical approach to discrete-time dynamics
Munakata, T. (Department of Applied Mathematics and Physics, Kyoto University, Kyoto 606 (Japan))
1994-09-01
A nonequilibrium statistical-mechanical approach to a general discrete-time dynamical system is presented. A generalized Langevin equation (GLE) with an alternative fluctuation-dissipation theorem is derived for a system with a stationary (invariant) distribution function. A linear response theory is also formulated within a similar framework. The results obtained here are not limited to map dynamics. This is illustrated by applying the GLE to a Hopfield neural network which is synchronously updated following Glauber dynamics.
Statistical dynamic modeling on ecosystem patterns
Yi Chen; Li He Chai; Xin Zhang
2010-01-01
Ecosystems are typical complex adaptive systems. By a universal principle (MFP) on pattern formation of ecosystems, the underlying microscopic dynamic mechanisms that induce complex patterns in ecosystems can be revealed. The ecosystem patterns are further simulated by invoking theoretical model of artificial neural network of Self-Organization Feature Map (SOM), by which evolution processes, structural classifications and fractal growth of ecosystem
Comparison of grain sorghum, soybean, and cotton production under spray, LEPA, and SDI
Technology Transfer Automated Retrieval System (TEKTRAN)
Crop production was compared under subsurface drip irrigation (SDI), low energy precision applicators (LEPA), low elevation spray applicators (LESA), and mid elevation spray applicators (MESA) at the USDA-Agricultural Research Service Conservation and Production Research Laboratory, Bushland, Tex., ...
Dynamical Ensembles in Nonequilibrium Statistical Mechanics
Gallavotti, G.; Cohen, E.G.D. [Dipartimento di Fisica, Universita di Roma, La Sapienza, 00185 Roma (Italy)] [Dipartimento di Fisica, Universita di Roma, La Sapienza, 00185 Roma (Italy); [The Rockefeller University, New York, New York 10021 (United States)
1995-04-03
Ruelle`s principle for turbulence leading to what is usually called the Sinai-Ruelle-Bowen (SRB) distribution is applied to the statistical mechanics of many particle systems in nonequilibrium stationary states. A specific prediction, obtained without the need to construct explicitly the SRB itself, is shown to be in agreement with a recent computer experiment on a strongly sheared fluid. This presents the first test of the principle on a many particle system far from equilibrium. A possible application to fluid mechanics is also discussed.
Statistical coarse-graining of molecular dynamics into peridynamics.
Silling, Stewart Andrew; Lehoucq, Richard B.
2007-10-01
This paper describes an elegant statistical coarse-graining of molecular dynamics at finite temperature into peridynamics, a continuum theory. Peridynamics is an efficient alternative to molecular dynamics enabling dynamics at larger length and time scales. In direct analogy with molecular dynamics, peridynamics uses a nonlocal model of force and does not employ stress/strain relationships germane to classical continuum mechanics. In contrast with classical continuum mechanics, the peridynamic representation of a system of linear springs and masses is shown to have the same dispersion relation as the original spring-mass system.
Protein electron transfer: Dynamics and statistics
NASA Astrophysics Data System (ADS)
Matyushov, Dmitry V.
2013-07-01
Electron transfer between redox proteins participating in energy chains of biology is required to proceed with high energetic efficiency, minimizing losses of redox energy to heat. Within the standard models of electron transfer, this requirement, combined with the need for unidirectional (preferably activationless) transitions, is translated into the need to minimize the reorganization energy of electron transfer. This design program is, however, unrealistic for proteins whose active sites are typically positioned close to the polar and flexible protein-water interface to allow inter-protein electron tunneling. The high flexibility of the interfacial region makes both the hydration water and the surface protein layer act as highly polar solvents. The reorganization energy, as measured by fluctuations, is not minimized, but rather maximized in this region. Natural systems in fact utilize the broad breadth of interfacial electrostatic fluctuations, but in the ways not anticipated by the standard models based on equilibrium thermodynamics. The combination of the broad spectrum of static fluctuations with their dispersive dynamics offers the mechanism of dynamical freezing (ergodicity breaking) of subsets of nuclear modes on the time of reaction/residence of the electron at a redox cofactor. The separation of time-scales of nuclear modes coupled to electron transfer allows dynamical freezing. In particular, the separation between the relaxation time of electro-elastic fluctuations of the interface and the time of conformational transitions of the protein caused by changing redox state results in dynamical freezing of the latter for sufficiently fast electron transfer. The observable consequence of this dynamical freezing is significantly different reorganization energies describing the curvature at the bottom of electron-transfer free energy surfaces (large) and the distance between their minima (Stokes shift, small). The ratio of the two reorganization energies establishes the parameter by which the energetic efficiency of protein electron transfer is increased relative to the standard expectations, thus minimizing losses of energy to heat. Energetically efficient electron transfer occurs in a chain of conformationally quenched cofactors and is characterized by flattened free energy surfaces, reminiscent of the flat and rugged landscape at the stability basin of a folded protein.
A statistical–dynamical method for predicting estuary morphology
Dominic E. Reeve; Harshinie Karunarathna
2011-01-01
A statistical–dynamical model for estuary morphodynamics is presented and demonstrated with a case study on the Humber Estuary,\\u000a UK. The model presented here is hybrid in nature where simplified process dynamics are combined with a data-driven approach.\\u000a The modelling methodology uses an inverse technique to construct an unknown source function in the model-governing equation,\\u000a using historic measurements of estuary bathymetry.
FACILITATING DATA EXPLORATION: DYNAMIC QUERIES ON A HEALTH STATISTICS MAP
Golbeck, Jennifer
FACILITATING DATA EXPLORATION: DYNAMIC QUERIES ON A HEALTH STATISTICS MAP Catherine Plaisant, Human. A thematic map of the United States is animated by adjusting sliders displayed on the side of the map. A time slider illustrates time trends. The other sliders control the filtering out of areas of the map according
Smooth Dynamics and New Theoretical Ideas in Nonequilibrium Statistical Mechanics
David Ruelle
1999-01-01
This paper reviews various applications of the theory of smooth dynamical systems to conceptual problems of nonequilibrium statistical mecanics. We adopt a new point of view which has emerged progressively in recent years, and which takes seriously into account the chaotic character of the microscopic time evolution. The emphasis is on nonequilibrium steady states rather than the traditional approach to
Statistical Analysis of Molecular Dynamics Simulations
NASA Astrophysics Data System (ADS)
Atkinson, R. A.
Available from UMI in association with The British Library. Requires signed TDF. This thesis is concerned with the specification and analysis of stochastic models of molecular motion and interaction in simple liquids. Basic chemical terminology is introduced and a brief description is given of the technique of molecular dynamics simulation. Stochastic process theory, in so far as it is relevant to the modelling of molecular trajectories and chemical reaction, is reviewed. First passage densities are shown to be important in the analysis of diffusion controlled chemical reaction. The relationship between first passage densities and flux or flow across the absorbing boundary is given. A formula proposed by Durbin is discussed and shown to be valid for diffusion processes under certain regularity conditions. The simplest integrated diffusion, integrated Brownian motion, is considered and a detailed derivation of McKean's half-winding formula is given. An explicit expression for the return-time density is derived, from which the large time asymptotics can be deduced. Goldman's formula for the density of the hitting-time of positive levels is extended to all real values and a simple intuitive derivation is given. Similar arguments enable the results of Gor'kov to be extended to a wider class of integrated diffusions. First passage time densities are computed numerically using the extension of Goldman's formula and compared with approximations which have been suggested by Hesse. Small drift asymptotics are derived for the escape probability of integrated Brownian motion with drift. A number of results are obtained for the integrated Ornstein -Uhlenbeck process, by using martingale methods. Finally, the empirical observations of Lynden-Bell, Hutchinson and Doyle are analysed. A stochastic model of single-particle motion based on the velocity autocorrelation function is proposed and shown to be in excellent agreement with the computer generated data.
Statistical dynamics of tropical wind in radiosonde data
NASA Astrophysics Data System (ADS)
Koh, T.-Y.; Djamil, Y. S.; Teo, C.-K.
2011-05-01
Weibull distributions were fitted to wind speed data from radiosonde stations in the global tropics. A statistical theory of independent wind contributions was proposed to partially explain the shape parameter k obtained over Malay Peninsula and the wider Equatorial Monsoon Zone. This statistical dynamical underpinning provides some justification for using empirical Weibull fits to derive wind speed thresholds for monitoring data quality. The regionally adapted thresholds retain more useful data than conventional ones defined from taking the regional mean plus three standard deviations. The new approach is shown to eliminate reports of atypically strong wind over Malay Peninsula which may have escaped detection in quality control of global datasets as the latter has assumed a larger spread of wind speed. New scientific questions are raised in the pursuit of statistical dynamical understanding of meteorological variables in the tropics.
Seasonal statistical-dynamical forecasts of droughts over Western Iberia
NASA Astrophysics Data System (ADS)
Ribeiro, Andreia; Pires, Carlos
2015-04-01
The Standard Precipitation Index (SPI) has been used here as a drought predictand in order to assess seasonal drought predictability over the western Iberia. Hybrid (statistical-dynamical) long-range forecasts of the drought index SPI are estimated with lead-times up to 6 months, over the period of 1987-2008. Operational forecasts of geopotential height and total precipitation from the UK Met Office operational forecasting system are considered. Past ERA-Interim reanalysis data, prior to the forecast launching, are used for the purpose of build a set of SPI predictors, integrating recent past observations. Then, a two-step hybridization procedure is adopted: in the first-step both forecasted and observational large-scale fields are subjected to a Principal Component Analysis (PCA) and forecasted PCs and persistent PCs are used as predictors. The second hybridization step consists on a statistical/hybrid downscaling to the regional scale based on regression techniques, after the selection of the statistically significant predictors. The large-scale filter predictors from past observations and operational forecasts are used to downscale SPI and the advantage of combining predictors with both dynamical and statistical background in the prediction of drought conditions at different lags is evaluated. The SPI estimations and the added value of combining dynamical and statistical methods are evaluated in cross-validation mode. Results show that winter is the most predictable season, and most of the predictive power is on the large-scale fields and at the shorter lead-times. The hybridization improves forecasting drought skill in comparison to purely dynamical forecasts, since the persistence of large-scale patterns displays the main role in the long-range predictability of precipitation. These findings provide clues about the predictability of the SPI, particularly in Portugal, and may contribute to the predictability of crops yields and to some guidance on users (such as farmers) decision making process.
Identification of sdiA-regulated genes in a mouse commensal strain of Enterobacter cloacae
Sabag-Daigle, Anice; Dyszel, Jessica L.; Gonzalez, Juan F.; Ali, Mohamed M.; Ahmer, Brian M. M.
2015-01-01
Many bacteria determine their population density using quorum sensing. The most intensively studied mechanism of quorum sensing utilizes proteins of the LuxI family to synthesize a signaling molecule of the acylhomoserine lactone (AHL) type, and a protein of the LuxR family to bind AHL and regulate transcription. Genes regulated by quorum sensing often encode functions that are most effective when a group of bacteria are working cooperatively (e.g., luminescence, biofilm formation, host interactions). Bacteria in the Escherichia, Salmonella, Klebsiella, and Enterobacter genera do not encode an AHL synthase but they do encode an AHL receptor of the LuxR family, SdiA. Instead of detecting their own AHL synthesis, these organisms use SdiA to detect the AHLs synthesized by other bacterial species. In this study, we used a genetic screen to identify AHL-responsive genes in a commensal Enterobacter cloacae strain that was isolated from a laboratory mouse. The genes include a putative type VI secretion system, copA (a copper transporter), and fepE (extends O-antigen chain length). A new transposon mutagenesis strategy and suicide vectors were used to construct an sdiA mutant of E. cloacae. The AHL-responsiveness of all fusions was entirely sdiA-dependent, although some genes were regulated by sdiA in the absence of AHL.
Statistical dynamics of equatorial waves in tropical radiosonde wind data
NASA Astrophysics Data System (ADS)
Koh, T.-Y.; Djamil, Y. S.; Teo, C. K.
2010-07-01
Weibull distributions were fitted to wind speed data from radiosonde stations in the global tropics. A statistical theory of equatorial waves was proposed to explain the shape parameter k obtained over Malay Peninsula and the wider Equatorial Monsoon Zone. The theory uses the (-5/3)-power law in quasi-2-D turbulence, classical Boltzmann statistics and the Central Limit Theorem. It provides a statistical dynamical basis for using empirical Weibull fits to derive wind speed thresholds for monitoring data quality. The regionally adapted thresholds retain more useful data than conventional ones defined from taking the regional mean plus three standard deviations. The new approach is shown to eliminate reports of atypically strong wind over Malay Peninsula which may have escaped detection in quality control of global datasets as the latter has assumed a larger spread of wind speed.
A Flow Field Approach for State Dynamics in Statistical Filtering
J. Clayton Kerce; George Brown
2007-01-01
We describe the representation of general state dynamics generated by a first order non-linear equation in flow form for application in statistical filtering. Some of the conse- quences of this framework are examined for Kalman filtering and estimation of derived parameters. These derived parameters can include quantities such as impact point, launch point, and ex- trapolated target position for sensor-to-sensor
Statistical energy conservation principle for inhomogeneous turbulent dynamical systems.
Majda, Andrew J
2015-07-21
Understanding the complexity of anisotropic turbulent processes over a wide range of spatiotemporal scales in engineering shear turbulence as well as climate atmosphere ocean science is a grand challenge of contemporary science with important societal impact. In such inhomogeneous turbulent dynamical systems there is a large dimensional phase space with a large dimension of unstable directions where a large-scale ensemble mean and the turbulent fluctuations exchange energy and strongly influence each other. These complex features strongly impact practical prediction and uncertainty quantification. A systematic energy conservation principle is developed here in a Theorem that precisely accounts for the statistical energy exchange between the mean flow and the related turbulent fluctuations. This statistical energy is a sum of the energy in the mean and the trace of the covariance of the fluctuating turbulence. This result applies to general inhomogeneous turbulent dynamical systems including the above applications. The Theorem involves an assessment of statistical symmetries for the nonlinear interactions and a self-contained treatment is presented below. Corollary 1 and Corollary 2 illustrate the power of the method with general closed differential equalities for the statistical energy in time either exactly or with upper and lower bounds, provided that the negative symmetric dissipation matrix is diagonal in a suitable basis. Implications of the energy principle for low-order closure modeling and automatic estimates for the single point variance are discussed below. PMID:26150510
Dynamics, stability, and statistics on lattices and networks
Livi, Roberto [Institut d' Etudes Avancées (IEA), Université de Cergy-Pontoise (France)
2014-07-15
These lectures aim at surveying some dynamical models that have been widely explored in the recent scientific literature as case studies of complex dynamical evolution, emerging from the spatio-temporal organization of several coupled dynamical variables. The first message is that a suitable mathematical description of such models needs tools and concepts borrowed from the general theory of dynamical systems and from out-of-equilibrium statistical mechanics. The second message is that the overall scenario is definitely reacher than the standard problems in these fields. For instance, systems exhibiting complex unpredictable evolution do not necessarily exhibit deterministic chaotic behavior (i.e., Lyapunov chaos) as it happens for dynamical models made of a few degrees of freedom. In fact, a very large number of spatially organized dynamical variables may yield unpredictable evolution even in the absence of Lyapunov instability. Such a mechanism may emerge from the combination of spatial extension and nonlinearity. Moreover, spatial extension allows one to introduce naturally disorder, or heterogeneity of the interactions as important ingredients for complex evolution. It is worth to point out that the models discussed in these lectures share such features, despite they have been inspired by quite different physical and biological problems. Along these lectures we describe also some of the technical tools employed for the study of such models, e.g., Lyapunov stability analysis, unpredictability indicators for “stable chaos,” hydrodynamic description of transport in low spatial dimension, spectral decomposition of stochastic dynamics on directed networks, etc.
Dynamics, stability, and statistics on lattices and networks
NASA Astrophysics Data System (ADS)
Livi, Roberto
2014-07-01
These lectures aim at surveying some dynamical models that have been widely explored in the recent scientific literature as case studies of complex dynamical evolution, emerging from the spatio-temporal organization of several coupled dynamical variables. The first message is that a suitable mathematical description of such models needs tools and concepts borrowed from the general theory of dynamical systems and from out-of-equilibrium statistical mechanics. The second message is that the overall scenario is definitely reacher than the standard problems in these fields. For instance, systems exhibiting complex unpredictable evolution do not necessarily exhibit deterministic chaotic behavior (i.e., Lyapunov chaos) as it happens for dynamical models made of a few degrees of freedom. In fact, a very large number of spatially organized dynamical variables may yield unpredictable evolution even in the absence of Lyapunov instability. Such a mechanism may emerge from the combination of spatial extension and nonlinearity. Moreover, spatial extension allows one to introduce naturally disorder, or heterogeneity of the interactions as important ingredients for complex evolution. It is worth to point out that the models discussed in these lectures share such features, despite they have been inspired by quite different physical and biological problems. Along these lectures we describe also some of the technical tools employed for the study of such models, e.g., Lyapunov stability analysis, unpredictability indicators for "stable chaos," hydrodynamic description of transport in low spatial dimension, spectral decomposition of stochastic dynamics on directed networks, etc.
Retarded Electromagnetic Interaction and Dynamic Foundation of Classical Statistical Mechanics
Xiao Chun, M
2002-01-01
It is provided in the paper that the non-conservative dissipative force and asymmetry of time reversal can be naturally introduced into classical statistical mechanics after retarded electromagnetic interaction between charged microparticles is considered. In this way, the rational dynamic foundation for classical statistical physics can established and the revised Liouville equation is obtained. The micro-canonical ensemble, the canonical ensemble, the distribution of near-independent subsystem, the distribution law of the Maxwell- Boltzmann and the Maxwell distribution of velocities are achieved directly from the Liouville equation without using the hypothesis of equal probability. The micro-canonical ensemble is considered unsuitable as the foundation of equivalent state theory again, for most of equivalent states of isolated systems are not the states with equal probabilities actually. The reversibility paradoxes in the processes of non-equivalent evolutions of macro-systems can be eliminated completely, ...
A multinational SDI-based system to facilitate disaster risk management in the Andean Community
Molina, Martín
A multinational SDI-based system to facilitate disaster risk management in the Andean Community: Spatial Data Infrastructure Disaster risk management Geoportal Thematic search engine a b s t r a c t A useful strategy for improving disaster risk management is sharing spatial data across different technical
Universality of Tsallis Non-Extensive Statistics and Fractal Dynamics for Complex Systems
G. P. Pavlos; M. N. Xenakis; L. P. Karakatsanis; A. C. Iliopoulos; A. E. G. Pavlos; D. V. Sarafopoulos
2012-03-25
Tsallis q-extension of statistics and fractal generalization of dynamics are two faces of the same physical reality, as well as the Kernel modern complexity theory. The fractal generalization dynamics is based at the multiscale - multifractal characters of complex dynamics in the physical space-time and the complex system's dynamical phase space. Tsallis q-triplet of non-extensive statistics can be used for the experiment test of q-statistic as well as of the fractal dynamics. In this study we present indicative experimental verifications of Tsallis theory in various complex systems such as solar plasmas, (planetic magnetospheres, cosmic stars and cosmic rays), atmospheric dynamics, seismogenesis and brain dynamics.
Dynamically strained ferroelastics: Statistical behavior in elastic and plastic regimes
NASA Astrophysics Data System (ADS)
Ding, X.; Lookman, T.; Zhao, Z.; Saxena, A.; Sun, J.; Salje, E. K. H.
2013-03-01
The dynamic evolution in ferroelastic crystals under external shear is explored by computer simulation of a two-dimensional model. The characteristic geometrical patterns obtained during shear deformation include dynamic tweed in the elastic regime as well as interpenetrating needle domains in the plastic regime. As a result, the statistics of jerk energy differ in the elastic and plastic regimes. In the elastic regime the distributions of jerk energy are sensitive to temperature and initial configurations. However, in the plastic regime the jerk distributions are rather robust and do not depend much on the details of the configurations, although the geometrical pattern formed after yield is strongly influenced by the elastic constants of the materials and the configurations we used. Specifically, for all geometrical configurations we studied, the energy distribution of jerks shows a power-law noise pattern P(E)˜E-(?-1)(?-1=1.3-2) at low temperatures and a Vogel-Fulcher distribution P(E) ˜ exp-(E/E0) at high temperatures. More complex behavior occurs at the crossover between these two regimes where our simulated jerk distributions are very well described by a generalized Poisson distributions P(E)˜E-(?-1) exp-(E/E0)n with n = 0.4-0.5 and ?-1 ? 0 (Kohlrausch law). The geometrical mechanisms for the evolution of the ferroelastic microstructure under strain deformation remain similar in all thermal regimes, whereas their thermodynamic behavior differs dramatically: on heating, from power-law statistics via the Kohlrausch law to a Vogel-Fulcher law. There is hence no simple way to predict the local evolution of the twin microstructure from just the observed statistical behavior of a ferroelastic crystal. It is shown that the Poisson distribution is a convenient way to describe the crossover behavior contained in all the experimental data without recourse to specific scaling functions or temperature-dependent cutoff lengths.
Statistical test for dynamical nonstationarity in observed time-series data Matthew B. Kennel*
Tennessee, University of
Statistical test for dynamical nonstationarity in observed time-series data Matthew B. Kennel observed data yields a test for ``nonstationarity.'' Framed in terms of a statistical hypothesis test, with corrections to overcome difficulties in real dynamical data which cause naive statistics to fail. S1063-651X
Moments of probable seas: statistical dynamics of Planet Ocean
NASA Astrophysics Data System (ADS)
Holloway, Greg
The ocean is too big. From the scale of planetary radius to scales of turbulent microstructure, the range of length scales is 109. Likewise for time scales. Classical geophysical fluid dynamics does not have an apparatus for dealing with such complexity, while `brute force' computing on the most powerful supercomputers, extant or presently foreseen, barely scratches this complexity. Yet the everywhere-swirling-churning ocean interacts unpredictably in climate history and climate future - against which we attempt to devise planetary stewardship. Can we better take into account the unpredictability of oceans to improve upon present ocean/climate forecasting? What to do? First, recognize that our goal is to comprehend probabilities of possible oceans. Questions we would ask are posed as moments (expectations). Then the dynamical goal is clear: we seek equations of motion of moments of probable oceans. Classical fluid mechanics offers part of the answer but fails to recognize statistical dynamical aspects (missing the arrow of time as past==>future). At probabilities of oceans, the missing physics emerges: moments are forced by gradients of entropy with respect to moments. Time regains its arrow, and first (simplest) approximations to entropy-gradient forces enhance the fidelity of ocean theories and practical models.
Neutral dynamics and cluster statistics in a tropical forest.
Seri, Efrat; Maruvka, Yosef E; Shnerb, Nadav M
2012-12-01
The neutral theory of biodiversity attributes community structure to the effects of chance alone, assuming that all species and individuals are demographically equivalent. Here we present a spatially explicit version of the neutral theory and test it against the Barro Colorado Island (BCI) data. Monitoring the dynamics of clusters, we show that the effect of local heterogeneities (e.g., microtopography) is weak, making a spatially homogenous model plausible. We then compare the cluster statistics of the three most frequent species with the patterns obtained from neutral dynamics, examining two families of recruitment kernels: one that interpolates between a limited distance and panmictic dispersal (local-global) and one that assumes a scale-free Cauchy kernel. The results rule out the local-global dispersal model and show that the spatial patterns fit very nicely those obtained from the fat-tailed kernel. Our work emphasizes the importance of spatiotemporal cluster dynamics as an instrument for detecting the factors that govern community assembly. PMID:23149409
Statistical characteristics of topographic surfaces and dynamic smoothing of landscapes
NASA Astrophysics Data System (ADS)
Bartlett, M. S.; Laio, F.; Ridolfi, L.; Vico, G.; Porporato, A. M.
2011-12-01
We analyze the local statistics of topographic surfaces, including slope and aspect, as a function of scale, and explore their relations with landscape features, such as age, vegetation, and geology. These results build upon the previous work of Vico and Porporato (JGR 114, F01011, 2009), which characterized slope using generalized t-Student distributions. We find that the number of degrees of freedom of such distributions, which determines the heaviness of their tails, is linked to the age of the topographic relief of the considered regions, tending to normal distributions for very old mountain ranges. Based on these findings, and inspired by models of critical phenomena, we develop physically-based, space-time stochastic differential equations that reproduce this dynamic smoothing of rough landscapes.
Forecasting: it is not about statistics, it is about dynamics.
Judd, Kevin; Stemler, Thomas
2010-01-13
In 1963, the mathematician and meteorologist Edward Lorenz published a paper (Lorenz 1963 J. Atmos. Sci. 20, 130-141) that changed the way scientists think about the prediction of geophysical systems, by introducing the ideas of chaos, attractors, sensitivity to initial conditions and the limitations to forecasting nonlinear systems. Three years earlier, the mathematician and engineer Rudolf Kalman had published a paper (Kalman 1960 Trans. ASME Ser. D, J. Basic Eng. 82, 35-45) that changed the way engineers thought about prediction of electronic and mechanical systems. Ironically, in recent years, geophysicists have become increasingly interested in Kalman filters, whereas engineers have become increasingly interested in chaos. It is argued that more often than not the tracking and forecasting of nonlinear systems has more to do with the nonlinear dynamics that Lorenz considered than it has to do with statistics that Kalman considered. A position with which both Lorenz and Kalman would appear to agree. PMID:19948555
Discrete dynamical models: combinatorics, statistics and continuum approximations
Kornyak, Vladimir V
2015-01-01
This essay advocates the view that any problem that has a meaningful empirical content, can be formulated in constructive, more definitely, finite terms. We consider combinatorial models of dynamical systems and approaches to statistical description of such models. We demonstrate that many concepts of continuous physics --- such as continuous symmetries, the principle of least action, Lagrangians, deterministic evolution equations --- can be obtained from combinatorial structures as a result of the large number approximation. We propose a constructive description of quantum behavior that provides, in particular, a natural explanation of appearance of complex numbers in the formalism of quantum mechanics. Some approaches to construction of discrete models of quantum evolution that involve gauge connections are discussed.
Quantum statistics and dynamics of nonlinear couplers with nonlinear exchange
Abdalla, M Sebawe; Perina, J
2011-01-01
In this paper we derive the quantum statistical and dynamical properties of nonlinear optical couplers composed of two nonlinear waveguides operating by the second subharmonic generation, which are coupled linearly through evanescent waves and nonlinearly through nondegenerate optical parametric interaction. Main attention is paid to generation and transmission of nonclassical light, based on a discussion of squeezing phenomenon, normalized second-order correlation function, and quasiprobability distribution functions. Initially coherent, number and thermal states of optical beams are considered. In particular, results are discussed in dependence on the strength of the nonlinear coupling relatively to the linear coupling. We show that if the Fock state $|1>$ enters the first waveguide and the vacuum state $|0>$ enters the second waveguide, the coupler can serve as a generator of squeezed vacuum state governed by the coupler parameters. Further, if thermal fields enter initially the waveguides the coupler play...
Multiscale dynamics of C60 from attosecond to statistical physics
NASA Astrophysics Data System (ADS)
Lépine, F.
2015-06-01
C60 is a fascinating object that has become remarkably useful for experimentalists and theoreticians to study photo-induced processes in large many-particle systems. In this review article, we discuss how the knowledge accumulated over the past 30 years on this molecule provides a large panel of mechanisms that occur from the intrinsic time scale of electronic motion that is attosecond, to long ‘macroscopic’ time scale (second). This illustrates the multiscale aspect of dynamics in photo-excited systems, which connects coherent quantum processes to classical and statistical mechanisms. This also shines light onto future experiments and theoretical work required to complete the global picture of light-induced mechanisms in fullerenes.
Pasta nucleosynthesis: Molecular dynamics simulations of nuclear statistical equilibrium
NASA Astrophysics Data System (ADS)
Caplan, M. E.; Schneider, A. S.; Horowitz, C. J.; Berry, D. K.
2015-06-01
Background: Exotic nonspherical nuclear pasta shapes are expected in nuclear matter at just below saturation density because of competition between short-range nuclear attraction and long-range Coulomb repulsion. Purpose: We explore the impact nuclear pasta may have on nucleosynthesis during neutron star mergers when cold dense nuclear matter is ejected and decompressed. Methods: We use a hybrid CPU/GPU molecular dynamics (MD) code to perform decompression simulations of cold dense matter with 51 200 and 409 600 nucleons from 0.080 fm-3 down to 0.00125 fm-3 . Simulations are run for proton fractions YP= 0.05, 0.10, 0.20, 0.30, and 0.40 at temperatures T = 0.5, 0.75, and 1.0 MeV. The final composition of each simulation is obtained using a cluster algorithm and compared to a constant density run. Results: Size of nuclei in the final state of decompression runs are in good agreement with nuclear statistical equilibrium (NSE) models for temperatures of 1 MeV while constant density runs produce nuclei smaller than the ones obtained with NSE. Our MD simulations produces unphysical results with large rod-like nuclei in the final state of T =0.5 MeV runs. Conclusions: Our MD model is valid at higher densities than simple nuclear statistical equilibrium models and may help determine the initial temperatures and proton fractions of matter ejected in mergers.
Statistical analysis of a dynamic model for dietary contaminant exposure.
Bertail, P; Clémençon, S; Tressou, J
2010-03-01
This paper is devoted to the statistical analysis of a stochastic model introduced in [P. Bertail, S. Clémençon, and J. Tressou, A storage model with random release rate for modelling exposure to food contaminants, Math. Biosci. Eng. 35 (1) (2008), pp. 35-60] for describing the phenomenon of exposure to a certain food contaminant. In this modelling, the temporal evolution of the contamination exposure is entirely determined by the accumulation phenomenon due to successive dietary intakes and the pharmacokinetics governing the elimination process inbetween intakes, in such a way that the exposure dynamic through time is described as a piecewise deterministic Markov process. Paths of the contamination exposure process are scarcely observable in practice, therefore intensive computer simulation methods are crucial for estimating the time-dependent or steady-state features of the process. Here we consider simulation estimators based on consumption and contamination data and investigate how to construct accurate bootstrap confidence intervals (CI) for certain quantities of considerable importance from the epidemiology viewpoint. Special attention is also paid to the problem of computing the probability of certain rare events related to the exposure process path arising in dietary risk analysis using multilevel splitting or importance sampling (IS) techniques. Applications of these statistical methods to a collection of data sets related to dietary methyl mercury contamination are discussed thoroughly. PMID:22876987
Statistical light-mode dynamics of multipulse passive mode locking.
Weill, Rafi; Well, Rafi; Vodonos, Boris; Gordon, Ariel; Gat, Omri; Fischer, Baruch
2007-09-01
We study the multipulse formation in passive mode locking in the framework of the statistical light-mode dynamics theory. It is a many-body theory that treats the complex many-mode laser system by statistical mechanics. We give a detailed theory and experimental verification for the important case of multiple-pulse formation in the laser cavity. We follow and extend our former work on the subject. We give a detailed analysis with a rigorous calculation of the partition function, the free energy, and the order parameter in the coarse-graining method within the mean-field theory that is exact in the light-mode system. The outcome is a comprehensive picture of multipulse formation and annihilation, pulse after pulse, in an almost quantized manner, as the noise ("temperature") or the light power is varied. We obtain the phase diagram of the system, showing a series of first-order phase transitions, each belonging to a different number of pulses. We also study the hysteresis behavior, typical for such thermodynamic systems. We elaborate on the role of the saturable absorber structure in determining the multipulse formation. The theoretical results are compared to experimental measurements that we obtained with mode-locked fiber lasers, and we find an excellent agreement. PMID:17930204
A statistical model for interpreting computerized dynamic posturography data
NASA Technical Reports Server (NTRS)
Feiveson, Alan H.; Metter, E. Jeffrey; Paloski, William H.
2002-01-01
Computerized dynamic posturography (CDP) is widely used for assessment of altered balance control. CDP trials are quantified using the equilibrium score (ES), which ranges from zero to 100, as a decreasing function of peak sway angle. The problem of how best to model and analyze ESs from a controlled study is considered. The ES often exhibits a skewed distribution in repeated trials, which can lead to incorrect inference when applying standard regression or analysis of variance models. Furthermore, CDP trials are terminated when a patient loses balance. In these situations, the ES is not observable, but is assigned the lowest possible score--zero. As a result, the response variable has a mixed discrete-continuous distribution, further compromising inference obtained by standard statistical methods. Here, we develop alternative methodology for analyzing ESs under a stochastic model extending the ES to a continuous latent random variable that always exists, but is unobserved in the event of a fall. Loss of balance occurs conditionally, with probability depending on the realized latent ES. After fitting the model by a form of quasi-maximum-likelihood, one may perform statistical inference to assess the effects of explanatory variables. An example is provided, using data from the NIH/NIA Baltimore Longitudinal Study on Aging.
SDI-based business processes: A territorial analysis web information system in Spain
NASA Astrophysics Data System (ADS)
Béjar, Rubén; Latre, Miguel Á.; Lopez-Pellicer, Francisco J.; Nogueras-Iso, Javier; Zarazaga-Soria, F. J.; Muro-Medrano, Pedro R.
2012-09-01
Spatial Data Infrastructures (SDIs) provide access to geospatial data and operations through interoperable Web services. These data and operations can be chained to set up specialized geospatial business processes, and these processes can give support to different applications. End users can benefit from these applications, while experts can integrate the Web services in their own business processes and developments. This paper presents an SDI-based territorial analysis Web information system for Spain, which gives access to land cover, topography and elevation data, as well as to a number of interoperable geospatial operations by means of a Web Processing Service (WPS). Several examples illustrate how different territorial analysis business processes are supported. The system has been established by the Spanish National SDI (Infraestructura de Datos Espaciales de España, IDEE) both as an experimental platform for geoscientists and geoinformation system developers, and as a mechanism to contribute to the Spanish citizens knowledge about their territory.
Dynamics of Statistical Fluctuations in Low-Current Microdischarges.
NASA Astrophysics Data System (ADS)
Khudik, Vladimir; Shvydky, Alex; Theodosiou, Constantine
2006-10-01
According to the Paschen's similarity law, when the product of the gas pressure and the system dimension is kept constant, pd = const, discharges in small and large systems exhibit the similar behavior. However, the influence of fluctuations (as well as nonlinear processes such as, for example, stepwise ionization and radiation trapping) on the discharge dynamics in systems with different dimensions is different: Their level is higher in smaller systems, so that statistical fluctuations change dramatically the discharge behavior in microdischarges operating in Townsend regime. We present a simple model that incorporates all main processes which cause fluctuations and that allows to describe analytically their dynamics. Close analogy to an oscillator driven by a random force is revealed. In this analogy, the voltage across the discharge gap is related to a generalized coordinate, the number of ions in subsequent generations is related to a generalized momentum, and fluctuations in the number of ions (i.e. fluctuations in the generalized momentum) play, in essence, role of the random force. In the same manner as a random force, fluctuations pump ``energy'' in natural oscillations of the discharge current. Without dissipation they grow in time which eventually leads to disruption of the discharge. Dissipation suppresses fluctuations and limits them at some level.
NASA Technical Reports Server (NTRS)
Schweikhard, W. G.; Chen, Y. S.
1986-01-01
The Melick method of inlet flow dynamic distortion prediction by statistical means is outlined. A hypothetic vortex model is used as the basis for the mathematical formulations. The main variables are identified by matching the theoretical total pressure rms ratio with the measured total pressure rms ratio. Data comparisons, using the HiMAT inlet test data set, indicate satisfactory prediction of the dynamic peak distortion for cases with boundary layer control device vortex generators. A method for the dynamic probe selection was developed. Validity of the probe selection criteria is demonstrated by comparing the reduced-probe predictions with the 40-probe predictions. It is indicated that the the number of dynamic probes can be reduced to as few as two and still retain good accuracy.
Characterizing Uncertainties in Hydrologic Extremes: Statistical vs. Dynamical Downscaling
NASA Astrophysics Data System (ADS)
Mauger, G. S.; Salathe, E. P., Jr.
2013-12-01
Numerous agencies are now charged with considering the impacts of climate change in management decisions, both from the standpoint of adapting to changing conditions and minimizing emissions of greenhouse gases. These decisions require robust projections of change and defensible estimates of their uncertainty. We present work that is specifically focused on characterizing the uncertainty in projections of hydrologic extremes. Much recent work has been devoted to characterizing the uncertainty in hydrologic projections due to differences in downscaling methodology (e.g., Abatzoglou and Brown, 2012; Bürger et al., 2012; Rasmussen et al., 2011; Wetterhall et al., 2012) and among hydrologic models (e.g., Bennett et al., 2012; Clark et al., 2008; Fenicia et al., 2008; Smith and Marshall, 2010; Vano et al., 2012). These have established a basis for such analyses, but have generally focused on the implications for monthly and annual flows rather than flow extremes. In addition, few among these have been focused within the Pacific Northwest. In this work we assess the uncertainty in projected changes to hydrologic extremes associated with dynamical vs. statistical downscaling. The analysis is focused on 3 distinct watersheds within the Pacific Northwest - the Skagit, Green, and Willamette river basins. Results highlight the sensitivity of flood projections to downscaling approach and hydrologic model assumptions. Sensitivities are characterized as a function of geographic location, hydrologic regime, and climate - identifying circumstances under which projections are reliable and others in which answers differ markedly based on methodology. For example, one notable result is that dynamically downscaled projections appear to refute the assumed relationship between watershed type (snow-dominant vs. rain-dominant) and projected changes to flood risk - currently considered a key indicator of future flood risk. Results presented here provide key information for decision-making as well as for prioritizing future impacts research.
Dynamic Statistical Graphics in the C2 Virtual Reality Environment J. Symanzik D. Cook
Symanzik, Jürgen
Dynamic Statistical Graphics in the C2 Virtual Reality Environment J. Symanzik D. Cook Department immersive virtual reality environ- ment that allows 3 dimensional projections of higher di- mensional virtual reality environment. So far, most applications of dynamic statistical graphics have involved
Modeling Insurgent Dynamics Including Heterogeneity. A Statistical Physics Approach
NASA Astrophysics Data System (ADS)
Johnson, Neil F.; Manrique, Pedro; Hui, Pak Ming
2013-05-01
Despite the myriad complexities inherent in human conflict, a common pattern has been identified across a wide range of modern insurgencies and terrorist campaigns involving the severity of individual events—namely an approximate power-law x - ? with exponent ??2.5. We recently proposed a simple toy model to explain this finding, built around the reported loose and transient nature of operational cells of insurgents or terrorists. Although it reproduces the 2.5 power-law, this toy model assumes every actor is identical. Here we generalize this toy model to incorporate individual heterogeneity while retaining the model's analytic solvability. In the case of kinship or team rules guiding the cell dynamics, we find that this 2.5 analytic result persists—however an interesting new phase transition emerges whereby this cell distribution undergoes a transition to a phase in which the individuals become isolated and hence all the cells have spontaneously disintegrated. Apart from extending our understanding of the empirical 2.5 result for insurgencies and terrorism, this work illustrates how other statistical physics models of human grouping might usefully be generalized in order to explore the effect of diverse human social, cultural or behavioral traits.
Nguyen, Y; Nguyen, Nam X.; Rogers, Jamie L.; Liao, Jun; MacMillan, John B.
2015-01-01
ABSTRACT Bacteria engage in chemical signaling, termed quorum sensing (QS), to mediate intercellular communication, mimicking multicellular organisms. The LuxR family of QS transcription factors regulates gene expression, coordinating population behavior by sensing endogenous acyl homoserine lactones (AHLs). However, some bacteria (such as Escherichia coli) do not produce AHLs. These LuxR orphans sense exogenous AHLs but also regulate transcription in the absence of AHLs. Importantly, this AHL-independent regulatory mechanism is still largely unknown. Here we present several structures of one such orphan LuxR-type protein, SdiA, from enterohemorrhagic E. coli (EHEC), in the presence and absence of AHL. SdiA is actually not in an apo state without AHL but is regulated by a previously unknown endogenous ligand, 1-octanoyl-rac-glycerol (OCL), which is ubiquitously found throughout the tree of life and serves as an energy source, signaling molecule, and substrate for membrane biogenesis. While exogenous AHL renders to SdiA higher stability and DNA binding affinity, OCL may function as a chemical chaperone placeholder that stabilizes SdiA, allowing for basal activity. Structural comparison between SdiA-AHL and SdiA-OCL complexes provides crucial mechanistic insights into the ligand regulation of AHL-dependent and -independent function of LuxR-type proteins. Importantly, in addition to its contribution to basic science, this work has implications for public health, inasmuch as the SdiA signaling system aids the deadly human pathogen EHEC to adapt to a commensal lifestyle in the gastrointestinal (GI) tract of cattle, its main reservoir. These studies open exciting and novel avenues to control shedding of this human pathogen in the environment. PMID:25827420
An open-source wireless sensor stack: from Arduino to SDI-12 to Water One Flow
NASA Astrophysics Data System (ADS)
Hicks, S.; Damiano, S. G.; Smith, K. M.; Olexy, J.; Horsburgh, J. S.; Mayorga, E.; Aufdenkampe, A. K.
2013-12-01
Implementing a large-scale streaming environmental sensor network has previously been limited by the high cost of the datalogging and data communication infrastructure. The Christina River Basin Critical Zone Observatory (CRB-CZO) is overcoming the obstacles to large near-real-time data collection networks by using Arduino, an open source electronics platform, in combination with XBee ZigBee wireless radio modules. These extremely low-cost and easy-to-use open source electronics are at the heart of the new DIY movement and have provided solutions to countless projects by over half a million users worldwide. However, their use in environmental sensing is in its infancy. At present a primary limitation to widespread deployment of open-source electronics for environmental sensing is the lack of a simple, open-source software stack to manage streaming data from heterogeneous sensor networks. Here we present a functioning prototype software stack that receives sensor data over a self-meshing ZigBee wireless network from over a hundred sensors, stores the data locally and serves it on demand as a CUAHSI Water One Flow (WOF) web service. We highlight a few new, innovative components, including: (1) a versatile open data logger design based the Arduino electronics platform and ZigBee radios; (2) a software library implementing SDI-12 communication protocol between any Arduino platform and SDI12-enabled sensors without the need for additional hardware (https://github.com/StroudCenter/Arduino-SDI-12); and (3) 'midStream', a light-weight set of Python code that receives streaming sensor data, appends it with metadata on the fly by querying a relational database structured on an early version of the Observations Data Model version 2.0 (ODM2), and uses the WOFpy library to serve the data as WaterML via SOAP and REST web services.
Statistical mechanical theory for non-equilibrium systems. IX. Stochastic molecular dynamics
Attard, Phil
Statistical mechanical theory for non-equilibrium systems. IX. Stochastic molecular dynamics Phil and the fluctuation. A stochastic molecular dynamics algorithm is developed for both equilibrium and nonequilibrium.1 The simplest equilibrium molecular dynamics algorithm uses Hamilton's equations of motion alone
Statistical Prediction and Molecular Dynamics Simulation Ben Cooke* and Scott C. Schmidleryz
Schmidler, Scott
Statistical Prediction and Molecular Dynamics Simulation Ben Cooke* and Scott C. Schmidleryz simulations of macromolecules. We emphasize the use of molecular dynamics simulations to calculate to replica exchange molecular dynamics simulations of a set of eight helical peptides under the AMBER
Journal of Statistical Physics, Vol. 82, Nos. 1/2, 1996 Molecular Dynamics Simulation of
Gallas, Jason
Journal of Statistical Physics, Vol. 82, Nos. 1/2, 1996 Molecular Dynamics Simulation of Size of a full 3D molecular dynamics simulation of size segregation by shaking, the so-called "Brazil nuts'4 and Stefan Sokolowski 1'5 Received May 22, 1995 We report the first three-dimensional molecular dynamics
Examining rainfall and cholera dynamics in Haiti using statistical and dynamic modeling approaches.
Eisenberg, Marisa C; Kujbida, Gregory; Tuite, Ashleigh R; Fisman, David N; Tien, Joseph H
2013-12-01
Haiti has been in the midst of a cholera epidemic since October 2010. Rainfall is thought to be associated with cholera here, but this relationship has only begun to be quantitatively examined. In this paper, we quantitatively examine the link between rainfall and cholera in Haiti for several different settings (including urban, rural, and displaced person camps) and spatial scales, using a combination of statistical and dynamic models. Statistical analysis of the lagged relationship between rainfall and cholera incidence was conducted using case crossover analysis and distributed lag nonlinear models. Dynamic models consisted of compartmental differential equation models including direct (fast) and indirect (delayed) disease transmission, where indirect transmission was forced by empirical rainfall data. Data sources include cholera case and hospitalization time series from the Haitian Ministry of Public Health, the United Nations Water, Sanitation and Health Cluster, International Organization for Migration, and Hôpital Albert Schweitzer. Rainfall data was obtained from rain gauges from the U.S. Geological Survey and Haiti Regeneration Initiative, and remote sensing rainfall data from the National Aeronautics and Space Administration Tropical Rainfall Measuring Mission. A strong relationship between rainfall and cholera was found for all spatial scales and locations examined. Increased rainfall was significantly correlated with increased cholera incidence 4-7 days later. Forcing the dynamic models with rainfall data resulted in good fits to the cholera case data, and rainfall-based predictions from the dynamic models closely matched observed cholera cases. These models provide a tool for planning and managing the epidemic as it continues. PMID:24267876
Marks, Laurence D.
2001-01-01
Acta Cryst. (2001). A57, 231±239 Chukhovskii et al. Statistical dynamical direct methods. II 231 Britain ± all rights reserved Statistical dynamical direct methods. II. The three- phase structure, conventional statistical direct methods will yield a reasonable approximation to the effective dynamical
Statistical Methods for Degradation Data with Dynamic Covariates Information and an Application and Xiaohong Gu Materials and Construction Research Division National Institute of Standards and Technology Gaithersburg, MD 20899 Abstract Degradation data provide a useful resource for obtaining reliability
Sapsis, Themistoklis
A framework for low-order predictive statistical modeling and uncertainty quantification in turbulent dynamical systems is developed here. These reduced-order, modified quasilinear Gaussian (ROMQG) algorithms apply to ...
Quantum statistical effects on fusion dynamics of heavy ions
Ayik, S. [Physics Department, Tennessee Technological University, Cookeville, Tennessee 38505 (United States); Yilmaz, B. [Physics Department, Ankara University, TR-06100 Ankara (Turkey); Physics Department, Middle East Technical University, TR-06531 Ankara (Turkey); Gokalp, A.; Yilmaz, O. [Physics Department, Middle East Technical University, TR-06531 Ankara (Turkey); Takigawa, N. [Department of Physics, Tohoku University, 980-8578 Sendai (Japan)
2005-05-01
To describe the fusion of two very heavy nuclei at near barrier energies, a generalized Langevin approach is proposed. The approach incorporates the quantum statistical fluctuations in accordance with the fluctuation and dissipation theorem. It is illustrated that the quantum statistical effects introduce an enhancement of the formation of a compound nucleus, though the quantum enhancement is somewhat less pronounced as indicated in the previous calculations.
Statistical and dynamical fluctuations of Binder ratios in heavy ion collisions
Zhiming Li; Fengbo Xiong; Yuanfang Wu
2013-01-31
Higher moments of net-proton Binder ratio, which is suggested to be a good experimental measurement to locate the QCD critical point, is measured in relativistic heavy ion collisions. We firstly estimate the effect of statistical fluctuations of the third and forth order Binder ratios. Then the dynamical Binder ratio is proposed and investigated in both transport and statistical models. The energy dependence of dynamical Binder ratios with different system sizes at RHIC beam scan energies are presented and discussed.
Statistical and dynamical fluctuations of Binder ratios in heavy ion collisions
Li, Zhiming; Wu, Yuanfang
2011-01-01
Higher moments of net-proton Binder ratio, which is suggested to be a good experimental measurement to locate the QCD critical point, is measured in relativistic heavy ion collisions. We firstly estimate the effect of statistical fluctuations of the third and the forth order Binder ratios. Then the dynamical Binder ratio is proposed and investigated in both transport and statistical models. The energy dependence of dynamical Binder ratios with different system sizes at RHIC beam scan energies are presented and discussed.
Statistically Converged Properties of Water from Ab Initio Molecular Dynamics Simulations
Matthias Heyden; Martina Havenith
\\u000a We present results from an ab initio molecular dynamics study of pure water. Using the resources available at the HLRB2 we were able to produce the first trajectories\\u000a of sufficient length and number, that allow to study dynamical processes on the picosecond timescale with statistically reliable\\u000a results. Additionally we computed a statistically converged infrared absorption spectrum from 0–4000?cm?1, which is
Statistical Test for Dynamical Nonstationarity in Observed Time-Series Data
Matthew B. Kennel
1995-12-21
Information in the time distribution of points in a state space reconstructed from observed data yields a test for ``nonstationarity''. Framed in terms of a statistical hypothesis test, this numerical algorithm can discern whether some underlying slow changes in parameters have taken place. The method examines a fundamental object in nonlinear dynamics, the geometry of orbits in state space, with corrections to overcome difficulties in real dynamical data which cause naive statistics to fail.
An Examination of Statistical Power in Multigroup Dynamic Structural Equation Models
ERIC Educational Resources Information Center
Prindle, John J.; McArdle, John J.
2012-01-01
This study used statistical simulation to calculate differential statistical power in dynamic structural equation models with groups (as in McArdle & Prindle, 2008). Patterns of between-group differences were simulated to provide insight into how model parameters influence power approximations. Chi-square and root mean square error of…
Johannes Berg; Michael Lässig; Andreas Wagner
2004-01-01
BACKGROUND: The structure of molecular networks derives from dynamical processes on evolutionary time scales. For protein interaction networks, global statistical features of their structure can now be inferred consistently from several large-throughput datasets. Understanding the underlying evolutionary dynamics is crucial for discerning random parts of the network from biologically important properties shaped by natural selection. RESULTS: We present a detailed
NASA Astrophysics Data System (ADS)
Amadei, A.; Chillemi, G.; Ceruso, M. A.; Grottesi, A.; Di Nola, A.
2000-01-01
From a specific definition of the roto-translational (external) and intramolecular (internal) coordinates, a constrained dynamics algorithm is derived for removing the roto-translational motions during molecular dynamics simulations, within the leap-frog integration scheme. In the paper the theoretical basis of this new method and its statistical mechanical consistency are reported, together with two applications.
Eduardo Garea Llano; Rainer Larin Fonseca
2009-01-01
In this paper we present a method for agro-ecological zonation of crops in Cuban mountain condi- tions in a Spatial Data Infrastructure (SDI) Environment. The proposed method is based on the com- bination of Geographical Information System (GIS) analysis techniques as map overlay, reclassifica- tion, and a proposed algorithm for indexation of the overlaid feature maps previously obtained by decision
Technology Transfer Automated Retrieval System (TEKTRAN)
Subsurface drip irrigation (SDI) as with all microirrigation systems is typically only used on crops with greater value. In the U.S. Great Plains region, the typical irrigated crops are the cereal and oil seed crops and cotton. These crops have less economic revenue than typical microirrigated cro...
Technology Transfer Automated Retrieval System (TEKTRAN)
An experimental field moisture controlled subsurface drip irrigation (SDI) system was designed and installed as a field trial in a Vertisol in the Alabama Black Belt region for two years. The system was designed to start hydraulic dosing only when field moisture was below field capacity. Results sho...
Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics
Crooks, Gavin; Sivak, David
2011-06-03
Many interesting divergence measures between conjugate ensembles of nonequilibrium trajectories can be experimentally determined from the work distribution of the process. Herein, we review the statistical and physical significance of several of these measures, in particular the relative entropy (dissipation), Jeffreys divergence (hysteresis), Jensen-Shannon divergence (time-asymmetry), Chernoff divergence (work cumulant generating function), and Renyi divergence.
A New Statistical Dynamic Analysis of Ecosystem Patterns
Xin Zhang; Li-He Chai
2010-01-01
While phenomenological investigations of ecosystem patterns often fail to reveal underlying dynamic mechanisms, we highlight\\u000a a universal principle for pattern formation in ecosystems. We consider ecosystems to be typical complex adaptive systems that\\u000a seek an optimal process to obtain maximized flux under given constraints. An analysis of the optimal process reveals underlying\\u000a microscopic dynamic mechanisms that induce complex patterns in
Statistical Anomaly Detection for Monitoring of Human Dynamics
NASA Astrophysics Data System (ADS)
Kamiya, K.; Fuse, T.
2015-05-01
Understanding of human dynamics has drawn attention to various areas. Due to the wide spread of positioning technologies that use GPS or public Wi-Fi, location information can be obtained with high spatial-temporal resolution as well as at low cost. By collecting set of individual location information in real time, monitoring of human dynamics is recently considered possible and is expected to lead to dynamic traffic control in the future. Although this monitoring focuses on detecting anomalous states of human dynamics, anomaly detection methods are developed ad hoc and not fully systematized. This research aims to define an anomaly detection problem of the human dynamics monitoring with gridded population data and develop an anomaly detection method based on the definition. According to the result of a review we have comprehensively conducted, we discussed the characteristics of the anomaly detection of human dynamics monitoring and categorized our problem to a semi-supervised anomaly detection problem that detects contextual anomalies behind time-series data. We developed an anomaly detection method based on a sticky HDP-HMM, which is able to estimate the number of hidden states according to input data. Results of the experiment with synthetic data showed that our proposed method has good fundamental performance with respect to the detection rate. Through the experiment with real gridded population data, an anomaly was detected when and where an actual social event had occurred.
Dynamic modeling of mean-reverting spreads for statistical arbitrage
Kostas Triantafyllopoulos; Giovanni Montana
2008-01-01
Statistical arbitrage strategies, such as pairs trading and its generalizations, rely on the construction of mean-reverting spreads enjoying a certain degree of predictability. Gaussian linear state-space processes have recently been proposed as a model for such spreads under the assumption that the observed process is a noisy realization of some hidden states. Real-time estimation of the unobserved spread process can
Dynamic modeling of mean-reverting spreads for statistical arbitrage
Kostas Triantafyllopoulos; Giovanni Montana
2011-01-01
Statistical arbitrage strategies, such as pairs trading and its generalizations rely on the construction of mean-reverting\\u000a spreads enjoying a certain degree of predictability. Gaussian linear state-space processes have recently been proposed as\\u000a a model for such spreads under the assumption that the observed process is a noisy realization of some hidden states. Real-time\\u000a estimation of the unobserved spread process can
Shankar, Manoharan; Ponraj, Paramasivan; Illakkiam, Devaraj; Rajendhran, Jeyaprakash; Gunasekaran, Paramasamy
2013-01-01
Enterobacter cloacae GS1 is a plant growth-promoting bacterium which colonizes rice roots. In the rhizosphere environment, N-acyl homoserine lactone (NAHL)-like quorum-sensing signals are known to be produced by host plants and other microbial inhabitants. E. cloacae GS1 was unable to synthesize NAHL quorum-sensing signals but had the NAHL-dependent transcriptional regulator-encoding gene sdiA. This study was aimed at understanding the effects of SdiA and NAHL-dependent cross talk in rice root colonization by E. cloacae GS1. Pleiotropic effects of sdiA inactivation included substantial increases in root colonization and biofilm formation, suggesting a negative role for SdiA in bacterial adhesion. We provide evidence that sdiA inactivation leads to elevated levels of biosynthesis of curli, which is involved in cellular adhesion. Extraneous addition of NAHLs had a negative effect on root colonization and biofilm formation. However, the sdiA mutant of E. cloacae GS1 was insensitive to NAHLs, suggesting that this NAHL-induced inhibition of root colonization and biofilm formation is SdiA dependent. Therefore, it is proposed that NAHLs produced by both plant and microbes in the rice rhizosphere act as cross-kingdom and interspecies signals to negatively impact cellular adhesion and, thereby, root colonization in E. cloacae GS1. PMID:23086212
Towards a statistical test for functional connectivity dynamics.
Zalesky, Andrew; Breakspear, Michael
2015-07-01
Sliding-window correlation is an emerging method for mapping time-resolved, resting-state functional connectivity. To avoid mapping spurious connectivity fluctuations (false positives), Leonardi and Van De Ville recently recommended choosing a window length exceeding the longest wavelength composing the BOLD signal, usually assumed to be ~100s. Here, we provide further statistical support for this rule of thumb. However, we demonstrate that non-stationary fluctuations in functional connectivity can in theory be detected with much shorter window lengths (e.g. 40s), while maintaining nominal control of false positives. We find that statistical power is near-maximal for window lengths chosen according to Leonardi and Van De Ville's rule of thumb. Furthermore, we lay some foundations for a parametric test to identify non-stationary fluctuations in functional connectivity, also noting limitations of the sinusoidal model upon which our work, and the work of Leonardi and Van De Ville, is based. Most notably, our analytical results pertain to covariances, as does our statistical test, whereas functional connectivity is more commonly measured using correlations. PMID:25818688
Bubble statistics and dynamics in double-stranded DNA.
Alexandrov, B S; Wille, L T; Rasmussen, K Ø; Bishop, A R; Blagoev, K B
2006-11-01
The dynamical properties of double-stranded DNA are studied in the framework of the Peyrard-Bishop-Dauxois model using Langevin dynamics. Our simulations are analyzed in terms of two distribution functions describing localized separations ("bubbles") of the double strand. The result that the bubble distributions are more sharply peaked at the active sites than thermodynamically obtained distributions is ascribed to the fact that the bubble lifetimes affect the distributions. Certain base-pair sequences are found to promote long-lived bubbles, and we argue that this is a result of length scale competition between the nonlinearity and disorder present in the system. PMID:17279870
Martin, Daniel R; Matyushov, Dmitry V
2012-08-30
We show that electrostatic fluctuations of the protein-water interface are globally non-Gaussian. The electrostatic component of the optical transition energy (energy gap) in a hydrated green fluorescent protein is studied here by classical molecular dynamics simulations. The distribution of the energy gap displays a high excess in the breadth of electrostatic fluctuations over the prediction of the Gaussian statistics. The energy gap dynamics include a nanosecond component. When simulations are repeated with frozen protein motions, the statistics shifts to the expectations of linear response and the slow dynamics disappear. We therefore suggest that both the non-Gaussian statistics and the nanosecond dynamics originate largely from global, low-frequency motions of the protein coupled to the interfacial water. The non-Gaussian statistics can be experimentally verified from the temperature dependence of the first two spectral moments measured at constant-volume conditions. Simulations at different temperatures are consistent with other indicators of the non-Gaussian statistics. In particular, the high-temperature part of the energy gap variance (second spectral moment) scales linearly with temperature and extrapolates to zero at a temperature characteristic of the protein glass transition. This result, violating the classical limit of the fluctuation-dissipation theorem, leads to a non-Boltzmann statistics of the energy gap and corresponding non-Arrhenius kinetics of radiationless electronic transitions, empirically described by the Vogel-Fulcher-Tammann law. PMID:22861814
Dynamics and statistics of heavy particles in turbulent flows
M. Cencini; J. Bec; L. Biferale; G. Boffetta; A. Celani; A. S. Lanotte; S. Musacchio; F. Toschi
2006-01-01
We present the results of Direct Numerical Simulations (DNS) of turbulent flows seeded with millions of passive inertial particles. The maximum Taylor's Reynolds number is around 200. We consider particles much heavier than the carrier flow in the limit when the Stokes drag force dominates their dynamical evolution. We discuss both the transient and the stationary regimes. In the transient
Lars Onsager Prize Lecture: Statistical Dynamics of Disordered Systems
NASA Astrophysics Data System (ADS)
Fisher, Daniel S.
2013-03-01
The properties of many systems are strongly affected by quenched disorder that arose from their past history but is frozen on the time scales of interest. Although equilibrium phases and phase transitions in disordered materials can be very different from their counterparts in pure systems, the most striking phenomena involve non-equilibrium dynamics. The state of understanding of some of these will be reviewed including approach to equilibrium in spin glasses and the onset of motion in driven systems such as vortices in superconductors or earthquakes on geological faults. The potential for developing understanding of short-term evolutionary dynamics of microbial populations by taking advantage of the randomness of their past histories and the biological complexities will be discussed briefly.
Statistics and dynamics of blends of linear and ring polymers.
NASA Astrophysics Data System (ADS)
Lang, Michael; Rubinstein, Michael
2008-03-01
This work focuses on conformations and dynamics of blends of linear and ring polymers. Rings in a melt of homo-polymer rings are compressed due to topology, if rings are significantly larger than the entanglement length. Dilute rings with degree of polymerization, Nr, immersed in a melt of linear polymers with degree of polymerization, Nl are almost ideal if Nl> Nr^1/2 and swell if Nl< Nr^1/2. Dynamics of pure ring melts is enhanced as compared to pure linear melts. Thus, minority of linear chains immersed in ring melt experiences enhancement of diffusion and relaxation. On the other hand, minority of long entangled rings immersed in melt of long entangled linear chains gets temporarily trapped. This leads to a clear reduction in diffusion coefficient while keeping relaxation (as determined by half ring relaxation) almost unaffected.
Viscoelastic effects in avalanche dynamics: a key to earthquake statistics.
Jagla, E A; Landes, François P; Rosso, Alberto
2014-05-01
In many complex systems a continuous input of energy over time can be suddenly relaxed in the form of avalanches. Conventional avalanche models disregard the possibility of internal dynamical effects in the interavalanche periods, and thus miss basic features observed in some real systems. We address this issue by studying a model with viscoelastic relaxation, showing how coherent oscillations of the stress field can emerge spontaneously. Remarkably, these oscillations generate avalanche patterns that are similar to those observed in seismic phenomena. PMID:24836251
Comparative Statistics by Adaptive Dynamics and the Correspondence Principle
Federico Echenique
2000-01-01
Federico Echenique JEL#: C61, C62, C72, C73 Keywords: Monotone comparative statics, supermodularity, strategic complements, learning, correspondence principle This paper formalizes the relation between comparative statics and the out-of-equilibrium explanation for how a system evolves after a change in parameters. The paper has two main results. First, an increase in an exogenous parameter sets o_ learning dynamics that involve larger values
Viscoelastic Effects in Avalanche Dynamics: A Key to Earthquake Statistics
NASA Astrophysics Data System (ADS)
Jagla, E. A.; Landes, François P.; Rosso, Alberto
2014-05-01
In many complex systems a continuous input of energy over time can be suddenly relaxed in the form of avalanches. Conventional avalanche models disregard the possibility of internal dynamical effects in the interavalanche periods, and thus miss basic features observed in some real systems. We address this issue by studying a model with viscoelastic relaxation, showing how coherent oscillations of the stress field can emerge spontaneously. Remarkably, these oscillations generate avalanche patterns that are similar to those observed in seismic phenomena.
A Statistical-Dynamical Model of the General Circulation of the Atmosphere
Yoshio Kurihara
1970-01-01
A statistical-dynamical, two-layer model of the atmosphere is constructed for the simulation of the climatic state of the global circulation.The meteorological variables, velocity, temperature and pressure, are decomposed into their zonal mean parts and eddy parts or deviations. The state of circulation is expressed by the zonal mean parts as well as eddy statistics which are the zonal averages of
Statistical methodologies for the control of dynamic remapping
NASA Technical Reports Server (NTRS)
Saltz, J. H.; Nicol, D. M.
1986-01-01
Following an initial mapping of a problem onto a multiprocessor machine or computer network, system performance often deteriorates with time. In order to maintain high performance, it may be necessary to remap the problem. The decision to remap must take into account measurements of performance deterioration, the cost of remapping, and the estimated benefits achieved by remapping. We examine the tradeoff between the costs and the benefits of remapping two qualitatively different kinds of problems. One problem assumes that performance deteriorates gradually, the other assumes that performance deteriorates suddenly. We consider a variety of policies for governing when to remap. In order to evaluate these policies, statistical models of problem behaviors are developed. Simulation results are presented which compare simple policies with computationally expensive optimal decision policies; these results demonstrate that for each problem type, the proposed simple policies are effective and robust.
Modeling dynamic controls on ice streams: a Bayesian statistical approach
Berliner, L. M.; Jezek, K.; Cressie, N.; Kim, Y.; Lam, C. Q.; van der Veen, Cornelis J.
2008-12-05
. Approximate importance sampling Monte Carlo for data assimilation. Physica D, 230(1–2), 37–49. Berliner, L.M., C.K. Wikle and N. Cressie. 2000. Long-lead prediction of Pacific SSTs via Bayesian dynamic modelling. J. Climate, 13(13), 3953–3968. Berliner, L... Bayesian tutorial for data assimilation. Physica D, 230(1–2), 1–16. Wikle, C.K., L.M. Berliner and R.F. Milliff. 2003. Hierarchical Bayesian approach to boundary value problems with stochastic boundary conditions. Mon. Weather Rev., 131(6), 1051...
Dynamic Cartographic Methods for Visualisation of Health Statistics
Radim Stampach; Milan Konecny; Petr Kubicek; Edvard Geryk
\\u000a The article deals with interdisciplinary research on health status data analysis and so-called ‘health cartography’ mapping\\u000a approaches. In the first part existing cognitive studies and recommendations on map design are discussed.\\u000a \\u000a \\u000a The following part describes current trends in cartographic visualisation and non-traditional methods for exploratory cartography.\\u000a Examples and possibilities of modern cartographic tools for dynamic presentation, publication, and analysis of
Monitoring of anticoagulant therapy applying a dynamic statistical model.
Nielsen, Peter Brønnum; Lundbye-Christensen, Søren; Larsen, Torben Bjerregaard; Kristensen, Søren Risom; Hejlesen, Ole Kristian
2013-06-01
Patients with an increased risk of thrombosis may require treatment with vitamin K-antagonists such as warfarin. Treatment with warfarin has been reported difficult mainly due to high inter- and intraindividual variability in response to the drug [1]. Using predictive models that can predict International Normalised Ratio (INR) values enables for a higher degree of individualised warfarin dosing regime. This paper reports the outcome of the development of a dynamic prediction model. It takes warfarin intake and INR values as inputs, and uses an individual sensitivity parameter to model response to warfarin intake. The model is set on state-space form and uses Kalman filtering technique to optimise individual parameters. Retrospective test of the model proved robustness to choices of initial parameters, and feasible prediction results of both INR values and suggested warfarin dosage, which may prove beneficial for both patients and healthcare takers. PMID:23305998
Human turnover dynamics during sleep: statistical behavior and its modeling.
Yoneyama, Mitsuru; Okuma, Yasuyuki; Utsumi, Hiroya; Terashi, Hiroo; Mitoma, Hiroshi
2014-03-01
Turnover is a typical intermittent body movement while asleep. Exploring its behavior may provide insights into the mechanisms and management of sleep. However, little is understood about the dynamic nature of turnover in healthy humans and how it can be modified in disease. Here we present a detailed analysis of turnover signals that are collected by accelerometry from healthy elderly subjects and age-matched patients with neurodegenerative disorders such as Parkinson's disease. In healthy subjects, the time intervals between consecutive turnover events exhibit a well-separated bimodal distribution with one mode at ?10 s and the other at ?100 s, whereas such bimodality tends to disappear in neurodegenerative patients. The discovery of bimodality and fine temporal structures (?10 s) is a contribution that is not revealed by conventional sleep recordings with less time resolution (?30 s). Moreover, we estimate the scaling exponent of the interval fluctuations, which also shows a clear difference between healthy subjects and patients. We incorporate these experimental results into a computational model of human decision making. A decision is to be made at each simulation step between two choices: to keep on sleeping or to make a turnover, the selection of which is determined dynamically by comparing a pair of random numbers assigned to each choice. This decision is weighted by a single parameter that reflects the depth of sleep. The resulting simulated behavior accurately replicates many aspects of observed turnover patterns, including the appearance or disappearance of bimodality and leads to several predictions, suggesting that the depth parameter may be useful as a quantitative measure for differentiating between normal and pathological sleep. These findings have significant clinical implications and may pave the way for the development of practical sleep assessment technologies. PMID:24730888
OneGeology Web Services and Portal as a global geological SDI - latest standards and technology
NASA Astrophysics Data System (ADS)
Duffy, Tim; Tellez-Arenas, Agnes
2014-05-01
The global coverage of OneGeology Web Services (www.onegeology.org and portal.onegeology.org) achieved since 2007 from the 120 participating geological surveys will be reviewed and issues arising discussed. Recent enhancements to the OneGeology Web Services capabilities will be covered including new up to 5 star service accreditation scheme utilising the ISO/OGC Web Mapping Service standard version 1.3, core ISO 19115 metadata additions and Version 2.0 Web Feature Services (WFS) serving the new IUGS-CGI GeoSciML V3.2 geological web data exchange language standard (http://www.geosciml.org/) with its associated 30+ IUGS-CGI available vocabularies (http://resource.geosciml.org/ and http://srvgeosciml.brgm.fr/eXist2010/brgm/client.html). Use of the CGI simpelithology and timescale dictionaries now allow those who wish to do so to offer data harmonisation to query their GeoSciML 3.2 based Web Feature Services and their GeoSciML_Portrayal V2.0.1 (http://www.geosciml.org/) Web Map Services in the OneGeology portal (http://portal.onegeology.org). Contributing to OneGeology involves offering to serve ideally 1:1000,000 scale geological data (in practice any scale now is warmly welcomed) as an OGC (Open Geospatial Consortium) standard based WMS (Web Mapping Service) service from an available WWW server. This may either be hosted within the Geological Survey or a neighbouring, regional or elsewhere institution that offers to serve that data for them i.e. offers to help technically by providing the web serving IT infrastructure as a 'buddy'. OneGeology is a standards focussed Spatial Data Infrastructure (SDI) and works to ensure that these standards work together and it is now possible for European Geological Surveys to register their INSPIRE web services within the OneGeology SDI (e.g. see http://www.geosciml.org/geosciml/3.2/documentation/cookbook/INSPIRE_GeoSciML_Cookbook%20_1.0.pdf). The Onegeology portal (http://portal.onegeology.org) is the first port of call for anyone wishing to discover the availability of global geological web services and has new functionality to view and use such services including multiple projection support. KEYWORDS : OneGeology; GeoSciML V 3.2; Data exchange; Portal; INSPIRE; Standards; OGC; Interoperability; GeoScience information; WMS; WFS; Cookbook.
Abed, Nadia; Grépinet, Olivier; Canepa, Sylvie; Hurtado-Escobar, Genaro A; Guichard, Nolwenn; Wiedemann, Agnès; Velge, Philippe; Virlogeux-Payant, Isabelle
2014-10-01
One important step for the pathogenesis of Salmonella is its ability to penetrate host cells. Recently, a new entry system involving the outer membrane protein Rck has been characterized. Previous studies have shown that the pefI-srgC locus, which contains rck, was regulated by the temperature and SdiA, the transcriptional regulator of quorum sensing in Salmonella. To decipher the regulation of rck by SdiA, we first confirmed the operon organization of the pefI-srgC locus. Using plasmid-based transcriptional fusions, we showed that only the predicted distal promoter upstream of pefI, PefIP2, displays an SdiA- and acyl-homoserine lactones-dependent activity while the predicted proximal PefIP1 promoter exhibits a very low activity independent on SdiA in our culture conditions. A direct and specific interaction of SdiA with this PefIP2 region was identified using electrophoretic mobility shift assays and surface plasmon resonance studies. We also observed that Rck expression is negatively regulated by the nucleoid-associated H-NS protein at both 25°C and 37°C. This work is the first demonstration of a direct regulation of genes by SdiA in Salmonella and will help further studies designed to identify environmental conditions required for Rck expression and consequently contribute to better characterize the role of this invasin in vivo. PMID:25080967
Statistical-Dynamical Approach for Streamflow Modeling at Malakal, Sudan, on the White Nile River
Paul Block; Balaji Rajagopalan
2010-01-01
The upper White Nile Basin above Malakal, Sudan, is considered to be one of the most complicated and diverse hydrologic settings on Earth. Accurately depicting and predicting the streamflow at Malakal is essential for water managers considering Nile Basin-wide initiatives and potential large-scale projects. Dynamical, statistical, and combination models are assessed for their ability to predict monthly streamflow at Malakal.
Dynamic Graphics in Excel for Teaching Statistics: Understanding the Probability Density Function
ERIC Educational Resources Information Center
Coll-Serrano, Vicente; Blasco-Blasco, Olga; Alvarez-Jareno, Jose A.
2011-01-01
In this article, we show a dynamic graphic in Excel that is used to introduce an important concept in our subject, Statistics I: the probability density function. This interactive graphic seeks to facilitate conceptual understanding of the main aspects analysed by the learners.
NASA Astrophysics Data System (ADS)
Schepen, Andrew; Wang, Q. J.
2015-03-01
The Australian Bureau of Meteorology produces statistical and dynamic seasonal streamflow forecasts. The statistical and dynamic forecasts are similarly reliable in ensemble spread; however, skill varies by catchment and season. Therefore, it may be possible to optimize forecasting skill by weighting and merging statistical and dynamic forecasts. Two model averaging methods are evaluated for merging forecasts for 12 locations. The first method, Bayesian model averaging (BMA), applies averaging to forecast probability densities (and thus cumulative probabilities) for a given forecast variable value. The second method, quantile model averaging (QMA), applies averaging to forecast variable values (quantiles) for a given cumulative probability (quantile fraction). BMA and QMA are found to perform similarly in terms of overall skill scores and reliability in ensemble spread. Both methods improve forecast skill across catchments and seasons. However, when both the statistical and dynamical forecasting approaches are skillful but produce, on special occasions, very different event forecasts, the BMA merged forecasts for these events can have unusually wide and bimodal distributions. In contrast, the distributions of the QMA merged forecasts for these events are narrower, unimodal and generally more smoothly shaped, and are potentially more easily communicated to and interpreted by the forecast users. Such special occasions are found to be rare. However, every forecast counts in an operational service, and therefore the occasional contrast in merged forecasts between the two methods may be more significant than the indifference shown by the overall skill and reliability performance.
Parametric imaging and statistical mapping of brain tumor in Ga68 EDTA dynamic PET studies
Yun Zhou; Sung-Cheng Huang; Shanglian Bao; Dean F. Wong
2001-01-01
To improve the reliability and sensitivity of quantitative analysis in the study and evaluation of brain tumor using Ga-68 EDTA dynamic PET, a linear parametric imaging algorithm was developed in this study for estimation of both distribution volume (DV) and blood brain barrier permeability. F statistics was used for separating tumor from normal tissue. A two-compartmental model was used to
Symanzik, Jürgen
Virtual reality and dynamic statistical graphics: A bidirectional link in a heterogeneous and real-time navigation are provided by typical virtual reality systems. Database function- ality must interact properly with the virtual reality/database system. This is easier said than done
Coupled flow-polymer dynamics via statistical field theory: modeling and computation
Bigelow, Stephen
Coupled flow-polymer dynamics via statistical field theory: modeling and computation Hector D interactions between polymers with interac- tions between polymers and one or more conjugate fields, offer successfully to investigate a wide range of polymer formulations at equilibrium, field-theoretic models often
Dynamical and statistical description of multifragmentation in heavy-ion collisions
NASA Astrophysics Data System (ADS)
Mao, Lihua; Wang, Ning; Ou, Li
2015-04-01
To explore the roles of the dynamical model and statistical model in the description of multifragmentation in heavy-ion collisions at intermediate energies, the fragments charge distributions of 197Au+197Au at 35 MeV/u are analyzed by using the hybrid model of improved quantum molecular dynamics (ImQMD) model plus the statistical model GEMINI. We find that, the ImQMD model can well describe the charge distributions of fragments produced in central and semicentral collisions. But for the peripheral collisions of Au+Au at 35 MeV/u, the statistical model is required at the end of the ImQMD simulations for the better description of the charge distribution of fragments. By using the hybrid model of ImQMD+GEMINI, the fragment charge distribution of Au+Au at 35 MeV/u can be reproduced reasonably well. The time evolution of the excitation energies of primary fragments is simultaneously investigated.
Influence of vortex dynamics and structure on turbulence statistics at large scales
NASA Astrophysics Data System (ADS)
Yoshimatsu, Katsunori; Anayama, Koujiro; Kaneda, Yukio
2015-05-01
The question whether the vortex dynamics and structure at small scales have significant influence on the statistics at large scales is addressed on the basis of quantitative comparison of two turbulent fields. One is a reference field generated by direct numerical simulation of turbulence of an incompressible fluid obeying the Navier-Stokes (NS) equation in a periodic box. The other is an artificial field in which the coherent vortical structures at small scales (˜?) that could be formed by the NS dynamics in the reference field are destroyed by an artificial computational operation, where ? is the Kolmogorov micro-length scale. The comparison of the two fields suggests that the statistics at larger scale (??) are not sensitive to the exact vortex dynamics and structure, at least in the case studied here.
An in-house alternative to traditional SDI services at Argonne National Laboratory
Noel, R.E.; Dominiak, R.R.
1997-02-20
Selective Dissemination of Information (SDIs) are based on automated, well-defined programs that regularly produce precise, relevant bibliographic information. Librarians have typically turned to information vendors such as Dialog or STN international to design and implement these searches for their users in business, academia, and the science community. Because Argonne National Laboratory (ANL) purchases the Institute for Scientific Information (ISI) Current Contents tapes (all subject areas excluding Humanities). ANL scientists enjoy the benefit of in-house developments with BASISplus software programming and no longer need to turn to outside companies for reliable SDI service. The database and its customized services are known as ACCESS (Argonne Current Contents Electronic Search Service). Through collaboration with librarians on Boolean logic and selection of terms, users can now design their own personal profiles to comb the new data, thereby avoiding service fees from outside providers. Based on the feedback from scientists, it seems that this new service can help transform the ANL distributed libraries into more efficient central functioning entities that better serve the users. One goal is to eliminate the routing of paper copies of many new journal issues to different library locations for users to browse; instead users may be expected to rely more on electronic dissemination of both table of contents and customized SDIs for new scientific and technical information.
Marks, Laurence D.
2000-01-01
research papers 458 Hu et al. Statistical dynamical direct methods. I Acta Cryst. (2000). A56, 458 reserved Statistical dynamical direct methods. I. The effective kinematical approximation J. J. Hu, F. N diffraction, substantial success has been achieved over the last few years in applying it via direct methods
Straub, John E.
On Monte Carlo and molecular dynamics methods inspired by Tsallis statistics: Methodology a generalized statistical distribution derived from a modification of the GibbsShannon entropy proposed of the phase space may result in distinct time averages. Statistical theories of chemical sys- tems are often
Modified statistical dynamical diffraction theory: analysis of model SiGe heterostructures
Shreeman, P. K.; Dunn, K. A.; Novak, S. W.; Matyi, R. J.
2013-01-01
A modified version of the statistical dynamical diffraction theory (mSDDT) permits full-pattern fitting of high-resolution X-ray diffraction scans from thin-film systems across the entire range from fully dynamic to fully kinematic scattering. The mSDDT analysis has been applied to a set of model SiGe/Si thin-film samples in order to define the capabilities of this approach. For defect-free materials that diffract at the dynamic limit, mSDDT analyses return structural information that is consistent with commercial dynamical diffraction simulation software. As defect levels increase and the diffraction characteristics shift towards the kinematic limit, the mSDDT provides new insights into the structural characteristics of these materials. PMID:24046498
a Statistical Dynamic Approach to Structural Evolution of Complex Capital Market Systems
NASA Astrophysics Data System (ADS)
Shao, Xiao; Chai, Li H.
As an important part of modern financial systems, capital market has played a crucial role on diverse social resource allocations and economical exchanges. Beyond traditional models and/or theories based on neoclassical economics, considering capital markets as typical complex open systems, this paper attempts to develop a new approach to overcome some shortcomings of the available researches. By defining the generalized entropy of capital market systems, a theoretical model and nonlinear dynamic equation on the operations of capital market are proposed from statistical dynamic perspectives. The US security market from 1995 to 2001 is then simulated and analyzed as a typical case. Some instructive results are discussed and summarized.
The applications of Complexity Theory and Tsallis Non-extensive Statistics at Solar Plasma Dynamics
NASA Astrophysics Data System (ADS)
Pavlos, George
2015-04-01
As the solar plasma lives far from equilibrium it is an excellent laboratory for testing complexity theory and non-equilibrium statistical mechanics. In this study, we present the highlights of complexity theory and Tsallis non extensive statistical mechanics as concerns their applications at solar plasma dynamics, especially at sunspot, solar flare and solar wind phenomena. Generally, when a physical system is driven far from equilibrium states some novel characteristics can be observed related to the nonlinear character of dynamics. Generally, the nonlinearity in space plasma dynamics can generate intermittent turbulence with the typical characteristics of the anomalous diffusion process and strange topologies of stochastic space plasma fields (velocity and magnetic fields) caused by the strange dynamics and strange kinetics (Zaslavsky, 2002). In addition, according to Zelenyi and Milovanov (2004) the complex character of the space plasma system includes the existence of non-equilibrium (quasi)-stationary states (NESS) having the topology of a percolating fractal set. The stabilization of a system near the NESS is perceived as a transition into a turbulent state determined by self-organization processes. The long-range correlation effects manifest themselves as a strange non-Gaussian behavior of kinetic processes near the NESS plasma state. The complex character of space plasma can also be described by the non-extensive statistical thermodynamics pioneered by Tsallis, which offers a consistent and effective theoretical framework, based on a generalization of Boltzmann - Gibbs (BG) entropy, to describe far from equilibrium nonlinear complex dynamics (Tsallis, 2009). In a series of recent papers, the hypothesis of Tsallis non-extensive statistics in magnetosphere, sunspot dynamics, solar flares, solar wind and space plasma in general, was tested and verified (Karakatsanis et al., 2013; Pavlos et al., 2014; 2015). Our study includes the analysis of solar plasma time series at three cases: sunspot index, solar flare and solar wind data. The non-linear analysis of the sunspot index is embedded in the non-extensive statistical theory of Tsallis (1988; 2004; 2009). The q-triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the sunspot index timeseries. Also the multifractal scaling exponent spectrum f(a), the generalized Renyi dimension spectrum D(q) and the spectrum J(p) of the structure function exponents were estimated experimentally and theoretically by using the q-entropy principle included in Tsallis non-extensive statistical theory, following Arimitsu and Arimitsu (2000, 2001). Our analysis showed clearly the following: (a) a phase transition process in the solar dynamics from high dimensional non-Gaussian SOC state to a low dimensional non-Gaussian chaotic state, (b) strong intermittent solar turbulence and anomalous (multifractal) diffusion solar process, which is strengthened as the solar dynamics makes a phase transition to low dimensional chaos in accordance to Ruzmaikin, Zelenyi and Milovanov's studies (Zelenyi and Milovanov, 1991; Milovanov and Zelenyi, 1993; Ruzmakin et al., 1996), (c) faithful agreement of Tsallis non-equilibrium statistical theory with the experimental estimations of: (i) non-Gaussian probability distribution function P(x), (ii) multifractal scaling exponent spectrum f(a) and generalized Renyi dimension spectrum Dq, (iii) exponent spectrum J(p) of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics. Also, the q-triplet of Tsallis as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the singular value decomposition (SVD) components of the solar flares timeseries. Also the multifractal scaling exponent spectrum f(a), the generalized Renyi dimension spectrum D(q) and the spectrum J(p) of the structure function exponents were estimated experimentally and theoretically by using the q-entropy principle included in Tsallis non-ext
NASA Astrophysics Data System (ADS)
Cortez, Vasco; Medina, Pablo; Goles, Eric; Zarama, Roberto; Rica, Sergio
2015-01-01
Statistical properties, fluctuations and probabilistic arguments are shown to explain the robust dynamics of the Schelling's social segregation model. With the aid of probability density functions we characterize the attractors for multiple external parameters and conditions. We discuss the role of the initial states and we show that, indeed, the system evolves towards well defined attractors. Finally, we provide probabilistic arguments to explain quantitatively the observed behavior.
An efficient climate model with a 3D ocean and statistical-dynamical atmosphere
I. V. Kamenkovich; A. P. Sokolov; P. H. Stone
2002-01-01
We describe a coupled climate model of intermediate complexity designed for use in global warming experiments. The atmospheric component is a two-dimensional (zonally averaged) statistical-dynamical model based on the Goddard Institute for Space Study's atmospheric general circulation model (GCM). In contrast with energy-balance models used in some climate models of intermediate complexity, this model includes full representation of the hydrological
Luis A. Dalguer; Hiroe Miyake; Steven M. Day; Kojiro Irikura
2008-01-01
In the context of the slip-weakening friction model and simplified asper- ity models for stress state, we calibrate dynamic rupture models for buried and surface-rupturing earthquakes constrained with statistical observations of past earth- quakes. These observations are the kinematic source models derived from source in- versions of ground-motion and empirical source models of seismic moment and rupture area. The calibrated
Fitting the dynamic model PCLake to a multi-lake survey through Bayesian Statistics
T. Aldenberg; J. H. Janse; P. R. G. Kramer
1995-01-01
A method is presented for the regression of dynamic lake ecosystem models on multi-lake data. The method draws upon Bayesian Statistics as the main inference engine, as outlined by Box and Draper (1965), M.J. Box (1971) and Box and Tiao (1973\\/1992). The Bayesian approach allows the calculation of the uncertainty of parameters and predictions both before and after the model
Statistical analysis of coronal shock dynamics implied by radio and white-light observations
NASA Astrophysics Data System (ADS)
Reiner, M. J.; Kaiser, M. L.; Gopalswamy, N.; Aurass, H.; Mann, G.; Vourlidas, A.; Maksimovic, M.
2001-11-01
For 19 solar eruptive events we present a statistical comparison of the shock dynamics derived from the measured frequency drift rates of metric and decametric-hectometric (D-H) type II radio bursts with the dynamics of the associated coronal mass ejection (CME). We find that the shock speed parameters derived from the D-H type II radio emissions generated in the high corona (~2-4RsolarRsolar=696,000km) are well correlated with the corresponding CME plane-of-the-sky speeds (correlation coefficient=0.71). On the other hand, we find no obvious correlation between the shock speed parameters derived from the metric type II radio bursts, generated in the middle corona (1.4-2Rsolar), and the corresponding CME speeds (correlation coefficient=-0.07). In general, we also find no clear correlation between the shock speed parameters derived from the metric type II bursts and the D-H radio emissions (correlation coefficient=0.3). However, the metric type II radio bursts sometimes include a second component that is possibly related to the D-H radio emissions. These statistical comparisons of the shock dynamics, implied by the observed metric and D-H type II frequency drift rates, provide further evidence for two distinct coronal shocks. Our statistical analyses are proceeded by two specific examples that illustrate the methodology used in this study.
NASA Astrophysics Data System (ADS)
Pan, Xue; Zhang, Fan; Li, Zhiming; Chen, Lizhu; Xu, Mingmei; Wu, Yuanfang
2014-01-01
Poisson-like statistical fluctuations, which are caused by the finite number of produced particles, are estimated for the cumulants of conserved charges, i.e., net baryon, net electric, and net strangeness. They turn out to be the same as those baselines derived from the hadron resonance gas model. The energy and centrality dependence of net-proton cumulants at the Relativistic Heavy-Ion Collider (RHIC) are demonstrated to be mainly caused by statistical fluctuations. By subtracting the statistical fluctuations, the dynamical kurtosis of net- and total-proton cumulants from two versions of a multi-phase transport model and the ultra-relativistic quantum molecular dynamics model at current RHIC collision energies are presented. It is found that the observed sign change of the dynamical kurtosis of the net-proton cumulant cannot be reproduced by these three transport models. There is no significant difference between the net- and total-proton kurtosis in model calculations, in contrast to the data at RHIC.
Model averaging methods to merge statistical and dynamic seasonal streamflow forecasts in Australia
NASA Astrophysics Data System (ADS)
Schepen, A.; Wang, Q. J.
2014-12-01
The Australian Bureau of Meteorology operates a statistical seasonal streamflow forecasting service. It has also developed a dynamic seasonal streamflow forecasting approach. The two approaches produce similarly reliable forecasts in terms of ensemble spread but can differ in forecast skill depending on catchment and season. Therefore, it may be possible to augment the skill of the existing service by objectively weighting and merging the forecasts. Bayesian model averaging (BMA) is first applied to merge statistical and dynamic forecasts for 12 locations using leave-five-years-out cross-validation. It is seen that the BMA merged forecasts can sometimes be too uncertain, as shown by ensemble spreads that are unrealistically wide and even bi-modal. The BMA method applies averaging to forecast probability densities (and thus cumulative probabilities) for a given forecast variable value. An alternative approach is quantile model averaging (QMA), whereby forecast variable values (quantiles) are averaged for a given cumulative probability (quantile fraction). For the 12 locations, QMA is compared to BMA. BMA and QMA perform similarly in terms of forecast accuracy skill scores and reliability in terms of ensemble spread. Both methods improve forecast skill across catchments and seasons by combining the different strengths of the statistical and dynamic approaches. A major advantage of QMA over BMA is that it always produces reasonably well defined forecast distributions, even in the special cases where BMA does not. Optimally estimated QMA weights and BMA weights are similar; however, BMA weights are more efficiently estimated.
Quench dynamics and statistics of measurements for a line of quantum spins in two dimensions
Jonathan Lux; Achim Rosch
2014-08-28
Motivated by recent experiments, we investigate the dynamics of a line of spin-down spins embedded in the ferromagnetic spin-up ground state of a two-dimensional xxz model close to the Ising limit. In a situation where the couplings in x and y direction are different, the quench dynamics of this system is governed by the interplay of one-dimensional excitations (kinks and holes) moving along the line and single-spin excitations evaporating into the two-dimensional background. A semiclassical approximation can be used to calculate the dynamics of this complex quantum system. Recently, it became possible to perform projective quantum measurements on such spin systems, allowing to determine, e.g., the z-component of each individual spin. We predict the statistical properties of such measurements which contain much more information than correlation functions.
NASA Astrophysics Data System (ADS)
Alfi, V.; Cristelli, M.; Pietronero, L.; Zaccaria, A.
2009-02-01
We present a detailed study of the statistical properties of the Agent Based Model introduced in paper I [Eur. Phys. J. B, DOI: 10.1140/epjb/e2009-00028-4] and of its generalization to the multiplicative dynamics. The aim of the model is to consider the minimal elements for the understanding of the origin of the stylized facts and their self-organization. The key elements are fundamentalist agents, chartist agents, herding dynamics and price behavior. The first two elements correspond to the competition between stability and instability tendencies in the market. The herding behavior governs the possibility of the agents to change strategy and it is a crucial element of this class of models. We consider a linear approximation for the price dynamics which permits a simple interpretation of the model dynamics and, for many properties, it is possible to derive analytical results. The generalized non linear dynamics results to be extremely more sensible to the parameter space and much more difficult to analyze and control. The main results for the nature and self-organization of the stylized facts are, however, very similar in the two cases. The main peculiarity of the non linear dynamics is an enhancement of the fluctuations and a more marked evidence of the stylized facts. We will also discuss some modifications of the model to introduce more realistic elements with respect to the real markets.
Displaying R spatial statistics on Google dynamic maps with web applications created by Rwui
2012-01-01
Background The R project includes a large variety of packages designed for spatial statistics. Google dynamic maps provide web based access to global maps and satellite imagery. We describe a method for displaying directly the spatial output from an R script on to a Google dynamic map. Methods This is achieved by creating a Java based web application which runs the R script and then displays the results on the dynamic map. In order to make this method easy to implement by those unfamiliar with programming Java based web applications, we have added the method to the options available in the R Web User Interface (Rwui) application. Rwui is an established web application for creating web applications for running R scripts. A feature of Rwui is that all the code for the web application being created is generated automatically so that someone with no knowledge of web programming can make a fully functional web application for running an R script in a matter of minutes. Results Rwui can now be used to create web applications that will display the results from an R script on a Google dynamic map. Results may be displayed as discrete markers and/or as continuous overlays. In addition, users of the web application may select regions of interest on the dynamic map with mouse clicks and the coordinates of the region of interest will automatically be made available for use by the R script. Conclusions This method of displaying R output on dynamic maps is designed to be of use in a number of areas. Firstly it allows statisticians, working in R and developing methods in spatial statistics, to easily visualise the results of applying their methods to real world data. Secondly, it allows researchers who are using R to study health geographics data, to display their results directly onto dynamic maps. Thirdly, by creating a web application for running an R script, a statistician can enable users entirely unfamiliar with R to run R coded statistical analyses of health geographics data. Fourthly, we envisage an educational role for such applications. PMID:22998945
Statistical properties of energy levels in quantum reaction dynamics: a case study
NASA Astrophysics Data System (ADS)
Peroncelli, Leonardo; Grossi, Gaia; Aquilanti, Vincenzo
2004-01-01
An account is presented of recent approaches to the characterization of the statistical properties of the energy level sequences of interest in quantum reaction dynamics. The case study of the quantum eigenvalues of the reactive process F+ H2? HF+ H as a function of the hyperradius (a measure of the total inertia of the three-body system) is illustrated. Previous work is extended by examining different angular momentum projection values for two recently proposed potential energy surfaces. We study spectral properties such as the standard deviation ? of the level spacings and the shape of the nearest-neighbour spacing distribution (NNSD), evaluating the q parameters of the Brody and Berry-Robnik distributions, which are alternative interpolations between the Poisson and the Wigner distributions. We also apply statistical tools, such as the ?3(L) of Dyson and Mehta) and the correlation coefficient C(r). This analysis, which is typical of current investigations on the topic of 'quantum chaos', gives insight into the nature of the reactive event and may be useful for the development of statistical theories in molecular dynamics.
Mechanical-statistical modeling in ecology: from outbreak detections to pest dynamics.
Soubeyrand, S; Neuvonen, S; Penttinen, A
2009-02-01
Knowledge about large-scale and long-term dynamics of (natural) populations is required to assess the efficiency of control strategies, the potential for long-term persistence, and the adaptability to global changes such as habitat fragmentation and global warming. For most natural populations, such as pest populations, large-scale and long-term surveys cannot be carried out at a high resolution. For instance, for population dynamics characterized by irregular abundance explosions, i.e., outbreaks, it is common to report detected outbreaks rather than measuring the population density at every location and time event. Here, we propose a mechanical-statistical model for analyzing such outbreak occurrence data and making inference about population dynamics. This spatio-temporal model contains the main mechanisms of the dynamics and describes the observation process. This construction enables us to account for the discrepancy between the phenomenon scale and the sampling scale. We propose the Bayesian method to estimate model parameters, pest densities and hidden factors, i.e., variables involved in the dynamics but not observed. The model was specified and used to learn about the dynamics of the European pine sawfly (Neodiprion sertifer Geoffr., an insect causing major defoliation of pines in northern Europe) based on Finnish sawfly data covering the years 1961-1990. In this application, a dynamical Beverton-Holt model including a hidden regime variable was incorporated into the model to deal with large variations in the population densities. Our results gave support to the idea that pine sawfly dynamics should be studied as metapopulations with alternative equilibria. The results confirmed the importance of extreme minimum winter temperatures for the occurrence of European pine sawfly outbreaks. The strong positive connection between the ratio of lake area over total area and outbreaks was quantified for the first time. PMID:18843520
California at Berkeley, University of
with the behavior of statisticalphysical avalanche models near a stationary critical state. These results supportScale-free statistics of spatiotemporal auroral emissions as depicted by POLAR UVI images: Dynamic magnetosphere is an avalanching system Vadim M. Uritsky1 and Alex J. Klimas NASA Goddard Space Flight Center
Specificity of mathematical description of statistical and dynamical properties of CELSS
NASA Astrophysics Data System (ADS)
Bartsev, Sergey
CELSS for long-term space missions has to be possessed high level of matter turnover closure. Designing, studying, and maintaining such kind of systems seems to be not possible without accounting their specificity -high closure. For measuring this specific property potentially universal coefficient of closure is suggested and disscussed. It can be shown standard statistical formulas are incorrect for estimating mean values of biomass of CELSS components. Account-ing closure as specific constraint of closed ecological systems allows obtaining correct formulas for calculating mean values of biomass and composition of chemical compounds of CELSS. Errors due to using standard statistical evaluations are discussed. Organisms composing bi-ological LSS consume and produce spectrum of different substances. Providing high level of closure -the absence of deadlocks -depends on accuracy of adjusting all organisms input and output to each other. This is practical objective of high importance. Adequate mathematical models ought to describe possibility of organisms to vary their consumption and production spectrum (stoichiometric ratio). Traditional ecological models describing dynamics of limiting element can not be adequately applied for describing CELSS dynamics over all possible oper-ating regimes. Possible use of adaptive metabolism models for providing correct description of CELSS dynamics is considered.
Heterogeneous Structure of Stem Cells Dynamics: Statistical Models and Quantitative Predictions
NASA Astrophysics Data System (ADS)
Bogdan, Paul; Deasy, Bridget M.; Gharaibeh, Burhan; Roehrs, Timo; Marculescu, Radu
2014-04-01
Understanding stem cell (SC) population dynamics is essential for developing models that can be used in basic science and medicine, to aid in predicting cells fate. These models can be used as tools e.g. in studying patho-physiological events at the cellular and tissue level, predicting (mal)functions along the developmental course, and personalized regenerative medicine. Using time-lapsed imaging and statistical tools, we show that the dynamics of SC populations involve a heterogeneous structure consisting of multiple sub-population behaviors. Using non-Gaussian statistical approaches, we identify the co-existence of fast and slow dividing subpopulations, and quiescent cells, in stem cells from three species. The mathematical analysis also shows that, instead of developing independently, SCs exhibit a time-dependent fractal behavior as they interact with each other through molecular and tactile signals. These findings suggest that more sophisticated models of SC dynamics should view SC populations as a collective and avoid the simplifying homogeneity assumption by accounting for the presence of more than one dividing sub-population, and their multi-fractal characteristics.
Cluster Statistics and Quasisoliton Dynamics in Microscopic Car-following Models
Bo Yang; Xihua Xu; John Z. F. Pang; Christopher Monterola
2014-08-20
Using the optimal velocity (OV) model as an example, we show that in the non-linear regime there is an emergent quantity that gives the extremum headways in the cluster formation, as well as the coexistence curve separating the absolute stable phase from the metastable phase. This emergent quantity is independent of the density of the traffic lane, and determines an intrinsic scale that characterizes the dynamics of localized quasisoliton structures given by the time derivative of the headways. The intrinsic scale is analogous to the "charge" of quasisolitons that controls the strength of interaction between multiple clusters, leading to non-trivial cluster statistics from random perturbations to initial uniform traffic. The cluster statistics depend both on the charge and the density of the traffic lane; the relationship is qualitatively universal for general car-following models.
Dynamic whole-body PET parametric imaging: II. Task-oriented statistical estimation
NASA Astrophysics Data System (ADS)
Karakatsanis, Nicolas A.; Lodge, Martin A.; Zhou, Y.; Wahl, Richard L.; Rahmim, Arman
2013-10-01
In the context of oncology, dynamic PET imaging coupled with standard graphical linear analysis has been previously employed to enable quantitative estimation of tracer kinetic parameters of physiological interest at the voxel level, thus, enabling quantitative PET parametric imaging. However, dynamic PET acquisition protocols have been confined to the limited axial field-of-view (˜15-20 cm) of a single-bed position and have not been translated to the whole-body clinical imaging domain. On the contrary, standardized uptake value (SUV) PET imaging, considered as the routine approach in clinical oncology, commonly involves multi-bed acquisitions, but is performed statically, thus not allowing for dynamic tracking of the tracer distribution. Here, we pursue a transition to dynamic whole-body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. In a companion study, we presented a novel clinically feasible dynamic (4D) multi-bed PET acquisition protocol as well as the concept of whole-body PET parametric imaging employing Patlak ordinary least squares (OLS) regression to estimate the quantitative parameters of tracer uptake rate Ki and total blood distribution volume V. In the present study, we propose an advanced hybrid linear regression framework, driven by Patlak kinetic voxel correlations, to achieve superior trade-off between contrast-to-noise ratio (CNR) and mean squared error (MSE) than provided by OLS for the final Ki parametric images, enabling task-based performance optimization. Overall, whether the observer's task is to detect a tumor or quantitatively assess treatment response, the proposed statistical estimation framework can be adapted to satisfy the specific task performance criteria, by adjusting the Patlak correlation-coefficient (WR) reference value. The multi-bed dynamic acquisition protocol, as optimized in the preceding companion study, was employed along with extensive Monte Carlo simulations and an initial clinical 18F-deoxyglucose patient dataset to validate and demonstrate the potential of the proposed statistical estimation methods. Both simulated and clinical results suggest that hybrid regression in the context of whole-body Patlak Ki imaging considerably reduces MSE without compromising high CNR. Alternatively, for a given CNR, hybrid regression enables larger reductions than OLS in the number of dynamic frames per bed, allowing for even shorter acquisitions of ˜30 min, thus further contributing to the clinical adoption of the proposed framework. Compared to the SUV approach, whole-body parametric imaging can provide better tumor quantification, and can act as a complement to SUV, for the task of tumor detection.
Dynamic whole body PET parametric imaging: II. Task-oriented statistical estimation
Karakatsanis, Nicolas A.; Lodge, Martin A.; Zhou, Y.; Wahl, Richard L.; Rahmim, Arman
2013-01-01
In the context of oncology, dynamic PET imaging coupled with standard graphical linear analysis has been previously employed to enable quantitative estimation of tracer kinetic parameters of physiological interest at the voxel level, thus, enabling quantitative PET parametric imaging. However, dynamic PET acquisition protocols have been confined to the limited axial field-of-view (~15–20cm) of a single bed position and have not been translated to the whole-body clinical imaging domain. On the contrary, standardized uptake value (SUV) PET imaging, considered as the routine approach in clinical oncology, commonly involves multi-bed acquisitions, but is performed statically, thus not allowing for dynamic tracking of the tracer distribution. Here, we pursue a transition to dynamic whole body PET parametric imaging, by presenting, within a unified framework, clinically feasible multi-bed dynamic PET acquisition protocols and parametric imaging methods. In a companion study, we presented a novel clinically feasible dynamic (4D) multi-bed PET acquisition protocol as well as the concept of whole body PET parametric imaging employing Patlak ordinary least squares (OLS) regression to estimate the quantitative parameters of tracer uptake rate Ki and total blood distribution volume V. In the present study, we propose an advanced hybrid linear regression framework, driven by Patlak kinetic voxel correlations, to achieve superior trade-off between contrast-to-noise ratio (CNR) and mean squared error (MSE) than provided by OLS for the final Ki parametric images, enabling task-based performance optimization. Overall, whether the observer's task is to detect a tumor or quantitatively assess treatment response, the proposed statistical estimation framework can be adapted to satisfy the specific task performance criteria, by adjusting the Patlak correlation-coefficient (WR) reference value. The multi-bed dynamic acquisition protocol, as optimized in the preceding companion study, was employed along with extensive Monte Carlo simulations and an initial clinical FDG patient dataset to validate and demonstrate the potential of the proposed statistical estimation methods. Both simulated and clinical results suggest that hybrid regression in the context of whole-body Patlak Ki imaging considerably reduces MSE without compromising high CNR. Alternatively, for a given CNR, hybrid regression enables larger reductions than OLS in the number of dynamic frames per bed, allowing for even shorter acquisitions of ~30min, thus further contributing to the clinical adoption of the proposed framework. Compared to the SUV approach, whole body parametric imaging can provide better tumor quantification, and can act as a complement to SUV, for the task of tumor detection. PMID:24080994
Dynamics and statistics of wave-particle interactions in a confined geometry
NASA Astrophysics Data System (ADS)
Gilet, Tristan
2014-11-01
A walker is a droplet bouncing on a liquid surface and propelled by the waves that it generates. This macroscopic wave-particle association exhibits behaviors reminiscent of quantum particles. This article presents a toy model of the coupling between a particle and a confined standing wave. The resulting two-dimensional iterated map captures many features of the walker dynamics observed in different configurations of confinement. These features include the time decomposition of the chaotic trajectory in quantized eigenstates and the particle statistics being shaped by the wave. It shows that deterministic wave-particle coupling expressed in its simplest form can account for some quantumlike behaviors.
NASA Astrophysics Data System (ADS)
Arbona, A.; Bona, C.; Miñano, B.; Plastino, A.
2014-09-01
The definition of complexity through Statistical Complexity Measures (SCM) has recently seen major improvements. Mostly, the effort is concentrated in measures on time series. We propose a SCM definition for spatial dynamical systems. Our definition is in line with the trend to combine entropy with measures of structure (such as disequilibrium). We study the behaviour of our definition against the vectorial noise model of Collective Motion. From a global perspective, we show how our SCM is minimal at both the microscale and macroscale, while it reaches a maximum at the ranges that define the mesoscale in this model. From a local perspective, the SCM is minimum both in highly ordered and disordered areas, while it reaches a maximum at the edges between such areas. These characteristics suggest this is a good candidate for detecting the mesoscale of arbitrary dynamical systems as well as regions where the complexity is maximal in such systems.
Memory effects in avalanche dynamics: a key to the statistical properties of earthquakes
Jagla, E A; Rosso, Alberto
2013-01-01
Many complex systems respond to continuous input of energy by accumulation of stress over time and sudden energy releases in the form of avalanches. Avalanches are paradigmatic non-equilibrium phenomena displaying power law size distribution and involving all the length scales in the system. Conventional avalanche models disregard memory effects and thus miss basic features observed in real systems. Notable examples are aftershocks and the anomalous exponent of the Gutenberg-Richter law which characterize earthquake statistics. We propose a model which accounts for memory effects through the introduction of viscoelastic relaxation at an intermediate time scale. We demonstrate that in the resulting dynamics, coherent oscillations of the stress field emerge spontaneously without fine tuning of any parameter. Remarkably, in two dimensions, which is relevant in seismicity, these oscillations generate instability patterns that produce realistic earthquake dynamics with the correct Gutenberg-Richter exponent.
Page, John
fluctuations are too complex for traditional Doppler ultrasound analysis. This Letter may be viewed as a wayMesoscopic Phase Statistics of Diffuse Ultrasound in Dynamic Matter M. L. Cowan,1,* D. Anache, we study time- dependent phase fluctuations of ultrasound in a dynamic, strongly scattering medium
Enhancing dynamic graphical analysis with the Lisp-Stat language and the ViSta statistical program.
Ledesma, Rubén; Molina, J Gabriel; Young, Forrest W
2005-11-01
Presented is a sample of computerized methods aimed at multidimensional scaling and psychometric item analysis that offer a dynamic graphical interface to execute analyses and help visualize the results. These methods show how the Lisp-Stat programming language and the ViSta statistical program can be jointly applied to develop powerful computer applications that enhance dynamic graphical analysis methods. The feasibility of this combined strategy relies on two main features: (1) The programming architecture of ViSta enables users to add new statistical methods as plug-ins, which are integrated into the program environment and can make use of all the functions already available in ViSta (e.g., data manipulation, editing, printing); and (2) the set of powerful statistical and graphical functions integrated into the Lisp-Stat programming language provides the means for developing statistical methods with dynamic graphical visualizations, which can be implemented as ViSta plug-ins. PMID:16629303
Randall A. LaViolette; Charles R. Tolle; Timothy R. McJunkin; Daphne L. Stoner
2004-02-05
We tested the natural combination of surrogate data analysis with the ApEn regularity statistic developed by Pincus [Proc. Natl. Acad. Sci. USA 88 (1991) 2297] by applying it to some popular models of nonlinear dynamics and publicly available experimental time series. We found that this easily implemented combination provided a useful method for discriminating signals governed by nonlinear dynamics from those governed by linear dynamics and noise. An apparently novel physical interpretation of ApEn also is supplied.
Statistics of reversible bond dynamics observed in force-clamp spectroscopy
Gregor Diezemann; Thomas Schlesier; Burkhard Geil; Andreas Janshoff
2010-10-30
We present a detailed analysis of two-state trajectories obtained from force-clamp spectroscopy (FCS) of reversibly bonded systems. FCS offers the unique possibility to vary the equilibrium constant in two-state kinetics, for instance the unfolding and refolding of biomolecules, over many orders of magnitude due to the force dependency of the respective rates. We discuss two different kinds of counting statistics, the event-counting usually employed in the statistical analysis of two-state kinetics and additionally the so-called cycle-counting. While in the former case all transitions are counted, cycle-counting means that we focus on one type of transitions. This might be advantageous in particular if the equilibrium constant is much larger or much smaller than unity because in these situations the temporal resolution of the experimental setup might not allow to capture all transitions of an event-counting analysis. We discuss how an analysis of FCS data for complex systems exhibiting dynamic disorder might be performed yielding information about the detailed force-dependence of the transition rates and about the time scale of the dynamic disorder. In addition, the question as to which extent the kinetic scheme can be viewed as a Markovian two-state model is discussed.
Velocity statistics of dynamic spinners in out-of-equilibrium magnetic suspensions.
Snezhko, Alexey; Aranson, Igor S
2015-08-14
We report on the velocity statistics of an out-of-equilibrium magnetic suspension in a spinner phase confined at a liquid interface. The suspension is energized by a uniaxial alternating magnetic field applied parallel to the interface. In a certain range of the magnetic field parameters the system spontaneously undergoes a transition into a dynamic spinner phase (ensemble of hydrodynamically coupled magnetic micro-rotors) comprised of two subsystems: self-assembled spinning chains and a gas of rotating single particles. Both subsystems coexist in a dynamic equilibrium via continuous exchange of the particles. Spinners excite surface flows that significantly increase particle velocity correlations in the system. For both subsystems the velocity distributions are strongly non-Maxwellian with nearly exponential high-energy tails, P(v) ? exp(-|v/v0|). The kurtosis, the measure of the deviation from the Gaussian statistics, is influenced by the frequency of the external magnetic field. We show that in the single-particle gas the dissipation is mostly collisional, whereas the viscous damping dominates over collisional dissipation for the self-assembled spinners. The dissipation increases with the frequency of the applied magnetic field. Our results provide insights into non-trivial dissipation mechanisms determining self-assembly processes in out-of-equilibrium magnetic suspensions. PMID:26133687
A Statistical Approach for the Concurrent Coupling of Molecular Dynamics and Finite Element Methods
NASA Technical Reports Server (NTRS)
Saether, E.; Yamakov, V.; Glaessgen, E.
2007-01-01
Molecular dynamics (MD) methods are opening new opportunities for simulating the fundamental processes of material behavior at the atomistic level. However, increasing the size of the MD domain quickly presents intractable computational demands. A robust approach to surmount this computational limitation has been to unite continuum modeling procedures such as the finite element method (FEM) with MD analyses thereby reducing the region of atomic scale refinement. The challenging problem is to seamlessly connect the two inherently different simulation techniques at their interface. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the typical boundary value problem used to define a coupled domain. The method uses statistical averaging of the atomistic MD domain to provide displacement interface boundary conditions to the surrounding continuum FEM region, which, in return, generates interface reaction forces applied as piecewise constant traction boundary conditions to the MD domain. The two systems are computationally disconnected and communicate only through a continuous update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM) as opposed to a direct coupling method where interface atoms and FEM nodes are individually related. The methodology is inherently applicable to three-dimensional domains, avoids discretization of the continuum model down to atomic scales, and permits arbitrary temperatures to be applied.
Technology Transfer Automated Retrieval System (TEKTRAN)
QseA and SdiA are two of several transcriptional regulators that regulate virulence gene expression of enterohemorrhagic Escherichia coli (EHEC) O157:H7 via quorum sensing (QS). QseA regulates the expression of the locus of enterocyte effacement (LEE). LEE encodes for a type III secretion (T3S) sys...
ERIC Educational Resources Information Center
Leggate, P.; And Others
During a 2-year period (1970, 1971) SDI (Selective Dissemination of Information) search profiles were written for 353 biologists and other research workers with a need for biological information in academic, industrial, and government research institutions. At the beginning of the experiment a questionnaire and interview survey was made of the…
ERIC Educational Resources Information Center
Olive, G.; And Others
A selective dissemination of information service based on computer scanning of Nuclear Science Abstracts tapes has operated at the Atomic Energy Research Establishment, Harwell, England since October, 1968. The performance of the mechanized SDI service has been compared with that of the pre-existing current awareness service which is based on…
Extreme-values statistics and dynamics of water at protein interfaces.
Korb, Jean-Pierre; Goddard, Yanina; Pajski, Jason; Diakova, Galina; Bryant, Robert G
2011-11-10
Immobilized proteins present a unique interface with water. The water translational diffusive motions affect the high-frequency dynamics and the nuclear spin-lattice relaxation as with all surfaces; however, rare binding sites for water in protein systems add very low-frequency components to the dynamics spectrum. Water binding sites in protein systems are not identical, thus distributions of free energies and consequent dynamics are expected. (2)H(2)O spin-lattice relaxation rate measurements as a function of magnetic field strength characterize the local rotational fluctuations for protein-bound water molecules. The measurements are sensitive to dynamics down to the kilohertz range. To account for the data, we show that the extreme-values statistics of rare events, i.e., water dynamics in rare binding sites, implies an exponential distribution of activation energies for the strongest binding events. In turn, for an activated dynamical process, the exponential energy distribution leads to a Pareto distribution for the reorientational correlation times and a power law in the Larmor frequency for the (2)H(2)O spin-lattice relaxation rate constants at low field strengths. The most strongly held water molecules escape from rare binding sites in times on the order of microseconds, which interrupts the intramolecular correlations and causes a plateau in the spin-lattice relaxation rate at very low magnetic field strengths. We examine the magnetic relaxation dispersion (MRD) data using two simple but related models: a protein-bound environment for water characterized by a single potential well and a protein-bound environment characterized by a double potential well where the potential functions for the local motions of the bound-state water are of different depth. This analysis is applied to D(2)O deuterium spin-lattice relaxation on cross-linked albumin and lysozyme, which is dominated by the intramolecular relaxation driven by the dynamical modulation of the nuclear electric quadrupole coupling. We also separate the intramolecular from the intermolecular contribution to water proton spin-lattice relaxation by isotope dilution and show that the intramolecular proton data map onto the deuterium relaxation by a scale factor implied by the relative strength of the quadrupole and dipolar couplings. The temperature and pH dependence of the magnetic relaxation dispersion are complex and accounted for by changing only the weighting factors in a superposition of contributions from single-well and double-well contributions. These experiments show that the reorientational dynamics spectrum for water, in and on a protein, is characterized by a strongly asymmetric distribution with a long-time tail that extends at least to microseconds. PMID:21932852
Statistical Testing of Dynamically Downscaled Rainfall Data for the East Coast of Australia
NASA Astrophysics Data System (ADS)
Parana Manage, Nadeeka; Lockart, Natalie; Willgoose, Garry; Kuczera, George
2015-04-01
This study performs a validation of statistical properties of downscaled climate data, concentrating on the rainfall which is required for hydrology predictions used in reservoir simulations. The data sets used in this study have been produced by the NARCliM (NSW/ACT Regional Climate Modelling) project which provides a dynamically downscaled climate dataset for South-East Australia at 10km resolution. NARCliM has used three configurations of the Weather Research Forecasting Regional Climate Model and four different GCMs (MIROC-medres 3.2, ECHAM5, CCCMA 3.1 and CSIRO mk3.0) from CMIP3 to perform twelve ensembles of simulations for current and future climates. Additionally to the GCM-driven simulations, three control run simulations driven by the NCEP/NCAR reanalysis for the entire period of 1950-2009 has also been performed by the project. The validation has been performed in the Upper Hunter region of Australia which is a semi-arid to arid region 200 kilometres North-West of Sydney. The analysis used the time series of downscaled rainfall data and ground based measurements for selected Bureau of Meteorology rainfall stations within the study area. The initial testing of the gridded rainfall was focused on the autoregressive characteristics of time series because the reservoir performance depends on long-term average runoffs. A correlation analysis was performed for fortnightly, monthly and annual averaged time resolutions showing a good statistical match between reanalysis and ground truth. The spatial variation of the statistics of gridded rainfall series were calculated and plotted at the catchment scale. The spatial correlation analysis shows a poor agreement between NARCliM data and ground truth at each time resolution. However, the spatial variability plots show a strong link between the statistics and orography at the catchment scale.
NASA Astrophysics Data System (ADS)
Ho, Chun Kit; Hawkins, Ed; Shaffrey, Len; Underwood, Fiona M.
2013-08-01
Accurate decadal climate predictions could be used to inform adaptation actions to a changing climate. The skill of such predictions from initialised dynamical global climate models (GCMs) may be assessed by comparing with predictions from statistical models which are based solely on historical observations. This paper presents two benchmark statistical models for predicting both the radiatively forced trend and internal variability of annual mean sea surface temperatures (SSTs) on a decadal timescale based on the gridded observation data set HadISST. For both statistical models, the trend related to radiative forcing is modelled using a linear regression of SST time series at each grid box on the time series of equivalent global mean atmospheric CO2 concentration. The residual internal variability is then modelled by (1) a first-order autoregressive model (AR1) and (2) a constructed analogue model (CA). From the verification of 46 retrospective forecasts with start years from 1960 to 2005, the correlation coefficient for anomaly forecasts using trend with AR1 is greater than 0.7 over parts of extra-tropical North Atlantic, the Indian Ocean and western Pacific. This is primarily related to the prediction of the forced trend. More importantly, both CA and AR1 give skillful predictions of the internal variability of SSTs in the subpolar gyre region over the far North Atlantic for lead time of 2-5 years, with correlation coefficients greater than 0.5. For the subpolar gyre and parts of the South Atlantic, CA is superior to AR1 for lead time of 6-9 years. These statistical forecasts are also compared with ensemble mean retrospective forecasts by DePreSys, an initialised GCM. DePreSys is found to outperform the statistical models over large parts of North Atlantic for lead times of 2-5 years and 6-9 years, however trend with AR1 is generally superior to DePreSys in the North Atlantic Current region, while trend with CA is superior to DePreSys in parts of South Atlantic for lead time of 6-9 years. These findings encourage further development of benchmark statistical decadal prediction models, and methods to combine different predictions.
On Coherent Vortex Dynamics Contribution to the Statistics of the Near-Wall Region
NASA Astrophysics Data System (ADS)
Dhanak, Manhar R.
1998-11-01
Statistical description of the activity in the near-wall region of a turbulent boundary layer, including the skin friction at the wall surface, Reynolds stress distribution and the spectra for kinetic energy and surface pressure fluctuations are considered in terms of the individual dynamics of an ensemble of independent coherent streamwise vortices in the vicinity of the wall. Together with low speed streaks, quasi-streamwise vortices are known to dominate the flow in the near-wall region. The cross-plane dynamics of the vortices, undergoing axial stretching, and their interaction with the wall is posed as an initial value problem and determined using exact solutions of the Navier-Stokes equations. The approach is based on the consideration by Orlandi and Jimenez (1994), but includes proper consideration of the longitudinal straining flow. Recent DNS calculations (see e.g., Schoppa & Hussain,1997) suggest a self sustaining mechanism whereby the coherent vortices generate the low speed streaks and the instability of the low speed streaks lead to the formation of the coherent vortices. The latter process is fully three dimensional and therefore beyond the scope of the present consideration. However, the dynamics of the ensuing vortices and their decay, as well as the formation of low speed streaks, are well captured by the cross-plane model and the computed results suggest that these processes have a significant bearing on the statitics of the near-wall region.
NASA Astrophysics Data System (ADS)
Turchaninova, A.
2012-04-01
The estimation of extreme avalanche runout distances, flow velocities, impact pressures and volumes is an essential part of snow engineering in mountain regions of Russia. It implies the avalanche hazard assessment and mapping. Russian guidelines accept the application of different avalanche models as well as approaches for the estimation of model input parameters. Consequently different teams of engineers in Russia apply various dynamics and statistical models for engineering practice. However it gives more freedom to avalanche practitioners and experts but causes lots of uncertainties in case of serious limitations of avalanche models. We discuss these problems by presenting the application results of different well known and widely used statistical (developed in Russia) and avalanche dynamics models for several avalanche test sites in the Khibini Mountains (The Kola Peninsula) and the Caucasus. The most accurate and well-documented data from different powder and wet, big rare and small frequent snow avalanche events is collected from 1960th till today in the Khibini Mountains by the Avalanche Safety Center of "Apatit". This data was digitized and is available for use and analysis. Then the detailed digital avalanche database (GIS) was created for the first time. It contains contours of observed avalanches (ESRI shapes, more than 50 years of observations), DEMs, remote sensing data, description of snow pits, photos etc. Thus, the Russian avalanche data is a unique source of information for understanding of an avalanche flow rheology and the future development and calibration of the avalanche dynamics models. GIS database was used to analyze model input parameters and to calibrate and verify avalanche models. Regarding extreme dynamic parameters the outputs using different models can differ significantly. This is unacceptable for the engineering purposes in case of the absence of the well-defined guidelines in Russia. The frequency curves for the runout distance in different avalanche sites were constructed using the field data. It allowed us to assess the probability (return period) of the calculated extreme runout distances using obtained frequency curves. Avalanche zoning is not yet used by land planning authorities to prevent construction in avalanche hazard zones in Russia. Our approach can be used for the future development of avalanche zoning in Russia.
Zhang, Qin; Dong, Chunling; Cui, Yan; Yang, Zhihui
2014-04-01
Graphical models for probabilistic reasoning are now in widespread use. Many approaches have been developed such as Bayesian network. A newly developed approach named as dynamic uncertain causality graph (DUCG) is initially presented in a previous paper, in which only the inference algorithm in terms of individual events and probabilities is addressed. In this paper, we first explain the statistic basis of DUCG. Then, we extend the algorithm to the form of matrices of events and probabilities. It is revealed that the representation of DUCG can be incomplete and the exact probabilistic inference may still be made. A real application of DUCG for fault diagnoses of a generator system of a nuclear power plant is demonstrated, which involves > 600 variables. Most inferences take < 1 s with a laptop computer. The causal logic between inference result and observations is graphically displayed to users so that they know not only the result, but also why the result obtained. PMID:24807944
Tanaka, Naoaki; Cole, Andrew J.; von Pechmann, Deidre; Wakeman, Daniel G.; Hämäläinen, Matti S.; Liu, Hesheng; Madsen, Joseph R.; Bourgeois, Blaise F.; Stufflebeam, Steven M.
2009-01-01
The purpose of this study is to assess the clinical value of spatiotemporal source analysis for analyzing ictal magnetoencephalography (MEG). Ictal MEG and simultaneous scalp EEG was recorded in five patients with medically intractable frontal lobe epilepsy. Dynamic statistical parametric maps (dSPMs) were calculated at the peak of early ictal spikes for the purpose of estimating the spatiotemporal cortical source distribution. DSPM solutions were mapped onto a cortical surface, which was derived from each patient's MRI. Equivalent current dipoles (ECDs) were calculated using a single-dipole model for comparison with dSPMs. In all patients, dSPMs tended to have a localized activation, consistent with the clinically-determined ictal onset zone, whereas most ECDs were considered to be inappropriate sources according to their goodness-of-fit values. Analyzing ictal MEG spikes by using dSPMs may provide useful information in presurgical evaluation of epilepsy. PMID:19394198
Emergent statistical-mechanical structure in the dynamics along the period-doubling route to chaos
NASA Astrophysics Data System (ADS)
Diaz-Ruelas, Alvaro; Robledo, Alberto
2014-02-01
We consider both the dynamics within and towards the supercycle attractors along the period-doubling route to chaos to analyze the development of a statistical-mechanical structure. In this structure the partition function consists of the sum of the attractor position distances known as supercycle diameters and the associated thermodynamic potential measures the rate of approach of trajectories to the attractor. The configurational weights for finite 2N, and infinite N\\rightarrow \\infty , periods can be expressed as power laws or deformed exponentials. For a finite period the structure is undeveloped in the sense that there is no true configurational degeneracy, but in the limit N\\rightarrow \\infty this is realized together with the analog property of a Legendre transform linking entropies of two ensembles. We also study the partition functions for all N and the action of the central limit theorem via a binomial approximation.
Defect-phase-dynamics approach to statistical domain-growth problem of clock models
NASA Technical Reports Server (NTRS)
Kawasaki, K.
1985-01-01
The growth of statistical domains in quenched Ising-like p-state clock models with p = 3 or more is investigated theoretically, reformulating the analysis of Ohta et al. (1982) in terms of a phase variable and studying the dynamics of defects introduced into the phase field when the phase variable becomes multivalued. The resulting defect/phase domain-growth equation is applied to the interpretation of Monte Carlo simulations in two dimensions (Kaski and Gunton, 1983; Grest and Srolovitz, 1984), and problems encountered in the analysis of related Potts models are discussed. In the two-dimensional case, the problem is essentially that of a purely dissipative Coulomb gas, with a sq rt t growth law complicated by vertex-pinning effects at small t.
Dislocation dynamics, plasticity and avalanche statistics using the phase-field crystal model
NASA Astrophysics Data System (ADS)
Angheluta, Luiza
2013-03-01
The plastic deformation of stressed crystalline materials is characterized by intermittency and scaling behavior. The sudden strain bursts arise from collective interactions between depinned crystal defects such as dislocations. Recent experiments on sheared nanocrystals provide insights into the connection between the crystal plasticity and the mean field theory of the depinning transition, based on the similar power-law statistics of avalanche events. However, a complete theoretical formulation of this connection is still lacking, as are high quality numerical data. Phase field crystal modelling provides an efficient numerical approach to simulating the dynamics of dislocations in plastic flows at finite temperature. Dislocations are naturally created as defects in a periodic ground state that is being sheared, without any ad hoc creation and annihilation rules. These crystal defects interact and annihilate with one another, generating a collective effect of avalanches in the global plastic strain rate. We examine the statistics of plastic avalanches both at finite and zero temperatures, and find good agreement with the predictions of the mean field interface depinning theory. Moreover, we predict universal scaling forms for the extreme statistics of avalanches and universal relations between the power-law exponents of avalanche duration, size and extreme value. These results account for the observed power-law distribution of the maximum amplitudes in acoustic emission experiments of crystal plasticity, but are also broadly applicable to other systems in the mean-field interface depinning universality class, ranging from magnets to earthquakes. The work reported here was performed in collaboration with: Georgios Tsekenis, Michael LeBlanc, Patrick Y Chan, Jon Dantzig, Karin Dahmen, and Nigel Goldenfeld. The plastic deformation of stressed crystalline materials is characterized by intermittency and scaling behavior. The sudden strain bursts arise from collective interactions between depinned crystal defects such as dislocations. Recent experiments on sheared nanocrystals provide insights into the connection between the crystal plasticity and the mean field theory of the depinning transition, based on the similar power-law statistics of avalanche events. However, a complete theoretical formulation of this connection is still lacking, as are high quality numerical data. Phase field crystal modelling provides an efficient numerical approach to simulating the dynamics of dislocations in plastic flows at finite temperature. Dislocations are naturally created as defects in a periodic ground state that is being sheared, without any ad hoc creation and annihilation rules. These crystal defects interact and annihilate with one another, generating a collective effect of avalanches in the global plastic strain rate. We examine the statistics of plastic avalanches both at finite and zero temperatures, and find good agreement with the predictions of the mean field interface depinning theory. Moreover, we predict universal scaling forms for the extreme statistics of avalanches and universal relations between the power-law exponents of avalanche duration, size and extreme value. These results account for the observed power-law distribution of the maximum amplitudes in acoustic emission experiments of crystal plasticity, but are also broadly applicable to other systems in the mean-field interface depinning universality class, ranging from magnets to earthquakes. The work reported here was performed in collaboration with: Georgios Tsekenis, Michael LeBlanc, Patrick Y Chan, Jon Dantzig, Karin Dahmen, and Nigel Goldenfeld. The work was supported by the Center for Physics of Geological Processes (Norway) through a post-doctoral grant, the National Science Foundation through grant NSF-DMR-03-25939, NSF_DMR-1005209 and NSF-DMS-1069224 and DOE Subcontract No. 4000076535 (J.D.)
NASA Astrophysics Data System (ADS)
Funk, C. C.; Shukla, S.; Hoerling, M. P.; Robertson, F. R.; Hoell, A.; Liebmann, B.
2013-12-01
During boreal spring, eastern portions of Kenya and Somalia have experienced more frequent droughts since 1999. Given the region's high levels of food insecurity, better predictions of these droughts could provide substantial humanitarian benefits. We show that dynamical-statistical seasonal climate forecasts, based on the latest generation of coupled atmosphere-ocean and uncoupled atmospheric models, effectively predict boreal spring rainfall in this area. Skill sources are assessed by comparing ensembles driven with full-ocean forcing with ensembles driven with ENSO-only sea surface temperatures (SSTs). Our analysis suggests that both ENSO and non-ENSO Indo-Pacific SST forcing have played an important role in the increase in drought frequencies. Over the past 30 years, La Niña drought teleconnections have strengthened, while non-ENSO Indo-Pacific convection patterns have also supported increased (decreased) Western Pacific (East African) rainfall. To further examine the relative contribution of ENSO, low frequency warming and the Pacific Decadal Oscillation, we present decompositions of ECHAM5, GFS, CAM4 and GMAO AMIP simulations. These decompositions suggest that rapid warming in the western Pacific and steeper western-to-central Pacific SST gradients have likely played an important role in the recent intensification of the Walker circulation, and the associated increase in East African aridity. A linear combination of time series describing the Pacific Decadal Oscillation and the strength of Indo-Pacific warming are shown to track East African rainfall reasonably well. The talk concludes with a few thoughts linking the potentially important interplay of attribution and prediction. At least for recent East African droughts, it appears that a characteristic Indo-Pacific SST and precipitation anomaly pattern can be linked statistically to support forecasts and attribution analyses. The combination of traditional AGCM attribution analyses with simple yet physically plausible statistical estimation procedures may help us better untangle some climate mysteries.
An Embedded Statistical Method for Coupling Molecular Dynamics and Finite Element Analyses
NASA Technical Reports Server (NTRS)
Saether, E.; Glaessgen, E.H.; Yamakov, V.
2008-01-01
The coupling of molecular dynamics (MD) simulations with finite element methods (FEM) yields computationally efficient models that link fundamental material processes at the atomistic level with continuum field responses at higher length scales. The theoretical challenge involves developing a seamless connection along an interface between two inherently different simulation frameworks. Various specialized methods have been developed to solve particular classes of problems. Many of these methods link the kinematics of individual MD atoms with FEM nodes at their common interface, necessarily requiring that the finite element mesh be refined to atomic resolution. Some of these coupling approaches also require simulations to be carried out at 0 K and restrict modeling to two-dimensional material domains due to difficulties in simulating full three-dimensional material processes. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the standard boundary value problem used to define a coupled domain. The method replaces a direct linkage of individual MD atoms and finite element (FE) nodes with a statistical averaging of atomistic displacements in local atomic volumes associated with each FE node in an interface region. The FEM and MD computational systems are effectively independent and communicate only through an iterative update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM). ESCM provides an enhanced coupling methodology that is inherently applicable to three-dimensional domains, avoids discretization of the continuum model to atomic scale resolution, and permits finite temperature states to be applied.
Yang, Jaw-Yen; Yan, Chih-Yuan; Diaz, Manuel; Huang, Juan-Chen; Li, Zhihui; Zhang, Hanxin
2014-01-01
The ideal quantum gas dynamics as manifested by the semiclassical ellipsoidal-statistical (ES) equilibrium distribution derived in Wu et al. (Wu et al. 2012 Proc. R. Soc. A 468, 1799-1823 (doi:10.1098/rspa.2011.0673)) is numerically studied for particles of three statistics. This anisotropic ES equilibrium distribution was derived using the maximum entropy principle and conserves the mass, momentum and energy, but differs from the standard Fermi-Dirac or Bose-Einstein distribution. The present numerical method combines the discrete velocity (or momentum) ordinate method in momentum space and the high-resolution shock-capturing method in physical space. A decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. Computations of two-dimensional Riemann problems are presented, and various contours of the quantities unique to this ES model are illustrated. The main flow features, such as shock waves, expansion waves and slip lines and their complex nonlinear interactions, are depicted and found to be consistent with existing calculations for a classical gas. PMID:24399919
NASA Astrophysics Data System (ADS)
Lecomte, Christophe
2013-05-01
This paper concerns the response of uncertain vibro-acoustic and structural dynamic systems. Here, exact expressions are presented for the statistics of systems with a random rank-one component. The expressions are derived using the Sherman-Morrison update formula that gives the exact expression of the disturbed response for any magnitude of the disturbance. It is shown that the probability density function (pdf) of any transfer function is a simple function of the pdf of the disturbance magnitude of the random component. The expressions for the mean, variance, and covariance of any transfer function, and at any frequency, of a random system necessitate non-trivial integrals. Exact, including closed-form, expressions of these integrals are derived in the particular cases of a real or complex normal disturbance magnitude, and qualitative differences between these two cases are highlighted. The theoretical and practical advantages of the theory are discussed and applied to a model of a bladed disk subjected to random damage. The comparison with Monte-Carlo simulations demonstrates that the statistics can be evaluated efficiently and precisely. The theory, derived formally in the context of discretised systems, is directly applicable to continuous systems.
Estimating dynamic lung images from high-dimension chest surface motion using 4D statistical model.
He, Tiancheng; Xue, Zhong; Yu, Nam; Nitsch, Paige L; Teh, Bin S; Wong, Stephen T
2014-01-01
Computed Tomography (CT) has been widely used in image-guided procedures such as intervention and radiotherapy of lung cancer. However, due to poor reproducibility of breath holding or respiratory cycles, discrepancies between static images and patient's current lung shape and tumor location could potentially reduce the accuracy for image guidance. Current methods are either using multiple intra-procedural scans or monitoring respiratory motion with tracking sensors. Although intra-procedural scanning provides more accurate information, it increases the radiation dose and still only provides snapshots of patient's chest. Tracking-based breath monitoring techniques can effectively detect respiratory phases but have not yet provided accurate tumor shape and location due to low dimensional signals. Therefore, estimating the lung motion and generating dynamic CT images from real-time captured high-dimensional sensor signals acts as a key component for image-guided procedures. This paper applies a principal component analysis (PCA)-based statistical model to establish the relationship between lung motion and chest surface motion from training samples, on a template space, and then uses this model to estimate dynamic images for a new patient from the chest surface motion. Qualitative and quantitative results showed that the proposed high-dimensional estimation algorithm yielded more accurate 4D-CT compared to fiducial marker-based estimation. PMID:25485372
Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method
Tao, Yinghua; Chen, Guang-Hong; Hacker, Timothy A.; Raval, Amish N.; Van Lysel, Michael S.; Speidel, Michael A.
2014-01-01
Purpose: Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition. Methods: Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution. Results: Forin vivo studies, the 500 mA FBP maps gave ?88.4%, ?96.0%, ?76.7%, and ?65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring ?94.7%, ?81.6%, ?84.0%, and ?72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, ?11.8%, and ?3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was ?9.7%, 8.8%, ?3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937.9% for the 500 mA FBP, 25 mA SIR, and 25 mA FBP, respectively. In numerical simulations, SIR mitigated streak artifacts in the low dose data and yielded flow maps with mean error <7% and standard deviation <9% of mean, for 30×30 pixel ROIs (12.9 × 12.9 mm2). In comparison, low dose FBP flow errors were ?38% to +258%, and standard deviation was 6%–93%. Additionally, low dose SIR achieved 4.6 times improvement in flow map CNR2 per unit input dose compared to low dose FBP. Conclusions: SIR reconstruction can reduce image noise and mitigate streaking artifacts caused by photon starvation in dynamic CT myocardial perfusion data sets acquired at low dose (low tube current), and improve perfusion map quality in comparison to FBP reconstruction at the same dose. PMID:24989392
Rodrigo Cofré; Bruno Cessac
2012-12-14
We investigate the effect of electric synapses (gap junctions) on collective neuronal dynamics and spike statistics in a conductance-based Integrate-and-Fire neural network, driven by a Brownian noise, where conductances depend upon spike history. We compute explicitly the time evolution operator and show that, given the spike-history of the network and the membrane potentials at a given time, the further dynamical evolution can be written in a closed form. We show that spike train statistics is described by a Gibbs distribution whose potential can be approximated with an explicit formula, when the noise is weak. This potential form encompasses existing models for spike trains statistics analysis such as maximum entropy models or Generalized Linear Models (GLM). We also discuss the different types of correlations: those induced by a shared stimulus and those induced by neurons interactions.
Dynamical and statistical downscaling of the French Mediterranean climate: uncertainty assessment
NASA Astrophysics Data System (ADS)
Vrac, M.; Drobinski, P.; Merlo, A.; Herrmann, M.; Lavaysse, C.; Li, L.; Somot, S.
2012-09-01
ERA-40 reanalyses, and simulations from three regional climate models (RCMs) (ALADIN, LMDZ, and WRF) and from one statistical downscaling model (CDF-t) are used to evaluate the uncertainty in downscaling of wind, temperature, and rainfall cumulative distribution functions (CDFs) for eight stations in the French Mediterranean basin over 1991-2000. The uncertainty is quantified using the Cramer-von Mises score (CvM) to measure the "distance" between the simulated and observed CDFs. The ability of the three RCMs and CDF-t to simulate the "climate" variability is quantified with the explained variance, variance ratio and extreme occurrence. The study shows that despite their differences, the three RCMs display very similar performance. In terms of global distributions (i.e. CvM), all models perform better than ERA-40 for both seasons and variables. However, looking at variance criteria, RCMs are not always much better than ERA-40 reanalyses, whereas CDF-t produces accurate results when applied to ERA-40. In a second step, a combined statistical/dynamical downscaling approach has been used, consisting in applying CDF-t to the RCM outputs. It shows that CDF-t applied to the RCM outputs does not necessarily produce better results than those from CDF-t directly applied to ERA-40. It also shows that CDF-t applied to RCMs generally improves the downscaled CDFs and that the "additional" added value of CDF-t applied to the RCMs is independent of the performance of the RCMs in terms of CvM, explained variance, variance ratio and extreme occurrence.
Spagnolo, Filippo
95 The Role of Dynamic Interactive Technology in Teaching and Learning Statistics Gail Burrill or no use of menus. The design of technology-based activities for learning statistics needs careful, Michigan State University, USA burrill@msu.edu Abstract Dynamic interactive technology brings new
Honvault, Pascal
at the low energy regime by means of a statistical quantum method Tomás González-Lezana,1,a) Pascal Honvault of a statistical quantum mechanical (SQM) method. Reaction probabilities and integral cross sections (ICSs) betweenDynamics of the D+ + H2 HD + H+ reaction at the low energy regime by means of a statistical
McCauley, Patrick I; Schanche, Nicole; Evans, Kaitlin E; Su, Chuan; McKillop, Sean; Reeves, Katharine K
2015-01-01
We present a statistical study of prominence and filament eruptions observed by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). Several properties are recorded for 904 events that were culled from the Heliophysics Event Knowledgebase (HEK) and incorporated into an online catalog for general use. These characteristics include the filament and eruption type, eruption symmetry and direction, apparent twisting and writhing motions, and the presence of vertical threads and coronal cavities. Associated flares and white-light coronal mass ejections (CME) are also recorded. Total rates are given for each property along with how they differ among filament types. We also examine the kinematics of 106 limb events to characterize the distinct slow- and fast-rise phases often exhibited by filament eruptions. The average fast-rise onset height, slow-rise duration, slow-rise velocity, maximum field-of-view (FOV) velocity, and maximum FOV acceleration are 83 Mm, 4.4 hours, 2.1 km/s, 106 km...
Roth, A E; Jones, C D; Durian, D J
2013-04-01
We report on the statistics of bubble size, topology, and shape and on their role in the coarsening dynamics for foams consisting of bubbles compressed between two parallel plates. The design of the sample cell permits control of the liquid content, through a constant pressure condition set by the height of the foam above a liquid reservoir. We find that in the scaling regime, all bubble distributions are independent not only of time, but also of liquid content. For coarsening, the average rate decreases with liquid content due to the blocking of gas diffusion by Plateau borders inflated with liquid; we achieve a factor of 4 reduction from the dry limit. By observing the growth rate of individual bubbles, we find that von Neumann's law becomes progressively violated with increasing wetness and decreasing bubble size. We successfully model this behavior by explicitly incorporating the border-blocking effect into the von Neumann argument. Two dimensionless bubble shape parameters naturally arise, one of which is primarily responsible for the violation of von Neumann's law for foams that are not perfectly dry. PMID:23679411
Wereszczynski, Jeff; McCammon, J. Andrew
2012-01-01
Molecular recognition plays a central role in biochemical processes. Although well studied, understanding the mechanisms of recognition is inherently difficult due to the range of potential interactions, the molecular rearrangement associated with binding, and the time and length scales involved. Computational methods have the potential for not only complementing experiments that have been performed, but also in guiding future ones through their predictive abilities. In this review, we discuss how molecular dynamics (MD) simulations may be used in advancing our understanding of the thermodynamics that drive biomolecular recognition. We begin with a brief review of the statistical mechanics that form a basis for these methods. This is followed by a description of some of the most commonly used methods: thermodynamic pathways employing alchemical transformations and potential of mean force calculations, along with end-point calculations for free energy differences, and harmonic and quasi-harmonic analysis for entropic calculations. Finally, a few of the fundamental findings that have resulted from these methods are discussed, such as the role of configurational entropy and solvent in intermolecular interactions, along with selected results of the model system T4 lysozyme to illustrate potential and current limitations of these methods. PMID:22082669
L. P. Karakatsanis; G. P. Pavlos; M. N. Xenakis
2012-04-03
In the second part of this study and similarly with part one, the nonlinear analysis of the solar flares index is embedded in the non-extensive statistical theory of Tsallis [1]. The triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the solar flares timeseries. Also the multifractal scaling exponent spectrum, the generalized Renyi dimension spectrum and the spectrum of the structure function exponents were estimated experimentally and theoretically by using the entropy principle included in Tsallis non extensive statistical theory, following Arimitsu and Arimitsu [2]. Our analysis showed clearly the following: a) a phase transition process in the solar flare dynamics from high dimensional non Gaussian SOC state to a low dimensional also non Gaussian chaotic state, b) strong intermittent solar corona turbulence and anomalous (multifractal) diffusion solar corona process, which is strengthened as the solar corona dynamics makes phase transition to low dimensional chaos: c) faithful agreement of Tsallis non equilibrium statistical theory with the experimental estimations of i) non-Gaussian probability distribution function, ii) multifractal scaling exponent spectrum and generalized Renyi dimension spectrum, iii) exponent spectrum of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics. e) The solar flare dynamical profile is revealed similar to the dynamical profile of the solar convection zone as far as the phase transition process from SOC to chaos state. However the solar low corona (solar flare) dynamical characteristics can be clearly discriminated from the dynamical characteristics of the solar convection zone.
NASA Astrophysics Data System (ADS)
McCauley, P. I.; Su, Y. N.; Schanche, N.; Evans, K. E.; Su, C.; McKillop, S.; Reeves, K. K.
2015-05-01
We present a statistical study of prominence and filament eruptions observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Several properties are recorded for 904 events that were culled from the Heliophysics Event Knowledgebase (HEK) and incorporated into an online catalog for general use. These characteristics include the filament and eruption type, eruption symmetry and direction, apparent twisting and writhing motions, and the presence of vertical threads and coronal cavities. Associated flares and white-light coronal mass ejections (CME) are also recorded. Total rates are given for each property along with how they differ among filament types. We also examine the kinematics of 106 limb events to characterize the distinct slow- and fast-rise phases often exhibited by filament eruptions. The average fast-rise onset height, slow-rise duration, slow-rise velocity, maximum field-of-view (FOV) velocity, and maximum FOV acceleration are 83 Mm, 4.4 hours, 2.1 km s-1, 106 km s-1, and 111 m s-2, respectively. All parameters exhibit lognormal probability distributions similar to that of CME speeds. A positive correlation between latitude and fast-rise onset height is found, which we attribute to a corresponding negative correlation in the average vertical magnetic field gradient, or decay index, estimated from potential field source surface (PFSS) extrapolations. We also find the decay index at the fast-rise onset point to be 1.1 on average, consistent with the critical instability threshold theorized for straight current channels. Finally, we explore relationships between the derived kinematics properties and apparent twisting motions. We find that events with evident twist have significantly faster CME speeds and significantly lower fast-rise onset heights, suggesting relationships between these values and flux rope helicity.
Statistical properties and pre-hit dynamics of price limit hits in the chinese stock markets.
Wan, Yu-Lei; Xie, Wen-Jie; Gu, Gao-Feng; Jiang, Zhi-Qiang; Chen, Wei; Xiong, Xiong; Zhang, Wei; Zhou, Wei-Xing
2015-01-01
Price limit trading rules are adopted in some stock markets (especially emerging markets) trying to cool off traders' short-term trading mania on individual stocks and increase market efficiency. Under such a microstructure, stocks may hit their up-limits and down-limits from time to time. However, the behaviors of price limit hits are not well studied partially due to the fact that main stock markets such as the US markets and most European markets do not set price limits. Here, we perform detailed analyses of the high-frequency data of all A-share common stocks traded on the Shanghai Stock Exchange and the Shenzhen Stock Exchange from 2000 to 2011 to investigate the statistical properties of price limit hits and the dynamical evolution of several important financial variables before stock price hits its limits. We compare the properties of up-limit hits and down-limit hits. We also divide the whole period into three bullish periods and three bearish periods to unveil possible differences during bullish and bearish market states. To uncover the impacts of stock capitalization on price limit hits, we partition all stocks into six portfolios according to their capitalizations on different trading days. We find that the price limit trading rule has a cooling-off effect (object to the magnet effect), indicating that the rule takes effect in the Chinese stock markets. We find that price continuation is much more likely to occur than price reversal on the next trading day after a limit-hitting day, especially for down-limit hits, which has potential practical values for market practitioners. PMID:25874716
Pavlos, G P; Xenakis, M N
2012-01-01
In this study, the nonlinear analysis of the sunspot index is embedded in the non-extensive statistical theory of Tsallis. The triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the sunspot index timeseries. Also the multifractal scaling exponent spectrum, the generalized Renyi dimension spectrum and the spectrum of the structure function exponents were estimated experimentally and theoretically by using the entropy principle included in Tsallis non extensive statistical theory, following Arimitsu and Arimitsu. Our analysis showed clearly the following: a) a phase transition process in the solar dynamics from high dimensional non Gaussian SOC state to a low dimensional non Gaussian chaotic state, b) strong intermittent solar turbulence and anomalous (multifractal) diffusion solar process, which is strengthened as the solar dynamics makes phase transition to low dimensional chaos in accordance to Ruzmaikin, Zeleny and Milovanov s...
Li Ou; Yingxun Zhang; Junlong Tian; Zhuxia Li
2007-01-01
Intermediate energy proton-induced spallation reactions with various targets are studied by the improved quantum molecular dynamics (ImQMD05) model incorporated with the statistical decay model. The influences of the different Skyrme interactions on the mechanism of spallation reaction and the double differential cross sections of emitted neutrons are studied. It is found that the different Skyrme interactions influence the low energy
Y. Shi; E. Zesta; L. R. Lyons; K. Yumoto; K. Kitamura
2006-01-01
In this paper, we statistically investigate the effect of solar wind dynamic pressure enhancements on the dawn-to-dusk ring current asymmetry by examining disturbances of the ASY-H index and low-latitude and midlatitude ground asymmetric perturbations in the north-south (H) component of the geomagnetic field during 186 events occurring from 1 June 2003 to 30 September 2004. Both storm time and nonstorm
R. M. MacKay; M. A. K. Khalil
1995-01-01
The zonally averaged response of the Global Change Research Center two-dimensional (2-D) statistical dynamical climate model (GCRC 2-D SDCM) to a doubling of atmospheric carbon dioxide (350 parts per million by volume (ppmv) to 700 ppmv) is reported. The model solves the two-dimensional primitive equations in finite difference form (mass continuity, Newton's second law, and the first law of thermodynamics)
G. P. Pavlos; L. P. Karakatsanis; M. N. Xenakis
2012-01-31
In this study, the nonlinear analysis of the sunspot index is embedded in the non-extensive statistical theory of Tsallis. The triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the sunspot index timeseries. Also the multifractal scaling exponent spectrum, the generalized Renyi dimension spectrum and the spectrum of the structure function exponents were estimated experimentally and theoretically by using the entropy principle included in Tsallis non extensive statistical theory, following Arimitsu and Arimitsu. Our analysis showed clearly the following: a) a phase transition process in the solar dynamics from high dimensional non Gaussian SOC state to a low dimensional non Gaussian chaotic state, b) strong intermittent solar turbulence and anomalous (multifractal) diffusion solar process, which is strengthened as the solar dynamics makes phase transition to low dimensional chaos in accordance to Ruzmaikin, Zeleny and Milovanov studies c) faithful agreement of Tsallis non equilibrium statistical theory with the experimental estimations of i) non-Gaussian probability distribution function, ii) multifractal scaling exponent spectrum and generalized Renyi dimension spectrum, iii) exponent spectrum of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics.
Observation and Nature of Non-statistical Dynamic Effects in Ordinary Organic Reactions
Quijano, Larisa Mae Mangaliman 1984-
2012-10-17
-Dynamics Trajectory Calculations To explore this idea, quasiclassical direct-dynamics trajectory calculation39 were used to study these reactions. The trajectories were carried out on an ONIOM potential energy surface using density functional theory (DFT...
NASA Astrophysics Data System (ADS)
Gauer, P.; Lied, K.; Bakkehoi, S.; Kronholm, K.; Rammer, L.; Hoeller, P.
2009-04-01
Hazard and risk assessment in avalanche prone areas involves the estimation of the runout of potential avalanches. Methods for determination of the runout may be grouped into two groups: 1) based on statistical methods such as the well known ? - Î² model or 2) based on numerical avalanche models such as the PCM-model or Voellmy-Salm type models (just to name the more traditional ones). The later method has the advantage that besides the runout also information on velocity and impact pressure distributions along the avalanche track can be obtained. However, the success of the dynamical models depends on the knowledge of suitable rheological models and their parameters. The statistical ?-Î² model was developed at NGI and governs maximum runout distance solely as a function of topography. The runout distance equations are found by regression analysis, correlating the longest registered runout distance from several hundred avalanche paths to a selection of topographic parameters. Similar regression analysis were also performed for different regions of United States, Canada or Austria. We re-evaluate the Norwegian and Austrian avalanche data on which the ? - Î² model were based with respect to dynamical measures. As all those avalanche data belong more or less to extreme events (i.e. avalanches with return periods of 100 years to more) the dynamical measures can give hints for suitable rheological model for dynamical models suitable for extreme avalanche events.
NASA Astrophysics Data System (ADS)
Hong, Mei; Zhang, Ren; Wang, Dong; Feng, Mang; Wang, Zhengxin; Singh, Vijay P.
2015-07-01
To address the inaccuracy of long-term El Niño-Southern Oscillation (ENSO) forecasts, a new dynamical-statistical forecasting model of the ENSO index was developed based on dynamical model reconstruction and improved self-memorization. To overcome the problem of single initial prediction values, the largest Lyapunov exponent was introduced to improve the traditional self-memorization function, thereby making it more effective for describing chaotic systems, such as ENSO. Equation reconstruction, based on actual data, was used as a dynamical core to overcome the problem of using a simple core. The developed dynamical-statistical forecasting model of the ENSO index is used to predict the sea surface temperature anomaly in the equatorial eastern Pacific and El Niño/La Niña events. The real-time predictive skills of the improved model were tested. The results show that our model predicted well within lead times of 12 months. Compared with six mature models, both temporal correlation and root mean square error of the improved model are slightly worse than those of the European Centre for Medium-Range Weather Forecasts model, but better than those of the other five models. Additionally, the margin between the forecast results in summer and those in winter is not great, which means that the improved model can overcome the "spring predictability barrier", to some extent. Finally, a real-time prediction experiment is carried out beginning in September 2014. Our model is a new exploration of the ENSO forecasting method.
NASA Astrophysics Data System (ADS)
Frossard, L.; Rieder, H. E.; Ribatet, M.; Staehelin, J.; Maeder, J. A.; Di Rocco, S.; Davison, A. C.; Peter, T.
2012-05-01
We use models for mean and extreme values of total column ozone on spatial scales to analyze "fingerprints" of atmospheric dynamics and chemistry on long-term ozone changes at northern and southern mid-latitudes. The r-largest order statistics method is used for pointwise analysis of extreme events in low and high total ozone (termed ELOs and EHOs, respectively). For the corresponding mean value analysis a pointwise autoregressive moving average model (ARMA) is used. The statistical models include important atmospheric covariates to describe the dynamical and chemical state of the atmosphere: the solar cycle, the Quasi-Biennial Oscillation (QBO), ozone depleting substances (ODS) in terms of equivalent effective stratospheric chlorine (EESC), the North Atlantic Oscillation (NAO), the Antarctic Oscillation (AAO), the El~Niño/Southern Oscillation (ENSO), and aerosol load after the volcanic eruptions of El Chichón and Mt. Pinatubo. The influence of the individual covariates on mean and extreme levels in total column ozone is derived on a grid cell basis. The results show that "fingerprints", i.e., significant influence, of dynamical and chemical features are captured in both the "bulk" and the tails of the ozone distribution, respectively described by means and EHOs/ELOs. While results for the solar cycle, QBO and EESC are in good agreement with findings of earlier studies, unprecedented spatial fingerprints are retrieved for the dynamical covariates.
Ginestet, Cedric E; Simmons, Andrew
2011-03-15
Network analysis has become a tool of choice for the study of functional and structural Magnetic Resonance Imaging (MRI) data. Little research, however, has investigated connectivity dynamics in relation to varying cognitive load. In fMRI, correlations among slow (<0.1 Hz) fluctuations of blood oxygen level dependent (BOLD) signal can be used to construct functional connectivity networks. Using an anatomical parcellation scheme, we produced undirected weighted graphs linking 90 regions of the brain representing major cortical gyri and subcortical nuclei, in a population of healthy adults (n=43). Topological changes in these networks were investigated under different conditions of a classical working memory task - the N-back paradigm. A mass-univariate approach was adopted to construct statistical parametric networks (SPNs) that reflect significant modifications in functional connectivity between N-back conditions. Our proposed method allowed the extraction of 'lost' and 'gained' functional networks, providing concise graphical summaries of whole-brain network topological changes. Robust estimates of functional networks are obtained by pooling information about edges and vertices over subjects. Graph thresholding is therefore here supplanted by inference. The analysis proceeds by firstly considering changes in weighted cost (i.e. mean between-region correlation) over the different N-back conditions and secondly comparing small-world topological measures integrated over network cost, thereby controlling for differences in mean correlation between conditions. The results are threefold: (i) functional networks in the four conditions were all found to satisfy the small-world property and cost-integrated global and local efficiency levels were approximately preserved across the different experimental conditions; (ii) weighted cost considerably decreased as working memory load increased; and (iii) subject-specific weighted costs significantly predicted behavioral performances on the N-back task (Wald F=13.39,df(1)=1,df(2)=83,p<0.001), and therefore conferred predictive validity to functional connectivity strength, as measured by weighted cost. The results were found to be highly sensitive to the frequency band used for the computation of the between-region correlations, with the relationship between weighted cost and behavioral performance being most salient at very low frequencies (0.01-0.03 Hz). These findings are discussed in relation to the integration/specialization functional dichotomy. The pruning of functional networks under increasing cognitive load may permit greater modular specialization, thereby enhancing performance. PMID:21095229
NASA Astrophysics Data System (ADS)
Grotjahn, Richard; Black, Robert; Leung, Ruby; Wehner, Michael F.; Barlow, Mathew; Bosilovich, Mike; Gershunov, Alexander; Gutowski, William J.; Gyakum, John R.; Katz, Richard W.; Lee, Yun-Young; Lim, Young-Kwon; Prabhat
2015-05-01
The objective of this paper is to review statistical methods, dynamics, modeling efforts, and trends related to temperature extremes, with a focus upon extreme events of short duration that affect parts of North America. These events are associated with large scale meteorological patterns (LSMPs). The statistics, dynamics, and modeling sections of this paper are written to be autonomous and so can be read separately. Methods to define extreme events statistics and to identify and connect LSMPs to extreme temperature events are presented. Recent advances in statistical techniques connect LSMPs to extreme temperatures through appropriately defined covariates that supplement more straightforward analyses. Various LSMPs, ranging from synoptic to planetary scale structures, are associated with extreme temperature events. Current knowledge about the synoptics and the dynamical mechanisms leading to the associated LSMPs is incomplete. Systematic studies of: the physics of LSMP life cycles, comprehensive model assessment of LSMP-extreme temperature event linkages, and LSMP properties are needed. Generally, climate models capture observed properties of heat waves and cold air outbreaks with some fidelity. However they overestimate warm wave frequency and underestimate cold air outbreak frequency, and underestimate the collective influence of low-frequency modes on temperature extremes. Modeling studies have identified the impact of large-scale circulation anomalies and land-atmosphere interactions on changes in extreme temperatures. However, few studies have examined changes in LSMPs to more specifically understand the role of LSMPs on past and future extreme temperature changes. Even though LSMPs are resolvable by global and regional climate models, they are not necessarily well simulated. The paper concludes with unresolved issues and research questions.
NASA Astrophysics Data System (ADS)
Frossard, L.; Rieder, H. E.; Ribatet, M.; Staehelin, J.; Maeder, J. A.; Di Rocco, S.; Davison, A. C.; Peter, T.
2013-01-01
We use statistical models for mean and extreme values of total column ozone to analyze "fingerprints" of atmospheric dynamics and chemistry on long-term ozone changes at northern and southern mid-latitudes on grid cell basis. At each grid cell, the r-largest order statistics method is used for the analysis of extreme events in low and high total ozone (termed ELOs and EHOs, respectively), and an autoregressive moving average (ARMA) model is used for the corresponding mean value analysis. In order to describe the dynamical and chemical state of the atmosphere, the statistical models include important atmospheric covariates: the solar cycle, the Quasi-Biennial Oscillation (QBO), ozone depleting substances (ODS) in terms of equivalent effective stratospheric chlorine (EESC), the North Atlantic Oscillation (NAO), the Antarctic Oscillation (AAO), the El Niño/Southern Oscillation (ENSO), and aerosol load after the volcanic eruptions of El Chichón and Mt. Pinatubo. The influence of the individual covariates on mean and extreme levels in total column ozone is derived on a grid cell basis. The results show that "fingerprints", i.e., significant influence, of dynamical and chemical features are captured in both the "bulk" and the tails of the statistical distribution of ozone, respectively described by mean values and EHOs/ELOs. While results for the solar cycle, QBO, and EESC are in good agreement with findings of earlier studies, unprecedented spatial fingerprints are retrieved for the dynamical covariates. Column ozone is enhanced over Labrador/Greenland, the North Atlantic sector and over the Norwegian Sea, but is reduced over Europe, Russia and the Eastern United States during the positive NAO phase, and vice-versa during the negative phase. The NAO's southern counterpart, the AAO, strongly influences column ozone at lower southern mid-latitudes, including the southern parts of South America and the Antarctic Peninsula, and the central southern mid-latitudes. Results for both NAO and AAO confirm the importance of atmospheric dynamics for ozone variability and changes from local/regional to global scales.
Statistical dynamics of classical systems: A self-consistent field approach
Grzetic, Douglas J., E-mail: dgrzetic@uoguelph.ca; Wickham, Robert A., E-mail: rwickham@uoguelph.ca [Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Shi, An-Chang, E-mail: shi@mcmaster.ca [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)
2014-06-28
We develop a self-consistent field theory for particle dynamics by extremizing the functional integral representation of a microscopic Langevin equation with respect to the collective fields. Although our approach is general, here we formulate it in the context of polymer dynamics to highlight satisfying formal analogies with equilibrium self-consistent field theory. An exact treatment of the dynamics of a single chain in a mean force field emerges naturally via a functional Smoluchowski equation, while the time-dependent monomer density and mean force field are determined self-consistently. As a simple initial demonstration of the theory, leaving an application to polymer dynamics for future work, we examine the dynamics of trapped interacting Brownian particles. For binary particle mixtures, we observe the kinetics of phase separation.
NASA Astrophysics Data System (ADS)
Pavlos, G. P.; Karakatsanis, L. P.; Xenakis, M. N.
2012-12-01
In this study, the non-linear analysis of the sunspot index is embedded in the non-extensive statistical theory of Tsallis (1988, 2004, 2009) [7,9,10]. The q-triplet of Tsallis, as well as the correlation dimension and the Lyapunov exponent spectrum were estimated for the SVD components of the sunspot index timeseries. Also the multifractal scaling exponent spectrum f(a), the generalized Renyi dimension spectrum D(q) and the spectrum J(p) of the structure function exponents were estimated experimentally and theoretically by using the q-entropy principle included in Tsallis non-extensive statistical theory, following Arimitsu and Arimitsu (2001, 2000) [76,77]. Our analysis showed clearly the following: (a) a phase transition process in the solar dynamics from high dimensional non-Gaussian SOC state to a low dimensional non-Gaussian chaotic state, (b) strong intermittent solar turbulence and anomalous (multifractal) diffusion solar process, which is strengthened as the solar dynamics makes a phase transition to low dimensional chaos in accordance to Ruzmaikin, Zeleny and Milovanov’s studies (Zelenyi and Milovanov (1991) [21]); Milovanov and Zelenyi (1993) [22]; Ruzmakin et al. (1996) [26]) (c) faithful agreement of Tsallis non-equilibrium statistical theory with the experimental estimations of (i) non-Gaussian probability distribution function P(x), (ii) multifractal scaling exponent spectrum f(a) and generalized Renyi dimension spectrum Dq, (iii) exponent spectrum J(p) of the structure functions estimated for the sunspot index and its underlying non equilibrium solar dynamics.
Jee-In Heo; Soo-Jin Oh; Yoon-Jung Kho; Jeong-Hyeon Kim; Hong-Joon Kang; Seong-Hoon Park; Hyun-Seok Kim; Jong-Yeon Shin; Min-Ju Kim; Sung Chan Kim; Jae-Bong Park; Jaebong Kim; Jae-Yong Lee
2011-01-01
Since anti-apoptotic effect of ERK has not been elucidated clearly in DNA-damage-induced cell death, the role of ERK was examined\\u000a in normal HEF cells treated with mild DNA damage using etoposide or camptothecin. ERK was activated by DNA damage in HEF cells.\\u000a PD98059 increased apoptosis and reduced DNA-damage-induced p21Waf1\\/Cip1\\/Sdi level. Depletion of p21Waf1\\/Cip1\\/Sdi induced cell death and PD98059 induced additional
Canavan, G.H.
1988-01-01
This report reviews previous attempt to develop strategic defenses, the technologies currently under consideration, their main unknowns, and their likely performance relative to evolving threats. 28 refs.
Technology Transfer Automated Retrieval System (TEKTRAN)
It is known that irrigation application method can impact crop water use and water use efficiency, but the mechanisms involved are incompletely understood, particularly in terms of the water and energy balances during the growing season from pre-irrigation through planting, early growth and yield de...
A dynamical equation for a maser with non-poissonian injection statistics
Michael Fleischhauer
2014-10-12
A derivation of the coarse grained dynamical equation for a maser with periodic injection of atoms suggested by Briegel and Englert [Phys.Rev.A. {\\bf 52}, 2361 (1995)] from the microscopic masterequation is presented.
Hu, Huyi
to that of uniformly hyperbolic systems, and the ergodic properties may be quite di#erent. It admit SRB measures or infinite SRB measures. In the latter case, the systems are statistically deterministic in the sense call it an infinite SRB measure. For some other deformation, the resulting system still admits an SRB
Static Numbers to Dynamic Statistics: Designing a Policy-Friendly Social Policy Indicator Framework
ERIC Educational Resources Information Center
Ahn, Sang-Hoon; Choi, Young Jun; Kim, Young-Mi
2012-01-01
In line with the economic crisis and rapid socio-demographic changes, the interest in "social" and "well-being" indicators has been revived. Social indicator movements of the 1960s resulted in the establishment of social indicator statistical frameworks; that legacy has remained intact in many national governments and international organisations.…
Friendship Networks Through Time: An Actor-Oriented Dynamic Statistical Network Model
Gerhard G. Van De Bunt; Marijtje A. J. Van Duijn; Tom A. B. Snijders
1999-01-01
We propose a class of actor-oriented statistical models for closed social networks in general, and friendship networks in particular. The models are random utility models developed within a rational choice framework. Based on social psychological and sociological theories about friendship, mathematical functions capturing ex- pected utility of individual actors with respect to friendship are constructed. Expected utility also contains a
NASA Astrophysics Data System (ADS)
Rosa, Bogdan; Parishani, Hossein; Ayala, Orlando; Wang, Lian-Ping; Grabowski, Wojciech W.
2011-12-01
In recent years, direct numerical simulation (DNS) approach has become a reliable tool for studying turbulent collision-coalescence of cloud droplets relevant to warm rain development. It has been shown that small-scale turbulent motion can enhance the collision rate of droplets by either enhancing the relative velocity and collision efficiency or by inertia-induced droplet clustering. A hybrid DNS approach incorporating DNS of air turbulence, disturbance flows due to droplets, and droplet equation of motion has been developed to quantify these effects of air turbulence. Due to the computational complexity of the approach, a major challenge is to increase the range of scales or size of the computation domain so that all scales affecting droplet pair statistics are simulated. Here we discuss our on-going work in this direction by improving the parallel scalability of the code, and by studying the effect of large-scale forcing on pair statistics relevant to turbulent collision. New results at higher grid resolutions show a saturation of pair and collision statistics with increasing flow Reynolds number, for given Kolmogorov scales and small droplet sizes. Furthermore, we examine the orientation dependence of pair statistics which reflects an interesting coupling of gravity and droplet clustering.
Kang, In-Sik
(SST) in the Indian Ocean. It is a linear regression model based on a lagged relationship between the Indian Ocean SST and the NINO3 SST. A new approach to the statistical modeling has been tried out affected by the regional ocean SST rather than the tropical Pacific SST. For example, the Indian Ocean SST
NASA Astrophysics Data System (ADS)
Papageorge, Michael; Fuest, Frederik; Sutton, Jeffret
2013-11-01
The objective of this work is to examine the space-time dynamics of conserved scalar transport and mixing in gas-phase, turbulent jets utilizing kHz-rate, planar laser diagnostics. This research is facilitated by the High-Energy Pulse-Burst Laser System (HEPBLS) at Ohio State, which is capable of delivering high-energy (~ 1 J) pulses at 532 nm at repetition rates of 10 kHz and higher. With this system, time-resolved 2-D scalar mixing fields are acquired with high signal-to-noise ratios. In this study Rayleigh scattering from a propane jet issuing into a low-speed air co-flow was used to measure mixture fraction at Re = 10,000 to 30,000 at axial locations of x/D = 10 to 40. Single- and multi-point time statistics are employed to gain a better understanding of the dynamics of large-scale features. Single point auto-correlations are used to calculate the integral time scale as a function of axial and radial location and Reynolds number with unprecedented spatial resolution. Multi-point time correlations are then used to examine the nature of scalar advection and spreading rate across the width of the jet. In addition to the statistical representation, both time scale and spreading rate are examined visually to gain an improved qualitative understanding of scalar mixing.
Bahlmann, Claus; Burkhardt, Hans
2004-03-01
In this paper, we give a comprehensive description of our writer-independent online handwriting recognition system frog on hand. The focus of this work concerns the presentation of the classification/training approach, which we call cluster generative statistical dynamic time warping (CSDTW). CSDTW is a general, scalable, HMM-based method for variable-sized, sequential data that holistically combines cluster analysis and statistical sequence modeling. It can handle general classification problems that rely on this sequential type of data, e.g., speech recognition, genome processing, robotics, etc. Contrary to previous attempts, clustering and statistical sequence modeling are embedded in a single feature space and use a closely related distance measure. We show character recognition experiments of frog on hand using CSDTW on the UNIPEN online handwriting database. The recognition accuracy is significantly higher than reported results of other handwriting recognition systems. Finally, we describe the real-time implementation of frog on hand on a Linux Compaq iPAQ embedded device. PMID:15376878
Statistical Mechanics with focus on
Johannesson, Henrik
Statistical Mechanics with focus on Liquids, Solutions and Colloidal Systems Course contents A. Foundations of statistical mechanics Classical dynamics Â Hamilton's and Liouville's equations The concept thermodynamics and statistical mechanics. B. Liquid state theory; Equilibrium statistical mechanics for liquids
NASA Astrophysics Data System (ADS)
Kissinger, J.; Wilder, F. D.; McPherron, R. L.; Hsu, T.-S.; Baker, J. B. H.; Kepko, L.
2013-08-01
Harang discontinuity is a longitudinally extended ionospheric signature near midnight of flow reversal from westward to eastward with decreasing latitude. Its occurrence indicates enhanced convection in the magnetotail that requires an upward field-aligned current from the ionosphere due to diamagnetic ion drift. Previous reports using event studies have been conflicting as to the occurrence of the Harang discontinuity during a mode of enhanced magnetotail response called steady magnetospheric convection (SMC). With a comprehensive list of SMC events from 1997 through 2007, we utilize data from the Super Dual Auroral Radar Network and a novel spatial superposition technique to statistically examine the occurrence of the Harang discontinuity during SMC events. We find that the statistical signature of the Harang discontinuity begins before SMC starts and strengthens as the SMC events progress. We also detail the typical size and strength of the Harang discontinuity and find that it is more pronounced during interplanetary magnetic field +By conditions.
Dynamic stability of the Solar System: Statistically inconclusive results from ensemble integrations
Zeebe, Richard E
2015-01-01
Due to the chaotic nature of the Solar System, the question of its long-term stability can only be answered in a statistical sense, for instance, based on numerical ensemble integrations of nearby orbits. Destabilization of the inner planets, leading to close encounters and/or collisions can be initiated through a large increase in Mercury's eccentricity, with a currently assumed likelihood of ~1%. However, little is known at present about the robustness of this number. Here I report ensemble integrations of the full equations of motion of the eight planets and Pluto over 5 Gyr, including contributions from general relativity. The results show that different numerical algorithms lead to statistically different results for the evolution of Mercury's eccentricity (eM). For instance, starting at present initial conditions (eM ~= 0.21), Mercury's maximum eccentricity achieved over 5 Gyr is on average significantly higher in symplectic ensemble integrations using heliocentricthan Jacobi coordinates and stricter er...
NASA Astrophysics Data System (ADS)
Gramsch, Christian; Rigol, Marcos
2012-11-01
We study the dynamics and the resulting state after relaxation in a quasidisordered integrable lattice system after a sudden quench. Specifically, we consider hard-core bosons in an isolated one-dimensional geometry in the presence of a quasiperiodic potential whose strength is abruptly changed to take the system out of equilibrium. In the delocalized regime, we find that the relaxation dynamics of one-body observables, such as the density, the momentum distribution function, and the occupation of the natural orbitals, follow, to a good approximation, power laws. In that regime, we also show that the observables after relaxation can be described by the generalized Gibbs ensemble, while such a description fails for the momentum distribution and the natural orbital occupations in the presence of localization. At the critical point, the relaxation dynamics is found to be slower than in the delocalized phase.
NASA Astrophysics Data System (ADS)
Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Wu, S.; Schwaerz, M.; Fritzer, J.; Zhang, S.; Carter, B. A.; Zhang, K.
2013-12-01
Navigation Satellite System (GNSS)-based radio occultation (RO) is a satellite remote sensing technique providing accurate profiles of the Earth's atmosphere for weather and climate applications. Above about 30 km altitude, however, statistical optimization is a critical process for initializing the RO bending angles in order to optimize the climate monitoring utility of the retrieved atmospheric profiles. Here we introduce an advanced dynamic statistical optimization algorithm, which uses bending angles from multiple days of European Centre for Medium-range Weather Forecasts (ECMWF) short-range forecast and analysis fields, together with averaged-observed bending angles, to obtain background profiles and associated error covariance matrices with geographically varying background uncertainty estimates on a daily updated basis. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.4 (OPSv5.4) algorithm, using several days of simulated MetOp and observed CHAMP and COSMIC data, for January and July conditions. We find the following for the new method's performance compared to OPSv5.4: 1.) it significantly reduces random errors (standard deviations), down to about half their size, and leaves less or about equal residual systematic errors (biases) in the optimized bending angles; 2.) the dynamic (daily) estimate of the background error correlation matrix alone already improves the optimized bending angles; 3.) the subsequently retrieved refractivity profiles and atmospheric (temperature) profiles benefit by improved error characteristics, especially above about 30 km. Based on these encouraging results, we work to employ similar dynamic error covariance estimation also for the observed bending angles and to apply the method to full months and subsequently to entire climate data records.
SU-E-J-261: Statistical Analysis and Chaotic Dynamics of Respiratory Signal of Patients in BodyFix
Michalski, D; Huq, M; Bednarz, G; Lalonde, R; Yang, Y; Heron, D [University of Pittsburgh Medical Center, Pittsburgh, PA (United States)
2014-06-01
Purpose: To quantify respiratory signal of patients in BodyFix undergoing 4DCT scan with and without immobilization cover. Methods: 20 pairs of respiratory tracks recorded with RPM system during 4DCT scan were analyzed. Descriptive statistic was applied to selected parameters of exhale-inhale decomposition. Standardized signals were used with the delay method to build orbits in embedded space. Nonlinear behavior was tested with surrogate data. Sample entropy SE, Lempel-Ziv complexity LZC and the largest Lyapunov exponents LLE were compared. Results: Statistical tests show difference between scans for inspiration time and its variability, which is bigger for scans without cover. The same is for variability of the end of exhalation and inhalation. Other parameters fail to show the difference. For both scans respiratory signals show determinism and nonlinear stationarity. Statistical test on surrogate data reveals their nonlinearity. LLEs show signals chaotic nature and its correlation with breathing period and its embedding delay time. SE, LZC and LLE measure respiratory signal complexity. Nonlinear characteristics do not differ between scans. Conclusion: Contrary to expectation cover applied to patients in BodyFix appears to have limited effect on signal parameters. Analysis based on trajectories of delay vectors shows respiratory system nonlinear character and its sensitive dependence on initial conditions. Reproducibility of respiratory signal can be evaluated with measures of signal complexity and its predictability window. Longer respiratory period is conducive for signal reproducibility as shown by these gauges. Statistical independence of the exhale and inhale times is also supported by the magnitude of LLE. The nonlinear parameters seem more appropriate to gauge respiratory signal complexity since its deterministic chaotic nature. It contrasts with measures based on harmonic analysis that are blind for nonlinear features. Dynamics of breathing, so crucial for 4D-based clinical technologies, can be better controlled if nonlinear-based methodology, which reflects respiration characteristic, is applied. Funding provided by Varian Medical Systems via Investigator Initiated Research Project.
Bayesian Statistics Applied to Dynamic Modification Experiments on Florida Cumulus Clouds
Joanne Simpson; William L. Woodley; Anthony Olsen; Jane C. Eden
1973-01-01
Randomized dynamic cumulus seeding programs were executed in 1968 and 1970 on isolated clouds and beginning in 1970 on groups of clouds, to promote mergers in a 4000 mi2 target area in south Florida. With the single clouds, 26 seeded and 26 control cases comprise an adequate sample. In the area experiment, 1970 1971 and 1972 produced only 7 random
A rarefied gas dynamic numerical method applied to problems in statistical turbulence
R. Srinivasan; D. P. Giddens; L. H. Bangert; J. C. Wu
1979-01-01
Lundgren's equation modeling the velocity probability distribution function for turbulence in a parallel flow closely resembles the BGK equation of kinetic theory. The turbulence equation has been solved numerically using a combination of finite differencing and discrete velocities, a method which has seen extensive service in the solution of rarefied gas dynamics problems. Several of the techniques and concepts of
Observation and Nature of Non-statistical Dynamic Effects in Ordinary Organic Reactions
Quijano, Larisa Mae Mangaliman 1984-
2012-10-17
/B Ratios?????????????. 23 3 Styrene Ozonolysis Product Ratios????????????????. 30 4 2,3-Dimethyl-1,3-butadiene Ozonolysis Product Ratios????????. 31 5 Trajectory Results for the Cycloaddition of Cyclopentadiene with Different Dienophiles... OF TABLES ?????????????????????????. xi I. INTRODUCTION ????????????????????????.. 1 1.1 Dynamic Effects ?????????????????????... 1 1.2 Kinetic Isotope Effects ???????????????????. 5 1.3 Theoretical Calculations ??????????????????... 10 II...
NASA Astrophysics Data System (ADS)
Eckert, Nicolas; Schläppy, Romain; Jomelli, Vincent; Naaim, Mohamed
2013-04-01
A crucial step for proposing relevant long-term mitigation measures in long term avalanche forecasting is the accurate definition of high return period avalanches. Recently, "statistical-dynamical" approach combining a numerical model with stochastic operators describing the variability of its inputs-outputs have emerged. Their main interests is to take into account the topographic dependency of snow avalanche runout distances, and to constrain the correlation structure between model's variables by physical rules, so as to simulate the different marginal distributions of interest (pressure, flow depth, etc.) with a reasonable realism. Bayesian methods have been shown to be well adapted to achieve model inference, getting rid of identifiability problems thanks to prior information. An important problem which has virtually never been considered before is the validation of the predictions resulting from a statistical-dynamical approach (or from any other engineering method for computing extreme avalanches). In hydrology, independent "fossil" data such as flood deposits in caves are sometimes confronted to design discharges corresponding to high return periods. Hence, the aim of this work is to implement a similar comparison between high return period avalanches obtained with a statistical-dynamical approach and independent validation data resulting from careful dendrogeomorphological reconstructions. To do so, an up-to-date statistical model based on the depth-averaged equations and the classical Voellmy friction law is used on a well-documented case study. First, parameter values resulting from another path are applied, and the dendrological validation sample shows that this approach fails in providing realistic prediction for the case study. This may be due to the strongly bounded behaviour of runouts in this case (the extreme of their distribution is identified as belonging to the Weibull attraction domain). Second, local calibration on the available avalanche chronicle is performed with various prior distributions resulting from expert knowledge and/or other paths. For all calibrations, a very successful convergence is obtained, which confirms the robustness of the used Metropolis-Hastings estimation algorithm. This also demonstrates the interest of the Bayesian framework for aggregating information by sequential assimilation in the frequently encountered case of limited data quantity. Confrontation with the dendrological sample stresses the predominant role of the Coulombian friction coefficient distribution's variance on predicted high magnitude runouts. The optimal fit is obtained for a strong prior reflecting the local bounded behavior, and results in a 10-40 m difference for return periods ranging between 10 and 300 years. Implementing predictive simulations shows that this is largely within the range of magnitude of uncertainties to be taken into account. On the other hand, the different priors tested for the turbulent friction coefficient influence predictive performances only slightly, but have a large influence on predicted velocity and flow depth distributions. This all may be of high interest to refine calibration and predictive use of the statistical-dynamical model for any engineering application.
Blumenfeld, R.
1993-11-01
I show that the evolution of a two dimensional surface in a Laplacian field can be described by Hamiltonian dynamics. First the growing region is mapped conformally to the interior of the unit circle, creating in the process a set of mathematical zeros and poles that evolve dynamically as the surface grows. Then the dynamics of these quasi-particles are transformed into a seperable action-angle Hamiltonian that describes an orbital motion on a torus. A specific case is discussed explicitly, which demonstrates the integrability of the surface-tension-free Laplacian growth process. This formulation holds as long as the singularities of the map are confined to within the unit circle. This approach further allows for surface tension to be introduced as an energetic term in the resulting Hamiltonian which effects repulsion between the quasi-particles and the surface. These results are used here to formulate a first-principles statistical theory of pattern formation in stochastic growth, where noise is a key player.
Technology Transfer Automated Retrieval System (TEKTRAN)
Quorum sensing transcriptional regulator SdiA has been shown to enhance the survival of Escherichia coli O157:H7 (O157) in the acidic compartment of bovine rumen in response to N-acyl-L-homoserine lactones (AHLs) produced by the rumen bacteria. Bacteria that survive the rumen environment subsequentl...
Cerpa, Alberto E.
SDI: Solar Dome Instrument for Solar Irradiance Monitoring Tao Liu1, Ankur U. Kamthe1, Varick L data for ground solar irradiance (direct normal and global irradiance) is a major obstacle for the de- velopment of adequate policies to promote and take advan- tage of existing solar technologies. Although
Bleicher, M; Liu, F M; Keränen, A; Aichelin, J; Bass, S A; Becattini, F; Redlich, K; Werner, K
2002-05-20
The Omega/Omega ratio originating from string decays is predicted to be larger than unity in proton-proton interactions at SPS energies ( E(lab) = 160 GeV). The antiomega dominance increases with decreasing beam energy. This surprising behavior is caused by the combinatorics of quark-antiquark production in small and low-mass strings. Since this behavior is not found in a statistical description of hadron production in proton-proton collisions, it may serve as a key observable to probe the hadronization mechanism in such collisions. PMID:12005560
Thompson, Keiran C.; Crittenden, Deborah L.; Kable, Scott H.; Jordan, Meredith J.T. [School of Chemistry, University of Sydney, New South Wales 2006 (Australia)
2006-01-28
Previous experimental and theoretical studies of the radical dissociation channel of T{sub 1} acetaldehyde show conflicting behavior in the HCO and CH{sub 3} product distributions. To resolve these conflicts, a full-dimensional potential-energy surface for the dissociation of CH{sub 3}CHO into HCO and CH{sub 3} fragments over the barrier on the T{sub 1} surface is developed based on RO-CCSD(T)/cc-pVTZ(DZ) ab initio calculations. 20 000 classical trajectories are calculated on this surface at each of five initial excess energies, spanning the excitation energies used in previous experimental studies, and translational, vibrational, and rotational distributions of the radical products are determined. For excess energies near the dissociation threshold, both the HCO and CH{sub 3} products are vibrationally cold; there is a small amount of HCO rotational excitation and little CH{sub 3} rotational excitation, and the reaction energy is partitioned dominantly (>90% at threshold) into relative translational motion. Close to threshold the HCO and CH{sub 3} rotational distributions are symmetrically shaped, resembling a Gaussian function, in agreement with observed experimental HCO rotational distributions. As the excess energy increases the calculated HCO and CH{sub 3} rotational distributions are observed to change from a Gaussian shape at threshold to one more resembling a Boltzmann distribution, a behavior also seen by various experimental groups. Thus the distribution of energy in these rotational degrees of freedom is observed to change from nonstatistical to apparently statistical, as excess energy increases. As the energy above threshold increases all the internal and external degrees of freedom are observed to gain population at a similar rate, broadly consistent with equipartitioning of the available energy at the transition state. These observations generally support the practice of separating the reaction dynamics into two reservoirs: an impulsive reservoir, fed by the exit channel dynamics, and a statistical reservoir, supported by the random distribution of excess energy above the barrier. The HCO rotation, however, is favored by approximately a factor of 3 over the statistical prediction. Thus, at sufficiently high excess energies, although the HCO rotational distribution may be considered statistical, the partitioning of energy into HCO rotation is not.
Statistical analysis of global wind dynamics in vigorous Rayleigh-Bénard convection.
Petschel, K; Wilczek, M; Breuer, M; Friedrich, R; Hansen, U
2011-08-01
Experimental and numerical studies of thermal convection have shown that sufficiently vigorous convective flows exhibit a large-scale thermal wind component sweeping along small-scale thermal boundary layer instabilities. A characteristic feature of these flows is an intermittent behavior in the form of irregular reversals in the orientation of the large-scale circulation. There have been several attempts toward a better understanding and description of the phenomenon of flow reversals, but so far most of these models are based on a statistical analysis of few-point measurements or on simplified theoretical assumptions. The analysis of long-term data sets (>5×10(5) turnover times ?(t)=d/u(rms)) obtained by numerical simulations of turbulent two-dimensional Rayleigh-Bénard convection allows us to get a more comprehensive view of the spatio-temporal flow behavior. By means of a global statistical analysis of the characteristic spatial modes of the flow we extract information about the stability of dominant large-scale modes as well as the reversal paths in state subspace. We examine probability density functions and drift vector fields of two-dimensional state subspaces spanned by different large-scale spatial modes. This also provides information about the coexistence of dominant modes. PMID:21929092
Dynamics and Statistical Mechanics of Rotating and non-Rotating Vortical Flows
Lim, Chjan [RPI] [RPI
2013-12-18
Three projects were analyzed with the overall aim of developing a computational/analytical model for estimating values of the energy, angular momentum, enstrophy and total variation of fluid height at phase transitions between disordered and self-organized flow states in planetary atmospheres. It is believed that these transitions in equilibrium statistical mechanics models play a role in the construction of large-scale, stable structures including super-rotation in the Venusian atmosphere and the formation of the Great Red Spot on Jupiter. Exact solutions of the spherical energy-enstrophy models for rotating planetary atmospheres by Kac's method of steepest descent predicted phase transitions to super-rotating solid-body flows at high energy to enstrophy ratio for all planetary spins and to sub-rotating modes if the planetary spin is large enough. These canonical statistical ensembles are well-defined for the long-range energy interactions that arise from 2D fluid flows on compact oriented manifolds such as the surface of the sphere and torus. This is because in Fourier space available through Hodge theory, the energy terms are exactly diagonalizable and hence has zero range, leading to well-defined heat baths.
Avalanche statistics and time-resolved grain dynamics for a driven heap
A. R. Abate; H. Katsuragi; D. J. Durian
2007-01-01
We probe the dynamics of intermittent avalanches caused by steady addition of grains to a quasi-two-dimensional heap. To characterize the time-dependent average avalanche flow speed v(t) , we image the top free surface. To characterize the grain fluctuation speed deltav(t) , we use speckle-visibility spectroscopy. During an avalanche, we find that the fluctuation speed is approximately one-tenth the average flow
End-to-End Internet Video Traffic Dynamics: Statistical Study and Analysis
Dmitri Loguinov; Hayder Radha
2002-01-01
In this paper, we analyze the dynamics of a seven- month real-time streaming experiment, which was conducted between a number of unicast dialup clients, connecting to the Internet through access points in more than 600 major U.S. cities, and a backbone video server. During the experiment, the clients streamed low-bitrate MPEG-4 video sequences from the server over paths with more
Regulation of signal duration and the statistical dynamics of kinase activation by scaffold proteins
Jason W. Locasale; Arup K. Chakraborty
2008-10-29
Scaffolding proteins that direct the assembly of multiple kinases into a spatially localized signaling complex are often essential for the maintenance of an appropriate biological response. Although scaffolds are widely believed to have dramatic effects on the dynamics of signal propagation, the mechanisms that underlie these consequences are not well understood. Here, Monte Carlo simulations of a model kinase cascade are used to investigate how the temporal characteristics of signaling cascades can be influenced by the presence of scaffold proteins. Specifically, we examine the effects of spatially localizing kinase components on a scaffold on signaling dynamics. The simulations indicate that a major effect that scaffolds exert on the dynamics of cell signaling is to control how the activation of protein kinases is distributed over time. Scaffolds can influence the timing of kinase activation by allowing for kinases to become activated over a broad range of times, thus allowing for signaling at both early and late times. Scaffold concentrations that result in optimal signal amplitude also result in the broadest distributions of times over which kinases are activated. These calculations provide insights into one mechanism that describes how the duration of a signal can potentially be regulated in a scaffold mediated protein kinase cascade. Our results illustrate another complexity in the broad array of control properties that emerge from the physical effects of spatially localizing components of kinase cascades on scaffold proteins.
NASA Technical Reports Server (NTRS)
Avissar, Roni
1992-01-01
A parameterization of land surfaces based on a statistical-dynamical approach is presented. With this approach, the most important characteristics of the soil-plant-atmosphere system that affect the partition of energy (e.g., plant stomatal conductance, soil humidity, and surface roughness) are represented by a pdf rather than by a single 'representative' value. A primary simplified version of this parameterization is used to estimate the land-surface energy fluxes that are produced at the grid scale by various distributions of stomatal conductance under a broad range of environmental conditions. To demonstrate the approach's potential, results are compared with the same fluxes calculated with a big leaf model using the mean stomatal conductance that corresponds to the distributions. Large absolute and relative differences are obtained between the two schemes for many combinations of stomatal conductance pdfs and environmental conditions.
Statistical Properties and Multifractal Behaviors of Market Returns by Ising Dynamic Systems
NASA Astrophysics Data System (ADS)
Fang, Wen; Wang, Jun
An interacting-agent model of speculative activity explaining price formation in financial markets is considered in the present paper, which based on the stochastic Ising model and the mean field theory. The model describes the interaction strength among the agents as well as an external field, and the corresponding random logarithmic price return process is investigated. According to the empirical research of the model, the time series formed by this Ising model exhibits the bursting typical of volatility clustering, the fat-tail phenomenon, the power-law distribution tails and the long-time memory. The statistical properties of the returns of Hushen 300 Index, Shanghai Stock Exchange (SSE) Composite Index and Shenzhen Stock Exchange (SZSE) Component Index are also studied for comparison between the real time series and the simulated ones. Further, the multifractal detrended fluctuation analysis is applied to investigate the time series returns simulated by Ising model have the distribution multifractality as well as the correlation multifractality.
DYNAMIC STABILITY OF THE SOLAR SYSTEM: STATISTICALLY INCONCLUSIVE RESULTS FROM ENSEMBLE INTEGRATIONS
Zeebe, Richard E., E-mail: zeebe@soest.hawaii.edu [School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, 1000 Pope Road, MSB 629, Honolulu, HI 96822 (United States)
2015-01-01
Due to the chaotic nature of the solar system, the question of its long-term stability can only be answered in a statistical sense, for instance, based on numerical ensemble integrations of nearby orbits. Destabilization of the inner planets, leading to close encounters and/or collisions can be initiated through a large increase in Mercury's eccentricity, with a currently assumed likelihood of ?1%. However, little is known at present about the robustness of this number. Here I report ensemble integrations of the full equations of motion of the eight planets and Pluto over 5 Gyr, including contributions from general relativity. The results show that different numerical algorithms lead to statistically different results for the evolution of Mercury's eccentricity (e{sub M}). For instance, starting at present initial conditions (e{sub M}?0.21), Mercury's maximum eccentricity achieved over 5 Gyr is, on average, significantly higher in symplectic ensemble integrations using heliocentric rather than Jacobi coordinates and stricter error control. In contrast, starting at a possible future configuration (e{sub M}?0.53), Mercury's maximum eccentricity achieved over the subsequent 500 Myr is, on average, significantly lower using heliocentric rather than Jacobi coordinates. For example, the probability for e{sub M} to increase beyond 0.53 over 500 Myr is >90% (Jacobi) versus only 40%-55% (heliocentric). This poses a dilemma because the physical evolution of the real system—and its probabilistic behavior—cannot depend on the coordinate system or the numerical algorithm chosen to describe it. Some tests of the numerical algorithms suggest that symplectic integrators using heliocentric coordinates underestimate the odds for destabilization of Mercury's orbit at high initial e{sub M}.
STATISTICAL METHODS STATISTICAL METHODS
Delorme, Arnaud
STATISTICAL METHODS 1 STATISTICAL METHODS Arnaud Delorme, Swartz Center for Computational@salk.edu. Keywords: statistical methods, inference, models, clinical, software, bootstrap, resampling, PCA, ICA Abstract: Statistics represents that body of methods by which characteristics of a population are inferred
Anisotropy and shear-layer edge dynamics of statistically unsteady, stratified turbulence
NASA Astrophysics Data System (ADS)
Wingstedt, E. M. M.; Fossum, H. E.; Pettersson Reif, B. A.; Werne, J.
2015-06-01
Direct numerical simulation data of an evolving Kelvin-Helmholtz instability have been analyzed in order to characterize the dynamic and kinematic response of shear-generated turbulent flow to imposed stable stratification. Particular emphasis was put on anisotropy and shear-layer edge dynamics in the net kinetic energy decay phase of the Kelvin-Helmholtz evolution. Results indicate a faster increase of small-scale anisotropy compared to large-scale anisotropy. Also, the anisotropy of thermal dissipation differs significantly from that of viscous dissipation. It is found that the Reynolds stress anisotropy increases up to a stratification level roughly corresponding to Rig ? 0.4, but subsequently decreases for higher levels of stratification, most likely due to relaminarization. Coherent large-scale turbulence structures are cylindrical in the center of the shear layer, whereas they become ellipsoidal in the strongly stratified edge-layer region. The structures of the Reynolds stresses are highly one-componental in the center and turn two-componental as stratification increases. Stratification affects all scales, but it seems to affect larger scales to a higher degree than smaller scales and thermal scales more strongly than momentum scales. The effect of strong stable stratification at the edge of the shear layer is highly reminiscent of the non-local pressure effects of solid walls. However, the kinematic blocking inherently associated with impermeable walls is not observed in the edge layer. Vertical momentum flux reversal is found in part of the shear layer. The roles of shear and buoyant production of turbulence kinetic energy are exchanged, and shear production is transferring energy into the mean flow field, which contributes to relaminarization. The change in dynamics near the edge of the shear layer has important implications for predictive turbulence model formulations.
Escape beam statistics and dynamical properties for a periodically corrugated waveguide
NASA Astrophysics Data System (ADS)
da Costa, Diogo Ricardo; Silva, Mário R.; Leonel, Edson D.
2014-04-01
Some escape and dynamical properties for a beam of light inside a corrugated waveguide are discussed by using Fresnel reflectance. The system is described by a mapping and is controlled by a parameter ? defining a transition from integrability (?=0) to non integrability (??0). The phase space is mixed containing periodic islands, chaotic seas and invariant tori. The histogram of escaping orbits is shown to be scaling invariant with respect to ?. The waveguide is immersed in a region with different refractive index. Different optical materials are used to overcame the results.
Avalanche statistics and time-resolved grain dynamics for a driven heap
A. R. Abate; H. Katsuragi; D. J. Durian
2007-01-01
We probe the dynamics of intermittent avalanches caused by steady addition of\\u000agrains to a quasi-two dimensional heap. To characterize the time-dependent\\u000aaverage avalanche flow speed v(t), we image the top free surface. To\\u000acharacterize the grain fluctuation speed dv(t), we use Speckle-Visibility\\u000aSpectroscopy. During an avalanche, we find that the fluctuation speed is\\u000aapproximately one-tenth the average flow speed,
Temporal Dynamics and Nonclassical Photon Statistics of Quadratically Coupled Optomechanical Systems
NASA Astrophysics Data System (ADS)
Singh, Shailendra Kumar; Muniandy, S. V.
2015-05-01
Quantum optomechanical system serves as an interface for coupling between photons and phonons due to mechanical oscillations. We used the Heisenberg-Langevin approach under Markovian white noise approximation to study a quadratically coupled optomechanical system which contains a thin dielectric membrane quadratically coupled to the cavity field. A decorrelation method is employed to solve for a larger number of coupled equations. Transient mean numbers of cavity photons and phonons that provide dynamical behaviour are computed for different coupling regime. We have also obtained the two-boson second-order correlation functions for the cavity field, membrane oscillator and their cross correlations that provide nonclassical properties governed by quadratic optomechanical system.
Temporal Dynamics and Nonclassical Photon Statistics of Quadratically Coupled Optomechanical Systems
Shailendra Kumar Singh; S. V. Muniandy
2015-06-24
Quantum optomechanical system serves as an interface for coupling between photons and phonons due to mechanical oscillations. We used the Heisenberg-Langevin approach under Markovian white noise approximation to study a quadratically coupled optomechanical system which contains a thin dielectric membrane quadratically coupled to the cavity field. A decorrelation method is employed to solve for a larger number of coupled equations. Transient mean numbers of cavity photons and phonons that provide dynamical behaviour are computed for different coupling regime. We have also obtained the two-boson second-order correlation functions for the cavity field, membrane oscillator and their cross correlations that provide nonclassical properties governed by quadratic optomechanical system.
Hawe, David; Hernández Fernández, Francisco R.; O’Suilleabháin, Liam; Huang, Jian; Wolsztynski, Eric; O’Sullivan, Finbarr
2012-01-01
In dynamic mode, positron emission tomography (PET) can be used to track the evolution of injected radio-labelled molecules in living tissue. This is a powerful diagnostic imaging technique that provides a unique opportunity to probe the status of healthy and pathological tissue by examining how it processes substrates. The spatial aspect of PET is well established in the computational statistics literature. This article focuses on its temporal aspect. The interpretation of PET time-course data is complicated because the measured signal is a combination of vascular delivery and tissue retention effects. If the arterial time-course is known, the tissue time-course can typically be expressed in terms of a linear convolution between the arterial time-course and the tissue residue. In statistical terms, the residue function is essentially a survival function - a familiar life-time data construct. Kinetic analysis of PET data is concerned with estimation of the residue and associated functionals such as flow, flux, volume of distribution and transit time summaries. This review emphasises a nonparametric approach to the estimation of the residue based on a piecewise linear form. Rapid implementation of this by quadratic programming is described. The approach provides a reference for statistical assessment of widely used one- and two-compartmental model forms. We illustrate the method with data from two of the most well-established PET radiotracers, 15O-H2O and 18F-fluorodeoxyglucose, used for assessment of blood perfusion and glucose metabolism respectively. The presentation illustrates the use of two open-source tools, AMIDE and R, for PET scan manipulation and model inference. PMID:23087780
Ramalingam, Shivaji G; Hamon, Lomig; Pré, Pascaline; Giraudet, Sylvain; Le Coq, Laurence; Le Cloirec, Pierre
2012-07-01
Adsorption of Volatile Organic Compounds (VOCs) is one of the best remediation techniques for controlling industrial air pollution. In this paper, a quantitative predictor model for the characteristic adsorption energy (E) of the Dubinin-Radushkevich (DR) isotherm model has been established with R(2) value of 0.94. A predictor model for characteristic adsorption energy (E) has been established by using Multiple Linear Regression (MLR) analysis in a statistical package MINITAB. The experimental value of characteristic adsorption energy was computed by modeling the isotherm equilibrium data (which contain 120 isotherms involving five VOCs and eight activated carbons at 293, 313, 333, and 353 K) with the Gauss-Newton method in a statistical package R-STAT. The MLR model has been validated with the experimental equilibrium isotherm data points, and it will be implemented in the dynamic adsorption simulation model PROSIM. By implementing this model, it predicts an enormous range of 1200 isotherm equilibrium coefficients of DR model at different temperatures such as 293, 313, 333, and 353K (each isotherm has 10 equilibrium points by changing the concentration) just by a simple MLR characteristic energy model without any experiments. PMID:22503987
How Electronic Dynamics with Pauli Exclusion Produces Fermi-Dirac Statistics
Triet Nguyen; Ravindra Nanguneri; John Parkhill
2015-01-15
It is important that any dynamics method approaches the correct population distribution at long times. In this paper, we derive a one-body reduced density matrix dynamics for electrons in energetic contact with a bath. We obtain a remarkable equation of motion which shows that in order to reach equilibrium properly, rates of electron transitions depend on the density matrix. Even though the bath drives the electrons towards a Boltzmann distribution, hole blocking factors in our equation of motion cause the electronic populations to relax to a Fermi-Dirac distribution. These factors are an old concept, but we show how they can be derived with a combination of time-dependent perturbation theory, and the extended normal ordering of Mukherjee and Kutzelnigg. The resulting non-equilibrium kinetic equations generalize the usual Redfield theory to many-electron systems, while ensuring that the orbital occupations remain between zero and one. In numerical applications of our equations, we show that relaxation rates of molecules are not constant because of the blocking effect. Other applications to model atomic chains are also presented which highlight the importance of treating both dephasing and relaxation. Finally we show how the bath localizes the electron density matrix.
Financial price dynamics and pedestrian counterflows: A comparison of statistical stylized facts
NASA Astrophysics Data System (ADS)
Parisi, Daniel R.; Sornette, Didier; Helbing, Dirk
2013-01-01
We propose and document the evidence for an analogy between the dynamics of granular counterflows in the presence of bottlenecks or restrictions and financial price formation processes. Using extensive simulations, we find that the counterflows of simulated pedestrians through a door display eight stylized facts observed in financial markets when the density around the door is compared with the logarithm of the price. Finding so many stylized facts is very rare indeed among all agent-based models of financial markets. The stylized properties are present when the agents in the pedestrian model are assumed to display a zero-intelligent behavior. If agents are given decision-making capacity and adapt to partially follow the majority, periods of herding behavior may additionally occur. This generates the very slow decay of the autocorrelation of absolute return due to an intermittent dynamics. Our findings suggest that the stylized facts in the fluctuations of the financial prices result from a competition of two groups with opposite interests in the presence of a constraint funneling the flow of transactions to a narrow band of prices with limited liquidity.
Dynamical phase transition for current statistics in a simple driven diffusive system
Carlos P. Espigares; Pedro L. Garrido; Pablo I. Hurtado
2012-12-19
We consider fluctuations of the time-averaged current in the one-dimensional weakly-asymmetric exclusion process on a ring. The optimal density profile which sustains a given fluctuation exhibits an instability for low enough currents, where it becomes time-dependent. This instability corresponds to a dynamical phase transition in the system fluctuation behavior: while typical current fluctuations result from the sum of weakly-correlated local events and are still associated with the flat, steady-state density profile, for currents below a critical threshold the system self-organizes into a macroscopic jammed state in the form of a coherent traveling wave, that hinders transport of particles and thus facilitates a time-averaged current fluctuation well below the average current. We analyze in detail this phenomenon using advanced Monte Carlo simulations, and work out macroscopic fluctuation theory predictions, finding very good agreement in all cases. In particular, we study not only the current large deviation function, but also the critical current threshold, the associated optimal density profiles and the traveling wave velocity, analyzing in depth finite-size effects and hence providing a detailed characterization of the dynamical transition.
Nichols, J.M.; Moniz, L.; Nichols, J.D.; Pecora, L.M.; Cooch, E.
2005-01-01
A number of important questions in ecology involve the possibility of interactions or ?coupling? among potential components of ecological systems. The basic question of whether two components are coupled (exhibit dynamical interdependence) is relevant to investigations of movement of animals over space, population regulation, food webs and trophic interactions, and is also useful in the design of monitoring programs. For example, in spatially extended systems, coupling among populations in different locations implies the existence of redundant information in the system and the possibility of exploiting this redundancy in the development of spatial sampling designs. One approach to the identification of coupling involves study of the purported mechanisms linking system components. Another approach is based on time series of two potential components of the same system and, in previous ecological work, has relied on linear cross-correlation analysis. Here we present two different attractor-based approaches, continuity and mutual prediction, for determining the degree to which two population time series (e.g., at different spatial locations) are coupled. Both approaches are demonstrated on a one-dimensional predator?prey model system exhibiting complex dynamics. Of particular interest is the spatial asymmetry introduced into the model as linearly declining resource for the prey over the domain of the spatial coordinate. Results from these approaches are then compared to the more standard cross-correlation analysis. In contrast to cross-correlation, both continuity and mutual prediction are clearly able to discern the asymmetry in the flow of information through this system.
A statistical study of plasma sheet dynamics using ISEE 1 and 2 energetic particle flux data
NASA Technical Reports Server (NTRS)
Dandouras, J.; Reme, H.; Saint-Marc, A.; Sauvaud, J. A.; Parks, G. K.
1986-01-01
Plasma sheet dynamics during substorms are studied by analyzing 461 cases of transient dropout events of the 1.5 and 6-keV particle fluxes detected by ISEE 1 and 2 satellites. The instruments for detecting low- and high-energy particles are described. The spatial distribution of flux dropout events, and the events' relationship to magnetospheric activity level are examined. Substorm events without observed flux dropout events are investigated. The data reveal that the flux dropout distribution is isotropic, between 12-23 earth radii, and is present in the entire nightside plasma sheet; and the substorms without flux dropout are more frequent near earth and magnetospheric flanks. It is observed that tailward of 12 earth radii the flux dropout events and substorms without flux dropout are similar. The Chao et al. (1977) MHD rarefaction wave propagation model and the Hones (1973, 1980) near-tail, X-type magnetic neutral line formation model are discussed and compared to the experimental data. It is noted that neither model explains the plasma sheet dynamics observed.
NASA Astrophysics Data System (ADS)
Habasaki, J.; Ngai, K. L.
2013-08-01
Molecular dynamics simulations have been performed to study the structures along the pressure-volume diagram of network-glasses and melts exemplified by the lithium disilicate system. Experimentally, densification of the disilicate glass by elevated pressure is known and this feature is reasonably reproduced by the simulations. During the process of densification or decompression of the system, the statistics of Qn (i.e., SiO4 tetrahedron unit with n bridging oxygen linked to the silicon atom where n = 0, 1, 2, 3, or 4) change, and the percentage of the Q3 structures show the maximum value near atmospheric pressure at around Tg. Changes of Qn distribution are driven by the changes of volume (or pressure) and are explained by the different volumes of structural units. Furthermore, some pairs of network structures with equi-volume, but having different distributions of Qn (or different heterogeneity), are found. Therefore, for molecular dynamics simulations of the Qn distributions, it is important to take into account the complex phase behavior including poly-structures with different heterogeneities as well as the position of the system in the P-V-T diagram.
Avalanche statistics and time-resolved grain dynamics for a driven heap
A. R. Abate; H. Katsuragi; D. J. Durian
2007-08-08
We probe the dynamics of intermittent avalanches caused by steady addition of grains to a quasi-two dimensional heap. To characterize the time-dependent average avalanche flow speed v(t), we image the top free surface. To characterize the grain fluctuation speed dv(t), we use Speckle-Visibility Spectroscopy. During an avalanche, we find that the fluctuation speed is approximately one-tenth the average flow speed, and that these speeds are largest near the beginning of an event. We also find that the distribution of event durations is peaked, and that event sizes are correlated with the time interval since the end of the previous event. At high rates of grain addition, where successive avalanches merge into smooth continuous flow, the relationship between average and fluctuation speeds changes to dv Sqrt[v].
A stochastic-dynamic model for global atmospheric mass field statistics
NASA Technical Reports Server (NTRS)
Ghil, M.; Balgovind, R.; Kalnay-Rivas, E.
1981-01-01
A model that yields the spatial correlation structure of atmospheric mass field forecast errors was developed. The model is governed by the potential vorticity equation forced by random noise. Expansion in spherical harmonics and correlation function was computed analytically using the expansion coefficients. The finite difference equivalent was solved using a fast Poisson solver and the correlation function was computed using stratified sampling of the individual realization of F(omega) and hence of phi(omega). A higher order equation for gamma was derived and solved directly in finite differences by two successive applications of the fast Poisson solver. The methods were compared for accuracy and efficiency and the third method was chosen as clearly superior. The results agree well with the latitude dependence of observed atmospheric correlation data. The value of the parameter c sub o which gives the best fit to the data is close to the value expected from dynamical considerations.
NASA Astrophysics Data System (ADS)
Vaittinada Ayar, Pradeebane; Vrac, Mathieu; Bastin, Sophie; Carreau, Julie; Déqué, Michel; Gallardo, Clemente
2015-05-01
Given the coarse spatial resolution of General Circulation Models, finer scale projections of variables affected by local-scale processes such as precipitation are often needed to drive impacts models, for example in hydrology or ecology among other fields. This need for high-resolution data leads to apply projection techniques called downscaling. Downscaling can be performed according to two approaches: dynamical and statistical models. The latter approach is constituted by various statistical families conceptually different. If several studies have made some intercomparisons of existing downscaling models, none of them included all those families and approaches in a manner that all the models are equally considered. To this end, the present study conducts an intercomparison exercise under the EURO- and MED-CORDEX initiative hindcast framework. Six Statistical Downscaling Models (SDMs) and five Regional Climate Models (RCMs) are compared in terms of precipitation outputs. The downscaled simulations are driven by the ERAinterim reanalyses over the 1989-2008 period over a common area at 0.44° of resolution. The 11 models are evaluated according to four aspects of the precipitation: occurrence, intensity, as well as spatial and temporal properties. For each aspect, one or several indicators are computed to discriminate the models. The results indicate that marginal properties of rain occurrence and intensity are better modelled by stochastic and resampling-based SDMs, while spatial and temporal variability are better modelled by RCMs and resampling-based SDM. These general conclusions have to be considered with caution because they rely on the chosen indicators and could change when considering other specific criteria. The indicators suit specific purpose and therefore the model evaluation results depend on the end-users point of view and how they intend to use with model outputs. Nevertheless, building on previous intercomparison exercises, this study provides a consistent intercomparison framework, including both SDMs and RCMs, which is designed to be flexible, i.e., other models and indicators can easily be added. More generally, this framework provides a tool to select the downscaling model to be used according to the statistical properties of the local-scale climate data to drive properly specific impact models.
Globus, Tatiana; Sizov, Igor; Gelmont, Boris
2014-01-01
Hydrogen bonds (H-bonds) in biological macromolecules are important for the molecular structure and functions. Since interactions via hydrogen bonds are weaker than covalent bonds, it can be expected that atomic movements involving H-bonds have low frequency vibrational modes. Sub-Terahertz (sub-THz) vibrational spectroscopy that combines measurements with molecular dynamics (MD) computational prediction has been demonstrated as a promising approach for biological molecule characterization. Multiple resonance absorption lines have been reported. The knowledge of relaxation times of atomic oscillations is critical for the successful application of THz spectroscopy for hydrogen bond characterization. The purpose of this work is to use atomic oscillations in the 0.35-0.7 THz range, found from molecular dynamic (MD) simulations of E.coli thioredoxin (2TRX), to study relaxation dynamics of two intra-molecular H-bonds, OH-N and OH-C. Two different complimentary techniques are used in this study, one is the analysis of the statistical distribution of relaxation time and dissipation factor values relevant to low frequency oscillations, and the second is the analysis of the autocorrelation function of low frequency quasi-periodic movements. By studying hydrogen bond atomic displacements, it was found that the atoms are involved in a number of collective oscillations, which are characterized by different relaxation time scales ranging from 2-3 ps to more than 150 ps. The existence of long lasting relaxation processes opens the possibility to directly observe and study H-bond vibrational modes in sub-THz absorption spectra of bio-molecules if measured with an appropriate spectral resolution. The results of measurements using a recently developed frequency domain spectroscopic sensor with a spectral resolution of 1 GHz confirm the MD analysis. PMID:25415676
NASA Astrophysics Data System (ADS)
Reyers, Mark; Pinto, Joaquim G.; Moemken, Julia
2015-04-01
A statistical-dynamical downscaling (SDD) approach for the regionalisation of wind energy output (Eout) over Europe with special focus on Germany is proposed. SDD uses an extended circulation weather type (CWT) analysis on global daily MSLP fields with the central point being located over Germany. 77 weather classes based on the associated circulation weather type and the intensity of the geostrophic flow are identified. Representatives of these classes are dynamical downscaled with the regional climate model COSMO-CLM. By using weather class frequencies of different datasets the simulated representatives are recombined to probability density functions (PDFs) of near-surface wind speed and finally to Eout of a sample wind turbine for present and future climate. This is performed for reanalysis, decadal hindcasts and long-term future projections. For evaluation purposes results of SDD are compared to wind observations and to simulated Eout of purely dynamical downscaling (DD) methods. For the present climate SDD is able to simulate realistic PDFs of 10m-wind speed for most stations in Germany. The resulting spatial Eout patterns are similar to DD simulated Eout. In terms of decadal hindcasts results of SDD are similar to DD simulated Eout over Germany, Poland, Czech Republic, and Benelux, for which high correlations between annual Eout timeseries of SDD and DD are detected for selected hindcasts. Lower correlation is found for other European countries. It is demonstrated that SDD can be used to downscale the full ensemble of the MPI-ESM decadal prediction system. Long-term climate change projections in SRES scenarios of ECHAM5/MPI-OM as obtained by SDD agree well to results of other studies using DD methods, with increasing Eout over Northern Europe and a negative trend over Southern Europe. Despite some biases it is concluded that SDD is an adequate tool to assess regional wind energy changes in large model ensembles.
NASA Astrophysics Data System (ADS)
Savcheva, A. S.; McKillop, S. C.; McCauley, P. I.; Hanson, E. M.; DeLuca, E. E.
2014-09-01
We present a new sigmoid catalog covering the duration of the Hinode mission and the Solar Dynamics Observatory (SDO) until the end of 2012. The catalog consists of 72 mostly long-lasting sigmoids. We collect and make available all X-ray and EUV data from Hinode, SDO, and the Solar TErrestrial RElations Observatory (STEREO), and we determine the sigmoid lifetimes, sizes, and aspect ratios. We also collect the line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) for SDO or the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO) to measure flux versus time for the lifetime of each region. We determine that the development of a sigmoidal shape and eruptive activity is more strongly correlated with flux cancelation than with emergence. We find that the eruptive properties of the regions correlate well with the maximum flux, largest change, and net change in flux in the regions. These results have implications for constraining future flux-rope models of ARs and gaining insight into their evolutionary properties.
Martín-Solís, José Ramón
Quiet-time statistics: A tool to probe the dynamics of self-organized-criticality systems from of a self- organized-criticality system even when the strong-overlapping or hydrodynamic regime in which.1103/PhysRevE.66.036124 PACS number s : 05.65. b, 45.70. n, 52.25.Fi I. INTRODUCTION Self-organized
NASA Astrophysics Data System (ADS)
Chatzopoulos, S.; Fritz, T. K.; Gerhard, O.; Gillessen, S.; Wegg, C.; Genzel, R.; Pfuhl, O.
2015-02-01
We derive new constraints on the mass, rotation, orbit structure, and statistical parallax of the Galactic old nuclear star cluster and the mass of the supermassive black hole. We combine star counts and kinematic data from Fritz et al., including 2500 line-of-sight velocities and 10 000 proper motions obtained with VLT instruments. We show that the difference between the proper motion dispersions ?l and ?b cannot be explained by rotation, but is a consequence of the flattening of the nuclear cluster. We fit the surface density distribution of stars in the central 1000 arcsec by a superposition of a spheroidal cluster with scale ˜100 arcsec and a much larger nuclear disc component. We compute the self-consistent two-integral distribution function f(E, Lz) for this density model, and add rotation self-consistently. We find that (i) the orbit structure of the f(E, Lz) gives an excellent match to the observed velocity dispersion profiles as well as the proper motion and line-of-sight velocity histograms, including the double-peak in the vl-histograms. (ii) This requires an axial ratio near q1 = 0.7 consistent with our determination from star counts, q1 = 0.73 ± 0.04 for r < 70 arcsec. (iii) The nuclear star cluster is approximately described by an isotropic rotator model. (iv) Using the corresponding Jeans equations to fit the proper motion and line-of-sight velocity dispersions, we obtain best estimates for the nuclear star cluster mass, black hole mass, and distance M*(r < 100 arcsec) = (8.94 ± 0.31|stat ± 0.9|syst) × 106 M?, M• = (3.86 ± 0.14|stat ± 0.4|syst) × 106 M?, and R0 = 8.27 ± 0.09|stat ± 0.1|syst kpc, where the estimated systematic errors account for additional uncertainties in the dynamical modelling. (v) The combination of the cluster dynamics with the S-star orbits around Sgr A* strongly reduces the degeneracy between black hole mass and Galactic Centre distance present in previous S-star studies. A joint statistical analysis with the results of Gillessen et al., gives M• = (4.23 ± 0.14) × 106 M? and R0 = 8.33 ± 0.11 kpc.
Purdue Agriculture Annual Statistical Report
, informatics and statistics, biophysics, molecular genetics, breeding, genetic engineering of plants Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 A bumpy road to energy
Wang, Hai-long; Zhang, Zhou-long
2014-09-01
Ultrasonic light scattering tomography system is a new imaging technique for breast function, which associates with diffused optical tomography (DOT) with ultrasonic examination. It locates breast neoplasm with ultrasonic examination and measures the total hemoglobin concentration inside the tumor with DOT photon emission to reflect the metabolic state of tumors and then comes to synthesis diagnostic index to judge benign and malignant tumors. This diagnosis method has significant affection on diagnosis of benign and malignant tumors at home and abroad. In the development of breast cancer, local tissue hypoxia leads to a large number of new blood vessels when the tumor grows faster than the rate of angiogenesis. A recent study found microvessel density (MVD), vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1 alpha (HIF-1?) play a major role in angiogenesis of breast cancer. This study analyses the relationship between breast cancer ultrasound synthesis diagnostic index (SDI) and the expression of MVD, VEGF and HIF-1? by testing the expression level of the breast cancer gene MVD, VEGF and HIF-1?. PMID:24659092
NASA Astrophysics Data System (ADS)
Mackay, R. M.; Khalil, M. A. K.
1995-10-01
The zonally averaged response of the Global Change Research Center two-dimensional (2-D) statistical dynamical climate model (GCRC 2-D SDCM) to a doubling of atmospheric carbon dioxide (350 parts per million by volume (ppmv) to 700 ppmv) is reported. The model solves the two-dimensional primitive equations in finite difference form (mass continuity, Newton's second law, and the first law of thermodynamics) for the prognostic variables: zonal mean density, zonal mean zonal velocity, zonal mean meridional velocity, and zonal mean temperature on a grid that has 18 nodes in latitude and 9 vertical nodes (plus the surface). The equation of state, p=?RT, and an assumed hydrostatic atmosphere, Delta;p=-?g?z, are used to diagnostically calculate the zonal mean pressure and vertical velocity for each grid node, and the moisture balance equation is used to estimate the precipitation rate. The model includes seasonal variations in solar intensity, including the effects of eccentricity, and has observed land and ocean fractions set for each zone. Seasonally varying values of cloud amounts, relative humidity profiles, ozone, and sea ice are all prescribed in the model. Equator to pole ocean heat transport is simulated in the model by turbulent diffusion. The change in global mean annual surface air temperature due to a doubling of atmospheric CO2 in the 2-D model is 1.61 K, which is close to that simulated by the one-dimensional (1-D) radiative convective model (RCM) which is at the heart of the 2-D model radiation code (1.67 K for the moist adiabatic lapse rate assumption in 1-D RCM). We find that the change in temperature structure of the model atmosphere has many of the characteristics common to General Circulation Models, including amplified warming at the poles and the upper tropical troposphere, and stratospheric cooling. Because of the potential importance of atmospheric circulation feedbacks on climate change, we have also investigated the response of the zonal wind field to a doubling of CO2 and have found distinct patterns of change that are related to the change in temperature structure. In addition, we find that both the global mean kinetic energy and simulated Hadley circulation increase when CO2 is doubled. The increase in mean kinetic energy is a result of the increase in upper level meridional temperature gradients simulated by the model. It is stressed that changes in atmospheric dynamics associated with increased carbon dioxide may also be very important to the final steady state distribution of such greenhouse gases as ozone and water vapor. Hence further research in this regard is warranted.
Statistical Applets: Statistical Significance
NSDL National Science Digital Library
Duckworth, William
Created by authors Duckworth, McCabe, Moore and Sclove for W.H. Freeman of Co., this applet is designed to help students visualize the rejection region of a statistical test by allowing them to set null and alternate hypotheses, population parameters, sample statistics, and significance level. It accompanies "Â?Â?Practice of Business Statistics," but can be used without this text. Even though brief, this is a nice interactive resource for an introductory statistics course.
NASA Astrophysics Data System (ADS)
Marino, Jamir; Silva, Alessandro
2014-01-01
We discuss the nonequilibrium dynamics of a quantum Ising chain following a quantum quench of the transverse field and in the presence of a Gaussian time-dependent noise. We discuss the probability distribution of the work done on the system both for static and dynamic noise. While the effect of static noise is to smooth the low energy threshold of the statistic of the work, appearing for sudden quenches, a dynamical noise protocol affects also the spectral weight of such features. We also provide a detailed derivation of the kinetic equation for the Green's functions on the Keldysh contour and the time evolution of observables of physical interest, extending previously reported results [Marino and Silva, Phys. Rev. B 86, 060408 (2012), 10.1103/PhysRevB.86.060408], and discussing the extension of the concept of prethermalization which can be used to study noisy quantum many-body Hamiltonians driven out of equilibrium.
NASA Technical Reports Server (NTRS)
Ramirez, Daniel Perez; Lyamani, H.; Olmo, F. J.; Whiteman, D. N.; Alados-Arboledas, L.
2012-01-01
This work presents the first analysis of longterm correlative day-to-night columnar aerosol optical properties. The aim is to better understand columnar aerosol dynamic from ground-based observations, which are poorly studied until now. To this end we have used a combination of sun-and-star photometry measurements acquired in the city of Granada (37.16 N, 3.60 W, 680 ma.s.l.; South-East of Spain) from 2007 to 2010. For the whole study period, mean aerosol optical depth (AOD) around 440 nm (+/-standard deviation) is 0.18 +/- 0.10 and 0.19 +/- 0.11 for daytime and nighttime, respectively, while the mean Angstr¨om exponent (alpha ) is 1.0 +/- 0.4 and 0.9 +/- 0.4 for daytime and nighttime. The ANOVA statistical tests reveal that there are no significant differences between AOD and obtained at daytime and those at nighttime. Additionally, the mean daytime values of AOD and obtained during this study period are coherent with the values obtained in the surrounding AERONET stations. On the other hand, AOD around 440 nm present evident seasonal patterns characterised by large values in summer (mean value of 0.20 +/- 0.10 both at daytime and nighttime) and low values in winter (mean value of 0.15 +/- 0.09 at daytime and 0.17 +/- 0.10 at nighttime). The Angstr¨om exponents also present seasonal patterns, but with low values in summer (mean values of 0.8 +/- 0.4 and 0.9 +/- 0.4 at dayand night-time) and relatively large values in winter (mean values of 1.2 +/- 0.4 and 1.0 +/- 0.3 at daytime and nighttime). These seasonal patterns are explained by the differences in the meteorological conditions and by the differences in the strength of the aerosol sources. To take more insight about the changes in aerosol particles between day and night, the spectral differences of the Angstrom exponent as function of the Angstr¨om exponent are also studied. These analyses reveal increases of the fine mode radius and of the fine mode contribution to AOD during nighttime, being more remarkable in the summer seasons. These variations are explained by the changes of the local aerosol sources and by the meteorological conditions between daytime and nighttime, as well as aerosol aging processes. Case studies during summer and winter for different aerosol loads and types are also presented to clearly illustrate these findings.
NASA Astrophysics Data System (ADS)
Sun, F.; Hall, A. D.; Walton, D.; Capps, S. B.; Qu, X.; Huang, H. J.; Berg, N.; Jousse, A.; Schwartz, M.; Nakamura, M.; Cerezo-Mota, R.
2012-12-01
Using a combination of dynamical and statistical downscaling techniques, we projected mid-21st century warming in the Los Angeles region at 2-km resolution. To account for uncertainty associated with the trajectory of future greenhouse gas emissions, we examined projections for both "business-as-usual" (RCP8.5) and "mitigation" (RCP2.6) emissions scenarios from the Fifth Coupled Model Intercomparison Project (CMIP5). To account for the considerable uncertainty associated with choice of global climate model, we downscaled results for all available global climate models in CMIP5. For the business-as-usual scenario, we find that by the mid-21st century, the most likely warming is roughly 2.6°C averaged over the region's land areas, with a 95% confidence that the warming lies between 0.9 and 4.2°C. The high resolution of the projections reveals a pronounced spatial pattern in the warming: High elevations and inland areas separated from the coast by at least one mountain complex warm 20 to 50% more than the areas near the coast or within the Los Angeles basin. This warming pattern is especially apparent in summertime. The summertime warming contrast between the inland and coastal zones has a large effect on the most likely expected number of extremely hot days per year. Coastal locations and areas within the Los Angeles basin see roughly two to three times the number of extremely hot days, while high elevations and inland areas typically experience approximately three to five times the number of extremely hot days. Under the mitigation emissions scenario, the most likely warming and increase in heat extremes are somewhat smaller. However, the majority of the warming seen in the business-as-usual scenario still occurs at all locations in the most likely case under the mitigation scenario, and heat extremes still increase significantly. This warming study is the first part of a series studies of our project. More climate change impacts on the Santa Ana wind, rainfall, snowfall and snowmelt, cloud and surface hydrology are forthcoming and could be found in www.atmos.ucla.edu/csrl.he ensemble-mean, annual-mean surface air temperature change and its uncertainty from the available CMIP5 GCMs under the RCP8.5 (left) and RCP2.6 (right) emissions scenarios, unit: °C.
... Data Consumer Opinion Surveys Home / Research & Statistics Injury Statistics This is the statistic reports page for scientific ... Home Appliances, Maintenance and Construction Injury Statistics Injury Statistics September 30, 2012 Submersions Related to Non-Pool ...
NASA Astrophysics Data System (ADS)
Russotto, P.; De Filippo, E.; Pagano, A.; Acosta, L.; Auditore, L.; Baran, V.; Berceanu, I.; Borderie, B.; Bougault, R.; Bruno, M.; Cap, T.; Cardella, G.; Cavallaro, S.; Chatterjee, M. B.; Chbihi, A.; Colonna, M.; D'Agostino, M.; Di Toro, M.; Francalanza, L.; Frankland, J.; Galichet, E.; Gawlikowicz, W.; Geraci, E.; Gnoffo, B.; Grzeszczuk, A.; Guazzoni, P.; Kowalski, S.; Lanzalone, G.; Lanzanò, G.; Le Neindre, N.; Lombardo, I.; Maiolino, C.; Minniti, T.; Pagano, E. V.; Papa, M.; Piasecki, E.; Pirrone, S.; P?aneta, R.; Politi, G.; Porto, F.; Quattrocchi, L.; Rivet, M. F.; Rosato, E.; Rizzo, F.; Schmidt, K.; Siwek-Wilczy?ska, K.; Skwira-Chalot, I.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.; Wieleczko, J. P.; Wilczy?ski, J.; Zetta, L.; Zipper, W.
2015-01-01
Background: In heavy-ion collisions at intermediate energies the production of light charged particles and intermediate mass fragments (IMFs) is due to different reaction mechanisms and different time scales, ranging from fast dynamical processes to statistical emission from the equilibrated system. Purpose: We compare the IMF statistical and dynamical emission probabilities in collisions of a neutron-rich 124Sn+64Ni system and a neutron-poor 112Sn+58Ni system at the laboratory energy of 35 A MeV. Method: The IMFs production mechanism in semiperipheral reactions has been investigated in our previous works. In this paper, the analysis is expanded for the same set of data and production cross sections have been evaluated for dynamical and statistical emission in a coherent way for light and heavy fragments. Results: The data analysis has evidenced a strong competition between dynamical and statistical emission mechanisms. Probability of the dynamical emission of IMFs is strongly influenced by the (N /Z ) ratio of the colliding system. Conclusions: It is demonstrated that the statistical emission is equally probable for the two systems, while the dynamical emission is enhanced for the neutron-rich system, especially for heavy fragments (Z ?6 ). The observed effect points at a high sensitivity of the prompt-dynamical emission to the (N /Z ) ratio of a given system.
NASA Astrophysics Data System (ADS)
Quiroz-Martinez, B.; Schmitt, F. G.; Dauvin, J.-C.
2012-01-01
We consider here the dynamics of two polychaete populations based on a 20 yr temporal benthic survey of two muddy fine sand communities in the Bay of Morlaix, Western English Channel. These populations display high temporal variability, which is analyzed here using scaling approaches. We find that population densities have heavy tailed probability density functions. We analyze the dynamics of relative species abundance in two different communities of polychaetes by estimating in a novel way a "mean square drift" coefficient which characterizes their fluctuations in relative abundance over time. We show the usefulness of using new tools to approach and model such highly variable population dynamics in marine ecosystems.
NASA Astrophysics Data System (ADS)
Kochendorfer, J. P.; Ramírez, J. A.
2010-10-01
The statistical-dynamical annual water balance model of Eagleson (1978) is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using separate potential rates of transpiration and bare-soil evaporation. Those potential rates, along with the rate of evaporation from canopy interception, are calculated using the two-component Shuttleworth-Wallace (1985) canopy model. In addition, the soil column is divided into two layers, with the upper layer representing the dynamic root zone. The resulting ability to account for changes in root-zone water storage allows for implementation at the monthly timescale. This new version of the Eagleson model is coined the Statistical-Dynamical Ecohydrology Model (SDEM). The ability of the SDEM to capture the seasonal dynamics of the local-scale soil-water balance is demonstrated for two grassland sites in the US Great Plains. Sensitivity of the results to variations in peak green leaf area index (LAI) suggests that the mean peak green LAI is determined by some minimum in root zone soil moisture during the growing season. That minimum appears to be close to the soil matric potential at which the dominant grass species begins to experience water stress and well above the wilting point, thereby suggesting an ecological optimality hypothesis in which the need to avoid water-stress-induced leaf abscission is balanced by the maximization of carbon assimilation (and associated transpiration). Finally, analysis of the sensitivity of model-determined peak green LAI to soil texture shows that the coupled model is able to reproduce the so-called "inverse texture effect", which consists of the observation that natural vegetation in dry climates tends to be most productive in sandier soils despite their lower water holding capacity. Although the determination of LAI based on complete or near-complete utilization of soil moisture is not a new approach in ecohydrology, this paper demonstrates its use for the first time with a new monthly statistical-dynamical model of the water balance. Accordingly, the SDEM provides a new framework for studying the controls of soil texture and climate on vegetation density and evapotranspiration.
Ruelle, David
conjecture. I shall thus not request that Yasha spend the new millenium proving some theorem or other for me. Rather, I would be very interested in having his informal opinion on some structural questions which I and regular behavior. For equilibrium statistical mechanics, simple behavior would be dilute gas, then liquids
P. Gauer; K. Lied; S. Bakkehoi; K. Kronholm; L. Rammer; P. Hoeller
2009-01-01
Hazard and risk assessment in avalanche prone areas involves the estimation of the runout of potential avalanches. Methods for determination of the runout may be grouped into two groups: 1) based on statistical methods such as the well known alpha - Î² model or 2) based on numerical avalanche models such as the PCM-model or Voellmy-Salm type models (just to
Takayanagi, Masayoshi; Iwahashi, Chiharu; Nagaoka, Masataka
2010-09-30
The structural dynamics of the clamshell rotation of photodissociated carbonmonoxy myoglobin, which is expected to be important for hemoglobin allostery, is investigated by the perturbation ensemble method. In this method, many pairs of perturbed and unperturbed molecular dynamics trajectories are ensemble-averaged to cancel out thermal noises and to detect subtle changes. The number of MD trajectory pairs, in this work 2000 pairs, should be determined to obtain physical properties of interest with statistically meaningful precisions. The calculated structural changes after 20 ps of the photodissociation are consistent with those by time-resolved X-ray diffraction at 100 ps delay time. In the heme proximal side region including the F and H helices, both helices displaced in the proximal direction. Meanwhile, in the heme distal side region including E and A helices, both helices moved toward the heme group after photodissociation. These proximal and distal side displacements occur on a fast time scale (almost complete within 3 ps) and are consistent with the clamshell rotation. Moreover, it was found that the ensemble-averaged structural dynamics of the photodissociated MbCO is independent of the amount of initial excess vibrational energy of the heme, or the difference of excitation photon wavelength. These results provide atomistic details on the functionally important dynamics of the clamshell rotation. Application of the present methodology to Hb will give new insight into the incipient stereochemical mechanism of hemoglobin allostery. PMID:20815354
NASA Astrophysics Data System (ADS)
Zhao, Jun-Hu; Yang, Liu; Hou, Wei; Liu, Gang; Zeng, Yu-Xing
2015-05-01
The cold vortex is a major high impact weather system in northeast China during the warm season, its frequent activities also affect the short-term climate throughout eastern China. How to objectively and quantitatively predict the intensity trend of the cold vortex is an urgent and difficult problem for current short-term climate prediction. Based on the dynamical-statistical combining principle, the predicted results of the Beijing Climate Center’s global atmosphere–ocean coupled model and rich historical data are used for dynamic-statistical extra-seasonal prediction testing and actual prediction of the summer 500-hPa geopotential height over the cold vortex activity area. The results show that this method can significantly reduce the model’s prediction error over the cold vortex activity area, and improve the prediction skills. Furthermore, the results of the sensitivity test reveal that the predicted results are highly dependent on the quantity of similar factors and the number of similar years. Project supported by the National Natural Science Foundation of China (Grant No. 41375078), the National Basic Research Program of China (Grant Nos. 2012CB955902 and 2013CB430204), and the Special Scientific Research Fund of Public Welfare Profession of China (Grant No. GYHY201306021).
Peter Gauer; Kalle Kronholm; Karstein Lied; Krister Kristensen; Steinar Bakkehøi
2010-01-01
Hazard and risk assessment in avalanche-prone areas involves estimation of runout distances of potential avalanches. Methods for determination of the runout may be divided into two categories: 1) methods based on statistical approaches such as the well known ?–? model or 2) methods based on numerical avalanche models such as the PCM-model or VS-type models (just to name the more
NASA Astrophysics Data System (ADS)
Volchenkov, D.; Blanchard, Ph.
2007-02-01
Different models of random walks on the dual graphs of compact urban structures are considered. Analysis of access times between streets helps to detect the city modularity. The statistical mechanics approach to the ensembles of lazy random walkers is developed. The complexity of city modularity can be measured by an informationlike parameter which plays the role of an individual fingerprint of Genius loci. Global structural properties of a city can be characterized by the thermodynamic parameters calculated in the random walk problem.
Statistical Laboratory & Department of Statistics
Statistical Laboratory & Department of Statistics Annual Report July 1, 2005 to December 31, 2006...............................................33 Statistical Computing Section ......................................34 CSSM and statistical methodology in the nutritional sciences. We were also very pleased to secure a permanent lecturer
Schuler, Ben
process enables the accurate analysis of both the resulting transfer efficiency histograms been addressed with these methods, including the mechanisms of molecular machines,2-4 protein and to observe dynamics of processes that are difficult to synchronize with the perturbation methods frequently
NASA Astrophysics Data System (ADS)
Albers, D. J.; Hripcsak, George
2010-02-01
Statistical physics and information theory is applied to the clinical chemistry measurements present in a patient database containing 2.5 million patients' data over a 20-year period. Despite the seemingly naive approach of aggregating all patients over all times (with respect to particular clinical chemistry measurements), both a diurnal signal in the decay of the time-delayed mutual information and the presence of two sub-populations with differing health are detected. This provides a proof in principle that the highly fragmented data in electronic health records has potential for being useful in defining disease and human phenotypes.
M. K. Cheong; M. J. Spearpoint; C. M. Fleischmann
2010-01-01
Computational tools such as one-dimensional models or Computational Fluid Dynamics (CFD) have been used for the fire safety\\u000a design of road tunnels. However, most of these analyses are performed using a specified fire source where the heat release\\u000a rate (HRR) in the tunnel is fixed by the user and the influences of ventilation conditions and tunnel geometry are not considered.
NASA Astrophysics Data System (ADS)
Perdigão, R. A. P.; Bloeschl, G.
2014-12-01
Emergent features of landscape-climate coevolution are evaluated on the basis of the sensitivity of floods to annual precipitation in space and time. For that purpose, a spatiotemporal sensitivity analysis is performed at regional scale using data from 804 catchments in Austria from 1976 to 2008. Results show that flood peaks are more responsive to spatial (regional) than to temporal (decadal) variability. Space-wise a 10% increase in precipitation leads to a 23% increase in flood peaks in Austria, whereas timewise a 10% increase in precipitation leads to an increase of just 6% in flood peaks. Catchments from dry lowlands and high wetlands exhibit similarity between the spatial and temporal sensitivities (spatiotemporal symmetry) and low landscape-climate codependence. This suggests that such regions are not coevolving significantly. However, intermediate regions show differences between those sensitivities (symmetry breaks) and higher landscape-climate codependence, suggesting undergoing coevolution. The break of symmetry is considered an emergent behavior of the coupled system. A new coevolution index is then proposed relating spatiotemporal symmetry with relative characteristic celerities. The descriptive assessment of coevolution is complemented by a simple nonlinear dynamical model of landscape-climate coevolution, in which landform evolution processes take place at the millennial scale (slow dynamics), and climate adjusts in years to decades (fast dynamics). Coevolution is expressed by the interplay between slow and fast dynamics, represented, respectively, by spatial and temporal characteristics. The model captures key features of the joint landscape-climate distribution, supporting the descriptive assessment. This paper ultimately brings to light signatures of coevolution that arise from the nonlinear coupling of the landscape-climate system at slow and fast time scales. The presented work builds on Perdigão and Blöschl (2014). Perdigão, R. A. P., and G. Blöschl (2014), Spatiotemporal flood sensitivity to annual precipitation: Evidence for landscape-climate coevolution, Water Resour. Res., 50, doi:10.1002/2014WR015365.
NASA Astrophysics Data System (ADS)
Verma, M.; Denker, C.
2014-03-01
Context. Solar pores are penumbra-lacking magnetic features, that mark two important transitions in the spectrum of magnetohydrodynamic processes: (1) the magnetic field becomes sufficiently strong to suppress the convective energy transport and (2) at some critical point some pores develop a penumbra and become sunspots. Aims: The purpose of this statistical study is to comprehensively describe solar pores in terms of their size, perimeter, shape, photometric properties, and horizontal proper motions. The seeing-free and uniform data of the Japanese Hinode mission provide an opportunity to compare flow fields in the vicinity of pores in different environments and at various stages of their evolution. Methods: The extensive database of high-resolution G-band images observed with the Hinode Solar Optical Telescope (SOT) is a unique resource to derive statistical properties of pores using advanced digital image processing techniques. The study is based on two data sets: (1) photometric and morphological properties inferred from single G-band images cover almost seven years from 2006 October 25 to 2013 August 31; and (2) horizontal flow fields derived from 356 one-hour sequences of G-band images using local correlation tracking (LCT) for a shorter period of time from 2006 November 3 to 2008 January 6 comprising 13 active regions. Results: A total of 7643/2863 (single/time-averaged) pores builds the foundation of the statistical analysis. Pores are preferentially observed at low latitudes in the southern hemisphere during the deep minimum of solar cycle No. 23. This imbalance reverses during the rise of cycle No. 24, when the pores migrate from high to low latitudes. Pores are rarely encountered in quiet-Sun G-band images, and only about 10% of pores exist in isolation. In general, pores do not exhibit a circular shape. Typical aspect ratios of the semi-major and -minor axes are 3:2 when ellipses are fitted to pores. Smaller pores (more than two-thirds are smaller than 5 Mm2) tend to be more circular, and their boundaries are less corrugated. Both the area and perimeter length of pores obey log-normal frequency distributions. The frequency distribution of the intensity can be reproduced by two Gaussians representing dark and bright components. Bright features resembling umbral dots and even light bridges cover about 20% of the pores' area. Averaged radial profiles show a peak in the intensity at normalized radius RN = r/Rpore = 2.1, followed by maxima of the divergence at RN = 2.3 and the radial component of the horizontal velocity at RN = 4.6. The divergence is negative within pores strongly suggesting converging flows towards the center of pores, whereas exterior flows are directed towards neighboring supergranular boundaries. The photometric radius of pores, where the intensity reaches quiet-Sun levels at RN = 1.4, corresponds to the position where the divergence is zero at RN = 1.6. Conclusions: Morphological and photometric properties as well as horizontal flow fields have been obtained for a statistically meaningful sample of pores. This provides critical boundary conditions for MHD simulations of magnetic flux concentrations, which eventually evolve into sunspots or just simply erode and fade away. Numerical models of pores (and sunspots) have to fit within these confines, and more importantly ensembles of pores have to agree with the frequency distributions of observed parameters.
... is not valid, please reenter the captcha code Statistics All statistics correspond with the U.S. Government fiscal year, which ... and ends on September 30. For example, adoption statistics for FY2014 show the period from October 1, ...
32. Statistics 1 32. STATISTICS
Masci, Frank
32. Statistics 1 32. STATISTICS Revised September 2007 by G. Cowan (RHUL). This chapter gives an overview of statistical methods used in High Energy Physics. In statistics, we are interested in using's validity or to determine the values of its parameters. There are two main approaches to statistical
Department of Statistics STATISTICS COLLOQUIUM
Department of Statistics STATISTICS COLLOQUIUM ERIC KOLACZYK Department of Statistics Boston University Statistical Analysis of Network Data: (Re)visiting the Foundations MONDAY, October 13, 2014, at 4, statistical methods and modeling have been central to these efforts. But how well do we truly understand
NASA Technical Reports Server (NTRS)
Mcmillan, S. L. W.
1986-01-01
The period immediately following the core collapse phase in the evolution of a globular cluster is studied using a hybrid N-body/Fokker-Planck stellar dynamical code. Several core oscillations of the type predicted in earlier work are seen. The oscillations are driven by the formation, hardening, and ejection of binaries by three-body processes, and appear to decay on a timescale of about 10 to the 7th yr, for the choice of 'typical' cluster parameters made here. There is no evidence that they are gravothermal in nature. The mechanisms responsible for the decay are discussed in some detail. The distribution of hard binaries produced by the oscillations is compared with theoretical expectations and the longer term evolution of the system is considered.
Diegert, Carl F.
2006-12-01
We define a new diagnostic method where computationally-intensive numerical solutions are used as an integral part of making difficult, non-contact, nanometer-scale measurements. The limited scope of this report comprises most of a due diligence investigation into implementing the new diagnostic for measuring dynamic operation of Sandia's RF Ohmic Switch. Our results are all positive, providing insight into how this switch deforms during normal operation. Future work should contribute important measurements on a variety of operating MEMS devices, with insights that are complimentary to those from measurements made using interferometry and laser Doppler methods. More generally, the work opens up a broad front of possibility where exploiting massive high-performance computers enable new measurements.
NASA Technical Reports Server (NTRS)
Balcer-Kubiczek, E. K.; Zhang, X. F.; Harrison, G. H.; Zhou, X. J.; Vigneulle, R. M.; Ove, R.; McCready, W. A.; Xu, J. F.
1999-01-01
PURPOSE: Differences in gene expression underlie the phenotypic differences between irradiated and unirradiated cells. The goal was to identify late-transcribed genes following irradiations differing in quality, and to determine the RBE of 1 GeV/n Fe ions. MATERIALS AND METHODS: Clonogenic assay was used to determine the RBE of Fe ions. Differential hybridization to cDNA target clones was used to detect differences in expression of corresponding genes in mRNA samples isolated from MCF7 cells irradiated with iso-survival doses of Fe ions (0 or 2.5 Gy) or fission neutrons (0 or 1.2 Gy) 7 days earlier. Northern analysis was used to confirm differential expression of cDNA-specific mRNA and to examine expression kinetics up to 2 weeks after irradiation. RESULTS: Fe ion RBE values were between 2.2 and 2.6 in the lines examined. Two of 17 differentially expressed cDNA clones were characterized. hpS2 mRNA was elevated from 1 to 14 days after irradiation, whereas CIP1/WAF1/SDI1 remained elevated from 3 h to 14 days after irradiation. Induction of hpS2 mRNA by irradiation was independent of p53, whereas induction of CIP1/WAF1/SDI1 was observed only in wild-type p53 lines. CONCLUSIONS: A set of coordinately regulated genes, some of which are independent of p53, is associated with change in gene expression during the first 2 weeks post-irradiation.
NASA Technical Reports Server (NTRS)
Zheng, Quanan; Yan, Xiao-Hai; Klemas, Vic
1993-01-01
The internal waves on the continental shelf on the Middle Atlantic Bight seen on Space Shuttle photographs taken during the STS-40 mission in June 1991 are measured and analyzed. The internal wave field in the sample area has a three-level structure which consists of packet groups, packets, and solitons. An average packet group wavelength of 17.5 km and an average soliton wavelength of 0.6 km are measured. Finite-depth theory is used to derive the dynamic parameters of the internal solitons: the maximum amplitude of 5.6 m, the characteristic phase speed of 0.42 m/s, the characteristic period of 23.8 min, the velocity amplitude of the water particles in the upper and lower layers of 0.13 m/s and 0.030 m/s respectively, and the theoretical energy per unit crest line of 6.8 x 10 exp 4 J/m. The frequency distribution of solitons is triple-peaked rather than continuous. The major generation source is at 160 m water depth, and a second is at 1800 m depth, corresponding to the upper and lower edges of the shelf break.
NASA Astrophysics Data System (ADS)
Sun, F.; Hall, A. D.; Walton, D.; Capps, S. B.; Reich, K.
2013-12-01
Using a combination of dynamical and statistical downscaling techniques, we produced 2-km-resolution regional climate reconstructions and future projections of surface warming and snowfall changes in the Los Angeles region at the middle and end of the 21st century. Projections for both time periods were compared to a validated simulation of a baseline period (1981-2000). We examined outcomes associated with two IPCC-AR5 greenhouse gas emissions scenarios: a "business-as-usual" scenario (RCP8.5) and a "mitigation" scenario (RCP2.6). Output from all available global climate models in the CMIP5 archive was downscaled. We first statistically downscaled surface warming and then applied a statistical model between the surface temperature and snowfall to project the snowfall change. By mid-century, the mountainous areas in the Los Angeles region are likely to receive substantially less snowfall than in the baseline period. In RCP8.5, about 60% of the snowfall is most likely to persist, while in RCP2.6, the likely amount remaining is somewhat higher (about 70%). By end-of-century, however, the two scenarios diverge significantly. In RCP8.5, snowfall sees a dramatic further reduction, with only about a third of baseline snowfall persisting. For RCP2.6, snowfall sees only a negligible further reduction from mid-century. Due to significant differences in climate change outcomes across the global models, we estimated these numbers associated with uncertainty, in the range of 15-30 percentage points. For both scenarios and both time slices, the snowfall loss is consistently greatest at low elevations, and the lower-lying mountain ranges are somewhat more vulnerable to snowfall loss. The similarity in the two scenarios' most likely snowfall outcomes at mid-century illustrates the inevitability of climate change in the coming decades, no matter what mitigation measures are taken. Their stark contrast at century's end reveals that reduction of greenhouse gas emissions will help avoid a dramatic loss of snowfall by the end of the century. In addition to snowfall projections, the warming-accelerated snow melting of the already reduced snowfall will be discussed as well.
Statistically Constrained Decimation of a Turbulence Model
Timothy Joe Williams
1988-01-01
The constrained decimation scheme (CDS) is applied to a turbulence model. The CDS is a statistical turbulence theory formulated in 1985 by Robert Kraichnan; it seeks to correctly describe the statistical behavior of a system using only a small sample of the actual dynamics. The full set of dynamical quantities is partitioned into groups, within each of which the statistical
Statistics on Family Caregivers and Family Caregiving Caregiving Population Economics of Caregiving Impact on Family Caregiver's Health ... Identified Family Caregivers, 2001. Top State by State Statistics The economic value of family caregiving is detailed ...
... About CDC.gov . Fungal Diseases Share Compartir Histoplasmosis Statistics How common is histoplasmosis? In the United States, ... Risk & Prevention Sources Diagnosis & Testing Treatment Health Professionals Statistics More Resources Blastomycosis Definition Symptoms People at Risk & ...
... success of efforts to control and manage cancer. Statistics at a Glance: The Burden of Cancer in ... 2010 and could reach $156 billion in 2020. Statistics at a Glance: The Burden of Cancer Worldwide ...
... www.nlm.nih.gov/medlineplus/usestatistics.html MedlinePlus Statistics To use the sharing features on this page, ... By Quarter View image full size Quarterly User Statistics Quarter Page Views Unique Visitors Oct-Dec-98 ...
ERIC Educational Resources Information Center
Petocz, Peter; Sowey, Eric
2012-01-01
The term "data snooping" refers to the practice of choosing which statistical analyses to apply to a set of data after having first looked at those data. Data snooping contradicts a fundamental precept of applied statistics, that the scheme of analysis is to be planned in advance. In this column, the authors shall elucidate the statistical…
M. Á. Latre; F. J. Zarazaga-Soria; R. Béjar; P. R. Muro-Medrano; Javier Nogueras-Iso
SDIGER is a pilot project on the implementation of the Infrastructure for Spatial Information in Europe (INSPIRE), funded by Statistical Office of The European Communities, that aims to demonstrate the feasibility and advantages of solutions for sharing spatial data and services proposed by the INSPIRE position papers and to estimate the costs of implementing interoperability-based solutions on the basis of
Term statistics Zipf's law text statistics
Lu, Jianguo
Term statistics Zipf's law text statistics October 20, 2014 text statistics 1 / 19 #12;Term statistics Zipf's law Overview 1 Term statistics 2 Zipf's law text statistics 2 / 19 #12;Term statistics Zipf's law Outline 1 Term statistics 2 Zipf's law text statistics 3 / 19 #12;Term statistics Zipf's law Model
Avalanche statistics of sand heaps
Buchholtz, V.; Poeschel, T. [Institut fuer Physik, Berlin (Germany)
1996-09-01
Large-scale computer simulations are presented to investigate the avalanche statistics of sandpiles using molecular dynamics. We show that different methods of measurement lead to contradictory conclusions, presumably due to avalanches not reaching the end of the experimental table.
Avalanche statistics of sand heaps
Volkhard Buchholtz; Thorsten Pöschel
1996-01-01
Large-scale computer simulations are presented to investigate the avalanche statistics of sandpiles using molecular dynamics. We show that different methods of measurement lead to contradictory conclusions, presumably due to avalanches not reaching the end of the experimental table.
Li, Zheng; Borner, Arnaud; Levin, Deborah A
2014-06-14
Homogeneous water condensation and ice formation in supersonic expansions to vacuum for stagnation pressures from 12 to 1000 mbar are studied using the particle-based Ellipsoidal-Statistical Bhatnagar-Gross-Krook (ES-BGK) method. We find that when condensation starts to occur, at a stagnation pressure of 96 mbar, the increase in the degree of condensation causes an increase in the rotational temperature due to the latent heat of vaporization. The simulated rotational temperature profiles along the plume expansion agree well with measurements confirming the kinetic homogeneous condensation models and the method of simulation. Comparisons of the simulated gas and cluster number densities, cluster size for different stagnation pressures along the plume centerline were made and it is found that the cluster size increase linearly with respect to stagnation pressure, consistent with classical nucleation theory. The sensitivity of our results to cluster nucleation model and latent heat values based on bulk water, specific cluster size, or bulk ice are examined. In particular, the ES-BGK simulations are found to be too coarse-grained to provide information on the phase or structure of the clusters formed. For this reason, molecular dynamics simulations of water condensation in a one-dimensional free expansion to simulate the conditions in the core of a plume are performed. We find that the internal structure of the clusters formed depends on the stagnation temperature. A larger cluster of average size 21 was tracked down the expansion, and a calculation of its average internal temperature as well as a comparison of its radial distribution functions (RDFs) with values measured for solid amorphous ice clusters lead us to conclude that this cluster is in a solid-like rather than liquid form. In another molecular-dynamics simulation at a much lower stagnation temperature, a larger cluster of size 324 and internal temperature 200 K was extracted from an expansion plume and equilibrated to determine its RDF and self-diffusion coefficient. The value of the latter shows that this cluster is formed in a supercooled liquid state rather than in an amorphous solid state. PMID:24929401
NSDL National Science Digital Library
Plonsky, Mark
This site contains materials for a college level undergraduate statistics course. The approach places emphasis on practical application. Examples are shown with hand computations and with the Minitab statistical program (V13.1). There are a couple of spreadsheets as well. Topics include: frequency distributions, graphing techniques, central tendency, variability, relative standing, correlation, dichotomous variables, continuous variables (1 and 2 sample), ANOVA: one way and two way, and nonparametric statistics.
NSDL National Science Digital Library
This article may help the user understand the concept of statistical significance and the meaning of the numbers produced by The Survey System. This article is presented in two parts. The first part simplifies the concept of statistical significance as much as possible; so that non-technical readers can use the concept to help make decisions based on their data. The second part provides more technical readers with a fuller discussion of the exact meaning of statistical significance numbers.
NASA Technical Reports Server (NTRS)
Yao, Mao-Sung; Stone, Peter H.
1987-01-01
The moist convection parameterization used in the GISS 3-D GCM is adapted for use in a two-dimensional (2-D) zonally averaged statistical-dynamical model. Experiments with different versions of the parameterization show that its impact on the general circulation in the 2-D model does not parallel its impact in the 3-D model unless the effect of zonal variations is parameterized in the moist convection calculations. A parameterization of the variations in moist static energy is introduced in which the temperature variations are calculated from baroclinic stability theory, and the relative humidity is assumed to be constant. Inclusion of the zonal variations of moist static energy in the 2-D moist convection parameterization allows just a fraction of a latitude circle to be unstable and enhances the amount of deep convection. This leads to a 2-D simulation of the general circulation very similar to that in the 3-D model. The experiments show that the general circulation is sensitive to the parameterized amount of deep convection in the subsident branch of the Hadley cell. The more there is, the weaker are the Hadley cell circulations and the westerly jets. The experiments also confirm the effects of momentum mixing associated with moist convection found by earlier investigators and, in addition, show that the momentum mixing weakens the Ferrel cell. An experiment in which the moist convection was removed while the hydrological cycle was retained and the eddy forcing was held fixed shows that moist convection by itself stabilizes the tropics, reduces the Hadley circulation, and reduces the maximum speeds in the westerly jets.
Statistical Inference in Graphical Models
Kevin Gimpel
2006-01-01
ABSTRACT Graphical models fuse probability theory and graph theory in such a way as to permit ef- ficient representation and computation with probability distributions. They intuitively capture statistical relationships among,random,variables in a distribution and exploit these relationships to permit tractable algorithms for statistical inference. In recent years, certain types of graphical models, particularly undirected graphical models, Bayesian networks, and dynamic
ERIC Educational Resources Information Center
Weed, Harrison D., Jr.
This brief text was written to provide more extensive treatment of descriptive statistics than is ordinarily available in modern statistics textbooks. It is intended for use in conjunction with any college level text. The booklet consists of an introduction, three content oriented chapters, and four appendices devoted to computer programming…
ERIC Educational Resources Information Center
Singer, Arlene; And Others
This guide outlines an Option Y course, which has seven learner objectives geared to providing students with an introduction to the concerns and methods of statistics and equipping pupils to deal with the many statistical matters of importance in society. Topics included in the course are graphs and charts, collection and organization of data,…
ERIC Educational Resources Information Center
Petocz, Peter; Sowey, Eric
2008-01-01
In this article, the authors focus on hypothesis testing--that peculiarly statistical way of deciding things. Statistical methods for testing hypotheses were developed in the 1920s and 1930s by some of the most famous statisticians, in particular Ronald Fisher, Jerzy Neyman and Egon Pearson, who laid the foundations of almost all modern methods of…
Statistical aspects of inhalation toxicokinetics
Michael Becka; Wolfgand Urfer
1996-01-01
The statistical analysis of dynamic processes is a useful tool to learn how environmental and ecological systems work and how they respond to disturbances. In the context of human risk assessment of potentially harmful chemicals, many complex dynamic processes in terms of kinetics have to be taken into account. Thorough research of direct influence of chemicals to humans depends on
Engineering Statistics From "Engineering Statistics" , Top &
Kovintavewat, Piya
Engineering Statistics From "Engineering Statistics" , Top & Wiley, Prapaisri & Pongchanun 2 From "Engineering Statistics" , Top & Wiley, Prapaisri & Pongchanun 3 " "(Sample) (Sampling) ""(Population) " "(Statistics) ""(Parameter) From "Engineering Statistics" , Top & Wiley, Prapaisri
Michele Arzano; Dario Benedetti
2008-09-04
Non-commutative quantum field theories and their global quantum group symmetries provide an intriguing attempt to go beyond the realm of standard local quantum field theory. A common feature of these models is that the quantum group symmetry of their Hilbert spaces induces additional structure in the multiparticle states which reflects a non-trivial momentum-dependent statistics. We investigate the properties of this "rainbow statistics" in the particular context of $\\kappa$-quantum fields and discuss the analogies/differences with models with twisted statistics.
NASA Technical Reports Server (NTRS)
Feiveson, Alan H.; Foy, Millennia; Ploutz-Snyder, Robert; Fiedler, James
2014-01-01
Do you have elevated p-values? Is the data analysis process getting you down? Do you experience anxiety when you need to respond to criticism of statistical methods in your manuscript? You may be suffering from Insufficient Statistical Support Syndrome (ISSS). For symptomatic relief of ISSS, come for a free consultation with JSC biostatisticians at our help desk during the poster sessions at the HRP Investigators Workshop. Get answers to common questions about sample size, missing data, multiple testing, when to trust the results of your analyses and more. Side effects may include sudden loss of statistics anxiety, improved interpretation of your data, and increased confidence in your results.
NASA Technical Reports Server (NTRS)
Giles, B. L.; Chappell, C. R.; Moore, T. E.; Comfort, R. H.; Waite, J. H., Jr.
1994-01-01
Core (0-50 eV) ion pitch angle measurements from the retarding ion mass spectrometer on Dynamics Explorer 1 are examined with respect to magnetic disturbance, invariant latitude, magnetic local time, and altitude for ions H(+), He(+), O(+), M/Z = 2 (D(+) or He(++)), and O(++). Included are outflow events in the auroral zone, polar cap, and cusp, separated into altitude regions below and above 3 R(sub E). In addition to the customary division into beam, conic, and upwelling distributions, the high-latitude observations fall into three categories corresponding to ion bulk speeds that are (1) less than, (2) comparable to, or (3) faster than that of the spacecraft. This separation, along with the altitude partition, serves to identify conditions under which ionospheric source ions are gravita- tionally bound and when they are more energetic and able to escape to the outer magnetosphere. Features of the cleft ion fountain inferred from single event studies are clearly identifiable in the statistical results. In addition, it is found that the dayside pre-noon cleft is a dayside afternoon cleft, or auroral zone, becomes an additional source for increased activity. The auroral oval as a whole appears to be a steady source of escape velocity H(+), a steady source of escape velocity He(+) ions for the dusk sector, and a source of escape velocity heavy ions for dusk local times primarily during increased activity. The polar cap above the auroral zone is a consistent source of low-energy ions, although only the lighter mass particles appear to have sufficient velocity, on average, to escape to higher altitudes. The observations support two concepts for outflow: (1) The cleft ion fountain consists of ionospheric plasma of 1-20 eV energy streaming upward into the magnetosphere where high-latitude convection electric fields cause poleward dispersion. (2) The auroral ion fountain involves field-aligned beams which flow out along auroral latitude field lines; and, in addition, for late afternoon local times, they experience additional acceleration such that the ion energy distribution tends to exceed the detection range of the instrument (greater than 50-60 eV).
NSDL National Science Digital Library
Started in 1997, the Badan Pusat Statistik (BPS-Statistics Indonesia) is a non-departmental Indonesian government institution directly responsible to the Indonesian president. As the law that created this valuable institution stipulates, the BPS is intended to provide data to the government and the public, along cooperating with other international statistical institutions. Visitors looking for statistics on any number of topics will not be disappointed, as the areas covered include agriculture, consumer price indices, employment, energy, foreign trade, mining, population, public finance, tourism, and social welfare. Additionally, there are monthly macro-economic statistical reports for the years from 1998 to 2001 that can be downloaded and viewed as well. The site is rounded out by a collection of some 21 papers from the past four years that analyze various economic data from the country, such as earning data and manufacturing production.
NSDL National Science Digital Library
Dudley, Richard
Created by Richard Dudley of the Massachusetts Institute of Technology, this lesson, Mathematical Statistics, is a graduate-level course featuring book chapters and sections presented as lecture notes, problem sets, exams, and a description for an optional term-paper. The course covers: decision theory, estimation, confidence intervals, hypothesis testing, asymptotic efficiency of estimates, exponential families, sequential analysis, and large sample theory. This is a comprehensive overview of this upper level statistics course.
V. Jaksi ´; C.-A. Pillet
1937-01-01
We review and further develop a mathematical framework for non-equilibrium quantum statistical mechanics recently proposed in (JP4, JP5, JP6, Ru3, Ru4, Ru5, Ru6). In the alge- braic formalism of quantum statistical mechanics we introduce notions of non-equilibrium steady states, entropy production and heat fluxes, and study their properties. Our basic paradigm is a model of a small (finite) quantum system
STATISTICAL LITERACY: THINKING CRITICALLY ABOUT STATISTICS
Milo Schield
Statistical literacy is the ability to read and interpret data: the ability to use statistics as evidence in arg u- ments. Statistical literacy is a competency: the ability to think critically about statistics. This introduction defines statistical literacy as a science of method, com- pares statistical literacy with traditional statistics and reviews some of the elements in reading and interpret-
Conditional Statistics of Interdependent, Terascale Turbulence Data
Mountziaris, T. J.
Conditional Statistics of Interdependent, Terascale Turbulence Data Amanda Pellerite University, Department of Mathematics and Statistics Abstract This research project works towards the development and implementation of computational statistical tools to explore the dynamics of a fully developed 'wake' in a 3D
NSDL National Science Digital Library
Annis, Charles
A good resource for problems in statistics in engineering. Contains some applets, and good textual examples related to engineering. Some topics include Monte Carlo method, Central Limit Theorem, Risk, Logistic Regression, Generalized Linear Models, and Confidence. Overall, this is a well presented and good site for anyone interested in engineering or mathematics.
Mitchell, Tom
, or a set of cdf's for a statistical problem based on data. Inference: Making predictions, computing of x that can be used for reasoning, decision making, predicting, communicating, etc. Task is often #12; Inference vs. Learning Estimation/Learning: Selecting parameters, a distribution over parameters
NSDL National Science Digital Library
Anderson-Cook, C.
This is a collection of applets regarding various topics in statistics. Topics include central limit theorem, probability distributions, hypothesis testing, power, confidence intervals, correlation, control charts, experimental design, data analysis, and regression. Each topic has a description page and links to one or more applets.
Statistical characterization of dislocation ensembles
El-Azab, A; Deng, J; Tang, M
2006-05-17
We outline a method to study the spatial and orientation statistics of dynamical dislocation systems by modeling the dislocations as a stochastic fiber process. Statistical measures have been introduced for the density, velocity, and flux of dislocations, and the connection between these measures and the dislocation state and plastic distortion rate in the crystal is explained. A dislocation dynamics simulation model has been used to extract numerical data to study the evolution of these statistical measures numerically in a body-centered cubic crystal under deformation. The orientation distribution of the dislocation density, velocity and dislocation flux, as well as the dislocation correlations have been computed. The importance of the statistical measures introduced here in building continuum models of dislocation systems is highlighted.
Four Faculty Positions Applied Statistics & Computational Statistics
Shepp, Larry
Four Faculty Positions Applied Statistics & Computational Statistics The Department of Statistics at the Assistant Professor rank. Two positions are open in the area of Applied Statistics, with a focus on the development of statistical methodology and statistical consulting. The other two positions are open
Nagler, Jan
Journal of Statistical Physics, Vol. 116, Nos. 5/6, September 2004 (© 2004) Of Dogs and Fleas the jumps of N fleas between two dogs. In each time step a single randomly selected flea jumps on the other dog. The more fleas there are on a dog, the more will jump off it. In the long time limit
Learning Statistics By Doing Statistics
NSDL National Science Digital Library
Smith, Gary
This article, created by Gary Smith of Pomona College, discusses a project-based approach to teaching statistics. The article focuses on the team aspect of learning, it introduces concepts such as: working with data, learning by doing, learning by writing, learning by speaking, and authentic assessment of material. An appendix contains a list of twenty projects that have been successfully assigned.
E. Bogomolny; U. Gerland; C. Schmit
2000-12-04
We consider the statistical distribution of zeros of random meromorphic functions whose poles are independent random variables. It is demonstrated that correlation functions of these zeros can be computed analytically and explicit calculations are performed for the 2-point correlation function. This problem naturally appears in e.g. rank-one perturbation of an integrable Hamiltonian and, in particular, when a $\\delta$-function potential is added to an integrable billiard.
NSDL National Science Digital Library
2013-06-21
Students will encounter the concept of a distribution, along with parameters that describe a distribution's "typical" values (average) and a distribution's spread (variance). To understand simple distributions and uncertainty propagation in the coming sections, it is necessary to be familiar with the concept of statistical independence. When two variables fluctuate independently, their covariance vanishes, and the variance of their sum is the sum of their variances.
This section of the BCSC web site details the information collected and used in research by the BCSC. Statistics includes charts and tables that provide an overview of the data collected. These data are used in a wide range of studies that evaluate the performance of mammography in community settings. Some studies analyze data collected from individual sites; others examine data pooled from two or more sites.
Hamiltonian statistical mechanics
Dorje C. Brody; David C. P. Ellis; Darryl D. Holm
2008-09-15
A framework for statistical-mechanical analysis of quantum Hamiltonians is introduced. The approach is based upon a gradient flow equation in the space of Hamiltonians such that the eigenvectors of the initial Hamiltonian evolve toward those of the reference Hamiltonian. The nonlinear double-bracket equation governing the flow is such that the eigenvalues of the initial Hamiltonian remain unperturbed. The space of Hamiltonians is foliated by compact invariant subspaces, which permits the construction of statistical distributions over the Hamiltonians. In two dimensions, an explicit dynamical model is introduced, wherein the density function on the space of Hamiltonians approaches an equilibrium state characterised by the canonical ensemble. This is used to compute quenched and annealed averages of quantum observables.
J. Mark Heinzle; Claes Uggla
2012-12-21
In this paper we explore stochastical and statistical properties of so-called recurring spike induced Kasner sequences. Such sequences arise in recurring spike formation, which is needed together with the more familiar BKL scenario to yield a complete description of generic spacelike singularities. In particular we derive a probability distribution for recurring spike induced Kasner sequences, complementing similar available BKL results, which makes comparisons possible. As examples of applications, we derive results for so-called large and small curvature phases and the Hubble-normalized Weyl scalar.
Mitrikas, V G
2014-01-01
The on-going 24th solar cycle (SC) is distinguished from the previous ones by low activity. On the contrary, levels of proton fluxes from galactic cosmic rays (GCR) are high, which increases the proton flow striking the Earth's radiation belts (ERB). Therefore, at present the absorbed dose from ERB protons should be calculated with consideration of the tangible increase of protons intensity built into the model descriptions based on experimental measurements during the minimum between cycles 19 and 20, and the cycle 21 maximum. The absorbed dose from GCR and ERB protons copies galactic protons dynamics, while the ERB electrons dose copies SC dynamics. The major factors that determine the absorbed dose value are SC phase, ISS orbital altitude and shielding of the dosimeter readings of which are used in analysis. The paper presents the results of dynamic analysis of absorbed doses measured by a variety of dosimeters, namely, R-16 (2 ionization chambers), DB8-1, DB8-2, DB8-3, DB8-4 as a function of ISS orbit altitude and SC phase. The existence of annual variation in the absorbed dose dynamics has been confirmed; several additional variations with the periods of 17 and 52 months have been detected. Modulation of absorbed dose variations by the SC and GCR amplitudes has been demonstrated. PMID:25035897
Corn production with Spray, LEPA, and SDI
Technology Transfer Automated Retrieval System (TEKTRAN)
Corn, a major irrigated crop in the U.S. Great Plains, has a large irrigation requirement making efficient, effective irrigation technology important. The objective of this paper was to compare corn productivity for different irrigation methods and irrigation rates in 2009 and 2010 at Bushland, Texa...
Statistical Properties of Synthetic Nanoflares
B. Viticchié; D. Del Moro; F. Berrilli
2006-01-01
Statistical properties of flares are a powerful tool for addressing the upper solar atmosphere heating problem. We simulate time series of synthetic flares by means of a dynamic model of the atmospheric magnetic field in which magnetic loop footpoints are controlled by photospheric flows computed through a n-body algorithm. The n-body simulation reproduces the behavior of a system where large
NASA Astrophysics Data System (ADS)
Graham, D. B.; Cairns, Iver H.; Skjaeraasen, O.; Robinson, P. A.
2012-02-01
The temperature ratio Ti/Te of ions to electrons affects both the ion-damping rate and the ion-acoustic speed in plasmas. The effects of changing the ion-damping rate and ion-acoustic speed are investigated for electrostatic strong turbulence and electromagnetic strong turbulence in three dimensions. When ion damping is strong, density wells relax in place and act as nucleation sites for the formation of new wave packets. In this case, the density perturbations are primarily density wells supported by the ponderomotive force. For weak ion damping, corresponding to low Ti/Te, ion-acoustic waves are launched radially outwards when wave packets dissipate at burnout, thereby increasing the level of density perturbations in the system and thus raising the level of scattering of Langmuir waves off density perturbations. Density wells no longer relax in place so renucleation at recent collapse sites no longer occurs, instead wave packets form in background low density regions, such as superpositions of troughs of propagating ion-acoustic waves. This transition is found to occur at Ti/Te ? 0.1. The change in behavior with Ti/Te is shown to change the bulk statistical properties, scaling behavior, spectra, and field statistics of strong turbulence. For Ti/Te>rsim0.1, the electrostatic results approach the predictions of the two-component model of Robinson and Newman, and good agreement is found for Ti/Te>rsim0.15.
Statistical ecology comes of age.
Gimenez, Olivier; Buckland, Stephen T; Morgan, Byron J T; Bez, Nicolas; Bertrand, Sophie; Choquet, Rémi; Dray, Stéphane; Etienne, Marie-Pierre; Fewster, Rachel; Gosselin, Frédéric; Mérigot, Bastien; Monestiez, Pascal; Morales, Juan M; Mortier, Frédéric; Munoz, François; Ovaskainen, Otso; Pavoine, Sandrine; Pradel, Roger; Schurr, Frank M; Thomas, Len; Thuiller, Wilfried; Trenkel, Verena; de Valpine, Perry; Rexstad, Eric
2014-12-01
The desire to predict the consequences of global environmental change has been the driver towards more realistic models embracing the variability and uncertainties inherent in ecology. Statistical ecology has gelled over the past decade as a discipline that moves away from describing patterns towards modelling the ecological processes that generate these patterns. Following the fourth International Statistical Ecology Conference (1-4 July 2014) in Montpellier, France, we analyse current trends in statistical ecology. Important advances in the analysis of individual movement, and in the modelling of population dynamics and species distributions, are made possible by the increasing use of hierarchical and hidden process models. Exciting research perspectives include the development of methods to interpret citizen science data and of efficient, flexible computational algorithms for model fitting. Statistical ecology has come of age: it now provides a general and mathematically rigorous framework linking ecological theory and empirical data. PMID:25540151
Quantum particles from classical statistics
C. Wetterich
2010-02-11
Quantum particles and classical particles are described in a common setting of classical statistical physics. The property of a particle being "classical" or "quantum" ceases to be a basic conceptual difference. The dynamics differs, however, between quantum and classical particles. We describe position, motion and correlations of a quantum particle in terms of observables in a classical statistical ensemble. On the other side, we also construct explicitly the quantum formalism with wave function and Hamiltonian for classical particles. For a suitable time evolution of the classical probabilities and a suitable choice of observables all features of a quantum particle in a potential can be derived from classical statistics, including interference and tunneling. Besides conceptual advances, the treatment of classical and quantum particles in a common formalism could lead to interesting cross-fertilization between classical statistics and quantum physics.
NASA Technical Reports Server (NTRS)
Vangelder, B. H. W.
1978-01-01
Non-Bayesian statistics were used in simulation studies centered around laser range observations to LAGEOS. The capabilities of satellite laser ranging especially in connection with relative station positioning are evaluated. The satellite measurement system under investigation may fall short in precise determinations of the earth's orientation (precession and nutation) and earth's rotation as opposed to systems as very long baseline interferometry (VLBI) and lunar laser ranging (LLR). Relative station positioning, determination of (differential) polar motion, positioning of stations with respect to the earth's center of mass and determination of the earth's gravity field should be easily realized by satellite laser ranging (SLR). The last two features should be considered as best (or solely) determinable by SLR in contrast to VLBI and LLR.
... Act and Program National Statistics (MQSA) MQSA National Statistics In this section of the MQSA Scorecard, we present the most commonly requested national statistics regarding the MQSA program. These statistics are updated ...
... Limb Loss Statistics > Limb Loss Statistics Limb Loss Statistics There are nearly 2 million people living with ... Disease Control and Prevention, National Center for Health Statistics; 1998. HCUP Nationwide Inpatient Sample (NIS). Healthcare Cost ...
NASA Technical Reports Server (NTRS)
Charlock, T. P.; Cattany-Carnes, K. M.; Potter, G. L.
1986-01-01
Cross-correlations were calculated between the radiation emitted and reflected from the top of the atmosphere and the temperature, horizontal wind and precipitable water in the middle troposphere. The study was extended to the time domain by filtering data for 1-2 and 2.5-6 day periods. The effects of cloud radiation were quantified by comparisons of IR full-sky and clear-sky values. Significant correlations were obtained between the middle atmospheric physical and dynamical parameters and the top of the atmosphere radiation.
Is there a statistical mechanics of turbulence
Kraichnan, R.H.; Chen, S.Y.
1988-09-01
The statistical-mechanical treatment of turbulence is made questionable by strong nonlinearity and strong disequilibrium that result in the creation of ordered structures imbedded in disorder. Model systems are described which may provide some hope that a compact, yet faithful, statistical description of turbulence nevertheless is possible. Some essential dynamic features of the models are captured by low-order statistical approximations despite strongly non-Gaussian behavior. 31 refs., 5 figs.
Generating Statistical Tables with Canned Statistical Software.
ERIC Educational Resources Information Center
McLean, James E.; Hebbler, Stephen W.
A method of generating common statistical tables using canned statistical computer software is presented. This method allows instructors to provide statistical tables for their students, tailored to their needs. The four most common tables used in elementary college statistics courses are z (standard normal), t, F, and chi square. Specific "p"…
Thanos Manos; Marko Robnik
2013-12-28
We study quantum kicked rotator in the classically fully chaotic regime, in the domain of the semiclassical behaviour. We use Izrailev's N-dimensional model for various N infinity tends to the quantized kicked rotator, not only for K=5 as studied previously, but for many different values of the classical kick parameter 5infinity and L is fixed we have always Poisson, even in fully chaotic regime. We study the eigenfunctions of the Floquet operator and characterize their localization properties using the information entropy measure describing the degree of dynamical localization of the eigenfunction. The resulting localization parameter is found to be almost equal to the Brody parameter. We show the existence of a scaling law between the localization parameter and the scaling variable L/N, now including the regimes of anomalous diffusion. The above findings are important also in time-independent Hamilton systems, like in mixed type billiards, where the Brody distribution is confirmed to a very high degree of precision for dynamically localized chaotic eigenstates.
NASA Astrophysics Data System (ADS)
Schläppy, Romain; Eckert, Nicolas; Jomelli, Vincent; Grancher, Delphine; Brunstein, Daniel; Stoffel, Markus; Naaim, Mohamed
2013-04-01
Documenting past avalanche activity represents an indispensable step in avalanche hazard assessment. Nevertheless, (i) archival records of past avalanche events do not normally yield data with satisfying spatial and temporal resolution and (ii) precision concerning runout distance is generally poorly defined. In addition, historic documentation is most often (iii) biased toward events that caused damage to structure or loss of life on the one hand and (iv) undersampled in unpopulated areas on the other hand. On forested paths dendrogeomorphology has been demonstrated to represent a powerful tool to reconstruct past activity of avalanches with annual resolution and for periods covering the past decades to centuries. This method is based on the fact that living trees may be affected by snow avalanches during their flow and deposition phases. Affected trees will react upon these disturbances with a certain growth response. An analysis of the responses recorded in tree rings coupled with an evaluation of the position of reacting trees within the path allows the dendrogeomorphic expert to identify past snow avalanche events and deduced their minimum runout distance. The objective of the work presented here is firstly to dendrochronogically -reconstruct snow avalanche activity in the Château Jouan path located near Montgenèvre in the French Alps. Minimal runout distances are then determined for each reconstructed event by considering the point of further reach along the topographic profile. Related empirical return intervals are evaluated, combining the extent of each event with the average local frequency of the dendrological record. In a second step, the runout distance distribution derived from dendrochronological reconstruction is compared to the one derived from historical archives and to high return period avalanches predicted by an up-to-date locally calibrated statistical-numerical model. It appears that dendrochronological reconstructions correspond mostly to rare events, i.e. to the tail of the local runout distance distribution. Furthermore, a good agreement exists with the statistical-numerical model's prediction, i.e. a 10-40 m difference for return periods ranging between 10 and 300 years, which is rather small with regards to the uncertainty levels to be considered in avalanche probabilistic modeling and dendrochronological reconstructions. It is important to note that such a cross validation on independent extreme predictions has never been undertaken before. It suggest that i) dendrochronological reconstruction can provide valuable information for anticipating future extreme avalanche events in the context of risk management, and, in turn, that ii) the statistical-numerical model, while properly calibrated, can be used with reasonable confidence to refine these predictions, with for instance evaluation of pressure and flow depth distributions at each position of the runout zone. A strong sensitivity to the determination of local avalanche and dendrological record frequencies is however highlighted, indicating that this step is an essential step for an accurate probabilistic characterization of large-extent events.
NASA Astrophysics Data System (ADS)
Yeung, Chi Ho
In this thesis, we study two interdisciplinary problems in the framework of statistical physics, which show the broad applicability of physics on problems with various origins. The first problem corresponds to an optimization problem in allocating resources on random regular networks. Frustrations arise from competition for resources. When the initial resources are uniform, different regimes with discrete fractions of satisfied nodes are observed, resembling the Devil's staircase. We apply the spin glass theory in analyses and demonstrate how functional recursions are converted to simple recursions of probabilities. Equilibrium properties such as the average energy and the fraction of free nodes are derived. When the initial resources are bimodally distributed, increases in the fraction of rich nodes induce a glassy transition, entering a glassy phase described by the existence of multiple metastable states, in which we employ the replica symmetry breaking ansatz for analysis. The second problem corresponds to the study of multi-agent systems modeling financial markets. Agents in the system trade among themselves, and self-organize to produce macroscopic trading behaviors resembling the real financial markets. These behaviors include the arbitraging activities, the setting up and the following of price trends. A phase diagram of these behaviors is obtained, as a function of the sensitivity of price and the market impact factor. We finally test the applicability of the models with real financial data including the Hang Seng Index, the Nasdaq Composite and the Dow Jones Industrial Average. A substantial fraction of agents gains faster than the inflation rate of the indices, suggesting the possibility of using multi-agent systems as a tool for real trading.
Statistical trajectory models for phonetic recognition
William David Goldenthal; James R. Glass
1994-01-01
The main goal of this work is to develop an alternative methodology for acoustic--phonetic modelling of speech sounds. The approach utilizes a segment--based frameworkto capture the dynamical behavior and statistical dependencies of the acousticattributes used to represent the speech waveform. Temporal behavior is modelledexplicitly by creating dynamic tracks of the acoustic attributes used to represent thewaveform, and by estimating the
NASA Astrophysics Data System (ADS)
Parey, A.; El Badaoui, M.; Guillet, F.; Tandon, N.
2006-06-01
Gears are one of the most common and important machine components in many advanced machines. An improved understanding of vibration signal is required for the early detection of incipient gear failure to achieve high reliability. This paper mainly consists of two parts: in the first part, a 6-degree-of-freedom gear dynamic model including localized tooth defect has been developed. The model consists of a spur gear pair, two shafts, two inertias representing load and prime mover and bearings. The model incorporates the effects of time-varying mesh stiffness and damping, backlash, excitation due to gear errors and profile modifications. The second part consists of signal processing of simulated and experimental signals. Empirical mode decomposition (EMD) is a method of breaking down a signal without leaving a time domain. The process is useful for analysing non-stationary and nonlinear signals. EMD decomposes a signal into some individual, nearly monocomponent signals, named as intrinsic mode function (IMF). Crest factor and kurtosis have been calculated of these IMFs. EMD pre-processed kurtosis and crest factor give early detection of pitting as compared to raw signal.
Graphene Statistical Mechanics
NASA Astrophysics Data System (ADS)
Bowick, Mark; Kosmrlj, Andrej; Nelson, David; Sknepnek, Rastko
2015-03-01
Graphene provides an ideal system to test the statistical mechanics of thermally fluctuating elastic membranes. The high Young's modulus of graphene means that thermal fluctuations over even small length scales significantly stiffen the renormalized bending rigidity. We study the effect of thermal fluctuations on graphene ribbons of width W and length L, pinned at one end, via coarse-grained Molecular Dynamics simulations and compare with analytic predictions of the scaling of width-averaged root-mean-squared height fluctuations as a function of distance along the ribbon. Scaling collapse as a function of W and L also allows us to extract the scaling exponent eta governing the long-wavelength stiffening of the bending rigidity. A full understanding of the geometry-dependent mechanical properties of graphene, including arrays of cuts, may allow the design of a variety of modular elements with desired mechanical properties starting from pure graphene alone. Supported by NSF grant DMR-1435794
Statistical Thermodynamics of Biomembranes
Devireddy, Ram V.
2010-01-01
An overview of the major issues involved in the statistical thermodynamic treatment of phospholipid membranes at the atomistic level is summarized: thermodynamic ensembles, initial configuration (or the physical system being modeled), force field representation as well as the representation of long-range interactions. This is followed by a description of the various ways that the simulated ensembles can be analyzed: area of the lipid, mass density profiles, radial distribution functions (RDFs), water orientation profile, Deuteurium order parameter, free energy profiles and void (pore) formation; with particular focus on the results obtained from our recent molecular dynamic (MD) simulations of phospholipids interacting with dimethylsulfoxide (Me2SO), a commonly used cryoprotective agent (CPA). PMID:19460363
Order Statistics and Applications
Yorke, James
Order Statistics and Applications Rosemary Smith #12;Introduction to Order Statistics Unordered Statistics and Observations Ordered Statistics and Observations #12;What kinds of problems are we trying of two order statistics. #12;Formula For We start with the standard formula for expected value Many
FISHERY STATISTICS UNITED STATES
FISHERY STATISTICS OF THE UNITED STATES 1972 STATISTICAL DIGEST NO. 66 Prepared by STATISTICS;ACKNOWLEDGMENTS The data in this edition of "Fishery Statistics of the United States" were collected in co- operation with the various States and tabulated by the staff of the Statistics and Market News Division
A. J. Rossini
Literate Statistical Practice (LSP) is an method for statistical practice which suggests that documentation and specication occur at the same time as statistical coding. It applies literate programming Knuth (1992) to the practice of statistics. We discuss 2 dierent approaches for LSP, one currently implemented using Emacs with Noweb and Emacs Speaks Statistics (ESS), and the other developed based on
Royal Statistical Society Center for Statistical Education
NSDL National Science Digital Library
Created by the Royal Statistical Society, this website's purpose it to promote the improvement of statistical education, training and understanding. You will find activities, resources and current news to help in teaching statistics. The site breaks down its resources in this manner: for school, higher education, for all levels, problem solving and MSOR@RSSCSE. The page is quite broad in scope. For this reason, it is a great resource for those interested in almost any aspect of statistics education.
Statistics Poker: Reinforcing Basic Statistical Concepts
ERIC Educational Resources Information Center
Leech, Nancy L.
2008-01-01
Learning basic statistical concepts does not need to be tedious or dry; it can be fun and interesting through cooperative learning in the small-group activity of Statistics Poker. This article describes a teaching approach for reinforcing basic statistical concepts that can help students who have high anxiety and makes learning and reinforcing…
NASA Astrophysics Data System (ADS)
Passarelli, Luigi; Rivalta, Eleonora; Simone, Cesca; Aoki, Yosuke
2014-05-01
The emplacement of magma-filled dikes often induce abundant seismicity in the surrounding host rocks. Most of the earthquakes are thought to occur close to the propagating tip (or edges, in 3D) of the dike, where stresses are concentrated. The resulting seismicity often appears as a swarm, controlled mainly by dike-induced stresses and stressing rate and by other factors, such as the background stressing rate, tectonic setting, regional stresses and tectonic history. The spatial distribution and focal mechanisms of the seismicity bear information on the interaction of the dike stress field and the tectonic setting of the area. The seismicity accompanying the intrusion of a dike is usually characterized by weak events, for which it is difficult to calculate the focal mechanisms. Therefore, only for a few well-recorded dike intrusions a catalog of focal mechanisms, allowing to perform a robust statistical analysis, is available. The 2000 dike intrusion at Miyakejima is in this sense an outstanding case, as about 18000 seismic events were recorded in a time span of three months. This seismic swarm was one of the most energetic ever recorded with five M>6 earthquakes. For this swarm a catalog of 1500 focal mechanisms is avalable (NIED, Japan). We perform a clustering analysis of the focal mechanism solutions, in order to infer the most frequent focal mechanism features prior to the intrusion (pre-diking period) and during the co-diking period. As previously suggested, we find that the dike stress field modified substantially the pre-existing seismicity pattern, by shadowing some non-optimally oriented strike-slip structures and increasing seismic rate on optimally oriented strike-slip tectonic structures. Alongside, during the co-diking period a large number of normal and oblique-normal faulting were observed. These events cannot be explained within the tectonics of the intrusion area. We suggest they are directly generated by the intense stress field induced at the dike edges. We further investigate the distribution of the two main clusters we identify, i.e. strike-slip and oblique-normal mechanisms. We find that the strike-slip family obeys a Gutenberg-Richter law with a b-value close to one. The oblique-normal family of events deviates from the Gutenberg-Richter distribution and is slightly bimodal, with a marked roll-off on its right-hand tail suggesting a lack of large magnitude events (M>5.5). This set of events seems to collect earthquakes rupturing above the dike, similar to graben faulting events widely observed in volcanic areas during diking. A possible explanation of the anomalous frequency-magnitude distribution is that these earthquakes may be limited in size by the thickness of the layer where they nucleate, being spatially constrained between the dike upper edge and the Earth's surface.
Statistical validation of stochastic models
Hunter, N.F. [Los Alamos National Lab., NM (United States). Engineering Science and Analysis Div.; Barney, P.; Paez, T.L. [Sandia National Labs., Albuquerque, NM (United States). Experimental Structural Dynamics Dept.; Ferregut, C.; Perez, L. [Univ. of Texas, El Paso, TX (United States). Dept. of Civil Engineering
1996-12-31
It is common practice in structural dynamics to develop mathematical models for system behavior, and the authors are now capable of developing stochastic models, i.e., models whose parameters are random variables. Such models have random characteristics that are meant to simulate the randomness in characteristics of experimentally observed systems. This paper suggests a formal statistical procedure for the validation of mathematical models of stochastic systems when data taken during operation of the stochastic system are available. The statistical characteristics of the experimental system are obtained using the bootstrap, a technique for the statistical analysis of non-Gaussian data. The authors propose a procedure to determine whether or not a mathematical model is an acceptable model of a stochastic system with regard to user-specified measures of system behavior. A numerical example is presented to demonstrate the application of the technique.
Decimation of a turbulence model under statistical constraints
Timothy J. Williams; E. R. Tracy; George Vahala
1989-01-01
A numerical implementation of Kraichnan's constrained decimation scheme (CDS) is formulated and applied to a turbulence model. The full set of dynamical variables in the model is reduced - decimated - to a small sample set. This decimated system is driven by stochastic forces that are subject to statistical constraints. This constraints exploit statistical similarities among dynamical variables to cause
... at NIMH News About Us Home > Health & Education Statistics Prevalence Disability Suicide Cost Global More Prevalence Disability ... those affected receive treatment. The information on these statistics pages includes the best statistics currently available on ...
Neuroendocrine Tumor: Statistics
... Statistics Request Permissions Print to PDF Neuroendocrine Tumor: Statistics Approved by the Cancer.Net Editorial Board , 04/ ... nodes or distant parts of the body. Survival statistics should be interpreted with caution. These estimates are ...
American Statistical Association: Statistics in Sports
NSDL National Science Digital Library
This section of the American Statistical Association website covers Statistics in Sports. Available here are a few older articles dealing with sports statistics and links to websites containing data for several professional and amateur sports, as well as websites with general news and information about sports, and a listing of official team websites for pro teams. A section called Statistics on the Web provides links to academic departments, conferences, and employers, while another section answers some frequently asked questions about sports statistics as a career. The website also provides an explanation of the Player Game Percentage (PGP) technique and uses the 2004 World Series as an example to demonstrate the technique. Educators will find a link to a website that offers suggestions of ways to incorporate sports statistics in the classroom.
Applied Statistics Spring 2010
Langseth, Helge
of the course is to give the students a solid foundation for use of basic statistical methods in science, statistical process control, contingency tables and nonparametric methods. Use of statistical computer package) · Nonparametric methods #12;19 Why is statistics important in science and industry? The book emphasizes "the
Francis Y. L. Chin; Gultekin Ozsoyoglu
1981-01-01
The security problem of a statistical database is to limit the use of the database so that no sequence of statistical queries is sufficient to deduce confidential or private information. In this paper it is suggested that the problem be investigated at the conceptual data model level. The design of a statistical database should utilize a statistical security management facility
Monetary and Financial Statistics
This Handbook provides an overview of the wide range of monetary and financial statistics collected by most central banks, as well as the main uses of these data. In an increasingly globalised financial system, several statistics collected by central banks are only useful if similar statistics are available for other economies. So international harmonisation of statistical frameworks and co-operation between
Sampling in Statistical Inference
NSDL National Science Digital Library
Lacey, Michelle
This site, presented by the Department of Statistics at Yale University, gives an explanation, a definition and an example of sampling in statistical inference. Topics include parameters, statistics, sampling distributions, bias, and variability. Overall, this is a great resource for any mathematics classroom studying statistics.
STATISTICAL METHODS INFECTIOUS METHODS
Appendix G STATISTICAL METHODS INFECTIOUS METHODS STATISTICAL ROADMAP Prepared in Support of: CDC for Environmental Health 1 #12;Statistical Methods for Analyzing Data Collected During the Churchill County Study 1 with the complex statistical analysis, investigators from the CDC contracted with Battelle for their assistance
Accelerated molecular dynamics methods
Perez, Danny [Los Alamos National Laboratory
2011-01-04
The molecular dynamics method, although extremely powerful for materials simulations, is limited to times scales of roughly one microsecond or less. On longer time scales, dynamical evolution typically consists of infrequent events, which are usually activated processes. This course is focused on understanding infrequent-event dynamics, on methods for characterizing infrequent-event mechanisms and rate constants, and on methods for simulating long time scales in infrequent-event systems, emphasizing the recently developed accelerated molecular dynamics methods (hyperdynamics, parallel replica dynamics, and temperature accelerated dynamics). Some familiarity with basic statistical mechanics and molecular dynamics methods will be assumed.
Statistical Applets: Animated Exercise
NSDL National Science Digital Library
Duckworth, William
This collection of statistical applets is designed to accompany the textbook, "Practice of Business Statistics." The applets can be used without the textbook and cover many introductory statistics concepts including mean, normal curve, correlation and regression, probability, the law of large numbers, the central limit theorem, confidence intervals, statistical significance, power, and ANOVA. This is a great collection of interactive materials for either instructors or students studying statistics.
THE ROYAL STATISTICAL SOCIETY AND STATISTICAL EDUCATION
Neville Hunt; Flavia Jolliffe; Neville Davies
2002-01-01
This paper describes the role of the Royal Statistical Society in shaping statistical education within the UK and further afield. Until 2001 the Society had four agencies concerned with education at all levels. The work of these is discussed and recent new arrangements are outlined. The Society's efforts to disseminate good practice through organising meetings and running a network of
Teaching Introductory Statistics: From dull to Dynamic!
Utts, Jessica
attacks, and other diseases Growing better plants (pest resistant, high yield, etc) Determining what-handed people die at a younger average age? Does listening to classical music improve scores on inte
Introductory statistical mechanics for electron storage rings
Jowett, J.M.
1986-07-01
These lectures introduce the beam dynamics of electron-positron storage rings with particular emphasis on the effects due to synchrotron radiation. They differ from most other introductions in their systematic use of the physical principles and mathematical techniques of the non-equilibrium statistical mechanics of fluctuating dynamical systems. A self-contained exposition of the necessary topics from this field is included. Throughout the development, a Hamiltonian description of the effects of the externally applied fields is maintained in order to preserve the links with other lectures on beam dynamics and to show clearly the extent to which electron dynamics in non-Hamiltonian. The statistical mechanical framework is extended to a discussion of the conceptual foundations of the treatment of collective effects through the Vlasov equation.
Institute of Mathematical Statistics COLLECTIONS
Jones, Galin
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Reverse Exchangeability and Extreme Order Statistics Yindeng Jiang and Michael D. PerlmanInstitute of Mathematical Statistics COLLECTIONS Volume 00 Advances in Modern Statistical Theory of Mathematical Statistics Beachwood, Ohio, USA #12;Institute of Mathematical Statistics Collections Series Editor
Bayes Estimation Bayes Statistical Thinking
Zhang, Li-Xin
Bayes Estimation Bayes Statistical Thinking Mathematical Statistics Chapter Seven Bayes Estimation #12;Bayes Estimation Bayes Statistical Thinking Method of Estimation (IV)---Bayes Estimation Part I. Three Types of Information in Statistical Inference #12;Bayes Estimation Bayes Statistical Thinking
R. VILELA MENDES
2005-01-01
Networks have been studied mainly by statistical methods which em- phasize their topological structure. Here one collects some mathematical tools and results which might be useful to study both the dynamics of
Statistics for Chemists: Exercises
NSDL National Science Digital Library
Wehrens, Ron
This website contains a group of exercises that allow students to practice basic statistical calculations for descriptive statistics, confidence intervals, hypothesis tests, regression and experimental design. The exercises are interactive and provide feedback for students who submit wrong answers.
Anaplasmosis: Statistics and Epidemiology
... States Geography Seasonality Persons at risk Further Reading Statistics and Epidemiology Annual Cases of Anaplasmosis in the ... PDF - 21 pages] Anaplasmosis Symptoms, Diagnosis, and Treatment Statistics and Epidemiology In-Depth Information Related Tick Topics ...
... About Blood > Blood Facts and Statistics Printable Version Blood Facts and Statistics Facts about blood needs Facts ... about American Red Cross Blood Services Facts about blood needs Every two seconds someone in the U.S. ...
Interpreting Accident Statistics
Ferreira, Joseph Jr.
Accident statistics have often been used to support the argument that an abnormally small proportion of drivers account for a large proportion of the accidents. This paper compares statistics developed from six-year data ...
Immigration and Naturalization Statistics
NSDL National Science Digital Library
United States. Immigration and Naturalization Service.
The Immigration and Naturalizations Service Statistics site provides "comprehensive annual immigration statistics from 1994-1996, as well as state estimates of the United States' illegal alien resident and foreign-born populations."
... Research AMIGAS Fighting Cervical Cancer Worldwide Stay Informed Statistics for Other Kinds of Cancer Breast Cervical Colorectal ( ... Skin Vaginal and Vulvar Cancer Home Uterine Cancer Statistics Language: English Español (Spanish) Recommend on Facebook Tweet ...
Pneumocystis Pneumonia Statistics
... CDC.gov . Fungal Diseases Share Compartir Pneumocystis pneumonia Statistics Before the beginning of the HIV/AIDS epidemic ... Risk & Prevention Sources Diagnosis & Testing Treatment Health Professionals Statistics More Resources Blastomycosis Definition Symptoms People at Risk & ...
Listeria (Listeriosis) Statistics
... page: About CDC.gov . Listeria (Listeriosis) Share Compartir Statistics Estimates CDC estimates that approximately 1600 illnesses and ... 12, 2011 Case Count Map Epi Curve Surveillance Statistics People at Risk Prevention Sources of Infection Diagnosis & ...
Valley Fever (Coccidioidomycosis) Statistics
... gov . Fungal Diseases Share Compartir Valley Fever (Coccidioidomycosis) Statistics How common is valley fever? In states where ... Risk & Prevention Sources Diagnosis & Testing Treatment Health Professionals Statistics More Resources Blastomycosis Definition Symptoms People at Risk & ...
... updates Please leave this field empty Brain Tumor Statistics SHARE Share on Facebook Preview your comments Share ... Close Finish Home > About Us > News > Brain Tumor Statistics Listen Brain Tumors do not discriminate. Primary brain ...
Ehrlichiosis: Statistics and Epidemiology
... Persons at risk Other Ehrlichiosis, Undetermined Further Reading Statistics and Epidemiology Annual Cases of Ehrlichiosis in the ... PDF - 21 pages] Ehrlichiosis Symptoms, Diagnosis, and Treatment Statistics and Epidemiology In-Depth Information Related Tick Topics ...
Background & Statistics FAQ About Homeless Veterans Homeless Veterans Facts Demographics of Homeless Veterans Incarcerated Veterans Research Briefs Sources FAQ ... VETERANS In May 2007, the Bureau of Justice Statistics released a special report on incarcerated veterans. The ...
Electronic Statistics Textbook
NSDL National Science Digital Library
"This Electronic Statistics Textbook offers training in the understanding and application of statistics ... and covers a wide variety of applications, including laboratory research (biomedical, agricultural, etc.), business statistics and forecasting, social science statistics and survey research, data mining, engineering and quality control applications, and many others." The contents of this site are too numerous to list, but it suffices to say that it will be difficult to find a concept not covered by this online text.
NSDL National Science Digital Library
Swift, J.
Created by J. Swift of the Royal Statistical Society, this article describes an exercise, probability and statistics, which develops a statistic that measures the variety of noun usage in order to distinguish two authors. The exercise emphasizes the use of frequency.
NSDL National Science Digital Library
Wehrens, R.
This site is a comprehensive resource on statistics, including information on descriptive statistics, confidence intervals, hypothesis testing, regression, ANOVA, experimental design, and multivariate statistics. Web-based exercises are interspersed throughout the text, allowing students to practice what they are learning and to obtain immediate feedback.
Deconstructing Statistics Anxiety.
ERIC Educational Resources Information Center
Earley, Mark A.; Mertler, Craig A.
A number of scales have been developed to measure the construct of statistics anxiety, the anxiety students feel when they take a statistics course, but few researchers have examined whether this anxiety is due solely to being enrolled in a statistics course or if there is some component that is simply a function of being a student (anxiety in any…
- mental statistics, epidemiology, financial modeling, image processing, massive data, machine control, robust methods, statistical computing, statistical genetics and link- age analysis, spatial opportunities through our collaborative Ph.D. program with the University of Texas M.D. Anderson Cancer Center
NSDL National Science Digital Library
Panchenko, Dmitry
Dmitry Panchenko of the Massachusetts Institute of Technology is an undergraduate course in Statistics for Applications. The site features lecture notes, a syllabus and assignments. Course topics include hypothesis testing and estimation, confidence intervals, chi-square tests, nonparametric statistics, analysis of variance, regression and correlation. This is a nice example of a course structure for an applied statistics course.
Giovanni Gallavotti STATISTICAL MECHANICS
Roma "La Sapienza", UniversitÃ di
Giovanni Gallavotti STATISTICAL MECHANICS Short Treatise Roma 1999 #12; . #12; Short treatise of Statistical Mechanics Giovanni Gallavotti Dipartimento di Fisica Universitâ??a di Roma La Sapienza 00185 Roma that started with my involvement as Coordinator of the Statistical Mechanics section of the Italian Encyclo
Giovanni Gallavotti STATISTICAL MECHANICS
Roma "La Sapienza", UniversitÃ di
Giovanni Gallavotti STATISTICAL MECHANICS Short Treatise Roma 1999 #12;. #12;Short treatise of Statistical Mechanics Giovanni Gallavotti Dipartimento di Fisica Universit`a di Roma La Sapienza 00185 Roma that started with my involvement as Coordinator of the Statistical Mechanics section of the Italian Encyclo
Teaching Statistics Using SAS.
ERIC Educational Resources Information Center
Mandeville, Garrett K.
The Statistical Analysis System (SAS) is presented as the single most appropriate statistical package to use as an aid in teaching statistics. A brief review of literature in which SAS is compared to SPSS, BMDP, and other packages is followed by six examples which demonstrate features unique to SAS which have pedagogical utility. Of particular…
Statistical quality management
NASA Astrophysics Data System (ADS)
Vanderlaan, Paul
1992-10-01
Some aspects of statistical quality management are discussed. Quality has to be defined as a concrete, measurable quantity. The concepts of Total Quality Management (TQM), Statistical Process Control (SPC), and inspection are explained. In most cases SPC is better than inspection. It can be concluded that statistics has great possibilities in the field of TQM.
Statistical Computing Software Reviews
Mark J. Schervish
1985-01-01
This department includes the two sections New Developments in Statistical Computing and Statistical Computing Software Reviews; suitable contents for each of these sections is described under the respective section heading. Articles submitted for the department, outside the two sections, should not be highly technical and should be relevant to the teaching or practice of statistical computing.This section is similar in
NSDL National Science Digital Library
Statistics Canada's website designed to teach secondary mathematics and information studies students statistical information. Each chapter is intended to be complete in itself, with exercises and lesson plans. The site covers a broad spectrum of topics involving statistics. Overall, it is a comprehensive view of this vast field.
NSDL National Science Digital Library
2012-01-01
This website provides links to all current and past issues of "The Statistics Teacher Network". This newsletter for K-12 teachers is published three times a year, and presents up to date articles that describe statistical activities that have been successful in the classroom. It also informs educators of statistical workshops, programs, and reviews of books, software, and calculators.
ERIC Educational Resources Information Center
Strasser, Nora
2007-01-01
Avoiding statistical mistakes is important for educators at all levels. Basic concepts will help you to avoid making mistakes using statistics and to look at data with a critical eye. Statistical data is used at educational institutions for many purposes. It can be used to support budget requests, changes in educational philosophy, changes to…
Statistical Convergence and Convergence in Statistics
Mark Burgin; Oktay Duman
2006-12-07
Statistical convergence was introduced in connection with problems of series summation. The main idea of the statistical convergence of a sequence l is that the majority of elements from l converge and we do not care what is going on with other elements. We show (Section 2) that being mathematically formalized the concept of statistical convergence is directly connected to convergence of such statistical characteristics as the mean and standard deviation. At the same time, it known that sequences that come from real life sources, such as measurement and computation, do not allow, in a general case, to test whether they converge or statistically converge in the strict mathematical sense. To overcome limitations induced by vagueness and uncertainty of real life data, neoclassical analysis has been developed. It extends the scope and results of the classical mathematical analysis by applying fuzzy logic to conventional mathematical objects, such as functions, sequences, and series. The goal of this work is the further development of neoclassical analysis. This allows us to reflect and model vagueness and uncertainty of our knowledge, which results from imprecision of measurement and inaccuracy of computation. In the context on the theory of fuzzy limits, we develop the structure of statistical fuzzy convergence and study its properties.
Shalabh Gupta; Dheeraj S. Singh; Asok Ray
2008-01-01
This paper addresses online monitoring of fatigue damage in polycrystalline alloy structures based on statistical pattern analysis of ultrasonic sensor signals. The real-time data-driven method for fatigue damage monitoring is based on the concepts derived from statistical mechanics, symbolic dynamics and statistical pattern identification. The underlying concept is detection and identification of small changes in statistical patterns of ultrasonic data
This article presents a general and versatile methodology for assessing sustainability with Fisher Information as a function of dynamic changes in urban systems. Using robust statistical methods, six Metropolitan Statistical Areas (MSAs) in Ohio were evaluated to comparatively as...
Random paths and current fluctuations in nonequilibrium statistical mechanics
Gaspard, Pierre [Center for Nonlinear Phenomena and Complex Systems and Department of Physics, Université Libre de Bruxelles, Code Postal 231, Campus Plaine, B-1050 Brussels (Belgium)
2014-07-15
An overview is given of recent advances in nonequilibrium statistical mechanics about the statistics of random paths and current fluctuations. Although statistics is carried out in space for equilibrium statistical mechanics, statistics is considered in time or spacetime for nonequilibrium systems. In this approach, relationships have been established between nonequilibrium properties such as the transport coefficients, the thermodynamic entropy production, or the affinities, and quantities characterizing the microscopic Hamiltonian dynamics and the chaos or fluctuations it may generate. This overview presents results for classical systems in the escape-rate formalism, stochastic processes, and open quantum systems.
BS in STATISTICS: Statistical Science Emphasis (695220) MAP Sheet Department of Statistics
Olsen Jr., Dan R.
BS in STATISTICS: Statistical Science Emphasis (695220) MAP Sheet Department of Statistics the following: Stat 121 Principles of Statistics Stat 151 Introduction to Bayesian Statistics Stat 201 Statistics for Engineers & Scientists Stat 301 Statistics & Probability for Sec Ed Note: Students who have
Springer Series in Statistics Springer Series in Statistics
Cappé, Olivier
Springer Series in Statistics Springer Series in Statistics Inference in Hidden Markov Models class of statistical models with applications in diverse areas such as communications engineering models, including both algo- rithms and statistical theory. Topics range from filtering and smoothing
NASA Technical Reports Server (NTRS)
Fleck, R. L.
1970-01-01
The use of the dynamic EKG study as a part of periodic health examination is considered to be a valuable complement to other forms of stress testing with its ability to detect abnormal heart responses to stress stimuli. It is believed that statistical correlations of dynamic EKG findings with physical examination results contribute greatly to the understanding of cardiac abnormalities.
The Relationship Between Statistics Anxiety and Attitudes Toward Statistics
Recep KOÇAK; Paul F. ZELHART
2007-01-01
As the applications of statistical techniques have increased, studies that investigate the problems faced while teaching statistics have increased as well. However, most problems faced in statistics teaching are not due to cognitive deficiencies but may be due to attitudinal factors such as statistics anxiety. In the present study, the relationship between statistics anxiety and attitudes towards statistics anxiety was
1 Statistics Statistics plays an important role throughout society, providing
Vertes, Akos
1 Statistics STATISTICS Statistics plays an important role throughout society, providing data. They also explore how those skills can be applied to develop new initiatives. Statistics is one. UNDERGRADUATE Bachelor's program · Bachelor of Science with a major in statistics (http:// bulletin.gwu.edu/arts-sciences/statistics
Ternary algebras with braided statistics
Azzouz Zinoun
2010-03-06
Algebraic relations that characterize quantum statistics (Bose-Einstein statistic, Fermi-Dirac statistic, supersymmetry, parastatistic, anyonic statistic, ...) are reformulated herein in terms of a new algebraic structure, which we call para-algebra.
Ternary algebras with braided statistics
Zinoun, Azzouz
2010-01-01
Algebraic relations that characterize quantum statistics (Bose-Einstein statistic, Fermi-Dirac statistic, supersymmetry, parastatistic, anyonic statistic, ...) are reformulated herein in terms of a new algebraic structure, which we call para-algebra.
Adoption and Foster Care Statistics
... Research » Adoption & Foster Care Statistics Adoption & Foster Care Statistics Listen The Adoption and Foster Care Analysis and ... 2003) State-by-State Adoption and Foster Care Statistics State-Specific Adoption Statistics 2013 2012 2011 2010 ...
NSDL National Science Digital Library
Abebe, Asheber
This online introductory statistics textbook covers basic descriptive, statistical, and graphical procedures for analyzing data sets and contains three data sets and a practice final exam. Chapter headings include: descriptive statistics, probability, resampling, discrete probability models, continuous probability models, central limit theorem, confidence intervals, tests of hypotheses, estimation of effect: two independent samples, design of experiments, and regression. The relation to this site includes exercises.
NSDL National Science Digital Library
Matt Laposata
Statistics play a vital role in the scientific enterprise. This activity provides background information and tutorials on basic statistics (mean, median, standard deviation, etc.) used in science. Topics include descriptive statistics (measures of central tendency and dispersion) and presenting data (tables, figures, and graphs). Sample datasets from actual scientific experiments are used to illustrate points. Links to an online statisitical tool and an online graphing application are also provided.
NSDL National Science Digital Library
Devine, Craig
Statistical Process Control is a lesson plan which provides an overview of Statistical Process Control, showing the value of collecting and analyzing data that enables people to systematically analyze and improve a process. After completing this module, students should be able to construct and interpret different statistical charts in order to evaluate a process. Note: This module is part of a modularized manufacturing technology curriculum created by the PSCME, found at www.pscme.org/educators.html.
SRB STATES AND NONEQUILIBRIUM STATISTICAL MECHANICS CLOSE TO EQUILIBRIUM.
Ruelle, David
SRB STATES AND NONEQUILIBRIUM STATISTICAL MECHANICS CLOSE TO EQUILIBRIUM. by Giovanni Gallavotti. Nonequilibrium statistical mechanics close to equilibrium is studied using SRB states and a formula [10 in this direction is to use nonequilibrium steady states, which are de#12;ned to be the SRB states for the dynamics
SYMBOL STATISTICS: A NEW TOOL FOR UNDERSTANDING MULTIPHASE FLOW PHENOMENA
Tennessee, University of
. In the language of nonlinear dynamics, we use symbol statistics to identify characteristic un- stableSYMBOL STATISTICS: A NEW TOOL FOR UNDERSTANDING MULTIPHASE FLOW PHENOMENA C.S. Daw Oak Ridge symbolization as a tool for identifying tempo- ral patterns in complex measurement signals. We describe
Statistical distribution sampling
NASA Technical Reports Server (NTRS)
Johnson, E. S.
1975-01-01
Determining the distribution of statistics by sampling was investigated. Characteristic functions, the quadratic regression problem, and the differential equations for the characteristic functions are analyzed.
NSDL National Science Digital Library
This free statistics textbook from Boundless Learning is based off openly available educational resources such as "government resources, open educational repositories, and other openly licensed websites." The textbook contains 14 chapters such as Introduction to Statistics and Statistical Thinking, Statistics in Practice, Visualizing Data, and Frequency Distributions. The textbook can be browsed on this page or downloaded as a pdf. Students can register for a free Boundless account to access a search engine and other study tools to efficiently find specific topics and master the content.
Statistical Inference Using Extreme Order Statistics
James Pickands III
1975-01-01
A method is presented for making statistical inferences about the upper tail of a distribution function. It is useful for estimating the probabilities of future extremely large observations. The method is applicable if the underlying distribution function satisfies a condition which holds for all common continuous distribution functions.
DEPARTMENT OF STATISTICS Statistics 101 Spring 2014
Buja, Andreas
will be distributed and managed via this website, and you will be able to monitor your grade entries throughout:30-5:30, in F96 JMHH COURSE WEBSITE: Statistics 101 uses the online system "Canvas". You can gain access, exams and scheduling. If you have questions, you must go there first to see whether your question has
Stellar Evolution A Statistical Model
van Dyk, David
Stellar Evolution A Statistical Model Statistical Computation Analysis of the Hyades Cluster Statistical Analysis of Stellar Evolution David A. van Dyk1 Steven DeGennaro2 Nathan Stein2 William H Statistical Analysis of Stellar Evolution #12;Stellar Evolution A Statistical Model Statistical Computation
Kulik, Rafal
R for Statistics Rafal Kulik Department of Mathematics and Statistics University of Ottawa Statistical Society of Ottawa 23 September 2011 Rafal Kulik #12;R for Statistics SSO meeting Plan Rafal Kulik 1 #12;R for Statistics SSO meeting Plan What is R? Rafal Kulik 1 #12;R for Statistics SSO meeting
Statistical complexity measure of pseudorandom bit generators
NASA Astrophysics Data System (ADS)
González, C. M.; Larrondo, H. A.; Rosso, O. A.
2005-08-01
Pseudorandom number generators (PRNG) are extensively used in Monte Carlo simulations, gambling machines and cryptography as substitutes of ideal random number generators (RNG). Each application imposes different statistical requirements to PRNGs. As L’Ecuyer clearly states “the main goal for Monte Carlo methods is to reproduce the statistical properties on which these methods are based whereas for gambling machines and cryptology, observing the sequence of output values for some time should provide no practical advantage for predicting the forthcoming numbers better than by just guessing at random”. In accordance with different applications several statistical test suites have been developed to analyze the sequences generated by PRNGs. In a recent paper a new statistical complexity measure [Phys. Lett. A 311 (2003) 126] has been defined. Here we propose this measure, as a randomness quantifier of a PRNGs. The test is applied to three very well known and widely tested PRNGs available in the literature. All of them are based on mathematical algorithms. Another PRNGs based on Lorenz 3D chaotic dynamical system is also analyzed. PRNGs based on chaos may be considered as a model for physical noise sources and important new results are recently reported. All the design steps of this PRNG are described, and each stage increase the PRNG randomness using different strategies. It is shown that the MPR statistical complexity measure is capable to quantify this randomness improvement. The PRNG based on the chaotic 3D Lorenz dynamical system is also evaluated using traditional digital signal processing tools for comparison.
Statistical Reference Datasets: Archives
NSDL National Science Digital Library
The datasets on this page are classified by analysis techniqueand by level of difficulty (lower, average, higher). They were originally intended to test statistical software. The sets cover these topics: ANOVA, linear regression, Markov Chain Monte Carlo, nonlinear regression, and univariate summary statistics. This is a nice collection as it not only contains raw data but also helps explain the different methods and tests.
Statistical Applets: Confidence Intervals
NSDL National Science Digital Library
Duckworth, William
Created by Duckworth, McCabe, Moore and Sclove for W.H. Freeman and Co., this applet is a visual representation of confidence levels and accompanies "Â?Â?Practice of Business Statistics;" however, it can be used without this text. Even though brief, this is a nice interactive resource for an introductory statistics course.
Statistical Applets: Probability
NSDL National Science Digital Library
Duckworth, William
Created by authors Duckworth, McCabe, Moore and Sclove for W.H. Freeman and Co., this applet simulates flipping a coin to show how observed probability approaches true probability over time. It accompanies "Â?Â?Practice of Business Statistics," but can be used without this text. Even though brief, this is still a fine resource for an introductory statistics course.
Some More Statistical Exercises
NSDL National Science Digital Library
Langan, James F.
A continuation of a previous unit, expanding to talk about standard deviation, tell some stories about statistics, show what statistics is, and provide three computer programs to demonstrate activities one may do in class, or students may use independently. In passing, it answers the question: How can you tell if the coin flips or the dice are random?
D A Kirzhnits; Yurii E Lozovik; Galina V Shpatakovskaya
1975-01-01
This review is devoted to the development of the statistical model of matter over the last twenty years. The ranges of applicability of the model for electron-nuclear systems (atoms, solids, plasmas) are considered. Effects lying beyond the scope of statistical model (exchange, correlation, quantum and shell effects) are analyzed. The relative roles of the effects enumerated are estimated in different
ERIC Educational Resources Information Center
Hodgson, Ted; Andersen, Lyle; Robison-Cox, Jim; Jones, Clain
2004-01-01
Water quality experiments, especially the use of macroinvertebrates as indicators of water quality, offer an ideal context for connecting statistics and science. In the STAR program for secondary students and teachers, water quality experiments were also used as a context for teaching statistics. In this article, we trace one activity that uses…
NSDL National Science Digital Library
Dinov, Ivo
This page, created by Ino Dinov of the University of California, Berkeley, provides distribution calculators for the binomial, normal, Student's T, Chi-square, and Fisher's F distributions. Users set the parameters and enter either the probability or the test statistic and the calculators return the missing value. This is a simple, yet effective, statistical tool for instructors and students.
Finite Order Statistic Experiment
NSDL National Science Digital Library
Kyle Siegrist
This resource consists of a Java applet and expository text. The applet is a simulation of the experiment of selecting n objects at random from the first m positive integers. The random variables of interest are the order statistics. The applet illustrates the distributions of the order statistics.
Weakly sufficient quantum statistics
Katarzyna Lubnauer; Andrzej ?uczak; Hanna Pods?dkowska
2009-11-23
Some aspects of weak sufficiency of quantum statistics are investigated. In particular, we give necessary and sufficient conditions for the existence of a weakly sufficient statistic for a given family of vector states, investigate the problem of its minimality, and find the relation between weak sufficiency and other notions of sufficiency employed so far.
Elementary Concepts in Statistics
NSDL National Science Digital Library
This introductory statistics introduction, by StatSoft, gives an overview of variables, classifications, measurements, relations, and other basic statistical concepts. There are also two animated graphs illustrating density and distribution functions, as well as how sample size influences sampling distribution.
The purpose of the Disability Statistics Center is to produce and disseminate statistical information on disability and the status of people with disabilities in American society and to establish and monitor indicators of how conditions are changing over time to meet their health...
Statistical Mapping by Computer.
ERIC Educational Resources Information Center
Utano, Jack J.
The function of a statistical map is to provide readers with a visual impression of the data so that they may be able to identify any geographic characteristics of the displayed phenomena. The increasingly important role played by the computer in the production of statistical maps is manifested by the varied examples of computer maps in recent…
Missing Children, Misleading Statistics.
ERIC Educational Resources Information Center
Best, Joel
1988-01-01
Examines the importance of defining terms in the process of gathering statistical data. Cites the example of the debate over the number of children abducted by strangers. Concludes that statistics are part of the persuasive rhetoric of social problem promotion and have social consequences. (FMW)
Explorations in Statistics: Correlation
ERIC Educational Resources Information Center
Curran-Everett, Douglas
2010-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This sixth installment of "Explorations in Statistics" explores correlation, a familiar technique that estimates the magnitude of a straight-line relationship between two variables. Correlation is meaningful only when the…
ERIC Educational Resources Information Center
Huizingh, Eelko K. R. E.
2007-01-01
Accessibly written and easy to use, "Applied Statistics Using SPSS" is an all-in-one self-study guide to SPSS and do-it-yourself guide to statistics. What is unique about Eelko Huizingh's approach is that this book is based around the needs of undergraduate students embarking on their own research project, and its self-help style is designed to…
Sunil K. JainandVishwani; Vishwani Agrawal
1985-01-01
Statistical Fault Analysis, or Stafan, is proposed as an alternative to fault simulation of digital circuits. This method defines Controllabilities and observabilities of circuit nodes as probabilities estimated from signal statistics of fault-free simulation. Special Procedures deal with these quantities at fanout and feedback nodes. The computed probabilities are used to derive unbiased estimates of fault detection probabilities and overall
Explorations in Statistics: Regression
ERIC Educational Resources Information Center
Curran-Everett, Douglas
2011-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This seventh installment of "Explorations in Statistics" explores regression, a technique that estimates the nature of the relationship between two things for which we may only surmise a mechanistic or predictive connection.…
Reform in Statistical Education
ERIC Educational Resources Information Center
Huck, Schuyler W.
2007-01-01
Two questions are considered in this article: (a) What should professionals in school psychology do in an effort to stay current with developments in applied statistics? (b) What should they do with their existing knowledge to move from surface understanding of statistics to deep understanding? Written for school psychologists who have completed…
Puzzles in Statistical Reasoning
ERIC Educational Resources Information Center
Tempelaar, Dirk T.; Gijselaers, Wim H.; van der Loeff, Sybrand Schim
2006-01-01
The Statistical Reasoning Assessment or SRA is one of the first objective instruments developed to assess students' statistical reasoning. Published in 1998 (Garfield, 1998a), it became widely available after the Garfield (2003) publication. Empirical studies applying the SRA by Garfield and co-authors brought forward two intriguing puzzles: the…
Scalable statistical bug isolation
Ben Liblit; Mayur Naik; Alice X. Zheng; Alexander Aiken; Michael I. Jordan
2005-01-01
We present a statistical debugging algorithm that isolates bugs in programs containing multiple undiagnosed bugs. Earlier statistical algorithms that focus solely on identifying predictors that correlate with program failure perform poorly when there are multiple bugs. Our new technique separates the effects of different bugs and identifies predictors that are associated with individual bugs. These predictors reveal both the circumstances
NSDL National Science Digital Library
This journals from The Institute of Mathematical Statistics is now available online. Statistical Science, Vols. 1-12 (1986-1997) is fully accessible to the hundreds of academic institutions participating in JSTOR. The journal may be searched by keyword, full-text, title, author, and abstract, or browsed by date of publication. A list of JSTOR participants is provided at the JSTOR site.
Categories and quantum statistics
NASA Astrophysics Data System (ADS)
Marcinek, W?adysz. xl; law
1996-10-01
The proposal for the general theory of commutation relations for creation and annihilation operators for a particle system equipped with arbitrary quantum statistics is given in terms of the theory of monoidal categories with duality. The space of quantum single particle states is an object in the category. The statistics is described as a natural isomorphism between right and left dual structure.
Vijayaraj, Veeraraghavan [ORNL; Cheriyadat, Anil M [ORNL; Bhaduri, Budhendra L [ORNL; Vatsavai, Raju [ORNL; Bright, Eddie A [ORNL
2008-01-01
Statistical properties of high-resolution overhead images representing different land use categories are analyzed using various local and global statistical image properties based on the shape of the power spectrum, image gradient distributions, edge co-occurrence, and inter-scale wavelet coefficient distributions. The analysis was performed on a database of high-resolution (1 meter) overhead images representing a multitude of different downtown, suburban, commercial, agricultural and wooded exemplars. Various statistical properties relating to these image categories and their relationship are discussed. The categorical variations in power spectrum contour shapes, the unique gradient distribution characteristics of wooded categories, the similarity in edge co-occurrence statistics for overhead and natural images, and the unique edge co-occurrence statistics of downtown categories are presented in this work. Though previous work on natural image statistics has showed some of the unique characteristics for different categories, the relationships for overhead images are not well understood. The statistical properties of natural images were used in previous studies to develop prior image models, to predict and index objects in a scene and to improve computer vision models. The results from our research findings can be used to augment and adapt computer vision algorithms that rely on prior image statistics to process overhead images, calibrate the performance of overhead image analysis algorithms, and derive features for better discrimination of overhead image categories.
NSDL National Science Digital Library
The US Department of Labor Bureau of Labor Statistics collects "succinct, up-to-the-minute background papers on current topics" at the Issues in Labor Statistics publication page. Each two-page edition addresses labor topics as diverse as auto dealer employment and highway fatalities with graphical summaries and BLS contacts for additional information.
Deconstructing Statistical Analysis
ERIC Educational Resources Information Center
Snell, Joel
2014-01-01
Using a very complex statistical analysis and research method for the sake of enhancing the prestige of an article or making a new product or service legitimate needs to be monitored and questioned for accuracy. 1) The more complicated the statistical analysis, and research the fewer the number of learned readers can understand it. This adds a…
NSDL National Science Digital Library
Great Britain. Parliament. House of Commons. Library.
1998-01-01
This new UK government report are from the House of Commons Library contains statistics on defense spending and manpower and addresses "the problems involved in using such statistics, particularly when making international comparisons." The report also contains numerous graphs and tables.
ERIC Educational Resources Information Center
Rike, Galen E., Ed.
1974-01-01
The Illinois State Library has compiled statistical and other information about the public libraries in the state. The first section lists each library alphabetically, gives the name of the head librarian, county and type of library, and lists statistics on population, fees, hours, transactions, staff, book and non-book resources, assessed…
Generalized interpolative quantum statistics
NASA Astrophysics Data System (ADS)
Ramanathan, R.
1992-06-01
A generalized interpolative quantum statistics is presented by conjecturing a certain reordering of phase space due to the presence of possible exotic objects other than bosons and fermions. Such an interpolation achieved through a Bose-counting strategy predicts the existence of an infinite quantum Boltzmann-Gibbs statistics akin to the one discovered by Greenberg recently.
Australian Bureau of Statistics
NSDL National Science Digital Library
For those looking for statistical information on a broad set of themes and geographical areas within Australia, they should visit the Australian Bureau of Statistics Web site. From the main page, visitors can view recent statistical reports, such as the Australian Consumer Price Index, information about the labor force (e.g., employment rates), and a series of occasional papers. Particularly helpful to the casual user will be the Themes section, which provides summary statistics about the environment, tourism, transportation, economic well-being, and education. Additionally, the Bureau publishes reports organized by administrative and regional divisions of the country, a feature that will be helpful to students doing research on a particular area of the country. If users are seeking to learn more about the organization, history, and mission of the Australian Bureau of Statistics, they will find this material located under the About the ABS section of the site.
Communication Dynamics of Blog Networks
NASA Astrophysics Data System (ADS)
Goldberg, Mark; Kelley, Stephen; Magdon-Ismail, Malik; Mertsalov, Konstantin; Wallace, William (Al)
We study the communication dynamics of Blog networks, focusing on the Russian section of LiveJournal as a case study. Communication (blogger-to-blogger links) in such online communication networks is very dynamic: over 60% of the links in the network are new from one week to the next, though the set of bloggers remains approximately constant. Two fundamental questions are: (i) what models adequately describe such dynamic communication behavior; and (ii) how does one detect the phase transitions, i.e. the changes that go beyond the standard high-level dynamics? We approach these questions through the notion of stable statistics. We give strong experimental evidence to the fact that, despite the extreme amount of communication dynamics, several aggregate statistics are remarkably stable. We use stable statistics to test our models of communication dynamics postulating that any good model should produce values for these statistics which are both stable and close to the observed ones. Stable statistics can also be used to identify phase transitions, since any change in a normally stable statistic indicates a substantial change in the nature of the communication dynamics. We describe models of the communication dynamics in large social networks based on the principle of locality of communication: a node's communication energy is spent mostly within its own "social area," the locality of the node.
Spectral statistics of nearly unidirectional quantum graphs
Maram Akila; Boris Gutkin
2015-03-04
The energy levels of a quantum graph with time reversal symmetry and unidirectional classical dynamics are doubly degenerate and obey the spectral statistics of the Gaussian Unitary Ensemble. These degeneracies, however, are lifted when the unidirectionality is broken in one of the graph's vertices by a singular perturbation. Based on a Random Matrix model we derive an analytic expression for the nearest neighbour distribution between energy levels of such systems. As we demonstrate the result agrees excellently with the actual statistics for graphs with a uniform distribution of eigenfunctions. Yet, it exhibits quite substantial deviations for classes of graphs which show strong scarring.
Learning Statistics Online: Tools for Teaching Science Methods and Statistics
NSDL National Science Digital Library
The Utah online Virtual Lab is a JAVA program run dynamically off a database. Instructors author a statistical virtual reality simulating theories and data in a specific research focus area by defining independent, predictor, and dependent variables and the relations among them. Students work in an online virtual environment to discover the principles of this simulated reality: they go to a library, read theoretical overviews and scientific puzzles, and then go to a lab, design a study, collect and analyze data, and write a report. A student's design and data analysis decisions are computer-graded and recorded in a database; the written research report can be read by the instructor or by other students in peer groups simulating scientific conventions.
Applied Math & Statistics: Statistics Minor Curriculum Chart: 2013-2014
Stuart, Josh
Applied Math & Statistics: Statistics Minor Curriculum Chart: 2013-2014 http PSYC 181 CMPE 108 SOCY 103A CMPS 142 TIM 230 Information on the Statistics Minor The statistics minor as preparation for a graduate degree in statistics or biostatistics. Course Information With permission from
Statistics 36-756: Advanced Statistics II Syllabus: Fall, 2006
Fienberg, Stephen E.
Statistics 36-756: Advanced Statistics II Syllabus: Fall, 2006 Instructor: Stephen E. Fienberg 132G: Â· To consider major topics from statistical theory and the foundations of inference not covered in Statistics 36-756: Advanced Statistics I, such as exchangeability, the axiomatic foundation of subjective probability
Statistics: Part 1 1. Why bother with statistics?
Francis, Paul
Statistics: Part 1 1. Why bother with statistics? Why is statistics so necessary for observational. But your data just don't seem to back up their claim. Statistics allows you to determine how confidently) practical introduction to those bits of statistics most vital to observational astronomy. 2. What
NSDL National Science Digital Library
Swinscow, T. D. V. (Thomas Douglas Victor)
Created by T.D.V. Swinscow for the BMJ Publishing group, this textbook for medical statistics covers many topics such as: data display and summary, mean, standard deviation, populations , samples, statements of probability, confidence intervals, differences between means: type I and type II errors and power, differences between percentages, paired alternatives, t-tests, chi-squared tests, exact probability test, rank score tests, correlation, regression, survival analysis, study design and choosing a statistical test. This is a great resource for those interested in a broad overview of many different statistical methods.
NSDL National Science Digital Library
The University of California Los Angeles Statistics Series presents a collection of more than 250 preprints covering a wide array of statistical topics, such as descriptive multivariate analysis, advanced linear models, survey construction and analysis, teaching statistics, and much more. The preprints are arranged by paper number only, hence users must browse the entire list to locate relevant items. Approximately half of the full-text preprints are accessible in HTML, .pdf, or postscript formats. To access preprints not available electronically, users must contact the authors of the papers; author addresses are provided.
Statistics and Probability Tutorial
NSDL National Science Digital Library
Berman, Harvey
This tutorial, created by Harvey Berman of Stat Trek, provides a basic introduction to many topics in statistics and probability. Topics include: sets and subsets, statistical experiments, counting, basic probability rules, Bayes' theorem, probability distributions, discrete versus continuous, binomial, negative binomial, hypergeometric, multinomial, Poisson, normal, sampling theory, central tendency, variability, sampling distributions, t-distribution, Chi-square distribution, F-distribution, estimation problems, hypothesis testing, power, survey sampling, simple random samples, stratified samples, cluster samples, sample size. This is a general overview of statistics and probability. It is geared towards a high school advanced placement level.
Criminal Justice Statistics Center
NSDL National Science Digital Library
Maintained by the Attorney General of California, this site "contains more than 3,400 statistical tables, 59 reports, 26 publications as well as links to federal, state, and local agency statistics." Recently posted materials include the Report on Violent Crimes Committed Against Senior Citizens in California, 1998 and Crime 1999 in Selected California Jurisdictions, January through June, Preliminary Report. The site posts statistics on every aspect of crime and corrections in the nation's most populous state, including types of crimes, arrests, expenditures, prison populations, probation, and more. Data tables are generally in .pdf format; reports are offered in .pdf and/or HTML formats.
Statistic Simulations and Demonstrations
NSDL National Science Digital Library
Over twenty Java applets from Online Statistics are presented on this site. The applets cover most of the major points taught in an introductory statistics course. One quality that makes this site stand out from others is the excellent background information presented with many applets, which lets users read about a concept and see it visually at the same time. Topics include applications of the central limit theorem, regression, analysis of variance, and many more. The applets are all very easy to use, and they are certainly valuable demonstrations for any high school or college student in statistics.
Statistical Theories of Fragmentation and Nuclear Disassembly
NASA Astrophysics Data System (ADS)
Chase, Kevin Charles
A general statistical study of fragmentation and aggregation processes is presented and applied to the fragmentation and thermodynamics of heated nuclear matter. Emphasis is placed on distinguishing combinatorial aspects from the statistical and thermodynamic ones. Combinatorial objects pertinent to fragmentation include integer, vector and set partitions as well as permutations. Algorithms for enumerating and randomly selecting these objects, important for statistical models invoking these objects, are presented. Statistical concepts introduced include approximate methods such as Monte Carlo sampling and Markov processes, and exact methods such as recursion relations and generating function identities. Statistical models introduced and solved exactly include the equipartition weight and the Gibbs weight. The canonical Gibbs model is studied extensively, and is shown to be related to symmetric functions and Polyade Bruijn enumeration theory. These exactly solvable models have been applied to Bose-Einstein condensation, the lambda transition in liquid ^4He, polymer gelation, Ewens' sampling formula in population genetics, group social dynamics, statistical shattering, and the enumeration of involutions, graphs and digraphs, indicating their flexibility and power. The application of these models to nuclear fragmentation results in a computationally simplified model which contains most of the essential physics. This model is shown to maintain its structure under coarse graining with suitable conditions on its parameters. The thermodynamics of nuclei allowed to fragment is studied in this context, and predictions are compared with experimental data. A critical comparison of this model to the competing percolation model indicates certain advantages to this approach.
Statistical Mechanics of Turbulent Dynamos
NASA Technical Reports Server (NTRS)
Shebalin, John V.
2014-01-01
Incompressible magnetohydrodynamic (MHD) turbulence and magnetic dynamos, which occur in magnetofluids with large fluid and magnetic Reynolds numbers, will be discussed. When Reynolds numbers are large and energy decays slowly, the distribution of energy with respect to length scale becomes quasi-stationary and MHD turbulence can be described statistically. In the limit of infinite Reynolds numbers, viscosity and resistivity become zero and if these values are used in the MHD equations ab initio, a model system called ideal MHD turbulence results. This model system is typically confined in simple geometries with some form of homogeneous boundary conditions, allowing for velocity and magnetic field to be represented by orthogonal function expansions. One advantage to this is that the coefficients of the expansions form a set of nonlinearly interacting variables whose behavior can be described by equilibrium statistical mechanics, i.e., by a canonical ensemble theory based on the global invariants (energy, cross helicity and magnetic helicity) of ideal MHD turbulence. Another advantage is that truncated expansions provide a finite dynamical system whose time evolution can be numerically simulated to test the predictions of the associated statistical mechanics. If ensemble predictions are the same as time averages, then the system is said to be ergodic; if not, the system is nonergodic. Although it had been implicitly assumed in the early days of ideal MHD statistical theory development that these finite dynamical systems were ergodic, numerical simulations provided sufficient evidence that they were, in fact, nonergodic. Specifically, while canonical ensemble theory predicted that expansion coefficients would be (i) zero-mean random variables with (ii) energy that decreased with length scale, it was found that although (ii) was correct, (i) was not and the expected ergodicity was broken. The exact cause of this broken ergodicity was explained, after much investigation, by greatly extending the statistical theory of ideal MHD turbulence. The mathematical details of broken ergodicity, in fact, give a quantitative explanation of how coherent structure, dynamic alignment and force-free states appear in turbulent magnetofluids. The relevance of these ideal results to real MHD turbulence occurs because broken ergodicity is most manifest in the ideal case at the largest length scales and it is in these largest scales that a real magnetofluid has the least dissipation, i.e., most closely approaches the behavior of an ideal magnetofluid. Furthermore, the effects grow stronger when cross and magnetic helicities grow large with respect to energy, and this is exactly what occurs with time in a real magnetofluid, where it is called selective decay. The relevance of these results found in ideal MHD turbulence theory to the real world is that they provide at least a qualitative explanation of why confined turbulent magnetofluids, such as the liquid iron that fills the Earth's outer core, produce stationary, large-scale magnetic fields, i.e., the geomagnetic field. These results should also apply to other planets as well as to plasma confinement devices on Earth and in space, and the effects should be manifest if Reynolds numbers are high enough and there is enough time for stationarity to occur, at least approximately. In the presentation, details will be given for both theoretical and numerical results, and references will be provided.
Poisson statistics in the high temperature QCD Dirac spectrum
Tamás G. Kovács; Ferenc Pittler
2011-11-15
We analyze the eigenvalue statistics of the staggered Dirac operator above $T_{c}$ in QCD with 2+1 flavors of dynamical quarks. We use physical quark masses in our simulations. We compare the eigenvalue statistics from several parts of the Dirac spectrum with the predictions of Random Matrix Theory for this universality class and with Poisson statistics. We show that at the low end of the spectrum the eigenmodes are localized and obey Poisson statistics. Above a boundary region the eigenmodes become delocalized and obey Random Matrix statistics. Thus the QCD Dirac spectrum with physical dynamical quarks also has the Poisson to Random Matrix transition previously seen in the quenched SU(2) theory.
Breaking of a bond: when is it statistical?
Yadav, Pankaj Kumar; Keshavamurthy, Srihari
2015-01-01
Unimolecular dissociation dynamics of a model three degree of freedom triatomic molecule is studied in order to understand the mechanisms for deviations from statisticality. Performing a wavelet based time-frequency analysis of the dynamics allows for the dynamics to be followed on the network of nonlinear resonances, also called as the Arnold web. The results indicate that the long lifetime trajectories spend a considerable amount of time trapped near junctions in the web. It is argued that characterizing the dynamics near such junctions might lead to deeper insights into the origins of nonstatistical dynamics. PMID:25614326
Stellar Evolution A Statistical Model
van Dyk, David
Stellar Evolution A Statistical Model Statistical Computation Analysis of the Hyades Cluster Embedding Computer Models for Stellar Evolution into a Coherent Statistical Analysis David A. van Dyk1 Analysis of Stellar Evolution #12;Stellar Evolution A Statistical Model Statistical Computation Analysis
FISHERY STATISTICS E UNITED STATES
SH 11 .A443X FISH FISHERY STATISTICS E UNITED STATES ^ 1951 &ch 3. \\§^ ^/'· m:^ STATISTICAL DIGEST. Farley, Director Statistical Digest 30 FISHERY STATISTICS OF THE UNITED STATES 1951 BY A. W. ANDERSON;Fishery Statistics of the United States and Alaska are compiled and published annually to make available
Convergence of Quantum Statistical Experiments
Guta, Madalin
Convergence of Quantum Statistical Experiments M!d!lin Gu"! University of Nottingham Jonas Kahn (Paris-Sud) Anna Jen#ová (Bratislava) Richard Gill (Leiden) #12;Statistical experiments and statistical decision problems Statistical experiment · Measure space: (, , P) · Statistical experiment over (dominated
Cooperative Learning in Statistics.
ERIC Educational Resources Information Center
Keeler, Carolyn M.; And Others
1994-01-01
Formal use of cooperative learning techniques proved effective in improving student performance and retention in a freshman level statistics course. Lectures interspersed with group activities proved effective in increasing conceptual understanding and overall class performance. (11 references) (Author)
How Statistics "Excel" Online.
ERIC Educational Resources Information Center
Chao, Faith; Davis, James
2000-01-01
Discusses the use of Microsoft Excel software and provides examples of its use in an online statistics course at Golden Gate University in the areas of randomness and probability, sampling distributions, confidence intervals, and regression analysis. (LRW)
Desforges, B; CERN. Geneva. SPS and LHC Division
2002-01-01
2002 SPS MACHINE STATISTICS Fixed Target Periods with Protons (comments on machine operation, tables and diagrams, comparative tables and diagrams) Fixed Target Periods with Ions (comments on machine operation, tables and diagrams, comparative tables and diagrams)
NSDL National Science Digital Library
This collaboratively built digital textbook for probability and statistics education integrates technology and pedagogical techniques, makes use of materials and instructional resources that are freely accessible over the web, and provides multi-language support (at the bottom of every chapter/section/page one may obtain a machine translation of the content into many languages). Topics include describing, exploring, and comparing data; probability and probability distributions; point and interval estimates; hypothesis testing; correlation and regression; analysis of variance; and others. The text is suitable for a general statistics curriculum, but also includes Advanced Placement materials. The E-Book was initially developed by the UCLA Statistics Online Computational Resource (SOCR), but all statistics instructors, researchers, and educators are encouraged to contribute and improve the content.
NSDL National Science Digital Library
Kyle Siegrist
This resource consists of a Java applet and expository text. The applet simulates the order statistics of a random sample from a given distribution. The sample size, order, and sampling distribution can be specified.
Titanic: A Statistical Exploration.
ERIC Educational Resources Information Center
Takis, Sandra L.
1999-01-01
Uses the available data about the Titanic's passengers to interest students in exploring categorical data and the chi-square distribution. Describes activities incorporated into a statistics class and gives additional resources for collecting information about the Titanic. (ASK)
NSDL National Science Digital Library
1994-01-01
The United States Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) has made full text of "Agricultural Statistics 1994" available via its Web site. Agricultural Statistics is an annual compendium of data (and selected charts) relating to all aspects of the U.S. agricultural economy. Subject coverage includes all major crop and livestock sectors, farm income and credit, stabilization and price support, agricultural conservation and forestry statistics, and fertilizers and pesticides, among others. Tables include both state and national breakdowns, and most national tables include between two and ten year time series. The book is available as one large Adobe Acrobat .PDF file (about 5 megabytes), so you'll need a fast connection to get it. You'll also need a free Acrobat Reader, which can be obtained at the same page. Acrobat allows selective searching for specific tables, as well as selective printing of those tables. (See Network Tools, below.)
Understanding Solar Flare Statistics
NASA Astrophysics Data System (ADS)
Wheatland, M. S.
2005-12-01
A review is presented of work aimed at understanding solar flare statistics, with emphasis on the well known flare power-law size distribution. Although avalanche models are perhaps the favoured model to describe flare statistics, their physical basis is unclear, and they are divorced from developing ideas in large-scale reconnection theory. An alternative model, aimed at reconciling large-scale reconnection models with solar flare statistics, is revisited. The solar flare waiting-time distribution has also attracted recent attention. Observed waiting-time distributions are described, together with what they might tell us about the flare phenomenon. Finally, a practical application of flare statistics to flare prediction is described in detail, including the results of a year of automated (web-based) predictions from the method.
Mathematics and Statistics Models
NSDL National Science Digital Library
Developed by Bob MacKay, Clark College. What are Mathematical and Statistical Models These types of models are obviously related, but there are also real differences between them. Mathematical Models: grow out of ...
Introduction to Descriptive Statistics
NSDL National Science Digital Library
Hill, Jay
This tutorial, authored by Jay Hill of the University of Illinois at Urbana-Champaign, introduces mean, median, mode, variance, and standard deviation using sports statistics from the Internet and class-generated statistics. Students should understand stem-and-leaf plots before using this tutorial. This material is intended for class use. Excel spreadsheets with sample data are also available for download. The relation links to a letter for teachers.
NSDL National Science Digital Library
Wen, Xiao-Gang
This course, created by Wen Xiao-Geng of the Massachusetts Institute of Technology, is the second in the series of undergraduate Statistical Physics courses and features comprehensive lecture notes and assignments. Course topics include: probability distributions for both classical and quantum systems. Additional topics include: microcanonical, canonical, grand canonical partition-functions, associated thermodynamic potentials, homogeneous and heterogeneous systems. This would be a valuable resource for either an instructor or student in a statistics class.
Veeraraghavan Vijayaraj; Anil M Cheriyadat; Phil Sallee; Brian Colder; Ranga Raju Vatsavai; Eddie A. Bright; Budhendra L. Bhaduri
2008-01-01
Statistical properties of high-resolution overhead images representing different land use categories are analyzed using various local and global statistical image properties based on the shape of the power spectrum, image gradient distributions, edge co-occurrence, and inter-scale wavelet coefficient distributions. The analysis was performed on a database of high-resolution (1 meter) overhead images representing a multitude of different downtown, suburban, commercial,
Environmental Quality Statistics
NSDL National Science Digital Library
Hosted by the Council on Environmental Quality (CEQ), this site contains updated monthly tables with statistics about United States environmental quality. The major topics covered in these tables are population, economy and the environment, public lands, ecosystems, air quality, aquatic resources, terrestrial resources, pollution prevention, energy, transportation, and the global environment. The tables indicate data sources, and an archive of statistics for earlier years is provided.
NSDL National Science Digital Library
This page, created by the Department of Statistics at the University of California, Los Angeles, has data sets used by statistics classes. The html files in the second column contain descriptions of a particular data set and a link to the data at the end of the file. There are also .dat and .dta files that contain just data, with no description. The site is simple, but still contains a great deal of useful data.
NSDL National Science Digital Library
This collection of datasets from the University of Massachusetts at Amherst is categorized by topic. Each dataset and its description are in text format. Topics include: analysis of variance, analysis of covariance, cluster analysis, contingency table analysis, correlation analysis, descriptive statistics, discriminant analysis, factor analysis, nonparametric analysis, multiple regression, nonlinear regression, logistic regression, survival analysis, and time series analysis. This is a large collection of data and software which can be implemented into different aspects of statistical study.
Local Statistics of Realizable Vertex Models
Zhongyang Li
2010-06-19
We study planar "vertex" models, which are probability measures on edge subsets of a planar graph, satisfying certain constraints at each vertex, examples including dimer model, and 1-2 model, which we will define. We express the local statistics of a large class of vertex models on a finite hexagonal lattice as a linear combination of the local statistics of dimers on the corresponding Fisher graph, with the help of a generalized holographic algorithm. Using an $n\\times n$ torus to approximate the periodic infinite graph, we give an explicit integral formula for the free energy and local statistics for configurations of the vertex model on an infinite bi-periodic graph. As an example, we simulate the 1-2 model by the technique of Glauber dynamics.
Statistical Inference: The Big Picture
Kass, Robert E.
2011-01-01
Statistics has moved beyond the frequentist-Bayesian controversies of the past. Where does this leave our ability to interpret results? I suggest that a philosophy compatible with statistical practice, labelled here statistical pragmatism, serves as a foundation for inference. Statistical pragmatism is inclusive and emphasizes the assumptions that connect statistical models with observed data. I argue that introductory courses often mis-characterize the process of statistical inference and I propose an alternative “big picture” depiction. PMID:21841892
A. Walter; C. D. Schönwiese
2003-01-01
Summary ¶The climate system can be regarded as a dynamic nonlinear system. Thus, traditional linear statistical methods fail to model the nonlinearities of such a system. These nonlinearities render it necessary to find alternative statistical techniques. Since artificial neural network models (NNM) represent such a nonlinear statistical method their use in analyzing the climate system has been studied for a
Statistics applied to safeguards
Picard, R.R.
1993-01-01
Statistical methods are central to safeguards work. Measurements forming the basis of much materials accountancy are not perfect - perfect'' in the sense of being error free. Other sessions in this course address the destructive and nondestructive measurement of nuclear material, together with the inherent limitations in those measurements. The bottom line is that measurement errors are a fact of life and, since we can't eliminate them, we have to find a rational way to deal with them. Which leads to the world of statistics. Beyond dealing with measurement errors, another area of statistical application involves the sampling of items for verification. Inspectors from the IAEA and domestic regulatory agencies periodically visit operating facilities and make measurements of selected items. By comparing their own measured values to those declared by the facilities, increased confidence is obtained. If verification measurements were not expensive, time consuming, and disruptive to operations, perhaps verification of 100% of the inventories would be desirable. In reality, many constraints lead to inspection of only a portion of those inventories. Drawing inferences about a larger population'' of declared items in a facility based on verification information obtained from a sample of those items is a statistical problem. There are few texts on statistics in safeguards. The lengthy exposition IAEA Safeguards: Statistical Concepts and Techniques'' and the US NRC book edited by Bowen and Bennet are two good sources of general information. In the next section, the subject of measurement quality is addressed. The third section covers the evaluation of MUFs, and discusses the related subjects of error propagation and sequential analysis. The final section covers verification, inspection sample size calculations, and the D statistic. The text is written at an elementary level, with references to the safeguards literature for more detailed treatment.
Statistics applied to safeguards
Picard, R.R.
1993-05-01
Statistical methods are central to safeguards work. Measurements forming the basis of much materials accountancy are not perfect - ``perfect`` in the sense of being error free. Other sessions in this course address the destructive and nondestructive measurement of nuclear material, together with the inherent limitations in those measurements. The bottom line is that measurement errors are a fact of life and, since we can`t eliminate them, we have to find a rational way to deal with them. Which leads to the world of statistics. Beyond dealing with measurement errors, another area of statistical application involves the sampling of items for verification. Inspectors from the IAEA and domestic regulatory agencies periodically visit operating facilities and make measurements of selected items. By comparing their own measured values to those declared by the facilities, increased confidence is obtained. If verification measurements were not expensive, time consuming, and disruptive to operations, perhaps verification of 100% of the inventories would be desirable. In reality, many constraints lead to inspection of only a portion of those inventories. Drawing inferences about a larger ``population`` of declared items in a facility based on verification information obtained from a sample of those items is a statistical problem. There are few texts on statistics in safeguards. The lengthy exposition ``IAEA Safeguards: Statistical Concepts and Techniques`` and the US NRC book edited by Bowen and Bennet are two good sources of general information. In the next section, the subject of measurement quality is addressed. The third section covers the evaluation of MUFs, and discusses the related subjects of error propagation and sequential analysis. The final section covers verification, inspection sample size calculations, and the D statistic. The text is written at an elementary level, with references to the safeguards literature for more detailed treatment.
NASA Astrophysics Data System (ADS)
Lukose, Rajan Mathew
The World Wide Web and the Internet are rapidly expanding spaces, of great economic and social significance, which offer an opportunity to study many phenomena, often previously inaccessible, on an unprecedented scale and resolution with relative ease. These phenomena are measurable on the scale of tens of millions of users and hundreds of millions of pages. By virtue of nearly complete electronic mediation, it is possible in principle to observe the time and ``spatial'' evolution of nearly all choices and interactions. This cyber-space therefore provides a view into a number of traditional research questions (from many academic disciplines) and creates its own new phenomena accessible for study. Despite its largely self-organized and dynamic nature, a number of robust quantitative regularities are found in the aggregate statistics of interesting and useful quantities. These regularities can be understood with the help of models that draw on ideas from statistical physics as well as other fields such as economics, psychology and decision theory. This thesis develops models that can account for regularities found in the statistics of Internet congestion and user surfing patterns and discusses some practical consequences. practical consequences.
Statistical Physics of Fracture
Alava, Mikko [Helsinki University of Technology, Helsinki, Finland; Nukala, Phani K [ORNL; Zapperi, Stefano [University of La Sapienza, Rome
2006-05-01
Disorder and long-range interactions are two of the key components that make material failure an interesting playfield for the application of statistical mechanics. The cornerstone in this respect has been lattice models of the fracture in which a network of elastic beams, bonds, or electrical fuses with random failure thresholds are subject to an increasing external load. These models describe on a qualitative level the failure processes of real, brittle, or quasi-brittle materials. This has been particularly important in solving the classical engineering problems of material strength: the size dependence of maximum stress and its sample-to-sample statistical fluctuations. At the same time, lattice models pose many new fundamental questions in statistical physics, such as the relation between fracture and phase transitions. Experimental results point out to the existence of an intriguing crackling noise in the acoustic emission and of self-affine fractals in the crack surface morphology. Recent advances in computer power have enabled considerable progress in the understanding of such models. Among these partly still controversial issues, are the scaling and size-effects in material strength and accumulated damage, the statistics of avalanches or bursts of microfailures, and the morphology of the crack surface. Here we present an overview of the results obtained with lattice models for fracture, highlighting the relations with statistical physics theories and more conventional fracture mechanics approaches.
The International Year of Statistics
NSDL National Science Digital Library
2013-01-01
Statistics is a subject for all seasons and years, but 2013 is the International Year of Statistics, a designation supported by almost 1,850 organizations. The primary movers behind this noble activity include the American Statistical Association, the International Biometric Society, and the Royal Statistical Society. The goal of this initiative is to promote "the importance of statistics to the scientific community, business and government data users, the media," and a range of other users. On the website, visitors can make their way through four main sections, including What is Statistics?, Statistics as a Career, Teacher Resources, and Statistics 2013 Posters. The Teacher Resources area is a real pip, as it features teacher resources for over two dozen countries, along with statistics education videos from the United States and Mexico. The site also includes a Statistic of the Day, a quote of the week, and a most efficacious Statistical Word of the Week.
UCL DEPARTMENT OF STATISTICAL SCIENCE Courses in Statistical Science
Guillas, Serge
(details of course COMP2003 Mathematics and Statistics are available from the Computer Science DepartmentUCL DEPARTMENT OF STATISTICAL SCIENCE Courses in Statistical Science for Undergraduates on Other courses offered by the Department of Statistical Science for: Undergraduates from other UCL departments
PHYSICS 5706 --STATISTICAL MECHANICS 2: NONEQUILIBRIUM STATISTICAL MECHANICS
TÃ¤uber, Uwe Claus
PHYSICS 5706 -- STATISTICAL MECHANICS 2: NONEQUILIBRIUM STATISTICAL MECHANICS Syllabus -- Fall 2014 Â Quantum and Statistical Mechanics. Literature: The lectures will draw from original papers and several. Cowan, Topics in statistical mechanics (Imperial College, 2005) H. Haken, Synergetics (Springer, 3rd ed
Experimental Statistics NBS Handbook 91: Experimental Statistics [1] was
Experimental Statistics NBS Handbook 91: Experimental Statistics [1] was first published in 1963 as a series of five Army Ordnance Pamphlets OSRDDP 20-110-114. The publication was prepared in the Statistical. Basic Statistical Concepts and Analysis and Inter- pretation of Measurement Data 2. Standard Techniques
Statistics and samples 1.1 What is statistics?
Irwin, Darren
1 1 Statistics and samples 1.1 What is statistics? Biologists study the properties of living things to get sam- pled and who did not. Statistics is a technology that describes and measures aspects of nature from samples. Most importantly, statistics lets us quantify the uncertainty of these meas- ures
Statistics and Differential Geometry 18-466 Mathematical Statistics
Le Ny, Jerome
Statistics and Differential Geometry 18-466 Mathematical Statistics Jerome Le Ny December 14, 2005 of statistical curvature [Efr75], that most of the main concepts and methods of differ- ential geometry are of substantial interest in connection with the theory of statistical inference. This report describes in simple
Introduction to Statistical Inference Introduction to Statistical Inference
for Statistical methods. Data collection. Data presentation Data analysis. We focus on the third and final step Inference Some important concepts Statistical methods There are two main problems of statistical analysis methods There are two main problems of statistical analysis. Estimation Testing of hypothesis. We
Statistically based multiwavelet denoising
NASA Astrophysics Data System (ADS)
Bacchelli, S.; Papi, S.
2007-12-01
In this work, we consider a statistically based multiwavelet thresholding method which acts on the empirical wavelet coefficients in groups, rather than individually, in order to obtain an edge-preserving image denoising technique. Our strategy allows us to exploit the dependencies between neighboring coefficients to make a simultaneous thresholding decision, so that estimation accuracy is increased. By interpreting the multiwavelet analysis in a statistical context, we propose a new weighted multiwavelet matrix thresholding rule, based on the statistical modeling of empirical coefficients. This allows the thresholding decision to be adapted to the local structure of the underlying image, hence producing edge-preserving denoising. Extensive numerical results are presented showing the performance of our denoising procedure.
UNESCO Institute for Statistics
NSDL National Science Digital Library
Established in 1999, the UNESCO Institute for Statistics (UIS) was designed to meet both the needs of UNESCO Member States and to provide the international community with a wide range of statistical information in order to "analyze the efficiency and effectiveness of their programmes and to inform their policy decisions." The UIC is hosted by the University of Montreal, and performs work around four primary themes, including education, literacy, culture & communication, and science & technology. Overall, the site is a remarkable source of information, including databases, working papers, country profiles, statistical tables, and methodological material about the conduct of their research. Several of these works are featured prominently on their homepage including a working paper on financing the expansion of educational opportunity in Latin America and the Caribbean and an electronic questionnaire on science and technology.
NASA Astrophysics Data System (ADS)
Joyner, Christopher H.; Müller, Sebastian; Sieber, Martin
2014-09-01
Energy level statistics following the Gaussian Symplectic Ensemble (GSE) of Random Matrix Theory have been predicted theoretically and observed numerically in numerous quantum chaotic systems. However, in all these systems there has been one unifying feature: the combination of half-integer spin and time-reversal invariance. Here we provide an alternative mechanism for obtaining GSE statistics that is derived from geometric symmetries of a quantum system which alleviates the need for spin. As an example, we construct a quantum graph with a discrete symmetry given by the quaternion group Q8 and observe GSE statistics within one of its subspectra. We then show how to isolate this subspectrum and construct a quantum graph with a scalar valued wave function and a pure GSE spectrum.
Suite versus composite statistics
Balsillie, J.H.; Tanner, W.F.
1999-01-01
Suite and composite methodologies, two statistically valid approaches for producing statistical descriptive measures, are investigated for sample groups representing a probability distribution where, in addition, each sample is probability distribution. Suite and composite means (first moment measures) are always equivalent. Composite standard deviations (second moment measures) are always larger than suite standard deviations. Suite and composite values for higher moment measures have more complex relationships. Very seldom, however, are they equivalent, and they normally yield statistically significant but different results. Multiple samples are preferable to single samples (including composites) because they permit the investigator to examine sample-to-sample variability. These and other relationships for suite and composite probability distribution analyses are investigated and reported using granulometric data.
Statistical quantification of brain shape deformation with homologous brain shape modeling
KOSUKE YAMAGUCHI; S. Kobashi; K. Kuramoto; Y. T. Kitamura; S. Imawaki; Y. Hata
2010-01-01
Brain shape is deformed regionally by kinds of cerebral diseases and the degree of progress. Therefore quantitative evaluation of the deformation using MR images is effective for diagnosis of cerebral diseases. We proposed a homologous brain shape modeling deformation for quantitative evaluation of the brain shape using sulcal-distribution index (SDI) in MR images. So in this paper, we propose the
Statistical Data Mining Tutorials
NSDL National Science Digital Library
Moore, Andrew W., Ph.D.
These tutorial, created by Professor Andrew Moore at Carnegie-Mellon University, cover a range of topics in statistical data mining "including the foundations of probability, the foundations of statistical data analysis, and most of the classic machine learning and data mining algorithms." Decision Trees, Information Gain, and Cross-Validation are just a few of the items presented here. Each topic contains a set of tutorial slides in PDF, excellent for converting into a classroom presentation or left as they are for a classroom handout or online learning resource.
Interactive Business Statistics
NSDL National Science Digital Library
This collection of applets, created by McGraw-Hill Higher Education, is designed illustrate key concepts described in "Statistical Techniques for Business and Economics," but does not require use of this textbook. Topics include: mean, median, mode, skewness, probability, probability distribution, comparing binomial distribution, normal distribution, central limit theorem, confidence intervals, ANOVA, simple linear regression, multiple linear regression, chi-square, Pareto charts, and time series forecasting. This is a nice collection of statistics modules. Although it was created in conjunction with a textbook, this resource is still free from the publisher.
Statistics Online Computational Resource
NSDL National Science Digital Library
2005-02-08
The Statistics Online Computational Resource (SOCR) is a collection of downloadable applets, computational and graphing tools, and instructional materials for use in online data analysis, visualization, and integration. The tools are organized into categories by use: distributions (interactive graphs and calculators); experiments (computer-generated analogs of popular games and processes); analyses (tools for statistical data analysis); games (interfaces and simulations to real-life processes); data modelers (tools for distribution, polynomial and spectral model-fitting and simulation); and graphs, plots, and charts (comprehensive web-based tools for exploratory data analysis). There is also a collaborative collection (Wiki) of activities and educational materials that use these tools.
Historical Statistics on Banking
NSDL National Science Digital Library
Historical Statistics on Banking (HSOB), from the Federal Deposit Insurance Corporation, "provides annual statistical information on the banking industry beginning in 1934." The site contains commercial banking reports, savings institution reports, and bank and thrift failure reports from 1934 to 1999. The Milestones feature offers a chronological retrospective on the FDIC's collection and use of data. Although the database is fairly easy to use, the HSOB Help section contains additional detailed instructions on saving and printing charts, and also offers a helpful glossary of terms used.
Functional Models and Dynamics
J. O Ramsay; Giles Hooker; Spencer Graves
This chapter brings us to the study of continuous time dynamics, where functional data analysis has, perhaps, its greatest\\u000a utility by providing direct access to relationships between derivatives that could otherwise be studied only indirectly. Although\\u000a dynamic systems are the subject of a large mathematical literature, they are relatively uncommon in statistics. We have therefore\\u000a devoted the first section of