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1

The Stability of Dynamic Feedback in an SDI System.  

ERIC Educational Resources Information Center

The SDI system now operational at the Institute for Atomic Research, Iowa State University, is implemented with the concept of feedback. The profile user is notified of a document which may be of interest to him and indicates his response to this document on the response card accompanying the notification. The profile words carry individual…

Anderson, R. R.; And Others

2

Statistics of football dynamics  

NASA Astrophysics Data System (ADS)

We investigate the dynamics of football matches. Our goal is to characterize statistically the temporal sequence of ball movements in this collective sport game, searching for traits of complex behavior. Data were collected over a variety of matches in South American, European and World championships throughout 2005 and 2006. We show that the statistics of ball touches presents power-law tails and can be described by q-gamma distributions. To explain such behavior we propose a model that provides information on the characteristics of football dynamics. Furthermore, we discuss the statistics of duration of out-of-play intervals, not directly related to the previous scenario.

Mendes, R. S.; Malacarne, L. C.; Anteneodo, C.

2007-06-01

3

Statistics of football dynamics  

E-print Network

We investigate the dynamics of football matches. Our goal is to characterize statistically the temporal sequence of ball movements in this collective sport game, searching for traits of complex behavior. Data were collected over a variety of matches in South American, European and World championships throughout 2005 and 2006. We show that the statistics of ball touches presents power-law tails and can be described by $q$-gamma distributions. To explain such behavior we propose a model that provides information on the characteristics of football dynamics. Furthermore, we discuss the statistics of duration of out-of-play intervals, not directly related to the previous scenario.

Mendes, R S; Anteneodo, C

2007-01-01

4

SDI CFD MODELING ANALYSIS  

SciTech Connect

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.

Lee, S.

2011-05-05

5

Statistics as a dynamical attractor  

E-print Network

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.

Michail Zak

2012-08-30

6

Dynamic Statistical Process Control  

NASA Astrophysics Data System (ADS)

Although some control techniques such as Shewhart and CUSUM Control Charts are not new, their application in industry for process control is relatively new. In recent years manufacturing industries have begun to discover and appreciate the power and efficiency of statistical process control techniques. These charts have been successfully used in some areas and have created confusion in others. The confusion is normally due to incorrect application of the methods and lack of sufficient understanding of the theory and assumptions underlying these charts. One of the important assumptions in using Shewhart and CUSUM charts is that the individual measurements are statistically independent. In many industrial situations this assumption is not valid. Namely, the measurements are correlated. As a result the application of the above techniques ends in incorrect conclusions and hence, confusion. The purpose of this paper is to discuss appropriate methods for dealing with these situations. Time series modeling will be discussed. It will be shown how the correlations in data can be used for more precisely predicting and controlling a process.

Azari, Rahman; Khorasani, Fred; Bickerstaff, Cynthia

1988-01-01

7

SDI (Strategic Defense Initiative): a policy analysis  

SciTech Connect

Contents include -- Foundations of Deterrence; A Model for Stability; Analysis of SDI/Stability; Related Issues; Treatment of Implementation Factors; Historical Evolution and Trends; The Strategic Choices and Flexible Response; The Planners' Perspective; The Impact of Strategic Defense on a Strategy of Flexible Response; Synthesis.

Fought, S.O.

1987-01-01

8

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...

9

1 of 3 DOE Response to EPA Question SDI(HCR)-1 on the SDI Planned Change Notice  

E-print Network

transported heated air from the SDI tests could be conductively transferred to the halite along the perimeter on the crushed salt and intact halite. Even if ventilation is not blocked during the heating phase, convectively of the SDI test. This figure shows that the heat energy is concentrated in the intact halite and crushed salt

10

Cumulative fatigue damage dynamic interference statistical model  

Microsoft Academic Search

After studying in depth the statistical characteristics of cumulative fatigue damage D(t) and its critical value Dc, a new dynamic interference statistical model for fatigue reliability analysis is presented in this paper. Because the non-linearity of fatigue damage accumulation has been taken into account, this model is able to predict the fatigue reliability for random spectrum loading. To verify the

Liao Min; Xu Xiaofei; Yang Qing-Xiong

1995-01-01

11

Artificial intelligence applications in space and SDI: A survey  

NASA Technical Reports Server (NTRS)

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.

Fiala, Harvey E.

1988-01-01

12

Statistical dynamics of religion evolutions  

E-print Network

A religion affiliation can be considered as a "degree of freedom" of an agent on the human genre network. A brief review is given on the state of the art in data analysis and modelization of religious "questions" in order to suggest and if possible initiate further research, ... after using a "statistical physics filter". We present a discussion of the evolution of 18 so called religions, as measured through their number of adherents between 1900 and 2000. Some emphasis is made on a few cases presenting a minimum or a maximum in the investigated time range, - thereby suggesting a competitive ingredient to be considered, beside the well accepted "at birth" attachement effect. The importance of the "external field" is still stressed through an Avrami late stage crystal growth-like parameter. The observed features and some intuitive interpretations point to opinion based models with vector, rather than scalar, like agents.

Ausloos, Marcel

2008-01-01

13

Statistical dynamics of religion evolutions  

NASA Astrophysics Data System (ADS)

A religion affiliation can be considered as a “degree of freedom” of an agent on the human genre network. A brief review is given on the state of the art in data analysis and modelization of religious “questions” in order to suggest and if possible initiate further research, after using a “statistical physics filter”. We present a discussion of the evolution of 18 so-called religions, as measured through their number of adherents between 1900 and 2000. Some emphasis is made on a few cases presenting a minimum or a maximum in the investigated time range-thereby suggesting a competitive ingredient to be considered, besides the well accepted “at birth” attachment effect. The importance of the “external field” is still stressed through an Avrami late stage crystal growth-like parameter. The observed features and some intuitive interpretations point to opinion based models with vector, rather than scalar, like agents.

Ausloos, M.; Petroni, F.

2009-10-01

14

SDI Considerations for North Carolina Growers and Producers  

Technology Transfer Automated Retrieval System (TEKTRAN)

Humid areas, such as the southeastern and midsouthern United States, have particular climate, topography, soils, cropping systems, and water sources that require special consideration when implementing a subsurface drip irrigation (SDI) system. These factors are normally different enough in value or...

15

Soviet SDI Rhetoric: The "Evil Empire" Vision of Mikhail Gorbachev.  

ERIC Educational Resources Information Center

The symbolic presence of Ronald Reagan's Strategic Defense Initiative (SDI) has been and continues to be the pivot point in all summitry rhetoric between the American President and Soviet General Secretary Mikhail Gorbachev. To examine some of the rhetorical choices made by Gorbachev to dramatize his vision of why Ronald Reagan refuses to…

Kelley, Colleen E.

16

Optimum Degree of User Participation in SDI Profile Generation.  

ERIC Educational Resources Information Center

A study was conducted of the International Information Service in Physics, Electrotechnology, Computers, and Control (INSPEC) selective dissemination of information (SDI) user profile generation. Five degrees of user involvement in the generation of profiles were investigated ranging from having the user provide only a statement of subject…

Evans, L.

17

SDI BED DESIGN COMPARISON FOR SOYBEAN EMERGENCE AND YIELD  

Technology Transfer Automated Retrieval System (TEKTRAN)

Subsurface drip irrigation (SDI) is gaining popularity with producers in the Southern and Central Great Plains region of the United States. Drip laterals are commonly installed in alternate furrows because it is cost prohibitive to install laterals in every bed for low value crops; however, crop ger...

18

Computerized Information Service--SDI. Annual Report 1974-75.  

ERIC Educational Resources Information Center

The Information and Documentation Centre of the Royal Institute of Technology Library performs research and development in information science. The two main areas of this continuing research and development programme are (1) development of a comprehensive SDI service and (2) investigations in interactive retrieval services. This annual report…

Hjerppe, Roland

19

SDI (Strategic Defense Initiative) and national security policy. Research report  

Microsoft Academic Search

The paper attempts to answer the fundamental question of Can SDI make a significant contribution to US national security. It uses as its evaluation criteria historical arms-control measurements of stability, reduction in the probability of war, reduction in the consequences of war, economic benefits, and political benefits. A historical discussion of US nuclear strategy development along with Soviet thinking is

1988-01-01

20

Stochastics and Statistics Exploiting structure in adaptive dynamic programming  

E-print Network

Stochastics and Statistics Exploiting structure in adaptive dynamic programming algorithms the importance of using structural results in dynamic programming al- gorithms. We consider the problem dynamic programming monotone algorithm that uses structure to preserve monotonicity of the estimates

Powell, Warren B.

21

STATISTICAL TOOLS FOR CLASSIFYING GALAXY GROUP DYNAMICS  

SciTech Connect

The dynamical state of galaxy groups at intermediate redshifts can provide information about the growth of structure in the universe. We examine three goodness-of-fit tests, the Anderson-Darling (A-D), Kolmogorov, and {chi}{sup 2} tests, in order to determine which statistical tool is best able to distinguish between groups that are relaxed and those that are dynamically complex. We perform Monte Carlo simulations of these three tests and show that the {chi}{sup 2} test is profoundly unreliable for groups with fewer than 30 members. Power studies of the Kolmogorov and A-D tests are conducted to test their robustness for various sample sizes. We then apply these tests to a sample of the second Canadian Network for Observational Cosmology Redshift Survey (CNOC2) galaxy groups and find that the A-D test is far more reliable and powerful at detecting real departures from an underlying Gaussian distribution than the more commonly used {chi}{sup 2} and Kolmogorov tests. We use this statistic to classify a sample of the CNOC2 groups and find that 34 of 106 groups are inconsistent with an underlying Gaussian velocity distribution, and thus do not appear relaxed. In addition, we compute velocity dispersion profiles (VDPs) for all groups with more than 20 members and compare the overall features of the Gaussian and non-Gaussian groups, finding that the VDPs of the non-Gaussian groups are distinct from those classified as Gaussian.

Hou, Annie; Parker, Laura C.; Harris, William E. [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada); Wilman, David J. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany)], E-mail: houa2@physics.mcmaster.ca, E-mail: lparker@physics.mcmaster.ca, E-mail: harris@physics.mcmaster.ca, E-mail: dwilman@mpe.mpg.de

2009-09-10

22

Teachers' Use of Transnumeration in Solving Statistical Tasks with Dynamic Statistical Software  

ERIC Educational Resources Information Center

This study examined a random stratified sample (n = 62) of teachers' work across eight institutions on three tasks that utilized dynamic statistical software. We considered how teachers may utilize and develop their statistical knowledge and technological statistical knowledge when investigating a statistical task. We examined how teachers…

Lee, Hollylynne S.; Kersaint, Gladis; Harper, Suzanne R.; Driskell, Shannon O.; Jones, Dusty L.; Leatham, Keith R.; Angotti, Robin L.; Adu-Gyamfi, Kwaku

2014-01-01

23

A Statistical Description of Neural Ensemble Dynamics  

PubMed Central

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

Long, John D.; Carmena, Jose M.

2011-01-01

24

Statistical Mechanics of Recurrent Neural Networks II Dynamics  

E-print Network

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

Coolen, ACC "Ton"

25

LDSG Workshop on Stochastic Dynamics and Nonequilibrium Statistical Mechanics  

E-print Network

LDSG Workshop on Stochastic Dynamics and Nonequilibrium Statistical Mechanics Organisers: Rosemary the same predictive power as that of equilibrium statistical mechanics? Though most researchers in statistical mechanics would hope and conjecture that the answer is yes, we do not have at present

Wright, Francis

26

An SDI program for distributing funding opportunities using electronic mail.  

PubMed

As the competition for funding increases, the need to make researchers aware of all available funding is becoming more acute. The solution presented here is a Selective Dissemination of Information (SDI) service which electronically mails funding information that matches a researcher's keywords. The keywords are part of extensive faculty profiles that make up a Faculty Expertise database. The funding information comes from the Sponsored Programs Information Network (SPIN) database. The software enables researchers to learn about appropriate funding opportunities without spending time actively searching for them. PMID:7950087

Keenan, P M; Montgomery, C H

1994-01-01

27

Dynamic Statistics of Crayfish Caudal Photoreceptors  

PubMed Central

Crayfish caudal photoreceptor units were monitored during transient and steady-state responses to light stimuli (step on, step off). A statistical analysis of interpulse interval distributions during quasi-stationary time periods was carried out. Firing statistics during transient conditions were superposable with statistics under whatever steady stimulation produced the same firing rate, indicating that mean firing rate is a sufficient statistic. Distributions encountered formed a continuum of possible shapes. Considerable variation in shape was found with temperature and also among species, with Orconectes clarkii tending to fire more regularly than Orconectes virilis. Some properties of O. virilis statistics are described, including a linear relation between mean and standard deviation, and a tendency for intervals to be nonindependent. The data are considered as constraints on closed form models of the photoreceptor nerve pulse generator. PMID:6035125

Hermann, Howard T.; Olsen, Richard E.

1967-01-01

28

SDI Citation Checking as a Measure of the Performance of Library Document Delivery Systems.  

ERIC Educational Resources Information Center

Document delivery support for selective dissemination of information (SDI) services provided by the Center for Information Services, University of California at Los Angeles, was measured by the following: (1) Obtaining copies of all steady-state SDI searches from Biological Abstracts'"BA Previews" data base delivered to the University of…

Bourne, Charles P.; Robinson, Jo.

29

The social dysfunction index (SDI) for patients with schizophrenia and related disorders  

Microsoft Academic Search

The social dysfunction index (SDI) is a new measure designed to assess social dysfunction in schizophrenia and other severe mental illnesses. It is intended to serve clinical and research purposes. Raters can be readily trained and there is low respondent burden with its use. Good psychometric properties were identified in three studies (sample sizes 33, 67 and 113). The SDI

Heather Munroe-Blum; Evan Collins; Lynn McCleary; Sandra Nuttall

1996-01-01

30

For more information, please contact: Professor Sandra Petersen, SDI Executive Director  

E-print Network

.umass.edu/sdi diversity science·technology·engineering·mathematics STEM DIVERSITY INSTITUTE University of Massachusetts 524 Goodell Bldg 140 Hicks Way Amherst, MA 01003-9272 www.umass.edu/sdi diversity science·technology·engineering development workshops for Ph.D.students diversity science·technology·engineering·mathematics diversity science·technology·engineering

Mountziaris, T. J.

31

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...

32

Quantum statistical and dynamical effects in vortex systems  

Microsoft Academic Search

We review some recent developments in the quantum statistical mechanics and in the quantum dynamics of the vortex system in high temperature- and in conventional high-resistivity thin-film superconductors.

G. Blatter; B. Ivlev; Yu. Kagan; V. Vinokur; Theoretische Physik

1994-01-01

33

Dynamically Individualizing Treatments Statistical Challenges and Some Solutions  

E-print Network

Dynamically Individualizing Treatments Statistical Challenges and Some Solutions Susan A. Murphy, 2010 #12;Treatment Policies Clinical Trial Design Secondary Data Analysis New Analysis Projects Outline Treatment Policies What? Why? Challenges Clinical Trial Design Sequential Multiple Assignment Randomized

Murphy, Susan A.

34

Dynamaps: Dynamic Queries on a Health Statistics Atlas  

E-print Network

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

Golbeck, Jennifer

35

Teaching Introductory Statistics: From dull to Dynamic!  

E-print Network

is important Societies and businesses want to have control over things like: Reducing rates of cancer, heart Individual Exercise Write down or remember your answers: 1. Think of something you know how to do very well are fair.) #12;Group Exercise Discuss these questions Why should students study elementary statistics? What

Utts, Jessica

36

Dynamical Ensembles in Nonequilibrium Statistical Mechanics  

Microsoft Academic Search

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

G. Gallavotti; E. G. D. Cohen

1995-01-01

37

Statistical mechanical analysis of the dynamics of learning in perceptrons  

E-print Network

Statistical mechanical analysis of the dynamics of learning in perceptrons C. W. H. MACE and A. C to analyse the dynamics of various classes of supervised learning rules in perceptrons. The character with constant learning rate 2.3. Perceptron learning with constant learning rate 2.4. AdaTron learning

Coolen, ACC "Ton"

38

Multivariate statistical batch process monitoring using dynamic independent component analysis  

Microsoft Academic Search

Use of independent component analysis (ICA) in developing statistical monitoring charts for batch processes has been reported previously. This paper extends the previous work by introducing time lag shifts to include process dynamics in the ICA model. Comparison of the dynamic ICA based method with other batch process monitoring approaches based on static ICA, static principal component analysis (PCA) and

Hamza Albazzaz; Xue Z. Wang

2006-01-01

39

Statistical dynamics of a non-Abelian anyonic quantum walk  

E-print Network

We study the single particle dynamics of a mobile non-Abelian anyon hopping around many pinned anyons on a surface. The dynamics is modelled by a discrete time quantum walk and the spatial degree of freedom of the mobile anyon becomes entangled with the fusion degrees of freedom of the collective system. Each quantum trajectory makes a closed braid on the world lines of the particles establishing a direct connection between statistical dynamics and quantum link invariants. We find that asymptotically a mobile Ising anyon becomes so entangled with its environment that its statistical dynamics reduces to a classical random walk with linear dispersion in contrast to particles with Abelian statistics which have quadratic dispersion.

Lauri Lehman; Vaclav Zatloukal; Gavin K. Brennen; Jiannis K. Pachos; Zhenghan Wang

2010-09-04

40

SDI and the lawyers: Evolving interpretations of international arms control accords  

SciTech Connect

This note surveys international agreements that SDI may violate and discusses the policies underlying these potential legal and diplomatic conflicts. Part I provides an overview of the ABM Treaty, with emphasis on the provisions involved in the present interpretation controversy. Part II considers five other international covenants containing provisions upon which SDI may ultimately encroach. Part III evaluates several policy proposals that would permit SDI to proceed consistently with American international diplomatic commitments. This part also examines how an outright abrogation of the ABM Treaty or other agreements might affect American credibility and the arms-control process.

Kaman, E.J.; Loprest, F.J. Jr.; Pisano, N.A.; Steiner, R.W.

1989-01-01

41

Fundamental theory of statistical particle dynamics.  

PubMed

We present a fundamental theory for the kinetics of systems of classical particles. The theory represents a unification of kinetic theory, Brownian motion, and field theory. It is self-consistent and is the dynamic generalization of the functional theory of fluids in equilibrium. This gives one a powerful tool for investigating the existence of ergodic-nonergodic transitions near the liquid-glass transition. PMID:20866373

Mazenko, Gene F

2010-06-01

42

Application of classical statistical mechanics to multifractals and dynamical systems  

E-print Network

Classical, self-consistent theory of statistical mechanics was developed for the thermodynamic and conservative Hamiltonian systems. Later there were many attempts (Sinai-Bowen-Ruelle's temperature, Tsallis' non-extensive theory) to apply similar formalism to non-Hamiltonian dynamical systems. Although these theories reveal aspects of complex behavior, they have limited applicability. This paper applies the classical Gibbs-Boltzmann statistical mechanics to complex systems such as i.i.d. processes, multifractals, and non-Hamiltonian dynamical systems with strange attractors. The effective thermolization of stochastic noise in the system is introduced and the formalism of a ruling (governing, free energy) potential is developed.

S. G. Abaimov

2008-05-03

43

Statistical Dynamics of Pressure-Coupled Burgerlence  

NASA Astrophysics Data System (ADS)

The probability distributions of shock structures in pressure-coupled burgerlence are discussed. A Fokker-Planck calculation of these distributions is compared and contrasted with a path integral approach. It is shown that the velocity structures lead to an asymmetric velocity PDF, as in ordinary Burgerlence. Pressure fluctuations, however, are symmetrically distributed. These symmetries are manifested in the generating function (action) of the dynamical system. The extremization of this action (instanton solution) suggests that the system maintains its characteristic directions in steady-state turbulence. Physically, this result implies equi-dissipation, not equipartition, of energy, supporting the earlier results from perturbation theory^1. ^1 J. Fleischer and P.H. Diamond, Phys. Rev. E 58, R2709 (1998).

Fleischer, J.; Diamond, P. H.

1999-11-01

44

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., ...

45

Smooth dynamics and new theoretical ideas in nonequilibrium statistical mechanics  

Microsoft Academic Search

This paper reviews various applications of the theory of smooth dynamical systems to conceptual problems of nonequilibrium statistical mechanics. 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

David Ruelle

1998-01-01

46

FACILITATING DATA EXPLORATION: DYNAMIC QUERIES ON A HEALTH STATISTICS MAP  

E-print Network

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

Golbeck, Jennifer

47

Statistical dynamics of tropical wind in radiosonde data  

NASA Astrophysics Data System (ADS)

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.

Koh, T.-Y.; Djamil, Y. S.; Teo, C.-K.

2011-05-01

48

SDI experiments will explore viability of ground-based laser  

SciTech Connect

A ground-based free-electron laser technical integration experiment (GBFEL/TIE) is planned for the White Sands Missile Range to test the feasibility of operation of a ground-based FEL with hundreds of megawatts of power in SDI applications. The staged experiment will begin with a modest power ND-YAG laser and eventually test an induction-powered FEL. An RF-powered unit is also receiving consideration for the full-scale tests. The FEL is to be about 1.8 km long and will include a wiggler about 200 m long and a vacuum tunnel to permit the beam to diffuse by diffraction to avoid damaging the beam optics. Phenomena to be studied in the tests are Raman scattering, thermal blooming, ionization of the air and the effects of atmospheric turbulence. Attempts will be made to compensate for atmospheric effects by sending a calibrated laser beam from space to the facility to measure atmospheric distortions, then distorting the FEL beam to compensate for the atmospheric effects. RFPs are soon to be issued for managing the integration of the facilities.

Not Available

1986-08-01

49

Spatial statistics and attentional dynamics in scene viewing.  

PubMed

In humans and in foveated animals visual acuity is highly concentrated at the center of gaze, so that choosing where to look next is an important example of online, rapid decision-making. Computational neuroscientists have developed biologically-inspired models of visual attention, termed saliency maps, which successfully predict where people fixate on average. Using point process theory for spatial statistics, we show that scanpaths contain, however, important statistical structure, such as spatial clustering on top of distributions of gaze positions. Here, we develop a dynamical model of saccadic selection that accurately predicts the distribution of gaze positions as well as spatial clustering along individual scanpaths. Our model relies on activation dynamics via spatially-limited (foveated) access to saliency information, and, second, a leaky memory process controlling the re-inspection of target regions. This theoretical framework models a form of context-dependent decision-making, linking neural dynamics of attention to behavioral gaze data. PMID:25589298

Engbert, Ralf; Trukenbrod, Hans A; Barthelmé, Simon; Wichmann, Felix A

2015-01-01

50

Geometry and Dynamics in Zero Temperature Statistical Mechanics Models  

E-print Network

We consider several models whose motivation arises from statistical mechanics. We begin by investigating some families of distributions of translation invariant subgraphs of some Cayley graphs, and in particular subgraphs of the square lattice. We then discuss some properties of the Spin-Glass model in that lattice. We continue in describing some properties of the Spin-Glass models in some other graphs. The last two parts of this work are devoted to the understanding of two dynamical processes on graphs. The first one is the well known zero-temperature Glauber dynamics on some families of graphs. The second dynamics, which we call the Loop Dynamics, is a natural generalization of the zero-temperature Glauber dynamics, which appears to have some interesting properties. We analyzed some of its properties for planar lattices, though the exact same techniques are applied for larger families of graphs as well.

Ran J Tessler

2010-08-31

51

SdiA aids enterohemorrhagic Escherichia coli carriage by cattle fed a forage or grain diet.  

PubMed

Enterohemorrhagic Escherichia coli (EHEC) causes hemorrhagic colitis and life-threatening complications. The main reservoirs for EHEC are healthy ruminants. We reported that SdiA senses acyl homoserine lactones (AHLs) in the bovine rumen to activate expression of the glutamate acid resistance (gad) genes priming EHEC's acid resistance before they pass into the acidic abomasum. Conversely, SdiA represses expression of the locus of enterocyte effacement (LEE) genes, whose expression is not required for bacterial survival in the rumen but is necessary for efficient colonization at the rectoanal junction (RAJ) mucosa. Our previous studies show that SdiA-dependent regulation was necessary for efficient EHEC colonization of cattle fed a grain diet. Here, we compared the SdiA role in EHEC colonization of cattle fed a forage hay diet. We detected AHLs in the rumen of cattle fed a hay diet, and these AHLs activated gad gene expression in an SdiA-dependent manner. The rumen fluid and fecal samples from hay-fed cattle were near neutrality, while the same digesta samples from grain-fed animals were acidic. Cattle fed either grain or hay and challenged with EHEC orally carried the bacteria similarly. EHEC was cleared from the rumen within days and from the RAJ mucosa after approximately one month. In competition trials, where animals were challenged with both wild-type and SdiA deletion mutant bacteria, diet did not affect the outcome that the wild-type strain was better able to persist and colonize. However, the wild-type strain had a greater advantage over the SdiA deletion mutant at the RAJ mucosa among cattle fed the grain diet. PMID:23836826

Sheng, Haiqing; Nguyen, Y N; Hovde, Carolyn J; Sperandio, Vanessa

2013-09-01

52

SdiA Aids Enterohemorrhagic Escherichia coli Carriage by Cattle Fed a Forage or Grain Diet  

PubMed Central

Enterohemorrhagic Escherichia coli (EHEC) causes hemorrhagic colitis and life-threatening complications. The main reservoirs for EHEC are healthy ruminants. We reported that SdiA senses acyl homoserine lactones (AHLs) in the bovine rumen to activate expression of the glutamate acid resistance (gad) genes priming EHEC's acid resistance before they pass into the acidic abomasum. Conversely, SdiA represses expression of the locus of enterocyte effacement (LEE) genes, whose expression is not required for bacterial survival in the rumen but is necessary for efficient colonization at the rectoanal junction (RAJ) mucosa. Our previous studies show that SdiA-dependent regulation was necessary for efficient EHEC colonization of cattle fed a grain diet. Here, we compared the SdiA role in EHEC colonization of cattle fed a forage hay diet. We detected AHLs in the rumen of cattle fed a hay diet, and these AHLs activated gad gene expression in an SdiA-dependent manner. The rumen fluid and fecal samples from hay-fed cattle were near neutrality, while the same digesta samples from grain-fed animals were acidic. Cattle fed either grain or hay and challenged with EHEC orally carried the bacteria similarly. EHEC was cleared from the rumen within days and from the RAJ mucosa after approximately one month. In competition trials, where animals were challenged with both wild-type and SdiA deletion mutant bacteria, diet did not affect the outcome that the wild-type strain was better able to persist and colonize. However, the wild-type strain had a greater advantage over the SdiA deletion mutant at the RAJ mucosa among cattle fed the grain diet. PMID:23836826

Sheng, Haiqing; Nguyen, Y. N.

2013-01-01

53

Fractional-power-law level statistics due to dynamical tunneling.  

PubMed

For systems with a mixed phase space we demonstrate that dynamical tunneling universally leads to a fractional power law of the level-spacing distribution P(s) over a wide range of small spacings s. Going beyond Berry-Robnik statistics, we take into account that dynamical tunneling rates between the regular and the chaotic region vary over many orders of magnitude. This results in a prediction of P(s) which excellently describes the spectral data of the standard map. Moreover, we show that the power-law exponent is proportional to the effective Planck constant h(eff). PMID:21405229

Bäcker, Arnd; Ketzmerick, Roland; Löck, Steffen; Mertig, Normann

2011-01-14

54

Statistical identification of structural rearrangement events in molecular dynamics trajectories  

NASA Astrophysics Data System (ADS)

We describe a statistical analysis method to detect simultaneous break points of the mean in multiple observables with Gaussian fluctuations as often observed in single molecule experiments and molecular dynamics trajectories. The maximum likelihood method finds the most likely break point in a given sequence of normally distributed multivariate observations using Hotteling's T2 statistic. In stochastic simulations we determine the threshold F-values for the acceptance of a break point in three dimensions and test the sensitivity and accuracy of the method. We present an algorithm that systematically identifies the most likely break points in a trajectory in a self-consistent manner. We test the method and algorithm with trajectories from molecular dynamics simulations on a prototypical atomistic glass former.

Bingemann, Dieter

2013-03-01

55

Statistical Computations Underlying the Dynamics of Memory Updating  

PubMed Central

Psychophysical and neurophysiological studies have suggested that memory is not simply a carbon copy of our experience: Memories are modified or new memories are formed depending on the dynamic structure of our experience, and specifically, on how gradually or abruptly the world changes. We present a statistical theory of memory formation in a dynamic environment, based on a nonparametric generalization of the switching Kalman filter. We show that this theory can qualitatively account for several psychophysical and neural phenomena, and present results of a new visual memory experiment aimed at testing the theory directly. Our experimental findings suggest that humans can use temporal discontinuities in the structure of the environment to determine when to form new memory traces. The statistical perspective we offer provides a coherent account of the conditions under which new experience is integrated into an old memory versus forming a new memory, and shows that memory formation depends on inferences about the underlying structure of our experience. PMID:25375816

Gershman, Samuel J.; Radulescu, Angela; Norman, Kenneth A.; Niv, Yael

2014-01-01

56

Statistical dynamics of equatorial waves in tropical radiosonde wind data  

NASA Astrophysics Data System (ADS)

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.

Koh, T.-Y.; Djamil, Y. S.; Teo, C. K.

2010-07-01

57

A study on modeling the dynamics of statistically dependent returns  

NASA Astrophysics Data System (ADS)

This paper develops a method to characterize the dynamic behavior of statistically dependent returns of assets via a scenario set. The proposed method uses heteroskedastic time series to model serial correlations of returns, as well as Cholesky decomposition to generate the set of scenarios such that the statistical dependence of different asset returns is preserved. In addition, this scenario generation method preserves marginal distributions of returns. To demonstrate the performance of the proposed method, a multi-period portfolio optimization model is presented. Then, the method is implemented through a number of stocks selected from New York Stock Exchange (NYSE). Computational results show a high performance of the proposed method from the statistical point of view. Also, results confirm sufficiency and in-sample stability of the generated scenario set. Besides, out-of-sample simulations, for both risk and return, illustrate a good performance of the proposed method.

Davari-Ardakani, Hamed; Aminnayeri, Majid; Seifi, Abbas

2014-07-01

58

On homogeneous statistical distributions exoplanets for their dynamic parameters  

E-print Network

Correct distributions of extrasolar systems for their orbital parameters (semi-major axes, period, eccentricity) and physical characteristics (mass, spectral type of parent star) are received. Orbital resonances in extrasolar systems are considered. It is shown, that the account of more thin effects, including with use of wavelet methods, in obviously incorrectly reduced distributions it is not justified, to what the homogeneous statistical distributions for dynamic parameters of exoplanets, received in the present work, testify.

Mushailov, B R; Teplitskaya, V S

2009-01-01

59

Dynamics, stability, and statistics on lattices and networks  

NASA Astrophysics Data System (ADS)

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.

Livi, Roberto

2014-07-01

60

Dynamics, stability, and statistics on lattices and networks  

SciTech Connect

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.

Livi, Roberto [Institut d' Etudes Avancées (IEA), Université de Cergy-Pontoise (France)

2014-07-15

61

Assessing North American Influenza Dynamics with a Statistical SIRS Model  

PubMed Central

We present a general statistical modeling framework to characterize continental-level influenza dynamics in the United States for the purposes of examining state-level epidemiological sources and sinks. The methods we describe depend directly on state-level influenza data that are prepared on a weekly basis by Google Flu Trends. The Google Flu Trends team has provided a powerful new approach to collecting and reporting epidemiological data and, when used in conjunction with sophisticated statistical models, can allow for the identification and quantification of the flow of influenza across the continental United States. Our proposed methods, when conditioned on such a comprehensive search query product, can provide unprecedented scientific learning about large-scale pathways and barriers to disease transmission which can ultimately be helpful for policy, remediation, and response efforts. PMID:21218144

Hooten, Mevin B.; Anderson, Jessica; Waller, Lance A.

2010-01-01

62

Hydrological responses to dynamically and statistically downscaled climate model output  

USGS Publications Warehouse

Daily rainfall and surface temperature series were simulated for the Animas River basin, Colorado using dynamically and statistically downscaled output from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis. A distributed hydrological model was then applied to the downscaled data. Relative to raw NCEP output, downscaled climate variables provided more realistic stimulations of basin scale hydrology. However, the results highlight the sensitivity of modeled processes to the choice of downscaling technique, and point to the need for caution when interpreting future hydrological scenarios.

Wilby, R.L.; Hay, L.E.; Gutowski, W.J., Jr.; Arritt, R.W.; Takle, E.S.; Pan, Z.; Leavesley, G.H.; Clark, M.P.

2000-01-01

63

A Mixed Method Approach for Evaluating Spatial Data Sharing Partnerships for SDI Development  

Microsoft Academic Search

In recent years inter-jurisdictional partnerships h ave emerged as an important mechanism for establishing an environment conducive to data sharing and hence the facilitation of SDI development. However, unless t he partnership arrangements are carefully designed and managed to meet the business objectives of each partner, it is unlikely that they will be successful or sustainabl e in the longer

Kevin McDougall; Abbas Rajabifard; Ian P. Williamson

64

CROP EMERGENCE WITH ALTERNATIVE SDI DESIGNS IN A PULLMAN CLAY LOAM SOIL  

Technology Transfer Automated Retrieval System (TEKTRAN)

We compared soybean emergence and yield for different bed designs for subsurface drip irrigation (SDI). The bed designs consisted of standard beds with drip laterals installed in alternate furrows, and wide beds with drip laterals centered in the bed between two plant rows. Both designs result in th...

65

Social Development in Hong Kong: Development Issues Identified by Social Development Index (SDI)  

ERIC Educational Resources Information Center

Surviving the aftermaths of the Asian Financial Crisis and SARS in 2003, Hong Kong's economy has re-gained its momentum and its economic growth has been quite remarkable too in recent few years. Nevertheless, as reflected by the Social Development Index (SDI), economic growth in Hong Kong does not seem to have benefited the people of the city at…

Chua, Hoi-wai; Wong, Anthony K. W.; Shek, Daniel T. L.

2010-01-01

66

Use of OGC web standard for a spatio-temporal enabled SDI for civil protection  

Microsoft Academic Search

In the last years, Geographic Information technologies have reached a mature state, providing a platform to support interoperability among different providers and users through Spatial Data Infrastructures (SDI). However, Civil Protection applications have specific requirements that make them different from typical Earth System Sciences research applications. Currently SDIs and the ESDI (European Spatial Data Infrastructure) only partially address user needs

Federico Prandi; Raffaele De Amicis; Giuseppe Conti; Alberto Debiasi

2012-01-01

67

SDI: PROSPECTS AND CHALLENGES FOR FEDERAL STATE DEVELOPING COUNTRIES (Case of Nigeria)  

Microsoft Academic Search

Implementation of SDIs in inherently complex, tension arises from various sources including the need for consensus on standards for example between federal and local agencies(Georgiadou et al., 2007). Despite the numerous benefits of SDI, there are still several failure of the project(Georgiadou and Harvey, 2007) and most of these failures are in developing countries. Factors affecting such failures include lack

O. A. Ogundelea; O. S. Somefunb; WG VII

68

SDI AND GOVERNANCE: PROSPECTS AND CHALLENGES FOR FEDERAL STATE DEVELOPING COUNTRIES (Case of Nigeria)  

Microsoft Academic Search

Implementation of SDIs in inherently complex, tension arises from various sources including the need for consensus on standards for example between federal and local agencies(Georgiadou et al., 2007). Despite the numerous benefits of SDI, there are still several failure of the project(Georgiadou and Harvey, 2007) and most of these failures are in developing countries. Factors affecting such failures include lack

O. A. Ogundele; O. S. Somefun

69

Universality of Tsallis Non-Extensive Statistics and Fractal Dynamics for Complex Systems  

E-print Network

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.

G. P. Pavlos; M. N. Xenakis; L. P. Karakatsanis; A. C. Iliopoulos; A. E. G. Pavlos; D. V. Sarafopoulos

2012-03-25

70

Path planning for mobile vehicles within dynamic worlds using statistical data  

Microsoft Academic Search

This paper proposes a new path planning approach based on statistical information, like the occupancy probability of partly or completely dynamic obstacles and\\/or the statistical flow of dynamic obstacles. With this new approach it is possible to integrate the expected behavior of moving obstacles into the preplanning of paths without knowing the individual movement of these dynamic obstacles. As the

R. Gutsche; C. Laloni; F. M. Wahl

1994-01-01

71

Enriching Spatial Data Infrastructure (sdi) by User Generated Contents for Transportation  

NASA Astrophysics Data System (ADS)

Spatial data is one of the most critical elements underpinning decision making for many disciplines. Accessing and sharing spatial data have always been a great struggle for researchers. Spatial data infrastructure (SDI) plays a key role in spatial data sharing by building a suitable platform for collaboration and cooperation among the different data producer organizations. In recent years, SDI vision has been moved toward a user-centric platform which has led to development of a new and enriched generation of SDI (third generation). This vision is to provide an environment where users can cooperate to handle spatial data in an effective and satisfactory way. User-centric SDI concentrates on users, their requirements and preferences while in the past, SDI initiatives were mainly concentrated on technological issues such as the data harmonization, standardized metadata models, standardized web services for data discovery, visualization and download. On the other hand, new technologies such as the GPS-equipped smart phones, navigation devices and Web 2.0 technologies have enabled citizens to actively participate in production and sharing of the spatial information. This has led to emergence of the new phenomenon called the Volunteered Geographic Information (VGI). VGI describes any type of content that has a geographic element which has been voluntarily collected. However, its distinctive element is the geographic information that can be collected and produced by citizens with different formal expertise and knowledge of the spatial or geographical concepts. Therefore, ordinary citizens can cooperate in providing massive sources of information that cannot be ignored. These can be considered as the valuable spatial information sources in SDI. These sources can be used for completing, improving and updating of the existing databases. Spatial information and technologies are an important part of the transportation systems. Planning, design and operation of the transportation systems requires the exchange of large volumes of spatial data and often close cooperation among the various organizations. However, there is no technical and organizational process to get a suitable data infrastructure to address diverse needs of the transportation. Hence, development of a common standards and a simple data exchange mechanism is strongly needed in the field of transportation for decision support. Since one of the main purposes of transportation projects is to improve the quality of services provided to users, it is necessary to involve the users themselves in the decision making processes. This should be done through a public participation and involvement in all stages of the transportation projects. In other words, using public knowledge and information as another source of information is very important to make better and more efficient decisions. Public participation in transportation projects can also help organizations to enhance their public supports; because the lack of public support can lead to failure of technically valid projects. However, due to complexity of the transportation tasks, lack of appropriate environment and methods for facilitation of the public participation, collection and analysis of the public information and opinions, public participation in this field has not been well considered so far. This paper reviews the previous researches based on the enriched SDI development and its movement toward the VGI by focusing on the public participation in transportation projects. To this end, methods and models that have been used in previous researches are studied and classified initially. Then, methods of the previous researchers on VGI and transportation are conceptualized in SDI. Finally, the suggested method for transportation projects is presented. Results indicate success of the new generation of SDI in integration with public participation for transportation projects.

Shakeri, M.; Alimohammadi, A.; Sadeghi-Niaraki, A.; Alesheikh, A. A.

2013-09-01

72

A statistical model for interpreting computerized dynamic posturography data  

NASA Technical Reports Server (NTRS)

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.

Feiveson, Alan H.; Metter, E. Jeffrey; Paloski, William H.

2002-01-01

73

Reconfiguring the Quorum-Sensing Regulator SdiA of Escherichia coli To Control Biofilm Formation via Indole and N-Acylhomoserine Lactones? †  

PubMed Central

SdiA is a homolog of quorum-sensing regulators that detects N-acylhomoserine lactone (AHL) signals from other bacteria. Escherichia coli uses SdiA to reduce its biofilm formation in the presence of both AHLs and its own signal indole. Here we reconfigured SdiA (240 amino acids) to control biofilm formation using protein engineering. Four SdiA variants were obtained with altered biofilm formation, including truncation variants SdiA1E11 (F7L, F59L, Y70C, M94K, and K153X) and SdiA14C3 (W9R, P49T, N87T, frameshift at N96, and L123X), which reduced biofilm formation by 5- to 20-fold compared to wild-type SdiA in the presence of endogenous indole. Whole-transcriptome profiling revealed that wild-type SdiA reduced biofilm formation by repressing genes related to indole synthesis and curli synthesis compared to when no SdiA was expressed, while variant SdiA1E11 induced genes related to indole synthesis in comparison to wild-type SdiA. These results suggested altered indole metabolism, and corroborating the DNA microarray results in regard to indole synthesis, variant SdiA1E11 produced ninefold more indole, which led to reduced swimming motility and cell density. Also, wild-type SdiA decreased curli production and tnaA transcription, while SdiA1E11 increased tnaA transcription (tnaA encodes tryptophanase, which forms indole) compared to wild-type SdiA. Hence, wild-type SdiA decreased biofilm formation by reducing curli production and motility, and SdiA1E11 reduced biofilm formation via indole. Furthermore, an AHL-sensitive variant (SdiA2D10, having four mutations at E31G, Y42F, R116H, and L165Q) increased biofilm formation sevenfold in the presence of N-octanoyl-dl-homoserine lactone and N-(3-oxododecatanoyl)-l-homoserine lactone. Therefore, SdiA can be evolved to increase or decrease biofilm formation, and biofilm formation may be controlled by altering sensors rather than signals. PMID:19168658

Lee, Jintae; Maeda, Toshinari; Hong, Seok Hoon; Wood, Thomas K.

2009-01-01

74

Static and dynamic Tokunaga stream networks: Statistical properties  

NASA Astrophysics Data System (ADS)

In this study we apply complex-network methods to advance conceptual models of environmental transport on river networks. It is well known that the topology of stream networks is closely approximated by so-called Tokunaga Self-Similar Trees (SSTs). Tokunaga SSTs represent a two-parameter class of trees specified by the parameter pair (a,c); the Shreve river network model is an example of a Tokunaga SST with (a,c)=(1,2). It has been shown that Tokunaga SSTs can describe most real river networks, by using different parameter values, distinct from those of Shreve’s model. Recent studies provide evidence that Tokunaga self-similarity is a characteristic property of general aggregation processes, with a broad range of applications not limited to hydrological settings. This motivates us to analyze here several essential properties of Tokunaga stream networks with a broadly varying range of parameter values. In particular, we relate the statistical description of the width function, including its self-similar properties, to the parameters (a,c). In addition, we further analyze the dynamic tree description of a stream network introduced by Zaliapin et al. (2010) and formulate a related, yet more physically relevant, concept of a dynamic network. The latter concept describes the mixing of fluxes initiated at different sources in a continuous downstream transport. Finally, Boolean delay equations (BDEs) are used to model the downstream transport along real and synthetic river networks.

Zaliapin, I.; Foufoula-Georgiou, E.; Ghil, M.

2010-12-01

75

Statistical prediction of dynamic distortion of inlet flow using minimum dynamic measurement. An application to the Melick statistical method and inlet flow dynamic distortion prediction without RMS measurements  

NASA Technical Reports Server (NTRS)

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.

Schweikhard, W. G.; Chen, Y. S.

1986-01-01

76

SDI-based business processes: A territorial analysis web information system in Spain  

NASA Astrophysics Data System (ADS)

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.

Béjar, Rubén; Latre, Miguel Á.; Lopez-Pellicer, Francisco J.; Nogueras-Iso, Javier; Zarazaga-Soria, F. J.; Muro-Medrano, Pedro R.

2012-09-01

77

Dynamical analogy between economical crisis and earthquake dynamics within the nonextensive statistical mechanics framework  

NASA Astrophysics Data System (ADS)

The field of study of complex systems considers that the dynamics of complex systems are founded on universal principles that may be used to describe a great variety of scientific and technological approaches of different types of natural, artificial, and social systems. Several authors have suggested that earthquake dynamics and the dynamics of economic (financial) systems can be analyzed within similar mathematical frameworks. We apply concepts of the nonextensive statistical physics, on time-series data of observable manifestations of the underlying complex processes ending up with these different extreme events, in order to support the suggestion that a dynamical analogy exists between a financial crisis (in the form of share or index price collapse) and a single earthquake. We also investigate the existence of such an analogy by means of scale-free statistics (the Gutenberg-Richter distribution of event sizes). We show that the populations of: (i) fracto-electromagnetic events rooted in the activation of a single fault, emerging prior to a significant earthquake, (ii) the trade volume events of different shares/economic indices, prior to a collapse, and (iii) the price fluctuation (considered as the difference of maximum minus minimum price within a day) events of different shares/economic indices, prior to a collapse, follow both the traditional Gutenberg-Richter law as well as a nonextensive model for earthquake dynamics, with similar parameter values. The obtained results imply the existence of a dynamic analogy between earthquakes and economic crises, which moreover follow the dynamics of seizures, magnetic storms and solar flares.

Potirakis, Stelios M.; Zitis, Pavlos I.; Eftaxias, Konstantinos

2013-07-01

78

Social Development in Hong Kong: Development Issues Identified by Social Development Index (SDI)  

Microsoft Academic Search

Surviving the aftermaths of the Asian Financial Crisis and SARS in 2003, Hong Kong’s economy has re-gained its momentum and\\u000a its economic growth has been quite remarkable too in recent few years. Nevertheless, as reflected by the Social Development\\u000a Index (SDI), economic growth in Hong Kong does not seem to have benefited the people of the city at large as

Hoi-wai Chua; Anthony K. W. Wong; Daniel T. L. Shek

2010-01-01

79

Activities in HPM effects phenomenology at LLNL under the DNA\\/SDI Lth6 effort  

Microsoft Academic Search

During the fiscal years 1984-1986, DNA funded an effort at the Lawrence Livermore National Laboratory under the SDI\\/Lth-6 program to develop models and to study the phenomenology of HPM interaction with systems. The effort concentrated on the following areas: linear coupling\\/modeling; linear coupling\\/experiments; nonlinear coupling\\/modeling; component failure\\/modeling; component characterization; and electronic subsystem characterization. This report sumarizes these subject areas.

H. S. Cabayan; R. J. King

1988-01-01

80

Activities in HPM effects phenomenology at LLNL under the DNA/SDI Lth-6 effort  

SciTech Connect

During the fiscal years 1984-1986, DNA funded an effort at the Lawrence Livermore National Laboratory under the SDI/Lth-6 program to develop models and to study the phenomenology of HPM interaction with systems. The effort concentrated on the following areas: linear coupling/modeling; linear coupling/experiments; nonlinear coupling/modeling; component failure/modeling; component characterization; and electronic subsystem characterization. This report sumarizes these subject areas.

Cabayan, H.S.; King, R.J.

1988-01-01

81

Dynamic focus window selection using a statistical color model  

NASA Astrophysics Data System (ADS)

We previously showed the necessity of utilizing dynamic methods to select focus window for passive autofocus in digital imaging systems. One possibility is to track the photographer's pupil through a modified viewfinder so that the region of interest in a target image can be determined, as previously described. Yet this assumes that a user is on site and he/she looks through the viewfinder, which is less and less practiced as a result of the availability of liquid crystal displays (LCD) on most consumer digital imaging systems. An alternative is to use pattern recognition to select focus windows when the imaging targets are known in advance and can be extracted from their background. In this paper, one of such cases, where the imaging targets are humans, is discussed in detail. The theoretical basis for dynamic focus window selection is briefly reviewed. And an example is given to demonstrate the effects of different focus windows on the imaging results. Then the focus window selecting technique using a statistical model of human skin colors is described in detail. The incoming target image in RGB color space is transformed into 2-dimension (r, g) space. Each pixel is binarized according to the relationship between its (r, g) value and the skin color distribution. Thus skin regions in the image are extracted. Morphological operations are then applied to the resultant binary image to reduce the number and irregularity of the skin regions. A rectangle can be fitted to the extracted skin region and used as the focus window. Experimental results are given to demonstrate the advantages of the proposed method.

Tian, Yibin

2006-02-01

82

Suppressing speckle noise for simultaneous differential extrasolar planet imaging (SDI) at the VLT and MMT  

NASA Astrophysics Data System (ADS)

We discuss data reduction techniques and results from the Simultaneous Differential Imager (SDI) implemented at the VLT (Lenzen et al. 2004a) and the MMT. SDI uses a quad filter to take images simultaneously at 3 wavelengths surrounding the 1.62 ?m methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be attenuated by a factor of >102. Non-trivial data reduction tools are necessary to pipeline the simultaneous differential imaging. Here we discuss a custom algorithm implemented in IDL to perform this reduction. The script performs basic data reduction tasks but also precisely aligns images taken in each of the filters using a custom shift and subtract routine. In our commissioning runs at the VLT and MMT, we achieved contrasts up to a factor of 45000 (?H=11.7) at a separation of 0.6" from the primary star. With this degree of attenuation, we should be able to image a 2-4 Jupiter mass planet at 5 AU around a 30 Myr star at 10 pc. We believe that our SDI images are the highest contrast astronomical images ever made from ground or space.

Biller, Beth A.; Close, Laird; Lenzen, Rainer; Brandner, Wolfgang; McCarthy, Donald W.; Nielsen, Eric; Hartung, Markus

2004-10-01

83

Modeling Insurgent Dynamics Including Heterogeneity. A Statistical Physics Approach  

NASA Astrophysics Data System (ADS)

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.

Johnson, Neil F.; Manrique, Pedro; Hui, Pak Ming

2013-05-01

84

Teachers' Statistical Problem Solving with Dynamic Technology: Research Results across Multiple Institutions  

ERIC Educational Resources Information Center

This study examined a random stratified sample (n = 62) of prospective teachers' work across eight institutions on three tasks that utilized dynamic statistical software. The authors considered how teachers utilized their statistical knowledge and technological statistical knowledge to engage in cycles of investigation. This paper characterizes…

Lee, Hollylynne Stohl; Kersaint, Gladis; Harper, Suzanne; Driskell, Shannon O.; Leatham, Keith R.

2012-01-01

85

Statistical properties of some spatially discretized dynamical systems  

Microsoft Academic Search

Computer simulations of dynamical systems are spatial discretizations in which the nite machine arithmetic space replaces the continuum state space of the original system. Any trajectory of a spatial discretization of a dynamical system is thus eventually periodic, so the dynamical behaviour of such computations are essentially determined by the cycles of the dis- cretized map. Such dynamical behaviour depends

P. Kloeden; J. Mustard; A. Pokrovski

1999-01-01

86

Examining rainfall and cholera dynamics in Haiti using statistical and dynamic modeling approaches.  

PubMed

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

Eisenberg, Marisa C; Kujbida, Gregory; Tuite, Ashleigh R; Fisman, David N; Tien, Joseph H

2013-12-01

87

Material Phase Causality or a Dynamics-Statistical Interpretation of Quantum Mechanics  

SciTech Connect

The internal phase dynamics of a quantum system interacting with an electromagnetic field is revealed in details. Theoretical and experimental evidences of a causal relation of the phase of the wave function to the dynamics of the quantum system are presented sistematically for the first time. A dynamics-statistical interpretation of the quantum mechanics is introduced.

Koprinkov, I. G. [Department of Applied Physics, Technical University of Sofia, 1756 Sofia (Bulgaria)

2010-11-25

88

Dynamical instability and statistical behaviour of N-body systems  

NASA Astrophysics Data System (ADS)

In this paper, we argue about a synthetic characterization of the qualitative properties of generic many-degrees-of-freedom (mdf) dynamical systems (DS's) by means of a geometric description of the dynamics [Geometro-Dynamical Approach (GDA)]. We exhaustively describe the mathematical framework needed to link geometry and dynamical (in)stability, discussing in particular which geometrical quantity is actually related to instability and why some others cannot give, in general, any indication of the occurrence of chaos. The relevance of the Schur theorem to select such Geometrodynamic Indicators (GDI) of instability is then emphasized, as its implications seem to have been underestimated in some of the previous works. We then compare the analytical and numerical results obtained by us and by Pettini and coworkers concerning the FPU chain, verifying a complete agreement between the outcomes of averaging the relevant GDI's over phase space (Casetti and Pettini, 1995) and our findings (Cipriani, 1993), obtained in a more conservative way, time-averaging along geodesics. Along with the check of the ergodic properties of GDI's, these results confirm that the mechanism responsible for chaos in realistic DS's largely depends on the fluctuations of curvatures rather than on their negative values, whose occurrence is very unlikely. On these grounds we emphasize the importance of the virialization process, which separates two different regimes of instability. This evolutionary path, predicted on the basis of analytical estimates, receives clear support from numerical simulations, which, at the same time, confirm also the features of the evolution of the GDI's along with their dependence on the number of degrees of freedom, N, and on the other relevant parameters of the system, pointing out the scarce relevance of negative curvature (for N ? 1) as a source of instability. The general arguments outlined above, are then concretely applied to two specific N-body problems, obtaining some new insights into known outcomes and also some new results The comparative analysis of the FPU chain and the gravitational N-body system allows us to suggest a new definition of strong stochasticity, for any DS. The generalization of the concept of dynamical time-scale, tD, is at the basis of this new criterion. We derive for both the mdf systems considered the ( N, ?)-dependence of tD (? being the specific energy) of the system. In light of this, the results obtained (Cerruti-Sola and Pettini, 1995), indeed turn out to be reliable, the perplexity there raised originating from the neglected N-dependence of tD, and not to an excessive degree of approximation in the averaged equations used. This points out also the peculiarities of gravitationally bound systems, which are always in a regime of strong instability; the dimensionless quantity L1 = ?1 · tD [? 1 is the maximal Lyapunov Characteristic Number (LCN)] being always positive and independent of ?, as it happens for the FPU chain only above the strong stochasticity threshold (SST). The numerical checks on the analytical estimates about the ( N, ?)-dependence of GDI's, allow us to single out their scaling laws, which support our claim that, for N ? 1, the probability of finding a negative value of Ricci curvature is practically negligible, always for the FPU chain, whereas in the case of the Gravitational N-body system, this is certainly true when the virial equilibrium has been attained. The strong stochasticity of the latter DS is clearly due to the large amplitude of curvature fluctuations. To prove the positivity of Ricci curvature, we need to discuss the pathologies of mathematical Newtonian interaction, which have some implications also on the ergodicity of the GDI's for this DS. We discuss the Statistical Mechanical properties of gravity, arguing how they are related to its long range nature rather than to its short scale divergencies. The N-scaling behaviour of the single terms entering the Ricci curvature show that the dominant contribution comes from the Laplacian of the potential e

Cipriani, Piero; Di Bari, Maria

1998-12-01

89

An open-source wireless sensor stack: from Arduino to SDI-12 to Water One Flow  

NASA Astrophysics Data System (ADS)

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.

Hicks, S.; Damiano, S. G.; Smith, K. M.; Olexy, J.; Horsburgh, J. S.; Mayorga, E.; Aufdenkampe, A. K.

2013-12-01

90

Acta Cryst. (2001). A57, 231239 Chukhovskii et al. Statistical dynamical direct methods. II 231 research papers  

E-print Network

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

Marks, Laurence D.

91

Different Fatigue Dynamics Under Statistically and Spectrally Similar Deterministic and  

E-print Network

and statistical signatures. Furthermore, the conven- tional rain-flow counting method considerably overestimates throughout the experiments. Thus, superposi- tion based cycle counting methods should be applicable. The rain-flow

Chelidze, David

92

Modeling dynamic controls on ice streams: a Bayesian statistical approach  

E-print Network

in glaciology (e.g. MacAyeal, 1993; Arthern and Hindmarsh, 2003; Gudmundsson, 2006) nor in the broad areas of the geosciences (e.g. data assimilation as practiced in numerical weather forecasting). We address the goal by formally modeling the uncertainties... present, then using Bayes’ theorem to deduce information about all unknowns in the data. We focus on the development of statistical models with strong reliance on physical modeling, a strategy Berliner (2003) called ‘physical–statistical modeling...

Berliner, L. M.; Jezek, K.; Cressie, N.; Kim, Y.; Lam, C. Q.; Van Der Veen, Cornelis J.

2008-12-05

93

Large scale testing and statistical analysis of dynamic fracture toughness of ductile cast iron  

Microsoft Academic Search

The present paper deals with the experimental determination and statistical analysis of dynamic fracture toughness values of ductile cast iron. KId data from 140mm thick single edge bend specimens of two dynamic fracture toughness test series on ductile cast iron from heavy-walled castings were analysed.At first, the statistical analysis of data at ?40°C was done based on ASME Code Case

Wolfram Baer; Peter Wossidlo; Behboud Abbasi; Matthias Cassau; Ralf Häcker; Reimund Kossert

2009-01-01

94

Statistical Test for Dynamical Nonstationarity in Observed Time-Series Data  

E-print Network

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.

Matthew B. Kennel

1995-12-21

95

An Examination of Statistical Power in Multigroup Dynamic Structural Equation Models  

ERIC Educational Resources Information Center

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…

Prindle, John J.; McArdle, John J.

2012-01-01

96

SERVIR's Contributions and Benefits to Belize thru Spatial Data Infrastructure (SDI) Development  

NASA Technical Reports Server (NTRS)

Dan Irwin, the SERVIR Project Manager is being honored with the privilege of delivering the opening remarks at Belize s second celebration of GIS Day, a weeklong event to be held at the University of Belize's campus in the nation s capital, Belmopan. The request has been extended by the GIS Day Planning Committee which operates under the auspices of Belize s Ministry of Natural Resources & the Environment, which is the focal ministry for SERVIR. In the 20-30 min. allotted for the opening remarks, the SERVIR Project Manager will expound on how SERVIR, operating under the auspices of NASA s Ecological Forecasting Program, contributes to spatial data infrastructure (SDI) development in Belize. NASA s contributions to the region - particularly work under the Mesoamerican Biological Corridor - will be highlighted. Continuing, the remarks will discuss SERVIR s role in Belize s steadily expanding SDI, particularly in the context of delivering integrated decision support products via web-based infrastructure. The remarks will close with a call to the parties assembled to work together in the application of Earth Observation Systems technologies for the benefit of Belizean society as a whole. NASA s strong presence in Belize s GIS Day celebrations will be highlighted as sustained goodwill of the American people - in partial fulfillment of goals set forth under the Global Earth Observation System of Systems (GEOSS).

Irwin, Daniel E.

2006-01-01

97

Barotropic Vortex Dynamics and Statistical Mechanics-application to  

E-print Network

sphere S2. In this paper, we shall give the detailed analysis of the non-rotating case, but summarize will focus on the variational analysis of the BVE; the second part summarizes a recent statistical mechanics model for barotropic vortical flows on the sphere. A common thread that runs through both

Lim, Chjan C.

98

Combined statistical and dynamical model of ternary nuclear fission  

Microsoft Academic Search

The statistical theory of particle evaporation from hot compound nuclei can be used to calculate the probability that particles are evaporated from the nuclear surface with not enough energy to surmount the Coulomb barrier. These quasievaporated particles exist between the nuclear surface and the Coulomb barrier for a short period of time before returning to the nuclear fluid. Occasionally, a

J. P. Lestone

2004-01-01

99

Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics  

SciTech Connect

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.

Crooks, Gavin; Sivak, David

2011-06-03

100

Functional relations in lattice statistical mechanics, enumerative combinatorics, and discrete dynamical systems  

Microsoft Academic Search

We recall some non-trivial, non-linear functional relations appearing in various domains of mathematics and physics, such as lattice statistical mechanics, quantum mechanics, or enumerative combinatorics. We focus, more particularly, on the analyticity properties of the solutions of these functional relations. We then consider discrete dynamical systems corresponding to birational transformations. The rational expressions for dynamical zeta functions obtained for a

J.-Ch. Anglès d'Auriac; S. Boukraa; J.-M. Maillard

1999-01-01

101

Teaching the principles of statistical dynamics Kingshuk Ghosh and Ken A. Dill  

E-print Network

the packing of DNA inside viruses7 and the stretching of DNA and RNA molecules.9,10 Similarly, videoTeaching the principles of statistical dynamics Kingshuk Ghosh and Ken A. Dill Department We describe a simple framework for teaching the principles that underlie the dynamical laws

Phillips, Rob

102

Theoretical and Experimental Evidences of Material Phase Causality. Dynamics-Statistical Interpretation of the Wave Function  

E-print Network

The internal phase dynamics of a quantum system is revealed in details. Theoretical and experimental evidences of existence of a causal relation of the phase of the wave function with the dynamics of the quantum system are presented sistematically for the first time. A new, dynamics-statistical interpretation of the quantum mechanics is introduced. A particle-wave duality picture incorporated in the wave function through its phase and amplitude is considered.

I. G. Koprinkov

2010-04-19

103

New Dynamical-Statistical Techniques for Wind Power Prediction  

NASA Astrophysics Data System (ADS)

The increased use of renewable energy sources, and especially of wind power, has revealed the significance of accurate environmental and wind power predictions over wind farms that critically affect the integration of the produced power in the general grid. This issue is studied in the present paper by means of high resolution physical and statistical models. Two numerical weather prediction (NWP) systems namely SKIRON and RAMS are used to simulate the flow characteristics in selected wind farms in Greece. The NWP model output is post-processed by utilizing Kalman and Kolmogorov statistics in order to remove systematic errors. Modeled wind predictions in combination with available on-site observations are used for estimation of the wind power potential by utilizing a variety of statistical power prediction models based on non-linear and hyperbolic functions. The obtained results reveal the strong dependence of the forecasts uncertainty on the wind variation, the limited influence of previously recorded power values and the advantages that nonlinear - non polynomial functions could have in the successful control of power curve characteristics. This methodology is developed at the framework of the FP7 projects WAUDIT and MARINA PLATFORM.

Stathopoulos, C.; Kaperoni, A.; Galanis, G.; Kallos, G.

2012-04-01

104

Applications of statistical mechanics in subcontinuum fluid dynamics  

Microsoft Academic Search

We show results of molecular dynamics studies of fluid flows in the Knudsen regime in which the mean free path is comparable to the system size. We elucidate the boundary conditions at the wall–fluid interface in such flows and find scenarios envisioned by Maxwell. We also find scenarios which do not agree with Maxwell's hypothesis. We focus primarily on the

Marek Cieplak; Joel Koplik; Jayanth R. Banavar

1999-01-01

105

Can subsurface drip irrigation (SDI) be a competitive irrigation system in the Great Plains region for commodity crops  

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...

106

Development and Evaluation of a Large-Scale System for Selective Dissemination of Information (SDI). Research and Development Technical Report.  

ERIC Educational Resources Information Center

The report describes a large-scale computerized system for Selective Dissemination of Information (SDI) developed over the past five years at the U.S. Army Electronics Command to serve its technical personnel. The system, which uses as its document base the current accessions of the Defense Documentation Center, was developed in three phases: (1)…

Wixon, D. W.; Housman, E. M.

107

Lars Onsager Prize Lecture: Statistical Dynamics of Disordered Systems  

NASA Astrophysics Data System (ADS)

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.

Fisher, Daniel S.

2013-03-01

108

Viscoelastic effects in avalanche dynamics: a key to earthquake statistics.  

PubMed

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

Jagla, E A; Landes, François P; Rosso, Alberto

2014-05-01

109

Inactivation of the Transcriptional Regulator-Encoding Gene sdiA Enhances Rice Root Colonization and Biofilm Formation in Enterobacter cloacae GS1  

PubMed Central

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

Shankar, Manoharan; Ponraj, Paramasivan; Illakkiam, Devaraj; Rajendhran, Jeyaprakash

2013-01-01

110

Dynamic Modelling and Statistical Analysis of Event Times  

PubMed Central

This review article provides an overview of recent work in the modelling and analysis of recurrent events arising in engineering, reliability, public health, biomedical, and other areas. Recurrent event modelling possesses unique facets making it different and more difficult to handle than single event settings. For instance, the impact of an increasing number of event occurrences needs to be taken into account, the effects of covariates should be considered, potential association among the inter-event times within a unit cannot be ignored, and the effects of performed interventions after each event occurrence need to be factored in. A recent general class of models for recurrent events which simultaneously accommodates these aspects is described. Statistical inference methods for this class of models are presented and illustrated through applications to real data sets. Some existing open research problems are described. PMID:17906740

Peña, Edsel A.

2006-01-01

111

Statistical mechanics of neocortical interactions - Dynamics of synaptic modification  

NASA Technical Reports Server (NTRS)

A recent study has demonstrated that several scales of neocortical interactions can be consistently analyzed with the use of methods of modern nonlinear nonequilibrium statistical mechanics. The formation, stability, and interaction of spatial-temporal patterns of columnar firings are explicitly calculated, to test hypothesized mechanisms relating to information processing. In this context, most probable patterns of columnar firings are associated with chemical and electrical synaptic modifications. It is stressed that synaptic modifications and shifts in most-probable firing patterns are highly nonlinear and interactive sets of phenomena. A detailed scenario of information processing is calculated of columnar coding of external stimuli, short-term storage via hysteresis, and long-term storage via synaptic modification.

Ingber, L.

1983-01-01

112

Statistical methodologies for the control of dynamic remapping  

NASA Technical Reports Server (NTRS)

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.

Saltz, J. H.; Nicol, D. M.

1986-01-01

113

Noisy inverted pendulums with time-delayed feedback: Statistical Dynamics  

NASA Astrophysics Data System (ADS)

The question of how an inverted pendulum can be stabilized has puzzled scientists for over 300 years. Studies of postural sway and stick balancing at the fingertip provide insights into how the human nervous system solves this problem. Time delays and noise are intrinsic features of the neural control and thus models are in the form of stochastic delay-differential equations. Examples are presented to show that the statistical properties of the fluctuations in posture and stick balancing are dominated by noise-dependent, nonlinear phenomena: noise-induced switching between limit cycle attractors (postural sway) and "on-off intermittency" arising from the stochastic forcing of a control parameter across a stability boundary (stick balancing). The existence of these phenomena is difficult to reconcile with classical concepts of neural feedback control.

Milton, John G.

2001-03-01

114

The scientists' opposition to SDI: How political views affect technical analysis  

SciTech Connect

This study examines the scientists' opposition to President Reagan's Strategic Defense Initiative (1983-1989) with a focus on the relationship between the scientists' political and strategic opposition to ballistic missile defenses (BMD) and their technical doubts about BMD technologies. The study begins with a review of the scientists' increased influence in United State's national security decision making because of the development of atomic weapons. The study then examines the scientists' role in developing and promoting a theory of arms control based upon mutual societal vulnerability. Because of this theory, a large segment of the American scientific community came to believe that the development of ballistic missile defenses would destabilize the strategic balance and therefore took the lead in arguing against BMD deployments. These background chapters conclude with an analysis of the scientists' involvement in the political campaign to stop the proposed Sentinel and Safeguard Anti-Ballistic Missile defense. The study then turns to the contemporary scientific opposition to BMD deployments and the SDI research program. After examining the polls and petitions that identify the scientists opposed to SDI, the study analyzes the tactics that three scientists use in their political effort to prevent BMD deployments. Next, an examination of the political and strategic assumptions behind the scientists' opposition to BMD reveals that a belief in the arms control process and deterrence by punishment, especially Assured Destruction deterrence, with a fear of an action-reaction arms race inspires much of the contemporary opposition to BMD. Finally, the scientists' technical doubts about BMD technologies are analyzed through the prism of peer critique. These critiques show that the scientists opposed to BMD deployments us pessimistic and unrealistic assumptions to skew their technical analysis of BMD technologies.

Tait, G.E.

1989-01-01

115

Process-oriented statistical-dynamical evaluation of LM precipitation forecasts  

NASA Astrophysics Data System (ADS)

The objective of this study is the scale dependent evaluation of precipitation forecasts of the Lokal-Modell (LM) from the German Weather Service in relation to dynamical and cloud parameters. For this purpose the newly designed Dynamic State Index (DSI) is correlated with clouds and precipitation. The DSI quantitatively describes the deviation and relative distance from a stationary and adiabatic solution of the primitive equations. A case study and statistical analysis of clouds and precipitation demonstrates the availability of the DSI as a dynamical threshold parameter. This confirms the importance of imbalances of the atmospheric flow field, which dynamically induce the generation of rainfall.

Claußnitzer, A.; Langer, I.; Névir, P.; Reimer, E.; Cubasch, U.

2008-04-01

116

The Soret and Dufour effects in statistical dynamics  

E-print Network

We set up a discrete space-time dynamical model of molecules with thermalised kinetic energy and repulsive cores, in an external potential. The state is specified by a probability on the sample space. One time-step is given by a bistochastic map, followed by a local thermalising map. The model obeys the first and second laws of thermodynamics. The continuum limit, obtained using a MAPLE program, gives rise to coupled nonlinear reaction-diffusion equations for the density and temperature fields. The system obeys Onsager symmetry and exhibits the Soret and Dufour effects.

R. F. Streater

1999-10-27

117

Novel dynamic measures of emetic behavior in musk shrews  

PubMed Central

The emetic reflex occurs as a pattern of motor responses produced by a network of neurons in the hindbrain. Despite an understanding of the sequence of motor outputs that form an emetic episode (EE), the variability in the dynamics of multiple EEs across time remains a mystery. Nearly all clinical studies rely on once a day patient recall of total amount of vomiting, and preclinical studies frequently report only the total number of EE per unit time. The aim of the current study was to develop novel temporal measures of emetic activation in a preclinical model. Male and female musk shrews were tested with prototypical emetic stimuli: motion exposure (1 Hz), nicotine (5 mg/kg, sc), and copper sulfate (120 mg/kg, ig). New emetic measures included duration (time from first to last episode), rate, standard deviation of the inter-episode interval (SD-I), and a survival analysis of emetic latency (analyzed with Cox regression). Behavioral patterns associated with emesis were also assessed using statistical temporal pattern (T-pattern) analysis to measure nausea-like behaviors (e.g., immobility). The emetic stimuli produced different levels of total EE number, duration, rate, and SD-I. A typical antiemetic, the neurokinin 1 receptor antagonist CP-99,994, suppressed the number of EEs but was less effective for reducing the duration or prolonging the emetic latency. Overall, the current study shows the use of novel dynamic behavioral measures to more comprehensively assess emesis and the impact of therapies. PMID:23953843

Horn, Charles C.; Wang, Hong; Estival, Laureline; Meyers, Kelly; Magnusson, Magnus

2013-01-01

118

Novel dynamic measures of emetic behavior in musk shrews.  

PubMed

The emetic reflex occurs as a pattern of motor responses produced by a network of neurons in the hindbrain. Despite an understanding of the sequence of motor outputs that form an emetic episode (EE), the variability in the dynamics of multiple EEs across time remains a mystery. Many clinical investigations rely on once a day patient recall of total amount of vomiting, and preclinical studies frequently report only the total number of EE per unit time. The aim of the current study was to develop novel temporal measures of emetic activation in a preclinical model. Male and female musk shrews were tested with prototypical emetic stimuli: motion exposure (1 Hz), nicotine (5 mg/kg, sc), and copper sulfate (120 mg/kg, ig). New emetic measures included duration (time from first to last episode), rate, standard deviation of the inter-episode interval (SD-I), and a survival analysis of emetic latency (analyzed with Cox regression). Behavioral patterns associated with emesis were also assessed using statistical temporal pattern (T-pattern) analysis to measure nausea-like behaviors (e.g., immobility). The emetic stimuli produced different levels of total EE number, duration, rate, and SD-I. A typical antiemetic, the neurokinin 1 receptor antagonist CP-99,994, suppressed the number of EEs but was less effective for reducing the duration or prolonging the emetic latency. Overall, the current study shows the use of novel dynamic behavioral measures to more comprehensively assess emesis and the impact of therapies. PMID:23953843

Horn, Charles C; Wang, Hong; Estival, Laureline; Meyers, Kelly; Magnusson, Magnus S

2013-12-01

119

The Statistical Mechanics of Dynamic Pathways to Self-Assembly.  

PubMed

This review describes some important physical characteristics of the pathways (i.e., dynamical processes) by which molecular, nanoscale, and micrometer-scale self-assembly occurs. We highlight the existence of features of self-assembly pathways that are common to a wide range of physical systems, even though those systems may differ with respect to their microscopic details. We summarize some existing theoretical descriptions of self-assembly pathways and highlight areas-notably, the description of self-assembly pathways that occur far from equilibrium-that are likely to become increasingly important. Expected final online publication date for the Annual Review of Physical Chemistry Volume 66 is March 31, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates. PMID:25493714

Whitelam, Stephen; Jack, Robert L

2014-12-01

120

Human turnover dynamics during sleep: Statistical behavior and its modeling  

NASA Astrophysics Data System (ADS)

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.

Yoneyama, Mitsuru; Okuma, Yasuyuki; Utsumi, Hiroya; Terashi, Hiroo; Mitoma, Hiroshi

2014-03-01

121

A statistically accurate modified quasilinear Gaussian closure for uncertainty quantification in turbulent dynamical systems  

NASA Astrophysics Data System (ADS)

We develop a novel second-order closure methodology for uncertainty quantification in damped forced nonlinear systems with high dimensional phase-space that possess a high-dimensional chaotic attractor. We focus on turbulent systems with quadratic nonlinearities where the finite size of the attractor is caused exclusively by the synergistic activity of persistent, linearly unstable directions and a nonlinear energy transfer mechanism. We first illustrate how existing UQ schemes that rely on the Gaussian assumption will fail to perform reliable UQ in the presence of unstable dynamics. To overcome these difficulties, a modified quasilinear Gaussian (MQG) closure is developed in two stages. First we exploit exact statistical relations between second order correlations and third order moments in statistical equilibrium in order to decompose the energy flux at equilibrium into precise additional damping and enhanced noise on suitable modes, while preserving statistical symmetries; in the second stage, we develop a nonlinear MQG dynamical closure which has this statistical equilibrium behavior as a stable fixed point of the dynamics. Our analysis, UQ schemes, and conclusions are illustrated through a specific toy-model, the forty-modes Lorenz 96 system, which despite its simple formulation, presents strongly turbulent behavior with a large number of unstable dynamical components in a variety of chaotic regimes. A suitable version of MQG successfully captures the mean and variance, in transient dynamics with initial data far from equilibrium and with large random fluctuations in forcing, very cheaply at the cost of roughly two ensemble members in a Monte-Carlo simulation.

Sapsis, Themistoklis P.; Majda, Andrew J.

2013-06-01

122

Quantum statistical mechanics of gases in terms of dynamical filling fractions and scattering amplitudes  

E-print Network

We develop a finite temperature field theory formalism in any dimension that has the filling fractions as the basic dynamical variables. The formalism efficiently decouples zero temperature dynamics from the quantum statistical sums. The zero temperature `data' is the scattering amplitudes. A saddle point condition leads to an integral equation which is similar in spirit to the thermodynamic Bethe ansatz for integrable models, and effectively resums infinite classes of diagrams. We present both relativistic and non-relativistic versions.

André LeClair

2006-11-17

123

Statistically accurate low-order models for uncertainty quantification in turbulent dynamical systems.  

PubMed

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 turbulent dynamical systems in which there is significant linear instability or linear nonnormal dynamics in the unperturbed system and energy-conserving nonlinear interactions that transfer energy from the unstable modes to the stable modes where dissipation occurs, resulting in a statistical steady state; such turbulent dynamical systems are ubiquitous in geophysical and engineering turbulence. The ROMQG method involves constructing a low-order, nonlinear, dynamical system for the mean and covariance statistics in the reduced subspace that has the unperturbed statistics as a stable fixed point and optimally incorporates the indirect effect of non-Gaussian third-order statistics for the unperturbed system in a systematic calibration stage. This calibration procedure is achieved through information involving only the mean and covariance statistics for the unperturbed equilibrium. The performance of the ROMQG algorithm is assessed on two stringent test cases: the 40-mode Lorenz 96 model mimicking midlatitude atmospheric turbulence and two-layer baroclinic models for high-latitude ocean turbulence with over 125,000 degrees of freedom. In the Lorenz 96 model, the ROMQG algorithm with just a single mode captures the transient response to random or deterministic forcing. For the baroclinic ocean turbulence models, the inexpensive ROMQG algorithm with 252 modes, less than 0.2% of the total, captures the nonlinear response of the energy, the heat flux, and even the one-dimensional energy and heat flux spectra. PMID:23918398

Sapsis, Themistoklis P; Majda, Andrew J

2013-08-20

124

Statistically accurate low-order models for uncertainty quantification in turbulent dynamical systems  

PubMed Central

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 turbulent dynamical systems in which there is significant linear instability or linear nonnormal dynamics in the unperturbed system and energy-conserving nonlinear interactions that transfer energy from the unstable modes to the stable modes where dissipation occurs, resulting in a statistical steady state; such turbulent dynamical systems are ubiquitous in geophysical and engineering turbulence. The ROMQG method involves constructing a low-order, nonlinear, dynamical system for the mean and covariance statistics in the reduced subspace that has the unperturbed statistics as a stable fixed point and optimally incorporates the indirect effect of non-Gaussian third-order statistics for the unperturbed system in a systematic calibration stage. This calibration procedure is achieved through information involving only the mean and covariance statistics for the unperturbed equilibrium. The performance of the ROMQG algorithm is assessed on two stringent test cases: the 40-mode Lorenz 96 model mimicking midlatitude atmospheric turbulence and two-layer baroclinic models for high-latitude ocean turbulence with over 125,000 degrees of freedom. In the Lorenz 96 model, the ROMQG algorithm with just a single mode captures the transient response to random or deterministic forcing. For the baroclinic ocean turbulence models, the inexpensive ROMQG algorithm with 252 modes, less than 0.2% of the total, captures the nonlinear response of the energy, the heat flux, and even the one-dimensional energy and heat flux spectra. PMID:23918398

Sapsis, Themistoklis P.; Majda, Andrew J.

2013-01-01

125

Pseudo-dynamic source modeling with 1-point and 2-point statistics of earthquake source parameters  

NASA Astrophysics Data System (ADS)

Dynamic rupture modeling considers physical processes during fault rupture, by incorporating conservation laws of continuum mechanics, the constitutive behavior of rocks on the fault plane, and the state of stress in the Earth crust. This approach has been successfully adopted for physics-based source and ground motion simulations in the last couple of decades. However, dynamic rupture calculations are still computationally expensive, especially for large events. Moreover, the required input parameters of stress and frictional properties are generally not well constrained. Therefore, pseudo-dynamic source modeling has been introduced (Guatteri et al, 2004), by combining strengths from both dynamic and kinematic modeling approaches i.e., keeping computational efficiency with kinematic source modeling, but trying to emulate the physics of the source process inferred from rupture dynamics and data observations. Song and Somerville (2010) propose a pseudo-dynamic source modeling method based on cross-correlation structures between kinematic source parameters, including both zero- and nonzero-offset correlations, which thus define a 2-point statistics of source parameters. In this study, we extend previous studies in the following ways: 1) The concept of 1-point statistics is included in both source characterization and modeling, 2) A new stochastic source modeling tool, based on the Cholesky factorization, is implemented, in addition to the previously proposed sequential Gaussian simulation with kriging method, 3) Ground motions are computed using both full- and pseudo-dynamic modeling methods, and then compared quantitatively. Our preliminary source and ground motion modeling results show that we can successfully capture the main characteristics of dynamic rupture models by applying 1-point and 2-point statistics, and hence also reproduce the main characteristics of ground motions generated by full dynamic rupture modeling.

Song, Seok Goo; Mai, Paul Martin; Dalguer, Luis Angel

2013-04-01

126

STATISTICAL METHODS FOR RECONSTRUCTION OF PARAMETRIC IMAGES FROM DYNAMIC PET DATA  

E-print Network

STATISTICAL METHODS FOR RECONSTRUCTION OF PARAMETRIC IMAGES FROM DYNAMIC PET DATA A Thesis equation OSEM ordered subset expectation maximization PA paper advance PCA principal component analysis PET least squares with Zhou regularization PSF point spread function PTAC plasma time activity curve RMSE

127

Coupled flow-polymer dynamics via statistical field theory: modeling and computation  

E-print Network

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

Bigelow, Stephen

128

Dynamic Graphics in Excel for Teaching Statistics: Understanding the Probability Density Function  

ERIC Educational Resources Information Center

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.

Coll-Serrano, Vicente; Blasco-Blasco, Olga; Alvarez-Jareno, Jose A.

2011-01-01

129

Collisional cross sections and momentum distributions in astrophysical plasmas: Dynamics and statistical mechanics link  

SciTech Connect

We show that in stellar core plasmas, the one-body momentum distribution function is strongly dependent, at least in the high velocity regime, on the microscopic dynamics of ion elastic collisions and therefore on the effective collisional cross sections if a random force field is present. We take into account two cross sections describing ion-dipole and ion-ion screened interactions. Furthermore, we introduce a third unusual cross section to link statistical distributions and a quantum effect originated by the energy-momentum uncertainty owing to many-body collisions. We also propose a possible physical interpretation in terms of a tidal-like force. We show that each collisional cross section gives rise to a slight peculiar correction on the Maxwellian momentum distribution function in a well defined velocity interval. We also find a possible link between microscopic dynamics of ions and statistical mechanics in interpreting our results in the framework of nonextensive statistical mechanics.

Ferro, F. [Dipartimento di Fisica, Politecnico di Torino, I-10129 Torino (Italy); INFN-Sezione di Torino, I-10125 Torino (Italy); Quarati, P. [Dipartimento di Fisica, Politecnico di Torino, I-10129 Torino (Italy); INFN-Sezione di Cagliari, I-09042 Monserrato (Italy)

2005-02-01

130

OneGeology Web Services and Portal as a global geological SDI - latest standards and technology  

NASA Astrophysics Data System (ADS)

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.

Duffy, Tim; Tellez-Arenas, Agnes

2014-05-01

131

The sexually dimorphic on the Y-chromosome gene (sdY) is a conserved male-specific Y-chromosome sequence in many salmonids  

PubMed Central

All salmonid species investigated to date have been characterized with a male heterogametic sex-determination system. However, as these species do not share any Y-chromosome conserved synteny, there remains a debate on whether they share a common master sex-determining gene. In this study, we investigated the extent of conservation and evolution of the rainbow trout (Oncorhynchus mykiss) master sex-determining gene, sdY (sexually dimorphic on the Y-chromosome), in 15 different species of salmonids. We found that the sdY sequence is highly conserved in all salmonids and that sdY is a male-specific Y-chromosome gene in the majority of these species. These findings demonstrate that most salmonids share a conserved sex-determining locus and also strongly suggest that sdY may be this conserved master sex-determining gene. However, in two whitefish species (subfamily Coregoninae), sdY was found both in males and females, suggesting that alternative sex-determination systems may have also evolved in this family. Based on the wide conservation of sdY as a male-specific Y-chromosome gene, efficient and easy molecular sexing techniques can now be developed that will be of great interest for studying these economically and environmentally important species. PMID:23745140

Yano, Ayaka; Nicol, Barbara; Jouanno, Elodie; Quillet, Edwige; Fostier, Alexis; Guyomard, René; Guiguen, Yann

2013-01-01

132

research papers 458 Hu et al. Statistical dynamical direct methods. I Acta Cryst. (2000). A56, 458469  

E-print Network

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

Marks, Laurence D.

133

On Monte Carlo and molecular dynamics methods inspired by Tsallis statistics: Methodology, optimization, and application to atomic clusters  

E-print Network

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

Straub, John E.

134

Unimolecular fragmentation induced by low-energy collision: statistically or dynamically driven?  

PubMed

By combining chemical dynamics simulations and RRKM statistical theory we have characterized collision induced dissociation (CID) mechanisms of [M(formamide)](2+) ions (M = Ca, Sr) at different timescales, from few femtoseconds to microseconds. Chemical dynamics simulations account for the short-time and dynamically driven reactivity, such as impulsive collision mechanism for formamide neutral loss. From the simulations, we also got the amounts of energy transferred during the collision and, especially important, the vibrational and rotational energy distributions of the ions that did not react during the simulation time length of 2.5 ps. These internal energy distributions were in turn used in combination with RRKM theory to estimate the rate constants of the possible reactive pathways. Hence, we performed a statistical analysis of the CID dynamics accounting for the long-time and statistical reactivity (i.e., through an IVR mechanism). This multiscale approach allowed us to account for all the products observed in the CID experimental spectra of [Ca(formamide)](2+) and [Sr(formamide)](2+) doubly charged cations, as well as the differences between them. PMID:25333680

Martín-Sómer, Ana; Yáñez, Manuel; Gaigeot, Marie-Pierre; Spezia, Riccardo

2014-11-20

135

Development of a current collection loss management system for SDI homopolar power supplies  

SciTech Connect

High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operated continuously at 2 kA/cm{sup 2}, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To data, no system has achieved these conditions simultaneously. This is the annual report covering the first year period of performance on DOE contract DE-AC03-86SF16518. Major areas covered include design and construction of a cryogenically-cooled brush test rig, design of a high speed brush test rig, loss analysis of the current collection system, and an application study which defines the air core homopolar construction necessary to achieve the goal of 80--90 kW/kg generator power density. 15 figs.

Hannan, W.F. III.

1987-01-01

136

Development of a current collection loss management system for SDI homopolar power supplies  

NASA Astrophysics Data System (ADS)

High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operate continuously at 2 kA/sq cm, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To date, no system has achieved these conditions simultaneously. This is the final report covering the three year period of performance on DOE contract AC03-86SF-16518. Major areas covered include design, construction and operation of a cryogenically cooled brush test rig, design and construction of a high speed brush test rig, optimization study for homopolar machines, loss analysis of the current collection system, and an application study which defines the air-core homopolar construction necessary to achieve the goal of 80 kW/kg generator power density.

Brown, D. W.

1991-04-01

137

Development of a current collection loss management system for SDI homopolar power supplies  

SciTech Connect

High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operate continuously at 2 kA/cm{sup 2}, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To data, no system has achieved these conditions simultaneously. This is the annual report covering the second year period of performance on DOE contract DE-AC03-86SF16518. Major areas covered include design, construction and operation of a cryogenically cooled brush test rig, design and construction of a high speed brush test rig, optimization study for homopolar machines, loss analysis of the current collection system, and an application study which defines the air-core homopolar construction necessary to achieve the goal of 80--90 kW/kg generator power density. 17 figs., 2 tabs.

Brown, D.W.

1989-01-01

138

A review of gas-cooled reactor concepts for SDI (Strategic Defense Initiative) applications  

SciTech Connect

We have completed a review of multimegawatt gas-cooled reactor concepts proposed for SDI applications. Our study concluded that the principal reason for considering gas-cooled reactors for burst-mode operation was the potential for significant system mass savings over closed-cycle systems if open-cycle gas-cooled operation (effluent exhausted to space) is acceptable. The principal reason for considering gas-cooled reactors for steady-state operation is that they may represent a lower technology risk than other approaches. In the review, nine gas-cooled reactor concepts were compared to identify the most promising. For burst-mode operation, the NERVA (Nuclear Engine for Rocket Vehicle Application) derivative reactor concept emerged as a strong first choice since its performance exceeds the anticipated operational requirements and the technology has been demonstrated and is retrievable. Although the NERVA derivative concepts were determined to be the lead candidates for the Multimegawatt Steady-State (MMWSS) mode as well, their lead over the other candidates is not as great as for the burst mode. 90 refs., 2 figs., 10 tabs.

Marshall, A.C.

1989-08-01

139

Modified statistical dynamical diffraction theory: analysis of model SiGe heterostructures  

PubMed Central

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

Shreeman, P. K.; Dunn, K. A.; Novak, S. W.; Matyi, R. J.

2013-01-01

140

Statistics and Statistical Mechanics  

Microsoft Academic Search

This chapter is somewhat more technical than the earlier ones. Its aim is to discuss some more recent results in dynamical\\u000a systems which refine our knowledge of statistical properties. These results follow from a combination of methods from statistics\\u000a and statistical mechanics.

Pierre Collet; Jean-Pierre Eckmann

141

Attractors, statistics and fluctuations of the dynamics of the Schelling's model for social segregation  

NASA Astrophysics Data System (ADS)

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.

Cortez, Vasco; Medina, Pablo; Goles, Eric; Zarama, Roberto; Rica, Sergio

2015-01-01

142

Wave climate projections along the French coastline: Dynamical versus statistical downscaling methods  

NASA Astrophysics Data System (ADS)

The estimation of possible impacts related to climate change on the wave climate is subject to several levels of uncertainty. In this work, we focus on the uncertainties inherent in the method applied to project the wave climate using atmospheric simulations. Two approaches are commonly used to obtain the regional wave climate: dynamical and statistical downscaling from atmospheric data. We apply both approaches based on the outputs of a global climate model (GCM), ARPEGE-CLIMAT, under three possible future scenarios (B1, A1B and A2) of the Fourth Assessment Report, AR4 (IPCC, 2007), along the French coast and evaluate their results for the wave climate with a high level of precision. The performance of the dynamical and the statistical methods is determined through a comparative analysis of the estimated means, standard deviations and monthly quantile distributions of significant wave heights, the joint probability distributions of wave parameters and seasonal and interannual variability. Analysis of the results shows that the statistical projections are able to reproduce the wave climatology as well as the dynamical projections, with some deficiencies being observed in the summer and for the upper tail of the significant wave height. In addition, with its low computational time requirements, the statistical downscaling method allows an ensemble of simulations to be calculated faster than the dynamical method. It then becomes possible to quantify the uncertainties associated with the choice of the GCM or the socio-economic scenarios, which will improve estimates of the impact of wave climate change along the French coast.

Laugel, Amélie; Menendez, Melisa; Benoit, Michel; Mattarolo, Giovanni; Méndez, Fernando

2014-12-01

143

Understanding the Multi-Scale and Multi-fractal Dynamics of Space Plasmas Through Tsallis Non-Extensive Statistical Theory  

E-print Network

In this study it is shown that the Tsallis q-extended statistical theory was found efficient to describe faithfully the space plasmas statistics in every case, from the planetic magnetospheres, to solar corona and solar dynamics, as well as cosmic rays and cosmic stars. Moreover, new theoretical concepts and experimental results are presented concerning the space plasma complex dynamics. The significant message of theoretical and experimental issues presented here is the necessity of generalized statistical and dynamical theory for understanding the non-equilibrium dynamics and the complex character of space plasmas. The q-extension of statistics coupled to the fractal extension of dynamics are the novel and appropriate theoretical framework for the description of space plasma complexity.

G. P. Pavlos

2012-03-18

144

The SdiA-regulated gene srgE encodes a type III secreted effector.  

PubMed

Salmonella enterica serovar Typhimurium is a food-borne pathogen that causes severe gastroenteritis. The ability of Salmonella to cause disease depends on two type III secretion systems (T3SSs) encoded in two distinct Salmonella pathogenicity islands, 1 and 2 (SPI1 and SPI2, respectively). S. Typhimurium encodes a solo LuxR homolog, SdiA, which can detect the acyl-homoserine lactones (AHLs) produced by other bacteria and upregulate the rck operon and the srgE gene. SrgE is predicted to encode a protein of 488 residues with a coiled-coil domain between residues 345 and 382. In silico studies have provided conflicting predictions as to whether SrgE is a T3SS substrate. Therefore, in this work, we tested the hypothesis that SrgE is a T3SS effector by two methods, a ?-lactamase activity assay and a split green fluorescent protein (GFP) complementation assay. SrgE with ?-lactamase fused to residue 40, 100, 150, or 300 was indeed expressed and translocated into host cells, but SrgE with ?-lactamase fused to residue 400 or 488 was not expressed, suggesting interference by the coiled-coil domain. Similarly, SrgE with GFP S11 fused to residue 300, but not to residue 488, was expressed and translocated into host cells. With both systems, translocation into host cells was dependent upon SPI2. A phylogenetic analysis indicated that srgE is found only within Salmonella enterica subspecies. It is found sporadically within both typhoidal and nontyphoidal serovars, although the SrgE protein sequences found within typhoidal serovars tend to cluster separately from those found in nontyphoidal serovars, suggesting functional diversification. PMID:24727228

Habyarimana, Fabien; Sabag-Daigle, Anice; Ahmer, Brian M M

2014-06-01

145

Argonne CW Linac (ACWL)—legacy from SDI and opportunities for the future  

NASA Astrophysics Data System (ADS)

The former Strategic Defense Initiative Organization (SDIO) invested significant resources over a 6-year period to develop and build an accelerator to demonstrate the launching of a cw beam with characteristics suitable for a space-based Neutral Particle Beam (NPB) system. This accelerator, the CWDD (Continuous Wave Deuterium Demonstrator) accelerator, was designed to accelerate 80 mA cw of D- to 7.5 MeV. A considerable amount of hardware was constructed and installed in the Argonne-based facility, and major performance milestones were achieved before program funding from the Department of Defense ended in October 1993. Existing assets have been turned over to Argonne. Assets include a fully functional 200 kV cw D- injector, a cw RFQ that has been tuned, leak checked and aligned, beam lines and a high-power beam stop, all installed in a shielded vault with appropriate safety and interlock systems. In addition, there are two high power (1 MW) cw rf amplifiers and all the ancillary power, cooling and control systems required for a high-power accelerator system. The SDI mission required that the CWDD accelerator structures operate at cryogenic temperatures (26K), a requirement that placed severe limitations on operating period (CWDD would have provided 20 seconds of cw beam every 90 minutes). However, the accelerator structures were designed for full-power rf operation with water cooling and ACWL (Argonne Continuous Wave Linac), the new name for CWDD in its water-cooled, positive-ion configuration, will be able to operate continuously. Project status and achievements will be reviewed. Preliminary design of a proton conversion for the RFQ, and other proposals for turning ACWL into a testbed for cw-linac engineering, will be discussed.

McMichael, G. E.; Yule, T. J.

1995-09-01

146

Quench dynamics and statistics of measurements for a line of quantum spins in two dimensions  

NASA Astrophysics Data System (ADS)

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 the x and y directions 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 us 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.

Lux, Jonathan; Rosch, Achim

2015-02-01

147

Alternative to the Well-known Statistical Dynamics of Linear Systems  

E-print Network

The problem of determining the mathematical model of the dynamics of multi-dimensional control systems in the presence of noise under the condition that the correlation functions cannot be found. Known statistical dynamics of linear systems is a more effective alternative. Background information is presented in the form of individual implementations nonergodic stochastic processes. Such a realization is deterministic functions. We introduce the concept of systems of sets of signals for the components on the semiring. For the system of sets of linearly dependent and linearly independent of the measured signals of a certain frequency properties. Frequency method is designed to deal with the noise on the set of deterministic functions. Example is the determination of the dynamic characteristics of the aircraft in accordance with the data obtained in one automatic landing.

V. N. Tibabishev

2013-01-22

148

Dynamically and statistically downscaled seasonal simulations of maximum surface air temperature over the southeastern United States  

NASA Astrophysics Data System (ADS)

Coarsely resolved surface air temperature (2 m height) seasonal integrations from the Florida State University/Center for Ocean-Atmospheric Prediction Studies Global Spectral Model (FSU/COAPS GSM) (~1.8° lon.-lat. (T63)) for the period of 1994 to 2002 (March through September each year) are downscaled to a fine spatial scale of ~20 km. Dynamical and statistical downscaling methods are applied for the southeastern United States region, covering Florida, Georgia, and Alabama. Dynamical downscaling is conducted by running the FSU/COAPS Nested Regional Spectral Model (NRSM), which is nested into the domain of the FSU/COAPS GSM. We additionally present a new statistical downscaling method. The rationale for the statistical approach is that clearer separation of prominent climate signals (e.g., seasonal cycle, intraseasonal, or interannual oscillations) in observation and GSM, respectively, over the training period can facilitate the identification of the statistical relationship in climate variability between two data sets. Cyclostationary Empirical Orthogonal Function (CSEOF) analysis and multiple regressions are trained with those data sets to extract their statistical relationship, which eventually leads to better prediction of regional climate from the large-scale simulations. Downscaled temperatures are compared with the FSU/COAPS GSM fields and observations. Downscaled seasonal anomalies exhibit strong agreement with observations and a reduction in bias relative to the direct GSM simulations. Interannual temperature change is also reasonably simulated at local grid points. A series of evaluations including mean absolute errors, anomaly correlations, frequency of extreme events, and categorical predictability reveal that both downscaling techniques can be reliably used for numerous seasonal climate applications.

Lim, Young-Kwon; Shin, D. W.; Cocke, Steven; LaRow, T. E.; Schoof, Justin T.; O'Brien, James J.; Chassignet, Eric P.

2007-12-01

149

High-resolution climate simulations for Central Europe: An assessment of dynamical and statistical downscaling techniques  

NASA Astrophysics Data System (ADS)

To bridge the resolution gap between the outputs of global climate models (GCMs) and finer-scale data needed for studies of the climate change impacts, two approaches are widely used: dynamical downscaling, based on application of regional climate models (RCMs) embedded into the domain of the GCM simulation, and statistical downscaling (SDS), using empirical transfer functions between the large-scale data generated by the GCM and local measurements. In our contribution, we compare the performance of different variants of both techniques for the region of Central Europe. The dynamical downscaling is represented by the outputs of two regional models run in the 10 km horizontal grid, ALADIN-CLIMATE/CZ (co-developed by the Czech Hydrometeorological Institute and Meteo-France) and RegCM3 (developed by the Abdus Salam Centre for Theoretical Physics). The applied statistical methods were based on multiple linear regression, as well as on several of its nonlinear alternatives, including techniques employing artificial neural networks. Validation of the downscaling outputs was carried out using measured data, gathered from weather stations in the Czech Republic, Slovakia, Austria and Hungary for the end of the 20th century; series of daily values of maximum and minimum temperature, precipitation and relative humidity were analyzed. None of the regional models or statistical downscaling techniques could be identified as the universally best one. For instance, while most statistical methods misrepresented the shape of the statistical distribution of the target variables (especially in the more challenging cases such as estimation of daily precipitation), RCM-generated data often suffered from severe biases. It is also shown that further enhancement of the simulated fields of climate variables can be achieved through a combination of dynamical downscaling and statistical postprocessing. This can not only be used to reduce biases and other systematic flaws in the generated time series, but also to further localize the RCM outputs beyond the resolution of their original grid. The resulting data then provide a suitable input for subsequent studies of the local climate and its change in the target region.

Miksovsky, J.; Huth, R.; Halenka, T.; Belda, M.; Farda, A.; Skalak, P.; Stepanek, P.

2009-12-01

150

Heterogeneous Structure of Stem Cells Dynamics: Statistical Models and Quantitative Predictions  

NASA Astrophysics Data System (ADS)

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.

Bogdan, Paul; Deasy, Bridget M.; Gharaibeh, Burhan; Roehrs, Timo; Marculescu, Radu

2014-04-01

151

Statistics of voltage drop in distribution circuits: a dynamic programming approach  

SciTech Connect

We analyze a power distribution line with high penetration of distributed generation and strong variations of power consumption and generation levels. In the presence of uncertainty the statistical description of the system is required to assess the risks of power outages. In order to find the probability of exceeding the constraints for voltage levels we introduce the probability distribution of maximal voltage drop and propose an algorithm for finding this distribution. The algorithm is based on the assumption of random but statistically independent distribution of loads on buses. Linear complexity in the number of buses is achieved through the dynamic programming technique. We illustrate the performance of the algorithm by analyzing a simple 4-bus system with high variations of load levels.

Turitsyn, Konstantin S [Los Alamos National Laboratory

2010-01-01

152

Non-Markovian Dynamics Impact on the Foundations of Statistical Mechanics  

E-print Network

The foundations of statistical mechanics, namely how equilibrium hypothesis emerges microscopically from quantum theory, is explored through investigating the environment-induced quantum decoherence processes. Based on the recent results on non-Markovian dynamics [Phys. Rev. Lett. 109, 170402 (2012)], we find that decoherence of quantum states manifests unexpected complexities. Indeed, an arbitrary given initial quantum state, under the influence of different reservoirs, can evolve into four different steady states: thermal, thermal-like, quantum memory and oscillating quantum memory states. The first two steady states \\textit{de facto} provided a rigorous proof how the system relaxes to thermal equilibrium with its environment. The latter two steady states, with strong non-Markovian effects, will maintain the initial state information and not reach thermal equilibrium, which is beyond the conventional wisdom of statistical mechanics.

Heng-Na Xiong; Ping-Yuan Lo; Wei-Min Zhang; Franco Nori; Da Hsuan Feng

2013-11-06

153

Statistical modelling of subdiffusive dynamics in the cytoplasm of living cells: A FARIMA approach  

NASA Astrophysics Data System (ADS)

Golding and Cox (Phys. Rev. Lett., 96 (2006) 098102) tracked the motion of individual fluorescently labelled mRNA molecules inside live E. coli cells. They found that in the set of 23 trajectories from 3 different experiments, the automatically recognized motion is subdiffusive and published an intriguing microscopy video. Here, we extract the corresponding time series from this video by image segmentation method and present its detailed statistical analysis. We find that this trajectory was not included in the data set already studied and has different statistical properties. It is best fitted by a fractional autoregressive integrated moving average (FARIMA) process with the normal-inverse Gaussian (NIG) noise and the negative memory. In contrast to earlier studies, this shows that the fractional Brownian motion is not the best model for the dynamics documented in this video.

Burnecki, K.; Muszkieta, M.; Sikora, G.; Weron, A.

2012-04-01

154

A statistical-dynamical model of the storm-wind climate of northwestern Europe  

NASA Astrophysics Data System (ADS)

While earthquakes and tropical hurricanes often receive considerably more media attention, mid-latitude winter storms are the cause of a considerable amount of damage. Indeed, some of the costliest events in modern history (in terms of insured losses) have resulted from strong winds associated with winter storms over northwestern Europe. A "storm-wind climate" model for northwestern Europe has been developed as an integration of the NCAR-NCEP Global Reanalysis Project data set and the 5th generation NCAR - Penn State University mesoscale model (MM5). In its statistical-dynamical (or Monte Carlo based ensemble) implementation, this model produces realistic return-period wind profiles when compared with those expected from extreme event statistics. In this presentation the model-system's design and performance will be discussed, including its use with an impact (loss) model.

Keller, J. L.; Dailey, P. S.; Fischer, M. D.

2003-04-01

155

Cluster Statistics and Quasisoliton Dynamics in Microscopic Car-following Models  

E-print Network

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.

Bo Yang; Xihua Xu; John Z. F. Pang; Christopher Monterola

2014-08-20

156

Dynamic whole body PET parametric imaging: II. Task-oriented statistical estimation  

PubMed Central

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

Karakatsanis, Nicolas A.; Lodge, Martin A.; Zhou, Y.; Wahl, Richard L.; Rahmim, Arman

2013-01-01

157

Loss of p21{sup Sdi1} expression in senescent cells after DNA damage accompanied with increase of miR-93 expression and reduced p53 interaction with p21{sup Sdi1} gene promoter  

SciTech Connect

Highlights: {yields} Reduced p21 expression in senescent cells treated with DNA damaging agents. {yields} Increase of [{sup 3}H]thymidine and BrdU incorporations in DNA damaged-senescent cells. {yields} Upregulation of miR-93 expression in senescent cells in response to DSB. {yields} Failure of p53 binding to p21 promoter in senescent cells in response to DSB. {yields} Molecular mechanism of increased cancer development in aged than young individuals. -- Abstract: To answer what is a critical event for higher incidence of tumor development in old than young individuals, primary culture of human diploid fibroblasts were employed and DNA damage was induced by doxorubicin or X-ray irradiation. Response to the damage was different between young and old cells; loss of p21{sup sdi1} expression in spite of p53{sup S15} activation in old cells along with [{sup 3}H]thymidine and BrdU incorporation, but not in young cells. The phenomenon was confirmed by other tissue fibroblasts obtained from different donor ages. Induction of miR-93 expression and reduced p53 binding to p21 gene promoter account for loss of p21{sup sdi1} expression in senescent cells after DNA damage, suggesting a mechanism of in vivo carcinogenesis in aged tissue without repair arrest.

Choi, Ok Ran [Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 443-721 (Korea, Republic of)] [Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 443-721 (Korea, Republic of); Lim, In Kyoung, E-mail: iklim@ajou.ac.kr [Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 443-721 (Korea, Republic of)

2011-04-08

158

q-deformed statistical-mechanical structure in the dynamics of the Feigenbaum attractor  

E-print Network

We show that the two complementary parts of the dynamics associated to the Feigenbaum attractor, inside and towards the attractor, form together a q -deformed statistical-mechanical structure. A time-dependent partition function produced by summing distances between neighboring positions of the attractor leads to a q-entropy that measures the fraction of ensemble trajectories still away at a given time from the attractor (and the repellor). The values of the q-indexes are given by the attractor's universal constants, while the thermodynamic framework is closely related to that first developed for multifractals.

A. Robledo

2007-10-04

159

Dynamics and statistics of wave-particle interactions in a confined geometry.  

PubMed

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. PMID:25493868

Gilet, Tristan

2014-11-01

160

Statistical study of flux ropes observed by the Solar Dynamics Observatory  

NASA Astrophysics Data System (ADS)

With the observations from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory, we statistically investigate the flux ropes from January 2013 to December 2013. 1417 ropes were detected during this period. 725 of the 1417 ropes were tracked by the eruptions or activities of filaments and surges, and the others were detected by emerging from the photosphere or brightening in the corona. 531 ropes, which occupied 38% of the total ropes, were detected in the northern hemisphere, implying a significant imbalance distribution of the ropes over the whole Sun.

Zhang, Jun; Yang, Shuhong; Li, Ting

161

Dynamics and statistics of wave-particle interactions in a confined geometry  

NASA Astrophysics Data System (ADS)

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.

Gilet, Tristan

2014-11-01

162

Statistical complexity measures as telltale of relevant scales in emergent dynamics of spatial systems  

NASA Astrophysics Data System (ADS)

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.

Arbona, A.; Bona, C.; Miñano, B.; Plastino, A.

2014-09-01

163

Dynamic thermo-mechanical coupled response of random particulate composites: A statistical two-scale method  

NASA Astrophysics Data System (ADS)

This paper focuses on the dynamic thermo-mechanical coupled response of random particulate composite materials. Both the inertia term and coupling term are considered in the dynamic coupled problem. The formulation of the problem by a statistical second-order two-scale (SSOTS) analysis method and the algorithm procedure based on the finite-element difference method are presented. Numerical results of coupled cases are compared with those of uncoupled cases. It shows that the coupling effects on temperature, thermal flux, displacement, and stresses are very distinct, and the micro-characteristics of particles affect the coupling effect of the random composites. Furthermore, the coupling effect causes a lag in the variations of temperature, thermal flux, displacement, and stresses.

Yang, Zi-Hao; Chen, Yun; Yang, Zhi-Qiang; Ma, Qiang

2014-07-01

164

Statistics of reversible bond dynamics observed in force-clamp spectroscopy  

E-print Network

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.

Gregor Diezemann; Thomas Schlesier; Burkhard Geil; Andreas Janshoff

2010-10-30

165

Probabilistic estimates of future changes in California temperature and precipitation using statistical and dynamical downscaling  

NASA Astrophysics Data System (ADS)

Sixteen global general circulation models were used to develop probabilistic projections of temperature (T) and precipitation (P) changes over California by the 2060s. The global models were downscaled with two statistical techniques and three nested dynamical regional climate models, although not all global models were downscaled with all techniques. Both monthly and daily timescale changes in T and P are addressed, the latter being important for a range of applications in energy use, water management, and agriculture. The T changes tend to agree more across downscaling techniques than the P changes. Year-to-year natural internal climate variability is roughly of similar magnitude to the projected T changes. In the monthly average, July temperatures shift enough that that the hottest July found in any simulation over the historical period becomes a modestly cool July in the future period. Januarys as cold as any found in the historical period are still found in the 2060s, but the median and maximum monthly average temperatures increase notably. Annual and seasonal P changes are small compared to interannual or intermodel variability. However, the annual change is composed of seasonally varying changes that are themselves much larger, but tend to cancel in the annual mean. Winters show modestly wetter conditions in the North of the state, while spring and autumn show less precipitation. The dynamical downscaling techniques project increasing precipitation in the Southeastern part of the state, which is influenced by the North American monsoon, a feature that is not captured by the statistical downscaling.

Pierce, David W.; Das, Tapash; Cayan, Daniel R.; Maurer, Edwin P.; Miller, Norman L.; Bao, Yan; Kanamitsu, M.; Yoshimura, Kei; Snyder, Mark A.; Sloan, Lisa C.; Franco, Guido; Tyree, Mary

2013-02-01

166

Statistical analysis of nonlinear dynamical systems using differential geometric sampling methods  

PubMed Central

Mechanistic models based on systems of nonlinear differential equations can help provide a quantitative understanding of complex physical or biological phenomena. The use of such models to describe nonlinear interactions in molecular biology has a long history; however, it is only recently that advances in computing have allowed these models to be set within a statistical framework, further increasing their usefulness and binding modelling and experimental approaches more tightly together. A probabilistic approach to modelling allows us to quantify uncertainty in both the model parameters and the model predictions, as well as in the model hypotheses themselves. In this paper, the Bayesian approach to statistical inference is adopted and we examine the significant challenges that arise when performing inference over nonlinear ordinary differential equation models describing cell signalling pathways and enzymatic circadian control; in particular, we address the difficulties arising owing to strong nonlinear correlation structures, high dimensionality and non-identifiability of parameters. We demonstrate how recently introduced differential geometric Markov chain Monte Carlo methodology alleviates many of these issues by making proposals based on local sensitivity information, which ultimately allows us to perform effective statistical analysis. Along the way, we highlight the deep link between the sensitivity analysis of such dynamic system models and the underlying Riemannian geometry of the induced posterior probability distributions. PMID:23226584

Calderhead, Ben; Girolami, Mark

2011-01-01

167

Statistical intercomparison of idealized rainfall measurements using a stochastic fractional dynamics model  

NASA Astrophysics Data System (ADS)

A statistical method is developed for comparing precipitation data from measurements performed by (hypothetical) perfect instruments using a recently developed stochastic model of rainfall. The stochastic dynamical equation that describes the underlying random process naturally leads to a consistent spectrum and incorporates the subtle interdependence of the length and time scales governing the statistical fluctuations of the rain rate field. The main attraction of such a model is that the complete set of second-moment statistics embodied in the space-time covariance of both the area-averaged instantaneous rain rate (represented by radar or passive microwave data near the ground) and the time-averaged point rain rate (represented by rain gauge data) can be expressed as suitable integrals over the spectrum. With the help of this framework, the model allows one to carry out a faithful intercomparison of precipitation estimates derived from radar or passive microwave remote sensing over an area with direct observations by rain gauges or disdrometers, assuming all the measuring instruments to be ideal. A standard linear regression analysis approach to the intercomparison of radar and gauge rain rate estimates is formulated in terms of the appropriate observed and model-derived quantities. We also estimate the relative sampling error as well as separate absolute sampling errors for radar and gauge measurements of rainfall from the spectral model.

Kundu, Prasun K.; Marks, David A.; Travis, James E.

2014-09-01

168

A Statistical Approach for the Concurrent Coupling of Molecular Dynamics and Finite Element Methods  

NASA Technical Reports Server (NTRS)

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.

Saether, E.; Yamakov, V.; Glaessgen, E.

2007-01-01

169

Statistical downscaling based on dynamically downscaled predictors: Application to monthly precipitation in Sweden  

NASA Astrophysics Data System (ADS)

A prerequisite of a successful statistical downscaling is that large-scale predictors simulated by the General Circulation Model (GCM) must be realistic. It is assumed here that features smaller than the GCM resolution are important in determining the realism of the large-scale predictors. It is tested whether a three-step method can improve conventional one-step statistical downscaling. The method uses predictors that are upscaled from a dynamical downscaling instead of predictors taken directly from a GCM simulation. The method is applied to downscaling of monthly precipitation in Sweden. The statistical model used is a multiple regression model that uses indices of large-scale atmospheric circulation and 850-hPa specific humidity as predictors. Data from two GCMs (HadCM2 and ECHAM4) and two RCM experiments of the Rossby Centre model (RCA1) driven by the GCMs are used. It is found that upscaled RCA1 predictors capture the seasonal cycle better than those from the GCMs, and hence increase the reliability of the downscaled precipitation. However, there are only slight improvements in the simulation of the seasonal cycle of downscaled precipitation. Due to the cost of the method and the limited improvements in the downscaling results, the three-step method is not justified to replace the one-step method for downscaling of Swedish precipitation.

Hellström, Cecilia; Chen, Deliang

2003-11-01

170

Dynamical study of metallic clusters using the statistical method of time series clustering  

NASA Astrophysics Data System (ADS)

We perform common neighbor analysis on the long-time series data generated by isothermal Brownian-type molecular dynamics simulations to study the thermal and dynamical properties of metallic clusters. In our common neighbor analysis, we introduce the common neighbor label (CNL) which is a group of atoms of a smaller size (than the cluster) designated by four numeric digits. The CNL thus describes topologically smaller size atomic configurations and is associated an abundance value which is the number of "degenerate" four digits all of which characterize the same CNL. When the cluster is in its lowest energy state, it has a fixed number of CNLs and hence abundances. At nonzero temperatures, the cluster undergoes different kinds of atomic activities such as vibrations, migrational relocation, permutational and topological isomer transitions, etc. depending on its lowest energy structure. As a result, the abundances of CNLs at zero temperature will change and new CNLs with their respective new abundances are created. To understand the temperature dependence of the CNL dynamics, and hence shed light on the cluster dynamics itself, we employ a novel method of statistical time series analysis. In this method, we perform statistical clustering at two time scales. First, we examine, at given temperature, the signs of abundance changes at a short-time scale, and assign CNLs to two short-time clusters. Quasi-periodic features can be seen in the time evolution of these short-time clusters, based on which we choose a long-time scale to compute the long-time correlations between CNL pairs. We then exploit the separation of correlation levels seen in these long-time correlations to extract strongly-correlated collections of CNLs, which we will identify as effective variables for the long-time cluster dynamics. It is found that certain effective variables show subtleties in their temperature dependences and these thermal traits bear a delicate relation to prepeaks and main peaks seen in clusters Ag 14, Cu 14 and Cu 13Au 1. We therefore infer from the temperature changes of effective variables and locate the temperatures at which these prepeaks and principal peaks appear, and they are evaluated by comparing with those deduced from the specific heat data.

Lai, S. K.; Lin, Yu-Ting; Hsu, P. J.; Cheong, S. A.

2011-04-01

171

A comparison of dynamical and statistical downscaling methods for regional wave climate projections along French coastlines.  

NASA Astrophysics Data System (ADS)

Wave climate forecasting is a major issue for numerous marine and coastal related activities, such as offshore industries, flooding risks assessment and wave energy resource evaluation, among others. Generally, there are two main ways to predict the impacts of the climate change on the wave climate at regional scale: the dynamical and the statistical downscaling of GCM (Global Climate Model). In this study, both methods have been applied on the French coast (Atlantic , English Channel and North Sea shoreline) under three climate change scenarios (A1B, A2, B1) simulated with the GCM ARPEGE-CLIMAT, from Météo-France (AR4, IPCC). The aim of the work is to characterise the wave climatology of the 21st century and compare the statistical and dynamical methods pointing out advantages and disadvantages of each approach. The statistical downscaling method proposed by the Environmental Hydraulics Institute of Cantabria (Spain) has been applied (Menendez et al., 2011). At a particular location, the sea-state climate (Predictand Y) is defined as a function, Y=f(X), of several atmospheric circulation patterns (Predictor X). Assuming these climate associations between predictor and predictand are stationary, the statistical approach has been used to project the future wave conditions with reference to the GCM. The statistical relations between predictor and predictand have been established over 31 years, from 1979 to 2009. The predictor is built as the 3-days-averaged squared sea level pressure gradient from the hourly CFSR database (Climate Forecast System Reanalysis, http://cfs.ncep.noaa.gov/cfsr/). The predictand has been extracted from the 31-years hindcast sea-state database ANEMOC-2 performed with the 3G spectral wave model TOMAWAC (Benoit et al., 1996), developed at EDF R&D LNHE and Saint-Venant Laboratory for Hydraulics and forced by the CFSR 10m wind field. Significant wave height, peak period and mean wave direction have been extracted with an hourly-resolution at 110 coastal locations along the French coast. The model, based on the BAJ parameterization of the source terms (Bidlot et al, 2007) was calibrated against ten years of GlobWave altimeter observations (2000-2009) and validated through deep and shallow water buoy observations. The dynamical downscaling method has been performed with the same numerical wave model TOMAWAC used for building ANEMOC-2. Forecast simulations are forced by the 10m wind fields of ARPEGE-CLIMAT (A1B, A2, B1) from 2010 to 2100. The model covers the Atlantic Ocean and uses a spatial resolution along the French and European coast of 10 and 20 km respectively. The results of the model are stored with a time resolution of one hour. References: Benoit M., Marcos F., and F. Becq, (1996). Development of a third generation shallow-water wave model with unstructured spatial meshing. Proc. 25th Int. Conf. on Coastal Eng., (ICCE'1996), Orlando (Florida, USA), pp 465-478. Bidlot J-R, Janssen P. and Adballa S., (2007). A revised formulation of ocean wave dissipation and its model impact, technical memorandum ECMWF n°509. Menendez, M., Mendez, F.J., Izaguirre,C., Camus, P., Espejo, A., Canovas, V., Minguez, R., Losada, I.J., Medina, R. (2011). Statistical Downscaling of Multivariate Wave Climate Using a Weather Type Approach, 12th International Workshop on Wave Hindcasting and Forecasting and 3rd Coastal Hazard Symposium, Kona (Hawaii).

Laugel, Amélie; Menendez, Melisa; Benoit, Michel; Mattarolo, Giovanni; Mendez, Fernando

2013-04-01

172

SELECTIVE DISSEMINATION OF INFORMATION (SDI). VOLUME I, PILOT TEST AT U.S. ARMY NATICK LABORATORIES. FINAL REPORT. ARMY TECHNICAL LIBRARY IMPROVEMENT STUDIES (ATLIS), REPORT NO. 15.  

ERIC Educational Resources Information Center

THIS VOLUME PRESENTS THE RESULTS OF A NINE-MONTH TEST OF A PROTOTYPE SELECTIVE DISSEMINATION OF INFORMATION (SDI) SYSTEM DEVELOPED FOR THE ARMY TECHNICAL LIBRARIES. DURING THE PILOT TEST ONE THOUSAND DOCUMENTS WERE CATALOGED, INDEXED, AND DISSEMINATED TO TWENTY-FIVE SCIENTIFIC AND TECHNICAL PERSONNEL. MATCHING OF THE INTEREST PROFILES OF THESE…

BIVONA, WILLIAM A.

173

Enterohemorrhagic Escherichia coli O157:H7 requires quorum sensing transcriptional regulators QseA and SdiA for colonization and persistence in the bovine intestinal tract  

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...

174

Evaluation of an S.D.I. System Based on "Nuclear Science Abstracts" and the Performance of Matching by Words in Titles Compared With Indexing Terms.  

ERIC Educational Resources Information Center

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…

Olive, G.; And Others

175

Kinematic and dynamic collision statistics of cloud droplets from high-resolution simulations  

NASA Astrophysics Data System (ADS)

We study the dynamic and kinematic collision statistics of cloud droplets for a range of flow Taylor microscale Reynolds numbers (up to 500), using a highly scalable hybrid direct numerical simulation approach. Accurate results of radial relative velocity (RRV) and radial distribution function (RDF) at contact have been obtained by taking advantage of their power-law scaling at short separation distances. Three specific but inter-related questions have been addressed in a systematic manner for geometric collisions of same-size droplets (of radius from 10 to 60 ?m) in a typical cloud turbulence (dissipation rate at 400 cm2 s-3). Firstly, both deterministic and stochastic forcing schemes were employed to test the sensitivity of the simulation results on the large-scale driving mechanism. We found that, in general, the results are quantitatively similar, with the deterministic forcing giving a slightly larger RDF and collision kernel. This difference, however, is negligible for droplets of radius less than 30 ?m. Secondly, we have shown that the dependence of pair statistics on the flow Reynolds number R? or larger scale fluid motion is of secondary importance, with a tendency for this effect to saturate at high enough R? leading to R?-independent results. Both DNS results and theoretical arguments show that the saturation happens at a smaller R? for smaller droplets. Finally, since most previous studies of turbulent collision of inertial particles concerned non-sedimenting particles, we have specifically addressed the role of gravity on collision statistics, by simultaneously simulating collision statistics with and without gravity. It is shown that the collision statistics is not affected by gravity when a < ac, where the critical droplet radius ac is found to be around 30 ?m for the RRV, and around 20 ?m for the RDF. For larger droplets, gravity alters the particle-eddy interaction time and significantly reduces the RRV. The effect of gravity on the RDF is rather complex: gravity reduces the RDF for intermediate-sized droplets but enhances the RDF for larger droplets. In addition, we have studied the scaling exponents of both RDF and RRV, and found that gravity modifies the RDF scaling exponents for both intermediate and large particles, in a manner very similar to the effect of gravity on the RDF at contact. Gravity is shown to cause the scaling exponents for RDF and RRV to level off for large droplets, in contrast to diminishing exponents for non-sedimenting particles.

Rosa, Bogdan; Parishani, Hossein; Ayala, Orlando; Grabowski, Wojciech W.; Wang, Lian-Ping

2013-04-01

176

Application of statistical and dynamics models for snow avalanche hazard assessment in mountain regions of Russia  

NASA Astrophysics Data System (ADS)

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.

Turchaninova, A.

2012-04-01

177

The inclusion of dynamic factors in statistical power system cost models, Part I  

SciTech Connect

Power system production cost models which rely upon statistical analysis of load distributions, such as load duration models and most probabilistic methods, do not include the dynamic cost associated with thermal plant startup, banking and the need to maintain adequate levels of operating reserve. This limits their ability to model the real cost of operating power systems, and may lead to substantial inaccuracies if the models are used to assess the value of certain types of plant investment. This paper shows how the transition-frequency function may be used to estimate plant startup and banking costs under various conditions, and demonstrates how the calculations can be performed in terms of cumulants of the functions involved, thus enabling a very efficient formulation.

Grubb, M.

1989-05-01

178

Emergent statistical-mechanical structure in the dynamics along the period-doubling route to chaos  

E-print Network

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 $2^{N}$, and infinite $N \\rightarrow \\infty $, periods can be expressed as power laws or deformed exponentials. For 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.

Alvaro Diaz-Ruelas; Alberto Robledo

2014-03-05

179

Dynamic statistical optimization of GNSS radio occultation bending angles: an advanced algorithm and its performance analysis  

NASA Astrophysics Data System (ADS)

We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS) based radio occultation (RO) measurements. The new algorithm estimates background and observation error covariance matrices with geographically-varying uncertainty profiles and realistic global-mean correlation matrices. The error covariance matrices estimated by the new approach are more accurate and realistic than in simplified existing approaches and can therefore be used in statistical optimization to provide optimal bending angle profiles for high-altitude initialization of the subsequent Abel transform retrieval of refractivity. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.6 (OPSv5.6) algorithm, using simulated data on two test days from January and July 2008 and real observed CHAMP and COSMIC measurements from the complete months of January and July 2008. The following is achieved for the new method's performance compared to OPSv5.6: (1) significant reduction in random errors (standard deviations) of optimized bending angles down to about two-thirds of their size or more; (2) reduction of the systematic differences in optimized bending angles for simulated MetOp data; (3) improved retrieval of refractivity and temperature profiles; (4) produces realistically estimated global-mean correlation matrices and realistic uncertainty fields for the background and observations. Overall the results indicate high suitability for employing the new dynamic approach in the processing of long-term RO data into a reference climate record, leading to well characterized and high-quality atmospheric profiles over the entire stratosphere.

Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Norman, R.; Yuan, Y. B.; Fritzer, J.; Schwaerz, M.; Zhang, K.

2015-01-01

180

Predicting and attributing recent East African Spring droughts with dynamical-statistical climate model ensembles  

NASA Astrophysics Data System (ADS)

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.

Funk, C. C.; Shukla, S.; Hoerling, M. P.; Robertson, F. R.; Hoell, A.; Liebmann, B.

2013-12-01

181

An Embedded Statistical Method for Coupling Molecular Dynamics and Finite Element Analyses  

NASA Technical Reports Server (NTRS)

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.

Saether, E.; Glaessgen, E.H.; Yamakov, V.

2008-01-01

182

Statistical-dynamical downscaling for the future urban climate of Hamburg, Germany  

NASA Astrophysics Data System (ADS)

In the framework of the interdisciplinary project KLIMZUG-NORD, adaptation measures to climate change are developed for the Metropolitan Region of Hamburg. For the development of these measures it is crucial to know how the urban climate of Hamburg, a city with a population of 1.8 Mio, will alter due to climate change. Regional climate models provide climate projections on a horizontal resolution of up to 10 km, which is still too coarse to sufficiently simulate urban related phenomena such as the urban heat island (UHI). Therefore, these climate projections have to be downscaled. Since the computational amount increases rapidly with increasing horizontal resolution, a statistical-dynamical method for the UHI was developed. As a first step of the downscaling method, synoptic situations which are relevant for the UHI are determined. This is done combining objective weather type classification of ERA-40 reanalysis data using k-means-based cluster analysis and a regression-based statistical model for the observed UHI of Hamburg. The meteorological variables and domain used for the weather type classification are chosen to explain the variability of the UHI as best as possible. The second step is the simulation of the resulting synoptic situations with the mesoscale meteorological model METRAS providing a horizontal resolution of 1 km. To get the average UHI for a certain period, the simulation results are statistically recombined according to the frequency of the synoptic weather types. This is done for present and future climate simulations for the A1B scenario conducted with the regional climate models REMO and CLM and for the A2 scenario conducted with the regional climate model CCAM to identify changes in Hamburg's UHI. In this presentation the method will be presented with focus on the weather type classification and on the simulation results for the summer season.

Hoffmann, P.; Flagg, D. D.; Grawe, D.; Katzfey, J. J.; Kirschner, P.; Linde, M.; Schlünzen, K. H.; Schoetter, R.

2011-12-01

183

A nonequilibrium statistical model of spectrally truncated Burgers-Hopf dynamics  

E-print Network

Exact spectral truncations of the unforced, inviscid Burgers-Hopf equation are Hamiltonian systems with many degrees of freedom which exhibit intrinsic stochasticity and coherent scaling behavior. For this reason recent studies have employed these systems as prototypes to test stochastic mode reduction strategies. In the present paper the Burgers-Hopf dynamics truncated to n Fourier modes is treated by a new statistical model reduction technique, and a closed system of evolution equations for the mean values of the m lowest modes is derived for m << n. In the reduced model the m-mode macrostates are associated with trial probability densities on the phase space of the n-mode microstates, and a cost functional is introduced to quantify the lack of fit of paths of these densities to the Liouville equation. The best-fit macrodynamics is obtained by minimizing the cost functional over paths, and the equations governing the closure are then derived from Hamilton-Jacobi theory. The resulting reduced equations have a fractional diffusion and modified nonlinear interactions, and the explicit form of both are determined up to a single closure parameter. The accuracy and range of validity of this nonequilibrium closure is assessed by comparison against direct numerical simulations of statistical ensembles, and the predicted behaviour is found to be well represented by the reduced equations.

Richard Kleeman; Bruce E. Turkington

2013-02-14

184

Assessing the performance of dynamical and statistical downscaling techniques to simulate crop yield in West Africa  

NASA Astrophysics Data System (ADS)

Global circulation models (GCM) are increasingly capable of making relevant predictions of seasonal and long-term climate variability, thus improving prospects of predicting impact on crop yields. This is particularly important for semi-arid West Africa where climate variability and drought threaten food security. Translating GCM outputs into attainable crop yields is difficult because GCM grid boxes are of larger scale than the processes governing yield, involving partitioning of rain among runoff, evaporation, transpiration, drainage and storage at plot scale. It therefore requires the use of downscaling methods. This study analyzes the performance of both dynamical and statistical downscaling techniques in simulating crop yield at local scale. A detailed case study is conducted using historical weather data for Senegal, applied to the crop model SARRAH for simulating several tropical cereals (sorghum, millet, maize) at local scale. This control simulation is used as a benchmark to evaluate a set of Regional Climate Models (RCM) simulations, forced by ERA-Interim, from the ENSEMBLES project and a statistical downscaling method, the CDF-Transform, used to correct biases in RCM outputs. We first evaluate each climate variable that drives the simulated yield in the control simulation (radiation, rainfall, temperatures). We then simulate crop yields with RCM outputs (with or without applying the CDG-Transform) and evaluate the performance of each RCM in regards to crop yield simulations.

Sultan, B.; Oettli, P.; Vrac, M.; Baron, C.

2010-12-01

185

Numerical solutions of ideal quantum gas dynamical flows governed by semiclassical ellipsoidal-statistical distribution.  

PubMed

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

Yang, Jaw-Yen; Yan, Chih-Yuan; Diaz, Manuel; Huang, Juan-Chen; Li, Zhihui; Zhang, Hanxin

2014-01-01

186

Extreme Wind Gusts within European Winter Storms estimated from Dynamical and Statistical Downscaling  

NASA Astrophysics Data System (ADS)

Extreme winter wind storms are major natural catastrophes leading to enormous socio-economic impacts in Europe. The impact of a single events depends on the severity and extent of the event itself but also on the region hit by the storm, combined with its specific exposure of values and vulnerability. The spatial distribution of exposed values and their vulnerability is highly heterogeneous. Therefore, it is necessary to analyze extremes of surface wind speeds within winter wind storms with high spatial resolution. This study analyzes if rather simple linear regression methods are suitable for estimating extreme surface wind gusts of high spatial resolution, using different coarse resolution predictors. The statistical relationships between coarse resolution predictors from ECMWF reanalysis data and high resolution (~7km x 7km) predictands, i.e. the maximum gusts, are derived from dynamical simulations of extreme historical events performed with the German Weather Service (DWD) model chain GME—COSMO-EU. Validation of the results of the statistical downscaling confirms the high skill of linear regressions for different European sub-regions. Hence, the application of these methods to more extensive datasets in order to estimate extreme wind gusts and their exceedance probabilities or return periods is justified.

Kruschke, T.; Lorenz, P.; Osinski, R.; Voigt, M.; Leckebusch, G. C.; Ulbrich, U.

2012-04-01

187

Numerical solutions of ideal quantum gas dynamical flows governed by semiclassical ellipsoidal-statistical distribution  

PubMed Central

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

Yang, Jaw-Yen; Yan, Chih-Yuan; Diaz, Manuel; Huang, Juan-Chen; Li, Zhihui; Zhang, Hanxin

2014-01-01

188

Dynamical and Statistical Wind Downscaling in the Northeast of the Iberian Peninsula  

NASA Astrophysics Data System (ADS)

Estimations of possible changes of wind variability at the regional scale as a response to the evolution of large scale climate entail relevant economic and ecological implications for society, as for instance, the assessment of the variations and sustainability in wind energy resources. Not only in this context but also from a meteorological point of view, the evaluation of surface wind variability involves many interesting aspects that are worth to be analyzed. The limited reliability of the general circulation models at the regional/local scale requires the use of downscaling techniques to derive regional climate variability from the large scale circulation. Dynamical, statistical or a combination or both approaches can be applied to the downscaling problem to explore the wind field behavior in the region of interest. In this work, the potential predictability of the wind speed is evaluated by means of its relationship with the atmospheric circulation over the North Atlantic area using different methodologies. For this aim, wind speed observations from the region of Navarra, Northeast of the Iberian Peninsula, are employed; the data span a 14 years period, from 1992 to 2005. A dynamical downscaling using the Weather Research and Forecast (WRF) model is used to analyze the wind variability at daily time scales. The spatial wind variability is analyzed by dividing the region into various subregions by means of cluster analysis. The temporal variability is addressed by classifying the wind fields into weather types (wind circulation types) with similar spatial structure. The model is skillful in identifying the observed subregions and in reproducing the temporal wind variability at most of them. In addition, the spatial structure of the wind circulation types is generally reproduced by the simulation, with a tendency to underestimate the spatial wind speed variability. The statistical methodology explores the variability of wind speed and also wind power production at monthly timescales and consists in a linear technique which isolates optimal correlated modes of variability between the synoptic fields over the North Atlantic and the observed wind velocity (Canonical Correlation Analysis). Results evidence the existence of wind predictability in the region of study at monthly timescales. An assessment of the sensitivity of the methodology is performed as a first step in the evaluation of the potential sources of uncertainty affecting the regional estimations of the wind field. The statistical relationship found during the period of available observations is used to perform a climatological reconstruction of the surface wind field within the last five centuries using reanalysis, observational and reconstruction data sources. This evaluation of past wind variability could have relevant applications for the study of regional wind predictability over the 21th century.

Gonzalez-Rouco, J.; Jimenez, P. A.; Bustamante, E. G.; Navarro, J.; Montavez, J.

2008-12-01

189

Estimating dynamic lung images from high-dimension chest surface motion using 4D statistical model.  

PubMed

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

He, Tiancheng; Xue, Zhong; Yu, Nam; Nitsch, Paige L; Teh, Bin S; Wong, Stephen T

2014-01-01

190

Prequantum Classical Statistical Field Theory: Schrödinger Dynamics of Entangled Systems as a Classical Stochastic Process  

NASA Astrophysics Data System (ADS)

The idea that quantum randomness can be reduced to randomness of classical fields (fluctuating at time and space scales which are essentially finer than scales approachable in modern quantum experiments) is rather old. Various models have been proposed, e.g., stochastic electrodynamics or the semiclassical model. Recently a new model, so called prequantum classical statistical field theory (PCSFT), was developed. By this model a "quantum system" is just a label for (so to say "prequantum") classical random field. Quantum averages can be represented as classical field averages. Correlations between observables on subsystems of a composite system can be as well represented as classical correlations. In particular, it can be done for entangled systems. Creation of such classical field representation demystifies quantum entanglement. In this paper we show that quantum dynamics (given by Schrödinger's equation) of entangled systems can be represented as the stochastic dynamics of classical random fields. The "effect of entanglement" is produced by classical correlations which were present at the initial moment of time, cf. views of Albert Einstein.

Khrennikov, Andrei

2011-03-01

191

Assessment of Future Storm Losses in Germany: Probabilistic Extension of the Statistical-Dynamical Downscaling Approach  

NASA Astrophysics Data System (ADS)

Future loss estimation is an important planning tool for insurance companies. In particular, good estimates of ranges of uncertainty are necessary for the assessment of climate change impacts and its implications. In this study, the probabilistic aspect of loss estimation is considered by prediction of loss distributions instead of best estimates for average values. For this purpose, downscaling of global climate model data is combined with regional modelling and a probabilistic loss function, which describes the relation between wind speeds and losses. The statistical-dynamical downscaling (SDD) approach is applied to reanalysis data and ECHAM5 climate scenarios for 1960-2100. The SDD consists of a cluster classification of storm relevant weather episodes, referred to as weather types (WT), dynamical downscaling for WT episodes and a recombination of wind speed distributions on the regional scale using frequencies of WT occurrences. Changes in wind distributions for different time periods are divided into external changes due to variability of WT frequencies and internal changes due to wind speed distributions within WT classes. The losses are estimated using generalized loss functions, which fit wind speeds locally to observed loss frequencies via quantile regression. The results corroborate earlier findings, which describe an enhancement of loss potentials for Germany associated with winter storms under future climate conditions. In addition, uncertainty ranges in terms of quantile functions allow for a discussion of loss potential changes with respect to the relative sizes of events.

Born, K.; Karremann, M. K.; Ludwig, P.; Pinto, J.

2010-09-01

192

Dynamics of rotating triple systems: statistical escape theory versus numerical simulations  

NASA Astrophysics Data System (ADS)

Dynamical evolution of 120000 equal-mass rotating triple systems is investigated. The system rotation is described by the parameter w=-L20E0/G2m50, where G is the gravitational constant, m0 is the mass of a body, and L0 and E0 are the angular momentum and the total energy of the triple system, respectively. We consider the values of w= 0.005, 0.1, 1, 2, 4 and 6. For each w, 20000 triple systems are studied. The initial coordinates and velocities of the components are randomly chosen. The initial data are chosen in two different ways: the first one assumes a hierarchical structure initially and the second one does not. The evolution of each triple system is calculated until either the escape of one of the bodies occurs or the time exceeds 1000 mean crossing times of the system. The orbital parameters of the final binary and the escaper are recorded for each run. We compare the results of numerical simulations and predictions of a statistical escape theory. The statistical theory is based on the assumption of ergodicity, that is, the only information on the initial conditions remaining at the time of the escape of the third body is contained in the conserved total energy, total angular momentum and the mass values. The distributions of various quantities are derived from the allowable phase-space volumes. The distribution of binary energy agrees with earlier results by Heggie, with the angular momentum dependence of Mikkola & Valtonen being added. The eccentricities are distributed in general accordance with Monaghan's work, while the triple systems break up like in radioactive decay, as was previously found by Valtonen & Aarseth. The escape directions are preferentially perpendicular to the total angular momentum vector; the more so, the greater the angular momentum. The escape-angle distributions are derived from the statistical theory and are found to be in agreement with the numerical data. The relative orientations and magnitudes of the binary and third-body angular momenta are also explained based on the statistical theory.

Valtonen, M.; Mylläri, A.; Orlov, V.; Rubinov, A.

2005-11-01

193

A Lagrangian dynamical theory for the mass function of cosmic structures - II. Statistics  

NASA Astrophysics Data System (ADS)

The statistical tools needed to obtain a mass function from realistic collapse-time estimates are presented. Collapse dynamics has been dealt with in Paper I of this series by means of the powerful Lagrangian perturbation theory and the simple ellipsoidal collapse model. The basic quantity considered here is the inverse collapse time F; it is a non-linear functional of the initial potential, with a non-Gaussian distribution. In the case of sharp k-space smoothing, it is demonstrated that the fraction of collapsed mass can be determined by extending to the F process the diffusion formalism introduced by Bond et al. The problem is then reduced to that of a random walk with a moving absorbing barrier, and numerically solved; an accurate analytical fit, valid for small and moderate resolutions, is found. For Gaussian smoothing, the F trajectories are strongly correlated in resolution. In this case, an approximation proposed by Peacock & Heavens can be used to determine the mass functions. Gaussian smoothing is preferred, as it optimizes the performances of dynamical predictions and stabilizes the F trajectories. The relation between resolution and mass is treated at a heuristic level, and the consequences of this approximation are discussed. The resulting mass functions, compared with the classical Press & Schechter one, are shifted toward large masses (confirming the findings of Monaco), and tend to give more intermediate-mass objects at the expense of small-mass objects. However, the small-mass part of the mass function, which depends on uncertain dynamics and is likely to be affected by uncertainties in the resolution-mass relation, is not considered a robust prediction of this theory.

Monaco, Pierluigi

1997-09-01

194

Comparison of statistical and dynamical downscaling of extreme precipitations over France in present-day and future climate  

Microsoft Academic Search

We present a comparison of two downscaling methods of extreme precipitations over France at a climatic time scale : a dynamical one performed with the Regional Climate Model ALADIN-Climate used at a resolution of 12 km, and a statistical one based on the weather regime approach and using the analog methodology to reconstruct daily fields of precipitations at a 8

Jeanne Colin; Michel Déqué; Emila Sanchez Gomez; Samuel Somot

2010-01-01

195

Statistical Software.  

ERIC Educational Resources Information Center

This buyer's guide to seven major types of statistics software packages for microcomputers reviews Edu-Ware Statistics 3.0; Financial Planning; Speed Stat; Statistics with DAISY; Human Systems Dynamics package of Stats Plus, ANOVA II, and REGRESS II; Maxistat; and Moore-Barnes' MBC Test Construction and MBC Correlation. (MBR)

Callamaras, Peter

1983-01-01

196

Dynamical and statistical behavior of discrete combustion waves: A theoretical and numerical study  

NASA Astrophysics Data System (ADS)

We present a detailed theoretical and numerical study of combustion waves in a discrete one-dimensional disordered system. The distances between neighboring reaction cells were modeled with a gamma distribution. The results show that the random structure of the microheterogeneous system plays a crucial role in the dynamical and statistical behavior of the system. This is a consequence of the nonlinear interaction of the random structure of the system with the thermal wave. An analysis of the experimental data on the combustion of a gasless system (Ti + xSi) and a wide range of thermite systems was performed in view of the developed model. We have shown that the burning rate of the powder system sensitively depends on its internal structure. The present model allows for reproducing theoretically the experimental data for a wide range of pyrotechnic mixtures. We show that Arrhenius’ macrokinetics at combustion of disperse systems can take place even in the absence of Arrhenius’ microkinetics; it can have a purely thermal nature and be related to their heterogeneity and to the existence of threshold temperature. It is also observed that the combustion of disperse systems always occurs in the microheterogeneous mode according to the relay-race mechanism.

Bharath, Naine Tarun; Rashkovskiy, Sergey A.; Tewari, Surya P.; Gundawar, Manoj Kumar

2013-04-01

197

Statistics of initial density perturbations in heavy ion collisions and their fluid dynamic response  

E-print Network

An interesting opportunity to determine thermodynamic and transport properties in more detail is to identify generic statistical properties of initial density perturbations. Here we study event-by-event fluctuations in terms of correlation functions for two models that can be solved analytically. The first assumes Gaussian fluctuations around a distribution that is fixed by the collision geometry but leads to non-Gaussian features after averaging over the reaction plane orientation at non-zero impact parameter. In this context, we derive a three-parameter extension of the commonly used Bessel-Gaussian event-by-event distribution of harmonic flow coefficients. Secondly, we study a model of N independent point sources for which connected n-point correlation functions of initial perturbations scale like 1/N^(n-1). This scaling is violated for non-central collisions in a way that can be characterized by its impact parameter dependence. We discuss to what extent these are generic properties that can be expected to hold for any model of initial conditions, and how this can improve the fluid dynamical analysis of heavy ion collisions.

Stefan Floerchinger; Urs Achim Wiedemann

2014-08-28

198

Sensitivity properties of a biosphere model based on BATS and a statistical-dynamical climate model  

NASA Technical Reports Server (NTRS)

A biosphere model based on the Biosphere-Atmosphere Transfer Scheme (BATS) and the Saltzman-Vernekar (SV) statistical-dynamical climate model is developed. Some equations of BATS are adopted either intact or with modifications, some are conceptually modified, and still others are replaced with equations of the SV model. The model is designed so that it can be run independently as long as the parameters related to the physiology and physiognomy of the vegetation, the atmospheric conditions, solar radiation, and soil conditions are given. With this stand-alone biosphere model, a series of sensitivity investigations, particularly the model sensitivity to fractional area of vegetation cover, soil surface water availability, and solar radiation for different types of vegetation, were conducted as a first step. These numerical experiments indicate that the presence of a vegetation cover greatly enhances the exchanges of momentum, water vapor, and energy between the atmosphere and the surface of the earth. An interesting result is that a dense and thick vegetation cover tends to serve as an environment conditioner or, more specifically, a thermostat and a humidistat, since the soil surface temperature, foliage temperature, and temperature and vapor pressure of air within the foliage are practically insensitive to variation of soil surface water availability and even solar radiation within a wide range. An attempt is also made to simulate the gradual deterioration of environment accompanying gradual degradation of a tropical forest to grasslands. Comparison with field data shows that this model can realistically simulate the land surface processes involving biospheric variations.

Zhang, Taiping

1994-01-01

199

Dynamical and statistical behavior of discrete combustion waves: a theoretical and numerical study.  

PubMed

We present a detailed theoretical and numerical study of combustion waves in a discrete one-dimensional disordered system. The distances between neighboring reaction cells were modeled with a gamma distribution. The results show that the random structure of the microheterogeneous system plays a crucial role in the dynamical and statistical behavior of the system. This is a consequence of the nonlinear interaction of the random structure of the system with the thermal wave. An analysis of the experimental data on the combustion of a gasless system (Ti + xSi) and a wide range of thermite systems was performed in view of the developed model. We have shown that the burning rate of the powder system sensitively depends on its internal structure. The present model allows for reproducing theoretically the experimental data for a wide range of pyrotechnic mixtures. We show that Arrhenius' macrokinetics at combustion of disperse systems can take place even in the absence of Arrhenius' microkinetics; it can have a purely thermal nature and be related to their heterogeneity and to the existence of threshold temperature. It is also observed that the combustion of disperse systems always occurs in the microheterogeneous mode according to the relay-race mechanism. PMID:23679470

Bharath, Naine Tarun; Rashkovskiy, Sergey A; Tewari, Surya P; Gundawar, Manoj Kumar

2013-04-01

200

Bubble statistics and coarsening dynamics for quasi-two dimensional foams with increasing liquid content  

E-print Network

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 state, 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. By observing the growth rate of individual bubbles, we find that von Neumann's law becomes progressively violated with increasing wetness and with 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.

A. E. Roth; C. D. Jones; D. J. Durian

2013-03-26

201

Modeling of adsorption dynamics at air-liquid interfaces using statistical rate theory (SRT).  

PubMed

A large number of natural and technological processes involve mass transfer at interfaces. Interfacial properties, e.g., adsorption, play a key role in such applications as wetting, foaming, coating, and stabilizing of liquid films. The mechanistic understanding of surface adsorption often assumes molecular diffusion in the bulk liquid and subsequent adsorption at the interface. Diffusion is well described by Fick's law, while adsorption kinetics is less understood and is commonly described using Langmuir-type empirical equations. In this study, a general theoretical model for adsorption kinetics/dynamics at the air-liquid interface is developed; in particular, a new kinetic equation based on the statistical rate theory (SRT) is derived. Similar to many reported kinetic equations, the new kinetic equation also involves a number of parameters, but all these parameters are theoretically obtainable. In the present model, the adsorption dynamics is governed by three dimensionless numbers: psi (ratio of adsorption thickness to diffusion length), lambda (ratio of square of the adsorption thickness to the ratio of adsorption to desorption rate constant), and Nk (ratio of the adsorption rate constant to the product of diffusion coefficient and bulk concentration). Numerical simulations for surface adsorption using the proposed model are carried out and verified. The difference in surface adsorption between the general and the diffusion controlled model is estimated and presented graphically as contours of deviation. Three different regions of adsorption dynamics are identified: diffusion controlled (deviation less than 10%), mixed diffusion and transfer controlled (deviation in the range of 10-90%), and transfer controlled (deviation more than 90%). These three different modes predominantly depend on the value of Nk. The corresponding ranges of Nk for the studied values of psi (10(-2)

Biswas, M E; Chatzis, I; Ioannidis, M A; Chen, P

2005-06-01

202

Dynamics of the D+ + H2 HD + H+ reaction at the low energy regime by means of a statistical quantum method  

E-print Network

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

Honvault, Pascal

203

Early Visible Adaptive Optics Science Results from MagAO's VisAO Camera in Simultaneous Differential Imaging (SDI) Mode: Disks and Point Sources  

NASA Astrophysics Data System (ADS)

We report on early science results from the newly-commissioned Magellan AO (MagAO) system's VisAO camera in Simultaneous Differential Imaging (SDI) mode. The MagAO Adaptive Secondary Mirror's high actuator pitch allow us to achieve AO correction into the visible wavelength regime, and VisAO is the first visible light science camera behind a large (d>6m) telescope AO system. This opens up an interesting new region of parameter space to high contrast, high spatial resolution science. As a natural guide star system, MagAO is optimized for circumstellar science, including both point source detection and high resolution imaging of circumstellar disks. Early SDI science results include the first circumstellar disk imaged in silhouette from the ground, high-resolution images of a binary propylid in Orion and high contrast images of an accreting point source at small separation.

Follette, Kate; Close, Laird; Wu, Ya-Lin; Males, Jared; Morzinski, Katie; Kopon, Derek

2013-07-01

204

Power-law dynamics in an auditory-nerve model can account for neural adaptation to sound-level statistics  

PubMed Central

Neurons in the auditory system respond to recent stimulus-level history by adapting their response functions according to the statistics of the stimulus, partially alleviating the so-called “dynamic-range problem.” However, the mechanism and source of this adaptation along the auditory pathway remain unknown. Inclusion of power-law dynamics in a phenomenological model of the inner hair cell (IHC)- auditory nerve (AN) synapse successfully explained neural adaptation to sound-level statistics, including the time course of adaptation of the mean firing rate and changes in the dynamic range observed in AN responses. A direct comparison between model responses to a dynamic stimulus and to an “inversely-gated” static background suggested that AN dynamic-range adaptation largely results from the adaptation produced by the response history. These results support the hypothesis that the potential mechanism underlying the dynamic-range adaptation observed at the level of the auditory nerve is located peripheral to the spike generation mechanism and central to the IHC receptor potential. PMID:20685981

Zilany, Muhammad S. A.; Carney, Laurel H.

2010-01-01

205

Tsallis non-extensive statistics, intermittent turbulence, SOC and chaos in the solar plasma. Part two: Solar Flares dynamics  

E-print Network

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.

L. P. Karakatsanis; G. P. Pavlos; M. N. Xenakis

2012-04-03

206

Comparison of dynamically and statistically downscaled seasonal climate forecasts for the cold season over the United States  

NASA Astrophysics Data System (ADS)

This study compares two approaches, dynamical and statistical downscaling, for their potential to improve regional seasonal forecasts for the United States (U.S.) during the cold season. In the MultiRCM Ensemble Downscaling (MRED) project, seven regional climate models (RCMs) are used to dynamically downscale the Climate Forecast System (CFS) seasonal prediction over the conterminous U.S. out to 5 months for the period of 1982-2003. The simulations cover December to April of next year with 10 ensemble members from each RCM with different initial and boundary conditions from the corresponding ensemble members. These dynamically downscaled forecasts are compared with statistically downscaled forecasts produced by two bias correction methods applied to both the CFS and RCM forecasts. Results of the comparison suggest that the RCMs add value in seasonal prediction application, but the improvements largely depend on location, forecast lead time, variables, and skill metrics used for evaluation. Generally, more improvements are found over the Northwest and North Central U.S. for the shorter lead times. The comparison results also suggest a hybrid forecast system that combines both dynamical and statistical downscaling methods have the potential to maximize prediction skill.

Yoon, Jin-Ho; Ruby Leung, L.; Correia, James, Jr.

2012-11-01

207

Statistical Properties and Pre-Hit Dynamics of Price Limit Hits in the Chinese Stock Markets  

PubMed Central

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

Wan, Yu-Lei; Xie, Wen-Jie; Gu, Gao-Feng; Jiang, Zhi-Qiang; Chen, Wei; Xiong, Xiong; Zhang, Wei; Zhou, Wei-Xing

2015-01-01

208

a Statistical-Dynamical Climate Model Applied to Trace Gas Transport and Chemistry in the Troposphere  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. A zonally averaged statistical-dynamical climate model, representing a single hemisphere from 1000 to 240 mb, is used to provide a mean circulation and eddy transfer coefficients for trace gas transport experiments. The annual mean model is highly parameterised for relevant physical processes. The model is first adapted for seasonally varying climate intergrations, which fail catastrophically. A positive feedback mechanism between Hadley Cell and latent heating is found to be responsible and averted by the addition of tropical eddy transfers of water vapour. Though stabilised, the model's seasonal temperature variation is extreme. Exploratory integrations reveal a tendency for the model's component radiation fields to mutually adjust to preserve an unrealistic net radiation distribution, and so too, temperature. A simple two box, energy balance model is considered to establish the mechanism. This temperature feedback in a freely responding, highly parameterised model implies such features may also be hidden in more specified models. The annual gross exchange rate of air between stratosphere and troposphere in the Northern Hemisphere is estimated to be 2.5(+/-2) * 10 ^{17} kg year^ {-1} from trace gas budgets. Assuming a tropopause folding mechanism for the exchange, this flux is distributed with latitude and time to give an upper boundary condition for the trace gas transport model. Annual mean and seasonal experiments concerning the transfer of stratospheric ozone to the troposphere, and its subsequent fate, are performed with the zonally averaged model. A hypothetical troposphere with no potential for photochemical ozone formation is considered. The sinks of ozone represented are surface deposition and a photochemical sink through photolysis, and subsequent reaction of singlet oxygen with water vapour. The net annual flux of ozone from stratosphere to troposphere, for this system, is estimated to be 1.7 * 10^{11} kg.

Follows, Michael John

1990-01-01

209

State-selected C2H2+ + C2H4 reaction: Controlled by dynamics or statistics?  

NASA Astrophysics Data System (ADS)

The reaction between acetylene ion and ethylene is revisited to investigate possible dynamical effects in one of the reactions, which are considered as benchmark systems for statistical models. Reactant ions are produced by photoionisation with synchrotron radiation and are selected in internal energy by a coincidence method between threshold photoelectrons and photoions. Measured absolute reaction cross-sections decrease with collision energy (0.1-1 eV CM), but increase with acetylene ion vibrational energy for the three exothermic channels giving C4H5+, C3H3+ and C2H4+ionic products. Even though RRKM calculations are shown to fit rather well experimental results for both the bimolecular (C2H2+ + C2H4) and unimolecular (C4H6+) systems, some experimental results clearly indicate dynamical effects in this reaction for the C2H4+ production channel, in particular the strongly backward peaked C2H4+ angular distribution. We propose an alternative model combining reaction control both by dynamics and by statistics: the first step in the reactant approach is the capture between reactants, followed by a charge transfer process controlled by dynamics. In a second step, either the two reactants separate leading to C2H4+ ionic products, or there is a rearrangement into 1,3-butadiene (C4H6+) ion which dissociates statistically into C4H5+ + H and C3H3+ + CH3 products. Charge transfer is shown to be possible at intermediate intermolecular distances, slightly shorter than the capture distance, provided that one takes into account the charge-quadrupole interaction in addition to the ion-induced dipole interaction. This work clearly shows that a good fit of experimental data by RRKM calculations does not prove that the reaction elementary mechanism is controlled by statistics.

Palm, Hartmut; Alcaraz, Christian; Millié, Philippe; Dutuit, Odile

2006-03-01

210

Statistical and dynamical downscaling of precipitation: An evaluation and comparison of scenarios for the European Alps  

Microsoft Academic Search

This paper compares six statistical downscaling models (SDMs) and three regional climate models (RCMs) in their ability to downscale daily precipitation statistics in a region of complex topography. The six SDMs include regression methods, weather typing methods, a conditional weather generator, and a bias correction and spatial disaggregation approach. The comparison is carried out over the European Alps for current

J. Schmidli; C. M. Goodess; C. Frei; M. R. Haylock; Y. Hundecha; J. Ribalaygua; T. Schmith

2007-01-01

211

Multivariate statistical monitoring of two-dimensional dynamic batch processes utilizing non-Gaussian information  

Microsoft Academic Search

Dynamics are inherent characteristics of batch processes, and they may exist not only within a particular batch, but also from batch to batch. To model and monitor such two-dimensional (2D) batch dynamics, two-dimensional dynamic principal component analysis (2D-DPCA) has been developed. However, the original 2D-DPCA calculates the monitoring control limits based on the multivariate Gaussian distribution assumption which may be

Yuan Yao; Tao Chen; Furong Gao

2010-01-01

212

Complex networks for climate model evaluation with application to statistical versus dynamical modeling of South American climate  

NASA Astrophysics Data System (ADS)

In this study we introduce two new node-weighted difference measures on complex networks as a tool for climate model evaluation. The approach facilitates the quantification of a model's ability to reproduce the spatial covariability structure of climatological time series. We apply our methodology to compare the performance of a statistical and a dynamical regional climate model simulating the South American climate, as represented by the variables 2 m temperature, precipitation, sea level pressure, and geopotential height field at 500 hPa. For each variable, networks are constructed from the model outputs and evaluated against a reference network, derived from the ERA-Interim reanalysis, which also drives the models. We compare two network characteristics, the (linear) adjacency structure and the (nonlinear) clustering structure, and relate our findings to conventional methods of model evaluation. To set a benchmark, we construct different types of random networks and compare them alongside the climate model networks. Our main findings are: (1) The linear network structure is better reproduced by the statistical model statistical analogue resampling scheme (STARS) in summer and winter for all variables except the geopotential height field, where the dynamical model CCLM prevails. (2) For the nonlinear comparison, the seasonal differences are more pronounced and CCLM performs almost as well as STARS in summer (except for sea level pressure), while STARS performs better in winter for all variables.

Feldhoff, Jan H.; Lange, Stefan; Volkholz, Jan; Donges, Jonathan F.; Kurths, Jürgen; Gerstengarbe, Friedrich-Wilhelm

2015-03-01

213

Combined statistical and dynamical assessment of simulated vegetation–rainfall in North Africa during the mid-Holocene*  

SciTech Connect

A negative feedback of vegetation cover on subsequent annual precipitation is simulated for the mid-Holocene over North Africa using a fully coupled general circulation model with dynamic vegetation, FOAM-LPJ (Fast Ocean Atmosphere Model-Lund Potsdam Jena Model). By computing a vegetation feedback parameter based on lagged autocovariances, the simulated impact of North African vegetation on precipitation is statistically quantified. The feedback is also dynamically assessed through initial value ensemble experiments, in which North African grass cover is initially reduced and the climatic response analyzed. The statistical and dynamical assessments of the negative vegetation feedback agree in sign and relative magnitude for FOAM-LPJ. The negative feedback on annual precipitation largely results from a competition between bare soil evaporation and plant transpiration, with increases in the former outweighing reductions in the latter given reduced grass cover. This negative feedback weakens and eventually reverses sign over time during a transient simulation from the mid-Holocene to present. A similar, but weaker, negative feedback is identified in Community Climate System Model Version 2 (CCSM2) over North Africa for the mid-Holocene.

Notaro, Michael; Wang, Yi; Liu, Zhengyu; Gallimore, Robert; Levis, Samuel

2008-01-05

214

Functional ANOVA and Regional Climate Experiments: A Statistical Analysis of Dynamic Downscaling  

E-print Network

of the United States to a few hundred grid points. Even the large western states are discretized to just a few for dynamic downscaling of global models. In this paper, we discuss an initial analysis of a subset, and it is a grand scientific challenge to model the dynamics of this system over time and in response to external

Sain, Steve

215

Statistical dynamics of classical systems: A self-consistent field approach  

SciTech Connect

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.

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

216

Dynamic Range Adaptation to Sound Level Statistics in the Auditory Nerve  

E-print Network

The auditory system operates over a vast range of sound pressure levels (100–120 dB) with nearly constant discrimination ability across most of the range, well exceeding the dynamic range of most auditory neurons (20–40 ...

Dean, Isabel

217

A dynamical equation for a maser with non-poissonian injection statistics  

E-print Network

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.

Michael Fleischhauer

2014-10-12

218

Statistical mechanics of coarse graining: Estimating dynamical speedups from excess entropies  

NASA Astrophysics Data System (ADS)

The excess entropy of fluids has been shown to play a decisive role in the determination of dynamical properties [Y. Rosenfeld, Phys. Rev. A 15, 2545 (1977), 10.1103/PhysRevA.15.2545]. We argue that it could play an equally important role in connecting dynamical properties of atomistic and coarse-grained models of molecular fluid systems. Molecular dynamics simulations for an atomistic and a coarse-grained model of water confirm the validity of this conjecture, showing that the sizable enhancement of the diffusion rate upon coarse-graining is a simple function of the difference in the excess entropy of the two models. This empirical observation could ease the way to a first-principles prediction of the relation of dynamical properties estimated from models at different resolution.

Armstrong, J. A.; Chakravarty, C.; Ballone, P.

2012-03-01

219

Static Numbers to Dynamic Statistics: Designing a Policy-Friendly Social Policy Indicator Framework  

ERIC Educational Resources Information Center

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.…

Ahn, Sang-Hoon; Choi, Young Jun; Kim, Young-Mi

2012-01-01

220

Virtual reality and dynamic statistical graphics: A bidirectional link in a heterogeneous, distributed computing environment  

E-print Network

framework for the design and management of mo- bile phone networks and the optimization of antenna positions internal communication structures. Finally, we recommend some software design rules with respect to our. XGobi is a software package particularly useful for the analysis of multivariate statistical data. RA

Symanzik, Jürgen

221

Dynamic Range Adaptation to Sound Level Statistics in the Auditory Nerve  

PubMed Central

The auditory system operates over a vast range of sound pressure levels (100–120 dB) with nearly constant discrimination ability across most of the range, well exceeding the dynamic range of most auditory neurons (20–40 dB). Dean et al. (Nat. Neurosci. 8:1684, 2005) have reported that the dynamic range of midbrain auditory neurons adapts to the distribution of sound levels in a continuous, dynamic stimulus by shifting towards the most frequently occurring level. Here we show that dynamic range adaptation, distinct from classic firing rate adaptation, also occurs in primary auditory neurons in anesthetized cats for tone and noise stimuli. Specifically, the range of sound levels over which firing rates of auditory-nerve (AN) fibers grows rapidly with level shifts nearly linearly with the most probable levels in a dynamic sound stimulus. This dynamic range adaptation was observed for fibers with all characteristic frequencies and spontaneous discharge rates. As in the midbrain, dynamic range adaptation improved the precision of level coding by the AN fiber population for the prevailing sound levels in the stimulus. However, dynamic range adaptation in the AN was weaker than in the midbrain, and not sufficient (0.25 dB/dB on average for broadband noise) to prevent a significant degradation of the precision of level coding by the AN population above 60 dB SPL. These findings suggest that adaptive processing of sound levels first occurs in the auditory periphery and is enhanced along the auditory pathway. PMID:19889991

Wen, Bo; Wang, Grace I.; Dean, Isabel; Delgutte, Bertrand

2009-01-01

222

q-Deformed Statistical-Mechanical Property in the Dynamics of Trajectories en route to the Feigenbaum Attractor  

E-print Network

We demonstrate that the dynamics towards and within the Feigenbaum attractor combine to form a q-deformed statistical-mechanical construction. The rate at which ensemble trajectories converge to the attractor (and to the repellor) is described by a q-entropy obtained from a partition function generated by summing distances between neighboring positions of the attractor. The values of the q-indices involved are given by the unimodal map universal constants, while the thermodynamic structure is closely related to that formerly developed for multifractals. As an essential component in our demonstration we expose, at a previously unknown level of detail, the features of the dynamics of trajectories that either evolve towards the Feigenbaum attractor or are captured by its matching repellor. The dynamical properties of the family of periodic superstable cycles in unimodal maps are seen to be key ingredients for the comprehension of the discrete scale invariance features present at the period-doubling transition to chaos. We make clear the dynamical origin of the anomalous thermodynamic framework existing at the Feigenbaum attractor.

A. Robledo; L. G. Moyano

2008-03-26

223

The value of model averaging and dynamical climate model predictions for improving statistical seasonal streamflow forecasts over Australia  

NASA Astrophysics Data System (ADS)

Seasonal streamflow forecasts are valuable for planning and allocation of water resources. In Australia, the Bureau of Meteorology employs a statistical method to forecast seasonal streamflows. The method uses predictors that are related to catchment wetness at the start of a forecast period and to climate during the forecast period. For the latter, a predictor is selected among a number of lagged climate indices as candidates to give the "best" model in terms of model performance in cross validation. This study investigates two strategies for further improvement in seasonal streamflow forecasts. The first is to combine, through Bayesian model averaging, multiple candidate models with different lagged climate indices as predictors, to take advantage of different predictive strengths of the multiple models. The second strategy is to introduce additional candidate models, using rainfall and sea surface temperature predictions from a global climate model as predictors. This is to take advantage of the direct simulations of various dynamic processes. The results show that combining forecasts from multiple statistical models generally yields more skillful forecasts than using only the best model and appears to moderate the worst forecast errors. The use of rainfall predictions from the dynamical climate model marginally improves the streamflow forecasts when viewed over all the study catchments and seasons, but the use of sea surface temperature predictions provide little additional benefit.

Pokhrel, Prafulla; Wang, Q. J.; Robertson, David E.

2013-10-01

224

Dynamics of localized waves in one-dimensional random potentials: Statistical theory of the coherent forward scattering peak  

NASA Astrophysics Data System (ADS)

As recently discovered [T. Karpiuk et al., Phys. Rev. Lett. 109, 190601 (2012), 10.1103/PhysRevLett.109.190601], Anderson localization in a bulk disordered system triggers the emergence of a coherent forward scattering (CFS) peak in momentum space, which twins the well-known coherent backscattering (CBS) peak observed in weak localization experiments. Going beyond the perturbative regime, we address here the long-time dynamics of the CFS peak in a one-dimensional random system and we relate this novel interference effect to the statistical properties of the eigenfunctions and eigenspectrum of the corresponding random Hamiltonian. Our numerical results show that the dynamics of the CFS peak is governed by the logarithmic level repulsion between localized states, with a time scale that is, with good accuracy, twice the Heisenberg time. This is in perfect agreement with recent findings based on the nonlinear sigma model. In the stationary regime, the width of the CFS peak in momentum space is inversely proportional to the localization length, reflecting the exponential decay of the eigenfunctions in real space, while its height is exactly twice the background, reflecting the Poisson statistical properties of the eigenfunctions. It would be interesting to extend our results to higher dimensional systems and other symmetry classes.

Lee, Kean Loon; Grémaud, Benoît; Miniatura, Christian

2014-10-01

225

The writer independent online handwriting recognition system frog on hand and cluster generative statistical dynamic time warping.  

PubMed

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

Bahlmann, Claus; Burkhardt, Hans

2004-03-01

226

Statistical properties and Hurst-Kolmogorov dynamics in climatic proxy data and temperature reconstructions  

NASA Astrophysics Data System (ADS)

The statistical properties of over 300 different proxy records of the last two thousand years derived from the PAGES 2k database years are stochastically analysed. Analyses include estimation of their first four moments and their autocorrelation functions (ACF), as well as the determination of the presence of Hurst-Kolmogorov behaviour (known also as long term persistence). The data are investigated in groups according to their proxy type and location, while their statistical properties are also compared to those of the final temperature reconstructions. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.

Koukas, Ioannis; Koukoravas, Vasilis; Mantesi, Konstantina; Sakellari, Katerina; Xanthopoulou, Themis-Demetra; Zarkadoulas, Akis; Markonis, Yannis; Papalexiou, Simon Michael; Koutsoyiannis, Demetris

2014-05-01

227

Nonequilibrium statistical mechanics of a two-temperature Ising ring with conserved dynamics.  

PubMed

The statistical mechanics of a one-dimensional Ising model in thermal equilibrium is well-established, textbook material. Yet, when driven far from equilibrium by coupling two sectors to two baths at different temperatures, it exhibits remarkable phenomena, including an unexpected "freezing by heating." These phenomena are explored through systematic numerical simulations. Our study reveals complicated relaxation processes as well as a crossover between two very different steady-state regimes. PMID:25615050

Borchers, Nicholas; Pleimling, Michel; Zia, R K P

2014-12-01

228

Overpopulation of Omegabar in pp Collisions: A Way to Distinguish Statistical Hadronization from String Dynamics  

Microsoft Academic Search

The Omegabar\\/Omega ratio originating from string decays is predicted to be larger than unity in proton-proton interactions at SPS energies ( Elab = 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

M. Bleicher; F. M. Liu; A. Keränen; J. Aichelin; S. A. Bass; F. Becattini; K. Redlich; K. Werner

2002-01-01

229

Dynamic treatment regimes for managing chronic health conditions: a statistical perspective.  

PubMed

Dynamic treatment regimes are an emerging and important methodological area in health research, particularly in the management of chronic health conditions. This paradigm encompasses the ideological shift in research from the acute care model to the chronic care model. It allows individualization of treatment (type, dosage, timing) at each stage of intervention. Constructing evidence-based dynamic treatment regimes requires implementation of cutting-edge design and analysis tools. Here I briefly discuss some of these modern tools, namely the sequential multiple assignment randomized trial (SMART) design and a regression-based analysis approach called Q-learning. PMID:21088260

Chakraborty, Bibhas

2011-01-01

230

Statistical Mechanics with focus on  

E-print Network

Statistical Mechanics with focus on Liquids, Solutions and Colloidal Systems Course contents A. Foundations of statistical mechanics Classical dynamics ­ Hamilton's and Liouville's equations The concept thermodynamics and statistical mechanics. B. Liquid state theory; Equilibrium statistical mechanics for liquids

Johannesson, Henrik

231

RF linacs for SDI  

NASA Astrophysics Data System (ADS)

Radio-frequency linear accelerators are key elements of Strategic Defense Initiative systems for producing neurtral particle beams and for producing photon radiation using free-electron lasers. The R&D work for these applications will result in significant advances in all aspects of accelerators and supporting systems that will also benefit the application of these devices in other areas. Aspects of the current development work are outlined, and prospects for broader application are discussed.

Jameson, R. A.

1987-04-01

232

Overpopulation of $\\bar \\Omega$ in pp collisions a way to distinguish statistical hadronization from string dynamics  

E-print Network

The $\\bar{\\Omega}/\\Omega$ ratio originating from string decays is predicted to be larger than unity in proton proton interactions at SPS energies ($E_{\\rm lab}$=160 GeV). The anti-omega 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.

Bleicher, M; Keränen, A; Aichelin, Jörg; Bass, S A; Becattini, F; Redlich, Krzysztof; Werner, K

2002-01-01

233

Overpopulation of $\\bar ?$ in pp collisions: a way to distinguish statistical hadronization from string dynamics  

E-print Network

The $\\bar{\\Omega}/\\Omega$ ratio originating from string decays is predicted to be larger than unity in proton proton interactions at SPS energies ($E_{\\rm lab}$=160 GeV). The anti-omega 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.

M. Bleicher; F. M. Liu; A. Keränen; J. Aichelin; S. A. Bass; F. Becattini; K. Redlich; K. Werner

2001-11-15

234

Statistics and dynamics of the boundary layer reattachments during the drag crisis transitions of a circular cylinder  

NASA Astrophysics Data System (ADS)

Time series of pressure measured on the periphery of the central section of a circular cylinder of aspect ratio 22 are used to investigate the dynamics of the local reattachments during the drag crisis transitions. A succession of multi-stable dynamics are identified and characterized through conditional statistical analysis as the Reynolds number is increased. The first transition marking an abrupt weakening of the periodic pressure fluctuations associated to the global shedding dynamics is accompanied by the appearance of symmetric and bistable perturbations. Afterwards, two scenarii of asymmetric and symmetric boundary layer reattachments are found. The asymmetric scenario leads to two transitions. During the first transition, the flow explores randomly three stable states to eventually stabilize on the state corresponding to the permanent reattachment on one side of the cylinder. The second transition is bistable and leads to the permanent reattachment on both sides. For the second symmetric scenario, the boundary layer reattachments occur simultaneously on both side of the cylinder. In that case, the flow explores randomly two stable states to eventually stabilize on the state of full reattachment. Pressure distributions of all of these states are characterized as well as their corresponding probabilities during the drag crisis transitions of the critical regime.

Cadot, O.; Desai, A.; Mittal, S.; Saxena, S.; Chandra, B.

2015-01-01

235

The inclusion of dynamic factors in statistical power system cost models, Part II  

SciTech Connect

This paper develops techniques for analysing the costs of maintaining adequate operating reserve on power systems, within probabilistic production costing models and others based upon load distribution functions. The aim is to show that such models can be developed to approximate the full range of dynamic penalties associated with practical power system operation. Algorithms for costing predetermined part loading are presented, including the need for bringing plant on-line out of strict merit order. The paper then describes how an prediction error function can be used to estimate the probability that the specified spinning reserve is insufficient, and hence approximate the cost of gas turbine or storage utilisation for dynamic control. This allows estimation of optimal reserve levels. The paper also discusses the analysis of longer term reserve from banked thermal units. Finally, some results of the model are compared with those reported from hourly simulation studies.

Grubb, M.

1989-05-01

236

Retrieval dynamics and retention in cross-situational statistical word learning.  

PubMed

Previous research on cross-situational word learning has demonstrated that learners are able to reduce ambiguity in mapping words to referents by tracking co-occurrence probabilities across learning events. In the current experiments, we examined whether learners are able to retain mappings over time. The results revealed that learners are able to retain mappings for up to 1 week later. However, there were interactions between the amount of retention and the different learning conditions. Interestingly, the strongest retention was associated with a learning condition that engendered retrieval dynamics that initially challenged the learner but eventually led to more successful retrieval toward the end of learning. The ease/difficulty of retrieval is a critical process underlying cross-situational word learning and is a powerful example of how learning dynamics affect long-term learning outcomes. PMID:24117698

Vlach, Haley A; Sandhofer, Catherine M

2014-01-01

237

Dynamics and Statistical Mechanics of Rotating and non-Rotating Vortical Flows  

SciTech Connect

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.

Lim, Chjan [RPI] [RPI

2013-12-18

238

Impact of accurate motion-corrected statistical reconstruction on dynamic PET kinetic parameter estimation  

Microsoft Academic Search

With continuing improvements in spatial resolution of PET scanners, small subject movements become a significant source of resolution degradation. This work assesses the impact of an accurate motion correction (MC) method, modeling the 'motion-induced' interaction of lines-of-response (LORs) inside and outside the field-of-view, on the task of kinetic parametric estimation in high resolution dynamic PET. Following extensive prior phantom and

A. Rahmim; K. Dinelle; J. C. Cheng; G. Topping; H. A. Vajihollahi; D. F. Wong; V. Sossi

2007-01-01

239

Links between nonlinear dynamics and statistical mechanics in a simple one-dimensional model  

E-print Network

We consider the links between nonlinear dynamics and thermodynamics in the framework of a simple nonlinear model for DNA. Two analyses of the phase transition, either with the transfer integral approach or by considering the instability of a nonlinear particular solution, are discussed. Conversely, the computation of the largest Lyapunov exponent is obtained within a thermodynamic treatment. Differences with the Peyrard-Bishop model are also discussed.

Hicham Qasmi; Julien Barre'; Thierry Dauxois

2004-07-26

240

Regulation of signal duration and the statistical dynamics of kinase activation by scaffold proteins  

E-print Network

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.

Jason W. Locasale; Arup K. Chakraborty

2008-10-29

241

STATISTICAL METHODS STATISTICAL METHODS  

E-print Network

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

Delorme, Arnaud

242

A dynamical and statistical investigation of the shape of splashform tektites  

NASA Astrophysics Data System (ADS)

Splash-form tektites are believed to represent molten rock that was ejected by a large impactor that solidified while in flight. These glassy rocks are found in a number of strewn fields around the Earth and are found in a number of intriguing shapes including near spheres, axisymmetric biconcave shapes as well as rods and "dumb-bells". In this contribution, we will present the results of a statistical study of the shapes of over 1000 tektites from South-East Asia and the results of a numerical study of the evolution of fluid droplets under the influence of a centrifugal force and surface tension. As we will show, the numerical simulations first evolve to an oblate, axisymmetric form before becoming subject to a non-axisymmetric instability which results in a prolate shape. The numerical model results are consistent with the measurements of real tektites that show that there is a dearth of weakly deformed, highly prolate tektites.

Butler, S. L.; Stauffer, M.

2008-12-01

243

Double precision errors in the logistic map: Statistical study and dynamical interpretation  

NASA Astrophysics Data System (ADS)

The nature of the round-off errors that occur in the usual double precision computation of the logistic map is studied in detail. Different iterative regimes from the whole panoply of behaviors exhibited in the bifurcation diagram are examined, histograms of errors in trajectories given, and for the case of fully developed chaos an explicit formula is found. It is shown that the statistics of the largest double precision error as a function of the map parameter is characterized by jumps whose location is determined by certain boundary crossings in the bifurcation diagram. Both jumps and locations seem to present geometric convergence characterized by the two first Feigenbaum constants. Eventually, a comparison with Benford’s law for the distribution of the leading digit of compilation of numbers is discussed.

Oteo, J. A.; Ros, J.

2007-09-01

244

Fermi statistics of weakly excited granular materials in a vibrating bed: molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations were carried out to test the thermodynamic theory of weakly excited, two-dimensional, granular systems [Hayakawa and Hong, Phys. Rev. Lett. 78 (1997) 2764], where granular materials are viewed as a collection of spinless Fermions. We first determine the global temperature T by fitting the steady-state density profile to the Fermi distribution function, and then measure the center of mass, < z( T)>, and its fluctuations, <(? z( T)) 2> as a function of T. We find a fairly good agreement between theory and simulations, in particular, in the estimation of the temperature and the scaling behavior of < z( T)> and <(? z( T)) 2>.

Quinn, Paul V.; Hong, Daniel C.

1999-12-01

245

Molecular structure and elastic properties of thermotropic liquid crystals: Integrated molecular dynamics—Statistical mechanical theory vs molecular field approach  

NASA Astrophysics Data System (ADS)

The connection between the molecular structure of liquid crystals and their elastic properties, which control the director deformations relevant for electro-optic applications, remains a challenging objective for theories and computations. Here, we compare two methods that have been proposed to this purpose, both characterized by a detailed molecular level description. One is an integrated molecular dynamics-statistical mechanical approach, where the bulk elastic constants of nematics are calculated from the direct correlation function (DCFs) and the single molecule orientational distribution function [D. A. McQuarrie, Statistical Mechanics (Harper & Row, New York, 1973)]. The latter is obtained from atomistic molecular dynamics trajectories, together with the radial distribution function, from which the DCF is then determined by solving the Ornstein-Zernike equation. The other approach is based on a molecular field theory, where the potential of mean torque experienced by a mesogen in the liquid crystal phase is parameterized according to its molecular surface. In this case, the calculation of elastic constants is combined with the Monte Carlo sampling of single molecule conformations. Using these different approaches, but the same description, at the level of molecular geometry and torsional potentials, we have investigated the elastic properties of the nematic phase of two typical mesogens, 4'-n-pentyloxy-4-cyanobiphenyl and 4'-n-heptyloxy-4-cyanobiphenyl. Both methods yield K3(bend) >K1 (splay) >K2 (twist), although there are some discrepancies in the average elastic constants and in their anisotropy. These are interpreted in terms of the different approximations and the different ways of accounting for the structural properties of molecules in the two approaches. In general, the results point to the role of the molecular shape, which is modulated by the conformational freedom and cannot be fully accounted for by a single descriptor such as the aspect ratio.

Capar, M. Ilk; Nar, A.; Ferrarini, A.; Frezza, E.; Greco, C.; Zakharov, A. V.; Vakulenko, A. A.

2013-03-01

246

SDI: Solar Dome Instrument for Solar Irradiance Monitoring Tao Liu1, Ankur U. Kamthe1, Varick L. Erickson1, Carlos F. M. Coimbra2 and Alberto E. Cerpa1  

E-print Network

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

Cerpa, Alberto E.

247

Financial price dynamics and pedestrian counterflows: A comparison of statistical stylized facts  

NASA Astrophysics Data System (ADS)

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.

Parisi, Daniel R.; Sornette, Didier; Helbing, Dirk

2013-01-01

248

Financial price dynamics and pedestrian counterflows: a comparison of statistical stylized facts.  

PubMed

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. PMID:23410385

Parisi, Daniel R; Sornette, Didier; Helbing, Dirk

2013-01-01

249

Assessing spatial coupling in complex population dynamics using mutual prediction and continuity statistics  

USGS Publications Warehouse

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.

Nichols, J.M.; Moniz, L.; Nichols, J.D.; Pecora, L.M.; Cooch, E.

2005-01-01

250

How electronic dynamics with Pauli exclusion produces Fermi-Dirac statistics.  

PubMed

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 for a general electronic state. 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. PMID:25854234

Nguyen, Triet S; Nanguneri, Ravindra; Parkhill, John

2015-04-01

251

Comparison of Predictive Skill Between the Statistically and the Dynamically Downscaled Temperature and Precipitation Over the Southeast United States  

NASA Astrophysics Data System (ADS)

Global model simulations from the FSUGSM (Florida State University Global Spectral Model) are statistically downscaled to construct the local climate scenario over the southeast US, covering Florida, Georgia, and Alabama. The basis of this downscaling method is that clearer separation of prominent local climate signals (e.g., seasonal cycle, dominant intraseasonal or interannual oscillations) over the training period leads to better prediction of local climate scenario from the large-scale simulations. To this end, 1) CSEOF (Cyclostationary EOF) analysis is conducted on both observation and FSUGSM runs over the training period, followed by 2) the multiple regression between lower modes of observation and GSM runs. 3) CSEOF PC time series for prediction domain is subsequently generated based on relationship identified from the first two steps. 4) The local scale data for the prediction domain are constructed from the generated PC time series and the eigenfunctions obtained from training. This procedure is repeated by withholding a particular year as a prediction domain for the sake of cross-validation. Daily precipitation and temperature (Tmax and Tmin) obtained from FSUGSM (~1.8° lon.-lat., T63) seasonal forecast run have been downscaled to local spatial scale of 0.2°×0.2° (~20 km) for the southeast US region. Correlation, error variance, and other skill scores reveal that statistical downscaling successfully produces the seasonal local climate scenario from coarsely resolved large-scale simulations. Biases unveiled from the FSUGSM have been significantly reduced by this downscaling technique. Comparison in predictability with dynamical downscaling (FSUNRSM (FSU nested regional spectral model)) shows that their skills are comparable to each other. Their capability that captures the event of above/below normal temperature and rainfall/no rainfall is faithful, specifically for the maximum temperature. However, observed variance of the variables is partly reduced by statistical downscaling, while RSM hardly loses the observed variance.

Lim, Y.; Shin, D.; Cocke, S.; Larow, T. E.

2006-12-01

252

Kinetic Analysis of Dynamic Positron Emission Tomography Data using Open-Source Image Processing and Statistical Inference Tools.  

PubMed

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, (15)O-H(2)O and (18)F-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

Hawe, David; Hernández Fernández, Francisco R; O'Suilleabháin, Liam; Huang, Jian; Wolsztynski, Eric; O'Sullivan, Finbarr

2012-05-01

253

A statistical and dynamical analysis of some Winter and Summer temperature extremes in Europe  

NASA Astrophysics Data System (ADS)

Over the last decades Europe has been facing strong extreme events, particularly temperature extremes, with foremost influence on economy, agriculture, water management and society in general. The study of the large-scale atmospheric mechanisms linked to their occurrence is thus significant and is going to be discussed for the winter and summer seasons in this region for 50 years (1961-2010). Additionally, a canonical correlation analysis, coupled with a principal component analysis (BPCCA), is applied between the monthly mean sea level pressure fields and the monthly occurrences of four temperature extreme indices (TN10p - cold nights, TN90p - warm nights, and TX90p - warm days, TX10p - cold days) within a large Euro-Atlantic sector. Each co-variability mode represents a large-scale forcing on the occurrence of those extremes. North Atlantic Oscillation-like patterns and strong anomalies in the atmospheric flow westwards of the British Isles are leading couplings between large-scale atmospheric circulation and wintertime occurrences of both cold (warm) nights and warm (cold) days in Europe. Although summer couplings show lower coherence between warm and cold events, their key driving mechanisms are significant to explain their atmospheric anomalies. In order to get a better insight for both seasons of these extremes, the main features of the statistical distributions of the minima (TNn and TXn) and maxima (TXx and TNx) are also analyzed. Moreover, statistically significant downward (upward) trends are detected in the cold nights and days (warm nights and days) occurrences over the period 1961-2010 throughout Europe for the winters. These tendencies can also be found in summer for the cold nights and warm days, which is in clear agreement with the overall warming. For the summer warm nights and cold days these tendencies are weaker and its signal is geographically dependent. This work is supported by European Union Funds (FEDER/COMPETE - Operational Competitiveness Programme) and by national funds (FCT - Portuguese Foundation for Science and Technology) under the project FCOMP-01-0124-FEDER-022692.

Andrade, Cristina; Santos, João

2013-04-01

254

Po river plume patterns variability and dynamics: a numerical modeling and statistical approach.  

NASA Astrophysics Data System (ADS)

Processes and dynamics of estuarine-shelf environments are defined by many drivers, some of the most important being riverine inputs, winds (and wind driven currents) and tides. Two of them are directly involved in the formation and spatial evolution of a coastal river plume: on the one hand the amount of fresh water entering into the sea through river' discharge, on the other hand the direction and intensity of winds blowing over the domain. The Adriatic Sea is generally considered a dilution basin due to the large amount of freshwater inputs received. These inputs have a significant influence on the basin, both from a physical point of view (by affecting buoyancy) and on the biogeochemical characteristics (by introducing large quantities of nutrients, which sustain primary production in the areas interested by the rivers' plumes). The Po River (mean daily discharge between 275 and 11600 m3/s, yearly mean of 1500 m3/s) is the single largest freshwater source of the Adriatic; its discharges result in a plume that directly influences the characteristics of the coastal areas of the whole Northern sub-basin and as far South as Ancona. The development of strong lateral gradients in salinity is an all year around driver (particularly in Spring and Autumn) of the general and coastal circulation, and influences the water column vertical structure and an important process such as the formation of the Northern Adriatic Dense Water. The Po plume generally follows two major patterns of evolution: southward along the Italian coasts in a ribbon that can fill the whole water column, or across the northern part of the basin toward the Istrian coasts in a generally more stratified condition. A model-based assessment, albeit semi-quantitative, of the dynamics and variability of the Po plume has not been yet reported in literature. In this work we investigated its dynamics by means of an 8 years (2003-2010) numerical simulation with the Regional Ocean Modelling System (ROMS). The model has been implemented on a 2 km regular grid for with surface fluxes come from an high-resolution meteorological model (COSMO I7), open boundary conditions at Otranto Straits come from an existing operational Mediterranean model (MFSTEP), main diurnal and semidiurnal tidal components are imposed at the open boundary, and main rivers discharge (including Po) are introduced as freshwater mass fluxes as measured by river gauges closest to the rivers' mouths.

Falcieri, Francesco M.; Benetazzo, Alvise; Bergamasco, Andrea; Bonaldo, Davide; Carniel, Sandro; Sclavo, Mauro; Russo, Aniello

2013-04-01

255

Avalanche statistics and time-resolved grain dynamics for a driven heap  

E-print Network

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. R. Abate; H. Katsuragi; D. J. Durian

2007-08-08

256

Statistical techniques for modeling extreme price dynamics in the energy market  

NASA Astrophysics Data System (ADS)

Extreme events have large impact throughout the span of engineering, science and economics. This is because extreme events often lead to failure and losses due to the nature unobservable of extra ordinary occurrences. In this context this paper focuses on appropriate statistical methods relating to a combination of quantile regression approach and extreme value theory to model the excesses. This plays a vital role in risk management. Locally, nonparametric quantile regression is used, a method that is flexible and best suited when one knows little about the functional forms of the object being estimated. The conditions are derived in order to estimate the extreme value distribution function. The threshold model of extreme values is used to circumvent the lack of adequate observation problem at the tail of the distribution function. The application of a selection of these techniques is demonstrated on the volatile fuel market. The results indicate that the method used can extract maximum possible reliable information from the data. The key attraction of this method is that it offers a set of ready made approaches to the most difficult problem of risk modeling.

Mbugua, L. N.; Mwita, P. N.

2013-02-01

257

Molecular dynamics study of network statistics in lithium disilicate: Qn distribution and the pressure-volume diagram  

NASA Astrophysics Data System (ADS)

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.

Habasaki, J.; Ngai, K. L.

2013-08-01

258

Scaling theory and spreading dynamics in systems with one absorbing state derived from an equilibrium statistical model.  

PubMed

We show that for systems with one absorbing state, the widely assumed scaling properties of the survival probability and of the probability density of the size of activity avalanches cannot be true in the asymptotic limit. Trying to answer the question, what is the true asymptotic limit of these quantities, we study Domany-Kinzel probabilistic cellular automata using an equilibrium statistical mechanic model (ESM). We are able to express important quantities of the avalanche dynamics by correlation functions of the ESM. The application of scaling theory to the ESM allows for the derivation of the scaling properties of quantities of the avalanche dynamics in the form of infinite series. From these results we can obtain possible solutions for the apparent scaling problem, but cannot decide definitely which one is true. The most appealing solution, for which some evidence is given, states that there is a narrow range around the critical point in which, for example, the survival probability has the same power-law behavior as on the critical point. Outside this narrow range, the usually assumed scaling should be approximately valid. PMID:11497657

Albat, R

2001-08-01

259

Statistical-dynamical downscaling for wind energy potentials: Evaluation and applications to decadal hindcasts and climate change projections  

NASA Astrophysics Data System (ADS)

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.

Pinto, Joaquim G.; Reyers, Mark; Mömken, Julia

2014-05-01

260

Global nannoplankton dynamics across the Paleocene-Eocene Thermal Maximum: A statistical approach  

NASA Astrophysics Data System (ADS)

Global warming during the Paleocene-Eocene Thermal Maximum (PETM; 55.8 Ma) had a profound effect on life on land and in the ocean. With global temperatures rising 5°C over ~20 kyr, the PETM is considered to be the most analogous interval to modern day climate change. Calcareous nannoplankton, a group of calcifying marine phytoplankton, have been extensively studied across this event. Results from these studies indicate nannoplankton assemblages responded to changing surface water temperatures and nutrient availability. Together, these records can provide a global picture of nannofossil assemblage dynamics during this critical interval. Issues such as the timing and nature of assemblage change on a global scale, the rate of assemblage change, and how assemblage shifts differ regionally can be further resolved. Here we use an ordination technique (detrended correspondence analysis; DCA), which condenses complex assemblage data and displays it in a simple, interpretable way. We applied the DCA to previously published nannofossil abundance data from 7 globally distributed sites and compared these results to published benthic and bulk ?13C records across the PETM. Our initial results show that changes in the nannofossil assemblage, as displayed through DCA 1, closely follow the trends of the ?13C curves at each site. This suggests that the organisms are closely linked to the carbon cycle in some way during this time period. From this study we will have a better understanding of how global nannoplankton populations responded to rapid climate change and when environmental alterations began to take place.

Schneider, L. J.; Bralower, T. J.; Patzkowsky, M.; Kump, L.

2012-12-01

261

A New Sigmoid Catalog from Hinode and the Solar Dynamics Observatory: Statistical Properties and Evolutionary Histories  

NASA Astrophysics Data System (ADS)

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.

Savcheva, A. S.; McKillop, S. C.; McCauley, P. I.; Hanson, E. M.; DeLuca, E. E.

2014-09-01

262

Numerical Simulations of Jupiter’s Moist Convection Layer: Structure and Dynamics in Statistically Steady States  

NASA Astrophysics Data System (ADS)

A series of long-term numerical simulations of moist convection in Jupiter's atmosphere are performed to investigate idealized characteristics of vertical structures of multi-composition clouds and convective motions associated with them, varying the deep abundances of condensible gases and the time constant of the auto-conversion process that is one of the most questionable parameters in the cloud microphysical parameterization. The simulations are conducted using a two-dimensional cloud resolving model that explicitly represents convective motion and microphysics of the three cloud components, H2O, NH3, and NH4SH. The results generally represent the following characteristics qualitatively similar to those found in Sugiyama et al (2011); stable layers associated with condensation and chemical reaction well behave as dynamical and compositional boundaries, intense cumulonimbus clouds develop with distinct temporal intermittency, and the active transport associated with the cumulonimbus clouds results in an establishment of the mean vertical profiles of condensates and condensible gases that are distinctly different from the hitherto accepted three-layered structure. Our results also demonstrate that the period of the intermittent cloud activity is roughly proportional to the deep abundance of H2O gas. The moist convection layer becomes potentially unstable with respect to an air parcel rising from below the H2O lifting condensation level (LCL) well before the development of cumulonimbus clouds. The instability accumulates until an appropriate trigger is provided by the H2O condensate that falls down through the H2O LCL; the H2O condensate drives a downward flow below the H2O LCL by latent cooling associated with re-evaporation of the condensate, and the returning updrafts carry moist air from below to the moist convection layer. The active cloud development is terminated when the instability is completely exhausted. The period of the intermittency is roughly equal to the time obtained by dividing the mean temperature increase caused by active cumulonimbus development, by the rate of body cooling.

Nakajima, Kensuke; Sugiyama, Ko-ichiro; Odaka, Masatsugu; Kuramoto, Kiyoshi; Hayashi, Yoshi-Yuki

2014-11-01

263

Tensile behavior and dynamic mechanical analysis of novel poly(lactide/?-valerolactone) statistical copolymers.  

PubMed

Lactide-co-?-valerolactone copolymers (PLVL) have not attracted as much research interest as the more popular poly(lactide-co-?-caprolactone) (PLCL) elastomeric materials. In this work the study of the mechanical performance is focused on the former with the aim of identifying the potential advantages of these thermoplastic elastomers for their application in the biomedical field. Mechanical testing (at 21°C and at 37°C) of at least 5 specimens and dynamic mechanical analysis (DMA) in duplicate were carried out on various PLVL, which include a moderately blocky l-lactide/?-valerolactone copolymer (~70% of l-LA and R=0.68) and several that showed a random distribution of sequences (R~1): some terpolymers based on l-lactide, d-lactide and ?-valerolactone (with a lactone content of ~25 and ~14%) and a series of copolymers of l-LA and ?-VL having l-LA molar contents ranging from 69 to 74%. In view of the results, it can be concluded that noteworthy improvements in stiffness and strength were achieved by adding ?-VL to the reaction mix instead of ?-CL, although both monomers have analogous chemical properties. For example, a PLVL with a 75:25M composition of l-LA/?-VL at 21°C presented a secant modulus of 213.7±36.5MPa and ?u=14.7±1.4MPa whereas a previously studied PLCL of equal composition had a secant modulus and an ultimate stress value of 19.4±1.3MPa and 3.2±0.6MPa, respectively. At 37°C, the differences in the mechanical properties between the different PLVLs of this work were far less relevant, with most of them showing a fully elastomeric behavior. Referring to the DMA measurements, the reduction in the peak of tan ? (from ~2.5 to 0.5) through the glass transition was a clear indicator that crystalline domains formed during hydrolytic degradation in some of the polymers. However, the more amorphous PLVLs with short l-LA average sequence lengths (ll-LA<2.91) did not undergo changes in the storage modulus and tan ? curves after two weeks submerged in PBS at 37°C. PMID:24732304

Fernández, J; Larrañaga, A; Etxeberria, A; Sarasua, J R

2014-07-01

264

Structure, Dynamics, and Thermodynamics of Small Molecules Adsorbed in Zeolite Micropores: Simulation and Statistical Mechanics.  

NASA Astrophysics Data System (ADS)

This thesis describes a fully detailed molecular simulation and modeling effort aimed at understanding the fundamentals of adsorption and diffusion of small molecules in zeolite micropores. The primary emphasis is on determining the relationship between the structure and chemistry of the zeolite adsorbent and the structure, dynamics, and thermodynamics of the adsorbed phase. Further emphasis is on developing simple, predictive models of zeolite adsorption and diffusion. We begin by presenting a Monte Carlo simulation of single component adsorption of xenon, methane, and argon in zeolite NaA. The form of the adsorbate density distribution indicates the presence of discrete adsorption sites which arrange in polyhedra whose geometry depends on the number and position of zeolite framework ions. Isotherm plateaus are attributed to either (i) a low energy adsorbate configuration or (ii) the saturation of polyhedral sites. Viewing the adsorbed phase as an ordered arrangement differs from the conventional delocalized model, yet it helps explain certain experimental observations. Next, a study of binary mixtures of small molecules in zeolite NaA using the Monte Carlo method is presented. The mixing in the pore is determined to be highly nonideal by comparison to a simple pore volume filling model. Strong selectivity for a more polarizable molecule (xenon) is observed only at low pore loading. At higher pore loading, a smaller, less polarizable molecule (argon) adsorbs selectively at a significantly lower pressure than predicted by the model. This enhanced selectivity is due to the ability of the smaller molecule to pack more efficiently inside of the pore. Finally, we present two simple lattice models whose forms are arrived at following careful consideration of simulation results. The first describes the adsorption of small molecules in a zeolite. A polyhedral lattice is postulated whose neighboring sites interact energetically and entropically. The second model describes the mobility of small molecules in a zeolite. Motion is assumed to be a series of activated site-to-site hops whose rate is governed by energetic and entropic barriers between sites. The topology of the lattice allows for hops within a zeolite cage and hops between cages. Both models offer improvement over existing models.

van Tassel, Paul Robert

1993-01-01

265

The old nuclear star cluster in the Milky Way: dynamics, mass, statistical parallax, and black hole mass  

NASA Astrophysics Data System (ADS)

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.

Chatzopoulos, S.; Fritz, T. K.; Gerhard, O.; Gillessen, S.; Wegg, C.; Genzel, R.; Pfuhl, O.

2015-02-01

266

Numerical simulations of Jupiter’s moist convection layer: Structure and dynamics in statistically steady states  

NASA Astrophysics Data System (ADS)

A series of long-term numerical simulations of moist convection in Jupiter’s atmosphere is performed in order to investigate the idealized characteristics of the vertical structure of multi-composition clouds and the convective motions associated with them, varying the deep abundances of condensable gases and the autoconversion time scale, the latter being one of the most questionable parameters in cloud microphysical parameterization. The simulations are conducted using a two-dimensional cloud resolving model that explicitly represents the convective motion and microphysics of the three cloud components, H2O, NH3, and NH4SH imposing a body cooling that substitutes the net radiative cooling. The results are qualitatively similar to those reported in Sugiyama et al. (Sugiyama, K. et al. [2011]. Intermittent cumulonimbus activity breaking the three-layer cloud structure of Jupiter. Geophys. Res. Lett. 38, L13201. doi:10.1029/2011GL047878): stable layers associated with condensation and chemical reaction act as effective dynamical and compositional boundaries, intense cumulonimbus clouds develop with distinct temporal intermittency, and the active transport associated with these clouds results in the establishment of mean vertical profiles of condensates and condensable gases that are distinctly different from the hitherto accepted three-layered structure (e.g., Atreya, S.K., Romani, P.N. [1985]. Photochemistry and clouds of Jupiter, Saturn and Uranus. In: Recent Advances in Planetary Meteorology. Cambridge Univ. Press, London, pp. 17-68). Our results also demonstrate that the period of intermittent cloud activity is roughly proportional to the deep abundance of H2O gas. The autoconversion time scale does not strongly affect the results, except for the vertical profiles of the condensates. Changing the autoconversion time scale by a factor of 100 changes the intermittency period by a factor of less than two, although it causes a dramatic increase in the amount of condensates in the upper troposphere. The moist convection layer becomes potentially unstable with respect to an air parcel rising from below the H2O lifting condensation level (LCL) well before the development of cumulonimbus clouds. The instability accumulates until an appropriate trigger is provided by the H2O condensate that falls down through the H2O LCL; the H2O condensate drives a downward flow below the H2O LCL as a result of the latent cooling associated with the re-evaporation of the condensate, and the returning updrafts carry moist air from below to the moist convection layer. Active cloud development is terminated when the instability is completely exhausted. The period of intermittency is roughly equal to the time obtained by dividing the mean temperature increase, which is caused by active cumulonimbus development, by the body cooling rate.

Sugiyama, K.; Nakajima, K.; Odaka, M.; Kuramoto, K.; Hayashi, Y.-Y.

2014-02-01

267

Dynamic calculation of rail vehicles: A concept for the application of the process of statistical linearization in the many body program system MEDYNA  

NASA Astrophysics Data System (ADS)

A substructure for the wheel sets is developed. The problem of relating the substructures to the general body system by the calculation of statistical linearized, generalized force vectors for various linear and nonlinear joining elements is solved. Nonlinear spring and damper connections, Coulomb translation friction dampers, and Coulomb rotation friction dampers are covered. Statistically linearized dynamic connecting elements are modelized. It is shown how the general differential equation system is to be constructed. The iteration process for the determination of the free linearization parameter is presented.

Renger, A.

268

Teaching Introductory Statistics Courses So That Nonstatisticians Experience Statistical Reasoning  

Microsoft Academic Search

The most critical point in developing dynamic introductory statistics courses for nonstatisticians is deciding whether to teach statistical reasoning (concepts and thinking), statistical methods (computations), or both. Statistical reasoning should precede statistical methods. Workshop-based courses effectively provide situated learning and an intimate teaching environment. Use real (or realistic) data, graphics, and teach exploratory data analysis before classical methods. Evaluate the

Thomas E. Bradstreet

1996-01-01

269

Statistically-based DLVO approach to the dynamic interaction of colloidal microparticles with topographically and chemically heterogeneous collectors.  

PubMed

Electrostatic surface heterogeneity on the order of a few nanometers is common in colloidal and bacterial systems, dominating adhesion and aggregation and inducing deviations from classical DLVO theory based on a uniform distribution of surface charge. Topographical heterogeneity and roughness also strongly influence adhesion. In this work, a model is introduced to quantify the spatial fluctuations in the interaction of microparticles in a flowing suspension with a wall aligned parallel to the flow. The wall contains nanoscale chemical and topographical heterogeneities ("patches") that are randomly distributed and produce localized attraction and repulsion. These attractive and repulsive regions induce fluctuations in the trajectories of the flowing particles that are critical to particle capture by the wall. The statistical distribution of patches is combined with mean-field DLVO calculations between a particle and two homogeneous surfaces: one with the surface potential of the patches and one with the potential of the underlying wall. These surface potentials could be obtained in experiments from zeta potential measurements for the bare wall and for one saturated with patches. This simple model reproduces the mean DLVO interaction force or energy vs. particle-wall separation distance, its variance, and particle adhesion thresholds from direct simulations of particle trajectories over patchy surfaces. The predictions of the model are consistent with experimental findings of significant microparticle deposition onto patchy, net-repulsive surfaces whose apparent zeta potential has the same sign as that of the particles. Deposition is significantly enhanced if the patches protrude even slightly from the surface. The model predictions are also in agreement with the observed variation of the adhesion threshold with the shear rate in published studies of dynamic microparticle adhesion on patchy surfaces. PMID:25804202

Bendersky, Marina; Santore, Maria M; Davis, Jeffrey M

2015-07-01

270

Statistical Applets: Statistical Significance  

NSDL National Science Digital Library

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.

Duckworth, William

271

Analysis of the relationship between ultrasound of breast cancer DOT-SDI and the expression of MVD, VEGF and HIF-1?.  

PubMed

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

Wang, Hai-long; Zhang, Zhou-long

2014-09-01

272

Modified Statistical Dynamical Diffraction Theory: A Novel Metrological Analysis Method for Partially Relaxed and Defective Carbon-doped Silicon and Silicon Germanium Heterostructures  

NASA Astrophysics Data System (ADS)

The statistical dynamical diffraction theory, which has been initially developed by late Kato remained in obscurity for many years due to intense and difficult mathematical treatment that proved to be quite challenging to implement and apply. With assistance of many authors in past (including Bushuev, Pavlov, Pungeov, and among the others), it became possible to implement this unique x-ray diffraction theory that combines the kinematical (ideally imperfect) and dynamical (the characteristically perfect diffraction) into a single system of equations controlled by two factors determined by long range order and correlation function within the structure. The first stage is completed by the publication (Shreeman and Matyi, J. Appl. Cryst., 43, 550 (2010)) demonstrating the functionality of this theory with new modifications hence called modified statistical dynamical diffraction theory (mSDDT). The foundation of the theory is also incorporated into this dissertation, and the next stage of testing the model against several ion-implanted SiGe materials has been published: (Shreeman and Matyi, physica status solidi (a)208(11), 2533-2538, 2011). The dissertation with all the previous results summarized, dives into comprehensive analysis of HRXRD analyses complete with several different types of reflections (symmetrical, asymmetrical and skewed geometry). The dynamical results (with almost no defects) are compared with well-known commercial software. The defective materials, to which commercially available modeling software falls short, is then characterized and discussed in depth. The results will exemplify the power of the novel approach in the modified statistical dynamical diffraction theory: Ability to detect and measure defective structures qualitatively and quantitatively. The analysis will be compared alongside with TEM data analysis for verification and confirmation. The application of this theory will accelerate the ability to quickly characterize the relaxed/partially relaxed/fully strained semiconductors using non-destructive HRXRD metrology.

Shreeman, Paul K.

273

Mid-Century Warming in the Los Angeles Region and its Uncertainty using Dynamical and Statistical Downscaling  

NASA Astrophysics Data System (ADS)

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.

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

274

Columnar Aerosol Properties from Sun-and-star Photometry: Statistical Comparisons and Day-to-night Dynamic  

NASA Technical Reports Server (NTRS)

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.

Ramirez, Daniel Perez; Lyamani, H.; Olmo, F. J.; Whiteman, D. N.; Alados-Arboledas, L.

2012-01-01

275

Expression of p21(WAF1/CIP1/SDI1) and p53 in apoptotic cells in the adrenal cortex and induction by ischemia/reperfusion injury.  

PubMed Central

p21(WAF1/CIP1/SDI1), an inhibitor of cyclin-dependent kinases, is expressed at varying levels in human adrenal glands removed during surgery or organ recovery. In glands with p21 mRNA, nuclear p21 immunoreactivity, which was occasionally extensive, colocalized with p53 immunoreactivity and DNA damage, as evidenced by in situ end-labeling. Many cells showed morphological features of apoptosis when observed by fluorescent DNA dye staining and electron microscopy. This pattern was also associated with high levels of cytoplasmic heat shock protein 70. To address the question of the origin of p21 expression in some human adrenal glands, rat adrenal glands were subjected to 30 min of ischemia followed by 8 h of reperfusion. Cells with nuclear p21 and p53 appeared in the adrenal cortex together with DNA damage detected by in situ end-labeling. Nuclear p21 immunoreactivity was also produced in adrenal tissue fragments incubated at 37 degrees C in vitro. However, in this case, p21 expression was confined to the cut edge of the tissue. In contrast, p21 in human adrenal glands, as in ischemic rat glands, was within the inner regions of the cortex, supporting an origin of the protein in vivo rather than postmortem. The p53/p21 pathway of reaction to cellular injury, potentially leading to apoptosis, may play a role in tissue damage such as that resulting from ischemia/reperfusion. In the human adrenal cortex this process may be a precursor of adrenal failure. PMID:8601638

Didenko, V V; Wang, X; Yang, L; Hornsby, P J

1996-01-01

276

Production cross sections for intermediate mass fragments from dynamical and statistical decay of projectile-like fragments in 124Sn+64Ni and 112Sn+58Ni collisions at 35 A MeV  

NASA Astrophysics Data System (ADS)

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.

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

277

A Statistical Model of the Sleep-Wake Dynamics of the Cardiac Rhythm PE McSharry1,2  

E-print Network

smoother Brownian motion ( = 2) [5]. During sleep the human body is less exposed to physical activity demands on the body and varying levels of physical and mental activity. The ability of the heart to adapt- vestigate the statistical properties of cardiac activity during sleep and during sleep-wake transitions

McSharry, Patrick E.

278

Random walks along the streets and canals in compact cities: Spectral analysis, dynamical modularity, information, and statistical mechanics  

Microsoft Academic Search

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

D. Volchenkovand; Ph. Blanchard

2007-01-01

279

Random Walks Along the Streets and Channels in Compact Cities: Spectral analysis, Dynamical Modularity, Information, and Statistical Mechanics  

E-print Network

Statistics of random walks in compact cities helps to detect their modularity.The complexity of city modularity can be measured by an information-like parameter which plays the role of an individual fingerprint of {\\it Genius loci}. Global structural properties of a city can be characterized by the thermodynamical parameters calculated in the random walks problem.

Volchenkov, D; Blanchard, Ph.

2006-01-01

280

Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model  

NASA Astrophysics Data System (ADS)

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 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.

Kochendorfer, J. P.; Ramírez, J. A.

2008-03-01

281

Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model  

NASA Astrophysics Data System (ADS)

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.

Kochendorfer, J. P.; Ramírez, J. A.

2010-10-01

282

Adoption Statistics  

MedlinePLUS

... Role Our Leadership Newsroom Publications Statistics Contact Us Statistics All statistics correspond with the U.S. Government fiscal year, which ... and ends on September 30. For example, adoption statistics for FY2013 show the period from October 1, ...

283

Retrieval the statistical-dynamical model of western Pacific subtropical high ridge line index and key members of Asian summer monsoon system  

NASA Astrophysics Data System (ADS)

The western Pacific subtropical high (WPSH) is closely correlated with the East Asian climate. To date, the underlying mechanisms and sustaining factors have not been positively elucidated. Based on the concept of dynamical system model reconstruction, this paper presents a nonlinear statistical-dynamical model of the subtropical high ridge line (SHRL) in concurrence with four summer monsoon factors. SHRL variations from 1990 to 2011 are subdivided into three categories, while parameter differences relating to three differing models are examined. Dynamical characteristics of SHRL are analyzed and an aberrance mechanism subsequently developed. Modeling suggests that different parameters may lead to significant variance pertaining to monsoon variables corresponding with numerous WPSH activities. Dynamical system bifurcation and mutation indicates that the South China Sea monsoon trough is a significant factor with respect to the occurrence and maintenance of the 'double-ridge' phenomenon. Moreover, the occurrence of the Mascarene cold high is predicted to cause an abnormal northward location of WPSH, resulting in the “empty plum” phenomenon.

Hong, Mei; Zhang, Ren; Wang, Dong; Chen, Xi; Shi, Jian; Singh, Vijay

2014-12-01

284

Structural dynamics of clamshell rotation during the incipient relaxation process of photodissociated carbonmonoxy myoglobin: statistical analysis by the perturbation ensemble method.  

PubMed

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

Takayanagi, Masayoshi; Iwahashi, Chiharu; Nagaoka, Masataka

2010-09-30

285

Hydro-Kansas Research Project: Multi-scale Dynamical Understanding of Statistical Scale Invariance in Floods and Riparian Evapotranspiration in River Networks  

NASA Astrophysics Data System (ADS)

The Hydro-Kansas (HK) is a multi-institutional, multi-investigator, multi-disciplinary research project. It represents the first illustrative example of a Natural Laboratory (NL), as described in the Water, Earth, Biota (WEB) report to the National Science Foundation (http://cires.colorado.edu/hydrology). HK combines theoretical analyses, numerical modeling, and an observational field program to understand and predict floods during periods of stationary and non-stationary changes in global hydro-climate. The framework is being generalized to include riparian evapotranspiration (RET). The central observational facility of HK is the 1,100 km2 Whitewater basin 50 km east of Wichita, Kansas. HK is addressing the long-standing problem of predicting spatial statistical scale invariance, or scaling, in floods and RET from bio-physical processes on multiple time scales that range from those of individual rainfall-runoff events to annual and longer. Physical predictions of statistical scaling involve non-linear interactions among hydrologic, geomorphologic, atmospheric, climatic, and ecologic processes in mesoscale basins. They require, (i) multi-scale dynamical formulations, (ii) a new ensemble approach to solve multi-scale dynamical equations on random self-similar (RSN) river networks, (iii) diagnostic analyses of theoretical predictions using observations, and (iv) a framework to generalize the results across global hydroclimates. Progress on these four sets of research challenges will be illustrated through examples.

Gupta, V. K.

2009-05-01

286

Overpopulation of $\\\\bar \\\\Omega$ in pp collisions:a way to distinguish statistical hadronization from string dynamics  

Microsoft Academic Search

The $\\\\bar{\\\\Omega}\\/\\\\Omega$ ratio originating from string decays is predicted to be larger than unity in proton proton interactions at SPS energies ($E_{\\\\rm lab}$=160 GeV). The anti-omega 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

M Bleicher; Liu Fu Ming; A Keränen; Jörg Aichelin; S A Bass; F Becattini; Krzysztof Redlich; K Werner

2001-01-01

287

Random walks along the streets and canals in compact cities: Spectral analysis, dynamical modularity, information, and statistical mechanics  

NASA Astrophysics Data System (ADS)

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.

Volchenkov, D.; Blanchard, Ph.

2007-02-01

288

Indicators of Structural Change in the Dynamics of Science: Entropy Statistics of the SCI Journal Citation Reports  

E-print Network

Can change in citation patterns among journals be used as an indicator of structural change in the organization of the sciences? Aggregated journal-journal citations for 1999 are compared with similar data in the Journal Citation Reports 1998 of the Science Citation Index. In addition to indicating local change, probabilistic entropy measures enable us to analyze changes in distributions at different levels of aggregation. The results of various statistics are discussed and compared by elaborating the journal-journal mappings. The relevance of this indicator for science and technology policies is further specified.

Leydesdorff, Loet

2009-01-01

289

Random walks along the streets and canals in compact cities: spectral analysis, dynamical modularity, information, and statistical mechanics.  

PubMed

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 information-like 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. PMID:17358391

Volchenkov, D; Blanchard, Ph

2007-02-01

290

Usage Statistics  

MedlinePLUS

... Topics Drugs & Supplements Videos & Cool Tools ESPAÑOL MedlinePlus Statistics To use the sharing features on this page, please enable JavaScript. Quarterly User Statistics Graph | Quarterly User Statistics Table | Number of Health ...

291

Horizontal flow fields observed in Hinode G-band images. IV. Statistical properties of the dynamical environment around pores  

NASA Astrophysics Data System (ADS)

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.

Verma, M.; Denker, C.

2014-03-01

292

Department of Statistics STATISTICS COLLOQUIUM  

E-print Network

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

293

Étude statistique et dynamique de la propagation d'épidémies dans un réseau de petit mondeStatistical and dynamical study of the epidemics propagation in a small world network  

NASA Astrophysics Data System (ADS)

We study numerically in this work the statistical and dynamical properties of the clusters in a one dimensional small world model. The parameters chosen correspond to a realistic network of children of school age where a disease like measles can propagate. Extensive results on the statistical behavior of the clusters around the percolation threshold, as well as the evoltion with time, are discussed. To cite this article: N. Zekri, J.P. Clerc, C. R. Physique 3 (2002) 741-747.

Zekri, Nouredine; Clerc, Jean Pierre

294

A statistical dynamical study of meteorite impactors: A case study based on parameters derived from the Bosumtwi impact event  

NASA Astrophysics Data System (ADS)

The study of meteorite craters on Earth provides information about the dynamic evolution of bodies within the Solar System. the Bosumtwi crater is a well studied, 10.5 km in diameter, ca. 1.07 Myr old impact structure located in Ghana. (Koeberl et al., 1997a). The impactor was ˜ 1 km in diameter, an ordinary chondrite and struck the Earth with an angle between 30o and 45o (Artemieva et al., 2004) from the horizontal. We have used a two phase backward integration to constrain the most probable parent region of the impactor. We find that the most likely source region is a high inclination object from the Middle Main Belt.

Galiazzo, M. A.; Bazsó, Á.; Huber, M. S.; Losiak, A.; Dvorak, R.; Koeberl, C.

2013-11-01

295

A unified N-body and statistical treatment of stellar dynamics. III - Early postcollapse evolution of globular clusters  

NASA Technical Reports Server (NTRS)

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.

Mcmillan, S. L. W.

1986-01-01

296

Model-based statistical estimation of Sandia RF ohmic switch dynamic operation form stroboscopic, x-ray imaging.  

SciTech Connect

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.

Diegert, Carl F.

2006-12-01

297

Real-time dynamic range and signal to noise enhancement in beam-scanning microscopy by integration of sensor characteristics, data acquisition hardware, and statistical methods  

PubMed Central

Despite the ubiquitous use of multi-photon and confocal microscopy measurements in biology, the core techniques typically suffer from fundamental compromises between signal to noise (S/N) and linear dynamic range (LDR). In this study, direct synchronous digitization of voltage transients coupled with statistical analysis is shown to allow S/N approaching the theoretical maximum throughout an LDR spanning more than 8 decades, limited only by the dark counts of the detector on the low end and by the intrinsic nonlinearities of the photomultiplier tube (PMT) detector on the high end. Synchronous digitization of each voltage transient represents a fundamental departure from established methods in confocal/multi-photon imaging, which are currently based on either photon counting or signal averaging. High information-density data acquisition (up to 3.2 GB/s of raw data) enables the smooth transition between the two modalities on a pixel-by-pixel basis and the ultimate writing of much smaller files (few kB/s). Modeling of the PMT response allows extraction of key sensor parameters from the histogram of voltage peak-heights. Applications in second harmonic generation (SHG) microscopy are described demonstrating S/N approaching the shot-noise limit of the detector over large dynamic ranges. PMID:24817799

Kissick, David J.; Muir, Ryan D.; Sullivan, Shane Z.; Oglesbee, Robert A.; Simpson, Garth J.

2014-01-01

298

Exact solutions for the statistics of extrema of some random 1D landscapes, application to the equilibrium and the dynamics of the toy model  

NASA Astrophysics Data System (ADS)

The real-space renormalization group (RSRG) method introduced previously for the Brownian landscape is generalized to obtain the joint probability distribution of the subset of the important extrema at large scales of other one-dimensional landscapes. For a large class of models we give exact solutions obtained either by the use of constrained path-integrals in the continuum limit, or by solving the RSRG equations via an Ansatz which leads to the Liouville equation. We apply in particular our results to the toy model energy landscape, which consists in a quadratic potential plus a Brownian potential, which describes, among others, the energy of a single domain wall in a 1D random field Ising model (RFIM) in the presence of a field gradient. The measure of the renormalized landscape is obtained explicitly in terms of Airy functions, and allows to study in detail the Boltzmann equilibrium of a particle at low temperature as well as its non-equilibrium dynamics. For the equilibrium, we give results for the statistics of the absolute minimum which dominates at zero temperature, and for the configurations with nearly degenerate minima which govern the thermal fluctuations at very low-temperature. For the dynamics, we compute the distribution over samples of the equilibration time, or equivalently the distribution of the largest barrier in the system. We also study the properties of the rare configurations presenting an anomalously large equilibration time which govern the long-time dynamics. We compute the disorder averaged diffusion front, which interpolates between the Kesten distribution of the Sinai model at short rescaled time and the reaching of equilibrium at long rescaled time. Finally, the method allows to describe the full coarsening (i.e., many domain walls) of the 1D RFIM in a field gradient as well as its equilibrium.

Le Doussal, Pierre; Monthus, Cécile

2003-01-01

299

Statistics Explained  

NSDL National Science Digital Library

This site contains 100 modules designed to introduce concepts in statistics. The modules are divided into categories such as descriptive statistics, inferential statistics, related measures, enumeration statistics and ANOVA. Click the green button on the side to start the modules, then click "Main Menu" at the top to see a list of topics. Topics include: describing numbers, normal curve, sampling distributions, hypothesis testing, regression and Chi-Square. The site also includes a glossary, statistical tables and simulations, and a personalized progress report.

Hoffman, Howard

300

Comparisons between statistics of low energy collision cascades generated by full molecular dynamics and by its binary collision approximation  

NASA Astrophysics Data System (ADS)

Collision cascades in Cu, Au and Cu3Au are generated by full molecular dynamics (MD) and by its binary collision approximation (BCA) with the Marlowe program. Cu and Au primaries have 1 keV initial energy. The same Molière repulsive potential is used in both models for close encounters. In the MD model, this potential is carefully splined to the pair component of the N-body potential developed by Ackland and Vitek. In the BCA, this N-body interaction is roughly modeled by a constant isotropic 4 eV binding energy of the target atoms to their rest positions. Time distributions of the number of atoms moving with a total energy higher than a threshold value Ed are compared and discussed. Recoil range distributions during the cascade development are discussed as well. The agreement between MD and BCA is fairly good in all cases for Ed larger than about 3 eV. In the case of smaller Ed-values, the BCA may result in an overestimate of the number of moving atoms in the late development of the cascades. This discrepancy is suggested to originate in the lack of attractive forces between the moving particles and the surrounding atoms in the BCA.

Hou, M.; Pan, Z. Y.

301

Statistical and dynamical analysis of internal waves on the continental shelf of the Middle Atlantic Bight from Space Shuttle photographs  

NASA Technical Reports Server (NTRS)

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.

Zheng, Quanan; Yan, Xiao-Hai; Klemas, Vic

1993-01-01

302

Dynamic biochemical information recovery in spontaneous human seminal fluid reactions via 1H NMR kinetic statistical total correlation spectroscopy.  

PubMed

Human seminal fluid (HSF) is a complex mixture of reacting glandular metabolite and protein secretions that provides critical support functions in fertilization. We have employed 600-MHz (1)H NMR spectroscopy to compare and contrast the temporal biochemical and biophysical changes in HSF from infertile men with spinal cord injury compared to age-matched controls. We have developed new approaches to data analysis and visualization to facilitate the interpretation of the results, including the first application of the recently published K-STOCSY concept to a biofluid, enhancing the extraction of information on biochemically related metabolites and assignment of resonances from the major seminal protein, semenogelin. Principal components analysis was also applied to evaluate the extent to which macromolecules influence the overall variation in the metabolic data set. The K-STOCSY concept was utilized further to determine the relationships between reaction rates and metabolite levels, revealing that choline, N-acetylglucosamine, and uridine are associated with higher peptidase activity. The novel approach adopted here has the potential to capture dynamic information in any complex mixture of reacting chemicals including other biofluids or cell extracts. PMID:19117456

Maher, Anthony D; Cloarec, Olivier; Patki, Prasad; Craggs, Michael; Holmes, Elaine; Lindon, John C; Nicholson, Jeremy K

2009-01-01

303

Estimation of statistical binding properties of ligand population during in vitro selection based on population dynamics theory.  

PubMed

During in vitro selection process, it is very valuable to monitor the binding properties of the ligand population in real time, particularly the population average of the association constant in the population. If this monitoring can be realized, the selection process can be controlled in a rational way. In this paper, we present a simple method to estimate the binding properties of the ligand population during in vitro selection. The framework of the method is as follows. First, the number of all the collected ligand molecules, which are eluted after incubation and washing, is measured. Ideally, this number corresponds to the number of all the ligand molecules bound with the target-receptor or other materials in a test tube. This measurement is performed through several successive rounds of selection. Second, the measured numbers of molecules are subjected to a theoretical analysis, based on the mathematical theory of population dynamics in the selection process. Then, we can estimate the probability density of the binding free energy in the ligand population. The validity of our method was confirmed by several computer simulations based on a physicochemical model. PMID:24239675

Aita, Takuyo; Nishigaki, Koichi; Husimi, Yuzuru

2014-01-01

304

Statistical analysis of the dynamics of secondary electrons in the flare of a high-voltage beam-type discharge  

SciTech Connect

In the present work, results of investigations into the dynamics of secondary electrons with helium atoms in the presence of the reverse electric field arising in the flare of a high-voltage pulsed beam-type discharge and leading to degradation of the primary electron beam are presented. The electric field in the discharge of this type at moderate pressures can reach several hundred V/cm and leads to considerable changes in the kinetics of secondary electrons created in the process of propagation of the electron beam generated in the accelerating gap with a grid anode. Moving in the accelerating electric field toward the anode, secondary electrons create the so-called compensating current to the anode. The character of electron motion and the compensating current itself are determined by the ratio of the field strength to the concentration of atoms (E/n). The energy and angular spectra of secondary electrons are calculated by the Monte Carlo method for different ratios E/n of the electric field strength to the helium atom concentration. The motion of secondary electrons with threshold energy is studied for inelastic collisions of helium atoms and differential analysis is carried out of the collisional processes causing energy losses of electrons in helium for different E/n values. The mechanism of creation and accumulation of slow electrons as a result of inelastic collisions of secondary electrons with helium atoms and selective population of metastable states of helium atoms is considered. It is demonstrated that in a wide range of E/n values the motion of secondary electrons in the beam-type discharge flare has the character of drift. At E/n values characteristic for the discharge of the given type, the drift velocity of these electrons is calculated and compared with the available experimental data.

Demkin, V. P.; Mel'nichuk, S. V. [National Research Tomsk State University, 36, Lenin Ave., 634050 Tomsk (Russian Federation)

2014-09-15

305

Delayed expression of hpS2 and prolonged expression of CIP1/WAF1/SDI1 in human tumour cells irradiated with X-rays, fission neutrons or 1 GeV/nucleon Fe ions  

NASA Technical Reports Server (NTRS)

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.

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

306

A statistical rain attenuation prediction model with application to the advanced communication technology satellite project. Part 2: Theoretical development of a dynamic model and application to rain fade durations and tolerable control delays for fade countermeasures  

NASA Technical Reports Server (NTRS)

A dynamic rain attenuation prediction model is developed for use in obtaining the temporal characteristics, on time scales of minutes or hours, of satellite communication link availability. Analagous to the associated static rain attenuation model, which yields yearly attenuation predictions, this dynamic model is applicable at any location in the world that is characterized by the static rain attenuation statistics peculiar to the geometry of the satellite link and the rain statistics of the location. Such statistics are calculated by employing the formalism of Part I of this report. In fact, the dynamic model presented here is an extension of the static model and reduces to the static model in the appropriate limit. By assuming that rain attenuation is dynamically described by a first-order stochastic differential equation in time and that this random attenuation process is a Markov process, an expression for the associated transition probability is obtained by solving the related forward Kolmogorov equation. This transition probability is then used to obtain such temporal rain attenuation statistics as attenuation durations and allowable attenuation margins versus control system delay.

Manning, Robert M.

1987-01-01

307

Projecting Mid- and End-of-Century Climate Change in the Los Angeles Mountainous Region by a Combination of Dynamical and Statistical Downscaling Techniques  

NASA Astrophysics Data System (ADS)

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.

Sun, F.; Hall, A. D.; Walton, D.; Capps, S. B.; Reich, K.

2013-12-01

308

A combined dynamical and statistical downscaling technique to reduce biases in climate projections: an example for winter precipitation and snowpack in the western United States  

NASA Astrophysics Data System (ADS)

Large biases associated with climate projections are problematic when it comes to their regional application in the assessment of water resources and ecosystems. Here, we demonstrate a method that can reduce systematic biases in regional climate projections. The global and regional climate models employed to demonstrate the technique are the Community Climate System Model (CCSM) and the Weather Research and Forecasting (WRF) model. The method first utilized a statistical regression technique and a global reanalysis dataset to correct biases in the CCSM-simulated variables (e.g., temperature, geopotential height, specific humidity, and winds) that are subsequently used to drive the WRF model. The WRF simulations were conducted for the western United States and were driven with (a) global reanalysis, (b) original CCSM, and (c) bias-corrected CCSM data. The bias-corrected CCSM data led to a more realistic regional climate simulation of precipitation and associated atmospheric dynamics, as well as snow water equivalent (SWE), in comparison to the original CCSM-driven WRF simulation. Since most climate applications rely on existing global model output as the forcing data (i.e., they cannot re-run or change the global model), which often contain large biases, this method provides an effective and economical tool to reduce biases in regional climate downscaling simulations of water resource variables.

Li, R.; Wang, S.-Y.; Gillies, R. R.

2015-03-01

309

Examining the phase transition behavior of amphiphilic lipids in solution using statistical temperature molecular dynamics and replica-exchange Wang-Landau methods  

PubMed Central

Two different techniques – replica-exchange Wang-Landau (REWL) and statistical temperature molecular dynamics (STMD) – were applied to systematically study the phase transition behavior of self-assembling lipids as a function of temperature using an off-lattice lipid model. Both methods allow the direct calculation of the density of states with improved efficiency compared to the original Wang-Landau method. A 3-segment model of amphiphilic lipids solvated in water has been studied with varied particle interaction energies (?) and lipid concentrations. The phase behavior of the lipid molecules with respect to bilayer formation has been characterized through the calculation of the heat capacity as a function of temperature, in addition to various order parameters and general visual inspection. The simulations conducted by both methods can go to very low temperatures with the whole system exhibiting well-ordered structures. With optimized parameters, several bilayer phases are observed within the temperature range studied, including gel phase bilayers with frozen water, mixed water (i.e., frozen and liquid water), and liquid water, and a more fluid bilayer with liquid water. The results obtained from both methods, STMD and REWL, are consistently in excellent agreement with each other, thereby validating both the methods and the results. PMID:23927268

Gai, Lili; Vogel, Thomas; Maerzke, Katie A.; Iacovella, Christopher R.; Landau, David P.; Cummings, Peter T.; McCabe, Clare

2013-01-01

310

Statistical fluid dynamics: Unstable fingers  

NASA Astrophysics Data System (ADS)

This paper is the first in a series by the authors devoted to the study of fingers in fluid surfaces. Fingers are a form of surface instability which occur on many length scales. In particular, they may occur on length scales small relative to the natural dimensions of the problem; in this sense the instability is similar to turbulance. In the present study, the transition from stability to instability is determined by a critical value in a viscosity ratio. This series of papers is devoted to methods of accurate numerical computation. We find that the random choice method gives excellent resolution of fingered surfaces and discontinuities. Even an unstable interface, with three to four well developed fingers can be resolved on a coarse grid of 10 to 15 zones wide.

Glimm, J.; Marchesin, D.; McBryan, O.

1980-02-01

311

Statistics Tools  

NSDL National Science Digital Library

This collection of calculators, created by Thomas Kirkman of the College of Saint Bendict/Saint Joseph, allows users to perform a number of statistical applications. Each provides background on the procedure and an example. Users can compute descriptive statistics and perform t-tests, Chi-square tests, Kolmogorov-Smirnov tests, Fisher's Exact Test, contingency tables, ANOVA, and regression. This is a nice collection of useful applications for a statistics classroom.

Kirkman, Thomas

312

Symbolic Dynamic Programming Scott Sanner  

E-print Network

Symbolic Dynamic Programming Scott Sanner NICTA, Statistical Machine Learning Group, Canberra Relational Dynamic Programming, Dynamic Programming for Relational Domains, Relational Value Iteration Definition Symbolic dynamic programming is a generalization of the dynamic program- ming technique

Kersting, Kristian

313

Avalanche statistics of sand heaps  

SciTech Connect

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.

Buchholtz, V.; Poeschel, T. [Institut fuer Physik, Berlin (Germany)

1996-09-01

314

Morbidity statistics  

PubMed Central

This paper is based on an analysis of questionnaires sent to the health ministries of Member States of WHO asking for information about the extent, nature, and scope of morbidity statistical information. It is clear that most countries collect some statistics of morbidity and many countries collect extensive data. However, few countries relate their collection to the needs of health administrators for information, and many countries collect statistics principally for publication in annual volumes which may appear anything up to 3 years after the year to which they refer. The desiderata of morbidity statistics may be summarized as reliability, representativeness, and relevance to current health problems. PMID:5306722

Smith, Alwyn

1969-01-01

315

Multi-scale study of condensation in water jets using ellipsoidal-statistical Bhatnagar-Gross-Krook and molecular dynamics modeling.  

PubMed

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

Li, Zheng; Borner, Arnaud; Levin, Deborah A

2014-06-14

316

Multi-scale study of condensation in water jets using ellipsoidal-statistical Bhatnagar-Gross-Krook and molecular dynamics modeling  

NASA Astrophysics Data System (ADS)

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.

Li, Zheng; Borner, Arnaud; Levin, Deborah A.

2014-06-01

317

Statistical Diversions  

ERIC Educational Resources Information Center

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…

Petocz, Peter; Sowey, Eric

2008-01-01

318

Statistics Clinic  

NASA Technical Reports Server (NTRS)

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.

Feiveson, Alan H.; Foy, Millennia; Ploutz-Snyder, Robert; Fiedler, James

2014-01-01

319

Rainbow statistics  

E-print Network

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.

Michele Arzano; Dario Benedetti

2008-09-04

320

Statistics Indonesia  

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.

321

Mathematical Statistics  

NSDL National Science Digital Library

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.

Dudley, Richard

322

Statistical Mechanics  

Microsoft Academic Search

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

V. Jaksi ´; C.-A. Pillet

1937-01-01

323

Statistical survey of pitch angle distributions in core (0-50 eV) ions from Dynamics Explorer 1: Outflow in the auroral zone, polar cap, and cusp  

NASA Technical Reports Server (NTRS)

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).

Giles, B. L.; Chappell, C. R.; Moore, T. E.; Comfort, R. H.; Waite, J. H., Jr.

1994-01-01

324

Health Statistics  

MedlinePLUS

... which people are catching the flu, the average cost of a medical procedure. These are all types of ... statistics to see patterns of diseases in groups of people. This can help in ... ways to control diseases and deciding which diseases should be studied.

325

Statistics Investigations  

NSDL National Science Digital Library

This webpage contains statistics investigations in the form of word problems. The investigations are located on the left hand side of the page on the navigation bar: the links are "Recommended Investigations" and "Additional Investigations". Within each investigation there are additional links to external resources that can be used to solve or illustrate the problem.

2013-01-01

326

Algorithmic statistics  

Microsoft Academic Search

While Kolmogorov (1965, 1983) complexity is the accepted absolute measure of information content of an individual finite object, a similarly absolute notion is needed for the relation between an individual data sample and an individual model summarizing the information in the data, for example, a finite set (or probability distribution) where the data sample typically came from. The statistical theory

Peter Gacs; John Tromp; Paul Vitanyi

2001-01-01

327

Algorithmic statistics  

Microsoft Academic Search

While Kolmogorov complexity is the accepted absolute measure of information content of an individual finite object, a similarly absolute notion is needed for the relation between an individual data sample and an individual model summarizing the information in the data, for example, a finite set (or probability distribution) where the data sample typically came from. The statistical theory based on

Péter Gács; John Tromp; Paul M. B. Vitányi

2001-01-01

328

Statistical Engineering  

NSDL National Science Digital Library

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.

Annis, Charles

329

STATISTICS GROUP  

E-print Network

STATISTICS GROUP :: WEEK #1 Jordan Webster 19 October 2011 1 #12;19 October 2011 2 19 October 2011(x|, x0) = 1 /2 2/2+(x-x0)2 divergent divergent mass of resonance Table 1: some basic info for commonly

330

Statistical Java  

NSDL National Science Digital Library

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.

Anderson-Cook, C.

331

Statistical characterization of dislocation ensembles  

SciTech Connect

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.

El-Azab, A; Deng, J; Tang, M

2006-05-17

332

Learning Statistics By Doing Statistics  

NSDL National Science Digital Library

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.

Smith, Gary

333

CRITIQUING AND IMPROVING DATA USE FROM HIGH STAKES TESTS: UNDERSTANDING VARIATION AND DISTRIBUTION IN RELATION TO EQUITY USING DYNAMIC STATISTICS SOFTWARE  

Microsoft Academic Search

Executive Summary: This paper reveals how current approaches to data use by schools, even with disaggregation by subgroup, can fail to recognize the importance of the statistical concepts of variation and distribution in monitoring systemic progress of all students. A case study in which a high poverty, majority Hispanic urban school dismantled its Standards-based reform program after the school was

Jere Confrey; Katie Makar

334

Journal of Statistical Physics, Vol. 116, Nos. 5/6, September 2004 ( 2004) Of Dogs and Fleas: The Dynamics of N Uncoupled  

E-print Network

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

Nagler, Jan

335

Statistics I  

NSDL National Science Digital Library

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.

2013-06-21

336

Statistical Shorts  

NSDL National Science Digital Library

In this statistics and probability activity students must determine whether each statement is always true, sometimes true, sometimes false, or always false. Students must have a basic understanding of probability statements and the foundation for understanding mean, median, and mode in order to complete this activity for all twelve statements. In addition to the task, tips for getting started, possible solutions, a teacher resource page, and a printable page are provided.

NRICH

2013-01-01

337

Statistical Optics  

NASA Astrophysics Data System (ADS)

The Wiley Classics Library consists of selected books that have become recognized classics in their respective fields. With these new unabridged and inexpensive editions, Wiley hopes to extend the life of these important works by making them available to future generations of mathematicians and scientists. Currently available in the Series: T. W. Anderson The Statistical Analysis of Time Series T. S. Arthanari & Yadolah Dodge Mathematical Programming in Statistics Emil Artin Geometric Algebra Norman T. J. Bailey The Elements of Stochastic Processes with Applications to the Natural Sciences Robert G. Bartle The Elements of Integration and Lebesgue Measure George E. P. Box & Norman R. Draper Evolutionary Operation: A Statistical Method for Process Improvement George E. P. Box & George C. Tiao Bayesian Inference in Statistical Analysis R. W. Carter Finite Groups of Lie Type: Conjugacy Classes and Complex Characters R. W. Carter Simple Groups of Lie Type William G. Cochran & Gertrude M. Cox Experimental Designs, Second Edition Richard Courant Differential and Integral Calculus, Volume I RIchard Courant Differential and Integral Calculus, Volume II Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume I Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume II D. R. Cox Planning of Experiments Harold S. M. Coxeter Introduction to Geometry, Second Edition Charles W. Curtis & Irving Reiner Representation Theory of Finite Groups and Associative Algebras Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume I Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume II Cuthbert Daniel Fitting Equations to Data: Computer Analysis of Multifactor Data, Second Edition Bruno de Finetti Theory of Probability, Volume I Bruno de Finetti Theory of Probability, Volume 2 W. Edwards Deming Sample Design in Business Research

Goodman, Joseph W.

2000-07-01

338

Spike statistics  

E-print Network

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.

J. Mark Heinzle; Claes Uggla

2012-12-21

339

[Results of statistical analysis of the dynamics of ionizing radiation dose fields in the service module of the International Space Station in 2000-2012].  

PubMed

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

Mitrikas, V G

2014-01-01

340

Covariant Equilibrium Statistical Mechanics  

E-print Network

A manifest covariant equilibrium statistical mechanics is constructed starting with a 8N dimensional extended phase space which is reduced to the 6N physical degrees of freedom using the Poincare-invariant constrained Hamiltonian dynamics describing the micro-dynamics of the system. The reduction of the extended phase space is initiated forcing the particles on energy shell and fixing their individual time coordinates with help of invariant time constraints. The Liouville equation and the equilibrium condition are formulated in respect to the scalar global evolution parameter which is introduced by the time fixation conditions. The applicability of the developed approach is shown for both, the perfect gas as well as the real gas. As a simple application the canonical partition integral of the monatomic perfect gas is calculated and compared with other approaches. Furthermore, thermodynamical quantities are derived. All considerations are shrinked on the classical Boltzmann gas composed of massive particles and hence quantum effects are discarded.

E. Lehmann

2006-02-25

341

Dynamics of the D+ + H2 ? HD + H+ reaction at the low energy regime by means of a statistical quantum method  

NASA Astrophysics Data System (ADS)

The D+ +H2(v = 0, j = 0, 1) ? HD+H+ reaction has been investigated at the low energy regime by means of a statistical quantum mechanical (SQM) method. Reaction probabilities and integral cross sections (ICSs) between a collisional energy of 10-4 eV and 0.1 eV have been calculated and compared with previously reported results of a time independent quantum mechanical (TIQM) approach. The TIQM results exhibit a dense profile with numerous narrow resonances down to Ec ˜ 10-2 eV and for the case of H2(v = 0, j = 0) a prominent peak is found at ˜2.5 × 10-4 eV. The analysis at the state-to-state level reveals that this feature is originated in those processes which yield the formation of rotationally excited HD(v' = 0, j' > 0). The statistical predictions reproduce reasonably well the overall behaviour of the TIQM ICSs at the larger energy range (Ec ? 10-3 eV). Thermal rate constants are in qualitative agreement for the whole range of temperatures investigated in this work, 10-100 K, although the SQM values remain above the TIQM results for both initial H2 rotational states, j = 0 and 1. The enlargement of the asymptotic region for the statistical approach is crucial for a proper description at low energies. In particular, we find that the SQM method leads to rate coefficients in terms of the energy in perfect agreement with previously reported measurements if the maximum distance at which the calculation is performed increases noticeably with respect to the value employed to reproduce the TIQM results.

González-Lezana, Tomás; Honvault, Pascal; Scribano, Yohann

2013-08-01

342

Dynamics of the D{sup +}+ H{sub 2}? HD + H{sup +} reaction at the low energy regime by means of a statistical quantum method  

SciTech Connect

The D{sup +}+H{sub 2}(v= 0, j= 0, 1) ? HD+H{sup +} reaction has been investigated at the low energy regime by means of a statistical quantum mechanical (SQM) method. Reaction probabilities and integral cross sections (ICSs) between a collisional energy of 10{sup ?4} eV and 0.1 eV have been calculated and compared with previously reported results of a time independent quantum mechanical (TIQM) approach. The TIQM results exhibit a dense profile with numerous narrow resonances down to E{sub c}? 10{sup ?2} eV and for the case of H{sub 2}(v= 0, j= 0) a prominent peak is found at ?2.5 × 10{sup ?4} eV. The analysis at the state-to-state level reveals that this feature is originated in those processes which yield the formation of rotationally excited HD(v?= 0, j? > 0). The statistical predictions reproduce reasonably well the overall behaviour of the TIQM ICSs at the larger energy range (E{sub c}? 10{sup ?3} eV). Thermal rate constants are in qualitative agreement for the whole range of temperatures investigated in this work, 10–100 K, although the SQM values remain above the TIQM results for both initial H{sub 2} rotational states, j= 0 and 1. The enlargement of the asymptotic region for the statistical approach is crucial for a proper description at low energies. In particular, we find that the SQM method leads to rate coefficients in terms of the energy in perfect agreement with previously reported measurements if the maximum distance at which the calculation is performed increases noticeably with respect to the value employed to reproduce the TIQM results.

González-Lezana, Tomás [Instituto de Física Fundamental, IFF-CSIC, Serrano 123, 28006 Madrid (Spain)] [Instituto de Física Fundamental, IFF-CSIC, Serrano 123, 28006 Madrid (Spain); Honvault, Pascal [Lab. Interdisciplinaire Carnot de Bourgogne, UMR CNRS 6303, Univ. Bourgogne, 21078 Dijon Cedex, France and UFR Sciences et Techniques, Univ. de Franche-Comté, 25030 Besançon cedex (France)] [Lab. Interdisciplinaire Carnot de Bourgogne, UMR CNRS 6303, Univ. Bourgogne, 21078 Dijon Cedex, France and UFR Sciences et Techniques, Univ. de Franche-Comté, 25030 Besançon cedex (France); Scribano, Yohann [Lab. Univers et Particules de Montpellier, Univ. de Montpellier II, LUPM - UMR CNRS 5299, 34095 Montpellier Cedex (France)] [Lab. Univers et Particules de Montpellier, Univ. de Montpellier II, LUPM - UMR CNRS 5299, 34095 Montpellier Cedex (France)

2013-08-07

343

Statistical mechanics of the vacuum  

E-print Network

The vacuum is full of virtual particles which exist for short moments of time. In this paper we construct a chaotic model of vacuum fluctuations associated with a fundamental entropic field that generates an arrow of time. The dynamics can be physically interpreted in terms of fluctuating virtual momenta. This model leads to a generalized statistical mechanics that distinguishes fundamental constants of nature.

Christian Beck

2012-03-01

344

Statistics of multiple stars  

NASA Astrophysics Data System (ADS)

The statistics of stellar systems of multiplicity three and higher is reviewed. They are frequent, 0.15-0.25 of all stellar systems. Some 700 multiples are expected among the 3383 stars of spectral type F, G, and K within 50 pc, while only 76 of them are actually known. Many (if not all) close binaries have distant tertiary components, indicating that angular momentum exchange within multiple systems was probably critical in forming short-period binaries. The ratio of outer to inner periods in the best-studied nearby multiples and in low-mass pre-main sequence multiples does not exceed 104 at the formation epoch; larger ratios are produced by subsequent orbital evolution. All multiples with well-defined orbits are dynamically stable, the eccentricities of outer orbits obey the empirical stability limit P[out](1 - e[out])3/P[in] > 5 that is more strict than current theoretical limits. Relative orientation of orbits in triple stars shows some degree of alignment, especially in weakly-hierarchical systems. The statistics support the idea that most multiple stars originated from dynamical interactions in small clusters.

Tokovinin, A.

2004-08-01

345

Topics in Statistical Mechanics: The Foundations of Molecular Simulation  

E-print Network

Topics in Statistical Mechanics: The Foundations of Molecular Simulation J. Schofield/R. van ZonQuarrie, Statistical Mechanics · D. Frenkel and B. Smit, Understanding Molecular Dynamics: From Algorithms

Schofield, Jeremy

346

Estimability and simple dynamical analyses of range (range-rate range-difference) observations to artificial satellites. [laser range observations to LAGEOS using non-Bayesian statistics  

NASA Technical Reports Server (NTRS)

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.

Vangelder, B. H. W.

1978-01-01

347

Quantum particles from classical statistics  

E-print Network

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.

C. Wetterich

2010-02-11

348

Statistical ecology comes of age.  

PubMed

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

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

349

Statistical ecology comes of age  

PubMed Central

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

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

2014-01-01

350

MQSA National Statistics  

MedlinePLUS

... 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 ...

351

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...

352

Statistical description of nuclear break-up  

E-print Network

We present an overview of concepts and results obtained with statistical models in study of nuclear multifragmentation. Conceptual differences between statistical and dynamical approaches, and selection of experimental observables for identification of these processes, are outlined. New and perspective developments, like inclusion of in-medium modifications of the properties of hot primary fragments, are discussed. We list important applications of statistical multifragmentation in other fields of research.

A. S. Botvina; I. N. Mishustin

2005-10-27

353

Steady state statistics of driven diffusions  

E-print Network

Steady state statistics of driven diffusions Christian Maes a , Karel Netocn´y b , and Bram Wynants, nonequilibrium steady state, dynamical fluctuations 1 Introduction Thermodynamics already ceases to be exact information about the steady state statistics. In recent years there has been a revival of nonequilibrium

Maes, Christian

354

Full Counting Statistics of Spin Currents  

E-print Network

We discuss how to detect fluctuating spin currents and derive full counting statistics of electron spin transfers. It is interesting to consider several detectors in series that simultaneously monitor different components of the spins transferred. We have found that in general the statistics of the measurement outcomes cannot be explained with the projection postulate and essentially depends on the quantum dynamics of the detectors.

Antonio Di Lorenzo; Yuli V. Nazarov

2003-12-01

355

Determination of snow avalanche return periods using a tree-ring based reconstruction in the French Alps: cross validation with the predictions of a statistical-dynamical model  

NASA Astrophysics Data System (ADS)

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.

Schläppy, Romain; Eckert, Nicolas; Jomelli, Vincent; Grancher, Delphine; Brunstein, Daniel; Stoffel, Markus; Naaim, Mohamed

2013-04-01

356

Statistical approach for supernova matter  

E-print Network

We formulate a statistical model for description of nuclear composition and equation of state of stellar matter at subnuclear densities and temperature up to 20 MeV, which are expected during the collapse and explosion of massive stars. The model includes nuclear, electromagnetic and weak interactions between all kinds of particles, under condition of statistical equilibrium. We emphasize importance of realistic description of the nuclear composition for understanding stellar dynamics and nucleosynthesis. It is demonstrated that the experience accumulated in studies of nuclear multifragmentation reactions can be used for better modelling properties of stellar medium.

A. S. Botvina; I. N. Mishustin

2008-11-16

357

Statistical study of the night-time F-layer dynamics at the magnetic equator in West Africa during the solar minimum period 1995-1997  

NASA Astrophysics Data System (ADS)

In this paper, we report on the night-time equatorial F-layer height behaviour at Korhogo (9.2° N, 5° W; 2.4° S dip lat), Ivory Coast, in the West African sector during the solar minimum period 1995-1997. The data were collected from quarter-hourly ionograms of an Ionospheric Prediction Service (IPS) 42-type vertical sounder. The main focus of this work was to study the seasonal changes in the F-layer height and to clarify the equinox transition process recently evidenced at Korhogo during 1995, the year of declining solar flux activity. The F-layer height was found to vary strongly with time, with up to three main phases. The night-to-night variability of these morphological phases was then analysed. The early post-sunset slow rise, commonly associated with rapid chemical recombination processes in the bottom part of the F layer, remained featureless and was observed regardless of the date. By contrast, the following event, either presented like the post-sunset height peak associated with the evening E × B drift, or was delayed to the midnight sector, thus involving another mechanism. The statistical analysis of the occurrence of these events throughout the solar minimum period 1995-1997 revealed two main F-layer height patterns, each characteristic of a specific season. The one with the post-sunset height peak was associated with the northern winter period, whereas the other, with the midnight height peak, characterized the northern summer period. The transition process from one pattern to the other took place during the equinox periods and was found to last only a few weeks. We discuss these results in the light of earlier works.

Tanoh, K. S.; Adohi, B. J.-P.; Coulibaly, I. S.; Amory-Mazaudier, C.; Kobea, A. T.; Assamoi, P.

2015-01-01

358

The application of statistical mechanics on the study of glassy behaviors in transportation networks and dynamics in models of financial markets  

NASA Astrophysics Data System (ADS)

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.

Yeung, Chi Ho

359

Statistical trajectory models for phonetic recognition  

Microsoft Academic Search

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

William David Goldenthal; James R. Glass

1994-01-01

360

Use of remote sensing, geographic information systems, and spatial statistics to assess spatio-temporal population dynamics of Heterodera glycines and soybean yield quantity and quality  

NASA Astrophysics Data System (ADS)

Soybean, Glycine max (L.) Merr., is an important source of oil and protein worldwide, and soybean cyst nematode (SCN), Heterodera glycines, is among the most important yield-limiting factors in soybean production worldwide. Early detection of SCN is difficult because soybean plants infected by SCN often do not exhibit visible symptoms. It was hypothesized, however, that reflectance data obtained by remote sensing from soybean canopies may be used to detect plant stress caused by SCN infection. Moreover, reflectance measurements may be related to soybean growth and yield. Two field experiments were conducted from 2000 to 2002 to study the relationships among reflectance data, quantity and quality of soybean yield, and SCN population densities. The best relationships between reflectance and the quantity of soybean grain yield occurred when reflectance data were obtained late August to early September. Similarly, reflectance was best related to seed oil and seed protein content and seed size when measured during late August/early September. Grain quality-reflectance relationships varied spatially and temporally. Reflectance measured early or late in the season had the best relationships with SCN population densities measured at planting. Soil properties likely affected reflectance measurements obtained at the beginning of the season and somehow may have been related to SCN population densities at planting. Reflectance data obtained at the end of the growing season likely was affected by early senescence of SCN-infected soybeans. Spatio-temporal aspects of SCN population densities in both experiments were assessed using spatial statistics and regression analyses. In the 2000 and 2001 growing seasons, spring-to-fall changes in SCN population densities were best related to SCN population densities at planting for both experiments. However, within-season changes in SCN population densities were best related to SCN population densities at harvest for both experiments in 2002. Variograms were fitted to the data to describe the spatial characteristics of SCN population densities in both fields at planting and at harvest from 2000 to 2003 and these parameters varied within seasons and during overwinter periods in both experiments. Distinct relationships between temporal and spatial changes in SCN population densities were not detected.

Moreira, Antonio Jose De Araujo

361

Statistical Thermodynamics of Biomembranes  

PubMed Central

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

Devireddy, Ram V.

2010-01-01

362

Statistical physics ""Beyond equilibrium  

SciTech Connect

The scientific challenges of the 21st century will increasingly involve competing interactions, geometric frustration, spatial and temporal intrinsic inhomogeneity, nanoscale structures, and interactions spanning many scales. We will focus on a broad class of emerging problems that will require new tools in non-equilibrium statistical physics and that will find application in new material functionality, in predicting complex spatial dynamics, and in understanding novel states of matter. Our work will encompass materials under extreme conditions involving elastic/plastic deformation, competing interactions, intrinsic inhomogeneity, frustration in condensed matter systems, scaling phenomena in disordered materials from glasses to granular matter, quantum chemistry applied to nano-scale materials, soft-matter materials, and spatio-temporal properties of both ordinary and complex fluids.

Ecke, Robert E [Los Alamos National Laboratory

2009-01-01

363

Renyi statistics in equilibrium statistical mechanics  

E-print Network

The Renyi statistics in the canonical and microcanonical ensembles is examined in the general case and in particular for the ideal gas. In the microcanonical ensemble the Renyi statistics is equivalent with the Boltzmann-Gibbs statistics. By the exact analytical results for the ideal gas, it is shown that in the canonical ensemble in the thermodynamic limit the Renyi statistics is also equivalent with the Boltzmann-Gibbs statistics. Furthermore it satisfies the requirements of the equilibrium thermodynamics, i.e. the thermodynamical potential of the statistical ensemble is a homogeneous function of degree 1 of its extensive variables of state. We conclude that the Renyi statistics duplicates the thermodynamical relations stemming from the Boltzmann-Gibbs statistics in the thermodynamical limit.

A. S. Parvan; T. S. Biro

2009-10-16

364

Statistical Ensemble of Large Eddy Simulations  

NASA Technical Reports Server (NTRS)

A statistical ensemble of large eddy simulations (LES) is run simultaneously for the same flow. The information provided by the different large scale velocity fields is used to propose an ensemble averaged version of the dynamic model. This produces local model parameters that only depend on the statistical properties of the flow. An important property of the ensemble averaged dynamic procedure is that it does not require any spatial averaging and can thus be used in fully inhomogeneous flows. Also, the ensemble of LES's provides statistics of the large scale velocity that can be used for building new models for the subgrid-scale stress tensor. The ensemble averaged dynamic procedure has been implemented with various models for three flows: decaying isotropic turbulence, forced isotropic turbulence, and the time developing plane wake. It is found that the results are almost independent of the number of LES's in the statistical ensemble provided that the ensemble contains at least 16 realizations.

Carati, Daniele; Rogers, Michael M.; Wray, Alan A.; Mansour, Nagi N. (Technical Monitor)

2001-01-01

365

9/6/10 9:41 PMAPS -51st Annual Meeting of the APS Division of Plasma Physics -Event -...onal Heating: Unsteady Dynamics and Scaling in Statistical Steady State Page 1 of 2http://meetings.aps.org/Meeting/DPP09/Event/109258  

E-print Network

extended to 3D. Random photospheric footpoint motion is applied to obtain converged average coronal heating://meetings.aps.org/Meeting/DPP09/Event/109258 scale 3D simulations, and discuss differences with previous scaling laws. To cite Heating: Unsteady Dynamics and Scaling in Statistical Steady State Page 1 of 2http

Ng, Chung-Sang

366

Neuroendocrine Tumor: Statistics  

MedlinePLUS

... 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 ...

367

Statistical properties of cosmological billiards  

NASA Astrophysics Data System (ADS)

Belinski, Khalatnikov, and Lifshitz pioneered the study of the statistical properties of the never-ending oscillatory behavior (among successive Kasner epochs) of the geometry near a spacelike singularity. We show how the use of a “cosmological billiard” description allows one to refine and deepen the understanding of these statistical properties. Contrary to previous treatments, we do not quotient the dynamics by its discrete symmetry group (of order 6), thereby uncovering new phenomena, such as correlations between the successive billiard corners in which the oscillations take place. Starting from the general integral invariants of Hamiltonian systems, we show how to construct invariant measures for various projections of the cosmological-billiard dynamics. In particular, we exhibit, for the first time, a (non-normalizable) invariant measure on the “Kasner circle” which parametrizes the exponents of successive Kasner epochs. Finally, we discuss the relation between: (i) the unquotiented dynamics of the Bianchi-IX (a, b, c or mixmaster) model; (ii) its quotienting by the group of permutations of (a, b, c); and (iii) the billiard dynamics that arose in recent studies suggesting the hidden presence of Kac-Moody symmetries in cosmological billiards.

Damour, Thibault; Lecian, Orchidea Maria

2011-02-01

368

Statistical properties of cosmological billiards  

SciTech Connect

Belinski, Khalatnikov, and Lifshitz pioneered the study of the statistical properties of the never-ending oscillatory behavior (among successive Kasner epochs) of the geometry near a spacelike singularity. We show how the use of a 'cosmological billiard' description allows one to refine and deepen the understanding of these statistical properties. Contrary to previous treatments, we do not quotient the dynamics by its discrete symmetry group (of order 6), thereby uncovering new phenomena, such as correlations between the successive billiard corners in which the oscillations take place. Starting from the general integral invariants of Hamiltonian systems, we show how to construct invariant measures for various projections of the cosmological-billiard dynamics. In particular, we exhibit, for the first time, a (non-normalizable) invariant measure on the 'Kasner circle' which parametrizes the exponents of successive Kasner epochs. Finally, we discuss the relation between: (i) the unquotiented dynamics of the Bianchi-IX (a, b, c or mixmaster) model; (ii) its quotienting by the group of permutations of (a, b, c); and (iii) the billiard dynamics that arose in recent studies suggesting the hidden presence of Kac-Moody symmetries in cosmological billiards.

Damour, Thibault [Institut des Hautes Etudes Scientifiques, 35, route de Chartres, 91440 Bures-sur-Yvette (France); ICRANet, Pescara (Italy); Lecian, Orchidea Maria [Institut des Hautes Etudes Scientifiques, 35, route de Chartres, 91440 Bures-sur-Yvette (France); ICRANet, Pescara (Italy); APC, UMR 7164 du CNRS, Universite Paris 7, 10, rue A. Domon et L. Duquet, 75205 Paris Cedex 13 (France)

2011-02-15

369

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.

370

Statistical Reference Datasets  

National Institute of Standards and Technology Data Gateway

Statistical Reference Datasets (Web, free access)   The Statistical Reference Datasets is also supported by the Standard Reference Data Program. The purpose of this project is to improve the accuracy of statistical software by providing reference datasets with certified computational results that enable the objective evaluation of statistical software.

371

STATISTICAL METHODS INFECTIOUS METHODS  

E-print Network

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

372

Statistical Parsing Inside Algorithm  

E-print Network

Parsing · Review · Statistical Parsing · SCFG · Inside Algorithm · Outside Algorithm NLP NLP statistical parsing 2 language and is often viewed as an important prerequisite for building A syntactic tree NLP statistical parsing 3 #12;Parsing Another syntactic tree NLP statistical parsing 4 #12

Ageno, Alicia

373

Statistical Reference Datasets  

NSDL National Science Digital Library

A project designed to improve the accuracy of statistical software by providing reference datasets with certified computational results that enable the objective evaluation of statistical software. Dataset archives (Analysis of Variance, Linear Regression, Nonlinear Regression, and Univariate Summary Statistics); background information; related resources and links; FAQs. A project component of of NIST's Tools for Evaluating Mathematical and Statistical Software.

374

Statistical Applets: Animated Exercise  

NSDL National Science Digital Library

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.

Duckworth, William

375

Dynamic Optimization  

NASA Technical Reports Server (NTRS)

We distinguish static and dynamic optimization of programs: whereas static optimization modifies a program before runtime and is based only on its syntactical structure, dynamic optimization is based on the statistical properties of the input source and examples of program execution. Explanation-based generalization is a commonly used dynamic optimization method, but its effectiveness as a speedup-learning method is limited, in part because it fails to separate the learning process from the program transformation process. This paper describes a dynamic optimization technique called a learn-optimize cycle that first uses a learning element to uncover predictable patterns in the program execution and then uses an optimization algorithm to map these patterns into beneficial transformations. The technique has been used successfully for dynamic optimization of pure Prolog.

Laird, Philip

1992-01-01

376

Statistics 5126 Introduction to Applied Statistics  

E-print Network

program. Instructions on obtaining and using R will be provided in class. Course Policy Classroom to the class on time. Opening and closing the classroom door in the middle of a class cause distractionStatistics 5126 Introduction to Applied Statistics Fall 2012 Course Information Class Meeting Time

Barbu, Adrian

377

Equilibrium statistical mechanics for incomplete nonextensive statistics  

E-print Network

The incomplete nonextensive statistics in the canonical and microcanonical ensembles is explored in the general case and in a particular case for the ideal gas. By exact analytical results for the ideal gas it is shown that taking the thermodynamic limit, with $z=q/(1-q)$ being an extensive variable of state, the incomplete nonextensive statistics satisfies the requirements of equilibrium thermodynamics. The thermodynamical potential of the statistical ensemble is a homogeneous function of the first degree of the extensive variables of state. In this case, the incomplete nonextensive statistics is equivalent to the usual Tsallis statistics. If $z$ is an intensive variable of state, i.e. the entropic index $q$ is a universal constant, the requirements of the equilibrium thermodynamics are violated.

A. S. Parvan; T. S. Biro

2010-03-29

378

Statistical dynamics of early river networks  

NASA Astrophysics Data System (ADS)

Based on local erosion rule and fluctuations in rainfall, geology and parameters of a river channel, a generalized Langevin equation is proposed to describe the random prolongation of a river channel. This equation is transformed into the Fokker-Plank equation to follow the early evolution of a river network and the variation of probability distribution of channel lengths. The general solution of the equation is in the product form of two terms. One term is in power form and the other is in exponent form. This distribution shows a complete history of a river network evolving from its infancy to “adulthood”). The infancy is characterized by the Gaussian distribution of the channel lengths, while the adulthood is marked by a power law distribution of the channel lengths. The variation of the distribution from the Gaussian to the power law displays a gradual developing progress of the river network. The distribution of basin areas is obtained by means of Hack's law. These provide us with new understandings towards river networks.

Wang, Xu-Ming; Wang, Peng; Zhang, Ping; Hao, Rui; Huo, Jie

2012-10-01

379

BAYESIAN DYNAMIC MODELLING Department of Statistical Science  

E-print Network

. Some key examples that underlie much of what is applied in forecasting and time series analysis.1 Introduction Bayesian time series and forecasting is a very broad field and any attempt at other than a very selectively notes some key models and ideas, leavened with extracts from a few time series analysis

West, Mike

380

Accelerated molecular dynamics methods  

SciTech Connect

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.

Perez, Danny [Los Alamos National Laboratory

2011-01-04

381

Statistical theory of cubic Langmuir turbulence  

NASA Technical Reports Server (NTRS)

The cubic direct interaction approximation is applied to a truncated (in Fourier space) version of the cubically nonlinear Schroedinger equation model of Langmuir physics. The results are compared (in the three-mode case) to those for an ensemble of numerical solutions of the dynamical equations with 10,000 different sets of Gaussianly distributed initial conditions. In the undriven, undamped case, the statistical theory (but not the ensemble) evolves to a state of thermal equilibrium. In the driven, damped case, the statistical theory appears to evolve to a state close to that corresponding to one of the limit cycles of the dynamical equations.

Sun, G.-Z.; Nicholson, D. R.; Rose, H. A.

1985-01-01

382

A statistical mechanical problem?  

PubMed Central

The problem of deriving the processes of perception and cognition or the modes of behavior from states of the brain appears to be unsolvable in view of the huge numbers of elements involved. However, neural activities are not random, nor independent, but constrained to form spatio-temporal patterns, and thanks to these restrictions, which in turn are due to connections among neurons, the problem can at least be approached. The situation is similar to what happens in large physical ensembles, where global behaviors are derived by microscopic properties. Despite the obvious differences between neural and physical systems a statistical mechanics approach is almost inescapable, since dynamics of the brain as a whole are clearly determined by the outputs of single neurons. In this paper it will be shown how, starting from very simple systems, connectivity engenders levels of increasing complexity in the functions of the brain depending on specific constraints. Correspondingly levels of explanations must take into account the fundamental role of constraints and assign at each level proper model structures and variables, that, on one hand, emerge from outputs of the lower levels, and yet are specific, in that they ignore irrelevant details. PMID:25228891

Costa, Tommaso; Ferraro, Mario

2014-01-01

383

Statistical regimes of random laser fluctuations  

SciTech Connect

Statistical fluctuations of the light emitted from amplifying random media are studied theoretically and numerically. The characteristic scales of the diffusive motion of light lead to Gaussian or power-law (Levy) distributed fluctuations depending on external control parameters. In the Levy regime, the output pulse is highly irregular leading to huge deviations from a mean-field description. Monte Carlo simulations of a simplified model which includes the population of the medium demonstrate the two statistical regimes and provide a comparison with dynamical rate equations. Different statistics of the fluctuations helps to explain recent experimental observations reported in the literature.

Lepri, Stefano [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy); Cavalieri, Stefano [Dipartimento di Fisica, Universita di Firenze, via G. Sansone 1, I-50019 Sesto Fiorentino (Italy); European Laboratory for Non-linear Spectroscopy, via N. Carrara 1, I-50019 Sesto Fiorentino (Italy); Oppo, Gian-Luca [SUPA and Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow, G4 0NG, Scotland (United Kingdom); Wiersma, Diederik S. [European Laboratory for Non-linear Spectroscopy, via N. Carrara 1, I-50019 Sesto Fiorentino (Italy); BEC-INFM Center, I-38050 Povo, Trento (Italy)

2007-06-15

384

Bayes Estimation Bayes Statistical Thinking  

E-print Network

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

Zhang, Li-Xin

385

Introductory statistical mechanics for electron storage rings  

SciTech Connect

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.

Jowett, J.M.

1986-07-01

386

Statistics for Chemists: Exercises  

NSDL National Science Digital Library

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.

Wehrens, Ron

387

Pneumocystis Pneumonia Statistics  

MedlinePLUS

... 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 & ...

388

Uterine Cancer Statistics  

MedlinePLUS

... 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 ...

389

Sleep Data and Statistics  

MedlinePLUS

... Sleep and Sleep Disorders Share Compartir Data and Statistics Behavioral Risk Factor Surveillance System ( BRFSS ) Population : Adults ... Podcasts and Sleep e-Cards Fact Sheets Data & Statistics Projects and Partners Resources Events File Formats Help: ...

390

Immigration and Naturalization Statistics  

NSDL National Science Digital Library

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."

United States. Immigration and Naturalization Service.

391

Environment for statistical computing  

Microsoft Academic Search

This paper is a short exposition on the current state of art as far as statistical software is concerned. The main aims are to take a look at current tendencies in information technologies for statistics and data analysis, especially for describing selected programs and systems.We start with statistical packages, i.e. a suite of computer programs that are specialized in statistical analysis,

Jaromír Antoch

2008-01-01

392

Statistical quality management  

NASA Astrophysics Data System (ADS)

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.

Vanderlaan, Paul

1992-10-01

393

Statistics for Applications  

NSDL National Science Digital Library

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.

Panchenko, Dmitry

394

Giovanni Gallavotti STATISTICAL MECHANICS  

E-print Network

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

Roma "La Sapienza", Università di

395

Giovanni Gallavotti STATISTICAL MECHANICS  

E-print Network

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

Roma "La Sapienza", Università di

396

Statistical Mechanics its applications  

E-print Network

Statistical Mechanics and its applications Dr A. Alavi Part II Chemistry 2007-2008 1 #12;I. INTRODUCTION Statistical Mechanics is concerned with how to describe the behaviour of systems containing large, and how this is done, as well as its theoretical justification, is the subject of Statistical Mechanics. A

Alavi, Ali

397

FISHERY STATISTICS UNITED STATES  

E-print Network

of the landings, by species Relative value of the landings, by species. Seed oyster fisheryFISHERY STATISTICS OF THE UNITED STATES 1974 STATISTICAL DIGEST NO. 68 Prepared by Data Management. These statistics include data on the volume and value of landed catches, employment, quantity of gear operated

398

Minnesota Health Statistics 1988.  

ERIC Educational Resources Information Center

This document comprises the 1988 annual statistical report of the Minnesota Center for Health Statistics. After introductory technical notes on changes in format, sources of data, and geographic allocation of vital events, an overview is provided of vital health statistics in all areas. Thereafter, separate sections of the report provide tables…

Minnesota State Dept. of Health, St. Paul.

399

Glossary of Statistical Terms  

Cancer.gov

Defines common statistical terms, NCI terminology, and the five key statistical measures of cancer: incidence, mortality, survival, prevalence, and lifetime risk. NCI monitors these cancer statistics to assess progress and to identify population subgroups and geographic areas in which cancer control efforts need to be concentrated.

400

Statistical Abstract: USA Statistics in Brief  

NSDL National Science Digital Library

This web page, authored by the United State Census Bureau, contains statistics about the current population. Some of these statistics include: sex, age, state population, births, deaths, households, housing, construction, education, government, social welfare, law enforcement, employment, income, poverty, prices, energy, transportation, communications, agriculture, business, finance and foreign commerce. As demonstrated this is a fairly comprehensive data set. The sets are contained in both html or Excel format.

401

Statistical Applets: Two Variable Statistical Calculator  

NSDL National Science Digital Library

Created by Duckworth, McCabe, Moore and Sclove for W.H. Freeman and Co., this applet calculates correlation and regression information and displays graphs for a number of data sets from the text "��Practice of Business Statistics."� Users can also enter their own data. Even though brief, this interactive resource is still valuable for an introductory statistics course.

Duckworth, William

402

Statistical Convergence and Convergence in Statistics  

E-print Network

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.

Mark Burgin; Oktay Duman

2006-12-07

403

Statistical mechanics of violent relaxation  

NASA Technical Reports Server (NTRS)

We propose a functional that is extremized through violent relaxation. It is based on the Ansatz that the wave-particle scattering during violent dynamical processes can be approximated as a sequence of discrete scattering events that occur near a particle's perigalacticon. This functional has an extremum whose structure closely resembles that of spheroidal stellar systems such as elliptical galaxies. The results described here, therefore, provide a simple framework for understanding the physical nature of violent relaxation and support the view that galaxies are structured in accord with fundamental statistical principles.

Spergel, David N.; Hernquist, Lars

1992-01-01

404

STATWIZ - AN ELECTRONIC STATISTICAL TOOL (ABSTRACT)  

EPA Science Inventory

StatWiz is a web-based, interactive, and dynamic statistical tool for researchers. It will allow researchers to input information and/or data and then receive experimental design options, or outputs from data analysis. StatWiz is envisioned as an expert system that will walk rese...

405

Statistical analysis of slow crack growth experiments  

Microsoft Academic Search

A common approach for the determination of slow crack growth (SCG) parameters are the static and dynamic loading method. Since materials with small Weibull module show a large variability in strength, a correct statistical analysis of the data is indispensable. In this work we propose the use of the Maximum Likelihood Method and a Baysian Analysis, which, in contrast to

Tobias Pfingsten; Karsten Glien

2006-01-01

406

UNIVERSITY OF CALIFORNIA, SANTA CRUZ DEPARTMENT OF APPLIED MATHEMATICS AND STATISTICS  

E-print Network

UNIVERSITY OF CALIFORNIA, SANTA CRUZ DEPARTMENT OF APPLIED MATHEMATICS AND STATISTICS On-Going Lecturer Pool The Department of Applied Mathematics and Statistics in the Baskin School of Engineering of applied mathematics and statistics: calculus, elementary statistics, control theory, fluid dynamics

California at Santa Cruz, University of

407

Statistical physics of active processes in cells  

NASA Astrophysics Data System (ADS)

Simple concepts from statistical physics are discussed to describe the transduction of chemical energy of a fuel to mechanical work on the molecular level. Such approaches can characterize general physical features of motor proteins that generate forces in the cell cytoskeleton. In integrated cellular systems such as cilia and hair bundles, cytoskeletal filaments and motors form complex structures and interact in large numbers. In such systems the interplay of filaments and motors can lead to emergent dynamic behaviors such as oscillating collective modes or to wave-like patterns. We discuss general aspects of such dynamic states and relate them to the dynamics of cytoskeletal structures in cells.

Jülicher, Frank

2006-09-01

408

Random paths and current fluctuations in nonequilibrium statistical mechanics  

SciTech Connect

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.

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

409

Social and economic sustainability of urban systems: comparative analysis of metropolitan statistical areas in Ohio, USA  

EPA Science Inventory

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...

410

1 Statistics Statistics plays an important role throughout society, providing  

E-print Network

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

Vertes, Akos

411

The Relationship Between Statistics Anxiety and Attitudes Toward Statistics  

Microsoft Academic Search

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

Recep KOÇAK; Paul F. ZELHART

2007-01-01

412

Statistics and Data Analysis  

NSDL National Science Digital Library

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.

Abebe, Asheber

413

Statistics and Graphing  

NSDL National Science Digital Library

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.

Matt Laposata

414

Statistics for Ecologists  

NSDL National Science Digital Library

This Website, maintained by Carlos Herrera of the Donana Biological Station in Seville, Spain, is "a collection of links to sites with mathematical and statistical material (software, documents) which may be useful to ecologists and evolutionary ecologists." Organized into eight sections, the site points users to resources from Ecologically-oriented software to General Statistical Libraries. For graduate students and researchers alike, this statistics resource is sure to come in handy.

415

Heat equation and Non-equilibrium (Classical) Statistical Mechanics  

E-print Network

. Now assume (Fourier Law) j = k u, then tu = div(k u) 2 #12;But Ludwig Eduard Boltzmann (1844 ­1906-equilibrium Statistical Mechanics and Dynamical Systems (Sinai, Ruelle, Gallavotti, .....) Kinetic limit and Boltzmann

Liverani, Carlangelo

416

Federal Law Enforcement Statistics  

NSDL National Science Digital Library

Supplies census statistics about federal employees with law enforcement authority. Provides additional information about the functionality, budget, expenditures, and staffing of federal crime labs and police departments.

U.S. Department of Justice

417

Cosmetic Plastic Surgery Statistics  

MedlinePLUS

... of Medical Specialties-recognized boards. © ASPS, 2013 2012 Cosmetic Plastic Surgery Statistics Cosmetic Procedure Trends COSMETIC SURGICAL PROCEDURES201220112000 % CHANGE 2012 vs. 2011 % CHANGE 2012 ...

418

Simple Interactive Statistical Analysis  

NSDL National Science Digital Library

Simple Interactive Statistical Analysis (SISA), designed by a research consultant in the Netherlands, "allows you to do statistical analysis directly on the Internet." The program will calculate a variety of statistical procedures, including T-Tests, Poisson Distributions, and other calculations. The ability to perform analysis online provides users an opportunity to assess the software, which is also for sale. The Guide to Procedures provides helpful explanations of the different statistical procedures and guidelines for deciding on the appropriate procedure and filling out the calculation form. Numerous spreadsheets are also available to download.

419

Statistics Open Textbook  

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.

420

Agricultural Statistics 1997  

NSDL National Science Digital Library

The latest volume of the United States Department of Agriculture's Agricultural Statistics is a detailed compilation of statistical charts and tables covering all aspects of the US agricultural economy. Most of the available tables aare based on a short (three and ten year) time series, and many are updated through 1996. The previous two Agricultural Statistics volumes are also available, and tables from the 1995-6 version can be viewed in plain text comma separated values (CSV) format for easier statistical manipulation. Data users can also request CSV formatted tables for the 1997 volume.

1997-01-01

421

Statistical distribution sampling  

NASA Technical Reports Server (NTRS)

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.

Johnson, E. S.

1975-01-01

422

DEPARTMENT OF STATISTICS Statistics 101 Spring 2012  

E-print Network

: "Statistics for Business: Decision Making and Analysis" by Robert A. Stine and Dean P. Foster. You not tend to email on a regular basis. Your primary source for questions and answers will be the web is using webCafe. You can gain access by going to http://webcafe.wharton.upenn.edu and following the link

Plotkin, Joshua B.

423

Statistical Inference Using Extreme Order Statistics  

Microsoft Academic Search

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.

James Pickands III

1975-01-01

424

Stellar Evolution A Statistical Model  

E-print Network

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

van Dyk, David

425

Steady state statistics of driven di#usions  

E-print Network

Steady state statistics of driven di#usions Christian Maes a , Karel NetoŸcnâ??y b , and Bram Wynants#usion, nonequilibrium steady state, dynamical fluctuations 1 Introduction Thermodynamics already ceases to be exact information about the steady state statistics. In recent years there has been a revival of nonequilibrium

Maes, Christian

426

Transportation Statistics Annual Report  

NSDL National Science Digital Library

The US Department of Transportation's Bureau of Transportation Statistics provides Transportation Statistics Annual Report (TSAR), a companion to NTS, in Adobe Acrobat (.pdf) format, from 1994 to the present at this time. Transportation in the United States: A Review, summarizing these four reports, is also available.

427

Multidimensional Visual Statistical Learning  

ERIC Educational Resources Information Center

Recent studies of visual statistical learning (VSL) have demonstrated that statistical regularities in sequences of visual stimuli can be automatically extracted, even without intent or awareness. Despite much work on this topic, however, several fundamental questions remain about the nature of VSL. In particular, previous experiments have not…

Turk-Browne, Nicholas B.; Isola, Phillip J.; Scholl, Brian J.; Treat, Teresa A.

2008-01-01

428

Transforms in Statistics  

Microsoft Academic Search

It is not an overstatement to say that statistics is based on various transformations of data. Basic statistical summaries such as the sample mean, variance, z-scores, histograms, etc., are all transformed data. Some more advanced summaries, such as principal components, periodograms, empirical characteristic functions, etc., are also examples of transformed data. To give a just coverage of transforms utilized in

Brani Vidakovic

2004-01-01

429

ROOT Statistical Software  

E-print Network

Advanced mathematical and statistical computational methods are required by the LHC experiments for analyzing their data. Some of these methods are provided by the ROOT project, a C++ Object Oriented framework for large scale data handling applications. We review the current mathematical and statistical classes present in ROOT, emphasizing the recent developments.

Moneta, Lorenzo; Brun, R; Kreshuk, Anna

2008-01-01

430

JSTOR: Statistical Science  

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.

431

Statistical multifragmentation of nuclei  

Microsoft Academic Search

This review is devoted to the Statistical Multifragmentation Model (SMFM) developed in Copenhagen more than 10 years ago and widely used now for interpreting experimental data on multiple fragment production in different nuclear reactions. The model is based on the assumption of simultaneous break-up of a thermalized nuclear system. Basic principles and different realizations of the statistical approach to the

J. P. Bondorf; A. S. Botvina; A. S. Iljinov; I. N. Mishustin; K. Sneppen

1995-01-01

432

Defence Statistics 1998  

NSDL National Science Digital Library

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.

Great Britain. Parliament. House of Commons. Library.

1998-01-01

433

Application Statistics 1987.  

ERIC Educational Resources Information Center

Summary statistics on application and registration patterns of applicants wishing to pursue full-time study in first-year places in Ontario universities (for the fall of 1987) are given. Data on registrations were received indirectly from the universities as part of their annual submission of USIS/UAR enrollment data to Statistics Canada and MCU.…

Council of Ontario Universities, Toronto.

434

Explorations in Statistics: Power  

ERIC Educational Resources Information Center

Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This fifth installment of "Explorations in Statistics" revisits power, a concept fundamental to the test of a null hypothesis. Power is the probability that we reject the null hypothesis when it is false. Four things affect…

Curran-Everett, Douglas

2010-01-01

435

Statistical Science Web  

NSDL National Science Digital Library

This site contains links in several statistical categories, including other meta-sites (catalogs), universities, statistics departments, software, journals, data sets, methodology, conferences, and teaching, among others. It has an Australian flavor, but is international in scope. Gordon K. Smyth, Research scientist and mathematician, maintains this site.

1998-01-01

436

Some More Statistical Exercises  

NSDL National Science Digital Library

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?

Langan, James F.

437

Finite Order Statistic Experiment  

NSDL National Science Digital Library

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.

Kyle Siegrist

438

Weakly sufficient quantum statistics  

E-print Network

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.

Katarzyna Lubnauer; Andrzej ?uczak; Hanna Pods?dkowska

2009-11-23

439

Deconstructing Statistical Analysis  

ERIC Educational Resources Information Center

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…

Snell, Joel

2014-01-01

440

Fast Statistical Alignment  

Microsoft Academic Search

We describe a new program for the alignment of multiple biological sequences that is both statistically motivated and fast enough for problem sizes that arise in practice. Our Fast Statistical Alignment program is based on pair hidden Markov models which approximate an insertion\\/deletion process on a tree and uses a sequence annealing algorithm to combine the posterior probabilities estimated from

Robert K. Bradley; Adam Roberts; Michael Smoot; Sudeep Juvekar; Jaeyoung Do; Colin Dewey; Ian Holmes; Lior Pachter

2009-01-01

441

Water Quality Statistics  

ERIC Educational Resources Information Center

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…

Hodgson, Ted; Andersen, Lyle; Robison-Cox, Jim; Jones, Clain

2004-01-01

442

Issues in Labor Statistics  

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.

443

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.

444

DISABILITY STATISTICS CENTER  

EPA Science Inventory

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...

445

Statistical Applets: Confidence Intervals  

NSDL National Science Digital Library

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.

Duckworth, William

446

Explorations in Statistics: Regression  

ERIC Educational Resources Information Center

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.…

Curran-Everett, Douglas

2011-01-01

447

Explorations in Statistics: Correlation  

ERIC Educational Resources Information Center

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…

Curran-Everett, Douglas

2010-01-01

448

Overhead Image Statistics  

SciTech Connect

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.

Vijayaraj, Veeraraghavan [ORNL; Cheriyadat, Anil M [ORNL; Bhaduri, Budhendra L [ORNL; Vatsavai, Raju [ORNL; Bright, Eddie A [ORNL

2008-01-01

449

Statistical Decision Functions  

Microsoft Academic Search

The foundations of a general theory of statistical decision functions, including the classical non-sequential case as well as the sequential case, was discussed by the author in a previous publication [3]. Several assumptions made in [3] appear, however, to be unnecessarily restrictive (see conditions 1-7, pp. 297 in [3]). These assumptions, moreover, are not always fulfilled for statistical problems in

Abraham Wald

1949-01-01

450

Careless Statistics Costs Lives  

E-print Network

Careless Statistics Costs Lives A tragi-comedy of errors of the first and second kind, both one (1982): 50% of published medical statistics is wrong. Today: about 15% This talk: #12;· intra the patient and the nursing staff are asked to register any potential side effect or adverse event

Gill, Richard D.

451

Statistical Mapping by Computer.  

ERIC Educational Resources Information Center

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…

Utano, Jack J.

452

Statistical Applets: Probability  

NSDL National Science Digital Library

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.

Duckworth, William

453

Economic Statistics Briefing Room  

NSDL National Science Digital Library

While more than a few curmudgeons have offered their honest opinions about statistics, we here at the Scout Report like to provide our readers with the facts and let them decide on their own. Fortunately, there are sites like the Economic Statistics Briefing Room provided by the White House. Here, visitors can peruse sections that offer information on income, output, transportation, and prices. Drawing on the research and statistical databases of several dozen federal agencies (including the National Agricultural Statistics Services), visitors can view tables and charts that offer such timely material as crude oil prices, poverty rates, and household wealth. Within each section, visitors can view summary statistics, and then if they wish, they can proceed to the homepage of the agency that provided each set of information.

454

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.

455

Statistical laws in linguistics  

E-print Network

Zipf's law is just one out of many universal laws proposed to describe statistical regularities in language. Here we review and critically discuss how these laws can be statistically interpreted, fitted, and tested (falsified). The modern availability of large databases of written text allows for tests with an unprecedent statistical accuracy and also a characterization of the fluctuations around the typical behavior. We find that fluctuations are usually much larger than expected based on simplifying statistical assumptions (e.g., independence and lack of correlations between observations).These simplifications appear also in usual statistical tests so that the large fluctuations can be erroneously interpreted as a falsification of the law. Instead, here we argue that linguistic laws are only meaningful (falsifiable) if accompanied by a model for which the fluctuations can be computed (e.g., a generative model of the text). The large fluctuations we report show that the constraints imposed by linguistic laws...

Altmann, Eduardo G

2015-01-01

456

STATS: Statistical Assessment Service  

NSDL National Science Digital Library

The Statistical Assessment Service (STATS) is a "non-partisan, non-profit research organization that serves as a resource for journalists by providing timely and well-researched analysis of current statistical and scientific disputes." STATS offers articles written by statistical experts in two formats -- selections from columns published in the national press and a monthly online newsletter, VitalSTATS. STATS also features a searchable archive of previous publications. The standard STATS article addresses some statistical information that has recently been widely distributed by the press and considers the potential or already-committed fallacies of reasoning the data is subject to in the hands of headline-seeking journalists. Visitors may find the Dubious Data Awards of 2000 particularly amusing as they give the top ten "silliest, most misleading stories of the New Millennium." Some people say statistics lie, but STATS offers itself as their Joe Friday, insisting that we take from them "just the facts."

457

More Intelligent Statistical Software and Statistical Expert Systems: Future Directions  

Microsoft Academic Search

Statistical computer programs are becoming increasingly accessible to people with limited statistical training. More intelligent statistical software is clearly needed. In this article, new or improved offerings—ranging from computer-based indexes of the literature to expert statistical systems—are discussed and illustrated. Three general levels of statistical software are differentiated: computerized statistical answering and referral services, expert guidance embedded in statistical programs,

Gerald J. Hahn

1985-01-01

458

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.

459

Lifetime statistics in chaotic dielectric microresonators  

SciTech Connect

We discuss the statistical properties of lifetimes of electromagnetic quasibound states in dielectric microresonators with fully chaotic ray dynamics. Using the example of a resonator of stadium geometry, we find that a recently proposed random-matrix model very well describes the lifetime statistics of long-lived resonances, provided that two effective parameters are appropriately renormalized. This renormalization is linked to the formation of short-lived resonances, a mechanism also known from the fractal Weyl law and the resonance-trapping phenomen0008.

Schomerus, Henning; Wiersig, Jan; Main, Joerg [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Institut fuer Theoretische Physik, Universitaet Magdeburg, Postfach 4120, D-39016 Magdeburg (Germany); 1. Institut fuer Theoretische Physik, Universitaet Stuttgart, 70550 Stuttgart (Germany)

2009-05-15