WorldWideScience

Sample records for time variability due

  1. Protecting chips against hold time violations due to variability

    CERN Document Server

    Neuberger, Gustavo; Reis, Ricardo

    2013-01-01

    With the development of Very-Deep Sub-Micron technologies, process variability is becoming increasingly important and is a very important issue in the design of complex circuits. Process variability is the statistical variation of process parameters, meaning that these parameters do not have always the same value, but become a random variable, with a given mean value and standard deviation. This effect can lead to several issues in digital circuit design.The logical consequence of this parameter variation is that circuit characteristics, as delay and power, also become random variables. Becaus

  2. Multi-Objective Flexible Flow Shop Scheduling Problem Considering Variable Processing Time due to Renewable Energy

    Directory of Open Access Journals (Sweden)

    Xiuli Wu

    2018-03-01

    Full Text Available Renewable energy is an alternative to non-renewable energy to reduce the carbon footprint of manufacturing systems. Finding out how to make an alternative energy-efficient scheduling solution when renewable and non-renewable energy drives production is of great importance. In this paper, a multi-objective flexible flow shop scheduling problem that considers variable processing time due to renewable energy (MFFSP-VPTRE is studied. First, the optimization model of the MFFSP-VPTRE is formulated considering the periodicity of renewable energy and the limitations of energy storage capacity. Then, a hybrid non-dominated sorting genetic algorithm with variable local search (HNSGA-II is proposed to solve the MFFSP-VPTRE. An operation and machine-based encoding method is employed. A low-carbon scheduling algorithm is presented. Besides the crossover and mutation, a variable local search is used to improve the offspring’s Pareto set. The offspring and the parents are combined and those that dominate more are selected to continue evolving. Finally, two groups of experiments are carried out. The results show that the low-carbon scheduling algorithm can effectively reduce the carbon footprint under the premise of makespan optimization and the HNSGA-II outperforms the traditional NSGA-II and can solve the MFFSP-VPTRE effectively and efficiently.

  3. Analysis of Modal Travel Time Variability Due to Mesoscale Ocean Structure

    National Research Council Canada - National Science Library

    Smith, Amy

    1997-01-01

    .... First, for an open ocean environment away from strong boundary currents, the effects of randomly phased linear baroclinic Rossby waves on acoustic travel time are shown to produce a variable overall...

  4. Maximum Lateness Scheduling on Two-Person Cooperative Games with Variable Processing Times and Common Due Date

    OpenAIRE

    Liu, Peng; Wang, Xiaoli

    2017-01-01

    A new maximum lateness scheduling model in which both cooperative games and variable processing times exist simultaneously is considered in this paper. The job variable processing time is described by an increasing or a decreasing function dependent on the position of a job in the sequence. Two persons have to cooperate in order to process a set of jobs. Each of them has a single machine and their processing cost is defined as the minimum value of maximum lateness. All jobs have a common due ...

  5. Time-dependent excitation and ionization modelling of absorption-line variability due to GRB080310

    DEFF Research Database (Denmark)

    Vreeswijk, P.M.; De Cia, A.; Jakobsson, P.

    2013-01-01

    .42743. To estimate the rest-frame afterglow brightness as a function of time, we use a combination of the optical VRI photometry obtained by the RAPTOR-T telescope array, which is presented in this paper, and Swift's X-Ray Telescope (XRT) observations. Excitation alone, which has been successfully applied...

  6. Maximum Lateness Scheduling on Two-Person Cooperative Games with Variable Processing Times and Common Due Date

    Directory of Open Access Journals (Sweden)

    Peng Liu

    2017-01-01

    Full Text Available A new maximum lateness scheduling model in which both cooperative games and variable processing times exist simultaneously is considered in this paper. The job variable processing time is described by an increasing or a decreasing function dependent on the position of a job in the sequence. Two persons have to cooperate in order to process a set of jobs. Each of them has a single machine and their processing cost is defined as the minimum value of maximum lateness. All jobs have a common due date. The objective is to maximize the multiplication of their rational positive cooperative profits. A division of those jobs should be negotiated to yield a reasonable cooperative profit allocation scheme acceptable to them. We propose the sufficient and necessary conditions for the problems to have positive integer solution.

  7. Pulse timing for cataclysmic variables

    International Nuclear Information System (INIS)

    Chester, T.J.

    1979-01-01

    It is shown that present pulse timing measurements of cataclysmic variables can be explained by models of accretion disks in these systems, and thus such measurements can constrain disk models. The model for DQ Her correctly predicts the amplitude variation of the continuum pulsation and can also perhaps explain the asymmetric amplitude of the pulsed lambda4686 emission line. Several other predictions can be made from the model. In particular, if pulse timing measurements that resolve emission lines both in wavelength and in binary phase can be made, the projected orbital radius of the white dwarf could be deduced

  8. variability of rainwater quality due to roof characteristics

    African Journals Online (AJOL)

    water. Although, some people typically consume collected rainwater without any type of ... variability of rain water quality due to roof characteristics was investigated using ... coverage of potable water, water supply still lags ... in getting projects executed; lack of adequate ... deterioration and its effects on health are scarce.

  9. Measured spatial variability of beach erosion due to aeolian processes.

    NARCIS (Netherlands)

    de Vries, S.; Verheijen, A.H.; Hoonhout, B.M.; Vos, S.E.; Cohn, Nicholas; Ruggiero, P; Aagaard, T.; Deigaard, R.; Fuhrman, D.

    2017-01-01

    This paper shows the first results of measured spatial variability of beach erosion due to aeolian processes during the recently conducted SEDEX2 field experiment at Long Beach, Washington, U.S.A.. Beach erosion and sedimentation were derived using series of detailed terrestrial LIDAR measurements

  10. Time-adjusted variable resistor

    Science.gov (United States)

    Heyser, R. C.

    1972-01-01

    Timing mechanism was developed effecting extremely precisioned highly resistant fixed resistor. Switches shunt all or portion of resistor; effective resistance is varied over time interval by adjusting switch closure rate.

  11. Estimation of power system variability due to wind power

    NARCIS (Netherlands)

    Papaefthymiou, G.; Verboomen, J.; Van der Sluis, L.

    2007-01-01

    The incorporation of wind power generation to the power system leads to an increase in the variability of the system power flows. The assessment of this variability is necessary for the planning of the necessary system reinforcements. For the assessment of this variability, the uncertainty in the

  12. Travel time variability and rational inattention

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Jiang, Gege

    2017-01-01

    This paper sets up a rational inattention model for the choice of departure time for a traveler facing random travel time. The traveler chooses how much information to acquire about the travel time out-come before choosing departure time. This reduces the cost of travel time variability compared...

  13. Additive measures of travel time variability

    DEFF Research Database (Denmark)

    Engelson, Leonid; Fosgerau, Mogens

    2011-01-01

    This paper derives a measure of travel time variability for travellers equipped with scheduling preferences defined in terms of time-varying utility rates, and who choose departure time optimally. The corresponding value of travel time variability is a constant that depends only on preference...... parameters. The measure is unique in being additive with respect to independent parts of a trip. It has the variance of travel time as a special case. Extension is provided to the case of travellers who use a scheduled service with fixed headway....

  14. Can time be a discrete dynamical variable

    International Nuclear Information System (INIS)

    Lee, T.D.

    1983-01-01

    The possibility that time can be regarded as a discrete dynamical variable is examined through all phases of mechanics: from classical mechanics to nonrelativistic quantum mechanics, and to relativistic quantum field theories. (orig.)

  15. Variability of the contrail radiative forcing due to crystal shape

    Science.gov (United States)

    Markowicz, K. M.; Witek, M. L.

    2011-12-01

    The aim of this study is to examine the influence of particles' shape and particles' optical properties on the contrail radiative forcing. Contrail optical properties in the shortwave and longwave range are derived using a ray-tracing geometric method and the discrete dipole approximation method, respectively. Both methods present good correspondence of the single scattering albedo and the asymmetry parameter in a transition range (3-7μm). We compare optical properties defined following simple 10 crystals habits randomly oriented: hexagonal plates, hexagonal columns with different aspect ratio, and spherical. There are substantial differences in single scattering properties between ten crystal models investigated here (e.g. hexagonal columns and plates with different aspect ratios, spherical particles). The single scattering albedo and the asymmetry parameter both vary up to 0.1 between various crystal shapes. Radiative forcing calculations were performed using a model which includes an interface between the state-of-the-art radiative transfer model Fu-Liou and databases containing optical properties of the atmosphere and surface reflectance and emissivity. This interface allows to determine radiative fluxes in the atmosphere and to estimate the contrail radiative forcing for clear- and all-sky (including natural clouds) conditions for various crystal shapes. The Fu-Liou code is fast and therefore it is suitable for computing radiative forcing on a global scale. At the same time it has sufficiently good accuracy for such global applications. A noticeable weakness of the Fu-Liou code is that it does not take into account the 3D radiative effects, e.g. cloud shading and horizontal. Radiative transfer model calculations were performed at horizontal resolution of 5x5 degree and time resolution of 20 min during day and 3 h during night. In order to calculate a geographic distribution of the global and annual mean contrail radiative forcing, the contrail cover must be

  16. Travel time variability and airport accessibility

    NARCIS (Netherlands)

    Koster, P.R.; Kroes, E.P.; Verhoef, E.T.

    2011-01-01

    We analyze the cost of access travel time variability for air travelers. Reliable access to airports is important since the cost of missing a flight is likely to be high. First, the determinants of the preferred arrival times at airports are analyzed. Second, the willingness to pay (WTP) for

  17. Infection due to Mycobacterium bovis in common variable immunodeficiency

    Directory of Open Access Journals (Sweden)

    Diana Andrea Herrera-Sánchez

    2015-02-01

    Full Text Available Common variable immunodeficiency (CVID is an heterogeneous group of disorders characterized by impaired antibody production. It shows a wide spectrum of manifestations including severe and recurrent respiratory infections (Streptococcus pneumoniae, Haemophilus and gastrointestinal (Campylobacter jejuni, rotavirus and Giardia lamblia. Viral infections caused by herpes zoster, cytomegalovirus (CMV and hepatitis C are rare. The opportunistic agents such as CMV, Pneumocystis jirovecii, cryptococcus and atypical mycobacteria have been reported as isolated cases. This paper reports the case of a 38-year-old female patient, who began six years before with weight loss of 7 kg in six months, fatigue, weakness, sweating, fever and abdominal pain. Furthermore, patient had intestinal obstruction and abdominal CT showed mesenteric lymph growth. The mesenteric lymph node biopsy revealed positives Mycobacterium PCR, Ziehl-Neelsen staining and culture for M. bovis. In the laparotomy postoperative period was complicated with nosocomial pneumonia, requiring mechanical ventilation and tracheostomy. Two years later, she developed right renal abscess that required surgical drainage, once again with a positive culture for Mycobacterium bovis. She was referred to highly specialized hospital and we documented panhypogammaglobulinemia and lymphopenia. Secondary causes of hypogammaglobulinemia were ruled out and common variable immunodeficiency (CVID was confirmed, we started IVIG replacement. Four years later she developed mixed cellularity Hodgkin’s lymphoma. Until today she continues with IVIG and chemotherapy. This report of a patient with CVID and Mycobacterium bovis infection, a unusual association, shows the cellular immunity susceptibility in this immunodeficiency, additional to the humoral defect.

  18. Public transport travel time and its variability

    OpenAIRE

    Mazloumi Shomali, Ehsan

    2017-01-01

    Executive Summary Public transport agencies around the world are constantly trying to improve the performance of their service, and to provide passengers with a more reliable service. Two major measures to evaluate the performance of a transit system include travel time and travel time variability. Information on these two measures provides operators with a capacity to identify the problematic locations in a transport system and improve operating plans. Likewise, users can benefit through...

  19. Travel time variability and airport accessibility

    OpenAIRE

    Koster, P.R.; Kroes, E.P.; Verhoef, E.T.

    2010-01-01

    This discussion paper resulted in a publication in Transportation Research Part B: Methodological (2011). Vol. 45(10), pages 1545-1559. This paper analyses the cost of access travel time variability for air travelers. Reliable access to airports is important since it is likely that the cost of missing a flight is high. First, the determinants of the preferred arrival times at airports are analyzed, including trip purpose, type of airport, flight characteristics, travel experience, type of che...

  20. Attributing uncertainty in streamflow simulations due to variable inputs via the Quantile Flow Deviation metric

    Science.gov (United States)

    Shoaib, Syed Abu; Marshall, Lucy; Sharma, Ashish

    2018-06-01

    Every model to characterise a real world process is affected by uncertainty. Selecting a suitable model is a vital aspect of engineering planning and design. Observation or input errors make the prediction of modelled responses more uncertain. By way of a recently developed attribution metric, this study is aimed at developing a method for analysing variability in model inputs together with model structure variability to quantify their relative contributions in typical hydrological modelling applications. The Quantile Flow Deviation (QFD) metric is used to assess these alternate sources of uncertainty. The Australian Water Availability Project (AWAP) precipitation data for four different Australian catchments is used to analyse the impact of spatial rainfall variability on simulated streamflow variability via the QFD. The QFD metric attributes the variability in flow ensembles to uncertainty associated with the selection of a model structure and input time series. For the case study catchments, the relative contribution of input uncertainty due to rainfall is higher than that due to potential evapotranspiration, and overall input uncertainty is significant compared to model structure and parameter uncertainty. Overall, this study investigates the propagation of input uncertainty in a daily streamflow modelling scenario and demonstrates how input errors manifest across different streamflow magnitudes.

  1. Sources of variability and systematic error in mouse timing behavior.

    Science.gov (United States)

    Gallistel, C R; King, Adam; McDonald, Robert

    2004-01-01

    In the peak procedure, starts and stops in responding bracket the target time at which food is expected. The variability in start and stop times is proportional to the target time (scalar variability), as is the systematic error in the mean center (scalar error). The authors investigated the source of the error and the variability, using head poking in the mouse, with target intervals of 5 s, 15 s, and 45 s, in the standard procedure, and in a variant with 3 different target intervals at 3 different locations in a single trial. The authors conclude that the systematic error is due to the asymmetric location of start and stop decision criteria, and the scalar variability derives primarily from sources other than memory.

  2. Response of orthotropic micropolar elastic medium due to time ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    namic response of anisotropic continuum has received the attention of ... linear theory of micropolar elasticity and bending of orthotropic micropolar ... medium due to time harmonic concentrated load, the continuum is divided into two half-.

  3. Induced voltage due to time-dependent magnetisation textures

    International Nuclear Information System (INIS)

    Kudtarkar, Santosh Kumar; Dhadwal, Renu

    2010-01-01

    We determine the induced voltage generated by spatial and temporal magnetisation textures (inhomogeneities) in metallic ferromagnets due to the spin diffusion of non-equilibrium electrons. Using time dependent semi-classical theory as formulated in Zhang and Li and the drift-diffusion model of transport it is shown that the voltage generated depends critically on the difference in the diffusion constants of up and down spins. Including spin relaxation results in a crucial contribution to the induced voltage. We also show that the presence of magnetisation textures results in the modification of the conductivity of the system. As an illustration, we calculate the voltage generated due to a time dependent field driven helimagnet by solving the Landau-Lifshitz equation with Gilbert damping and explicitly calculate the dependence on the relaxation and damping parameters.

  4. Increased timing variability in schizophrenia and bipolar disorder.

    Directory of Open Access Journals (Sweden)

    Amanda R Bolbecker

    Full Text Available Theoretical and empirical evidence suggests that impaired time perception and the neural circuitry underlying internal timing mechanisms may contribute to severe psychiatric disorders, including psychotic and mood disorders. The degree to which alterations in temporal perceptions reflect deficits that exist across psychosis-related phenotypes and the extent to which mood symptoms contribute to these deficits is currently unknown. In addition, compared to schizophrenia, where timing deficits have been more extensively investigated, sub-second timing has been studied relatively infrequently in bipolar disorder. The present study compared sub-second duration estimates of schizophrenia (SZ, schizoaffective disorder (SA, non-psychotic bipolar disorder (BDNP, bipolar disorder with psychotic features (BDP, and healthy non-psychiatric controls (HC on a well-established time perception task using sub-second durations. Participants included 66 SZ, 37 BDNP, 34 BDP, 31 SA, and 73 HC who participated in a temporal bisection task that required temporal judgements about auditory durations ranging from 300 to 600 milliseconds. Timing variability was significantly higher in SZ, BDP, and BDNP groups compared to healthy controls. The bisection point did not differ across groups. These findings suggest that both psychotic and mood symptoms may be associated with disruptions in internal timing mechanisms. Yet unexpected findings emerged. Specifically, the BDNP group had significantly increased variability compared to controls, but the SA group did not. In addition, these deficits appeared to exist independent of current symptom status. The absence of between group differences in bisection point suggests that increased variability in the SZ and bipolar disorder groups are due to alterations in perceptual timing in the sub-second range, possibly mediated by the cerebellum, rather than cognitive deficits.

  5. Enhancement of Transistor-to-Transistor Variability Due to Total Dose Effects in 65-nm MOSFETs

    CERN Document Server

    Gerardin, S; Cornale, D; Ding, L; Mattiazzo, S; Paccagnella, A; Faccio, F; Michelis, S

    2015-01-01

    We studied device-to-device variations as a function of total dose in MOSFETs, using specially designed test structures and procedures aimed at maximizing matching between transistors. Degradation in nMOSFETs is less severe than in pMOSFETs and does not show any clear increase in sample-to-sample variability due to the exposure. At doses smaller than 1 Mrad( SiO2) variability in pMOSFETs is also practically unaffected, whereas at very high doses-in excess of tens of Mrad( SiO2)-variability in the on-current is enhanced in a way not correlated to pre-rad variability. The phenomenon is likely due to the impact of random dopant fluctuations on total ionizing dose effects.

  6. Commuters’ valuation of travel time variability in Barcelona

    OpenAIRE

    Javier Asensio; Anna Matas

    2007-01-01

    The value given by commuters to the variability of travel times is empirically analysed using stated preference data from Barcelona (Spain). Respondents are asked to choose between alternatives that differ in terms of cost, average travel time, variability of travel times and departure time. Different specifications of a scheduling choice model are used to measure the influence of various socioeconomic characteristics. Our results show that travel time variability.

  7. First-Passage-Time Distribution for Variable-Diffusion Processes

    Science.gov (United States)

    Barney, Liberty; Gunaratne, Gemunu H.

    2017-05-01

    First-passage-time distribution, which presents the likelihood of a stock reaching a pre-specified price at a given time, is useful in establishing the value of financial instruments and in designing trading strategies. First-passage-time distribution for Wiener processes has a single peak, while that for stocks exhibits a notable second peak within a trading day. This feature has only been discussed sporadically—often dismissed as due to insufficient/incorrect data or circumvented by conversion to tick time—and to the best of our knowledge has not been explained in terms of the underlying stochastic process. It was shown previously that intra-day variations in the market can be modeled by a stochastic process containing two variable-diffusion processes (Hua et al. in, Physica A 419:221-233, 2015). We show here that the first-passage-time distribution of this two-stage variable-diffusion model does exhibit a behavior similar to the empirical observation. In addition, we find that an extended model incorporating overnight price fluctuations exhibits intra- and inter-day behavior similar to those of empirical first-passage-time distributions.

  8. Characterizing Uncertainty In Electrical Resistivity Tomography Images Due To Subzero Temperature Variability

    Science.gov (United States)

    Herring, T.; Cey, E. E.; Pidlisecky, A.

    2017-12-01

    Time-lapse electrical resistivity tomography (ERT) is used to image changes in subsurface electrical conductivity (EC), e.g. due to a saline contaminant plume. Temperature variation also produces an EC response, which interferes with the signal of interest. Temperature compensation requires the temperature distribution and the relationship between EC and temperature, but this relationship at subzero temperatures is not well defined. The goal of this study is to examine how uncertainty in the subzero EC/temperature relationship manifests in temperature corrected ERT images, especially with respect to relevant plume parameters (location, contaminant mass, etc.). First, a lab experiment was performed to determine the EC of fine-grained glass beads over a range of temperatures (-20° to 20° C) and saturations. The measured EC/temperature relationship was then used to add temperature effects to a hypothetical EC model of a conductive plume. Forward simulations yielded synthetic field data to which temperature corrections were applied. Varying the temperature/EC relationship used in the temperature correction and comparing the temperature corrected ERT results to the synthetic model enabled a quantitative analysis of the error of plume parameters associated with temperature variability. Modeling possible scenarios in this way helps to establish the feasibility of different time-lapse ERT applications by quantifying the uncertainty associated with parameter(s) of interest.

  9. Spot Welding Characterizations With Time Variable

    International Nuclear Information System (INIS)

    Abdul Hafid; Pinitoyo, A.; History; Paidjo, Andryansyah; Sagino, Sudarmin; Tamzil, M.

    2001-01-01

    For obtain spot welding used effective data, this research is made, so that time operational of machine increasing. Welding parameters are material classification, electrical current, and weld time. All of the factors are determined welding quality. If the plate more thick, the time must be longer when the current constant. Another factor as determined welding quality are surface condition of electrode, surface condition of weld material, and material classifications. In this research, the weld machine type IP32A2 VI (110 V), Rivoira trademark is characterized

  10. The new Toyota variable valve timing and lift system

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, K.; Fuwa, N.; Yoshihara, Y. [Toyota Motor Corporation (Japan); Hori, K. [Toyota Boshoku Corporation (Japan)

    2007-07-01

    A continuously variable valve timing (duration and phase) and lift system was developed. This system was applied to the valvetrain of a new 2.0L L4 engine (3ZRFAE) for the Japanese market. The system has rocker arms, which allow continuously variable timing and lift, situated between a conventional roller-rocker arm and the camshaft, an electromotor actuator to drive it and a phase mechanism for intake and exhaust camshafts (Dual VVT-i). The rocking center of the rocker arm is stationary, and the axial linear motion of a helical spline changes the initial phase of the rocker arm which varies the timing and lift. The linear motion mechanism uses an original planetary roller screw and is driven by a brushless motor with a built-in electric control unit. Since the rocking center and the linear motion helical spline center coincide, a compact cylinder head design was possible, and the cylinder head is a common design with a conventional engine. Since the ECU controls intake valve duration and timing, a fuel economy gain of maximum 10% (depending on driving condition) is obtained by reducing light to medium load pumping losses. Also intake efficiency was maximized throughout the speed range, resulting in a power gain of 10%. Further, HC emissions were reduced due to increased air speed at low valve lift. (orig.)

  11. Trends and Variability of Global Fire Emissions Due To Historical Anthropogenic Activities

    Science.gov (United States)

    Ward, Daniel S.; Shevliakova, Elena; Malyshev, Sergey; Rabin, Sam

    2018-01-01

    Globally, fires are a major source of carbon from the terrestrial biosphere to the atmosphere, occurring on a seasonal cycle and with substantial interannual variability. To understand past trends and variability in sources and sinks of terrestrial carbon, we need quantitative estimates of global fire distributions. Here we introduce an updated version of the Fire Including Natural and Agricultural Lands model, version 2 (FINAL.2), modified to include multiday burning and enhanced fire spread rate in forest crowns. We demonstrate that the improved model reproduces the interannual variability and spatial distribution of fire emissions reported in present-day remotely sensed inventories. We use FINAL.2 to simulate historical (post-1700) fires and attribute past fire trends and variability to individual drivers: land use and land cover change, population growth, and lightning variability. Global fire emissions of carbon increase by about 10% between 1700 and 1900, reaching a maximum of 3.4 Pg C yr-1 in the 1910s, followed by a decrease to about 5% below year 1700 levels by 2010. The decrease in emissions from the 1910s to the present day is driven mainly by land use change, with a smaller contribution from increased fire suppression due to increased human population and is largest in Sub-Saharan Africa and South Asia. Interannual variability of global fire emissions is similar in the present day as in the early historical period, but present-day wildfires would be more variable in the absence of land use change.

  12. Is Reaction Time Variability in ADHD Mainly at Low Frequencies?

    Science.gov (United States)

    Karalunas, Sarah L.; Huang-Pollock, Cynthia L.; Nigg, Joel T.

    2013-01-01

    Background: Intraindividual variability in reaction times (RT variability) has garnered increasing interest as an indicator of cognitive and neurobiological dysfunction in children with attention deficit hyperactivity disorder (ADHD). Recent theory and research has emphasized specific low-frequency patterns of RT variability. However, whether…

  13. Response of ENSO amplitude to global warming in CESM large ensemble: uncertainty due to internal variability

    Science.gov (United States)

    Zheng, Xiao-Tong; Hui, Chang; Yeh, Sang-Wook

    2018-06-01

    El Niño-Southern Oscillation (ENSO) is the dominant mode of variability in the coupled ocean-atmospheric system. Future projections of ENSO change under global warming are highly uncertain among models. In this study, the effect of internal variability on ENSO amplitude change in future climate projections is investigated based on a 40-member ensemble from the Community Earth System Model Large Ensemble (CESM-LE) project. A large uncertainty is identified among ensemble members due to internal variability. The inter-member diversity is associated with a zonal dipole pattern of sea surface temperature (SST) change in the mean along the equator, which is similar to the second empirical orthogonal function (EOF) mode of tropical Pacific decadal variability (TPDV) in the unforced control simulation. The uncertainty in CESM-LE is comparable in magnitude to that among models of the Coupled Model Intercomparison Project phase 5 (CMIP5), suggesting the contribution of internal variability to the intermodel uncertainty in ENSO amplitude change. However, the causations between changes in ENSO amplitude and the mean state are distinct between CESM-LE and CMIP5 ensemble. The CESM-LE results indicate that a large ensemble of 15 members is needed to separate the relative contributions to ENSO amplitude change over the twenty-first century between forced response and internal variability.

  14. Enhancement of Continuous Variable Entanglement in Four-Wave Mixing due to Atomic Memory Effects

    International Nuclear Information System (INIS)

    Yu-Zhu, Zhu; Xiang-Ming, Hu; Fei, Wang; Jing-Yan, Li

    2010-01-01

    We explore the effects of atomic memory on quantum correlations of two-mode light fields from four-wave mixing. A three-level atomic system in Λ configuration is considered, in which the atomic relaxation times are comparable to or longer than the cavity relaxation times and thus there exists the atomic memory. The quantum correlation spectrum in the output is calculated without the adiabatic elimination of atomic variables. It is shown that the continuous variable entanglement is enhanced over a wide range of the normalized detuning in the intermediate and bad cavity cases compared with the good cavity case. In some situations more significant enhancement occurs at sidebands

  15. Pulsar timing residuals due to individual non-evolving gravitational wave sources

    International Nuclear Information System (INIS)

    Tong Ming-Lei; Zhao Cheng-Shi; Yan Bao-Rong; Yang Ting-Gao; Gao Yu-Ping

    2014-01-01

    The pulsar timing residuals induced by gravitational waves from non-evolving single binary sources are affected by many parameters related to the relative positions of the pulsar and the gravitational wave sources. We will analyze the various effects due to different parameters. The standard deviations of the timing residuals will be calculated with a variable parameter fixing a set of other parameters. The orbits of the binary sources will be generally assumed to be elliptical. The influences of different eccentricities on the pulsar timing residuals will also be studied in detail. We find that the effects of the related parameters are quite different, and some of them display certain regularities

  16. Enhanced biennial variability in the Pacific due to Atlantic capacitor effect.

    Science.gov (United States)

    Wang, Lei; Yu, Jin-Yi; Paek, Houk

    2017-03-20

    The El Niño-Southern Oscillation (ENSO) and the variability in the Pacific subtropical highs (PSHs) have major impacts on social and ecological systems. Here we present an Atlantic capacitor effect mechanism to suggest that the Atlantic is a key pacemaker of the biennial variability in the Pacific including that in ENSO and the PSHs during recent decades. The 'charging' (that is, ENSO imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and 'discharging' (that is, the NTA SST triggering the following ENSO via a subtropical teleconnection mechanism) processes alternate, generating the biennial rhythmic changes in the Pacific. Since the early 1990s, a warmer Atlantic due to the positive phase of Atlantic multidecadal oscillation and global warming trend has provided more favourable background state for the Atlantic capacitor effect, giving rise to enhanced biennial variability in the Pacific that may increase the occurrence frequency of severe natural hazard events.

  17. Variability of textural features in FDG PET images due to different acquisition modes and reconstruction parameters

    DEFF Research Database (Denmark)

    Galavis, P.E.; Hollensen, Christian; Jallow, N.

    2010-01-01

    Background. Characterization of textural features (spatial distributions of image intensity levels) has been considered as a tool for automatic tumor segmentation. The purpose of this work is to study the variability of the textural features in PET images due to different acquisition modes...... reconstruction parameters. Lesions were segmented on a default image using the threshold of 40% of maximum SUV. Fifty different texture features were calculated inside the tumors. The range of variations of the features were calculated with respect to the average value. Results. Fifty textural features were...... classified based on the range of variation in three categories: small, intermediate and large variability. Features with small variability (range 30%). Conclusion. Textural features such as entropy-first order, energy, maximal correlation coefficient, and low-gray level run emphasis exhibited small...

  18. Shift of biome patterns due to simulated climate variability and climate change

    International Nuclear Information System (INIS)

    Claussen, M.

    1993-01-01

    The variability of simulated equilibrium-response patterns of biomes caused by simulated climate variability and climate shift is analysed. This investigation is based on various realisations of simulated present-day climate and climate shift. It has been found that the difference between biomes computed from three 10-year climatologies and from the corresponding 30-year climatology, simulated by the Hamburg climate model at T21 resolution, amounts to approximately 6% of the total land area, Antarctica excluded. This difference is mainly due to differences in annual moisture availability and winter temperatures. When intercomparing biomes from the 10-year climatologies a 10% difference is seen, but there is no unique difference pattern. In contrast to the interdecadal variability, the shift of conditions favorable for biomes due to a shift in climate in the next 100 years, caused by an increase in sea-surface temperatures and atmospheric CO 2 , reveals a unique trend pattern. It turns out that the strongest and most significant signal is the north-east shift of conditions for boreal biomes. This signal is caused by an increase of annual temperature sums as well as mean temperatures of the coldest and warmest months. Trends in annual moisture availability are of secondary importance globally. Regionally, a decrease in water availability affects biomes in Central and East Europe and an increase of water availability leads to a potential increase in tropical rain forest. In total, all differences amount to roughly 30% of the total land surface, Antarctica excluded. (orig./KW)

  19. Spatial and temporal variability of interhemispheric transport times

    Science.gov (United States)

    Wu, Xiaokang; Yang, Huang; Waugh, Darryn W.; Orbe, Clara; Tilmes, Simone; Lamarque, Jean-Francois

    2018-05-01

    The seasonal and interannual variability of transport times from the northern midlatitude surface into the Southern Hemisphere is examined using simulations of three idealized age tracers: an ideal age tracer that yields the mean transit time from northern midlatitudes and two tracers with uniform 50- and 5-day decay. For all tracers the largest seasonal and interannual variability occurs near the surface within the tropics and is generally closely coupled to movement of the Intertropical Convergence Zone (ITCZ). There are, however, notable differences in variability between the different tracers. The largest seasonal and interannual variability in the mean age is generally confined to latitudes spanning the ITCZ, with very weak variability in the southern extratropics. In contrast, for tracers subject to spatially uniform exponential loss the peak variability tends to be south of the ITCZ, and there is a smaller contrast between tropical and extratropical variability. These differences in variability occur because the distribution of transit times from northern midlatitudes is very broad and tracers with more rapid loss are more sensitive to changes in fast transit times than the mean age tracer. These simulations suggest that the seasonal-interannual variability in the southern extratropics of trace gases with predominantly NH midlatitude sources may differ depending on the gases' chemical lifetimes.

  20. Predictor Variables for Marathon Race Time in Recreational Female Runners

    OpenAIRE

    Schmid, Wiebke; Knechtle, Beat; Knechtle, Patrizia; Barandun, Ursula; Rüst, Christoph Alexander; Rosemann, Thomas; Lepers, Romuald

    2012-01-01

    Purpose We intended to determine predictor variables of anthropometry and training for marathon race time in recreational female runners in order to predict marathon race time for future novice female runners. Methods Anthropometric characteristics such as body mass, body height, body mass index, circumferences of limbs, thicknesses of skin-folds and body fat as well as training variables such as volume and speed in running training were related to marathon race time using bi- and multi-varia...

  1. Variability of textural features in FDG PET images due to different acquisition modes and reconstruction parameters.

    Science.gov (United States)

    Galavis, Paulina E; Hollensen, Christian; Jallow, Ngoneh; Paliwal, Bhudatt; Jeraj, Robert

    2010-10-01

    Characterization of textural features (spatial distributions of image intensity levels) has been considered as a tool for automatic tumor segmentation. The purpose of this work is to study the variability of the textural features in PET images due to different acquisition modes and reconstruction parameters. Twenty patients with solid tumors underwent PET/CT scans on a GE Discovery VCT scanner, 45-60 minutes post-injection of 10 mCi of [(18)F]FDG. Scans were acquired in both 2D and 3D modes. For each acquisition the raw PET data was reconstructed using five different reconstruction parameters. Lesions were segmented on a default image using the threshold of 40% of maximum SUV. Fifty different texture features were calculated inside the tumors. The range of variations of the features were calculated with respect to the average value. Fifty textural features were classified based on the range of variation in three categories: small, intermediate and large variability. Features with small variability (range ≤ 5%) were entropy-first order, energy, maximal correlation coefficient (second order feature) and low-gray level run emphasis (high-order feature). The features with intermediate variability (10% ≤ range ≤ 25%) were entropy-GLCM, sum entropy, high gray level run emphsis, gray level non-uniformity, small number emphasis, and entropy-NGL. Forty remaining features presented large variations (range > 30%). Textural features such as entropy-first order, energy, maximal correlation coefficient, and low-gray level run emphasis exhibited small variations due to different acquisition modes and reconstruction parameters. Features with low level of variations are better candidates for reproducible tumor segmentation. Even though features such as contrast-NGTD, coarseness, homogeneity, and busyness have been previously used, our data indicated that these features presented large variations, therefore they could not be considered as a good candidates for tumor

  2. Variability of textural features in FDG PET images due to different acquisition modes and reconstruction parameters

    International Nuclear Information System (INIS)

    Galavis, Paulina E.; Jallow, Ngoneh; Paliwal, Bhudatt; Jeraj, Robert; Hollensen, Christian

    2010-01-01

    Background. Characterization of textural features (spatial distributions of image intensity levels) has been considered as a tool for automatic tumor segmentation. The purpose of this work is to study the variability of the textural features in PET images due to different acquisition modes and reconstruction parameters. Material and methods. Twenty patients with solid tumors underwent PET/CT scans on a GE Discovery VCT scanner, 45-60 minutes post-injection of 10 mCi of [ 18 F]FDG. Scans were acquired in both 2D and 3D modes. For each acquisition the raw PET data was reconstructed using five different reconstruction parameters. Lesions were segmented on a default image using the threshold of 40% of maximum SUV. Fifty different texture features were calculated inside the tumors. The range of variations of the features were calculated with respect to the average value. Results. Fifty textural features were classified based on the range of variation in three categories: small, intermediate and large variability. Features with small variability (range = 5%) were entropy-first order, energy, maximal correlation coefficient (second order feature) and low-gray level run emphasis (high-order feature). The features with intermediate variability (10% = range = 25%) were entropy-GLCM, sum entropy, high gray level run emphasis, gray level non-uniformity, small number emphasis, and entropy-NGL. Forty remaining features presented large variations (range > 30%). Conclusion. Textural features such as entropy-first order, energy, maximal correlation coefficient, and low-gray level run emphasis exhibited small variations due to different acquisition modes and reconstruction parameters. Features with low level of variations are better candidates for reproducible tumor segmentation. Even though features such as contrast-NGTD, coarseness, homogeneity, and busyness have been previously used, our data indicated that these features presented large variations, therefore they could not be

  3. Surgeon and type of anesthesia predict variability in surgical procedure times.

    Science.gov (United States)

    Strum, D P; Sampson, A R; May, J H; Vargas, L G

    2000-05-01

    Variability in surgical procedure times increases the cost of healthcare delivery by increasing both the underutilization and overutilization of expensive surgical resources. To reduce variability in surgical procedure times, we must identify and study its sources. Our data set consisted of all surgeries performed over a 7-yr period at a large teaching hospital, resulting in 46,322 surgical cases. To study factors associated with variability in surgical procedure times, data mining techniques were used to segment and focus the data so that the analyses would be both technically and intellectually feasible. The data were subdivided into 40 representative segments of manageable size and variability based on headers adopted from the common procedural terminology classification. Each data segment was then analyzed using a main-effects linear model to identify and quantify specific sources of variability in surgical procedure times. The single most important source of variability in surgical procedure times was surgeon effect. Type of anesthesia, age, gender, and American Society of Anesthesiologists risk class were additional sources of variability. Intrinsic case-specific variability, unexplained by any of the preceding factors, was found to be highest for shorter surgeries relative to longer procedures. Variability in procedure times among surgeons was a multiplicative function (proportionate to time) of surgical time and total procedure time, such that as procedure times increased, variability in surgeons' surgical time increased proportionately. Surgeon-specific variability should be considered when building scheduling heuristics for longer surgeries. Results concerning variability in surgical procedure times due to factors such as type of anesthesia, age, gender, and American Society of Anesthesiologists risk class may be extrapolated to scheduling in other institutions, although specifics on individual surgeons may not. This research identifies factors associated

  4. Uncertainty in Earthquake Source Imaging Due to Variations in Source Time Function and Earth Structure

    KAUST Repository

    Razafindrakoto, H. N. T.

    2014-03-25

    One way to improve the accuracy and reliability of kinematic earthquake source imaging is to investigate the origin of uncertainty and to minimize their effects. The difficulties in kinematic source inversion arise from the nonlinearity of the problem, nonunique choices in the parameterization, and observational errors. We analyze particularly the uncertainty related to the choice of the source time function (STF) and the variability in Earth structure. We consider a synthetic data set generated from a spontaneous dynamic rupture calculation. Using Bayesian inference, we map the solution space of peak slip rate, rupture time, and rise time to characterize the kinematic rupture in terms of posterior density functions. Our test to investigate the effect of the choice of STF reveals that all three tested STFs (isosceles triangle, regularized Yoffe with acceleration time of 0.1 and 0.3 s) retrieve the patch of high slip and slip rate around the hypocenter. However, the use of an isosceles triangle as STF artificially accelerates the rupture to propagate faster than the target solution. It additionally generates an artificial linear correlation between rupture onset time and rise time. These appear to compensate for the dynamic source effects that are not included in the symmetric triangular STF. The exact rise time for the tested STFs is difficult to resolve due to the small amount of radiated seismic moment in the tail of STF. To highlight the effect of Earth structure variability, we perform inversions including the uncertainty in the wavespeed only, and variability in both wavespeed and layer depth. We find that little difference is noticeable between the resulting rupture model uncertainties from these two parameterizations. Both significantly broaden the posterior densities and cause faster rupture propagation particularly near the hypocenter due to the major velocity change at the depth where the fault is located.

  5. Uncertainty in Earthquake Source Imaging Due to Variations in Source Time Function and Earth Structure

    KAUST Repository

    Razafindrakoto, H. N. T.; Mai, Paul Martin

    2014-01-01

    One way to improve the accuracy and reliability of kinematic earthquake source imaging is to investigate the origin of uncertainty and to minimize their effects. The difficulties in kinematic source inversion arise from the nonlinearity of the problem, nonunique choices in the parameterization, and observational errors. We analyze particularly the uncertainty related to the choice of the source time function (STF) and the variability in Earth structure. We consider a synthetic data set generated from a spontaneous dynamic rupture calculation. Using Bayesian inference, we map the solution space of peak slip rate, rupture time, and rise time to characterize the kinematic rupture in terms of posterior density functions. Our test to investigate the effect of the choice of STF reveals that all three tested STFs (isosceles triangle, regularized Yoffe with acceleration time of 0.1 and 0.3 s) retrieve the patch of high slip and slip rate around the hypocenter. However, the use of an isosceles triangle as STF artificially accelerates the rupture to propagate faster than the target solution. It additionally generates an artificial linear correlation between rupture onset time and rise time. These appear to compensate for the dynamic source effects that are not included in the symmetric triangular STF. The exact rise time for the tested STFs is difficult to resolve due to the small amount of radiated seismic moment in the tail of STF. To highlight the effect of Earth structure variability, we perform inversions including the uncertainty in the wavespeed only, and variability in both wavespeed and layer depth. We find that little difference is noticeable between the resulting rupture model uncertainties from these two parameterizations. Both significantly broaden the posterior densities and cause faster rupture propagation particularly near the hypocenter due to the major velocity change at the depth where the fault is located.

  6. A model for AGN variability on multiple time-scales

    Science.gov (United States)

    Sartori, Lia F.; Schawinski, Kevin; Trakhtenbrot, Benny; Caplar, Neven; Treister, Ezequiel; Koss, Michael J.; Urry, C. Megan; Zhang, C. E.

    2018-05-01

    We present a framework to link and describe active galactic nuclei (AGN) variability on a wide range of time-scales, from days to billions of years. In particular, we concentrate on the AGN variability features related to changes in black hole fuelling and accretion rate. In our framework, the variability features observed in different AGN at different time-scales may be explained as realisations of the same underlying statistical properties. In this context, we propose a model to simulate the evolution of AGN light curves with time based on the probability density function (PDF) and power spectral density (PSD) of the Eddington ratio (L/LEdd) distribution. Motivated by general galaxy population properties, we propose that the PDF may be inspired by the L/LEdd distribution function (ERDF), and that a single (or limited number of) ERDF+PSD set may explain all observed variability features. After outlining the framework and the model, we compile a set of variability measurements in terms of structure function (SF) and magnitude difference. We then combine the variability measurements on a SF plot ranging from days to Gyr. The proposed framework enables constraints on the underlying PSD and the ability to link AGN variability on different time-scales, therefore providing new insights into AGN variability and black hole growth phenomena.

  7. Online Synthesis for Operation Execution Time Variability on Digital Microfluidic Biochips

    DEFF Research Database (Denmark)

    Alistar, Mirela; Pop, Paul

    2014-01-01

    have assumed that each biochemical operation in an application is characterized by a worst-case execution time (wcet). However, during the execution of the application, due to variability and randomness in biochemical reactions, operations may finish earlier than their wcets. In this paper we propose...... an online synthesis strategy that re-synthesizes the application at runtime when operations experience variability in their execution time, obtaining thus shorter application execution times. The proposed strategy has been evaluated using several benchmarks....

  8. THE TIME DOMAIN SPECTROSCOPIC SURVEY: VARIABLE SELECTION AND ANTICIPATED RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Morganson, Eric; Green, Paul J. [Harvard Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Anderson, Scott F.; Ruan, John J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Eracleous, Michael; Brandt, William Nielsen [Department of Astronomy and Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States); Kelly, Brandon [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530 (United States); Badenes, Carlos [Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O’Hara St, Pittsburgh, PA 15260 (United States); Bañados, Eduardo [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin, 475 N. Charter St., Madison, WI 53706 (United States); Borissova, Jura [Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, and Millennium Institute of Astrophysics (MAS), Santiago (Chile); Burgett, William S. [GMTO Corp, Suite 300, 251 S. Lake Ave, Pasadena, CA 91101 (United States); Chambers, Kenneth, E-mail: emorganson@cfa.harvard.edu [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); and others

    2015-06-20

    We present the selection algorithm and anticipated results for the Time Domain Spectroscopic Survey (TDSS). TDSS is an Sloan Digital Sky Survey (SDSS)-IV Extended Baryon Oscillation Spectroscopic Survey (eBOSS) subproject that will provide initial identification spectra of approximately 220,000 luminosity-variable objects (variable stars and active galactic nuclei across 7500 deg{sup 2} selected from a combination of SDSS and multi-epoch Pan-STARRS1 photometry. TDSS will be the largest spectroscopic survey to explicitly target variable objects, avoiding pre-selection on the basis of colors or detailed modeling of specific variability characteristics. Kernel Density Estimate analysis of our target population performed on SDSS Stripe 82 data suggests our target sample will be 95% pure (meaning 95% of objects we select have genuine luminosity variability of a few magnitudes or more). Our final spectroscopic sample will contain roughly 135,000 quasars and 85,000 stellar variables, approximately 4000 of which will be RR Lyrae stars which may be used as outer Milky Way probes. The variability-selected quasar population has a smoother redshift distribution than a color-selected sample, and variability measurements similar to those we develop here may be used to make more uniform quasar samples in large surveys. The stellar variable targets are distributed fairly uniformly across color space, indicating that TDSS will obtain spectra for a wide variety of stellar variables including pulsating variables, stars with significant chromospheric activity, cataclysmic variables, and eclipsing binaries. TDSS will serve as a pathfinder mission to identify and characterize the multitude of variable objects that will be detected photometrically in even larger variability surveys such as Large Synoptic Survey Telescope.

  9. The cost of travel time variability: three measures with properties

    DEFF Research Database (Denmark)

    Engelson, Leonid; Fosgerau, Mogens

    2016-01-01

    This paper explores the relationships between three types of measures of the cost of travel time variability: measures based on scheduling preferences and implicit departure time choice, Bernoulli type measures based on a univariate function of travel time, and mean-dispersion measures. We...

  10. Variability of Travel Times on New Jersey Highways

    Science.gov (United States)

    2011-06-01

    This report presents the results of a link and path travel time study conducted on selected New Jersey (NJ) highways to produce estimates of the corresponding variability of travel time (VTT) by departure time of the day and days of the week. The tra...

  11. Discrete-time BAM neural networks with variable delays

    Science.gov (United States)

    Liu, Xin-Ge; Tang, Mei-Lan; Martin, Ralph; Liu, Xin-Bi

    2007-07-01

    This Letter deals with the global exponential stability of discrete-time bidirectional associative memory (BAM) neural networks with variable delays. Using a Lyapunov functional, and linear matrix inequality techniques (LMI), we derive a new delay-dependent exponential stability criterion for BAM neural networks with variable delays. As this criterion has no extra constraints on the variable delay functions, it can be applied to quite general BAM neural networks with a broad range of time delay functions. It is also easy to use in practice. An example is provided to illustrate the theoretical development.

  12. Discrete-time BAM neural networks with variable delays

    International Nuclear Information System (INIS)

    Liu Xinge; Tang Meilan; Martin, Ralph; Liu Xinbi

    2007-01-01

    This Letter deals with the global exponential stability of discrete-time bidirectional associative memory (BAM) neural networks with variable delays. Using a Lyapunov functional, and linear matrix inequality techniques (LMI), we derive a new delay-dependent exponential stability criterion for BAM neural networks with variable delays. As this criterion has no extra constraints on the variable delay functions, it can be applied to quite general BAM neural networks with a broad range of time delay functions. It is also easy to use in practice. An example is provided to illustrate the theoretical development

  13. Imprecision in estimates of dose from ingested 137Cs due to variability in human biological characteristics

    International Nuclear Information System (INIS)

    Schwarz, G.; Dunning, D.E. Jr.

    1982-01-01

    An attempt has been made to quantify the variability in human biological parameters determining dose to man from ingestion of a unit activity of soluble 137 Cs and the resulting imprecision in the predicted total-body dose commitment. The analysis is based on an extensive review of the literature along with the application of statistical methods to determine parameter variability, correlations between parameters, and predictive imprecision. The variability in the principal biological parameters (biological half-time and total-body mass) involved can be described by a geometric standard deviation of 1.2-1.5 for adults and 1.6-1.9 for children/ adolescents of age 0.1-18 yr. The estimated predictive imprecision (using a Monte Carlo technique) in the total-body dose commitment from ingested 137 Cs can be described by a geometric standard deviation on the order of 1.3-1.4, meaning that the 99th percentile of the predicted distribution of dose is within approximately 2.1 times the mean value. The mean dose estimate is 0.009 Sv/MBq (34 mrem/μ Ci) for children/adolescents and 0.01 Sv/MBq (38 mrem/μ Ci) for adults. Little evidence of age dependence in the total-body dose from ingested 137 Cs is observed. (author)

  14. Periodicity and stability for variable-time impulsive neural networks.

    Science.gov (United States)

    Li, Hongfei; Li, Chuandong; Huang, Tingwen

    2017-10-01

    The paper considers a general neural networks model with variable-time impulses. It is shown that each solution of the system intersects with every discontinuous surface exactly once via several new well-proposed assumptions. Moreover, based on the comparison principle, this paper shows that neural networks with variable-time impulse can be reduced to the corresponding neural network with fixed-time impulses under well-selected conditions. Meanwhile, the fixed-time impulsive systems can be regarded as the comparison system of the variable-time impulsive neural networks. Furthermore, a series of sufficient criteria are derived to ensure the existence and global exponential stability of periodic solution of variable-time impulsive neural networks, and to illustrate the same stability properties between variable-time impulsive neural networks and the fixed-time ones. The new criteria are established by applying Schaefer's fixed point theorem combined with the use of inequality technique. Finally, a numerical example is presented to show the effectiveness of the proposed results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Variability in reaction time performance of younger and older adults.

    Science.gov (United States)

    Hultsch, David F; MacDonald, Stuart W S; Dixon, Roger A

    2002-03-01

    Age differences in three basic types of variability were examined: variability between persons (diversity), variability within persons across tasks (dispersion), and variability within persons across time (inconsistency). Measures of variability were based on latency performance from four measures of reaction time (RT) performed by a total of 99 younger adults (ages 17--36 years) and 763 older adults (ages 54--94 years). Results indicated that all three types of variability were greater in older compared with younger participants even when group differences in speed were statistically controlled. Quantile-quantile plots showed age and task differences in the shape of the inconsistency distributions. Measures of within-person variability (dispersion and inconsistency) were positively correlated. Individual differences in RT inconsistency correlated negatively with level of performance on measures of perceptual speed, working memory, episodic memory, and crystallized abilities. Partial set correlation analyses indicated that inconsistency predicted cognitive performance independent of level of performance. The results indicate that variability of performance is an important indicator of cognitive functioning and aging.

  16. Accurate light-time correction due to a gravitating mass

    Energy Technology Data Exchange (ETDEWEB)

    Ashby, Neil [Department of Physics, University of Colorado, Boulder, CO (United States); Bertotti, Bruno, E-mail: ashby@boulder.nist.go [Dipartimento di Fisica Nucleare e Teorica, Universita di Pavia (Italy)

    2010-07-21

    This technical paper of mathematical physics arose as an aftermath of the 2002 Cassini experiment (Bertotti et al 2003 Nature 425 374-6), in which the PPN parameter {gamma} was measured with an accuracy {sigma}{sub {gamma}} = 2.3 x 10{sup -5} and found consistent with the prediction {gamma} = 1 of general relativity. The Orbit Determination Program (ODP) of NASA's Jet Propulsion Laboratory, which was used in the data analysis, is based on an expression (8) for the gravitational delay {Delta}t that differs from the standard formula (2); this difference is of second order in powers of m-the gravitational radius of the Sun-but in Cassini's case it was much larger than the expected order of magnitude m{sup 2}/b, where b is the distance of the closest approach of the ray. Since the ODP does not take into account any other second-order terms, it is necessary, also in view of future more accurate experiments, to revisit the whole problem, to systematically evaluate higher order corrections and to determine which terms, and why, are larger than the expected value. We note that light propagation in a static spacetime is equivalent to a problem in ordinary geometrical optics; Fermat's action functional at its minimum is just the light-time between the two end points A and B. A new and powerful formulation is thus obtained. This method is closely connected with the much more general approach of Le Poncin-Lafitte et al (2004 Class. Quantum Grav. 21 4463-83), which is based on Synge's world function. Asymptotic power series are necessary to provide a safe and automatic way of selecting which terms to keep at each order. Higher order approximations to the required quantities, in particular the delay and the deflection, are easily obtained. We also show that in a close superior conjunction, when b is much smaller than the distances of A and B from the Sun, say of order R, the second-order correction has an enhanced part of order m{sup 2}R/b{sup 2}, which

  17. Variability of phase and amplitude fronts due to horizontal refraction in shallow water.

    Science.gov (United States)

    Katsnelson, Boris G; Grigorev, Valery A; Lynch, James F

    2018-01-01

    The variability of the interference pattern of a narrow-band sound signal in a shallow water waveguide in the horizontal plane in the presence of horizontal stratification, in particular due to linear internal waves, is studied. It is shown that lines of constant phase (a phase front) and lines of constant amplitude/envelope (an amplitude front) for each waveguide mode may have different directions in the spatial vicinity of the point of reception. The angle between them depends on the waveguide's parameters, the mode number, and the sound frequency. Theoretical estimates and data processing methodology for obtaining these angles from experimental data recorded by a horizontal line array are proposed. The behavior of the angles, which are obtained for two episodes from the Shallow Water 2006 (SW06) experiment, show agreement with the theory presented.

  18. Seasonal variability of rocky reef fish assemblages: Detecting functional and structural changes due to fishing effects

    Science.gov (United States)

    Henriques, Sofia; Pais, Miguel Pessanha; Costa, Maria José; Cabral, Henrique Nogueira

    2013-05-01

    The present study analyzed the effects of seasonal variation on the stability of fish-based metrics and their capability to detect changes in fish assemblages, which is yet poorly understood despite the general idea that guilds are more resilient to natural variability than species abundances. Three zones subject to different levels of fishing pressure inside the Arrábida Marine Protected Area (MPA) were sampled seasonally. The results showed differences between warm (summer and autumn) and cold (winter and spring) seasons, with the autumn clearly standing out. In general, the values of the metrics density of juveniles, density of invertebrate feeders and density of omnivores increased in warm seasons, which can be attributed to differences in recruitment patterns, spawning migrations and feeding activity among seasons. The density of generalist/opportunistic individuals was sensitive to the effect of fishing, with higher values at zones with the lowest level of protection, while the density of individuals with high commercial value only responded to fishing in the autumn, due to a cumulative result of both juveniles and adults abundances during this season. Overall, this study showed that seasonal variability affects structural and functional features of the fish assemblage and that might influence the detection of changes as a result of anthropogenic pressures. The choice of a specific season, during warm sea conditions after the spawning period (July-October), seems to be more adequate to assess changes on rocky-reef fish assemblages.

  19. Quantifying uncertainty due to internal variability using high-resolution regional climate model simulations

    Science.gov (United States)

    Gutmann, E. D.; Ikeda, K.; Deser, C.; Rasmussen, R.; Clark, M. P.; Arnold, J. R.

    2015-12-01

    The uncertainty in future climate predictions is as large or larger than the mean climate change signal. As such, any predictions of future climate need to incorporate and quantify the sources of this uncertainty. One of the largest sources comes from the internal, chaotic, variability within the climate system itself. This variability has been approximated using the 30 ensemble members of the Community Earth System Model (CESM) large ensemble. Here we examine the wet and dry end members of this ensemble for cool-season precipitation in the Colorado Rocky Mountains with a set of high-resolution regional climate model simulations. We have used the Weather Research and Forecasting model (WRF) to simulate the periods 1990-2000, 2025-2035, and 2070-2080 on a 4km grid. These simulations show that the broad patterns of change depicted in CESM are inherited by the high-resolution simulations; however, the differences in the height and location of the mountains in the WRF simulation, relative to the CESM simulation, means that the location and magnitude of the precipitation changes are very different. We further show that high-resolution simulations with the Intermediate Complexity Atmospheric Research model (ICAR) predict a similar spatial pattern in the change signal as WRF for these ensemble members. We then use ICAR to examine the rest of the CESM Large Ensemble as well as the uncertainty in the regional climate model due to the choice of physics parameterizations.

  20. NOTE ON TRAVEL TIME SHIFTS DUE TO AMPLITUDE MODULATION IN TIME-DISTANCE HELIOSEISMOLOGY MEASUREMENTS

    International Nuclear Information System (INIS)

    Nigam, R.; Kosovichev, A. G.

    2010-01-01

    Correct interpretation of acoustic travel times measured by time-distance helioseismology is essential to get an accurate understanding of the solar properties that are inferred from them. It has long been observed that sunspots suppress p-mode amplitude, but its implications on travel times have not been fully investigated so far. It has been found in test measurements using a 'masking' procedure, in which the solar Doppler signal in a localized quiet region of the Sun is artificially suppressed by a spatial function, and using numerical simulations that the amplitude modulations in combination with the phase-speed filtering may cause systematic shifts of acoustic travel times. To understand the properties of this procedure, we derive an analytical expression for the cross-covariance of a signal that has been modulated locally by a spatial function that has azimuthal symmetry and then filtered by a phase-speed filter typically used in time-distance helioseismology. Comparing this expression to the Gabor wavelet fitting formula without this effect, we find that there is a shift in the travel times that is introduced by the amplitude modulation. The analytical model presented in this paper can be useful also for interpretation of travel time measurements for the non-uniform distribution of oscillation amplitude due to observational effects.

  1. Timing variability in children with early-treated congenital hypothyroidism

    NARCIS (Netherlands)

    Kooistra, L.; Snijders, T.A.B.; Schellekens, J.M.H.; Kalverboer, A.F.; Geuze, R.H.

    This study reports on central and peripheral determinants of timing variability in self-paced tapping by children with early-treated congenital hypothyroidism (CH). A theoretical model of the timing of repetitive movements developed by Wing and Kristofferson was applied to estimate the central

  2. Predicting travel time variability for cost-benefit analysis

    NARCIS (Netherlands)

    Peer, S.; Koopmans, C.; Verhoef, E.T.

    2010-01-01

    Unreliable travel times cause substantial costs to travelers. Nevertheless, they are not taken into account in many cost-benefit-analyses (CBA), or only in very rough ways. This paper aims at providing simple rules on how variability can be predicted, based on travel time data from Dutch highways.

  3. A moving mesh method with variable relaxation time

    OpenAIRE

    Soheili, Ali Reza; Stockie, John M.

    2006-01-01

    We propose a moving mesh adaptive approach for solving time-dependent partial differential equations. The motion of spatial grid points is governed by a moving mesh PDE (MMPDE) in which a mesh relaxation time \\tau is employed as a regularization parameter. Previously reported results on MMPDEs have invariably employed a constant value of the parameter \\tau. We extend this standard approach by incorporating a variable relaxation time that is calculated adaptively alongside the solution in orde...

  4. Space and time evolution of two nonlinearly coupled variables

    International Nuclear Information System (INIS)

    Obayashi, H.; Totsuji, H.; Wilhelmsson, H.

    1976-12-01

    The system of two coupled linear differential equations are studied assuming that the coupling terms are proportional to the product of the dependent variables, representing e.g. intensities or populations. It is furthermore assumed that these variables experience different linear dissipation or growth. The derivations account for space as well as time dependence of the variables. It is found that certain particular solutions can be obtained to this system, whereas a full solution in space and time as an initial value problem is outside the scope of the present paper. The system has a nonlinear equilibrium solution for which the nonlinear coupling terms balance the terms of linear dissipation. The case of space and time evolution of a small perturbation of the nonlinear equilibrium state, given the initial one-dimensional spatial distribution of the perturbation, is also considered in some detail. (auth.)

  5. Verification of models for ballistic movement time and endpoint variability.

    Science.gov (United States)

    Lin, Ray F; Drury, Colin G

    2013-01-01

    A hand control movement is composed of several ballistic movements. The time required in performing a ballistic movement and its endpoint variability are two important properties in developing movement models. The purpose of this study was to test potential models for predicting these two properties. Twelve participants conducted ballistic movements of specific amplitudes using a drawing tablet. The measured data of movement time and endpoint variability were then used to verify the models. This study was successful with Hoffmann and Gan's movement time model (Hoffmann, 1981; Gan and Hoffmann 1988) predicting more than 90.7% data variance for 84 individual measurements. A new theoretically developed ballistic movement variability model, proved to be better than Howarth, Beggs, and Bowden's (1971) model, predicting on average 84.8% of stopping-variable error and 88.3% of aiming-variable errors. These two validated models will help build solid theoretical movement models and evaluate input devices. This article provides better models for predicting end accuracy and movement time of ballistic movements that are desirable in rapid aiming tasks, such as keying in numbers on a smart phone. The models allow better design of aiming tasks, for example button sizes on mobile phones for different user populations.

  6. Variation in the estimations of ETo and crop water use due to the sensor accuracy of the meteorological variables

    Directory of Open Access Journals (Sweden)

    R. Moratiel

    2013-06-01

    Full Text Available In agricultural ecosystems the use of evapotranspiration (ET to improve irrigation water management is generally widespread. Commonly, the crop ET (ETc is estimated by multiplying the reference crop evapotranspiration (ETo by a crop coefficient (Kc. Accurate estimation of ETo is critical because it is the main factor affecting the calculation of crop water use and water management. The ETo is generally estimated from recorded meteorological variables at reference weather stations. The main objective of this paper was assessing the effect of the uncertainty due to random noise in the sensors used for measurement of meteorological variables on the estimation of ETo, crop ET and net irrigation requirements of grain corn and alfalfa in three irrigation districts of the middle Ebro River basin. Five scenarios were simulated, four of them individually considering each recorded meteorological variable (temperature, relative humidity, solar radiation and wind speed and a fifth scenario combining together the uncertainty of all sensors. The uncertainty in relative humidity for irrigation districts Riegos del Alto Aragón (RAA and Bardenas (BAR, and temperature for irrigation district Canal de Aragón y Cataluña (CAC, were the two most important factors affecting the estimation of ETo, corn ET (ETc_corn, alfalfa ET (ETc_alf, net corn irrigation water requirements (IRncorn and net alfalfa irrigation water requirements (IRnalf. Nevertheless, this effect was never greater than ±0.5% over annual scale time. The wind speed variable (Scenario 3 was the third variable more influential in the fluctuations (± of evapotranspiration, followed by solar radiation. Considering the accuracy for all sensors over annual scale time, the variation was about ±1% of ETo, ETc_corn, ETc_alf, IRncorn, and IRnalf. The fluctuations of evapotranspiration were higher at shorter time scale. ETo daily fluctuation remained lower than 5 % during the growing season of corn and

  7. Variable selection for mixture and promotion time cure rate models.

    Science.gov (United States)

    Masud, Abdullah; Tu, Wanzhu; Yu, Zhangsheng

    2016-11-16

    Failure-time data with cured patients are common in clinical studies. Data from these studies are typically analyzed with cure rate models. Variable selection methods have not been well developed for cure rate models. In this research, we propose two least absolute shrinkage and selection operators based methods, for variable selection in mixture and promotion time cure models with parametric or nonparametric baseline hazards. We conduct an extensive simulation study to assess the operating characteristics of the proposed methods. We illustrate the use of the methods using data from a study of childhood wheezing. © The Author(s) 2016.

  8. Variable Selection in Time Series Forecasting Using Random Forests

    Directory of Open Access Journals (Sweden)

    Hristos Tyralis

    2017-10-01

    Full Text Available Time series forecasting using machine learning algorithms has gained popularity recently. Random forest is a machine learning algorithm implemented in time series forecasting; however, most of its forecasting properties have remained unexplored. Here we focus on assessing the performance of random forests in one-step forecasting using two large datasets of short time series with the aim to suggest an optimal set of predictor variables. Furthermore, we compare its performance to benchmarking methods. The first dataset is composed by 16,000 simulated time series from a variety of Autoregressive Fractionally Integrated Moving Average (ARFIMA models. The second dataset consists of 135 mean annual temperature time series. The highest predictive performance of RF is observed when using a low number of recent lagged predictor variables. This outcome could be useful in relevant future applications, with the prospect to achieve higher predictive accuracy.

  9. Variability of gastric emptying time using standardized radiolabeled meals

    International Nuclear Information System (INIS)

    Christian, P.E.; Brophy, C.M.; Egger, M.J.; Taylor, A.; Moore, J.G.

    1984-01-01

    To define the range of inter- and intra-subject variability on gastric emptying measurements, eight healthy male subjects (ages 19-40) received meals on four separate occasions. The meal consisted of 150 g of beef stew labeled with Tc-99m SC labeled liver (600 μCi) and 150 g of orange juice containing In-111 DTPA (100 μCi) as the solid- and liquid-phase markers respectively. Images of the solid and liquid phases were obtained at 20 min intervals immediately after meal ingestion. The stomach region was selected from digital images and data were corrected for radionuclide interference, radioactive decay and the geometric mean of anterior and posterior counts. More absolute variability was seen with the solid than the liquid marker emptying for the group. The mean solid half-emptying time was 58 +- 17 min (range 29-92) while the mean liquid half-emptying time was 24 +- 8 min (range 12-37). A nested random effects analysis of variance showed moderate intra-subject variability for solid half-emptying times (rho = 0.4594), and high intra-subject variability was implied by a low correlation (rho = 0.2084) for liquid half-emptying. The average inter-subject differences were 58.3% of the total variance for solids (rho = 0.0017). For liquids, the inter-subject variability was 69.1% of the total variance, but was only suggestive of statistical significance (rho = 0.0666). The normal half emptying time for gastric emptying of liquids and solids is a variable phenomenon in healthy subjects and has great inter- and intra-individual day-to-day differences

  10. Variability of gastric emptying time using standardized radiolabeled meals

    Energy Technology Data Exchange (ETDEWEB)

    Christian, P.E.; Brophy, C.M.; Egger, M.J.; Taylor, A.; Moore, J.G.

    1984-01-01

    To define the range of inter- and intra-subject variability on gastric emptying measurements, eight healthy male subjects (ages 19-40) received meals on four separate occasions. The meal consisted of 150 g of beef stew labeled with Tc-99m SC labeled liver (600 ..mu..Ci) and 150 g of orange juice containing In-111 DTPA (100 ..mu..Ci) as the solid- and liquid-phase markers respectively. Images of the solid and liquid phases were obtained at 20 min intervals immediately after meal ingestion. The stomach region was selected from digital images and data were corrected for radionuclide interference, radioactive decay and the geometric mean of anterior and posterior counts. More absolute variability was seen with the solid than the liquid marker emptying for the group. The mean solid half-emptying time was 58 +- 17 min (range 29-92) while the mean liquid half-emptying time was 24 +- 8 min (range 12-37). A nested random effects analysis of variance showed moderate intra-subject variability for solid half-emptying times (rho = 0.4594), and high intra-subject variability was implied by a low correlation (rho = 0.2084) for liquid half-emptying. The average inter-subject differences were 58.3% of the total variance for solids (rho = 0.0017). For liquids, the inter-subject variability was 69.1% of the total variance, but was only suggestive of statistical significance (rho = 0.0666). The normal half emptying time for gastric emptying of liquids and solids is a variable phenomenon in healthy subjects and has great inter- and intra-individual day-to-day differences.

  11. Predictor variables for marathon race time in recreational female runners.

    Science.gov (United States)

    Schmid, Wiebke; Knechtle, Beat; Knechtle, Patrizia; Barandun, Ursula; Rüst, Christoph Alexander; Rosemann, Thomas; Lepers, Romuald

    2012-06-01

    We intended to determine predictor variables of anthropometry and training for marathon race time in recreational female runners in order to predict marathon race time for future novice female runners. Anthropometric characteristics such as body mass, body height, body mass index, circumferences of limbs, thicknesses of skin-folds and body fat as well as training variables such as volume and speed in running training were related to marathon race time using bi- and multi-variate analysis in 29 female runners. The marathoners completed the marathon distance within 251 (26) min, running at a speed of 10.2 (1.1) km/h. Body mass (r=0.37), body mass index (r=0.46), the circumferences of thigh (r=0.51) and calf (r=0.41), the skin-fold thicknesses of front thigh (r=0.38) and of medial calf (r=0.40), the sum of eight skin-folds (r=0.44) and body fat percentage (r=0.41) were related to marathon race time. For the variables of training, maximal distance ran per week (r=- 0.38), number of running training sessions per week (r=- 0.46) and the speed of the training sessions (r= - 0.60) were related to marathon race time. In the multi-variate analysis, the circumference of calf (P=0.02) and the speed of the training sessions (P=0.0014) were related to marathon race time. Marathon race time might be partially (r(2)=0.50) predicted by the following equation: Race time (min)=184.4 + 5.0 x (circumference calf, cm) -11.9 x (speed in running during training, km/h) for recreational female marathoners. Variables of both anthropometry and training were related to marathon race time in recreational female marathoners and cannot be reduced to one single predictor variable. For practical applications, a low circumference of calf and a high running speed in training are associated with a fast marathon race time in recreational female runners.

  12. Physical attraction to reliable, low variability nervous systems: Reaction time variability predicts attractiveness.

    Science.gov (United States)

    Butler, Emily E; Saville, Christopher W N; Ward, Robert; Ramsey, Richard

    2017-01-01

    The human face cues a range of important fitness information, which guides mate selection towards desirable others. Given humans' high investment in the central nervous system (CNS), cues to CNS function should be especially important in social selection. We tested if facial attractiveness preferences are sensitive to the reliability of human nervous system function. Several decades of research suggest an operational measure for CNS reliability is reaction time variability, which is measured by standard deviation of reaction times across trials. Across two experiments, we show that low reaction time variability is associated with facial attractiveness. Moreover, variability in performance made a unique contribution to attractiveness judgements above and beyond both physical health and sex-typicality judgements, which have previously been associated with perceptions of attractiveness. In a third experiment, we empirically estimated the distribution of attractiveness preferences expected by chance and show that the size and direction of our results in Experiments 1 and 2 are statistically unlikely without reference to reaction time variability. We conclude that an operating characteristic of the human nervous system, reliability of information processing, is signalled to others through facial appearance. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Long Pulse Integrator of Variable Integral Time Constant

    International Nuclear Information System (INIS)

    Wang Yong; Ji Zhenshan; Du Xiaoying; Wu Yichun; Li Shi; Luo Jiarong

    2010-01-01

    A kind of new long pulse integrator was designed based on the method of variable integral time constant and deducting integral drift by drift slope. The integral time constant can be changed by choosing different integral resistors, in order to improve the signal-to-noise ratio, and avoid output saturation; the slope of integral drift of a certain period of time can be calculated by digital signal processing, which can be used to deduct the drift of original integral signal in real time to reduce the integral drift. The tests show that this kind of long pulse integrator is good at reducing integral drift, which also can eliminate the effects of changing integral time constant. According to experiments, the integral time constant can be changed by remote control and manual adjustment of integral drift is avoided, which can improve the experiment efficiency greatly and can be used for electromagnetic measurement in Tokamak experiment. (authors)

  14. Inverse Ising problem in continuous time: A latent variable approach

    Science.gov (United States)

    Donner, Christian; Opper, Manfred

    2017-12-01

    We consider the inverse Ising problem: the inference of network couplings from observed spin trajectories for a model with continuous time Glauber dynamics. By introducing two sets of auxiliary latent random variables we render the likelihood into a form which allows for simple iterative inference algorithms with analytical updates. The variables are (1) Poisson variables to linearize an exponential term which is typical for point process likelihoods and (2) Pólya-Gamma variables, which make the likelihood quadratic in the coupling parameters. Using the augmented likelihood, we derive an expectation-maximization (EM) algorithm to obtain the maximum likelihood estimate of network parameters. Using a third set of latent variables we extend the EM algorithm to sparse couplings via L1 regularization. Finally, we develop an efficient approximate Bayesian inference algorithm using a variational approach. We demonstrate the performance of our algorithms on data simulated from an Ising model. For data which are simulated from a more biologically plausible network with spiking neurons, we show that the Ising model captures well the low order statistics of the data and how the Ising couplings are related to the underlying synaptic structure of the simulated network.

  15. Complexity Variability Assessment of Nonlinear Time-Varying Cardiovascular Control

    Science.gov (United States)

    Valenza, Gaetano; Citi, Luca; Garcia, Ronald G.; Taylor, Jessica Noggle; Toschi, Nicola; Barbieri, Riccardo

    2017-02-01

    The application of complex systems theory to physiology and medicine has provided meaningful information about the nonlinear aspects underlying the dynamics of a wide range of biological processes and their disease-related aberrations. However, no studies have investigated whether meaningful information can be extracted by quantifying second-order moments of time-varying cardiovascular complexity. To this extent, we introduce a novel mathematical framework termed complexity variability, in which the variance of instantaneous Lyapunov spectra estimated over time serves as a reference quantifier. We apply the proposed methodology to four exemplary studies involving disorders which stem from cardiology, neurology and psychiatry: Congestive Heart Failure (CHF), Major Depression Disorder (MDD), Parkinson’s Disease (PD), and Post-Traumatic Stress Disorder (PTSD) patients with insomnia under a yoga training regime. We show that complexity assessments derived from simple time-averaging are not able to discern pathology-related changes in autonomic control, and we demonstrate that between-group differences in measures of complexity variability are consistent across pathologies. Pathological states such as CHF, MDD, and PD are associated with an increased complexity variability when compared to healthy controls, whereas wellbeing derived from yoga in PTSD is associated with lower time-variance of complexity.

  16. Seasonal Variability in Regional Ice Flow Due to Meltwater Injection Into the Shear Margins of Jakobshavn Isbræ

    Science.gov (United States)

    Cavanagh, J. P.; Lampkin, D. J.; Moon, T.

    2017-12-01

    The impact of meltwater injection into the shear margins of Jakobshavn Isbræ via drainage from water-filled crevasses on ice flow is examined. We use Landsat-8 Operational Land Imager panchromatic, high-resolution imagery to monitor the spatiotemporal variability of seven water-filled crevasse ponds during the summers of 2013 to 2015. The timing of drainage from water-filled crevasses coincides with an increase of 2 to 20% in measured ice velocity beyond Jakobshavn Isbræ shear margins, which we define as extramarginal ice velocity. Some water-filled crevasse groups demonstrate multiple drainage events within a single melt season. Numerical simulations show that hydrologic shear weakening due to water-filled crevasse drainage can accelerate extramarginal flow by as much as 35% within 10 km of the margins and enhance mass flux through the shear margins by 12%. This work demonstrates a novel mechanism through which surface melt can influence regional ice flow.

  17. Important variables in explaining real-time peak price in the independent power market of Ontario

    International Nuclear Information System (INIS)

    Rueda, I.E.A.; Marathe, A.

    2005-01-01

    This paper uses support vector machines (SVM) based learning algorithm to select important variables that help explain the real-time peak electricity price in the Ontario market. The Ontario market was opened to competition only in May 2002. Due to the limited number of observations available, finding a set of variables that can explain the independent power market of Ontario (IMO) real-time peak price is a significant challenge for the traders and analysts. The kernel regressions of the explanatory variables on the IMO real-time average peak price show that non-linear dependencies exist between the explanatory variables and the IMO price. This non-linear relationship combined with the low variable-observation ratio rule out conventional statistical analysis. Hence, we use an alternative machine learning technique to find the important explanatory variables for the IMO real-time average peak price. SVM sensitivity analysis based results find that the IMO's predispatch average peak price, the actual import peak volume, the peak load of the Ontario market and the net available supply after accounting for load (energy excess) are some of the most important variables in explaining the real-time average peak price in the Ontario electricity market. (author)

  18. Automatic classification of time-variable X-ray sources

    International Nuclear Information System (INIS)

    Lo, Kitty K.; Farrell, Sean; Murphy, Tara; Gaensler, B. M.

    2014-01-01

    To maximize the discovery potential of future synoptic surveys, especially in the field of transient science, it will be necessary to use automatic classification to identify some of the astronomical sources. The data mining technique of supervised classification is suitable for this problem. Here, we present a supervised learning method to automatically classify variable X-ray sources in the Second XMM-Newton Serendipitous Source Catalog (2XMMi-DR2). Random Forest is our classifier of choice since it is one of the most accurate learning algorithms available. Our training set consists of 873 variable sources and their features are derived from time series, spectra, and other multi-wavelength contextual information. The 10 fold cross validation accuracy of the training data is ∼97% on a 7 class data set. We applied the trained classification model to 411 unknown variable 2XMM sources to produce a probabilistically classified catalog. Using the classification margin and the Random Forest derived outlier measure, we identified 12 anomalous sources, of which 2XMM J180658.7–500250 appears to be the most unusual source in the sample. Its X-ray spectra is suggestive of a ultraluminous X-ray source but its variability makes it highly unusual. Machine-learned classification and anomaly detection will facilitate scientific discoveries in the era of all-sky surveys.

  19. Automatic classification of time-variable X-ray sources

    Energy Technology Data Exchange (ETDEWEB)

    Lo, Kitty K.; Farrell, Sean; Murphy, Tara; Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia)

    2014-05-01

    To maximize the discovery potential of future synoptic surveys, especially in the field of transient science, it will be necessary to use automatic classification to identify some of the astronomical sources. The data mining technique of supervised classification is suitable for this problem. Here, we present a supervised learning method to automatically classify variable X-ray sources in the Second XMM-Newton Serendipitous Source Catalog (2XMMi-DR2). Random Forest is our classifier of choice since it is one of the most accurate learning algorithms available. Our training set consists of 873 variable sources and their features are derived from time series, spectra, and other multi-wavelength contextual information. The 10 fold cross validation accuracy of the training data is ∼97% on a 7 class data set. We applied the trained classification model to 411 unknown variable 2XMM sources to produce a probabilistically classified catalog. Using the classification margin and the Random Forest derived outlier measure, we identified 12 anomalous sources, of which 2XMM J180658.7–500250 appears to be the most unusual source in the sample. Its X-ray spectra is suggestive of a ultraluminous X-ray source but its variability makes it highly unusual. Machine-learned classification and anomaly detection will facilitate scientific discoveries in the era of all-sky surveys.

  20. Numerical counting ratemeter with variable time constant and integrated circuits

    International Nuclear Information System (INIS)

    Kaiser, J.; Fuan, J.

    1967-01-01

    We present here the prototype of a numerical counting ratemeter which is a special version of variable time-constant frequency meter (1). The originality of this work lies in the fact that the change in the time constant is carried out automatically. Since the criterion for this change is the accuracy in the annunciated result, the integration time is varied as a function of the frequency. For the prototype described in this report, the time constant varies from 1 sec to 1 millisec. for frequencies in the range 10 Hz to 10 MHz. This prototype is built entirely of MECL-type integrated circuits from Motorola and is thus contained in two relatively small boxes. (authors) [fr

  1. Quadratic time dependent Hamiltonians and separation of variables

    International Nuclear Information System (INIS)

    Anzaldo-Meneses, A.

    2017-01-01

    Time dependent quantum problems defined by quadratic Hamiltonians are solved using canonical transformations. The Green’s function is obtained and a comparison with the classical Hamilton–Jacobi method leads to important geometrical insights like exterior differential systems, Monge cones and time dependent Gaussian metrics. The Wei–Norman approach is applied using unitary transformations defined in terms of generators of the associated Lie groups, here the semi-direct product of the Heisenberg group and the symplectic group. A new explicit relation for the unitary transformations is given in terms of a finite product of elementary transformations. The sequential application of adequate sets of unitary transformations leads naturally to a new separation of variables method for time dependent Hamiltonians, which is shown to be related to the Inönü–Wigner contraction of Lie groups. The new method allows also a better understanding of interacting particles or coupled modes and opens an alternative way to analyze topological phases in driven systems. - Highlights: • Exact unitary transformation reducing time dependent quadratic quantum Hamiltonian to zero. • New separation of variables method and simultaneous uncoupling of modes. • Explicit examples of transformations for one to four dimensional problems. • New general evolution equation for quadratic form in the action, respectively Green’s function.

  2. Prewhitening of hydroclimatic time series? Implications for inferred change and variability across time scales

    Science.gov (United States)

    Razavi, Saman; Vogel, Richard

    2018-02-01

    Prewhitening, the process of eliminating or reducing short-term stochastic persistence to enable detection of deterministic change, has been extensively applied to time series analysis of a range of geophysical variables. Despite the controversy around its utility, methodologies for prewhitening time series continue to be a critical feature of a variety of analyses including: trend detection of hydroclimatic variables and reconstruction of climate and/or hydrology through proxy records such as tree rings. With a focus on the latter, this paper presents a generalized approach to exploring the impact of a wide range of stochastic structures of short- and long-term persistence on the variability of hydroclimatic time series. Through this approach, we examine the impact of prewhitening on the inferred variability of time series across time scales. We document how a focus on prewhitened, residual time series can be misleading, as it can drastically distort (or remove) the structure of variability across time scales. Through examples with actual data, we show how such loss of information in prewhitened time series of tree rings (so-called "residual chronologies") can lead to the underestimation of extreme conditions in climate and hydrology, particularly droughts, reconstructed for centuries preceding the historical period.

  3. Valuing travel time variability: Characteristics of the travel time distribution on an urban road

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Fukuda, Daisuke

    2012-01-01

    This paper provides a detailed empirical investigation of the distribution of travel times on an urban road for valuation of travel time variability. Our investigation is premised on the use of a theoretical model with a number of desirable properties. The definition of the value of travel time...... variability depends on certain properties of the distribution of random travel times that require empirical verification. Applying a range of nonparametric statistical techniques to data giving minute-by-minute travel times for a congested urban road over a period of five months, we show that the standardized...... travel time is roughly independent of the time of day as required by the theory. Except for the extreme right tail, a stable distribution seems to fit the data well. The travel time distributions on consecutive links seem to share a common stability parameter such that the travel time distribution...

  4. Time variable cosmological constants from the age of universe

    International Nuclear Information System (INIS)

    Xu Lixin; Lu Jianbo; Li Wenbo

    2010-01-01

    In this Letter, time variable cosmological constant, dubbed age cosmological constant, is investigated motivated by the fact: any cosmological length scale and time scale can introduce a cosmological constant or vacuum energy density into Einstein's theory. The age cosmological constant takes the form ρ Λ =3c 2 M P 2 /t Λ 2 , where t Λ is the age or conformal age of our universe. The effective equation of state (EoS) of age cosmological constant are w Λ eff =-1+2/3 (√(Ω Λ ))/c and w Λ eff =-1+2/3 (√(Ω Λ ))/c (1+z) when the age and conformal age of universe are taken as the role of cosmological time scales respectively. The EoS are the same as the so-called agegraphic dark energy models. However, the evolution histories are different from the agegraphic ones for their different evolution equations.

  5. Time and space variability of spectral estimates of atmospheric pressure

    Science.gov (United States)

    Canavero, Flavio G.; Einaudi, Franco

    1987-01-01

    The temporal and spatial behaviors of atmospheric pressure spectra over the northern Italy and the Alpine massif were analyzed using data on surface pressure measurements carried out at two microbarograph stations in the Po Valley, one 50 km south of the Alps, the other in the foothills of the Dolomites. The first 15 days of the study overlapped with the Alpex Intensive Observation Period. The pressure records were found to be intrinsically nonstationary and were found to display substantial time variability, implying that the statistical moments depend on time. The shape and the energy content of spectra depended on different time segments. In addition, important differences existed between spectra obtained at the two stations, indicating a substantial effect of topography, particularly for periods less than 40 min.

  6. Quadratic time dependent Hamiltonians and separation of variables

    Science.gov (United States)

    Anzaldo-Meneses, A.

    2017-06-01

    Time dependent quantum problems defined by quadratic Hamiltonians are solved using canonical transformations. The Green's function is obtained and a comparison with the classical Hamilton-Jacobi method leads to important geometrical insights like exterior differential systems, Monge cones and time dependent Gaussian metrics. The Wei-Norman approach is applied using unitary transformations defined in terms of generators of the associated Lie groups, here the semi-direct product of the Heisenberg group and the symplectic group. A new explicit relation for the unitary transformations is given in terms of a finite product of elementary transformations. The sequential application of adequate sets of unitary transformations leads naturally to a new separation of variables method for time dependent Hamiltonians, which is shown to be related to the Inönü-Wigner contraction of Lie groups. The new method allows also a better understanding of interacting particles or coupled modes and opens an alternative way to analyze topological phases in driven systems.

  7. Mechanisms of northeastern Brazil rainfall anomalies due to Southern Tropical Atlantic variability

    Science.gov (United States)

    Neelin, J.; Su, H.

    2004-05-01

    Observational studies have shown that the rainfall anomalies in eastern equatorial South America, including Nordeste Brazil, have a positive correlation with tropical southern Atlantic sea surface temperature (SST) anomalies. Such relationships are reproduced in model simulations with the quasi-equilibrium tropical circulation model (QTCM), which includes a simple land model. A suite of model ensemble experiments is analysed using observed SST over the tropical oceans, the tropical Atlantic and the tropical southern Atlantic (30S-0), respectively (with climatological SST in the remainder of the oceans). Warm tropical south Atlantic SST anomalies yield positive precipitation anomalies over the Nordeste and the southern edge of the Atlantic marine intertropical convergence zone (ITCZ). Mechanisms associated with moisture variations are responsible for the land precipitation changes. Increases in moisture over the Atlantic cause positive anomalies in moisture advection, spreading increased moisture downwind. Where the basic state is far from the convective stability threshold, moisture changes have little effect, but the margins of the climatological convection zone are affected. The increased moisture supply due to advection is enhanced by increases in low-level convergence required by moist static energy balances. The moisture convergence term is several times larger, but experiments altering the moisture advection confirm that the feedback is initiated by wind acting on moisture gradient. This mechanism has several features in common with the recently published "upped-ante" mechanism for El Nino impacts on this region. In that case, the moisture gradient is initiated by warm free tropospheric temperature anomalies increasing the typical value of low-level moisture required to sustain convection in the convection zones. Both mechanisms suggest the usefulness of coordinating ocean and land in situ observations of boundary layer moisture.

  8. SU-E-T-41: Analysis of GI Dose Variability Due to Intrafraction Setup Variance

    International Nuclear Information System (INIS)

    Phillips, J; Wolfgang, J

    2014-01-01

    Purpose: Proton SBRT (stereotactic body radiation therapy) can be an effective modality for treatment of gastrointestinal tumors, but limited in practice due to sensitivity with respect to variation in the RPL (radiological path length). Small, intrafractional shifts in patient anatomy can lead to significant changes in the dose distribution. This study describes a tool designed to visualize uncertainties in radiological depth in patient CT's and aid in treatment plan design. Methods: This project utilizes the Shadie toolkit, a GPU-based framework that allows for real-time interactive calculations for volume visualization. Current SBRT simulation practice consists of a serial CT acquisition for the assessment of inter- and intra-fractional motion utilizing patient specific immobilization systems. Shadie was used to visualize potential uncertainties, including RPL variance and changes in gastric content. Input for this procedure consisted of two patient CT sets, contours of the desired organ, and a pre-calculated dose. In this study, we performed rigid registrations between sets of 4DCT's obtained from a patient with varying setup conditions. Custom visualizations are written by the user in Shadie, permitting one to create color-coded displays derived from a calculation along each ray. Results: Serial CT data acquired on subsequent days was analyzed for variation in RPB and gastric content. Specific shaders were created to visualize clinically relevant features, including RPL (radiological path length) integrated up to organs of interest. Using pre-calculated dose distributions and utilizing segmentation masks as additional input allowed us to further refine the display output from Shadie and create tools suitable for clinical usage. Conclusion: We have demonstrated a method to visualize potential uncertainty for intrafractional proton radiotherapy. We believe this software could prove a useful tool to guide those looking to design treatment plans least

  9. System-theoretic analysis of due-time performance in production systems

    OpenAIRE

    Jacobs David; Meerkov Semyon M.

    1995-01-01

    Along with the average production rate, the due-time performance is an important characteristic of manufacturing systems. Unlike the production rate, the due-time performance has received relatively little attention in the literature, especially in the context of large volume production. This paper is devoted to this topic. Specifically, the notion of due-time performance is formalized as the probability that the number of parts produced during the shipping period reaches the required shipme...

  10. Time dependent analysis of assay comparability: a novel approach to understand intra- and inter-site variability over time

    Science.gov (United States)

    Winiwarter, Susanne; Middleton, Brian; Jones, Barry; Courtney, Paul; Lindmark, Bo; Page, Ken M.; Clark, Alan; Landqvist, Claire

    2015-09-01

    We demonstrate here a novel use of statistical tools to study intra- and inter-site assay variability of five early drug metabolism and pharmacokinetics in vitro assays over time. Firstly, a tool for process control is presented. It shows the overall assay variability but allows also the following of changes due to assay adjustments and can additionally highlight other, potentially unexpected variations. Secondly, we define the minimum discriminatory difference/ratio to support projects to understand how experimental values measured at different sites at a given time can be compared. Such discriminatory values are calculated for 3 month periods and followed over time for each assay. Again assay modifications, especially assay harmonization efforts, can be noted. Both the process control tool and the variability estimates are based on the results of control compounds tested every time an assay is run. Variability estimates for a limited set of project compounds were computed as well and found to be comparable. This analysis reinforces the need to consider assay variability in decision making, compound ranking and in silico modeling.

  11. Variable dead time counters: 2. A computer simulation

    International Nuclear Information System (INIS)

    Hooton, B.W.; Lees, E.W.

    1980-09-01

    A computer model has been developed to give a pulse train which simulates that generated by a variable dead time counter (VDC) used in safeguards determination of Pu mass. The model is applied to two algorithms generally used for VDC analysis. It is used to determine their limitations at high counting rates and to investigate the effects of random neutrons from (α,n) reactions. Both algorithms are found to be deficient for use with masses of 240 Pu greater than 100g and one commonly used algorithm is shown, by use of the model and also by theory, to yield a result which is dependent on the random neutron intensity. (author)

  12. Single-machine common/slack due window assignment problems with linear decreasing processing times

    Science.gov (United States)

    Zhang, Xingong; Lin, Win-Chin; Wu, Wen-Hsiang; Wu, Chin-Chia

    2017-08-01

    This paper studies linear non-increasing processing times and the common/slack due window assignment problems on a single machine, where the actual processing time of a job is a linear non-increasing function of its starting time. The aim is to minimize the sum of the earliness cost, tardiness cost, due window location and due window size. Some optimality results are discussed for the common/slack due window assignment problems and two O(n log n) time algorithms are presented to solve the two problems. Finally, two examples are provided to illustrate the correctness of the corresponding algorithms.

  13. Years of Life Gained Due to Leisure-Time Physical Activity in the United States

    Science.gov (United States)

    Janssen, Ian; Carson, Valerie; Lee, I-Min; Katzmarzyk, Peter T.; Blair, Steven N.

    2013-01-01

    Background Physical inactivity is an important modifiable risk factor for non-communicable disease. The degree to which physical activity affects the life expectancy of Americans is unknown. This study estimated the potential years of life gained due to leisure-time physical activity across the adult lifespan in the United States. Methods Data from the National Health and Nutrition Examination Survey (2007–2010), National Health Interview Study mortality linkage (1990–2006), and US Life Tables (2006) were used to estimate and compare life expectancy at each age of adult life for inactive (no moderate-to-vigorous physical activity), somewhat active (some moderate-to-vigorous activity but active (≥500 metabolic equivalent min/week of moderate-to-vigorous activity) adults. Analyses were conducted in 2012. Results Somewhat active and active non-Hispanic white men had a life expectancy at age 20 that was around 2.4 years longer than the inactive men; this life expectancy advantage was 1.2 years at age 80. Similar observations were made in non-Hispanic white women, with a higher life expectancy within the active category of 3.0 years at age 20 and 1.6 years at age 80. In non-Hispanic black women, as many as 5.5 potential years of life were gained due to physical activity. Significant increases in longevity were also observed within somewhat active and active non-Hispanic black men; however, among Hispanics the years of life gained estimates were more variable and not significantly different from 0 years gained. Conclusions Leisure-time physical activity is associated with increases in longevity in the United States. PMID:23253646

  14. Total sitting time, leisure time physical activity and risk of hospitalization due to low back pain

    DEFF Research Database (Denmark)

    Balling, Mie; Holmberg, Teresa; Petersen, Christina B

    2018-01-01

    AIMS: This study aimed to test the hypotheses that a high total sitting time and vigorous physical activity in leisure time increase the risk of low back pain and herniated lumbar disc disease. METHODS: A total of 76,438 adults answered questions regarding their total sitting time and physical...... activity during leisure time in the Danish Health Examination Survey 2007-2008. Information on low back pain diagnoses up to 10 September 2015 was obtained from The National Patient Register. The mean follow-up time was 7.4 years. Data were analysed using Cox regression analysis with adjustment...... disc disease. However, moderate or vigorous physical activity, as compared to light physical activity, was associated with increased risk of low back pain (HR = 1.16, 95% CI: 1.03-1.30 and HR = 1.45, 95% CI: 1.15-1.83). Moderate, but not vigorous physical activity was associated with increased risk...

  15. Electrical Activity in a Time-Delay Four-Variable Neuron Model under Electromagnetic Induction

    Directory of Open Access Journals (Sweden)

    Keming Tang

    2017-11-01

    Full Text Available To investigate the effect of electromagnetic induction on the electrical activity of neuron, the variable for magnetic flow is used to improve Hindmarsh–Rose neuron model. Simultaneously, due to the existence of time-delay when signals are propagated between neurons or even in one neuron, it is important to study the role of time-delay in regulating the electrical activity of the neuron. For this end, a four-variable neuron model is proposed to investigate the effects of electromagnetic induction and time-delay. Simulation results suggest that the proposed neuron model can show multiple modes of electrical activity, which is dependent on the time-delay and external forcing current. It means that suitable discharge mode can be obtained by selecting the time-delay or external forcing current, which could be helpful for further investigation of electromagnetic radiation on biological neuronal system.

  16. Variable slip wind generator modeling for real-time simulation

    Energy Technology Data Exchange (ETDEWEB)

    Gagnon, R.; Brochu, J.; Turmel, G. [Hydro-Quebec, Varennes, PQ (Canada). IREQ

    2006-07-01

    A model of a wind turbine using a variable slip wound-rotor induction machine was presented. The model was created as part of a library of generic wind generator models intended for wind integration studies. The stator winding of the wind generator was connected directly to the grid and the rotor was driven by the turbine through a drive train. The variable resistors was synthesized by an external resistor in parallel with a diode rectifier. A forced-commutated power electronic device (IGBT) was connected to the wound rotor by slip rings and brushes. Simulations were conducted in a Matlab/Simulink environment using SimPowerSystems blocks to model power systems elements and Simulink blocks to model the turbine, control system and drive train. Detailed descriptions of the turbine, the drive train and the control system were provided. The model's implementation in the simulator was also described. A case study demonstrating the real-time simulation of a wind generator connected at the distribution level of a power system was presented. Results of the case study were then compared with results obtained from the SimPowerSystems off-line simulation. Results showed good agreement between the waveforms, demonstrating the conformity of the real-time and the off-line simulations. The capability of Hypersim for real-time simulation of wind turbines with power electronic converters in a distribution network was demonstrated. It was concluded that hardware-in-the-loop (HIL) simulation of wind turbine controllers for wind integration studies in power systems is now feasible. 5 refs., 1 tab., 6 figs.

  17. System-theoretic analysis of due-time performance in production systems

    Directory of Open Access Journals (Sweden)

    David Jacobs

    1995-01-01

    Full Text Available Along with the average production rate, the due-time performance is an important characteristic of manufacturing systems. Unlike the production rate, the due-time performance has received relatively little attention in the literature, especially in the context of large volume production. This paper is devoted to this topic. Specifically, the notion of due-time performance is formalized as the probability that the number of parts produced during the shipping period reaches the required shipment size. This performance index is analyzed for both lean and mass manufacturing environments. In particular, it is shown that, to achieve a high due-time performance in a lean environment, the production system should be scheduled for a sufficiently small fraction of its average production rate. In mass production, due-time performance arbitrarily close to one can be achieved for any scheduling practice, up to the average production rate.

  18. Variability of interconnected wind plants: correlation length and its dependence on variability time scale

    Science.gov (United States)

    St. Martin, Clara M.; Lundquist, Julie K.; Handschy, Mark A.

    2015-04-01

    The variability in wind-generated electricity complicates the integration of this electricity into the electrical grid. This challenge steepens as the percentage of renewably-generated electricity on the grid grows, but variability can be reduced by exploiting geographic diversity: correlations between wind farms decrease as the separation between wind farms increases. But how far is far enough to reduce variability? Grid management requires balancing production on various timescales, and so consideration of correlations reflective of those timescales can guide the appropriate spatial scales of geographic diversity grid integration. To answer ‘how far is far enough,’ we investigate the universal behavior of geographic diversity by exploring wind-speed correlations using three extensive datasets spanning continents, durations and time resolution. First, one year of five-minute wind power generation data from 29 wind farms span 1270 km across Southeastern Australia (Australian Energy Market Operator). Second, 45 years of hourly 10 m wind-speeds from 117 stations span 5000 km across Canada (National Climate Data Archive of Environment Canada). Finally, four years of five-minute wind-speeds from 14 meteorological towers span 350 km of the Northwestern US (Bonneville Power Administration). After removing diurnal cycles and seasonal trends from all datasets, we investigate dependence of correlation length on time scale by digitally high-pass filtering the data on 0.25-2000 h timescales and calculating correlations between sites for each high-pass filter cut-off. Correlations fall to zero with increasing station separation distance, but the characteristic correlation length varies with the high-pass filter applied: the higher the cut-off frequency, the smaller the station separation required to achieve de-correlation. Remarkable similarities between these three datasets reveal behavior that, if universal, could be particularly useful for grid management. For high

  19. Accretion torques due to three-dimensional channelled flows in magnetic cataclysmic variables

    International Nuclear Information System (INIS)

    Campbell, C.G.

    1986-01-01

    Angular momentum transfer due to three-dimensional magnetically channelled accretion flows in cataclysmic binaries is considered. The white dwarf experiences a torque due to the twist in that part of its magnetic field which interacts with the accretion stream. The channelling process can also enhance angular momentum exchange between the stream and the orbit by increasing the gravitational torques. The components of the accretion torque are calculated for an arbitrary static magnetic orientation of the white dwarf, and their variation with orientation is presented. For high inclinations of the accreting pole to the orbital plane the component of the accretion torque parallel to this plane can be comparable to its perpendicular component. It is shown that the parallel component of the torque is still significant relative to the perpendicular component if material links to the white dwarf's magnetic field well away from the L 1 region. (author)

  20. Time-scales of stellar rotational variability and starspot diagnostics

    Science.gov (United States)

    Arkhypov, Oleksiy V.; Khodachenko, Maxim L.; Lammer, Helmut; Güdel, Manuel; Lüftinger, Teresa; Johnstone, Colin P.

    2018-01-01

    The difference in stability of starspot distribution on the global and hemispherical scales is studied in the rotational spot variability of 1998 main-sequence stars observed by Kepler mission. It is found that the largest patterns are much more stable than smaller ones for cool, slow rotators, whereas the difference is less pronounced for hotter stars and/or faster rotators. This distinction is interpreted in terms of two mechanisms: (1) the diffusive decay of long-living spots in activity complexes of stars with saturated magnetic dynamos, and (2) the spot emergence, which is modulated by gigantic turbulent flows in convection zones of stars with a weaker magnetism. This opens a way for investigation of stellar deep convection, which is yet inaccessible for asteroseismology. Moreover, a subdiffusion in stellar photospheres was revealed from observations for the first time. A diagnostic diagram was proposed that allows differentiation and selection of stars for more detailed studies of these phenomena.

  1. Correlates of adolescent sleep time and variability in sleep time: the role of individual and health related characteristics.

    Science.gov (United States)

    Moore, Melisa; Kirchner, H Lester; Drotar, Dennis; Johnson, Nathan; Rosen, Carol; Redline, Susan

    2011-03-01

    Adolescents are predisposed to short sleep duration and irregular sleep patterns due to certain host characteristics (e.g., age, pubertal status, gender, ethnicity, socioeconomic class, and neighborhood distress) and health-related variables (e.g., ADHD, asthma, birth weight, and BMI). The aim of the current study was to investigate the relationship between such variables and actigraphic measures of sleep duration and variability. Cross-sectional study of 247 adolescents (48.5% female, 54.3% ethnic minority, mean age of 13.7years) involved in a larger community-based cohort study. Significant univariate predictors of sleep duration included gender, minority ethnicity, neighborhood distress, parent income, and BMI. In multivariate models, gender, minority status, and BMI were significantly associated with sleep duration (all pminority adolescents, and those of a lower BMI obtaining more sleep. Univariate models demonstrated that age, minority ethnicity, neighborhood distress, parent education, parent income, pubertal status, and BMI were significantly related to variability in total sleep time. In the multivariate model, age, minority status, and BMI were significantly related to variability in total sleep time (all pminority adolescents, and those of a lower BMI obtaining more regular sleep. These data show differences in sleep patterns in population sub-groups of adolescents which may be important in understanding pediatric health risk profiles. Sub-groups that may particularly benefit from interventions aimed at improving sleep patterns include boys, overweight, and minority adolescents. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Prolonged river water pollution due to variable-density flow and solute transport in the riverbed

    Science.gov (United States)

    Jin, Guangqiu; Tang, Hongwu; Li, Ling; Barry, D. A.

    2015-04-01

    A laboratory experiment and numerical modeling were used to examine effects of density gradients on hyporheic flow and solute transport under the condition of a solute pulse input to a river with regular bed forms. Relatively low-density gradients due to an initial salt pulse concentration of 1.55 kg m-3 applied in the experiment were found to modulate significantly the pore-water flow and solute transport in the riverbed. Such density gradients increased downward flow and solute transport in the riverbed by factors up to 1.6. This resulted in a 12.2% increase in the total salt transfer from the water column to the riverbed over the salt pulse period. As the solute pulse passed, the effect of the density gradients reversed, slowing down the release of the solute back to the river water by a factor of 3.7. Numerical modeling indicated that these density effects intensified as salt concentrations in the water column increased. Simulations further showed that the density gradients might even lead to unstable flow and result in solute fingers in the bed of large bed forms. The slow release of solute from the bed back to the river led to a long tail of solute concentration in the river water. These findings have implications for assessment of impact of pollution events on river systems, in particular, long-term effects on both the river water and riverbed due to the hyporheic exchange.

  3. Single Machine Scheduling and Due Date Assignment with Past-Sequence-Dependent Setup Time and Position-Dependent Processing Time

    Directory of Open Access Journals (Sweden)

    Chuan-Li Zhao

    2014-01-01

    Full Text Available This paper considers single machine scheduling and due date assignment with setup time. The setup time is proportional to the length of the already processed jobs; that is, the setup time is past-sequence-dependent (p-s-d. It is assumed that a job's processing time depends on its position in a sequence. The objective functions include total earliness, the weighted number of tardy jobs, and the cost of due date assignment. We analyze these problems with two different due date assignment methods. We first consider the model with job-dependent position effects. For each case, by converting the problem to a series of assignment problems, we proved that the problems can be solved in On4 time. For the model with job-independent position effects, we proved that the problems can be solved in On3 time by providing a dynamic programming algorithm.

  4. Efficient conservative ADER schemes based on WENO reconstruction and space-time predictor in primitive variables

    Science.gov (United States)

    Zanotti, Olindo; Dumbser, Michael

    2016-01-01

    schemes provide less oscillatory solutions when compared to ADER finite volume schemes based on the reconstruction in conserved variables, especially for the RMHD and the Baer-Nunziato equations. For the RHD and RMHD equations, the overall accuracy is improved and the CPU time is reduced by about 25 %. Because of its increased accuracy and due to the reduced computational cost, we recommend to use this version of ADER as the standard one in the relativistic framework. At the end of the paper, the new approach has also been extended to ADER-DG schemes on space-time adaptive grids (AMR).

  5. European seasonal mortality and influenza incidence due to winter temperature variability

    Science.gov (United States)

    Rodó, X.; Ballester, J.; Robine, J. M.; Herrmann, F. R.

    2017-12-01

    Recent studies have vividly emphasized the lack of consensus on the degree of vulnerability (sensu IPCC) of European societies to current and future winter temperatures. Here we consider several climate factors, influenza incidence and daily numbers of deaths to characterize the relationship between winter temperature and mortality in a very large ensemble of European regions representing more than 400 million people. Analyses highlight the strong association between the year-to-year fluctuations in winter mean temperature and mortality, with higher seasonal cases during harsh winters, in all of the countries except the United Kingdom, the Netherlands and Belgium. This spatial distribution contrasts with the well-documented latitudinal orientation of the dependency between daily temperature and mortality within the season. A theoretical framework is proposed to reconcile the apparent contradictions between recent studies, offering an interpretation to regional differences in the vulnerability to daily, seasonal and long-term winter temperature variability. Despite the lack of a strong year-to-year association between winter mean values in some countries, it can be concluded that warmer winters will contribute to the decrease in winter mortality everywhere in Europe. More information in Ballester J, et al. (2016) Nature Climate Change 6, 927-930, doi:10.1038/NCLIMATE3070.

  6. The Intrinsic Variability in the Water Vapor Saturation Ratio due to Turbulence

    Science.gov (United States)

    Anderson, J. C.; Cantrell, W. H.; Chandrakar, K. K.; Kostinski, A. B.; Niedermeier, D.; Shaw, R. A.

    2017-12-01

    In the atmosphere, the concentration of water vapor plays an important role in Earth's weather and climate. The mean concentration of water vapor is key to its efficiency as a greenhouse gas; the fluctuations about the mean are important for heat fluxes near the surface of earth. In boundary layer clouds, fluctuations in the water vapor concentration are linked to turbulence. Conditions representative of boundary layer clouds are simulated in Michigan Tech's multiphase, turbulent reaction chamber, the ∏ chamber, where the boundary conditions are controlled and repeatable. Measurements for temperature and water vapor concentration were recorded under forced Rayleigh-Bénard convection. As expected, the distributions for temperature and water vapor concentration broaden as the turbulence becomes more vigorous. From these two measurements the saturation ratio can be calculated. The fluctuations in the water vapor concentration are more important to the variability in the saturation ratio than fluctuations in temperature. In a cloud, these fluctuations in the saturation ratio can result in some cloud droplets experiencing much higher supersaturations. Those "lucky" droplets grow by condensation at a faster rate than other cloud droplets. The difference in the droplet growth rate could contribute to a broadened droplet distribution, which leads to the onset of collision-coalescence. With more intense turbulence these effect will become more pronounced as the fluctuations about the mean saturation ratio become more pronounced.

  7. Perfectionistic Cognitions: Stability, Variability, and Changes Over Time.

    Science.gov (United States)

    Prestele, Elisabeth; Altstötter-Gleich, Christine

    2018-02-01

    The construct of perfectionistic cognitions is defined as a state-like construct resulting from a perfectionistic self-schema and activated by specific situational demands. Only a few studies have investigated whether and how perfectionistic cognitions change across different situations and whether they reflect stable between-person differences or also within-person variations over time. We conducted 2 studies to investigate the variability and stability of 3 dimensions of perfectionistic cognitions while situational demands changed (Study 1) and on a daily level during a highly demanding period of time (Study 2). The results of both studies revealed that stable between-person differences accounted for the largest proportion of variance in the dimensions of perfectionistic cognitions and that these differences were validly associated with between-person differences in affect. The frequency of perfectionistic cognitions increased during students' first semester at university, and these average within-person changes were different for the 3 dimensions of perfectionistic cognitions (Study 1). In addition, there were between-person differences in the within-person changes that were validly associated with concurrent changes in closely related constructs (unpleasant mood and tense arousal). Within-person variations in perfectionistic cognitions were also validly associated with variations in unpleasant mood and tense arousal from day to day (Study 2).

  8. Chaos synchronization in time-delayed systems with parameter mismatches and variable delay times

    International Nuclear Information System (INIS)

    Shahverdiev, E.M.; Nuriev, R.A.; Hashimov, R.H.; Shore, K.A.

    2004-06-01

    We investigate synchronization between two undirectionally linearly coupled chaotic nonidentical time-delayed systems and show that parameter mismatches are of crucial importance to achieve synchronization. We establish that independent of the relation between the delay time in the coupled systems and the coupling delay time, only retarded synchronization with the coupling delay time is obtained. We show that with parameter mismatch or without it neither complete nor anticipating synchronization occurs. We derive existence and stability conditions for the retarded synchronization manifold. We demonstrate our approach using examples of the Ikeda and Mackey Glass models. Also for the first time we investigate chaos synchronization in time-delayed systems with variable delay time and find both existence and sufficient stability conditions for the retarded synchronization manifold with the coupling-delay lag time. (author)

  9. Investigating Intergenerational Differences in Human PCB Exposure due to Variable Emissions and Reproductive Behaviors

    Science.gov (United States)

    Quinn, Cristina L.; Wania, Frank; Czub, Gertje; Breivik, Knut

    2011-01-01

    Background Reproductive behaviors—such as age of childbearing, parity, and breast-feeding prevalence—have changed over the same historical time period as emissions of polychlorinated biphenyls (PCB) and may produce intergenerational differences in human PCB exposure. Objectives Our goal in this study was to estimate prenatal, postnatal, and lifetime PCB exposures for women at different ages according to year of birth, and to evaluate the impact of reproductive characteristics on intergenerational differences in exposure. Methods We used the time-variant mechanistic model CoZMoMAN to calculate human bioaccumulation of PCBs, assuming both hypothetical constant and realistic time-variant emissions. Results Although exposure primarily depends on when an individual was born relative to the emission history of PCBs, reproductive behaviors can have a significant impact. Our model suggests that a mother’s reproductive history has a greater influence on the prenatal and postnatal exposures of her children than it does on her own cumulative lifetime exposure. In particular, a child’s birth order appears to have a strong influence on their prenatal exposure, whereas postnatal exposure is determined by the type of milk (formula or breast milk) fed to the infant. Conclusions Prenatal PCB exposure appears to be delayed relative to the time of PCB emissions, particularly among those born after the PCB production phaseout. Consequently, the health repercussions of environmental PCBs can be expected to persist for several decades, despite bans on their production for > 40 years. PMID:21156396

  10. Fractal and variability analysis of simulations in ozone level due to oxides of nitrogen and sulphur

    Science.gov (United States)

    Bhardwaj, Rashmi; Pruthi, Dimple

    2017-10-01

    Air pollution refers to the release of pollutants into the air. These pollutants are detrimental to human the planet as a whole. Apart from causing respiratory infections and pulmonary disorders, rising levels of Nitrogen Dioxide is worsening ozone pollution. Formation of Ground-level ozone involves nitrogen oxides and volatile gases in the sunlight. Volatile gases are emitted from vehicles primarily. Ozone is harmful gas and its exposure can trigger serious health effects as it damages lung tissues. In order to decrease the level of ozone, level of oxides leading to ozone formation has to be dealt with. This paper deals with the simulations in ozone due to oxides of nitrogen and sulphur. The data from Central Pollution Control Board shows positive correlation for ozone with oxides of sulphur and nitrogen for RK Puram, Delhi in India where high concentration of ozone has been found. The correlation between ozone and sulphur, nitrogen oxides is moderate during summer while weak during winters. Ozone with nitrogen and sulphur dioxide follow persistent behavior as Hurst exponent is between 0.5 and 1. The fractal dimension for Sulphur dioxide is 1.4957 indicating the Brownian motion. The behavior of ozone is unpredictable as index of predictability is close to zero.

  11. [Deaths due to motorcycle accidents and their association with variables related to social reproduction in a northeastern Brazilian state].

    Science.gov (United States)

    Silva, Paul Hindenburg Nobre de Vasconcelos; Lima, Maria Luiza Carvalho; Souza, Wayner Vieira; Moreira, Rafael da Silveira; Oliveira, Fernando José Moreira

    2015-09-01

    The objective of this article was to identify the association between motorcycle deaths and variables related to Samaja's theory of social reproduction in the period 2000-2005 in the state of Pernambuco. An ecological, case-control study was carried out, with municipalities as the unit of analysis. Cases were defined as the 20% of municipalities with the highest local empirical Bayesian coefficients for mortality due to motorcycle accidents, and controls as the 40% with the lowest coefficients. The municipalities with the greatest chances of high coefficients for mortality due to motorcycle accidents showed high population growth factors and increases in the total fleet of motorcycles, with low population densities, low GDP per capita, and more than 20 motorcycles per thousand inhabitants. We conclude that the variables related to macro-policies proved to have greater force in explaining higher chances of motorcycle death.

  12. [Chonic diarrhea and malabsorption due to common variable immunodeficiency, gastrectomy and giardiasis infection: a difficult nutritional management].

    Science.gov (United States)

    Domínguez-López, M E; González-molero, I; Ramírez-Plaza, C P; Soriguer, F; Olveira, G

    2011-01-01

    Gastric cancer is a frequent cause of cancer-related mortality in the world. Surgery is the only potentially curative therapy, although the adverse effects of surgery are common and considerable. Common variable immunodeficiency is in many cases cause of gastrointestinal system problems such as chronic diarrhea caused by infestation with giardia lamblia, nodular lymphoid hiperplasia ad loss of villi leading frequently to malapsortion and malnutrition. Nutritional deficiencies due to malapsorption (postgastrectomy and secondary to loss of villi, giardiasis and common variable inmunodeficiency) are common. We present the case of a patient with gastric cancer who underwent a gastrectomy with common variable hipogammaglobulinemia and chronic infestation by giardia lamblia, with serious diarrhea resistant to treatment and malabsorption.

  13. Analysis of time variable gravity data over Africa

    International Nuclear Information System (INIS)

    Barletta, Valentina R.; Aoudia, Abdelkarim

    2010-01-01

    Africa, in principle, is a unique laboratory where to address the individual contribution of the different facets of the Earth system as well as their interactions. However, it shows both a rich hydrology that exhibits complex characteristics of rivers and wide basins of different sizes in addition to the hydrology of lakes, and other wetlands and storage reservoirs and groundwater aquifers, and continuous and discontinuous changes in the physical properties of the Earth interior. Stretching and heating processes are accompanied by punctuated episodes of faulting and/or volcanism, and longer-term changes in surface elevation that disrupt river drainage and climate. Space gravity missions GRACE, flying since 2002, was expressly designed to detect the time-dependent gravity field in order to study the hydrological cycle of the Earth, but has also evidenced Solid Earth phenomena such as Post Glacial Rebound (PGR) and the signature of a giant earthquake such as the 2004 Sumatra. Hence the idea to analyze time variable gravity data over Africa in order to retrieve fingerprints of geophysical phenomena. The exploitation of the GRACE data for geophysics, however, is not straightforward. Indeed, the quality of the signal is not uniform worldwide and gravity is always the superposition of contributions from solid Earth as well as climate-related phenomena, that cannot be easily distinguished, at a first glance, both in time and space. In the present study we show that mass changes cannot be classified simply as trends or periodic signals. We follow an alternative way to separate complementary components, periodic and non-periodic signals, without loosing information. We show that the a priori periodic and linear trend fitting function is not everywhere appropriate and in some cases it is even so poor to result in misinterpreting the data. Variations in long term behavior and periodicities higher than the usual annual (and semi-annual) indeed occur, related to geophysical

  14. The Chameleon Effect: Characterization Challenges Due to the Variability of Nanoparticles and Their Surfaces

    Directory of Open Access Journals (Sweden)

    Donald R. Baer

    2018-05-01

    Full Text Available Nanoparticles in a variety of forms are increasing important in fundamental research, technological and medical applications, and environmental or toxicology studies. Physical and chemical drivers that lead to multiple types of particle instabilities complicate both the ability to produce, appropriately characterize, and consistently deliver well-defined particles, frequently leading to inconsistencies, and conflicts in the published literature. This perspective suggests that provenance information, beyond that often recorded or reported, and application of a set of core characterization methods, including a surface sensitive technique, consistently applied at critical times can serve as tools in the effort minimize reproducibility issues.

  15. The Chameleon Effect: characterization challenges due to the variability of nanoparticles and their surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Baer, Donald R.

    2018-05-07

    Nanoparticles in a variety of forms are of increasing importance in fundamental research, technological and medical applications, and environmental or toxicology studies. Physical and chemical drivers that lead to multiple types of particle instabilities complicate both the ability to produce and consistently deliver well defined particles and their appropriate characterization, frequently leading to inconsistencies and conflicts in the published literature. This perspective suggests that provenance information, beyond that often recorded or reported, and application of a set of core characterization methods, including a surface sensitive technique, consistently applied at critical times can serve as tools in the effort minimize reproducibility issues.

  16. Synthesis of Biochemical Applications on Digital Microfluidic Biochips with Operation Execution Time Variability

    DEFF Research Database (Denmark)

    Alistar, Mirela; Pop, Paul

    2015-01-01

    that each biochemical operation in an application is characterized by a worst-case execution time (wcet). However, during the execution of the application, due to variability and randomness in biochemical reactions, operations may finish earlier than their wcetswcets, resulting in unexploited slack...... in the schedule. In this paper, we first propose an online synthesis strategy that re-synthesizes the application at runtime when operations experience variability in their execution time, exploiting thus the slack to obtain shorter application completion times. We also propose a quasi-static synthesis strategy...... approaches have been proposed for the synthesis of digital microfluidic biochips, which, starting from a biochemical application and a given biochip architecture, determine the allocation, resource binding, scheduling, placement and routing of the operations in the application. Researchers have assumed...

  17. Leisure Time of Young Due to Some Socio-Demographic Characteristics

    Science.gov (United States)

    Ðuranovic, Marina; Opic, Siniša

    2014-01-01

    The aim of this paper is to explore the prevalence of activities in leisure time of the young. A survey was conducted on 1062 students in 8 primary (n=505; 47,6%) and high schools (n=557; 52,4%) in Sisak - Moslavina County in the Republic of Croatia. The questionnaire of spending leisure time used was made up of 30 variables on a five-degree scale…

  18. Interannual Variation of Surface Circulation in the Japan/East Sea due to External Forcings and Intrinsic Variability

    Science.gov (United States)

    Choi, Byoung-Ju; Cho, Seong Hun; Jung, Hee Seok; Lee, Sang-Ho; Byun, Do-Seong; Kwon, Kyungman

    2018-03-01

    The interannual variation of surface ocean currents can be as large as seasonal variation in the Japan/East Sea (JES). To identify the major factors that cause such interannual variability of surface ocean circulation in the JES, surface circulation was simulated from 1998 to 2009 using a three-dimensional model. Contributions of atmospheric forcing (ATM), open boundary data (OBC), and intrinsic variability (ITV) of the surface flow in the JES on the interannual variability of surface ocean circulation were separately examined using numerical simulations. Variability in surface circulation was quantified in terms of variance in sea surface height, 100-m depth water temperature, and surface currents. ITV was found to be the dominant factor that induced interannual variabilities of surface circulation, the main path of the East Korea Warm Current (EKWC), and surface kinetic energy on a time scale of 2-4 years. OBC and ATM were secondary factors contributing to the interannual variation of surface circulation. Interannual variation of ATM changed the separation latitude of EKWC and increased the variability of surface circulation in the Ulleung Basin. Interannual variation of OBC enhanced low-frequency changes in surface circulation and eddies in the Yamato Basin. It also modulated basin-wide uniform oscillations of sea level. This study suggests that precise estimation of initial conditions using data assimilation is essential for long-term prediction of surface circulation in the JES.

  19. Density perturbations due to the inhomogeneous discrete spatial structure of space-time

    International Nuclear Information System (INIS)

    Wolf, C.

    1998-01-01

    For the case that space-time permits an inhomogeneous discrete spatial structure due to varying gravitational fields or a foam-like structure of space-time, it is demonstrated that thermodynamic reasoning implies that matter-density perturbations will arise in the early universe

  20. Risk Reduction Effects Due to the Start Time Extension of EDGs in OPR-1000

    International Nuclear Information System (INIS)

    Lim, Ho-Gon; Yang, Joon-Eon; Hwang, Mee-Jeong

    2006-01-01

    Under the condition that the ECCS rule in Korea will be revised based on the new U.S. 10 CFR 50.46, the risk impact due to the EDG start time extension is analyzed in the present study. This paper is composed of 6 sections. In the section 2, the LOCA break size that cannot be mitigable under the condition of extended EDG start time is obtained from the thermal hydraulic analysis. The section 3 discusses the frequency of the immitigable LOCA and the probability of the LOOP given a LOCA. In the section 4, the effect of the EDG start time extension on its failure probability is discussed with a qualitative manner. Finally, the whole risk change due to the EDG start time extension is calculated in the section 5 with the conclusions given in the section 6

  1. Leisure time physical activity, screen time, social background, and environmental variables in adolescents.

    Science.gov (United States)

    Mota, Jorge; Gomes, Helena; Almeida, Mariana; Ribeiro, José Carlos; Santos, Maria Paula

    2007-08-01

    This study analyzes the relationships between leisure time physical activity (LTPA), sedentary behaviors, socioeconomic status, and perceived environmental variables. The sample comprised 815 girls and 746 boys. In girls, non-LTPA participants reported significantly more screen time. Girls with safety concerns were more likely to be in the non-LTPA group (OR = 0.60) and those who agreed with the importance of aesthetics were more likely to be in the active-LTPA group (OR = 1.59). In girls, an increase of 1 hr of TV watching was a significant predictor of non-LTPA (OR = 0.38). LTPA for girls, but not for boys, seems to be influenced by certain modifiable factors of the built environment, as well as by time watching TV.

  2. Single-machine scheduling with release dates, due dates and family setup times

    NARCIS (Netherlands)

    Schutten, Johannes M.J.; van de Velde, S.L.; van de Velde, S.L.; Zijm, Willem H.M.

    1996-01-01

    We address the NP-hard problem of scheduling n independent jobs with release dates, due dates, and family setup times on a single machine to minimize the maximum lateness. This problem arises from the constant tug-of-war going on in manufacturing between efficient production and delivery

  3. Single-machine scheduling with release dates, due dates, and family setup times

    NARCIS (Netherlands)

    J.M.J. Schutten (Marco); S.L. van de Velde (Steef); W.H.M. Zijm

    1996-01-01

    textabstractWe address the NP-hard problem of scheduling n independent jobs with release dates, due dates, and family setup times on a single machine to minimize the maximum lateness. This problem arises from the constant tug-of-war going on in manufacturing between efficient production and delivery

  4. Mechanical and thermal stresses in a functionally graded rotating disk with variable thickness due to radially symmetry loads

    International Nuclear Information System (INIS)

    Bayat, Mehdi; Saleem, M.; Sahari, B.B.; Hamouda, A.M.S.; Mahdi, E.

    2009-01-01

    Rotating disks have many applications in the aerospace industry such as gas turbines and gears. These disks normally work under thermo mechanical loads. Minimizing the weight of such components can help reduce the overall payload in aerospace industry. For this purpose, a rotating functionally graded (FG) disk with variable thickness under a steady temperature field is considered in this paper. Thermo elastic solutions and the weight of the disk are related to the material grading index and the geometry of the disk. It is found that a disk with parabolic or hyperbolic convergent thickness profile has smaller stresses and displacements compared to a uniform thickness disk. Maximum radial stress due to centrifugal load in the solid disk with parabolic thickness profile may not be at the center unlike uniform thickness disk. Functionally graded disk with variable thickness has smaller stresses due to thermal load compared to those with uniform thickness. It is seen that for a given value of grading index, the FG disk having concave thickness profile is the lightest in weight whereas the FG disk with uniform thickness profile is the heaviest. Also for any given thickness profile, the weight of the FG disk lies in between the weights of the all-metal and the all-ceramic disks.

  5. Time-dependent inelastic analysis of metallic media using constitutive relations with state variables

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, V; Mukherjee, S [Cornell Univ., Ithaca, N.Y. (USA)

    1977-03-01

    A computational technique in terms of stress, strain and displacement rates is presented for the solution of boundary value problems for metallic structural elements at uniform elevated temperatures subjected to time varying loads. This method can accommodate any number of constitutive relations with state variables recently proposed by other researchers to model the inelastic deformation of metallic media at elevated temperatures. Numerical solutions are obtained for several structural elements subjected to steady loads. The constitutive relations used for these numerical solutions are due to Hart. The solutions are discussed in the context of the computational scheme and Hart's theory.

  6. Dynamics of macroeconomic and financial variables in different time horizons

    OpenAIRE

    Kim Karlsson, Hyunjoo

    2012-01-01

    This dissertation consists of an introductory chapter and four papers dealing with financial issues of open economies, which can be in two broad categorizations: 1) exchange rate movements and 2) stock market interdependence. The first paper covers how the exchange rate changes affect the prices of internationally traded goods. With the variables (the price of exports in exporters’ currency and the exchange rate, both of which are in logarithmic form) being cointegrated, a model with both lon...

  7. Time-of-flight depth image enhancement using variable integration time

    Science.gov (United States)

    Kim, Sun Kwon; Choi, Ouk; Kang, Byongmin; Kim, James Dokyoon; Kim, Chang-Yeong

    2013-03-01

    Time-of-Flight (ToF) cameras are used for a variety of applications because it delivers depth information at a high frame rate. These cameras, however, suffer from challenging problems such as noise and motion artifacts. To increase signal-to-noise ratio (SNR), the camera should calculate a distance based on a large amount of infra-red light, which needs to be integrated over a long time. On the other hand, the integration time should be short enough to suppress motion artifacts. We propose a ToF depth imaging method to combine advantages of short and long integration times exploiting an imaging fusion scheme proposed for color imaging. To calibrate depth differences due to the change of integration times, a depth transfer function is estimated by analyzing the joint histogram of depths in the two images of different integration times. The depth images are then transformed into wavelet domains and fused into a depth image with suppressed noise and low motion artifacts. To evaluate the proposed method, we captured a moving bar of a metronome with different integration times. The experiment shows the proposed method could effectively remove the motion artifacts while preserving high SNR comparable to the depth images acquired during long integration time.

  8. Critical time delay of the pineal melatonin rhythm in humans due to weak electromagnetic exposure.

    Science.gov (United States)

    Halgamuge, Malka N

    2013-08-01

    Electromagnetic fields (EMFs) can increase free radicals, activate the stress response and alter enzyme reactions. Intracellular signalling is mediated by free radicals and enzyme kinetics is affected by radical pair recombination rates. The magnetic field component of an external EMF can delay the "recombination rate" of free radical pairs. Magnetic fields thus increase radical life-times in biological systems. Although measured in nanoseconds, this extra time increases the potential to do more damage. Melatonin regulates the body's sleep-wake cycle or circadian rhythm. The World Health Organization (WHO) has confirmed that prolonged alterations in sleep patterns suppress the body's ability to make melatonin. Considerable cancer rates have been attributed to the reduction of melatonin production as a result of jet lag and night shift work. In this study, changes in circadian rhythm and melatonin concentration are observed due to the external perturbation of chemical reaction rates. We further analyze the pineal melatonin rhythm and investigate the critical time delay or maturation time of radical pair recombination rates, exploring the impact of the mRNA degradation rate on the critical time delay. The results show that significant melatonin interruption and changes to the circadian rhythm occur due to the perturbation of chemical reaction rates, as also reported in previous studies. The results also show the influence of the mRNA degradation rate on the circadian rhythm's critical time delay or maturation time. The results support the hypothesis that exposure to weak EMFs via melatonin disruption can adversely affect human health.

  9. Seasonal variability of the Red Sea, from GRACE time-variable gravity and altimeter sea surface height measurements

    Science.gov (United States)

    Wahr, John; Smeed, David; Leuliette, Eric; Swenson, Sean

    2014-05-01

    Seasonal variability of sea surface height and mass within the Red Sea, occurs mostly through the exchange of heat with the atmosphere and wind-driven inflow and outflow of water through the strait of Bab el Mandab that opens into the Gulf of Aden to the south. The seasonal effects of precipitation and evaporation, of water exchange through the Suez Canal to the north, and of runoff from the adjacent land, are all small. The flow through the Bab el Mandab involves a net mass transfer into the Red Sea during the winter and a net transfer out during the summer. But that flow has a multi-layer pattern, so that in the summer there is actually an influx of cool water at intermediate (~100 m) depths. Thus, summer water in the southern Red Sea is warmer near the surface due to higher air temperatures, but cooler at intermediate depths (especially in the far south). Summer water in the northern Red Sea experiences warming by air-sea exchange only. The temperature profile affects the water density, which impacts the sea surface height but has no effect on vertically integrated mass. Here, we study this seasonal cycle by combining GRACE time-variable mass estimates, altimeter (Jason-1, Jason-2, and Envisat) measurements of sea surface height, and steric sea surface height contributions derived from depth-dependent, climatological values of temperature and salinity obtained from the World Ocean Atlas. We find good consistency, particularly in the northern Red Sea, between these three data types. Among the general characteristics of our results are: (1) the mass contributions to seasonal SSHT variations are much larger than the steric contributions; (2) the mass signal is largest in winter, consistent with winds pushing water into the Red Sea through the Strait of Bab el Mandab in winter, and out during the summer; and (3) the steric signal is largest in summer, consistent with summer sea surface warming.

  10. An Epidemic Model of Computer Worms with Time Delay and Variable Infection Rate

    Directory of Open Access Journals (Sweden)

    Yu Yao

    2018-01-01

    Full Text Available With rapid development of Internet, network security issues become increasingly serious. Temporary patches have been put on the infectious hosts, which may lose efficacy on occasions. This leads to a time delay when vaccinated hosts change to susceptible hosts. On the other hand, the worm infection is usually a nonlinear process. Considering the actual situation, a variable infection rate is introduced to describe the spread process of worms. According to above aspects, we propose a time-delayed worm propagation model with variable infection rate. Then the existence condition and the stability of the positive equilibrium are derived. Due to the existence of time delay, the worm propagation system may be unstable and out of control. Moreover, the threshold τ0 of Hopf bifurcation is obtained. The worm propagation system is stable if time delay is less than τ0. When time delay is over τ0, the system will be unstable. In addition, numerical experiments have been performed, which can match the conclusions we deduce. The numerical experiments also show that there exists a threshold in the parameter a, which implies that we should choose appropriate infection rate β(t to constrain worm prevalence. Finally, simulation experiments are carried out to prove the validity of our conclusions.

  11. Nonlinear response of vessel walls due to short-time thermomechanical loading

    International Nuclear Information System (INIS)

    Pfeiffer, P.A.; Kulak, R.F.

    1994-01-01

    Maintaining structural integrity of the reactor pressure vessel (RPV) during a postulated core melt accident is an important safety consideration in the design of the vessel. This study addresses the failure predictions of the vessel due to thermal and pressure loadings fro the molten core debris depositing on the lower head of the vessel. Different loading combinations were considered based on the dead load, yield stress assumptions, material response and internal pressurization. The analyses considered only short term failure (quasi static) modes, long term failure modes were not considered. Short term failure modes include plastic instabilities of the structure and failure due to exceeding the failure strain. Long term failure odes would be caused by creep rupture that leads to plastic instability of the structure. Due to the sort time durations analyzed, creep was not considered in the analyses presented

  12. On time-frequence analysis of heart rate variability

    NARCIS (Netherlands)

    H.G. van Steenis (Hugo)

    2002-01-01

    textabstractThe aim of this research is to develop a time-frequency method suitable to study HRV in greater detail. The following approach was used: • two known time-frequency representations were applied to HRV to understand its advantages and disadvantages in describing HRV in frequency and in

  13. Implications on 1 + 1 D Tsunami Runup Modeling due to Time Features of the Earthquake Source

    Science.gov (United States)

    Fuentes, M.; Riquelme, S.; Ruiz, J.; Campos, J.

    2018-04-01

    The time characteristics of the seismic source are usually neglected in tsunami modeling, due to the difference in the time scale of both processes. Nonetheless, there are just a few analytical studies that intended to explain separately the role of the rise time and the rupture velocity. In this work, we extend an analytical 1 + 1 D solution for the shoreline motion time series, from the static case to the kinematic case, by including both rise time and rupture velocity. Our results show that the static case corresponds to a limit case of null rise time and infinite rupture velocity. Both parameters contribute in shifting the arrival time, but maximum runup may be affected by very slow ruptures and long rise time. Parametric analysis reveals that runup is strictly decreasing with the rise time while is highly amplified in a certain range of slow rupture velocities. For even lower rupture velocities, the tsunami excitation vanishes and for larger, quicker approaches to the instantaneous case.

  14. Implications on 1 + 1 D Tsunami Runup Modeling due to Time Features of the Earthquake Source

    Science.gov (United States)

    Fuentes, M.; Riquelme, S.; Ruiz, J.; Campos, J.

    2018-02-01

    The time characteristics of the seismic source are usually neglected in tsunami modeling, due to the difference in the time scale of both processes. Nonetheless, there are just a few analytical studies that intended to explain separately the role of the rise time and the rupture velocity. In this work, we extend an analytical 1 + 1 D solution for the shoreline motion time series, from the static case to the kinematic case, by including both rise time and rupture velocity. Our results show that the static case corresponds to a limit case of null rise time and infinite rupture velocity. Both parameters contribute in shifting the arrival time, but maximum runup may be affected by very slow ruptures and long rise time. Parametric analysis reveals that runup is strictly decreasing with the rise time while is highly amplified in a certain range of slow rupture velocities. For even lower rupture velocities, the tsunami excitation vanishes and for larger, quicker approaches to the instantaneous case.

  15. A variable reaction rate model for chlorine decay in drinking water due to the reaction with dissolved organic matter.

    Science.gov (United States)

    Hua, Pei; Vasyukova, Ekaterina; Uhl, Wolfgang

    2015-05-15

    A second order kinetic model for simulating chlorine decay in bulk water due to the reaction with dissolved organic matter (DOM) was developed. It takes into account the decreasing reactivity of dissolved organic matter using a variable reaction rate coefficient (VRRC) which decreases with an increasing conversion. The concentration of reducing species is surrogated by the maximum chlorine demand. Temperature dependency, respectively, is described by the Arrhenius-relationship. The accuracy and adequacy of the proposed model to describe chlorine decay in bulk water were evaluated and shown for very different waters and different conditions such as water mixing or rechlorination by applying statistical tests. It is thus very well suited for application in water quality modeling for distribution systems. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Fluorescence microscopy point spread function model accounting for aberrations due to refractive index variability within a specimen.

    Science.gov (United States)

    Ghosh, Sreya; Preza, Chrysanthe

    2015-07-01

    A three-dimensional (3-D) point spread function (PSF) model for wide-field fluorescence microscopy, suitable for imaging samples with variable refractive index (RI) in multilayered media, is presented. This PSF model is a key component for accurate 3-D image restoration of thick biological samples, such as lung tissue. Microscope- and specimen-derived parameters are combined with a rigorous vectorial formulation to obtain a new PSF model that accounts for additional aberrations due to specimen RI variability. Experimental evaluation and verification of the PSF model was accomplished using images from 175-nm fluorescent beads in a controlled test sample. Fundamental experimental validation of the advantage of using improved PSFs in depth-variant restoration was accomplished by restoring experimental data from beads (6  μm in diameter) mounted in a sample with RI variation. In the investigated study, improvement in restoration accuracy in the range of 18 to 35% was observed when PSFs from the proposed model were used over restoration using PSFs from an existing model. The new PSF model was further validated by showing that its prediction compares to an experimental PSF (determined from 175-nm beads located below a thick rat lung slice) with a 42% improved accuracy over the current PSF model prediction.

  17. Variable Neighbourhood Search and Mathematical Programming for Just-in-Time Job-Shop Scheduling Problem

    Directory of Open Access Journals (Sweden)

    Sunxin Wang

    2014-01-01

    Full Text Available This paper presents a combination of variable neighbourhood search and mathematical programming to minimize the sum of earliness and tardiness penalty costs of all operations for just-in-time job-shop scheduling problem (JITJSSP. Unlike classical E/T scheduling problem with each job having its earliness or tardiness penalty cost, each operation in this paper has its earliness and tardiness penalties, which are paid if the operation is completed before or after its due date. Our hybrid algorithm combines (i a variable neighbourhood search procedure to explore the huge feasible solution spaces efficiently by alternating the swap and insertion neighbourhood structures and (ii a mathematical programming model to optimize the completion times of the operations for a given solution in each iteration procedure. Additionally, a threshold accepting mechanism is proposed to diversify the local search of variable neighbourhood search. Computational results on the 72 benchmark instances show that our algorithm can obtain the best known solution for 40 problems, and the best known solutions for 33 problems are updated.

  18. Handling Time-dependent Variables : Antibiotics and Antibiotic Resistance

    NARCIS (Netherlands)

    Munoz-Price, L. Silvia; Frencken, Jos F.; Tarima, Sergey; Bonten, Marc

    2016-01-01

    Elucidating quantitative associations between antibiotic exposure and antibiotic resistance development is important. In the absence of randomized trials, observational studies are the next best alternative to derive such estimates. Yet, as antibiotics are prescribed for varying time periods,

  19. Towards Uniform Accelerometry Analysis: A Standardization Methodology to Minimize Measurement Bias Due to Systematic Accelerometer Wear-Time Variation

    Directory of Open Access Journals (Sweden)

    Tarun R. Katapally, Nazeem Muhajarine

    2014-06-01

    Full Text Available Accelerometers are predominantly used to objectively measure the entire range of activity intensities – sedentary behaviour (SED, light physical activity (LPA and moderate to vigorous physical activity (MVPA. However, studies consistently report results without accounting for systematic accelerometer wear-time variation (within and between participants, jeopardizing the validity of these results. This study describes the development of a standardization methodology to understand and minimize measurement bias due to wear-time variation. Accelerometry is generally conducted over seven consecutive days, with participants' data being commonly considered 'valid' only if wear-time is at least 10 hours/day. However, even within ‘valid’ data, there could be systematic wear-time variation. To explore this variation, accelerometer data of Smart Cities, Healthy Kids study (www.smartcitieshealthykids.com were analyzed descriptively and with repeated measures multivariate analysis of variance (MANOVA. Subsequently, a standardization method was developed, where case-specific observed wear-time is controlled to an analyst specified time period. Next, case-specific accelerometer data are interpolated to this controlled wear-time to produce standardized variables. To understand discrepancies owing to wear-time variation, all analyses were conducted pre- and post-standardization. Descriptive analyses revealed systematic wear-time variation, both between and within participants. Pre- and post-standardized descriptive analyses of SED, LPA and MVPA revealed a persistent and often significant trend of wear-time’s influence on activity. SED was consistently higher on weekdays before standardization; however, this trend was reversed post-standardization. Even though MVPA was significantly higher on weekdays both pre- and post-standardization, the magnitude of this difference decreased post-standardization. Multivariable analyses with standardized SED, LPA and

  20. Earth System Data Records of Mass Transport from Time-Variable Gravity Data

    Science.gov (United States)

    Zlotnicki, V.; Talpe, M.; Nerem, R. S.; Landerer, F. W.; Watkins, M. M.

    2014-12-01

    Satellite measurements of time variable gravity have revolutionized the study of Earth, by measuring the ice losses of Greenland, Antarctica and land glaciers, changes in groundwater including unsustainable losses due to extraction of groundwater, the mass and currents of the oceans and their redistribution during El Niño events, among other findings. Satellite measurements of gravity have been made primarily by four techniques: satellite tracking from land stations using either lasers or Doppler radio systems, satellite positioning by GNSS/GPS, satellite to satellite tracking over distances of a few hundred km using microwaves, and through a gravity gradiometer (radar altimeters also measure the gravity field, but over the oceans only). We discuss the challenges in the measurement of gravity by different instruments, especially time-variable gravity. A special concern is how to bridge a possible gap in time between the end of life of the current GRACE satellite pair, launched in 2002, and a future GRACE Follow-On pair to be launched in 2017. One challenge in combining data from different measurement systems consists of their different spatial and temporal resolutions and the different ways in which they alias short time scale signals. Typically satellite measurements of gravity are expressed in spherical harmonic coefficients (although expansions in terms of 'mascons', the masses of small spherical caps, has certain advantages). Taking advantage of correlations among spherical harmonic coefficients described by empirical orthogonal functions and derived from GRACE data it is possible to localize the otherwise coarse spatial resolution of the laser and Doppler derived gravity models. This presentation discusses the issues facing a climate data record of time variable mass flux using these different data sources, including its validation.

  1. Recent salmon declines: a result of lost feeding opportunities due to bad timing?

    Directory of Open Access Journals (Sweden)

    Cedar M Chittenden

    Full Text Available As the timing of spring productivity blooms in near-shore areas advances due to warming trends in global climate, the selection pressures on out-migrating salmon smolts are shifting. Species and stocks that leave natal streams earlier may be favoured over later-migrating fish. The low post-release survival of hatchery fish during recent years may be in part due to static release times that do not take the timing of plankton blooms into account. This study examined the effects of release time on the migratory behaviour and survival of wild and hatchery-reared coho salmon (Oncorhynchus kisutch using acoustic and coded-wire telemetry. Plankton monitoring and near-shore seining were also conducted to determine which habitat and food sources were favoured. Acoustic tags (n = 140 and coded-wire tags (n = 266,692 were implanted into coho salmon smolts at the Seymour and Quinsam Rivers, in British Columbia, Canada. Differences between wild and hatchery fish, and early and late releases were examined during the entire lifecycle. Physiological sampling was also carried out on 30 fish from each release group. The smolt-to-adult survival of coho salmon released during periods of high marine productivity was 1.5- to 3-fold greater than those released both before and after, and the fish's degree of smoltification affected their downstream migration time and duration of stay in the estuary. Therefore, hatchery managers should consider having smolts fully developed and ready for release during the peak of the near-shore plankton blooms. Monitoring chlorophyll a levels and water temperature early in the spring could provide a forecast of the timing of these blooms, giving hatcheries time to adjust their release schedule.

  2. Real-time laser cladding control with variable spot size

    Science.gov (United States)

    Arias, J. L.; Montealegre, M. A.; Vidal, F.; Rodríguez, J.; Mann, S.; Abels, P.; Motmans, F.

    2014-03-01

    Laser cladding processing has been used in different industries to improve the surface properties or to reconstruct damaged pieces. In order to cover areas considerably larger than the diameter of the laser beam, successive partially overlapping tracks are deposited. With no control over the process variables this conduces to an increase of the temperature, which could decrease mechanical properties of the laser cladded material. Commonly, the process is monitored and controlled by a PC using cameras, but this control suffers from a lack of speed caused by the image processing step. The aim of this work is to design and develop a FPGA-based laser cladding control system. This system is intended to modify the laser beam power according to the melt pool width, which is measured using a CMOS camera. All the control and monitoring tasks are carried out by a FPGA, taking advantage of its abundance of resources and speed of operation. The robustness of the image processing algorithm is assessed, as well as the control system performance. Laser power is decreased as substrate temperature increases, thus maintaining a constant clad width. This FPGA-based control system is integrated in an adaptive laser cladding system, which also includes an adaptive optical system that will control the laser focus distance on the fly. The whole system will constitute an efficient instrument for part repair with complex geometries and coating selective surfaces. This will be a significant step forward into the total industrial implementation of an automated industrial laser cladding process.

  3. Concentrated Hitting Times of Randomized Search Heuristics with Variable Drift

    DEFF Research Database (Denmark)

    Lehre, Per Kristian; Witt, Carsten

    2014-01-01

    Drift analysis is one of the state-of-the-art techniques for the runtime analysis of randomized search heuristics (RSHs) such as evolutionary algorithms (EAs), simulated annealing etc. The vast majority of existing drift theorems yield bounds on the expected value of the hitting time for a target...

  4. Generating k-independent variables in constant time

    DEFF Research Database (Denmark)

    Christiani, Tobias Lybecker; Pagh, Rasmus

    2014-01-01

    The generation of pseudorandom elements over finite fields is fundamental to the time, space and randomness complexity of randomized algorithms and data structures. We consider the problem of generating k-independent random values over a finite field F in a word RAM model equipped with constant...

  5. Stability Criteria for Differential Equations with Variable Time Delays

    Science.gov (United States)

    Schley, D.; Shail, R.; Gourley, S. A.

    2002-01-01

    Time delays are an important aspect of mathematical modelling, but often result in highly complicated equations which are difficult to treat analytically. In this paper it is shown how careful application of certain undergraduate tools such as the Method of Steps and the Principle of the Argument can yield significant results. Certain delay…

  6. Corrosion resistance of biomimetic calcium phosphate coatings on magnesium due to varying pretreatment time

    Energy Technology Data Exchange (ETDEWEB)

    Waterman, J., E-mail: jay.waterman@pg.canterbury.ac.nz [Department of Mechanical Engineering, University of Canterbury, Christchurch (New Zealand); Pietak, A. [Department of Anatomy and Structural Biology, University of Otago, Dunedin (New Zealand); Birbilis, N. [Department of Materials Engineering, Monash University (Australia); Woodfield, T. [Department of Mechanical Engineering, University of Canterbury, Christchurch (New Zealand); Department of Orthopaedic Surgery, University of Otago, Christchurch (New Zealand); Dias, G. [Department of Anatomy and Structural Biology, University of Otago, Dunedin (New Zealand); Staiger, M.P., E-mail: mark.staiger@canterbury.ac.nz [Department of Mechanical Engineering, University of Canterbury, Christchurch (New Zealand)

    2011-12-15

    Calcium phosphate coatings were prepared on magnesium substrates via a biomimetic coating process. The effects of a magnesium hydroxide pretreatment on the formation and the ultimate corrosion protection of the coatings were studied. The pretreatment layer was found to affect the amount of defects present in the coatings. Corrosion resistance of the coatings was studied in vitro using two simulated body fluids, 0.8% NaCl and Hanks solution. In NaCl, the resistance to corrosion of all samples decreases with time as corrosion proceeded through cracks and other defects in the coatings. Samples with no pretreatment displayed the highest corrosion resistance as these samples had the fewest defects in the coating. However, in Hanks solution, corrosion resistance increased with time due to additional nucleation of calcium phosphate from the fluid on to the substrate. In this solution, additional pretreatment time was beneficial to the overall corrosion resistance.

  7. Start time variability and predictability in railroad train and engine freight and passenger service employees.

    Science.gov (United States)

    2014-04-01

    Start time variability in work schedules is often hypothesized to be a cause of railroad employee fatigue because unpredictable work start times prevent employees from planning sleep and personal activities. This report examines work start time diffe...

  8. Holocene Climate Variability on the Centennial and Millennial Time Scale

    Directory of Open Access Journals (Sweden)

    Eun Hee Lee

    2014-12-01

    Full Text Available There have been many suggestions and much debate about climate variability during the Holocene. However, their complex forcing factors and mechanisms have not yet been clearly identified. In this paper, we have examined the Holocene climate cycles and features based on the wavelet analyses of 14C, 10Be, and 18O records. The wavelet results of the 14C and 10Be data show that the cycles of ~2180-2310, ~970, ~500-520, ~350-360, and ~210-220 years are dominant, and the ~1720 and ~1500 year cycles are relatively weak and subdominant. In particular, the ~2180-2310 year periodicity corresponding to the Hallstatt cycle is constantly significant throughout the Holocene, while the ~970 year cycle corresponding to the Eddy cycle is mainly prominent in the early half of the Holocene. In addition, distinctive signals of the ~210-220 year period corresponding to the de Vries cycle appear recurrently in the wavelet distribution of 14C and 10Be, which coincide with the grand solar minima periods. These de Vries cycle events occurred every ~2270 years on average, implying a connection with the Hallstatt cycle. In contrast, the wavelet results of 18O data show that the cycles of ~1900-2000, ~900-1000, and ~550-560 years are dominant, while the ~2750 and ~2500 year cycles are subdominant. The periods of ~2750, ~2500, and ~1900 years being derived from the 18O records of NGRIP, GRIP and GISP2 ice cores, respectively, are rather longer or shorter than the Hallstatt cycle derived from the 14C and 10Be records. The records of these three sites all show the ~900-1000 year periodicity corresponding to the Eddy cycle in the early half of the Holocene.

  9. Methodology for estimation of time-dependent surface heat flux due to cryogen spray cooling.

    Science.gov (United States)

    Tunnell, James W; Torres, Jorge H; Anvari, Bahman

    2002-01-01

    Cryogen spray cooling (CSC) is an effective technique to protect the epidermis during cutaneous laser therapies. Spraying a cryogen onto the skin surface creates a time-varying heat flux, effectively cooling the skin during and following the cryogen spurt. In previous studies mathematical models were developed to predict the human skin temperature profiles during the cryogen spraying time. However, no studies have accounted for the additional cooling due to residual cryogen left on the skin surface following the spurt termination. We formulate and solve an inverse heat conduction (IHC) problem to predict the time-varying surface heat flux both during and following a cryogen spurt. The IHC formulation uses measured temperature profiles from within a medium to estimate the surface heat flux. We implement a one-dimensional sequential function specification method (SFSM) to estimate the surface heat flux from internal temperatures measured within an in vitro model in response to a cryogen spurt. Solution accuracy and experimental errors are examined using simulated temperature data. Heat flux following spurt termination appears substantial; however, it is less than that during the spraying time. The estimated time-varying heat flux can subsequently be used in forward heat conduction models to estimate temperature profiles in skin during and following a cryogen spurt and predict appropriate timing for onset of the laser pulse.

  10. Between-Trial Forgetting Due to Interference and Time in Motor Adaptation.

    Directory of Open Access Journals (Sweden)

    Sungshin Kim

    Full Text Available Learning a motor task with temporally spaced presentations or with other tasks intermixed between presentations reduces performance during training, but can enhance retention post training. These two effects are known as the spacing and contextual interference effect, respectively. Here, we aimed at testing a unifying hypothesis of the spacing and contextual interference effects in visuomotor adaptation, according to which forgetting between trials due to either spaced presentations or interference by another task will promote between-trial forgetting, which will depress performance during acquisition, but will promote retention. We first performed an experiment with three visuomotor adaptation conditions: a short inter-trial-interval (ITI condition (SHORT-ITI; a long ITI condition (LONG-ITI; and an alternating condition with two alternated opposite tasks (ALT, with the same single-task ITI as in LONG-ITI. In the SHORT-ITI condition, there was fastest increase in performance during training and largest immediate forgetting in the retention tests. In contrast, in the ALT condition, there was slowest increase in performance during training and little immediate forgetting in the retention tests. Compared to these two conditions, in the LONG-ITI, we found intermediate increase in performance during training and intermediate immediate forgetting. To account for these results, we fitted to the data six possible adaptation models with one or two time scales, and with interference in the fast, or in the slow, or in both time scales. Model comparison confirmed that two time scales and some degree of interferences in either time scale are needed to account for our experimental results. In summary, our results suggest that retention following adaptation is modulated by the degree of between-trial forgetting, which is due to time-based decay in single adaptation task and interferences in multiple adaptation tasks.

  11. Describing temporal variability of the mean Estonian precipitation series in climate time scale

    Science.gov (United States)

    Post, P.; Kärner, O.

    2009-04-01

    Applicability of the random walk type models to represent the temporal variability of various atmospheric temperature series has been successfully demonstrated recently (e.g. Kärner, 2002). Main problem in the temperature modeling is connected to the scale break in the generally self similar air temperature anomaly series (Kärner, 2005). The break separates short-range strong non-stationarity from nearly stationary longer range variability region. This is an indication of the fact that several geophysical time series show a short-range non-stationary behaviour and a stationary behaviour in longer range (Davis et al., 1996). In order to model series like that the choice of time step appears to be crucial. To characterize the long-range variability we can neglect the short-range non-stationary fluctuations, provided that we are able to model properly the long-range tendencies. The structure function (Monin and Yaglom, 1975) was used to determine an approximate segregation line between the short and the long scale in terms of modeling. The longer scale can be called climate one, because such models are applicable in scales over some decades. In order to get rid of the short-range fluctuations in daily series the variability can be examined using sufficiently long time step. In the present paper, we show that the same philosophy is useful to find a model to represent a climate-scale temporal variability of the Estonian daily mean precipitation amount series over 45 years (1961-2005). Temporal variability of the obtained daily time series is examined by means of an autoregressive and integrated moving average (ARIMA) family model of the type (0,1,1). This model is applicable for daily precipitation simulating if to select an appropriate time step that enables us to neglet the short-range non-stationary fluctuations. A considerably longer time step than one day (30 days) is used in the current paper to model the precipitation time series variability. Each ARIMA (0

  12. Variable valve timing in a homogenous charge compression ignition engine

    Science.gov (United States)

    Lawrence, Keith E.; Faletti, James J.; Funke, Steven J.; Maloney, Ronald P.

    2004-08-03

    The present invention relates generally to the field of homogenous charge compression ignition engines, in which fuel is injected when the cylinder piston is relatively close to the bottom dead center position for its compression stroke. The fuel mixes with air in the cylinder during the compression stroke to create a relatively lean homogeneous mixture that preferably ignites when the piston is relatively close to the top dead center position. However, if the ignition event occurs either earlier or later than desired, lowered performance, engine misfire, or even engine damage, can result. The present invention utilizes internal exhaust gas recirculation and/or compression ratio control to control the timing of ignition events and combustion duration in homogeneous charge compression ignition engines. Thus, at least one electro-hydraulic assist actuator is provided that is capable of mechanically engaging at least one cam actuated intake and/or exhaust valve.

  13. Methods of approaching decoherence in the flavor sector due to space-time foam

    Science.gov (United States)

    Mavromatos, N. E.; Sarkar, Sarben

    2006-08-01

    In the first part of this work we discuss possible effects of stochastic space-time foam configurations of quantum gravity on the propagation of “flavored” (Klein-Gordon and Dirac) neutral particles, such as neutral mesons and neutrinos. The formalism is not the usually assumed Lindblad one, but it is based on random averages of quantum fluctuations of space-time metrics over which the propagation of the matter particles is considered. We arrive at expressions for the respective oscillation probabilities between flavors which are quite distinct from the ones pertaining to Lindblad-type decoherence, including in addition to the (expected) Gaussian decay with time, a modification to oscillation behavior, as well as a power-law cutoff of the time-profile of the respective probability. In the second part we consider space-time foam configurations of quantum-fluctuating charged-black holes as a way of generating (parts of) neutrino mass differences, mimicking appropriately the celebrated Mikheyev-Smirnov-Wolfenstein (MSW) effects of neutrinos in stochastically fluctuating random media. We pay particular attention to disentangling genuine quantum-gravity effects from ordinary effects due to the propagation of a neutrino through ordinary matter. Our results are of interest to precision tests of quantum-gravity models using neutrinos as probes.

  14. Signal enhancement due to high-Z nanofilm electrodes in parallel plate ionization chambers with variable microgaps.

    Science.gov (United States)

    Brivio, Davide; Sajo, Erno; Zygmanski, Piotr

    2017-12-01

    We developed a method for measuring signal enhancement produced by high-Z nanofilm electrodes in parallel plate ionization chambers with variable thickness microgaps. We used a laboratory-made variable gap parallel plate ionization chamber with nanofilm electrodes made of aluminum-aluminum (Al-Al) and aluminum-tantalum (Al-Ta). The electrodes were evaporated on 1 mm thick glass substrates. The interelectrode air gap was varied from 3 μm to 1 cm. The gap size was measured using a digital micrometer and it was confirmed by capacitance measurements. The electric field in the chamber was kept between 0.1 kV/cm and 1 kV/cm for all the gap sizes by applying appropriate compensating voltages. The chamber was exposed to 120 kVp X-rays. The current was measured using a commercial data acquisition system with temporal resolution of 600 Hz. In addition, radiation transport simulations were carried out to characterize the dose, D(x), high-energy electron current, J(x), and deposited charge, Q(x), as a function of distance, x, from the electrodes. A deterministic method was selected over Monte Carlo due to its ability to produce results with 10 nm spatial resolution without stochastic uncertainties. Experimental signal enhancement ratio, SER(G) which we defined as the ratio of signal for Al-air-Ta to signal for Al-air-Al for each gap size, was compared to computations. The individual contributions of dose, electron current, and charge deposition to the signal enhancement were determined. Experimental signals matched computed data for all gap sizes after accounting for several contributions to the signal: (a) charge carrier generated via ionization due to the energy deposited in the air gap, D(x); (b) high-energy electron current, J(x), leaking from high-Z electrode (Ta) toward low-Z electrode (Al); (c) deposited charge in the air gap, Q(x); and (d) the decreased collection efficiency for large gaps (>~500 μm). Q(x) accounts for the electrons below 100 eV, which are

  15. Selective attrition and intraindividual variability in response time moderate cognitive change.

    Science.gov (United States)

    Yao, Christie; Stawski, Robert S; Hultsch, David F; MacDonald, Stuart W S

    2016-01-01

    Selection of a developmental time metric is useful for understanding causal processes that underlie aging-related cognitive change and for the identification of potential moderators of cognitive decline. Building on research suggesting that time to attrition is a metric sensitive to non-normative influences of aging (e.g., subclinical health conditions), we examined reason for attrition and intraindividual variability (IIV) in reaction time as predictors of cognitive performance. Three hundred and four community dwelling older adults (64-92 years) completed annual assessments in a longitudinal study. IIV was calculated from baseline performance on reaction time tasks. Multilevel models were fit to examine patterns and predictors of cognitive change. We show that time to attrition was associated with cognitive decline. Greater IIV was associated with declines on executive functioning and episodic memory measures. Attrition due to personal health reasons was also associated with decreased executive functioning compared to that of individuals who remained in the study. These findings suggest that time to attrition is a useful metric for representing cognitive change, and reason for attrition and IIV are predictive of non-normative influences that may underlie instances of cognitive loss in older adults.

  16. Study of time variation of terrestrial gamma radiation due to depth distribution of soil moisture content

    International Nuclear Information System (INIS)

    Yoshioka, Katsuhiro

    1994-01-01

    An empirical equation was deduced from studies of time variations of terrestrial gamma exposure rate and soil moisture content with depth distribution in the surface layer. It was definitely suggested that the variation of terrestrial gamma exposure rate is most strongly influenced by the change of soil moisture content at 5 cm depth. The seasonal variation with a relative maximum in early autumn and a relative minimum in early spring was clearly obtained in the consequence of long time measurements of terrestrial gamma exposure rate and degree of soil dryness. The diurnal change and phase difference due to the effect of depth were also obtained in the dynamic characteristics of soil moisture content at 3 different depths. From the comparison between measured terrestrial gamma exposure rate and that evaluated from soil moisture content using the empirical equation, it was seen that seasonal variations of the both agreed fairly well as a whole. (author)

  17. Nonlinear Heart Rate Variability features for real-life stress detection. Case study: students under stress due to university examination.

    Science.gov (United States)

    Melillo, Paolo; Bracale, Marcello; Pecchia, Leandro

    2011-11-07

    This study investigates the variations of Heart Rate Variability (HRV) due to a real-life stressor and proposes a classifier based on nonlinear features of HRV for automatic stress detection. 42 students volunteered to participate to the study about HRV and stress. For each student, two recordings were performed: one during an on-going university examination, assumed as a real-life stressor, and one after holidays. Nonlinear analysis of HRV was performed by using Poincaré Plot, Approximate Entropy, Correlation dimension, Detrended Fluctuation Analysis, Recurrence Plot. For statistical comparison, we adopted the Wilcoxon Signed Rank test and for development of a classifier we adopted the Linear Discriminant Analysis (LDA). Almost all HRV features measuring heart rate complexity were significantly decreased in the stress session. LDA generated a simple classifier based on the two Poincaré Plot parameters and Approximate Entropy, which enables stress detection with a total classification accuracy, a sensitivity and a specificity rate of 90%, 86%, and 95% respectively. The results of the current study suggest that nonlinear HRV analysis using short term ECG recording could be effective in automatically detecting real-life stress condition, such as a university examination.

  18. Effects of implementing time-variable postgraduate training programmes on the organization of teaching hospital departments.

    Science.gov (United States)

    van Rossum, Tiuri R; Scheele, Fedde; Sluiter, Henk E; Paternotte, Emma; Heyligers, Ide C

    2018-01-31

    As competency-based education has gained currency in postgraduate medical education, it is acknowledged that trainees, having individual learning curves, acquire the desired competencies at different paces. To accommodate their different learning needs, time-variable curricula have been introduced making training no longer time-bound. This paradigm has many consequences and will, predictably, impact the organization of teaching hospitals. The purpose of this study was to determine the effects of time-variable postgraduate education on the organization of teaching hospital departments. We undertook exploratory case studies into the effects of time-variable training on teaching departments' organization. We held semi-structured interviews with clinical teachers and managers from various hospital departments. The analysis yielded six effects: (1) time-variable training requires flexible and individual planning, (2) learners must be active and engaged, (3) accelerated learning sometimes comes at the expense of clinical expertise, (4) fast-track training for gifted learners jeopardizes the continuity of care, (5) time-variable training demands more of supervisors, and hence, they need protected time for supervision, and (6) hospital boards should support time-variable training. Implementing time-variable education affects various levels within healthcare organizations, including stakeholders not directly involved in medical education. These effects must be considered when implementing time-variable curricula.

  19. Flicker Noise in GNSS Station Position Time Series: How much is due to Crustal Loading Deformations?

    Science.gov (United States)

    Rebischung, P.; Chanard, K.; Metivier, L.; Altamimi, Z.

    2017-12-01

    The presence of colored noise in GNSS station position time series was detected 20 years ago. It has been shown since then that the background spectrum of non-linear GNSS station position residuals closely follows a power-law process (known as flicker noise, 1/f noise or pink noise), with some white noise taking over at the highest frequencies. However, the origin of the flicker noise present in GNSS station position time series is still unclear. Flicker noise is often described as intrinsic to the GNSS system, i.e. due to errors in the GNSS observations or in their modeling, but no such error source has been identified so far that could explain the level of observed flicker noise, nor its spatial correlation.We investigate another possible contributor to the observed flicker noise, namely real crustal displacements driven by surface mass transports, i.e. non-tidal loading deformations. This study is motivated by the presence of power-law noise in the time series of low-degree (≤ 40) and low-order (≤ 12) Stokes coefficients observed by GRACE - power-law noise might also exist at higher degrees and orders, but obscured by GRACE observational noise. By comparing GNSS station position time series with loading deformation time series derived from GRACE gravity fields, both with their periodic components removed, we therefore assess whether GNSS and GRACE both plausibly observe the same flicker behavior of surface mass transports / loading deformations. Taking into account GRACE observability limitations, we also quantify the amount of flicker noise in GNSS station position time series that could be explained by such flicker loading deformations.

  20. The time aspect of bioenergy. Climate impacts of bioenergy due to differences in carbon uptake rates

    Energy Technology Data Exchange (ETDEWEB)

    Zetterberg, Lars [IVL Swedish Environmental Research Institute, Stockholm (Sweden); Chen, Deliang [Dept. of Earth Sciences, Univ. of Gothenburg, Gothenburg (Sweden)

    2011-07-01

    This paper investigates the climate impacts from bioenergy due to how they influence carbon stocks over time and more specifically how fast combustion related carbon emissions are compensated by uptake of atmospheric carbon. A set of fuel types representing different uptake rates are investigated, namely willow, branches and tops, stumps and coal. Net emissions are defined as emissions from utilizing the fuel minus emissions from a reference case of no utilisation. In the case of forest residues, the compensating 'uptake' is avoided emissions from the reference case of leaving the residues to decompose on the ground. Climate impacts are estimated using the measures radiative forcing and global average surface temperature, which have been calculated by an energy balance climate model. We conclude that there is a climate impact from using bioenergy due to how fast the emission pulse is compensated by uptake of atmospheric carbon (or avoided emissions). Biofuels with slower uptake rates have a stronger climate impact than fuels with a faster uptake rate, assuming all other parameters equal. The time perspective over which the analysis is done is crucial for the climate impact of biofuels. If only biogenic fluxes are considered, our results show that over a 100 year perspective branches and tops are better for climate mitigation than stumps which in turn are better than coal. Over a 20 year time perspective this conclusion holds, but the differences between these fuels are relatively smaller. Establishing willow on earlier crop land may reduce atmospheric carbon, provided new land is available. However, these results are inconclusive since we haven't considered the effects, if needed, of producing the traditional agricultural crops elsewhere. The analysis is not a life cycle assessment of different fuels and does therefore not consider the use of fossil fuels for logging, transportation and refining, other greenhouse gases than carbon or energy

  1. Evaluation of Online Log Variables That Estimate Learners' Time Management in a Korean Online Learning Context

    Science.gov (United States)

    Jo, Il-Hyun; Park, Yeonjeong; Yoon, Meehyun; Sung, Hanall

    2016-01-01

    The purpose of this study was to identify the relationship between the psychological variables and online behavioral patterns of students, collected through a learning management system (LMS). As the psychological variable, time and study environment management (TSEM), one of the sub-constructs of MSLQ, was chosen to verify a set of time-related…

  2. Constructing Proxy Variables to Measure Adult Learners' Time Management Strategies in LMS

    Science.gov (United States)

    Jo, Il-Hyun; Kim, Dongho; Yoon, Meehyun

    2015-01-01

    This study describes the process of constructing proxy variables from recorded log data within a Learning Management System (LMS), which represents adult learners' time management strategies in an online course. Based on previous research, three variables of total login time, login frequency, and regularity of login interval were selected as…

  3. Years of life gained due to leisure-time physical activity in the U.S.

    Science.gov (United States)

    Janssen, Ian; Carson, Valerie; Lee, I-Min; Katzmarzyk, Peter T; Blair, Steven N

    2013-01-01

    Physical inactivity is an important modifiable risk factor for noncommunicable disease. The degree to which physical activity affects the life expectancy of Americans is unknown. This study estimated the potential years of life gained due to leisure-time physical activity in the U.S. Data from the National Health and Nutrition Examination Survey (2007-2010); National Health Interview Study mortality linkage (1990-2006); and U.S. Life Tables (2006) were used to estimate and compare life expectancy at each age of adult life for inactive (no moderate to vigorous physical activity); somewhat-active (some moderate to vigorous activity but active (≥ 500 MET minutes/week of moderate to vigorous activity) adults. Analyses were conducted in 2012. Somewhat-active and active non-Hispanic white men had a life expectancy at age 20 years that was ~2.4 years longer than that for the inactive men; this life expectancy advantage was 1.2 years at age 80 years. Similar observations were made in non-Hispanic white women, with a higher life expectancy within the active category of 3.0 years at age 20 years and 1.6 years at age 80 years. In non-Hispanic black women, as many as 5.5 potential years of life were gained due to physical activity. Significant increases in longevity were also observed within somewhat-active and active non-Hispanic black men; however, among Hispanics the years-of-life-gained estimates were not significantly different from 0 years gained. Leisure-time physical activity is associated with increases in longevity. Copyright © 2013 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

  4. Analytical model for time to cover cracking in RC structures due to rebar corrosion

    International Nuclear Information System (INIS)

    Bhargava, Kapilesh; Ghosh, A.K.; Mori, Yasuhiro; Ramanujam, S.

    2006-01-01

    The structural degradation of concrete structures due to reinforcement corrosion is a major worldwide problem. Reinforcement corrosion causes a volume increase due to the oxidation of metallic iron, which is mainly responsible for exerting the expansive radial pressure at the steel-concrete interface and development of hoop tensile stresses in the surrounding concrete. Cracking occurs, once the maximum hoop tensile stress exceeds the tensile strength of the concrete. The cracking begins at the steel-concrete interface and propagates outwards and eventually results in the thorough cracking of the cover concrete and this would indicate the loss of service life for the corrosion affected structures. An analytical model is proposed to predict the time required for cover cracking and the weight loss of reinforcing bar in corrosion affected reinforced concrete structures. The modelling aspects of the residual strength of cracked concrete and the stiffness contribution from the combination of reinforcement and expansive corrosion products have also been incorporated in the model. The problem is modeled as a boundary value problem and the governing equations are expressed in terms of the radial displacement. The analytical solutions are presented considering a simple two-zone model for the cover concrete, viz. cracked or uncracked. Reasonable estimation of the various parameters in the model related to the composition and properties of expansive corrosion products based on the available published experimental data has also been discussed. The performance of the proposed corrosion cracking model is then investigated through its ability to reproduce available experimental trends. Reasonably good agreement between experimental results and the analytical predictions has been obtained. It has also been found that tensile strength and initial tangent modulus of cover concrete, annual mean corrosion rate and modulus of elasticity of reinforcement plus corrosion products combined

  5. Between-centre variability versus variability over time in DXA whole body measurements evaluated using a whole body phantom

    Energy Technology Data Exchange (ETDEWEB)

    Louis, Olivia [Department of Radiology, AZ-VUB, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussel (Belgium)]. E-mail: olivia.louis@az.vub.ac.be; Verlinde, Siska [Belgian Study Group for Pediatric Endocrinology (Belgium); Thomas, Muriel [Belgian Study Group for Pediatric Endocrinology (Belgium); De Schepper, Jean [Department of Pediatrics, AZ-VUB, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussel (Belgium)

    2006-06-15

    This study aimed to compare the variability of whole body measurements, using dual energy X-ray absorptiometry (DXA), among geographically distinct centres versus that over time in a given centre. A Hologic-designed 28 kg modular whole body phantom was used, including high density polyethylene, gray polyvinylchloride and aluminium. It was scanned on seven Hologic QDR 4500 DXA devices, located in seven centres and was also repeatedly (n = 18) scanned in the reference centre, over a time span of 5 months. The mean between-centre coefficient of variation (CV) ranged from 2.0 (lean mass) to 5.6% (fat mass) while the mean within-centre CV ranged from 0.3 (total mass) to 4.7% (total area). Between-centre variability compared well with within-centre variability for total area, bone mineral content and bone mineral density, but was significantly higher for fat (p < 0.001), lean (p < 0.005) and total mass (p < 0.001). Our results suggest that, even when using the same device, the between-centre variability remains a matter of concern, particularly where body composition is concerned.

  6. Time-dependent 2-D modeling of edge plasma transport with high intermittency due to blobs

    International Nuclear Information System (INIS)

    Pigarov, A. Yu.; Krasheninnikov, S. I.; Rognlien, T. D.

    2012-01-01

    The results on time-dependent 2-D fluid modeling of edge plasmas with non-diffusive intermittent transport across the magnetic field (termed cross-field) based on the novel macro-blob approach are presented. The capability of this approach to simulate the long temporal evolution (∼0.1 s) of the background plasma and simultaneously the fast spatiotemporal dynamics of blobs (∼10 −4 s) is demonstrated. An analysis of a periodic sequence of many macro-blobs (PSMB) is given showing that the resulting plasma attains a dynamic equilibrium. Plasma properties in the dynamic equilibrium are discussed. In PSMB modeling, the effect of macro-blob generation frequency on edge plasma parameters is studied. Comparison between PSMB modeling and experimental profile data is given. The calculations are performed for the same plasma discharge using two different models for anomalous cross-field transport: time-average convection and PSMB. Parametric analysis of edge plasma variation with transport coefficients in these models is presented. The capability of the models to accurately simulate enhanced transport due to blobs is compared. Impurity dynamics in edge plasma with macro-blobs is also studied showing strong impact of macro-blob on profiles of impurity charge states caused by enhanced outward transport of high-charge states and simultaneous inward transport of low-charge states towards the core. Macro-blobs cause enhancement of sputtering rates, increase radiation and impurity concentration in plasma, and change erosion/deposition patterns.

  7. Age and Sex Differences in Intra-Individual Variability in a Simple Reaction Time Task

    Science.gov (United States)

    Ghisletta, Paolo; Renaud, Olivier; Fagot, Delphine; Lecerf, Thierry; de Ribaupierre, Anik

    2018-01-01

    While age effects in reaction time (RT) tasks across the lifespan are well established for level of performance, analogous findings have started appearing also for indicators of intra-individual variability (IIV). Children are not only slower, but also display more variability than younger adults in RT. Yet, little is known about potential…

  8. EEG phase reset due to auditory attention: an inverse time-scale approach

    International Nuclear Information System (INIS)

    Low, Yin Fen; Strauss, Daniel J

    2009-01-01

    We propose a novel tool to evaluate the electroencephalograph (EEG) phase reset due to auditory attention by utilizing an inverse analysis of the instantaneous phase for the first time. EEGs were acquired through auditory attention experiments with a maximum entropy stimulation paradigm. We examined single sweeps of auditory late response (ALR) with the complex continuous wavelet transform. The phase in the frequency band that is associated with auditory attention (6–10 Hz, termed as theta–alpha border) was reset to the mean phase of the averaged EEGs. The inverse transform was applied to reconstruct the phase-modified signal. We found significant enhancement of the N100 wave in the reconstructed signal. Analysis of the phase noise shows the effects of phase jittering on the generation of the N100 wave implying that a preferred phase is necessary to generate the event-related potential (ERP). Power spectrum analysis shows a remarkable increase of evoked power but little change of total power after stabilizing the phase of EEGs. Furthermore, by resetting the phase only at the theta border of no attention data to the mean phase of attention data yields a result that resembles attention data. These results show strong connections between EEGs and ERP, in particular, we suggest that the presentation of an auditory stimulus triggers the phase reset process at the theta–alpha border which leads to the emergence of the N100 wave. It is concluded that our study reinforces other studies on the importance of the EEG in ERP genesis

  9. EEG phase reset due to auditory attention: an inverse time-scale approach.

    Science.gov (United States)

    Low, Yin Fen; Strauss, Daniel J

    2009-08-01

    We propose a novel tool to evaluate the electroencephalograph (EEG) phase reset due to auditory attention by utilizing an inverse analysis of the instantaneous phase for the first time. EEGs were acquired through auditory attention experiments with a maximum entropy stimulation paradigm. We examined single sweeps of auditory late response (ALR) with the complex continuous wavelet transform. The phase in the frequency band that is associated with auditory attention (6-10 Hz, termed as theta-alpha border) was reset to the mean phase of the averaged EEGs. The inverse transform was applied to reconstruct the phase-modified signal. We found significant enhancement of the N100 wave in the reconstructed signal. Analysis of the phase noise shows the effects of phase jittering on the generation of the N100 wave implying that a preferred phase is necessary to generate the event-related potential (ERP). Power spectrum analysis shows a remarkable increase of evoked power but little change of total power after stabilizing the phase of EEGs. Furthermore, by resetting the phase only at the theta border of no attention data to the mean phase of attention data yields a result that resembles attention data. These results show strong connections between EEGs and ERP, in particular, we suggest that the presentation of an auditory stimulus triggers the phase reset process at the theta-alpha border which leads to the emergence of the N100 wave. It is concluded that our study reinforces other studies on the importance of the EEG in ERP genesis.

  10. Constructing the reduced dynamical models of interannual climate variability from spatial-distributed time series

    Science.gov (United States)

    Mukhin, Dmitry; Gavrilov, Andrey; Loskutov, Evgeny; Feigin, Alexander

    2016-04-01

    We suggest a method for empirical forecast of climate dynamics basing on the reconstruction of reduced dynamical models in a form of random dynamical systems [1,2] derived from observational time series. The construction of proper embedding - the set of variables determining the phase space the model works in - is no doubt the most important step in such a modeling, but this task is non-trivial due to huge dimension of time series of typical climatic fields. Actually, an appropriate expansion of observational time series is needed yielding the number of principal components considered as phase variables, which are to be efficient for the construction of low-dimensional evolution operator. We emphasize two main features the reduced models should have for capturing the main dynamical properties of the system: (i) taking into account time-lagged teleconnections in the atmosphere-ocean system and (ii) reflecting the nonlinear nature of these teleconnections. In accordance to these principles, in this report we present the methodology which includes the combination of a new way for the construction of an embedding by the spatio-temporal data expansion and nonlinear model construction on the basis of artificial neural networks. The methodology is aplied to NCEP/NCAR reanalysis data including fields of sea level pressure, geopotential height, and wind speed, covering Northern Hemisphere. Its efficiency for the interannual forecast of various climate phenomena including ENSO, PDO, NAO and strong blocking event condition over the mid latitudes, is demonstrated. Also, we investigate the ability of the models to reproduce and predict the evolution of qualitative features of the dynamics, such as spectral peaks, critical transitions and statistics of extremes. This research was supported by the Government of the Russian Federation (Agreement No. 14.Z50.31.0033 with the Institute of Applied Physics RAS) [1] Y. I. Molkov, E. M. Loskutov, D. N. Mukhin, and A. M. Feigin, "Random

  11. Dissociable effects of practice variability on learning motor and timing skills.

    Science.gov (United States)

    Caramiaux, Baptiste; Bevilacqua, Frédéric; Wanderley, Marcelo M; Palmer, Caroline

    2018-01-01

    Motor skill acquisition inherently depends on the way one practices the motor task. The amount of motor task variability during practice has been shown to foster transfer of the learned skill to other similar motor tasks. In addition, variability in a learning schedule, in which a task and its variations are interweaved during practice, has been shown to help the transfer of learning in motor skill acquisition. However, there is little evidence on how motor task variations and variability schedules during practice act on the acquisition of complex motor skills such as music performance, in which a performer learns both the right movements (motor skill) and the right time to perform them (timing skill). This study investigated the impact of rate (tempo) variability and the schedule of tempo change during practice on timing and motor skill acquisition. Complete novices, with no musical training, practiced a simple musical sequence on a piano keyboard at different rates. Each novice was assigned to one of four learning conditions designed to manipulate the amount of tempo variability across trials (large or small tempo set) and the schedule of tempo change (randomized or non-randomized order) during practice. At test, the novices performed the same musical sequence at a familiar tempo and at novel tempi (testing tempo transfer), as well as two novel (but related) sequences at a familiar tempo (testing spatial transfer). We found that practice conditions had little effect on learning and transfer performance of timing skill. Interestingly, practice conditions influenced motor skill learning (reduction of movement variability): lower temporal variability during practice facilitated transfer to new tempi and new sequences; non-randomized learning schedule improved transfer to new tempi and new sequences. Tempo (rate) and the sequence difficulty (spatial manipulation) affected performance variability in both timing and movement. These findings suggest that there is a

  12. Using exogenous variables in testing for monotonic trends in hydrologic time series

    Science.gov (United States)

    Alley, William M.

    1988-01-01

    One approach that has been used in performing a nonparametric test for monotonic trend in a hydrologic time series consists of a two-stage analysis. First, a regression equation is estimated for the variable being tested as a function of an exogenous variable. A nonparametric trend test such as the Kendall test is then performed on the residuals from the equation. By analogy to stagewise regression and through Monte Carlo experiments, it is demonstrated that this approach will tend to underestimate the magnitude of the trend and to result in some loss in power as a result of ignoring the interaction between the exogenous variable and time. An alternative approach, referred to as the adjusted variable Kendall test, is demonstrated to generally have increased statistical power and to provide more reliable estimates of the trend slope. In addition, the utility of including an exogenous variable in a trend test is examined under selected conditions.

  13. Morbidity and mortality due to malaria in Est Mono district, Togo, from 2005 to 2010: a times series analysis

    Directory of Open Access Journals (Sweden)

    Landoh Essoya D

    2012-11-01

    Full Text Available Abstract Background In 2004, Togo adopted a regional strategy for malaria control that made use of insecticide-treated nets (ITNs, followed by the use of rapid diagnostic tests (RDTs, artemisinin-based combination therapy (ACT. Community health workers (CHWs became involved in 2007. In 2010, the impact of the implementation of these new malaria control strategies had not yet been evaluated. This study sought to assess the trends of malaria incidence and mortality due to malaria in Est Mono district from 2005 to 2010. Methods Secondary data on confirmed and suspected malaria cases reported by health facilities from 2005 to 2010 were obtained from the district health information system. Rainfall and temperature data were provided by the national Department of Meteorology. Chi square test or independent student’s t-test were used to compare trends of variables at a 95% confidence interval. An interrupted time series analysis was performed to assess the effect of meteorological factors and the use of ACT and CHWs on morbidity and mortality due to malaria. Results From January 2005 to December 2010, 114,654 malaria cases (annual mean 19,109 ± 6,622 were reported with an increase of all malaria cases from 10,299 in 2005 to 26,678 cases in 2010 (p Conclusion This study showed an increase of malaria prevalence despite the implementation of the use of ACT and CHW strategies. Multicentre data analysis over longer periods should be carried out in similar settings to assess the impact of malaria control strategies on the burden of the disease. Integrated malaria vector control management should be implemented in Togo to reduce malaria transmission.

  14. Resting heart rate variability is associated with ex-Gaussian metrics of intra-individual reaction time variability.

    Science.gov (United States)

    Spangler, Derek P; Williams, DeWayne P; Speller, Lassiter F; Brooks, Justin R; Thayer, Julian F

    2018-03-01

    The relationships between vagally mediated heart rate variability (vmHRV) and the cognitive mechanisms underlying performance can be elucidated with ex-Gaussian modeling-an approach that quantifies two different forms of intra-individual variability (IIV) in reaction time (RT). To this end, the current study examined relations of resting vmHRV to whole-distribution and ex-Gaussian IIV. Subjects (N = 83) completed a 5-minute baseline while vmHRV (root mean square of successive differences; RMSSD) was measured. Ex-Gaussian (sigma, tau) and whole-distribution (standard deviation) estimates of IIV were derived from reaction times on a Stroop task. Resting vmHRV was found to be inversely related to tau (exponential IIV) but not to sigma (Gaussian IIV) or the whole-distribution standard deviation of RTs. Findings suggest that individuals with high vmHRV can better prevent attentional lapses but not difficulties with motor control. These findings inform the differential relationships of cardiac vagal control to the cognitive processes underlying human performance. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  15. Predictor variables for a half marathon race time in recreational male runners.

    Science.gov (United States)

    Rüst, Christoph Alexander; Knechtle, Beat; Knechtle, Patrizia; Barandun, Ursula; Lepers, Romuald; Rosemann, Thomas

    2011-01-01

    The aim of this study was to investigate predictor variables of anthropometry, training, and previous experience in order to predict a half marathon race time for future novice recreational male half marathoners. Eighty-four male finishers in the 'Half Marathon Basel' completed the race distance within (mean and standard deviation, SD) 103.9 (16.5) min, running at a speed of 12.7 (1.9) km/h. After multivariate analysis of the anthropometric characteristics, body mass index (r = 0.56), suprailiacal (r = 0.36) and medial calf skin fold (r = 0.53) were related to race time. For the variables of training and previous experience, speed in running of the training sessions (r = -0.54) were associated with race time. After multivariate analysis of both the significant anthropometric and training variables, body mass index (P = 0.0150) and speed in running during training (P = 0.0045) were related to race time. Race time in a half marathon might be partially predicted by the following equation (r(2) = 0.44): Race time (min) = 72.91 + 3.045 * (body mass index, kg/m(2)) -3.884 * (speed in running during training, km/h) for recreational male runners. To conclude, variables of both anthropometry and training were related to half marathon race time in recreational male half marathoners and cannot be reduced to one single predictor variable.

  16. Arctic energy budget in relation to sea-ice variability on monthly to annual time scales

    Science.gov (United States)

    Krikken, Folmer; Hazeleger, Wilco

    2015-04-01

    The strong decrease in Arctic sea-ice in recent years has triggered a strong interest in Arctic sea-ice predictions on seasonal to decadal time scales. Hence, it is key to understand physical processes that provide enhanced predictability beyond persistence of sea ice anomalies. The authors report on an analysis of natural variability of Arctic sea-ice from an energy budget perspective, using 15 CMIP5 climate models, and comparing these results to atmospheric and oceanic reanalyses data. We quantify the persistence of sea ice anomalies and the cross-correlation with the surface and top energy budget components. The Arctic energy balance components primarily indicate the important role of the seasonal sea-ice albedo feedback, in which sea-ice anomalies in the melt season reemerge in the growth season. This is a robust anomaly reemergence mechanism among all 15 climate models. The role of ocean lies mainly in storing heat content anomalies in spring, and releasing them in autumn. Ocean heat flux variations only play a minor role. The role of clouds is further investigated. We demonstrate that there is no direct atmospheric response of clouds to spring sea-ice anomalies, but a delayed response is evident in autumn. Hence, there is no cloud-ice feedback in late spring and summer, but there is a cloud-ice feedback in autumn, which strengthens the ice-albedo feedback. Anomalies in insolation are positively correlated with sea-ice variability. This is primarily a result of reduced multiple-reflection of insolation due to an albedo decrease. This effect counteracts the sea-ice albedo effect up to 50%. ERA-Interim and ORAS4 confirm the main findings from the climate models.

  17. ENSO Modulations due to Interannual Variability of Freshwater Forcing and Ocean Biology-induced Heating in the Tropical Pacific.

    Science.gov (United States)

    Zhang, Rong-Hua; Gao, Chuan; Kang, Xianbiao; Zhi, Hai; Wang, Zhanggui; Feng, Licheng

    2015-12-18

    Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the El Niño-Southern Oscillation (ENSO). The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances ENSO variability and slightly prolongs the simulated ENSO period, while the interannual OBH reduces ENSO variability and slightly shortens the ENSO period, with their feedback effects tending to counteract each other.

  18. Instrumental variables estimation of exposure effects on a time-to-event endpoint using structural cumulative survival models.

    Science.gov (United States)

    Martinussen, Torben; Vansteelandt, Stijn; Tchetgen Tchetgen, Eric J; Zucker, David M

    2017-12-01

    The use of instrumental variables for estimating the effect of an exposure on an outcome is popular in econometrics, and increasingly so in epidemiology. This increasing popularity may be attributed to the natural occurrence of instrumental variables in observational studies that incorporate elements of randomization, either by design or by nature (e.g., random inheritance of genes). Instrumental variables estimation of exposure effects is well established for continuous outcomes and to some extent for binary outcomes. It is, however, largely lacking for time-to-event outcomes because of complications due to censoring and survivorship bias. In this article, we make a novel proposal under a class of structural cumulative survival models which parameterize time-varying effects of a point exposure directly on the scale of the survival function; these models are essentially equivalent with a semi-parametric variant of the instrumental variables additive hazards model. We propose a class of recursive instrumental variable estimators for these exposure effects, and derive their large sample properties along with inferential tools. We examine the performance of the proposed method in simulation studies and illustrate it in a Mendelian randomization study to evaluate the effect of diabetes on mortality using data from the Health and Retirement Study. We further use the proposed method to investigate potential benefit from breast cancer screening on subsequent breast cancer mortality based on the HIP-study. © 2017, The International Biometric Society.

  19. SOLAR CYCLE VARIABILITY AND SURFACE DIFFERENTIAL ROTATION FROM Ca II K-LINE TIME SERIES DATA

    Energy Technology Data Exchange (ETDEWEB)

    Scargle, Jeffrey D.; Worden, Simon P. [NASA Ames Research Center, Moffett Field, CA, 94035 (United States); Keil, Stephen L. [National Solar Observatory, P.O. Box 57, Sunspot, NM 88349 (United States)

    2013-07-01

    Analysis of over 36 yr of time series data from the NSO/AFRL/Sac Peak K-line monitoring program elucidates 5 components of the variation of the 7 measured chromospheric parameters: (a) the solar cycle (period {approx} 11 yr), (b) quasi-periodic variations (periods {approx} 100 days), (c) a broadband stochastic process (wide range of periods), (d) rotational modulation, and (e) random observational errors, independent of (a)-(d). Correlation and power spectrum analyses elucidate periodic and aperiodic variation of these parameters. Time-frequency analysis illuminates periodic and quasi-periodic signals, details of frequency modulation due to differential rotation, and in particular elucidates the rather complex harmonic structure (a) and (b) at timescales in the range {approx}0.1-10 yr. These results using only full-disk data suggest that similar analyses will be useful for detecting and characterizing differential rotation in stars from stellar light curves such as those being produced by NASA's Kepler observatory. Component (c) consists of variations over a range of timescales, in the manner of a 1/f random process with a power-law slope index that varies in a systematic way. A time-dependent Wilson-Bappu effect appears to be present in the solar cycle variations (a), but not in the more rapid variations of the stochastic process (c). Component (d) characterizes differential rotation of the active regions. Component (e) is of course not characteristic of solar variability, but the fact that the observational errors are quite small greatly facilitates the analysis of the other components. The data analyzed in this paper can be found at the National Solar Observatory Web site http://nsosp.nso.edu/cak{sub m}on/, or by file transfer protocol at ftp://ftp.nso.edu/idl/cak.parameters.

  20. The added value of time-variable microgravimetry to the understanding of how volcanoes work

    Science.gov (United States)

    Carbone, Daniele; Poland, Michael; Greco, Filippo; Diament, Michel

    2017-01-01

    During the past few decades, time-variable volcano gravimetry has shown great potential for imaging subsurface processes at active volcanoes (including some processes that might otherwise remain “hidden”), especially when combined with other methods (e.g., ground deformation, seismicity, and gas emissions). By supplying information on changes in the distribution of bulk mass over time, gravimetry can provide information regarding processes such as magma accumulation in void space, gas segregation at shallow depths, and mechanisms driving volcanic uplift and subsidence. Despite its potential, time-variable volcano gravimetry is an underexploited method, not widely adopted by volcano researchers or observatories. The cost of instrumentation and the difficulty in using it under harsh environmental conditions is a significant impediment to the exploitation of gravimetry at many volcanoes. In addition, retrieving useful information from gravity changes in noisy volcanic environments is a major challenge. While these difficulties are not trivial, neither are they insurmountable; indeed, creative efforts in a variety of volcanic settings highlight the value of time-variable gravimetry for understanding hazards as well as revealing fundamental insights into how volcanoes work. Building on previous work, we provide a comprehensive review of time-variable volcano gravimetry, including discussions of instrumentation, modeling and analysis techniques, and case studies that emphasize what can be learned from campaign, continuous, and hybrid gravity observations. We are hopeful that this exploration of time-variable volcano gravimetry will excite more scientists about the potential of the method, spurring further application, development, and innovation.

  1. Real-time variables dictionary (RTVD), and expert system for development of real-time applications in nuclear power plants

    International Nuclear Information System (INIS)

    Senra Martinez, A.; Schirru, R.; Dutra Thome Filho, Z.

    1990-01-01

    It is presented in this paper a computerized methodology based on a data dictionary managed by an expert system called Real-Time Variables Dictionary (RTVD). This system is very usefull for development of real-time applications in nuclear power plants. It is described in details the RTVD functions and its implantation in a VAX 8600 computer. It is also pointed out the concepts of artificial intelligence used in teh RTVD

  2. Preferences for travel time variability – A study of Danish car drivers

    DEFF Research Database (Denmark)

    Hjorth, Katrine; Rich, Jeppe

    Travel time variability (TTV) is a measure of the extent of unpredictability in travel times. It is generally accepted that TTV has a negative effect on travellers’ wellbeing and overall utility of travelling, and valuation of variability is an important issue in transport demand modelling...... preferences, to exclude non-traders, and to avoid complicated issues related to scheduled public transport services. The survey uses customised Internet questionnaires, containing a series of questions related to the traveller’s most recent morning trip to work, e.g.: • Travel time experienced on this day......, • Number of stops along the way, their duration, and whether these stops involved restrictions on time of day, • Restrictions regarding departure time from home or arrival time at work, • How often such a trip was made within the last month and the range of experienced travel times, • What the traveller...

  3. Stability of Delayed Hopfield Neural Networks with Variable-Time Impulses

    Directory of Open Access Journals (Sweden)

    Yangjun Pei

    2014-01-01

    Full Text Available In this paper the globally exponential stability criteria of delayed Hopfield neural networks with variable-time impulses are established. The proposed criteria can also be applied in Hopfield neural networks with fixed-time impulses. A numerical example is presented to illustrate the effectiveness of our theoretical results.

  4. Lyapunov-based constrained engine torque control using electronic throttle and variable cam timing

    NARCIS (Netherlands)

    Feru, E.; Lazar, M.; Gielen, R.H.; Kolmanovsky, I.V.; Di Cairano, S.

    2012-01-01

    In this paper, predictive control of a spark ignition engine equipped with an electronic throttle and a variable cam timing actuator is considered. The objective is to adjust the throttle angle and the engine cam timing in order to reduce the exhaust gas emissions while maintaining fast and

  5. General practice cooperatives: long waiting times for home visits due to long distances?

    Science.gov (United States)

    Giesen, Paul; van Lin, Nieke; Mokkink, Henk; van den Bosch, Wil; Grol, Richard

    2007-02-12

    The introduction of large-scale out-of-hours GP cooperatives has led to questions about increased distances between the GP cooperatives and the homes of patients and the increasing waiting times for home visits in urgent cases. We studied the relationship between the patient's waiting time for a home visit and the distance to the GP cooperative. Further, we investigated if other factors (traffic intensity, home visit intensity, time of day, and degree of urgency) influenced waiting times. Cross-sectional study at four GP cooperatives. We used variance analysis to calculate waiting times for various categories of traffic intensity, home visit intensity, time of day, and degree of urgency. We used multiple logistic regression analysis to calculate to what degree these factors affected the ability to meet targets in urgent cases. The average waiting time for 5827 consultations was 30.5 min. Traffic intensity, home visit intensity, time of day and urgency of the complaint all seemed to affect waiting times significantly. A total of 88.7% of all patients were seen within 1 hour. In the case of life-threatening complaints (U1), 68.8% of the patients were seen within 15 min, and 95.6% of those with acute complaints (U2) were seen within 1 hour. For patients with life-threatening complaints (U1) the percentage of visits that met the time target of 15 minutes decreased from 86.5% (less than 2.5 km) to 16.7% (equals or more than 20 km). Although home visits waiting times increase with increasing distance from the GP cooperative, it appears that traffic intensity, home visit intensity, and urgency also influence waiting times. For patients with life-threatening complaints waiting times increase sharply with the distance.

  6. Norm-times : a design for production time and variability reduction for Faes Cases

    NARCIS (Netherlands)

    Karandeinos, Georgios

    2008-01-01

    This project deals with the production process of Faes Cases business unit. This company is producing custom-made packaging and sells standard solutions with customized interior. During the last years, it was observed that the throughput time of the production is increasing and is hard to forecast

  7. Evaluation of fixed and variable hospital costs due to Clostridium difficile infection: institutional incentives and directions for future research.

    Science.gov (United States)

    Ryan, P; Skally, M; Duffy, F; Farrelly, M; Gaughan, L; Flood, P; McFadden, E; Fitzpatrick, F

    2017-04-01

    Economic analysis of Clostridium difficile infection (CDI) should consider the incentives facing institutional decision-makers. To avoid overstating the financial benefits of infection prevention, fixed and variable costs should be distinguished. To quantify CDI fixed and variable costs in a tertiary referral hospital during August 2015. A micro-costing analysis estimated CDI costs per patient, including the additional costs of a CDI outbreak. Resource use was quantified after review of patient charts, pharmacy data, administrative resource input, and records of salary and cleaning/decontamination expenditure. The incremental cost of CDI was €75,680 (mean: €5,820 per patient) with key cost drivers being cleaning, pharmaceuticals, and length of stay (LOS). Additional LOS ranged from 1.75 to 22.55 days. For seven patients involved in a CDI outbreak, excluding the value of the 58 lost bed-days (€34,585); costs were 30% higher (€7,589 per patient). Therefore, total spending on CDI was €88,062 (mean: €6,773 across all patients). Potential savings from variable costs were €1,026 (17%) or €1,768 (26%) if outbreak costs were included. Investment in an antimicrobial pharmacist would require 47 CDI cases to be prevented annually. Prevention of 5%, 10% and 20% CDI would reduce attributable costs by €4,403, €8,806 and €17,612. Increasing the incremental LOS attributable to CDI to seven days per patient would have increased costs to €7,478 or €8,431 (if outbreak costs were included). As much CDI costs are fixed, potential savings from infection prevention are limited. Future analysis must consider more effectively this distinction and its impact on institutional decision-making. Copyright © 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

  8. Simulating variable-density flows with time-consistent integration of Navier-Stokes equations

    Science.gov (United States)

    Lu, Xiaoyi; Pantano, Carlos

    2017-11-01

    In this talk, we present several features of a high-order semi-implicit variable-density low-Mach Navier-Stokes solver. A new formulation to solve pressure Poisson-like equation of variable-density flows is highlighted. With this formulation of the numerical method, we are able to solve all variables with a uniform order of accuracy in time (consistent with the time integrator being used). The solver is primarily designed to perform direct numerical simulations for turbulent premixed flames. Therefore, we also address other important elements, such as energy-stable boundary conditions, synthetic turbulence generation, and flame anchoring method. Numerical examples include classical non-reacting constant/variable-density flows, as well as turbulent premixed flames.

  9. Quantitative analysis of the improvement in high zoom maritime tracking due to real-time image enhancement

    CSIR Research Space (South Africa)

    Bachoo, AK

    2011-04-01

    Full Text Available This work aims to evaluate the improvement in the performance of tracking small maritime targets due to real-time enhancement of the video streams from high zoom cameras on pan-tilt pedestal. Due to atmospheric conditions these images can frequently...

  10. X-ray spectra and time variability of active galactic nuclei

    International Nuclear Information System (INIS)

    Mushotzky, R.F.

    1984-02-01

    The X-ray spectra of broad line active galactic nuclei (AGN) of all types (Seyfert I's, NELG's, broadline radio galaxies) are well fit by a power law in the .5 to 100 keV band of man energy slope alpha .68 + or - .15. There is, as yet, no strong evidence for time variability of this slope in a given object. The constraints that this places on simple models of the central energy source are discussed. BL Lac objects have quite different X-ray spectral properties and show pronounced X-ray spectral variability. On time scales longer than 12 hours most radio quiet AGN do not show strong, delta I/I .5, variability. The probability of variability of these AGN seems to be inversely related to their luminosity. However characteristics timescales for variability have not been measured for many objects. This general lack of variability may imply that most AGN are well below the Eddington limit. Radio bright AGN tend to be more variable than radio quiet AGN on long, tau approx 6 month, timescales

  11. A Time-Series Water Level Forecasting Model Based on Imputation and Variable Selection Method.

    Science.gov (United States)

    Yang, Jun-He; Cheng, Ching-Hsue; Chan, Chia-Pan

    2017-01-01

    Reservoirs are important for households and impact the national economy. This paper proposed a time-series forecasting model based on estimating a missing value followed by variable selection to forecast the reservoir's water level. This study collected data from the Taiwan Shimen Reservoir as well as daily atmospheric data from 2008 to 2015. The two datasets are concatenated into an integrated dataset based on ordering of the data as a research dataset. The proposed time-series forecasting model summarily has three foci. First, this study uses five imputation methods to directly delete the missing value. Second, we identified the key variable via factor analysis and then deleted the unimportant variables sequentially via the variable selection method. Finally, the proposed model uses a Random Forest to build the forecasting model of the reservoir's water level. This was done to compare with the listing method under the forecasting error. These experimental results indicate that the Random Forest forecasting model when applied to variable selection with full variables has better forecasting performance than the listing model. In addition, this experiment shows that the proposed variable selection can help determine five forecast methods used here to improve the forecasting capability.

  12. A Time-Series Water Level Forecasting Model Based on Imputation and Variable Selection Method

    Directory of Open Access Journals (Sweden)

    Jun-He Yang

    2017-01-01

    Full Text Available Reservoirs are important for households and impact the national economy. This paper proposed a time-series forecasting model based on estimating a missing value followed by variable selection to forecast the reservoir’s water level. This study collected data from the Taiwan Shimen Reservoir as well as daily atmospheric data from 2008 to 2015. The two datasets are concatenated into an integrated dataset based on ordering of the data as a research dataset. The proposed time-series forecasting model summarily has three foci. First, this study uses five imputation methods to directly delete the missing value. Second, we identified the key variable via factor analysis and then deleted the unimportant variables sequentially via the variable selection method. Finally, the proposed model uses a Random Forest to build the forecasting model of the reservoir’s water level. This was done to compare with the listing method under the forecasting error. These experimental results indicate that the Random Forest forecasting model when applied to variable selection with full variables has better forecasting performance than the listing model. In addition, this experiment shows that the proposed variable selection can help determine five forecast methods used here to improve the forecasting capability.

  13. Energy decay of a variable-coefficient wave equation with nonlinear time-dependent localized damping

    Directory of Open Access Journals (Sweden)

    Jieqiong Wu

    2015-09-01

    Full Text Available We study the energy decay for the Cauchy problem of the wave equation with nonlinear time-dependent and space-dependent damping. The damping is localized in a bounded domain and near infinity, and the principal part of the wave equation has a variable-coefficient. We apply the multiplier method for variable-coefficient equations, and obtain an energy decay that depends on the property of the coefficient of the damping term.

  14. Reaction Time Variability in Children With ADHD Symptoms and/or Dyslexia

    OpenAIRE

    Gooch, Debbie; Snowling, Margaret J.; Hulme, Charles

    2012-01-01

    Reaction time (RT) variability on a Stop Signal task was examined among children with attention deficit hyperactivity disorder (ADHD) symptoms and/or dyslexia in comparison to typically developing (TD) controls. Children’s go-trial RTs were analyzed using a novel ex-Gaussian method. Children with ADHD symptoms had increased variability in the fast but not the slow portions of their RT distributions compared to those without ADHD symptoms. The RT distributions of children with d...

  15. Competency-Based, Time-Variable Education in the Health Professions: Crossroads.

    Science.gov (United States)

    Lucey, Catherine R; Thibault, George E; Ten Cate, Olle

    2018-03-01

    Health care systems around the world are transforming to align with the needs of 21st-century patients and populations. Transformation must also occur in the educational systems that prepare the health professionals who deliver care, advance discovery, and educate the next generation of physicians in these evolving systems. Competency-based, time-variable education, a comprehensive educational strategy guided by the roles and responsibilities that health professionals must assume to meet the needs of contemporary patients and communities, has the potential to catalyze optimization of educational and health care delivery systems. By designing educational and assessment programs that require learners to meet specific competencies before transitioning between the stages of formal education and into practice, this framework assures the public that every physician is capable of providing high-quality care. By engaging learners as partners in assessment, competency-based, time-variable education prepares graduates for careers as lifelong learners. While the medical education community has embraced the notion of competencies as a guiding framework for educational institutions, the structure and conduct of formal educational programs remain more aligned with a time-based, competency-variable paradigm.The authors outline the rationale behind this recommended shift to a competency-based, time-variable education system. They then introduce the other articles included in this supplement to Academic Medicine, which summarize the history of, theories behind, examples demonstrating, and challenges associated with competency-based, time-variable education in the health professions.

  16. A study of fluid flow and combustion with variable valve timing

    Energy Technology Data Exchange (ETDEWEB)

    Soederberg, F

    1998-10-01

    The effects of variable valve timing (VVT) were examined by in-cylinder Laser Doppler Velocimetry flow measurements and heat-release calculations. A single-cylinder Volvo B5254 engine was used for all experiments and the valve timing was altered by phasing or exchanging the camshaft. Special cam lobes were developed for simulation of throttle-less operation. With the standard double camshaft, a tumbling flow was generated and with valve deactivation, a swirling flow was generated. The turbulence was increased with valve deactivation. This increased the combustion rate making lean burn possible. The standard camshaft with inlet valve deactivation and late cam phasing had a faster combustion at {lambda} = 1.8 than the standard camshaft with normal cam phasing at {lambda} = 1.0. Early and late inlet valve closing was used for enabling throttle-less operation. Early inlet valve closing (EIVC) generated a very slow tumble with low turbulence. Late inlet valve closing generated both very high and low turbulence. The net indicated efficiency was improved with up to 10%. Some reduction was observed for the gross indicated efficiency, due to a too large reduction in effective compression ratio. A very stable combustion was obtained for EIVC with gasoline, possibly due to a sheering flow over the inlet valves resulting in improved fuel-air preparation. Wavelet analysis was used for dividing LDV flow measurements into time and frequency resolved information. The technique rendered the same flow results as the moving window technique, but with a separation of the turbulence into different frequencies. The choice of wavelet was shown not to be crucial. The frequency resolved turbulence was studied for tumble and swirl. A tumbling flow had a larger transfer of energy from low frequency turbulence into high frequency turbulence than a swirling flow. This is caused by the tumble breakdown. A correlation against heat-release indicated that high frequency turbulence have a larger

  17. The swan song in context: long-time-scale X-ray variability of NGC 4051

    Science.gov (United States)

    Uttley, P.; McHardy, I. M.; Papadakis, I. E.; Guainazzi, M.; Fruscione, A.

    1999-07-01

    On 1998 May 9-11, the highly variable, low-luminosity Seyfert 1 galaxy NGC 4051 was observed in an unusual low-flux state by BeppoSAX, RXTE and EUVE. We present fits of the 4-15keV RXTE spectrum and BeppoSAX MECS spectrum obtained during this observation, which are consistent with the interpretation that the source had switched off, leaving only the spectrum of pure reflection from distant cold matter. We place this result in context by showing the X-ray light curve of NGC 4051 obtained by our RXTE monitoring campaign over the past two and a half years, which shows that the low state lasted for ~150d before the May observations (implying that the reflecting material is >10^17cm from the continuum source) and forms part of a light curve showing distinct variations in long-term average flux over time-scales > months. We show that the long-time-scale component to X-ray variability is intrinsic to the primary continuum and is probably distinct from the variability at shorter time-scales. The long-time-scale component to variability maybe associated with variations in the accretion flow of matter on to the central black hole. As the source approaches the low state, the variability process becomes non-linear. NGC 4051 may represent a microcosm of all X-ray variability in radio-quiet active galactic nuclei (AGNs), displaying in a few years a variety of flux states and variability properties which more luminous AGNs may pass through on time-scales of decades to thousands of years.

  18. Long time scale hard X-ray variability in Seyfert 1 galaxies

    Science.gov (United States)

    Markowitz, Alex Gary

    This dissertation examines the relationship between long-term X-ray variability characteristics, black hole mass, and luminosity of Seyfert 1 Active Galactic Nuclei. High dynamic range power spectral density functions (PSDs) have been constructed for six Seyfert 1 galaxies. These PSDs show "breaks" or characteristic time scales, typically on the order of a few days. There is resemblance to PSDs of lower-mass Galactic X-ray binaries (XRBs), with the ratios of putative black hole masses and variability time scales approximately the same (106--7) between the two classes of objects. The data are consistent with a linear correlation between Seyfert PSD break time scale and black hole mass estimate; the relation extrapolates reasonably well over 6--7 orders of magnitude to XRBs. All of this strengthens the case for a physical similarity between Seyfert galaxies and XRBs. The first six years of RXTE monitoring of Seyfert 1s have been systematically analyzed to probe hard X-ray variability on multiple time scales in a total of 19 Seyfert is in an expansion of the survey of Markowitz & Edelson (2001). Correlations between variability amplitude, luminosity, and black hole mass are explored, the data support the model of PSD movement with black hole mass suggested by the PSD survey. All of the continuum variability results are consistent with relatively more massive black holes hosting larger X-ray emission regions, resulting in 'slower' observed variability. Nearly all sources in the sample exhibit stronger variability towards softer energies, consistent with softening as they brighten. Direct time-resolved spectral fitting has been performed on continuous RXTE monitoring of seven Seyfert is to study long-term spectral variability and Fe Kalpha variability characteristics. The Fe Kalpha line displays a wide range of behavior but varies less strongly than the broadband continuum. Overall, however, there is no strong evidence for correlated variability between the line and

  19. Wigner-Eisenbud-Smith photoionization time delay due to autoioinization resonances

    Science.gov (United States)

    Deshmukh, P. C.; Kumar, A.; Varma, H. R.; Banerjee, S.; Manson, Steven T.; Dolmatov, V. K.; Kheifets, A. S.

    2018-03-01

    An empirical ansatz for the complex photoionization amplitude and Wigner-Eisenbud-Smith time delay in the vicinity of a Fano autoionization resonance are proposed to evaluate and interpret the time delay in the resonant region. The utility of this expression is evaluated in comparison with accurate numerical calculations employing the ab initio relativistic random phase approximation and relativistic multichannel quantum defect theory. The indisputably good qualitative agreement (and semiquantitative agreement) between corresponding results of the proposed model and results produced by the ab initio theories proves the usability of the model. In addition, the phenomenology of the time delay in the vicinity of multichannel autoionizing resonances is detailed.

  20. Variability in Benthic Exchange Rate, Depth, and Residence Time Beneath a Shallow Coastal Estuary

    Science.gov (United States)

    Russoniello, Christopher J.; Heiss, James W.; Michael, Holly A.

    2018-03-01

    Hydrodynamically driven benthic exchange of water between the water column and shallow seabed aquifer is a significant and dynamic component of coastal and estuarine fluid budgets. Associated exchange of solutes promotes ecologically important chemical reactions, so quantifying benthic exchange rates, depths, and residence times constrains coastal chemical cycling estimates. We present the first combined field, numerical, and analytical modeling investigation of wave-induced exchange. Temporal variability of exchange was calculated with data collected by instruments deployed in a shallow estuary for 11 days. Differential pressure sensors recorded pressure gradients across the seabed, and up- and down-looking ADCPs recorded currents and pressures to determine wave parameters, surface-water currents, and water depth. Wave-induced exchange was calculated (1) directly from differential pressure measurements, and indirectly with an analytical model based on wave parameters from (2) ADCP and (3) wind data. Wave-induced exchange from pressure measurements and ADCP-measured wave parameters matched well, but both exceeded wind-based values. Exchange induced by tidal pumping and current-bed form interaction—the other primary drivers in shallow coastal waters were calculated from tidal stage variation and ADCP-measured currents. Exchange from waves (mean = 20.0 cm/d; range = 1.75-92.3 cm/d) greatly exceeded exchange due to tides (mean = 3.7 cm/d) and current-bed form interaction (mean = 6.5 × 10-2 cm/d). Groundwater flow models showed aquifer properties affect wave-driven benthic exchange: residence time and depth increased and exchange rates decreased with increasing hydraulic diffusivity (ratio of aquifer permeability to compressibility). This new understanding of benthic exchange will help managers assess its control over chemical fluxes to marine systems.

  1. Low-Energy Real-Time OS Using Voltage Scheduling Algorithm for Variable Voltage Processors

    OpenAIRE

    Okuma, Takanori; Yasuura, Hiroto

    2001-01-01

    This paper presents a real-time OS based on $ mu $ITRON using proposed voltage scheduling algorithm for variable voltage processors which can vary supply voltage dynamically. The proposed voltage scheduling algorithms assign voltage level for each task dynamically in order to minimize energy consumption under timing constraints. Using the presented real-time OS, running tasks with low supply voltage leads to drastic energy reduction. In addition, the presented voltage scheduling algorithm is ...

  2. Real-Time Vehicle Routing for Repairing Damaged Infrastructures Due to Natural Disasters

    Directory of Open Access Journals (Sweden)

    Huey-Kuo Chen

    2011-01-01

    Full Text Available We address the task of repairing damaged infrastructures as a series of multidepot vehicle-routing problems with time windows in a time-rolling frame. The network size of the tackled problems changes from time to time, as new disaster nodes will be added to and serviced disaster nodes will be deleted from the current network. In addition, an inaccessible disaster node would become accessible when one of its adjacent disaster nodes has been repaired. By the “take-and-conquer” strategy, the repair sequence of the disaster nodes in the affected area can be suitably scheduled. Thirteen instances were tested with our proposed heuristic, that is, Chen et al.'s approach. For comparison, Hsueh et al.'s approach (2008 with necessary modification was also tested. The results show that Chen et al.'s approach performs slightly better for larger size networks in terms of objective value.

  3. Continuous performance task in ADHD: Is reaction time variability a key measure?

    Science.gov (United States)

    Levy, Florence; Pipingas, Andrew; Harris, Elizabeth V; Farrow, Maree; Silberstein, Richard B

    2018-01-01

    To compare the use of the Continuous Performance Task (CPT) reaction time variability (intraindividual variability or standard deviation of reaction time), as a measure of vigilance in attention-deficit hyperactivity disorder (ADHD), and stimulant medication response, utilizing a simple CPT X-task vs an A-X-task. Comparative analyses of two separate X-task vs A-X-task data sets, and subgroup analyses of performance on and off medication were conducted. The CPT X-task reaction time variability had a direct relationship to ADHD clinician severity ratings, unlike the CPT A-X-task. Variability in X-task performance was reduced by medication compared with the children's unmedicated performance, but this effect did not reach significance. When the coefficient of variation was applied, severity measures and medication response were significant for the X-task, but not for the A-X-task. The CPT-X-task is a useful clinical screening test for ADHD and medication response. In particular, reaction time variability is related to default mode interference. The A-X-task is less useful in this regard.

  4. ARRIVAL TIME DIFFERENCES BETWEEN GRAVITATIONAL WAVES AND ELECTROMAGNETIC SIGNALS DUE TO GRAVITATIONAL LENSING

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Ryuichi [Faculty of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561 (Japan)

    2017-01-20

    In this study we demonstrate that general relativity predicts arrival time differences between gravitational wave (GW) and electromagnetic (EM) signals caused by the wave effects in gravitational lensing. The GW signals can arrive earlier than the EM signals in some cases if the GW/EM signals have passed through a lens, even if both signals were emitted simultaneously by a source. GW wavelengths are much larger than EM wavelengths; therefore, the propagation of the GWs does not follow the laws of geometrical optics, including the Shapiro time delay, if the lens mass is less than approximately 10{sup 5} M {sub ⊙}( f /Hz){sup −1}, where f is the GW frequency. The arrival time difference can reach ∼0.1 s ( f /Hz){sup −1} if the signals have passed by a lens of mass ∼8000 M {sub ⊙}( f /Hz){sup −1} with the impact parameter smaller than the Einstein radius; therefore, it is more prominent for lower GW frequencies. For example, when a distant supermassive black hole binary (SMBHB) in a galactic center is lensed by an intervening galaxy, the time lag becomes of the order of 10 days. Future pulsar timing arrays including the Square Kilometre Array and X-ray detectors may detect several time lags by measuring the orbital phase differences between the GW/EM signals in the SMBHBs. Gravitational lensing imprints a characteristic modulation on a chirp waveform; therefore, we can deduce whether a measured arrival time lag arises from intrinsic source properties or gravitational lensing. Determination of arrival time differences would be extremely useful in multimessenger observations and tests of general relativity.

  5. Level crossings and excess times due to a superposition of uncorrelated exponential pulses

    Science.gov (United States)

    Theodorsen, A.; Garcia, O. E.

    2018-01-01

    A well-known stochastic model for intermittent fluctuations in physical systems is investigated. The model is given by a superposition of uncorrelated exponential pulses, and the degree of pulse overlap is interpreted as an intermittency parameter. Expressions for excess time statistics, that is, the rate of level crossings above a given threshold and the average time spent above the threshold, are derived from the joint distribution of the process and its derivative. Limits of both high and low intermittency are investigated and compared to previously known results. In the case of a strongly intermittent process, the distribution of times spent above threshold is obtained analytically. This expression is verified numerically, and the distribution of times above threshold is explored for other intermittency regimes. The numerical simulations compare favorably to known results for the distribution of times above the mean threshold for an Ornstein-Uhlenbeck process. This contribution generalizes the excess time statistics for the stochastic model, which find applications in a wide diversity of natural and technological systems.

  6. MODELING TIME DISPERSION DUE TO OPTICAL PATH LENGTH DIFFERENCES IN SCINTILLATION DETECTORS*

    Science.gov (United States)

    Moses, W.W.; Choong, W.-S.; Derenzo, S.E.

    2015-01-01

    We characterize the nature of the time dispersion in scintillation detectors caused by path length differences of the scintillation photons as they travel from their generation point to the photodetector. Using Monte Carlo simulation, we find that the initial portion of the distribution (which is the only portion that affects the timing resolution) can usually be modeled by an exponential decay. The peak amplitude and decay time depend both on the geometry of the crystal, the position within the crystal that the scintillation light originates from, and the surface finish. In a rectangular parallelpiped LSO crystal with 3 mm × 3 mm cross section and polished surfaces, the decay time ranges from 10 ps (for interactions 1 mm from the photodetector) up to 80 ps (for interactions 50 mm from the photodetector). Over that same range of distances, the peak amplitude ranges from 100% (defined as the peak amplitude for interactions 1 mm from the photodetector) down to 4% for interactions 50 mm from the photodetector. Higher values for the decay time are obtained for rough surfaces, but the exact value depends on the simulation details. Estimates for the decay time and peak amplitude can be made for different cross section sizes via simple scaling arguments. PMID:25729464

  7. Improvement of attention span and reaction time with hyperbaric oxygen treatment in patients with toxic injury due to mold exposure.

    Science.gov (United States)

    Ezra, N; Dang, K; Heuser, G

    2011-01-01

    It is, by now, well established that mold toxins (mycotoxins) can cause significant adverse health effects. In this study, 15 subjects who developed an attention deficit disorder (ADD) and slowing of reaction time at the time of exposure to mold toxins were identified. Deficits in attention span and reaction time were documented not only by taking a careful history, but also by performing a Test of Variables of Attention (TOVA). The TOVA test provides an objective measure of these two variables. It was found that mold-exposed subjects show statistically significant decreases in attention span and significant increases in reaction time to stimuli compared to controls. After ten sessions of hyperbaric oxygen treatment (HBOT), a statistically significant improvement was seen in both measures. This preliminary study suggests promising outcomes in treating mold-exposed patients with hyperbaric oxygen.

  8. Effect of heat waves on morbidity and mortality due to Parkinson's disease in Madrid: A time-series analysis.

    Science.gov (United States)

    Linares, Cristina; Martinez-Martin, Pablo; Rodríguez-Blázquez, Carmen; Forjaz, Maria João; Carmona, Rocío; Díaz, Julio

    2016-01-01

    Parkinson's disease (PD) is one of the factors which are associated with a higher risk of mortality during heat waves. The use of certain neuroleptic medications to control some of this disease's complications would appear to be related to an increase in heat-related mortality. To analyse the relationship and quantify the short-term effect of high temperatures during heat wave episodes in Madrid on daily mortality and PD-related hospital admissions. We used an ecological time-series study and fit Poisson regression models. We analysed the daily number of deaths due to PD and the number of daily PD-related emergency hospital admissions in the city of Madrid, using maximum daily temperature (°C) as the main environmental variable and chemical air pollution as covariates. We controlled for trend, seasonalities, and the autoregressive nature of the series. There was a maximum daily temperature of 30°C at which PD-related admissions were at a minimum. Similarly, a temperature of 34°C coincides with an increase in the number of admissions. For PD-related admissions, the Relative Risk (RR) for every increase of 1°C above the threshold temperature was 1.13 IC95%:(1.03-1.23) at lags 1 and 5; and for daily PD-related mortality, the RR was 1.14 IC95%:(1.01-1.28) at lag 3. Our results indicate that suffering from PD is a risk factor that contributes to the excess morbidity and mortality associated with high temperatures, and is relevant from the standpoint of public health prevention plans. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. The influence of bed friction variability due to land cover on storm-driven barrier island morphodynamics

    Science.gov (United States)

    Passeri, Davina L.; Long, Joseph W.; Plant, Nathaniel G.; Bilskie, Matthew V.; Hagen, Scott C.

    2018-01-01

    Variations in bed friction due to land cover type have the potential to influence morphologic change during storm events; the importance of these variations can be studied through numerical simulation and experimentation at locations with sufficient observational data to initialize realistic scenarios, evaluate model accuracy and guide interpretations. Two-dimensional in the horizontal plane (2DH) morphodynamic (XBeach) simulations were conducted to assess morphodynamic sensitivity to spatially varying bed friction at Dauphin Island, AL using hurricanes Ivan (2004) and Katrina (2005) as experimental test cases. For each storm, three bed friction scenarios were simulated: (1) a constant Chezy coefficient across land and water, (2) a constant Chezy coefficient across land and depth-dependent Chezy coefficients across water, and (3) spatially varying Chezy coefficients across land based on land use/land cover (LULC) data and depth-dependent Chezy coefficients across water. Modeled post-storm bed elevations were compared qualitatively and quantitatively with post-storm lidar data. Results showed that implementing spatially varying bed friction influenced the ability of XBeach to accurately simulate morphologic change during both storms. Accounting for frictional effects due to large-scale variations in vegetation and development reduced cross-barrier sediment transport and captured overwash and breaching more accurately. Model output from the spatially varying friction scenarios was used to examine the need for an existing sediment transport limiter, the influence of pre-storm topography and the effects of water level gradients on storm-driven morphodynamics.

  10. Modified Pressure-Correction Projection Methods: Open Boundary and Variable Time Stepping

    KAUST Repository

    Bonito, Andrea

    2014-10-31

    © Springer International Publishing Switzerland 2015. In this paper, we design and study two modifications of the first order standard pressure increment projection scheme for the Stokes system. The first scheme improves the existing schemes in the case of open boundary condition by modifying the pressure increment boundary condition, thereby minimizing the pressure boundary layer and recovering the optimal first order decay. The second scheme allows for variable time stepping. It turns out that the straightforward modification to variable time stepping leads to unstable schemes. The proposed scheme is not only stable but also exhibits the optimal first order decay. Numerical computations illustrating the theoretical estimates are provided for both new schemes.

  11. Modified Pressure-Correction Projection Methods: Open Boundary and Variable Time Stepping

    KAUST Repository

    Bonito, Andrea; Guermond, Jean-Luc; Lee, Sanghyun

    2014-01-01

    © Springer International Publishing Switzerland 2015. In this paper, we design and study two modifications of the first order standard pressure increment projection scheme for the Stokes system. The first scheme improves the existing schemes in the case of open boundary condition by modifying the pressure increment boundary condition, thereby minimizing the pressure boundary layer and recovering the optimal first order decay. The second scheme allows for variable time stepping. It turns out that the straightforward modification to variable time stepping leads to unstable schemes. The proposed scheme is not only stable but also exhibits the optimal first order decay. Numerical computations illustrating the theoretical estimates are provided for both new schemes.

  12. Daylight saving time transitions and hospital treatments due to accidents or manic episodes

    Directory of Open Access Journals (Sweden)

    Lönnqvist Jouko

    2008-02-01

    Full Text Available Abstract Background Daylight saving time affects millions of people annually but its impacts are still widely unknown. Sleep deprivation and the change of circadian rhythm can trigger mental illness and cause higher accident rates. Transitions into and out of daylight saving time changes the circadian rhythm and may cause sleep deprivation. Thus it seems plausible that the prevalence of accidents and/or manic episodes may be higher after transition into and out of daylight saving time. The aim of this study was to explore the effects of transitions into and out of daylight saving time on the incidence of accidents and manic episodes in the Finnish population during the years of 1987 to 2003. Methods The nationwide data were derived from the Finnish Hospital Discharge Register. From the register we obtained the information about the hospital-treated accidents and manic episodes during two weeks before and two weeks after the transitions in 1987–2003. Results The results were negative, as the transitions into or out of daylight saving time had no significant effect on the incidence of accidents or manic episodes. Conclusion One-hour transitions do not increase the incidence of manic episodes or accidents which require hospital treatment.

  13. Daylight saving time transitions and hospital treatments due to accidents or manic episodes

    Science.gov (United States)

    Lahti, Tuuli A; Haukka, Jari; Lönnqvist, Jouko; Partonen, Timo

    2008-01-01

    Background Daylight saving time affects millions of people annually but its impacts are still widely unknown. Sleep deprivation and the change of circadian rhythm can trigger mental illness and cause higher accident rates. Transitions into and out of daylight saving time changes the circadian rhythm and may cause sleep deprivation. Thus it seems plausible that the prevalence of accidents and/or manic episodes may be higher after transition into and out of daylight saving time. The aim of this study was to explore the effects of transitions into and out of daylight saving time on the incidence of accidents and manic episodes in the Finnish population during the years of 1987 to 2003. Methods The nationwide data were derived from the Finnish Hospital Discharge Register. From the register we obtained the information about the hospital-treated accidents and manic episodes during two weeks before and two weeks after the transitions in 1987–2003. Results The results were negative, as the transitions into or out of daylight saving time had no significant effect on the incidence of accidents or manic episodes. Conclusion One-hour transitions do not increase the incidence of manic episodes or accidents which require hospital treatment. PMID:18302734

  14. Evidence for a time-invariant phase variable in human ankle control.

    Directory of Open Access Journals (Sweden)

    Robert D Gregg

    Full Text Available Human locomotion is a rhythmic task in which patterns of muscle activity are modulated by state-dependent feedback to accommodate perturbations. Two popular theories have been proposed for the underlying embodiment of phase in the human pattern generator: a time-dependent internal representation or a time-invariant feedback representation (i.e., reflex mechanisms. In either case the neuromuscular system must update or represent the phase of locomotor patterns based on the system state, which can include measurements of hundreds of variables. However, a much simpler representation of phase has emerged in recent designs for legged robots, which control joint patterns as functions of a single monotonic mechanical variable, termed a phase variable. We propose that human joint patterns may similarly depend on a physical phase variable, specifically the heel-to-toe movement of the Center of Pressure under the foot. We found that when the ankle is unexpectedly rotated to a position it would have encountered later in the step, the Center of Pressure also shifts forward to the corresponding later position, and the remaining portion of the gait pattern ensues. This phase shift suggests that the progression of the stance ankle is controlled by a biomechanical phase variable, motivating future investigations of phase variables in human locomotor control.

  15. Variability of African Farming Systems from Phenological Analysis of NDVI Time Series

    Science.gov (United States)

    Vrieling, Anton; deBeurs, K. M.; Brown, Molly E.

    2011-01-01

    Food security exists when people have access to sufficient, safe and nutritious food at all times to meet their dietary needs. The natural resource base is one of the many factors affecting food security. Its variability and decline creates problems for local food production. In this study we characterize for sub-Saharan Africa vegetation phenology and assess variability and trends of phenological indicators based on NDVI time series from 1982 to 2006. We focus on cumulated NDVI over the season (cumNDVI) which is a proxy for net primary productivity. Results are aggregated at the level of major farming systems, while determining also spatial variability within farming systems. High temporal variability of cumNDVI occurs in semiarid and subhumid regions. The results show a large area of positive cumNDVI trends between Senegal and South Sudan. These correspond to positive CRU rainfall trends found and relate to recovery after the 1980's droughts. We find significant negative cumNDVI trends near the south-coast of West Africa (Guinea coast) and in Tanzania. For each farming system, causes of change and variability are discussed based on available literature (Appendix A). Although food security comprises more than the local natural resource base, our results can perform an input for food security analysis by identifying zones of high variability or downward trends. Farming systems are found to be a useful level of analysis. Diversity and trends found within farming system boundaries underline that farming systems are dynamic.

  16. Real time monitoring automation of dose rate absorbed in air due to environmental gamma radiation

    International Nuclear Information System (INIS)

    Dominguez Ley, Orlando; Capote Ferrera, Eduardo; Carrazana Gonzalez, Jorge A.; Manzano de Armas, Jose F.; Alonso Abad, Dolores; Prendes Alonso, Miguel; Tomas Zerquera, Juan; Caveda Ramos, Celia A.; Kalber, Olof; Fabelo Bonet, Orlando; Montalvan Estrada, Adelmo; Cartas Aguila, Hector; Leyva Fernandez, Julio C.

    2005-01-01

    The Center of Radiation Protection and Hygiene (CPHR) as the head institution of the National Radiological Environmental Surveillance Network (RNVRA) has strengthened its detection and response capacity for a radiological emergency situation. The measurements of gamma dose rate at the main point of the RNVRA are obtained in real time and the CPHR receives the data coming from those points in a short time. To achieve the operability of the RNVRA it was necessary to complete the existent monitoring facilities using 4 automatic gamma probes, implementing in this way a real time measurement system. The software, GenitronProbe for obtaining the data automatically from the probe, Data Mail , for sending the data via e-mail, and Gamma Red , for receiving and processing the data in the head institution ,were developed

  17. Prediction of the pressure-time history due to fuel-sodium interaction in a subassembly

    International Nuclear Information System (INIS)

    Jacobs, H.

    1975-01-01

    A local cooling disturbance may lead to complete voiding of a subassembly and melt down of the fuel pins. Thus molten fuel may be accumulated and mixed with liquid sodium returning accidentally into the subassembly. The resulting fuel-sodium interaction (FSI) produces a pressure load on the surrounding core structures. It is necessary to prove that the corresponding core deformation neither initiates a nuclear excursion nor renders the shut down system inoperable. This requires the knowledge of the initiating FSI pressure time history. In this paper a theoretical pressure time history is presented which differs completely from all calculations known so far. (Auth.)

  18. Loss of labor time due to malfunctioning ICTs and ICT skill insufficiencies

    NARCIS (Netherlands)

    van Deursen, Alexander Johannes Aloysius Maria; van Dijk, Johannes A.G.M.

    2014-01-01

    Purpose – The purpose of this paper is to unexplore the area of information and communication technology (ICT) use in organizations related to the assumed productivity gains by the use of ICTs. On the one hand, the paper focus on the losses of labor time that are caused by malfunctioning hardware or

  19. Time-dependent inversion of surface subsidence due to dynamic reservoir compaction

    NARCIS (Netherlands)

    Muntendam-Bos, A.G.; Kroon, I.C.; Fokker, P.A.

    2008-01-01

    We introduce a novel, time-dependent inversion scheme for resolving temporal reservoir pressure drop from surface subsidence observations (from leveling or GPS data, InSAR, tiltmeter monitoring) in a single procedure. The theory is able to accommodate both the absence of surface subsidence estimates

  20. Compensation for the distortion in satellite laser range predictions due to varying pulse travel times

    Science.gov (United States)

    Paunonen, Matti

    1993-01-01

    A method for compensating for the effect of the varying travel time of a transmitted laser pulse to a satellite is described. The 'observed minus predicted' range differences then appear to be linear, which makes data screening or use in range gating more effective.

  1. Hydroelectric production from Brazil's São Francisco River could cease due to climate change and inter-annual variability.

    Science.gov (United States)

    de Jong, Pieter; Tanajura, Clemente Augusto Souza; Sánchez, Antonio Santos; Dargaville, Roger; Kiperstok, Asher; Torres, Ednildo Andrade

    2018-09-01

    By the end of this century higher temperatures and significantly reduced rainfall are projected for the Brazilian North and Northeast (NE) regions due to Global Warming. This study examines the impact of these long-term rainfall changes on the Brazilian Northeast's hydroelectric production. Various studies that use different IPCC models are examined in order to determine the average rainfall reduction by the year 2100 in comparison to baseline data from the end of the 20th century. It was found that average annual rainfall in the NE region could decrease by approximately 25-50% depending on the emissions scenario. Analysis of historical rainfall data in the São Francisco basin during the last 57years already shows a decline of more than 25% from the 1961-90 long-term average. Moreover, average annual rainfall in the basin has been below its long-term average every year bar one since 1992. If this declining trend continues, rainfall reduction in the basin could be even more severe than the most pessimistic model projections. That is, the marked drop in average rainfall projected for 2100, based on the IPCC high emissions scenario, could actually eventuate before 2050. Due to the elasticity factor between rainfall and streamflow and because of increased amounts of irrigation in the São Francisco basin, the reduction in the NE's average hydroelectric production in the coming decades could be double the predicted decline in rainfall. Conversely, it is estimated that wind power potential in the Brazilian NE will increase substantially by 2100. Therefore both wind and solar power will need to be significantly exploited in order for the NE region to sustainably replace lost hydroelectric production. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. Predictor variables for a half marathon race time in recreational male runners

    Directory of Open Access Journals (Sweden)

    Rüst CA

    2011-08-01

    Full Text Available Christoph Alexander Rüst1, Beat Knechtle1,2, Patrizia Knechtle2, Ursula Barandun1, Romuald Lepers3, Thomas Rosemann11Institute of General Practice and Health Services Research, University of Zurich, Zurich, Switzerland; 2Gesundheitszentrum St Gallen, St Gallen, Switzerland; 3INSERM U887, University of Burgundy, Faculty of Sport Sciences, Dijon, FranceAbstract: The aim of this study was to investigate predictor variables of anthropometry, training, and previous experience in order to predict a half marathon race time for future novice recreational male half marathoners. Eighty-four male finishers in the ‘Half Marathon Basel’ completed the race distance within (mean and standard deviation, SD 103.9 (16.5 min, running at a speed of 12.7 (1.9 km/h. After multivariate analysis of the anthropometric characteristics, body mass index (r = 0.56, suprailiacal (r = 0.36 and medial calf skin fold (r = 0.53 were related to race time. For the variables of training and previous experience, speed in running of the training sessions (r = –0.54 were associated with race time. After multivariate analysis of both the significant anthropometric and training variables, body mass index (P = 0.0150 and speed in running during training (P = 0.0045 were related to race time. Race time in a half marathon might be partially predicted by the following equation (r2 = 0.44: Race time (min = 72.91 + 3.045 * (body mass index, kg/m2 –3.884 * (speed in running during training, km/h for recreational male runners. To conclude, variables of both anthropometry and training were related to half marathon race time in recreational male half marathoners and cannot be reduced to one single predictor variable.Keywords: anthropometry, body fat, skin-folds, training, endurance

  3. BAYESIAN TECHNIQUES FOR COMPARING TIME-DEPENDENT GRMHD SIMULATIONS TO VARIABLE EVENT HORIZON TELESCOPE OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Junhan; Marrone, Daniel P.; Chan, Chi-Kwan; Medeiros, Lia; Özel, Feryal; Psaltis, Dimitrios, E-mail: junhankim@email.arizona.edu [Department of Astronomy and Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States)

    2016-12-01

    The Event Horizon Telescope (EHT) is a millimeter-wavelength, very-long-baseline interferometry (VLBI) experiment that is capable of observing black holes with horizon-scale resolution. Early observations have revealed variable horizon-scale emission in the Galactic Center black hole, Sagittarius A* (Sgr A*). Comparing such observations to time-dependent general relativistic magnetohydrodynamic (GRMHD) simulations requires statistical tools that explicitly consider the variability in both the data and the models. We develop here a Bayesian method to compare time-resolved simulation images to variable VLBI data, in order to infer model parameters and perform model comparisons. We use mock EHT data based on GRMHD simulations to explore the robustness of this Bayesian method and contrast it to approaches that do not consider the effects of variability. We find that time-independent models lead to offset values of the inferred parameters with artificially reduced uncertainties. Moreover, neglecting the variability in the data and the models often leads to erroneous model selections. We finally apply our method to the early EHT data on Sgr A*.

  4. Detection of time-varying harmonic amplitude alterations due to spectral interpolations between musical instrument tones.

    Science.gov (United States)

    Horner, Andrew B; Beauchamp, James W; So, Richard H Y

    2009-01-01

    Gradated spectral interpolations between musical instrument tone pairs were used to investigate discrimination as a function of time-averaged spectral difference. All possible nonidentical pairs taken from a collection of eight musical instrument sounds consisting of bassoon, clarinet, flute, horn, oboe, saxophone, trumpet, and violin were tested. For each pair, several tones were generated with different balances between the primary and secondary instruments, where the balance was fixed across the duration of each tone. Among primary instruments it was found that changes to horn and bassoon [corrected] were most easily discriminable, while changes to saxophone and trumpet timbres were least discriminable. Among secondary instruments, the clarinet had the strongest effect on discrimination, whereas the bassoon had the least effect. For primary instruments, strong negative correlations were found between discrimination and their spectral incoherences, suggesting that the presence of dynamic spectral variations tends to increase the difficulty of detecting time-varying alterations such as spectral interpolation.

  5. On the impact of topography and building mask on time varying gravity due to local hydrology

    Science.gov (United States)

    Deville, S.; Jacob, T.; Chéry, J.; Champollion, C.

    2013-01-01

    We use 3 yr of surface absolute gravity measurements at three sites on the Larzac plateau (France) to quantify the changes induced by topography and the building on gravity time-series, with respect to an idealized infinite slab approximation. Indeed, local topography and buildings housing ground-based gravity measurement have an effect on the distribution of water storage changes, therefore affecting the associated gravity signal. We first calculate the effects of surrounding topography and building dimensions on the gravity attraction for a uniform layer of water. We show that a gravimetric interpretation of water storage change using an infinite slab, the so-called Bouguer approximation, is generally not suitable. We propose to split the time varying gravity signal in two parts (1) a surface component including topographic and building effects (2) a deep component associated to underground water transfer. A reservoir modelling scheme is herein presented to remove the local site effects and to invert for the effective hydrological properties of the unsaturated zone. We show that effective time constants associated to water transfer vary greatly from site to site. We propose that our modelling scheme can be used to correct for the local site effects on gravity at any site presenting a departure from a flat topography. Depending on sites, the corrected signal can exceed measured values by 5-15 μGal, corresponding to 120-380 mm of water using the Bouguer slab formula. Our approach only requires the knowledge of daily precipitation corrected for evapotranspiration. Therefore, it can be a useful tool to correct any kind of gravimetric time-series data.

  6. A search for time variability and its possible regularities in linear polarization of Be stars

    International Nuclear Information System (INIS)

    Huang, L.; Guo, Z.H.; Hsu, J.C.; Huang, L.

    1989-01-01

    Linear polarization measurements are presented for 14 Be stars obtained at McDonald Observatory during four observing runs from June to November of 1983. Methods of observation and data reduction are described. Seven of eight program stars which were observed on six or more nights exhibited obvious polarimetric variations on time-scales of days or months. The incidence is estimated as 50% and may be as high as 93%. No connection can be found between polarimetric variability and rapid periodic light or spectroscopic variability for our stars. Ultra-rapid variability on time-scale of minutes was searched for with negative results. In all cases the position angles also show variations indicating that the axis of symmetry of the circumstellar envelope changes its orientation in space. For the Be binary CX Dra the variations in polarization seems to have a period which is just half of the orbital period

  7. SiPM optical crosstalk amplification due to scintillator crystal: effects on timing performance

    International Nuclear Information System (INIS)

    Gola, Alberto; Ferri, Alessandro; Tarolli, Alessandro; Zorzi, Nicola; Piemonte, Claudio

    2014-01-01

    For a given photon detection efficiency (PDE), the primary, Poisson distributed, dark count rate of the detector (DCR 0 ) is one of the most limiting factors affecting the timing resolution of a silicon photomultiplier (SiPM) in the scintillation light readout. If the effects of DCR 0  are removed through a suitable baseline compensation algorithm or by cooling, it is possible to clearly observe another phenomenon that limits the PDE, and thus the timing resolution of the detector. It is caused by the optical crosstalk of the SiPM, which is significantly increased by the presence of the scintillator. In this paper, we describe this phenomenon, which is also easily observed from the reverse I–V curve of the device, and we relate it to the measured coincidence resolving time in 511 keV γ-ray measurements. We discuss its consequences on the SiPM design and, in particular, we observe that there is an optimal cell size, dependent on both SiPM and crystal parameters, that maximizes the PDE in presence of optical crosstalk. Finally, we report on a crosstalk simulator developed to study the phenomenon and we compare the simulation results obtained for different SiPM technologies, featuring different approaches to the reduction of the crosstalk. (paper)

  8. On the physical processes which lie at the bases of time variability of GRBs

    International Nuclear Information System (INIS)

    Ruffini, R.; Bianco, C. L.; Fraschetti, F.; Xue, S-S.

    2001-01-01

    The relative-space-time-transformation (RSTT) paradigm and the interpretation of the burst-structure (IBS) paradigm are applied to probe the origin of the time variability of GRBs. Again GRB 991216 is used as a prototypical case, thanks to the precise data from the CGRO, RXTE and Chandra satellites. It is found that with the exception of the relatively inconspicuous but scientifically very important signal originating from the initial proper gamma ray burst (P-GRB), all the other spikes and time variabilities can be explained by the interaction of the accelerated-baryonic-matter pulse with inhomogeneities in the interstellar matter. This can be demonstrated by using the RSTT paradigm as well as the IBS paradigm, to trace a typical spike observed in arrival time back to the corresponding one in the laboratory time. Using these paradigms, the identification of the physical nature of the time variability of the GRBs can be made most convincingly. It is made explicit the dependence of a) the intensities of the afterglow, b) the spikes amplitude and c) the actual time structure on the Lorentz gamma factor of the accelerated-baryonic-matter pulse. In principle it is possible to read off from the spike structure the detailed density contrast of the interstellar medium in the host galaxy, even at very high redshift

  9. Drivers and potential predictability of summer time North Atlantic polar front jet variability

    Science.gov (United States)

    Hall, Richard J.; Jones, Julie M.; Hanna, Edward; Scaife, Adam A.; Erdélyi, Róbert

    2017-06-01

    The variability of the North Atlantic polar front jet stream is crucial in determining summer weather around the North Atlantic basin. Recent extreme summers in western Europe and North America have highlighted the need for greater understanding of this variability, in order to aid seasonal forecasting and mitigate societal, environmental and economic impacts. Here we find that simple linear regression and composite models based on a few predictable factors are able to explain up to 35 % of summertime jet stream speed and latitude variability from 1955 onwards. Sea surface temperature forcings impact predominantly on jet speed, whereas solar and cryospheric forcings appear to influence jet latitude. The cryospheric associations come from the previous autumn, suggesting the survival of an ice-induced signal through the winter season, whereas solar influences lead jet variability by a few years. Regression models covering the earlier part of the twentieth century are much less effective, presumably due to decreased availability of data, and increased uncertainty in observational reanalyses. Wavelet coherence analysis identifies that associations fluctuate over the study period but it is not clear whether this is just internal variability or genuine non-stationarity. Finally we identify areas for future research.

  10. Eye movements discriminate fatigue due to chronotypical factors and time spent on task--a double dissociation.

    Directory of Open Access Journals (Sweden)

    Dario Cazzoli

    Full Text Available Systematic differences in circadian rhythmicity are thought to be a substantial factor determining inter-individual differences in fatigue and cognitive performance. The synchronicity effect (when time of testing coincides with the respective circadian peak period seems to play an important role. Eye movements have been shown to be a reliable indicator of fatigue due to sleep deprivation or time spent on cognitive tasks. However, eye movements have not been used so far to investigate the circadian synchronicity effect and the resulting differences in fatigue. The aim of the present study was to assess how different oculomotor parameters in a free visual exploration task are influenced by: a fatigue due to chronotypical factors (being a 'morning type' or an 'evening type'; b fatigue due to the time spent on task. Eighteen healthy participants performed a free visual exploration task of naturalistic pictures while their eye movements were recorded. The task was performed twice, once at their optimal and once at their non-optimal time of the day. Moreover, participants rated their subjective fatigue. The non-optimal time of the day triggered a significant and stable increase in the mean visual fixation duration during the free visual exploration task for both chronotypes. The increase in the mean visual fixation duration correlated with the difference in subjectively perceived fatigue at optimal and non-optimal times of the day. Conversely, the mean saccadic speed significantly and progressively decreased throughout the duration of the task, but was not influenced by the optimal or non-optimal time of the day for both chronotypes. The results suggest that different oculomotor parameters are discriminative for fatigue due to different sources. A decrease in saccadic speed seems to reflect fatigue due to time spent on task, whereas an increase in mean fixation duration a lack of synchronicity between chronotype and time of the day.

  11. Time-variable gravity fields derived from GPS tracking of Swarm

    Czech Academy of Sciences Publication Activity Database

    Bezděk, Aleš; Sebera, Josef; da Encarnacao, J.T.; Klokočník, Jaroslav

    2016-01-01

    Roč. 205, č. 3 (2016), s. 1665-1669 ISSN 0956-540X R&D Projects: GA MŠk LG14026; GA ČR GA13-36843S Institutional support: RVO:67985815 Keywords : satellite geodesy * time variable gravity * global change from geodesy Subject RIV: DD - Geochemistry Impact factor: 2.414, year: 2016

  12. Improved theory of time domain reflectometry with variable coaxial cable length for electrical conductivity measurements

    Science.gov (United States)

    Although empirical models have been developed previously, a mechanistic model is needed for estimating electrical conductivity (EC) using time domain reflectometry (TDR) with variable lengths of coaxial cable. The goals of this study are to: (1) derive a mechanistic model based on multisection tra...

  13. Using Derivative Estimates to Describe Intraindividual Variability at Multiple Time Scales

    Science.gov (United States)

    Deboeck, Pascal R.; Montpetit, Mignon A.; Bergeman, C. S.; Boker, Steven M.

    2009-01-01

    The study of intraindividual variability is central to the study of individuals in psychology. Previous research has related the variance observed in repeated measurements (time series) of individuals to traitlike measures that are logically related. Intraindividual measures, such as intraindividual standard deviation or the coefficient of…

  14. The Chameleon Effect: characterization challenges due to the variability of nanoparticles and their surfaces of nanoparticles and their surfaces

    Science.gov (United States)

    Baer, Donald R.

    2018-05-01

    Nanoparticles in a variety of forms are increasing important in fundamental research, technological and medical applications, and environmental or toxicology studies. Physical and chemical drivers that lead to multiple types of particle instabilities complicate both the ability to produce, appropriately characterize, and consistently deliver well-defined particles, frequently leading to inconsistencies and conflicts in the published literature. This perspective suggests that provenance information, beyond that often recorded or reported, and application of a set of core characterization methods, including a surface sensitive technique, consistently applied at critical times can serve as tools in the effort minimize reproducibility issues.

  15. Dephasing times in quantum dots due to elastic LO phonon-carrier collisions

    DEFF Research Database (Denmark)

    Uskov, A. V.; Jauho, Antti-Pekka; Tromborg, Bjarne

    2000-01-01

    Interpretation of experiments on quantum dot (QD) lasers presents a challenge: the phonon bottleneck, which should strongly suppress relaxation and dephasing of the discrete energy states, often seems to be inoperative. We suggest and develop a theory for an intrinsic mechanism for dephasing in Q......: second-order elastic interaction between quantum dot charge carriers and LO phonons. The calculated dephasing times are of the order of 200 fs at room temperature, consistent with experiments. The phonon bottleneck thus does not prevent significant room temperature dephasing....

  16. The reliable solution and computation time of variable parameters Logistic model

    OpenAIRE

    Pengfei, Wang; Xinnong, Pan

    2016-01-01

    The reliable computation time (RCT, marked as Tc) when applying a double precision computation of a variable parameters logistic map (VPLM) is studied. First, using the method proposed, the reliable solutions for the logistic map are obtained. Second, for a time-dependent non-stationary parameters VPLM, 10000 samples of reliable experiments are constructed, and the mean Tc is then computed. The results indicate that for each different initial value, the Tcs of the VPLM are generally different...

  17. Predictor variables for half marathon race time in recreational female runners

    OpenAIRE

    Knechtle, Beat; Knechtle, Patrizia; Barandun, Ursula; Rosemann, Thomas; Lepers, Romuald

    2011-01-01

    INTRODUCTION: The relationship between skin-fold thickness and running performance has been investigated from 100 m to the marathon distance, except the half marathon distance. OBJECTIVE: To investigate whether anthropometry characteristics or training practices were related to race time in 42 recreational female half marathoners to determine the predictor variables of half-marathon race time and to inform future novice female half marathoners. METHODS: Observational field study at the ‘Half ...

  18. A Time-Series Water Level Forecasting Model Based on Imputation and Variable Selection Method

    OpenAIRE

    Jun-He Yang; Ching-Hsue Cheng; Chia-Pan Chan

    2017-01-01

    Reservoirs are important for households and impact the national economy. This paper proposed a time-series forecasting model based on estimating a missing value followed by variable selection to forecast the reservoir's water level. This study collected data from the Taiwan Shimen Reservoir as well as daily atmospheric data from 2008 to 2015. The two datasets are concatenated into an integrated dataset based on ordering of the data as a research dataset. The proposed time-series forecasting m...

  19. A study of applying variable valve timing to highly rated diesel engines

    Energy Technology Data Exchange (ETDEWEB)

    Stone, C R; Leonard, H J [comps.; Brunel Univ., Uxbridge (United Kingdom); Charlton, S J [comp.; Bath Univ. (United Kingdom)

    1992-10-01

    The main objective of the research was to use Simulation Program for Internal Combustion Engines (SPICE) to quantify the potential offered by Variable Valve Timing (VVT) in improving engine performance. A model has been constructed of a particular engine using SPICE. The model has been validated with experimental data, and it has been shown that accurate predictions are made when the valve timing is changed. (author)

  20. Intraindividual Stepping Reaction Time Variability Predicts Falls in Older Adults With Mild Cognitive Impairment

    OpenAIRE

    Bunce, D; Haynes, BI; Lord, SR; Gschwind, YJ; Kochan, NA; Reppermund, S; Brodaty, H; Sachdev, PS; Delbaere, K

    2017-01-01

    Background: Reaction time measures have considerable potential to aid neuropsychological assessment in a variety of health care settings. One such measure, the intraindividual reaction time variability (IIV), is of particular interest as it is thought to reflect neurobiological disturbance. IIV is associated with a variety of age-related neurological disorders, as well as gait impairment and future falls in older adults. However, although persons diagnosed with Mild Cognitive Impairment (MCI)...

  1. Error Analysis of a Fractional Time-Stepping Technique for Incompressible Flows with Variable Density

    KAUST Repository

    Guermond, J.-L.; Salgado, Abner J.

    2011-01-01

    In this paper we analyze the convergence properties of a new fractional time-stepping technique for the solution of the variable density incompressible Navier-Stokes equations. The main feature of this method is that, contrary to other existing algorithms, the pressure is determined by just solving one Poisson equation per time step. First-order error estimates are proved, and stability of a formally second-order variant of the method is established. © 2011 Society for Industrial and Applied Mathematics.

  2. Bounds of Double Integral Dynamic Inequalities in Two Independent Variables on Time Scales

    Directory of Open Access Journals (Sweden)

    S. H. Saker

    2011-01-01

    Full Text Available Our aim in this paper is to establish some explicit bounds of the unknown function in a certain class of nonlinear dynamic inequalities in two independent variables on time scales which are unbounded above. These on the one hand generalize and on the other hand furnish a handy tool for the study of qualitative as well as quantitative properties of solutions of partial dynamic equations on time scales. Some examples are considered to demonstrate the applications of the results.

  3. Pollen exposure and hospitalization due to asthma exacerbations: daily time series in a European city

    Science.gov (United States)

    Osborne, Nicholas J.; Alcock, Ian; Wheeler, Benedict W.; Hajat, Shakoor; Sarran, Christophe; Clewlow, Yolanda; McInnes, Rachel N.; Hemming, Deborah; White, Mathew; Vardoulakis, Sotiris; Fleming, Lora E.

    2017-10-01

    Exposure to pollen can contribute to increased hospital admissions for asthma exacerbation. This study applied an ecological time series analysis to examine associations between atmospheric concentrations of different pollen types and the risk of hospitalization for asthma in London from 2005 to 2011. The analysis examined short-term associations between daily pollen counts and hospital admissions in the presence of seasonal and long-term patterns, and allowed for time lags between exposure and admission. Models were adjusted for temperature, precipitation, humidity, day of week, and air pollutants. Analyses revealed an association between daily counts (continuous) of grass pollen and adult hospital admissions for asthma in London, with a 4-5-day lag. When grass pollen concentrations were categorized into Met Office pollen `alert' levels, `very high' days (vs. `low') were associated with increased admissions 2-5 days later, peaking at an incidence rate ratio of 1.46 (95%, CI 1.20-1.78) at 3 days. Increased admissions were also associated with `high' versus `low' pollen days at a 3-day lag. Results from tree pollen models were inconclusive and likely to have been affected by the shorter pollen seasons and consequent limited number of observation days with higher tree pollen concentrations. Future reductions in asthma hospitalizations may be achieved by better understanding of environmental risks, informing improved alert systems and supporting patients to take preventive measures.

  4. Time Dependent Frictional Changes in Ice due to Contact Area Changes

    Science.gov (United States)

    Sevostianov, V.; Lipovsky, B. P.; Rubinstein, S.; Dillavou, S.

    2017-12-01

    Sliding processes along the ice-bed interface of Earth's great ice sheets are the largest contributor to our uncertainty in future sea level rise. Laboratory experiments that have probed sliding processes have ubiquitously shown that ice-rock interfaces strengthen while in stationary contact (Schulson and Fortt, 2013; Zoet et al., 2013; McCarthy et al., 2017). This so-called frictional ageing effect may have profound consequences for ice sheet dynamics because it introduces the possibility of basal strength hysteresis. Furthermore this effect is quite strong in ice-rock interfaces (more than an order of magnitude more pronounced than in rock-rock sliding) and can double in frictional strength in a matter of minutes, much faster than most frictional aging (Dieterich, 1972; Baumberger and Caroli, 2006). Despite this importance, the underling physics of frictional ageing of ice remain poorly understood. Here we conduct laboratory experiments to image the microscopic points of contact along an ice-glass interface. We optically measure changes in the real area of contact over time using measurements of this reflected optical light intensity. We show that contact area increases with time of stationary contact. This result suggests that thermally enhanced creep of microscopic icy contacts is responsible for the much larger frictional ageing observed in ice-rock versus rock-rock interfaces. Furthermore, this supports a more physically detailed description of the thermal dependence of basal sliding than that used in the current generation of large scale ice sheet models.

  5. Variability in benthic exchange rate, depth, and residence time beneath a shallow coastal estuary

    Science.gov (United States)

    Russoniello, C. J.; Michael, H. A.; Heiss, J.

    2017-12-01

    Hydrodynamically-driven exchange of water between the water column and shallow seabed aquifer, benthic exchange, is a significant and dynamic component of coastal and estuarine fluid budgets, but wave-induced benthic exchange has not been measured in the field. Mixing between surface water and groundwater solutes promotes ecologically important chemical reactions, so quantifying benthic exchange rates, depths, and residence times, constrains estimates of coastal chemical cycling. In this study, we present the first field-based direct measurements of wave-induced exchange and compare it to exchange induced by the other primary drivers of exchange - tides, and currents. We deployed instruments in a shallow estuary to measure benthic exchange and temporal variability over an 11-day period. Differential pressure sensors recorded pressure gradients across the seabed, and up-and down-looking ADCPs recorded currents and pressures from which wave parameters, surface-water currents, and water depth were determined. Wave-induced exchange was calculated directly from 1) differential pressure measurements, and indirectly with an analytical solution based on wave parameters from 2) ADCP and 3) weather station data. Groundwater flow models were used to assess the effects of aquifer properties on benthic exchange depth and residence time. Benthic exchange driven by tidal pumping or current-bedform interaction was calculated from tidal stage variation and from ADCP-measured currents at the bed, respectively. Waves were the primary benthic exchange driver (average = 20.0 cm/d, maximum = 92.3 cm/d) during the measurement period. Benthic exchange due to tides (average = 3.7 cm/d) and current-bedform interaction (average = 6.5x10-2 cm/d) was much lower. Wave-induced exchange calculated from pressure measurements and ADCP-measured wave parameters matched well, but wind-based rates underestimated wave energy and exchange. Groundwater models showed that residence time and depth increased

  6. GPS Imaging of Time-Variable Earthquake Hazard: The Hilton Creek Fault, Long Valley California

    Science.gov (United States)

    Hammond, W. C.; Blewitt, G.

    2016-12-01

    The Hilton Creek Fault, in Long Valley, California is a down-to-the-east normal fault that bounds the eastern edge of the Sierra Nevada/Great Valley microplate, and lies half inside and half outside the magmatically active caldera. Despite the dense coverage with GPS networks, the rapid and time-variable surface deformation attributable to sporadic magmatic inflation beneath the resurgent dome makes it difficult to use traditional geodetic methods to estimate the slip rate of the fault. While geologic studies identify cumulative offset, constrain timing of past earthquakes, and constrain a Quaternary slip rate to within 1-5 mm/yr, it is not currently possible to use geologic data to evaluate how the potential for slip correlates with transient caldera inflation. To estimate time-variable seismic hazard of the fault we estimate its instantaneous slip rate from GPS data using a new set of algorithms for robust estimation of velocity and strain rate fields and fault slip rates. From the GPS time series, we use the robust MIDAS algorithm to obtain time series of velocity that are highly insensitive to the effects of seasonality, outliers and steps in the data. We then use robust imaging of the velocity field to estimate a gridded time variable velocity field. Then we estimate fault slip rate at each time using a new technique that forms ad-hoc block representations that honor fault geometries, network complexity, connectivity, but does not require labor-intensive drawing of block boundaries. The results are compared to other slip rate estimates that have implications for hazard over different time scales. Time invariant long term seismic hazard is proportional to the long term slip rate accessible from geologic data. Contemporary time-invariant hazard, however, may differ from the long term rate, and is estimated from the geodetic velocity field that has been corrected for the effects of magmatic inflation in the caldera using a published model of a dipping ellipsoidal

  7. Spontaneous variability of pre-dialysis concentrations of uremic toxins over time in stable hemodialysis patients.

    Directory of Open Access Journals (Sweden)

    Sunny Eloot

    Full Text Available Numerous outcome studies and interventional trials in hemodialysis (HD patients are based on uremic toxin concentrations determined at one single or a limited number of time points. The reliability of these studies however entirely depends on how representative these cross-sectional concentrations are. We therefore investigated the variability of predialysis concentrations of uremic toxins over time.Prospectively collected predialysis serum samples of the midweek session of week 0, 1, 2, 3, 4, 8, 12, and 16 were analyzed for a panel of uremic toxins in stable chronic HD patients (N = 18 while maintaining dialyzer type and dialysis mode during the study period.Concentrations of the analyzed uremic toxins varied substantially between individuals, but also within stable HD patients (intra-patient variability. For urea, creatinine, beta-2-microglobulin, and some protein-bound uremic toxins, Intra-class Correlation Coefficient (ICC was higher than 0.7. However, for phosphorus, uric acid, symmetric and asymmetric dimethylarginine, and the protein-bound toxins hippuric acid and indoxyl sulfate, ICC values were below 0.7, implying a concentration variability within the individual patient even exceeding 65% of the observed inter-patient variability.Intra-patient variability may affect the interpretation of the association between a single concentration of certain uremic toxins and outcomes. When performing future outcome and interventional studies with uremic toxins other than described here, one should quantify their intra-patient variability and take into account that for solutes with a large intra-patient variability associations could be missed.

  8. Reducing Glucose Variability Due to Meals and Postprandial Exercise in T1DM Using Switched LPV Control: In Silico Studies.

    Science.gov (United States)

    Colmegna, Patricio H; Sánchez-Peña, Ricardo S; Gondhalekar, Ravi; Dassau, Eyal; Doyle, Francis J

    2016-05-01

    Time-varying dynamics is one of the main issues for achieving safe blood glucose control in type 1 diabetes mellitus (T1DM) patients. In addition, the typical disturbances considered for controller design are meals, which increase the glucose level, and physical activity (PA), which increases the subject's sensitivity to insulin. In previous works the authors have applied a linear parameter-varying (LPV) control technique to manage unannounced meals. A switched LPV controller that switches between 3 LPV controllers, each with a different level of aggressiveness, is designed to further cope with both unannounced meals and postprandial PA. Thus, the proposed control strategy has a "standard" mode, an "aggressive" mode, and a "conservative" mode. The "standard" mode is designed to be applied most of the time, while the "aggressive" mode is designed to deal only with hyperglycemia situations. On the other hand, the "conservative" mode is focused on postprandial PA control. An ad hoc simulator has been developed to test the proposed controller. This simulator is based on the distribution version of the UVA/Padova model and includes the effect of PA based on Schiavon.(1) The test results obtained when using this simulator indicate that the proposed control law substantially reduces the risk of hypoglycemia with the conservative strategy, while the risk of hyperglycemia is scarcely affected. It is demonstrated that the announcement, or anticipation, of exercise is indispensable for letting a mono-hormonal artificial pancreas deal with the consequences of postprandial PA. In view of this the proposed controller allows switching into a conservative mode when notified of PA by the user. © 2016 Diabetes Technology Society.

  9. Changes in tumor cell response due to prolonged dose delivery times in fractionated radiation therapy

    International Nuclear Information System (INIS)

    Paganetti, Harald

    2005-01-01

    Purpose: Dynamic radiation therapy, such as intensity-modulated radiation therapy, delivers more complex treatment fields than conventional techniques. The increased complexity causes longer dose delivery times for each fraction. The cellular damage after a full treatment may depend on the dose rate, because sublethal radiation damage can be repaired more efficiently during prolonged dose delivery. The goal of this study was to investigate the significance of this effect in fractionated radiation therapy. Methods and Materials: The lethal/potentially lethal model was used to calculate lesion induction rates for repairable and nonrepairable lesions. Dose rate effects were analyzed for 9 different cell lines (8 human tumor xenografts and a C3H10T1/2 cell line). The effects of single-fraction as well as fractionated irradiation for different dose rates were studied. Results: Significant differences can be seen for dose rates lower than about 0.1 Gy/min for all cell lines considered. For 60 Gy delivered in 30 fractions, the equivalent dose is reduced by between 1.3% and 12% comparing 2 Gy delivery over 30 min per fraction with 2 Gy delivery over 1 min per fraction. The effect is higher for higher doses per fraction. Furthermore, the results show that dose rate effects do not show a simple correlation with the α/β ratio for ratios between 3 Gy and 31 Gy. Conclusions: If the total dose delivery time for a treatment fraction in radiation therapy increases to about 20 min, a correction for dose rate effects may have to be considered in treatment planning. Adjustments in effective dose may be necessary when comparing intensity-modulated radiation therapy with conventional treatment plans

  10. Spectral analysis of uneven time series of geological variables; Analisis espectral de series temporales de variables geologicas con muestreo irregular

    Energy Technology Data Exchange (ETDEWEB)

    Pardo-Iguzquiza, E.; Rodriguez-Tovar, F. J.

    2013-06-01

    In geosciences the sampling of a time series tends to afford uneven results, sometimes because the sampling itself is random or because of hiatuses or even completely missing data or due to difficulties involved in the conversion of data from a spatial to a time scale when the sedimentation rate was not constant. Whatever the case, the best solution does not lie in interpolation but rather in resorting to a method that deals with the irregular data. We show here how the use of the smoothed Lomb-Scargle periodogram is both a practical and efficient choice. We describe the effects on the estimated power spectrum of the type of irregular sampling, the number of data, interpolation, and the presence of drift. We propose the permutation test as being an efficient way of calculating statistical confidence levels. By applying the Lomb-Scargle periodogram to a synthetic series with a known spectral content we are able to confirm the validity of this method in the face of the difficulties mentioned above. A case study with real data, including hiatuses, representing the thickness of the annual banding in a stalagmite, is chosen to demonstrate an application using the statistical and physical interpretation of spectral peaks. (Author)

  11. A variable-order time-dependent neutron transport method for nuclear reactor kinetics using analytically-integrated space-time characteristics

    International Nuclear Information System (INIS)

    Hoffman, A. J.; Lee, J. C.

    2013-01-01

    A new time-dependent neutron transport method based on the method of characteristics (MOC) has been developed. Whereas most spatial kinetics methods treat time dependence through temporal discretization, this new method treats time dependence by defining the characteristics to span space and time. In this implementation regions are defined in space-time where the thickness of the region in time fulfills an analogous role to the time step in discretized methods. The time dependence of the local source is approximated using a truncated Taylor series expansion with high order derivatives approximated using backward differences, permitting the solution of the resulting space-time characteristic equation. To avoid a drastic increase in computational expense and memory requirements due to solving many discrete characteristics in the space-time planes, the temporal variation of the boundary source is similarly approximated. This allows the characteristics in the space-time plane to be represented analytically rather than discretely, resulting in an algorithm comparable in implementation and expense to one that arises from conventional time integration techniques. Furthermore, by defining the boundary flux time derivative in terms of the preceding local source time derivative and boundary flux time derivative, the need to store angularly-dependent data is avoided without approximating the angular dependence of the angular flux time derivative. The accuracy of this method is assessed through implementation in the neutron transport code DeCART. The method is employed with variable-order local source representation to model a TWIGL transient. The results demonstrate that this method is accurate and more efficient than the discretized method. (authors)

  12. An Outbreak of Food-Borne Typhoid Fever Due to Salmonella enterica Serotype Typhi in Japan Reported for the First Time in 16 Years

    Science.gov (United States)

    Kobayashi, Tetsuro; Kutsuna, Satoshi; Hayakawa, Kayoko; Kato, Yasuyuki; Ohmagari, Norio; Uryu, Hideko; Yamada, Ritsuko; Kashiwa, Naoyuki; Nei, Takahito; Ehara, Akihito; Takei, Reiko; Mori, Nobuaki; Yamada, Yasuhiro; Hayasaka, Tomomi; Kagawa, Narito; Sugawara, Momoko; Suzaki, Ai; Takahashi, Yuno; Nishiyama, Hiroyuki; Morita, Masatomo; Izumiya, Hidemasa; Ohnishi, Makoto

    2016-01-01

    For the first time in 16 years, a food-borne outbreak of typhoid fever due to Salmonella enterica serotype Typhi was reported in Japan. Seven patients consumed food in an Indian buffet at a restaurant in the center of Tokyo, while one was a Nepali chef in the restaurant, an asymptomatic carrier and the implicated source of this outbreak. The multiple-locus variable-number tandem repeat analysis showed 100% consistency in the genomic sequence for five of the eight cases. PMID:26621565

  13. Numerical Solution of the Time-Dependent Navier–Stokes Equation for Variable Density–Variable Viscosity. Part I

    Czech Academy of Sciences Publication Activity Database

    Axelsson, Owe; Xin, H.; Neytcheva, M.

    2015-01-01

    Roč. 20, č. 2 (2015), s. 232-260 ISSN 1392-6292 Institutional support: RVO:68145535 Keywords : variable density * phase-field model * Navier-Stokes equations * preconditioning * variable viscosity Subject RIV: BA - General Mathematics Impact factor: 0.468, year: 2015 http://www.tandfonline.com/doi/abs/10.3846/13926292.2015.1021395

  14. Space-time variability of hydrological drought and wetness in Iran using NCEP/NCAR and GPCC datasets

    Directory of Open Access Journals (Sweden)

    T. Raziei

    2010-10-01

    Full Text Available Space-time variability of hydrological drought and wetness over Iran is investigated using the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR reanalysis and the Global Precipitation Climatology Centre (GPCC dataset for the common period 1948–2007. The aim is to complement previous studies on the detection of long-term trends in drought/wetness time series and on the applicability of reanalysis data for drought monitoring in Iran. Climate conditions of the area are assessed through the Standardized Precipitation Index (SPI on 24-month time scale, while Principal Component Analysis (PCA and Varimax rotation are used for investigating drought/wetness variability, and drought regionalization, respectively. Singular Spectrum Analysis (SSA is applied to the time series of interest to extract the leading nonlinear components and compare them with linear fittings.

    Differences in drought and wetness area coverage resulting from the two datasets are discussed also in relation to the change occurred in recent years. NCEP/NCAR and GPCC are in good agreement in identifying four sub-regions as principal spatial modes of drought variability. However, the climate variability in each area is not univocally represented by the two datasets: a good agreement is found for south-eastern and north-western regions, while noticeable discrepancies occur for central and Caspian sea regions. A comparison with NCEP Reanalysis II for the period 1979–2007, seems to exclude that the discrepancies are merely due to the introduction of satellite data into the reanalysis assimilation scheme.

  15. Application of several variable-valve-timing concepts to an LHR engine

    Science.gov (United States)

    Morel, T.; Keribar, R.; Sawlivala, M.; Hakim, N.

    1987-01-01

    The paper discusses advantages provided by electronically controlled hydraulically activated valves (ECVs) when applied to low heat rejection (LHR) engines. The ECV concept provides additional engine control flexibility by allowing for a variable valve timing as a function of speed and load, or for a given transient condition. The results of a study carried out to assess the benefits that this flexibility can offer to an LHR engine indicated that, when judged on the benefits to BSFC, volumetric efficiency, and peak firing pressure, ECVs would provide only modest benefits in comparison to conventional valve profiles. It is noted, however, that once installed on the engine, the ECVs would permit a whole range of certain more sophisticated variable valve timing strategies not otherwise possible, such as high compression cranking, engine braking, cylinder cutouts, and volumetric efficiency timing with engine speed.

  16. Continuous-variable quantum computing in optical time-frequency modes using quantum memories.

    Science.gov (United States)

    Humphreys, Peter C; Kolthammer, W Steven; Nunn, Joshua; Barbieri, Marco; Datta, Animesh; Walmsley, Ian A

    2014-09-26

    We develop a scheme for time-frequency encoded continuous-variable cluster-state quantum computing using quantum memories. In particular, we propose a method to produce, manipulate, and measure two-dimensional cluster states in a single spatial mode by exploiting the intrinsic time-frequency selectivity of Raman quantum memories. Time-frequency encoding enables the scheme to be extremely compact, requiring a number of memories that are a linear function of only the number of different frequencies in which the computational state is encoded, independent of its temporal duration. We therefore show that quantum memories can be a powerful component for scalable photonic quantum information processing architectures.

  17. Three-Factor Market-Timing Models with Fama and French's Spread Variables

    Directory of Open Access Journals (Sweden)

    Joanna Olbryś

    2010-01-01

    Full Text Available The traditional performance measurement literature has attempted to distinguish security selection, or stock-picking ability, from market-timing, or the ability to predict overall market returns. However, the literature finds that it is not easy to separate ability into such dichotomous categories. Some researchers have developed models that allow the decomposition of manager performance into market-timing and selectivity skills. The main goal of this paper is to present modified versions of classical market-timing models with Fama and French’s spread variables SMB and HML, in the case of Polish equity mutual funds. (original abstract

  18. Time-varying surrogate data to assess nonlinearity in nonstationary time series: application to heart rate variability.

    Science.gov (United States)

    Faes, Luca; Zhao, He; Chon, Ki H; Nollo, Giandomenico

    2009-03-01

    We propose a method to extend to time-varying (TV) systems the procedure for generating typical surrogate time series, in order to test the presence of nonlinear dynamics in potentially nonstationary signals. The method is based on fitting a TV autoregressive (AR) model to the original series and then regressing the model coefficients with random replacements of the model residuals to generate TV AR surrogate series. The proposed surrogate series were used in combination with a TV sample entropy (SE) discriminating statistic to assess nonlinearity in both simulated and experimental time series, in comparison with traditional time-invariant (TIV) surrogates combined with the TIV SE discriminating statistic. Analysis of simulated time series showed that using TIV surrogates, linear nonstationary time series may be erroneously regarded as nonlinear and weak TV nonlinearities may remain unrevealed, while the use of TV AR surrogates markedly increases the probability of a correct interpretation. Application to short (500 beats) heart rate variability (HRV) time series recorded at rest (R), after head-up tilt (T), and during paced breathing (PB) showed: 1) modifications of the SE statistic that were well interpretable with the known cardiovascular physiology; 2) significant contribution of nonlinear dynamics to HRV in all conditions, with significant increase during PB at 0.2 Hz respiration rate; and 3) a disagreement between TV AR surrogates and TIV surrogates in about a quarter of the series, suggesting that nonstationarity may affect HRV recordings and bias the outcome of the traditional surrogate-based nonlinearity test.

  19. Intraindividual variability in reaction time before and after neoadjuvant chemotherapy in women diagnosed with breast cancer.

    Science.gov (United States)

    Yao, Christie; Rich, Jill B; Tirona, Kattleya; Bernstein, Lori J

    2017-12-01

    Women treated with chemotherapy for breast cancer experience subtle cognitive deficits. Research has focused on mean performance level, yet recent work suggests that within-person variability in reaction time performance may underlie cognitive symptoms. We examined intraindividual variability (IIV) in women diagnosed with breast cancer and treated with neoadjuvant chemotherapy. Patients (n = 28) were assessed at baseline before chemotherapy (T1), approximately 1 month after chemotherapy but prior to surgery (T2), and after surgery about 9 months post chemotherapy (T3). Healthy women of similar age and education (n = 20) were assessed at comparable time intervals. Using a standardized regression-based approach, we examined changes in mean performance level and IIV (eg, intraindividual standard deviation) on a Stroop task and self-report measures of cognitive function from T1 to T2 and T1 to T3. At T1, women with breast cancer were more variable than controls as task complexity increased. Change scores from T1 to T2 were similar between groups on all Stroop performance measures. From T1 to T3, controls improved more than women with breast cancer. IIV was more sensitive than mean reaction time in capturing group differences. Additional analyses showed increased cognitive symptoms reported by women with breast cancer from T1 to T3. Specifically, change in language symptoms was positively correlated with change in variability. Women with breast cancer declined in attention and inhibitory control relative to pretreatment performance. Future studies should include measures of variability, because they are an important sensitive indicator of change in cognitive function. Copyright © 2016 John Wiley & Sons, Ltd.

  20. Towards a More Biologically-meaningful Climate Characterization: Variability in Space and Time at Multiple Scales

    Science.gov (United States)

    Christianson, D. S.; Kaufman, C. G.; Kueppers, L. M.; Harte, J.

    2013-12-01

    fine-spatial scales (sub-meter to 10-meter) shows greater temperature variability with warmer mean temperatures. This is inconsistent with the inherent assumption made in current species distribution models that fine-scale variability is static, implying that current projections of future species ranges may be biased -- the direction and magnitude requiring further study. While we focus our findings on the cross-scaling characteristics of temporal and spatial variability, we also compare the mean-variance relationship between 1) experimental climate manipulations and observed conditions and 2) temporal versus spatial variance, i.e., variability in a time-series at one location vs. variability across a landscape at a single time. The former informs the rich debate concerning the ability to experimentally mimic a warmer future. The latter informs space-for-time study design and analyses, as well as species persistence via a combined spatiotemporal probability of suitable future habitat.

  1. The Propagation of Movement Variability in Time: A Methodological Approach for Discrete Movements with Multiple Degrees of Freedom

    Science.gov (United States)

    Krüger, Melanie; Straube, Andreas; Eggert, Thomas

    2017-01-01

    In recent years, theory-building in motor neuroscience and our understanding of the synergistic control of the redundant human motor system has significantly profited from the emergence of a range of different mathematical approaches to analyze the structure of movement variability. Approaches such as the Uncontrolled Manifold method or the Noise-Tolerance-Covariance decomposition method allow to detect and interpret changes in movement coordination due to e.g., learning, external task constraints or disease, by analyzing the structure of within-subject, inter-trial movement variability. Whereas, for cyclical movements (e.g., locomotion), mathematical approaches exist to investigate the propagation of movement variability in time (e.g., time series analysis), similar approaches are missing for discrete, goal-directed movements, such as reaching. Here, we propose canonical correlation analysis as a suitable method to analyze the propagation of within-subject variability across different time points during the execution of discrete movements. While similar analyses have already been applied for discrete movements with only one degree of freedom (DoF; e.g., Pearson's product-moment correlation), canonical correlation analysis allows to evaluate the coupling of inter-trial variability across different time points along the movement trajectory for multiple DoF-effector systems, such as the arm. The theoretical analysis is illustrated by empirical data from a study on reaching movements under normal and disturbed proprioception. The results show increased movement duration, decreased movement amplitude, as well as altered movement coordination under ischemia, which results in a reduced complexity of movement control. Movement endpoint variability is not increased under ischemia. This suggests that healthy adults are able to immediately and efficiently adjust the control of complex reaching movements to compensate for the loss of proprioceptive information. Further, it is

  2. The first-passage time distribution for the diffusion model with variable drift

    DEFF Research Database (Denmark)

    Blurton, Steven Paul; Kesselmeier, Miriam; Gondan, Matthias

    2017-01-01

    across trials. This extra flexibility allows accounting for slow errors that often occur in response time experiments. So far, the predicted response time distributions were obtained by numerical evaluation as analytical solutions were not available. Here, we present an analytical expression...... for the cumulative first-passage time distribution in the diffusion model with normally distributed trial-to-trial variability in the drift. The solution is obtained with predefined precision, and its evaluation turns out to be extremely fast.......The Ratcliff diffusion model is now arguably the most widely applied model for response time data. Its major advantage is its description of both response times and the probabilities for correct as well as incorrect responses. The model assumes a Wiener process with drift between two constant...

  3. Squeezing more information out of time variable gravity data with a temporal decomposition approach

    DEFF Research Database (Denmark)

    Barletta, Valentina Roberta; Bordoni, A.; Aoudia, A.

    2012-01-01

    an explorative approach based on a suitable time series decomposition, which does not rely on predefined time signatures. The comparison and validation against the fitting approach commonly used in GRACE literature shows a very good agreement for what concerns trends and periodic signals on one side......A measure of the Earth's gravity contains contributions from solid Earth as well as climate-related phenomena, that cannot be easily distinguished both in time and space. After more than 7years, the GRACE gravity data available now support more elaborate analysis on the time series. We propose...... used to assess the possibility of finding evidence of meaningful geophysical signals different from hydrology over Africa in GRACE data. In this case we conclude that hydrological phenomena are dominant and so time variable gravity data in Africa can be directly used to calibrate hydrological models....

  4. Countermovement jump height: gender and sport-specific differences in the force-time variables.

    Science.gov (United States)

    Laffaye, Guillaume; Wagner, Phillip P; Tombleson, Tom I L

    2014-04-01

    The goal of this study was to assess (a) the eccentric rate of force development, the concentric force, and selected time variables on vertical performance during countermovement jump, (b) the existence of gender differences in these variables, and (c) the sport-specific differences. The sample was composed of 189 males and 84 females, all elite athletes involved in college and professional sports (primarily football, basketball, baseball, and volleyball). The subjects performed a series of 6 countermovement jumps on a force plate (500 Hz). Average eccentric rate of force development (ECC-RFD), total time (TIME), eccentric time (ECC-T), Ratio between eccentric and total time (ECC-T:T) and average force (CON-F) were extracted from force-time curves and the vertical jumping performance, measured by impulse momentum. Results show that CON-F (r = 0.57; p differ between both sexes (p differ, showing a similar temporal structure. The best way to jump high is to increase CON-F and ECC-RFD thus minimizing the ECC-T. Principal component analysis (PCA) accounted for 76.8% of the JH variance and revealed that JH is predicted by a temporal and a force component. Furthermore, the PCA comparison made among athletes revealed sport-specific signatures: volleyball players revealed a temporal-prevailing profile, a weak-force with large ECC-T:T for basketball players and explosive and powerful profiles for football and baseball players.

  5. Low Computational Signal Acquisition for GNSS Receivers Using a Resampling Strategy and Variable Circular Correlation Time

    Directory of Open Access Journals (Sweden)

    Yeqing Zhang

    2018-02-01

    Full Text Available For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work on conventional acquisition algorithms by resampling the main lobe of received broadband signals with a much lower frequency. Variable circular correlation time is designed to adapt to different signal strength conditions and thereby increase the operation flexibility of GNSS signal acquisition. The acquisition threshold is defined as the ratio of the highest and second highest correlation results in the search space of carrier frequency and code phase. Moreover, computational complexity of signal acquisition is formulated by amounts of multiplication and summation operations in the acquisition process. Comparative experiments and performance analysis are conducted on four sets of real GPS L2C signals with different sampling frequencies. The results indicate that the resampling strategy can effectively decrease computation and time cost by nearly 90–94% with just slight loss of acquisition sensitivity. With circular correlation time varying from 10 ms to 20 ms, the time cost of signal acquisition has increased by about 2.7–5.6% per millisecond, with most satellites acquired successfully.

  6. Trend Change Detection in NDVI Time Series: Effects of Inter-Annual Variability and Methodology

    Science.gov (United States)

    Forkel, Matthias; Carvalhais, Nuno; Verbesselt, Jan; Mahecha, Miguel D.; Neigh, Christopher S.R.; Reichstein, Markus

    2013-01-01

    Changing trends in ecosystem productivity can be quantified using satellite observations of Normalized Difference Vegetation Index (NDVI). However, the estimation of trends from NDVI time series differs substantially depending on analyzed satellite dataset, the corresponding spatiotemporal resolution, and the applied statistical method. Here we compare the performance of a wide range of trend estimation methods and demonstrate that performance decreases with increasing inter-annual variability in the NDVI time series. Trend slope estimates based on annual aggregated time series or based on a seasonal-trend model show better performances than methods that remove the seasonal cycle of the time series. A breakpoint detection analysis reveals that an overestimation of breakpoints in NDVI trends can result in wrong or even opposite trend estimates. Based on our results, we give practical recommendations for the application of trend methods on long-term NDVI time series. Particularly, we apply and compare different methods on NDVI time series in Alaska, where both greening and browning trends have been previously observed. Here, the multi-method uncertainty of NDVI trends is quantified through the application of the different trend estimation methods. Our results indicate that greening NDVI trends in Alaska are more spatially and temporally prevalent than browning trends. We also show that detected breakpoints in NDVI trends tend to coincide with large fires. Overall, our analyses demonstrate that seasonal trend methods need to be improved against inter-annual variability to quantify changing trends in ecosystem productivity with higher accuracy.

  7. Low Computational Signal Acquisition for GNSS Receivers Using a Resampling Strategy and Variable Circular Correlation Time

    Science.gov (United States)

    Zhang, Yeqing; Wang, Meiling; Li, Yafeng

    2018-01-01

    For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work on conventional acquisition algorithms by resampling the main lobe of received broadband signals with a much lower frequency. Variable circular correlation time is designed to adapt to different signal strength conditions and thereby increase the operation flexibility of GNSS signal acquisition. The acquisition threshold is defined as the ratio of the highest and second highest correlation results in the search space of carrier frequency and code phase. Moreover, computational complexity of signal acquisition is formulated by amounts of multiplication and summation operations in the acquisition process. Comparative experiments and performance analysis are conducted on four sets of real GPS L2C signals with different sampling frequencies. The results indicate that the resampling strategy can effectively decrease computation and time cost by nearly 90–94% with just slight loss of acquisition sensitivity. With circular correlation time varying from 10 ms to 20 ms, the time cost of signal acquisition has increased by about 2.7–5.6% per millisecond, with most satellites acquired successfully. PMID:29495301

  8. A new variable interval schedule with constant hazard rate and finite time range.

    Science.gov (United States)

    Bugallo, Mehdi; Machado, Armando; Vasconcelos, Marco

    2018-05-27

    We propose a new variable interval (VI) schedule that achieves constant probability of reinforcement in time while using a bounded range of intervals. By sampling each trial duration from a uniform distribution ranging from 0 to 2 T seconds, and then applying a reinforcement rule that depends linearly on trial duration, the schedule alternates reinforced and unreinforced trials, each less than 2 T seconds, while preserving a constant hazard function. © 2018 Society for the Experimental Analysis of Behavior.

  9. DYNAMIC RESPONSE OF THICK PLATES ON TWO PARAMETER ELASTIC FOUNDATION UNDER TIME VARIABLE LOADING

    OpenAIRE

    Ozgan, Korhan; Daloglu, Ayse T.

    2014-01-01

    In this paper, behavior of foundation plates with transverse shear deformation under time variable loading is presented using modified Vlasov foundation model. Finite element formulation of thick plates on elastic foundation is derived by using an 8-noded finite element based on Mindlin plate theory. Selective reduced integration technique is used to avoid shear locking problem which arises when smaller plate thickness is considered for the evaluation of the stiffness matrices. After comparis...

  10. Antipersistent dynamics in short time scale variability of self-potential signals

    OpenAIRE

    Cuomo, V.; Lanfredi, M.; Lapenna, V.; Macchiato, M.; Ragosta, M.; Telesca, L.

    2000-01-01

    Time scale properties of self-potential signals are investigated through the analysis of the second order structure function (variogram), a powerful tool to investigate the spatial and temporal variability of observational data. In this work we analyse two sequences of self-potential values measured by means of a geophysical monitoring array located in a seismically active area of Southern Italy. The range of scales investigated goes from a few minutes to several days. It is shown that signal...

  11. Enhanced Requirements for Assessment in a Competency-Based, Time-Variable Medical Education System.

    Science.gov (United States)

    Gruppen, Larry D; Ten Cate, Olle; Lingard, Lorelei A; Teunissen, Pim W; Kogan, Jennifer R

    2018-03-01

    Competency-based, time-variable medical education has reshaped the perceptions and practices of teachers, curriculum designers, faculty developers, clinician educators, and program administrators. This increasingly popular approach highlights the fact that learning among different individuals varies in duration, foundation, and goal. Time variability places particular demands on the assessment data that are so necessary for making decisions about learner progress. These decisions may be formative (e.g., feedback for improvement) or summative (e.g., decisions about advancing a student). This article identifies challenges to collecting assessment data and to making assessment decisions in a time-variable system. These challenges include managing assessment data, defining and making valid assessment decisions, innovating in assessment, and modeling the considerable complexity of assessment in real-world settings and richly interconnected social systems. There are hopeful signs of creativity in assessment both from researchers and practitioners, but the transition from a traditional to a competency-based medical education system will likely continue to create much controversy and offer opportunities for originality and innovation in assessment.

  12. Discrete-time bidirectional associative memory neural networks with variable delays

    International Nuclear Information System (INIS)

    Liang Jinling; Cao Jinde; Ho, Daniel W.C.

    2005-01-01

    Based on the linear matrix inequality (LMI), some sufficient conditions are presented in this Letter for the existence, uniqueness and global exponential stability of the equilibrium point of discrete-time bidirectional associative memory (BAM) neural networks with variable delays. Some of the stability criteria obtained in this Letter are delay-dependent, and some of them are delay-independent, they are less conservative than the ones reported so far in the literature. Furthermore, the results provide one more set of easily verified criteria for determining the exponential stability of discrete-time BAM neural networks

  13. Discrete-time bidirectional associative memory neural networks with variable delays

    Science.gov (United States)

    Liang, variable delays [rapid communication] J.; Cao, J.; Ho, D. W. C.

    2005-02-01

    Based on the linear matrix inequality (LMI), some sufficient conditions are presented in this Letter for the existence, uniqueness and global exponential stability of the equilibrium point of discrete-time bidirectional associative memory (BAM) neural networks with variable delays. Some of the stability criteria obtained in this Letter are delay-dependent, and some of them are delay-independent, they are less conservative than the ones reported so far in the literature. Furthermore, the results provide one more set of easily verified criteria for determining the exponential stability of discrete-time BAM neural networks.

  14. Time-variable gravity potential components for optical clock comparisons and the definition of international time scales

    International Nuclear Information System (INIS)

    Voigt, C.; Denker, H.; Timmen, L.

    2016-01-01

    The latest generation of optical atomic clocks is approaching the level of one part in 10 18 in terms of frequency stability and uncertainty. For clock comparisons and the definition of international time scales, a relativistic redshift effect of the clock frequencies has to be taken into account at a corresponding uncertainty level of about 0.1 m 2 s -2 and 0.01 m in terms of gravity potential and height, respectively. Besides the predominant static part of the gravity potential, temporal variations must be considered in order to avoid systematic frequency shifts. Time-variable gravity potential components induced by tides and non-tidal mass redistributions are investigated with regard to the level of one part in 10 18 . The magnitudes and dominant time periods of the individual gravity potential contributions are investigated globally and for specific laboratory sites together with the related uncertainty estimates. The basics of the computation methods are presented along with the applied models, data sets and software. Solid Earth tides contribute by far the most dominant signal with a global maximum amplitude of 4.2 m 2 s -2 for the potential and a range (maximum-to-minimum) of up to 1.3 and 10.0 m 2 s -2 in terms of potential differences between specific laboratories over continental and intercontinental scales, respectively. Amplitudes of the ocean tidal loading potential can amount up to 1.25 m 2 s -2 , while the range of the potential between specific laboratories is 0.3 and 1.1 m 2 s -2 over continental and intercontinental scales, respectively. These are the only two contributors being relevant at a 10 -17 level. However, several other time-variable potential effects can particularly affect clock comparisons at the 10 -18 level. Besides solid Earth pole tides, these are non-tidal mass redistributions in the atmosphere, the oceans and the continental water storage. (authors)

  15. Molecular dynamics based enhanced sampling of collective variables with very large time steps

    Science.gov (United States)

    Chen, Pei-Yang; Tuckerman, Mark E.

    2018-01-01

    Enhanced sampling techniques that target a set of collective variables and that use molecular dynamics as the driving engine have seen widespread application in the computational molecular sciences as a means to explore the free-energy landscapes of complex systems. The use of molecular dynamics as the fundamental driver of the sampling requires the introduction of a time step whose magnitude is limited by the fastest motions in a system. While standard multiple time-stepping methods allow larger time steps to be employed for the slower and computationally more expensive forces, the maximum achievable increase in time step is limited by resonance phenomena, which inextricably couple fast and slow motions. Recently, we introduced deterministic and stochastic resonance-free multiple time step algorithms for molecular dynamics that solve this resonance problem and allow ten- to twenty-fold gains in the large time step compared to standard multiple time step algorithms [P. Minary et al., Phys. Rev. Lett. 93, 150201 (2004); B. Leimkuhler et al., Mol. Phys. 111, 3579-3594 (2013)]. These methods are based on the imposition of isokinetic constraints that couple the physical system to Nosé-Hoover chains or Nosé-Hoover Langevin schemes. In this paper, we show how to adapt these methods for collective variable-based enhanced sampling techniques, specifically adiabatic free-energy dynamics/temperature-accelerated molecular dynamics, unified free-energy dynamics, and by extension, metadynamics, thus allowing simulations employing these methods to employ similarly very large time steps. The combination of resonance-free multiple time step integrators with free-energy-based enhanced sampling significantly improves the efficiency of conformational exploration.

  16. Intraindividual variability in reaction time predicts cognitive outcomes 5 years later.

    Science.gov (United States)

    Bielak, Allison A M; Hultsch, David F; Strauss, Esther; Macdonald, Stuart W S; Hunter, Michael A

    2010-11-01

    Building on results suggesting that intraindividual variability in reaction time (inconsistency) is highly sensitive to even subtle changes in cognitive ability, this study addressed the capacity of inconsistency to predict change in cognitive status (i.e., cognitive impairment, no dementia [CIND] classification) and attrition 5 years later. Two hundred twelve community-dwelling older adults, initially aged 64-92 years, remained in the study after 5 years. Inconsistency was calculated from baseline reaction time performance. Participants were assigned to groups on the basis of their fluctuations in CIND classification over time. Logistic and Cox regressions were used. Baseline inconsistency significantly distinguished among those who remained or transitioned into CIND over the 5 years and those who were consistently intact (e.g., stable intact vs. stable CIND, Wald (1) = 7.91, p < .01, Exp(β) = 1.49). Average level of inconsistency over time was also predictive of study attrition, for example, Wald (1) = 11.31, p < .01, Exp(β) = 1.24. For both outcomes, greater inconsistency was associated with a greater likelihood of being in a maladaptive group 5 years later. Variability based on moderately cognitively challenging tasks appeared to be particularly sensitive to longitudinal changes in cognitive ability. Mean rate of responding was a comparable predictor of change in most instances, but individuals were at greater relative risk of being in a maladaptive outcome group if they were more inconsistent rather than if they were slower in responding. Implications for the potential utility of intraindividual variability in reaction time as an early marker of cognitive decline are discussed. (c) 2010 APA, all rights reserved

  17. Dissecting Time- from Tumor-Related Gene Expression Variability in Bilateral Breast Cancer

    Directory of Open Access Journals (Sweden)

    Maurizio Callari

    2018-01-01

    Full Text Available Metachronous (MBC and synchronous bilateral breast tumors (SBC are mostly distinct primaries, whereas paired primaries and their local recurrences (LRC share a common origin. Intra-pair gene expression variability in MBC, SBC, and LRC derives from time/tumor microenvironment-related and tumor genetic background-related factors and pairs represents an ideal model for trying to dissect tumor-related from microenvironment-related variability. Pairs of tumors derived from women with SBC (n = 18, MBC (n = 11, and LRC (n = 10 undergoing local-regional treatment were profiled for gene expression; similarity between pairs was measured using an intraclass correlation coefficient (ICC computed for each gene and compared using analysis of variance (ANOVA. When considering biologically unselected genes, the highest correlations were found for primaries and paired LRC, and the lowest for MBC pairs. By instead limiting the analysis to the breast cancer intrinsic genes, correlations between primaries and paired LRC were enhanced, while lower similarities were observed for SBC and MBC. Focusing on stromal-related genes, the ICC values decreased for MBC and were significantly different from SBC. These findings indicate that it is possible to dissect intra-pair gene expression variability into components that are associated with genetic origin or with time and microenvironment by using specific gene subsets.

  18. Health-related effects of early part-time sick leave due to musculoskeletal disorders: a randomized controlled trial.

    Science.gov (United States)

    Shiri, Rahman; Kausto, Johanna; Martimo, Kari-Pekka; Kaila-Kangas, Leena; Takala, Esa-Pekka; Viikari-Juntura, Eira

    2013-01-01

    Previously we reported that early part-time sick leave enhances return to work (RTW) among employees with musculoskeletal disorders (MSD). This paper assesses the health-related effects of this intervention. Patients aged 18-60 years who were unable to perform their regular work due to MSD were randomized to part- or full-time sick leave groups. In the former, workload was reduced by halving working time. Using validated questionnaires, we assessed pain intensity and interference with work and sleep, region-specific disability due to MSD, self-rated general health, health-related quality of life (measured via EuroQol), productivity loss, depression, and sleep disturbance at baseline, 1, 3, 8, 12, and 52 weeks. We analyzed the repeated measures data (171-356 observations) with the generalized estimating equation approach. The intervention (part-time sick leave) and control (full-time sick leave) groups did not differ with regard to pain intensity, pain interference with work and sleep, region-specific disability, productivity loss, depression, or sleep disturbance. The intervention group reported better self-rated general health (adjusted P=0.07) and health-related quality of life (adjusted P=0.02) than the control group. In subgroup analyses, the intervention was more effective among the patients whose current problem began occurring part-time sick leave did not exacerbate pain-related symptoms and functional disability, but improved self-rated general health and health-related quality of life in the early stage of work disability due to MSD.

  19. Time allocation shifts and pollutant exposure due to traffic congestion: an analysis using the national human activity pattern survey.

    Science.gov (United States)

    Zhang, Kai; Batterman, Stuart A

    2009-10-15

    Traffic congestion increases air pollutant exposures of commuters and urban populations due to the increased time spent in traffic and the increased vehicular emissions that occur in congestion, especially "stop-and-go" traffic. Increased time in traffic also decreases time in other microenvironments, a trade-off that has not been considered in previous time activity pattern (TAP) analyses conducted for exposure assessment purposes. This research investigates changes in time allocations and exposures that result from traffic congestion. Time shifts were derived using data from the National Human Activity Pattern Survey (NHAPS), which was aggregated to nine microenvironments (six indoor locations, two outdoor locations and one transport location). After imputing missing values, handling outliers, and conducting other quality checks, these data were stratified by respondent age, employment status and period (weekday/weekend). Trade-offs or time-shift coefficients between time spent in vehicles and the eight other microenvironments were then estimated using robust regression. For children and retirees, congestion primarily reduced the time spent at home; for older children and working adults, congestion shifted the time spent at home as well as time in schools, public buildings, and other indoor environments. Changes in benzene and PM(2.5) exposure were estimated for the current average travel delay in the U.S. (9 min day(-1)) and other scenarios using the estimated time shifts coefficients, concentrations in key microenvironments derived from the literature, and a probabilistic analysis. Changes in exposures depended on the duration of the congestion and the pollutant. For example, a 30 min day(-1) travel delay was determined to account for 21+/-12% of current exposure to benzene and 14+/-8% of PM(2.5) exposure. The time allocation shifts and the dynamic approach to TAPs improve estimates of exposure impacts from congestion and other recurring events.

  20. X-ray time and spectral variability as probes of ultraluminous x-ray sources

    Science.gov (United States)

    Pasham, Dheeraj Ranga Reddy

    A long-standing debate in the field of ultraluminous X-ray sources (ULXs: luminosities > 3x1039 ergs s-1) is whether these objects are powered by stellar-mass black holes (mass range of 3-25 solar masses) undergoing hyper-accretion/emission or if they host the long-sought after class of intermediate-mass black holes (mass range of a few 100-1000 solar masses) accreting material at sub-Eddington rates. We present X-ray time and energy spectral variability studies of ULXs in order to understand their physical environments and accurately weigh their compact objects. A sample of ULXs exhibit quasi-periodic oscillations (QPOs) with centroid frequencies in the range of 10-200 mHz. The nature of the power density spectra (PDS) of these sources is qualitatively similar to stellar-mass black holes when they exhibit the so-called type-C low-frequency QPOs (frequency range of 0.2-15 Hz). However, the crucial difference is that the characteristic frequencies within the PDS of ULXs, viz., the break frequencies and the centroid frequencies of the QPOs, are scaled down by a factor of approximately 10-100 compared to stellar-mass black holes. It has thus been argued that the ULX mHz QPOs are the type-C low-frequency QPO analogs of stellar-mass black holes and that the observed difference in the frequencies (a fewx0.01 Hz compared with a few Hz) is due to the presence of intermediate-mass black holes ( MULX = (QPOstellar-mass black hole }/QPOULX)xM stellar-mass black hole, where M and QPO are the mass and the QPO frequency, respectively) within these ULXs. We analyzed all the archival XMM-Newton X-ray data of ULXs NGC 5408 X-1 and M82 X-1 in order to test the hypothesis that the ULX mHz QPOs are the type-C analogs by searching for a correlation between the mHz QPO frequency and the energy spectral power-law index as type-C QPOs show such a dependence. From our multi-epoch timing and spectral analysis of ULXs NGC 5408 X-1 and M82 X-1, we found that the mHz QPOs of these sources vary

  1. Elevated temperature inelastic analysis of metallic media under time varying loads using state variable theories

    International Nuclear Information System (INIS)

    Kumar, V.; Mukherjee, S.

    1977-01-01

    In the present paper a general time-dependent inelastic analysis procedure for three-dimensional bodies subjected to arbitrary time varying mechanical and thermal loads using these state variable theories is presented. For the purpose of illustrations, the problems of hollow spheres, cylinders and solid circular shafts subjected to various combinations of internal and external pressures, axial force (or constraint) and torque are analyzed using the proposed solution procedure. Various cyclic thermal and mechanical loading histories with rectangular or sawtooth type waves with or without hold-time are considered. Numerical results for these geometrical shapes for various such loading histories are presented using Hart's theory (Journal of Engineering Materials and Technology 1976). The calculations are performed for nickel in the temperature range of 25 0 C to 400 0 C. For integrating forward in time, a method of solving a stiff system of ordinary differential equations is employed which corrects the step size and order of the method automatically. The limit loads for hollow spheres and cylinders are calculated using the proposed method and Hart's theory, and comparisons are made against the known theoretical results. The numerical results for other loading histories are discussed in the context of Hart's state variable type constitutive relations. The significance of phenomena such as strain rate sensitivity, Bauschinger's effect, crep recovery, history dependence and material softening with regard to these multiaxial problems are discussed in the context of Hart's theory

  2. Retention time variability as a mechanism for animal mediated long-distance dispersal.

    Directory of Open Access Journals (Sweden)

    Vishwesha Guttal

    Full Text Available Long-distance dispersal (LDD events, although rare for most plant species, can strongly influence population and community dynamics. Animals function as a key biotic vector of seeds and thus, a mechanistic and quantitative understanding of how individual animal behaviors scale to dispersal patterns at different spatial scales is a question of critical importance from both basic and applied perspectives. Using a diffusion-theory based analytical approach for a wide range of animal movement and seed transportation patterns, we show that the scale (a measure of local dispersal of the seed dispersal kernel increases with the organisms' rate of movement and mean seed retention time. We reveal that variations in seed retention time is a key determinant of various measures of LDD such as kurtosis (or shape of the kernel, thinkness of tails and the absolute number of seeds falling beyond a threshold distance. Using empirical data sets of frugivores, we illustrate the importance of variability in retention times for predicting the key disperser species that influence LDD. Our study makes testable predictions linking animal movement behaviors and gut retention times to dispersal patterns and, more generally, highlights the potential importance of animal behavioral variability for the LDD of seeds.

  3. Multiscale time irreversibility of heart rate and blood pressure variability during orthostasis

    International Nuclear Information System (INIS)

    Chladekova, L; Czippelova, B; Turianikova, Z; Tonhajzerova, I; Calkovska, A; Javorka, M; Baumert, M

    2012-01-01

    Time irreversibility is a characteristic feature of non-equilibrium, complex systems such as the cardiovascular control mediated by the autonomic nervous system (ANS). Time irreversibility analysis of heart rate variability (HRV) and blood pressure variability (BPV) represents a new approach to assess cardiovascular regulatory mechanisms. The aim of this paper was to assess the changes in HRV and BPV irreversibility during the active orthostatic test (a balance of ANS shifted towards sympathetic predominance) in 28 healthy young subjects. We used three different time irreversibility indices—Porta’s, Guzik's and Ehler's indices (P%, G% and E, respectively) derived from data segments containing 1000 beat-to-beat intervals on four timescales. We observed an increase in the HRV and a decrease in the BPV irreversibility during standing compared to the supine position. The postural change in irreversibility was confirmed by surrogate data analysis. The differences were more evident in G% and E than P% and for higher scale factors. Statistical analysis showed a close relationship between G% and E. Contrary to this, the association between P% and G% and P% and E was not proven. We conclude that time irreversibility of beat-to-beat HRV and BPV is significantly altered during orthostasis, implicating involvement of the autonomous nervous system in its generation. (paper)

  4. Bidecadal North Atlantic ocean circulation variability controlled by timing of volcanic eruptions.

    Science.gov (United States)

    Swingedouw, Didier; Ortega, Pablo; Mignot, Juliette; Guilyardi, Eric; Masson-Delmotte, Valérie; Butler, Paul G; Khodri, Myriam; Séférian, Roland

    2015-03-30

    While bidecadal climate variability has been evidenced in several North Atlantic paleoclimate records, its drivers remain poorly understood. Here we show that the subset of CMIP5 historical climate simulations that produce such bidecadal variability exhibits a robust synchronization, with a maximum in Atlantic Meridional Overturning Circulation (AMOC) 15 years after the 1963 Agung eruption. The mechanisms at play involve salinity advection from the Arctic and explain the timing of Great Salinity Anomalies observed in the 1970s and the 1990s. Simulations, as well as Greenland and Iceland paleoclimate records, indicate that coherent bidecadal cycles were excited following five Agung-like volcanic eruptions of the last millennium. Climate simulations and a conceptual model reveal that destructive interference caused by the Pinatubo 1991 eruption may have damped the observed decreasing trend of the AMOC in the 2000s. Our results imply a long-lasting climatic impact and predictability following the next Agung-like eruption.

  5. Variability of Cost and Time Delivery of Educational Buildings in Nigeria

    Directory of Open Access Journals (Sweden)

    Aghimien, Douglas Omoregie

    2017-09-01

    Full Text Available Cost and time overrun in construction projects has become a reoccurring problem in construction industries around the world especially in developing countries. This situation is unhealthy for public educational buildings which are executed with limited government funds, and are in most cases time sensitive, as they need to cater for the influx of students into the institutions. This study therefore assessed the variability of cost and time delivery of educational buildings in Nigeria, using a study of selected educational buildings within the country. A pro forma was used to gather cost and time data on selected building projects, while structured questionnaire was used to harness information on the possible measures for reducing the variability from the construction participants that were involved in the delivery of these projects. Paired sample t-test, percentage, relative importance index, and Kruskal-Walis test were adopted for data analyses. The study reveals that there is a significant difference between the initial and final cost of delivering educational buildings, as an average of 4.87% deviation, with a sig. p-value of 0.000 was experienced on all assessed projects. For time delivery, there is also a significant difference between the initial estimated time and final time of construction as a whopping 130% averaged deviation with a sig. p-value of 0.000 was discovered. To remedy these problems, the study revealed that prompt payment for executed works, predicting market price fluctuation and inculcating it into the initial estimate, and owner’s involvement at the planning and design phase are some of the possible measures to be adopted.

  6. Separating different scales of motion in time series of meteorological variables

    International Nuclear Information System (INIS)

    Eskridge, R.E.; Rao, S.T.; Porter, P.S.

    1997-01-01

    In this study, four methods are evaluated for detecting and tracking changes in time series of climate variables. The PEST algorithm and the monthly anomaly technique are shown to have shortcomings, while the wavelet transform and Kolmogorov-Zurbenko (KZ) filter methods are shown to be capable of separating time scales with minimal errors. The behavior of the filters are examined by transfer functions. The KZ filter, anomaly technique, and PEST were also applied to temperature data to estimate long-term trends. The KZ filter provides estimates with about 10 times higher confidence than the other methods. Advantages of the KZ filter over the wavelet transform method are that it may be applied to datasets containing missing observations and is very easy to use. 10 refs., 8 figs., 1 tab

  7. Use of a prototype pulse oximeter for time series analysis of heart rate variability

    Science.gov (United States)

    González, Erika; López, Jehú; Hautefeuille, Mathieu; Velázquez, Víctor; Del Moral, Jésica

    2015-05-01

    This work presents the development of a low cost pulse oximeter prototype consisting of pulsed red and infrared commercial LEDs and a broad spectral photodetector used to register time series of heart rate and oxygen saturation of blood. This platform, besides providing these values, like any other pulse oximeter, processes the signals to compute a power spectrum analysis of the patient heart rate variability in real time and, additionally, the device allows access to all raw and analyzed data if databases construction is required or another kind of further analysis is desired. Since the prototype is capable of acquiring data for long periods of time, it is suitable for collecting data in real life activities, enabling the development of future wearable applications.

  8. Antipersistent dynamics in short time scale variability of self-potential signals

    Directory of Open Access Journals (Sweden)

    M. Ragosta

    2000-06-01

    Full Text Available Time scale properties of self-potential signals are investigated through the analysis of the second order structure function (variogram, a powerful tool to investigate the spatial and temporal variability of observational data. In this work we analyse two sequences of self-potential values measured by means of a geophysical monitoring array located in a seismically active area of Southern Italy. The range of scales investigated goes from a few minutes to several days. It is shown that signal fluctuations are characterised by two time scale ranges in which self-potential variability appears to follow slightly different dynamical behaviours. Results point to the presence of fractal, non stationary features expressing a long term correlation with scaling coefficients which are the clue of stabilising mechanisms. In the scale ranges in which the series show scale invariant behaviour, self-potentials evolve like fractional Brownian motions with anticorrelated increments typical of processes regulated by negative feedback mechanisms (antipersistence. On scales below about 6 h the strength of such an antipersistence appears to be slightly greater than that observed on larger time scales where the fluctuations are less efficiently stabilised.

  9. Walking speed-related changes in stride time variability: effects of decreased speed

    Directory of Open Access Journals (Sweden)

    Dubost Veronique

    2009-08-01

    Full Text Available Abstract Background Conflicting results have been reported regarding the relationship between stride time variability (STV and walking speed. While some studies failed to establish any relationship, others reported either a linear or a non-linear relationship. We therefore sought to determine the extent to which decrease in self-selected walking speed influenced STV among healthy young adults. Methods The mean value, the standard deviation and the coefficient of variation of stride time, as well as the mean value of stride velocity were recorded while steady-state walking using the GAITRite® system in 29 healthy young adults who walked consecutively at 88%, 79%, 71%, 64%, 58%, 53%, 46% and 39% of their preferred walking speed. Results The decrease in stride velocity increased significantly mean values, SD and CoV of stride time (p Conclusion The results support the assumption that gait variability increases while walking speed decreases and, thus, gait might be more unstable when healthy subjects walk slower compared with their preferred walking speed. Furthermore, these results highlight that a decrease in walking speed can be a potential confounder while evaluating STV.

  10. Investigation of a rotary valving system with variable valve timing for internal combustion engines

    Science.gov (United States)

    Cross, Paul C.; Hansen, Craig N.

    1994-11-01

    The objective of the program was to provide a functional demonstration of the Hansen Rotary Valving System with Variable Valve Timing (HRVS/VVT), capable of throttleless inlet charge control, as an alternative to conventional poppet-valves for use in spark ignited internal combustion engines. The goal of this new technology is to secure benefits in fuel economy, broadened torque band, vibration reduction, and overhaul accessibility. Additionally, use of the variable valve timing capability to vary the effective compression ratio is expected to improve multifuel tolerance and efficiency. Efforts directed at the design of HRVS components proved to be far more extensive than had been anticipated, ultimately requiring that proof-trial design/development work be performed. Although both time and funds were exhausted before optical or ion-probe types of in-cylinder investigation could be undertaken, a great deal of laboratory data was acquired during the course of the design/development work. This laboratory data is the basis for the information presented in this final report.

  11. A Real-Time Analysis Method for Pulse Rate Variability Based on Improved Basic Scale Entropy

    Directory of Open Access Journals (Sweden)

    Yongxin Chou

    2017-01-01

    Full Text Available Base scale entropy analysis (BSEA is a nonlinear method to analyze heart rate variability (HRV signal. However, the time consumption of BSEA is too long, and it is unknown whether the BSEA is suitable for analyzing pulse rate variability (PRV signal. Therefore, we proposed a method named sliding window iterative base scale entropy analysis (SWIBSEA by combining BSEA and sliding window iterative theory. The blood pressure signals of healthy young and old subjects are chosen from the authoritative international database MIT/PhysioNet/Fantasia to generate PRV signals as the experimental data. Then, the BSEA and the SWIBSEA are used to analyze the experimental data; the results show that the SWIBSEA reduces the time consumption and the buffer cache space while it gets the same entropy as BSEA. Meanwhile, the changes of base scale entropy (BSE for healthy young and old subjects are the same as that of HRV signal. Therefore, the SWIBSEA can be used for deriving some information from long-term and short-term PRV signals in real time, which has the potential for dynamic PRV signal analysis in some portable and wearable medical devices.

  12. Sodium bicarbonate ingestion and individual variability in time-to-peak pH.

    Science.gov (United States)

    Sparks, Andy; Williams, Emily; Robinson, Amy; Miller, Peter; Bentley, David J; Bridge, Craig; Mc Naughton, Lars R

    2017-01-01

    This study determined variability in time-to-peak pH after consumption of 300 mg kg - 1 of sodium bicarbonate. Seventeen participants (mean ± SD: age 21.38 ± 1.5 years; mass 75.8 ± 5.8 kg; height 176.8 ± 7.6 cm) reported to the laboratory where a resting capillary sample was taken. Then, 300 mg kg -1 of NaHCO 3 in 450 ml of flavoured water was ingested. Participants rested for 90 min and repeated blood samples were procured at 10 min intervals for 60 min and then every 5 min until 90 min. Blood pH concentrations were measured. Results suggested that time-to-peak pH (64.41 ± 18.78 min) was variable with a range of 10-85 min and a coefficient of variation of 29.16%. A bimodal distribution occurred, at 65 and 75 min. In conclusion, athletes, when using NaHCO 3 as an ergogenic aid, should determine their time-to-peak pH to best utilize the added buffering capacity this substance allows.

  13. Variable dead time counters. 1 - theoretical responses and the effects of neutron multiplication

    International Nuclear Information System (INIS)

    Lees, E.W.; Hooton, B.W.

    1978-10-01

    A theoretical expression is derived for calculating the response of any variable dead time counter (VDC) used in the passive assay of plutonium by neutron counting of the natural spontaneous fission activity. The effects of neutron multiplication in the sample arising from interactions of the original spontaneous fission neutrons is shown to modify the linear relationship between VDC signal and Pu mass. Numerical examples are shown for the Euratom VDC and a systematic investigation of the various factors affecting neutron multiplication is reported. Limited comparisons between the calculations and experimental data indicate provisional validity of the calculations. (author)

  14. Smart Device for the Determination of Heart Rate Variability in Real Time

    Directory of Open Access Journals (Sweden)

    David Naranjo-Hernández

    2017-01-01

    Full Text Available This work presents a first approach to the design, development, and implementation of a smart device for the real-time measurement and detection of alterations in heart rate variability (HRV. The smart device follows a modular design scheme, which consists of an electrocardiogram (ECG signal acquisition module, a processing module and a wireless communications module. From five-minute ECG signals, the processing module algorithms perform a spectral estimation of the HRV. The experimental results demonstrate the viability of the smart device and the proposed processing algorithms.

  15. Global exponential stability for discrete-time neural networks with variable delays

    International Nuclear Information System (INIS)

    Chen Wuhua; Lu Xiaomei; Liang Dongying

    2006-01-01

    This Letter provides new exponential stability criteria for discrete-time neural networks with variable delays. The main technique is to reduce exponential convergence estimation of the neural network solution to that of one component of the corresponding solution by constructing Lyapunov function based on M-matrix. By introducing the tuning parameter diagonal matrix, the delay-independent and delay-dependent exponential stability conditions have been unified in the same mathematical formula. The effectiveness of the new results are illustrated by three examples

  16. Boundedness and stability for recurrent neural networks with variable coefficients and time-varying delays

    International Nuclear Information System (INIS)

    Liang Jinling; Cao Jinde

    2003-01-01

    In this Letter, the problems of boundedness and stability for a general class of non-autonomous recurrent neural networks with variable coefficients and time-varying delays are analyzed via employing Young inequality technique and Lyapunov method. Some simple sufficient conditions are given for boundedness and stability of the solutions for the recurrent neural networks. These results generalize and improve the previous works, and they are easy to check and apply in practice. Two illustrative examples and their numerical simulations are also given to demonstrate the effectiveness of the proposed results

  17. Resolución del Response Time Variability Problem mediante tabu search

    OpenAIRE

    Corominas Subias, Albert; García Villoria, Alberto; Pastor Moreno, Rafael

    2009-01-01

    El Response Time Variability Problem (RTVP) es un problema combinatorio de scheduling publicado recientemente en la literatura. Dicho problema de optimización combinatoria es muy fácil de formular pero muy difícil de resolver de forma exacta (es NP-hard). El RTVP se presenta cuando productos, clientes o tareas se han de secuenciar minimizando la variabilidad entre los instantes de tiempo en los que reciben los recursos que ellos necesitan. Este problema tiene una gran cantidad de aplicaciones...

  18. Evaluation of angiographic delayed vasospasm due to ruptured aneurysm in comparison with cerebral circulation time measured by IA-DSA

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Yoshikazu; Shima, Takeshi; Nishida, Masahiro; Yamane, Kanji; Okita, Shinji; Hatayama, Takashi; Yoshida, Akira; Naoe, Yasutaka; Shiga, Naoko (Chugoku Rosai Hospital, Hiroshima (Japan))

    1994-05-01

    Delayed vasospasm due to ruptured aneurysm has been basically evaluated by angiographic changes in contrast to clinical features such as delayed ischemic neurological deficits (DIND). However, the discrepancies between angiographic and clinical findings have been pointed out. In this study, angiographic changes and cerebral circulation time in ruptured aneurysms were simultaneously investigated with IA-DSA. Thirty-two patients, who had ruptured aneurysms at the anterior circle of Willis and neck clippings at the acute stage, were investigated. Carotid angiogram was performed with IA-DSA on the 7-13th day after the attack. Angiographic changes were evaluated by Fischer's classification and circulation time was calculated in the following way. A time-density curve was obtained at the two ROI's: the C3-C4 portion and the rolandic vein. Circulation time was defined by the difference between the time showing peak optical density at the carotid and the venous portion. The control value of this circulation time obtained from 20 cases with non-rupture aneurysm and epilepsy was 3.4 sec (53 year old) on the average. X-ray CT scan examination was performed at the same time and clinical features were observed every day. Angiographically, 3 cases were free from vasospasm, 18 cases were found to present slight to moderate vasospasm, and 11 cases showed severe vasospasm. Circulation time in patients with no spasm was 3.6 seconds, in patients with slight to moderate vasospasm it was 4.3 seconds and in patients with severe vasospasm it was 6.8 seconds. Ten patients showing cerebral infarction on CT scans demonstrated significantly long circulation time, 7.0 seconds on the average. And all patients having severe vasospasm with circulation time more than 6 seconds presented DIND such as hemiparesis. (author).

  19. Sensitivity of adaptive enrichment trial designs to accrual rates, time to outcome measurement, and prognostic variables

    Directory of Open Access Journals (Sweden)

    Tianchen Qian

    2017-12-01

    Full Text Available Adaptive enrichment designs involve rules for restricting enrollment to a subset of the population during the course of an ongoing trial. This can be used to target those who benefit from the experimental treatment. Trial characteristics such as the accrual rate and the prognostic value of baseline variables are typically unknown when a trial is being planned; these values are typically assumed based on information available before the trial starts. Because of the added complexity in adaptive enrichment designs compared to standard designs, it may be of special concern how sensitive the trial performance is to deviations from assumptions. Through simulation studies, we evaluate the sensitivity of Type I error, power, expected sample size, and trial duration to different design characteristics. Our simulation distributions mimic features of data from the Alzheimer's Disease Neuroimaging Initiative cohort study, and involve two subpopulations based on a genetic marker. We investigate the impact of the following design characteristics: the accrual rate, the time from enrollment to measurement of a short-term outcome and the primary outcome, and the prognostic value of baseline variables and short-term outcomes. To leverage prognostic information in baseline variables and short-term outcomes, we use a semiparametric, locally efficient estimator, and investigate its strengths and limitations compared to standard estimators. We apply information-based monitoring, and evaluate how accurately information can be estimated in an ongoing trial.

  20. MODELING THE TIME VARIABILITY OF SDSS STRIPE 82 QUASARS AS A DAMPED RANDOM WALK

    International Nuclear Information System (INIS)

    MacLeod, C. L.; Ivezic, Z.; Bullock, E.; Kimball, A.; Sesar, B.; Westman, D.; Brooks, K.; Gibson, R.; Becker, A. C.; Kochanek, C. S.; Kozlowski, S.; Kelly, B.; De Vries, W. H.

    2010-01-01

    We model the time variability of ∼9000 spectroscopically confirmed quasars in SDSS Stripe 82 as a damped random walk (DRW). Using 2.7 million photometric measurements collected over 10 yr, we confirm the results of Kelly et al. and Kozlowski et al. that this model can explain quasar light curves at an impressive fidelity level (0.01-0.02 mag). The DRW model provides a simple, fast (O(N) for N data points), and powerful statistical description of quasar light curves by a characteristic timescale (τ) and an asymptotic rms variability on long timescales (SF ∞ ). We searched for correlations between these two variability parameters and physical parameters such as luminosity and black hole mass, and rest-frame wavelength. Our analysis shows SF ∞ to increase with decreasing luminosity and rest-frame wavelength as observed previously, and without a correlation with redshift. We find a correlation between SF ∞ and black hole mass with a power-law index of 0.18 ± 0.03, independent of the anti-correlation with luminosity. We find that τ increases with increasing wavelength with a power-law index of 0.17, remains nearly constant with redshift and luminosity, and increases with increasing black hole mass with a power-law index of 0.21 ± 0.07. The amplitude of variability is anti-correlated with the Eddington ratio, which suggests a scenario where optical fluctuations are tied to variations in the accretion rate. However, we find an additional dependence on luminosity and/or black hole mass that cannot be explained by the trend with Eddington ratio. The radio-loudest quasars have systematically larger variability amplitudes by about 30%, when corrected for the other observed trends, while the distribution of their characteristic timescale is indistinguishable from that of the full sample. We do not detect any statistically robust differences in the characteristic timescale and variability amplitude between the full sample and the small subsample of quasars detected

  1. Radiative forcing over the conterminous United States due to contemporary land cover land use change and sensitivity to snow and interannual albedo variability

    Science.gov (United States)

    Barnes, Christopher A.; Roy, David P.

    2010-01-01

    Satellite-derived land cover land use (LCLU), snow and albedo data, and incoming surface solar radiation reanalysis data were used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing for 58 ecoregions covering 69% of the conterminous United States. A net positive surface radiative forcing (i.e., warming) of 0.029 Wm−2 due to LCLU albedo change from 1973 to 2000 was estimated. The forcings for individual ecoregions were similar in magnitude to current global forcing estimates, with the most negative forcing (as low as −0.367 Wm−2) due to the transition to forest and the most positive forcing (up to 0.337 Wm−2) due to the conversion to grass/shrub. Snow exacerbated both negative and positive forcing for LCLU transitions between snow-hiding and snow-revealing LCLU classes. The surface radiative forcing estimates were highly sensitive to snow-free interannual albedo variability that had a percent average monthly variation from 1.6% to 4.3% across the ecoregions. The results described in this paper enhance our understanding of contemporary LCLU change on surface radiative forcing and suggest that future forcing estimates should model snow and interannual albedo variation.

  2. Complexity and time asymmetry of heart rate variability are altered in acute mental stress.

    Science.gov (United States)

    Visnovcova, Z; Mestanik, M; Javorka, M; Mokra, D; Gala, M; Jurko, A; Calkovska, A; Tonhajzerova, I

    2014-07-01

    We aimed to study the complexity and time asymmetry of short-term heart rate variability (HRV) as an index of complex neurocardiac control in response to stress using symbolic dynamics and time irreversibility methods. ECG was recorded at rest and during and after two stressors (Stroop, arithmetic test) in 70 healthy students. Symbolic dynamics parameters (NUPI, NCI, 0V%, 1V%, 2LV%, 2UV%), and time irreversibility indices (P%, G%, E) were evaluated. Additionally, HRV magnitude was quantified by linear parameters: spectral powers in low (LF) and high frequency (HF) bands. Our results showed a reduction of HRV complexity in stress (lower NUPI with both stressors, lower NCI with Stroop). Pattern classification analysis revealed significantly higher 0V% and lower 2LV% with both stressors, indicating a shift in sympathovagal balance, and significantly higher 1V% and lower 2UV% with Stroop. An unexpected result was found in time irreversibility: significantly lower G% and E with both stressors, P% index significantly declined only with arithmetic test. Linear HRV analysis confirmed vagal withdrawal (lower HF) with both stressors; LF significantly increased with Stroop and decreased with arithmetic test. Correlation analysis revealed no significant associations between symbolic dynamics and time irreversibility. Concluding, symbolic dynamics and time irreversibility could provide independent information related to alterations of neurocardiac control integrity in stress-related disease.

  3. Complexity and time asymmetry of heart rate variability are altered in acute mental stress

    International Nuclear Information System (INIS)

    Visnovcova, Z; Mestanik, M; Javorka, M; Mokra, D; Calkovska, A; Tonhajzerova, I; Gala, M; Jurko, A

    2014-01-01

    We aimed to study the complexity and time asymmetry of short-term heart rate variability (HRV) as an index of complex neurocardiac control in response to stress using symbolic dynamics and time irreversibility methods. ECG was recorded at rest and during and after two stressors (Stroop, arithmetic test) in 70 healthy students. Symbolic dynamics parameters (NUPI, NCI, 0V%, 1V%, 2LV%, 2UV%), and time irreversibility indices (P%, G%, E) were evaluated. Additionally, HRV magnitude was quantified by linear parameters: spectral powers in low (LF) and high frequency (HF) bands. Our results showed a reduction of HRV complexity in stress (lower NUPI with both stressors, lower NCI with Stroop). Pattern classification analysis revealed significantly higher 0V% and lower 2LV% with both stressors, indicating a shift in sympathovagal balance, and significantly higher 1V% and lower 2UV% with Stroop. An unexpected result was found in time irreversibility: significantly lower G% and E with both stressors, P% index significantly declined only with arithmetic test. Linear HRV analysis confirmed vagal withdrawal (lower HF) with both stressors; LF significantly increased with Stroop and decreased with arithmetic test. Correlation analysis revealed no significant associations between symbolic dynamics and time irreversibility. Concluding, symbolic dynamics and time irreversibility could provide independent information related to alterations of neurocardiac control integrity in stress-related disease. (paper)

  4. A model for estimating pathogen variability in shellfish and predicting minimum depuration times.

    Science.gov (United States)

    McMenemy, Paul; Kleczkowski, Adam; Lees, David N; Lowther, James; Taylor, Nick

    2018-01-01

    Norovirus is a major cause of viral gastroenteritis, with shellfish consumption being identified as one potential norovirus entry point into the human population. Minimising shellfish norovirus levels is therefore important for both the consumer's protection and the shellfish industry's reputation. One method used to reduce microbiological risks in shellfish is depuration; however, this process also presents additional costs to industry. Providing a mechanism to estimate norovirus levels during depuration would therefore be useful to stakeholders. This paper presents a mathematical model of the depuration process and its impact on norovirus levels found in shellfish. Two fundamental stages of norovirus depuration are considered: (i) the initial distribution of norovirus loads within a shellfish population and (ii) the way in which the initial norovirus loads evolve during depuration. Realistic assumptions are made about the dynamics of norovirus during depuration, and mathematical descriptions of both stages are derived and combined into a single model. Parameters to describe the depuration effect and norovirus load values are derived from existing norovirus data obtained from U.K. harvest sites. However, obtaining population estimates of norovirus variability is time-consuming and expensive; this model addresses the issue by assuming a 'worst case scenario' for variability of pathogens, which is independent of mean pathogen levels. The model is then used to predict minimum depuration times required to achieve norovirus levels which fall within possible risk management levels, as well as predictions of minimum depuration times for other water-borne pathogens found in shellfish. Times for Escherichia coli predicted by the model all fall within the minimum 42 hours required for class B harvest sites, whereas minimum depuration times for norovirus and FRNA+ bacteriophage are substantially longer. Thus this study provides relevant information and tools to assist

  5. Analysis of agility, reaction time and balance variables at badminton players aged 9-14 years

    Directory of Open Access Journals (Sweden)

    Seydi Ahmet Ağaoğlu

    2017-12-01

    Full Text Available Aim: The aim of this study was investigated agility, static and dynamic balance and reaction time variables of badminton players aged between 9-14 and relate with among variables. Material and Methods: In Samsun, 19 males (sport age, 3.42±1.64 years and 12 females (3.00±1.28 years active badminton players were voluntarily participated in who are in 9-14 ages range. Agility was measured by “T” test, CSMI-Tecnobody Pk-252 isokinetic balance system measuring instrument was used to test static balance and dynamic balance and Mozart Lafayette reaction measuring instrument was used to test visual and auditory reaction times of players. Spearman correlation analysis was applied so as to correlation analysis. The level of significance was taken as p<0.05. Results: For female athletes, a positive relation was determined between the agility and the perimeter (mm used (r=0.727; p<0.01 through the static balance measure double foot and eyes are open. For male athletes, a positive relation was determined between the visual reaction time and the perimeter (mm used (r=0.725; p<0.01 through the static balance measure dominant foot and eyes are open. For male and female athletes were not found any correlation between reaction time and dynamic balance. Conclusion: It was determined that audio (ears and visual (eyes reaction time was effective on balance. While badminton players are closed eyes, audio sensors are more influence on balance test through measure dominant foot.

  6. Practical performance of real-time shot-noise measurement in continuous-variable quantum key distribution

    Science.gov (United States)

    Wang, Tao; Huang, Peng; Zhou, Yingming; Liu, Weiqi; Zeng, Guihua

    2018-01-01

    In a practical continuous-variable quantum key distribution (CVQKD) system, real-time shot-noise measurement (RTSNM) is an essential procedure for preventing the eavesdropper exploiting the practical security loopholes. However, the performance of this procedure itself is not analyzed under the real-world condition. Therefore, we indicate the RTSNM practical performance and investigate its effects on the CVQKD system. In particular, due to the finite-size effect, the shot-noise measurement at the receiver's side may decrease the precision of parameter estimation and consequently result in a tight security bound. To mitigate that, we optimize the block size for RTSNM under the ensemble size limitation to maximize the secure key rate. Moreover, the effect of finite dynamics of amplitude modulator in this scheme is studied and its mitigation method is also proposed. Our work indicates the practical performance of RTSNM and provides the real secret key rate under it.

  7. Return to work after early part-time sick leave due to musculoskeletal disorders: a randomized controlled trial.

    Science.gov (United States)

    Viikari-Juntura, Eira; Kausto, Johanna; Shiri, Rahman; Kaila-Kangas, Leena; Takala, Esa-Pekka; Karppinen, Jaro; Miranda, Helena; Luukkonen, Ritva; Martimo, Kari-Pekka

    2012-03-01

    The purpose of this study was to assess the effects of early part-time sick leave on return to work (RTW) and sickness absence among patients with musculoskeletal disorders. A randomized controlled trial was conducted in six occupational health units of medium- and large-size enterprises. Patients aged 18-60 years with musculoskeletal disorders (N=63) unable to perform their regular work were randomly allocated to part- or full-time sick leave. In the former group, workload was reduced by restricting work time by about a half. Remaining work tasks were modified when necessary, as specified in a "fit note" from the physician. The main outcomes were time to return to regular work activities and sickness absence during 12-month follow-up. Time to RTW sustained for ≥4 weeks was shorter in the intervention group (median 12 versus 20 days, P=0.10). Hazard ratio of RTW adjusted for age was 1.60 [95% confidence interval (95% CI) 0.98-2.63] and 1.76 (95% CI 1.21-2.56) after further adjustment for pain interference with sleep and previous sickness absence at baseline. Total sickness absence during the 12-month follow-up was about 20% lower in the intervention than the control group. Compliance with the intervention was high with no discontinuations of part-time sick leave due to musculoskeletal reasons. Early part-time sick leave may provide a faster and more sustainable return to regular duties than full-time sick leave among patients with musculoskeletal disorders. This is the first study to show that work participation can be safely increased with early part-time sick leave.

  8. Effects of time-variable exposure regimes of the insecticide chlorpyrifos on freshwater invertebrate communities in microcosms

    NARCIS (Netherlands)

    Zafar, M.I.; Wijngaarden, van R.; Roessink, I.; Brink, van den P.J.

    2011-01-01

    The present study compared the effects of different time-variable exposure regimes having the same time-weighted average (TWA) concentration of the organophosphate insecticide chlorpyrifos on freshwater invertebrate communities to enable extrapolation of effects across exposure regimes. The

  9. Lung lesion doubling times: values and variability based on method of volume determination

    International Nuclear Information System (INIS)

    Eisenbud Quint, Leslie; Cheng, Joan; Schipper, Matthew; Chang, Andrew C.; Kalemkerian, Gregory

    2008-01-01

    Purpose: To determine doubling times (DTs) of lung lesions based on volumetric measurements from thin-section CT imaging. Methods: Previously untreated patients with ≥ two thin-section CT scans showing a focal lung lesion were identified. Lesion volumes were derived using direct volume measurements and volume calculations based on lesion area and diameter. Growth rates (GRs) were compared by tissue diagnosis and measurement technique. Results: 54 lesions were evaluated including 8 benign lesions, 10 metastases, 3 lymphomas, 15 adenocarcinomas, 11 squamous carcinomas, and 7 miscellaneous lung cancers. Using direct volume measurements, median DTs were 453, 111, 15, 181, 139 and 137 days, respectively. Lung cancer DTs ranged from 23-2239 days. There were no significant differences in GRs among the different lesion types. There was considerable variability among GRs using different volume determination methods. Conclusions: Lung cancer doubling times showed a substantial range, and different volume determination methods gave considerably different DTs

  10. Modelling a variable valve timing spark ignition engine using different neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Beham, M. [BMW AG, Munich (Germany); Yu, D.L. [John Moores University, Liverpool (United Kingdom). Control Systems Research Group

    2004-10-01

    In this paper different neural networks (NN) are compared for modelling a variable valve timing spark-ignition (VVT SI) engine. The overall system is divided for each output into five neural multi-input single output (MISO) subsystems. Three kinds of NN, multilayer Perceptron (MLP), pseudo-linear radial basis function (PLRBF), and local linear model tree (LOLIMOT) networks, are used to model each subsystem. Real data were collected when the engine was under different operating conditions and these data are used in training and validation of the developed neural models. The obtained models are finally tested in a real-time online model configuration on the test bench. The neural models run independently of the engine in parallel mode. The model outputs are compared with process output and compared among different models. These models performed well and can be used in the model-based engine control and optimization, and for hardware in the loop systems. (author)

  11. Industrial implementation of spatial variability control by real-time SPC

    Science.gov (United States)

    Roule, O.; Pasqualini, F.; Borde, M.

    2016-10-01

    Advanced technology nodes require more and more information to get the wafer process well setup. The critical dimension of components decreases following Moore's law. At the same time, the intra-wafer dispersion linked to the spatial non-uniformity of tool's processes is not capable to decrease in the same proportions. APC systems (Advanced Process Control) are being developed in waferfab to automatically adjust and tune wafer processing, based on a lot of process context information. It can generate and monitor complex intrawafer process profile corrections between different process steps. It leads us to put under control the spatial variability, in real time by our SPC system (Statistical Process Control). This paper will outline the architecture of an integrated process control system for shape monitoring in 3D, implemented in waferfab.

  12. Real-time Continuous Assessment Method for Mental and Physiological Condition using Heart Rate Variability

    Science.gov (United States)

    Yoshida, Yutaka; Yokoyama, Kiyoko; Ishii, Naohiro

    It is necessary to monitor the daily health condition for preventing stress syndrome. In this study, it was proposed the method assessing the mental and physiological condition, such as the work stress or the relaxation, using heart rate variability at real time and continuously. The instantanuous heart rate (HR), and the ratio of the number of extreme points (NEP) and the number of heart beats were calculated for assessing mental and physiological condition. In this method, 20 beats heart rate were used to calculate these indexes. These were calculated in one beat interval. Three conditions, which are sitting rest, performing mental arithmetic and watching relaxation movie, were assessed using our proposed algorithm. The assessment accuracies were 71.9% and 55.8%, when performing mental arithmetic and watching relaxation movie respectively. In this method, the mental and physiological condition was assessed using only 20 regressive heart beats, so this method is considered as the real time assessment method.

  13. The effect of time trial cycling position on physiological and aerodynamic variables.

    Science.gov (United States)

    Fintelman, D M; Sterling, M; Hemida, H; Li, F-X

    2015-01-01

    To reduce aerodynamic resistance cyclists lower their torso angle, concurrently reducing Peak Power Output (PPO). However, realistic torso angle changes in the range used by time trial cyclists have not yet been examined. Therefore the aim of this study was to investigate the effect of torso angle on physiological parameters and frontal area in different commonly used time trial positions. Nineteen well-trained male cyclists performed incremental tests on a cycle ergometer at five different torso angles: their preferred torso angle and at 0, 8, 16 and 24°. Oxygen uptake, carbon dioxide expiration, minute ventilation, gross efficiency, PPO, heart rate, cadence and frontal area were recorded. The frontal area provides an estimate of the aerodynamic drag. Overall, results showed that lower torso angles attenuated performance. Maximal values of all variables, attained in the incremental test, decreased with lower torso angles (P aerodynamic drag and physiological functioning.

  14. Life time fatality risk assessment due to variation of indoor radon concentration in dwellings in western Haryana, India

    International Nuclear Information System (INIS)

    Kansal, Sandeep; Mehra, Rohit; Singh, N.P.

    2012-01-01

    Indoor radon measurements in 60 dwellings belonging to 12 villages of Sirsa, Fatehbad and Hisar districts of western Haryana, India, have been carried out, using LR-115 type II cellulose nitrate films in the bare mode. The annual average indoor radon value in the studied area varies from 76.00 to 115.46 Bq m −3 , which is well within the recommended action level 200–300 Bq m −3 (). The winter/summer ratio of indoor radon ranges from 0.78 to 2.99 with an average of 1.52. The values of annual average dose received by the residents and Life time fatality risk assessment due to variation of indoor radon concentration in dwellings of studied area suggests that there is no significance threat to the human beings due to the presence of natural radon in the dwellings. - Highlights: ► The radon concentration values in the dwellings are 2–3 times more than the world average of 40 Bq m −3 . ► These values are lower than the recommended action level of 200–300 Bq m −3 (). ► The annual effective dose is less than the recommended action level of 3–10 mSv per year (). ► The values of life time fatality risk determined for the studied area are within safe standards. ► There is no significant threat to the human beings due to the presence of natural radon in the dwellings.

  15. Excitation of Earth Rotation Variations "Observed" by Time-Variable Gravity

    Science.gov (United States)

    Chao, Ben F.; Cox, C. M.

    2005-01-01

    Time variable gravity measurements have been made over the past two decades using the space geodetic technique of satellite laser ranging, and more recently by the GRACE satellite mission with improved spatial resolutions. The degree-2 harmonic components of the time-variable gravity contain important information about the Earth s length-of-day and polar motion excitation functions, in a way independent to the traditional "direct" Earth rotation measurements made by, for example, the very-long-baseline interferometry and GPS. In particular, the (degree=2, order= 1) components give the mass term of the polar motion excitation; the (2,O) component, under certain mass conservation conditions, gives the mass term of the length-of-day excitation. Combining these with yet another independent source of angular momentum estimation calculated from global geophysical fluid models (for example the atmospheric angular momentum, in both mass and motion terms), in principle can lead to new insights into the dynamics, particularly the role or the lack thereof of the cores, in the excitation processes of the Earth rotation variations.

  16. Dissociating neural variability related to stimulus quality and response times in perceptual decision-making.

    Science.gov (United States)

    Bode, Stefan; Bennett, Daniel; Sewell, David K; Paton, Bryan; Egan, Gary F; Smith, Philip L; Murawski, Carsten

    2018-03-01

    According to sequential sampling models, perceptual decision-making is based on accumulation of noisy evidence towards a decision threshold. The speed with which a decision is reached is determined by both the quality of incoming sensory information and random trial-by-trial variability in the encoded stimulus representations. To investigate those decision dynamics at the neural level, participants made perceptual decisions while functional magnetic resonance imaging (fMRI) was conducted. On each trial, participants judged whether an image presented under conditions of high, medium, or low visual noise showed a piano or a chair. Higher stimulus quality (lower visual noise) was associated with increased activation in bilateral medial occipito-temporal cortex and ventral striatum. Lower stimulus quality was related to stronger activation in posterior parietal cortex (PPC) and dorsolateral prefrontal cortex (DLPFC). When stimulus quality was fixed, faster response times were associated with a positive parametric modulation of activation in medial prefrontal and orbitofrontal cortex, while slower response times were again related to more activation in PPC, DLPFC and insula. Our results suggest that distinct neural networks were sensitive to the quality of stimulus information, and to trial-to-trial variability in the encoded stimulus representations, but that reaching a decision was a consequence of their joint activity. Copyright © 2018 Elsevier Ltd. All rights reserved.

  17. Quantitative estimation of time-variable earthquake hazard by using fuzzy set theory

    Science.gov (United States)

    Deyi, Feng; Ichikawa, M.

    1989-11-01

    In this paper, the various methods of fuzzy set theory, called fuzzy mathematics, have been applied to the quantitative estimation of the time-variable earthquake hazard. The results obtained consist of the following. (1) Quantitative estimation of the earthquake hazard on the basis of seismicity data. By using some methods of fuzzy mathematics, seismicity patterns before large earthquakes can be studied more clearly and more quantitatively, highly active periods in a given region and quiet periods of seismic activity before large earthquakes can be recognized, similarities in temporal variation of seismic activity and seismic gaps can be examined and, on the other hand, the time-variable earthquake hazard can be assessed directly on the basis of a series of statistical indices of seismicity. Two methods of fuzzy clustering analysis, the method of fuzzy similarity, and the direct method of fuzzy pattern recognition, have been studied is particular. One method of fuzzy clustering analysis is based on fuzzy netting, and another is based on the fuzzy equivalent relation. (2) Quantitative estimation of the earthquake hazard on the basis of observational data for different precursors. The direct method of fuzzy pattern recognition has been applied to research on earthquake precursors of different kinds. On the basis of the temporal and spatial characteristics of recognized precursors, earthquake hazards in different terms can be estimated. This paper mainly deals with medium-short-term precursors observed in Japan and China.

  18. Kelvin wave coupling from TIMED and GOCE: Inter/intra-annual variability and solar activity effects

    Science.gov (United States)

    Gasperini, Federico; Forbes, Jeffrey M.; Doornbos, Eelco N.; Bruinsma, Sean L.

    2018-06-01

    The primary mechanism through which energy and momentum are transferred from the lower atmosphere to the thermosphere is through the generation and propagation of atmospheric waves. It is becoming increasingly evident that a few waves from the tropical wave spectrum preferentially propagate into the thermosphere and contribute to modify satellite drag. Two of the more prominent and well-established tropical waves are Kelvin waves: the eastward-propagating 3-day ultra-fast Kelvin wave (UFKW) and the eastward-propagating diurnal tide with zonal wave number 3 (DE3). In this work, Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures at 110 km and Gravity field and steady-state Ocean Circulation Explorer (GOCE) neutral densities and cross-track winds near 260 km are used to demonstrate vertical coupling in this height regime due to the UFKW and DE3. Significant inter- and intra-annual variability is found in DE3 and the UFKW, with evidence of latitudinal broadening and filtering of the latitude structures with height due to the effect of dissipation and mean winds. Additionally, anti-correlation between the vertical penetration of these waves to the middle thermosphere and solar activity level is established and explained through the effect of molecular dissipation.

  19. Time variability of C-reactive protein: implications for clinical risk stratification.

    Directory of Open Access Journals (Sweden)

    Peter Bogaty

    Full Text Available C-reactive protein (CRP is proposed as a screening test for predicting risk and guiding preventive approaches in coronary artery disease (CAD. However, the stability of repeated CRP measurements over time in subjects with and without CAD is not well defined. We sought to determine the stability of serial CRP measurements in stable subjects with distinct CAD manifestations and a group without CAD while carefully controlling for known confounders.We prospectively studied 4 groups of 25 stable subjects each 1 a history of recurrent acute coronary events; 2 a single myocardial infarction ≥7 years ago; 3 longstanding CAD (≥7 years that had never been unstable; 4 no CAD. Fifteen measurements of CRP were obtained to cover 21 time-points: 3 times during one day; 5 consecutive days; 4 consecutive weeks; 4 consecutive months; and every 3 months over the year. CRP risk threshold was set at 2.0 mg/L. We estimated variance across time-points using standard descriptive statistics and Bayesian hierarchical models.Median CRP values of the 4 groups and their pattern of variability did not differ substantially so all subjects were analyzed together. The median individual standard deviation (SD CRP values within-day, within-week, between-weeks and between-months were 0.07, 0.19, 0.36 and 0.63 mg/L, respectively. Forty-six percent of subjects changed CRP risk category at least once and 21% had ≥4 weekly and monthly CRP values in both low and high-risk categories.Considering its large intra-individual variability, it may be problematic to rely on CRP values for CAD risk prediction and therapeutic decision-making in individual subjects.

  20. Trends and variability in streamflow and snowmelt runoff timing in the southern Tianshan Mountains

    Science.gov (United States)

    Shen, Yan-Jun; Shen, Yanjun; Fink, Manfred; Kralisch, Sven; Chen, Yaning; Brenning, Alexander

    2018-02-01

    Streamflow and snowmelt runoff timing of mountain rivers are susceptible to climate change. Trends and variability in streamflow and snowmelt runoff timing in four mountain basins in the southern Tianshan were analyzed in this study. Streamflow trends were detected by Mann-Kendall tests and changes in snowmelt runoff timing were analyzed based on the winter/spring snowmelt runoff center time (WSCT). Pearson's correlation coefficient was further calculated to analyze the relationships between climate variables, streamflow and WSCT. Annual streamflow increased significantly in past decades in the southern Tianshan, especially in spring and winter months. However, the relations between streamflow and temperature/precipitation depend on the different streamflow generation processes. Annual precipitation plays a vital role in controlling recharge in the Toxkon basin, while the Kaidu and Huangshuigou basins are governed by both precipitation and temperature. Seasonally, temperature has a strong effect on streamflow in autumn and winter, while summer streamflow appears more sensitive to changes in precipitation. However, temperature is the dominant factor for streamflow in the glacierized Kunmalik basin at annual and seasonal scales. An uptrend in streamflow begins in the 1990s at both annual and seasonal scales, which is generally consistent with temperature and precipitation fluctuations. Average WSCT dates in the Kaidu and Huangshuigou basins are earlier than in the Toxkon and Kunmalik basins, and shifted towards earlier dates since the mid-1980s in all the basins. It is plausible that WSCT dates are more sensitive to warmer temperature in spring period compared to precipitation, except for the Huangshuigou basin. Taken together, these findings are useful for applications in flood risk regulation, future hydropower projects and integrated water resources management.

  1. A stochastic fractional dynamics model of space-time variability of rain

    Science.gov (United States)

    Kundu, Prasun K.; Travis, James E.

    2013-09-01

    varies in space and time in a highly irregular manner and is described naturally in terms of a stochastic process. A characteristic feature of rainfall statistics is that they depend strongly on the space-time scales over which rain data are averaged. A spectral model of precipitation has been developed based on a stochastic differential equation of fractional order for the point rain rate, which allows a concise description of the second moment statistics of rain at any prescribed space-time averaging scale. The model is thus capable of providing a unified description of the statistics of both radar and rain gauge data. The underlying dynamical equation can be expressed in terms of space-time derivatives of fractional orders that are adjusted together with other model parameters to fit the data. The form of the resulting spectrum gives the model adequate flexibility to capture the subtle interplay between the spatial and temporal scales of variability of rain but strongly constrains the predicted statistical behavior as a function of the averaging length and time scales. We test the model with radar and gauge data collected contemporaneously at the NASA TRMM ground validation sites located near Melbourne, Florida and on the Kwajalein Atoll, Marshall Islands in the tropical Pacific. We estimate the parameters by tuning them to fit the second moment statistics of radar data at the smaller spatiotemporal scales. The model predictions are then found to fit the second moment statistics of the gauge data reasonably well at these scales without any further adjustment.

  2. Listing of 502 Times When the Ulysses Magnetic Fields Instrument Observed Waves Due to Newborn Interstellar Pickup Protons

    International Nuclear Information System (INIS)

    Cannon, Bradford E.; Smith, Charles W.; Isenberg, Philip A.; Vasquez, Bernard J.; Joyce, Colin J.; Murphy, Neil; Nuno, Raquel G.

    2017-01-01

    In two earlier publications we analyzed 502 intervals of magnetic waves excited by newborn interstellar pickup protons that were observed by the Ulysses spacecraft. Due to the considerable effort required in identifying these events, we provide a list of the times for the 502 wave event intervals previously identified. In the process, we provide a brief description of how the waves were found and what their properties are. We also remind the reader of the conditions that permit the waves to reach observable levels and explain why the waves are not seen more often.

  3. Listing of 502 Times When the Ulysses Magnetic Fields Instrument Observed Waves Due to Newborn Interstellar Pickup Protons

    Energy Technology Data Exchange (ETDEWEB)

    Cannon, Bradford E. [Physics Department, Florida State University, Tallahassee, Florida (United States); Smith, Charles W.; Isenberg, Philip A.; Vasquez, Bernard J.; Joyce, Colin J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire (United States); Murphy, Neil [Jet Propulsion Laboratory, Mail Stop 180-600, 4800 Oak Grove Drive, Pasadena, California (United States); Nuno, Raquel G., E-mail: bc13h@my.fsu.edu, E-mail: Charles.Smith@unh.edu, E-mail: Phil.Isenberg@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: Colin.Joyce@unh.edu, E-mail: Neil.Murphy@jpl.nasa.gov, E-mail: rgnuno@ucla.edu [Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, CA (United States)

    2017-05-01

    In two earlier publications we analyzed 502 intervals of magnetic waves excited by newborn interstellar pickup protons that were observed by the Ulysses spacecraft. Due to the considerable effort required in identifying these events, we provide a list of the times for the 502 wave event intervals previously identified. In the process, we provide a brief description of how the waves were found and what their properties are. We also remind the reader of the conditions that permit the waves to reach observable levels and explain why the waves are not seen more often.

  4. Time-variable gravity fields and ocean mass change from 37 months of kinematic Swarm orbits

    Science.gov (United States)

    Lück, Christina; Kusche, Jürgen; Rietbroek, Roelof; Löcher, Anno

    2018-03-01

    Measuring the spatiotemporal variation of ocean mass allows for partitioning of volumetric sea level change, sampled by radar altimeters, into mass-driven and steric parts. The latter is related to ocean heat change and the current Earth's energy imbalance. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) mission has provided monthly snapshots of the Earth's time-variable gravity field, from which one can derive ocean mass variability. However, GRACE has reached the end of its lifetime with data degradation and several gaps occurred during the last years, and there will be a prolonged gap until the launch of the follow-on mission GRACE-FO. Therefore, efforts focus on generating a long and consistent ocean mass time series by analyzing kinematic orbits from other low-flying satellites, i.e. extending the GRACE time series. Here we utilize data from the European Space Agency's (ESA) Swarm Earth Explorer satellites to derive and investigate ocean mass variations. For this aim, we use the integral equation approach with short arcs (Mayer-Gürr, 2006) to compute more than 500 time-variable gravity fields with different parameterizations from kinematic orbits. We investigate the potential to bridge the gap between the GRACE and the GRACE-FO mission and to substitute missing monthly solutions with Swarm results of significantly lower resolution. Our monthly Swarm solutions have a root mean square error (RMSE) of 4.0 mm with respect to GRACE, whereas directly estimating constant, trend, annual, and semiannual (CTAS) signal terms leads to an RMSE of only 1.7 mm. Concerning monthly gaps, our CTAS Swarm solution appears better than interpolating existing GRACE data in 13.5 % of all cases, when artificially removing one solution. In the case of an 18-month artificial gap, 80.0 % of all CTAS Swarm solutions were found closer to the observed GRACE data compared to interpolated GRACE data. Furthermore, we show that precise modeling of non-gravitational forces

  5. Predictor variables for half marathon race time in recreational female runners

    Directory of Open Access Journals (Sweden)

    Beat Knechtle

    2011-01-01

    Full Text Available INTRODUCTION: The relationship between skin-fold thickness and running performance has been investigated from 100 m to the marathon distance, except the half marathon distance. OBJECTIVE: To investigate whether anthropometry characteristics or training practices were related to race time in 42 recreational female half marathoners to determine the predictor variables of half-marathon race time and to inform future novice female half marathoners. METHODS: Observational field study at the 'Half Marathon Basel' in Switzerland. RESULTS: In the bivariate analysis, body mass (r = 0.60, body mass index (r = 0.48, body fat (r = 0.56, skin-fold at pectoral (r = 0.61, mid-axilla (r = 0.69, triceps (r = 0.49, subscapular (r = 0.61, abdominal (r = 0.59, suprailiac (r = 0.55 medial calf (r = 0.53 site, and speed of the training sessions (r = -0.68 correlated to race time. Mid-axilla skin-fold (p = 0.04 and speed of the training sessions (p = 0.0001 remained significant after multi-variate analysis. Race time in a half marathon might be predicted by the following equation (r² = 0.71: Race time (min = 166.7 + 1.7x (mid-axilla skin-fold, mm - 6.4x (speed in training, km/h. Running speed during training was related to skinfold thickness at mid-axilla (r = -0.31, subscapular (r = -0.38, abdominal (r = -0.44, suprailiacal (r = -0.41, the sum of eight skin-folds (r = -0.36 and percent body fat (r = -0.31. CONCLUSION: Anthropometric and training variables were related to half-marathon race time in recreational female runners. Skin-fold thicknesses at various upper body locations were related to training intensity. High running speed in training appears to be important for fast half-marathon race times and may reduce upper body skin-fold thicknesses in recreational female half marathoners.

  6. Predictor variables for half marathon race time in recreational female runners.

    Science.gov (United States)

    Knechtle, Beat; Knechtle, Patrizia; Barandun, Ursula; Rosemann, Thomas; Lepers, Romuald

    2011-01-01

    The relationship between skin-fold thickness and running performance has been investigated from 100 m to the marathon distance, except the half marathon distance. To investigate whether anthropometry characteristics or training practices were related to race time in 42 recreational female half marathoners to determine the predictor variables of half-marathon race time and to inform future novice female half marathoners. Observational field study at the 'Half Marathon Basel' in Switzerland. In the bivariate analysis, body mass (r = 0.60), body mass index (r = 0.48), body fat (r = 0.56), skin-fold at pectoral (r = 0.61), mid-axilla (r = 0.69), triceps (r = 0.49), subscapular (r = 0.61), abdominal (r = 0.59), suprailiac (r = 0.55) medial calf (r = 0.53) site, and speed of the training sessions (r = -0.68) correlated to race time. Mid-axilla skin-fold (p = 0.04) and speed of the training sessions (p = 0.0001) remained significant after multi-variate analysis. Race time in a half marathon might be predicted by the following equation (r² = 0.71): Race time (min) = 166.7 + 1.7x (mid-axilla skin-fold, mm) - 6.4x (speed in training, km/h). Running speed during training was related to skinfold thickness at mid-axilla (r = -0.31), subscapular (r = -0.38), abdominal (r = -0.44), suprailiacal (r = -0.41), the sum of eight skin-folds (r = -0.36) and percent body fat (r = -0.31). Anthropometric and training variables were related to half-marathon race time in recreational female runners. Skin-fold thicknesses at various upper body locations were related to training intensity. High running speed in training appears to be important for fast half-marathon race times and may reduce upper body skin-fold thicknesses in recreational female half marathoners.

  7. Temperature field due to time-dependent heat sources in a large rectangular grid. Application for the KBS-3 repository

    International Nuclear Information System (INIS)

    Probert, T.; Claesson, Johan

    1997-04-01

    In the KBS-3 concept canisters containing nuclear waste are deposited along parallel tunnels over a large rectangular area deep below the ground surface. The temperature field in rock due to such a rectangular grid of heat-releasing canisters is studied. An analytical solution for this problem for any heat source has been presented in a preceding paper. The complete solution is summarized in this paper. The solution is by superposition divided into two main parts. There is a global temperature field due to the large rectangular canister area, while a local field accounts for the remaining heat source problem. In this sequel to the first report, the local solution is discussed in detail. The local solution consists of three parts corresponding to line heat sources along tunnels, point heat sources along a tunnel and a line heat source along a canister. Each part depends on two special variables only. These parts are illustrated in dimensionless form. Inside the repository the local temperature field is periodic in the horizontal directions and has a short extent in the vertical direction. This allows us to look at the solution in a parallelepiped around a canister. The solution in the parallelepiped is valid for all canisters that are not too close to the repository edges. The total temperature field is calculated for the KBS-3 case. The temperature field is calculated using a heat release that is valid for the first 10 000 years after deposition. The temperature field is shown in 23 figures in order to illustrate different aspects of the complex thermal process

  8. Time-dependent London approach: Dissipation due to out-of-core normal excitations by moving vortices

    Science.gov (United States)

    Kogan, V. G.

    2018-03-01

    The dissipative currents due to normal excitations are included in the London description. The resulting time-dependent London equations are solved for a moving vortex and a moving vortex lattice. It is shown that the field distribution of a moving vortex loses its cylindrical symmetry. It experiences contraction that is stronger in the direction of the motion than in the direction normal to the velocity v . The London contribution of normal currents to dissipation is small relative to the Bardeen-Stephen core dissipation at small velocities, but it approaches the latter at high velocities, where this contribution is no longer proportional to v2. To minimize the London contribution to dissipation, the vortex lattice is oriented so as to have one of the unit cell vectors along the velocity. This effect is seen in experiments and predicted within the time-dependent Ginzburg-Landau theory.

  9. Drivers of time-activity budget variability during breeding in a pelagic seabird.

    Directory of Open Access Journals (Sweden)

    Gavin M Rishworth

    Full Text Available During breeding, animal behaviour is particularly sensitive to environmental and food resource availability. Additionally, factors such as sex, body condition, and offspring developmental stage can influence behaviour. Amongst seabirds, behaviour is generally predictably affected by local foraging conditions and has therefore been suggested as a potentially useful proxy to indicate prey state. However, besides prey availability and distribution, a range of other variables also influence seabird behavior, and these need to be accounted for to increase the signal-to-noise ratio when assessing specific characteristics of the environment based on behavioural attributes. The aim of this study was to use continuous, fine-scale time-activity budget data from a pelagic seabird (Cape gannet, Morus capensis to determine the influence of intrinsic (sex and body condition and extrinsic (offspring and time variables on parent behaviour during breeding. Foraging trip duration and chick provisioning rates were clearly sex-specific and associated with chick developmental stage. Females made fewer, longer foraging trips and spent less time at the nest during chick provisioning. These sex-specific differences became increasingly apparent with chick development. Additionally, parents in better body condition spent longer periods at their nests and those which returned later in the day had longer overall nest attendance bouts. Using recent technological advances, this study provides new insights into the foraging behaviour of breeding seabirds, particularly during the post-guarding phase. The biparental strategy of chick provisioning revealed in this study appears to be an example where the costs of egg development to the female are balanced by paternal-dominated chick provisioning particularly as the chick nears fledging.

  10. Increasing work-time influence: consequences for flexibility, variability, regularity and predictability.

    Science.gov (United States)

    Nabe-Nielsen, Kirsten; Garde, Anne Helene; Aust, Birgit; Diderichsen, Finn

    2012-01-01

    This quasi-experimental study investigated how an intervention aiming at increasing eldercare workers' influence on their working hours affected the flexibility, variability, regularity and predictability of the working hours. We used baseline (n = 296) and follow-up (n = 274) questionnaire data and interviews with intervention-group participants (n = 32). The work units in the intervention group designed their own intervention comprising either implementation of computerised self-scheduling (subgroup A), collection of information about the employees' work-time preferences by questionnaires (subgroup B), or discussion of working hours (subgroup C). Only computerised self-scheduling changed the working hours and the way they were planned. These changes implied more flexible but less regular working hours and an experience of less predictability and less continuity in the care of clients and in the co-operation with colleagues. In subgroup B and C, the participants ended up discussing the potential consequences of more work-time influence without actually implementing any changes. Employee work-time influence may buffer the adverse effects of shift work. However, our intervention study suggested that while increasing the individual flexibility, increasing work-time influence may also result in decreased regularity of the working hours and less continuity in the care of clients and co-operation with colleagues.

  11. Variable-Field Analytical Ultracentrifugation: I. Time-Optimized Sedimentation Equilibrium

    Science.gov (United States)

    Ma, Jia; Metrick, Michael; Ghirlando, Rodolfo; Zhao, Huaying; Schuck, Peter

    2015-01-01

    Sedimentation equilibrium (SE) analytical ultracentrifugation (AUC) is a gold standard for the rigorous determination of macromolecular buoyant molar masses and the thermodynamic study of reversible interactions in solution. A significant experimental drawback is the long time required to attain SE, which is usually on the order of days. We have developed a method for time-optimized SE (toSE) with defined time-varying centrifugal fields that allow SE to be attained in a significantly (up to 10-fold) shorter time than is usually required. To achieve this, numerical Lamm equation solutions for sedimentation in time-varying fields are computed based on initial estimates of macromolecular transport properties. A parameterized rotor-speed schedule is optimized with the goal of achieving a minimal time to equilibrium while limiting transient sample preconcentration at the base of the solution column. The resulting rotor-speed schedule may include multiple over- and underspeeding phases, balancing the formation of gradients from strong sedimentation fluxes with periods of high diffusional transport. The computation is carried out in a new software program called TOSE, which also facilitates convenient experimental implementation. Further, we extend AUC data analysis to sedimentation processes in such time-varying centrifugal fields. Due to the initially high centrifugal fields in toSE and the resulting strong migration, it is possible to extract sedimentation coefficient distributions from the early data. This can provide better estimates of the size of macromolecular complexes and report on sample homogeneity early on, which may be used to further refine the prediction of the rotor-speed schedule. In this manner, the toSE experiment can be adapted in real time to the system under study, maximizing both the information content and the time efficiency of SE experiments. PMID:26287634

  12. Decreased reaction time variability is associated with greater cardiovascular responses to acute stress.

    Science.gov (United States)

    Wawrzyniak, Andrew J; Hamer, Mark; Steptoe, Andrew; Endrighi, Romano

    2016-05-01

    Cardiovascular (CV) responses to mental stress are prospectively associated with poor CV outcomes. The association between CV responses to mental stress and reaction times (RTs) in aging individuals may be important but warrants further investigation. The present study assessed RTs to examine associations with CV responses to mental stress in healthy, older individuals using robust regression techniques. Participants were 262 men and women (mean age = 63.3 ± 5.5 years) from the Whitehall II cohort who completed a RT task (Stroop) and underwent acute mental stress (mirror tracing) to elicit CV responses. Blood pressure, heart rate, and heart rate variability were measured at baseline, during acute stress, and through a 75-min recovery. RT measures were generated from an ex-Gaussian distribution that yielded three predictors: mu-RT, sigma-RT, and tau-RT, the mean, standard deviation, and mean of the exponential component of the normal distribution, respectively. Decreased intraindividual RT variability was marginally associated with greater systolic (B = -.009, SE = .005, p = .09) and diastolic (B = -.004, SE = .002, p = .08) blood pressure reactivity. Decreased intraindividual RT variability was associated with impaired systolic blood pressure recovery (B = -.007, SE = .003, p = .03) and impaired vagal tone (B = -.0047, SE = .0024, p = .045). Study findings offer tentative support for an association between RTs and CV responses. Despite small effect sizes and associations not consistent across predictors, these data may point to a link between intrinsic neuronal plasticity and CV responses. © 2016 The Authors. Psychophysiology published by Wiley Periodicals, Inc. on behalf of Society for Psychophysiological Research.

  13. Variable School Start Times and Middle School Student's Sleep Health and Academic Performance.

    Science.gov (United States)

    Lewin, Daniel S; Wang, Guanghai; Chen, Yao I; Skora, Elizabeth; Hoehn, Jessica; Baylor, Allison; Wang, Jichuan

    2017-08-01

    Improving sleep health among adolescents is a national health priority and implementing healthy school start times (SSTs) is an important strategy to achieve these goals. This study leveraged the differences in middle school SST in a large district to evaluate associations between SST, sleep health, and academic performance. This cross-sectional study draws data from a county-wide surveillance survey. Participants were three cohorts of eighth graders (n = 26,440). The school district is unique because SST ranged from 7:20 a.m. to 8:10 a.m. Path analysis and probit regression were used to analyze associations between SST and self-report measures of weekday sleep duration, grades, and homework controlling for demographic variables (sex, race, and socioeconomic status). The independent contributions of SST and sleep duration to academic performance were also analyzed. Earlier SST was associated with decreased sleep duration (χ 2  = 173, p academic performance, and academic effort. Path analysis models demonstrated the independent contributions of sleep duration, SST, and variable effects for demographic variables. This is the first study to evaluate the independent contributions of SST and sleep to academic performance in a large sample of middle school students. Deficient sleep was prevalent, and the earliest SST was associated with decrements in sleep and academics. These findings support the prioritization of policy initiatives to implement healthy SST for younger adolescents and highlight the importance of sleep health education disparities among race and gender groups. Copyright © 2017 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  14. Space and time variability of heating requirements for greenhouse tomato production in the Euro-Mediterranean area.

    Science.gov (United States)

    Mariani, Luigi; Cola, Gabriele; Bulgari, Roberta; Ferrante, Antonio; Martinetti, Livia

    2016-08-15

    The Euro-Mediterranean area is the seat of a relevant greenhouse activity, meeting the needs of important markets. A quantitative assessment of greenhouse energy consumption and of its variability in space and time is an important decision support tool for both greenhouse-sector policies and farmers. A mathematical model of greenhouse energy balance was developed and parameterized for a state-of-the-art greenhouse to evaluate the heating requirements for vegetables growing. Tomato was adopted as reference crop, due to its high energy requirement for fruit setting and ripening and its economic relevance. In order to gain a proper description of the Euro-Mediterranean area, 56 greenhouse areas located within the ranges 28°N-72°N and 11°W-55°E were analyzed over the period 1973-2014. Moreover, the two 1973-1987 and 1988-2014 sub-periods were separately studied to describe climate change effects on energy consumption. Results account for the spatial variability of energy needs for tomato growing, highlighting the strong influence of latitude on the magnitude of heat requirements. The comparison between the two selected sub-periods shows a decrease of energy demand in the current warm phase, more relevant for high latitudes. Finally, suggestions to reduce energy consumptions are provided. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Intraindividual Variability in Basic Reaction Time Predicts Middle-Aged and Older Pilots’ Flight Simulator Performance

    Science.gov (United States)

    2013-01-01

    Objectives. Intraindividual variability (IIV) is negatively associated with cognitive test performance and is positively associated with age and some neurological disorders. We aimed to extend these findings to a real-world task, flight simulator performance. We hypothesized that IIV predicts poorer initial flight performance and increased rate of decline in performance among middle-aged and older pilots. Method. Two-hundred and thirty-six pilots (40–69 years) completed annual assessments comprising a cognitive battery and two 75-min simulated flights in a flight simulator. Basic and complex IIV composite variables were created from measures of basic reaction time and shifting and divided attention tasks. Flight simulator performance was characterized by an overall summary score and scores on communication, emergencies, approach, and traffic avoidance components. Results. Although basic IIV did not predict rate of decline in flight performance, it had a negative association with initial performance for most flight measures. After taking into account processing speed, basic IIV explained an additional 8%–12% of the negative age effect on initial flight performance. Discussion. IIV plays an important role in real-world tasks and is another aspect of cognition that underlies age-related differences in cognitive performance. PMID:23052365

  16. Intraindividual variability in basic reaction time predicts middle-aged and older pilots' flight simulator performance.

    Science.gov (United States)

    Kennedy, Quinn; Taylor, Joy; Heraldez, Daniel; Noda, Art; Lazzeroni, Laura C; Yesavage, Jerome

    2013-07-01

    Intraindividual variability (IIV) is negatively associated with cognitive test performance and is positively associated with age and some neurological disorders. We aimed to extend these findings to a real-world task, flight simulator performance. We hypothesized that IIV predicts poorer initial flight performance and increased rate of decline in performance among middle-aged and older pilots. Two-hundred and thirty-six pilots (40-69 years) completed annual assessments comprising a cognitive battery and two 75-min simulated flights in a flight simulator. Basic and complex IIV composite variables were created from measures of basic reaction time and shifting and divided attention tasks. Flight simulator performance was characterized by an overall summary score and scores on communication, emergencies, approach, and traffic avoidance components. Although basic IIV did not predict rate of decline in flight performance, it had a negative association with initial performance for most flight measures. After taking into account processing speed, basic IIV explained an additional 8%-12% of the negative age effect on initial flight performance. IIV plays an important role in real-world tasks and is another aspect of cognition that underlies age-related differences in cognitive performance.

  17. Variability of scaling time series in the Arctic sea-ice drift dynamics

    Directory of Open Access Journals (Sweden)

    A. Chmel

    2010-02-01

    Full Text Available The motion of an individual ice floe in the Arctic Ocean was monitored at the Russian research station North Pole 35 established on the ice pack in 2008. The ice floe speed (V was found to be correlated with wind speed (v in main features, such as the positions of maxima and minima of V and v. However, the fine structure of the V-variation cannot be explained by the wind forcing alone. There were periods of time when the floe drift was affected by the interactions of ice floes between each other or by the periodical forcing due to either the Coriolis inertia effect or the tidal activity. These data were compared with the "waiting times" statistics that are the distributions of time intervals between subsequent, sufficiently strong changes in the kinetic energy of drifting ice floe. These distributions were measured in several time windows differing in the average wind speed and wind direction, and/or in the mechanical state of the ice pack. The distribution functions N (t>τ, where N is the number of successive events of energy change separated by the time interval t that exceeds τ, constructed in different time windows demonstrate fractal or a multifractal nature of the time series during motion in the consolidated ice pack but were truly random when the ice floe drifted in the highly fragmented sea ice. The latter result shows the existence of a relationship between the long-range mechanical interactions in the pack and long-term memory (time scaling behaviour of the sea-ice motion.

  18. 34 CFR Appendix C to Part 682 - Procedures for Curing Violations of the Due Diligence in Collection and Timely Filing of Claims...

    Science.gov (United States)

    2010-07-01

    ... 34 Education 3 2010-07-01 2010-07-01 false Procedures for Curing Violations of the Due Diligence... Appendix C to Part 682—Procedures for Curing Violations of the Due Diligence in Collection and Timely... lenders to use (1) to cure violations of the requirements for due diligence in collection (“due diligence...

  19. Fuzzy central tendency measure for time series variability analysis with application to fatigue electromyography signals.

    Science.gov (United States)

    Xie, Hong-Bo; Dokos, Socrates

    2013-01-01

    A new method, namely fuzzy central tendency measure (fCTM) analysis, that could enable measurement of the variability of a time series, is presented in this study. Tests on simulated data sets show that fCTM is superior to the conventional central tendency measure (CTM) in several respects, including improved relative consistency and robustness to noise. The proposed fCTM method was applied to electromyograph (EMG) signals recorded during sustained isometric contraction for tracking local muscle fatigue. The results showed that the fCTM increased significantly during the development of muscle fatigue, and it was more sensitive to the fatigue phenomenon than mean frequency (MNF), the most commonly-used muscle fatigue indicator.

  20. Variable speed wind turbine control by discrete-time sliding mode approach.

    Science.gov (United States)

    Torchani, Borhen; Sellami, Anis; Garcia, Germain

    2016-05-01

    The aim of this paper is to propose a new design variable speed wind turbine control by discrete-time sliding mode approach. This methodology is designed for linear saturated system. The saturation constraint is reported on inputs vector. To this end, the back stepping design procedure is followed to construct a suitable sliding manifold that guarantees the attainment of a stabilization control objective. It is well known that the mechanisms are investigated in term of the most proposed assumptions to deal with the damping, shaft stiffness and inertia effect of the gear. The objectives are to synthesize robust controllers that maximize the energy extracted from wind, while reducing mechanical loads and rotor speed tracking combined with an electromagnetic torque. Simulation results of the proposed scheme are presented. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  1. Development of a time-variable nuclear pulser for half life measurements

    International Nuclear Information System (INIS)

    Zahn, Guilherme S.; Domienikan, Claudio; Carvalhaes, Roberto P. M.; Genezini, Frederico A.

    2013-01-01

    In this work a time-variable pulser system with an exponentially-decaying pulse frequency is presented, which was developed using the low-cost, open-source Arduino microcontroler plataform. In this system, the microcontroller produces a TTL signal in the selected rate and a pulse shaper board adjusts it to be entered in an amplifier as a conventional pulser signal; both the decay constant and the initial pulse rate can be adjusted using a user-friendly control software, and the pulse amplitude can be adjusted using a potentiometer in the pulse shaper board. The pulser was tested using several combinations of initial pulse rate and decay constant, and the results show that the system is stable and reliable, and is suitable to be used in half-life measurements.

  2. Development of a time-variable nuclear pulser for half life measurements

    Energy Technology Data Exchange (ETDEWEB)

    Zahn, Guilherme S.; Domienikan, Claudio; Carvalhaes, Roberto P. M.; Genezini, Frederico A. [Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP. P.O. Box 11049, Sao Paulo, 05422-970 (Brazil)

    2013-05-06

    In this work a time-variable pulser system with an exponentially-decaying pulse frequency is presented, which was developed using the low-cost, open-source Arduino microcontroler plataform. In this system, the microcontroller produces a TTL signal in the selected rate and a pulse shaper board adjusts it to be entered in an amplifier as a conventional pulser signal; both the decay constant and the initial pulse rate can be adjusted using a user-friendly control software, and the pulse amplitude can be adjusted using a potentiometer in the pulse shaper board. The pulser was tested using several combinations of initial pulse rate and decay constant, and the results show that the system is stable and reliable, and is suitable to be used in half-life measurements.

  3. Similar star formation rate and metallicity variability time-scales drive the fundamental metallicity relation

    Science.gov (United States)

    Torrey, Paul; Vogelsberger, Mark; Hernquist, Lars; McKinnon, Ryan; Marinacci, Federico; Simcoe, Robert A.; Springel, Volker; Pillepich, Annalisa; Naiman, Jill; Pakmor, Rüdiger; Weinberger, Rainer; Nelson, Dylan; Genel, Shy

    2018-06-01

    The fundamental metallicity relation (FMR) is a postulated correlation between galaxy stellar mass, star formation rate (SFR), and gas-phase metallicity. At its core, this relation posits that offsets from the mass-metallicity relation (MZR) at a fixed stellar mass are correlated with galactic SFR. In this Letter, we use hydrodynamical simulations to quantify the time-scales over which populations of galaxies oscillate about the average SFR and metallicity values at fixed stellar mass. We find that Illustris and IllustrisTNG predict that galaxy offsets from the star formation main sequence and MZR oscillate over similar time-scales, are often anticorrelated in their evolution, evolve with the halo dynamical time, and produce a pronounced FMR. Our models indicate that galaxies oscillate about equilibrium SFR and metallicity values - set by the galaxy's stellar mass - and that SFR and metallicity offsets evolve in an anticorrelated fashion. This anticorrelated variability of the metallicity and SFR offsets drives the existence of the FMR in our models. In contrast to Illustris and IllustrisTNG, we speculate that the SFR and metallicity evolution tracks may become decoupled in galaxy formation models dominated by feedback-driven globally bursty SFR histories, which could weaken the FMR residual correlation strength. This opens the possibility of discriminating between bursty and non-bursty feedback models based on the strength and persistence of the FMR - especially at high redshift.

  4. The reliable solution and computation time of variable parameters logistic model

    Science.gov (United States)

    Wang, Pengfei; Pan, Xinnong

    2018-05-01

    The study investigates the reliable computation time (RCT, termed as T c) by applying a double-precision computation of a variable parameters logistic map (VPLM). Firstly, by using the proposed method, we obtain the reliable solutions for the logistic map. Secondly, we construct 10,000 samples of reliable experiments from a time-dependent non-stationary parameters VPLM and then calculate the mean T c. The results indicate that, for each different initial value, the T cs of the VPLM are generally different. However, the mean T c trends to a constant value when the sample number is large enough. The maximum, minimum, and probable distribution functions of T c are also obtained, which can help us to identify the robustness of applying a nonlinear time series theory to forecasting by using the VPLM output. In addition, the T c of the fixed parameter experiments of the logistic map is obtained, and the results suggest that this T c matches the theoretical formula-predicted value.

  5. The analytical description of high temperature tensile creep for cavitating materials subjected to time variable loads

    International Nuclear Information System (INIS)

    Bocek, M.

    A phenomenological cavitation model is presented by means of which the life time as well as the creep curve equations can be calculated for cavitating materials subjected to time variable tensile loads. The model precludes the proportionality between the damage A and the damage rate (dA/dt) resp. Both are connected by the life time function tau. The latter is derived from static stress rupture tests and contains the loading conditions. From this model the life fraction rule (LFR) is derived. The model is used to calculate the creep curves of cavitating materials subjected at high temperatures to non-stationary tensile loading conditions. In the present paper the following loading procedures are considered: creep at constant load F and true stress s; creep at linear load increase ((dF/dt)=const) and creep at constant load amplitude cycling (CLAC). For these loading procedures the creep equations for cavitating and non-cavitating specimens are derived. Under comparable conditions the creep rate of cavitating materials are higher than for non-cavitating ones. (author)

  6. Time variability of X-ray binaries: observations with INTEGRAL. Modeling

    International Nuclear Information System (INIS)

    Cabanac, Clement

    2007-01-01

    The exact origin of the observed X and Gamma ray variability in X-ray binaries is still an open debate in high energy astrophysics. Among others, these objects are showing aperiodic and quasi-periodic luminosity variations on timescales as small as the millisecond. This erratic behavior must put constraints on the proposed emission processes occurring in the vicinity of the neutrons star or the stellar mass black-hole held by these objects. We propose here to study their behavior following 3 different ways: first we examine the evolution of a particular X-ray source discovered by INTEGRAL, IGR J19140+0951. Using timing and spectral data given by different instruments, we show that the source type is plausibly consistent with a High Mass X-ray Binary hosting a neutrons star. Subsequently, we propose a new method dedicated to the study of timing data coming from coded mask aperture instruments. Using it on INTEGRAL/ISGRI real data, we detect the presence of periodic and quasi-periodic features in some pulsars and micro-quasars at energies as high as a hundred keV. Finally, we suggest a model designed to describe the low frequency variability of X-ray binaries in their hardest state. This model is based on thermal comptonization of soft photons by a warm corona in which a pressure wave is propagating in cylindrical geometry. By computing both numerical simulations and analytical solution, we show that this model should be suitable to describe some of the typical features observed in X-ray binaries power spectra in their hard state and their evolution such as aperiodic noise and low frequency quasi-periodic oscillations. (author) [fr

  7. Statistical Learning and Adaptive Decision-Making Underlie Human Response Time Variability in Inhibitory Control

    Directory of Open Access Journals (Sweden)

    Ning eMa

    2015-08-01

    Full Text Available Response time (RT is an oft-reported behavioral measure in psychological and neurocognitive experiments, but the high level of observed trial-to-trial variability in this measure has often limited its usefulness. Here, we combine computational modeling and psychophysics to examine the hypothesis that fluctuations in this noisy measure reflect dynamic computations in human statistical learning and corresponding cognitive adjustments. We present data from the stop-signal task, in which subjects respond to a go stimulus on each trial, unless instructed not to by a subsequent, infrequently presented stop signal. We model across-trial learning of stop signal frequency, P(stop, and stop-signal onset time, SSD (stop-signal delay, with a Bayesian hidden Markov model, and within-trial decision-making with an optimal stochastic control model. The combined model predicts that RT should increase with both expected P(stop and SSD. The human behavioral data (n=20 bear out this prediction, showing P(stop and SSD both to be significant, independent predictors of RT, with P(stop being a more prominent predictor in 75% of the subjects, and SSD being more prominent in the remaining 25%. The results demonstrate that humans indeed readily internalize environmental statistics and adjust their cognitive/behavioral strategy accordingly, and that subtle patterns in RT variability can serve as a valuable tool for validating models of statistical learning and decision-making. More broadly, the modeling tools presented in this work can be generalized to a large body of behavioral paradigms, in order to extract insights about cognitive and neural processing from apparently quite noisy behavioral measures. We also discuss how this behaviorally validated model can then be used to conduct model-based analysis of neural data, in order to help identify specific brain areas for representing and encoding key computational quantities in learning and decision-making.

  8. Assessing the Time Variability of Jupiter's Tropospheric Properties from 1996 to 2011

    Science.gov (United States)

    Orton, G. S.; Fletcher, L. N.; Yanamandra-Fisher, P. A.; Simon-Miller, A. A.; Greco, J.; Wakefield, L.

    2012-01-01

    We acquired and analyzed mid-infrared images of Jupiter's disk at selected wavelengths from NASA's Infrared Telescope Facility (IRTF) from 1996 to 2011, including a period of large-scale changes of cloud color and albedo. We derived the 100-300 mbar temperature structure, together with tracers of vertical motion: the thickness of a 600- mbar cloud layer, the 300-mbar abundance of the condensable gas NH3, and the 400- mbar para- vs. ortho-H2 ratio. The biggest visual change was detected in the normally dark South Equatorial Belt (SEB) that 'faded' to a light color in 2010, during which both cloud thickness and NH3 abundance rose; both returned to their pre-fade levels in 2011, as the SEB regained its normal dark color. The cloud thickness in Jupiter's North Temperate Belt (NTB) increased in 2002, coincident with its visible brightening, and its NH3 abundance spiked in 2002-2003. Jupiter's Equatorial Zone (EZ), a region marked by more subtle but widespread color and albedo change, showed high cloud thickness variability between 2007 and 2009. In Jupiter's North Equatorial Belt (NEB), the cloud thickened in 2005, then slowly decreased to a minimum value in 2010-2011. No temperature variations were associated with any of these changes, but we discovered temperature oscillations of approx.2-4 K in all regions, with 4- or 8-year periods and phasing that was dissimilar in the different regions. There was also no detectable change in the para- vs. ortho-H2 ratio over time, leading to the possibility that it is driven from much deeper atmospheric levels and may be time-invariant. Our future work will continue to survey the variability of these properties through the Juno mission, which arrives at Jupiter in 2016, and to connect these observations with those made using raster-scanned images from 1980 to 1993 (Orton et al. 1996 Science 265, 625).

  9. Statistical learning and adaptive decision-making underlie human response time variability in inhibitory control.

    Science.gov (United States)

    Ma, Ning; Yu, Angela J

    2015-01-01

    Response time (RT) is an oft-reported behavioral measure in psychological and neurocognitive experiments, but the high level of observed trial-to-trial variability in this measure has often limited its usefulness. Here, we combine computational modeling and psychophysics to examine the hypothesis that fluctuations in this noisy measure reflect dynamic computations in human statistical learning and corresponding cognitive adjustments. We present data from the stop-signal task (SST), in which subjects respond to a go stimulus on each trial, unless instructed not to by a subsequent, infrequently presented stop signal. We model across-trial learning of stop signal frequency, P(stop), and stop-signal onset time, SSD (stop-signal delay), with a Bayesian hidden Markov model, and within-trial decision-making with an optimal stochastic control model. The combined model predicts that RT should increase with both expected P(stop) and SSD. The human behavioral data (n = 20) bear out this prediction, showing P(stop) and SSD both to be significant, independent predictors of RT, with P(stop) being a more prominent predictor in 75% of the subjects, and SSD being more prominent in the remaining 25%. The results demonstrate that humans indeed readily internalize environmental statistics and adjust their cognitive/behavioral strategy accordingly, and that subtle patterns in RT variability can serve as a valuable tool for validating models of statistical learning and decision-making. More broadly, the modeling tools presented in this work can be generalized to a large body of behavioral paradigms, in order to extract insights about cognitive and neural processing from apparently quite noisy behavioral measures. We also discuss how this behaviorally validated model can then be used to conduct model-based analysis of neural data, in order to help identify specific brain areas for representing and encoding key computational quantities in learning and decision-making.

  10. Sensitivity of Variables with Time for Degraded RC Shear Wall with Low Steel Ratio under Seismic Load

    International Nuclear Information System (INIS)

    Park, Jun Hee; Choun, Young Sun; Choi, In Kil

    2011-01-01

    Various factors lead to the degradation of reinforced concrete (RC) shear wall over time. The steel section loss, concrete spalling and strength of material have been considered for the structural analysis of degraded shear wall. When all variables with respect to degradation are considered for probabilistic evaluation of degraded shear wall, many of time and effort were demanded. Therefore, it is required to define important variables related to structural behavior for effectively conducting probabilistic seismic analysis of structures with age-related degradation. In this study, variables were defined by applying the function of time to consider degradation with time. Importance of variables with time on the seismic response was investigated by conducting sensitivity analysis

  11. Methods for assessment of climate variability and climate changes in different time-space scales

    International Nuclear Information System (INIS)

    Lobanov, V.; Lobanova, H.

    2004-01-01

    Main problem of hydrology and design support for water projects connects with modern climate change and its impact on hydrological characteristics as observed as well as designed. There are three main stages of this problem: - how to extract a climate variability and climate change from complex hydrological records; - how to assess the contribution of climate change and its significance for the point and area; - how to use the detected climate change for computation of design hydrological characteristics. Design hydrological characteristic is the main generalized information, which is used for water management and design support. First step of a research is a choice of hydrological characteristic, which can be as a traditional one (annual runoff for assessment of water resources, maxima, minima runoff, etc) as well as a new one, which characterizes an intra-annual function or intra-annual runoff distribution. For this aim a linear model has been developed which has two coefficients connected with an amplitude and level (initial conditions) of seasonal function and one parameter, which characterizes an intensity of synoptic and macro-synoptic fluctuations inside a year. Effective statistical methods have been developed for a separation of climate variability and climate change and extraction of homogeneous components of three time scales from observed long-term time series: intra annual, decadal and centural. The first two are connected with climate variability and the last (centural) with climate change. Efficiency of new methods of decomposition and smoothing has been estimated by stochastic modeling and well as on the synthetic examples. For an assessment of contribution and statistical significance of modern climate change components statistical criteria and methods have been used. Next step has been connected with a generalization of the results of detected climate changes over the area and spatial modeling. For determination of homogeneous region with the same

  12. Diurnal Alterations of Refraction, Anterior Segment Biometrics, and Intraocular Pressure in Long-Time Dehydration due to Religious Fasting.

    Science.gov (United States)

    Baser, Gonen; Cengiz, Hakan; Uyar, Murat; Seker Un, Emine

    2016-01-01

    To investigate the effects of dehydration due to fasting on diurnal changes of intraocular pressure, anterior segment biometrics, and refraction. The intraocular pressures, anterior segment biometrics (axial length: AL; Central corneal thickness: CCT; Lens thickness: LT; Anterior chamber depth: ACD), and refractive measurements of 30 eyes of 15 fasting healthy male volunteers were recorded at 8:00 in the morning and 17:00 in the evening in the Ramadan of 2013 and two months later. The results were compared and the statistical analyses were performed using the Rstudio software version 0.98.501. The variables were investigated using visual (histograms, probability plots) and analytical methods (Kolmogorov-Smirnov/Shapiro-Wilk test) to determine whether or not they were normally distributed. The refractive values remained stable in the fasting as well as in the control period (p = 0.384). The axial length measured slightly shorter in the fasting period (p = 0.001). The corneal thickness presented a diurnal variation, in which the cornea measured thinner in the evening. The difference between the fasting and control period was not statistically significant (p = 0.359). The major differences were observed in the anterior chamber depth and IOP. The ACD was shallower in the evening during the fasting period, where it was deeper in the control period. The diurnal IOP difference was greater in the fasting period than the control period. Both were statistically significant (p = 0.001). The LT remained unchanged in both periods. The major difference was shown in the anterior chamber shallowing in the evening hours and IOP. Our study contributes the hypothesis that the posterior segment of the eye is more responsible for the axial length alterations and normovolemia has a more dominant influence on diurnal IOP changes.

  13. New Tree-Ring Evidence from the Pyrenees Reveals Western Mediterranean Climate Variability since Medieval Times

    Czech Academy of Sciences Publication Activity Database

    Büntgen, Ulf; Krusic, P. J.; Verstege, A.; Sanguesa-Barreda, G.; Wagner, S.; Camarero, J. J.; Ljungqvist, F. C.; Zorita, E.; Oppenheimer, C.; Konter, O.; Tegel, W.; Gärtner, H.; Cherubini, P.; Reinig, F.; Esper, J.

    2017-01-01

    Roč. 30, č. 14 (2017), s. 5295-5318 ISSN 0894-8755 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : Europe * Volcanoes * Climate variability * Interannual variability * Multidecadal variability * Trends Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 4.161, year: 2016

  14. North atlantic multidecadal climate variability: An investigation of dominant time scales and processes

    NARCIS (Netherlands)

    Frankcombe, L.M.|info:eu-repo/dai/nl/304829838; von der Heydt, A.S.|info:eu-repo/dai/nl/245567526; Dijkstra, H.A.|info:eu-repo/dai/nl/073504467

    2010-01-01

    The issue of multidecadal variability in the North Atlantic has been an important topic of late. It is clear that there are multidecadal variations in several climate variables in the North Atlantic, such as sea surface temperature and sea level height. The details of this variability, in particular

  15. Intraindividual Stepping Reaction Time Variability Predicts Falls in Older Adults With Mild Cognitive Impairment.

    Science.gov (United States)

    Bunce, David; Haynes, Becky I; Lord, Stephen R; Gschwind, Yves J; Kochan, Nicole A; Reppermund, Simone; Brodaty, Henry; Sachdev, Perminder S; Delbaere, Kim

    2017-06-01

    Reaction time measures have considerable potential to aid neuropsychological assessment in a variety of health care settings. One such measure, the intraindividual reaction time variability (IIV), is of particular interest as it is thought to reflect neurobiological disturbance. IIV is associated with a variety of age-related neurological disorders, as well as gait impairment and future falls in older adults. However, although persons diagnosed with Mild Cognitive Impairment (MCI) are at high risk of falling, the association between IIV and prospective falls is unknown. We conducted a longitudinal cohort study in cognitively intact (n = 271) and MCI (n = 154) community-dwelling adults aged 70-90 years. IIV was assessed through a variety of measures including simple and choice hand reaction time and choice stepping reaction time tasks (CSRT), the latter administered as a single task and also with a secondary working memory task. Logistic regression did not show an association between IIV on the hand-held tasks and falls. Greater IIV in both CSRT tasks, however, did significantly increase the risk of future falls. This effect was specific to the MCI group, with a stronger effect in persons exhibiting gait, posture, or physiological impairment. The findings suggest that increased stepping IIV may indicate compromised neural circuitry involved in executive function, gait, and posture in persons with MCI increasing their risk of falling. IIV measures have potential to assess neurobiological disturbance underlying physical and cognitive dysfunction in old age, and aid fall risk assessment and routine care in community and health care settings. © The Author 2016. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  16. Time-dependence in relativistic collisionless shocks: theory of the variable

    Energy Technology Data Exchange (ETDEWEB)

    Spitkovsky, A

    2004-02-05

    We describe results from time-dependent numerical modeling of the collisionless reverse shock terminating the pulsar wind in the Crab Nebula. We treat the upstream relativistic wind as composed of ions and electron-positron plasma embedded in a toroidal magnetic field, flowing radially outward from the pulsar in a sector around the rotational equator. The relativistic cyclotron instability of the ion gyrational orbit downstream of the leading shock in the electron-positron pairs launches outward propagating magnetosonic waves. Because of the fresh supply of ions crossing the shock, this time-dependent process achieves a limit-cycle, in which the waves are launched with periodicity on the order of the ion Larmor time. Compressions in the magnetic field and pair density associated with these waves, as well as their propagation speed, semi-quantitatively reproduce the behavior of the wisp and ring features described in recent observations obtained using the Hubble Space Telescope and the Chandra X-Ray Observatory. By selecting the parameters of the ion orbits to fit the spatial separation of the wisps, we predict the period of time variability of the wisps that is consistent with the data. When coupled with a mechanism for non-thermal acceleration of the pairs, the compressions in the magnetic field and plasma density associated with the optical wisp structure naturally account for the location of X-ray features in the Crab. We also discuss the origin of the high energy ions and their acceleration in the equatorial current sheet of the pulsar wind.

  17. Mixing times towards demographic equilibrium in insect populations with temperature variable age structures.

    Science.gov (United States)

    Damos, Petros

    2015-08-01

    In this study, we use entropy related mixing rate modules to measure the effects of temperature on insect population stability and demographic breakdown. The uncertainty in the age of the mother of a randomly chosen newborn, and how it is moved after a finite act of time steps, is modeled using a stochastic transformation of the Leslie matrix. Age classes are represented as a cycle graph and its transitions towards the stable age distribution are brought forth as an exact Markov chain. The dynamics of divergence, from a non equilibrium state towards equilibrium, are evaluated using the Kolmogorov-Sinai entropy. Moreover, Kullback-Leibler distance is applied as information-theoretic measure to estimate exact mixing times of age transitions probabilities towards equilibrium. Using empirically data, we show that on the initial conditions and simulated projection's trough time, that population entropy can effectively be applied to detect demographic variability towards equilibrium under different temperature conditions. Changes in entropy are correlated with the fluctuations of the insect population decay rates (i.e. demographic stability towards equilibrium). Moreover, shorter mixing times are directly linked to lower entropy rates and vice versa. This may be linked to the properties of the insect model system, which in contrast to warm blooded animals has the ability to greatly change its metabolic and demographic rates. Moreover, population entropy and the related distance measures that are applied, provide a means to measure these rates. The current results and model projections provide clear biological evidence why dynamic population entropy may be useful to measure population stability. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. A Stochastic Model of Space-Time Variability of Tropical Rainfall: I. Statistics of Spatial Averages

    Science.gov (United States)

    Kundu, Prasun K.; Bell, Thomas L.; Lau, William K. M. (Technical Monitor)

    2002-01-01

    Global maps of rainfall are of great importance in connection with modeling of the earth s climate. Comparison between the maps of rainfall predicted by computer-generated climate models with observation provides a sensitive test for these models. To make such a comparison, one typically needs the total precipitation amount over a large area, which could be hundreds of kilometers in size over extended periods of time of order days or months. This presents a difficult problem since rain varies greatly from place to place as well as in time. Remote sensing methods using ground radar or satellites detect rain over a large area by essentially taking a series of snapshots at infrequent intervals and indirectly deriving the average rain intensity within a collection of pixels , usually several kilometers in size. They measure area average of rain at a particular instant. Rain gauges, on the other hand, record rain accumulation continuously in time but only over a very small area tens of centimeters across, say, the size of a dinner plate. They measure only a time average at a single location. In making use of either method one needs to fill in the gaps in the observation - either the gaps in the area covered or the gaps in time of observation. This involves using statistical models to obtain information about the rain that is missed from what is actually detected. This paper investigates such a statistical model and validates it with rain data collected over the tropical Western Pacific from ship borne radars during TOGA COARE (Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Response Experiment). The model incorporates a number of commonly observed features of rain. While rain varies rapidly with location and time, the variability diminishes when averaged over larger areas or longer periods of time. Moreover, rain is patchy in nature - at any instant on the average only a certain fraction of the observed pixels contain rain. The fraction of area covered by

  19. Variable flip angle excitation for reduced acquisition time magnetic resonance imaging

    International Nuclear Information System (INIS)

    Mills, T.C.; Ortendahl, D.A.; Hylton, N.M.; Carlson, J.W.; Crooks, L.E.; Kaufman, L.

    1987-01-01

    This paper describes an MRI technique which can be used to acquire images at short TR values while maintaining the sensitivity to disease found in longer TR images. For spin echo imaging there are three acquisition parameters that can be set in the imaging protocol; TR, the repetition interval; TE, the time of echo and Θ, the excitation flip angle. Standard imaging techniques set Θ to 90 degrees regardless of the TR value. With Θ fixed, imaging systems have been optimized by varying the value for TE and TR with the results in general indicating the need for long TR values. However, if the flip angle is included as a variable acquisition parameter the optimal operating point can be changed. The solution to the Bloch equation shows a functional relationship between the flip angle and the ratio TR/T1. This functionality was first observed by Ernst and Anderson as a method to increase the signal generated in fourier transform magnetic resonance spectroscopy. When TR/T1<1 the optimum flip angle for producing maximum magnetization in the transverse plane is less then 90 degrees. Therefore, by reducing both TR and flip angle it is possible to maintain signal intensity while reducing the time of data acquisition

  20. Study on a new type variable valve lift timing mechanism with a three dimensional cam; Sanjigen cam ni yoru shinkahen valve lift timing kiko ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, M; Song, C [Nippon Institute of Technology, Saitama (Japan)

    1997-10-01

    The variable valve timing mechanism was invented to get a torque band at wide engine speed, and to reduce a compression job and pumping loss by a miler cycle at partial load. In this paper, the new type variable valve timing mechanism applying a three dimensional cam was proposed. Also, the feature of mechanism and the control system was done obviously. Further, about a miler cycle, a thermodynamics -like consideration was described. 5 refs., 8 figs.

  1. The variability of SE2 tide extracted from TIMED/SABER observations

    Science.gov (United States)

    Li, X.; Wan, W.; Ren, Z.

    2017-12-01

    Based on the temperature observations of the TIMED/SABER in mesosphere/lower thermosphere region (70-110 km altitudes) and at the low latitude and midlatitude (45°S-45°N) from 2002 to 2012, the variability of the nonmigrating tide SE2 with 1 day resolution is analyzed. It is found that the climatological features (large-scale variability) of the semidiurnal nonmigrating tide with zonal wave number 2 (SE2) tide are similar with the results from the previous research works. The SE2 tide manifests mainly at the low-mid latitudes around ±30°. The northern hemisphere tidal amplitudes below 110 km are larger than the southern hemisphere tide. SE2 peaks below 110 km mainly present between 100 and 110 km altitude. The tidal amplitudes below 110 km occur a north-south asymmetry about the equator in the annual variation: in the southern hemisphere, SE2 occurs with an obvious annual variation with a maximum of tidal amplitudes in December, while in the northern one, the semiannual variations with maximum at the equinoxes. Herein, owing to the high-resolution tidal data, we could research the short-term (day-to-day) variations of SE2. We found that the day-to-day variations manifest mainly at between 100 and 110 km altitudes; it increases gradually with latitudes, and it is stronger at the low-mid latitudes; it is relatively slightly stronger around solstices than equinoxes; and it does not present a remarkably interannual variation. The SE2 day-to-day variations may be composed by the absolute amplitudes' variance and the impact of the wave phases, and the latter ones are more important.

  2. Infrared-metabolomics approach in detecting changes in Andrographis paniculata metabolites due to different harvesting ages and times.

    Science.gov (United States)

    Yusof, Nur A'thifah; Isha, Azizul; Ismail, Intan Safinar; Khatib, Alfi; Shaari, Khozirah; Abas, Faridah; Rukayadi, Yaya

    2015-09-01

    The metabolite changes in three germplasm accessions of Malaysia Andrographis paniculata (Burm. F.) Nees, viz. 11265 (H), 11341 (P) and 11248 (T), due to their different harvesting ages and times were successfully evaluated by attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy and translated through multivariate data analysis of principal component analysis (PCA) and orthogonal partial least square-discriminant analysis (OPLS-DA). This present study revealed the feasibility of ATR-FTIR in detecting the trend changes of the major metabolites - andrographolide and neoandrographolide - functional groups in A. paniculata leaves of different accessions. The harvesting parameter was set at three different ages of 120, 150 and 180 days after transplanting (DAT) and at two different time sessions of morning (7:30-10:30 am) and evening (2:30-5.30 pm). OPLS-DA successfully discriminated the A. paniculata crude extracts into groups of which the main constituents - andrographolide and neoandrographolide - could be mainly observed in the morning session of 120 DAT for P and T, while H gave the highest intensities of these constituents at 150 DAT. The information extracted from ATR-FTIR data through OPLS-DA could be useful in tailoring this plant harvest stage in relation to the content of its two major diterpene lactones: andrographolide and neoandrographolide. © 2014 Society of Chemical Industry.

  3. Multi-site study of diffusion metric variability: effects of site, vendor, field strength, and echo time on regions-of-interest and histogram-bin analyses.

    Science.gov (United States)

    Helmer, K G; Chou, M-C; Preciado, R I; Gimi, B; Rollins, N K; Song, A; Turner, J; Mori, S

    2016-02-27

    It is now common for magnetic-resonance-imaging (MRI) based multi-site trials to include diffusion-weighted imaging (DWI) as part of the protocol. It is also common for these sites to possess MR scanners of different manufacturers, different software and hardware, and different software licenses. These differences mean that scanners may not be able to acquire data with the same number of gradient amplitude values and number of available gradient directions. Variability can also occur in achievable b-values and minimum echo times. The challenge of a multi-site study then, is to create a common protocol by understanding and then minimizing the effects of scanner variability and identifying reliable and accurate diffusion metrics. This study describes the effect of site, scanner vendor, field strength, and TE on two diffusion metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA) using two common analyses (region-of-interest and mean-bin value of whole brain histograms). The goal of the study was to identify sources of variability in diffusion-sensitized imaging and their influence on commonly reported metrics. The results demonstrate that the site, vendor, field strength, and echo time all contribute to variability in FA and MD, though to different extent. We conclude that characterization of the variability of DTI metrics due to site, vendor, field strength, and echo time is a worthwhile step in the construction of multi-center trials.

  4. Temporal variability of the NPP-GPP ratio at seasonal and interannual time scales in a temperate beech forest

    Directory of Open Access Journals (Sweden)

    M. Campioli

    2011-09-01

    Full Text Available The allocation of carbon (C taken up by the tree canopy for respiration and production of tree organs with different construction and maintenance costs, life span and decomposition rate, crucially affects the residence time of C in forests and their C cycling rate. The carbon-use efficiency, or ratio between net primary production (NPP and gross primary production (GPP, represents a convenient way to analyse the C allocation at the stand level. In this study, we extend the current knowledge on the NPP-GPP ratio in forests by assessing the temporal variability of the NPP-GPP ratio at interannual (for 8 years and seasonal (for 1 year scales for a young temperate beech stand, reporting dynamics for both leaves and woody organs, in particular stems. NPP was determined with biometric methods/litter traps, whereas the GPP was estimated via the eddy covariance micrometeorological technique.

    The interannual variability of the proportion of C allocated to leaf NPP, wood NPP and leaf plus wood NPP (on average 11% yr−1, 29% yr−1 and 39% yr−1, respectively was significant among years with up to 12% yr−1 variation in NPP-GPP ratio. Studies focusing on the comparison of NPP-GPP ratio among forests and models using fixed allocation schemes should take into account the possibility of such relevant interannual variability. Multiple linear regressions indicated that the NPP-GPP ratio of leaves and wood significantly correlated with environmental conditions. Previous year drought and air temperature explained about half of the NPP-GPP variability of leaves and wood, respectively, whereas the NPP-GPP ratio was not decreased by severe drought, with large NPP-GPP ratio on 2003 due mainly to low GPP. During the period between early May and mid June, the majority of GPP was allocated to leaf and stem NPP, whereas these sinks were of little importance later on. Improved estimation of seasonal GPP and of the

  5. Temporal relationships between awakening cortisol and psychosocial variables in inpatients with anorexia nervosa - A time series approach.

    Science.gov (United States)

    Wild, Beate; Stadnitski, Tatjana; Wesche, Daniela; Stroe-Kunold, Esther; Schultz, Jobst-Hendrik; Rudofsky, Gottfried; Maser-Gluth, Christiane; Herzog, Wolfgang; Friederich, Hans-Christoph

    2016-04-01

    The aim of the study was to investigate the characteristics of the awakening salivary cortisol in patients with anorexia nervosa (AN) using a time series design. We included ten AN inpatients, six with a very low BMI (high symptom severity, HSS group) and four patients with less severe symptoms (low symptom severity, LSS group). Patients collected salivary cortisol daily upon awakening. The number of collected saliva samples varied across patients between n=65 and n=229 (due to the different lengths of their inpatient stay). In addition, before retiring, the patients answered questions daily on the handheld regarding disorder-related psychosocial variables. The analysis of cortisol and diary data was conducted by using a time series approach. Time series showed that the awakening cortisol of the AN patients was elevated as compared to a control group. Cortisol measurements of patients with LSS essentially fluctuated in a stationary manner around a constant mean. The series of patients with HSS were generally less stable; four HSS patients showed a non-stationary cortisol awakening series. Antipsychotic medication did not change awakening cortisol in a specific way. The lagged dependencies between cortisol and depressive feelings became significant for four patients. Here, higher cortisol values were temporally associated with higher values of depressive feelings. Upon awakening, the cortisol of all AN patients was in the standard range but elevated as compared to healthy controls. Patients with HSS appeared to show less stable awakening cortisol time series compared to patients with LSS. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Nonlinear dynamic modeling of a simple flexible rotor system subjected to time-variable base motions

    Science.gov (United States)

    Chen, Liqiang; Wang, Jianjun; Han, Qinkai; Chu, Fulei

    2017-09-01

    Rotor systems carried in transportation system or under seismic excitations are considered to have a moving base. To study the dynamic behavior of flexible rotor systems subjected to time-variable base motions, a general model is developed based on finite element method and Lagrange's equation. Two groups of Euler angles are defined to describe the rotation of the rotor with respect to the base and that of the base with respect to the ground. It is found that the base rotations would cause nonlinearities in the model. To verify the proposed model, a novel test rig which could simulate the base angular-movement is designed. Dynamic experiments on a flexible rotor-bearing system with base angular motions are carried out. Based upon these, numerical simulations are conducted to further study the dynamic response of the flexible rotor under harmonic angular base motions. The effects of base angular amplitude, rotating speed and base frequency on response behaviors are discussed by means of FFT, waterfall, frequency response curve and orbits of the rotor. The FFT and waterfall plots of the disk horizontal and vertical vibrations are marked with multiplications of the base frequency and sum and difference tones of the rotating frequency and the base frequency. Their amplitudes will increase remarkably when they meet the whirling frequencies of the rotor system.

  7. Reprocessing WFC3/IR Exposures Affected by Time-Variable Backgrounds

    Science.gov (United States)

    Brammer, G.

    2016-11-01

    The background seen in WFC3/IR observations frequently shows strong time-dependent behavior above the constant flux expected for zodiacal continuum light. This is often caused by an emission line of helium at 1.083 μm excited in the sun-illuminated upper atmosphere, when seen in the filters (F105W, F110W) and grisms (G102, G141) sensitive to the feature. The default behavior of the calwf3 pipeline assumes constant source-plus-background fluxes when it performs up-the-ramp fitting to identify cosmic rays and determine the average count rate within a MULTIACCUM IR exposure. calwf3 provides undesirable results in the presence of strongly variable backgrounds, primarily in the form of elevated and non-Gaussian noise in the FLT products. Here we describe methods to improve the noise properties of the reduced products. In the first, we simply turn off the calwf3 crcorr step, treating the IR detector as if it were a CCD, i.e., accumulating flux and reading it out at the end of the exposure. Next, we artificially flatten the ramps in the IMA products and then allow calwf3 to proceed as normal fitting the ramp and identifying CRs. Either of these procedures enable recovery of datasets otherwise corrupted beyond repair and have no discernible effects on photometry of sources in deep combined images.

  8. Time-Variable Gravity from Space: Quarter Century of Observations, Mysteries, and Prospects

    Science.gov (United States)

    Chao, Benjamin F.; Boy, John-Paul

    2003-01-01

    Any large mass transport in the Earth system produces changes in the gravity field. Via the space geodetic technique of satellite-laser ranging in the last quarter century, the Earth's dynamic oblateness J2 (the lowest-degree harmonic component of the gravity field) has been observed to undergo a slight decrease -- until around 1998, when it switched quite suddenly to an increase trend which has continued to 2001 before sharply turning back to the value which it is "supposed to be"!. The secular decrease in J2 has long been attributed primarily to the post-glacial rebound in the mantle; the present increase signifies an even larger change in global mass distribution whose J2 effect overshadows that of the post-glacial rebound, at least over interannual timescales. Intriguing evidences have been found in the ocean water distribution, especially in the extratropical Pacific basins, that may be responsible for this J2 change. New techniques based on satellite-to-satellite tracking will yield greatly improved observations for time-variable gravity, with much higher precision and spatial resolution (i.e., much higher harmonic degrees). The most important example is the GRACE mission launched in March 2002, following the success of the CHAMP mission. Such observations are becoming a new and powerful tool for remote sensing of geophysical fluid processes that involve larger-scale mass transports.

  9. On the Inversion for Mass (Re)Distribution from Global (Time-Variable) Gravity Field

    Science.gov (United States)

    Chao, Benjamin F.

    2004-01-01

    The well-known non-uniqueness of the gravitational inverse problem states the following: The external gravity field, even if completely and exactly known, cannot Uniquely determine the density distribution of the body that produces the gravity field. This is an intrinsic property of a field that obeys the Laplace equation, as already treated in mathematical as well as geophysical literature. In this paper we provide conceptual insight by examining the problem in terms of spherical harmonic expansion of the global gravity field. By comparing the multipoles and the moments of the density function, we show that in 3-S the degree of knowledge deficiency in trying to inversely recover the density distribution from external gravity field is (n+l)(n+2)/2 - (2n+l) = n(n-1)/2 for each harmonic degree n. On the other hand, on a 2-D spherical shell we show via a simple relationship that the inverse solution of the surface density distribution is unique. The latter applies quite readily in the inversion of time-variable gravity signals (such as those observed by the GRACE space mission) where the sources over a wide range of the scales largely come from the Earth's Surface.

  10. Influence of climate variability on anchovy reproductive timing off northern Chile

    Science.gov (United States)

    Contreras-Reyes, Javier E.; Canales, T. Mariella; Rojas, Pablo M.

    2016-12-01

    We investigated the relationship between environmental variables and the Gonadosomatic Monthly Mean (GMM) index of anchovy (Engraulis ringens) to understand how the environment affects the dynamics of anchovy reproductive timing. The data examined corresponds to biological information collected from samples of the landings off northern Chile (18°21‧S, 24°00‧S) during the period 1990-2010. We used the Humboldt Current Index (HCI) and the Multivariate ENSO Index (MEI), which combine several physical-oceanographic factors in the Tropical and South Pacific regions. Using the GMM index, we studied the dynamics of anchovy reproductive timing at different intervals of length, specifically females with a length between 11.5 and 14 cm (medium class) and longer than 14 cm (large class). Seasonal Autoregressive Integrated Mobile Average (SARIMA) was used to predict missing observations. The trends of the environment and reproductive indexes were explored via the Breaks For Additive Season and Trend (BFAST) statistical technique and the relationship between these indexes via cross-correlation functions (CCF) analysis. Our results showed that the habitat of anchovy switched from cool to warm condition, which also influenced gonad development. This was revealed by two and three significant changes (breaks) in the trend of the HCI and MEI indexes, and two significant breaks in the GMM of each time series of anchovy females (medium and large). Negative cross-correlation between the MEI index and GMM of medium and large class females was found, indicating that as the environment gets warmer (positive value of MEI) a decrease in the reproductive activity of anchovy can be expected. Correlation between the MEI index and larger females was stronger than with medium females. Additionally, our results indicate that the GMM index of anchovy for both length classes reaches two maximums per year; the first from August to September and the second from December to January. The

  11. Field Soil Water Retention of the Prototype Hanford Barrier and Its Variability with Space and Time

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. F.

    2015-08-14

    Engineered surface barriers are used to isolate underlying contaminants from water, plants, animals, and humans. To understand the flow processes within a barrier and the barrier’s ability to store and release water, the field hydraulic properties of the barrier need to be known. In situ measurement of soil hydraulic properties and their variation over time is challenging because most measurement methods are destructive. A multiyear test of the Prototype Hanford Barrier (PHB) has yielded in situ soil water content and pressure data for a nine-year period. The upper 2 m layer of the PHB is a silt loam. Within this layer, water content and water pressure were monitored at multiple depths at 12 water balance stations using a neutron probe and heat dissipation units. Valid monitoring data from 1995 to 2003 for 4 depths at 12 monitoring stations were used to determine the field water retention of the silt loam layer. The data covered a wide range of wetness, from near saturation to the permanent wilt point, and each retention curve contained 51 to 96 data points. The data were described well with the commonly used van Genuchten water retention model. It was found that the spatial variation of the saturated and residual water content and the pore size distribution parameter were relatively small, while that of the van Genuchten alpha was relatively large. The effects of spatial variability of the retention properties appeared to be larger than the combined effects of added 15% w/w pea gravel and plant roots on the properties. Neither of the primary hydrological processes nor time had a detectible effect on the water retention of the silt loam barrier.

  12. Time series analysis of embodied interaction: Movement variability and complexity matching as dyadic properties

    Directory of Open Access Journals (Sweden)

    Leonardo Zapata-Fonseca

    2016-12-01

    Full Text Available There is a growing consensus that a fuller understanding of social cognition depends on more systematic studies of real-time social interaction. Such studies require methods that can deal with the complex dynamics taking place at multiple interdependent temporal and spatial scales, spanning sub-personal, personal, and dyadic levels of analysis. We demonstrate the value of adopting an extended multi-scale approach by re-analyzing movement time series generated in a study of embodied dyadic interaction in a minimal virtual reality environment (a perceptual crossing experiment. Reduced movement variability revealed an interdependence between social awareness and social coordination that cannot be accounted for by either subjective or objective factors alone: it picks out interactions in which subjective and objective conditions are convergent (i.e. elevated coordination is perceived as clearly social, and impaired coordination is perceived as socially ambiguous. This finding is consistent with the claim that interpersonal interaction can be partially constitutive of direct social perception. Clustering statistics (Allan Factor of salient events revealed fractal scaling. Complexity matching defined as the similarity between these scaling laws was significantly more pronounced in pairs of participants as compared to surrogate dyads. This further highlights the multi-scale and distributed character of social interaction and extends previous complexity matching results from dyadic conversation to nonverbal social interaction dynamics. Trials with successful joint interaction were also associated with an increase in local coordination. Consequently, a local coordination pattern emerges on the background of complex dyadic interactions in the PCE task and makes joint successful performance possible.

  13. Does physical fitness affect injury occurrence and time loss due to injury in elite vocational ballet students?

    Science.gov (United States)

    Twitchett, Emily; Brodrick, Anna; Nevill, Alan M; Koutedakis, Yiannis; Angioi, Manuela; Wyon, Matthew

    2010-01-01

    Most ballet dancers will suffer at least one injury a year. There are numerous causes of injury in dance, and while many investigators have documented risk factors such as anatomical characteristics, past medical history, menstrual history, dance experience, length of dance training, fatigue, and stress, risk factors related to body characteristics and nutrient intake, levels of conditioning, or physical fitness parameters have only recently received the same amount of attention. The aim of the present study was, therefore, to investigate correlations between ballet injury and body fat percentage, active and passive flexibility, lower limb power, upper body and core endurance, and aerobic capacity. Low levels of aerobic fitness were significantly associated with many of the injuries sustained over a 15-week period (r=.590, p=0.034), and body fat percentage was significantly associated with the length of time a dancer was forced to modify activity due to injury (r=-.614, p=0.026). This information may be of benefit to dancers, teachers, physical therapists and physicians in dance schools and companies when formulating strategies to prevent injury.

  14. Expressing Environment Assumptions and Real-time Requirements for a Distributed Embedded System with Shared Variables

    DEFF Research Database (Denmark)

    Tjell, Simon; Fernandes, João Miguel

    2008-01-01

    In a distributed embedded system, it is often necessary to share variables among its computing nodes to allow the distribution of control algorithms. It is therefore necessary to include a component in each node that provides the service of variable sharing. For that type of component, this paper...

  15. [Modelling the effect of local climatic variability on dengue transmission in Medellin (Colombia) by means of time series analysis].

    Science.gov (United States)

    Rúa-Uribe, Guillermo L; Suárez-Acosta, Carolina; Chauca, José; Ventosilla, Palmira; Almanza, Rita

    2013-09-01

    Dengue fever is a major impact on public health vector-borne disease, and its transmission is influenced by entomological, sociocultural and economic factors. Additionally, climate variability plays an important role in the transmission dynamics. A large scientific consensus has indicated that the strong association between climatic variables and disease could be used to develop models to explain the incidence of the disease. To develop a model that provides a better understanding of dengue transmission dynamics in Medellin and predicts increases in the incidence of the disease. The incidence of dengue fever was used as dependent variable, and weekly climatic factors (maximum, mean and minimum temperature, relative humidity and precipitation) as independent variables. Expert Modeler was used to develop a model to better explain the behavior of the disease. Climatic variables with significant association to the dependent variable were selected through ARIMA models. The model explains 34% of observed variability. Precipitation was the climatic variable showing statistically significant association with the incidence of dengue fever, but with a 20 weeks delay. In Medellin, the transmission of dengue fever was influenced by climate variability, especially precipitation. The strong association dengue fever/precipitation allowed the construction of a model to help understand dengue transmission dynamics. This information will be useful to develop appropriate and timely strategies for dengue control.

  16. Time Variations of the Radial Velocity of H2O Masers in the Semi-Regular Variable R Crt

    Science.gov (United States)

    Sudou, Hiroshi; Shiga, Motoki; Omodaka, Toshihiro; Nakai, Chihiro; Ueda, Kazuki; Takaba, Hiroshi

    2017-12-01

    H2O maser emission {at 22 GHz} in the circumstellar envelope is one of the good tracers of detailed physics and inematics in the mass loss process of asymptotic giant branch stars. Long-term monitoring of an H2O maser spectrum with high time resolution enables us to clarify acceleration processes of the expanding shell in the stellar atmosphere. We monitored the H2O maser emission of the semi-regular variable R Crt with the Kagoshima 6-m telescope, and obtained a large data set of over 180 maser spectra over a period of 1.3 years with an observational span of a few days. Using an automatic peak detection method based on least-squares fitting, we exhaustively detected peaks as significant velocity components with the radial velocity on a 0.1 km s^{-1} scale. This analysis result shows that the radial velocity of red-shifted and blue-shifted components exhibits a change between acceleration and deceleration on the time scale of a few hundred days. These velocity variations are likely to correlate with intensity variations, in particular during flaring state of H2O masers. It seems reasonable to consider that the velocity variation of the maser source is caused by shock propagation in the envelope due to stellar pulsation.However, it is difficult to explain the relationship between the velocity variation and the intensity variation only from shock propagation effects. We found that a time delay of the integrated maser intensity with respect to the optical light curve is about 150 days.

  17. Effects of the lateral amplitude and regularity of upper body fluctuation on step time variability evaluated using return map analysis.

    Science.gov (United States)

    Chidori, Kazuhiro; Yamamoto, Yuji

    2017-01-01

    The aim of this study was to evaluate the effects of the lateral amplitude and regularity of upper body fluctuation on step time variability. Return map analysis was used to clarify the relationship between step time variability and a history of falling. Eleven healthy, community-dwelling older adults and twelve younger adults participated in the study. All of the subjects walked 25 m at a comfortable speed. Trunk acceleration was measured using triaxial accelerometers attached to the third lumbar vertebrae (L3) and the seventh cervical vertebrae (C7). The normalized average magnitude of acceleration, the coefficient of determination ($R^2$) of the return map, and the step time variabilities, were calculated. Cluster analysis using the average fluctuation and the regularity of C7 fluctuation identified four walking patterns in the mediolateral (ML) direction. The participants with higher fluctuation and lower regularity showed significantly greater step time variability compared with the others. Additionally, elderly participants who had fallen in the past year had higher amplitude and a lower regularity of fluctuation during walking. In conclusion, by focusing on the time evolution of each step, it is possible to understand the cause of stride and/or step time variability that is associated with a risk of falls.

  18. Influence of variable heat transfer coefficient of fireworks and crackers on thermal explosion critical ambient temperature and time to ignition

    Directory of Open Access Journals (Sweden)

    Guo Zerong

    2016-01-01

    Full Text Available To study the effect of variable heat transfer coefficient of fireworks and crackers on thermal explosion critical ambient temperature and time to ignition, considering the heat transfer coefficient as the power function of temperature, mathematical thermal explosion steady state and unsteady-state model of finite cylindrical fireworks and crackers with complex shell structures are established based on two-dimensional steady state thermal explosion theory. The influence of variable heat transfer coefficient on thermal explosion critical ambient temperature and time to ignition are analyzed. When heat transfer coefficient is changing with temperature and in the condition of natural convection heat transfer, critical ambient temperature lessen, thermal explosion time to ignition shorten. If ambient temperature is close to critical ambient temperature, the influence of variable heat transfer coefficient on time to ignition become large. For firework with inner barrel in example analysis, the critical ambient temperature of propellant is 463.88 K and the time to ignition is 4054.9s at 466 K, 0.26 K and 450.8s less than without considering the change of heat transfer coefficient respectively. The calculation results show that the influence of variable heat transfer coefficient on thermal explosion time to ignition is greater in this example. Therefore, the effect of variable heat transfer coefficient should be considered into thermal safety evaluation of fireworks to reduce potential safety hazard.

  19. Seasonal Changes in Estuarine Dissolved Organic Matter Due to Variations in Discharge, Flushing Times and Wind-driven Mixing Events

    Science.gov (United States)

    Dixon, Jennifer Louise

    Estuaries are highly productive habitats that transport and transform organic matter (OM), experience large changes in ionic composition and act as a transition zone between terrestrial and marine environments (Paerl et al. 1998; Markager et al. 2011; Osburn et al. 2012). OM source and matrix effects (such as salinity and pH) influence the chemical structure of DOM in estuaries and therefore affect its bioavailability, photo-reactivity, and its overall fate in these systems (Jaffe et al. 2004; Boyd et al. 2010; Pace et al. 2012; Osburn et al. 2012; Cawley et al. 2013). Within estuaries, dissolved organic matter (DOM) is a heterogeneous mixture of aromatic and aliphatic compounds, and its composition in aquatic systems varies spatially and temporally with source (Bauer and Bianchi 2011). However, the main source of DOM in estuaries, rivers and other aquatic systems, originates from vascular plant detritus, soil humus, older fossil (i.e., petrogenic) organic carbon, black carbon, marine OM and in situ production (Hedges 2002; Houghton 2007; Bauer and Bianchi 2011). Chromophoric dissolved organic matter (CDOM), the light absorbing fraction of DOM, can be characterized using optical methods such as absorption and fluorescence spectroscopy (e.g. Coble, 1996; Stedmon and Markager, 2003). By analyzing the spatial and temporal variability of DOM and CDOM within estuaries, information pertaining to OM source and fate across the freshwater-marine continuum can be obtained. These methods offer an inexpensive, non-destructive means for obtaining sensitive measurements of a diverse group of organic compounds. By using this technology to analyze the spatial and temporal variability of CDOM within estuaries, information pertaining to OM source and fate across the freshwater-marine continuum can be obtained (Fellman et al. 2011; Osburn et al. 2012; Murphy et al. 2014). Chemical biomarkers are also routinely used to identify DOM sources in coastal waters. Examples are carbon stable

  20. Prospective memory and intraindividual variability in ongoing task response times in an adult lifespan sample: the role of cue focality.

    Science.gov (United States)

    Ihle, Andreas; Ghisletta, Paolo; Kliegel, Matthias

    2017-03-01

    To contribute to the ongoing conceptual debate of what traditional mean-level ongoing task (OT) costs tell us about the attentional processes underlying prospective memory (PM), we investigated costs to intraindividual variability (IIV) in OT response times as a potentially sensitive indicator of attentional processes. Particularly, we tested whether IIV in OT responses may reflect controlled employment of attentional processes versus lapses of controlled attention, whether these processes differ across adulthood, and whether it is moderated by cue focality. We assessed 150 individuals (19-82 years) in a focal and a nonfocal PM condition. In addition, external measures of inhibition and working memory were assessed. In line with the predictions of the lapses-of-attention/inefficient-executive-control account, our data support the view that costs to IIV in OT trials of PM tasks reflect fluctuations in the efficiency of executive functioning, which was related to failures in prospective remembering, particularly in nonfocal PM tasks, potentially due to their increased executive demands. The additional value of considering costs to IIV over and beyond traditional mean-level OT costs in PM research is discussed.

  1. Time Course of Heart Rate Variability Response to PM2.5 Exposure from Secondhand Smoke.

    Directory of Open Access Journals (Sweden)

    Jennifer L Garza

    Full Text Available Exposure to secondhand smoke (SHS has been associated with decreased heart rate variability (HRV. However, the time course of this association is unclear. Therefore, the objective of this study was to investigate the association between 15-240 minute SHS-related fine particulate matter (PM2.5 moving averages and indices of HRV.With a panel study design, we used personal monitors to continuously measure PM2.5 and HRV of 35 participants who were exposed to SHS for approximately 6 hours.We observed negative, significant associations between 5-minute HRV indices and 15 minute PM2.5 moving averages and 240 minute PM2.5 moving averages: there was a significant (p<0.01 7.5% decrease in the 5-minute square root of the mean squared differences of successive normal heart beats associated with (RMSSD, and a significant (p<0.01 14.7% decrease in the 5-minute high frequency (HF power associated with the 15 minute PM2.5 moving averages; there was also a significant (p<0.01 46.9% decrease in the 5-minute RMSSD, and a significant (p<0.01 77.7% decrease in the 5-minute high frequency (HF power associated with the 240 minute PM2.5 moving averages.Our findings that exposure to SHS related PM2.5 was associated with HRV support the hypothesis that SHS can affect the cardiovascular system. The negative associations reported between short and longer term PM2.5 and HRV indicate adverse effects of SHS on the cardiovascular system.

  2. Computational procedure of optimal inventory model involving controllable backorder rate and variable lead time with defective units

    Science.gov (United States)

    Lee, Wen-Chuan; Wu, Jong-Wuu; Tsou, Hsin-Hui; Lei, Chia-Ling

    2012-10-01

    This article considers that the number of defective units in an arrival order is a binominal random variable. We derive a modified mixture inventory model with backorders and lost sales, in which the order quantity and lead time are decision variables. In our studies, we also assume that the backorder rate is dependent on the length of lead time through the amount of shortages and let the backorder rate be a control variable. In addition, we assume that the lead time demand follows a mixture of normal distributions, and then relax the assumption about the form of the mixture of distribution functions of the lead time demand and apply the minimax distribution free procedure to solve the problem. Furthermore, we develop an algorithm procedure to obtain the optimal ordering strategy for each case. Finally, three numerical examples are also given to illustrate the results.

  3. Hypocretin measurement: shelf age of radioimmunoassay kit, but not freezer time, influences assay variability.

    Science.gov (United States)

    Keating, Glenda; Bliwise, Donald L; Saini, Prabhjyot; Rye, David B; Trotti, Lynn Marie

    2017-09-01

    The hypothalamic peptide hypocretin 1 (orexin A) may be assayed in cerebrospinal fluid to diagnose narcolepsy type 1. This testing is not commercially available, and factors contributing to assay variability have not previously been comprehensively explored. In the present study, cerebrospinal fluid hypocretin concentrations were determined in duplicate in 155 patient samples, across a range of sleep disorders. Intra-assay variability of these measures was analyzed. Inter-assay correlation between samples tested at Emory and at Stanford was high (r = 0.79, p hypocretin values, such that kits closer to expiration exhibit significantly more variability.

  4. AN EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF VARIABLE VALVE TIMING ON THE PERFORMANCE IN SPARK IGNITION ENGINE

    Directory of Open Access Journals (Sweden)

    Ali AKBAŞ

    2001-01-01

    Full Text Available In this study, an alternative prototype has been designed and constructed for variable valve timing systems which are used in spark ignition engines. The effects of intake valve timing and lift changing on engine performance have been investigated without changing the opening duration of the valves. A four stroke, single cylinder, spark ignition engine has been used for these experiments.

  5. Explicit Bounds to Some New Gronwall-Bellman-Type Delay Integral Inequalities in Two Independent Variables on Time Scales

    Directory of Open Access Journals (Sweden)

    Fanwei Meng

    2011-01-01

    Full Text Available Some new Gronwall-Bellman-type delay integral inequalities in two independent variables on time scales are established, which provide a handy tool in the research of qualitative and quantitative properties of solutions of delay dynamic equations on time scales. The established inequalities generalize some of the results in the work of Zhang and Meng 2008, Pachpatte 2002, and Ma 2010.

  6. Change in intraindividual variability over time as a key metric for defining performance-based cognitive fatigability.

    Science.gov (United States)

    Wang, Chao; Ding, Mingzhou; Kluger, Benzi M

    2014-03-01

    Cognitive fatigability is conventionally quantified as the increase over time in either mean reaction time (RT) or error rate from two or more time periods during sustained performance of a prolonged cognitive task. There is evidence indicating that these mean performance measures may not sufficiently reflect the response characteristics of cognitive fatigue. We hypothesized that changes in intraindividual variability over time would be a more sensitive and ecologically meaningful metric for investigations of fatigability of cognitive performance. To test the hypothesis fifteen young adults were recruited. Trait fatigue perceptions in various domains were assessed with the Multidimensional Fatigue Index (MFI). Behavioral data were then recorded during performance of a three-hour continuous cued Stroop task. Results showed that intraindividual variability, as quantified by the coefficient of variation of RT, increased linearly over the course of three hours and demonstrated a significantly greater effect size than mean RT or accuracy. Change in intraindividual RT variability over time was significantly correlated with relevant subscores of the MFI including reduced activity, reduced motivation and mental fatigue. While change in mean RT over time was also correlated with reduced motivation and mental fatigue, these correlations were significantly smaller than those associated with intraindividual RT variability. RT distribution analysis using an ex-Gaussian model further revealed that change in intraindividual variability over time reflects an increase in the exponential component of variance and may reflect attentional lapses or other breakdowns in cognitive control. These results suggest that intraindividual variability and its change over time provide important metrics for measuring cognitive fatigability and may prove useful for inferring the underlying neuronal mechanisms of both perceptions of fatigue and objective changes in performance. Copyright © 2014

  7. Time-Dependent Drug Administration in Hypertension and its Effect on Blood Pressure Variability

    Directory of Open Access Journals (Sweden)

    Magdás Annamária

    2017-06-01

    Full Text Available Background: Optimizing blood pressure variability seems to represent a new therapeutic target in the management of hypertension. It is emphasized that scheduling at least one antihypertensive agent at bedtime, has the ability to reduce blood pressure.

  8. Time-Dependent Drug Administration in Hypertension and its Effect on Blood Pressure Variability

    OpenAIRE

    Magdás Annamária; Podoleanu Cristian; Tusa Anna-Boróka; Găburoi Adina; Incze Alexandru

    2017-01-01

    Background: Optimizing blood pressure variability seems to represent a new therapeutic target in the management of hypertension. It is emphasized that scheduling at least one antihypertensive agent at bedtime, has the ability to reduce blood pressure.

  9. Constant versus variable response signal delays in speed accuracy trade-offs : Effects of advance preparation for processing time

    OpenAIRE

    Miller, Jeff; Sproesser, Gudrun; Ulrich, Rolf

    2008-01-01

    In two experiments, we used response signals (RSs) to control processing time and trace out speed accuracy trade-off (SAT) functions in a difficult perceptual discrimination task. Each experiment compared performance in blocks of trials with constant and, hence, temporally predictable RS lags against performance in blocks with variable, unpredictable RS lags. In both experiments, essentially equivalent SAT functions were observed with constant and variable RS lags. We conclude that there is l...

  10. Integrated assessment of space, time, and management-related variability of soil hydraulic properties

    Energy Technology Data Exchange (ETDEWEB)

    Es, H.M. van; Ogden, C.B.; Hill, R.L.; Schindelbeck, R.R.; Tsegaye, T.

    1999-12-01

    Computer-based models that simulate soil hydrologic processes and their impacts on crop growth and contaminant transport depend on accurate characterization of soil hydraulic properties. Soil hydraulic properties have numerous sources of variability related to spatial, temporal, and management-related processes. Soil type is considered to be the dominant source of variability, and parameterization is typically based on soil survey databases. This study evaluated the relative significance of other sources of variability: spatial and temporal at multiple scales, and management-related factors. Identical field experiments were conducted for 3 yr. at two sites in New York on clay loam and silt loam soils, and at two sites in Maryland on silt loam and sandy loam soils, all involving replicated plots with plow-till and no-till treatments. Infiltrability was determined from 2054 measurements using parameters, and Campbell's a and b parameters were determined based on water-retention data from 875 soil cores. Variance component analysis showed that differences among the sites were the most important source of variability for a (coefficient of variation, CV = 44%) and b (CV = 23%). Tillage practices were the most important source of variability for infiltrability (CV = 10%). For all properties, temporal variability was more significant than field-scale spatial variability. Temporal and tillage effects were more significant for the medium- and fine-textured soils, and correlated to initial soil water conditions. The parameterization of soil hydraulic properties solely based on soil type may not be appropriate for agricultural lands since soil-management factors are more significant. Sampling procedures should give adequate recognition to soil-management and temporal processes at significant sources of variability to avoid biased results.

  11. TIME VARIABILITY OF EMISSION LINES FOR FOUR ACTIVE T TAURI STARS. I. OCTOBER–DECEMBER IN 2010

    International Nuclear Information System (INIS)

    Chou, Mei-Yin; Takami, Michihiro; Karr, Jennifer L.; Shang Hsien; Liu, Hauyu Baobab; Manset, Nadine; Beck, Tracy; Pyo, Tae-Soo; Chen, Wen-Ping; Panwar, Neelam

    2013-01-01

    We present optical spectrophotometric monitoring of four active T Tauri stars (DG Tau, RY Tau, XZ Tau, RW Aur A) at high spectral resolution (R ∼> 1 × 10 4 ), to investigate the correlation between time variable mass ejection seen in the jet/wind structure of the driving source and time variable mass accretion probed by optical emission lines. This may allow us to constrain the understanding of the jet/wind launching mechanism, the location of the launching region, and the physical link with magnetospheric mass accretion. In 2010, observations were made at six different epochs to investigate how daily and monthly variability might affect such a study. We perform comparisons between the line profiles we observed and those in the literature over a period of decades and confirm the presence of time variability separate from the daily and monthly variability during our observations. This is so far consistent with the idea that these line profiles have a long-term variability (3-20 yr) related to episodic mass ejection suggested by the structures in the extended flow components. We also investigate the correlations between equivalent widths and between luminosities for different lines. We find that these correlations are consistent with the present paradigm of steady magnetospheric mass accretion and emission line regions that are close to the star.

  12. TIME VARIABILITY OF EMISSION LINES FOR FOUR ACTIVE T TAURI STARS. I. OCTOBER-DECEMBER IN 2010

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Mei-Yin; Takami, Michihiro; Karr, Jennifer L.; Shang Hsien; Liu, Hauyu Baobab [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Manset, Nadine [Canada-France-Hawaii Telescope, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743 (United States); Beck, Tracy [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Pyo, Tae-Soo [Subaru Telescope, 650 North Aohoku Place, Hilo, HI 96720 (United States); Chen, Wen-Ping; Panwar, Neelam [Institute of Astronomy, National Central University, Taoyuan County 32001, Taiwan (China)

    2013-04-15

    We present optical spectrophotometric monitoring of four active T Tauri stars (DG Tau, RY Tau, XZ Tau, RW Aur A) at high spectral resolution (R {approx}> 1 Multiplication-Sign 10{sup 4}), to investigate the correlation between time variable mass ejection seen in the jet/wind structure of the driving source and time variable mass accretion probed by optical emission lines. This may allow us to constrain the understanding of the jet/wind launching mechanism, the location of the launching region, and the physical link with magnetospheric mass accretion. In 2010, observations were made at six different epochs to investigate how daily and monthly variability might affect such a study. We perform comparisons between the line profiles we observed and those in the literature over a period of decades and confirm the presence of time variability separate from the daily and monthly variability during our observations. This is so far consistent with the idea that these line profiles have a long-term variability (3-20 yr) related to episodic mass ejection suggested by the structures in the extended flow components. We also investigate the correlations between equivalent widths and between luminosities for different lines. We find that these correlations are consistent with the present paradigm of steady magnetospheric mass accretion and emission line regions that are close to the star.

  13. Both Reaction Time and Accuracy Measures of Intraindividual Variability Predict Cognitive Performance in Alzheimer's Disease

    Directory of Open Access Journals (Sweden)

    Björn U. Christ

    2018-04-01

    Full Text Available Dementia researchers around the world prioritize the urgent need for sensitive measurement tools that can detect cognitive and functional change at the earliest stages of Alzheimer's disease (AD. Sensitive indicators of underlying neural pathology assist in the early detection of cognitive change and are thus important for the evaluation of early-intervention clinical trials. One method that may be particularly well-suited to help achieve this goal involves the quantification of intraindividual variability (IIV in cognitive performance. The current study aimed to directly compare two methods of estimating IIV (fluctuations in accuracy-based scores vs. those in latency-based scores to predict cognitive performance in AD. Specifically, we directly compared the relative sensitivity of reaction time (RT—and accuracy-based estimates of IIV to cognitive compromise. The novelty of the present study, however, centered on the patients we tested [a group of patients with Alzheimer's disease (AD] and the outcome measures we used (a measure of general cognitive function and a measure of episodic memory function. Hence, we compared intraindividual standard deviations (iSDs from two RT tasks and three accuracy-based memory tasks in patients with possible or probable Alzheimer's dementia (n = 23 and matched healthy controls (n = 25. The main analyses modeled the relative contributions of RT vs. accuracy-based measures of IIV toward the prediction of performance on measures of (a overall cognitive functioning, and (b episodic memory functioning. Results indicated that RT-based IIV measures are superior predictors of neurocognitive impairment (as indexed by overall cognitive and memory performance than accuracy-based IIV measures, even after adjusting for the timescale of measurement. However, one accuracy-based IIV measure (derived from a recognition memory test also differentiated patients with AD from controls, and significantly predicted episodic memory

  14. Constant versus variable response signal delays in speed--accuracy trade-offs: effects of advance preparation for processing time.

    Science.gov (United States)

    Miller, Jeff; Sproesser, Gudrun; Ulrich, Rolf

    2008-07-01

    In two experiments, we used response signals (RSs) to control processing time and trace out speed--accuracy trade-off(SAT) functions in a difficult perceptual discrimination task. Each experiment compared performance in blocks of trials with constant and, hence, temporally predictable RS lags against performance in blocks with variable, unpredictable RS lags. In both experiments, essentially equivalent SAT functions were observed with constant and variable RS lags. We conclude that there is little effect of advance preparation for a given processing time, suggesting that the discrimination mechanisms underlying SAT functions are driven solely by bottom-up information processing in perceptual discrimination tasks.

  15. Norepinephrine genes predict response time variability and methylphenidate-induced changes in neuropsychological function in attention deficit hyperactivity disorder.

    Science.gov (United States)

    Kim, Bung-Nyun; Kim, Jae-Won; Cummins, Tarrant D R; Bellgrove, Mark A; Hawi, Ziarih; Hong, Soon-Beom; Yang, Young-Hui; Kim, Hyo-Jin; Shin, Min-Sup; Cho, Soo-Churl; Kim, Ji-Hoon; Son, Jung-Woo; Shin, Yun-Mi; Chung, Un-Sun; Han, Doug-Hyun

    2013-06-01

    Noradrenergic dysfunction may be associated with cognitive impairments in attention-deficit/hyperactivity disorder (ADHD), including increased response time variability, which has been proposed as a leading endophenotype for ADHD. The aim of this study was to examine the relationship between polymorphisms in the α-2A-adrenergic receptor (ADRA2A) and norepinephrine transporter (SLC6A2) genes and attentional performance in ADHD children before and after pharmacological treatment.One hundred one medication-naive ADHD children were included. All subjects were administered methylphenidate (MPH)-OROS for 12 weeks. The subjects underwent a computerized comprehensive attention test to measure the response time variability at baseline before MPH treatment and after 12 weeks. Additive regression analyses controlling for ADHD symptom severity, age, sex, IQ, and final dose of MPH examined the association between response time variability on the comprehensive attention test measures and allelic variations in single-nucleotide polymorphisms of the ADRA2A and SLC6A2 before and after MPH treatment.Increasing possession of an A allele at the G1287A polymorphism of SLC6A2 was significantly related to heightened response time variability at baseline in the sustained (P = 2.0 × 10) and auditory selective attention (P = 1.0 × 10) tasks. Response time variability at baseline increased additively with possession of the T allele at the DraI polymorphism of the ADRA2A gene in the auditory selective attention task (P = 2.0 × 10). After medication, increasing possession of a G allele at the MspI polymorphism of the ADRA2A gene was associated with increased MPH-related change in response time variability in the flanker task (P = 1.0 × 10).Our study suggested an association between norepinephrine gene variants and response time variability measured at baseline and after MPH treatment in children with ADHD. Our results add to a growing body of evidence, suggesting that response time

  16. Expressing Environment Assumptions and Real-time Requirements for a Distributed Embedded System with Shared Variables

    DEFF Research Database (Denmark)

    Tjell, Simon; Fernandes, João Miguel

    2008-01-01

    In a distributed embedded system, it is often necessary to share variables among its computing nodes to allow the distribution of control algorithms. It is therefore necessary to include a component in each node that provides the service of variable sharing. For that type of component, this paper...... for the component. The CPN model can be used to validate the environment assumptions and the requirements. The validation is performed by execution of the model during which traces of events and states are automatically generated and evaluated against the requirements....

  17. The Key to Successful Operational Due Diligence: The right data, at the right time, analysed in the right way

    DEFF Research Database (Denmark)

    Haubjerg, Mathias; Porsgaard, Chris Berg; Herbert-Hansen, Zaza Nadja Lee

    Purpose: The purpose of this paper is to describe both qualitative and quantitative operational determinants influencing the acquisition decision in the due diligence phase of a Merger & acquisition (M&A). The operational due diligence (ODD) process is largely unexplored in extant literature....... ● Scalability & Risk – Capabilities, technologies and external environment. ● Improvement Potentials – Rationalization and Efficiency. ● Synergies - Facility consolidation, Overhead reduction, purchasing power, other redundancies.Each of these areas is supported by a range of underlying data points...... and researchers by (i) identifying operational determinants influencing the acquisition decision in the due diligence phase, and (ii) structuring a practical end-to-end framework which incorporates all supply chain elements, ensuring a comprehensive ODD. Practical implications: The research is focused around...

  18. Indian monsoon variability at different time scales: Marine and terrestrial proxy records

    Digital Repository Service at National Institute of Oceanography (India)

    Patnaik, R.; Gupta, A; Naidu, P.D.; Yadav, R.R.; Bhattacharyya, A; Kumar, M.

    Here, we present a review of the work done in India during 2007-2011 on various proxy records of monsoon variability preserved in the marine (Central Indian Basin, western, northern and eastern Arabian Sea and the Bay of Bengal) and terrestrial...

  19. Convolutions of Heavy Tailed Random Variables and Applications to Portfolio Diversification and MA(1) Time Series

    NARCIS (Netherlands)

    J.L. Geluk (Jaap); L. Peng (Liang); C.G. de Vries (Casper)

    1999-01-01

    textabstractThe paper characterizes first and second order tail behavior of convolutions of i.i.d. heavy tailed random variables with support on the real line. The result is applied to the problem of risk diversification in portfolio analysis and to the estimation of the parameter in a MA(1) model.

  20. Quantitative analysis of the improvement in omnidirectional maritime surveillance and tracking due to real-time image enhancement

    CSIR Research Space (South Africa)

    De Villiers, JP

    2011-04-01

    Full Text Available Omnidirectional camera systems are used to supplement RADAR in tracking small craft close in to the ship in a maritime environment. They can simultaneously track multiple targets to provide a more complete situational awareness. Due to their wide...

  1. Influence of climate variability versus change at multi-decadal time scales on hydrological extremes

    Science.gov (United States)

    Willems, Patrick

    2014-05-01

    Recent studies have shown that rainfall and hydrological extremes do not randomly occur in time, but are subject to multidecadal oscillations. In addition to these oscillations, there are temporal trends due to climate change. Design statistics, such as intensity-duration-frequency (IDF) for extreme rainfall or flow-duration-frequency (QDF) relationships, are affected by both types of temporal changes (short term and long term). This presentation discusses these changes, how they influence water engineering design and decision making, and how this influence can be assessed and taken into account in practice. The multidecadal oscillations in rainfall and hydrological extremes were studied based on a technique for the identification and analysis of changes in extreme quantiles. The statistical significance of the oscillations was evaluated by means of a non-parametric bootstrapping method. Oscillations in large scale atmospheric circulation were identified as the main drivers for the temporal oscillations in rainfall and hydrological extremes. They also explain why spatial phase shifts (e.g. north-south variations in Europe) exist between the oscillation highs and lows. Next to the multidecadal climate oscillations, several stations show trends during the most recent decades, which may be attributed to climate change as a result of anthropogenic global warming. Such attribution to anthropogenic global warming is, however, uncertain. It can be done based on simulation results with climate models, but it is shown that the climate model results are too uncertain to enable a clear attribution. Water engineering design statistics, such as extreme rainfall IDF or peak or low flow QDF statistics, obviously are influenced by these temporal variations (oscillations, trends). It is shown in the paper, based on the Brussels 10-minutes rainfall data, that rainfall design values may be about 20% biased or different when based on short rainfall series of 10 to 15 years length, and

  2. Estimating inter-annual variability in winter wheat sowing dates from satellite time series in Camargue, France

    Science.gov (United States)

    Manfron, Giacinto; Delmotte, Sylvestre; Busetto, Lorenzo; Hossard, Laure; Ranghetti, Luigi; Brivio, Pietro Alessandro; Boschetti, Mirco

    2017-05-01

    Crop simulation models are commonly used to forecast the performance of cropping systems under different hypotheses of change. Their use on a regional scale is generally constrained, however, by a lack of information on the spatial and temporal variability of environment-related input variables (e.g., soil) and agricultural practices (e.g., sowing dates) that influence crop yields. Satellite remote sensing data can shed light on such variability by providing timely information on crop dynamics and conditions over large areas. This paper proposes a method for analyzing time series of MODIS satellite data in order to estimate the inter-annual variability of winter wheat sowing dates. A rule-based method was developed to automatically identify a reliable sample of winter wheat field time series, and to infer the corresponding sowing dates. The method was designed for a case study in the Camargue region (France), where winter wheat is characterized by vernalization, as in other temperate regions. The detection criteria were chosen on the grounds of agronomic expertise and by analyzing high-confidence time-series vegetation index profiles for winter wheat. This automatic method identified the target crop on more than 56% (four-year average) of the cultivated areas, with low commission errors (11%). It also captured the seasonal variability in sowing dates with errors of ±8 and ±16 days in 46% and 66% of cases, respectively. Extending the analysis to the years 2002-2012 showed that sowing in the Camargue was usually done on or around November 1st (±4 days). Comparing inter-annual sowing date variability with the main local agro-climatic drivers showed that the type of preceding crop and the weather conditions during the summer season before the wheat sowing had a prominent role in influencing winter wheat sowing dates.

  3. Time Scales of the European Surface Air Temperature Variability: The Role of the 7-8 Year Cycle

    Czech Academy of Sciences Publication Activity Database

    Jajcay, Nikola; Hlinka, Jaroslav; Kravtsov, S.; Tsonis, A.A.; Paluš, Milan

    2016-01-01

    Roč. 43, č. 2 (2016), s. 902-909 ISSN 0094-8276 R&D Projects: GA MŠk LH14001 Institutional support: RVO:67985807 Keywords : 7-8 year cycle * air temperature variability * annual cycle amplitude * cross-scale interactions * seasonality * time scales Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 4.253, year: 2016

  4. Longitudinal Reliability of Self-Reported Age at Menarche in Adolescent Girls: Variability across Time and Setting

    Science.gov (United States)

    Dorn, Lorah D.; Sontag-Padilla, Lisa M.; Pabst, Stephanie; Tissot, Abbigail; Susman, Elizabeth J.

    2013-01-01

    Age at menarche is critical in research and clinical settings, yet there is a dearth of studies examining its reliability in adolescents. We examined age at menarche during adolescence, specifically, (a) average method reliability across 3 years, (b) test-retest reliability between time points and methods, (c) intraindividual variability of…

  5. A formal method for identifying distinct states of variability in time-varying sources: SGR A* as an example

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, L.; Witzel, G.; Ghez, A. M. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Longstaff, F. A. [UCLA Anderson School of Management, University of California, Los Angeles, CA 90095-1481 (United States)

    2014-08-10

    Continuously time variable sources are often characterized by their power spectral density and flux distribution. These quantities can undergo dramatic changes over time if the underlying physical processes change. However, some changes can be subtle and not distinguishable using standard statistical approaches. Here, we report a methodology that aims to identify distinct but similar states of time variability. We apply this method to the Galactic supermassive black hole, where 2.2 μm flux is observed from a source associated with Sgr A* and where two distinct states have recently been suggested. Our approach is taken from mathematical finance and works with conditional flux density distributions that depend on the previous flux value. The discrete, unobserved (hidden) state variable is modeled as a stochastic process and the transition probabilities are inferred from the flux density time series. Using the most comprehensive data set to date, in which all Keck and a majority of the publicly available Very Large Telescope data have been merged, we show that Sgr A* is sufficiently described by a single intrinsic state. However, the observed flux densities exhibit two states: noise dominated and source dominated. Our methodology reported here will prove extremely useful to assess the effects of the putative gas cloud G2 that is on its way toward the black hole and might create a new state of variability.

  6. Temperature field due to time-dependent heat sources in a large rectangular grid - Derivation of analytical solution

    International Nuclear Information System (INIS)

    Claesson, J.; Probert, T.

    1996-01-01

    The temperature field in rock due to a large rectangular grid of heat releasing canisters containing nuclear waste is studied. The solution is by superposition divided into different parts. There is a global temperature field due to the large rectangular canister area, while a local field accounts for the remaining heat source problem. The global field is reduced to a single integral. The local field is also solved analytically using solutions for a finite line heat source and for an infinite grid of point sources. The local solution is reduced to three parts, each of which depends on two spatial coordinates only. The temperatures at the envelope of a canister are given by a single thermal resistance, which is given by an explicit formula. The results are illustrated by a few numerical examples dealing with the KBS-3 concept for storage of nuclear waste. 8 refs

  7. Predictor variables for a half marathon race time in recreational male runners

    OpenAIRE

    Rüst, C A; Knechtle, B; Knechtle, P; Barandun, U; Lepers, R; Rosemann, T

    2011-01-01

    Christoph Alexander Rüst1, Beat Knechtle1,2, Patrizia Knechtle2, Ursula Barandun1, Romuald Lepers3, Thomas Rosemann11Institute of General Practice and Health Services Research, University of Zurich, Zurich, Switzerland; 2Gesundheitszentrum St Gallen, St Gallen, Switzerland; 3INSERM U887, University of Burgundy, Faculty of Sport Sciences, Dijon, FranceAbstract: The aim of this study was to investigate predictor variables of anthropometry, training, and previous experience in order to ...

  8. Photometry of Variable Stars, and System Transformability Over Long Time Intervals

    Directory of Open Access Journals (Sweden)

    Sterken C.

    2003-12-01

    Full Text Available The fundamental problem of long-term photometric monitoring of variable stars and of multi-wavelength photometric campaigns is the problem of bringing the data to a common standard. Such homogenization can be achieved only when the measurements are made in photometric systems that are truly transformable. This fundamental problem is of a technical nature, and photometric observers, sometimes, are not aware of the problems. This frequently leads to over-interpretation of the data.

  9. Area-averaged surface fluxes and their time-space variability over the FIFE experimental domain

    Science.gov (United States)

    Smith, E. A.; Hsu, A. Y.; Crosson, W. L.; Field, R. T.; Fritschen, L. J.; Gurney, R. J.; Kanemasu, E. T.; Kustas, W. P.; Nie, D.; Shuttleworth, W. J.

    1992-01-01

    The underlying mean and variance properties of surface net radiation, sensible-latent heat fluxes and soil heat flux are studied over the densely instrumented grassland region encompassing FIFE. Flux variability is discussed together with the problem of scaling up to area-averaged fluxes. Results are compared and contrasted for cloudy and clear situations and examined for the influence of surface-induced biophysical controls (burn and grazing treatments) and topographic controls (aspect ratios and slope factors).

  10. Convolutions of Heavy Tailed Random Variables and Applications to Portfolio Diversification and MA(1) Time Series

    OpenAIRE

    Geluk, Jaap; Peng, Liang; de Vries, Casper G.

    1999-01-01

    Suppose X1,X2 are independent random variables satisfying a second-order regular variation condition on the tail-sum and a balance condition on the tails. In this paper we give a description of the asymptotic behaviour as t → ∞ for P(X1 + X2 > t). The result is applied to the problem of risk diversification in portfolio analysis and to the estimation of the parameter in a MA(1) model.

  11. A Computational Model for Real-Time Calculation of Electric Field due to Transcranial Magnetic Stimulation in Clinics

    Directory of Open Access Journals (Sweden)

    Alessandra Paffi

    2015-01-01

    Full Text Available The aim of this paper is to propose an approach for an accurate and fast (real-time computation of the electric field induced inside the whole brain volume during a transcranial magnetic stimulation (TMS procedure. The numerical solution implements the admittance method for a discretized realistic brain model derived from Magnetic Resonance Imaging (MRI. Results are in a good agreement with those obtained using commercial codes and require much less computational time. An integration of the developed code with neuronavigation tools will permit real-time evaluation of the stimulated brain regions during the TMS delivery, thus improving the efficacy of clinical applications.

  12. Variability in stratification and flushing times of the Gautami-Godavari estuary, India

    Digital Repository Service at National Institute of Oceanography (India)

    Sridevi, B.; Sarma, V.V.S.S.; Murty, T.V.R.; Sadhuram, Y.; Reddy, N.P.C.; Vijaykumar, K.; Raju, N.S.N.; JawaharKumar, CH.; Raju, Y.S.N.; Luis, R.; Kumar, M.D.; Prasad, K.V.S.R.

    –Godavari estuary (G–GE) during spring and neap tide periods covering entire spectrum of discharge over a distance of 36 km from the mouth. The bathymetry of the estuary was recently changed due to dredging of ~20 km of the estuary from the mouth for transportation...

  13. Injury hospitalizations due to unintentional falls among the Aboriginal population of British Columbia, Canada: incidence, changes over time, and ecological analysis of risk markers, 1991-2010.

    Directory of Open Access Journals (Sweden)

    Andrew Jin

    Full Text Available Aboriginal people in British Columbia (BC have higher injury incidence than the general population. Our project describes variability among injury categories, time periods, and geographic, demographic and socio-economic groups. This report focuses on unintentional falls.We used BC's universal health care insurance plan as a population registry, linked to hospital separation and vital statistics databases. We identified Aboriginal people by insurance premium group and birth and death record notations. We identified residents of specific Aboriginal communities by postal code. We calculated crude incidence and Standardized Relative Risk (SRR of hospitalization for unintentional fall injury, standardized for age, gender and Health Service Delivery Area (HSDA, relative to the total population of BC. We tested hypothesized associations of geographic, socio-economic, and employment-related characteristics with community SRR of injury by linear regression.During 1991 through 2010, the crude rate of hospitalization for unintentional fall injury in BC was 33.6 per 10,000 person-years. The Aboriginal rate was 49.9 per 10,000 and SRR was 1.89 (95% confidence interval 1.85-1.94. Among those living on reserves SRR was 2.00 (95% CI 1.93-2.07. Northern and non-urban HSDAs had higher SRRs, within both total and Aboriginal populations. In every age and gender category, the HSDA-standardized SRR was higher among the Aboriginal than among the total population. Between 1991 and 2010, crude rates and SRRs declined substantially, but proportionally more among the Aboriginal population, so the gap between the Aboriginal and total population is narrowing, particularly among females and older adults. These community characteristics were associated with higher risk: lower income, lower educational level, worse housing conditions, and more hazardous types of employment.Over the years, as socio-economic conditions improve, risk of hospitalization due to unintentional fall

  14. Injury hospitalizations due to unintentional falls among the Aboriginal population of British Columbia, Canada: incidence, changes over time, and ecological analysis of risk markers, 1991-2010.

    Science.gov (United States)

    Jin, Andrew; Lalonde, Christopher E; Brussoni, Mariana; McCormick, Rod; George, M Anne

    2015-01-01

    Aboriginal people in British Columbia (BC) have higher injury incidence than the general population. Our project describes variability among injury categories, time periods, and geographic, demographic and socio-economic groups. This report focuses on unintentional falls. We used BC's universal health care insurance plan as a population registry, linked to hospital separation and vital statistics databases. We identified Aboriginal people by insurance premium group and birth and death record notations. We identified residents of specific Aboriginal communities by postal code. We calculated crude incidence and Standardized Relative Risk (SRR) of hospitalization for unintentional fall injury, standardized for age, gender and Health Service Delivery Area (HSDA), relative to the total population of BC. We tested hypothesized associations of geographic, socio-economic, and employment-related characteristics with community SRR of injury by linear regression. During 1991 through 2010, the crude rate of hospitalization for unintentional fall injury in BC was 33.6 per 10,000 person-years. The Aboriginal rate was 49.9 per 10,000 and SRR was 1.89 (95% confidence interval 1.85-1.94). Among those living on reserves SRR was 2.00 (95% CI 1.93-2.07). Northern and non-urban HSDAs had higher SRRs, within both total and Aboriginal populations. In every age and gender category, the HSDA-standardized SRR was higher among the Aboriginal than among the total population. Between 1991 and 2010, crude rates and SRRs declined substantially, but proportionally more among the Aboriginal population, so the gap between the Aboriginal and total population is narrowing, particularly among females and older adults. These community characteristics were associated with higher risk: lower income, lower educational level, worse housing conditions, and more hazardous types of employment. Over the years, as socio-economic conditions improve, risk of hospitalization due to unintentional fall injury has

  15. Cost consequences due to reduced ulcer healing times - analyses based on the Swedish Registry of Ulcer Treatment.

    Science.gov (United States)

    Öien, Rut F; Forssell, Henrik; Ragnarson Tennvall, Gunnel

    2016-10-01

    Resource use and costs for topical treatment of hard-to-heal ulcers based on data from the Swedish Registry of Ulcer Treatment (RUT) were analysed in patients recorded in RUT as having healed between 2009 and 2012, in order to estimate potential cost savings from reductions in frequency of dressing changes and healing times. RUT is used to capture areas of improvement in ulcer care and to enable structured wound management by registering patients with hard-to-heal leg, foot and pressure ulcers. Patients included in the registry are treated in primary care, community care, private care, and inpatient hospital care. Cost calculations were based on resource use data on healing time and frequency of dressing changes in Swedish patients with hard-to-heal ulcers who healed between 2009 and 2012. Per-patient treatment costs decreased from SEK38 223 in 2009 to SEK20 496 in 2012, mainly because of shorter healing times. Frequency of dressing changes was essentially the same during these years, varying from 1·4 to 1·6 per week. The total healing time was reduced by 38%. Treatment costs for the management of hard-to-heal ulcers can be reduced with well-developed treatment strategies resulting in shortened healing times as shown in RUT. © 2015 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

  16. Hong-Ou-Mandel effect in terms of the temporal biphoton wave function with two arrival-time variables

    Science.gov (United States)

    Fedorov, M. V.; Sysoeva, A. A.; Vintskevich, S. V.; Grigoriev, D. A.

    2018-03-01

    The well-known Hong-Ou-Mandel effect is revisited. Two physical reasons are discussed for the effect to be less pronounced or even to disappear: differing polarizations of photons coming to the beamsplitter and delay time of photons in one of two channels. For the latter we use the concepts of biphoton frequency and temporal wave functions depending, correspondingly, on two frequency continuous variables of photons and on two time variables t 1 and t 2 interpreted as the arrival times of photons to the beamsplitter. Explicit expressions are found for the probability densities and total probabilities for photon pairs to be split between two channels after the beamsplitter and to be unsplit, when two photons appear together in one of two channels.

  17. Using Variable Dwell Time to Accelerate Gaze-based Web Browsing with Two-step Selection

    OpenAIRE

    Chen, Zhaokang; Shi, Bertram E.

    2017-01-01

    In order to avoid the "Midas Touch" problem, gaze-based interfaces for selection often introduce a dwell time: a fixed amount of time the user must fixate upon an object before it is selected. Past interfaces have used a uniform dwell time across all objects. Here, we propose an algorithm for adjusting the dwell times of different objects based on the inferred probability that the user intends to select them. In particular, we introduce a probabilistic model of natural gaze behavior while sur...

  18. Modelling accuracy and variability of motor timing in treated and untreated Parkinson’s disease and healthy controls

    Directory of Open Access Journals (Sweden)

    Catherine Rhian Gwyn Jones

    2011-12-01

    Full Text Available Parkinson’s disease (PD is characterised by difficulty with the timing of movements. Data collected using the synchronization-continuation paradigm, an established motor timing paradigm, have produced varying results but with most studies finding impairment. Some of this inconsistency comes from variation in the medication state tested, in the inter-stimulus intervals (ISI selected, and in changeable focus on either the synchronization (tapping in time with a tone or continuation (maintaining the rhythm in the absence of the tone phase. We sought to re-visit the paradigm by testing across four groups of participants: healthy controls, medication naïve de novo PD patients, and treated PD patients both ‘on’ and ‘off’ dopaminergic medication. Four finger tapping intervals (ISI were used: 250ms, 500ms, 1000ms and 2000ms. Categorical predictors (group, ISI, and phase were used to predict accuracy and variability using a linear mixed model. Accuracy was defined as the relative error of a tap, and variability as the deviation of the participant’s tap from group predicted relative error. Our primary finding is that the treated PD group (PD patients ‘on’ and ‘off’ dopaminergic therapy showed a significantly different pattern of accuracy compared to the de novo group and the healthy controls at the 250ms interval. At this interval, the treated PD patients performed ‘ahead’ of the beat whilst the other groups performed ‘behind’ the beat. We speculate that this ‘hastening’ relates to the clinical phenomenon of motor festination. Across all groups, variability was smallest for both phases at the 500 ms interval, suggesting an innate preference for finger tapping within this range. Tapping variability for the two phases became increasingly divergent at the longer intervals, with worse performance in the continuation phase. The data suggest that patients with PD can be best discriminated from healthy controls on measures of

  19. Physiological age at harvest regulates the variability in postharvest ripening, sensory and nutritional characteristics of mango (Mangifera indica L.) cv. Coghshall due to growing conditions.

    Science.gov (United States)

    Joas, Jacques; Vulcain, Emmanuelle; Desvignes, Claire; Morales, Emeline; Léchaudel, Mathieu

    2012-04-01

    Climacteric fruits are harvested at the green-mature stage and ripen during their marketing cycle. However, growing conditions induce variability into the maturity stage of mangoes at harvest, with an impact on their final quality. Assuming that the physiological age can be correctly evaluated by a criterion based on the variable chlorophyll fluorescence of the skin (F(v)) and that differences in physiological age depend on growing conditions, controlled stress experiments were carried out on mango fruit by manipulating either the leaf/fruit ratio or the light environment. Delays from 9 to 30 days were observed, depending on stress level and harvest stage, to obtain the same F(v) value. For moderate stress, fruit composition after ripening was partially compensated for, with little or no difference in sugar, dry matter, carotenoid and aroma contents. For more pronounced stress, the major metabolites were not particularly affected, but the synthesis capacity of carotenoids and aromas was lower after maturity. The ripening ability of a fruit is acquired on the tree and defines its postharvest changes. Control of the physiological age at harvest can minimise the variability observed under natural conditions and guarantee fruit batches whose postharvest changes will be relatively homogeneous. Copyright © 2011 Society of Chemical Industry.

  20. Real-time prediction of extreme ambient carbon monoxide concentrations due to vehicular exhaust emissions using univariate linear stochastic models

    International Nuclear Information System (INIS)

    Sharma, P.; Khare, M.

    2000-01-01

    Historical data of the time-series of carbon monoxide (CO) concentration was analysed using Box-Jenkins modelling approach. Univariate Linear Stochastic Models (ULSMs) were developed to examine the degree of prediction possible for situations where only a limited data set, restricted only to the past record of pollutant data are available. The developed models can be used to provide short-term, real-time forecast of extreme CO concentrations for an Air Quality Control Region (AQCR), comprising a major traffic intersection in a Central Business District of Delhi City, India. (author)

  1. Leisure time physical activity and the risk of hip or knee replacement due to primary osteoarthritis: a population based cohort study (The HUNT Study).

    Science.gov (United States)

    Johnsen, Marianne Bakke; Hellevik, Alf Inge; Baste, Valborg; Furnes, Ove; Langhammer, Arnulf; Flugsrud, Gunnar; Nordsletten, Lars; Zwart, John Anker; Storheim, Kjersti

    2016-02-16

    The relationship between leisure time physical activity (LPA) and hip and knee OA and subsequent joint replacement has not yet been clearly defined. Some studies have found the risk of knee replacement (TKR) to increase with high levels of LPA, while others have found no overall relationship to either TKR or hip replacement (THR). The aim was to investigate the association between LPA and the risk of severe end-stage OA, defined as THR or TKR due to primary OA, in a large population-based cohort. Participants in the Nord-Trøndelag Health Study (HUNT) were followed prospectively to identify THR and TKR using the Norwegian Arthroplasty Register. Self-reported LPA was classified as inactive, low, moderate or high. The Cox proportional hazards model was used to calculate hazard ratios (HRs) according to levels of LPA with adjustments for confounding variables. Analyses were performed by age (<45, 45-59 and ≥60 years) and sex. A total of 66 964 participants (mean age 46.8 years (SD 16.3) were included in the analyses. We identified 1636 THRs and 1016 TKRs due to primary OA during 17.0 years (median) of follow-up. High LPA was significantly associated with THR for women <45 years (HR 1.78, 95 % CI 1.08-2.94) and men between 45-59 years (HR 1.53, 95 % CI 1.10-2.13) at baseline. A significant trend was found only among women < 45 years at baseline (p = 0.02). We found that LPA was significantly associated with TKR for women only (HR 1.45, 95 % CI 1.03-2.04). No measures of LPA were associated with TKR for men. In this population-based study, high level of LPA was associated with increased risk of THR where a significant trend of LPA was seen among women <45 years at baseline. For TKR, high LPA was associated with increased risk only in women. In contrast to previous studies, this study shows a possible association between high LPA and the risk of THR.

  2. Time dependence of the UV resonance lines in the cataclysmic variables SU UMa, RX And and 0623+71

    International Nuclear Information System (INIS)

    Woods, J.A.; Drew, J.E.; Verbunt, Frank

    1990-01-01

    We present IUE observations of the dwarf novae SU UMa and RX And, and of the nova-like variable 0623 + 71. At the time of observation, SU UMa and RX And were in outburst. All three systems show variability in the wind-formed UV resonance lines of N v λ 1240, Si IV λ 1397 and C IV λ 1549 on timescale of hours. The amplitude of variation is smallest in RX And and largest in 0623 + 71. There is evidence that the variations observed in SU UMa's UV spectrum repeat on the orbital period. Our observations of SU UMa also reveal variability in the continuum flux during the decline from outburst maximum that is much more marked in the UV than at optical wavelengths. (author)

  3. Determining patterns of variability in ecological communities: time lag analysis revisited

    NARCIS (Netherlands)

    Kampichler, C.; Van der Jeugd, H.P.

    2013-01-01

    All ecological communities experience change over time. One method to quantify temporal variation in the patterns of relative abundance of communities is time lag analysis (TLA). It uses a distance-based approach to study temporal community dynamics by regressing community dissimilarity over

  4. Determinants of variability in waiting times for radiotherapy in the treatment of breast cancer

    International Nuclear Information System (INIS)

    Bouche, Gauthier; Ingrand, Isabelle; Mathoulin-Pelissier, Simone; Ingrand, Pierre; Breton-Callu, Christel; Migeot, Virginie

    2010-01-01

    Purpose: To examine psycho-social and geographic determinants of delay in starting radiotherapy in early invasive breast cancer patients. Material and methods: Waiting time was defined as the time elapsed until the beginning of radiotherapy, starting from the date of surgery (in absence of chemotherapy) or from the end of chemotherapy. Results: Eight hundred and ninety six women aged 24-89 took part in the study. Mean waiting times were 52 days (sd = 19) between surgery and radiotherapy and 31 days (sd = 14) between chemotherapy and radiotherapy. Differences between radiotherapy centres (p < 0.0001) accounted for 30% and 12%, respectively, of total variance in waiting times. Using a multivariate mixed analysis that took into account intra-centre correlation, the time between surgery and radiotherapy was shorter for young patients (p = 0.020), those who had sought information about their illness (p = 0.024) and those who had undergone surgery and radiotherapy in the same centre (p = 0.021). On the other hand, no patient characteristic was associated with the time between chemotherapy and radiotherapy. Conclusion: Centre is the major factor that explained longer waiting times in radiotherapy, emphasising the structural hypothesis. It is important to pursue initiatives to improve the organization within radiotherapy centres and then to verify that these initiatives have succeeded in shortening waiting times.

  5. Modeling category-level purchase timing with brand-level marketing variables

    NARCIS (Netherlands)

    D. Fok (Dennis); R. Paap (Richard)

    2003-01-01

    textabstractPurchase timing of households is usually modeled at the category level. Marketing efforts are however only available at the brand level. Hence, to describe category-level interpurchase times using marketing efforts one has to construct a category-level measure of marketing efforts from

  6. Compaction creep of sands due to time-dependent grain failure : Effects of chemical environment, applied stress, and grain size

    NARCIS (Netherlands)

    Brzesowsky, R. H.; Hangx, S. J. T.|info:eu-repo/dai/nl/30483579X; Brantut, N.; Spiers, C. J.|info:eu-repo/dai/nl/304829323

    2014-01-01

    Time-dependent brittle creep plays a role in controlling compaction of sands and sandstones under upper crustal conditions, influencing phenomena such as production-induced reservoir compaction, surface subsidence, and induced seismicity. Brittle creep also plays a role in determining the mechanical

  7. Short time-scale optical variability properties of the largest AGN sample observed with Kepler/K2

    Science.gov (United States)

    Aranzana, E.; Körding, E.; Uttley, P.; Scaringi, S.; Bloemen, S.

    2018-05-01

    We present the first short time-scale (˜hours to days) optical variability study of a large sample of active galactic nuclei (AGNs) observed with the Kepler/K2 mission. The sample contains 252 AGN observed over four campaigns with ˜30 min cadence selected from the Million Quasar Catalogue with R magnitude <19. We performed time series analysis to determine their variability properties by means of the power spectral densities (PSDs) and applied Monte Carlo techniques to find the best model parameters that fit the observed power spectra. A power-law model is sufficient to describe all the PSDs of our sample. A variety of power-law slopes were found indicating that there is not a universal slope for all AGNs. We find that the rest-frame amplitude variability in the frequency range of 6 × 10-6-10-4 Hz varies from 1to10 per cent with an average of 1.7 per cent. We explore correlations between the variability amplitude and key parameters of the AGN, finding a significant correlation of rest-frame short-term variability amplitude with redshift. We attribute this effect to the known `bluer when brighter' variability of quasars combined with the fixed bandpass of Kepler data. This study also enables us to distinguish between Seyferts and blazars and confirm AGN candidates. For our study, we have compared results obtained from light curves extracted using different aperture sizes and with and without detrending. We find that limited detrending of the optimal photometric precision light curve is the best approach, although some systematic effects still remain present.

  8. Uncertainty in the Future Distribution of Tropospheric Ozone over West Africa due to Variability in Anthropogenic Emissions Estimates between 2025 and 2050

    Directory of Open Access Journals (Sweden)

    J. E. Williams

    2011-01-01

    Full Text Available Particle and trace gas emissions due to anthropogenic activity are expected to increase significantly in West Africa over the next few decades due to rising population and more energy intensive lifestyles. Here we perform 3D global chemistry-transport model calculations for 2025 and 2050 using both a “business-as-usual” (A1B and “clean economy” (B1 future anthropogenic emission scenario to focus on the changes in the distribution and uncertainties associated with tropospheric O3 due to the various projected emission scenarios. When compared to the present-day troposphere we find that there are significant increases in tropospheric O3 for the A1B emission scenario, with the largest increases being located in the lower troposphere near the source regions and into the Sahel around 15–20°N. In part this increase is due to more efficient NOx re-cycling related to increases in the background methane concentrations. Examining the uncertainty across different emission inventories reveals that there is an associated uncertainty of up to ~20% in the predicted increases at 2025 and 2050. For the upper troposphere, where increases in O3 have a more pronounced impact on radiative forcing, the uncertainty is influenced by transport of O3 rich air from Asia on the Tropical Easterly Jet.

  9. Estimate of the global-scale joule heating rates in the thermosphere due to time mean currents

    International Nuclear Information System (INIS)

    Roble, R.G.; Matsushita, S.

    1975-01-01

    An estimate of the global-scale joule heating rates in the thermosphere is made based on derived global equivalent overhead electric current systems in the dynamo region during geomagnetically quiet and disturbed periods. The equivalent total electric field distribution is calculated from Ohm's law. The global-scale joule heating rates are calculated for various monthly average periods in 1965. The calculated joule heating rates maximize at high latitudes in the early evening and postmidnight sectors. During geomagnetically quiet times the daytime joule heating rates are considerably lower than heating by solar EUV radiation. However, during geomagnetically disturbed periods the estimated joule heating rates increase by an order of magnitude and can locally exceed the solar EUV heating rates. The results show that joule heating is an important and at times the dominant energy source at high latitudes. However, the global mean joule heating rates calculated near solar minimum are generally small compared to the global mean solar EUV heating rates. (auth)

  10. Time-dependent changes in pulmonary surfactant function and composition in acute respiratory distress syndrome due to pneumonia or aspiration

    Directory of Open Access Journals (Sweden)

    Kuchenbuch Tim

    2007-07-01

    Full Text Available Abstract Background Alterations to pulmonary surfactant composition have been encountered in the Acute Respiratory Distress Syndrome (ARDS. However, only few data are available regarding the time-course and duration of surfactant changes in ARDS patients, although this information may largely influence the optimum design of clinical trials addressing surfactant replacement therapy. We therefore examined the time-course of surfactant changes in 15 patients with direct ARDS (pneumonia, aspiration over the first 8 days after onset of mechanical ventilation. Methods Three consecutive bronchoalveolar lavages (BAL were performed shortly after intubation (T0, and four days (T1 and eight days (T2 after intubation. Fifteen healthy volunteers served as controls. Phospholipid-to-protein ratio in BAL fluids, phospholipid class profiles, phosphatidylcholine (PC molecular species, surfactant proteins (SP-A, -B, -C, -D, and relative content and surface tension properties of large surfactant aggregates (LA were assessed. Results At T0, a severe and highly significant reduction in SP-A, SP-B and SP-C, the LA fraction, PC and phosphatidylglycerol (PG percentages, and dipalmitoylation of PC (DPPC was encountered. Surface activity of the LA fraction was greatly impaired. Over time, significant improvements were encountered especially in view of LA content, DPPC, PG and SP-A, but minimum surface tension of LA was not fully restored (15 mN/m at T2. A highly significant correlation was observed between PaO2/FiO2 and minimum surface tension (r = -0.83; p Conclusion We concluded that a profound impairment of pulmonary surfactant composition and function occurs in the very early stage of the disease and only gradually resolves over time. These observations may explain why former surfactant replacement studies with a short treatment duration failed to improve outcome and may help to establish optimal composition and duration of surfactant administration in future

  11. Time evolution of scattering states and velocity increase due to nonlinear processes in the quantum hall regime

    International Nuclear Information System (INIS)

    Riess, J.; Duport, C.

    1991-01-01

    We report the first numerical results (with realistic parameter values) for the time evolution of a scattered Landau function in a model system. They give a striking illustration for the Hall velocity increase beyond the classical value of the conduction electrons in the quantum Hall regime. This phenomenon, which is crucial for the integer quantum Hall effect, is caused by a special kind of nonclassical particle dynamics induced by disorder and cannot be described by linear response theory

  12. Estimate of overdiagnosis of breast cancer due to mammography after adjustment for lead time. A service screening study in Italy

    Science.gov (United States)

    Paci, Eugenio; Miccinesi, Guido; Puliti, Donella; Baldazzi, Paola; De Lisi, Vincenzo; Falcini, Fabio; Cirilli, Claudia; Ferretti, Stefano; Mangone, Lucia; Finarelli, Alba Carola; Rosso, Stefano; Segnan, Nereo; Stracci, Fabrizio; Traina, Adele; Tumino, Rosario; Zorzi, Manuel

    2006-01-01

    Introduction Excess of incidence rates is the expected consequence of service screening. The aim of this paper is to estimate the quota attributable to overdiagnosis in the breast cancer screening programmes in Northern and Central Italy. Methods All patients with breast cancer diagnosed between 50 and 74 years who were resident in screening areas in the six years before and five years after the start of the screening programme were included. We calculated a corrected-for-lead-time number of observed cases for each calendar year. The number of observed incident cases was reduced by the number of screen-detected cases in that year and incremented by the estimated number of screen-detected cases that would have arisen clinically in that year. Results In total we included 13,519 and 13,999 breast cancer cases diagnosed in the pre-screening and screening years, respectively. In total, the excess ratio of observed to predicted in situ and invasive cases was 36.2%. After correction for lead time the excess ratio was 4.6% (95% confidence interval 2 to 7%) and for invasive cases only it was 3.2% (95% confidence interval 1 to 6%). Conclusion The remaining excess of cancers after individual correction for lead time was lower than 5%. PMID:17147789

  13. Supervised learning based model for predicting variability-induced timing errors

    NARCIS (Netherlands)

    Jiao, X.; Rahimi, A.; Narayanaswamy, B.; Fatemi, H.; Pineda de Gyvez, J.; Gupta, R.K.

    2015-01-01

    Circuit designers typically combat variations in hardware and workload by increasing conservative guardbanding that leads to operational inefficiency. Reducing this excessive guardband is highly desirable, but causes timing errors in synchronous circuits. We propose a methodology for supervised

  14. Flexible and scalable methods for quantifying stochastic variability in the era of massive time-domain astronomical data sets

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Brandon C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530 (United States); Becker, Andrew C. [Department of Astronomy, University of Washington, P.O. Box 351580, Seattle, WA 98195-1580 (United States); Sobolewska, Malgosia [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716, Warsaw (Poland); Siemiginowska, Aneta [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Uttley, Phil [Astronomical Institute Anton Pannekoek, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands)

    2014-06-10

    We present the use of continuous-time autoregressive moving average (CARMA) models as a method for estimating the variability features of a light curve, and in particular its power spectral density (PSD). CARMA models fully account for irregular sampling and measurement errors, making them valuable for quantifying variability, forecasting and interpolating light curves, and variability-based classification. We show that the PSD of a CARMA model can be expressed as a sum of Lorentzian functions, which makes them extremely flexible and able to model a broad range of PSDs. We present the likelihood function for light curves sampled from CARMA processes, placing them on a statistically rigorous foundation, and we present a Bayesian method to infer the probability distribution of the PSD given the measured light curve. Because calculation of the likelihood function scales linearly with the number of data points, CARMA modeling scales to current and future massive time-domain data sets. We conclude by applying our CARMA modeling approach to light curves for an X-ray binary, two active galactic nuclei, a long-period variable star, and an RR Lyrae star in order to illustrate their use, applicability, and interpretation.

  15. Assessing the Impact of Climate Variability on Cropland Productivity in the Canadian Prairies Using Time Series MODIS FAPAR

    Directory of Open Access Journals (Sweden)

    Taifeng Dong

    2016-03-01

    Full Text Available Cropland productivity is impacted by climate. Knowledge on spatial-temporal patterns of the impacts at the regional scale is extremely important for improving crop management under limiting climatic factors. The aim of this study was to investigate the effects of climate variability on cropland productivity in the Canadian Prairies between 2000 and 2013 based on time series of MODIS (Moderate Resolution Imaging Spectroradiometer FAPAR (Fraction of Absorbed Photosynthetically Active Radiation product. Key phenological metrics, including the start (SOS and end of growing season (EOS, and the cumulative FAPAR (CFAPAR during the growing season (between SOS and EOS, were extracted and calculated from the FAPAR time series with the Parametric Double Hyperbolic Tangent (PDHT method. The Mann-Kendall test was employed to assess the trends of cropland productivity and climatic variables, and partial correlation analysis was conducted to explore the potential links between climate variability and cropland productivity. An assessment using crop yield statistical data showed that CFAPAR can be taken as a surrogate of cropland productivity in the Canadian Prairies. Cropland productivity showed an increasing trend in most areas of Canadian Prairies, in general, during the period from 2000 to 2013. Interannual variability in cropland productivity on the Canadian Prairies was influenced positively by rainfall variation and negatively by mean air temperature.

  16. Flexible and scalable methods for quantifying stochastic variability in the era of massive time-domain astronomical data sets

    International Nuclear Information System (INIS)

    Kelly, Brandon C.; Becker, Andrew C.; Sobolewska, Malgosia; Siemiginowska, Aneta; Uttley, Phil

    2014-01-01

    We present the use of continuous-time autoregressive moving average (CARMA) models as a method for estimating the variability features of a light curve, and in particular its power spectral density (PSD). CARMA models fully account for irregular sampling and measurement errors, making them valuable for quantifying variability, forecasting and interpolating light curves, and variability-based classification. We show that the PSD of a CARMA model can be expressed as a sum of Lorentzian functions, which makes them extremely flexible and able to model a broad range of PSDs. We present the likelihood function for light curves sampled from CARMA processes, placing them on a statistically rigorous foundation, and we present a Bayesian method to infer the probability distribution of the PSD given the measured light curve. Because calculation of the likelihood function scales linearly with the number of data points, CARMA modeling scales to current and future massive time-domain data sets. We conclude by applying our CARMA modeling approach to light curves for an X-ray binary, two active galactic nuclei, a long-period variable star, and an RR Lyrae star in order to illustrate their use, applicability, and interpretation.

  17. Modeling category-level purchase timing with brand-level marketing variables

    OpenAIRE

    Fok, D.; Paap, R.

    2003-01-01

    textabstractPurchase timing of households is usually modeled at the category level. Marketing efforts are however only available at the brand level. Hence, to describe category-level interpurchase times using marketing efforts one has to construct a category-level measure of marketing efforts from the marketing mix of individual brands. In this paper we discuss two standard approaches suggested in the literature to solve this problem, that is, using individual choice shares as weights to aver...

  18. Quantum Stephani exact cosmological solutions and the selection of time variable

    International Nuclear Information System (INIS)

    Pedram, P; Jalalzadeh, S; Gousheh, S S

    2007-01-01

    We study a perfect fluid Stephani quantum cosmological model. In the present work, the Schutz's variational formalism which recovers the notion of time is applied. This gives rise to a Wheeler-DeWitt equation for the scale factor. We use the eigenfunctions in order to construct wave packets for each case. We study the time-dependent behavior of the expectation value of the scale factor, using many-worlds and de Broglie-Bohm interpretations of quantum mechanics

  19. Total sitting time, leisure time physical activity and risk of hospitalization due to low back pain: The Danish Health Examination Survey cohort 2007-2008.

    Science.gov (United States)

    Balling, Mie; Holmberg, Teresa; Petersen, Christina B; Aadahl, Mette; Meyrowitsch, Dan W; Tolstrup, Janne S

    2018-02-01

    This study aimed to test the hypotheses that a high total sitting time and vigorous physical activity in leisure time increase the risk of low back pain and herniated lumbar disc disease. A total of 76,438 adults answered questions regarding their total sitting time and physical activity during leisure time in the Danish Health Examination Survey 2007-2008. Information on low back pain diagnoses up to 10 September 2015 was obtained from The National Patient Register. The mean follow-up time was 7.4 years. Data were analysed using Cox regression analysis with adjustment for potential confounders. Multiple imputations were performed for missing values. During the follow-up period, 1796 individuals were diagnosed with low back pain, of whom 479 were diagnosed with herniated lumbar disc disease. Total sitting time was not associated with low back pain or herniated lumbar disc disease. However, moderate or vigorous physical activity, as compared to light physical activity, was associated with increased risk of low back pain (HR = 1.16, 95% CI: 1.03-1.30 and HR = 1.45, 95% CI: 1.15-1.83). Moderate, but not vigorous physical activity was associated with increased risk of herniated lumbar disc disease. The results suggest that total sitting time is not associated with low back pain, but moderate and vigorous physical activity is associated with increased risk of low back pain compared with light physical activity.

  20. Time series pCO2 at a coastal mooring: Internal consistency, seasonal cycles, and interannual variability

    Science.gov (United States)

    Reimer, Janet J.; Cai, Wei-Jun; Xue, Liang; Vargas, Rodrigo; Noakes, Scott; Hu, Xinping; Signorini, Sergio R.; Mathis, Jeremy T.; Feely, Richard A.; Sutton, Adrienne J.; Sabine, Christopher; Musielewicz, Sylvia; Chen, Baoshan; Wanninkhof, Rik

    2017-08-01

    Marine carbonate system monitoring programs often consist of multiple observational methods that include underway cruise data, moored autonomous time series, and discrete water bottle samples. Monitored parameters include all, or some of the following: partial pressure of CO2 of the water (pCO2w) and air, dissolved inorganic carbon (DIC), total alkalinity (TA), and pH. Any combination of at least two of the aforementioned parameters can be used to calculate the others. In this study at the Gray's Reef (GR) mooring in the South Atlantic Bight (SAB) we: examine the internal consistency of pCO2w from underway cruise, moored autonomous time series, and calculated from bottle samples (DIC-TA pairing); describe the seasonal to interannual pCO2w time series variability and air-sea flux (FCO2), as well as describe the potential sources of pCO2w variability; and determine the source/sink for atmospheric pCO2. Over the 8.5 years of GR mooring time series, mooring-underway and mooring-bottle calculated-pCO2w strongly correlate with r-values > 0.90. pCO2w and FCO2 time series follow seasonal thermal patterns; however, seasonal non-thermal processes, such as terrestrial export, net biological production, and air-sea exchange also influence variability. The linear slope of time series pCO2w increases by 5.2 ± 1.4 μatm y-1 with FCO2 increasing 51-70 mmol m-2 y-1. The net FCO2 sign can switch interannually with the magnitude varying greatly. Non-thermal pCO2w is also increasing over the time series, likely indicating that terrestrial export and net biological processes drive the long term pCO2w increase.

  1. Method for Assessing Grid Frequency Deviation Due to Wind Power Fluctuation Based on “Time-Frequency Transformation”

    DEFF Research Database (Denmark)

    Jin, Lin; Yuan-zhang, Sun; Sørensen, Poul Ejnar

    2012-01-01

    published studies are based entirely on deterministic methodology. This paper presents a novel assessment method based on Time-Frequency Transformation to overcome shortcomings of existing methods. The main contribution of the paper is to propose a stochastic process simulation model which is a better...... alternative of the existing dynamic frequency deviation simulation model. In this way, the method takes the stochastic wind power fluctuation into full account so as to give a quantitative risk assessment of grid frequency deviation to grid operators, even without using any dynamic simulation tool. The case...

  2. Uncertainty in real-time voltage stability assessment methods based on Thevenin equivalent due to PMU’s accuracy

    DEFF Research Database (Denmark)

    Perez, Angel; Møller, Jakob Glarbo; Jóhannsson, Hjörtur

    2014-01-01

    This article studies the influence of PMU’s accuracy in voltage stability assessment, considering the specific case of Th ́ evenin equivalent based methods that include wide-area information in its calculations. The objective was achieved by producing a set of synthesized PMU measurements from...... a time domain simulation and using the Monte Carlo method to reflect the accuracy for the PMUs. This is given by the maximum value for the Total Vector Error defined in the IEEE standard C37.118. Those measurements allowed to estimate the distribution pa- rameters (mean and standard deviation...

  3. Toward a Real-Time Measurement-Based System for Estimation of Helicopter Engine Degradation Due to Compressor Erosion

    Science.gov (United States)

    Litt, Jonathan S.; Simo, Donald L.

    2007-01-01

    This paper presents a preliminary demonstration of an automated health assessment tool, capable of real-time on-board operation using existing engine control hardware. The tool allows operators to discern how rapidly individual turboshaft engines are degrading. As the compressor erodes, performance is lost, and with it the ability to generate power. Thus, such a tool would provide an instant assessment of the engine s fitness to perform a mission, and would help to pinpoint any abnormal wear or performance anomalies before they became serious, thereby decreasing uncertainty and enabling improved maintenance scheduling. The research described in the paper utilized test stand data from a T700-GE-401 turboshaft engine that underwent sand-ingestion testing to scale a model-based compressor efficiency degradation estimation algorithm. This algorithm was then applied to real-time Health Usage and Monitoring System (HUMS) data from a T700-GE-701C to track compressor efficiency on-line. The approach uses an optimal estimator called a Kalman filter. The filter is designed to estimate the compressor efficiency using only data from the engine s sensors as input.

  4. Culture of human dental pulp cells at variable times post-tooth extraction

    Directory of Open Access Journals (Sweden)

    BENÍCIO Daniela Ferreira Araújo

    2018-02-01

    Full Text Available Abstract The aim of this study was to investigate the viability of human dental pulp cells from extracted teeth kept at standard room temperature and atmospheric pressure for different periods of time. Twenty-one healthy permanent teeth were used. They were divided into five groups according to the expected time from extraction to processing. One group was tested immediately after extraction; the other groups were each tested at one of the following time points: 30 minutes, 1 hour, 2 hours, and 5 hours post-extraction. Cell morphology was analysed by light microscopy; cell proliferation was analysed using MTT assay and by counting the viable cells in a haemocytometer. Similar results were observed in all groups (p < 0.05. A delay of up to five hours for tooth processing and tissue collection does not preclude the establishment of dental pulp cell cultures, affect the morphology of these cells, or reduce their proliferative potential.

  5. Inter- and intra-observer variability of time-lapse annotations

    DEFF Research Database (Denmark)

    Sundvall, Linda; Ingerslev, Hans Jakob; Breth Knudsen, Ulla

    2013-01-01

    . This provides the basis for further investigation of embryo assessment and selection by time-lapse imaging in prospective trials. Study funding/competing interest(s): Research at the Fertility Clinic was funded by an unrestricted grant from Ferring and MSD. The authors have no competing interests to declare.......Study question: How consistent is the time-lapse annotation of dynamic and static morphologic parameters of embryo development, within and between observers? Summary answer: The assessment of dynamic parameters is characterized by almost perfect agreement within and between observers. What is known...... already: The commonly employed method used to assess embryos in IVF treatments is based on static evaluation of morphology in a microscope, but this is limited by substantial intra- and inter-observer variation. Time-lapse imaging has been proposed as a method to refine embryo selection by adding new...

  6. Assessing the Impact of Climate Variability on Cropland Productivity in the Canadian Prairies Using Time Series MODIS FAPAR

    OpenAIRE

    Taifeng Dong; Jiangui Liu; Jiali Shang; Budong Qian; Ted Huffman; Yinsuo Zhang; Catherine Champagne; Bahram Daneshfar

    2016-01-01

    Cropland productivity is impacted by climate. Knowledge on spatial-temporal patterns of the impacts at the regional scale is extremely important for improving crop management under limiting climatic factors. The aim of this study was to investigate the effects of climate variability on cropland productivity in the Canadian Prairies between 2000 and 2013 based on time series of MODIS (Moderate Resolution Imaging Spectroradiometer) FAPAR (Fraction of Absorbed Photosynthetically Active Radiation...

  7. Pure radiation in space-time models that admit integration of the eikonal equation by the separation of variables method

    Science.gov (United States)

    Osetrin, Evgeny; Osetrin, Konstantin

    2017-11-01

    We consider space-time models with pure radiation, which admit integration of the eikonal equation by the method of separation of variables. For all types of these models, the equations of the energy-momentum conservation law are integrated. The resulting form of metric, energy density, and wave vectors of radiation as functions of metric for all types of spaces under consideration is presented. The solutions obtained can be used for any metric theories of gravitation.

  8. Statistical Metadata Analysis of the Variability of Latency, Device Transfer Time, and Coordinate Position from Smartphone-Recorded Infrasound Data

    Science.gov (United States)

    Garces, E. L.; Garces, M. A.; Christe, A.

    2017-12-01

    The RedVox infrasound recorder app uses microphones and barometers in smartphones to record infrasound, low-frequency sound below the threshold of human hearing. We study a device's metadata, which includes position, latency time, the differences between the device's internal times and the server times, and the machine time, searching for patterns and possible errors or discontinuities in these scaled parameters. We highlight metadata variability through scaled multivariate displays (histograms, distribution curves, scatter plots), all created and organized through software development in Python. This project is helpful in ascertaining variability and honing the accuracy of smartphones, aiding the emergence of portable devices as viable geophysical data collection instruments. It can also improve the app and cloud service by increasing efficiency and accuracy, allowing to better document and foresee drastic natural movements like tsunamis, earthquakes, volcanic eruptions, storms, rocket launches, and meteor impacts; recorded data can later be used for studies and analysis by a variety of professions. We expect our final results to produce insight on how to counteract problematic issues in data mining and improve accuracy in smartphone data-collection. By eliminating lurking variables and minimizing the effect of confounding variables, we hope to discover efficient processes to reduce superfluous precision, unnecessary errors, and data artifacts. These methods should conceivably be transferable to other areas of software development, data analytics, and statistics-based experiments, contributing a precedent of smartphone metadata studies from geophysical rather than societal data. The results should facilitate the rise of civilian-accessible, hand-held, data-gathering mobile sensor networks and yield more straightforward data mining techniques.

  9. Optimization of a shorter variable-acquisition time for legs to achieve true whole-body PET/CT images.

    Science.gov (United States)

    Umeda, Takuro; Miwa, Kenta; Murata, Taisuke; Miyaji, Noriaki; Wagatsuma, Kei; Motegi, Kazuki; Terauchi, Takashi; Koizumi, Mitsuru

    2017-12-01

    The present study aimed to qualitatively and quantitatively evaluate PET images as a function of acquisition time for various leg sizes, and to optimize a shorter variable-acquisition time protocol for legs to achieve better qualitative and quantitative accuracy of true whole-body PET/CT images. The diameters of legs to be modeled as phantoms were defined based on data derived from 53 patients. This study analyzed PET images of a NEMA phantom and three plastic bottle phantoms (diameter, 5.68, 8.54 and 10.7 cm) that simulated the human body and legs, respectively. The phantoms comprised two spheres (diameters, 10 and 17 mm) containing fluorine-18 fluorodeoxyglucose solution with sphere-to-background ratios of 4 at a background radioactivity level of 2.65 kBq/mL. All PET data were reconstructed with acquisition times ranging from 10 to 180, and 1200 s. We visually evaluated image quality and determined the coefficient of variance (CV) of the background, contrast and the quantitative %error of the hot spheres, and then determined two shorter variable-acquisition protocols for legs. Lesion detectability and quantitative accuracy determined based on maximum standardized uptake values (SUV max ) in PET images of a patient using the proposed protocols were also evaluated. A larger phantom and a shorter acquisition time resulted in increased background noise on images and decreased the contrast in hot spheres. A visual score of ≥ 1.5 was obtained when the acquisition time was ≥ 30 s for three leg phantoms, and ≥ 120 s for the NEMA phantom. The quantitative %errors of the 10- and 17-mm spheres in the leg phantoms were ± 15 and ± 10%, respectively, in PET images with a high CV (scan mean SUV max of three lesions using the current fixed-acquisition and two proposed variable-acquisition time protocols in the clinical study were 3.1, 3.1 and 3.2, respectively, which did not significantly differ. Leg acquisition time per bed position of even 30-90

  10. Simplex optimization of the variables influencing the determination of pefloxacin by time-resolved chemiluminescence

    Science.gov (United States)

    Murillo Pulgarín, José A.; Alañón Molina, Aurelia; Jiménez García, Elisa

    2018-03-01

    A new chemiluminescence (CL) detection system combined with flow injection analysis (FIA) for the determination of Pefloxacin is proposed. The determination is based on an energy transfer from Pefloxacin to terbium (III). The metal ion enhances the weak CL signal produced by the KMnO4/H2SO3/Pefloxacin system. A modified simplex method was used to optimize chemical and instrumental variables. The influence of the interaction of the permanganate, Tb (III), sodium sulphite and sulphuric acid concentrations, flow rate and injected sample volume was thoroughly investigated by using a modified simplex optimization procedure. The results revealed a strong direct relationship between flow rate and CL intensity throughout the studied range that was confirmed by a gamma test. The response factor for the CL emission intensity was used to assess performance in order to identify the optimum conditions for maximization of the response. Under such conditions, the CL response was proportional to the Pefloxacin concentration over a wide range. The detection limit as calculated according to Clayton's criterion 13.7 μg L- 1. The analyte was successfully determined in milk samples with an average recovery of 100.6 ± 9.8%.

  11. Fast Determination of Distribution-Connected PV Impacts Using a Variable Time-Step Quasi-Static Time-Series Approach: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Mather, Barry

    2017-08-24

    The increasing deployment of distribution-connected photovoltaic (DPV) systems requires utilities to complete complex interconnection studies. Relatively simple interconnection study methods worked well for low penetrations of photovoltaic systems, but more complicated quasi-static time-series (QSTS) analysis is required to make better interconnection decisions as DPV penetration levels increase. Tools and methods must be developed to support this. This paper presents a variable-time-step solver for QSTS analysis that significantly shortens the computational time and effort to complete a detailed analysis of the operation of a distribution circuit with many DPV systems. Specifically, it demonstrates that the proposed variable-time-step solver can reduce the required computational time by as much as 84% without introducing any important errors to metrics, such as the highest and lowest voltage occurring on the feeder, number of voltage regulator tap operations, and total amount of losses realized in the distribution circuit during a 1-yr period. Further improvement in computational speed is possible with the introduction of only modest errors in these metrics, such as a 91 percent reduction with less than 5 percent error when predicting voltage regulator operations.

  12. Events at blood collection area due to nonconforming blood bags and plateletpheresis kits: need for timely corrective and preventive actions.

    Science.gov (United States)

    Verma, Anupam; Sachan, Deepti; Elhence, Priti; Pandey, Hem; Dubey, Anju

    2012-07-01

    Good blood banking practice requires that every effort should be made to detect any deviation or defect in blood bank products and to identify any potential risk to blood donor or recipient(s). We report the findings of an exercise that provide an insight into why feedback from the user side is crucial. Various events involving blood bags and plateletpheresis kits and the corresponding appropriate actions instituted for remedial measures were recorded. These scattered events were recorded for 6 months following the use of a new batch of improved blood bags with add-on features. Several events related to plateletpheresis kits from three different manufacturers were also recorded for 1 year. The affected blood bags were utilized with no untoward incident. The complaint was closed following satisfactory response from the blood bag manufacturing company that acted in a timely manner in addressing the root causes of the problems. However, corrective and preventive actions (CAPA) could not be implemented for plateletpheresis kits. The rate of undesirable events was higher with plateletpheresis kits as compared with whole blood bags (1.75% vs. 0.06%). As defects or deviations that trigger the need for CAPA can stem from numerous sources, it is important to clearly identify and document the problems and level of risk so that appropriate investigations can be instituted and remedial actions can be taken in a timely manner. This study demonstrates the usefulness of a quality initiative to collate and analyze blood product faults in conjunction with blood product manufacturers. © 2012 American Association of Blood Banks.

  13. Effects of Variable Production Rate and Time-Dependent Holding Cost for Complementary Products in Supply Chain Model

    Directory of Open Access Journals (Sweden)

    Mitali Sarkar

    2017-01-01

    Full Text Available Recently, a major trend is going to redesign a production system by controlling or making variable the production rate within some fixed interval to maintain the optimal level. This strategy is more effective when the holding cost is time-dependent as it is interrelated with holding duration of products and rate of production. An effort is made to make a supply chain model (SCM to show the joint effect of variable production rate and time-varying holding cost for specific type of complementary products, where those products are made by two different manufacturers and a common retailer makes them bundle and sells bundles to end customers. Demand of each product is specified by stochastic reservation prices with a known potential market size. Those players of the SCM are considered with unequal power. Stackelberg game approach is employed to obtain global optimum solution of the model. An illustrative numerical example, graphical representation, and managerial insights are given to illustrate the model. Results prove that variable production rate and time-dependent holding cost save more than existing literature.

  14. Estimating space-time mean concentrations of nutrients in surface waters of variable depth

    NARCIS (Netherlands)

    Knotters, M.; Brus, D.J.

    2010-01-01

    A monitoring scheme has been designed to test whether the space-time mean concentration total Nitrogen (N-total) in the surface water in the Northern Frisian Woodlands (NFW, The Netherlands) complies with standards of the European Water Framework directive. Since in statistical testing for

  15. The variability of the trunk forward bending in standing activities during work vs. leisure time

    DEFF Research Database (Denmark)

    Villumsen, Morten; Madeleine, Pascal; Jørgensen, Marie Birk

    2017-01-01

    . The study was conducted on 657 blue-collar workers. Two accelerometers were used to identify the body posture and forward bending of the trunk during work and leisure time. The pattern of forward bending was analyzed using exposure variation analysis (EVA). The recordings comprised of 2.6 ± 0.97 working...

  16. Arctic energy budget in relation to sea ice variability on monthly-to-annual time scales

    NARCIS (Netherlands)

    Krikken, F.; Hazeleger, W.

    2015-01-01

    The large decrease in Arctic sea ice in recent years has triggered a strong interest in Arctic sea ice predictions on seasonal-to-decadal time scales. Hence, it is important to understand physical processes that provide enhanced predictability beyond persistence of sea ice anomalies. This study

  17. Natural variability of atmospheric temperatures and geomagnetic intensity over a wide range of time scales.

    Science.gov (United States)

    Pelletier, Jon D

    2002-02-19

    The majority of numerical models in climatology and geomagnetism rely on deterministic finite-difference techniques and attempt to include as many empirical constraints on the many processes and boundary conditions applicable to their very complex systems. Despite their sophistication, many of these models are unable to reproduce basic aspects of climatic or geomagnetic dynamics. We show that a simple stochastic model, which treats the flux of heat energy in the atmosphere by convective instabilities with random advection and diffusive mixing, does a remarkable job at matching the observed power spectrum of historical and proxy records for atmospheric temperatures from time scales of one day to one million years (Myr). With this approach distinct changes in the power-spectral form can be associated with characteristic time scales of ocean mixing and radiative damping. Similarly, a simple model of the diffusion of magnetic intensity in Earth's core coupled with amplification and destruction of the local intensity can reproduce the observed 1/f noise behavior of Earth's geomagnetic intensity from time scales of 1 (Myr) to 100 yr. In addition, the statistics of the fluctuations in the polarity reversal rate from time scales of 1 Myr to 100 Myr are consistent with the hypothesis that reversals are the result of variations in 1/f noise geomagnetic intensity above a certain threshold, suggesting that reversals may be associated with internal fluctuations rather than changes in mantle thermal or magnetic boundary conditions.

  18. Assessment of the methods for determining net radiation at different time-scales of meteorological variables

    Directory of Open Access Journals (Sweden)

    Ni An

    2017-04-01

    Full Text Available When modeling the soil/atmosphere interaction, it is of paramount importance to determine the net radiation flux. There are two common calculation methods for this purpose. Method 1 relies on use of air temperature, while Method 2 relies on use of both air and soil temperatures. Nowadays, there has been no consensus on the application of these two methods. In this study, the half-hourly data of solar radiation recorded at an experimental embankment are used to calculate the net radiation and long-wave radiation at different time-scales (half-hourly, hourly, and daily using the two methods. The results show that, compared with Method 2 which has been widely adopted in agronomical, geotechnical and geo-environmental applications, Method 1 is more feasible for its simplicity and accuracy at shorter time-scale. Moreover, in case of longer time-scale, daily for instance, less variations of net radiation and long-wave radiation are obtained, suggesting that no detailed soil temperature variations can be obtained. In other words, shorter time-scales are preferred in determining net radiation flux.

  19. Inter and intra-observer variability of time-lapse annotations

    DEFF Research Database (Denmark)

    Sundvall Germeys, Linda Karin M; Ingerslev, Hans Jakob; Knudsen, Ulla Breth

    . This provides the basis for further investigation of embryo assessment and selection by time-lapse imaging in prospective trials. Study funding/competing interest(s): Research at the Fertility Clinic was funded by an unrestricted grant from Ferring and MSD. The authors have no competing interests to declare....

  20. THE TIME-DOMAIN SPECTROSCOPIC SURVEY: UNDERSTANDING THE OPTICALLY VARIABLE SKY WITH SEQUELS IN SDSS-III

    Energy Technology Data Exchange (ETDEWEB)

    Ruan, John J.; Anderson, Scott F.; Davenport, James R. A. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Green, Paul J.; Morganson, Eric [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Eracleous, Michael; Brandt, William N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Myers, Adam D. [Department of Physics and Astronomy 3905, University of Wyoming, 1000 E. University, Laramie, WY 82071 (United States); Badenes, Carles [Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics, and Cosmology Center (PITT-PACC), University of Pittsburgh (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin-Madison, 475 N. Charter Street, Madison, WI 53706 (United States); Chambers, Kenneth C.; Flewelling, Heather; Kaiser, Nick [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Dawson, Kyle S. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Heckman, Timothy M. [Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Isler, Jedidah C. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Kneib, Jean-Paul [Laboratoire d’astrophysique, Ecole Polytechnique Fédérale de Lausanne Observatoire de Sauverny, 1290 Versoix (Switzerland); MacLeod, Chelsea L.; Ross, Nicholas P. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ (United Kingdom); Paris, Isabelle, E-mail: jruan@astro.washington.edu [INAF—Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34131 Trieste (Italy); and others

    2016-07-10

    The Time-Domain Spectroscopic Survey (TDSS) is an SDSS-IV eBOSS subproject primarily aimed at obtaining identification spectra of ∼220,000 optically variable objects systematically selected from SDSS/Pan-STARRS1 multi-epoch imaging. We present a preview of the science enabled by TDSS, based on TDSS spectra taken over ∼320 deg{sup 2} of sky as part of the SEQUELS survey in SDSS-III, which is in part a pilot survey for eBOSS in SDSS-IV. Using the 15,746 TDSS-selected single-epoch spectra of photometrically variable objects in SEQUELS, we determine the demographics of our variability-selected sample and investigate the unique spectral characteristics inherent in samples selected by variability. We show that variability-based selection of quasars complements color-based selection by selecting additional redder quasars and mitigates redshift biases to produce a smooth quasar redshift distribution over a wide range of redshifts. The resulting quasar sample contains systematically higher fractions of blazars and broad absorption line quasars than from color-selected samples. Similarly, we show that M dwarfs in the TDSS-selected stellar sample have systematically higher chromospheric active fractions than the underlying M-dwarf population based on their H α emission. TDSS also contains a large number of RR Lyrae and eclipsing binary stars with main-sequence colors, including a few composite-spectrum binaries. Finally, our visual inspection of TDSS spectra uncovers a significant number of peculiar spectra, and we highlight a few cases of these interesting objects. With a factor of ∼15 more spectra, the main TDSS survey in SDSS-IV will leverage the lessons learned from these early results for a variety of time-domain science applications.

  1. THE TIME-DOMAIN SPECTROSCOPIC SURVEY: UNDERSTANDING THE OPTICALLY VARIABLE SKY WITH SEQUELS IN SDSS-III

    International Nuclear Information System (INIS)

    Ruan, John J.; Anderson, Scott F.; Davenport, James R. A.; Green, Paul J.; Morganson, Eric; Eracleous, Michael; Brandt, William N.; Myers, Adam D.; Badenes, Carles; Bershady, Matthew A.; Chambers, Kenneth C.; Flewelling, Heather; Kaiser, Nick; Dawson, Kyle S.; Heckman, Timothy M.; Isler, Jedidah C.; Kneib, Jean-Paul; MacLeod, Chelsea L.; Ross, Nicholas P.; Paris, Isabelle

    2016-01-01

    The Time-Domain Spectroscopic Survey (TDSS) is an SDSS-IV eBOSS subproject primarily aimed at obtaining identification spectra of ∼220,000 optically variable objects systematically selected from SDSS/Pan-STARRS1 multi-epoch imaging. We present a preview of the science enabled by TDSS, based on TDSS spectra taken over ∼320 deg 2 of sky as part of the SEQUELS survey in SDSS-III, which is in part a pilot survey for eBOSS in SDSS-IV. Using the 15,746 TDSS-selected single-epoch spectra of photometrically variable objects in SEQUELS, we determine the demographics of our variability-selected sample and investigate the unique spectral characteristics inherent in samples selected by variability. We show that variability-based selection of quasars complements color-based selection by selecting additional redder quasars and mitigates redshift biases to produce a smooth quasar redshift distribution over a wide range of redshifts. The resulting quasar sample contains systematically higher fractions of blazars and broad absorption line quasars than from color-selected samples. Similarly, we show that M dwarfs in the TDSS-selected stellar sample have systematically higher chromospheric active fractions than the underlying M-dwarf population based on their H α emission. TDSS also contains a large number of RR Lyrae and eclipsing binary stars with main-sequence colors, including a few composite-spectrum binaries. Finally, our visual inspection of TDSS spectra uncovers a significant number of peculiar spectra, and we highlight a few cases of these interesting objects. With a factor of ∼15 more spectra, the main TDSS survey in SDSS-IV will leverage the lessons learned from these early results for a variety of time-domain science applications.

  2. Possible changes in the dose of biologically active ultraviolet radiation received by the biosphere in the summertime Arctic due to total ozone interannual variability

    Energy Technology Data Exchange (ETDEWEB)

    Gruzdev, Aleksandr N. (Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow (Russian Federation))

    1994-12-01

    Data for total ozone measurements since 1972 from the world ozone measuring network have been analyzed to study ozone interannual variability and estimate its possible effect on the UV-B dose received by the arctic biosphere. Possible interannual changes in the UV-B dose received by DNA associated with overall interannual ozone variability, as well as with the quasi-biennial oscillation (QBO) in total ozone were computed for different summer months. In general, the largest interannual variations in UV-B dose may occur in the Russian Arctic, whereas the possible variations in the Canadian Arctic are the smallest. Overall variations in the UV-B dose received by DNA can exceed 25% (2[sigma] criterion) in the Taimyr and Severnaya Zemlya for June and July, and 30% in the Laptev Sea for August. In the European sector of the Arctic, the possible variations are greater than 10%, and can exceed 15% in the north Norwegian Sea for July and 20% in Spitsbergen for August. Possible overall variations in the Canadian Arctic and Alaska are [<=]10%, reaching 15% in Alaska for August, however. The total ozone QBO can also cause essential and (statistically) predicted changes in UV-B radiation. In general, the UV-B dose received by DNA is found to be greater in the Arctic during the westerly phase of the QBO of the equatorial stratospheric wind at 50 mb level than during the easterly phase. The difference can reach or exceed 15% (relative to the mean value) in Taimyr for June and in Severnaya Zemlya for July and August. In northern Europe and Iceland, the difference can reach 10% for August. In the Canadian Arctic, the QBO-related effect is small. In Alaska, the appropriate difference in UV-B dose has an opposite sign for August, exceeding 5% in magnitude

  3. Long-term exposure to mobile communication radiation: An analysis of time-variability of electric field level in GSM900 down-link channels

    International Nuclear Information System (INIS)

    Miclaus, S.; Bechet, P.; Gheorghevici, M.

    2013-01-01

    Interest for knowing long-term human exposure levels due to mobile communications has increased in the last years. It has been shown that short-term exposure assessment made under standard procedural restrictions is not reliable when it comes to conclusions on long-term exposure levels. The present work is the result of a several week analysis of time variability of electric field level inside traffic and control channels of the GSM900 mobile communication down-link band and it indicates that a temporal model to allow future predictions of exposure on the long run is obtainable. Collecting, processing and statistically analysing the data provide expression of the maximum and weighted field strengths and their evolution in time. Specific electromagnetic footprints of the channels have been extracted, differentiations between their characteristics have been emphasised and practical advice is provided, with the scope of contributing to the development of reliable procedures for long-term exposure assessment. (authors)

  4. Characteristic time series and operation region of the system of two tank reactors (CSTR) with variable division of recirculation stream

    International Nuclear Information System (INIS)

    Merta, Henryk

    2006-01-01

    The paper deals with a system of a cascade of two tank reactors, being characterized by the variable stream of recirculating fluid at each stage. The assumed mathematical model enables one to determine the system's dynamics for the case when there is no time delay and for the opposite case. The time series of the conversion degree and of the dimensionless fluid temperature, characteristic for the system considered as well as the operation regions-the latter-basing on Feingenbaum diagrams with respect to the division ratio of the recirculating stream are presented

  5. Cancer incidence due to excess body weight and leisure-time physical inactivity in Canada: implications for prevention.

    Science.gov (United States)

    Brenner, Darren R

    2014-09-01

    This analysis aimed to estimate the number of incident cases of various cancers attributable to excess body weight (overweight, obesity) and leisure-time physical inactivity annually in Canada. The number of attributable cancers was estimated using the population attributable fraction (PAF), risk estimates from recent meta-analyses and population exposure prevalence estimates obtained from the Canadian Community Health Survey (2000). Age-sex-site-specific cancer incidence was obtained from Statistics Canada tables for the most up-to-date year with full national data, 2007. Where the evidence for association has been deemed sufficient, we estimated the number of incident cases of the following cancers attributable to obesity: colon, breast, endometrium, esophagus (adenocarcinomas), gallbladder, pancreas and kidney; and to physical inactivity: colon, breast, endometrium, prostate, lung and/or bronchus, and ovarian. Overall, estimates of all cancer incidence in 2007 suggest that at least 3.5% (n=5771) and 7.9% (n=12,885) are attributed to excess body weight and physical inactivity respectively. For both risk factors the burden of disease was greater among women than among men. Thousands of incident cases of cancer could be prevented annually in Canada as good evidence exists for effective interventions to reduce these risk factors in the population. Copyright © 2014. Published by Elsevier Inc.

  6. Time domain heart rate variability in Boxer dogs with arrhythmogenic right ventricular cardiomyopathy

    Directory of Open Access Journals (Sweden)

    Evandro Zacché

    Full Text Available ABSTRACT: The aim of the present study was to assess heart rate variability (HRV in Boxer dogs affected by arrhythmogenic right ventricular cardiomyopathy (ARVC. Fourteen Boxer dogs classified as affected and 28 classified as unaffected were included in a prospective case-control study. Dogs underwent 24-hour ambulatory ECG and were classified as affected (>1,000 VPCs/24 hours or unaffected (<20 VPCs/24 hours by ARVC based on the number of ventricular arrhythmias. HRV was assessed using 24-h Holter ECG monitoring; the studied parameters were SDNN, SDANN, SDNNIDX, rMSSD and pNN50. Data were submitted to logarithmic transformation and HRV parameters were compared between groups and correlated according to the disease status, number and severity of ventricular arrhythmias using Student’s t test, linear regression and Spearman’s test. There was no interaction between the HRV parameters and the number and severity of ventricular arrhythmias. SDNNlog (2.35±0.14 vs. 2.46±0.12, P=0.01, SDNNIDXlog (2.18±0.14 vs. 2.24±0.10, P=0.002 and pNN50log (1.47±0.19 vs. 1.64±0.13, P=0.002 were significantly lower in the affected group compared with the unaffected. According to this study, HRV are different in a population of Boxers dogs affected by ARVC compared to a population of unaffected dogs, and these differences are not consequences of low cardiac output caused by ventricular arrhythmias since animals that had higher number and complexity of arrhythmias were not those who had lower values of HRV.

  7. Effect of treadmill versus overground running on the structure of variability of stride timing.

    Science.gov (United States)

    Lindsay, Timothy R; Noakes, Timothy D; McGregor, Stephen J

    2014-04-01

    Gait timing dynamics of treadmill and overground running were compared. Nine trained runners ran treadmill and track trials at 80, 100, and 120% of preferred pace for 8 min. each. Stride time series were generated for each trial. To each series, detrended fluctuation analysis (DFA), power spectral density (PSD), and multiscale entropy (MSE) analysis were applied to infer the regime of control along the randomness-regularity axis. Compared to overground running, treadmill running exhibited a higher DFA and PSD scaling exponent, as well as lower entropy at non-preferred speeds. This indicates a more ordered control for treadmill running, especially at non-preferred speeds. The results suggest that the treadmill itself brings about greater constraints and requires increased voluntary control. Thus, the quantification of treadmill running gait dynamics does not necessarily reflect movement in overground settings.

  8. Analysis on diurnal global geomagnetic variability under quiet-time conditions

    OpenAIRE

    Klausner, Virginia; Domingues, Margarete Oliveira; Mendes Jr, Odim; Papa, Andres Reinaldo Rodriguez; Frick, Peter

    2012-01-01

    This paper describes a methodology (or treatment) to establish a representative signal of the global magnetic diurnal variation based on a spatial distribution in both longitude and latitude of a set of magnetic stations as well as their magnetic behavior on a time basis. For that, we apply the Principal Component Analysis (PCA) technique implemented using gapped wavelet transform and wavelet correlation. The continuous gapped wavelet and the wavelet correlation techniques were used to descri...

  9. Time-lagged autoencoders: Deep learning of slow collective variables for molecular kinetics

    Science.gov (United States)

    Wehmeyer, Christoph; Noé, Frank

    2018-06-01

    Inspired by the success of deep learning techniques in the physical and chemical sciences, we apply a modification of an autoencoder type deep neural network to the task of dimension reduction of molecular dynamics data. We can show that our time-lagged autoencoder reliably finds low-dimensional embeddings for high-dimensional feature spaces which capture the slow dynamics of the underlying stochastic processes—beyond the capabilities of linear dimension reduction techniques.

  10. Variable uplift rate through time: Holocene coral reef and neotectonics of Lutao, eastern Taiwan

    Science.gov (United States)

    Shen, Chuan-Chou; Wu, Chung-Che; Dai, Chang-Feng; Gong, Shou-Yeh

    2018-05-01

    Significant discrepancies have existed regarding rate and timing of the uplift of Lutao (Green Island), located at the border of the ongoing collision between the Eurasia continental plate and the Philippine Sea Plate. To document its neotectonic history, two cores were drilled into Holocene coral reefs exposed at the southeastern coast of Lutao. Twelve pristine fossil corals, nine taken from cores and three on the surface, were 230Th dated. The results show that the coral reefs started to develop at 8,736 ± 56 yr BP (before 1950 CE) with uplift rate varying from 3.6 mm/yr during 8.7-6.0 kyr BP to 1.2 mm/yr in the past six thousand years. Our study strongly suggests that the uplift rate can vary significantly on millennial time scale. Caution should be used when extrapolating uplift rate estimates based on Mid-late Holocene corals to early times for tectonic active locations, such as Lutao.

  11. Essential Oil Variability and Biological Activities of Tetraclinis articulata (Vahl) Mast. Wood According to the Extraction Time.

    Science.gov (United States)

    Djouahri, Abderrahmane; Saka, Boualem; Boudarene, Lynda; Baaliouamer, Aoumeur

    2016-12-01

    In the present work, the hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD) kinetics of essential oil (EO) extracted from Tetraclinis articulata (Vahl) Mast. wood was conducted, in order to assess the impact of extraction time and technique on chemical composition and biological activities. Gas chromatography (GC) and GC/mass spectrometry analyses showed significant differences between the extracted EOs, where each family class or component presents a specific kinetic according to extraction time, technique and especially for the major components: camphene, linalool, cedrol, carvacrol and α-acorenol. Furthermore, our findings showed a high variability for both antioxidant and anti-inflammatory activities, where each activity has a specific effect according to extraction time and technique. The highlighted variability reflects the high impact of extraction time and technique on chemical composition and biological activities, which led to conclude that we should select EOs to be investigated carefully depending on extraction time and technique, in order to isolate the bioactive components or to have the best quality of EO in terms of biological activities and preventive effects in food. © 2016 Wiley-VHCA AG, Zurich, Switzerland.

  12. Attempt to determine radon entry rate and air exchange rate variable in time from the time course of indoor radon concentration

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, J [State Office for Nuclear Protection, Prague (Czech Republic)

    1996-12-31

    For radon diagnosis in houses the `ventilation experiment` was used as a standard method. After removal of indoor radon by draught the build-up of radon concentration a(t) [Bq/m{sup 3}] was measured continuously and from the time course the constant radon entry rate A [Bq/h] and the exchange rate k [h{sup -1}] was calculated by regression analysis using model relation a(t) A(1-e{sup -kt})/kV with V [m{sup 3}] for volume of the room. The conditions have to be stable for several hours so that the assumption of constant A and k was justified. During the day both quantities were independently (?) changing, therefore a method to determine variable entry rate A(t) and exchange rate k(t) is needed for a better understanding of the variability of the indoor radon concentration. Two approaches are given for the determination of variable in time radon entry rates and air exchange rates from continuously measured indoor radon concentration - numerical solution of the equivalent difference equations in deterministic or statistic form. The approaches are not always successful. Failures giving a right ration for the searched rates but not of the rates them self could not be explained.

  13. Time course of cell death due to acoustic overstimulation in the mouse medial geniculate body and primary auditory cortex

    Directory of Open Access Journals (Sweden)

    Felix Frohlich

    2017-01-01

    Full Text Available It has previously been shown that acoustic overstimulation induces cell death and extensive cell loss in key structures of the central auditory pathway. A correlation between noise-induced apoptosis and cell loss was hypothesized for the cochlear nucleus and colliculus inferior. To determine the role of cell death in noise-induced cell loss in thalamic and cortical structures, the present mouse study (NMRI strain describes the time course following noise exposure of cell death mechanisms for the ventral medial geniculate body (vMGB, medial MGB (mMGB, and dorsal MGB (dMGB and the six histological layers of the primary auditory cortex (AI 1–6. Therefore, a terminal deoxynucleotidyl transferase dioxyuridine triphosphate nick-end labeling assay (TUNEL was performed in these structures 24 h, 7 days, and 14 days after noise exposure (3 h, 115 dB sound pressure level, 5–20 kHz, as well as in unexposed controls. In the dMGB, TUNEL was statistically significant elevated 24 h postexposure. AI-1 showed a decrease in TUNEL after 14 days. There was no statistically significant difference between groups for the other brain areas investigated. dMGB’s widespread connection within the central auditory pathway and its nontonotopical organization might explain its prominent increase in TUNEL compared to the other MGB subdivisions and the AI. It is assumed that the onset and peak of noise-induced cell death is delayed in higher areas of the central auditory pathway and takes place between 24 h and 7 days postexposure in thalamic and cortical structures.

  14. Time domain contact model for tyre/road interaction including nonlinear contact stiffness due to small-scale roughness

    Science.gov (United States)

    Andersson, P. B. U.; Kropp, W.

    2008-11-01

    Rolling resistance, traction, wear, excitation of vibrations, and noise generation are all attributes to consider in optimisation of the interaction between automotive tyres and wearing courses of roads. The key to understand and describe the interaction is to include a wide range of length scales in the description of the contact geometry. This means including scales on the order of micrometres that have been neglected in previous tyre/road interaction models. A time domain contact model for the tyre/road interaction that includes interfacial details is presented. The contact geometry is discretised into multiple elements forming pairs of matching points. The dynamic response of the tyre is calculated by convolving the contact forces with pre-calculated Green's functions. The smaller-length scales are included by using constitutive interfacial relations, i.e. by using nonlinear contact springs, for each pair of contact elements. The method is presented for normal (out-of-plane) contact and a method for assessing the stiffness of the nonlinear springs based on detailed geometry and elastic data of the tread is suggested. The governing equations of the nonlinear contact problem are solved with the Newton-Raphson iterative scheme. Relations between force, indentation, and contact stiffness are calculated for a single tread block in contact with a road surface. The calculated results have the same character as results from measurements found in literature. Comparison to traditional contact formulations shows that the effect of the small-scale roughness is large; the contact stiffness is only up to half of the stiffness that would result if contact is made over the whole element directly to the bulk of the tread. It is concluded that the suggested contact formulation is a suitable model to include more details of the contact interface. Further, the presented result for the tread block in contact with the road is a suitable input for a global tyre/road interaction model

  15. Two-Body Orbit Expansion Due to Time-Dependent Relative Acceleration Rate of the Cosmological Scale Factor

    Directory of Open Access Journals (Sweden)

    Lorenzo Iorio

    2014-01-01

    Full Text Available By phenomenologically assuming a slow temporal variation of the percent acceleration rate S̈S -1 of the cosmic scale factor S(t, it is shown that the orbit of a local binary undergoes a secular expansion. To first order in the power expansion of S̈S -1 around the present epoch t0, a non-vanishing shift per orbit (Δr of the two-body relative distance r occurs for eccentric trajectories. A general relativistic expression, which turns out to be cubic in the Hubble parameter H0 at the present epoch, is explicitly calculated for it in the case of matter-dominated epochs with Dark Energy. For a highly eccentric Oort comet orbit with period Pb ≈ 31 Myr, the general relativistic distance shift per orbit turns out to be of the order of (Δr ≈ 70 km. For the Large Magellanic Cloud, assumed on a bound elliptic orbit around the Milky Way, the shift per orbit is of the order of (Δr ≈ 2–4 pc. Our result has a general validity since it holds in any cosmological model admitting the Hubble law and a slowly varying S̈S-1(t. More generally, it is valid for an arbitrary Hooke-like extra-acceleration whose “elastic” parameter κ is slowly time-dependent, irrespectively of the physical mechanism which may lead to it. The coefficient κ1 of the first-order term of the power expansion of κ(t can be preliminarily constrained in a model-independent way down to a κ1 ≲ 2 x 10-13 year-3 level from latest Solar System’s planetary observations. The radial velocities of the double lined spectroscopic binary ALPHA Cen AB yield κ1 ≲ 10-8 year-3.

  16. Variable sampling-time technique for improving count rate performance of scintillation detectors

    International Nuclear Information System (INIS)

    Tanaka, E.; Nohara, N.; Murayama, H.

    1979-01-01

    A new technique is presented to improve the count rate capability of a scintillation spectrometer or a position sensitive detector with minimum loss of resolution. The technique is based on the combination of pulse shortening and selective integration in which the integration period is not fixed but shortened by the arrival of the following pulse. Theoretical analysis of the degradation of the statiscal component of resolution is made for the proposed system with delay line pulse shortening, and the factor of resolution loss is formulated as a function of the input pulse rate. A new method is also presented for determining the statistical component of resolution separately from the non-statistical system resolution. Preliminary experiments with a NaI(Tl) detector have been carried out, the results of which are consistent with the theoretical prediction. However, due to the non-exponential scintillation decay of the NaI(Tl) crystal, a simple delay line clipping is not satisfactory, and an RC high-pass filter has been added, which results in further degradation of the statistical resolution. (Auth.)

  17. The Time Variability of Individual Geysers in the Plume of Enceladus

    Science.gov (United States)

    Trumbo, S. K.; Ewald, S. P.; Ingersoll, A. P.

    2016-12-01

    Porco et al. (2014) [1] published the locations of 100 jets along the so-called "tiger stripes" that feed the massive plume of Enceladus. Hedman et al. (2013) [2] observed fluctuations in integrated plume brightness in response to periodic tidal forcing on the orbital timescale of Enceladus, in which the plume is brightest near apocenter and dimmest near pericenter. The thin crack models of Hurford et al. (2007, 2012) [3, 4] suggest that individual jets should respond to the same forces on similar timescales. However, if the jets are produced via vapor and liquid propagation through thin subterranean cracks, then they may also be controlled thermodynamically and dependent on the timescale of ice buildup on the conduit walls. Ingersoll and Ewald (2016) [5] demonstrate that the plume also varies on decadal timescales, perhaps as a result of an eleven-year tide or long-term ice accumulation within source cracks. We examine Cassini ISS Narrow Angle Camera images spanning 2005 - 2012 in order to assess the temporal variability of individual geysers and regional emission in the plume. We observe both the appearance and disappearance of individual jets, as well as visible changes in regional emission. Our observations suggest localized variations on timescales of months to years that are not easily tied to mean anomaly, but that may be indicative of subsurface processes. Theoretical models of the geyser mechanisms and subsurface plumbing predict closure timescales of individual cracks that are dependent on model parameters, such as crack width, crack tortuosity, and water table depth [6, 7, 8]. Thus, we discuss possible implications of these observations for both the mechanism and anatomy of an Enceladus geyser. [1] Porco et al. (2014), AJ, 148, 3. [2] Hedman et al. (2013), Nature, 500, 182 - 184. [3] Hurford et al. (2007), Nature, 447, 292 - 294. [4] Hurford et al. (2012), Icarus, 220, 896 - 903. [5] Ingersoll and Ewald (2016), Icarus, in review. [6] Ingersoll and

  18. Seismic Cycle Variability in Space and Time: The Sumatran Sunda Megathrust as a Behavior Catalog

    Science.gov (United States)

    Philibosian, B.; Sieh, K.; Natawidjaja, D. H.; Avouac, J. P.; Chiang, H. W.; WU, C. C.; Shen, C. C.; Perfettini, H.; Daryono, M. R.; Suwargadi, B. W.

    2015-12-01

    very shallow portions also occasionally rupture seismically, though less frequently than the primary seismogenic area. This patchwork of frictional properties, presumably rooted in structure and rheology along the fault interface, ultimately produces both the short-term rupture variability and the longer-term segmentation we observe.

  19. A critical oscillation constant as a variable of time scales for half-linear dynamic equations

    Czech Academy of Sciences Publication Activity Database

    Řehák, Pavel

    2010-01-01

    Roč. 60, č. 2 (2010), s. 237-256 ISSN 0139-9918 R&D Projects: GA AV ČR KJB100190701 Institutional research plan: CEZ:AV0Z10190503 Keywords : dynamic equation * time scale * half-linear equation * (non)oscillation criteria * Hille-Nehari criteria * Kneser criteria * critical constant * oscillation constant * Hardy inequality Subject RIV: BA - General Mathematics Impact factor: 0.316, year: 2010 http://link.springer.com/article/10.2478%2Fs12175-010-0009-7

  20. Burner flow regulators with mechanisms performing two variable function. Meccanismi che generano una funzione di due variabili applicati alla regolazione dei bruciatori

    Energy Technology Data Exchange (ETDEWEB)

    Borelli, L.; Tagliaferro, B. (R.B.L. Riello Bruciatori, Legnago Spa, Legnago (Italy)); Cossalter, V.; Da Lio, M. (Padua Univ. (Italy). Dip. di Ingegneria Meccanica)

    1993-08-01

    A new class of fuel oil burners has recently been developed by an Italian firm with the aim of obtaining high performances in terms of both energy efficiency and air pollution abatement. The innovative feature of these burners is that they are equipped with a device which permits the automatic and optimum regulation of the air fuel mixture independent of ambient and operating conditions. To reduce costs, the regulation system is a mechanical one instead of electronic which would require an expensive lambda probe. The mechanical regulating system controls air intake by simply taking into account two main combustion factors - ambient temperature and the nominal fuel flow rate. The special cam mechanism is thus classified as one which performs a single function with two degrees of freedom, i.e., the independent variables of ambient temperature and nominal fuel flow. One of the air intake valve's movements is governed by a temperature transducer, the other (primary), by a screw which allows the registering of the air flow during burner installation or upon completion of periodic maintenance checks. In addition to optimizing combustion control, this control technique affords the possibility to adapt the air flow to the different fuel flows obtained by changing the type of nozzle or supply pressure.

  1. Time trend of malaria in relation to climate variability in Papua New Guinea.

    Science.gov (United States)

    Park, Jae-Won; Cheong, Hae-Kwan; Honda, Yasushi; Ha, Mina; Kim, Ho; Kolam, Joel; Inape, Kasis; Mueller, Ivo

    2016-01-01

    This study was conducted to describe the regional malaria incidence in relation to the geographic and climatic conditions and describe the effect of altitude on the expansion of malaria over the last decade in Papua New Guinea. Malaria incidence was estimated in five provinces from 1996 to 2008 using national health surveillance data. Time trend of malaria incidence was compared with rainfall and minimum/maximum temperature. In the Eastern Highland Province, time trend of malaria incidence over the study period was stratified by altitude. Spatio-temporal pattern of malaria was analyzed. Nationwide, malaria incidence was stationary. Regionally, the incidence increased markedly in the highland region (292.0/100000/yr, p =0.021), and remained stationary in the other regions. Seasonality of the malaria incidence was related with rainfall. Decreasing incidence of malaria was associated with decreasing rainfall in the southern coastal region, whereas it was not evident in the northern coastal region. In the Eastern Highland Province, malaria incidence increased in areas below 1700 m, with the rate of increase being steeper at higher altitudes. Increasing trend of malaria incidence was prominent in the highland region of Papua New Guinea, while long-term trend was dependent upon baseline level of rainfall in coastal regions.

  2. Time trend of malaria in relation to climate variability in Papua New Guinea

    Directory of Open Access Journals (Sweden)

    Jae-Won Park

    2016-02-01

    Full Text Available Objectives This study was conducted to describe the regional malaria incidence in relation to the geographic and climatic conditions and describe the effect of altitude on the expansion of malaria over the last decade in Papua New Guinea. Methods Malaria incidence was estimated in five provinces from 1996 to 2008 using national health surveillance data. Time trend of malaria incidence was compared with rainfall and minimum/maximum temperature. In the Eastern Highland Province, time trend of malaria incidence over the study period was stratified by altitude. Spatio-temporal pattern of malaria was analyzed. Results Nationwide, malaria incidence was stationary. Regionally, the incidence increased markedly in the highland region (292.0/100000/yr, p =0.021, and remained stationary in the other regions. Seasonality of the malaria incidence was related with rainfall. Decreasing incidence of malaria was associated with decreasing rainfall in the southern coastal region, whereas it was not evident in the northern coastal region. In the Eastern Highland Province, malaria incidence increased in areas below 1700 m, with the rate of increase being steeper at higher altitudes. Conclusions Increasing trend of malaria incidence was prominent in the highland region of Papua New Guinea, while long-term trend was dependent upon baseline level of rainfall in coastal regions.

  3. Time trend of malaria in relation to climate variability in Papua New Guinea

    Science.gov (United States)

    Kolam, Joel; Inape, Kasis

    2016-01-01

    Objectives This study was conducted to describe the regional malaria incidence in relation to the geographic and climatic conditions and describe the effect of altitude on the expansion of malaria over the last decade in Papua New Guinea. Methods Malaria incidence was estimated in five provinces from 1996 to 2008 using national health surveillance data. Time trend of malaria incidence was compared with rainfall and minimum/maximum temperature. In the Eastern Highland Province, time trend of malaria incidence over the study period was stratified by altitude. Spatio-temporal pattern of malaria was analyzed. Results Nationwide, malaria incidence was stationary. Regionally, the incidence increased markedly in the highland region (292.0/100000/yr, p =0.021), and remained stationary in the other regions. Seasonality of the malaria incidence was related with rainfall. Decreasing incidence of malaria was associated with decreasing rainfall in the southern coastal region, whereas it was not evident in the northern coastal region. In the Eastern Highland Province, malaria incidence increased in areas below 1700 m, with the rate of increase being steeper at higher altitudes. Conclusions Increasing trend of malaria incidence was prominent in the highland region of Papua New Guinea, while long-term trend was dependent upon baseline level of rainfall in coastal regions. PMID:26987606

  4. Optimal conservation resource allocation under variable economic and ecological time discounting rates in boreal forest.

    Science.gov (United States)

    Mazziotta, Adriano; Pouzols, Federico Montesino; Mönkkönen, Mikko; Kotiaho, Janne S; Strandman, Harri; Moilanen, Atte

    2016-09-15

    Resource allocation to multiple alternative conservation actions is a complex task. A common trade-off occurs between protection of smaller, expensive, high-quality areas versus larger, cheaper, partially degraded areas. We investigate optimal allocation into three actions in boreal forest: current standard forest management rules, setting aside of mature stands, or setting aside of clear-cuts. We first estimated how habitat availability for focal indicator species and economic returns from timber harvesting develop through time as a function of forest type and action chosen. We then developed an optimal resource allocation by accounting for budget size and habitat availability of indicator species in different forest types. We also accounted for the perspective adopted towards sustainability, modeled via temporal preference and economic and ecological time discounting. Controversially, we found that in boreal forest set-aside followed by protection of clear-cuts can become a winning cost-effective strategy when accounting for habitat requirements of multiple species, long planning horizon, and limited budget. It is particularly effective when adopting a long-term sustainability perspective, and accounting for present revenues from timber harvesting. The present analysis assesses the cost-effective conditions to allocate resources into an inexpensive conservation strategy that nevertheless has potential to produce high ecological values in the future. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Modeling Time-Dependent Behavior of Concrete Affected by Alkali Silica Reaction in Variable Environmental Conditions.

    Science.gov (United States)

    Alnaggar, Mohammed; Di Luzio, Giovanni; Cusatis, Gianluca

    2017-04-28

    Alkali Silica Reaction (ASR) is known to be a serious problem for concrete worldwide, especially in high humidity and high temperature regions. ASR is a slow process that develops over years to decades and it is influenced by changes in environmental and loading conditions of the structure. The problem becomes even more complicated if one recognizes that other phenomena like creep and shrinkage are coupled with ASR. This results in synergistic mechanisms that can not be easily understood without a comprehensive computational model. In this paper, coupling between creep, shrinkage and ASR is modeled within the Lattice Discrete Particle Model (LDPM) framework. In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is then used within physics-based formulations of cracking, creep and shrinkage. The overall model is calibrated and validated on the basis of experimental data available in the literature. Results show that even during free expansions (zero macroscopic stress), a significant degree of coupling exists because ASR induced expansions are relaxed by meso-scale creep driven by self-equilibriated stresses at the meso-scale. This explains and highlights the importance of considering ASR and other time dependent aging and deterioration phenomena at an appropriate length scale in coupled modeling approaches.

  6. Seasonal and local time variability of ripples from airglow imager observations in US and Japan

    Directory of Open Access Journals (Sweden)

    J. Yue

    2010-07-01

    Full Text Available Ripples as seen in airglow imagers are small wavy structures with short horizontal wavelengths (<15 km. Ripples are thought to form as the result of local instabilities, which are believed to occur when the amplitude of gravity waves becomes large enough. We have investigated ripple formation based on years of airglow imager observations located at Fort Collins, Colorado (41° N, 105° W and Misato Observatory, Japan (34° N, 135° E/Shigaraki MU Observatory (35° N, 136° E. Na temperature-wind lidar observations are employed to detect convective and dynamic instabilities in the mesosphere and lower thermosphere (MLT region over Fort Collins, Colorado. Seasonal variation of the ripple occurrence in Colorado is compared to that of the lidar-measured instability. The occurrence frequency of ripples varies semiannually, with maxima occurring during solstices and minima during equinoxes in both Colorado and Japan. However, the probability of convective and dynamic instabilities varies annually with a peak in Colorado winter. The seasonal variation of the occurrence frequency of ripples correlates with that of the gravity wave variances in the MLT. Ripple occurrence over Colorado also shows strong local time dependence, but it bears little resemblance to the local time dependence of instability probability.

  7. People typically experience extended periods of relative happiness or unhappiness due to positive feedback loops between LS and variables which are both causes and consequences of LS

    NARCIS (Netherlands)

    Headey, Bruce; Muffels, R.J.A.

    2015-01-01

    Long term panel data enable researchers to construct trajectories of LS for individuals over time. Bar charts of trajectories, and subsequent statistical analysis, show that respondents typically spend multiple consecutive years above and below their own long-term mean level of LS. We attempt to

  8. Coulomb stress change sensitivity due to variability in mainshock source models and receiving fault parameters: A case study of the 2010-2011 Christchurch, New Zealand, earthquakes

    Science.gov (United States)

    Zhan, Zhongwen; Jin, Bikai; Wei, Shengji; Graves, Robert W.

    2011-01-01

    Strong aftershocks following major earthquakes present significant challenges for infrastructure recovery as well as for emergency rescue efforts. A tragic instance of this is the 22 February 2011 Mw 6.3 Christchurch aftershock in New Zealand, which caused more than 100 deaths while the 2010 Mw 7.1 Canterbury mainshock did not cause a single fatality (Figure 1). Therefore, substantial efforts have been directed toward understanding the generation mechanisms of aftershocks as well as mitigating hazards due to aftershocks. Among these efforts are the prediction of strong aftershocks, earthquake early warning, and aftershock probability assessment. Zhang et al. (1999) reported a successful case of strong aftershock prediction with precursory data such as changes in seismicity pattern, variation of b-value, and geomagnetic anomalies. However, official reports of such successful predictions in geophysical journals are extremely rare, implying that deterministic prediction of potentially damaging aftershocks is not necessarily more scientifically feasible than prediction of mainshocks.

  9. Temporal variability of surface runoff due to cropping systems in cultivated catchment areas: Use of the DIAR model for the assessment of environmental public policies in the Pays de Caux (France).

    Science.gov (United States)

    Martin, P; Joannon, A; Piskiewicz, N

    2010-01-01

    This article proposes the use of a new model, DIAR (Diagnostic Agronomique du Ruissellement, or Agronomic Assessment of Runoff), for the prediction of the timing of the risk of runoff. DIAR is dedicated to loamy soils which are very sensitive to surface crusting, leading to runoff, soil erosion and muddy flows. The approach is proposed for the north-western European loess belt regions where muddy flows severely impact human activities. The likelihood of runoff is assessed from the sequence of soil surface states generated by cultivation practices. DIAR is based on the calculation of curve number values, for each stage of the soil-surface-state sequence, for calculating runoff for each of these stages. In this study, DIAR is applied to a catchment of 912 ha, cultivated by 26 farmers in the Pays de Caux (Normandy, France) where infrastructures located at the outlet have been damaged several times by muddy flows. Local public authorities involved in reducing muddy flows are eager to limit the agricultural upstream runoff by extending the planting of mustard as a winter cover crop. We tested the efficiency of such a policy on the reduction of the mean runoff. We also tested the year-to-year variability of this efficiency using the acreages of four successive years (1999-2000 to 2002-2003). Finally, the cost-efficiency of the policy was also considered. Though we used the same weather scenario, the initial situation (without much mustard cover) showed a wide year-to-year variation in the total runoff. This variation can be associated with the structure of the farms that cultivate the catchment (Utilised Agricultural Area (UAA) of each farm and percentage of this UAA inside the catchment). Our results showed that the widespread planting of winter cover crops could reduce the runoff by 10-20% compared with the initial situation (depending on the year), and also reduce the year-to-year variability of runoff. For each of the 4 tested years, the cost of the infiltrated m(3

  10. Gear fault diagnosis under variable conditions with intrinsic time-scale decomposition-singular value decomposition and support vector machine

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Zhanqiang; Qu, Jianfeng; Chai, Yi; Tang, Qiu; Zhou, Yuming [Chongqing University, Chongqing (China)

    2017-02-15

    The gear vibration signal is nonlinear and non-stationary, gear fault diagnosis under variable conditions has always been unsatisfactory. To solve this problem, an intelligent fault diagnosis method based on Intrinsic time-scale decomposition (ITD)-Singular value decomposition (SVD) and Support vector machine (SVM) is proposed in this paper. The ITD method is adopted to decompose the vibration signal of gearbox into several Proper rotation components (PRCs). Subsequently, the singular value decomposition is proposed to obtain the singular value vectors of the proper rotation components and improve the robustness of feature extraction under variable conditions. Finally, the Support vector machine is applied to classify the fault type of gear. According to the experimental results, the performance of ITD-SVD exceeds those of the time-frequency analysis methods with EMD and WPT combined with SVD for feature extraction, and the classifier of SVM outperforms those for K-nearest neighbors (K-NN) and Back propagation (BP). Moreover, the proposed approach can accurately diagnose and identify different fault types of gear under variable conditions.

  11. A possible interrelation between Earth rotation and climatic variability at decadal time-scale

    Directory of Open Access Journals (Sweden)

    Leonid Zotov

    2016-05-01

    Full Text Available Using multichannel singular spectrum analysis (MSSA we decomposed climatic time series into principal components, and compared them with Earth rotation parameters. The global warming trends were initially subtracted. Similar quasi 60 and 20 year periodic oscillations have been found in the global mean Earth temperature anomaly (HadCRUT4 and global mean sea level (GMSL. Similar cycles were also found in Earth rotation variation. Over the last 160 years multi-decadal change of Earth's rotation velocity is correlated with the 60-year temperature anomaly, and Chandler wobble envelope reproduces the form of the 60-year oscillation noticed in GMSL. The quasi 20-year oscillation observed in GMSL is correlated with the Chandler wobble excitation. So, we assume that Earth's rotation and climate indexes are connected. Despite of all the clues hinting this connection, no sound conclusion can be done as far as ocean circulation modelling is not able to correctly catch angular momentum of the oscillatory modes.

  12. Space-time variability of citrus leprosis as strategic planning for crop management.

    Science.gov (United States)

    Andrade, Daniel J; Lorençon, José R; Siqueira, Diego S; Novelli, Valdenice M; Bassanezi, Renato B

    2018-01-31

    Citrus leprosis is the most important viral disease of citrus. Knowledge of its spatiotemporal structure is fundamental to a representative sampling plan focused on the disease control approach. Such a well-crafted sampling design helps to reduce pesticide use in agriculture to control pests and diseases. Despite the use of acaricides to control citrus leprosis vector (Brevipalpus spp.) populations, the disease has spread rapidly through experimental areas. Citrus leprosis has an aggregate spatial distribution, with high dependence among symptomatic plants. Temporal variation in disease incidence increased among symptomatic plants by 4% per month. Use of acaricides alone to control the vector of leprosis is insufficient to avoid its incidence in healthy plants. Preliminary investigation into the time and space variation in the incidence of the disease is fundamental to select a sampling plan and determine effective strategies for disease management. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

  13. Cometary science. Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko.

    Science.gov (United States)

    Hässig, M; Altwegg, K; Balsiger, H; Bar-Nun, A; Berthelier, J J; Bieler, A; Bochsler, P; Briois, C; Calmonte, U; Combi, M; De Keyser, J; Eberhardt, P; Fiethe, B; Fuselier, S A; Galand, M; Gasc, S; Gombosi, T I; Hansen, K C; Jäckel, A; Keller, H U; Kopp, E; Korth, A; Kührt, E; Le Roy, L; Mall, U; Marty, B; Mousis, O; Neefs, E; Owen, T; Rème, H; Rubin, M; Sémon, T; Tornow, C; Tzou, C-Y; Waite, J H; Wurz, P

    2015-01-23

    Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface. Copyright © 2015, American Association for the Advancement of Science.

  14. Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko

    Science.gov (United States)

    Hässig, M.; Altwegg, K.; Balsiger, H.; Bar-Nun, A.; Berthelier, J. J.; Bieler, A.; Bochsler, P.; Briois, C.; Calmonte, U.; Combi, M.; De Keyser, J.; Eberhardt, P.; Fiethe, B.; Fuselier, S. A.; Galand, M.; Gasc, S.; Gombosi, T. I.; Hansen, K. C.; Jäckel, A.; Keller, H. U.; Kopp, E.; Korth, A.; Kührt, E.; Le Roy, L.; Mall, U.; Marty, B.; Mousis, O.; Neefs, E.; Owen, T.; Rème, H.; Rubin, M.; Sémon, T.; Tornow, C.; Tzou, C.-Y.; Waite, J. H.; Wurz, P.

    2015-01-01

    Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface.

  15. Microparticles variability in fresh frozen plasma: preparation protocol and storage time effects.

    Science.gov (United States)

    Kriebardis, Anastasios G; Antonelou, Marianna H; Georgatzakou, Hara T; Tzounakas, Vassilis L; Stamoulis, Konstantinos E; Papassideri, Issidora S

    2016-05-01

    Extracellular vesicles or microparticles exhibiting procoagulant and thrombogenic activity may contribute to the haemostatic potential of fresh frozen plasma. Fresh frozen plasma was prepared from platelet-rich plasma at 20 °C (Group-1 donors) or directly from whole blood at 4 °C (Group-2 donors). Each unit was aseptically divided into three parts, stored frozen for specific periods of time, and analysed by flow cytometry for procoagulant activity immediately after thaw or following post-thaw storage for 24 h at 4 °C. Donors' haematologic, biochemical and life-style profiles as well as circulating microparticles were analysed in parallel. Circulating microparticles exhibited a considerable interdonor but not intergroup variation. Fresh frozen plasma units were enriched in microparticles compared to plasma in vivo. Duration of storage significantly affected platelet- and red cell-derived microparticles. Fresh frozen plasma prepared directly from whole blood contained more residual platelets and more platelet-derived microparticles compared to fresh frozen plasma prepared from platelet-rich plasma. Consequently, there was a statistically significant difference in total, platelet- and red cell-derived microparticles between the two preparation protocols over storage time in the freezer. Preservation of the thawed units for 24 h at 4 °C did not significantly alter microparticle accumulation. Microparticle accumulation and anti-oxidant capacity of fresh frozen plasma was positively or negatively correlated, respectively, with the level of circulating microparticles in individual donors. The preparation protocol and the duration of storage in the freezer, independently and in combination, influenced the accumulation of microparticles in fresh frozen plasma units. In contrast, storage of thawed units for 24 h at 4 °C had no significant effect on the concentration of microparticles.

  16. [Hypothesis on the equilibrium point and variability of amplitude, speed and time of single-joint movement].

    Science.gov (United States)

    Latash, M; Gottleib, G

    1990-01-01

    Problems of single-joint movement variability are analysed in the framework of the equilibrium-point hypothesis (the lambda-model). Control of the movements is described with three parameters related to movement amplitude speed, and time. Three strategies emerge from this description. Only one of them is likely to lead to a Fitts' type speed-accuracy trade-off. Experiments were performed to test one of the predictions of the model. Subjects performed identical sets of single-joint fast movements with open or closed eyes and some-what different instructions. Movements performed with closed eyes were characterized with higher peak speeds and unchanged variability in seeming violation of the Fitt's law and in a good correspondence to the model.

  17. Longitudinal variability of phosphorus fractions in sediments of a canyon reservoir due to cascade dam construction: a case study in Lancang River, China.

    Directory of Open Access Journals (Sweden)

    Qi Liu

    Full Text Available Dam construction causes the accumulation of phosphorus in the sediments of reservoirs and increases the release rate of internal phosphorus (P loading. This study investigated the longitudinal variability of phosphorus fractions in sediments and the relationship between the contents of phosphorus fractions and its influencing factors of the Manwan Reservoir, Lancang River, Yunnan Province, China. Five sedimentary phosphorus fractions were quantified separately: loosely bound P (ex-P; reductant soluble P (BD-P; metal oxide-bound P (NaOH-P; calcium-bound P (HCl-P, and residual-P. The results showed that the total phosphorus contents ranged from 623 to 899 µg/g and were correlated positively with iron content in the sediments of the reservoir. The rank order of P fractions in sediments of the mainstream was HCl-P>NaOH-P>residual-P>BD-P>ex-P, while it was residual-P>HCl-P>NaOH-P>BD-P>ex-P in those of the tributaries. The contents of bio-available phosphorus in the tributaries, including ex-P, BD-P and NaOH-P, were significantly lower than those in the mainstream. The contents of ex-P, BD-P, NaOH-P showed a similar increasing trend from the tail to the head of the Manwan Reservoir, which contributed to the relatively higher content of bio-available phosphorus, and represents a high bio-available phosphorus releasing risk within a distance of 10 km from Manwan Dam. Correlation and redundancy analyses showed that distance to Manwan Dam and the silt/clay fraction of sediments were related closely to the spatial variation of bio-available phosphorus.

  18. Tempts to determine radon entry rate and air exchange rate variable in time from the time course of indoor radon concentration

    International Nuclear Information System (INIS)

    Thomas, J.

    1996-01-01

    For the study and explanation of the diurnal variability of the indoor radon concentration a(t) [Bq/m 3 ], which is proportional to the ratio of the radon entry rate A [Bq/h] and the air exchange rate k [1/h], it would be of advantage to know separately the diurnal variability of both determining quantities A(t) and k(t). To measure directly and continuously the radon entry rate A(t) is possible only in special studies (mostly in experimental rooms) and also continuous measuring of the air exchange rate k(t) is possible also only in special studies for a short time. But continuously measuring radon meters are now common, do not trouble people in normal living regime during day and night. The goal of this endeavour would be the evaluation of the time courses of both determining quantities from the time courses of the indoor radon concentration directly without additional experimental work and so a better utilisation of such measurements. (author)

  19. Variable elasticity of substituition in a discrete time Solow–Swan growth model with differential saving

    International Nuclear Information System (INIS)

    Brianzoni, Serena; Mammana, Cristiana; Michetti, Elisabetta

    2012-01-01

    Highlights: ► One dimensional piecewise smooth map: border collision bifurcations. ► Numerical simulations: complex dynamics. ► Ves production function in the solow–swan growth model and comparison with the ces production function. - Abstract: We study the dynamics shown by the discrete time neoclassical one-sector growth model with differential savings as in Bohm and Kaas while assuming VES production function in the form given by Revankar . It is shown that the model can exhibit unbounded endogenous growth despite the absence of exogenous technical change and the presence of non-reproducible factors if the elasticity of substitution is greater than one. We then consider parameters range related to non-trivial dynamics (i.e. the elasticity of substitution in less than one and shareholders save more than workers) and we focus on local and global bifurcations causing the transition to more and more complex asymptotic dynamics. In particular, as our map is non-differentiable in a subset of the states space, we show that border collision bifurcations occur. Several numerical simulations support the analysis.

  20. On a random area variable arising in discrete-time queues and compact directed percolation

    International Nuclear Information System (INIS)

    Kearney, Michael J

    2004-01-01

    A well-known discrete-time, single-server queueing system with mean arrival rate λ and mean departure rate μ is considered from the perspective of the area, A, swept out by the queue occupation process during a busy period. We determine the exact form of the tail of the distribution, Pr(A > x); in particular, we show that Pr(A > x) ∼ Cx -1/4 exp(-Dx 1/2 ) for all ρ ≠ 1, where ρ ≡ λ/μ, and expressions for C and D are given. For the critical case ρ = 1 we show that Pr(A > x) ∼ C'x -1/3 , with C' also given. A simple mapping, used in the derivation, establishes a connection with compact directed percolation on a square lattice. As a corollary, therefore, we are also able to specify the large-area asymptotic behaviour of this model at all points in the phase diagram. This extends previous scaling results, which are only valid close to the percolation threshold