Periodic solutions of second-order nonlinear difference equations containing a small parameter. IV - Multi-discrete time method

NASA Technical Reports Server (NTRS)

Mickens, Ronald E.

1987-01-01

It is shown that a discrete multi-time method can be constructed to obtain approximations to the periodic solutions of a special class of second-order nonlinear difference equations containing a small parameter. Three examples illustrating the method are presented.

Periodic trim solutions with hp-version finite elements in time

NASA Technical Reports Server (NTRS)

Peters, David A.; Hou, Lin-Jun

1990-01-01

Finite elements in time as an alternative strategy for rotorcraft trim problems are studied. The research treats linear flap and linearized flap-lag response both for quasi-trim and trim cases. The connection between Fourier series analysis and hp-finite elements for periodic a problem is also examined. It is proved that Fourier series is a special case of space-time finite elements in which one element is used with a strong displacement formulation. Comparisons are made with respect to accuracy among Fourier analysis, displacement methods, and mixed methods over a variety parameters. The hp trade-off is studied for the periodic trim problem to provide an optimum step size and order of polynomial for a given error criteria. It is found that finite elements in time can outperform Fourier analysis for periodic problems, and for some given error criteria. The mixed method provides better results than does the displacement method.

Sampling maternal care behaviour in domestic dogs: What's the best approach?

PubMed

Czerwinski, Veronika H; Smith, Bradley P; Hynd, Philip I; Hazel, Susan J

2017-07-01

Our understanding of the frequency and duration of maternal care behaviours in the domestic dog during the first two postnatal weeks is limited, largely due to the inconsistencies in the sampling methodologies that have been employed. In order to develop a more concise picture of maternal care behaviour during this period, and to help establish the sampling method that represents these behaviours best, we compared a variety of time sampling methods Six litters were continuously observed for a total of 96h over postnatal days 3, 6, 9 and 12 (24h per day). Frequent (dam presence, nursing duration, contact duration) and infrequent maternal behaviours (anogenital licking duration and frequency) were coded using five different time sampling methods that included: 12-h night (1800-0600h), 12-h day (0600-1800h), one hour period during the night (1800-0600h), one hour period during the day (0600-1800h) and a one hour period anytime. Each of the one hour time sampling method consisted of four randomly chosen 15-min periods. Two random sets of four 15-min period were also analysed to ensure reliability. We then determined which of the time sampling methods averaged over the three 24-h periods best represented the frequency and duration of behaviours. As might be expected, frequently occurring behaviours were adequately represented by short (oneh) sampling periods, however this was not the case with the infrequent behaviour. Thus, we argue that the time sampling methodology employed must match the behaviour of interest. This caution applies to maternal behaviour in altricial species, such as canids, as well as all systematic behavioural observations utilising time sampling methodology. Copyright © 2017. Published by Elsevier B.V.

Optical properties of electrohydrodynamic convection patterns: rigorous and approximate methods.

PubMed

Bohley, Christian; Heuer, Jana; Stannarius, Ralf

2005-12-01

We analyze the optical behavior of two-dimensionally periodic structures that occur in electrohydrodynamic convection (EHC) patterns in nematic sandwich cells. These structures are anisotropic, locally uniaxial, and periodic on the scale of micrometers. For the first time, the optics of these structures is investigated with a rigorous method. The method used for the description of the electromagnetic waves interacting with EHC director patterns is a numerical approach that discretizes directly the Maxwell equations. It works as a space-grid-time-domain method and computes electric and magnetic fields in time steps. This so-called finite-difference-time-domain (FDTD) method is able to generate the fields with arbitrary accuracy. We compare this rigorous method with earlier attempts based on ray-tracing and analytical approximations. Results of optical studies of EHC structures made earlier based on ray-tracing methods are confirmed for thin cells, when the spatial periods of the pattern are sufficiently large. For the treatment of small-scale convection structures, the FDTD method is without alternatives.

Price of gasoline: forecasting comparisons. [Box-Jenkins, econometric, and regression methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bopp, A.E.; Neri, J.A.

Gasoline prices are simulated using three popular forecasting methodologies: A Box--Jenkins type method, an econometric method, and a regression method. One-period-ahead and 18-period-ahead comparisons are made. For the one-period-ahead method, a Box--Jenkins type time-series model simulated best, although all do well. However, for the 18-period simulation, the econometric and regression methods perform substantially better than the Box-Jenkins formulation. A rationale for and implications of these results ae discussed. 11 references.

A stacking method and its applications to Lanzarote tide gauge records

NASA Astrophysics Data System (ADS)

Zhu, Ping; van Ruymbeke, Michel; Cadicheanu, Nicoleta

2009-12-01

A time-period analysis tool based on stacking is introduced in this paper. The original idea comes from the classical tidal analysis method. It is assumed that the period of each major tidal component is precisely determined based on the astronomical constants and it is unchangeable with time at a given point in the Earth. We sum the tidal records at a fixed tidal component center period T then take the mean of it. The stacking could significantly increase the signal-to-noise ratio (SNR) if a certain number of stacking circles is reached. The stacking results were fitted using a sinusoidal function, the amplitude and phase of the fitting curve is computed by the least squares methods. The advantage of the method is that: (1) an individual periodical signal could be isolated by stacking; (2) one can construct a linear Stacking-Spectrum (SSP) by changing the stacking period Ts; (3) the time-period distribution of the singularity component could be approximated by a Sliding-Stacking approach. The shortcoming of the method is that in order to isolate a low energy frequency or separate the nearby frequencies, we need a long enough series with high sampling rate. The method was tested with a numeric series and then it was applied to 1788 days Lanzarote tide gauge records as an example.

Method of preparing size-selected metal clusters

DOEpatents

Elam, Jeffrey W.; Pellin, Michael J.; Stair, Peter C.

2010-05-11

The invention provides a method for depositing catalytic clusters on a surface, the method comprising confining the surface to a controlled atmosphere; contacting the surface with catalyst containing vapor for a first period of time; removing the vapor from the controlled atmosphere; and contacting the surface with a reducing agent for a second period of time so as to produce catalyst-containing nucleation sites.

Contribution to harmonic balance calculations of self-sustained periodic oscillations with focus on single-reed instruments.

PubMed

Farner, Snorre; Vergez, Christophe; Kergomard, Jean; Lizée, Aude

2006-03-01

The harmonic balance method (HBM) was originally developed for finding periodic solutions of electronical and mechanical systems under a periodic force, but has been adapted to self-sustained musical instruments. Unlike time-domain methods, this frequency-domain method does not capture transients and so is not adapted for sound synthesis. However, its independence of time makes it very useful for studying any periodic solution, whether stable or unstable, without care of particular initial conditions in time. A computer program for solving general problems involving nonlinearly coupled exciter and resonator, HARMBAL, has been developed based on the HBM. The method as well as convergence improvements and continuation facilities are thoroughly presented and discussed in the present paper. Applications of the method are demonstrated, especially on problems with severe difficulties of convergence: the Helmholtz motion (square signals) of single-reed instruments when no losses are taken into account, the reed being modeled as a simple spring.

Comparison of calculation methods for estimating annual carbon stock change in German forests under forest management in the German greenhouse gas inventory.

PubMed

Röhling, Steffi; Dunger, Karsten; Kändler, Gerald; Klatt, Susann; Riedel, Thomas; Stümer, Wolfgang; Brötz, Johannes

2016-12-01

The German greenhouse gas inventory in the land use change sector strongly depends on national forest inventory data. As these data were collected periodically 1987, 2002, 2008 and 2012, the time series on emissions show several "jumps" due to biomass stock change, especially between 2001 and 2002 and between 2007 and 2008 while within the periods the emissions seem to be constant due to the application of periodical average emission factors. This does not reflect inter-annual variability in the time series, which would be assumed as the drivers for the carbon stock changes fluctuate between the years. Therefore additional data, which is available on annual basis, should be introduced into the calculations of the emissions inventories in order to get more plausible time series. This article explores the possibility of introducing an annual rather than periodical approach to calculating emission factors with the given data and thus smoothing the trajectory of time series for emissions from forest biomass. Two approaches are introduced to estimate annual changes derived from periodic data: the so-called logging factor method and the growth factor method. The logging factor method incorporates annual logging data to project annual values from periodic values. This is less complex to implement than the growth factor method, which additionally adds growth data into the calculations. Calculation of the input variables is based on sound statistical methodologies and periodically collected data that cannot be altered. Thus a discontinuous trajectory of the emissions over time remains, even after the adjustments. It is intended to adopt this approach in the German greenhouse gas reporting in order to meet the request for annually adjusted values.

Time-series analysis of multiple foreign exchange rates using time-dependent pattern entropy

NASA Astrophysics Data System (ADS)

Ishizaki, Ryuji; Inoue, Masayoshi

2018-01-01

Time-dependent pattern entropy is a method that reduces variations to binary symbolic dynamics and considers the pattern of symbols in a sliding temporal window. We use this method to analyze the instability of daily variations in multiple foreign exchange rates. The time-dependent pattern entropy of 7 foreign exchange rates (AUD/USD, CAD/USD, CHF/USD, EUR/USD, GBP/USD, JPY/USD, and NZD/USD) was found to be high in the long period after the Lehman shock, and be low in the long period after Mar 2012. We compared the correlation matrix between exchange rates in periods of high and low of the time-dependent pattern entropy.

Quasi-Periodic Pulse Amplitude Modulation in the Accreting Millisecond Pulsar IGR J00291+5934

NASA Technical Reports Server (NTRS)

Bult, Peter; van Doesburgh, Marieke; van der Klis, Michiel

2017-01-01

We introduce a new method for analyzing the a periodic variability of coherent pulsations in accreting millisecond X-ray pulsars (AMXPs). Our method involves applying a complex frequency correction to the time-domain lightcurve, allowing for the aperiodic modulation of the pulse amplitude to be robustly extracted in the frequency domain. We discuss the statistical properties of the resulting modulation spectrum and show how it can be correlated with the non-pulsed emission to determine if the periodic and a periodic variability are coupled processes. Using this method, we study the 598.88 Hz coherent pulsations of the AMXP IGR J00291+5934 as observed with the Rossi X-ray Timing Explorer and XMM-Newton. We demonstrate that our method easily confirms the known coupling between the pulsations and a strong 8 mHz quasi-periodic oscillation (QPO) in XMM-Newton observations. Applying our method to the RXTE observations, we further show, for the first time, that the much weaker 20 mHz QPO and its harmonic are also coupled with the pulsations. We discuss the implications of this coupling and indicate how it may be used to extract new information on the underlying accretion process.

[Local fractal analysis of noise-like time series by all permutations method for 1-115 min periods].

PubMed

Panchelyuga, V A; Panchelyuga, M S

2015-01-01

Results of local fractal analysis of 329-per-day time series of 239Pu alpha-decay rate fluctuations by means of all permutations method (APM) are presented. The APM-analysis reveals in the time series some steady frequency set. The coincidence of the frequency set with the Earth natural oscillations was demonstrated. A short review of works by different authors who analyzed the time series of fluctuations in processes of different nature is given. We have shown that the periods observed in those works correspond to the periods revealed in our study. It points to a common mechanism of the phenomenon observed.

Selecting a proper design period for heliostat field layout optimization using Campo code

NASA Astrophysics Data System (ADS)

Saghafifar, Mohammad; Gadalla, Mohamed

2016-09-01

In this paper, different approaches are considered to calculate the cosine factor which is utilized in Campo code to expand the heliostat field layout and maximize its annual thermal output. Furthermore, three heliostat fields containing different number of mirrors are taken into consideration. Cosine factor is determined by considering instantaneous and time-average approaches. For instantaneous method, different design days and design hours are selected. For the time average method, daily time average, monthly time average, seasonally time average, and yearly time averaged cosine factor determinations are considered. Results indicate that instantaneous methods are more appropriate for small scale heliostat field optimization. Consequently, it is proposed to consider the design period as the second design variable to ensure the best outcome. For medium and large scale heliostat fields, selecting an appropriate design period is more important. Therefore, it is more reliable to select one of the recommended time average methods to optimize the field layout. Optimum annual weighted efficiency for heliostat fields (small, medium, and large) containing 350, 1460, and 3450 mirrors are 66.14%, 60.87%, and 54.04%, respectively.

Long-Term Prediction of the Arctic Ionospheric TEC Based on Time-Varying Periodograms

PubMed Central

Liu, Jingbin; Chen, Ruizhi; Wang, Zemin; An, Jiachun; Hyyppä, Juha

2014-01-01

Knowledge of the polar ionospheric total electron content (TEC) and its future variations is of scientific and engineering relevance. In this study, a new method is developed to predict Arctic mean TEC on the scale of a solar cycle using previous data covering 14 years. The Arctic TEC is derived from global positioning system measurements using the spherical cap harmonic analysis mapping method. The study indicates that the variability of the Arctic TEC results in highly time-varying periodograms, which are utilized for prediction in the proposed method. The TEC time series is divided into two components of periodic oscillations and the average TEC. The newly developed method of TEC prediction is based on an extrapolation method that requires no input of physical observations of the time interval of prediction, and it is performed in both temporally backward and forward directions by summing the extrapolation of the two components. The backward prediction indicates that the Arctic TEC variability includes a 9 years period for the study duration, in addition to the well-established periods. The long-term prediction has an uncertainty of 4.8–5.6 TECU for different period sets. PMID:25369066

10 CFR Appendix Y to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Battery Chargers

Code of Federal Regulations, 2011 CFR

2011-01-01

... power (i.e., watts) consumed as the time series integral of the power consumed over a 1-hour test period...) consumed as the time series integral of the power consumed over a 1-hour test period, divided by the period...-maintenance mode and standby mode over time periods defined in the test procedure. b. Active mode is the...

10 CFR Appendix Y to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Battery Chargers

Code of Federal Regulations, 2010 CFR

2010-01-01

... power (i.e., watts) consumed as the time series integral of the power consumed over a 1-hour test period...) consumed as the time series integral of the power consumed over a 1-hour test period, divided by the period...-maintenance mode and standby mode over time periods defined in the test procedure. b. Active mode is the...

Stochastic model stationarization by eliminating the periodic term and its effect on time series prediction

NASA Astrophysics Data System (ADS)

Moeeni, Hamid; Bonakdari, Hossein; Fatemi, Seyed Ehsan

2017-04-01

Because time series stationarization has a key role in stochastic modeling results, three methods are analyzed in this study. The methods are seasonal differencing, seasonal standardization and spectral analysis to eliminate the periodic effect on time series stationarity. First, six time series including 4 streamflow series and 2 water temperature series are stationarized. The stochastic term for these series obtained with ARIMA is subsequently modeled. For the analysis, 9228 models are introduced. It is observed that seasonal standardization and spectral analysis eliminate the periodic term completely, while seasonal differencing maintains seasonal correlation structures. The obtained results indicate that all three methods present acceptable performance overall. However, model accuracy in monthly streamflow prediction is higher with seasonal differencing than with the other two methods. Another advantage of seasonal differencing over the other methods is that the monthly streamflow is never estimated as negative. Standardization is the best method for predicting monthly water temperature although it is quite similar to seasonal differencing, while spectral analysis performed the weakest in all cases. It is concluded that for each monthly seasonal series, seasonal differencing is the best stationarization method in terms of periodic effect elimination. Moreover, the monthly water temperature is predicted with more accuracy than monthly streamflow. The criteria of the average stochastic term divided by the amplitude of the periodic term obtained for monthly streamflow and monthly water temperature were 0.19 and 0.30, 0.21 and 0.13, and 0.07 and 0.04 respectively. As a result, the periodic term is more dominant than the stochastic term for water temperature in the monthly water temperature series compared to streamflow series.

Interpreting Significant Discrete-Time Periods in Survival Analysis.

ERIC Educational Resources Information Center

Schumacker, Randall E.; Denson, Kathleen B.

Discrete-time survival analysis is a new method for educational researchers to employ when looking at the timing of certain educational events. Previous continuous-time methods do not allow for the flexibility inherent in a discrete-time method. Because both time-invariant and time-varying predictor variables can now be used, the interaction of…

An improved correlation method for determining the period of a torsion pendulum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo Jie; Wang Dianhong

Considering variation of environment temperature and unhomogeneity of background gravitational field, an improved correlation method was proposed to determine the variational period of a torsion pendulum with high precision. The result of processing experimental data shows that the uncertainty of determining the period with this method has been improved about twofolds than traditional correlation method, which is significant for the determination of gravitational constant with time-of-swing method.

Stable and verifiable state estimation methods and systems with spacecraft applications

NASA Technical Reports Server (NTRS)

Li, Rongsheng (Inventor); Wu, Yeong-Wei Andy (Inventor)

2001-01-01

The stability of a recursive estimator process (e.g., a Kalman filter is assured for long time periods by periodically resetting an error covariance P(t.sub.n) of the system to a predetermined reset value P.sub.r. The recursive process is thus repetitively forced to start from a selected covariance and continue for a time period that is short compared to the system's total operational time period. The time period in which the process must maintain its numerical stability is significantly reduced as is the demand on the system's numerical stability. The process stability for an extended operational time period T.sub.o is verified by performing the resetting step at the end of at least one reset time period T.sub.r whose duration is less than the operational time period T.sub.o and then confirming stability of the process over the reset time period T.sub.r. Because the recursive process starts from a selected covariance at the beginning of each reset time period T.sub.r, confirming stability of the process over at least one reset time period substantially confirms stability over the longer operational time period T.sub.o.

On the discretization and control of an SEIR epidemic model with a periodic impulsive vaccination

NASA Astrophysics Data System (ADS)

Alonso-Quesada, S.; De la Sen, M.; Ibeas, A.

2017-01-01

This paper deals with the discretization and control of an SEIR epidemic model. Such a model describes the transmission of an infectious disease among a time-varying host population. The model assumes mortality from causes related to the disease. Our study proposes a discretization method including a free-design parameter to be adjusted for guaranteeing the positivity of the resulting discrete-time model. Such a method provides a discrete-time model close to the continuous-time one without the need for the sampling period to be as small as other commonly used discretization methods require. This fact makes possible the design of impulsive vaccination control strategies with less burden of measurements and related computations if one uses the proposed instead of other discretization methods. The proposed discretization method and the impulsive vaccination strategy designed on the resulting discretized model are the main novelties of the paper. The paper includes (i) the analysis of the positivity of the obtained discrete-time SEIR model, (ii) the study of stability of the disease-free equilibrium point of a normalized version of such a discrete-time model and (iii) the existence and the attractivity of a globally asymptotically stable disease-free periodic solution under a periodic impulsive vaccination. Concretely, the exposed and infectious subpopulations asymptotically converge to zero as time tends to infinity while the normalized subpopulations of susceptible and recovered by immunization individuals oscillate in the context of such a solution. Finally, a numerical example illustrates the theoretic results.

Comparison of detrending methods for fluctuation analysis in hydrology

NASA Astrophysics Data System (ADS)

Zhang, Qiang; Zhou, Yu; Singh, Vijay P.; Chen, Yongqin David

2011-03-01

SummaryTrends within a hydrologic time series can significantly influence the scaling results of fluctuation analysis, such as rescaled range (RS) analysis and (multifractal) detrended fluctuation analysis (MF-DFA). Therefore, removal of trends is important in the study of scaling properties of the time series. In this study, three detrending methods, including adaptive detrending algorithm (ADA), Fourier-based method, and average removing technique, were evaluated by analyzing numerically generated series and observed streamflow series with obvious relative regular periodic trend. Results indicated that: (1) the Fourier-based detrending method and ADA were similar in detrending practices, and given proper parameters, these two methods can produce similarly satisfactory results; (2) detrended series by Fourier-based detrending method and ADA lose the fluctuation information at larger time scales, and the location of crossover points is heavily impacted by the chosen parameters of these two methods; and (3) the average removing method has an advantage over the other two methods, i.e., the fluctuation information at larger time scales is kept well-an indication of relatively reliable performance in detrending. In addition, the average removing method performed reasonably well in detrending a time series with regular periods or trends. In this sense, the average removing method should be preferred in the study of scaling properties of the hydrometeorolgical series with relative regular periodic trend using MF-DFA.

How complete is the ISC-GEM Global Earthquake Catalog?

USGS Publications Warehouse

Michael, Andrew J.

2014-01-01

The International Seismological Centre, in collaboration with the Global Earthquake Model effort, has released a new global earthquake catalog, covering the time period from 1900 through the end of 2009. In order to use this catalog for global earthquake studies, I determined the magnitude of completeness (Mc) as a function of time by dividing the earthquakes shallower than 60 km into 7 time periods based on major changes in catalog processing and data availability and applying 4 objective methods to determine Mc, with uncertainties determined by non-parametric bootstrapping. Deeper events were divided into 2 time periods. Due to differences between the 4 methods, the final Mc was determined subjectively by examining the features that each method focused on in both the cumulative and binned magnitude frequency distributions. The time periods and Mc values for shallow events are: 1900-1917, Mc=7.7; 1918-1939, Mc=7.0; 1940-1954, Mc=6.8; 1955-1963, Mc=6.5; 1964-1975, Mc=6.0; 1976-2003, Mc=5.8; and 2004-2009, Mc=5.7. Using these Mc values for the longest time periods they are valid for (e.g. 1918-2009, 1940-2009,…) the shallow data fits a Gutenberg-Richter distribution with b=1.05 and a=8.3, within 1 standard deviation, with no declustering. The exception is for time periods that include 1900-1917 in which there are only 33 events with M≥ Mc and for those few data b=2.15±0.46. That result calls for further investigations for this time period, ideally having a larger number of earthquakes. For deep events, the results are Mc=7.1 for 1900-1963, although the early data are problematic; and Mc=5.7 for 1964-2009. For that later time period, b=0.99 and a=7.3.

A comparison of estimators from self-controlled case series, case-crossover design, and sequence symmetry analysis for pharmacoepidemiological studies.

PubMed

Takeuchi, Yoshinori; Shinozaki, Tomohiro; Matsuyama, Yutaka

2018-01-08

Despite the frequent use of self-controlled methods in pharmacoepidemiological studies, the factors that may bias the estimates from these methods have not been adequately compared in real-world settings. Here, we comparatively examined the impact of a time-varying confounder and its interactions with time-invariant confounders, time trends in exposures and events, restrictions, and misspecification of risk period durations on the estimators from three self-controlled methods. This study analyzed self-controlled case series (SCCS), case-crossover (CCO) design, and sequence symmetry analysis (SSA) using simulated and actual electronic medical records datasets. We evaluated the performance of the three self-controlled methods in simulated cohorts for the following scenarios: 1) time-invariant confounding with interactions between the confounders, 2) time-invariant and time-varying confounding without interactions, 3) time-invariant and time-varying confounding with interactions among the confounders, 4) time trends in exposures and events, 5) restricted follow-up time based on event occurrence, and 6) patient restriction based on event history. The sensitivity of the estimators to misspecified risk period durations was also evaluated. As a case study, we applied these methods to evaluate the risk of macrolides on liver injury using electronic medical records. In the simulation analysis, time-varying confounding produced bias in the SCCS and CCO design estimates, which aggravated in the presence of interactions between the time-invariant and time-varying confounders. The SCCS estimates were biased by time trends in both exposures and events. Erroneously short risk periods introduced bias to the CCO design estimate, whereas erroneously long risk periods introduced bias to the estimates of all three methods. Restricting the follow-up time led to severe bias in the SSA estimates. The SCCS estimates were sensitive to patient restriction. The case study showed that although macrolide use was significantly associated with increased liver injury occurrence in all methods, the value of the estimates varied. The estimations of the three self-controlled methods depended on various underlying assumptions, and the violation of these assumptions may cause non-negligible bias in the resulting estimates. Pharmacoepidemiologists should select the appropriate self-controlled method based on how well the relevant key assumptions are satisfied with respect to the available data.

Detection of Diurnal Variation of Tomato Transcriptome through the Molecular Timetable Method in a Sunlight-Type Plant Factory.

PubMed

Higashi, Takanobu; Tanigaki, Yusuke; Takayama, Kotaro; Nagano, Atsushi J; Honjo, Mie N; Fukuda, Hirokazu

2016-01-01

The timing of measurement during plant growth is important because many genes are expressed periodically and orchestrate physiological events. Their periodicity is generated by environmental fluctuations as external factors and the circadian clock as the internal factor. The circadian clock orchestrates physiological events such as photosynthesis or flowering and it enables enhanced growth and herbivory resistance. These characteristics have possible applications for agriculture. In this study, we demonstrated the diurnal variation of the transcriptome in tomato (Solanum lycopersicum) leaves through molecular timetable method in a sunlight-type plant factory. Molecular timetable methods have been developed to detect periodic genes and estimate individual internal body time from these expression profiles in mammals. We sampled tomato leaves every 2 h for 2 days and acquired time-course transcriptome data by RNA-Seq. Many genes were expressed periodically and these expressions were stable across the 1st and 2nd days of measurement. We selected 143 time-indicating genes whose expression indicated periodically, and estimated internal time in the plant from these expression profiles. The estimated internal time was generally the same as the external environment time; however, there was a difference of more than 1 h between the two for some sampling points. Furthermore, the stress-responsive genes also showed weakly periodic expression, implying that they were usually expressed periodically, regulated by light-dark cycles as an external factor or the circadian clock as the internal factor, and could be particularly expressed when the plant experiences some specific stress under agricultural situations. This study suggests that circadian clock mediate the optimization for fluctuating environments in the field and it has possibilities to enhance resistibility to stress and floral induction by controlling circadian clock through light supplement and temperature control.

Detection of Diurnal Variation of Tomato Transcriptome through the Molecular Timetable Method in a Sunlight-Type Plant Factory

PubMed Central

Higashi, Takanobu; Tanigaki, Yusuke; Takayama, Kotaro; Nagano, Atsushi J.; Honjo, Mie N.; Fukuda, Hirokazu

2016-01-01

The timing of measurement during plant growth is important because many genes are expressed periodically and orchestrate physiological events. Their periodicity is generated by environmental fluctuations as external factors and the circadian clock as the internal factor. The circadian clock orchestrates physiological events such as photosynthesis or flowering and it enables enhanced growth and herbivory resistance. These characteristics have possible applications for agriculture. In this study, we demonstrated the diurnal variation of the transcriptome in tomato (Solanum lycopersicum) leaves through molecular timetable method in a sunlight-type plant factory. Molecular timetable methods have been developed to detect periodic genes and estimate individual internal body time from these expression profiles in mammals. We sampled tomato leaves every 2 h for 2 days and acquired time-course transcriptome data by RNA-Seq. Many genes were expressed periodically and these expressions were stable across the 1st and 2nd days of measurement. We selected 143 time-indicating genes whose expression indicated periodically, and estimated internal time in the plant from these expression profiles. The estimated internal time was generally the same as the external environment time; however, there was a difference of more than 1 h between the two for some sampling points. Furthermore, the stress-responsive genes also showed weakly periodic expression, implying that they were usually expressed periodically, regulated by light–dark cycles as an external factor or the circadian clock as the internal factor, and could be particularly expressed when the plant experiences some specific stress under agricultural situations. This study suggests that circadian clock mediate the optimization for fluctuating environments in the field and it has possibilities to enhance resistibility to stress and floral induction by controlling circadian clock through light supplement and temperature control. PMID:26904059

MEM spectral analysis for predicting influenza epidemics in Japan.

PubMed

Sumi, Ayako; Kamo, Ken-ichi

2012-03-01

The prediction of influenza epidemics has long been the focus of attention in epidemiology and mathematical biology. In this study, we tested whether time series analysis was useful for predicting the incidence of influenza in Japan. The method of time series analysis we used consists of spectral analysis based on the maximum entropy method (MEM) in the frequency domain and the nonlinear least squares method in the time domain. Using this time series analysis, we analyzed the incidence data of influenza in Japan from January 1948 to December 1998; these data are unique in that they covered the periods of pandemics in Japan in 1957, 1968, and 1977. On the basis of the MEM spectral analysis, we identified the periodic modes explaining the underlying variations of the incidence data. The optimum least squares fitting (LSF) curve calculated with the periodic modes reproduced the underlying variation of the incidence data. An extension of the LSF curve could be used to predict the incidence of influenza quantitatively. Our study suggested that MEM spectral analysis would allow us to model temporal variations of influenza epidemics with multiple periodic modes much more effectively than by using the method of conventional time series analysis, which has been used previously to investigate the behavior of temporal variations in influenza data.

Series-nonuniform rational B-spline signal feedback: From chaos to any embedded periodic orbit or target point.

PubMed

Shao, Chenxi; Xue, Yong; Fang, Fang; Bai, Fangzhou; Yin, Peifeng; Wang, Binghong

2015-07-01

The self-controlling feedback control method requires an external periodic oscillator with special design, which is technically challenging. This paper proposes a chaos control method based on time series non-uniform rational B-splines (SNURBS for short) signal feedback. It first builds the chaos phase diagram or chaotic attractor with the sampled chaotic time series and any target orbit can then be explicitly chosen according to the actual demand. Second, we use the discrete timing sequence selected from the specific target orbit to build the corresponding external SNURBS chaos periodic signal, whose difference from the system current output is used as the feedback control signal. Finally, by properly adjusting the feedback weight, we can quickly lead the system to an expected status. We demonstrate both the effectiveness and efficiency of our method by applying it to two classic chaotic systems, i.e., the Van der Pol oscillator and the Lorenz chaotic system. Further, our experimental results show that compared with delayed feedback control, our method takes less time to obtain the target point or periodic orbit (from the starting point) and that its parameters can be fine-tuned more easily.

Series-nonuniform rational B-spline signal feedback: From chaos to any embedded periodic orbit or target point

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Chenxi, E-mail: cxshao@ustc.edu.cn; Xue, Yong; Fang, Fang

2015-07-15

The self-controlling feedback control method requires an external periodic oscillator with special design, which is technically challenging. This paper proposes a chaos control method based on time series non-uniform rational B-splines (SNURBS for short) signal feedback. It first builds the chaos phase diagram or chaotic attractor with the sampled chaotic time series and any target orbit can then be explicitly chosen according to the actual demand. Second, we use the discrete timing sequence selected from the specific target orbit to build the corresponding external SNURBS chaos periodic signal, whose difference from the system current output is used as the feedbackmore » control signal. Finally, by properly adjusting the feedback weight, we can quickly lead the system to an expected status. We demonstrate both the effectiveness and efficiency of our method by applying it to two classic chaotic systems, i.e., the Van der Pol oscillator and the Lorenz chaotic system. Further, our experimental results show that compared with delayed feedback control, our method takes less time to obtain the target point or periodic orbit (from the starting point) and that its parameters can be fine-tuned more easily.« less

Labeling research in support of through-the-season area estimation

NASA Technical Reports Server (NTRS)

Colwell, R. N. (Principal Investigator); Hay, C. M.; Sheffner, E. J.

1982-01-01

The development of LANDSAT-based through-the-season labeling procedures for corn and soybeans is discussed. A model for predicting labeling accuracy within key time periods throughout the growing season is outlined. Two methods for establishing the starting point of one key time period, viz., early season, are described. In addition, spectral-temporal characteristics for separating crops in the early season time period are discussed.

Time-varying singular value decomposition for periodic transient identification in bearing fault diagnosis

NASA Astrophysics Data System (ADS)

Zhang, Shangbin; Lu, Siliang; He, Qingbo; Kong, Fanrang

2016-09-01

For rotating machines, the defective faults of bearings generally are represented as periodic transient impulses in acquired signals. The extraction of transient features from signals has been a key issue for fault diagnosis. However, the background noise reduces identification performance of periodic faults in practice. This paper proposes a time-varying singular value decomposition (TSVD) method to enhance the identification of periodic faults. The proposed method is inspired by the sliding window method. By applying singular value decomposition (SVD) to the signal under a sliding window, we can obtain a time-varying singular value matrix (TSVM). Each column in the TSVM is occupied by the singular values of the corresponding sliding window, and each row represents the intrinsic structure of the raw signal, namely time-singular-value-sequence (TSVS). Theoretical and experimental analyses show that the frequency of TSVS is exactly twice that of the corresponding intrinsic structure. Moreover, the signal-to-noise ratio (SNR) of TSVS is improved significantly in comparison with the raw signal. The proposed method takes advantages of the TSVS in noise suppression and feature extraction to enhance fault frequency for diagnosis. The effectiveness of the TSVD is verified by means of simulation studies and applications to diagnosis of bearing faults. Results indicate that the proposed method is superior to traditional methods for bearing fault diagnosis.

Force measuring valve assemblies, systems including such valve assemblies and related methods

DOEpatents

DeWall, Kevin George [Pocatello, ID; Garcia, Humberto Enrique [Idaho Falls, ID; McKellar, Michael George [Idaho Falls, ID

2012-04-17

Methods of evaluating a fluid condition may include stroking a valve member and measuring a force acting on the valve member during the stroke. Methods of evaluating a fluid condition may include measuring a force acting on a valve member in the presence of fluid flow over a period of time and evaluating at least one of the frequency of changes in the measured force over the period of time and the magnitude of the changes in the measured force over the period of time to identify the presence of an anomaly in a fluid flow and, optionally, its estimated location. Methods of evaluating a valve condition may include directing a fluid flow through a valve while stroking a valve member, measuring a force acting on the valve member during the stroke, and comparing the measured force to a reference force. Valve assemblies and related systems are also disclosed.

Distinguishing non-resonant four-wave-mixing noise in coherent stokes and anti-stokes Raman scattering

NASA Technical Reports Server (NTRS)

Marks, Daniel L. (Inventor); Boppart, Stephen A. (Inventor)

2009-01-01

A method of examining a sample comprises exposing the sample to a pump pulse of electromagnetic radiation for a first period of time, exposing the sample to a stimulant pulse of electromagnetic radiation for a second period of time which overlaps in time with at least a portion of the first exposing, to produce a signal pulse of electromagnetic radiation for a third period of time, and interfering the signal pulse with a reference pulse of electromagnetic radiation, to determine which portions of the signal pulse were produced during the exposing of the sample to the stimulant pulse. The first and third periods of time are each greater than the second period of time.

Periodic-Zone Model Predictive Control for Diurnal Closed-Loop Operation of an Artificial Pancreas

PubMed Central

Gondhalekar, Ravi; Dassau, Eyal; Zisser, Howard C.; Doyle, Francis J.

2013-01-01

Background The objective of this research is an artificial pancreas (AP) that performs automatic regulation of blood glucose levels in people with type 1 diabetes mellitus. This article describes a control strategy that performs algorithmic insulin dosing for maintaining safe blood glucose levels over prolonged, overnight periods of time and furthermore was designed with outpatient, multiday deployment in mind. Of particular concern is the prevention of nocturnal hypoglycemia, because during sleep, subjects cannot monitor themselves and may not respond to alarms. An AP intended for prolonged and unsupervised outpatient deployment must strategically reduce the risk of hypoglycemia during times of sleep, without requiring user interaction. Methods A diurnal insulin delivery strategy based on predictive control methods is proposed. The so-called “periodic-zone model predictive control” (PZMPC) strategy employs periodically time-dependent blood glucose output target zones and furthermore enforces periodically time-dependent insulin input constraints to modulate its behavior based on the time of day. Results The proposed strategy was evaluated through an extensive simulation-based study and a preliminary clinical trial. Results indicate that the proposed method delivers insulin more conservatively during nighttime than during daytime while maintaining safe blood glucose levels at all times. In clinical trials, the proposed strategy delivered 77% of the amount of insulin delivered by a time-invariant control strategy; specifically, it delivered on average 1.23 U below, compared with 0.31 U above, the nominal basal rate overnight while maintaining comparable, and safe, blood glucose values. Conclusions The proposed PZMPC algorithm strategically prevents nocturnal hypoglycemia and is considered a significant step toward deploying APs into outpatient environments for extended periods of time in full closed-loop operation. PMID:24351171

Method for detection and correction of errors in speech pitch period estimates

NASA Technical Reports Server (NTRS)

Bhaskar, Udaya (Inventor)

1989-01-01

A method of detecting and correcting received values of a pitch period estimate of a speech signal for use in a speech coder or the like. An average is calculated of the nonzero values of received pitch period estimate since the previous reset. If a current pitch period estimate is within a range of 0.75 to 1.25 times the average, it is assumed correct, while if not, a correction process is carried out. If correction is required successively for more than a preset number of times, which will most likely occur when the speaker changes, the average is discarded and a new average calculated.

Time-series analysis of foreign exchange rates using time-dependent pattern entropy

NASA Astrophysics Data System (ADS)

Ishizaki, Ryuji; Inoue, Masayoshi

2013-08-01

Time-dependent pattern entropy is a method that reduces variations to binary symbolic dynamics and considers the pattern of symbols in a sliding temporal window. We use this method to analyze the instability of daily variations in foreign exchange rates, in particular, the dollar-yen rate. The time-dependent pattern entropy of the dollar-yen rate was found to be high in the following periods: before and after the turning points of the yen from strong to weak or from weak to strong, and the period after the Lehman shock.

Applying Sparse Machine Learning Methods to Twitter: Analysis of the 2012 Change in Pap Smear Guidelines. A Sequential Mixed-Methods Study.

PubMed

Lyles, Courtney Rees; Godbehere, Andrew; Le, Gem; El Ghaoui, Laurent; Sarkar, Urmimala

2016-06-10

It is difficult to synthesize the vast amount of textual data available from social media websites. Capturing real-world discussions via social media could provide insights into individuals' opinions and the decision-making process. We conducted a sequential mixed methods study to determine the utility of sparse machine learning techniques in summarizing Twitter dialogues. We chose a narrowly defined topic for this approach: cervical cancer discussions over a 6-month time period surrounding a change in Pap smear screening guidelines. We applied statistical methodologies, known as sparse machine learning algorithms, to summarize Twitter messages about cervical cancer before and after the 2012 change in Pap smear screening guidelines by the US Preventive Services Task Force (USPSTF). All messages containing the search terms "cervical cancer," "Pap smear," and "Pap test" were analyzed during: (1) January 1-March 13, 2012, and (2) March 14-June 30, 2012. Topic modeling was used to discern the most common topics from each time period, and determine the singular value criterion for each topic. The results were then qualitatively coded from top 10 relevant topics to determine the efficiency of clustering method in grouping distinct ideas, and how the discussion differed before vs. after the change in guidelines . This machine learning method was effective in grouping the relevant discussion topics about cervical cancer during the respective time periods (~20% overall irrelevant content in both time periods). Qualitative analysis determined that a significant portion of the top discussion topics in the second time period directly reflected the USPSTF guideline change (eg, "New Screening Guidelines for Cervical Cancer"), and many topics in both time periods were addressing basic screening promotion and education (eg, "It is Cervical Cancer Awareness Month! Click the link to see where you can receive a free or low cost Pap test.") It was demonstrated that machine learning tools can be useful in cervical cancer prevention and screening discussions on Twitter. This method allowed us to prove that there is publicly available significant information about cervical cancer screening on social media sites. Moreover, we observed a direct impact of the guideline change within the Twitter messages.

Development of Matched (migratory Analytical Time Change Easy Detection) Method for Satellite-Tracked Migratory Birds

NASA Astrophysics Data System (ADS)

Doko, Tomoko; Chen, Wenbo; Higuchi, Hiroyoshi

2016-06-01

Satellite tracking technology has been used to reveal the migration patterns and flyways of migratory birds. In general, bird migration can be classified according to migration status. These statuses include the wintering period, spring migration, breeding period, and autumn migration. To determine the migration status, periods of these statuses should be individually determined, but there is no objective method to define 'a threshold date' for when an individual bird changes its status. The research objective is to develop an effective and objective method to determine threshold dates of migration status based on satellite-tracked data. The developed method was named the "MATCHED (Migratory Analytical Time Change Easy Detection) method". In order to demonstrate the method, data acquired from satellite-tracked Tundra Swans were used. MATCHED method is composed by six steps: 1) dataset preparation, 2) time frame creation, 3) automatic identification, 4) visualization of change points, 5) interpretation, and 6) manual correction. Accuracy was tested. In general, MATCHED method was proved powerful to identify the change points between migration status as well as stopovers. Nevertheless, identifying "exact" threshold dates is still challenging. Limitation and application of this method was discussed.

EnvironmentalWaveletTool: Continuous and discrete wavelet analysis and filtering for environmental time series

NASA Astrophysics Data System (ADS)

Galiana-Merino, J. J.; Pla, C.; Fernandez-Cortes, A.; Cuezva, S.; Ortiz, J.; Benavente, D.

2014-10-01

A MATLAB-based computer code has been developed for the simultaneous wavelet analysis and filtering of several environmental time series, particularly focused on the analyses of cave monitoring data. The continuous wavelet transform, the discrete wavelet transform and the discrete wavelet packet transform have been implemented to provide a fast and precise time-period examination of the time series at different period bands. Moreover, statistic methods to examine the relation between two signals have been included. Finally, the entropy of curves and splines based methods have also been developed for segmenting and modeling the analyzed time series. All these methods together provide a user-friendly and fast program for the environmental signal analysis, with useful, practical and understandable results.

Forward Period Analysis Method of the Periodic Hamiltonian System.

PubMed

Wang, Pengfei

2016-01-01

Using the forward period analysis (FPA), we obtain the period of a Morse oscillator and mathematical pendulum system, with the accuracy of 100 significant digits. From these results, the long-term [0, 1060] (time unit) solutions, ranging from the Planck time to the age of the universe, are computed reliably and quickly with a parallel multiple-precision Taylor series (PMT) scheme. The application of FPA to periodic systems can greatly reduce the computation time of long-term reliable simulations. This scheme provides an efficient way to generate reference solutions, against which long-term simulations using other schemes can be tested.

Low temperature route to uranium nitride

DOEpatents

Burrell, Anthony K.; Sattelberger, Alfred P.; Yeamans, Charles; Hartmann, Thomas; Silva, G. W. Chinthaka; Cerefice, Gary; Czerwinski, Kenneth R.

2009-09-01

A method of preparing an actinide nitride fuel for nuclear reactors is provided. The method comprises the steps of a) providing at least one actinide oxide and optionally zirconium oxide; b) mixing the oxide with a source of hydrogen fluoride for a period of time and at a temperature sufficient to convert the oxide to a fluoride salt; c) heating the fluoride salt to remove water; d) heating the fluoride salt in a nitrogen atmosphere for a period of time and at a temperature sufficient to convert the fluorides to nitrides; and e) heating the nitrides under vacuum and/or inert atmosphere for a period of time sufficient to convert the nitrides to mononitrides.

Entropy method of measuring and evaluating periodicity of quasi-periodic trajectories

NASA Astrophysics Data System (ADS)

Ni, Yanshuo; Turitsyn, Konstantin; Baoyin, Hexi; Junfeng, Li

2018-06-01

This paper presents a method for measuring the periodicity of quasi-periodic trajectories by applying discrete Fourier transform (DFT) to the trajectories and analyzing the frequency domain within the concept of entropy. Having introduced the concept of entropy, analytical derivation and numerical results indicate that entropies increase as a logarithmic function of time. Periodic trajectories typically have higher entropies, and trajectories with higher entropies mean the periodicities of the motions are stronger. Theoretical differences between two trajectories expressed as summations of trigonometric functions are also derived analytically. Trajectories in the Henon-Heiles system and the circular restricted three-body problem (CRTBP) are analyzed with the indicator entropy and compared with orthogonal fast Lyapunov indicator (OFLI). The results show that entropy is a better tool for discriminating periodicity in quasiperiodic trajectories than OFLI and can detect periodicity while excluding the spirals that are judged as periodic cases by OFLI. Finally, trajectories in the vicinity of 243 Ida and 6489 Golevka are considered as examples, and the numerical results verify these conclusions. Some trajectories near asteroids look irregular, but their higher entropy values as analyzed by this method serve as evidence of frequency regularity in three directions. Moreover, these results indicate that applying DFT to the trajectories in the vicinity of irregular small bodies and calculating their entropy in the frequency domain provides a useful quantitative analysis method for evaluating orderliness in the periodicity of quasi-periodic trajectories within a given time interval.

Time-delayed feedback technique for suppressing instabilities in time-periodic flow

NASA Astrophysics Data System (ADS)

Shaabani-Ardali, Léopold; Sipp, Denis; Lesshafft, Lutz

2017-11-01

A numerical method is presented that allows to compute time-periodic flow states, even in the presence of hydrodynamic instabilities. The method is based on filtering nonharmonic components by way of delayed feedback control, as introduced by Pyragas [Phys. Lett. A 170, 421 (1992), 10.1016/0375-9601(92)90745-8]. Its use in flow problems is demonstrated here for the case of a periodically forced laminar jet, subject to a subharmonic instability that gives rise to vortex pairing. The optimal choice of the filter gain, which is a free parameter in the stabilization procedure, is investigated in the context of a low-dimensional model problem, and it is shown that this model predicts well the filter performance in the high-dimensional flow system. Vortex pairing in the jet is efficiently suppressed, so that the unstable periodic flow state in response to harmonic forcing is accurately retrieved. The procedure is straightforward to implement inside any standard flow solver. Memory requirements for the delayed feedback control can be significantly reduced by means of time interpolation between checkpoints. Finally, the method is extended for the treatment of periodic problems where the frequency is not known a priori. This procedure is demonstrated for a three-dimensional cubic lid-driven cavity in supercritical conditions.

Practical considerations for estimating clinical trial accrual periods: application to a multi-center effectiveness study

PubMed Central

Carter, Rickey E; Sonne, Susan C; Brady, Kathleen T

2005-01-01

Background Adequate participant recruitment is vital to the conduct of a clinical trial. Projected recruitment rates are often over-estimated, and the time to recruit the target population (accrual period) is often under-estimated. Methods This report illustrates three approaches to estimating the accrual period and applies the methods to a multi-center, randomized, placebo controlled trial undergoing development. Results Incorporating known sources of accrual variation can yield a more justified estimate of the accrual period. Simulation studies can be incorporated into a clinical trial's planning phase to provide estimates for key accrual summaries including the mean and standard deviation of the accrual period. Conclusion The accrual period of a clinical trial should be carefully considered, and the allocation of sufficient time for participant recruitment is a fundamental aspect of planning a clinical trial. PMID:15796782

Applying Sparse Machine Learning Methods to Twitter: Analysis of the 2012 Change in Pap Smear Guidelines. A Sequential Mixed-Methods Study

PubMed Central

Godbehere, Andrew; Le, Gem; El Ghaoui, Laurent; Sarkar, Urmimala

2016-01-01

Background It is difficult to synthesize the vast amount of textual data available from social media websites. Capturing real-world discussions via social media could provide insights into individuals’ opinions and the decision-making process. Objective We conducted a sequential mixed methods study to determine the utility of sparse machine learning techniques in summarizing Twitter dialogues. We chose a narrowly defined topic for this approach: cervical cancer discussions over a 6-month time period surrounding a change in Pap smear screening guidelines. Methods We applied statistical methodologies, known as sparse machine learning algorithms, to summarize Twitter messages about cervical cancer before and after the 2012 change in Pap smear screening guidelines by the US Preventive Services Task Force (USPSTF). All messages containing the search terms “cervical cancer,” “Pap smear,” and “Pap test” were analyzed during: (1) January 1–March 13, 2012, and (2) March 14–June 30, 2012. Topic modeling was used to discern the most common topics from each time period, and determine the singular value criterion for each topic. The results were then qualitatively coded from top 10 relevant topics to determine the efficiency of clustering method in grouping distinct ideas, and how the discussion differed before vs. after the change in guidelines . Results This machine learning method was effective in grouping the relevant discussion topics about cervical cancer during the respective time periods (~20% overall irrelevant content in both time periods). Qualitative analysis determined that a significant portion of the top discussion topics in the second time period directly reflected the USPSTF guideline change (eg, “New Screening Guidelines for Cervical Cancer”), and many topics in both time periods were addressing basic screening promotion and education (eg, “It is Cervical Cancer Awareness Month! Click the link to see where you can receive a free or low cost Pap test.”) Conclusions It was demonstrated that machine learning tools can be useful in cervical cancer prevention and screening discussions on Twitter. This method allowed us to prove that there is publicly available significant information about cervical cancer screening on social media sites. Moreover, we observed a direct impact of the guideline change within the Twitter messages. PMID:27288093

Financial time series analysis based on information categorization method

NASA Astrophysics Data System (ADS)

Tian, Qiang; Shang, Pengjian; Feng, Guochen

2014-12-01

The paper mainly applies the information categorization method to analyze the financial time series. The method is used to examine the similarity of different sequences by calculating the distances between them. We apply this method to quantify the similarity of different stock markets. And we report the results of similarity in US and Chinese stock markets in periods 1991-1998 (before the Asian currency crisis), 1999-2006 (after the Asian currency crisis and before the global financial crisis), and 2007-2013 (during and after global financial crisis) by using this method. The results show the difference of similarity between different stock markets in different time periods and the similarity of the two stock markets become larger after these two crises. Also we acquire the results of similarity of 10 stock indices in three areas; it means the method can distinguish different areas' markets from the phylogenetic trees. The results show that we can get satisfactory information from financial markets by this method. The information categorization method can not only be used in physiologic time series, but also in financial time series.

[Fast determination of induction period of motor gasoline using Fourier transform attenuated total reflection infrared spectroscopy].

PubMed

Liu, Ya-Fei; Yuan, Hong-Fu; Song, Chun-Feng; Xie, Jin-Chun; Li, Xiao-Yu; Yan, De-Lin

2014-11-01

A new method is proposed for the fast determination of the induction period of gasoline using Fourier transform attenuated total reflection infrared spectroscopy (ATR-FTIR). A dedicated analysis system with the function of spectral measurement, data processing, display and storage was designed and integrated using a Fourier transform infrared spectrometer module and chemometric software. The sample presentation accessory designed which has advantages of constant optical path, convenient sample injection and cleaning is composed of a nine times reflection attenuated total reflectance (ATR) crystal of zinc selenide (ZnSe) coated with a diamond film and a stainless steel lid with sealing device. The influence of spectral scanning number and repeated sample loading times on the spectral signal-to-noise ratio was studied. The optimum spectral scanning number is 15 times and the optimum sample loading number is 4 times. Sixty four different gasoline samples were collected from the Beijing-Tianjin area and the induction period values were determined as reference data by standard method GB/T 8018-87. The infrared spectra of these samples were collected in the operating condition mentioned above using the dedicated fast analysis system. Spectra were pretreated using mean centering and 1st derivative to reduce the influence of spectral noise and baseline shift A PLS calibration model for the induction period was established by correlating the known induction period values of the samples with their spectra. The correlation coefficient (R2), standard error of calibration (SEC) and standard error of prediction (SEP) of the model are 0.897, 68.3 and 91.9 minutes, respectively. The relative deviation of the model for gasoline induction period prediction is less than 5%, which meets the requirements of repeatability tolerance in GB method. The new method is simple and fast. It takes no more than 3 minutes to detect one sample. Therefore, the method is feasible for implementing fast determination of gasoline induction period, and of a positive meaning in the evaluation of fuel quality.

Applying Toyota Production System principles to a psychiatric hospital: making transfers safer and more timely.

PubMed

Young, John Q; Wachter, Robert M

2009-09-01

Health care organizations have increasingly embraced industrial methods, such as the Toyota Production System (TPS), to improve quality, safety, timeliness, and efficiency. However, the use of such methods in psychiatric hospitals has been limited. A psychiatric hospital applied TPS principles to patient transfers to the outpatient medication management clinics (MMCs) from all other inpatient and outpatient services within the hospital's system. Sources of error and delay were identified, and a new process was designed to improve timely access (measured by elapsed time from request for transfer to scheduling of an appointment and to the actual visit) and patient safety by decreasing communication errors (measured by number of failed transfers). Complexity was substantially reduced, with one streamlined pathway replacing five distinct and more complicated pathways. To assess sustainability, the postintervention period was divided into Period 1 (first 12 months) and Period 2 (next 24 months). Time required to process the transfer and schedule the first appointment was reduced by 74.1% in Period 1 (p < .001) and by an additional 52.7% in Period 2 (p < .0001) for an overall reduction of 87% (p < .0001). Similarly, time to the actual appointment was reduced 31.2% in Period 1 (p < .0001), but was stable in Period 2 (p = .48). The number of transfers per month successfully processed and scheduled increased 95% in the postintervention period compared with the pre-implementation period (p = .015). Finally, data for failed transfers were only available for the postintervention period, and the rate decreased 89% in Period 2 compared with Period 1 (p = .017). The application of TPS principles enhanced access and safety through marked and sustained improvements in the transfer process's timeliness and reliability. Almost all transfer processes have now been standardized.

Early efforts in modeling the incubation period of infectious diseases with an acute course of illness.

PubMed

Nishiura, Hiroshi

2007-05-11

The incubation period of infectious diseases, the time from infection with a microorganism to onset of disease, is directly relevant to prevention and control. Since explicit models of the incubation period enhance our understanding of the spread of disease, previous classic studies were revisited, focusing on the modeling methods employed and paying particular attention to relatively unknown historical efforts. The earliest study on the incubation period of pandemic influenza was published in 1919, providing estimates of the incubation period of Spanish flu using the daily incidence on ships departing from several ports in Australia. Although the study explicitly dealt with an unknown time of exposure, the assumed periods of exposure, which had an equal probability of infection, were too long, and thus, likely resulted in slight underestimates of the incubation period. After the suggestion that the incubation period follows lognormal distribution, Japanese epidemiologists extended this assumption to estimates of the time of exposure during a point source outbreak. Although the reason why the incubation period of acute infectious diseases tends to reveal a right-skewed distribution has been explored several times, the validity of the lognormal assumption is yet to be fully clarified. At present, various different distributions are assumed, and the lack of validity in assuming lognormal distribution is particularly apparent in the case of slowly progressing diseases. The present paper indicates that (1) analysis using well-defined short periods of exposure with appropriate statistical methods is critical when the exact time of exposure is unknown, and (2) when assuming a specific distribution for the incubation period, comparisons using different distributions are needed in addition to estimations using different datasets, analyses of the determinants of incubation period, and an understanding of the underlying disease mechanisms.

A Simple yet Accurate Method for Students to Determine Asteroid Rotation Periods from Fragmented Light Curve Data

ERIC Educational Resources Information Center

Beare, R. A.

2008-01-01

Professional astronomers use specialized software not normally available to students to determine the rotation periods of asteroids from fragmented light curve data. This paper describes a simple yet accurate method based on Microsoft Excel[R] that enables students to find periods in asteroid light curve and other discontinuous time series data of…

Period changes of two contact binaries: DF Hya and WZ And

NASA Astrophysics Data System (ADS)

Bulut, A.; Bulut, I.

2018-02-01

Orbital period variations of two contact binaries DF Hya and WZ And are analyzed with the least-squares method by using all available minima times. It is shown that the period variations of these systems are due mainly to the Light-Time Effect (LITE) due originates from gravitational influence of a third body. New LITE elements such as, orbital periods and minimum masses of possibility third bodies are given.

Phase locking route behind complex periodic windows in a forced oscillator

NASA Astrophysics Data System (ADS)

Jan, Hengtai; Tsai, Kuo-Ting; Kuo, Li-wei

2013-09-01

Chaotic systems have complex reactions against an external driving force; even in cases with low-dimension oscillators, the routes to synchronization are diverse. We proposed a stroboscope-based method for analyzing driven chaotic systems in their phase space. According to two statistic quantities generated from time series, we could realize the system state and the driving behavior simultaneously. We demonstrated our method in a driven bi-stable system, which showed complex period windows under a proper driving force. With increasing periodic driving force, a route from interior periodic oscillation to phase synchronization through the chaos state could be found. Periodic windows could also be identified and the circumstances under which they occurred distinguished. Statistical results were supported by conditional Lyapunov exponent analysis to show the power in analyzing the unknown time series.

[SIMULTANEOUS MEASUREMENT OF INTRAVENTRICULAR AND PARENCHYMAL INTRACRANIAL PRESSURE IN PATIENTS WITH SEVERE TRAUMA BRAIN INJURY].

PubMed

Oshorov, A V; Popugaev, K A; Savin, I A; Potapov, A A

2016-01-01

"Standard" assessment of ICP by measuring liquor ventricular pressure recently questioned. THE OBJECTIVE OF THE STUDY: Compare the values of ventricular and parenchymal ICP against the closure of open liquor drainage and during active CSF drainage. Examined 7 patients with TBI and intracranial hypertension syndrome, GCS 5.6 ± 1.2 points, 4.2 ± age 33 years. Compared parenchymal and ventricular ICP in three time periods: 1--during closure of ventricular drainage, 2--during of the open drains and drainage at the level of 14-15 mmHg, 3--during the period of active drainage. When comparing two methods of measurement used Bland-Altman method. 1. During time period of the closed drainage correlation coefficient was r = 0.83, p < 0.001. Bland-Altman method: the difference of the two measurements is equal to the minimum and 0.7 mm Hg, the standard deviation of 2.02 mm Hg 2. During time period of the open drainage was reduction of the correlation coefficient to r = 0.46, p < 0.01. Bland-Altman method: an increase in the difference of the two measurements to -0.84 mmHg, standard deviation 2.8 mm Hg 3. During time period of the active drainage of cerebrospinal fluid was marked difference between methods of measurement. Bland-Altman method: the difference was 8.64 mm Hg, and a standard deviation of 2.6 mm Hg. 1. During the closure of the ventricular drainage were good correlation between ventricular and parenchymal ICR 2. During open the liquor drainage correlation between the two methods of measuring the intracranial pressure is reduced. 3. During the active CSF drainage correlation between the two methods of measuring intracranial pressure can be completely lost. Under these conditions, CSF pressure is not correctly reflect the ICP 4. For an accurate and continuous measurement of intracranial pressure on the background of the active CSF drainage should be carried out simultaneous parenchymal ICP measurement.

Microbial detection method based on sensing molecular hydrogen

NASA Technical Reports Server (NTRS)

Wilkins, J. R.; Stoner, G. E.; Boykin, E. H.

1974-01-01

A simple method for detecting bacteria, based on the time of hydrogen evolution, was developed and tested against various members of the Enterobacteriaceae group. The test system consisted of (1) two electrodes, platinum and a reference electrode, (2) a buffer amplifier, and (3) a strip-chart recorder. Hydrogen evolution was measured by an increase in voltage in the negative (cathodic) direction. A linear relationship was established between inoculum size and the time hydrogen was detected (lag period). Lag times ranged from 1 h for 1 million cells/ml to 7 h for 1 cell/ml. For each 10-fold decrease in inoculum, length of the lag period increased 60 to 70 min. Based on the linear relationship between inoculum and lag period, these results indicate the potential application of the hydrogen-sensing method for rapidly detecting coliforms and other gas-producing microorganisms in a variety of clinical, food, and other samples.

High-order fuzzy time-series based on multi-period adaptation model for forecasting stock markets

NASA Astrophysics Data System (ADS)

Chen, Tai-Liang; Cheng, Ching-Hsue; Teoh, Hia-Jong

2008-02-01

Stock investors usually make their short-term investment decisions according to recent stock information such as the late market news, technical analysis reports, and price fluctuations. To reflect these short-term factors which impact stock price, this paper proposes a comprehensive fuzzy time-series, which factors linear relationships between recent periods of stock prices and fuzzy logical relationships (nonlinear relationships) mined from time-series into forecasting processes. In empirical analysis, the TAIEX (Taiwan Stock Exchange Capitalization Weighted Stock Index) and HSI (Heng Seng Index) are employed as experimental datasets, and four recent fuzzy time-series models, Chen’s (1996), Yu’s (2005), Cheng’s (2006) and Chen’s (2007), are used as comparison models. Besides, to compare with conventional statistic method, the method of least squares is utilized to estimate the auto-regressive models of the testing periods within the databases. From analysis results, the performance comparisons indicate that the multi-period adaptation model, proposed in this paper, can effectively improve the forecasting performance of conventional fuzzy time-series models which only factor fuzzy logical relationships in forecasting processes. From the empirical study, the traditional statistic method and the proposed model both reveal that stock price patterns in the Taiwan stock and Hong Kong stock markets are short-term.

State Medicaid reimbursement for nursing homes, 1978-86

PubMed Central

Swan, James H.; Harrington, Charlene; Grant, Leslie A.

1988-01-01

State Medicaid reimbursement methods and rates are reported for the period 1978-86 for skilled nursing and intermediate care facilities. A cross-sectional time series regression analysis of Medicaid reimbursement rates on methods showed that States using prospective class reimbursement had significantly lower rates for the period 1982-86. States using prospective facility-specific reimbursement methods had lower rates than retrospective methods in 1983-84. PMID:10312516

Time-periodic solutions of the Benjamin-Ono equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ambrose , D.M.; Wilkening, Jon

2008-04-01

We present a spectrally accurate numerical method for finding non-trivial time-periodic solutions of non-linear partial differential equations. The method is based on minimizing a functional (of the initial condition and the period) that is positive unless the solution is periodic, in which case it is zero. We solve an adjoint PDE to compute the gradient of this functional with respect to the initial condition. We include additional terms in the functional to specify the free parameters, which, in the case of the Benjamin-Ono equation, are the mean, a spatial phase, a temporal phase and the real part of one ofmore » the Fourier modes at t = 0. We use our method to study global paths of non-trivial time-periodic solutions connecting stationary and traveling waves of the Benjamin-Ono equation. As a starting guess for each path, we compute periodic solutions of the linearized problem by solving an infinite dimensional eigenvalue problem in closed form. We then use our numerical method to continue these solutions beyond the realm of linear theory until another traveling wave is reached (or until the solution blows up). By experimentation with data fitting, we identify the analytical form of the solutions on the path connecting the one-hump stationary solution to the two-hump traveling wave. We then derive exact formulas for these solutions by explicitly solving the system of ODE's governing the evolution of solitons using the ansatz suggested by the numerical simulations.« less

Earthquake Forecasting Through Semi-periodicity Analysis of Labeled Point Processes

NASA Astrophysics Data System (ADS)

Quinteros Cartaya, C. B. M.; Nava Pichardo, F. A.; Glowacka, E.; Gomez-Trevino, E.

2015-12-01

Large earthquakes have semi-periodic behavior as result of critically self-organized processes of stress accumulation and release in some seismogenic region. Thus, large earthquakes in a region constitute semi-periodic sequences with recurrence times varying slightly from periodicity. Nava et al., 2013 and Quinteros et al., 2013 realized that not all earthquakes in a given region need belong to the same sequence, since there can be more than one process of stress accumulation and release in it; they also proposed a method to identify semi-periodic sequences through analytic Fourier analysis. This work presents improvements on the above-mentioned method: the influence of earthquake size on the spectral analysis, and its importance in semi-periodic events identification, which means that earthquake occurrence times are treated as a labeled point process; the estimation of appropriate upper limit uncertainties to use in forecasts; and the use of Bayesian analysis to evaluate the forecast performance. This improved method is applied to specific regions: the southwestern coast of Mexico, the northeastern Japan Arc, the San Andreas Fault zone at Parkfield, and northeastern Venezuela.

Periodical capacity setting methods for make-to-order multi-machine production systems

PubMed Central

Altendorfer, Klaus; Hübl, Alexander; Jodlbauer, Herbert

2014-01-01

The paper presents different periodical capacity setting methods for make-to-order, multi-machine production systems with stochastic customer required lead times and stochastic processing times to improve service level and tardiness. These methods are developed as decision support when capacity flexibility exists, such as, a certain range of possible working hours a week for example. The methods differ in the amount of information used whereby all are based on the cumulated capacity demand at each machine. In a simulation study the methods’ impact on service level and tardiness is compared to a constant provided capacity for a single and a multi-machine setting. It is shown that the tested capacity setting methods can lead to an increase in service level and a decrease in average tardiness in comparison to a constant provided capacity. The methods using information on processing time and customer required lead time distribution perform best. The results found in this paper can help practitioners to make efficient use of their flexible capacity. PMID:27226649

Extraction of Rice Phenological Differences under Heavy Metal Stress Using EVI Time-Series from HJ-1A/B Data.

PubMed

Liu, Shuyuan; Liu, Xiangnan; Liu, Meiling; Wu, Ling; Ding, Chao; Huang, Zhi

2017-05-30

An effective method to monitor heavy metal stress in crops is of critical importance to assure agricultural production and food security. Phenology, as a sensitive indicator of environmental change, can respond to heavy metal stress in crops and remote sensing is an effective method to detect plant phenological changes. This study focused on identifying the rice phenological differences under varied heavy metal stress using EVI (enhanced vegetation index) time-series, which was obtained from HJ-1A/B CCD images and fitted with asymmetric Gaussian model functions. We extracted three phenological periods using first derivative analysis: the tillering period, heading period, and maturation period; and constructed two kinds of metrics with phenological characteristics: date-intervals and time-integrated EVI, to explore the rice phenological differences under mild and severe stress levels. Results indicated that under severe stress the values of the metrics for presenting rice phenological differences in the experimental areas of heavy metal stress were smaller than the ones under mild stress. This finding represents a new method for monitoring heavy metal contamination through rice phenology.

Prominence of scientific publications towards peri-implant complications in implantology: A bibliometric analysis using the H-classics method.

PubMed

Chiang, H-S; Huang, R-Y; Weng, P-W; Mau, L-P; Tsai, Y-W C; Chung, M-P; Chung, C-H; Yeh, H-W; Shieh, Y-S; Cheng, W-C

2018-03-01

Current bibliometric analyses of the evolving trends in research scope category across different time periods using the H-classics method in implantology are considerably limited. The purpose of this study was to identify the classic articles in implantology to analyse bibliometric characteristics and associated factors in implantology for the past four decades. H-Classics in implantology were identified within four time periods between 1977 and 2016, based on the h-index from the Scopus ® database. For each article, the principal bibliometric parameters of authorship, geographic origin, country origin, and institute origin, collaboration, centralisation, article type, scope of study and other associated factors were analysed in four time periods. A significant increase in mean numbers of authors per H-Classics was found across time. Both Europe and North America were the most productive region/country and steadily dominated this field in each time period. Collaborations of author, internationally and inter-institutionally had significantly increased across time. A significant decentralisation in authorships, institutes and journals was noted in past four decades. The journal of Clinical Oral Implant Researches has raised its importance for almost 30 years (1987-2016). Research on Complications, peri-implant infection/pathology/therapy had been increasing in production throughout each period. This is the first study to evaluate research trends in implantology in the past 40 years using the H-classics method, which through analysing via principle bibliometric characteristics reflected a historical perspective on evolutionary mainstream in the field. Prominence of research regarding complications may forecast innovative advancements in future. © 2018 John Wiley & Sons Ltd.

Production Planning and Simulation for Reverse Supply Chain

NASA Astrophysics Data System (ADS)

Murayama, Takeshi; Yoda, Mitsunobu; Eguchi, Toru; Oba, Fuminori

This paper describes a production planning method for a reverse supply chain, in which a disassembly company takes reusable components from returned used products and supplies the reusable components for a product manufacturer. This method addresses the issue that the timings and quantities of returned products and reusable components obtained from them are unknown. This method first predicts the quantities of returned products and reusable components at each time period by using reliability models. Using the prediction result, the method performs production planning based on Material Requirements Planning (MRP). This method enables us to plan at each time period: the quantity of the products to be disassembled; the quantity of the reusable components to be used; and the quantity of the new components to be produced. The flow of the components and products through a forward and reverse supply chain is simulated to show the effectiveness of the method.

Robustness analysis of multirate and periodically time varying systems

NASA Technical Reports Server (NTRS)

Berg, Martin C.; Mason, Gregory S.

1991-01-01

A new method for analyzing the stability and robustness of multirate and periodically time varying systems is presented. It is shown that a multirate or periodically time varying system can be transformed into an equivalent time invariant system. For a SISO system, traditional gain and phase margins can be found by direct application of the Nyquist criterion to this equivalent time invariant system. For a MIMO system, structured and unstructured singular values can be used to determine the system's robustness. The limitations and implications of utilizing this equivalent time invariant system for calculating gain and phase margins, and for estimating robustness via singular value analysis are discussed.

A space-time lower-upper symmetric Gauss-Seidel scheme for the time-spectral method

NASA Astrophysics Data System (ADS)

Zhan, Lei; Xiong, Juntao; Liu, Feng

2016-05-01

The time-spectral method (TSM) offers the advantage of increased order of accuracy compared to methods using finite-difference in time for periodic unsteady flow problems. Explicit Runge-Kutta pseudo-time marching and implicit schemes have been developed to solve iteratively the space-time coupled nonlinear equations resulting from TSM. Convergence of the explicit schemes is slow because of the stringent time-step limit. Many implicit methods have been developed for TSM. Their computational efficiency is, however, still limited in practice because of delayed implicit temporal coupling, multiple iterative loops, costly matrix operations, or lack of strong diagonal dominance of the implicit operator matrix. To overcome these shortcomings, an efficient space-time lower-upper symmetric Gauss-Seidel (ST-LU-SGS) implicit scheme with multigrid acceleration is presented. In this scheme, the implicit temporal coupling term is split as one additional dimension of space in the LU-SGS sweeps. To improve numerical stability for periodic flows with high frequency, a modification to the ST-LU-SGS scheme is proposed. Numerical results show that fast convergence is achieved using large or even infinite Courant-Friedrichs-Lewy (CFL) numbers for unsteady flow problems with moderately high frequency and with the use of moderately high numbers of time intervals. The ST-LU-SGS implicit scheme is also found to work well in calculating periodic flow problems where the frequency is not known a priori and needed to be determined by using a combined Fourier analysis and gradient-based search algorithm.

Spectral analysis for GNSS coordinate time series using chirp Fourier transform

NASA Astrophysics Data System (ADS)

Feng, Shengtao; Bo, Wanju; Ma, Qingzun; Wang, Zifan

2017-12-01

Spectral analysis for global navigation satellite system (GNSS) coordinate time series provides a principal tool to understand the intrinsic mechanism that affects tectonic movements. Spectral analysis methods such as the fast Fourier transform, Lomb-Scargle spectrum, evolutionary power spectrum, wavelet power spectrum, etc. are used to find periodic characteristics in time series. Among spectral analysis methods, the chirp Fourier transform (CFT) with less stringent requirements is tested with synthetic and actual GNSS coordinate time series, which proves the accuracy and efficiency of the method. With the length of series only limited to even numbers, CFT provides a convenient tool for windowed spectral analysis. The results of ideal synthetic data prove CFT accurate and efficient, while the results of actual data show that CFT is usable to derive periodic information from GNSS coordinate time series.

The method ADAMONT v1.0 for statistical adjustment of climate projections applicable to energy balance land surface models

NASA Astrophysics Data System (ADS)

Verfaillie, Deborah; Déqué, Michel; Morin, Samuel; Lafaysse, Matthieu

2017-11-01

We introduce the method ADAMONT v1.0 to adjust and disaggregate daily climate projections from a regional climate model (RCM) using an observational dataset at hourly time resolution. The method uses a refined quantile mapping approach for statistical adjustment and an analogous method for sub-daily disaggregation. The method ultimately produces adjusted hourly time series of temperature, precipitation, wind speed, humidity, and short- and longwave radiation, which can in turn be used to force any energy balance land surface model. While the method is generic and can be employed for any appropriate observation time series, here we focus on the description and evaluation of the method in the French mountainous regions. The observational dataset used here is the SAFRAN meteorological reanalysis, which covers the entire French Alps split into 23 massifs, within which meteorological conditions are provided for several 300 m elevation bands. In order to evaluate the skills of the method itself, it is applied to the ALADIN-Climate v5 RCM using the ERA-Interim reanalysis as boundary conditions, for the time period from 1980 to 2010. Results of the ADAMONT method are compared to the SAFRAN reanalysis itself. Various evaluation criteria are used for temperature and precipitation but also snow depth, which is computed by the SURFEX/ISBA-Crocus model using the meteorological driving data from either the adjusted RCM data or the SAFRAN reanalysis itself. The evaluation addresses in particular the time transferability of the method (using various learning/application time periods), the impact of the RCM grid point selection procedure for each massif/altitude band configuration, and the intervariable consistency of the adjusted meteorological data generated by the method. Results show that the performance of the method is satisfactory, with similar or even better evaluation metrics than alternative methods. However, results for air temperature are generally better than for precipitation. Results in terms of snow depth are satisfactory, which can be viewed as indicating a reasonably good intervariable consistency of the meteorological data produced by the method. In terms of temporal transferability (evaluated over time periods of 15 years only), results depend on the learning period. In terms of RCM grid point selection technique, the use of a complex RCM grid points selection technique, taking into account horizontal but also altitudinal proximity to SAFRAN massif centre points/altitude couples, generally degrades evaluation metrics for high altitudes compared to a simpler grid point selection method based on horizontal distance.

Investigating light curve modulation via kernel smoothing. I. Application to 53 fundamental mode and first-overtone Cepheids in the LMC

NASA Astrophysics Data System (ADS)

Süveges, Maria; Anderson, Richard I.

2018-03-01

Context. Recent studies have revealed a hitherto unknown complexity of Cepheid pulsations by discovering irregular modulated variability using photometry, radial velocities, and interferometry. Aim. We aim to perform a statistically rigorous search and characterization of such phenomena in continuous time, applying it to 53 classical Cepheids from the OGLE-III catalog. Methods: We have used local kernel regression to search for both period and amplitude modulations simultaneously in continuous time and to investigate their detectability. We determined confidence intervals using parametric and non-parametric bootstrap sampling to estimate significance, and investigated multi-periodicity using a modified pre-whitening approach that relies on time-dependent light curve parameters. Results: We find a wide variety of period and amplitude modulations and confirm that first overtone pulsators are less stable than fundamental mode Cepheids. Significant temporal variations in period are more frequently detected than those in amplitude. We find a range of modulation intensities, suggesting that both amplitude and period modulations are ubiquitous among Cepheids. Over the 12-year baseline offered by OGLE-III, we find that period changes are often nonlinear, sometimes cyclic, suggesting physical origins beyond secular evolution. Our method detects modulations (period and amplitude) more efficiently than conventional methods that are reliant on certain features in the Fourier spectrum, and pre-whitens time series more accurately than using constant light curve parameters, removing spurious secondary peaks effectively. Conclusions: Period and amplitude modulations appear to be ubiquitous among Cepheids. Current detectability is limited by observational cadence and photometric precision: detection of amplitude modulation below 3 mmag requires space-based facilities. Recent and ongoing space missions (K2, BRITE, MOST, CoRoT) as well as upcoming ones (TESS, PLATO) will significantly improve detectability of fast modulations, such as cycle-to-cycle variations, by providing high-cadence high-precision photometry. High-quality long-term ground-based photometric time series will remain crucial to study longer-term modulations and to disentangle random fluctuations from secular evolution.

Method and apparatus for assessing cardiovascular risk

NASA Technical Reports Server (NTRS)

Albrecht, Paul (Inventor); Bigger, J. Thomas (Inventor); Cohen, Richard J. (Inventor)

1998-01-01

The method for assessing risk of an adverse clinical event includes detecting a physiologic signal in the subject and determining from the physiologic signal a sequence of intervals corresponding to time intervals between heart beats. The long-time structure of fluctuations in the intervals over a time period of more than fifteen minutes is analyzed to assess risk of an adverse clinical event. In a preferred embodiment, the physiologic signal is an electrocardiogram and the time period is at least fifteen minutes. A preferred method for analyzing the long-time structure variability in the intervals includes computing the power spectrum and fitting the power spectrum to a power law dependence on frequency over a selected frequency range such as 10.sup.-4 to 10.sup.-2 Hz. Characteristics of the long-time structure fluctuations in the intervals is used to assess risk of an adverse clinical event.

A statistical forecast model using the time-scale decomposition technique to predict rainfall during flood period over the middle and lower reaches of the Yangtze River Valley

NASA Astrophysics Data System (ADS)

Hu, Yijia; Zhong, Zhong; Zhu, Yimin; Ha, Yao

2018-04-01

In this paper, a statistical forecast model using the time-scale decomposition method is established to do the seasonal prediction of the rainfall during flood period (FPR) over the middle and lower reaches of the Yangtze River Valley (MLYRV). This method decomposites the rainfall over the MLYRV into three time-scale components, namely, the interannual component with the period less than 8 years, the interdecadal component with the period from 8 to 30 years, and the interdecadal component with the period larger than 30 years. Then, the predictors are selected for the three time-scale components of FPR through the correlation analysis. At last, a statistical forecast model is established using the multiple linear regression technique to predict the three time-scale components of the FPR, respectively. The results show that this forecast model can capture the interannual and interdecadal variation of FPR. The hindcast of FPR during 14 years from 2001 to 2014 shows that the FPR can be predicted successfully in 11 out of the 14 years. This forecast model performs better than the model using traditional scheme without time-scale decomposition. Therefore, the statistical forecast model using the time-scale decomposition technique has good skills and application value in the operational prediction of FPR over the MLYRV.

Contraceptive counseling and postpartum contraceptive use.

PubMed

Zapata, Lauren B; Murtaza, Sarah; Whiteman, Maura K; Jamieson, Denise J; Robbins, Cheryl L; Marchbanks, Polly A; D'Angelo, Denise V; Curtis, Kathryn M

2015-02-01

The objective of the study was to examine the associations between prenatal and postpartum contraceptive counseling and postpartum contraceptive use. The Pregnancy Risk Assessment Monitoring System 2004-2008 data were analyzed from Missouri, New York state, and New York City (n = 9536). We used multivariable logistic regression to assess the associations between prenatal and postpartum contraceptive counseling and postpartum contraceptive use, defined as any method and more effective methods (sterilization, intrauterine device, or hormonal methods). The majority of women received prenatal (78%) and postpartum (86%) contraceptive counseling; 72% received both. Compared with those who received no counseling, those counseled during 1 time period (adjusted odds ratio [AOR], 2.10; 95% confidence interval [CI], 1.65-2.67) and both time periods (AOR, 2.33; 95% CI, 1.87-2.89) had significantly increased odds of postpartum use of a more effective contraceptive method (32% vs 49% and 56%, respectively; P for trend < .0001). Results for counseling during both time periods differed by type of health insurance before pregnancy, with greater odds of postpartum use of a more effective method observed for women with no insurance (AOR, 3.51; 95% CI, 2.18-5.66) and Medicaid insurance (AOR, 3.74; 95% CI, 1.98-7.06) than for those with private insurance (AOR, 1.87; 95% CI, 1.44-2.43) before pregnancy. Findings were similar for postpartum use of any contraceptive method, except that no differences by insurance status were detected. The prevalence of postpartum contraceptive use, including the use of more effective methods, was highest when contraceptive counseling was provided during both prenatal and postpartum time periods. Women with Medicaid or no health insurance before pregnancy benefited the most. Published by Elsevier Inc.

Influence of mobile phone traffic on base station exposure of the general public.

PubMed

Joseph, Wout; Verloock, Leen

2010-11-01

The influence of mobile phone traffic on temporal radiofrequency exposure due to base stations during 7 d is compared for five different sites with Erlang data (representing average mobile phone traffic intensity during a period of time). The time periods of high exposure and high traffic during a day are compared and good agreement is obtained. The minimal required measurement periods to obtain accurate estimates for maximal and average long-period exposure (7 d) are determined. It is shown that these periods may be very long, indicating the necessity of new methodologies to estimate maximal and average exposure from short-period measurement data. Therefore, a new method to calculate the fields at a time instant from fields at another time instant using normalized Erlang values is proposed. This enables the estimation of maximal and average exposure during a week from short-period measurements using only Erlang data and avoids the necessity of long measurement times.

Mass Communication Research Trends from 1980 to 1999.

ERIC Educational Resources Information Center

Kamhawi, Rasha; Weaver, David

2003-01-01

Uses thematic meta-analysis to examine study method, medium and area of focus, theoretical approach, funding source, and time period covered in research articles published in 10 major mass communications journals during the 1980 to 1999 period. Finds that qualitative research methods continued to be much less common than quantitative methods…

A charged particle in a homogeneous magnetic field accelerated by a time-periodic Aharonov-Bohm flux

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalvoda, T.; Stovicek, P., E-mail: stovicek@kmlinux.fjfi.cvut.cz

2011-10-15

We consider a nonrelativistic quantum charged particle moving on a plane under the influence of a uniform magnetic field and driven by a periodically time-dependent Aharonov-Bohm flux. We observe an acceleration effect in the case when the Aharonov-Bohm flux depends on time as a sinusoidal function whose frequency is in resonance with the cyclotron frequency. In particular, the energy of the particle increases linearly for large times. An explicit formula for the acceleration rate is derived with the aid of the quantum averaging method, and then it is checked against a numerical solution and a very good agreement is found.more » - Highlights: > A nonrelativistic quantum charged particle on a plane. > A homogeneous magnetic field and a periodically time-dependent Aharonov-Bohm flux. > The quantum averaging method applied to a time-dependent system. > A resonance of the AB flux with the cyclotron frequency. > An acceleration with linearly increasing energy; a formula for the acceleration rate.« less

Spatio-temporal interpolation of precipitation during monsoon periods in Pakistan

NASA Astrophysics Data System (ADS)

Hussain, Ijaz; Spöck, Gunter; Pilz, Jürgen; Yu, Hwa-Lung

2010-08-01

Spatio-temporal estimation of precipitation over a region is essential to the modeling of hydrologic processes for water resources management. The changes of magnitude and space-time heterogeneity of rainfall observations make space-time estimation of precipitation a challenging task. In this paper we propose a Box-Cox transformed hierarchical Bayesian multivariate spatio-temporal interpolation method for the skewed response variable. The proposed method is applied to estimate space-time monthly precipitation in the monsoon periods during 1974-2000, and 27-year monthly average precipitation data are obtained from 51 stations in Pakistan. The results of transformed hierarchical Bayesian multivariate spatio-temporal interpolation are compared to those of non-transformed hierarchical Bayesian interpolation by using cross-validation. The software developed by [11] is used for Bayesian non-stationary multivariate space-time interpolation. It is observed that the transformed hierarchical Bayesian method provides more accuracy than the non-transformed hierarchical Bayesian method.

Efficient Fourier-based algorithms for time-periodic unsteady problems

NASA Astrophysics Data System (ADS)

Gopinath, Arathi Kamath

2007-12-01

This dissertation work proposes two algorithms for the simulation of time-periodic unsteady problems via the solution of Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. These algorithms use a Fourier representation in time and hence solve for the periodic state directly without resolving transients (which consume most of the resources in a time-accurate scheme). In contrast to conventional Fourier-based techniques which solve the governing equations in frequency space, the new algorithms perform all the calculations in the time domain, and hence require minimal modifications to an existing solver. The complete space-time solution is obtained by iterating in a fifth pseudo-time dimension. Various time-periodic problems such as helicopter rotors, wind turbines, turbomachinery and flapping-wings can be simulated using the Time Spectral method. The algorithm is first validated using pitching airfoil/wing test cases. The method is further extended to turbomachinery problems, and computational results verified by comparison with a time-accurate calculation. The technique can be very memory intensive for large problems, since the solution is computed (and hence stored) simultaneously at all time levels. Often, the blade counts of a turbomachine are rescaled such that a periodic fraction of the annulus can be solved. This approximation enables the solution to be obtained at a fraction of the cost of a full-scale time-accurate solution. For a viscous computation over a three-dimensional single-stage rescaled compressor, an order of magnitude savings is achieved. The second algorithm, the reduced-order Harmonic Balance method is applicable only to turbomachinery flows, and offers even larger computational savings than the Time Spectral method. It simulates the true geometry of the turbomachine using only one blade passage per blade row as the computational domain. In each blade row of the turbomachine, only the dominant frequencies are resolved, namely, combinations of neighbor's blade passing. An appropriate set of frequencies can be chosen by the analyst/designer based on a trade-off between accuracy and computational resources available. A cost comparison with a time-accurate computation for an Euler calculation on a two-dimensional multi-stage compressor obtained an order of magnitude savings, and a RANS calculation on a three-dimensional single-stage compressor achieved two orders of magnitude savings, with comparable accuracy.

Detecting critical periods in larval flatfish populations

NASA Astrophysics Data System (ADS)

Chambers, R. Christopher; Witting, David A.; Lewis, Stephen J.

2001-06-01

We evaluate the time-course of deaths and evidence of periods of increased mortality (i.e., critical periods) in laboratory populations of larval flatfish. First, we make the distinction between age-at-death and abundance-at-time data for fish larvae, the latter being typical in studies of natural populations. Next, we describe an experimental investigation of age- and temperature-dependent mortality in larval winter flounder, Pseudopleuronectes americanus. The survivorship curves of these populations differed significantly in both the magnitude and time-course of mortality among the four water temperatures evaluated (7, 10, 13, and 16°C). Mortality was highest in the cooler temperatures and concentrated in the third quarter of larval life, largely concurrent with settlement of surviving members of the cohort. Among the statistical methods for analysing survival data, the proportional-hazards model with time-varying covariates proved best at capturing the patterns of age-specific mortalities. We conclude that fair appraisals of recruitment hypotheses which are predicated on periods of high, age-specific mortality that vary with environmental conditions (e.g., Hjort's critical period hypothesis) will require: (1) data that are based on age, not time; (2) data that are of higher temporal resolution than commonly available at present and (3) analytical methods that are sensitive to irregularities in survivorship curves. We suggest four research approaches for evaluating critical periods in nature.

Visualizations of Travel Time Performance Based on Vehicle Reidentification Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, Stanley Ernest; Sharifi, Elham; Day, Christopher M.

This paper provides a visual reference of the breadth of arterial performance phenomena based on travel time measures obtained from reidentification technology that has proliferated in the past 5 years. These graphical performance measures are revealed through overlay charts and statistical distribution as revealed through cumulative frequency diagrams (CFDs). With overlays of vehicle travel times from multiple days, dominant traffic patterns over a 24-h period are reinforced and reveal the traffic behavior induced primarily by the operation of traffic control at signalized intersections. A cumulative distribution function in the statistical literature provides a method for comparing traffic patterns from variousmore » time frames or locations in a compact visual format that provides intuitive feedback on arterial performance. The CFD may be accumulated hourly, by peak periods, or by time periods specific to signal timing plans that are in effect. Combined, overlay charts and CFDs provide visual tools with which to assess the quality and consistency of traffic movement for various periods throughout the day efficiently, without sacrificing detail, which is a typical byproduct of numeric-based performance measures. These methods are particularly effective for comparing before-and-after median travel times, as well as changes in interquartile range, to assess travel time reliability.« less

Robust Period Estimation Using Mutual Information for Multiband Light Curves in the Synoptic Survey Era

NASA Astrophysics Data System (ADS)

Huijse, Pablo; Estévez, Pablo A.; Förster, Francisco; Daniel, Scott F.; Connolly, Andrew J.; Protopapas, Pavlos; Carrasco, Rodrigo; Príncipe, José C.

2018-05-01

The Large Synoptic Survey Telescope (LSST) will produce an unprecedented amount of light curves using six optical bands. Robust and efficient methods that can aggregate data from multidimensional sparsely sampled time-series are needed. In this paper we present a new method for light curve period estimation based on quadratic mutual information (QMI). The proposed method does not assume a particular model for the light curve nor its underlying probability density and it is robust to non-Gaussian noise and outliers. By combining the QMI from several bands the true period can be estimated even when no single-band QMI yields the period. Period recovery performance as a function of average magnitude and sample size is measured using 30,000 synthetic multiband light curves of RR Lyrae and Cepheid variables generated by the LSST Operations and Catalog simulators. The results show that aggregating information from several bands is highly beneficial in LSST sparsely sampled time-series, obtaining an absolute increase in period recovery rate up to 50%. We also show that the QMI is more robust to noise and light curve length (sample size) than the multiband generalizations of the Lomb–Scargle and AoV periodograms, recovering the true period in 10%–30% more cases than its competitors. A python package containing efficient Cython implementations of the QMI and other methods is provided.

A Multiple Period Problem in Distributed Energy Management Systems Considering CO2 Emissions

NASA Astrophysics Data System (ADS)

Muroda, Yuki; Miyamoto, Toshiyuki; Mori, Kazuyuki; Kitamura, Shoichi; Yamamoto, Takaya

Consider a special district (group) which is composed of multiple companies (agents), and where each agent responds to an energy demand and has a CO2 emission allowance imposed. A distributed energy management system (DEMS) optimizes energy consumption of a group through energy trading in the group. In this paper, we extended the energy distribution decision and optimal planning problem in DEMSs from a single period problem to a multiple periods one. The extension enabled us to consider more realistic constraints such as demand patterns, the start-up cost, and minimum running/outage times of equipment. At first, we extended the market-oriented programming (MOP) method for deciding energy distribution to the multiple periods problem. The bidding strategy of each agent is formulated by a 0-1 mixed non-linear programming problem. Secondly, we proposed decomposing the problem into a set of single period problems in order to solve it faster. In order to decompose the problem, we proposed a CO2 emission allowance distribution method, called an EP method. We confirmed that the proposed method was able to produce solutions whose group costs were close to lower-bound group costs by computational experiments. In addition, we verified that reduction in computational time was achieved without losing the quality of solutions by using the EP method.

Electrosynthesis of nanofibers and nano-composite films

DOEpatents

Lin, Yuehe; Liang, Liang; Liu, Jun

2006-10-17

A method for producing an array of oriented nanofibers that involves forming a solution that includes at least one electroactive species. An electrode substrate is brought into contact with the solution. A current density is applied to the electrode substrate that includes at least a first step of applying a first substantially constant current density for a first time period and a second step of applying a second substantially constant current density for a second time period. The first and second time periods are of sufficient duration to electrically deposit on the electrode substrate an array of oriented nanofibers produced from the electroactive species. Also disclosed are films that include arrays or networks of oriented nanofibers and a method for amperometrically detecting or measuring at least one analyte in a sample.

Use of the landmark method to address immortal person-time bias in comparative effectiveness research: a simulation study.

PubMed

Mi, Xiaojuan; Hammill, Bradley G; Curtis, Lesley H; Lai, Edward Chia-Cheng; Setoguchi, Soko

2016-11-20

Observational comparative effectiveness and safety studies are often subject to immortal person-time, a period of follow-up during which outcomes cannot occur because of the treatment definition. Common approaches, like excluding immortal time from the analysis or naïvely including immortal time in the analysis, are known to result in biased estimates of treatment effect. Other approaches, such as the Mantel-Byar and landmark methods, have been proposed to handle immortal time. Little is known about the performance of the landmark method in different scenarios. We conducted extensive Monte Carlo simulations to assess the performance of the landmark method compared with other methods in settings that reflect realistic scenarios. We considered four landmark times for the landmark method. We found that the Mantel-Byar method provided unbiased estimates in all scenarios, whereas the exclusion and naïve methods resulted in substantial bias when the hazard of the event was constant or decreased over time. The landmark method performed well in correcting immortal person-time bias in all scenarios when the treatment effect was small, and provided unbiased estimates when there was no treatment effect. The bias associated with the landmark method tended to be small when the treatment rate was higher in the early follow-up period than it was later. These findings were confirmed in a case study of chronic obstructive pulmonary disease. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Stature in archeological samples from central Italy: methodological issues and diachronic changes.

PubMed

Giannecchini, Monica; Moggi-Cecchi, Jacopo

2008-03-01

Stature reconstructions from skeletal remains are usually obtained through regression equations based on the relationship between height and limb bone length. Different equations have been employed to reconstruct stature in skeletal samples, but this is the first study to provide a systematic analysis of the reliability of the different methods for Italian historical samples. Aims of this article are: 1) to analyze the reliability of different regression methods to estimate stature for populations living in Central Italy from the Iron Age to Medieval times; 2) to search for trends in stature over this time period by applying the most reliable regression method. Long bone measurements were collected from 1,021 individuals (560 males, 461 females), from 66 archeological sites for males and 54 for females. Three time periods were identified: Iron Age, Roman period, and Medieval period. To determine the most appropriate equation to reconstruct stature the Delta parameter of Gini (Memorie di metodologia statistica. Milano: Giuffre A. 1939), in which stature estimates derived from different limb bones are compared, was employed. The equations proposed by Pearson (Philos Trans R Soc London 192 (1899) 169-244) and Trotter and Gleser for Afro-Americans (Am J Phys Anthropol 10 (1952) 463-514; Am J Phys Anthropol 47 (1977) 355-356) provided the most consistent estimates when applied to our sample. We then used the equation by Pearson for further analyses. Results indicate a reduction in stature in the transition from the Iron Age to the Roman period, and a subsequent increase in the transition from the Roman period to the Medieval period. Changes of limb lengths over time were more pronounced in the distal than in the proximal elements in both limbs. 2007 Wiley-Liss, Inc.

A procedure of multiple period searching in unequally spaced time-series with the Lomb-Scargle method

NASA Technical Reports Server (NTRS)

Van Dongen, H. P.; Olofsen, E.; VanHartevelt, J. H.; Kruyt, E. W.; Dinges, D. F. (Principal Investigator)

1999-01-01

Periodogram analysis of unequally spaced time-series, as part of many biological rhythm investigations, is complicated. The mathematical framework is scattered over the literature, and the interpretation of results is often debatable. In this paper, we show that the Lomb-Scargle method is the appropriate tool for periodogram analysis of unequally spaced data. A unique procedure of multiple period searching is derived, facilitating the assessment of the various rhythms that may be present in a time-series. All relevant mathematical and statistical aspects are considered in detail, and much attention is given to the correct interpretation of results. The use of the procedure is illustrated by examples, and problems that may be encountered are discussed. It is argued that, when following the procedure of multiple period searching, we can even benefit from the unequal spacing of a time-series in biological rhythm research.

Geographic and temporal validity of prediction models: Different approaches were useful to examine model performance

PubMed Central

Austin, Peter C.; van Klaveren, David; Vergouwe, Yvonne; Nieboer, Daan; Lee, Douglas S.; Steyerberg, Ewout W.

2017-01-01

Objective Validation of clinical prediction models traditionally refers to the assessment of model performance in new patients. We studied different approaches to geographic and temporal validation in the setting of multicenter data from two time periods. Study Design and Setting We illustrated different analytic methods for validation using a sample of 14,857 patients hospitalized with heart failure at 90 hospitals in two distinct time periods. Bootstrap resampling was used to assess internal validity. Meta-analytic methods were used to assess geographic transportability. Each hospital was used once as a validation sample, with the remaining hospitals used for model derivation. Hospital-specific estimates of discrimination (c-statistic) and calibration (calibration intercepts and slopes) were pooled using random effects meta-analysis methods. I2 statistics and prediction interval width quantified geographic transportability. Temporal transportability was assessed using patients from the earlier period for model derivation and patients from the later period for model validation. Results Estimates of reproducibility, pooled hospital-specific performance, and temporal transportability were on average very similar, with c-statistics of 0.75. Between-hospital variation was moderate according to I2 statistics and prediction intervals for c-statistics. Conclusion This study illustrates how performance of prediction models can be assessed in settings with multicenter data at different time periods. PMID:27262237

The effect of vehicle protection on spine injuries in military conflict.

PubMed

Possley, Daniel R; Blair, James A; Freedman, Brett A; Schoenfeld, Andrew J; Lehman, Ronald A; Hsu, Joseph R

2012-09-01

To evaluate the effect of critical time periods in vehicle protection on spine injuries in the Global War on Terror. To characterize the effect of method of movement on and around the battlefield during Operation Enduring Freedom and Operation Iraqi Freedom from 2001 to 2009 in terms of its impact on the incidence and severity of spinal fractures sustained in combat. Retrospective study. Mounted and dismounted American servicemembers who were injured during combat. Extracted medical records of servicemembers identified in the Joint Theater Trauma Registry from October 2001 to December 2009. Methods of movement were defined as mounted or dismounted. Two time periods were compared. Cohorts were created for 2×2 analysis based on method of movement and the time period in which the injury occurred. Time period 1 and 2 were separated by April 1, 2007, which correlates with the initial fielding of the modern class of uparmored fighting vehicles with thickened underbelly armor and a V-shaped hull. Our four comparison groups were Dismounted in Time Period 1 (D1), Dismounted in Time Period 2 (D2), Mounted in Time Period 1 (M1), and Mounted in Time Period 2 (M2). In total, 1,819 spine fractures occurred over the entire study period. Four hundred seventy-two fractures (26%) were sustained in 145 servicemembers who were mounted at the time of injury, and 1,347 (74%) were sustained by 404 servicemembers who were dismounted (p<.0005). The incidence of fractures in the dismounted cohort (D1+D2) was significantly higher than in the mounted cohort (M1+M2) in both time periods (D1 vs. M1, 13.75 vs. 3.95/10,000 warrior-years [p<.001] and D2 vs. M2, 11.15 vs. 4.89/10,000 warrior-years [p<.0001]). In both the mounted and dismounted groups, the thoracolumbar (TL) junction was the most common site of injury (36.1%). Fractures to the TL junction (T10-L3) increased significantly from Time Period 1 to 2 (34% vs. 40% of all fractures, respectively, p=.03). Thoracolumbar fractures were significantly more severe in that there were more Arbeitsgemeinschaft fur Osteosynthesefragen/Magerl Type A injuries versus all TL fractures, 1.75 versus 2.68/10,000 or 27% of all spine fractures in Time Period 1 versus 40% in Time Period 2 (p=.007). Furthermore, there were significantly fewer minor fractures (spinous process and transverse process fractures) (p<.0001). In Time Period 2, significantly more TL spine fractures were classified as major fractures, according to the Denis classification system, in both the mounted and dismounted groups; M1 group, 61 of 226 (27%) versus the M2 group, 86 of 246 (34%) (p<.0005) and 173 of 786 (22%) in the D1 group versus 193 of 561 (34%) in the D2 group. The spinal cord injury (SCI) incidence did not change in the mounted groups in Time Period 1 (7 of 71, 9.9%) versus Time Period 2 (7 of 74, 9.5%) (p=.935). In the dismounted groups, SCI actually decreased from D1 (55 of 228, 24%) to D2 (28 of 176, 16%) (p=.0428). The incidence of spine fractures and SCI is significantly higher in dismounted operations. The data suggest that current uparmored vehicles convey greater protection against spinal fracture compared with dismounted operations in which servicemembers are engaged on foot, outside their vehicles. The TL junction is at greatest risk for spine fractures sustained in mounted and dismounted combat operations. Recently, the incidence of TL fractures, especially severe fractures, has significantly increased in mounted operations. Although there has been an increased incidence of TL spine fractures, in context of the number of servicemembers deployed in support of Operation Enduring Freedom/Operation Iraqi Freedom, these severe fractures still represent a relatively rare event. Published by Elsevier Inc.

A probabilistic method for constructing wave time-series at inshore locations using model scenarios

USGS Publications Warehouse

Long, Joseph W.; Plant, Nathaniel G.; Dalyander, P. Soupy; Thompson, David M.

2014-01-01

Continuous time-series of wave characteristics (height, period, and direction) are constructed using a base set of model scenarios and simple probabilistic methods. This approach utilizes an archive of computationally intensive, highly spatially resolved numerical wave model output to develop time-series of historical or future wave conditions without performing additional, continuous numerical simulations. The archive of model output contains wave simulations from a set of model scenarios derived from an offshore wave climatology. Time-series of wave height, period, direction, and associated uncertainties are constructed at locations included in the numerical model domain. The confidence limits are derived using statistical variability of oceanographic parameters contained in the wave model scenarios. The method was applied to a region in the northern Gulf of Mexico and assessed using wave observations at 12 m and 30 m water depths. Prediction skill for significant wave height is 0.58 and 0.67 at the 12 m and 30 m locations, respectively, with similar performance for wave period and direction. The skill of this simplified, probabilistic time-series construction method is comparable to existing large-scale, high-fidelity operational wave models but provides higher spatial resolution output at low computational expense. The constructed time-series can be developed to support a variety of applications including climate studies and other situations where a comprehensive survey of wave impacts on the coastal area is of interest.

Finite element solution of nonlinear eddy current problems with periodic excitation and its industrial applications☆

PubMed Central

Bíró, Oszkár; Koczka, Gergely; Preis, Kurt

2014-01-01

An efficient finite element method to take account of the nonlinearity of the magnetic materials when analyzing three-dimensional eddy current problems is presented in this paper. The problem is formulated in terms of vector and scalar potentials approximated by edge and node based finite element basis functions. The application of Galerkin techniques leads to a large, nonlinear system of ordinary differential equations in the time domain. The excitations are assumed to be time-periodic and the steady-state periodic solution is of interest only. This is represented either in the frequency domain as a finite Fourier series or in the time domain as a set of discrete time values within one period for each finite element degree of freedom. The former approach is the (continuous) harmonic balance method and, in the latter one, discrete Fourier transformation will be shown to lead to a discrete harmonic balance method. Due to the nonlinearity, all harmonics, both continuous and discrete, are coupled to each other. The harmonics would be decoupled if the problem were linear, therefore, a special nonlinear iteration technique, the fixed-point method is used to linearize the equations by selecting a time-independent permeability distribution, the so-called fixed-point permeability in each nonlinear iteration step. This leads to uncoupled harmonics within these steps. As industrial applications, analyses of large power transformers are presented. The first example is the computation of the electromagnetic field of a single-phase transformer in the time domain with the results compared to those obtained by traditional time-stepping techniques. In the second application, an advanced model of the same transformer is analyzed in the frequency domain by the harmonic balance method with the effect of the presence of higher harmonics on the losses investigated. Finally a third example tackles the case of direct current (DC) bias in the coils of a single-phase transformer. PMID:24829517

Finite element solution of nonlinear eddy current problems with periodic excitation and its industrial applications.

PubMed

Bíró, Oszkár; Koczka, Gergely; Preis, Kurt

2014-05-01

An efficient finite element method to take account of the nonlinearity of the magnetic materials when analyzing three-dimensional eddy current problems is presented in this paper. The problem is formulated in terms of vector and scalar potentials approximated by edge and node based finite element basis functions. The application of Galerkin techniques leads to a large, nonlinear system of ordinary differential equations in the time domain. The excitations are assumed to be time-periodic and the steady-state periodic solution is of interest only. This is represented either in the frequency domain as a finite Fourier series or in the time domain as a set of discrete time values within one period for each finite element degree of freedom. The former approach is the (continuous) harmonic balance method and, in the latter one, discrete Fourier transformation will be shown to lead to a discrete harmonic balance method. Due to the nonlinearity, all harmonics, both continuous and discrete, are coupled to each other. The harmonics would be decoupled if the problem were linear, therefore, a special nonlinear iteration technique, the fixed-point method is used to linearize the equations by selecting a time-independent permeability distribution, the so-called fixed-point permeability in each nonlinear iteration step. This leads to uncoupled harmonics within these steps. As industrial applications, analyses of large power transformers are presented. The first example is the computation of the electromagnetic field of a single-phase transformer in the time domain with the results compared to those obtained by traditional time-stepping techniques. In the second application, an advanced model of the same transformer is analyzed in the frequency domain by the harmonic balance method with the effect of the presence of higher harmonics on the losses investigated. Finally a third example tackles the case of direct current (DC) bias in the coils of a single-phase transformer.

26 CFR 1.263A-9 - The avoided cost method.

Code of Federal Regulations, 2012 CFR

2012-04-01

... least four times during the taxable year (or consecutive 12-month period in the case of a short taxable... computation period with two measurement dates within each computation period. Corporation X must identify... date during the period and dividing the sum of these amounts by two. Under paragraph (c)(5)(iii)(C) of...

26 CFR 1.263A-9 - The avoided cost method.

Code of Federal Regulations, 2013 CFR

2013-04-01

... least four times during the taxable year (or consecutive 12-month period in the case of a short taxable... computation period with two measurement dates within each computation period. Corporation X must identify... date during the period and dividing the sum of these amounts by two. Under paragraph (c)(5)(iii)(C) of...

26 CFR 1.263A-9 - The avoided cost method.

Code of Federal Regulations, 2011 CFR

2011-04-01

... least four times during the taxable year (or consecutive 12-month period in the case of a short taxable... computation period with two measurement dates within each computation period. Corporation X must identify... date during the period and dividing the sum of these amounts by two. Under paragraph (c)(5)(iii)(C) of...

Quasi-periodic Pulse Amplitude Modulation in the Accreting Millisecond Pulsar IGR J00291+5934

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bult, Peter; Doesburgh, Marieke van; Klis, Michiel van der

We introduce a new method for analyzing the aperiodic variability of coherent pulsations in accreting millisecond X-ray pulsars (AMXPs). Our method involves applying a complex frequency correction to the time-domain light curve, allowing for the aperiodic modulation of the pulse amplitude to be robustly extracted in the frequency domain. We discuss the statistical properties of the resulting modulation spectrum and show how it can be correlated with the non-pulsed emission to determine if the periodic and aperiodic variability are coupled processes. Using this method, we study the 598.88 Hz coherent pulsations of the AMXP IGR J00291+5934 as observed with themore » Rossi X-ray Timing Explorer and XMM-Newton . We demonstrate that our method easily confirms the known coupling between the pulsations and a strong 8 mHz quasi-periodic oscillation (QPO) in XMM-Newton observations. Applying our method to the RXTE observations, we further show, for the first time, that the much weaker 20 mHz QPO and its harmonic are also coupled with the pulsations. We discuss the implications of this coupling and indicate how it may be used to extract new information on the underlying accretion process.« less

Aerosol Index Dynamics over Athens and Beijing

NASA Astrophysics Data System (ADS)

Christodoulakis, J.; Varotsos, C.; Tzanis, C.; Xue, Y.

2014-11-01

We present the analysis of monthly mean Aerosol Index (AI) values, over Athens, Greece, and Beijing, China, for the period 1979-2012. The aim of the analysis is the identification of time scaling in the AI time series, by using a data analysis technique that would not be affected by the non-stationarity of the data. The appropriate technique satisfying this criterion is the Detrended Fluctuation Analysis (DF A). For the deseasonalization of time series classic Wiener method was applied filtering out the seasonal - 3 months, semiannual - 6 months and annual - 12 months periods. The data analysis for both Athens and Beijing revealed that the exponents α for both time periods are greater than 0.5 indicating that persistence of the correlations in the fluctuations of the deseasonalized AI values exists for time scales between about 4 months and 3.5 years (for the period 1979-1993) or 4 years (for the period 1996-2012).

Aerosol Index Dynamics over Athens and Beijing

NASA Astrophysics Data System (ADS)

Christodoulakis, J.; Varotsos, C.; Tzanis, C.; Xue, Y.

2014-11-01

We present the analysis of monthly mean Aerosol Index (AI) values, over Athens, Greece, and Beijing, China, for the period 1979- 2012. The aim of the analysis is the identification of time scaling in the AI time series, by using a data analysis technique that would not be affected by the non-stationarity of the data. The appropriate technique satisfying this criterion is the Detrended Fluctuation Analysis (DFA). For the deseasonalization of time series classic Wiener method was applied filtering out the seasonal - 3 months, semiannual - 6 months and annual - 12 months periods. The data analysis for both Athens and Beijing revealed that the exponents α for both time periods are greater than 0.5 indicating that persistence of the correlations in the fluctuations of the deseasonalized AI values exists for time scales between about 4 months and 3.5 years (for the period 1979-1993) or 4 years (for the period 1996-2012).

A low-complexity attitude control method for large-angle agile maneuvers of a spacecraft with control moment gyros

NASA Astrophysics Data System (ADS)

Kawajiri, Shota; Matunaga, Saburo

2017-10-01

This study examines a low-complexity control method that satisfies mechanical constraints by using control moment gyros for an agile maneuver. The method is designed based on the fact that a simple rotation around an Euler's principal axis corresponds to a well-approximated solution of a time-optimal rest-to-rest maneuver. With respect to an agile large-angle maneuver using CMGs, it is suggested that there exists a coasting period in which all gimbal angles are constant, and a constant body angular velocity is almost along the Euler's principal axis. The gimbals are driven such that the coasting period is generated in the proposed method. This allows the problem to be converted into obtaining only a coasting time and gimbal angles such that their combination maximizes body angular velocity along the rotational axis of the maneuver. The effectiveness of the proposed method is demonstrated by using numerical simulations. The results indicate that the proposed method shortens the settling time by 20-70% when compared to that of a traditional feedback method. Additionally, a comparison with an existing path planning method shows that the proposed method achieves a low computational complexity (that is approximately 150 times faster) and a certain level of shortness in the settling time.

Daily Light Exposure Patterns Reveal Phase and Period of the Human Circadian Clock.

PubMed

Woelders, Tom; Beersma, Domien G M; Gordijn, Marijke C M; Hut, Roelof A; Wams, Emma J

2017-06-01

Light is the most potent time cue that synchronizes (entrains) the circadian pacemaker to the 24-h solar cycle. This entrainment process is an interplay between an individual's daily light perception and intrinsic pacemaker period under free-running conditions. Establishing individual estimates of circadian phase and period can be time-consuming. We show that circadian phase can be accurately predicted (SD = 1.1 h for dim light melatonin onset, DLMO) using 9 days of ambulatory light and activity data as an input to Kronauer's limit-cycle model for the human circadian system. This approach also yields an estimated circadian period of 24.2 h (SD = 0.2 h), with longer periods resulting in later DLMOs. A larger amount of daylight exposure resulted in an earlier DLMO. Individuals with a long circadian period also showed shorter intervals between DLMO and sleep timing. When a field-based estimation of tau can be validated under laboratory studies in a wide variety of individuals, the proposed methods may prove to be essential tools for individualized chronotherapy and light treatment for shift work and jetlag applications. These methods may improve our understanding of fundamental properties of human circadian rhythms under daily living conditions.

Daily Light Exposure Patterns Reveal Phase and Period of the Human Circadian Clock

PubMed Central

Woelders, Tom; Beersma, Domien G. M.; Gordijn, Marijke C. M.; Hut, Roelof A.; Wams, Emma J.

2017-01-01

Light is the most potent time cue that synchronizes (entrains) the circadian pacemaker to the 24-h solar cycle. This entrainment process is an interplay between an individual’s daily light perception and intrinsic pacemaker period under free-running conditions. Establishing individual estimates of circadian phase and period can be time-consuming. We show that circadian phase can be accurately predicted (SD = 1.1 h for dim light melatonin onset, DLMO) using 9 days of ambulatory light and activity data as an input to Kronauer’s limit-cycle model for the human circadian system. This approach also yields an estimated circadian period of 24.2 h (SD = 0.2 h), with longer periods resulting in later DLMOs. A larger amount of daylight exposure resulted in an earlier DLMO. Individuals with a long circadian period also showed shorter intervals between DLMO and sleep timing. When a field-based estimation of tau can be validated under laboratory studies in a wide variety of individuals, the proposed methods may prove to be essential tools for individualized chronotherapy and light treatment for shift work and jetlag applications. These methods may improve our understanding of fundamental properties of human circadian rhythms under daily living conditions. PMID:28452285

Determination of the Conservation Time of Periodicals for Optimal Shelf Maintenance of a Library.

ERIC Educational Resources Information Center

Miyamoto, Sadaaki; Nakayama, Kazuhiko

1981-01-01

Presents a method based on a constrained optimization technique that determines the time of removal of scientific periodicals from the shelf of a library. A geometrical interpretation of the theoretical result is given, and a numerical example illustrates how the technique is applicable to real bibliographic data. (FM)

26 CFR 1.410(a)-7 - Elapsed time.

Code of Federal Regulations, 2011 CFR

2011-04-01

... period of severance from service in order to determine a “break in service” (see paragraph (a)(3)(v) of... employers maintaining the plan. The purpose of the period of severance is to apply the statutory “break in... plan using the elapsed time method of crediting service for one or more classifications of employees...

26 CFR 1.410(a)-7 - Elapsed time.

Code of Federal Regulations, 2012 CFR

2012-04-01

... period of severance from service in order to determine a “break in service” (see paragraph (a)(3)(v) of... employers maintaining the plan. The purpose of the period of severance is to apply the statutory “break in... plan using the elapsed time method of crediting service for one or more classifications of employees...

Time delay and distance measurement

NASA Technical Reports Server (NTRS)

Abshire, James B. (Inventor); Sun, Xiaoli (Inventor)

2011-01-01

A method for measuring time delay and distance may include providing an electromagnetic radiation carrier frequency and modulating one or more of amplitude, phase, frequency, polarization, and pointing angle of the carrier frequency with a return to zero (RZ) pseudo random noise (PN) code. The RZ PN code may have a constant bit period and a pulse duration that is less than the bit period. A receiver may detect the electromagnetic radiation and calculate the scattering profile versus time (or range) by computing a cross correlation function between the recorded received signal and a three-state RZ PN code kernel in the receiver. The method also may be used for pulse delay time (i.e., PPM) communications.

GIS Based System for Post-Earthquake Crisis Managment Using Cellular Network

NASA Astrophysics Data System (ADS)

Raeesi, M.; Sadeghi-Niaraki, A.

2013-09-01

Earthquakes are among the most destructive natural disasters. Earthquakes happen mainly near the edges of tectonic plates, but they may happen just about anywhere. Earthquakes cannot be predicted. Quick response after disasters, like earthquake, decreases loss of life and costs. Massive earthquakes often cause structures to collapse, trapping victims under dense rubble for long periods of time. After the earthquake and destroyed some areas, several teams are sent to find the location of the destroyed areas. The search and rescue phase usually is maintained for many days. Time reduction for surviving people is very important. A Geographical Information System (GIS) can be used for decreasing response time and management in critical situations. Position estimation in short period of time time is important. This paper proposes a GIS based system for post-earthquake disaster management solution. This system relies on several mobile positioning methods such as cell-ID and TA method, signal strength method, angel of arrival method, time of arrival method and time difference of arrival method. For quick positioning, the system can be helped by any person who has a mobile device. After positioning and specifying the critical points, the points are sent to a central site for managing the procedure of quick response for helping. This solution establishes a quick way to manage the post-earthquake crisis.

Statistical methods for detecting and comparing periodic data and their application to the nycthemeral rhythm of bodily harm: A population based study

PubMed Central

2010-01-01

Background Animals, including humans, exhibit a variety of biological rhythms. This article describes a method for the detection and simultaneous comparison of multiple nycthemeral rhythms. Methods A statistical method for detecting periodic patterns in time-related data via harmonic regression is described. The method is particularly capable of detecting nycthemeral rhythms in medical data. Additionally a method for simultaneously comparing two or more periodic patterns is described, which derives from the analysis of variance (ANOVA). This method statistically confirms or rejects equality of periodic patterns. Mathematical descriptions of the detecting method and the comparing method are displayed. Results Nycthemeral rhythms of incidents of bodily harm in Middle Franconia are analyzed in order to demonstrate both methods. Every day of the week showed a significant nycthemeral rhythm of bodily harm. These seven patterns of the week were compared to each other revealing only two different nycthemeral rhythms, one for Friday and Saturday and one for the other weekdays. PMID:21059197

Identification of periods of clear sky irradiance in time series of GHI measurements

DOE PAGES

Reno, Matthew J.; Hansen, Clifford W.

2016-01-18

In this study, we present a simple algorithm for identifying periods of time with broadband global horizontal irradiance (GHI) similar to that occurring during clear sky conditions from a time series of GHI measurements. Other available methods to identify these periods do so by identifying periods with clear sky conditions using additional measurements, such as direct or diffuse irradiance. Our algorithm compares characteristics of the time series of measured GHI with the output of a clear sky model without requiring additional measurements. We validate our algorithm using data from several locations by comparing our results with those obtained from amore » clear sky detection algorithm, and with satellite and ground-based sky imagery.« less

Identification of periods of clear sky irradiance in time series of GHI measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reno, Matthew J.; Hansen, Clifford W.

In this study, we present a simple algorithm for identifying periods of time with broadband global horizontal irradiance (GHI) similar to that occurring during clear sky conditions from a time series of GHI measurements. Other available methods to identify these periods do so by identifying periods with clear sky conditions using additional measurements, such as direct or diffuse irradiance. Our algorithm compares characteristics of the time series of measured GHI with the output of a clear sky model without requiring additional measurements. We validate our algorithm using data from several locations by comparing our results with those obtained from amore » clear sky detection algorithm, and with satellite and ground-based sky imagery.« less

Multiple Power-Saving MSSs Scheduling Methods for IEEE802.16e Broadband Wireless Networks

PubMed Central

2014-01-01

This work proposes two enhanced multiple mobile subscriber stations (MSSs) power-saving scheduling methods for IEEE802.16e broadband wireless networks. The proposed methods are designed for the Unsolicited Grant Service (UGS) of IEEE802.16e. To reduce the active periods of all power-saving MSSs, the base station (BS) allocates each MSS fewest possible transmission frames to retrieve its data from the BS. The BS interlaces the active periods of each MSS to increase the amount of scheduled MSSs and splits the overflowing transmission frames to maximize the bandwidth utilization. Simulation results reveal that interlacing the active periods of MSSs can increase the number of scheduled MSSs to more than four times of that in the Direct scheduling method. The bandwidth utilization can thus be improved by 60%–70%. Splitting the overflowing transmission frames can improve bandwidth utilization by more than 10% over that achieved using the method of interlacing active periods, with a sacrifice of only 1% of the sleep periods in the interlacing active period method. PMID:24523656

10 CFR 905.11 - What must an IRP include?

Code of Federal Regulations, 2010 CFR

2010-01-01

... forecasting method, including but not limited to the time series, end-use, and econometric methods. The... projected durability of such savings measured over time; and must treat demand and supply resources on a... implement its IRP. (i) The IRP must state the time period that the action plan covers, and the action plan...

10 CFR 905.11 - What must an IRP include?

Code of Federal Regulations, 2011 CFR

2011-01-01

... forecasting method, including but not limited to the time series, end-use, and econometric methods. The... projected durability of such savings measured over time; and must treat demand and supply resources on a... implement its IRP. (i) The IRP must state the time period that the action plan covers, and the action plan...

10 CFR 905.11 - What must an IRP include?

Code of Federal Regulations, 2012 CFR

2012-01-01

... forecasting method, including but not limited to the time series, end-use, and econometric methods. The... projected durability of such savings measured over time; and must treat demand and supply resources on a... implement its IRP. (i) The IRP must state the time period that the action plan covers, and the action plan...

10 CFR 905.11 - What must an IRP include?

Code of Federal Regulations, 2014 CFR

2014-01-01

... forecasting method, including but not limited to the time series, end-use, and econometric methods. The... projected durability of such savings measured over time; and must treat demand and supply resources on a... implement its IRP. (i) The IRP must state the time period that the action plan covers, and the action plan...

10 CFR 905.11 - What must an IRP include?

Code of Federal Regulations, 2013 CFR

2013-01-01

... forecasting method, including but not limited to the time series, end-use, and econometric methods. The... projected durability of such savings measured over time; and must treat demand and supply resources on a... implement its IRP. (i) The IRP must state the time period that the action plan covers, and the action plan...

A variational numerical method based on finite elements for the nonlinear solution characteristics of the periodically forced Chen system

NASA Astrophysics Data System (ADS)

Khan, Sabeel M.; Sunny, D. A.; Aqeel, M.

2017-09-01

Nonlinear dynamical systems and their solutions are very sensitive to initial conditions and therefore need to be approximated carefully. In this article, we present and analyze nonlinear solution characteristics of the periodically forced Chen system with the application of a variational method based on the concept of finite time-elements. Our approach is based on the discretization of physical time space into finite elements where each time-element is mapped to a natural time space. The solution of the system is then determined in natural time space using a set of suitable basis functions. The numerical algorithm is presented and implemented to compute and analyze nonlinear behavior at different time-step sizes. The obtained results show an excellent agreement with the classical RK-4 and RK-5 methods. The accuracy and convergence of the method is shown by comparing numerically computed results with the exact solution for a test problem. The presented method has shown a great potential in dealing with the solutions of nonlinear dynamical systems and thus can be utilized in delineating different features and characteristics of their solutions.

Time/Frequency Analysis of Terrestrial Impack Crater Records

NASA Astrophysics Data System (ADS)

Chang, Heon-Young

2006-09-01

The terrestrial impact cratering record recently has been examined in the time domain by Chang & Moon (2005). It was found that the ˜ 26 Myr periodicity in the impact cratering rate exists over the last ˜ 250 Myrs. Such a periodicity can be found regardless of the lower limit of the diameter up to D ˜ 35 km. It immediately called pros and cons. The aim of this paper is two-fold: (1) to test if reported periodicities can be obtained with an independent method, (2) to see, as attempted earlier, if the phase is modulated. To achieve these goals we employ the time/frequency analysis and for the first time apply this method to the terrestrial impact cratering records. We have confirmed that without exceptions noticeable peaks appear around ˜ 25 Myr, corresponding to a frequency of ˜ 0.04 (Myr)^{-1}. We also find periodicities in the data base including small impact craters, which are longer. Though the time/frequency analysis allows us to observe directly phase variations, we cannot find any indications of such changes. Instead, modes display slow variations of power in time. The time/frequency analysis shows a nonstationary behavior of the modes. The power can grow from just above the noise level and then decrease back to its initial level in a time of order of 10 Myrs.

The short time Fourier transform and local signals

NASA Astrophysics Data System (ADS)

Okumura, Shuhei

In this thesis, I examine the theoretical properties of the short time discrete Fourier transform (STFT). The STFT is obtained by applying the Fourier transform by a fixed-sized, moving window to input series. We move the window by one time point at a time, so we have overlapping windows. I present several theoretical properties of the STFT, applied to various types of complex-valued, univariate time series inputs, and their outputs in closed forms. In particular, just like the discrete Fourier transform, the STFT's modulus time series takes large positive values when the input is a periodic signal. One main point is that a white noise time series input results in the STFT output being a complex-valued stationary time series and we can derive the time and time-frequency dependency structure such as the cross-covariance functions. Our primary focus is the detection of local periodic signals. I present a method to detect local signals by computing the probability that the squared modulus STFT time series has consecutive large values exceeding some threshold after one exceeding observation following one observation less than the threshold. We discuss a method to reduce the computation of such probabilities by the Box-Cox transformation and the delta method, and show that it works well in comparison to the Monte Carlo simulation method.

Interval sampling methods and measurement error: a computer simulation.

PubMed

Wirth, Oliver; Slaven, James; Taylor, Matthew A

2014-01-01

A simulation study was conducted to provide a more thorough account of measurement error associated with interval sampling methods. A computer program simulated the application of momentary time sampling, partial-interval recording, and whole-interval recording methods on target events randomly distributed across an observation period. The simulation yielded measures of error for multiple combinations of observation period, interval duration, event duration, and cumulative event duration. The simulations were conducted up to 100 times to yield measures of error variability. Although the present simulation confirmed some previously reported characteristics of interval sampling methods, it also revealed many new findings that pertain to each method's inherent strengths and weaknesses. The analysis and resulting error tables can help guide the selection of the most appropriate sampling method for observation-based behavioral assessments. © Society for the Experimental Analysis of Behavior.

Temporal variations in Global Seismic Stations ambient noise power levels

USGS Publications Warehouse

Ringler, A.T.; Gee, L.S.; Hutt, C.R.; McNamara, D.E.

2010-01-01

Recent concerns about time-dependent response changes in broadband seismometers have motivated the need for methods to monitor sensor health at Global Seismographic Network (GSN) stations. We present two new methods for monitoring temporal changes in data quality and instrument response transfer functions that are independent of Earth seismic velocity and attenuation models by comparing power levels against different baseline values. Our methods can resolve changes in both horizontal and vertical components in a broad range of periods (∼0.05 to 1,000 seconds) in near real time. In this report, we compare our methods with existing techniques and demonstrate how to resolve instrument response changes in long-period data (>100 seconds) as well as in the microseism bands (5 to 20 seconds).

Toward an optimal solver for time-spectral fluid-dynamic and aeroelastic solutions on unstructured meshes

NASA Astrophysics Data System (ADS)

Mundis, Nathan L.; Mavriplis, Dimitri J.

2017-09-01

The time-spectral method applied to the Euler and coupled aeroelastic equations theoretically offers significant computational savings for purely periodic problems when compared to standard time-implicit methods. However, attaining superior efficiency with time-spectral methods over traditional time-implicit methods hinges on the ability rapidly to solve the large non-linear system resulting from time-spectral discretizations which become larger and stiffer as more time instances are employed or the period of the flow becomes especially short (i.e. the maximum resolvable wave-number increases). In order to increase the efficiency of these solvers, and to improve robustness, particularly for large numbers of time instances, the Generalized Minimal Residual Method (GMRES) is used to solve the implicit linear system over all coupled time instances. The use of GMRES as the linear solver makes time-spectral methods more robust, allows them to be applied to a far greater subset of time-accurate problems, including those with a broad range of harmonic content, and vastly improves the efficiency of time-spectral methods. In previous work, a wave-number independent preconditioner that mitigates the increased stiffness of the time-spectral method when applied to problems with large resolvable wave numbers has been developed. This preconditioner, however, directly inverts a large matrix whose size increases in proportion to the number of time instances. As a result, the computational time of this method scales as the cube of the number of time instances. In the present work, this preconditioner has been reworked to take advantage of an approximate-factorization approach that effectively decouples the spatial and temporal systems. Once decoupled, the time-spectral matrix can be inverted in frequency space, where it has entries only on the main diagonal and therefore can be inverted quite efficiently. This new GMRES/preconditioner combination is shown to be over an order of magnitude more efficient than the previous wave-number independent preconditioner for problems with large numbers of time instances and/or large reduced frequencies.

Getting It Right Matters: Climate Spectra and Their Estimation

NASA Astrophysics Data System (ADS)

Privalsky, Victor; Yushkov, Vladislav

2018-06-01

In many recent publications, climate spectra estimated with different methods from observed, GCM-simulated, and reconstructed time series contain many peaks at time scales from a few years to many decades and even centuries. However, respective spectral estimates obtained with the autoregressive (AR) and multitapering (MTM) methods showed that spectra of climate time series are smooth and contain no evidence of periodic or quasi-periodic behavior. Four order selection criteria for the autoregressive models were studied and proven sufficiently reliable for 25 time series of climate observations at individual locations or spatially averaged at local-to-global scales. As time series of climate observations are short, an alternative reliable nonparametric approach is Thomson's MTM. These results agree with both the earlier climate spectral analyses and the Markovian stochastic model of climate.

Optimal Alignment of Structures for Finite and Periodic Systems.

PubMed

Griffiths, Matthew; Niblett, Samuel P; Wales, David J

2017-10-10

Finding the optimal alignment between two structures is important for identifying the minimum root-mean-square distance (RMSD) between them and as a starting point for calculating pathways. Most current algorithms for aligning structures are stochastic, scale exponentially with the size of structure, and the performance can be unreliable. We present two complementary methods for aligning structures corresponding to isolated clusters of atoms and to condensed matter described by a periodic cubic supercell. The first method (Go-PERMDIST), a branch and bound algorithm, locates the global minimum RMSD deterministically in polynomial time. The run time increases for larger RMSDs. The second method (FASTOVERLAP) is a heuristic algorithm that aligns structures by finding the global maximum kernel correlation between them using fast Fourier transforms (FFTs) and fast SO(3) transforms (SOFTs). For periodic systems, FASTOVERLAP scales with the square of the number of identical atoms in the system, reliably finds the best alignment between structures that are not too distant, and shows significantly better performance than existing algorithms. The expected run time for Go-PERMDIST is longer than FASTOVERLAP for periodic systems. For finite clusters, the FASTOVERLAP algorithm is competitive with existing algorithms. The expected run time for Go-PERMDIST to find the global RMSD between two structures deterministically is generally longer than for existing stochastic algorithms. However, with an earlier exit condition, Go-PERMDIST exhibits similar or better performance.

Kubo formulas for dispersion in heterogeneous periodic nonequilibrium systems.

PubMed

Guérin, T; Dean, D S

2015-12-01

We consider the dispersion properties of tracer particles moving in nonequilibrium heterogeneous periodic media. The tracer motion is described by a Fokker-Planck equation with arbitrary spatially periodic (but constant in time) local diffusion tensors and drifts, eventually with the presence of obstacles. We derive a Kubo-like formula for the time-dependent effective diffusion tensor valid in any dimension. From this general formula, we derive expressions for the late time effective diffusion tensor and drift in these systems. In addition, we find an explicit formula for the late finite-time corrections to these transport coefficients. In one dimension, we give a closed analytical formula for the transport coefficients. The formulas derived here are very general and provide a straightforward method to compute the dispersion properties in arbitrary nonequilibrium periodic advection-diffusion systems.

Methods and Applications of Time Series Analysis. Part I. Regression, Trends, Smoothing, and Differencing.

DTIC Science & Technology

1980-07-01

FUNCTION ( t) CENTERED AT C WITH PERIOD n -nr 0 soTIME t FIGURE 3.4S RECTAPOOLAR PORN )=C FUNCTION g t) CENTERED AT 0 WITH PERIOD n n n 52n tI y I (h...of a typical family in Kabiria (a city in Northern Algeria) over the time period Jan.-Feb. 1975 through Nov.-Dec. 1977. We would like to obtain a...values of y .. .. ... -75- Table 4.2 The Average Bi-Monthly Expenses of a Family in Kabiria and Their Fourier Representation Fourier Coefficients x k

Coming of age in Roman Britain: Osteological evidence for pubertal timing.

PubMed

Arthur, Nichola A; Gowland, Rebecca L; Redfern, Rebecca C

2016-04-01

Puberty is a key transitional phase of the human life course, with important biological and social connotations. Novel methods for the identification of the pubertal growth spurt and menarche in skeletal remains have recently been proposed (Shapland and Lewis, 2013, 2014). In this study we applied the methods to two Romano-British cemetery samples (1st-early 5th centuries AD) in order to investigate the timing of puberty during this period and further assess the veracity of the methods. Shapland and Lewis' methods (2013, 2014) were applied to 38 adolescents (aged 8-20 years) from the British cemetery sites of Roman London (1st-early 5th centuries AD) and Queenford Farm, Oxfordshire (4th-early 5th centuries AD). Overall, the Romano-British males and females experienced the onset of puberty at similar ages to modern European adolescents, but subsequently experienced a longer period of pubertal development. Menarche occurred between the ages of 15 and 17 years for these Romano-British females, around 2 to 4 years later than for present-day European females. The observed Romano-British pattern of pubertal timing has various possible explanations, including exposure to environmental stressors in early urban environments. The pattern of pubertal timing is largely congruent with social age transitions alluded to in ancient texts and funerary evidence for this period. While there are limitations to the application of these techniques to archaeological samples, they were successfully applied in this study, and may have important implications for understandings of past life courses, as well as providing a long-term perspective on pubertal timing and biocultural interactions. © 2016 Wiley Periodicals, Inc.

Bifurcation to large period oscillations in physical systems controlled by delay

NASA Astrophysics Data System (ADS)

Erneux, Thomas; Walther, Hans-Otto

2005-12-01

An unusual bifurcation to time-periodic oscillations of a class of delay differential equations is investigated. As we approach the bifurcation point, both the amplitude and the frequency of the oscillations go to zero. The class of delay differential equations is a nonlinear extension of a nonevasive control method and is motivated by a recent study of the foreign exchange rate oscillations. By using asymptotic methods, we determine the bifurcation scaling laws for the amplitude and the period of the oscillations.

Monitoring trends in waiting periods in Canada for elective surgery: validation of a method using administrative data.

PubMed

Shortt, Samuel E D; Shaw, Ralph A; Elliott, David; Mackillop, William J

2004-06-01

Provincial governments require timely, economical methods to monitor surgical waiting periods. Although use of prospective procedure-specific registers would be the ideal method, a less elaborate system has been proposed that is based on physician billing data. This study assessed the validity of using the date of the last service billed prior to surgery as a proxy for the beginning of the post-referral, pre-surgical waiting period. We examined charts for 31,824 elective surgical encounters between 1992 and 1996 at an Ontario teaching hospital. The date of the last service before surgery (the last billing date) was compared with the date of the consultant's letter indicating a decision to book surgery (i.e., to begin waiting). Several surgical specialties (but excluding cardiac, orthopedic and gynecologic) had a close correlation between the dates of the last pre-surgery visit and those of the actual decision to place the patient on the waiting list. Similar results were found for 12 of 15 individually studied procedures, including some orthopedic and gynecological procedures. Used judiciously, billing data is a timely, inexpensive and generally accurate method by which provincial governments could monitor trends in waiting times for appropriately selected surgical procedures.

A New Hybrid Method for Remote Sensing Time Series Reconstruction in Support of Land Surface Phenology

NASA Astrophysics Data System (ADS)

Barreto-Munoz, A.; Didan, K.; Riveracamacho, J.; Yitayew, M.

2010-12-01

Remote sensing vegetation indices (NDVI, EVI, and EVI2) are proxies for studying vegetation states and enable the effective and consistent monitoring of global vegetation. Records of daily global satellite images are available from the last three decades, however, the presence of clouds, aerosols, variable viewing geometry and less than ideal processing techniques makes it difficult to obtain high quality data every time; resulting in incomplete daily coverage (80% of the data is either missing or useless sometimes). In order to improve the temporal frequency and coverage, gap fill techniques are usually employed. There are several methods that are mostly based on the use of complex Fourier Transform (TF) functions, Gaussian fitting models, or simple compositing techniques. The first two methods are extremely CPU and memory intensive and the results tend to be biased towards the periods of time when data is available . The composite-method sacrifices the temporal frequency in order to achieve higher quality data over longer periods of time by combining several images into one to insure the elimination of problematic data Long composite period interval tend to inhibit proper change detection during periods of rapid change and periods of land cover disturbance. Because this method is based on maximizing the vegetation index value during the composite period, longer composite interval will shift the start of season towards later dates, the end of season towards earlier dates, and consequently shorter growing season. These slight errors and uncertainties interfere with accurate change detection as they add a level of uncertainty to the estimated Phenology parameters. In this research we’re developing a new technique that aims at producing consistently high quality vegetation index data, while preserving adequate temporal resolution to support accurate phenological studies. This method involves finding the optimum number of days for compositing and then using an interpolation approach for filling the remaining temporal gaps. The seasonally variable per-pixel optimum composite period is obtained by minimizing the number of temporal gaps when varying the composite period from 1 day to 16 days. Remaining gaps are then estimated using a local linear function that uses as input only the nearest high quality observation days. We further constrain this method by a moving window long term average to address biases that may result from over- or under-fitting. This method was evaluated using the 30+ year Climate Modeling Grid resolution (CMG, 0.05 deg.) records of AVHRR and MODIS Terra/Aqua daily surface reflectance. We note several advantages to this method: 1) Simpler and less computer intensive to implement, 2) Superior to other methods since it only looked at the data around the temporal gap which helps eliminate the biases that may result from methods that simultaneously use the full annual cycle, and 3) Most importantly it kept a balance between providing higher frequency and high quality data and the potential noise that results from daily data. It is currently being implemented as a package to support the estimation of global phenology and to generate high quality long term Earth System Data Records of Vegetation Index from multiple sensors.

Spatio-temporal cluster detection of chickenpox in Valencia, Spain in the period 2008-2012.

PubMed

Iftimi, Adina; Martínez-Ruiz, Francisco; Míguez Santiyán, Ana; Montes, Francisco

2015-05-18

Chickenpox is a highly contagious airborne disease caused by Varicella zoster, which affects nearly all non-immune children worldwide with an annual incidence estimated at 80-90 million cases. To analyze the spatiotemporal pattern of the chickenpox incidence in the city of Valencia, Spain two complementary statistical approaches were used. First, we evaluated the existence of clusters and spatio-temporal interaction; secondly, we used this information to find the locations of the spatio-temporal clusters via the space-time permutation model. The first method used detects any aggregation in our data but does not provide the spatial and temporal information. The second method gives the locations, areas and time-frame for the spatio-temporal clusters. An overall decreasing time trend, a pronounced 12-monthly periodicity and two complementary periods were observed. Several areas with high incidence, surrounding the center of the city were identified. The existence of aggregation in time and space was observed, and a number of spatio-temporal clusters were located.

Monitoring trends in waiting periods in Canada for elective surgery: validation of a method using administrative data

PubMed Central

Shortt, Samuel E.D.; Shaw, Ralph A.; Elliott, David; Mackillop, William J.

2004-01-01

Background Provincial governments require timely, economical methods to monitor surgical waiting periods. Although use of prospective procedure-specific registers would be the ideal method, a less elaborate system has been proposed that is based on physician billing data. This study assessed the validity of using the date of the last service billed prior to surgery as a proxy for the beginning of the post-referral, pre-surgical waiting period. Method We examined charts for 31 824 elective surgical encounters between 1992 and 1996 at an Ontario teaching hospital. The date of the last service before surgery (the last billing date) was compared with the date of the consultant's letter indicating a decision to book surgery (i.e., to begin waiting). Results Several surgical specialties (but excluding cardiac, orthopedic and gynecologic) had a close correlation between the dates of the last pre-surgery visit and those of the actual decision to place the patient on the waiting list. Similar results were found for 12 of 15 individually studied procedures, including some orthopedic and gynecological procedures. Conclusion Used judiciously, billing data is a timely, inexpensive and generally accurate method by which provincial governments could monitor trends in waiting times for appropriately selected surgical procedures. PMID:15264378

Leaking in history space: A way to analyze systems subjected to arbitrary driving

NASA Astrophysics Data System (ADS)

Kaszás, Bálint; Feudel, Ulrike; Tél, Tamás

2018-03-01

Our aim is to unfold phase space structures underlying systems with a drift in their parameters. Such systems are non-autonomous and belong to the class of non-periodically driven systems where the traditional theory of chaos (based e.g., on periodic orbits) does not hold. We demonstrate that even such systems possess an underlying topological horseshoe-like structure at least for a finite period of time. This result is based on a specifically developed method which allows to compute the corresponding time-dependent stable and unstable foliations. These structures can be made visible by prescribing a certain type of history for an ensemble of trajectories in phase space and by analyzing the trajectories fulfilling this constraint. The process can be considered as a leaking in history space—a generalization of traditional leaking, a method that has become widespread in traditional chaotic systems, to leaks depending on time.

Predicting long-term temperature increase for time-dependent SAR levels with a single short-term temperature response.

PubMed

Carluccio, Giuseppe; Bruno, Mary; Collins, Christopher M

2016-05-01

Present a novel method for rapid prediction of temperature in vivo for a series of pulse sequences with differing levels and distributions of specific energy absorption rate (SAR). After the temperature response to a brief period of heating is characterized, a rapid estimate of temperature during a series of periods at different heating levels is made using a linear heat equation and impulse-response (IR) concepts. Here the initial characterization and long-term prediction for a complete spine exam are made with the Pennes' bioheat equation where, at first, core body temperature is allowed to increase and local perfusion is not. Then corrections through time allowing variation in local perfusion are introduced. The fast IR-based method predicted maximum temperature increase within 1% of that with a full finite difference simulation, but required less than 3.5% of the computation time. Even higher accelerations are possible depending on the time step size chosen, with loss in temporal resolution. Correction for temperature-dependent perfusion requires negligible additional time and can be adjusted to be more or less conservative than the corresponding finite difference simulation. With appropriate methods, it is possible to rapidly predict temperature increase throughout the body for actual MR examinations. © 2015 Wiley Periodicals, Inc.

Period-dependent source rupture behavior of the 2011 Tohoku earthquake estimated by multi period-band Bayesian waveform inversion

NASA Astrophysics Data System (ADS)

Kubo, H.; Asano, K.; Iwata, T.; Aoi, S.

2014-12-01

Previous studies for the period-dependent source characteristics of the 2011 Tohoku earthquake (e.g., Koper et al., 2011; Lay et al., 2012) were based on the short and long period source models using different method. Kubo et al. (2013) obtained source models of the 2011 Tohoku earthquake using multi period-bands waveform data by a common inversion method and discussed its period-dependent source characteristics. In this study, to achieve more in detail spatiotemporal source rupture behavior of this event, we introduce a new fault surface model having finer sub-fault size and estimate the source models in multi period-bands using a Bayesian inversion method combined with a multi-time-window method. Three components of velocity waveforms at 25 stations of K-NET, KiK-net, and F-net of NIED are used in this analysis. The target period band is 10-100 s. We divide this period band into three period bands (10-25 s, 25-50 s, and 50-100 s) and estimate a kinematic source model in each period band using a Bayesian inversion method with MCMC sampling (e.g., Fukuda & Johnson, 2008; Minson et al., 2013, 2014). The parameterization of spatiotemporal slip distribution follows the multi-time-window method (Hartzell & Heaton, 1983). The Green's functions are calculated by the 3D FDM (GMS; Aoi & Fujiwara, 1999) using a 3D velocity structure model (JIVSM; Koketsu et al., 2012). The assumed fault surface model is based on the Pacific plate boundary of JIVSM and is divided into 384 subfaults of about 16 * 16 km^2. The estimated source models in multi period-bands show the following source image: (1) First deep rupture off Miyagi at 0-60 s toward down-dip mostly radiating relatively short period (10-25 s) seismic waves. (2) Shallow rupture off Miyagi at 45-90 s toward up-dip with long duration radiating long period (50-100 s) seismic wave. (3) Second deep rupture off Miyagi at 60-105 s toward down-dip radiating longer period seismic waves then that of the first deep rupture. (4) Deep rupture off Fukushima at 90-135 s. The dominant-period difference of the seismic-wave radiation between two deep ruptures off Miyagi may result from the mechanism that small-scale heterogeneities on the fault are removed by the first rupture. This difference can be also interpreted by the concept of multi-scale dynamic rupture (Ide & Aochi, 2005).

Prediction Analysis for Measles Epidemics

NASA Astrophysics Data System (ADS)

Sumi, Ayako; Ohtomo, Norio; Tanaka, Yukio; Sawamura, Sadashi; Olsen, Lars Folke; Kobayashi, Nobumichi

2003-12-01

A newly devised procedure of prediction analysis, which is a linearized version of the nonlinear least squares method combined with the maximum entropy spectral analysis method, was proposed. This method was applied to time series data of measles case notification in several communities in the UK, USA and Denmark. The dominant spectral lines observed in each power spectral density (PSD) can be safely assigned as fundamental periods. The optimum least squares fitting (LSF) curve calculated using these fundamental periods can essentially reproduce the underlying variation of the measles data. An extension of the LSF curve can be used to predict measles case notification quantitatively. Some discussions including a predictability of chaotic time series are presented.

A new method of real-time detection of changes in periodic data stream

NASA Astrophysics Data System (ADS)

Lyu, Chen; Lu, Guoliang; Cheng, Bin; Zheng, Xiangwei

2017-07-01

The change point detection in periodic time series is much desirable in many practical usages. We present a novel algorithm for this task, which includes two phases: 1) anomaly measure- on the basis of a typical regression model, we propose a new computation method to measure anomalies in time series which does not require any reference data from other measurement(s); 2) change detection- we introduce a new martingale test for detection which can be operated in an unsupervised and nonparametric way. We have conducted extensive experiments to systematically test our algorithm. The results make us believe that our algorithm can be directly applicable in many real-world change-point-detection applications.

Spectral methods in time for a class of parabolic partial differential equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ierley, G.; Spencer, B.; Worthing, R.

1992-09-01

In this paper, we introduce a fully spectral solution for the partial differential equation u[sub t] + uu[sub x] + vu[sub xx] + [mu]u[sub xxx] + [lambda]u[sub xxxx] = O. For periodic boundary conditions in space, the use of a Fourier expansion in x admits of a particularly efficient algorithm with respect to expansion of the time dependence in a Chebyshev series. Boundary conditions other than periodic may still be treated with reasonable, though lesser, efficiency. for all cases, very high accuracy is attainable at moderate computational cost relative to the expense of variable order finite difference methods in time.more » 14 refs., 9 figs.« less

Trends in Worker Hearing Loss by Industry Sector, 1981–2010

PubMed Central

Masterson, Elizabeth A.; Deddens, James A.; Themann, Christa L.; Bertke, Stephen; Calvert, Geoffrey M.

2015-01-01

Background The purpose of this study was to estimate the incidence and prevalence of hearing loss for noise-exposed U.S. workers by industry sector and 5-year time period, covering 30 years. Methods Audiograms for 1.8 million workers from 1981–2010 were examined. Incidence and prevalence were estimated by industry sector and time period. The adjusted risk of incident hearing loss within each time period and industry sector as compared with a reference time period was also estimated. Results The adjusted risk for incident hearing loss decreased over time when all industry sectors were combined. However, the risk remained high for workers in Healthcare and Social Assistance, and the prevalence was consistently high for Mining and Construction workers. Conclusions While progress has been made in reducing the risk of incident hearing loss within most industry sectors, additional efforts are needed within Mining, Construction and Healthcare and Social Assistance. PMID:25690583

Method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

DOEpatents

Stevens, Fred J.

1992-01-01

A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation.

Local discretization method for overdamped Brownian motion on a potential with multiple deep wells.

PubMed

Nguyen, P T T; Challis, K J; Jack, M W

2016-11-01

We present a general method for transforming the continuous diffusion equation describing overdamped Brownian motion on a time-independent potential with multiple deep wells to a discrete master equation. The method is based on an expansion in localized basis states of local metastable potentials that match the full potential in the region of each potential well. Unlike previous basis methods for discretizing Brownian motion on a potential, this approach is valid for periodic potentials with varying multiple deep wells per period and can also be applied to nonperiodic systems. We apply the method to a range of potentials and find that potential wells that are deep compared to five times the thermal energy can be associated with a discrete localized state while shallower wells are better incorporated into the local metastable potentials of neighboring deep potential wells.

Local discretization method for overdamped Brownian motion on a potential with multiple deep wells

NASA Astrophysics Data System (ADS)

Nguyen, P. T. T.; Challis, K. J.; Jack, M. W.

2016-11-01

We present a general method for transforming the continuous diffusion equation describing overdamped Brownian motion on a time-independent potential with multiple deep wells to a discrete master equation. The method is based on an expansion in localized basis states of local metastable potentials that match the full potential in the region of each potential well. Unlike previous basis methods for discretizing Brownian motion on a potential, this approach is valid for periodic potentials with varying multiple deep wells per period and can also be applied to nonperiodic systems. We apply the method to a range of potentials and find that potential wells that are deep compared to five times the thermal energy can be associated with a discrete localized state while shallower wells are better incorporated into the local metastable potentials of neighboring deep potential wells.

Estimating time-varying exposure-outcome associations using case-control data: logistic and case-cohort analyses.

PubMed

Keogh, Ruth H; Mangtani, Punam; Rodrigues, Laura; Nguipdop Djomo, Patrick

2016-01-05

Traditional analyses of standard case-control studies using logistic regression do not allow estimation of time-varying associations between exposures and the outcome. We present two approaches which allow this. The motivation is a study of vaccine efficacy as a function of time since vaccination. Our first approach is to estimate time-varying exposure-outcome associations by fitting a series of logistic regressions within successive time periods, reusing controls across periods. Our second approach treats the case-control sample as a case-cohort study, with the controls forming the subcohort. In the case-cohort analysis, controls contribute information at all times they are at risk. Extensions allow left truncation, frequency matching and, using the case-cohort analysis, time-varying exposures. Simulations are used to investigate the methods. The simulation results show that both methods give correct estimates of time-varying effects of exposures using standard case-control data. Using the logistic approach there are efficiency gains by reusing controls over time and care should be taken over the definition of controls within time periods. However, using the case-cohort analysis there is no ambiguity over the definition of controls. The performance of the two analyses is very similar when controls are used most efficiently under the logistic approach. Using our methods, case-control studies can be used to estimate time-varying exposure-outcome associations where they may not previously have been considered. The case-cohort analysis has several advantages, including that it allows estimation of time-varying associations as a continuous function of time, while the logistic regression approach is restricted to assuming a step function form for the time-varying association.

Non-stationary dynamics in the bouncing ball: A wavelet perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Behera, Abhinna K., E-mail: abhinna@iiserkol.ac.in; Panigrahi, Prasanta K., E-mail: pprasanta@iiserkol.ac.in; Sekar Iyengar, A. N., E-mail: ansekar.iyengar@saha.ac.in

2014-12-01

The non-stationary dynamics of a bouncing ball, comprising both periodic as well as chaotic behavior, is studied through wavelet transform. The multi-scale characterization of the time series displays clear signatures of self-similarity, complex scaling behavior, and periodicity. Self-similar behavior is quantified by the generalized Hurst exponent, obtained through both wavelet based multi-fractal detrended fluctuation analysis and Fourier methods. The scale dependent variable window size of the wavelets aptly captures both the transients and non-stationary periodic behavior, including the phase synchronization of different modes. The optimal time-frequency localization of the continuous Morlet wavelet is found to delineate the scales corresponding tomore » neutral turbulence, viscous dissipation regions, and different time varying periodic modulations.« less

Criminal investigations: pupil pharmacological reactivity as method for assessing time since death is fallacious.

PubMed

Orrico, Marco; Melotti, Roberto; Mantovani, Anna; Avesani, Barbara; De Marco, Roberto; De Leo, Domenico

2008-12-01

Determination of the time since death in the early postmortem period is one of the most critical issues to be faced by criminal investigators. One of the techniques is the evaluation of the pupil pharmacological reactivity. In the present work, we aim at identifying whether an objective and single method, based on pharmacological pupil reaction, is feasible or not. Between 2002 and 2003 calendar years, we observed 309 bodies, whose eyes have been each instilled apart, within 26 hours since death, with either a myotic substance or a mydriatic solution. Our results show that the real effectiveness of pupil pharmacological reactivity as method for assessing the time since death in early postmortem period is not only questionable but even highly misleading if not replaced by alternative objective physiological tests and appropriate professional judgments by the investigators.

Data quality at the Singapore Cancer Registry: An overview of comparability, completeness, validity and timeliness.

PubMed

Fung, Janice Wing Mei; Lim, Sandra Bee Lay; Zheng, Huili; Ho, William Ying Tat; Lee, Bee Guat; Chow, Khuan Yew; Lee, Hin Peng

2016-08-01

To provide a comprehensive evaluation of the quality of the data at the Singapore Cancer Registry (SCR). Quantitative and semi-quantitative methods were used to assess the comparability, completeness, accuracy and timeliness of data for the period of 1968-2013, with focus on the period 2008-2012. The SCR coding and classification systems follow international standards. The overall completeness was estimated at 98.1% using the flow method and 97.5% using the capture-recapture method, for the period of 2008-2012. For the same period, 91.9% of the cases were morphologically verified (site-specific range: 40.4-100%) with 1.1% DCO cases. The under-reporting in 2011 and 2012 due to timely publication was estimated at 0.03% and 0.51% respectively. This review shows that the processes in place at the SCR yields data which are internationally comparable, relatively complete, valid, and timely, allowing for greater confidence in the use of quality data in the areas of cancer prevention, treatment and control. Copyright © 2016 Elsevier Ltd. All rights reserved.

From Networks to Time Series

NASA Astrophysics Data System (ADS)

Shimada, Yutaka; Ikeguchi, Tohru; Shigehara, Takaomi

2012-10-01

In this Letter, we propose a framework to transform a complex network to a time series. The transformation from complex networks to time series is realized by the classical multidimensional scaling. Applying the transformation method to a model proposed by Watts and Strogatz [Nature (London) 393, 440 (1998)], we show that ring lattices are transformed to periodic time series, small-world networks to noisy periodic time series, and random networks to random time series. We also show that these relationships are analytically held by using the circulant-matrix theory and the perturbation theory of linear operators. The results are generalized to several high-dimensional lattices.

Extension of the Time-Spectral Approach to Overset Solvers for Arbitrary Motion

NASA Technical Reports Server (NTRS)

Leffell, Joshua Isaac; Murman, Scott M.; Pulliam, Thomas H.

2012-01-01

Forced periodic flows arise in a broad range of aerodynamic applications such as rotorcraft, turbomachinery, and flapping wing configurations. Standard practice involves solving the unsteady flow equations forward in time until the initial transient exits the domain and a statistically stationary flow is achieved. It is often required to simulate through several periods to remove the initial transient making unsteady design optimization prohibitively expensive for most realistic problems. An effort to reduce the computational cost of these calculations led to the development of the Harmonic Balance method [1, 2] which capitalizes on the periodic nature of the solution. The approach exploits the fact that forced temporally periodic flow, while varying in the time domain, is invariant in the frequency domain. Expanding the temporal variation at each spatial node into a Fourier series transforms the unsteady governing equations into a steady set of equations in integer harmonics that can be tackled with the acceleration techniques afforded to steady-state flow solvers. Other similar approaches, such as the Nonlinear Frequency Domain [3,4,5], Reduced Frequency [6] and Time-Spectral [7, 8, 9] methods, were developed shortly thereafter. Additionally, adjoint-based optimization techniques can be applied [10, 11] as well as frequency-adaptive methods [12, 13, 14] to provide even more flexibility to the method. The Fourier temporal basis functions imply spectral convergence as the number of harmonic modes, and correspondingly number of time samples, N, is increased. Some elect to solve the equations in the frequency domain directly, while others choose to transform the equations back into the time domain to simplify the process of adding this capability to existing solvers, but each harnesses the underlying steady solution in the frequency domain. These temporal projection methods will herein be collectively referred to as Time-Spectral methods. Time-Spectral methods have demonstrated marked success in reducing the computational costs associated with simulating periodic forced flows, but have yet to be fully applied to overset or Cartesian solvers for arbitrary motion with dynamic hole-cutting. Overset and Cartesian grid methodologies are versatile techniques capable of handling complex geometry configurations in practical engineering applications, and the combination of the Time-Spectral approach with this general capability potentially provides an enabling new design and analysis tool. In an arbitrary moving-body scenario for these approaches, a Lagrangian body moves through a fixed Eulerian mesh and mesh points in the Eulerian mesh interior to the solid body are removed (cut or blanked), leaving a hole in the Eulerian mesh. During the dynamic motion some gridpoints in the domain are blanked and do not have a complete set of time-samples preventing a direct implementation of the Time-Spectral method. Murman[6] demonstrated the Time-Spectral approach for a Cartesian solver with a rigid domain motion, wherein the hole cutting remains constant. Similarly, Custer et al. [15, 16] used the NASA overset OVERFLOW solver and limited the amount of relative motion to ensure static hole-cutting and interpolation. Recently, Mavriplis and Mundis[17] demonstrated a qualitative method for applying the Time-Spectral approach to an unstructured overset solver for arbitrary motion. The goal of the current work is to develop a robust and general method for handling arbitrary motion with the Time-Spectral approach within an overset or Cartesian mesh method, while still approaching the spectral convergence rate of the original Time-Spectral approach. The viscous OVERFLOW solver will be augmented with the new Time-Spectral algorithm and the capability of the method for benchmark problems in rotorcraft and turbomachinery will be demonstrated. This abstract begins with a brief synopsis of the Time-Spectral approach for overset grids and provides details of e current approach to allow for arbitrary motion. Model problem results in one and two dimensions are included to demonstrate the viability of the method and the convergence properties. Section IV briefly outlines the implementation into the OVERFLOW solver, and the abstract closes with a description of the benchmark test cases which will be included in the final paper.

The effect of temperature and extraction period of time on the chemicals content of emprit ginger ethanol extract (Zingiber officinale var. Rubrum)

NASA Astrophysics Data System (ADS)

Ratnaningrum, Diah; Endah, Een Sri; Pudjiraharti, Sri

2017-01-01

Research on extraction method of emprit ginger using ethanol with agitation of 100 rpm at different temperatures (ambient temperature, 40, and 50°C) and various extraction period of times (30, 60, and 90 minutes) was conducted. Analysis of chemicals content i.e. total phenolic and total flavonoid. The objective of this work was to study the effect of temperatures and extraction period of times on the chemicals content of its ethanol extract. Based on the results of the test, the highest content total flavonoid (5.17% w/w) was resulted at 40°C for 90 minutes, while the total phenolic content was not affected by either temperature or extraction period of times used. The content of total phenolic was around 2.39% to 2.65% w/w.

Method and apparatus for measuring the gas permeability of a solid sample

DOEpatents

Carstens, D.H.W.

1984-01-27

The disclosure is directed to an apparatus and method for measuring the permeability of a gas in a sample. The gas is allowed to reach a steady flow rate through the sample. A measurable amount of the gas is collected during a given time period and then delivered to a sensitive quadrupole. The quadrupole signal, adjusted for background, is proportional to the amount of gas collected during the time period. The quadrupole can be calibrated with a standard helium leak. The gas can be deuterium and the sample can be polyvinyl alcohol.

[Intrauterine device, the best method for spacing births in breastfeeding mothers].

PubMed

Blum, M; Kaplan, B

1992-11-01

Twenty-nine breastfeeding women, with a mean age of 36.5 years, were fitted with an IUD, Nova T or Multi load 375, at an average time of 3.6 months after delivery. Insertion at this time was easy, without dilatation, pain or bleeding. During a follow up of 18 months, the IUD has to be discontinued in one woman (3.4%) because of excessive menstrual bleeding, at a time when she was no more fully breastfeeding. The continuation rate was 96.56%, as compared to only 82% for a general population of 216 women fitted with IUD at the same period after delivery and followed up for the same period of time. The IUD is in our opinion the birthspacing method of choice for breastfeeding mothers.

Hybrid transfer-matrix FDTD method for layered periodic structures.

PubMed

Deinega, Alexei; Belousov, Sergei; Valuev, Ilya

2009-03-15

A hybrid transfer-matrix finite-difference time-domain (FDTD) method is proposed for modeling the optical properties of finite-width planar periodic structures. This method can also be applied for calculation of the photonic bands in infinite photonic crystals. We describe the procedure of evaluating the transfer-matrix elements by a special numerical FDTD simulation. The accuracy of the new method is tested by comparing computed transmission spectra of a 32-layered photonic crystal composed of spherical or ellipsoidal scatterers with the results of direct FDTD and layer-multiple-scattering calculations.

Solar differential rotation in the period 1964-2016 determined by the Kanzelhöhe data set

NASA Astrophysics Data System (ADS)

Poljančić Beljan, I.; Jurdana-Šepić, R.; Brajša, R.; Sudar, D.; Ruždjak, D.; Hržina, D.; Pötzi, W.; Hanslmeier, A.; Veronig, A.; Skokić, I.; Wöhl, H.

2017-10-01

Context. Kanzelhöhe Observatory for Solar and Environmental Research (KSO) provides daily multispectral synoptic observations of the Sun using several telescopes. In this work we made use of sunspot drawings and full disk white light CCD images. Aims: The main aim of this work is to determine the solar differential rotation by tracing sunspot groups during the period 1964-2016, using the KSO sunspot drawings and white light images. We also compare the differential rotation parameters derived in this paper from the KSO with those collected fromf other data sets and present an investigation of the north - south rotational asymmetry. Methods: Two procedures for the determination of the heliographic positions were applied: an interactive procedure on the KSO sunspot drawings (1964-2008, solar cycles Nos. 20-23) and an automatic procedure on the KSO white light images (2009-2016, solar cycle No. 24). For the determination of the synodic angular rotation velocities two different methods have been used: a daily shift (DS) method and a robust linear least-squares fit (rLSQ) method. Afterwards, the rotation velocities had to be converted from synodic to sidereal, which were then used in the least-squares fitting for the solar differential rotation law. A comparison of the interactive and automatic procedures was performed for the year 2014. Results: The interactive procedure of position determination is fairly accurate but time consuming. In the case of the much faster automatic procedure for position determination, we found the rLSQ method for calculating rotational velocities to be more reliable than the DS method. For the test data from 2014, the rLSQ method gives a relative standard error for the differential rotation parameter B that is three times smaller than the corresponding relative standard error derived for the DS method. The best fit solar differential rotation profile for the whole time period is ω(b) = (14.47 ± 0.01)-(2.66 ± 0.10)sin2b (deg/day) for the DS method and ω(b) = (14.50 ± 0.01)-(2.87 ± 0.12)sin2b (deg/day) for the rLSQ method. A barely noticeable north - south asymmetry is observed for the whole time period 1964-2016 in the present paper. Rotation profiles, using different data sets, presented by other authors for the same time periods and the same tracer types, are in good agreement with our results. Conclusions: The KSO data set used in this paper is in good agreement with the Debrecen Photoheliographic Data and Greenwich Photoheliographic Results and is suitable for the investigation of the long-term variabilities in the solar rotation profile. Also, the quality of the KSO sunspot drawings has gradually increased during the last 50 yr.

Comparison study of global and local approaches describing critical phenomena on the Polish stock exchange market

NASA Astrophysics Data System (ADS)

Czarnecki, Łukasz; Grech, Dariusz; Pamuła, Grzegorz

2008-12-01

We confront global and local methods to analyze the financial crash-like events on the Polish financial market from the critical phenomena point of view. These methods are based on the analysis of log-periodicity and the local fractal properties of financial time series in the vicinity of phase transitions (crashes). The whole history (1991-2008) of Warsaw Stock Exchange Index (WIG) describing the largest developing financial market in Europe, is analyzed in a daily time horizon. We find that crash-like events on the Polish financial market are described better by the log-divergent price model decorated with log-periodic behavior than the corresponding power-law-divergent price model. Predictions coming from log-periodicity scenario are verified for all main crashes that took place in WIG history. It is argued that crash predictions within log-periodicity model strongly depend on the amount of data taken to make a fit and therefore are likely to contain huge inaccuracies. Turning to local fractal description, we calculate the so-called local (time dependent) Hurst exponent H for the WIG time series and we find the dependence between the behavior of the local fractal properties of the WIG time series and the crashes appearance on the financial market. The latter method seems to work better than the global approach - both for developing as for developed markets. The current situation on the market, particularly related to the Fed intervention in September’07 and the situation on the market immediately after this intervention is also analyzed from the fractional Brownian motion point of view.

Searching for planets around eclipsing binary stars using timing method: NSVS 14256825

NASA Astrophysics Data System (ADS)

Nasiroglu, Ilham; Goździewski, Krzysztof; Słowikowska, Aga; Krzeszowski, Krzysztof; Żejmo, Michal; Zola, Staszek; Er, Huseyin

2018-04-01

We present four new mid eclipse times and an updated O-C diagram of the short period eclipsing binary NSVS14256825. The new data follow the (O-C) trend and its model proposed in Nasiroglu et al. (2017). The (O-C) diagram shows quasi-periodic variations that can be explained with the presence of a brown-dwarf in a quasi-circular circumbinary orbit.

Periodic equivalence ratio modulation method and apparatus for controlling combustion instability

DOEpatents

Richards, George A.; Janus, Michael C.; Griffith, Richard A.

2000-01-01

The periodic equivalence ratio modulation (PERM) method and apparatus significantly reduces and/or eliminates unstable conditions within a combustion chamber. The method involves modulating the equivalence ratio for the combustion device, such that the combustion device periodically operates outside of an identified unstable oscillation region. The equivalence ratio is modulated between preselected reference points, according to the shape of the oscillation region and operating parameters of the system. Preferably, the equivalence ratio is modulated from a first stable condition to a second stable condition, and, alternatively, the equivalence ratio is modulated from a stable condition to an unstable condition. The method is further applicable to multi-nozzle combustor designs, whereby individual nozzles are alternately modulated from stable to unstable conditions. Periodic equivalence ratio modulation (PERM) is accomplished by active control involving periodic, low frequency fuel modulation, whereby low frequency fuel pulses are injected into the main fuel delivery. Importantly, the fuel pulses are injected at a rate so as not to affect the desired time-average equivalence ratio for the combustion device.

A high-order boundary integral method for surface diffusions on elastically stressed axisymmetric rods.

PubMed

Li, Xiaofan; Nie, Qing

2009-07-01

Many applications in materials involve surface diffusion of elastically stressed solids. Study of singularity formation and long-time behavior of such solid surfaces requires accurate simulations in both space and time. Here we present a high-order boundary integral method for an elastically stressed solid with axi-symmetry due to surface diffusions. In this method, the boundary integrals for isotropic elasticity in axi-symmetric geometry are approximated through modified alternating quadratures along with an extrapolation technique, leading to an arbitrarily high-order quadrature; in addition, a high-order (temporal) integration factor method, based on explicit representation of the mean curvature, is used to reduce the stability constraint on time-step. To apply this method to a periodic (in axial direction) and axi-symmetric elastically stressed cylinder, we also present a fast and accurate summation method for the periodic Green's functions of isotropic elasticity. Using the high-order boundary integral method, we demonstrate that in absence of elasticity the cylinder surface pinches in finite time at the axis of the symmetry and the universal cone angle of the pinching is found to be consistent with the previous studies based on a self-similar assumption. In the presence of elastic stress, we show that a finite time, geometrical singularity occurs well before the cylindrical solid collapses onto the axis of symmetry, and the angle of the corner singularity on the cylinder surface is also estimated.

40 CFR 63.11094 - What are my recordkeeping requirements?

Code of Federal Regulations, 2010 CFR

2010-07-01

...: Test pressure; pressure or vacuum change, mm of water; time period of test; number of leaks found with... § 63.11092(f)(1) and periodic railcar bubble leak testing performed under § 63.11092(f)(2). (2) The... Certification Test—Method 27 or Periodic Railcar Bubble Leak Test Procedure. (ii) Cargo tank owner's name and...

Drift-Free Position Estimation of Periodic or Quasi-Periodic Motion Using Inertial Sensors

PubMed Central

Latt, Win Tun; Veluvolu, Kalyana Chakravarthy; Ang, Wei Tech

2011-01-01

Position sensing with inertial sensors such as accelerometers and gyroscopes usually requires other aided sensors or prior knowledge of motion characteristics to remove position drift resulting from integration of acceleration or velocity so as to obtain accurate position estimation. A method based on analytical integration has previously been developed to obtain accurate position estimate of periodic or quasi-periodic motion from inertial sensors using prior knowledge of the motion but without using aided sensors. In this paper, a new method is proposed which employs linear filtering stage coupled with adaptive filtering stage to remove drift and attenuation. The prior knowledge of the motion the proposed method requires is only approximate band of frequencies of the motion. Existing adaptive filtering methods based on Fourier series such as weighted-frequency Fourier linear combiner (WFLC), and band-limited multiple Fourier linear combiner (BMFLC) are modified to combine with the proposed method. To validate and compare the performance of the proposed method with the method based on analytical integration, simulation study is performed using periodic signals as well as real physiological tremor data, and real-time experiments are conducted using an ADXL-203 accelerometer. Results demonstrate that the performance of the proposed method outperforms the existing analytical integration method. PMID:22163935

Spectral methods for time dependent partial differential equations

NASA Technical Reports Server (NTRS)

Gottlieb, D.; Turkel, E.

1983-01-01

The theory of spectral methods for time dependent partial differential equations is reviewed. When the domain is periodic Fourier methods are presented while for nonperiodic problems both Chebyshev and Legendre methods are discussed. The theory is presented for both hyperbolic and parabolic systems using both Galerkin and collocation procedures. While most of the review considers problems with constant coefficients the extension to nonlinear problems is also discussed. Some results for problems with shocks are presented.

Support vector machines for TEC seismo-ionospheric anomalies detection

NASA Astrophysics Data System (ADS)

Akhoondzadeh, M.

2013-02-01

Using time series prediction methods, it is possible to pursue the behaviors of earthquake precursors in the future and to announce early warnings when the differences between the predicted value and the observed value exceed the predefined threshold value. Support Vector Machines (SVMs) are widely used due to their many advantages for classification and regression tasks. This study is concerned with investigating the Total Electron Content (TEC) time series by using a SVM to detect seismo-ionospheric anomalous variations induced by the three powerful earthquakes of Tohoku (11 March 2011), Haiti (12 January 2010) and Samoa (29 September 2009). The duration of TEC time series dataset is 49, 46 and 71 days, for Tohoku, Haiti and Samoa earthquakes, respectively, with each at time resolution of 2 h. In the case of Tohoku earthquake, the results show that the difference between the predicted value obtained from the SVM method and the observed value reaches the maximum value (i.e., 129.31 TECU) at earthquake time in a period of high geomagnetic activities. The SVM method detected a considerable number of anomalous occurrences 1 and 2 days prior to the Haiti earthquake and also 1 and 5 days before the Samoa earthquake in a period of low geomagnetic activities. In order to show that the method is acting sensibly with regard to the results extracted during nonevent and event TEC data, i.e., to perform some null-hypothesis tests in which the methods would also be calibrated, the same period of data from the previous year of the Samoa earthquake date has been taken into the account. Further to this, in this study, the detected TEC anomalies using the SVM method were compared to the previous results (Akhoondzadeh and Saradjian, 2011; Akhoondzadeh, 2012) obtained from the mean, median, wavelet and Kalman filter methods. The SVM detected anomalies are similar to those detected using the previous methods. It can be concluded that SVM can be a suitable learning method to detect the novelty changes of a nonlinear time series such as variations of earthquake precursors.

Reconstruction of ensembles of coupled time-delay systems from time series.

PubMed

Sysoev, I V; Prokhorov, M D; Ponomarenko, V I; Bezruchko, B P

2014-06-01

We propose a method to recover from time series the parameters of coupled time-delay systems and the architecture of couplings between them. The method is based on a reconstruction of model delay-differential equations and estimation of statistical significance of couplings. It can be applied to networks composed of nonidentical nodes with an arbitrary number of unidirectional and bidirectional couplings. We test our method on chaotic and periodic time series produced by model equations of ensembles of diffusively coupled time-delay systems in the presence of noise, and apply it to experimental time series obtained from electronic oscillators with delayed feedback coupled by resistors.

The eclipsing binary star RZ Cas: accretion-driven variability of the multimode oscillation spectrum

NASA Astrophysics Data System (ADS)

Mkrtichian, D. E.; Lehmann, H.; Rodríguez, E.; Olson, E.; Kim, S.-L.; Kusakin, A. V.; Lee, J. W.; Youn, J.-H.; Kwon, S.-G.; López-González, M. J.; Janiashvili, E.; Tiwari, S. K.; Joshi, Santosh; Lampens, P.; Van Cauteren, P.; Glazunova, L.; Gamarova, A.; Grankin, K. N.; Rovithis-Livaniou, E.; Svoboda, P.; Uhlar, R.; Tsymbal, V.; Kokumbaeva, R.; Urushadze, T.; Kuratov, K.; Shin, H.-C.; Kang, Y.-W.; Soonthornthum, B.

2018-04-01

We analysed photometric time series of the active, semidetached Algol-type system RZ Cas obtained in 1999-2009, in order to search for seasonal and short-term variations in the oscillation spectrum of RZ Cas A. The orbital period shows ±1 s cyclic variations on time-scales of 6-9 years. We detected six low-degree p-mode oscillations with periods between 22.3 and 26.22 min and obtained safe mode identifications using the periodic spatial filter method. The amplitudes and frequencies of all modes vary.

Improving regression-model-based streamwater constituent load estimates derived from serially correlated data

USGS Publications Warehouse

Aulenbach, Brent T.

2013-01-01

A regression-model based approach is a commonly used, efficient method for estimating streamwater constituent load when there is a relationship between streamwater constituent concentration and continuous variables such as streamwater discharge, season and time. A subsetting experiment using a 30-year dataset of daily suspended sediment observations from the Mississippi River at Thebes, Illinois, was performed to determine optimal sampling frequency, model calibration period length, and regression model methodology, as well as to determine the effect of serial correlation of model residuals on load estimate precision. Two regression-based methods were used to estimate streamwater loads, the Adjusted Maximum Likelihood Estimator (AMLE), and the composite method, a hybrid load estimation approach. While both methods accurately and precisely estimated loads at the model’s calibration period time scale, precisions were progressively worse at shorter reporting periods, from annually to monthly. Serial correlation in model residuals resulted in observed AMLE precision to be significantly worse than the model calculated standard errors of prediction. The composite method effectively improved upon AMLE loads for shorter reporting periods, but required a sampling interval of at least 15-days or shorter, when the serial correlations in the observed load residuals were greater than 0.15. AMLE precision was better at shorter sampling intervals and when using the shortest model calibration periods, such that the regression models better fit the temporal changes in the concentration–discharge relationship. The models with the largest errors typically had poor high flow sampling coverage resulting in unrepresentative models. Increasing sampling frequency and/or targeted high flow sampling are more efficient approaches to ensure sufficient sampling and to avoid poorly performing models, than increasing calibration period length.

Evolution of orbits of the Apollo group asteroids over 11550 years.

NASA Astrophysics Data System (ADS)

Zausaev, A. F.; Pushkarev, A. N.

The Everhart method is used to study the evolution of the orbits of 20 asteroids of the Apollo group over the time period from 9300 B.C. to 2250 A.D. Minimum distances of the asteroids to the major planets over the evolution process are calculated. The stability of resonances with Venus and Earth over the 9300 B.C.to 2250 A.D. time period is shown. Theoretical coordinates of radiants for the initial and final integration times are presented.

A Robust Apnea Period Detection Method in Changing Sleep Posture by Average Mutual Information of Heartbeat and Respiration

NASA Astrophysics Data System (ADS)

Kurihara, Yosuke; Watanabe, Kajiro; Kobayashi, Kazuyuki; Tanaka, Tanaka

Sleep disorders disturb the recovery from mental and physical fatigues, one of the functions of the sleep. The majority of those who with the disorders are suffering from Sleep Apnea Syndrome (SAS). Continuous Hypoxia during sleep due to SAS cause Circulatory Disturbances, such as hypertension and ischemic heart disease, and Malfunction of Autonomic Nervous System, and other severe complications, often times bringing the suffers to death. In order to prevent these from happening, it is important to detect the SAS in its early stage by monitoring the daily respirations during sleep, and to provide appropriate treatments at medical institutions. In this paper, the Pneumatic Method to detect the Apnea period during sleep is proposed. Pneumatic method can measure heartbeat and respiration signal. Respiration signal can be considered as noise against heartbeat signal, and the decrease in the respiration signal due to Apnea increases the Average Mutual Information of heartbeat. The result of scaling analysis of the average mutual information is defined as threshold to detect the apnea period. The root mean square error between the lengths of Apnea measured by Strain Gauge using for reference and those measured by using the proposed method was 3.1 seconds. And, error of the number of apnea times judged by doctor and proposal method in OSAS patients was 3.3 times.

Empirical mode decomposition and long-range correlation analysis of sunspot time series

NASA Astrophysics Data System (ADS)

Zhou, Yu; Leung, Yee

2010-12-01

Sunspots, which are the best known and most variable features of the solar surface, affect our planet in many ways. The number of sunspots during a period of time is highly variable and arouses strong research interest. When multifractal detrended fluctuation analysis (MF-DFA) is employed to study the fractal properties and long-range correlation of the sunspot series, some spurious crossover points might appear because of the periodic and quasi-periodic trends in the series. However many cycles of solar activities can be reflected by the sunspot time series. The 11-year cycle is perhaps the most famous cycle of the sunspot activity. These cycles pose problems for the investigation of the scaling behavior of sunspot time series. Using different methods to handle the 11-year cycle generally creates totally different results. Using MF-DFA, Movahed and co-workers employed Fourier truncation to deal with the 11-year cycle and found that the series is long-range anti-correlated with a Hurst exponent, H, of about 0.12. However, Hu and co-workers proposed an adaptive detrending method for the MF-DFA and discovered long-range correlation characterized by H≈0.74. In an attempt to get to the bottom of the problem in the present paper, empirical mode decomposition (EMD), a data-driven adaptive method, is applied to first extract the components with different dominant frequencies. MF-DFA is then employed to study the long-range correlation of the sunspot time series under the influence of these components. On removing the effects of these periods, the natural long-range correlation of the sunspot time series can be revealed. With the removal of the 11-year cycle, a crossover point located at around 60 months is discovered to be a reasonable point separating two different time scale ranges, H≈0.72 and H≈1.49. And on removing all cycles longer than 11 years, we have H≈0.69 and H≈0.28. The three cycle-removing methods—Fourier truncation, adaptive detrending and the proposed EMD-based method—are further compared, and possible reasons for the different results are given. Two numerical experiments are designed for quantitatively evaluating the performances of these three methods in removing periodic trends with inexact/exact cycles and in detecting the possible crossover points.

Method and system for turbomachinery surge detection

DOEpatents

Faymon, David K.; Mays, Darrell C.; Xiong, Yufei

2004-11-23

A method and system for surge detection within a gas turbine engine, comprises: measuring the compressor discharge pressure (CDP) of the gas turbine over a period of time; determining a time derivative (CDP.sub.D ) of the measured (CDP) correcting the CDP.sub.D for altitude, (CDP.sub.DCOR); estimating a short-term average of CDP.sub.DCOR.sup.2 ; estimating a short-term average of CDP.sub.DCOR ; and determining a short-term variance of corrected CDP rate of change (CDP.sub.roc) based upon the short-term average of CDP.sub.DCOR and the short-term average of CDP.sub.DCOR.sup.2. The method and system then compares the short-term variance of corrected CDP rate of change with a pre-determined threshold (CDP.sub.proc) and signals an output when CDP.sub.roc >CDP.sub.proc. The method and system provides a signal of a surge within the gas turbine engine when CDP.sub.roc remains>CDP.sub.proc for pre-determined period of time.

Wavelet-based analysis of circadian behavioral rhythms.

PubMed

Leise, Tanya L

2015-01-01

The challenging problems presented by noisy biological oscillators have led to the development of a great variety of methods for accurately estimating rhythmic parameters such as period and amplitude. This chapter focuses on wavelet-based methods, which can be quite effective for assessing how rhythms change over time, particularly if time series are at least a week in length. These methods can offer alternative views to complement more traditional methods of evaluating behavioral records. The analytic wavelet transform can estimate the instantaneous period and amplitude, as well as the phase of the rhythm at each time point, while the discrete wavelet transform can extract the circadian component of activity and measure the relative strength of that circadian component compared to those in other frequency bands. Wavelet transforms do not require the removal of noise or trend, and can, in fact, be effective at removing noise and trend from oscillatory time series. The Fourier periodogram and spectrogram are reviewed, followed by descriptions of the analytic and discrete wavelet transforms. Examples illustrate application of each method and their prior use in chronobiology is surveyed. Issues such as edge effects, frequency leakage, and implications of the uncertainty principle are also addressed. © 2015 Elsevier Inc. All rights reserved.

Load Balancing Using Time Series Analysis for Soft Real Time Systems with Statistically Periodic Loads

NASA Technical Reports Server (NTRS)

Hailperin, Max

1993-01-01

This thesis provides design and analysis of techniques for global load balancing on ensemble architectures running soft-real-time object-oriented applications with statistically periodic loads. It focuses on estimating the instantaneous average load over all the processing elements. The major contribution is the use of explicit stochastic process models for both the loading and the averaging itself. These models are exploited via statistical time-series analysis and Bayesian inference to provide improved average load estimates, and thus to facilitate global load balancing. This thesis explains the distributed algorithms used and provides some optimality results. It also describes the algorithms' implementation and gives performance results from simulation. These results show that our techniques allow more accurate estimation of the global system load ing, resulting in fewer object migration than local methods. Our method is shown to provide superior performance, relative not only to static load-balancing schemes but also to many adaptive methods.

Calculation of power spectrums from digital time series with missing data points

NASA Technical Reports Server (NTRS)

Murray, C. W., Jr.

1980-01-01

Two algorithms are developed for calculating power spectrums from the autocorrelation function when there are missing data points in the time series. Both methods use an average sampling interval to compute lagged products. One method, the correlation function power spectrum, takes the discrete Fourier transform of the lagged products directly to obtain the spectrum, while the other, the modified Blackman-Tukey power spectrum, takes the Fourier transform of the mean lagged products. Both techniques require fewer calculations than other procedures since only 50% to 80% of the maximum lags need be calculated. The algorithms are compared with the Fourier transform power spectrum and two least squares procedures (all for an arbitrary data spacing). Examples are given showing recovery of frequency components from simulated periodic data where portions of the time series are missing and random noise has been added to both the time points and to values of the function. In addition the methods are compared using real data. All procedures performed equally well in detecting periodicities in the data.

Using statistical process control methods to trace small changes in perinatal mortality after a training program in a low-resource setting.

PubMed

Mduma, Estomih R; Ersdal, Hege; Kvaloy, Jan Terje; Svensen, Erling; Mdoe, Paschal; Perlman, Jeffrey; Kidanto, Hussein Lessio; Soreide, Eldar

2018-05-01

To trace and document smaller changes in perinatal survival over time. Prospective observational study, with retrospective analysis. Labor ward and operating theater at Haydom Lutheran Hospital in rural north-central Tanzania. All women giving birth and birth attendants. Helping Babies Breathe (HBB) simulation training on newborn care and resuscitation and some other efforts to improve perinatal outcome. Perinatal survival, including fresh stillbirths and early (24-h) newborn survival. The variable life-adjusted plot and cumulative sum chart revealed a steady improvement in survival over time, after the baseline period. There were some variations throughout the study period, and some of these could be linked to different interventions and events. To our knowledge, this is the first time statistical process control methods have been used to document changes in perinatal mortality over time in a rural Sub-Saharan hospital, showing a steady increase in survival. These methods can be utilized to continuously monitor and describe changes in patient outcomes.

Reliability of fitness tests using methods and time periods common in sport and occupational management.

PubMed

Burnstein, Bryan D; Steele, Russell J; Shrier, Ian

2011-01-01

Fitness testing is used frequently in many areas of physical activity, but the reliability of these measurements under real-world, practical conditions is unknown. To evaluate the reliability of specific fitness tests using the methods and time periods used in the context of real-world sport and occupational management. Cohort study. Eighteen different Cirque du Soleil shows. Cirque du Soleil physical performers who completed 4 consecutive tests (6-month intervals) and were free of injury or illness at each session (n = 238 of 701 physical performers). Performers completed 6 fitness tests on each assessment date: dynamic balance, Harvard step test, handgrip, vertical jump, pull-ups, and 60-second jump test. We calculated the intraclass coefficient (ICC) and limits of agreement between baseline and each time point and the ICC over all 4 time points combined. Reliability was acceptable (ICC > 0.6) over an 18-month time period for all pairwise comparisons and all time points together for the handgrip, vertical jump, and pull-up assessments. The Harvard step test and 60-second jump test had poor reliability (ICC < 0.6) between baseline and other time points. When we excluded the baseline data and calculated the ICC for 6-month, 12-month, and 18-month time points, both the Harvard step test and 60-second jump test demonstrated acceptable reliability. Dynamic balance was unreliable in all contexts. Limit-of-agreement analysis demonstrated considerable intraindividual variability for some tests and a learning effect by administrators on others. Five of the 6 tests in this battery had acceptable reliability over an 18-month time frame, but the values for certain individuals may vary considerably from time to time for some tests. Specific tests may require a learning period for administrators.

A multi-harmonic generalized energy balance method for studying autonomous oscillations of nonlinear conservative systems

NASA Astrophysics Data System (ADS)

Balaji, Nidish Narayanaa; Krishna, I. R. Praveen; Padmanabhan, C.

2018-05-01

The Harmonic Balance Method (HBM) is a frequency-domain based approximation approach used for obtaining the steady state periodic behavior of forced dynamical systems. Intrinsically these systems are non-autonomous and the method offers many computational advantages over time-domain methods when the fundamental period of oscillation is known (generally fixed as the forcing period itself or a corresponding sub-harmonic if such behavior is expected). In the current study, a modified approach, based on He's Energy Balance Method (EBM), is applied to obtain the periodic solutions of conservative systems. It is shown that by this approach, periodic solutions of conservative systems on iso-energy manifolds in the phase space can be obtained very efficiently. The energy level provides the additional constraint on the HBM formulation, which enables the determination of the period of the solutions. The method is applied to the linear harmonic oscillator, a couple of nonlinear oscillators, the elastic pendulum and the Henon-Heiles system. The approach is used to trace the bifurcations of the periodic solutions of the last two, being 2 degree-of-freedom systems demonstrating very rich dynamical behavior. In the process, the advantages offered by the current formulation of the energy balance is brought out. A harmonic perturbation approach is used to evaluate the stability of the solutions for the bifurcation diagram.

A possible third component in the eclipsing binary system HS 2231+2441

NASA Astrophysics Data System (ADS)

Vidmachenko, A. P.; Romanyuk, Ya. O.; Shliahetskaya, Ya. O.

2016-05-01

We used a differential photometry method in which we compared the flow of program star and standard one. Observations of the 21 nights in the period from July 26 to December 2, 2015 are used for processing. The accuracy of determining for each measurement is in the range 0,003...0,009 m for different nights. On the basis of obtained data were created corresponding light curves. Next, we calculate the time difference between the centers of transits. Its time dependence showed the presence of a possible periodic change in the deflection of the middle transit time from the calculated average value. This may indicate the presence of a third object in the eclipsing binary system. It has been found that the periodic variation of the orbital period can be explained by the gravitational influence of a third companion on the central binary system with an orbital period of about 97±10 d.

Expert Advisor (EA) Evaluation System Using Web-based ELECTRE Method in Foreign Exchange (Forex) Market

NASA Astrophysics Data System (ADS)

Satibi; Widodo, Catur Edi; Farikhin

2018-02-01

This research aims to optimize forex trading profit automatically using EA but its still keep considering accuracy and drawdown levels. The evaluation system will classify EA performance based on trading market sessions (Sydney, Tokyo, London and New York) to determine the right EA to be used in certain market sessions. This evaluation system is a web-based ELECTRE methods that interact in real-time with EA through web service and are able to present real-time charts performance dashboard using web socket protocol communications. Web applications are programmed using NodeJs. In the testing period, all EAs had been simulated 24 hours in all market sessions for three months, the best EA is valued by its profit, accuracy and drawdown criteria that calculated using web-based ELECTRE method. The ideas of this research are to compare the best EA on testing period with collaboration performances of each best classified EA by market sessions. This research uses three months historical data of EUR/USD as testing period and other 3 months as validation period. As a result, performance of collaboration four best EA classified by market sessions can increase profits percentage consistently in testing and validation periods and keep securing accuracy and drawdown levels.

Pilot-in-the-Loop CFD Method Development

DTIC Science & Technology

2017-04-20

the methods on the NAVAIR Manned Flight Simulator. Activities this period During this report period, we implemented the CRAFT CFD code on the...Penn State VLRCROE Flight simulator and performed the first Pilot-in-the-Loop PILCFD tests at Penn State using the COCOA5 clusters. The initial tests...integration of the flight simulator and Penn State computing infrastructure. Initial tests showed slower performance than real-time (3x slower than real

Understanding the effects of time on collaborative learning processes in problem based learning: a mixed methods study.

PubMed

Hommes, J; Van den Bossche, P; de Grave, W; Bos, G; Schuwirth, L; Scherpbier, A

2014-10-01

Little is known how time influences collaborative learning groups in medical education. Therefore a thorough exploration of the development of learning processes over time was undertaken in an undergraduate PBL curriculum over 18 months. A mixed-methods triangulation design was used. First, the quantitative study measured how various learning processes developed within and over three periods in the first 1,5 study years of an undergraduate curriculum. Next, a qualitative study using semi-structured individual interviews focused on detailed development of group processes driving collaborative learning during one period in seven tutorial groups. The hierarchic multilevel analyses of the quantitative data showed that a varying combination of group processes developed within and over the three observed periods. The qualitative study illustrated development in psychological safety, interdependence, potency, group learning behaviour, social and task cohesion. Two new processes emerged: 'transactive memory' and 'convergence in mental models'. The results indicate that groups are dynamic social systems with numerous contextual influences. Future research should thus include time as an important influence on collaborative learning. Practical implications are discussed.

DNS of Flows over Periodic Hills using a Discontinuous-Galerkin Spectral-Element Method

NASA Technical Reports Server (NTRS)

Diosady, Laslo T.; Murman, Scott M.

2014-01-01

Direct numerical simulation (DNS) of turbulent compressible flows is performed using a higher-order space-time discontinuous-Galerkin finite-element method. The numerical scheme is validated by performing DNS of the evolution of the Taylor-Green vortex and turbulent flow in a channel. The higher-order method is shown to provide increased accuracy relative to low-order methods at a given number of degrees of freedom. The turbulent flow over a periodic array of hills in a channel is simulated at Reynolds number 10,595 using an 8th-order scheme in space and a 4th-order scheme in time. These results are validated against previous large eddy simulation (LES) results. A preliminary analysis provides insight into how these detailed simulations can be used to improve Reynoldsaveraged Navier-Stokes (RANS) modeling

Inference on periodicity of circadian time series.

PubMed

Costa, Maria J; Finkenstädt, Bärbel; Roche, Véronique; Lévi, Francis; Gould, Peter D; Foreman, Julia; Halliday, Karen; Hall, Anthony; Rand, David A

2013-09-01

Estimation of the period length of time-course data from cyclical biological processes, such as those driven by the circadian pacemaker, is crucial for inferring the properties of the biological clock found in many living organisms. We propose a methodology for period estimation based on spectrum resampling (SR) techniques. Simulation studies show that SR is superior and more robust to non-sinusoidal and noisy cycles than a currently used routine based on Fourier approximations. In addition, a simple fit to the oscillations using linear least squares is available, together with a non-parametric test for detecting changes in period length which allows for period estimates with different variances, as frequently encountered in practice. The proposed methods are motivated by and applied to various data examples from chronobiology.

Phase-Locked Loop for Precisely Timed Acoustic Stimulation during Sleep

PubMed Central

Santostasi, Giovanni; Malkani, Roneil; Riedner, Brady; Bellesi, Michele; Tononi, Giulio; Paller, Ken A.; Zee, Phyllis C.

2016-01-01

Background A Brain-Computer Interface could potentially enhance the various benefits of sleep. New Method We describe a strategy for enhancing slow-wave sleep (SWS) by stimulating the sleeping brain with periodic acoustic stimuli that produce resonance in the form of enhanced slow-wave activity in the electroencephalogram (EEG). The system delivers each acoustic stimulus at a particular phase of an electrophysiological rhythm using a Phase-Locked Loop (PLL). Results The PLL is computationally economical and well suited to follow and predict the temporal behavior of the EEG during slow-wave sleep. Comparison with Existing Methods Acoustic stimulation methods may be able to enhance SWS without the risks inherent in electrical stimulation or pharmacological methods. The PLL method differs from other acoustic stimulation methods that are based on detecting a single slow wave rather than modeling slow-wave activity over an extended period of time. Conclusions By providing real-time estimates of the phase of ongoing EEG oscillations, the PLL can rapidly adjust to physiological changes, thus opening up new possibilities to study brain dynamics during sleep. Future application of these methods hold promise for enhancing sleep quality and associated daytime behavior and improving physiologic function. PMID:26617321

Multi-period project portfolio selection under risk considerations and stochastic income

NASA Astrophysics Data System (ADS)

Tofighian, Ali Asghar; Moezzi, Hamid; Khakzar Barfuei, Morteza; Shafiee, Mahmood

2018-02-01

This paper deals with multi-period project portfolio selection problem. In this problem, the available budget is invested on the best portfolio of projects in each period such that the net profit is maximized. We also consider more realistic assumptions to cover wider range of applications than those reported in previous studies. A novel mathematical model is presented to solve the problem, considering risks, stochastic incomes, and possibility of investing extra budget in each time period. Due to the complexity of the problem, an effective meta-heuristic method hybridized with a local search procedure is presented to solve the problem. The algorithm is based on genetic algorithm (GA), which is a prominent method to solve this type of problems. The GA is enhanced by a new solution representation and well selected operators. It also is hybridized with a local search mechanism to gain better solution in shorter time. The performance of the proposed algorithm is then compared with well-known algorithms, like basic genetic algorithm (GA), particle swarm optimization (PSO), and electromagnetism-like algorithm (EM-like) by means of some prominent indicators. The computation results show the superiority of the proposed algorithm in terms of accuracy, robustness and computation time. At last, the proposed algorithm is wisely combined with PSO to improve the computing time considerably.

Identifying stochastic oscillations in single-cell live imaging time series using Gaussian processes

PubMed Central

Manning, Cerys; Rattray, Magnus

2017-01-01

Multiple biological processes are driven by oscillatory gene expression at different time scales. Pulsatile dynamics are thought to be widespread, and single-cell live imaging of gene expression has lead to a surge of dynamic, possibly oscillatory, data for different gene networks. However, the regulation of gene expression at the level of an individual cell involves reactions between finite numbers of molecules, and this can result in inherent randomness in expression dynamics, which blurs the boundaries between aperiodic fluctuations and noisy oscillators. This underlies a new challenge to the experimentalist because neither intuition nor pre-existing methods work well for identifying oscillatory activity in noisy biological time series. Thus, there is an acute need for an objective statistical method for classifying whether an experimentally derived noisy time series is periodic. Here, we present a new data analysis method that combines mechanistic stochastic modelling with the powerful methods of non-parametric regression with Gaussian processes. Our method can distinguish oscillatory gene expression from random fluctuations of non-oscillatory expression in single-cell time series, despite peak-to-peak variability in period and amplitude of single-cell oscillations. We show that our method outperforms the Lomb-Scargle periodogram in successfully classifying cells as oscillatory or non-oscillatory in data simulated from a simple genetic oscillator model and in experimental data. Analysis of bioluminescent live-cell imaging shows a significantly greater number of oscillatory cells when luciferase is driven by a Hes1 promoter (10/19), which has previously been reported to oscillate, than the constitutive MoMuLV 5’ LTR (MMLV) promoter (0/25). The method can be applied to data from any gene network to both quantify the proportion of oscillating cells within a population and to measure the period and quality of oscillations. It is publicly available as a MATLAB package. PMID:28493880

Nitrogen fertilizer replacement value of cattle slurry in grassland as affected by method and timing of application.

PubMed

Lalor, S T J; Schröder, J J; Lantinga, E A; Oenema, O; Kirwan, L; Schulte, R P O

2011-01-01

Slurry application with methods such as trailing shoe (TS) results in reduced emissions of ammonia (NH3) compared with broadcast application using splashplate (SP). Timing the application during cool and wet weather conditions also contributes to low NH3 emissions. From this perspective, we investigated whether reduced NH3 emissions due to improved slurry application method and timing results in an increase in the nitrogen (N) fertilizer replacement value (NFRV). The effects of application timing (June vs. April) and application method (TS vs. SP) on the apparent N recovery (ANR) and NFRV from cattle slurry applied to grassland were examined on three sites over 3 yr in randomized block experiments. The NFRV was calculated using two methods: (i) NFRV(N) based on the ANR of slurry N relative to mineral N fertilizer; and (ii) NFRV(DM) based on DM yield. The TS method increased the ANR, NFRV(N), and NFRV(DM) compared with SP in the 40- to 50-d period following slurry application by 0.09, 0.10, and 0.10 kg kg(-1), respectively. These values were reduced to 0.07, 0.06, and 0.05 kg kg(-1), respectively, when residual harvests during the rest of the year were included. The highest NFRV(DM) for the first harvest period was with application in April using STS (0.30 kg kg(-1)), while application in June with SP had the Slowest (0.12 kg kg(-1)). The highest NFRV(DM) for the cumulative harvest period was with application in April using TS (0.38 kg kg(-1)), while application in June with SP had the lowest (0.17 kg kg(-1)). Improved management of application method, by using TS instead of SP, and timing, by applying slurry in April rather than June, offer potential to increase the NFRV(DM) of cattle slurry applied to grassland.

Is flow cytometric evaluation of DNA degradation a reliable method to investigate the early postmortem period?

PubMed

Di Nunno, N R; Costantinides, F; Bernasconi, P; Bottin, C; Melato, M

1998-03-01

The time of death can be established by determining the length of the postmortem interval. Many methods have been proposed to achieve this goal. Flow cytometric evaluation of DNA degradation seems to be reliable for the first 72 hours after death. Our study evaluated the correspondence of the corruption process between in vitro and corpse tissues. We chose spleen tissue to perform our investigation because it is rich in nucleated cells. Results showed a precise correspondence between the two kinds of samples in the time period between 24 and 36 hours. The period from 36 to 72 hours is characterized by a much looser correspondence than that found in the first period. After the first 72 hours, DNA denaturation is massive and does not allow useful cytofluorimetric readings. The spleen does not seem to be the most suitable organ for this type of investigation because it tends to colliquate very rapidly. We therefore are evaluating other organs to identify a more suitable tissue source for the investigation of longer postmortem period using flow cytometry.

A Review of the Study Designs and Statistical Methods Used in the Determination of Predictors of All-Cause Mortality in HIV-Infected Cohorts: 2002–2011

PubMed Central

Otwombe, Kennedy N.; Petzold, Max; Martinson, Neil; Chirwa, Tobias

2014-01-01

Background Research in the predictors of all-cause mortality in HIV-infected people has widely been reported in literature. Making an informed decision requires understanding the methods used. Objectives We present a review on study designs, statistical methods and their appropriateness in original articles reporting on predictors of all-cause mortality in HIV-infected people between January 2002 and December 2011. Statistical methods were compared between 2002–2006 and 2007–2011. Time-to-event analysis techniques were considered appropriate. Data Sources Pubmed/Medline. Study Eligibility Criteria Original English-language articles were abstracted. Letters to the editor, editorials, reviews, systematic reviews, meta-analysis, case reports and any other ineligible articles were excluded. Results A total of 189 studies were identified (n = 91 in 2002–2006 and n = 98 in 2007–2011) out of which 130 (69%) were prospective and 56 (30%) were retrospective. One hundred and eighty-two (96%) studies described their sample using descriptive statistics while 32 (17%) made comparisons using t-tests. Kaplan-Meier methods for time-to-event analysis were commonly used in the earlier period (n = 69, 76% vs. n = 53, 54%, p = 0.002). Predictors of mortality in the two periods were commonly determined using Cox regression analysis (n = 67, 75% vs. n = 63, 64%, p = 0.12). Only 7 (4%) used advanced survival analysis methods of Cox regression analysis with frailty in which 6 (3%) were used in the later period. Thirty-two (17%) used logistic regression while 8 (4%) used other methods. There were significantly more articles from the first period using appropriate methods compared to the second (n = 80, 88% vs. n = 69, 70%, p-value = 0.003). Conclusion Descriptive statistics and survival analysis techniques remain the most common methods of analysis in publications on predictors of all-cause mortality in HIV-infected cohorts while prospective research designs are favoured. Sophisticated techniques of time-dependent Cox regression and Cox regression with frailty are scarce. This motivates for more training in the use of advanced time-to-event methods. PMID:24498313

A Social Network Analysis of 140 Community‐Academic Partnerships for Health: Examining the Healthier Wisconsin Partnership Program

PubMed Central

Ahmed, Syed M.; Maurana, Cheryl A.; DeFino, Mia C.; Brewer, Devon D.

2015-01-01

Abstract Introduction: Social Network Analysis (SNA) provides an important, underutilized approach to evaluating Community Academic Partnerships for Health (CAPHs). This study examines administrative data from 140 CAPHs funded by the Healthier Wisconsin Partnership Program (HWPP). Methods: Funder data was normalized to maximize number of interconnections between funded projects and 318 non‐redundant community partner organizations in a dual mode analysis, examining the period from 2003–2013.Two strategic planning periods, 2003–2008 vs. 2009–2014, allowed temporal comparison. Results: Connectivity of the network was largely unchanged over time, with most projects and partner organizations connected to a single large component in both time periods. Inter‐partner ties formed in HWPP projects were transient. Most community partners were only involved in projects during one strategic time period. Community organizations participating in both time periods were involved in significantly more projects during the first time period than partners participating in the first time period only (Cohen's d = 0.93). Discussion: This approach represents a significant step toward using objective (non‐survey) data for large clusters of health partnerships and has implications for translational science in community settings. Considerations for government, funders, and communities are offered. Examining partnerships within health priority areas, orphaned projects, and faculty ties to these networks are areas for future research. PMID:25974413

Quantifying Risk Over the Life Course – Latency, Age-Related Susceptibility, and Other Time-Varying Exposure Metrics

PubMed Central

Wang, Molin; Liao, Xiaomei; Laden, Francine; Spiegelman, Donna

2016-01-01

Identification of the latency period and age-related susceptibility, if any, is an important aspect of assessing risks of environmental, nutritional and occupational exposures. We consider estimation and inference for latency and age-related susceptibility in relative risk and excess risk models. We focus on likelihood-based methods for point and interval estimation of the latency period and age-related windows of susceptibility coupled with several commonly considered exposure metrics. The method is illustrated in a study of the timing of the effects of constituents of air pollution on mortality in the Nurses’ Health Study. PMID:26750582

Radioactive anomaly discrimination from spectral ratios

DOEpatents

Maniscalco, James; Sjoden, Glenn; Chapman, Mac Clements

2013-08-20

A method for discriminating a radioactive anomaly from naturally occurring radioactive materials includes detecting a first number of gamma photons having energies in a first range of energy values within a predetermined period of time and detecting a second number of gamma photons having energies in a second range of energy values within the predetermined period of time. The method further includes determining, in a controller, a ratio of the first number of gamma photons having energies in the first range and the second number of gamma photons having energies in the second range, and determining that a radioactive anomaly is present when the ratio exceeds a threshold value.

Prolonged in vivo imaging of Xenopus laevis.

PubMed

Hamilton, Paul W; Henry, Jonathan J

2014-08-01

While live imaging of embryonic development over long periods of time is a well established method for embryos of the frog Xenopus laevis, once development has progressed to the swimming stages, continuous live imaging becomes more challenging because the tadpoles must be immobilized. Current imaging techniques for these advanced stages generally require bringing the tadpoles in and out of anesthesia for short imaging sessions at selected time points, severely limiting the resolution of the data. Here we demonstrate that creating a constant flow of diluted tricaine methanesulfonate (MS-222) over a tadpole greatly improves their survival under anesthesia. Based on this result, we describe a new method for imaging stage 48 to 65 X. laevis, by circulating the anesthetic using a peristaltic pump. This supports the animal during continuous live imaging sessions for at least 48 hr. The addition of a stable optical window allows for high quality imaging through the anesthetic solution. This automated imaging system provides for the first time a method for continuous observations of developmental and regenerative processes in advanced stages of Xenopus over 2 days. Developmental Dynamics 243:1011-1019, 2014. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.

Methods and apparatus to produce stick-slip motion of logging tool attached to a wireline drawn upward by a continuously rotating wireline drum

DOEpatents

Vail, III, William Banning; Momii, Steven Thomas

1998-01-01

Methods and apparatus are described to produce stick-slip motion of a logging tool within a cased well attached to a wireline that is drawn upward by a continuously rotating wireline drum. The stick-slip motion results in the periodic upward movement of the tool in the cased well described in terms of a dwell time during which time the tool is stationary, the move time during which time the tool moves, and the stroke that is upward distance that the tool translates during the "slip" portion of the stick-slip motion. This method of measurement is used to log the well at different vertical positions of the tool. Therefore, any typical "station-to-station logging tool" may be modified to be a "continuous logging tool", where "continuous" means that the wireline drum continually rotates while the tool undergoes stick-slip motion downhole and measurements are performed during the dwell times when the tool is momentarily stationary. The stick-slip methods of operation and the related apparatus are particularly described in terms of making measurements of formation resistivity from within a cased well during the dwell times when the tool is momentarily stationary during the periodic stick-slip motion of the logging tool.

Methods and apparatus to produce stick-slip motion of logging tool attached to a wireline drawn upward by a continuously rotating wireline drum

DOEpatents

Vail, W.B. III; Momii, S.T.

1998-02-10

Methods and apparatus are described to produce stick-slip motion of a logging tool within a cased well attached to a wireline that is drawn upward by a continuously rotating wireline drum. The stick-slip motion results in the periodic upward movement of the tool in the cased well described in terms of a dwell time during which time the tool is stationary, the move time during which time the tool moves, and the stroke that is upward distance that the tool translates during the ``slip`` portion of the stick-slip motion. This method of measurement is used to log the well at different vertical positions of the tool. Therefore, any typical ``station-to-station logging tool`` may be modified to be a ``continuous logging tool,`` where ``continuous`` means that the wireline drum continually rotates while the tool undergoes stick-slip motion downhole and measurements are performed during the dwell times when the tool is momentarily stationary. The stick-slip methods of operation and the related apparatus are particularly described in terms of making measurements of formation resistivity from within a cased well during the dwell times when the tool is momentarily stationary during the periodic stick-slip motion of the logging tool. 12 figs.

Seasonality and synchrony of reproduction in three species of nectarivorous Philippines bats.

PubMed

Heideman, Paul D; Utzurrum, Ruth C B

2003-11-21

Differences among species and among years in reproductive seasonality (the tendency for clusters of events to fall at approximately the same point in each year) and synchrony (amount of clustering of events within a year) have been intensively studied in bats, but are difficult to assess. Here, we use randomization methods with circular statistics to test for synchrony and seasonality of reproduction in three species of nectarivorous megachiropteran bats on Negros Island in the central Philippines. In Rousettus amplexicaudatus, estimated dates of birth were both highly synchronous and highly seasonal. In Macroglossus minimus, estimated births were seasonal and significantly clustered within years, but within each year births occurred over a broad period, indicating a low level of synchrony. In Eonycteris spelaea, estimated births were also seasonal and had statistically significant synchrony, with birth periods within years intermediate in synchrony between R. amplexicaudatus and M. minimus. All three species had a similar seasonal pattern, with two birth periods in each year, centered on March or April and August or September. In one species, R. amplexicaudatus, primigravid females (in their first pregnancy) produced their young in June and July, a birth period significantly different in timing from the two birth periods of older adult females. This more conservative pattern of young females may allow higher survival of parents and offspring at cost of a lost reproductive opportunity. There was weak evidence that in some years primigravid females of M. minimus might differ in timing from older adults. There were few significant differences in reproductive timing among different years, and those differences were generally less than two weeks, even during a severe drought in the severe el Niño of 1983. The results suggest that these species follow an obligately seasonal pattern of reproductive timing with very little phenotypic plasticity. The resampling methods were sensitive to differences in timing of under two weeks, in some cases, suggesting that these are useful methods for analyses of seasonality in wild populations of bats.

Period Changes in Pulsating Red Supergiant Stars: A Science and Education Project

NASA Astrophysics Data System (ADS)

Percy, J. R.; Favaro, E.; Glasheen, J.; Ho, B.; Sato, H.

2008-12-01

We describe research done as part of the University of Toronto Mentorship Program, which enables outstanding senior high school students to work on research projects at the university. The students began with extensive background reading on variable stars, and became familiar with various forms of time-series analysis by applying them to a few red supergiant variables in the AAVSO International Database; we report on the results. They also prepared a useful manual for our publicly-available self-correlation analysis software. They undertook an intensive analysis of the period changes in BC Cyg, using the AAVSO and Turner data and the (O-C) method, in the hope that evolutionary period changes could be observed. The (O-C) diagram, however, is dominated by errors in determining the times of maximum, and by the effects of cycle-to-cycle period fluctuations. As a result, the (O-C) method is generally not effective for these stars. We also describe the Mentorship Program and its elements, and reflect on the students' experience.

A Fourier spectral-discontinuous Galerkin method for time-dependent 3-D Schrödinger-Poisson equations with discontinuous potentials

NASA Astrophysics Data System (ADS)

Lu, Tiao; Cai, Wei

2008-10-01

In this paper, we propose a high order Fourier spectral-discontinuous Galerkin method for time-dependent Schrödinger-Poisson equations in 3-D spaces. The Fourier spectral Galerkin method is used for the two periodic transverse directions and a high order discontinuous Galerkin method for the longitudinal propagation direction. Such a combination results in a diagonal form for the differential operators along the transverse directions and a flexible method to handle the discontinuous potentials present in quantum heterojunction and supperlattice structures. As the derivative matrices are required for various time integration schemes such as the exponential time differencing and Crank Nicholson methods, explicit derivative matrices of the discontinuous Galerkin method of various orders are derived. Numerical results, using the proposed method with various time integration schemes, are provided to validate the method.

Comparison of methods for non-stationary hydrologic frequency analysis: Case study using annual maximum daily precipitation in Taiwan

NASA Astrophysics Data System (ADS)

Chen, Po-Chun; Wang, Yuan-Heng; You, Gene Jiing-Yun; Wei, Chih-Chiang

2017-02-01

Future climatic conditions likely will not satisfy stationarity assumption. To address this concern, this study applied three methods to analyze non-stationarity in hydrologic conditions. Based on the principle of identifying distribution and trends (IDT) with time-varying moments, we employed the parametric weighted least squares (WLS) estimation in conjunction with the non-parametric discrete wavelet transform (DWT) and ensemble empirical mode decomposition (EEMD). Our aim was to evaluate the applicability of non-parameter approaches, compared with traditional parameter-based methods. In contrast to most previous studies, which analyzed the non-stationarity of first moments, we incorporated second-moment analysis. Through the estimation of long-term risk, we were able to examine the behavior of return periods under two different definitions: the reciprocal of the exceedance probability of occurrence and the expected recurrence time. The proposed framework represents an improvement over stationary frequency analysis for the design of hydraulic systems. A case study was performed using precipitation data from major climate stations in Taiwan to evaluate the non-stationarity of annual maximum daily precipitation. The results demonstrate the applicability of these three methods in the identification of non-stationarity. For most cases, no significant differences were observed with regard to the trends identified using WLS, DWT, and EEMD. According to the results, a linear model should be able to capture time-variance in either the first or second moment while parabolic trends should be used with caution due to their characteristic rapid increases. It is also observed that local variations in precipitation tend to be overemphasized by DWT and EEMD. The two definitions provided for the concept of return period allows for ambiguous interpretation. With the consideration of non-stationarity, the return period is relatively small under the definition of expected recurrence time comparing to the estimation using the reciprocal of the exceedance probability of occurrence. However, the calculation of expected recurrence time is based on the assumption of perfect knowledge of long-term risk, which involves high uncertainty. When the risk is decreasing with time, the expected recurrence time will lead to the divergence of return period and make this definition inapplicable for engineering purposes.

The long-range correlation and evolution law of centennial-scale temperatures in Northeast China.

PubMed

Zheng, Xiaohui; Lian, Yi; Wang, Qiguang

2018-01-01

This paper applies the detrended fluctuation analysis (DFA) method to investigate the long-range correlation of monthly mean temperatures from three typical measurement stations at Harbin, Changchun, and Shenyang in Northeast China from 1909 to 2014. The results reveal the memory characteristics of the climate system in this region. By comparing the temperatures from different time periods and investigating the variations of its scaling exponents at the three stations during these different time periods, we found that the monthly mean temperature has long-range correlation, which indicates that the temperature in Northeast China has long-term memory and good predictability. The monthly time series of temperatures over the past 106 years also shows good long-range correlation characteristics. These characteristics are also obviously observed in the annual mean temperature time series. Finally, we separated the centennial-length temperature time series into two time periods. These results reveal that the long-range correlations at the Harbin station over these two time periods have large variations, whereas no obvious variations are observed at the other two stations. This indicates that warming affects the regional climate system's predictability differently at different time periods. The research results can provide a quantitative reference point for regional climate predictability assessment and future climate model evaluation.

Tracking and detecting occupational diseases for teachers with infrared imaging method

NASA Astrophysics Data System (ADS)

Chen, Shu-wang; An, Sheng-biao; Wang, Shu-hai

2009-05-01

Most academic teachers are chairborne and often revise the exercises for students for a long time, so they often have some occupational diseases, such as sciatica, vertebral ache, and so on. Some early diseases are so difficult to be detected that the patients lose the better curable time. The infrared imaging is a non-touch and harmless method and it is efficient in prophylactic iatrology. The paper introduces a method to track and detect the occupational diseases for academic teachers. The infrared pictures of the same position for the same person are collected at the different period. The position is one of the usually parts of the teacher's occupational diseases, such as the neck, the shoulder, the back, the wrist, and so on. For each position of a certain person, the infrared pictures are collected and saved at different period. The period may be 6 month or one year. Infrared pictures are collected by the infrared imaging device, and a database of the infrared pictures is established. According to the difference of the infrared pictures of the same position at different period, the latent disease part may be found out and the ailing degree can be detected.

Global and Local Approaches Describing Critical Phenomena on the Developing and Developed Financial Markets

NASA Astrophysics Data System (ADS)

Grech, Dariusz

We define and confront global and local methods to analyze the financial crash-like events on the financial markets from the critical phenomena point of view. These methods are based respectively on the analysis of log-periodicity and on the local fractal properties of financial time series in the vicinity of phase transitions (crashes). The log-periodicity analysis is made in a daily time horizon, for the whole history (1991-2008) of Warsaw Stock Exchange Index (WIG) connected with the largest developing financial market in Europe. We find that crash-like events on the Polish financial market are described better by the log-divergent price model decorated with log-periodic behavior than by the power-law-divergent price model usually discussed in log-periodic scenarios for developed markets. Predictions coming from log-periodicity scenario are verified for all main crashes that took place in WIG history. It is argued that crash predictions within log-periodicity model strongly depend on the amount of data taken to make a fit and therefore are likely to contain huge inaccuracies. Next, this global analysis is confronted with the local fractal description. To do so, we provide calculation of the so-called local (time dependent) Hurst exponent H loc for the WIG time series and for main US stock market indices like DJIA and S&P 500. We point out dependence between the behavior of the local fractal properties of financial time series and the crashes appearance on the financial markets. We conclude that local fractal method seems to work better than the global approach - both for developing and developed markets. The very recent situation on the market, particularly related to the Fed intervention in September 2007 and the situation immediately afterwards is also analyzed within fractal approach. It is shown in this context how the financial market evolves through different phases of fractional Brownian motion. Finally, the current situation on American market is analyzed in fractal language. This is to show how far we still are from the end of recession and from the beginning of a new boom on US financial market or on other world leading stocks.

Chaotic phase synchronization in bursting-neuron models driven by a weak periodic force

NASA Astrophysics Data System (ADS)

Ando, Hiroyasu; Suetani, Hiromichi; Kurths, Jürgen; Aihara, Kazuyuki

2012-07-01

We investigate the entrainment of a neuron model exhibiting a chaotic spiking-bursting behavior in response to a weak periodic force. This model exhibits two types of oscillations with different characteristic time scales, namely, long and short time scales. Several types of phase synchronization are observed, such as 1:1 phase locking between a single spike and one period of the force and 1:l phase locking between the period of slow oscillation underlying bursts and l periods of the force. Moreover, spiking-bursting oscillations with chaotic firing patterns can be synchronized with the periodic force. Such a type of phase synchronization is detected from the position of a set of points on a unit circle, which is determined by the phase of the periodic force at each spiking time. We show that this detection method is effective for a system with multiple time scales. Owing to the existence of both the short and the long time scales, two characteristic phenomena are found around the transition point to chaotic phase synchronization. One phenomenon shows that the average time interval between successive phase slips exhibits a power-law scaling against the driving force strength and that the scaling exponent has an unsmooth dependence on the changes in the driving force strength. The other phenomenon shows that Kuramoto's order parameter before the transition exhibits stepwise behavior as a function of the driving force strength, contrary to the smooth transition in a model with a single time scale.

Evolutionary orbital period change in BH Virginis

NASA Astrophysics Data System (ADS)

Gebrehiwot, Y. M.; Tessema, S. B.; Berdnikov, L. N.

2017-04-01

The study of orbital period change of close binaries, such as BH Virginis (BH Vir), using very long time baseline is vital to understand evolutionary processes of the system. In this paper, we use photometric data to analyze the evolutionary orbital period change of the short period RS CVn-type binary system, BH Vir, with a time baseline spanning 123 years. We used the software version of the Hertzsprung method to describe the O-C curve of the system, and we found that the orbital period secularly decreases at a rate of dp/dt=-(0.0013000 ± 0.0000863) s yr^{-1}. Because BH Vir is a typical detached binary system and both components are late type (G0 V + G2 V) stars, the evolutionary period change could be caused by the angular momentum loss due to tides coupled with magnetic breaking.

Effect of selected water temperatures used in Mycoplasma gallisepticum vaccine reconstitution on titer at selected time intervals.

PubMed

Branton, S L; Leigh, S A; Roush, W B; Purswell, J L; Olanrewaju, H A; Collier, S D

2008-06-01

Numerous methods are currently used throughout the poultry industry for the administration of vaccines. Each utilizes water for vaccine reconstitution and/or administration, including two of the three commercially available live Mycoplasma gallisepticum (MG) vaccines. Selected water temperatures were used to reconstitute and/or dilute the three commercially available live MG vaccines. Water temperatures included 4 C, 22 C (room temperature), and 32 C, and titer (color change units) was recorded at four time intervals, at point of reconstitution (time 0), 15, 30, and 60 min postreconstitution of the vaccines (time periods 15, 30, and 60, respectively). Results for F strain MG (FMG) vaccine showed significant decreases in titer from time 0 to time 15 for the 22 C and 32 C water temperatures but no significant decrease for any time period for FMG reconstituted with 4 C water. For 6/85 strain MG no significant difference in titer was noted for any of four time periods within any of the three water temperatures. For ts-11 strain MG a significant decrease was observed in titer at each of the four postdilution time periods when diluted with 32 C water. There was no significant decrease in titer at any time period for ts-11 MG vaccine when diluted with either 4 C or 22 C water.

Methods for synthesizing metal oxide nanowires

DOEpatents

Sunkara, Mahendra Kumar; Kumar, Vivekanand; Kim, Jeong H.; Clark, Ezra Lee

2016-08-09

A method of synthesizing a metal oxide nanowire includes the steps of: combining an amount of a transition metal or a transition metal oxide with an amount of an alkali metal compound to produce a mixture; activating a plasma discharge reactor to create a plasma discharge; exposing the mixture to the plasma discharge for a first predetermined time period such that transition metal oxide nanowires are formed; contacting the transition metal oxide nanowires with an acid solution such that an alkali metal ion is exchanged for a hydrogen ion on each of the transition metal oxide nanowires; and exposing the transition metal oxide nanowires to the plasma discharge for a second predetermined time period to thermally anneal the transition metal oxide nanowires. Transition metal oxide nanowires produced using the synthesis methods described herein are also provided.

Emergence and space-time structure of lump solution to the (2+1)-dimensional generalized KP equation

NASA Astrophysics Data System (ADS)

Tan, Wei; Dai, Houping; Dai, Zhengde; Zhong, Wenyong

2017-11-01

A periodic breather-wave solution is obtained using homoclinic test approach and Hirota's bilinear method with a small perturbation parameter u0 for the (2+1)-dimensional generalized Kadomtsev-Petviashvili equation. Based on the periodic breather-wave, a lump solution is emerged by limit behaviour. Finally, three different forms of the space-time structure of the lump solution are investigated and discussed using the extreme value theory.

40 CFR 75.41 - Precision criteria.

Code of Federal Regulations, 2011 CFR

2011-07-01

... for the entire 30- to 90-day period. (9) The owner or operator shall provide two separate time series... time where the vertical axis represents the percentage difference between each paired hourly reading... monitoring system (or reference method) readings versus time where the vertical axis represents hourly...

40 CFR 75.41 - Precision criteria.

Code of Federal Regulations, 2014 CFR

2014-07-01

... for the entire 30- to 90-day period. (9) The owner or operator shall provide two separate time series... time where the vertical axis represents the percentage difference between each paired hourly reading... monitoring system (or reference method) readings versus time where the vertical axis represents hourly...

40 CFR 75.41 - Precision criteria.

Code of Federal Regulations, 2010 CFR

2010-07-01

... for the entire 30- to 90-day period. (9) The owner or operator shall provide two separate time series... time where the vertical axis represents the percentage difference between each paired hourly reading... monitoring system (or reference method) readings versus time where the vertical axis represents hourly...

40 CFR 75.41 - Precision criteria.

Code of Federal Regulations, 2013 CFR

2013-07-01

... for the entire 30- to 90-day period. (9) The owner or operator shall provide two separate time series... time where the vertical axis represents the percentage difference between each paired hourly reading... monitoring system (or reference method) readings versus time where the vertical axis represents hourly...

40 CFR 75.41 - Precision criteria.

Code of Federal Regulations, 2012 CFR

2012-07-01

... for the entire 30- to 90-day period. (9) The owner or operator shall provide two separate time series... time where the vertical axis represents the percentage difference between each paired hourly reading... monitoring system (or reference method) readings versus time where the vertical axis represents hourly...

Environmental stress cracking of polymers

NASA Technical Reports Server (NTRS)

Mahan, K. I.

1980-01-01

A two point bending method for use in studying the environmental stress cracking and crazing phenomena is described and demonstrated for a variety of polymer/solvent systems. Critical strain values obtained from these curves are reported for various polymer/solvent systems including a considerable number of systems for which critical strain values have not been previously reported. Polymers studied using this technique include polycarbonate (PC), ABS, high impact styrene (HIS), polyphenylene oxide (PPO), and polymethyl methacrylate (PMMA). Critical strain values obtained using this method compared favorably with available existing data. The major advantage of the technique is the ability to obtain time vs. strain curves over a short period of time. The data obtained suggests that over a short period of time the transition in most of the polymer solvent systems is more gradual than previously believed.

Test of synthetic DNA tracers in a periodic hydrodynamic system for time-variable transit time distribution assessment

NASA Astrophysics Data System (ADS)

Dahlke, H. E.; Wang, C.; McNew, C.; McLaughlin, S.; Lyon, S. W.

2016-12-01

Recent research on time-varying transport through hydrologic systems proposed using decomposed over-printed tracer breakthrough curves to directly observe transport through complex flow systems. This method, also known as the PERTH (Periodic Tracer Hierarchy) method requires periodic flow and multiple tracer injections to reveal changes in flow pathways and transport behavior. Time-variable transit time distributions (TTD) estimated from tracer breakthrough curves often vary with the storage state of the system, which in turn is influenced by internal and external variabilities, such as the arrangement of flow pathways and fluctuations in system inputs. Deciphering internal from external variabilities in TTDs might help to advance the use of TTDs for estimating the physical state of a system; however, thus far the finite number of unique conservative tracers available for tracing has limited deeper insights. Synthetic DNA tracers consisting of short strands of synthetic DNA encapsulated by polylactic acid (PLA) microspheres could potentially provide multiple unique tracers with identical transport properties needed to explore time varying transport through hydrologic systems in more detail. An experiment was conducted on the miniLeo hillslope, a 1 m3 sloping lysimeter, within the Biosphere 2 Landscape Evolution Observatory near Tucson, AZ to investigate transit time variability. The goal of the experiment was to 1) test the suitability of using synthetic DNA tracers for estimating TTDs in a hydrologic system and 2) to determine the TTDs of individual tracer pulses under periodic steady-state conditions. Five DNA tracers, consisting of four unique, encapsulated DNA sequences and one free/non-encapsulated DNA sequence, were applied as reference and probe tracers together with deuterium, using the PERTH method. The lysimeter received three 2-hour pulses of rainfall at a rate of 30 mm/hr for 10 days. Initial results show that both the encapsulated and free DNA tracers were successfully transported in a pulsed manner through the system, but had overall longer breakthrough times than the reference deuterium tracer. Comparison of the DNA probe tracers indicate differences in transit times, likely related to differences in tracer mobilization in response to the time-variant rainfall input.

Modeling laser-induced periodic surface structures: Finite-difference time-domain feedback simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skolski, J. Z. P., E-mail: j.z.p.skolski@utwente.nl; Vincenc Obona, J.; Römer, G. R. B. E.

2014-03-14

A model predicting the formation of laser-induced periodic surface structures (LIPSSs) is presented. That is, the finite-difference time domain method is used to study the interaction of electromagnetic fields with rough surfaces. In this approach, the rough surface is modified by “ablation after each laser pulse,” according to the absorbed energy profile, in order to account for inter-pulse feedback mechanisms. LIPSSs with a periodicity significantly smaller than the laser wavelength are found to “grow” either parallel or orthogonal to the laser polarization. The change in orientation and periodicity follow from the model. LIPSSs with a periodicity larger than the wavelengthmore » of the laser radiation and complex superimposed LIPSS patterns are also predicted by the model.« less

Evaluation of the foetal time to death in mice after application of direct and indirect euthanasia methods.

PubMed

Muñoz-Mediavilla, C; Cámara, J A; Salazar, S; Segui, B; Sanguino, D; Mulero, F; de la Cueva, E; Blanco, I

2016-04-01

Directive 2010/63/EU on the protection of animals used for scientific purposes requires that the killing of mammal foetuses during the last third of their gestational period should be accomplished through effective and humane methods. The fact that murine foetuses are resistant to hypoxia-mediated euthanasia renders the current euthanasia methods ineffective or humane for the foetuses when these methods are applied to pregnant female mice. We have assessed the time to death of foetuses after performing either indirect (dam euthanasia) or direct (via intraplacental injection--a new approach to euthanasia) euthanasia methods in order to determine a euthanasia method that is appropriate, ethical and efficient for the killing of mouse foetuses. The respective times to death of foetuses after performing the three most commonly used euthanasia methods (namely cervical dislocation, CO2inhalation and intraperitoneal sodium pentobarbital administration) were recorded. Absence of foetal heartbeat was monitored via ultrasound. We consider that the most effective and humane method of foetal euthanasia was the one able to achieve foetal death within the shortest possible period of time. Among the indirect euthanasia methods assessed, the administration of a sodium pentobarbital overdose to pregnant female mice was found to be the fastest for foetuses, with an average post-treatment foetal death of approximately 29.8 min. As for the direct euthanasia method assessed, foetal time to death after intraplacental injection of sodium pentobarbital was approximately 14 min. Significant differences among the different mouse strains employed were found. Based on the results obtained in our study, we consider that the administration of a sodium pentobarbital overdose by intraplacental injection to be an effective euthanasia method for murine foetuses. © The Author(s) 2015.

Effects of climate change on water requirements and phenological period of major crops in Heihe River basin, China - Based on the accumulated temperature threshold method

NASA Astrophysics Data System (ADS)

Han, Dongmei; Xu, Xinyi; Yan, Denghua

2016-04-01

In recent years, global climate change has significantly caused a serious crisis of water resources throughout the world. However, mainly through variations in temperature, climate change will affect water requirements of crop. It is obvious that the rise of temperature affects growing period and phenological period of crop directly, then changes the water demand quota of crop. Methods including accumulated temperature threshold and climatic tendency rate were adopted, which made up for the weakness of phenological observations, to reveal the response of crop phenological change during the growing period. Then using Penman-Menteith model and crop coefficients from the United Nations Food& Agriculture Organization (FAO), the paper firstly explored crop water requirements in different growth periods, and further forecasted quantitatively crop water requirements in Heihe River Basin, China under different climate change scenarios. Results indicate that: (i) The results of crop phenological change established in the method of accumulated temperature threshold were in agreement with measured results, and (ii) there were many differences in impacts of climate warming on water requirement of different crops. The growth periods of wheat and corn had tendency of shortening as well as the length of growth periods. (ii)Results of crop water requirements under different climate change scenarios showed: when temperature increased by 1°C, the start time of wheat growth period changed, 2 days earlier than before, and the length of total growth period shortened 2 days. Wheat water requirements increased by 1.4mm. However, corn water requirements decreased by almost 0.9mm due to the increasing temperature of 1°C. And the start time of corn growth period become 3 days ahead, and the length of total growth period shortened 4 days. Therefore, the contradiction between water supply and water demands are more obvious under the future climate warming in Heihe River Basin, China.

MO-DE-207A-08: Four-Dimensional Cone-Beam CT Iterative Reconstruction with Time-Ordered Chain Graph Model for Non-Periodic Organ Motion and Deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakano, M; Haga, A; Hanaoka, S

2016-06-15

Purpose: The purpose of this study is to propose a new concept of four-dimensional (4D) cone-beam CT (CBCT) reconstruction for non-periodic organ motion using the Time-ordered Chain Graph Model (TCGM), and to compare the reconstructed results with the previously proposed methods, the total variation-based compressed sensing (TVCS) and prior-image constrained compressed sensing (PICCS). Methods: CBCT reconstruction method introduced in this study consisted of maximum a posteriori (MAP) iterative reconstruction combined with a regularization term derived from a concept of TCGM, which includes a constraint coming from the images of neighbouring time-phases. The time-ordered image series were concurrently reconstructed in themore » MAP iterative reconstruction framework. Angular range of projections for each time-phase was 90 degrees for TCGM and PICCS, and 200 degrees for TVCS. Two kinds of projection data, an elliptic-cylindrical digital phantom data and two clinical patients’ data, were used for reconstruction. The digital phantom contained an air sphere moving 3 cm along longitudinal axis, and temporal resolution of each method was evaluated by measuring the penumbral width of reconstructed moving air sphere. The clinical feasibility of non-periodic time-ordered 4D CBCT reconstruction was also examined using projection data of prostate cancer patients. Results: The results of reconstructed digital phantom shows that the penumbral widths of TCGM yielded the narrowest result; PICCS and TCGM were 10.6% and 17.4% narrower than that of TVCS, respectively. This suggests that the TCGM has the better temporal resolution than the others. Patients’ CBCT projection data were also reconstructed and all three reconstructed results showed motion of rectal gas and stool. The result of TCGM provided visually clearer and less blurring images. Conclusion: The present study demonstrates that the new concept for 4D CBCT reconstruction, TCGM, combined with MAP iterative reconstruction framework enables time-ordered image reconstruction with narrower time-window.« less

EVALUATION OF DIOXIN EMISSIONS MONITORING SYSTEMS

EPA Science Inventory

Continuous samplers and real or semi-real-time continuous monitors for polychlorinated dibenzodioxins and furans provide significant advantages relative to conventional methods of extractive sampling. Continuous samplers collect long term samples over a time period of days to wee...

The biologic error in gestational length related to the use of the first day of last menstrual period as a proxy for the start of pregnancy.

PubMed

Nakling, Jakob; Buhaug, Harald; Backe, Bjorn

2005-10-01

In a large unselected population of normal spontaneous pregnancies, to estimate the biologic variation of the interval from the first day of the last menstrual period to start of pregnancy, and the biologic variation of gestational length to delivery; and to estimate the random error of routine ultrasound assessment of gestational age in mid-second trimester. Cohort study of 11,238 singleton pregnancies, with spontaneous onset of labour and reliable last menstrual period. The day of delivery was predicted with two independent methods: According to the rule of Nägele and based on ultrasound examination in gestational weeks 17-19. For both methods, the mean difference between observed and predicted day of delivery was calculated. The variances of the differences were combined to estimate the variances of the two partitions of pregnancy. The biologic variation of the time from last menstrual period to pregnancy start was estimated to 7.0 days (standard deviation), and the standard deviation of the time to spontaneous delivery was estimated to 12.4 days. The estimate of the standard deviation of the random error of ultrasound assessed foetal age was 5.2 days. Even when the last menstrual period is reliable, the biologic variation of the time from last menstrual period to the real start of pregnancy is substantial, and must be taken into account. Reliable information about the first day of the last menstrual period is not equivalent with reliable information about the start of pregnancy.

Here Be Dragons: Effective (X-ray) Timing with the Cospectrum

NASA Astrophysics Data System (ADS)

Huppenkothen, Daniela; Bachetti, Matteo

2018-01-01

In recent years, the cross spectrum has received considerable attention as a means of characterising the variability of astronomical sources as a function of wavelength. While much has been written about the statistics of time and phase lags, the cospectrum—the real part of the cross spectrum—has only recently been understood as means of mitigating instrumental effects dependent on temporal frequency in astronomical detectors, as well as a method of characterizing the coherent variability in two wavelength ranges on different time scales. In this talk, I will present recent advances made in understanding the statistical properties of cospectra, leading to much improved inferences for periodic and quasi-periodic signals. I will also present a new method to reliably mitigate instrumental effects such as dead time in X-ray detectors, and show how we can use the cospectrum to model highly variable sources such as X-ray binaries or Active Galactic Nuclei.

A comparison of methods for deriving solute flux rates using long-term data from streams in the mirror lake watershed

USGS Publications Warehouse

Bukaveckas, P.A.; Likens, G.E.; Winter, T.C.; Buso, D.C.

1998-01-01

Calculation of chemical flux rates for streams requires integration of continuous measurements of discharge with discrete measurements of solute concentrations. We compared two commonly used methods for interpolating chemistry data (time-averaging and flow-weighting) to determine whether discrepancies between the two methods were large relative to other sources of error in estimating flux rates. Flux rates of dissolved Si and SO42- were calculated from 10 years of data (1981-1990) for the NW inlet and Outlet of Mirror Lake and for a 40-day period (March 22 to April 30, 1993) during which we augmented our routine (weekly) chemical monitoring with collection of daily samples. The time-averaging method yielded higher estimates of solute flux during high-flow periods if no chemistry samples were collected corresponding to peak discharge. Concentration-discharge relationships should be used to interpolate stream chemistry during changing flow conditions if chemical changes are large. Caution should be used in choosing the appropriate time-scale over which data are pooled to derive the concentration-discharge regressions because the model parameters (slope and intercept) were found to be sensitive to seasonal and inter-annual variation. Both methods approximated solute flux to within 2-10% for a range of solutes that were monitored during the intensive sampling period. Our results suggest that errors arising from interpolation of stream chemistry data are small compared with other sources of error in developing watershed mass balances.

A Case Study on Reducing Children's Screen Time: The Project of Screen Free Week

ERIC Educational Resources Information Center

Kara, Hatice Gözde Ertürk

2018-01-01

The current study aims to direct children to alternative activities within a week period by applying the project of screen free week to voluntary families. The ultimate aim of the study is to reduce children's screen time. The instrumental case study method; one of the qualitative research methods, was employed. Five children attending the…

[Enteral zond feeding in patients with insolvensy of duodenum stump].

PubMed

Borodin, N A; Zaĭtsev, E Iu

2008-01-01

The most effective method of insolvency duodenum stump treatment is an active drenage of stump--zone within enteral zond feeding. Using of Y-shaped enterostomia with compressive intestine anastomosis avows to fulfill feeding during a long period of time. It is not followed with new complication even in peritonitis case. The method allows to lower the death level in two times.

Single-step methods for predicting orbital motion considering its periodic components

NASA Astrophysics Data System (ADS)

Lavrov, K. N.

1989-01-01

Modern numerical methods for integration of ordinary differential equations can provide accurate and universal solutions to celestial mechanics problems. The implicit single sequence algorithms of Everhart and multiple step computational schemes using a priori information on periodic components can be combined to construct implicit single sequence algorithms which combine their advantages. The construction and analysis of the properties of such algorithms are studied, utilizing trigonometric approximation of the solutions of differential equations containing periodic components. The algorithms require 10 percent more machine memory than the Everhart algorithms, but are twice as fast, and yield short term predictions valid for five to ten orbits with good accuracy and five to six times faster than algorithms using other methods.

COMPARISON OF GESTATIONAL AGE AT DELIVERY BASED ON LAST MENSTRUAL PERIOD AND EARLY ULTRASOUND

EPA Science Inventory

Reported date of last menstrual period (LMP) is commonly used to estimate gestational age but may be unreliable if recall is inaccurate or time between menstruation and ovulation differs from the presumed 15-day interval. Early ultrasound is generally a more accurate method than ...

Analysis of Nonlinear Periodic and Aperiodic Media: Application to Optical Logic Gates

NASA Astrophysics Data System (ADS)

Yu, Yisheng

This dissertation is about the analysis of nonlinear periodic and aperiodic media and their application to the design of intensity controlled all optical logic gates: AND, OR, and NOT. A coupled nonlinear differential equation that characterizes the electromagnetic wave propagation in a nonlinear periodic (and aperiodic) medium has been derived from the first principle. The equations are general enough that it reflects the effect of transverse modal fields and can be used to analyze both co-propagating and counter propagating waves. A numerical technique based on the finite differences method and absorbing boundary condition has been developed to solve the coupled differential equations here. The numerical method is simple and accurate. Unlike the method based on characteristics that has been reported in the literature, this method does not involve integration and step sizes of time and space coordinates are decoupled. The decoupling provides independent choice for time and space step sizes. The concept of "gap soliton" has also been re-examined. The dissertation consists of four manuscripts. Manuscript I reports on the design of all optical logic gates: AND, OR, and NOT based on the bistability property of nonlinear periodic and aperiodic waveguiding structures. The functioning of the logic gates has been shown by analysis. The numerical technique that has been developed to solve the nonlinear differential equations are addressed in manuscript II. The effect of transverse modal fields on the bistable property of nonlinear periodic medium is reported in manuscript III. The concept of "gap soliton" that are generated in a nonlinear periodic medium has been re-examined. The details on the finding of the re-examination are discussed in manuscript IV.

Singular boundary method for wave propagation analysis in periodic structures

NASA Astrophysics Data System (ADS)

Fu, Zhuojia; Chen, Wen; Wen, Pihua; Zhang, Chuanzeng

2018-07-01

A strong-form boundary collocation method, the singular boundary method (SBM), is developed in this paper for the wave propagation analysis at low and moderate wavenumbers in periodic structures. The SBM is of several advantages including mathematically simple, easy-to-program, meshless with the application of the concept of origin intensity factors in order to eliminate the singularity of the fundamental solutions and avoid the numerical evaluation of the singular integrals in the boundary element method. Due to the periodic behaviors of the structures, the SBM coefficient matrix can be represented as a block Toeplitz matrix. By employing three different fast Toeplitz-matrix solvers, the computational time and storage requirements are significantly reduced in the proposed SBM analysis. To demonstrate the effectiveness of the proposed SBM formulation for wave propagation analysis in periodic structures, several benchmark examples are presented and discussed The proposed SBM results are compared with the analytical solutions, the reference results and the COMSOL software.

Identification of PARMA Models and Their Application to the Modeling of River flows

NASA Astrophysics Data System (ADS)

Tesfaye, Y. G.; Meerschaert, M. M.; Anderson, P. L.

2004-05-01

The generation of synthetic river flow samples that can reproduce the essential statistical features of historical river flows is essential to the planning, design and operation of water resource systems. Most river flow series are periodically stationary; that is, their mean and covariance functions are periodic with respect to time. We employ a periodic ARMA (PARMA) model. The innovation algorithm can be used to obtain parameter estimates for PARMA models with finite fourth moment as well as infinite fourth moment but finite variance. Anderson and Meerschaert (2003) provide a method for model identification when the time series has finite fourth moment. This article, an extension of the previous work by Anderson and Meerschaert, demonstrates the effectiveness of the technique using simulated data. An application to monthly flow data for the Frazier River in British Columbia is also included to illustrate the use of these methods.

Adaptive pitch control for variable speed wind turbines

DOEpatents

Johnson, Kathryn E [Boulder, CO; Fingersh, Lee Jay [Westminster, CO

2012-05-08

An adaptive method for adjusting blade pitch angle, and controllers implementing such a method, for achieving higher power coefficients. Average power coefficients are determined for first and second periods of operation for the wind turbine. When the average power coefficient for the second time period is larger than for the first, a pitch increment, which may be generated based on the power coefficients, is added (or the sign is retained) to the nominal pitch angle value for the wind turbine. When the average power coefficient for the second time period is less than for the first, the pitch increment is subtracted (or the sign is changed). A control signal is generated based on the adapted pitch angle value and sent to blade pitch actuators that act to change the pitch angle of the wind turbine to the new or modified pitch angle setting, and this process is iteratively performed.

Functional feature embedded space mapping of fMRI data.

PubMed

Hu, Jin; Tian, Jie; Yang, Lei

2006-01-01

We have proposed a new method for fMRI data analysis which is called Functional Feature Embedded Space Mapping (FFESM). Our work mainly focuses on the experimental design with periodic stimuli which can be described by a number of Fourier coefficients in the frequency domain. A nonlinear dimension reduction technique Isomap is applied to the high dimensional features obtained from frequency domain of the fMRI data for the first time. Finally, the presence of activated time series is identified by the clustering method in which the information theoretic criterion of minimum description length (MDL) is used to estimate the number of clusters. The feasibility of our algorithm is demonstrated by real human experiments. Although we focus on analyzing periodic fMRI data, the approach can be extended to analyze non-periodic fMRI data (event-related fMRI) by replacing the Fourier analysis with a wavelet analysis.

Quasi-periodic concave microlens array for liquid refractive index sensing fabricated by femtosecond laser assisted with chemical etching.

PubMed

Zhang, F; Wang, C; Yin, K; Dong, X R; Song, Y X; Tian, Y X; Duan, J A

2018-02-05

In this study, a high-efficiency single-pulsed femtosecond laser assisted with chemical wet etching method has been proposed to obtain large-area concave microlens array (MLA). The quasi-periodic MLA consisting of about two million microlenses with tunable diameter and sag height by adjusting laser scanning speed and etching time is uniformly manufactured on fused silica and sapphire within 30 minutes. Moreover, the fabricated MLA behaves excellent optical focusing and imaging performance, which could be used to sense the change of the liquid refractive index (RI). In addition, it is demonstrated that small period and high RI of MLA could acquire high sensitivity and broad dynamic measurement range, respectively. Furthermore, the theoretical diffraction efficiency is calculated by the finite domain time difference (FDTD) method, which is in good agreement with the experimental results.

Predicting Long-term Temperature Increase for Time-Dependent SAR Levels with a Single Short-term Temperature Response

PubMed Central

Carluccio, Giuseppe; Bruno, Mary; Collins, Christopher M.

2015-01-01

Purpose Present a novel method for rapid prediction of temperature in vivo for a series of pulse sequences with differing levels and distributions of specific energy absorption rate (SAR). Methods After the temperature response to a brief period of heating is characterized, a rapid estimate of temperature during a series of periods at different heating levels is made using a linear heat equation and Impulse-Response (IR) concepts. Here the initial characterization and long-term prediction for a complete spine exam are made with the Pennes’ bioheat equation where, at first, core body temperature is allowed to increase and local perfusion is not. Then corrections through time allowing variation in local perfusion are introduced. Results The fast IR-based method predicted maximum temperature increase within 1% of that with a full finite difference simulation, but required less than 3.5% of the computation time. Even higher accelerations are possible depending on the time step size chosen, with loss in temporal resolution. Correction for temperature-dependent perfusion requires negligible additional time, and can be adjusted to be more or less conservative than the corresponding finite difference simulation. Conclusion With appropriate methods, it is possible to rapidly predict temperature increase throughout the body for actual MR examinations. (200/200 words) PMID:26096947

Temporal clustering of floods in Germany: Do flood-rich and flood-poor periods exist?

NASA Astrophysics Data System (ADS)

Merz, Bruno; Nguyen, Viet Dung; Vorogushyn, Sergiy

2016-10-01

The repeated occurrence of exceptional floods within a few years, such as the Rhine floods in 1993 and 1995 and the Elbe and Danube floods in 2002 and 2013, suggests that floods in Central Europe may be organized in flood-rich and flood-poor periods. This hypothesis is studied by testing the significance of temporal clustering in flood occurrence (peak-over-threshold) time series for 68 catchments across Germany for the period 1932-2005. To assess the robustness of the results, different methods are used: Firstly, the index of dispersion, which quantifies the departure from a homogeneous Poisson process, is investigated. Further, the time-variation of the flood occurrence rate is derived by non-parametric kernel implementation and the significance of clustering is evaluated via parametric and non-parametric tests. Although the methods give consistent overall results, the specific results differ considerably. Hence, we recommend applying different methods when investigating flood clustering. For flood estimation and risk management, it is of relevance to understand whether clustering changes with flood severity and time scale. To this end, clustering is assessed for different thresholds and time scales. It is found that the majority of catchments show temporal clustering at the 5% significance level for low thresholds and time scales of one to a few years. However, clustering decreases substantially with increasing threshold and time scale. We hypothesize that flood clustering in Germany is mainly caused by catchment memory effects along with intra- to inter-annual climate variability, and that decadal climate variability plays a minor role.

Ergodic theory and visualization. II. Fourier mesochronic plots visualize (quasi)periodic sets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levnajić, Zoran; Department of Mechanical Engineering, University of California Santa Barbara, Santa Barbara, California 93106; Mezić, Igor

We present an application and analysis of a visualization method for measure-preserving dynamical systems introduced by I. Mezić and A. Banaszuk [Physica D 197, 101 (2004)], based on frequency analysis and Koopman operator theory. This extends our earlier work on visualization of ergodic partition [Z. Levnajić and I. Mezić, Chaos 20, 033114 (2010)]. Our method employs the concept of Fourier time average [I. Mezić and A. Banaszuk, Physica D 197, 101 (2004)], and is realized as a computational algorithms for visualization of periodic and quasi-periodic sets in the phase space. The complement of periodic phase space partition contains chaotic zone,more » and we show how to identify it. The range of method's applicability is illustrated using well-known Chirikov standard map, while its potential in illuminating higher-dimensional dynamics is presented by studying the Froeschlé map and the Extended Standard Map.« less

Ergodic theory and visualization. II. Fourier mesochronic plots visualize (quasi)periodic sets.

PubMed

Levnajić, Zoran; Mezić, Igor

2015-05-01

We present an application and analysis of a visualization method for measure-preserving dynamical systems introduced by I. Mezić and A. Banaszuk [Physica D 197, 101 (2004)], based on frequency analysis and Koopman operator theory. This extends our earlier work on visualization of ergodic partition [Z. Levnajić and I. Mezić, Chaos 20, 033114 (2010)]. Our method employs the concept of Fourier time average [I. Mezić and A. Banaszuk, Physica D 197, 101 (2004)], and is realized as a computational algorithms for visualization of periodic and quasi-periodic sets in the phase space. The complement of periodic phase space partition contains chaotic zone, and we show how to identify it. The range of method's applicability is illustrated using well-known Chirikov standard map, while its potential in illuminating higher-dimensional dynamics is presented by studying the Froeschlé map and the Extended Standard Map.

Stochastic response and bifurcation of periodically driven nonlinear oscillators by the generalized cell mapping method

NASA Astrophysics Data System (ADS)

Han, Qun; Xu, Wei; Sun, Jian-Qiao

2016-09-01

The stochastic response of nonlinear oscillators under periodic and Gaussian white noise excitations is studied with the generalized cell mapping based on short-time Gaussian approximation (GCM/STGA) method. The solutions of the transition probability density functions over a small fraction of the period are constructed by the STGA scheme in order to construct the GCM over one complete period. Both the transient and steady-state probability density functions (PDFs) of a smooth and discontinuous (SD) oscillator are computed to illustrate the application of the method. The accuracy of the results is verified by direct Monte Carlo simulations. The transient responses show the evolution of the PDFs from being Gaussian to non-Gaussian. The effect of a chaotic saddle on the stochastic response is also studied. The stochastic P-bifurcation in terms of the steady-state PDFs occurs with the decrease of the smoothness parameter, which corresponds to the deterministic pitchfork bifurcation.

Propagation of nonlinear shock waves for the generalised Oskolkov equation and its dynamic motions in the presence of an external periodic perturbation

NASA Astrophysics Data System (ADS)

Ak, Turgut; Aydemir, Tugba; Saha, Asit; Kara, Abdul Hamid

2018-06-01

Propagation of nonlinear shock waves for the generalised Oskolkov equation and dynamic motions of the perturbed Oskolkov equation are investigated. Employing the unified method, a collection of exact shock wave solutions for the generalised Oskolkov equations is presented. Collocation finite element method is applied to the generalised Oskolkov equation for checking the accuracy of the proposed method by two test problems including the motion of shock wave and evolution of waves with Gaussian and undular bore initial conditions. Considering an external periodic perturbation, the dynamic motions of the perturbed generalised Oskolkov equation are studied depending on the system parameters with the help of phase portrait and time series plot. The perturbed generalised Oskolkov equation exhibits period-3, quasiperiodic and chaotic motions for some special values of the system parameters, whereas the generalised Oskolkov equation presents shock waves in the absence of external periodic perturbation.

Quantifying risk over the life course - latency, age-related susceptibility, and other time-varying exposure metrics.

PubMed

Wang, Molin; Liao, Xiaomei; Laden, Francine; Spiegelman, Donna

2016-06-15

Identification of the latency period and age-related susceptibility, if any, is an important aspect of assessing risks of environmental, nutritional, and occupational exposures. We consider estimation and inference for latency and age-related susceptibility in relative risk and excess risk models. We focus on likelihood-based methods for point and interval estimation of the latency period and age-related windows of susceptibility coupled with several commonly considered exposure metrics. The method is illustrated in a study of the timing of the effects of constituents of air pollution on mortality in the Nurses' Health Study. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Chimpanzee sleep stages.

NASA Technical Reports Server (NTRS)

Freemon, F. R.; Mcnew, J. J.; Adey, W. R.

1971-01-01

The electroencephalogram and electro-oculogram of two unrestrained juvenile chimpanzees was monitored for 7 consecutive nights using telemetry methods. Of the sleeping time, 23% was spent in the rapid eye movement of REM type of sleep, whereas 8, 4, 15, and 10% were spent in non-REM stages 1 through 4, respectively. Seven to nine periods of REM sleep occurred per night. The average time from the beginning of one REM period to the beginning of the next was approximately 85 min.

Load Balancing Using Time Series Analysis for Soft Real Time Systems with Statistically Periodic Loads

NASA Technical Reports Server (NTRS)

Hailperin, M.

1993-01-01

This thesis provides design and analysis of techniques for global load balancing on ensemble architectures running soft-real-time object-oriented applications with statistically periodic loads. It focuses on estimating the instantaneous average load over all the processing elements. The major contribution is the use of explicit stochastic process models for both the loading and the averaging itself. These models are exploited via statistical time-series analysis and Bayesian inference to provide improved average load estimates, and thus to facilitate global load balancing. This thesis explains the distributed algorithms used and provides some optimality results. It also describes the algorithms' implementation and gives performance results from simulation. These results show that the authors' techniques allow more accurate estimation of the global system loading, resulting in fewer object migrations than local methods. The authors' method is shown to provide superior performance, relative not only to static load-balancing schemes but also to many adaptive load-balancing methods. Results from a preliminary analysis of another system and from simulation with a synthetic load provide some evidence of more general applicability.

Variation of Time Domain Failure Probabilities of Jack-up with Wave Return Periods

NASA Astrophysics Data System (ADS)

Idris, Ahmad; Harahap, Indra S. H.; Ali, Montassir Osman Ahmed

2018-04-01

This study evaluated failure probabilities of jack up units on the framework of time dependent reliability analysis using uncertainty from different sea states representing different return period of the design wave. Surface elevation for each sea state was represented by Karhunen-Loeve expansion method using the eigenfunctions of prolate spheroidal wave functions in order to obtain the wave load. The stochastic wave load was propagated on a simplified jack up model developed in commercial software to obtain the structural response due to the wave loading. Analysis of the stochastic response to determine the failure probability in excessive deck displacement in the framework of time dependent reliability analysis was performed by developing Matlab codes in a personal computer. Results from the study indicated that the failure probability increases with increase in the severity of the sea state representing a longer return period. Although the results obtained are in agreement with the results of a study of similar jack up model using time independent method at higher values of maximum allowable deck displacement, it is in contrast at lower values of the criteria where the study reported that failure probability decreases with increase in the severity of the sea state.

Phase correlation of foreign exchange time series

NASA Astrophysics Data System (ADS)

Wu, Ming-Chya

2007-03-01

Correlation of foreign exchange rates in currency markets is investigated based on the empirical data of USD/DEM and USD/JPY exchange rates for a period from February 1 1986 to December 31 1996. The return of exchange time series is first decomposed into a number of intrinsic mode functions (IMFs) by the empirical mode decomposition method. The instantaneous phases of the resultant IMFs calculated by the Hilbert transform are then used to characterize the behaviors of pricing transmissions, and the correlation is probed by measuring the phase differences between two IMFs in the same order. From the distribution of phase differences, our results show explicitly that the correlations are stronger in daily time scale than in longer time scales. The demonstration for the correlations in periods of 1986-1989 and 1990-1993 indicates two exchange rates in the former period were more correlated than in the latter period. The result is consistent with the observations from the cross-correlation calculation.

Determining postural stability

NASA Technical Reports Server (NTRS)

Forth, Katharine E. (Inventor); Paloski, William H. (Inventor); Lieberman, Erez (Inventor)

2011-01-01

A method for determining postural stability of a person can include acquiring a plurality of pressure data points over a period of time from at least one pressure sensor. The method can also include the step of identifying a postural state for each pressure data point to generate a plurality of postural states. The method can include the step of determining a postural state of the person at a point in time based on at least the plurality of postural states.

A novel way to detect correlations on multi-time scales, with temporal evolution and for multi-variables

NASA Astrophysics Data System (ADS)

Yuan, Naiming; Xoplaki, Elena; Zhu, Congwen; Luterbacher, Juerg

2016-06-01

In this paper, two new methods, Temporal evolution of Detrended Cross-Correlation Analysis (TDCCA) and Temporal evolution of Detrended Partial-Cross-Correlation Analysis (TDPCCA), are proposed by generalizing DCCA and DPCCA. Applying TDCCA/TDPCCA, it is possible to study correlations on multi-time scales and over different periods. To illustrate their properties, we used two climatological examples: i) Global Sea Level (GSL) versus North Atlantic Oscillation (NAO); and ii) Summer Rainfall over Yangtze River (SRYR) versus previous winter Pacific Decadal Oscillation (PDO). We find significant correlations between GSL and NAO on time scales of 60 to 140 years, but the correlations are non-significant between 1865-1875. As for SRYR and PDO, significant correlations are found on time scales of 30 to 35 years, but the correlations are more pronounced during the recent 30 years. By combining TDCCA/TDPCCA and DCCA/DPCCA, we proposed a new correlation-detection system, which compared to traditional methods, can objectively show how two time series are related (on which time scale, during which time period). These are important not only for diagnosis of complex system, but also for better designs of prediction models. Therefore, the new methods offer new opportunities for applications in natural sciences, such as ecology, economy, sociology and other research fields.

The correlation between infectivity and incubation period of measles, estimated from households with two cases.

PubMed

Klinkenberg, Don; Nishiura, Hiroshi

2011-09-07

The generation time of an infectious disease is the time between infection of a primary case and infection of a secondary case by the primary case. Its distribution plays a key role in understanding the dynamics of infectious diseases in populations, e.g. in estimating the basic reproduction number. Moreover, the generation time and incubation period distributions together characterize the effectiveness of control by isolation and quarantine. In modelling studies, a relation between the two is often not made specific, but a correlation is biologically plausible. However, it is difficult to establish such correlation, because of the unobservable nature of infection events. We have quantified a joint distribution of generation time and incubation period by a novel estimation method for household data with two susceptible individuals, consisting of time intervals between disease onsets of two measles cases. We used two such datasets, and a separate incubation period dataset. Results indicate that the mean incubation period and the generation time of measles are positively correlated, and that both lie in the range of 11-12 days, suggesting that infectiousness of measles cases increases significantly around the time of symptom onset. The correlation between times from infection to secondary transmission and to symptom onset could critically affect the predicted effectiveness of isolation and quarantine. Copyright © 2011 Elsevier Ltd. All rights reserved.

40 CFR Appendix G to Part 60 - Provisions for an Alternative Method of Demonstrating Compliance With 40 CFR 60.43 for the Newton...

Code of Federal Regulations, 2011 CFR

2011-07-01

... bypass damper must be fully closed. The DAFGDS bypass may be opened only during periods of DAFGDS startup... day rolling average only during the following times: 3.5.1Periods of DAFGDS startup. 3.5.2Periods of... startup, or DAFGDS shutdown, CEMs emissions data from Unit 2 shall continue to be included in the daily...

A Comparison of Several Methods of Measuring Ignition Lag in a Compression-ignition Engine

NASA Technical Reports Server (NTRS)

Spanogle, J A

1934-01-01

The ignition lag of a fuel oil in the combustion chamber of a high speed compression-ignition engine was measured by three different methods. The start of injection of the fuel as observed with a Stoborama was taken as the start of the period of ignition lag in all cases. The end of the period of ignition lag was determined by observation of the appearance of incandescence in the combustion chamber, by inspection of a pressure-time card for evidence of pressure rise, and by analysis of the indicator card for evidence of the combustion of a small but definite quantity of fuel. A comparison of the values for ignition lags obtained by these three methods indicates that the appearance of incandescence is later than other evidences of the start of combustion, that visual inspection of a pressure-time diagram gives consistent and usable values with a minimum requirement of time and/or apparatus, and that analysis of the indicator card is not worth while for ignition lag alone.

Interpretation of link fluctuations in climate networks during El Niño periods

NASA Astrophysics Data System (ADS)

Martin, E. A.; Paczuski, M.; Davidsen, J.

2013-05-01

Recent work has shown that the topologies of functional climate networks are sensitive to El Niño events. One important interpretation of the findings was that parts of the globe act in correlated relationships which become weaker, on average, during El Niño periods (this was shown using monthly averaged data where no time lag is required, and with daily averaged data where time lags were utilized). In contrast to this, we show that El Niño periods actually exhibit higher correlations than “Normal” climate conditions, while typically having lower correlations than La Niña periods. We also show that it is crucial to establish the sensitivity and the robustness of a given method used to extract functional climate networks —parameters such as time lags can significantly influence and even totally alter the outcome.

Chaos control by electric current in an enzymatic reaction.

PubMed

Lekebusch, A; Förster, A; Schneider, F W

1996-09-01

We apply the continuous delayed feedback method of Pyragas to control chaos in the enzymatic Peroxidase-Oxidase (PO) reaction, using the electric current as the control parameter. At each data point in the time series, a time delayed feedback function applies a small amplitude perturbation to inert platinum electrodes, which causes redox processes on the surface of the electrodes. These perturbations are calculated as the difference between the previous (time delayed) signal and the actual signal. Unstable periodic P1, 1(1), and 1(2) orbits (UPOs) were stabilized in the CSTR (continuous stirred tank reactor) experiments. The stabilization is demonstrated by at least three conditions: A minimum in the experimental dispersion function, the equality of the delay time with the period of the stabilized attractor and the embedment of the stabilized periodic attractor in the chaotic attractor.

Statistical Analysis of Categorical Time Series of Atmospheric Elementary Circulation Mechanisms - Dzerdzeevski Classification for the Northern Hemisphere

PubMed Central

Brenčič, Mihael

2016-01-01

Northern hemisphere elementary circulation mechanisms, defined with the Dzerdzeevski classification and published on a daily basis from 1899–2012, are analysed with statistical methods as continuous categorical time series. Classification consists of 41 elementary circulation mechanisms (ECM), which are assigned to calendar days. Empirical marginal probabilities of each ECM were determined. Seasonality and the periodicity effect were investigated with moving dispersion filters and randomisation procedure on the ECM categories as well as with the time analyses of the ECM mode. The time series were determined as being non-stationary with strong time-dependent trends. During the investigated period, periodicity interchanges with periods when no seasonality is present. In the time series structure, the strongest division is visible at the milestone of 1986, showing that the atmospheric circulation pattern reflected in the ECM has significantly changed. This change is result of the change in the frequency of ECM categories; before 1986, the appearance of ECM was more diverse, and afterwards fewer ECMs appear. The statistical approach applied to the categorical climatic time series opens up new potential insight into climate variability and change studies that have to be performed in the future. PMID:27116375

Statistical Analysis of Categorical Time Series of Atmospheric Elementary Circulation Mechanisms - Dzerdzeevski Classification for the Northern Hemisphere.

PubMed

Brenčič, Mihael

2016-01-01

Northern hemisphere elementary circulation mechanisms, defined with the Dzerdzeevski classification and published on a daily basis from 1899-2012, are analysed with statistical methods as continuous categorical time series. Classification consists of 41 elementary circulation mechanisms (ECM), which are assigned to calendar days. Empirical marginal probabilities of each ECM were determined. Seasonality and the periodicity effect were investigated with moving dispersion filters and randomisation procedure on the ECM categories as well as with the time analyses of the ECM mode. The time series were determined as being non-stationary with strong time-dependent trends. During the investigated period, periodicity interchanges with periods when no seasonality is present. In the time series structure, the strongest division is visible at the milestone of 1986, showing that the atmospheric circulation pattern reflected in the ECM has significantly changed. This change is result of the change in the frequency of ECM categories; before 1986, the appearance of ECM was more diverse, and afterwards fewer ECMs appear. The statistical approach applied to the categorical climatic time series opens up new potential insight into climate variability and change studies that have to be performed in the future.

Time-varying phononic crystals

NASA Astrophysics Data System (ADS)

Wright, Derek Warren

The primary objective of this thesis was to gain a deeper understanding of acoustic wave propagation in phononic crystals, particularly those that include materials whose properties can be varied periodically in time. This research was accomplished in three ways. First, a 2D phononic crystal was designed, created, and characterized. Its properties closely matched those determined through simulation. The crystal demonstrated band gaps, dispersion, and negative refraction. It served as a means of elucidating the practicalities of phononic crystal design and construction and as a physical verification of their more interesting properties. Next, the transmission matrix method for analyzing 1D phononic crystals was extended to include the effects of time-varying material parameters. The method was then used to provide a closed-form solution for the case of periodically time-varying material parameters. Some intriguing results from the use of the extended method include dramatically altered transmission properties and parametric amplification. New insights can be gained from the governing equations and have helped to identify the conditions that lead to parametric amplification in these structures. Finally, 2D multiple scattering theory was modified to analyze scatterers with time-varying material parameters. It is shown to be highly compatible with existing multiple scattering theories. It allows the total scattered field from a 2D time-varying phononic crystal to be determined. It was shown that time-varying material parameters significantly affect the phononic crystal transmission spectrum, and this was used to switch an incident monochromatic wave. Parametric amplification can occur under certain circumstances, and this effect was investigated using the closed-form solutions provided by the new 1D method. The complexity of the extended methods grows logarithmically as opposed linearly with existing methods, resulting in superior computational complexity for large numbers of scatterers. Also, since both extended methods provide analytic solutions, they may give further insights into the factors that govern the behaviour of time-varying phononic crystals. These extended methods may now be used to design an active phononic crystal that could demonstrate new or enhanced properties.

Real-Time Frequency Response Estimation Using Joined-Wing SensorCraft Aeroelastic Wind-Tunnel Data

NASA Technical Reports Server (NTRS)

Grauer, Jared A; Heeg, Jennifer; Morelli, Eugene A

2012-01-01

A new method is presented for estimating frequency responses and their uncertainties from wind-tunnel data in real time. The method uses orthogonal phase-optimized multi- sine excitation inputs and a recursive Fourier transform with a least-squares estimator. The method was first demonstrated with an F-16 nonlinear flight simulation and results showed that accurate short period frequency responses were obtained within 10 seconds. The method was then applied to wind-tunnel data from a previous aeroelastic test of the Joined- Wing SensorCraft. Frequency responses describing bending strains from simultaneous control surface excitations were estimated in a time-efficient manner.

Latent class instrumental variables: A clinical and biostatistical perspective

PubMed Central

Baker, Stuart G.; Kramer, Barnett S.; Lindeman, Karen S.

2015-01-01

In some two-arm randomized trials, some participants receive the treatment assigned to the other arm as a result of technical problems, refusal of a treatment invitation, or a choice of treatment in an encouragement design. In some before-and-after studies, the availability of a new treatment changes from one time period to this next. Under assumptions that are often reasonable, the latent class instrumental variable (IV) method estimates the effect of treatment received in the aforementioned scenarios involving all-or-none compliance and all-or-none availability. Key aspects are four initial latent classes (sometimes called principal strata) based on treatment received if in each randomization group or time period, the exclusion restriction assumption (in which randomization group or time period is an instrumental variable), the monotonicity assumption (which drops an implausible latent class from the analysis), and the estimated effect of receiving treatment in one latent class (sometimes called efficacy, the local average treatment effect, or the complier average causal effect). Since its independent formulations in the biostatistics and econometrics literatures, the latent class IV method (which has no well-established name) has gained increasing popularity. We review the latent class IV method from a clinical and biostatistical perspective, focusing on underlying assumptions, methodological extensions, and applications in our fields of obstetrics and cancer research. PMID:26239275

Solar wind variations and geomagnetic storms - A study of individual storms based on high time resolution ISEE 3 data

NASA Technical Reports Server (NTRS)

Akasofu, S.-I.; Olmsted, C.; Smith, E. J.; Tsurutani, B.; Okida, R.; Baker, D. N.

1985-01-01

Two independent methods are employed to determine the relationship between the parameter epsilon and total energy dissipation rate of the magnetosphere U sub T by selecting disturbed periods from the same data d set used by Baker et al. (1983). Specifically, four storms are examined in detail, since the accuracy of estimating U sub T is significantly improved during disturbed periods. The first method assumes that U sub T = M sub A exp.2- alpha(epsilon) where M sub A is the Alfven Mach number and alpha varies with time. The second method considers a linear, time-invariant dynamic system with epsilon as input and U sub T as output. This means that U sub T = W(asterisk)epsilon where asterisk is the convolution and W is a transfer function characteristic of the system. It is found that alpha values fluctuate mainly between 0 and -0.25. The transfer function analysis indicates that W often resembles a delta-function or a narrow rectangular impulse. Both results give the same implication (namely that U sub T is approximately equal to epsilon) and thus are consistent with the view that the magnetosphere is primarily a directly driven system during disturbed periods.

Separation of Main and Tail Rotor Noise Sources from Ground-Based Acoustic Measurements Using Time-Domain De-Dopplerization

NASA Technical Reports Server (NTRS)

Greenwood, Eric II; Schmitz, Fredric H.

2009-01-01

A new method of separating the contributions of helicopter main and tail rotor noise sources is presented, making use of ground-based acoustic measurements. The method employs time-domain de-Dopplerization to transform the acoustic pressure time-history data collected from an array of ground-based microphones to the equivalent time-history signals observed by an array of virtual inflight microphones traveling with the helicopter. The now-stationary signals observed by the virtual microphones are then periodically averaged with the main and tail rotor once per revolution triggers. The averaging process suppresses noise which is not periodic with the respective rotor, allowing for the separation of main and tail rotor pressure time-histories. The averaged measurements are then interpolated across the range of directivity angles captured by the microphone array in order to generate separate acoustic hemispheres for the main and tail rotor noise sources. The new method is successfully applied to ground-based microphone measurements of a Bell 206B3 helicopter and demonstrates the strong directivity characteristics of harmonic noise radiation from both the main and tail rotors of that helicopter.

Fast measurement of bacterial susceptibility to antibiotics

NASA Technical Reports Server (NTRS)

Chappelle, E. W.; Picciolo, G. L.; Schrock, C. G.

1977-01-01

Method, based on photoanalysis of adenosine triphosphate using light-emitting reaction with luciferase-luciferin technique, saves time by eliminating isolation period required by conventional methods. Technique is also used to determine presence of infection as well as susceptibilities to several antibiotics.

Minimum and Maximum Times Required to Obtain Representative Suspended Sediment Samples

NASA Astrophysics Data System (ADS)

Gitto, A.; Venditti, J. G.; Kostaschuk, R.; Church, M. A.

2014-12-01

Bottle sampling is a convenient method of obtaining suspended sediment measurements for the development of sediment budgets. While these methods are generally considered to be reliable, recent analysis of depth-integrated sampling has identified considerable uncertainty in measurements of grain-size concentration between grain-size classes of multiple samples. Point-integrated bottle sampling is assumed to represent the mean concentration of suspended sediment but the uncertainty surrounding this method is not well understood. Here we examine at-a-point variability in velocity, suspended sediment concentration, grain-size distribution, and grain-size moments to determine if traditional point-integrated methods provide a representative sample of suspended sediment. We present continuous hour-long observations of suspended sediment from the sand-bedded portion of the Fraser River at Mission, British Columbia, Canada, using a LISST laser-diffraction instrument. Spectral analysis suggests that there are no statistically significant peak in energy density, suggesting the absence of periodic fluctuations in flow and suspended sediment. However, a slope break in the spectra at 0.003 Hz corresponds to a period of 5.5 minutes. This coincides with the threshold between large-scale turbulent eddies that scale with channel width/mean velocity and hydraulic phenomena related to channel dynamics. This suggests that suspended sediment samples taken over a period longer than 5.5 minutes incorporate variability that is larger scale than turbulent phenomena in this channel. Examination of 5.5-minute periods of our time series indicate that ~20% of the time a stable mean value of volumetric concentration is reached within 30 seconds, a typical bottle sample duration. In ~12% of measurements a stable mean was not reached over the 5.5 minute sample duration. The remaining measurements achieve a stable mean in an even distribution over the intervening interval.

Time-reversibility and particle sedimentation

NASA Technical Reports Server (NTRS)

Golubitsky, Martin; Krupa, Martin; Lim, Chjan

1991-01-01

This paper studies an ODE model, called the Stokeslet model, and describes sedimentation of small clusters of particles in a highly viscous fluid. This model has a trivial solution in which the n particles arrange themselves at the vertices of a regular n-sided polygon. When n = 3, Hocking and Caflisch et al. (1988) proved the existence of periodic motion (in the frame moving with the center of gravity in the cluster) in which the particles form an isosceles triangle. Here, the study of periodic and quasi-periodic solutions of the Stokeslet model is continued, with emphasis on the spatial and time-reversal symmetry of the model. For three particles, the existence of a second family of periodic solutions and a family of quasi-periodic solutions is proved. It is also indicated how the methods generalize to the case of n particles.

An Extension of the Time-Spectral Method to Overset Solvers

NASA Technical Reports Server (NTRS)

Leffell, Joshua Isaac; Murman, Scott M.; Pulliam, Thomas

2013-01-01

Relative motion in the Cartesian or overset framework causes certain spatial nodes to move in and out of the physical domain as they are dynamically blanked by moving solid bodies. This poses a problem for the conventional Time-Spectral approach, which expands the solution at every spatial node into a Fourier series spanning the period of motion. The proposed extension to the Time-Spectral method treats unblanked nodes in the conventional manner but expands the solution at dynamically blanked nodes in a basis of barycentric rational polynomials spanning partitions of contiguously defined temporal intervals. Rational polynomials avoid Runge's phenomenon on the equidistant time samples of these sub-periodic intervals. Fourier- and rational polynomial-based differentiation operators are used in tandem to provide a consistent hybrid Time-Spectral overset scheme capable of handling relative motion. The hybrid scheme is tested with a linear model problem and implemented within NASA's OVERFLOW Reynolds-averaged Navier- Stokes (RANS) solver. The hybrid Time-Spectral solver is then applied to inviscid and turbulent RANS cases of plunging and pitching airfoils and compared to time-accurate and experimental data. A limiter was applied in the turbulent case to avoid undershoots in the undamped turbulent eddy viscosity while maintaining accuracy. The hybrid scheme matches the performance of the conventional Time-Spectral method and converges to the time-accurate results with increased temporal resolution.

Methods and optical fibers that decrease pulse degradation resulting from random chromatic dispersion

DOEpatents

Chertkov, Michael; Gabitov, Ildar

2004-03-02

The present invention provides methods and optical fibers for periodically pinning an actual (random) accumulated chromatic dispersion of an optical fiber to a predicted accumulated dispersion of the fiber through relatively simple modifications of fiber-optic manufacturing methods or retrofitting of existing fibers. If the pinning occurs with sufficient frequency (at a distance less than or are equal to a correlation scale), pulse degradation resulting from random chromatic dispersion is minimized. Alternatively, pinning may occur quasi-periodically, i.e., the pinning distance is distributed between approximately zero and approximately two to three times the correlation scale.

Development of real-time monitors for gaseous formaldehyde. Final report, 1 December 1988-30 September 1989

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelly, T.J.; Barnes, R.H.

1990-11-01

Two new methods for real-time measurement of gaseous formaldehyde have been developed. One is a spectroscopic method based on direct fluorescence detection of gaseous formaldehyde following excitation with UV light. This method has been developed to the prototype stage by modifications of a commercial fluorescence SO2 detector to convert it to formaldehyde detection. The prototype spectroscopic formaldehyde monitor exhibits a detection limit of <30 ppbv, with a time response of about one minute. The second method is based on derivatization of formaldehyde in aqueous solution to form a fluorescent product. The detection of fluorescent product was made more sensitive bymore » using intense 254 nm light from a mercury lamp for excitation, thereby allowing use of a simple and efficient glass coil scrubber for collection of gaseous formaldehyde. The wet chemical formaldehyde monitor incorportating these improvements exhibits a detection limit for gaseous formaldehyde of 0.2 ppbv and for aqueous formaldehyde of 0.2 micromolar with time response of about one minute, following a lag time of 2 minutes. Both instruments were tested in the laboratory with gaseous formaldehyde standards, and the aqueous scrubbing/analysis method was field tested by continuous operation over a 10-day period in which outdoor and indoor air were sampled for alternate half-hour periods. A comparison of real-time (aqueous scrubbing/analysis) and integrated measurements, using dinitrophenylhydrazine (DNPH) impingers, showed close agreement between the real-time and DNPH data, even at concentrations as low as 1 ppbv.« less

Rolling bearing fault diagnosis based on time-delayed feedback monostable stochastic resonance and adaptive minimum entropy deconvolution

NASA Astrophysics Data System (ADS)

Li, Jimeng; Li, Ming; Zhang, Jinfeng

2017-08-01

Rolling bearings are the key components in the modern machinery, and tough operation environments often make them prone to failure. However, due to the influence of the transmission path and background noise, the useful feature information relevant to the bearing fault contained in the vibration signals is weak, which makes it difficult to identify the fault symptom of rolling bearings in time. Therefore, the paper proposes a novel weak signal detection method based on time-delayed feedback monostable stochastic resonance (TFMSR) system and adaptive minimum entropy deconvolution (MED) to realize the fault diagnosis of rolling bearings. The MED method is employed to preprocess the vibration signals, which can deconvolve the effect of transmission path and clarify the defect-induced impulses. And a modified power spectrum kurtosis (MPSK) index is constructed to realize the adaptive selection of filter length in the MED algorithm. By introducing the time-delayed feedback item in to an over-damped monostable system, the TFMSR method can effectively utilize the historical information of input signal to enhance the periodicity of SR output, which is beneficial to the detection of periodic signal. Furthermore, the influence of time delay and feedback intensity on the SR phenomenon is analyzed, and by selecting appropriate time delay, feedback intensity and re-scaling ratio with genetic algorithm, the SR can be produced to realize the resonance detection of weak signal. The combination of the adaptive MED (AMED) method and TFMSR method is conducive to extracting the feature information from strong background noise and realizing the fault diagnosis of rolling bearings. Finally, some experiments and engineering application are performed to evaluate the effectiveness of the proposed AMED-TFMSR method in comparison with a traditional bistable SR method.

Soliton and periodic solutions for time-dependent coefficient non-linear equation

NASA Astrophysics Data System (ADS)

Guner, Ozkan

2016-01-01

In this article, we establish exact solutions for the generalized (3+1)-dimensional variable coefficient Kadomtsev-Petviashvili (GVCKP) equation. Using solitary wave ansatz in terms of ? functions and the modified sine-cosine method, we find exact analytical bright soliton solutions and exact periodic solutions for the considered model. The physical parameters in the soliton solutions are obtained as function of the dependent model coefficients. The effectiveness and reliability of the method are shown by its application to the GVCKP equation.

Reliability of Fitness Tests Using Methods and Time Periods Common in Sport and Occupational Management

PubMed Central

Burnstein, Bryan D.; Steele, Russell J.; Shrier, Ian

2011-01-01

Context: Fitness testing is used frequently in many areas of physical activity, but the reliability of these measurements under real-world, practical conditions is unknown. Objective: To evaluate the reliability of specific fitness tests using the methods and time periods used in the context of real-world sport and occupational management. Design: Cohort study. Setting: Eighteen different Cirque du Soleil shows. Patients or Other Participants: Cirque du Soleil physical performers who completed 4 consecutive tests (6-month intervals) and were free of injury or illness at each session (n = 238 of 701 physical performers). Intervention(s): Performers completed 6 fitness tests on each assessment date: dynamic balance, Harvard step test, handgrip, vertical jump, pull-ups, and 60-second jump test. Main Outcome Measure(s): We calculated the intraclass coefficient (ICC) and limits of agreement between baseline and each time point and the ICC over all 4 time points combined. Results: Reliability was acceptable (ICC > 0.6) over an 18-month time period for all pairwise comparisons and all time points together for the handgrip, vertical jump, and pull-up assessments. The Harvard step test and 60-second jump test had poor reliability (ICC < 0.6) between baseline and other time points. When we excluded the baseline data and calculated the ICC for 6-month, 12-month, and 18-month time points, both the Harvard step test and 60-second jump test demonstrated acceptable reliability. Dynamic balance was unreliable in all contexts. Limit-of-agreement analysis demonstrated considerable intraindividual variability for some tests and a learning effect by administrators on others. Conclusions: Five of the 6 tests in this battery had acceptable reliability over an 18-month time frame, but the values for certain individuals may vary considerably from time to time for some tests. Specific tests may require a learning period for administrators. PMID:22488138

Time-REferenced data Kriging (TREK): mapping hydrological statistics given their time of reference

NASA Astrophysics Data System (ADS)

Porcheron, Delphine; Leblois, Etienne; Sauquet, Eric

2016-04-01

A major issue in water sciences is to predict runoff parameters at ungauged sites. Estimates can be obtained by various methods. Among them, geostatistical approaches provide interpolation methods that consequently use explicit assumptions on the variable of interest. Geostatistical techniques have been applied to precipitation and temperature fields and later extended to estimate runoff features considered as basin-support variates along the river network (e.g. Gottschalk, 1993; Sauquet et al., 2000; Skoien et al., 2006; Gottschalk et al., 2011). To obtain robust estimations, the first step is to collect a relevant dataset. Sauquet et al. (2000) and Sauquet (2006) suggest including a large number of catchments with long and common observation periods to ensure both reliability and temporal consistency in runoff estimates. However most observation networks evolve with time. Several choices are thus possible to define an optimal reference period maximizing either spatial or temporal overlap. However, the constraints usually lead to discard a significant number of stations. Time-REferenced data Kriging method (TREK) has been developed to overcome this issue. Here is proposed a method of geostatistical estimation considering the temporal support over which a hydrological statistic has been estimated. This allows attenuating the loss of data previously caused by the application of a strict reference period. The time reference remains for the targeted map itself. The weights depend on the observation period of the data included in the dataset and how near this is to the target period. In this presentation, the concepts of TREK will be introduced and thereafter illustrated to map mean annual runoff in France. References Gottschalk, L., 1993, Correlation and covariance of runoff. Stochastic Hydrology and Hydraulics 7(2), 85-101. Sauquet, E., Gottschalk, L. and Leblois, E., 2000, Mapping average annual runoff: a hierarchical approach applying a stochastic interpolation scheme. Hydrological Sciences Journal 45(6), 799-815. Skoien, J.O., Merz, R. and Bloschl, G., 2006, Top-kriging - geostatistics on stream networks. Hydrology and Earth System Sciences 10(2), 277-287. Gottschalk, L., Leblois, E. and Skoien, J.O., 2011, Correlation and covariance of runoff revisited. Journal of Hydrology 398(1-2), 76-90. Sauquet, E., 2006, Mapping mean annual river discharges: Geostatistical developments for incorporating river network dependencies. Journal of Hydrology 331(1-2), 300-314.

Project Lifespan-based Nonstationary Hydrologic Design Methods for Changing Environment

NASA Astrophysics Data System (ADS)

Xiong, L.

2017-12-01

Under changing environment, we must associate design floods with the design life period of projects to ensure the hydrologic design is really relevant to the operation of the hydrologic projects, because the design value for a given exceedance probability over the project life period would be significantly different from that over other time periods of the same length due to the nonstationarity of probability distributions. Several hydrologic design methods that take the design life period of projects into account have been proposed in recent years, i.e. the expected number of exceedances (ENE), design life level (DLL), equivalent reliability (ER), and average design life level (ADLL). Among the four methods to be compared, both the ENE and ER methods are return period-based methods, while DLL and ADLL are risk/reliability- based methods which estimate design values for given probability values of risk or reliability. However, the four methods can be unified together under a general framework through a relationship transforming the so-called representative reliability (RRE) into the return period, i.e. m=1/1(1-RRE), in which we compute the return period m using the representative reliability RRE.The results of nonstationary design quantiles and associated confidence intervals calculated by ENE, ER and ADLL were very similar, since ENE or ER was a special case or had a similar expression form with respect to ADLL. In particular, the design quantiles calculated by ENE and ADLL were the same when return period was equal to the length of the design life. In addition, DLL can yield similar design values if the relationship between DLL and ER/ADLL return periods is considered. Furthermore, ENE, ER and ADLL had good adaptability to either an increasing or decreasing situation, yielding not too large or too small design quantiles. This is important for applications of nonstationary hydrologic design methods in actual practice because of the concern of choosing the emerging nonstationary methods versus the traditional stationary methods. There is still a long way to go for the conceptual transition from stationarity to nonstationarity in hydrologic design.

Experiencing the Research Process in a Single Class Period

ERIC Educational Resources Information Center

Cook, Kathleen E.

2008-01-01

Books and courses on research methods, statistics, or both, often necessarily focus on one topic at a time. This compartmentalized approach prevents students from seeing the big picture. To address this shortcoming, I developed an exercise through which students experience the whole research process in a single class period. From posing a…

Periodic Methods for Controlling a Satellite in Formation

DTIC Science & Technology

2002-03-01

5 5. Clohessy - Wiltshire Reference Frame................................................................... 10 6...techniques to study relative position errors within a satellite cluster [19, 24]. The dynamics were based on Clohessy - Wiltshire equations with near...dynamics model by solving the time periodic, linearized system using Floquet Theory. More accurate than the Clohessy - Wiltshire solutions used in previous

New shape models of asteroids reconstructed from sparse-in-time photometry

NASA Astrophysics Data System (ADS)

Durech, Josef; Hanus, Josef; Vanco, Radim; Oszkiewicz, Dagmara Anna

2015-08-01

Asteroid physical parameters - the shape, the sidereal rotation period, and the spin axis orientation - can be reconstructed from the disk-integrated photometry either dense (classical lightcurves) or sparse in time by the lightcurve inversion method. We will review our recent progress in asteroid shape reconstruction from sparse photometry. The problem of finding a unique solution of the inverse problem is time consuming because the sidereal rotation period has to be found by scanning a wide interval of possible periods. This can be efficiently solved by splitting the period parameter space into small parts that are sent to computers of volunteers and processed in parallel. We will show how this approach of distributed computing works with currently available sparse photometry processed in the framework of project Asteroids@home. In particular, we will show the results based on the Lowell Photometric Database. The method produce reliable asteroid models with very low rate of false solutions and the pipelines and codes can be directly used also to other sources of sparse photometry - Gaia data, for example. We will present the distribution of spin axis of hundreds of asteroids, discuss the dependence of the spin obliquity on the size of an asteroid,and show examples of spin-axis distribution in asteroid families that confirm the Yarkovsky/YORP evolution scenario.

Maximum Entropy Method applied to Real-time Time-Dependent Density Functional Theory

NASA Astrophysics Data System (ADS)

Zempo, Yasunari; Toogoshi, Mitsuki; Kano, Satoru S.

Maximum Entropy Method (MEM) is widely used for the analysis of a time-series data such as an earthquake, which has fairly long-periodicity but short observable data. We have examined MEM to apply to the optical analysis of the time-series data from the real-time TDDFT. In the analysis, usually Fourier Transform (FT) is used, and we have to pay our attention to the lower energy part such as the band gap, which requires the long time evolution. The computational cost naturally becomes quite expensive. Since MEM is based on the autocorrelation of the signal, in which the periodicity can be described as the difference of time-lags, its value in the lower energy naturally gets small compared to that in the higher energy. To improve the difficulty, our MEM has the two features: the raw data is repeated it many times and concatenated, which provides the lower energy resolution in high resolution; together with the repeated data, an appropriate phase for the target frequency is introduced to reduce the side effect of the artificial periodicity. We have compared our improved MEM and FT spectrum using small-to-medium size molecules. We can see the clear spectrum of MEM, compared to that of FT. Our new technique provides higher resolution in fewer steps, compared to that of FT. This work was partially supported by JSPS Grants-in-Aid for Scientific Research (C) Grant number 16K05047, Sumitomo Chemical, Co. Ltd., and Simulatio Corp.

Real-time method and apparatus for measuring the decay-time constant of a fluorescing phosphor

DOEpatents

Britton, Jr., Charles L.; Beshears, David L.; Simpson, Marc L.; Cates, Michael R.; Allison, Steve W.

1999-01-01

A method for determining the decay-time constant of a fluorescing phosphor is provided, together with an apparatus for performing the method. The apparatus includes a photodetector for detecting light emitted by a phosphor irradiated with an excitation pulse and for converting the detected light into an electrical signal. The apparatus further includes a differentiator for differentiating the electrical signal and a zero-crossing discrimination circuit that outputs a pulse signal having a pulse width corresponding to the time period between the start of the excitation pulse and the time when the differentiated electrical signal reaches zero. The width of the output pulse signal is proportional to the decay-time constant of the phosphor.

Fabrication of Large Bulk High Temperature Superconducting Articles

NASA Technical Reports Server (NTRS)

Koczor, Ronald (Inventor); Hiser, Robert A. (Inventor)

2003-01-01

A method of fabricating large bulk high temperature superconducting articles which comprises the steps of selecting predetermined sizes of crystalline superconducting materials and mixing these specific sizes of particles into a homogeneous mixture which is then poured into a die. The die is placed in a press and pressurized to predetermined pressure for a predetermined time and is heat treated in the furnace at predetermined temperatures for a predetermined time. The article is left in the furnace to soak at predetermined temperatures for a predetermined period of time and is oxygenated by an oxygen source during the soaking period.

Automated algorithms for detecting sleep period time using a multi-sensor pattern-recognition activity monitor from 24 h free-living data in older adults.

PubMed

Cabanas-Sánchez, Verónica; Higueras-Fresnillo, Sara; De la Cámara, Miguel Ángel; Veiga, Oscar L; Martinez-Gomez, David

2018-05-16

The aims of the present study were (i) to develop automated algorithms to identify the sleep period time in 24 h data from the Intelligent Device for Energy Expenditure and Activity (IDEEA) in older adults, and (ii) to analyze the agreement between these algorithms to identify the sleep period time as compared to self-reported data and expert visual analysis of accelerometer raw data. This study comprised 50 participants, aged 65-85 years. Fourteen automated algorithms were developed. Participants reported their bedtime and waking time on the days on which they wore the device. A well-trained expert reviewed each IDEEA file in order to visually identify bedtime and waking time on each day. To explore the agreement between methods, Pearson correlations, mean differences, mean percentage errors, accuracy, sensitivity and specificity, and the Bland-Altman method were calculated. With 87 d of valid data, algorithms 6, 7, 11 and 12 achieved higher levels of agreement in determining sleep period time when compared to self-reported data (mean difference  =  -0.34 to 0.01 h d -1 ; mean absolute error  =  10.66%-11.44%; r  =  0.515-0.686; accuracy  =  95.0%-95.6%; sensitivity  =  93.0%-95.8%; specificity  =  95.7%-96.4%) and expert visual analysis (mean difference  =  -0.04 to 0.31 h d -1 ; mean absolute error  =  5.0%-6.97%; r  =  0.620-0.766; accuracy  =  97.2%-98.0%; sensitivity  =  94.5%-97.6%; specificity  =  98.4%-98.8%). Bland-Altman plots showed no systematic biases in these comparisons (all p  >  0.05). Differences between methods did not vary significantly by gender, age, obesity, self-rated health, or the presence of chronic conditions. These four algorithms can be used to identify easily and with adequate accuracy the sleep period time using the IDEEA activity monitor from 24 h free-living data in older adults.

Periodicity and time trends in the prevalence of total births and conceptions with congenital malformations among Jews and Muslims in Israel, 1999-2006: a time series study of 823,966 births.

PubMed

Agay-Shay, Keren; Friger, Michael; Linn, Shai; Peled, Ammatzia; Amitai, Yona; Peretz, Chava

2012-06-01

BACKGROUND Congenital malformations (CMs) are a leading cause of infant disability. Geophysical patterns such as 2-year, yearly, half-year, 3-month, and lunar cycles regulate much of the temporal biology of all life on Earth and may affect birth and birth outcomes in humans. Therefore, the aim of this study was to evaluate and compare trends and periodicity in total births and CM conceptions in two Israeli populations. METHODS Poisson nonlinear models (polynomial) were applied to study and compare trends and geophysical periodicity cycles of weekly births and weekly prevalence rate of CM (CMPR), in a time-series design of conception date within and between Jews and Muslims. The population included all live births and stillbirths (n = 823,966) and CM (three anatomic systems, eight CM groups [n = 2193]) in Israel during 2000 to 2006. Data were obtained from the Ministry of Health. RESULTS We describe the trend and periodicity cycles for total birth conceptions. Of eight groups of CM, periodicity cycles were statistically significant in four CM groups for either Jews or Muslims. Lunar month and biennial periodicity cycles not previously investigated in the literature were found to be statistically significant. Biennial cycle was significant in total births (Jews and Muslims) and syndactyly (Muslims), whereas lunar month cycle was significant in total births (Muslims) and atresia of small intestine (Jews). CONCLUSION We encourage others to use the method we describe as an important tool to investigate the effects of different geophysical cycles on human health and pregnancy outcomes, especially CM, and to compare between populations. Copyright © 2012 Wiley Periodicals, Inc.

Identification of ground motion features for high-tech facility under far field seismic waves using wavelet packet transform

NASA Astrophysics Data System (ADS)

Huang, Shieh-Kung; Loh, Chin-Hsiung; Chen, Chin-Tsun

2016-04-01

Seismic records collected from earthquake with large magnitude and far distance may contain long period seismic waves which have small amplitude but with dominant period up to 10 sec. For a general situation, the long period seismic waves will not endanger the safety of the structural system or cause any uncomfortable for human activity. On the contrary, for those far distant earthquakes, this type of seismic waves may cause a glitch or, furthermore, breakdown to some important equipments/facilities (such as the high-precision facilities in high-tech Fab) and eventually damage the interests of company if the amplitude becomes significant. The previous study showed that the ground motion features such as time-variant dominant frequencies extracted using moving window singular spectrum analysis (MWSSA) and amplitude characteristics of long-period waves identified from slope change of ground motion Arias Intensity can efficiently indicate the damage severity to the high-precision facilities. However, embedding a large hankel matrix to extract long period seismic waves make the MWSSA become a time-consumed process. In this study, the seismic ground motion data collected from broadband seismometer network located in Taiwan were used (with epicenter distance over 1000 km). To monitor the significant long-period waves, the low frequency components of these seismic ground motion data are extracted using wavelet packet transform (WPT) to obtain wavelet coefficients and the wavelet entropy of coefficients are used to identify the amplitude characteristics of long-period waves. The proposed method is a timesaving process compared to MWSSA and can be easily implemented for real-time detection. Comparison and discussion on this method among these different seismic events and the damage severity to the high-precision facilities in high-tech Fab is made.

Accurate frequency domain measurement of the best linear time-invariant approximation of linear time-periodic systems including the quantification of the time-periodic distortions

NASA Astrophysics Data System (ADS)

Louarroudi, E.; Pintelon, R.; Lataire, J.

2014-10-01

Time-periodic (TP) phenomena occurring, for instance, in wind turbines, helicopters, anisotropic shaft-bearing systems, and cardiovascular/respiratory systems, are often not addressed when classical frequency response function (FRF) measurements are performed. As the traditional FRF concept is based on the linear time-invariant (LTI) system theory, it is only approximately valid for systems with varying dynamics. Accordingly, the quantification of any deviation from this ideal LTI framework is more than welcome. The “measure of deviation” allows us to define the notion of the best LTI (BLTI) approximation, which yields the best - in mean square sense - LTI description of a linear time-periodic LTP system. By taking into consideration the TP effects, it is shown in this paper that the variability of the BLTI measurement can be reduced significantly compared with that of classical FRF estimators. From a single experiment, the proposed identification methods can handle (non-)linear time-periodic [(N)LTP] systems in open-loop with a quantification of (i) the noise and/or the NL distortions, (ii) the TP distortions and (iii) the transient (leakage) errors. Besides, a geometrical interpretation of the BLTI approximation is provided, leading to a framework called vector FRF analysis. The theory presented is supported by numerical simulations as well as real measurements mimicking the well-known mechanical Mathieu oscillator.

Workflow Optimization in Vertebrobasilar Occlusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamper, Lars, E-mail: lars.kamper@helios-kliniken.de; Meyn, Hannes; Rybacki, Konrad

2012-06-15

Objective: In vertebrobasilar occlusion, rapid recanalization is the only substantial means to improve the prognosis. We introduced a standard operating procedure (SOP) for interventional therapy to analyze the effects on interdisciplinary time management. Methods: Intrahospital time periods between hospital admission and neuroradiological intervention were retrospectively analyzed, together with the patients' outcome, before (n = 18) and after (n = 20) implementation of the SOP. Results: After implementation of the SOP, we observed statistically significant improvement of postinterventional patient neurological status (p = 0.017). In addition, we found a decrease of 5:33 h for the mean time period from hospital admissionmore » until neuroradiological intervention. The recanalization rate increased from 72.2% to 80% after implementation of the SOP. Conclusion: Our results underscore the relevance of SOP implementation and analysis of time management for clinical workflow optimization. Both may trigger awareness for the need of efficient interdisciplinary time management. This could be an explanation for the decreased time periods and improved postinterventional patient status after SOP implementation.« less

Non-nuclear methods for HMA density measurements : final report, June 2008.

DOT National Transportation Integrated Search

2008-05-01

Non-nuclear methods for the measurement of hot-mix asphalt (HMA) density offer the ability to take numerous density readings in a very short period of time, without the need for intensive licensing, training, and maintenance efforts common to nuclear...

Production of hydrocarbons from hydrates. [DOE patent application

DOEpatents

McGuire, P.L.

1981-09-08

An economical and safe method of producing hydrocarbons (or natural gas) from in situ hydrocarbon-containing hydrates is given. Once started, the method will be self-driven and will continue producing hydrocarbons over an extended period of time (i.e., many days).

Using New Theory and Experimental Methods to Understand the Relative Controls of Storage, Antecedent Conditions and Precipitation Intensity on Transit Time Distributions through a Sloping Soil Lysimeter

NASA Astrophysics Data System (ADS)

Kim, M.; Pangle, L. A.; Cardoso, C.; Lora, M.; Wang, Y.; Harman, C. J.; Troch, P. A. A.

2014-12-01

Transit time distributions (TTD) are an efficient way of characterizing transport through the complex flow dynamics of a hydrologic system, and can serve as a basis for spatially-integrated solute transport modeling. Recently there has been progress in the development of a theory of time-variable TTDs that captures the effect of temporal variability in the timing of fluxes as well as changes in flow pathways. Furthermore, a new formulation of this theory allows the essential transport properties of a system to be parameterized by a physically meaningful time-variable probability distribution, the Ω function. This distribution determines how the age distribution of water in storage is sampled by the outflow. The form of the Ω function varies if the flow pathways change, but is not determined by the timing of fluxes (unlike the TTD). In this study, we use this theory to characterize transport by transient flows through a homogeneously packed 1 m3 sloping soil lysimeter. The transit time distribution associated with each of four irrigation periods (repeated daily for 24 days) are compared to examine the significance of changes in the Ω function due to variations in total storage, antecedent conditions, and precipitation intensity. We observe both the time-variable TTD and the Ω function experimentally by applying the PERTH method (Harman and Kim, 2014, GRL, 41, 1567-1575). The method allows us to observe multiple overlapping time-variable TTD in controlled experiments using only two conservative tracers. We hypothesize that both the TTD and the Ω function will vary in time, even in this small scale, because water will take different flow pathways depending on the initial state of the lysimeter and irrigation intensity. However, based on primarily modeling, we conjecture that major variability in the Ω function will be limited to a period during and immediately after each irrigation. We anticipate the Ω function is almost time-invariant (or scales simply with total storage) during the recession period because flow pathways are stable during this period. This is one of the first experimental studies of this type, and the results offer insights into solute transport in transient, variably-saturated systems.

Femtosecond Carrier Processes in Compound Semiconductors and Real Time Signal Processing

DTIC Science & Technology

1993-03-10

Blocks in Real Schur Form" ................... 179 5. "The Periodic Schur Decomposition. Algorithms and A p p lication s...existence of short period superlattices (confined LO GaAs and AlAs vibrations) on all samples produced with this method. The degret of deposition zone...small amount of zone intermixing occurs in the spatially separated growth mode (see 1 Figure 1b), the short period superlattices have graded interfaces

An Empirical Analysis of the Cascade Secret Key Reconciliation Protocol for Quantum Key Distribution

DTIC Science & Technology

2011-09-01

performance with the parity checks within each pass increasing and as a result, the processing time is expected to increase as well. A conclusion is drawn... timely manner has driven efforts to develop new key distribution methods. The most promising method is Quantum Key Distribution (QKD) and is...thank the QKD Project Team for all of the insight and support they provided in such a short time period. Thanks are especially in order for my

Methodological challenges to control for immortal time bias in addressing drug effects in type 2 diabetes

PubMed Central

Yang, Xi-Lin; Huo, Xiao-Xu; Chan, Juliana CN

2015-01-01

There are multiple biases in using observational studies to examine treatment effects such as those from prevalent drug users, immortal time and drug indications. We used renin angiotensin system (RAS) inhibitors and statins as reference drugs with proven efficacies in randomized clinical trials (RCTs) and examined their effectiveness in the prospective Hong Kong Diabetes Registry using adjustment methods proposed in the literature. Using time-dependent exposures to drug treatments yielded greatly inflated hazard ratios (HR) regarding the treatment effects of these drugs for cardiovascular disease (CVD) in type 2 diabetes. These errors were probably due to changing indications to use these drugs during follow up periods, especially at the time of drug commencement making time-dependent analysis extremely problematic. Using time-fixed analysis with exclusion of immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of RAS inhibitors for CVD was comparable to that in RCT. The result supported the use of the Registry for performing pharmacoepidemiological analysis which revealed an attenuated low low-density lipoprotein cholesterol related cancer risk with RAS inhibitors. On the other hand, time-fixed analysis with including immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of statins for CVD was similar to that in the RCT. Our results highlight the complexity and difficulty in removing these biases. We call for validations of the methods to cope with immortal time and drug use indications before applying them to particular research questions, so to avoid making erroneous conclusions. PMID:26413484

Methodological challenges to control for immortal time bias in addressing drug effects in type 2 diabetes.

PubMed

Yang, Xi-Lin; Huo, Xiao-Xu; Chan, Juliana Cn

2015-09-26

There are multiple biases in using observational studies to examine treatment effects such as those from prevalent drug users, immortal time and drug indications. We used renin angiotensin system (RAS) inhibitors and statins as reference drugs with proven efficacies in randomized clinical trials (RCTs) and examined their effectiveness in the prospective Hong Kong Diabetes Registry using adjustment methods proposed in the literature. Using time-dependent exposures to drug treatments yielded greatly inflated hazard ratios (HR) regarding the treatment effects of these drugs for cardiovascular disease (CVD) in type 2 diabetes. These errors were probably due to changing indications to use these drugs during follow up periods, especially at the time of drug commencement making time-dependent analysis extremely problematic. Using time-fixed analysis with exclusion of immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of RAS inhibitors for CVD was comparable to that in RCT. The result supported the use of the Registry for performing pharmacoepidemiological analysis which revealed an attenuated low low-density lipoprotein cholesterol related cancer risk with RAS inhibitors. On the other hand, time-fixed analysis with including immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of statins for CVD was similar to that in the RCT. Our results highlight the complexity and difficulty in removing these biases. We call for validations of the methods to cope with immortal time and drug use indications before applying them to particular research questions, so to avoid making erroneous conclusions.

Indirect spectrophotometric determination of arbutin, whitening agent through oxidation by periodate and complexation with ferric chloride

NASA Astrophysics Data System (ADS)

Barsoom, B. N.; Abdelsamad, A. M. E.; Adib, N. M.

2006-07-01

A simple and accurate spectrophotometric method for the determination of arbutin (glycosylated hydroquinone) is described. It is based on the oxidation of arbutin by periodate in presence of iodate. Excess periodate causes liberation of iodine at pH 8.0. The unreacted periodate is determined by measurement of the liberated iodine spectrophotometrically in the wavelength range (300-500 nm). A calibration curve was constructed for more accurate results and the correlation coefficient of linear regression analysis was -0.9778. The precision of this method was better than 6.17% R.S.D. ( n = 3). Regression analysis of Bear-Lambert plot shows good correlation in the concentration range 25-125 ug/ml. The identification limit was determined to be 25 ug/ml a detailed study of the reaction conditions was carried out, including effect of changing pH, time, temperature and volume of periodate. Analyzing pure and authentic samples containing arbutin tested the validity of the proposed method which has an average percent recovery of 100.86%. An alternative method is also proposed which involves a complexation reaction between arbutin and ferric chloride solution. The produced complex which is yellowish-green in color was determined spectophotometrically.

Tracing temperature in a nanometer size region in a picosecond time period.

PubMed

Nakajima, Kaoru; Kitayama, Takumi; Hayashi, Hiroaki; Matsuda, Makoto; Sataka, Masao; Tsujimoto, Masahiko; Toulemonde, Marcel; Bouffard, Serge; Kimura, Kenji

2015-08-21

Irradiation of materials with either swift heavy ions or slow highly charged ions leads to ultrafast heating on a timescale of several picosecond in a region of several nanometer. This ultrafast local heating result in formation of nanostructures, which provide a number of potential applications in nanotechnologies. These nanostructures are believed to be formed when the local temperature rises beyond the melting or boiling point of the material. Conventional techniques, however, are not applicable to measure temperature in such a localized region in a short time period. Here, we propose a novel method for tracing temperature in a nanometer region in a picosecond time period by utilizing desorption of gold nanoparticles around the ion impact position. The feasibility is examined by comparing with the temperature evolution predicted by a theoretical model.

Exponential synchronization of chaotic systems with time-varying delays and parameter mismatches via intermittent control.

PubMed

Cai, Shuiming; Hao, Junjun; Liu, Zengrong

2011-06-01

This paper studies the synchronization of coupled chaotic systems with time-varying delays in the presence of parameter mismatches by means of periodically intermittent control. Some novel and useful quasisynchronization criteria are obtained by using the methods which are different from the techniques employed in the existing works, and the derived results are less conservative. Especially, a strong constraint on the control width that the control width should be larger than the time delay imposed by the current references is released in this paper. Moreover, our results show that the synchronization criteria depend on the ratio of control width to control period, but not the control width or the control period. Finally, some numerical simulations are given to show the effectiveness of the theoretical results.

Seasonality and synchrony of reproduction in three species of nectarivorous Philippines bats

PubMed Central

Heideman, Paul D; Utzurrum, Ruth CB

2003-01-01

Background Differences among species and among years in reproductive seasonality (the tendency for clusters of events to fall at approximately the same point in each year) and synchrony (amount of clustering of events within a year) have been intensively studied in bats, but are difficult to assess. Here, we use randomization methods with circular statistics to test for synchrony and seasonality of reproduction in three species of nectarivorous megachiropteran bats on Negros Island in the central Philippines. Results In Rousettus amplexicaudatus, estimated dates of birth were both highly synchronous and highly seasonal. In Macroglossus minimus, estimated births were seasonal and significantly clustered within years, but within each year births occurred over a broad period, indicating a low level of synchrony. In Eonycteris spelaea, estimated births were also seasonal and had statistically significant synchrony, with birth periods within years intermediate in synchrony between R. amplexicaudatus and M. minimus. All three species had a similar seasonal pattern, with two birth periods in each year, centered on March or April and August or September. In one species, R. amplexicaudatus, primigravid females (in their first pregnancy) produced their young in June and July, a birth period significantly different in timing from the two birth periods of older adult females. This more conservative pattern of young females may allow higher survival of parents and offspring at cost of a lost reproductive opportunity. There was weak evidence that in some years primigravid females of M. minimus might differ in timing from older adults. There were few significant differences in reproductive timing among different years, and those differences were generally less than two weeks, even during a severe drought in the severe el Niño of 1983. Conclusion The results suggest that these species follow an obligately seasonal pattern of reproductive timing with very little phenotypic plasticity. The resampling methods were sensitive to differences in timing of under two weeks, in some cases, suggesting that these are useful methods for analyses of seasonality in wild populations of bats. PMID:14633285

PERIODOGRAMS FOR MULTIBAND ASTRONOMICAL TIME SERIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

VanderPlas, Jacob T.; Ivezic, Željko

This paper introduces the multiband periodogram, a general extension of the well-known Lomb–Scargle approach for detecting periodic signals in time-domain data. In addition to advantages of the Lomb–Scargle method such as treatment of non-uniform sampling and heteroscedastic errors, the multiband periodogram significantly improves period finding for randomly sampled multiband light curves (e.g., Pan-STARRS, DES, and LSST). The light curves in each band are modeled as arbitrary truncated Fourier series, with the period and phase shared across all bands. The key aspect is the use of Tikhonov regularization which drives most of the variability into the so-called base model common tomore » all bands, while fits for individual bands describe residuals relative to the base model and typically require lower-order Fourier series. This decrease in the effective model complexity is the main reason for improved performance. After a pedagogical development of the formalism of least-squares spectral analysis, which motivates the essential features of the multiband model, we use simulated light curves and randomly subsampled SDSS Stripe 82 data to demonstrate the superiority of this method compared to other methods from the literature and find that this method will be able to efficiently determine the correct period in the majority of LSST’s bright RR Lyrae stars with as little as six months of LSST data, a vast improvement over the years of data reported to be required by previous studies. A Python implementation of this method, along with code to fully reproduce the results reported here, is available on GitHub.« less

7 CFR 550.22 - Payment.

Code of Federal Regulations, 2010 CFR

2010-01-01

... GENERAL ADMINISTRATIVE POLICY FOR NON-ASSISTANCE COOPERATIVE AGREEMENTS Management of Agreements Financial Management § 550.22 Payment. (a) Payment methods shall minimize the time elapsing between the transfer of...) The time period covered by the invoice; and (vii) Total dollar amount itemized by budget categories...

The evolution of spillover effects between oil and stock markets across multi-scales using a wavelet-based GARCH-BEKK model

NASA Astrophysics Data System (ADS)

Liu, Xueyong; An, Haizhong; Huang, Shupei; Wen, Shaobo

2017-01-01

Aiming to investigate the evolution of mean and volatility spillovers between oil and stock markets in the time and frequency dimensions, we employed WTI crude oil prices, the S&P 500 (USA) index and the MICEX index (Russia) for the period Jan. 2003-Dec. 2014 as sample data. We first applied a wavelet-based GARCH-BEKK method to examine the spillover features in frequency dimension. To consider the evolution of spillover effects in time dimension at multiple-scales, we then divided the full sample period into three sub-periods, pre-crisis period, crisis period, and post-crisis period. The results indicate that spillover effects vary across wavelet scales in terms of strength and direction. By analysis the time-varying linkage, we found the different evolution features of spillover effects between the Oil-US stock market and Oil-Russia stock market. The spillover relationship between oil and US stock market is shifting to short-term while the spillover relationship between oil and Russia stock market is changing to all time scales. That result implies that the linkage between oil and US stock market is weakening in the long-term, and the linkage between oil and Russia stock market is getting close in all time scales. This may explain the phenomenon that the US stock index and the Russia stock index showed the opposite trend with the falling of oil price in the post-crisis period.

First-order reactant in homogeneous turbulence before the final period of decay. [contaminant fluctuations in chemical reaction

NASA Technical Reports Server (NTRS)

Kumar, P.; Patel, S. R.

1974-01-01

A method is described for studying theoretically the concentration fluctuations of a dilute contaminate undergoing a first-order chemical reaction. The method is based on Deissler's (1958) theory for homogeneous turbulence for times before the final period, and it follows the approach used by Loeffler and Deissler (1961) to study temperature fluctuations in homogeneous turbulence. Four-point correlation equations are obtained; it is assumed that terms containing fifth-order correlation are very small in comparison with those containing fourth-order correlations, and can therefore be neglected. A spectrum equation is obtained in a form which can be solved numerically, yielding the decay law for the concentration fluctuations in homogeneous turbulence for the period much before the final period of decay.

Analysis of Nonstationary Time Series for Biological Rhythms Research.

PubMed

Leise, Tanya L

2017-06-01

This article is part of a Journal of Biological Rhythms series exploring analysis and statistics topics relevant to researchers in biological rhythms and sleep research. The goal is to provide an overview of the most common issues that arise in the analysis and interpretation of data in these fields. In this article on time series analysis for biological rhythms, we describe some methods for assessing the rhythmic properties of time series, including tests of whether a time series is indeed rhythmic. Because biological rhythms can exhibit significant fluctuations in their period, phase, and amplitude, their analysis may require methods appropriate for nonstationary time series, such as wavelet transforms, which can measure how these rhythmic parameters change over time. We illustrate these methods using simulated and real time series.

Apparatus and method for maximizing power delivered by a photovoltaic array

DOEpatents

Muljadi, Eduard; Taylor, Roger W.

1998-01-01

A method and apparatus for maximizing the electric power output of a photovoltaic array connected to a battery where the voltage across the photovoltaic array is adjusted through a range of voltages to find the voltage across the photovoltaic array that maximizes the electric power generated by the photovoltaic array and then is held constant for a period of time. After the period of time has elapsed, the electric voltage across the photovoltaic array is again adjusted through a range of voltages and the process is repeated. The electric energy and the electric power generated by the photovoltaic array is delivered to the battery which stores the electric energy and the electric power for later delivery to a load.

Apparatus and method for maximizing power delivered by a photovoltaic array

DOEpatents

Muljadi, E.; Taylor, R.W.

1998-05-05

A method and apparatus for maximizing the electric power output of a photovoltaic array connected to a battery where the voltage across the photovoltaic array is adjusted through a range of voltages to find the voltage across the photovoltaic array that maximizes the electric power generated by the photovoltaic array and then is held constant for a period of time. After the period of time has elapsed, the electric voltage across the photovoltaic array is again adjusted through a range of voltages and the process is repeated. The electric energy and the electric power generated by the photovoltaic array is delivered to the battery which stores the electric energy and the electric power for later delivery to a load. 20 figs.

The role of parents in motivation for orthodontic treatment for children.

PubMed

Karasiunok, Anna Ye; Smahliuk, Liubov V

2018-01-01

Introduction: One of the main features of orthodontic treatment is the cooperation of the doctor with the patient. Active growth of a child's organism at the age from 6 to 12 has not only physiological but also psychological aspects of development. Motivation for orthodontic treatment is absent during mixed dentition. Only taking into account the somato-psychological status and the psycho-emotional condition of the patient during the orthodontic treatment allows to choose an optimal treatment option and to predict its effectiveness. The aim: The aim of our study was to increase the motivation for orthodontic treatment for children during the period of mixed dentition by using informative and accessible psychological methods to raise awareness and the role of parents. Materials and methods: 30 patients at the age from 6 to 12 received orthodontic treatment. The treatment contains targeted psychological training, aimed at activating, strengthening and reinforcing the motivation for treatment for children and their parents. Results: The proposed method gives a significant reduction in the percentage of treatment interruption - according to the literature up to 35.7%, in our study - up to 13.4%. The active treatment period decreased by 1.6 times, and the patient's lack of discipline - by 4 times compared with the control group. There were 2.5 times less undisciplined patients in the experimental group than in the control group. Conclusions: The obtained results testify to the necessity of using psychological methods to increase the motivation for orthodontic treatment for children during the period of mixed dentition.

Downlink Probability Density Functions for EOS-McMurdo Sound

NASA Technical Reports Server (NTRS)

Christopher, P.; Jackson, A. H.

1996-01-01

The visibility times and communication link dynamics for the Earth Observations Satellite (EOS)-McMurdo Sound direct downlinks have been studied. The 16 day EOS periodicity may be shown with the Goddard Trajectory Determination System (GTDS) and the entire 16 day period should be simulated for representative link statistics. We desire many attributes of the downlink, however, and a faster orbital determination method is desirable. We use the method of osculating elements for speed and accuracy in simulating the EOS orbit. The accuracy of the method of osculating elements is demonstrated by closely reproducing the observed 16 day Landsat periodicity. An autocorrelation function method is used to show the correlation spike at 16 days. The entire 16 day record of passes over McMurdo Sound is then used to generate statistics for innage time, outage time, elevation angle, antenna angle rates, and propagation loss. The levation angle probability density function is compared with 1967 analytic approximation which has been used for medium to high altitude satellites. One practical result of this comparison is seen to be the rare occurrence of zenith passes. The new result is functionally different than the earlier result, with a heavy emphasis on low elevation angles. EOS is one of a large class of sun synchronous satellites which may be downlinked to McMurdo Sound. We examine delay statistics for an entire group of sun synchronous satellites ranging from 400 km to 1000 km altitude. Outage probability density function results are presented three dimensionally.

Quantum gates by periodic driving

PubMed Central

Shi, Z. C.; Wang, W.; Yi, X. X.

2016-01-01

Topological quantum computation has been extensively studied in the past decades due to its robustness against decoherence. One way to realize the topological quantum computation is by adiabatic evolutions—it requires relatively long time to complete a gate, so the speed of quantum computation slows down. In this work, we present a method to realize single qubit quantum gates by periodic driving. Compared to adiabatic evolution, the single qubit gates can be realized at a fixed time much shorter than that by adiabatic evolution. The driving fields can be sinusoidal or square-well field. With the sinusoidal driving field, we derive an expression for the total operation time in the high-frequency limit, and an exact analytical expression for the evolution operator without any approximations is given for the square well driving. This study suggests that the period driving could provide us with a new direction in regulations of the operation time in topological quantum computation. PMID:26911900

Quantum gates by periodic driving.

PubMed

Shi, Z C; Wang, W; Yi, X X

2016-02-25

Topological quantum computation has been extensively studied in the past decades due to its robustness against decoherence. One way to realize the topological quantum computation is by adiabatic evolutions-it requires relatively long time to complete a gate, so the speed of quantum computation slows down. In this work, we present a method to realize single qubit quantum gates by periodic driving. Compared to adiabatic evolution, the single qubit gates can be realized at a fixed time much shorter than that by adiabatic evolution. The driving fields can be sinusoidal or square-well field. With the sinusoidal driving field, we derive an expression for the total operation time in the high-frequency limit, and an exact analytical expression for the evolution operator without any approximations is given for the square well driving. This study suggests that the period driving could provide us with a new direction in regulations of the operation time in topological quantum computation.

Flexibly imposing periodicity in kernel independent FMM: A multipole-to-local operator approach

NASA Astrophysics Data System (ADS)

Yan, Wen; Shelley, Michael

2018-02-01

An important but missing component in the application of the kernel independent fast multipole method (KIFMM) is the capability for flexibly and efficiently imposing singly, doubly, and triply periodic boundary conditions. In most popular packages such periodicities are imposed with the hierarchical repetition of periodic boxes, which may give an incorrect answer due to the conditional convergence of some kernel sums. Here we present an efficient method to properly impose periodic boundary conditions using a near-far splitting scheme. The near-field contribution is directly calculated with the KIFMM method, while the far-field contribution is calculated with a multipole-to-local (M2L) operator which is independent of the source and target point distribution. The M2L operator is constructed with the far-field portion of the kernel function to generate the far-field contribution with the downward equivalent source points in KIFMM. This method guarantees the sum of the near-field & far-field converge pointwise to results satisfying periodicity and compatibility conditions. The computational cost of the far-field calculation observes the same O (N) complexity as FMM and is designed to be small by reusing the data computed by KIFMM for the near-field. The far-field calculations require no additional control parameters, and observes the same theoretical error bound as KIFMM. We present accuracy and timing test results for the Laplace kernel in singly periodic domains and the Stokes velocity kernel in doubly and triply periodic domains.

Photonic time crystals.

PubMed

Zeng, Lunwu; Xu, Jin; Wang, Chengen; Zhang, Jianhua; Zhao, Yuting; Zeng, Jing; Song, Runxia

2017-12-07

When space (time) translation symmetry is spontaneously broken, the space crystal (time crystal) forms; when permittivity and permeability periodically vary with space (time), the photonic crystal (photonic time crystal) forms. We proposed the concept of photonic time crystal and rewritten the Maxwell's equations. Utilizing Finite Difference Time Domain (FDTD) method, we simulated electromagnetic wave propagation in photonic time crystal and photonic space-time crystal, the simulation results show that more intensive scatter fields can obtained in photonic time crystal and photonic space-time crystal.

Effects of shallow-layer reverberation on measurement of teleseismic P-wave travel times for ocean bottom seismograph data

NASA Astrophysics Data System (ADS)

Obayashi, Masayuki; Ishihara, Yasushi; Suetsugu, Daisuke

2017-03-01

We conducted synthetic experiments to evaluate the effects of shallow-layer reverberation in oceanic regions on P-wave travel times measured by waveform cross-correlation. Time shift due to waveform distortion by the reverberation was estimated as a function of period. Reverberations in the crystalline crust advance the P-waves by a frequency-independent time shift of about 0.3 s in oceans. Sediment does not affect the time shifts in the mid-ocean regions, but effects as large as -0.8 s or more occur where sediment thickness is greater than 600 m for periods longer than 15 s. The water layer causes time delays (+0.3 s) in the relatively shallow (<3500 m) water region for periods longer than 20 s. The time shift may influence mantle images obtained if the reverberation effects are not accounted for in seismic tomography. We propose a simple method to correct relative P-wave travel times at two sites for shallow-layer reverberation by the cross-convolution of the crustal responses at the two sites. [Figure not available: see fulltext. Caption: .

Novel blood pressure and pulse pressure estimation based on pulse transit time and stroke volume approximation.

PubMed

Lee, Joonnyong; Sohn, JangJay; Park, Jonghyun; Yang, SeungMan; Lee, Saram; Kim, Hee Chan

2018-06-18

Non-invasive continuous blood pressure monitors are of great interest to the medical community due to their value in hypertension management. Recently, studies have shown the potential of pulse pressure as a therapeutic target for hypertension, but not enough attention has been given to non-invasive continuous monitoring of pulse pressure. Although accurate pulse pressure estimation can be of direct value to hypertension management and indirectly to the estimation of systolic blood pressure, as it is the sum of pulse pressure and diastolic blood pressure, only a few inadequate methods of pulse pressure estimation have been proposed. We present a novel, non-invasive blood pressure and pulse pressure estimation method based on pulse transit time and pre-ejection period. Pre-ejection period and pulse transit time were measured non-invasively using electrocardiogram, seismocardiogram, and photoplethysmogram measured from the torso. The proposed method used the 2-element Windkessel model to model pulse pressure with the ratio of stroke volume, approximated by pre-ejection period, and arterial compliance, estimated by pulse transit time. Diastolic blood pressure was estimated using pulse transit time, and systolic blood pressure was estimated as the sum of the two estimates. The estimation method was verified in 11 subjects in two separate conditions with induced cardiovascular response and the results were compared against a reference measurement and values obtained from a previously proposed method. The proposed method yielded high agreement with the reference (pulse pressure correlation with reference R ≥ 0.927, diastolic blood pressure correlation with reference R ≥ 0.854, systolic blood pressure correlation with reference R ≥ 0.914) and high estimation accuracy in pulse pressure (mean root-mean-squared error ≤ 3.46 mmHg) and blood pressure (mean root-mean-squared error ≤ 6.31 mmHg for diastolic blood pressure and ≤ 8.41 mmHg for systolic blood pressure) over a wide range of hemodynamic changes. The proposed pulse pressure estimation method provides accurate estimates in situations with and without significant changes in stroke volume. The proposed method improves upon the currently available systolic blood pressure estimation methods by providing accurate pulse pressure estimates.

Arima model and exponential smoothing method: A comparison

NASA Astrophysics Data System (ADS)

Wan Ahmad, Wan Kamarul Ariffin; Ahmad, Sabri

2013-04-01

This study shows the comparison between Autoregressive Moving Average (ARIMA) model and Exponential Smoothing Method in making a prediction. The comparison is focused on the ability of both methods in making the forecasts with the different number of data sources and the different length of forecasting period. For this purpose, the data from The Price of Crude Palm Oil (RM/tonne), Exchange Rates of Ringgit Malaysia (RM) in comparison to Great Britain Pound (GBP) and also The Price of SMR 20 Rubber Type (cents/kg) with three different time series are used in the comparison process. Then, forecasting accuracy of each model is measured by examinethe prediction error that producedby using Mean Squared Error (MSE), Mean Absolute Percentage Error (MAPE), and Mean Absolute deviation (MAD). The study shows that the ARIMA model can produce a better prediction for the long-term forecasting with limited data sources, butcannot produce a better prediction for time series with a narrow range of one point to another as in the time series for Exchange Rates. On the contrary, Exponential Smoothing Method can produce a better forecasting for Exchange Rates that has a narrow range of one point to another for its time series, while itcannot produce a better prediction for a longer forecasting period.

Joint distribution of temperature and precipitation in the Mediterranean, using the Copula method

NASA Astrophysics Data System (ADS)

Lazoglou, Georgia; Anagnostopoulou, Christina

2018-03-01

This study analyses the temperature and precipitation dependence among stations in the Mediterranean. The first station group is located in the eastern Mediterranean (EM) and includes two stations, Athens and Thessaloniki, while the western (WM) one includes Malaga and Barcelona. The data was organized in two time periods, the hot-dry period and the cold-wet one, composed of 5 months, respectively. The analysis is based on a new statistical technique in climatology: the Copula method. Firstly, the calculation of the Kendall tau correlation index showed that temperatures among stations are dependant during both time periods whereas precipitation presents dependency only between the stations located in EM or WM and only during the cold-wet period. Accordingly, the marginal distributions were calculated for each studied station, as they are further used by the copula method. Finally, several copula families, both Archimedean and Elliptical, were tested in order to choose the most appropriate one to model the relation of the studied data sets. Consequently, this study achieves to model the dependence of the main climate parameters (temperature and precipitation) with the Copula method. The Frank copula was identified as the best family to describe the joint distribution of temperature, for the majority of station groups. For precipitation, the best copula families are BB1 and Survival Gumbel. Using the probability distribution diagrams, the probability of a combination of temperature and precipitation values between stations is estimated.

Public Health and Law Collaboration: The Philadelphia Lead Court Study

PubMed Central

Gracely, Ed; Pan, Sarah; Cummings, Curtis; Palermo, Peter; Gould, George

2013-01-01

Objectives. We determined whether Philadelphia Lead Court is effective in enforcing lead hazard remediation in the homes of children with elevated blood lead levels. Methods. We created a deidentified data set for properties with an initial failed home inspection (IFHI) for lead hazards from January 1, 1998, through December 31, 2008, and compared compliance rates within the first year and time to compliance for lead hazard remediation between 1998 and 2002 (precourt period) and between 2003 and 2008 (court period). We evaluated predictors of time to compliance. Results. Within 1 year of the IFHI, 6.6% of the precourt and 76.8% of the court cases achieved compliance (P < .001) for the 3764 homes with data. Four years after the IFHI, 18% had attained compliance in the precourt period compared with 83.1% for the court period (P < .001). A proportional hazard analysis found that compliance was 8 times more likely in the court than the precourt period (P < .001). Conclusions. Lead court was more effective than precourt enforcement strategies. Most properties were remediated within 1 year of the IFHI, and time to compliance was significantly reduced. This model court could be replicated in other cities with similar enforcement problems. PMID:23678927

An observational method for fast stochastic X-ray polarimetry timing

NASA Astrophysics Data System (ADS)

Ingram, Adam R.; Maccarone, Thomas J.

2017-11-01

The upcoming launch of the first space based X-ray polarimeter in ˜40 yr will provide powerful new diagnostic information to study accreting compact objects. In particular, analysis of rapid variability of the polarization degree and angle will provide the opportunity to probe the relativistic motions of material in the strong gravitational fields close to the compact objects, and enable new methods to measure black hole and neutron star parameters. However, polarization properties are measured in a statistical sense, and a statistically significant polarization detection requires a fairly long exposure, even for the brightest objects. Therefore, the sub-minute time-scales of interest are not accessible using a direct time-resolved analysis of polarization degree and angle. Phase-folding can be used for coherent pulsations, but not for stochastic variability such as quasi-periodic oscillations. Here, we introduce a Fourier method that enables statistically robust detection of stochastic polarization variability for arbitrarily short variability time-scales. Our method is analogous to commonly used spectral-timing techniques. We find that it should be possible in the near future to detect the quasi-periodic swings in polarization angle predicted by Lense-Thirring precession of the inner accretion flow. This is contingent on the mean polarization degree of the source being greater than ˜4-5 per cent, which is consistent with the best current constraints on Cygnus X-1 from the late 1970s.

Method for determining the concentration of atomic species in gases and solids

DOEpatents

Loge, G.W.

1998-02-03

Method is described for determining the concentration of atomic species in gases and solids. The method involves measurement of at least two emission intensities from a species in a sample that is excited by incident laser radiation. This generates a plasma therein after a sufficient time period has elapsed and during a second time period, permits an instantaneous temperature to be established within the sample. The concentration of the atomic species to be determined is then derived from the known emission intensity of a predetermined concentration of that species in the sample at the measured temperature, a quantity which is measured prior to the determination of the unknown concentration, and the actual measured emission from the unknown species, or by this latter emission and the emission intensity of a species having known concentration within the sample such as nitrogen for gaseous air samples. 4 figs.

Mesoporous metal oxides and processes for preparation thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suib, Steven L.; Poyraz, Altug Suleyman

A process for preparing a mesoporous metal oxide, i.e., transition metal oxide. Lanthanide metal oxide, a post-transition metal oxide and metalloid oxide. The process comprises providing an acidic mixture comprising a metal precursor, an interface modifier, a hydrotropic ion precursor, and a surfactant; and heating the acidic mixture at a temperature and for a period of time sufficient to form the mesoporous metal oxide. A mesoporous metal oxide prepared by the above process. A method of controlling nano-sized wall crystallinity and mesoporosity in mesoporous metal oxides. The method comprises providing an acidic mixture comprising a metal precursor, an interface modifier,more » a hydrotropic ion precursor, and a surfactant; and heating the acidic mixture at a temperature and for a period of time sufficient to control nano-sized wall crystallinity and mesoporosity in the mesoporous metal oxides. Mesoporous metal oxides and a method of tuning structural properties of mesoporous metal oxides.« less

Method and apparatus for producing drops using a drop-on-demand dispenser

DOEpatents

Chen, Alvin U.; Basaran, Osman A.

2003-01-01

A method and apparatus for dispensing fluid from a drop-on-demand (DOD) fluid dispenser. The method involves withdrawing fluid in the dispenser for a first duration of time, followed by a second duration of time during which the fluid is propelled toward the orifice of the dispenser. Following the period during which the fluid is propelled, there is a second withdrawing of the fluid into the dispenser. The duration of the propelling period is shorter than the duration of either the first withdrawing or the second withdrawing. The propelling of the fluid results in the extension of a small tongue of fluid from the meniscus of the fluid. The second withdrawing of the fluid results in a retraction of the meniscus into the passageway such that only the small tongue of fluid separates and is ejected from the dispenser.

Methods for estimating population density in data-limited areas: evaluating regression and tree-based models in Peru.

PubMed

Anderson, Weston; Guikema, Seth; Zaitchik, Ben; Pan, William

2014-01-01

Obtaining accurate small area estimates of population is essential for policy and health planning but is often difficult in countries with limited data. In lieu of available population data, small area estimate models draw information from previous time periods or from similar areas. This study focuses on model-based methods for estimating population when no direct samples are available in the area of interest. To explore the efficacy of tree-based models for estimating population density, we compare six different model structures including Random Forest and Bayesian Additive Regression Trees. Results demonstrate that without information from prior time periods, non-parametric tree-based models produced more accurate predictions than did conventional regression methods. Improving estimates of population density in non-sampled areas is important for regions with incomplete census data and has implications for economic, health and development policies.

Methods for Estimating Population Density in Data-Limited Areas: Evaluating Regression and Tree-Based Models in Peru

PubMed Central

Anderson, Weston; Guikema, Seth; Zaitchik, Ben; Pan, William

2014-01-01

Obtaining accurate small area estimates of population is essential for policy and health planning but is often difficult in countries with limited data. In lieu of available population data, small area estimate models draw information from previous time periods or from similar areas. This study focuses on model-based methods for estimating population when no direct samples are available in the area of interest. To explore the efficacy of tree-based models for estimating population density, we compare six different model structures including Random Forest and Bayesian Additive Regression Trees. Results demonstrate that without information from prior time periods, non-parametric tree-based models produced more accurate predictions than did conventional regression methods. Improving estimates of population density in non-sampled areas is important for regions with incomplete census data and has implications for economic, health and development policies. PMID:24992657

A wavelet analysis of scaling laws and long-memory in stock market volatility

NASA Astrophysics Data System (ADS)

Vuorenmaa, Tommi A.

2005-05-01

This paper studies the time-varying behavior of scaling laws and long-memory. This is motivated by the earlier finding that in the FX markets a single scaling factor might not always be sufficient across all relevant timescales: a different region may exist for intradaily time-scales and for larger time-scales. In specific, this paper investigates (i) if different scaling regions appear in stock market as well, (ii) if the scaling factor systematically differs from the Brownian, (iii) if the scaling factor is constant in time, and (iv) if the behavior can be explained by the heterogenuity of the players in the market and/or by intraday volatility periodicity. Wavelet method is used because it delivers a multiresolution decomposition and has excellent local adaptiviness properties. As a consequence, a wavelet-based OLS method allows for consistent estimation of long-memory. Thus issues (i)-(iv) shed light on the magnitude and behavior of a long-memory parameter, as well. The data are the 5-minute volatility series of Nokia Oyj at the Helsinki Stock Exchange around the burst of the IT-bubble. Period one represents the era of "irrational exuberance" and another the time after it. The results show that different scaling regions (i.e. multiscaling) may appear in the stock markets and not only in the FX markets, the scaling factor and the long-memory parameter are systematically different from the Brownian and they do not have to be constant in time, and that the behavior can be explained for a significant part by an intraday volatility periodicity called the New York effect. This effect was magnified by the frenzy trading of short-term speculators in the bubble period. The found stronger long-memory is also attributable to irrational exuberance.

Reconstruction of fluorophore concentration variation in dynamic fluorescence molecular tomography.

PubMed

Zhang, Xuanxuan; Liu, Fei; Zuo, Simin; Shi, Junwei; Zhang, Guanglei; Bai, Jing; Luo, Jianwen

2015-01-01

Dynamic fluorescence molecular tomography (DFMT) is a potential approach for drug delivery, tumor detection, diagnosis, and staging. The purpose of DFMT is to quantify the changes of fluorescent agents in the bodies, which offer important information about the underlying physiological processes. However, the conventional method requires that the fluorophore concentrations to be reconstructed are stationary during the data collection period. As thus, it cannot offer the dynamic information of fluorophore concentration variation within the data collection period. In this paper, a method is proposed to reconstruct the fluorophore concentration variation instead of the fluorophore concentration through a linear approximation. The fluorophore concentration variation rate is introduced by the linear approximation as a new unknown term to be reconstructed and is used to obtain the time courses of fluorophore concentration. Simulation and phantom studies are performed to validate the proposed method. The results show that the method is able to reconstruct the fluorophore concentration variation rates and the time courses of fluorophore concentration with relative errors less than 0.0218.

Time Series Analysis of Sexual Assault Case Characteristics and the 2007–2008 Period of Post-Election Violence in Kenya

PubMed Central

Anastario, Michael P.; Adhiambo Onyango, Monica; Nyanyuki, Joan; Naimer, Karen; Muthoga, Rachel; Sirkin, Susannah; Barrick, Kelle; van Hasselt, Martijn; Aruasa, Wilson; Kibet, Cynthia; Omollo, Grace

2014-01-01

Background Following the declaration that President Mwai Kibaki was the winner of the Kenyan presidential election held on December 27, 2007, a period of post-election violence (PEV) took place. In this study, we aimed to identify whether the period of PEV in Kenya was associated with systematic changes in sexual assault case characteristics. Methods and Findings Medical records of 1,615 patients diagnosed with sexual assault between 2007 and 2011 at healthcare facilities in Eldoret (n = 569), Naivasha (n = 534), and Nakuru (n = 512) were retrospectively reviewed to examine characteristics of sexual assault cases over time. Time series and linear regression were used to examine temporal variation in case characteristics relative to the period of post-election violence in Kenya. Key informant interviews with healthcare workers at the sites were employed to triangulate findings. The time series of sexual assault case characteristics at these facilities were examined, with a specific focus on the December 2007–February 2008 period of post-election violence. Prais-Winsten estimates indicated that the three-month period of post-election violence was associated with a 22 percentage-point increase in cases where survivors did not know the perpetrator, a 20 percentage-point increase in cases with more than one perpetrator, and a 4 percentage-point increase in cases that had evidence of abdominal injury. The post-election violence period was also associated with an 18 percentage-point increase in survivors waiting >1 month to report to a healthcare facility. Sensitivity analyses confirmed that these characteristics were specific to the post-election violence time period. Conclusion These results demonstrate systematic patterns in sexual assault characteristics during the PEV period in Kenya. PMID:25170917

Verification of the ISO calibration method for field pyranometers under tropical sky conditions

NASA Astrophysics Data System (ADS)

Janjai, Serm; Tohsing, Korntip; Pattarapanitchai, Somjet; Detkhon, Pasakorn

2017-02-01

Field pyranomters need to be annually calibrated and the International Organization for Standardization (ISO) has defined a standard method (ISO 9847) for calibrating these pyranometers. According to this standard method for outdoor calibration, the field pyranometers have to be compared to a reference pyranometer for the period of 2 to 14 days, depending on sky conditions. In this work, the ISO 9847 standard method was verified under tropical sky conditions. To verify the standard method, calibration of field pyranometers was conducted at a tropical site located in Nakhon Pathom (13.82o N, 100.04o E), Thailand under various sky conditions. The conditions of the sky were monitored by using a sky camera. The calibration results for different time periods used for the calibration under various sky conditions were analyzed. It was found that the calibration periods given by this standard method could be reduced without significant change in the final calibration result. In addition, recommendation and discussion on the use of this standard method in the tropics were also presented.

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

NASA Astrophysics Data System (ADS)

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.

Capability of simultaneous Rayleigh LiDAR and O2 airglow measurements in exploring the short period wave characteristics

NASA Astrophysics Data System (ADS)

Taori, Alok; Raghunath, Karnam; Jayaraman, Achuthan

We use combination of simultaneous measurements made with Rayleigh lidar and O2 airglow monitoring to improve lidar investigation capability to cover a higher altitude range. We feed instantaneous O2 airglow temperatures instead the model values at the top altitude for subsequent integration method of temperature retrieval using Rayleigh lidar back scattered signals. Using this method, errors in the lidar temperature estimates converges at higher altitudes indicating better altitude coverage compared to regular methods where model temperatures are used instead of real-time measurements. This improvement enables the measurements of short period waves at upper mesospheric altitudes (~90 km). With two case studies, we show that above 60 km the few short period wave amplitude drastically increases while, some of the short period wave show either damping or saturation. We claim that by using such combined measurements, a significant and cost effective progress can be made in the understanding of short period wave processes which are important for the coupling across the different atmospheric regions.

Split-field FDTD method for oblique incidence study of periodic dispersive metallic structures.

PubMed

Baida, F I; Belkhir, A

2009-08-15

The study of periodic structures illuminated by a normally incident plane wave is a simple task that can be numerically simulated by the finite-difference time-domain (FDTD) method. On the contrary, for off-normal incidence, a widely modified algorithm must be developed in order to bypass the frequency dependence appearing in the periodic boundary conditions. After recently implementing this FDTD algorithm for pure dielectric materials, we here extend it to the study of metallic structures where dispersion can be described by analytical models. The accuracy of our code is demonstrated through comparisons with already-published results in the case of 1D and 3D structures.

Modeling long correlation times using additive binary Markov chains: Applications to wind generation time series.

PubMed

Weber, Juliane; Zachow, Christopher; Witthaut, Dirk

2018-03-01

Wind power generation exhibits a strong temporal variability, which is crucial for system integration in highly renewable power systems. Different methods exist to simulate wind power generation but they often cannot represent the crucial temporal fluctuations properly. We apply the concept of additive binary Markov chains to model a wind generation time series consisting of two states: periods of high and low wind generation. The only input parameter for this model is the empirical autocorrelation function. The two-state model is readily extended to stochastically reproduce the actual generation per period. To evaluate the additive binary Markov chain method, we introduce a coarse model of the electric power system to derive backup and storage needs. We find that the temporal correlations of wind power generation, the backup need as a function of the storage capacity, and the resting time distribution of high and low wind events for different shares of wind generation can be reconstructed.

Modeling long correlation times using additive binary Markov chains: Applications to wind generation time series

NASA Astrophysics Data System (ADS)

Weber, Juliane; Zachow, Christopher; Witthaut, Dirk

2018-03-01

Wind power generation exhibits a strong temporal variability, which is crucial for system integration in highly renewable power systems. Different methods exist to simulate wind power generation but they often cannot represent the crucial temporal fluctuations properly. We apply the concept of additive binary Markov chains to model a wind generation time series consisting of two states: periods of high and low wind generation. The only input parameter for this model is the empirical autocorrelation function. The two-state model is readily extended to stochastically reproduce the actual generation per period. To evaluate the additive binary Markov chain method, we introduce a coarse model of the electric power system to derive backup and storage needs. We find that the temporal correlations of wind power generation, the backup need as a function of the storage capacity, and the resting time distribution of high and low wind events for different shares of wind generation can be reconstructed.

Long-Term Warming Trends in Korea and Contribution of Urbanization: An Updated Assessment

NASA Astrophysics Data System (ADS)

Park, Bo-Joung; Kim, Yeon-Hee; Min, Seung-Ki; Kim, Maeng-Ki; Choi, Youngeun; Boo, Kyung-On; Shim, Sungbo

2017-10-01

This study conducted an updated analysis of the long-term temperature trends over South Korea and reassessed the contribution of the urbanization effect to the local warming trends. Linear trends were analyzed for three different periods over South Korea in order to consider possible inhomogeneity due to changes in the number of available stations: recent 103 years (1912-2014), 61 years (1954-2014), and 42 years (1973-2014). The local temperature has increased by 1.90°C, 1.35°C, and 0.99°C during the three periods, respectively, which are found 1.4-2.6 times larger than the global land mean trends. The countries located in the northern middle and high latitudes exhibit similar warming trends (about 1.5 times stronger than the global mean), suggesting a weak influence of urbanization on the local warming over South Korea. Urbanization contribution is assessed using two methods. First, results from "city minus rural" methods showed that 30-45% of the local warming trends during recent four decades are likely due to the urbanization effect, depending on station classification methods and analysis periods. Results from an "observation minus reanalysis" method using the Twentieth Century Reanalysis (20CR) data sets (v2 and v2c) indicated about 25-30% contribution of the urbanization effect to the local warming trend during the recent six decades. However, the urbanization contribution was estimated as low as 3-11% when considering the century-long period. Our results confirm large uncertainties in the estimation of urbanization contribution when using shorter-term periods and suggest that the urbanization contribution to the century-long warming trends could be much lower.

Method for reducing peak phase current and decreasing staring time for an internal combustion engine having an induction machine

DOEpatents

Amey, David L.; Degner, Michael W.

2002-01-01

A method for reducing the starting time and reducing the peak phase currents for an internal combustion engine that is started using an induction machine starter/alternator. The starting time is reduced by pre-fluxing the induction machine and the peak phase currents are reduced by reducing the flux current command after a predetermined period of time has elapsed and concurrent to the application of the torque current command. The method of the present invention also provides a strategy for anticipating the start command for an internal combustion engine and determines a start strategy based on the start command and the operating state of the internal combustion engine.

Real-time method and apparatus for measuring the temperature of a fluorescing phosphor

DOEpatents

Britton, Jr., Charles L.; Beshears, David L.; Simpson, Marc L.; Cates, Michael R.; Allison, Steve W.

1999-01-01

A method for determining the temperature of a fluorescing phosphor is provided, together with an apparatus for performing the method. The apparatus includes a photodetector for detecting light emitted by a phosphor irradiated with an excitation pulse and for converting the detected light into an electrical signal. The apparatus further includes a differentiator for differentiating the electrical signal and a zero-crossing discrimination circuit that outputs a pulse signal having a pulse width corresponding to the time period between the start of the excitation pulse and the time when the differentiated electrical signal reaches zero. The width of the output pulse signal is proportional to the decay-time constant of the phosphor.

[Analgesic quality in a postoperative pain service: continuous assessment with the cumulative sum (cusum) method].

PubMed

Baptista Macaroff, W M; Castroman Espasandín, P

2007-01-01

The aim of this study was to assess the cumulative sum (cusum) method for evaluating the performance of our hospital's acute postoperative pain service. The period of analysis was 7 months. Analgesic failure was defined as a score of 3 points or more on a simple numerical scale. Acceptable failure (p0) was set at 20% of patients upon admission to the postanesthetic recovery unit and at 7% 24 hours after surgery. Unacceptable failure was set at double the p0 rate at each time (40% and 14%, respectively). The unit's patient records were used to generate a cusum graph for each evaluation. Nine hundred four records were included. The rate of failure was 31.6% upon admission to the unit and 12.1% at the 24-hour postoperative assessment. The curve rose rapidly to the value set for p0 at both evaluation times (n = 14 and n = 17, respectively), later leveled off, and began to fall after 721 and 521 cases, respectively. Our study shows the efficacy of the cusum method for monitoring a proposed quality standard. The graph also showed periods of suboptimal performance that would not have been evident from analyzing the data en block. Thus the cusum method would facilitate rapid detection of periods in which quality declines.

Trend analysis of salt load and evaluation of the frequency of water-quality measurements for the Gunnison, the Colorado, and the Dolores rivers in Colorado and Utah

USGS Publications Warehouse

Kircher, J.E.; Dinicola, Richard S.; Middelburg, R.F.

1984-01-01

Monthly values were computed for water-quality constituents at four streamflow gaging stations in the Upper Colorado River basin for the determination of trends. Seasonal regression and seasonal Kendall trend analysis techniques were applied to two monthly data sets at each station site for four different time periods. A recently developed method for determining optimal water-discharge data-collection frequency was also applied to the monthly water-quality data. Trend analysis results varied with each monthly load computational method, period of record, and trend detection model used. No conclusions could be reached regarding which computational method was best to use in trend analysis. Time-period selection for analysis was found to be important with regard to intended use of the results. Seasonal Kendall procedures were found to be applicable to most data sets. Seasonal regression models were more difficult to apply and were sometimes of questionable validity; however, those results were more informative than seasonal Kendall results. The best model to use depends upon the characteristics of the data and the amount of trend information needed. The measurement-frequency optimization method had potential for application to water-quality data, but refinements are needed. (USGS)

Discretization of Continuous Time Discrete Scale Invariant Processes: Estimation and Spectra

NASA Astrophysics Data System (ADS)

Rezakhah, Saeid; Maleki, Yasaman

2016-07-01

Imposing some flexible sampling scheme we provide some discretization of continuous time discrete scale invariant (DSI) processes which is a subsidiary discrete time DSI process. Then by introducing some simple random measure we provide a second continuous time DSI process which provides a proper approximation of the first one. This enables us to provide a bilateral relation between covariance functions of the subsidiary process and the new continuous time processes. The time varying spectral representation of such continuous time DSI process is characterized, and its spectrum is estimated. Also, a new method for estimation time dependent Hurst parameter of such processes is provided which gives a more accurate estimation. The performance of this estimation method is studied via simulation. Finally this method is applied to the real data of S & P500 and Dow Jones indices for some special periods.

Equilibrium Solutions of the Logarithmic Hamiltonian Leapfrog for the N-body Problem

NASA Astrophysics Data System (ADS)

Minesaki, Yukitaka

2018-04-01

We prove that a second-order logarithmic Hamiltonian leapfrog for the classical general N-body problem (CGNBP) designed by Mikkola and Tanikawa and some higher-order logarithmic Hamiltonian methods based on symmetric multicompositions of the logarithmic algorithm exactly reproduce the orbits of elliptic relative equilibrium solutions in the original CGNBP. These methods are explicit symplectic methods. Before this proof, only some implicit discrete-time CGNBPs proposed by Minesaki had been analytically shown to trace the orbits of elliptic relative equilibrium solutions. The proof is therefore the first existence proof for explicit symplectic methods. Such logarithmic Hamiltonian methods with a variable time step can also precisely retain periodic orbits in the classical general three-body problem, which generic numerical methods with a constant time step cannot do.

Biometrical issues in the analysis of adverse events within the benefit assessment of drugs.

PubMed

Bender, Ralf; Beckmann, Lars; Lange, Stefan

2016-07-01

The analysis of adverse events plays an important role in the benefit assessment of drugs. Consequently, results on adverse events are an integral part of reimbursement dossiers submitted by pharmaceutical companies to health policy decision-makers. Methods applied in the analysis of adverse events commonly include simple standard methods for contingency tables. However, the results produced may be misleading if observations are censored at the time of discontinuation due to treatment switching or noncompliance, resulting in unequal follow-up periods. In this paper, we present examples to show that the application of inadequate methods for the analysis of adverse events in the reimbursement dossier can lead to a downgrading of the evidence on a drug's benefit in the subsequent assessment, as greater harm from the drug cannot be excluded with sufficient certainty. Legal regulations on the benefit assessment of drugs in Germany are presented, in particular, with regard to the analysis of adverse events. Differences in safety considerations between the drug approval process and the benefit assessment are discussed. We show that the naive application of simple proportions in reimbursement dossiers frequently leads to uninterpretable results if observations are censored and the average follow-up periods differ between treatment groups. Likewise, the application of incidence rates may be misleading in the case of recurrent events and unequal follow-up periods. To allow for an appropriate benefit assessment of drugs, adequate survival time methods accounting for time dependencies and duration of follow-up are required, not only for time-to-event efficacy endpoints but also for adverse events. © 2016 The Authors. Pharmaceutical Statistics published by John Wiley & Sons Ltd. © 2016 The Authors. Pharmaceutical Statistics published by John Wiley & Sons Ltd.

Record of the Solar Activity and of Other Geophysical Phenomenons in Tree Ring

NASA Astrophysics Data System (ADS)

Rigozo, Nivaor Rodolfo

1999-01-01

Tree ring studies are usually used to determine or verify climatic factors which prevail in a given place or region and may cause tree ring width variations. Few studies are dedicated to the geophysical phenomena which may underlie these tree ring width variations. In order to look for periodicities which may be associated to the solar activity and/or to other geophysical phenomena which may influence tree ring growth, a new interactive image analysis method to measure tree ring width was developed and is presented here. This method makes use of a computer and a high resolution flatbed scanner; a program was also developed in Interactive Data Language (IDL 5.0) to study ring digitized images and transform them into time series. The main advantage of this method is the tree ring image interactive analysis without needing complex and high cost instrumentation. Thirty-nine samples were collected: 12 from Concordia - S. C., 9 from Canela - R. S., 14 from Sao Francisco de Paula - R. S., one from Nova Petropolis - R. S., 2 from Sao Martinho da Serra - R. S. e one from Chile. Fit functions are applied to ring width time series to obtain the best long time range trend (growth rate of every tree) curves and are eliminated through a standardization process that gives the tree ring index time series from which is performed spectral analysis by maximum entropy method and iterative regression. The results obtained show periodicities close to 11 yr, 22 yr Hale solar cycles and 5.5 yr for all sampling locations 52 yr and Gleissberg cycles for Concordia - S. C. and Chile samples. El Nino events were also observed with periods around 4 e 7 yr.

Breathers, quasi-periodic and travelling waves for a generalized ?-dimensional Yu-Toda-Sasa-Fukayama equation in fluids

NASA Astrophysics Data System (ADS)

Hu, Wen-Qiang; Gao, Yi-Tian; Zhao, Chen; Jia, Shu-Liang; Lan, Zhong-Zhou

2017-07-01

Under investigation in this paper is a generalized ?-dimensional Yu-Toda-Sasa-Fukayama equation for the interfacial wave in a two-layer fluid or the elastic quasi-plane wave in a liquid lattice. By virtue of the binary Bell polynomials, bilinear form of this equation is obtained. With the help of the bilinear form, N-soliton solutions are obtained via the Hirota method, and a bilinear Bäcklund transformation is derived to verify the integrability. Homoclinic breather waves are obtained according to the homoclinic test approach, which is not only the space-periodic breather but also the time-periodic breather via the graphic analysis. Via the Riemann theta function, quasi one-periodic waves are constructed, which can be viewed as a superposition of the overlapping solitary waves, placed one period apart. Finally, soliton-like, periodical triangle-type, rational-type and solitary bell-type travelling waves are obtained by means of the polynomial expansion method.

Integrated pest management models and their dynamical behaviour.

PubMed

Tang, Sanyi; Xiao, Yanni; Chen, Lansun; Cheke, Robert A

2005-01-01

Two impulsive models of integrated pest management (IPM) strategies are proposed, one with fixed intervention times and the other with these unfixed. The first model allows natural enemies to survive but under some conditions may lead to extinction of the pest. We use a simple prey-dependent consumption model with fixed impulsive effects and show that there exists a globally stable pest-eradication periodic solution when the impulsive period is less than certain critical values. The effects of pest resistance to pesticides are also studied. The second model is constructed in the light of IPM practice such that when the pest population reaches the economic injury level (EIL), a combination of biological, cultural, and chemical tactics that reduce pests to tolerable levels is invoked. Using analytical methods, we show that there exists an orbitally asymptotically stable periodic solution with a maximum value no larger than the given Economic Threshold (ET). The complete expression for this periodic solution is given and the ET is evaluated for given parameters. We also show that in some cases control costs can be reduced by replacing IPM interventions at unfixed times with periodic interventions. Further, we show that small perturbations of the system do not affect the existence and stability of the periodic solution. Thus, we provide the first demonstration using mathematical models that an IPM strategy is more effective than classical control methods.

Accuracy of two geocoding methods for geographic information system-based exposure assessment in epidemiological studies.

PubMed

Faure, Elodie; Danjou, Aurélie M N; Clavel-Chapelon, Françoise; Boutron-Ruault, Marie-Christine; Dossus, Laure; Fervers, Béatrice

2017-02-24

Environmental exposure assessment based on Geographic Information Systems (GIS) and study participants' residential proximity to environmental exposure sources relies on the positional accuracy of subjects' residences to avoid misclassification bias. Our study compared the positional accuracy of two automatic geocoding methods to a manual reference method. We geocoded 4,247 address records representing the residential history (1990-2008) of 1,685 women from the French national E3N cohort living in the Rhône-Alpes region. We compared two automatic geocoding methods, a free-online geocoding service (method A) and an in-house geocoder (method B), to a reference layer created by manually relocating addresses from method A (method R). For each automatic geocoding method, positional accuracy levels were compared according to the urban/rural status of addresses and time-periods (1990-2000, 2001-2008), using Chi Square tests. Kappa statistics were performed to assess agreement of positional accuracy of both methods A and B with the reference method, overall, by time-periods and by urban/rural status of addresses. Respectively 81.4% and 84.4% of addresses were geocoded to the exact address (65.1% and 61.4%) or to the street segment (16.3% and 23.0%) with methods A and B. In the reference layer, geocoding accuracy was higher in urban areas compared to rural areas (74.4% vs. 10.5% addresses geocoded to the address or interpolated address level, p < 0.0001); no difference was observed according to the period of residence. Compared to the reference method, median positional errors were 0.0 m (IQR = 0.0-37.2 m) and 26.5 m (8.0-134.8 m), with positional errors <100 m for 82.5% and 71.3% of addresses, for method A and method B respectively. Positional agreement of method A and method B with method R was 'substantial' for both methods, with kappa coefficients of 0.60 and 0.61 for methods A and B, respectively. Our study demonstrates the feasibility of geocoding residential addresses in epidemiological studies not initially recorded for environmental exposure assessment, for both recent addresses and residence locations more than 20 years ago. Accuracy of the two automatic geocoding methods was comparable. The in-house method (B) allowed a better control of the geocoding process and was less time consuming.

Wave-vector and polarization dependent impedance model for a hexagonal periodic metasurface exemplified through finite-difference time-domain simulations.

PubMed

Ding, Yi S; He, Yang

2017-08-21

An isotropic impedance sheet model is proposed for a loop-type hexagonal periodic metasurface. Both frequency and wave-vector dispersion are considered near the resonance frequency. Therefore both the angle and polarization dependences of the metasurface impedance can be properly and simultaneously described in our model. The constitutive relation of this model is transformed into auxiliary differential equations which are integrated into the finite-difference time-domain algorithm. Finally, a finite large metasurface sample under oblique illumination is used to test the model and the algorithm. Our model and algorithm can significantly increase the accuracy of the homogenization methods for modeling periodic metasurfaces.

''Smart'' watchdog safety switch

DOEpatents

Kronberg, J.W.

1991-10-01

A method and apparatus for monitoring a process having a periodic output so that the process equipment is not damaged in the event of a controller failure, comprising a low-pass and peak clipping filter, an event detector that generates an event pulse for each valid change in magnitude of the filtered periodic output, a timing pulse generator, a counter that increments upon receipt of any timing pulse and resets to zero on receipt of any event pulse, an alarm that alerts when the count reaches some preselected total count, and a set of relays that opens to stop power to process equipment. An interface module can be added to allow the switch to accept a variety of periodic output signals. 21 figures.

"Smart" watchdog safety switch

DOEpatents

Kronberg, James W.

1991-01-01

A method and apparatus for monitoring a process having a periodic output so that the process equipment is not damaged in the event of a controller failure, comprising a low-pass and peak clipping filter, an event detector that generates an event pulse for each valid change in magnitude of the filtered periodic output, a timing pulse generator, a counter that increments upon receipt of any timing pulse and resets to zero on receipt of any event pulse, an alarm that alerts when the count reaches some preselected total count, and a set of relays that opens to stop power to process equipment. An interface module can be added to allow the switch to accept a variety of periodic output signals.

Liquidity spillover in international stock markets through distinct time scales.

PubMed

Righi, Marcelo Brutti; Vieira, Kelmara Mendes

2014-01-01

This paper identifies liquidity spillovers through different time scales based on a wavelet multiscaling method. We decompose daily data from U.S., British, Brazilian and Hong Kong stock markets indices in order to calculate the scale correlation between their illiquidities. The sample is divided in order to consider non-crisis, sub-prime crisis and Eurozone crisis. We find that there are changes in correlations of distinct scales and different periods. Association in finest scales is smaller than in coarse scales. There is a rise on associations in periods of crisis. In frequencies, there is predominance for significant distinctions involving the coarsest scale, while for crises periods there is predominance for distinctions on the finest scale.

Liquidity Spillover in International Stock Markets through Distinct Time Scales

PubMed Central

Righi, Marcelo Brutti; Vieira, Kelmara Mendes

2014-01-01

This paper identifies liquidity spillovers through different time scales based on a wavelet multiscaling method. We decompose daily data from U.S., British, Brazilian and Hong Kong stock markets indices in order to calculate the scale correlation between their illiquidities. The sample is divided in order to consider non-crisis, sub-prime crisis and Eurozone crisis. We find that there are changes in correlations of distinct scales and different periods. Association in finest scales is smaller than in coarse scales. There is a rise on associations in periods of crisis. In frequencies, there is predominance for significant distinctions involving the coarsest scale, while for crises periods there is predominance for distinctions on the finest scale. PMID:24465918

A mathematical approach for evaluating Markov models in continuous time without discrete-event simulation.

PubMed

van Rosmalen, Joost; Toy, Mehlika; O'Mahony, James F

2013-08-01

Markov models are a simple and powerful tool for analyzing the health and economic effects of health care interventions. These models are usually evaluated in discrete time using cohort analysis. The use of discrete time assumes that changes in health states occur only at the end of a cycle period. Discrete-time Markov models only approximate the process of disease progression, as clinical events typically occur in continuous time. The approximation can yield biased cost-effectiveness estimates for Markov models with long cycle periods and if no half-cycle correction is made. The purpose of this article is to present an overview of methods for evaluating Markov models in continuous time. These methods use mathematical results from stochastic process theory and control theory. The methods are illustrated using an applied example on the cost-effectiveness of antiviral therapy for chronic hepatitis B. The main result is a mathematical solution for the expected time spent in each state in a continuous-time Markov model. It is shown how this solution can account for age-dependent transition rates and discounting of costs and health effects, and how the concept of tunnel states can be used to account for transition rates that depend on the time spent in a state. The applied example shows that the continuous-time model yields more accurate results than the discrete-time model but does not require much computation time and is easily implemented. In conclusion, continuous-time Markov models are a feasible alternative to cohort analysis and can offer several theoretical and practical advantages.

A Simple Microsoft Excel Method to Predict Antibiotic Outbreaks and Underutilization.

PubMed

Miglis, Cristina; Rhodes, Nathaniel J; Avedissian, Sean N; Zembower, Teresa R; Postelnick, Michael; Wunderink, Richard G; Sutton, Sarah H; Scheetz, Marc H

2017-07-01

Benchmarking strategies are needed to promote the appropriate use of antibiotics. We have adapted a simple regressive method in Microsoft Excel that is easily implementable and creates predictive indices. This method trends consumption over time and can identify periods of over- and underuse at the hospital level. Infect Control Hosp Epidemiol 2017;38:860-862.

Complexity analysis based on generalized deviation for financial markets

NASA Astrophysics Data System (ADS)

Li, Chao; Shang, Pengjian

2018-03-01

In this paper, a new modified method is proposed as a measure to investigate the correlation between past price and future volatility for financial time series, known as the complexity analysis based on generalized deviation. In comparison with the former retarded volatility model, the new approach is both simple and computationally efficient. The method based on the generalized deviation function presents us an exhaustive way showing the quantization of the financial market rules. Robustness of this method is verified by numerical experiments with both artificial and financial time series. Results show that the generalized deviation complexity analysis method not only identifies the volatility of financial time series, but provides a comprehensive way distinguishing the different characteristics between stock indices and individual stocks. Exponential functions can be used to successfully fit the volatility curves and quantify the changes of complexity for stock market data. Then we study the influence for negative domain of deviation coefficient and differences during the volatile periods and calm periods. after the data analysis of the experimental model, we found that the generalized deviation model has definite advantages in exploring the relationship between the historical returns and future volatility.

Quasi-equilibria in reduced Liouville spaces.

PubMed

Halse, Meghan E; Dumez, Jean-Nicolas; Emsley, Lyndon

2012-06-14

The quasi-equilibrium behaviour of isolated nuclear spin systems in full and reduced Liouville spaces is discussed. We focus in particular on the reduced Liouville spaces used in the low-order correlations in Liouville space (LCL) simulation method, a restricted-spin-space approach to efficiently modelling the dynamics of large networks of strongly coupled spins. General numerical methods for the calculation of quasi-equilibrium expectation values of observables in Liouville space are presented. In particular, we treat the cases of a time-independent Hamiltonian, a time-periodic Hamiltonian (with and without stroboscopic sampling) and powder averaging. These quasi-equilibrium calculation methods are applied to the example case of spin diffusion in solid-state nuclear magnetic resonance. We show that there are marked differences between the quasi-equilibrium behaviour of spin systems in the full and reduced spaces. These differences are particularly interesting in the time-periodic-Hamiltonian case, where simulations carried out in the reduced space demonstrate ergodic behaviour even for small spins systems (as few as five homonuclei). The implications of this ergodic property on the success of the LCL method in modelling the dynamics of spin diffusion in magic-angle spinning experiments of powders is discussed.

Post-exercise heart rate variability recovery: a time-frequency analysis.

PubMed

Peçanha, Tiago; de Paula-Ribeiro, Marcelle; Nasario-Junior, Olivassé; de Lima, Jorge Roberto Perrout

2013-12-01

Most studies investigating the effects of non-pharmacological interventions, such as physical training (PT), on cardiac autonomic control, assessed the HRV only in resting conditions. Recently, a new time-frequency mathematical approach based on the short-time Fourier transform (STFT) method has been validated for the assessment of HRV in non-stationary conditions such as the immediate post-exercise period. The aim of this study was to evaluate the effects of the PT on post-exercise cardiac autonomic control using the time-frequency STFT analysis of the HRV. Twenty-one healthy male volunteers participated in this study. The subjects were initially evaluated for their physical exercise/sport practice and allocated to groups of low physical training ((Low)PT, n = 13) or high physical training (H(igh)PT, n = 8). The post-exercise HRV was assessed by the STFT method, which provides the analysis of dynamic changes in the power of the low- and high-frequency spectral components (LF and HF, respectively) of the HRV during the whole recovery period. Greater LF (from the min 5 to 10) and HF (from the min 6 to 10) in the post-exercise period in the H(igh)PT compared to the (Low)PT group (P < 0.05) was observed. These results indicate that exercise training exerts beneficial effects on post-exercise cardiac autonomic control.

Reconstruction and analysis of the past five centuries of streamflow on northern slopes on Tianshan Mountains in Northern Xinjiang, China

NASA Astrophysics Data System (ADS)

Yang, Yuhui; Chen, Yaning; Wang, Minzhong; Sun, Huilan

2017-07-01

We examined the changes in streamflow on the northern slopes of the Tianshan Mountains in northern Xinjiang, China, over two time scales: the past 500 years, based on dendrochronology data; and the past 50 years, based on streamflow data from hydrological stations. The method of artificial neural networks built from the data of the 50-year period was used to reconstruct the streamflow of the 500-year period. The results indicate that streamflow has undergone seven high-flow periods and four low-flow periods during the past 500 years. To identify possible transition points in the streamflow, we applied the Mann-Kendall and running T tests to the 50- and 500-year periods, respectively. During the past 500 years, streamflow has changed significantly from low to high flow about three to four times, and from high to low flow about three to five times. Over the recent 50 years, there have been three phases of variation in river runoff, and the most distinct transition of streamflow occurred in 1996.

Submillisecond fireball timing using de Bruijn timecodes

NASA Astrophysics Data System (ADS)

Howie, Robert M.; Paxman, Jonathan; Bland, Philip A.; Towner, Martin C.; Sansom, Eleanor K.; Devillepoix, Hadrien A. R.

2017-08-01

Long-exposure fireball photographs have been used to systematically record meteoroid trajectories, calculate heliocentric orbits, and determine meteorite fall positions since the mid-20th century. Periodic shuttering is used to determine meteoroid velocity, but up until this point, a separate method of precisely determining the arrival time of a meteoroid was required. We show it is possible to encode precise arrival times directly into the meteor image by driving the periodic shutter according to a particular pattern—a de Bruijn sequence—and eliminate the need for a separate subsystem to record absolute fireball timing. The Desert Fireball Network has implemented this approach using a microcontroller driven electro-optic shutter synchronized with GNSS UTC time to create small, simple, and cost-effective high-precision fireball observatories with submillisecond timing accuracy.

Does time of day influence cancer detection and recall rates in mammography?

NASA Astrophysics Data System (ADS)

Stinton, Chris; Jenkinson, David; Adekanmbi, Victor; Clarke, Aileen; Taylor-Phillips, Sian

2017-03-01

Background: The interpretation of screening mammograms is influenced by factors such as reader experience and their annual interpretative volume. There is some evidence that time of day can also have an effect, with better diagnostic accuracy for readings conducted early in the day. This is not a consistent finding, however. The aim of our study is to provide further evidence on whether there is an effect of time of day on recall- and breast cancer detection rates. Method: We analysed breast screening data from 222,577 women from the Midlands of England. Data were split into three eight hour periods: 0900-1700, 1700-0100, 0100-0900. Differences in recall- and cancer detection rates were analysed using multilevel logistic regression models. Results: Recall rates were lowest for mammograms read between the 1700-0100 time period. Cancer detection rates were lowest during the 0100-0900 time period. Conclusions: Our findings suggest that there are fluctuations in recall- and cancer detection rates over the course of the day.

Accelerated in-vitro release testing methods for extended-release parenteral dosage forms.

PubMed

Shen, Jie; Burgess, Diane J

2012-07-01

This review highlights current methods and strategies for accelerated in-vitro drug release testing of extended-release parenteral dosage forms such as polymeric microparticulate systems, lipid microparticulate systems, in-situ depot-forming systems and implants. Extended-release parenteral dosage forms are typically designed to maintain the effective drug concentration over periods of weeks, months or even years. Consequently, 'real-time' in-vitro release tests for these dosage forms are often run over a long time period. Accelerated in-vitro release methods can provide rapid evaluation and therefore are desirable for quality control purposes. To this end, different accelerated in-vitro release methods using United States Pharmacopeia (USP) apparatus have been developed. Different mechanisms of accelerating drug release from extended-release parenteral dosage forms, along with the accelerated in-vitro release testing methods currently employed are discussed. Accelerated in-vitro release testing methods with good discriminatory ability are critical for quality control of extended-release parenteral products. Methods that can be used in the development of in-vitro-in-vivo correlation (IVIVC) are desirable; however, for complex parenteral products this may not always be achievable. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

A combined approach for weak fault signature extraction of rolling element bearing using Hilbert envelop and zero frequency resonator

NASA Astrophysics Data System (ADS)

Kumar, Keshav; Shukla, Sumitra; Singh, Sachin Kumar

2018-04-01

Periodic impulses arise due to localised defects in rolling element bearing. At the early stage of defects, the weak impulses are immersed in strong machinery vibration. This paper proposes a combined approach based upon Hilbert envelop and zero frequency resonator for the detection of the weak periodic impulses. In the first step, the strength of impulses is increased by taking normalised Hilbert envelop of the signal. It also helps in better localization of these impulses on time axis. In the second step, Hilbert envelope of the signal is passed through the zero frequency resonator for the exact localization of the periodic impulses. Spectrum of the resonator output gives peak at the fault frequency. Simulated noisy signal with periodic impulses is used to explain the working of the algorithm. The proposed technique is verified with experimental data also. A comparison of the proposed method with Hilbert-Haung transform (HHT) based method is presented to establish the effectiveness of the proposed method.

Light-Cone Effect of Radiation Fields in Cosmological Radiative Transfer Simulations

NASA Astrophysics Data System (ADS)

Ahn, Kyungjin

2015-02-01

We present a novel method to implement time-delayed propagation of radiation fields in cosmo-logical radiative transfer simulations. Time-delayed propagation of radiation fields requires construction of retarded-time fields by tracking the location and lifetime of radiation sources along the corresponding light-cones. Cosmological radiative transfer simulations have, until now, ignored this "light-cone effect" or implemented ray-tracing methods that are computationally demanding. We show that radiative trans-fer calculation of the time-delayed fields can be easily achieved in numerical simulations when periodic boundary conditions are used, by calculating the time-discretized retarded-time Green's function using the Fast Fourier Transform (FFT) method and convolving it with the source distribution. We also present a direct application of this method to the long-range radiation field of Lyman-Werner band photons, which is important in the high-redshift astrophysics with first stars.

Stochastic entrainment of a stochastic oscillator.

PubMed

Wang, Guanyu; Peskin, Charles S

2015-01-01

In this work, we consider a stochastic oscillator described by a discrete-state continuous-time Markov chain, in which the states are arranged in a circle, and there is a constant probability per unit time of jumping from one state to the next in a specified direction around the circle. At each of a sequence of equally spaced times, the oscillator has a specified probability of being reset to a particular state. The focus of this work is the entrainment of the oscillator by this periodic but stochastic stimulus. We consider a distinguished limit, in which (i) the number of states of the oscillator approaches infinity, as does the probability per unit time of jumping from one state to the next, so that the natural mean period of the oscillator remains constant, (ii) the resetting probability approaches zero, and (iii) the period of the resetting signal approaches a multiple, by a ratio of small integers, of the natural mean period of the oscillator. In this distinguished limit, we use analytic and numerical methods to study the extent to which entrainment occurs.

Method of sintering materials with microwave radiation

DOEpatents

Kimrey, Jr., Harold D.; Holcombe, Jr., Cressie E.; Dykes, Norman L.

1994-01-01

A method of sintering ceramic materials following: A compacted article comprising inorganic particles coated with carbon is provided, the carbon providing improved microwave coupling. The compacted article is then heated by microwave radiation to a temperature and for a period of time sufficient to sinter the compacted article.

Impact of a social franchise intervention program on the adoption of long and short acting family planning methods in hard to reach communities in Myanmar.

PubMed

Aung, Tin; Thet, May Me; Sudhinaraset, May; Diamond-Smith, Nadia

2018-03-12

Myanmar has experienced slowly rising levels of contraceptive use in recent years. Between 2014 and 2016, Population Services International (PSI)/Myanmar implemented a multi-pronged intervention to increase contraceptive use by leveraging its social marketing clinics and providers, and providing additional community outreach. The aim of this study is to explore trends over time in contraceptive uptake and assess whether exposure to the PSI program was associated with women adopting a method. Baseline and end line data were collected using a repeated cross-sectional survey of married women of reproductive age in 2014 and 2016. We find that use of the implant and intrauterine device (IUD) has increased among contraceptive users over time, although there was no significant association for short-term methods. There was also an increase in all types of method use between time periods compared to non-users of contraception. Women who reported seeing a PSI contraception pamphlet had increased odds of having adopted an IUD or implant in the study period. This suggests that interventions that address both supply and demand side barriers to contraception can have an impact on contraceptive uptake, especially more effective long acting methods.

Rehabilitation time before disability pension

PubMed Central

2012-01-01

Background The decision to grant a disability pension is usually the end of a long process of medical examinations, treatment and rehabilitation attempts. This study investigates to what extent the time spent on rehabilitation time prior to disability pension is associated with characteristics of the individual or the local employment and welfare office, measured as municipality variance. Methods A study of 2,533 40 to 42 year olds who received disability pension over a period of 18 years. The logarithm of the rehabilitation time before granting a disability pension was analysed with multilevel regression. Results The rehabilitation time before a disability pension was granted ranged from 30 to 5,508 days. Baseline health characteristics were only moderately associated with rehabilitation time. Younger people and people with unemployment periods had longer rehabilitation time before a disability pension was granted. There were only minor differences in rehabilitation time between men and women and between different levels of education. Approximately 2% of the total variance in rehabilitation time could be attributed to the municipality of residence. Conclusions There is a higher threshold for granting a disability pension to younger persons and those who are expecting periods of unemployment, which is reflected in the extended rehabilitation requirements for these groups. The longer rehabilitation period for persons with psychiatric disorders might reflect a lack of common knowledge on the working capacity of and the fitted rehabilitation programs for people with psychiatric disorders. PMID:23110397

Latent class instrumental variables: a clinical and biostatistical perspective.

PubMed

Baker, Stuart G; Kramer, Barnett S; Lindeman, Karen S

2016-01-15

In some two-arm randomized trials, some participants receive the treatment assigned to the other arm as a result of technical problems, refusal of a treatment invitation, or a choice of treatment in an encouragement design. In some before-and-after studies, the availability of a new treatment changes from one time period to this next. Under assumptions that are often reasonable, the latent class instrumental variable (IV) method estimates the effect of treatment received in the aforementioned scenarios involving all-or-none compliance and all-or-none availability. Key aspects are four initial latent classes (sometimes called principal strata) based on treatment received if in each randomization group or time period, the exclusion restriction assumption (in which randomization group or time period is an instrumental variable), the monotonicity assumption (which drops an implausible latent class from the analysis), and the estimated effect of receiving treatment in one latent class (sometimes called efficacy, the local average treatment effect, or the complier average causal effect). Since its independent formulations in the biostatistics and econometrics literatures, the latent class IV method (which has no well-established name) has gained increasing popularity. We review the latent class IV method from a clinical and biostatistical perspective, focusing on underlying assumptions, methodological extensions, and applications in our fields of obstetrics and cancer research. Copyright © 2015 John Wiley & Sons, Ltd.

Out-of-plane ultrasonic velocity measurement

DOEpatents

Hall, M.S.; Brodeur, P.H.; Jackson, T.G.

1998-07-14

A method for improving the accuracy of measuring the velocity and time of flight of ultrasonic signals through moving web-like materials such as paper, paperboard and the like, includes a pair of ultrasonic transducers disposed on opposing sides of a moving web-like material. In order to provide acoustical coupling between the transducers and the web-like material, the transducers are disposed in fluid-filled wheels. Errors due to variances in the wheel thicknesses about their circumference which can affect time of flight measurements and ultimately the mechanical property being tested are compensated by averaging the ultrasonic signals for a predetermined number of revolutions. The invention further includes a method for compensating for errors resulting from the digitization of the ultrasonic signals. More particularly, the invention includes a method for eliminating errors known as trigger jitter inherent with digitizing oscilloscopes used to digitize the signals for manipulation by a digital computer. In particular, rather than cross-correlate ultrasonic signals taken during different sample periods as is known in the art in order to determine the time of flight of the ultrasonic signal through the moving web, a pulse echo box is provided to enable cross-correlation of predetermined transmitted ultrasonic signals with predetermined reflected ultrasonic or echo signals during the sample period. By cross-correlating ultrasonic signals in the same sample period, the error associated with trigger jitter is eliminated. 20 figs.

Out-of-plane ultrasonic velocity measurement

DOEpatents

Hall, Maclin S.; Brodeur, Pierre H.; Jackson, Theodore G.

1998-01-01

A method for improving the accuracy of measuring the velocity and time of flight of ultrasonic signals through moving web-like materials such as paper, paperboard and the like, includes a pair of ultrasonic transducers disposed on opposing sides of a moving web-like material. In order to provide acoustical coupling between the transducers and the web-like material, the transducers are disposed in fluid-filled wheels. Errors due to variances in the wheel thicknesses about their circumference which can affect time of flight measurements and ultimately the mechanical property being tested are compensated by averaging the ultrasonic signals for a predetermined number of revolutions. The invention further includes a method for compensating for errors resulting from the digitization of the ultrasonic signals. More particularly, the invention includes a method for eliminating errors known as trigger jitter inherent with digitizing oscilloscopes used to digitize the signals for manipulation by a digital computer. In particular, rather than cross-correlate ultrasonic signals taken during different sample periods as is known in the art in order to determine the time of flight of the ultrasonic signal through the moving web, a pulse echo box is provided to enable cross-correlation of predetermined transmitted ultrasonic signals with predetermined reflected ultrasonic or echo signals during the sample period. By cross-correlating ultrasonic signals in the same sample period, the error associated with trigger jitter is eliminated.

Accelerated/abbreviated test methods of the low-cost silicon solar array project. Study 4, task 3: Encapsulation

NASA Technical Reports Server (NTRS)

Kolyer, J. M.; Mann, N. R.

1977-01-01

Methods of accelerated and abbreviated testing were developed and applied to solar cell encapsulants. These encapsulants must provide protection for as long as 20 years outdoors at different locations within the United States. Consequently, encapsulants were exposed for increasing periods of time to the inherent climatic variables of temperature, humidity, and solar flux. Property changes in the encapsulants were observed. The goal was to predict long term behavior of encapsulants based upon experimental data obtained over relatively short test periods.

Development and validation of a new method for the registration of overuse injuries in sports injury epidemiology: the Oslo Sports Trauma Research Centre (OSTRC) overuse injury questionnaire.

PubMed

Clarsen, Benjamin; Myklebust, Grethe; Bahr, Roald

2013-05-01

Current methods for injury registration in sports injury epidemiology studies may substantially underestimate the true burden of overuse injuries due to a reliance on time-loss injury definitions. To develop and validate a new method for the registration of overuse injuries in sports. A new method, including a new overuse injury questionnaire, was developed and validated in a 13-week prospective study of injuries among 313 athletes from five different sports, cross-country skiing, floorball, handball, road cycling and volleyball. All athletes completed a questionnaire by email each week to register problems in the knee, lower back and shoulder. Standard injury registration methods were also used to record all time-loss injuries that occurred during the study period. The new method recorded 419 overuse problems in the knee, lower back and shoulder during the 3-month-study period. Of these, 142 were classified as substantial overuse problems, defined as those leading to moderate or severe reductions in sports performance or participation, or time loss. Each week, an average of 39% of athletes reported having overuse problems and 13% reported having substantial problems. In contrast, standard methods of injury registration registered only 40 overuse injuries located in the same anatomical areas, the majority of which were of minimal or mild severity. Standard injury surveillance methods only capture a small percentage of the overuse problems affecting the athletes, largely because few problems led to time loss from training or competition. The new method captured a more complete and nuanced picture of the burden of overuse injuries in this cohort.

A straightforward frequency-estimation technique for GPS carrier-phase time transfer.

PubMed

Hackman, Christine; Levine, Judah; Parker, Thomas E; Piester, Dirk; Becker, Jürgen

2006-09-01

Although Global Positioning System (GPS) carrier-phase time transfer (GPSCPTT) offers frequency stability approaching 10-15 at averaging times of 1 d, a discontinuity occurs in the time-transfer estimates between the end of one processing batch (1-3 d in length) and the beginning of the next. The average frequency over a multiday analysis period often has been computed by first estimating and removing these discontinuities, i.e., through concatenation. We present a new frequency-estimation technique in which frequencies are computed from the individual batches then averaged to obtain the mean frequency for a multiday period. This allows the frequency to be computed without the uncertainty associated with the removal of the discontinuities and requires fewer computational resources. The new technique was tested by comparing the fractional frequency-difference values it yields to those obtained using a GPSCPTT concatenation method and those obtained using two-way satellite time-and-frequency transfer (TWSTFT). The clocks studied were located in Braunschweig, Germany, and in Boulder, CO. The frequencies obtained from the GPSCPTT measurements using either method agreed with those obtained from TWSTFT at several parts in 1016. The frequency values obtained from the GPSCPTT data by use of the new method agreed with those obtained using the concatenation technique at 1-4 x 10(-16).

Prediction of final error level in learning and repetitive control

NASA Astrophysics Data System (ADS)

Levoci, Peter A.

Repetitive control (RC) is a field that creates controllers to eliminate the effects of periodic disturbances on a feedback control system. The methods have applications in spacecraft problems, to isolate fine pointing equipment from periodic vibration disturbances such as slight imbalances in momentum wheels or cryogenic pumps. A closely related field of control design is iterative learning control (ILC) which aims to eliminate tracking error in a task that repeats, each time starting from the same initial condition. Experiments done on a robot at NASA Langley Research Center showed that the final error levels produced by different candidate repetitive and learning controllers can be very different, even when each controller is analytically proven to converge to zero error in the deterministic case. Real world plant and measurement noise and quantization noise (from analog to digital and digital to analog converters) in these control methods are acted on as if they were error sources that will repeat and should be cancelled, which implies that the algorithms amplify such errors. Methods are developed that predict the final error levels of general first order ILC, of higher order ILC including current cycle learning, and of general RC, in the presence of noise, using frequency response methods. The method involves much less computation than the corresponding time domain approach that involves large matrices. The time domain approach was previously developed for ILC and handles a certain class of ILC methods. Here methods are created to include zero-phase filtering that is very important in creating practical designs. Also, time domain methods are developed for higher order ILC and for repetitive control. Since RC and ILC must be implemented digitally, all of these methods predict final error levels at the sample times. It is shown here that RC can easily converge to small error levels between sample times, but that ILC in most applications will have large and diverging intersample error if in fact zero error is reached at the sample times. This is independent of the ILC law used, and is purely a property of the physical system. Methods are developed to address this issue.

Response of Bighead Carp and Silver Carp to repeated water gun operation in an enclosed shallow pond

USGS Publications Warehouse

Romine, Jason G.; Jensen, Nathan; Parsley, Michael J.; Gaugush, Robert F.; Severson, Todd J.; Hatton, Tyson W.; Adams, Ryan F.; Gaikowski, Mark P.

2015-01-01

The Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix are nonnative species that pose a threat to Great Lakes ecosystems should they advance into those areas. Thus, technologies to impede Asian carp movement into the Great Lakes are needed; one potential technology is the seismic water gun. We evaluated the efficacy of a water gun array as a behavioral deterrent to the movement of acoustic-tagged Bighead Carp and Silver Carp in an experimental pond. Behavioral responses were evaluated by using four metrics: (1) fish distance from the water guns (D); (2) spatial area of the fish's utilization distribution (UD); (3) persistence velocity (Vp); and (4) number of times a fish transited the water gun array. For both species, average D increased by 10 m during the firing period relative to the pre-firing period. During the firing period, the spatial area of use within the pond decreased. Carp were located throughout the pond during the pre-firing period but were concentrated in the north end of the pond during the firing period, thus reducing their UDs by roughly 50%. Overall, Vp decreased during the firing period relative to the pre-firing period, as fish movement became more tortuous and confined, suggesting that the firing of the guns elicited a change in carp behavior. The water gun array was partially successful at impeding carp movement, but some fish did transit the array. Bighead Carp moved past the guns a total of 78 times during the pre-firing period and 15 times during the firing period; Silver Carp moved past the guns 96 times during the pre-firing period and 13 times during the firing period. Although the water guns did alter carp behavior, causing the fish to move away from the guns, this method was not 100% effective as a passage deterrent.

ON THE CALIBRATION OF DK-02 AND KID DOSIMETERS (in Estonian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehvaert, H.

1963-01-01

For the periodic calibration of the DK-02 and WD dosimeters, the rotating stand method which is more advantageous than the usual method is recommended. The calibration can be accomplished in a strong gamma field, reducing considerably the time necessary for calibration. Using a point source, the dose becomes a simple function of time and geometrical parameters. The experimental values are in good agreement with theoretical values. (tr-auth)

Bäcklund transformation, infinitely-many conservation laws, solitary and periodic waves of an extended (3 + 1)-dimensional Jimbo-Miwa equation with time-dependent coefficients

NASA Astrophysics Data System (ADS)

Deng, Gao-Fu; Gao, Yi-Tian; Gao, Xin-Yi

2018-07-01

In this paper, an extended (3+1)-dimensional Jimbo-Miwa equation with time-dependent coefficients is investigated, which comes from the second member of the Kadomtsev-Petviashvili hierarchy and is shown to be conditionally integrable. Bilinear form, Bäcklund transformation, Lax pair and infinitely-many conservation laws are derived via the binary Bell polynomials and symbolic computation. With the help of the bilinear form, one-, two- and three-soliton solutions are obtained via the Hirota method, one-periodic wave solutions are constructed via the Riemann theta function. Additionally, propagation and interaction of the solitons are investigated analytically and graphically, from which we find that the interaction between the solitons is elastic and the time-dependent coefficients can affect the soliton velocities, but the soliton amplitudes remain unchanged. One-periodic waves approach the one-solitary waves with the amplitudes vanishing and can be viewed as a superposition of the overlapping solitary waves, placed one period apart.

Effect of sample storage time on detection of hybridization signals in Checkerboard DNA-DNA hybridization.

PubMed

do Nascimento, Cássio; Muller, Katia; Sato, Sandra; Albuquerque Junior, Rubens Ferreira

2012-04-01

Long-term sample storage can affect the intensity of the hybridization signals provided by molecular diagnostic methods that use chemiluminescent detection. The aim of this study was to evaluate the effect of different storage times on the hybridization signals of 13 bacterial species detected by the Checkerboard DNA-DNA hybridization method using whole-genomic DNA probes. Ninety-six subgingival biofilm samples were collected from 36 healthy subjects, and the intensity of hybridization signals was evaluated at 4 different time periods: (1) immediately after collecting (n = 24) and (2) after storage at -20 °C for 6 months (n = 24), (3) for 12 months (n = 24), and (4) for 24 months (n = 24). The intensity of hybridization signals obtained from groups 1 and 2 were significantly higher than in the other groups (p < 0.001). No differences were found between groups 1 and 2 (p > 0.05). The Checkerboard DNA-DNA hybridization method was suitable to detect hybridization signals from all groups evaluated, and the intensity of signals decreased significantly after long periods of sample storage.

Is ET often oversimplified in hydrologic models? Using long records to elucidate unaccounted for controls on ET

NASA Astrophysics Data System (ADS)

Kelleher, Christa A.; Shaw, Stephen B.

2018-02-01

Recent research has found that hydrologic modeling over decadal time periods often requires time variant model parameters. Most prior work has focused on assessing time variance in model parameters conceptualizing watershed features and functions. In this paper, we assess whether adding a time variant scalar to potential evapotranspiration (PET) can be used in place of time variant parameters. Using the HBV hydrologic model and four different simple but common PET methods (Hamon, Priestly-Taylor, Oudin, and Hargreaves), we simulated 60+ years of daily discharge on four rivers in New York state. Allowing all ten model parameters to vary in time achieved good model fits in terms of daily NSE and long-term water balance. However, allowing single model parameters to vary in time - including a scalar on PET - achieved nearly equivalent model fits across PET methods. Overall, varying a PET scalar in time is likely more physically consistent with known biophysical controls on PET as compared to varying parameters conceptualizing innate watershed properties related to soil properties such as wilting point and field capacity. This work suggests that the seeming need for time variance in innate watershed parameters may be due to overly simple evapotranspiration formulations that do not account for all factors controlling evapotranspiration over long time periods.

A two dimensional power spectral estimate for some nonstationary processes. M.S. Thesis

NASA Technical Reports Server (NTRS)

Smith, Gregory L.

1989-01-01

A two dimensional estimate for the power spectral density of a nonstationary process is being developed. The estimate will be applied to helicopter noise data which is clearly nonstationary. The acoustic pressure from the isolated main rotor and isolated tail rotor is known to be periodically correlated (PC) and the combined noise from the main and tail rotors is assumed to be correlation autoregressive (CAR). The results of this nonstationary analysis will be compared with the current method of assuming that the data is stationary and analyzing it as such. Another method of analysis is to introduce a random phase shift into the data as shown by Papoulis to produce a time history which can then be accurately modeled as stationary. This method will also be investigated for the helicopter data. A method used to determine the period of a PC process when the period is not know is discussed. The period of a PC process must be known in order to produce an accurate spectral representation for the process. The spectral estimate is developed. The bias and variability of the estimate are also discussed. Finally, the current method for analyzing nonstationary data is compared to that of using a two dimensional spectral representation. In addition, the method of phase shifting the data is examined.

Secular Variation and Physical Characteristics Determination of the HADS Star EH Lib

NASA Astrophysics Data System (ADS)

Pena, J. H.; Villarreal, C.; Pina, D. S.; Renteria, A.; Soni, A., Guillen, J. Calderon, J.

2017-12-01

Physical parameters of EH Lib have been determined based on observations carried out in 2015 with photometry. They have also served, along with samples from the years 1969 and 1986, to analyse the frequency content of EH Lib with Fourier Transforms. Recent CCD observations increased the times of maximum with twelve new times which helped us study the secular variation of the period with a method based on the minimization of the standard deviation of the O-C residuals. It is concluded that there may be a long-term period change.

Analysis and prediction of ocean swell using instrumented buoys

NASA Technical Reports Server (NTRS)

Mettlach, Theodore; Wang, David; Wittmann, Paul

1994-01-01

During the period 20-23 September 1990, the remnants of Supertyphoon Flo moved into the central North Pacific Ocean with sustained wind speeds of 28 m/s. The strong wind and large fetch area associated with this storm generated long-period swell that propagated to the west coast of North America. National Data Buoy Center moored-buoy stations, located in a network that ranged from the Gulf of Alaska to the California Bight, provided wave spectral estimates of the swell from this storm. The greatest dominant wave periods measured were approximately 20-25 s, and significant wave heights measured ranged from 3 to 8 m. Wave spectra from an array of three nondirectional buoys are used to find the source of the long-period swell. Directional wave spectra from a heave-pitch-roll buoy are also used to make an independent estimate of the source of the swell. The ridge-line method, using time-frequency contour plots of wave spectral energy density, is used to determine the time of swell generation, which is used with the appropriate surface pressure analysis to infer the swell generation area. The diagnosed sources of the swell are also compared with nowcasts from the Global Spectral Ocean Wave Model of the Fleet Numerical Oceanography Center. A simple method of predicting the propagation of ocean swell, by applying a simple kinematic model of wave propagation to the estimated point and time source, is demonstrated.

Early oral feeding after pancreatoduodenectomy enhances recovery without increasing morbidity

PubMed Central

Gerritsen, Arja; Wennink, Roos A W; Besselink, Marc G H; van Santvoort, Hjalmar C; Tseng, Dorine S J; Steenhagen, Elles; Borel Rinkes, Inne H M; Molenaar, I Quintus

2014-01-01

Objective The aim of this study was to evaluate whether a change in the routine feeding strategy applied after pancreatoduodenectomy (PD) from nasojejunal tube (NJT) feeding to early oral feeding improved clinical outcomes. Methods An observational cohort study was performed in 102 consecutive patients undergoing PD. In period 1 (n = 51, historical controls), the routine postoperative feeding strategy was NJT feeding. This was changed to a protocol of early oral feeding with on-demand NJT feeding in period 2 (n = 51, consecutive prospective cohort). The primary outcome was time to resumption of adequate oral intake. Results The baseline characteristics of study subjects in both periods were comparable. In period 1, 98% (n = 50) of patients received NJT feeding, whereas in period 2, 53% (n = 27) of patients did so [for delayed gastric empting (DGE) (n = 20) or preoperative malnutrition (n = 7)]. The time to resumption of adequate oral intake significantly decreased from 12 days in period 1 to 9 days in period 2 (P = 0.015), and the length of hospital stay shortened from 18 days in period 1 to 13 days in period 2 (P = 0.015). Overall, there were no differences in the incidences of complications of Clavien–Dindo Grade III or higher, DGE, pancreatic fistula, postoperative haemorrhage and mortality between the two periods. Conclusions The introduction of an early oral feeding strategy after PD reduced the time to resumption of adequate oral intake and length of hospital stay without negatively impacting postoperative morbidity. PMID:24308458

Photometric Variability of the mCP Star CS Vir: Evolution of the Rotation Period

NASA Astrophysics Data System (ADS)

Ozuyar, D.; Sener, H. T.; Stevens, I. R.

2018-01-01

The aim of this study is to accurately calculate the rotational period of CS Vir by using STEREO observations and investigate a possible period variation of the star with the help of all accessible data. The STEREO data that cover 5-yr time interval between 2007 and 2011 are analysed by means of the Lomb-Scargle and Phase Dispersion Minimization methods. In order to obtain a reliable rotation period and its error value, computational algorithms such as the Levenberg-Marquardt and Monte Carlo simulation algorithms are applied to the data sets. Thus, the rotation period of CS Vir is improved to be 9.29572(12) d by using the 5-yr of combined data set. Also, the light elements are calculated as HJD max = 2454715.975(11) + 9d . 29572(12) × E + 9d . 78(1.13) × 10 - 8 × E 2 by means of the extremum times derived from the STEREO light curves and archives. Moreover, with this study, a period variation is revealed for the first time, and it is found that the period has lengthened by 0.66(8) s y-1, equivalent to 66 s per century. Additionally, a time-scale for a possible spin-down is calculated around τSD 106 yr. The differential rotation and magnetic braking are thought to be responsible of the mentioned rotational deceleration. It is deduced that the spin-down time-scale of the star is nearly three orders of magnitude shorter than its main-sequence lifetime (τMS 109 yr). It is, in return, suggested that the process of increase in the period might be reversible.

Method for determining the concentration of atomic species in gases and solids

DOEpatents

Loge, Gary W.

1999-01-01

Method for determining the concentration of atomic species in gases and solids. Measurement of at least two emission intensities from a species in a plasma containing the species after a sufficient time period has elapsed after the generation of the plasma and during a second time period, permits an instantaneous temperature to be established within the sample. The concentration of the atomic species to be determined is then derived from the known emission intensity of a predetermined concentration of that species in the sample at the measured temperature, a quantity which is measured prior to the determination of the unknown concentration, and the actual measured emission from the unknown species, or by this latter emission and the emission intensity of a species having known concentration within the sample.

The Long and Short Incubation Periods of Plasmodium vivax Malaria in Korea: The Characteristics and Relating Factors

PubMed Central

Kim, Sun-Ja; Kim, Si-Heon; Jo, Soo-Nam; Gwack, Jin; Youn, Seung-Ki

2013-01-01

Background The cases of Plasmodium vivax malaria in Korea are mixed with long and short incubation periods. This study aims to define clinico-epidemiologic chracteristcs of Plasmodium vivax malaria in Korea. Materials and Methods We selected the civilian cases infected with P. vivax malaria in Korea from the epidemiological investigation data of 2001 to 2010, whose incubation periods could be estimated. The long and short incubation periods were defined by duration of infection and onset time, and the cases were compared by demographic factors and clinical symptom, infection and onset time. The correlation was analyzed between the proportion of cases in the infected region with the long incubation period and meteorological factors along with latitude. Results The length of the mean short and long incubation periods for the cases were 25.5 days and 329.4 days, respectively. The total number of the study subjects was 897, and the number cases of short and long incubation periods was 575 (64.1%) and 322 (35.9%), respectively. The aspect of incubation period showed a significant difference by region of infection; there was a higher proportion of long incubation period infection cases in Gangwon-do than in Gyeonggi-do and Incheon. The proportion of long incubation period cases showed significant correlation with latitude and temperature of August and September of the infected regions. Conclusions Incubation period of P. vivax malaria in Korea showed significant difference by infected region, infection and onset time and the proportion of long incubation period cases showed significant correlation with latitude and meteorological factors of the infected regions. PMID:24265966

Mapped Chebyshev Pseudo-Spectral Method for Dynamic Aero-Elastic Problem of Limit Cycle Oscillation

NASA Astrophysics Data System (ADS)

Im, Dong Kyun; Kim, Hyun Soon; Choi, Seongim

2018-05-01

A mapped Chebyshev pseudo-spectral method is developed as one of the Fourier-spectral approaches and solves nonlinear PDE systems for unsteady flows and dynamic aero-elastic problem in a given time interval, where the flows or elastic motions can be periodic, nonperiodic, or periodic with an unknown frequency. The method uses the Chebyshev polynomials of the first kind for the basis function and redistributes the standard Chebyshev-Gauss-Lobatto collocation points more evenly by a conformal mapping function for improved numerical stability. Contributions of the method are several. It can be an order of magnitude more efficient than the conventional finite difference-based, time-accurate computation, depending on the complexity of solutions and the number of collocation points. The method reformulates the dynamic aero-elastic problem in spectral form for coupled analysis of aerodynamics and structures, which can be effective for design optimization of unsteady and dynamic problems. A limit cycle oscillation (LCO) is chosen for the validation and a new method to determine the LCO frequency is introduced based on the minimization of a second derivative of the aero-elastic formulation. Two examples of the limit cycle oscillation are tested: nonlinear, one degree-of-freedom mass-spring-damper system and two degrees-of-freedom oscillating airfoil under pitch and plunge motions. Results show good agreements with those of the conventional time-accurate simulations and wind tunnel experiments.

Determination of the Electronics Charge--Electrolysis of Water Method.

ERIC Educational Resources Information Center

Venkatachar, Arun C.

1985-01-01

Presents an alternative method for measuring the electronic charge using data from the electrolysis of acidified distilled water. The process (carried out in a commercially available electrolytic cell) has the advantage of short completion time so that students can determine electron charge and mass in one laboratory period. (DH)

Perfluorocarbon tracer method for air-infiltration measurements

DOEpatents

Dietz, R.N.

1982-09-23

A method of measuring air infiltration rates suitable for use in rooms of homes and buildings comprises the steps of emitting perfluorocarbons in the room to be measured, sampling the air containing the emitted perfluorocarbons over a period of time, and analyzing the samples at a laboratory or other facility.

Termite and boring insect ground barrier for the protection of wooden structures

DOEpatents

Voris, Peter Van; Cataldo, Dominic A.

1998-01-01

A method and device are disclosed which prevent the intrusion of insects onto wood structures by using a controlled release device capable of releasing insecticide. In the disclosed method, the device maintains a minimal effective level of insecticide for a predetermined period of time.

Method of sintering materials with microwave radiation

DOEpatents

Kimrey, H.D. Jr.; Holcombe, C.E. Jr.; Dykes, N.L.

1994-06-14

Disclosed is a method of sintering ceramic materials. A compacted article comprising inorganic particles coated with carbon is provided, the carbon providing improved microwave coupling. The compacted article is then heated by microwave radiation to a temperature and for a period of time sufficient to sinter the compacted article. No Drawings

Optimal Ranking Regime Analysis of TreeFlow Dendrohydrological Reconstructions

NASA Astrophysics Data System (ADS)

Mauget, S. A.

2017-12-01

The Optimal Ranking Regime (ORR) method was used to identify 6-100 year time windows containing significant ranking sequences in 55 western U.S. streamflow reconstructions, and reconstructions of the level of the Great Salt Lake and San Francisco Bay salinity during 1500-2007. The method's ability to identify optimally significant and non-overlapping runs of low and high rankings allows it to re-express a reconstruction time series as a simplified sequence of regime segments marking intra- to multi-decadal (IMD) periods of low or high streamflow, lake level, or salinity. Those ORR sequences, referred to here as Z-lines, can be plotted to identify consistent regime patterns in the analysis of numerous reconstructions. The Z-lines for the 57 reconstructions evaluated here show a common pattern of IMD cycles of drought and pluvial periods during the late 16th and 17th centuries, a relatively dormant period during the 18th century, and the reappearance of alternating dry and wet IMD periods during the 19th and early 20th centuries. Although this pattern suggests the possibility of similarly active and inactive oceanic modes in the North Pacific and North Atlantic, such centennial-scale patterns are not evident in the ORR analyses of reconstructed Pacific Decadal Oscillation (PDO), El Niño-Southern Oscillation, and North Atlantic seas-surface temperature variation. But given the inconsistency in the analyses of four PDO reconstructions the possible role of centennial-scale oceanic mechanisms is uncertain. In future research the ORR method might be applied to climate reconstructions around the Pacific Basin to try to resolve this uncertainty. Given its ability to compare regime patterns in climate reconstructions derived using different methods and proxies, the method may also be used in future research to evaluate long-term regional temperature reconstructions.

Similarity measure and topology evolution of foreign exchange markets using dynamic time warping method: Evidence from minimal spanning tree

NASA Astrophysics Data System (ADS)

Wang, Gang-Jin; Xie, Chi; Han, Feng; Sun, Bo

2012-08-01

In this study, we employ a dynamic time warping method to study the topology of similarity networks among 35 major currencies in international foreign exchange (FX) markets, measured by the minimal spanning tree (MST) approach, which is expected to overcome the synchronous restriction of the Pearson correlation coefficient. In the empirical process, firstly, we subdivide the analysis period from June 2005 to May 2011 into three sub-periods: before, during, and after the US sub-prime crisis. Secondly, we choose NZD (New Zealand dollar) as the numeraire and then, analyze the topology evolution of FX markets in terms of the structure changes of MSTs during the above periods. We also present the hierarchical tree associated with the MST to study the currency clusters in each sub-period. Our results confirm that USD and EUR are the predominant world currencies. But USD gradually loses the most central position while EUR acts as a stable center in the MST passing through the crisis. Furthermore, an interesting finding is that, after the crisis, SGD (Singapore dollar) becomes a new center currency for the network.

Streamflow variability over the 1881–2011 period in northern Quebec: comparison of hydrological reconstructions based on tree rings and geopotential height field reanalysis

DOE PAGES

Brigode, Pierre; Brissette, Francois; Nicault, Antoine; ...

2016-09-06

Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Québec (Canada), leading to the reconstruction of flow time series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir and compare the obtained streamflow time series against time series derived from dendrohydrology by other authors on the same catchment and study the natural streamflow variability over themore » 1881–2011 period in that region. This new reconstruction is based not on natural proxies but on a historical reanalysis of global geopotential height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall–runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, in terms of both monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows and the other on spring floods. In terms of mean annual flows, the interannual variability in the reconstructed flows was similar (except for the 1930–1940 decade), with noteworthy changes seen in wetter and drier years. For spring floods, the reconstructed interannual variabilities were quite similar for the 1955–2011 period, but strongly different between 1880 and 1940. Here, the results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions and, finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.« less

Streamflow variability over the 1881–2011 period in northern Quebec: comparison of hydrological reconstructions based on tree rings and geopotential height field reanalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brigode, Pierre; Brissette, Francois; Nicault, Antoine

Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Québec (Canada), leading to the reconstruction of flow time series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir and compare the obtained streamflow time series against time series derived from dendrohydrology by other authors on the same catchment and study the natural streamflow variability over themore » 1881–2011 period in that region. This new reconstruction is based not on natural proxies but on a historical reanalysis of global geopotential height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall–runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, in terms of both monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows and the other on spring floods. In terms of mean annual flows, the interannual variability in the reconstructed flows was similar (except for the 1930–1940 decade), with noteworthy changes seen in wetter and drier years. For spring floods, the reconstructed interannual variabilities were quite similar for the 1955–2011 period, but strongly different between 1880 and 1940. Here, the results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions and, finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.« less

Continuous control of chaos based on the stability criterion.

PubMed

Yu, Hong Jie; Liu, Yan Zhu; Peng, Jian Hua

2004-06-01

A method of chaos control based on stability criterion is proposed in the present paper. This method can stabilize chaotic systems onto a desired periodic orbit by a small time-continuous perturbation nonlinear feedback. This method does not require linearization of the system around the stabilized orbit and only an approximate location of the desired periodic orbit is required which can be automatically detected in the control process. The control can be started at any moment by choosing appropriate perturbation restriction condition. It seems that more flexibility and convenience are the main advantages of this method. The discussions on control of attitude motion of a spacecraft, Rössler system, and two coupled Duffing oscillators are given as numerical examples.

Optimal design of aperiodic, vertical silicon nanowire structures for photovoltaics.

PubMed

Lin, Chenxi; Povinelli, Michelle L

2011-09-12

We design a partially aperiodic, vertically-aligned silicon nanowire array that maximizes photovoltaic absorption. The optimal structure is obtained using a random walk algorithm with transfer matrix method based electromagnetic forward solver. The optimal, aperiodic structure exhibits a 2.35 times enhancement in ultimate efficiency compared to its periodic counterpart. The spectral behavior mimics that of a periodic array with larger lattice constant. For our system, we find that randomly-selected, aperiodic structures invariably outperform the periodic array.

Prevention of Hamstring Injuries in Collegiate Sprinters

PubMed Central

Sugiura, Yusaku; Sakuma, Kazuhiko; Sakuraba, Keishoku; Sato, Yamato

2017-01-01

Background: No studies have been reported on how strength, agility, and flexibility training reduce the occurrence of hamstring injuries in sprinters. Therefore, a program for preventing hamstring injury in these athletes has not been established. Purpose: To document the incidence of hamstring injuries during times when different prevention strategies were employed to see whether a particular prevention program reduced their occurrence. Study Design: Descriptive epidemiology study. Methods: The study subjects were a total of 613 collegiate male sprinters trained by the same coach over 24 seasons. Tow training was used throughout the research period as a normal sprint training method. The hamstring injury prevention program evolved over time. From 1988 to 1991 (period 1), prevention focused on strength training alone; from 1992 to 1999 (period 2), a combination of strength and agility training was used; and from 2000 to 2011 (period 3), the program incorporated strength, agility, and flexibility training. The incidence of hamstring injuries was compared for each of the 3 prevention strategies. Results: The incidence of hamstring injuries per athlete-seasons was 137.9 for period 1, 60.6 for period 2, and 6.7 for period 3. A significant difference was observed in the incidence of hamstring injury according to the different prevention programs (χ2(2) = 31.78, P < .001, effect size: Cramer V = 0.23, 1 − β = 0.999). Residual analysis showed that the number of hamstring injuries for period 1 was significantly greater than the expected value (P < .01), whereas that for period 3 was significantly lower than the expected value (P < .01). Conclusion: The incidence of hamstring injuries in sprinters decreased as agility and flexibility were added to strength training. PMID:28210652

Temporal compressive sensing systems

DOEpatents

Reed, Bryan W.

2017-12-12

Methods and systems for temporal compressive sensing are disclosed, where within each of one or more sensor array data acquisition periods, one or more sensor array measurement datasets comprising distinct linear combinations of time slice data are acquired, and where mathematical reconstruction allows for calculation of accurate representations of the individual time slice datasets.

A general theory on frequency and time-frequency analysis of irregularly sampled time series based on projection methods - Part 1: Frequency analysis

NASA Astrophysics Data System (ADS)

Lenoir, Guillaume; Crucifix, Michel

2018-03-01

We develop a general framework for the frequency analysis of irregularly sampled time series. It is based on the Lomb-Scargle periodogram, but extended to algebraic operators accounting for the presence of a polynomial trend in the model for the data, in addition to a periodic component and a background noise. Special care is devoted to the correlation between the trend and the periodic component. This new periodogram is then cast into the Welch overlapping segment averaging (WOSA) method in order to reduce its variance. We also design a test of significance for the WOSA periodogram, against the background noise. The model for the background noise is a stationary Gaussian continuous autoregressive-moving-average (CARMA) process, more general than the classical Gaussian white or red noise processes. CARMA parameters are estimated following a Bayesian framework. We provide algorithms that compute the confidence levels for the WOSA periodogram and fully take into account the uncertainty in the CARMA noise parameters. Alternatively, a theory using point estimates of CARMA parameters provides analytical confidence levels for the WOSA periodogram, which are more accurate than Markov chain Monte Carlo (MCMC) confidence levels and, below some threshold for the number of data points, less costly in computing time. We then estimate the amplitude of the periodic component with least-squares methods, and derive an approximate proportionality between the squared amplitude and the periodogram. This proportionality leads to a new extension for the periodogram: the weighted WOSA periodogram, which we recommend for most frequency analyses with irregularly sampled data. The estimated signal amplitude also permits filtering in a frequency band. Our results generalise and unify methods developed in the fields of geosciences, engineering, astronomy and astrophysics. They also constitute the starting point for an extension to the continuous wavelet transform developed in a companion article (Lenoir and Crucifix, 2018). All the methods presented in this paper are available to the reader in the Python package WAVEPAL.

Modeling of time trends and interactions in vital rates using restricted regression splines.

PubMed

Heuer, C

1997-03-01

For the analysis of time trends in incidence and mortality rates, the age-period-cohort (apc) model has became a widely accepted method. The considered data are arranged in a two-way table by age group and calendar period, which are mostly subdivided into 5- or 10-year intervals. The disadvantage of this approach is the loss of information by data aggregation and the problems of estimating interactions in the two-way layout without replications. In this article we show how splines can be useful when yearly data, i.e., 1-year age groups and 1-year periods, are given. The estimated spline curves are still smooth and represent yearly changes in the time trends. Further, it is straightforward to include interaction terms by the tensor product of the spline functions. If the data are given in a nonrectangular table, e.g., 5-year age groups and 1-year periods, the period and cohort variables can be parameterized by splines, while the age variable is parameterized as fixed effect levels, which leads to a semiparametric apc model. An important methodological issue in developing the nonparametric and semiparametric models is stability of the estimated spline curve at the boundaries. Here cubic regression splines will be used, which are constrained to be linear in the tails. Another point of importance is the nonidentifiability problem due to the linear dependency of the three time variables. This will be handled by decomposing the basis of each spline by orthogonal projection into constant, linear, and nonlinear terms, as suggested by Holford (1983, Biometrics 39, 311-324) for the traditional apc model. The advantage of using splines for yearly data compared to the traditional approach for aggregated data is the more accurate curve estimation for the nonlinear trend changes and the simple way of modeling interactions between the time variables. The method will be demonstrated with hypothetical data as well as with cancer mortality data.

Comparison of Techniques for Sampling Adult Necrophilous Insects From Pig Carcasses.

PubMed

Cruise, Angela; Hatano, Eduardo; Watson, David W; Schal, Coby

2018-02-06

Studies of the pre-colonization interval and mechanisms driving necrophilous insect ecological succession depend on effective sampling of adult insects and knowledge of their diel and successional activity patterns. The number of insects trapped, their diversity, and diel periodicity were compared with four sampling methods on neonate pigs. Sampling method, time of day and decomposition age of the pigs significantly affected the number of insects sampled from pigs. We also found significant interactions of sampling method and decomposition day, time of sampling and decomposition day. No single method was superior to the other methods during all three decomposition days. Sampling times after noon yielded the largest samples during the first 2 d of decomposition. On day 3 of decomposition however, all sampling times were equally effective. Therefore, to maximize insect collections from neonate pigs, the method used to sample must vary by decomposition day. The suction trap collected the most species-rich samples, but sticky trap samples were the most diverse, when both species richness and evenness were factored into a Shannon diversity index. Repeated sampling during the noon to 18:00 hours period was most effective to obtain the maximum diversity of trapped insects. The integration of multiple sampling techniques would most effectively sample the necrophilous insect community. However, because all four tested methods were deficient at sampling beetle species, future work should focus on optimizing the most promising methods, alone or in combinations, and incorporate hand-collections of beetles. © The Author(s) 2018. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

A new time calibration method for switched-capacitor-array-based waveform samplers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, H.; Chen, C. -T.; Eclov, N.

2014-08-24

Here we have developed a new time calibration method for the DRS4 waveform sampler that enables us to precisely measure the non-uniform sampling interval inherent in the switched-capacitor cells of the DRS4. The method uses the proportionality between the differential amplitude and sampling interval of adjacent switched-capacitor cells responding to a sawtooth-shape pulse. In the experiment, a sawtooth-shape pulse with a 40 ns period generated by a Tektronix AWG7102 is fed to a DRS4 evaluation board for calibrating the sampling intervals of all 1024 cells individually. The electronic time resolution of the DRS4 evaluation board with the new time calibrationmore » is measured to be ~2.4 ps RMS by using two simultaneous Gaussian pulses with 2.35 ns full-width at half-maximum and applying a Gaussian fit. The time resolution dependencies on the time difference with the new time calibration are measured and compared to results obtained by another method. Ultimately, the new method could be applicable for other switched-capacitor-array technology-based waveform samplers for precise time calibration.« less

A new time calibration method for switched-capacitor-array-based waveform samplers

NASA Astrophysics Data System (ADS)

Kim, H.; Chen, C.-T.; Eclov, N.; Ronzhin, A.; Murat, P.; Ramberg, E.; Los, S.; Moses, W.; Choong, W.-S.; Kao, C.-M.

2014-12-01

We have developed a new time calibration method for the DRS4 waveform sampler that enables us to precisely measure the non-uniform sampling interval inherent in the switched-capacitor cells of the DRS4. The method uses the proportionality between the differential amplitude and sampling interval of adjacent switched-capacitor cells responding to a sawtooth-shape pulse. In the experiment, a sawtooth-shape pulse with a 40 ns period generated by a Tektronix AWG7102 is fed to a DRS4 evaluation board for calibrating the sampling intervals of all 1024 cells individually. The electronic time resolution of the DRS4 evaluation board with the new time calibration is measured to be 2.4 ps RMS by using two simultaneous Gaussian pulses with 2.35 ns full-width at half-maximum and applying a Gaussian fit. The time resolution dependencies on the time difference with the new time calibration are measured and compared to results obtained by another method. The new method could be applicable for other switched-capacitor-array technology-based waveform samplers for precise time calibration.

A New Time Calibration Method for Switched-capacitor-array-based Waveform Samplers.

PubMed

Kim, H; Chen, C-T; Eclov, N; Ronzhin, A; Murat, P; Ramberg, E; Los, S; Moses, W; Choong, W-S; Kao, C-M

2014-12-11

We have developed a new time calibration method for the DRS4 waveform sampler that enables us to precisely measure the non-uniform sampling interval inherent in the switched-capacitor cells of the DRS4. The method uses the proportionality between the differential amplitude and sampling interval of adjacent switched-capacitor cells responding to a sawtooth-shape pulse. In the experiment, a sawtooth-shape pulse with a 40 ns period generated by a Tektronix AWG7102 is fed to a DRS4 evaluation board for calibrating the sampling intervals of all 1024 cells individually. The electronic time resolution of the DRS4 evaluation board with the new time calibration is measured to be ~2.4 ps RMS by using two simultaneous Gaussian pulses with 2.35 ns full-width at half-maximum and applying a Gaussian fit. The time resolution dependencies on the time difference with the new time calibration are measured and compared to results obtained by another method. The new method could be applicable for other switched-capacitor-array technology-based waveform samplers for precise time calibration.

A New Time Calibration Method for Switched-capacitor-array-based Waveform Samplers

PubMed Central

Kim, H.; Chen, C.-T.; Eclov, N.; Ronzhin, A.; Murat, P.; Ramberg, E.; Los, S.; Moses, W.; Choong, W.-S.; Kao, C.-M.

2014-01-01

We have developed a new time calibration method for the DRS4 waveform sampler that enables us to precisely measure the non-uniform sampling interval inherent in the switched-capacitor cells of the DRS4. The method uses the proportionality between the differential amplitude and sampling interval of adjacent switched-capacitor cells responding to a sawtooth-shape pulse. In the experiment, a sawtooth-shape pulse with a 40 ns period generated by a Tektronix AWG7102 is fed to a DRS4 evaluation board for calibrating the sampling intervals of all 1024 cells individually. The electronic time resolution of the DRS4 evaluation board with the new time calibration is measured to be ~2.4 ps RMS by using two simultaneous Gaussian pulses with 2.35 ns full-width at half-maximum and applying a Gaussian fit. The time resolution dependencies on the time difference with the new time calibration are measured and compared to results obtained by another method. The new method could be applicable for other switched-capacitor-array technology-based waveform samplers for precise time calibration. PMID:25506113

Effect of growth time to the properties of Al-doped ZnO nanorod arrays

NASA Astrophysics Data System (ADS)

Ismail, A. S.; Mamat, M. H.; Malek, M. F.; Saidi, S. A.; Yusoff, M. M.; Mohamed, R.; Sin, N. D. Md; Suriani, A. B.; Rusop, M.

2018-05-01

Aluminum (Al)-doped zinc oxide (ZnO) nanorod array films were successfully deposited at different growth time on zinc oxide (ZnO) seed layer coated glass substrate using sol-gel immersion method. The morphology images of the films showed that the thicknesses of the films were increased parallel with the increment of growth period. The surface topology of the films displayed an increment of roughness as the growth period increased. Optical properties of the samples exposed that the percentage of transmittances reduced at higher growth time. Besides, the Urbach energy of the films slightly increased as the immersion time increased. The current-voltage (I-V) measurement indicated that the resistance increased as the immersion time increased owing to the appearance of intrinsic layer on top of the nanorods.

Study on reservoir time-varying design flood of inflow based on Poisson process with time-dependent parameters

NASA Astrophysics Data System (ADS)

Li, Jiqing; Huang, Jing; Li, Jianchang

2018-06-01

The time-varying design flood can make full use of the measured data, which can provide the reservoir with the basis of both flood control and operation scheduling. This paper adopts peak over threshold method for flood sampling in unit periods and Poisson process with time-dependent parameters model for simulation of reservoirs time-varying design flood. Considering the relationship between the model parameters and hypothesis, this paper presents the over-threshold intensity, the fitting degree of Poisson distribution and the design flood parameters are the time-varying design flood unit period and threshold discriminant basis, deduced Longyangxia reservoir time-varying design flood process at 9 kinds of design frequencies. The time-varying design flood of inflow is closer to the reservoir actual inflow conditions, which can be used to adjust the operating water level in flood season and make plans for resource utilization of flood in the basin.

Adaptive Event-Triggered Control Based on Heuristic Dynamic Programming for Nonlinear Discrete-Time Systems.

PubMed

Dong, Lu; Zhong, Xiangnan; Sun, Changyin; He, Haibo

2017-07-01

This paper presents the design of a novel adaptive event-triggered control method based on the heuristic dynamic programming (HDP) technique for nonlinear discrete-time systems with unknown system dynamics. In the proposed method, the control law is only updated when the event-triggered condition is violated. Compared with the periodic updates in the traditional adaptive dynamic programming (ADP) control, the proposed method can reduce the computation and transmission cost. An actor-critic framework is used to learn the optimal event-triggered control law and the value function. Furthermore, a model network is designed to estimate the system state vector. The main contribution of this paper is to design a new trigger threshold for discrete-time systems. A detailed Lyapunov stability analysis shows that our proposed event-triggered controller can asymptotically stabilize the discrete-time systems. Finally, we test our method on two different discrete-time systems, and the simulation results are included.

Tau-independent Phase Analysis: A Novel Method for Accurately Determining Phase Shifts.

PubMed

Tackenberg, Michael C; Jones, Jeff R; Page, Terry L; Hughey, Jacob J

2018-06-01

Estimations of period and phase are essential in circadian biology. While many techniques exist for estimating period, comparatively few methods are available for estimating phase. Current approaches to analyzing phase often vary between studies and are sensitive to coincident changes in period and the stage of the circadian cycle at which the stimulus occurs. Here we propose a new technique, tau-independent phase analysis (TIPA), for quantifying phase shifts in multiple types of circadian time-course data. Through comprehensive simulations, we show that TIPA is both more accurate and more precise than the standard actogram approach. TIPA is computationally simple and therefore will enable accurate and reproducible quantification of phase shifts across multiple subfields of chronobiology.

Long-term weather predictability: Ural case study

NASA Astrophysics Data System (ADS)

Kubyshen, Alexander; Shopin, Sergey

2016-04-01

The accuracy of the state-of-the-art long-term meteorological forecast (at the seasonal level) is still low. Here it is presented approach (RAMES method) realizing different forecasting methodology. It provides prediction horizon of up to 19-22 years under equal probabilities of determination of parameters in every analyzed period [1]. Basic statements of the method are the following. 1. Long-term forecast on the basis of numerical modeling of the global meteorological process is principally impossible. Extension of long-term prediction horizon could be obtained only by the revealing and using a periodicity of meteorological situations at one point of observation. 2. Conventional calendar is unsuitable for generalization of meteorological data and revealing of cyclicity of meteorological processes. RAMES method uses natural time intervals: one day, synodic month and one year. It was developed a set of special calendars using these natural periods and the Metonic cycle. 3. Long-term time series of meteorological data is not a uniform universal set, it is a sequence of 28 universal sets appropriately superseding each other in time. The specifics of the method are: 1. Usage of the original research toolkit consisting of - a set of calendars based on the Metonic cycle; - a set of charts (coordinate systems) for the construction of sequence diagrams (of daily variability of a meteorological parameter during the analyzed year; of daily variability of a meteorological parameter using long-term dynamical time series of periods-analogues; of monthly and yearly variability of accumulated value of meteorological parameter). 2. Identification and usage of new virtual meteorological objects having several degrees of generalization appropriately located in the used coordinate systems. 3. All calculations are integrated into the single technological scheme providing comparison and mutual verification of calculation results. During the prolonged testing in the Ural region, it was proved the efficiency of the method for forecasting the following meteorological parameters: ­- air temperature (minimum, maximum, daily mean, diurnal variation, last spring and first autumn freeze); - periods of winds with speeds of >5m/s and the maximal expected wind speed; - precipitation periods and amount of precipitations; -­ relative humidity; - atmospheric pressure. Atmospheric events (thunderstorms, fog) and hydrometeors also occupy the appropriate positions at the sequence diagrams that provides a possibility of long-term forecasting also for these events. Accuracy of forecasts was tested in 2006-2009 years. The difference between the forecasted monthly mean temperature and actual values was <0.5°C in 40.9% of cases, between 0.5°C and 1°C in 18.2% of cases, between 1°C and 1.5°C in 18.2% of cases, <2°C in 86% of cases. The RAMES method provides the toolkit to successfully forecast the weather conditions in advance of several years. 1. A.F. Kubyshen, "RAMES method: revealing the periodicity of meteorological processes and it usage for long-term forecast [Metodika «RAMES»: vyjavlenie periodichnosti meteorologicheskih processov i ee ispol'zovanie dlja dolgosrochnogo prognozirovanija]", in A.E. Fedorov (ed.), Sistema «Planeta Zemlja»: 200 let so dnja rozhdenija Izmaila Ivanovicha Sreznevskogo. 100 let so dnja izdanija ego slovarja drevnerusskogo jazyka. LENAND. Moscow. pp. 305-311. (In Russian)

Comparison of GPS-TEC variation during quiet and disturbed period using the Holt-Winter method and IRI-2012 model over Malaysia

NASA Astrophysics Data System (ADS)

Ahmed Ismail, Nouf Abd Emunim; Abdullah, Mardina; Hasbi, Alina Marie

2016-07-01

Total Electron Content (TEC) is the main parameter in the ionosphere that has significant effects on radio wave; it changes the speed and direction of the signal propagation, causing the delay of the Global Positioning System (GPS) signals. Therefore, it is crucial to validate the performance of the ionospheric model to reveal the variety of ionospheric behaviour during quiet and disturbed period. This research presents the performance evaluation of the statistical Holt-Winter method and IRI-2012 model using three topside electron density options: IRI-2001, IRI01-corr and NeQuick with the observed GPS-TEC during quiet and disturbed period. The GPS-TEC data were derived from the dual frequency GPS receiver at JUPEM (Department of Survey and Mapping Malaysia), from the UUMK station (north Peninsular Malaysia) at geographic coordinates of 6.46°N-100.50°E and geomagnetic coordinates of 3.32°S-172.99°E and TGPG station (south Peninsular Malaysia) at geographic coordinates of 1.36°N-104.10°E and geomagnetic coordinates of 8.43°S -176.53°E, during March of 2013. The maximum value of the GPS-TEC was at the post noon time at 17:00 LT and the minimum was in the early morning from 6:00-7:00 LT. During the quiet period, the maximum GPS-TEC at the UUMK station was 52 TECU while at the TGPG station, it was 60 TECU. During the disturbed period, when intense geomagnetic storm occurred on 17 March 2013, the maximum GPS-TEC recorded was 58 TECU and 65 TECU in UUMK and TGPG station, respectively. The diurnal hourly variation during the quiet period indicated that IRI-2001, IRI01-corr, and NeQuick had overestimation agreement during the day hours except for the time between 11:00-19:00 LT when IRI01-corr and NeQuick showed underestimation, while during 13:00-20:00 LT, IRI-2001 showed slight underestimation whereas the Holt-Winter method showed good agreement with GPS-TEC. During the disturbed period, IRI-2001 showed overestimation agreement for all hours, while the IRI01-corr and NeQuick model did not show any changes during the geomagnetic storm event. The Holt-Winter method showed better agreement with the GPS-TEC for both the UUMK and TGPG stations. The correlation between the observed and modeled GPS-TEC during the quiet and disturbed period for the UUMK station showed a slightly better correlation compared to the TGPG station. The Holt-Winter method showed good correlation of around 0.98 during the quiet period and 0.95 during the disturbed period, while IRI-2001, IRI01-corr, and NeQuick had comparatively lower correlation of around ≈ 0.8 during the quiet period and ≈ 0.7 during the disturbed period. Overall, this research concludes that the Holt-Winter method effectively the GPS-TEC with good correlation during the quiet and disturbed period in the equatorial region over Malaysia.

Enrollment of women and minorities in NINDS trials

PubMed Central

Burke, J.F.; Lisabeth, L.D.; Sanchez, B.N.; Morgenstern, L.B.

2011-01-01

Objective: To determine policy-associated changes over time in 1) the enrollment of women and minorities in National Institute of Neurological Disorders and Stroke (NINDS)–funded clinical trials and 2) the trial publication reporting of race/ethnicity and gender. Methods: All NINDS-funded phase III trials published between 1985 and 2008 were identified. Percent of African Americans, Hispanic Americans, and women enrolled in the trials was calculated for those trials with available data. Z tests were used to compare reporting and enrollment data from before (period 1) and after (period 2) 1995 when NIH enacted their policies regarding race, ethnicity, and gender. Percent of main trial publications reporting enrollment of African Americans, Hispanic Americans, and women was also calculated. Results: Of the 56 trials identified, 100%, 48%, and 25% reported enrollment by gender, race, and ethnicity. Women constituted 42.1% of the trial population. Enrollment of women increased over time (36.9% period 1; 49.0% period 2, p < 0.001). African Americans constituted 19.8% of the enrollees in trials with available data and enrollment increased over time (11.6% period 1; 30.7% period 2, p < 0.001). Hispanic Americans constituted 5.8% of subjects in trials with available data and enrollment decreased over time (7.4% period 1; 5.0% period 2, p < 0.001). Conclusions: Improvements in reporting of race/ethnicity in publications and enrollment of Hispanics in NINDS trials are needed. While African American representation is above population levels, Hispanic Americans are underrepresented in NINDS trials and representation is declining despite Hispanics' increasing representation in the US population. PMID:21209376

A precipitation regionalization and regime for Iran based on multivariate analysis

NASA Astrophysics Data System (ADS)

Raziei, Tayeb

2018-02-01

Monthly precipitation time series of 155 synoptic stations distributed over Iran, covering 1990-2014 time period, were used to identify areas with different precipitation time variability and regimes utilizing S-mode principal component analysis (PCA) and cluster analysis (CA) preceded by T-mode PCA, respectively. Taking into account the maximum loading values of the rotated components, the first approach revealed five sub-regions characterized by different precipitation time variability, while the second method delineated eight sub-regions featured with different precipitation regimes. The sub-regions identified by the two used methods, although partly overlapping, are different considering their areal extent and complement each other as they are useful for different purposes and applications. Northwestern Iran and the Caspian Sea area were found as the two most distinctive Iranian precipitation sub-regions considering both time variability and precipitation regime since they were well captured with relatively identical areas by the two used approaches. However, the areal extents of the other three sub-regions identified by the first approach were not coincident with the coverage of their counterpart sub-regions defined by the second approach. Results suggest that the precipitation sub-region identified by the two methods would not be necessarily the same, as the first method which accounts for the variance of the data grouped stations with similar temporal variability while the second one which considers a fixed climatology defined by the average over the period 1990-2014 clusters stations having a similar march of monthly precipitation.

Glimpses of stellar surfaces. II. Origins of the photometric modulations and timing variations of KOI-1452

NASA Astrophysics Data System (ADS)

Ioannidis, P.; Schmitt, J. H. M. M.

2016-10-01

The deviations of the mid-transit times of an exoplanet from a linear ephemeris are usually the result of gravitational interactions with other bodies in the system. However, these types of transit timing variations (TTV) can also be introduced by the influences of star spots on the shape of the transit profile. Here we use the method of unsharp masking to investigate the photometric light curves of planets with ambiguous TTV to compare the features in their O-C diagram with the occurrence and in-transit positions of spot-crossing events. This method seems to be particularly useful for the examination of transit light curves with only small numbers of in-transit data points, I.e., the long cadence light curves from Kepler satellite. As a proof of concept we apply this method to the light curve and the estimated eclipse timing variations of the eclipsing binary KOI-1452, for which we prove their non-gravitational nature. Furthermore, we use the method to study the rotation properties of the primary star of the system KOI-1452 and show that the spots responsible for the timing variations rotate with different periods than the most prominent periods of the system's light curve. We argue that the main contribution in the measured photometric variability of KOI-1452 originates in g-mode oscillations, which makes the primary star of the system a γ-Dor type variable candidate.

A review of hybrid implicit explicit finite difference time domain method

NASA Astrophysics Data System (ADS)

Chen, Juan

2018-06-01

The finite-difference time-domain (FDTD) method has been extensively used to simulate varieties of electromagnetic interaction problems. However, because of its Courant-Friedrich-Levy (CFL) condition, the maximum time step size of this method is limited by the minimum size of cell used in the computational domain. So the FDTD method is inefficient to simulate the electromagnetic problems which have very fine structures. To deal with this problem, the Hybrid Implicit Explicit (HIE)-FDTD method is developed. The HIE-FDTD method uses the hybrid implicit explicit difference in the direction with fine structures to avoid the confinement of the fine spatial mesh on the time step size. So this method has much higher computational efficiency than the FDTD method, and is extremely useful for the problems which have fine structures in one direction. In this paper, the basic formulations, time stability condition and dispersion error of the HIE-FDTD method are presented. The implementations of several boundary conditions, including the connect boundary, absorbing boundary and periodic boundary are described, then some applications and important developments of this method are provided. The goal of this paper is to provide an historical overview and future prospects of the HIE-FDTD method.

An Empirical Method for Determining the Lunar Gravity Field. Ph.D. Thesis - George Washington Univ.

NASA Technical Reports Server (NTRS)

Ferrari, A. J.

1971-01-01

A method has been devised to determine the spherical harmonic coefficients of the lunar gravity field. This method consists of a two-step data reduction and estimation process. In the first step, a weighted least-squares empirical orbit determination scheme is applied to Doppler tracking data from lunar orbits to estimate long-period Kepler elements and rates. Each of the Kepler elements is represented by an independent function of time. The long-period perturbing effects of the earth, sun, and solar radiation are explicitly modeled in this scheme. Kepler element variations estimated by this empirical processor are ascribed to the non-central lunar gravitation features. Doppler data are reduced in this manner for as many orbits as are available. In the second step, the Kepler element rates are used as input to a second least-squares processor that estimates lunar gravity coefficients using the long-period Lagrange perturbation equations.

Use of cervical vertebral maturation to determine skeletal age.

PubMed

Wong, Ricky W K; Alkhal, Hessa A; Rabie, A Bakr M

2009-10-01

The purpose of this study was to evaluate the validity of the cervical vertebral maturation (CVM) method as an indicator of skeletal age in the circumpubertal period by correlating it to the hand-wrist method (HWM). Hand-wrist and lateral cephalometric radiographs of 400 Chinese subjects were randomly selected. Their ages were 10 to 15 years for girls and 12 to 17 years for boys, so they were within the circumpubertal period. Skeletal ages were assessed according to the CVM method and the HWM. The CVM was significantly correlated with HWM skeletal age (Spearman r = 0.9521 [boys] and 0.9408 [girls]). All patients in cervical vertebral stage 3 of the CVM corresponded to stages MP3-FG or MP3-G (around the peak of the growth spurt) in the HWM. The CVM is a valid indicator of skeletal growth during the circumpubertal period, providing information for timing of growth modification.

Periodic, Quasi-periodic and Chaotic Dynamics in Simple Gene Elements with Time Delays

PubMed Central

Suzuki, Yoko; Lu, Mingyang; Ben-Jacob, Eshel; Onuchic, José N.

2016-01-01

Regulatory gene circuit motifs play crucial roles in performing and maintaining vital cellular functions. Frequently, theoretical studies of gene circuits focus on steady-state behaviors and do not include time delays. In this study, the inclusion of time delays is shown to entirely change the time-dependent dynamics for even the simplest possible circuits with one and two gene elements with self and cross regulations. These elements can give rise to rich behaviors including periodic, quasi-periodic, weak chaotic, strong chaotic and intermittent dynamics. We introduce a special power-spectrum-based method to characterize and discriminate these dynamical modes quantitatively. Our simulation results suggest that, while a single negative feedback loop of either one- or two-gene element can only have periodic dynamics, the elements with two positive/negative feedback loops are the minimalist elements to have chaotic dynamics. These elements typically have one negative feedback loop that generates oscillations, and another unit that allows frequent switches among multiple steady states or between oscillatory and non-oscillatory dynamics. Possible dynamical features of several simple one- and two-gene elements are presented in details. Discussion is presented for possible roles of the chaotic behavior in the robustness of cellular functions and diseases, for example, in the context of cancer. PMID:26876008

Periodic, Quasi-periodic and Chaotic Dynamics in Simple Gene Elements with Time Delays

NASA Astrophysics Data System (ADS)

Suzuki, Yoko; Lu, Mingyang; Ben-Jacob, Eshel; Onuchic, José N.

2016-02-01

Regulatory gene circuit motifs play crucial roles in performing and maintaining vital cellular functions. Frequently, theoretical studies of gene circuits focus on steady-state behaviors and do not include time delays. In this study, the inclusion of time delays is shown to entirely change the time-dependent dynamics for even the simplest possible circuits with one and two gene elements with self and cross regulations. These elements can give rise to rich behaviors including periodic, quasi-periodic, weak chaotic, strong chaotic and intermittent dynamics. We introduce a special power-spectrum-based method to characterize and discriminate these dynamical modes quantitatively. Our simulation results suggest that, while a single negative feedback loop of either one- or two-gene element can only have periodic dynamics, the elements with two positive/negative feedback loops are the minimalist elements to have chaotic dynamics. These elements typically have one negative feedback loop that generates oscillations, and another unit that allows frequent switches among multiple steady states or between oscillatory and non-oscillatory dynamics. Possible dynamical features of several simple one- and two-gene elements are presented in details. Discussion is presented for possible roles of the chaotic behavior in the robustness of cellular functions and diseases, for example, in the context of cancer.

Surge Block Method for Controlling Well Clogging and Sampling Sediment during Bioremediation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Wei-min; Watson, David B; Luo, Jian

2013-01-01

A surge block treatment method (i.e. inserting a solid rod plunger with a flat seal that closely fits the casing interior into a well and stocking it up and down) was performed for the rehabilitation of wells clogged with biomass and for the collection of time series sediment samples during in situ bioremediation tests for U(VI) immobilization at a the U.S. Department of Energy site in Oak Ridge, TN. The clogging caused by biomass growth had been controlled by using routine surge block treatment for18 times over a nearly four year test period. The treatment frequency was dependent of themore » dosage of electron donor injection and microbial community developed in the subsurface. Hydraulic tests showed that the apparent aquifer transmissivity at a clogged well with an inner diameter (ID) of 10.16 cm was increased by 8 13 times after the rehabilitation, indicating the effectiveness of the rehabilitation. Simultaneously with the rehabilitation, the surge block method was successfully used for collecting time series sediment samples composed of fine particles (clay and silt) from wells with ID 1.9 10.16 cm for the analysis of mineralogical and geochemical composition and microbial community during the same period. Our results demonstrated that the surge block method provided a cost-effective approach for both well rehabilitation and frequent solid sampling at the same location.« less

Multiscale reconstruction for MR fingerprinting.

PubMed

Pierre, Eric Y; Ma, Dan; Chen, Yong; Badve, Chaitra; Griswold, Mark A

2016-06-01

To reduce the acquisition time needed to obtain reliable parametric maps with Magnetic Resonance Fingerprinting. An iterative-denoising algorithm is initialized by reconstructing the MRF image series at low image resolution. For subsequent iterations, the method enforces pixel-wise fidelity to the best-matching dictionary template then enforces fidelity to the acquired data at slightly higher spatial resolution. After convergence, parametric maps with desirable spatial resolution are obtained through template matching of the final image series. The proposed method was evaluated on phantom and in vivo data using the highly undersampled, variable-density spiral trajectory and compared with the original MRF method. The benefits of additional sparsity constraints were also evaluated. When available, gold standard parameter maps were used to quantify the performance of each method. The proposed approach allowed convergence to accurate parametric maps with as few as 300 time points of acquisition, as compared to 1000 in the original MRF work. Simultaneous quantification of T1, T2, proton density (PD), and B0 field variations in the brain was achieved in vivo for a 256 × 256 matrix for a total acquisition time of 10.2 s, representing a three-fold reduction in acquisition time. The proposed iterative multiscale reconstruction reliably increases MRF acquisition speed and accuracy. Magn Reson Med 75:2481-2492, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Fertility Awareness

MedlinePlus

... time the couple using only fertility awareness for birth control who does not want to get pregnant should ... period. In general, how well each type of birth control method works depends on a lot of things. ...

Using volcanic tremor for eruption forecasting at White Island volcano (Whakaari), New Zealand

NASA Astrophysics Data System (ADS)

Chardot, Lauriane; Jolly, Arthur D.; Kennedy, Ben M.; Fournier, Nicolas; Sherburn, Steven

2015-09-01

Eruption forecasting is a challenging task because of the inherent complexity of volcanic systems. Despite remarkable efforts to develop complex models in order to explain volcanic processes prior to eruptions, the material Failure Forecast Method (FFM) is one of the very few techniques that can provide a forecast time for an eruption. However, the method requires testing and automation before being used as a real-time eruption forecasting tool at a volcano. We developed an automatic algorithm to issue forecasts from volcanic tremor increase episodes recorded by Real-time Seismic Amplitude Measurement (RSAM) at one station and optimised this algorithm for the period August 2011-January 2014 which comprises the recent unrest period at White Island volcano (Whakaari), New Zealand. A detailed residual analysis was paramount to select the most appropriate model explaining the RSAM time evolutions. In a hindsight simulation, four out of the five small eruptions reported during this period occurred within a failure window forecast by our optimised algorithm and the probability of an eruption on a day within a failure window was 0.21, which is 37 times higher than the probability of having an eruption on any day during the same period (0.0057). Moreover, the forecasts were issued prior to the eruptions by a few hours which is important from an emergency management point of view. Whereas the RSAM time evolutions preceding these four eruptions have a similar goodness-of-fit with the FFM, their spectral characteristics are different. The duration-amplitude distributions of the precursory tremor episodes support the hypothesis that several processes were likely occurring prior to these eruptions. We propose that slow rock failure and fluid flow processes are plausible candidates for the tremor source of these episodes. This hindsight exercise can be useful for future real-time implementation of the FFM at White Island. A similar methodology could also be tested at other volcanoes even if only a limited network is available.

An Observationally-Centred Method to Quantify the Changing Shape of Local Temperature Distributions

NASA Astrophysics Data System (ADS)

Chapman, S. C.; Stainforth, D. A.; Watkins, N. W.

2014-12-01

For climate sensitive decisions and adaptation planning, guidance on how local climate is changing is needed at the specific thresholds relevant to particular impacts or policy endeavours. This requires the quantification of how the distributions of variables, such as daily temperature, are changing at specific quantiles. These temperature distributions are non-normal and vary both geographically and in time. We present a method[1,2] for analysing local climatic time series data to assess which quantiles of the local climatic distribution show the greatest and most robust changes. We have demonstrated this approach using the E-OBS gridded dataset[3] which consists of time series of local daily temperature across Europe over the last 60 years. Our method extracts the changing cumulative distribution function over time and uses a simple mathematical deconstruction of how the difference between two observations from two different time periods can be assigned to the combination of natural statistical variability and/or the consequences of secular climate change. The change in temperature can be tracked at a temperature threshold, at a likelihood, or at a given return time, independently for each geographical location. Geographical correlations are thus an output of our method and reflect both climatic properties (local and synoptic), and spatial correlations inherent in the observation methodology. We find as an output many regionally consistent patterns of response of potential value in adaptation planning. For instance, in a band from Northern France to Denmark the hottest days in the summer temperature distribution have seen changes of at least 2°C over a 43 year period; over four times the global mean change over the same period. We discuss methods to quantify the robustness of these observed sensitivities and their statistical likelihood. This approach also quantifies the level of detail at which one might wish to see agreement between climate models and observations if such models are to be used directly as tools to assess climate change impacts at local scales. [1] S C Chapman, D A Stainforth, N W Watkins, 2013, Phil. Trans. R. Soc. A, 371 20120287. [2] D A Stainforth, S C Chapman, N W Watkins, 2013, Environ. Res. Lett. 8, 034031 [3] Haylock, M.R. et al., 2008, J. Geophys. Res (Atmospheres), 113, D20119

Nonlinear analysis of a closed-loop tractor-semitrailer vehicle system with time delay

NASA Astrophysics Data System (ADS)

Liu, Zhaoheng; Hu, Kun; Chung, Kwok-wai

2016-08-01

In this paper, a nonlinear analysis is performed on a closed-loop system of articulated heavy vehicles with driver steering control. The nonlinearity arises from the nonlinear cubic tire force model. An integration method is employed to derive an analytical periodic solution of the system in the neighbourhood of the critical speed. The results show that excellent accuracy can be achieved for the calculation of periodic solutions arising from Hopf bifurcation of the vehicle motion. A criterion is obtained for detecting the Bautin bifurcation which separates branches of supercritical and subcritical Hopf bifurcations. The integration method is compared to the incremental harmonic balance method in both supercritical and subcritical scenarios.

Weather Forecasting Systems and Methods

NASA Technical Reports Server (NTRS)

Mecikalski, John (Inventor); MacKenzie, Wayne M., Jr. (Inventor); Walker, John Robert (Inventor)

2014-01-01

A weather forecasting system has weather forecasting logic that receives raw image data from a satellite. The raw image data has values indicative of light and radiance data from the Earth as measured by the satellite, and the weather forecasting logic processes such data to identify cumulus clouds within the satellite images. For each identified cumulus cloud, the weather forecasting logic applies interest field tests to determine a score indicating the likelihood of the cumulus cloud forming precipitation and/or lightning in the future within a certain time period. Based on such scores, the weather forecasting logic predicts in which geographic regions the identified cumulus clouds will produce precipitation and/or lighting within during the time period. Such predictions may then be used to provide a weather map thereby providing users with a graphical illustration of the areas predicted to be affected by precipitation within the time period.

Time variation analysis of the daily Forbush decrease indices

NASA Astrophysics Data System (ADS)

Patra, Sankar Narayan; Ghosh, Koushik; Panja, Subhash Chandra

2011-08-01

In the present paper we have analyzed the daily Forbush decrease indices from January 1, 1967 to December 31, 2003. First filtering the time series by Simple Exponential Smoothing, we have applied Scargle Method of Periodogram on the processed time series in order to search for its time variation. Study exhibits periodicities around 174, 245, 261, 321, 452, 510, 571, 584, 662, 703, 735, 741, 767, 774, 820, 970, 1062, 1082, 1489, 1715, 2317, 2577, 2768, 3241 and 10630 days with confidence levels higher than 90%. Some of these periods are significantly similar to the observed periodicities of other solar activities, like solar filament activity, solar electron flare occurrence, solar-flare rate, solar proton events, solar neutrino flux, solar irradiance, cosmic ray intensity and flare, spectrum of the sunspot, solar wind, southern coronal hole area and solar cycle, which may suggest that the Forbush decrease behaves similarly to these solar activities and these activities may have a common origin.

Detecting daily routines of older adults using sensor time series clustering.

PubMed

Hajihashemi, Zahra; Yefimova, Maria; Popescu, Mihail

2014-01-01

The aim of this paper is to develop an algorithm to identify deviations in patterns of day-to-day activities of older adults to generate alerts to the healthcare providers for timely interventions. Daily routines, such as bathroom visits, can be monitored by automated in-home sensor systems. We present a novel approach that finds periodicity in sensor time series data using clustering approach. For this study, we used data set from TigerPlace, a retirement community in Columbia, MO, where apartments are equipped with a network of motion, pressure and depth sensors. A retrospective multiple case study (N=3) design was used to quantify bathroom visits as parts of the older adult's daily routine, over a 10-day period. The distribution of duration, number, and average time between sensor hits was used to define the confidence level for routine visit extraction. Then, a hierarchical clustering was applied to extract periodic patterns. The performance of the proposed method was evaluated through experimental results.

Optimal replenishment and credit policy in supply chain inventory model under two levels of trade credit with time- and credit-sensitive demand involving default risk

NASA Astrophysics Data System (ADS)

Mahata, Puspita; Mahata, Gour Chandra; Kumar De, Sujit

2018-03-01

Traditional supply chain inventory modes with trade credit usually only assumed that the up-stream suppliers offered the down-stream retailers a fixed credit period. However, in practice the retailers will also provide a credit period to customers to promote the market competition. In this paper, we formulate an optimal supply chain inventory model under two levels of trade credit policy with default risk consideration. Here, the demand is assumed to be credit-sensitive and increasing function of time. The major objective is to determine the retailer's optimal credit period and cycle time such that the total profit per unit time is maximized. The existence and uniqueness of the optimal solution to the presented model are examined, and an easy method is also shown to find the optimal inventory policies of the considered problem. Finally, numerical examples and sensitive analysis are presented to illustrate the developed model and to provide some managerial insights.

Constructing a multidimensional free energy surface like a spider weaving a web.

PubMed

Chen, Changjun

2017-10-15

Complete free energy surface in the collective variable space provides important information of the reaction mechanisms of the molecules. But, sufficient sampling in the collective variable space is not easy. The space expands quickly with the number of the collective variables. To solve the problem, many methods utilize artificial biasing potentials to flatten out the original free energy surface of the molecule in the simulation. Their performances are sensitive to the definitions of the biasing potentials. Fast-growing biasing potential accelerates the sampling speed but decreases the accuracy of the free energy result. Slow-growing biasing potential gives an optimized result but needs more simulation time. In this article, we propose an alternative method. It adds the biasing potential to a representative point of the molecule in the collective variable space to improve the conformational sampling. And the free energy surface is calculated from the free energy gradient in the constrained simulation, not given by the negative of the biasing potential as previous methods. So the presented method does not require the biasing potential to remove all the barriers and basins on the free energy surface exactly. Practical applications show that the method in this work is able to produce the accurate free energy surfaces for different molecules in a short time period. The free energy errors are small in the cases of various biasing potentials. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

What can we learn from simulating Stratospheric Sudden Warming periods with the Thermosphere-Ionosphere-Mesosphere-Electrodynamics GCM?

NASA Astrophysics Data System (ADS)

Maute, A. I.; Hagan, M. E.; Roble, R. G.; Richmond, A. D.; Yudin, V. A.; Liu, H.; Goncharenko, L. P.; Burns, A. G.; Maruyama, N.

2013-12-01

The ionosphere-thermosphere system is not only influenced from geospace but also by meteorological variability. Ionospheric observations of GPS TEC during the current solar cycle have shown that the meteorological variability is important during solar minimum, but also can have significant ionospheric effects during solar medium to maximum conditions. Numerical models can be used to help understand the mechanisms that couple the lower and upper atmosphere over the solar cycle. Numerical modelers invoke different methods to simulate realistic, specified events of meteorological variability, e.g. specify the lower boundary forcing, nudge the middle atmosphere, data assimilation. To study the vertical coupling, we first need to assess the numerical models and the various methods used to simulate realistic events with respect to the dynamics of the mesosphere-lower thermosphere (MLT) region, the electrodynamics, and the ionosphere. This study focuses on Stratospheric Sudden Warming (SSW) periods since these are associated with a strongly disturbed middle atmosphere which can have effects up to the ionosphere. We will use the NCAR Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation model (TIME-GCM) to examine several recent SSW periods, e.g. 2009, 2012, and 2013. The SSW period in TIME-GCM will be specified in three different ways: 1. using reanalysis data to specify the lower boundary; 2. nudging the neutral atmosphere (temperature and winds) with the Whole Atmosphere Community Climate Model (WACCM)/Goddard Earth Observing System Model, Version 5 (GEOS-5) results; 3. nudging the background atmosphere (temperature and winds) with WACCM/GEOS5 results. The different forcing methods will be evaluated for the SSW periods with respect to the dynamics of the MLT region, the low latitude vertical drift changes, and the ionospheric effects for the different SSW periods. With the help of ionospheric data at different longitudinal sectors it will be possible to assess the simulations of the SSW periods and provide guidance for future studies.

A new method to assess damage to RCMRFs from period elongation and Park-Ang damage index using IDA

NASA Astrophysics Data System (ADS)

Aghagholizadeh, Mehrdad; Massumi, Ali

2016-09-01

Despite a significant progress in loading and design codes of seismic resistant structures and technology improvements in building structures, the field of civil engineering is still facing critical challenges. An example of those challenges is the assessment of the state of damage that has been imposed to a structure after earthquakes of different intensities. To determine the operability of a structure and its resistance to probable future earthquakes, quick assessment of damages and determining the operability of a structure after an earthquake are crucial. Present methods to calculate damage to structures are time consuming and do not accurately provide the rate of damage. Damage estimation is important task in the fields of structural health monitoring and decision-making. This study examines the relationship between period elongation and the Park-Ang damage index. A dynamic non-linear analysis is employed with IDARC program to calculate the amount of damage and period of the current state. This new method is shown to be a quick and accurate technique for damage assessment. It is easy to calculate the period of an existing structure and changes in the period which reflects changes in the stiffness matrix.

Identifying and Correcting Timing Errors at Seismic Stations in and around Iran

DOE PAGES

Syracuse, Ellen Marie; Phillips, William Scott; Maceira, Monica; ...

2017-09-06

A fundamental component of seismic research is the use of phase arrival times, which are central to event location, Earth model development, and phase identification, as well as derived products. Hence, the accuracy of arrival times is crucial. However, errors in the timing of seismic waveforms and the arrival times based on them may go unidentified by the end user, particularly when seismic data are shared between different organizations. Here, we present a method used to analyze travel-time residuals for stations in and around Iran to identify time periods that are likely to contain station timing problems. For the 14more » stations with the strongest evidence of timing errors lasting one month or longer, timing corrections are proposed to address the problematic time periods. Finally, two additional stations are identified with incorrect locations in the International Registry of Seismograph Stations, and one is found to have erroneously reported arrival times in 2011.« less

A nudging-based data assimilation method: the Back and Forth Nudging (BFN) algorithm

NASA Astrophysics Data System (ADS)

Auroux, D.; Blum, J.

2008-03-01

This paper deals with a new data assimilation algorithm, called Back and Forth Nudging. The standard nudging technique consists in adding to the equations of the model a relaxation term that is supposed to force the observations to the model. The BFN algorithm consists in repeatedly performing forward and backward integrations of the model with relaxation (or nudging) terms, using opposite signs in the direct and inverse integrations, so as to make the backward evolution numerically stable. This algorithm has first been tested on the standard Lorenz model with discrete observations (perfect or noisy) and compared with the variational assimilation method. The same type of study has then been performed on the viscous Burgers equation, comparing again with the variational method and focusing on the time evolution of the reconstruction error, i.e. the difference between the reference trajectory and the identified one over a time period composed of an assimilation period followed by a prediction period. The possible use of the BFN algorithm as an initialization for the variational method has also been investigated. Finally the algorithm has been tested on a layered quasi-geostrophic model with sea-surface height observations. The behaviours of the two algorithms have been compared in the presence of perfect or noisy observations, and also for imperfect models. This has allowed us to reach a conclusion concerning the relative performances of the two algorithms.

The effect of adopting new storage methods for extending product validity periods on manufacturers expected inventory costs.

PubMed

Chen, Po-Yu

2014-01-01

The validness of the expiration dates (validity period) that manufacturers provide on food product labels is a crucial food safety problem. Governments must study how to use their authority by implementing fair awards and punishments to prompt manufacturers into adopting rigorous considerations, such as the effect of adopting new storage methods for extending product validity periods on expected costs. Assuming that a manufacturer sells fresh food or drugs, this manufacturer must respond to current stochastic demands at each unit of time to determine the purchase amount of products for sale. If this decision maker is capable and an opportunity arises, new packaging methods (e.g., aluminum foil packaging, vacuum packaging, high-temperature sterilization after glass packaging, or packaging with various degrees of dryness) or storage methods (i.e., adding desiccants or various antioxidants) can be chosen to extend the validity periods of products. To minimize expected costs, this decision maker must be aware of the processing costs of new storage methods, inventory standards, inventory cycle lengths, and changes in relationships between factors such as stochastic demand functions in a cycle. Based on these changes in relationships, this study established a mathematical model as a basis for discussing the aforementioned topics.

Extrasolar planet detection by binary stellar eclipse timing: evidence for a third body around CM Draconis

NASA Astrophysics Data System (ADS)

Deeg, H. J.; Ocaña, B.; Kozhevnikov, V. P.; Charbonneau, D.; O'Donovan, F. T.; Doyle, L. R.

2008-03-01

Aims:Our objective is to elucidate the physical process that causes the observed observed-minus-calculated (O-C) behavior in the M4.5/M4.5 binary CM Dra and to test for any evidence of a third body around the CM Dra system. Methods: New eclipse minimum timings of CM Dra were obtained between the years 2000 and 2007. The O-C times of the system are fitted against several functions, representing different physical origins of the timing variations. Results: Using our observational data in conjunction with published timings going back to 1977, a clear non-linearity in O-C times is apparent. An analysis using model-selection statistics gives about equal weight to a parabolic and to a sinusoidal fitting function. Attraction from a third body, either at large distance in a quasi-constant constellation across the years of observations or from a body on a shorter orbit generating periodicities in O-C times is the most likely source of the observed O-C times. The white dwarf GJ 630.1B, a proper motion companion of CM Dra, can however be rejected as the responsible third body. Also, no further evidence of the short-periodic planet candidate described by Deeg et al. (2000, A&A, 358, L5) is found, whereas other mechanisms, such as period changes from stellar winds or Applegate's mechanism can be rejected. Conclusions: A third body, being either a few-Jupiter-mass object with a period of 18.5 ± 4.5 years or an object in the mass range of 1.5 M_jup to 0.1 M⊙ with periods of hundreds to thousands of years is the most likely origin of the observed minimum timing behavior.

Portable automation of static chamber sample collection for quantifying soil gas flux

USDA-ARS?s Scientific Manuscript database

The collection of soil gas flux using the static chamber method is labor intensive. The number of chambers that can be sampled in a given time period is limited by the spacing between chambers and the availability of trained research technicians. However, the static chamber method can limit spatial ...

Detection of faults in rotating machinery using periodic time-frequency sparsity

NASA Astrophysics Data System (ADS)

Ding, Yin; He, Wangpeng; Chen, Binqiang; Zi, Yanyang; Selesnick, Ivan W.

2016-11-01

This paper addresses the problem of extracting periodic oscillatory features in vibration signals for detecting faults in rotating machinery. To extract the feature, we propose an approach in the short-time Fourier transform (STFT) domain where the periodic oscillatory feature manifests itself as a relatively sparse grid. To estimate the sparse grid, we formulate an optimization problem using customized binary weights in the regularizer, where the weights are formulated to promote periodicity. In order to solve the proposed optimization problem, we develop an algorithm called augmented Lagrangian majorization-minimization algorithm, which combines the split augmented Lagrangian shrinkage algorithm (SALSA) with majorization-minimization (MM), and is guaranteed to converge for both convex and non-convex formulation. As examples, the proposed approach is applied to simulated data, and used as a tool for diagnosing faults in bearings and gearboxes for real data, and compared to some state-of-the-art methods. The results show that the proposed approach can effectively detect and extract the periodical oscillatory features.

Spectrum interrogation of fiber acoustic sensor based on self-fitting and differential method.

PubMed

Fu, Xin; Lu, Ping; Ni, Wenjun; Liao, Hao; Wang, Shun; Liu, Deming; Zhang, Jiangshan

2017-02-20

In this article, we propose an interrogation method of fiber acoustic sensor to recover the time-domain signal from the sensor spectrum. The optical spectrum of the sensor will show a ripple waveform when responding to acoustic signal due to the scanning process in a certain wavelength range. The reason behind this phenomenon is the dynamic variation of the sensor spectrum while the intensity of different wavelength is acquired at different time in a scanning period. The frequency components can be extracted from the ripple spectrum assisted by the wavelength scanning speed. The signal is able to be recovered by differential between the ripple spectrum and its self-fitted curve. The differential process can eliminate the interference caused by environmental perturbations such as temperature or refractive index (RI), etc. The proposed method is appropriate for fiber acoustic sensors based on gratings or interferometers. A long period grating (LPG) is adopted as an acoustic sensor head to prove the feasibility of the interrogation method in experiment. The ability to compensate the environmental fluctuations is also demonstrated.

Periodicity and eclipse minima timing of CM Draconis.

NASA Astrophysics Data System (ADS)

Vázquez-Martín, S.; Deeg, H. J.; Dreizler, S.; von Essen, C.; Kozhevnikov, V. P.

2015-05-01

Periodic deviations from a linear ephemeris of a binary star's eclipses can indicate the presence of a third body in orbit around both. Hints for such companion around the M4.5/M4.5 binary CMDra were published by Deeg et al. (2008). The assignment of a planet in the CMDra system can however only be accepted if the earlier observed periodicity trends can be verified through further observations over several years. For eclipsing binary stars of low mass, the method of eclipse minimum timing allows one to set mass limits for the detection of a third body. Deeg et al. (2008) concluded that the two possibilities for the source of CMDra's timing variations that remain valid are a planet of a few Jupiter masses on a two decade-long orbit, or an object on a century-to-millenium long orbit with masses 1.5M_J < M_{p} < 0.1M_{⊙}. However, they concluded that it is necessary to do continued observations of the timing of CMDra's eclipses to be decisive regarding the continued viability of the sinusoidal-fit-model, and hence, about the validity of a Jovian-type planet in a circumbinary orbiting around the system. Here we update the analysis of Deeg et al. (2008), including further data presented in Morales et al. (2009r) and new observations taken at Ural Observatory (2008-2013). Eclipse minimum times were obtained using the Kwee-van-Woerden method.

Characterizing the Recurrence of Hydrologic Droughts

NASA Astrophysics Data System (ADS)

Cancelliere, A.; Salas, J. D.

2002-12-01

Characterizing periods of deficit and drought has been an important aspect in planning and management of water resources systems for many decades. An extreme drought is a complex phenomenon that evolves through time and space in a random fashion. It may be characterized by its initiation, duration, severity (magnitude or intensity), spatial extent, and termination. These characteristics may be determined by comparing the water supply time series versus the corresponding water demand series in the area of consideration. Because the water supply quantities such as rainfall and streamflow are stochastic variables the ensuing drought characteristics are random and must be described in probabilistic terms. Let us consider a periodic stochastic water supply and a variable water demand series. A drought event is defined as a succession of consecutive periods (run) in which the water supply remains below the water demand. Thus, the drought length L (negative run length) is the number of consecutive time intervals (seasons) in which the water supply remains below the water demand, preceded and followed by (at least one season where) the water supply is equal or greater than the demand. Likewise, the difference between the water demand and the supply at time t is the magnitude of the deficit at time t so that the accumulated deficit D (drought magnitude) is the sum of the deficits over the drought duration L. In the study reported herein, the probability density functions (pdf) of drought length and drought magnitude and their low order moments are derived assuming that the underlying water supply series after is clipped by a constant or periodic water demand results in a periodic dependent binary series that is represented by a periodic two-state Markov chain. The derived pdfs allow estimating the occurrence probabilities of droughts of a given length where either the drought begins in a given season or regardless of the initial season. In addition, the return periods of droughts (based on length and magnitude) are determined. The applicability of the drought formulations is illustrated using several series of precipitation and streamflow in Sicily, Italy and Colorado, USA. The results obtained show an excellent agreement between the observed and theoretical results. In conclusion, the proposed methods appear to be a useful addition for drought analysis and characterization using stochastic methods.

On the bistable zone of milling processes

PubMed Central

Dombovari, Zoltan; Stepan, Gabor

2015-01-01

A modal-based model of milling machine tools subjected to time-periodic nonlinear cutting forces is introduced. The model describes the phenomenon of bistability for certain cutting parameters. In engineering, these parameter domains are referred to as unsafe zones, where steady-state milling may switch to chatter for certain perturbations. In mathematical terms, these are the parameter domains where the periodic solution of the corresponding nonlinear, time-periodic delay differential equation is linearly stable, but its domain of attraction is limited due to the existence of an unstable quasi-periodic solution emerging from a secondary Hopf bifurcation. A semi-numerical method is presented to identify the borders of these bistable zones by tracking the motion of the milling tool edges as they might leave the surface of the workpiece during the cutting operation. This requires the tracking of unstable quasi-periodic solutions and the checking of their grazing to a time-periodic switching surface in the infinite-dimensional phase space. As the parameters of the linear structural behaviour of the tool/machine tool system can be obtained by means of standard modal testing, the developed numerical algorithm provides efficient support for the design of milling processes with quick estimates of those parameter domains where chatter can still appear in spite of setting the parameters into linearly stable domains. PMID:26303918

Identifying Time Periods of Minimal Thermal Gradient for Temperature-Driven Structural Health Monitoring

PubMed Central

Reilly, John; Glisic, Branko

2018-01-01

Temperature changes play a large role in the day to day structural behavior of structures, but a smaller direct role in most contemporary Structural Health Monitoring (SHM) analyses. Temperature-Driven SHM will consider temperature as the principal driving force in SHM, relating a measurable input temperature to measurable output generalized strain (strain, curvature, etc.) and generalized displacement (deflection, rotation, etc.) to create three-dimensional signatures descriptive of the structural behavior. Identifying time periods of minimal thermal gradient provides the foundation for the formulation of the temperature–deformation–displacement model. Thermal gradients in a structure can cause curvature in multiple directions, as well as non-linear strain and stress distributions within the cross-sections, which significantly complicates data analysis and interpretation, distorts the signatures, and may lead to unreliable conclusions regarding structural behavior and condition. These adverse effects can be minimized if the signatures are evaluated at times when thermal gradients in the structure are minimal. This paper proposes two classes of methods based on the following two metrics: (i) the range of raw temperatures on the structure, and (ii) the distribution of the local thermal gradients, for identifying time periods of minimal thermal gradient on a structure with the ability to vary the tolerance of acceptable thermal gradients. The methods are tested and validated with data collected from the Streicker Bridge on campus at Princeton University. PMID:29494496

Identifying Time Periods of Minimal Thermal Gradient for Temperature-Driven Structural Health Monitoring.

PubMed

Reilly, John; Glisic, Branko

2018-03-01

Temperature changes play a large role in the day to day structural behavior of structures, but a smaller direct role in most contemporary Structural Health Monitoring (SHM) analyses. Temperature-Driven SHM will consider temperature as the principal driving force in SHM, relating a measurable input temperature to measurable output generalized strain (strain, curvature, etc.) and generalized displacement (deflection, rotation, etc.) to create three-dimensional signatures descriptive of the structural behavior. Identifying time periods of minimal thermal gradient provides the foundation for the formulation of the temperature-deformation-displacement model. Thermal gradients in a structure can cause curvature in multiple directions, as well as non-linear strain and stress distributions within the cross-sections, which significantly complicates data analysis and interpretation, distorts the signatures, and may lead to unreliable conclusions regarding structural behavior and condition. These adverse effects can be minimized if the signatures are evaluated at times when thermal gradients in the structure are minimal. This paper proposes two classes of methods based on the following two metrics: (i) the range of raw temperatures on the structure, and (ii) the distribution of the local thermal gradients, for identifying time periods of minimal thermal gradient on a structure with the ability to vary the tolerance of acceptable thermal gradients. The methods are tested and validated with data collected from the Streicker Bridge on campus at Princeton University.

A time series modeling approach in risk appraisal of violent and sexual recidivism.

PubMed

Bani-Yaghoub, Majid; Fedoroff, J Paul; Curry, Susan; Amundsen, David E

2010-10-01

For over half a century, various clinical and actuarial methods have been employed to assess the likelihood of violent recidivism. Yet there is a need for new methods that can improve the accuracy of recidivism predictions. This study proposes a new time series modeling approach that generates high levels of predictive accuracy over short and long periods of time. The proposed approach outperformed two widely used actuarial instruments (i.e., the Violence Risk Appraisal Guide and the Sex Offender Risk Appraisal Guide). Furthermore, analysis of temporal risk variations based on specific time series models can add valuable information into risk assessment and management of violent offenders.

Spectral-decomposition techniques for the identification of radon anomalies temporally associated with earthquakes occurring in the UK in 2002 and 2008.

NASA Astrophysics Data System (ADS)

Crockett, R. G. M.; Gillmore, G. K.

2009-04-01

During the second half of 2002, the University of Northampton Radon Research Group operated two continuous hourly-sampling radon detectors 2.25 km apart in Northampton, in the (English) East Midlands. This period included the Dudley earthquake (22/09/2002) which was widely noticed by members of the public in the Northampton area. Also, at various periods during 2008 the Group has operated another pair of continuous hourly-sampling radon detectors similar distances apart in Northampton. One such period included the Market Rasen earthquake (27/02/2008) which was also widely noticed by members of the public in the Northampton area. During each period of monitoring, two time-series of radon readings were obtained, one from each detector. These have been analysed for evidence of simultaneous similar anomalies: the premise being that big disturbances occurring at big distances (in relation to the detector separation) should produce simultaneous similar anomalies but that simultaneous anomalies occurring by chance will be dissimilar. As previously reported, cross-correlating the two 2002 time-series over periods of 1-30 days duration, rolled forwards through the time-series at one-hour intervals produced two periods of significant correlation, i.e. two periods of simultaneous similar behaviour in the radon concentrations. One of these periods corresponded in time to the Dudley earthquake, the other corresponded in time to a smaller earthquake which occurred in the English Channel (26/08/2002). We here report subsequent investigation of the 2002 time-series and the 2008 time-series using spectral-decomposition techniques. These techniques have revealed additional simultaneous similar behaviour in the two radon concentrations, not revealed by the rolling correlation on the raw data. These correspond in time to the Manchester earthquake swarm of October 2002 and the Market Rasen earthquake of February 2008. The spectral-decomposition techniques effectively ‘de-noise' the data, and also remove lower-frequency variations (e.g. tidal variations), revealing the simultaneous similarities. Whilst this is very much work in progress, there is the potential that such techniques enhance the possibility that simultaneous real-time monitoring of radon levels - for short-term simultaneous anomalies - at several locations in earthquake areas might provide the core of an earthquake prediction method. Keywords: Radon; earthquakes; time series; cross-correlation; spectral-decomposition; real-time simultaneous monitoring.

Analysis of the impact of crude oil price fluctuations on China's stock market in different periods-Based on time series network model

NASA Astrophysics Data System (ADS)

An, Yang; Sun, Mei; Gao, Cuixia; Han, Dun; Li, Xiuming

2018-02-01

This paper studies the influence of Brent oil price fluctuations on the stock prices of China's two distinct blocks, namely, the petrochemical block and the electric equipment and new energy block, applying the Shannon entropy of information theory. The co-movement trend of crude oil price and stock prices is divided into different fluctuation patterns with the coarse-graining method. Then, the bivariate time series network model is established for the two blocks stock in five different periods. By joint analysis of the network-oriented metrics, the key modes and underlying evolutionary mechanisms were identified. The results show that the both networks have different fluctuation characteristics in different periods. Their co-movement patterns are clustered in some key modes and conversion intermediaries. The study not only reveals the lag effect of crude oil price fluctuations on the stock in Chinese industry blocks but also verifies the necessity of research on special periods, and suggests that the government should use different energy policies to stabilize market volatility in different periods. A new way is provided to study the unidirectional influence between multiple variables or complex time series.

Economic Sanctions, Military Activity, and Road Traffic Crashes in Vojvodina, Serbia

PubMed Central

Ðurić, Predrag; Peek-Asa, Corinne

2008-01-01

Objectives Political violence has not been examined as a risk factor for traumatic injuries from road traffic crashes. We identify trends in road traffic crashes related to war-related military activity and international economic sanctions in the Autonomous Province of Vojvodina, Serbia. Methods Overall road traffic crashes and crashes leading to hospitalization and fatality in Vojvodina, Serbia were examined from 1996 through 2001. Rates were calculated per 100,000 population and per 10,000 registered vehicles. Three time periods were examined: years with international sanctions and military activity; years with international sanctions but no military activity; and, years with neither sanctions nor military activity. Results Compared to the period with neither sanctions nor military activity, severe injury crashes were 1.23 times more frequent (95% CI = 1.19 – 1.27) during the period with sanctions and military activity and 1.21 times more frequent (95% CI= 1.16 – 1.27) during the period with sanctions but no military activity. Conclusions Our data suggest that vehicle travel became safer following the end of military action and economic sanctions. Road traffic safety needs to be a priority both during periods of political unrest and its recovery phase. PMID:19074242

Analysis of arson fire debris by low temperature dynamic headspace adsorption porous layer open tubular columns.

PubMed

Nichols, Jessica E; Harries, Megan E; Lovestead, Tara M; Bruno, Thomas J

2014-03-21

In this paper we present results of the application of PLOT-cryoadsorption (PLOT-cryo) to the analysis of ignitable liquids in fire debris. We tested ignitable liquids, broadly divided into fuels and solvents (although the majority of the results presented here were obtained with gasoline and diesel fuel) on three substrates: Douglas fir, oak plywood and Nylon carpet. We determined that PLOT-cryo allows the analyst to distinguish all of the ignitable liquids tested by use of a very rapid sampling protocol, and performs better (more recovered components, higher efficiency, lower elution solvent volumes) than a conventional purge and trap method. We also tested the effect of latency (the time period between applying the ignitable liquid and ignition), and we tested a variety of sampling times and a variety of PLOT capillary lengths. Reliable results can be obtained with sampling time periods as short as 3min, and on PLOT capillaries as short as 20cm. The variability of separate samples was also assessed, a study made possible by the high throughput nature of the PLOT-cryo method. We also determined that the method performs better than the conventional carbon strip method that is commonly used in fire debris analysis. Published by Elsevier B.V.

Comparison of floods non-stationarity detection methods: an Austrian case study

NASA Astrophysics Data System (ADS)

Salinas, Jose Luis; Viglione, Alberto; Blöschl, Günter

2016-04-01

Non-stationarities in flood regimes have a huge impact in any mid and long term flood management strategy. In particular the estimation of design floods is very sensitive to any kind of flood non-stationarity, as they should be linked to a return period, concept that can be ill defined in a non-stationary context. Therefore it is crucial when analyzing existent flood time series to detect and, where possible, attribute flood non-stationarities to changing hydroclimatic and land-use processes. This works presents the preliminary results of applying different non-stationarity detection methods on annual peak discharges time series over more than 400 gauging stations in Austria. The kind of non-stationarities analyzed include trends (linear and non-linear), breakpoints, clustering beyond stochastic randomness, and detection of flood rich/flood poor periods. Austria presents a large variety of landscapes, elevations and climates that allow us to interpret the spatial patterns obtained with the non-stationarity detection methods in terms of the dominant flood generation mechanisms.

Advanced techniques for determining long term compatibility of materials with propellants

NASA Technical Reports Server (NTRS)

Green, R. L.; Stebbins, J. P.; Smith, A. W.; Pullen, K. E.

1973-01-01

A method for the prediction of propellant-material compatibility for periods of time up to ten years is presented. Advanced sensitive measurement techniques used in the prediction method are described. These include: neutron activation analysis, radioactive tracer technique, and atomic absorption spectroscopy with a graphite tube furnace sampler. The results of laboratory tests performed to verify the prediction method are presented.

Ionic Liquids as templating agents in formation of uranium-containing nanomaterials

DOEpatents

Visser, Ann E; Bridges, Nicholas J

2014-06-10

A method for forming nanoparticles containing uranium oxide is described. The method includes combining a uranium-containing feedstock with an ionic liquid to form a mixture and holding the mixture at an elevated temperature for a period of time to form the product nanoparticles. The method can be carried out at low temperatures, for instance less than about 300.degree. C.

The adjusting factor method for weight-scaling truckloads of mixed hardwood sawlogs

Treesearch

Edward L. Adams

1976-01-01

A new method of weight-scaling truckloads of mixed hardwood sawlogs systematically adjusts for changes in the weight/volume ratio of logs coming into a sawmill. It uses a conversion factor based on the running average of weight/volume ratios of randomly selected sample loads. A test of the method indicated that over a period of time the weight-scaled volume should...

Changes to habitats over time in Narragansett Bay and setting management targets using BCG approaches

EPA Science Inventory

We compare changes in the distributions of seagrass, benthic, macroalgal, saltmarsh, and shellfish habitat in Narragansett Bay (U.S.A.) since the 1700s to changes in stressors and management decisions over the same time period, and describe a method that management programs can u...

Intra- to Multi-Decadal Temperature Variability over the Continental United States: 1896-2012

USDA-ARS?s Scientific Manuscript database

The Optimal Ranking Regime (ORR) method was used to identify intra- to multi-decadal (IMD) time windows containing significant ranking sequences in U.S. climate division temperature data. The simplicity of the ORR procedure’s output – a time series’ most significant non-overlapping periods of high o...

Optimal ranking regime analysis of intra- to multidecadal U.S. climate variability. Part I: Temperature

USDA-ARS?s Scientific Manuscript database

The Optimal Ranking Regime (ORR) method was used to identify intra- to multi-decadal (IMD) time windows containing significant ranking sequences in U.S. climate division temperature data. The simplicity of the ORR procedure’s output – a time series’ most significant non-overlapping periods of high o...

A general statistical test for correlations in a finite-length time series.

PubMed

Hanson, Jeffery A; Yang, Haw

2008-06-07

The statistical properties of the autocorrelation function from a time series composed of independently and identically distributed stochastic variables has been studied. Analytical expressions for the autocorrelation function's variance have been derived. It has been found that two common ways of calculating the autocorrelation, moving-average and Fourier transform, exhibit different uncertainty characteristics. For periodic time series, the Fourier transform method is preferred because it gives smaller uncertainties that are uniform through all time lags. Based on these analytical results, a statistically robust method has been proposed to test the existence of correlations in a time series. The statistical test is verified by computer simulations and an application to single-molecule fluorescence spectroscopy is discussed.

The ACGME case log: General surgery resident experience in pediatric surgery

PubMed Central

Gow, Kenneth W.; Drake, F. Thurston; Aarabi, Shahram; Waldhausen, John H.

2014-01-01

Background General surgery (GS) residents in ACGME programs log cases performed during their residency. We reviewed designated pediatric surgery (PS) cases to assess for changes in performed cases over time. Methods The ACGME case logs for graduating GS residents were reviewed from academic year (AY) 1989–1990 to 2010–2011 for designated pediatric cases. Overall and designated PS cases were analyzed. Data were combined into five blocks: Period I (AY1989–90 to AY1993–94), Period II (AY1994–95 to AY1998–99), Period III (AY1999–00 to AY2002–03), Period IV (AY2003–04 to AY2006–07), and Period V (AY2007–08 to AY2010–11). Periods IV and V were delineated by implementation of duty hour restrictions. Student t-tests compared averages among the time periods with significance at P < .05. Results Overall GS case load remained relatively stable. Of total cases, PS cases accounted for 5.4% in Period I and 3.7% in Period V. Designated pediatric cases declined for each period from an average of 47.7 in Period I to 33.8 in Period V. These changes are due to a decline in hernia repairs, which account for half of cases. All other cases contributed only minimally to the pediatric cases. The only laparoscopic cases in the database were anti-reflux procedures, which increased over time. Conclusions GS residents perform a diminishing number of designated PS cases. This decline occurred before the onset of work-hour restrictions. These changes have implications on the capabilities of the current graduating workforce. However, the case log does not reflect all cases trainees may be exposed to, so revision of this list is recommended. PMID:23932601

Profiling defect depth in composite materials using thermal imaging NDE

NASA Astrophysics Data System (ADS)

Obeidat, Omar; Yu, Qiuye; Han, Xiaoyan

2018-04-01

Sonic Infrared (IR) NDE, is a relatively new NDE technology; it has been demonstrated as a reliable and sensitive method to detect defects. SIR uses ultrasonic excitation with IR imaging to detect defects and flaws in the structures being inspected. An IR camera captures infrared radiation from the target for a period of time covering the ultrasound pulse. This period of time may be much longer than the pulse depending on the defect depth and the thermal properties of the materials. With the increasing deployment of composites in modern aerospace and automobile structures, fast, wide-area and reliable NDE methods are necessary. Impact damage is one of the major concerns in modern composites. Damage can occur at a certain depth without any visual indication on the surface. Defect depth information can influence maintenance decisions. Depth profiling relies on the time delays in the captured image sequence. We'll present our work on the defect depth profiling by using the temporal information of IR images. An analytical model is introduced to describe heat diffusion from subsurface defects in composite materials. Depth profiling using peak time is introduced as well.

Method for determining the concentration of atomic species in gases and solids

DOEpatents

Loge, Gary W.

1998-01-01

Method for determining the concentration of atomic species in gases and solids. Measurement of at least two emission intensities from a species in a sample that is excited by incident laser radiation. Which generates a plasma therein after a sufficient time period has elapsed and during a second time period, permits an instantaneous temperature to be established within the sample. The concentration of the atomic species to be determined is then derived from the known emission intensity of a predetermined concentration of that species in the sample at the measured temperature, a quantity which is measured prior to the determination of the unknown concentration, and the actual measured emission from the unknown species, or by this latter emission and the emission intensity of a species having known concentration within the sample such as nitrogen for gaseous air samples.

Continuous-Time Bilinear System Identification

NASA Technical Reports Server (NTRS)

Juang, Jer-Nan

2003-01-01

The objective of this paper is to describe a new method for identification of a continuous-time multi-input and multi-output bilinear system. The approach is to make judicious use of the linear-model properties of the bilinear system when subjected to a constant input. Two steps are required in the identification process. The first step is to use a set of pulse responses resulting from a constant input of one sample period to identify the state matrix, the output matrix, and the direct transmission matrix. The second step is to use another set of pulse responses with the same constant input over multiple sample periods to identify the input matrix and the coefficient matrices associated with the coupling terms between the state and the inputs. Numerical examples are given to illustrate the concept and the computational algorithm for the identification method.

Identification of the period of stability in a balance test after stepping up using a simplified cumulative sum.

PubMed

Safieddine, Doha; Chkeir, Aly; Herlem, Cyrille; Bera, Delphine; Collart, Michèle; Novella, Jean-Luc; Dramé, Moustapha; Hewson, David J; Duchêne, Jacques

2017-11-01

Falls are a major cause of death in older people. One method used to predict falls is analysis of Centre of Pressure (CoP) displacement, which provides a measure of balance quality. The Balance Quality Tester (BQT) is a device based on a commercial bathroom scale that calculates instantaneous values of vertical ground reaction force (Fz) as well as the CoP in both anteroposterior (AP) and mediolateral (ML) directions. The entire testing process needs to take no longer than 12 s to ensure subject compliance, making it vital that calculations related to balance are only calculated for the period when the subject is static. In the present study, a method is presented to detect the stabilization period after a subject has stepped onto the BQT. Four different phases of the test are identified (stepping-on, stabilization, balancing, stepping-off), ensuring that subjects are static when parameters from the balancing phase are calculated. The method, based on a simplified cumulative sum (CUSUM) algorithm, could detect the change between unstable and stable stance. The time taken to stabilize significantly affected the static balance variables of surface area and trajectory velocity, and was also related to Timed-up-and-Go performance. Such a finding suggests that the time to stabilize could be a worthwhile parameter to explore as a potential indicator of balance problems and fall risk in older people. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

[Gene method for inconsistent hydrological frequency calculation. I: Inheritance, variability and evolution principles of hydrological genes].

PubMed

Xie, Ping; Wu, Zi Yi; Zhao, Jiang Yan; Sang, Yan Fang; Chen, Jie

2018-04-01

A stochastic hydrological process is influenced by both stochastic and deterministic factors. A hydrological time series contains not only pure random components reflecting its inheri-tance characteristics, but also deterministic components reflecting variability characteristics, such as jump, trend, period, and stochastic dependence. As a result, the stochastic hydrological process presents complicated evolution phenomena and rules. To better understand these complicated phenomena and rules, this study described the inheritance and variability characteristics of an inconsistent hydrological series from two aspects: stochastic process simulation and time series analysis. In addition, several frequency analysis approaches for inconsistent time series were compared to reveal the main problems in inconsistency study. Then, we proposed a new concept of hydrological genes origined from biological genes to describe the inconsistent hydrolocal processes. The hydrologi-cal genes were constructed using moments methods, such as general moments, weight function moments, probability weight moments and L-moments. Meanwhile, the five components, including jump, trend, periodic, dependence and pure random components, of a stochastic hydrological process were defined as five hydrological bases. With this method, the inheritance and variability of inconsistent hydrological time series were synthetically considered and the inheritance, variability and evolution principles were fully described. Our study would contribute to reveal the inheritance, variability and evolution principles in probability distribution of hydrological elements.

The Effect of maceration period on contents and color brightness of phycoerythrin from Gracilaria sp.

NASA Astrophysics Data System (ADS)

Lidiana, H.; Sulmartiwi, L.; Andriyono, S.

2018-04-01

Natural pigment from seaweed, is currently required by humans as one of active compounds that are usefull in the field of health, cosmetics and food. One of the pigments which potentially can be developed is red phycobilin pigment. The pigment can be obtained from Gracilaria sp. throught maceration method. This research aims to find out wheter there is influence from the long maceration time toward to the content and the phycoerytrin color brightness of Gracilaria sp. The reseach method used experimental experiment with complete randomized design (CRD) which was consisted of nine treatments of long time maceration period three replications. Data analysis was used the Analysis of Variance (ANOVA) and continued to Duncan’s Multiple Distance Test to. The result showed that treatments with the time of maceration for 30 hours was the best treatment on phycoerytrin content about 0.98 mg/g with the brightness value was 19.73 L*, reddish value was 7.23 a*, and yellowish value was 2.87 b* of Gracilaria sp.

Evapotranspiration Partitioning Using Rapid Measurements of Isotopic Composition of Water Vapor in a Semi Arid Evergreen Forest

NASA Astrophysics Data System (ADS)

Meuth, J. A.; Dominguez, F.

2011-12-01

Evapotranspiration partitioning into transpiration and evaporation is an important step in understanding the relative contribution of the vegetated land surface to total atmospheric moisture in an area. This type of study has rarely been done over long time periods focusing on small time scales of variation. The relative contributions of whole canopy transpiration and soil evaporation to total evapotranspiration were determined in a mid-latitude semi arid evergreen forest using stable isotope measurements of atmospheric water vapor. We used a cavity ringdown spectrometer to collect continuous 5-second average isotopic and water vapor measurements throughout the ecosystem boundary layer. In addition, we analyzed the isotopic composition of liquid water extracted from soil, leaf and stem samples to obtain relative contributions of transpiration and evaporation to whole canopy evapotranspriation. The results from this method provided many time periods throughout the day with statistically significant data. This method can be used to follow daily, monthly, or yearly cycles of evapotranspiration partitioning with relative ease and accuracy.

Nonlinear dynamics analysis of the spur gear system for railway locomotive

NASA Astrophysics Data System (ADS)

Wang, Junguo; He, Guangyue; Zhang, Jie; Zhao, Yongxiang; Yao, Yuan

2017-02-01

Considering the factors such as the nonlinearity backlash, static transmission error and time-varying meshing stiffness, a three-degree-of-freedom torsional vibration model of spur gear transmission system for a typical locomotive is developed, in which the wheel/rail adhesion torque is considered as uncertain but bounded parameter. Meantime, the Ishikawa method is used for analysis and calculation of the time-varying mesh stiffness of the gear pair in meshing process. With the help of bifurcation diagrams, phase plane diagrams, Poincaré maps, time domain response diagrams and amplitude-frequency spectrums, the effects of the pinion speed and stiffness on the dynamic behavior of gear transmission system for locomotive are investigated in detail by using the numerical integration method. Numerical examples reveal various types of nonlinear phenomena and dynamic evolution mechanism involving one-period responses, multi-periodic responses, bifurcation and chaotic responses. Some research results present useful information to dynamic design and vibration control of the gear transmission system for railway locomotive.

Comparison of carbon uptake estimates from forest inventory and Eddy-Covariance for a montane rainforest in central Sulawesi

NASA Astrophysics Data System (ADS)

Heimsch, Florian; Kreilein, Heiner; Rauf, Abdul; Knohl, Alexander

2016-04-01

Rainforests in general and montane rainforests in particular have rarely been studied over longer time periods. We aim to provide baseline information of a montane tropical forest's carbon uptake over time in order to quantify possible losses through land-use change. Thus we conducted a re-inventory of 22 10-year old forest inventory plots, giving us a rare opportunity to quantify carbon uptake over such a long time period by traditional methods. We discuss shortfalls of such techniques and why our estimate of 1.5 Mg/ha/a should be considered as the lower boundary and not the mean carbon uptake per year. At the same location as the inventory, CO2 fluxes were measured with the Eddy-Covariance technique. Measurements were conducted at 48m height with an LI 7500 open-path infrared gas analyser. We will compare carbon uptake estimates from these measurements to those of the more conventional inventory method and discuss, which factors are probably responsible for differences.

Spectral Estimation Techniques for time series with Long Gaps: Applications to Paleomagnetism and Geomagnetic Depth Sounding

NASA Astrophysics Data System (ADS)

Smith-Boughner, Lindsay

Many Earth systems cannot be studied directly. One cannot measure the velocities of convecting fluid in the Earth's core but can measure the magnetic field generated by these motions on the surface. Examining how the magnetic field changes over long periods of time, using power spectral density estimation provides insight into the dynamics driving the system. The changes in the magnetic field can also be used to study Earth properties - variations in magnetic fields outside of Earth like the ring-current induce currents to flow in the Earth, generating magnetic fields. Estimating the transfer function between the external changes and the induced response characterizes the electromagnetic response of the Earth. From this response inferences can be made about the electrical conductivity of the Earth. However, these types of time series, and many others have long breaks in the record with no samples available and limit the analysis. Standard methods require interpolation or section averaging, with associated problems of introducing bias or reducing the frequency resolution. Extending the methods of Fodor and Stark (2000), who adapt a set of orthogonal multi-tapers to compensate for breaks in sampling- an algorithm and software package for applying these techniques is developed. Methods of empirically estimating the average transfer function of a set of tapers and confidence intervals are also tested. These methods are extended for cross-spectral, coherence and transfer function estimation in the presence of noise. With these methods, new analysis of a highly interrupted ocean sediment core from the Oligocene (Hartl et al., 1993) reveals a quasi-periodic signal in the calibrated paleointensity time series at 2.5 cpMy. The power in the magnetic field during this period appears to be dominated by reversal rate processes with less overall power than the early Oligocene. Previous analysis of the early Oligocene by Constable et al. (1998) detected a signal near 8 cpMy. These results suggest that a strong magnetic field inhibits reversals and has more variability in shorter term field changes. Using over 9 years of data from the CHAMP low-Earth orbiting magnetic satellite and the techniques developed here, more robust estimates of the electromagnetic response of the Earth can be made. The tapers adapted for gaps provide flexibility to study the effects of local time, storm conditions on Earth's 1-D electromagnetic response as well as providing robust estimates of the C-response at longer periods than previous satellite studies.

Nano-material and method of fabrication

DOEpatents

Menchhofer, Paul A; Seals, Roland D; Howe, Jane Y; Wang, Wei

2015-02-03

A fluffy nano-material and method of manufacture are described. At 2000.times. magnification the fluffy nanomaterial has the appearance of raw, uncarded wool, with individual fiber lengths ranging from approximately four microns to twenty microns. Powder-based nanocatalysts are dispersed in the fluffy nanomaterial. The production of fluffy nanomaterial typically involves flowing about 125 cc/min of organic vapor at a pressure of about 400 torr over powder-based nano-catalysts for a period of time that may range from approximately thirty minutes to twenty-four hours.

Passive acoustic monitoring of beaked whale densities in the Gulf of Mexico.

PubMed

Hildebrand, John A; Baumann-Pickering, Simone; Frasier, Kaitlin E; Trickey, Jennifer S; Merkens, Karlina P; Wiggins, Sean M; McDonald, Mark A; Garrison, Lance P; Harris, Danielle; Marques, Tiago A; Thomas, Len

2015-11-12

Beaked whales are deep diving elusive animals, difficult to census with conventional visual surveys. Methods are presented for the density estimation of beaked whales, using passive acoustic monitoring data collected at sites in the Gulf of Mexico (GOM) from the period during and following the Deepwater Horizon oil spill (2010-2013). Beaked whale species detected include: Gervais' (Mesoplodon europaeus), Cuvier's (Ziphius cavirostris), Blainville's (Mesoplodon densirostris) and an unknown species of Mesoplodon sp. (designated as Beaked Whale Gulf - BWG). For Gervais' and Cuvier's beaked whales, we estimated weekly animal density using two methods, one based on the number of echolocation clicks, and another based on the detection of animal groups during 5 min time-bins. Density estimates derived from these two methods were in good general agreement. At two sites in the western GOM, Gervais' beaked whales were present throughout the monitoring period, but Cuvier's beaked whales were present only seasonally, with periods of low density during the summer and higher density in the winter. At an eastern GOM site, both Gervais' and Cuvier's beaked whales had a high density throughout the monitoring period.

Wavelet application to the time series analysis of DORIS station coordinates

NASA Astrophysics Data System (ADS)

Bessissi, Zahia; Terbeche, Mekki; Ghezali, Boualem

2009-06-01

The topic developed in this article relates to the residual time series analysis of DORIS station coordinates using the wavelet transform. Several analysis techniques, already developed in other disciplines, were employed in the statistical study of the geodetic time series of stations. The wavelet transform allows one, on the one hand, to provide temporal and frequential parameter residual signals, and on the other hand, to determine and quantify systematic signals such as periodicity and tendency. Tendency is the change in short or long term signals; it is an average curve which represents the general pace of the signal evolution. On the other hand, periodicity is a process which is repeated, identical to itself, after a time interval called the period. In this context, the topic of this article consists, on the one hand, in determining the systematic signals by wavelet analysis of time series of DORIS station coordinates, and on the other hand, in applying the denoising signal to the wavelet packet, which makes it possible to obtain a well-filtered signal, smoother than the original signal. The DORIS data used in the treatment are a set of weekly residual time series from 1993 to 2004 from eight stations: DIOA, COLA, FAIB, KRAB, SAKA, SODB, THUB and SYPB. It is the ign03wd01 solution expressed in stcd format, which is derived by the IGN/JPL analysis center. Although these data are not very recent, the goal of this study is to detect the contribution of the wavelet analysis method on the DORIS data, compared to the other analysis methods already studied.

Dynamic control of droplets and pockets formation in homogeneous porous media immiscible displacements

NASA Astrophysics Data System (ADS)

Lins, T. F.; Azaiez, J.

2018-03-01

Interfacial instabilities of immiscible two-phase radial flow displacements in homogeneous porous media are analyzed for constant and time-dependent sinusoidal cyclic injection schemes. The analysis is carried out through numerical simulations based on the immersed interface and level set methods. The effects of the fluid properties and the injection flow parameters, namely, the period and the amplitude, on the formation of droplets and pockets are analyzed. It was found that larger capillary numbers or smaller viscosity ratios lead to more droplets/pockets that tend to appear earlier in time. Furthermore, the period and amplitude of the cyclic schemes were found to have a strong effect on droplets/pockets formations, and depending on their values, these can be enhanced or attenuated. In particular, the results revealed that there is a critical amplitude above which droplets and pockets formation is suppressed up to a specified time. This critical amplitude depends on the fluid properties, namely, the viscosity ratio and surface tension as well as on the period of the time-dependent scheme. The results of this study indicate that it is possible to use time-dependent cyclic schemes to control the formation and development of droplets/pockets in the flow and in particular to delay their appearance through an appropriate combination of the displacement scheme's amplitude and period.

The clinical evaluation of International Normalized Ratio variability and control in conventional oral anticoagulant administration by use of the variance growth rate.

PubMed

Ibrahim, S; Jespersen, J; Poller, L

2013-08-01

The time in target International Normalized Ratio (INR) range (TIR) is used to assess the control and intensity of oral anticoagulation, but it does not measure variation in the INR. The value of assessing INR variability by use of the variance growth rate (VGR) as a predictor of events was investigated in patients treated with warfarin. Three different methods of VGR determination (A, B1, and B2) together with the TIR were studied. Method A measures both INR variability and control, but methods B1 and B2 measure variability only. The VGR and TIR were determined over three time periods: overall follow-up to an event, and 6 months and 3 months before an event. Six hundred and sixty-one control patients were matched to 158 cases (bleeding, thromboembolism, or death). With all VGR methods, the risk of an event was greater in unstable patients at 6 months before an event than in stable patients. Method A demonstrated the greatest risk 3 months before an event in the unstable VGR group as compared with the stable group (odds ratio 3.3, 95% confidence interval 1.9-5.7, P < 0.005). The risk of an event was 1.9 times greater in patients with a low TIR (< 39%) than in those with a high TIR (> 80%) in the 3-month period (P = 0.02). Risk of bleeding was significantly greater in the 3-month period in patients with unstable VGR, with the greatest risk found with method B2 (P < 0.01). Patients with unstable anticoagulation have a significantly increased risk of 'clinical events' at 3 and 6 months before an event. The VGR can be incorporated into computer-dosage programs, and may offer additional safety when oral anticoagulation is monitored. © 2013 International Society on Thrombosis and Haemostasis.

Maximum likelihood estimation for life distributions with competing failure modes

NASA Technical Reports Server (NTRS)

Sidik, S. M.

1979-01-01

Systems which are placed on test at time zero, function for a period and die at some random time were studied. Failure may be due to one of several causes or modes. The parameters of the life distribution may depend upon the levels of various stress variables the item is subject to. Maximum likelihood estimation methods are discussed. Specific methods are reported for the smallest extreme-value distributions of life. Monte-Carlo results indicate the methods to be promising. Under appropriate conditions, the location parameters are nearly unbiased, the scale parameter is slight biased, and the asymptotic covariances are rapidly approached.

[Experience summary of professor WANG Fuchun's "Zhenjing Anshen" acupuncture method for insomnia].

PubMed

Li, Tie; Ha, Lijuan; Cao, Fang; Zhi, Mujun; Wang, Fuchun

2015-11-01

The experience of "Zhenjing Anshen" acupuncture method originally created by professor WANG Fuchun for treatment of insomnia was introduced in this paper. From aspects of insomnia pathogenesis, theoretical foundation, characteristics of acupoint selection, needing methods, needing time, etc., the experience of Professor WANG Fuchun for treatment of insomnia was explained. The "Zhenjing Anshen" acupuncture method proposed, for the first time, "new three layers" method of acupoint selection, including Sishencong (EX-HN 1), Shenmen (HT 7), Sanyinjiao (SP 6). This method presents the principles of acupoint selection along meridian, acupoint selection based on essence-qi-spirit, harmony of yin and yang. The acupuncture manipulation is emphasized, and treating time (the period of the day from 3 pm to 5 pm) is focused on; acupoint selection is simple but essential, and acupoint combination is scientific, which receives notable therapeutic effect in clinic.

10 CFR Appendix I to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Conventional Ranges, Conventional...

Code of Federal Regulations, 2013 CFR

2013-01-01

..., set the clock time to 3:23 and use the average power approach described in Section 5, Paragraph 5.3.2... conventional ranges, conventional cooking tops, conventional ovens, and microwave ovens at this time. However... finite period of time after the end of the heating function, where the end of the heating function is...

Validation of prediction models: examining temporal and geographic stability of baseline risk and estimated covariate effects

PubMed Central

Austin, Peter C.; van Klaveren, David; Vergouwe, Yvonne; Nieboer, Daan; Lee, Douglas S.; Steyerberg, Ewout W.

2018-01-01

Background Stability in baseline risk and estimated predictor effects both geographically and temporally is a desirable property of clinical prediction models. However, this issue has received little attention in the methodological literature. Our objective was to examine methods for assessing temporal and geographic heterogeneity in baseline risk and predictor effects in prediction models. Methods We studied 14,857 patients hospitalized with heart failure at 90 hospitals in Ontario, Canada, in two time periods. We focussed on geographic and temporal variation in baseline risk (intercept) and predictor effects (regression coefficients) of the EFFECT-HF mortality model for predicting 1-year mortality in patients hospitalized for heart failure. We used random effects logistic regression models for the 14,857 patients. Results The baseline risk of mortality displayed moderate geographic variation, with the hospital-specific probability of 1-year mortality for a reference patient lying between 0.168 and 0.290 for 95% of hospitals. Furthermore, the odds of death were 11% lower in the second period than in the first period. However, we found minimal geographic or temporal variation in predictor effects. Among 11 tests of differences in time for predictor variables, only one had a modestly significant P value (0.03). Conclusions This study illustrates how temporal and geographic heterogeneity of prediction models can be assessed in settings with a large sample of patients from a large number of centers at different time periods. PMID:29350215

Comparison of VLBI, TV and traveling clock techniques for time transfer

NASA Technical Reports Server (NTRS)

Spencer, J. H.; Waltman, E. B.; Johnston, K. J.; Santini, N. J.; Klepczynski, W. J.; Matsakis, D. N.; Angerhofer, P. E.; Kaplan, G. M.

1982-01-01

A three part experiment was conducted to develop and compare time transfer techniques. The experiment consisted of (1) a very long baseline interferometer (VLBI), (2) a high precision portable clock time transfer system between the two sites, and (3) a television time transfer. A comparison of the VLBI and traveling clock shows each technique can perform satisfactorily at the five nsec level. There was a systematic offset of 59 nsec between the two methods, which we attributed to a difference in epochs between VLBI formatter and station clock. The VLBI method had an internal random error of one nsec at the three sigma level for a two day period. Thus, the Mark II system performed well, and VLBI shows promise of being an accurate method of time transfer. The TV system, which had technical problems during the experiment, transferred time with a random error of about 50 nsec.

Solar wind plasma periodicities observed at 1 AU by IMP 8

NASA Technical Reports Server (NTRS)

Paularena, K. I.; Szabo, A.; Lazarus, A. J.

1995-01-01

The IMP 8 spacecraft has been in Earth orbit since 1973, gathering plasma data over one complete 22-year solar cycle. These data are being examined to look for periodicities at time scales ranging from several hours to the entire span of the data set. A 1.3-year periodicity in the radial speed observed by IMP 8 and Voyager 2 has already been reported for the years from 1987 to 1993. The periodogram method, useful for unevenly sampled data such as the IMP 8 plasma data, has been used to search for other periods. It is interesting to note that the 13-year period is not present in the out-of-the-ecliptic component of the velocity (Vz), although a 1-year period is very obvious both visually and on the periodogram. Both components show a very strong peak associated with the 11-year solar cycle variation. This work will be extended to the thermal speed (a measure of the wind's temperature) and density, although the frequent correlations between these parameters and the velocity are expected to cause similar results. Additionally, the fine resolution data will be examined for shorter time periods than are visible using the hourly average data which are appropriate for longer periods. A comparison with periods observed at other spacecraft may also be made.

An approach for finding long period elliptical orbits for precursor SEI missions

NASA Technical Reports Server (NTRS)

Fraietta, Michael F.; Bond, Victor R.

1993-01-01

Precursors for Solar System Exploration Initiative (SEI) missions may require long period elliptical orbits about a planet. These orbits will typically have periods on the order of tens to hundreds of days. Some potential uses for these orbits may include the following: studying the effects of galactic cosmic radiation, parking orbits for engineering and operational test of systems, and ferrying orbits between libration points and low altitude orbits. This report presents an approach that can be used to find these orbits. The approach consists of three major steps. First, it uses a restricted three-body targeting algorithm to determine the initial conditions which satisfy certain desired final conditions in a system of two massive primaries. Then the initial conditions are transformed to an inertial coordinate system for use by a special perturbation method. Finally, using the special perturbation method, other perturbations (e.g., sun third body and solar radiation pressure) can be easily incorporated to determine their effects on the nominal trajectory. An algorithm potentially suitable for on-board guidance will also be discussed. This algorithm uses an analytic method relying on Chebyshev polynomials to compute the desired position and velocity of the satellite as a function of time. Together with navigation updates, this algorithm can be implemented to predict the size and timing for AV corrections.

Safety of long-term subcutaneous free flap skin banking after skin-sparing mastectomy

PubMed Central

Verstappen, Ralph; Djedovic, Gabriel; Morandi, Evi Maria; Heiser, Dietmar; Rieger, Ulrich Michael; Bauer, Thomas

2018-01-01

Background A persistent problem in autologous breast reconstruction in skin-sparing mastectomies is skin restoration after skin necrosis or secondary oncological resection. As a solution to facilitate reconstruction, skin banking of free-flap skin has been proposed in cases where the overlying skin envelope must be resected, as this technique spares the patient an additional donor site. Herein, we present the largest series to date in which this method was used. We investigated its safety and the possibility of skin banking for prolonged periods of time. Methods All skin-sparing mastectomies and immediate autologous breast reconstructions from December 2009 until June 2013 at our institution were analysed. Results We identified 31 patients who underwent 33 free flap reconstructions in which skin banking was performed. Our median skin banking period was 7 days, with a maximum duration of 171 days. In 22.5% of cases, the banked skin was used to reconstruct overlying skin defects, and in 9.6% of cases to reconstruct the nipple-areolar complex. Microbiological and histological investigations of the banked skin revealed neither clinical infections nor malignancies. Conclusions In situ skin banking, even for prolonged periods of time, is a safe and cost-effective method to ensure that skin defects due to necrosis or secondary oncological resection can be easily reconstructed. PMID:29506331

Approximate solution of space and time fractional higher order phase field equation

NASA Astrophysics Data System (ADS)

Shamseldeen, S.

2018-03-01

This paper is concerned with a class of space and time fractional partial differential equation (STFDE) with Riesz derivative in space and Caputo in time. The proposed STFDE is considered as a generalization of a sixth-order partial phase field equation. We describe the application of the optimal homotopy analysis method (OHAM) to obtain an approximate solution for the suggested fractional initial value problem. An averaged-squared residual error function is defined and used to determine the optimal convergence control parameter. Two numerical examples are studied, considering periodic and non-periodic initial conditions, to justify the efficiency and the accuracy of the adopted iterative approach. The dependence of the solution on the order of the fractional derivative in space and time and model parameters is investigated.

A criterion for delimiting active periods within turbulent flows

NASA Astrophysics Data System (ADS)

Keylock, C. J.

2008-06-01

Delimiting effectively the extent of the major motions in atmospheric, tidal and fluvial turbulent flows is an important task for studies of mixing and particle transport. The most common method for this (quadrant analysis) is closely linked to the turbulent stresses but subdivides active periods in the flow into separate events. A method based on the pointwise Hölder characteristics of the velocity data is introduced in this paper and applied to extract the whole duration of the active periods, within which turbulence intensities and stresses are high for some of the time. The cross-correlation structure of the Hölder series permits a simple threshold to be adopted. The technique is tested on data from a turbulent wake in a wind tunnel and flow over a forest canopy.

Spectral-decomposition techniques for the identification of periodic and anomalous phenomena in radon time-series.

NASA Astrophysics Data System (ADS)

Crockett, R. G. M.; Perrier, F.; Richon, P.

2009-04-01

Building on independent investigations by research groups at both IPGP, France, and the University of Northampton, UK, hourly-sampled radon time-series of durations exceeding one year have been investigated for periodic and anomalous phenomena using a variety of established and novel techniques. These time-series have been recorded in locations having no routine human behaviour and thus are effectively free of significant anthropogenic influences. With regard to periodic components, the long durations of these time-series allow, in principle, very high frequency resolutions for established spectral-measurement techniques such as Fourier and maximum-entropy. However, as has been widely observed, the stochastic nature of radon emissions from rocks and soils, coupled with sensitivity to a wide variety influences such as temperature, wind-speed and soil moisture-content has made interpretation of the results obtained by such techniques very difficult, with uncertain results, in many cases. We here report developments in the investigation of radon-time series for periodic and anomalous phenomena using spectral-decomposition techniques. These techniques, in variously separating ‘high', ‘middle' and ‘low' frequency components, effectively ‘de-noise' the data by allowing components of interest to be isolated from others which (might) serve to obscure weaker information-containing components. Once isolated, these components can be investigated using a variety of techniques. Whilst this is very much work in early stages of development, spectral decomposition methods have been used successfully to indicate the presence of diurnal and sub-diurnal cycles in radon concentration which we provisionally attribute to tidal influences. Also, these methods have been used to enhance the identification of short-duration anomalies, attributable to a variety of causes including, for example, earthquakes and rapid large-magnitude changes in weather conditions. Keywords: radon; earthquakes; tidal-influences; anomalies; time series; spectral-decomposition.

A new method of presentation the large-scale magnetic field structure on the Sun and solar corona

NASA Technical Reports Server (NTRS)

Ponyavin, D. I.

1995-01-01

The large-scale photospheric magnetic field, measured at Stanford, has been analyzed in terms of surface harmonics. Changes of the photospheric field which occur within whole solar rotation period can be resolved by this analysis. For this reason we used daily magnetograms of the line-of-sight magnetic field component observed from Earth over solar disc. We have estimated the period during which day-to-day full disc magnetograms must be collected. An original algorithm was applied to resolve time variations of spherical harmonics that reflect time evolution of large-scale magnetic field within solar rotation period. This method of magnetic field presentation can be useful enough in lack of direct magnetograph observations due to sometimes bad weather conditions. We have used the calculated surface harmonics to reconstruct the large-scale magnetic field structure on the source surface near the sun - the origin of heliospheric current sheet and solar wind streams. The obtained results have been compared with spacecraft in situ observations and geomagnetic activity. We tried to show that proposed technique can trace shon-time variations of heliospheric current sheet and short-lived solar wind streams. We have compared also our results with those obtained traditionally from potential field approximation and extrapolation using synoptic charts as initial boundary conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, S; Zhu, X; Zhang, M

Purpose Half-beam block is a field matching technique frequently used in radiotherapy. With no setup error, a well calibrated linac, and no internal organ motion, two photon fields can be matched seamlessly dosimetry-wise with their central axes passing the match line. However, in actual clinical situations, internal organ motion is often inevitable. This study was conducted to investigate its influence on radiation dose to patient internal points directly under the matching line. Methods A clinical setting is modeled as two half-space (x<0 and x<0) radiation fields that are turned on sequentially with a time gap of integer times of themore » patient internal organ motion period (T{sub 0}). Our point of interest moves with patient internal organs periodically and evenly in and out of the radiation fields, resulting in an average location at x=0. When the fields are delivered without any motion management, the initial phase of the point’s movement is unknown. Statistical methods are used to compute the expected value () and variance (σ) of the point dose given the uncertainty. Results Analytical solutions are obtained for and s of dose received by a point directly under the match line. is proportional to the total beam-on time (T1), and σ demonstrates previously unknown periodic behavior. /« less

The theoretical accuracy of Runge-Kutta time discretizations for the initial boundary value problem: A careful study of the boundary error

NASA Technical Reports Server (NTRS)

Carpenter, Mark H.; Gottlieb, David; Abarbanel, Saul; Don, Wai-Sun

1993-01-01

The conventional method of imposing time dependent boundary conditions for Runge-Kutta (RK) time advancement reduces the formal accuracy of the space-time method to first order locally, and second order globally, independently of the spatial operator. This counter intuitive result is analyzed in this paper. Two methods of eliminating this problem are proposed for the linear constant coefficient case: (1) impose the exact boundary condition only at the end of the complete RK cycle, (2) impose consistent intermediate boundary conditions derived from the physical boundary condition and its derivatives. The first method, while retaining the RK accuracy in all cases, results in a scheme with much reduced CFL condition, rendering the RK scheme less attractive. The second method retains the same allowable time step as the periodic problem. However it is a general remedy only for the linear case. For non-linear hyperbolic equations the second method is effective only for for RK schemes of third order accuracy or less. Numerical studies are presented to verify the efficacy of each approach.

EXTRACTING PERIODIC TRANSIT SIGNALS FROM NOISY LIGHT CURVES USING FOURIER SERIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samsing, Johan

We present a simple and powerful method for extracting transit signals associated with a known transiting planet from noisy light curves. Assuming the orbital period of the planet is known and the signal is periodic, we illustrate that systematic noise can be removed in Fourier space at all frequencies by only using data within a fixed time frame with a width equal to an integer number of orbital periods. This results in a reconstruction of the full transit signal, which on average is unbiased despite no prior knowledge of either the noise or the transit signal itself being used inmore » the analysis. The method therefore has clear advantages over standard phase folding, which normally requires external input such as nearby stars or noise models for removing systematic components. In addition, we can extract the full orbital transit signal (360°) simultaneously, and Kepler-like data can be analyzed in just a few seconds. We illustrate the performance of our method by applying it to a dataset composed of light curves from Kepler with a fake injected signal emulating a planet with rings. For extracting periodic transit signals, our presented method is in general the optimal and least biased estimator and could therefore lead the way toward the first detections of, e.g., planet rings and exo-trojan asteroids.« less

Trainee competence in thoracoscopic esophagectomy in the prone position: evaluation using cumulative sum techniques.

PubMed

Oshikiri, Taro; Yasuda, Takashi; Yamamoto, Masashi; Kanaji, Shingo; Yamashita, Kimihiro; Matsuda, Takeru; Sumi, Yasuo; Nakamura, Tetsu; Fujino, Yasuhiro; Tominaga, Masahiro; Suzuki, Satoshi; Kakeji, Yoshihiro

2016-09-01

Minimally invasive esophagectomy (MIE) has less morbidity than the open approach. In particular, thoracoscopic esophagectomy in the prone position (TEP) has been performed worldwide. Using the cumulative sum control chart (CUSUM) method, this study aimed to confirm whether a trainee surgeon who learned established standards would become skilled in TEP with a shorter learning curve than that of the mentoring surgeon. Surgeon A performed TEP in 100 patients; the first 22 patients comprised period 1. His learning curve, defined based on the operation time (OT) of the thoracic procedure, was evaluated using the CUSUM method, and short-term outcomes were assessed. Another 22 patients underwent TEP performed by surgeon B, with outcomes compared to those of surgeon A's period 1. Using the CUSUM chart, the peak point of the thoracic procedure OT occurred at the 44th case in surgeon A's experience of 100 cases. With surgeon A's first 22 cases (period 1), the peak point of the thoracic procedure OT could not be confirmed and graph is expanding soaring at CUSUM chart. The CUSUM chart of surgeon B's experience of 22 cases clearly indicated that the peak point of the thoracic procedure OT occurred at the 17th case. The rate of recurrent laryngeal nerve palsy for surgeon B (9 %) was significantly lower than for surgeon A in period 1 (36 %) (p = 0.0266). There is some possibility for a trainee surgeon to attain the required basic skills to perform TEP in a relatively short period of time using a standardized procedure developed by a mentoring surgeon. The CUSUM method should be useful in evaluating trainee competence during an initial series of procedures, by assessing the learning curve defined by OT.

A Multipixel Time Series Analysis Method Accounting for Ground Motion, Atmospheric Noise, and Orbital Errors

NASA Astrophysics Data System (ADS)

Jolivet, R.; Simons, M.

2018-02-01

Interferometric synthetic aperture radar time series methods aim to reconstruct time-dependent ground displacements over large areas from sets of interferograms in order to detect transient, periodic, or small-amplitude deformation. Because of computational limitations, most existing methods consider each pixel independently, ignoring important spatial covariances between observations. We describe a framework to reconstruct time series of ground deformation while considering all pixels simultaneously, allowing us to account for spatial covariances, imprecise orbits, and residual atmospheric perturbations. We describe spatial covariances by an exponential decay function dependent of pixel-to-pixel distance. We approximate the impact of imprecise orbit information and residual long-wavelength atmosphere as a low-order polynomial function. Tests on synthetic data illustrate the importance of incorporating full covariances between pixels in order to avoid biased parameter reconstruction. An example of application to the northern Chilean subduction zone highlights the potential of this method.

A Nonlinear Dynamical Systems based Model for Stochastic Simulation of Streamflow

NASA Astrophysics Data System (ADS)

Erkyihun, S. T.; Rajagopalan, B.; Zagona, E. A.

2014-12-01

Traditional time series methods model the evolution of the underlying process as a linear or nonlinear function of the autocorrelation. These methods capture the distributional statistics but are incapable of providing insights into the dynamics of the process, the potential regimes, and predictability. This work develops a nonlinear dynamical model for stochastic simulation of streamflows. In this, first a wavelet spectral analysis is employed on the flow series to isolate dominant orthogonal quasi periodic timeseries components. The periodic bands are added denoting the 'signal' component of the time series and the residual being the 'noise' component. Next, the underlying nonlinear dynamics of this combined band time series is recovered. For this the univariate time series is embedded in a d-dimensional space with an appropriate lag T to recover the state space in which the dynamics unfolds. Predictability is assessed by quantifying the divergence of trajectories in the state space with time, as Lyapunov exponents. The nonlinear dynamics in conjunction with a K-nearest neighbor time resampling is used to simulate the combined band, to which the noise component is added to simulate the timeseries. We demonstrate this method by applying it to the data at Lees Ferry that comprises of both the paleo reconstructed and naturalized historic annual flow spanning 1490-2010. We identify interesting dynamics of the signal in the flow series and epochal behavior of predictability. These will be of immense use for water resources planning and management.

Nonconvex model predictive control for commercial refrigeration

NASA Astrophysics Data System (ADS)

Gybel Hovgaard, Tobias; Boyd, Stephen; Larsen, Lars F. S.; Bagterp Jørgensen, John

2013-08-01

We consider the control of a commercial multi-zone refrigeration system, consisting of several cooling units that share a common compressor, and is used to cool multiple areas or rooms. In each time period we choose cooling capacity to each unit and a common evaporation temperature. The goal is to minimise the total energy cost, using real-time electricity prices, while obeying temperature constraints on the zones. We propose a variation on model predictive control to achieve this goal. When the right variables are used, the dynamics of the system are linear, and the constraints are convex. The cost function, however, is nonconvex due to the temperature dependence of thermodynamic efficiency. To handle this nonconvexity we propose a sequential convex optimisation method, which typically converges in fewer than 5 or so iterations. We employ a fast convex quadratic programming solver to carry out the iterations, which is more than fast enough to run in real time. We demonstrate our method on a realistic model, with a full year simulation and 15-minute time periods, using historical electricity prices and weather data, as well as random variations in thermal load. These simulations show substantial cost savings, on the order of 30%, compared to a standard thermostat-based control system. Perhaps more important, we see that the method exhibits sophisticated response to real-time variations in electricity prices. This demand response is critical to help balance real-time uncertainties in generation capacity associated with large penetration of intermittent renewable energy sources in a future smart grid.

Insights from two industrial hygiene pilot e-cigarette passive vaping studies.

PubMed

Maloney, John C; Thompson, Michael K; Oldham, Michael J; Stiff, Charles L; Lilly, Patrick D; Patskan, George J; Shafer, Kenneth H; Sarkar, Mohamadi A

2016-01-01

While several reports have been published using research methods of estimating exposure risk to e-cigarette vapors in nonusers, only two have directly measured indoor air concentrations from vaping using validated industrial hygiene sampling methodology. Our first study was designed to measure indoor air concentrations of nicotine, menthol, propylene glycol, glycerol, and total particulates during the use of multiple e-cigarettes in a well-characterized room over a period of time. Our second study was a repeat of the first study, and it also evaluated levels of formaldehyde. Measurements were collected using active sampling, near real-time and direct measurement techniques. Air sampling incorporated industrial hygiene sampling methodology using analytical methods established by the National Institute of Occupational Safety and Health and the Occupational Safety and Health Administration. Active samples were collected over a 12-hr period, for 4 days. Background measurements were taken in the same room the day before and the day after vaping. Panelists (n = 185 Study 1; n = 145 Study 2) used menthol and non-menthol MarkTen prototype e-cigarettes. Vaping sessions (six, 1-hr) included 3 prototypes, with total number of puffs ranging from 36-216 per session. Results of the active samples were below the limit of quantitation of the analytical methods. Near real-time data were below the lowest concentration on the established calibration curves. Data from this study indicate that the majority of chemical constituents sampled were below quantifiable levels. Formaldehyde was detected at consistent levels during all sampling periods. These two studies found that indoor vaping of MarkTen prototype e-cigarette does not produce chemical constituents at quantifiable levels or background levels using standard industrial hygiene collection techniques and analytical methods.

Standardized Reporting System Use During Handoffs Reduces Patient Length of Stay in the Emergency Department

PubMed Central

Dahlquist, Robert T.; Reyner, Karina; Robinson, Richard D.; Farzad, Ali; Laureano-Phillips, Jessica; Garrett, John S.; Young, Joseph M.; Zenarosa, Nestor R.; Wang, Hao

2018-01-01

Background Emergency department (ED) shift handoffs are potential sources of delay in care. We aimed to determine the impact that using standardized reporting tool and process may have on throughput metrics for patients undergoing a transition of care at shift change. Methods We performed a prospective, pre- and post-intervention quality improvement study from September 1 to November 30, 2015. A handoff procedure intervention, including a mandatory workshop and personnel training on a standard reporting system template, was implemented. The primary endpoint was patient length of stay (LOS). A comparative analysis of differences between patient LOS and various handoff communication methods were assessed pre- and post-intervention. Communication methods were entered a multivariable logistic regression model independently as risk factors for patient LOS. Results The final analysis included 1,006 patients, with 327 comprising the pre-intervention and 679 comprising the post-intervention populations. Bedside rounding occurred 45% of the time without a standard reporting during pre-intervention and increased to 85% of the time with the use of a standard reporting system in the post-intervention period (P < 0.001). Provider time (provider-initiated care to patient care completed) in the pre-intervention period averaged 297 min, but decreased to 265 min in the post-intervention period (P < 0.001). After adjusting for other communication methods, the use of a standard reporting system during handoff was associated with shortened ED LOS (OR = 0.60, 95% CI 0.40 - 0.90, P < 0.05). Conclusions Standard reporting system use during emergency physician handoffs at shift change improves ED throughput efficiency and is associated with shorter ED LOS. PMID:29581808

Contributions to the phytochemical study of Bidens tripartitae herba from Romania. I. Tannins.

PubMed

Zagnat, M; Cheptea, Corina; Spac, A F

2013-01-01

To analyze qualitatively and quantitatively tannins in the native plant, collected during the whole vegetation period from different areas of the country, and in its different organs (flower, stem, leaf). For quantitative analysis, the plant product was extracted by repeated maceration (3 days) with 80% methanol. Proanthocyanidins in the extract were quantified by spectrophotometric methods. condensed tannins were present while hydrolyzed tannins were absent. Chromatographic analysis showed that tannins spectrum is similar in all plant organs and in plants collected at different times throughout the vegetation period. The differences are only quantitative. The maximum amount of tannins was found during the flowering stage (10.32%). In terms of tannin content, flowering is the best time to collect. However, collection throughout the whole vegetation period is acceptable.

What time is it? Deep learning approaches for circadian rhythms.

PubMed

Agostinelli, Forest; Ceglia, Nicholas; Shahbaba, Babak; Sassone-Corsi, Paolo; Baldi, Pierre

2016-06-15

Circadian rhythms date back to the origins of life, are found in virtually every species and every cell, and play fundamental roles in functions ranging from metabolism to cognition. Modern high-throughput technologies allow the measurement of concentrations of transcripts, metabolites and other species along the circadian cycle creating novel computational challenges and opportunities, including the problems of inferring whether a given species oscillate in circadian fashion or not, and inferring the time at which a set of measurements was taken. We first curate several large synthetic and biological time series datasets containing labels for both periodic and aperiodic signals. We then use deep learning methods to develop and train BIO_CYCLE, a system to robustly estimate which signals are periodic in high-throughput circadian experiments, producing estimates of amplitudes, periods, phases, as well as several statistical significance measures. Using the curated data, BIO_CYCLE is compared to other approaches and shown to achieve state-of-the-art performance across multiple metrics. We then use deep learning methods to develop and train BIO_CLOCK to robustly estimate the time at which a particular single-time-point transcriptomic experiment was carried. In most cases, BIO_CLOCK can reliably predict time, within approximately 1 h, using the expression levels of only a small number of core clock genes. BIO_CLOCK is shown to work reasonably well across tissue types, and often with only small degradation across conditions. BIO_CLOCK is used to annotate most mouse experiments found in the GEO database with an inferred time stamp. All data and software are publicly available on the CircadiOmics web portal: circadiomics.igb.uci.edu/ fagostin@uci.edu or pfbaldi@uci.edu Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press.

What time is it? Deep learning approaches for circadian rhythms

PubMed Central

Agostinelli, Forest; Ceglia, Nicholas; Shahbaba, Babak; Sassone-Corsi, Paolo; Baldi, Pierre

2016-01-01

Motivation: Circadian rhythms date back to the origins of life, are found in virtually every species and every cell, and play fundamental roles in functions ranging from metabolism to cognition. Modern high-throughput technologies allow the measurement of concentrations of transcripts, metabolites and other species along the circadian cycle creating novel computational challenges and opportunities, including the problems of inferring whether a given species oscillate in circadian fashion or not, and inferring the time at which a set of measurements was taken. Results: We first curate several large synthetic and biological time series datasets containing labels for both periodic and aperiodic signals. We then use deep learning methods to develop and train BIO_CYCLE, a system to robustly estimate which signals are periodic in high-throughput circadian experiments, producing estimates of amplitudes, periods, phases, as well as several statistical significance measures. Using the curated data, BIO_CYCLE is compared to other approaches and shown to achieve state-of-the-art performance across multiple metrics. We then use deep learning methods to develop and train BIO_CLOCK to robustly estimate the time at which a particular single-time-point transcriptomic experiment was carried. In most cases, BIO_CLOCK can reliably predict time, within approximately 1 h, using the expression levels of only a small number of core clock genes. BIO_CLOCK is shown to work reasonably well across tissue types, and often with only small degradation across conditions. BIO_CLOCK is used to annotate most mouse experiments found in the GEO database with an inferred time stamp. Availability and Implementation: All data and software are publicly available on the CircadiOmics web portal: circadiomics.igb.uci.edu/. Contacts: fagostin@uci.edu or pfbaldi@uci.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27307647

Scheduling Anesthesia Time Reduces Case Cancellations and Improves Operating Room Workflow in a University Hospital Setting.

PubMed

van Veen-Berkx, Elizabeth; van Dijk, Menno V; Cornelisse, Diederich C; Kazemier, Geert; Mokken, Fleur C

2016-08-01

A new method of scheduling anesthesia-controlled time (ACT) was implemented on July 1, 2012 in an academic inpatient operating room (OR) department. This study examined the relationship between this new scheduling method and OR performance. The new method comprised the development of predetermined time frames per anesthetic technique based on historical data of the actual time needed for anesthesia induction and emergence. Seven "anesthesia scheduling packages" (0 to 6) were established. Several options based on the quantity of anesthesia monitoring and the complexity of the patient were differentiated in time within each package. This was a quasi-experimental time-series design. Relevant data were divided into 4 equal periods of time. These time periods were compared with ANOVA with contrast analysis: an intervention, pre-intervention, and post-intervention contrast were tested. All emergency cases were excluded. A total of 34,976 inpatient elective cases performed from January 1, 2010 to December 31, 2014 were included for statistical analyses. The intervention contrast showed a significant decrease (p < 0.001) of 4.5% in the prediction error. The total number of cancellations decreased to 19.9%. The ANOVA with contrast analyses showed no significant differences with respect to under- and over-used OR time and raw use. Unanticipated results derived from this study, allowing for a smoother workflow: eg anesthesia nurses know exactly which medical equipment and devices need to be assembled and tested beforehand, based on the scheduled anesthesia package. Scheduling the 2 major components of a procedure (anesthesia- and surgeon-controlled time) more accurately leads to fewer case cancellations, lower prediction errors, and smoother OR workflow in a university hospital setting. Copyright © 2016 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

An Adaptive Multiscale Finite Element Method for Large Scale Simulations

DTIC Science & Technology

2015-09-28

Illinois at Urbana-Champaign Abstract Hypersonic vehicles are subjected to extreme acoustic, thermal and mechanical loading with strong spatial and temporal...07/15/2012 Reporting Period End Date 07/14/2015 Abstract Hypersonic vehicles are subjected to extreme acoustic, thermal and mechanical loading with...gradients and for extended periods of time. Long duration, 3-D simulations of non-linear response of these vehicles , is prohibitively expensive using