Computational system identification of continuous-time nonlinear systems using approximate Bayesian computation

NASA Astrophysics Data System (ADS)

Krishnanathan, Kirubhakaran; Anderson, Sean R.; Billings, Stephen A.; Kadirkamanathan, Visakan

2016-11-01

In this paper, we derive a system identification framework for continuous-time nonlinear systems, for the first time using a simulation-focused computational Bayesian approach. Simulation approaches to nonlinear system identification have been shown to outperform regression methods under certain conditions, such as non-persistently exciting inputs and fast-sampling. We use the approximate Bayesian computation (ABC) algorithm to perform simulation-based inference of model parameters. The framework has the following main advantages: (1) parameter distributions are intrinsically generated, giving the user a clear description of uncertainty, (2) the simulation approach avoids the difficult problem of estimating signal derivatives as is common with other continuous-time methods, and (3) as noted above, the simulation approach improves identification under conditions of non-persistently exciting inputs and fast-sampling. Term selection is performed by judging parameter significance using parameter distributions that are intrinsically generated as part of the ABC procedure. The results from a numerical example demonstrate that the method performs well in noisy scenarios, especially in comparison to competing techniques that rely on signal derivative estimation.

Bispectral Inversion: The Construction of a Time Series from Its Bispectrum

DTIC Science & Technology

1988-04-13

take the inverse transform . Since the goal is to compute a time series given its bispectrum, it would also be nice to stay entirely in the frequency...domain and be able to go directly from the bispectrum to the Fourier transform of the time series without the need to inverse transform continuous...the picture. The approximations arise from representing the bicovariance, which is the inverse transform of a continuous function, by the inverse disrte

Online adaptive optimal control for continuous-time nonlinear systems with completely unknown dynamics

NASA Astrophysics Data System (ADS)

Lv, Yongfeng; Na, Jing; Yang, Qinmin; Wu, Xing; Guo, Yu

2016-01-01

An online adaptive optimal control is proposed for continuous-time nonlinear systems with completely unknown dynamics, which is achieved by developing a novel identifier-critic-based approximate dynamic programming algorithm with a dual neural network (NN) approximation structure. First, an adaptive NN identifier is designed to obviate the requirement of complete knowledge of system dynamics, and a critic NN is employed to approximate the optimal value function. Then, the optimal control law is computed based on the information from the identifier NN and the critic NN, so that the actor NN is not needed. In particular, a novel adaptive law design method with the parameter estimation error is proposed to online update the weights of both identifier NN and critic NN simultaneously, which converge to small neighbourhoods around their ideal values. The closed-loop system stability and the convergence to small vicinity around the optimal solution are all proved by means of the Lyapunov theory. The proposed adaptation algorithm is also improved to achieve finite-time convergence of the NN weights. Finally, simulation results are provided to exemplify the efficacy of the proposed methods.

Pitch angle scattering of relativistic electrons from stationary magnetic waves: Continuous Markov process and quasilinear theory

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

Lemons, Don S.

2012-01-15

We develop a Markov process theory of charged particle scattering from stationary, transverse, magnetic waves. We examine approximations that lead to quasilinear theory, in particular the resonant diffusion approximation. We find that, when appropriate, the resonant diffusion approximation simplifies the result of the weak turbulence approximation without significant further restricting the regime of applicability. We also explore a theory generated by expanding drift and diffusion rates in terms of a presumed small correlation time. This small correlation time expansion leads to results valid for relatively small pitch angle and large wave energy density - a regime that may govern pitchmore » angle scattering of high-energy electrons into the geomagnetic loss cone.« less

An E-Portfolio to Enhance Sustainable Vocabulary Learning in English

ERIC Educational Resources Information Center

Tanaka, Hiroya; Yonesaka, Suzanne M.; Ueno, Yukie

2015-01-01

Vocabulary is an area that requires foreign language learners to work independently and continuously both in and out of class. In the Japanese EFL setting, for example, more than 97% of the population experiences approximately six years of English education at secondary school during which time they are required to learn approximately 3,000 words…

Optimal estimation of parameters and states in stochastic time-varying systems with time delay

NASA Astrophysics Data System (ADS)

Torkamani, Shahab; Butcher, Eric A.

2013-08-01

In this study estimation of parameters and states in stochastic linear and nonlinear delay differential systems with time-varying coefficients and constant delay is explored. The approach consists of first employing a continuous time approximation to approximate the stochastic delay differential equation with a set of stochastic ordinary differential equations. Then the problem of parameter estimation in the resulting stochastic differential system is represented as an optimal filtering problem using a state augmentation technique. By adapting the extended Kalman-Bucy filter to the resulting system, the unknown parameters of the time-delayed system are estimated from noise-corrupted, possibly incomplete measurements of the states.

Convergence of discrete Aubry–Mather model in the continuous limit

NASA Astrophysics Data System (ADS)

Su, Xifeng; Thieullen, Philippe

2018-05-01

We develop two approximation schemes for solving the cell equation and the discounted cell equation using Aubry–Mather–Fathi theory. The Hamiltonian is supposed to be Tonelli, time-independent and periodic in space. By Legendre transform it is equivalent to find a fixed point of some nonlinear operator, called Lax-Oleinik operator, which may be discounted or not. By discretizing in time, we are led to solve an additive eigenvalue problem involving a discrete Lax–Oleinik operator. We show how to approximate the effective Hamiltonian and some weak KAM solutions by letting the time step in the discrete model tend to zero. We also obtain a selected discrete weak KAM solution as in Davini et al (2016 Invent. Math. 206 29–55), and show that it converges to a particular solution of the cell equation. In order to unify the two settings, continuous and discrete, we develop a more general formalism of the short-range interactions.

Revisiting the time until fixation of a neutral mutant in a finite population - A coalescent theory approach.

PubMed

Greenbaum, Gili

2015-09-07

Evaluation of the time scale of the fixation of neutral mutations is crucial to the theoretical understanding of the role of neutral mutations in evolution. Diffusion approximations of the Wright-Fisher model are most often used to derive analytic formulations of genetic drift, as well as for the time scales of the fixation of neutral mutations. These approximations require a set of assumptions, most notably that genetic drift is a stochastic process in a continuous allele-frequency space, an assumption appropriate for large populations. Here equivalent approximations are derived using a coalescent theory approach which relies on a different set of assumptions than the diffusion approach, and adopts a discrete allele-frequency space. Solutions for the mean and variance of the time to fixation of a neutral mutation derived from the two approaches converge for large populations but slightly differ for small populations. A Markov chain analysis of the Wright-Fisher model for small populations is used to evaluate the solutions obtained, showing that both the mean and the variance are better approximated by the coalescent approach. The coalescence approximation represents a tighter upper-bound for the mean time to fixation than the diffusion approximation, while the diffusion approximation and coalescence approximation form an upper and lower bound, respectively, for the variance. The converging solutions and the small deviations of the two approaches strongly validate the use of diffusion approximations, but suggest that coalescent theory can provide more accurate approximations for small populations. Copyright © 2015 Elsevier Ltd. All rights reserved.

Development of a continuous radon concentration monitoring system in underground soil

NASA Astrophysics Data System (ADS)

Yamamoto, S.; Tarutani, K.; Yamasoto, K.; Iskandar, D.; Iida, T.

2001-06-01

A continuous radon (Rn-222) concentration monitoring system for use in underground soil was developed and tested. The system consists of a 19-mm-diameter, 1100-mm-long detector assembly and a microprocessor based data logger. A small volume chamber is installed at the tip of the detector assembly. A thin ZnS(Ag) scintillator film inside the chamber and a photomultiplier tube (PMT) detect alpha particles from radon and its daughters. When the system is in measurement, the detector part is buried into underground soil. An energy resolution of approximately 70% full width half maximum (FWHM) was obtained for 5.5 MeV alpha particles from Am-241. Both the rise time and fall time for the system were measured to be approximately 1-2 h. Temporal variations in underground radon concentration at different depths were investigated simultaneously using four sets of the developed system. The results confirmed that the developed system is useful for continuous measurement of radon concentration in underground soil.

Adaptive hybrid simulations for multiscale stochastic reaction networks

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

Hepp, Benjamin; Gupta, Ankit; Khammash, Mustafa

2015-01-21

The probability distribution describing the state of a Stochastic Reaction Network (SRN) evolves according to the Chemical Master Equation (CME). It is common to estimate its solution using Monte Carlo methods such as the Stochastic Simulation Algorithm (SSA). In many cases, these simulations can take an impractical amount of computational time. Therefore, many methods have been developed that approximate sample paths of the underlying stochastic process and estimate the solution of the CME. A prominent class of these methods include hybrid methods that partition the set of species and the set of reactions into discrete and continuous subsets. Such amore » partition separates the dynamics into a discrete and a continuous part. Simulating such a stochastic process can be computationally much easier than simulating the exact discrete stochastic process with SSA. Moreover, the quasi-stationary assumption to approximate the dynamics of fast subnetworks can be applied for certain classes of networks. However, as the dynamics of a SRN evolves, these partitions may have to be adapted during the simulation. We develop a hybrid method that approximates the solution of a CME by automatically partitioning the reactions and species sets into discrete and continuous components and applying the quasi-stationary assumption on identifiable fast subnetworks. Our method does not require any user intervention and it adapts to exploit the changing timescale separation between reactions and/or changing magnitudes of copy-numbers of constituent species. We demonstrate the efficiency of the proposed method by considering examples from systems biology and showing that very good approximations to the exact probability distributions can be achieved in significantly less computational time. This is especially the case for systems with oscillatory dynamics, where the system dynamics change considerably throughout the time-period of interest.« less

Adaptive hybrid simulations for multiscale stochastic reaction networks.

PubMed

Hepp, Benjamin; Gupta, Ankit; Khammash, Mustafa

2015-01-21

The probability distribution describing the state of a Stochastic Reaction Network (SRN) evolves according to the Chemical Master Equation (CME). It is common to estimate its solution using Monte Carlo methods such as the Stochastic Simulation Algorithm (SSA). In many cases, these simulations can take an impractical amount of computational time. Therefore, many methods have been developed that approximate sample paths of the underlying stochastic process and estimate the solution of the CME. A prominent class of these methods include hybrid methods that partition the set of species and the set of reactions into discrete and continuous subsets. Such a partition separates the dynamics into a discrete and a continuous part. Simulating such a stochastic process can be computationally much easier than simulating the exact discrete stochastic process with SSA. Moreover, the quasi-stationary assumption to approximate the dynamics of fast subnetworks can be applied for certain classes of networks. However, as the dynamics of a SRN evolves, these partitions may have to be adapted during the simulation. We develop a hybrid method that approximates the solution of a CME by automatically partitioning the reactions and species sets into discrete and continuous components and applying the quasi-stationary assumption on identifiable fast subnetworks. Our method does not require any user intervention and it adapts to exploit the changing timescale separation between reactions and/or changing magnitudes of copy-numbers of constituent species. We demonstrate the efficiency of the proposed method by considering examples from systems biology and showing that very good approximations to the exact probability distributions can be achieved in significantly less computational time. This is especially the case for systems with oscillatory dynamics, where the system dynamics change considerably throughout the time-period of interest.

Linearized semiclassical initial value time correlation functions with maximum entropy analytic continuation.

PubMed

Liu, Jian; Miller, William H

2008-09-28

The maximum entropy analytic continuation (MEAC) method is used to extend the range of accuracy of the linearized semiclassical initial value representation (LSC-IVR)/classical Wigner approximation for real time correlation functions. LSC-IVR provides a very effective "prior" for the MEAC procedure since it is very good for short times, exact for all time and temperature for harmonic potentials (even for correlation functions of nonlinear operators), and becomes exact in the classical high temperature limit. This combined MEAC+LSC/IVR approach is applied here to two highly nonlinear dynamical systems, a pure quartic potential in one dimensional and liquid para-hydrogen at two thermal state points (25 and 14 K under nearly zero external pressure). The former example shows the MEAC procedure to be a very significant enhancement of the LSC-IVR for correlation functions of both linear and nonlinear operators, and especially at low temperature where semiclassical approximations are least accurate. For liquid para-hydrogen, the LSC-IVR is seen already to be excellent at T=25 K, but the MEAC procedure produces a significant correction at the lower temperature (T=14 K). Comparisons are also made as to how the MEAC procedure is able to provide corrections for other trajectory-based dynamical approximations when used as priors.

Producing approximate answers to database queries

NASA Technical Reports Server (NTRS)

Vrbsky, Susan V.; Liu, Jane W. S.

1993-01-01

We have designed and implemented a query processor, called APPROXIMATE, that makes approximate answers available if part of the database is unavailable or if there is not enough time to produce an exact answer. The accuracy of the approximate answers produced improves monotonically with the amount of data retrieved to produce the result. The exact answer is produced if all of the needed data are available and query processing is allowed to continue until completion. The monotone query processing algorithm of APPROXIMATE works within the standard relational algebra framework and can be implemented on a relational database system with little change to the relational architecture. We describe here the approximation semantics of APPROXIMATE that serves as the basis for meaningful approximations of both set-valued and single-valued queries. We show how APPROXIMATE is implemented to make effective use of semantic information, provided by an object-oriented view of the database, and describe the additional overhead required by APPROXIMATE.

A Satellite-Derived Climate-Quality Data Record of the Clear-Sky Surface Temperature of the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

Hall, Dorothy K.; Comiso, Josefino C.; DiGirolamo, Nicolo E.; Shuman, Christopher A.; Key, Jeffrey R.; Koenig, Lora S.

2011-01-01

We have developed a climate-quality data record of the clear-sky surface temperature of the Greenland Ice Sheet using the Moderate-Resolution Imaging Spectroradiometer (MODIS) Terra ice-surface temperature (1ST) algorithm. A climate-data record (CDR) is a time series of measurements of sufficient length, consistency, and continuity to determine climate variability and change. We present daily and monthly Terra MODIS ISTs of the Greenland Ice Sheet beginning on 1 March 2000 and continuing through 31 December 2010 at 6.25-km spatial resolution on a polar stereographic grid within +/-3 hours of 17:00Z or 2:00 PM Local Solar Time. Preliminary validation of the ISTs at Summit Camp, Greenland, during the 2008-09 winter, shows that there is a cold bias using the MODIS IST which underestimates the measured surface temperature by approximately 3 C when temperatures range from approximately -50 C to approximately -35 C. The ultimate goal is to develop a CDR that starts in 1981 with the Advanced Very High Resolution (AVHRR) Polar Pathfinder (APP) dataset and continues with MODIS data from 2000 to the present. Differences in the APP and MODIS cloud masks have so far precluded the current IST records from spanning both the APP and MODIS IST time series in a seamless manner though this will be revisited when the APP dataset has been reprocessed. The Greenland IST climate-quality data record is suitable for continuation using future Visible Infrared Imager Radiometer Suite (VIIRS) data and will be elevated in status to a CDR when at least 9 more years of climate-quality data become available either from MODIS Terra or Aqua, or from the VIIRS. The complete MODIS IST data record will be available online in the summer of 2011.

Suboptimal Scheduling in Switched Systems With Continuous-Time Dynamics: A Least Squares Approach.

PubMed

Sardarmehni, Tohid; Heydari, Ali

2018-06-01

Two approximate solutions for optimal control of switched systems with autonomous subsystems and continuous-time dynamics are presented. The first solution formulates a policy iteration (PI) algorithm for the switched systems with recursive least squares. To reduce the computational burden imposed by the PI algorithm, a second solution, called single loop PI, is presented. Online and concurrent training algorithms are discussed for implementing each solution. At last, effectiveness of the presented algorithms is evaluated through numerical simulations.

Kinetic analysis of beer primary fermentation using yeast cells immobilized by ceramic support adsorption and alginate gel entrapment.

PubMed

Zhang, Yongming; Kennedy, John F; Knill, Charles J; Panesar, Parmjit S

2006-01-01

Yeast cells were immobilized by absorption onto porous ceramic support and evaluated for continuous beer primary fermentation using a bioreactor in comparison to yeast cells immobilized by entrapment in calcium alginate gel. The effects of temperature and flow rate as a function of reaction/fermentation time on fermentation rate were investigated. The fermentation reaction (in terms of loss of total soluble solids in the beer wort as a function of time) was first-order with half-lifes in the range of approximately 9-11 hours at approximately 10-12 degrees C at beer wort linear flow rates of approximately 0.8-1.6 cm/minute for ceramic support, compared with approximately 16 hours for Ca-alginate gel, the former support matrix being more efficient and demonstrating greater potential for future commercial application.

Wealth and price distribution by diffusive approximation in a repeated prediction market

NASA Astrophysics Data System (ADS)

Bottazzi, Giulio; Giachini, Daniele

2017-04-01

The approximate agents' wealth and price invariant densities of a repeated prediction market model is derived using the Fokker-Planck equation of the associated continuous-time jump process. We show that the approximation obtained from the evolution of log-wealth difference can be reliably exploited to compute all the quantities of interest in all the acceptable parameter space. When the risk aversion of the trader is high enough, we are able to derive an explicit closed-form solution for the price distribution which is asymptotically correct.

Communication: On the calculation of time-dependent electron flux within the Born-Oppenheimer approximation: A flux-flux reflection principle

NASA Astrophysics Data System (ADS)

Albert, Julian; Hader, Kilian; Engel, Volker

2017-12-01

It is commonly assumed that the time-dependent electron flux calculated within the Born-Oppenheimer (BO) approximation vanishes. This is not necessarily true if the flux is directly determined from the continuity equation obeyed by the electron density. This finding is illustrated for a one-dimensional model of coupled electronic-nuclear dynamics. There, the BO flux is in perfect agreement with the one calculated from a solution of the time-dependent Schrödinger equation for the coupled motion. A reflection principle is derived where the nuclear BO flux is mapped onto the electronic flux.

Continuous real-time water information: an important Kansas resource

USGS Publications Warehouse

Loving, Brian L.; Putnam, James E.; Turk, Donita M.

2014-01-01

Continuous real-time information on streams, lakes, and groundwater is an important Kansas resource that can safeguard lives and property, and ensure adequate water resources for a healthy State economy. The U.S. Geological Survey (USGS) operates approximately 230 water-monitoring stations at Kansas streams, lakes, and groundwater sites. Most of these stations are funded cooperatively in partnerships with local, tribal, State, or other Federal agencies. The USGS real-time water-monitoring network provides long-term, accurate, and objective information that meets the needs of many customers. Whether the customer is a water-management or water-quality agency, an emergency planner, a power or navigational official, a farmer, a canoeist, or a fisherman, all can benefit from the continuous real-time water information gathered by the USGS.

Considering Time-Scale Requirements for the Future

DTIC Science & Technology

2013-05-01

geocentric reference frame with the SI second realized on the rotating geoid as the scale unit. It is a continuous atomic time scale that was...the B8lycentric and Geocentric Celestial Reference Systems, two time scales, Barycentric Coor- dinate Time (TCB) and Geocentric Coordinate Time (TCG...defined in 2006 as a linear scaling of TCB having the approximate rate of TT. TCG is the time coordinate for the four dimensional geocentric coordinate

CLAY MINERALS AND THE ACCUMULATION OF SOIL ORGANIC MATTER IN NORTHWESTERN U.S. FORESTS

EPA Science Inventory

Globally soils are an important terrestrial reservoir of carbon, storing approximately 3 times the carbon held in vegetation and 2 times the amount contained in the atmosphere. With the potential for global climate change it is imperative that world soils continue to be a sink f...

Reinforcement learning for adaptive optimal control of unknown continuous-time nonlinear systems with input constraints

NASA Astrophysics Data System (ADS)

Yang, Xiong; Liu, Derong; Wang, Ding

2014-03-01

In this paper, an adaptive reinforcement learning-based solution is developed for the infinite-horizon optimal control problem of constrained-input continuous-time nonlinear systems in the presence of nonlinearities with unknown structures. Two different types of neural networks (NNs) are employed to approximate the Hamilton-Jacobi-Bellman equation. That is, an recurrent NN is constructed to identify the unknown dynamical system, and two feedforward NNs are used as the actor and the critic to approximate the optimal control and the optimal cost, respectively. Based on this framework, the action NN and the critic NN are tuned simultaneously, without the requirement for the knowledge of system drift dynamics. Moreover, by using Lyapunov's direct method, the weights of the action NN and the critic NN are guaranteed to be uniformly ultimately bounded, while keeping the closed-loop system stable. To demonstrate the effectiveness of the present approach, simulation results are illustrated.

The formation of compact groups of galaxies. I: Optical properties

NASA Technical Reports Server (NTRS)

Diaferio, Antonaldo; Geller, Margaret J.; Ramella, Massimo

1994-01-01

The small crossing time of compact groups of galaxies (t(sub cr)H(sub 0) approximately less than 0.02) makes it hard to understand why they are observable at all. Our dissipationless N-body simulations show that within a single rich collapsing group compact groups of galaxies continually form. The mean lifetime of a particular compact configuration if approximately 1 Gyr. On this time scale, members may merge and/or other galaxies in the loose group may join the compact configuration. In other words, compact configurations are continually replaced by new systems. The frequency of this process explains the observability of compact groups. Our model produces compact configurations (compact groups (CG's) with optical properties remarkably similar to Hickson's (1982) compact groups (HCG's): (1) CG's have a frequency distribution of members similar to that of HCG's; (2) CG's are approximately equals 10 times as dense as loose groups; (3) CG's have dynamical properties remarkably similar to those of HCG's; (4) most of the galaxy members of CG's are not merger remnants. The crucial aspect of the model is the relationship between CG's and the surrounding rich loose group. Our model predicts the frequency of occurrence of CG's. A preliminary analysis of 18 rich loose groups is consistent with the model prediction. We suggest further observational tests of the model.

Stochastic optimal control of ultradiffusion processes with application to dynamic portfolio management

NASA Astrophysics Data System (ADS)

Marcozzi, Michael D.

2008-12-01

We consider theoretical and approximation aspects of the stochastic optimal control of ultradiffusion processes in the context of a prototype model for the selling price of a European call option. Within a continuous-time framework, the dynamic management of a portfolio of assets is effected through continuous or point control, activation costs, and phase delay. The performance index is derived from the unique weak variational solution to the ultraparabolic Hamilton-Jacobi equation; the value function is the optimal realization of the performance index relative to all feasible portfolios. An approximation procedure based upon a temporal box scheme/finite element method is analyzed; numerical examples are presented in order to demonstrate the viability of the approach.

Discrete-time stability of continuous-time controller designs for large space structures

NASA Technical Reports Server (NTRS)

Balas, M. J.

1982-01-01

In most of the stable control designs for flexible structures, continuous time is assumed. However, in view of the implementation of the controllers by on-line digital computers, the discrete-time stability of such controllers is an important consideration. In the case of direct-velocity feedback (DVFB), involving negative feedback from collocated force actuators and velocity sensors, it is not immediately apparent how much delay due to digital implementation of DVFB can be tolerated without loss of stability. The present investigation is concerned with such questions. A study is conducted of the discrete-time stability of DVFB, taking into account an employment of Euler's method of approximation of the time derivative. The obtained result gives an indication of the acceptable time-step size for stable digital implementation of DVFB. A result derived in connection with the consideration of the discrete-time stability of stable continuous-time systems provides a general condition under which digital implementation of such a system will remain stable.

Gulf of Mexico

Atmospheric Science Data Center

2014-05-15

article title:  Continued Spread of Gulf of Mexico Oil Slick       View ... passed over the Deepwater Horizon oil slick in the Gulf of Mexico on May 8, 2010, at approximately 16:50 UTC (11:50 a.m. local time), then ...

Parameter estimation in nonlinear distributed systems - Approximation theory and convergence results

NASA Technical Reports Server (NTRS)

Banks, H. T.; Reich, Simeon; Rosen, I. G.

1988-01-01

An abstract approximation framework and convergence theory is described for Galerkin approximations applied to inverse problems involving nonlinear distributed parameter systems. Parameter estimation problems are considered and formulated as the minimization of a least-squares-like performance index over a compact admissible parameter set subject to state constraints given by an inhomogeneous nonlinear distributed system. The theory applies to systems whose dynamics can be described by either time-independent or nonstationary strongly maximal monotonic operators defined on a reflexive Banach space which is densely and continuously embedded in a Hilbert space. It is demonstrated that if readily verifiable conditions on the system's dependence on the unknown parameters are satisfied, and the usual Galerkin approximation assumption holds, then solutions to the approximating problems exist and approximate a solution to the original infinite-dimensional identification problem.

Recent Advances in 3D Time-Resolved Contrast-Enhanced MR Angiography

PubMed Central

Riederer, Stephen J.; Haider, Clifton R.; Borisch, Eric A.; Weavers, Paul T.; Young, Phillip M.

2015-01-01

Contrast-enhanced MR angiography (CE-MRA) was first introduced for clinical studies approximately 20 years ago. Early work provided 3 to 4 mm spatial resolution with acquisition times in the 30 sec range. Since that time there has been continuing effort to provide improved spatial resolution with reduced acquisition time, allowing high resolution three-dimensional (3D) time-resolved studies. The purpose of this work is to describe how this has been accomplished. Specific technical enablers have been: improved gradients allowing reduced repetition times, improved k-space sampling and reconstruction methods, parallel acquisition particularly in two directions, and improved and higher count receiver coil arrays. These have collectively made high resolution time-resolved studies readily available for many anatomic regions. Depending on the application, approximate 1 mm isotropic resolution is now possible with frame times of several seconds. Clinical applications of time-resolved CE-MRA are briefly reviewed. PMID:26032598

Fixation, transient landscape, and diffusion dilemma in stochastic evolutionary game dynamics

NASA Astrophysics Data System (ADS)

Zhou, Da; Qian, Hong

2011-09-01

Agent-based stochastic models for finite populations have recently received much attention in the game theory of evolutionary dynamics. Both the ultimate fixation and the pre-fixation transient behavior are important to a full understanding of the dynamics. In this paper, we study the transient dynamics of the well-mixed Moran process through constructing a landscape function. It is shown that the landscape playing a central theoretical “device” that integrates several lines of inquiries: the stable behavior of the replicator dynamics, the long-time fixation, and continuous diffusion approximation associated with asymptotically large population. Several issues relating to the transient dynamics are discussed: (i) multiple time scales phenomenon associated with intra- and inter-attractoral dynamics; (ii) discontinuous transition in stochastically stationary process akin to Maxwell construction in equilibrium statistical physics; and (iii) the dilemma diffusion approximation facing as a continuous approximation of the discrete evolutionary dynamics. It is found that rare events with exponentially small probabilities, corresponding to the uphill movements and barrier crossing in the landscape with multiple wells that are made possible by strong nonlinear dynamics, plays an important role in understanding the origin of the complexity in evolutionary, nonlinear biological systems.

Real-Time Bridge Monitoring : Developing Wireless Nanosensors to Monitor Structural Integrity

DOT National Transportation Integrated Search

2013-04-17

With steel bridges representing approximately 34 percent of the nearly 600,000 highway bridges in the United States, continual monitoring and early detection of deterioration in these structures is vital to prevent expensive repairs or catastrophic f...

Discrete linear canonical transforms based on dilated Hermite functions.

PubMed

Pei, Soo-Chang; Lai, Yun-Chiu

2011-08-01

Linear canonical transform (LCT) is very useful and powerful in signal processing and optics. In this paper, discrete LCT (DLCT) is proposed to approximate LCT by utilizing the discrete dilated Hermite functions. The Wigner distribution function is also used to investigate DLCT performances in the time-frequency domain. Compared with the existing digital computation of LCT, our proposed DLCT possess additivity and reversibility properties with no oversampling involved. In addition, the length of input/output signals will not be changed before and after the DLCT transformations, which is consistent with the time-frequency area-preserving nature of LCT; meanwhile, the proposed DLCT has very good approximation of continuous LCT.

Online Solution of Two-Player Zero-Sum Games for Continuous-Time Nonlinear Systems With Completely Unknown Dynamics.

PubMed

Fu, Yue; Chai, Tianyou

2016-12-01

Regarding two-player zero-sum games of continuous-time nonlinear systems with completely unknown dynamics, this paper presents an online adaptive algorithm for learning the Nash equilibrium solution, i.e., the optimal policy pair. First, for known systems, the simultaneous policy updating algorithm (SPUA) is reviewed. A new analytical method to prove the convergence is presented. Then, based on the SPUA, without using a priori knowledge of any system dynamics, an online algorithm is proposed to simultaneously learn in real time either the minimal nonnegative solution of the Hamilton-Jacobi-Isaacs (HJI) equation or the generalized algebraic Riccati equation for linear systems as a special case, along with the optimal policy pair. The approximate solution to the HJI equation and the admissible policy pair is reexpressed by the approximation theorem. The unknown constants or weights of each are identified simultaneously by resorting to the recursive least square method. The convergence of the online algorithm to the optimal solutions is provided. A practical online algorithm is also developed. Simulation results illustrate the effectiveness of the proposed method.

Hybrid Discrete-Continuous Markov Decision Processes

NASA Technical Reports Server (NTRS)

Feng, Zhengzhu; Dearden, Richard; Meuleau, Nicholas; Washington, Rich

2003-01-01

This paper proposes a Markov decision process (MDP) model that features both discrete and continuous state variables. We extend previous work by Boyan and Littman on the mono-dimensional time-dependent MDP to multiple dimensions. We present the principle of lazy discretization, and piecewise constant and linear approximations of the model. Having to deal with several continuous dimensions raises several new problems that require new solutions. In the (piecewise) linear case, we use techniques from partially- observable MDPs (POMDPS) to represent value functions as sets of linear functions attached to different partitions of the state space.

The value of continuity: Refined isogeometric analysis and fast direct solvers

DOE PAGES

Garcia, Daniel; Pardo, David; Dalcin, Lisandro; ...

2016-08-24

Here, we propose the use of highly continuous finite element spaces interconnected with low continuity hyperplanes to maximize the performance of direct solvers. Starting from a highly continuous Isogeometric Analysis (IGA) discretization, we introduce C0-separators to reduce the interconnection between degrees of freedom in the mesh. By doing so, both the solution time and best approximation errors are simultaneously improved. We call the resulting method “refined Isogeometric Analysis (rIGA)”. To illustrate the impact of the continuity reduction, we analyze the number of Floating Point Operations (FLOPs), computational times, and memory required to solve the linear system obtained by discretizing themore » Laplace problem with structured meshes and uniform polynomial orders. Theoretical estimates demonstrate that an optimal continuity reduction may decrease the total computational time by a factor between p 2 and p 3, with pp being the polynomial order of the discretization. Numerical results indicate that our proposed refined isogeometric analysis delivers a speed-up factor proportional to p 2. In a 2D mesh with four million elements and p=5, the linear system resulting from rIGA is solved 22 times faster than the one from highly continuous IGA. In a 3D mesh with one million elements and p=3, the linear system is solved 15 times faster for the refined than the maximum continuity isogeometric analysis.« less

Polynomial approximation of non-Gaussian unitaries by counting one photon at a time

NASA Astrophysics Data System (ADS)

Arzani, Francesco; Treps, Nicolas; Ferrini, Giulia

2017-05-01

In quantum computation with continuous-variable systems, quantum advantage can only be achieved if some non-Gaussian resource is available. Yet, non-Gaussian unitary evolutions and measurements suited for computation are challenging to realize in the laboratory. We propose and analyze two methods to apply a polynomial approximation of any unitary operator diagonal in the amplitude quadrature representation, including non-Gaussian operators, to an unknown input state. Our protocols use as a primary non-Gaussian resource a single-photon counter. We use the fidelity of the transformation with the target one on Fock and coherent states to assess the quality of the approximate gate.

Approximation-based adaptive tracking control of pure-feedback nonlinear systems with multiple unknown time-varying delays.

PubMed

Wang, Min; Ge, Shuzhi Sam; Hong, Keum-Shik

2010-11-01

This paper presents adaptive neural tracking control for a class of non-affine pure-feedback systems with multiple unknown state time-varying delays. To overcome the design difficulty from non-affine structure of pure-feedback system, mean value theorem is exploited to deduce affine appearance of state variables x(i) as virtual controls α(i), and of the actual control u. The separation technique is introduced to decompose unknown functions of all time-varying delayed states into a series of continuous functions of each delayed state. The novel Lyapunov-Krasovskii functionals are employed to compensate for the unknown functions of current delayed state, which is effectively free from any restriction on unknown time-delay functions and overcomes the circular construction of controller caused by the neural approximation of a function of u and [Formula: see text] . Novel continuous functions are introduced to overcome the design difficulty deduced from the use of one adaptive parameter. To achieve uniformly ultimate boundedness of all the signals in the closed-loop system and tracking performance, control gains are effectively modified as a dynamic form with a class of even function, which makes stability analysis be carried out at the present of multiple time-varying delays. Simulation studies are provided to demonstrate the effectiveness of the proposed scheme.

An Approximate Markov Model for the Wright-Fisher Diffusion and Its Application to Time Series Data.

PubMed

Ferrer-Admetlla, Anna; Leuenberger, Christoph; Jensen, Jeffrey D; Wegmann, Daniel

2016-06-01

The joint and accurate inference of selection and demography from genetic data is considered a particularly challenging question in population genetics, since both process may lead to very similar patterns of genetic diversity. However, additional information for disentangling these effects may be obtained by observing changes in allele frequencies over multiple time points. Such data are common in experimental evolution studies, as well as in the comparison of ancient and contemporary samples. Leveraging this information, however, has been computationally challenging, particularly when considering multilocus data sets. To overcome these issues, we introduce a novel, discrete approximation for diffusion processes, termed mean transition time approximation, which preserves the long-term behavior of the underlying continuous diffusion process. We then derive this approximation for the particular case of inferring selection and demography from time series data under the classic Wright-Fisher model and demonstrate that our approximation is well suited to describe allele trajectories through time, even when only a few states are used. We then develop a Bayesian inference approach to jointly infer the population size and locus-specific selection coefficients with high accuracy and further extend this model to also infer the rates of sequencing errors and mutations. We finally apply our approach to recent experimental data on the evolution of drug resistance in influenza virus, identifying likely targets of selection and finding evidence for much larger viral population sizes than previously reported. Copyright © 2016 by the Genetics Society of America.

Dynamic partitioning for hybrid simulation of the bistable HIV-1 transactivation network.

PubMed

Griffith, Mark; Courtney, Tod; Peccoud, Jean; Sanders, William H

2006-11-15

The stochastic kinetics of a well-mixed chemical system, governed by the chemical Master equation, can be simulated using the exact methods of Gillespie. However, these methods do not scale well as systems become more complex and larger models are built to include reactions with widely varying rates, since the computational burden of simulation increases with the number of reaction events. Continuous models may provide an approximate solution and are computationally less costly, but they fail to capture the stochastic behavior of small populations of macromolecules. In this article we present a hybrid simulation algorithm that dynamically partitions the system into subsets of continuous and discrete reactions, approximates the continuous reactions deterministically as a system of ordinary differential equations (ODE) and uses a Monte Carlo method for generating discrete reaction events according to a time-dependent propensity. Our approach to partitioning is improved such that we dynamically partition the system of reactions, based on a threshold relative to the distribution of propensities in the discrete subset. We have implemented the hybrid algorithm in an extensible framework, utilizing two rigorous ODE solvers to approximate the continuous reactions, and use an example model to illustrate the accuracy and potential speedup of the algorithm when compared with exact stochastic simulation. Software and benchmark models used for this publication can be made available upon request from the authors.

Probabilistic Reasoning for Plan Robustness

NASA Technical Reports Server (NTRS)

Schaffer, Steve R.; Clement, Bradley J.; Chien, Steve A.

2005-01-01

A planning system must reason about the uncertainty of continuous variables in order to accurately project the possible system state over time. A method is devised for directly reasoning about the uncertainty in continuous activity duration and resource usage for planning problems. By representing random variables as parametric distributions, computing projected system state can be simplified in some cases. Common approximation and novel methods are compared for over-constrained and lightly constrained domains. The system compares a few common approximation methods for an iterative repair planner. Results show improvements in robustness over the conventional non-probabilistic representation by reducing the number of constraint violations witnessed by execution. The improvement is more significant for larger problems and problems with higher resource subscription levels but diminishes as the system is allowed to accept higher risk levels.

Approximate solutions for diffusive fracture-matrix transfer: Application to storage of dissolved CO 2 in fractured rocks

DOE PAGES

Zhou, Quanlin; Oldenburg, Curtis M.; Spangler, Lee H.; ...

2017-01-05

Analytical solutions with infinite exponential series are available to calculate the rate of diffusive transfer between low-permeability blocks and high-permeability zones in the subsurface. Truncation of these series is often employed by neglecting the early-time regime. Here in this paper, we present unified-form approximate solutions in which the early-time and the late-time solutions are continuous at a switchover time. The early-time solutions are based on three-term polynomial functions in terms of square root of dimensionless time, with the first coefficient dependent only on the dimensionless area-to-volume ratio. The last two coefficients are either determined analytically for isotropic blocks (e.g., spheresmore » and slabs) or obtained by fitting the exact solutions, and they solely depend on the aspect ratios for rectangular columns and parallelepipeds. For the late-time solutions, only the leading exponential term is needed for isotropic blocks, while a few additional exponential terms are needed for highly anisotropic rectangular blocks. The optimal switchover time is between 0.157 and 0.229, with highest relative approximation error less than 0.2%. The solutions are used to demonstrate the storage of dissolved CO 2 in fractured reservoirs with low-permeability matrix blocks of single and multiple shapes and sizes. These approximate solutions are building blocks for development of analytical and numerical tools for hydraulic, solute, and thermal diffusion processes in low-permeability matrix blocks.« less

Fourth-order convergence of a compact scheme for the one-dimensional biharmonic equation

NASA Astrophysics Data System (ADS)

Fishelov, D.; Ben-Artzi, M.; Croisille, J.-P.

2012-09-01

The convergence of a fourth-order compact scheme to the one-dimensional biharmonic problem is established in the case of general Dirichlet boundary conditions. The compact scheme invokes value of the unknown function as well as Pade approximations of its first-order derivative. Using the Pade approximation allows us to approximate the first-order derivative within fourth-order accuracy. However, although the truncation error of the discrete biharmonic scheme is of fourth-order at interior point, the truncation error drops to first-order at near-boundary points. Nonetheless, we prove that the scheme retains its fourth-order (optimal) accuracy. This is done by a careful inspection of the matrix elements of the discrete biharmonic operator. A number of numerical examples corroborate this effect. We also present a study of the eigenvalue problem uxxxx = νu. We compute and display the eigenvalues and the eigenfunctions related to the continuous and the discrete problems. By the positivity of the eigenvalues, one can deduce the stability of of the related time-dependent problem ut = -uxxxx. In addition, we study the eigenvalue problem uxxxx = νuxx. This is related to the stability of the linear time-dependent equation uxxt = νuxxxx. Its continuous and discrete eigenvalues and eigenfunction (or eigenvectors) are computed and displayed graphically.

A simple method to calculate first-passage time densities with arbitrary initial conditions

NASA Astrophysics Data System (ADS)

Nyberg, Markus; Ambjörnsson, Tobias; Lizana, Ludvig

2016-06-01

Numerous applications all the way from biology and physics to economics depend on the density of first crossings over a boundary. Motivated by the lack of general purpose analytical tools for computing first-passage time densities (FPTDs) for complex problems, we propose a new simple method based on the independent interval approximation (IIA). We generalise previous formulations of the IIA to include arbitrary initial conditions as well as to deal with discrete time and non-smooth continuous time processes. We derive a closed form expression for the FPTD in z and Laplace-transform space to a boundary in one dimension. Two classes of problems are analysed in detail: discrete time symmetric random walks (Markovian) and continuous time Gaussian stationary processes (Markovian and non-Markovian). Our results are in good agreement with Langevin dynamics simulations.

A theory of cerebellar cortex and adaptive motor control based on two types of universal function approximation capability.

PubMed

Fujita, Masahiko

2016-03-01

Lesions of the cerebellum result in large errors in movements. The cerebellum adaptively controls the strength and timing of motor command signals depending on the internal and external environments of movements. The present theory describes how the cerebellar cortex can control signals for accurate and timed movements. A model network of the cerebellar Golgi and granule cells is shown to be equivalent to a multiple-input (from mossy fibers) hierarchical neural network with a single hidden layer of threshold units (granule cells) that receive a common recurrent inhibition (from a Golgi cell). The weighted sum of the hidden unit signals (Purkinje cell output) is theoretically analyzed regarding the capability of the network to perform two types of universal function approximation. The hidden units begin firing as the excitatory inputs exceed the recurrent inhibition. This simple threshold feature leads to the first approximation theory, and the network final output can be any continuous function of the multiple inputs. When the input is constant, this output becomes stationary. However, when the recurrent unit activity is triggered to decrease or the recurrent inhibition is triggered to increase through a certain mechanism (metabotropic modulation or extrasynaptic spillover), the network can generate any continuous signals for a prolonged period of change in the activity of recurrent signals, as the second approximation theory shows. By incorporating the cerebellar capability of two such types of approximations to a motor system, in which learning proceeds through repeated movement trials with accompanying corrections, accurate and timed responses for reaching the target can be adaptively acquired. Simple models of motor control can solve the motor error vs. sensory error problem, as well as the structural aspects of credit (or error) assignment problem. Two physiological experiments are proposed for examining the delay and trace conditioning of eyelid responses, as well as saccade adaptation, to investigate this novel idea of cerebellar processing. Copyright © 2015 Elsevier Ltd. All rights reserved.

Extended Operation of Turbojet Engine with Pentaborane

NASA Technical Reports Server (NTRS)

Useller, James W; Jones, William L

1957-01-01

A full-scale turbojet engine was operated with pentaborane fuel continuously for 22 minutes at conditions simulating flight at a Mach number of 0.8 at an altitude of 50,000 feet. This period of operation is approximately three times longer than previously reported operation times. Although the specific fuel consumption was reduced from 1.3 with JP-4 fuel to 0.98 with pentaborane, a 13.2-percent reduction in net thrust was also encountered. A portion of this thrust loss is potentially recoverable with proper design of the engine components. The boron oxide deposition and erosion processes within the engine approached an equilibrium condition after approximately 22 minutes of operation with pentaborane.

Species measurements in a hypersonic, hydrogen-air, combustion wake

NASA Technical Reports Server (NTRS)

Skinner, K. A.; Stalker, R. J.

1995-01-01

A continuously sampling, time-of-flight mass spectrometer has been used to measure relative species concentrations in a two-dimensional, hydrogen-air combustion wake at mainstream Mach numbers exceeding 5. The experiments, which were conducted in a free piston shock tunnel, yielded distributions of hydrogen, oxygen, nitrogen, water and nitric oxide at stagnation enthalpies ranging from 5.6 MJ kg(exp -1) to 1.2 MJ kg(exp -1) and at a distance of approximately 100 times the thickness of the initial hydrogen jet. The amount of hydrogen that was mixed in stoichiometric proportions was approximately independent of the stagnation enthalpy, in spite of the fact that the proportion of hydrogen in the wake increased with stagnation enthalpy. Roughly 50 percent of the mixed hydrogen underwent combustion at the highest enthalpy. The proportion of hydrogen reacting to water could be approximately predicted using reaction rates based on mainstream temperatures.

Methods of producing continuous boron carbide fibers

DOEpatents

Garnier, John E.; Griffith, George W.

2015-12-01

Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

Event-Triggered Adaptive Dynamic Programming for Continuous-Time Systems With Control Constraints.

PubMed

Dong, Lu; Zhong, Xiangnan; Sun, Changyin; He, Haibo

2016-08-31

In this paper, an event-triggered near optimal control structure is developed for nonlinear continuous-time systems with control constraints. Due to the saturating actuators, a nonquadratic cost function is introduced and the Hamilton-Jacobi-Bellman (HJB) equation for constrained nonlinear continuous-time systems is formulated. In order to solve the HJB equation, an actor-critic framework is presented. The critic network is used to approximate the cost function and the action network is used to estimate the optimal control law. In addition, in the proposed method, the control signal is transmitted in an aperiodic manner to reduce the computational and the transmission cost. Both the networks are only updated at the trigger instants decided by the event-triggered condition. Detailed Lyapunov analysis is provided to guarantee that the closed-loop event-triggered system is ultimately bounded. Three case studies are used to demonstrate the effectiveness of the proposed method.

Sessional Academic Success: A Distributed Framework for Academic Support and Development

ERIC Educational Resources Information Center

Hamilton, Jillian; Fox, Michelle; McEwan, Mitchell

2013-01-01

With approximately half of Australian university teaching now performed by Sessional Academics, there has been growing recognition of the contribution they make to student learning. At the same time, sector-wide research and institutional audits continue to raise concerns about academic development, quality assurance, recognition and belonging…

Sorption of Heterotrophic and Enteric Bacteria to Glass Surfaces in the Continuous Culture of River Water

PubMed Central

Hendricks, Charles W.

1974-01-01

A natural population of heterotrophic bacteria, including enterics, was observed to sorb to glass surfaces and multiply during the continuous culture of river water. An initial rate of attachment equivalent to a doubling time of about 2 h was observed with a corresponding increase in the suspended population. After 24 h both the sorbed and suspended populations stabilized with a mass doubling time approximating 100 h at a dilution rate of 0.012/h. On the basis of respiration and degradative enzymatic data, the sorbed microorganisms appeared to be somewhat more metabolically active than the organisms in suspension. PMID:4424694

A new continuous light source for high-speed imaging

NASA Astrophysics Data System (ADS)

Paton, R. T.; Hall, R. E.; Skews, B. W.

2017-02-01

Xenon arc lamps have been identified as a suitable continuous light source for high-speed imaging, specifically high-speed Schlieren and shadowgraphy. One issue when setting us such systems is the time that it takes to reduce a finite source to the approximation of a point source for z-type schlieren. A preliminary design of a compact compound lens for use with a commercial Xenon arc lamp was tested for suitability. While it was found that there is some dimming of the illumination at the spot periphery, the overall spectral and luminance distribution of the compact source is quite acceptable, especially considering the time benefit that it represents.

Fringe pattern demodulation using the one-dimensional continuous wavelet transform: field-programmable gate array implementation.

PubMed

Abid, Abdulbasit

2013-03-01

This paper presents a thorough discussion of the proposed field-programmable gate array (FPGA) implementation for fringe pattern demodulation using the one-dimensional continuous wavelet transform (1D-CWT) algorithm. This algorithm is also known as wavelet transform profilometry. Initially, the 1D-CWT is programmed using the C programming language and compiled into VHDL using the ImpulseC tool. This VHDL code is implemented on the Altera Cyclone IV GX EP4CGX150DF31C7 FPGA. A fringe pattern image with a size of 512×512 pixels is presented to the FPGA, which processes the image using the 1D-CWT algorithm. The FPGA requires approximately 100 ms to process the image and produce a wrapped phase map. For performance comparison purposes, the 1D-CWT algorithm is programmed using the C language. The C code is then compiled using the Intel compiler version 13.0. The compiled code is run on a Dell Precision state-of-the-art workstation. The time required to process the fringe pattern image is approximately 1 s. In order to further reduce the execution time, the 1D-CWT is reprogramed using Intel Integrated Primitive Performance (IPP) Library Version 7.1. The execution time was reduced to approximately 650 ms. This confirms that at least sixfold speedup was gained using FPGA implementation over a state-of-the-art workstation that executes heavily optimized implementation of the 1D-CWT algorithm.

Rational Exponentials and Continued Fractions

ERIC Educational Resources Information Center

Denny, J. K.

2012-01-01

Using continued fraction expansions, we can approximate constants, such as pi and e, using an appropriate integer n raised to the power x[superscript 1/x], x a suitable rational. We review continued fractions and give an algorithm for producing these approximations.

A unified framework for approximation in inverse problems for distributed parameter systems

NASA Technical Reports Server (NTRS)

Banks, H. T.; Ito, K.

1988-01-01

A theoretical framework is presented that can be used to treat approximation techniques for very general classes of parameter estimation problems involving distributed systems that are either first or second order in time. Using the approach developed, one can obtain both convergence and stability (continuous dependence of parameter estimates with respect to the observations) under very weak regularity and compactness assumptions on the set of admissible parameters. This unified theory can be used for many problems found in the recent literature and in many cases offers significant improvements to existing results.

Robust synchronization of master-slave chaotic systems using approximate model: An experimental study.

PubMed

Ahmed, Hafiz; Salgado, Ivan; Ríos, Héctor

2018-02-01

Robust synchronization of master slave chaotic systems are considered in this work. First an approximate model of the error system is obtained using the ultra-local model concept. Then a Continuous Singular Terminal Sliding-Mode (CSTSM) Controller is designed for the purpose of synchronization. The proposed approach is output feedback-based and uses fixed-time higher order sliding-mode (HOSM) differentiator for state estimation. Numerical simulation and experimental results are given to show the effectiveness of the proposed technique. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

State-space prediction model for chaotic time series

NASA Astrophysics Data System (ADS)

Alparslan, A. K.; Sayar, M.; Atilgan, A. R.

1998-08-01

A simple method for predicting the continuation of scalar chaotic time series ahead in time is proposed. The false nearest neighbors technique in connection with the time-delayed embedding is employed so as to reconstruct the state space. A local forecasting model based upon the time evolution of the topological neighboring in the reconstructed phase space is suggested. A moving root-mean-square error is utilized in order to monitor the error along the prediction horizon. The model is tested for the convection amplitude of the Lorenz model. The results indicate that for approximately 100 cycles of the training data, the prediction follows the actual continuation very closely about six cycles. The proposed model, like other state-space forecasting models, captures the long-term behavior of the system due to the use of spatial neighbors in the state space.

Texturing of continuous LOD meshes with the hierarchical texture atlas

NASA Astrophysics Data System (ADS)

Birkholz, Hermann

2006-02-01

For the rendering of detailed virtual environments, trade-offs have to be made between image quality and rendering time. An immersive experience of virtual reality always demands high frame-rates with the best reachable image qual-ity. Continuous Level of Detail (cLoD) triangle-meshes provide an continuous spectrum of detail for a triangle mesh that can be used to create view-dependent approximations of the environment in real-time. This enables the rendering with a constant number of triangles and thus with constant frame-rates. Normally the construction of such cLoD mesh representations leads to the loss of all texture information of the original mesh. To overcome this problem, a parameter domain can be created, in order to map the surface properties (colour, texture, normal) to it. This parameter domain can be used to map the surface properties back to arbitrary approximations of the original mesh. The parameter domain is often a simplified version of the mesh to be parameterised. This limits the reachable simplification to the domain mesh which has to map the surface of the original mesh with the least possible stretch. In this paper, a hierarchical domain mesh is presented, that scales between very coarse domain meshes and good property-mapping.

The Effect of Condensate Inundation on Steam Condensation Heat Transfer to Wire-Wrapped Tubing.

DTIC Science & Technology

1983-06-01

wrapped in a helical manner. The measured condensing coefficient was approximately three times that predicted by the Nusselt equation for a smooth tube...Du. Em0At Block 20 (continued) --"- condensing coefficient measured for 30 smooth tubes was 0.59 times the Nusselt coefficient calculated for the...of 0.029 was found, while it was 0.061 for the roped tubes. The average condensing coefficient measured for 30 smooth tubes was 0.59 times the Nusselt

76 FR 24457 - Proposed Information Collection; Comment Request; Survey of Income and Program Participation...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-02

... the SIPP, which is a household-based survey designed as a continuous series of national panels. New... the panel. The core is supplemented with questions designed to address specific needs, such as... be measured over time. The 2008 panel is currently scheduled for approximately 6 years and will...

Framing Young People's Educational Transitions: The Role of Local and Contemporary Economic Contexts

ERIC Educational Resources Information Center

Evans, Ceryn

2017-01-01

Despite rates of participation in post-compulsory full-time education reaching approximately 84% in Wales, social class inequalities continue to shape young people's transitions from compulsory to post-compulsory education. This article draws upon data from a project which explored how young people's educational decisions and transitions in Wales,…

Connecting Two Worlds: Collaboration between Higher Education and Corporate Learning

ERIC Educational Resources Information Center

Masie, Elliott

2012-01-01

Colleges and universities enroll approximately 15 million full-time students in the United States. Most of these learners will soon be joining the more than 139 million employees in the U.S. workforce, where their education will continue through corporate education, training, and development. There are many similarities between the learning and…

A Study of Vocational Education Programs in the Michigan Department of Corrections.

ERIC Educational Resources Information Center

Dirkx, John M.; Kielbaso, Gloria; Corley, Charles

Rapid expansion of the prison population in Michigan has created concern for consistency, continuity, and articulation within the Michigan Department of Corrections vocational programs, which serve approximately 1,800 prisoners at a time. For this reason, a study was undertaken to determine how vocational education within Michigan's prisons might…

On the r-mode spectrum of relativistic stars in the low-frequency approximation

NASA Astrophysics Data System (ADS)

Ruoff, Johannes; Kokkotas, Kostas D.

2001-12-01

The axial modes for non-barotropic relativistic rotating neutron stars with uniform angular velocity are studied, using the slow-rotation formalism together with the low-frequency approximation, first investigated by Kojima. The time-independent form of the equations leads to a singular eigenvalue problem, which admits a continuous spectrum. We show that for l=2, it is nevertheless also possible to find discrete mode solutions (the r modes). However, under certain conditions related to the equation of state and the compactness of the stellar model, the eigenfrequency lies inside the continuous band and the associated velocity perturbation is divergent; hence these solutions have to be discarded as being unphysical. We corroborate our results by explicitly integrating the time-dependent equations. For stellar models admitting a physical r-mode solution, it can indeed be excited by arbitrary initial data. For models admitting only an unphysical mode solution, the evolutions do not show any tendency to oscillate with the respective frequency. For higher values of l it seems that in certain cases there are no mode solutions at all.

Reporting Recommended Patch Density from Vehicle Panel Vibration Convergence Studies using both DAF and TBL Fits of the Spatial Correlation Function

NASA Technical Reports Server (NTRS)

Smith, Andrew M.; Davis, Robert Ben; LaVerde, Bruce T.; Jones, Douglas C.; Band, Jonathon L.

2012-01-01

Using the patch method to represent the continuous spatial correlation function of a phased pressure field over a structural surface is an approximation. The approximation approaches the continuous function as patches become smaller. Plotting comparisons of the approximation vs the continuous function may provide insight revealing: (1) For what patch size/density should the approximation be very good? (2) What the approximation looks like when it begins to break down? (3) What the approximation looks like when the patch size is grossly too large. Following these observations with a convergence study using one FEM may allow us to see the importance of patch density. We may develop insights that help us to predict sufficient patch density to provide adequate convergence for the intended purpose frequency range of interest

Lasers' spectral and temporal profile can affect visual glare disability.

PubMed

Beer, Jeremy M A; Freeman, David A

2012-12-01

Experiments measured the effects of laser glare on visual orientation and motion perception. Laser stimuli were varied according to spectral composition and temporal presentation as subjects identified targets' tilt (Experiment 1) and movement (Experiment 2). The objective was to determine whether the glare parameters would alter visual disruption. Three spectral profiles (monochromatic Green vs. polychromatic White vs. alternating Red-Green) were used to produce a ring of laser glare surrounding a target. Two experiments were performed to measure the minimum contrast required to report target orientation or motion direction. The temporal glare profile was also varied: the ring was illuminated either continuously or discontinuously. Time-averaged luminance of the glare stimuli was matched across all conditions. In both experiments, threshold (deltaL) values were approximately 0.15 log units higher in monochromatic Green than in polychromatic White conditions. In Experiment 2 (motion identification), thresholds were approximately 0.17 log units higher in rapidly flashing (6, 10, or 14 Hz) than in continuous exposure conditions. Monochromatic extended-source laser glare disrupted orientation and motion identification more than polychromatic glare. In the motion task, pulse trains faster than 6 Hz (but below flicker fusion) elevated thresholds more than continuous glare with the same time-averaged luminance. Under these conditions, alternating the wavelength of monochromatic glare over time did not aggravate disability relative to green-only glare. Repetitively flashing monochromatic laser glare induced occasional episodes of impaired motion identification, perhaps resulting from cognitive interference. Interference speckle might play a role in aggravating monochromatic glare effects.

Neural Approximation-Based Adaptive Control for a Class of Nonlinear Nonstrict Feedback Discrete-Time Systems.

PubMed

Yan-Jun Liu; Shu Li; Shaocheng Tong; Chen, C L Philip

2017-07-01

In this paper, an adaptive control approach-based neural approximation is developed for a class of uncertain nonlinear discrete-time (DT) systems. The main characteristic of the considered systems is that they can be viewed as a class of multi-input multioutput systems in the nonstrict feedback structure. The similar control problem of this class of systems has been addressed in the past, but it focused on the continuous-time systems. Due to the complicacies of the system structure, it will become more difficult for the controller design and the stability analysis. To stabilize this class of systems, a new recursive procedure is developed, and the effect caused by the noncausal problem in the nonstrict feedback DT structure can be solved using a semirecurrent neural approximation. Based on the Lyapunov difference approach, it is proved that all the signals of the closed-loop system are semiglobal, ultimately uniformly bounded, and a good tracking performance can be guaranteed. The feasibility of the proposed controllers can be validated by setting a simulation example.

Continuous in vitro evolution of catalytic function.

PubMed

Wright, M C; Joyce, G F

1997-04-25

A population of RNA molecules that catalyze the template-directed ligation of RNA substrates was made to evolve in a continuous manner in the test tube. A simple serial transfer procedure was used to achieve approximately 300 successive rounds of catalysis and selective amplification in 52 hours. During this time, the population size was maintained against an overall dilution of 3 x 10(298). Both the catalytic rate and amplification rate of the RNAs improved substantially as a consequence of mutations that accumulated during the evolution process. Continuous in vitro evolution makes it possible to maintain laboratory "cultures" of catalytic molecules that can be perpetuated indefinitely.

Continuous in vitro evolution of catalytic function

NASA Technical Reports Server (NTRS)

Wright, M. C.; Joyce, G. F.

1997-01-01

A population of RNA molecules that catalyze the template-directed ligation of RNA substrates was made to evolve in a continuous manner in the test tube. A simple serial transfer procedure was used to achieve approximately 300 successive rounds of catalysis and selective amplification in 52 hours. During this time, the population size was maintained against an overall dilution of 3 x 10(298). Both the catalytic rate and amplification rate of the RNAs improved substantially as a consequence of mutations that accumulated during the evolution process. Continuous in vitro evolution makes it possible to maintain laboratory "cultures" of catalytic molecules that can be perpetuated indefinitely.

[Physical activity, screen time, and use of medicines among adolescents: the 1993 Pelotas (Brazil) birth cohort study].

PubMed

Bergmann, Gabriel Gustavo; Bertoldi, Andréa Dâmaso; Mielke, Grégore Iven; Camargo, Aline Lins; Matijasevich, Alicia; Hallal, Pedro Curi

2016-01-01

This study aimed to evaluate cross-sectional and longitudinal associations between physical activity, screen time, and use of medicines among adolescents from the 1993 Pelotas (Brazil) birth cohort study, followed at 11 (N = 4,452), 15 (N = 4,325), and 18 years of age (N = 4,106). The study recorded the use of medicines in the previous 15 days, continuous use of some medication, level of physical activity (by questionnaire and accelerometry), and screen time (TV, computer, and videogame). One-third of adolescents had used at least one medicine in the previous 15 days and approximately 10% were on some continuous medication. In the adjusted analysis, the results showed that higher levels of physical activity at 18 years and less screen time at 15 years in boys were associated with lower overall use of medicines (p < 0.05). For boys, physical activity at 11 and 18 years were inversely related to continuous medication (p < 0.05). More physically active boys and those with less screen time in adolescence showed lower use of medicines at 18 years of age.

Window of visibility - A psychophysical theory of fidelity in time-sampled visual motion displays

NASA Technical Reports Server (NTRS)

Watson, A. B.; Ahumada, A. J., Jr.; Farrell, J. E.

1986-01-01

A film of an object in motion presents on the screen a sequence of static views, while the human observer sees the object moving smoothly across the screen. Questions related to the perceptual identity of continuous and stroboscopic displays are examined. Time-sampled moving images are considered along with the contrast distribution of continuous motion, the contrast distribution of stroboscopic motion, the frequency spectrum of continuous motion, the frequency spectrum of stroboscopic motion, the approximation of the limits of human visual sensitivity to spatial and temporal frequencies by a window of visibility, the critical sampling frequency, the contrast distribution of staircase motion and the frequency spectrum of this motion, and the spatial dependence of the critical sampling frequency. Attention is given to apparent motion, models of motion, image recording, and computer-generated imagery.

Reliability of the Parabola Approximation Method in Heart Rate Variability Analysis Using Low-Sampling-Rate Photoplethysmography.

PubMed

Baek, Hyun Jae; Shin, JaeWook; Jin, Gunwoo; Cho, Jaegeol

2017-10-24

Photoplethysmographic signals are useful for heart rate variability analysis in practical ambulatory applications. While reducing the sampling rate of signals is an important consideration for modern wearable devices that enable 24/7 continuous monitoring, there have not been many studies that have investigated how to compensate the low timing resolution of low-sampling-rate signals for accurate heart rate variability analysis. In this study, we utilized the parabola approximation method and measured it against the conventional cubic spline interpolation method for the time, frequency, and nonlinear domain variables of heart rate variability. For each parameter, the intra-class correlation, standard error of measurement, Bland-Altman 95% limits of agreement and root mean squared relative error were presented. Also, elapsed time taken to compute each interpolation algorithm was investigated. The results indicated that parabola approximation is a simple, fast, and accurate algorithm-based method for compensating the low timing resolution of pulse beat intervals. In addition, the method showed comparable performance with the conventional cubic spline interpolation method. Even though the absolute value of the heart rate variability variables calculated using a signal sampled at 20 Hz were not exactly matched with those calculated using a reference signal sampled at 250 Hz, the parabola approximation method remains a good interpolation method for assessing trends in HRV measurements for low-power wearable applications.

Update Direct-Strike Lightning Environment for Stockpile-to-Target Sequence (Second Revision)

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

Uman, Martin A.; Rakov, V. A.; Elisme, J. O.

2010-10-05

The University of Florida has surveyed all relevant publications reporting lightning characteristics and presents here an up-to-date version of the direct-strike lightning environment specifications for nuclear weapons published in 1989 by R. J. Fisher and M. A. Uman. Further, we present functional expressions for current vs. time, current derivative vs. time, second current derivative vs. time, charge transfer vs. time, and action integral (specific energy) vs. time for positive and negative first return strokes, for negative subsequent return strokes, and for positive and negative continuing currents; and we give sets of constants for these functional expressions so that the resultantmore » waveforms exhibit approximately the median and extreme lightning parameters presented in the updated direct strike environment. Fourier transforms of the return stroke current waveforms are presented. The results of our literature survey are included in three Appendices entitled Return Stroke Current, Continuing Current, and Positive Lightning.« less

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

Zhou, Quanlin; Oldenburg, Curtis M.; Spangler, Lee H.

Analytical solutions with infinite exponential series are available to calculate the rate of diffusive transfer between low-permeability blocks and high-permeability zones in the subsurface. Truncation of these series is often employed by neglecting the early-time regime. Here in this paper, we present unified-form approximate solutions in which the early-time and the late-time solutions are continuous at a switchover time. The early-time solutions are based on three-term polynomial functions in terms of square root of dimensionless time, with the first coefficient dependent only on the dimensionless area-to-volume ratio. The last two coefficients are either determined analytically for isotropic blocks (e.g., spheresmore » and slabs) or obtained by fitting the exact solutions, and they solely depend on the aspect ratios for rectangular columns and parallelepipeds. For the late-time solutions, only the leading exponential term is needed for isotropic blocks, while a few additional exponential terms are needed for highly anisotropic rectangular blocks. The optimal switchover time is between 0.157 and 0.229, with highest relative approximation error less than 0.2%. The solutions are used to demonstrate the storage of dissolved CO 2 in fractured reservoirs with low-permeability matrix blocks of single and multiple shapes and sizes. These approximate solutions are building blocks for development of analytical and numerical tools for hydraulic, solute, and thermal diffusion processes in low-permeability matrix blocks.« less

New mode of operating a magnetized coaxial plasma gun for injecting magnetic helicity into a spheromak.

PubMed

Woodruff, S; Hill, D N; Stallard, B W; Bulmer, R; Cohen, B; Holcomb, C T; Hooper, E B; McLean, H S; Moller, J; Wood, R D

2003-03-07

By operating a magnetized coaxial plasma gun continuously with just sufficient current to enable plasma ejection, large gun-voltage spikes (approximately 1 kV) are produced, giving the highest sustained voltage approximately 500 V and highest sustained helicity injection rate observed in the Sustained Spheromak Physics Experiment. The spheromak magnetic field increases monotonically with time, exhibiting the lowest fluctuation levels observed during formation of any spheromak (B/B>/=2%). The results suggest an important mechanism for field generation by helicity injection, namely, the merging of helicity-carrying filaments.

Boussinesq approximation of the Cahn-Hilliard-Navier-Stokes equations.

PubMed

Vorobev, Anatoliy

2010-11-01

We use the Cahn-Hilliard approach to model the slow dissolution dynamics of binary mixtures. An important peculiarity of the Cahn-Hilliard-Navier-Stokes equations is the necessity to use the full continuity equation even for a binary mixture of two incompressible liquids due to dependence of mixture density on concentration. The quasicompressibility of the governing equations brings a short time-scale (quasiacoustic) process that may not affect the slow dynamics but may significantly complicate the numerical treatment. Using the multiple-scale method we separate the physical processes occurring on different time scales and, ultimately, derive the equations with the filtered-out quasiacoustics. The derived equations represent the Boussinesq approximation of the Cahn-Hilliard-Navier-Stokes equations. This approximation can be further employed as a universal theoretical model for an analysis of slow thermodynamic and hydrodynamic evolution of the multiphase systems with strongly evolving and diffusing interfacial boundaries, i.e., for the processes involving dissolution/nucleation, evaporation/condensation, solidification/melting, polymerization, etc.

Continuous fermentation of food waste leachate for the production of volatile fatty acids and potential as a denitrification carbon source.

PubMed

Kim, Hakchan; Kim, Jaai; Shin, Seung Gu; Hwang, Seokhwan; Lee, Changsoo

2016-05-01

This study investigated the simultaneous effects of hydraulic retention time (HRT) and pH on the continuous production of VFAs from food waste leachate using response surface analysis. The response surface approximations (R(2)=0.895, p<0.05) revealed that pH has a dominant effect on the specific VFA production (PTVFA) within the explored space (1-4-day HRT, pH 4.5-6.5). The estimated maximum PTVFA was 0.26g total VFAs/g CODf at 2.14-day HRT and pH 6.44, and the approximation was experimentally validated by running triplicate reactors under the estimated optimum conditions. The mixture of the filtrates recovered from these reactors was tested as a denitrification carbon source and demonstrated superior performance in terms of reaction rate and lag length relative to other chemicals, including acetate and methanol. The overall results provide helpful information for better design and control of continuous fermentation for producing waste-derived VFAs, an alternative carbon source for denitrification. Copyright © 2016 Elsevier Ltd. All rights reserved.

A fast quadrature-based numerical method for the continuous spectrum biphasic poroviscoelastic model of articular cartilage.

PubMed

Stuebner, Michael; Haider, Mansoor A

2010-06-18

A new and efficient method for numerical solution of the continuous spectrum biphasic poroviscoelastic (BPVE) model of articular cartilage is presented. Development of the method is based on a composite Gauss-Legendre quadrature approximation of the continuous spectrum relaxation function that leads to an exponential series representation. The separability property of the exponential terms in the series is exploited to develop a numerical scheme that can be reduced to an update rule requiring retention of the strain history at only the previous time step. The cost of the resulting temporal discretization scheme is O(N) for N time steps. Application and calibration of the method is illustrated in the context of a finite difference solution of the one-dimensional confined compression BPVE stress-relaxation problem. Accuracy of the numerical method is demonstrated by comparison to a theoretical Laplace transform solution for a range of viscoelastic relaxation times that are representative of articular cartilage. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Transition probabilities for general birth-death processes with applications in ecology, genetics, and evolution

PubMed Central

Crawford, Forrest W.; Suchard, Marc A.

2011-01-01

A birth-death process is a continuous-time Markov chain that counts the number of particles in a system over time. In the general process with n current particles, a new particle is born with instantaneous rate λn and a particle dies with instantaneous rate μn. Currently no robust and efficient method exists to evaluate the finite-time transition probabilities in a general birth-death process with arbitrary birth and death rates. In this paper, we first revisit the theory of continued fractions to obtain expressions for the Laplace transforms of these transition probabilities and make explicit an important derivation connecting transition probabilities and continued fractions. We then develop an efficient algorithm for computing these probabilities that analyzes the error associated with approximations in the method. We demonstrate that this error-controlled method agrees with known solutions and outperforms previous approaches to computing these probabilities. Finally, we apply our novel method to several important problems in ecology, evolution, and genetics. PMID:21984359

Regenerating time series from ordinal networks.

PubMed

McCullough, Michael; Sakellariou, Konstantinos; Stemler, Thomas; Small, Michael

2017-03-01

Recently proposed ordinal networks not only afford novel methods of nonlinear time series analysis but also constitute stochastic approximations of the deterministic flow time series from which the network models are constructed. In this paper, we construct ordinal networks from discrete sampled continuous chaotic time series and then regenerate new time series by taking random walks on the ordinal network. We then investigate the extent to which the dynamics of the original time series are encoded in the ordinal networks and retained through the process of regenerating new time series by using several distinct quantitative approaches. First, we use recurrence quantification analysis on traditional recurrence plots and order recurrence plots to compare the temporal structure of the original time series with random walk surrogate time series. Second, we estimate the largest Lyapunov exponent from the original time series and investigate the extent to which this invariant measure can be estimated from the surrogate time series. Finally, estimates of correlation dimension are computed to compare the topological properties of the original and surrogate time series dynamics. Our findings show that ordinal networks constructed from univariate time series data constitute stochastic models which approximate important dynamical properties of the original systems.

Regenerating time series from ordinal networks

NASA Astrophysics Data System (ADS)

McCullough, Michael; Sakellariou, Konstantinos; Stemler, Thomas; Small, Michael

2017-03-01

Recently proposed ordinal networks not only afford novel methods of nonlinear time series analysis but also constitute stochastic approximations of the deterministic flow time series from which the network models are constructed. In this paper, we construct ordinal networks from discrete sampled continuous chaotic time series and then regenerate new time series by taking random walks on the ordinal network. We then investigate the extent to which the dynamics of the original time series are encoded in the ordinal networks and retained through the process of regenerating new time series by using several distinct quantitative approaches. First, we use recurrence quantification analysis on traditional recurrence plots and order recurrence plots to compare the temporal structure of the original time series with random walk surrogate time series. Second, we estimate the largest Lyapunov exponent from the original time series and investigate the extent to which this invariant measure can be estimated from the surrogate time series. Finally, estimates of correlation dimension are computed to compare the topological properties of the original and surrogate time series dynamics. Our findings show that ordinal networks constructed from univariate time series data constitute stochastic models which approximate important dynamical properties of the original systems.

The national occupational therapy practice analysis: findings and implications for competence.

PubMed

Dunn, W; Cada, E

1998-10-01

This article reports some of the findings from a national study of occupational therapy practice conducted by the National Board for Certification in Occupational Therapy (NBCOT) as part of its fiduciary responsibility to ensure that its entry-level certification examination is formulated on the basis of current practice. The NBCOT developed a survey with input from approximately 200 occupational therapy leaders and then used it to solicit information about current practice from 4,000 occupational therapists and 3,000 occupational therapy assistants. The sample included geographical location, experience level, and practice area distributions. Approximately 50% of the sample responded to the survey. Data indicate similarities and differences in occupational therapist and occupational therapy assistant practice (e.g., occupational therapists spend more time conducting evaluations, planning interventions, and supervising, whereas occupational therapy assistants spend more time providing interventions), an increased emphasis on population-based services (e.g., serving a business or industry rather than an individual worker), and an emphasis on occupation as a core knowledge base for practice. From a continuing competency perspective, the data can be useful to the profession; we can plan continuing education to address topics that practitioners have indicated are critical to their practice. The findings will be useful for revising the entry-level certification examination and may guide thinking about the parameters of continuing competence because the responses represent a cross-section of the profession.

Regularized Chapman-Enskog expansion for scalar conservation laws

NASA Technical Reports Server (NTRS)

Schochet, Steven; Tadmor, Eitan

1990-01-01

Rosenau has recently proposed a regularized version of the Chapman-Enskog expansion of hydrodynamics. This regularized expansion resembles the usual Navier-Stokes viscosity terms at law wave-numbers, but unlike the latter, it has the advantage of being a bounded macroscopic approximation to the linearized collision operator. The behavior of Rosenau regularization of the Chapman-Enskog expansion (RCE) is studied in the context of scalar conservation laws. It is shown that thie RCE model retains the essential properties of the usual viscosity approximation, e.g., existence of traveling waves, monotonicity, upper-Lipschitz continuity..., and at the same time, it sharpens the standard viscous shock layers. It is proved that the regularized RCE approximation converges to the underlying inviscid entropy solution as its mean-free-path epsilon approaches 0, and the convergence rate is estimated.

Approximation of optimal filter for Ornstein-Uhlenbeck process with quantised discrete-time observation

NASA Astrophysics Data System (ADS)

Bania, Piotr; Baranowski, Jerzy

2018-02-01

Quantisation of signals is a ubiquitous property of digital processing. In many cases, it introduces significant difficulties in state estimation and in consequence control. Popular approaches either do not address properly the problem of system disturbances or lead to biased estimates. Our intention was to find a method for state estimation for stochastic systems with quantised and discrete observation, that is free of the mentioned drawbacks. We have formulated a general form of the optimal filter derived by a solution of Fokker-Planck equation. We then propose the approximation method based on Galerkin projections. We illustrate the approach for the Ornstein-Uhlenbeck process, and derive analytic formulae for the approximated optimal filter, also extending the results for the variant with control. Operation is illustrated with numerical experiments and compared with classical discrete-continuous Kalman filter. Results of comparison are substantially in favour of our approach, with over 20 times lower mean squared error. The proposed filter is especially effective for signal amplitudes comparable to the quantisation thresholds. Additionally, it was observed that for high order of approximation, state estimate is very close to the true process value. The results open the possibilities of further analysis, especially for more complex processes.

Late Time Multi-Wavelength Observations of Swift J1644+5734: A Luminous Optical/IR Bump and Quiescent X-Ray Emission

NASA Technical Reports Server (NTRS)

Levan, A. J.; Tanvir, N. R.; Brown, G. C.; Metzger, B.D.; Page, K. L.; Cenko, S. B.; O'Brien, P. T.; Lyman, J. D.; Wiersema, K.; Stanway, E. R.;

On the Motion of Agents across Terrain with Obstacles

NASA Astrophysics Data System (ADS)

Kuznetsov, A. V.

2018-01-01

The paper is devoted to finding the time optimal route of an agent travelling across a region from a given source point to a given target point. At each point of this region, a maximum allowed speed is specified. This speed limit may vary in time. The continuous statement of this problem and the case when the agent travels on a grid with square cells are considered. In the latter case, the time is also discrete, and the number of admissible directions of motion at each point in time is eight. The existence of an optimal solution of this problem is proved, and estimates of the approximate solution obtained on the grid are obtained. It is found that decreasing the size of cells below a certain limit does not further improve the approximation. These results can be used to estimate the quasi-optimal trajectory of the agent motion across the rugged terrain produced by an algorithm based on a cellular automaton that was earlier developed by the author.

Stochastic parameter estimation in nonlinear time-delayed vibratory systems with distributed delay

NASA Astrophysics Data System (ADS)

Torkamani, Shahab; Butcher, Eric A.

2013-07-01

The stochastic estimation of parameters and states in linear and nonlinear time-delayed vibratory systems with distributed delay is explored. The approach consists of first employing a continuous time approximation to approximate the delayed integro-differential system with a large set of ordinary differential equations having stochastic excitations. Then the problem of state and parameter estimation in the resulting stochastic ordinary differential system is represented as an optimal filtering problem using a state augmentation technique. By adapting the extended Kalman-Bucy filter to the augmented filtering problem, the unknown parameters of the time-delayed system are estimated from noise-corrupted, possibly incomplete measurements of the states. Similarly, the upper bound of the distributed delay can also be estimated by the proposed technique. As an illustrative example to a practical problem in vibrations, the parameter, delay upper bound, and state estimation from noise-corrupted measurements in a distributed force model widely used for modeling machine tool vibrations in the turning operation is investigated.

Time Varying Compensator Design for Reconfigurable Structures Using Non-Collocated Feedback

NASA Technical Reports Server (NTRS)

Scott, Michael A.

1996-01-01

Analysis and synthesis tools are developed to improved the dynamic performance of reconfigurable nonminimum phase, nonstrictly positive real-time variant systems. A novel Spline Varying Optimal (SVO) controller is developed for the kinematic nonlinear system. There are several advantages to using the SVO controller, in which the spline function approximates the system model, observer, and controller gain. They are: The spline function approximation is simply connected, thus the SVO controller is more continuous than traditional gain scheduled controllers when implemented on a time varying plant; ft is easier for real-time implementations in storage and computational effort; where system identification is required, the spline function requires fewer experiments, namely four experiments; and initial startup estimator transients are eliminated. The SVO compensator was evaluated on a high fidelity simulation of the Shuttle Remote Manipulator System. The SVO controller demonstrated significant improvement over the present arm performance: (1) Damping level was improved by a factor of 3; and (2) Peak joint torque was reduced by a factor of 2 following Shuttle thruster firings.

Transient nucleation induction time from the birth-death equations

NASA Technical Reports Server (NTRS)

Shneidman, Vitaly A.; Weinberg, Michael C.

1992-01-01

For the set of finite-difference equations of Becker-Doering an exact formula for the induction time, which is expressed in terms of rapidly convergent sums, is presented. The form of the result is particularly amenable for analytical study, and the latter is carried out to obtain approximations of the exact expression in a rigorous manner and to assess its sensitivity to the choice of the nucleation model. The induction time is found to be governed by two main nucleation parameters, the normalized barrier height, and the number of molecules in the critical cluster. The ratio of these two parameters provides an assessment of the importance of discreteness effects. The exact expression is studied in both the continuous and the asymptotic limits. The accuracy of the Zeldovich equation, which is produced in the continuous limit, is discussed for several nucleation models.

The Nordkapp Basin, Norway: Development of salt and sediment interplays for hydrocarbon exploration

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

Lerche, I.; Toerudbakken, B.O.

1996-12-31

Investigation of a particular salt diapir in the Nordkapp Basin, Barents Sea has revealed the following sequence of events: (1) salt started to rise when approximately 1.5 {+-} 0.3 km of sedimentary cover was present (Carboniferous/Permian time); (2) salt reached the sediment surface when about 3.5 {+-} 0.7 km of sediment had been deposited (Triassic time); (3) the mushroom cap on the salt stock top developed over a period of about 75--100 Ma (i.e. during the time when about another km of sediment had been deposited) (Triassic through Base Cretaceous time); (4) the mushroom cap started to dip down significantlymore » ({approximately}1 km) into the sediments around Cretaceous to Tertiary erosion time; (5) oil generation started in the deep sediments of the Carboniferous around the time that salt reached the surface (Triassic time) and continues to the present day at sedimentary depths between about 4 to 7 km (currently Triassic and deeper sediments); (6)gas generation started around mushroom cap development time and continues to the present day at sedimentary depths greater than about 6--7 km (Permian/Carboniferous); (7) the salt stock is currently 3--4 km wide, considerably less than the mushroom cap which is 9 km wide and 1 km thick. The relative timing of mushroom cap development, bed upturning, and hydrocarbon generation makes the salt diapir an attractive exploration target, with suggested reservoir trapping under the downturned mushroom cap on the deep basin side of the salt. In addition, rough estimates of rim syncline fill suggest the basin had an original salt thickness of 2.4--3.3 km, depending upon the amount of salt removed at the Tertiary erosion event.« less

Drivers' misjudgement of vigilance state during prolonged monotonous daytime driving.

PubMed

Schmidt, Eike A; Schrauf, Michael; Simon, Michael; Fritzsche, Martin; Buchner, Axel; Kincses, Wilhelm E

2009-09-01

To investigate the effects of monotonous daytime driving on vigilance state and particularly the ability to judge this state, a real road driving study was conducted. To objectively assess vigilance state, performance (auditory reaction time) and physiological measures (EEG: alpha spindle rate, P3 amplitude; ECG: heart rate) were recorded continuously. Drivers judged sleepiness, attention to the driving task and monotony retrospectively every 20 min. Results showed that prolonged daytime driving under monotonous conditions leads to a continuous reduction in vigilance. Towards the end of the drive, drivers reported a subjectively improved vigilance state, which was contrary to the continued decrease in vigilance as indicated by all performance and physiological measures. These findings indicate a lack of self-assessment abilities after approximately 3h of continuous monotonous daytime driving.

76 FR 52991 - Notice of an Open Meeting of the Advisory Committee on Apprenticeship (ACA)

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-24

...; as amended 5 U.S.C., App. 2), notice is hereby given to announce an open meeting of the Advisory... Labor, in accordance with the provisions of the Federal Advisory Committee Act (FACA), as amended 5 U.S... Time on Thursday, September 22, 2011, and continue until approximately 5 p.m. The meeting will...

Reinforcement-Learning-Based Robust Controller Design for Continuous-Time Uncertain Nonlinear Systems Subject to Input Constraints.

PubMed

Liu, Derong; Yang, Xiong; Wang, Ding; Wei, Qinglai

2015-07-01

The design of stabilizing controller for uncertain nonlinear systems with control constraints is a challenging problem. The constrained-input coupled with the inability to identify accurately the uncertainties motivates the design of stabilizing controller based on reinforcement-learning (RL) methods. In this paper, a novel RL-based robust adaptive control algorithm is developed for a class of continuous-time uncertain nonlinear systems subject to input constraints. The robust control problem is converted to the constrained optimal control problem with appropriately selecting value functions for the nominal system. Distinct from typical action-critic dual networks employed in RL, only one critic neural network (NN) is constructed to derive the approximate optimal control. Meanwhile, unlike initial stabilizing control often indispensable in RL, there is no special requirement imposed on the initial control. By utilizing Lyapunov's direct method, the closed-loop optimal control system and the estimated weights of the critic NN are proved to be uniformly ultimately bounded. In addition, the derived approximate optimal control is verified to guarantee the uncertain nonlinear system to be stable in the sense of uniform ultimate boundedness. Two simulation examples are provided to illustrate the effectiveness and applicability of the present approach.

Continuous relaxation and retardation spectrum method for viscoelastic characterization of asphalt concrete

NASA Astrophysics Data System (ADS)

Bhattacharjee, Sudip; Swamy, Aravind Krishna; Daniel, Jo S.

2012-08-01

This paper presents a simple and practical approach to obtain the continuous relaxation and retardation spectra of asphalt concrete directly from the complex (dynamic) modulus test data. The spectra thus obtained are continuous functions of relaxation and retardation time. The major advantage of this method is that the continuous form is directly obtained from the master curves which are readily available from the standard characterization tests of linearly viscoelastic behavior of asphalt concrete. The continuous spectrum method offers efficient alternative to the numerical computation of discrete spectra and can be easily used for modeling viscoelastic behavior. In this research, asphalt concrete specimens have been tested for linearly viscoelastic characterization. The linearly viscoelastic test data have been used to develop storage modulus and storage compliance master curves. The continuous spectra are obtained from the fitted sigmoid function of the master curves via the inverse integral transform. The continuous spectra are shown to be the limiting case of the discrete distributions. The continuous spectra and the time-domain viscoelastic functions (relaxation modulus and creep compliance) computed from the spectra matched very well with the approximate solutions. It is observed that the shape of the spectra is dependent on the master curve parameters. The continuous spectra thus obtained can easily be implemented in material mix design process. Prony-series coefficients can be easily obtained from the continuous spectra and used in numerical analysis such as finite element analysis.

Observations of the scatter-free solar-flare electrons in the energy range 20-1000 keV

NASA Technical Reports Server (NTRS)

Wang, J. R.; Fisk, L. A.; Lin, R. P.

1971-01-01

Observations of the scatter-free electron events from solar active region McMath No. 8905 are presented. The measurements were made on Explorer 33 satellite. The data show that more than 80% of the electrons from these events undergo no or little scattering and that these electrons travel only approximately 1.5 a.u. between the sun and the earth. The duration of these events cannot be accounted fully by velocity dispersion alone. It is suggested that these electrons could be continuously injected into interplanetary medium for a time interval of approximately 2 to 3 minutes. Energy spectra of these electrons are discussed.

Quantitative analysis of seismic fault zone waves in the rupture zone of the 1992 Landers, California, earthquake: Evidence for a shallow trapping structure

USGS Publications Warehouse

Peng, Z.; Ben-Zion, Y.; Michael, A.J.; Zhu, L.

2003-01-01

We analyse quantitatively a waveform data set of 238 earthquakes recorded by a dense seismic array across and along the rupture zone of the 1992 Landers earthquake. A grid-search method with station delay corrections is used to locate events that do not have catalogue locations. The quality of fault zone trapped waves generated by each event is determined from the ratios of seismic energy in time windows corresponding to trapped waves and direct S waves at stations close to and off the fault zone. Approximately 70 per cent of the events with S-P times of less than 2 s, including many clearly off the fault, produce considerable trapped wave energy. This distribution is in marked contrast with previous claims that trapped waves are generated only by sources close to or inside the Landers rupture zone. The time difference between the S arrival and trapped waves group does not grow systematically with increasing hypocentral distance and depth. The dispersion measured from the trapped waves is weak. These results imply that the seismic trapping structure at the Landers rupture zone is shallow and does not extend continuously along-strike by more than a few kilometres. Synthetic waveform modelling indicates that the fault zone waveguide has depth of approximately 2-4 km, a width of approximately 200 m, an S-wave velocity reduction relative to the host rock of approximately 30-40 per cent and an S-wave attenuation coefficient of approximately 20-30. The fault zone waveguide north of the array appears to be shallower and weaker than that south of the array. The waveform modelling also indicates that the seismic trapping structure below the array is centred approximately 100 m east of the surface break.

NE VIII lambda 774 and time variable associated absorption in the QSO UM 675

NASA Technical Reports Server (NTRS)

Hamann, Fred; Barlow, Thomas A.; Beaver, E. A.; Burbidge, E. M.; Cohen, Ross D.; Junkkarinen, Vesa; Lyons, R.

1995-01-01

We discuss measurements of Ne VIII lambda 774 absorption and the time variability of other lines in the z(sub a) approximately equal z(sub e) absorption system of the z(sub e) = 2.15 QSO UM 675 (0150-203). The C IV lambda 1549 and N V 1240 doublets at z(sub a) = 2.1340 (shifted approximately 1500 km/s from z(sub e) strengthened by a factor of approximately 3 between observations by Sargent, Boksenberg and Steidel (1981 November) and our earliest measurements (1990 November and December). We have no information on changes in other z(sub a) approximately equal z(sub e) absorption lines. Continued monitoring since 1990 November shows no clear changes in any of the absorptions between approximately 1100 and 1640 A rest. The short timescale of the variability (less than or approximately equal to 2.9 yr rest) strongly suggests that the clouds are dense, compact, close to the QSO, and photoionized by the QSO continuum. If the line variability is caused by changes in the ionization, the timescale requires densities greater than approximately 4000/cu cm. Photoionization calculations place the absorbing clouds within approximately 200 pc of the continuum source. The full range of line ionizations (from Ne VIII lambda 774 to C III lambda 977) in optically thin gas (no Lyman limit) implies that the absorbing regions span a factor of more than approximately 10 in distance or approximately 100 in density. Across these regions, the total hydrogen (H I + H II) column ranges from a few times 10(exp 18)/sq cm in the low-ionization gas to approximately 10(exp 20)/sq cm where the Ne VIII doublet forms. The metallicity is roughly solar or higher, with nitrogen possibly more enhanced by factors of a few. The clouds might contribute significant line emission if they nearly envelop the QSO. The presence of highly ionized Ne VIII lambda 774 absorption near the QSO supports recent studies that link z(sub a) approximately equal to z(sub e) systems with X-ray 'wamr absorbers. We show that the Ne VIII absorbing gas would itself produce measurable warm absorption -- characterized by bound-free O VII or O VIII edegs near 0.8 keV -- if the column densities were N(sub H) greater than or approximately equal to 10(exp 21)/sq cm (for solar abundances).

NE VIII lambda 774 and time variable associated absorption in the QSO UM 675

NASA Astrophysics Data System (ADS)

Hamann, Fred; Barlow, Thomas A.; Beaver, E. A.; Burbidge, E. M.; Cohen, Ross D.; Junkkarinen, Vesa; Lyons, R.

1995-04-01

We discuss measurements of Ne VIII lambda 774 absorption and the time variability of other lines in the za approximately equal ze absorption system of the ze = 2.15 QSO UM 675 (0150-203). The C IV lambda 1549 and N V 1240 doublets at za = 2.1340 (shifted approximately 1500 km/s from ze strengthened by a factor of approximately 3 between observations by Sargent, Boksenberg and Steidel (1981 November) and our earliest measurements (1990 November and December). We have no information on changes in other za approximately equal ze absorption lines. Continued monitoring since 1990 November shows no clear changes in any of the absorptions between approximately 1100 and 1640 A rest. The short timescale of the variability (less than or approximately equal to 2.9 yr rest) strongly suggests that the clouds are dense, compact, close to the QSO, and photoionized by the QSO continuum. If the line variability is caused by changes in the ionization, the timescale requires densities greater than approximately 4000/cu cm. Photoionization calculations place the absorbing clouds within approximately 200 pc of the continuum source. The full range of line ionizations (from Ne VIII lambda 774 to C III lambda 977) in optically thin gas (no Lyman limit) implies that the absorbing regions span a factor of more than approximately 10 in distance or approximately 100 in density. Across these regions, the total hydrogen (H I + H II) column ranges from a few times 1018/sq cm in the low-ionization gas to approximately 1020/sq cm where the Ne VIII doublet forms. The metallicity is roughly solar or higher, with nitrogen possibly more enhanced by factors of a few. The clouds might contribute significant line emission if they nearly envelop the QSO. The presence of highly ionized Ne VIII lambda 774 absorption near the QSO supports recent studies that link za approximately equal to ze systems with X-ray 'wamr absorbers. We show that the Ne VIII absorbing gas would itself produce measurable warm absorption -- characterized by bound-free O VII or O VIII edegs near 0.8 keV -- if the column densities were NH greater than or approximately equal to 1021/sq cm (for solar abundances).

Dynamical cluster approximation plus semiclassical approximation study for a Mott insulator and d-wave pairing

NASA Astrophysics Data System (ADS)

Kim, SungKun; Lee, Hunpyo

2017-06-01

Via a dynamical cluster approximation with N c = 4 in combination with a semiclassical approximation (DCA+SCA), we study the doped two-dimensional Hubbard model. We obtain a plaquette antiferromagnetic (AF) Mott insulator, a plaquette AF ordered metal, a pseudogap (or d-wave superconductor) and a paramagnetic metal by tuning the doping concentration. These features are similar to the behaviors observed in copper-oxide superconductors and are in qualitative agreement with the results calculated by the cluster dynamical mean field theory with the continuous-time quantum Monte Carlo (CDMFT+CTQMC) approach. The results of our DCA+SCA differ from those of the CDMFT+CTQMC approach in that the d-wave superconducting order parameters are shown even in the high doped region, unlike the results of the CDMFT+CTQMC approach. We think that the strong plaquette AF orderings in the dynamical cluster approximation (DCA) with N c = 4 suppress superconducting states with increasing doping up to strongly doped region, because frozen dynamical fluctuations in a semiclassical approximation (SCA) approach are unable to destroy those orderings. Our calculation with short-range spatial fluctuations is initial research, because the SCA can manage long-range spatial fluctuations in feasible computational times beyond the CDMFT+CTQMC tool. We believe that our future DCA+SCA calculations should supply information on the fully momentum-resolved physical properties, which could be compared with the results measured by angle-resolved photoemission spectroscopy experiments.

On the derivation of the semiclassical approximation to the quantum propagator

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

Fischer, Stefan G., E-mail: stefan.fischer@physik.uni-freiburg.de; Buchleitner, Andreas

2015-07-15

In order to rigorously derive the amplitude factor of the semiclassical approximation to the quantum propagator, we extend an existing method originally devised to evaluate Gaussian path-integral expressions. Using a result which relates the determinant of symmetric block-tridiagonal matrices to the determinants of their blocks, two difference equations are obtained. The first one allows to establish the connection of the amplitude factor to Jacobi’s accessory equations in the continuous-time limit, while the second one leads to an additional factor which, however, contributes to the final result only in exceptional cases. In order to demonstrate the wide applicability of these differencemore » equations, we treat explicitly the case where the time-sliced Lagrangian is written in generalized coordinates, for which a general derivation has so far been unavailable.« less

Continuous-time adaptive critics.

PubMed

Hanselmann, Thomas; Noakes, Lyle; Zaknich, Anthony

2007-05-01

A continuous-time formulation of an adaptive critic design (ACD) is investigated. Connections to the discrete case are made, where backpropagation through time (BPTT) and real-time recurrent learning (RTRL) are prevalent. Practical benefits are that this framework fits in well with plant descriptions given by differential equations and that any standard integration routine with adaptive step-size does an adaptive sampling for free. A second-order actor adaptation using Newton's method is established for fast actor convergence for a general plant and critic. Also, a fast critic update for concurrent actor-critic training is introduced to immediately apply necessary adjustments of critic parameters induced by actor updates to keep the Bellman optimality correct to first-order approximation after actor changes. Thus, critic and actor updates may be performed at the same time until some substantial error build up in the Bellman optimality or temporal difference equation, when a traditional critic training needs to be performed and then another interval of concurrent actor-critic training may resume.

Profilometric characterization of DOEs with continuous microrelief

NASA Astrophysics Data System (ADS)

Korolkov, V. P.; Ostapenko, S. V.; Shimansky, R. V.

2008-09-01

Methodology of local characterization of continuous-relief diffractive optical elements has been discussed. The local profile depth can be evaluated using "approximated depth" defined without taking a profile near diffractive zone boundaries into account. Several methods to estimate the approximated depth have been offered.

On the derivation of approximations to cellular automata models and the assumption of independence.

PubMed

Davies, K J; Green, J E F; Bean, N G; Binder, B J; Ross, J V

2014-07-01

Cellular automata are discrete agent-based models, generally used in cell-based applications. There is much interest in obtaining continuum models that describe the mean behaviour of the agents in these models. Previously, continuum models have been derived for agents undergoing motility and proliferation processes, however, these models only hold under restricted conditions. In order to narrow down the reason for these restrictions, we explore three possible sources of error in deriving the model. These sources are the choice of limiting arguments, the use of a discrete-time model as opposed to a continuous-time model and the assumption of independence between the state of sites. We present a rigorous analysis in order to gain a greater understanding of the significance of these three issues. By finding a limiting regime that accurately approximates the conservation equation for the cellular automata, we are able to conclude that the inaccuracy between our approximation and the cellular automata is completely based on the assumption of independence. Copyright © 2014 Elsevier Inc. All rights reserved.

The distance to the heliospheric VLF emission region

NASA Technical Reports Server (NTRS)

Mcnutt, R. L., Jr.; Lazarus, A. J.; Belcher, J. W.; Lyon, J.; Goodrich, C. C.; Kulkarni, R.

1995-01-01

Two major episodes of heliospheric VLF emissions near 3 kHz have been observed by the Voyager spacecraft in 1983/84 and 1992/3. This higher-frequency component is apparently triggered by solar wind transients with sufficiently large spatial extents and energies to continue to propagate as shocks in the heliosheath. Entrainment of previously unshocked material and changed flow conditions in the heliosheath both tend to slow the shock propagation. The shock evolution is not self-similar. Rather, it is intermediate to two blast-wave similarity solutions in the moving solar wind frame. In one solution the shock moves as time to the 2/3 power and in the other as time to the 4/5 power. Using these models, the shock/Forbush decrease observed at Voyager 2 in September, 1991 and the turn-on of the 1992 emission is consistent with an emission region distance of approximately 130 AU (assuming no additional slowing of the shock in the heliosheath). If the termination shock was at approximately 70 AU when the transient shock collided with it, the true distance to the source region was probably closer to approximately 115 AU.

Smoothing data series by means of cubic splines: quality of approximation and introduction of a repeating spline approach

NASA Astrophysics Data System (ADS)

Wüst, Sabine; Wendt, Verena; Linz, Ricarda; Bittner, Michael

2017-09-01

Cubic splines with equidistant spline sampling points are a common method in atmospheric science, used for the approximation of background conditions by means of filtering superimposed fluctuations from a data series. What is defined as background or superimposed fluctuation depends on the specific research question. The latter also determines whether the spline or the residuals - the subtraction of the spline from the original time series - are further analysed.Based on test data sets, we show that the quality of approximation of the background state does not increase continuously with an increasing number of spline sampling points and/or decreasing distance between two spline sampling points. Splines can generate considerable artificial oscillations in the background and the residuals.We introduce a repeating spline approach which is able to significantly reduce this phenomenon. We apply it not only to the test data but also to TIMED-SABER temperature data and choose the distance between two spline sampling points in a way that is sensitive for a large spectrum of gravity waves.

Green's functions in equilibrium and nonequilibrium from real-time bold-line Monte Carlo

NASA Astrophysics Data System (ADS)

Cohen, Guy; Gull, Emanuel; Reichman, David R.; Millis, Andrew J.

2014-03-01

Green's functions for the Anderson impurity model are obtained within a numerically exact formalism. We investigate the limits of analytical continuation for equilibrium systems, and show that with real time methods even sharp high-energy features can be reliably resolved. Continuing to an Anderson impurity in a junction, we evaluate two-time correlation functions, spectral properties, and transport properties, showing how the correspondence between the spectral function and the differential conductance breaks down when nonequilibrium effects are taken into account. Finally, a long-standing dispute regarding this model has involved the voltage splitting of the Kondo peak, an effect which was predicted over a decade ago by approximate analytical methods but never successfully confirmed by numerics. We settle the issue by demonstrating in an unbiased manner that this splitting indeed occurs. Yad Hanadiv-Rothschild Foundation, TG-DMR120085, TG-DMR130036, NSF CHE-1213247, NSF DMR 1006282, DOE ER 46932.

Spin coherent-state path integrals and the instanton calculus

NASA Astrophysics Data System (ADS)

Garg, Anupam; Kochetov, Evgueny; Park, Kee-Su; Stone, Michael

2003-01-01

We use an instanton approximation to the continuous-time spin coherent-state path integral to obtain the tunnel splitting of classically degenerate ground states. We show that provided the fluctuation determinant is carefully evaluated, the path integral expression is accurate to order O(1/j). We apply the method to the LMG model and to the molecular magnet Fe8 in a transverse field.

Well-Balanced Second-Order Approximation of the Shallow Water Equations With Friction via Continuous Galerkin Finite Elements

NASA Astrophysics Data System (ADS)

Quezada de Luna, M.; Farthing, M.; Guermond, J. L.; Kees, C. E.; Popov, B.

2017-12-01

The Shallow Water Equations (SWEs) are popular for modeling non-dispersive incompressible water waves where the horizontal wavelength is much larger than the vertical scales. They can be derived from the incompressible Navier-Stokes equations assuming a constant vertical velocity. The SWEs are important in Geophysical Fluid Dynamics for modeling surface gravity waves in shallow regimes; e.g., in the deep ocean. Some common geophysical applications are the evolution of tsunamis, river flooding and dam breaks, storm surge simulations, atmospheric flows and others. This work is concerned with the approximation of the time-dependent Shallow Water Equations with friction using explicit time stepping and continuous finite elements. The objective is to construct a method that is at least second-order accurate in space and third or higher-order accurate in time, positivity preserving, well-balanced with respect to rest states, well-balanced with respect to steady sliding solutions on inclined planes and robust with respect to dry states. Methods fulfilling the desired goals are common within the finite volume literature. However, to the best of our knowledge, schemes with the above properties are not well developed in the context of continuous finite elements. We start this work based on a finite element method that is second-order accurate in space, positivity preserving and well-balanced with respect to rest states. We extend it by: modifying the artificial viscosity (via the entropy viscosity method) to deal with issues of loss of accuracy around local extrema, considering a singular Manning friction term handled via an explicit discretization under the usual CFL condition, considering a water height regularization that depends on the mesh size and is consistent with the polynomial approximation, reducing dispersive errors introduced by lumping the mass matrix and others. After presenting the details of the method we show numerical tests that demonstrate the well-balanced nature of the scheme and its convergence properties. We conclude with well-known benchmark problems including the Malpasset dam break (see the attached figure). All numerical experiments are performed and available in the Proteus toolkit, which is an open source python package for modeling continuum mechanical processes and fluid flow.

Linear analysis of time dependent properties of Child-Langmuir flow

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

Rokhlenko, A.

We continue our analysis of the time dependent behavior of the electron flow in the Child-Langmuir system, removing an approximation used earlier. We find a modified set of oscillatory decaying modes with frequencies of the same order as the inverse of the electron transient time. This range (typically MHz) allows simple experimental detection and maybe exploitation. We then study the time evolution of the current in response to a slow change of the anode voltage where the same modes of oscillations appear too. The cathode current in this case is systematically advanced or retarded depending on the direction of themore » voltage change.« less

Linear analysis of time dependent properties of Child-Langmuir flow

NASA Astrophysics Data System (ADS)

Rokhlenko, A.

2013-01-01

We continue our analysis of the time dependent behavior of the electron flow in the Child-Langmuir system, removing an approximation used earlier. We find a modified set of oscillatory decaying modes with frequencies of the same order as the inverse of the electron transient time. This range (typically MHz) allows simple experimental detection and maybe exploitation. We then study the time evolution of the current in response to a slow change of the anode voltage where the same modes of oscillations appear too. The cathode current in this case is systematically advanced or retarded depending on the direction of the voltage change.

Low-traffic limit and first-passage times for a simple model of the continuous double auction

NASA Astrophysics Data System (ADS)

Scalas, Enrico; Rapallo, Fabio; Radivojević, Tijana

2017-11-01

We consider a simplified model of the continuous double auction where prices are integers varying from 1 to N with limit orders and market orders, but quantity per order limited to a single share. For this model, the order process is equivalent to two M / M / 1 queues. We study the behavior of the auction in the low-traffic limit where limit orders are immediately matched by market orders. In this limit, the distribution of prices can be computed exactly and gives a reasonable approximation of the price distribution when the ratio between the rate of order arrivals and the rate of order executions is below 1 / 2. This is further confirmed by the analysis of the first-passage time in 1 or N.

Adaptive near-optimal neuro controller for continuous-time nonaffine nonlinear systems with constrained input.

PubMed

Esfandiari, Kasra; Abdollahi, Farzaneh; Talebi, Heidar Ali

2017-09-01

In this paper, an identifier-critic structure is introduced to find an online near-optimal controller for continuous-time nonaffine nonlinear systems having saturated control signal. By employing two Neural Networks (NNs), the solution of Hamilton-Jacobi-Bellman (HJB) equation associated with the cost function is derived without requiring a priori knowledge about system dynamics. Weights of the identifier and critic NNs are tuned online and simultaneously such that unknown terms are approximated accurately and the control signal is kept between the saturation bounds. The convergence of NNs' weights, identification error, and system states is guaranteed using Lyapunov's direct method. Finally, simulation results are performed on two nonlinear systems to confirm the effectiveness of the proposed control strategy. Copyright © 2017 Elsevier Ltd. All rights reserved.

The development of mixer machine for organic animal feed production: Proposed study

NASA Astrophysics Data System (ADS)

Leman, A. M.; Wahab, R. Abdul; Zakaria, Supaat; Feriyanto, Dafit; Nor, M. I. F. Che Mohd; Muzarpar, Syafiq

2017-09-01

Mixer machine plays a major role in producing homogenous composition of animal feed. Long time production, inhomogeneous and minor agglomeration has been observed by existing mixer. Therefore, this paper proposed continuous mixer to enhance mixing efficiency with shorter time of mixing process in order to abbreviate the whole process in animal feed production. Through calculation of torque, torsion, bending, power and energy consumption will perform in mixer machine process. Proposed mixer machine is designed by two layer buckets with purpose for continuity of mixing process. Mixing process was performed by 4 blades which consists of various arm length such as 50, 100,150 and 225 mm in 60 rpm velocity clockwise rotation. Therefore by using this machine will produce the homogenous composition of animal feed through nutrition analysis and short operation time of mixing process approximately of 5 minutes. Therefore, the production of animal feed will suitable for various animals including poultry and aquatic fish. This mixer will available for various organic material in animal feed production. Therefore, this paper will highlights some areas such as continues animal feed supply chain and bio-based animal feed.

Evaluation of ConPrim: A three-part model for continuing education in primary health care.

PubMed

Berggren, Erika; Strang, Peter; Orrevall, Ylva; Ödlund Olin, Ann; Sandelowsky, Hanna; Törnkvist, Lena

2016-11-01

To overcome the gap between existing knowledge and the application of this knowledge in practice, a three-part continuing educational model for primary health care professionals (ConPrim) was developed. It includes a web-based program, a practical exercise and a case seminar. To evaluate professionals' perceptions of the design, pedagogy and adaptation to primary health care of the ConPrim continuing educational model as applied in a subject-specific intervention. A total of 67 professionals (nurses and physicians) completed a computer-based questionnaire evaluating the model's design, pedagogy and adaptation to primary health care one week after the intervention. Descriptive statistics were used. Over 90% found the design of the web-based program and case seminar attractive; 86% found the design of the practical exercise attractive. The professionals agreed that the time spent on two of the three parts was acceptable. The exception was the practical exercise: 32% did not fully agree. Approximately 90% agreed that the contents of all parts were relevant to their work and promoted interactive and interprofessional learning. In response to the statements about the intervention as whole, approximately 90% agreed that the intervention was suitable to primary health care, that it had increased their competence in the subject area, and that they would be able to use what they had learned in their work. ConPrim is a promising model for continuing educational interventions in primary health care. However, the time spent on the practical exercise should be adjusted and the instructions for the exercise clarified. ConPrim should be tested in other subject-specific interventions and its influence on clinical practice should be evaluated. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

A mathematical approach to HIV infection dynamics

NASA Astrophysics Data System (ADS)

Ida, A.; Oharu, S.; Oharu, Y.

2007-07-01

In order to obtain a comprehensive form of mathematical models describing nonlinear phenomena such as HIV infection process and AIDS disease progression, it is efficient to introduce a general class of time-dependent evolution equations in such a way that the associated nonlinear operator is decomposed into the sum of a differential operator and a perturbation which is nonlinear in general and also satisfies no global continuity condition. An attempt is then made to combine the implicit approach (usually adapted for convective diffusion operators) and explicit approach (more suited to treat continuous-type operators representing various physiological interactions), resulting in a semi-implicit product formula. Decomposing the operators in this way and considering their individual properties, it is seen that approximation-solvability of the original model is verified under suitable conditions. Once appropriate terms are formulated to describe treatment by antiretroviral therapy, the time-dependence of the reaction terms appears, and such product formula is useful for generating approximate numerical solutions to the governing equations. With this knowledge, a continuous model for HIV disease progression is formulated and physiological interpretations are provided. The abstract theory is then applied to show existence of unique solutions to the continuous model describing the behavior of the HIV virus in the human body and its reaction to treatment by antiretroviral therapy. The product formula suggests appropriate discrete models describing the dynamics of host pathogen interactions with HIV1 and is applied to perform numerical simulations based on the model of the HIV infection process and disease progression. Finally, the results of our numerical simulations are visualized and it is observed that our results agree with medical and physiological aspects.

Assessing the potential of reservoir outflow management to reduce sedimentation using continuous turbidity monitoring and reservoir modelling

USGS Publications Warehouse

Lee, Casey; Foster, Guy

2013-01-01

In-stream sensors are increasingly deployed as part of ambient water quality-monitoring networks. Temporally dense data from these networks can be used to better understand the transport of constituents through streams, lakes or reservoirs. Data from existing, continuously recording in-stream flow and water quality monitoring stations were coupled with the two-dimensional hydrodynamic CE-QUAL-W2 model to assess the potential of altered reservoir outflow management to reduce sediment trapping in John Redmond Reservoir, located in east-central Kansas. Monitoring stations upstream and downstream from the reservoir were used to estimate 5.6 million metric tons of sediment transported to John Redmond Reservoir from 2007 through 2010, 88% of which was trapped within the reservoir. The two-dimensional model was used to estimate the residence time of 55 equal-volume releases from the reservoir; sediment trapping for these releases varied from 48% to 97%. Smaller trapping efficiencies were observed when the reservoir was maintained near the normal operating capacity (relative to higher flood pool levels) and when average residence times were relatively short. An idealized, alternative outflow management scenario was constructed, which minimized reservoir elevations and the length of time water was in the reservoir, while continuing to meet downstream flood control end points identified in the reservoir water control manual. The alternative scenario is projected to reduce sediment trapping in the reservoir by approximately 3%, preventing approximately 45 000 metric tons of sediment from being deposited within the reservoir annually. This article presents an approach to quantify the potential of reservoir management using existing in-stream data; actual management decisions need to consider the effects on other reservoir benefits, such as downstream flood control and aquatic life.

Exploiting Fast-Variables to Understand Population Dynamics and Evolution

NASA Astrophysics Data System (ADS)

Constable, George W. A.; McKane, Alan J.

2018-07-01

We describe a continuous-time modelling framework for biological population dynamics that accounts for demographic noise. In the spirit of the methodology used by statistical physicists, transitions between the states of the system are caused by individual events while the dynamics are described in terms of the time-evolution of a probability density function. In general, the application of the diffusion approximation still leaves a description that is quite complex. However, in many biological applications one or more of the processes happen slowly relative to the system's other processes, and the dynamics can be approximated as occurring within a slow low-dimensional subspace. We review these time-scale separation arguments and analyse the more simple stochastic dynamics that result in a number of cases. We stress that it is important to retain the demographic noise derived in this way, and emphasise this point by showing that it can alter the direction of selection compared to the prediction made from an analysis of the corresponding deterministic model.

Exploiting Fast-Variables to Understand Population Dynamics and Evolution

NASA Astrophysics Data System (ADS)

Constable, George W. A.; McKane, Alan J.

2017-11-01

We describe a continuous-time modelling framework for biological population dynamics that accounts for demographic noise. In the spirit of the methodology used by statistical physicists, transitions between the states of the system are caused by individual events while the dynamics are described in terms of the time-evolution of a probability density function. In general, the application of the diffusion approximation still leaves a description that is quite complex. However, in many biological applications one or more of the processes happen slowly relative to the system's other processes, and the dynamics can be approximated as occurring within a slow low-dimensional subspace. We review these time-scale separation arguments and analyse the more simple stochastic dynamics that result in a number of cases. We stress that it is important to retain the demographic noise derived in this way, and emphasise this point by showing that it can alter the direction of selection compared to the prediction made from an analysis of the corresponding deterministic model.

Discrete Variational Approach for Modeling Laser-Plasma Interactions

NASA Astrophysics Data System (ADS)

Reyes, J. Paxon; Shadwick, B. A.

2014-10-01

The traditional approach for fluid models of laser-plasma interactions begins by approximating fields and derivatives on a grid in space and time, leading to difference equations that are manipulated to create a time-advance algorithm. In contrast, by introducing the spatial discretization at the level of the action, the resulting Euler-Lagrange equations have particular differencing approximations that will exactly satisfy discrete versions of the relevant conservation laws. For example, applying a spatial discretization in the Lagrangian density leads to continuous-time, discrete-space equations and exact energy conservation regardless of the spatial grid resolution. We compare the results of two discrete variational methods using the variational principles from Chen and Sudan and Brizard. Since the fluid system conserves energy and momentum, the relative errors in these conserved quantities are well-motivated physically as figures of merit for a particular method. This work was supported by the U. S. Department of Energy under Contract No. DE-SC0008382 and by the National Science Foundation under Contract No. PHY-1104683.

Retrospective cost-effectiveness analyses for polio vaccination in the United States.

PubMed

Thompson, Kimberly M; Tebbens, Radboud J Duintjer

2006-12-01

The history of polio vaccination in the United States spans 50 years and includes different phases of the disease, multiple vaccines, and a sustained significant commitment of resources. We estimated cost-effectiveness ratios and assessed the net benefits of polio vaccination applicable at various points in time from the societal perspective and we discounted these back to appropriate points in time. We reconstructed vaccine price data from available sources and used these to retrospectively estimate the total costs of the U.S. historical polio vaccination strategies (all costs reported in year 2002 dollars). We estimate that the United States invested approximately US dollars 35 billion (1955 net present value, discount rate of 3%) in polio vaccines between 1955 and 2005 and will invest approximately US dollars 1.4 billion (1955 net present value, or US dollars 6.3 billion in 2006 net present value) between 2006 and 2015 assuming a policy of continued use of inactivated poliovirus vaccine (IPV) for routine vaccination. The historical and future investments translate into over 1.7 billion vaccinations that prevent approximately 1.1 million cases of paralytic polio and over 160,000 deaths (1955 net present values of approximately 480,000 cases and 73,000 deaths). Due to treatment cost savings, the investment implies net benefits of approximately US dollars 180 billion (1955 net present value), even without incorporating the intangible costs of suffering and death and of averted fear. Retrospectively, the U.S. investment in polio vaccination represents a highly valuable, cost-saving public health program. Observed changes in the cost-effectiveness ratio estimates over time suggest the need for living economic models for interventions that appropriately change with time. This article also demonstrates that estimates of cost-effectiveness ratios at any single time point may fail to adequately consider the context of the investment made to date and the importance of population and other dynamics, and shows the importance of dynamic modeling.

Path statistics, memory, and coarse-graining of continuous-time random walks on networks

PubMed Central

Kion-Crosby, Willow; Morozov, Alexandre V.

2015-01-01

Continuous-time random walks (CTRWs) on discrete state spaces, ranging from regular lattices to complex networks, are ubiquitous across physics, chemistry, and biology. Models with coarse-grained states (for example, those employed in studies of molecular kinetics) or spatial disorder can give rise to memory and non-exponential distributions of waiting times and first-passage statistics. However, existing methods for analyzing CTRWs on complex energy landscapes do not address these effects. Here we use statistical mechanics of the nonequilibrium path ensemble to characterize first-passage CTRWs on networks with arbitrary connectivity, energy landscape, and waiting time distributions. Our approach can be applied to calculating higher moments (beyond the mean) of path length, time, and action, as well as statistics of any conservative or non-conservative force along a path. For homogeneous networks, we derive exact relations between length and time moments, quantifying the validity of approximating a continuous-time process with its discrete-time projection. For more general models, we obtain recursion relations, reminiscent of transfer matrix and exact enumeration techniques, to efficiently calculate path statistics numerically. We have implemented our algorithm in PathMAN (Path Matrix Algorithm for Networks), a Python script that users can apply to their model of choice. We demonstrate the algorithm on a few representative examples which underscore the importance of non-exponential distributions, memory, and coarse-graining in CTRWs. PMID:26646868

Beyond the Golden Ratio: A Calculator-Based Investigation.

ERIC Educational Resources Information Center

Glidden, Peter L.

2001-01-01

Describes computation of a continued radical to approximate the golden ratio and presents two well-known geometric interpretations of it. Uses guided-discovery to investigate different repeated radicals to see what values they approximate, the golden-rectangle interpretation of these continued radicals, and the golden-section interpretation. (KHR)

A policy iteration approach to online optimal control of continuous-time constrained-input systems.

PubMed

Modares, Hamidreza; Naghibi Sistani, Mohammad-Bagher; Lewis, Frank L

2013-09-01

This paper is an effort towards developing an online learning algorithm to find the optimal control solution for continuous-time (CT) systems subject to input constraints. The proposed method is based on the policy iteration (PI) technique which has recently evolved as a major technique for solving optimal control problems. Although a number of online PI algorithms have been developed for CT systems, none of them take into account the input constraints caused by actuator saturation. In practice, however, ignoring these constraints leads to performance degradation or even system instability. In this paper, to deal with the input constraints, a suitable nonquadratic functional is employed to encode the constraints into the optimization formulation. Then, the proposed PI algorithm is implemented on an actor-critic structure to solve the Hamilton-Jacobi-Bellman (HJB) equation associated with this nonquadratic cost functional in an online fashion. That is, two coupled neural network (NN) approximators, namely an actor and a critic are tuned online and simultaneously for approximating the associated HJB solution and computing the optimal control policy. The critic is used to evaluate the cost associated with the current policy, while the actor is used to find an improved policy based on information provided by the critic. Convergence to a close approximation of the HJB solution as well as stability of the proposed feedback control law are shown. Simulation results of the proposed method on a nonlinear CT system illustrate the effectiveness of the proposed approach. Copyright © 2013 ISA. All rights reserved.

High-power closed-cycle 4He cryostat with top-loading sample exchange

NASA Astrophysics Data System (ADS)

Piegsa, F. M.; van den Brandt, B.; Kirch, K.

2017-10-01

We report on the development of a versatile cryogen-free laboratory cryostat based upon a commercial pulse tube cryocooler. It provides enough cooling power for continuous recondensation of circulating 4He gas at a condensation pressure of approximately 250 mbar. Moreover, the cryostat allows for exchange of different cryostat-inserts as well as fast and easy ;wet; top-loading of samples directly into the 1 K pot with a turn-over time of less than 75 min. Starting from room temperature and using a 4He cryostat-insert, a base temperature of 1.0 K is reached within approximately seven hours and a cooling power of 250 mW is established at 1.24 K.

Validity of the local approximation in iron pnictides and chalcogenides

DOE PAGES

Sémon, Patrick; Haule, Kristjan; Kotliar, Gabriel

2017-05-08

We introduce a methodology to treat different degrees of freedom at different levels of approximation. We use cluster DMFT (dynamical mean field theory) for the t 2g electrons and single site DMFT for the e g electrons to study the normal state of the iron pnictides and chalcogenides. Furthermore, in the regime of moderate mass renormalizations, the self-energy is very local, justifying the success of single site DMFT for these materials and for other Hunds metals. Here we solve the corresponding impurity model with CTQMC (continuous time quantum Monte Carlo) and find that the minus sign problem is not severemore » in regimes of moderate mass renormalization.« less

Analytic Approximations to the Free Boundary and Multi-dimensional Problems in Financial Derivatives Pricing

NASA Astrophysics Data System (ADS)

Lau, Chun Sing

This thesis studies two types of problems in financial derivatives pricing. The first type is the free boundary problem, which can be formulated as a partial differential equation (PDE) subject to a set of free boundary condition. Although the functional form of the free boundary condition is given explicitly, the location of the free boundary is unknown and can only be determined implicitly by imposing continuity conditions on the solution. Two specific problems are studied in details, namely the valuation of fixed-rate mortgages and CEV American options. The second type is the multi-dimensional problem, which involves multiple correlated stochastic variables and their governing PDE. One typical problem we focus on is the valuation of basket-spread options, whose underlying asset prices are driven by correlated geometric Brownian motions (GBMs). Analytic approximate solutions are derived for each of these three problems. For each of the two free boundary problems, we propose a parametric moving boundary to approximate the unknown free boundary, so that the original problem transforms into a moving boundary problem which can be solved analytically. The governing parameter of the moving boundary is determined by imposing the first derivative continuity condition on the solution. The analytic form of the solution allows the price and the hedging parameters to be computed very efficiently. When compared against the benchmark finite-difference method, the computational time is significantly reduced without compromising the accuracy. The multi-stage scheme further allows the approximate results to systematically converge to the benchmark results as one recasts the moving boundary into a piecewise smooth continuous function. For the multi-dimensional problem, we generalize the Kirk (1995) approximate two-asset spread option formula to the case of multi-asset basket-spread option. Since the final formula is in closed form, all the hedging parameters can also be derived in closed form. Numerical examples demonstrate that the pricing and hedging errors are in general less than 1% relative to the benchmark prices obtained by numerical integration or Monte Carlo simulation. By exploiting an explicit relationship between the option price and the underlying probability distribution, we further derive an approximate distribution function for the general basket-spread variable. It can be used to approximate the transition probability distribution of any linear combination of correlated GBMs. Finally, an implicit perturbation is applied to reduce the pricing errors by factors of up to 100. When compared against the existing methods, the basket-spread option formula coupled with the implicit perturbation turns out to be one of the most robust and accurate approximation methods.

Deriving the exact nonadiabatic quantum propagator in the mapping variable representation.

PubMed

Hele, Timothy J H; Ananth, Nandini

2016-12-22

We derive an exact quantum propagator for nonadiabatic dynamics in multi-state systems using the mapping variable representation, where classical-like Cartesian variables are used to represent both continuous nuclear degrees of freedom and discrete electronic states. The resulting Liouvillian is a Moyal series that, when suitably approximated, can allow for the use of classical dynamics to efficiently model large systems. We demonstrate that different truncations of the exact Liouvillian lead to existing approximate semiclassical and mixed quantum-classical methods and we derive an associated error term for each method. Furthermore, by combining the imaginary-time path-integral representation of the Boltzmann operator with the exact Liouvillian, we obtain an analytic expression for thermal quantum real-time correlation functions. These results provide a rigorous theoretical foundation for the development of accurate and efficient classical-like dynamics to compute observables such as electron transfer reaction rates in complex quantized systems.

Domain decomposition methods for systems of conservation laws: Spectral collocation approximations

NASA Technical Reports Server (NTRS)

Quarteroni, Alfio

1989-01-01

Hyperbolic systems of conversation laws are considered which are discretized in space by spectral collocation methods and advanced in time by finite difference schemes. At any time-level a domain deposition method based on an iteration by subdomain procedure was introduced yielding at each step a sequence of independent subproblems (one for each subdomain) that can be solved simultaneously. The method is set for a general nonlinear problem in several space variables. The convergence analysis, however, is carried out only for a linear one-dimensional system with continuous solutions. A precise form of the error reduction factor at each iteration is derived. Although the method is applied here to the case of spectral collocation approximation only, the idea is fairly general and can be used in a different context as well. For instance, its application to space discretization by finite differences is straight forward.

Neural network-based optimal adaptive output feedback control of a helicopter UAV.

PubMed

Nodland, David; Zargarzadeh, Hassan; Jagannathan, Sarangapani

2013-07-01

Helicopter unmanned aerial vehicles (UAVs) are widely used for both military and civilian operations. Because the helicopter UAVs are underactuated nonlinear mechanical systems, high-performance controller design for them presents a challenge. This paper introduces an optimal controller design via an output feedback for trajectory tracking of a helicopter UAV, using a neural network (NN). The output-feedback control system utilizes the backstepping methodology, employing kinematic and dynamic controllers and an NN observer. The online approximator-based dynamic controller learns the infinite-horizon Hamilton-Jacobi-Bellman equation in continuous time and calculates the corresponding optimal control input by minimizing a cost function, forward-in-time, without using the value and policy iterations. Optimal tracking is accomplished by using a single NN utilized for the cost function approximation. The overall closed-loop system stability is demonstrated using Lyapunov analysis. Finally, simulation results are provided to demonstrate the effectiveness of the proposed control design for trajectory tracking.

Real-time absorption and scattering characterization of slab-shaped turbid samples obtained by a combination of angular and spatially resolved measurements.

PubMed

Dam, Jan S; Yavari, Nazila; Sørensen, Søren; Andersson-Engels, Stefan

2005-07-10

We present a fast and accurate method for real-time determination of the absorption coefficient, the scattering coefficient, and the anisotropy factor of thin turbid samples by using simple continuous-wave noncoherent light sources. The three optical properties are extracted from recordings of angularly resolved transmittance in addition to spatially resolved diffuse reflectance and transmittance. The applied multivariate calibration and prediction techniques are based on multiple polynomial regression in combination with a Newton--Raphson algorithm. The numerical test results based on Monte Carlo simulations showed mean prediction errors of approximately 0.5% for all three optical properties within ranges typical for biological media. Preliminary experimental results are also presented yielding errors of approximately 5%. Thus the presented methods show a substantial potential for simultaneous absorption and scattering characterization of turbid media.

Photon migration through a turbid slab described by a model based on diffusion approximation. I. Theory.

PubMed

Contini, D; Martelli, F; Zaccanti, G

1997-07-01

The diffusion approximation of the radiative transfer equation is a model used widely to describe photon migration in highly diffusing media and is an important matter in biological tissue optics. An analysis of the time-dependent diffusion equation together with its solutions for the slab geometry and for a semi-infinite diffusing medium are reported. These solutions, presented for both the time-dependent and the continuous wave source, account for the refractive index mismatch between the turbid medium and the surrounding medium. The results have been compared with those obtained when different boundary conditions were assumed. The comparison has shown that the effect of the refractive index mismatch cannot be disregarded. This effect is particularly important for the transmittance. The discussion of results also provides an analysis of the role of the absorption coefficient in the expression of the diffusion coefficient.

Resonant oscillations in open axisymmetric tubes

NASA Astrophysics Data System (ADS)

Amundsen, D. E.; Mortell, M. P.; Seymour, B. R.

2017-12-01

We study the behaviour of the isentropic flow of a gas in both a straight tube of constant cross section and a cone, open at one end and forced at or near resonance at the other. A continuous transition between these configurations is provided through the introduction of a geometric parameter k associated with the opening angle of the cone where the tube corresponds to k=0. The primary objective is to find long-time resonant and near-resonant approximate solutions for the open tube, i.e. k→ 0. Detailed analysis for both the tube and cone in the limit of small forcing (O(ɛ 3)) is carried out, where ɛ 3 is the Mach number of the forcing function and the resulting flow has Mach number O(ɛ ). The resulting approximate solutions are compared with full numerical simulations. Interesting distinctions between the cone and the tube emerge. Depending on the damping and detuning, the responses for the tube are continuous and of O(ɛ ). In the case of the cone, the resonant response involves an amplification of the fundamental resonant mode, usually called the dominant first-mode approximation. However, higher modes must be included for the tube to account for the nonlinear generation of higher-order resonances. Bridging these distinct solution behaviours is a transition layer of O(ɛ 2) in k. It is found that an appropriately truncated set of modes provides the requisite modal approximation, again comparing well to numerical simulations.

Malnutrition among vaccinated children aged 0-5 years in Batouri, Republic of Cameroon.

PubMed

Nagahori, Chikako; Kinjo, Yoshihide; Tchuani, Jean Paul; Yamauchi, Taro

2017-12-01

Malnutrition continues to contribute to a high infant mortality rate. This study aimed to determine the prevalence of malnutrition and its potential association with the time at which complementary feeding was introduced among children aged 0-5 years in Batouri, Republic of Cameroon. Mothers (n=212) were interviewed using a structured questionnaire. Child height or length, and weight measurements were determined and the appropriate Z -scores calculated. Multiple regression analysis was performed with the values of all nutritional status indicators as dependent variables and the time of commencing complementary feeding, and the child's age and sex, as independent variables. The prevalence of stunting (height/length for age<-2 standard deviation [SD]), underweight (weight for age<-2SD), and wasting (weight for height/length<-2SD) was 45.8%, 30.2%, and 11.3%, respectively. Even taking into consideration the biological variables, there was a significant association in the effects of time of starting complementary foods on the nutritional status indicators. Furthermore, adding socio-economic variables did not produce a rise in adjusted R 2 values for all age group models concerned. Approximately 30% of the children in the study region were underweight, and approximately half of the children exhibited stunting, indicating chronic malnutrition. Commencing complementary feeding at an appropriate time had a positive effect on nutritional status from approximately 2 years of age.

Fall-Back Disks in Long and Short GRBS

NASA Technical Reports Server (NTRS)

Cannizo, John K.; Troja, E.; Gehrels, N.

2011-01-01

We present numerical time-dependent calculations for fall-back disks relevant for GRBs in which the disk of material surrounding the black hole (BH) powering the GRB jet modulates the mass flow, and hence the strength of the jet. Given the initial existence of a small mass appr oximately less than 10(exp -4) M(solar) near the progenitor with a circularization radius approximately 10(exp 10) - 10(exp 11) cm, an una voidable consequence will be the formation of an "external disk" whose outer edge continually moves to larger radii due to angular momentum transport and lack of a confining torque. For long GRBs, if the mass distribution in the initial fall-back disk traces the progenitor envelope, then a radius approximates 10(exp 11) cm gives a time scale app roximately 10(exp 4) s for the X-ray plateau. For late times t > 10(exp 7) s a steepening due to a cooling front in the disk may have obser vational support in GRB 060729. For short GRBs, one expects most of t he mass initially to lie at small radii < 10(exp 8) cm; however the presence of even a trace amount approximately 10(exp -9) M(solar) of hi gh angular material can give a brief plateau in the light curve.

Autonomous microfluidic sample preparation system for protein profile-based detection of aerosolized bacterial cells and spores.

PubMed

Stachowiak, Jeanne C; Shugard, Erin E; Mosier, Bruce P; Renzi, Ronald F; Caton, Pamela F; Ferko, Scott M; Van de Vreugde, James L; Yee, Daniel D; Haroldsen, Brent L; VanderNoot, Victoria A

2007-08-01

For domestic and military security, an autonomous system capable of continuously monitoring for airborne biothreat agents is necessary. At present, no system meets the requirements for size, speed, sensitivity, and selectivity to warn against and lead to the prevention of infection in field settings. We present a fully automated system for the detection of aerosolized bacterial biothreat agents such as Bacillus subtilis (surrogate for Bacillus anthracis) based on protein profiling by chip gel electrophoresis coupled with a microfluidic sample preparation system. Protein profiling has previously been demonstrated to differentiate between bacterial organisms. With the goal of reducing response time, multiple microfluidic component modules, including aerosol collection via a commercially available collector, concentration, thermochemical lysis, size exclusion chromatography, fluorescent labeling, and chip gel electrophoresis were integrated together to create an autonomous collection/sample preparation/analysis system. The cycle time for sample preparation was approximately 5 min, while total cycle time, including chip gel electrophoresis, was approximately 10 min. Sensitivity of the coupled system for the detection of B. subtilis spores was 16 agent-containing particles per liter of air, based on samples that were prepared to simulate those collected by wetted cyclone aerosol collector of approximately 80% efficiency operating for 7 min.

Multi-Chromatic Ultrashort Pulse Filamentation and Bulk Modification in Dielectrics

DTIC Science & Technology

2016-05-05

multi -pulse fields 7 6 Filamentation and bulk modification by spatio-temporally chirped pulses 8 7 Quantum modeling of photoionization and nonlinear...pulses. (b) two co-propagating pulses of di↵erent frequencies. 4) Develop non-time-averaged multi -chromatic quantum -mechanical models of photoion- ization...very well with those of the extended multi -rate equation using the relaxation approximation, which is much faster. A continued collaboration to also

Variability of Bed Load Transport During Six Summers of Continuous Measurements in Two Austrian Mountain Streams (Fischbach and Ruetz)

NASA Astrophysics Data System (ADS)

Rickenmann, Dieter

2018-01-01

Previous measurements of bed load transport in gravel bed streams revealed a large temporal and spatial variability of bed load transport rates. Using an impact plate geophone system, continuous bed load transport measurements were made during 6 years in two mountain streams in Austria. The two streams have a snow-melt and glacier-melt dominated hydrologic regime resulting in frequent transport activity during the summer half year. Periods of days to weeks were identified which are associated with approximately constant Shields values that indicate quasi-stable bed conditions. Between these stable periods, the position of the bed load transport function varied while its steepness remained approximately constant. For integration time scales of several hours to 1 day, the fluctuations in bed load transport decreased and the correlation between bed load transport and water discharge increased. For integration times of about 70-100 days, bed load transport is determined by discharge or shear stress to within a factor of about 2, relative to the 6 year mean level. Bed load texture increased with increasing mean flow strength and mean transport intensity. Weak and predominantly clockwise daily hysteresis of bed load transport was found for the first half of the summer period.

Fast measurement of proton exchange membrane fuel cell impedance based on pseudo-random binary sequence perturbation signals and continuous wavelet transform

NASA Astrophysics Data System (ADS)

Debenjak, Andrej; Boškoski, Pavle; Musizza, Bojan; Petrovčič, Janko; Juričić, Đani

2014-05-01

This paper proposes an approach to the estimation of PEM fuel cell impedance by utilizing pseudo-random binary sequence as a perturbation signal and continuous wavelet transform with Morlet mother wavelet. With the approach, the impedance characteristic in the frequency band from 0.1 Hz to 500 Hz is identified in 60 seconds, approximately five times faster compared to the conventional single-sine approach. The proposed approach was experimentally evaluated on a single PEM fuel cell of a larger fuel cell stack. The quality of the results remains at the same level compared to the single-sine approach.

Continuous-variable quantum teleportation in bosonic structured environments

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

He Guangqiang; Zhang Jingtao; Zhu Jun

2011-09-15

The effects of dynamics of continuous-variable entanglement under the various kinds of environments on quantum teleportation are quantitatively investigated. Only under assumption of the weak system-reservoir interaction, the evolution of teleportation fidelity is analytically derived and is numerically plotted in terms of environment parameters including reservoir temperature and its spectral density, without Markovian and rotating wave approximations. We find that the fidelity of teleportation is a monotonically decreasing function for Markovian interaction in Ohmic-like environments, while it oscillates for non-Markovian ones. According to the dynamical laws of teleportation, teleportation with better performances can be implemented by selecting the appropriate time.

High-resolution multiphoton microscopy with a low-power continuous wave laser pump.

PubMed

Chen, Xiang-Dong; Li, Shen; Du, Bo; Dong, Yang; Wang, Ze-Hao; Guo, Guang-Can; Sun, Fang-Wen

2018-02-15

Multiphoton microscopy (MPM) has been widely used for three-dimensional biological imaging. Here, based on the photon-induced charge state conversion process, we demonstrated a low-power high-resolution MPM with a nitrogen vacancy (NV) center in diamond. Continuous wave green and orange lasers were used to pump and detect the two-photon charge state conversion, respectively. The power of the laser for multiphoton excitation was 40 μW. Both the axial and lateral resolutions were improved approximately 1.5 times compared with confocal microscopy. The results can be used to improve the resolution of the NV center-based quantum sensing and biological imaging.

Continuous analog of multiplicative algebraic reconstruction technique for computed tomography

NASA Astrophysics Data System (ADS)

Tateishi, Kiyoko; Yamaguchi, Yusaku; Abou Al-Ola, Omar M.; Kojima, Takeshi; Yoshinaga, Tetsuya

2016-03-01

We propose a hybrid dynamical system as a continuous analog to the block-iterative multiplicative algebraic reconstruction technique (BI-MART), which is a well-known iterative image reconstruction algorithm for computed tomography. The hybrid system is described by a switched nonlinear system with a piecewise smooth vector field or differential equation and, for consistent inverse problems, the convergence of non-negatively constrained solutions to a globally stable equilibrium is guaranteed by the Lyapunov theorem. Namely, we can prove theoretically that a weighted Kullback-Leibler divergence measure can be a common Lyapunov function for the switched system. We show that discretizing the differential equation by using the first-order approximation (Euler's method) based on the geometric multiplicative calculus leads to the same iterative formula of the BI-MART with the scaling parameter as a time-step of numerical discretization. The present paper is the first to reveal that a kind of iterative image reconstruction algorithm is constructed by the discretization of a continuous-time dynamical system for solving tomographic inverse problems. Iterative algorithms with not only the Euler method but also the Runge-Kutta methods of lower-orders applied for discretizing the continuous-time system can be used for image reconstruction. A numerical example showing the characteristics of the discretized iterative methods is presented.

Pythagorean Approximations and Continued Fractions

ERIC Educational Resources Information Center

Peralta, Javier

2008-01-01

In this article, we will show that the Pythagorean approximations of [the square root of] 2 coincide with those achieved in the 16th century by means of continued fractions. Assuming this fact and the known relation that connects the Fibonacci sequence with the golden section, we shall establish a procedure to obtain sequences of rational numbers…

26 CFR 1.7872-16 - Loans to an exchange facilitator under § 1.468B-6.

Code of Federal Regulations, 2010 CFR

2010-04-01

... TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES General Actuarial Valuations § 1.7872-16 Loans to... of approximate method permitted. The taxpayer and exchange facilitator may use the approximate method to determine the amount of forgone interest on any exchange facilitator loan. (f) Exemption for...

Discrete factor approximations in simultaneous equation models: estimating the impact of a dummy endogenous variable on a continuous outcome.

PubMed

Mroz, T A

1999-10-01

This paper contains a Monte Carlo evaluation of estimators used to control for endogeneity of dummy explanatory variables in continuous outcome regression models. When the true model has bivariate normal disturbances, estimators using discrete factor approximations compare favorably to efficient estimators in terms of precision and bias; these approximation estimators dominate all the other estimators examined when the disturbances are non-normal. The experiments also indicate that one should liberally add points of support to the discrete factor distribution. The paper concludes with an application of the discrete factor approximation to the estimation of the impact of marriage on wages.

Control-based continuation: Bifurcation and stability analysis for physical experiments

NASA Astrophysics Data System (ADS)

Barton, David A. W.

2017-02-01

Control-based continuation is technique for tracking the solutions and bifurcations of nonlinear experiments. The idea is to apply the method of numerical continuation to a feedback-controlled physical experiment such that the control becomes non-invasive. Since in an experiment it is not (generally) possible to set the state of the system directly, the control target becomes a proxy for the state. Control-based continuation enables the systematic investigation of the bifurcation structure of a physical system, much like if it was numerical model. However, stability information (and hence bifurcation detection and classification) is not readily available due to the presence of stabilising feedback control. This paper uses a periodic auto-regressive model with exogenous inputs (ARX) to approximate the time-varying linearisation of the experiment around a particular periodic orbit, thus providing the missing stability information. This method is demonstrated using a physical nonlinear tuned mass damper.

From CONT to VGOS: the Evolution of the CONT Campaigns

NASA Astrophysics Data System (ADS)

Thomas, Cynthia C.; Behrend, Dirk; MacMillan, Daniel S.

2016-12-01

Continuous VLBI campaigns (CONT) started in 1994 with the goal of demonstrating state-of-the-art VLBI over a continuous period of time. The first CONT was followed by campaigns in 1995 and 1996. After a six year hiatus, CONT campaigns were organized approximately every three years from 2002 through 2014. In this paper we primarily focus on the cornerstones of each CONT campaign. Specifically, we review the developments in networks, scheduling techniques, recording media, correlation, and other resources used. A timeline of the history of the CONTs and the goals for future campaigns will be presented. The CONTs used a significant amount of IVS resources to produce a large volume of high quality data and demonstrated the advantages of continuous observing which will soon be realized with VGOS.

Effects of low-frequency repetitive transcranial magnetic stimulation on event-related potential P300

NASA Astrophysics Data System (ADS)

Torii, Tetsuya; Sato, Aya; Iwahashi, Masakuni; Iramina, Keiji

2012-04-01

The present study analyzed the effects of repetitive transcranial magnetic stimulation (rTMS) on brain activity. P300 latency of event-related potential (ERP) was used to evaluate the effects of low-frequency and short-term rTMS by stimulating the supramarginal gyrus (SMG), which is considered to be the related area of P300 origin. In addition, the prolonged stimulation effects on P300 latency were analyzed after applying rTMS. A figure-eight coil was used to stimulate left-right SMG, and intensity of magnetic stimulation was 80% of motor threshold. A total of 100 magnetic pulses were applied for rTMS. The effects of stimulus frequency at 0.5 or 1 Hz were determined. Following rTMS, an odd-ball task was performed and P300 latency of ERP was measured. The odd-ball task was performed at 5, 10, and 15 min post-rTMS. ERP was measured prior to magnetic stimulation as a control. Electroencephalograph (EEG) was measured at Fz, Cz, and Pz that were indicated by the international 10-20 electrode system. Results demonstrated that different effects on P300 latency occurred between 0.5-1 Hz rTMS. With 1 Hz low-frequency magnetic stimulation to the left SMG, P300 latency decreased. Compared to the control, the latency time difference was approximately 15 ms at Cz. This decrease continued for approximately 10 min post-rTMS. In contrast, 0.5 Hz rTMS resulted in delayed P300 latency. Compared to the control, the latency time difference was approximately 20 ms at Fz, and this delayed effect continued for approximately 15 min post-rTMS. Results demonstrated that P300 latency varied according to rTMS frequency. Furthermore, the duration of the effect was not similar for stimulus frequency of low-frequency rTMS.

Stochastic Games for Continuous-Time Jump Processes Under Finite-Horizon Payoff Criterion

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

Wei, Qingda, E-mail: weiqd@hqu.edu.cn; Chen, Xian, E-mail: chenxian@amss.ac.cn

In this paper we study two-person nonzero-sum games for continuous-time jump processes with the randomized history-dependent strategies under the finite-horizon payoff criterion. The state space is countable, and the transition rates and payoff functions are allowed to be unbounded from above and from below. Under the suitable conditions, we introduce a new topology for the set of all randomized Markov multi-strategies and establish its compactness and metrizability. Then by constructing the approximating sequences of the transition rates and payoff functions, we show that the optimal value function for each player is a unique solution to the corresponding optimality equation andmore » obtain the existence of a randomized Markov Nash equilibrium. Furthermore, we illustrate the applications of our main results with a controlled birth and death system.« less

A new approach of optimal control for a class of continuous-time chaotic systems by an online ADP algorithm

NASA Astrophysics Data System (ADS)

Song, Rui-Zhuo; Xiao, Wen-Dong; Wei, Qing-Lai

2014-05-01

We develop an online adaptive dynamic programming (ADP) based optimal control scheme for continuous-time chaotic systems. The idea is to use the ADP algorithm to obtain the optimal control input that makes the performance index function reach an optimum. The expression of the performance index function for the chaotic system is first presented. The online ADP algorithm is presented to achieve optimal control. In the ADP structure, neural networks are used to construct a critic network and an action network, which can obtain an approximate performance index function and the control input, respectively. It is proven that the critic parameter error dynamics and the closed-loop chaotic systems are uniformly ultimately bounded exponentially. Our simulation results illustrate the performance of the established optimal control method.

Evaluation of a fast single-photon avalanche photodiode for measurement of early transmitted photons through diffusive media.

PubMed

Mu, Ying; Valim, Niksa; Niedre, Mark

2013-06-15

We tested the performance of a fast single-photon avalanche photodiode (SPAD) in measurement of early transmitted photons through diffusive media. In combination with a femtosecond titanium:sapphire laser, the overall instrument temporal response time was 59 ps. Using two experimental models, we showed that the SPAD allowed measurement of photon-density sensitivity functions that were approximately 65% narrower than the ungated continuous wave case at very early times. This exceeds the performance that we have previously achieved with photomultiplier-tube-based systems and approaches the theoretical maximum predicted by time-resolved Monte Carlo simulations.

Beyond mean-field approximations for accurate and computationally efficient models of on-lattice chemical kinetics

NASA Astrophysics Data System (ADS)

Pineda, M.; Stamatakis, M.

2017-07-01

Modeling the kinetics of surface catalyzed reactions is essential for the design of reactors and chemical processes. The majority of microkinetic models employ mean-field approximations, which lead to an approximate description of catalytic kinetics by assuming spatially uncorrelated adsorbates. On the other hand, kinetic Monte Carlo (KMC) methods provide a discrete-space continuous-time stochastic formulation that enables an accurate treatment of spatial correlations in the adlayer, but at a significant computation cost. In this work, we use the so-called cluster mean-field approach to develop higher order approximations that systematically increase the accuracy of kinetic models by treating spatial correlations at a progressively higher level of detail. We further demonstrate our approach on a reduced model for NO oxidation incorporating first nearest-neighbor lateral interactions and construct a sequence of approximations of increasingly higher accuracy, which we compare with KMC and mean-field. The latter is found to perform rather poorly, overestimating the turnover frequency by several orders of magnitude for this system. On the other hand, our approximations, while more computationally intense than the traditional mean-field treatment, still achieve tremendous computational savings compared to KMC simulations, thereby opening the way for employing them in multiscale modeling frameworks.

Non-linear continuous time random walk models★

NASA Astrophysics Data System (ADS)

Stage, Helena; Fedotov, Sergei

2017-11-01

A standard assumption of continuous time random walk (CTRW) processes is that there are no interactions between the random walkers, such that we obtain the celebrated linear fractional equation either for the probability density function of the walker at a certain position and time, or the mean number of walkers. The question arises how one can extend this equation to the non-linear case, where the random walkers interact. The aim of this work is to take into account this interaction under a mean-field approximation where the statistical properties of the random walker depend on the mean number of walkers. The implementation of these non-linear effects within the CTRW integral equations or fractional equations poses difficulties, leading to the alternative methodology we present in this work. We are concerned with non-linear effects which may either inhibit anomalous effects or induce them where they otherwise would not arise. Inhibition of these effects corresponds to a decrease in the waiting times of the random walkers, be this due to overcrowding, competition between walkers or an inherent carrying capacity of the system. Conversely, induced anomalous effects present longer waiting times and are consistent with symbiotic, collaborative or social walkers, or indirect pinpointing of favourable regions by their attractiveness. Contribution to the Topical Issue "Continuous Time Random Walk Still Trendy: Fifty-year History, Current State and Outlook", edited by Ryszard Kutner and Jaume Masoliver.

Violation of the continuity equation in the Krieger-Li-Iafrate approximation for current-density functional theory

NASA Astrophysics Data System (ADS)

Siegmund, Marc; Pankratov, Oleg

2011-01-01

We show that the exchange-correlation scalar and vector potentials obtained from the optimized effective potential (OEP) equations and from the Krieger-Li-Iafrate (KLI) approximation for the current-density functional theory (CDFT) change under a gauge transformation such that the energy functional remains invariant. This alone does not assure, however, the theory’s compliance with the continuity equation. Using the model of a quantum ring with a broken angular symmetry which is penetrated by a magnetic flux we demonstrate that the physical current density calculated with the exact-exchange CDFT in the KLI approximation violates the continuity condition. In contrast, the current found from a solution of the full OEP equations satisfies this condition. We argue that the continuity violation stems from the fact that the KLI potentials are not (in general) the exact functional derivatives of a gauge-invariant exchange-correlation functional.

Continuous depth-of-interaction encoding using phosphor-coated scintillators.

PubMed

Du, Huini; Yang, Yongfeng; Glodo, Jarek; Wu, Yibao; Shah, Kanai; Cherry, Simon R

2009-03-21

We investigate a novel detector using a lutetium oxyorthosilicate (LSO) scintillator and YGG (yttrium-aluminum-gallium oxide:cerium, Y(3)(Al,Ga)(5)O(12):Ce) phosphor to construct a detector with continuous depth-of-interaction (DOI) information. The far end of the LSO scintillator is coated with a thin layer of YGG phosphor powder which absorbs some fraction of the LSO scintillation light and emits wavelength-shifted photons with a characteristic decay time of approximately 50 ns. The near end of the LSO scintillator is directly coupled to a photodetector. The photodetector detects a mixture of the LSO light and the light emitted by YGG. With appropriate placement of the coating, the ratio of the light converted from the YGG coating with respect to the unconverted LSO light can be made to depend on the interaction depth. DOI information can then be estimated by inspecting the overall light pulse decay time. Experiments were conducted to optimize the coating method. 19 ns decay time differences across the length of the detector were achieved experimentally when reading out a 1.5 x 1.5 x 20 mm(3) LSO crystal with unpolished surfaces and half-coated with YGG phosphor. The same coating scheme was applied to a 4 x 4 LSO array. Pulse shape discrimination (PSD) methods were studied to extract DOI information from the pulse shape changes. The DOI full-width-half-maximum (FWHM) resolution was found to be approximately 8 mm for this 2 cm thick array.

Perceived Effectiveness of Clinical E-Learning for Georgia Midwives

ERIC Educational Resources Information Center

Hunter, Adrienne

2014-01-01

In the state of Georgia, approximately nine out of every 1,000 babies die during birth and approximately 18.6 out of every 1,000 women die from a pregnancy-related cause (Georgia Department of Public Health, 2011). Continuing to build capacities for the continuing education of midwives--specifically Certified Nurse Midwives (CNMs)--can ensure they…

Theory and operational rules for the discrete Hankel transform.

PubMed

Baddour, Natalie; Chouinard, Ugo

2015-04-01

Previous definitions of a discrete Hankel transform (DHT) have focused on methods to approximate the continuous Hankel integral transform. In this paper, we propose and evaluate the theory of a DHT that is shown to arise from a discretization scheme based on the theory of Fourier-Bessel expansions. The proposed transform also possesses requisite orthogonality properties which lead to invertibility of the transform. The standard set of shift, modulation, multiplication, and convolution rules are derived. In addition to the theory of the actual manipulated quantities which stand in their own right, this DHT can be used to approximate the continuous forward and inverse Hankel transform in the same manner that the discrete Fourier transform is known to be able to approximate the continuous Fourier transform.

Simulation-based decision support framework for dynamic ambulance redeployment in Singapore.

PubMed

Lam, Sean Shao Wei; Ng, Clarence Boon Liang; Nguyen, Francis Ngoc Hoang Long; Ng, Yih Yng; Ong, Marcus Eng Hock

2017-10-01

Dynamic ambulance redeployment policies tend to introduce much more flexibilities in improving ambulance resource allocation by capitalizing on the definite geospatial-temporal variations in ambulance demand patterns over the time-of-the-day and day-of-the-week effects. A novel modelling framework based on the Approximate Dynamic Programming (ADP) approach leveraging on a Discrete Events Simulation (DES) model for dynamic ambulance redeployment in Singapore is proposed in this paper. The study was based on the Singapore's national Emergency Medical Services (EMS) system. Based on a dataset comprising 216,973 valid incidents over a continuous two-years study period from 1 January 2011-31 December 2012, a DES model for the EMS system was developed. An ADP model based on linear value function approximations was then evaluated using the DES model via the temporal difference (TD) learning family of algorithms. The objective of the ADP model is to derive approximate optimal dynamic redeployment policies based on the primary outcome of ambulance coverage. Considering an 8min response time threshold, an estimated 5% reduction in the proportion of calls that cannot be reached within the threshold (equivalent to approximately 8000 dispatches) was observed from the computational experiments. The study also revealed that the redeployment policies which are restricted within the same operational division could potentially result in a more promising response time performance. Furthermore, the best policy involved the combination of redeploying ambulances whenever they are released from service and that of relocating ambulances that are idle in bases. This study demonstrated the successful application of an approximate modelling framework based on ADP that leverages upon a detailed DES model of the Singapore's EMS system to generate approximate optimal dynamic redeployment plans. Various policies and scenarios relevant to the Singapore EMS system were evaluated. Copyright © 2017 Elsevier B.V. All rights reserved.

Energy Efficiency and Productivity Enhancement of Microbial Electrosynthesis of Acetate

PubMed Central

LaBelle, Edward V.; May, Harold D.

2017-01-01

It was hypothesized that a lack of acetogenic biomass (biocatalyst) at the cathode of a microbial electrosynthesis system, due to electron and nutrient limitations, has prevented further improvement in acetate productivity and efficiency. In order to increase the biomass at the cathode and thereby performance, a bioelectrochemical system with this acetogenic community was operated under galvanostatic control and continuous media flow through a reticulated vitreous carbon (RVC) foam cathode. The combination of galvanostatic control and the high surface area cathode reduced the electron limitation and the continuous flow overcame the nutrient limitation while avoiding the accumulation of products and potential inhibitors. These conditions were set with the intention of operating the biocathode through the production of H2. Biofilm growth occurred on and within the unmodified RVC foam regardless of vigorous H2 generation on the cathode surface. A maximum volumetric rate or space time yield for acetate production of 0.78 g/Lcatholyte/h was achieved with 8 A/Lcatholyte (83.3 A/m2projected surface area of cathode) supplied to the continuous flow/culture bioelectrochemical reactors. The total Coulombic efficiency in H2 and acetate ranged from approximately 80–100%, with a maximum of 35% in acetate. The overall energy efficiency ranged from approximately 35–42% with a maximum to acetate of 12%. PMID:28515713

Energy Efficiency and Productivity Enhancement of Microbial Electrosynthesis of Acetate.

PubMed

LaBelle, Edward V; May, Harold D

2017-01-01

It was hypothesized that a lack of acetogenic biomass (biocatalyst) at the cathode of a microbial electrosynthesis system, due to electron and nutrient limitations, has prevented further improvement in acetate productivity and efficiency. In order to increase the biomass at the cathode and thereby performance, a bioelectrochemical system with this acetogenic community was operated under galvanostatic control and continuous media flow through a reticulated vitreous carbon (RVC) foam cathode. The combination of galvanostatic control and the high surface area cathode reduced the electron limitation and the continuous flow overcame the nutrient limitation while avoiding the accumulation of products and potential inhibitors. These conditions were set with the intention of operating the biocathode through the production of H 2 . Biofilm growth occurred on and within the unmodified RVC foam regardless of vigorous H 2 generation on the cathode surface. A maximum volumetric rate or space time yield for acetate production of 0.78 g/L catholyte /h was achieved with 8 A/L catholyte (83.3 A/m 2 projected surface area of cathode) supplied to the continuous flow/culture bioelectrochemical reactors. The total Coulombic efficiency in H 2 and acetate ranged from approximately 80-100%, with a maximum of 35% in acetate. The overall energy efficiency ranged from approximately 35-42% with a maximum to acetate of 12%.

Fast simulation techniques for switching converters

NASA Technical Reports Server (NTRS)

King, Roger J.

1987-01-01

Techniques for simulating a switching converter are examined. The state equations for the equivalent circuits, which represent the switching converter, are presented and explained. The uses of the Newton-Raphson iteration, low ripple approximation, half-cycle symmetry, and discrete time equations to compute the interval durations are described. An example is presented in which these methods are illustrated by applying them to a parallel-loaded resonant inverter with three equivalent circuits for its continuous mode of operation.

Stochastic differential equation model for linear growth birth and death processes with immigration and emigration

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

Granita, E-mail: granitafc@gmail.com; Bahar, A.

This paper discusses on linear birth and death with immigration and emigration (BIDE) process to stochastic differential equation (SDE) model. Forward Kolmogorov equation in continuous time Markov chain (CTMC) with a central-difference approximation was used to find Fokker-Planckequation corresponding to a diffusion process having the stochastic differential equation of BIDE process. The exact solution, mean and variance function of BIDE process was found.

Achieving algorithmic resilience for temporal integration through spectral deferred corrections

DOE PAGES

Grout, Ray; Kolla, Hemanth; Minion, Michael; ...

2017-05-08

Spectral deferred corrections (SDC) is an iterative approach for constructing higher-order-accurate numerical approximations of ordinary differential equations. SDC starts with an initial approximation of the solution defined at a set of Gaussian or spectral collocation nodes over a time interval and uses an iterative application of lower-order time discretizations applied to a correction equation to improve the solution at these nodes. Each deferred correction sweep increases the formal order of accuracy of the method up to the limit inherent in the accuracy defined by the collocation points. In this paper, we demonstrate that SDC is well suited to recovering frommore » soft (transient) hardware faults in the data. A strategy where extra correction iterations are used to recover from soft errors and provide algorithmic resilience is proposed. Specifically, in this approach the iteration is continued until the residual (a measure of the error in the approximation) is small relative to the residual of the first correction iteration and changes slowly between successive iterations. Here, we demonstrate the effectiveness of this strategy for both canonical test problems and a comprehensive situation involving a mature scientific application code that solves the reacting Navier-Stokes equations for combustion research.« less

GRB110721A: An Extreme Peak Energy and Signatures of the Photosphere

NASA Technical Reports Server (NTRS)

Axelsson, M.; Baldini, L.; Barbiellini, G.; Baring, M. G.; Bellazzini, R.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Caliandro, G. A.;

Achieving algorithmic resilience for temporal integration through spectral deferred corrections

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

Grout, Ray; Kolla, Hemanth; Minion, Michael

2017-05-08

Spectral deferred corrections (SDC) is an iterative approach for constructing higher- order accurate numerical approximations of ordinary differential equations. SDC starts with an initial approximation of the solution defined at a set of Gaussian or spectral collocation nodes over a time interval and uses an iterative application of lower-order time discretizations applied to a correction equation to improve the solution at these nodes. Each deferred correction sweep increases the formal order of accuracy of the method up to the limit inherent in the accuracy defined by the collocation points. In this paper, we demonstrate that SDC is well suited tomore » recovering from soft (transient) hardware faults in the data. A strategy where extra correction iterations are used to recover from soft errors and provide algorithmic resilience is proposed. Specifically, in this approach the iteration is continued until the residual (a measure of the error in the approximation) is small relative to the residual on the first correction iteration and changes slowly between successive iterations. We demonstrate the effectiveness of this strategy for both canonical test problems and a comprehen- sive situation involving a mature scientific application code that solves the reacting Navier-Stokes equations for combustion research.« less

Achieving algorithmic resilience for temporal integration through spectral deferred corrections

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

Grout, Ray; Kolla, Hemanth; Minion, Michael

2017-05-08

Spectral deferred corrections (SDC) is an iterative approach for constructing higher-order-accurate numerical approximations of ordinary differential equations. SDC starts with an initial approximation of the solution defined at a set of Gaussian or spectral collocation nodes over a time interval and uses an iterative application of lower-order time discretizations applied to a correction equation to improve the solution at these nodes. Each deferred correction sweep increases the formal order of accuracy of the method up to the limit inherent in the accuracy defined by the collocation points. In this paper, we demonstrate that SDC is well suited to recovering frommore » soft (transient) hardware faults in the data. A strategy where extra correction iterations are used to recover from soft errors and provide algorithmic resilience is proposed. Specifically, in this approach the iteration is continued until the residual (a measure of the error in the approximation) is small relative to the residual of the first correction iteration and changes slowly between successive iterations. We demonstrate the effectiveness of this strategy for both canonical test problems and a comprehensive situation involving a mature scientific application code that solves the reacting Navier-Stokes equations for combustion research.« less

Hypergeometric continuation of divergent perturbation series: II. Comparison with Shanks transformation and Padé approximation

NASA Astrophysics Data System (ADS)

Sanders, Sören; Holthaus, Martin

2017-11-01

We explore in detail how analytic continuation of divergent perturbation series by generalized hypergeometric functions is achieved in practice. Using the example of strong-coupling perturbation series provided by the two-dimensional Bose-Hubbard model, we compare hypergeometric continuation to Shanks and Padé techniques, and demonstrate that the former yields a powerful, efficient and reliable alternative for computing the phase diagram of the Mott insulator-to-superfluid transition. In contrast to Shanks transformations and Padé approximations, hypergeometric continuation also allows us to determine the exponents which characterize the divergence of correlation functions at the transition points. Therefore, hypergeometric continuation constitutes a promising tool for the study of quantum phase transitions.

Generation of tunable laser sidebands in the far-infrared region

NASA Technical Reports Server (NTRS)

Farhoomand, J.; Frerking, M. A.; Pickett, H. M.; Blake, G. A.

1985-01-01

In recent years, several techniques have been developed for the generation of tunable coherent radiation at submillimeter and far-infrared (FIR) wavelengths. The harmonic generation of conventional microwave sources has made it possible to produce spectrometers capable of continuous operation to above 1000 GHz. However, the sensitivity of such instruments drops rapidly with frequency. For this reason, a great deal of attention is given to laser-based methods, which could cover the entire FIR region. Tunable FIR radiation (approximately 100 nW) has been produced by mixing FIR molecular lasers and conventional microwave sources in both open and closed mixer mounts. The present investigation is concerned with improvements in this approach. These improvements provide approximately thirty times more output power than previous results.

Analysis of Phase-Type Stochastic Petri Nets With Discrete and Continuous Timing

NASA Technical Reports Server (NTRS)

Jones, Robert L.; Goode, Plesent W. (Technical Monitor)

2000-01-01

The Petri net formalism is useful in studying many discrete-state, discrete-event systems exhibiting concurrency, synchronization, and other complex behavior. As a bipartite graph, the net can conveniently capture salient aspects of the system. As a mathematical tool, the net can specify an analyzable state space. Indeed, one can reason about certain qualitative properties (from state occupancies) and how they arise (the sequence of events leading there). By introducing deterministic or random delays, the model is forced to sojourn in states some amount of time, giving rise to an underlying stochastic process, one that can be specified in a compact way and capable of providing quantitative, probabilistic measures. We formalize a new non-Markovian extension to the Petri net that captures both discrete and continuous timing in the same model. The approach affords efficient, stationary analysis in most cases and efficient transient analysis under certain restrictions. Moreover, this new formalism has the added benefit in modeling fidelity stemming from the simultaneous capture of discrete- and continuous-time events (as opposed to capturing only one and approximating the other). We show how the underlying stochastic process, which is non-Markovian, can be resolved into simpler Markovian problems that enjoy efficient solutions. Solution algorithms are provided that can be easily programmed.

Feedback between neutral winds and auroral arc electrodynamics

NASA Technical Reports Server (NTRS)

Lyons, L. R.; Walterscheid, R. L.

1986-01-01

The feedback between neutral atmospheric winds and the electrodynamics of a stable, discrete auroral arc is analyzed. The ionospheric current continuity equation and the equation for neutral gas acceleration by ion drag are solved simultaneously, as a function of time. The results show that, in general, the electric field in the ionosphere adjusts to neutral wind acceleration so as to keep auroral field-aligned currents and electron acceleration approximately independent of time. It is thus concluded that the neutral winds that develop as a result of the electrodynamical forcing associated with an arc do not significantly affect the intensity of the arc.

[Cataract surgery under topical anesthesia with oral anticoagulants].

PubMed

Wirbelauer, C; Weller, A; Häberle, H; Pham, D T

2004-09-01

Approximately 14 % of cataract surgery patients receive blood-thinning agents. In a prospective study, the influence of oral anticoagulants on intraoperative and postoperative hemorrhages in patients undergoing cataract surgery in topical anesthesia was investigated. 128 patients presenting for cataract surgery under oral anticoagulation were included. The mean preoperative prothrombin time was 39 +/- 18 %. Most patients (81 %) continued their oral anticoagulation (prothrombin time 34 +/- 13 %). All surgeries were performed in topical anesthesia. In 9 patients (7 %) an ocular hemorrhagic event was observed. These were not sight-threatening and resorbed spontaneously within a few days. Only one patient (0.8 %) had a slight hemorrhage in the anterior chamber. There were no differences (P > 0.05) between patients with or without hemorrhagic complications in the postoperative visual acuity, the intraocular pressure, the prothrombin time or the discontinuation of oral anticoagulants. Cataract surgery in topical anesthesia under oral anticoagulation did not increase the risk of sight-threatening hemorrhages. The continuation of oral anticoagulation seems particularly indicated for ambulatory cataract surgery.

Birth/birth-death processes and their computable transition probabilities with biological applications.

PubMed

Ho, Lam Si Tung; Xu, Jason; Crawford, Forrest W; Minin, Vladimir N; Suchard, Marc A

2018-03-01

Birth-death processes track the size of a univariate population, but many biological systems involve interaction between populations, necessitating models for two or more populations simultaneously. A lack of efficient methods for evaluating finite-time transition probabilities of bivariate processes, however, has restricted statistical inference in these models. Researchers rely on computationally expensive methods such as matrix exponentiation or Monte Carlo approximation, restricting likelihood-based inference to small systems, or indirect methods such as approximate Bayesian computation. In this paper, we introduce the birth/birth-death process, a tractable bivariate extension of the birth-death process, where rates are allowed to be nonlinear. We develop an efficient algorithm to calculate its transition probabilities using a continued fraction representation of their Laplace transforms. Next, we identify several exemplary models arising in molecular epidemiology, macro-parasite evolution, and infectious disease modeling that fall within this class, and demonstrate advantages of our proposed method over existing approaches to inference in these models. Notably, the ubiquitous stochastic susceptible-infectious-removed (SIR) model falls within this class, and we emphasize that computable transition probabilities newly enable direct inference of parameters in the SIR model. We also propose a very fast method for approximating the transition probabilities under the SIR model via a novel branching process simplification, and compare it to the continued fraction representation method with application to the 17th century plague in Eyam. Although the two methods produce similar maximum a posteriori estimates, the branching process approximation fails to capture the correlation structure in the joint posterior distribution.

Solution of the advection-dispersion equation: Continuous load of finite duration

USGS Publications Warehouse

Runkel, R.L.

1996-01-01

Field studies of solute fate and transport in streams and rivers often involve an. experimental release of solutes at an upstream boundary for a finite period of time. A review of several standard references on surface-water-quality modeling indicates that the analytical solution to the constant-parameter advection-dispersion equation for this type of boundary condition has been generally overlooked. Here an exact analytical solution that considers a continuous load of unite duration is compared to an approximate analytical solution presented elsewhere. Results indicate that the exact analytical solution should be used for verification of numerical solutions and other solute-transport problems wherein a high level of accuracy is required. ?? ASCE.

Order reduction of z-transfer functions via multipoint Jordan continued-fraction expansion

NASA Technical Reports Server (NTRS)

Lee, Ying-Chin; Hwang, Chyi; Shieh, Leang S.

1992-01-01

The order reduction problem of z-transfer functions is solved by using the multipoint Jordan continued-fraction expansion (MJCFE) technique. An efficient algorithm that does not require the use of complex algebra is presented for obtaining an MJCFE from a stable z-transfer function with expansion points selected from the unit circle and/or the positive real axis of the z-plane. The reduced-order models are exactly the multipoint Pade approximants of the original system and, therefore, they match the (weighted) time-moments of the impulse response and preserve the frequency responses of the system at some characteristic frequencies, such as gain crossover frequency, phase crossover frequency, bandwidth, etc.

A clustering-based graph Laplacian framework for value function approximation in reinforcement learning.

PubMed

Xu, Xin; Huang, Zhenhua; Graves, Daniel; Pedrycz, Witold

2014-12-01

In order to deal with the sequential decision problems with large or continuous state spaces, feature representation and function approximation have been a major research topic in reinforcement learning (RL). In this paper, a clustering-based graph Laplacian framework is presented for feature representation and value function approximation (VFA) in RL. By making use of clustering-based techniques, that is, K-means clustering or fuzzy C-means clustering, a graph Laplacian is constructed by subsampling in Markov decision processes (MDPs) with continuous state spaces. The basis functions for VFA can be automatically generated from spectral analysis of the graph Laplacian. The clustering-based graph Laplacian is integrated with a class of approximation policy iteration algorithms called representation policy iteration (RPI) for RL in MDPs with continuous state spaces. Simulation and experimental results show that, compared with previous RPI methods, the proposed approach needs fewer sample points to compute an efficient set of basis functions and the learning control performance can be improved for a variety of parameter settings.

Shifting the closed-loop spectrum in the optimal linear quadratic regulator problem for hereditary systems

NASA Technical Reports Server (NTRS)

Gibson, J. S.; Rosen, I. G.

1985-01-01

In the optimal linear quadratic regulator problem for finite dimensional systems, the method known as an alpha-shift can be used to produce a closed-loop system whose spectrum lies to the left of some specified vertical line; that is, a closed-loop system with a prescribed degree of stability. This paper treats the extension of the alpha-shift to hereditary systems. As infinite dimensions, the shift can be accomplished by adding alpha times the identity to the open-loop semigroup generator and then solving an optimal regulator problem. However, this approach does not work with a new approximation scheme for hereditary control problems recently developed by Kappel and Salamon. Since this scheme is among the best to date for the numerical solution of the linear regulator problem for hereditary systems, an alternative method for shifting the closed-loop spectrum is needed. An alpha-shift technique that can be used with the Kappel-Salamon approximation scheme is developed. Both the continuous-time and discrete-time problems are considered. A numerical example which demonstrates the feasibility of the method is included.

Shifting the closed-loop spectrum in the optimal linear quadratic regulator problem for hereditary systems

NASA Technical Reports Server (NTRS)

Gibson, J. S.; Rosen, I. G.

1987-01-01

In the optimal linear quadratic regulator problem for finite dimensional systems, the method known as an alpha-shift can be used to produce a closed-loop system whose spectrum lies to the left of some specified vertical line; that is, a closed-loop system with a prescribed degree of stability. This paper treats the extension of the alpha-shift to hereditary systems. As infinite dimensions, the shift can be accomplished by adding alpha times the identity to the open-loop semigroup generator and then solving an optimal regulator problem. However, this approach does not work with a new approximation scheme for hereditary control problems recently developed by Kappel and Salamon. Since this scheme is among the best to date for the numerical solution of the linear regulator problem for hereditary systems, an alternative method for shifting the closed-loop spectrum is needed. An alpha-shift technique that can be used with the Kappel-Salamon approximation scheme is developed. Both the continuous-time and discrete-time problems are considered. A numerical example which demonstrates the feasibility of the method is included.

A Magnetoresistive Heat Switch for the Continuous ADR

NASA Technical Reports Server (NTRS)

Canavan, E. R.; Dipirro, M. J.; Jackson, M.; Panek, J.; Shirron, P. J.; Tuttle, J. G.; Krebs, C. (Technical Monitor)

2001-01-01

In compensated elemental metals at low temperature, a several Tesla field can suppress electronic heat conduction so thoroughly that heat is effectively carried by phonons alone. In approximately one mm diameter single crystal samples with impurity concentrations low enough that electron conduction is limited by surface scattering, the ratio of zerofield to high-field thermal conductivity can exceed ten thousand. We have used this phenomenon to build a compact, solid-state heat switch with no moving parts and no enclosed fluids. The time scale for switching states is limited by time scale for charging the magnet that supplies the controlling field. Our design and fabrication techniques overcome the difficulties associated with manufacturing and assembling parts from single crystal tungsten. A clear disadvantage of the magnetoresistive switch is the mass and complexity of the magnet system for the controlling field. We have discovered a technique of minimizing this mass and complexity, applicable to the continuous adiabatic demagnetization refrigerator.

Real-time continuous-wave terahertz line scanner based on a compact 1 × 240 InGaAs Schottky barrier diode array detector.

PubMed

Han, Sang-Pil; Ko, Hyunsung; Kim, Namje; Lee, Won-Hui; Moon, Kiwon; Lee, Il-Min; Lee, Eui Su; Lee, Dong Hun; Lee, Wangjoo; Han, Seong-Tae; Choi, Sung-Wook; Park, Kyung Hyun

2014-11-17

We demonstrate real-time continuous-wave terahertz (THz) line-scanned imaging based on a 1 × 240 InGaAs Schottky barrier diode (SBD) array detector with a scan velocity of 25 cm/s, a scan line length of 12 cm, and a pixel size of 0.5 × 0.5 mm². Foreign substances, such as a paper clip with a spatial resolution of approximately 1 mm that is hidden under a cracker, are clearly detected by this THz line-scanning system. The system consists of the SBD array detector, a 200-GHz gyrotron source, a conveyor system, and several optical components such as a high-density polyethylene cylindrical lens, metal cylindrical mirror, and THz wire-grid polarizer. Using the THz polarizer, the signal-to-noise ratio of the SBD array detector improves because the quality of the source beam is enhanced.

Probabilistic inference using linear Gaussian importance sampling for hybrid Bayesian networks

NASA Astrophysics Data System (ADS)

Sun, Wei; Chang, K. C.

2005-05-01

Probabilistic inference for Bayesian networks is in general NP-hard using either exact algorithms or approximate methods. However, for very complex networks, only the approximate methods such as stochastic sampling could be used to provide a solution given any time constraint. There are several simulation methods currently available. They include logic sampling (the first proposed stochastic method for Bayesian networks, the likelihood weighting algorithm) the most commonly used simulation method because of its simplicity and efficiency, the Markov blanket scoring method, and the importance sampling algorithm. In this paper, we first briefly review and compare these available simulation methods, then we propose an improved importance sampling algorithm called linear Gaussian importance sampling algorithm for general hybrid model (LGIS). LGIS is aimed for hybrid Bayesian networks consisting of both discrete and continuous random variables with arbitrary distributions. It uses linear function and Gaussian additive noise to approximate the true conditional probability distribution for continuous variable given both its parents and evidence in a Bayesian network. One of the most important features of the newly developed method is that it can adaptively learn the optimal important function from the previous samples. We test the inference performance of LGIS using a 16-node linear Gaussian model and a 6-node general hybrid model. The performance comparison with other well-known methods such as Junction tree (JT) and likelihood weighting (LW) shows that LGIS-GHM is very promising.

Interpolated Sounding and Gridded Sounding Value-Added Products

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

Toto, T.; Jensen, M.

Standard Atmospheric Radiation Measurement (ARM) Climate Research Facility sounding files provide atmospheric state data in one dimension of increasing time and height per sonde launch. Many applications require a quick estimate of the atmospheric state at higher time resolution. The INTERPOLATEDSONDE (i.e., Interpolated Sounding) Value-Added Product (VAP) transforms sounding data into continuous daily files on a fixed time-height grid, at 1-minute time resolution, on 332 levels, from the surface up to a limit of approximately 40 km. The grid extends that high so the full height of soundings can be captured; however, most soundings terminate at an altitude between 25more » and 30 km, above which no data is provided. Between soundings, the VAP linearly interpolates atmospheric state variables in time for each height level. In addition, INTERPOLATEDSONDE provides relative humidity scaled to microwave radiometer (MWR) observations.The INTERPOLATEDSONDE VAP, a continuous time-height grid of relative humidity-corrected sounding data, is intended to provide input to higher-order products, such as the Merged Soundings (MERGESONDE; Troyan 2012) VAP, which extends INTERPOLATEDSONDE by incorporating model data. The INTERPOLATEDSONDE VAP also is used to correct gaseous attenuation of radar reflectivity in products such as the KAZRCOR VAP.« less

[Clinical research of hyperbaric, isobaric, and hypobaric solutions of bupivacaine in continuous spinal anesthesia].

PubMed

Yang, Hong-wei; Bai, Nian-yue; Guo, Qu-lian

2005-02-01

To compare the anesthesia properities of hyperbaric bupivacaine with those of isobaric and hypobaric solutions when administered in the supine position undergoing hip surgery or lower limb surgery using continuous spinal anesthesia. Sixty patients( ASA I approximately III ) scheduled for hip or lower limb surgery were randomly divided into 3 groups with 20 patients in each group: Group A: 0. 375% hyperbaric bupivacaine solutions; Group B :0.375% isobaric bupivacaine solutions; and Group C: 0. 375% hypobaric bupivacaine solutions. The following variables were measured every 2 minutes during the first 30 minutes after the intrathecal injection : the onset time of sensation block, the highest plane of analgesia, the time to reach complete motor blockade, and the plane of analgesia and the extent of lower extremities' movement (modified bromage score, BMS) at different time after the administration. Meanwhile the changes of hemodynamics were recorded. There was no statistical difference among the basic conditions ( P > 0.05). The onset time of sensation block, and the time to reach complete motor blockade, and the time receiving the highest sharp pain sensory block in Group A were significantly shorter than those in Group B and Group C ( P < 0.01 ). The plane of analgesia obtained in the hyperbaric group was significantly higher than in both the isobaric and the hypobaric groups ( P < 0.01). The mean arterial pressure(MAP) , HR in the hyperbaric group decreased significantly after the intrathecal injection( P < 0.05 ). The 0.375% Isobaric bupivacaine used during contiuous spinal anesthesia in the supine position produces a suitable and a more "controllable" anesthesia, but a minimum dosage of 10 approximately 12.5 mg is required to obtain adequate anesthesic conditions with moderate hemodynamic changes and satisfying analgesia effects. Under similar conditions, 0. 375% hyperbaric bupivacaine produces major hemodynamic consequences with high cephalad spread and 0. 375% hypobaric bupivacaine has a too long onset time.

nu-Anomica: A Fast Support Vector Based Novelty Detection Technique

NASA Technical Reports Server (NTRS)

Das, Santanu; Bhaduri, Kanishka; Oza, Nikunj C.; Srivastava, Ashok N.

2009-01-01

In this paper we propose nu-Anomica, a novel anomaly detection technique that can be trained on huge data sets with much reduced running time compared to the benchmark one-class Support Vector Machines algorithm. In -Anomica, the idea is to train the machine such that it can provide a close approximation to the exact decision plane using fewer training points and without losing much of the generalization performance of the classical approach. We have tested the proposed algorithm on a variety of continuous data sets under different conditions. We show that under all test conditions the developed procedure closely preserves the accuracy of standard one-class Support Vector Machines while reducing both the training time and the test time by 5 - 20 times.

A study of the application of singular perturbation theory. [development of a real time algorithm for optimal three dimensional aircraft maneuvers

NASA Technical Reports Server (NTRS)

Mehra, R. K.; Washburn, R. B.; Sajan, S.; Carroll, J. V.

1979-01-01

A hierarchical real time algorithm for optimal three dimensional control of aircraft is described. Systematic methods are developed for real time computation of nonlinear feedback controls by means of singular perturbation theory. The results are applied to a six state, three control variable, point mass model of an F-4 aircraft. Nonlinear feedback laws are presented for computing the optimal control of throttle, bank angle, and angle of attack. Real Time capability is assessed on a TI 9900 microcomputer. The breakdown of the singular perturbation approximation near the terminal point is examined Continuation methods are examined to obtain exact optimal trajectories starting from the singular perturbation solutions.

Single-shot quantum state estimation via a continuous measurement in the strong backaction regime

NASA Astrophysics Data System (ADS)

Cook, Robert L.; Riofrío, Carlos A.; Deutsch, Ivan H.

2014-09-01

We study quantum tomography based on a stochastic continuous-time measurement record obtained from a probe field collectively interacting with an ensemble of identically prepared systems. In comparison to previous studies, we consider here the case in which the measurement-induced backaction has a non-negligible effect on the dynamical evolution of the ensemble. We formulate a maximum likelihood estimate for the initial quantum state given only a single instance of the continuous diffusive measurement record. We apply our estimator to the simplest problem: state tomography of a single pure qubit, which, during the course of the measurement, is also subjected to dynamical control. We identify a regime where the many-body system is well approximated at all times by a separable pure spin coherent state, whose Bloch vector undergoes a conditional stochastic evolution. We simulate the results of our estimator and show that we can achieve close to the upper bound of fidelity set by the optimal generalized measurement. This estimate is compared to, and significantly outperforms, an equivalent estimator that ignores measurement backaction.

Sleep-wake behavior in the rat: ultradian rhythms in a light-dark cycle and continuous bright light.

PubMed

Stephenson, Richard; Lim, Joonbum; Famina, Svetlana; Caron, Aimee M; Dowse, Harold B

2012-12-01

Ultradian rhythms are a prominent but little-studied feature of mammalian sleep-wake and rest-activity patterns. They are especially evident in long-term records of behavioral state in polyphasic animals such as rodents. However, few attempts have been made to incorporate ultradian rhythmicity into models of sleep-wake dynamics, and little is known about the physiological mechanisms that give rise to ultradian rhythms in sleep-wake state. This study investigated ultradian dynamics in sleep and wakefulness in rats entrained to a 12-h:12-h light-dark cycle (LD) and in rats whose circadian rhythms were suppressed and free-running following long-term exposure to uninterrupted bright light (LL). We recorded sleep-wake state continuously for 7 to 12 consecutive days and used time-series analysis to quantify the dynamics of net cumulative time in each state (wakefulness [WAKE], rapid eye movement sleep [REM], and non-REM sleep [NREM]) in each animal individually. Form estimates and autocorrelation confirmed the presence of significant ultradian and circadian rhythms; maximum entropy spectral analysis allowed high-resolution evaluation of multiple periods within the signal, and wave-by-wave analysis enabled a statistical evaluation of the instantaneous period, peak-trough range, and phase of each ultradian wave in the time series. Significant ultradian periodicities were present in all 3 states in all animals. In LD, ultradian range was approximately 28% of circadian range. In LL, ultradian range was slightly reduced relative to LD, and circadian range was strongly attenuated. Ultradian rhythms were found to be quasiperiodic in both LD and LL. That is, ultradian period varied randomly around a mean of approximately 4 h, with no relationship between ultradian period and time of day.

Effects of hydraulic retention time on cultivation of indigenous microalgae as a renewable energy source using secondary effluent.

PubMed

Takabe, Yugo; Hidaka, Taira; Tsumori, Jun; Minamiyama, Mizuhiko

2016-05-01

Secondary effluent from wastewater treatment plants is suitable media for cultivating microalgae as a renewable energy source, and hydraulic retention time (HRT) control in culture is important to conduct well-planned outdoor indigenous microalgae cultivation with secondary effluent. This study revealed cultivation characteristics under various HRT by continuous 6-month experiments. In addition, effects of HRT on cultivation were determined by a mathematical model that described indigenous microalgae growth. Cultivated biomass mainly consisted of Chlorophyceae and its detritus regardless of HRT, and 5.93-14.8g/m(2)/day of biomass yield was obtained. The cultivated biomass had a stable higher heating value of 16kJ/g. Sensitivity analysis of the model suggests that HRT control had great effects on biomass yield, and 2-3days of HRT were recommended to obtain maximum biomass yield under certain weather conditions (temperature: approximately 12-25°C and solar radiation: approximately 8-19MJ/m(2)/day). Copyright © 2016 Elsevier Ltd. All rights reserved.

Markov-modulated Markov chains and the covarion process of molecular evolution.

PubMed

Galtier, N; Jean-Marie, A

2004-01-01

The covarion (or site specific rate variation, SSRV) process of biological sequence evolution is a process by which the evolutionary rate of a nucleotide/amino acid/codon position can change in time. In this paper, we introduce time-continuous, space-discrete, Markov-modulated Markov chains as a model for representing SSRV processes, generalizing existing theory to any model of rate change. We propose a fast algorithm for diagonalizing the generator matrix of relevant Markov-modulated Markov processes. This algorithm makes phylogeny likelihood calculation tractable even for a large number of rate classes and a large number of states, so that SSRV models become applicable to amino acid or codon sequence datasets. Using this algorithm, we investigate the accuracy of the discrete approximation to the Gamma distribution of evolutionary rates, widely used in molecular phylogeny. We show that a relatively large number of classes is required to achieve accurate approximation of the exact likelihood when the number of analyzed sequences exceeds 20, both under the SSRV and among site rate variation (ASRV) models.

Accurate approximation of in-ecliptic trajectories for E-sail with constant pitch angle

NASA Astrophysics Data System (ADS)

Huo, Mingying; Mengali, Giovanni; Quarta, Alessandro A.

2018-05-01

Propellantless continuous-thrust propulsion systems, such as electric solar wind sails, may be successfully used for new space missions, especially those requiring high-energy orbit transfers. When the mass-to-thrust ratio is sufficiently large, the spacecraft trajectory is characterized by long flight times with a number of revolutions around the Sun. The corresponding mission analysis, especially when addressed within an optimal context, requires a significant amount of simulation effort. Analytical trajectories are therefore useful aids in a preliminary phase of mission design, even though exact solution are very difficult to obtain. The aim of this paper is to present an accurate, analytical, approximation of the spacecraft trajectory generated by an electric solar wind sail with a constant pitch angle, using the latest mathematical model of the thrust vector. Assuming a heliocentric circular parking orbit and a two-dimensional scenario, the simulation results show that the proposed equations are able to accurately describe the actual spacecraft trajectory for a long time interval when the propulsive acceleration magnitude is sufficiently small.

Continental Drift and Speciation of the Cryptococcus neoformans and Cryptococcus gattii Species Complexes

PubMed Central

Freij, Joudeh B.; Hann-Soden, Christopher; Taylor, John

2017-01-01

ABSTRACT Genomic analysis has placed the origins of two human-pathogenic fungi, the Cryptococcus gattii species complex and the Cryptococcus neoformans species complex, in South America and Africa, respectively. Molecular clock calculations suggest that the two species separated ~80 to 100 million years ago. This time closely approximates the breakup of the supercontinent Pangea, which gave rise to South America and Africa. On the basis of the geographic distribution of these two species complexes and the coincidence of the evolutionary divergence and Pangea breakup times, we propose that a spatial separation caused by continental drift resulted in the emergence of the C. gattii and C. neoformans species complexes from a Pangean ancestor. We note that, despite the spatial and temporal separation that occurred approximately 100 million years ago, these two species complexes are morphologically similar, share virulence factors, and cause very similar diseases. Continuation of these phenotypic characteristics despite ancient separation suggests the maintenance of similar selection pressures throughout geologic ages. PMID:28435888

Continental Drift and Speciation of the Cryptococcus neoformans and Cryptococcus gattii Species Complexes.

PubMed

Casadevall, Arturo; Freij, Joudeh B; Hann-Soden, Christopher; Taylor, John

2017-01-01

Genomic analysis has placed the origins of two human-pathogenic fungi, the Cryptococcus gattii species complex and the Cryptococcus neoformans species complex, in South America and Africa, respectively. Molecular clock calculations suggest that the two species separated ~80 to 100 million years ago. This time closely approximates the breakup of the supercontinent Pangea, which gave rise to South America and Africa. On the basis of the geographic distribution of these two species complexes and the coincidence of the evolutionary divergence and Pangea breakup times, we propose that a spatial separation caused by continental drift resulted in the emergence of the C. gattii and C. neoformans species complexes from a Pangean ancestor. We note that, despite the spatial and temporal separation that occurred approximately 100 million years ago, these two species complexes are morphologically similar, share virulence factors, and cause very similar diseases. Continuation of these phenotypic characteristics despite ancient separation suggests the maintenance of similar selection pressures throughout geologic ages.

Framework for cascade size calculations on random networks

NASA Astrophysics Data System (ADS)

Burkholz, Rebekka; Schweitzer, Frank

2018-04-01

We present a framework to calculate the cascade size evolution for a large class of cascade models on random network ensembles in the limit of infinite network size. Our method is exact and applies to network ensembles with almost arbitrary degree distribution, degree-degree correlations, and, in case of threshold models, for arbitrary threshold distribution. With our approach, we shift the perspective from the known branching process approximations to the iterative update of suitable probability distributions. Such distributions are key to capture cascade dynamics that involve possibly continuous quantities and that depend on the cascade history, e.g., if load is accumulated over time. As a proof of concept, we provide two examples: (a) Constant load models that cover many of the analytically tractable casacade models, and, as a highlight, (b) a fiber bundle model that was not tractable by branching process approximations before. Our derivations cover the whole cascade dynamics, not only their steady state. This allows us to include interventions in time or further model complexity in the analysis.

The nature of earthquake prediction

USGS Publications Warehouse

Lindh, A.G.

1991-01-01

Earthquake prediction is inherently statistical. Although some people continue to think of earthquake prediction as the specification of the time, place, and magnitude of a future earthquake, it has been clear for at least a decade that this is an unrealistic and unreasonable definition. the reality is that earthquake prediction starts from the long-term forecasts of place and magnitude, with very approximate time constraints, and progresses, at least in principle, to a gradual narrowing of the time window as data and understanding permit. Primitive long-term forecasts are clearly possible at this time on a few well-characterized fault systems. Tightly focuses monitoring experiments aimed at short-term prediction are already underway in Parkfield, California, and in the Tokai region in Japan; only time will tell how much progress will be possible. 

Adaptive critic designs for discrete-time zero-sum games with application to H(infinity) control.

PubMed

Al-Tamimi, Asma; Abu-Khalaf, Murad; Lewis, Frank L

2007-02-01

In this correspondence, adaptive critic approximate dynamic programming designs are derived to solve the discrete-time zero-sum game in which the state and action spaces are continuous. This results in a forward-in-time reinforcement learning algorithm that converges to the Nash equilibrium of the corresponding zero-sum game. The results in this correspondence can be thought of as a way to solve the Riccati equation of the well-known discrete-time H(infinity) optimal control problem forward in time. Two schemes are presented, namely: 1) a heuristic dynamic programming and 2) a dual-heuristic dynamic programming, to solve for the value function and the costate of the game, respectively. An H(infinity) autopilot design for an F-16 aircraft is presented to illustrate the results.

Modeling of phonon scattering in n-type nanowire transistors using one-shot analytic continuation technique

NASA Astrophysics Data System (ADS)

Bescond, Marc; Li, Changsheng; Mera, Hector; Cavassilas, Nicolas; Lannoo, Michel

2013-10-01

We present a one-shot current-conserving approach to model the influence of electron-phonon scattering in nano-transistors using the non-equilibrium Green's function formalism. The approach is based on the lowest order approximation (LOA) to the current and its simplest analytic continuation (LOA+AC). By means of a scaling argument, we show how both LOA and LOA+AC can be easily obtained from the first iteration of the usual self-consistent Born approximation (SCBA) algorithm. Both LOA and LOA+AC are then applied to model n-type silicon nanowire field-effect-transistors and are compared to SCBA current characteristics. In this system, the LOA fails to describe electron-phonon scattering, mainly because of the interactions with acoustic phonons at the band edges. In contrast, the LOA+AC still well approximates the SCBA current characteristics, thus demonstrating the power of analytic continuation techniques. The limits of validity of LOA+AC are also discussed, and more sophisticated and general analytic continuation techniques are suggested for more demanding cases.

Inference of epidemiological parameters from household stratified data

PubMed Central

Walker, James N.; Ross, Joshua V.

2017-01-01

We consider a continuous-time Markov chain model of SIR disease dynamics with two levels of mixing. For this so-called stochastic households model, we provide two methods for inferring the model parameters—governing within-household transmission, recovery, and between-household transmission—from data of the day upon which each individual became infectious and the household in which each infection occurred, as might be available from First Few Hundred studies. Each method is a form of Bayesian Markov Chain Monte Carlo that allows us to calculate a joint posterior distribution for all parameters and hence the household reproduction number and the early growth rate of the epidemic. The first method performs exact Bayesian inference using a standard data-augmentation approach; the second performs approximate Bayesian inference based on a likelihood approximation derived from branching processes. These methods are compared for computational efficiency and posteriors from each are compared. The branching process is shown to be a good approximation and remains computationally efficient as the amount of data is increased. PMID:29045456

Frequency distributions from birth, death, and creation processes.

PubMed

Bartley, David L; Ogden, Trevor; Song, Ruiguang

2002-01-01

The time-dependent frequency distribution of groups of individuals versus group size was investigated within a continuum approximation, assuming a simplified individual growth, death and creation model. The analogy of the system to a physical fluid exhibiting both convection and diffusion was exploited in obtaining various solutions to the distribution equation. A general solution was approximated through the application of a Green's function. More specific exact solutions were also found to be useful. The solutions were continually checked against the continuum approximation through extensive simulation of the discrete system. Over limited ranges of group size, the frequency distributions were shown to closely exhibit a power-law dependence on group size, as found in many realizations of this type of system, ranging from colonies of mutated bacteria to the distribution of surnames in a given population. As an example, the modeled distributions were successfully fit to the distribution of surnames in several countries by adjusting the parameters specifying growth, death and creation rates.

Atomic density functional and diagram of structures in the phase field crystal model

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

Ankudinov, V. E., E-mail: vladimir@ankudinov.org; Galenko, P. K.; Kropotin, N. V.

2016-02-15

The phase field crystal model provides a continual description of the atomic density over the diffusion time of reactions. We consider a homogeneous structure (liquid) and a perfect periodic crystal, which are constructed from the one-mode approximation of the phase field crystal model. A diagram of 2D structures is constructed from the analytic solutions of the model using atomic density functionals. The diagram predicts equilibrium atomic configurations for transitions from the metastable state and includes the domains of existence of homogeneous, triangular, and striped structures corresponding to a liquid, a body-centered cubic crystal, and a longitudinal cross section of cylindricalmore » tubes. The method developed here is employed for constructing the diagram for the homogeneous liquid phase and the body-centered iron lattice. The expression for the free energy is derived analytically from density functional theory. The specific features of approximating the phase field crystal model are compared with the approximations and conclusions of the weak crystallization and 2D melting theories.« less

Earth Observations

NASA Image and Video Library

2010-09-20

ISS024-E-015121 (20 Sept. 2010) --- Twitchell Canyon Fire in central Utah is featured in this image photographed by an Expedition 24 crew member on the International Space Station (ISS). The Twitchell Canyon Fire near central Utah?s Fishlake National Forest is reported to have an area of approximately 13,383 hectares (approximately 134 square kilometers, or 33,071 acres). This detailed image shows smoke plumes generated by several fire spots close to the southwestern edge of the burned area. The fire was started by a lightning strike on July 20, 2010. Whereas many of the space station images of Earth are looking straight down (nadir), this photograph was exposed at an angle. The space station was located over a point approximately 509 kilometers (316 miles) to the northeast, near the Colorado/Wyoming border, at the time the image was taken on Sept. 20. Southwesterly winds were continuing to extend smoke plumes from the fire to the northeast. While the Twitchell Canyon region is sparsely populated, Interstate Highway 15 is visible at upper left.

A Variational Formulation of Macro-Particle Algorithms for Kinetic Plasma Simulations

NASA Astrophysics Data System (ADS)

Shadwick, B. A.

2013-10-01

Macro-particle based simulations methods are in widespread use in plasma physics; their computational efficiency and intuitive nature are largely responsible for their longevity. In the main, these algorithms are formulated by approximating the continuous equations of motion. For systems governed by a variational principle (such as collisionless plasmas), approximations of the equations of motion is known to introduce anomalous behavior, especially in system invariants. We present a variational formulation of particle algorithms for plasma simulation based on a reduction of the distribution function onto a finite collection of macro-particles. As in the usual Particle-In-Cell (PIC) formulation, these macro-particles have a definite momentum and are spatially extended. The primary advantage of this approach is the preservation of the link between symmetries and conservation laws. For example, nothing in the reduction introduces explicit time dependence to the system and, therefore, the continuous-time equations of motion exactly conserve energy; thus, these models are free of grid-heating. In addition, the variational formulation allows for constructing models of arbitrary spatial and temporal order. In contrast, the overall accuracy of the usual PIC algorithm is at most second due to the nature of the force interpolation between the gridded field quantities and the (continuous) particle position. Again in contrast to the usual PIC algorithm, here the macro-particle shape is arbitrary; the spatial extent is completely decoupled from both the grid-size and the ``smoothness'' of the shape; smoother particle shapes are not necessarily larger. For simplicity, we restrict our discussion to one-dimensional, non-relativistic, un-magnetized, electrostatic plasmas. We comment on the extension to the electromagnetic case. Supported by the US DoE under contract numbers DE-FG02-08ER55000 and DE-SC0008382.

Relaxation and approximate factorization methods for the unsteady full potential equation

NASA Technical Reports Server (NTRS)

Shankar, V.; Ide, H.; Gorski, J.

1984-01-01

The unsteady form of the full potential equation is solved in conservation form, using implicit methods based on approximate factorization and relaxation schemes. A local time linearization for density is introduced to enable solution to the equation in terms of phi, the velocity potential. A novel flux-biasing technique is applied to generate proper forms of the artificial viscosity, to treat hyperbolic regions with shocks and sonic lines present. The wake is properly modeled by accounting not only for jumps in phi, but also for jumps in higher derivatives of phi obtained from requirements of density continuity. The far field is modeled using the Riemann invariants to simulate nonreflecting boundary conditions. Results are presented for flows over airfoils, cylinders, and spheres. Comparisons are made with available Euler and full potential results.

Martian tidal pressure and wind fields obtained from the Mariner 9 infrared spectroscopy experiment

NASA Technical Reports Server (NTRS)

Pirraglia, J. A.; Conrath, B. J.

1973-01-01

Using temperature fields derived from the Mariner 9 infrared spectroscopy experiment, the Martian atmospheric tidal pressure and wind fields are calculated. Temperature as a function of local time, latitude, and atmospheric pressure level is obtained by secular and longitudinal averaging of the data. The resulting temperature field is approximated by a spherical harmonic expansion, retaining one symmetric and one asymmetric term for wavenumber zero and wavenumber one. Vertical averaging of the linearized momentum and continuity equations results in an inhomogeneous tidal equation for surface pressure fluctuations with the driving function related to the temperature field through the geopotential function and the hydrostatic equation. Solutions of the tidal equation show a diurnal fractional pressure amplitude approximately equal to one half of the vertically averaged diurnal fractional temperature amplitude.

Martian tidal pressure and wind fields obtained from the Mariner 9 infrared spectroscopy experiment

NASA Technical Reports Server (NTRS)

Pirraglia, J. A.; Conrath, B. J.

1974-01-01

Using temperature fields derived from the Mariner 9 infrared spectroscopy experiment, the Martian atmospheric tidal pressure and wind fields are calculated. Temperature as a function of local time, latitude, and atmospheric pressure level is obtained by secular and longitudinal averaging of the data. The resulting temperature field is approximated by a spherical harmonic expansion, retaining one symmetric and one asymmetric term each for wavenumber zero and wavenumber one. Vertical averaging of the linearized momentum and continuity equations results in an inhomogeneous tidal equation for surface pressure fluctuations with the driving function related to the temperature field through the geopotential function and the hydrostatic equation. Solutions of the tidal equation show a diurnal fractional pressure amplitude approximately equal to one-half the vertically averaged diurnal fractional temperature amplitude.

Low-speed impact phenomena and orbital resonances in the moon- and planet-building process

NASA Technical Reports Server (NTRS)

Chapman, C. R.

1977-01-01

A simulation of collisional and gravitational interaction in the early solar system generates planets approximately 1000 km in diameter from an initial swarm of kilometer sized planetesimals. The model treats collisions according to experimental and theoretical impact results (such as rebound, cratering, and catastrophic fragmentation) for a variety of materials whose parameters span plausible values for early solid objects. The small planets form in approximately 1000 yr, during which time most of the mass of the system continues to reside in particles near the original size. The simulation is terminated when the largest objects' random motion is of smaller dimension than their collision cross-sections. The few 1000 km planets may act as seeds for the subsequent, gradual, accretional growth into full-sized planets.

Synthesis of recurrent neural networks for dynamical system simulation.

PubMed

Trischler, Adam P; D'Eleuterio, Gabriele M T

2016-08-01

We review several of the most widely used techniques for training recurrent neural networks to approximate dynamical systems, then describe a novel algorithm for this task. The algorithm is based on an earlier theoretical result that guarantees the quality of the network approximation. We show that a feedforward neural network can be trained on the vector-field representation of a given dynamical system using backpropagation, then recast it as a recurrent network that replicates the original system's dynamics. After detailing this algorithm and its relation to earlier approaches, we present numerical examples that demonstrate its capabilities. One of the distinguishing features of our approach is that both the original dynamical systems and the recurrent networks that simulate them operate in continuous time. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evidence that the X-Ray Plasma in Microflares is in a Sequence of Subresolution Magnetic Tubes

NASA Technical Reports Server (NTRS)

Moore, Ronald L.; Falconer, D. A.; Porter, Jason G.

1998-01-01

We analyze the cooling of the X-ray emitting thermal plasma in microflares observed in active regions by the Yohkoh Soft X-ray Telescope. A typical microflare appears to be a transient brightening of an entire small magnetic loop, often having a diameter near the limit of resolution (approximately 2 x 10(exp 8) cm) (Shimizu 1995, PASJ, 47, 251). The X-ray plasma in the loop cools by emission of XUV radiation and by heat conduction to the cooler plasma at the feet of the loop. The cooling rate is determined by the plasma temperature and density and the loop length. The plasma density is determined from the observed X-ray brightness of the loop in combination with the temperature, the loop diameter, and the filling factor. The filling factor is the volume fraction of the loop occupied by the subset of magnetic tubes that is filled by the X-ray plasma and that contains practically all of the X-ray plasma present in the microflare loop. Taking typical values from the hundreds of microflares measured by Shimizu (1995) (X-ray brightness through the thin aluminum filter approximately 4 x 10(exp 3) DN/s/pixel, lifetime approximately 5 min, temperature approximately 6 x 10(exp 6) K, loop length approximately 10(exp 9) cm, loop diameter approximately 3 x 10(exp 8) cm), we find that for filling factors greater than approximately 1% (1) the cooling time is much shorter than the duration of the microflare, and (2) conductive cooling strongly dominates over radiative cooling. Because the cooling time is so short and because the conductive heat flux goes mainly into increasing the plasma density via chromospheric evaporation, we are compelled to conclude that (1) heating to X-ray temperatures continues through nearly the entire life of a microflare, (2) the heating keeps changing to different field lines, so that any one magnetic tube in the sequence of heated tubes emits X-rays only briefly in the life of the microflare, and (3) at any instant during the microflare the tubes filled with X-ray plasma occupy only a small fraction (less than approximately 10%) of the microflare loop. Hence, we expect that coronal X-ray images with spatial resolution 2-3 times better than from Yohkoh will show plenty of rapidly changing filamentary substructure in microflares.

Waiting time distribution for continuous stochastic systems

NASA Astrophysics Data System (ADS)

Gernert, Robert; Emary, Clive; Klapp, Sabine H. L.

2014-12-01

The waiting time distribution (WTD) is a common tool for analyzing discrete stochastic processes in classical and quantum systems. However, there are many physical examples where the dynamics is continuous and only approximately discrete, or where it is favourable to discuss the dynamics on a discretized and a continuous level in parallel. An example is the hindered motion of particles through potential landscapes with barriers. In the present paper we propose a consistent generalization of the WTD from the discrete case to situations where the particles perform continuous barrier crossing characterized by a finite duration. To this end, we introduce a recipe to calculate the WTD from the Fokker-Planck (Smoluchowski) equation. In contrast to the closely related first passage time distribution (FPTD), which is frequently used to describe continuous processes, the WTD contains information about the direction of motion. As an application, we consider the paradigmatic example of an overdamped particle diffusing through a washboard potential. To verify the approach and to elucidate its numerical implications, we compare the WTD defined via the Smoluchowski equation with data from direct simulation of the underlying Langevin equation and find full consistency provided that the jumps in the Langevin approach are defined properly. Moreover, for sufficiently large energy barriers, the WTD defined via the Smoluchowski equation becomes consistent with that resulting from the analytical solution of a (two-state) master equation model for the short-time dynamics developed previously by us [Phys. Rev. E 86, 061135 (2012), 10.1103/PhysRevE.86.061135]. Thus, our approach "interpolates" between these two types of stochastic motion. We illustrate our approach for both symmetric systems and systems under constant force.

Improving timing sensitivity in the microhertz frequency regime: limits from PSR J1713+0747 on gravitational waves produced by supermassive black hole binaries

NASA Astrophysics Data System (ADS)

Perera, B. B. P.; Stappers, B. W.; Babak, S.; Keith, M. J.; Antoniadis, J.; Bassa, C. G.; Caballero, R. N.; Champion, D. J.; Cognard, I.; Desvignes, G.; Graikou, E.; Guillemot, L.; Janssen, G. H.; Karuppusamy, R.; Kramer, M.; Lazarus, P.; Lentati, L.; Liu, K.; Lyne, A. G.; McKee, J. W.; Osłowski, S.; Perrodin, D.; Sanidas, S. A.; Sesana, A.; Shaifullah, G.; Theureau, G.; Verbiest, J. P. W.; Taylor, S. R.

2018-07-01

We search for continuous gravitational waves (CGWs) produced by individual supermassive black hole binaries in circular orbits using high-cadence timing observations of PSR J1713+0747. We observe this millisecond pulsar using the telescopes in the European Pulsar Timing Array with an average cadence of approximately 1.6 d over the period between 2011 April and 2015 July, including an approximately daily average between 2013 February and 2014 April. The high-cadence observations are used to improve the pulsar timing sensitivity across the gravitational wave frequency range of 0.008-5μHz. We use two algorithms in the analysis, including a spectral fitting method and a Bayesian approach. For an independent comparison, we also use a previously published Bayesian algorithm. We find that the Bayesian approaches provide optimal results and the timing observations of the pulsar place a 95 per cent upper limit on the sky-averaged strain amplitude of CGWs to be ≲3.5 × 10-13 at a reference frequency of 1 μHz. We also find a 95 per cent upper limit on the sky-averaged strain amplitude of low-frequency CGWs to be ≲1.4 × 10-14 at a reference frequency of 20 nHz.

Improving timing sensitivity in the microhertz frequency regime: limits from PSR J1713+0747 on gravitational waves produced by super-massive black-hole binaries

NASA Astrophysics Data System (ADS)

Perera, B. B. P.; Stappers, B. W.; Babak, S.; Keith, M. J.; Antoniadis, J.; Bassa, C. G.; Caballero, R. N.; Champion, D. J.; Cognard, I.; Desvignes, G.; Graikou, E.; Guillemot, L.; Janssen, G. H.; Karuppusamy, R.; Kramer, M.; Lazarus, P.; Lentati, L.; Liu, K.; Lyne, A. G.; McKee, J. W.; Osłowski, S.; Perrodin, D.; Sanidas, S. A.; Sesana, A.; Shaifullah, G.; Theureau, G.; Verbiest, J. P. W.; Taylor, S. R.

2018-05-01

We search for continuous gravitational waves (CGWs) produced by individual super-massive black-hole binaries (SMBHBs) in circular orbits using high-cadence timing observations of PSR J1713+0747. We observe this millisecond pulsar using the telescopes in the European Pulsar Timing Array (EPTA) with an average cadence of approximately 1.6 days over the period between April 2011 and July 2015, including an approximately daily average between February 2013 and April 2014. The high-cadence observations are used to improve the pulsar timing sensitivity across the GW frequency range of 0.008 - 5 μHz. We use two algorithms in the analysis, including a spectral fitting method and a Bayesian approach. For an independent comparison, we also use a previously published Bayesian algorithm. We find that the Bayesian approaches provide optimal results and the timing observations of the pulsar place a 95 per cent upper limit on the sky-averaged strain amplitude of CGWs to be ≲ 3.5 × 10-13 at a reference frequency of 1 μHz. We also find a 95 per cent upper limit on the sky-averaged strain amplitude of low-frequency CGWs to be ≲ 1.4 × 10-14 at a reference frequency of 20 nHz.

Faster and exact implementation of the continuous cellular automaton for anisotropic etching simulations

NASA Astrophysics Data System (ADS)

Ferrando, N.; Gosálvez, M. A.; Cerdá, J.; Gadea, R.; Sato, K.

2011-02-01

The current success of the continuous cellular automata for the simulation of anisotropic wet chemical etching of silicon in microengineering applications is based on a relatively fast, approximate, constant time stepping implementation (CTS), whose accuracy against the exact algorithm—a computationally slow, variable time stepping implementation (VTS)—has not been previously analyzed in detail. In this study we show that the CTS implementation can generate moderately wrong etch rates and overall etching fronts, thus justifying the presentation of a novel, exact reformulation of the VTS implementation based on a new state variable, referred to as the predicted removal time (PRT), and the use of a self-balanced binary search tree that enables storage and efficient access to the PRT values in each time step in order to quickly remove the corresponding surface atom/s. The proposed PRT method reduces the simulation cost of the exact implementation from {O}(N^{5/3}) to {O}(N^{3/2} log N) without introducing any model simplifications. This enables more precise simulations (only limited by numerical precision errors) with affordable computational times that are similar to the less precise CTS implementation and even faster for low reactivity systems.

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

Duchaineau, M.; Wolinsky, M.; Sigeti, D.E.

Real-time terrain rendering for interactive visualization remains a demanding task. We present a novel algorithm with several advantages over previous methods: our method is unusually stingy with polygons yet achieves real-time performance and is scalable to arbitrary regions and resolutions. The method provides a continuous terrain mesh of specified triangle count having provably minimum error in restricted but reasonably general classes of permissible meshes and error metrics. Our method provides an elegant solution to guaranteeing certain elusive types of consistency in scenes produced by multiple scene generators which share a common finest-resolution database but which otherwise operate entirely independently. Thismore » consistency is achieved by exploiting the freedom of choice of error metric allowed by the algorithm to provide, for example, multiple exact lines-of-sight in real-time. Our methods rely on an off-line pre-processing phase to construct a multi-scale data structure consisting of triangular terrain approximations enhanced ({open_quotes}thickened{close_quotes}) with world-space error information. In real time, this error data is efficiently transformed into screen-space where it is used to guide a greedy top-down triangle subdivision algorithm which produces the desired minimal error continuous terrain mesh. Our algorithm has been implemented and it operates at real-time rates.« less

A Depth-Averaged 2-D Simulation for Coastal Barrier Breaching Processes

DTIC Science & Technology

2011-05-01

including bed change and variable flow density in the flow continuity and momentum equations. The model adopts the HLL approximate Riemann solver to handle...flow density in the flow continuity and momentum equations. The model adopts the HLL approximate Riemann solver to handle the mixed-regime flows near...18 547 Keulegan equation or the Bernoulli equation, and the breach morphological change is determined using simplified sediment transport models

PREDICTION OF SOLAR FLARE SIZE AND TIME-TO-FLARE USING SUPPORT VECTOR MACHINE REGRESSION

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

Boucheron, Laura E.; Al-Ghraibah, Amani; McAteer, R. T. James

We study the prediction of solar flare size and time-to-flare using 38 features describing magnetic complexity of the photospheric magnetic field. This work uses support vector regression to formulate a mapping from the 38-dimensional feature space to a continuous-valued label vector representing flare size or time-to-flare. When we consider flaring regions only, we find an average error in estimating flare size of approximately half a geostationary operational environmental satellite (GOES) class. When we additionally consider non-flaring regions, we find an increased average error of approximately three-fourths a GOES class. We also consider thresholding the regressed flare size for the experimentmore » containing both flaring and non-flaring regions and find a true positive rate of 0.69 and a true negative rate of 0.86 for flare prediction. The results for both of these size regression experiments are consistent across a wide range of predictive time windows, indicating that the magnetic complexity features may be persistent in appearance long before flare activity. This is supported by our larger error rates of some 40 hr in the time-to-flare regression problem. The 38 magnetic complexity features considered here appear to have discriminative potential for flare size, but their persistence in time makes them less discriminative for the time-to-flare problem.« less

Recurrent papillary craniopharyngioma with BRAF V600E mutation treated with dabrafenib: case report.

PubMed

Himes, Benjamin T; Ruff, Michael W; Van Gompel, Jaimie J; Park, Sean S; Galanis, Evanthia; Kaufmann, Timothy J; Uhm, Joon H

2018-04-27

The authors present the case of a man with a papillary craniopharyngioma, first diagnosed at 47 years of age, who experienced multiple recurrences. Review of the pathologic specimen from his first resection demonstrated the BRAF V600E mutation. With his most recent recurrence following previous surgery and radiotherapy, at 52 years of age, the decision was made to initiate treatment with the BRAF V600E inhibitor dabrafenib. Imaging following initiation of dabrafenib demonstrated reduction in tumor size. He remained on dabrafenib therapy for approximately 1 year and continued to demonstrate a good clinical result. At that time the decision was made to discontinue dabrafenib therapy and follow up with serial imaging. After more than 1 year of follow-up since stopping dabrafenib, the patient has continued to do well with no radiographic evidence of tumor progression and continues to be monitored with frequent interval imaging.

27 CFR 9.141 - Escondido Valley.

Code of Federal Regulations, 2012 CFR

2012-04-01

... westerly direction approximately 17 miles; (5) The boundary continues to follow the 3000 foot contour line... intermittent stream approximately 18 miles east of the city of Fort Stockton (standard reference GE3317 on the... easterly direction approximately 9 miles until a southbound trail diverges from I-10 just past the point...

27 CFR 9.141 - Escondido Valley.

Code of Federal Regulations, 2010 CFR

2010-04-01

... westerly direction approximately 17 miles; (5) The boundary continues to follow the 3000 foot contour line... intermittent stream approximately 18 miles east of the city of Fort Stockton (standard reference GE3317 on the... easterly direction approximately 9 miles until a southbound trail diverges from I-10 just past the point...

27 CFR 9.141 - Escondido Valley.

Code of Federal Regulations, 2014 CFR

2014-04-01

... westerly direction approximately 17 miles; (5) The boundary continues to follow the 3000 foot contour line... intermittent stream approximately 18 miles east of the city of Fort Stockton (standard reference GE3317 on the... easterly direction approximately 9 miles until a southbound trail diverges from I-10 just past the point...

27 CFR 9.141 - Escondido Valley.

Code of Federal Regulations, 2013 CFR

2013-04-01

... westerly direction approximately 17 miles; (5) The boundary continues to follow the 3000 foot contour line... intermittent stream approximately 18 miles east of the city of Fort Stockton (standard reference GE3317 on the... easterly direction approximately 9 miles until a southbound trail diverges from I-10 just past the point...

27 CFR 9.141 - Escondido Valley.

Code of Federal Regulations, 2011 CFR

2011-04-01

... westerly direction approximately 17 miles; (5) The boundary continues to follow the 3000 foot contour line... intermittent stream approximately 18 miles east of the city of Fort Stockton (standard reference GE3317 on the... easterly direction approximately 9 miles until a southbound trail diverges from I-10 just past the point...

Photometric behavior and general characteristics of the nova HR Delphini

NASA Astrophysics Data System (ADS)

Raikova, D.

The light curve and the B-V color-index curve of HR Del were constructed on the basis of published UBV observations. From the normal color indices, the effective photosphere temperature and radius were determined using calibrations for normal stars. As the brightness reached its peak, the effective photosphere was expanding with a velocity of approximately 23 km/s, which is more than 10 times less than the gas velocity. This phenomenon is explained by decreasing continuous opacity as the ejected gas expands.

Simplified stock markets described by number operators

NASA Astrophysics Data System (ADS)

Bagarello, F.

2009-06-01

In this paper we continue our systematic analysis of the operatorial approach previously proposed in an economical context and we discuss a mixed toy model of a simplified stock market, i.e. a model in which the price of the shares is given as an input. We deduce the time evolution of the portfolio of the various traders of the market, as well as of other observable quantities. As in a previous paper, we solve the equations of motion by means of a fixed point like approximation.

Composite superconducting wires obtained by high-rate tinning in molten Bi-Pb-Sr-Ca-Cu-O system

NASA Technical Reports Server (NTRS)

Grozav, A. D.; Konopko, L. A.; Leporda, N. I.

1990-01-01

The preparation of high-T(sub c) superconducting long composite wires by short-time tinning of the metal wires in a molten Bi-Pb-Sr-Ca-Cu-O compound is discussed. The application of this method to the high-T(sub c) materials is tested, possibly for the first time. The initial materials used for this experiment were ceramic samples with nominal composition Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) and T(sub c) = 80 K prepared by the ordinary solid-state reaction, and industrial copper wires from 100 to 400 microns in diameter and from 0.5 to 1 m long. The continuously moving wires were let through a small molten zone (approximately 100 cubic mm). The Bi-based high-T(sub c) ceramics in a molten state is a viscous liquid and it has a strongly pronounced ability to spread on metal wire surfaces. The maximum draw rate of the Cu-wire, at which a dense covering is still possible, corresponds to the time of direct contact of wire surfaces and liquid ceramics for less than 0.1 s. A high-rate draw of the wire permits a decrease in the reaction of the oxide melt and Cu-wire. This method of manufacture led to the fabrication of wire with a copper core in a dense covering with uniform thickness of about h approximately equal to 5 to 50 microns. Composite wires with h approximately equal to 10 microns (h/d approximately equal to 0.1) sustained bending on a 15 mm radius frame without cracking during flexing.

Flexible echolocation behavior of trawling bats during approach of continuous or transient prey cues

PubMed Central

Übernickel, Kirstin; Tschapka, Marco; Kalko, Elisabeth K. V.

2013-01-01

Trawling bats use echolocation not only to detect and classify acoustically continuous cues originated from insects at and above water surfaces, but also to detect small water-dwelling prey items breaking the water surface for a very short time, producing only transient cues to be perceived acoustically. Generally, bats need to adjust their echolocation behavior to the specific task on hand, and because of the diversity of prey cues they use in hunting, trawling bats should be highly flexible in their echolocation behavior. We studied the adaptations in the behavior of Noctilio leporinus when approaching either a continuous cue or a transient cue that disappeared during the approach of the bat. Normally the bats reacted by dipping their feet in the water at the cue location. We found that the bats typically started to adapt their calling behavior at approximately 410 ms before prey contact in continuous cue trials, but were also able to adapt their approach behavior to stimuli onsets as short as 177 ms before contact, within a minimum reaction time of 50.9 ms in response to transient cues. In both tasks the approach phase ended between 32 and 53 ms before prey contact. Call emission always continued after the end of the approach phase until around prey contact. In some failed capture attempts, call emission did not cease at all after prey contact. Probably bats used spatial memory to dip at the original location of the transient cue after its disappearance. The duration of the pointed dips was significantly longer in transient cue trials than in continuous cue trials. Our results suggest that trawling bats possess the ability to modify their generally rather stereotyped echolocation behavior during approaches within very short reaction times depending on the sensory information available. PMID:23675352

Anomaly in the quiet-time helium spectrum at 1 MeV per nucleon

NASA Technical Reports Server (NTRS)

Gloeckler, G.; Hovestadt, D.; Klecker, B.; Vollmer, O.; Fan, C. Y.

1975-01-01

An unusual spectral feature and anomalously large abundance of helium between 0.6 and approximately 2 MeV per nucleon observed during the most quiet time periods in 1974 and 1975 indicate the presence of low energy helium of an unknown origin. Alphas below 0.6 MeV per nucleon and protons below 1.5 MeV have an E to the minus 1.8 power spectrum and the proton to alpha ratio is about 30. These less than or equal 1 MeV particles are found to be emitted continuously by the sun even during its most inactive periods.

Semiclassical Wheeler-DeWitt equation: Solutions for long-wavelength fields

NASA Astrophysics Data System (ADS)

Salopek, D. S.; Stewart, J. M.; Parry, J.

1993-07-01

In the long-wavelength approximation, a general set of semiclassical wave functionals is given for gravity and matter interacting in 3+1 dimensions. In the long-wavelength theory, one neglects second-order spatial gradients in the energy constraint. These solutions satisfy the Hamilton-Jacobi equation, the momentum constraint, and the equation of continuity. It is essential to introduce inhomogeneities to discuss the role of time. The time hypersurface is chosen to be a homogeneous field in the wave functional. It is shown how to introduce tracer particles through a dust field χ into the dynamical system. The formalism can be used to describe stochastic inflation.

Seismological Aspects of the August 7th Zhouqu Debris Flows

NASA Astrophysics Data System (ADS)

Dan, Y.; Huang, X.

2016-12-01

Broadband seismic records have been proven to be a sufficient tool in extracting movement characteristics of debris flows in the last decades. The catastrophic Sanyanyu and Luojiayu debris flows, which were induced by a heavy rainfall, occurred at approximately the midnight of August 7th, 2010 (Beijing time, UTC+8) and claimed 1,765 lives. Broadband seismic signals recorded by the Zhouqu seismic station positioned only 150 meters away from the exit are acquired and analyzed in this study. Seismic signals reveal that the Sanyanyu debris flow started developing after a major rock collapse at approximately 23:23:50. The formation time of the Sanyanyu debris flow to separate its development stage and maturity stage was determined at 23:33:15 using spectrograms and amplitude variation patterns of seismic signals. Seismic signals, before and after the formation time, have distinctively different frequency characteristics. The frequency content of seismic signals generated by the maturity stage is more regular than that generated by the development stage. The maturity stage was further divided into five sub stages according to its amplitude variation patterns, including three increase sub stages and two stable sub stages alternately distributed. These five sub stages belong to two processes of the Sanyanyu debris flow which generate seismic signals with different frequency contents. The main frequency band of the first four sub stages continuously varies from approximately 2 - 8.5 Hz at start to approximately 3 - 9.5 Hz in the end. For the last sub stage, the upper boundary of the main frequency increases in a near linear way and reaches approximately 13 - 16 Hz in the end. Two sub stages are recognized from the satellite image of the Sanyanyu flow path, and the mean movement velocities of the Sanyanyu debris flow during these two sub stages are estimated to be 9.2 m/s and 9.7 m/s respectively.

Skin welding using pulsed laser radiation and a dye

NASA Astrophysics Data System (ADS)

Fried, Nathaniel M.; Walsh, Joseph T., Jr.

1998-07-01

Previous skin welding studies have used continuous wave (CW) delivery of radiation. However, heat diffusion during irradiation prevents strong welds from being achieved without creating large zones of thermal damage to surrounding tissue. This damage may prevent normal wound healing. Strong welds and minimal thermal damage can be achieved by introducing a dye and delivering the radiation in a pulsed mode. Two-cm-long, full-thickness incisions were made in guinea pig skin. India ink was used as an absorber, and egg white albumin was used as an adhesive. A 5-mm-diameter spot of CW, 1.06-micrometer Nd:YAG laser radiation was scanned over the weld site, producing 100 millisecond pulses. The cooling time between scans and number of scans was varied. Thermal damage zones were measured using a transmission polarizing microscope to identify birefringence changes in tissue. Tensile strengths were measured using a tensiometer. For pulsed welding and long cooling times, weld strengths of 2.4 kg/cm2 were measured, and thermal damage to the epidermis was limited to approximately 500 micrometers. With CW welding, comparable weld strengths resulted in approximately 2700 micrometer of thermal damage. CW laser radiation weld strengths were only 0.6 kg/cm2 when thermal damage in the epidermis was limited to approximately 500 micrometers.

Method of conditional moments (MCM) for the Chemical Master Equation: a unified framework for the method of moments and hybrid stochastic-deterministic models.

PubMed

Hasenauer, J; Wolf, V; Kazeroonian, A; Theis, F J

2014-09-01

The time-evolution of continuous-time discrete-state biochemical processes is governed by the Chemical Master Equation (CME), which describes the probability of the molecular counts of each chemical species. As the corresponding number of discrete states is, for most processes, large, a direct numerical simulation of the CME is in general infeasible. In this paper we introduce the method of conditional moments (MCM), a novel approximation method for the solution of the CME. The MCM employs a discrete stochastic description for low-copy number species and a moment-based description for medium/high-copy number species. The moments of the medium/high-copy number species are conditioned on the state of the low abundance species, which allows us to capture complex correlation structures arising, e.g., for multi-attractor and oscillatory systems. We prove that the MCM provides a generalization of previous approximations of the CME based on hybrid modeling and moment-based methods. Furthermore, it improves upon these existing methods, as we illustrate using a model for the dynamics of stochastic single-gene expression. This application example shows that due to the more general structure, the MCM allows for the approximation of multi-modal distributions.

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.

Linear self-focusing of continuous UV laser beam in photo-thermo-refractive glasses.

PubMed

Sidorov, Alexander I; Gorbyak, Veronika V; Nikonorov, Nikolay V

2018-03-19

The experimental and theoretical study of continuous UV laser beam propagation through thick silver-containing photo-thermo-refractive glass is presented. It is shown for the first time that self-action of UV Gaussian beam in glass results in its self-focusing. The observed linear effect is non-reversible and is caused by the transformation of subnanosized charged silver molecular clusters to neutral state under UV laser radiation. Such transformation is accompanied by the increase of molecular clusters polarizability and the refractive index increase in irradiated area. As a result, an extended positive lens is formed in glass bulk. In a theoretical study of linear self-focusing effect, the "aberration-free" approximation was used, taking into account spatial distribution of induced absorption.

Continuous supercritical synthesis and dielectric behaviour of the whole BST solid solution.

PubMed

Reverón, H; Elissalde, C; Aymonier, C; Bousquet, C; Maglione, M; Cansell, F

2006-07-28

In this study we show that pure and well crystallized nanoparticles of Ba(x)Sr(1-x)TiO(3) (BST) can be synthesized over the entire range of composition through the hydrolysis and further crystallization of alkoxide precursors under supercritical conditions. To our knowledge, this is the first time that the whole ferroelectric solid solution has been produced in a continuous way, using the same experimental conditions. The composition of the powder can be easily controlled by adjusting the feed solution composition. The powders consist of soft-aggregated monocrystalline nanoparticles with an average particle size ranging from approximately 20 to 40 nm. Ferroelectric ceramics with accurately adjustable Curie temperature (100-390 K) can thus be obtained by sintering.

Evaluation of Criteria for the Detection of Fires in Underground Conveyor Belt Haulageways.

PubMed

Litton, Charles D; Perera, Inoka Eranda

2012-07-01

Large-scale experiments were conducted in an above-ground gallery to simulate typical fires that develop along conveyor belt transport systems within underground coal mines. In the experiments, electrical strip heaters, imbedded ~5 cm below the top surface of a large mass of coal rubble, were used to ignite the coal, producing an open flame. The flaming coal mass subsequently ignited 1.83-meter-wide conveyor belts located approximately 0.30 m above the coal surface. Gas samples were drawn through an averaging probe located approximately 20 m downstream of the coal for continuous measurement of CO, CO 2 , and O 2 as the fire progressed through the stages of smoldering coal, flaming coal, and flaming conveyor belt. Also located approximately 20 m from the fire origin and approximately 0.5 m below the roof of the gallery were two commercially available smoke detectors, a light obscuration meter, and a sampling probe for measurement of total mass concentration of smoke particles. Located upstream of the fire origin and also along the wall of the gallery at approximately 14 m and 5 m upstream were two video cameras capable of both smoke and flame detection. During the experiments, alarm times of the smoke detectors and video cameras were measured while the smoke obscuration and total smoke mass were continually measured. Twelve large-scale experiments were conducted using three different types of fire-resistant conveyor belts and four air velocities for each belt. The air velocities spanned the range from 1.0 m/s to 6.9 m/s. The results of these experiments are compared to previous large-scale results obtained using a smaller fire gallery and much narrower (1.07-m) conveyor belts to determine if the fire detection criteria previously developed (1) remained valid for the wider conveyor belts. Although some differences between these and the previous experiments did occur, the results, in general, compare very favorably. Differences are duly noted and their impact on fire detection discussed.

Global Ultraviolet Imaging Processing for the GGS Polar Visible Imaging System (VIS)

NASA Technical Reports Server (NTRS)

Frank, L. A.

1997-01-01

The Visible Imaging System (VIS) on Polar spacecraft of the NASA Goddard Space Flight Center was launched into orbit about Earth on February 24, 1996. Since shortly after launch, the Earth Camera subsystem of the VIS has been operated nearly continuously to acquire far ultraviolet, global images of Earth and its northern and southern auroral ovals. The only exceptions to this continuous imaging occurred for approximately 10 days at the times of the Polar spacecraft re-orientation maneuvers in October, 1996 and April, 1997. Since launch, approximately 525,000 images have been acquired with the VIS Earth Camera. The VIS instrument operational health continues to be excellent. Since launch, all systems have operated nominally with all voltages, currents, and temperatures remaining at nominal values. In addition, the sensitivity of the Earth Camera to ultraviolet light has remained constant throughout the operation period. Revised flight software was uploaded to the VIS in order to compensate for the spacecraft wobble. This is accomplished by electronic shuttering of the sensor in synchronization with the 6-second period of the wobble, thus recovering the original spatial resolution obtainable with the VIS Earth Camera. In addition, software patches were uploaded to make the VIS immune to signal dropouts that occur in the sliprings of the despun platform mechanism. These changes have worked very well. The VIS and in particular the VIS Earth Camera is fully operational and will continue to acquire global auroral images as the sun progresses toward solar maximum conditions after the turn of the century.

Insights into shallow magmatic processes at Kīlauea Volcano, Hawaíi, from a multiyear continuous gravity time series

NASA Astrophysics Data System (ADS)

Poland, Michael P.; Carbone, Daniele

2016-07-01

Continuous gravity data collected near the summit eruptive vent at Kīlauea Volcano, Hawaíi, during 2011-2015 show a strong correlation with summit-area surface deformation and the level of the lava lake within the vent over periods of days to weeks, suggesting that changes in gravity reflect variations in volcanic activity. Joint analysis of gravity and lava level time series data indicates that over the entire time period studied, the average density of the lava within the upper tens to hundreds of meters of the summit eruptive vent remained low—approximately 1000-1500 kg/m3. The ratio of gravity change (adjusted for Earth tides and instrumental drift) to lava level change measured over 15 day windows rose gradually over the course of 2011-2015, probably reflecting either (1) a small increase in the density of lava within the eruptive vent or (2) an increase in the volume of lava within the vent due to gradual vent enlargement. Superimposed on the overall time series were transient spikes of mass change associated with inflation and deflation of Kīlauea's summit and coincident changes in lava level. The unexpectedly strong mass variations during these episodes suggest magma flux to and from the shallow magmatic system without commensurate deformation, perhaps indicating magma accumulation within, and withdrawal from, void space—a process that might not otherwise be apparent from lava level and deformation data alone. Continuous gravity data thus provide unique insights into magmatic processes, arguing for continued application of the method at other frequently active volcanoes.

Uplift and submarine formation of some Melanesian porphyry copper deposits: Stable isotope evidence

USGS Publications Warehouse

Chivas, A.R.; O'Neil, J.R.; Katchan, G.

1984-01-01

Hydrogen and oxygen isotope analyses of sericites and kaolinites from four young porphyry copper deposits (Ok Tedi (1.2 Ma) and Yandera (6.5 Ma), Papua New Guinea; Koloula (1.5 Ma), Solomon Islands; and Waisoi (<5 Ma), Fiji) indicate that the fluids from which these minerals precipitated were of mixed magmatic and non-magmatic sources. The non-magmatic component of the fluid from the island arc deposits (Koloula, Waisoi) was ocean water. For Ok Tedi, the non-magmatic component was a meteoric water with an isotopic composition different from that of the present meteoric water in the region. The isotopic signature of the former meteoric water is consistent with a surface elevation of 200 m a.s.l. or less at the time of mineralization. The deposit was later exposed and supergene kaolinitization commenced at approximately 1200 m a.s.l. Uplift and erosion has continued to the present at which time the elevation of the exposed deposit is 1800 m a.s.l. This rate of uplift is consistent with that known from other geological evidence. If the rate of uplift were approximately constant during the last 1.2 Ma, the age of supergene enrichment can be dated at approximately 0.4 Ma B.P. Similarly, influx of meteoric water at Yandera occurred when the ground surface above the deposit was at an elevation of approximately 600 m a.s.l. The deposit's present elevation is 1600 m a.s.l. In this case a total uplift of approximately 2.2 km is indicated, with removal of 1.2 km of overburden by erosion. ?? 1984.

Analytical solution of the transient temperature profile in gain medium of passively Q-switched microchip laser.

PubMed

Han, Xiahui; Li, Jianlang

2014-11-01

The transient temperature evolution in the gain medium of a continuous wave (CW) end-pumped passively Q-switched microchip (PQSM) laser is analyzed. By approximating the time-dependent population inversion density as a sawtooth function of time and treating the time-dependent pump absorption of a CW end-pumped PQSM laser as the superposition of an infinite series of short pumping pulses, the analytical expressions of transient temperature evolution and distribution in the gain medium for four- and three-level laser systems, respectively, are given. These analytical solutions are applied to evaluate the transient temperature evolution and distribution in the gain medium of CW end-pumped PQSM Nd:YAG and Yb:YAG lasers.

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

M. P. Jensen; Toto, T.

Standard Atmospheric Radiation Measurement (ARM) Climate Research Facility sounding files provide atmospheric state data in one dimension of increasing time and height per sonde launch. Many applications require a quick estimate of the atmospheric state at higher time resolution. The INTERPOLATEDSONDE (i.e., Interpolated Sounding) Value-Added Product (VAP) transforms sounding data into continuous daily files on a fixed time-height grid, at 1-minute time resolution, on 332 levels, from the surface up to a limit of approximately 40 km. The grid extends that high so the full height of soundings can be captured; however, most soundings terminate at an altitude between 25more » and 30 km, above which no data is provided. Between soundings, the VAP linearly interpolates atmospheric state variables in time for each height level. In addition, INTERPOLATEDSONDE provides relative humidity scaled to microwave radiometer (MWR) observations.« less

27 CFR 9.194 - San Antonio Valley.

Code of Federal Regulations, 2014 CFR

2014-04-01

... southeast in a straight line for approximately 5 miles across sections 24 and 25, T23S, R9E, and sections 30... Tierra Redonda Mountain map; then (3) Continue southeast in a straight line for approximately 3.25 miles... the Bradley map; then (4) Proceed straight south for approximately 2.5 miles along the eastern...

27 CFR 9.134 - Oakville.

Code of Federal Regulations, 2014 CFR

2014-04-01

... Highway 29, then continuing in a straight line approximately .1 mile to the peak of the 320+ foot hill... direction in a straight line approximately 1.7 miles along Skellenger Lane, past its intersection with Conn... quadrangle map); (2) Then south along the center of the river bed approximately .4 miles to the point where...

27 CFR 9.134 - Oakville.

Code of Federal Regulations, 2012 CFR

2012-04-01

... Highway 29, then continuing in a straight line approximately .1 mile to the peak of the 320+ foot hill... direction in a straight line approximately 1.7 miles along Skellenger Lane, past its intersection with Conn... quadrangle map); (2) Then south along the center of the river bed approximately .4 miles to the point where...

A general theory on frequency and time-frequency analysis of irregularly sampled time series based on projection methods - Part 2: Extension to time-frequency analysis

NASA Astrophysics Data System (ADS)

Lenoir, Guillaume; Crucifix, Michel

2018-03-01

Geophysical time series are sometimes sampled irregularly along the time axis. The situation is particularly frequent in palaeoclimatology. Yet, there is so far no general framework for handling the continuous wavelet transform when the time sampling is irregular. Here we provide such a framework. To this end, we define the scalogram as the continuous-wavelet-transform equivalent of the extended Lomb-Scargle periodogram defined in Part 1 of this study (Lenoir and Crucifix, 2018). The signal being analysed is modelled as the sum of a locally periodic component in the time-frequency plane, a polynomial trend, and a background noise. The mother wavelet adopted here is the Morlet wavelet classically used in geophysical applications. The background noise model is a stationary Gaussian continuous autoregressive-moving-average (CARMA) process, which is more general than the traditional Gaussian white and red noise processes. The scalogram is smoothed by averaging over neighbouring times in order to reduce its variance. The Shannon-Nyquist exclusion zone is however defined as the area corrupted by local aliasing issues. The local amplitude in the time-frequency plane is then estimated with least-squares methods. We also derive an approximate formula linking the squared amplitude and the scalogram. Based on this property, we define a new analysis tool: the weighted smoothed scalogram, which we recommend for most analyses. The estimated signal amplitude also gives access to band and ridge filtering. Finally, we design a test of significance for the weighted smoothed scalogram against the stationary Gaussian CARMA background noise, and provide algorithms for computing confidence levels, either analytically or with Monte Carlo Markov chain methods. All the analysis tools presented in this article are available to the reader in the Python package WAVEPAL.

Development of a solar-powered infrared injection laser microminiature transmitting system

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

Falter, D.D.; Alley, G.T.; Falter, K.G.

1989-01-01

A solar-powered infrared microminiature transmitting system is being developed to provide scientists with a tool to continuously track and study Africanized bees. Present tracking methods have limited ranges and lack the capability of continuously tracking individual insects. Preliminary field tests of a stationary prototypic transmitter have demonstrated a range of 1.1 km. The basic design consists of an array of nine 1-mm{sup 2} solar cells, which collect energy for storage in a 1.0-{mu}F tantalum chip capacitor. When the capacitor has been charged to a sufficient level, the circuitry that monitors the capacitor voltage level wakes up'' and fires a 5-{mu}smore » pulse through an 840-nm GaAlAs injection laser diode. The process is then repeated, making the signal frequency (which ranges from 50 to 300 Hz) dependent on solar luminance. The solar cells, capacitor, and laser diode are mounted in hybrid microcircuit fashion directly on the silicon substrate containing the CMOS control and driver circuitry. The transmitter measures {approximately}4 {times} 6 mm and weighs {approximately}65 mg. The receiving system is based on an 8-in. telescope and a Si PIN diode detector. 8 refs., 10 figs.« less

Spike solutions in Gierer#x2013;Meinhardt model with a time dependent anomaly exponent

NASA Astrophysics Data System (ADS)

Nec, Yana

2018-01-01

Experimental evidence of complex dispersion regimes in natural systems, where the growth of the mean square displacement in time cannot be characterised by a single power, has been accruing for the past two decades. In such processes the exponent γ(t) in ⟨r2⟩ ∼ tγ(t) at times might be approximated by a piecewise constant function, or it can be a continuous function. Variable order differential equations are an emerging mathematical tool with a strong potential to model these systems. However, variable order differential equations are not tractable by the classic differential equations theory. This contribution illustrates how a classic method can be adapted to gain insight into a system of this type. Herein a variable order Gierer-Meinhardt model is posed, a generic reaction- diffusion system of a chemical origin. With a fixed order this system possesses a solution in the form of a constellation of arbitrarily situated localised pulses, when the components' diffusivity ratio is asymptotically small. The pattern was shown to exist subject to multiple step-like transitions between normal diffusion and sub-diffusion, as well as between distinct sub-diffusive regimes. The analytical approximation obtained permits qualitative analysis of the impact thereof. Numerical solution for typical cross-over scenarios revealed such features as earlier equilibration and non-monotonic excursions before attainment of equilibrium. The method is general and allows for an approximate numerical solution with any reasonably behaved γ(t).

Mixture Factor Analysis for Approximating a Nonnormally Distributed Continuous Latent Factor with Continuous and Dichotomous Observed Variables

ERIC Educational Resources Information Center

Wall, Melanie M.; Guo, Jia; Amemiya, Yasuo

2012-01-01

Mixture factor analysis is examined as a means of flexibly estimating nonnormally distributed continuous latent factors in the presence of both continuous and dichotomous observed variables. A simulation study compares mixture factor analysis with normal maximum likelihood (ML) latent factor modeling. Different results emerge for continuous versus…

Fast Mix Table Construction for Material Discretization

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

Johnson, Seth R

2013-01-01

An effective hybrid Monte Carlo--deterministic implementation typically requires the approximation of a continuous geometry description with a discretized piecewise-constant material field. The inherent geometry discretization error can be reduced somewhat by using material mixing, where multiple materials inside a discrete mesh voxel are homogenized. Material mixing requires the construction of a ``mix table,'' which stores the volume fractions in every mixture so that multiple voxels with similar compositions can reference the same mixture. Mix table construction is a potentially expensive serial operation for large problems with many materials and voxels. We formulate an efficient algorithm to construct a sparse mix table inmore » $$O(\\text{number of voxels}\\times \\log \\text{number of mixtures})$$ time. The new algorithm is implemented in ADVANTG and used to discretize continuous geometries onto a structured Cartesian grid. When applied to an end-of-life MCNP model of the High Flux Isotope Reactor with 270 distinct materials, the new method improves the material mixing time by a factor of 100 compared to a naive mix table implementation.« less

The time lapse experiment in Al Wasse water pumping field in Saudi Arabia by an ultra-stable seismic source (ACROSS)

NASA Astrophysics Data System (ADS)

AlAnezi, Ghunaim; Kasahara, Junzo; AlDamegh, Khaled S.; Lafouza, Omar; AlYousef, Khaled; Almalki, Fahad; Nishiyama, Eichiro

2015-04-01

We have developed the time lapse technology for EOR (enhanced oil recovery) and CCS (Carbon Capture and Storage) using a very stable and continuous seismic source called ACROSS (Accurately Controlled Routinely Operated Signal System) with multi-geophones. Since 2011, we have tested this technology in the context of carbonate rocks in Saudi Arabia. The Al Wasee water pumping site approximately 120 km east of Riyadh city has been selected as a trail-site. The intention is to observe the changes in aquifers induced by pumping operations. One ACROSS source unit was installed at the Al Wasee site in December 2011 and we are continuing the field test. The instrument has been operated from 10 to 50 Hz with 40 tons-f at 50 Hz. Using alternatively clockwise and counter-clockwise rotations we can synthesize vertical and horizontal forces, respectively. 31 3C-geophones in 2 km x 3 km area and four nearby 3Cgeophones have been used to monitor the seismic changes from pumping the water. The one and half month data between December 2012 and February 2013 show continuous and clear change of observed waveforms for all 31 stations while the source signature did not change. The change is closest and fastest at the station #42. The cause of continuous change with time is interpreted as pumping of water by 64 wells located in this field.

Parental preference and perspectives on continuous pulse oximetry in infants and children with bronchiolitis

PubMed Central

Hendaus, Mohamed A; Nassar, Suzan; Leghrouz, Bassil A; Alhammadi, Ahmed H; Alamri, Mohammed

2018-01-01

Objective The purpose of the study was to investigate parental preference of continuous pulse oximetry in infants and children with bronchiolitis. Materials and methods A cross-sectional prospective study was conducted at Hamad Medical Corporation in Qatar. Parents of infants and children <24 months old and hospitalized with bronchiolitis were offered an interview survey. Results A total of 132 questionnaires were completed (response rate 100%). Approximately 90% of participants were 20–40 years of age, and 85% were females. The mean age of children was 7.2±5.8 months. Approximately eight in ten parents supported the idea of continuous pulse oximetry in children with bronchiolitis. Almost 43% of parents believed that continuous pulse-oximetry monitoring would delay their children’s hospital discharge. Interestingly, approximately 85% of caregivers agreed that continuous pulse oximetry had a good impact on their children’s health. In addition, around one in two of the participants stated that good bedside examinations can obviate the need for continuous pulse oximetry. Furthermore, 80% of parents believed that continuous pulse-oximetry monitoring would give the health-care provider a good sense of security regarding the child’s health. Finally, being a male parent was associated with significantly increased risk of reporting unnecessary fatigue, attributed to the sound of continuous pulse oximetry (P=0.031). Conclusion Continuous pulse-oximetry monitoring in children with bronchiolitis was perceived as reassuring for parents. Involving parents in decision-making is considered essential in the better management of children with bronchiolitis or any other disease. The first step to decrease continuous pulse oximetry will require provider education and change as well. Furthermore, we recommend proper counseling for parents, emphasizing that medical technology is not always essential, but is a complementary mode of managing a disease. PMID:29662305

Susceptible-infected-susceptible epidemics on networks with general infection and cure times.

PubMed

Cator, E; van de Bovenkamp, R; Van Mieghem, P

2013-06-01

The classical, continuous-time susceptible-infected-susceptible (SIS) Markov epidemic model on an arbitrary network is extended to incorporate infection and curing or recovery times each characterized by a general distribution (rather than an exponential distribution as in Markov processes). This extension, called the generalized SIS (GSIS) model, is believed to have a much larger applicability to real-world epidemics (such as information spread in online social networks, real diseases, malware spread in computer networks, etc.) that likely do not feature exponential times. While the exact governing equations for the GSIS model are difficult to deduce due to their non-Markovian nature, accurate mean-field equations are derived that resemble our previous N-intertwined mean-field approximation (NIMFA) and so allow us to transfer the whole analytic machinery of the NIMFA to the GSIS model. In particular, we establish the criterion to compute the epidemic threshold in the GSIS model. Moreover, we show that the average number of infection attempts during a recovery time is the more natural key parameter, instead of the effective infection rate in the classical, continuous-time SIS Markov model. The relative simplicity of our mean-field results enables us to treat more general types of SIS epidemics, while offering an easier key parameter to measure the average activity of those general viral agents.

Susceptible-infected-susceptible epidemics on networks with general infection and cure times

NASA Astrophysics Data System (ADS)

Cator, E.; van de Bovenkamp, R.; Van Mieghem, P.

2013-06-01

The classical, continuous-time susceptible-infected-susceptible (SIS) Markov epidemic model on an arbitrary network is extended to incorporate infection and curing or recovery times each characterized by a general distribution (rather than an exponential distribution as in Markov processes). This extension, called the generalized SIS (GSIS) model, is believed to have a much larger applicability to real-world epidemics (such as information spread in online social networks, real diseases, malware spread in computer networks, etc.) that likely do not feature exponential times. While the exact governing equations for the GSIS model are difficult to deduce due to their non-Markovian nature, accurate mean-field equations are derived that resemble our previous N-intertwined mean-field approximation (NIMFA) and so allow us to transfer the whole analytic machinery of the NIMFA to the GSIS model. In particular, we establish the criterion to compute the epidemic threshold in the GSIS model. Moreover, we show that the average number of infection attempts during a recovery time is the more natural key parameter, instead of the effective infection rate in the classical, continuous-time SIS Markov model. The relative simplicity of our mean-field results enables us to treat more general types of SIS epidemics, while offering an easier key parameter to measure the average activity of those general viral agents.

Hybrid deterministic/stochastic simulation of complex biochemical systems.

PubMed

Lecca, Paola; Bagagiolo, Fabio; Scarpa, Marina

2017-11-21

In a biological cell, cellular functions and the genetic regulatory apparatus are implemented and controlled by complex networks of chemical reactions involving genes, proteins, and enzymes. Accurate computational models are indispensable means for understanding the mechanisms behind the evolution of a complex system, not always explored with wet lab experiments. To serve their purpose, computational models, however, should be able to describe and simulate the complexity of a biological system in many of its aspects. Moreover, it should be implemented by efficient algorithms requiring the shortest possible execution time, to avoid enlarging excessively the time elapsing between data analysis and any subsequent experiment. Besides the features of their topological structure, the complexity of biological networks also refers to their dynamics, that is often non-linear and stiff. The stiffness is due to the presence of molecular species whose abundance fluctuates by many orders of magnitude. A fully stochastic simulation of a stiff system is computationally time-expensive. On the other hand, continuous models are less costly, but they fail to capture the stochastic behaviour of small populations of molecular species. We introduce a new efficient hybrid stochastic-deterministic computational model and the software tool MoBioS (MOlecular Biology Simulator) implementing it. The mathematical model of MoBioS uses continuous differential equations to describe the deterministic reactions and a Gillespie-like algorithm to describe the stochastic ones. Unlike the majority of current hybrid methods, the MoBioS algorithm divides the reactions' set into fast reactions, moderate reactions, and slow reactions and implements a hysteresis switching between the stochastic model and the deterministic model. Fast reactions are approximated as continuous-deterministic processes and modelled by deterministic rate equations. Moderate reactions are those whose reaction waiting time is greater than the fast reaction waiting time but smaller than the slow reaction waiting time. A moderate reaction is approximated as a stochastic (deterministic) process if it was classified as a stochastic (deterministic) process at the time at which it crosses the threshold of low (high) waiting time. A Gillespie First Reaction Method is implemented to select and execute the slow reactions. The performances of MoBios were tested on a typical example of hybrid dynamics: that is the DNA transcription regulation. The simulated dynamic profile of the reagents' abundance and the estimate of the error introduced by the fully deterministic approach were used to evaluate the consistency of the computational model and that of the software tool.

Galerkin v. discrete-optimal projection in nonlinear model reduction

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

Carlberg, Kevin Thomas; Barone, Matthew Franklin; Antil, Harbir

Discrete-optimal model-reduction techniques such as the Gauss{Newton with Approximated Tensors (GNAT) method have shown promise, as they have generated stable, accurate solutions for large-scale turbulent, compressible ow problems where standard Galerkin techniques have failed. However, there has been limited comparative analysis of the two approaches. This is due in part to difficulties arising from the fact that Galerkin techniques perform projection at the time-continuous level, while discrete-optimal techniques do so at the time-discrete level. This work provides a detailed theoretical and experimental comparison of the two techniques for two common classes of time integrators: linear multistep schemes and Runge{Kutta schemes.more » We present a number of new ndings, including conditions under which the discrete-optimal ROM has a time-continuous representation, conditions under which the two techniques are equivalent, and time-discrete error bounds for the two approaches. Perhaps most surprisingly, we demonstrate both theoretically and experimentally that decreasing the time step does not necessarily decrease the error for the discrete-optimal ROM; instead, the time step should be `matched' to the spectral content of the reduced basis. In numerical experiments carried out on a turbulent compressible- ow problem with over one million unknowns, we show that increasing the time step to an intermediate value decreases both the error and the simulation time of the discrete-optimal reduced-order model by an order of magnitude.« less

Kinetic Temperature and Carbon Dioxide from Broadband Infrared Limb Emission Measurements Taken from the TIMED/SABER Instrument

NASA Technical Reports Server (NTRS)

Mertens, Christopher J.; Russell III, James M.; Mlynczak, Martin G.; She, Chiao-Yao; Schmidlin, Francis J.; Goldberg, Richard A.; Lopez-Puertas, Manuel; Wintersteiner, Peter P.; Picard, Richard H.; Winick, Jeremy R.;

Pseudospectral collocation methods for fourth order differential equations

NASA Technical Reports Server (NTRS)

Malek, Alaeddin; Phillips, Timothy N.

1994-01-01

Collocation schemes are presented for solving linear fourth order differential equations in one and two dimensions. The variational formulation of the model fourth order problem is discretized by approximating the integrals by a Gaussian quadrature rule generalized to include the values of the derivative of the integrand at the boundary points. Collocation schemes are derived which are equivalent to this discrete variational problem. An efficient preconditioner based on a low-order finite difference approximation to the same differential operator is presented. The corresponding multidomain problem is also considered and interface conditions are derived. Pseudospectral approximations which are C1 continuous at the interfaces are used in each subdomain to approximate the solution. The approximations are also shown to be C3 continuous at the interfaces asymptotically. A complete analysis of the collocation scheme for the multidomain problem is provided. The extension of the method to the biharmonic equation in two dimensions is discussed and results are presented for a problem defined in a nonrectangular domain.

Stabilization of kerogen thermal maturation: Evidence from geothermometry and burial history reconstruction, Niobrara Limestone, Berthoud oil field, western Denver Basin, Colorado

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

Barker, C.E.; Crysdale, B.L.

1990-05-01

The burial history of this fractured Niobrara Limestone reservoir and source rock offers a setting for studying the stabilization of thermal maturity because soon after peak temperature of approximately 100{degree}C was reached, exhumation lowered temperature to about 60-70{degree}C. Vitrinite reflectance (Rm = 0.6-0.7%) and published clay mineralogy data from the Niobrara Limestone indicate that peak paleotemperature was approximately 100{degree}C. Fluid inclusion data also indicate oil migration occurred at 100{degree}C. Burial history reconstruction indicates 100{degree}C was reached in the Niobrara Limestone only during minimum burial, which occurred at 70 Ma and 8000 ft depth. However, erosion beginning at 70 Ma andmore » continuing until 50 Ma removed over 3,000 ft of rock. This depth of erosion agrees with an Rm of 0.4% measured in surface samples of the Pierre Shale. The exhumation of the reservoir decreased temperature by about 30{degree}C to near the corrected bottom-hole temperature of 50-70{degree}C. Lopatin time-temperature index (TTI) analysis suggests the Niobrara Limestone as a source rock matured to the oil generation stage (TTI = 10) about 25 Ma, significantly later than maximum burial, and after exhumation caused cooling. The Lopatin TTI method in this case seems to overestimate the influence of heating time. If time is an important factor, thermal maturity should continue to increase after peak burial and temperature so that vitrinite reflectance will not be comparable to peak paleotemperatures estimated from geothermometers set at near-peak temperature and those estimated from burial history reconstruction. The agreement between geothermometry and the burial history reconstruction in Berthoud State 4 suggests that the influence of heating time must be small. The elapsed time available at near peak temperatures was sufficient to allow stabilization of thermal maturation in this case.« less

Continuous monitoring and intrafraction target position correction during treatment improves target coverage for patients undergoing SBRT prostate therapy.

PubMed

Lovelock, D Michael; Messineo, Alessandra P; Cox, Brett W; Kollmeier, Marisa A; Zelefsky, Michael J

2015-03-01

To compare the potential benefits of continuous monitoring of prostate position and intervention (CMI) using 2-mm displacement thresholds during stereotactic body radiation therapy (SBRT) treatment to those of a conventional image-guided procedure involving single localization prior to treatment. Eighty-nine patients accrued to a prostate SBRT dose escalation protocol were implanted with radiofrequency transponder beacons. The planning target volume (PTV) margin was 5 mm in all directions, except for 3 mm in the posterior direction. The prostate was kept within 2 mm of its planned position by the therapists halting dose delivery and, if necessary, correcting the couch position. We computed the number, type, and time required for interventions and where the prostate would have been during dose delivery had there been, instead, a single image-guided setup procedure prior to each treatment. Distributions of prostate displacements were computed as a function of time. After the initial setup, 1.7 interventions per fraction were required, with a concomitant increase in time for dose delivery of approximately 65 seconds. Small systematic drifts in prostate position in the posterior and inferior directions were observed in the study patients. Without CMI, intrafractional motion would have resulted in approximately 10% of patients having a delivered dose that did not meet our clinical coverage requirement, that is, a PTV D95 of >90%. The posterior PTV margin required for 95% of the dose to be delivered with the target positioned within the PTV was computed as a function of time. The margin necessary was found to increase by 2 mm every 5 minutes, starting from the time of the imaging procedure. CMI using a tight 2-mm displacement threshold was not only feasible but was found to deliver superior PTV coverage compared with the conventional image-guided procedure in the SBRT setting. Copyright © 2015 Elsevier Inc. All rights reserved.

Continuous Monitoring and Intrafraction Target Position Correction During Treatment Improves Target Coverage for Patients Undergoing SBRT Prostate Therapy

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

Lovelock, D. Michael, E-mail: lovelocm@mskcc.org; Messineo, Alessandra P.; Cox, Brett W.

2015-03-01

Purpose: To compare the potential benefits of continuous monitoring of prostate position and intervention (CMI) using 2-mm displacement thresholds during stereotactic body radiation therapy (SBRT) treatment to those of a conventional image-guided procedure involving single localization prior to treatment. Methods and Materials: Eighty-nine patients accrued to a prostate SBRT dose escalation protocol were implanted with radiofrequency transponder beacons. The planning target volume (PTV) margin was 5 mm in all directions, except for 3 mm in the posterior direction. The prostate was kept within 2 mm of its planned position by the therapists halting dose delivery and, if necessary, correcting themore » couch position. We computed the number, type, and time required for interventions and where the prostate would have been during dose delivery had there been, instead, a single image-guided setup procedure prior to each treatment. Distributions of prostate displacements were computed as a function of time. Results: After the initial setup, 1.7 interventions per fraction were required, with a concomitant increase in time for dose delivery of approximately 65 seconds. Small systematic drifts in prostate position in the posterior and inferior directions were observed in the study patients. Without CMI, intrafractional motion would have resulted in approximately 10% of patients having a delivered dose that did not meet our clinical coverage requirement, that is, a PTV D95 of >90%. The posterior PTV margin required for 95% of the dose to be delivered with the target positioned within the PTV was computed as a function of time. The margin necessary was found to increase by 2 mm every 5 minutes, starting from the time of the imaging procedure. Conclusions: CMI using a tight 2-mm displacement threshold was not only feasible but was found to deliver superior PTV coverage compared with the conventional image-guided procedure in the SBRT setting.« less

Speed of feedforward and recurrent processing in multilayer networks of integrate-and-fire neurons.

PubMed

Panzeri, S; Rolls, E T; Battaglia, F; Lavis, R

2001-11-01

The speed of processing in the visual cortical areas can be fast, with for example the latency of neuronal responses increasing by only approximately 10 ms per area in the ventral visual system sequence V1 to V2 to V4 to inferior temporal visual cortex. This has led to the suggestion that rapid visual processing can only be based on the feedforward connections between cortical areas. To test this idea, we investigated the dynamics of information retrieval in multiple layer networks using a four-stage feedforward network modelled with continuous dynamics with integrate-and-fire neurons, and associative synaptic connections between stages with a synaptic time constant of 10 ms. Through the implementation of continuous dynamics, we found latency differences in information retrieval of only 5 ms per layer when local excitation was absent and processing was purely feedforward. However, information latency differences increased significantly when non-associative local excitation was included. We also found that local recurrent excitation through associatively modified synapses can contribute significantly to processing in as little as 15 ms per layer, including the feedforward and local feedback processing. Moreover, and in contrast to purely feed-forward processing, the contribution of local recurrent feedback was useful and approximately this rapid even when retrieval was made difficult by noise. These findings suggest that cortical information processing can benefit from recurrent circuits when the allowed processing time per cortical area is at least 15 ms long.

A digital beacon receiver

NASA Technical Reports Server (NTRS)

Ransome, Peter D.

1988-01-01

A digital satellite beacon receiver is described which provides measurement information down to a carrier/noise density ratio approximately 15 dB below that required by a conventional (phase locked loop) design. When the beacon signal fades, accuracy degrades gracefully, and is restored immediately (without hysteresis) on signal recovery, even if the signal has faded into the noise. Benefits of the digital processing approach used include the minimization of operator adjustments, stability of the phase measuring circuits with time, repeatability between units, and compatibility with equipment not specifically designed for propagation measuring. The receiver has been developed for the European Olympus satellite which has continuous wave (CW) beacons at 12.5 and 29.7 GHz, and a switched polarization beacon at 19.8 GHz approximately, but the system can be reconfigured for CW and polarization-switched beacons at other frequencies.

A new pulse width reduction technique for pulsed electron paramagnetic resonance spectroscopy.

PubMed

Ohba, Yasunori; Nakazawa, Shigeaki; Kazama, Shunji; Mizuta, Yukio

2008-03-01

We present a new technique for a microwave pulse modulator that generates a short microwave pulse of approximately 1ns for use in an electron paramagnetic resonance (EPR) spectrometer. A quadruple-frequency multiplier that generates a signal of 16-20GHz from an input of 4-5GHz was employed to reduce the rise and fall times of the pulse prepared by a PIN diode switch. We examined the transient response characteristics of a commercial frequency multiplier and found that the device can function as a multiplier for pulsed signal even though it was designed for continuous wave operation. We applied the technique to a Ku band pulsed EPR spectrometer and successfully observed a spin echo signal with a broad excitation bandwidth of approximately 1.6mT using 80 degrees pulses of 1.5ns.

Kinetics of killing Listeria monocytogenes by macrophages: rapid killing accompanying phagocytosis

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

Davies, W.A.

1983-08-01

The kinetics of bactericidal activity of activated macrophages can be precisely described by a mathematical model in which phagocytosis, killing, digestion, and release of degraded bacterial material are considered to occur continuously. To gain a better understanding of these events, I have determined the period of time between first contact of bacteria with macrophages and the onset of killing. Activated rat peritoneal macrophages were incubated for various times up to 15 min with Listeria monocytogenes previously labeled with /sup 3/H-thymidine and the unassociated bacteria removed by two centrifugations through a density interface. Both cell-associated radioactivity and cell-associated viable bacteria, determinedmore » as colony forming units after sonication of the cell pellet, increased with time of incubation. However, the specific viability of these bacteria, expressed as the ratio of number of viable bacteria per unit radioactivity declined with time, as an approximate inverse exponential, after a lag period of 2.9 +/- 0.8 min. Evidence is given that other possible causes for this decline in specific viability, other than death of the bacteria, such as preferential ingestion of dead Listeria, clumping of bacteria, variations in autolytic activity, or release of Listericidins are unlikely. I conclude therefore that activated macrophages kill Listeria approximately 3 min after the cell and the bacterium first make contact.« less

Accretion of low-metallicity gas by the Milky Way.

PubMed

Wakker, B P; Howk, J C; Savage, B D; van Woerden, H; Tufte, S L; Schwarz, U J; Benjamin, R; Reynolds, R J; Peletier, R F; Kalberla, P M

1999-11-25

Models of the chemical evolution of the Milky Way suggest that the observed abundances of elements heavier than helium ('metals') require a continuous infall of gas with metallicity (metal abundance) about 0.1 times the solar value. An infall rate integrated over the entire disk of the Milky Way of approximately 1 solar mass per year can solve the 'G-dwarf problem'--the observational fact that the metallicities of most long-lived stars near the Sun lie in a relatively narrow range. This infall dilutes the enrichment arising from the production of heavy elements in stars, and thereby prevents the metallicity of the interstellar medium from increasing steadily with time. However, in other spiral galaxies, the low-metallicity gas needed to provide this infall has been observed only in associated dwarf galaxies and in the extreme outer disk of the Milky Way. In the distant Universe, low-metallicity hydrogen clouds (known as 'damped Ly alpha absorbers') are sometimes seen near galaxies. Here we report a metallicity of 0.09 times solar for a massive cloud that is falling into the disk of the Milky Way. The mass flow associated with this cloud represents an infall per unit area of about the theoretically expected rate, and approximately 0.1-0.2 times the amount required for the whole Galaxy.

Expansions for infinite or finite plane circular time-reversal mirrors and acoustic curtains for wave-field-synthesis.

PubMed

Mellow, Tim; Kärkkäinen, Leo

2014-03-01

An acoustic curtain is an array of microphones used for recording sound which is subsequently reproduced through an array of loudspeakers in which each loudspeaker reproduces the signal from its corresponding microphone. Here the sound originates from a point source on the axis of symmetry of the circular array. The Kirchhoff-Helmholtz integral for a plane circular curtain is solved analytically as fast-converging expansions, assuming an ideal continuous array, to speed up computations and provide insight. By reversing the time sequence of the recording (or reversing the direction of propagation of the incident wave so that the point source becomes an "ideal" point sink), the curtain becomes a time reversal mirror and the analytical solution for this is given simultaneously. In the case of an infinite planar array, it is demonstrated that either a monopole or dipole curtain will reproduce the diverging sound field of the point source on the far side. However, although the real part of the sound field of the infinite time-reversal mirror is reproduced, the imaginary part is an approximation due to the missing singularity. It is shown that the approximation may be improved by using the appropriate combination of monopole and dipole sources in the mirror.

Distributed Optimal Consensus Control for Multiagent Systems With Input Delay.

PubMed

Zhang, Huaipin; Yue, Dong; Zhao, Wei; Hu, Songlin; Dou, Chunxia; Huaipin Zhang; Dong Yue; Wei Zhao; Songlin Hu; Chunxia Dou; Hu, Songlin; Zhang, Huaipin; Dou, Chunxia; Yue, Dong; Zhao, Wei

2018-06-01

This paper addresses the problem of distributed optimal consensus control for a continuous-time heterogeneous linear multiagent system subject to time varying input delays. First, by discretization and model transformation, the continuous-time input-delayed system is converted into a discrete-time delay-free system. Two delicate performance index functions are defined for these two systems. It is shown that the performance index functions are equivalent and the optimal consensus control problem of the input-delayed system can be cast into that of the delay-free system. Second, by virtue of the Hamilton-Jacobi-Bellman (HJB) equations, an optimal control policy for each agent is designed based on the delay-free system and a novel value iteration algorithm is proposed to learn the solutions to the HJB equations online. The proposed adaptive dynamic programming algorithm is implemented on the basis of a critic-action neural network (NN) structure. Third, it is proved that local consensus errors of the two systems and weight estimation errors of the critic-action NNs are uniformly ultimately bounded while the approximated control policies converge to their target values. Finally, two simulation examples are presented to illustrate the effectiveness of the developed method.

Discretization analysis of bifurcation based nonlinear amplifiers

NASA Astrophysics Data System (ADS)

Feldkord, Sven; Reit, Marco; Mathis, Wolfgang

2017-09-01

Recently, for modeling biological amplification processes, nonlinear amplifiers based on the supercritical Andronov-Hopf bifurcation have been widely analyzed analytically. For technical realizations, digital systems have become the most relevant systems in signal processing applications. The underlying continuous-time systems are transferred to the discrete-time domain using numerical integration methods. Within this contribution, effects on the qualitative behavior of the Andronov-Hopf bifurcation based systems concerning numerical integration methods are analyzed. It is shown exemplarily that explicit Runge-Kutta methods transform the truncated normalform equation of the Andronov-Hopf bifurcation into the normalform equation of the Neimark-Sacker bifurcation. Dependent on the order of the integration method, higher order terms are added during this transformation.A rescaled normalform equation of the Neimark-Sacker bifurcation is introduced that allows a parametric design of a discrete-time system which corresponds to the rescaled Andronov-Hopf system. This system approximates the characteristics of the rescaled Hopf-type amplifier for a large range of parameters. The natural frequency and the peak amplitude are preserved for every set of parameters. The Neimark-Sacker bifurcation based systems avoid large computational effort that would be caused by applying higher order integration methods to the continuous-time normalform equations.

Past observable dynamics of a continuously monitored qubit

NASA Astrophysics Data System (ADS)

García-Pintos, Luis Pedro; Dressel, Justin

2017-12-01

Monitoring a quantum observable continuously in time produces a stochastic measurement record that noisily tracks the observable. For a classical process, such noise may be reduced to recover an average signal by minimizing the mean squared error between the noisy record and a smooth dynamical estimate. We show that for a monitored qubit, this usual procedure returns unusual results. While the record seems centered on the expectation value of the observable during causal generation, examining the collected past record reveals that it better approximates a moving-mean Gaussian stochastic process centered at a distinct (smoothed) observable estimate. We show that this shifted mean converges to the real part of a generalized weak value in the time-continuous limit without additional postselection. We verify that this smoothed estimate minimizes the mean squared error even for individual measurement realizations. We go on to show that if a second observable is weakly monitored concurrently, then that second record is consistent with the smoothed estimate of the second observable based solely on the information contained in the first observable record. Moreover, we show that such a smoothed estimate made from incomplete information can still outperform estimates made using full knowledge of the causal quantum state.

The continuous similarity model of bulk soil-water evaporation

NASA Technical Reports Server (NTRS)

Clapp, R. B.

1983-01-01

The continuous similarity model of evaporation is described. In it, evaporation is conceptualized as a two stage process. For an initially moist soil, evaporation is first climate limited, but later it becomes soil limited. During the latter stage, the evaporation rate is termed evaporability, and mathematically it is inversely proportional to the evaporation deficit. A functional approximation of the moisture distribution within the soil column is also included in the model. The model was tested using data from four experiments conducted near Phoenix, Arizona; and there was excellent agreement between the simulated and observed evaporation. The model also predicted the time of transition to the soil limited stage reasonably well. For one of the experiments, a third stage of evaporation, when vapor diffusion predominates, was observed. The occurrence of this stage was related to the decrease in moisture at the surface of the soil. The continuous similarity model does not account for vapor flow. The results show that climate, through the potential evaporation rate, has a strong influence on the time of transition to the soil limited stage. After this transition, however, bulk evaporation is independent of climate until the effects of vapor flow within the soil predominate.

Investigation of furfural biodegradation in a continuous inflow cyclic biological reactor.

PubMed

Moussavi, Gholamreza; Leili, Mostafa; Nadafi, Kazem

2016-01-01

The performance of a continuous inflow cyclic biological reactor (CBR) containing moving media was investigated for the degradation of high concentrations of furfural. The effects of hydraulic retention time (HRT) and furfural initial concentrations (loading rate), as main operating parameters, on the bioreactor performance were studied. The results indicated that the CBR could remove over 98% of furfural and 71% of its chemical oxygen demand (COD) at inlet furfural concentrations up to 1,200 mg L(-1) (2.38 g L(-1) d(-1)), a 6-h cycle time and HRT of 12.1 h. The removal efficiency decreased slightly from 98 to 94% when HRT decreased from 12.1 to 10.5 h. The average removal efficiency of furfural and COD during the 345-day operational period under steady-state conditions were 97.7% and 82.1%, respectively. The efficiency also increased approximately 17.2% after addition of synthetic polyurethane cubes as moving media at a filling ratio of 10%.

Multiclass Posterior Probability Twin SVM for Motor Imagery EEG Classification.

PubMed

She, Qingshan; Ma, Yuliang; Meng, Ming; Luo, Zhizeng

2015-01-01

Motor imagery electroencephalography is widely used in the brain-computer interface systems. Due to inherent characteristics of electroencephalography signals, accurate and real-time multiclass classification is always challenging. In order to solve this problem, a multiclass posterior probability solution for twin SVM is proposed by the ranking continuous output and pairwise coupling in this paper. First, two-class posterior probability model is constructed to approximate the posterior probability by the ranking continuous output techniques and Platt's estimating method. Secondly, a solution of multiclass probabilistic outputs for twin SVM is provided by combining every pair of class probabilities according to the method of pairwise coupling. Finally, the proposed method is compared with multiclass SVM and twin SVM via voting, and multiclass posterior probability SVM using different coupling approaches. The efficacy on the classification accuracy and time complexity of the proposed method has been demonstrated by both the UCI benchmark datasets and real world EEG data from BCI Competition IV Dataset 2a, respectively.

Decentralized stabilization for a class of continuous-time nonlinear interconnected systems using online learning optimal control approach.

PubMed

Liu, Derong; Wang, Ding; Li, Hongliang

2014-02-01

In this paper, using a neural-network-based online learning optimal control approach, a novel decentralized control strategy is developed to stabilize a class of continuous-time nonlinear interconnected large-scale systems. First, optimal controllers of the isolated subsystems are designed with cost functions reflecting the bounds of interconnections. Then, it is proven that the decentralized control strategy of the overall system can be established by adding appropriate feedback gains to the optimal control policies of the isolated subsystems. Next, an online policy iteration algorithm is presented to solve the Hamilton-Jacobi-Bellman equations related to the optimal control problem. Through constructing a set of critic neural networks, the cost functions can be obtained approximately, followed by the control policies. Furthermore, the dynamics of the estimation errors of the critic networks are verified to be uniformly and ultimately bounded. Finally, a simulation example is provided to illustrate the effectiveness of the present decentralized control scheme.

Micturition patterns of an unrestrained chimpanzee under entrained and free running conditions.

NASA Technical Reports Server (NTRS)

Hoshizaki, T.; Mcnew, J. J.; Sabbot, I.; Adey, W. R.

1972-01-01

A young male chimpanzee was subjected to 30 days of isolation. Urine volumes and voiding times were recorded every hour beginning 14 days prior to isolation, ending 6 days after isolation, and approximately 2 months later for 10 days as a control. Observed during most periods of the experiment were (1) clear circadian micturition rhythms with the voiding peak occurring immediately after the subject awoke and (2) urine flow rhythms with the maximum volume voided in the morning hours. A 24-hour rhythm was seen when the subject was entrained to 12L:12D treatments and 24.8-hour rhythm when he was exposed to continuous light. A possible underlying 24-hour micturition rhythm was also seen during the continuous light period. Distorted rhythm curves indicating possible stress were obtained for the pre-isolation adaptation period and the initial period of isolation. As time passed, the curves were more like the controls, perhaps indicating a decrease in stress.

A CO trace gas detection system based on continuous wave DFB-QCL

NASA Astrophysics Data System (ADS)

Dang, Jingmin; Yu, Haiye; Sun, Yujing; Wang, Yiding

2017-05-01

A compact and mobile system was demonstrated for the detection of carbon monoxide (CO) at trace level. This system adopted a high-power, continuous wave (CW), distributed feedback quantum cascade laser (DFB-QCL) operating at ∼22 °C as excitation source. Wavelength modulation spectroscopy (WMS) as well as second harmonic detection was used to isolate complex, overlapping spectral absorption features typical of ambient pressures and to achieve excellent specificity and high detection sensitivity. For the selected P(11) absorption line of CO molecule, located at 2099.083 cm-1, a limit of detection (LoD) of 26 ppb by volume (ppbv) at atmospheric pressure was achieved with a 1 s acquisition time. Allan deviation analysis was performed to investigate the long term performance of the CO detection system, and a measurement precision of 3.4 ppbv was observed with an optimal integration time of approximate 114 s, which verified the reliable and robust operation of the developed system.

High performance hybrid functional Petri net simulations of biological pathway models on CUDA.

PubMed

Chalkidis, Georgios; Nagasaki, Masao; Miyano, Satoru

2011-01-01

Hybrid functional Petri nets are a wide-spread tool for representing and simulating biological models. Due to their potential of providing virtual drug testing environments, biological simulations have a growing impact on pharmaceutical research. Continuous research advancements in biology and medicine lead to exponentially increasing simulation times, thus raising the demand for performance accelerations by efficient and inexpensive parallel computation solutions. Recent developments in the field of general-purpose computation on graphics processing units (GPGPU) enabled the scientific community to port a variety of compute intensive algorithms onto the graphics processing unit (GPU). This work presents the first scheme for mapping biological hybrid functional Petri net models, which can handle both discrete and continuous entities, onto compute unified device architecture (CUDA) enabled GPUs. GPU accelerated simulations are observed to run up to 18 times faster than sequential implementations. Simulating the cell boundary formation by Delta-Notch signaling on a CUDA enabled GPU results in a speedup of approximately 7x for a model containing 1,600 cells.

Properties of the Magnitude Terms of Orthogonal Scaling Functions.

PubMed

Tay, Peter C; Havlicek, Joseph P; Acton, Scott T; Hossack, John A

2010-09-01

The spectrum of the convolution of two continuous functions can be determined as the continuous Fourier transform of the cross-correlation function. The same can be said about the spectrum of the convolution of two infinite discrete sequences, which can be determined as the discrete time Fourier transform of the cross-correlation function of the two sequences. In current digital signal processing, the spectrum of the contiuous Fourier transform and the discrete time Fourier transform are approximately determined by numerical integration or by densely taking the discrete Fourier transform. It has been shown that all three transforms share many analogous properties. In this paper we will show another useful property of determining the spectrum terms of the convolution of two finite length sequences by determining the discrete Fourier transform of the modified cross-correlation function. In addition, two properties of the magnitude terms of orthogonal wavelet scaling functions are developed. These properties are used as constraints for an exhaustive search to determine an robust lower bound on conjoint localization of orthogonal scaling functions.

Contingency Planning for Planetary Rovers

NASA Technical Reports Server (NTRS)

Dearden, Richard; Meuleau, Nicolas; Ramakrishnan, Sailesh; Smith, David; Washington, Rich; Clancy, Daniel (Technical Monitor)

2002-01-01

There has been considerable work in AI on planning under uncertainty. But this work generally assumes an extremely simple model of action that does not consider continuous time and resources. These assumptions are not reasonable for a Mars rover, which must cope with uncertainty about the duration of tasks, the power required, the data storage necessary, along with its position and orientation. In this paper, we outline an approach to generating contingency plans when the sources of uncertainty involve continuous quantities such as time and resources. The approach involves first constructing a "seed" plan, and then incrementally adding contingent branches to this plan in order to improve utility. The challenge is to figure out the best places to insert contingency branches. This requires an estimate of how much utility could be gained by building a contingent branch at any given place in the seed plan. Computing this utility exactly is intractable, but we outline an approximation method that back propagates utility distributions through a graph structure similar to that of a plan graph.

Incremental Contingency Planning

NASA Technical Reports Server (NTRS)

Dearden, Richard; Meuleau, Nicolas; Ramakrishnan, Sailesh; Smith, David E.; Washington, Rich

2003-01-01

There has been considerable work in AI on planning under uncertainty. However, this work generally assumes an extremely simple model of action that does not consider continuous time and resources. These assumptions are not reasonable for a Mars rover, which must cope with uncertainty about the duration of tasks, the energy required, the data storage necessary, and its current position and orientation. In this paper, we outline an approach to generating contingency plans when the sources of uncertainty involve continuous quantities such as time and resources. The approach involves first constructing a "seed" plan, and then incrementally adding contingent branches to this plan in order to improve utility. The challenge is to figure out the best places to insert contingency branches. This requires an estimate of how much utility could be gained by building a contingent branch at any given place in the seed plan. Computing this utility exactly is intractable, but we outline an approximation method that back propagates utility distributions through a graph structure similar to that of a plan graph.

21 CFR 878.4011 - Tissue adhesive with adjunct wound closure device for topical approximation of skin.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY... approximated skin edges of wounds from surgical incisions, including punctures from minimally invasive surgery...

21 CFR 878.4011 - Tissue adhesive with adjunct wound closure device for topical approximation of skin.

Code of Federal Regulations, 2012 CFR

2012-04-01

... ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY... approximated skin edges of wounds from surgical incisions, including punctures from minimally invasive surgery...

21 CFR 878.4011 - Tissue adhesive with adjunct wound closure device for topical approximation of skin.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY... approximated skin edges of wounds from surgical incisions, including punctures from minimally invasive surgery...

An architecture for a continuous, user-driven, and data-driven application of clinical guidelines and its evaluation.

PubMed

Shalom, Erez; Shahar, Yuval; Lunenfeld, Eitan

2016-02-01

Design, implement, and evaluate a new architecture for realistic continuous guideline (GL)-based decision support, based on a series of requirements that we have identified, such as support for continuous care, for multiple task types, and for data-driven and user-driven modes. We designed and implemented a new continuous GL-based support architecture, PICARD, which accesses a temporal reasoning engine, and provides several different types of application interfaces. We present the new architecture in detail in the current paper. To evaluate the architecture, we first performed a technical evaluation of the PICARD architecture, using 19 simulated scenarios in the preeclampsia/toxemia domain. We then performed a functional evaluation with the help of two domain experts, by generating patient records that simulate 60 decision points from six clinical guideline-based scenarios, lasting from two days to four weeks. Finally, 36 clinicians made manual decisions in half of the scenarios, and had access to the automated GL-based support in the other half. The measures used in all three experiments were correctness and completeness of the decisions relative to the GL. Mean correctness and completeness in the technical evaluation were 1±0.0 and 0.96±0.03 respectively. The functional evaluation produced only several minor comments from the two experts, mostly regarding the output's style; otherwise the system's recommendations were validated. In the clinically oriented evaluation, the 36 clinicians applied manually approximately 41% of the GL's recommended actions. Completeness increased to approximately 93% when using PICARD. Manual correctness was approximately 94.5%, and remained similar when using PICARD; but while 68% of the manual decisions included correct but redundant actions, only 3% of the actions included in decisions made when using PICARD were redundant. The PICARD architecture is technically feasible and is functionally valid, and addresses the realistic continuous GL-based application requirements that we have defined; in particular, the requirement for care over significant time frames. The use of the PICARD architecture in the domain we examined resulted in enhanced completeness and in reduction of redundancies, and is potentially beneficial for general GL-based management of chronic patients. Copyright © 2015 Elsevier Inc. All rights reserved.

New class of photonic quantum error correction codes

NASA Astrophysics Data System (ADS)

Silveri, Matti; Michael, Marios; Brierley, R. T.; Salmilehto, Juha; Albert, Victor V.; Jiang, Liang; Girvin, S. M.

We present a new class of quantum error correction codes for applications in quantum memories, communication and scalable computation. These codes are constructed from a finite superposition of Fock states and can exactly correct errors that are polynomial up to a specified degree in creation and destruction operators. Equivalently, they can perform approximate quantum error correction to any given order in time step for the continuous-time dissipative evolution under these errors. The codes are related to two-mode photonic codes but offer the advantage of requiring only a single photon mode to correct loss (amplitude damping), as well as the ability to correct other errors, e.g. dephasing. Our codes are also similar in spirit to photonic ''cat codes'' but have several advantages including smaller mean occupation number and exact rather than approximate orthogonality of the code words. We analyze how the rate of uncorrectable errors scales with the code complexity and discuss the unitary control for the recovery process. These codes are realizable with current superconducting qubit technology and can increase the fidelity of photonic quantum communication and memories.

Comparative DMFT study of the eg-orbital Hubbard model in thin films

NASA Astrophysics Data System (ADS)

Rüegg, Andreas; Hung, Hsiang-Hsuan; Gull, Emanuel; Fiete, Gregory A.

2014-02-01

Heterostructures of transition-metal oxides have emerged as a new route to engineer electronic systems with desired functionalities. Motivated by these developments, we study a two-orbital Hubbard model in a thin-film geometry confined along the cubic [001] direction using the dynamical mean-field theory. We contrast the results of two approximate impurity solvers (exact diagonalization and one-crossing approximation) to the results of the numerically exact continuous-time quantum Monte Carlo solver. Consistent with earlier studies, we find that the one-crossing approximation performs well in the insulating regime, while the advantage of the exact-diagonalization-based solver is more pronounced in the metallic regime. We then investigate various aspects of strongly correlated eg-orbital systems in thin-film geometries. In particular, we show how the interfacial orbital polarization dies off quickly a few layers from the interface and how the film thickness affects the location of the interaction-driven Mott transition. In addition, we explore the changes in the electronic structure with varying carrier concentration and identify large variations of the orbital polarization in the strongly correlated regime.

A semi-analytical study of positive corona discharge in wire-plane electrode configuration

NASA Astrophysics Data System (ADS)

Yanallah, K.; Pontiga, F.; Chen, J. H.

2013-08-01

Wire-to-plane positive corona discharge in air has been studied using an analytical model of two species (electrons and positive ions). The spatial distributions of electric field and charged species are obtained by integrating Gauss's law and the continuity equations of species along the Laplacian field lines. The experimental values of corona current intensity and applied voltage, together with Warburg's law, have been used to formulate the boundary condition for the electron density on the corona wire. To test the accuracy of the model, the approximate electric field distribution has been compared with the exact numerical solution obtained from a finite element analysis. A parametrical study of wire-to-plane corona discharge has then been undertaken using the approximate semi-analytical solutions. Thus, the spatial distributions of electric field and charged particles have been computed for different values of the gas pressure, wire radius and electrode separation. Also, the two dimensional distribution of ozone density has been obtained using a simplified plasma chemistry model. The approximate semi-analytical solutions can be evaluated in a negligible computational time, yet provide precise estimates of corona discharge variables.

Phase unwrapping algorithm using polynomial phase approximation and linear Kalman filter.

PubMed

Kulkarni, Rishikesh; Rastogi, Pramod

2018-02-01

A noise-robust phase unwrapping algorithm is proposed based on state space analysis and polynomial phase approximation using wrapped phase measurement. The true phase is approximated as a two-dimensional first order polynomial function within a small sized window around each pixel. The estimates of polynomial coefficients provide the measurement of phase and local fringe frequencies. A state space representation of spatial phase evolution and the wrapped phase measurement is considered with the state vector consisting of polynomial coefficients as its elements. Instead of using the traditional nonlinear Kalman filter for the purpose of state estimation, we propose to use the linear Kalman filter operating directly with the wrapped phase measurement. The adaptive window width is selected at each pixel based on the local fringe density to strike a balance between the computation time and the noise robustness. In order to retrieve the unwrapped phase, either a line-scanning approach or a quality guided strategy of pixel selection is used depending on the underlying continuous or discontinuous phase distribution, respectively. Simulation and experimental results are provided to demonstrate the applicability of the proposed method.

Conditions in the z = 0.692 absorber toward 3CR 286

NASA Technical Reports Server (NTRS)

Cohen, Ross D.; Barlow, Thomas A.; Beaver, E. A.; Junkkarinen, Vesa T.; Lyons, Ronald W.; Smith, Harding E.

1994-01-01

We present Hubble Space Telescope/Faint Object Spectrograph (HST/FOS) ultraviolet and ground-based optical spectra of the z = 0.692 21 cm absorption system in the quasi-stellar object (QSO) 3CR 286. The strength of the damped Lyman-alpha absorption implies an H I column density, N(H I) approximately 2 x 10(exp 21)/sq cm. We derive a high spin temperature for the H I gas, T(sub s) greater than or approximately equal to 10(exp 3) K, as has been found for other high-redshift 21 cm absorbing systems; at least 80% of the H I is hotter than 1200 K. Curve-of-growth analysis yields Mg(+) and Fe(+) abundances which are approximately 1-2 dex below solar values; the Ca(+) abundance is even lower implying some depletion onto dust grains. The H2 fraction is not high. We speculate that the high inferred T(sub s) for the gas may reflect continuing active star formation at the 5-8 Gyr look-back time to the absorbing galaxy.

Brownian dynamics simulations on a hypersphere in 4-space

NASA Astrophysics Data System (ADS)

Nissfolk, Jarl; Ekholm, Tobias; Elvingson, Christer

2003-10-01

We describe an algorithm for performing Brownian dynamics simulations of particles diffusing on S3, a hypersphere in four dimensions. The system is chosen due to recent interest in doing computer simulations in a closed space where periodic boundary conditions can be avoided. We specifically address the question how to generate a random walk on the 3-sphere, starting from the solution of the corresponding diffusion equation, and we also discuss an efficient implementation based on controlled approximations. Since S3 is a closed manifold (space), the average square displacement during a random walk is no longer proportional to the elapsed time, as in R3. Instead, its time rate of change is continuously decreasing, and approaches zero as time becomes large. We show, however, that the effective diffusion coefficient can still be obtained from the time dependence of the square displacement.

Integrated simulation of continuous-scale and discrete-scale radiative transfer in metal foams

NASA Astrophysics Data System (ADS)

Xia, Xin-Lin; Li, Yang; Sun, Chuang; Ai, Qing; Tan, He-Ping

2018-06-01

A novel integrated simulation of radiative transfer in metal foams is presented. It integrates the continuous-scale simulation with the direct discrete-scale simulation in a single computational domain. It relies on the coupling of the real discrete-scale foam geometry with the equivalent continuous-scale medium through a specially defined scale-coupled zone. This zone holds continuous but nonhomogeneous volumetric radiative properties. The scale-coupled approach is compared to the traditional continuous-scale approach using volumetric radiative properties in the equivalent participating medium and to the direct discrete-scale approach employing the real 3D foam geometry obtained by computed tomography. All the analyses are based on geometrical optics. The Monte Carlo ray-tracing procedure is used for computations of the absorbed radiative fluxes and the apparent radiative behaviors of metal foams. The results obtained by the three approaches are in tenable agreement. The scale-coupled approach is fully validated in calculating the apparent radiative behaviors of metal foams composed of very absorbing to very reflective struts and that composed of very rough to very smooth struts. This new approach leads to a reduction in computational time by approximately one order of magnitude compared to the direct discrete-scale approach. Meanwhile, it can offer information on the local geometry-dependent feature and at the same time the equivalent feature in an integrated simulation. This new approach is promising to combine the advantages of the continuous-scale approach (rapid calculations) and direct discrete-scale approach (accurate prediction of local radiative quantities).

A time reversal algorithm in acoustic media with Dirac measure approximations

NASA Astrophysics Data System (ADS)

Bretin, Élie; Lucas, Carine; Privat, Yannick

2018-04-01

This article is devoted to the study of a photoacoustic tomography model, where one is led to consider the solution of the acoustic wave equation with a source term writing as a separated variables function in time and space, whose temporal component is in some sense close to the derivative of the Dirac distribution at t  =  0. This models a continuous wave laser illumination performed during a short interval of time. We introduce an algorithm for reconstructing the space component of the source term from the measure of the solution recorded by sensors during a time T all along the boundary of a connected bounded domain. It is based at the same time on the introduction of an auxiliary equivalent Cauchy problem allowing to derive explicit reconstruction formula and then to use of a deconvolution procedure. Numerical simulations illustrate our approach. Finally, this algorithm is also extended to elasticity wave systems.

Wave packet dynamics for a non-linear Schrödinger equation describing continuous position measurements

NASA Astrophysics Data System (ADS)

Zander, C.; Plastino, A. R.; Díaz-Alonso, J.

2015-11-01

We investigate time-dependent solutions for a non-linear Schrödinger equation recently proposed by Nassar and Miret-Artés (NM) to describe the continuous measurement of the position of a quantum particle (Nassar, 2013; Nassar and Miret-Artés, 2013). Here we extend these previous studies in two different directions. On the one hand, we incorporate a potential energy term in the NM equation and explore the corresponding wave packet dynamics, while in the previous works the analysis was restricted to the free-particle case. On the other hand, we investigate time-dependent solutions while previous studies focused on a stationary one. We obtain exact wave packet solutions for linear and quadratic potentials, and approximate solutions for the Morse potential. The free-particle case is also revisited from a time-dependent point of view. Our analysis of time-dependent solutions allows us to determine the stability properties of the stationary solution considered in Nassar (2013), Nassar and Miret-Artés (2013). On the basis of these results we reconsider the Bohmian approach to the NM equation, taking into account the fact that the evolution equation for the probability density ρ =| ψ | 2 is not a continuity equation. We show that the effect of the source term appearing in the evolution equation for ρ has to be explicitly taken into account when interpreting the NM equation from a Bohmian point of view.

Structural Response Prediction: Full-field, Dynamic Pressure and Displacement Measurements of a Panel Excited by Shock Boundary-layer Interaction

DTIC Science & Technology

2015-02-01

research cell14. The RC-19 facility is a continuous flow wind tunnel designed to study the mechanisms that govern the mixing and combustion process... angle of 39° from the tunnel bottom wall. The shock generator can translate 170 mm in the flow direction to allow for the shock wave to impinge from...approximate absolute pressure of 20.5 kPa. A series of “ wind -off” images for PSP were collected at that time. The tunnel was then started by setting the

Survival time of the susceptible-infected-susceptible infection process on a graph.

PubMed

van de Bovenkamp, Ruud; Van Mieghem, Piet

2015-09-01

The survival time T is the longest time that a virus, a meme, or a failure can propagate in a network. Using the hitting time of the absorbing state in an uniformized embedded Markov chain of the continuous-time susceptible-infected-susceptible (SIS) Markov process, we derive an exact expression for the average survival time E[T] of a virus in the complete graph K_{N} and the star graph K_{1,N-1}. By using the survival time, instead of the average fraction of infected nodes, we propose a new method to approximate the SIS epidemic threshold τ_{c} that, at least for K_{N} and K_{1,N-1}, correctly scales with the number of nodes N and that is superior to the epidemic threshold τ_{c}^{(1)}=1/λ_{1} of the N-intertwined mean-field approximation, where λ_{1} is the spectral radius of the adjacency matrix of the graph G. Although this new approximation of the epidemic threshold offers a more intuitive understanding of the SIS process, it remains difficult to compare outbreaks in different graph types. For example, the survival in an arbitrary graph seems upper bounded by the complete graph and lower bounded by the star graph as a function of the normalized effective infection rate τ/τ_{c}^{(1)}. However, when the average fraction of infected nodes is used as a basis for comparison, the virus will survive in the star graph longer than in any other graph, making the star graph the worst-case graph instead of the complete graph. Finally, in non-Markovian SIS, the distribution of the spreading attempts over the infectious period of a node influences the survival time, even if the expected number of spreading attempts during an infectious period (the non-Markovian equivalent of the effective infection rate) is kept constant. Both early and late infection attempts lead to shorter survival times. Interestingly, just as in Markovian SIS, the survival times appear to be exponentially distributed, regardless of the infection and curing time distributions.

Insights into shallow magmatic processes at Kīlauea Volcano, Hawaiʻi, from a multiyear continuous gravity time series

USGS Publications Warehouse

Poland, Michael P.; Carbone, Daniele

2016-01-01

Continuous gravity data collected near the summit eruptive vent at Kīlauea Volcano, Hawaiʻi, during 2011–2015 show a strong correlation with summit-area surface deformation and the level of the lava lake within the vent over periods of days to weeks, suggesting that changes in gravity reflect variations in volcanic activity. Joint analysis of gravity and lava level time series data indicates that over the entire time period studied, the average density of the lava within the upper tens to hundreds of meters of the summit eruptive vent remained low—approximately 1000–1500 kg/m3. The ratio of gravity change (adjusted for Earth tides and instrumental drift) to lava level change measured over 15 day windows rose gradually over the course of 2011–2015, probably reflecting either (1) a small increase in the density of lava within the eruptive vent or (2) an increase in the volume of lava within the vent due to gradual vent enlargement. Superimposed on the overall time series were transient spikes of mass change associated with inflation and deflation of Kīlauea's summit and coincident changes in lava level. The unexpectedly strong mass variations during these episodes suggest magma flux to and from the shallow magmatic system without commensurate deformation, perhaps indicating magma accumulation within, and withdrawal from, void space—a process that might not otherwise be apparent from lava level and deformation data alone. Continuous gravity data thus provide unique insights into magmatic processes, arguing for continued application of the method at other frequently active volcanoes.

Enhanced aerodynamic reach of vapor and aerosol sampling for real-time mass spectrometric detection using Venturi-assisted entrainment and ionization

PubMed Central

Forbes, Thomas P.; Staymates, Matthew

2017-01-01

Venturi-assisted ENTrainment and Ionization (VENTI) was developed, demonstrating efficient entrainment, collection, and transport of remotely sampled vapors, aerosols, and dust particulate for real-time mass spectrometry (MS) detection. Integrating the Venturi and Coandă effects at multiple locations generated flow and analyte transport from non-proximate locations and more importantly enhanced the aerodynamic reach at the point of collection. Transport through remote sampling probes up to 2.5 m in length was achieved with residence times on the order of 10-2 s to 10-1 s and Reynolds numbers on the order of 103 to 104. The Venturi-assisted entrainment successfully enhanced vapor collection and detection by greater than an order of magnitude at 20 cm stand-off (limit of simple suction). This enhancement is imperative, as simple suction restricts sampling to the immediate vicinity, requiring close proximity to the vapor source. In addition, the overall aerodynamic reach distance was increased by approximately 3-fold over simple suction under the investigated conditions. Enhanced aerodynamic reach was corroborated and observed with laser-light sheet flow visualization and schlieren imaging. Coupled with atmospheric pressure chemical ionization (APCI), the detection of a range of volatile chemical vapors; explosive vapors; explosive, narcotic, and mustard gas surrogate (methyl salicylate) aerosols; and explosive dust particulate was demonstrated. Continuous real-time Venturi-assisted monitoring of a large room (approximately 90 m2 area, 570 m3 volume) was demonstrated for a 60-minute period without the remote sampling probe, exhibiting detection of chemical vapors and methyl salicylate at approximately 3 m stand-off distances within 2 minutes of exposure. PMID:28107830

Enhanced aerodynamic reach of vapor and aerosol sampling for real-time mass spectrometric detection using Venturi-assisted entrainment and ionization.

PubMed

Forbes, Thomas P; Staymates, Matthew

2017-03-08

Venturi-assisted ENTrainment and Ionization (VENTI) was developed, demonstrating efficient entrainment, collection, and transport of remotely sampled vapors, aerosols, and dust particulate for real-time mass spectrometry (MS) detection. Integrating the Venturi and Coandă effects at multiple locations generated flow and analyte transport from non-proximate locations and more importantly enhanced the aerodynamic reach at the point of collection. Transport through remote sampling probes up to 2.5 m in length was achieved with residence times on the order of 10 -2  s to 10 -1  s and Reynolds numbers on the order of 10 3 to 10 4 . The Venturi-assisted entrainment successfully enhanced vapor collection and detection by greater than an order of magnitude at 20 cm stand-off (limit of simple suction). This enhancement is imperative, as simple suction restricts sampling to the immediate vicinity, requiring close proximity to the vapor source. In addition, the overall aerodynamic reach distance was increased by approximately 3-fold over simple suction under the investigated conditions. Enhanced aerodynamic reach was corroborated and observed with laser-light sheet flow visualization and schlieren imaging. Coupled with atmospheric pressure chemical ionization (APCI), the detection of a range of volatile chemical vapors; explosive vapors; explosive, narcotic, and mustard gas surrogate (methyl salicylate) aerosols; and explosive dust particulate was demonstrated. Continuous real-time Venturi-assisted monitoring of a large room (approximately 90 m 2 area, 570 m 3 volume) was demonstrated for a 60-min period without the remote sampling probe, exhibiting detection of chemical vapors and methyl salicylate at approximately 3 m stand-off distances within 2 min of exposure. Published by Elsevier B.V.

Study on coal char ignition by radiant heat flux.

NASA Astrophysics Data System (ADS)

Korotkikh, A. G.; Slyusarskiy, K. V.

2017-11-01

The study on coal char ignition by CO2-continuous laser was carried out. The coal char samples of T-grade bituminous coal and 2B-grade lignite were studied via CO2-laser ignition setup. Ignition delay times were determined at ambient condition in heat flux density range 90-200 W/cm2. The average ignition delay time value for lignite samples were 2 times lower while this difference is larger in high heat flux region and lower in low heat flux region. The kinetic constants for overall oxidation reaction were determined using analytic solution of simplified one-dimensional heat transfer equation with radiant heat transfer boundary condition. The activation energy for lignite char was found to be less than it is for bituminous coal char by approximately 20 %.

27 CFR 9.46 - Livermore Valley.

Code of Federal Regulations, 2014 CFR

2014-04-01

... straight line approximately 4.2 miles, passing onto the Cedar Mtn. map, to BM 1878, 40 feet north of Mines..., R1E; then (18) Continue northwest in a straight line approximately 1.1 miles to an unnamed, 1,291-foot..., 840-foot peak, T3S, R2W; then (24) Proceed north-northeast in a straight line approximately 3.4 miles...

27 CFR 9.46 - Livermore Valley.

Code of Federal Regulations, 2012 CFR

2012-04-01

... straight line approximately 4.2 miles, passing onto the Cedar Mtn. map, to BM 1878, 40 feet north of Mines..., R1E; then (18) Continue northwest in a straight line approximately 1.1 miles to an unnamed, 1,291-foot..., 840-foot peak, T3S, R2W; then (24) Proceed north-northeast in a straight line approximately 3.4 miles...

27 CFR 9.46 - Livermore Valley.

Code of Federal Regulations, 2013 CFR

2013-04-01

... straight line approximately 4.2 miles, passing onto the Cedar Mtn. map, to BM 1878, 40 feet north of Mines..., R1E; then (18) Continue northwest in a straight line approximately 1.1 miles to an unnamed, 1,291-foot..., 840-foot peak, T3S, R2W; then (24) Proceed north-northeast in a straight line approximately 3.4 miles...

Approximate analytic solutions to 3D unconfined groundwater flow within regional 2D models

NASA Astrophysics Data System (ADS)

Luther, K.; Haitjema, H. M.

2000-04-01

We present methods for finding approximate analytic solutions to three-dimensional (3D) unconfined steady state groundwater flow near partially penetrating and horizontal wells, and for combining those solutions with regional two-dimensional (2D) models. The 3D solutions use distributed singularities (analytic elements) to enforce boundary conditions on the phreatic surface and seepage faces at vertical wells, and to maintain fixed-head boundary conditions, obtained from the 2D model, at the perimeter of the 3D model. The approximate 3D solutions are analytic (continuous and differentiable) everywhere, including on the phreatic surface itself. While continuity of flow is satisfied exactly in the infinite 3D flow domain, water balance errors can occur across the phreatic surface.

Two-stage continuous operation of recombinant Escherichia coli using the bacteriophage lambda Q- vector.

PubMed

Oh, Jeong Seok; Cho, Daechul; Park, Tai Hyun

2005-11-01

A two-stage continuous culture of Escherichia coli in combination with a bacteriophage lambda system was performed in order to overcome the intrinsic plasmid instability that is frequently observed in recombinant fermentation. A phage lambda vector with a Q(-) mutation was used to enhance the expression of the lambda system. The optimal values of the important operational variables such as the substrate concentration, the dilution rate, and the mean residence time on the expression of the cloned gene were determined in both batch and continuous cultures. For all culturing modes, the full induction of the cloned gene was observed 4 h after the temperature shift. In the two stage continuous culture, the overproduction reached their maxima at D=0.25 h(-1) with 1.5 S(0) of the medium supply. The maximum productivity of the total beta-galactosidase was 16.3x10(6) U l(-1) h(-1), which was approximately seven times higher than that in the single-copy lysogenic stage. The recombinant cells were stable in the lysogenic state for more than 260 h, while they were stable for 40 h in the lytic state. The instability that developed rapidly in the second tank is believed to be due to the accumulation of lysis proteins as a result of vector leakage during the operation.

Novel optoacoustic system for noninvasive continuous monitoring of cerebral venous blood oxygenation

NASA Astrophysics Data System (ADS)

Petrov, Yuriy; Petrov, Irene Y.; Prough, Donald S.; Esenaliev, Rinat O.

2012-02-01

Traumatic brain injury (TBI) and spinal cord injury are a major cause of death for individuals under 50 years of age. In the USA alone, 150,000 patients per year suffer moderate or severe TBI. Moreover, TBI is a major cause of combatrelated death. Monitoring of cerebral venous blood oxygenation is critically important for management of TBI patients because cerebral venous blood oxygenation below 50% results in death or severe neurologic complications. At present, there is no technique for noninvasive, accurate monitoring of this clinically important variable. We proposed to use optoacoustic technique for noninvasive monitoring of cerebral venous blood oxygenation by probing cerebral veins such as the superior sagittal sinus (SSS) and validated it in animal studies. In this work, we developed a novel, medical grade optoacoustic system for continuous, real-time cerebral venous blood oxygenation monitoring and tested it in human subjects at normal conditions and during hyperventilation to simulate changes that may occur in patients with TBI. We designed and built a highly-sensitive optoacoustic probe for SSS signal detection. Continuous measurements were performed in the near infrared spectral range and the SSS oxygenation absolute values were automatically calculated in real time using a special algorithm developed by our group. Continuous measurements performed at normal conditions and during hyperventilation demonstrated that hyperventilation resulted in approximately 12% decrease of cerebral venous blood oxygenation.

Spatiotemporal interpolation of discharge across a river network by using synthetic SWOT satellite data

NASA Astrophysics Data System (ADS)

Paiva, Rodrigo C. D.; Durand, Michael T.; Hossain, Faisal

2015-01-01

Recent efforts have sought to estimate river discharge and other surface water-related quantities using spaceborne sensors, with better spatial coverage but worse temporal sampling as compared with in situ measurements. The Surface Water and Ocean Topography (SWOT) mission will provide river discharge estimates globally from space. However, questions on how to optimally use the spatially distributed but asynchronous satellite observations to generate continuous fields still exist. This paper presents a statistical model (River Kriging-RK), for estimating discharge time series in a river network in the context of the SWOT mission. RK uses discharge estimates at different locations and times to produce a continuous field using spatiotemporal kriging. A key component of RK is the space-time river discharge covariance, which was derived analytically from the diffusive wave approximation of Saint Venant's equations. The RK covariance also accounts for the loss of correlation at confluences. The model performed well in a case study on Ganges-Brahmaputra-Meghna (GBM) River system in Bangladesh using synthetic SWOT observations. The correlation model reproduced empirically derived values. RK (R2=0.83) outperformed other kriging-based methods (R2=0.80), as well as a simple time series linear interpolation (R2=0.72). RK was used to combine discharge from SWOT and in situ observations, improving estimates when the latter is included (R2=0.91). The proposed statistical concepts may eventually provide a feasible framework to estimate continuous discharge time series across a river network based on SWOT data, other altimetry missions, and/or in situ data.

A continuous tensor field approximation of discrete DT-MRI data for extracting microstructural and architectural features of tissue.

PubMed

Pajevic, Sinisa; Aldroubi, Akram; Basser, Peter J

2002-01-01

The effective diffusion tensor of water, D, measured by diffusion tensor MRI (DT-MRI), is inherently a discrete, noisy, voxel-averaged sample of an underlying macroscopic effective diffusion tensor field, D(x). Within fibrous tissues this field is presumed to be continuous and smooth at a gross anatomical length scale. Here a new, general mathematical framework is proposed that uses measured DT-MRI data to produce a continuous approximation to D(x). One essential finding is that the continuous tensor field representation can be constructed by repeatedly performing one-dimensional B-spline transforms of the DT-MRI data. The fidelity and noise-immunity of this approximation are tested using a set of synthetically generated tensor fields to which background noise is added via Monte Carlo methods. Generally, these tensor field templates are reproduced faithfully except at boundaries where diffusion properties change discontinuously or where the tensor field is not microscopically homogeneous. Away from such regions, the tensor field approximation does not introduce bias in useful DT-MRI parameters, such as Trace(D(x)). It also facilitates the calculation of several new parameters, particularly differential quantities obtained from the tensor of spatial gradients of D(x). As an example, we show that they can identify tissue boundaries across which diffusion properties change rapidly using in vivo human brain data. One important application of this methodology is to improve the reliability and robustness of DT-MRI fiber tractography.

Kinetic studies of a doubly bound red cell antigen-antibody system.

PubMed

Oberhardt, B J; Miller, I F

1972-08-01

The Polybrene method for detection of red cell antibodies which utilizes continuous flow equipment was modified so that kinetic studies could be performed on red cell antibodies doubly bound between adjacent red cells. In the anti-Rh(o)-Rh(o) erythrocyte system, deaggregation by temperature was studied over an antibody concentration range of from approximately 1 to 500 antibody molecules per erythrocyte, a residence time range of approximately eightfold, and a temperature range of from 10 to 55 degrees C. The rate of dissociation of antigen-antibody complex, as determined from deaggregation of antibody-dependent red cell aggregates, was found to be of apparent zero order. The apparent activation energy for the antigen-antibody reaction under the experimental conditions was determined and found to be higher than would be expected for singly bound antigen-antibody systems. Possible explanations are considered for these findings in terms of an antigen-antibody bond-breaking model.

Extending the Utility of the Parabolic Approximation in Medical Ultrasound Using Wide-Angle Diffraction Modeling.

PubMed

Soneson, Joshua E

2017-04-01

Wide-angle parabolic models are commonly used in geophysics and underwater acoustics but have seen little application in medical ultrasound. Here, a wide-angle model for continuous-wave high-intensity ultrasound beams is derived, which approximates the diffraction process more accurately than the commonly used Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation without increasing implementation complexity or computing time. A method for preventing the high spatial frequencies often present in source boundary conditions from corrupting the solution is presented. Simulations of shallowly focused axisymmetric beams using both the wide-angle and standard parabolic models are compared to assess the accuracy with which they model diffraction effects. The wide-angle model proposed here offers improved focusing accuracy and less error throughout the computational domain than the standard parabolic model, offering a facile method for extending the utility of existing KZK codes.

The role of litterfall in transferring Fukushima-derived radiocesium to a coniferous forest floor.

PubMed

Teramage, Mengistu T; Onda, Yuichi; Kato, Hiroaki; Gomi, Takashi

2014-08-15

The deposition of Fukushima-derived radiocesium via falling litter in a coniferous forest 180 km downwind immediately following the nuclear power plant accident was investigated. The litterfall contribution to the transfer of radiocesium from the forest canopy to the forest floor was determined, and this pathway was compared with hydrological pathways. The results demonstrated that during the observation period, a total of approximately 5.5 kBq m(-2) of Fukushima-derived radiocesium was deposited on the forest floor through throughfall (53%), stemflow (2.3%) and litterfall (45%) routes. The data revealed that the contributions of hydrological pathways became less important as time passed. However, the litterfall route, which transferred approximately 31% (2.5±0.6 kBq m(-2)) of the local fallout within the observation period, continued depositing radiocesium onto the forest floor. Copyright © 2014 Elsevier B.V. All rights reserved.

Development of programmable artificial neural networks

NASA Technical Reports Server (NTRS)

Meade, Andrew J.

1993-01-01

Conventionally programmed digital computers can process numbers with great speed and precision, but do not easily recognize patterns or imprecise or contradictory data. Instead of being programmed in the conventional sense, artificial neural networks are capable of self-learning through exposure to repeated examples. However, the training of an ANN can be a time consuming and unpredictable process. A general method is being developed to mate the adaptability of the ANN with the speed and precision of the digital computer. This method was successful in building feedforward networks that can approximate functions and their partial derivatives from examples in a single iteration. The general method also allows the formation of feedforward networks that can approximate the solution to nonlinear ordinary and partial differential equations to desired accuracy without the need of examples. It is believed that continued research will produce artificial neural networks that can be used with confidence in practical scientific computing and engineering applications.

Shadows, signals, and stability in Einsteinian cubic gravity

NASA Astrophysics Data System (ADS)

Hennigar, Robie A.; Jahani Poshteh, Mohammad Bagher; Mann, Robert B.

2018-03-01

We conduct a preliminary investigation into the phenomenological implications of Einsteinian cubic gravity (ECG), a four-dimensional theory of gravity cubic in curvature of interest for its unique formulation and properties. We find an analytic approximation for a spherically symmetric black hole solution to this theory using a continued fraction ansatz. This approximate solution is valid everywhere outside of the horizon and we use it to study the orbit of massive test bodies near a black hole, specifically computing the innermost stable circular orbit. We compute constraints on the ECG coupling parameter imposed by Shapiro time delay. We then compute the shadow of an ECG black hole and find it to be larger than its Einsteinian counterpart in general relativity for the same value of the mass. Applying our results to Sgr A*, we find that departures from general relativity are small but in principle distinguishable.

Permeability of gypsum samples dehydrated in air

NASA Astrophysics Data System (ADS)

Milsch, Harald; Priegnitz, Mike; Blöcher, Guido

2011-09-01

We report on changes in rock permeability induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air (dry) for up to 800 h at ambient pressure and temperatures between 378 and 423 K. Subsequently, the reaction kinetics, so induced changes in porosity, and the concurrent evolution of sample permeability were constrained. Weighing the heated samples in predefined time intervals yielded the reaction progress where the stoichiometric mass balance indicated an ultimate and complete dehydration to anhydrite regardless of temperature. Porosity showed to continuously increase with reaction progress from approximately 2% to 30%, whilst the initial bulk volume remained unchanged. Within these limits permeability significantly increased with porosity by almost three orders of magnitude from approximately 7 × 10-19 m2 to 3 × 10-16 m2. We show that - when mechanical and hydraulic feedbacks can be excluded - permeability, reaction progress, and porosity are related unequivocally.

Asian longhorned beetle cooperative eradication program: program accomplishments 2001

Treesearch

Christine Markham

2003-01-01

APHIS spent approximately $3 million to continue ALB eradication activities in New York and Illinois in FY 2001. In New York 6,615 trees were removed, over 4,500 trees replanted, and approximately 121 square miles were under quarantine.

What is the correct cost functional for variational data assimilation?

NASA Astrophysics Data System (ADS)

Bröcker, Jochen

2018-03-01

Variational approaches to data assimilation, and weakly constrained four dimensional variation (WC-4DVar) in particular, are important in the geosciences but also in other communities (often under different names). The cost functions and the resulting optimal trajectories may have a probabilistic interpretation, for instance by linking data assimilation with maximum aposteriori (MAP) estimation. This is possible in particular if the unknown trajectory is modelled as the solution of a stochastic differential equation (SDE), as is increasingly the case in weather forecasting and climate modelling. In this situation, the MAP estimator (or "most probable path" of the SDE) is obtained by minimising the Onsager-Machlup functional. Although this fact is well known, there seems to be some confusion in the literature, with the energy (or "least squares") functional sometimes been claimed to yield the most probable path. The first aim of this paper is to address this confusion and show that the energy functional does not, in general, provide the most probable path. The second aim is to discuss the implications in practice. Although the mentioned results pertain to stochastic models in continuous time, they do have consequences in practice where SDE's are approximated by discrete time schemes. It turns out that using an approximation to the SDE and calculating its most probable path does not necessarily yield a good approximation to the most probable path of the SDE proper. This suggest that even in discrete time, a version of the Onsager-Machlup functional should be used, rather than the energy functional, at least if the solution is to be interpreted as a MAP estimator.

Optical trapping of nanoparticles by ultrashort laser pulses.

PubMed

Usman, Anwar; Chiang, Wei-Yi; Masuhara, Hiroshi

2013-01-01

Optical trapping with continuous-wave lasers has been a fascinating field in the optical manipulation. It has become a powerful tool for manipulating micrometer-sized objects, and has been widely applied in physics, chemistry, biology, material, and colloidal science. Replacing the continuous-wave- with pulsed-mode laser in optical trapping has already revealed some novel phenomena, including the stable trap, modifiable trapping positions, and controllable directional optical ejections of particles in nanometer scales. Due to two distinctive features; impulsive peak powers and relaxation time between consecutive pulses, the optical trapping with the laser pulses has been demonstrated to have some advantages over conventional continuous-wave lasers, particularly when the particles are within Rayleigh approximation. This would open unprecedented opportunities in both fundamental science and application. This Review summarizes recent advances in the optical trapping with laser pulses and discusses the electromagnetic formulations and physical interpretations of the new phenomena. Its aim is rather to show how beautiful and promising this field will be, and to encourage the in-depth study of this field.

Pilot-scale study on the acid-catalyzed steam explosion of rice straw using a continuous pretreatment system.

PubMed

Chen, Wen-Hua; Tsai, Chia-Chin; Lin, Chih-Feng; Tsai, Pei-Yuan; Hwang, Wen-Song

2013-01-01

A continuous acid-catalyzed steam explosion pretreatment process and system to produce cellulosic ethanol was developed at the pilot-scale. The effects of the following parameters on the pretreatment efficiency of rice straw feedstocks were investigated: the acid concentration, the reaction temperature, the residence time, the feedstock size, the explosion pressure and the screw speed. The optimal presteaming horizontal reactor conditions for the pretreatment process are as follows: 1.7 rpm and 100-110 °C with an acid concentration of 1.3% (w/w). An acid-catalyzed steam explosion is then performed in the vertical reactor at 185 °C for 2 min. Approximately 73% of the total saccharification yield was obtained after the rice straw was pretreated under optimal conditions and subsequent enzymatic hydrolysis at a combined severity factor of 0.4-0.7. Moreover, good long-term stability and durability of the pretreatment system under continuous operation was observed. Copyright © 2012 Elsevier Ltd. All rights reserved.

Expanding Continuous Quality Improvement Capacity in the Medical Intensive Care Unit: Prehealth Volunteers as a Solution.

PubMed

Priest, Kelsey C; Lobingier, Hannah; McCully, Nancy; Lombard, Jackie; Hansen, Mark; Uchiyama, Makoto; Hagg, Daniel S

2016-01-01

Health care delivery systems are challenged to support the increasing demands for improving patient safety, satisfaction, and outcomes. Limited resources and staffing are common barriers for making significant and sustained improvements. At Oregon Health & Science University, the medical intensive care unit (MICU) leadership team faced internal capacity limitations for conducting continuous quality improvement, specifically for the implementation and evaluation of the mobility portion of an evidence-based care bundle. The MICU team successfully addressed this capacity challenge using the person power of prehealth volunteers. In the first year of the project, 52 trained volunteers executed an evidence-based mobility intervention for 305 critically ill patients, conducting more than 200 000 exercise repetitions. The volunteers contributed to real-time evaluation of the project, with the collection of approximately 26 950 process measure data points. Prehealth volunteers are an untapped resource for effectively expanding internal continuous quality improvement capacity in the MICU and beyond.

The dynamics of smoking-related disturbed methylation: a two time-point study of methylation change in smokers, non-smokers and former smokers.

PubMed

Wilson, Rory; Wahl, Simone; Pfeiffer, Liliane; Ward-Caviness, Cavin K; Kunze, Sonja; Kretschmer, Anja; Reischl, Eva; Peters, Annette; Gieger, Christian; Waldenberger, Melanie

2017-10-18

The evidence for epigenome-wide associations between smoking and DNA methylation continues to grow through cross-sectional studies. However, few large-scale investigations have explored the associations using observations for individuals at multiple time-points. Here, through the use of the Illumina 450K BeadChip and data collected at two time-points separated by approximately 7 years, we investigate changes in methylation over time associated with quitting smoking or remaining a former smoker, and those associated with continued smoking. Our results indicate that after quitting smoking the most rapid reversion of altered methylation occurs within the first two decades, with reversion rates related to the initial differences in methylation. For 52 CpG sites, the change in methylation from baseline to follow-up is significantly different for former smokers relative to the change for never smokers (lowest p-value 3.61 x 10 -39 for cg26703534, gene AHRR). Most of these sites' respective regions have been previously implicated in smoking-associated diseases. Despite the early rapid change, dynamism of methylation appears greater in former smokers vs never smokers even four decades after cessation. Furthermore, our study reveals the heterogeneous effect of continued smoking: the methylation levels of some loci further diverge between smokers and non-smokers, while others re-approach. Though intensity of smoking habit appears more significant than duration, results remain inconclusive. This study improves the understanding of the dynamic link between cigarette smoking and methylation, revealing the continued fluctuation of methylation levels decades after smoking cessation and demonstrating that continuing smoking can have an array of effects. The results can facilitate insights into the molecular mechanisms behind smoking-induced disturbed methylation, improving the possibility for development of biomarkers of past smoking behavior and increasing the understanding of the molecular path from exposure to disease.

Litigated Metal Clusters - Structures, Energy and Reactivity

DTIC Science & Technology

2016-04-01

projection superposition approximation ( PSA ) algorithm through a more careful consideration of how to calculate cross sections for elongated molecules...superposition approximation ( PSA ) is now complete. We have made it available free of charge to the scientific community on a dedicated website at UCSB. We...by AFOSR. We continued to improve the projection superposition approximation ( PSA ) algorithm through a more careful consideration of how to calculate

Update Direct-Strike Lightning Environment for Stockpile-to-Target Sequence

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

Uman, M A; Rakov, V A; Elisme, J O

2008-10-01

The University of Florida has surveyed all relevant publications reporting lightning characteristics and presents here an up-to-date version of the direct-strike lightning environment specifications for nuclear weapons published in 1989 by R. J. Fisher and M. A. Uman. Further, we present functional expressions for current vs. time, current derivative vs. time, second current derivative vs. time, charge transfer vs. time, and action integral (specific energy) vs. time for first return strokes, for subsequent return strokes, and for continuing currents; and we give sets of constants for these expressions so that they yield approximately the median and extreme negative lightning parametersmore » presented in this report. Expressions for the median negative lightning waveforms are plotted. Finally, we provide information on direct-strike lightning damage to metals such as stainless steel, which could be used as components of storage containers for nuclear waste materials; and we describe UF's new experimental research program to add to the sparse data base on the properties of positive lightning. Our literature survey, referred to above, is included in four Appendices. The following four sections (II, III, IV, and V) of this final report deal with related aspects of the research: Section II. Recommended Direct-Strike Median and Extreme Parameters; Section III. Time-Domain Waveforms for First Strokes, Subsequent Strokes, and Continuing Currents; Section IV. Damage to Metal Surfaces by Lightning Currents; and Section V. Measurement of the Characteristics of Positive Lightning. Results of the literature search used to derive the material in Section II and Section IV are found in the Appendices: Appendix 1. Return Stroke Current, Appendix 2. Continuing Current, Appendix 3. Positive Lightning, and Appendix 4. Lightning Damage to Metal Surfaces.« less

Time to relapse following treatment for methamphetamine use: a long-term perspective on patterns and predictors.

PubMed

Brecht, Mary-Lynn; Herbeck, Diane

2014-06-01

This paper describes methamphetamine (MA) use patterns, specifically the duration of continuing abstinence ("time to relapse") for periods averaging 5 years post-discharge from treatment for MA use, and the relationship with selected user and treatment characteristics. A sample of 350 treatment admissions from a large county substance use disorder (SUD) treatment system was randomly selected (within gender, race/ethnicity, treatment modality strata). Retrospective self-report data are from natural history interviews (NHI) conducted approximately 3 years after treatment and a follow-up of 2-3 years later. Relapse is defined as any use of MA with time as the number of months of continuous MA abstinence after treatment discharge until relapse. This outcome was constructed from a monthly MA use timeline using NHI data. A Cox model was used to examine time to relapse and predictors. Sixty-one percent of the sample relapsed to MA use within 1 year after treatment discharge and 14% during years 2-5. Significant protective factors predicting longer time to relapse included having experienced serious MA-related psychiatric/behavioral problems (hazard ratio [HR]=0.75, p=0.027), longer duration of the index treatment episode (HR=0.93, p=0.001), and participating in self-help or other treatment during the post-treatment abstinence period (HR=0.29, p<0.001); risk factors for shorter time to relapse included having a parent with alcohol and/or drug use problems (HR=1.35, p=0.020) and involvement in MA sales (HR=1.48, p=0.002). Results contribute a long-term perspective on patterns of MA use following treatment and support a need for early post-treatment and long-term continuing care and relapse-prevention services. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Input-output characterization of an ultrasonic testing system by digital signal analysis

NASA Technical Reports Server (NTRS)

Williams, J. H., Jr.; Lee, S. S.; Karagulle, H.

1986-01-01

Ultrasonic test system input-output characteristics were investigated by directly coupling the transmitting and receiving transducers face to face without a test specimen. Some of the fundamentals of digital signal processing were summarized. Input and output signals were digitized by using a digital oscilloscope, and the digitized data were processed in a microcomputer by using digital signal-processing techniques. The continuous-time test system was modeled as a discrete-time, linear, shift-invariant system. In estimating the unit-sample response and frequency response of the discrete-time system, it was necessary to use digital filtering to remove low-amplitude noise, which interfered with deconvolution calculations. A digital bandpass filter constructed with the assistance of a Blackman window and a rectangular time window were used. Approximations of the impulse response and the frequency response of the continuous-time test system were obtained by linearly interpolating the defining points of the unit-sample response and the frequency response of the discrete-time system. The test system behaved as a linear-phase bandpass filter in the frequency range 0.6 to 2.3 MHz. These frequencies were selected in accordance with the criterion that they were 6 dB below the maximum peak of the amplitude of the frequency response. The output of the system to various inputs was predicted and the results were compared with the corresponding measurements on the system.

Bolus intrathecal injection of ziconotide (Prialt®) to evaluate the option of continuous administration via an implanted intrathecal drug delivery (ITDD) system: a pilot study.

PubMed

Mohammed, Salma I; Eldabe, Sam; Simpson, Karen H; Brookes, Morag; Madzinga, Grace; Gulve, Ashish; Baranidharan, Ganesan; Radford, Helen; Crowther, Tracey; Buchser, Eric; Perruchoud, Christophe; Batterham, Alan Mark

2013-01-01

This study evaluated efficacy and safety of bolus doses of ziconotide (Prialt®, Eisai Limited, Hertfordshire, UK) to assess the option of continuous administration of this drug via an implanted intrathecal drug delivery system. Twenty adults with severe chronic pain who were under consideration for intrathecal (IT) therapy were enrolled in this open label, nonrandomized, pilot study. Informed consent was obtained. Demographics, medical/pain history, pain scores, and concomitant medications were recorded. A physical examination was performed. Creatine kinase was measured. Initial visual analog scale (VAS), blood pressure, heart rate, and respiratory rate were recorded. All patients received an initial bolus dose of 2.5 mcg ziconotide; the dose in the subsequent visits was modified according to response. Subsequent doses were 2.5 mcg, 1.2 mcg, or 3.75 mcg as per protocol. A good response (≥30% reduction in baseline pain VAS) with no side-effects on two occasions was considered a successful trial. Data were analyzed using a generalized estimating equations model, with pain VAS as the outcome and time (seven time points; preinjection and one to six hours postinjection) as the predictor. Generalized estimating equations analysis of summary measures showed a mean reduction of pain VAS of approximately 25% at the group level; of 11 responders, seven underwent pump implantation procedure, two withdrew because of adverse effects, one refused an implant, and one could not have an implant (lack of funding from the Primary Care Trust). Our data demonstrated that mean VAS was reduced by approximately 25% at the group level after IT ziconotide bolus. Treatment efficacy did not vary with sex, center, age, or pain etiology. Ziconotide bolus was generally well tolerated. Larger studies are needed to determine if bolus dosing with ziconotide is a good predictor of response to continuous IT ziconotide via an intrathecal drug delivery system. © 2012 International Neuromodulation Society.

Relationship between mass-flux reduction and source-zone mass removal: analysis of field data.

PubMed

Difilippo, Erica L; Brusseau, Mark L

2008-05-26

The magnitude of contaminant mass-flux reduction associated with a specific amount of contaminant mass removed is a key consideration for evaluating the effectiveness of a source-zone remediation effort. Thus, there is great interest in characterizing, estimating, and predicting relationships between mass-flux reduction and mass removal. Published data collected for several field studies were examined to evaluate relationships between mass-flux reduction and source-zone mass removal. The studies analyzed herein represent a variety of source-zone architectures, immiscible-liquid compositions, and implemented remediation technologies. There are two general approaches to characterizing the mass-flux-reduction/mass-removal relationship, end-point analysis and time-continuous analysis. End-point analysis, based on comparing masses and mass fluxes measured before and after a source-zone remediation effort, was conducted for 21 remediation projects. Mass removals were greater than 60% for all but three of the studies. Mass-flux reductions ranging from slightly less than to slightly greater than one-to-one were observed for the majority of the sites. However, these single-snapshot characterizations are limited in that the antecedent behavior is indeterminate. Time-continuous analysis, based on continuous monitoring of mass removal and mass flux, was performed for two sites, both for which data were obtained under water-flushing conditions. The reductions in mass flux were significantly different for the two sites (90% vs. approximately 8%) for similar mass removals ( approximately 40%). These results illustrate the dependence of the mass-flux-reduction/mass-removal relationship on source-zone architecture and associated mass-transfer processes. Minimal mass-flux reduction was observed for a system wherein mass removal was relatively efficient (ideal mass-transfer and displacement). Conversely, a significant degree of mass-flux reduction was observed for a site wherein mass removal was inefficient (non-ideal mass-transfer and displacement). The mass-flux-reduction/mass-removal relationship for the latter site exhibited a multi-step behavior, which cannot be predicted using some of the available simple estimation functions.

Accelerated autoantibody clearance by intravenous immunoglobulin therapy: studies in experimental models to determine the magnitude and time course of the effect.

PubMed

Bleeker, W K; Teeling, J L; Hack, C E

2001-11-15

Recently, it has been postulated that the beneficial effect of intravenous immunoglobulins (IVIGs) in antibody-mediated autoimmune disorders is based on accelerated catabolism of autoantibodies. In the current study, in vivo experiments were performed with mice in which autoantibody production was mimicked by continuous infusion of monoclonal antibodies. In this model, a single dose of IVIG reduced the plasma concentrations of the infused immunoglobulin (Ig)G1 monoclonal antibody (mAb) by approximately 40% after 3 days, whereas the concentration of an IgA mAb was not affected. To extrapolate these findings to humans, a computational model for IgG clearance was established that accurately predicted the time course and magnitude of the decrease in IgG plasma levels observed in mice. Adapted for humans, this model predicted a gradually occurring decrease in autoantibody levels after IVIG administration (2 g/kg), with a maximum reduction of approximately 25% after 3 to 4 weeks and a continued decrease of several months. In conclusion, a single high dose of IVIG induces a relatively small but long-lasting reduction of autoantibody levels by accelerated IgG clearance. This mechanism has clinical relevance in the sense that it can fully explain, as the sole mechanism, the gradual decrease in autoantibody levels observed in several patient studies. However, in some clinical studies, larger or more rapid effects have been observed that cannot be explained by accelerated clearance. Hence, IVIG can also reduce autoantibody levels through mechanisms such as down-regulation of antibody production or neutralization by anti-idiotypic antibodies.

Single product lot-sizing on unrelated parallel machines with non-decreasing processing times

NASA Astrophysics Data System (ADS)

Eremeev, A.; Kovalyov, M.; Kuznetsov, P.

2018-01-01

We consider a problem in which at least a given quantity of a single product has to be partitioned into lots, and lots have to be assigned to unrelated parallel machines for processing. In one version of the problem, the maximum machine completion time should be minimized, in another version of the problem, the sum of machine completion times is to be minimized. Machine-dependent lower and upper bounds on the lot size are given. The product is either assumed to be continuously divisible or discrete. The processing time of each machine is defined by an increasing function of the lot volume, given as an oracle. Setup times and costs are assumed to be negligibly small, and therefore, they are not considered. We derive optimal polynomial time algorithms for several special cases of the problem. An NP-hard case is shown to admit a fully polynomial time approximation scheme. An application of the problem in energy efficient processors scheduling is considered.

Evaluation of Criteria for the Detection of Fires in Underground Conveyor Belt Haulageways

PubMed Central

Litton, Charles D.; Perera, Inoka Eranda

2015-01-01

Large-scale experiments were conducted in an above-ground gallery to simulate typical fires that develop along conveyor belt transport systems within underground coal mines. In the experiments, electrical strip heaters, imbedded ~5 cm below the top surface of a large mass of coal rubble, were used to ignite the coal, producing an open flame. The flaming coal mass subsequently ignited 1.83-meter-wide conveyor belts located approximately 0.30 m above the coal surface. Gas samples were drawn through an averaging probe located approximately 20 m downstream of the coal for continuous measurement of CO, CO2, and O2 as the fire progressed through the stages of smoldering coal, flaming coal, and flaming conveyor belt. Also located approximately 20 m from the fire origin and approximately 0.5 m below the roof of the gallery were two commercially available smoke detectors, a light obscuration meter, and a sampling probe for measurement of total mass concentration of smoke particles. Located upstream of the fire origin and also along the wall of the gallery at approximately 14 m and 5 m upstream were two video cameras capable of both smoke and flame detection. During the experiments, alarm times of the smoke detectors and video cameras were measured while the smoke obscuration and total smoke mass were continually measured. Twelve large-scale experiments were conducted using three different types of fire-resistant conveyor belts and four air velocities for each belt. The air velocities spanned the range from 1.0 m/s to 6.9 m/s. The results of these experiments are compared to previous large-scale results obtained using a smaller fire gallery and much narrower (1.07-m) conveyor belts to determine if the fire detection criteria previously developed (1) remained valid for the wider conveyor belts. Although some differences between these and the previous experiments did occur, the results, in general, compare very favorably. Differences are duly noted and their impact on fire detection discussed. PMID:26566298

Objective assessment of MPEG-2 video quality

NASA Astrophysics Data System (ADS)

Gastaldo, Paolo; Zunino, Rodolfo; Rovetta, Stefano

2002-07-01

The increasing use of video compression standards in broadcasting television systems has required, in recent years, the development of video quality measurements that take into account artifacts specifically caused by digital compression techniques. In this paper we present a methodology for the objective quality assessment of MPEG video streams by using circular back-propagation feedforward neural networks. Mapping neural networks can render nonlinear relationships between objective features and subjective judgments, thus avoiding any simplifying assumption on the complexity of the model. The neural network processes an instantaneous set of input values, and yields an associated estimate of perceived quality. Therefore, the neural-network approach turns objective quality assessment into adaptive modeling of subjective perception. The objective features used for the estimate are chosen according to the assessed relevance to perceived quality and are continuously extracted in real time from compressed video streams. The overall system mimics perception but does not require any analytical model of the underlying physical phenomenon. The capability to process compressed video streams represents an important advantage over existing approaches, like avoiding the stream-decoding process greatly enhances real-time performance. Experimental results confirm that the system provides satisfactory, continuous-time approximations for actual scoring curves concerning real test videos.

Changes in cell-cycle kinetics responsible for limiting somatic growth in mice

PubMed Central

Chang, Maria; Parker, Elizabeth A.; Muller, Tessa J. M.; Haenen, Caroline; Mistry, Maanasi; Finkielstain, Gabriela P.; Murphy-Ryan, Maureen; Barnes, Kevin M.; Sundaram, Rajeshwari; Baron, Jeffrey

2009-01-01

In mammals, the rate of somatic growth is rapid in early postnatal life but then slows with age, approaching zero as the animal approaches adult body size. To investigate the underlying changes in cell-cycle kinetics, [methyl-3H]thymidine and 5’-bromo-2’deoxyuridine were used to double-label proliferating cells in 1-, 2-, and 3-week-old mice for four weeks. Proliferation of renal tubular epithelial cells and hepatocytes decreased with age. The average cell-cycle time did not increase in liver and increased only 1.7 fold in kidney. The fraction of cells in S-phase that will divide again declined approximately 10 fold with age. Concurrently, average cell area increased approximately 2 fold. The findings suggest that somatic growth deceleration primarily results not from an increase in cell-cycle time but from a decrease in growth fraction (fraction of cells that continue to proliferate). During the deceleration phase, cells appear to reach a proliferative limit and undergo their final cell divisions, staggered over time. Concomitantly, cells enlarge to a greater volume, perhaps because they are relieved of the size constraint imposed by cell division. In conclusion, a decline in growth fraction with age causes somatic growth deceleration and thus sets a fundamental limit on adult body size. PMID:18535488

Using NDVI to assess vegetative land cover change in central Puget Sound.

PubMed

Morawitz, Dana F; Blewett, Tina M; Cohen, Alex; Alberti, Marina

2006-03-01

We used the Normalized Difference Vegetation Index (NDVI) in the rapidly growing Puget Sound region over three 5-year time blocks between 1986-1999 at three spatial scales in 42 Watershed Administrative Units (WAUs) to assess changes in the amounts and patterns of green vegetation. On average, approximately 20% of the area in each WAU experienced significant NDVI change over each 5-year time block. Cumulative NDVI change over 15 years (summing change over each 5-year time block) was an average of approximately 60% of each WAU, but was as high as 100% in some. At the regional scale, seasonal weather patterns and green-up from logging were the primary drivers of observed increases in NDVI values. At the WAU scale, anthropogenic factors were important drivers of both positive and negative NDVI change. For example, population density was highly correlated with negative NDVI change over 15 years (r = 0.66, P < 0.01), as was road density (r = 0.71, P < 0.01). At the smallest scale (within 3 case study WAUs) land use differences such as preserving versus harvesting forest lands drove vegetation change. We conclude that large areas within most watersheds are continually and heavily impacted by the high levels of human use and development over short time periods. Our results indicate that varying patterns and processes can be detected at multiple scales using changes in NDVIa values.

Heat assisted magnetic recording with patterned FePt recording media using a lollipop near field transducer

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

Ghoreyshi, Ali; Victora, R. H., E-mail: victora@umn.edu

In heat-assisted magnetic recording, optical energy is transferred to a small optical spot on the recording media using a near field transducer. In this study, a scattered field finite difference time domain simulation is used to analyze the performance of a lollipop transducer in heat assisted magnetic recording on both a patterned FePt media and a continuous thin film. To represent wear, sharp corners of the peg are approximated with curved ones, which are found to narrow the track width without excessive loss of intensity. Compared with continuous media, the patterned media exhibits higher energy efficiency and a better concentratedmore » optical beam spot. This effect is due to the near field effects of patterned media on the performance of the transducer.« less

Cobalt adatoms on graphene: Effects of anisotropies on the correlated electronic structure

NASA Astrophysics Data System (ADS)

Mozara, R.; Valentyuk, M.; Krivenko, I.; Şaşıoǧlu, E.; Kolorenč, J.; Lichtenstein, A. I.

2018-02-01

Impurities on surfaces experience a geometric symmetry breaking induced not only by the on-site crystal-field splitting and the orbital-dependent hybridization, but also by different screening of the Coulomb interaction in different directions. We present a many-body study of the Anderson impurity model representing a Co adatom on graphene, taking into account all anisotropies of the effective Coulomb interaction, which we obtained by the constrained random-phase approximation. The most pronounced differences are naturally displayed by the many-body self-energy projected onto the single-particle states. For the solution of the Anderson impurity model and analytical continuation of the Matsubara data, we employed new implementations of the continuous-time hybridization expansion quantum Monte Carlo and the stochastic optimization method, and we verified the results in parallel with the exact diagonalization method.

Quantum mechanical streamlines. I - Square potential barrier

NASA Technical Reports Server (NTRS)

Hirschfelder, J. O.; Christoph, A. C.; Palke, W. E.

1974-01-01

Exact numerical calculations are made for scattering of quantum mechanical particles hitting a square two-dimensional potential barrier (an exact analog of the Goos-Haenchen optical experiments). Quantum mechanical streamlines are plotted and found to be smooth and continuous, to have continuous first derivatives even through the classical forbidden region, and to form quantized vortices around each of the nodal points. A comparison is made between the present numerical calculations and the stationary wave approximation, and good agreement is found between both the Goos-Haenchen shifts and the reflection coefficients. The time-independent Schroedinger equation for real wavefunctions is reduced to solving a nonlinear first-order partial differential equation, leading to a generalization of the Prager-Hirschfelder perturbation scheme. Implications of the hydrodynamical formulation of quantum mechanics are discussed, and cases are cited where quantum and classical mechanical motions are identical.

Temporal Behavior of the Ionospheric Electron Density at Low Latitudes: First Glimpse

NASA Astrophysics Data System (ADS)

Gjerloev, J. W.; Humberset, B. K.; Gonzalez, S. A.; Garnett Marques Brum, C.

2013-12-01

In this paper we address the spatiotemporal characteristics of the electron density at 150 km altitude in the low latitude ionosphere above the Arecibo Observatory. We utilize a new pointing mode that allows us to probe the same volume in the ionosphere for a continuous period of approximately 25 min. or more. The ISR profiles have 150 m range resolution and samples have a 10-second time resolution; we probed 60 individual regions uniformly spaced in local times and covering the full 24 hours. For each time series we determine the total derivative of the electron density using a narrow Hanning bandpass filter that allow us to determine the variability at different frequencies. This is done for each of the 60 local time regions. We further compare to widely used static statistical models and test their underlying assumption: Dynamics can be ignored.

Galerkin v. least-squares Petrov–Galerkin projection in nonlinear model reduction

DOE PAGES

Carlberg, Kevin Thomas; Barone, Matthew F.; Antil, Harbir

2016-10-20

Least-squares Petrov–Galerkin (LSPG) model-reduction techniques such as the Gauss–Newton with Approximated Tensors (GNAT) method have shown promise, as they have generated stable, accurate solutions for large-scale turbulent, compressible flow problems where standard Galerkin techniques have failed. Furthermore, there has been limited comparative analysis of the two approaches. This is due in part to difficulties arising from the fact that Galerkin techniques perform optimal projection associated with residual minimization at the time-continuous level, while LSPG techniques do so at the time-discrete level. This work provides a detailed theoretical and computational comparison of the two techniques for two common classes of timemore » integrators: linear multistep schemes and Runge–Kutta schemes. We present a number of new findings, including conditions under which the LSPG ROM has a time-continuous representation, conditions under which the two techniques are equivalent, and time-discrete error bounds for the two approaches. Perhaps most surprisingly, we demonstrate both theoretically and computationally that decreasing the time step does not necessarily decrease the error for the LSPG ROM; instead, the time step should be ‘matched’ to the spectral content of the reduced basis. In numerical experiments carried out on a turbulent compressible-flow problem with over one million unknowns, we show that increasing the time step to an intermediate value decreases both the error and the simulation time of the LSPG reduced-order model by an order of magnitude.« less

Galerkin v. least-squares Petrov–Galerkin projection in nonlinear model reduction

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

Carlberg, Kevin Thomas; Barone, Matthew F.; Antil, Harbir

Least-squares Petrov–Galerkin (LSPG) model-reduction techniques such as the Gauss–Newton with Approximated Tensors (GNAT) method have shown promise, as they have generated stable, accurate solutions for large-scale turbulent, compressible flow problems where standard Galerkin techniques have failed. Furthermore, there has been limited comparative analysis of the two approaches. This is due in part to difficulties arising from the fact that Galerkin techniques perform optimal projection associated with residual minimization at the time-continuous level, while LSPG techniques do so at the time-discrete level. This work provides a detailed theoretical and computational comparison of the two techniques for two common classes of timemore » integrators: linear multistep schemes and Runge–Kutta schemes. We present a number of new findings, including conditions under which the LSPG ROM has a time-continuous representation, conditions under which the two techniques are equivalent, and time-discrete error bounds for the two approaches. Perhaps most surprisingly, we demonstrate both theoretically and computationally that decreasing the time step does not necessarily decrease the error for the LSPG ROM; instead, the time step should be ‘matched’ to the spectral content of the reduced basis. In numerical experiments carried out on a turbulent compressible-flow problem with over one million unknowns, we show that increasing the time step to an intermediate value decreases both the error and the simulation time of the LSPG reduced-order model by an order of magnitude.« less

Inference for dynamics of continuous variables: the extended Plefka expansion with hidden nodes

NASA Astrophysics Data System (ADS)

Bravi, B.; Sollich, P.

2017-06-01

We consider the problem of a subnetwork of observed nodes embedded into a larger bulk of unknown (i.e. hidden) nodes, where the aim is to infer these hidden states given information about the subnetwork dynamics. The biochemical networks underlying many cellular and metabolic processes are important realizations of such a scenario as typically one is interested in reconstructing the time evolution of unobserved chemical concentrations starting from the experimentally more accessible ones. We present an application to this problem of a novel dynamical mean field approximation, the extended Plefka expansion, which is based on a path integral description of the stochastic dynamics. As a paradigmatic model we study the stochastic linear dynamics of continuous degrees of freedom interacting via random Gaussian couplings. The resulting joint distribution is known to be Gaussian and this allows us to fully characterize the posterior statistics of the hidden nodes. In particular the equal-time hidden-to-hidden variance—conditioned on observations—gives the expected error at each node when the hidden time courses are predicted based on the observations. We assess the accuracy of the extended Plefka expansion in predicting these single node variances as well as error correlations over time, focussing on the role of the system size and the number of observed nodes.

Eulerian velocity reconstruction in ideal atmospheric dynamics using potential vorticity and potential temperature

NASA Astrophysics Data System (ADS)

Blender, R.

2009-04-01

An approach for the reconstruction of atmospheric flow is presented which uses space- and time-dependent fields of density ?, potential vorticity Q and potential temperature Î& cedil;[J. Phys. A, 38, 6419 (2005)]. The method is based on the fundamental equations without approximation. The basic idea is to consider the time-dependent continuity equation as a condition for zero divergence of momentum in four dimensions (time and space, with unit velocity in time). This continuity equation is solved by an ansatz for the four-dimensional momentum using three conserved stream functions, the potential vorticity, potential temperature and a third field, denoted as ?-potential. In zonal flows, the ?-potential identifies the initial longitude of particles, whereas potential vorticity and potential temperature identify mainly meridional and vertical positions. Since the Lagrangian tracers Q, Î&,cedil; and ? determine the Eulerian velocity field, the reconstruction combines the Eulerian and the Lagrangian view of hydrodynamics. In stationary flows, the ?-potential is related to the Bernoulli function. The approach requires that the gradients of the potential vorticity and potential temperature do not vanish when the velocity remains finite. This behavior indicates a possible interrelation with stability conditions. Examples with analytical solutions are presented for a Rossby wave and zonal and rotational shear flows.

Dynamic Cerebral Autoregulation Changes during Sub-Maximal Handgrip Maneuver

PubMed Central

Nogueira, Ricardo C.; Bor-Seng-Shu, Edson; Santos, Marcelo R.; Negrão, Carlos E.; Teixeira, Manoel J.; Panerai, Ronney B.

2013-01-01

Purpose We investigated the effect of handgrip (HG) maneuver on time-varying estimates of dynamic cerebral autoregulation (CA) using the autoregressive moving average technique. Methods Twelve healthy subjects were recruited to perform HG maneuver during 3 minutes with 30% of maximum contraction force. Cerebral blood flow velocity, end-tidal CO2 pressure (PETCO2), and noninvasive arterial blood pressure (ABP) were continuously recorded during baseline, HG and recovery. Critical closing pressure (CrCP), resistance area-product (RAP), and time-varying autoregulation index (ARI) were obtained. Results PETCO2 did not show significant changes during HG maneuver. Whilst ABP increased continuously during the maneuver, to 27% above its baseline value, CBFV raised to a plateau approximately 15% above baseline. This was sustained by a parallel increase in RAP, suggestive of myogenic vasoconstriction, and a reduction in CrCP that could be associated with metabolic vasodilation. The time-varying ARI index dropped at the beginning and end of the maneuver (p<0.005), which could be related to corresponding alert reactions or to different time constants of the myogenic, metabolic and/or neurogenic mechanisms. Conclusion Changes in dynamic CA during HG suggest a complex interplay of regulatory mechanisms during static exercise that should be considered when assessing the determinants of cerebral blood flow and metabolism. PMID:23967113

The virtual slice setup.

PubMed

Lytton, William W; Neymotin, Samuel A; Hines, Michael L

2008-06-30

In an effort to design a simulation environment that is more similar to that of neurophysiology, we introduce a virtual slice setup in the NEURON simulator. The virtual slice setup runs continuously and permits parameter changes, including changes to synaptic weights and time course and to intrinsic cell properties. The virtual slice setup permits shocks to be applied at chosen locations and activity to be sampled intra- or extracellularly from chosen locations. By default, a summed population display is shown during a run to indicate the level of activity and no states are saved. Simulations can run for hours of model time, therefore it is not practical to save all of the state variables. These, in any case, are primarily of interest at discrete times when experiments are being run: the simulation can be stopped momentarily at such times to save activity patterns. The virtual slice setup maintains an automated notebook showing shocks and parameter changes as well as user comments. We demonstrate how interaction with a continuously running simulation encourages experimental prototyping and can suggest additional dynamical features such as ligand wash-in and wash-out-alternatives to typical instantaneous parameter change. The virtual slice setup currently uses event-driven cells and runs at approximately 2 min/h on a laptop.

The potential for lithoautotrophic life on Mars: application to shallow interfacial water environments.

PubMed

Jepsen, Steven M; Priscu, John C; Grimm, Robert E; Bullock, Mark A

2007-04-01

We developed a numerical model to assess the lithoautotrophic habitability of Mars based on metabolic energy, nutrients, water availability, and temperature. Available metabolic energy and nutrient sources were based on a laboratory-produced Mars-analog inorganic chemistry. For this specific reference chemistry, the most efficient lithoautotrophic microorganisms would use Fe(2+) as a primary metabolic electron donor and NO(3)(-) or gaseous O(2) as a terminal electron acceptor. In a closed model system, biomass production was limited by the electron donor Fe(2+) and metabolically required P, and typically amounted to approximately 800 pg of dry biomass/ml ( approximately 8,500 cells/ml). Continued growth requires propagation of microbes to new fecund environments, delivery of fresh pore fluid, or continued reaction with the host material. Within the shallow cryosphere--where oxygen can be accessed by microbes and microbes can be accessed by exploration-lithoautotrophs can function within as little as three monolayers of interfacial water formed either by adsorption from the atmosphere or in regions of ice stability where temperatures are within some tens of degrees of the ice melting point. For the selected reference host material (shergottite analog) and associated inorganic fluid chemistry, complete local reaction of the host material potentially yields a time-integrated biomass of approximately 0.1 mg of dry biomass/g of host material ( approximately 10(9) cells/g). Biomass could also be sustained where solutes can be delivered by advection (cryosuction) or diffusion in interfacial water; however, both of these processes are relatively inefficient. Lithoautotrophs in near-surface thin films of water, therefore, would optimize their metabolism by deriving energy and nutrients locally. Although the selected chemistry and associated model output indicate that lithoautotrophic microbial biomass could accrue within shallow interfacial water on Mars, it is likely that these organisms would spend long periods in maintenance or survival modes, with instantaneous biomass comparable to or less than that observed in extreme environments on Earth.

26 CFR 1.985-3 - United States dollar approximate separate transactions method.

Code of Federal Regulations, 2011 CFR

2011-04-01

... gross income in that category. Similarly, if a group of assets, such as short-term bank deposits... apply and DASTM loss attributable to a group of assets exceeds the income generated by such assets. (vi... TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Export Trade Corporations § 1.985-3...

Stabilizing potentials in bound state analytic continuation methods for electronic resonances in polyatomic molecules

DOE PAGES

White, Alec F.; Head-Gordon, Martin; McCurdy, C. William

2017-01-30

The computation of Siegert energies by analytic continuation of bound state energies has recently been applied to shape resonances in polyatomic molecules by several authors. Here, we critically evaluate a recently proposed analytic continuation method based on low order (type III) Padé approximants as well as an analytic continuation method based on high order (type II) Padé approximants. We compare three classes of stabilizing potentials: Coulomb potentials, Gaussian potentials, and attenuated Coulomb potentials. These methods are applied to a model potential where the correct answer is known exactly and to the 2Π g shape resonance of N 2 - whichmore » has been studied extensively by other methods. Both the choice of stabilizing potential and method of analytic continuation prove to be important to the accuracy of the results. We then conclude that an attenuated Coulomb potential is the most effective of the three for bound state analytic continuation methods. With the proper potential, such methods show promise for algorithmic determination of the positions and widths of molecular shape resonances.« less

Stabilizing potentials in bound state analytic continuation methods for electronic resonances in polyatomic molecules

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

White, Alec F.; Head-Gordon, Martin; McCurdy, C. William

The computation of Siegert energies by analytic continuation of bound state energies has recently been applied to shape resonances in polyatomic molecules by several authors. Here, we critically evaluate a recently proposed analytic continuation method based on low order (type III) Padé approximants as well as an analytic continuation method based on high order (type II) Padé approximants. We compare three classes of stabilizing potentials: Coulomb potentials, Gaussian potentials, and attenuated Coulomb potentials. These methods are applied to a model potential where the correct answer is known exactly and to the 2Π g shape resonance of N 2 - whichmore » has been studied extensively by other methods. Both the choice of stabilizing potential and method of analytic continuation prove to be important to the accuracy of the results. We then conclude that an attenuated Coulomb potential is the most effective of the three for bound state analytic continuation methods. With the proper potential, such methods show promise for algorithmic determination of the positions and widths of molecular shape resonances.« less

Analytical approximation for the Einstein-dilaton-Gauss-Bonnet black hole metric

NASA Astrophysics Data System (ADS)

Kokkotas, K. D.; Konoplya, R. A.; Zhidenko, A.

2017-09-01

We construct an analytical approximation for the numerical black hole metric of P. Kanti et al. [Phys. Rev. D 54, 5049 (1996), 10.1103/PhysRevD.54.5049] in the four-dimensional Einstein-dilaton-Gauss-Bonnet (EdGB) theory. The continued fraction expansion in terms of a compactified radial coordinate, used here, converges slowly when the dilaton coupling approaches its extremal values, but for a black hole far from the extremal state, the analytical formula has a maximal relative error of a fraction of one percent already within the third order of the continued fraction expansion. The suggested analytical representation of the numerical black hole metric is relatively compact and a good approximation in the whole space outside the black hole event horizon. Therefore, it can serve in the same way as an exact solution when analyzing particles' motion, perturbations, quasinormal modes, Hawking radiation, accreting disks, and many other problems in the vicinity of a black hole. In addition, we construct the approximate analytical expression for the dilaton field.

An ultrashort mixing length micromixer: the shear superposition micromixer.

PubMed

Bottausci, Frédéric; Cardonne, Caroline; Meinhart, Carl; Mezić, Igor

2007-03-01

We report for the first time a laminar high-performance continuous micromixing process of two fluids over a length of 200 microns in under 10 milliseconds achieved by an optimization of the control parameters amplitude and frequency in the mixing device denoted as 'Shear Superposition Micromixer'. We improve mixing time by approximately 5 orders of magnitude over diffusion-limited mixing. The data indicate that rapid mixing is a result of the combined action of Taylor-Aris dispersion in the main and secondary microchannels and unsteady vortex motion that occurs at finite Reynolds number, which occurs above a threshold amplitude and frequency. The mixing performance is quantified using micron-resolution particle image velocimetry (micro-PIV) and computational fluid dynamics (CFD) simulations.

Probabilistic objective functions for sensor management

NASA Astrophysics Data System (ADS)

Mahler, Ronald P. S.; Zajic, Tim R.

2004-08-01

This paper continues the investigation of a foundational and yet potentially practical basis for control-theoretic sensor management, using a comprehensive, intuitive, system-level Bayesian paradigm based on finite-set statistics (FISST). In this paper we report our most recent progress, focusing on multistep look-ahead -- i.e., allocation of sensor resources throughout an entire future time-window. We determine future sensor states in the time-window using a "probabilistically natural" sensor management objective function, the posterior expected number of targets (PENT). This objective function is constructed using a new "maxi-PIMS" optimization strategy that hedges against unknowable future observation-collections. PENT is used in conjuction with approximate multitarget filters: the probability hypothesis density (PHD) filter or the multi-hypothesis correlator (MHC) filter.

Cavitation pitting and erosion of aluminum 6061-T6 in mineral oil water

NASA Technical Reports Server (NTRS)

Rao, B. C. S.; Buckley, D. H.

1983-01-01

Cavitation erosion studies of aluminum 6061-T6 in mineral oil and in ordinary tap water are presented. The maximum erosion rate (MDPR, or mean depth of penetration rate) in mineral oil was about four times that in water. The MDPR in mineral oil decreased continuously with time, but the MDPR in water remained approximately constant. The cavitation pits in mineral oil were of smaller diameter and depth than the pits in water. Treating the pits as spherical segments, we computed the radius r of the sphere. The logarithm of h/a, where h is the pit depth and 2a is the top width of the pit, was linear when plotted against the logarithm of 2r/h - 1.

Experimental confirmation of a PDE-based approach to design of feedback controls

NASA Technical Reports Server (NTRS)

Banks, H. T.; Smith, Ralph C.; Brown, D. E.; Silcox, R. J.; Metcalf, Vern L.

1995-01-01

Issues regarding the experimental implementation of partial differential equation based controllers are discussed in this work. While the motivating application involves the reduction of vibration levels for a circular plate through excitation of surface-mounted piezoceramic patches, the general techniques described here will extend to a variety of applications. The initial step is the development of a PDE model which accurately captures the physics of the underlying process. This model is then discretized to yield a vector-valued initial value problem. Optimal control theory is used to determine continuous-time voltages to the patches, and the approximations needed to facilitate discrete time implementation are addressed. Finally, experimental results demonstrating the control of both transient and steady state vibrations through these techniques are presented.

Faster Trees: Strategies for Accelerated Training and Prediction of Random Forests for Classification of Polsar Images

NASA Astrophysics Data System (ADS)

Hänsch, Ronny; Hellwich, Olaf

2018-04-01

Random Forests have continuously proven to be one of the most accurate, robust, as well as efficient methods for the supervised classification of images in general and polarimetric synthetic aperture radar data in particular. While the majority of previous work focus on improving classification accuracy, we aim for accelerating the training of the classifier as well as its usage during prediction while maintaining its accuracy. Unlike other approaches we mainly consider algorithmic changes to stay as much as possible independent of platform and programming language. The final model achieves an approximately 60 times faster training and a 500 times faster prediction, while the accuracy is only marginally decreased by roughly 1 %.

On-chip programmable ultra-wideband microwave photonic phase shifter and true time delay unit.

PubMed

Burla, Maurizio; Cortés, Luis Romero; Li, Ming; Wang, Xu; Chrostowski, Lukas; Azaña, José

2014-11-01

We proposed and experimentally demonstrated an ultra-broadband on-chip microwave photonic processor that can operate both as RF phase shifter (PS) and true-time-delay (TTD) line, with continuous tuning. The processor is based on a silicon dual-phase-shifted waveguide Bragg grating (DPS-WBG) realized with a CMOS compatible process. We experimentally demonstrated the generation of delay up to 19.4 ps over 10 GHz instantaneous bandwidth and a phase shift of approximately 160° over the bandwidth 22-29 GHz. The available RF measurement setup ultimately limits the phase shifting demonstration as the device is capable of providing up to 300° phase shift for RF frequencies over a record bandwidth approaching 1 THz.

Nuclear reactor transient analysis via a quasi-static kinetics Monte Carlo method

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

Jo, YuGwon; Cho, Bumhee; Cho, Nam Zin, E-mail: nzcho@kaist.ac.kr

2015-12-31

The predictor-corrector quasi-static (PCQS) method is applied to the Monte Carlo (MC) calculation for reactor transient analysis. To solve the transient fixed-source problem of the PCQS method, fission source iteration is used and a linear approximation of fission source distributions during a macro-time step is introduced to provide delayed neutron source. The conventional particle-tracking procedure is modified to solve the transient fixed-source problem via MC calculation. The PCQS method with MC calculation is compared with the direct time-dependent method of characteristics (MOC) on a TWIGL two-group problem for verification of the computer code. Then, the results on a continuous-energy problemmore » are presented.« less

Continuous sweep versus discrete step protocols for studying effects of wearable robot assistance magnitude.

PubMed

Malcolm, Philippe; Rossi, Denise Martineli; Siviy, Christopher; Lee, Sangjun; Quinlivan, Brendan Thomas; Grimmer, Martin; Walsh, Conor J

2017-07-12

Different groups developed wearable robots for walking assistance, but there is still a need for methods to quickly tune actuation parameters for each robot and population or sometimes even for individual users. Protocols where parameters are held constant for multiple minutes have traditionally been used for evaluating responses to parameter changes such as metabolic rate or walking symmetry. However, these discrete protocols are time-consuming. Recently, protocols have been proposed where a parameter is changed in a continuous way. The aim of the present study was to compare effects of continuously varying assistance magnitude with a soft exosuit against discrete step conditions. Seven participants walked on a treadmill wearing a soft exosuit that assists plantarflexion and hip flexion. In Continuous-up, peak exosuit ankle moment linearly increased from approximately 0 to 38% of biological moment over 10 min. Continuous-down was the opposite. In Discrete, participants underwent five periods of 5 min with steady peak moment levels distributed over the same range as Continuous-up and Continuous-down. We calculated metabolic rate for the entire Continuous-up and Continuous-down conditions and the last 2 min of each Discrete force level. We compared kinematics, kinetics and metabolic rate between conditions by curve fitting versus peak moment. Reduction in metabolic rate compared to Powered-off was smaller in Continuous-up than in Continuous-down at most peak moment levels, due to physiological dynamics causing metabolic measurements in Continuous-up and Continuous-down to lag behind the values expected during steady-state testing. When evaluating the average slope of metabolic reduction over the entire peak moment range there was no significant difference between Continuous-down and Discrete. Attempting to correct the lag in metabolics by taking the average of Continuous-up and Continuous-down removed all significant differences versus Discrete. For kinematic and kinetic parameters, there were no differences between all conditions. The finding that there were no differences in biomechanical parameters between all conditions suggests that biomechanical parameters can be recorded with the shortest protocol condition (i.e. single Continuous directions). The shorter time and higher resolution data of continuous sweep protocols hold promise for the future study of human interaction with wearable robots.

Presence of the Corexit component dioctyl sodium sulfosuccinate in Gulf of Mexico waters after the 2010 Deepwater Horizon oil spill

USGS Publications Warehouse

Gray, James L.; Kanagy, Leslie K.; Furlong, Edward T.; Kanagy, Chris J.; McCoy, Jeff W.; Mason, Andrew; Lauenstein, Gunnar

2014-01-01

Between April 22 and July 15, 2010, approximately 4.9 million barrels of oil were released into the Gulf of Mexico from the Deepwater Horizon oil well. Approximately 16% of the oil was chemically dispersed, at the surface and at 1500 m depth, using Corexit 9527 and Corexit 9500, which contain dioctyl sodium sulfosuccinate (DOSS) as a major surfactant component. This was the largest documented release of oil in history at substantial depth, and the first time large quantities of dispersant (0.77 million gallons of approximately 1.9 million gallons total) were applied to a subsurface oil plume. During two cruises in late May and early June, water samples were collected at the surface and at depth for DOSS analysis. Real-time fluorimetry data was used to infer the presence of oil components to select appropriate sampling depths. Samples were stored frozen and in the dark for approximately 6 months prior to analysis by liquid chromatography/tandem mass spectrometry with isotope-dilution quantification. The blank-limited method detection limit (0.25 μg L−1) was substantially less than the U.S. Environmental Protection Agency’s (USEPA) aquatic life benchmark of 40 μg L−1. Concentrations of DOSS exceeding 200 μg L−1 were observed in one surface sample near the well site; in subsurface samples DOSS did not exceed 40 μg L−1. Although DOSS was present at high concentration in the immediate vicinity of the well where it was being continuously applied, a combination of biodegradation, photolysis, and dilution likely reduced persistence at concentrations exceeding the USEPA aquatic life benchmark beyond this immediate area.

Optimal Power Flow Pursuit

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

Dall'Anese, Emiliano; Simonetto, Andrea

This paper considers distribution networks featuring inverter-interfaced distributed energy resources, and develops distributed feedback controllers that continuously drive the inverter output powers to solutions of AC optimal power flow (OPF) problems. Particularly, the controllers update the power setpoints based on voltage measurements as well as given (time-varying) OPF targets, and entail elementary operations implementable onto low-cost microcontrollers that accompany power-electronics interfaces of gateways and inverters. The design of the control framework is based on suitable linear approximations of the AC power-flow equations as well as Lagrangian regularization methods. Convergence and OPF-target tracking capabilities of the controllers are analytically established. Overall,more » the proposed method allows to bypass traditional hierarchical setups where feedback control and optimization operate at distinct time scales, and to enable real-time optimization of distribution systems.« less

Billion frames per second spectrum measurement for high-repetition-rate optical pulses based on time stretching technique

NASA Astrophysics Data System (ADS)

Furukawa, Hideaki; Makino, Takeshi; Asghari, Mohammad H.; Trinh, Paul; Jalali, Bahram; Wang, Xiaomin; Kobayashi, Tetsuya; Man, Wai S.; Tsang, Kwong Shing; Wada, Naoya

2017-02-01

Single-shot and long record length spectrum measurements of high-repetition-rate optical pulses are essential for research on nonlinear dynamics as well as for applications in sensing and communication. To achieve a continuous measurements we employ the Time Stretch Dispersive Fourier Transform. We show single-shot measurements of millions of sequential pulses at high repetition rate of 1 Giga spectra per second. Results were obtained using -100 ps/nm dispersive Fourier transform module and a 50 Gsample/s real-time digitizer of 16 GHz bandwidth. Single-shot spectroscopy of 1 GHz optical pulse train was achieved with the wavelength resolution of approximately 150 pm. This instrument is ideal for observation of complex nonlinear dynamics such as switching, mode locking and soliton dynamics in high repetition rate lasers.

Quantum mechanics of hyperbolic orbits in the Kepler problem

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

Rauh, Alexander; Parisi, Juergen

2011-04-15

The problem of deriving macroscopic properties from the Hamiltonian of the hydrogen atom is resumed by extending previous results in the literature, which predicted elliptic orbits, into the region of hyperbolic orbits. As a main tool, coherent states of the harmonic oscillator are used which are continued to imaginary frequencies. The Kustaanheimo-Stiefel (KS) map is applied to transform the original configuration space into the product space of four harmonic oscillators with a constraint. The relation derived between real time and oscillator (pseudo) time includes quantum corrections. In the limit ({h_bar}/2{pi}){yields}0, the time-dependent mean values of position and velocity describe themore » classical motion on a hyperbola and a circular hodograph, respectively. Moreover, the connection between pseudotime and real time comes out in analogy to Kepler's equation for elliptic orbits. The mean-square-root deviations of position and velocity components behave similarly in time to the corresponding ones of a spreading Gaussian wave packet in free space. To check the approximate treatment of the constraint, its contribution to the mean energy is determined with the result that it is negligible except for energy values close to the parabolic orbit with eccentricity equal to 1. It is inevitable to introduce a suitable scalar product in R{sup 4} which makes both the transformed Hamiltonian and the velocity operators Hermitian. An elementary necessary criterion is given for the energy interval where the constraint can be approximated by averaging.« less

Real-time 4D electrical resistivity imaging of tracer transport within an energically stimulated fracture zone

NASA Astrophysics Data System (ADS)

Johnson, T. C.

2016-12-01

Hydraulic fracture stimulation is used extensively in the subsurface energy sector to improve access between energy bearing formations and production boreholes. However, large uncertainties exist concerning the location and extent of stimulated fractures, and concerning the behavior of flow within those fractures. This uncertainty often results in significant risks, including induced seismicity and contamination of potable groundwater aquifers. Time-lapse electrical resistivity tomography (ERT) is a proven method of imaging fluid flow within fracture networks, by imaging the change in bulk conductivity induced by the presence of an electrically anomalous tracer within the fracture. In this work we demonstrate characterization and flow monitoring of a stimulated fracture using real-time four-dimensional ERT imaging within an unsaturated rhyolite formation. After stimulation, a conductive tracer was injected into the fracture zone. ERT survey data were continuously and autonomously collected, pre-processed on site, submitted to an off-site high performance computing system for inversion, and returned to the field for inspection. Surveys were collected at approximately 12 minute intervals. Data transmission and inversion required approximately 2 minutes per survey. The time-lapse imaging results show the dominant flow-paths within the stimulated fracture zone, thereby revealing the location and extent of the fracture, and the behavior of tracer flow within the fracture. Ultimately real-time imaging will enable site operators to better understand stimulation operations, and control post-stimulation reservoir operations for optimal performance and environmental protection.

Recovery of sparse translation-invariant signals with continuous basis pursuit

PubMed Central

Ekanadham, Chaitanya; Tranchina, Daniel; Simoncelli, Eero

2013-01-01

We consider the problem of decomposing a signal into a linear combination of features, each a continuously translated version of one of a small set of elementary features. Although these constituents are drawn from a continuous family, most current signal decomposition methods rely on a finite dictionary of discrete examples selected from this family (e.g., shifted copies of a set of basic waveforms), and apply sparse optimization methods to select and solve for the relevant coefficients. Here, we generate a dictionary that includes auxiliary interpolation functions that approximate translates of features via adjustment of their coefficients. We formulate a constrained convex optimization problem, in which the full set of dictionary coefficients represents a linear approximation of the signal, the auxiliary coefficients are constrained so as to only represent translated features, and sparsity is imposed on the primary coefficients using an L1 penalty. The basis pursuit denoising (BP) method may be seen as a special case, in which the auxiliary interpolation functions are omitted, and we thus refer to our methodology as continuous basis pursuit (CBP). We develop two implementations of CBP for a one-dimensional translation-invariant source, one using a first-order Taylor approximation, and another using a form of trigonometric spline. We examine the tradeoff between sparsity and signal reconstruction accuracy in these methods, demonstrating empirically that trigonometric CBP substantially outperforms Taylor CBP, which in turn offers substantial gains over ordinary BP. In addition, the CBP bases can generally achieve equally good or better approximations with much coarser sampling than BP, leading to a reduction in dictionary dimensionality. PMID:24352562

Does Churning in Medicaid Affect Health Care Use?

PubMed Central

Roberts, Eric T.; Pollack, Craig Evan

2017-01-01

Background Transitions into and out of Medicaid, termed churning, may disrupt access to and continuity of care. Low-income, working adults who became eligible for Medicaid under the Affordable Care Act are particularly susceptible to income and employment changes that lead to churning. Objective To compare health care use among adults who do and do not churn into and out of Medicaid. Data Longitudinal data from 6 panels of the Medical Expenditure Panel Survey. Methods We used differences-in-differences regression to compare health care use when adults reenrolled in Medicaid following a loss of coverage, to utilization in a control group of continuously enrolled adults. Outcome Measures Emergency department (ED) visits, ED visits resulting in an inpatient admission, and visits to office-based providers. Results During the study period, 264 adults churned into and out of Medicaid and 627 had continuous coverage. Churning adults had an average of approximately 0.05 Medicaid-covered office-based visits per month 4 months before reenrolling in Medicaid, significantly below the rate of approximately 0.20 visits in the control group. Visits to office-based providers did not reach the control group rate until several months after churning adults had resumed Medicaid coverage. Our comparisons found no evidence of significantly elevated ED and inpatient admission rates in the churning group following reenrollment. Conclusions Adults who lose Medicaid tend to defer their use of office-based care to periods when they are insured. Although this suggests that enrollment disruptions lead to suboptimal timing of care, we do not find evidence that adults reenroll in Medicaid with elevated acute care needs. PMID:26908088

Smoking cessation and subsequent weight change.

PubMed

Robertson, Lindsay; McGee, Rob; Hancox, Robert J

2014-06-01

People who quit smoking tend to gain more weight over time than those who continue to smoke. Previous research using clinical samples of smokers suggests that quitters typically experience a weight gain of approximately 5 kg in the year following smoking cessation, but these studies may overestimate the extent of weight gain in the general population. The existing population-based research in this area has some methodological limitations. We assessed a cohort of individuals born in Dunedin, New Zealand, between 1972-1973 at regular intervals from age 15 to 38. We used multiple linear regression analysis to investigate the association between smoking cessation at ages 21 years to 38 years and subsequent change in body mass index (BMI) and weight, controlling for baseline BMI, socioeconomic status, physical activity, alcohol use, and parity (women). Smoking status and outcome data were available at baseline and at follow-up for 914 study members. People who smoked at age 21 and who had quit by age 38 had a BMI on average 1.5 kg/m(2) greater than those who continued to smoke at age 38. This equated to a weight gain of approximately 5.7 kg in men and 5.1 kg in women above that of continuing smokers. However, the weight gain between age 21 and 38 among quitters was not significantly different to that of never-smokers. The amount of long-term weight gained after quitting smoking is likely to be lower than previous estimates based on research with clinical samples. On average, quitters do not experience greater weight gain than never-smokers.

MO-FG-202-03: Efficient Data Collection of Continuous 2D and Discrete Relative Dosimetric Data for Annual LINAC QA Using TrueBeam Developer Mode and a 1D Scanning Tank

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

Knutson, N; Schmidt, M; University of Rhode Island, Kingston, RI

2016-06-15

Purpose: To develop a method to exploit real-time dynamic machine and couch parameter control during linear accelerator (LINAC) beam delivery to facilitate efficient performance of TG-142 suggested, Annual LINAC QA tests. Methods: Varian’s TrueBeam Developer Mode (Varian Medical Systems, Palo Alto, CA) facilitates control of Varian’s TrueBeam LINAC via instructions provided in Extensible Markup Language (XML) files. This allows machine and couch parameters to be varied dynamically, in real-time, during beam delivery. Custom XML files were created to allow for the collection of (1) continuous Tissue Maximum Ratios (TMRs), (2) beam profiles, and (3) continuous output factors using a 1D-scanningmore » tank. TMRs were acquired by orienting an ionization chamber (IC) at isocenter (depth=25cm) and synchronizing a depth scan towards the water surface while lowering the couch at 1mm/s. For beam profiles, the couch was driven laterally and longitudinally while logging IC electrometer readings. Output factors (OFs) where collected by continually varying field sizes (4×4 to 30×30-cm{sup 2}) at a constant speed of 6.66 mm/s. To validate measurements, comparisons were made to data collected using traditional methods (e.g. 1D or 3D tank). Results: All data collecting using the proposed methods agreed with traditionally collected data (TMRs within 1%, OFs within 0.5% and beam profile agreement within 1% / 1mm) while taking less time to collect (factor of approximately 1/10) and with a finer sample resolution. Conclusion: TrueBeam developer mode facilitates collection of continuous data with the same accuracy as traditionally collected data with a finer resolution in less time. Results demonstrate an order of magnitude increase in sampled resolution and an order of magnitude reduction in collection time compared to traditional acquisition methods (e.g. 3D scanning tank). We are currently extending this approach to perform other TG-142 tasks.« less

Solution of the two-dimensional spectral factorization problem

NASA Technical Reports Server (NTRS)

Lawton, W. M.

1985-01-01

An approximation theorem is proven which solves a classic problem in two-dimensional (2-D) filter theory. The theorem shows that any continuous two-dimensional spectrum can be uniformly approximated by the squared modulus of a recursively stable finite trigonometric polynomial supported on a nonsymmetric half-plane.

Efficient High-Order Accurate Methods using Unstructured Grids for Hydrodynamics and Acoustics

DTIC Science & Technology

2007-08-31

Leer. On upstream differencing and godunov-type schemes for hyperbolic conservation laws. SIAM Review, 25(1):35-61, 1983. [46] F . Eleuterio Toro ...early stage [4-61. The basic idea can be surmised from simple approximation theory. If a continuous function f is to be approximated over a set of...a2f 4h4 a4ff(x+eh) = f (x)+-- + _ •-+• e +0 +... (1) where 0 < e < 1 for approximations inside the interval of width h. For a second-order approximation

Rational positive real approximations for LQG optimal compensators arising in active stabilization of flexible structures

NASA Technical Reports Server (NTRS)

Desantis, A.

1994-01-01

In this paper the approximation problem for a class of optimal compensators for flexible structures is considered. The particular case of a simply supported truss with an offset antenna is dealt with. The nonrational positive real optimal compensator transfer function is determined, and it is proposed that an approximation scheme based on a continued fraction expansion method be used. Comparison with the more popular modal expansion technique is performed in terms of stability margin and parameters sensitivity of the relative approximated closed loop transfer functions.

Phase control and fast start-up of a magnetron using modulation of an addressable faceted cathode

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

Browning, J., E-mail: JimBrowning@BoiseState.edu; Fernandez-Gutierrez, S.; Lin, M. C.

The use of an addressable, faceted cathode has been proposed as a method of modulating current injection in a magnetron to improve performance and control phase. To implement the controllable electron emission, five-sided and ten-sided faceted planar cathodes employing gated field emitters are considered as these emitters could be fabricated on flat substrates. For demonstration, the conformal finite-difference time-domain particle-in-cell simulation, as implemented in VORPAL, has been used to model a ten-cavity, rising sun magnetron using the modulated current sources and benchmarked against a typical continuous current source. For the modulated, ten-sided faceted cathode case, the electrons are injected frommore » three emitter elements on each of the ten facets. Each emitter is turned ON and OFF in sequence at the oscillating frequency with five emitters ON at one time to drive the five electron spokes of the π-mode. The emitter duty cycle is then 1/6th the Radio-Frequency (RF) period. Simulations show a fast start-up time as low as 35 ns for the modulated case compared to 100 ns for the continuous current cases. Analysis of the RF phase using the electron spoke locations and the RF magnetic field components shows that the phase is controlled for the modulated case while it is random, as typical, for the continuous current case. Active phase control during oscillation was demonstrated by shifting the phase of the electron injection 180° after oscillations started. The 180° phase shift time was approximately 25 RF cycles.« less

Implementation Strategies for Large-Scale Transport Simulations Using Time Domain Particle Tracking

NASA Astrophysics Data System (ADS)

Painter, S.; Cvetkovic, V.; Mancillas, J.; Selroos, J.

2008-12-01

Time domain particle tracking is an emerging alternative to the conventional random walk particle tracking algorithm. With time domain particle tracking, particles are moved from node to node on one-dimensional pathways defined by streamlines of the groundwater flow field or by discrete subsurface features. The time to complete each deterministic segment is sampled from residence time distributions that include the effects of advection, longitudinal dispersion, a variety of kinetically controlled retention (sorption) processes, linear transformation, and temporal changes in groundwater velocities and sorption parameters. The simulation results in a set of arrival times at a monitoring location that can be post-processed with a kernel method to construct mass discharge (breakthrough) versus time. Implementation strategies differ for discrete flow (fractured media) systems and continuous porous media systems. The implementation strategy also depends on the scale at which hydraulic property heterogeneity is represented in the supporting flow model. For flow models that explicitly represent discrete features (e.g., discrete fracture networks), the sampling of residence times along segments is conceptually straightforward. For continuous porous media, such sampling needs to be related to the Lagrangian velocity field. Analytical or semi-analytical methods may be used to approximate the Lagrangian segment velocity distributions in aquifers with low-to-moderate variability, thereby capturing transport effects of subgrid velocity variability. If variability in hydraulic properties is large, however, Lagrangian velocity distributions are difficult to characterize and numerical simulations are required; in particular, numerical simulations are likely to be required for estimating the velocity integral scale as a basis for advective segment distributions. Aquifers with evolving heterogeneity scales present additional challenges. Large-scale simulations of radionuclide transport at two potential repository sites for high-level radioactive waste will be used to demonstrate the potential of the method. The simulations considered approximately 1000 source locations, multiple radionuclides with contrasting sorption properties, and abrupt changes in groundwater velocity associated with future glacial scenarios. Transport pathways linking the source locations to the accessible environment were extracted from discrete feature flow models that include detailed representations of the repository construction (tunnels, shafts, and emplacement boreholes) embedded in stochastically generated fracture networks. Acknowledgment The authors are grateful to SwRI Advisory Committee for Research, the Swedish Nuclear Fuel and Waste Management Company, and Posiva Oy for financial support.

Anomalous transport in turbulent plasmas and continuous time random walks

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

Balescu, R.

1995-05-01

The possibility of a model of anomalous transport problems in a turbulent plasma by a purely stochastic process is investigated. The theory of continuous time random walks (CTRW`s) is briefly reviewed. It is shown that a particular class, called the standard long tail CTRW`s is of special interest for the description of subdiffusive transport. Its evolution is described by a non-Markovian diffusion equation that is constructed in such a way as to yield exact values for all the moments of the density profile. The concept of a CTRW model is compared to an exact solution of a simple test problem:more » transport of charged particles in a fluctuating magnetic field in the limit of infinite perpendicular correlation length. Although the well-known behavior of the mean square displacement proportional to {ital t}{sup 1/2} is easily recovered, the exact density profile cannot be modeled by a CTRW. However, the quasilinear approximation of the kinetic equation has the form of a non-Markovian diffusion equation and can thus be generated by a CTRW.« less

Using Buoy and Radar Data to Study Sudden Wind Gusts Over Coastal Regions

NASA Technical Reports Server (NTRS)

Priftis, Georgios; Chronis, Themis; Lang, Timothy J.

2017-01-01

Significant sudden wind gusts can pose a threat to aviation near the coastline, as well as small (sailing) boats and commercial ships approaching the ports. Such cases can result in wind speed changes of more than an order of magnitude within 5 minutes, which can then last up to 20 minutes or more. Although the constellation of scatterometers is a good means of studying maritime convection, those sudden gusts are not easily captured because of the low time resolution. The National Data Buoy Center (NDBC) provides continuous measurements of wind speed and direction along the US coastal regions every 6 minutes. Buoys are platforms placed at specific places on the seas, especially along coastlines, providing data for atmospheric and oceanic studies. Next Generation Radars (NEXRADs), after the recent upgrade of the network to dual-pol systems, offer enhanced capabilities to study atmospheric phenomena. NEXRADs provide continuous full-volume scans approximately every 5 minutes and therefore are close to the time resolution of the buoy measurements. Use of single- Doppler retrievals might also provide a means of further validation.

Fast mix table construction for material discretization

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

Johnson, S. R.

2013-07-01

An effective hybrid Monte Carlo-deterministic implementation typically requires the approximation of a continuous geometry description with a discretized piecewise-constant material field. The inherent geometry discretization error can be reduced somewhat by using material mixing, where multiple materials inside a discrete mesh voxel are homogenized. Material mixing requires the construction of a 'mix table,' which stores the volume fractions in every mixture so that multiple voxels with similar compositions can reference the same mixture. Mix table construction is a potentially expensive serial operation for large problems with many materials and voxels. We formulate an efficient algorithm to construct a sparse mixmore » table in O(number of voxels x log number of mixtures) time. The new algorithm is implemented in ADVANTG and used to discretize continuous geometries onto a structured Cartesian grid. When applied to an end-of-life MCNP model of the High Flux Isotope Reactor with 270 distinct materials, the new method improves the material mixing time by a factor of 100 compared to a naive mix table implementation. (authors)« less

Data-Driven Zero-Sum Neuro-Optimal Control for a Class of Continuous-Time Unknown Nonlinear Systems With Disturbance Using ADP.

PubMed

Wei, Qinglai; Song, Ruizhuo; Yan, Pengfei

2016-02-01

This paper is concerned with a new data-driven zero-sum neuro-optimal control problem for continuous-time unknown nonlinear systems with disturbance. According to the input-output data of the nonlinear system, an effective recurrent neural network is introduced to reconstruct the dynamics of the nonlinear system. Considering the system disturbance as a control input, a two-player zero-sum optimal control problem is established. Adaptive dynamic programming (ADP) is developed to obtain the optimal control under the worst case of the disturbance. Three single-layer neural networks, including one critic and two action networks, are employed to approximate the performance index function, the optimal control law, and the disturbance, respectively, for facilitating the implementation of the ADP method. Convergence properties of the ADP method are developed to show that the system state will converge to a finite neighborhood of the equilibrium. The weight matrices of the critic and the two action networks are also convergent to finite neighborhoods of their optimal ones. Finally, the simulation results will show the effectiveness of the developed data-driven ADP methods.

PAQ: Persistent Adaptive Query Middleware for Dynamic Environments

NASA Astrophysics Data System (ADS)

Rajamani, Vasanth; Julien, Christine; Payton, Jamie; Roman, Gruia-Catalin

Pervasive computing applications often entail continuous monitoring tasks, issuing persistent queries that return continuously updated views of the operational environment. We present PAQ, a middleware that supports applications' needs by approximating a persistent query as a sequence of one-time queries. PAQ introduces an integration strategy abstraction that allows composition of one-time query responses into streams representing sophisticated spatio-temporal phenomena of interest. A distinguishing feature of our middleware is the realization that the suitability of a persistent query's result is a function of the application's tolerance for accuracy weighed against the associated overhead costs. In PAQ, programmers can specify an inquiry strategy that dictates how information is gathered. Since network dynamics impact the suitability of a particular inquiry strategy, PAQ associates an introspection strategy with a persistent query, that evaluates the quality of the query's results. The result of introspection can trigger application-defined adaptation strategies that alter the nature of the query. PAQ's simple API makes developing adaptive querying systems easily realizable. We present the key abstractions, describe their implementations, and demonstrate the middleware's usefulness through application examples and evaluation.

ORACLS: A system for linear-quadratic-Gaussian control law design

NASA Technical Reports Server (NTRS)

Armstrong, E. S.

1978-01-01

A modern control theory design package (ORACLS) for constructing controllers and optimal filters for systems modeled by linear time-invariant differential or difference equations is described. Numerical linear-algebra procedures are used to implement the linear-quadratic-Gaussian (LQG) methodology of modern control theory. Algorithms are included for computing eigensystems of real matrices, the relative stability of a matrix, factored forms for nonnegative definite matrices, the solutions and least squares approximations to the solutions of certain linear matrix algebraic equations, the controllability properties of a linear time-invariant system, and the steady state covariance matrix of an open-loop stable system forced by white noise. Subroutines are provided for solving both the continuous and discrete optimal linear regulator problems with noise free measurements and the sampled-data optimal linear regulator problem. For measurement noise, duality theory and the optimal regulator algorithms are used to solve the continuous and discrete Kalman-Bucy filter problems. Subroutines are also included which give control laws causing the output of a system to track the output of a prescribed model.

Simulation of Trajectories for High Specific Impulse Deep Space Exploration

NASA Technical Reports Server (NTRS)

Polsgrove, Tara; Adams, Robert B.; Brady, Hugh J. (Technical Monitor)

2002-01-01

Difficulties in approximating flight times and deliverable masses for continuous thrust propulsion systems have complicated comparison and evaluation of proposed propulsion concepts. These continuous thrust propulsion systems are of interest to many groups, not the least of which are the electric propulsion and fusion communities. Several charts plotting the results of well-known trajectory simulation codes were developed and are contained in this paper. These charts illustrate the dependence of time of flight and payload ratio on jet power, initial mass, specific impulse and specific power. These charts are intended to be a tool by which people in the propulsion community can explore the possibilities of their propulsion system concepts. Trajectories were simulated using the tools VARITOP and IPOST. VARITOP is a well known trajectory optimization code that involves numerical integration based on calculus of variations. IPOST has several methods of trajectory simulation; the one used in this paper is Cowell's method for full integration of the equations of motion. The analytical method derived in the companion paper was also used to simulate the trajectory. The accuracy of this method is discussed in the paper.

A comparison of kinesthetic-tactual and visual displays via a critical tracking task. [for aircraft control

NASA Technical Reports Server (NTRS)

Jagacinski, R. J.; Miller, D. P.; Gilson, R. D.

1979-01-01

The feasibility of using the critical tracking task to evaluate kinesthetic-tactual displays was examined. The test subjects were asked to control a first-order unstable system with a continuously decreasing time constant by using either visual or tactual unidimensional displays. The results indicate that the critical tracking task is both a feasible and a reliable methodology for assessing tactual tracking. Further, that the critical tracking methodology is as sensitive and valid a measure of tactual tracking as visual tracking is demonstrated by the approximately equal effects of quickening for the tactual and visual displays.

Preconditioning and the limit to the incompressible flow equations

NASA Technical Reports Server (NTRS)

Turkel, E.; Fiterman, A.; Vanleer, B.

1993-01-01

The use of preconditioning methods to accelerate the convergence to a steady state for both the incompressible and compressible fluid dynamic equations are considered. The relation between them for both the continuous problem and the finite difference approximation is also considered. The analysis relies on the inviscid equations. The preconditioning consists of a matrix multiplying the time derivatives. Hence, the steady state of the preconditioned system is the same as the steady state of the original system. For finite difference methods the preconditioning can change and improve the steady state solutions. An application to flow around an airfoil is presented.

An employee assistance program for caregiver support.

PubMed

Mains, Douglas A; Fairchild, Thomas J; René, Antonio A

2006-01-01

The Comprehensive Caregiver Choices Program provided support for employee caregivers of elderly people for employees at a hospital in Fort Worth, Texas. Key informant interviews and focus groups provided direction for program development and implementation. A full-time MSW and professionals with expertise in gerontology/geriatrics provided education and care coordination services to caregivers. Approximately 4% of the hospital's workforce participated in the program. Attendees evaluated educational sessions and follow-up interviews were conducted with program participants. Caregiver support programs must continue to seek innovative and creative marketing and service delivery methods to reach out and assist working caregivers in need of support.

Modeling of confined turbulent fluid-particle flows using Eulerian and Lagrangian schemes

NASA Technical Reports Server (NTRS)

Adeniji-Fashola, A.; Chen, C. P.

1990-01-01

Two important aspects of fluid-particulate interaction in dilute gas-particle turbulent flows (the turbulent particle dispersion and the turbulence modulation effects) are addressed, using the Eulerian and Lagrangian modeling approaches to describe the particulate phase. Gradient-diffusion approximations are employed in the Eulerian formulation, while a stochastic procedure is utilized to simulate turbulent dispersion in the Lagrangina formulation. The k-epsilon turbulence model is used to characterize the time and length scales of the continuous phase turbulence. Models proposed for both schemes are used to predict turbulent fully-developed gas-solid vertical pipe flow with reasonable accuracy.

Test Results for the 2.5-kVA Ground Fault Detector.

DTIC Science & Technology

1986-01-01

powered through Q1 is delayed in turning off by capacitor C4 for approximately 12 msec. When the relay does drop out, the triac Q7 (a bidirectional...SECONDS) CALBIRATIONS, ETC.) / / -. L a 2 33 ( j4 -40 7 S’f9 I! Note time of con pletlon o test series . .I1 " , -3 TEST DATA FORM Bc (CONTINUATION...test series . 2 *51/7 ,6. L7.. i K-t TEST CATA FORM D OCEAN OPERABILITY TESTS FOR ELEETRIC FIELD DETECTOR AND GROUND FAULT DETECTORS This data form is to

Continuous state-space representation of a bucket-type rainfall-runoff model: a case study with the GR4 model using state-space GR4 (version 1.0)

NASA Astrophysics Data System (ADS)

Santos, Léonard; Thirel, Guillaume; Perrin, Charles

2018-04-01

In many conceptual rainfall-runoff models, the water balance differential equations are not explicitly formulated. These differential equations are solved sequentially by splitting the equations into terms that can be solved analytically with a technique called operator splitting. As a result, only the solutions of the split equations are used to present the different models. This article provides a methodology to make the governing water balance equations of a bucket-type rainfall-runoff model explicit and to solve them continuously. This is done by setting up a comprehensive state-space representation of the model. By representing it in this way, the operator splitting, which makes the structural analysis of the model more complex, could be removed. In this state-space representation, the lag functions (unit hydrographs), which are frequent in rainfall-runoff models and make the resolution of the representation difficult, are first replaced by a so-called Nash cascade and then solved with a robust numerical integration technique. To illustrate this methodology, the GR4J model is taken as an example. The substitution of the unit hydrographs with a Nash cascade, even if it modifies the model behaviour when solved using operator splitting, does not modify it when the state-space representation is solved using an implicit integration technique. Indeed, the flow time series simulated by the new representation of the model are very similar to those simulated by the classic model. The use of a robust numerical technique that approximates a continuous-time model also improves the lag parameter consistency across time steps and provides a more time-consistent model with time-independent parameters.

On the Use of Statistics in Design and the Implications for Deterministic Computer Experiments

NASA Technical Reports Server (NTRS)

Simpson, Timothy W.; Peplinski, Jesse; Koch, Patrick N.; Allen, Janet K.

1997-01-01

Perhaps the most prevalent use of statistics in engineering design is through Taguchi's parameter and robust design -- using orthogonal arrays to compute signal-to-noise ratios in a process of design improvement. In our view, however, there is an equally exciting use of statistics in design that could become just as prevalent: it is the concept of metamodeling whereby statistical models are built to approximate detailed computer analysis codes. Although computers continue to get faster, analysis codes always seem to keep pace so that their computational time remains non-trivial. Through metamodeling, approximations of these codes are built that are orders of magnitude cheaper to run. These metamodels can then be linked to optimization routines for fast analysis, or they can serve as a bridge for integrating analysis codes across different domains. In this paper we first review metamodeling techniques that encompass design of experiments, response surface methodology, Taguchi methods, neural networks, inductive learning, and kriging. We discuss their existing applications in engineering design and then address the dangers of applying traditional statistical techniques to approximate deterministic computer analysis codes. We conclude with recommendations for the appropriate use of metamodeling techniques in given situations and how common pitfalls can be avoided.

Raising the Bar, Building Capacity: Driving Improvement in California's Continuation High Schools

ERIC Educational Resources Information Center

de Velasco, Jorge Ruiz; McLaughlin, Milbrey

2012-01-01

California's approximately 500 continuation high schools are estimated to serve more than 115,000 California high school students each year--a number that approaches almost 10 percent of all high school students and as many as one of every seven high school seniors. Continuation schools are, however, more racially and ethnically concentrated than…

Stochastic dynamics and non-equilibrium thermodynamics of a bistable chemical system: the Schlögl model revisited.

PubMed

Vellela, Melissa; Qian, Hong

2009-10-06

Schlögl's model is the canonical example of a chemical reaction system that exhibits bistability. Because the biological examples of bistability and switching behaviour are increasingly numerous, this paper presents an integrated deterministic, stochastic and thermodynamic analysis of the model. After a brief review of the deterministic and stochastic modelling frameworks, the concepts of chemical and mathematical detailed balances are discussed and non-equilibrium conditions are shown to be necessary for bistability. Thermodynamic quantities such as the flux, chemical potential and entropy production rate are defined and compared across the two models. In the bistable region, the stochastic model exhibits an exchange of the global stability between the two stable states under changes in the pump parameters and volume size. The stochastic entropy production rate shows a sharp transition that mirrors this exchange. A new hybrid model that includes continuous diffusion and discrete jumps is suggested to deal with the multiscale dynamics of the bistable system. Accurate approximations of the exponentially small eigenvalue associated with the time scale of this switching and the full time-dependent solution are calculated using Matlab. A breakdown of previously known asymptotic approximations on small volume scales is observed through comparison with these and Monte Carlo results. Finally, in the appendix section is an illustration of how the diffusion approximation of the chemical master equation can fail to represent correctly the mesoscopically interesting steady-state behaviour of the system.

Evolution of the entanglement of the N00N-type of states in a coupled two cavity system via an adiabatic approximation

NASA Astrophysics Data System (ADS)

Chakrabarti, R.; Sreekumari, G.; Yogesh, V.

2018-06-01

We study a system of two cavities each encapsulating a qubit and an oscillator degrees of freedom. An ultrastrong interaction between the qubit and the oscillator is assumed, and the photons are allowed to hop between the cavities. A partition of the time scale between the fast-moving oscillator and the slow moving qubit allows us to set up an adiabatic approximation procedure where we employ the delocalized degrees of freedom to diagonalize the Hamiltonian. The time evolution of the N00N-type initial states now furnishes, for instance, the reduced density matrix of a bipartite system of two qubits. For a macroscopic size of the N00N component of the initial state the sudden death of the entanglement between the qubits and its continued null value are prominently manifest as the information percolates to the qubits after long intervals. For the low photon numbers of the initial states the dynamics produces almost maximally entangled two-qubit states, which by utilizing the Hilbert–Schmidt distance between the density matrices, are observed to be nearly pure generalized Bell states.

Dipolar effects on propagation of ultrashort laser pulse in one-dimensional para-nitroaniline (pNA) molecules

NASA Astrophysics Data System (ADS)

Zhao, Ke; Li, Hong-Yu; Liu, Ji-Cai; Wang, Chuan-Kui; Luo, Yi

2005-12-01

The dynamic behaviour of ultrashort (femtosecond) laser pulses in a molecular medium is studied by solving the full Maxwell-Bloch equations beyond the limits of the slowly varying envelope approximation and the rotating-wave approximation under the resonant and the non-resonant conditions. A one-dimensional asymmetric charge-transfer molecule, para-nitroaniline, is used as a model molecule whose electronic properties are calculated with the time-dependent hybrid density functional theory. Under the one-photon resonant condition, 4π pulse is separated into two sub-pulses. The weight of the second-harmonic component mainly contributed by the two-photon excitation becomes stronger with longer propagation time. Under the two-photon resonant condition, the separation of 4π pulse is not induced and many higher-order spectral components beyond the second-harmonic generation occur. Interestingly, when the pulse propagates for long enough, the carrier modification becomes so significant that a continuous spectrum is generated. The Fourier transform of the high-harmonic spectrum demonstrates that an even shorter laser pulse can be produced in both resonant and non-resonant propagations. The effects of permanent dipole moments on the pulse evolution are discussed.

Topics in Multivariate Approximation Theory.

DTIC Science & Technology

1982-05-01

once that a continuous function f can be approximated from Sa :o span (N3 )B63 to within *(f, 131 ), with 13 t- sup3 e3 dian PS The simple approximation...N(C) 3- U P s P3AC 0 0 ) . Then, as in Lebesgue’s inequality, we could conclude that f - Qf - f-p - Q(f-p) , for all p e k k therefore I(f-0f) JCI 4 I

Approximate Evaluation of Reliability and Availability via Perturbation Analysis.

DTIC Science & Technology

1986-12-01

generating the dxact answers to which the results of the approximation will be compared are discussed:." - 87 7" 2 04 2LOISTRIGUTIONIAVAILASILITYI OF...appropriately, constructing the Markov process that approximately governs interclass behavior from the result above (this is called the enlarged... compared to a numerical or analytical computation of the aame quantities. This work and its continuation represents our progress so far on Goal 3. 2.4I

From Prime to Extended Mission: Evolution of the MER Tactical Uplink Process

NASA Technical Reports Server (NTRS)

Mishkin, Andrew H.; Laubach, Sharon

2006-01-01

To support a 90-day surface mission for two robotic rovers, the Mars Exploration Rover mission designed and implemented an intensive tactical operations process, enabling daily commanding of each rover. Using a combination of new processes, custom software tools, a Mars-time staffing schedule, and seven-day-a-week operations, the MER team was able to compress the traditional weeks-long command-turnaround for a deep space robotic mission to about 18 hours. However, the pace of this process was never intended to be continued indefinitely. Even before the end of the three-month prime mission, MER operations began evolving towards greater sustainability. A combination of continued software tool development, increasing team experience, and availability of reusable sequences first reduced the mean process duration to approximately 11 hours. The number of workshifts required to perform the process dropped, and the team returned to a modified 'Earth-time' schedule. Additional process and tool adaptation eventually provided the option of planning multiple Martian days of activity within a single workshift, making 5-day-a-week operations possible. The vast majority of the science team returned to their home institutions, continuing to participate fully in the tactical operations process remotely. MER has continued to operate for over two Earth-years as many of its key personnel have moved on to other projects, the operations team and budget have shrunk, and the rovers have begun to exhibit symptoms of aging.

Measurement of the Perception of Control during Continuous Movement using Electroencephalography

PubMed Central

Wen, Wen; Yamashita, Atsushi; Asama, Hajime

2017-01-01

“Sense of control” refers to the subjective feeling of control over external events. Numerous neuropsychological studies have investigated the neural basis of the sense of control during action performance; however, most previous studies have focused on responses to a single discrete action outcome rather than real-time processing of action-outcome sequences. In the present study, we aimed to identify whether certain patterns of brain activation are associated with the perceived control during continuous movement. We recorded electroencephalography (EEG) signals while participants continuously moved a right-handed mouse in an attempt to control multiple visual stimuli. When participants perceived a sense of control over the stimuli, we observed a positive potential approximately 550 ms after the onset of movement, while no similar potential was observed when participants reported a lack of control. The appearance of this potential was consistent with the time window of awareness of control in a behavioral test using the same task, and likely reflected the explicit allocation of attention to control. Moreover, we found that the alpha-mu rhythm, which is linked to sensorimotor processing, was significantly suppressed after participants came to a conclusion regarding the level of control, regardless of whether control or lack of control was perceived. In summary, our results suggest that the late positive potential after the onset of the movement and the suppression of alpha-mu rhythm can be used as markers of the perception of control during continuous action performance and feedback monitoring. PMID:28798677

Migrant Education Binational Program.

ERIC Educational Resources Information Center

Dolson, David P.; Villasenor, Gildardo

The Binational Program promotes the continuity of education for approximately 45,000 students who migrate between Mexico and the United States each year, a pattern related to their parents' work as migrant agricultural laborers. Begun in California, the program now encompasses approximately 10 U.S. and 32 Mexican states (including the Federal…

21 CFR 878.4011 - Tissue adhesive with adjunct wound closure device for topical approximation of skin.

Code of Federal Regulations, 2011 CFR

2011-04-01

... ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY... approximated skin edges of wounds from surgical incisions, including punctures from minimally invasive surgery, and simple, thoroughly cleansed, trauma-induced lacerations. It may be used in conjunction with, but...

Continuation of probability density functions using a generalized Lyapunov approach

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

Baars, S., E-mail: s.baars@rug.nl; Viebahn, J.P., E-mail: viebahn@cwi.nl; Mulder, T.E., E-mail: t.e.mulder@uu.nl

Techniques from numerical bifurcation theory are very useful to study transitions between steady fluid flow patterns and the instabilities involved. Here, we provide computational methodology to use parameter continuation in determining probability density functions of systems of stochastic partial differential equations near fixed points, under a small noise approximation. Key innovation is the efficient solution of a generalized Lyapunov equation using an iterative method involving low-rank approximations. We apply and illustrate the capabilities of the method using a problem in physical oceanography, i.e. the occurrence of multiple steady states of the Atlantic Ocean circulation.

Scalable and continuous fabrication of bio-inspired dry adhesives with a thermosetting polymer.

PubMed

Lee, Sung Ho; Kim, Sung Woo; Kang, Bong Su; Chang, Pahn-Shick; Kwak, Moon Kyu

2018-04-04

Many research groups have developed unique micro/nano-structured dry adhesives by mimicking the foot of the gecko with the use of molding methods. Through these previous works, polydimethylsiloxane (PDMS) has been developed and become the most commonly used material for making artificial dry adhesives. The material properties of PDMS are well suited for making dry adhesives, such as conformal contacts with almost zero preload, low elastic moduli for stickiness, and easy cleaning with low surface energy. From a performance point of view, dry adhesives made with PDMS can be highly advantageous but are limited by its low productivity, as production takes an average of approximately two hours. Given the low productivity of PDMS, some research groups have developed dry adhesives using UV-curable materials, which are capable of continuous roll-to-roll production processes. However, UV-curable materials were too rigid to produce good adhesion. Thus, we established a PDMS continuous-production system to achieve good productivity and adhesion performance. We designed a thermal roll-imprinting lithography (TRL) system for the continuous production of PDMS microstructures by shortening the curing time by controlling the curing temperature (the production speed is up to 150 mm min-1). Dry adhesives composed of PDMS were fabricated continuously via the TRL system.

Tracking inorganic foulants irreversibly accumulated on low-pressure membranes for treating surface water.

PubMed

Yamamura, Hiroshi; Kimura, Katsuki; Higuchi, Kumiko; Watanabe, Yoshimasa; Ding, Qing; Hafuka, Akira

2015-12-15

While low-pressure membrane filtration processes (i.e., microfiltration and ultrafiltration) can offer precise filtration than sand filtration, they pose the problem of reduced efficiency due to membrane fouling. Although many studies have examined membrane fouling by organic substances, there is still not enough data available concerning membrane fouling by inorganic substances. The present research investigated changes in the amounts of inorganic components deposited on the surface of membrane filters over time using membrane specimens sampled thirteen times at arbitrary time intervals during pilot testing in order to determine the mechanism by which irreversible fouling by inorganic substances progresses. The experiments showed that the inorganic components that primarily contribute to irreversible fouling vary as filtration continues. It was discovered that, in the initial stage of operation, the main membrane-fouling substance was iron, whereas the primary membrane-fouling substances when operation finished were manganese, calcium, and silica. The amount of iron accumulated on the membrane increased up to the thirtieth day of operation, after which it reached a steady state. After the accumulation of iron became static, subsequent accumulation of manganese was observed. The fact that the removal rates of these inorganic components also increased gradually shows that the size of the exclusion pores of the membrane filter narrows as operation continues. Studying particle size distributions of inorganic components contained in source water revealed that while many iron particles are approximately the same size as membrane pores, the fraction of manganese particles slightly smaller than the pores in diameter was large. From these results, it is surmised that iron particles approximately the same size as the pores block them soon after the start of operation, and as the membrane pores narrow with the development of fouling, they become further blocked by manganese particles approximately the same size as the narrowed pores. Calcium and silica are assumed to accumulate on the membrane due to their cross-linking action and/or complex formation with organic substances such as humic compounds. The present research is the first to clearly show that the inorganic components that contribute to membrane fouling differ according to the stage of membrane fouling progression; the information obtained by this research should enable chemical cleaning or operational control in accordance with the stage of membrane fouling progression. Copyright © 2015 Elsevier Ltd. All rights reserved.

Sleep During Pregnancy: The nuMoM2b Pregnancy and Sleep Duration and Continuity Study.

PubMed

Reid, Kathryn J; Facco, Francesca L; Grobman, William A; Parker, Corette B; Herbas, Marcos; Hunter, Shannon; Silver, Robert M; Basner, Robert C; Saade, George R; Pien, Grace W; Manchanda, Shalini; Louis, Judette M; Nhan-Chang, Chia-Lang; Chung, Judith H; Wing, Deborah A; Simhan, Hyagriv N; Haas, David M; Iams, Jay; Parry, Samuel; Zee, Phyllis C

2017-05-01

To characterize sleep duration, timing and continuity measures in pregnancy and their association with key demographic variables. Multisite prospective cohort study. Women enrolled in the nuMoM2b study (nulliparous women with a singleton gestation) were recruited at the second study visit (16-21 weeks of gestation) to participate in the Sleep Duration and Continuity substudy. Women <18 years of age or with pregestational diabetes or chronic hypertension were excluded from participation. Women wore a wrist activity monitor and completed a sleep log for 7 consecutive days. Time in bed, sleep duration, fragmentation index, sleep efficiency, wake after sleep onset, and sleep midpoint were averaged across valid primary sleep periods for each participant. Valid data were available from 782 women with mean age of 27.3 (5.5) years. Median sleep duration was 7.4 hours. Approximately 27.9% of women had a sleep duration of <7 hours; 2.6% had a sleep duration of >9 hours. In multivariable models including age, race/ethnicity, body mass index, insurance status, and recent smoking history, sleep duration was significantly associated with race/ethnicity and insurance status, while time in bed was only associated with insurance status. Sleep continuity measures and sleep midpoint were significantly associated with all covariates in the model, with the exception of age for fragmentation index and smoking for wake after sleep onset. Our results demonstrate the relationship between sleep and important demographic characteristics during pregnancy. © Sleep Research Society 2017. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

Absolute continuity for operator valued completely positive maps on C∗-algebras

NASA Astrophysics Data System (ADS)

Gheondea, Aurelian; Kavruk, Ali Şamil

2009-02-01

Motivated by applicability to quantum operations, quantum information, and quantum probability, we investigate the notion of absolute continuity for operator valued completely positive maps on C∗-algebras, previously introduced by Parthasarathy [in Athens Conference on Applied Probability and Time Series Analysis I (Springer-Verlag, Berlin, 1996), pp. 34-54]. We obtain an intrinsic definition of absolute continuity, we show that the Lebesgue decomposition defined by Parthasarathy is the maximal one among all other Lebesgue-type decompositions and that this maximal Lebesgue decomposition does not depend on the jointly dominating completely positive map, we obtain more flexible formulas for calculating the maximal Lebesgue decomposition, and we point out the nonuniqueness of the Lebesgue decomposition as well as a sufficient condition for uniqueness. In addition, we consider Radon-Nikodym derivatives for absolutely continuous completely positive maps that, in general, are unbounded positive self-adjoint operators affiliated to a certain von Neumann algebra, and we obtain a spectral approximation by bounded Radon-Nikodym derivatives. An application to the existence of the infimum of two completely positive maps is indicated, and formulas in terms of Choi's matrices for the Lebesgue decomposition of completely positive maps in matrix algebras are obtained.

Air bubbles induce a critical continuous stress to prevent marine biofouling accumulation

NASA Astrophysics Data System (ADS)

Belden, Jesse; Menesses, Mark; Dickenson, Natasha; Bird, James

2017-11-01

Significant shear stresses are needed to remove established hard fouling organisms from a ship hull. Given that there is a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. One approach to mitigate marine biofouling is to continuously introduce a curtain of air bubbles under a submerged surface; it is believed that this aeration exploits the small stresses induced by rising bubbles to continuously prevent accumulation. Although curtains of rising bubbles have successfully prevented biofouling accumulation, it is unclear if a single stream of bubbles could maintain a clean surface. In this talk, we show that single bubble stream aeration can prevent biofouling accumulation in regions for which the average wall stress exceeds approximately 0.01 Pa. This value is arrived at by comparing observations of biofouling growth and prevention from field studies with laboratory measurements that probe the associated flow fields. We also relate the spatial and temporal characteristics of the flow to the size and frequency of the rising bubbles, which informs the basic operating conditions required for aeration to continuously prevent biofouling accumulation.

Shedding New Light on Exploding Stars: Terascale Simulations of Nuetrino-Dreiven Supernovas and Their Nucleosynthesis

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

Dennis C. Smolarski, S.J.

Project Abstract This project was a continuation of work begun under a subcontract issued off of TSI-DOE Grant 1528746, awarded to the University of Illinois Urbana-Champaign. Dr. Anthony Mezzacappa is the Principal Investigator on the Illinois award. A separate award was issued to Santa Clara University to continue the collaboration during the time period May 2003 ? 2004. Smolarski continued to work on preconditioner technology and its interface with various iterative methods. He worked primarily with F. Dough Swesty (SUNY-Stony Brook) in continuing software development started in the 2002-03 academic year. Special attention was paid to the development and testingmore » of difference sparse approximate inverse preconditioners and their use in the solution of linear systems arising from radiation transport equations. The target was a high performance platform on which efficient implementation is a critical component of the overall effort. Smolarski also focused on the integration of the adaptive iterative algorithm, Chebycode, developed by Tom Manteuffel and Steve Ashby and adapted by Ryan Szypowski for parallel platforms, into the radiation transport code being developed at SUNY-Stony Brook.« less

Map of the approximate inland extent of saltwater at the base of the Biscayne aquifer in the Model Land Area of Miami-Dade County, Florida, 2016

USGS Publications Warehouse

Prinos, Scott T.

2017-07-11

The inland extent of saltwater at the base of the Biscayne aquifer in the Model Land Area of Miami-Dade County, Florida, was mapped in 2011. Since that time, the saltwater interface has continued to move inland. The interface is near several active well fields; therefore, an updated approximation of the inland extent of saltwater and an improved understanding of the rate of movement of the saltwater interface are necessary. A geographic information system was used to create a map using the data collected by the organizations that monitor water salinity in this area. An average rate of saltwater interface movement of 140 meters per year was estimated by dividing the distance between two monitoring wells (TPGW-7L and Sec34-MW-02-FS) by the travel time. The travel time was determined by estimating the dates of arrival of the saltwater interface at the wells and computing the difference. This estimate assumes that the interface is traveling east to west between the two monitoring wells. Although monitoring is spatially limited in this area and some of the wells are not ideally designed for salinity monitoring, the monitoring network in this area is improving in spatial distribution and most of the new wells are well designed for salinity monitoring. The approximation of the inland extent of the saltwater interface and the estimated rate of movement of the interface are dependent on existing data. Improved estimates could be obtained by installing uniformly designed monitoring wells in systematic transects extending landward of the advancing saltwater interface.

Compact D-D Neutron Source-Driven Subcritical Multiplier and Beam-Shaping Assembly for Boron Neutron Capture Therapy

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

Francesco Ganda; Jasmina Vujic; Ehud Greenspan

2010-12-01

This work assesses the feasibility of using a small, safe, and inexpensive keff 0.98 subcritical fission assembly [subcritical neutron multiplier (SCM)] to amplify the treatment neutron beam intensity attainable from a compact deuterium-deuterium (D-D) fusion neutron source delivering [approximately]1012 n/s. The objective is to reduce the treatment time for deep-seated brain tumors to [approximately]1 h. The paper describes the optimal SCM design and two optimal beam-shaping assemblies (BSAs) - one designed to maximize the dose rate and the other designed to maximize the total dose that can be delivered to a deep-seated tumor. The neutron beam intensity amplification achieved withmore » the optimized SCM and BSA results in an increase in the treatment dose rate by a factor of 18: from 0.56 Gy/h without the SCM to 10.1 Gy/h. The entire SCM is encased in an aluminum structure. The total amount of 20% enriched uranium required for the SCM is 8.5 kg, and the cost (not including fabrication) is estimated to be less than $60,000. The SCM power level is estimated at 400 W when driven by a 1012 n/s D-D neutron source. This translates into consumption of only [approximately]0.6% of the initially loaded 235U atoms during 50 years of continuous operation and implies that the SCM could operate continuously for the entire lifetime of the facility without refueling. Cooling the SCM does not pose a challenge; it may be accomplished by natural circulation as the maximum heat flux is only 0.034 W/cm2.« less

Brownian dynamics simulations of a flexible polymer chain which includes continuous resistance and multibody hydrodynamic interactions

NASA Astrophysics Data System (ADS)

Butler, Jason E.; Shaqfeh, Eric S. G.

2005-01-01

Using methods adapted from the simulation of suspension dynamics, we have developed a Brownian dynamics algorithm with multibody hydrodynamic interactions for simulating the dynamics of polymer molecules. The polymer molecule is modeled as a chain composed of a series of inextensible, rigid rods with constraints at each joint to ensure continuity of the chain. The linear and rotational velocities of each segment of the polymer chain are described by the slender-body theory of Batchelor [J. Fluid Mech. 44, 419 (1970)]. To include hydrodynamic interactions between the segments of the chain, the line distribution of forces on each segment is approximated by making a Legendre polynomial expansion of the disturbance velocity on the segment, where the first two terms of the expansion are retained in the calculation. Thus, the resulting linear force distribution is specified by a center of mass force, couple, and stresslet on each segment. This method for calculating the hydrodynamic interactions has been successfully used to simulate the dynamics of noncolloidal suspensions of rigid fibers [O. G. Harlen, R. R. Sundararajakumar, and D. L. Koch, J. Fluid Mech. 388, 355 (1999); J. E. Butler and E. S. G. Shaqfeh, J. Fluid Mech. 468, 204 (2002)]. The longest relaxation time and center of mass diffusivity are among the quantities calculated with the simulation technique. Comparisons are made for different levels of approximation of the hydrodynamic interactions, including multibody interactions, two-body interactions, and the "freely draining" case with no interactions. For the short polymer chains studied in this paper, the results indicate a difference in the apparent scaling of diffusivity with polymer length for the multibody versus two-body level of approximation for the hydrodynamic interactions.

Brownian dynamics simulations of a flexible polymer chain which includes continuous resistance and multibody hydrodynamic interactions.

PubMed

Butler, Jason E; Shaqfeh, Eric S G

2005-01-01

Using methods adapted from the simulation of suspension dynamics, we have developed a Brownian dynamics algorithm with multibody hydrodynamic interactions for simulating the dynamics of polymer molecules. The polymer molecule is modeled as a chain composed of a series of inextensible, rigid rods with constraints at each joint to ensure continuity of the chain. The linear and rotational velocities of each segment of the polymer chain are described by the slender-body theory of Batchelor [J. Fluid Mech. 44, 419 (1970)]. To include hydrodynamic interactions between the segments of the chain, the line distribution of forces on each segment is approximated by making a Legendre polynomial expansion of the disturbance velocity on the segment, where the first two terms of the expansion are retained in the calculation. Thus, the resulting linear force distribution is specified by a center of mass force, couple, and stresslet on each segment. This method for calculating the hydrodynamic interactions has been successfully used to simulate the dynamics of noncolloidal suspensions of rigid fibers [O. G. Harlen, R. R. Sundararajakumar, and D. L. Koch, J. Fluid Mech. 388, 355 (1999); J. E. Butler and E. S. G. Shaqfeh, J. Fluid Mech. 468, 204 (2002)]. The longest relaxation time and center of mass diffusivity are among the quantities calculated with the simulation technique. Comparisons are made for different levels of approximation of the hydrodynamic interactions, including multibody interactions, two-body interactions, and the "freely draining" case with no interactions. For the short polymer chains studied in this paper, the results indicate a difference in the apparent scaling of diffusivity with polymer length for the multibody versus two-body level of approximation for the hydrodynamic interactions. (c) 2005 American Institute of Physics.

Association of the Duration of Active Pushing With Obstetric Outcomes.

PubMed

Grobman, William A; Bailit, Jennifer; Lai, Yinglei; Reddy, Uma M; Wapner, Ronald J; Varner, Michael W; Caritis, Steve N; Prasad, Mona; Tita, Alan T N; Saade, George; Sorokin, Yoram; Rouse, Dwight J; Blackwell, Sean C; Tolosa, Jorge E

2016-04-01

To estimate the associations between the duration of active pushing during the second stage of labor and maternal and neonatal outcomes. We performed an observational study in which data were obtained by trained abstractors from maternal and neonatal charts of deliveries at 25 hospitals over a 3-year period. In this secondary analysis, women with no prior cesarean delivery who had a term, singleton, cephalic gestation and reached complete dilation were analyzed. The duration of pushing, defined as the time from initiation of pushing to either vaginal delivery or the decision to proceed with a cesarean delivery, was determined. The primary maternal outcome was cesarean delivery and the primary neonatal outcome was a composite that included: mechanical ventilation, proven sepsis, brachial plexus palsy, clavicular fracture, skull fracture, other fracture, seizures, hypoxic-ischemic encephalopathy, or death. Nulliparous and parous women were analyzed separately in univariable and then multivariable analyses. A total of 53,285 women were analyzed. In both nulliparous and parous women, longer duration of pushing was associated with increased odds of both cesarean delivery and the neonatal adverse outcome composite. Nevertheless, even after 4 hours of pushing, approximately 78% of nulliparous women who continued with active pushing had a vaginal delivery and more than 97% did not have the composite adverse neonatal outcome. Similarly, after more than 2 hours of pushing, approximately 82% of parous women who continued active pushing delivered vaginally and more than 97% did not have the adverse neonatal outcome. A longer duration of pushing is associated with an increased relative risk, but small absolute difference in risk, of neonatal complications. Approximately 78% of nulliparous women delivered vaginally even after 4 hours of pushing.

Association of the Duration of Active Pushing With Obstetric Outcomes

PubMed Central

Grobman, William A.; Bailit, Jennifer; Lai, Yinglei; Reddy, Uma M.; Wapner, Ronald J.; Varner, Michael W.; Caritis, Steve N.; Prasad, Mona; Tita, Alan T.N.; Saade, George; Sorokin, Yoram; Rouse, Dwight J.; Blackwell, Sean C.; Tolosa, Jorge E.

2016-01-01

Objective To estimate the associations between the duration of active pushing during the second stage of labor and maternal and neonatal outcomes. Methods We performed an observational study in which data were obtained by trained abstractors from maternal and neonatal charts of deliveries at 25 hospitals over a 3-year period. In this secondary analysis, women with no prior cesarean delivery who had a term, singleton, cephalic gestation and reached complete dilation were analyzed. The duration of pushing, defined as the time from initiation of pushing to either vaginal delivery or the decision to proceed with a cesarean, was determined. The primary maternal outcome was cesarean delivery and the primary neonatal outcome was a composite that included: mechanical ventilation, proven sepsis, brachial plexus palsy, clavicular fracture, skull fracture, other fracture, seizures, hypoxic ischemic encephalopathy, or death. Nulliparous and parous women were analyzed separately in univariable and then multivariable analyses. Results Fifty three thousand two hundred eighty five women were analyzed. In both nulliparous and parous women, longer duration of pushing was associated with increased odds of both cesarean delivery and the neonatal adverse outcome composite. Nevertheless, even after 4 hours of pushing, approximately 78% of nulliparous women who continued with active pushing had a vaginal delivery and over 97% did not have the composite adverse neonatal outcome. Similarly, after more than 2 hours of pushing, approximately 82% of parous women who continued active pushing delivered vaginally and over 97% did not have the adverse neonatal outcome. Conclusion A longer duration of pushing is associated with an increased relative risk, but small absolute difference in risk, of neonatal complications. Approximately 78% of nulliparous women delivered vaginally even after 4 hours of pushing. PMID:26959213

Effect of continuous negative-pressure breathing on skin blood flow during exercise in a hot environment.

PubMed

Nagashima, K; Nose, H; Takamata, A; Morimoto, T

1998-06-01

To assess the impact of continuous negative-pressure breathing (CNPB) on the regulation of skin blood flow, we measured forearm blood flow (FBF) by venous-occlusion plethysmography and laser-Doppler flow (LDF) at the anterior chest during exercise in a hot environment (ambient temperature = 30 degreesC, relative humidity = approximately 30%). Seven male subjects exercised in the upright position at an intensity of 60% peak oxygen consumption rate for 40 min with and without CNPB after 20 min of exercise. The esophageal temperature (Tes) in both conditions increased to 38.1 degreesC by the end of exercise, without any significant differences between the two trials. Mean arterial pressure (MAP) increased by approximately 15 mmHg by 8 min of exercise, without any significant difference between the two trials before CNPB. However, CNPB reduced MAP by approximately 10 mmHg after 24 min of exercise (P < 0.05). The increase in FBF and LDF in the control condition leveled off after 18 min of exercise above a Tes of 37.7 degreesC, whereas in the CNPB trial the increase continued, with a rise in Tes despite the decrease in MAP. These results suggest that CNPB enhances vasodilation of skin above a Tes of approximately 38 degrees C by stretching intrathoracic baroreceptors such as cardiopulmonary baroreceptors.

Bi-directional ultrasonic wave coupling to FBGs in continuously bonded optical fiber sensing.

PubMed

Wee, Junghyun; Hackney, Drew; Bradford, Philip; Peters, Kara

2017-09-01

Fiber Bragg grating (FBG) sensors are typically spot-bonded onto the surface of a structure to detect ultrasonic waves in laboratory demonstrations. However, to protect the rest of the optical fiber from any environmental damage during real applications, bonding the entire length of fiber, called continuous bonding, is commonly done. In this paper, we investigate the impact of continuously bonding FBGs on the measured Lamb wave signal. In theory, the ultrasonic wave signal can bi-directionally transfer between the optical fiber and the plate at any adhered location, which could potentially produce output signal distortion for the continuous bonding case. Therefore, an experiment is performed to investigate the plate-to-fiber and fiber-to-plate signal transfer, from which the signal coupling coefficient of each case is theoretically estimated based on the experimental data. We demonstrate that the two coupling coefficients are comparable, with the plate-to-fiber case approximately 19% larger than the fiber-to-plate case. Finally, the signal waveform and arrival time of the output FBG responses are compared between the continuous and spot bonding cases. The results indicate that the resulting Lamb wave signal output is only that directly detected at the FBG location; however, a slight difference in signal waveform is observed between the two bonding configurations. This paper demonstrates the practicality of using continuously bonded FBGs for ultrasonic wave detection in structural health monitoring (SHM) applications.

Umatilla River Basin Anadromous Fsh Habitat Enhancement Project : 2000 Annual Report.

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

Shaw, R. Todd

2001-12-31

The Umatilla River Basin Anadromous Fish Habitat Enhancement Project continued to identify impacted stream reaches throughout the Umatilla River Basin for habitat improvements during the 2000 project period. Public outreach efforts, biological and physical monitoring, and continued development of a Umatilla River Basin Watershed Assessment assisted the project in fostering public cooperation, targeting habitat deficiencies and determining habitat recovery measures. Habitat enhancement projects continued to be maintained on 44 private properties, four riparian easements and one in-stream enhancement agreement were secured, two new projects implemented and two existing projects improved to enhance anadromous fish habitat and natural fisheries production capabilitiesmore » in the Umatilla River Basin. New project locations included sites on the mid Umatilla River and Buckaroo Creek. Improvements were implemented at existing project sites on the upper Umatilla River and Wildhorse Creek. A stream bank stabilization project was implemented at approximately River Mile 37.4 Umatilla River to stabilize 760 feet of eroding stream bank and improve in-stream habitat diversity. Habitat enhancements at this site included construction of six rock barbs with one large conifer root wad incorporated into each barb, stinging approximately 10,000 native willow cuttings, planting 195 tubling willows and 1,800 basin wildrye grass plugs, and seeding 40 pounds of native grass seed. Staff time to assist in development of a subcontract and fence materials were provided to establish eight spring sites for off-stream watering and to protect wetlands within the Buckaroo Creek Watershed. A gravel bar was moved and incorporated into an adjacent point bar to reduce stream energy and stream channel confinement within the existing project area at River Mile 85 Umatilla River. Approximately 10,000 native willow cuttings were stung and trenched into the stream channel margins and stream banks, and 360 basin wildrye grass plugs planted and 190 pounds of native grass seed broadcast on terraces between River Mile 10 and 12.5 within the existing Wildhorse Creek Project Area. Approximately 70 pounds of native grasses were seeded in the existing McKay Creek Project Area at approximately River Mile 21.5. Financial and in-kind cost share assistance was provided by the Confederated Tribes of the Umatilla Indian Reservation, U.S. Bureau of Indian Affairs, U.S. Department of Agriculture, U.S. Fish and Wildlife Service, National Fish and Wildlife Federation and the Umatilla National Forest for the enhancements at River Mile 37.4 Umatilla River and within the Buckaroo Creek Watershed. Monitoring continued to quantify effects of habitat enhancements in the upper basin. Maximum, minimum and average daily stream temperatures were collected from June through September at 22 sites. Suspended sediment samples were obtained at three gage stations to arrive at daily sediment load estimates. Photographs were taken at 94 existing and two newly established photo points to document habitat recovery. Umatilla Basin Watershed Assessment efforts were continued under a subcontract with Washington State University. This endeavor involves compiling existing information, identifying data gaps, determining habitat-limiting factors and recommending actions to improve anadromous fisheries habitat. This watershed assessment document and working databases will be completed in fiscal year 2002 and made available to assist project personnel with sub-watershed prioritization of habitat needs.« less

A fast, time-accurate unsteady full potential scheme

NASA Technical Reports Server (NTRS)

Shankar, V.; Ide, H.; Gorski, J.; Osher, S.

1985-01-01

The unsteady form of the full potential equation is solved in conservation form by an implicit method based on approximate factorization. At each time level, internal Newton iterations are performed to achieve time accuracy and computational efficiency. A local time linearization procedure is introduced to provide a good initial guess for the Newton iteration. A novel flux-biasing technique is applied to generate proper forms of the artificial viscosity to treat hyperbolic regions with shocks and sonic lines present. The wake is properly modeled by accounting not only for jumps in phi, but also for jumps in higher derivatives of phi, obtained by imposing the density to be continuous across the wake. The far field is modeled using the Riemann invariants to simulate nonreflecting boundary conditions. The resulting unsteady method performs well which, even at low reduced frequency levels of 0.1 or less, requires fewer than 100 time steps per cycle at transonic Mach numbers. The code is fully vectorized for the CRAY-XMP and the VPS-32 computers.

Progress on a Multichannel, Dual-Mixer Stability Analyzer

NASA Technical Reports Server (NTRS)

Kirk, Albert; Cole, Steven; Stevens, Gary; Tucker, Blake; Greenhall, Charles

2005-01-01

Several documents describe aspects of the continuing development of a multichannel, dual-mixer system for simultaneous characterization of the instabilities of multiple precise, low-noise oscillators. One of the oscillators would be deemed to be a reference oscillator, its frequency would be offset by an amount (100 Hz) much greater than the desired data rate, and each of the other oscillators would be compared with the frequency-offset signal by operation of a combination of hardware and software. A high-rate time-tag counter would collect zero-crossing times of the approximately equal 100-Hz beat notes. The system would effect a combination of interpolation and averaging to process the time tags into low-rate phase residuals at the desired grid times. Circuitry that has been developed since the cited prior article includes an eight-channel timer board to replace an obsolete commercial time-tag counter, plus a custom offset generator, cleanup loop, distribution amplifier, zero-crossing detector, and frequency divider.

Lapse in Institutional Animal Care and Use Committee Continuing Reviews.

PubMed

Tsan, Min-Fu; Grabenbauer, Michael; Nguyen, Yen

2016-01-01

The United States federal animal welfare regulations and the Public Health Service Policy on Humane Care and Use of Laboratory Animals require that institutional animal care and use committees (IACUCs) conduct continuing reviews of all animal research activities. However, little is known about the lapse rate of IACUC continuing reviews, and how frequently investigators continue research activities during the lapse. It is also not clear what factors may contribute to an institution's lapse in IACUC continuing reviews. As part of the quality assurance program, the Department of Veterans Affairs (VA) has collected performance metric data for animal care and use programs since 2011. We analyzed IACUC continuing review performance data at 74-75 VA research facilities from 2011 through 2015. The IACUC continuing review lapse rates improved from 5.6% in 2011 to 2.7% in 2015. The rate of investigators continuing research activities during the lapse also decreased from 47.2% in 2012 to 7.4% in 2015. The type of IACUCs used and the size of animal research programs appeared to have no effect in facility's rates of lapse in IACUC continuing reviews. While approximately 80% of facilities reported no lapse in IACUC continuing reviews, approximately 14% of facilities had lapse rates of >10% each year. Some facilities appeared to be repeat offenders. Four facilities had IACUC lapse rates of >10% in at least 3 out of 5 years, suggesting a system problem in these facilities requiring remedial actions to improve their IACUC continuing review processes.

Handheld low-temperature plasma probe for portable "point-and-shoot" ambient ionization mass spectrometry.

PubMed

Wiley, Joshua S; Shelley, Jacob T; Cooks, R Graham

2013-07-16

We describe a handheld, wireless low-temperature plasma (LTP) ambient ionization source and its performance on a benchtop and a miniature mass spectrometer. The source, which is inexpensive to build and operate, is battery-powered and utilizes miniature helium cylinders or air as the discharge gas. Comparison of a conventional, large-scale LTP source against the handheld LTP source, which uses less helium and power than the large-scale version, revealed that the handheld source had similar or slightly better analytical performance. Another advantage of the handheld LTP source is the ability to quickly interrogate a gaseous, liquid, or solid sample without requiring any setup time. A small, 7.4-V Li-polymer battery is able to sustain plasma for 2 h continuously, while the miniature helium cylinder supplies gas flow for approximately 8 continuous hours. Long-distance ion transfer was achieved for distances up to 1 m.

Promoting employee health by integrating health protection, health promotion, and continuous improvement: a longitudinal quasi-experimental intervention study.

PubMed

von Thiele Schwarz, Ulrica; Augustsson, Hanna; Hasson, Henna; Stenfors-Hayes, Terese

2015-02-01

To test the effects of integrating health protection and health promotion with a continuous improvement system (Kaizen) on proximal employee outcomes (health promotion, integration, and Kaizen) and distal outcomes (workability, productivity, self-rated health and self-rated sickness absence). Twelve units in a county hospital in Sweden were randomized to control or intervention groups using a quasiexperimental study design. All staff (approximately 500) provided self-ratings in questionnaires at baseline, and a 12- and 24-month follow-up (response rate, 79% to 87.5%). There was a significant increase in the proximal outcomes over time in the intervention group compared with the control group, and a trend toward improvement in the distal outcomes workability and productivity. Integration seems to promote staff engagement in health protection and promotion, as well as to improve their understanding of the link between work and health.

Probing quantumness with joint continuous measurements of non-commuting qubit observables

NASA Astrophysics Data System (ADS)

Garcia-Pintos, Luis Pedro; Dressel, Justin

In this talk we consider continuous weak measurements as a means to probe foundational issues in quantum mechanics. We consider the simultaneous monitoring of two noncommuting observables-as recently implemented by the Siddiqi group at UC Berkeley. Contrary to naive expectation, the output of such experiment can be used to simultaneously track the approximate observable dynamics. Despite this seeming realism, we also show that the readouts violate macrorealistic Leggett-Garg inequalities for arbitrarily short temporal correlations, and that the derived inequalities are manifestly violated even in the absence of Hamiltonian evolution. Such violations should indicate the failure of at least one postulate of macrorealism: either physical quantities do not have well defined values at all times, or the measurement process itself disturbs what is being measured. Despite this macrorealism violation, we construct a realistic, but epistemically restricted, model that perfectly emulates both the qubit evolution and the observed noisy signals, thus also emulating the violations.

Fuzzy Adaptive Control Design and Discretization for a Class of Nonlinear Uncertain Systems.

PubMed

Zhao, Xudong; Shi, Peng; Zheng, Xiaolong

2016-06-01

In this paper, tracking control problems are investigated for a class of uncertain nonlinear systems in lower triangular form. First, a state-feedback controller is designed by using adaptive backstepping technique and the universal approximation ability of fuzzy logic systems. During the design procedure, a developed method with less computation is proposed by constructing one maximum adaptive parameter. Furthermore, adaptive controllers with nonsymmetric dead-zone are also designed for the systems. Then, a sampled-data control scheme is presented to discretize the obtained continuous-time controller by using the forward Euler method. It is shown that both proposed continuous and discrete controllers can ensure that the system output tracks the target signal with a small bounded error and the other closed-loop signals remain bounded. Two simulation examples are presented to verify the effectiveness and applicability of the proposed new design techniques.

Monitoring Invasive Aquatic Vegetation in Lake Okeechobee, Florida, Using NDVI Derived from Modis Data

NASA Technical Reports Server (NTRS)

Woods, Kate; Brozen, Madeline; Malik, Sadaf; Maki, Angela

2009-01-01

Lake Okeechobee, located in southern Florida, encompasses approximately 1,700 sq km and is a vital part of the Lake Okeechobee and Everglades ecosystem. Major cyanobacterial blooms have been documented in Lake Okeechobee since the 1970s and have continued to plague the ecosystem. Similarly, hydrilla, water hyacinth, and water lettuce have been documented in the lake and continue to threaten the ecosystem by their rapid growth. This study examines invasive aquatic vegetation occurrence through the use of the Normalized Difference Vegetation Index (NDVI) calculated on MOD09 surface reflectance imagery. Occurrence during 2008 was analyzed using the Time Series Product Tool (TSPT), a MATLAB-based program developed at John C. Stennis Space Center. This project tracked spatial and temporal variability of cyanobacterial blooms, and overgrowth of water lettuce, water hyacinth, and hydrilla. In addition, this study presents an application of Moderate Resolution Imaging Spectroradiometer (MODIS) data to assist in water quality management.

A boundedness result for the direct heuristic dynamic programming.

PubMed

Liu, Feng; Sun, Jian; Si, Jennie; Guo, Wentao; Mei, Shengwei

2012-08-01

Approximate/adaptive dynamic programming (ADP) has been studied extensively in recent years for its potential scalability to solve large state and control space problems, including those involving continuous states and continuous controls. The applicability of ADP algorithms, especially the adaptive critic designs has been demonstrated in several case studies. Direct heuristic dynamic programming (direct HDP) is one of the ADP algorithms inspired by the adaptive critic designs. It has been shown applicable to industrial scale, realistic and complex control problems. In this paper, we provide a uniformly ultimately boundedness (UUB) result for the direct HDP learning controller under mild and intuitive conditions. By using a Lyapunov approach we show that the estimation errors of the learning parameters or the weights in the action and critic networks remain UUB. This result provides a useful controller convergence guarantee for the first time for the direct HDP design. Copyright © 2012 Elsevier Ltd. All rights reserved.

Method for using acoustic sounder categories to determine atmospheric stability

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

Schubert, J.F.

1979-01-01

Capabilities of the diffusion meteorologist have been expanded by the acoustic sounder, an economical tool for monitoring in real time the height of the mixed layer. The acoustic sounder continuously measures the rate of change in the height of the mixed layer which is an important parameter in calculating the transport and diffusion of radioactive and nonradioactive air pollutants. Continuous record of convective cells, gravity waves, inversions, and frontal systems permit analysis of the synoptic (analysis of stability in terms of simultaneous weather information) and complex (analysis of the stability of a single place by the relative frequencies of variousmore » stability types or groups of such types) stabilities of the local area. Sounder data obtained at the Savannah River Plant was compared on an hourly basis to data obtained at the WJBF-TV tower located approximately 20 km northwest of the acoustic sounder site.« less

Adaptive multiresolution modeling of groundwater flow in heterogeneous porous media

NASA Astrophysics Data System (ADS)

Malenica, Luka; Gotovac, Hrvoje; Srzic, Veljko; Andric, Ivo

2016-04-01

Proposed methodology was originally developed by our scientific team in Split who designed multiresolution approach for analyzing flow and transport processes in highly heterogeneous porous media. The main properties of the adaptive Fup multi-resolution approach are: 1) computational capabilities of Fup basis functions with compact support capable to resolve all spatial and temporal scales, 2) multi-resolution presentation of heterogeneity as well as all other input and output variables, 3) accurate, adaptive and efficient strategy and 4) semi-analytical properties which increase our understanding of usually complex flow and transport processes in porous media. The main computational idea behind this approach is to separately find the minimum number of basis functions and resolution levels necessary to describe each flow and transport variable with the desired accuracy on a particular adaptive grid. Therefore, each variable is separately analyzed, and the adaptive and multi-scale nature of the methodology enables not only computational efficiency and accuracy, but it also describes subsurface processes closely related to their understood physical interpretation. The methodology inherently supports a mesh-free procedure, avoiding the classical numerical integration, and yields continuous velocity and flux fields, which is vitally important for flow and transport simulations. In this paper, we will show recent improvements within the proposed methodology. Since "state of the art" multiresolution approach usually uses method of lines and only spatial adaptive procedure, temporal approximation was rarely considered as a multiscale. Therefore, novel adaptive implicit Fup integration scheme is developed, resolving all time scales within each global time step. It means that algorithm uses smaller time steps only in lines where solution changes are intensive. Application of Fup basis functions enables continuous time approximation, simple interpolation calculations across different temporal lines and local time stepping control. Critical aspect of time integration accuracy is construction of spatial stencil due to accurate calculation of spatial derivatives. Since common approach applied for wavelets and splines uses a finite difference operator, we developed here collocation one including solution values and differential operator. In this way, new improved algorithm is adaptive in space and time enabling accurate solution for groundwater flow problems, especially in highly heterogeneous porous media with large lnK variances and different correlation length scales. In addition, differences between collocation and finite volume approaches are discussed. Finally, results show application of methodology to the groundwater flow problems in highly heterogeneous confined and unconfined aquifers.

Femtosecond/picosecond time-resolved fluorescence study of hydrophilic polymer fine particles.

PubMed

Nanjo, Daisuke; Hosoi, Haruko; Fujino, Tatsuya; Tahara, Tahei; Korenaga, Takashi

2007-03-22

Femtosecond/picosecond time-resolved fluorescence study of hydrophilic polymer fine particles (polyacrylamide, PAAm) was reported. Ultrafast fluorescence dynamics of polymer/water solution was monitored using a fluorescent probe molecule (C153). In the femtosecond time-resolved fluorescence measurement at 480 nm, slowly decay components having lifetimes of tau(1) approximately 53 ps and tau(2) approximately 5 ns were observed in addition to rapid fluorescence decay. Picosecond time-resolved fluorescence spectra of C153/PAAm/H2O solution were also measured. In the time-resolved fluorescence spectra of C153/PAAm/H2O, a peak shift from 490 to 515 nm was measured, which can be assigned to the solvation dynamics of polymer fine particles. The fluorescence peak shift was related to the solvation response function and two time constants were determined (tau(3) approximately 50 ps and tau(4) approximately 467 ps). Therefore, the tau(1) component observed in the femtosecond time-resolved fluorescence measurement was assigned to the solvation dynamics that was observed only in the presence of polymer fine particles. Rotational diffusion measurements were also carried out on the basis of the picosecond time-resolved fluorescence spectra. In the C153/PAAm/H2O solution, anisotropy decay having two different time constants was also derived (tau(6) approximately 76 ps and tau(7) approximately 676 ps), indicating the presence of two different microscopic molecular environments around the polymer surface. Using the Stokes-Einstein-Debye (SED) equation, microscopic viscosity around the polymer surface was evaluated. For the area that gave a rotational diffusion time of tau(6) approximately 76 ps, the calculated viscosity is approximately 1.1 cP and for tau(7) approximately 676 ps, it is approximately 10 cP. The calculated viscosity values clearly revealed that there are two different molecular environments around the polyacrylamide fine particles.

The rise and fall of an ancient Adélie penguin `supercolony' at Cape Adare, Antarctica

NASA Astrophysics Data System (ADS)

Emslie, Steven D.; McKenzie, Ashley; Patterson, William P.

2018-04-01

We report new discoveries and radiocarbon dates on active and abandoned Adélie penguin (Pygoscelis adeliae) colonies at Cape Adare, Antarctica. This colony, first established at approximately 2000 BP (calendar years before present, i.e. 1950), is currently the largest for this species with approximately 338 000 breeding pairs, most located on low-lying Ridley Beach. We hypothesize that this colony first formed after fast ice began blocking open-water access by breeding penguins to the Scott Coast in the southern Ross Sea during a cooling period also at approximately 2000 BP. Our results suggest that the new colony at Cape Adare continued to grow, expanding to a large upper terrace above Ridley Beach, until it exceeded approximately 500 000 breeding pairs (a `supercolony') by approximately 1200 BP. The high marine productivity associated with the Ross Sea polynya and continental shelf break supported this growth, but the colony collapsed to its present size for unknown reasons after approximately 1200 BP. Ridley Beach will probably be abandoned in the near future due to rising sea level in this region. We predict that penguins will retreat to higher elevations at Cape Adare and that the Scott Coast will be reoccupied by breeding penguins as fast ice continues to dissipate earlier each summer, restoring open-water access to beaches there.

The rise and fall of an ancient Adélie penguin 'supercolony' at Cape Adare, Antarctica.

PubMed

Emslie, Steven D; McKenzie, Ashley; Patterson, William P

2018-04-01

We report new discoveries and radiocarbon dates on active and abandoned Adélie penguin ( Pygoscelis adeliae ) colonies at Cape Adare, Antarctica. This colony, first established at approximately 2000 BP (calendar years before present, i.e. 1950), is currently the largest for this species with approximately 338 000 breeding pairs, most located on low-lying Ridley Beach. We hypothesize that this colony first formed after fast ice began blocking open-water access by breeding penguins to the Scott Coast in the southern Ross Sea during a cooling period also at approximately 2000 BP. Our results suggest that the new colony at Cape Adare continued to grow, expanding to a large upper terrace above Ridley Beach, until it exceeded approximately 500 000 breeding pairs (a 'supercolony') by approximately 1200 BP. The high marine productivity associated with the Ross Sea polynya and continental shelf break supported this growth, but the colony collapsed to its present size for unknown reasons after approximately 1200 BP. Ridley Beach will probably be abandoned in the near future due to rising sea level in this region. We predict that penguins will retreat to higher elevations at Cape Adare and that the Scott Coast will be reoccupied by breeding penguins as fast ice continues to dissipate earlier each summer, restoring open-water access to beaches there.

The rise and fall of an ancient Adélie penguin ‘supercolony’ at Cape Adare, Antarctica

PubMed Central

McKenzie, Ashley; Patterson, William P.

2018-01-01

We report new discoveries and radiocarbon dates on active and abandoned Adélie penguin (Pygoscelis adeliae) colonies at Cape Adare, Antarctica. This colony, first established at approximately 2000 BP (calendar years before present, i.e. 1950), is currently the largest for this species with approximately 338 000 breeding pairs, most located on low-lying Ridley Beach. We hypothesize that this colony first formed after fast ice began blocking open-water access by breeding penguins to the Scott Coast in the southern Ross Sea during a cooling period also at approximately 2000 BP. Our results suggest that the new colony at Cape Adare continued to grow, expanding to a large upper terrace above Ridley Beach, until it exceeded approximately 500 000 breeding pairs (a ‘supercolony’) by approximately 1200 BP. The high marine productivity associated with the Ross Sea polynya and continental shelf break supported this growth, but the colony collapsed to its present size for unknown reasons after approximately 1200 BP. Ridley Beach will probably be abandoned in the near future due to rising sea level in this region. We predict that penguins will retreat to higher elevations at Cape Adare and that the Scott Coast will be reoccupied by breeding penguins as fast ice continues to dissipate earlier each summer, restoring open-water access to beaches there. PMID:29765656

Discrete-continuous variable structural synthesis using dual methods

NASA Technical Reports Server (NTRS)

Schmit, L. A.; Fleury, C.

1980-01-01

Approximation concepts and dual methods are extended to solve structural synthesis problems involving a mix of discrete and continuous sizing type of design variables. Pure discrete and pure continuous variable problems can be handled as special cases. The basic mathematical programming statement of the structural synthesis problem is converted into a sequence of explicit approximate primal problems of separable form. These problems are solved by constructing continuous explicit dual functions, which are maximized subject to simple nonnegativity constraints on the dual variables. A newly devised gradient projection type of algorithm called DUAL 1, which includes special features for handling dual function gradient discontinuities that arise from the discrete primal variables, is used to find the solution of each dual problem. Computational implementation is accomplished by incorporating the DUAL 1 algorithm into the ACCESS 3 program as a new optimizer option. The power of the method set forth is demonstrated by presenting numerical results for several example problems, including a pure discrete variable treatment of a metallic swept wing and a mixed discrete-continuous variable solution for a thin delta wing with fiber composite skins.

Outdoor air pollution in close proximity to a continuous point source

NASA Astrophysics Data System (ADS)

Klepeis, Neil E.; Gabel, Etienne B.; Ott, Wayne R.; Switzer, Paul

Data are lacking on human exposure to air pollutants occurring in ground-level outdoor environments within a few meters of point sources. To better understand outdoor exposure to tobacco smoke from cigarettes or cigars, and exposure to other types of outdoor point sources, we performed more than 100 controlled outdoor monitoring experiments on a backyard residential patio in which we released pure carbon monoxide (CO) as a tracer gas for continuous time periods lasting 0.5-2 h. The CO was emitted from a single outlet at a fixed per-experiment rate of 120-400 cc min -1 (˜140-450 mg min -1). We measured CO concentrations every 15 s at up to 36 points around the source along orthogonal axes. The CO sensors were positioned at standing or sitting breathing heights of 2-5 ft (up to 1.5 ft above and below the source) and at horizontal distances of 0.25-2 m. We simultaneously measured real-time air speed, wind direction, relative humidity, and temperature at single points on the patio. The ground-level air speeds on the patio were similar to those we measured during a survey of 26 outdoor patio locations in 5 nearby towns. The CO data exhibited a well-defined proximity effect similar to the indoor proximity effect reported in the literature. Average concentrations were approximately inversely proportional to distance. Average CO levels were approximately proportional to source strength, supporting generalization of our results to different source strengths. For example, we predict a cigarette smoker would cause average fine particle levels of approximately 70-110 μg m -3 at horizontal distances of 0.25-0.5 m. We also found that average CO concentrations rose significantly as average air speed decreased. We fit a multiplicative regression model to the empirical data that predicts outdoor concentrations as a function of source emission rate, source-receptor distance, air speed and wind direction. The model described the data reasonably well, accounting for ˜50% of the log-CO variability in 5-min CO concentrations.

Development of an ultrahigh-temperature process for the enzymatic hydrolysis of lactose. IV. Immobilization of two thermostable beta-glycosidases and optimization of a packed-bed reactor for lactose conversion.

PubMed

Petzelbauer, Inge; Kuhn, Bernhard; Splechtna, Barbara; Kulbe, Klaus D; Nidetzky, Bernd

2002-03-20

Recombinant hyperthermostable beta-glycosidases from the archaea Sulfolobus solfataricus (Ss beta Gly) and Pyrococcus furiosus (CelB) were covalently attached onto the insoluble carriers chitosan, controlled pore glass (CPG), and Eupergit C. For each enzyme/carrier pair, the protein-binding capacity, the immobilization yield, the pH profiles for activity and stability, the activity/temperature profile, and the kinetic constants for lactose hydrolysis at 70 degrees C were determined. Eupergit C was best among the carriers in regard to retention of native-like activity and stability of Ss beta Gly and CelB over the pH range 3.0-7.5. Its protein binding capacity of approximately 0.003 (on a mass basis) was one-third times that of CPG, while immobilization yields were typically 80% in each case. Activation energies for lactose conversion by the immobilized enzymes at pH 5.5 were in the range 50-60 kJ/mol. This is compared to values of approximately 75 kJ/mol for the free enzymes. Immobilization expands the useful pH range for CelB and Ss beta Gly by approximately 1.5 pH units toward pH 3.5 and pH 4.5, respectively. A packed-bed enzyme reactor was developed for the continuous conversion of lactose in different media, including whey and milk, and operated over extended reaction times of up to 14 days. The productivities of the Eupergit C-immobilized enzyme reactor were determined at dilution rates between 1 and 12 h(-1), and using 45 and 170 g/L initial lactose. Results of kinetic modeling for the same reactor, assuming plug flow and steady state, suggest the presence of mass-transfer limitation of the reaction rate under the conditions used. Formation of galacto-oligosaccharides in the continuous packed-bed reactor and in the batch reactor using free enzyme was closely similar in regard to yield and individual saccharide components produced. Copyright 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 619-631, 2002; DOI 10.1002/bit.10110

Scaling behavior of nonisothermal phase separation.

PubMed

Rüllmann, Max; Alig, Ingo

2004-04-22

The phase separation process in a critical mixture of polydimethylsiloxane and polyethylmethylsiloxane (PDMS/PEMS, a system with an upper critical solution temperature) was investigated by time-resolved light scattering during continuous quenches from the one-phase into the two-phase region. Continuous quenches were realized by cooling ramps with different cooling rates kappa. Phase separation kinetics is studied by means of the temporal evolution of the scattering vector qm and the intensity Im at the scattering peak. The curves qm(t) for different cooling rates can be shifted onto a single mastercurve. The curves Im(t) show similar behavior. As shift factors, a characteristic length Lc and a characteristic time tc are introduced. Both characteristic quantities depend on the cooling rate through power laws: Lc approximately kappa(-delta) and tc approximately kappa(-rho). Scaling behavior in isothermal critical demixing is well known. There the temporal evolutions of qm and Im for different quench depths DeltaT can be scaled with the correlation length xi and the interdiffusion coefficient D, both depending on DeltaT through critical power laws. We show in this paper that the cooling rate scaling in nonisothermal demixing is a consequence of the quench depth scaling in the isothermal case. The exponents delta and rho are related to the critical exponents nu and nu* of xi and D, respectively. The structure growth during nonisothermal demixing can be described with a semiempirical model based on the hydrodynamic coarsening mechanism well known in the isothermal case. In very late stages of nonisothermal phase separation a secondary scattering maximum appears. This is due to secondary demixing. We explain the onset of secondary demixing by a competition between interdiffusion and coarsening. (c) 2004 American Institute of Physics

Medical use, medical misuse, and nonmedical use of prescription opioids: results from a longitudinal study.

PubMed

McCabe, Sean Esteban; West, Brady T; Boyd, Carol J

2013-05-01

The objective of this study was to examine the prevalence and patterns associated with past-year medical use, medical misuse, and nonmedical use of prescription opioids (NMUPO) among adolescents over a 2-year time period and to examine substance abuse, sleeping problems, and physical pain symptoms associated with these patterns of medical use, medical misuse, and NMUPO. A Web-based survey was self-administered by a longitudinal sample of 2050 middle and high school students in 2009-2010 (Year 1) and again in 2010-2011 (Year 2). The study was set in 2 southeastern Michigan school districts. The longitudinal sample consisted of 50% females, 67% Whites, 28% African-Americans, and 5% from other racial/ethnic categories. Main outcome measures were past-year medical use, medical misuse, and NMUPO. Of those reporting appropriate medical use of prescription opioids in Year 1, approximately 34% continued medical use in Year 2. Of those reporting past-year NMUPO in Year 1, approximately 25% continued NMUPO in Year 2. Appropriate medical use and NMUPO for pain relief was more prevalent among girls than boys. Multiple logistic regression analyses indicated that the odds of a positive screen for substance abuse in Year 2 were greater for adolescents who reported medical misuse or NMUPO for non-pain-relief motives in Year 1 compared with those who did not use prescription opioids. The findings indicate an increased risk for substance abuse among adolescents who report medical misuse or NMUPO for non-pain-relief motives over time. The findings have important clinical implications for interventions to reduce medical misuse and NMUPO among adolescents. Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Plasma extraction rate enhancement scheme for a real-time and continuous blood plasma separation device using a sheathless cell concentrator

NASA Astrophysics Data System (ADS)

Kang, Dong-Hyun; Kim, Kyongtae; Kim, Yong-Jun

2018-02-01

Microfluidic devices for plasma extraction are popular because they offer the advantage of smaller reagent consumption compared to conventional centrifugations. The plasma yield (volume percentage of plasma that can be extracted) is an important factor for diagnoses in microdevices with small reagent consumptions. However, recently designed microfluidic devices tend to have a low plasma yield because they have been optimized to improve the purity of extracted plasma. Thus, these devices require large amounts of reagents, and this complexity has eliminated the advantage of microfluidic devices that can operate with only small amounts of reagents. We therefore propose a continuous, real-time, blood plasma separation device, for plasma extraction rate enhancements. Moreover, a blood plasma separation device was designed to achieve improved plasma yields with high-purity efficiency. To obtain a high plasma yield, microstructures were placed on the bottom side of the channel to increase the concentration of blood cells. Plasma separation was then accomplished via microfluidic networks based on the Zweifach-Fung effect. The proposed device was fabricated based on the polydimethylsiloxane molding process using the SU-8 microfluidic channel for the fabrication of the mold and bottom structures. Human blood diluted in a phosphate buffered saline solution (25% hematocrit) was injected into the inlet of the device. The purity efficiencies were approximately equal to 96% with a maximum of 96.75% at a flow rate of 2 µl min-1, while the plasma yield was approximately 59% with a maximum of 59.92% at a flow rate of 4 µl min-1. Compared to results obtained using other devices, our proposed device could obtain comparable or higher plasma purity and a high plasma yield.

Stress loading from viscous flow in the lower crust and triggering of aftershocks following the 1994 Northridge, California, earthquake

USGS Publications Warehouse

Deng, J.; Hudnut, K.; Gurnis, M.; Hauksson, E.

1999-01-01

Following the M(w) 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.Following the Mw 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.

Improving Palliative Care Team Meetings: Structure, Inclusion, and "Team Care".

PubMed

Brennan, Caitlin W; Kelly, Brittany; Skarf, Lara Michal; Tellem, Rotem; Dunn, Kathleen M; Poswolsky, Sheila

2016-07-01

Increasing demands on palliative care teams point to the need for continuous improvement to ensure teams are working collaboratively and efficiently. This quality improvement initiative focused on improving interprofessional team meeting efficiency and subsequently patient care. Meeting start and end times improved from a mean of approximately 9 and 6 minutes late in the baseline period, respectively, to a mean of 4.4 minutes late (start time) and ending early in our sustainability phase. Mean team satisfaction improved from 2.4 to 4.5 on a 5-point Likert-type scale. The improvement initiative clarified communication about patients' plans of care, thus positively impacting team members' ability to articulate goals to other professionals, patients, and families. We propose several recommendations in the form of a team meeting "toolkit." © The Author(s) 2015.

Geomagnetic temporal change: 1903-1982 - A spline representation

NASA Technical Reports Server (NTRS)

Langel, R. A.; Kerridge, D. J.; Barraclough, D. R.; Malin, S. R. C.

1986-01-01

The secular variation of the earth's magnetic field is itself subject to temporal variations. These are investigated with the aid of the coefficients of a series of spherical harmonic models of secular variation deduced from data for the interval 1903-1982 from the worldwide network of magnetic observatories. For some studies it is convenient to approximate the time variation of the spherical harmonic coefficients with a smooth, continuous, function; for this a spline fitting is used. The phenomena that are investigated include periodicities, discontinuities, and correlation with the length of day. The numerical data presented will be of use for further investigations and for the synthesis of secular variation at any place and at any time within the interval of the data - they are not appropriate for temporal extrapolations.

Cathodochromic storage device

NASA Technical Reports Server (NTRS)

Bosomworth, D. R.; Moles, W. H.

1969-01-01

A memory and display device has been developed by combing a fast phosphor layer with a cathodochromic layer in a cathode ray tube. Images are stored as patterns of electron beam induced optical density in the cathodo-chromic material. The stored information is recovered by exciting the backing, fast phosphor layer with a constant current electron beam and detecting the emitted radiation which is modulated by absorption in the cathodochromic layer. The storage can be accomplished in one or more TV frames (1/30 sec each). More than 500 TV line resolution and close to 2:1 contrast ratio are possible. The information storage time in a dark environment is approximately 24 hours. A reconstituted (readout) electronic video signal can be generated continuously for times in excess of 10 minutes or periodically for several hours.

Search for low-mass exoplanets by gravitational microlensing at high magnification.

PubMed

Abe, F; Bennett, D P; Bond, I A; Eguchi, S; Furuta, Y; Hearnshaw, J B; Kamiya, K; Kilmartin, P M; Kurata, Y; Masuda, K; Matsubara, Y; Muraki, Y; Noda, S; Okajima, K; Rakich, A; Rattenbury, N J; Sako, T; Sekiguchi, T; Sullivan, D J; Sumi, T; Tristram, P J; Yanagisawa, T; Yock, P C M; Gal-Yam, A; Lipkin, Y; Maoz, D; Ofek, E O; Udalski, A; Szewczyk, O; Zebrun, K; Soszynski, I; Szymanski, M K; Kubiak, M; Pietrzynski, G; Wyrzykowski, L

2004-08-27

Observations of the gravitational microlensing event MOA 2003-BLG-32/OGLE 2003-BLG-219 are presented, for which the peak magnification was over 500, the highest yet reported. Continuous observations around the peak enabled a sensitive search for planets orbiting the lens star. No planets were detected. Planets 1.3 times heavier than Earth were excluded from more than 50% of the projected annular region from approximately 2.3 to 3.6 astronomical units surrounding the lens star, Uranus-mass planets were excluded from 0.9 to 8.7 astronomical units, and planets 1.3 times heavier than Saturn were excluded from 0.2 to 60 astronomical units. These are the largest regions of sensitivity yet achieved in searches for extrasolar planets orbiting any star.

Search for Low-Mass Exoplanets by Gravitational Microlensing at High Magnification

NASA Astrophysics Data System (ADS)

Abe, F.; Bennett, D. P.; Bond, I. A.; Eguchi, S.; Furuta, Y.; Hearnshaw, J. B.; Kamiya, K.; Kilmartin, P. M.; Kurata, Y.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Noda, S.; Okajima, K.; Rakich, A.; Rattenbury, N. J.; Sako, T.; Sekiguchi, T.; Sullivan, D. J.; Sumi, T.; Tristram, P. J.; Yanagisawa, T.; Yock, P. C. M.; Gal-Yam, A.; Lipkin, Y.; Maoz, D.; Ofek, E. O.; Udalski, A.; Szewczyk, O.; Żebruń, K.; Soszyński, I.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Wyrzykowski, L.

2004-08-01

Observations of the gravitational microlensing event MOA 2003-BLG-32/OGLE 2003-BLG-219 are presented, for which the peak magnification was over 500, the highest yet reported. Continuous observations around the peak enabled a sensitive search for planets orbiting the lens star. No planets were detected. Planets 1.3 times heavier than Earth were excluded from more than 50% of the projected annular region from approximately 2.3 to 3.6 astronomical units surrounding the lens star, Uranus-mass planets were excluded from 0.9 to 8.7 astronomical units, and planets 1.3 times heavier than Saturn were excluded from 0.2 to 60 astronomical units. These are the largest regions of sensitivity yet achieved in searches for extrasolar planets orbiting any star.

Where Are the Academic Jobs? Interactive Exploration of Job Advertisements in Geospatial and Topical Space

NASA Astrophysics Data System (ADS)

Zoss, Angela M.; Conover, Michael; Börner, Katy

This paper details a methodology for capturing, analyzing, and communicating one specific type of real time data: advertisements of currently available academic jobs. The work was inspired by the American Recovery and Reinvestment Act of 2009 (ARRA) [2] that provides approximately 100 billion for education, creating a historic opportunity to create and save hundreds of thousands of jobs. Here, we discuss methodological challenges and practical problems when developing interactive visual interfaces to real time data streams such as job advertisements. Related work is discussed, preliminary solutions are presented, and future work is outlined. The presented approach should be valuable to deal with the enormous volume and complexity of social and behavioral data that evolve continuously in real time, and analyses of them need to be communicated to a broad audience of researchers, practitioners, clients, educators, and interested policymakers, as originally suggested by Hemmings and Wilkinson [1].

Quantization improves stabilization of dynamical systems with delayed feedback

NASA Astrophysics Data System (ADS)

Stepan, Gabor; Milton, John G.; Insperger, Tamas

2017-11-01

We show that an unstable scalar dynamical system with time-delayed feedback can be stabilized by quantizing the feedback. The discrete time model corresponds to a previously unrecognized case of the microchaotic map in which the fixed point is both locally and globally repelling. In the continuous-time model, stabilization by quantization is possible when the fixed point in the absence of feedback is an unstable node, and in the presence of feedback, it is an unstable focus (spiral). The results are illustrated with numerical simulation of the unstable Hayes equation. The solutions of the quantized Hayes equation take the form of oscillations in which the amplitude is a function of the size of the quantization step. If the quantization step is sufficiently small, the amplitude of the oscillations can be small enough to practically approximate the dynamics around a stable fixed point.

Development of a BPM Lock-In Diagnostic System

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

Richard Dickson

2003-05-12

A system has been developed for the acquisition and analysis of high rate, time coherent BPM data across the Jefferson Lab's Continuous Electron Beam Accelerator Facility (CEBAF). This system will allow the acquisition of Beam Position Monitor (BPM) position and intensity information at a rate in excess 7 KHz for approximately 200 BPMs in a time synchronous manner. By inducing minute sinusoidal transverse beam motion in the CEBAF injector, with known phase relative to the synchronized BPM acquisition, it is possible to derive several types of useful information. Analysis of the BPM intensity data, which is proportional to beam current,more » by beating the signal with an in-phase sinusoidal representation of the transverse kick can localize beam scraping to a particular BPM. Similarly, real-time optics information may be deduced with an analysis of BPM position data. This paper will detail the frequency lock-in technique applied and present status.« less

Recurrent epidemic cycles driven by intervention in a population of two susceptibility types

NASA Astrophysics Data System (ADS)

Juanico, Drandreb Earl O.

2014-03-01

Epidemics have been known to persist in the form of recurrence cycles. Despite intervention efforts through vaccination and targeted social distancing, infectious diseases like influenza continue to appear intermittently over time. I have undertaken an analysis of a stochastic epidemic model to explore the hypothesis that intervention efforts actually drive epidemic cycles. Time series from simulations of the model reveal oscillations exhibiting a similar temporal signature as influenza epidemics. The power-spectral density indicates a resonant frequency, which approximately corresponds to the apparent annual seasonality of influenza in temperate zones. Asymptotic solution to the backward Kolmogorov equation of the dynamics corresponds to an exponentially-decaying mean-exit time as a function of the intervention rate. Intervention must be implemented at a sufficiently high rate to extinguish the infection. The results demonstrate that intervention efforts can induce epidemic cycles, and that the temporal signature of cycles can provide early warning of imminent outbreaks.

The behaviour of cow blastocyst in vitro: cinematographic and morphometric analysis.

PubMed Central

Massip, A; Mulnard, J; Vanderzwalmen, P; Hanzen, C; Ectors, F

1982-01-01

The behaviour of the cow blastocyst in vitro was studied by time-lapse cinematography and analysed by morphometry. Three types of behaviour were observed: continuous expansion followed by hatching; discontinuous expansion interrupted by few contractions and followed by hatching; discontinuous expansion interrupted by several rapid contractions without hatching. This demonstrated that the pulsatile activity of the blastocyst is not a necessary condition of hatching but also that only a moderate pulsatile activity is compatible with normal hatching. The time of hatching in vitro corresponded approximately with the time of zona loss in vivo (9-10 days). Rupture of the zona occurred at any point of the trophoblast layer. Hatching by herniation through a reduced opening of the zona was occasionally observed. The behavior of the embryos from a particular animal was very similar but differences were noted between embryos from different animals. Images Fig. 3 PMID:7076563

Comparison of three methods for wind turbine capacity factor estimation.

PubMed

Ditkovich, Y; Kuperman, A

2014-01-01

Three approaches to calculating capacity factor of fixed speed wind turbines are reviewed and compared using a case study. The first "quasiexact" approach utilizes discrete wind raw data (in the histogram form) and manufacturer-provided turbine power curve (also in discrete form) to numerically calculate the capacity factor. On the other hand, the second "analytic" approach employs a continuous probability distribution function, fitted to the wind data as well as continuous turbine power curve, resulting from double polynomial fitting of manufacturer-provided power curve data. The latter approach, while being an approximation, can be solved analytically thus providing a valuable insight into aspects, affecting the capacity factor. Moreover, several other merits of wind turbine performance may be derived based on the analytical approach. The third "approximate" approach, valid in case of Rayleigh winds only, employs a nonlinear approximation of the capacity factor versus average wind speed curve, only requiring rated power and rotor diameter of the turbine. It is shown that the results obtained by employing the three approaches are very close, enforcing the validity of the analytically derived approximations, which may be used for wind turbine performance evaluation.

Discrete-Time Stable Generalized Self-Learning Optimal Control With Approximation Errors.

PubMed

Wei, Qinglai; Li, Benkai; Song, Ruizhuo

2018-04-01

In this paper, a generalized policy iteration (GPI) algorithm with approximation errors is developed for solving infinite horizon optimal control problems for nonlinear systems. The developed stable GPI algorithm provides a general structure of discrete-time iterative adaptive dynamic programming algorithms, by which most of the discrete-time reinforcement learning algorithms can be described using the GPI structure. It is for the first time that approximation errors are explicitly considered in the GPI algorithm. The properties of the stable GPI algorithm with approximation errors are analyzed. The admissibility of the approximate iterative control law can be guaranteed if the approximation errors satisfy the admissibility criteria. The convergence of the developed algorithm is established, which shows that the iterative value function is convergent to a finite neighborhood of the optimal performance index function, if the approximate errors satisfy the convergence criterion. Finally, numerical examples and comparisons are presented.

Continuous millennial decrease of the Earth's magnetic axial dipole

NASA Astrophysics Data System (ADS)

Poletti, Wilbor; Biggin, Andrew J.; Trindade, Ricardo I. F.; Hartmann, Gelvam A.; Terra-Nova, Filipe

2018-01-01

Since the establishment of direct estimations of the Earth's magnetic field intensity in the first half of the nineteenth century, a continuous decay of the axial dipole component has been observed and variously speculated to be linked to an imminent reversal of the geomagnetic field. Furthermore, indirect estimations from anthropologically made materials and volcanic derivatives suggest that this decrease began significantly earlier than direct measurements have been available. Here, we carefully reassess the available archaeointensity dataset for the last two millennia, and show a good correspondence between direct (observatory/satellite) and indirect (archaeomagnetic) estimates of the axial dipole moment creating, in effect, a proxy to expand our analysis back in time. Our results suggest a continuous linear decay as the most parsimonious long-term description of the axial dipole variation for the last millennium. We thus suggest that a break in the symmetry of axial dipole moment advective sources occurred approximately 1100 years earlier than previously described. In addition, based on the observed dipole secular variation timescale, we speculate that the weakening of the axial dipole may end soon.

Optimal control of a hybrid rhythmic-discrete task: the bouncing ball revisited.

PubMed

Ronsse, Renaud; Wei, Kunlin; Sternad, Dagmar

2010-05-01

Rhythmically bouncing a ball with a racket is a hybrid task that combines continuous rhythmic actuation of the racket with the control of discrete impact events between racket and ball. This study presents experimental data and a two-layered modeling framework that explicitly addresses the hybrid nature of control: a first discrete layer calculates the state to reach at impact and the second continuous layer smoothly drives the racket to this desired state, based on optimality principles. The testbed for this hybrid model is task performance at a range of increasingly slower tempos. When slowing the rhythm of the bouncing actions, the continuous cycles become separated into a sequence of discrete movements interspersed by dwell times and directed to achieve the desired impact. Analyses of human performance show increasing variability of performance measures with slower tempi, associated with a change in racket trajectories from approximately sinusoidal to less symmetrical velocity profiles. Matching results of model simulations give support to a hybrid control model based on optimality, and therefore suggest that optimality principles are applicable to the sensorimotor control of complex movements such as ball bouncing.

Rates and predictors of seizure freedom in resective epilepsy surgery: an update

PubMed Central

Englot, Dario J.; Chang, Edward F.

2017-01-01

Epilepsy is a debilitating neurological disorder affecting approximately 1 % of the world’s population. Drug-resistant focal epilepsies are potentially surgically remediable. Although epilepsy surgery is dramatically underutilized among medically refractory patients, there is an expanding collection of evidence supporting its efficacy which may soon compel a paradigm shift. Of note is that a recent randomized controlled trial demonstrated that early resection leads to considerably better seizure outcomes than continued medical therapy in patients with pharmacoresistant temporal lobe epilepsy. In the present review, we provide a timely update of seizure freedom rates and predictors in resective epilepsy surgery, organized by the distinct pathological entities most commonly observed. Class I evidence, meta-analyses, and individual observational case series are considered, including the experiences of both our institution and others. Overall, resective epilepsy surgery leads to seizure freedom in approximately two thirds of patients with intractable temporal lobe epilepsy and about one half of individuals with focal neocortical epilepsy, although only the former observation is supported by class I evidence. Two common modifiable predictors of postoperative seizure freedom are early operative intervention and, in the case of a discrete lesion, gross total resection. Evidence-based practice guidelines recommend that epilepsy patients who continue to have seizures after trialing two or more medication regimens should be referred to a comprehensive epilepsy center for multidisciplinary evaluation, including surgical consideration. PMID:24497269

Design and hydraulic characteristics of a field-scale bi-phasic bioretention rain garden system for storm water management.

PubMed

Yang, H; Florence, D C; McCoy, E L; Dick, W A; Grewal, P S

2009-01-01

A field-scale bioretention rain garden system was constructed using a novel bi-phasic (i.e. sequence of anaerobic to aerobic) concept for improving retention and removal of storm water runoff pollutants. Hydraulic tests with bromide tracer and simulated runoff pollutants (nitrate-N, phosphate-P, Cu, Pb, and Zn) were performed in the system under a simulated continuous rainfall. The objectives of the tests were (1) to determine hydraulic characteristics of the system, and (2) to evaluate the movement of runoff pollutants through the system. For the 180 mm/24 h rainfall, the bi-phasic bioretention system effectively reduced both peak flow (approximately 70%) and runoff volume (approximately 42%). The breakthrough curves (BTCs) of bromide tracer suggest that the transport pattern of the system is similar to dispersed plug flow under this large runoff event. The BTCs of bromide showed mean 10% and 90% breakthrough times of 5.7 h and 12.5 h, respectively. Under the continuous rainfall, a significantly different transport pattern was found between each runoff pollutant. Nitrate-N was easily transported through the system with potential leaching risk from the initial soil medium, whereas phosphate-P and metals were significantly retained indicating sorption-mediated transport. These findings support the importance of hydraulics, in combination with the soil medium, when creating bioretention systems for bioremediation that are effective for various rainfall sizes and intervals.

On the Definition of Surface Potentials for Finite-Difference Operators

NASA Technical Reports Server (NTRS)

Tsynkov, S. V.; Bushnell, Dennis M. (Technical Monitor)

2001-01-01

For a class of linear constant-coefficient finite-difference operators of the second order, we introduce the concepts similar to those of conventional single- and double-layer potentials for differential operators. The discrete potentials are defined completely independently of any notion related to the approximation of the continuous potentials on the grid. We rather use all approach based on differentiating, and then inverting the differentiation of a function with surface discontinuity of a particular kind, which is the most general way of introducing surface potentials in the theory of distributions. The resulting finite-difference "surface" potentials appear to be solutions of the corresponding continuous potentials. Primarily, this pertains to the possibility of representing a given solution to the homogeneous equation on the domain as a variety of surface potentials, with the density defined on the domain's boundary. At the same time the discrete surface potentials can be interpreted as one specific realization of the generalized potentials of Calderon's type, and consequently, their approximation properties can be studied independently in the framework of the difference potentials method by Ryaben'kii. The motivation for introducing and analyzing the discrete surface potentials was provided by the problems of active shielding and control of sound, in which the aforementioned source terms that drive the potentials are interpreted as the acoustic control sources that cancel out the unwanted noise on a predetermined region of interest.

Learning to reach by reinforcement learning using a receptive field based function approximation approach with continuous actions.

PubMed

Tamosiunaite, Minija; Asfour, Tamim; Wörgötter, Florentin

2009-03-01

Reinforcement learning methods can be used in robotics applications especially for specific target-oriented problems, for example the reward-based recalibration of goal directed actions. To this end still relatively large and continuous state-action spaces need to be efficiently handled. The goal of this paper is, thus, to develop a novel, rather simple method which uses reinforcement learning with function approximation in conjunction with different reward-strategies for solving such problems. For the testing of our method, we use a four degree-of-freedom reaching problem in 3D-space simulated by a two-joint robot arm system with two DOF each. Function approximation is based on 4D, overlapping kernels (receptive fields) and the state-action space contains about 10,000 of these. Different types of reward structures are being compared, for example, reward-on- touching-only against reward-on-approach. Furthermore, forbidden joint configurations are punished. A continuous action space is used. In spite of a rather large number of states and the continuous action space these reward/punishment strategies allow the system to find a good solution usually within about 20 trials. The efficiency of our method demonstrated in this test scenario suggests that it might be possible to use it on a real robot for problems where mixed rewards can be defined in situations where other types of learning might be difficult.

Hunting stability analysis of high-speed train bogie under the frame lateral vibration active control

NASA Astrophysics Data System (ADS)

Yao, Yuan; Wu, Guosong; Sardahi, Yousef; Sun, Jian-Qiao

2018-02-01

In this paper, we study a multi-objective optimal design of three different frame vibration control configurations and compare their performances in improving the lateral stability of a high-speed train bogie. The existence of the time-delay in the control system and its impact on the bogie hunting stability are also investigated. The continuous time approximation method is used to approximate the time-delay system dynamics and then the root locus curves of the system before and after applying control are depicted. The analysis results show that the three control cases could improve the bogie hunting stability effectively. But the root locus of low- frequency hunting mode of bogie which determinates the system critical speed is different, thus affecting the system stability with the increasing of speed. Based on the stability analysis at different bogie dynamics parameters, the robustness of the control case (1) is the strongest. However, the case (2) is more suitable for the dynamic performance requirements of bogie. For the case (1), the time-delay over 10 ms may lead to instability of the control system which will affect the bogie hunting stability seriously. For the case (2) and (3), the increasing time-delay reduces the hunting stability gradually over the high-speed range. At a certain speed, such as 200 km/h, an appropriate time-delay is favourable to the bogie hunting stability. The mechanism is proposed according to the root locus analysis of time-delay system. At last, the nonlinear bifurcation characteristics of the bogie control system are studied by the numerical integration methods to verify the effects of these active control configurations and the delay on the bogie hunting stability.

Resolution of the COBE Earth sensor anomaly

NASA Technical Reports Server (NTRS)

Sedler, J.

1993-01-01

Since its launch on November 18, 1989, the Earth sensors on the Cosmic Background Explorer (COBE) have shown much greater noise than expected. The problem was traced to an error in Earth horizon acquisition-of-signal (AOS) times. Due to this error, the AOS timing correction was ignored, causing Earth sensor split-to-index (SI) angles to be incorrectly time-tagged to minor frame synchronization times. Resulting Earth sensor residuals, based on gyro-propagated fine attitude solutions, were as large as plus or minus 0.45 deg (much greater than plus or minus 0.10 deg from scanner specifications (Reference 1)). Also, discontinuities in single-frame coarse attitude pitch and roll angles (as large as 0.80 and 0.30 deg, respectively) were noted several times during each orbit. However, over the course of the mission, each Earth sensor was observed to independently and unexpectedly reset and then reactivate into a new configuration. Although the telemetered AOS timing corrections are still in error, a procedure has been developed to approximate and apply these corrections. This paper describes the approach, analysis, and results of approximating and applying AOS timing adjustments to correct Earth scanner data. Furthermore, due to the continuing degradation of COBE's gyroscopes, gyro-propagated fine attitude solutions may soon become unavailable, requiring an alternative method for attitude determination. By correcting Earth scanner AOS telemetry, as described in this paper, more accurate single-frame attitude solutions are obtained. All aforementioned pitch and roll discontinuities are removed. When proper AOS corrections are applied, the standard deviation of pitch residuals between coarse attitude and gyro-propagated fine attitude solutions decrease by a factor of 3. Also, the overall standard deviation of SI residuals from fine attitude solutions decrease by a factor of 4 (meeting sensor specifications) when AOS corrections are applied.

Plate tectonics and continental basaltic geochemistry throughout Earth history

NASA Astrophysics Data System (ADS)

Keller, Brenhin; Schoene, Blair

2018-01-01

Basaltic magmas constitute the primary mass flux from Earth's mantle to its crust, carrying information about the conditions of mantle melting through which they were generated. As such, changes in the average basaltic geochemistry through time reflect changes in underlying parameters such as mantle potential temperature and the geodynamic setting of mantle melting. However, sampling bias, preservation bias, and geological heterogeneity complicate the calculation of representative average compositions. Here we use weighted bootstrap resampling to minimize sampling bias over the heterogeneous rock record and obtain maximally representative average basaltic compositions through time. Over the approximately 4 Ga of the continental rock record, the average composition of preserved continental basalts has evolved along a generally continuous trajectory, with decreasing compatible element concentrations and increasing incompatible element concentrations, punctuated by a comparatively rapid transition in some variables such as La/Yb ratios and Zr, Nb, and Ti abundances approximately 2.5 Ga ago. Geochemical modeling of mantle melting systematics and trace element partitioning suggests that these observations can be explained by discontinuous changes in the mineralogy of mantle partial melting driven by a gradual decrease in mantle potential temperature, without appealing to any change in tectonic process. This interpretation is supported by the geochemical record of slab fluid input to continental basalts, which indicates no long-term change in the global proportion of arc versus non-arc basaltic magmatism at any time in the preserved rock record.

An interplanetary magnetic field ensemble at 1 AU

NASA Technical Reports Server (NTRS)

Matthaeus, W. H.; Goldstein, M. L.; King, J. H.

1985-01-01

A method for calculation ensemble averages from magnetic field data is described. A data set comprising approximately 16 months of nearly continuous ISEE-3 magnetic field data is used in this study. Individual subintervals of this data, ranging from 15 hours to 15.6 days comprise the ensemble. The sole condition for including each subinterval in the averages is the degree to which it represents a weakly time-stationary process. Averages obtained by this method are appropriate for a turbulence description of the interplanetary medium. The ensemble average correlation length obtained from all subintervals is found to be 4.9 x 10 to the 11th cm. The average value of the variances of the magnetic field components are in the approximate ratio 8:9:10, where the third component is the local mean field direction. The correlation lengths and variances are found to have a systematic variation with subinterval duration, reflecting the important role of low-frequency fluctuations in the interplanetary medium.

Numerical solution of differential equations by artificial neural networks

NASA Technical Reports Server (NTRS)

Meade, Andrew J., Jr.

1995-01-01

Conventionally programmed digital computers can process numbers with great speed and precision, but do not easily recognize patterns or imprecise or contradictory data. Instead of being programmed in the conventional sense, artificial neural networks (ANN's) are capable of self-learning through exposure to repeated examples. However, the training of an ANN can be a time consuming and unpredictable process. A general method is being developed by the author to mate the adaptability of the ANN with the speed and precision of the digital computer. This method has been successful in building feedforward networks that can approximate functions and their partial derivatives from examples in a single iteration. The general method also allows the formation of feedforward networks that can approximate the solution to nonlinear ordinary and partial differential equations to desired accuracy without the need of examples. It is believed that continued research will produce artificial neural networks that can be used with confidence in practical scientific computing and engineering applications.

FANTOM5 CAGE profiles of human and mouse samples.

PubMed

Noguchi, Shuhei; Arakawa, Takahiro; Fukuda, Shiro; Furuno, Masaaki; Hasegawa, Akira; Hori, Fumi; Ishikawa-Kato, Sachi; Kaida, Kaoru; Kaiho, Ai; Kanamori-Katayama, Mutsumi; Kawashima, Tsugumi; Kojima, Miki; Kubosaki, Atsutaka; Manabe, Ri-Ichiroh; Murata, Mitsuyoshi; Nagao-Sato, Sayaka; Nakazato, Kenichi; Ninomiya, Noriko; Nishiyori-Sueki, Hiromi; Noma, Shohei; Saijyo, Eri; Saka, Akiko; Sakai, Mizuho; Simon, Christophe; Suzuki, Naoko; Tagami, Michihira; Watanabe, Shoko; Yoshida, Shigehiro; Arner, Peter; Axton, Richard A; Babina, Magda; Baillie, J Kenneth; Barnett, Timothy C; Beckhouse, Anthony G; Blumenthal, Antje; Bodega, Beatrice; Bonetti, Alessandro; Briggs, James; Brombacher, Frank; Carlisle, Ailsa J; Clevers, Hans C; Davis, Carrie A; Detmar, Michael; Dohi, Taeko; Edge, Albert S B; Edinger, Matthias; Ehrlund, Anna; Ekwall, Karl; Endoh, Mitsuhiro; Enomoto, Hideki; Eslami, Afsaneh; Fagiolini, Michela; Fairbairn, Lynsey; Farach-Carson, Mary C; Faulkner, Geoffrey J; Ferrai, Carmelo; Fisher, Malcolm E; Forrester, Lesley M; Fujita, Rie; Furusawa, Jun-Ichi; Geijtenbeek, Teunis B; Gingeras, Thomas; Goldowitz, Daniel; Guhl, Sven; Guler, Reto; Gustincich, Stefano; Ha, Thomas J; Hamaguchi, Masahide; Hara, Mitsuko; Hasegawa, Yuki; Herlyn, Meenhard; Heutink, Peter; Hitchens, Kelly J; Hume, David A; Ikawa, Tomokatsu; Ishizu, Yuri; Kai, Chieko; Kawamoto, Hiroshi; Kawamura, Yuki I; Kempfle, Judith S; Kenna, Tony J; Kere, Juha; Khachigian, Levon M; Kitamura, Toshio; Klein, Sarah; Klinken, S Peter; Knox, Alan J; Kojima, Soichi; Koseki, Haruhiko; Koyasu, Shigeo; Lee, Weonju; Lennartsson, Andreas; Mackay-Sim, Alan; Mejhert, Niklas; Mizuno, Yosuke; Morikawa, Hiromasa; Morimoto, Mitsuru; Moro, Kazuyo; Morris, Kelly J; Motohashi, Hozumi; Mummery, Christine L; Nakachi, Yutaka; Nakahara, Fumio; Nakamura, Toshiyuki; Nakamura, Yukio; Nozaki, Tadasuke; Ogishima, Soichi; Ohkura, Naganari; Ohno, Hiroshi; Ohshima, Mitsuhiro; Okada-Hatakeyama, Mariko; Okazaki, Yasushi; Orlando, Valerio; Ovchinnikov, Dmitry A; Passier, Robert; Patrikakis, Margaret; Pombo, Ana; Pradhan-Bhatt, Swati; Qin, Xian-Yang; Rehli, Michael; Rizzu, Patrizia; Roy, Sugata; Sajantila, Antti; Sakaguchi, Shimon; Sato, Hiroki; Satoh, Hironori; Savvi, Suzana; Saxena, Alka; Schmidl, Christian; Schneider, Claudio; Schulze-Tanzil, Gundula G; Schwegmann, Anita; Sheng, Guojun; Shin, Jay W; Sugiyama, Daisuke; Sugiyama, Takaaki; Summers, Kim M; Takahashi, Naoko; Takai, Jun; Tanaka, Hiroshi; Tatsukawa, Hideki; Tomoiu, Andru; Toyoda, Hiroo; van de Wetering, Marc; van den Berg, Linda M; Verardo, Roberto; Vijayan, Dipti; Wells, Christine A; Winteringham, Louise N; Wolvetang, Ernst; Yamaguchi, Yoko; Yamamoto, Masayuki; Yanagi-Mizuochi, Chiyo; Yoneda, Misako; Yonekura, Yohei; Zhang, Peter G; Zucchelli, Silvia; Abugessaisa, Imad; Arner, Erik; Harshbarger, Jayson; Kondo, Atsushi; Lassmann, Timo; Lizio, Marina; Sahin, Serkan; Sengstag, Thierry; Severin, Jessica; Shimoji, Hisashi; Suzuki, Masanori; Suzuki, Harukazu; Kawai, Jun; Kondo, Naoto; Itoh, Masayoshi; Daub, Carsten O; Kasukawa, Takeya; Kawaji, Hideya; Carninci, Piero; Forrest, Alistair R R; Hayashizaki, Yoshihide

2017-08-29

In the FANTOM5 project, transcription initiation events across the human and mouse genomes were mapped at a single base-pair resolution and their frequencies were monitored by CAGE (Cap Analysis of Gene Expression) coupled with single-molecule sequencing. Approximately three thousands of samples, consisting of a variety of primary cells, tissues, cell lines, and time series samples during cell activation and development, were subjected to a uniform pipeline of CAGE data production. The analysis pipeline started by measuring RNA extracts to assess their quality, and continued to CAGE library production by using a robotic or a manual workflow, single molecule sequencing, and computational processing to generate frequencies of transcription initiation. Resulting data represents the consequence of transcriptional regulation in each analyzed state of mammalian cells. Non-overlapping peaks over the CAGE profiles, approximately 200,000 and 150,000 peaks for the human and mouse genomes, were identified and annotated to provide precise location of known promoters as well as novel ones, and to quantify their activities.

FANTOM5 CAGE profiles of human and mouse samples

PubMed Central

Noguchi, Shuhei; Arakawa, Takahiro; Fukuda, Shiro; Furuno, Masaaki; Hasegawa, Akira; Hori, Fumi; Ishikawa-Kato, Sachi; Kaida, Kaoru; Kaiho, Ai; Kanamori-Katayama, Mutsumi; Kawashima, Tsugumi; Kojima, Miki; Kubosaki, Atsutaka; Manabe, Ri-ichiroh; Murata, Mitsuyoshi; Nagao-Sato, Sayaka; Nakazato, Kenichi; Ninomiya, Noriko; Nishiyori-Sueki, Hiromi; Noma, Shohei; Saijyo, Eri; Saka, Akiko; Sakai, Mizuho; Simon, Christophe; Suzuki, Naoko; Tagami, Michihira; Watanabe, Shoko; Yoshida, Shigehiro; Arner, Peter; Axton, Richard A.; Babina, Magda; Baillie, J. Kenneth; Barnett, Timothy C.; Beckhouse, Anthony G.; Blumenthal, Antje; Bodega, Beatrice; Bonetti, Alessandro; Briggs, James; Brombacher, Frank; Carlisle, Ailsa J.; Clevers, Hans C.; Davis, Carrie A.; Detmar, Michael; Dohi, Taeko; Edge, Albert S.B.; Edinger, Matthias; Ehrlund, Anna; Ekwall, Karl; Endoh, Mitsuhiro; Enomoto, Hideki; Eslami, Afsaneh; Fagiolini, Michela; Fairbairn, Lynsey; Farach-Carson, Mary C.; Faulkner, Geoffrey J.; Ferrai, Carmelo; Fisher, Malcolm E.; Forrester, Lesley M.; Fujita, Rie; Furusawa, Jun-ichi; Geijtenbeek, Teunis B.; Gingeras, Thomas; Goldowitz, Daniel; Guhl, Sven; Guler, Reto; Gustincich, Stefano; Ha, Thomas J.; Hamaguchi, Masahide; Hara, Mitsuko; Hasegawa, Yuki; Herlyn, Meenhard; Heutink, Peter; Hitchens, Kelly J.; Hume, David A.; Ikawa, Tomokatsu; Ishizu, Yuri; Kai, Chieko; Kawamoto, Hiroshi; Kawamura, Yuki I.; Kempfle, Judith S.; Kenna, Tony J.; Kere, Juha; Khachigian, Levon M.; Kitamura, Toshio; Klein, Sarah; Klinken, S. Peter; Knox, Alan J.; Kojima, Soichi; Koseki, Haruhiko; Koyasu, Shigeo; Lee, Weonju; Lennartsson, Andreas; Mackay-sim, Alan; Mejhert, Niklas; Mizuno, Yosuke; Morikawa, Hiromasa; Morimoto, Mitsuru; Moro, Kazuyo; Morris, Kelly J.; Motohashi, Hozumi; Mummery, Christine L.; Nakachi, Yutaka; Nakahara, Fumio; Nakamura, Toshiyuki; Nakamura, Yukio; Nozaki, Tadasuke; Ogishima, Soichi; Ohkura, Naganari; Ohno, Hiroshi; Ohshima, Mitsuhiro; Okada-Hatakeyama, Mariko; Okazaki, Yasushi; Orlando, Valerio; Ovchinnikov, Dmitry A.; Passier, Robert; Patrikakis, Margaret; Pombo, Ana; Pradhan-Bhatt, Swati; Qin, Xian-Yang; Rehli, Michael; Rizzu, Patrizia; Roy, Sugata; Sajantila, Antti; Sakaguchi, Shimon; Sato, Hiroki; Satoh, Hironori; Savvi, Suzana; Saxena, Alka; Schmidl, Christian; Schneider, Claudio; Schulze-Tanzil, Gundula G.; Schwegmann, Anita; Sheng, Guojun; Shin, Jay W.; Sugiyama, Daisuke; Sugiyama, Takaaki; Summers, Kim M.; Takahashi, Naoko; Takai, Jun; Tanaka, Hiroshi; Tatsukawa, Hideki; Tomoiu, Andru; Toyoda, Hiroo; van de Wetering, Marc; van den Berg, Linda M.; Verardo, Roberto; Vijayan, Dipti; Wells, Christine A.; Winteringham, Louise N.; Wolvetang, Ernst; Yamaguchi, Yoko; Yamamoto, Masayuki; Yanagi-Mizuochi, Chiyo; Yoneda, Misako; Yonekura, Yohei; Zhang, Peter G.; Zucchelli, Silvia; Abugessaisa, Imad; Arner, Erik; Harshbarger, Jayson; Kondo, Atsushi; Lassmann, Timo; Lizio, Marina; Sahin, Serkan; Sengstag, Thierry; Severin, Jessica; Shimoji, Hisashi; Suzuki, Masanori; Suzuki, Harukazu; Kawai, Jun; Kondo, Naoto; Itoh, Masayoshi; Daub, Carsten O.; Kasukawa, Takeya; Kawaji, Hideya; Carninci, Piero; Forrest, Alistair R.R.; Hayashizaki, Yoshihide

2017-01-01

In the FANTOM5 project, transcription initiation events across the human and mouse genomes were mapped at a single base-pair resolution and their frequencies were monitored by CAGE (Cap Analysis of Gene Expression) coupled with single-molecule sequencing. Approximately three thousands of samples, consisting of a variety of primary cells, tissues, cell lines, and time series samples during cell activation and development, were subjected to a uniform pipeline of CAGE data production. The analysis pipeline started by measuring RNA extracts to assess their quality, and continued to CAGE library production by using a robotic or a manual workflow, single molecule sequencing, and computational processing to generate frequencies of transcription initiation. Resulting data represents the consequence of transcriptional regulation in each analyzed state of mammalian cells. Non-overlapping peaks over the CAGE profiles, approximately 200,000 and 150,000 peaks for the human and mouse genomes, were identified and annotated to provide precise location of known promoters as well as novel ones, and to quantify their activities. PMID:28850106

Towards an ab-initio treatment of nonlocal electronic correlations with dynamical vertex approximation

NASA Astrophysics Data System (ADS)

Galler, Anna; Gunacker, Patrik; Tomczak, Jan; Thunström, Patrik; Held, Karsten

Recently, approaches such as the dynamical vertex approximation (D ΓA) or the dual-fermion method have been developed. These diagrammatic approaches are going beyond dynamical mean field theory (DMFT) by including nonlocal electronic correlations on all length scales as well as the local DMFT correlations. Here we present our efforts to extend the D ΓA methodology to ab-initio materials calculations (ab-initio D ΓA). Our approach is a unifying framework which includes both GW and DMFT-type of diagrams, but also important nonlocal correlations beyond, e.g. nonlocal spin fluctuations. In our multi-band implementation we are using a worm sampling technique within continuous-time quantum Monte Carlo in the hybridization expansion to obtain the DMFT vertex, from which we construct the reducible vertex function using the two particle-hole ladders. As a first application we show results for transition metal oxides. Support by the ERC project AbinitioDGA (306447) is acknowledged.

Low-density homogeneous symmetric nuclear matter: Disclosing dinucleons in coexisting phases

NASA Astrophysics Data System (ADS)

Arellano, Hugo F.; Delaroche, Jean-Paul

2015-01-01

The effect of in-medium dinucleon bound states on self-consistent single-particle fields in Brueckner, Bethe and Goldstone theory is investigated in symmetric nuclear matter at zero temperature. To this end, dinucleon bound state occurences in the 1 S 0 and 3 SD 1 channels are explicitly accounted for --within the continuous choice for the auxiliary fields-- while imposing self-consistency in Brueckner-Hartree-Fock approximation calculations. Searches are carried out at Fermi momenta in the range fm-1, using the Argonne bare nucleon-nucleon potential without resorting to the effective-mass approximation. As a result, two distinct solutions meeting the self-consistency requirement are found with overlapping domains in the interval 0.130 fm-1 0.285 fm-1, corresponding to mass densities between and g cm-3. Effective masses as high as three times the nucleon mass are found in the coexistence domain. The emergence of superfluidity in relationship with BCS pairing gap solutions is discussed.

Evolution of microstructure and elastic wave velocities in dehydrated gypsum samples

NASA Astrophysics Data System (ADS)

Milsch, Harald; Priegnitz, Mike

2012-12-01

We report on changes in P and S-wave velocities and rock microstructure induced by devolatilization reactions using gypsum as a reference analog material. Cylindrical samples of natural alabaster were dehydrated in air, at ambient pressure, and temperatures between 378 and 423 K. Dehydration did not proceed homogeneously but via a reaction front moving sample inwards separating an outer highly porous rim from the remaining gypsum which, above approximately 393 (±5) K, concurrently decomposed into hemihydrate. Overall porosity was observed to continuously increase with reaction progress from approximately 2% for fully hydrated samples to 30% for completely dehydrated ones. Concurrently, P and S-wave velocities linearly decreased with porosity from 5.2 and 2.7 km/s to 1.0 and 0.7 km/s, respectively. It is concluded that a linearized empirical Raymer-type model extended by a critical porosity term and based on the respective time dependent mineral and pore volumes reasonably replicates the P and S-wave data in relation to reaction progress and porosity.

Competition in high dimensional spaces using a sparse approximation of neural fields.

PubMed

Quinton, Jean-Charles; Girau, Bernard; Lefort, Mathieu

2011-01-01

The Continuum Neural Field Theory implements competition within topologically organized neural networks with lateral inhibitory connections. However, due to the polynomial complexity of matrix-based implementations, updating dense representations of the activity becomes computationally intractable when an adaptive resolution or an arbitrary number of input dimensions is required. This paper proposes an alternative to self-organizing maps with a sparse implementation based on Gaussian mixture models, promoting a trade-off in redundancy for higher computational efficiency and alleviating constraints on the underlying substrate.This version reproduces the emergent attentional properties of the original equations, by directly applying them within a continuous approximation of a high dimensional neural field. The model is compatible with preprocessed sensory flows but can also be interfaced with artificial systems. This is particularly important for sensorimotor systems, where decisions and motor actions must be taken and updated in real-time. Preliminary tests are performed on a reactive color tracking application, using spatially distributed color features.

About one discrete model of splitting by the physical processes of a piezoconductive medium with gas hydrate inclusions

NASA Astrophysics Data System (ADS)

Poveshchenko, Yu A.; Podryga, V. O.; Rahimly, P. I.; Sharova, Yu S.

2018-01-01

The thermodynamically equilibrium model for splitting by the physical processes of a two-component three-phase filtration fluid dynamics with gas hydrate inclusions is considered in the paper, for which a family of two-layer completely conservative difference schemes of the support operators method with time weights profiled in space is constructed. On the irregular grids of the theory of the support-operators method applied to the specifics of the processes of transfer of saturations and internal energies of water and gas in a medium with gas hydrate inclusions, methods of directwind approximation of these processes are considered. These approximations preserve the continual properties of divergence-gradient operations in their difference form and are related to the velocity field providing saturations transfer and internal energies of fluids. Fluid dynamics with gas hydrate inclusions are also calculated on the basis of the proposed approach, in particular, in areas of severe pressure depression in the collector space.

The topography of frequency and time representation in primate auditory cortices

PubMed Central

Baumann, Simon; Joly, Olivier; Rees, Adrian; Petkov, Christopher I; Sun, Li; Thiele, Alexander; Griffiths, Timothy D

2015-01-01

Natural sounds can be characterised by their spectral content and temporal modulation, but how the brain is organized to analyse these two critical sound dimensions remains uncertain. Using functional magnetic resonance imaging, we demonstrate a topographical representation of amplitude modulation rate in the auditory cortex of awake macaques. The representation of this temporal dimension is organized in approximately concentric bands of equal rates across the superior temporal plane in both hemispheres, progressing from high rates in the posterior core to low rates in the anterior core and lateral belt cortex. In A1 the resulting gradient of modulation rate runs approximately perpendicular to the axis of the tonotopic gradient, suggesting an orthogonal organisation of spectral and temporal sound dimensions. In auditory belt areas this relationship is more complex. The data suggest a continuous representation of modulation rate across several physiological areas, in contradistinction to a separate representation of frequency within each area. DOI: http://dx.doi.org/10.7554/eLife.03256.001 PMID:25590651

Accelerated viscoelastic characterization of T300-5208 graphite-epoxy laminates

NASA Technical Reports Server (NTRS)

Tuttle, M. E.; Brinson, H. F.

1985-01-01

A viscoelastic response scheme for the accelerated characterization of polymer-based composite laminates in applied to T300/5208 graphite/epoxy. The response of uni-directional specimens is modeled. The transient component of the viscoelastic creep compliance is assumed to follow a power law approximation. A recursive relationship is developed, based upon the Schapery single-integral equation, which allows approximation of a continuous time-varying uniaxial load using discrete steps in stress. The viscoelastic response of T300/5208 to transverse normal and shear stresses is determined unsing 90 deg and 10 deg off-axis tensile specimens. In each case the seven viscoelastic material parameters required in the analysis are determined experimentally using short-term creep and creep recovery tests. It is shown that an accurate measure of the power law exponent is crucial for accurate long-term prediction. A short term test cycle selection procedure is proposed, which should provide useful guidelines for the evaluation of other viscoelastic materials.

Recovery and removal of nutrients from swine wastewater by using a novel integrated reactor for struvite decomposition and recycling

PubMed Central

Huang, Haiming; Xiao, Dean; Liu, Jiahui; Hou, Li; Ding, Li

2015-01-01

In the present study, struvite decomposition was performed by air stripping for ammonia release and a novel integrated reactor was designed for the simultaneous removal and recovery of total ammonia-nitrogen (TAN) and total orthophosphate (PT) from swine wastewater by internal struvite recycling. Decomposition of struvite by air stripping was found to be feasible. Without supplementation with additional magnesium and phosphate sources, the removal ratio of TAN from synthetic wastewater was maintained at >80% by recycling of the struvite decomposition product formed under optimal conditions, six times. Continuous operation of the integrated reactor indicated that approximately 91% TAN and 97% PT in the swine wastewater could be removed and recovered by the proposed recycling process with the supplementation of bittern. Economic evaluation of the proposed system showed that struvite precipitation cost can be saved by approximately 54% by adopting the proposed recycling process in comparison with no recycling method. PMID:25960246

Simultaneous removal of nitrate and pentachlorophenol from simulated groundwater using a biodenitrification reactor packed with corncob.

PubMed

Wang, Xuming; Xing, Lijun; Qiu, Tianlei; Han, Meilin

2013-04-01

Both nitrate and pentachlorophenol (PCP) are familiar pollutants in aqueous environment. This research is focused on the simultaneous removal of nitrate and PCP from simulated contaminated groundwater using a laboratory-scale denitrification reactor packed with corncob as both carbon source and biofilm support. The reactor could be started up readily, and the removal efficiencies of nitrate and PCP reached up to approximately 98% and 40-45% when their initial concentrations were 50 mg N/L and 5 mg/L, respectively, after 15-day continuous operation at 10 h of hydraulic retention time (HRT) and 25 °C. Approximately 91% of PCP removal efficiency was achieved, with 2.47 mg/L of chloride ion release at 24 h of HRT. Eighty-two percent of chlorine in PCP removed was ionized. The productions of 3-chlorophenol and phenol and chloride ion release indicate that the reductive dechlorination reaction is a major degradation pathway of PCP under the experimental conditions.

Long-term frequency and amplitude stability of a solid-nitrogen-cooled, continuous wave THz quantum cascade laser

NASA Astrophysics Data System (ADS)

Danylov, Andriy A.; Waldman, Jerry; Light, Alexander R.; Goyette, Thomas M.; Giles, Robert H.; Qian, Xifeng; Chandrayan, Neelima; Goodhue, William D.; Nixon, William E.

2012-02-01

Operational temperature increase of CW THz QCLs to 77 K has enabled us to employ solid nitrogen (SN2) as the cryogen. A roughing pump was used to solidify liquid nitrogen and when the residual vapor pressure in the nitrogen reservoir reached the pumping system's minimum pressure the temperature equilibrated and remained constant until all the nitrogen sublimated. The hold time compared to liquid helium has thereby increased approximately 70-fold, and at a greatly reduced cost. The milliwatt CW QCL was at a temperature of approximately 60 K, dissipating 5 W of electrical power. To measure the long-term frequency, current, and temperature stability, we heterodyned the free-running 2.31 THz QCL with a CO2 pumped far-infrared gas laser line in methanol (2.314 THz) in a corner-cube Schottky diode and recorded the IF frequency, current and temperature. Under these conditions the performance characteristics of the QCL, which will be reported, exceeded that of a device mounted in a mechanical cryocooler.

Use of Electronic Health Records in Disaster Response: The Experience of Department of Veterans Affairs After Hurricane Katrina

PubMed Central

Brown, Steven H.; Fischetti, Linda F.; Graham, Gail; Bates, Jack; Lancaster, Anne E.; McDaniel, David; Gillon, Joseph; Darbe, Melody; Kolodner, Robert M.

2007-01-01

Objectives. We describe electronic health data use by the Department of Veterans Affairs (VA) in the month after Katrina, including supporting technologies, the extent and nature of information accessed, and lessons learned. Methods. We conducted a retrospective study using cross-sectional panels of data collected sequentially over time. Results. By September 30, 2005, clinical data were accessed electronically for at least 38% (14941 of 39910) of patients cared for prior to Hurricane Katrina by New Orleans–area VA medical facilities. Approximately 1000 patients per day had data accessed during the month following Hurricane Katrina, a rate approximately two thirds of pre-Katrina values. Health care data were transmitted to more than 200 sites in 48 states and to at least 2300 users. Conclusions. The VA electronic health records supported continuity of care for evacuated veterans after Katrina. Our findings suggest that pharmacy and laboratory computerization alone will not be sufficient for future disaster support systems. PMID:17413082

Adaptive Detector Arrays for Optical Communications Receivers

NASA Technical Reports Server (NTRS)

Vilnrotter, V.; Srinivasan, M.

2000-01-01

The structure of an optimal adaptive array receiver for ground-based optical communications is described and its performance investigated. Kolmogorov phase screen simulations are used to model the sample functions of the focal-plane signal distribution due to turbulence and to generate realistic spatial distributions of the received optical field. This novel array detector concept reduces interference from background radiation by effectively assigning higher confidence levels at each instant of time to those detector elements that contain significant signal energy and suppressing those that do not. A simpler suboptimum structure that replaces the continuous weighting function of the optimal receiver by a hard decision on the selection of the signal detector elements also is described and evaluated. Approximations and bounds to the error probability are derived and compared with the exact calculations and receiver simulation results. It is shown that, for photon-counting receivers observing Poisson-distributed signals, performance improvements of approximately 5 dB can be obtained over conventional single-detector photon-counting receivers, when operating in high background environments.

Optical fiber nanoprobe preparation for near-field optical microscopy by chemical etching under surface tension and capillary action.

PubMed

Mondal, Samir K; Mitra, Anupam; Singh, Nahar; Sarkar, S N; Kapur, Pawan

2009-10-26

We propose a technique of chemical etching for fabrication of near perfect optical fiber nanoprobe (NNP). It uses photosensitive single mode optical fiber to etch in hydro fluoric (HF) acid solution. The difference in etching rate for cladding and photosensitive core in HF acid solution creates capillary ring along core-cladding boundary under a given condition. The capillary ring is filled with acid solution due to surface tension and capillary action. Finally it creates near perfect symmetric tip at the apex of the fiber as the height of the acid level in capillary ring decreases while width of the ring increases with continuous etching. Typical tip features are short taper length (approximately 4 microm), large cone angle (approximately 38 degrees ), and small probe tip dimension (<100 nm). A finite difference time domain (FDTD) analysis is also presented to compare near field optics of the NNP with conventional nanoprobe (CNP). The probe may be ideal for near field optical imaging and sensor applications.

Portable bioimpedance monitor evaluation for continuous impedance measurements. Towards wearable plethysmography applications.

PubMed

Ferreira, J; Seoane, F; Lindecrantz, K

2013-01-01

Personalised Health Systems (PHS) that could benefit the life quality of the patients as well as decreasing the health care costs for society among other factors are arisen. The purpose of this paper is to study the capabilities of the System-on-Chip Impedance Network Analyser AD5933 performing high speed single frequency continuous bioimpedance measurements. From a theoretical analysis, the minimum continuous impedance estimation time was determined, and the AD5933 with a custom 4-Electrode Analog Front-End (AFE) was used to experimentally determine the maximum continuous impedance estimation frequency as well as the system impedance estimation error when measuring a 2R1C electrical circuit model. Transthoracic Electrical Bioimpedance (TEB) measurements in a healthy subject were obtained using 3M gel electrodes in a tetrapolar lateral spot electrode configuration. The obtained TEB raw signal was filtered in MATLAB to obtain the respiration and cardiogenic signals, and from the cardiogenic signal the impedance derivative signal (dZ/dt) was also calculated. The results have shown that the maximum continuous impedance estimation rate was approximately 550 measurements per second with a magnitude estimation error below 1% on 2R1C-parallel bridge measurements. The displayed respiration and cardiac signals exhibited good performance, and they could be used to obtain valuable information in some plethysmography monitoring applications. The obtained results suggest that the AD5933-based monitor could be used for the implementation of a portable and wearable Bioimpedance plethysmograph that could be used in applications such as Impedance Cardiography. These results combined with the research done in functional garments and textile electrodes might enable the implementation of PHS applications in a relatively short time from now.

Dynamical Studies of the Middle Atmosphere Using High Resolution Doppler Imager Observations

NASA Technical Reports Server (NTRS)

Skinner, Wilbert

2002-01-01

This report summarizes the activities of NASA grant NAG5-11068, "Dynamicai Studies of the Middle Atmosphere Using High Resolution Doppler Imager Observations." The High Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) has been providing direct measurements of the Earth's horizontal wind field in the stratosphere, mesosphere and lower thermosphere. Mesospheric temperatures, ozone, and O((sup 1) D) densities, and stratospheric aerosol extinctions coefficients, are also retrieved. The goal of HRDI is to measure the vector winds in the stratosphere (10-40 km), mesosphere, and lower thermosphere (approximately 50-120 km) during the day, and the lower thermosphere at night (approximately 95 km) to an accuracy of 5 m/s. The horizontal wind vector is measured by observing the Doppler shift of rotational lines of molecular oxygen along two lines of sight. In addition to winds, temperatures and volume emission rates are determined in the mesosphere and lower thermosphere, from which ozone and O((sup 1) D) concentrations can be derived, and aerosol scattering coefficients are determined in the stratosphere. UARS was launched on September 12, 1991, into a 585-km circular orbit inclined 57 degrees to the equator HRDI was activated September 28, 1991 and following a period of checkout and adjustment of the instrument parameters, scientific observations began November 2, 199 1. HRDI operated nearly continuously from launch until April 1995. At that time the UARS solar array drive failed, forcing the instruments to time-share the available power. From July 1995 to July 1996 HRDI operated approximately 50% of the time. At that point, one of the three spacecraft batteries failed and from then until September 1998 the duty cycle was less than 20% per month, At that time it was determined that HRDI could operate during each daytime pass, which increased the daytime duty cycle to close to l00%, while nighttime operations were limited to about a week per month. In the fall of 1999, the second tape recorder failed requiring a real time contact with a TRDSS satellite to retrieve that data. This resulted in about 60% data collection efficiency. Finally, in the summer of 2000, the second star sensor failed requiring the spacecraft attitude to be controlled by a three axis magnetometer and sun sensor. This resulted in a loss of attitude knowledge but operations continue with the anticipation of correcting the attitude. A new method for determining the tide and mean structure from satellite data in conjunction with a new tidal model has been devised. For brevity, it shall be referred to as the TMAT or Tide-Mean Assimilation Technique. Most previous methods of tidal analysis are based on various ways of slicing the data set.

Fiber Optic Immunochemical Sensors For Continuous Monitoring Of Hapten Concentrations

NASA Astrophysics Data System (ADS)

Miller, W. Greg; Anderson, F. Philip

1989-06-01

We describe a fiber optic sensor based on a homogeneous fluorescence energy transfer immunoassay which operates in a continuous, reversible manner to quantitate the anticonvulsant drug phenytoin. B-phycoerythrin-phenytoin and Texas Red labeled anti-phenytoin antibody were sealed inside a short length of cellulose dialysis tubing which was cemented to the distal end of an optical fiber. When the sensor was placed into a solution of phenytoin, the drug crossed the dialysis membrane, displaced a fraction of the B-phycoerythrin-phenytoin from the antibody, and produced a change in fluorescence signal which was measured with a fiber optic fluorometer. The sensor had a concentration response of 5 to 500μmo1/L phenytoin with a response time of 5 to 15 min and precision of <2.5% CV. The chemical kinetics of the antibody-hapten indicator reaction were modeled mathematically and simulation showed that response time in the minutes range can be achieved when the dissociation rate constant is greater than approximately 10-3 sec-1. The dissociation rate constant influences the time to reach equilibrium and the unbound P* concentration range available for instrumental measurement. The ratio of the labeled and unlabeled hapten dissociation rate constants influences the analyte concentration range to which the sensor will respond.

Method of Implementing Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Stephens, Scott A. (Inventor); Thomas, J. Brooks (Inventor)

1997-01-01

In a new formulation for digital phase-locked loops, loop-filter constants are determined from loop roots that can each be selectively placed in the s-plane on the basis of a new set of parameters, each with simple and direct physical meaning in terms of loop noise bandwidth, root-specific decay rate, and root-specific damping. Loops of first to fourth order are treated in the continuous-update approximation (B(sub L)T approaches 0) and in a discrete-update formulation with arbitrary B(sub L)T. Deficiencies of the continuous-update approximation in large-B(sub L)T applications are avoided in the new discrete-update formulation.

Stochastic maps, continuous approximation, and stable distribution

NASA Astrophysics Data System (ADS)

Kessler, David A.; Burov, Stanislav

2017-10-01

A continuous approximation framework for general nonlinear stochastic as well as deterministic discrete maps is developed. For the stochastic map with uncorelated Gaussian noise, by successively applying the Itô lemma, we obtain a Langevin type of equation. Specifically, we show how nonlinear maps give rise to a Langevin description that involves multiplicative noise. The multiplicative nature of the noise induces an additional effective force, not present in the absence of noise. We further exploit the continuum description and provide an explicit formula for the stable distribution of the stochastic map and conditions for its existence. Our results are in good agreement with numerical simulations of several maps.

Transverse forces on a vortex in lattice models of superfluids

NASA Astrophysics Data System (ADS)

Sonin, E. B.

2013-12-01

The paper derives the transverse forces (the Magnus and the Lorentz forces) in the lattice models of superfluids in the continuous approximation. The continuous approximation restores translational invariance absent in the original lattice model, but the theory is not Galilean invariant. As a result, calculation of the two transverse forces on the vortex, Magnus force and Lorentz force, requires the analysis of two balances, for the true momentum of particles in the lattice (Magnus force) and for the quasimomentum (Lorentz force) known from the Bloch theory of particles in the periodic potential. While the developed theory yields the same Lorentz force, which was well known before, a new general expression for the Magnus force was obtained. The theory demonstrates how a small Magnus force emerges in the Josephson-junction array if the particle-hole symmetry is broken. The continuous approximation for the Bose-Hubbard model close to the superfluid-insulator transition was developed, which was used for calculation of the Magnus force. The theory shows that there is an area in the phase diagram for the Bose-Hubbard model, where the Magnus force has an inverse sign with respect to that which is expected from the sign of velocity circulation.

Feasibility of utilizing bioindicators for testing microbial inactivation in sweetpotato purees processed with a continuous-flow microwave system.

PubMed

Brinley, T A; Dock, C N; Truong, V-D; Coronel, P; Kumar, P; Simunovic, J; Sandeep, K P; Cartwright, G D; Swartzel, K R; Jaykus, L-A

2007-06-01

Continuous-flow microwave heating has potential in aseptic processing of various food products, including purees from sweetpotatoes and other vegetables. Establishing the feasibility of a new processing technology for achieving commercial sterility requires evaluating microbial inactivation. This study aimed to assess the feasibility of using commercially available plastic pouches of bioindicators containing spores of Geobacillius stearothermophilus ATCC 7953 and Bacillus subtilis ATCC 35021 for evaluating the degree of microbial inactivation achieved in vegetable purees processed in a continuous-flow microwave heating unit. Sweetpotato puree seeded with the bioindicators was subjected to 3 levels of processing based on the fastest particles: undertarget process (F(0) approximately 0.65), target process (F(0) approximately 2.8), and overtarget process (F(0) approximately 10.10). After initial experiments, we found it was necessary to engineer a setup with 2 removable tubes connected to the continuous-flow microwave system to facilitate the injection of indicators into the unit without interrupting the puree flow. Using this approach, 60% of the indicators injected into the system could be recovered postprocess. Spore survival after processing, as evaluated by use of growth indicator dyes and standard plating methods, verified inactivation of the spores in sweetpotato puree. The log reduction results for B. subtilis were equivalent to the predesigned degrees of sterilization (F(0)). This study presents the first report suggesting that bioindicators such as the flexible, food-grade plastic pouches can be used for microbial validation of commercial sterilization in aseptic processing of foods using a continuous-flow microwave system.

The first full-resolution measurements of Auroral Medium Frequency Burst Emissions

NASA Astrophysics Data System (ADS)

Bunch, N. L.; Labelle, J.; Weatherwax, A.; Hughes, J.

2008-12-01

Auroral MF burst is a naturally occurring auroral radio emission which appears unstructured on resolution of previous measurements, is observed in the frequency range of 0.8-4.5 MHz, and has typical amplitudes of around 10-14 V2/m2Hz, and durations of a few minutes. The emission occurs at substorm onset. Since Sept 2006, Dartmouth has operated a broadband (0-5 MHz) interferometer at Toolik Lake, Alaska (68° 38' N, 149° 36' W, 68.51 deg. magnetic latitude), designed for the study of auroral MF burst emissions. Normal operation involves taking snapshots of waveforms from four spaced antennas from which wave spectral and directional information is obtained. However, the experiment can also be run in "continuous mode" whereby the signal from a selected antenna is sampled continuously at 10 M samples/second. A "continuous mode" campaign was run 0800-1200 UT (~2200-0200 MLT) daily from March 21 to April 19, 2008. During this campaign more than twenty auroral MF burst emissions were observed, including three extraordinarily intense examples lasting approximately two minutes each. These observations represent the highest time and frequency resolution data ever collected of MF burst emissions. These data allow us to better characterize the null near twice the electron gyrofrequency identified in previous experiments, since examples of this feature observed during this campaign display a strong null ~50 kHz in bandwidth, with sharp boundaries and occasionally coincident with 2 fce auroral roar. These data also allow us to search for frequency-time structures embedded in MF-burst. One prominent feature appears to be a strong single frequency emission which broadens down to lower frequencies over time, spreading to approximately 500 kHz in bandwidth over ~10 ms. Among other features observed are a diffuse and unstructured emission, as well as what could potentially be several separate emission sources, with multiple emissions occurring simultaneously, appearing as weaker "ghosts" behind the main MF burst emission. These data in will additionally allow us to search for the presence of sub-millisecond wave packets, sometimes quasi-periodic, reported by LaBelle et al. [1997, J. Geophys. Res. 102, 22221]. Finally, a search for frequency dispersion or absence thereof will provide a test of theories which speculate that different frequencies originate at different altitudes in the ionosphere.

Carbon-enhanced electrical conductivity during fracture of rocks

NASA Astrophysics Data System (ADS)

Roberts, J. J.; Duba, A. G.; Mathez, E. A.; Shankland, T. J.; Kinzler, R.

1999-01-01

Changes in electrical resistance during rock fracture in the presence of a carbonaceous atmosphere have been investigated using Nugget sandstone and Westerly granite. The experiments were performed in an internally heated, gas-pressure vessel with a load train that produced strain rates between 10-6 and 10-5 s-1. Samples were deformed at temperatures of 354° to 502°C and pressures of 100 to 170 MPa in atmospheres of Ar or mixtures of 95% CO2 with 5% CO or 5% CH4, compositions that are well within the field of graphite stability at the run conditions. In experiments using Nugget sandstone, resistance reached a minimum value when the maximum temperature was achieved and good electrode contact was made. The resistance then increased as the experiment continued, probably due to dry out of the sample, a change in the oxidation state of the Fe-oxide associated with the cement, or destruction of current-bearing pathways. At approximately 200-MPa end load, the rock sample failed. Plots of load and resistance versus time show several interesting features. In one experiment, for example, as the end load reached about 175 MPa, resistance stopped increasing and remained fairly constant for a period of approximately 0.5 hour. During loading, the end load displayed small decreases that were simultaneous with small decreases in resistance; when the end load (and the displacement) indicated rock failure, resistance decreased dramatically, from ˜150 MΩ to 100 MΩ. In a single experiment, the Westerly granite also showed a decrease in resistance during dilatancy. The nature and distribution of carbon in the run products were studied by electron microprobe and time-of-flight secondary-ion mass spectroscopy (TOP-SIMS). Carbon observed by mapping with the former is clearly observed on micro-cracks that, based on the microtexture, are interpreted to have formed during the deformation. The TOF-SIMS data confirm the electron-probe observations that carbon is present on fracture surfaces. These observations and experimental results lead to the hypothesis that as microfractures open in the time leading up to failure along a fracture, carbon is deposited as a continuous film on the new, reactive mineral surfaces, and this produces a decrease in resistance. Subsequent changes in resistance occur as connectivity of the initial fracture network is altered by continued deformation. Such a process may explain some electromagnetic effects associated with earthquakes.

Rehabilitation after cell transplantation for cartilage defects.

PubMed

Deszczynski, J; Slynarski, K

2006-01-01

Rehabilitation is a key element of successful treatment of cartilage defects with cell transplantation. The process of graft maturation takes approximately 18 months and cannot be accelerated, but requires carefully introduced steps leading to early recovery of joint function. Rehabilitation starts at 8 hours after surgery with the continuous passive motion (CPM) exercises and physiotherapy. For the first 6 weeks, patients continue with CPM in the range of 0 degrees to 45 degrees for femoral and tibial defects and 0 degrees to 30 degrees for patellofemoral joint reconstruction. Isometric muscle training and scar manual therapy are introduced. Patients are allowed to weight-bear as tolerated from the second week after surgery. After this initial phase, from 6 to 8 weeks after surgery, rehabilitation is accelerated with increased load-bearing and progressive range of motion to full flexion. Usually patients are able to walk without crutches in this time. Proprioceptive training is introduced with the advance of pain-free full range of motion and no discomfort with full weight-bearing. At 6 months after surgery, most patients recover joint function, making it possible for them to return to daily living activities. However, they need to continue with muscle, proprioceptive, and sports-specific rehabilitation exercises. The rehabilitation process is complicated, requiring close cooperation between the patient and surgeon-physiotherapist team to understand the symptoms and address them in a timely fashion.

Deep galaxy counts in the K band with the Kech telescope

NASA Technical Reports Server (NTRS)

Djorgovski, S.; Soifer, B. T.; Pahre, M. A.; Larkin, J. E.; Smith, J. D.; Neugebauer, G.; Smail, I.; Matthews, K.; Hogg, D. W.; Blandford, R. D.

1995-01-01

We present deep galaxy counts in the K (lambda 2.2 micrometer) band, obtained at the W. M. Kech 10 m telescope. The data reach limiting magnitudes K approximately 24 mag, about 5 times deeper than the deepest published K-band images to date. The counts are performed in three small (approximately 1 min), widely separated high-latitude fields. Extensive Monte Carlo tests were used to derive the comleteness corrections and minimize photometric biases. The counts continue to rise, with no sign of a turnover, down to the limits of our data, with the logarithmic slope of d log N/dm = 0.315 +/- 0.02 between K = 20 and 24 mag. This implies a cumulative surface density of approximately 5 x 10(exp 5) galaxies/sq deg, or approximately 2 x 10(exp 10) over the entire sky, down to K = 24 mag. Our counts are in good agreement with, although slightly lower than, those from the Hawaii Deep Survey by Cowie and collaborators; the discrepancies may be due to the small differences in the aperture corrections. We compare our counts with some of the available theoretical predictions. The data do not require models with a high value of Omega(sub 0), but can be well fitted by models with no (or little) evolution, and cosmologies with a low value of Omega(sub 0). Given the uncertainties in the models, it may be premature to put useful constrains on the value of Omega(sub 0) from the counts alone. Optical-to-IR colors are computed, using CCD data obtaind previously at Palomar. We find a few red galaxies with (r-K) approximately greater than 5 mag, or (i-K) approximately greater than 5 mag; these may be ellipticals at z approximately 1. While the redshift distribution of galaxies in our counts is still unknown, the flux limits reached would allow us to detect unobscured L(sub *) galaxies out to substantial redshifts (z greater than 3?).

High resolution humidity, temperature and aerosol profiling with MeteoSwiss Raman lidar

NASA Astrophysics Data System (ADS)

Dinoev, Todor; Arshinov, Yuri; Bobrovnikov, Sergei; Serikov, Ilya; Calpini, Bertrand; van den Bergh, Hubert; Parlange, Marc B.; Simeonov, Valentin

2010-05-01

Meteorological services rely, in part, on numerical weather prediction (NWP). Twice a day radiosonde observations of water vapor provide the required data for assimilation but this time resolution is insufficient to resolve certain meteorological phenomena. High time resolution temperature profiles from microwave radiometers are available as well but have rather low vertical resolution. The Raman LIDARs are able to provide temperature and humidity profiles with high time and range resolution, suitable for NWP model assimilation and validation. They are as well indispensible tools for continuous aerosol profiling for high resolution atmospheric boundary layer studies. To improve the database available for direct meteorological applications the Swiss meteo-service (MeteoSwiss), the Swiss Federal Institute of Technology in Lausanne (EPFL) and the Swiss National Science Foundation (SNSF) initiated a project to design and build an automated Raman lidar for day and night vertical profiling of tropospheric water vapor with the possibility to further upgrade it with an aerosol and temperature channels. The project was initiated in 2004 and RALMO (Raman Lidar for meteorological observations) was inaugurated in August 2008 at MeteoSwiss aerological station at Payerne. RALMO is currently operational and continuously profiles water vapor mixing ratio, aerosol backscatter ratio and aerosol extinction. The instrument is a fully automated, self-contained, eye-safe Raman lidar operated at 355 nm. Narrow field-of-view multi-telescope receiver and narrow band detection allow day and night-time vertical profiling of the atmospheric humidity. The rotational-vibrational Raman lidar responses from water vapor and nitrogen are spectrally separated by a high-throughput fiber coupled diffraction grating polychromator. The elastic backscatter and pure-rotational Raman lidar responses (PRR) from oxygen and nitrogen are spectrally isolated by a double grating polychromator and are used to derive vertical profiles of aerosol backscatter ratio and aerosol extinction at 355 nm. Set of Stokes and anti-Stokes PRR lines are separated by the polychromator to derive temperature profiles. The humidity profiles have vertical resolution from 15 m (within the boundary layer) to 100-450 m (within the free troposphere), time resolution of 30 min and 5 km vertical range at daytime and 10 km at night-time. The aerosol backscatter ratio and extinction profiles have similar resolution with vertical range of approximately 10 km. The temperature profiles are derived from PRR lidar signals, simultaneously recorded in analog and photon counting mode, allowing vertical range of approximately 10 km. Vaisala RS-92 and Snow-White chilled mirror hygrometer radiosondes were used for calibration of the water vapor and temperature channels. Continuous temperature profiles were obtained and were coupled with the available water vapor mixing ratio profiles to obtain relative humidity time series. Lidar derived aerosol backscatter ratio profiles will be used for estimation of the boundary layer height and validation of NWP model results. Optical thickness time series are currently compared to independent measurements from a collocated sun photometer to assess the performance of the aerosol channel.

A Snapshot of the Continuous Emission of the Active Galactic Nucleus in NGC 3783 from Gamma-Ray to Radio Wavelengths

NASA Technical Reports Server (NTRS)

Alloin, D.; Santos-Lleo, M.; Peterson, B. M.; Wamsteker, W.; Altieri, B.; Brinkmann, W.; Clavel, J.; Crenshaw, D. M.; George, I. M.; Glass, I. S.;

Warming and glacier recession in the Rakaia valley, Southern Alps of New Zealand, during Heinrich Stadial 1

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

Aaron E. Putnam; Joerg M. Schaefe; George H .Denton

2013-11-01

The termination of the last ice age featured a major reconfiguration of Earth's climate and cryosphere, yet the underlying causes of these massive changes continue to be debated. Documenting the spatial and temporal variations of atmospheric temperature during deglaciation can help discriminate among potential drivers. Here, we present a 10Be surface-exposure chronology and glaciological reconstruction of ice recession following the Last Glacial Maximum (LGM) in the Rakaia valley, Southern Alps of New Zealand. Innermost LGM moraines at Big Ben have an age of 17,840 +/- 240 yrs, whereas ice-marginal moraines or ice-molded bedrock surfaces at distances up-valley from Big Benmore » of 12.5 km (Lake Coleridge), approximately 25 km (Castle Hill), approximately 28 km (Double Hill), approximately 43 km (Prospect Hill), and approximately 58 km (Reischek knob) have ages of 17,020 +/- 70 yrs, 17,100 +/- 110 yrs, 16,960 +/- 370 yrs, 16,250 +/- 340 yrs, and 15,660 +/- 160 yrs, respectively. These results indicate extensive recession of the Rakaia glacier, which we attribute primarily to the effects of climatic warming. In conjunction with geomorphological maps and a glaciological reconstruction for the Rakaia valley, we use our chronology to infer timing and magnitude of past atmospheric temperature changes. Compared to an overall temperature rise of approximately 4.65?degrees C between the end of the LGM and the start of the Holocene, the glacier recession between approximately 17,840 and approximately 15,660 yrs ago is attributable to a net temperature increase of approximately 4.0?degrees C (from -6.25 to -2.25?degrees C), accounting for approximately 86% of the overall warming. Approximately 3.75?degrees C (approximately 70%) of the warming occurred between approximately 17,840 and approximately 16,250 yrs ago, with a further 0.75?degrees C (approximately 16%) increase between approximately 16,250 and approximately 15,660 yrs ago. A sustained southward shift of the Subtropical Front (STF) south of Australia between approximately 17,800 and approximately 16,000 yrs ago coincides with the warming over the Rakaia valley, and suggests a close link between Southern Ocean frontal boundary positions and southern mid-latitude climate. Most of the deglacial warming in the Southern Alps occurred during the early part of Heinrich Stadial 1 (HS1) of the North Atlantic region. Because the STF is associated with the position of the westerly wind belt, our findings support the concept that a southward shift of Earth's wind belts accompanied the early part of HS1 cooling in the North Atlantic, leading to warming and deglaciation in southern middle latitudes.« less

Time and Memory Efficient Online Piecewise Linear Approximation of Sensor Signals.

PubMed

Grützmacher, Florian; Beichler, Benjamin; Hein, Albert; Kirste, Thomas; Haubelt, Christian

2018-05-23

Piecewise linear approximation of sensor signals is a well-known technique in the fields of Data Mining and Activity Recognition. In this context, several algorithms have been developed, some of them with the purpose to be performed on resource constrained microcontroller architectures of wireless sensor nodes. While microcontrollers are usually constrained in computational power and memory resources, all state-of-the-art piecewise linear approximation techniques either need to buffer sensor data or have an execution time depending on the segment’s length. In the paper at hand, we propose a novel piecewise linear approximation algorithm, with a constant computational complexity as well as a constant memory complexity. Our proposed algorithm’s worst-case execution time is one to three orders of magnitude smaller and its average execution time is three to seventy times smaller compared to the state-of-the-art Piecewise Linear Approximation (PLA) algorithms in our experiments. In our evaluations, we show that our algorithm is time and memory efficient without sacrificing the approximation quality compared to other state-of-the-art piecewise linear approximation techniques, while providing a maximum error guarantee per segment, a small parameter space of only one parameter, and a maximum latency of one sample period plus its worst-case execution time.

Mean Field Games for Stochastic Growth with Relative Utility

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

Huang, Minyi, E-mail: mhuang@math.carleton.ca; Nguyen, Son Luu, E-mail: sonluu.nguyen@upr.edu

This paper considers continuous time stochastic growth-consumption optimization in a mean field game setting. The individual capital stock evolution is determined by a Cobb–Douglas production function, consumption and stochastic depreciation. The individual utility functional combines an own utility and a relative utility with respect to the population. The use of the relative utility reflects human psychology, leading to a natural pattern of mean field interaction. The fixed point equation of the mean field game is derived with the aid of some ordinary differential equations. Due to the relative utility interaction, our performance analysis depends on some ratio based approximation errormore » estimate.« less

An efficient method for the computation of Legendre moments.

PubMed

Yap, Pew-Thian; Paramesran, Raveendran

2005-12-01

Legendre moments are continuous moments, hence, when applied to discrete-space images, numerical approximation is involved and error occurs. This paper proposes a method to compute the exact values of the moments by mathematically integrating the Legendre polynomials over the corresponding intervals of the image pixels. Experimental results show that the values obtained match those calculated theoretically, and the image reconstructed from these moments have lower error than that of the conventional methods for the same order. Although the same set of exact Legendre moments can be obtained indirectly from the set of geometric moments, the computation time taken is much longer than the proposed method.

A Ulexite-based animation recording system by random reference patterns

NASA Astrophysics Data System (ADS)

Ishii, Yuko; Irisawa, Misako; Takayama, Yoshihisa; Watanabe, Eriko; Kodate, Kashiko

2006-02-01

We propose a simple, compact and high-security holographic optical memory system using Ulexite in order to produce random patterns of reference beam. 100 hologram multiplexing was achieved by multiplexing exposure, rotating Ulexite by 0.2 degrees every time with LiNbO 3 crystal as a recording medium. Moreover, with this system, animation readout images can play for approximately 8 seconds by continuous rotation of Ulexite. As a natural stone, the exactly same Ulexite is very difficult to be found or replicated. Basic experimental results show that Ulexite can be used as a security key for its image-reproducibility and BER calculations.

Oxidation of SO2 by NO2 and O3 on carbon - Implications to tropospheric chemistry

NASA Technical Reports Server (NTRS)

Cofer, W. R., III; Schryer, D. R.; Rogowski, R. S.

1984-01-01

The oxidation of SO2 to sulfate in air at 65 percent relative humidity on carbon particles was investigated gravimetrically in the presence of NO2 and O3. Approximately 1 mg samples of carbon black were exposed to continuously flowing ppbv mixtures of SO2, SO2 + NO2 and SO2 + O3 for prescribed periods of time before desorption into dry N2. Wet chemical analysis of the particles followed desorption. NO2 and O3 were found to have little, if any, effect relative to air on sulfate yields at the concentrations studied.

Closed-form solutions of performability. [in computer systems

NASA Technical Reports Server (NTRS)

Meyer, J. F.

1982-01-01

It is noted that if computing system performance is degradable then system evaluation must deal simultaneously with aspects of both performance and reliability. One approach is the evaluation of a system's performability which, relative to a specified performance variable Y, generally requires solution of the probability distribution function of Y. The feasibility of closed-form solutions of performability when Y is continuous are examined. In particular, the modeling of a degradable buffer/multiprocessor system is considered whose performance Y is the (normalized) average throughput rate realized during a bounded interval of time. Employing an approximate decomposition of the model, it is shown that a closed-form solution can indeed be obtained.