Modeling chloride transport using travel time distributions at Plynlimon, Wales

NASA Astrophysics Data System (ADS)

Benettin, Paolo; Kirchner, James W.; Rinaldo, Andrea; Botter, Gianluca

2015-05-01

Here we present a theoretical interpretation of high-frequency, high-quality tracer time series from the Hafren catchment at Plynlimon in mid-Wales. We make use of the formulation of transport by travel time distributions to model chloride transport originating from atmospheric deposition and compute catchment-scale travel time distributions. The relevance of the approach lies in the explanatory power of the chosen tools, particularly to highlight hydrologic processes otherwise clouded by the integrated nature of the measured outflux signal. The analysis reveals the key role of residual storages that are poorly visible in the hydrological response, but are shown to strongly affect water quality dynamics. A significant accuracy in reproducing data is shown by our calibrated model. A detailed representation of catchment-scale travel time distributions has been derived, including the time evolution of the overall dispersion processes (which can be expressed in terms of time-varying storage sampling functions). Mean computed travel times span a broad range of values (from 80 to 800 days) depending on the catchment state. Results also suggest that, in the average, discharge waters are younger than storage water. The model proves able to capture high-frequency fluctuations in the measured chloride concentrations, which are broadly explained by the sharp transition between groundwaters and faster flows originating from topsoil layers. This article was corrected on 22 JUN 2015. See the end of the full text for details.

The impact of travel distance, travel time and waiting time on health-related quality of life of diabetes patients: An investigation in six European countries.

PubMed

Konerding, Uwe; Bowen, Tom; Elkhuizen, Sylvia G; Faubel, Raquel; Forte, Paul; Karampli, Eleftheria; Mahdavi, Mahdi; Malmström, Tomi; Pavi, Elpida; Torkki, Paulus

2017-04-01

The effects of travel distance and travel time to the primary diabetes care provider and waiting time in the practice on health-related quality of life (HRQoL) of patients with type 2 diabetes are investigated. Survey data of 1313 persons with type 2 diabetes from six regions in England (274), Finland (163), Germany (254), Greece (165), the Netherlands (354), and Spain (103) were analyzed. Various multiple linear regression analyses with four different EQ-5D-3L indices (English, German, Dutch and Spanish index) as target variables, with travel distance, travel time, and waiting time in the practice as focal predictors and with control for study region, patient's gender, patient's age, patient's education, time since diagnosis, thoroughness of provider-patient communication were computed. Interactions of regions with the remaining five control variables and the three focal predictors were also tested. There are no interactions of regions with control variables or focal predictors. The indices decrease with increasing travel time to the provider and increasing waiting time in the provider's practice. HRQoL of patients with type 2 diabetes might be improved by decreasing travel time to the provider and waiting time in the provider's practice. Copyright © 2017 Elsevier B.V. All rights reserved.

Accurate traveltime computation in complex anisotropic media with discontinuous Galerkin method

NASA Astrophysics Data System (ADS)

Le Bouteiller, P.; Benjemaa, M.; Métivier, L.; Virieux, J.

2017-12-01

Travel time computation is of major interest for a large range of geophysical applications, among which source localization and characterization, phase identification, data windowing and tomography, from decametric scale up to global Earth scale.Ray-tracing tools, being essentially 1D Lagrangian integration along a path, have been used for their efficiency but present some drawbacks, such as a rather difficult control of the medium sampling. Moreover, they do not provide answers in shadow zones. Eikonal solvers, based on an Eulerian approach, have attracted attention in seismology with the pioneering work of Vidale (1988), while such approach has been proposed earlier by Riznichenko (1946). They have been used now for first-arrival travel-time tomography at various scales (Podvin & Lecomte (1991). The framework for solving this non-linear partial differential equation is now well understood and various finite-difference approaches have been proposed, essentially for smooth media. We propose a novel finite element approach which builds a precise solution for strongly heterogeneous anisotropic medium (still in the limit of Eikonal validity). The discontinuous Galerkin method we have developed allows local refinement of the mesh and local high orders of interpolation inside elements. High precision of the travel times and its spatial derivatives is obtained through this formulation. This finite element method also honors boundary conditions, such as complex topographies and absorbing boundaries for mimicking an infinite medium. Applications from travel-time tomography, slope tomography are expected, but also for migration and take-off angles estimation, thanks to the accuracy obtained when computing first-arrival times.References:Podvin, P. and Lecomte, I., 1991. Finite difference computation of traveltimes in very contrasted velocity model: a massively parallel approach and its associated tools, Geophys. J. Int., 105, 271-284.Riznichenko, Y., 1946. Geometrical seismics of layered media, Trudy Inst. Theor. Geophysics, Vol II, Moscow (in Russian).Vidale, J., 1988. Finite-difference calculation of travel times, Bull. seism. Soc. Am., 78, 2062-2076.

Quantum information processing with a travelling wave of light

NASA Astrophysics Data System (ADS)

Serikawa, Takahiro; Shiozawa, Yu; Ogawa, Hisashi; Takanashi, Naoto; Takeda, Shuntaro; Yoshikawa, Jun-ichi; Furusawa, Akira

2018-02-01

We exploit quantum information processing on a traveling wave of light, expecting emancipation from thermal noise, easy coupling to fiber communication, and potentially high operation speed. Although optical memories are technically challenging, we have an alternative approach to apply multi-step operations on traveling light, that is, continuous-variable one-way computation. So far our achievement includes generation of a one-million-mode entangled chain in time-domain, mode engineering of nonlinear resource states, and real-time nonlinear feedforward. Although they are implemented with free space optics, we are also investigating photonic integration and performed quantum teleportation with a passive liner waveguide chip as a demonstration of entangling, measurement, and feedforward. We also suggest a loop-based architecture as another model of continuous-variable computing.

A wavefront orientation method for precise numerical determination of tsunami travel time

NASA Astrophysics Data System (ADS)

Fine, I. V.; Thomson, R. E.

2013-04-01

We present a highly accurate and computationally efficient method (herein, the "wavefront orientation method") for determining the travel time of oceanic tsunamis. Based on Huygens principle, the method uses an eight-point grid-point pattern and the most recent information on the orientation of the advancing wave front to determine the time for a tsunami to travel to a specific oceanic location. The method is shown to provide improved accuracy and reduced anisotropy compared with the conventional multiple grid-point method presently in widespread use.

0-6767 : evaluation of existing smartphone applications and data needs for travel survey.

DOT National Transportation Integrated Search

2014-08-01

Current and reliable data on traffic movements : play a key role in transportation planning, : modeling, and air quality analysis. Traditional : travel surveys conducted via paper or computer : are costly, time consuming, and labor intensive : for su...

An efficient General Transit Feed Specification (GTFS) enabled algorithm for dynamic transit accessibility analysis.

PubMed

Fayyaz S, S Kiavash; Liu, Xiaoyue Cathy; Zhang, Guohui

2017-01-01

The social functions of urbanized areas are highly dependent on and supported by the convenient access to public transportation systems, particularly for the less privileged populations who have restrained auto ownership. To accurately evaluate the public transit accessibility, it is critical to capture the spatiotemporal variation of transit services. This can be achieved by measuring the shortest paths or minimum travel time between origin-destination (OD) pairs at each time-of-day (e.g. every minute). In recent years, General Transit Feed Specification (GTFS) data has been gaining popularity for between-station travel time estimation due to its interoperability in spatiotemporal analytics. Many software packages, such as ArcGIS, have developed toolbox to enable the travel time estimation with GTFS. They perform reasonably well in calculating travel time between OD pairs for a specific time-of-day (e.g. 8:00 AM), yet can become computational inefficient and unpractical with the increase of data dimensions (e.g. all times-of-day and large network). In this paper, we introduce a new algorithm that is computationally elegant and mathematically efficient to address this issue. An open-source toolbox written in C++ is developed to implement the algorithm. We implemented the algorithm on City of St. George's transit network to showcase the accessibility analysis enabled by the toolbox. The experimental evidence shows significant reduction on computational time. The proposed algorithm and toolbox presented is easily transferable to other transit networks to allow transit agencies and researchers perform high resolution transit performance analysis.

An efficient General Transit Feed Specification (GTFS) enabled algorithm for dynamic transit accessibility analysis

PubMed Central

Fayyaz S., S. Kiavash; Zhang, Guohui

2017-01-01

The social functions of urbanized areas are highly dependent on and supported by the convenient access to public transportation systems, particularly for the less privileged populations who have restrained auto ownership. To accurately evaluate the public transit accessibility, it is critical to capture the spatiotemporal variation of transit services. This can be achieved by measuring the shortest paths or minimum travel time between origin-destination (OD) pairs at each time-of-day (e.g. every minute). In recent years, General Transit Feed Specification (GTFS) data has been gaining popularity for between-station travel time estimation due to its interoperability in spatiotemporal analytics. Many software packages, such as ArcGIS, have developed toolbox to enable the travel time estimation with GTFS. They perform reasonably well in calculating travel time between OD pairs for a specific time-of-day (e.g. 8:00 AM), yet can become computational inefficient and unpractical with the increase of data dimensions (e.g. all times-of-day and large network). In this paper, we introduce a new algorithm that is computationally elegant and mathematically efficient to address this issue. An open-source toolbox written in C++ is developed to implement the algorithm. We implemented the algorithm on City of St. George’s transit network to showcase the accessibility analysis enabled by the toolbox. The experimental evidence shows significant reduction on computational time. The proposed algorithm and toolbox presented is easily transferable to other transit networks to allow transit agencies and researchers perform high resolution transit performance analysis. PMID:28981544

Computing travel time when the exact address is unknown: a comparison of point and polygon ZIP code approximation methods.

PubMed

Berke, Ethan M; Shi, Xun

2009-04-29

Travel time is an important metric of geographic access to health care. We compared strategies of estimating travel times when only subject ZIP code data were available. Using simulated data from New Hampshire and Arizona, we estimated travel times to nearest cancer centers by using: 1) geometric centroid of ZIP code polygons as origins, 2) population centroids as origin, 3) service area rings around each cancer center, assigning subjects to rings by assuming they are evenly distributed within their ZIP code, 4) service area rings around each center, assuming the subjects follow the population distribution within the ZIP code. We used travel times based on street addresses as true values to validate estimates. Population-based methods have smaller errors than geometry-based methods. Within categories (geometry or population), centroid and service area methods have similar errors. Errors are smaller in urban areas than in rural areas. Population-based methods are superior to the geometry-based methods, with the population centroid method appearing to be the best choice for estimating travel time. Estimates in rural areas are less reliable.

Predicting river travel time from hydraulic characteristics

USGS Publications Warehouse

Jobson, H.E.

2001-01-01

Predicting the effect of a pollutant spill on downstream water quality is primarily dependent on the water velocity, longitudinal mixing, and chemical/physical reactions. Of these, velocity is the most important and difficult to predict. This paper provides guidance on extrapolating travel-time information from one within bank discharge to another. In many cases, a time series of discharge (such as provided by a U.S. Geological Survey stream gauge) will provide an excellent basis for this extrapolation. Otherwise, the accuracy of a travel time extrapolation based on a resistance equation can be greatly improved by assuming the total flow area is composed of two parts, an active and an inactive area. For 60 reaches of 12 rivers with slopes greater than about 0.0002, travel times could be predicted to within about 10% by computing the active flow area using the Manning equation with n = 0.035 and assuming a constant inactive area for each reach. The predicted travel times were not very sensitive to the assumed values of bed slope or channel width.

Users' manual for computer program for three-dimensional analysis of coupler-cavity traveling wave tubes

NASA Technical Reports Server (NTRS)

Omalley, T. A.

1984-01-01

The use of the coupled cavity traveling wave tube for space communications has led to an increased interest in improving the efficiency of the basic interaction process in these devices through velocity resynchronization and other methods. A flexible, three dimensional, axially symmetric, large signal computer program was developed for use on the IBM 370 time sharing system. A users' manual for this program is included.

Computer Simulation For Design Of TWT's

NASA Technical Reports Server (NTRS)

Bartos, Karen F.; Fite, E. Brian; Shalkhauser, Kurt A.; Sharp, G. Richard

1992-01-01

A three-dimensional finite-element analytical technique facilitates design and fabrication of traveling-wave-tube (TWT) slow-wave structures. Used to perform thermal and mechanical analyses of TWT designed with variety of configurations, geometries, and materials. Using three-dimensional computer analysis, designer able to simulate building and testing of TWT, with consequent substantial saving of time and money. Technique enables detailed look into operation of traveling-wave tubes to help improve performance for future communications systems.

CAESAR: Commissioned Assignments Executive Support for the US Army.

DTIC Science & Technology

1986-03-27

travel between jobs ? b. Detailed Narrative The documented source code of CAESAR can be found in Appendix B. An explanatory listing of variables used is...Compute Match Preference PREFFORM SSI index a, b a,b Match Match Leave ADSPEC SC2 and Travel a, b Time ab a , b ~~N4 4. ORB Mac Matyh ,. ac ASI ASI SReport...sufficient time between assignments for the officer to 44 take 30 days leave and travel . While this is not a manda- tory consideration, it is common to

Users' manual for computer program for one-dimensional analysis of coupled-cavity traveling wave tubes

NASA Technical Reports Server (NTRS)

Omalley, T. A.; Connolly, D. J.

1977-01-01

The use of the coupled cavity traveling wave tube for space communications has led to an increased interest in improving the efficiency of the basic interaction process in these devices through velocity resynchronization and other methods. To analyze these methods, a flexible, large signal computer program for use on the IBM 360/67 time-sharing system has been developed. The present report is a users' manual for this program.

Frozen Gaussian approximation for 3D seismic tomography

NASA Astrophysics Data System (ADS)

Chai, Lihui; Tong, Ping; Yang, Xu

2018-05-01

Three-dimensional (3D) wave-equation-based seismic tomography is computationally challenging in large scales and high-frequency regime. In this paper, we apply the frozen Gaussian approximation (FGA) method to compute 3D sensitivity kernels and seismic tomography of high-frequency. Rather than standard ray theory used in seismic inversion (e.g. Kirchhoff migration and Gaussian beam migration), FGA is used to compute the 3D high-frequency sensitivity kernels for travel-time or full waveform inversions. Specifically, we reformulate the equations of the forward and adjoint wavefields for the purpose of convenience to apply FGA, and with this reformulation, one can efficiently compute the Green’s functions whose convolutions with source time function produce wavefields needed for the construction of 3D kernels. Moreover, a fast summation method is proposed based on local fast Fourier transform which greatly improves the speed of reconstruction as the last step of FGA algorithm. We apply FGA to both the travel-time adjoint tomography and full waveform inversion (FWI) on synthetic crosswell seismic data with dominant frequencies as high as those of real crosswell data, and confirm again that FWI requires a more sophisticated initial velocity model for the convergence than travel-time adjoint tomography. We also numerically test the accuracy of applying FGA to local earthquake tomography. This study paves the way to directly apply wave-equation-based seismic tomography methods into real data around their dominant frequencies.

Surface-Source Downhole Seismic Analysis in R

USGS Publications Warehouse

Thompson, Eric M.

2007-01-01

This report discusses a method for interpreting a layered slowness or velocity model from surface-source downhole seismic data originally presented by Boore (2003). I have implemented this method in the statistical computing language R (R Development Core Team, 2007), so that it is freely and easily available to researchers and practitioners that may find it useful. I originally applied an early version of these routines to seismic cone penetration test data (SCPT) to analyze the horizontal variability of shear-wave velocity within the sediments in the San Francisco Bay area (Thompson et al., 2006). A more recent version of these codes was used to analyze the influence of interface-selection and model assumptions on velocity/slowness estimates and the resulting differences in site amplification (Boore and Thompson, 2007). The R environment has many benefits for scientific and statistical computation; I have chosen R to disseminate these routines because it is versatile enough to program specialized routines, is highly interactive which aids in the analysis of data, and is freely and conveniently available to install on a wide variety of computer platforms. These scripts are useful for the interpretation of layered velocity models from surface-source downhole seismic data such as deep boreholes and SCPT data. The inputs are the travel-time data and the offset of the source at the surface. The travel-time arrivals for the P- and S-waves must already be picked from the original data. An option in the inversion is to include estimates of the standard deviation of the travel-time picks for a weighted inversion of the velocity profile. The standard deviation of each travel-time pick is defined relative to the standard deviation of the best pick in a profile and is based on the accuracy with which the travel-time measurement could be determined from the seismogram. The analysis of the travel-time data consists of two parts: the identification of layer-interfaces, and the inversion for the velocity of each layer. The analyst usually picks layer-interfaces by visual inspection of the travel-time data. I have also developed an algorithm that automatically finds boundaries which can save a significant amount of the time when analyzing a large number of sites. The results of the automatic routines should be reviewed to check that they are reasonable. The interactivity of these scripts allows the user to add and to remove layers quickly, thus allowing rapid feedback on how the residuals are affected by each additional parameter in the inversion. In addition, the script allows many models to be compared at the same time.

Calculating Path-Dependent Travel Time Prediction Variance and Covariance fro a Global Tomographic P-Velocity Model

NASA Astrophysics Data System (ADS)

Ballard, S.; Hipp, J. R.; Encarnacao, A.; Young, C. J.; Begnaud, M. L.; Phillips, W. S.

2012-12-01

Seismic event locations can be made more accurate and precise by computing predictions of seismic travel time through high fidelity 3D models of the wave speed in the Earth's interior. Given the variable data quality and uneven data sampling associated with this type of model, it is essential that there be a means to calculate high-quality estimates of the path-dependent variance and covariance associated with the predicted travel times of ray paths through the model. In this paper, we describe a methodology for accomplishing this by exploiting the full model covariance matrix and show examples of path-dependent travel time prediction uncertainty computed from SALSA3D, our global, seamless 3D tomographic P-velocity model. Typical global 3D models have on the order of 1/2 million nodes, so the challenge in calculating the covariance matrix is formidable: 0.9 TB storage for 1/2 of a symmetric matrix, necessitating an Out-Of-Core (OOC) blocked matrix solution technique. With our approach the tomography matrix (G which includes Tikhonov regularization terms) is multiplied by its transpose (GTG) and written in a blocked sub-matrix fashion. We employ a distributed parallel solution paradigm that solves for (GTG)-1 by assigning blocks to individual processing nodes for matrix decomposition update and scaling operations. We first find the Cholesky decomposition of GTG which is subsequently inverted. Next, we employ OOC matrix multiplication methods to calculate the model covariance matrix from (GTG)-1 and an assumed data covariance matrix. Given the model covariance matrix, we solve for the travel-time covariance associated with arbitrary ray-paths by summing the model covariance along both ray paths. Setting the paths equal and taking the square root yields the travel prediction uncertainty for the single path.

The vertical propagation of disturbances triggered by seismic waves of the 11 March 2011 M9.0 Tohoku earthquake over Taiwan

NASA Astrophysics Data System (ADS)

Liu, J. Y.; Chen, C. H.; Sun, Y. Y.; Chen, C. H.; Tsai, H. F.; Yen, H. Y.; Chum, J.; Lastovicka, J.; Yang, Q. S.; Chen, W. S.; Wen, S.

2016-02-01

In this paper, concurrent/colocated measurements of seismometers, infrasonic systems, magnetometers, HF-CW (high frequency-continuous wave) Doppler sounding systems, and GPS receivers are employed to detect disturbances triggered by seismic waves of the 11 March 2011 M9.0 Tohoku earthquake. No time delay between colocated infrasonic (i.e., super long acoustic) waves and seismic waves indicates that the triggered acoustic and/or gravity waves in the atmosphere (or seismo-traveling atmospheric disturbances, STADs) near the Earth's surface can be immediately activated by vertical ground motions. The circle method is used to find the origin and compute the observed horizontal traveling speed of the triggered infrasonic waves. The speed of about 3.3 km/s computed from the arrival time versus the epicentral distance suggests that the infrasonic waves (i.e., STADs) are mainly induced by the Rayleigh waves. The agreements in the travel time at various heights between the observation and theoretical calculation suggest that the STADs triggered by the vertical motion of ground surface caused by the Tohoku earthquake traveled vertically from the ground to the ionosphere with speed of the sound in the atmosphere over Taiwan.

Global and Regional 3D Tomography for Improved Seismic Event Location and Uncertainty in Explosion Monitoring

NASA Astrophysics Data System (ADS)

Downey, N.; Begnaud, M. L.; Hipp, J. R.; Ballard, S.; Young, C. S.; Encarnacao, A. V.

2017-12-01

The SALSA3D global 3D velocity model of the Earth was developed to improve the accuracy and precision of seismic travel time predictions for a wide suite of regional and teleseismic phases. Recently, the global SALSA3D model was updated to include additional body wave phases including mantle phases, core phases, reflections off the core-mantle boundary and underside reflections off the surface of the Earth. We show that this update improves travel time predictions and leads directly to significant improvements in the accuracy and precision of seismic event locations as compared to locations computed using standard 1D velocity models like ak135, or 2½D models like RSTT. A key feature of our inversions is that path-specific model uncertainty of travel time predictions are calculated using the full 3D model covariance matrix computed during tomography, which results in more realistic uncertainty ellipses that directly reflect tomographic data coverage. Application of this method can also be done at a regional scale: we present a velocity model with uncertainty obtained using data obtained from the University of Utah Seismograph Stations. These results show a reduction in travel-time residuals for re-located events compared with those obtained using previously published models.

Measuring the Speed of Sound Using Only a Computer

ERIC Educational Resources Information Center

Bin, Mo

2013-01-01

corresponding time to cover that distance. But sound travels rapidly, covering about one meter in three milliseconds. This challenge can be met by using only a computer and an external microphone. A fixed frequency (1000 Hz) is fed into the computer's speaker and the…

Fast and Efficient Discrimination of Traveling Salesperson Problem Stimulus Difficulty

ERIC Educational Resources Information Center

Dry, Matthew J.; Fontaine, Elizabeth L.

2014-01-01

The Traveling Salesperson Problem (TSP) is a computationally difficult combinatorial optimization problem. In spite of its relative difficulty, human solvers are able to generate close-to-optimal solutions in a close-to-linear time frame, and it has been suggested that this is due to the visual system's inherent sensitivity to certain geometric…

TrigDB back-filling method in EEW for the regional earthquake for reducing false location of the deep focus earthquake event by considering neighborhood triggers and forced association.

NASA Astrophysics Data System (ADS)

Park, J. H.; Chi, H. C.; Lim, I. S.; Seong, Y. J.; Pak, J.

2017-12-01

During the first phase of EEW(Earthquake Early Warning) service to the public by KMA (Korea Meteorological Administration) from 2015 in Korea, KIGAM(Korea Institute of Geoscience and Mineral Resources) has adopted ElarmS2 of UC Berkeley BSL and modified local magnitude relation, travel time curves and association procedures so called TrigDB back-filling method. The TrigDB back-filling method uses a database of sorted lists of stations based on epicentral distances of the pre-defined events located on the grids for 1,401 × 1,601 = 2,243,001 events around the Korean Peninsula at a grid spacing of 0.05 degrees. When the version of an event is updated, the TrigDB back-filling method is invoked. First, the grid closest to the epicenter of an event is chosen from the database and candidate stations, which are stations corresponding to the chosen grid and also adjacent to the already-associated stations, are selected. Second, the directions from the chosen grid to the associated stations are averaged to represent the direction of wave propagation, which is used as a reference for computing apparent travel times. The apparent travel times for the associated stations are computed using a P wave velocity of 5.5 km/s from the grid to the projected points in the reference direction. The travel times for the triggered candidate stations are also computed and used to obtain the difference between the apparent travel times of the associated stations and the triggered candidates. Finally, if the difference in the apparent travel times is less than that of the arrival times, the method forces the triggered candidate station to be associated with the event and updates the event location. This method is useful to reduce false locations of events which could be generated from the deep (> 500 km) and regional distance earthquakes happening on the subduction pacific plate boundaries. In comparison of the case study between TrigDB back-filling applied system and the others, we could get the more reliable results in the early stagy of the version updating by forced association of the neighbored stations.

MOVANAID: An Interactive Aid for Analysis of Movement Capabilities.

ERIC Educational Resources Information Center

Cooper, George E.; And Others

A computer-drive interactive aid for movement analysis, called MOVANAID, has been developed to be of assistance in the performance of certain Army intelligence processing tasks in a tactical environment. It can compute fastest travel times and paths through road networks for military units of various types, as well as fastest times in which…

Deep Water Ocean Acoustics (DWOA): The Philippine Sea, OBSANP, and THAAW Experiments

DTIC Science & Technology

2015-09-30

the travel times. 4 The ocean state estimates were then re-computed to fit the acoustic travel times as integrals of the sound speed, and...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Deep Water Ocean Acoustics (DWOA): The Philippine Sea...deep-water acoustic propagation and ambient noise has been collected in a wide variety of environments over the last few years with ONR support

Computer-Assisted Traffic Engineering Using Assignment, Optimal Signal Setting, and Modal Split

DOT National Transportation Integrated Search

1978-05-01

Methods of traffic assignment, traffic signal setting, and modal split analysis are combined in a set of computer-assisted traffic engineering programs. The system optimization and user optimization traffic assignments are described. Travel time func...

Reentrainment of the circadian pacemaker during jet lag: East-west asymmetry and the effects of north-south travel.

PubMed

Diekman, Casey O; Bose, Amitabha

2018-01-21

The normal alignment of circadian rhythms with the 24-h light-dark cycle is disrupted after rapid travel between home and destination time zones, leading to sleep problems, indigestion, and other symptoms collectively known as jet lag. Using mathematical and computational analysis, we study the process of reentrainment to the light-dark cycle of the destination time zone in a model of the human circadian pacemaker. We calculate the reentrainment time for travel between any two points on the globe at any time of the day and year. We construct one-dimensional entrainment maps to explain several properties of jet lag, such as why most people experience worse jet lag after traveling east than west. We show that this east-west asymmetry depends on the endogenous period of the traveler's circadian clock as well as daylength. Thus the critical factor is not simply whether the endogenous period is greater than or less than 24 h as is commonly assumed. We show that the unstable fixed point of an entrainment map determines whether a traveler reentrains through phase advances or phase delays, providing an understanding of the threshold that separates orthodromic and antidromic modes of reentrainment. Contrary to the conventional wisdom that jet lag only occurs after east-west travel across multiple time zones, we predict that the change in daylength encountered during north-south travel can cause jet lag even when no time zones are crossed. Our techniques could be used to provide advice to travelers on how to minimize jet lag on trips involving multiple destinations and a combination of transmeridian and translatitudinal travel. Copyright © 2017 Elsevier Ltd. All rights reserved.

Optimization of the time-dependent traveling salesman problem with Monte Carlo methods.

PubMed

Bentner, J; Bauer, G; Obermair, G M; Morgenstern, I; Schneider, J

2001-09-01

A problem often considered in operations research and computational physics is the traveling salesman problem, in which a traveling salesperson has to find the shortest closed tour between a certain set of cities. This problem has been extended to more realistic scenarios, e.g., the "real" traveling salesperson has to take rush hours into consideration. We will show how this extended problem is treated with physical optimization algorithms. We will present results for a specific instance of Reinelt's library TSPLIB95, in which we define a zone with traffic jams in the afternoon.

Analog Processor To Solve Optimization Problems

NASA Technical Reports Server (NTRS)

Duong, Tuan A.; Eberhardt, Silvio P.; Thakoor, Anil P.

1993-01-01

Proposed analog processor solves "traveling-salesman" problem, considered paradigm of global-optimization problems involving routing or allocation of resources. Includes electronic neural network and auxiliary circuitry based partly on concepts described in "Neural-Network Processor Would Allocate Resources" (NPO-17781) and "Neural Network Solves 'Traveling-Salesman' Problem" (NPO-17807). Processor based on highly parallel computing solves problem in significantly less time.

Acquisition of Ice-Tethered Profilers with Velocity (ITP-V) Instruments for Future Arctic Studies

DTIC Science & Technology

2016-11-15

instrument that measures sea water temperature and salinity versus depth, the ITP-V adds a multi-axis acoustic -travel-time current meter and...housing capped by an ultra-high-molecular-weight polyethylene dome. The electronics case sits within a foam body designed to provide buoyancy for...then transmits them by satellite to a logger computer at WHO I. The ITP-V instruments add a multi-axis acoustic -travel-time current meter and

Estimating Travel Time in Bank Filtration Systems from a Numerical Model Based on DTS Measurements.

PubMed

des Tombe, Bas F; Bakker, Mark; Schaars, Frans; van der Made, Kees-Jan

2018-03-01

An approach is presented to determine the seasonal variations in travel time in a bank filtration system using a passive heat tracer test. The temperature in the aquifer varies seasonally because of temperature variations of the infiltrating surface water and at the soil surface. Temperature was measured with distributed temperature sensing along fiber optic cables that were inserted vertically into the aquifer with direct push equipment. The approach was applied to a bank filtration system consisting of a sequence of alternating, elongated recharge basins and rows of recovery wells. A SEAWAT model was developed to simulate coupled flow and heat transport. The model of a two-dimensional vertical cross section is able to simulate the temperature of the water at the well and the measured vertical temperature profiles reasonably well. MODPATH was used to compute flowpaths and the travel time distribution. At the study site, temporal variation of the pumping discharge was the dominant factor influencing the travel time distribution. For an equivalent system with a constant pumping rate, variations in the travel time distribution are caused by variations in the temperature-dependent viscosity. As a result, travel times increase in the winter, when a larger fraction of the water travels through the warmer, lower part of the aquifer, and decrease in the summer, when the upper part of the aquifer is warmer. © 2017 The Authors. Groundwater published by Wiley Periodicals, Inc. on behalf of National Ground Water Association.

A fast marching algorithm for the factored eikonal equation

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

Treister, Eran, E-mail: erantreister@gmail.com; Haber, Eldad, E-mail: haber@math.ubc.ca; Department of Mathematics, The University of British Columbia, Vancouver, BC

The eikonal equation is instrumental in many applications in several fields ranging from computer vision to geoscience. This equation can be efficiently solved using the iterative Fast Sweeping (FS) methods and the direct Fast Marching (FM) methods. However, when used for a point source, the original eikonal equation is known to yield inaccurate numerical solutions, because of a singularity at the source. In this case, the factored eikonal equation is often preferred, and is known to yield a more accurate numerical solution. One application that requires the solution of the eikonal equation for point sources is travel time tomography. Thismore » inverse problem may be formulated using the eikonal equation as a forward problem. While this problem has been solved using FS in the past, the more recent choice for applying it involves FM methods because of the efficiency in which sensitivities can be obtained using them. However, while several FS methods are available for solving the factored equation, the FM method is available only for the original eikonal equation. In this paper we develop a Fast Marching algorithm for the factored eikonal equation, using both first and second order finite-difference schemes. Our algorithm follows the same lines as the original FM algorithm and requires the same computational effort. In addition, we show how to obtain sensitivities using this FM method and apply travel time tomography, formulated as an inverse factored eikonal equation. Numerical results in two and three dimensions show that our algorithm solves the factored eikonal equation efficiently, and demonstrate the achieved accuracy for computing the travel time. We also demonstrate a recovery of a 2D and 3D heterogeneous medium by travel time tomography using the eikonal equation for forward modeling and inversion by Gauss–Newton.« less

2D and 3D Traveling Salesman Problem

ERIC Educational Resources Information Center

Haxhimusa, Yll; Carpenter, Edward; Catrambone, Joseph; Foldes, David; Stefanov, Emil; Arns, Laura; Pizlo, Zygmunt

2011-01-01

When a two-dimensional (2D) traveling salesman problem (TSP) is presented on a computer screen, human subjects can produce near-optimal tours in linear time. In this study we tested human performance on a real and virtual floor, as well as in a three-dimensional (3D) virtual space. Human performance on the real floor is as good as that on a…

A New Approach for Solving the Generalized Traveling Salesman Problem

NASA Astrophysics Data System (ADS)

Pop, P. C.; Matei, O.; Sabo, C.

The generalized traveling problem (GTSP) is an extension of the classical traveling salesman problem. The GTSP is known to be an NP-hard problem and has many interesting applications. In this paper we present a local-global approach for the generalized traveling salesman problem. Based on this approach we describe a novel hybrid metaheuristic algorithm for solving the problem using genetic algorithms. Computational results are reported for Euclidean TSPlib instances and compared with the existing ones. The obtained results point out that our hybrid algorithm is an appropriate method to explore the search space of this complex problem and leads to good solutions in a reasonable amount of time.

Efficient constraint handling in electromagnetism-like algorithm for traveling salesman problem with time windows.

PubMed

Yurtkuran, Alkın; Emel, Erdal

2014-01-01

The traveling salesman problem with time windows (TSPTW) is a variant of the traveling salesman problem in which each customer should be visited within a given time window. In this paper, we propose an electromagnetism-like algorithm (EMA) that uses a new constraint handling technique to minimize the travel cost in TSPTW problems. The EMA utilizes the attraction-repulsion mechanism between charged particles in a multidimensional space for global optimization. This paper investigates the problem-specific constraint handling capability of the EMA framework using a new variable bounding strategy, in which real-coded particle's boundary constraints associated with the corresponding time windows of customers, is introduced and combined with the penalty approach to eliminate infeasibilities regarding time window violations. The performance of the proposed algorithm and the effectiveness of the constraint handling technique have been studied extensively, comparing it to that of state-of-the-art metaheuristics using several sets of benchmark problems reported in the literature. The results of the numerical experiments show that the EMA generates feasible and near-optimal results within shorter computational times compared to the test algorithms.

Efficient Constraint Handling in Electromagnetism-Like Algorithm for Traveling Salesman Problem with Time Windows

PubMed Central

Yurtkuran, Alkın

2014-01-01

The traveling salesman problem with time windows (TSPTW) is a variant of the traveling salesman problem in which each customer should be visited within a given time window. In this paper, we propose an electromagnetism-like algorithm (EMA) that uses a new constraint handling technique to minimize the travel cost in TSPTW problems. The EMA utilizes the attraction-repulsion mechanism between charged particles in a multidimensional space for global optimization. This paper investigates the problem-specific constraint handling capability of the EMA framework using a new variable bounding strategy, in which real-coded particle's boundary constraints associated with the corresponding time windows of customers, is introduced and combined with the penalty approach to eliminate infeasibilities regarding time window violations. The performance of the proposed algorithm and the effectiveness of the constraint handling technique have been studied extensively, comparing it to that of state-of-the-art metaheuristics using several sets of benchmark problems reported in the literature. The results of the numerical experiments show that the EMA generates feasible and near-optimal results within shorter computational times compared to the test algorithms. PMID:24723834

Staff Recall Travel Time for ST Elevation Myocardial Infarction Impacted by Traffic Congestion and Distance: A Digitally Integrated Map Software Study.

PubMed

Cole, Justin; Beare, Richard; Phan, Thanh G; Srikanth, Velandai; MacIsaac, Andrew; Tan, Christianne; Tong, David; Yee, Susan; Ho, Jesslyn; Layland, Jamie

2017-01-01

Recent evidence suggests hospitals fail to meet guideline specified time to percutaneous coronary intervention (PCI) for a proportion of ST elevation myocardial infarction (STEMI) presentations. Implicit in achieving this time is the rapid assembly of crucial catheter laboratory staff. As a proof-of-concept, we set out to create regional maps that graphically show the impact of traffic congestion and distance to destination on staff recall travel times for STEMI, thereby producing a resource that could be used by staff to improve reperfusion time for STEMI. Travel times for staff recalled to one inner and one outer metropolitan hospital at midnight, 6 p.m., and 7 a.m. were estimated using Google Maps Application Programming Interface. Computer modeling predictions were overlaid on metropolitan maps showing color coded staff recall travel times for STEMI, occurring within non-peak and peak hour traffic congestion times. Inner metropolitan hospital staff recall travel times were more affected by traffic congestion compared with outer metropolitan times, and the latter was more affected by distance. The estimated mean travel times to hospital during peak hour were greater than midnight travel times by 13.4 min to the inner and 6.0 min to the outer metropolitan hospital at 6 p.m. ( p  < 0.001). At 7 a.m., the mean difference was 9.5 min to the inner and 3.6 min to the outer metropolitan hospital ( p  < 0.001). Only 45% of inner metropolitan staff were predicted to arrive within 30 min at 6 p.m. compared with 100% at midnight ( p  < 0.001), and 56% of outer metropolitan staff at 6 p.m. ( p  = 0.021). Our results show that integration of map software with traffic congestion data, distance to destination and travel time can predict optimal residence of staff when on-call for PCI.

Time-of-travel and reaeration data for seven small streams in Alabama, June 1983 to August 1984

USGS Publications Warehouse

Gardner, R.A.

1986-01-01

Time-of-travel and reaeration data were collected between June 1983 and August 1984 for seven small streams in Alabama. Rhodamine WT was used as a tracer for all the studies and propane was used in the reaeration studies. Mean velocities through the study reaches ranged from 0.06 to 0.67 ft/sec. Computed reaeration coefficients, corrected to 20 C, ranged from 1.7 to 45.8 days-1. (USGS)

Implementation of a Pseudo-Bending Seismic Travel-Time Calculator in a Distributed Parallel Computing Environment

DTIC Science & Technology

2008-09-01

algorithms that have been proposed to accomplish it fall into three broad categories. Eikonal solvers (e.g., Vidale, 1988, 1990; Podvin and Lecomte, 1991...difference eikonal solvers, the FMM algorithm works by following a wavefront as it moves across a volume of grid points, updating the travel times in...the grid according to the eikonal differential equation, using a second-order finite-difference scheme. We chose to use FMM for our comparison because

A High-Performance Genetic Algorithm: Using Traveling Salesman Problem as a Case

PubMed Central

Tsai, Chun-Wei; Tseng, Shih-Pang; Yang, Chu-Sing

2014-01-01

This paper presents a simple but efficient algorithm for reducing the computation time of genetic algorithm (GA) and its variants. The proposed algorithm is motivated by the observation that genes common to all the individuals of a GA have a high probability of surviving the evolution and ending up being part of the final solution; as such, they can be saved away to eliminate the redundant computations at the later generations of a GA. To evaluate the performance of the proposed algorithm, we use it not only to solve the traveling salesman problem but also to provide an extensive analysis on the impact it may have on the quality of the end result. Our experimental results indicate that the proposed algorithm can significantly reduce the computation time of GA and GA-based algorithms while limiting the degradation of the quality of the end result to a very small percentage compared to traditional GA. PMID:24892038

A high-performance genetic algorithm: using traveling salesman problem as a case.

PubMed

Tsai, Chun-Wei; Tseng, Shih-Pang; Chiang, Ming-Chao; Yang, Chu-Sing; Hong, Tzung-Pei

2014-01-01

This paper presents a simple but efficient algorithm for reducing the computation time of genetic algorithm (GA) and its variants. The proposed algorithm is motivated by the observation that genes common to all the individuals of a GA have a high probability of surviving the evolution and ending up being part of the final solution; as such, they can be saved away to eliminate the redundant computations at the later generations of a GA. To evaluate the performance of the proposed algorithm, we use it not only to solve the traveling salesman problem but also to provide an extensive analysis on the impact it may have on the quality of the end result. Our experimental results indicate that the proposed algorithm can significantly reduce the computation time of GA and GA-based algorithms while limiting the degradation of the quality of the end result to a very small percentage compared to traditional GA.

Bayesian Travel Time Inversion adopting Gaussian Process Regression

NASA Astrophysics Data System (ADS)

Mauerberger, S.; Holschneider, M.

2017-12-01

A major application in seismology is the determination of seismic velocity models. Travel time measurements are putting an integral constraint on the velocity between source and receiver. We provide insight into travel time inversion from a correlation-based Bayesian point of view. Therefore, the concept of Gaussian process regression is adopted to estimate a velocity model. The non-linear travel time integral is approximated by a 1st order Taylor expansion. A heuristic covariance describes correlations amongst observations and a priori model. That approach enables us to assess a proxy of the Bayesian posterior distribution at ordinary computational costs. No multi dimensional numeric integration nor excessive sampling is necessary. Instead of stacking the data, we suggest to progressively build the posterior distribution. Incorporating only a single evidence at a time accounts for the deficit of linearization. As a result, the most probable model is given by the posterior mean whereas uncertainties are described by the posterior covariance.As a proof of concept, a synthetic purely 1d model is addressed. Therefore a single source accompanied by multiple receivers is considered on top of a model comprising a discontinuity. We consider travel times of both phases - direct and reflected wave - corrupted by noise. Left and right of the interface are assumed independent where the squared exponential kernel serves as covariance.

32 CFR Appendix A to Part 292 - Uniform Agency Fees for Search and Duplication Under the Freedom of Information Act (as Amended)

Code of Federal Regulations, 2011 CFR

2011-07-01

... a. above) for the computer/operator/programmer determining how to conduct and subsequently executing the search will be recorded as part of the computer search. c. Actual time spent travelling to a...

Seismic Barrier Protection of Critical Infrastructure from Earthquakes

DTIC Science & Technology

2017-05-01

structure composed of opposing boreholes or trenches to mitigate seismic waves from diffracting and traveling in the vertical plane. Computational...dams, etc., pose significant risk to civilians while adding tremendous cost and recovery time to regain their functionality. Lower energy earthquakes...the most destructive are surface waves (Rayleigh, Love, shear) which can travel great distances in the far field from the earthquake hypocenter and

Vehicle energy conservation indicating device and process for use

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

Crump, J.M.

A vehicle energy conservation indicating device comprises an integrated instrument cluster functioning basically as a nomographic computing mechanism. The odometer distance traveled indicator computing mechanism is linked with the fuel indicating gauge mechanism such that a three variable equation computing mechanism is obtained. The three variables are distance traveled, quantity of fuel consumed and distance traveled per unit of fuel consumed. Energy conservation is achieved by operating the vehicle under such performance conditions as to produce the highest possible value for distance traveled per unit of fuel consumed. The instrument panel cluster brings the operator's attention to focus upon andmore » continuously stimulated to conserving energy. Furthermore, the vehicle energy conservation indicating device can be adapted for recording these performance variables on tape type print out. The speedometer advises the vehicle operator when he is obeying or breaking the speed laws which are enforced and monitored by the police with specific punishment prescribed for violations of the law. At this time there is no comparable procedure for enforcing vehicle energy conservation. Thus, this direct read out of distance traveled per unit of energy will moderate the operation in an analogous manner similar to subliminal advertising. This device becomes the focal point of the instrument panel along with the speedometer, thereby providing constant motivation to obey both the speed and energy conservation laws.« less

pySeismicFMM: Python based Travel Time Calculation in Regular 2D and 3D Grids in Cartesian and Geographic Coordinates using Fast Marching Method

NASA Astrophysics Data System (ADS)

Wilde-Piorko, M.; Polkowski, M.

2016-12-01

Seismic wave travel time calculation is the most common numerical operation in seismology. The most efficient is travel time calculation in 1D velocity model - for given source, receiver depths and angular distance time is calculated within fraction of a second. Unfortunately, in most cases 1D is not enough to encounter differentiating local and regional structures. Whenever possible travel time through 3D velocity model has to be calculated. It can be achieved using ray calculation or time propagation in space. While single ray path calculation is quick it is complicated to find the ray path that connects source with the receiver. Time propagation in space using Fast Marching Method seems more efficient in most cases, especially when there are multiple receivers. In this presentation final release of a Python module pySeismicFMM is presented - simple and very efficient tool for calculating travel time from sources to receivers. Calculation requires regular 2D or 3D velocity grid either in Cartesian or geographic coordinates. On desktop class computer calculation speed is 200k grid cells per second. Calculation has to be performed once for every source location and provides travel time to all receivers. pySeismicFMM is free and open source. Development of this tool is a part of authors PhD thesis. Source code of pySeismicFMM will be published before Fall Meeting. National Science Centre Poland provided financial support for this work via NCN grant DEC-2011/02/A/ST10/00284.

19 CFR 103.10 - Fees for services.

Code of Federal Regulations, 2011 CFR

2011-04-01

... Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY... each hour or fraction thereof. If a computer search is required because of the nature of the records... based on computer time and supplies necessary to comply with the request. (4) Searches requiring travel...

48 CFR 2052.215-75 - Proposal presentation and format.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., education, and employment history of its employees, subcontractor personnel, and consultants, through... and categories, materials, subcontracts, travel, computer time, etc., must be included so that the...

Connecting People to Places : Spatiotemporal Analysis of Transit Supply Using Travel Time Cubes

DOT National Transportation Integrated Search

2016-06-01

Despite its importance, temporal measures of accessibility are rarely used in transit research or practice. This is primarily due to the inherent difficulty and complexity in computing time-based accessibility metrics. Estimating origin-to-destinatio...

Simulation of TunneLadder traveling-wave tube cold-test characteristics: Implementation of the three-dimensional, electromagnetic circuit analysis code micro-SOS

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Wilson, Jeffrey D.

1993-01-01

The three-dimensional, electromagnetic circuit analysis code, Micro-SOS, can be used to reduce expensive time-consuming experimental 'cold-testing' of traveling-wave tube (TWT) circuits. The frequency-phase dispersion characteristics and beam interaction impedance of a TunneLadder traveling-wave tube slow-wave structure were simulated using the code. When reasonable dimensional adjustments are made, computer results agree closely with experimental data. Modifications to the circuit geometry that would make the TunneLadder TWT easier to fabricate for higher frequency operation are explored.

Googling Service Boundaries for Endovascular Clot Retrieval Hub Hospitals in a Metropolitan Setting: Proof-of-Concept Study.

PubMed

Phan, Thanh G; Beare, Richard; Chen, Jian; Clissold, Benjamin; Ly, John; Singhal, Shaloo; Ma, Henry; Srikanth, Velandai

2017-05-01

There is great interest in how endovascular clot retrieval hubs provide services to a population. We applied a computational method to objectively generate service boundaries for such endovascular clot retrieval hubs, defined by traveling time to hub. Stroke incidence data merged with population census to estimate numbers of stroke in metropolitan Melbourne, Australia. Traveling time from randomly generated addresses to 4 endovascular clot retrieval-capable hubs (Royal Melbourne Hospital [RMH], Monash Medical Center [MMC], Alfred Hospital [ALF], and Austin Hospital [AUS]) estimated using Google Map application program interface. Boundary maps generated based on traveling time at various times of day for combinations of hubs. In a 2-hub model, catchment was best distributed when RMH was paired with MMC (model 1a, RMH 1765 km 2 and MMC 1164 km 2 ) or with AUS (model 1c, RMH 1244 km 2 and AUS 1685 km 2 ), with no statistical difference between models ( P =0.20). Catchment was poorly distributed when RMH was paired with ALF (model 1b, RMH 2252 km 2 and ALF 676 km 2 ), significantly different from both models 1a and 1c (both P <0.05). Model 1a had the greatest proportion of patients arriving within ideal time of 30 minutes followed by model 1c ( P <0.001). In a 3-hub model, the combination of RMH, MMC, and AUS was superior to that of RMH, MMC, and ALF in catchment distribution and travel time. The method was also successfully applied to the city of Adelaide demonstrating wider applicability. We provide proof of concept for a novel computational method to objectively designate service boundaries for endovascular clot retrieval hubs. © 2017 American Heart Association, Inc.

Regional variations in pedal cyclist injuries in New Zealand: safety in numbers or risk in scarcity?

PubMed

Tin, Sandar Tin; Woodward, Alistair; Thornley, Simon; Ameratunga, Shanthi

2011-08-01

To assess regional variations in rates of traffic injuries to pedal cyclists resulting in death or hospital inpatient treatment, in relation to time spent cycling and time spent travelling in a car. Cycling injuries were identified from the Mortality Collection and the National Minimum Dataset. Time spent cycling and time spent travelling as a driver or passenger in a car/van/ute/SUV were computed from National Household Travel Surveys. There are 16 census regions in New Zealand, some of which were combined for this analysis to ensure an adequate sample size, resulting in eight regional groups. Analyses were undertaken for 1996-99 and 2003-07. Injury rates, per million hours spent cycling, varied widely across regions (11 to 33 injuries during 1996-99 and 12 to 78 injuries during 2003-07). The injury rate increased with decreasing per capita time spent cycling. The rate also increased with increasing per capita time spent travelling in a car. There was an inverse association between the injury rate and the ratio of time spent cycling to time spent travelling in a car. The expected number of cycling injuries increased with increasing total time spent cycling but at a decreasing rate particularly after adjusting for total time spent travelling in a car. The findings indicate a 'risk in scarcity' effect for New Zealand cyclists such that risk profiles of cyclists are likely to deteriorate if fewer people use a bicycle and more use a car. Cooperative efforts to promote cycling and its safety and to restrict car use may reverse the risk in scarcity effect. © 2011 The Authors. ANZJPH © 2011 Public Health Association of Australia.

Adapting to the Era of Information

ERIC Educational Resources Information Center

Stuart, Reginald

2008-01-01

Despite having wireless connectivity to the Internet on campus, the students at Northwest Indian College could not afford a laptop computer of their own to access the Internet. Using the school's three computer labs was also problematic, as many students were working parents who traveled long distances and had little time to stay on campus after…

The Ordered Clustered Travelling Salesman Problem: A Hybrid Genetic Algorithm

PubMed Central

Ahmed, Zakir Hussain

2014-01-01

The ordered clustered travelling salesman problem is a variation of the usual travelling salesman problem in which a set of vertices (except the starting vertex) of the network is divided into some prespecified clusters. The objective is to find the least cost Hamiltonian tour in which vertices of any cluster are visited contiguously and the clusters are visited in the prespecified order. The problem is NP-hard, and it arises in practical transportation and sequencing problems. This paper develops a hybrid genetic algorithm using sequential constructive crossover, 2-opt search, and a local search for obtaining heuristic solution to the problem. The efficiency of the algorithm has been examined against two existing algorithms for some asymmetric and symmetric TSPLIB instances of various sizes. The computational results show that the proposed algorithm is very effective in terms of solution quality and computational time. Finally, we present solution to some more symmetric TSPLIB instances. PMID:24701148

Spatial gradients of protein-level time delays set the pace of the traveling segmentation clock waves

PubMed Central

Ay, Ahmet; Holland, Jack; Sperlea, Adriana; Devakanmalai, Gnanapackiam Sheela; Knierer, Stephan; Sangervasi, Sebastian; Stevenson, Angel; Özbudak, Ertuğrul M.

2014-01-01

The vertebrate segmentation clock is a gene expression oscillator controlling rhythmic segmentation of the vertebral column during embryonic development. The period of oscillations becomes longer as cells are displaced along the posterior to anterior axis, which results in traveling waves of clock gene expression sweeping in the unsegmented tissue. Although various hypotheses necessitating the inclusion of additional regulatory genes into the core clock network at different spatial locations have been proposed, the mechanism underlying traveling waves has remained elusive. Here, we combined molecular-level computational modeling and quantitative experimentation to solve this puzzle. Our model predicts the existence of an increasing gradient of gene expression time delays along the posterior to anterior direction to recapitulate spatiotemporal profiles of the traveling segmentation clock waves in different genetic backgrounds in zebrafish. We validated this prediction by measuring an increased time delay of oscillatory Her1 protein production along the unsegmented tissue. Our results refuted the need for spatial expansion of the core feedback loop to explain the occurrence of traveling waves. Spatial regulation of gene expression time delays is a novel way of creating dynamic patterns; this is the first report demonstrating such a control mechanism in any tissue and future investigations will explore the presence of analogous examples in other biological systems. PMID:25336742

A computer program to trace seismic ray distribution in complex two-dimensional geological models

USGS Publications Warehouse

Yacoub, Nazieh K.; Scott, James H.

1970-01-01

A computer program has been developed to trace seismic rays and their amplitudes and energies through complex two-dimensional geological models, for which boundaries between elastic units are defined by a series of digitized X-, Y-coordinate values. Input data for the program includes problem identification, control parameters, model coordinates and elastic parameter for the elastic units. The program evaluates the partitioning of ray amplitude and energy at elastic boundaries, computes the total travel time, total travel distance and other parameters for rays arising at the earth's surface. Instructions are given for punching program control cards and data cards, and for arranging input card decks. An example of printer output for a simple problem is presented. The program is written in FORTRAN IV language. The listing of the program is shown in the Appendix, with an example output from a CDC-6600 computer.

Optimal routing of hazardous substances in time-varying, stochastic transportation networks

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

Woods, A.L.; Miller-Hooks, E.; Mahmassani, H.S.

This report is concerned with the selection of routes in a network along which to transport hazardous substances, taking into consideration several key factors pertaining to the cost of transport and the risk of population exposure in the event of an accident. Furthermore, the fact that travel time and the risk measures are not constant over time is explicitly recognized in the routing decisions. Existing approaches typically assume static conditions, possibly resulting in inefficient route selection and unnecessary risk exposure. The report described the application of recent advances in network analysis methodologies to the problem of routing hazardous substances. Severalmore » specific problem formulations are presented, reflecting different degrees of risk aversion on the part of the decision-maker, as well as different possible operational scenarios. All procedures explicitly consider travel times and travel costs (including risk measures) to be stochastic time-varying quantities. The procedures include both exact algorithms, which may require extensive computational effort in some situations, as well as more efficient heuristics that may not guarantee a Pareto-optimal solution. All procedures are systematically illustrated for an example application using the Texas highway network, for both normal and incident condition scenarios. The application illustrates the trade-offs between the information obtained in the solution and computational efficiency, and highlights the benefits of incorporating these procedures in a decision-support system for hazardous substance shipment routing decisions.« less

Computer program for analysis of coupled-cavity traveling wave tubes

NASA Technical Reports Server (NTRS)

Connolly, D. J.; Omalley, T. A.

1977-01-01

A flexible, accurate, large signal computer program was developed for the design of coupled cavity traveling wave tubes. The program is written in FORTRAN IV for an IBM 360/67 time sharing system. The beam is described by a disk model and the slow wave structure by a sequence of cavities, or cells. The computational approach is arranged so that each cavity may have geometrical or electrical parameters different from those of its neighbors. This allows the program user to simulate a tube of almost arbitrary complexity. Input and output couplers, severs, complicated velocity tapers, and other features peculiar to one or a few cavities may be modeled by a correct choice of input data. The beam-wave interaction is handled by an approach in which the radio frequency fields are expanded in solutions to the transverse magnetic wave equation. All significant space harmonics are retained. The program was used to perform a design study of the traveling-wave tube developed for the Communications Technology Satellite. Good agreement was obtained between the predictions of the program and the measured performance of the flight tube.

Computationally-Efficient Minimum-Time Aircraft Routes in the Presence of Winds

NASA Technical Reports Server (NTRS)

Jardin, Matthew R.

2004-01-01

A computationally efficient algorithm for minimizing the flight time of an aircraft in a variable wind field has been invented. The algorithm, referred to as Neighboring Optimal Wind Routing (NOWR), is based upon neighboring-optimal-control (NOC) concepts and achieves minimum-time paths by adjusting aircraft heading according to wind conditions at an arbitrary number of wind measurement points along the flight route. The NOWR algorithm may either be used in a fast-time mode to compute minimum- time routes prior to flight, or may be used in a feedback mode to adjust aircraft heading in real-time. By traveling minimum-time routes instead of direct great-circle (direct) routes, flights across the United States can save an average of about 7 minutes, and as much as one hour of flight time during periods of strong jet-stream winds. The neighboring optimal routes computed via the NOWR technique have been shown to be within 1.5 percent of the absolute minimum-time routes for flights across the continental United States. On a typical 450-MHz Sun Ultra workstation, the NOWR algorithm produces complete minimum-time routes in less than 40 milliseconds. This corresponds to a rate of 25 optimal routes per second. The closest comparable optimization technique runs approximately 10 times slower. Airlines currently use various trial-and-error search techniques to determine which of a set of commonly traveled routes will minimize flight time. These algorithms are too computationally expensive for use in real-time systems, or in systems where many optimal routes need to be computed in a short amount of time. Instead of operating in real-time, airlines will typically plan a trajectory several hours in advance using wind forecasts. If winds change significantly from forecasts, the resulting flights will no longer be minimum-time. The need for a computationally efficient wind-optimal routing algorithm is even greater in the case of new air-traffic-control automation concepts. For air-traffic-control automation, thousands of wind-optimal routes may need to be computed and checked for conflicts in just a few minutes. These factors motivated the need for a more efficient wind-optimal routing algorithm.

Diesel Bus Performance Simulation Program

DOT National Transportation Integrated Search

1979-04-01

A diesel bus performance computer simulation program was developed. This program provides information on acceleration, velocity, horsepower, distance traveled, and fuel consumption as a function of time from the originating station. The program was w...

Neural activity in the medial temporal lobe reveals the fidelity of mental time travel.

PubMed

Kragel, James E; Morton, Neal W; Polyn, Sean M

2015-02-18

Neural circuitry in the medial temporal lobe (MTL) is critically involved in mental time travel, which involves the vivid retrieval of the details of past experience. Neuroscientific theories propose that the MTL supports memory of the past by retrieving previously encoded episodic information, as well as by reactivating a temporal code specifying the position of a particular event within an episode. However, the neural computations supporting these abilities are underspecified. To test hypotheses regarding the computational mechanisms supported by different MTL subregions during mental time travel, we developed a computational model that linked a blood oxygenation level-dependent signal to cognitive operations, allowing us to predict human performance in a memory search task. Activity in the posterior MTL, including parahippocampal cortex, reflected how strongly one reactivates the temporal context of a retrieved memory, allowing the model to predict whether the next memory will correspond to a nearby moment in the study episode. A signal in the anterior MTL, including perirhinal cortex, indicated the successful retrieval of list items, without providing information regarding temporal organization. A hippocampal signal reflected both processes, consistent with theories that this region binds item and context information together to form episodic memories. These findings provide evidence for modern theories that describe complementary roles of the hippocampus and surrounding parahippocampal and perirhinal cortices during the retrieval of episodic memories, shaping how humans revisit the past. Copyright © 2015 the authors 0270-6474/15/352914-13$15.00/0.

12 CFR 563.170 - Examinations and audits; appraisals; establishment and maintenance of records.

Code of Federal Regulations, 2010 CFR

2010-01-01

... any time, by the Office, with appraisals when deemed advisable, in accordance with general policies from time to time established by the Office. The costs, as computed by the Office, of any examinations made by it, including office analysis, overhead, per diem, travel expense, other supervision by the...

76 FR 37062 - Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-24

..., computer assisted real-time transcription (CART), and sign language interpreters will be available at the... Washington, DC, Monday through Wednesday, July 11-13, 2011, at the times and location noted below. DATES: The... Governments; and Terry Moakley, Association of Travel Instruction). 1:30-3 p.m.--Board Meeting (guest speaker...

Determining mode excitations of vacuum electronics devices via three-dimensional simulations using the SOS code

NASA Technical Reports Server (NTRS)

Warren, Gary

1988-01-01

The SOS code is used to compute the resonance modes (frequency-domain information) of sample devices and separately to compute the transient behavior of the same devices. A code, DOT, is created to compute appropriate dot products of the time-domain and frequency-domain results. The transient behavior of individual modes in the device is then plotted. Modes in a coupled-cavity traveling-wave tube (CCTWT) section excited beam in separate simulations are analyzed. Mode energy vs. time and mode phase vs. time are computed and it is determined whether the transient waves are forward or backward waves for each case. Finally, the hot-test mode frequencies of the CCTWT section are computed.

Designing Programs for Multiple Configurations: "You Mean Everyone Doesn't Have a Pentium or Better!"

ERIC Educational Resources Information Center

Conkright, Thomas D.; Joliat, Judy

1996-01-01

Discusses the challenges, solutions, and compromises involved in creating computer-delivered training courseware for Apollo Travel Services, a company whose 50,000 agents must access a mainframe from many different computing configurations. Initial difficulties came in trying to manage random access memory and quicken response time, but the future…

Concussions in Kids

MedlinePlus

... nights, and no sleepovers. Rest also involves a mental time out. No using a computer, cell phone, or ... a place for exercise at…Social PhobiaRead Article >>Mental HealthSocial ... Living Travel Occupational Health First Aid and Injury Prevention Crisis ...

Adapting the traveling salesman problem to an adiabatic quantum computer

NASA Astrophysics Data System (ADS)

Warren, Richard H.

2013-04-01

We show how to guide a quantum computer to select an optimal tour for the traveling salesman. This is significant because it opens a rapid solution method for the wide range of applications of the traveling salesman problem, which include vehicle routing, job sequencing and data clustering.

A hybrid meta-heuristic algorithm for the vehicle routing problem with stochastic travel times considering the driver's satisfaction

NASA Astrophysics Data System (ADS)

Tavakkoli-Moghaddam, Reza; Alinaghian, Mehdi; Salamat-Bakhsh, Alireza; Norouzi, Narges

2012-05-01

A vehicle routing problem is a significant problem that has attracted great attention from researchers in recent years. The main objectives of the vehicle routing problem are to minimize the traveled distance, total traveling time, number of vehicles and cost function of transportation. Reducing these variables leads to decreasing the total cost and increasing the driver's satisfaction level. On the other hand, this satisfaction, which will decrease by increasing the service time, is considered as an important logistic problem for a company. The stochastic time dominated by a probability variable leads to variation of the service time, while it is ignored in classical routing problems. This paper investigates the problem of the increasing service time by using the stochastic time for each tour such that the total traveling time of the vehicles is limited to a specific limit based on a defined probability. Since exact solutions of the vehicle routing problem that belong to the category of NP-hard problems are not practical in a large scale, a hybrid algorithm based on simulated annealing with genetic operators was proposed to obtain an efficient solution with reasonable computational cost and time. Finally, for some small cases, the related results of the proposed algorithm were compared with results obtained by the Lingo 8 software. The obtained results indicate the efficiency of the proposed hybrid simulated annealing algorithm.

Expression for time travel based on diffusive wave theory: applicability and considerations

NASA Astrophysics Data System (ADS)

Aguilera, J. C.; Escauriaza, C. R.; Passalacqua, P.; Gironas, J. A.

2017-12-01

Prediction of hydrological response is of utmost importance when dealing with urban planning, risk assessment, or water resources management issues. With the advent of climate change, special care must be taken with respect to variations in rainfall and runoff due to rising temperature averages. Nowadays, while typical workstations have adequate power to run distributed routing hydrological models, it is still not enough for modeling on-the-fly, a crucial ability in a natural disaster context, where rapid decisions must be made. Semi-distributed time travel models, which compute a watershed's hydrograph without explicitly solving the full shallow water equations, appear as an attractive approach to rainfall-runoff modeling since, like fully distributed models, also superimpose a grid on the watershed, and compute runoff based on cell parameter values. These models are heavily dependent on the travel time expression for an individual cell. Many models make use of expressions based on kinematic wave theory, which is not applicable in cases where watershed storage is important, such as mild slopes. This work presents a new expression for concentration times in overland flow, based on diffusive wave theory, which considers not only the effects of storage but also the effects on upstream contribution. Setting upstream contribution equal to zero gives an expression consistent with previous work on diffusive wave theory; on the other hand, neglecting storage effects (i.e.: diffusion,) is shown to be equivalent to kinematic wave theory, currently used in many spatially distributed time travel models. The newly found expression is shown to be dependent on plane discretization, particularly when dealing with very non-kinematic cases. This is shown to be the result of upstream contribution, which gets larger downstream, versus plane length. This result also provides some light on the limits on applicability of the expression: when a certain kinematic threshold is reached, the expression is no longer valid, and one must fall back to kinematic wave theory, for lack of a better option. This expression could be used for improving currently published spatially distributed time travel models, since they would become applicable in many new cases.

Three-dimensional simulation of helix traveling-wave tube cold-test characteristics using MAFIA

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

Kory, C.L.

1996-12-31

A critically important step in the traveling-wave tube (TWT) design process is the cold-testing of the slow-wave circuit for dispersion, beam interaction impedance and RF losses. Experimental cold-tests can be very time-consuming and expensive, thus limiting the freedom to examine numerous variations to the test circuit. This makes the need for computational methods crucial as they can lower cost, reduce tube development time and allow the freedom to introduce novel and improved designs. The cold-test parameters have been calculated for a C-Band Northrop-Grumman helix TWT slow-wave circuit using MAFIA, the three-dimensional electromagnetic finite-integration computer code. Measured and simulated cold-test datamore » for the Northrop-Grumman helix TWT including dispersion, impedance and attenuation will be presented. Close agreement between simulated and measured values of the dispersion, impedance and attenuation has been obtained.« less

A Hybrid Symbiotic Organisms Search Algorithm with Variable Neighbourhood Search for Solving Symmetric and Asymmetric Traveling Salesman Problem

NASA Astrophysics Data System (ADS)

Umam, M. I. H.; Santosa, B.

2018-04-01

Combinatorial optimization has been frequently used to solve both problems in science, engineering, and commercial applications. One combinatorial problems in the field of transportation is to find a shortest travel route that can be taken from the initial point of departure to point of destination, as well as minimizing travel costs and travel time. When the distance from one (initial) node to another (destination) node is the same with the distance to travel back from destination to initial, this problems known to the Traveling Salesman Problem (TSP), otherwise it call as an Asymmetric Traveling Salesman Problem (ATSP). The most recent optimization techniques is Symbiotic Organisms Search (SOS). This paper discuss how to hybrid the SOS algorithm with variable neighborhoods search (SOS-VNS) that can be applied to solve the ATSP problem. The proposed mechanism to add the variable neighborhoods search as a local search is to generate the better initial solution and then we modify the phase of parasites with adapting mechanism of mutation. After modification, the performance of the algorithm SOS-VNS is evaluated with several data sets and then the results is compared with the best known solution and some algorithm such PSO algorithm and SOS original algorithm. The SOS-VNS algorithm shows better results based on convergence, divergence and computing time.

Data-driven layer-stripping strategy in 3-D joint refraction and reflection travel-time tomography with TOMO3D

NASA Astrophysics Data System (ADS)

Meléndez, Adrià; Korenaga, Jun; Sallarès, Valentí; Miniussi, Alain; Ranero, César

2015-04-01

We present a new 3-D travel-time tomography code (TOMO3D) for the modelling of active-source seismic data that uses the arrival times of both refracted and reflected seismic phases to derive the propagation velocity distribution and the geometry of reflecting boundaries in the subsurface. The combination of refracted and reflected data provides a denser coverage of the study area. Moreover, because refractions only depend on the velocity parameters, they contribute to the mitigation of the negative effect of the ambiguity between layer thickness and propagation velocity that is intrinsic to the reflections that define these boundaries. This code is based on its renowned 2-D version TOMO2D from which it inherited the methods to solve the forward and inverse problems. The forward travel-time calculations are conducted using a hybrid ray-tracing technique combining the graph or shortest path method and the bending method. The LSQR algorithm is used to perform the iterative inversion of travel-time residuals to update the initial velocity and depth models. In order to cope with the increased computational demand due to the incorporation of the third dimension, the forward problem solver, which takes by far most of the run time (~90%), has been parallelised with a combination of MP and MPI standards. This parallelisation distributes the ray-tracing and travel-time calculations among the available computational resources, allowing the user to set the number of nodes, processors and cores to be used. The code's performance was evaluated with a complex synthetic case simulating a subduction zone. The objective is to retrieve the velocity distribution of both upper and lower plates and the geometry of the interplate and Moho boundaries. Our tomography method is designed to deal with a single reflector per inversion, and we show that a data-driven layer-stripping strategy allows to successfully recover several reflectors in successive inversions. This strategy consists in building the final velocity model layer by layer, sequentially extending it down with each inversion of a new, deeper reflector. One advantage of layer stripping is that it allows us to introduce and keep strong velocity contrasts associated to geological discontinuities that would otherwise be smoothened. Another advantage is that it poses simpler inverse problems at each step, facilitating the minimisation of travel-time residuals and ensuring a good control on each partial model before adding new data corresponding to deeper layers. Finally, we discuss the parallel performance of the code in this particular synthetic case.

A hydraulic tomography approach coupling travel time inversion with steady shape analysis based on aquifer analogue study in coarsely clastic fluvial glacial deposit

NASA Astrophysics Data System (ADS)

Hu, R.; Brauchler, R.; Herold, M.; Bayer, P.; Sauter, M.

2009-04-01

Rarely is it possible to draw a significant conclusion about the geometry and the properties of geological structures of the underground using the information which is typically obtained from boreholes, since soil exploration is only representative of the position where the soil sample is taken from. Conventional aquifer investigation methods like pumping tests can provide hydraulic properties of a larger area; however, they lead to integral information. This information is insufficient to develop groundwater models, especially contaminant transport models, which require information about the spatial distribution of the hydraulic properties of the subsurface. Hydraulic tomography is an innovative method which has the potential to spatially resolve three dimensional structures of natural aquifer bodies. The method employs hydraulic short term tests performed between two or more wells, whereby the pumped intervals (sources) and the observation points (receivers) are separated by double packer systems. In order to optimize the computationally intensive tomographic inversion of transient hydraulic data we have decided to couple two inversion approaches (a) hydraulic travel time inversion and (b) steady shape inversion. (a) Hydraulic travel time inversion is based on the solution of the travel time integral, which describes the relationship between travel time of maximum signal variation of a transient hydraulic signal and the diffusivity between source and receiver. The travel time inversion is computationally extremely effective and robust, however, it is limited to the determination of diffusivity. In order to overcome this shortcoming we use the estimated diffusivity distribution as starting model for the steady shape inversion with the goal to separate the estimated diffusivity distribution into its components, hydraulic conductivity and specific storage. (b) The steady shape inversion utilizes the fact that at steady shape conditions, drawdown varies with time but the hydraulic gradient does not. By this trick, transient data can be analyzed with the computational efficiency of a steady state model, which proceeds hundreds of times faster than transient models. Finally, a specific storage distribution can be calculated from the diffusivity and hydraulic conductivity reconstructions derived from travel time and steady shape inversion. The groundwork of this study is the aquifer-analogue study from BAYER (1999), in which six parallel profiles of a natural sedimentary body with a size of 16m x 10m x 7m were mapped in high resolution with respect to structural and hydraulic parameters. Based on these results and using geostatistical interpolation methods, MAJI (2005) designed a three dimensional hydraulic model with a resolution of 5cm x 5cm x 5cm. This hydraulic model was used to simulate a large number of short term pumping tests in a tomographical array. The high resolution parameter reconstructions gained from the inversion of simulated pumping test data demonstrate that the proposed inversion scheme allows reconstructing the individual architectural elements and their hydraulic properties with a higher resolution compared to conventional hydraulic and geological investigation methods. Bayer P (1999) Aquifer-Analog-Studium in grobklastischen braided river Ablagerungen: Sedimentäre/hydrogeologische Wandkartierung und Kalibrierung von Georadarmessungen, Diplomkartierung am Lehrstuhl für Angewandte Geologie, Universität Tübingen, 25 pp. Maji, R. (2005) Conditional Stochastic Modelling of DNAPL Migration and Dissolution in a High-resolution Aquifer Analog, Ph.D. thesis at the University of Waterloo, 187 pp.

Three-Dimensional Simulation of Traveling-Wave Tube Cold-Test Characteristics Using MAFIA

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Wilson, Jeffrey D.

1995-01-01

The three-dimensional simulation code MAFIA was used to compute the cold-test parameters - frequency-phase dispersion, beam on-axis interaction impedance, and attenuation - for two types of traveling-wave tube (TWT) slow-wave circuits. The potential for this electromagnetic computer modeling code to reduce the time and cost of TWT development is demonstrated by the high degree of accuracy achieved in calculating these parameters. Generalized input files were developed for ferruled coupled-cavity and TunneLadder slow-wave circuits. These files make it easy to model circuits of arbitrary dimensions. The utility of these files was tested by applying each to a specific TWT slow-wave circuit and comparing the results with experimental data. Excellent agreement was obtained.

Ferruleless coupled-cavity traveling-wave tube cold-test characteristics simulated with micro-SOS

NASA Technical Reports Server (NTRS)

Schroeder, Dana L.; Wilson, Jeffrey D.

1993-01-01

The three-dimensional, electromagnetic circuit analysis code, Micro-SOS, can be used to reduce expensive and time consuming experimental 'cold-testing' of traveling-wave tube (TWT) circuits. The frequency-phase dispersion and beam interaction impedance characteristics of a ferruleless coupled-cavity traveling-wave tube slow-wave circuit were simulated using the code. Computer results agree closely with experimental data. Variations in the cavity geometry dimensions of period length and gap-to-period ratio were modeled. These variations can be used in velocity taper designs to reduce the radiofrequency (RF) phase velocity in synchronism with the decelerating electron beam. Such circuit designs can result in enhanced TWT power and efficiency.

Route profile analysis system and method

DOEpatents

Mullenhoff, Donald J.; Wilson, Stephen W.

1986-01-01

A system for recording terrain profile information is disclosed. The system accurately senses incremental distances traveled by a vehicle along with vehicle inclination, recording both with elapsed time. The incremental distances can subsequently be differentiated with respect to time to obtain acceleration. The acceleration can then be used by the computer to correct the sensed inclination.

Route profile analysis system and method

DOEpatents

Mullenhoff, D.J.; Wilson, S.W.

1982-07-29

A system for recording terrain profile information is disclosed. The system accurately senses incremental distances traveled by a vehicle along with vehicle inclination, recording both with elapsed time. The incremental distances can subsequently be differentiated with respect to time to obtain acceleration. The computer acceleration can then be used to correct the sensed inclination.

Accounting for Long Term Sediment Storage in a Watershed Scale Numerical Model for Suspended Sediment Routing

NASA Astrophysics Data System (ADS)

Keeler, J. J.; Pizzuto, J. E.; Skalak, K.; Karwan, D. L.; Benthem, A.; Ackerman, T. R.

2015-12-01

Quantifying the delivery of suspended sediment from upland sources to downstream receiving waters is important for watershed management, but current routing models fail to accurately represent lag times in delivery resulting from sediment storage. In this study, we route suspended sediment tagged by a characteristic tracer using a 1-dimensional model that implicitly includes storage and remobilization processes and timescales. From an input location where tagged sediment is added, the model advects suspended sediment downstream at the velocity of the stream (adjusted for the intermittency of transport events). Deposition rates are specified by the fraction of the suspended load stored per kilometer of downstream transport (presumably available from a sediment budget). Tagged sediment leaving storage is evaluated from a convolution equation based on the probability distribution function (pdf) of sediment storage waiting times; this approach avoids the difficulty of accurately representing complex processes of sediment remobilization from floodplain and other deposits. To illustrate the role of storage on sediment delivery, we compare exponential and bounded power-law waiting time pdfs with identical means of 94 years. In both cases, the median travel time for sediment to reach the depocenter in fluvial systems less than 40km long is governed by in-channel transport and is unaffected by sediment storage. As the channel length increases, however, the median sediment travel time reflects storage rather than in-channel transport; travel times do not vary significantly between the two different waiting time functions. At distances of 50, 100, and 200 km, the median travel time for suspended sediment is 36, 136, and 325 years, orders of magnitude slower than travel times associated with in-channel transport. These computations demonstrate that storage can be neglected for short rivers, but for longer systems, storage controls the delivery of suspended sediment.

Quantum Computing since Democritus

NASA Astrophysics Data System (ADS)

Aaronson, Scott

2013-03-01

1. Atoms and the void; 2. Sets; 3. Gödel, Turing, and friends; 4. Minds and machines; 5. Paleocomplexity; 6. P, NP, and friends; 7. Randomness; 8. Crypto; 9. Quantum; 10. Quantum computing; 11. Penrose; 12. Decoherence and hidden variables; 13. Proofs; 14. How big are quantum states?; 15. Skepticism of quantum computing; 16. Learning; 17. Interactive proofs and more; 18. Fun with the Anthropic Principle; 19. Free will; 20. Time travel; 21. Cosmology and complexity; 22. Ask me anything.

Univariate and multivariate spatial models of health facility utilisation for childhood fevers in an area on the coast of Kenya.

PubMed

Ouma, Paul O; Agutu, Nathan O; Snow, Robert W; Noor, Abdisalan M

2017-09-18

Precise quantification of health service utilisation is important for the estimation of disease burden and allocation of health resources. Current approaches to mapping health facility utilisation rely on spatial accessibility alone as the predictor. However, other spatially varying social, demographic and economic factors may affect the use of health services. The exclusion of these factors can lead to the inaccurate estimation of health facility utilisation. Here, we compare the accuracy of a univariate spatial model, developed only from estimated travel time, to a multivariate model that also includes relevant social, demographic and economic factors. A theoretical surface of travel time to the nearest public health facility was developed. These were assigned to each child reported to have had fever in the Kenya demographic and health survey of 2014 (KDHS 2014). The relationship of child treatment seeking for fever with travel time, household and individual factors from the KDHS2014 were determined using multilevel mixed modelling. Bayesian information criterion (BIC) and likelihood ratio test (LRT) tests were carried out to measure how selected factors improve parsimony and goodness of fit of the time model. Using the mixed model, a univariate spatial model of health facility utilisation was fitted using travel time as the predictor. The mixed model was also used to compute a multivariate spatial model of utilisation, using travel time and modelled surfaces of selected household and individual factors as predictors. The univariate and multivariate spatial models were then compared using the receiver operating area under the curve (AUC) and a percent correct prediction (PCP) test. The best fitting multivariate model had travel time, household wealth index and number of children in household as the predictors. These factors reduced BIC of the time model from 4008 to 2959, a change which was confirmed by the LRT test. Although there was a high correlation of the two modelled probability surfaces (Adj R 2  = 88%), the multivariate model had better AUC compared to the univariate model; 0.83 versus 0.73 and PCP 0.61 versus 0.45 values. Our study shows that a model that uses travel time, as well as household and individual-level socio-demographic factors, results in a more accurate estimation of use of health facilities for the treatment of childhood fever, compared to one that relies on only travel time.

Eikonal-Based Inversion of GPR Data from the Vaucluse Karst Aquifer

NASA Astrophysics Data System (ADS)

Yedlin, M. J.; van Vorst, D.; Guglielmi, Y.; Cappa, F.; Gaffet, S.

2009-12-01

In this paper, we present an easy-to-implement eikonal-based travel time inversion algorithm and apply it to borehole GPR measurement data obtained from a karst aquifer located in the Vaucluse in Provence. The boreholes are situated with a fault zone deep inside the aquifer, in the Laboratoire Souterrain à Bas Bruit (LSBB). The measurements were made using 250 MHz MALA RAMAC borehole GPR antennas. The inversion formulation is unique in its application of a fast-sweeping eikonal solver (Zhao [1]) to the minimization of an objective functional that is composed of a travel time misfit and a model-based regularization [2]. The solver is robust in the presence of large velocity contrasts, efficient, easy to implement, and does not require the use of a sorting algorithm. The computation of sensitivities, which are required for the inversion process, is achieved by tracing rays backward from receiver to source following the gradient of the travel time field [2]. A user wishing to implement this algorithm can opt to avoid the ray tracing step and simply perturb the model to obtain the required sensitivities. Despite the obvious computational inefficiency of such an approach, it is acceptable for 2D problems. The relationship between travel time and the velocity profile is non-linear, requiring an iterative approach to be used. At each iteration, a set of matrix equations is solved to determine the model update. As the inversion continues, the weighting of the regularization parameter is adjusted until an appropriate data misfit is obtained. The inversion results, shown in the attached image, are consistent with previously obtained geological structure. Future work will look at improving inversion resolution and incorporating other measurement methodologies, with the goal of providing useful data for groundwater analysis. References: [1] H. Zhao, “A fast sweeping method for Eikonal equations,” Mathematics of Computation, vol. 74, no. 250, pp. 603-627, 2004. [2] D. Aldridge and D. Oldenburg, “Two-dimensional tomographic inversion with finite-difference traveltimes,” Journal of Seismic Exploration, vol. 2, pp. 257-274, 1993. Recovered Permittivity Profiles

hypoDD-A Program to Compute Double-Difference Hypocenter Locations

USGS Publications Warehouse

Waldhauser, Felix

2001-01-01

HypoDD is a Fortran computer program package for relocating earthquakes with the double-difference algorithm of Waldhauser and Ellsworth (2000). This document provides a brief introduction into how to run and use the programs ph2dt and hypoDD to compute double-difference (DD) hypocenter locations. It gives a short overview of the DD technique, discusses the data preprocessing using ph2dt, and leads through the earthquake relocation process using hypoDD. The appendices include the reference manuals for the two programs and a short description of auxiliary programs and example data. Some minor subroutines are presently in the c language, and future releases will be in c. Earthquake location algorithms are usually based on some form of Geiger’s method, the linearization of the travel time equation in a first order Taylor series that relates the difference between the observed and predicted travel time to unknown adjustments in the hypocentral coordinates through the partial derivatives of travel time with respect to the unknowns. Earthquakes can be located individually with this algorithm, or jointly when other unknowns link together the solutions to indivdual earthquakes, such as station corrections in the joint hypocenter determination (JHD) method, or the earth model in seismic tomography. The DD technique (described in detail in Waldhauser and Ellsworth, 2000) takes advantage of the fact that if the hypocentral separation between two earthquakes is small compared to the event-station distance and the scale length of velocity heterogeneity, then the ray paths between the source region and a common station are similar along almost the entire ray path (Fréchet, 1985; Got et al., 1994). In this case, the difference in travel times for two events observed at one station can be attributed to the spatial offset between the events with high accuracy. DD equations are built by differencing Geiger’s equation for earthquake location. In this way, the residual between observed and calculated travel-time difference (or double-difference) between two events at a common station are a related to adjustments in the relative position of the hypocenters and origin times through the partial derivatives of the travel times for each event with respect to the unknown. HypoDD calculates travel times in a layered velocity model (where velocity depends only on depth) for the current hypocenters at the station where the phase was recorded. The double-difference residuals for pairs of earthquakes at each station are minimized by weighted least squares using the method of singular value decomposition (SVD) or the conjugate gradients method (LSQR, Paige and Saunders, 1982). Solutions are found by iteratively adjusting the vector difference between nearby hypocentral pairs, with the locations and partial derivatives being updated after each iteration. Details about the algorithm can be found in Waldhauser and Ellsworth (2000). When the earthquake location problem is linearized using the double-difference equations, the common mode errors cancel, principally those related to the receiver-side structure. Thus we avoid the need for station corrections or high-accuracy of predicted travel times for the portion of the raypath that lies outside the focal volume. This approach is especially useful in regions with a dense distribution of seismicity, i.e. where distances between neighboring events are only a few hundred meters. The improvement of double-difference locations over ordinary JHD locations is shown in Figure 1 for about 10,000 earthquakes that occurred during the 1997 seismic crisis in the Long Valley caldera, California. While the JHD locations (left panel) show a diffuse picture of the seismicity, double-difference locations (right panel) bring structural details such as the location of active fault planes into sharp focus.

Bi-criteria travelling salesman subtour problem with time threshold

NASA Astrophysics Data System (ADS)

Kumar Thenepalle, Jayanth; Singamsetty, Purusotham

2018-03-01

This paper deals with the bi-criteria travelling salesman subtour problem with time threshold (BTSSP-T), which comes from the family of the travelling salesman problem (TSP) and is NP-hard in the strong sense. The problem arises in several application domains, mainly in routing and scheduling contexts. Here, the model focuses on two criteria: total travel distance and gains attained. The BTSSP-T aims to determine a subtour that starts and ends at the same city and visits a subset of cities at a minimum travel distance with maximum gains, such that the time spent on the tour does not exceed the predefined time threshold. A zero-one integer-programming problem is adopted to formulate this model with all practical constraints, and it includes a finite set of feasible solutions (one for each tour). Two algorithms, namely, the Lexi-Search Algorithm (LSA) and the Tabu Search (TS) algorithm have been developed to solve the BTSSP-T problem. The proposed LSA implicitly enumerates the feasible patterns and provides an efficient solution with backtracking, whereas the TS, which is metaheuristic, will give the better approximate solution. A numerical example is demonstrated in order to understand the search mechanism of the LSA. Numerical experiments are carried out in the MATLAB environment, on the different benchmark instances available in the TSPLIB domain as well as on randomly generated test instances. The experimental results show that the proposed LSA works better than the TS algorithm in terms of solution quality and, computationally, both LSA and TS are competitive.

Exact parallel algorithms for some members of the traveling salesman problem family

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

Pekny, J.F.

1989-01-01

The traveling salesman problem and its many generalizations comprise one of the best known combinatorial optimization problem families. Most members of the family are NP-complete problems so that exact algorithms require an unpredictable and sometimes large computational effort. Parallel computers offer hope for providing the power required to meet these demands. A major barrier to applying parallel computers is the lack of parallel algorithms. The contributions presented in this thesis center around new exact parallel algorithms for the asymmetric traveling salesman problem (ATSP), prize collecting traveling salesman problem (PCTSP), and resource constrained traveling salesman problem (RCTSP). The RCTSP is amore » particularly difficult member of the family since finding a feasible solution is an NP-complete problem. An exact sequential algorithm is also presented for the directed hamiltonian cycle problem (DHCP). The DHCP algorithm is superior to current heuristic approaches and represents the first exact method applicable to large graphs. Computational results presented for each of the algorithms demonstrates the effectiveness of combining efficient algorithms with parallel computing methods. Performance statistics are reported for randomly generated ATSPs with 7,500 cities, PCTSPs with 200 cities, RCTSPs with 200 cities, DHCPs with 3,500 vertices, and assignment problems of size 10,000. Sequential results were collected on a Sun 4/260 engineering workstation, while parallel results were collected using a 14 and 100 processor BBN Butterfly Plus computer. The computational results represent the largest instances ever solved to optimality on any type of computer.« less

Fast surface-based travel depth estimation algorithm for macromolecule surface shape description.

PubMed

Giard, Joachim; Alface, Patrice Rondao; Gala, Jean-Luc; Macq, Benoît

2011-01-01

Travel Depth, introduced by Coleman and Sharp in 2006, is a physical interpretation of molecular depth, a term frequently used to describe the shape of a molecular active site or binding site. Travel Depth can be seen as the physical distance a solvent molecule would have to travel from a point of the surface, i.e., the Solvent-Excluded Surface (SES), to its convex hull. Existing algorithms providing an estimation of the Travel Depth are based on a regular sampling of the molecule volume and the use of the Dijkstra's shortest path algorithm. Since Travel Depth is only defined on the molecular surface, this volume-based approach is characterized by a large computational complexity due to the processing of unnecessary samples lying inside or outside the molecule. In this paper, we propose a surface-based approach that restricts the processing to data defined on the SES. This algorithm significantly reduces the complexity of Travel Depth estimation and makes possible the analysis of large macromolecule surface shape description with high resolution. Experimental results show that compared to existing methods, the proposed algorithm achieves accurate estimations with considerably reduced processing times.

WHAMII - An enumeration and insertion procedure with binomial bounds for the stochastic time-constrained traveling salesman problem

NASA Technical Reports Server (NTRS)

Dahl, Roy W.; Keating, Karen; Salamone, Daryl J.; Levy, Laurence; Nag, Barindra; Sanborn, Joan A.

1987-01-01

This paper presents an algorithm (WHAMII) designed to solve the Artificial Intelligence Design Challenge at the 1987 AIAA Guidance, Navigation and Control Conference. The problem under consideration is a stochastic generalization of the traveling salesman problem in which travel costs can incur a penalty with a given probability. The variability in travel costs leads to a probability constraint with respect to violating the budget allocation. Given the small size of the problem (eleven cities), an approach is considered that combines partial tour enumeration with a heuristic city insertion procedure. For computational efficiency during both the enumeration and insertion procedures, precalculated binomial probabilities are used to determine an upper bound on the actual probability of violating the budget constraint for each tour. The actual probability is calculated for the final best tour, and additional insertions are attempted until the actual probability exceeds the bound.

Genetic Algorithm for Traveling Salesman Problem with Modified Cycle Crossover Operator

PubMed Central

Mohamd Shoukry, Alaa; Gani, Showkat

2017-01-01

Genetic algorithms are evolutionary techniques used for optimization purposes according to survival of the fittest idea. These methods do not ensure optimal solutions; however, they give good approximation usually in time. The genetic algorithms are useful for NP-hard problems, especially the traveling salesman problem. The genetic algorithm depends on selection criteria, crossover, and mutation operators. To tackle the traveling salesman problem using genetic algorithms, there are various representations such as binary, path, adjacency, ordinal, and matrix representations. In this article, we propose a new crossover operator for traveling salesman problem to minimize the total distance. This approach has been linked with path representation, which is the most natural way to represent a legal tour. Computational results are also reported with some traditional path representation methods like partially mapped and order crossovers along with new cycle crossover operator for some benchmark TSPLIB instances and found improvements. PMID:29209364

Genetic Algorithm for Traveling Salesman Problem with Modified Cycle Crossover Operator.

PubMed

Hussain, Abid; Muhammad, Yousaf Shad; Nauman Sajid, M; Hussain, Ijaz; Mohamd Shoukry, Alaa; Gani, Showkat

2017-01-01

Genetic algorithms are evolutionary techniques used for optimization purposes according to survival of the fittest idea. These methods do not ensure optimal solutions; however, they give good approximation usually in time. The genetic algorithms are useful for NP-hard problems, especially the traveling salesman problem. The genetic algorithm depends on selection criteria, crossover, and mutation operators. To tackle the traveling salesman problem using genetic algorithms, there are various representations such as binary, path, adjacency, ordinal, and matrix representations. In this article, we propose a new crossover operator for traveling salesman problem to minimize the total distance. This approach has been linked with path representation, which is the most natural way to represent a legal tour. Computational results are also reported with some traditional path representation methods like partially mapped and order crossovers along with new cycle crossover operator for some benchmark TSPLIB instances and found improvements.

49 CFR 1245.5 - Classification of job titles.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., Computer Programmer, Computer Analyst, Market Analyst, Pricing Analyst, Employment Supervisor, Research..., Traveling Auditors or Accountants Title is descriptive Traveling Auditor, Accounting Specialist Auditors... 21; adds new titles. 207 Supervising and Chief Claim Agents Title is descriptive Chief Claim Agent...

49 CFR 1245.5 - Classification of job titles.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., Computer Programmer, Computer Analyst, Market Analyst, Pricing Analyst, Employment Supervisor, Research..., Traveling Auditors or Accountants Title is descriptive Traveling Auditor, Accounting Specialist Auditors... 21; adds new titles. 207 Supervising and Chief Claim Agents Title is descriptive Chief Claim Agent...

49 CFR 1245.5 - Classification of job titles.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., Computer Programmer, Computer Analyst, Market Analyst, Pricing Analyst, Employment Supervisor, Research..., Traveling Auditors or Accountants Title is descriptive Traveling Auditor, Accounting Specialist Auditors... 21; adds new titles. 207 Supervising and Chief Claim Agents Title is descriptive Chief Claim Agent...

49 CFR 1245.5 - Classification of job titles.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., Computer Programmer, Computer Analyst, Market Analyst, Pricing Analyst, Employment Supervisor, Research..., Traveling Auditors or Accountants Title is descriptive Traveling Auditor, Accounting Specialist Auditors... 21; adds new titles. 207 Supervising and Chief Claim Agents Title is descriptive Chief Claim Agent...

49 CFR 1245.5 - Classification of job titles.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., Computer Programmer, Computer Analyst, Market Analyst, Pricing Analyst, Employment Supervisor, Research..., Traveling Auditors or Accountants Title is descriptive Traveling Auditor, Accounting Specialist Auditors... 21; adds new titles. 207 Supervising and Chief Claim Agents Title is descriptive Chief Claim Agent...

DEMONSTRATION OF THE ANALYTIC ELEMENT METHOD FOR WELLHEAD PROTECTION

EPA Science Inventory

A new computer program has been developed to determine time-of-travel capture zones in relatively simple geohydrological settings. The WhAEM package contains an analytic element model that uses superposition of (many) closed form analytical solutions to generate a ground-water fl...

LLNL's Regional Model Calibration and Body-Wave Discrimination Research in the Former Soviet Union using Peaceful Nuclear Explosions (PNEs)

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

Bhattacharyya, J.; Rodgers, A.; Swenson, J.

2000-07-14

Long-range seismic profiles from Peaceful Nuclear Explosions (PNE) in the Former Soviet Union (FSU) provide a unique data set to investigate several important issues in regional Comprehensive Nuclear-Test-Ban Treaty (CTBT) monitoring. The recording station spacing ({approx}15 km) allows for extremely dense sampling of the propagation from the source to {approx} 3300 km. This allows us to analyze the waveforms at local, near- and far-regional and teleseismic distances. These data are used to: (1) study the evolution of regional phases and phase amplitude ratios along the profile; (2) infer one-dimensional velocity structure along the profile; and (3) evaluate the spatial correlationmore » of regional and teleseismic travel times and regional phase amplitude ratios. We analyzed waveform data from four PNE's (m{sub b} = 5.1-5.6) recorded along profile KRATON, which is an east-west trending profile located in northern Sibertil. Short-period regional discriminants, such as P/S amplitude ratios, will be essential for seismic monitoring of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) at small magnitudes (m{sub b} < 4.0). However, P/S amplitude ratios in the short-period band, 0.5-5.0 Hz, show some scatter. This scatter is primarily due to propagation and site effects, which arise from variability in the elastic and anelastic structure of the crustal waveguide. Preliminary results show that Pg and Lg propagate efficiently in north Siberia at regional distances. The amplitude ratios show some variability between adjacent stations that are modeled by simple distance trends. The effect of topography, sediment and crustal thickness, and upper mantle discontinuities on these ratios, after removal of the distance trends, will be investigated. The travel times of the body wave phases recorded on KEATON have been used to compute the one-dimensional structure of the crust and upper mantle in this region. The path-averaged one-dimensional velocity model was computed by minimizing the first arriving P-phase travel-time residuals for all distances ({Delta} = 300-2300 km). A grid search approach was used in the minimization. The most significant features of this model are the negative lid-gradient and a low-velocity zone in the upper mantle between the depths of 100-200 km; precise location of the LVZ is poorly constrained by the travel time data. We will extend our investigation to additional PNE lines to further investigate the amplitude and travel-time variations in eastern and central Eurasia. Finally, the dense station spacing of the PNE profiles allows us to model the spatial correlation of travel times and amplitude ratios through variogram modeling. The statistical analysis suggests that the correlation lengths of the travel-time and amplitude measurements are 12{sup o} and 10{sup o}, respectively.« less

A Kirchhoff approach to seismic modeling and prestack depth migration

NASA Astrophysics Data System (ADS)

Liu, Zhen-Yue

1993-05-01

The Kirchhoff integral provides a robust method for implementing seismic modeling and prestack depth migration, which can handle lateral velocity variation and turning waves. With a little extra computation cost, the Kirchoff-type migration can obtain multiple outputs that have the same phase but different amplitudes, compared with that of other migration methods. The ratio of these amplitudes is helpful in computing some quantities such as reflection angle. I develop a seismic modeling and prestack depth migration method based on the Kirchhoff integral, that handles both laterally variant velocity and a dip beyond 90 degrees. The method uses a finite-difference algorithm to calculate travel times and WKBJ amplitudes for the Kirchhoff integral. Compared to ray-tracing algorithms, the finite-difference algorithm gives an efficient implementation and single-valued quantities (first arrivals) on output. In my finite difference algorithm, the upwind scheme is used to calculate travel times, and the Crank-Nicolson scheme is used to calculate amplitudes. Moreover, interpolation is applied to save computation cost. The modeling and migration algorithms require a smooth velocity function. I develop a velocity-smoothing technique based on damped least-squares to aid in obtaining a successful migration.

The constant displacement scheme for tracking particles in heterogeneous aquifers

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

Wen, X.H.; Gomez-Hernandez, J.J.

1996-01-01

Simulation of mass transport by particle tracking or random walk in highly heterogeneous media may be inefficient from a computational point of view if the traditional constant time step scheme is used. A new scheme which adjusts automatically the time step for each particle according to the local pore velocity, so that each particle always travels a constant distance, is shown to be computationally faster for the same degree of accuracy than the constant time step method. Using the constant displacement scheme, transport calculations in a 2-D aquifer model, with nature log-transmissivity variance of 4, can be 8.6 times fastermore » than using the constant time step scheme.« less

Neurally and Ocularly Informed Graph-Based Models for Searching 3D Environments

DTIC Science & Technology

2014-06-03

hBCI = hybrid brain–computer interface, TAG = transductive annotation by graph, CV = computer vision, TSP = traveling salesman problem . are navigated...environment that are most likely to contain objects that the subject would like to visit. 2.9. Route planning A traveling salesman problem (TSP) solver...fixations in a visual search task using fixation-related potentials J. Vis. 13 Croes G 1958 A method for solving traveling - salesman problems Oper. Res

SENSITIVITY OF HELIOSEISMIC TRAVEL TIMES TO THE IMPOSITION OF A LORENTZ FORCE LIMITER IN COMPUTATIONAL HELIOSEISMOLOGY

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

Moradi, Hamed; Cally, Paul S., E-mail: hamed.moradi@monash.edu

The rapid exponential increase in the Alfvén wave speed with height above the solar surface presents a serious challenge to physical modeling of the effects of magnetic fields on solar oscillations, as it introduces a significant Courant-Friedrichs-Lewy time-step constraint for explicit numerical codes. A common approach adopted in computational helioseismology, where long simulations in excess of 10 hr (hundreds of wave periods) are often required, is to cap the Alfvén wave speed by artificially modifying the momentum equation when the ratio between the Lorentz and hydrodynamic forces becomes too large. However, recent studies have demonstrated that the Alfvén wave speedmore » plays a critical role in the MHD mode conversion process, particularly in determining the reflection height of the upwardly propagating helioseismic fast wave. Using numerical simulations of helioseismic wave propagation in constant inclined (relative to the vertical) magnetic fields we demonstrate that the imposition of such artificial limiters significantly affects time-distance travel times unless the Alfvén wave-speed cap is chosen comfortably in excess of the horizontal phase speeds under investigation.« less

DEMONSTRATION OF THE ANALYTIC ELEMENT METHOD FOR WELLHEAD PROJECTION - PROJECT SUMMARY

EPA Science Inventory

A new computer program has been developed to determine time-of-travel capture zones in relatively simple geohydrological settings. The WhAEM package contains an analytic element model that uses superposition of (many) closed form analytical solutions to generate a ground-water fl...

Utilizing Traveler Demand Modeling to Predict Future Commercial Flight Schedules in the NAS

NASA Technical Reports Server (NTRS)

Viken, Jeff; Dollyhigh, Samuel; Smith, Jeremy; Trani, Antonio; Baik, Hojong; Hinze, Nicholas; Ashiabor, Senanu

2006-01-01

The current work incorporates the Transportation Systems Analysis Model (TSAM) to predict the future demand for airline travel. TSAM is a multi-mode, national model that predicts the demand for all long distance travel at a county level based upon population and demographics. The model conducts a mode choice analysis to compute the demand for commercial airline travel based upon the traveler s purpose of the trip, value of time, cost and time of the trip,. The county demand for airline travel is then aggregated (or distributed) to the airport level, and the enplanement demand at commercial airports is modeled. With the growth in flight demand, and utilizing current airline flight schedules, the Fratar algorithm is used to develop future flight schedules in the NAS. The projected flights can then be flown through air transportation simulators to quantify the ability of the NAS to meet future demand. A major strength of the TSAM analysis is that scenario planning can be conducted to quantify capacity requirements at individual airports, based upon different future scenarios. Different demographic scenarios can be analyzed to model the demand sensitivity to them. Also, it is fairly well know, but not well modeled at the airport level, that the demand for travel is highly dependent on the cost of travel, or the fare yield of the airline industry. The FAA projects the fare yield (in constant year dollars) to keep decreasing into the future. The magnitude and/or direction of these projections can be suspect in light of the general lack of airline profits and the large rises in airline fuel cost. Also, changes in travel time and convenience have an influence on the demand for air travel, especially for business travel. Future planners cannot easily conduct sensitivity studies of future demand with the FAA TAF data, nor with the Boeing or Airbus projections. In TSAM many factors can be parameterized and various demand sensitivities can be predicted for future travel. These resulting demand scenarios can be incorporated into future flight schedules, therefore providing a quantifiable demand for flights in the NAS for a range of futures. In addition, new future airline business scenarios are investigated that illustrate when direct flights can replace connecting flights and larger aircraft can be substituted, only when justified by demand.

pick_xwell, a program for interactive picking of crosswell seismic and radar data

USGS Publications Warehouse

Ellefsen, K.J.

1999-01-01

travel times can be plotted on the computer screen or printed to a file in postscript format. The program is written in the IDL programming language, and it is executed, in command-line mode, within the IDL program. The IDL program must be run from an X-window terminal that is connected to a computer with the Unix operating system. The data must be in the SU format.

Time-periodic solutions of the Benjamin-Ono equation

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

Ambrose , D.M.; Wilkening, Jon

2008-04-01

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

TRAVEL FORECASTER

NASA Technical Reports Server (NTRS)

Mauldin, L. E.

1994-01-01

Business travel planning within an organization is often a time-consuming task. Travel Forecaster is a menu-driven, easy-to-use program which plans, forecasts cost, and tracks actual vs. planned cost for business-related travel of a division or branch of an organization and compiles this information into a database to aid the travel planner. The program's ability to handle multiple trip entries makes it a valuable time-saving device. Travel Forecaster takes full advantage of relational data base properties so that information that remains constant, such as per diem rates and airline fares (which are unique for each city), needs entering only once. A typical entry would include selection with the mouse of the traveler's name and destination city from pop-up lists, and typed entries for number of travel days and purpose of the trip. Multiple persons can be selected from the pop-up lists and multiple trips are accommodated by entering the number of days by each appropriate month on the entry form. An estimated travel cost is not required of the user as it is calculated by a Fourth Dimension formula. With this information, the program can produce output of trips by month with subtotal and total cost for either organization or sub-entity of an organization; or produce outputs of trips by month with subtotal and total cost for international-only travel. It will also provide monthly and cumulative formats of planned vs. actual outputs in data or graph form. Travel Forecaster users can do custom queries to search and sort information in the database, and it can create custom reports with the user-friendly report generator. Travel Forecaster 1.1 is a database program for use with Fourth Dimension Runtime 2.1.1. It requires a Macintosh Plus running System 6.0.3 or later, 2Mb of RAM and a hard disk. The standard distribution medium for this package is one 3.5 inch 800K Macintosh format diskette. Travel Forecaster was developed in 1991. Macintosh is a registered trademark of Apple Computer, Inc. Fourth Dimension is a registered trademark of Acius, Inc.

20 CFR 617.46 - Travel allowance.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Travel allowance. 617.46 Section 617.46... FOR WORKERS UNDER THE TRADE ACT OF 1974 Relocation Allowances § 617.46 Travel allowance. (a) Computation. The amount of travel allowance (including lodging and meals) payable under § 617.45(a)(1) shall...

Link calibration against receiver calibration: an assessment of GPS time transfer uncertainties

NASA Astrophysics Data System (ADS)

Rovera, G. D.; Torre, J.-M.; Sherwood, R.; Abgrall, M.; Courde, C.; Laas-Bourez, M.; Uhrich, P.

2014-10-01

We present a direct comparison between two different techniques for the relative calibration of time transfer between remote time scales when using the signals transmitted by the Global Positioning System (GPS). Relative calibration estimates the delay of equipment or the delay of a time transfer link with respect to reference equipment. It is based on the circulation of some travelling GPS equipment between the stations in the network, against which the local equipment is measured. Two techniques can be considered: first a station calibration by the computation of the hardware delays of the local GPS equipment; second the computation of a global hardware delay offset for the time transfer between the reference points of two remote time scales. This last technique is called a ‘link’ calibration, with respect to the other one, which is a ‘receiver’ calibration. The two techniques require different measurements on site, which change the uncertainty budgets, and we discuss this and related issues. We report on one calibration campaign organized during Autumn 2013 between Observatoire de Paris (OP), Paris, France, Observatoire de la Côte d'Azur (OCA), Calern, France, and NERC Space Geodesy Facility (SGF), Herstmonceux, United Kingdom. The travelling equipment comprised two GPS receivers of different types, along with the required signal generator and distribution amplifier, and one time interval counter. We show the different ways to compute uncertainty budgets, leading to improvement factors of 1.2 to 1.5 on the hardware delay uncertainties when comparing the relative link calibration to the relative receiver calibration.

Path-Dependent Travel Time Prediction Variance and Covariance for a Global Tomographic P- and S-Velocity Model

NASA Astrophysics Data System (ADS)

Hipp, J. R.; Ballard, S.; Begnaud, M. L.; Encarnacao, A. V.; Young, C. J.; Phillips, W. S.

2015-12-01

Recently our combined SNL-LANL research team has succeeded in developing a global, seamless 3D tomographic P- and S-velocity model (SALSA3D) that provides superior first P and first S travel time predictions at both regional and teleseismic distances. However, given the variable data quality and uneven data sampling associated with this type of model, it is essential that there be a means to calculate high-quality estimates of the path-dependent variance and covariance associated with the predicted travel times of ray paths through the model. In this paper, we describe a methodology for accomplishing this by exploiting the full model covariance matrix and show examples of path-dependent travel time prediction uncertainty computed from our latest tomographic model. Typical global 3D SALSA3D models have on the order of 1/2 million nodes, so the challenge in calculating the covariance matrix is formidable: 0.9 TB storage for 1/2 of a symmetric matrix, necessitating an Out-Of-Core (OOC) blocked matrix solution technique. With our approach the tomography matrix (G which includes a prior model covariance constraint) is multiplied by its transpose (GTG) and written in a blocked sub-matrix fashion. We employ a distributed parallel solution paradigm that solves for (GTG)-1 by assigning blocks to individual processing nodes for matrix decomposition update and scaling operations. We first find the Cholesky decomposition of GTG which is subsequently inverted. Next, we employ OOC matrix multiplication methods to calculate the model covariance matrix from (GTG)-1 and an assumed data covariance matrix. Given the model covariance matrix, we solve for the travel-time covariance associated with arbitrary ray-paths by summing the model covariance along both ray paths. Setting the paths equal and taking the square root yields the travel prediction uncertainty for the single path.

Population movement can sustain STI prevalence in remote Australian indigenous communities.

PubMed

Hui, Ben B; Gray, Richard T; Wilson, David P; Ward, James S; Smith, Anthony M A; Philip, David J; Law, Matthew G; Hocking, Jane S; Regan, David G

2013-04-25

For almost two decades, chlamydia and gonorrhoea diagnosis rates in remote Indigenous communities have been up to 30 times higher than for non-Indigenous Australians. The high levels of population movement known to occur between remote communities may contribute to these high rates. We developed an individual-based computer simulation model to study the relationship between population movement and the persistence of gonorrhoea and chlamydia transmission within hypothetical remote communities. Results from our model suggest that short-term population movement can facilitate gonorrhoea and chlamydia persistence in small populations. By fixing the number of short-term travellers in accordance with census data, we found that these STIs can persist if at least 20% of individuals in the population seek additional partners while away from home and if the time away from home is less than 21 days. Periodic variations in travel patterns can contribute to increased sustainable levels of infection. Expanding existing STI testing and treatment programs to cater for short-term travellers is shown to be ineffective due to their short duration of stay. Testing and treatment strategies tailored to movement patterns, such as encouraging travellers to seek testing and treatment upon return from travel, will likely be more effective. High population mobility is likely to contribute to the high levels of STIs observed in remote Indigenous communities of Australia. More detailed data on mobility patterns and sexual behaviour of travellers will be invaluable for designing and assessing STI control programs in highly mobile communities.

7 CFR 3560.303 - Housing project budgets.

Code of Federal Regulations, 2010 CFR

2010-01-01

... personnel costs of permanent and part-time staff assigned directly to the project site. This includes... incentive or annual bonuses; (I) Direct costs of travel to off-site locations by on-site staff for property... computers are also included (if approved by the Agency). (J) Real estate taxes (personal tangible property...

WHAEM: PROGRAM DOCUMENTATION FOR THE WELLHEAD ANALYTIC ELEMENT MODEL (EPA/600/SR-94/210)

EPA Science Inventory

A new computer program has been developed to determine time-of-travel capture zones in relatively simple geohydrological settings. The WhAEM package contains an analytic element model that uses superposition of (many) closed form analytical solutions to generate a groundwater flo...

Three-Dimensional Simulation of Traveling-Wave Tube Cold-Test Characteristics Using CST MICROWAVE STUDIO

NASA Technical Reports Server (NTRS)

Chevalier, Christine T.; Herrmann, Kimberly A.; Kory, Carol L.; Wilson, Jeffrey D.; Cross, Andrew W.; Santana , Samuel

2003-01-01

The electromagnetic field simulation software package CST MICROWAVE STUDIO (MWS) was used to compute the cold-test parameters - frequency-phase dispersion, on-axis impedance, and attenuation - for a traveling-wave tube (TWT) slow-wave circuit. The results were compared to experimental data, as well as to results from MAFIA, another three-dimensional simulation code from CST currently used at the NASA Glenn Research Center (GRC). The strong agreement between cold-test parameters simulated with MWS and those measured experimentally demonstrates the potential of this code to reduce the time and cost of TWT development.

A traveling-salesman-based approach to aircraft scheduling in the terminal area

NASA Technical Reports Server (NTRS)

Luenberger, Robert A.

1988-01-01

An efficient algorithm is presented, based on the well-known algorithm for the traveling salesman problem, for scheduling aircraft arrivals into major terminal areas. The algorithm permits, but strictly limits, reassigning an aircraft from its initial position in the landing order. This limitation is needed so that no aircraft or aircraft category is unduly penalized. Results indicate, for the mix of arrivals investigated, a potential increase in capacity in the 3 to 5 percent range. Furthermore, it is shown that the computation time for the algorithm grows only linearly with problem size.

Road crash fatality rates in France: a comparison of road user types, taking account of travel practices.

PubMed

Bouaoun, Liacine; Haddak, Mohamed Mouloud; Amoros, Emmanuelle

2015-02-01

Travel practices are changing: bicycle and motorized two-wheeler (MTW) use are rising in some of France's large cities. These are cheaper modes of transport and therefore attractive at a time of economic crisis, but they also allow their users to avoid traffic congestion. At the same time, active transport modes such as walking and cycling are encouraged because they are beneficial to health and reduce pollution. It is therefore important to find out more about the road crash risks of the different modes of transport. To do this, we need to take account of the number of individuals who use each, and, even better, their travel levels. We estimated the exposure-based fatality rates for road traffic crashes in France, on the basis of the ratio between the number of fatalities and exposure to road accident risk. Fatality data were obtained from the French national police database of road traffic casualties in the period 2007-2008. Exposure data was estimated from the latest national household travel survey (ENTD) which was conducted from April 2007 to April 2008. Three quantities of travel were computed for each mode of transport: (1) the number of trips, (2) the distance traveled and (3) the time spent traveling. Annual fatality rates were assessed by road user type, age and sex. The overall annual fatality rates were 6.3 per 100 million trips, 5.8 per billion kilometers traveled and 0.20 per million hours spent traveling. The fatality rates differed according to road user type, age and sex. The risk of being killed was 20 to 32 times higher for motorized two-wheeler users than for car occupants. For cyclists, the risk of being killed, both on the basis of time spent traveling and the number of trips was about 1.5 times higher than for car occupants. Risk for pedestrians compared to car occupants was similar according to time spent traveling, lower according to the number of trips and higher according to the distance traveled. People from the 17-20 and 21-29 age groups and those aged 70 and over had the highest rates. Males had higher rates than females, by a factor of between 2 and 3. When exposure is taken into account, the risks for motorized two-wheeler users are extremely high compared to other types of road user. This disparity can be explained by the combination of speed and a lack of protection (except for helmets). The differential is so great that prevention measures could probably not eliminate it. The question that arises is as follows: with regard to public health, should not the use of MTW, or at least of motorcycles, be deterred? The difference between the fatality risk of cyclists and of car occupants is much smaller (1.5 times higher); besides, there is much room for improvements in cyclist safety, for instance by increasing the use of helmets and conspicuity equipment. Traffic calming could also benefit cyclists, pedestrians and perhaps moped users. Copyright © 2014 Elsevier Ltd. All rights reserved.

Traveling by Bus Instead of Car on Urban Major Roads: Safety Benefits for Vehicle Occupants, Pedestrians, and Cyclists.

PubMed

Morency, Patrick; Strauss, Jillian; Pépin, Félix; Tessier, François; Grondines, Jocelyn

2018-04-01

Some studies have estimated fatality and injury rates for bus occupants, but data was aggregated at the country level and made no distinction between bus types. Also, injured pedestrians and cyclists, as a result of bus travel, were overlooked. We compared injury rates for car and city bus occupants on specific urban major roads, as well as the cyclist and pedestrian injuries associated with car and bus travel. We selected ten bus routes along major urban arterials (in Montreal, Canada). Passenger-kilometers traveled were estimated from vehicle counts at intersections (2002-2010) and from bus passenger counts (2008). Police accident reports (2001-2010) provided injury data for all modes. Injury rates associated with car and bus travel were calculated for vehicle occupants, pedestrians, and cyclists. Injury rate ratios were also computed. The safety benefits of bus travel, defined as the number of vehicle occupant, cyclist, and pedestrian injuries saved, were estimated for each route. Overall, for all ten routes, the ratio between car and bus occupant injury rates is 3.7 (95% CI [3.4, 4.0]). The rates of pedestrian and cyclist injuries per hundred million passenger-kilometers are also significantly greater for car travel than that for bus travel: 4.1 (95% CI [3.5, 4.9]) times greater for pedestrian injuries; 5.3 (95% CI [3.8, 7.6]) times greater for cyclist injuries. Similar results were observed for fatally and severely injured vehicle occupants, cyclists, and pedestrians. At the route level, the safety benefits of bus travel increase with the difference in injury rate associated with car and bus travel but also with the amount of passenger-kilometers by bus. Results show that city bus is a safer mode than car, for vehicle occupants but also for cyclists and pedestrians traveling along these bus routes. The safety benefits of bus travel greatly vary across urban routes; this spatial variation is most likely linked to environmental factors. Understanding the safety benefits of public transit for specific transport routes is likely to provide valuable information for mobilizing city and transportation planners.

An Analysis of Delay and Travel Times at Sao Paulo International Airport (AISP/GRU): Planning Based on Simulation Model

NASA Technical Reports Server (NTRS)

Santana, Erico Soriano Martins; Mueller, Carlos

2003-01-01

The occurrence of flight delays in Brazil, mostly verified at the ground (airfield), is responsible for serious disruptions at the airport level but also for the unchaining of problems in all the airport system, affecting also the airspace. The present study develops an analysis of delay and travel times at Sao Paulo International Airport/ Guarulhos (AISP/GRU) airfield based on simulation model. Different airport physical and operational scenarios had been analyzed by means of simulation. SIMMOD Plus 4.0, the computational tool developed to represent aircraft operation in the airspace and airside of airports, was used to perform these analysis. The study was mainly focused on aircraft operations on ground, at the airport runway, taxi-lanes and aprons. The visualization of the operations with increasing demand facilitated the analyses. The results generated in this work certify the viability of the methodology, they also indicated the solutions capable to solve the delay problem by travel time analysis, thus diminishing the costs for users mainly airport authority. It also indicated alternatives for airport operations, assisting the decision-making process and in the appropriate timing of the proposed changes in the existing infrastructure.

Interpretation of a seismic refraction profile across the Roosevelt Hot Springs, Utah and vicinity

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

Gertson, R.C.; Smith, R.B.

1979-03-01

In April 1977, a seismic refraction profile was recorded across the Milford Valley, the Roosevelt Hot Springs KGRA, and the northern Mineral Mountains in southwestern Utah. Seven shot points were used to provide multiple subsurface seismic refraction coverage along the 30 km east-west profile line. Since an inspection of power spectrums revealed large components of 60 Hz noise on some traces, computer routines were used to low-pass filter all seismograms. Amplitude information was utilized by normalizing all traces that recorded the same blast. Subsurface structural modeling was conducted by means of first arrival P-wave delay-time analysis and ray tracing. Herglotz-Wiechertmore » travel-time inversion was used for the velocity-depth distribution in the Mineral Mountains. The interpretation of the P-wave travel-times suggests that the Milford Valley fill consists of two units with a total thickness of at least 1.8 km. In the vicinity of the Roosevelt KGRA, a thin low velocity alluvial layer covers a basement igneous complex with a velocity of 5.2 km/s. Granite velocities between 3.3 km/s and 4.0 km/s were calculated from the travel-times in the Mineral Mountains.« less

Travel time and concurrent-schedule choice: retrospective versus prospective control.

PubMed

Davison, M; Elliffe, D

2000-01-01

Six pigeons were trained on concurrent variable-interval schedules in which two different travel times between alternatives, 4.5 and 0.5 s, were randomly arranged. In Part 1, the next travel time was signaled while the subjects were responding on each alternative. Generalized matching analyses of performance in the presence of the two travel-time signals showed significantly higher response and time sensitivity when the longer travel time was signaled compared to when the shorter time was signaled. When the data were analyzed as a function of the previous travel time, there were no differences in sensitivity. Dwell times on the alternatives were consistently longer in the presence of the stimulus that signaled the longer travel time than they were in the presence of the stimulus that signaled the shorter travel time. These results are in accord with a recent quantitative account of the effects of travel time. In Part 2, no signals indicating the next travel time were given. When these data were analyzed as a function of the previous travel time, time-allocation sensitivity after the 4.5-s travel time was significantly greater than that after the 0.5-s travel time, but no such difference was found for response allocation. Dwell times were also longer when the previous travel time had been longer.

NAS Demand Predictions, Transportation Systems Analysis Model (TSAM) Compared with Other Forecasts

NASA Technical Reports Server (NTRS)

Viken, Jeff; Dollyhigh, Samuel; Smith, Jeremy; Trani, Antonio; Baik, Hojong; Hinze, Nicholas; Ashiabor, Senanu

2006-01-01

The current work incorporates the Transportation Systems Analysis Model (TSAM) to predict the future demand for airline travel. TSAM is a multi-mode, national model that predicts the demand for all long distance travel at a county level based upon population and demographics. The model conducts a mode choice analysis to compute the demand for commercial airline travel based upon the traveler s purpose of the trip, value of time, cost and time of the trip,. The county demand for airline travel is then aggregated (or distributed) to the airport level, and the enplanement demand at commercial airports is modeled. With the growth in flight demand, and utilizing current airline flight schedules, the Fratar algorithm is used to develop future flight schedules in the NAS. The projected flights can then be flown through air transportation simulators to quantify the ability of the NAS to meet future demand. A major strength of the TSAM analysis is that scenario planning can be conducted to quantify capacity requirements at individual airports, based upon different future scenarios. Different demographic scenarios can be analyzed to model the demand sensitivity to them. Also, it is fairly well know, but not well modeled at the airport level, that the demand for travel is highly dependent on the cost of travel, or the fare yield of the airline industry. The FAA projects the fare yield (in constant year dollars) to keep decreasing into the future. The magnitude and/or direction of these projections can be suspect in light of the general lack of airline profits and the large rises in airline fuel cost. Also, changes in travel time and convenience have an influence on the demand for air travel, especially for business travel. Future planners cannot easily conduct sensitivity studies of future demand with the FAA TAF data, nor with the Boeing or Airbus projections. In TSAM many factors can be parameterized and various demand sensitivities can be predicted for future travel. These resulting demand scenarios can be incorporated into future flight schedules, therefore providing a quantifiable demand for flights in the NAS for a range of futures. In addition, new future airline business scenarios are investigated that illustrate when direct flights can replace connecting flights and larger aircraft can be substituted, only when justified by demand.

Examining Hurricane Track Length and Stage Duration Since 1980

NASA Astrophysics Data System (ADS)

Fandrich, K. M.; Pennington, D.

2017-12-01

Each year, tropical systems impact thousands of people worldwide. Current research shows a correlation between the intensity and frequency of hurricanes and the changing climate. However, little is known about other prominent hurricane features. This includes information about hurricane track length (the total distance traveled from tropical depression through a hurricane's final category assignment) and how this distance may have changed with time. Also unknown is the typical duration of a hurricane stage, such as tropical storm to category one, and if the time spent in each stage has changed in recent decades. This research aims to examine changes in hurricane stage duration and track lengths for the 319 storms in NOAA's National Ocean Service Hurricane Reanalysis dataset that reached Category 2 - 5 from 1980 - 2015. Based on evident ocean warming, it is hypothesized that a general increase in track length with time will be detected, thus modern hurricanes are traveling a longer distance than past hurricanes. It is also expected that stage durations are decreasing with time so that hurricanes mature faster than in past decades. For each storm, coordinates are acquired at 4-times daily intervals throughout its duration and track lengths are computed for each 6-hour period. Total track lengths are then computed and storms are analyzed graphically and statistically by category for temporal track length changes. The stage durations of each storm are calculated as the time difference between two consecutive stages. Results indicate that average track lengths for Cat 2 and 3 hurricanes are increasing through time. These findings show that these hurricanes are traveling a longer distance than earlier Cat 2 and 3 hurricanes. In contrast, average track lengths for Cat 4 and 5 hurricanes are decreasing through time, showing less distance traveled than earlier decades. Stage durations for all Cat 2, 4 and 5 storms decrease through the decades but Cat 3 storms show a positive increase though time. This compliments the results of the track length analysis indicating that as storms intensify faster, they are doing so over a shorter distance. It is expected that this research could be used to improve hurricane track forecasting and provide information about the effects of climate change on tropical systems and the tropical environment.

Is Travel Time to Colonoscopy Associated With Late-Stage Colorectal Cancer Among Medicare Beneficiaries in Iowa?

PubMed

Charlton, Mary E; Matthews, Kevin A; Gaglioti, Anne; Bay, Camden; McDowell, Bradley D; Ward, Marcia M; Levy, Barcey T

2016-09-01

Colorectal cancer (CRC) screening has been shown to decrease the incidence of late-stage colorectal cancer, yet a substantial proportion of Americans do not receive screening. Those in rural areas may face barriers to colonoscopy services based on travel time, and previous studies have demonstrated lower screening among rural residents. Our purpose was to assess factors associated with late-stage CRC, and specifically to determine if longer travel time to colonoscopy was associated with late-stage CRC among an insured population in Iowa. SEER-Medicare data were used to identify individuals ages 65 to 84 years old diagnosed with CRC in Iowa from 2002 to 2009. The distance between the centroid of the ZIP code of residence and the ZIP code of colonoscopy was computed for each individual who had continuous Medicare fee-for-service coverage for a 3- to 4-month period prior to diagnosis, and a professional claim for colonoscopy within that time frame. Demographic characteristics and travel times were compared between those diagnosed with early- versus late-stage CRC. Also, demographic differences between those who had colonoscopy claims identified within 3-4 months prior to diagnosis (81%) were compared to patients with no colonoscopy claims identified (19%). A total of 5,792 subjects met inclusion criteria; 31% were diagnosed with early-stage versus 69% with late-stage CRC. Those divorced or widowed (vs married) were more likely to be diagnosed with late-stage CRC (OR: 1.20, 95% CI: 1.06-1.37). Travel time was not associated with diagnosis of late-stage CRC. Among a Medicare-insured population, there was no relationship between travel time to colonoscopy and disease stage at diagnosis. It is likely that factors other than distance to colonoscopy present more pertinent barriers to screening in this insured population. Additional research should be done to determine reasons for nonadherence to screening among those with access to CRC screening services, given that over two-thirds of these insured individuals were diagnosed with late-stage CRC. © 2015 National Rural Health Association.

The time machine in our mind.

PubMed

Stocker, Kurt

2012-04-01

This article provides the first comprehensive conceptual account for the imagistic mental machinery that allows us to travel through time--for the time machine in our mind. It is argued that language reveals this imagistic machine and how we use it. Findings from a range of cognitive fields are theoretically unified and a recent proposal about spatialized mental time travel is elaborated on. The following novel distinctions are offered: external versus internal viewing of time; ''watching" time versus projective ''travel" through time; optional versus obligatory mental time travel; mental time travel into anteriority or posteriority versus mental time travel into the past or future; single mental time travel versus nested dual mental time travel; mental time travel in episodic memory versus mental time travel in semantic memory; and ''seeing" versus ''sensing" mental imagery. Theoretical, empirical, and applied implications are discussed. Copyright © 2012 Cognitive Science Society, Inc.

Evaluation of the capability of local helioseismology to discern between monolithic and spaghetti sunspot models

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

Felipe, T.; Crouch, A. D.; Birch, A. C., E-mail: tobias@nwra.com

2014-06-20

The helioseismic properties of the wave scattering generated by monolithic and spaghetti sunspots are analyzed by means of numerical simulations. In these computations, an incident f- or p {sub 1}-mode travels through the sunspot model, which produces absorption and phase shift of the waves. The scattering is studied by inspecting the wavefield, computing travel-time shifts, and performing Fourier-Hankel analysis. The comparison between the results obtained for both sunspot models reveals that the differences in the absorption coefficient can be detected above noise level. The spaghetti model produces a steep increase of the phase shift with the degree of the modemore » at short wavelengths, while mode mixing is more efficient for the monolithic model. These results provide a clue for what to look for in solar observations to discern the constitution of sunspots between the proposed monolithic and spaghetti models.« less

Battery cars on superconducting magnetically levitated carriers: One commuting solution

NASA Technical Reports Server (NTRS)

Briggs, B. Mike; Oman, Henry

1992-01-01

Commuting to work in an urban-suburban metropolitan environment is becoming an unpleasant time-wasting process. We applied the technology of communication management to this commuting problem. Communication management is a system-engineering tool that produced today's efficient telephone network. The resulting best commuting option is magnetically levitated carriers of two-passenger, battery-powered, personally-owned local-travel cars. A commuter drives a car to a nearby station, selects a destination, drives on a waiting carrier, and enters an accelerating ramp. A central computer selects an optimum 100 miles-per-hour trunk route, considering existing and forecast traffic; assigns the commuter a travel slot, and subsequently orders switching-station actions. The commuter uses the expensive facilities for only a few minutes during each trip. The cost of travel could be less than 6 cents per mile.

Integrating information about location and value of resources by white-faced saki monkeys (Pithecia pithecia).

PubMed

Cunningham, Elena; Janson, Charles

2007-07-01

Most studies of spatial memory in primates focus on species that inhabit large home ranges and have dispersed, patchy resources. Researchers assume that primates use memory to minimize distances traveled between resources. We investigated the use of spatial memory in a group of six white-faced sakis (Pithecia pithecia) on 12.8-ha Round Island, Guri Lake, Venezuela during a period of fruit abundance. The sakis' movements were analyzed with logistic regressions, a predictive computer model and a computer model that simulates movements. We considered all the resources available to the sakis and compared observed distances to predicted distances from a computer model for foragers who know nothing about the location of resources. Surprisingly, the observed distances were four times greater than the predicted distances, suggesting that the sakis passed by a majority of the available fruit trees without feeding. The odds of visiting a food tree, however, were significantly increased if the tree had been visited in the previous 3 days and had more than 100 fruit. The sakis' preferred resources were highly productive fruit trees, Capparis trees, and trees with water holes. They traveled efficiently to these sites. The sakis choice of feeding sites indicate that they combined knowledge acquired by repeatedly traveling through their home range with 'what' and 'where' information gained from individual visits to resources. Although the sakis' foraging choices increased the distance they traveled overall, choosing more valued sites allowed the group to minimize intra-group feeding competition, maintain intergroup dominance over important resources, and monitor the state of resources throughout their home range. The sakis' foraging decisions appear to have used spatial memory, elements of episodic-like memory and social and nutritional considerations.

Human Performance on Hard Non-Euclidean Graph Problems: Vertex Cover

ERIC Educational Resources Information Center

Carruthers, Sarah; Masson, Michael E. J.; Stege, Ulrike

2012-01-01

Recent studies on a computationally hard visual optimization problem, the Traveling Salesperson Problem (TSP), indicate that humans are capable of finding close to optimal solutions in near-linear time. The current study is a preliminary step in investigating human performance on another hard problem, the Minimum Vertex Cover Problem, in which…

Travel in Time: Tradition to Technology. Proceedings of the 1985 ABC International Convention (Chicago, Illinois, October 1985).

ERIC Educational Resources Information Center

Bruno, Sam J., Ed.; Pettit, John D., Jr., Ed.

These conference proceedings contain the following 23 presentations: "Development of a Communication Skill Model Using Interpretive Structural Modeling" (Karen S. Nantz and Linda Gammill); "The Coincidence of Needs: An Inventional Model for Audience Analysis" (Gina Burchard); "A Computer Algorithm for Measuring Readability" (Terry D. Lundgren);…

Heterogeneous Data Fusion Method to Estimate Travel Time Distributions in Congested Road Networks

PubMed Central

Lam, William H. K.; Li, Qingquan

2017-01-01

Travel times in congested urban road networks are highly stochastic. Provision of travel time distribution information, including both mean and variance, can be very useful for travelers to make reliable path choice decisions to ensure higher probability of on-time arrival. To this end, a heterogeneous data fusion method is proposed to estimate travel time distributions by fusing heterogeneous data from point and interval detectors. In the proposed method, link travel time distributions are first estimated from point detector observations. The travel time distributions of links without point detectors are imputed based on their spatial correlations with links that have point detectors. The estimated link travel time distributions are then fused with path travel time distributions obtained from the interval detectors using Dempster-Shafer evidence theory. Based on fused path travel time distribution, an optimization technique is further introduced to update link travel time distributions and their spatial correlations. A case study was performed using real-world data from Hong Kong and showed that the proposed method obtained accurate and robust estimations of link and path travel time distributions in congested road networks. PMID:29210978

Heterogeneous Data Fusion Method to Estimate Travel Time Distributions in Congested Road Networks.

PubMed

Shi, Chaoyang; Chen, Bi Yu; Lam, William H K; Li, Qingquan

2017-12-06

Travel times in congested urban road networks are highly stochastic. Provision of travel time distribution information, including both mean and variance, can be very useful for travelers to make reliable path choice decisions to ensure higher probability of on-time arrival. To this end, a heterogeneous data fusion method is proposed to estimate travel time distributions by fusing heterogeneous data from point and interval detectors. In the proposed method, link travel time distributions are first estimated from point detector observations. The travel time distributions of links without point detectors are imputed based on their spatial correlations with links that have point detectors. The estimated link travel time distributions are then fused with path travel time distributions obtained from the interval detectors using Dempster-Shafer evidence theory. Based on fused path travel time distribution, an optimization technique is further introduced to update link travel time distributions and their spatial correlations. A case study was performed using real-world data from Hong Kong and showed that the proposed method obtained accurate and robust estimations of link and path travel time distributions in congested road networks.

Travel-time source-specific station correction improves location accuracy

NASA Astrophysics Data System (ADS)

Giuntini, Alessandra; Materni, Valerio; Chiappini, Stefano; Carluccio, Roberto; Console, Rodolfo; Chiappini, Massimo

2013-04-01

Accurate earthquake locations are crucial for investigating seismogenic processes, as well as for applications like verifying compliance to the Comprehensive Test Ban Treaty (CTBT). Earthquake location accuracy is related to the degree of knowledge about the 3-D structure of seismic wave velocity in the Earth. It is well known that modeling errors of calculated travel times may have the effect of shifting the computed epicenters far from the real locations by a distance even larger than the size of the statistical error ellipses, regardless of the accuracy in picking seismic phase arrivals. The consequences of large mislocations of seismic events in the context of the CTBT verification is particularly critical in order to trigger a possible On Site Inspection (OSI). In fact, the Treaty establishes that an OSI area cannot be larger than 1000 km2, and its larger linear dimension cannot be larger than 50 km. Moreover, depth accuracy is crucial for the application of the depth event screening criterion. In the present study, we develop a method of source-specific travel times corrections based on a set of well located events recorded by dense national seismic networks in seismically active regions. The applications concern seismic sequences recorded in Japan, Iran and Italy. We show that mislocations of the order of 10-20 km affecting the epicenters, as well as larger mislocations in hypocentral depths, calculated from a global seismic network and using the standard IASPEI91 travel times can be effectively removed by applying source-specific station corrections.

Catchment Dispersion Mechanisms in an Urban Context

NASA Astrophysics Data System (ADS)

Gironas, J. A.; Mejia, A.; Rossel, F.; Rinaldo, A.; Rodriguez, F.

2014-12-01

Dispersion mechanisms have been examined in-depth in natural catchments in previous studies. However, these dispersion mechanisms have been studied little in urban catchments, where artificial transport elements and morphological arrangements are expected to modify travel times and mobilize excess rainfall from spatially distributed impervious sites. Thus, these features can modify the variance of the catchment's travel times and hence the total dispersion. This work quantifies the dispersion mechanisms in an urban catchment using the theory of transport by travel times as represented by the Urban Morpho-climatic Instantaneous Unit Hydrograph (U-McIUH) model. This model computes travel times based on kinematic wave theory and accounts explicitly for the path heterogeneities and altered connectivity patterns characteristic of an urban drainage network. The analysis is illustrated using the Aubinière urban catchment (France) as a case study. We found that kinematic dispersion is dominant for small rainfall intensities, whereas geomorphologic dispersion becomes more dominant for larger intensities. The total dispersion scales with the drainage area in a power law fashion. The kinematic dispersion is dominant across spatial scales up to a threshold of approximately 2-3 km2, after which the geomorphologic dispersion becomes more dominant. Overall, overland flow is responsible for most of the dispersion, while conduits tend to counteract the increase of the geomorphologic dispersion with a negative kinematic dispersion. Further studies with other catchments are needed to assess whether the latter is a general feature of urban drainage networks.

Spatial characterization of catchment dispersion mechanisms in an urban context

NASA Astrophysics Data System (ADS)

Rossel, Florian; Gironás, Jorge; Mejía, Alfonso; Rinaldo, Andrea; Rodriguez, Fabrice

2014-12-01

Previous studies have examined in-depth the dispersion mechanisms in natural catchments. In contrast, these dispersion mechanisms have been studied little in urban catchments, where artificial transport elements and morphological arrangements are expected to modify travel times and mobilize excess rainfall from spatially distributed impervious sites. This has the ability to modify the variance of the catchment's travel times and hence the total dispersion. This work quantifies the dispersion mechanisms in an urban catchment using the theory of transport by travel times as represented by the Urban Morpho-climatic Instantaneous Unit Hydrograph (U-McIUH) model. The U-McIUH computes travel times based on kinematic wave theory and accounts explicitly for the path heterogeneities and altered connectivity patterns characteristic of an urban drainage network. The analysis is illustrated using the Aubinière urban catchment in France as a case study. We found that kinematic dispersion is dominant for small rainfall intensities, whereas geomorphologic dispersion becomes more dominant for larger intensities. The total dispersion scales with the drainage area in a power law fashion. The kinematic dispersion is dominant across spatial scales up to a threshold of approximately 2-3 km2, after which the geomorphologic dispersion becomes more dominant. Overall, overland flow is responsible for most of the dispersion in the catchment, while conduits tend to counteract the increase of the geomorphologic dispersion with a negative kinematic dispersion. Further study with other catchments is needed to asses if the latter is a general feature of urban drainage networks.

Travel demand forecasting models: a comparison of EMME/2 and QUR II using a real-world network.

DOT National Transportation Integrated Search

2000-10-01

In order to automate the travel demand forecasting process in urban transportation planning, a number of : commercial computer based travel demand forecasting models have been developed, which have provided : transportation planners with powerful and...

Development of seismic tomography software for hybrid supercomputers

NASA Astrophysics Data System (ADS)

Nikitin, Alexandr; Serdyukov, Alexandr; Duchkov, Anton

2015-04-01

Seismic tomography is a technique used for computing velocity model of geologic structure from first arrival travel times of seismic waves. The technique is used in processing of regional and global seismic data, in seismic exploration for prospecting and exploration of mineral and hydrocarbon deposits, and in seismic engineering for monitoring the condition of engineering structures and the surrounding host medium. As a consequence of development of seismic monitoring systems and increasing volume of seismic data, there is a growing need for new, more effective computational algorithms for use in seismic tomography applications with improved performance, accuracy and resolution. To achieve this goal, it is necessary to use modern high performance computing systems, such as supercomputers with hybrid architecture that use not only CPUs, but also accelerators and co-processors for computation. The goal of this research is the development of parallel seismic tomography algorithms and software package for such systems, to be used in processing of large volumes of seismic data (hundreds of gigabytes and more). These algorithms and software package will be optimized for the most common computing devices used in modern hybrid supercomputers, such as Intel Xeon CPUs, NVIDIA Tesla accelerators and Intel Xeon Phi co-processors. In this work, the following general scheme of seismic tomography is utilized. Using the eikonal equation solver, arrival times of seismic waves are computed based on assumed velocity model of geologic structure being analyzed. In order to solve the linearized inverse problem, tomographic matrix is computed that connects model adjustments with travel time residuals, and the resulting system of linear equations is regularized and solved to adjust the model. The effectiveness of parallel implementations of existing algorithms on target architectures is considered. During the first stage of this work, algorithms were developed for execution on supercomputers using multicore CPUs only, with preliminary performance tests showing good parallel efficiency on large numerical grids. Porting of the algorithms to hybrid supercomputers is currently ongoing.

Improved work zone design guidelines and enhanced model of travel delays in work zones : Phase I, portability and scalability of interarrival and service time probability distribution functions for different locations in Ohio and the establishment of impr

DOT National Transportation Integrated Search

2006-01-01

The project focuses on two major issues - the improvement of current work zone design practices and an analysis of : vehicle interarrival time (IAT) and speed distributions for the development of a digital computer simulation model for : queues and t...

Rapid Human-Computer Interactive Conceptual Design of Mobile and Manipulative Robot Systems

DTIC Science & Technology

2015-05-19

algorithm based on Age-Fitness Pareto Optimization (AFPO) ([9]) with an additional user prefer- ence objective and a neural network-based user model, we...greater than 40, which is about 5 times further than any robot traveled in our experiments. 6 3.3 Methods The algorithm uses a client -server computational...architecture. The client here is an interactive pro- gram which takes a pair of controllers as input, simulates4 two copies of the robot with

Discrete-State Simulated Annealing For Traveling-Wave Tube Slow-Wave Circuit Optimization

NASA Technical Reports Server (NTRS)

Wilson, Jeffrey D.; Bulson, Brian A.; Kory, Carol L.; Williams, W. Dan (Technical Monitor)

2001-01-01

Algorithms based on the global optimization technique of simulated annealing (SA) have proven useful in designing traveling-wave tube (TWT) slow-wave circuits for high RF power efficiency. The characteristic of SA that enables it to determine a globally optimized solution is its ability to accept non-improving moves in a controlled manner. In the initial stages of the optimization, the algorithm moves freely through configuration space, accepting most of the proposed designs. This freedom of movement allows non-intuitive designs to be explored rather than restricting the optimization to local improvement upon the initial configuration. As the optimization proceeds, the rate of acceptance of non-improving moves is gradually reduced until the algorithm converges to the optimized solution. The rate at which the freedom of movement is decreased is known as the annealing or cooling schedule of the SA algorithm. The main disadvantage of SA is that there is not a rigorous theoretical foundation for determining the parameters of the cooling schedule. The choice of these parameters is highly problem dependent and the designer needs to experiment in order to determine values that will provide a good optimization in a reasonable amount of computational time. This experimentation can absorb a large amount of time especially when the algorithm is being applied to a new type of design. In order to eliminate this disadvantage, a variation of SA known as discrete-state simulated annealing (DSSA), was recently developed. DSSA provides the theoretical foundation for a generic cooling schedule which is problem independent, Results of similar quality to SA can be obtained, but without the extra computational time required to tune the cooling parameters. Two algorithm variations based on DSSA were developed and programmed into a Microsoft Excel spreadsheet graphical user interface (GUI) to the two-dimensional nonlinear multisignal helix traveling-wave amplifier analysis program TWA3. The algorithms were used to optimize the computed RF efficiency of a TWT by determining the phase velocity profile of the slow-wave circuit. The mathematical theory and computational details of the DSSA algorithms will be presented and results will be compared to those obtained with a SA algorithm.

Colored Traveling Salesman Problem.

PubMed

Li, Jun; Zhou, MengChu; Sun, Qirui; Dai, Xianzhong; Yu, Xiaolong

2015-11-01

The multiple traveling salesman problem (MTSP) is an important combinatorial optimization problem. It has been widely and successfully applied to the practical cases in which multiple traveling individuals (salesmen) share the common workspace (city set). However, it cannot represent some application problems where multiple traveling individuals not only have their own exclusive tasks but also share a group of tasks with each other. This work proposes a new MTSP called colored traveling salesman problem (CTSP) for handling such cases. Two types of city groups are defined, i.e., each group of exclusive cities of a single color for a salesman to visit and a group of shared cities of multiple colors allowing all salesmen to visit. Evidences show that CTSP is NP-hard and a multidepot MTSP and multiple single traveling salesman problems are its special cases. We present a genetic algorithm (GA) with dual-chromosome coding for CTSP and analyze the corresponding solution space. Then, GA is improved by incorporating greedy, hill-climbing (HC), and simulated annealing (SA) operations to achieve better performance. By experiments, the limitation of the exact solution method is revealed and the performance of the presented GAs is compared. The results suggest that SAGA can achieve the best quality of solutions and HCGA should be the choice making good tradeoff between the solution quality and computing time.

Revision of earthquake hypocentre locations in global bulletin data sets using source-specific station terms

NASA Astrophysics Data System (ADS)

Nooshiri, Nima; Saul, Joachim; Heimann, Sebastian; Tilmann, Frederik; Dahm, Torsten

2017-02-01

Global earthquake locations are often associated with very large systematic travel-time residuals even for clear arrivals, especially for regional and near-regional stations in subduction zones because of their strongly heterogeneous velocity structure. Travel-time corrections can drastically reduce travel-time residuals at regional stations and, in consequence, improve the relative location accuracy. We have extended the shrinking-box source-specific station terms technique to regional and teleseismic distances and adopted the algorithm for probabilistic, nonlinear, global-search location. We evaluated the potential of the method to compute precise relative hypocentre locations on a global scale. The method has been applied to two specific test regions using existing P- and pP-phase picks. The first data set consists of 3103 events along the Chilean margin and the second one comprises 1680 earthquakes in the Tonga-Fiji subduction zone. Pick data were obtained from the GEOFON earthquake bulletin, produced using data from all available, global station networks. A set of timing corrections varying as a function of source position was calculated for each seismic station. In this way, we could correct the systematic errors introduced into the locations by the inaccuracies in the assumed velocity structure without explicitly solving for a velocity model. Residual statistics show that the median absolute deviation of the travel-time residuals is reduced by 40-60 per cent at regional distances, where the velocity anomalies are strong. Moreover, the spread of the travel-time residuals decreased by ˜20 per cent at teleseismic distances (>28°). Furthermore, strong variations in initial residuals as a function of recording distance are smoothed out in the final residuals. The relocated catalogues exhibit less scattered locations in depth and sharper images of the seismicity associated with the subducting slabs. Comparison with a high-resolution local catalogue reveals that our relocation process significantly improves the hypocentre locations compared to standard locations.

Improved Phase Corrections for Transoceanic Tsunami Data in Spatial and Temporal Source Estimation: Application to the 2011 Tohoku Earthquake

NASA Astrophysics Data System (ADS)

Ho, Tung-Cheng; Satake, Kenji; Watada, Shingo

2017-12-01

Systemic travel time delays of up to 15 min relative to the linear long waves for transoceanic tsunamis have been reported. A phase correction method, which converts the linear long waves into dispersive waves, was previously proposed to consider seawater compressibility, the elasticity of the Earth, and gravitational potential change associated with tsunami motion. In the present study, we improved this method by incorporating the effects of ocean density stratification, actual tsunami raypath, and actual bathymetry. The previously considered effects amounted to approximately 74% for correction of the travel time delay, while the ocean density stratification, actual raypath, and actual bathymetry, contributed to approximately 13%, 4%, and 9% on average, respectively. The improved phase correction method accounted for almost all the travel time delay at far-field stations. We performed single and multiple time window inversions for the 2011 Tohoku tsunami using the far-field data (>3 h travel time) to investigate the initial sea surface displacement. The inversion result from only far-field data was similar to but smoother than that from near-field data and all stations, including a large sea surface rise increasing toward the trench followed by a migration northward along the trench. For the forward simulation, our results showed good agreement between the observed and computed waveforms at both near-field and far-field tsunami gauges, as well as with satellite altimeter data. The present study demonstrates that the improved method provides a more accurate estimate for the waveform inversion and forward prediction of far-field data.

5 CFR 550.1404 - Creditable travel time.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Creditable travel time. 550.1404 Section... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1404 Creditable travel time. (a) General. Subject... off for time in a travel status if— (1) The employee is required to travel away from the official duty...

5 CFR 550.1404 - Creditable travel time.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 5 Administrative Personnel 1 2014-01-01 2014-01-01 false Creditable travel time. 550.1404 Section... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1404 Creditable travel time. (a) General. Subject... off for time in a travel status if— (1) The employee is required to travel away from the official duty...

5 CFR 550.1404 - Creditable travel time.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 5 Administrative Personnel 1 2013-01-01 2013-01-01 false Creditable travel time. 550.1404 Section... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1404 Creditable travel time. (a) General. Subject... off for time in a travel status if— (1) The employee is required to travel away from the official duty...

5 CFR 550.1404 - Creditable travel time.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Creditable travel time. 550.1404 Section... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1404 Creditable travel time. (a) General. Subject... off for time in a travel status if— (1) The employee is required to travel away from the official duty...

5 CFR 550.1404 - Creditable travel time.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Creditable travel time. 550.1404 Section... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1404 Creditable travel time. (a) General. Subject... off for time in a travel status if— (1) The employee is required to travel away from the official duty...

Travel Mode Detection with Varying Smartphone Data Collection Frequencies

PubMed Central

Shafique, Muhammad Awais; Hato, Eiji

2016-01-01

Smartphones are becoming increasingly popular day-by-day. Modern smartphones are more than just calling devices. They incorporate a number of high-end sensors that provide many new dimensions to smartphone experience. The use of smartphones, however, can be extended from the usual telecommunication field to applications in other specialized fields including transportation. Sensors embedded in the smartphones like GPS, accelerometer and gyroscope can collect data passively, which in turn can be processed to infer the travel mode of the smartphone user. This will solve most of the shortcomings associated with conventional travel survey methods including biased response, no response, erroneous time recording, etc. The current study uses the sensors’ data collected by smartphones to extract nine features for classification. Variables including data frequency, moving window size and proportion of data to be used for training, are dealt with to achieve better results. Random forest is used to classify the smartphone data among six modes. An overall accuracy of 99.96% is achieved, with no mode less than 99.8% for data collected at 10 Hz frequency. The accuracy is observed to decrease with decrease in data frequency, but at the same time the computation time also decreases. PMID:27213380

Cortical travelling waves: mechanisms and computational principles

PubMed Central

Muller, Lyle; Chavane, Frédéric; Reynolds, John

2018-01-01

Multichannel recording technologies have revealed travelling waves of neural activity in multiple sensory, motor and cognitive systems. These waves can be spontaneously generated by recurrent circuits or evoked by external stimuli. They travel along brain networks at multiple scales, transiently modulating spiking and excitability as they pass. Here, we review recent experimental findings that have found evidence for travelling waves at single-area (mesoscopic) and whole-brain (macroscopic) scales. We place these findings in the context of the current theoretical understanding of wave generation and propagation in recurrent networks. During the large low-frequency rhythms of sleep or the relatively desynchronized state of the awake cortex, travelling waves may serve a variety of functions, from long-term memory consolidation to processing of dynamic visual stimuli. We explore new avenues for experimental and computational understanding of the role of spatiotemporal activity patterns in the cortex. PMID:29563572

TARCMO: Theory and Algorithms for Robust, Combinatorial, Multicriteria Optimization

DTIC Science & Technology

2016-11-28

objective 9 4.6 On The Recoverable Robust Traveling Salesman Problem . . . . . 11 4.7 A Bicriteria Approach to Robust Optimization...be found. 4.6 On The Recoverable Robust Traveling Salesman Problem The traveling salesman problem (TSP) is a well-known combinatorial optimiza- tion...procedure for the robust traveling salesman problem . While this iterative algorithms results in an optimal solution to the robust TSP, computation

Estimating crustal heterogeneity from double-difference tomography

USGS Publications Warehouse

Got, J.-L.; Monteiller, V.; Virieux, J.; Okubo, P.

2006-01-01

Seismic velocity parameters in limited, but heterogeneous volumes can be inferred using a double-difference tomographic algorithm, but to obtain meaningful results accuracy must be maintained at every step of the computation. MONTEILLER et al. (2005) have devised a double-difference tomographic algorithm that takes full advantage of the accuracy of cross-spectral time-delays of large correlated event sets. This algorithm performs an accurate computation of theoretical travel-time delays in heterogeneous media and applies a suitable inversion scheme based on optimization theory. When applied to Kilauea Volcano, in Hawaii, the double-difference tomography approach shows significant and coherent changes to the velocity model in the well-resolved volumes beneath the Kilauea caldera and the upper east rift. In this paper, we first compare the results obtained using MONTEILLER et al.'s algorithm with those obtained using the classic travel-time tomographic approach. Then, we evaluated the effect of using data series of different accuracies, such as handpicked arrival-time differences ("picking differences"), on the results produced by double-difference tomographic algorithms. We show that picking differences have a non-Gaussian probability density function (pdf). Using a hyperbolic secant pdf instead of a Gaussian pdf allows improvement of the double-difference tomographic result when using picking difference data. We completed our study by investigating the use of spatially discontinuous time-delay data. ?? Birkha??user Verlag, Basel, 2006.

Validation of travel times to hospital estimated by GIS.

PubMed

Haynes, Robin; Jones, Andrew P; Sauerzapf, Violet; Zhao, Hongxin

2006-09-19

An increasing number of studies use GIS estimates of car travel times to health services, without presenting any evidence that the estimates are representative of real travel times. This investigation compared GIS estimates of travel times with the actual times reported by a sample of 475 cancer patients who had travelled by car to attend clinics at eight hospitals in the North of England. Car travel times were estimated by GIS using the shortest road route between home address and hospital and average speed assumptions. These estimates were compared with reported journey times and straight line distances using graphical, correlation and regression techniques. There was a moderately strong association between reported times and estimated travel times (r = 0.856). Reported travel times were similarly related to straight line distances. Altogether, 50% of travel time estimates were within five minutes of the time reported by respondents, 77% were within ten minutes and 90% were within fifteen minutes. The distribution of over- and under-estimates was symmetrical, but estimated times tended to be longer than reported times with increasing distance from hospital. Almost all respondents rounded their travel time to the nearest five or ten minutes. The reason for many cases of reported journey times exceeding the estimated times was confirmed by respondents' comments as traffic congestion. GIS estimates of car travel times were moderately close approximations to reported times. GIS travel time estimates may be superior to reported travel times for modelling purposes because reported times contain errors and can reflect unusual circumstances. Comparison with reported times did not suggest that estimated times were a more sensitive measure than straight line distance.

Towards an accurate real-time locator of infrasonic sources

NASA Astrophysics Data System (ADS)

Pinsky, V.; Blom, P.; Polozov, A.; Marcillo, O.; Arrowsmith, S.; Hofstetter, A.

2017-11-01

Infrasonic signals propagate from an atmospheric source via media with stochastic and fast space-varying conditions. Hence, their travel time, the amplitude at sensor recordings and even manifestation in the so-called "shadow zones" are random. Therefore, the traditional least-squares technique for locating infrasonic sources is often not effective, and the problem for the best solution must be formulated in probabilistic terms. Recently, a series of papers has been published about Bayesian Infrasonic Source Localization (BISL) method based on the computation of the posterior probability density function (PPDF) of the source location, as a convolution of a priori probability distribution function (APDF) of the propagation model parameters with likelihood function (LF) of observations. The present study is devoted to the further development of BISL for higher accuracy and stability of the source location results and decreasing of computational load. We critically analyse previous algorithms and propose several new ones. First of all, we describe the general PPDF formulation and demonstrate that this relatively slow algorithm might be among the most accurate algorithms, provided the adequate APDF and LF are used. Then, we suggest using summation instead of integration in a general PPDF calculation for increased robustness, but this leads us to the 3D space-time optimization problem. Two different forms of APDF approximation are considered and applied for the PPDF calculation in our study. One of them is previously suggested, but not yet properly used is the so-called "celerity-range histograms" (CRHs). Another is the outcome from previous findings of linear mean travel time for the four first infrasonic phases in the overlapping consecutive distance ranges. This stochastic model is extended here to the regional distance of 1000 km, and the APDF introduced is the probabilistic form of the junction between this travel time model and range-dependent probability distributions of the phase arrival time picks. To illustrate the improvements in both computation time and location accuracy achieved, we compare location results for the new algorithms, previously published BISL-type algorithms and the least-squares location technique. This comparison is provided via a case study of different typical spatial data distributions and statistical experiment using the database of 36 ground-truth explosions from the Utah Test and Training Range (UTTR) recorded during the US summer season at USArray transportable seismic stations when they were near the site between 2006 and 2008.

Special Relativity in the School Laboratory: A Simple Apparatus for Cosmic-Ray Muon Detection

ERIC Educational Resources Information Center

Singh, P.; Hedgeland, H.

2015-01-01

We use apparatus based on two Geiger-Müller tubes, a simple electronic circuit and a Raspberry Pi computer to illustrate relativistic time dilation affecting cosmic-ray muons travelling through the atmosphere to the Earth's surface. The experiment we describe lends itself to both classroom demonstration to accompany the topic of special relativity…

Mental Time Travel, Memory and the Social Learning Strategies Tournament

ERIC Educational Resources Information Center

Fogarty, L.; Rendell, L.; Laland, K. N.

2012-01-01

The social learning strategies tournament was an open computer-based tournament investigating the best way to learn in a changing environment. Here we present an analysis of the impact of memory on the ability of strategies entered into the social learning strategies tournament (Rendell, Boyd, et al., 2010) to modify their own behavior to suit a…

Application of wildfire simulation models for risk analysis

Treesearch

Alan A. Ager; Mark A. Finney

2009-01-01

Wildfire simulation models are being widely used by fire and fuels specialists in the U.S. to support tactical and strategic decisions related to the mitigation of wildfire risk. Much of this application has resulted from the development of a minimum travel time (MTT) fire spread algorithm (M. Finney) that makes it computationally feasible to simulate thousands of...

Theoretical study of network design methodologies for the aerial relay system. [energy consumption and air traffic control

NASA Technical Reports Server (NTRS)

Rivera, J. M.; Simpson, R. W.

1980-01-01

The aerial relay system network design problem is discussed. A generalized branch and bound based algorithm is developed which can consider a variety of optimization criteria, such as minimum passenger travel time and minimum liner and feeder operating costs. The algorithm, although efficient, is basically useful for small size networks, due to its nature of exponentially increasing computation time with the number of variables.

Human mobility and time spent at destination: impact on spatial epidemic spreading.

PubMed

Poletto, Chiara; Tizzoni, Michele; Colizza, Vittoria

2013-12-07

Host mobility plays a fundamental role in the spatial spread of infectious diseases. Previous theoretical works based on the integration of network theory into the metapopulation framework have shown that the heterogeneities that characterize real mobility networks favor the propagation of epidemics. Nevertheless, the studies conducted so far assumed the mobility process to be either Markovian (in which the memory of the origin of each traveler is lost) or non-Markovian with a fixed traveling time scale (in which individuals travel to a destination and come back at a constant rate). Available statistics however show that the time spent by travelers at destination is characterized by wide fluctuations, ranging from a single day up to several months. Such varying length of stay crucially affects the chance and duration of mixing events among hosts and may therefore have a strong impact on the spread of an emerging disease. Here, we present an analytical and a computational study of epidemic processes on a complex subpopulation network where travelers have memory of their origin and spend a heterogeneously distributed time interval at their destination. Through analytical calculations and numerical simulations we show that the heterogeneity of the length of stay alters the expression of the threshold between local outbreak and global invasion, and, moreover, it changes the epidemic behavior of the system in case of a global outbreak. Additionally, our theoretical framework allows us to study the effect of changes in the traveling behavior in response to the infection, by considering a scenario in which sick individuals do not leave their home location. Finally, we compare the results of our non-Markovian framework with those obtained with a classic Markovian approach and find relevant differences between the two, in the estimate of the epidemic invasion potential, as well as of the timing and the pattern of its spatial spread. These results highlight the importance of properly accounting for host trip duration in epidemic models and open the path to the inclusion of such an additional layer of complexity to the existing modeling approaches. © 2013 Elsevier Ltd. All rights reserved.

50 CFR 260.79 - Travel and other expenses.

Code of Federal Regulations, 2013 CFR

2013-10-01

... based on an hourly rate, an additional hourly charge may be made for travel time including time spent waiting for transportation as well as time spent traveling, but not to exceed 8 hours of travel time for... charge may be made for travel time outside the employee's official work hours. ...

50 CFR 260.79 - Travel and other expenses.

Code of Federal Regulations, 2014 CFR

2014-10-01

... based on an hourly rate, an additional hourly charge may be made for travel time including time spent waiting for transportation as well as time spent traveling, but not to exceed 8 hours of travel time for... charge may be made for travel time outside the employee's official work hours. ...

50 CFR 260.79 - Travel and other expenses.

Code of Federal Regulations, 2011 CFR

2011-10-01

... based on an hourly rate, an additional hourly charge may be made for travel time including time spent waiting for transportation as well as time spent traveling, but not to exceed 8 hours of travel time for... charge may be made for travel time outside the employee's official work hours. ...

50 CFR 260.79 - Travel and other expenses.

Code of Federal Regulations, 2012 CFR

2012-10-01

... based on an hourly rate, an additional hourly charge may be made for travel time including time spent waiting for transportation as well as time spent traveling, but not to exceed 8 hours of travel time for... charge may be made for travel time outside the employee's official work hours. ...

50 CFR 260.79 - Travel and other expenses.

Code of Federal Regulations, 2010 CFR

2010-10-01

... based on an hourly rate, an additional hourly charge may be made for travel time including time spent waiting for transportation as well as time spent traveling, but not to exceed 8 hours of travel time for... charge may be made for travel time outside the employee's official work hours. ...

Regional travel-time residual studies and station correction from 1-D velocity models for some stations around Peninsular Malaysia and Singapore

NASA Astrophysics Data System (ADS)

Osagie, Abel U.; Nawawi, Mohd.; Khalil, Amin Esmail; Abdullah, Khiruddin

2017-06-01

We have investigated the average P-wave travel-time residuals for some stations around Southern Thailand, Peninsular Malaysia and Singapore at regional distances. Six years (January, 2010-December, 2015) record of events from central and northern Sumatra was obtained from the digital seismic archives of Integrated Research Institute for Seismology (IRIS). The criteria used for the data selection are designed to be above the magnitude of mb 4.5, depth less than 200 km and an epicentral distance shorter than 1000 km. Within this window a total number of 152 earthquakes were obtained. Furthermore, data were filtered based on the clarity of the seismic phases that are manually picked. A total of 1088 P-wave arrivals and 962 S-wave arrivals were hand-picked from 10 seismic stations around the Peninsula. Three stations IPM, KUM, and KOM from Peninsular Malaysia, four stations BTDF, NTU, BESC and KAPK from Singapore and three stations SURA, SRIT and SKLT located in the southern part of Thailand are used. Station NTU was chosen as the Ref. station because it recorded the large number of events. Travel-times were calculated using three 1-D models (Preliminary Ref. Earth Model PREM (Dziewonski and Anderson, 1981, IASP91, and Lienert et al., 1986) and an adopted two-point ray tracing algorithm. For the three models, we corroborate our calculated travel-times with the results from the use of TAUP travel-time calculation software. Relative to station NTU, our results show that the average P wave travel-time residual for PREM model ranges from -0.16 to 0.45 s for BESC and IPM respectively. For IASP91 model, the average residual ranges from -0.25 to 0.24 s for SRIT and SKLT respectively, and ranges from -0.22 to 0.30 s for KAPK and IPM respectively for Lienert et al. (1986) model. Generally, most stations have slightly positive residuals relative to station NTU. These corrections reflect the difference between actual and estimated model velocities along ray paths to stations and can compensate for heterogeneous velocity structure near individual stations. The computed average travel-time residuals can reduce errors attributable to station correction in the inversion of hypocentral parameters around the Peninsula. Due to the heterogeneity occasioned by the numerous fault systems, a better 1-D velocity model for the Peninsula is desired for more reliable hypocentral inversion and other seismic investigations.

Injection of mineral dust into the free troposphere during fire events observed with polarization lidar at Limassol, Cyprus

NASA Astrophysics Data System (ADS)

Nisantzi, A.; Mamouri, R. E.; Ansmann, A.; Hadjimitsis, D.

2014-06-01

Four-year observations (2010-2014) with EARLINET polarization lidar and AERONET sun/sky photometer at Limassol (34.7° N, 33° E), Cyprus, were used to study the soil dust content in lofted fire smoke plumes advected from Turkey. This first systematic attempt to characterize less than 3 days old smoke plumes in terms of particle depolarization contributes to the more general effort to properly describe the life cycle of free-tropospheric smoke-dust mixtures from the emission event to phases of long-range transport (>4 days after emission). We found significant differences in the particle depolarization ratio (PDR) with values from 9-18% in lofted aerosol layers when Turkish fires contributed to the aerosol burden and of 3-13% when Turkish fires were absent. High Ångström exponents of 1.4-2.2 during all these events with lofted smoke layers, occuring between 1 and 3 km height, suggest the absence of a pronounced particle coarse mode. When plotted vs. the travel time (spatial distance between Limassol and last fire area), PDR decreased strongly from initial values around 16-18% (one day travel) to 4-8% after 4 days of travel caused by deposition processes. This behavior was found to be in close agreement with the literature. Computation of particle extinction coefficient and mass concentrations, separately for fine-mode dust, coarse-mode dust, and non-dust aerosol components show extinction-related dust fractions of the order of 10% (for PDR = 4%, travel times >4 days) and 50% (PDR = 15%, one day travel time) and mass-related dust fractions of 25% (PDR = 4%) to 80% (PDR = 15%). Biomass burning should be considered as another source of free tropospheric soil dust.

41 CFR 301-52.14 - What must I do with any travel advance outstanding at the time I submit my travel claim?

Code of Federal Regulations, 2013 CFR

2013-07-01

... travel advance outstanding at the time I submit my travel claim? 301-52.14 Section 301-52.14 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES... § 301-52.14 What must I do with any travel advance outstanding at the time I submit my travel claim? You...

41 CFR 301-52.14 - What must I do with any travel advance outstanding at the time I submit my travel claim?

Code of Federal Regulations, 2010 CFR

2010-07-01

... travel advance outstanding at the time I submit my travel claim? 301-52.14 Section 301-52.14 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES... § 301-52.14 What must I do with any travel advance outstanding at the time I submit my travel claim? You...

41 CFR 301-52.14 - What must I do with any travel advance outstanding at the time I submit my travel claim?

Code of Federal Regulations, 2012 CFR

2012-07-01

... travel advance outstanding at the time I submit my travel claim? 301-52.14 Section 301-52.14 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES... § 301-52.14 What must I do with any travel advance outstanding at the time I submit my travel claim? You...

41 CFR 301-52.14 - What must I do with any travel advance outstanding at the time I submit my travel claim?

Code of Federal Regulations, 2014 CFR

2014-07-01

... travel advance outstanding at the time I submit my travel claim? 301-52.14 Section 301-52.14 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES... § 301-52.14 What must I do with any travel advance outstanding at the time I submit my travel claim? You...

41 CFR 301-52.14 - What must I do with any travel advance outstanding at the time I submit my travel claim?

Code of Federal Regulations, 2011 CFR

2011-07-01

... travel advance outstanding at the time I submit my travel claim? 301-52.14 Section 301-52.14 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES... § 301-52.14 What must I do with any travel advance outstanding at the time I submit my travel claim? You...

Dynamic origin-to-destination routing of wirelessly connected, autonomous vehicles on a congested network

NASA Astrophysics Data System (ADS)

Davis, L. C.

2017-07-01

Up-to-date information wirelessly communicated among vehicles can be used to select the optimal route between a given origin and destination. To elucidate how to make use of such information, simulations are performed for autonomous vehicles traveling on a square lattice of roads. All the possible routes between the origin and the destination (without backtracking) are of the same length. Congestion is the only determinant of delay. At each intersection, right-of-way is given to the closest vehicle. There are no traffic lights. Trip times of a subject vehicle are recorded for various initial conditions using different routing algorithms. Surprisingly, the simplest algorithm, which is based on the total number of vehicles on a route, is as good as one based on computing travel times from the average velocity of vehicles on each road segment.

5 CFR 551.422 - Time spent traveling.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Time spent traveling. 551.422 Section 551... Activities § 551.422 Time spent traveling. (a) Time spent traveling shall be considered hours of work if: (1... who is permitted to use an alternative mode of transportation, or an employee who travels at a time...

5 CFR 551.422 - Time spent traveling.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 5 Administrative Personnel 1 2013-01-01 2013-01-01 false Time spent traveling. 551.422 Section 551... Activities § 551.422 Time spent traveling. (a) Time spent traveling shall be considered hours of work if: (1... who is permitted to use an alternative mode of transportation, or an employee who travels at a time...

5 CFR 551.422 - Time spent traveling.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Time spent traveling. 551.422 Section 551... Activities § 551.422 Time spent traveling. (a) Time spent traveling shall be considered hours of work if: (1... who is permitted to use an alternative mode of transportation, or an employee who travels at a time...

5 CFR 551.422 - Time spent traveling.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Time spent traveling. 551.422 Section 551... Activities § 551.422 Time spent traveling. (a) Time spent traveling shall be considered hours of work if: (1... who is permitted to use an alternative mode of transportation, or an employee who travels at a time...

5 CFR 551.422 - Time spent traveling.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 5 Administrative Personnel 1 2014-01-01 2014-01-01 false Time spent traveling. 551.422 Section 551... Activities § 551.422 Time spent traveling. (a) Time spent traveling shall be considered hours of work if: (1... who is permitted to use an alternative mode of transportation, or an employee who travels at a time...

Trip-oriented travel time prediction (TOTTP) with historical vehicle trajectories

NASA Astrophysics Data System (ADS)

Xu, Tao; Li, Xiang; Claramunt, Christophe

2018-06-01

Accurate travel time prediction is undoubtedly of importance to both traffic managers and travelers. In highly-urbanized areas, trip-oriented travel time prediction (TOTTP) is valuable to travelers rather than traffic managers as the former usually expect to know the travel time of a trip which may cross over multiple road sections. There are two obstacles to the development of TOTTP, including traffic complexity and traffic data coverage.With large scale historical vehicle trajectory data and meteorology data, this research develops a BPNN-based approach through integrating multiple factors affecting trip travel time into a BPNN model to predict trip-oriented travel time for OD pairs in urban network. Results of experiments demonstrate that it helps discover the dominate trends of travel time changes daily and weekly, and the impact of weather conditions is non-trivial.

Distributed Optimization of Multi-Agent Systems: Framework, Local Optimizer, and Applications

NASA Astrophysics Data System (ADS)

Zu, Yue

Convex optimization problem can be solved in a centralized or distributed manner. Compared with centralized methods based on single-agent system, distributed algorithms rely on multi-agent systems with information exchanging among connected neighbors, which leads to great improvement on the system fault tolerance. Thus, a task within multi-agent system can be completed with presence of partial agent failures. By problem decomposition, a large-scale problem can be divided into a set of small-scale sub-problems that can be solved in sequence/parallel. Hence, the computational complexity is greatly reduced by distributed algorithm in multi-agent system. Moreover, distributed algorithm allows data collected and stored in a distributed fashion, which successfully overcomes the drawbacks of using multicast due to the bandwidth limitation. Distributed algorithm has been applied in solving a variety of real-world problems. Our research focuses on the framework and local optimizer design in practical engineering applications. In the first one, we propose a multi-sensor and multi-agent scheme for spatial motion estimation of a rigid body. Estimation performance is improved in terms of accuracy and convergence speed. Second, we develop a cyber-physical system and implement distributed computation devices to optimize the in-building evacuation path when hazard occurs. The proposed Bellman-Ford Dual-Subgradient path planning method relieves the congestion in corridor and the exit areas. At last, highway traffic flow is managed by adjusting speed limits to minimize the fuel consumption and travel time in the third project. Optimal control strategy is designed through both centralized and distributed algorithm based on convex problem formulation. Moreover, a hybrid control scheme is presented for highway network travel time minimization. Compared with no controlled case or conventional highway traffic control strategy, the proposed hybrid control strategy greatly reduces total travel time on test highway network.

On computing the global time-optimal motions of robotic manipulators in the presence of obstacles

NASA Technical Reports Server (NTRS)

Shiller, Zvi; Dubowsky, Steven

1991-01-01

A method for computing the time-optimal motions of robotic manipulators is presented that considers the nonlinear manipulator dynamics, actuator constraints, joint limits, and obstacles. The optimization problem is reduced to a search for the time-optimal path in the n-dimensional position space. A small set of near-optimal paths is first efficiently selected from a grid, using a branch and bound search and a series of lower bound estimates on the traveling time along a given path. These paths are further optimized with a local path optimization to yield the global optimal solution. Obstacles are considered by eliminating the collision points from the tessellated space and by adding a penalty function to the motion time in the local optimization. The computational efficiency of the method stems from the reduced dimensionality of the searched spaced and from combining the grid search with a local optimization. The method is demonstrated in several examples for two- and six-degree-of-freedom manipulators with obstacles.

Towards the computation of time-periodic inertial range dynamics

NASA Astrophysics Data System (ADS)

van Veen, L.; Vela-Martín, A.; Kawahara, G.

2018-04-01

We explore the possibility of computing simple invariant solutions, like travelling waves or periodic orbits, in Large Eddy Simulation (LES) on a periodic domain with constant external forcing. The absence of material boundaries and the simple forcing mechanism make this system a comparatively simple target for the study of turbulent dynamics through invariant solutions. We show, that in spite of the application of eddy viscosity the computations are still rather challenging and must be performed on GPU cards rather than conventional coupled CPUs. We investigate the onset of turbulence in this system by means of bifurcation analysis, and present a long-period, large-amplitude unstable periodic orbit that is filtered from a turbulent time series. Although this orbit is computed on a coarse grid, with only a small separation between the integral scale and the LES filter length, the periodic dynamics seem to capture a regeneration process of the large-scale vortices.

Measuring the Seismic and Acoustic Time of Flight - Lessons in Earthquakes and Thunder

NASA Astrophysics Data System (ADS)

Leeman, J.; Ammon, C. J.

2016-12-01

When teaching the fundamentals of waves and wave propagation, students must appreciate and understand that different waves travel through different materials at different speeds. We describe a simple experiment to explore acoustic wave propagation through the ground and the air and how to use those observations to locate the source of the waves. The experiment that can be performed with a geophone, a microphone, and an oscilloscope. For this activity, students will strike a metal plate, equipped with a vibration trigger, with a hammer. The blow triggers an oscilloscope to begin recording data in a "single-shot" mode. The two channels of the oscilloscope record the output of the microphone (measuring the energy of sound waves in the air) and the geophone (measuring the seismic wave energy in the ground). Seismic waves reach the geophone earlier than the sound waves since they travel at approximately ten times the speed. Students can measure the travel time on the oscilloscope, or using data downloaded to a computer. With measurements of the travel time and distance to the hammer, students can calculate the velocity of each wave. Then, the hammer can be used at other distances from the sensors and by measuring the difference in arrival time of the two waves, students can estimate the distance to the source which they check by direct measurement. This exercise can be directly connected to common observations such as seeing lighting before hearing thunder. The activity also connects directly to concepts related to earthquake location. We describe pedagogical materials, including experiment instructions, videos and data for those who do not have access to the equipment, and simple exercise suggestions for classroom activities.

Measuring workplace travel behaviour: validity and reliability of survey questions.

PubMed

Petrunoff, Nicholas A; Xu, Huilan; Rissel, Chris; Wen, Li Ming; van der Ploeg, Hidde P

2013-01-01

The purpose of this study was to assess the (previously untested) reliability and validity of survey questions commonly used to assess travel mode and travel time. Sixty-five respondents from a staff survey of travel behaviour conducted in a south-western Sydney hospital agreed to complete a travel diary for a week, wear an accelerometer over the same period, and twice complete an online travel survey an average of 21 days apart. The agreement in travel modes between the self-reported online survey and travel diary was examined with the kappa statistic. Spearman's correlation coefficient was used to examine agreement of travel time from home to workplace measured between the self-reported online survey and four-day travel diary. Moderate-to-vigorous physical activity (MVPA) time of active and nonactive travellers was compared by t-test. There was substantial agreement between travel modes (K = 0.62, P < 0.0001) and a moderate correlation for travel time (ρ = 0.75, P < 0.0001) reported in the travel diary and online survey. There was a high level of agreement for travel mode (K = 0.82, P < 0.0001) and travel time (ρ = 0.83, P < 0.0001) between the two travel surveys. Accelerometer data indicated that for active travellers, 16% of the journey-to-work time is MVPA, compared with 6% for car drivers. Active travellers were significantly more active across the whole workday. The survey question "How did you travel to work this week? If you used more than one transport mode specify the one you used for the longest (distance) portion of your journey" is reliable over 21 days and agrees well with a travel diary.

Measuring Workplace Travel Behaviour: Validity and Reliability of Survey Questions

PubMed Central

Petrunoff, Nicholas A.; Xu, Huilan; van der Ploeg, Hidde P.

2013-01-01

Background. The purpose of this study was to assess the (previously untested) reliability and validity of survey questions commonly used to assess travel mode and travel time. Methods. Sixty-five respondents from a staff survey of travel behaviour conducted in a south-western Sydney hospital agreed to complete a travel diary for a week, wear an accelerometer over the same period, and twice complete an online travel survey an average of 21 days apart. The agreement in travel modes between the self-reported online survey and travel diary was examined with the kappa statistic. Spearman's correlation coefficient was used to examine agreement of travel time from home to workplace measured between the self-reported online survey and four-day travel diary. Moderate-to-vigorous physical activity (MVPA) time of active and nonactive travellers was compared by t-test. Results. There was substantial agreement between travel modes (K = 0.62, P < 0.0001) and a moderate correlation for travel time (ρ = 0.75, P < 0.0001) reported in the travel diary and online survey. There was a high level of agreement for travel mode (K = 0.82, P < 0.0001) and travel time (ρ = 0.83, P < 0.0001) between the two travel surveys. Accelerometer data indicated that for active travellers, 16% of the journey-to-work time is MVPA, compared with 6% for car drivers. Active travellers were significantly more active across the whole workday. Conclusions. The survey question “How did you travel to work this week? If you used more than one transport mode specify the one you used for the longest (distance) portion of your journey” is reliable over 21 days and agrees well with a travel diary. PMID:23956757

Simulated groundwater flow paths, travel time, and advective transport of nitrogen in the Kirkwood-Cohansey aquifer system, Barnegat Bay–Little Egg Harbor Watershed, New Jersey

USGS Publications Warehouse

Voronin, Lois M.; Cauller, Stephen J.

2017-07-31

Elevated concentrations of nitrogen in groundwater that discharges to surface-water bodies can degrade surface-water quality and habitats in the New Jersey Coastal Plain. An analysis of groundwater flow in the Kirkwood-Cohansey aquifer system and deeper confined aquifers that underlie the Barnegat Bay–Little Egg Harbor (BB-LEH) watershed and estuary was conducted by using groundwater-flow simulation, in conjunction with a particle-tracking routine, to provide estimates of groundwater flow paths and travel times to streams and the BB-LEH estuary.Water-quality data from the Ambient Groundwater Quality Monitoring Network, a long-term monitoring network of wells distributed throughout New Jersey, were used to estimate the initial nitrogen concentration in recharge for five different land-use classes—agricultural cropland or pasture, agricultural orchard or vineyard, urban non-residential, urban residential, and undeveloped. Land use at the point of recharge within the watershed was determined using a geographic information system (GIS). Flow path starting locations were plotted on land-use maps for 1930, 1973, 1986, 1997, and 2002. Information on the land use at the time and location of recharge, time of travel to the discharge location, and the point of discharge were determined for each simulated flow path. Particle-tracking analysis provided the link from the point of recharge, along the particle flow path, to the point of discharge, and the particle travel time. The travel time of each simulated particle established the recharge year. Land use during the year of recharge was used to define the nitrogen concentration associated with each flow path. The recharge-weighted average nitrogen concentration for all flow paths that discharge to the Toms River upstream from streamflow-gaging station 01408500 or to the BB-LEH estuary was calculated.Groundwater input into the Barnegat Bay–Little Egg Harbor estuary from two main sources— indirect discharge from base flow to streams that eventually flow into the bay and groundwater discharge directly into the estuary and adjoining coastal wetlands— is summarized by quantity, travel time, and estimated nitrogen concentration. Simulated average groundwater discharge to streams in the watershed that flow into the BB-LEH estuary is approximately 400 million gallons per day. Particle-tracking results indicate that the travel time of 56 percent of this discharge is less than 7 years. Fourteen percent of the groundwater discharge to the streams in the BB-LEH watershed has a travel time of less than 7 years and originates in urban land. Analysis of flow-path simulations indicate that approximately 13 percent of the total groundwater flow through the study area discharges directly to the estuary and adjoining coastal wetlands (approximately 64 million gallons per day). The travel time of 19 percent of this discharge is less than 7 years. Ten percent of this discharge (1 percent of the total groundwater flow through the study area) originates in urban areas and has a travel time of less than 7 years. Groundwater that discharges to the streams that flow into the BB-LEH, in general, has shorter travel times, and a higher percentage of it originates in urban areas than does direct groundwater discharge to the Barnegat Bay–Little Egg Harbor estuary.The simulated average nitrogen concentration in groundwater that discharges to the Toms River, upstream from streamflow-gaging station 01408500 was computed and compared to summary concentrations determined from analysis of multiple surface-water samples. The nitrogen concentration in groundwater that discharges directly to the estuary and adjoining coastal wetlands is a current data gap. The particle tracking methodology used in this study provides an estimate of this concentration."

Self-motion perception compresses time experienced in return travel.

PubMed

Seno, Takeharu; Ito, Hiroyuki; Shoji, Sunaga

2011-01-01

It is often anecdotally reported that time experienced in return travel (back to the start point) seems shorter than time spent in outward travel (travel to a new destination). Here, we report the first experimental results showing that return travel time is experienced as shorter than the actual time. This discrepancy is induced by the existence of self-motion perception.

Iterative Bayesian Estimation of Travel Times on Urban Arterials: Fusing Loop Detector and Probe Vehicle Data.

PubMed

Liu, Kai; Cui, Meng-Ying; Cao, Peng; Wang, Jiang-Bo

2016-01-01

On urban arterials, travel time estimation is challenging especially from various data sources. Typically, fusing loop detector data and probe vehicle data to estimate travel time is a troublesome issue while considering the data issue of uncertain, imprecise and even conflicting. In this paper, we propose an improved data fusing methodology for link travel time estimation. Link travel times are simultaneously pre-estimated using loop detector data and probe vehicle data, based on which Bayesian fusion is then applied to fuse the estimated travel times. Next, Iterative Bayesian estimation is proposed to improve Bayesian fusion by incorporating two strategies: 1) substitution strategy which replaces the lower accurate travel time estimation from one sensor with the current fused travel time; and 2) specially-designed conditions for convergence which restrict the estimated travel time in a reasonable range. The estimation results show that, the proposed method outperforms probe vehicle data based method, loop detector based method and single Bayesian fusion, and the mean absolute percentage error is reduced to 4.8%. Additionally, iterative Bayesian estimation performs better for lighter traffic flows when the variability of travel time is practically higher than other periods.

Iterative Bayesian Estimation of Travel Times on Urban Arterials: Fusing Loop Detector and Probe Vehicle Data

PubMed Central

Cui, Meng-Ying; Cao, Peng; Wang, Jiang-Bo

2016-01-01

On urban arterials, travel time estimation is challenging especially from various data sources. Typically, fusing loop detector data and probe vehicle data to estimate travel time is a troublesome issue while considering the data issue of uncertain, imprecise and even conflicting. In this paper, we propose an improved data fusing methodology for link travel time estimation. Link travel times are simultaneously pre-estimated using loop detector data and probe vehicle data, based on which Bayesian fusion is then applied to fuse the estimated travel times. Next, Iterative Bayesian estimation is proposed to improve Bayesian fusion by incorporating two strategies: 1) substitution strategy which replaces the lower accurate travel time estimation from one sensor with the current fused travel time; and 2) specially-designed conditions for convergence which restrict the estimated travel time in a reasonable range. The estimation results show that, the proposed method outperforms probe vehicle data based method, loop detector based method and single Bayesian fusion, and the mean absolute percentage error is reduced to 4.8%. Additionally, iterative Bayesian estimation performs better for lighter traffic flows when the variability of travel time is practically higher than other periods. PMID:27362654

Innovative methods for calculation of freeway travel time using limited data : executive summary report.

DOT National Transportation Integrated Search

2008-08-01

ODOTs policy for Dynamic Message Sign : utilization requires travel time(s) to be displayed as : a default message. The current method of : calculating travel time involves a workstation : operator estimating the travel time based upon : observati...

Fellow travellers: Working memory and mental time travel in rodents.

PubMed

Dere, Ekrem; Dere, Dorothea; de Souza Silva, Maria Angelica; Huston, Joseph P; Zlomuzica, Armin

2017-03-19

The impairment of mental time travel is a severe cognitive symptom in patients with brain lesions and a number of neuropsychiatric disorders. Whether animals are also able to mentally travel in time both forward and backward is still a matter of debate. In this regard, we have proposed a continuum of mental time travel abilities across different animal species, with humans being the species with the ability to perform most sophisticated forms of mental time travel. In this review and perspective article, we delineate a novel approach to understand the evolution, characteristics and function of human and animal mental time travel. Furthermore, we propose a novel approach to measure mental time travel in rodents in a comprehensive manner using a test battery composed of well-validated and easy applicable tests. Copyright © 2017. Published by Elsevier B.V.

In-well time-of-travel approach to evaluate optimal purge duration during low-flow sampling of monitoring wells

USGS Publications Warehouse

Harte, Philip T.

2017-01-01

A common assumption with groundwater sampling is that low (<0.5 L/min) pumping rates during well purging and sampling captures primarily lateral flow from the formation through the well-screened interval at a depth coincident with the pump intake. However, if the intake is adjacent to a low hydraulic conductivity part of the screened formation, this scenario will induce vertical groundwater flow to the pump intake from parts of the screened interval with high hydraulic conductivity. Because less formation water will initially be captured during pumping, a substantial volume of water already in the well (preexisting screen water or screen storage) will be captured during this initial time until inflow from the high hydraulic conductivity part of the screened formation can travel vertically in the well to the pump intake. Therefore, the length of the time needed for adequate purging prior to sample collection (called optimal purge duration) is controlled by the in-well, vertical travel times. A preliminary, simple analytical model was used to provide information on the relation between purge duration and capture of formation water for different gross levels of heterogeneity (contrast between low and high hydraulic conductivity layers). The model was then used to compare these time–volume relations to purge data (pumping rates and drawdown) collected at several representative monitoring wells from multiple sites. Results showed that computation of time-dependent capture of formation water (as opposed to capture of preexisting screen water), which were based on vertical travel times in the well, compares favorably with the time required to achieve field parameter stabilization. If field parameter stabilization is an indicator of arrival time of formation water, which has been postulated, then in-well, vertical flow may be an important factor at wells where low-flow sampling is the sample method of choice.

Evaluation of a real-time travel time prediction system in a freeway construction work zone : executive summary.

DOT National Transportation Integrated Search

2001-03-01

A real-time travel time prediction system (TIPS) was evaluated in a construction work : zone. TIPS includes changeable message signs (CMSs) displaying the travel time and : distance to the end of the work zone to motorists. The travel times displayed...

The Role of Perspective in Mental Time Travel.

PubMed

Ansuini, Caterina; Cavallo, Andrea; Pia, Lorenzo; Becchio, Cristina

2016-01-01

Recent years have seen accumulating evidence for the proposition that people process time by mapping it onto a linear spatial representation and automatically "project" themselves on an imagined mental time line. Here, we ask whether people can adopt the temporal perspective of another person when travelling through time. To elucidate similarities and differences between time travelling from one's own perspective or from the perspective of another person, we asked participants to mentally project themselves or someone else (i.e., a coexperimenter) to different time points. Three basic properties of mental time travel were manipulated: temporal location (i.e., where in time the travel originates: past, present, and future), motion direction (either backwards or forwards), and temporal duration (i.e., the distance to travel: one, three, or five years). We found that time travels originating in the present lasted longer in the self- than in the other-perspective. Moreover, for self-perspective, but not for other-perspective, time was differently scaled depending on where in time the travel originated. In contrast, when considering the direction and the duration of time travelling, no dissimilarities between the self- and the other-perspective emerged. These results suggest that self- and other-projection, despite some differences, share important similarities in structure.

Effectiveness of different approaches to disseminating traveler information on travel time reliability. [supporting datasets

DOT National Transportation Integrated Search

2013-11-30

Travel time reliability information includes static data about traffic speeds or trip times that capture historic variations from day to day, and it can help individuals understand the level of variation in traffic. Unlike real-time travel time infor...

Monitoring and Modeling Performance of Communications in Computational Grids

NASA Technical Reports Server (NTRS)

Frumkin, Michael A.; Le, Thuy T.

2003-01-01

Computational grids may include many machines located in a number of sites. For efficient use of the grid we need to have an ability to estimate the time it takes to communicate data between the machines. For dynamic distributed grids it is unrealistic to know exact parameters of the communication hardware and the current communication traffic and we should rely on a model of the network performance to estimate the message delivery time. Our approach to a construction of such a model is based on observation of the messages delivery time with various message sizes and time scales. We record these observations in a database and use them to build a model of the message delivery time. Our experiments show presence of multiple bands in the logarithm of the message delivery times. These multiple bands represent multiple paths messages travel between the grid machines and are incorporated in our multiband model.

Interactive home telehealth and burns: A pilot study.

PubMed

Hickey, Sean; Gomez, Jason; Meller, Benjamin; Schneider, Jeffery C; Cheney, Meredith; Nejad, Shamim; Schulz, John; Goverman, Jeremy

2017-09-01

The objective of this study is to review our experience incorporating Interactive Home Telehealth (IHT) visits into follow-up burn care. A retrospective review of all burn patients participating in IHT encounters over the course of 15 months was performed. Connections were established through secure video conferencing and call-routing software. Patients connected with a personal computer or tablet and providers connected with a desktop computer with a high-definition web camera. In some cases, high-definition digital images were emailed to the provider prior to the virtual consultation. For each patient, the following was collected: (1) patient and injury demographics (diagnosis, prognosis, and clinical management), (2) total number of encounters, (3) service for each encounter (burn, psychiatry, and rehabilitation), (4) length of visit, including travel distance and time saved and, (5) complications, including re-admissions and connectivity issues. 52 virtual encounters were performed with 31 patients during the first year of the pilot project from March 2015 to June 2016. Mean age of the participant was 44 years (range 18-83 years). Mean total burn surface area of the participant was 12% (range 1-80%). Average roundtrip travel distance saved was 188 miles (range 4-822 miles). Average round trip travel time saved was 201min (range 20-564min). There were no unplanned re-admissions and no complications. Five connectivity issues were reported, none of which prevented completion of the visit. Interactive Home Telehealth is a safe and feasible modality for delivering follow-up care to burn patients. Burn care providers benefit from the potential to improve outpatient clinic utilization. Patients benefit from improved access to multiple members of their specialized burn care team, as well as cost-reductions for patient travel expenses. Future studies are needed to ensure patient and provider satisfaction and to further validate the significance, cost-effectiveness and safety. Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.

Network structure and travel time perception.

PubMed

Parthasarathi, Pavithra; Levinson, David; Hochmair, Hartwig

2013-01-01

The purpose of this research is to test the systematic variation in the perception of travel time among travelers and relate the variation to the underlying street network structure. Travel survey data from the Twin Cities metropolitan area (which includes the cities of Minneapolis and St. Paul) is used for the analysis. Travelers are classified into two groups based on the ratio of perceived and estimated commute travel time. The measures of network structure are estimated using the street network along the identified commute route. T-test comparisons are conducted to identify statistically significant differences in estimated network measures between the two traveler groups. The combined effect of these estimated network measures on travel time is then analyzed using regression models. The results from the t-test and regression analyses confirm the influence of the underlying network structure on the perception of travel time.

Travel time data collection handbook

DOT National Transportation Integrated Search

1998-03-01

This Travel Time Data Collection Handbook provides guidance to transportation : professionals and practitioners for the collection, reduction, and presentation : of travel time data. The handbook should be a useful reference for designing : travel ti...

Patterns of health behaviour associated with active travel: a compositional data analysis.

PubMed

Foley, Louise; Dumuid, Dorothea; Atkin, Andrew J; Olds, Timothy; Ogilvie, David

2018-03-21

Active travel (walking or cycling for transport) is associated with favourable health outcomes in adults. However, little is known about the concurrent patterns of health behaviour associated with active travel. We used compositional data analysis to explore differences in how people doing some active travel used their time compared to those doing no active travel, incorporating physical activity, sedentary behaviour and sleep. We analysed cross-sectional data from the 2014/15 United Kingdom Harmonised European Time Use Survey. Participants recorded two diary days of activity, and we randomly selected one day from participants aged 16 years or over. Activities were categorised into six mutually exclusive sets, accounting for the entire 24 h: (1) sleep; (2) leisure moderate to vigorous physical activity (MVPA); (3) leisure sedentary screen time; (4) non-discretionary time (work, study, chores and caring duties); (5) travel and (6) other. This mixture of activities was defined as a time-use composition. A binary variable was created indicating whether participants reported any active travel on their selected diary day. We used compositional multivariate analysis of variance (MANOVA) to test whether mean time-use composition differed between individuals reporting some active travel and those reporting no active travel, adjusted for covariates. We then used adjusted linear regression models and bootstrap confidence intervals to identify which of the six activity sets differed between groups. 6143 participants (mean age 48 years; 53% female) provided a valid diary day. There was a statistically significant difference in time-use composition between those reporting some active travel and those reporting no active travel. Those undertaking active travel reported a relatively greater amount of time in leisure MVPA and travel, and a relatively lower amount of time in leisure sedentary screen time and sleep. Compared to those not undertaking active travel, those who did active travel reported 11 min more in leisure MVPA and 18 min less in screen time per day, and reported lower sleep. From a health perspective, higher MVPA and lower screen time is favourable, but the pattern of sleep is more complex. Overall, active travel was associated with a broadly health-promoting composition of time across multiple behavioural domains, which supports the public health case for active travel.

Monitoring the impact of decentralised chronic care services on patient travel time in rural Africa--methods and results in Northern Malawi.

PubMed

Houben, Rein M G J; Van Boeckel, Thomas P; Mwinuka, Venance; Mzumara, Peter; Branson, Keith; Linard, Catherine; Chimbwandira, Frank; French, Neil; Glynn, Judith R; Crampin, Amelia C

2012-11-15

Decentralised health services form a key part of chronic care strategies in resource-limited settings by reducing the distance between patient and clinic and thereby the time and costs involved in travelling. However, few tools exist to evaluate the impact of decentralisation on patient travel time or what proportion of patients attend their nearest clinic. Here we develop methods to monitor changes in travel time, using data from the antiretroviral therapy (ART) roll-out in a rural district in North Malawi. Clinic position was combined with GPS information on the home village of patients accessing ART services in Karonga District (North Malawi) between July 2005 and July 2009. Potential travel time was estimated as the travel time for an individual attending their nearest clinic, and estimated actual travel time as the time to the clinic attended. This allowed us to calculate changes in potential and actual travel time as new clinics opened and track the proportion and origin of patients not accessing their nearest clinic. The model showed how the opening of further ART clinics in Karonga District reduced median potential travel time from 83 to 43 minutes, and median actual travel time fell from 83 to 47 minutes. The proportion of patients not attending their nearest clinic increased from 6% when two clinics were open, to 12% with four open. Integrating GPS information with patient data shows the impact of decentralisation on travel time and clinic choice to inform policy and research questions. In our case study, travel time decreased, accompanied by an increased uptake of services. However, the model also identified an increasing proportion of ART patients did not attend their nearest clinic.

Multilevel and quasi-Monte Carlo methods for uncertainty quantification in particle travel times through random heterogeneous porous media

NASA Astrophysics Data System (ADS)

Crevillén-García, D.; Power, H.

2017-08-01

In this study, we apply four Monte Carlo simulation methods, namely, Monte Carlo, quasi-Monte Carlo, multilevel Monte Carlo and multilevel quasi-Monte Carlo to the problem of uncertainty quantification in the estimation of the average travel time during the transport of particles through random heterogeneous porous media. We apply the four methodologies to a model problem where the only input parameter, the hydraulic conductivity, is modelled as a log-Gaussian random field by using direct Karhunen-Loéve decompositions. The random terms in such expansions represent the coefficients in the equations. Numerical calculations demonstrating the effectiveness of each of the methods are presented. A comparison of the computational cost incurred by each of the methods for three different tolerances is provided. The accuracy of the approaches is quantified via the mean square error.

Walkyourplace - Evaluating Neighbourhood Accessibility at Street Level

NASA Astrophysics Data System (ADS)

Steiniger, S.; Poorazizi, M. E.; Hunter, A. J. S.

2013-05-01

The popularity of a neighbourhood is often explained by its perceived "higher" quality of life. Good access to shops, restaurants, parks, etc., is seen as an indicator that reflects improved quality of life. We present a web-based tool for assessment of accessibility to such services. The system evaluates in real time an area that is accessible using pedestrian, transit, and cycling infrastructure. The accessible area is evaluated using "quality of life" indicators, such as the number of grocery stores, shopping and recreation facilities, and local crime within that area. This tool sets itself apart from pre-computed and neighbourhood-level walkability indices, because it makes use of detailed street-level data, rather than block-level generalizations. It uses real network travel time, and, when transit data are provided, permits the creation and evaluation of accessibility areas for a combination of travel modes such as walking with transit use.

Analysis of residual chlorine in simple drinking water distribution system with intermittent water supply

NASA Astrophysics Data System (ADS)

Goyal, Roopali V.; Patel, H. M.

2015-09-01

Knowledge of residual chlorine concentration at various locations in drinking water distribution system is essential final check to the quality of water supplied to the consumers. This paper presents a methodology to find out the residual chlorine concentration at various locations in simple branch network by integrating the hydraulic and water quality model using first-order chlorine decay equation with booster chlorination nodes for intermittent water supply. The explicit equations are developed to compute the residual chlorine in network with a long distribution pipe line at critical nodes. These equations are applicable to Indian conditions where intermittent water supply is the most common system of water supply. It is observed that in intermittent water supply, the residual chlorine at farthest node is sensitive to water supply hours and travelling time of chlorine. Thus, the travelling time of chlorine can be considered to justify the requirement of booster chlorination for intermittent water supply.

Mobility and Congestion in Dynamical Multilayer Networks with Finite Storage Capacity

NASA Astrophysics Data System (ADS)

Manfredi, S.; Di Tucci, E.; Latora, V.

2018-02-01

Multilayer networks describe well many real interconnected communication and transportation systems, ranging from computer networks to multimodal mobility infrastructures. Here, we introduce a model in which the nodes have a limited capacity of storing and processing the agents moving over a multilayer network, and their congestions trigger temporary faults which, in turn, dynamically affect the routing of agents seeking for uncongested paths. The study of the network performance under different layer velocities and node maximum capacities reveals the existence of delicate trade-offs between the number of served agents and their time to travel to destination. We provide analytical estimates of the optimal buffer size at which the travel time is minimum and of its dependence on the velocity and number of links at the different layers. Phenomena reminiscent of the slower is faster effect and of the Braess' paradox are observed in our dynamical multilayer setup.

Mobility and Congestion in Dynamical Multilayer Networks with Finite Storage Capacity.

PubMed

Manfredi, S; Di Tucci, E; Latora, V

2018-02-09

Multilayer networks describe well many real interconnected communication and transportation systems, ranging from computer networks to multimodal mobility infrastructures. Here, we introduce a model in which the nodes have a limited capacity of storing and processing the agents moving over a multilayer network, and their congestions trigger temporary faults which, in turn, dynamically affect the routing of agents seeking for uncongested paths. The study of the network performance under different layer velocities and node maximum capacities reveals the existence of delicate trade-offs between the number of served agents and their time to travel to destination. We provide analytical estimates of the optimal buffer size at which the travel time is minimum and of its dependence on the velocity and number of links at the different layers. Phenomena reminiscent of the slower is faster effect and of the Braess' paradox are observed in our dynamical multilayer setup.

Inverting travel times with a triplication. [spline fitting technique applied to lunar seismic data reduction

NASA Technical Reports Server (NTRS)

Jarosch, H. S.

1982-01-01

A method based on the use of constrained spline fits is used to overcome the difficulties arising when body-wave data in the form of T-delta are reduced to the tau-p form in the presence of cusps. In comparison with unconstrained spline fits, the method proposed here tends to produce much smoother models which lie approximately in the middle of the bounds produced by the extremal method. The method is noniterative and, therefore, computationally efficient. The method is applied to the lunar seismic data, where at least one triplication is presumed to occur in the P-wave travel-time curve. It is shown, however, that because of an insufficient number of data points for events close to the antipode of the center of the lunar network, the present analysis is not accurate enough to resolve the problem of a possible lunar core.

Multilevel and quasi-Monte Carlo methods for uncertainty quantification in particle travel times through random heterogeneous porous media.

PubMed

Crevillén-García, D; Power, H

2017-08-01

In this study, we apply four Monte Carlo simulation methods, namely, Monte Carlo, quasi-Monte Carlo, multilevel Monte Carlo and multilevel quasi-Monte Carlo to the problem of uncertainty quantification in the estimation of the average travel time during the transport of particles through random heterogeneous porous media. We apply the four methodologies to a model problem where the only input parameter, the hydraulic conductivity, is modelled as a log-Gaussian random field by using direct Karhunen-Loéve decompositions. The random terms in such expansions represent the coefficients in the equations. Numerical calculations demonstrating the effectiveness of each of the methods are presented. A comparison of the computational cost incurred by each of the methods for three different tolerances is provided. The accuracy of the approaches is quantified via the mean square error.

Multilevel and quasi-Monte Carlo methods for uncertainty quantification in particle travel times through random heterogeneous porous media

PubMed Central

Power, H.

2017-01-01

In this study, we apply four Monte Carlo simulation methods, namely, Monte Carlo, quasi-Monte Carlo, multilevel Monte Carlo and multilevel quasi-Monte Carlo to the problem of uncertainty quantification in the estimation of the average travel time during the transport of particles through random heterogeneous porous media. We apply the four methodologies to a model problem where the only input parameter, the hydraulic conductivity, is modelled as a log-Gaussian random field by using direct Karhunen–Loéve decompositions. The random terms in such expansions represent the coefficients in the equations. Numerical calculations demonstrating the effectiveness of each of the methods are presented. A comparison of the computational cost incurred by each of the methods for three different tolerances is provided. The accuracy of the approaches is quantified via the mean square error. PMID:28878974

Evaluation of a real-time travel time prediction system in a freeway construction work zone : final report, March 2001.

DOT National Transportation Integrated Search

2001-03-01

A real-time travel time prediction system (TIPS) was evaluated in a construction work zone. TIPS includes changeable message signs (CMSs) displaying the travel time and distance to the end of the work zone to motorists. The travel times displayed by ...

48 CFR 752.7002 - Travel and transportation.

Code of Federal Regulations, 2010 CFR

2010-10-01

... referred to as the Standardized Regulations—as from time to time amended, for not more than the travel time...” clause of this contract, time spent away from post resulting from educational travel will be counted as... time amended, for not more than the travel time required by scheduled commercial air carrier using the...

Travel reliability inventory for Chicago.

DOT National Transportation Integrated Search

2013-04-01

The overarching goal of this research project is to enable state DOTs to document and monitor the reliability performance : of their highway networks. To this end, a computer tool, TRIC, was developed to produce travel reliability inventories from : ...

The prevalence of leisure time sedentary behaviour and physical activity in adolescent boys: an ecological momentary assessment approach.

PubMed

Gorely, Trish; Biddle, Stuart J H; Marshall, Simon J; Cameron, Noel

2009-01-01

To use ecological momentary assessment to describe how adolescent boys in the United Kingdom spend their leisure time. Design. Cross-sectional, stratified, random sample from secondary schools in 15 regions within the United Kingdom. The data are from a larger study of adolescent lifestyles (Project STIL). A total of 561 boys with a mean age of 14.6 years (range 12.7-16.7 years). The majority were white-European (86.5%). Television viewing occupied the most leisure time on both weekdays (131 minutes) and weekend (202.5 minutes) days. On weekdays the five most time consuming sedentary activities (television viewing, homework, motorised travel, playing computer/video games and shopping/hanging out) occupied on average 272.2 minutes. On weekend days, the five most time consuming sedentary activities (television viewing, shopping/hanging out, motorised travel, sitting and talking and playing computer/video games) occupied 405.5 minutes. In total, 54 minutes were occupied by active transport or sports and exercise per weekday and 81 minutes per weekend day. Only a minority watched more than 4 hours of TV per day (8.9% on weekdays and 33.8% on weekend days). Differences were noted in the means and prevalence between weekend and weekdays, reflecting the greater discretionary time available at the weekend. Adolescent boys engage in a variety of sedentary and active free time behaviours. It appears prudent to encourage adolescents to adopt overall healthy lifestyles by considering the combination of both active and sedentary pursuits an individual engages in and by moving beyond a focus on any one single behaviour.

5 CFR 630.207 - Travel time.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Travel time. 630.207 Section 630.207... and General Provisions for Annual and Sick Leave § 630.207 Travel time. The travel time granted an employee under section 6303(d) of title 5, United States Code, is inclusive of the time necessarily...

5 CFR 630.207 - Travel time.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Travel time. 630.207 Section 630.207... and General Provisions for Annual and Sick Leave § 630.207 Travel time. The travel time granted an employee under section 6303(d) of title 5, United States Code, is inclusive of the time necessarily...

5 CFR 630.207 - Travel time.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 5 Administrative Personnel 1 2014-01-01 2014-01-01 false Travel time. 630.207 Section 630.207... and General Provisions for Annual and Sick Leave § 630.207 Travel time. The travel time granted an employee under section 6303(d) of title 5, United States Code, is inclusive of the time necessarily...

5 CFR 630.207 - Travel time.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Travel time. 630.207 Section 630.207... and General Provisions for Annual and Sick Leave § 630.207 Travel time. The travel time granted an employee under section 6303(d) of title 5, United States Code, is inclusive of the time necessarily...

5 CFR 630.207 - Travel time.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 5 Administrative Personnel 1 2013-01-01 2013-01-01 false Travel time. 630.207 Section 630.207... and General Provisions for Annual and Sick Leave § 630.207 Travel time. The travel time granted an employee under section 6303(d) of title 5, United States Code, is inclusive of the time necessarily...

Simultaneous travel time tomography for updating both velocity and reflector geometry in triangular/tetrahedral cell model

NASA Astrophysics Data System (ADS)

Bai, Chao-ying; He, Lei-yu; Li, Xing-wang; Sun, Jia-yu

2018-05-01

To conduct forward and simultaneous inversion in a complex geological model, including an irregular topography (or irregular reflector or velocity anomaly), we in this paper combined our previous multiphase arrival tracking method (referred as triangular shortest-path method, TSPM) in triangular (2D) or tetrahedral (3D) cell model and a linearized inversion solver (referred to as damped minimum norms and constrained least squares problem solved using the conjugate gradient method, DMNCLS-CG) to formulate a simultaneous travel time inversion method for updating both velocity and reflector geometry by using multiphase arrival times. In the triangular/tetrahedral cells, we deduced the partial derivative of velocity variation with respective to the depth change of reflector. The numerical simulation results show that the computational accuracy can be tuned to a high precision in forward modeling and the irregular velocity anomaly and reflector geometry can be accurately captured in the simultaneous inversion, because the triangular/tetrahedral cell can be easily used to stitch the irregular topography or subsurface interface.

Simultaneous travel time tomography for updating both velocity and reflector geometry in triangular/tetrahedral cell model

NASA Astrophysics Data System (ADS)

Bai, Chao-ying; He, Lei-yu; Li, Xing-wang; Sun, Jia-yu

2017-12-01

To conduct forward and simultaneous inversion in a complex geological model, including an irregular topography (or irregular reflector or velocity anomaly), we in this paper combined our previous multiphase arrival tracking method (referred as triangular shortest-path method, TSPM) in triangular (2D) or tetrahedral (3D) cell model and a linearized inversion solver (referred to as damped minimum norms and constrained least squares problem solved using the conjugate gradient method, DMNCLS-CG) to formulate a simultaneous travel time inversion method for updating both velocity and reflector geometry by using multiphase arrival times. In the triangular/tetrahedral cells, we deduced the partial derivative of velocity variation with respective to the depth change of reflector. The numerical simulation results show that the computational accuracy can be tuned to a high precision in forward modeling and the irregular velocity anomaly and reflector geometry can be accurately captured in the simultaneous inversion, because the triangular/tetrahedral cell can be easily used to stitch the irregular topography or subsurface interface.

Active versus passive transportation to school-differences in screen time, socio-economic position and perceived environmental characteristics in adolescent girls.

PubMed

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

2007-01-01

The aims of this study were (1) to assess the relationships between transport to and from school (active vs. passive), sedentary behaviours, measures of socio-economic position and perceived environmental variables, and (2) to determine which, if any, variables were predictors of active transportation. The sample comprised 705 girls with mean age of 14.7 (SD = 1.6) years old. Questionnaires were used to describe travel mode to school and to estimate weekly television and computer use (screen time). Girls were assigned to active transportation (AT) or passive transportation (PT) groups depending on whether they walked or bicycled (AT) to and from school or travelled by car or bus (PT). Screen time was determined by the number of hours they reported watching television and using computers in the week preceding the examination, including weekends. Socio-economic position was established by parental occupation and educational level. A questionnaire assessed Perceived Neighbourhood Environments. No statistically significant differences were seen for screen time between travel groups. Occupational status of both mother (r = -0.17) and father (r = -0.15) and father's educational level (r = -0.10) were significantly and negatively associated with AT, while street connectivity (r = 0.10) was positively and significantly associated with AT. Logistic regression analysis showed that the likelihood of active commuting decreased by around 50% with increasing father's occupation (odds ratio (OR) = 0.51; p

Passive radiation shielding considerations for the proposed space elevator

NASA Astrophysics Data System (ADS)

Jorgensen, A. M.; Patamia, S. E.; Gassend, B.

2007-02-01

The Earth's natural van Allen radiation belts present a serious hazard to space travel in general, and to travel on the space elevator in particular. The average radiation level is sufficiently high that it can cause radiation sickness, and perhaps death, for humans spending more than a brief period of time in the belts without shielding. The exact dose and the level of the related hazard depends on the type or radiation, the intensity of the radiation, the length of exposure, and on any shielding introduced. For the space elevator the radiation concern is particularly critical since it passes through the most intense regions of the radiation belts. The only humans who have ever traveled through the radiation belts have been the Apollo astronauts. They received radiation doses up to approximately 1 rem over a time interval less than an hour. A vehicle climbing the space elevator travels approximately 200 times slower than the moon rockets did, which would result in an extremely high dose up to approximately 200 rem under similar conditions, in a timespan of a few days. Technological systems on the space elevator, which spend prolonged periods of time in the radiation belts, may also be affected by the high radiation levels. In this paper we will give an overview of the radiation belts in terms relevant to space elevator studies. We will then compute the expected radiation doses, and evaluate the required level of shielding. We concentrate on passive shielding using aluminum, but also look briefly at active shielding using magnetic fields. We also look at the effect of moving the space elevator anchor point and increasing the speed of the climber. Each of these mitigation mechanisms will result in a performance decrease, cost increase, and technical complications for the space elevator.

Creating an Online Laboratory

DTIC Science & Technology

2015-03-18

Problem (TSP) to solve, a canonical computer science problem that involves identifying the shortest itinerary for a hypothetical salesman traveling among a...also created working versions of the travelling salesperson problem , prisoners’ dilemma, public goods game, ultimatum game, word ladders, and...the task within networks of others performing the task. Thus, we built five problems which could be embedded in networks: the traveling salesperson

Network Structure and Travel Time Perception

PubMed Central

Parthasarathi, Pavithra; Levinson, David; Hochmair, Hartwig

2013-01-01

The purpose of this research is to test the systematic variation in the perception of travel time among travelers and relate the variation to the underlying street network structure. Travel survey data from the Twin Cities metropolitan area (which includes the cities of Minneapolis and St. Paul) is used for the analysis. Travelers are classified into two groups based on the ratio of perceived and estimated commute travel time. The measures of network structure are estimated using the street network along the identified commute route. T-test comparisons are conducted to identify statistically significant differences in estimated network measures between the two traveler groups. The combined effect of these estimated network measures on travel time is then analyzed using regression models. The results from the t-test and regression analyses confirm the influence of the underlying network structure on the perception of travel time. PMID:24204932

Geographic Freedom

NASA Technical Reports Server (NTRS)

2000-01-01

Kennedy Space Center's need to conduct real-time monitoring of Space Shuttle operations led to the development of Netlander Inc.'s JTouch system. The technology behind JTouch allows engineers to view Space Shuttle and ground support data from any desktop computer using a web browser. Companies can make use of JTouch to better monitor locations scattered around the world, increasing decision-making speed and reducing travel costs for site visits.

7 CFR 52.50 - Travel and other expenses.

Code of Federal Regulations, 2014 CFR

2014-01-01

... travel time incurred in connection with the performance of any inspection service, including appeal... time spent traveling, but not to exceed eight hours of travel time for any one person for any one day... 7 Agriculture 2 2014-01-01 2014-01-01 false Travel and other expenses. 52.50 Section 52.50...

7 CFR 52.50 - Travel and other expenses.

Code of Federal Regulations, 2013 CFR

2013-01-01

... travel time incurred in connection with the performance of any inspection service, including appeal... time spent traveling, but not to exceed eight hours of travel time for any one person for any one day... 7 Agriculture 2 2013-01-01 2013-01-01 false Travel and other expenses. 52.50 Section 52.50...

Wireless data collection system for travel time estimation and traffic performance evaluation.

DOT National Transportation Integrated Search

2010-09-01

Having accurate and continually updated travel time and other performance data for the road and highway system has many benefits. From the perspective of the road users, having real-time updates on travel times will permit better travel and route pla...

Validation and augmentation of Inrix arterial travel time data using independent sources : [research summary].

DOT National Transportation Integrated Search

2015-02-01

Although the freeway travel time data has been validated extensively in recent : years, the quality of arterial travel time data is not well known. This project : presents a comprehensive validation scheme for arterial travel time data based : on GPS...

Leisure time activities in teenagers in urban and rural areas.

PubMed

Borzecki, Andrzej; Nieradko, Barbara; Gnasś, Bogumiła; Sieklucka-Dziuba, Maria

2002-01-01

The work aimed to determine the leisure time activities in teenagers on weekdays, weekends, during winter and summer holidays. Vast majority of teenagers spend their leisure time resting in a passive way, i.e. watching TV or playing computer games irrespectively of the season. As a result of this, the number of kids with posture defects increase. On weekdays the country teenagers spend much more time doing outdoor sports and games than town children. They also more often help their parents and less frequently travel away from their homes than children living in towns.

Minimal Representation and Decision Making for Networked Autonomous Agents

DTIC Science & Technology

2015-08-27

to a multi-vehicle version of the Travelling Salesman Problem (TSP). We further provided a direct formula for computing the number of robots...the sensor. As a first stab at this, the two-agent rendezvous problem is considered where one agent (the target) is equipped with no sensors and is...by the total distance traveled by all agents. For agents with limited sensing and communication capabilities, we give a formula that computes the

Applications manual for logit modes of express bus-fringe parking choices.

DOT National Transportation Integrated Search

1976-01-01

Manual computations and computerized applications of logit models are described. The models demonstrated reflect travel behavior concerning express bus-fringe parking transit. The specific travel issues addressed include the basic automobile vs. expr...

41 CFR 302-10.101 - Must I furnish actual odometer readings on the travel claim?

Code of Federal Regulations, 2010 CFR

2010-07-01

... Management Federal Travel Regulation System RELOCATION ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS USED AS A PRIMARY RESIDENCE Computation of Distance...

Using a numerical model to understand the connection between the ocean and acoustic travel-time measurements.

PubMed

Powell, Brian S; Kerry, Colette G; Cornuelle, Bruce D

2013-10-01

Measurements of acoustic ray travel-times in the ocean provide synoptic integrals of the ocean state between source and receiver. It is known that the ray travel-time is sensitive to variations in the ocean at the transmission time, but the sensitivity of the travel-time to spatial variations in the ocean prior to the acoustic transmission have not been quantified. This study examines the sensitivity of ray travel-time to the temporally and spatially evolving ocean state in the Philippine Sea using the adjoint of a numerical model. A one year series of five day backward integrations of the adjoint model quantify the sensitivity of travel-times to varying dynamics that can alter the travel-time of a 611 km ray by 200 ms. The early evolution of the sensitivities reveals high-mode internal waves that dissipate quickly, leaving the lowest three modes, providing a connection to variations in the internal tide generation prior to the sample time. They are also strongly sensitive to advective effects that alter density along the ray path. These sensitivities reveal how travel-time measurements are affected by both nearby and distant waters. Temporal nonlinearity of the sensitivities suggests that prior knowledge of the ocean state is necessary to exploit the travel-time observations.

Chemotaxis can provide biological organisms with good solutions to the travelling salesman problem.

PubMed

Reynolds, A M

2011-05-01

The ability to find good solutions to the traveling salesman problem can benefit some biological organisms. Bacterial infection would, for instance, be eradicated most promptly if cells of the immune system minimized the total distance they traveled when moving between bacteria. Similarly, foragers would maximize their net energy gain if the distance that they traveled between multiple dispersed prey items was minimized. The traveling salesman problem is one of the most intensively studied problems in combinatorial optimization. There are no efficient algorithms for even solving the problem approximately (within a guaranteed constant factor from the optimum) because the problem is nondeterministic polynomial time complete. The best approximate algorithms can typically find solutions within 1%-2% of the optimal, but these are computationally intensive and can not be implemented by biological organisms. Biological organisms could, in principle, implement the less efficient greedy nearest-neighbor algorithm, i.e., always move to the nearest surviving target. Implementation of this strategy does, however, require quite sophisticated cognitive abilities and prior knowledge of the target locations. Here, with the aid of numerical simulations, it is shown that biological organisms can simply use chemotaxis to solve, or at worst provide good solutions (comparable to those found by the greedy algorithm) to, the traveling salesman problem when the targets are sources of a chemoattractant and are modest in number (n < 10). This applies to neutrophils and macrophages in microbial defense and to some predators.

10 CFR 719.43 - What is the treatment of travel costs?

Code of Federal Regulations, 2014 CFR

2014-01-01

...-46, as appropriate, to be reimbursable. (b) Travel time may be allowed at a full hourly rate for the... remaining travel time shall be reimbursed at 50 percent of the full hourly rate, except that in no event will travel time spent working for other clients be allowable. Also, for long distance travel that...

23 CFR 511.309 - Provisions for traffic and travel conditions reporting.

Code of Federal Regulations, 2012 CFR

2012-04-01

... requirements for traffic and travel conditions made available by real-time information programs are: (1... or less from the time the hazardous conditions, blockage, or closure is observed. (4) Travel time information. The timeliness for the availability of travel time information along limited access roadway...

Material identification based upon energy-dependent attenuation of neutrons

DOEpatents

Marleau, Peter

2015-10-06

Various technologies pertaining to identifying a material in a sample and imaging the sample are described herein. The material is identified by computing energy-dependent attenuation of neutrons that is caused by presence of the sample in travel paths of the neutrons. A mono-energetic neutron generator emits the neutron, which is downscattered in energy by a first detector unit. The neutron exits the first detector unit and is detected by a second detector unit subsequent to passing through the sample. Energy-dependent attenuation of neutrons passing through the sample is computed based upon a computed energy of the neutron, wherein such energy can be computed based upon 1) known positions of the neutron generator, the first detector unit, and the second detector unit; or 2) computed time of flight of neutrons between the first detector unit and the second detector unit.

Effects of packet retransmission with finite packet lifetime on traffic capacity in scale-free networks

NASA Astrophysics Data System (ADS)

Jiang, Zhong-Yuan; Ma, Jian-Feng

Existing routing strategies such as the global dynamic routing [X. Ling, M. B. Hu, R. Jiang and Q. S. Wu, Phys. Rev. E 81, 016113 (2010)] can achieve very high traffic capacity at the cost of extremely long packet traveling delay. In many real complex networks, especially for real-time applications such as the instant communication software, extremely long packet traveling time is unacceptable. In this work, we propose to assign a finite Time-to-Live (TTL) parameter for each packet. To guarantee every packet to arrive at its destination within its TTL, we assume that a packet is retransmitted by its source once its TTL expires. We employ source routing mechanisms in the traffic model to avoid the routing-flaps induced by the global dynamic routing. We compose extensive simulations to verify our proposed mechanisms. With small TTL, the effects of packet retransmission on network traffic capacity are obvious, and the phase transition from flow free state to congested state occurs. For the purpose of reducing the computation frequency of the routing table, we employ a computing cycle Tc within which the routing table is recomputed once. The simulation results show that the traffic capacity decreases with increasing Tc. Our work provides a good insight into the understanding of effects of packet retransmission with finite packet lifetime on traffic capacity in scale-free networks.

Personal travel assistants and the world wide web

DOT National Transportation Integrated Search

1997-01-01

To be successful, handheld computers known as Personal Travel Assistants (PTAs) must be connected to external information sources. The viability of using the Internet and the world wide web (www) as such sources is explored. Considerations include wh...

Large-Scale Traffic Microsimulation From An MPO Perspective

DOT National Transportation Integrated Search

1997-01-01

One potential advancement of the four-step travel model process is the forecasting and simulation of individual activities and travel. A common concern with such an approach is that the data and computational requirements for a large-scale, regional ...

Kinematics and dynamics of vortex rings in a tube

NASA Technical Reports Server (NTRS)

Brasseur, J. G.

1979-01-01

Kinematic theory and flow visualization experiments were combined to examine the dynamic processes which control the evolution of vortex rings from very low to very high Reynolds numbers, and to assess the effects of the wall as a vortex ring travels up a tube. The kinematic relationships among the size, shape, speed, and strength of vortex rings in a tube were computed from the theory. Relatively simple flow visualization measurements were used to calculate the total circulation of a vortex rings at a given time. Using this method, the strength was computated and plotted as a function of time for experimentally produced vortex rings. Reynolds number relationships are established and quantitative differences among the three Reynolds number groups are discussed.

7 CFR 52.50 - Travel and other expenses.

Code of Federal Regulations, 2010 CFR

2010-01-01

... and other expenses. Charges may be made to cover the cost of travel time incurred in connection with... hour. This includes time spent waiting for transportation as well as time spent traveling, but not to exceed eight hours of travel time for any one person for any one day: And provided further, that if...

7 CFR 52.50 - Travel and other expenses.

Code of Federal Regulations, 2011 CFR

2011-01-01

... and other expenses. Charges may be made to cover the cost of travel time incurred in connection with... hour. This includes time spent waiting for transportation as well as time spent traveling, but not to exceed eight hours of travel time for any one person for any one day: And provided further, that if...

77 FR 45415 - Preparation of an Environmental Impact Statement for the Redlands; Passenger Rail Project in the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-31

..., travel times, and corridor safety. DATES: The date, time, and location for the public scoping meetings... mobility, travel times, and corridor safety while minimizing adverse environmental impacts. The RPRP would provide travelers and commuters with a new mobility option that would achieve more-efficient travel times...

7 CFR 52.50 - Travel and other expenses.

Code of Federal Regulations, 2012 CFR

2012-01-01

... and other expenses. Charges may be made to cover the cost of travel time incurred in connection with... hour. This includes time spent waiting for transportation as well as time spent traveling, but not to exceed eight hours of travel time for any one person for any one day: And provided further, that if...

Travelers’ Value of Time and Reliability as Measured on Katy Freeway : Final Report.

DOT National Transportation Integrated Search

2016-09-01

The value of travel time savings (VOT) is an estimate of what travelers would be willing to pay in order to save time on a particular trip. If travelers would pay $1 to reduce their travel time by six minutes, then they have a VOT of $10 per hour. VO...

The travel-time ellipse: An approximate zone of transport

USGS Publications Warehouse

Almendinger, J.E.

1994-01-01

A zone of transport for a well is defined as the area in the horizontal plane bounded by a contour of equal ground-water travel time to the well. For short distances and ground-water travel times near a well, the potentiometric surface may be simulated analytically as that for a fully penetrating well in a uniform flow field. The zone of transport for this configuration is nearly elliptical. A simple method is derived to calculate a travel-time ellipse that approximates the zone of transport for a well in a uniform flow field. The travel-time ellipse was nearly congruent with the exact solution for the theoretical zone of transport for ground-water travel times of at least 10 years and for aquifer property values appropriate for southeastern Minnesota. For distances and travel times approaching infinity, however, the ellipse becomes slightly wider at its midpoint and narrower near its upgradient boundary than the theoretical zone of transport. The travel-time ellipse also may be used to simulate the plume area surrounding an injection well. However, the travel-time ellipse is an approximation that does not account for the effect of dispersion in enlarging the true area of an injection plume or zone of transport; hence, caution is advised in the use and interpretation of this simple construction.

Dynamic Bus Travel Time Prediction Models on Road with Multiple Bus Routes

PubMed Central

Bai, Cong; Peng, Zhong-Ren; Lu, Qing-Chang; Sun, Jian

2015-01-01

Accurate and real-time travel time information for buses can help passengers better plan their trips and minimize waiting times. A dynamic travel time prediction model for buses addressing the cases on road with multiple bus routes is proposed in this paper, based on support vector machines (SVMs) and Kalman filtering-based algorithm. In the proposed model, the well-trained SVM model predicts the baseline bus travel times from the historical bus trip data; the Kalman filtering-based dynamic algorithm can adjust bus travel times with the latest bus operation information and the estimated baseline travel times. The performance of the proposed dynamic model is validated with the real-world data on road with multiple bus routes in Shenzhen, China. The results show that the proposed dynamic model is feasible and applicable for bus travel time prediction and has the best prediction performance among all the five models proposed in the study in terms of prediction accuracy on road with multiple bus routes. PMID:26294903

Dynamic Bus Travel Time Prediction Models on Road with Multiple Bus Routes.

PubMed

Bai, Cong; Peng, Zhong-Ren; Lu, Qing-Chang; Sun, Jian

2015-01-01

Accurate and real-time travel time information for buses can help passengers better plan their trips and minimize waiting times. A dynamic travel time prediction model for buses addressing the cases on road with multiple bus routes is proposed in this paper, based on support vector machines (SVMs) and Kalman filtering-based algorithm. In the proposed model, the well-trained SVM model predicts the baseline bus travel times from the historical bus trip data; the Kalman filtering-based dynamic algorithm can adjust bus travel times with the latest bus operation information and the estimated baseline travel times. The performance of the proposed dynamic model is validated with the real-world data on road with multiple bus routes in Shenzhen, China. The results show that the proposed dynamic model is feasible and applicable for bus travel time prediction and has the best prediction performance among all the five models proposed in the study in terms of prediction accuracy on road with multiple bus routes.

26 CFR 1.274-4 - Disallowance of certain foreign travel expenses.

Code of Federal Regulations, 2010 CFR

2010-04-01

... paragraph (d) of this section) constitutes 25 percent or more of the total time on such travel. (c) Travel... percent or more of travel time under paragraph (d) of this section and for purposes of allocating expenses... percent or more of travel time—(1) In general. This section does not apply to any expense of travel...

26 CFR 1.274-4 - Disallowance of certain foreign travel expenses.

Code of Federal Regulations, 2011 CFR

2011-04-01

... paragraph (d) of this section) constitutes 25 percent or more of the total time on such travel. (c) Travel... percent or more of travel time under paragraph (d) of this section and for purposes of allocating expenses... percent or more of travel time—(1) In general. This section does not apply to any expense of travel...

26 CFR 1.274-4 - Disallowance of certain foreign travel expenses.

Code of Federal Regulations, 2014 CFR

2014-04-01

... paragraph (d) of this section) constitutes 25 percent or more of the total time on such travel. (c) Travel... percent or more of travel time under paragraph (d) of this section and for purposes of allocating expenses... percent or more of travel time—(1) In general. This section does not apply to any expense of travel...

26 CFR 1.274-4 - Disallowance of certain foreign travel expenses.

Code of Federal Regulations, 2013 CFR

2013-04-01

... paragraph (d) of this section) constitutes 25 percent or more of the total time on such travel. (c) Travel... percent or more of travel time under paragraph (d) of this section and for purposes of allocating expenses... percent or more of travel time—(1) In general. This section does not apply to any expense of travel...

26 CFR 1.274-4 - Disallowance of certain foreign travel expenses.

Code of Federal Regulations, 2012 CFR

2012-04-01

... paragraph (d) of this section) constitutes 25 percent or more of the total time on such travel. (c) Travel... percent or more of travel time under paragraph (d) of this section and for purposes of allocating expenses... percent or more of travel time—(1) In general. This section does not apply to any expense of travel...

Travel during Pregnancy

MedlinePlus

... are 36 weeks pregnant. When is the best time to travel during pregnancy? The best time to travel is the middle of your pregnancy—between week ... Sitting or not moving for long periods of time, such as during long-distance travel, can increase the risk of DVT. Pregnancy further ...

Assessing segment- and corridor-based travel-time reliability on urban freeways tech transfer summary : tech transfer summary.

DOT National Transportation Integrated Search

2016-09-01

Travel time and travel-time reliability have been used as performance : measures to evaluate traffic system conditions and develop advanced : traveler information and traffic management systems. The objectives of this research were to: : - Quantify s...

Traveller Information System for Heterogeneous Traffic Condition: A Case Study in Thiruvananthapuram City, India

NASA Astrophysics Data System (ADS)

Satyakumar, M.; Anil, R.; Sreeja, G. S.

2017-12-01

Traffic in Kerala has been growing at a rate of 10-11% every year, resulting severe congestion especially in urban areas. Because of the limitation of spaces it is not always possible to construct new roads. Road users rely on travel time information for journey planning and route choice decisions, while road system managers are increasingly viewing travel time as an important network performance indicator. More recently Advanced Traveler Information Systems (ATIS) are being developed to provide real-time information to roadway users. For ATIS various methodologies have been developed for dynamic travel time prediction. For this work the Kalman Filter Algorithm was selected for dynamic travel time prediction of different modes. The travel time data collected using handheld GPS device were used for prediction. Congestion Index were calculated and Range of CI values were determined according to the percentage speed drop. After prediction using Kalman Filter, the predicted values along with the GPS data was integrated to GIS and using Network Analysis of ArcGIS the offline route navigation guide was prepared. Using this database a program for route navigation based on travel time was developed. This system will help the travelers with pre-trip information.

Special relativity in the school laboratory: a simple apparatus for cosmic-ray muon detection

NASA Astrophysics Data System (ADS)

Singh, P.; Hedgeland, H.

2015-05-01

We use apparatus based on two Geiger-Müller tubes, a simple electronic circuit and a Raspberry Pi computer to illustrate relativistic time dilation affecting cosmic-ray muons travelling through the atmosphere to the Earth’s surface. The experiment we describe lends itself to both classroom demonstration to accompany the topic of special relativity and to extended investigations for more inquisitive students.

Interstellar journeys in human lifetimes: numerical computations

NASA Astrophysics Data System (ADS)

Riggs, Peter J.

2017-05-01

Contrary to some contemporary accounts, a spacecraft with low acceleration can reach speeds very close to the speed of light in just a few years. In support of the teaching of special relativity, an easy to use software application has been created which calculates the values for travel times and distances to astronomical objects for such a spacecraft. This spreadsheet application may be conveniently employed as a basis for class exercises.

Dynamics and Stability of Acoustic Wavefronts in the Ocean

DTIC Science & Technology

2012-09-30

has been developed to solve the eikonal equation and calculate wavefront and ray trajectory displacements, which are required to be small over a...solution of the eikonal equation lies in the eikonal (and acoustic travel time) being a multi-valued function of position. A number of computational...approaches to solve the eikonal equation without ray tracing have been developed in mathematical and seismological communities (Vidale, 1990; Sava and

Dynamics and Stability of Acoustic Wavefronts in the Ocean

DTIC Science & Technology

2011-09-01

developed to solve the eikonal equation and calculate wavefront and ray trajectory displacements, which are required to be small over a correlation length...with a direct modeling of acoustic wavefronts in the ocean through numerical solution of the eikonal equation lies in the eikonal (and acoustic...travel time) being a multi-valued function of position. A number of computational approaches to solve the eikonal equation without ray tracing have been

41 CFR 301-71.306 - Are there exceptions to collecting an advance at the time the employee files a travel claim?

Code of Federal Regulations, 2014 CFR

2014-07-01

... collecting an advance at the time the employee files a travel claim? 301-71.306 Section 301-71.306 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...-71.306 Are there exceptions to collecting an advance at the time the employee files a travel claim...

41 CFR 301-71.306 - Are there exceptions to collecting an advance at the time the employee files a travel claim?

Code of Federal Regulations, 2013 CFR

2013-07-01

... collecting an advance at the time the employee files a travel claim? 301-71.306 Section 301-71.306 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...-71.306 Are there exceptions to collecting an advance at the time the employee files a travel claim...

41 CFR 301-71.306 - Are there exceptions to collecting an advance at the time the employee files a travel claim?

Code of Federal Regulations, 2012 CFR

2012-07-01

... collecting an advance at the time the employee files a travel claim? 301-71.306 Section 301-71.306 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...-71.306 Are there exceptions to collecting an advance at the time the employee files a travel claim...

41 CFR 301-71.306 - Are there exceptions to collecting an advance at the time the employee files a travel claim?

Code of Federal Regulations, 2010 CFR

2010-07-01

... collecting an advance at the time the employee files a travel claim? 301-71.306 Section 301-71.306 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...-71.306 Are there exceptions to collecting an advance at the time the employee files a travel claim...

41 CFR 301-71.306 - Are there exceptions to collecting an advance at the time the employee files a travel claim?

Code of Federal Regulations, 2011 CFR

2011-07-01

... collecting an advance at the time the employee files a travel claim? 301-71.306 Section 301-71.306 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...-71.306 Are there exceptions to collecting an advance at the time the employee files a travel claim...

Injection of mineral dust into the free troposphere during fire events observed with polarization lidar at Limassol, Cyprus

NASA Astrophysics Data System (ADS)

Nisantzi, A.; Mamouri, R. E.; Ansmann, A.; Hadjimitsis, D.

2014-11-01

Four-year observations (2010-2014) with EARLINET polarization lidar and AERONET sun/sky photometer at Limassol (34.7° N, 33° E), Cyprus, were used to study the soil dust content in lofted fire smoke plumes advected from Turkey. This first systematic attempt to characterize less than 3-day-old smoke plumes in terms of particle linear depolarization ratio (PDR), measured with lidar, contributes to the more general effort to properly describe the life cycle of free-tropospheric smoke-dust mixtures from the emission event to phases of long-range transport (> 4 days after emission). We found significant PDR differences with values from 9 to 18% in lofted aerosol layers when Turkish fires contributed to the aerosol burden and of 3-13 % when Turkish fires were absent. High Ångström exponents of 1.4-2.2 during all these events with lofted smoke layers, occurring between 1 and 3 km height, suggest the absence of a pronounced particle coarse mode. When plotted vs. travel time (spatial distance between Limassol and last fire area), PDR decreased strongly from initial values around 16-18% (1 day travel) to 4-8% after 4 days of travel caused by deposition processes. This behavior was found to be in close agreement with findings described in the literature. Computation of particle extinction coefficient and mass concentrations, derived from the lidar observations, separately for fine-mode dust, coarse-mode dust, and non-dust aerosol components show extinction-related dust fractions on the order of 10% (for PDR =4%, travel times > 4 days) and 50% (PDR =15%, 1 day travel time) and respective mass-related dust fractions of 25% (PDR =4%) to 80% (PDR =15%). Biomass burning should therefore be considered as another source of free tropospheric soil dust.

76 FR 1501 - Preparation of Environmental Impact Statement for Transit Improvements in the US 90A/Southwest...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-10

... limited traffic capacity on existing streets and highways resulting in increased travel time, delays, and... result, bus travel times are influenced by roadway congestion which is anticipated to increase. Peak period bus travel times can be as much as 30 percent longer than travel times during off-peak periods. In...

Field deployment to quantify the value of real-time information by integrating driver routing decisions and route assignment strategies.

DOT National Transportation Integrated Search

2014-05-01

Advanced Traveler Information Systems (ATIS) have been proposed as a mechanism to generate and : distribute real-time travel information to drivers for the purpose of improving travel experience : represented by experienced travel time and enhancing ...

Optimized Waterspace Management and Scheduling Using Mixed-Integer Linear Programming

DTIC Science & Technology

2016-01-01

Complete [30]. Proposition 4.1 satisfies the first criterion. For the second criterion, we will use the Traveling Salesman Problem (TSP), which has been...A branch and cut algorithm for the symmetric generalized traveling salesman problem , Operations Research 45 (1997) 378–394. [33] J. Silberholz, B...Golden, The generalized traveling salesman problem : A new genetic algorithm ap- proach, Extended Horizons: Advances in Computing, Optimization, and

Tsunamis generated by subaerial mass flows

USGS Publications Warehouse

Walder, S.J.; Watts, P.; Sorensen, O.E.; Janssen, K.

2003-01-01

Tsunamis generated in lakes and reservoirs by subaerial mass flows pose distinctive problems for hazards assessment because the domain of interest is commonly the "near field," beyond the zone of complex splashing but close enough to the source that wave propagation effects are not predominant. Scaling analysis of the equations governing water wave propagation shows that near-field wave amplitude and wavelength should depend on certain measures of mass flow dynamics and volume. The scaling analysis motivates a successful collapse (in dimensionless space) of data from two distinct sets of experiments with solid block "wave makers." To first order, wave amplitude/water depth is a simple function of the ratio of dimensionless wave maker travel time to dimensionless wave maker volume per unit width. Wave amplitude data from previous laboratory investigations with both rigid and deformable wave makers follow the same trend in dimensionless parameter space as our own data. The characteristic wavelength/water depth for all our experiments is simply proportional to dimensionless wave maker travel time, which is itself given approximately by a simple function of wave maker length/water depth. Wave maker shape and rigidity do not otherwise influence wave features. Application of the amplitude scaling relation to several historical events yields "predicted" near-field wave amplitudes in reasonable agreement with measurements and observations. Together, the scaling relations for near-field amplitude, wavelength, and submerged travel time provide key inputs necessary for computational wave propagation and hazards assessment.

Random vibration analysis of train-bridge under track irregularities and traveling seismic waves using train-slab track-bridge interaction model

NASA Astrophysics Data System (ADS)

Zeng, Zhi-Ping; Zhao, Yan-Gang; Xu, Wen-Tao; Yu, Zhi-Wu; Chen, Ling-Kun; Lou, Ping

2015-04-01

The frequent use of bridges in high-speed railway lines greatly increases the probability that trains are running on bridges when earthquakes occur. This paper investigates the random vibrations of a high-speed train traversing a slab track on a continuous girder bridge subjected to track irregularities and traveling seismic waves by the pseudo-excitation method (PEM). To derive the equations of motion of the train-slab track-bridge interaction system, the multibody dynamics and finite element method models are used for the train and the track and bridge, respectively. By assuming track irregularities to be fully coherent random excitations with time lags between different wheels and seismic accelerations to be uniformly modulated, non-stationary random excitations with time lags between different foundations, the random load vectors of the equations of motion are transformed into a series of deterministic pseudo-excitations based on PEM and the wheel-rail contact relationship. A computer code is developed to obtain the time-dependent random responses of the entire system. As a case study, the random vibration characteristics of an ICE-3 high-speed train traversing a seven-span continuous girder bridge simultaneously excited by track irregularities and traveling seismic waves are analyzed. The influence of train speed and seismic wave propagation velocity on the random vibration characteristics of the bridge and train are discussed.

Work, family and daily mobility: a new approach to the problem through a mobility survey.

PubMed

Olabarria, Marta; Pérez, Katherine; Santamariña-Rubio, Elena; Aragay, Josep Maria; Capdet, Mayte; Peiró, Rosana; Rodríguez-Sanz, Maica; Artazcoz, Lucía; Borrell, Carme

2013-01-01

To analyze gender inequalities in socioeconomic factors affecting the amount of time spent travelling for work-related and home-related reasons among working individuals aged between 30 and 44 years old during a weekday in Catalonia (Spain). A cross-sectional study was conducted. Data were obtained from employed individuals aged between 30 and 44 years of age who reported travelling on the day prior to the interview in the Catalan Mobility Survey 2006 (N = 23,424). Multivariate logistic regression models were adjusted to determine the factors associated with longer time spent travelling according to the reason for travelling (work- or home-related journeys). Odds ratios and 95% confidence intervals are presented. A higher proportion of men travelled and spent more time travelling for work-related reasons, while a higher proportion of women travelled and spend more time travelling for home-related reasons. A higher educational level was associated with greater time spent travelling for work-related reasons in both men and women but was related to an increase in travelling time for home-related reasons only in men. In women, a larger household was associated with greater travel time for home-related reasons and with less travel time for work-related reasons. This study confirms the different mobility patterns in men and women, related to their distinct positions in the occupational, family and domestic spheres. Gender inequalities in mobility within the working population are largely determined by the greater responsibility of women in the domestic and family sphere. This finding should be taken into account in the design of future transport policies. Copyright © 2012 SESPAS. Published by Elsevier Espana. All rights reserved.

31 CFR 515.564 - Professional research and professional meetings in Cuba.

Code of Federal Regulations, 2010 CFR

2010-07-01

... to professional research by full-time professionals who travel to Cuba to conduct professional... transactions as are directly incident to travel to Cuba by full-time professionals to attend professional... such a provider; and (ii) The traveler's schedule of activities does not include free time, travel, or...

31 CFR 515.564 - Professional research and professional meetings in Cuba.

Code of Federal Regulations, 2012 CFR

2012-07-01

... research by full-time professionals who travel to Cuba to conduct professional research in their... directly incident to travel to Cuba by full-time professionals to attend professional meetings or... provider; and (ii) The traveler's schedule of activities does not include free time, travel, or recreation...

31 CFR 515.564 - Professional research and professional meetings in Cuba.

Code of Federal Regulations, 2014 CFR

2014-07-01

... research by full-time professionals who travel to Cuba to conduct professional research in their... directly incident to travel to Cuba by full-time professionals to attend professional meetings or... provider; and (ii) The traveler's schedule of activities does not include free time, travel, or recreation...

31 CFR 515.564 - Professional research and professional meetings in Cuba.

Code of Federal Regulations, 2011 CFR

2011-07-01

... research by full-time professionals who travel to Cuba to conduct professional research in their... directly incident to travel to Cuba by full-time professionals to attend professional meetings or... provider; and (ii) The traveler's schedule of activities does not include free time, travel, or recreation...

31 CFR 515.564 - Professional research and professional meetings in Cuba.

Code of Federal Regulations, 2013 CFR

2013-07-01

... research by full-time professionals who travel to Cuba to conduct professional research in their... directly incident to travel to Cuba by full-time professionals to attend professional meetings or... provider; and (ii) The traveler's schedule of activities does not include free time, travel, or recreation...

The cost of simplifying air travel when modeling disease spread.

PubMed

Lessler, Justin; Kaufman, James H; Ford, Daniel A; Douglas, Judith V

2009-01-01

Air travel plays a key role in the spread of many pathogens. Modeling the long distance spread of infectious disease in these cases requires an air travel model. Highly detailed air transportation models can be over determined and computationally problematic. We compared the predictions of a simplified air transport model with those of a model of all routes and assessed the impact of differences on models of infectious disease. Using U.S. ticket data from 2007, we compared a simplified "pipe" model, in which individuals flow in and out of the air transport system based on the number of arrivals and departures from a given airport, to a fully saturated model where all routes are modeled individually. We also compared the pipe model to a "gravity" model where the probability of travel is scaled by physical distance; the gravity model did not differ significantly from the pipe model. The pipe model roughly approximated actual air travel, but tended to overestimate the number of trips between small airports and underestimate travel between major east and west coast airports. For most routes, the maximum number of false (or missed) introductions of disease is small (<1 per day) but for a few routes this rate is greatly underestimated by the pipe model. If our interest is in large scale regional and national effects of disease, the simplified pipe model may be adequate. If we are interested in specific effects of interventions on particular air routes or the time for the disease to reach a particular location, a more complex point-to-point model will be more accurate. For many problems a hybrid model that independently models some frequently traveled routes may be the best choice. Regardless of the model used, the effect of simplifications and sensitivity to errors in parameter estimation should be analyzed.

Human Mobility Networks, Travel Restrictions, and the Global Spread of 2009 H1N1 Pandemic

PubMed Central

Ramasco, Jose J.; Tizzoni, Michele; Colizza, Vittoria; Vespignani, Alessandro

2011-01-01

After the emergence of the H1N1 influenza in 2009, some countries responded with travel-related controls during the early stage of the outbreak in an attempt to contain or slow down its international spread. These controls along with self-imposed travel limitations contributed to a decline of about 40% in international air traffic to/from Mexico following the international alert. However, no containment was achieved by such restrictions and the virus was able to reach pandemic proportions in a short time. When gauging the value and efficacy of mobility and travel restrictions it is crucial to rely on epidemic models that integrate the wide range of features characterizing human mobility and the many options available to public health organizations for responding to a pandemic. Here we present a comprehensive computational and theoretical study of the role of travel restrictions in halting and delaying pandemics by using a model that explicitly integrates air travel and short-range mobility data with high-resolution demographic data across the world and that is validated by the accumulation of data from the 2009 H1N1 pandemic. We explore alternative scenarios for the 2009 H1N1 pandemic by assessing the potential impact of mobility restrictions that vary with respect to their magnitude and their position in the pandemic timeline. We provide a quantitative discussion of the delay obtained by different mobility restrictions and the likelihood of containing outbreaks of infectious diseases at their source, confirming the limited value and feasibility of international travel restrictions. These results are rationalized in the theoretical framework characterizing the invasion dynamics of the epidemics at the metapopulation level. PMID:21304943

Direct Numerical Simulations of an Unpremixed Turbulent Jet Flame

DTIC Science & Technology

1988-03-01

shear layer. As the vortices reach the outflow boundary, the zero-gradient condition seems to allow them to travel out of the computational domain...ei Ii-t salp . Thiey- used pint ihe ustial d ependent variales. I1 Imerefre for r’- H(1/2 act1ig flows tile dimniensiomalit v of tilie vystveni call...seems to allow them to travel out of the computational domain. As mentioned in the previous section, the errors associated with this boundary condition

Evans function computation for the stability of travelling waves

NASA Astrophysics Data System (ADS)

Barker, B.; Humpherys, J.; Lyng, G.; Lytle, J.

2018-04-01

In recent years, the Evans function has become an important tool for the determination of stability of travelling waves. This function, a Wronskian of decaying solutions of the eigenvalue equation, is useful both analytically and computationally for the spectral analysis of the linearized operator about the wave. In particular, Evans-function computation allows one to locate any unstable eigenvalues of the linear operator (if they exist); this allows one to establish spectral stability of a given wave and identify bifurcation points (loss of stability) as model parameters vary. In this paper, we review computational aspects of the Evans function and apply it to multidimensional detonation waves. This article is part of the theme issue `Stability of nonlinear waves and patterns and related topics'.

[Travel times of patients to ambulatory care physicians in Germany].

PubMed

Schang, Laura; Kopetsch, Thomas; Sundmacher, Leonie

2017-12-01

The time needed by patients to get to a doctor's office represents an important indicator of realised access to care. In Germany, findings on travel times are only available from surveys or for some regions. For the first time, this study examines nationwide and physician group-specific travel times in the ambulatory care sector in Germany and describes demographic, supply-side and spatial determinants of variations. Using a full review of patient consultations in the statutory health insurance system from 2009/2010 for 14 physician groups (approximately 518 million cases), case-related travel times by car between patients' places of residence and physician's practices were estimated at the municipal level. Physicians were reached in less than 30 min in 90.8% of cases for primary care physicians and up to 63% of cases for radiologists. Patients between 18 and under 30 years of age travel longer to get to the doctor than other age groups. The average travel time at the county level systematically differs between urban and rural planning areas. In the case of gynecologists, dermatologists and ophthalmologists, the average journey time decreases with increasing physician density at the county level, but remains approximately constant from a recognisable point of inflection. There is no association between primary care physician density and travel time at the district level. Spatial analyses show physician group-specific patterns of regional concentrations with an increased proportion of cases with very long travel times. Patients' travel times are influenced by supply- and demand-side determinants. Interactions between influential determinants should be analysed in depth to examine the extent to which the time travelled is an expression of regional under- or over-supply rather than an expression of patient preferences.

Travelers' Health: Yellow Fever

MedlinePlus

... and local rate of virus transmission at the time of travel. Although reported cases of human disease are the ... be receiving yellow fever vaccine for the first time. If travel is unavoidable, the decision to vaccinate travelers aged ≥ ...

Measurement of ground water velocity using Rhodamine WT dye near Sheffield, Illinois

USGS Publications Warehouse

Garklavs, George; Toler, L.G.

1985-01-01

Ground-water flow velocity was estimated in a tract of land adjacent to a low-level radioactive-waste disposal site near Sheffield, Illinois, by measuring the time-of-travel between two wells spaced 110 feet apart. Rhodamine WT dye was the principal tracer used in the test. The leading edge and peak concentrations of Rhodamine WT were well defined. A ground-water velocity of 6.9 feet per day (2,500 feet per year) was computed from the arrival time of the leading edge of the tracer cloud. (USGS)

A Simple Mathematical Model Inspired by the Purkinje Cells: From Delayed Travelling Waves to Fractional Diffusion.

PubMed

Dipierro, Serena; Valdinoci, Enrico

2018-07-01

Recently, several experiments have demonstrated the existence of fractional diffusion in the neuronal transmission occurring in the Purkinje cells, whose malfunctioning is known to be related to the lack of voluntary coordination and the appearance of tremors. Also, a classical mathematical feature is that (fractional) parabolic equations possess smoothing effects, in contrast with the case of hyperbolic equations, which typically exhibit shocks and discontinuities. In this paper, we show how a simple toy-model of a highly ramified structure, somehow inspired by that of the Purkinje cells, may produce a fractional diffusion via the superposition of travelling waves that solve a hyperbolic equation. This could suggest that the high ramification of the Purkinje cells might have provided an evolutionary advantage of "smoothing" the transmission of signals and avoiding shock propagations (at the price of slowing a bit such transmission). Although an experimental confirmation of the possibility of such evolutionary advantage goes well beyond the goals of this paper, we think that it is intriguing, as a mathematical counterpart, to consider the time fractional diffusion as arising from the superposition of delayed travelling waves in highly ramified transmission media. The case of a travelling concave parabola with sufficiently small curvature is explicitly computed. The new link that we propose between time fractional diffusion and hyperbolic equation also provides a novelty with respect to the usual paradigm relating time fractional diffusion with parabolic equations in the limit. This paper is written in such a way as to be of interest to both biologists and mathematician alike. In order to accomplish this aim, both complete explanations of the objects considered and detailed lists of references are provided.

Global-scale Joint Body and Surface Wave Tomography with Vertical Transverse Isotropy for Seismic Monitoring Applications

NASA Astrophysics Data System (ADS)

Simmons, Nathan; Myers, Steve

2017-04-01

We continue to develop more advanced models of Earth's global seismic structure with specific focus on improving predictive capabilities for future seismic events. Our most recent version of the model combines high-quality P and S wave body wave travel times and surface-wave group and phase velocities into a joint (simultaneous) inversion process to tomographically image Earth's crust and mantle. The new model adds anisotropy (known as vertical transverse isotropy) to the model, which is necessitated by the addition of surface waves to the tomographic data set. Like previous versions of the model the new model consists of 59 surfaces and 1.6 million model nodes from the surface to the core-mantle boundary, overlaying a 1-D outer and inner core model. The model architecture is aspherical and we directly incorporate Earth's expected hydrostatic shape (ellipticity and mantle stretching). We also explicitly honor surface undulations including the Moho, several internal crustal units, and the upper mantle transition zone undulations as predicated by previous studies. The explicit Earth model design allows for accurate travel time computation using our unique 3-D ray tracing algorithms, capable of 3-D ray tracing more than 20 distinct seismic phases including crustal, regional, teleseismic, and core phases. Thus, we can now incorporate certain secondary (and sometimes exotic) phases into source location determination and other analyses. New work on model uncertainty quantification assesses the error covariance of the model, which when completed will enable calculation of path-specific estimates of uncertainty for travel times computed using our previous model (LLNL-G3D-JPS) which is available to the monitoring and broader research community and we encourage external evaluation and validation. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

76 FR 61622 - Potential Closing of Morses Line Border Crossing

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-05

... travelers would need to travel to an alternate crossing which could cost them both time and money. CBP does... measured the distance and estimated time for each combination assuming they could not travel through Morses Line. By comparing the distance and travel time for the fastest route to those for the fastest route...

5 CFR 610.123 - Travel on official time.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 5 Administrative Personnel 1 2014-01-01 2014-01-01 false Travel on official time. 610.123 Section... DUTY Weekly and Daily Scheduling of Work Work Schedules § 610.123 Travel on official time. Insofar as practicable travel during nonduty hours shall not be required of an employee. When it is essential that this...

5 CFR 610.123 - Travel on official time.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Travel on official time. 610.123 Section... DUTY Weekly and Daily Scheduling of Work Work Schedules § 610.123 Travel on official time. Insofar as practicable travel during nonduty hours shall not be required of an employee. When it is essential that this...

5 CFR 610.123 - Travel on official time.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Travel on official time. 610.123 Section... DUTY Weekly and Daily Scheduling of Work Work Schedules § 610.123 Travel on official time. Insofar as practicable travel during nonduty hours shall not be required of an employee. When it is essential that this...

5 CFR 610.123 - Travel on official time.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 5 Administrative Personnel 1 2013-01-01 2013-01-01 false Travel on official time. 610.123 Section... DUTY Weekly and Daily Scheduling of Work Work Schedules § 610.123 Travel on official time. Insofar as practicable travel during nonduty hours shall not be required of an employee. When it is essential that this...

5 CFR 610.123 - Travel on official time.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Travel on official time. 610.123 Section... DUTY Weekly and Daily Scheduling of Work Work Schedules § 610.123 Travel on official time. Insofar as practicable travel during nonduty hours shall not be required of an employee. When it is essential that this...

Travel costs associated with flood closures of state highways near Centralia/Chehalis, Washington.

DOT National Transportation Integrated Search

2014-09-01

This report discusses the travel costs associated with the closure of roads in the greater : Centralia/Chehalis, Washington region due to 100-year flood conditions starting on the Chehalis River. The costs : were computed for roadway closures on I-5,...

5 CFR 550.1403 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Compensatory Time Off for Travel § 550.1403 Definitions. In this subpart: Accrued compensatory time off means... pay limitations. Compensatory time off means compensatory time off for travel that is credited under... of determining whether travel time is compensable for the purpose of determining overtime pay...

5 CFR 550.1403 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) Compensatory Time Off for Travel § 550.1403 Definitions. In this subpart: Accrued compensatory time off means... pay limitations. Compensatory time off means compensatory time off for travel that is credited under... of determining whether travel time is compensable for the purpose of determining overtime pay...

5 CFR 550.1403 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) Compensatory Time Off for Travel § 550.1403 Definitions. In this subpart: Accrued compensatory time off means... pay limitations. Compensatory time off means compensatory time off for travel that is credited under... of determining whether travel time is compensable for the purpose of determining overtime pay...

5 CFR 550.1403 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) Compensatory Time Off for Travel § 550.1403 Definitions. In this subpart: Accrued compensatory time off means... pay limitations. Compensatory time off means compensatory time off for travel that is credited under... of determining whether travel time is compensable for the purpose of determining overtime pay...

5 CFR 550.1403 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) Compensatory Time Off for Travel § 550.1403 Definitions. In this subpart: Accrued compensatory time off means... pay limitations. Compensatory time off means compensatory time off for travel that is credited under... of determining whether travel time is compensable for the purpose of determining overtime pay...

Inferring atmospheric weather conditions in volcanic environments using infrasound

NASA Astrophysics Data System (ADS)

Ortiz, H. D.; Johnson, J. B.; Ruiz, M. C.

2015-12-01

We use infrasound produced by Tungurahua Volcano (Ecuador) to infer local time-varying atmospheric conditions, which can be used to improve gas flux measurements and tephra dispersal modeling. Physical properties of the atmosphere, including wind and temperature (which controls adiabatic sound speed), can be quantified by studying the travel times of acoustic waves produced during volcanic activity. The travel times between Tungurahua's vent and five infrasound stations located in a network configuration over an area of 90 km2 were used in this study. We are able to quantify the arrival time differences of acoustic waves for ten unique station pairs and use this information to model the average speed of sound between source and receiver. To identify what parameters best fit the observed arrival times, we perform a grid search for a homogeneous two-dimensional wind velocity as well as for air temperature. Due to travel time dependence on the specific path taken by waves, we account for topography using a 5 meter resolution digital elevation model of Tungurahua. To investigate the time-varying atmospheric structure we use data recorded at Tungurahua volcano, during a strombolian eruptive phase in August 2012, however the methodology can be applied to continuous network infrasound data collected since July 2006 as part of the Japanese-Ecuadorian Cooperation Project: "Enhancement of the Volcano Monitoring Capacity in Ecuador". We propose that the computation of wind velocities will help to improve gas flux measurements that are based on remote sensing techniques like Differential Optical Absorption Spectroscopy (DOAS), resulting in better estimates of sulfur fluxes that can then be related to magma fluxing into the volcanic system. Further, wind field quantification close to the volcano can improve numerical models that are used to forecast tephra deposits, thereby helping to mitigate their effect on inhabitants, infrastructure, livestock, and crops.

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?

Code of Federal Regulations, 2010 CFR

2010-07-01

... departure/arrival dates and times on my travel claim? 301-11.10 Section 301-11.10 Public Contracts and... dates and times on my travel claim? You must record the date of departure from, and arrival at, the... visited. You do not have to record departure/arrival times, but you must annotate your travel claim when...

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?

Code of Federal Regulations, 2013 CFR

2013-07-01

... departure/arrival dates and times on my travel claim? 301-11.10 Section 301-11.10 Public Contracts and... dates and times on my travel claim? You must record the date of departure from, and arrival at, the... visited. You do not have to record departure/arrival times, but you must annotate your travel claim when...

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?

Code of Federal Regulations, 2012 CFR

2012-07-01

... departure/arrival dates and times on my travel claim? 301-11.10 Section 301-11.10 Public Contracts and... dates and times on my travel claim? You must record the date of departure from, and arrival at, the... visited. You do not have to record departure/arrival times, but you must annotate your travel claim when...

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?

Code of Federal Regulations, 2011 CFR

2011-07-01

... departure/arrival dates and times on my travel claim? 301-11.10 Section 301-11.10 Public Contracts and... dates and times on my travel claim? You must record the date of departure from, and arrival at, the... visited. You do not have to record departure/arrival times, but you must annotate your travel claim when...

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?

Code of Federal Regulations, 2014 CFR

2014-07-01

... departure/arrival dates and times on my travel claim? 301-11.10 Section 301-11.10 Public Contracts and... dates and times on my travel claim? You must record the date of departure from, and arrival at, the... visited. You do not have to record departure/arrival times, but you must annotate your travel claim when...

Value of travel time.

DOT National Transportation Integrated Search

2016-08-01

Knowingly or not, people generally place economic value on their time. Wage workers are paid a rate per hour, and service providers may charge per hour of their time. In the transportation realm, travelers place a value on their travel time and have ...

The impact of travel time on geographic distribution of dialysis patients.

PubMed

Kashima, Saori; Matsumoto, Masatoshi; Ogawa, Takahiko; Eboshida, Akira; Takeuchi, Keisuke

2012-01-01

The geographic disparity of prevalence rates among dialysis patients is unclear. We evaluate the association between travel time to dialysis facilities and prevalence rates of dialysis patients living in 1,867 census areas of Hiroshima, Japan. Furthermore, we study the effects of geographic features (mainland or island) on the prevalence rates and assess if these effects modify the association between travel time and prevalence. The study subjects were all 7,374 people that were certified as the "renal disabled" by local governments in 2011. The travel time from each patient to the nearest available dialysis facility was calculated by incorporating both travel time and the capacity of all 98 facilities. The effect of travel time on the age- and sex-adjusted standard prevalence rate (SPR) and 95% confidence intervals (CIs) at each census area was evaluated in two-level Poisson regression models with 1,867 census areas (level 1) nested within 35 towns or cities (level 2). The results were adjusted for area-based parameters of socioeconomic status, urbanity, and land type. Furthermore, the SPR of dialysis patients was calculated in each specific subgroup of population for travel time, land type, and combination of land type and travel time. In the regression analysis, SPR decreased by 5.2% (95% CI: -7.9--2.3) per 10-min increase in travel time even after adjusting for potential confounders. The effect of travel time on prevalence was different in the mainland and island groups. There was no travel time-dependent SPR disparity on the islands. The SPR among remote residents (>30 min from facilities) in the mainland was lower (0.77, 95% CI: 0.71-0.85) than that of closer residents (≤ 30 min; 0.95, 95% CI: 0.92-0.97). The prevalence of dialysis patients was lower among remote residents. Geographic difficulties for commuting seem to decrease the prevalence rate.

The influence of travel time on breast cancer characteristics, receipt of primary therapy, and surveillance mammography.

PubMed

Onega, Tracy; Cook, Andrea; Kirlin, Beth; Shi, Xun; Alford-Teaster, Jennifer; Tuzzio, Leah; Buist, Diana S M

2011-08-01

Travel time has been shown to influence some aspects of cancer characteristics at diagnosis and care for women with breast cancer, but important gaps remain in our understanding of its impact. We examined the influence of travel time to the nearest radiology facility on breast cancer characteristics, treatment, and surveillance for women with early-stage invasive breast cancer. We included 1,012 women with invasive breast cancer (stages I and II) who had access to care within an integrated health care delivery system in western Washington State. The travel times to the nearest radiology facility were calculated for all the U.S. Census blocks within the study area and assigned to women based on residence at diagnosis. We collected cancer characteristics, primary and adjuvant therapies, and surveillance mammography for at least 2.5 years post diagnosis and used multivariable analyses to test the associations of travel time. The majority of women (68.6%) lived within 20 min of the nearest radiology facility, had stage I disease (72.7%), received breast conserving therapy (68.7%), and had annual surveillance mammography the first 2 years after treatment (73.7%). The travel time was not significantly associated with the stage or surveillance mammography after adjusting for covariates. Primary therapy was significantly related to travel time, with greater travel time (>30 min vs. ≤ 10 min) associated with a higher likelihood of mastectomy compared to breast conserving surgery (RR = 1.53; 95% CI, 1.16-2.01). The travel time was not associated with the stage at diagnosis or surveillance mammography receipt. The travel time does seem to influence the type of primary therapy among women with breast cancer, suggesting that women may prefer low frequency services, such as mastectomy, if geographic access to a radiology facility is limited.

Accurate Cold-Test Model of Helical TWT Slow-Wave Circuits

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Dayton, James A., Jr.

1997-01-01

Recently, a method has been established to accurately calculate cold-test data for helical slow-wave structures using the three-dimensional electromagnetic computer code, MAFIA. Cold-test parameters have been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment. The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits. The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation.

Time-Dependent Traveling Wave Tube Model for Intersymbol Interference Investigations

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Andro, Monty; Downey, Alan (Technical Monitor)

2001-01-01

For the first time, a computational model has been used to provide a direct description of the effects of the traveling wave tube (TWT) on modulated digital signals. The TWT model comprehensively takes into account the effects of frequency dependent AM/AM and AM/PM conversion, gain and phase ripple; drive-induced oscillations; harmonic generation; intermodulation products; and backward waves. Thus, signal integrity can be investigated in the presence of these sources of potential distortion as a function of the physical geometry of the high power amplifier and the operational digital signal. This method promises superior predictive fidelity compared to methods using TWT models based on swept-amplitude and/or swept-frequency data. The fully three-dimensional (3D), time-dependent, TWT interaction model using the electromagnetic code MAFIA is presented. This model is used to investigate assumptions made in TWT black-box models used in communication system level simulations. In addition, digital signal performance, including intersymbol interference (ISI), is compared using direct data input into the MAFIA model and using the system level analysis tool, SPW.

Intersymbol Interference Investigations Using a 3D Time-Dependent Traveling Wave Tube Model

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Andro, Monty; Downey, Alan (Technical Monitor)

2001-01-01

For the first time, a physics based computational model has been used to provide a direct description of the effects of the TWT (Traveling Wave Tube) on modulated digital signals. The TWT model comprehensively takes into account the effects of frequency dependent AM/AM and AM/PM conversion; gain and phase ripple; drive-induced oscillations; harmonic generation; intermodulation products; and backward waves. Thus, signal integrity can be investigated in the presence of these sources of potential distortion as a function of the physical geometry of the high power amplifier and the operational digital signal. This method promises superior predictive fidelity compared to methods using TWT models based on swept amplitude and/or swept frequency data. The fully three-dimensional (3D), time-dependent, TWT interaction model using the electromagnetic code MAFIA is presented. This model is used to investigate assumptions made in TWT black box models used in communication system level simulations. In addition, digital signal performance, including intersymbol interference (ISI), is compared using direct data input into the MAFIA model and using the system level analysis tool, SPW (Signal Processing Worksystem).

East Pacific Rise axial structure from a joint tomographic inversion of traveltimes picked on downward continued and standard shot gathers collected by 3D MCS surveying

NASA Astrophysics Data System (ADS)

Newman, Kori; Nedimović, Mladen; Delescluse, Matthias; Menke, William; Canales, J. Pablo; Carbotte, Suzanne; Carton, Helene; Mutter, John

2010-05-01

We present traveltime tomographic models along closely spaced (~250 m), strike-parallel profiles that flank the axis of the East Pacific Rise at 9°41' - 9°57' N. The data were collected during a 3D (multi-streamer) multichannel seismic (MCS) survey of the ridge. Four 6-km long hydrophone streamers were towed by the ship along three along-axis sail lines, yielding twelve possible profiles over which to compute tomographic models. Based on the relative location between source-receiver midpoints and targeted subsurface structures, we have chosen to compute models for four of those lines. MCS data provide for a high density of seismic ray paths with which to constrain the model. Potentially, travel times for ~250,000 source-receiver pairs can be picked over the 30 km length of each model. However, such data density does not enhance the model resolution, so, for computational efficiency, the data are decimated so that ~15,000 picks per profile are used. Downward continuation of the shot gathers simulates an experimental geometry in which the sources and receivers are positioned just above the sea floor. This allows the shallowest sampling refracted arrivals to be picked and incorporated into the inversion whereas they would otherwise not be usable with traditional first-arrival travel-time tomographic techniques. Some of the far-offset deep-penetrating 2B refractions cannot be picked on the downward continued gathers due to signal processing artifacts. For this reason, we run a joint inversion by also including 2B traveltime picks from standard shot gathers. Uppermost velocity structure (seismic layer 2A thickness and velocity) is primarily constrained from 1D inversion of the nearest offset (<500 m) source-receiver travel-time picks for each downward continued shot gather. Deeper velocities are then computed in a joint 2D inversion that uses all picks from standard and downward continued shot gathers and incorporates the 1D results into the starting model. The resulting velocity models extend ~1 km into the crust. Preliminary results show thicker layer 2A and faster layer 2A velocities at fourth order ridge segment boundaries. Additionally, layer 2A thickens north of 9° 52' N, which is consistent with earlier investigations of this ridge segment. Slower layer 2B velocities are resolved in the vicinity of documented hydrothermal vent fields. We anticipate that additional analyses of the results will yield further insight into fine scale variations in near-axis mid-ocean ridge structure.

77 FR 69920 - Notice of Availability for Public Review of the Draft Tier 1 Environmental Impact Statement for...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-21

... would provide an alternative to automobile, bus, and air travel by decreasing travel times, increasing... and need criteria by: decreasing travel times; increasing frequency of service; improving service... current and future demand for travel in the Study area. The need stems from travel demand and increasing...

Visiting Astronomers Travel Guide | CTIO

Science.gov Websites

please advise Ximena Herreros at the time that you initiate travel plans, if your stay in Chile will , well in advance of their travel time, regarding current visa requirements for Chile. back to top Visiting Astronomers Travel Guide Director's Discretionary (DD) Time CTIO 2016 Ephemeris ToO Policy CTIO

11 CFR 100.93 - Travel by aircraft or other means of transportation.

Code of Federal Regulations, 2014 CFR

2014-01-01

... traveled or within seven (7) calendar days thereof. The payment rate must be determined by the time the... travel on an aircraft that is owned or leased under a shared-ownership or other time-share arrangement... travel on an aircraft that is owned or leased under a shared-ownership or other time-share arrangement...

29 CFR 785.39 - Travel away from home community.

Code of Federal Regulations, 2011 CFR

2011-07-01

... employee's workday. The employee is simply substituting travel for other duties. The time is not only hours... travel time during these hours is worktime on Saturday and Sunday as well as on the other days. Regular... that time spent in travel away from home outside of regular working hours as a passenger on an airplane...

29 CFR 785.39 - Travel away from home community.

Code of Federal Regulations, 2014 CFR

2014-07-01

... employee's workday. The employee is simply substituting travel for other duties. The time is not only hours... travel time during these hours is worktime on Saturday and Sunday as well as on the other days. Regular... that time spent in travel away from home outside of regular working hours as a passenger on an airplane...

29 CFR 785.39 - Travel away from home community.

Code of Federal Regulations, 2013 CFR

2013-07-01

... employee's workday. The employee is simply substituting travel for other duties. The time is not only hours... travel time during these hours is worktime on Saturday and Sunday as well as on the other days. Regular... that time spent in travel away from home outside of regular working hours as a passenger on an airplane...

11 CFR 100.93 - Travel by airplane or other means of transportation.

Code of Federal Regulations, 2010 CFR

2010-01-01

... committee on behalf of which the travel is conducted pays the service provider, within the required time... traveled or within seven (7) calendar days thereof. The payment rate must be determined by the time the... travel on an aircraft that is owned or leased under a shared-ownership or other time-share arrangement...

29 CFR 785.39 - Travel away from home community.

Code of Federal Regulations, 2010 CFR

2010-07-01

... employee's workday. The employee is simply substituting travel for other duties. The time is not only hours... travel time during these hours is worktime on Saturday and Sunday as well as on the other days. Regular... that time spent in travel away from home outside of regular working hours as a passenger on an airplane...

29 CFR 785.39 - Travel away from home community.

Code of Federal Regulations, 2012 CFR

2012-07-01

... employee's workday. The employee is simply substituting travel for other duties. The time is not only hours... travel time during these hours is worktime on Saturday and Sunday as well as on the other days. Regular... that time spent in travel away from home outside of regular working hours as a passenger on an airplane...

Wireless data collection system for real-time arterial travel time estimates.

DOT National Transportation Integrated Search

2011-03-01

This project pursued several objectives conducive to the implementation and testing of a Bluetooth (BT) based system to collect travel time data, including the deployment of a BT-based travel time data collection system to perform comprehensive testi...

Vertically inhomogeneous models of the upper crust for the seismoactive region of western Bohemia

NASA Astrophysics Data System (ADS)

Malek, J.; Jansky, J.; Novotny, O.; Rossler, D.

2003-04-01

In the framework of the CELEBRATION 2000 seismic refraction experiment, one international profile crossed the region of earthquake swarms in West-Bohemia/Vogtland. In addition to this main profile, two shorter supplementary profiles and a semicircle were proposed to study the epicentral area in greater detail. Moreover, the shots were also recorded at permanent stations in the region. The observed travel times of the first arrivals are used here to derive vertically inhomogeneous velocity models of the upper crust. After a polynomial or rational smoothing of the observed data, the Wiechert-Herglotz method is used to compute the velocity models. Typical features of the derived models, as opposed to many previous models, are low surface velocities and a prominent velocity increase within the uppermost crust to a depth of about one kilometre. The scatter of observed travel times is discussed in terms of lateral inhomogeneities and anisotropy. In particular, significant differences have been revealed between the Saxothuringian (northern) and adjacent southern parts of the studied area.

Implementation and testing of the travel time prediction system (TIPS) : final report, May 2001.

DOT National Transportation Integrated Search

2001-05-01

The Travel Time Prediction System (TIPS) is a portable automated system for predicting and displaying travel time for motorists in advance of and through freeway construction work zones, on a real-time basis. It collects real-time traffic flow data u...

Implementation and testing of the travel time prediction system (TIPS) : executive summary, May 2001.

DOT National Transportation Integrated Search

2001-05-01

The Travel Time Prediction System (TIPS) is a portable automated system for predicting and displaying travel time for motorists in advance of and through freeway construction work zones, on a real-time basis. It collects real-time traffic flow data u...

The impact of mass gatherings and holiday traveling on the course of an influenza pandemic: a computational model.

PubMed

Shi, Pengyi; Keskinocak, Pinar; Swann, Julie L; Lee, Bruce Y

2010-12-21

During the 2009 H1N1 influenza pandemic, concerns arose about the potential negative effects of mass public gatherings and travel on the course of the pandemic. Better understanding the potential effects of temporal changes in social mixing patterns could help public officials determine if and when to cancel large public gatherings or enforce regional travel restrictions, advisories, or surveillance during an epidemic. We develop a computer simulation model using detailed data from the state of Georgia to explore how various changes in social mixing and contact patterns, representing mass gatherings and holiday traveling, may affect the course of an influenza pandemic. Various scenarios with different combinations of the length of the mass gatherings or traveling period (range: 0.5 to 5 days), the proportion of the population attending the mass gathering events or on travel (range: 1% to 50%), and the initial reproduction numbers R0 (1.3, 1.5, 1.8) are explored. Mass gatherings that occur within 10 days before the epidemic peak can result in as high as a 10% relative increase in the peak prevalence and the total attack rate, and may have even worse impacts on local communities and travelers' families. Holiday traveling can lead to a second epidemic peak under certain scenarios. Conversely, mass traveling or gatherings may have little effect when occurring much earlier or later than the epidemic peak, e.g., more than 40 days earlier or 20 days later than the peak when the initial R0 = 1.5. Our results suggest that monitoring, postponing, or cancelling large public gatherings may be warranted close to the epidemic peak but not earlier or later during the epidemic. Influenza activity should also be closely monitored for a potential second peak if holiday traveling occurs when prevalence is high.

Integrating pro-environmental behavior with transportation network modeling: User and system level strategies, implementation, and evaluation

NASA Astrophysics Data System (ADS)

Aziz, H. M. Abdul

Personal transport is a leading contributor to fossil fuel consumption and greenhouse (GHG) emissions in the U.S. The U.S. Energy Information Administration (EIA) reports that light-duty vehicles (LDV) are responsible for 61% of all transportation related energy consumption in 2012, which is equivalent to 8.4 million barrels of oil (fossil fuel) per day. The carbon content in fossil fuels is the primary source of GHG emissions that links to the challenge associated with climate change. Evidently, it is high time to develop actionable and innovative strategies to reduce fuel consumption and GHG emissions from the road transportation networks. This dissertation integrates the broader goal of minimizing energy and emissions into the transportation planning process using novel systems modeling approaches. This research aims to find, investigate, and evaluate strategies that minimize carbon-based fuel consumption and emissions for a transportation network. We propose user and system level strategies that can influence travel decisions and can reinforce pro-environmental attitudes of road users. Further, we develop strategies that system operators can implement to optimize traffic operations with emissions minimization goal. To complete the framework we develop an integrated traffic-emissions (EPA-MOVES) simulation framework that can assess the effectiveness of the strategies with computational efficiency and reasonable accuracy. The dissertation begins with exploring the trade-off between emissions and travel time in context of daily travel decisions and its heterogeneous nature. Data are collected from a web-based survey and the trade-off values indicating the average additional travel minutes a person is willing to consider for reducing a lb. of GHG emissions are estimated from random parameter models. Results indicate that different trade-off values for male and female groups. Further, participants from high-income households are found to have higher trade-off values compared with other groups. Next, we propose personal mobility carbon allowance (PMCA) scheme to reduce emissions from personal travel. PMCA is a market-based scheme that allocates carbon credits to users at no cost based on the emissions reduction goal of the system. Users can spend carbon credits for travel and a market place exists where users can buy or sell credits. This dissertation addresses two primary dimensions: the change in travel behavior of the users and the impact at network level in terms of travel time and emissions when PMCA is implemented. To understand this process, a real-time experimental game tool is developed where players are asked to make travel decisions within the carbon budget set by PMCA and they are allowed to trade carbon credits in a market modeled as a double auction game. Random parameter models are estimated to examine the impact of PMCA on short-term travel decisions. Further, to assess the impact at system level, a multi-class dynamic user equilibrium model is formulated that captures the travel behavior under PMCA scheme. The equivalent variational inequality problem is solved using projection method. Results indicate that PMCA scheme is able to reduce GHG emissions from transportation networks. Individuals with high value of travel time (VOTT) are less sensitive to PMCA scheme in context of work trips. High and medium income users are more likely to have non-work trips with lower carbon cost (higher travel time) to save carbon credits for work trips. Next, we focus on the strategies from the perspectives of system operators in transportation networks. Learning based signal control schemes are developed that can reduce emissions from signalized urban networks. The algorithms are implemented and tested in VISSIM micro simulator. Finally, an integrated emissions-traffic simulator framework is outlined that can be used to evaluate the effectiveness of the strategies. The integrated framework uses MOVES2010b as the emissions simulator. To estimate the emissions efficiently we propose a hierarchical clustering technique with dynamic time warping similarity measures (HC-DTW) to find the link driving schedules for MOVES2010b. Test results using the data from a five-intersection corridor show that HC-DTW technique can significantly reduce emissions estimation time without compromising the accuracy. The benefits are found to be most significant when the level of congestion variation is high. In addition to finding novel strategies for reducing emissions from transportation networks, this dissertation has broader impacts on behavior based energy policy design and transportation network modeling research. The trade-off values can be a useful indicator to identify which policies are most effective to reinforce pro-environmental travel choices. For instance, the model can estimate the distribution of trade-off between emissions and travel time, and provide insights on the effectiveness of policies for New York City if we are able to collect data to construct a representative sample. The probability of route choice decisions vary across population groups and trip contexts. The probability as a function of travel and demographic attributes can be used as behavior rules for agents in an agent-based traffic simulation. Finally, the dynamic user equilibrium based network model provides a general framework for energy policies such carbon tax, tradable permit, and emissions credits system.

Dynamic travel time estimation using regression trees.

DOT National Transportation Integrated Search

2008-10-01

This report presents a methodology for travel time estimation by using regression trees. The dissemination of travel time information has become crucial for effective traffic management, especially under congested road conditions. In the absence of c...

Evaluation of Effective Factors on Travel Time in Optimization of Bus Stops Placement Using Genetic Algorithm

NASA Astrophysics Data System (ADS)

Bargegol, Iraj; Ghorbanzadeh, Mahyar; Ghasedi, Meisam; Rastbod, Mohammad

2017-10-01

In congested cities, locating and proper designing of bus stops according to the unequal distribution of passengers is crucial issue economically and functionally, since this subject plays an important role in the use of bus system by passengers. Location of bus stops is a complicated subject; by reducing distances between stops, walking time decreases, but the total travel time may increase. In this paper, a specified corridor in the city of Rasht in north of Iran is studied. Firstly, a new formula is presented to calculate the travel time, by which the number of stops and consequently, the travel time can be optimized. An intended corridor with specified number of stops and distances between them is addressed, the related formulas to travel time are created, and its travel time is calculated. Then the corridor is modelled using a meta-heuristic method in order that the placement and the optimal distances of bus stops for that are determined. It was found that alighting and boarding time along with bus capacity are the most effective factors affecting travel time. Consequently, it is better to have more concentration on indicated factors for improving the efficiency of bus system.

Automating Web Collection and Validation of GPS data for Longitudinal Urban Travel Studies

DOT National Transportation Integrated Search

2012-08-01

Traditional paper and phone travel surveys are expensive, time consuming, and have problems of missing trips, illogical trip sequences, and : imprecise travel time. GPS-based travel surveys can avoid many of these problems and are becoming increasing...

Automatic computation of the travelling wave solutions to nonlinear PDEs

NASA Astrophysics Data System (ADS)

Liang, Songxin; Jeffrey, David J.

2008-05-01

Various extensions of the tanh-function method and their implementations for finding explicit travelling wave solutions to nonlinear partial differential equations (PDEs) have been reported in the literature. However, some solutions are often missed by these packages. In this paper, a new algorithm and its implementation called TWS for solving single nonlinear PDEs are presented. TWS is implemented in MAPLE 10. It turns out that, for PDEs whose balancing numbers are not positive integers, TWS works much better than existing packages. Furthermore, TWS obtains more solutions than existing packages for most cases. Program summaryProgram title:TWS Catalogue identifier:AEAM_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAM_v1_0.html Program obtainable from:CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions:Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.:1250 No. of bytes in distributed program, including test data, etc.:78 101 Distribution format:tar.gz Programming language:Maple 10 Computer:A laptop with 1.6 GHz Pentium CPU Operating system:Windows XP Professional RAM:760 Mbytes Classification:5 Nature of problem:Finding the travelling wave solutions to single nonlinear PDEs. Solution method:Based on tanh-function method. Restrictions:The current version of this package can only deal with single autonomous PDEs or ODEs, not systems of PDEs or ODEs. However, the PDEs can have any finite number of independent space variables in addition to time t. Unusual features:For PDEs whose balancing numbers are not positive integers, TWS works much better than existing packages. Furthermore, TWS obtains more solutions than existing packages for most cases. Additional comments:It is easy to use. Running time:Less than 20 seconds for most cases, between 20 to 100 seconds for some cases, over 100 seconds for few cases. References: [1] E.S. Cheb-Terrab, K. von Bulow, Comput. Phys. Comm. 90 (1995) 102. [2] S.A. Elwakil, S.K. El-Labany, M.A. Zahran, R. Sabry, Phys. Lett. A 299 (2002) 179. [3] E. Fan, Phys. Lett. 277 (2000) 212. [4] W. Malfliet, Amer. J. Phys. 60 (1992) 650. [5] W. Malfliet, W. Hereman, Phys. Scripta 54 (1996) 563. [6] E.J. Parkes, B.R. Duffy, Comput. Phys. Comm. 98 (1996) 288.

Evaluation of the traffic parameters in a metropolitan area by fusing visual perceptions and CNN processing of webcam images.

PubMed

Faro, Alberto; Giordano, Daniela; Spampinato, Concetto

2008-06-01

This paper proposes a traffic monitoring architecture based on a high-speed communication network whose nodes are equipped with fuzzy processors and cellular neural network (CNN) embedded systems. It implements a real-time mobility information system where visual human perceptions sent by people working on the territory and video-sequences of traffic taken from webcams are jointly processed to evaluate the fundamental traffic parameters for every street of a metropolitan area. This paper presents the whole methodology for data collection and analysis and compares the accuracy and the processing time of the proposed soft computing techniques with other existing algorithms. Moreover, this paper discusses when and why it is recommended to fuse the visual perceptions of the traffic with the automated measurements taken from the webcams to compute the maximum traveling time that is likely needed to reach any destination in the traffic network.

HARPA: A versatile three-dimensional Hamiltonian ray-tracing program for acoustic waves in the atmosphere above irregular terrain

NASA Astrophysics Data System (ADS)

Jones, R. M.; Riley, J. P.; Georges, T. M.

1986-08-01

The modular FORTRAN 77 computer program traces the three-dimensional paths of acoustic rays through continuous model atmospheres by numerically integrating Hamilton's equations (a differential expression of Fermat's principle). The user specifies an atmospheric model by writing closed-form formulas for its three-dimensional wind and temperature (or sound speed) distribution, and by defining the height of the reflecting terrain vs. geographic latitude and longitude. Some general-purpose models are provided, or users can readily design their own. In addition to computing the geometry of each raypath, HARPA can calculate pulse travel time, phase time, Doppler shift (if the medium varies in time), absorption, and geometrical path length. The program prints a step-by-step account of a ray's progress. The 410-page documentation describes the ray-tracing equations and the structure of the program, and provides complete instructions, illustrated by a sample case.

Dynamic route and departure time choice model based on self-adaptive reference point and reinforcement learning

NASA Astrophysics Data System (ADS)

Li, Xue-yan; Li, Xue-mei; Yang, Lingrun; Li, Jing

2018-07-01

Most of the previous studies on dynamic traffic assignment are based on traditional analytical framework, for instance, the idea of Dynamic User Equilibrium has been widely used in depicting both the route choice and the departure time choice. However, some recent studies have demonstrated that the dynamic traffic flow assignment largely depends on travelers' rationality degree, travelers' heterogeneity and what the traffic information the travelers have. In this paper, we develop a new self-adaptive multi agent model to depict travelers' behavior in Dynamic Traffic Assignment. We use Cumulative Prospect Theory with heterogeneous reference points to illustrate travelers' bounded rationality. We use reinforcement-learning model to depict travelers' route and departure time choosing behavior under the condition of imperfect information. We design the evolution rule of travelers' expected arrival time and the algorithm of traffic flow assignment. Compared with the traditional model, the self-adaptive multi agent model we proposed in this paper can effectively help travelers avoid the rush hour. Finally, we report and analyze the effect of travelers' group behavior on the transportation system, and give some insights into the relation between travelers' group behavior and the performance of transportation system.

Integrated Intermodal Passenger Transportation System

NASA Technical Reports Server (NTRS)

Klock, Ryan; Owens, David; Schwartz, Henry; Plencner, Robert

2012-01-01

Modern transportation consists of many unique modes of travel. Each of these modes and their respective industries has evolved independently over time, forming a largely incoherent and inefficient overall transportation system. Travelers today are forced to spend unnecessary time and efforts planning a trip through varying modes of travel each with their own scheduling, pricing, and services; causing many travelers to simply rely on their relatively inefficient and expensive personal automobile. This paper presents a demonstration program system to not only collect and format many different sources of trip planning information, but also combine these independent modes of travel in order to form optimal routes and itineraries of travel. The results of this system show a mean decrease in inter-city travel time of 10 percent and a 25 percent reduction in carbon dioxide emissions over personal automobiles. Additionally, a 55 percent reduction in carbon dioxide emissions is observed for intra-city travel. A conclusion is that current resources are available, if somewhat hidden, to drastically improve point to point transportation in terms of time spent traveling, the cost of travel, and the ecological impact of a trip. Finally, future concepts are considered which could dramatically improve the interoperability and efficiency of the transportation infrastructure.

41 CFR 302-3.219 - Is there a limit on how many times I may receive reimbursement for tour renewal travel?

Code of Federal Regulations, 2011 CFR

2011-07-01

... many times I may receive reimbursement for tour renewal travel? 302-3.219 Section 302-3.219 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES RELOCATION....219 Is there a limit on how many times I may receive reimbursement for tour renewal travel? (a) If you...

41 CFR 302-3.315 - May I be granted an extension to the time limit for beginning my separation travel?

Code of Federal Regulations, 2014 CFR

2014-07-01

... extension to the time limit for beginning my separation travel? 302-3.315 Section 302-3.315 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES RELOCATION ALLOWANCES 3... be granted an extension to the time limit for beginning my separation travel? Yes, your agency may...

41 CFR 302-3.219 - Is there a limit on how many times I may receive reimbursement for tour renewal travel?

Code of Federal Regulations, 2014 CFR

2014-07-01

... many times I may receive reimbursement for tour renewal travel? 302-3.219 Section 302-3.219 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES RELOCATION....219 Is there a limit on how many times I may receive reimbursement for tour renewal travel? (a) If you...

41 CFR 302-3.315 - May I be granted an extension to the time limit for beginning my separation travel?

Code of Federal Regulations, 2012 CFR

2012-07-01

... extension to the time limit for beginning my separation travel? 302-3.315 Section 302-3.315 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES RELOCATION ALLOWANCES 3... be granted an extension to the time limit for beginning my separation travel? Yes, your agency may...

41 CFR 302-3.315 - May I be granted an extension to the time limit for beginning my separation travel?

Code of Federal Regulations, 2013 CFR

2013-07-01

... extension to the time limit for beginning my separation travel? 302-3.315 Section 302-3.315 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES RELOCATION ALLOWANCES 3... be granted an extension to the time limit for beginning my separation travel? Yes, your agency may...

41 CFR 302-3.219 - Is there a limit on how many times I may receive reimbursement for tour renewal travel?

Code of Federal Regulations, 2010 CFR

2010-07-01

... many times I may receive reimbursement for tour renewal travel? 302-3.219 Section 302-3.219 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES RELOCATION....219 Is there a limit on how many times I may receive reimbursement for tour renewal travel? (a) If you...

41 CFR 302-3.219 - Is there a limit on how many times I may receive reimbursement for tour renewal travel?

Code of Federal Regulations, 2013 CFR

2013-07-01

... many times I may receive reimbursement for tour renewal travel? 302-3.219 Section 302-3.219 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES RELOCATION....219 Is there a limit on how many times I may receive reimbursement for tour renewal travel? (a) If you...

41 CFR 302-3.219 - Is there a limit on how many times I may receive reimbursement for tour renewal travel?

Code of Federal Regulations, 2012 CFR

2012-07-01

... many times I may receive reimbursement for tour renewal travel? 302-3.219 Section 302-3.219 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES RELOCATION....219 Is there a limit on how many times I may receive reimbursement for tour renewal travel? (a) If you...

Applications of Combinatorial Programming to Data Analysis: The Traveling Salesman and Related Problems

ERIC Educational Resources Information Center

Hubert, Lawrence J.; Baker, Frank B.

1978-01-01

The "Traveling Salesman" and similar combinatorial programming tasks encountered in operations research are discussed as possible data analysis models in psychology, for example, in developmental scaling, Guttman scaling, profile smoothing, and data array clustering. A short overview of various computational approaches from this area of…

On the Computing Potential of Intracellular Vesicles

PubMed Central

Mayne, Richard; Adamatzky, Andrew

2015-01-01

Collision-based computing (CBC) is a form of unconventional computing in which travelling localisations represent data and conditional routing of signals determines the output state; collisions between localisations represent logical operations. We investigated patterns of Ca2+-containing vesicle distribution within a live organism, slime mould Physarum polycephalum, with confocal microscopy and observed them colliding regularly. Vesicles travel down cytoskeletal ‘circuitry’ and their collisions may result in reflection, fusion or annihilation. We demonstrate through experimental observations that naturally-occurring vesicle dynamics may be characterised as a computationally-universal set of Boolean logical operations and present a ‘vesicle modification’ of the archetypal CBC ‘billiard ball model’ of computation. We proceed to discuss the viability of intracellular vesicles as an unconventional computing substrate in which we delineate practical considerations for reliable vesicle ‘programming’ in both in vivo and in vitro vesicle computing architectures and present optimised designs for both single logical gates and combinatorial logic circuits based on cytoskeletal network conformations. The results presented here demonstrate the first characterisation of intracelluar phenomena as collision-based computing and hence the viability of biological substrates for computing. PMID:26431435

Qualifying the benefit of Advanced Traveler Information Systems (ATIS)

DOT National Transportation Integrated Search

2000-11-21

ATIS Yields Time Management Benefits: No conflict between survey and empirical research : ATIS users correctly perceive that they save time Field studies correctly measured only small changes in in-vehicle travel times. When travel behavior f...

Reliability of Travel Time: Challenges Posed by a Multimodal Transport Participation

NASA Astrophysics Data System (ADS)

Wanjek, Monika; Hauger, Georg

2017-10-01

Travel time reliability represents an essential component in individual decision making processes for transport participants, particularly regarding mode choices. As criteria that describe the quality of both transportation systems and transportation modes, travel time reliability is already frequently compiled, analysed and quoted as an argument. Currently, travel time reliability is solely mentioned on monomodal trips, while it has remained unconsidered on multimodal transport participation. Given the fact that multimodality gained significantly in importance, it is crucial to discuss how travel time reliability could be determined on multimodal trips. This paper points out the challenges that occur for applying travel time reliability on multimodal transport participation. Therefore, examples will be given within this paper. In order to illustrate theoretical ideas, trips and influencing factors that could be expected within the everyday transport behaviour of commuters in a (sub)urban area will be described.

Wandering tales: evolutionary origins of mental time travel and language

PubMed Central

Corballis, Michael C.

2013-01-01

A central component of mind wandering is mental time travel, the calling to mind of remembered past events and of imagined future ones. Mental time travel may also be critical to the evolution of language, which enables us to communicate about the non-present, sharing memories, plans, and ideas. Mental time travel is indexed in humans by hippocampal activity, and studies also suggest that the hippocampus in rats is active when the animals replay or pre play activity in a spatial environment, such as a maze. Mental time travel may have ancient origins, contrary to the view that it is unique to humans. Since mental time travel is also thought to underlie language, these findings suggest that language evolved gradually from pre-existing cognitive capacities, contrary to the view of Chomsky and others that language and symbolic thought emerged abruptly, in a single step, within the past 100,000 years. PMID:23908641

Variability of Travel Times on New Jersey Highways

DOT National Transportation Integrated Search

2011-06-01

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

Assessment and refinement of real-time travel time algorithms for use in practice : final report, October 2008.

DOT National Transportation Integrated Search

2008-10-01

The FHWA has strongly encouraged transportation departments to display travel times on their Dynamic Message Signs (DMS). The Oregon : Department of Transportation (ODOT) currently displays travel time estimates on three DMSs in the Portland metropol...

User's guide for a large signal computer model of the helical traveling wave tube

NASA Technical Reports Server (NTRS)

Palmer, Raymond W.

1992-01-01

The use is described of a successful large-signal, two-dimensional (axisymmetric), deformable disk computer model of the helical traveling wave tube amplifier, an extensively revised and operationally simplified version. We also discuss program input and output and the auxiliary files necessary for operation. Included is a sample problem and its input data and output results. Interested parties may now obtain from the author the FORTRAN source code, auxiliary files, and sample input data on a standard floppy diskette, the contents of which are described herein.

An Adaptive Evolutionary Algorithm for Traveling Salesman Problem with Precedence Constraints

PubMed Central

Sung, Jinmo; Jeong, Bongju

2014-01-01

Traveling sales man problem with precedence constraints is one of the most notorious problems in terms of the efficiency of its solution approach, even though it has very wide range of industrial applications. We propose a new evolutionary algorithm to efficiently obtain good solutions by improving the search process. Our genetic operators guarantee the feasibility of solutions over the generations of population, which significantly improves the computational efficiency even when it is combined with our flexible adaptive searching strategy. The efficiency of the algorithm is investigated by computational experiments. PMID:24701158

An adaptive evolutionary algorithm for traveling salesman problem with precedence constraints.

PubMed

Sung, Jinmo; Jeong, Bongju

2014-01-01

Traveling sales man problem with precedence constraints is one of the most notorious problems in terms of the efficiency of its solution approach, even though it has very wide range of industrial applications. We propose a new evolutionary algorithm to efficiently obtain good solutions by improving the search process. Our genetic operators guarantee the feasibility of solutions over the generations of population, which significantly improves the computational efficiency even when it is combined with our flexible adaptive searching strategy. The efficiency of the algorithm is investigated by computational experiments.

Travel Times for Screening Mammography: Impact of Geographic Expansion by a Large Academic Health System.

PubMed

Rosenkrantz, Andrew B; Liang, Yu; Duszak, Richard; Recht, Michael P

2017-09-01

This study aims to assess the impact of off-campus facility expansion by a large academic health system on patient travel times for screening mammography. Screening mammograms performed from 2013 to 2015 and associated patient demographics were identified using the NYU Langone Medical Center Enterprise Data Warehouse. During this time, the system's number of mammography facilities increased from 6 to 19, reflecting expansion beyond Manhattan throughout the New York metropolitan region. Geocoding software was used to estimate driving times from patients' homes to imaging facilities. For 147,566 screening mammograms, the mean estimated patient travel time was 19.9 ± 15.2 minutes. With facility expansion, travel times declined significantly (P < 0.001) from 26.8 ± 18.9 to 18.5 ± 13.3 minutes (non-Manhattan residents: from 31.4 ± 20.3 to 18.7 ± 13.6). This decline occurred consistently across subgroups of patient age, race, ethnicity, payer status, and rurality, leading to decreased variation in travel times between such subgroups. However, travel times to pre-expansion facilities remained stable (initial: 26.8 ± 18.9 minutes, final: 26.7 ± 18.6 minutes). Among women undergoing mammography before and after expansion, travel times were shorter for the postexpansion mammogram in only 6.3%, but this rate varied significantly (all P < 0.05) by certain demographic factors (higher in younger and non-Hispanic patients) and was as high as 18.2%-18.9% of patients residing in regions with the most active expansion. Health system mammography facility geographic expansion can improve average patient travel burden and reduce travel time variation among sociodemographic populations. Nonetheless, existing patients strongly tend to return to established facilities despite potentially shorter travel time locations, suggesting strong site loyalty. Variation in travel times likely relates to various factors other than facility proximity. Copyright © 2017 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

VA Telemedicine: An Analysis of Cost and Time Savings.

PubMed

Russo, Jack E; McCool, Ryan R; Davies, Louise

2016-03-01

The Veterans Affairs (VA) healthcare system provides beneficiary travel reimbursement ("travel pay") to qualifying patients for traveling to appointments. Travel pay is a large expense for the VA and hence the U.S. Government, projected to cost nearly $1 billion in 2015. Telemedicine in the VA system has the potential to save money by reducing patient travel and thus the amount of travel pay disbursed. In this study, we quantify this savings and also report trends in VA telemedicine volumes over time. All telemedicine visits based at the VA Hospital in White River Junction, VT between 2005 and 2013 were reviewed (5,695 visits). Travel distance and time saved as a result of telemedicine were calculated. Clinical volume in the mental health department, which has had the longest participation in telemedicine, was analyzed. Telemedicine resulted in an average travel savings of 145 miles and 142 min per visit. This led to an average travel payment savings of $18,555 per year. Telemedicine volume grew significantly over the study period such that by the final year the travel pay savings had increased to $63,804, or about 3.5% of the total travel pay disbursement for that year. The number of mental health telemedicine visits rose over the study period but remained small relative to the number of face-to-face visits. A higher proportion of telemedicine visits involved new patients. Telemedicine at the VA saves travel distance and time, although the reduction in travel payments remains modest at current telemedicine volumes.

Time-of-travel data for Nebraska streams, 1968 to 1977

USGS Publications Warehouse

Petri, L.R.

1984-01-01

This report documents the results of 10 time-of-travel studies, using ' dye-tracer ' methods, conducted on five streams in Nebraska during the period 1968 to 1977. Streams involved in the studies were the North Platte, North Loup, Elkhorn, and Big Blue Rivers and Salt Creek. Rhodamine WT dye in a 20 percent solution was used as the tracer for all 10 time-of-travel studies. Water samples were collected at several points below each injection site. Concentrations of dye in the samples were measured by determining fluorescence of the sample and comparing that value to fluorescence-concentration curves. Stream discharges were measured before and during each study. Results of each time-by-travel study are shown on two tables and on graph. The first table shows water discharge at injection and sampling sites, distance between sites, and time and rate of travel of the dye between sites. The second table provides descriptions of study sites, amounts of dye injected in the streams, actual sampling times, and actual concentrations of dye detected. The graphs for each time-of-travel study provide indications of changing travel rates between sampling sites, information on length of dye clouds, and times for dye passage past given points. (USGS)

Coordinated platooning with multiple speeds

DOE PAGES

Luo, Fengqiao; Larson, Jeffrey; Munson, Todd

2018-03-22

In a platoon, vehicles travel one after another with small intervehicle distances; trailing vehicles in a platoon save fuel because they experience less aerodynamic drag. This work presents a coordinated platooning model with multiple speed options that integrates scheduling, routing, speed selection, and platoon formation/dissolution in a mixed-integer linear program that minimizes the total fuel consumed by a set of vehicles while traveling between their respective origins and destinations. The performance of this model is numerically tested on a grid network and the Chicago-area highway network. We find that the fuel-savings factor of a multivehicle system significantly depends on themore » time each vehicle is allowed to stay in the network; this time affects vehicles’ available speed choices, possible routes, and the amount of time for coordinating platoon formation. For problem instances with a large number of vehicles, we propose and test a heuristic decomposed approach that applies a clustering algorithm to partition the set of vehicles and then routes each group separately. When the set of vehicles is large and the available computational time is small, the decomposed approach finds significantly better solutions than does the full model.« less

Coordinated platooning with multiple speeds

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

Luo, Fengqiao; Larson, Jeffrey; Munson, Todd

In a platoon, vehicles travel one after another with small intervehicle distances; trailing vehicles in a platoon save fuel because they experience less aerodynamic drag. This work presents a coordinated platooning model with multiple speed options that integrates scheduling, routing, speed selection, and platoon formation/dissolution in a mixed-integer linear program that minimizes the total fuel consumed by a set of vehicles while traveling between their respective origins and destinations. The performance of this model is numerically tested on a grid network and the Chicago-area highway network. We find that the fuel-savings factor of a multivehicle system significantly depends on themore » time each vehicle is allowed to stay in the network; this time affects vehicles’ available speed choices, possible routes, and the amount of time for coordinating platoon formation. For problem instances with a large number of vehicles, we propose and test a heuristic decomposed approach that applies a clustering algorithm to partition the set of vehicles and then routes each group separately. When the set of vehicles is large and the available computational time is small, the decomposed approach finds significantly better solutions than does the full model.« less

Calculating Path-Dependent Travel Time Prediction Variance and Covariance for the SALSA3D Global Tomographic P-Velocity Model with a Distributed Parallel Multi-Core Computer

NASA Astrophysics Data System (ADS)

Hipp, J. R.; Encarnacao, A.; Ballard, S.; Young, C. J.; Phillips, W. S.; Begnaud, M. L.

2011-12-01

Recently our combined SNL-LANL research team has succeeded in developing a global, seamless 3D tomographic P-velocity model (SALSA3D) that provides superior first P travel time predictions at both regional and teleseismic distances. However, given the variable data quality and uneven data sampling associated with this type of model, it is essential that there be a means to calculate high-quality estimates of the path-dependent variance and covariance associated with the predicted travel times of ray paths through the model. In this paper, we show a methodology for accomplishing this by exploiting the full model covariance matrix. Our model has on the order of 1/2 million nodes, so the challenge in calculating the covariance matrix is formidable: 0.9 TB storage for 1/2 of a symmetric matrix, necessitating an Out-Of-Core (OOC) blocked matrix solution technique. With our approach the tomography matrix (G which includes Tikhonov regularization terms) is multiplied by its transpose (GTG) and written in a blocked sub-matrix fashion. We employ a distributed parallel solution paradigm that solves for (GTG)-1 by assigning blocks to individual processing nodes for matrix decomposition update and scaling operations. We first find the Cholesky decomposition of GTG which is subsequently inverted. Next, we employ OOC matrix multiply methods to calculate the model covariance matrix from (GTG)-1 and an assumed data covariance matrix. Given the model covariance matrix we solve for the travel-time covariance associated with arbitrary ray-paths by integrating the model covariance along both ray paths. Setting the paths equal gives variance for that path. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Incorporating travel time reliability into the Highway Capacity Manual.

DOT National Transportation Integrated Search

2014-01-01

This final report documents the activities performed during SHRP 2 Reliability Project L08: Incorporating Travel Time Reliability into the Highway Capacity Manual. It serves as a supplement to the proposed chapters for incorporating travel time relia...

Validation and augmentation of Inrix arterial travel time data using independent sources.

DOT National Transportation Integrated Search

2015-02-01

Travel time data is a key input to Intelligent Transportation Systems (ITS) applications. Advancement in vehicle : tracking and identification technologies and proliferation of location-aware and connected devices has made network-wide travel time da...

Comparison of methods for measuring travel time at Florida freeways and arterials.

DOT National Transportation Integrated Search

2014-07-01

Travel time is an important performance measure used to assess the traffic operational quality of various types of highway : facilities. Previous research funded by the Florida Department of Transportation (FDOT) on travel time reliability developed,...

Analysis of travel time reliability on Indiana interstates.

DOT National Transportation Integrated Search

2009-09-15

Travel-time reliability is a key performance measure in any transportation system. It is a : measure of quality of travel time experienced by transportation system users and reflects the efficiency : of the transportation system to serve citizens, bu...

7 CFR 56.46 - On a fee basis.

Code of Federal Regulations, 2011 CFR

2011-01-01

... required to perform the grading, waiting time, travel time, and any clerical costs involved in issuing a... required to perform the audit, waiting time, travel time, travel expenses and any clerical costs involved... services will be based on the time required to perform the services. The hourly charge shall be $74.08...

7 CFR 70.71 - On a fee basis.

Code of Federal Regulations, 2011 CFR

2011-01-01

... required to perform the work, waiting time, travel time, and any clerical costs involved in issuing a... perform the audit, waiting time, travel time, travel expenses and any clerical costs involved in issuing a... specified in this section. (b) Fees for grading services will be based on the time required to perform such...

7 CFR 70.71 - On a fee basis.

Code of Federal Regulations, 2013 CFR

2013-01-01

... required to perform the work, waiting time, travel time, and any clerical costs involved in issuing a... perform the audit, waiting time, travel time, travel expenses and any clerical costs involved in issuing a... specified in this section. (b) Fees for grading services will be based on the time required to perform such...

78 FR 58516 - Information Collection; Direct Loan Servicing-Regular

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-24

... than travel time) were added as part of this revision. DATES: We will consider comments that we receive..., response actions, or time increases (other than travel time) were added as part of this revision. Estimate of Average Time to respond: 19 minutes per response. The average travel time, which is included in...

7 CFR 70.71 - On a fee basis.

Code of Federal Regulations, 2012 CFR

2012-01-01

... required to perform the work, waiting time, travel time, and any clerical costs involved in issuing a... perform the audit, waiting time, travel time, travel expenses and any clerical costs involved in issuing a... specified in this section. (b) Fees for grading services will be based on the time required to perform such...

5 CFR 550.1405 - Crediting compensatory time off.

Code of Federal Regulations, 2011 CFR

2011-01-01

... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1405 Crediting compensatory time off. (a) Upon a... employee is entitled to credit for compensatory time off for travel under the conditions specified in this... employee's request for credit of compensatory time off for travel may be denied if the request is not filed...

5 CFR 550.1405 - Crediting compensatory time off.

Code of Federal Regulations, 2014 CFR

2014-01-01

... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1405 Crediting compensatory time off. (a) Upon a... employee is entitled to credit for compensatory time off for travel under the conditions specified in this... employee's request for credit of compensatory time off for travel may be denied if the request is not filed...

7 CFR 56.46 - On a fee basis.

Code of Federal Regulations, 2014 CFR

2014-01-01

... required to perform the grading, waiting time, travel time, and any clerical costs involved in issuing a... required to perform the audit, waiting time, travel time, travel expenses and any clerical costs involved... services will be based on the time required to perform the services. The hourly charge shall be $74.08...

7 CFR 56.46 - On a fee basis.

Code of Federal Regulations, 2013 CFR

2013-01-01

... required to perform the grading, waiting time, travel time, and any clerical costs involved in issuing a... required to perform the audit, waiting time, travel time, travel expenses and any clerical costs involved... services will be based on the time required to perform the services. The hourly charge shall be $74.08...

5 CFR 550.1405 - Crediting compensatory time off.

Code of Federal Regulations, 2012 CFR

2012-01-01

... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1405 Crediting compensatory time off. (a) Upon a... employee is entitled to credit for compensatory time off for travel under the conditions specified in this... employee's request for credit of compensatory time off for travel may be denied if the request is not filed...

7 CFR 56.46 - On a fee basis.

Code of Federal Regulations, 2012 CFR

2012-01-01

... required to perform the grading, waiting time, travel time, and any clerical costs involved in issuing a... required to perform the audit, waiting time, travel time, travel expenses and any clerical costs involved... services will be based on the time required to perform the services. The hourly charge shall be $74.08...

5 CFR 550.1405 - Crediting compensatory time off.

Code of Federal Regulations, 2013 CFR

2013-01-01

... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1405 Crediting compensatory time off. (a) Upon a... employee is entitled to credit for compensatory time off for travel under the conditions specified in this... employee's request for credit of compensatory time off for travel may be denied if the request is not filed...

7 CFR 70.71 - On a fee basis.

Code of Federal Regulations, 2010 CFR

2010-01-01

... required to perform the work, waiting time, travel time, and any clerical costs involved in issuing a... perform the audit, waiting time, travel time, travel expenses and any clerical costs involved in issuing a... specified in this section. (b) Fees for grading services will be based on the time required to perform such...

7 CFR 70.71 - On a fee basis.

Code of Federal Regulations, 2014 CFR

2014-01-01

... required to perform the work, waiting time, travel time, and any clerical costs involved in issuing a... perform the audit, waiting time, travel time, travel expenses and any clerical costs involved in issuing a... specified in this section. (b) Fees for grading services will be based on the time required to perform such...

7 CFR 56.46 - On a fee basis.

Code of Federal Regulations, 2010 CFR

2010-01-01

... required to perform the grading, waiting time, travel time, and any clerical costs involved in issuing a... required to perform the audit, waiting time, travel time, travel expenses and any clerical costs involved... services will be based on the time required to perform the services. The hourly charge shall be $74.08...

5 CFR 550.1405 - Crediting compensatory time off.

Code of Federal Regulations, 2010 CFR

2010-01-01

... ADMINISTRATION (GENERAL) Compensatory Time Off for Travel § 550.1405 Crediting compensatory time off. (a) Upon a... employee is entitled to credit for compensatory time off for travel under the conditions specified in this... employee's request for credit of compensatory time off for travel may be denied if the request is not filed...

41 CFR 301-10.137 - What exceptions to the Fly America Act requirements apply when I travel solely outside the United...

Code of Federal Regulations, 2014 CFR

2014-07-01

... or more; or (b) Extend your travel time by 6 hours or more; or (c) Require a connecting time of 4... Fly America Act requirements apply when I travel solely outside the United States, and a U.S. flag air... Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...

41 CFR 301-10.137 - What exceptions to the Fly America Act requirements apply when I travel solely outside the United...

Code of Federal Regulations, 2013 CFR

2013-07-01

... or more; or (b) Extend your travel time by 6 hours or more; or (c) Require a connecting time of 4... Fly America Act requirements apply when I travel solely outside the United States, and a U.S. flag air... Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...

41 CFR 301-10.137 - What exceptions to the Fly America Act requirements apply when I travel solely outside the United...

Code of Federal Regulations, 2010 CFR

2010-07-01

... or more; or (b) Extend your travel time by 6 hours or more; or (c) Require a connecting time of 4... Fly America Act requirements apply when I travel solely outside the United States, and a U.S. flag air... Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...

41 CFR 301-10.137 - What exceptions to the Fly America Act requirements apply when I travel solely outside the United...

Code of Federal Regulations, 2011 CFR

2011-07-01

... or more; or (b) Extend your travel time by 6 hours or more; or (c) Require a connecting time of 4... Fly America Act requirements apply when I travel solely outside the United States, and a U.S. flag air... Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...

41 CFR 301-10.137 - What exceptions to the Fly America Act requirements apply when I travel solely outside the United...

Code of Federal Regulations, 2012 CFR

2012-07-01

... or more; or (b) Extend your travel time by 6 hours or more; or (c) Require a connecting time of 4... Fly America Act requirements apply when I travel solely outside the United States, and a U.S. flag air... Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES...

41 CFR 302-4.204 - If my spouse does not accompany me but travels unaccompanied at a different time, what per diem...

Code of Federal Regulations, 2010 CFR

2010-07-01

... accompany me but travels unaccompanied at a different time, what per diem rate will he/she receive? 302-4.204 Section 302-4.204 Public Contracts and Property Management Federal Travel Regulation System... my spouse does not accompany me but travels unaccompanied at a different time, what per diem rate...

48 CFR 47.403-1 - Availability and unavailability of U.S.-flag air carrier service.

Code of Federal Regulations, 2014 CFR

2014-10-01

... the time in a travel status, including delay at origin and accelerated arrival at destination, by at... gateway airport in the United States would extend time in a travel status by at least 6 hours more than... the time in a travel status by at least 6 hours more than travel by a foreign-flag air carrier...

48 CFR 47.403-1 - Availability and unavailability of U.S.-flag air carrier service.

Code of Federal Regulations, 2010 CFR

2010-10-01

... the time in a travel status, including delay at origin and accelerated arrival at destination, by at... gateway airport in the United States would extend time in a travel status by at least 6 hours more than... the time in a travel status by at least 6 hours more than travel by a foreign-flag air carrier...

Travel Time to Hospital for Childbirth: Comparing Calculated Versus Reported Travel Times in France.

PubMed

Pilkington, Hugo; Prunet, Caroline; Blondel, Béatrice; Charreire, Hélène; Combier, Evelyne; Le Vaillant, Marc; Amat-Roze, Jeanne-Marie; Zeitlin, Jennifer

2018-01-01

Objectives Timely access to health care is critical in obstetrics. Yet obtaining reliable estimates of travel times to hospital for childbirth poses methodological challenges. We compared two measures of travel time, self-reported and calculated, to assess concordance and to identify determinants of long travel time to hospital for childbirth. Methods Data came from the 2010 French National Perinatal Survey, a national representative sample of births (N = 14 681). We compared both travel time measures by maternal, maternity unit and geographic characteristics in rural, peri-urban and urban areas. Logistic regression models were used to study factors associated with reported and calculated times ≥30 min. Cohen's kappa coefficients were also calculated to estimate the agreement between reported and calculated times according to women's characteristics. Results In urban areas, the proportion of women with travel times ≥30 min was higher when reported rather than calculated times were used (11.0 vs. 3.6%). Longer reported times were associated with non-French nationality [adjusted odds ratio (aOR) 1.3 (95% CI 1.0-1.7)] and inadequate prenatal care [aOR 1.5 (95% CI 1.2-2.0)], but not for calculated times. Concordance between the two measures was higher in peri-urban and rural areas (52.4 vs. 52.3% for rural areas). Delivery in a specialised level 2 or 3 maternity unit was a principal determinant of long reported and measured times in peri-urban and rural areas. Conclusions for Practice The level of agreement between reported and calculated times varies according to geographic context. Poor measurement of travel time in urban areas may mask problems in accessibility.

Temporal and environmental patterns of sedentary and active behaviors during adolescents' leisure time.

PubMed

Biddle, Stuart J H; Marshall, Simon J; Gorely, Trish; Cameron, Noel

2009-01-01

There is great interest in young people's overweight and obesity. Few data, however, describe when sedentary and physically active behaviors are likely to occur during the day or how these behaviors are related to location. The purpose of this study was to describe sedentary and active leisure-time behaviors of adolescents across the day and setting. Adolescents (male n = 579, female n = 967; aged 13-16 years) completed time-use diaries for three weekdays and one weekend day. At 15 min intervals, participants recorded what they were doing and where they were. TV viewing and sports/exercise peaked at different times in the day, although TV viewing was two to three times more likely to occur than sports/exercise. TV viewing was most likely to occur during the middle to late evening. The playing of computer games was low, particularly for girls. Weekend data showed TV viewing was the most reported activity throughout the day. For boys, "being in the garden" was highly predictive of engaging in sports/exercise, but this declined rapidly with age. Motorized travel to school was reported twice as often as active travel. Momentary assessments of behavior, in conjunction with contemporaneous reports of environmental factors, describe important patterns of leisure-time active and sedentary behaviors in youth.

Comparison of acoustic travel-time measurements of solar meridional circulation from SDO/HMI and SOHO/MDI

NASA Astrophysics Data System (ADS)

Liang, Zhi-Chao; Birch, Aaron C.; Duvall, Thomas L., Jr.; Gizon, Laurent; Schou, Jesper

2017-05-01

Context. Time-distance helioseismology is one of the primary tools for studying the solar meridional circulation, especially in the lower convection zone. However, travel-time measurements of the subsurface meridional flow suffer from a variety of systematic errors, such as a center-to-limb variation and an offset due to the position angle (P-angle) uncertainty of solar images. It has been suggested that the center-to-limb variation can be removed by subtracting east-west from south-north travel-time measurements. This ad hoc method for the removal of the center-to-limb effect has been adopted widely but not tested for travel distances corresponding to the lower convection zone. Aims: We explore the effects of two major sources of the systematic errors, the P-angle error arising from the instrumental misalignment and the center-to-limb variation, on the acoustic travel-time measurements in the south-north direction. Methods: We apply the time-distance technique to contemporaneous medium-degree Dopplergrams produced by SOHO/MDI and SDO/HMI to obtain the travel-time difference caused by meridional circulation throughout the solar convection zone. The P-angle offset in MDI images is measured by cross-correlating MDI and HMI images. The travel-time measurements in the south-north and east-west directions are averaged over the same observation period (May 2010 to Apr. 2011) for the two data sets and then compared to examine the consistency of MDI and HMI travel times after applying the above-mentioned corrections. Results: The offsets in the south-north travel-time difference from MDI data induced by the P-angle error gradually diminish with increasing travel distance. However, these offsets become noisy for travel distances corresponding to waves that reach the base of the convection zone. This suggests that a careful treatment of the P-angle problem is required when studying a deep meridional flow. After correcting the P-angle and the removal of the center-to-limb effect, the travel-time measurements from MDI and HMI are consistent within the error bars for meridional circulation covering the entire convection zone. The fluctuations observed in both data sets are highly correlated and thus indicate their solar origin rather than an instrumental origin. Although our results demonstrate that the ad hoc correction is capable of reducing the wide discrepancy in the travel-time measurements from MDI and HMI, we cannot exclude the possibility that there exist other systematic effects acting on the two data sets in the same way.

Approximate Bayesian algorithm to estimate the basic reproduction number in an influenza pandemic using arrival times of imported cases.

PubMed

Chong, Ka Chun; Zee, Benny Chung Ying; Wang, Maggie Haitian

2018-04-10

In an influenza pandemic, arrival times of cases are a proxy of the epidemic size and disease transmissibility. Because of intense surveillance of travelers from infected countries, detection is more rapid and complete than on local surveillance. Travel information can provide a more reliable estimation of transmission parameters. We developed an Approximate Bayesian Computation algorithm to estimate the basic reproduction number (R 0 ) in addition to the reporting rate and unobserved epidemic start time, utilizing travel, and routine surveillance data in an influenza pandemic. A simulation was conducted to assess the sampling uncertainty. The estimation approach was further applied to the 2009 influenza A/H1N1 pandemic in Mexico as a case study. In the simulations, we showed that the estimation approach was valid and reliable in different simulation settings. We also found estimates of R 0 and the reporting rate to be 1.37 (95% Credible Interval [CI]: 1.26-1.42) and 4.9% (95% CI: 0.1%-18%), respectively, in the 2009 influenza pandemic in Mexico, which were robust to variations in the fixed parameters. The estimated R 0 was consistent with that in the literature. This method is useful for officials to obtain reliable estimates of disease transmissibility for strategic planning. We suggest that improvements to the flow of reporting for confirmed cases among patients arriving at different countries are required. Copyright © 2018 Elsevier Ltd. All rights reserved.

Ash level meter for a fixed-bed coal gasifier

DOEpatents

Fasching, George E.

1984-01-01

An ash level meter for a fixed-bed coal gasifier is provided which utilizes the known ash level temperature profile to monitor the ash bed level. A bed stirrer which travels up and down through the extent of the bed ash level is modified by installing thermocouples to measure the bed temperature as the stirrer travels through the stirring cycle. The temperature measurement signals are transmitted to an electronic signal process system by an FM/FM telemetry system. The processing system uses the temperature signals together with an analog stirrer position signal, taken from a position transducer disposed to measure the stirrer position to compute the vertical location of the ash zone upper boundary. The circuit determines the fraction of each total stirrer cycle time the stirrer-derived bed temperature is below a selected set point, multiplies this fraction by the average stirrer signal level, multiplies this result by an appropriate constant and adds another constant such that a 1 to 5 volt signal from the processor corresponds to a 0 to 30 inch span of the ash upper boundary level. Three individual counters in the processor store clock counts that are representative of: (1) the time the stirrer temperature is below the set point (500.degree. F.), (2) the time duration of the corresponding stirrer travel cycle, and (3) the corresponding average stirrer vertical position. The inputs to all three counters are disconnected during any period that the stirrer is stopped, eliminating corruption of the measurement by stirrer stoppage.

Evaluating the effect of internal aperture variability on transport in kilometer scale discrete fracture networks

DOE PAGES

Makedonska, Nataliia; Hyman, Jeffrey D.; Karra, Satish; ...

2016-08-01

The apertures of natural fractures in fractured rock are highly heterogeneous. However, in-fracture aperture variability is often neglected in flow and transport modeling and individual fractures are assumed to have uniform aperture distribution. The relative importance of in-fracture variability in flow and transport modeling within kilometer-scale fracture networks has been under debate for a long time, since the flow in each single fracture is controlled not only by in-fracture variability but also by boundary conditions. Computational limitations have previously prohibited researchers from investigating the relative importance of in-fracture variability in flow and transport modeling within large-scale fracture networks. We addressmore » this question by incorporating internal heterogeneity of individual fractures into flow simulations within kilometer scale three-dimensional fracture networks, where fracture intensity, P 32 (ratio between total fracture area and domain volume) is between 0.027 and 0.031 [1/m]. The recently developed discrete fracture network (DFN) simulation capability, dfnWorks, is used to generate kilometer scale DFNs that include in-fracture aperture variability represented by a stationary log-normal stochastic field with various correlation lengths and variances. The Lagrangian transport parameters, non-reacting travel time, , and cumulative retention, , are calculated along particles streamlines. As a result, it is observed that due to local flow channeling early particle travel times are more sensitive to in-fracture aperture variability than the tails of travel time distributions, where no significant effect of the in-fracture aperture variations and spatial correlation length is observed.« less

Evaluating the effect of internal aperture variability on transport in kilometer scale discrete fracture networks

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

Makedonska, Nataliia; Hyman, Jeffrey D.; Karra, Satish

The apertures of natural fractures in fractured rock are highly heterogeneous. However, in-fracture aperture variability is often neglected in flow and transport modeling and individual fractures are assumed to have uniform aperture distribution. The relative importance of in-fracture variability in flow and transport modeling within kilometer-scale fracture networks has been under debate for a long time, since the flow in each single fracture is controlled not only by in-fracture variability but also by boundary conditions. Computational limitations have previously prohibited researchers from investigating the relative importance of in-fracture variability in flow and transport modeling within large-scale fracture networks. We addressmore » this question by incorporating internal heterogeneity of individual fractures into flow simulations within kilometer scale three-dimensional fracture networks, where fracture intensity, P 32 (ratio between total fracture area and domain volume) is between 0.027 and 0.031 [1/m]. The recently developed discrete fracture network (DFN) simulation capability, dfnWorks, is used to generate kilometer scale DFNs that include in-fracture aperture variability represented by a stationary log-normal stochastic field with various correlation lengths and variances. The Lagrangian transport parameters, non-reacting travel time, , and cumulative retention, , are calculated along particles streamlines. As a result, it is observed that due to local flow channeling early particle travel times are more sensitive to in-fracture aperture variability than the tails of travel time distributions, where no significant effect of the in-fracture aperture variations and spatial correlation length is observed.« less

Burrowing Through Time

NASA Astrophysics Data System (ADS)

Gott, Richard J.

2002-05-01

This excerpt is from a book written by J. Richard Gott III titled Time Travel in Einstein's Universe. He describes what it would be like to travel through space and time by way of wormholes. The author is a professor of astrophysical sciences at Princeton University and a leading expert in the physics of time travel.

5 CFR 550.1401 - Purpose.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) Compensatory Time Off for Travel § 550.1401 Purpose. This subpart contains OPM regulations implementing 5 U.S.C. 5550b, which establishes a separate type of compensatory time off. Subject to the conditions specified... for time in a travel status away from the employee's official duty station when the travel time is not...

5 CFR 550.1401 - Purpose.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) Compensatory Time Off for Travel § 550.1401 Purpose. This subpart contains OPM regulations implementing 5 U.S.C. 5550b, which establishes a separate type of compensatory time off. Subject to the conditions specified... for time in a travel status away from the employee's official duty station when the travel time is not...

5 CFR 550.1401 - Purpose.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) Compensatory Time Off for Travel § 550.1401 Purpose. This subpart contains OPM regulations implementing 5 U.S.C. 5550b, which establishes a separate type of compensatory time off. Subject to the conditions specified... for time in a travel status away from the employee's official duty station when the travel time is not...

5 CFR 550.1401 - Purpose.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) Compensatory Time Off for Travel § 550.1401 Purpose. This subpart contains OPM regulations implementing 5 U.S.C. 5550b, which establishes a separate type of compensatory time off. Subject to the conditions specified... for time in a travel status away from the employee's official duty station when the travel time is not...

5 CFR 550.1401 - Purpose.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Compensatory Time Off for Travel § 550.1401 Purpose. This subpart contains OPM regulations implementing 5 U.S.C. 5550b, which establishes a separate type of compensatory time off. Subject to the conditions specified... for time in a travel status away from the employee's official duty station when the travel time is not...

Non-Normal Projectile Penetration in Soil and Rock: User’s Guide for Computer Code PENC02D.

DTIC Science & Technology

1982-09-01

the path traveled , with projec- tile orientation shown every FREQI projectile lengths. In this run, FREQI was input as 2.5. The horizontal lines...must be a closed surface in the direction of travel ; the bluntness of the nose requires a near 90-deg element for closure. Sheet 3 shows the beginning...plots for this problem. Sheets 1 and 2 automatically verify the projectile shape and path traveled . Sheets 3, 4, and 5 show the axial deceleration

On-time reliability impacts of advanced traveler information services (ATIS). Volume II, Extensions and applications of the simulated yoked study concept

DOT National Transportation Integrated Search

2002-03-01

In a simulated yoke study, estimates of roadway travel times are archived from web-based Advanced Traveler Information Systems (ATIS) and used to recreate hypothetical, retrospective paired driving trials between travelers with and without ATIS. Prev...

Arterial link travel time estimation using loop detector data : phase 1

DOT National Transportation Integrated Search

1997-11-01

The envisioned operational tests of Advanced Traveler Information Systems (ATIS) and Advanced Traffic Management Systems (ATMS) in the Minneapolis/St. Paul area call for the provision of timely and reliable travel times over an entire rod network. Un...

Effectiveness of different approaches to disseminating traveler information on travel time reliability.

DOT National Transportation Integrated Search

2014-01-01

The second Strategic Highway Research Program (SHRP 2) Reliability program aims to improve trip time reliability by reducing the frequency and effects of events that cause travel times to fluctuate unpredictably. Congestion caused by unreliable, or n...

Innovative methods for calculation of freeway travel time using limited data : final report.

DOT National Transportation Integrated Search

2008-01-01

Description: Travel time estimations created by processing of simulated freeway loop detector data using proposed method have been compared with travel times reported from VISSIM model. An improved methodology was proposed to estimate freeway corrido...

Existence, Uniqueness and Asymptotic Stability of Time Periodic Traveling Waves for a Periodic Lotka-Volterra Competition System with Diffusion

PubMed Central

Zhao, Guangyu; Ruan, Shigui

2011-01-01

We study the existence, uniqueness, and asymptotic stability of time periodic traveling wave solutions to a periodic diffusive Lotka-Volterra competition system. Under certain conditions, we prove that there exists a maximal wave speed c* such that for each wave speed c ≤ c*, there is a time periodic traveling wave connecting two semi-trivial periodic solutions of the corresponding kinetic system. It is shown that such a traveling wave is unique modulo translation and is monotone with respect to its co-moving frame coordinate. We also show that the traveling wave solutions with wave speed c < c* are asymptotically stable in certain sense. In addition, we establish the nonexistence of time periodic traveling waves for nonzero speed c > c*. PMID:21572575

Processing data, for improved, accuracy, from device for measuring speed of sound in a gas

DOEpatents

Owen, Thomas E.

2006-09-19

A method, used in connection with a pulse-echo type sensor for determining the speed of sound in a gas, for improving the accuracy of speed of sound measurements. The sensor operates on the principle that speed of sound can be derived from the difference between the two-way travel time of signals reflected from two different target faces of the sensor. This time difference is derived by computing the cross correlation between the two reflections. The cross correlation function may be fitted to a parabola whose vertex represents the optimum time coordinate of the coherence peak, thereby providing an accurate measure of the two-way time diffference.

The influence of travel time on breast cancer characteristics, receipt of primary therapy, and surveillance mammography

PubMed Central

Cook, Andrea; Kirlin, Beth; Shi, Xun; Alford-Teaster, Jennifer; Tuzzio, Leah; Buist, Diana S. M.

2013-01-01

Travel time has been shown to influence some aspects of cancer characteristics at diagnosis and care for women with breast cancer, but important gaps remain in our understanding of its impact. We examined the influence of travel time to the nearest radiology facility on breast cancer characteristics, treatment, and surveillance for women with early-stage invasive breast cancer. We included 1,012 women with invasive breast cancer (stages I and II) who had access to care within an integrated health care delivery system in western Washington State. The travel times to the nearest radiology facility were calculated for all the U.S. Census blocks within the study area and assigned to women based on residence at diagnosis. We collected cancer characteristics, primary and adjuvant therapies, and surveillance mammography for at least 2.5 years post diagnosis and used multivariable analyses to test the associations of travel time. The majority of women (68.6%) lived within 20 min of the nearest radiology facility, had stage I disease (72.7%), received breast conserving therapy (68.7%), and had annual surveillance mammography the first 2 years after treatment (73.7%). The travel time was not significantly associated with the stage or surveillance mammography after adjusting for covariates. Primary therapy was significantly related to travel time, with greater travel time (>30 min vs. ≤ 10 min) associated with a higher likelihood of mastectomy compared to breast conserving surgery (RR = 1.53; 95% CI, 1.16–2.01). The travel time was not associated with the stage at diagnosis or surveillance mammography receipt. The travel time does seem to influence the type of primary therapy among women with breast cancer, suggesting that women may prefer low frequency services, such as mastectomy, if geographic access to a radiology facility is limited. PMID:21553117

Bridging Numerical and Analytical Models of Transient Travel Time Distributions: Challenges and Opportunities

NASA Astrophysics Data System (ADS)

Danesh Yazdi, M.; Klaus, J.; Condon, L. E.; Maxwell, R. M.

2017-12-01

Recent advancements in analytical solutions to quantify water and solute time-variant travel time distributions (TTDs) and the related StorAge Selection (SAS) functions synthesize catchment complexity into a simplified, lumped representation. While these analytical approaches are easy and efficient in application, they require high frequency hydrochemical data for parameter estimation. Alternatively, integrated hydrologic models coupled to Lagrangian particle-tracking approaches can directly simulate age under different catchment geometries and complexity at a greater computational expense. Here, we compare and contrast the two approaches by exploring the influence of the spatial distribution of subsurface heterogeneity, interactions between distinct flow domains, diversity of flow pathways, and recharge rate on the shape of TTDs and the relating SAS functions. To this end, we use a parallel three-dimensional variably saturated groundwater model, ParFlow, to solve for the velocity fields in the subsurface. A particle-tracking model, SLIM, is then implemented to determine the age distributions at every real time and domain location, facilitating a direct characterization of the SAS functions as opposed to analytical approaches requiring calibration of such functions. Steady-state results reveal that the assumption of random age sampling scheme might only hold in the saturated region of homogeneous catchments resulting in an exponential TTD. This assumption is however violated when the vadose zone is included as the underlying SAS function gives a higher preference to older ages. The dynamical variability of the true SAS functions is also shown to be largely masked by the smooth analytical SAS functions. As the variability of subsurface spatial heterogeneity increases, the shape of TTD approaches a power-law distribution function, including a broader distribution of shorter and longer travel times. We further found that larger (smaller) magnitude of effective precipitation shifts the scale of TTD towards younger (older) travel times, while the shape of the TTD remains untouched. This work constitutes a first step in linking a numerical transport model and analytical solutions of TTD to study their assumptions and limitations, providing physical inferences for empirical parameters.

Accuracy of time-domain and frequency-domain methods used to characterize catchment transit time distributions

NASA Astrophysics Data System (ADS)

Godsey, S. E.; Kirchner, J. W.

2008-12-01

The mean residence time - the average time that it takes rainfall to reach the stream - is a basic parameter used to characterize catchment processes. Heterogeneities in these processes lead to a distribution of travel times around the mean residence time. By examining this travel time distribution, we can better predict catchment response to contamination events. A catchment system with shorter residence times or narrower distributions will respond quickly to contamination events, whereas systems with longer residence times or longer-tailed distributions will respond more slowly to those same contamination events. The travel time distribution of a catchment is typically inferred from time series of passive tracers (e.g., water isotopes or chloride) in precipitation and streamflow. Variations in the tracer concentration in streamflow are usually damped compared to those in precipitation, because precipitation inputs from different storms (with different tracer signatures) are mixed within the catchment. Mathematically, this mixing process is represented by the convolution of the travel time distribution and the precipitation tracer inputs to generate the stream tracer outputs. Because convolution in the time domain is equivalent to multiplication in the frequency domain, it is relatively straightforward to estimate the parameters of the travel time distribution in either domain. In the time domain, the parameters describing the travel time distribution are typically estimated by maximizing the goodness of fit between the modeled and measured tracer outputs. In the frequency domain, the travel time distribution parameters can be estimated by fitting a power-law curve to the ratio of precipitation spectral power to stream spectral power. Differences between the methods of parameter estimation in the time and frequency domain mean that these two methods may respond differently to variations in data quality, record length and sampling frequency. Here we evaluate how well these two methods of travel time parameter estimation respond to different sources of uncertainty and compare the methods to one another. We do this by generating synthetic tracer input time series of different lengths, and convolve these with specified travel-time distributions to generate synthetic output time series. We then sample both the input and output time series at various sampling intervals and corrupt the time series with realistic error structures. Using these 'corrupted' time series, we infer the apparent travel time distribution, and compare it to the known distribution that was used to generate the synthetic data in the first place. This analysis allows us to quantify how different record lengths, sampling intervals, and error structures in the tracer measurements affect the apparent mean residence time and the apparent shape of the travel time distribution.

76 FR 68734 - Taking and Importing Marine Mammals: Taking Marine Mammals Incidental to Navy Training Exercises...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-07

... marine mammal is likely to travel during the time associated with the TDFD's time delay, and that... Navy provided the approximate distance that an animal would typically travel within a given time-delay... Speed and Length of Time-Delay Potential distance Species group Swim speed Time-delay traveled Delphinid...

Time Travel: Separating Science Fact from Science Fiction.

ERIC Educational Resources Information Center

Al-Khalili, Jim

2003-01-01

Suggests that the subject of time travel is the best topic to introduce ideas behind some of the most beautiful and fundamental theories about the nature of space and time. Explains the distinction between the two directions of time travel and how relativity theory forced the abandonment of Newtonian notions about the nature of time. (Author/KHR)

Collection and analysis of 2013-2014 travel time data.

DOT National Transportation Integrated Search

2017-07-04

This report documents the findings of Planning Study 27, Collection and Analysis of 2013-2014 Travel Time Data, which is a continuation of Planning Study 24, Analysis of Historical Travel Time Data. The main scope is to analyze newly acquired link-re...

Assessing segment- and corridor-based travel-time reliability on urban freeways : final report.

DOT National Transportation Integrated Search

2016-09-01

Travel time and its reliability are intuitive performance measures for freeway traffic operations. The objective of this project was to quantify segment-based and corridor-based travel time reliability measures on urban freeways. To achieve this obje...

Freeway travel time estimation using existing fixed traffic sensors : phase 2.

DOT National Transportation Integrated Search

2015-03-01

Travel time, one of the most important freeway performance metrics, can be easily estimated using the : data collected from fixed traffic sensors, avoiding the need to install additional travel time data collectors. : This project is aimed at fully u...

Construction and installation of travel time signs on I-35 in Austin.

DOT National Transportation Integrated Search

2016-08-01

Dynamic travel time signs (DTTS) provide current travel times to a specific destination via one or more : routes. These signs aid motorists in making route choice decisions en route. Through this project, three : DTTS were fabricated and installed on...

DOTD support for UTC project : travel time estimation using bluetooth, [research project capsule].

DOT National Transportation Integrated Search

2013-10-01

Travel time estimates are useful tools for measuring congestion in an urban area. Current : practice involves using probe vehicles or video cameras to measure travel time, but this is a laborintensive and expensive means of obtaining the information....

Index of time-of-travel studies of the US Geological Survey

USGS Publications Warehouse

Boning, Charles W.

1973-01-01

This index identifies locations on streams where the U. S. Geological Survey has investigated the time of travel of a highly soluble material moving through a reach of stream channel. This index provides information only on the location of studied stream reaches; it contains no basic data. It does contain, however, a list of references to published data and analytical reports on time of travel and a list of U.S. Geological Survey offices where basic time-of-travel data are on file.

Then and Now: Comparing the Flow of Foreign Fighters to AQI and the Islamic State

DTIC Science & Technology

2016-12-01

State during separate blocks of time . Second, it provides insight into the local travel and flow of foreign fighters across time , and the mobilization...who joined the Islamic State during that latter time period also traveled alone more frequently. When they didn’t travel alone, they arrived in...arriving at the caliphate are larger than they were during the time period covered by the Sinjar records. A couple of cases of group travel to Syria

Analyses of Sea Surface Height, Bottom Pressure and Acoustic Travel Time in the Japan/East Sea

DTIC Science & Technology

2006-01-01

ANALYSES OF SEA SURFACE HEIGHT, BOTTOM PRESSURE AND ACOUSTIC TRAVEL TIME IN THE JAPAN/EAST SEA BY YONGSHENG XU A DISSERTATION SUBMITTED IN PARTIAL...COVERED 00-00-2006 to 00-00-2006 4. TITLE AND SUBTITLE Analyses of Sea Surface Height, Bottom Pressure and Acoustic Travel Time in the Japan/East Sea...1999 to July 2001. The PIESs recorded hourly vertical acoustic travel time and pressure, which are respectively good proxies of baroclinic and

[Mental Space Navigation and Mental Time Travel].

PubMed

Kawamura, Mitsuru

2017-11-01

We examined patients with mental space navigation or mental time travel disorder to identify regions in the brain that may play a critical role in mental time travel in terms of clinical neuropsychology. These regions included the precneus, posterior cingulate gyrus, retrosplenial cortex, and hippocampus, as well as the orbitofrontal cortex: the anterior and posterior medial areas were both shown to be important in this process. Further studies are required to define whether these form a network for mental time travel.

tomo3d: a new 3-D joint refraction and reflection travel-time tomography code for active-source seismic data

NASA Astrophysics Data System (ADS)

Meléndez, A.; Korenaga, J.; Sallares, V.; Ranero, C. R.

2012-12-01

We present the development state of tomo3d, a code for three-dimensional refraction and reflection travel-time tomography of wide-angle seismic data based on the previous two-dimensional version of the code, tomo2d. The core of both forward and inverse problems is inherited from the 2-D version. The ray tracing is performed by a hybrid method combining the graph and bending methods. The graph method finds an ordered array of discrete model nodes, which satisfies Fermat's principle, that is, whose corresponding travel time is a global minimum within the space of discrete nodal connections. The bending method is then applied to produce a more accurate ray path by using the nodes as support points for an interpolation with beta-splines. Travel time tomography is formulated as an iterative linearized inversion, and each step is solved using an LSQR algorithm. In order to avoid the singularity of the sensitivity kernel and to reduce the instability of inversion, regularization parameters are introduced in the inversion in the form of smoothing and damping constraints. Velocity models are built as 3-D meshes, and velocity values at intermediate locations are obtained by trilinear interpolation within the corresponding pseudo-cubic cell. Meshes are sheared to account for topographic relief. A floating reflector is represented by a 2-D grid, and depths at intermediate locations are calculated by bilinear interpolation within the corresponding square cell. The trade-off between the resolution of the final model and the associated computational cost is controlled by the relation between the selected forward star for the graph method (i.e. the number of nodes that each node considers as its neighbors) and the refinement of the velocity mesh. Including reflected phases is advantageous because it provides a better coverage and allows us to define the geometry of those geological interfaces with velocity contrasts sharp enough to be observed on record sections. The code also offers the possibility of including water-layer multiples in the modeling, which is useful whenever these phases can be followed to greater offsets than the primary ones. This increases the amount of information available from the data, yielding more extensive and better constrained velocity and geometry models. We will present synthetic results from benchmark tests for the forward and inverse problems, as well as from more complex inversion tests for different inversions possibilities such as one with travel times from refracted waves only (i.e. first arrivals) and one with travel-times from both refracted and reflected waves. In addition, we will show some preliminary results for the inversion of real 3-D OBS data acquired off-shore Ecuador and Colombia.

Racial disparities in travel time to radiotherapy facilities in the Atlanta metropolitan area

PubMed Central

Peipins, Lucy A.; Graham, Shannon; Young, Randall; Lewis, Brian; Flanagan, Barry

2018-01-01

Low-income women with breast cancer who rely on public transportation may have difficulty in completing recommended radiation therapy due to inadequate access to radiation facilities. Using a geographic information system (GIS) and network analysis we quantified spatial accessibility to radiation treatment facilities in the Atlanta, Georgia metropolitan area. We built a transportation network model that included all bus and rail routes and stops, system transfers and walk and wait times experienced by public transportation system travelers. We also built a private transportation network to model travel times by automobile. We calculated travel times to radiation therapy facilities via public and private transportation from a population-weighted center of each census tract located within the study area. We broadly grouped the tracts by low, medium and high household access to a private vehicle and by race. Facility service areas were created using the network model to map the extent of areal coverage at specified travel times (30, 45 and 60 min) for both public and private modes of transportation. The median public transportation travel time to the nearest radiotherapy facility was 56 min vs. approximately 8 min by private vehicle. We found that majority black census tracts had longer public transportation travel times than white tracts across all categories of vehicle access and that 39% of women in the study area had longer than 1 h of public transportation travel time to the nearest facility. In addition, service area analyses identified locations where the travel time barriers are the greatest. Spatial inaccessibility, especially for women who must use public transportation, is one of the barriers they face in receiving optimal treatment. PMID:23726213

Racial disparities in travel time to radiotherapy facilities in the Atlanta metropolitan area.

PubMed

Peipins, Lucy A; Graham, Shannon; Young, Randall; Lewis, Brian; Flanagan, Barry

2013-07-01

Low-income women with breast cancer who rely on public transportation may have difficulty in completing recommended radiation therapy due to inadequate access to radiation facilities. Using a geographic information system (GIS) and network analysis we quantified spatial accessibility to radiation treatment facilities in the Atlanta, Georgia metropolitan area. We built a transportation network model that included all bus and rail routes and stops, system transfers and walk and wait times experienced by public transportation system travelers. We also built a private transportation network to model travel times by automobile. We calculated travel times to radiation therapy facilities via public and private transportation from a population-weighted center of each census tract located within the study area. We broadly grouped the tracts by low, medium and high household access to a private vehicle and by race. Facility service areas were created using the network model to map the extent of areal coverage at specified travel times (30, 45 and 60 min) for both public and private modes of transportation. The median public transportation travel time to the nearest radiotherapy facility was 56 min vs. approximately 8 min by private vehicle. We found that majority black census tracts had longer public transportation travel times than white tracts across all categories of vehicle access and that 39% of women in the study area had longer than 1 h of public transportation travel time to the nearest facility. In addition, service area analyses identified locations where the travel time barriers are the greatest. Spatial inaccessibility, especially for women who must use public transportation, is one of the barriers they face in receiving optimal treatment. Published by Elsevier Ltd.

Optimizing integrated airport surface and terminal airspace operations under uncertainty

NASA Astrophysics Data System (ADS)

Bosson, Christabelle S.

In airports and surrounding terminal airspaces, the integration of surface, arrival and departure scheduling and routing have the potential to improve the operations efficiency. Moreover, because both the airport surface and the terminal airspace are often altered by random perturbations, the consideration of uncertainty in flight schedules is crucial to improve the design of robust flight schedules. Previous research mainly focused on independently solving arrival scheduling problems, departure scheduling problems and surface management scheduling problems and most of the developed models are deterministic. This dissertation presents an alternate method to model the integrated operations by using a machine job-shop scheduling formulation. A multistage stochastic programming approach is chosen to formulate the problem in the presence of uncertainty and candidate solutions are obtained by solving sample average approximation problems with finite sample size. The developed mixed-integer-linear-programming algorithm-based scheduler is capable of computing optimal aircraft schedules and routings that reflect the integration of air and ground operations. The assembled methodology is applied to a Los Angeles case study. To show the benefits of integrated operations over First-Come-First-Served, a preliminary proof-of-concept is conducted for a set of fourteen aircraft evolving under deterministic conditions in a model of the Los Angeles International Airport surface and surrounding terminal areas. Using historical data, a representative 30-minute traffic schedule and aircraft mix scenario is constructed. The results of the Los Angeles application show that the integration of air and ground operations and the use of a time-based separation strategy enable both significant surface and air time savings. The solution computed by the optimization provides a more efficient routing and scheduling than the First-Come-First-Served solution. Additionally, a data driven analysis is performed for the Los Angeles environment and probabilistic distributions of pertinent uncertainty sources are obtained. A sensitivity analysis is then carried out to assess the methodology performance and find optimal sampling parameters. Finally, simulations of increasing traffic density in the presence of uncertainty are conducted first for integrated arrivals and departures, then for integrated surface and air operations. To compare the optimization results and show the benefits of integrated operations, two aircraft separation methods are implemented that offer different routing options. The simulations of integrated air operations and the simulations of integrated air and surface operations demonstrate that significant traveling time savings, both total and individual surface and air times, can be obtained when more direct routes are allowed to be traveled even in the presence of uncertainty. The resulting routings induce however extra take off delay for departing flights. As a consequence, some flights cannot meet their initial assigned runway slot which engenders runway position shifting when comparing resulting runway sequences computed under both deterministic and stochastic conditions. The optimization is able to compute an optimal runway schedule that represents an optimal balance between total schedule delays and total travel times.

Traveling with breathing problems

MedlinePlus

... obstructive lung disease - travel; Chronic bronchitis - travel; Emphysema - travel ... you: Are short of breath most of the time Get short of breath ... doctor if you plan to travel in a place at a high altitude (such ...

Skype clinics after intestinal transplantation - follow-up beyond post codes.

PubMed

Gerlach, Undine A; Vrakas, Georgios; Holdaway, Lydia; O'Connor, Marion; Macedo, Rubens; Reddy, Srikanth; Friend, Peter J; Giele, Henk; Vaidya, Anil

2016-07-01

The follow-up after intestinal transplantation (ITX) is complex and limited to specialized centers. ITX recipients often travel all over the country to be seen in the outpatient clinic of specialized centers which is costly and time-consuming. Videoconferences through Skype have been implemented to eliminate travel time, costs, and to improve patient compliance without jeopardizing safety. Eighteen of 19 patients followed up after ITX or modified multivisceral transplantation (MMVTX) in conventional outpatient clinics in Oxford agreed to attend additional Skype clinics. All patients who were followed up through Skype clinics after ITX/MMVTX received a questionnaire to measure their satisfaction with methods and technical aspects of videoconferencing as well as time/mode of traveling, travel expenses/costs, waiting time in outpatient clinic and patients' satisfaction. Mean travel distance to Oxford was 236 ± 168 miles, mean travel time was 277 ± 175 min, and mean travel cost was 200 ± 56 Great Britain Pounds. A total of 56% had to take time off work and/or find child/family care for the time spent in travel. These patients reported a satisfaction score of 4.38 ± 0.77 of 5 points as opposed to 2.88 ± 0.90 for attending the conventional outpatient clinic. Skype clinics have been proven successful and feasible in highly specialized fields like ITX in eligible patients. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Screen time and passive school travel as independent predictors of cardiorespiratory fitness in youth.

PubMed

Sandercock, Gavin R H; Ogunleye, Ayodele A

2012-05-01

The most prevalent sedentary behaviours in children and adolescents are engagement with small screen media (screen-time) and passive travel (by motorised vehicle). The objective of this research was to assess the independence of these behaviours from one another and from physical activity as predictors of cardiorespiratory fitness in youth. We measured cardiorespiratory fitness in n=6819 10-16 year olds (53% male) who self-reported their physical activity (7-day recall) school travel and screen time habits. Travel was classified as active (walking, cycling) or passive; screen time as <2 h, 2-4 h or >4 h. The multivariate odds of being fit were higher in active travel (Boys: OR 1.32, 95% CI: 1.09-1.59; Girls: OR 1.46, 1.15-1.84) than in passive travel groups. Boys reporting low screen time were more likely to be fit than those reporting >4 h (OR 2.11, 95% CI: 1.68-2.63) as were girls (OR 1.66, 95% CI: 1.24-2.20). These odds remained significant after additionally controlling for physical activity. Passive travel and high screen time are independently associated with poor cardiorespiratory fitness in youth, and this relationship is independent of physical activity levels. A lifestyle involving high screen time and habitual passive school travel appears incompatible with healthful levels of cardiorespiratory fitness in youth. Copyright © 2012 Elsevier Inc. All rights reserved.

76 FR 18827 - Submission for OMB Review; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-05

... individuals. Time to conduct study: 90 minutes. Estimated travel time to and from site: 30 minutes. Estimated... minutes. Estimated travel time to and from site: 30 minutes. Estimated floater burden: 84 hours (24 x 210... study: 90 minutes. Estimated travel time to and from site: 30 minutes. Estimated participant burden: 50...

Improved UUV Positioning Using Acoustic Communications and a Potential for Real-Time Networking and Collaboration

DTIC Science & Technology

2017-06-01

12 III. ACOUSTIC WAVE TRAVEL TIME ESTIMATION...Mission ...............................125 Table 8. Average Horizontal Distance from the UUV to the Reference Points when a Travel Time Measurement is...Taken ............................................126 Table 9. Average UUV Depth when a Travel Time Measurement is Taken .........126 Table 10. Ratio

78 FR 10608 - David Grant United States Air Force Medical Center Specialty Care Travel Reimbursement...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-14

... appropriately trained provider within 4 weeks or sooner, if required, and within 1-hour travel time from the beneficiary's residence. The geographic area that represents 1-hour travel time surrounding an MTF is referred... Specialty Care Travel Reimbursement Demonstration Project AGENCY: Department of Defense. ACTION: Notice of...

8 CFR 217.5 - Electronic System for Travel Authorization.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Waiver Program (VWP) must, within the time specified in paragraph (b) of this section, receive a travel... period of time the travel authorization is valid. An authorization under ESTA is not a determination that... 8 Aliens and Nationality 1 2013-01-01 2013-01-01 false Electronic System for Travel Authorization...

76 FR 2290 - TRICARE; Reimbursement for Travel for Specialty Care Under Exceptional Circumstances

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-13

... miles but more than 60 minutes in drive time to access needed specialty care. This travel reimbursement... specialty care requiring travel beyond a 60-minute drive time but within 100 miles of the military treatment...] TRICARE; Reimbursement for Travel for Specialty Care Under Exceptional Circumstances AGENCY: Office of the...

8 CFR 217.5 - Electronic System for Travel Authorization.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Waiver Program (VWP) must, within the time specified in paragraph (b) of this section, receive a travel... period of time the travel authorization is valid. An authorization under ESTA is not a determination that... 8 Aliens and Nationality 1 2014-01-01 2014-01-01 false Electronic System for Travel Authorization...

8 CFR 217.5 - Electronic System for Travel Authorization.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Waiver Program (VWP) must, within the time specified in paragraph (b) of this section, receive a travel... admission under the VWP during the period of time the travel authorization is valid. An authorization under... 8 Aliens and Nationality 1 2010-01-01 2010-01-01 false Electronic System for Travel Authorization...

Summer Travel: Plan Ahead To Stay Healthy

MedlinePlus

... Twery says. “It’s especially important before and during travel to consciously schedule time to sleep.” Too little sleep leads to poor ... and their ability to meet the challenges of travel.” Jet lag is another sleep concern for travelers crossing multiple time zones. Jet lag is often more severe for ...

8 CFR 217.5 - Electronic System for Travel Authorization.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Waiver Program (VWP) must, within the time specified in paragraph (b) of this section, receive a travel... period of time the travel authorization is valid. An authorization under ESTA is not a determination that... 8 Aliens and Nationality 1 2012-01-01 2012-01-01 false Electronic System for Travel Authorization...

8 CFR 217.5 - Electronic System for Travel Authorization.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Waiver Program (VWP) must, within the time specified in paragraph (b) of this section, receive a travel... period of time the travel authorization is valid. An authorization under ESTA is not a determination that... 8 Aliens and Nationality 1 2011-01-01 2011-01-01 false Electronic System for Travel Authorization...

Developing corridor-level truck travel time estimates and other freight performance measures from archived ITS data.

DOT National Transportation Integrated Search

2009-08-01

The objectives of this research were to retrospectively study the feasibility for using truck transponder data to produce freight corridor performance measures (travel times) and real-time traveler information. To support this analysis, weigh-in-moti...

APPLICATION OF TRAVEL TIME RELIABILITY FOR PERFORMANCE ORIENTED OPERATIONAL PLANNING OF EXPRESSWAYS

NASA Astrophysics Data System (ADS)

Mehran, Babak; Nakamura, Hideki

Evaluation of impacts of congestion improvement scheme s on travel time reliability is very significant for road authorities since travel time reliability repr esents operational performance of expressway segments. In this paper, a methodology is presented to estimate travel tim e reliability prior to implementation of congestion relief schemes based on travel time variation modeling as a function of demand, capacity, weather conditions and road accident s. For subject expressway segmen ts, traffic conditions are modeled over a whole year considering demand and capacity as random variables. Patterns of demand and capacity are generated for each five minute interval by appl ying Monte-Carlo simulation technique, and accidents are randomly generated based on a model that links acci dent rate to traffic conditions. A whole year analysis is performed by comparing de mand and available capacity for each scenario and queue length is estimated through shockwave analysis for each time in terval. Travel times are estimated from refined speed-flow relationships developed for intercity expressways and buffer time index is estimated consequently as a measure of travel time reliability. For validation, estimated reliability indices are compared with measured values from empirical data, and it is shown that the proposed method is suitable for operational evaluation and planning purposes.

Integrating stochastic time-dependent travel speed in solution methods for the dynamic dial-a-ride problem.

PubMed

Schilde, M; Doerner, K F; Hartl, R F

2014-10-01

In urban areas, logistic transportation operations often run into problems because travel speeds change, depending on the current traffic situation. If not accounted for, time-dependent and stochastic travel speeds frequently lead to missed time windows and thus poorer service. Especially in the case of passenger transportation, it often leads to excessive passenger ride times as well. Therefore, time-dependent and stochastic influences on travel speeds are relevant for finding feasible and reliable solutions. This study considers the effect of exploiting statistical information available about historical accidents, using stochastic solution approaches for the dynamic dial-a-ride problem (dynamic DARP). The authors propose two pairs of metaheuristic solution approaches, each consisting of a deterministic method (average time-dependent travel speeds for planning) and its corresponding stochastic version (exploiting stochastic information while planning). The results, using test instances with up to 762 requests based on a real-world road network, show that in certain conditions, exploiting stochastic information about travel speeds leads to significant improvements over deterministic approaches.

Commuting to work: RN travel time to employment in rural and urban areas.

PubMed

Rosenberg, Marie-Claire; Corcoran, Sean P; Kovner, Christine; Brewer, Carol

2011-02-01

To investigate the variation in average daily travel time to work among registered nurses (RNs) living in urban, suburban, and rural areas. We examine how travel time varies across RN characteristics, job setting, and availability of local employment opportunities. Descriptive statistics and linear regression using a 5% sample from the 2000 Census and a longitudinal survey of newly licensed RNs (NLRN). Travel time for NLRN respondents was estimated using geographic information systems (GIS) software. In the NLRN, rural nurses and those living in small towns had significantly longer average commute times. Young married RNs and RNs with children also tended to have longer commute times, as did RNs employed by hospitals. The findings indicate that travel time to work varies significantly across locale types. Further research is needed to understand whether and to what extent lengthy commute times impact RN workforce needs in rural and urban areas.

Computers in Astronomy: Astronomy on an Apple Macintosh.

ERIC Educational Resources Information Center

Mosley, John E.

1987-01-01

Presents a review of computer programs written for the Apple Macintosh computer that teach astronomy. Reviews general programs, along with some which deal more specifically with sky travel, star charting, the solar system, Halley's Comet, and stargazing. Includes the name and address of each producer. (TW)

Multisensor system for tunnel inspection

NASA Astrophysics Data System (ADS)

Idoux, Maurice

2005-01-01

The system is aimed at assisting inspection and monitoring of the degradation of tunnels in order to minimize maintenance and repair time. ATLAS 70 is a complete sensors/software package which enables thorough diagnosis of tunnel wall conditions. The data collected locally are stored on a computer hard disk for subsequent analysis in a remote location via elaborate dedicated software. The sensors and local computer are loaded onto a rail and/or road vehicle of specific design, i.e. with even travelling speed of 2 to 5 km/h. Originally, the system has been developed for the Paris Underground Company and has since been applied to rail and road tunnels, large town sewage systems, clean water underground aqueducts and electric cable tunnels.

A method for generating an illusion of backwards time travel using immersive virtual reality-an exploratory study.

PubMed

Friedman, Doron; Pizarro, Rodrigo; Or-Berkers, Keren; Neyret, Solène; Pan, Xueni; Slater, Mel

2014-01-01

We introduce a new method, based on immersive virtual reality (IVR), to give people the illusion of having traveled backwards through time to relive a sequence of events in which they can intervene and change history. The participant had played an important part in events with a tragic outcome-deaths of strangers-by having to choose between saving 5 people or 1. We consider whether the ability to go back through time, and intervene, to possibly avoid all deaths, has an impact on how the participant views such moral dilemmas, and also whether this experience leads to a re-evaluation of past unfortunate events in their own lives. We carried out an exploratory study where in the "Time Travel" condition 16 participants relived these events three times, seeing incarnations of their past selves carrying out the actions that they had previously carried out. In a "Repetition" condition another 16 participants replayed the same situation three times, without any notion of time travel. Our results suggest that those in the Time Travel condition did achieve an illusion of "time travel" provided that they also experienced an illusion of presence in the virtual environment, body ownership, and agency over the virtual body that substituted their own. Time travel produced an increase in guilt feelings about the events that had occurred, and an increase in support of utilitarian behavior as the solution to the moral dilemma. Time travel also produced an increase in implicit morality as judged by an implicit association test. The time travel illusion was associated with a reduction of regret associated with bad decisions in their own lives. The results show that when participants have a third action that they can take to solve the moral dilemma (that does not immediately involve choosing between the 1 and the 5) then they tend to take this option, even though it is useless in solving the dilemma, and actually results in the deaths of a greater number.

Degradable transportation network with the addition of electric vehicles: Network equilibrium analysis.

PubMed

Zhang, Rui; Yao, Enjian; Yang, Yang

2017-01-01

Introducing electric vehicles (EVs) into urban transportation network brings higher requirement on travel time reliability and charging reliability. Specifically, it is believed that travel time reliability is a key factor influencing travelers' route choice. Meanwhile, due to the limited cruising range, EV drivers need to better learn about the required energy for the whole trip to make decisions about whether charging or not and where to charge (i.e., charging reliability). Since EV energy consumption is highly related to travel speed, network uncertainty affects travel time and charging demand estimation significantly. Considering the network uncertainty resulted from link degradation, which influences the distribution of travel demand on transportation network and the energy demand on power network, this paper aims to develop a reliability-based network equilibrium framework for accommodating degradable road conditions with the addition of EVs. First, based on the link travel time distribution, the mean and variance of route travel time and monetary expenses related to energy consumption are deduced, respectively. And the charging time distribution of EVs with charging demand is also estimated. Then, a nested structure is considered to deal with the difference of route choice behavior derived by the different uncertainty degrees between the routes with and without degradable links. Given the expected generalized travel cost and a psychological safety margin, a traffic assignment model with the addition of EVs is formulated. Subsequently, a heuristic solution algorithm is developed to solve the proposed model. Finally, the effects of travelers' risk attitude, network degradation degree, and EV penetration rate on network performance are illustrated through an example network. The numerical results show that the difference of travelers' risk attitudes does have impact on the route choice, and the widespread adoption of EVs can cut down the total system travel cost effectively when the transportation network is more reliable.

Perinatal outcomes and travel time from home to hospital: Welsh data from 1995 to 2009.

PubMed

Paranjothy, Shantini; Watkins, W John; Rolfe, Kim; Adappa, Roshan; Gong, Yi; Dunstan, Frank; Kotecha, Sailesh

2014-12-01

To study the association between travel time from home to hospital and birth outcomes. For all registrable births to women resident in Wales (1995-2009), we calculated the travel time between the mother's residence and the postcode-based location for both the birth hospital and all hospitals with maternity services that were open. Using logistic regression, we obtained odds ratios for the association between travel time and each birth outcome, adjusted for confounders. In our analysis of 412 827 singleton births, for every 15-min increase in travel time to the birth hospital, there was an increased risk of early (n = 609; OR: 1.13; 95%CI: 1.07, 1.20) and late neonatal death (n = 251; OR: 1.15; 95%CI: 1.05, 1.26). Results for intrapartum stillbirth were inconclusive (n = 135; OR: 1.13; 95%CI: 0.98, 1.30). For the above-combined (n = 995) results, we get OR: 1.15, 95%CI: 1.09, 1.20. No association was found with travel time to the nearest hospital (OR: 1.01; 95%CI: 0.90, 1.13 per 15-min increase in travel time) for the composite outcome of intrapartum stillbirth and neonatal deaths. Longer travel time to the birth hospital was associated with increased risk of neonatal deaths, but there was no strong evidence of association with the geographical location of maternity services. ©2014 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

Existence and Stability of Traveling Waves for Degenerate Reaction-Diffusion Equation with Time Delay

NASA Astrophysics Data System (ADS)

Huang, Rui; Jin, Chunhua; Mei, Ming; Yin, Jingxue

2018-01-01

This paper deals with the existence and stability of traveling wave solutions for a degenerate reaction-diffusion equation with time delay. The degeneracy of spatial diffusion together with the effect of time delay causes us the essential difficulty for the existence of the traveling waves and their stabilities. In order to treat this case, we first show the existence of smooth- and sharp-type traveling wave solutions in the case of c≥c^* for the degenerate reaction-diffusion equation without delay, where c^*>0 is the critical wave speed of smooth traveling waves. Then, as a small perturbation, we obtain the existence of the smooth non-critical traveling waves for the degenerate diffusion equation with small time delay τ >0 . Furthermore, we prove the global existence and uniqueness of C^{α ,β } -solution to the time-delayed degenerate reaction-diffusion equation via compactness analysis. Finally, by the weighted energy method, we prove that the smooth non-critical traveling wave is globally stable in the weighted L^1 -space. The exponential convergence rate is also derived.

Existence and Stability of Traveling Waves for Degenerate Reaction-Diffusion Equation with Time Delay

NASA Astrophysics Data System (ADS)

Huang, Rui; Jin, Chunhua; Mei, Ming; Yin, Jingxue

2018-06-01

This paper deals with the existence and stability of traveling wave solutions for a degenerate reaction-diffusion equation with time delay. The degeneracy of spatial diffusion together with the effect of time delay causes us the essential difficulty for the existence of the traveling waves and their stabilities. In order to treat this case, we first show the existence of smooth- and sharp-type traveling wave solutions in the case of c≥c^* for the degenerate reaction-diffusion equation without delay, where c^*>0 is the critical wave speed of smooth traveling waves. Then, as a small perturbation, we obtain the existence of the smooth non-critical traveling waves for the degenerate diffusion equation with small time delay τ >0. Furthermore, we prove the global existence and uniqueness of C^{α ,β }-solution to the time-delayed degenerate reaction-diffusion equation via compactness analysis. Finally, by the weighted energy method, we prove that the smooth non-critical traveling wave is globally stable in the weighted L^1-space. The exponential convergence rate is also derived.

Completion of construction and installation of travel time signs on I-35 in Austin : project summary.

DOT National Transportation Integrated Search

2015-08-31

Drivers desire real-time information when : traveling in order to make route choice : decisions. One type of information that can be : provided is current (dynamic) travel times on : two possible routes that serve a common : destination. In this way,...

23 CFR 511.303 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-04-01

... values are present in the attributes (e.g., speed and travel time are attributes of traffic) that require... means the level at which transportation system performance is unacceptable due to excessive travel times... enable the State to satisfy the provisions for traffic and travel time conditions reporting stated in...

Computational and theoretical analysis of free surface flow in a thin liquid film under zero and normal gravity

NASA Technical Reports Server (NTRS)

Faghri, Amir; Swanson, Theodore D.

1988-01-01

The results of a numerical computation and theoretical analysis are presented for the flow of a thin liquid film in the presence and absence of a gravitational body force. Five different flow systems were used. Also presented are the governing equations and boundary conditions for the situation of a thin liquid emanating from a pressure vessel; traveling along a horizontal plate with a constant initial height and uniform initial velocity; and traveling radially along a horizontal disk with a constant initial height and uniform initial velocity.

General Electromagnetic Model for the Analysis of Complex Systems (GEMACS) Computer Code Documentation (Version 3). Volume 3. Part 2.

DTIC Science & Technology

1983-09-01

F.P. PX /AMPZIJ/ REFH /AMPZIJ/ REFV /AI4PZIJ/ * RHOX /AI4PZIJ/ RHOY /At4PZIJ/ RHOZ /AI4PZIJ/ S A-ZJ SA /AMPZIJ/ SALP /AMPZIJ/ 6. CALLING ROUTINE: FLDDRV...US3NG ALGORITHM 72 COMPUTE P- YES .~:*:.~~ USING* *. 1. NAME: PLAINT (GTD) ] 2. PURPOSE: To determine if a ray traveling from a given source loca...determine if a source ray reflection from plate MP occurs. If a ray traveling from the source image location in the reflected ray direction passes through

41 CFR 301-10.301 - How do I compute my mileage reimbursement?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 41 Public Contracts and Property Management 4 2010-07-01 2010-07-01 false How do I compute my...-TRANSPORTATION EXPENSES Privately Owned Vehicle (POV) § 301-10.301 How do I compute my mileage reimbursement? You compute mileage reimbursement by multiplying the distance traveled, determined under § 301-10.302 of this...

Attack rates of dengue fever in Swedish travellers.

PubMed

Rocklöv, Joacim; Lohr, Wolfgang; Hjertqvist, Marika; Wilder-Smith, Annelies

2014-06-01

Dengue is endemic in many countries visited by Swedish travellers. We aimed to determine the attack rate of dengue in Swedish travellers and analyse the trends over time and the geographical variation. We obtained the following data from the Swedish Institute for Communicable Disease Control for the y 1995-2010: number of Swedish residents with confirmed dengue, the country and year of infection. We also obtained registers on the Swedish annual air traveller arrivals to dengue endemic areas from the United Nations World Tourist Organization for the time period. We estimated attack rates with 95% confidence intervals (CI). In total, 925 Swedish travellers with confirmed dengue were reported. We found an increasing trend over time for most destinations. The majority of the dengue cases were acquired in Thailand (492 out of 925 travellers; 53%), with an attack rate of 13.6 (95% CI 12.7, 14.4) per 100,000 travellers. However, the 2 highest attack rates per 100,000 travellers were found for Sri Lanka (45.3, 95% CI 34.3, 56.4) and Bangladesh (42.6, 95% CI 23.8, 61.5). Information on attack rates in travellers is more helpful in guiding travel medicine practitioners than reports of absolute numbers, as the latter reflect travel preferences rather than the true risk. Although the majority of dengue infections in Swedish travellers were acquired in Thailand, the attack rates for dengue in travellers to Sri Lanka and Bangladesh were much higher. These data aid in refining information on the risk of dengue in travellers.

77 FR 33718 - Taking and Importing Marine Mammals: Taking Marine Mammals Incidental to Navy Training Exercises...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-07

...). Here, the Navy identifies the distance that a marine mammal is likely to travel during the time... typically travel within a given time-delay period (Table 1). Based on acoustic propagation modeling... Speed and Length of Time-Delay Potential Species group Swim speed Time-delay (min) distance traveled (yd...

SYSTEMATIC CENTER-TO-LIMB VARIATION IN MEASURED HELIOSEISMIC TRAVEL TIMES AND ITS EFFECT ON INFERENCES OF SOLAR INTERIOR MERIDIONAL FLOWS

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

Zhao Junwei; Nagashima, Kaori; Bogart, R. S.

We report on a systematic center-to-limb variation in measured helioseismic travel times, which must be taken into account for an accurate determination of solar interior meridional flows. The systematic variation, found in time-distance helioseismology analysis using SDO/HMI and SDO/AIA observations, is different in both travel-time magnitude and variation trend for different observables. It is not clear what causes this systematic effect. Subtracting the longitude-dependent east-west travel times, obtained along the equatorial area, from the latitude-dependent north-south travel times, obtained along the central meridian area, gives remarkably similar results for different observables. We suggest this as an effective procedure for removingmore » the systematic center-to-limb variation. The subsurface meridional flows obtained from inversion of the corrected travel times are approximately 10 m s{sup -1} slower than those obtained without removing the systematic effect. The detected center-to-limb variation may have important implications in the derivation of meridional flows in the deep interior and needs to be better understood.« less

Systematic Center-To-Limb Variation in Measured Helioseismic Travel Times and Its Effect on Inferences of Solar Interior Meridional Flows

NASA Technical Reports Server (NTRS)

Zhao, Junwei; Nagashima, Kaori; Bogart, R. S.; Kosovichev, Alexander; Duvall, T. L., Jr.

2012-01-01

We report on a systematic center-to-limb variation in measured helioseismic travel times, which must be taken into account for an accurate determination of solar interior meridional flows. The systematic variation, found in time-distance helioseismology analysis using SDO/HMI and SDO/AIA observations, is different in both travel-time magnitude and variation trend for different observables. It is not clear what causes this systematic effect. Subtracting the longitude-dependent east-west travel times, obtained along the equatorial area, from the latitude-dependent north-south travel times, obtained along the central meridian area, gives remarkably similar results for different observables. We suggest this as an effective procedure for removing the systematic center-to-limb variation. The subsurface meridional flows obtained from inversion of the corrected travel times are approximately 10 m s-1 slower than those obtained without removing the systematic effect. The detected center-to-limb variation may have important implications in the derivation of meridional flows in the deep interior and needs to be better understood.

77 FR 62221 - Renewal of the Board of Visitors of the U.S. Air Force Academy

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-12

... be reimbursed under Government travel regulations for travel expenses. If a member of the Board fails... for consultation. These advisors shall, with the exception of travel and per diem for official travel...-time or part-time government employees, shall be appointed by the Secretary of Defense according to...

Error assessment for emerging traffic data collection devices.

DOT National Transportation Integrated Search

2014-06-01

Because access to travel time information can significantly influence the decision making of both agencies : and travelers, accurate and reliable travel time information is increasingly needed. One important step in : providing that information is to...

Error assessment for emerging traffic data collection devices.

DOT National Transportation Integrated Search

2014-09-01

Providing accurate and reliable travel time information to roadway users is a critical part of Advanced Traffic Management Systems (ATMS) and : Advanced Travelers Information Systems (ATIS). Access to travel time information can significantly influen...

Implementation and Comparison of Acoustic Travel-Time Measurement Procedures for the Helioseismic and Magnetic Imager Time-Distance Helioseismology Pipeline

NASA Technical Reports Server (NTRS)

Couvidat, S.; Zhao, J.; Birch, A. C.; Kosovichev, A. G.; Duvall, T. L., Jr.; Parchevsky, K.; Scherrer, P. H.

2009-01-01

The Helioseismic and Magnetic Imager (HMI) instrument on board the Solar Dynamics Observatory (SDO) satellite is designed to produce high-resolution Doppler velocity maps of oscillations at the solar surface with high temporal cadence. To take advantage of these high-quality oscillation data, a time-distance helioseismology pipeline has been implemented at the Joint Science Operations Center (JSOC) at Stanford University. The aim of this pipeline is to generate maps of acoustic travel times from oscillations on the solar surface, and to infer subsurface 3D flow velocities and sound-speed perturbations. The wave travel times are measured from cross covariances of the observed solar oscillation signals. For implementation into the pipeline we have investigated three different travel-time definitions developed in time-distance helioseismology: a Gabor wavelet fitting (Kosovichev and Duvall, 1997), a minimization relative to a reference cross-covariance function (Gizon and Birch, 2002), and a linearized version of the minimization method (Gizon and Birch, 2004). Using Doppler velocity data from the Michelson Doppler Imager (MDI) instrument on board SOHO, we tested and compared these definitions for the mean and difference travel-time perturbations measured from reciprocal signals. Although all three procedures return similar travel times in a quiet Sun region, the method of Gizon and Birch (2004) gives travel times that are significantly different from the others in a magnetic (active) region. Thus, for the pipeline implementation we chose the procedures of Kosovichev and Duvall (1997) and Gizon and Birch (2002). We investigated the relationships among these three travel-time definitions, their sensitivities to fitting parameters, and estimated the random errors they produce

Daily travel distances of zoo-housed chimpanzees and gorillas: implications for welfare assessments and space requirements.

PubMed

Ross, Stephen R; Shender, Marisa A

2016-07-01

The degree to which the relatively smaller area of artificial environments (compared with natural habitats) has measureable effects on the behavior and welfare of captive animals has been debated for many years. While there is little question that these spaces provide far less opportunity for natural ranging behavior and travel, less is known about the degree to which captive animals travel within their environments and what factors influence these travel patterns. We intensively studied the movement of zoo-housed chimpanzees and gorillas using a computer map interface and determined their mean daily travel and found they travelled similar distances each day when restricted to their indoor areas, but when provided additional outdoor space, chimpanzees tended to increase their travel to a greater extent than did gorillas. Both species travelled shorter distances than has been recorded for their wild counterparts, however, when given access to their full indoor-outdoor exhibit; those differences were not as substantive. These findings suggest that while large, complex naturalistic environments might not stimulate comparable species-typical travel patterns in captive apes, larger spaces that include outdoor areas may be better at replicating this behavioral pattern than smaller, indoor areas.

Multivariate regression methods for estimating velocity of ictal discharges from human microelectrode recordings

NASA Astrophysics Data System (ADS)

Liou, Jyun-you; Smith, Elliot H.; Bateman, Lisa M.; McKhann, Guy M., II; Goodman, Robert R.; Greger, Bradley; Davis, Tyler S.; Kellis, Spencer S.; House, Paul A.; Schevon, Catherine A.

2017-08-01

Objective. Epileptiform discharges, an electrophysiological hallmark of seizures, can propagate across cortical tissue in a manner similar to traveling waves. Recent work has focused attention on the origination and propagation patterns of these discharges, yielding important clues to their source location and mechanism of travel. However, systematic studies of methods for measuring propagation are lacking. Approach. We analyzed epileptiform discharges in microelectrode array recordings of human seizures. The array records multiunit activity and local field potentials at 400 micron spatial resolution, from a small cortical site free of obstructions. We evaluated several computationally efficient statistical methods for calculating traveling wave velocity, benchmarking them to analyses of associated neuronal burst firing. Main results. Over 90% of discharges met statistical criteria for propagation across the sampled cortical territory. Detection rate, direction and speed estimates derived from a multiunit estimator were compared to four field potential-based estimators: negative peak, maximum descent, high gamma power, and cross-correlation. Interestingly, the methods that were computationally simplest and most efficient (negative peak and maximal descent) offer non-inferior results in predicting neuronal traveling wave velocities compared to the other two, more complex methods. Moreover, the negative peak and maximal descent methods proved to be more robust against reduced spatial sampling challenges. Using least absolute deviation in place of least squares error minimized the impact of outliers, and reduced the discrepancies between local field potential-based and multiunit estimators. Significance. Our findings suggest that ictal epileptiform discharges typically take the form of exceptionally strong, rapidly traveling waves, with propagation detectable across millimeter distances. The sequential activation of neurons in space can be inferred from clinically-observable EEG data, with a variety of straightforward computation methods available. This opens possibilities for systematic assessments of ictal discharge propagation in clinical and research settings.

Comparison of Travel-Time and Amplitude Measurements for Deep-Focusing Time-Distance Helioseismology

NASA Astrophysics Data System (ADS)

Pourabdian, Majid; Fournier, Damien; Gizon, Laurent

2018-04-01

The purpose of deep-focusing time-distance helioseismology is to construct seismic measurements that have a high sensitivity to the physical conditions at a desired target point in the solar interior. With this technique, pairs of points on the solar surface are chosen such that acoustic ray paths intersect at this target (focus) point. Considering acoustic waves in a homogeneous medium, we compare travel-time and amplitude measurements extracted from the deep-focusing cross-covariance functions. Using a single-scattering approximation, we find that the spatial sensitivity of deep-focusing travel times to sound-speed perturbations is zero at the target location and maximum in a surrounding shell. This is unlike the deep-focusing amplitude measurements, which have maximum sensitivity at the target point. We compare the signal-to-noise ratio for travel-time and amplitude measurements for different types of sound-speed perturbations, under the assumption that noise is solely due to the random excitation of the waves. We find that, for highly localized perturbations in sound speed, the signal-to-noise ratio is higher for amplitude measurements than for travel-time measurements. We conclude that amplitude measurements are a useful complement to travel-time measurements in time-distance helioseismology.

Reduced rank models for travel time estimation of low order mode pulses.

PubMed

Chandrayadula, Tarun K; Wage, Kathleen E; Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A; Andrew, Rex K; Howe, Bruce M

2013-10-01

Mode travel time estimation in the presence of internal waves (IWs) is a challenging problem. IWs perturb the sound speed, which results in travel time wander and mode scattering. A standard approach to travel time estimation is to pulse compress the broadband signal, pick the peak of the compressed time series, and average the peak time over multiple receptions to reduce variance. The peak-picking approach implicitly assumes there is a single strong arrival and does not perform well when there are multiple arrivals due to scattering. This article presents a statistical model for the scattered mode arrivals and uses the model to design improved travel time estimators. The model is based on an Empirical Orthogonal Function (EOF) analysis of the mode time series. Range-dependent simulations and data from the Long-range Ocean Acoustic Propagation Experiment (LOAPEX) indicate that the modes are represented by a small number of EOFs. The reduced-rank EOF model is used to construct a travel time estimator based on the Matched Subspace Detector (MSD). Analysis of simulation and experimental data show that the MSDs are more robust to IW scattering than peak picking. The simulation analysis also highlights how IWs affect the mode excitation by the source.

41 CFR 301-51.200 - For what expenses may I receive a travel advance?

Code of Federal Regulations, 2013 CFR

2013-07-01

... personal check, or travelers check) Any time you are on official travel. (1) M&IE covered by the per diem... receive a travel advance? 301-51.200 Section 301-51.200 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES ARRANGING FOR TRAVEL SERVICES, PAYING...

41 CFR 301-51.200 - For what expenses may I receive a travel advance?

Code of Federal Regulations, 2011 CFR

2011-07-01

... personal check, or travelers check) Any time you are on official travel. (1) M&IE covered by the per diem... receive a travel advance? 301-51.200 Section 301-51.200 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES ARRANGING FOR TRAVEL SERVICES, PAYING...

41 CFR 301-51.200 - For what expenses may I receive a travel advance?

Code of Federal Regulations, 2010 CFR

2010-07-01

... personal check, or travelers check) Any time you are on official travel. (1) M&IE covered by the per diem... receive a travel advance? 301-51.200 Section 301-51.200 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES ARRANGING FOR TRAVEL SERVICES, PAYING...

41 CFR 301-51.200 - For what expenses may I receive a travel advance?

Code of Federal Regulations, 2012 CFR

2012-07-01

... personal check, or travelers check) Any time you are on official travel. (1) M&IE covered by the per diem... receive a travel advance? 301-51.200 Section 301-51.200 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES ARRANGING FOR TRAVEL SERVICES, PAYING...

41 CFR 301-11.20 - May my agency authorize a rest period for me while I am traveling?

Code of Federal Regulations, 2013 CFR

2013-07-01

... scheduled flight time, including stopovers, exceeds 14 hours; (3) Travel is by a direct or usually traveled... rest period for me while I am traveling? 301-11.20 Section 301-11.20 Public Contracts and Property Management Federal Travel Regulation System TEMPORARY DUTY (TDY) TRAVEL ALLOWANCES ALLOWABLE TRAVEL EXPENSES...

ROUTES: a computer program for preliminary route location.

Treesearch

S.E. Reutebuch

1988-01-01

An analytical description of the ROUTES computer program is presented. ROUTES is part of the integrated preliminary harvest- and transportation-planning software package, PLANS. The ROUTES computer program is useful where grade and sideslope limitations are important in determining routes for vehicular travel. With the program, planners can rapidly identify route...

The evaluation of advanced traveler information services (ATIS) impacts on truck travel time reliability : using the simulated yoked study concept

DOT National Transportation Integrated Search

2004-03-01

The ability of Advanced Traveler Information Systems (ATIS) to improve the on-time reliability of urban truck movements is evaluated through the application of the Heuristic On-Line Web- : Linked Arrival Time Estimation (HOWLATE) methodology. In HOWL...

METHOD OF ESTIMATING THE TRAVEL TIME OF NONINTERACTING SOLUTES THROUGH COMPACTED SOIL MATERIAL

EPA Science Inventory

The pollutant travel time through compacted soil material (i.e., when a pollutant introduced at the top first appears at the bottom) cannot be accurately predicted from the permeability (saturated hydraulic conductivity) alone. The travel time is also dependent on the effective p...

Annual Report of the ECSU Home-Institution Support Program (1993)

DTIC Science & Technology

1993-09-30

summer of 1992. Stephanie plans to attend graduate school at the University of Alabama at Birmingham. r 3 . Deborah Jones has attended the ISSP program for...computer equipment Component #2 A visiting lecturer series Component # 3 : Students pay & faculty release time Component #4 Student/sponsor travel program...DTXC QUA, ty rNpBT 3 S. 0. CODE: 1133 DISBURSING CODE: N001 79 AGO CODE: N66005 CAGE CODE: OJLKO 3 PART I: A succinct narrative which should

Precision Thickness Variation Mapping Via One-Transducer Ultrasonic High Resolution Profilometry for Sample With Irregular or Rough Surface

NASA Technical Reports Server (NTRS)

Roth, Don J. (Inventor)

1996-01-01

An apparatus and method for determination of sample thickness and surface depression utilizing ultrasonic pulses is discussed. The sample is held in a predetermined position by a support member having a reference surface. Ultrasonic pulses travel through a medium of known velocity propagation and reflect off the reference surface and a sample surface. Time of flight data of surface echoes are converted to distances between sample surfaces to obtain computer-generated thickness profiles and surface mappings.

If BZ medium did spanning trees these would be the same trees as Physarum built

NASA Astrophysics Data System (ADS)

Adamatzky, Andrew

2009-03-01

A sub-excitable Belousov-Zhabotinsky (BZ) medium exhibits self-localized wave-fragments which may travel for relatively long time preserving their shape. Using Oregonator model of the BZ medium we imitate foraging behavior of a true slime mold, Physarum polycephalum, on a nutrient-poor substrate. We show that given erosion post-processing operations the BZ medium can approximate a spanning tree of a planar set and thus is computationally equivalent to Physarum in the domain of proximity graph construction.

Algorithms and Heuristics for Time-Window-Constrained Traveling Salesman Problems.

DTIC Science & Technology

1985-09-01

w-r.- v-- n - ,u-,, u- v-v-.: .r-r-ri v-. r, - t -. \\ _ . . . S :.:, 1 .J - 1 5 ,*’:: C - V * t_ t. . 4’ *,W Ii NAVAL POSTGRADUATE SCHOOL Monterey...q- -- Computational experience is re- ported for all the heuristics and algorithms we develop. DD IFOAN3 1473 EDITION OF I NOV 65 IS OBSOLETE N ...Approved by Ri .R n ~~Advisor Ric E... a, R. shencSo deader A-lan R. Washburn Chairman, -~ Department of Operaiions Research Knealg--.T _ yarshall

Travel and the home advantage.

PubMed

Pace, A; Carron, A V

1992-03-01

The purpose of the present study was to examine the relative contributions of various travel related variables to visiting team success in the National Hockey League. A multiple regression design was used with game outcome as the dependent variable. The independent variables of interest included, as main effects and interactions, number of time zones crossed, direction of travel, distance traveled, preparation/adjustment time, time of season, game number on the road trip, and the home stand. Visiting team success was negatively associated with the interaction of number of time zones crossed and increased preparation time between games, and was positively associated with game number on the road. It was concluded that only a small portion of the variance in the home advantage/visitor disadvantage can be explained by travel related factors.

A simple method to assess unsaturated zone time lag in the travel time from ground surface to receptor.

PubMed

Sousa, Marcelo R; Jones, Jon P; Frind, Emil O; Rudolph, David L

2013-01-01

In contaminant travel from ground surface to groundwater receptors, the time taken in travelling through the unsaturated zone is known as the unsaturated zone time lag. Depending on the situation, this time lag may or may not be significant within the context of the overall problem. A method is presented for assessing the importance of the unsaturated zone in the travel time from source to receptor in terms of estimates of both the absolute and the relative advective times. A choice of different techniques for both unsaturated and saturated travel time estimation is provided. This method may be useful for practitioners to decide whether to incorporate unsaturated processes in conceptual and numerical models and can also be used to roughly estimate the total travel time between points near ground surface and a groundwater receptor. This method was applied to a field site located in a glacial aquifer system in Ontario, Canada. Advective travel times were estimated using techniques with different levels of sophistication. The application of the proposed method indicates that the time lag in the unsaturated zone is significant at this field site and should be taken into account. For this case, sophisticated and simplified techniques lead to similar assessments when the same knowledge of the hydraulic conductivity field is assumed. When there is significant uncertainty regarding the hydraulic conductivity, simplified calculations did not lead to a conclusive decision. Copyright © 2012 Elsevier B.V. All rights reserved.

Tile Drainage Density Reduces Groundwater Travel Times and Compromises Riparian Buffer Effectiveness.

PubMed

Schilling, Keith E; Wolter, Calvin F; Isenhart, Thomas M; Schultz, Richard C

2015-11-01

Strategies to reduce nitrate-nitrogen (nitrate) pollution delivered to streams often seek to increase groundwater residence time to achieve measureable results, yet the effects of tile drainage on residence time have not been well documented. In this study, we used a geographic information system groundwater travel time model to quantify the effects of artificial subsurface drainage on groundwater travel times in the 7443-ha Bear Creek watershed in north-central Iowa. Our objectives were to evaluate how mean groundwater travel times changed with increasing drainage intensity and to assess how tile drainage density reduces groundwater contributions to riparian buffers. Results indicate that mean groundwater travel times are reduced with increasing degrees of tile drainage. Mean groundwater travel times decreased from 5.6 to 1.1 yr, with drainage densities ranging from 0.005 m (7.6 mi) to 0.04 m (62 mi), respectively. Model simulations indicate that mean travel times with tile drainage are more than 150 times faster than those that existed before settlement. With intensive drainage, less than 2% of the groundwater in the basin appears to flow through a perennial stream buffer, thereby reducing the effectiveness of this practice to reduce stream nitrate loads. Hence, strategies, such as reconnecting tile drainage to buffers, are promising because they increase groundwater residence times in tile-drained watersheds. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Effects of northbound long-haul international air travel on sleep quantity and subjective jet lag and wellness in professional Australian soccer players.

PubMed

Fowler, Peter; Duffield, Rob; Howle, Kieran; Waterson, Adam; Vaile, Joanna

2015-07-01

The current study examined the effects of 10-h northbound air travel across 1 time zone on sleep quantity, together with subjective jet lag and wellness ratings, in 16 male professional Australian football (soccer) players. Player wellness was measured throughout the week before (home training week) and the week of (away travel week) travel from Australia to Japan for a preseason tour. Sleep quantity and subjective jet lag were measured 2 d before (Pre 1 and 2), the day of, and for 5 d after travel (Post 1-5). Sleep duration was significantly reduced during the night before travel (Pre 1; 4.9 [4.2-5.6] h) and night of competition (Post 2; 4.2 [3.7-4.7] h) compared with every other night (P<.01, d>0.90). Moreover, compared with the day before travel, subjective jet lag was significantly greater for the 5 d after travel (P<.05, d>0.90), and player wellness was significantly lower 1 d post-match (Post 3) than at all other time points (P<.05, d>0.90). Results from the current study suggest that sleep disruption, as a result of an early travel departure time (8 PM) and evening match (7:30 PM), and fatigue induced by competition had a greater effect on wellness ratings than long-haul air travel with a minimal time-zone change. Furthermore, subjective jet lag may have been misinterpreted as fatigue from sleep disruption and competition, especially by the less experienced players. Therefore, northbound air travel across 1 time zone from Australia to Asia appears to have negligible effects on player preparedness for subsequent training and competition.

Impact of a University-Based Outpatient Telemedicine Program on Time Savings, Travel Costs, and Environmental Pollutants.

PubMed

Dullet, Navjit W; Geraghty, Estella M; Kaufman, Taylor; Kissee, Jamie L; King, Jesse; Dharmar, Madan; Smith, Anthony C; Marcin, James P

2017-04-01

The objective of this study was to estimate travel-related and environmental savings resulting from the use of telemedicine for outpatient specialty consultations with a university telemedicine program. The study was designed to retrospectively analyze the telemedicine consultation database at the University of California Davis Health System (UCDHS) between July 1996 and December 2013. Travel distances and travel times were calculated between the patient home, the telemedicine clinic, and the UCDHS in-person clinic. Travel cost savings and environmental impact were calculated by determining differences in mileage reimbursement rate and emissions between those incurred in attending telemedicine appointments and those that would have been incurred if a visit to the hub site had been necessary. There were 19,246 consultations identified among 11,281 unique patients. Telemedicine visits resulted in a total travel distance savings of 5,345,602 miles, a total travel time savings of 4,708,891 minutes or 8.96 years, and a total direct travel cost savings of $2,882,056. The mean per-consultation round-trip distance savings were 278 miles, average travel time savings were 245 minutes, and average cost savings were $156. Telemedicine consultations resulted in a total emissions savings of 1969 metric tons of CO 2 , 50 metric tons of CO, 3.7 metric tons of NO x , and 5.5 metric tons of volatile organic compounds. This study demonstrates the positive impact of a health system's outpatient telemedicine program on patient travel time, patient travel costs, and environmental pollutants. Copyright © 2017 International Society for Pharmacoeconomics and Outcomes Research (ISPOR). Published by Elsevier Inc. All rights reserved.

Defining travel-associated cases of enteric fever.

PubMed

Freedman, Joanne; Lighton, Lorraine; Jones, Jane

2014-01-01

There is no internationally recognized case-definition for travel-associated enteric fever in non-endemic countries. This study describes the patterns of case reporting between 2007 and 2011 as travel-associated or not from the surveillance data in England, Wales and Northern Ireland (EWNI), before and after a change in the time component of the case-definition in January 2011. It examines in particular the role of a time frame based on the reported typical incubation period in defining a case of travel-associated enteric fever. The results showed no significant differences in the distribution of cases of enteric fever in regards to the interval between the onset and UK arrival in 2011 compared to 2007-2010 (p=0.98 for typhoid and paratyphoid A); the distribution for paratyphoid B was also similar in both time periods. During 2007-2010, 93% (1730/1853) of all of the cases were classified as travel-associated compared to 94% (448/477) in 2011. This difference was not statistically significant. Changing the time component of the definition of travel-associated enteric fever did not make a significant difference to the proportion of travel-associated cases reported by investigators. Our analysis suggests that time might be subordinate to other considerations when investigators classify a case as travel-associated. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Predicting traffic load impact of alternative recreation developments

Treesearch

Gary H. Elsner; Ronald A. Oliveira

1973-01-01

Traffic load changes as a result of expansion of recreation facilities may be predicted through computations based on estimates of (a) drawing power of the recreation attracttions, overnight accommodations, and in- or out-terminals; (b) probable types of travel; (c) probable routes of travel; and (d) total number of cars in the recreation system. Once the basic model...