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Sample records for groundwater travel times

  1. Reliability of travel times to groundwater abstraction wells: Application of the Netherlands Groundwater Model - LGM

    NARCIS (Netherlands)

    Kovar K; Leijnse A; Uffink G; Pastoors MJH; Mulschlegel JHC; Zaadnoordijk WJ; LDL; IMD; TNO/NITG; Haskoning

    2005-01-01

    A modelling approach was developed, incorporated in the finite-element method based program LGMLUC, making it possible to determine the reliability of travel times of groundwater flowing to groundwater abstraction sites. The reliability is seen here as a band (zone) around the expected travel-time i

  2. Characterizing groundwater contribution to lowland streams using Travel Time Distribution

    Science.gov (United States)

    Petrus Kaandorp, Vincentius; Gerardus Bernardus de Louw, Petrus; Kuijper, Martina Johanna Maria; Broers, Hans Peter

    2015-04-01

    In recent years, it has become apparent that European freshwaters will fail to meet the ecological guidelines set for 2015 by the Water Framework Directive. 55 % of European surface water bodies have been reported to have a less than good ecological status, while the goal for 2015 is to have a good status for all water bodies. The deterioration of freshwater aquatic ecosystems is a problem worldwide. The current study, part of the EU FP7 project Managing Aquatic ecosystems and water Resources under multiple Stress (MARS), addresses this issue by focusing on the effect of multiple stressors. Freshwater ecosystems are directly linked to the characteristics of catchments and streams they are located in as this determines the habitats present. One of these characteristics, the groundwater contribution to streams, is important for aquatic ecosystems as it influences (1) river discharge, (2) water quality and (3) temperature and (4) the riparian zone. Groundwater provides streams with sufficient base flow, good quality water and a stable temperature. Compared to hilly slope catchments, the lowland catchments of The Netherlands lack much topography and surface runoff, and as such, virtually all stream water originates from groundwater. Current approaches do not sufficiently address the contribution of groundwater to stream flow in lowland catchments, as existing hydrograph separation methods provide little informative value about the groundwater contribution itself. The amount and quality of groundwater input to streams depends on its flow path and travel time. Especially in lowland catchments the groundwater input in streams is composed of a wide range of travel times which vary in time and space and have different quantitative and qualitative characteristics. Thus in order to successfully manage lowland streams, it is critical to specify the input of groundwater in more detail and take in account the temporal and spatial variability in travel times. We will present an

  3. Flow calculations for Yucca Mountain groundwater travel time (GWTT-95)

    Energy Technology Data Exchange (ETDEWEB)

    Altman, S.J.; Arnold, B.W.; Barnard, R.W.; Barr, G.E.; Ho, C.K.; McKenna, S.A.; Eaton, R.R.

    1996-09-01

    In 1983, high-level radioactive waste repository performance requirements related to groundwater travel time were defined by NRC subsystem regulation 10 CFR 60.113. Although DOE is not presently attempting to demonstrate compliance with that regulation, understanding of the prevalence of fast paths in the groundwater flow system remains a critical element of any safety analyses for a potential repository system at Yucca Mountain, Nevada. Therefore, this analysis was performed to allow comparison of fast-path flow against the criteria set forth in the regulation. Models developed to describe the conditions for initiation, propagation, and sustainability of rapid groundwater movement in both the unsaturated and saturated zones will form part of the technical basis for total- system analyses to assess site viability and site licensability. One of the most significant findings is that the fastest travel times in both unsaturated and saturated zones are in the southern portion of the potential repository, so it is recommended that site characterization studies concentrate on this area. Results support the assumptions regarding the importance of an appropriate conceptual model of groundwater flow and the incorporation of heterogeneous material properties into the analyses. Groundwater travel times are sensitive to variation/uncertainty in hydrologic parameters and in infiltration flux at upper boundary of the problem domain. Simulated travel times are also sensitive to poorly constrained parameters of the interaction between flow in fractures and in the matrix.

  4. Dissolved Organic Carbon 14C in Southern Nevada Groundwater and Implications for Groundwater Travel Times

    Energy Technology Data Exchange (ETDEWEB)

    Hershey, Ronald L. [Nevada University, Reno, NV (United States). Desert Research Institute; Fereday, Wyall [Nevada University, Reno, NV (United States). Desert Research Institute; Thomas, James M [Nevada University, Reno, NV (United States). Desert Research Institute

    2016-08-01

    Dissolved inorganic carbon (DIC) carbon-14 (14C) ages must be corrected for complex chemical and physical reactions and processes that change the amount of 14C in groundwater as it flows from recharge to downgradient areas. Because of these reactions, DIC 14C can produce unrealistically old ages and long groundwater travel times that may, or may not, agree with travel times estimated by other methods. Dissolved organic carbon (DOC) 14C ages are often younger than DIC 14C ages because there are few chemical reactions or physical processes that change the amount of DOC 14C in groundwater. However, there are several issues that create uncertainty in DOC 14C groundwater ages including limited knowledge of the initial (A0) DOC 14C in groundwater recharge and potential changes in DOC composition as water moves through an aquifer. This study examines these issues by quantifying A0 DOC 14C in recharge areas of southern Nevada groundwater flow systems and by evaluating changes in DOC composition as water flows from recharge areas to downgradient areas. The effect of these processes on DOC 14C groundwater ages is evaluated and DOC and DIC 14C ages are then compared along several southern Nevada groundwater flow paths. Twenty-seven groundwater samples were collected from springs and wells in southern Nevada in upgradient, midgradient, and downgradient locations. DOC 14C for upgradient samples ranged from 96 to 120 percent modern carbon (pmc) with an average of 106 pmc, verifying modern DOC 14C ages in recharge areas, which decreases uncertainty in DOC 14C A0 values, groundwater ages, and travel times. The HPLC spectra of groundwater along a flow path in the Spring Mountains show the same general pattern indicating that the DOC compound composition does not change along this flow path

  5. Sensitivity studies of unsaturated groundwater flow modeling for groundwater travel time calculations at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Altman, S.J.; Ho, C.K.; Arnold, B.W.; McKenna, S.A.

    1995-12-31

    Unsaturated flow has been modeled through four cross-sections at Yucca Mountain, Nevada, for the purpose of determining groundwater particle travel times from the potential repository to the water table. This work will be combined with the results of flow modeling in the saturated zone for the purpose of evaluating the suitability of the potential repository under the criteria of 10CFR960. One criterion states, in part, that the groundwater travel time (GWTT) from the repository to the accessible environment must exceed 1,000 years along the fastest path of likely and significant radionuclide travel. Sensitivity analyses have been conducted for one geostatistical realization of one cross-section for the purpose of (1) evaluating the importance of hydrological parameters having some uncertainty and (2) examining conceptual models of flow by altering the numerical implementation of the conceptual model (dual permeability (DK) and the equivalent continuum model (ECM). Results of comparisons of the ECM and DK model are also presented in Ho et al.

  6. Sensitivity studies of unsaturated groundwater flow modeling for groundwater travel time calculations at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Altman, S.J.; Ho, C.K.; Arnold, B.W.; McKenna, S.A. [Sandia National Labs., Albuquerque, NM (United States)

    1996-12-01

    Unsaturated flow has been modeled through four cross-sections at Yucca Mountain, Nevada, for the purpose of determining groundwater particle travel times from the potential repository to the water table. This work will be combined with the results of flow modeling in the saturated zone for the purpose of evaluating the suitability of the potential repository under the criteria of 10CFR960. One criterion states, in part, that the groundwater travel time (GWTT) from the repository to the accessible environment must exceed 1,000 years along the fastest path of likely and significant radionuclide travel. Sensitivity analyses have been conducted for one geostatistical realization of one cross-section for the purpose of (1) evaluating the importance of hydrological parameters having some uncertainty (infiltration, fracture-matrix connectivity, fracture frequency, and matrix air entry pressure or van Genuchten {alpha}); and (2) examining conceptual models of flow by altering the numerical implementation of the conceptual model (dual permeability (DK) and the equivalent continuum model (ECM)). Results of comparisons of the ECM and DK model are also presented in Ho et al.

  7. Quantifying groundwater travel time near managed recharge operations using 35S as an intrinsic tracer

    Science.gov (United States)

    Urióstegui, Stephanie H.; Bibby, Richard K.; Esser, Bradley K.; Clark, Jordan F.

    2016-12-01

    Identifying groundwater retention times near managed aquifer recharge (MAR) facilities is a high priority for managing water quality, especially for operations that incorporate recycled wastewater. To protect public health, California guidelines for Groundwater Replenishment Reuse Projects require a minimum 2-6 month subsurface retention time for recycled water depending on the level of disinfection, which highlights the importance of quantifying groundwater travel times on short time scales. This study developed and evaluated a new intrinsic tracer method using the naturally occurring radioisotope sulfur-35 (35S). The 87.5 day half-life of 35S is ideal for investigating groundwater travel times on the managers. Natural concentrations of 35S found in water as dissolved sulfate (35SO4) were measured in source waters and groundwater at the Rio Hondo Spreading Grounds in Los Angeles County, CA, and Orange County Groundwater Recharge Facilities in Orange County, CA. 35SO4 travel times are comparable to travel times determined by well-established deliberate tracer studies. The study also revealed that 35SO4 in MAR source water can vary seasonally and therefore careful characterization of 35SO4 is needed to accurately quantify groundwater travel time. More data is needed to fully assess whether or not this tracer could become a valuable tool for managers.

  8. Viruses as groundwater tracers: using ecohydrology to characterize short travel times in aquifers

    Science.gov (United States)

    Hunt, Randall J.; Borchardt, Mark A.; Bradbury, Kenneth R.

    2014-01-01

    Viruses are attractive tracers of short (travel times in aquifers because they have unique genetic signatures, are detectable in trace quantities, and are mobile in groundwater. Virus “snaphots” result from infection and disappearance in a population over time; therefore, the virus snapshot shed in the fecal wastes of an infected population at a specific point in time can serve as a marker for tracking virus and groundwater movement. The virus tracing approach and an example application are described to illustrate their ability to characterize travel times in high-groundwater velocity settings, and provide insight unavailable from standard hydrogeologic approaches. Although characterization of preferential flowpaths does not usually characterize the majority of other travel times occurring in the groundwater system (e.g., center of plume mass; tail of the breakthrough curve), virus approaches can trace very short times of transport, and thus can fill an important gap in our current hydrogeology toolbox.

  9. Viruses as groundwater tracers: using ecohydrology to characterize short travel times in aquifers.

    Science.gov (United States)

    Hunt, Randall J; Borchardt, Mark A; Bradbury, Kenneth R

    2014-01-01

    Viruses are attractive tracers of short (aquifers because they have unique genetic signatures, are detectable in trace quantities, and are mobile in groundwater. Virus "snaphots" result from infection and disappearance in a population over time; therefore, the virus snapshot shed in the fecal wastes of an infected population at a specific point in time can serve as a marker for tracking virus and groundwater movement. The virus tracing approach and an example application are described to illustrate their ability to characterize travel times in high-groundwater velocity settings, and provide insight unavailable from standard hydrogeologic approaches. Although characterization of preferential flowpaths does not usually characterize the majority of other travel times occurring in the groundwater system (e.g., center of plume mass; tail of the breakthrough curve), virus approaches can trace very short times of transport, and thus can fill an important gap in our current hydrogeology toolbox.

  10. Viruses as groundwater tracers: using ecohydrology to characterize short travel times in aquifers

    Science.gov (United States)

    Viruses are attractive tracers of short (travel times in aquifers because they have unique genetic signatures, are detectable in trace quantities, and are mobile and stable in groundwater. Virus “snaphots” result from infection and disappearance over time as a community develops resistance. T...

  11. Analyzing the effects of geological and parameter uncertainty on prediction of groundwater head and travel time

    DEFF Research Database (Denmark)

    He, X.; Sonneborg, T.O.; Jørgensen, F.

    2013-01-01

    in three scenarios involving simulation of groundwater head distribution and travel time. The first scenario implied 100 stochastic geological models all assigning the same hydraulic parameters for the same geological units. In the second scenario the same 100 geological models were subjected to model...

  12. Analyzing the effects of geological and parameter uncertainty on prediction of groundwater head and travel time

    Directory of Open Access Journals (Sweden)

    X. He

    2013-08-01

    Full Text Available Uncertainty of groundwater model predictions has in the past mostly been related to uncertainty in the hydraulic parameters, whereas uncertainty in the geological structure has not been considered to the same extent. Recent developments in theoretical methods for quantifying geological uncertainty have made it possible to consider this factor in groundwater modeling. In this study we have applied the multiple-point geostatistical method (MPS integrated in the Stanford Geostatistical Modeling Software (SGeMS for exploring the impact of geological uncertainty on groundwater flow patterns for a site in Denmark. Realizations from the geostatistical model were used as input to a groundwater model developed from Modular three-dimensional finite-difference ground-water model (MODFLOW within the Groundwater Modeling System (GMS modeling environment. The uncertainty analysis was carried out in three scenarios involving simulation of groundwater head distribution and travel time. The first scenario implied 100 stochastic geological models all assigning the same hydraulic parameters for the same geological units. In the second scenario the same 100 geological models were subjected to model optimization, where the hydraulic parameters for each of them were estimated by calibration against observations of hydraulic head and stream discharge. In the third scenario each geological model was run with 216 randomized sets of parameters. The analysis documented that the uncertainty on the conceptual geological model was as significant as the uncertainty related to the embedded hydraulic parameters.

  13. Groundwater vulnerability assessment for the karst aquifer of Tanour and Rasoun spring using EPIK, COP, and travel time methods

    Science.gov (United States)

    Hamdan, Ibraheem; Sauter, Martin; Margane, Armin; Ptak, Thomas; Wiegand, Bettina

    2016-04-01

    Key words: Karst, groundwater vulnerability, EPIK, COP, travel time, Jordan. Karst aquifers are especially sensitive to short-lived contaminants because of fast water travel times and a low storage capacity in the conduit system. Tanour and Rasoun karst springs located around 75 km northwest of the city of Amman in Jordan represent the main domestic water supply for the surrounding villages. Both springs suffer from pollution events especially during the winter season, either by microbiological contamination due to wastewater leakage from septic tanks or by wastewater discharge from local olive oil presses. To assess the vulnerability of the karst aquifer of Tanour and Rasoun spring and its sensitivity for pollution, two different intrinsic groundwater vulnerability methods were applied: EPIK and COP. In addition, a travel time vulnerability method was applied to determine the time water travels from different points in the catchment to the streams, as a function of land surface gradients and presumed lateral flow within the epikarst. For the application of the COP and EPIK, a detailed geological survey was carried out to determine karst features and the karst network development within the catchment area. In addition, parameters, such as soil data, long term daily precipitation data, land use and topographical data were collected. For the application of the travel time vulnerability method, flow length, hydraulic conductivity, effective porosity, and slope gradient was used in order to determining the travel time in days. ArcGIS software was used for map preparation. The results of the combined vulnerability methods (COP, EPIK and travel time) show a high percentage of "very high" to "moderate" vulnerable areas within the catchment area of Tanour and Rasoun karst springs. Therefore, protection of the catchment area of Tanour and Rasoun springs from pollution and proper management of land use types is urgently needed to maintain the quality of drinking water in the

  14. Contributing recharge areas, groundwater travel time, and groundwater water quality of the Missouri River alluvial aquifer near the City of Independence, Missouri, well field, 1997-2008

    Science.gov (United States)

    Kelly, Brian P.

    2011-01-01

    The City of Independence, Missouri, operates a well field in the Missouri River alluvial aquifer. Contributing recharge areas (CRA) were last determined for the well field in 1996. Since that time, eight supply wells have been installed in the area north of the Missouri River and well pumpage has changed for the older supply wells. The change in pumping has altered groundwater flow and substantially changed the character of the CRA and groundwater travel times to the supply wells. The U.S Geological Survey, in a cooperative study with the City of Independence, Missouri, simulated steady-state groundwater flow for 2007 well pumpage, average annual river stage, and average annual recharge. Particle-tracking analysis was used to determine the CRA for supply wells and monitoring wells, and the travel time from recharge areas to supply wells, recharge areas to monitoring wells, and monitoring wells to supply wells. The simulated CRA for the well field is elongated in the upstream direction and extends to both sides of the Missouri River. Groundwater flow paths and recharge areas estimated for monitoring wells indicate the origin of water to each monitoring well, the travel time of that water from the recharge area, the flow path from the vicinity of each monitoring well to a supply well, and the travel time from the monitoring well to the supply well. Monitoring wells 14a and 14b have the shortest groundwater travel time from their contributing recharge area of 0.30 years and monitoring well 29a has the longest maximum groundwater travel time from its contributing recharge area of 1,701 years. Monitoring well 22a has the shortest groundwater travel time of 0.5 day to supply well 44 and monitoring well 3b has the longest maximum travel time of 31.91 years to supply well 10. Water-quality samples from the Independence groundwater monitoring well network were collected from 1997 to 2008 by USGS personnel during ongoing annual sampling within the 10-year contributing

  15. Evaluation of Groundwater Pathways and Travel Times From the Nevada Test Site to the Potential Yucca Mountain Repository

    Science.gov (United States)

    Pohlmann, K. F.; Zhu, J.; Ye, M.; Carroll, R. W.; Chapman, J. B.; Russell, C. E.; Shafer, D. S.

    2006-12-01

    Yucca Mountain (YM), Nevada has been recommended as a deep geological repository for the disposal of spent fuel and high-level radioactive waste. If YM is licensed as a repository by the Nuclear Regulatory Commission, it will be important to identify the potential for radionuclides to migrate from underground nuclear testing areas located on the Nevada Test Site (NTS) to the hydraulically downgradient repository area to ensure that monitoring does not incorrectly attribute repository failure to radionuclides originating from other sources. In this study, we use the Death Valley Regional Flow System (DVRFS) model developed by the U.S. Geological Survey to investigate potential groundwater migration pathways and associated travel times from the NTS to the proposed YM repository area. Using results from the calibrated DVRFS model and the particle tracking post-processing package MODPATH we modeled three-dimensional groundwater advective pathways in the NTS and YM region. Our study focuses on evaluating the potential for groundwater pathways between the NTS and YM withdrawal area and whether travel times for advective flow along these pathways coincide with the prospective monitoring time frame at the proposed repository. We include uncertainty in effective porosity as this is a critical variable in the determination of time for radionuclides to travel from the NTS region to the YM withdrawal area. Uncertainty in porosity is quantified through evaluation of existing site data and expert judgment and is incorporated in the model through Monte Carlo simulation. Since porosity information is limited for this region, the uncertainty is quite large and this is reflected in the results as a large range in simulated groundwater travel times.

  16. Time travel?

    CERN Document Server

    Deser, Stanley D; Deser, Stanley; Jackiw, Roman

    1992-01-01

    To travel into the past, to observe it, perhaps to influence it and correct mistakes of one's youth, has been an abiding fantasy of mankind for as long as we have been aware of a past. Here are described some recent scientific investigations on this topic.

  17. Unsaturated-zone fast-path flow calculations for Yucca Mountain groundwater travel time analyses (GWTT-94)

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, B.W.; Altman, S.J. [Sandia National Labs., Albuquerque, NM (United States); Robey, T.H. [Spectra Research Institute, Albuquerque, NM (United States)] [and others

    1995-08-01

    Evaluation of groundwater travel time (GWTT) is required as part of the investigation of the suitability of Yucca Mountain as a potential high-level nuclear-waste repository site. The Nuclear Regulatory Commission`s GWTT regulation is considered to be a measure of the intrinsic ability of the site to contain radionuclide releases from the repository. The work reported here is the first step in a program to provide an estimate of GWTT at the Yucca Mountain site in support of the DOE`s Technical Site Suitability and as a component of a license application. Preliminary estimation of the GWTT distribution in the unsaturated zone was accomplished using a numerical model of the physical processes of groundwater flow in the fractured, porous medium of the bedrock. Based on prior investigations of groundwater flow at the site, fractures are thought to provide the fastest paths for groundwater flow; conditions that lead to flow in fractures were investigated and simulated. Uncertainty in the geologic interpretation of Yucca Mountain was incorporated through the use of geostatistical simulations, while variability of hydrogeologic parameters within each unit was accounted for by the random sampling of parameter probability density functions. The composite-porosity formulation of groundwater flow was employed to simulate flow in both the matrix and fracture domains. In this conceptualization, the occurrence of locally saturated conditions within the unsaturated zone is responsible for the initiation of fast-path flow through fractures. The results of the GWTT-94 study show that heterogeneity in the hydraulic properties of the model domain is an important factor in simulating local regions of high groundwater saturation. Capillary-pressure conditions at the surface boundary influence the extent of the local saturation simulated.

  18. 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

    Science.gov (United States)

    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

  19. Application of hydrogeology and groundwater-age estimates to assess the travel time of groundwater at the site of a landfill to the Mahomet Aquifer, near Clinton, Illinois

    Science.gov (United States)

    Kay, Robert T.; Buszka, Paul M.

    2016-03-02

    The U.S. Geological Survey used interpretations of hydrogeologic conditions and tritium-based groundwater age estimates to assess the travel time of groundwater at a landfill site near Clinton, Illinois (the “Clinton site”) where a chemical waste unit (CWU) was proposed to be within the Clinton landfill unit #3 (CLU#3). Glacial deposits beneath the CWU consist predominantly of low-permeability silt- and clay-rich till interspersed with thin (typically less than 2 feet in thickness) layers of more permeable deposits, including the Upper and Lower Radnor Till Sands and the Organic Soil unit. These glacial deposits are about 170 feet thick and overlie the Mahomet Sand Member of the Banner Formation. The Mahomet aquifer is composed of the Mahomet Sand Member and is used for water supply in much of east-central Illinois.Eight tritium analyses of water from seven wells were used to evaluate the overall age of recharge to aquifers beneath the Clinton site. Groundwater samples were collected from six monitoring wells on or adjacent to the CLU#3 that were open to glacial deposits above the Mahomet aquifer (the upper and lower parts of the Radnor Till Member and the Organic Soil unit) and one proximal production well (approximately 0.5 miles from the CLU#3) that is screened in the Mahomet aquifer. The tritium-based age estimates were computed with a simplifying, piston-flow assumption: that groundwater moves in discrete packets to the sampled interval by advection, without hydrodynamic dispersion or mixing.Tritium concentrations indicate a recharge age of at least 59 years (pre-1953 recharge) for water sampled from deposits below the upper part of the Radnor Till Member at the CLU#3, with older water expected at progressively greater depth in the tills. The largest tritium concentration from a well sampled by this study (well G53S; 0.32 ± 0.10 tritium units) was in groundwater from a sand deposit in the upper part of the Radnor Till Member; the shallowest permeable unit

  20. Increased reliability of mean travel time predictions of river-groundwater exchange fluxes using optimal design techniques

    Science.gov (United States)

    Wöhling, Thomas; Gosses, Moritz; Osenbrück, Karsten

    2014-05-01

    In this study, we follow up on previous work at the Steinlach test site (Osenbrück et al, 2013) near Tübingen, Germany, to investigate hyporheic exchange fluxes in a shallow riparian aquifer. A steady-state MODFLOW model has been developed for the site and calibrated using an existing network of 14 observation wells. Due to a relatively steep hydraulic gradient (0.012 m/m) between the upstream and downstream flow stages of the river bend, water infiltrates from the river into the shallow aquifer along the upstream section of the river and is forced to re-enter the river at the downstream end. The passage through the aquifer potentially allows for mitigation and transformation of river water-bound pollutants. One important factor to estimate attenuation potentials are travel (and exposure) times through (parts of) the aquifer. In our approach we used forward particle tracking (MODPATH) and a flux-weighting scheme to estimate travel time distributions for the river-groundwater exchange fluxes in the study domain. Travel times vary significantly within the domain, however, estimates of mean travel times derived from deconvolution of EC and δ18O-H2O data at selected wells exhibit a consistent pattern with modelled travel times. The flux-weighted mean travel time of all river water that passed the riparian aquifer was calculated to 26.1 days. The uncertainty of the flux-weighted mean travel time was calculated using the prediction error variance approach by Moore and Doherty (2005) which resulted in a post-calibration uncertainty of ±93.5 d (1σ), i.e. about 350% of the actual prediction. We further analysed the worth of potential new observations to reduce the large uncertainty of this model prediction. In our optimization framework, we extend the method by Moore and Doherty (2005) to simultaneously optimize multiple observations using a modified Genetic Algorithm (GA) that can also sample from past states for higher efficiency. The observations considered are

  1. Determination of groundwater travel time in a karst aquifer by stable water isotopes, Tanour and Rasoun spring (Jordan)

    Science.gov (United States)

    Hamdan, Ibraheem; Wiegand, Bettina; Sauter, Martin; Ptak, Thomas

    2016-04-01

    Key words: karst aquifers, stable isotopes, water travel time, Jordan. Tanour and Rasoun karst springs are located about 75 kilometers northwest of the city of Amman in Jordan. The aquifer is composed of Upper Cretaceous limestone that exhibits a moderate to high degree of karstification. The two springs represent the main drinking water resources for the surrounding villages. The yearly water production is about 1,135,000 m3/yr for Tanour spring and 125,350 m3/yr for Rasoun spring (MWI 2015). Due to contamination from microbiological pollution (leakage of wastewater from septic tanks) or infiltration of wastewater from local olive presses, drinking water supply from the two springs is frequently interrupted. From November 2014 through March 2015, spring water samples were collected from Tanour and Rasoun spring for the analysis of stable hydrogen and oxygen isotopes to investigate spring response to precipitation and snowmelt events. Both Tanour and Rasoun spring show a fast response to precipitation and snowmelt events, implying short water travel times. Based on the variation of δ 18O and δ 2H in spring discharge, the average maximum water travel time is in the order of 8 days for Tanour spring and 6 days for Rasoun spring. Due to fast water travel times, Tanour and Rasoun spring can be considered as highly vulnerable to pollutants. δ 18O and δ 2H values of Tanour and Rasoun springs parallel other monitored parameter like water temperature, turbidity, electrical conductivity and spring discharge. In addition, a high turbidity peak was monitored in Tanour spring during a pollution event from olive mills wastewater (Hamdan et al., 2016; Hamdan, in prep.). The fast response in both Tanour and Rasoun springs to precipitation events requires monitoring potential sources of pollution within the catchment area. References: MWI (Ministry of Water and Irrigation) (2015) Monthly Production values for Tanour and Rasoun Springs for the time period between 1996 and 2014

  2. Application of hydrogeology and groundwater-age estimates to assess the travel time of groundwater at the site of a landfill to the Mahomet Aquifer, near Clinton, Illinois

    Science.gov (United States)

    Kay, Robert T.; Buszka, Paul M.

    2016-03-02

    The U.S. Geological Survey used interpretations of hydrogeologic conditions and tritium-based groundwater age estimates to assess the travel time of groundwater at a landfill site near Clinton, Illinois (the “Clinton site”) where a chemical waste unit (CWU) was proposed to be within the Clinton landfill unit #3 (CLU#3). Glacial deposits beneath the CWU consist predominantly of low-permeability silt- and clay-rich till interspersed with thin (typically less than 2 feet in thickness) layers of more permeable deposits, including the Upper and Lower Radnor Till Sands and the Organic Soil unit. These glacial deposits are about 170 feet thick and overlie the Mahomet Sand Member of the Banner Formation. The Mahomet aquifer is composed of the Mahomet Sand Member and is used for water supply in much of east-central Illinois.Eight tritium analyses of water from seven wells were used to evaluate the overall age of recharge to aquifers beneath the Clinton site. Groundwater samples were collected from six monitoring wells on or adjacent to the CLU#3 that were open to glacial deposits above the Mahomet aquifer (the upper and lower parts of the Radnor Till Member and the Organic Soil unit) and one proximal production well (approximately 0.5 miles from the CLU#3) that is screened in the Mahomet aquifer. The tritium-based age estimates were computed with a simplifying, piston-flow assumption: that groundwater moves in discrete packets to the sampled interval by advection, without hydrodynamic dispersion or mixing.Tritium concentrations indicate a recharge age of at least 59 years (pre-1953 recharge) for water sampled from deposits below the upper part of the Radnor Till Member at the CLU#3, with older water expected at progressively greater depth in the tills. The largest tritium concentration from a well sampled by this study (well G53S; 0.32 ± 0.10 tritium units) was in groundwater from a sand deposit in the upper part of the Radnor Till Member; the shallowest permeable unit

  3. Modelling urban travel times

    NARCIS (Netherlands)

    Zheng, F.

    2011-01-01

    Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain tr

  4. Modelling urban travel times

    NARCIS (Netherlands)

    Zheng, F.

    2011-01-01

    Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain

  5. Modelling urban travel times

    NARCIS (Netherlands)

    Zheng, F.

    2011-01-01

    Urban travel times are intrinsically uncertain due to a lot of stochastic characteristics of traffic, especially at signalized intersections. A single travel time does not have much meaning and is not informative to drivers or traffic managers. The range of travel times is large such that certain tr

  6. Pre-waste-emplacement ground-water travel time sensitivity and uncertainty analyses for Yucca Mountain, Nevada; Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, P.G.

    1993-01-01

    Yucca Mountain, Nevada is a potential site for a high-level radioactive-waste repository. Uncertainty and sensitivity analyses were performed to estimate critical factors in the performance of the site with respect to a criterion in terms of pre-waste-emplacement ground-water travel time. The degree of failure in the analytical model to meet the criterion is sensitive to the estimate of fracture porosity in the upper welded unit of the problem domain. Fracture porosity is derived from a number of more fundamental measurements including fracture frequency, fracture orientation, and the moisture-retention characteristic inferred for the fracture domain.

  7. Time a traveler's guide

    CERN Document Server

    Pickover, Clifford A

    1998-01-01

    ""Bucky Fuller thought big,"" Wired magazine recently noted, ""Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both."" In his newest book, Cliff Pickover outdoes even himself, probing a mystery that has baffled mystics, philosophers, and scientists throughout history--What is the nature of time? In Time: A Traveler's Guide, Pickover takes readers to the forefront of science as he illuminates the most mysterious phenomenon in the universe--time itself. Is time travel possible? Is time real? Does it flow in one direction only? Does it have a beginning and an end? What is eternity? P

  8. Travel time and travel cost in European air travel

    OpenAIRE

    Dusek, Tamas

    2012-01-01

    The aim of the study is to examine two issues of consumer air travel accessibility in Europe, namely flight time and ticket costs. The first part of the paper discusses the various methodological problems of creating time matrix and cost matrix of air travel. Because of problems of conceptualizing of the air travel network and the modifiable areal unit problem the analysis is conducted on several spatial levels. The smallest network consists of 15 busiest airports and the largest network has ...

  9. Time - A Traveler's Guide

    Science.gov (United States)

    Pickover, Clifford A.

    1999-09-01

    "Bucky Fuller thought big," Wired magazine recently noted, "Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." In his newest book, Cliff Pickover outdoes even himself, probing a mystery that has baffled mystics, philosophers, and scientists throughout history--What is the nature of time?In Time: A Traveler's Guide , Pickover takes readers to the forefront of science as he illuminates the most mysterious phenomenon in the universe--time itself. Is time travel possible? Is time real? Does it flow in one direction only? Does it have a beginning and an end? What is eternity? Pickover's book offers a stimulating blend of Chopin, philosophy, Einstein, and modern physics, spiced with diverting side-trips to such topics as the history of clocks, the nature of free will, and the reason gold glitters. Numerous diagrams ensure readers will have no trouble following along.By the time we finish this book, we understand a wide variety of scientific concepts pertaining to time. And most important, we will understand that time travel is, indeed, possible.

  10. Time travel a history

    CERN Document Server

    Gleick, James

    2016-01-01

    From the acclaimed author of The Information and Chaos, here is a mind-bending exploration of time travel: its subversive origins, its evolution in literature and science, and its influence on our understanding of time itself. The story begins at the turn of the previous century, with the young H. G. Wells writing and rewriting the fantastic tale that became his first book and an international sensation: The Time Machine. It was an era when a host of forces was converging to transmute the human understanding of time, some philosophical and some technological: the electric telegraph, the steam railroad, the discovery of buried civilizations, and the perfection of clocks. James Gleick tracks the evolution of time travel as an idea that becomes part of contemporary culture—from Marcel Proust to Doctor Who, from Jorge Luis Borges to Woody Allen. He investigates the inevitable looping paradoxes and examines the porous boundary between pulp fiction and modern physics. Finally, he delves into a temporal shift that...

  11. Time, travel and infection.

    Science.gov (United States)

    Cliff, Andrew; Haggett, Peter

    2004-01-01

    The collapse of geographical space over the last 200 years has had profound effects on the circulation of human populations and on the transfer of infectious diseases. Three examples are used to illustrate the process: (a) the impact of the switch from sail to steamships in importing measles into Fiji over a 40-year period; (b) changes in measles epidemic behaviour in Iceland over a 150-year period; and (c) changes in the spread of cholera within the United States over a 35-year period. In each case, the link between time, travel and disease has been an intimate one.

  12. Solar wind travel time

    Science.gov (United States)

    Russell, C. T.

    A useful rule of thumb in solar terrestrial studies is that the solar wind travels 4 Earth radii (RE) per minute. Long-term studies of solar wind velocity [e.g., Luhmann et al., 1993; 1994] show that the median velocity is about 420 km/s, corresponding to 3.96 RE min-1. The quartiles are about 370 km/s and 495 km/s, corresponding to 3.48 Re min-1 and 4.66 Re min-1 respectively. This number helps estimate the delays expected when observing a discontinuity at a solar wind monitor; one example is ISEE-3 when it was at the forward libration point (about 60 min). It is also helpful for estimating how much time passes before the dayside magnetosphere is compressed as denser solar wind flows by (about 2.5 min).

  13. Beijing Time Travel

    Institute of Scientific and Technical Information of China (English)

    ROBERT T.TUOHEY

    2010-01-01

    @@ Dally travel within Beijing need not be anymore troublesome than going about any major metropolis.Simply,certain basic facts need to be kept in mind,and ordinary precautions taken.Essentially,it's the same situation as midtown Manhattan or downtown Tokyo,except everyone's speaking Chinese.

  14. Beijing Time Travel

    Institute of Scientific and Technical Information of China (English)

    ROBERT; T.TUOHEY

    2010-01-01

    Daily travel within Beijing need not be anymore troublesome than going about any major metropolis.Simply,certain basic facts need to be kept in mind,and ordinary precautions taken.Essentially,it’s the same situation as midtown Manhattan or downtown Tokyo,except everyone’s speaking Chinese.

  15. Monitoring Travel Time Reliability on Freeways

    NARCIS (Netherlands)

    Tu, Huizhao

    2008-01-01

    Travel time and travel time reliability are important attributes of a trip. The current measures of reliability have in common that in general they all relate to the variability of travel times. However, travel time reliability does not only rely on variability but also on the stability of travel

  16. Monitoring Travel Time Reliability on Freeways

    NARCIS (Netherlands)

    Tu, Huizhao

    2008-01-01

    Travel time and travel time reliability are important attributes of a trip. The current measures of reliability have in common that in general they all relate to the variability of travel times. However, travel time reliability does not only rely on variability but also on the stability of travel ti

  17. Valuation of Travel Time and TravelIer Information

    NARCIS (Netherlands)

    Rietveld, Piet

    2003-01-01

    The value of travel time plays an important role in cost benefit analysis of infrastructureprojects. However, the issue of uncertainty on travel times and the implications this has forestimations of travel time values has received much less attention in the literature. In thispaper we compare

  18. Valuation of Travel Time and TravelIer Information

    NARCIS (Netherlands)

    Rietveld, Piet

    2003-01-01

    The value of travel time plays an important role in cost benefit analysis of infrastructureprojects. However, the issue of uncertainty on travel times and the implications this has forestimations of travel time values has received much less attention in the literature. In thispaper we compare variou

  19. Paradoxes of time travel

    CERN Document Server

    Krasnikov, S V

    1997-01-01

    Paradoxes that can supposedly occur if a time machine is created are discussed. It is shown that the existence of trajectories of ``multiplicity zero'' (i.e. trajectories that describe a ball hitting its younger self so that the latter cannot fall into the time machine) is not paradoxical by itself. This {\\em apparent paradox} can be resolved (at least sometimes) without any harm to local physics or to the time machine. Also a simple model is adduced for which the absence of {\\em true} paradoxes caused by self-interaction is proved.

  20. Value of travel time savings

    DEFF Research Database (Denmark)

    Le Masurier, P.; Polak, J.; Pawlak, Janet

    2015-01-01

    A team of specialist market researchers and Value of Time experts comprising members from SYSTRA, Imperial College London and the Technical University of Denmark has conducted a formal audit and peer review of research undertaken by Arup/ITS Leeds/Accent to derive Value of Travel Time Savings...... Preference (RP) models that were used to derive final Values of Travel Time (VTT). This report contains the findings of our audit and peer review of the procedures adopted by the research team during data collection of the three surveys (SP, RP and Employers Surveys); a peer review of the reported approach...

  1. Time Travel in the Library

    Science.gov (United States)

    Brown, Donna W.

    2005-01-01

    A Time Travel project in the library gives enthusiasm to students to connect with the past and reinforces their research skills while instilling respect for the past years. The librarian should choose one specific decade to highlight in the library and create an extravaganza that would allow memorabilia from that time period to be located without…

  2. Catchment mixing processes and travel time distributions

    National Research Council Canada - National Science Library

    Botter, Gianluca

    2012-01-01

    ...) of travel, residence and evapotranspiration times, which are comprehensive descriptors of the fate of rainfall water particles traveling through catchments, and provide key information on hydrologic...

  3. The value of travel time variance

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Engelson, Leonid

    2011-01-01

    This paper considers the value of travel time variability under scheduling preferences that are defined in terms of linearly time varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability...... that does not depend on the shape of the travel time distribution. The related measure of travel time variability is the variance of travel time. These conclusions apply equally to travellers who can freely choose departure time and to travellers who use a scheduled service with fixed headway. Depending...... on parameters, travellers may be risk averse or risk seeking and the value of travel time may increase or decrease in the mean travel time....

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

    Science.gov (United States)

    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.

  5. Complex groundwater flow systems as traveling agent models

    CERN Document Server

    López-Corona, Oliver; Escolero, Oscar; González, Tomás; Morales-Casique, Eric

    2014-01-01

    Analyzing field data from pumping tests, we show that as with many other natural phenomena, groundwater flow exhibits a complex dynamics described by 1/f power spectrum. This result is theoretically studied within an agent perspective. Using a traveling agent model, we prove that this statistical behavior emerges when the medium is complex. Some heuristic reasoning is provided to justify both spatial and dynamic complexity, as the result of the superposition of an infinite number of stochastic processes. Even more, we show that this implies that non-Kolmogorovian probability is needed for its study, and provide a set of new partial differential equations for groundwater flow.

  6. The value of travel time variance

    OpenAIRE

    Fosgerau, Mogens; Engelson, Leonid

    2010-01-01

    This paper considers the value of travel time variability under scheduling preferences that are de�fined in terms of linearly time-varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability that does not depend on the shape of the travel time distribution. The related measure of travel time variability is the variance of travel time. These conclusions apply equally to travellers who can free...

  7. 5 CFR 630.207 - Travel time.

    Science.gov (United States)

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Travel time. 630.207 Section 630.207 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS ABSENCE AND LEAVE Definitions and General Provisions for Annual and Sick Leave § 630.207 Travel time. The travel time granted an...

  8. Coronal Mass Ejections travel time

    Science.gov (United States)

    Braga, Carlos Roberto; Souza de Mendonça, Rafael Rodrigues; Dal Lago, Alisson; Echer, Ezequiel

    2017-10-01

    Coronal mass ejections (CMEs) are the main source of intense geomagnetic storms when they are earthward directed. Studying their travel time is a key-point to understand when the disturbance will be observed at Earth. In this work, we study the CME that originated the interplanetary disturbance observed on 2013/10/02. According to the observations, the CME that caused the interplanetary disturbance was ejected on 2013/09/29. We obtained the CME speed and estimate of the time of arrival at the Lagrangian Point L1 using the concept of expansion speed. We found that observed and estimated times of arrival of the shock differ between 2 and 23 hours depending on method used to estimate the radial speed.

  9. Additive measures of travel time variability

    DEFF Research Database (Denmark)

    Engelson, Leonid; Fosgerau, Mogens

    2011-01-01

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

  10. Network structure and travel time perception.

    Science.gov (United States)

    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.

  11. Accurate estimation of indoor travel times

    DEFF Research Database (Denmark)

    Prentow, Thor Siiger; Blunck, Henrik; Stisen, Allan

    2014-01-01

    The ability to accurately estimate indoor travel times is crucial for enabling improvements within application areas such as indoor navigation, logistics for mobile workers, and facility management. In this paper, we study the challenges inherent in indoor travel time estimation, and we propose...... the InTraTime method for accurately estimating indoor travel times via mining of historical and real-time indoor position traces. The method learns during operation both travel routes, travel times and their respective likelihood---both for routes traveled as well as for sub-routes thereof. InTraTime...... allows to specify temporal and other query parameters, such as time-of-day, day-of-week or the identity of the traveling individual. As input the method is designed to take generic position traces and is thus interoperable with a variety of indoor positioning systems. The method's advantages include...

  12. The Archaeology of Time travel – An introduction

    OpenAIRE

    Petersson, Bodil; Holtorf, Cornelius

    2010-01-01

    This article introduces the concept of Time Travel as a new way to approach the past in our age. The article deals with the question: What role does the past play for people in our time? The time travel discussion focusses on the following themes: Time travel between materality and virtuality; Time travel on the market of experiences; Designing time travel; Evaluating time travel.

  13. Travel Time Variability and Airport Accessibility

    OpenAIRE

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

    2010-01-01

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

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

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Fukuda, Daisuke

    2012-01-01

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

  15. Nonlinear refraction and reflection travel time tomography

    Science.gov (United States)

    Zhang, Jiahua; ten Brink, U.S.; Toksoz, M.N.

    1998-01-01

    We develop a rapid nonlinear travel time tomography method that simultaneously inverts refraction and reflection travel times on a regular velocity grid. For travel time and ray path calculations, we apply a wave front method employing graph theory. The first-arrival refraction travel times are calculated on the basis of cell velocities, and the later refraction and reflection travel times are computed using both cell velocities and given interfaces. We solve a regularized nonlinear inverse problem. A Laplacian operator is applied to regularize the model parameters (cell slownesses and reflector geometry) so that the inverse problem is valid for a continuum. The travel times are also regularized such that we invert travel time curves rather than travel time points. A conjugate gradient method is applied to minimize the nonlinear objective function. After obtaining a solution, we perform nonlinear Monte Carlo inversions for uncertainty analysis and compute the posterior model covariance. In numerical experiments, we demonstrate that combining the first arrival refraction travel times with later reflection travel times can better reconstruct the velocity field as well as the reflector geometry. This combination is particularly important for modeling crustal structures where large velocity variations occur in the upper crust. We apply this approach to model the crustal structure of the California Borderland using ocean bottom seismometer and land data collected during the Los Angeles Region Seismic Experiment along two marine survey lines. Details of our image include a high-velocity zone under the Catalina Ridge, but a smooth gradient zone between. Catalina Ridge and San Clemente Ridge. The Moho depth is about 22 km with lateral variations. Copyright 1998 by the American Geophysical Union.

  16. Ocean acoustic tomography - Travel time biases

    Science.gov (United States)

    Spiesberger, J. L.

    1985-01-01

    The travel times of acoustic rays traced through a climatological sound-speed profile are compared with travel times computed through the same profile containing an eddy field. The accuracy of linearizing the relations between the travel time difference and the sound-speed deviation at long ranges is assessed using calculations made for two different eddy fields measured in the eastern Atlantic. Significant nonlinearities are found in some cases, and the relationships of the values of these nonlinearities to the range between source and receiver, to the anomaly size associated with the eddies, and to the positions of the eddies are studied. An analytical model of the nonlinearities is discussed.

  17. The cost of travel time variability

    DEFF Research Database (Denmark)

    Engelson, Leonid; Fosgerau, Mogens

    2016-01-01

    This paper explores the relationships between three types of measures of the cost of travel time variability: measures based on scheduling preferences and implicit departure time choice, Bernoulli type measures based on a univariate function of travel time, and mean-dispersion measures. We...... result on the utility rates in an additive scheduling measure. These insights are useful for selecting cost measures to use in applications....

  18. Multimodal Network Equilibrium with Stochastic Travel Times

    Directory of Open Access Journals (Sweden)

    M. Meng

    2014-01-01

    Full Text Available The private car, unlike public traffic modes (e.g., subway, trolley running along dedicated track-ways, is invariably subject to various uncertainties resulting in travel time variation. A multimodal network equilibrium model is formulated that explicitly considers stochastic link capacity variability in the road network. The travel time of combined-mode trips is accumulated based on the concept of the mean excess travel time (METT which is a summation of estimated buffer time and tardy time. The problem is characterized by an equivalent VI (variational inequality formulation where the mode choice is expressed in a hierarchical logit structure. Specifically, the supernetwork theory and expansion technique are used herein to represent the multimodal transportation network, which completely represents the combined-mode trips as constituting multiple modes within a trip. The method of successive weighted average is adopted for problem solutions. The model and solution method are further applied to study the trip distribution and METT variations caused by the different levels of the road conditions. Results of numerical examples show that travelers prefer to choose the combined travel mode as road capacity decreases. Travelers with different attitudes towards risk are shown to exhibit significant differences when making travel choice decisions.

  19. Highway travel time estimation with data fusion

    CERN Document Server

    Soriguera Martí, Francesc

    2016-01-01

    This monograph presents a simple, innovative approach for the measurement and short-term prediction of highway travel times based on the fusion of inductive loop detector and toll ticket data. The methodology is generic and not technologically captive, allowing it to be easily generalized for other equivalent types of data. The book shows how Bayesian analysis can be used to obtain fused estimates that are more reliable than the original inputs, overcoming some of the drawbacks of travel-time estimations based on unique data sources. The developed methodology adds value and obtains the maximum (in terms of travel time estimation) from the available data, without recurrent and costly requirements for additional data. The application of the algorithms to empirical testing in the AP-7 toll highway in Barcelona proves that it is possible to develop an accurate real-time, travel-time information system on closed-toll highways with the existing surveillance equipment, suggesting that highway operators might provide...

  20. Regular transport dynamics produce chaotic travel times.

    Science.gov (United States)

    Villalobos, Jorge; Muñoz, Víctor; Rogan, José; Zarama, Roberto; Johnson, Neil F; Toledo, Benjamín; Valdivia, Juan Alejandro

    2014-06-01

    In the hope of making passenger travel times shorter and more reliable, many cities are introducing dedicated bus lanes (e.g., Bogota, London, Miami). Here we show that chaotic travel times are actually a natural consequence of individual bus function, and hence of public transport systems more generally, i.e., chaotic dynamics emerge even when the route is empty and straight, stops and lights are equidistant and regular, and loading times are negligible. More generally, our findings provide a novel example of chaotic dynamics emerging from a single object following Newton's laws of motion in a regularized one-dimensional system.

  1. On the relationship between travel time and travel distance in the Netherlands

    NARCIS (Netherlands)

    Rietveld, P.; Zwart, B.; van Wee, B.; van der Hoorn, A.I.J.M.

    1999-01-01

    This paper gives a detailed empirical analysis of the relationships between different indicators of costs of commuting trips by car: difference as the crow flies, shortest travel time according to route planner, corresponding travel distance, and reported travel time. Reported travel times are

  2. On the relationship between travel time and travel distance in the Netherlands

    NARCIS (Netherlands)

    Rietveld, P.; Zwart, B.; van Wee, B.; van der Hoorn, A.I.J.M.

    1999-01-01

    This paper gives a detailed empirical analysis of the relationships between different indicators of costs of commuting trips by car: difference as the crow flies, shortest travel time according to route planner, corresponding travel distance, and reported travel time. Reported travel times are usual

  3. A constant travel time budget? In search for explanations for an increase in average travel time

    NARCIS (Netherlands)

    Rietveld, P.; Wee, van B.

    2002-01-01

    Recent research suggests that during the past decades the average travel time of the Dutch population has probably increased. However, different datasources show different levels of increase. Possible causes of the increase in average travel time are presented here. Increased incomes have probablyre

  4. A constant travel time budget? In search for explanations for an increase in average travel time

    NARCIS (Netherlands)

    Rietveld, P.; Wee, van B.

    2002-01-01

    Recent research suggests that during the past decades the average travel time of the Dutch population has probably increased. However, different datasources show different levels of increase. Possible causes of the increase in average travel time are presented here. Increased incomes have

  5. A constant travel time budget? In search for explanations for an increase in average travel time

    NARCIS (Netherlands)

    Rietveld, P.; Wee, van B.

    2002-01-01

    Recent research suggests that during the past decades the average travel time of the Dutch population has probably increased. However, different datasources show different levels of increase. Possible causes of the increase in average travel time are presented here. Increased incomes have probablyre

  6. Groundwater dating for understanding nitrogen in groundwater systems - Time lag, fate, and detailed flow path ways

    Science.gov (United States)

    Morgenstern, Uwe; Hadfield, John; Stenger, Roland

    2014-05-01

    Nitrate contamination of groundwater is a problem world-wide. Nitrate from land use activities can leach out of the root zone of the crop into the deeper part of the unsaturated zone and ultimately contaminate the underlying groundwater resources. Nitrate travels with the groundwater and then discharges into surface water causing eutrophication of surface water bodies. To understand the source, fate, and future nitrogen loads to ground and surface water bodies, detailed knowledge of the groundwater flow dynamics is essential. Groundwater sampled at monitoring wells or discharges may not yet be in equilibrium with current land use intensity due to the time lag between leaching out of the root zone and arrival at the sampling location. Anoxic groundwater zones can act as nitrate sinks through microbial denitrification. However, the effect of denitrification on overall nitrate fluxes depends on the fraction of the groundwater flowing through such zones. We will show results from volcanic aquifers in the central North Island of New Zealand where age tracers clearly indicate that the groundwater discharges into large sensitive lakes like Lake Taupo and Lake Rotorua are not yet fully realising current land use intensity. The majority of the water discharging into these lakes is decades and up to over hundred years old. Therefore, increases in dairy farming over the last decades are not yet reflected in these old water discharges, but over time these increased nitrate inputs will eventually work their way through the large groundwater systems and increasing N loads to the lakes are to be expected. Anoxic zones are present in some of these aquifers, indicating some denitrification potential, however, age tracer results from nested piezo wells show young groundwater in oxic zones indicating active flow in these zones, while anoxic zones tend to have older water indicating poorer hydraulic conductivity in these zones. Consequently, to evaluate the effect of denitrification

  7. 5 CFR 551.422 - Time spent traveling.

    Science.gov (United States)

    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...

  8. Self-motion perception compresses time experienced in return travel.

    Science.gov (United States)

    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.

  9. Guided Wave Travel Time Tomography for Bends

    NARCIS (Netherlands)

    Volker, A.W.F.; Zon, A.T. van

    2012-01-01

    The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography has been developed to map the wall thickness using the travel times of guided waves. The method

  10. Guided wave travel time tomography for bends

    NARCIS (Netherlands)

    Volker, A.W.F.; Bloom, J.G.P.

    2010-01-01

    The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography has been developed to map the wall thickness using the travel times of guided waves. The method

  11. Using travel times to simulate multi-dimensional bioreactive transport in time-periodic flows.

    Science.gov (United States)

    Sanz-Prat, Alicia; Lu, Chuanhe; Finkel, Michael; Cirpka, Olaf A

    2016-04-01

    In travel-time models, the spatially explicit description of reactive transport is replaced by associating reactive-species concentrations with the travel time or groundwater age at all locations. These models have been shown adequate for reactive transport in river-bank filtration under steady-state flow conditions. Dynamic hydrological conditions, however, can lead to fluctuations of infiltration velocities, putting the validity of travel-time models into question. In transient flow, the local travel-time distributions change with time. We show that a modified version of travel-time based reactive transport models is valid if only the magnitude of the velocity fluctuates, whereas its spatial orientation remains constant. We simulate nonlinear, one-dimensional, bioreactive transport involving oxygen, nitrate, dissolved organic carbon, aerobic and denitrifying bacteria, considering periodic fluctuations of velocity. These fluctuations make the bioreactive system pulsate: The aerobic zone decreases at times of low velocity and increases at those of high velocity. For the case of diurnal fluctuations, the biomass concentrations cannot follow the hydrological fluctuations and a transition zone containing both aerobic and obligatory denitrifying bacteria is established, whereas a clear separation of the two types of bacteria prevails in the case of seasonal velocity fluctuations. We map the 1-D results to a heterogeneous, two-dimensional domain by means of the mean groundwater age for steady-state flow in both domains. The mapped results are compared to simulation results of spatially explicit, two-dimensional, advective-dispersive-bioreactive transport subject to the same relative fluctuations of velocity as in the one-dimensional model. The agreement between the mapped 1-D and the explicit 2-D results is excellent. We conclude that travel-time models of nonlinear bioreactive transport are adequate in systems of time-periodic flow if the flow direction does not change

  12. Empirical Study of Travel Time Estimation and Reliability

    OpenAIRE

    Ruimin Li; Huajun Chai; Jin Tang

    2013-01-01

    This paper explores the travel time distribution of different types of urban roads, the link and path average travel time, and variance estimation methods by analyzing the large-scale travel time dataset detected from automatic number plate readers installed throughout Beijing. The results show that the best-fitting travel time distribution for different road links in 15 min time intervals differs for different traffic congestion levels. The average travel time for all links on all days can b...

  13. Demonstrating trend reversal of groundwater quality in relation to time of recharge determined by 3H/3He

    NARCIS (Netherlands)

    Visser, A.; Broers, H.P.; Grift, B. van der; Bierkens, M.F.P.

    2007-01-01

    Recent EU legislation is directed to reverse the upward trends in the concentrations of agricultural pollutants in groundwater. However, uncertainty of the groundwater travel time towards the screens of the groundwater quality monitoring networks complicates the demonstration of trend reversal. We i

  14. Demonstrating trend reversal of groundwater quality in relation to time of recharge determined by 3H/3He

    NARCIS (Netherlands)

    Visser, A.; Broers, H.P.; Grift, B. van der; Bierkens, M.F.P.

    2007-01-01

    Recent EU legislation is directed to reverse the upward trends in the concentrations of agricultural pollutants in groundwater. However, uncertainty of the groundwater travel time towards the screens of the groundwater quality monitoring networks complicates the demonstration of trend reversal. We

  15. Travel Time Estimation Using Floating Car Data

    CERN Document Server

    Sevlian, Raffi

    2010-01-01

    This report explores the use of machine learning techniques to accurately predict travel times in city streets and highways using floating car data (location information of user vehicles on a road network). The aim of this report is twofold, first we present a general architecture of solving this problem, then present and evaluate few techniques on real floating car data gathered over a month on a 5 Km highway in New Delhi.

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

    Science.gov (United States)

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

    2017-08-05

    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.

  17. Contact frequency, travel time, and travel costs for patients with rheumatoid arthritis

    DEFF Research Database (Denmark)

    Sørensen, Jan; Linde, Louise; Hetland, Merete Lund

    2014-01-01

    across Denmark recruited patients to the study. Data collected included frequency, travel time and travel costs for contacts at rheumatology outpatient clinics, other outpatient clinics, general practitioners, privately practicing medical specialists, inpatient hospitals and accident and emergency...

  18. 5 CFR 550.1404 - Creditable travel time.

    Science.gov (United States)

    2010-01-01

    ... the net savings to the Government from reduced lodging costs, considering the value of lost labor time... 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...

  19. An inversion strategy for hydraulic tomography: Coupling travel time and amplitude inversion

    Science.gov (United States)

    Brauchler, R.; Cheng, J.-T.; Dietrich, P.; Everett, M.; Johnson, B.; Liedl, R.; Sauter, M.

    2007-10-01

    SummaryWe present a hydraulic tomographic inversion strategy with an emphasis on the reduction of ambiguity of hydraulic travel time inversion results and the separation of the estimated diffusivity values into hydraulic conductivity and specific storage. Our tomographic inversion strategy is tested by simulated multilevel interference slug tests in which the positions of the sources (injection ports) and the receivers (observation ports) isolated with packers are varied. Simulations include the delaying effect of wellbore storage on travel times which are quantified and shown to be of increasing importance for shorter travel distances. For the reduction of ambiguity of travel time inversion, we use the full travel time data set, as well as smaller data subsets of specified source-receiver angles. The inversion results of data subsets show different resolution characteristics and improve the reliability of the interpretation. The travel time of a pressure pulse is a function of the diffusivity of the medium between the source and receiver. Thus, it is difficult to directly derive values for hydraulic conductivity and specific storage by inverting travel times. In order to overcome this limitation, we exploit the great computational efficiency of hydraulic travel time tomography to define the aquifer structure, which is then input into the underlying groundwater flow model MODFLOW-96. Finally, we perform a model calibration (amplitude inversion) using the automatic parameter estimator PEST, enabling us to separate diffusivity into its two components hydraulic conductivity and specific storage.

  20. Relative Travel Time Tomography for East Asia

    Science.gov (United States)

    Chang, S. J.; CHO, S.

    2016-12-01

    Japan island region is one of the most seismically active region in the world. As a large number of earthquakes have recently occurred along circum-Pacific belt called the ring of fire, concern over earthquakes is increasing in South Korea close to Japan. In this study, we perform seismic imaging based on relative S-wave travel-times to examine S-wave velocity upper mantle structure of East Asia. We used teleseismic events recorded at the Korea Institute of Geoscience and Mineral Resources (KIGAM) network and F-net network operated by the National Research Institute for Earth Science and Disaster Prevention (NIED). Relative travel-time residuals were obtained by a multi-channel cross-correlation method designed to automatically determine accurate relative phase arrival times. The resulting images show high-velocity anomalies along East and South side of Japan island region. These anomalies may indicate subducting Pacific and Philippine Sea plates, respectively. The velocity structure beneath southwest Japan is revealed very complex because the two slabs interact with each other there. Velocity structure of East Asia is useful to understand the tectonic evolution and the mechanism of earthquakes that occur in this region.

  1. Image Fusion for Travel Time Tomography Inversion

    Directory of Open Access Journals (Sweden)

    Liu Linan

    2015-09-01

    Full Text Available The travel time tomography technology had achieved wide application, the hinge of tomography was inversion algorithm, the ray path tracing technology had a great impact on the inversion results. In order to improve the SNR of inversion image, comprehensive utilization of inversion results with different ray tracing can be used. We presented an imaging fusion method based on improved Wilkinson iteration method. Firstly, the shortest path method and the linear travel time interpolation were used for forward calculation; then combined the improved Wilkinson iteration method with super relaxation precondition method to reduce the condition number of matrix and accelerate iterative speed, the precise integration method was used to solve the inverse matrix more precisely in tomography inversion process; finally, use wavelet transform for image fusion, obtain the final image. Therefore, the ill-conditioned linear equations were changed into iterative normal system through two times of treatment and using images with different forward algorithms for image fusion, it reduced the influence effect of measurement error on imaging. Simulation results showed that, this method can eliminate the artifacts in images effectively, it had extensive practical significance.

  2. Travel-time-based thermal tracer tomography

    Science.gov (United States)

    Somogyvári, Márk; Bayer, Peter; Brauchler, Ralf

    2016-05-01

    Active thermal tracer testing is a technique to get information about the flow and transport properties of an aquifer. In this paper we propose an innovative methodology using active thermal tracers in a tomographic setup to reconstruct cross-well hydraulic conductivity profiles. This is facilitated by assuming that the propagation of the injected thermal tracer is mainly controlled by advection. To reduce the effects of density and viscosity changes and thermal diffusion, early-time diagnostics are used and specific travel times of the tracer breakthrough curves are extracted. These travel times are inverted with an eikonal solver using the staggered grid method to reduce constraints from the pre-defined grid geometry and to improve the resolution. Finally, non-reliable pixels are removed from the derived hydraulic conductivity tomograms. The method is applied to successfully reconstruct cross-well profiles as well as a 3-D block of a high-resolution fluvio-aeolian aquifer analog data set. Sensitivity analysis reveals a negligible role of the injection temperature, but more attention has to be drawn to other technical parameters such as the injection rate. This is investigated in more detail through model-based testing using diverse hydraulic and thermal conditions in order to delineate the feasible range of applications for the new tomographic approach.

  3. Macroscopic travel time reliability diagrams for freeway networks

    NARCIS (Netherlands)

    Tu, H.; Li, H.; Van Lint, J.W.C.; Knoop, V.L.; Sun, L.

    2013-01-01

    Travel time reliability is considered to be one of the key indicators of transport system performance. Knowledge of the mechanisms of travel time unreliability enables the derivation of explanatory models with which travel time reliability can be predicted and utilized in traffic management.

  4. Travel-Time Maps: Linear Cartograms with Fixed Vertex Locations

    NARCIS (Netherlands)

    Buchin, Kevin; Goethem, Arthur van; Hoffmann, Michael; van Kreveld, Marc; Speckmann, Bettina; Michael, P.

    2014-01-01

    Linear cartograms visualize travel times between locations, usually by deforming the underlying map such that Euclidean distance corresponds to travel time. We introduce an alternative model, where the map and the locations remain fixed, but edges are drawn as sinusoid curves. Now the travel time ov

  5. Macroscopic travel time reliability diagrams for freeway networks

    NARCIS (Netherlands)

    Tu, H.; Li, H.; Van Lint, J.W.C.; Knoop, V.L.; Sun, L.

    2013-01-01

    Travel time reliability is considered to be one of the key indicators of transport system performance. Knowledge of the mechanisms of travel time unreliability enables the derivation of explanatory models with which travel time reliability can be predicted and utilized in traffic management. Inspire

  6. 5 CFR 610.123 - Travel on official time.

    Science.gov (United States)

    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...

  7. Predicting travel time variability for cost-benefit analysis

    NARCIS (Netherlands)

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

    2010-01-01

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

  8. Predicting travel time variability for cost-benefit analysis

    NARCIS (Netherlands)

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

    2010-01-01

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

  9. A hybrid travel time prediction framework for planned motorway roadworks

    NARCIS (Netherlands)

    Calvert, S.C.; Lint, J.W.C. van; Hoogendoorn, S.P.

    2010-01-01

    In this paper we propose a hybrid motorway travel time prediction framework aimed at providing pre-trip travel information in case of roadworks. The framework utilises a first order macroscopic traffic flow model to predict the consequences in travel time of changes in both traffic demand and roadwa

  10. Prediction of travel time variability for cost-benefit analysis

    NARCIS (Netherlands)

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

    2012-01-01

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

  11. Validation of travel times to hospital estimated by GIS

    Directory of Open Access Journals (Sweden)

    Sauerzapf Violet

    2006-09-01

    Full Text Available Abstract Background 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. Methods 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. Results 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. Conclusion 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.

  12. Children's mental time travel during mind wandering.

    Science.gov (United States)

    Ye, Qun; Song, Xiaolan; Zhang, Yi; Wang, Qinqin

    2014-01-01

    The prospective bias is a salient feature of mind wandering in healthy adults, yet little is known about the temporal focus of children's mind wandering. In the present study, (I) we developed the temporal focus of mind wandering questionnaire for school-age children (TFMWQ-C), a 12-item scale with good test-retest reliability and construct validity. (II) The criterion validity was tested by thought sampling in both choice reaction time task and working memory task. A positive correlation was found between the temporal focus measured by the questionnaire and the one adopted during task-unrelated thoughts (TUTs) by thought sampling probes, especially in the trait level of future-oriented mind wandering. At the same time, children who experienced more TUTs tended to show worse behavioral performance during tasks. (III) The children in both tasks experienced more future-oriented TUTs than past-oriented ones, which was congruent with the results observed in adults; however, in contrast with previous research on adults, the prospective bias was not influenced by task demands. Together these results indicate that the prospective bias of mind wandering has emerged since the school-age (9∼13 years old), and that the relationship between mental time travel (MTT) during mind wandering and the use of cognitive resources differs between children and adults. Our study provides new insights into how this interesting feature of mind wandering may adaptively contribute to the development of children's MTT.

  13. Searching the Internet for evidence of time travelers

    CERN Document Server

    Nemiroff, Robert J

    2013-01-01

    Time travel has captured the public imagination for much of the past century, but little has been done to actually search for time travelers. Here, three implementations of Internet searches for time travelers are described, all seeking a prescient mention of information not previously available. The first search covered prescient content placed on the Internet, highlighted by a comprehensive search for specific terms in tweets on Twitter. The second search examined prescient inquiries submitted to a search engine, highlighted by a comprehensive search for specific search terms submitted to a popular astronomy web site. The third search involved a request for a direct Internet communication, either by email or tweet, pre-dating to the time of the inquiry. Given practical verifiability concerns, only time travelers from the future were investigated. No time travelers were discovered. Although these negative results do not disprove time travel, given the great reach of the Internet, this search is perhaps the m...

  14. A REVIEW ON TRAVEL TIME RELIAB ILITY OF ROAD TRANSPORTATION

    Science.gov (United States)

    Nakayama, Sho-Ichiro

    These days, providing reliable road transportation services is required. The reliability of road transportation can be classified into connectivity reliability, travel time reliability and safety/comfort reliability according to required functions. The trav el time reliability is concerned in this study. The variability of traffic flow and travel time is review ed, and travel time reliability indices proposed in previous studies and their properties are organized. Trav el behavior models with travel time reliability are classified, and the value of travel time reliability is examined based on the estimation results of the models. Then, a method for travel time reliability benefit is proposed. This would be helpful for cost-benefit analysis with reliability or road tr affic management which increases the reliability.

  15. Time Travel: Separating Science Fact from Science Fiction.

    Science.gov (United States)

    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)

  16. Phase Behavior and Implications for Travel time Observables (PHASE 2)

    Science.gov (United States)

    2015-09-30

    Phase behavior and implications for travel - time observables (PHASE-2) Emmanuel Skarsoulis Foundation for Research and Technology Hellas...perturbation behavior of travel time observables due to sound-speed perturbations. OBJECTIVES The objective is to study the behavior of the wave-theoretic...for this work came from the results of previous studies, supported by ONR, suggesting that the perturbation behavior of different travel - time

  17. Online Learning Solutions for Freeway Travel Time Prediction

    NARCIS (Netherlands)

    Van Lint, J.W.C.

    2008-01-01

    Providing travel time information to travelers on available route alternatives in traffic networks is widely believed to yield positive effects on individual drive behavior and (route/departure time) choice behavior, as well as on collective traffic operations in terms of, for example, overall time

  18. Online Learning Solutions for Freeway Travel Time Prediction

    NARCIS (Netherlands)

    Van Lint, J.W.C.

    2008-01-01

    Providing travel time information to travelers on available route alternatives in traffic networks is widely believed to yield positive effects on individual drive behavior and (route/departure time) choice behavior, as well as on collective traffic operations in terms of, for example, overall time

  19. Contaminant Travel Times From the Nevada Test Site to Yucca Mountain: Sensitivity to Porosity

    Science.gov (United States)

    Pohlmann, K. F.; Zhu, J.; Chapman, J. B.; Russell, C. E.; Carroll, R. W.; Shafer, D. S.

    2008-12-01

    Yucca Mountain (YM), Nevada, has been proposed by the U.S. Department of Energy as a geologic repository for spent nuclear fuel and high-level radioactive waste. In this study, we investigate the potential for groundwater advective pathways from underground nuclear testing areas on the Nevada Test Site (NTS) to the YM area by estimating the time frame for advective travel and its uncertainty resulting from porosity value uncertainty for hydrogeologic units (HGUs) in the region. We perform sensitivity analysis to determine the most influential HGUs on advective radionuclide travel times from the NTS to the YM area. Groundwater pathways and advective travel times are obtained using the particle tracking package MODPATH and flow results from the Death Valley Regional Flow System (DVRFS) model by the U.S. Geological Survey. Values and uncertainties of HGU porosities are quantified through evaluation of existing site porosity data and expert professional judgment and are incorporated through Monte Carlo simulations to estimate mean travel times and uncertainties. We base our simulations on two steady state flow scenarios for the purpose of long term prediction and monitoring. The first represents pre-pumping conditions prior to groundwater development in the area in 1912 (the initial stress period of the DVRFS model). The second simulates 1998 pumping (assuming steady state conditions resulting from pumping in the last stress period of the DVRFS model). Considering underground tests in a clustered region around Pahute Mesa on the NTS as initial particle positions, we track these particles forward using MODPATH to identify hydraulically downgradient groundwater discharge zones and to determine which flowpaths will intercept the YM area. Out of the 71 tests in the saturated zone, flowpaths of 23 intercept the YM area under the pre-pumping scenario. For the 1998 pumping scenario, flowpaths from 55 of the 71 tests intercept the YM area. The results illustrate that mean

  20. The Role of Perspective in Mental Time Travel.

    Science.gov (United States)

    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.

  1. Critical capacity, travel time delays and travel time distribution of rapid mass transit systems

    Science.gov (United States)

    Legara, Erika Fille; Monterola, Christopher; Lee, Kee Khoon; Hung, Gih Guang

    2014-07-01

    We set up a mechanistic agent-based model of a rapid mass transit system. Using empirical data from Singapore's unidentifiable smart fare card, we validate our model by reconstructing actual travel demand and duration of travel statistics. We subsequently use this model to investigate two phenomena that are known to significantly affect the dynamics within the RTS: (1) overloading in trains and (2) overcrowding in the RTS platform. We demonstrate that by varying the loading capacity of trains, a tipping point emerges at which an exponential increase in the duration of travel time delays is observed. We also probe the impact on the rail system dynamics of three types of passenger growth distribution across stations: (i) Dirac delta, (ii) uniform and (iii) geometric, which is reminiscent of the effect of land use on transport. Under the assumption of a fixed loading capacity, we demonstrate the dependence of a given origin-destination (OD) pair on the flow volume of commuters in station platforms.

  2. ABSTRACT: CONTAMINANT TRAVEL TIMES FROM THE NEVADA TEST SITE TO YUCCA MOUNTAIN: SENSITIVITY TO POROSITY

    Energy Technology Data Exchange (ETDEWEB)

    Karl F. Pohlmann; Jianting Zhu; Jenny B. Chapman; Charles E. Russell; Rosemary W. H. Carroll; David S. Shafer

    2008-09-05

    Yucca Mountain (YM), Nevada, has been proposed by the U.S. Department of Energy as a geologic repository for spent nuclear fuel and high-level radioactive waste. In this study, we investigate the potential for groundwater advective pathways from underground nuclear testing areas on the Nevada Test Site (NTS) to the YM area by estimating the timeframe for advective travel and its uncertainty resulting from porosity value uncertainty for hydrogeologic units (HGUs) in the region. We perform sensitivity analysis to determine the most influential HGUs on advective radionuclide travel times from the NTS to the YM area. Groundwater pathways and advective travel times are obtained using the particle tracking package MODPATH and flow results from the Death Valley Regional Flow System (DVRFS) model by the U.S. Geological Survey. Values and uncertainties of HGU porosities are quantified through evaluation of existing site porosity data and expert professional judgment and are incorporated through Monte Carlo simulations to estimate mean travel times and uncertainties. We base our simulations on two steady state flow scenarios for the purpose of long term prediction and monitoring. The first represents pre-pumping conditions prior to groundwater development in the area in 1912 (the initial stress period of the DVRFS model). The second simulates 1998 pumping (assuming steady state conditions resulting from pumping in the last stress period of the DVRFS model). Considering underground tests in a clustered region around Pahute Mesa on the NTS as initial particle positions, we track these particles forward using MODPATH to identify hydraulically downgradient groundwater discharge zones and to determine which flowpaths will intercept the YM area. Out of the 71 tests in the saturated zone, flowpaths of 23 intercept the YM area under the pre-pumping scenario. For the 1998 pumping scenario, flowpaths from 55 of the 71 tests intercept the YM area. The results illustrate that mean

  3. Backus-Gilbert inversion of travel time data

    Science.gov (United States)

    Johnson, L. E.

    1972-01-01

    Application of the Backus-Gilbert theory for geophysical inverse problems to the seismic body wave travel-time problem is described. In particular, it is shown how to generate earth models that fit travel-time data to within one standard error and having generated such models how to describe their degree of uniqueness. An example is given to illustrate the process.

  4. Mode choice endogeneity in value of travel time estimation

    DEFF Research Database (Denmark)

    Mabit, Stefan Lindhard; Fosgerau, Mogens

    The current way to estimate value of travel time is to use a mode-specific sample and hence to estimate mode-specific value of travel times. This approach raises certain questions concerning how to generalise the values to a population. A problem would be if there is an uncontrolled sample...... selection mechanism. This is the case if there is correlation between mode choice and the value of travel time that is not controlled for by explanatory variables. What could confuse the estimated values is the difficulty to separate mode effects from user effect. An example would be the effect of income...... of travel time we use a stated choice dataset. These data include binary choice within mode for car and bus. The first approach is to use a probit model to model mode choice using instruments and then use this in the estimation of the value of travel time. The second approach is based on the use of a very...

  5. Wandering Tales: Evolutionary origins of mental time travel and language

    Directory of Open Access Journals (Sweden)

    Michael Charles Corballis

    2013-07-01

    Full Text Available 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 nonpresent, 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.

  6. Wandering tales: evolutionary origins of mental time travel and language.

    Science.gov (United States)

    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.

  7. Valuation of travel time savings for intercity travel: The Madrid-Barcelona corridor

    DEFF Research Database (Denmark)

    Roman, Concepcion; Carlos Martin, Juan; Espino, Raquel

    2014-01-01

    We derive values of travel time savings (VOT) for the Madrid-Barcelona corridor, linking the two largest cities in Spain, based on the estimation of discrete choice models among the main public transport services in the corridor: air transport, high speed rail (HSR) and bus. The new HSR alternative...... to provide useful information to quantify users' benefits during the lifespan of a given project. We found, as expected, that HSR and air transport users exhibit substantially higher values for saving travel time than bus travellers. Also as expected, savings of waiting time are more valued than savings...... (which started to operate in February 2008) competes directly with one of the densest airline domestic markets in the world, and its introduction produced substantial improvements in level of service, achieving reductions in travel time of more than 50% over the conventional train. A specifically...

  8. MODPATH particle-tracking analysis of groundwater flow and travel times to the Barnegat Bay-Little Egg Harbor estuary and streams within the Barnegat Bay-Little Egg Harbor watershed, New Jersey

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — A groundwater-flow model that was previously developed by the U. S. Geological Survey of Ocean County, N.J. (https://doi.org/10.3133/sir20165035) was used in an...

  9. Catchment residence and travel time distributions: The master equation

    National Research Council Canada - National Science Library

    Gianluca Botter; Enrico Bertuzzo; Andrea Rinaldo

    2011-01-01

      Travel/residence time pdf's are related objects with different physical meaning A Master Equation for the residence time pdf is derived and solved analytically We develop a mathematical framework...

  10. How travellers’ schedule their trips under uncertain travel times

    DEFF Research Database (Denmark)

    Hjorth, Katrine

    Travel times play an important role when people decide where, when and how much to travel. But travel times are not always predictable from the traveller’s point of view: They may vary from day to day due to demand fluctuations, weather conditions, accidents and other unforeseen events that cause...... road capacity to decrease. We refer to this uncertainty as travel time variability (TTV). TTV is likely to affect how travellers schedule their trips, since it affects their probability of arriving late at their destination. We would like to account for TTV in traffic models and cost-benefit analyses......, but in practice there are limits to the kinds of behaviour that can be accommodated in such applications. For that reason, we are not solely interested in explaining travellers’ behaviour, but also in whether this behaviour can be approximated by behavioural models that are simple enough to be applied in traffic...

  11. A Dynamic Travel Time Estimation Model Based on Connected Vehicles

    Directory of Open Access Journals (Sweden)

    Daxin Tian

    2015-01-01

    Full Text Available With advances in connected vehicle technology, dynamic vehicle route guidance models gradually become indispensable equipment for drivers. Traditional route guidance models are designed to direct a vehicle along the shortest path from the origin to the destination without considering the dynamic traffic information. In this paper a dynamic travel time estimation model is presented which can collect and distribute traffic data based on the connected vehicles. To estimate the real-time travel time more accurately, a road link dynamic dividing algorithm is proposed. The efficiency of the model is confirmed by simulations, and the experiment results prove the effectiveness of the travel time estimation method.

  12. A steady-state saturation model to determine the subsurface travel time (STT in complex hillslopes

    Directory of Open Access Journals (Sweden)

    T. Sabzevari

    2010-06-01

    Full Text Available The travel time of subsurface flow in complex hillslopes (hillslopes with different plan shape and profile curvature is an important parameter in predicting the subsurface flow in catchments. This time depends on the hillslopes geometry (plan shape and profile curvature, soil properties and climate conditions. The saturation capacity of hillslopes affect the travel time of subsurface flow. The saturation capacity, and subsurface travel time of compound hillslopes depend on parameters such as soil depth, porosity, soil hydraulic conductivity, plan shape (convergent, parallel or divergent, hillslope length, profile curvature (concave, straight or convex and recharge rate to the groundwater table. An equation for calculating subsurface travel time for all complex hillslopes was presented. This equation is a function of the saturation zone length (SZL on the surface. Saturation zone length of the complex hillslopes was calculated numerically by using the hillslope-storage kinematic wave equation for subsurface flow, so an analytical equation was presented for calculating the saturation zone length of the straight hillslopes and all plan shapes geometries. Based on our results, the convergent hillslopes become saturated very soon and they showed longer SZL with shorter travel time compared to the parallel and divergent ones. The subsurface average flow rate in convergent hillslopes is much less than the divergent ones in the steady state conditions. Concerning to subsurface travel time, convex hillslopes have more travel time in comparison to straight and concave hillslopes. The convex hillslopes exhibit more average flow rate than concave hillslopes and their saturation capacity is very low. Finally, the effects of recharge rate variations, average bedrock slope and soil depth on saturation zone extension were investigated.

  13. Vehicle Travel Time Predication based on Multiple Kernel Regression

    Directory of Open Access Journals (Sweden)

    Wenjing Xu

    2014-07-01

    Full Text Available With the rapid development of transportation and logistics economy, the vehicle travel time prediction and planning become an important topic in logistics. Travel time prediction, which is indispensible for traffic guidance, has become a key issue for researchers in this field. At present, the prediction of travel time is mainly short term prediction, and the predication methods include artificial neural network, Kaman filter and support vector regression (SVR method etc. However, these algorithms still have some shortcomings, such as highcomputationcomplexity, slow convergence rate etc. This paper exploits the learning ability of multiple kernel learning regression (MKLR in nonlinear prediction processing characteristics, logistics planning based on MKLR for vehicle travel time prediction. The method for Vehicle travel time prediction includes the following steps: (1 preprocessing historical data; (2 selecting appropriate kernel function, training the historical data and performing analysis ;(3 predicting the vehicle travel time based on the trained model. The experimental results show that, through the analysis of using different methods for prediction, the vehicle travel time prediction method proposed in this paper, archives higher accuracy than other methods. It also illustrates the feasibility and effectiveness of the proposed prediction method.

  14. Prisms to travel in time: Investigation of time-space association through prismatic adaptation effect on mental time travel.

    Science.gov (United States)

    Anelli, Filomena; Ciaramelli, Elisa; Arzy, Shahar; Frassinetti, Francesca

    2016-11-01

    Accumulating evidence suggests that humans process time and space in similar veins. Humans represent time along a spatial continuum, and perception of temporal durations can be altered through manipulations of spatial attention by prismatic adaptation (PA). Here, we investigated whether PA-induced manipulations of spatial attention can also influence more conceptual aspects of time, such as humans' ability to travel mentally back and forward in time (mental time travel, MTT). Before and after leftward- and rightward-PA, participants projected themselves in the past, present or future time (i.e., self-projection), and, for each condition, determined whether a series of events were located in the past or the future with respect to that specific self-location in time (i.e., self-reference). The results demonstrated that leftward and rightward shifts of spatial attention facilitated recognition of past and future events, respectively. These findings suggest that spatial attention affects the temporal processing of the human self.

  15. Smart Travel Based on Space-Time Behavior Study

    Institute of Scientific and Technical Information of China (English)

    Chai; Yanwei; Shen; Yue; Ta; Na; Qian; Fang

    2015-01-01

    In view of the significant demands and development trends of urbanization during the 12 th Five-Year Plan period, "smart city" has attracted wide attention as an advanced city development concept in China. Under the circumstance of rapid urbanization, traffic congestion and accessibility defi ciency become major challenges to many Chinese cities, as transportation and travel are closely related to the effi ciency of a city’s operation and the quality of people’s life. As essential part of smart city planning and management, smart travel offers an effective behavior planning countermeasure to reduce the amount of urban traffi c and optimize the space-time distribution of travels and provides an effective technology to enrich the theories and methodologies of urban and transportation planning. Orienting at the practical demand of citizens and focusing on their travel behavior, this paper carries out a discussion on the smart travel framework based on space-time behavior study and analyzes smart travel planning and its policy route from multiple perspectives, including a prediction on travel demand, transportation planning, public policy-making, and urban planning. What’s more, the paper suggests travel services for citizens based on space-time behavior analysis, such as providing personalized information, smart decision-making support, and individual behavior planning.

  16. Assessing the Predictability of Scheduled-Vehicle Travel Times

    DEFF Research Database (Denmark)

    Tiesyte, Dalia; Jensen, Christian Søndergaard

    2009-01-01

    One of the most desired and challenging services in collective transport systems is the real-time prediction of the near-future travel times of scheduled vehicles, especially public buses, thus improving the experience of the transportation users, who may be able to better schedule their travel...... of travel times with the actual prediction errors for real bus trajectories. We have applied the proposed framework to real-time data collected from buses operating in Copenhagen, Denmark......., and also enabling system operators to perform real-time monitoring. While travel-time prediction has been researched extensively during the past decade, the accuracies of existing techniques fall short of what is desired, and proposed mathematical prediction models are often not transferable to other...

  17. Accuracy of Travel Time Estimation using Bluetooth Technology

    DEFF Research Database (Denmark)

    Araghi, Bahar Namaki; Skoven Pedersen, Kristian; Tørholm Christensen, Lars

    2012-01-01

    , the concept of outliers and corresponding impacts on travel time accuracy are discussed. Four different estimators named Min-BT, Max-BT, Med-BT and Avg-BT with different outlier detection logic are presented in this paper. These methods are used to estimate travel times using a BT derived dataset. In order...... to quantify the accuracy and robustness of these estimators against outliers, a comparative study between BT and Floating Car Data (FCD) is conducted. Results show that the Min-BT and Med-BT are more robust concerning the existence of outliers in the dataset and can provide more accurate travel time estimates...

  18. Faster than light motion does not imply time travel

    CERN Document Server

    Andréka, H; Németi, I; Stannett, M; Székely, G

    2014-01-01

    Seeing the many examples in the literature of causality violations based on faster-than- light (FTL) signals one naturally thinks that FTL motion leads inevitably to the possibility of time travel. We show that this logical inference is invalid by demonstrating a model, based on (3+1)-dimensional Minkowski spacetime, in which FTL motion is permitted (in every direction without any limitation on speed) yet which does not admit time travel. Moreover, the Principle of Relativity is true in this model in the sense that all observers are equivalent. In short, FTL motion does not imply time travel after all.

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

    DEFF Research Database (Denmark)

    Engelson, Leonid; Fosgerau, Mogens

    2016-01-01

    This paper explores the relationships between three types of measures of the cost of travel time variability: measures based on scheduling preferences and implicit departure time choice, Bernoulli type measures based on a univariate function of travel time, and mean-dispersion measures. We...... result on the utility rates in an additive scheduling measure. These insights are useful for selecting cost measures to use in applications....

  20. Assessing the Predictability of Scheduled-Vehicle Travel Times

    DEFF Research Database (Denmark)

    Tiesyte, Dalia; Jensen, Christian Søndergaard

    2009-01-01

    One of the most desired and challenging services in collective transport systems is the real-time prediction of the near-future travel times of scheduled vehicles, especially public buses, thus improving the experience of the transportation users, who may be able to better schedule their travel......, and also enabling system operators to perform real-time monitoring. While travel-time prediction has been researched extensively during the past decade, the accuracies of existing techniques fall short of what is desired, and proposed mathematical prediction models are often not transferable to other...... systems because the properties of the travel-time-related data of vehicles are highly context-dependent, making the models difficult to fit. We propose a framework for evaluating various predictability types of the data independently of the model, and we also compare predictability analysis results...

  1. The A-priori Traveling Salesman Problem with Time Windows

    DEFF Research Database (Denmark)

    Larsen, Allan; Madsen, Oli B.G.; Solomon, Marius M.

    2004-01-01

    In this paper we examine the traveling saleman problem with time windows for various degrees of dynamism. In contrast to the static problem, where the dispatcher can plan ahead, in the dynamic version, part or all of the necessary information becomes available only during the day of operation. We...... seek to minimize lateness and examine the impact of this criterion choice on the distance traveled. Our focus on lateness is motivated by the problem faced by overnight mail service providers. We propose a real-time solution method that requires the vehicle, when idle, to wait at the current customer...... the least extra distance to be traveled among the relocation policies....

  2. Hydraulic Travel Time Tomography Appraisal Using Synthetic Data Sets

    Science.gov (United States)

    Brauchler, R.; Cheng, J.; Dietrich, P.; Everett, M.; Johnson, B.

    2003-12-01

    Hydraulic tomography is an aquifer characterization method allowing the two and three dimensional spatial identification of hydraulic properties in the subsurface. Such information is essential for rigorous analysis of a variety of engineering, geotechnical and hydrogeological problems within the context of water resources management. We propose a tomographic approach providing the inversion of travel times of multiwell slug tests. The inversion is based on the relation between the travel times of a recorded transient pressure curve and the diffusivity of the geological medium. Usually, just one value of a measured hydraulic signal, mostly the peak time, is used as the data for the inversion in order to reconstruct the diffusivity field of the investigated system. This situation is not satisfying because much information is lost. Therefore, we have developed a transformation factor allowing to apply our approach to several travel times characterizing each signal. Thereby, each travel time is inverted separately. The main focus is to appraise the influence of the various travel times on the inversion results. It can be assumed that early travel times are dominated by preferential flow along fast, high permeability paths, while the inversion results based on late travel times reflect an integration of the received signal over many flow paths. Synthetic data sets were created using the Finite Element Heat and Mass Transfer Code (FEHM) from Los Alamos National Laboratory. The data base of the inversion comprises simulated slug tests, in which the position of the sources (injection ports) and the receivers (observation ports) isolated with packers, are varied between the tests. We also investigate the effects of input parameters such as the number of source-receiver positions used, borehole storage and permeability distribution. The hydraulic tomography appraisal shows a strong dependence of the inversion results on the used travel times and input parameters. Results of

  3. A Search on the Internet for Evidence of Time Travel

    Science.gov (United States)

    Nemiroff, Robert J.; Wilson, T.

    2014-01-01

    Time travel has captured the public imagination for much of the past century, but few searches for evidence of time travel have ever been done. Here three searches on the Internet for evidence of time travel are described, all three seeking a prescient mention of information not available before a given date. The first investigation sought prescient content placed on the Internet, highlighted by a comprehensive search for specific terms in tweets on Twitter. The second investigation sought prescient inquiries submitted to a search engine, highlighted by a comprehensive search for specific search terms submitted to the Astronomy Picture of the Day (APOD) web site. The third investigation involved a request for a direct Internet communication, either by email or tweet, pre-dating to the time of the inquiry. Given practical verifiability concerns, only time travel from the future was investigated. The main terms searched for involved Comet ISON and Pope Francis, as they became popular during our search window -- between 2006 and 2013. No evidence for time travel was discovered. Although these negative results do not disprove time travel, given the great reach of the Internet, this search is perhaps the most comprehensive to date.

  4. Back or to the future? Preferences of time travelers

    Directory of Open Access Journals (Sweden)

    Ralph Hertwig

    2012-07-01

    Full Text Available Popular culture reflects whatever piques our imagination. Think of the myriad movies and books that take viewers and readers on an imaginary journey to the past or the future (e.g., Gladiator, The Time Machine. Despite the ubiquity of time travel as a theme in cultural expression, the factors that underlie people's preferences concerning the direction of time travel have gone unexplored. What determines whether a person would prefer to visit the (certain past or explore the (uncertain future? We identified three factors that markedly affect people's preference for (hypothetical travel to the past or the future, respectively. Those who think of themselves as courageous, those with a more conservative worldview, and---perhaps counterintuitively---those who are advanced in age prefer to travel into the future. We discuss implications of these initial results.

  5. Trends in groundwater quality in relation to groundwater age

    NARCIS (Netherlands)

    Visser, A.

    2009-01-01

    Groundwater is a valuable natural resource and as such should be protected from chemical pollution. Because of the long travel times of pollutants through groundwater bodies, early detection of groundwater quality deterioration is necessary to efficiently protect groundwater bodies. The aim of this

  6. Trends in groundwater quality in relation to groundwater age

    NARCIS (Netherlands)

    Visser, A.

    2009-01-01

    Groundwater is a valuable natural resource and as such should be protected from chemical pollution. Because of the long travel times of pollutants through groundwater bodies, early detection of groundwater quality deterioration is necessary to efficiently protect groundwater bodies. The aim of this

  7. The meandering mind: vection and mental time travel.

    Directory of Open Access Journals (Sweden)

    Lynden K Miles

    Full Text Available BACKGROUND: The ability to travel mentally through time sets humans apart from many other species, yet little is known about this core cognitive capacity. In particular, what shapes the passage of the mind's journey through time? Guided by the viewpoint that higher cognitive activity can have a sensory-motor grounding, we explored the possibility that mental time travel is influenced by apparent movement through space. METHODOLOGY/PRINCIPAL FINDINGS: Participants performed a mundane vigilance task, during which they were expected to daydream, while viewing a display that elicited an illusion of self-motion (i.e., vection. Afterwards, the contents of their mind wandering experiences were probed. The results revealed that the direction of apparent motion influenced the temporal focus of mental time travel. While backward vection prompted thinking about the past, forward vection triggered a preponderance of future-oriented thoughts. CONCLUSIONS/SIGNIFICANCE: Consistent with recent evidence that traveling mentally through time entails associated movements in space, the current results demonstrate the converse relationship-apparent movement through space influenced the temporal locus of mental activity. Together, these findings corroborate the viewpoint that mental time travel may be grounded in the embodiment of spatiotemporal information in a bidirectional manner.

  8. 41 CFR 301-52.14 - What must I do with any travel advance outstanding at the time I submit my travel claim?

    Science.gov (United States)

    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...

  9. Extended time-travelling objects in Misner space

    CERN Document Server

    Levanony, Dana

    2011-01-01

    Misner space is a two-dimensional (2D) locally-flat spacetime which elegantly demonstrates the emergence of closed timelike curves from causally well-behaved initial conditions. Here we explore the motion of rigid extended objects in this time-machine spacetime. This kind of 2D time-travel is found to be risky due to inevitable self-collisions (i.e. collisions of the object with itself). However, in a straightforward four-dimensional generalization of Misner space (a physically more relevant spacetime obviously), we find a wide range of "safe" time-travel orbits free of any self-collisions.

  10. Splitting Travel Time Based on AFC Data: Estimating Walking, Waiting, Transfer, and In-Vehicle Travel Times in Metro System

    Directory of Open Access Journals (Sweden)

    Yong-Sheng Zhang

    2015-01-01

    Full Text Available The walking, waiting, transfer, and delayed in-vehicle travel times mainly contribute to route’s travel time reliability in the metro system. The automatic fare collection (AFC system provides huge amounts of smart card records which can be used to estimate all these times distributions. A new estimation model based on Bayesian inference formulation is proposed in this paper by integrating the probability measurement of the OD pair with only one effective route, in which all kinds of times follow the truncated normal distributions. Then, Markov Chain Monte Carlo method is designed to estimate all parameters endogenously. Finally, based on AFC data in Guangzhou Metro, the estimations show that all parameters can be estimated endogenously and identifiably. Meanwhile, the truncated property of the travel time is significant and the threshold tested by the surveyed data is reliable. Furthermore, the superiority of the proposed model over the existing model in estimation and forecasting accuracy is also demonstrated.

  11. Similarity-Based Prediction of Travel Times for Vehicles Traveling on Known Routes

    DEFF Research Database (Denmark)

    Tiesyte, Dalia; Jensen, Christian Søndergaard

    2008-01-01

    , historical data in combination with real-time data may be used to predict the future travel times of vehicles more accurately, thus improving the experience of the users who rely on such information. We propose a Nearest-Neighbor Trajectory (NNT) technique that identifies the historical trajectory......The use of centralized, real-time position tracking is proliferating in the areas of logistics and public transportation. Real-time positions can be used to provide up-to-date information to a variety of users, and they can also be accumulated for uses in subsequent data analyses. In particular...... of vehicles that travel along known routes. In empirical studies with real data from buses, we evaluate how well the proposed distance functions are capable of predicting future vehicle movements. Second, we propose a main-memory index structure that enables incremental similarity search and that is capable...

  12. Extremal inversion of lunar travel time data. [seismic velocity structure

    Science.gov (United States)

    Burkhard, N.; Jackson, D. D.

    1975-01-01

    The tau method, developed by Bessonova et al. (1974), of inversion of travel times is applied to lunar P-wave travel time data to find limits on the velocity structure of the moon. Tau is the singular solution to the Clairaut equation. Models with low-velocity zones, with low-velocity zones at differing depths, and without low-velocity zones, were found to be consistent with data and within the determined limits. Models with and without a discontinuity at about 25-km depth have been found which agree with all travel time data to within two standard deviations. In other words, the existence of the discontinuity and its size and location have not been uniquely resolved. Models with low-velocity channels are also possible.

  13. Valuation of travel time for international long-distance travel - results from the Fehmarn Belt stated choice experiment

    DEFF Research Database (Denmark)

    Mabit, Stefan Lindhard; Rich, Jeppe; Burge, Peter

    2013-01-01

    significant interactions among travel cost and time, and journey characteristics, such as distance and duration. This had direct impact on the VTTS, which was shown to decrease with distance and duration. Thirdly, we found that air travel implies a higher average VTTS, which is to be expected but rarely......The geographical scope of travel varies from short distances in urban areas to long distances across cities and countries. While urban travel has been widely analysed in the literature, travel over longer distances and particularly across countries, has received much less attention. While this may...... be justified due to the number of travellers it cannot be justified when looking at the mileage consumption and its resulting environmental impacts. In this paper, we investigate international long-distance travel preferences related to travel between Scandinavia and Central Europe with particular focus...

  14. Breast cancer stage at diagnosis: is travel time important?

    Science.gov (United States)

    Henry, Kevin A; Boscoe, Francis P; Johnson, Christopher J; Goldberg, Daniel W; Sherman, Recinda; Cockburn, Myles

    2011-12-01

    Recent studies have produced inconsistent results in their examination of the potential association between proximity to healthcare or mammography facilities and breast cancer stage at diagnosis. Using a multistate dataset, we re-examine this issue by investigating whether travel time to a patient's diagnosing facility or nearest mammography facility impacts breast cancer stage at diagnosis. We studied 161,619 women 40 years and older diagnosed with invasive breast cancer from ten state population based cancer registries in the United States. For each woman, we calculated travel time to their diagnosing facility and nearest mammography facility. Logistic multilevel models of late versus early stage were fitted, and odds ratios were calculated for travel times, controlling for age, race/ethnicity, census tract poverty, rural/urban residence, health insurance, and state random effects. Seventy-six percent of women in the study lived less than 20 min from their diagnosing facility, and 93 percent lived less than 20 min from the nearest mammography facility. Late stage at diagnosis was not associated with increasing travel time to diagnosing facility or nearest mammography facility. Diagnosis age under 50, Hispanic and Non-Hispanic Black race/ethnicity, high census tract poverty, and no health insurance were all significantly associated with late stage at diagnosis. Travel time to diagnosing facility or nearest mammography facility was not a determinant of late stage of breast cancer at diagnosis, and better geographic proximity did not assure more favorable stage distributions. Other factors beyond geographic proximity that can affect access should be evaluated more closely, including facility capacity, insurance acceptance, public transportation, and travel costs.

  15. Does the self drive mental time travel?

    Science.gov (United States)

    Shao, Yi; Yao, Xiang; Ceci, Stephen J; Wang, Qi

    2010-11-01

    Research on autobiographical remembering has shown the intertwined relationship between the self and memory. Very little is known about the role of the self in the anticipation of the future. To investigate the association, European American (N=61) and Chinese (N=60) college students each reported two past autobiographical events and anticipated two future events, and described themselves in the past, present, and future. The results from a content analysis found that, regardless of culture, the future self and events were more positive and socially oriented than the past self and events. In general, European Americans provided more positive events and self-descriptions than Chinese. Men showed more personal focus in both experiences and self-descriptions than women at all time epochs. Importantly, independent of culture and gender, the self rather than the past events predicted the valence and personal focus of future events. These findings offer new insights into the dynamic relations between the self and episodic thinking.

  16. How superluminal motion can lead to backward time travel

    CERN Document Server

    Nemiroff, Robert J

    2015-01-01

    It is commonly asserted that superluminal particle motion can enable backward time travel, but little has been written providing details. It is shown here that the simplest example of a "closed loop" event -- a twin paradox scenario where a single spaceship both traveling out and returning back superluminally -- does {\\it not} result in that ship straightforwardly returning to its starting point before it left. However, a more complicated scenario -- one where the superluminal ship first arrives at an intermediate destination moving subluminally -- can result in backwards time travel. This intermediate step might seem physically inconsequential but is shown to break Lorentz-invariance and be oddly tied to the sudden creation of a pair of spacecraft, one of which remains and one of which annihilates with the original spacecraft.

  17. Reducing employee travelling time through smart commuting

    Science.gov (United States)

    Rahman, A. N. N. A.; Yusoff, Z. M.; Aziz, I. S.; Omar, D.

    2014-02-01

    Extremely congested roads will definitely delay the arrival time of each trip.This certainly impacted the journey of employees. Tardiness at the workplace has become a perturbing issue for companies where traffic jams are the most common worker excuses. A depressing consequence on daily life and productivity of the employee occurs. The issues of commuting distance between workplace and resident area become the core point of this research. This research will emphasize the use of Geographical Information System (GIS) technique to explore the distance parameter to the employment area and will focus on the accessibility pattern of low-cost housing. The research methodology consists of interview sessions and a questionnaire to residents of low-cost housing areas in Melaka Tengah District in Malaysia. The combination of these processes will show the criteria from the selected parameter for each respondent from their resident area to the employment area. This will further help in the recommendation of several options for a better commute or improvement to the existing routes and public transportations system. Thus enhancing quality of life for employees and helping to reduce stress, decrease lateness, absenteeism and improving productivity in workplace.

  18. Object-based high contrast travel time tomography

    CERN Document Server

    Lin, Yenting

    2013-01-01

    We consider travel time tomography problems involving detection of high contrast, discrete high velocity structures. This results in a discrete nonlinear inverse problem, for which traditional grid-based models and iterative linearized least-squares reconstruction algorithms are not suitable. This is because travel paths change significantly near the high contrast velocity structure, making it more difficult to inversely calculate the travel path and infer the velocity along the path. We propose a model-based approach to describe the high velocity structure using pre-defined elementary objects. Compared to a grid-based model, our approach has complexity that increases as a function of the number of objects, rather than increasing with the number of cells (usually very large). A new reconstruction algorithm is developed that provides estimates of the probability that a high velocity structure appears at any point in the region of interest. Simulation results show that our method can efficiently sample the mode...

  19. A Data Model for Determining Weather's Impact on Travel Time

    DEFF Research Database (Denmark)

    Andersen, Ove; Torp, Kristian

    2017-01-01

    for storing and map-matching GPS data, and integrating this data with detailed weather data. The model is generic in the sense that it can be used anywhere GPS data and weather data is available. Next, we analyze the correlation between travel time and the weather classes dry, fog, rain, and snow along...

  20. Issues in the valuation of travel time savings

    DEFF Research Database (Denmark)

    Gissel, Stine

    1998-01-01

    The subject of the paper is the valuation of travel time savings (emanating from investment in transport infrastructure). In the first part of the paper the question is approached within a microeconomic framework. It is discussed if and how the theory can give indications on the relative value...

  1. A simple data fusion method for instantaneous travel time estimation

    NARCIS (Netherlands)

    Do, Michael; Pueboobpaphan, R.; Miska, Marc; Kuwahara, Masao; van Arem, Bart; Viegas, J.M.; Macario, R.

    2010-01-01

    Travel time is one of the most understandable parameters to describe traffic condition and an important input to many intelligent transportation systems applications. Direct measurement from Electronic Toll Collection (ETC) system is promising but the data arrives too late, only after the vehicles

  2. Extending Regional Seismic Travel Time (RSTT) Tomography to New Regions

    Science.gov (United States)

    2011-09-01

    Seism . Soc. Am. 59, 1365–1398. Flanagan, M. P., D. A. Dodge, and S. C. Myers (2008). GT merge process: Version 2.0, LLNL technical report, LLNL-TR...Validation of regional and teleseismic travel-time models by relocating ground-truth events, Bull. Seism . Soc. Amer. 94: 897–919. Zhao, L.-S. (1993

  3. Recent developments in guided wave travel time tomography

    NARCIS (Netherlands)

    Zon, A.T. van; Volker, A.W.F.

    2014-01-01

    The concept of predictive maintenance using permanent sensors that monitor the integrity of an installation is an interesting addition to the current method of periodic inspections. Guided wave tomography had been developed to create a map of the wall thickness using the travel times of guided waves

  4. A simple data fusion method for instantaneous travel time estimation

    NARCIS (Netherlands)

    Do, Michael; Pueboobpaphan, Rattaphol; Miska, Marc; Kuwahara, Masao; Arem, van Bart

    2010-01-01

    Travel time is one of the most understandable parameters to describe traffic condition and an important input to many intelligent transportation systems applications. Direct measurement from Electronic Toll Collection (ETC) system is promising but the data arrives too late, only after the vehicles c

  5. The A-priori Traveling Salesman Problem with Time Windows

    DEFF Research Database (Denmark)

    Larsen, Allan; Madsen, Oli B.G.; Solomon, Marius M.

    2004-01-01

    In this paper we examine the traveling saleman problem with time windows for various degrees of dynamism. In contrast to the static problem, where the dispatcher can plan ahead, in the dynamic version, part or all of the necessary information becomes available only during the day of operation. We...

  6. On frequency and time domain models of traveling wave tubes

    CERN Document Server

    Théveny, Stéphane; Elskens, Yves

    2016-01-01

    We discuss the envelope modulation assumption of frequency-domain models of traveling wave tubes (TWTs) and test its consistency with the Maxwell equations. We compare the predictions of usual frequency-domain models with those of a new time domain model of the TWT.

  7. Uncertainty and Sensitivity of Contaminant Travel Times from the Upgradient Nevada Test Site to the Yucca Mountain Area

    Energy Technology Data Exchange (ETDEWEB)

    J. Zhu; K. Pohlmann; J. Chapman; C. Russell; R.W.H. Carroll; D. Shafer

    2009-09-10

    Yucca Mountain (YM), Nevada, has been proposed by the U.S. Department of Energy as the nation’s first permanent geologic repository for spent nuclear fuel and highlevel radioactive waste. In this study, the potential for groundwater advective pathways from underground nuclear testing areas on the Nevada Test Site (NTS) to intercept the subsurface of the proposed land withdrawal area for the repository is investigated. The timeframe for advective travel and its uncertainty for possible radionuclide movement along these flow pathways is estimated as a result of effective-porosity value uncertainty for the hydrogeologic units (HGUs) along the flow paths. Furthermore, sensitivity analysis is conducted to determine the most influential HGUs on the advective radionuclide travel times from the NTS to the YM area. Groundwater pathways are obtained using the particle tracking package MODPATH and flow results from the Death Valley regional groundwater flow system (DVRFS) model developed by the U.S. Geological Survey (USGS). Effectiveporosity values for HGUs along these pathways are one of several parameters that determine possible radionuclide travel times between the NTS and proposed YM withdrawal areas. Values and uncertainties of HGU porosities are quantified through evaluation of existing site effective-porosity data and expert professional judgment and are incorporated in the model through Monte Carlo simulations to estimate mean travel times and uncertainties. The simulations are based on two steady-state flow scenarios, the pre-pumping (the initial stress period of the DVRFS model), and the 1998 pumping (assuming steady-state conditions resulting from pumping in the last stress period of the DVRFS model) scenarios for the purpose of long-term prediction and monitoring. The pumping scenario accounts for groundwater withdrawal activities in the Amargosa Desert and other areas downgradient of YM. Considering each detonation in a clustered region around Pahute Mesa (in

  8. Models of travel time and reliability for freight transport

    Energy Technology Data Exchange (ETDEWEB)

    Terziev, M.N.; Roberts, P.O.

    1976-12-01

    The model produces a probability distribution of the trip time associated with the shipment of freight between a given origin and destination by a given mode and route. Using distributions of the type produced by the model, it is possible to determine two important measures of the quality of service offered by the carrier. These measures are the main travel time and the reliability of delivery. The reliability measure describes the spread of the travel-time distribution. The model described herein was developed originally as part of the railroad rationalization study conducted at MIT and sponsored by the Federal Railroad Administration. This work built upon earlier research in railroad reliability models. Because of the predominantly rail background of this model, the initial discussion focuses on the problem of modeling rail-trip-time reliability. Then, it is shown that the model can also be used to study truck and barge operations.

  9. Consequences of mixing assumptions for time-variable travel time distributions

    NARCIS (Netherlands)

    Velde, van der Y.; Heidbüchel, I.; Lyon, S.W.; Nyberg, L.; Rodhe, A.; Bishop, K.; Troch, P.A.

    2015-01-01

    The current generation of catchment travel time distribution (TTD) research, integrating nearly three decades of work since publication of Water's Journey from Rain to Stream, seeks to represent the full distribution in catchment travel times and its temporal variability. Here, we compare conceptual

  10. Consequences of mixing assumptions for time-variable travel time distributions

    NARCIS (Netherlands)

    Velde, van der Y.; Heidbüchel, I.; Lyon, S.W.; Nyberg, L.; Rodhe, A.; Bishop, K.; Troch, P.A.

    2015-01-01

    The current generation of catchment travel time distribution (TTD) research, integrating nearly three decades of work since publication of Water's Journey from Rain to Stream, seeks to represent the full distribution in catchment travel times and its temporal variability. Here, we compare

  11. Eye movements during mental time travel follow a diagonal line.

    Science.gov (United States)

    Hartmann, Matthias; Martarelli, Corinna S; Mast, Fred W; Stocker, Kurt

    2014-11-01

    Recent research showed that past events are associated with the back and left side, whereas future events are associated with the front and right side of space. These spatial-temporal associations have an impact on our sensorimotor system: thinking about one's past and future leads to subtle body sways in the sagittal dimension of space (Miles, Nind, & Macrae, 2010). In this study we investigated whether mental time travel leads to sensorimotor correlates in the horizontal dimension of space. Participants were asked to mentally displace themselves into the past or future while measuring their spontaneous eye movements on a blank screen. Eye gaze was directed more rightward and upward when thinking about the future than when thinking about the past. Our results provide further insight into the spatial nature of temporal thoughts, and show that not only body, but also eye movements follow a (diagonal) "time line" during mental time travel.

  12. Real-time travel time prediction framework for departure time and route advice

    NARCIS (Netherlands)

    Calvert, S.C.; Snelder, M.; Bakri, T.; Heijligers, B.; Knoop, V.L.

    2015-01-01

    Heavily used urban networks remain a challenge for travel time prediction because traffic flow is rarely homogeneous and is also subject to a wide variety of disturbances. Various models, some of which use traffic flow theory and some of which are data driven, have been developed to predict traffic

  13. Real-time travel time prediction framework for departure time and route advice

    NARCIS (Netherlands)

    Calvert, S.C.; Snelder, M.; Bakri, T.; Heijligers, B.; Knoop, V.L.

    2015-01-01

    Heavily used urban networks remain a challenge for travel time prediction because traffic flow is rarely homogeneous and is also subject to a wide variety of disturbances. Various models, some of which use traffic flow theory and some of which are data driven, have been developed to predict traffic

  14. Influence of queue propagation and dissipation on route travel times

    DEFF Research Database (Denmark)

    Raovic, Nevena

    The representation of queue spillbacks in a congested network plays an important role in transportation network analysis. Dynamic network loading (DNL) models that are able to represent queue spillbacks suggest two approaches to represent traffic flow propagation. One is based on the kinemtic wave...... into account (Bliemer, 2008). Yperman (2007) indicates that there is a significant difference in queue-propagation and queue-dissipation between the LTM and DQM. This results in different route travel times, and can further affect route choice. In this paper, different approaches to represent queue propagation...... and dissipation through the CTM, LTM and DQM are studied. A simple network allows to show how these approaches influence route travel time. Furthermore, the possibility of changing the existing DQM is considered in order to more realistically represent queue propagation and dissipation, which would lead to more...

  15. Future decision-making without episodic mental time travel.

    Science.gov (United States)

    Kwan, Donna; Craver, Carl F; Green, Leonard; Myerson, Joel; Boyer, Pascal; Rosenbaum, R Shayna

    2012-06-01

    Deficits in episodic memory are associated with deficits in the ability to imagine future experiences (i.e., mental time travel). We show that K.C., a person with episodic amnesia and an inability to imagine future experiences, nonetheless systematically discounts the value of future rewards, and his discounting is within the range of controls in terms of both rate and consistency. Because K.C. is neither able to imagine personal uses for the rewards nor provide a rationale for selecting larger future rewards over smaller current rewards, this study demonstrates a dissociation between imagining and making decisions involving the future. Thus, although those capable of mental time travel may use it in making decisions about future rewards, these results demonstrate that it is not required for such decisions.

  16. Spirals in protoplanetary disks from photon travel time

    CERN Document Server

    Kama, M; Heays, A N

    2016-01-01

    Spiral structures are a common feature in scattered-light images of protoplanetary disks, and of great interest as possible tracers of the presence of planets. However, other mechanisms have been put foward to explain them, including self-gravity, disk-envelope interactions, and dead zone boundaries. These mechanisms explain many spirals very well, but are unable to easily account for very loosely wound spirals and single spiral arms. We study the effect of light travel time on the shape of a shadow cast by a clump orbiting close (within ${\\sim}1\\,$au) of the central star, where there can be significant orbital motion during the light travel time from the clump to the outer disk and then to the sky plane. This delay in light rays reaching the sky plane gives rise to a variety of spiral- and arc-shaped shadows, which we describe with a general fitting formula for a flared, inclined disk.

  17. Probabilistic Health Risk Assessment of Chemical Mixtures: Importance of Travel Times and Connectivity

    Science.gov (United States)

    Henri, Christopher V.; Fernàndez-Garcia, Daniel; de Barros, Felipe P. J.

    2014-05-01

    Subsurface contamination cases giving rise to groundwater pollutions are extensively found in all industrialized countries. Under this pressure, risk assessment methods play an important role in population protection by (1) quantifying the potential impact on human health of an aquifer contamination and (2) helping and driving decisions of groundwater-resource managers. Many reactive components such as chlorinated solvents or nitrates potentially experience attenuation processes under common geochemical conditions. This represents an attractive and extensively used remediation solution but leads often to the production of by-products before to reach a harmless chemical form. This renders mixtures of contaminants a common issue for groundwater resources managers. In this case, the threat posed by these contaminants to human health at a given sensitive location greatly depends on the competition between reactive and advective-dispersive characteristic times. However, hydraulic properties of the aquifer are known to be spatially variable, which can lead to the formation of preferential flow channels and fast contamination pathways. Therefore, the uncertainty on the spatial distribution of the aquifer properties controlling the plume travel time may then play a particular role in the human health risk assessment of chemical mixtures. We investigate here the risk related to a multispecies system in response to different degrees of heterogeneity of the hydraulic conductivity (K or Y =ln(K)). This work focuses on a Perchloroethylene (PCE) contamination problem followed by the sequential first-order production/biodegradation of its daughter species Trichloroethylene (TCE), Dichloroethylene (DCE) and Vinyl Chlorine (VC). For this specific case, VC is known to be a highly toxic contaminant. By performing numerical experiments, we evaluate transport through three-dimensional mildly (σY 2=1.0) and highly (σY 2=4.0) heterogeneous aquifers. Uncertainty on the hydraulic

  18. Change of Measure between Light Travel Time and Euclidean Distances

    Directory of Open Access Journals (Sweden)

    Heymann Y.

    2013-04-01

    Full Text Available The problem of cosmological distances is approached using a method based on the propagation of light in an expanding Universe. From the chan ge of measure between Light Travel Time and Euclidean Distances, a formula is deri ved to compute distances as a function of redshift. This formula is identical to Matti g’s formula (with q 0 = 1 / 2 which is based on Friedmann’s equations of general relativi ty.

  19. Time machine tales the science fiction adventures and philosophical puzzles of time travel

    CERN Document Server

    Nahin, Paul J

    2017-01-01

    This book contains a broad overview of time travel in science fiction, along with a detailed examination of the philosophical implications of time travel. The emphasis of this book is now on the philosophical and on science fiction, rather than on physics, as in the author's earlier books on the subject. In that spirit there are, for example, no Tech Notes filled with algebra, integrals, and differential equations, as there are in the first and second editions of TIME MACHINES. Writing about time travel is, today, a respectable business. It hasn’t always been so. After all, time travel, prima facie, appears to violate a fundamental law of nature; every effect has a cause, with the cause occurring before the effect. Time travel to the past, however, seems to allow, indeed to demand, backwards causation, with an effect (the time traveler emerging into the past as he exits from his time machine) occurring before its cause (the time traveler pushing the start button on his machine’s control panel to start his...

  20. [Mental time travel - the neurocognitive basis of future thinking].

    Science.gov (United States)

    Weiler, Julia A; Daum, Irene

    2008-09-01

    The ability to travel in time mentally, i. e. the re-experiencing of personal past events as well as the ability to mentally simulate potential future events, forms part of the "episodic memory" concept. Evidence for the notion that episodic memory and episodic future thinking share a common neural basis stems from different lines of research, namely functional neuroimaging, assessment of clinical groups, behavioral investigations of the phenomenological characteristics of mental time travel, and developmental research. The present article summarises the evidence from these lines of research which indicate a common neural network underlying episodic memory and episodic future thinking, consisting of medial prefrontal, medial temporal, medial parietal, lateral parieto-occipital, as well as lateral temporal regions. Both abilities, episodic memory and future thinking, seem to develop around the age of four years, feature similar phenomenological characteristics, and are impaired to a similar extent by brain lesions and brain dysfunction. These findings yielded different hypotheses concerning the function and evolutional significance of the mental time travel network, which will also be addressed.

  1. Soil water storage, mixing dynamics and resulting travel times through the critical zone in northern latitudes

    Science.gov (United States)

    Sprenger, Matthias; Tetzlaff, Doerthe; Weiler, Markus; Soulsby, Chris

    2017-04-01

    Water partitioning in the unsaturated zone into groundwater recharge, plant transpiration, and evaporation is fundamental for estimating storages and travel times. How water is mixed and routed through the soil is of broad interest to understand plant available water, contamination transport and weathering rates in the critical zone. Earlier work has shown how seasonal changes in hydroclimate influence the time variant character of travel times. A strong seasonality characterizes the northern latitudes which are particularly sensitive to climate and land use changes. It is crucial to understand how variation and change in hydroclimate and vegetation phenology impact time variant storage dynamics and flow path partitioning in the unsaturated zone. To better understand the influence of these ecohydrological processes on travel times of evaporative, transpiration and recharge fluxes in northern latitudes, we characterized soil physical properties, hydrometric conditions and soil water isotopic composition in the upper soil profile in two different land scape units in the long term experimental catchment, Bruntland Burn in the Scottish Highlands. Our two sampling locations are characterized by podzol soils with high organic matter content but they differ with regard to their vegetation cover with either Scots Pine (Pinus sylvestris) or heather (Calluna sp. and Erica Sp). To assess storage and mixing dynamics in the vadose zone, we parameterized a numerical 1-D flow model using the soil textural information along with soil moisture and soil water stable isotopes (δ2H and δ18O). The water flow and transport were simulated based on the Richards and the advection dispersion equation. Differences between water flows of mobile and tightly bound soil waters and the mixing between the two pore spaces were considered. Isotopic fractionation due to evaporation from soil and interception storage was taken into account, while plant water uptake did not alter the isotopic

  2. Model Passengers’ Travel Time for Conventional Bus Stop

    Directory of Open Access Journals (Sweden)

    Guangzhao Xin

    2014-01-01

    Full Text Available Limited number of berths can result in a subsequent bus stopping at the upstream of a bus stop when all berths are occupied. When this traffic phenomenon occurs, passengers waiting on the platform usually prefer walking to the stopped bus, which leads to additional walking time before boarding the bus. Therefore, passengers’ travel time consumed at a bus stop is divided into waiting time, additional walking time, and boarding time. This paper proposed a mathematical model for analyzing passengers’ travel time at conventional bus stop based on theory of stochastic service system. Field-measured and simulated data were designated to demonstrate the effectiveness of the proposed model. By analyzing the results, conclusion was conducted that short headway can reduce passengers’ waiting time at bus stop. Meanwhile, the theoretical analysis explained the inefficiency of bus stops with more than three berths from the perspective of passengers’ additional walking time. Additional walking time will increase in a large scale when the number of berths at a bus stop exceedsthe threshold of three.

  3. Monitoring travel times in an urban network using video, GPS and Bluetooth

    OpenAIRE

    Jie, L.; van Zuylen, H.J.; Chunhua, L.; Shoufeng, L.

    2011-01-01

    The travel time is an important measure for the quality of traffic. This paper discusses a few methods to measure or estimate the travel time in urban road networks. First of all, it is important to know that urban travel times display a large variation, so that the measurement of a single (average) travel time is not so meaningful. The travel time distribution is more relevant than the single value of the average. This distribution can be obtained from observations of travel times of individ...

  4. Travelling waves in the expanding spatially homogeneous space-times

    CERN Document Server

    Alekseev, George

    2014-01-01

    Some classes of the so called "travelling wave" solutions of Einstein and Einstein - Maxwell equations in General Relativity and of dynamical equations for massless bosonic fields in string gravity in four and higher dimensions are presented. Similarly to the well known pp-waves, these travelling wave solutions may depend on arbitrary functions of a null coordinate which determine the arbitrary profiles and polarizations of the waves. However, in contrast with pp-waves, these waves do not admit the null Killing vector fields and can exist in some curved (expanding and spatially homogeneous) background space-times, where these waves propagate in certain directions without any scattering. Mathematically, some of these classes of solutions arise as the fixed points of Kramer-Neugebauer transformations for hyperbolic integrable reductions of the mentioned above field equations, or, in the other cases, -- after imposing of the ansatz that these waves do not change the part of spatial metric transversal to the dire...

  5. Time series analysis of travel trends in Vermont

    Science.gov (United States)

    Varna M. Ramaswamy; Walter F. Kuentzel

    1995-01-01

    Vermont's travel and tourism industry is not keeping pace with the nation-wide growth in the travel industry. While travel indicators such as domestic travel expenditures, tourism generated employment, payroll and tax receipts have been steadily increasing across the United States, these indicators in Vermont peaked in 1978 and have declined ever since. The state...

  6. Simulation of Transient Groundwater Age Distribution in Space and Time, Wairarapa Valley, New Zealand

    Science.gov (United States)

    Toews, M. W.; Daughney, C.; Morgenstern, U.; Petrus, K.; Evison, R.; Jackson, B. M.; Cornaton, F. J.

    2013-12-01

    The 3000 km2 Wairarapa Valley is an important agricultural region near Wellington, New Zealand. Improved management of land and water within the region requires understanding of the spatial and temporal variations of water age. This study combines the two main methods currently available for determination of water age: numerical groundwater models and hydrological tracers. A transient finite element groundwater flow and mass transport model was calibrated to match time series measurements of groundwater level and tritium concentration. The groundwater flow model incorporates spatio-temporal recharge, variable stream flow and levels, and variable pump rates. The time-marching Laplace transform Galerkin (TMLTG) technique was then used to evaluate the full spectrum of groundwater age (i.e. age distribution) at each model node and at each time step. To our knowledge this study is the first application of the TMLTG technique to a real-world example, made possible by the rich time-series dataset of tritium measurements that exists for the Wairarapa Valley. Results showed that travel time from the land surface through the aquifer system varies from a few years to several decades and is strongly dependent on location and time. Results also demonstrated important differences between the transient age distributions derived from the TMLTG technique compared to the much simpler steady-state lumped parameter models that are frequently applied to interpret age tracer data. Finally, results had direct application to land and water management, for example for identification of land areas where age distributions vary seasonally, affecting the security of groundwater supplies used for drinking water.

  7. The Electric Traveling Salesman Problem with Time Windows

    DEFF Research Database (Denmark)

    Roberti, Roberto; Wen, Min

    2016-01-01

    integer linear formulation that can solve 20-customer instances in short computing times and a Three-Phase Heuristic algorithm based on General Variable Neighborhood Search and Dynamic Programming.Computational results show that the heuristic algorithm can find the optimal solution in most small......To minimize greenhouse gas emissions, the logistic field has seen an increasing usage of electric vehicles. The resulting distribution planning problems present new computational challenges.We address a problem, called Electric Traveling Salesman Problem with Time Windows. We propose a mixed...

  8. Using prospect theory to investigate the low value of travel time for small time changes

    DEFF Research Database (Denmark)

    Hjorth, Katrine; Fosgerau, Mogens

    A common finding in stated preference studies that measure the value of travel time (VTT), is that the measured per-minute VTT increases with the size of the time change considered, in conflict with standard neoclassical theory. The current paper tests prospect theory as a possible explanation......: More specifically, whether the phenomenon is generated by preferences being reference-dependent and exhibiting diminishing sensitivity for gains and losses, with a stronger degree of diminishing sensitivity for money than for travel time. We use stated preference data with trade-offs between travel...... time and money that pro- vide identification of the degrees of diminishing sensitivity for time and money gains and losses, thus enabling us to test and potentially falsify the prospect theory explanation. We apply a discrete choice model, in which choice depends on a reference-free value of travel...

  9. Online travel time estimation in urban areas using the occupancy of long loop detectors

    NARCIS (Netherlands)

    Mak, W.K.; Viti, F.; Hoogendoorn, S.P.; Hegyi, A.

    2010-01-01

    Roads in the Netherlands are often heavily congested. Real-time travel time information can be a valuable instrument to reduce the impact of increasing traffic demand on travel time with advantages for traffic participants as well as for the traffic network managers. For urban roads travel time

  10. Roads, travel, and time ‘across Jordan' in Byzantine and early Islamic times

    DEFF Research Database (Denmark)

    Walmsley, Alan George

    2009-01-01

    Roads, means of travel and travel times required to journey from one place to another in antiquity are essential components in assessing the political, cultural and economic history of a region. This paper reviews archaeological and documentary material detailing the major routes that crossed...... Jordan, the manner in which they were transversed, and the time required to travel over them in the period ca. 300-800 CE. In this post-Roman period, roadways took on new meaning as the needs of empire gave way to wider, and more self-defining, social and economic requirements of late antiquity...

  11. SAPS onset timing during substorms and the westward traveling surge

    Science.gov (United States)

    Mishin, Evgeny, V.

    2016-07-01

    We present multispacecraft observations in the magnetosphere and conjugate ionosphere of the onset time of subauroral polarization streams (SAPS) and tens of keV ring current injections on the duskside in three individual substorms. This is probably the first unequivocal determination of the substorm SAPS onset timing. The time lag between the SAPS and substorm onsets is much shorter than the gradient-curvature drift time of ˜10 keV ions in the plasmasphere. It seemingly depends on the propagation time of substorm-injected plasma from the dipolarization onset region to the plasmasphere, as well as on the SAPS position. These observations suggest that fast onset SAPS and ring current injections are causally related to the two-loop system of the westward traveling surge.

  12. Investigating the distribution of the value of travel time savings

    DEFF Research Database (Denmark)

    Fosgerau, Mogens

    2006-01-01

    The distribution of the value of travel time savings (VTTS) is investigated employing various nonparametric techniques to a large dataset originating from a stated choice experiment. The data contain choices between a fast and more expensive alternative and a slow and less expensive alternative....... Increasing the implicit price of time leads to an increased share of respondents who decline to pay to save time. But a significant proportion of respondents, 13%, remain willing to pay to save time at the highest price of time in the design. This means that the right tail of the VTTS distribution...... is not observed and hence the mean VTTS cannot be evaluated without additional assumptions. When socio-economic and situational variables are introduced into a semiparametric model it becomes possible to accept that the whole VTTS distribution is observed. Sixteen candidates for parametric VTTS distributions...

  13. Children’s Mental Time Travel during Mind Wandering

    Directory of Open Access Journals (Sweden)

    Qun eYe

    2014-08-01

    Full Text Available The prospective bias is a salient feature of mind wandering in healthy adults, yet little is known about the temporal focus of children’s mind wandering. In the present study, (I we developed the Temporal Focus of Mind Wandering Questionnaire for school-age children (TFMWQ-C, a 12-item scale with good test-retest reliability and construct validity. (II The criterion validity was tested by thought sampling in both Choice Reaction Time Task (CRT and Working Memory Task (WMT. A positive correlation was found between the temporal focus measured by the questionnaire and the one adopted during task-unrelated thoughts (TUTs by thought sampling probes, especially in the trait level of future-oriented mind wandering. At the same time, children who experienced more TUTs tended to show worse behavioral performance during tasks. (III The children in both tasks experienced more future-oriented TUTs than past-oriented ones, which was congruent with the results observed in adults; however, in contrast with previous research on adults, the prospective bias was not influenced by task demands. Together these results indicate that the prospective bias of mind wandering has emerged since the school age (9~13 years old, and that the relationship between mental time travel during mind wandering and the use of cognitive resources differs between children and adults. Our study provides new insights into how this interesting feature of mind wandering may adaptively contribute to the development of children’s mental time travel.

  14. Sensor Distribution Design of Travel Time Tomography in Explosion

    Directory of Open Access Journals (Sweden)

    Yali Guo

    2014-07-01

    Full Text Available Optimal sensor distribution in explosion testing is important in saving test costs and improving experiment efficiency. Aiming at travel time tomography in an explosion, an optimizing method in sensor distribution is proposed to improve the inversion stability. The influence factors of inversion stability are analyzed and the evaluating function on optimizing sensor distribution is proposed. This paper presents a sub-region and multi-scale cell partition method, according to the characteristics of a shock wave in an explosion. An adaptive escaping particle swarm optimization algorithm is employed to achieve the optimal sensor distribution. The experimental results demonstrate that optimal sensor distribution has improved both indexes and inversion stability.

  15. Sensor distribution design of travel time tomography in explosion.

    Science.gov (United States)

    Guo, Yali; Han, Yan; Wang, Liming; Liu, Linmao

    2014-07-15

    Optimal sensor distribution in explosion testing is important in saving test costs and improving experiment efficiency. Aiming at travel time tomography in an explosion, an optimizing method in sensor distribution is proposed to improve the inversion stability. The influence factors of inversion stability are analyzed and the evaluating function on optimizing sensor distribution is proposed. This paper presents a sub-region and multi-scale cell partition method, according to the characteristics of a shock wave in an explosion. An adaptive escaping particle swarm optimization algorithm is employed to achieve the optimal sensor distribution. The experimental results demonstrate that optimal sensor distribution has improved both indexes and inversion stability.

  16. On the income elasticity of the value of travel time

    DEFF Research Database (Denmark)

    Börjesson, Maria; Fosgerau, Mogens; Algers, Staffan

    2012-01-01

    Transport infrastructure is long-term and in appraisal it is necessary to value travel time savings for future years. This requires knowing how the value of time (VTT) will develop over time as incomes grow. This paper investigates if the cross-sectional income elasticity of the VTT is equal...... to inter-temporal income elasticity. The study is based on two identical stated choice experiments conducted with a 13 year interval. Results indicate that the relationship between income and the VTT in the cross-section has remained unchanged over time. As a consequence, the inter-temporal income...... elasticity of the VTT can be predicted based on cross-sectional income elasticity. However, the income elasticity of the VTT is not a constant but increases with income. For this reason, the average income elasticity of the VTT in the cross-sections has increased between the two survey years and can...

  17. Monitoring travel times in an urban network using video, GPS and Bluetooth

    NARCIS (Netherlands)

    Jie, L.; Van Zuylen, H.J.; Chunhua, L.; Shoufeng, L.

    2011-01-01

    The travel time is an important measure for the quality of traffic. This paper discusses a few methods to measure or estimate the travel time in urban road networks. First of all, it is important to know that urban travel times display a large variation, so that the measurement of a single (average)

  18. Monitoring travel times in an urban network using video, GPS and Bluetooth

    NARCIS (Netherlands)

    Jie, L.; Van Zuylen, H.J.; Chunhua, L.; Shoufeng, L.

    2011-01-01

    The travel time is an important measure for the quality of traffic. This paper discusses a few methods to measure or estimate the travel time in urban road networks. First of all, it is important to know that urban travel times display a large variation, so that the measurement of a single (average)

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

    Science.gov (United States)

    Xu, Tao; Li, Xiang; Claramunt, Christophe

    2017-03-01

    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.

  20. STUDI TENTANG TRAVELLING SALESMAN DAN VEHICLE ROUTING PROBLEM DENGAN TIME WINDOWS

    OpenAIRE

    I Nyoman Sutapa; I Gede Agus Widyadana; Christine Christine

    2003-01-01

    The article shows the study of model development of travelling salesman problem. Three models are studied, i.e. travelling salesman problem with time windows, vehicle routing problem, and vehicle routing problem with time windows. Abstract in Bahasa Indonesia : Dalam artikel ini dipaparkan kajian mengenai pengembangan model travelling salesman problem. Ada tiga model yang dikaji yaitu travelling salesman problem dengan time windows, vehicle routing problem, serta vehicle routing problem denga...

  1. Dissociating memory traces and scenario construction in mental time travel.

    Science.gov (United States)

    Cheng, Sen; Werning, Markus; Suddendorf, Thomas

    2016-01-01

    There has been a persistent debate about how to define episodic memory and whether it is a uniquely human capacity. On the one hand, many animal cognition studies employ content-based criteria, such as the what-where-when criterion, and argue that nonhuman animals possess episodic memory. On the other hand, many human cognition studies emphasize the subjective experience during retrieval as an essential property of episodic memory and the distinctly human foresight it purportedly enables. We propose that both perspectives may examine distinct but complementary aspects of episodic memory by drawing a conceptual distinction between episodic memory traces and mental time travel. Episodic memory traces are sequential mnemonic representations of particular, personally experienced episodes. Mental time travel draws on these traces, but requires other components to construct scenarios and embed them into larger narratives. Various nonhuman animals may store episodic memory traces, and yet it is possible that only humans are able to construct and reflect on narratives of their lives - and flexibly compare alternative scenarios of the remote future.

  2. Spirals in protoplanetary disks from photon travel time

    Science.gov (United States)

    Kama, M.; Pinilla, P.; Heays, A. N.

    2016-09-01

    Spiral structures are a common feature in scattered-light images of protoplanetary disks, and of great interest as possible tracers of the presence of planets. However, other mechanisms have been put forward to explain them, including self-gravity, disk-envelope interactions, and dead zone boundaries. These mechanisms explain many spirals very well, but are unable to easily account for very loosely wound spirals and single spiral arms. We study the effect of light travel time on the shape of a shadow cast by a clump orbiting close (within ~ 1 au) of the central star, where there can be significant orbital motion during the light travel time from the clump to the outer disk and then to the sky plane. This delay in light rays reaching the sky plane gives rise to a variety of spiral- and arc-shaped shadows, which we describe with a general fitting formula for a flared, inclined disk. The three movies are available at http://www.aanda.org

  3. Valuation of travel time savings in viewpoint of WTA.

    Science.gov (United States)

    Shao, Chang-Qiao; Liu, Yang; Liu, Xiao-Ming

    2014-01-01

    In order to investigate the issues in measurement of value of travel time savings (VTTS), the willingness-to-accept (WTA) for the private car owner is studied by using surveyed data. It is convincing that trip purpose, trip length, time savings, cost savings, income, and allowance from employee have effects on the WTA. Moreover, influences of these variables are not the same for different trip purposes. For commuting trips, effects of income and allowance from employee are significant while time savings and cost savings are dominated for leisure and shopping trips. It is also found that WTA is much higher than expected which implies that there are a group of drivers who are not prone to switching to other trip modes other than passenger car.

  4. Valuation of Travel Time Savings in Viewpoint of WTA

    Directory of Open Access Journals (Sweden)

    Chang-qiao Shao

    2014-01-01

    Full Text Available In order to investigate the issues in measurement of value of travel time savings (VTTS, the willingness-to-accept (WTA for the private car owner is studied by using surveyed data. It is convincing that trip purpose, trip length, time savings, cost savings, income, and allowance from employee have effects on the WTA. Moreover, influences of these variables are not the same for different trip purposes. For commuting trips, effects of income and allowance from employee are significant while time savings and cost savings are dominated for leisure and shopping trips. It is also found that WTA is much higher than expected which implies that there are a group of drivers who are not prone to switching to other trip modes other than passenger car.

  5. Groundwater residence time and movement in the Maltese islands - A geochemical approach

    Energy Technology Data Exchange (ETDEWEB)

    Stuart, M.E., E-mail: mest@bgs.ac.uk [British Geological Survey, Wallingford, Oxfordshire OX10 8BB (United Kingdom); Maurice, L. [British Geological Survey, Wallingford, Oxfordshire OX10 8BB (United Kingdom); Heaton, T.H.E. [British Geological Survey, NERC Isotope Geoscience Laboratory, Keyworth, Nottinghamshire NG12 5GG (United Kingdom); Sapiano, M.; Micallef Sultana, M. [Malta Resources Authority, Marsa MRS 9065 (Malta); Gooddy, D.C.; Chilton, P.J. [British Geological Survey, Wallingford, Oxfordshire OX10 8BB (United Kingdom)

    2010-05-15

    The Maltese islands are composed of two limestone aquifers, the Upper and Lower Coralline Limestone separated by an aquitard, the 'Blue Clay'. The Lower Coralline Limestone is overlain in part by the poorly permeable Globigerina Limestone. The upper perched aquifers are discontinuous and have very limited saturated thickness and a short water level response time to rainfall. Frequent detections of coliforms suggest a rapid route to groundwater. However, the unsaturated zone has a considerable thickness in places and the primary porosity of the Upper Coralline Limestone is high, so there is likely to be older recharge by slow matrix flow as well as rapid recharge from fractures. Measurement of SF{sub 6} from a pumping station in a deep part of one of the perched aquifers indicated a mean saturated zone age of about 15 a. The Main Sea Level aquifers (MSL) on both Malta and Gozo have a large unsaturated thickness as water levels are close to sea level. On Malta, parts of the aquifer are capped by the perched aquifers and more extensively by the Globigerina Limestone. The limited detection of coliform bacteria suggests only some rapid recharge from the surface via fractures or karst features. Transmissivity is low and {sup 3}H and CFC/SF{sub 6} data indicate that saturated zone travel times are in the range 15-40 a. On Gozo the aquifer is similar but is more-extensively capped by impermeable Blue Clay. CFC data show the saturated zone travel time is from 25 a to possibly more than 60 a. Groundwater age is clearly related to the extent of low-permeability cover. The {delta}{sup 13}C signature of groundwater is related to the geochemical processes which occur along the flowpath and is consistent with residence time ages in the sequence; perched aquifers < Malta MSL < Gozo MSL. The {sup 18}O and {sup 2}H enriched isotopic signature of post 1983 desalinated water can be seen in more-modern groundwater, particularly the urbanized areas of the perched and Malta MSL

  6. STUDI TENTANG TRAVELLING SALESMAN DAN VEHICLE ROUTING PROBLEM DENGAN TIME WINDOWS

    Directory of Open Access Journals (Sweden)

    I Nyoman Sutapa

    2003-01-01

    Full Text Available The article shows the study of model development of travelling salesman problem. Three models are studied, i.e. travelling salesman problem with time windows, vehicle routing problem, and vehicle routing problem with time windows. Abstract in Bahasa Indonesia : Dalam artikel ini dipaparkan kajian mengenai pengembangan model travelling salesman problem. Ada tiga model yang dikaji yaitu travelling salesman problem dengan time windows, vehicle routing problem, serta vehicle routing problem dengan time windows. Kata-kunci: travelling salesman problem, vehicle routing problem, time windows.

  7. Time lag estimates for nitrate travel through the vadose zone in Southland, New Zealand

    Science.gov (United States)

    Wilson, Scott; Chanut, Pierre; Ledgard, George; Rissmann, Clint

    2014-05-01

    A regional-scale study was carried out to calculate the travel time of a nitrate particle from the ground surface into shallow groundwater. The aim of the study was to obtain preliminary answers to two questions. Firstly, if leaching limits are set, how long would it take to see an improvement in shallow groundwater quality? Secondly, have groundwater nitrate concentrations reached equilibrium from recent dairy expansion in the region, or could we expect future increases? We applied a methodology that provides a balance between the detail and generalisation that is required for a regional-scale study. Steady-state advective transport through the vadose zone was modelled with water retention curves. These curves enable an estimate of the average volumetric water content of the vadose zone. The percentage saturation can then be used to calculate the vadose zone transit time if effective porosity, depth to the water table and annual average soil drainage are known. A time for mixing in the uppermost part of the aquifer has also been calculated. Two different vadose zone water retention curve models were used for comparison, the Brooks-Corey (1964), and the Van Genuchten (1980) methods. The water retention curves were parameterised by sediment texture via the Rawls and Brakensiek (1985) pedotransfer functions. Hydraulic properties were derived by positioning sediment textural descriptions on the Folk textural triangle, estimates of effective porosity from literature, and hydraulic conductivity values from aquifer tests. Uncertainty of parameter estimates was included by assigning standard deviations and appropriate probability distributions. Vadose zone saturation was modelled at 6,450 sites across the region with a Monte Carlo simulation involving 10,000 realisations. This generated a probability distribution of saturation for each site. Average volumetric water content of the vadose zone ranged from 8.5 to 40.7 % for the Brooks-Corey model and 12.9 to 36.3% for the

  8. Groundwater.

    Science.gov (United States)

    Braids, Olin C.; Gillies, Nola P.

    1978-01-01

    Presents a literature review of groundwater quality covering publications of 1977. This review includes: (1) sources of groundwater contamination; and (2) management of groundwater. A list of 59 references is also presented. (HM)

  9. Getting pre-stack time migration travel times from the single square root operator

    Institute of Scientific and Technical Information of China (English)

    Liu Guofeng; Liu Hong; Li Bo; Meng Xiaohong

    2009-01-01

    Improving the focusing capability of pre-stack time migration allows the imaged section to reflect structural characteristics, depth, and interface shape and it is a key step for the preparation of the initial depth migration velocity model. The traditional symmetrical travel time equation is derived based on the assumption of a layered model. It is difficult to achieve the desired effect of focusing in media with strong lateral variation. The non-symmetrical travel time equation based on Lie algebra and a pseudo-differential operator contains a lateral velocity derivative which can improve the focusing capability even in strongly lateral variable media and also the computation precision of the weight coefficients for relative amplitude preservation. Compared with the symmetrical methods, the non-symmetrical method is more effective. In this paper, we describe several key steps of non-symmetric pre-staek travel time calculation and present some test results using synthetic and real data.

  10. Cognitive mapping in mental time travel and mental space navigation.

    Science.gov (United States)

    Gauthier, Baptiste; van Wassenhove, Virginie

    2016-09-01

    The ability to imagine ourselves in the past, in the future or in different spatial locations suggests that the brain can generate cognitive maps that are independent of the experiential self in the here and now. Using three experiments, we asked to which extent Mental Time Travel (MTT; imagining the self in time) and Mental Space Navigation (MSN; imagining the self in space) shared similar cognitive operations. For this, participants judged the ordinality of real historical events in time and in space with respect to different mental perspectives: for instance, participants mentally projected themselves in Paris in nine years, and judged whether an event occurred before or after, or, east or west, of where they mentally stood. In all three experiments, symbolic distance effects in time and space dimensions were quantified using Reaction Times (RT) and Error Rates (ER). When self-projected, participants were slower and were less accurate (absolute distance effects); participants were also faster and more accurate when the spatial and temporal distances were further away from their mental viewpoint (relative distance effects). These effects show that MTT and MSN require egocentric mapping and that self-projection requires map transformations. Additionally, participants' performance was affected when self-projection was made in one dimension but judgements in another, revealing a competition between temporal and spatial mapping (Experiment 2 & 3). Altogether, our findings suggest that MTT and MSN are separately mapped although they require comparable allo- to ego-centric map conversion.

  11. Suburb-to-suburb intercity travel: Energy, time and dollar expenditures

    Science.gov (United States)

    Fels, M. F.

    1976-01-01

    The effect of adding suburb to terminal and terminal to suburb travel is examined. The energy consumed in entire trips was estimated. The total energy costs are compared with total travel times, and dollar costs to the traveler. Trips between origins in seven suburbs of Newark, New Jersey and destinations in two Washington, D. C. suburbs are analyzed.

  12. Using prospect theory to investigate the low marginal value of travel time for small time changes

    DEFF Research Database (Denmark)

    Hjorth, Katrine; Fosgerau, Mogens

    2012-01-01

    A common finding in stated preference studies that measure the value of travel time (VTT) is that the measured VTT increases with the size of the time change considered, in conflict with standard neoclassical economic theory. We present a new test of a possible explanation for the phenomenon...

  13. Modelling travel time perception in transport mode choices

    NARCIS (Netherlands)

    Varotto, S.F.; Glerum, A.; Stathopoulos, A.; Bierlaire, M.; Longo, G.

    2015-01-01

    Travel behaviour models typically rely on data afflicted by errors, in perception (e.g., over/under-estimation by traveller) and measurement (e.g., software or researcher imputation error). Such errors are shown to have a relevant impact on model outputs. So far a comprehensive framework to deal

  14. Modelling travel time perception in transport mode choices

    NARCIS (Netherlands)

    Varotto, S.F.; Glerum, A.; Stathopoulos, A.; Bierlaire, M.; Longo, G.

    2015-01-01

    Travel behaviour models typically rely on data afflicted by errors, in perception (e.g., over/under-estimation by traveller) and measurement (e.g., software or researcher imputation error). Such errors are shown to have a relevant impact on model outputs. So far a comprehensive framework to deal wit

  15. Determination of Scheduled Travel Time for a Fixed Transit Route Based on Multistate Model

    Institute of Scientific and Technical Information of China (English)

    Shukai Chen; Daniel Jian Sun; and Rui Xue

    2016-01-01

    In order to provide the guideline for bus drivers to adjust speed to minimize scheduled deviation, the method for setting bus scheduled travel time is proposed. Firstly, multistate model is introduced to fit historical travel time data and identify different service states. Based on the calibrated travel time distribution parameters, an optimization model is proposed, followed by a Monte Carlo ( MC) simulation based genetic algorithm ( GA) procedure to obtain the optimal scheduled time. A case study from a fixed bus route from Shenzhen is used to demonstrate the model applicability. The sensitivity analysis is conducted to study the effects of parameters setting on optimal slack time for each segment. The results show that multistate model fits travel time under peak hours better than Lognormal distribution, and the length of scheduled travel time basically reflects travel time reliability.

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

    DEFF Research Database (Denmark)

    Hjorth, Katrine; Rich, Jeppe

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

  17. Survival analysis of car travel time near a bus stop in developing countries

    Institute of Scientific and Technical Information of China (English)

    YANG XiaoBao; GAO ZiYou; GUO HongWei; HUAN Mei

    2012-01-01

    This paper presents an important investigation into car travel time affected by mixed traffic flow near a bus stop on the basis of survival analysis theory.Travel time data associated with mixed traffic characteristics near a bus stop were collected by video cameras.A hazard-based duration model was introduced to analyze the effects of mixed traffic flow on car travel time.The results indicate that mixed traffic flow impacts car travel time significantly.And the presence of bus berthing violation would delay car travel time.The proposed model can be used to forecast temporal shifts in car travel time due to changes in mixed traffic flow.The influential factors related to mixed traffic flow should be given full consideration in the planning and designing of bus stops in developing countries.

  18. A dynamic programming heuristic for vehicle routing with time-dependent travel times and required breaks

    NARCIS (Netherlands)

    Kok, A.L.; Hans, E.W.; Schutten, J.M.J.; Zijm, W.H.M.

    2010-01-01

    For the intensively studied vehicle routing problem (VRP), two real-life restrictions have received only minor attention in the VRP-literature: traffic congestion and driving hours regulations. Traffic congestion causes late arrivals at customers and long travel times resulting in large transport co

  19. A dynamic programming heuristic for vehicle routing with time-dependent travel times and required breaks.

    NARCIS (Netherlands)

    Kok, A.L.; Hans, Elias W.; Schutten, Johannes M.J.; Zijm, Willem H.M.

    2010-01-01

    For the intensively studied vehicle routing problem (VRP), two real-life restrictions have received only minor attention in the VRP-literature: traffic congestion and driving hours regulations. Traffic congestion causes late arrivals at customers and long travel times resulting in large transport

  20. 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.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  2. Travel time seismic tomography on Reykjanes, SW Iceland

    Science.gov (United States)

    Jousset, Philippe; Ágústsson, Kristjan; Blanck, Hanna; Metz, Malte; Franke, Steven; Pàll Hersir, Gylfi; Bruhn, David; Flovenz, Ólafur; Friðleifsson, Guðmundur

    2017-04-01

    We present updated tomographic results obtained using seismic data recorded around geothermal reservoirs located both on-land Reykjanes, SW-Iceland and offshore along Reykjanes Ridge. We gathered records from a network of 234 seismic stations (including 24 Ocean Bottom Seismometers) deployed between April 2014 and August 2015. In order to determine the orientation of the OBS stations, we used Rayleigh waves planar particle motions from large magnitude earthquakes. This method proved suitable using the on-land stations: orientations determined using this method with the orientations measured using a giro-compass agreed. We focus on the 3D velocity images using local earthquakes to perform travel time tomography. The processing includes first arrival picking of P- and S- phases using an automatic detection and picking technique based on Akaike Information Criteria. We locate earthquakes by using a non-linear localization technique, as a priori information for deriving a 1D velocity model. We then computed 3D velocity model by joint inversion of each earthquake's location and velocity lateral anomalies with respect to the 1D model. Our models confirms previous models obtained in the area, with enhanced details. In a second step, we performed inversion of the Vp/Vs ratio. Results indicate a low Vp/Vs ratio anomaly at depth suggesting the absence of large magmatic body under Reykjanes, unlike results obtained at other geothermal field, sucha as Krafla and Hengill. We discuss implications of those results in the light of recent IDDP drilling in Reykjanes.

  3. Travel Times of Water Derived from Three Naturally Occurring Cosmogenic Radioactive Isotopes

    Science.gov (United States)

    Visser, Ate; Thaw, Melissa; Deinhart, Amanda; Bibby, Richard; Esser, Brad

    2017-04-01

    Hydrological travel times are studied on scales that span six orders of magnitude, from daily event water in stream flow to pre-Holocene groundwater in wells. Groundwater vulnerability to contamination, groundwater surface water interactions and catchment response are often focused on "modern" water that recharged after the introduction of anthropogenic tritium in precipitation in 1953. Shorter residence times are expected in smaller catchments, resulting in immediate vulnerability to contamination. We studied a small (4.6 km2) alpine (1660-2117 m) catchment in a Mediterranean climate (8 ˚ C, 1200 mm/yr) in the California Sierra Nevada to assess subsurface storage and investigate the response to the recent California drought. We analyzed a combination of three cosmogenic radioactive isotopes with half-lives varying from 87 days (sulfur-35), 2.6 years (sodium-22) to 12.3 years (tritium) in precipitation and stream samples. Tritium samples (1 L) are analyzed by noble gas mass spectrometry after helium-3 accumulation. Samples for sulfur-35 and sodium-22 are collected by processing 20-1000 L of water through an anion and cation exchange column in-situ. Sulfur-35 is analyzed by liquid scintillation counting after chemical purification and precipitation. Sodium-22 is analyzed by gamma counting after eluting the cations into a 4L Marinelli beaker. Monthly collected precipitation samples show variability of deposition rate for tritium and sulfur-35. Sodium-22 levels in cumulative yearly precipitation samples are consistent with recent studies in the US and Japan. The observed variability of deposition rates complicates direct estimation of stream water age fractions. The level and variability of tritium in monthly stream samples indicate a mean residence time on the order of 10 years and only small contributions of younger water during high flow conditions. Estimates of subsurface storage are in agreement with estimates from geophysical studies. Detections of sodium-22

  4. Electric Vehicle Routing Problem with Charging Time and Variable Travel Time

    Directory of Open Access Journals (Sweden)

    Sai Shao

    2017-01-01

    Full Text Available An electric vehicle routing problem with charging time and variable travel time is developed to address some operational issues such as range limitation and charging demand. The model is solved by using genetic algorithm to obtain the routes, the vehicle departure time at the depot, and the charging plan. Meanwhile, a dynamic Dijkstra algorithm is applied to find the shortest path between any two adjacent nodes along the routes. To prevent the depletion of all battery power and ensure safe operation in transit, electric vehicles with insufficient battery power can be repeatedly recharged at charging stations. The fluctuations in travel time are implemented to reflect a dynamic traffic environment. In conclusion, a large and realistic case study with a road network in the Beijing urban area is conducted to evaluate the model performance and the solution technology and analyze the results.

  5. Rural population travel time to health services, mapped on Geographic Information System (GIS

    Directory of Open Access Journals (Sweden)

    Ricardo Vicente Ferreira

    2014-04-01

    Full Text Available Distance and travel time are important parameters in the evaluation of access to health services, especially for the population living in the countryside. In the present work, a GIS-based methodology is developed for the mapping of rural road networks and the determination of travel impedances in order to optimize the travel time of the rural population to health care facilities. Data on rural roads classes, slope, sinuosity, visibility and land use are considered in the composition of the impedances synthesis and its application on car travel time. The methodology was applied to the region of Registro (SP, and the results indicate an unequal distribution of health services.

  6. Travel Time Estimation and Prediction using Mobile Phones: A Cost Effective Method for Developing Countries

    Directory of Open Access Journals (Sweden)

    Satyakumar, M.

    2014-01-01

    Full Text Available Conventional data collection methods lack real time information and involve excessive cost of installation and maintenance. A real-time, low cost travel time data collection system can be developed using mobile phones. This project examines the use of mobile phones for travel time prediction of public transit vehicles and develops a dynamic travel time prediction model. Personnel were employed in public transit vehicles with mobile phones and these mobile phones were tracked continuously. Space information of the mobile phones represents the position of the buses and movement pattern of these mobile phones in turn represents the movement pattern of the public buses. The starting and arrival time at sections obtained from the cellular database were used to get the travel time and speed. Results obtained were statistically significant and it shows that use of mobile phone for travel time data collection is a low cost data collection technique for Indian cities.

  7. Developing an Analysis Program to Estimate and Prediction Groundwater Droughts in Korea from Groundwater Time-Series Data.

    Science.gov (United States)

    Cho, S.; Woo, N. C.; Lee, J. M.

    2015-12-01

    This study is aimed at developing process to analyze and predict groundwater drought potentials for Winter and Spring droughts in Korea using a long-term groundwater monitoring data. So far, most drought researches have been focused on precipitation and stream-flow data, although these data are considered to be non-linear. Subsequently, the prediction of drought events has been very difficult in practice. In this study, we targets to analyze the groundwater system as an intermediate stage between precipitation and stream-flow, but still has semi-linear characteristics. By the analysis of past trends of groundwater time-series compared with drought events, we will identify characteristics of fluctuation between groundwater-level and precipitation of the year before the droughts. Then, the characteristics will be tested with recent drought events in Korea. For this analysis, The updated ATGT (Analysis Tool for Groundwater Time-series data program version 1.0 based on JAVA), that was developed for analyzing and presenting groundwater time-series data, basically to identify abnormal changes in groundwater fluctuations, will be presented with additional functions including cross-correlation between groundwater and drought based on the PYTHON language.

  8. Multi-tracer investigation of groundwater residence time in a karstic aquifer: Bitter Lakes National Wildlife Refuge, New Mexico, USA

    Science.gov (United States)

    Land, Lewis; Huff, G. F.

    2010-03-01

    Several natural and anthropogenic tracers have been used to evaluate groundwater residence time within a karstic limestone aquifer in southeastern New Mexico, USA. Natural groundwater discharge occurs in the lower Pecos Valley from a region of karst springs, wetlands and sinkhole lakes at Bitter Lakes National Wildlife Refuge, on the northeast margin of the Roswell Artesian Basin. The springs and sinkholes are formed in gypsum bedrock that serves as a leaky confining unit for an artesian aquifer in the underlying San Andres limestone. Because wetlands on the Refuge provide habitat for threatened and endangered species, there is concern about the potential for contamination by anthropogenic activity in the aquifer recharge area. Estimates of the time required for groundwater to travel through the artesian aquifer vary widely because of uncertainties regarding karst conduit flow. A better understanding of groundwater residence time is required to make informed decisions about management of water resources and wildlife habitat at Bitter Lakes. Results indicate that the artesian aquifer contains a significant component of water recharged within the last 10-50 years, combined with pre-modern groundwater originating from deeper underlying aquifers, some of which may be indirectly sourced from the high Sacramento Mountains to the west.

  9. Spectral basis neural networks for real-time travel time forecasting

    Energy Technology Data Exchange (ETDEWEB)

    Park, D.; Rilett, L.R.; Han, G.

    1999-12-01

    This paper examines how real-time information gathered as part of intelligent transportation systems can be used to predict link travel times for one through five time periods ahead (of 5-min duration). The study employed a spectral basis artificial neural network (SNN) that utilizes a sinusoidal transformation technique to increase the linear separability of the input features. Link travel times from Houston that had been collected as part of the automatic vehicle identification system of the TranStar system were used as a test bed. It was found that the SNN outperformed a conventional artificial neural network and gave similar results to that of modular neural networks. However, the SNN requires significantly less effort on the part of the modeler than modular neural networks. The results, of the best SNN were compared with conventional link travel time prediction techniques including a Kalman filtering model, exponential smoothing model, historical profile, and real-time profile. It was found that the SNN gave the best overall results.

  10. Sequential and parallel local search for the time-constrained travelling salesman problem

    NARCIS (Netherlands)

    G.A.P. Kindervater (Gerard); J.K. Lenstra; M.W.P. Savelsbergh (Martin)

    1990-01-01

    textabstractLocal search has proven to be an effective solution approach for the traveling salesman problem. We consider variants of the TSP in which each city is to be visited within one or more given time windows. The travel times are symmetric and satisfy the triangle inequality; therobjective is

  11. Mental time travel : A conceptual overview of social psychological perspectives on a fundamental human capacity

    NARCIS (Netherlands)

    Epstude, K.; Peetz, J.

    Humans have the unique capacity to mentally travel through time, that is, to reflect on the past, anticipate the future, and construct alternate realities in their minds. The ability to mentally travel through time affects a variety of social psychological topics. Representations of events can

  12. Mental time travel : A conceptual overview of social psychological perspectives on a fundamental human capacity

    NARCIS (Netherlands)

    Epstude, K.; Peetz, J.

    2012-01-01

    Humans have the unique capacity to mentally travel through time, that is, to reflect on the past, anticipate the future, and construct alternate realities in their minds. The ability to mentally travel through time affects a variety of social psychological topics. Representations of events can diffe

  13. Making Decisions with the Future in Mind: Developmental and Comparative Identification of Mental Time Travel

    Science.gov (United States)

    Suddendorf, T.; Busby, J.

    2005-01-01

    Mechanisms that produce behavior which increase future survival chances provide an adaptive advantage. The flexibility of human behavior is at least partly the result of one such mechanism, our ability to travel mentally in time and entertain potential future scenarios. We can study mental time travel in children using language. Current results…

  14. Self-Efficacy Beliefs and Mental Time Travel Ability: Uncovering a Hidden Relationship in Educational Settings

    Science.gov (United States)

    Eren, Altay

    2009-01-01

    The aim of this study was threefold: first, it was to explore the profiles of student teachers' mental time travel ability; second, it was to examine the relationship between student teachers' mental time travel ability and self-efficacy beliefs; and third, it was to investigate the role of self-efficacy beliefs in relationship between the past…

  15. Does Involuntary Mental Time Travel Make Sense in Prospective Teachers' Feelings and Behaviors during Lessons?

    Science.gov (United States)

    Eren, Altay; Yesilbursa, Amanda

    2013-01-01

    This study examined the effects of involuntary mental time travel into the past and into the future on prospective teachers' feelings and behaviors during the period of a class hour. A total of 110 prospective teachers participated voluntarily in the study. The results of the present study showed that (a) the involuntary mental time travel into…

  16. Time travel and warp drives a scientific guide to shortcuts through time and space

    CERN Document Server

    Everett, Allen

    2012-01-01

    Sci-fi makes it look so easy. Receive a distress call from Alpha Centauri? No problem: punch the warp drive and you're there in minutes. Facing a catastrophe that can't be averted? Just pop back in the timestream and stop it before it starts. But for those of us not lucky enough to live in a science-fictional universe, are these ideas merely flights of fancy—or could it really be possible to travel through time or take shortcuts between stars?Cutting-edge physics may not be able to answer those questions yet, but it does offer up some tantalizing possibilities. In Time Travel and W

  17. Improving The Accuracy Of Bluetooth Based Travel Time Estimation Using Low-Level Sensor Data

    DEFF Research Database (Denmark)

    Araghi, Bahar Namaki; Tørholm Christensen, Lars; Krishnan, Rajesh

    2013-01-01

    triggered by a single device. This could lead to location ambiguity and reduced accuracy of travel time estimation. Therefore, the accuracy of travel time estimations by Bluetooth Technology (BT) depends upon how location ambiguity is handled by the estimation method. The issue of multiple detection events...... in the context of travel time estimation by BT has been considered by various researchers. However, treatment of this issue has remained simplistic so far. Most previous studies simply used the first detection event (Enter-Enter) as the best estimate. No systematic analysis for exploring the most accurate method...... of estimating travel time using multiple detection events has been conducted. In this study different aspects of BT detection zone, including size and its impact on the accuracy of travel time estimation, are discussed. Moreover, four alternative methods are applied; namely, Enter-Enter, Leave-Leave, Peak...

  18. Travelling Beneath Crows: Representing socio-geographical concepts of time and travel in early medieval England

    Directory of Open Access Journals (Sweden)

    L. A. Symonds

    2002-11-01

    Full Text Available Landscape has always been an important aspect of archaeological research. Recently there has been emphasis placed not on the identification of specific sites and artefacts but on past attitudes towards social interaction within the landscape. This has stimulated debate on how people, both as individuals and collective societies, understand space and human action. Many of these studies integrate computer applications and quantitative methods with current theoretical agendas focusing on landscape and social practice. The combination of theory and practice is essential to archaeological enquiry, enabling hypotheses to stand upon firm data. This article explores theoretical understandings of space and landscape and the practical application of these agendas in a study which focuses on the production and consumption of artefacts, specifically pottery, in Anglo-Scandinavian Lincolnshire. Many archaeological approaches to landscape studies involve the ways in which monuments and monumental landscapes structure and are structured by the societies which built them and inhabited them. Alternatively, this article focuses on how the social practices associated with the production and consumption of pottery participated in the social cognition of the landscape. It specifically concentrates on how travel practices can be associated with artefact distributions by measuring the distances in hours rather than kilometers, travelling beneath the crows rather than following their straight line of flight. Much of the analysis and exploration of the data was done via a GIS (Geographical Information System. In order to simulate this interactive process, java applets were employed to allow the reader to investigate the patterns of data for themselves. This enables the author and reader to establish a discourse through the reader's participation in the cognitive processes involved in the analysis of data and the interpretation of maps and landscape.

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

    Science.gov (United States)

    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.

  20. On the validity of travel-time based nonlinear bioreactive transport models in steady-state flow.

    Science.gov (United States)

    Sanz-Prat, Alicia; Lu, Chuanhe; Finkel, Michael; Cirpka, Olaf A

    2015-01-01

    Travel-time based models simplify the description of reactive transport by replacing the spatial coordinates with the groundwater travel time, posing a quasi one-dimensional (1-D) problem and potentially rendering the determination of multidimensional parameter fields unnecessary. While the approach is exact for strictly advective transport in steady-state flow if the reactive properties of the porous medium are uniform, its validity is unclear when local-scale mixing affects the reactive behavior. We compare a two-dimensional (2-D), spatially explicit, bioreactive, advective-dispersive transport model, considered as "virtual truth", with three 1-D travel-time based models which differ in the conceptualization of longitudinal dispersion: (i) neglecting dispersive mixing altogether, (ii) introducing a local-scale longitudinal dispersivity constant in time and space, and (iii) using an effective longitudinal dispersivity that increases linearly with distance. The reactive system considers biodegradation of dissolved organic carbon, which is introduced into a hydraulically heterogeneous domain together with oxygen and nitrate. Aerobic and denitrifying bacteria use the energy of the microbial transformations for growth. We analyze six scenarios differing in the variance of log-hydraulic conductivity and in the inflow boundary conditions (constant versus time-varying concentration). The concentrations of the 1-D models are mapped to the 2-D domain by means of the kinematic (for case i), and mean groundwater age (for cases ii & iii), respectively. The comparison between concentrations of the "virtual truth" and the 1-D approaches indicates extremely good agreement when using an effective, linearly increasing longitudinal dispersivity in the majority of the scenarios, while the other two 1-D approaches reproduce at least the concentration tendencies well. At late times, all 1-D models give valid approximations of two-dimensional transport. We conclude that the

  1. A PSO-SVM Model for Short-Term Travel Time Prediction Based on Bluetooth Technology

    Institute of Scientific and Technical Information of China (English)

    Qun Wang; Zhuyun Liu; Zhongren Peng

    2015-01-01

    The accurate prediction of travel time along roadway provides valuable traffic information for travelers and traffic managers. Aiming at short⁃term travel time forecasting on urban arterials, a prediction model ( PSO⁃SVM) combining support vector machine ( SVM) and particle swarm optimization ( PSO) is developed. Travel time data collected with Bluetooth devices are used to calibrate the proposed model. Field experiments show that the PSO⁃SVM model ’ s error indicators are lower than the single SVM model and the BP neural network (BPNN)model. Particularly, the mean⁃absolute percentage error (MAPE) of PSO⁃SVM is only 9�453 4 %which is less than that of the single SVM model ( 12�230 2 %) and the BPNN model ( 15�314 7 %) . The results indicate that the proposed PSO⁃SVM model is feasible and more effective than other models for short⁃term travel time prediction on urban arterials.

  2. Groundwater similarity across a watershed derived from time-warped and flow-corrected time series

    Science.gov (United States)

    Rinderer, M.; McGlynn, B. L.; van Meerveld, H. J.

    2017-05-01

    Information about catchment-scale groundwater dynamics is necessary to understand how catchments store and release water and why water quantity and quality varies in streams. However, groundwater level monitoring is often restricted to a limited number of sites. Knowledge of the factors that determine similarity between monitoring sites can be used to predict catchment-scale groundwater storage and connectivity of different runoff source areas. We used distance-based and correlation-based similarity measures to quantify the spatial and temporal differences in shallow groundwater similarity for 51 monitoring sites in a Swiss prealpine catchment. The 41 months long time series were preprocessed using Dynamic Time-Warping and a Flow-corrected Time Transformation to account for small timing differences and bias toward low-flow periods. The mean distance-based groundwater similarity was correlated to topographic indices, such as upslope contributing area, topographic wetness index, and local slope. Correlation-based similarity was less related to landscape position but instead revealed differences between seasons. Analysis of variance and partial Mantel tests showed that landscape position, represented by the topographic wetness index, explained 52% of the variability in mean distance-based groundwater similarity, while spatial distance, represented by the Euclidean distance, explained only 5%. The variability in distance-based similarity and correlation-based similarity between groundwater and streamflow time series was significantly larger for midslope locations than for other landscape positions. This suggests that groundwater dynamics at these midslope sites, which are important to understand runoff source areas and hydrological connectivity at the catchment scale, are most difficult to predict.

  3. An international meta-analysis of values of travel time savings.

    Science.gov (United States)

    Shires, J D; de Jong, G C

    2009-11-01

    Values of travel time savings are often used in cost-benefit analysis of transport projects and policies, and also to compute generalised travel costs. There has been considerable debate as to whether different research methods (e.g. stated versus revealed preference) will lead to different values of travel time savings, and which segmentations (e.g. by income or mode) are most important to capture the heterogeneity in these values. In addition there are many countries where no specific valuation studies have been done. In this paper new equations are estimated on the outcomes of value of travel time savings studies from various countries. In the data set, several countries appear more than once, which is taken into account by estimating random effects panel models. The meta-analysis sheds some new light on the variation of the value of travel time savings by income, country, travel purpose, mode, distance and by survey method. Furthermore, the resulting meta-models are applied to produce new values of travel time savings for business travel, commuting and for other purposes in passenger transport, for 25 European Union Member states. Similar methods could be used to statistically analyse studies carried out on other non-monetary effects, both for transport and non-transport projects, and for inclusion in cost-benefit analysis.

  4. Scoping Calculations for Potential Groundwater Impacts from Operation of the APT Facility at SRS

    Energy Technology Data Exchange (ETDEWEB)

    Thibault, J.J.

    1999-10-07

    The purpose of this study was to determine the potential travel times and paths of the postulated activated groundwater beneath the facility and to examine the fate and transport of this activated groundwater.

  5. Robust user equilibrium model based on cumulative prospect theory under distribution-free travel time

    Institute of Scientific and Technical Information of China (English)

    王伟; 孙会君; 吴建军

    2015-01-01

    The assumption widely used in the user equilibrium model for stochastic network was that the probability distributions of the travel time were known explicitly by travelers. However, this distribution may be unavailable in reality. By relaxing the restrictive assumption, a robust user equilibrium model based on cumulative prospect theory under distribution-free travel time was presented. In the absence of the cumulative distribution function of the travel time, the exact cumulative prospect value (CPV) for each route cannot be obtained. However, the upper and lower bounds on the CPV can be calculated by probability inequalities. Travelers were assumed to choose the routes with the best worst-case CPVs. The proposed model was formulated as a variational inequality problem and solved via a heuristic solution algorithm. A numerical example was also provided to illustrate the application of the proposed model and the efficiency of the solution algorithm.

  6. Behavioural decisions of travel-time ratios for work, maintenance and leisure activities in the Netherlands.

    NARCIS (Netherlands)

    Susilo, Y.S.; Dijst, M.J.

    2010-01-01

    Using the 2005 Dutch National Travel Survey data-set this paper investigates the influences of socio-demographics, journey patterns and built environment factors on the ratio of travel time and activity duration that an individual spends when engaging in work, daily shopping, non-daily shopping

  7. Behavioural decisions of travel-time ratios for work, maintenance and leisure activities in the Netherlands.

    NARCIS (Netherlands)

    Susilo, Y.S.; Dijst, M.J.

    2010-01-01

    Using the 2005 Dutch National Travel Survey data-set this paper investigates the influences of socio-demographics, journey patterns and built environment factors on the ratio of travel time and activity duration that an individual spends when engaging in work, daily shopping, non-daily shopping and

  8. Behavioural decisions of travel-time ratios for work, maintenance and leisure activities in the Netherlands.

    NARCIS (Netherlands)

    Susilo, Y.S.; Dijst, M.J.

    2010-01-01

    Using the 2005 Dutch National Travel Survey data-set this paper investigates the influences of socio-demographics, journey patterns and built environment factors on the ratio of travel time and activity duration that an individual spends when engaging in work, daily shopping, non-daily shopping and

  9. Parsimonious wave-equation travel-time inversion for refraction waves

    KAUST Repository

    Fu, Lei

    2017-02-14

    We present a parsimonious wave-equation travel-time inversion technique for refraction waves. A dense virtual refraction dataset can be generated from just two reciprocal shot gathers for the sources at the endpoints of the survey line, with N geophones evenly deployed along the line. These two reciprocal shots contain approximately 2N refraction travel times, which can be spawned into O(N2) refraction travel times by an interferometric transformation. Then, these virtual refraction travel times are used with a source wavelet to create N virtual refraction shot gathers, which are the input data for wave-equation travel-time inversion. Numerical results show that the parsimonious wave-equation travel-time tomogram has about the same accuracy as the tomogram computed by standard wave-equation travel-time inversion. The most significant benefit is that a reciprocal survey is far less time consuming than the standard refraction survey where a source is excited at each geophone location.

  10. Empirical Assessment on Factors Affecting Travel Time of Bus Rapid Transit

    Directory of Open Access Journals (Sweden)

    Fergyanto E Gunawan

    2015-02-01

    Full Text Available Since the beginning of the century, many cities around the world adopt the bus rapid transit (BRT system to fulfill their need of mass transportation system. The system features with platform-level boarding, bus lanes in the central verge of the road, off-vehicle fare collection, and physically protected busway. So far, these criteria are considered to be the most important aspects with respect to the BRT performance. In this research, we intend to study to what extent the BRT performance may be affected by the interference of the mixed traffic during the BRT operation. We adopt an empirical approach by observing the phenomenon unfolding in the eleven TransJakarta BRT corridors. The TransJakarta BRT operates in the city of Jakarta, the capital of the Republic of Indonesia. We record the travel time data from station to station for the case where the TransJakarta bus can travel smoothly and the case where the traveling bus is interfered with the mixed traffic. For the cases, we evaluate the travel time variation. As the results, we found that the Corridor 1 of TransJakarta BRT has the best performance in term of the travel time variation. For the two directions, the corridor has the mean travel time of 34 min, the standard deviation of 3 min, and the travel time variation of 8%. On this corridor, the mixed-traffic interference is relatively negligible. On the Corridor 7, the two-direction travel times have the mean of 45 min, the standard deviation of 8 min, and the travel time variation of 16%. On the Corridor 9, the twodirection travel times have the mean of 1 hr and 25 min, the standard deviation of 11 min, and the travel time variation of 14%. On the last two corridors, the busways are heavily interfered by the mixed traffic; thus, the end-to-end travel times are significantly uncertain although only very few road segments are interfered. The research leads us to a conclusion that the interference, although only occurs on a road segment, may

  11. M/G/c/c state dependent travel time models and properties

    Science.gov (United States)

    MacGregor Smith, J.; Cruz, F. R. B.

    2014-02-01

    One of the most important problems in today’s modeling of transportation networks is an accurate estimate of travel time on arterial links, highway, and freeways. There are a number of deterministic formulas that have been developed over the years to achieve a simple and direct way to estimate travel times for this complex task. Realistically, however, travel time is a random variable. These deterministic formula are briefly reviewed and also a new way to compute travel time over arterial links, highway, and freeways, is presented based on an analytical state dependent queueing model. One of the features of the queueing model is that it is analyzed within the context of the theoretical three-phase traffic flow model. We show that the model provides a quantitative foundation alternative to qualitative three-phase traffic flow theory. An important property shown with the model is that the travel time function is not convex, but a sigmoid S-shaped (i.e. logistic curve). Extensive analytical and simulation experiments are shown to verify the S-shaped nature of the travel time function and the use of the model’s method of estimation of travel time over vehicular traffic links as compared with traditional approaches. Finally, it is shown that the point-of-inflection of the S-shaped curve represents the threshold point where the traffic flow volume switches from Free Flow to Congested Flow.

  12. Commuting to work: RN travel time to employment in rural and urban areas.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. Impact of connected vehicle guidance information on network-wide average travel time

    Directory of Open Access Journals (Sweden)

    Jiangfeng Wang

    2016-12-01

    Full Text Available With the emergence of connected vehicle technologies, the potential positive impact of connected vehicle guidance on mobility has become a research hotspot by data exchange among vehicles, infrastructure, and mobile devices. This study is focused on micro-modeling and quantitatively evaluating the impact of connected vehicle guidance on network-wide travel time by introducing various affecting factors. To evaluate the benefits of connected vehicle guidance, a simulation architecture based on one engine is proposed representing the connected vehicle–enabled virtual world, and connected vehicle route guidance scenario is established through the development of communication agent and intelligent transportation systems agents using connected vehicle application programming interface considering the communication properties, such as path loss and transmission power. The impact of connected vehicle guidance on network-wide travel time is analyzed by comparing with non-connected vehicle guidance in response to different market penetration rate, following rate, and congestion level. The simulation results explore that average network-wide travel time in connected vehicle guidance shows a significant reduction versus that in non–connected vehicle guidance. Average network-wide travel time in connected vehicle guidance have an increase of 42.23% comparing to that in non-connected vehicle guidance, and average travel time variability (represented by the coefficient of variance increases as the travel time increases. Other vital findings include that higher penetration rate and following rate generate bigger savings of average network-wide travel time. The savings of average network-wide travel time increase from 17% to 38% according to different congestion levels, and savings of average travel time in more serious congestion have a more obvious improvement for the same penetration rate or following rate.

  15. Seismic model of Mars. 2. Free oscillations and travel times

    Science.gov (United States)

    Gudkova, Tamara; Lognonne, Philippe; Raevskiy, Sergey; Zharkov, Vladimir

    When constructing an interior structure model of a planet, it is common used method to describe the model by a restricted set of parameters: the thickness of the crust, the location of phase transitions, the core radius. The variation of these parameters originates from the uncertainties in temperature profile, composition, elastic and anelastic properties of relevant minerals. Water content should also be considered as a compositional variable in the mantle. Olivine and its high pressure phases, wadsleyite and ringwoodite are particularly important as they constitute about 60 wt% of the Martian mantle and have probably large capacity for water in the Martian mantle (Zharkov and Gudkova, 2014). At present Mars’ internal density distribution is constrained by the recent estimates of the moment of inertia and the Love number k _{2} (Konoplive et al., 2011). Below we use the data from Earth studies and laboratory data (Mao et al., 2010, 2011, 2012,extrapolated for P-T conditions in Mars, and show how the admixture of water in the main Martian minerals influences velocity drops at phase transition boundaries in Martian interiors and study the effects of hydration on the periods of free oscillations and travel times for P, PcP, S, ScS waves , which could serve as additional constraints, if upcoming seismic experiments are successful, as they can potentially constrain mantle composition and make more precise the location of transition zones. It is of importance to determine the depth of the phase transitions in the mantle, as it will fix the temperature profile in Mars. Our analysis is based on a trial seismic model M14_3 from (Zharkov et al., 2009). The crust is 50 km thick (with density of 2.9 g/cm (3) ), the molar ratio Fe/(Fe+Mg) in the mantle is 0.20, the Fe-Ni core contains 70 mol % H in addition to 14 wt % S with radius of 1800 km. The bulk Fe/Si ratio is close to chondritic 1.7. The upper mantle extends down to 1590 km depth. Olivine-wadsleite transition zone

  16. Screen time and passive school travel as independent predictors of cardiorespiratory fitness in youth.

    Science.gov (United States)

    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 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.

  17. Between-mode-differences in the value of travel time: Self-selection or strategic behaviour?

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Hjorth, Katrine; Lyk-Jensen, Stéphanie Vincent

    2010-01-01

    Using stated preference survey data, we measure the value of travel time for several transport modes. We find, like many before us, that the value of travel time varies across modes in the opposite direction of what would be the consequence of differences in comfort. We examine three candidate...... causes for the observed differences: Comfort effects, self-selection and strategic behaviour of respondents. Using experiments with both the current and an alternative mode we find that the differences in the value of travel time are consistent with self-selection and comfort effects. Moreover...

  18. Petri Net Decomposition Approach for Bi-Objective Routing for AGV Systems Minimizing Total Traveling Time and Equalizing Delivery Time

    National Research Council Canada - National Science Library

    EDA, Shuhei; NISHI, Tatsushi; MARIYAMA, Toshisada; KATAOKA, Satomi; SHODA, Kazuya; MATSUMURA, Katsuhiko

    2012-01-01

    .... The objective is minimizing total traveling time and equalizing delivery time simultaneously. The dispatching and conflict-free routing problem for AGVs is represented as a bi-objective optimal firing sequence problem for Petri Net...

  19. Travel cost inference from sparse, spatio-temporally correlated time series using markov models

    DEFF Research Database (Denmark)

    Yang, B.; Guo, C.; Jensen, C.S.

    2013-01-01

    of such time series offers insight into the underlying system and enables prediction of system behavior. While the techniques presented in the paper apply more generally, we consider the case of transportation systems and aim to predict travel cost from GPS tracking data from probe vehicles. Specifically, each...... road segment has an associated travel-cost time series, which is derived from GPS data. We use spatio-temporal hidden Markov models (STHMM) to model correlations among different traffic time series. We provide algorithms that are able to learn the parameters of an STHMM while contending...... with the sparsity, spatio-temporal correlation, and heterogeneity of the time series. Using the resulting STHMM, near future travel costs in the transportation network, e.g., travel time or greenhouse gas emissions, can be inferred, enabling a variety of routing services, e.g., eco-routing. Empirical studies...

  20. Age-ranked hydrological budgets and a travel time description of catchment hydrology

    Science.gov (United States)

    Rigon, Riccardo; Bancheri, Marialaura; Green, Timothy R.

    2016-12-01

    The theory of travel time and residence time distributions is reworked from the point of view of the hydrological storages and fluxes involved. The forward and backward travel time distribution functions are defined in terms of conditional probabilities. Previous approaches that used fixed travel time distributions are not consistent with our new derivation. We explain Niemi's formula and show how it can be interpreted as an expression of the Bayes theorem. Some connections between this theory and population theory are identified by introducing an expression which connects life expectancy with travel times. The theory can be applied to conservative solutes, including a method of estimating the storage selection functions. An example, based on the Nash hydrograph, illustrates some key aspects of the theory. Generalization to an arbitrary number of reservoirs is presented.

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

    Science.gov (United States)

    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.

  2. IYL Blog: Astronomers travel in time and space with light

    Science.gov (United States)

    Mather, John C.

    2015-01-01

    As an astronomer, I use light to travel through the universe, and to look back in time to when the universe was young. So do you! All of us see things as they were when the light was emitted, not as they are now. The farthest thing you can easily see without a telescope is the Andromeda Nebula, which is a galaxy like the Milky Way, about 2.5 million light years away. You see it as it was 2.5 million years ago, and we really don't know what it looks like today; the disk will have rotated a bit, new stars will have been born, there could have been all kinds of exploding stars, and the black hole in the middle could be lighting up. People may be skeptical of the Big Bang theory, even though we have a TV show named for it, but we (I should say Penzias and Wilson) measured its heat radiation 51 years ago at Bell Telephone Labs in New Jersey. Their discovery marks the beginning of the era of cosmology as a measurement science rather than speculation. Penzias and Wilson received the Nobel Prize in 1978 for their finding, which had been predicted in 1948 by Alpher and Herman. By the way, heat radiation is just another form of light - we call it radiation because we can't see it, but it's exactly the same phenomenon of electromagnetic waves, and the only difference is the wavelength. In the old days of analog television, if you tuned your TV in between channels, about 1% of the snow that you could see came from the Big Bang. So when we look at the heat radiation of the early universe, we really are gazing right at what seems to us a cosmic fireball, which surrounds us completely. It's a bit of an illusion; if you can imagine what astronomers in other galaxies would see, they would also feel surrounded by the fireball, and they would also think they were in the middle. So from a mathematical version of imagination, we conclude that there is no observable center and no edge of our universe, and that the heat of the fireball fills the entire universe uniformly. Astronomers are

  3. APPLICATION OF TRAVEL TIME RELIABILITY FOR PERFORMANCE ORIENTED OPERATIONAL PLANNING OF EXPRESSWAYS

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  5. A new phase space method for recovering index of refraction from travel times

    OpenAIRE

    Chung, Eric; Qian, Jianliang; Uhlmann, Gunther; Zhao, Hongkai

    2007-01-01

    We develop a new phase space method for reconstructing the index of refraction of a medium from travel time measurements. The method is based on the so-called Stefanov–Uhlmann identity which links two Riemannian metrics with their travel time information. We design a numerical algorithm to solve the resulting inverse problem. The new algorithm is a hybrid approach that combines both Lagrangian and Eulerian formulations. In particular the Lagrangian formulation in phase space can take into acc...

  6. Inpatient child mortality by travel time to hospital in a rural area of Tanzania

    OpenAIRE

    Manongi, R; Mtei, F; Mtove, G; Nadjm, B; Muro, F; Alegana, V; Noor, AM; J. Todd; Reyburn, H.

    2014-01-01

    ObjectiveTo investigate the association, if any, between child mortality and distance to the nearest hospital. MethodsThe study was based on data from a 1-year study of the cause of illness in febrile paediatric admissions to a district hospital in north-east Tanzania. All villages in the catchment population were geolocated, and travel times were estimated from availability of local transport. Using bands of travel time to hospital, we compared admission rates, inpatient case fatality rates ...

  7. Discussion on Travel Time Budget%出行时耗预算机理解析

    Institute of Scientific and Technical Information of China (English)

    蔡军; 张奕

    2014-01-01

    从20世纪60年代开始,一些学者发现城市居民人均日出行时耗在不同年份表现出一定的稳定性;扎·哈维提出日平均出行时耗预算相对恒定假设。首先,通过国内外全日、单次出行平均时耗变化的历史数据,验证了出行时耗的相对稳定性。在解析出行时耗相对恒定形成机理的基础上,重点分析单次通勤出行时耗分布机理,并提出相应的模拟公式。同时,探讨交通拥堵状况对出行时耗分布的影响作用,分析表明较小的出行时耗增加可能隐含较大程度的交通拥堵。最后指出,应结合中国城市居民的出行时耗预算,为其适宜的交通模式规划路网和城市用地布局。%Starting 1960s, scholars have found that the average daily travel time of urban residents tends to be stable in different years. Y. Zahavi developed a hypothesis that daily travel time budget is relatively con-stant. Through the data analysis of daily travel time and single-trip travel time both at home and abroad, this paper proves the relative stability of travel time assumption. Based on the analysis of mechanism of rel-ative stable travel time, the paper focuses on the distribution of single commuting travel time and proposes the simulation formula accordingly. By discussing the impact of traffic congestion on travel time distribu-tion, the paper reveals that a small travel time increase can result in severe traffic congestion. Finally, the paper points out that roadway network and urban land use plan should consider Chinese residents’travel time budget and travel modes.

  8. The Optimization of Passengers’ Travel Time under Express-Slow Mode Based on Suburban Line

    Directory of Open Access Journals (Sweden)

    Xiaobing Ding

    2016-01-01

    Full Text Available The suburban line connects the suburbs and the city centre; it is of huge advantage to attempt the express-slow mode. The passengers’ average travel time is the key factor to reflect the level of rail transport services, especially under the express-slow mode. So it is important to study the passengers’ average travel time under express-slow, which can get benefit on the optimization of operation scheme. First analyze the main factor that affects passengers’ travel time and then mine the dynamic interactive relationship among the factors. Second, a new passengers’ travel time evolution algorithm is proposed after studying the stop schedule and the proportion of express/slow train, and then membrane computing theory algorithm is introduced to solve the model. Finally, Shanghai Metro Line 22 is set as an example to apply the optimization model to calculate the total passengers’ travel time; the result shows that the total average travel time under the express-slow mode can save 1 minute and 38 seconds; the social influence and value of it are very huge. The proposed calculation model is of great help for the decision of stop schedule and provides theoretical and methodological support to determine the proportion of express/slow trains, improves the service level, and enriches and complements the rail transit operation scheme optimization theory system.

  9. Development of a process-oriented vulnerability concept for water travel time in karst aquifers-case study of Tanour and Rasoun springs catchment area.

    Science.gov (United States)

    Hamdan, Ibraheem; Sauter, Martin; Ptak, Thomas; Wiegand, Bettina; Margane, Armin; Toll, Mathias

    2017-04-01

    Key words: Karst aquifer, water travel time, vulnerability assessment, Jordan. The understanding of the groundwater pathways and movement through karst aquifers, and the karst aquifer response to precipitation events especially in the arid to semi-arid areas is fundamental to evaluate pollution risks from point and non-point sources. In spite of the great importance of the karst aquifer for drinking purposes, karst aquifers are highly sensitive to contamination events due to the fast connections between the land-surface and the groundwater (through the karst features) which is makes groundwater quality issues within karst systems very complicated. Within this study, different methods and approaches were developed and applied in order to characterise the karst aquifer system of the Tanour and Rasoun springs (NW-Jordan) and the flow dynamics within the aquifer, and to develop a process-oriented method for vulnerability assessment based on the monitoring of different multi-spatially variable parameters of water travel time in karst aquifer. In general, this study aims to achieve two main objectives: 1. Characterization of the karst aquifer system and flow dynamics. 2. Development of a process-oriented method for vulnerability assessment based on spatially variable parameters of travel time. In order to achieve these aims, different approaches and methods were applied starting from the understanding of the geological and hydrogeological characteristics of the karst aquifer and its vulnerability against pollutants, to using different methods, procedures and monitored parameters in order to determine the water travel time within the aquifer and investigate its response to precipitation event and, finally, with the study of the aquifer response to pollution events. The integrated breakthrough signal obtained from the applied methods and procedures including the using of stable isotopes of oxygen and hydrogen, the monitoring of multi qualitative and quantitative parameters

  10. Time-use and well-being impacts of travel-to-work and travel-for-work

    OpenAIRE

    Wheatley, D; Bickerton, C

    2016-01-01

    This article contributes to understanding of the complex patterns of travel-to-work and travel-for-work which \\ud increasingly characterize highly skilled employment, using 2015 data from a UK Midlands study comprising an online survey and follow-up interviews. Travel-to-work essentially lengthens the working day, and is difficult to use productively, especially when commuting by car. Travel-for-work, by contrast, results in intense schedules \\ud especially when requiring overnight stays. Own...

  11. Model-based Integration of Past & Future in TimeTravel

    DEFF Research Database (Denmark)

    Khalefa, Mohamed E.; Fischer, Ulrike; Pedersen, Torben Bach

    2012-01-01

    We demonstrate TimeTravel, an efficient DBMS system for seamless integrated querying of past and (forecasted) future values of time series, allowing the user to view past and future values as one joint time series. This functionality is important for advanced application domain like energy....... The main idea is to compactly represent time series as models. By using models, the TimeTravel system answers queries approximately on past and future data with error guarantees (absolute error and confidence) one order of magnitude faster than when accessing the time series directly. In addition...... it to answer approximate and exact queries. TimeTravel is implemented into PostgreSQL, thus achieving complete user transparency at the query level. In the demo, we show the easy building of a hierarchical model index for a real-world time series and the effect of varying the error guarantees on the speed up...

  12. Analysis of Time of Day Fare Discounts on Urban Mass Transit Travel Behavior, Crowding, and Waiting Time

    Directory of Open Access Journals (Sweden)

    Xiao Guo

    2014-01-01

    Full Text Available Every morning, commuters select the regularly dispatched urban mass transit for traveling from a residential area to a workplace. This paper aims to find an optimal discount fare and time intervals on morning peak hour. As a direct and flexible traffic economic instrument, fares can influence commuters’ behavior. Therefore, fare discount has been proposed to regulate traffic flow in different time. Two models have been analyzed to describe it with schedule delay because of the travel demand size. The first objective function is constructed on pressure equalization when the travel demand is small. The other objective function is to minimize total waiting time when the travel demand is large. In the end, numerical examples based on an artificial network are performed to characterize fare discount models.

  13. A Quantitative Analysis of the Relationship Between Radiation Therapy Use and Travel Time.

    Science.gov (United States)

    Liu, Emma; Santibáñez, Pablo; Puterman, Martin L; Weber, Leah; Ma, Xiang; Sauré, Antoine; Olivotto, Ivo A; Halperin, Ross; French, John; Tyldesley, Scott

    2015-11-01

    To model and quantify the relationship between radiation therapy (RT) use and travel time to RT services. Population-based registries and databases were used to identify both incident cancer patient and patients receiving RT within 1 year of diagnosis (RT1y) in British Columbia, Canada, between 1992 and 2011. The effects of age, gender, diagnosis year, income, prevailing wait time, and travel duration for RT on RT1y were assessed. Significant factors from univariate analyses were included in a multivariable logistic regression model. The shape of the travel time-RT1y curve was represented by generalized additive and segmented regression models. Analyses were conducted for breast, lung, and genitourinary cancer separately and for all cancer sites combined. After adjustment for age, gender, diagnosis year, income, and prevailing wait times, increasing travel time to the closest RT facility had a negative impact RT1y. The shape of the travel time-RT1y curve varied with cancer type. For breast cancer, the odds of RT1y were constant for the first 2 driving hours and decreased at 17% per hour thereafter. For lung cancer, the odds of RT1y decreased by 16% after 20 minutes and then decreased at 6% per hour. Genitourinary cancer RT1y was relatively independent of travel time. For all cancer sites combined, the odds of RT1y were constant within the first 2 driving hours and decreased at 7% per hour thereafter. Travel time to receive RT has a different impact on RT1y for different tumor sites. The results provide evidence-based insights for the configuration of catchment areas for new and existing cancer centers providing RT. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  14. Pickup and Delivery Problem with Stochastic Travel Times for Semiconductor Supply Chains

    Science.gov (United States)

    Lai, Chun-Mei

    2011-11-01

    As the supply chain has been constructed comprehensively, the pickup and delivery activities between supply-chain members are very complicated. In semiconductor factories, highly capacity utilization and efficiently production scheduling are essential due to the intensive capital investment. Because of travel time uncertainty, requests may fail to arrive within time window and may result in capacity idle and even deferral delivery when ignoring randomness of travel times. Therefore, taking the travel time uncertainty and time windows into account is of great importance when planning vehicle routes and schedules. Furthermore, in the fleet, some vehicles are with special facilities dedicated to carry 8" wafers, some are dedicated for 12" wafers, while other vehicles are open for carrying all products. When assigning requests to vehicles, the product/vehicle compatibility must be taken into account. In this study, we consider the pickup and delivery problem for semiconductor supply chains (PDPSSC), which involves constraints on stochastic travel times, time windows, product/vehicle compatibility, pickup and delivery, and vehicle capacity constraints. We describe the PDPSSC and formulate a chance constrained programming model to minimize total travel distances under two kinds of chance constraints, time windows and driver duration, hold with prescribed probabilities. By the implementation of the proposed model, the vehicle routing problem in semiconductor supply chain can be more integrated and applicable for the real-world applications.

  15. Dynamic Travel Time Prediction Models for Buses Using Only GPS Data

    Directory of Open Access Journals (Sweden)

    Wei Fan

    2015-01-01

    Full Text Available Providing real-time and accurate travel time information of transit vehicles can be very helpful as it assists passengers in planning their trips to minimize waiting times. The purpose of this research is to develop and compare dynamic travel time prediction models which can provide accurate prediction of bus travel time in order to give real-time information at a given downstream bus stop using only global positioning system (GPS data. Historical Average (HA, Kalman Filtering (KF and Artificial Neural Network (ANN models are considered and developed in this paper. A case has been studied by making use of the three models. Promising results are obtained from the case study, indicating that the models can be used to implement an Advanced Public Transport System. The implementation of this system could assist transit operators in improving the reliability of bus services, thus attracting more travelers to transit vehicles and helping relieve congestion. The performances of the three models were assessed and compared with each other under two criteria: overall prediction accuracy and robustness. It was shown that the ANN outperformed the other two models in both aspects. In conclusion, it is shown that bus travel time information can be reasonably provided using only arrival and departure time information at stops even in the absence of traffic-stream data.

  16. Narrative time in video games and films: from loop to travel in time

    Directory of Open Access Journals (Sweden)

    Lluís Anyó

    2015-09-01

    Full Text Available Within the broad framework of audiovisual theories, this paper deals with the analysis of narrative time in video games. Starting with the concept of participation time, which is taken from the interactive media, the now classic concepts of the narratology of film studies are applied to clarify the main mutual influences between the two media in relation to narrative time. Unlike the cinema, the narrative character of video games is not always clear. Generally, video games are always games and often also stories. Certainly, the playable character of these stories confers on them a few specific characteristics that need to be explored. Two aspects of narrative time are relevant here. Firstly, the loop as an elementary control structure of computer programming and as a characteristic narrative form of time structure in video games, and secondly, the paradox of travel in time in the discrepancy between the time order at the level of the story and at the level of the narrative.

  17. Perinatal outcomes and travel time from home to hospital: Welsh data from 1995 to 2009.

    Science.gov (United States)

    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.

  18. Road Short-Term Travel Time Prediction Method Based on Flow Spatial Distribution and the Relations

    Directory of Open Access Journals (Sweden)

    Mingjun Deng

    2016-01-01

    Full Text Available There are many short-term road travel time forecasting studies based on time series, but indeed, road travel time not only relies on the historical travel time series, but also depends on the road and its adjacent sections history flow. However, few studies have considered that. This paper is based on the correlation of flow spatial distribution and the road travel time series, applying nearest neighbor and nonparametric regression method to build a forecasting model. In aspect of spatial nearest neighbor search, three different space distances are defined. In addition, two forecasting functions are introduced: one combines the forecasting value by mean weight and the other uses the reciprocal of nearest neighbors distance as combined weight. Three different distances are applied in nearest neighbor search, which apply to the two forecasting functions. For travel time series, the nearest neighbor and nonparametric regression are applied too. Then minimizing forecast error variance is utilized as an objective to establish the combination model. The empirical results show that the combination model can improve the forecast performance obviously. Besides, the experimental results of the evaluation for the computational complexity show that the proposed method can satisfy the real-time requirement.

  19. [Travel time and distances to Norwegian out-of-hours casualty clinics].

    Science.gov (United States)

    Raknes, Guttorm; Morken, Tone; Hunskår, Steinar

    2014-11-01

    Geographical factors have an impact on the utilisation of out-of-hours services. In this study we have investigated the travel distance to out-of-hours casualty clinics in Norwegian municipalities in 2011 and the number of municipalities covered by the proposed recommendations for secondary on-call arrangements due to long distances. We estimated the average maximum travel times and distances in Norwegian municipalities using a postcode-based method. Separate analyses were performed for municipalities with a single, permanently located casualty clinic. Altogether 417 out of 430 municipalities were included. We present the median value of the maximum travel times and distances for the included municipalities. The median maximum average travel distance for the municipalities was 19 km. The median maximum average travel time was 22 minutes. In 40 of the municipalities (10 %) the median maximum average travel time exceeded 60 minutes, and in 97 municipalities (23 %) the median maximum average travel time exceeded 40 minutes. The population of these groups comprised 2 % and 5 % of the country's total population respectively. For municipalities with permanent emergency facilities(N = 316), the median average flight time 16 minutes and median average distance 13 km.. In many municipalities, the inhabitants have a long average journey to out-of-hours emergency health services, but seen as a whole, the inhabitants of these municipalities account for a very small proportion of the Norwegian population. The results indicate that the proposed recommendations for secondary on-call duty based on long distances apply to only a small number of inhabitants. The recommendations should therefore be adjusted and reformulated to become more relevant.

  20. Spatially distributed characterization of soil-moisture dynamics using travel-time distributions

    Science.gov (United States)

    Heße, Falk; Zink, Matthias; Kumar, Rohini; Samaniego, Luis; Attinger, Sabine

    2017-01-01

    Travel-time distributions are a comprehensive tool for the characterization of hydrological system dynamics. Unlike the streamflow hydrograph, they describe the movement and storage of water within and throughout the hydrological system. Until recently, studies using such travel-time distributions have generally either been applied to lumped models or to real-world catchments using available time series, e.g., stable isotopes. Whereas the former are limited in their realism and lack information on the spatial arrangements of the relevant quantities, the latter are limited in their use of available data sets. In our study, we employ the spatially distributed mesoscale Hydrological Model (mHM) and apply it to a catchment in central Germany. Being able to draw on multiple large data sets for calibration and verification, we generate a large array of spatially distributed states and fluxes. These hydrological outputs are then used to compute the travel-time distributions for every grid cell in the modeling domain. A statistical analysis indicates the general soundness of the upscaling scheme employed in mHM and reveals precipitation, saturated soil moisture and potential evapotranspiration as important predictors for explaining the spatial heterogeneity of mean travel times. In addition, we demonstrate and discuss the high information content of mean travel times for characterization of internal hydrological processes.

  1. Characterizing corridor-level travel time distributions based on stochastic flows and segment capacities

    Directory of Open Access Journals (Sweden)

    Hao Lei

    2015-12-01

    Full Text Available Trip travel time reliability is an important measure of transportation system performance and a key factor affecting travelers’ choices. This paper explores a method for estimating travel time distributions for corridors that contain multiple bottlenecks. A set of analytical equations are used to calculate the number of queued vehicles ahead of a probe vehicle and further capture many important factors affecting travel times: the prevailing congestion level, queue discharge rates at the bottlenecks, and flow rates associated with merges and diverges. Based on multiple random scenarios and a vector of arrival times, the lane-by-lane delay at each bottleneck along the corridor is recursively estimated to produce a route-level travel time distribution. The model incorporates stochastic variations of bottleneck capacity and demand and explains the travel time correlations between sequential links. Its data needs are the entering and exiting flow rates and a sense of the lane-by-lane distribution of traffic at each bottleneck. A detailed vehicle trajectory data-set from the Next Generation SIMulation (NGSIM project has been used to verify that the estimated distributions are valid, and the sources of estimation error are examined.

  2. Investigation of Bicycle Travel Time Estimation Using Bluetooth Sensors for Low Sampling Rates

    Directory of Open Access Journals (Sweden)

    Zhenyu Mei

    2014-10-01

    Full Text Available Filtering the data for bicycle travel time using Bluetooth sensors is crucial to the estimation of link travel times on a corridor. The current paper describes an adaptive filtering algorithm for estimating bicycle travel times using Bluetooth data, with consideration of low sampling rates. The data for bicycle travel time using Bluetooth sensors has two characteristics. First, the bicycle flow contains stable and unstable conditions. Second, the collected data have low sampling rates (less than 1%. To avoid erroneous inference, filters are introduced to “purify” multiple time series. The valid data are identified within a dynamically varying validity window with the use of a robust data-filtering procedure. The size of the validity window varies based on the number of preceding sampling intervals without a Bluetooth record. Applications of the proposed algorithm to the dataset from Genshan East Road and Moganshan Road in Hangzhou demonstrate its ability to track typical variations in bicycle travel time efficiently, while suppressing high frequency noise signals.

  3. Assessment of Smolt Condition for Travel Time Analysis, 1991-1992 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Maule, Alec G.; Beeman, John W.; Schrock, Robin M. (Seattle National Fishery Research Center, Columbia River Field Station, Cook, WA)

    1994-05-01

    Regression techniques were used to determine the effects of several biotic and abiotic variables on the migration rates of juvenile spring chinook salmon and steelhead in the Columbia and Snake rivers. Comparisons of the effects of river flow and smoltification, assessed using gill Na{sup +}-K{sup +} ATPase activity, were of primary interest. Day of the year, water temperature, change in flow, condition factor, and fork length were also considered as independent variables. Groups of fish were sampled to assess smoltification 2-3 times per week during the spring outmigrations during 1989-1992. These groups were assumed to be representative of other fish which were PIT-tagged and released as a part of the Smolt Monitoring Program in the Columbia Basin. River flow, gill ATPase activity, condition factor, water temperature, and change in flow were significant variables in regressions predicting the time for juvenile spring chinook salmon to travel between specific points (travel time), whereas river flow was the only significant contributor to models describing travel times of steelhead. Predicted travel times of wild steelhead were shorter than those of hatchery steelhead. River flow was the only variable common to all regression equations. Based on the characteristic, changes in river flow would be the most logical means to decrease travel times of both juvenile spring chinook salmon and steelhead in the Columbia and Snake rivers.

  4. Application of Time-Series Model to Predict Groundwater Dynamic in Sanjiang Plain,Northeast China

    Institute of Scientific and Technical Information of China (English)

    LUAN Zhaoqing; LIU Guihua; YAN Baixing

    2011-01-01

    To study the groundwater dynamic in the typical region of Sanjiang Plain,long-term groundwater level observation data in the Honghe State Farm were collected and analyzed in this paper.The seasonal and long-term groundwater dynamic was explored.From 1996 to 2008,groundwater level kept declining due to intensive exploitation of groundwater resources for rice irrigation.A decline of nearly 5 m was found for almost all the monitoring wells.A time-series method was established to model the groundwater dynamic.Modeled results by time-series model showed that the groundwater level in this region would keep declining according to the current exploitation intensity.A total dropdown of 1.07 m would occur from 2009 to 2012.Time-series model can be used to model and forecast the groundwater dynamic with high accuracy.Measures including control on groundwater exploitation amount and application of water saving irrigation technique should be taken to prevent the continuing declining of groundwater in the Sanjiang Plain.

  5. Time Traveling with Children's Literature. Pull-Out Feature 1.

    Science.gov (United States)

    Aronson, Melissa; And Others

    1996-01-01

    Presents a series of lesson plans that include investigations in science, mathematics, geography, current events, and social studies. The cross-curricular activities help students broaden their understanding of time as well as of the "neighbors" who live in their own and other time zones. (MJP)

  6. Seismic ray-tracing calculation based on parabolic travel-time interpolation

    Institute of Scientific and Technical Information of China (English)

    周竹生; 张赛民; 陈灵君

    2004-01-01

    A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method are used to compute seismic travel-time and ray-path in a 2-D grid cell model. Firstly, some basic concepts are introduced. The calculations of travel-time and ray-path are carried out only at cell boundaries. So, the ray-path is always straight in the same cells with uniform velocity. Two steps are applied in PTI and LTI method, step 1 computes travel-time and step 2 traces ray-path. Then, the derivation of LTI formulas is described. Because of the presence of refraction wave in shot cell, the formula aiming at shot cell is also derived. Finally, PTI method is presented. The calculation of PTI method is more complex than that of LTI method, but the error is limited. The results of numerical model show that PTI method can trace ray-path more accurately and efficiently than LTI method does.

  7. Tomography and Methods of Travel-Time Calculation for Regional Seismic Location

    Energy Technology Data Exchange (ETDEWEB)

    Myers, S; Ballard, S; Rowe, C; Wagoner, G; Antolik, M; Phillips, S; Ramirez, A; Begnaud, M; Pasyanos, M E; Dodge, D A; Flanagan, M P; Hutchenson, K; Barker, G; Dwyer, J; Russell, D

    2007-07-02

    We are developing a laterally variable velocity model of the crust and upper mantle across Eurasia and North Africa to reduce event location error by improving regional travel-time prediction accuracy. The model includes both P and S velocities and we describe methods to compute travel-times for Pn, Sn, Pg, and Lg phases. For crustal phases Pg and Lg we assume that the waves travel laterally at mid-crustal depths, with added ray segments from the event and station to the mid crustal layer. Our work on Pn and Sn travel-times extends the methods described by Zhao and Xie (1993). With consideration for a continent scale model and application to seismic location, we extend the model parameterization of Zhao and Xie (1993) by allowing the upper-mantle velocity gradient to vary laterally. This extension is needed to accommodate the large variation in gradient that is known to exist across Eurasia and North African. Further, we extend the linear travel-time calculation method to mantle-depth events, which is needed for seismic locators that test many epicenters and depths. Using these methods, regional travel times are computed on-the-fly from the velocity model in milliseconds, forming the basis of a flexible travel time facility that may be implemented in an interactive locator. We use a tomographic technique to improve upon a laterally variable starting velocity model that is based on Lawrence Livermore and Los Alamos National Laboratory model compilation efforts. Our tomographic data set consists of approximately 50 million regional arrivals from events that meet the ground truth (GT) criteria of Bondar et al. (2004) and other non-seismic constraints. Each datum is tested to meet strict quality control standards that include comparison with established distance-dependent travel-time residual populations relative to the IASPIE91 model. In addition to bulletin measurements, nearly 50 thousand arrival measurements were made at the national laboratories. The tomographic

  8. Effective time management: surgery, research, service, travel, fitness, and family.

    Science.gov (United States)

    Porta, C Rees; Anderson, Michael R; Steele, Scott R

    2013-12-01

    Over 1,500 years ago, the St. Benedictine Monks used planning and strict schedules to increase their productivity. Since then, surgeons have developed several different strategies to manage our time effectively. Finding a balance among career, family, and hobbies is essential for maintaining satisfaction and optimizing productivity. Several recurring themes throughout the medical literature offer potential solutions to help maximize the little time surgeons possess. In this article, we will explore some of the methods and strategies available to help surgeons minimize waste and make the most of the most precious commodity we have-our time.

  9. Understanding the variability of daily travel-time expenditures using GPS trajectory data

    CERN Document Server

    Gallotti, Riccardo; Rambaldi, Sandro

    2015-01-01

    Transportation planning is strongly influenced by the assumption that every individual has for his daily mobility a constant daily budget of ~1 hour. However, recent experimental results are proving this assumption as wrong. Here, we study the differences in daily travel-time expenditures among 24 Italian cities, extracted from a large set of GPS data on vehicles mobility. To understand these variations at the level of individual behaviour, we introduce a trip duration model that allows for a description of the distribution of travel-time expenditures in a given city using two parameters. The first parameter reflects the accessibility of desired destinations, whereas the second one can be associated to a travel-time budget and represents physiological limits due to stress and fatigue. Within the same city, we observe variations in the distributions according to home position, number of mobility days and a driver's average number of daily trips. These results can be interpreted by a stochastic time-consumption...

  10. Urban Link Travel Time Estimation Based on Low Frequency Probe Vehicle Data

    Directory of Open Access Journals (Sweden)

    Xiyang Zhou

    2016-01-01

    Full Text Available To improve the accuracy and robustness of urban link travel time estimation with limited resources, this research developed a methodology to estimate the urban link travel time using low frequency GPS probe vehicle data. First, focusing on the case without reporting points for the GPS probe vehicle on the target link in the current estimation time window, a virtual report point creation model based on the K-Nearest Neighbour Rule was proposed. Then an improved back propagation neural network model was used to estimate the link travel time. The proposed method was applied to a case study based on an arterial road in Changchun, China: comparisons with the traditional artificial neural network method and the spatiotemporal moving average method revealed that the proposed method offered a higher estimation accuracy and better robustness.

  11. Branch-and-cut-and-price for the traveling salesman problem with time windows

    DEFF Research Database (Denmark)

    Røpke, Stefan; Madsen, Oli B.G.

    In the traveling salesman problem with time windows (TSPTW) one is given a depot and a set of nodes to be visited by a salesman. The salesman starts his trip at the depot and must visit all nodes while respecting time windows at the nodes. The objective of the problem is to minimize the total...... distance traveled by the salesman. The TSPTW is formulated as a set-partitioning problem which is solved by using combined cut and column generation. The pricing sub problem in the column generation procedure is a shortest path problem with time window constraints and 2-cycle elimination. A standard column...

  12. St. Augustine’s Reflections on Memory and Time and the Current Concept of Subjective Time in Mental Time Travel

    Directory of Open Access Journals (Sweden)

    Jean-Christophe Cassel

    2013-04-01

    Full Text Available Reconstructing the past and anticipating the future, i.e., the ability of travelling in mental time, is thought to be at the heart of consciousness and, by the same token, at the center of human cognition. This extraordinary mental activity is possible thanks to the ability of being aware of ‘subjective time’. In the present study, we attempt to trace back the first recorded reflections on the relations between time and memory, to the end of the fourth century’s work, the Confessions, by the theologian and philosopher, St. Augustine. We concentrate on Book 11, where he extensively developed a series of articulated and detailed observations on memory and time. On the bases of selected paragraphs, we endeavor to highlight some concepts that may be considered as the product of the first or, at least, very early reflections related to our current notions of subjective time in mental time travel. We also draw a fundamental difference inherent to the frameworks within which the questions were raised. The contribution of St. Augustine on time and memory remains significant, notwithstanding the 16 centuries elapsed since it was made, likely because of the universality of its contents.

  13. A Hydraulic Tomographic Approach: Coupling of Travel Time and Amplitude Inversion Using Multivariate Statistics

    Science.gov (United States)

    Brauchler, R.; Cheng, J.; Dietrich, P.; Everett, M.; Johnson, B.; Sauter, M.

    2005-12-01

    Knowledge about the spatial variations in hydraulic properties plays an important role controlling solute movement in saturated flow systems. Traditional hydrogeological approaches appear to have difficulties providing high resolution parameter estimates. Thus, we have decided to develop an approach coupling the two existing hydraulic tomographic approaches: a) Inversion of the drawdown as a function of time (amplitude inversion) and b) the inversion of travel times of the pressure disturbance. The advantages of hydraulic travel time tomography are its high structural resolution and computational efficiency. However, travel times are primarily controlled by the aquifer diffusivity making it difficult to determine hydraulically conductivity and storage. Amplitude inversion on the other hand is able to determine hydraulic conductivity and storage separately, but the heavy computational burden of the amplitude inversion is often a shortcoming, especially for larger data sets. Our coupled inversion approach was developed and tested using synthetic data sets. The data base of the inversion comprises simulated slug tests, in which the position of the sources (injection ports) isolated with packers, are varied between the tests. The first step was the inversion of several characteristic travel times (e.g. early, intermediate and late travel times) in order to determine the diffusivity distribution. Secondly, the resulting diffusivity distributions were classified into homogeneous groups in order to differentiate between hydrogeological units characterized by a significant diffusivity contrast. The classification was performed by using multivariate statistics. With a numerical flow model and an automatic parameter estimator the amplitude inversion was performed in a final step. The classified diffusivity distribution is an excellent starting model for the amplitude inversion and allows to reduce strongly the calculation time. The final amplitude inversion overcomes

  14. Characterization of mean transit time at large springs in the Upper Colorado River Basin, USA: a tool for assessing groundwater discharge vulnerability

    Science.gov (United States)

    Solder, John E.; Stolp, Bernard J.; Heilweil, Victor M.; Susong, David D.

    2016-07-01

    Environmental tracers (noble gases, tritium, industrial gases, stable isotopes, and radio-carbon) and hydrogeology were interpreted to determine groundwater transit-time distribution and calculate mean transit time (MTT) with lumped parameter modeling at 19 large springs distributed throughout the Upper Colorado River Basin (UCRB), USA. The predictive value of the MTT to evaluate the pattern and timing of groundwater response to hydraulic stress (i.e., vulnerability) is examined by a statistical analysis of MTT, historical spring discharge records, and the Palmer Hydrological Drought Index. MTTs of the springs range from 10 to 15,000 years and 90 % of the cumulative discharge-weighted travel-time distribution falls within the range of 2-10,000 years. Historical variability in discharge was assessed as the ratio of 10-90 % flow-exceedance (R 10/90%) and ranged from 2.8 to 1.1 for select springs with available discharge data. The lag-time (i.e., delay in discharge response to drought conditions) was determined by cross-correlation analysis and ranged from 0.5 to 6 years for the same select springs. Springs with shorter MTTs (<80 years) statistically correlate with larger discharge variations and faster responses to drought, indicating MTT can be used for estimating the relative magnitude and timing of groundwater response. Results indicate that groundwater discharge to streams in the UCRB will likely respond on the order of years to climate variation and increasing groundwater withdrawals.

  15. Being (un)moved by mental time travel.

    Science.gov (United States)

    Stins, John; Habets, Laura; Jongeling, Rowie; Cañal-Bruland, Rouwen

    2016-05-01

    Mental imagery of events in the past or future, and of unpleasant or pleasant events, has been found to lead to spontaneous backward/forward bodily motions. Both time and emotion are represented along a spatial continuum, and activation of these representations seems to be simulated in spontaneous changes in body posture. We performed a conceptual replication and extension of an earlier study by Miles, Nind, and Macrae (2010) who reported clear postural effects when thinking of the past and the future. We additionally tested whether changes in posture appear when thinking of an emotional event. Volunteers engaged in mental imagery, involving combinations of time intervals and emotions. We simultaneously recorded center-of-pressure (COP) changes. Results revealed neither an effect of imagery of time nor of emotion on body posture. We conclude that embodied effects of imagery of abstract items on body posture may be less robust than suggested by previous literature. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Reliability of Bluetooth Technology for Travel Time Estimation

    DEFF Research Database (Denmark)

    Araghi, Bahar Namaki; Olesen, Jonas Hammershøj; Krishnan, Rajesh

    2015-01-01

    .1 seconds), the size and shape of the sensor's detection zone, and the time span that the Bluetooth-enabled device is within the detection zone. The influences of size of Bluetooth sensor detection zones and Bluetooth discovery procedure on multiple detection events have been mentioned in previous research...

  17. Assessment of Smolt Condition for Travel Time Analysis Project, 1987-1997 Project Review.

    Energy Technology Data Exchange (ETDEWEB)

    Schrock, Robin M.; Hans, Karen M.; Beeman, John W. [US Geological Survey, Western Fisheries Research Center, Columbia River Research Laboratory, Cook, WA

    1997-12-01

    The assessment of Smolt Condition for Travel Time Analysis Project (Bonneville Power Administration Project 87-401) monitored attributes of salmonid smolt physiology in the Columbia and Snake River basins from 1987 to 1997, under the Northwest Power Planning Council Fish and Wildlife Program, in cooperation with the Smolt Monitoring Program of the Fish Passage Center. The primary goal of the project was to investigate the physiological development of juvenile salmonids related to migration rates. The assumption was made that the level of smolt development, interacting with environmental factos such as flow, would be reflected in travel times. The Fish Passage Center applied the physiological measurements of smolt condition to Water Budget management, to regulate flows so as to decrease travel time and increase survival.

  18. Approaching the brachistochrone using inclined planes—striving for shortest or equal travelling times

    Science.gov (United States)

    Theilmann, Florian

    2017-01-01

    The classical brachistochrone problem asks for the path on which a mobile point M just driven by its own gravity will travel in the shortest possible time between two given points A and B. The resulting curve, the cycloid, will also be the tautochrone curve, i.e. the travelling time of the mobile point will not depend on its starting position. We discuss three similar problems of increasing complexity that restrict the motion to inclined planes. Without using calculus we derive the respective optimal geometry and compare the theoretical values to measured travelling times. The observed discrepancies are quantitatively modelled by including angular motion and friction. We also investigate the correspondence between the original problem and our setups. The topic provides a conceptually simple yet non-trivial problem setting inviting for problem based learning and complex learning activities such as planing suitable experiments or modelling the relevant kinematics.

  19. Shallow-water acoustic tomography from angle measurements instead of travel-time measurements.

    Science.gov (United States)

    Aulanier, Florian; Nicolas, Barbara; Mars, Jérôme I; Roux, Philippe; Brossier, Romain

    2013-10-01

    For shallow-water waveguides and mid-frequency broadband acoustic signals, ocean acoustic tomography (OAT) is based on the multi-path aspect of wave propagation. Using arrays in emission and reception and advanced array processing, every acoustic arrival can be isolated and matched to an eigenray that is defined not only by its travel time but also by its launch and reception angles. Classically, OAT uses travel-time variations to retrieve sound-speed perturbations; this assumes very accurate source-to-receiver clock synchronization. This letter uses numerical simulations to demonstrate that launch-and-reception-angle tomography gives similar results to travel-time tomography without the same requirement for high-precision synchronization.

  20. Connected Traveler

    Energy Technology Data Exchange (ETDEWEB)

    2016-06-01

    The Connected Traveler framework seeks to boost the energy efficiency of personal travel and the overall transportation system by maximizing the accuracy of predicted traveler behavior in response to real-time feedback and incentives. It is anticipated that this approach will establish a feedback loop that 'learns' traveler preferences and customizes incentives to meet or exceed energy efficiency targets by empowering individual travelers with information needed to make energy-efficient choices and reducing the complexity required to validate transportation system energy savings. This handout provides an overview of NREL's Connected Traveler project, including graphics, milestones, and contact information.

  1. Travel with a Time Lord: Using Media to Enhance Literacy

    Science.gov (United States)

    Harrett, Jacqueline; Benjamin, Theresa

    2009-01-01

    This article reports on a UKLA-funded project in which a group of 10 teachers in South Wales were involved. The televised science fiction drama "Doctor Who" was chosen as the theme as it was based on popular culture as well as being of local and national interest. The main character in this television drama is an alien who can fly through time and…

  2. Characterization of mean transit time at large springs in the Upper Colorado River Basin, USA: a tool for assessing groundwater discharge vulnerability

    Science.gov (United States)

    Solder, John E.; Stolp, Bernard J.; Heilweil, Victor M.; Susong, David D.

    2016-12-01

    Environmental tracers (noble gases, tritium, industrial gases, stable isotopes, and radio-carbon) and hydrogeology were interpreted to determine groundwater transit-time distribution and calculate mean transit time (MTT) with lumped parameter modeling at 19 large springs distributed throughout the Upper Colorado River Basin (UCRB), USA. The predictive value of the MTT to evaluate the pattern and timing of groundwater response to hydraulic stress (i.e., vulnerability) is examined by a statistical analysis of MTT, historical spring discharge records, and the Palmer Hydrological Drought Index. MTTs of the springs range from 10 to 15,000 years and 90 % of the cumulative discharge-weighted travel-time distribution falls within the range of 2-10,000 years. Historical variability in discharge was assessed as the ratio of 10-90 % flow-exceedance ( R 10/90%) and ranged from 2.8 to 1.1 for select springs with available discharge data. The lag-time (i.e., delay in discharge response to drought conditions) was determined by cross-correlation analysis and ranged from 0.5 to 6 years for the same select springs. Springs with shorter MTTs (groundwater response. Results indicate that groundwater discharge to streams in the UCRB will likely respond on the order of years to climate variation and increasing groundwater withdrawals.

  3. Improving The Accuracy Of Bluetooth Based Travel Time Estimation Using Low-Level Sensor Data

    DEFF Research Database (Denmark)

    Araghi, Bahar Namaki; Tørholm Christensen, Lars; Krishnan, Rajesh

    2013-01-01

    Bluetooth sensors have a large detection zone compared to other static Vehicle Re-Identification Systems (VRIS). Although a larger detection zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, it increases the probability of multiple detection events...... triggered by a single device. This could lead to location ambiguity and reduced accuracy of travel time estimation. Therefore, the accuracy of travel time estimations by Bluetooth Technology (BT) depends upon how location ambiguity is handled by the estimation method. The issue of multiple detection events...

  4. LHC 2008 talks Peut-on voyager dans le temps? (Is time travel possible?)

    CERN Multimedia

    2008-01-01

    Scientific magazines (and sometimes even scientists themselves) regularly talk about the possibility of travelling through time. It has also been the subject of many science-fiction novels. We will first discuss what we mean when we talk about time travel, then explain what contemporary physics has to say about it. Thursday, 12 June 2008 at 8.00 p.m. Peut-on voyager dans le temps ? Etienne Klein Physicist at CEA and Doctor of Philosophy of Science The Globe, first floor No specialist knowledge required. Entrance free. http://www.cern.ch/globe

  5. Effect of Travel Distance and Time to Radiotherapy on Likelihood of Receiving Mastectomy

    Science.gov (United States)

    Goyal, Sharad; Chandwani, Sheenu; Haffty, Bruce G.; Demissie, Kitaw

    2016-01-01

    Background Breast-conserving surgery (BCS) followed by adjuvant radiation therapy (RT) is the standard of care for women with early-stage breast cancer as an alternative to mastectomy. The purpose of this study was to examine the relationship between receipt of mastectomy and travel distance and time to RT facility in New Jersey (NJ). Methods Data were collected from a cohort of 634 NJ women diagnosed with early-stage breast cancer. In patients receiving RT, the precise RT facility was used, whereas in patients not receiving RT, surgeons were contacted to determine the location of RT referral. Travel distance and time to RT facility from the patients’ residential address were modeled separately using multiple binomial regression to examine their association with choice of surgery while adjusting for clinical and sociodemographic factors. Results Overall, 58.5 % patients underwent BCS with median travel distance to the radiation facility of 4.8 miles (vs. 6.6 miles for mastectomy) and median travel time of 12.0 min (vs. 15.0 min for mastectomy). Patients residing >9.2 miles compared with ≤9.2 miles from radiation facility were 44 % more likely to receive mastectomy. Additionally, patients requiring >19 min compared with ≤19 min of travel time were 36 % more likely to receive mastectomy. Conclusions These data found that travel distance and time from RT facility act as barriers to undergoing BCS in women with early-stage breast cancer. Despite being in an urban region, a significant number of women in NJ with early-stage breast cancer did not receive BCS. PMID:25245129

  6. Black Holes Traveling Exhibition: This Time, It's Personal.

    Science.gov (United States)

    Dussault, Mary E.; Braswell, E. L.; Sunbury, S.; Wasser, M.; Gould, R. R.

    2012-01-01

    How can you make a topic as abstract as black holes seem relevant to the life of the average museum visitor? In 2009, the Harvard-Smithsonian Center for Astrophysics developed a 2500 square foot interactive museum exhibition, "Black Holes: Space Warps & Time Twists,” with funding from the National Science Foundation and NASA. The exhibition has been visited by more than a quarter million museum-goers, and is about to open in its sixth venue at the Reuben H. Fleet Science Center in San Diego, California. We have found that encouraging visitors to adopt a custom black hole explorer's identity can help to make the science of black holes more accessible and meaningful. The Black Holes exhibition uses networked exhibit technology that serves to personalize the visitor experience, to support learning over time including beyond the gallery, and to provide a rich quantitative source of embedded evaluation data. Visitors entering the exhibition create their own bar-coded "Black Holes Explorer's Card” which they use throughout the exhibition to collect and record images, movies, their own predictions and conclusions, and other black hole artifacts. This digital database of personal discoveries grows as visitors navigate through the gallery, and an automated web-content authoring system creates a personalized online journal of their experience that they can access once they get home. We report here on new intriguing results gathered from data generated by 112,000 visitors across five different venues. For example, an initial review of the data reveals correlations between visitors’ black hole explorer identity choices and their engagement with the exhibition. We will also discuss correlations between learning gains and personalization.

  7. Use of Low-Level Sensor Data to Improve the Accuracy of Bluetooth-Based Travel Time Estimation

    DEFF Research Database (Denmark)

    Araghi, Bahar Namaki; Christensen, Lars Tørholm; Krishnan, Rajesh

    2013-01-01

    by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple detection...... events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first detection event (enter-enter) as the best estimate. No systematic analysis has been conducted...... to explore the most accurate method of travel time estimation with multiple detection events. In this study, different aspects of the Bluetooth detection zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter...

  8. Use of Low-Level Sensor Data to Improve the Accuracy of Bluetooth-Based Travel Time Estimation

    DEFF Research Database (Denmark)

    Araghi, Bahar Namaki; Christensen, Lars Tørholm; Krishnan, Rajesh

    2013-01-01

    by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple detection...... events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first detection event (enter-enter) as the best estimate. No systematic analysis has been conducted...... to explore the most accurate method of travel time estimation with multiple detection events. In this study, different aspects of the Bluetooth detection zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter...

  9. Travel during Pregnancy

    Science.gov (United States)

    ... Events Advocacy For Patients About ACOG Travel During Pregnancy Home For Patients Search FAQs Travel During Pregnancy ... Pregnancy FAQ055, February 2016 PDF Format Travel During Pregnancy Pregnancy When is the best time to travel ...

  10. Local algorithm for computing complex travel time based on the complex eikonal equation.

    Science.gov (United States)

    Huang, Xingguo; Sun, Jianguo; Sun, Zhangqing

    2016-04-01

    The traditional algorithm for computing the complex travel time, e.g., dynamic ray tracing method, is based on the paraxial ray approximation, which exploits the second-order Taylor expansion. Consequently, the computed results are strongly dependent on the width of the ray tube and, in regions with dramatic velocity variations, it is difficult for the method to account for the velocity variations. When solving the complex eikonal equation, the paraxial ray approximation can be avoided and no second-order Taylor expansion is required. However, this process is time consuming. In this case, we may replace the global computation of the whole model with local computation by taking both sides of the ray as curved boundaries of the evanescent wave. For a given ray, the imaginary part of the complex travel time should be zero on the central ray. To satisfy this condition, the central ray should be taken as a curved boundary. We propose a nonuniform grid-based finite difference scheme to solve the curved boundary problem. In addition, we apply the limited-memory Broyden-Fletcher-Goldfarb-Shanno technology for obtaining the imaginary slowness used to compute the complex travel time. The numerical experiments show that the proposed method is accurate. We examine the effectiveness of the algorithm for the complex travel time by comparing the results with those from the dynamic ray tracing method and the Gauss-Newton Conjugate Gradient fast marching method.

  11. MINIMIZING COMPUTATIONAL ERRORS OF TSUNAMI WAVE-RAY AND TRAVEL TIME

    Directory of Open Access Journals (Sweden)

    Andrei G. Marchuk

    2008-01-01

    Full Text Available There are many methods for computing tsunami kinematics directly and inversely. The direct detection of waves in the deep ocean makes it possible to establish tsunami source characteristics and origin. Thus, accuracy of computational methods is very important in obtaining reliable results. In a non-homogeneous medium where tsunami wave propagation velocity varies, it is not very easy to determine a wave-ray that connects two given points along a path. The present study proposes modification in the methodology of determining tsunami travel-times and of wave-ray paths. An approximate ray trace path can be developed from a source origin point to any other point on a computational grid by solving directly the problem - and thus obtain the tsunami travel- times. The initial ray approximation can be optimized with the use of an algorithm that calculates all potential variations and applies corrections to travel-time values. Such an algorithm was tested in an area with model bathymetry and compared with a non-optimized method. The latter exceeded the optimized method by one minute of travel-time for every hour of tsunami propagation time.

  12. Local algorithm for computing complex travel time based on the complex eikonal equation

    Science.gov (United States)

    Huang, Xingguo; Sun, Jianguo; Sun, Zhangqing

    2016-04-01

    The traditional algorithm for computing the complex travel time, e.g., dynamic ray tracing method, is based on the paraxial ray approximation, which exploits the second-order Taylor expansion. Consequently, the computed results are strongly dependent on the width of the ray tube and, in regions with dramatic velocity variations, it is difficult for the method to account for the velocity variations. When solving the complex eikonal equation, the paraxial ray approximation can be avoided and no second-order Taylor expansion is required. However, this process is time consuming. In this case, we may replace the global computation of the whole model with local computation by taking both sides of the ray as curved boundaries of the evanescent wave. For a given ray, the imaginary part of the complex travel time should be zero on the central ray. To satisfy this condition, the central ray should be taken as a curved boundary. We propose a nonuniform grid-based finite difference scheme to solve the curved boundary problem. In addition, we apply the limited-memory Broyden-Fletcher-Goldfarb-Shanno technology for obtaining the imaginary slowness used to compute the complex travel time. The numerical experiments show that the proposed method is accurate. We examine the effectiveness of the algorithm for the complex travel time by comparing the results with those from the dynamic ray tracing method and the Gauss-Newton Conjugate Gradient fast marching method.

  13. Using ERS spaceborne microwave soil moisture observations to predict groundwater head in space and time

    NARCIS (Netherlands)

    Sutanudjaja, E.H.; De Jong, S.M.; Van Geer, F.C.; Bierkens, M.F.P.

    2013-01-01

    The study presented in this paper is to investigate the possibility of using spaceborne remote sensing data for groundwater head prediction. Remotely-sensed soil moisture time series of SWI (Soil Water Index) derived from ERS (European Remote Sensing) scatterometers are used to predict groundwater

  14. Using ERS spaceborne microwave soil moisture observations to predict groundwater heads in space and time

    NARCIS (Netherlands)

    Sutanudjaja, E.H.; Jong, S.M. de; Bierkens, M.F.P.; Geer, F.C. van

    2013-01-01

    The study presented in this paper is to investigate the possibility of using spaceborne remote sensing data for groundwater head prediction. Remotely-sensed soil moisture time series of SWI (Soil Water Index) derived from ERS (European Remote Sensing) scatterometers are used to predict groundwater

  15. The effect of centralization of health care services on travel time and its equality.

    Science.gov (United States)

    Kobayashi, Daisuke; Otsubo, Tetsuya; Imanaka, Yuichi

    2015-03-01

    To analyze the regional variations in travel time between patient residences and medical facilities for the treatment of ischemic heart disease and breast cancer, and to simulate the effects of health care services centralization on travel time and equality of access. We used medical insurance claims data for inpatients and outpatients for the two target diseases that had been filed between September 2008 and May 2009 in Kyoto Prefecture, Japan. Using a geographical information system, patient travel times were calculated based on the driving distance between patient residences and hospitals via highways and toll roads. Locations of residences and hospital locations were identified using postal codes. We then conducted a simulation analysis of centralization of health care services to designated regional core hospitals. The simulated changes in potential spatial access to care were examined. Inequalities in access to care were examined using Gini coefficients, which ranged from 0.4109 to 0.4574. Simulations of health care services centralization showed reduced travel time for most patients and overall improvements in equality of access, except in breast cancer outpatients. Our findings may contribute to the decision-making process in policies aimed at improving the potential spatial access to health care services. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  16. Travel Time Model of Left-Turning Vehicles at Signalized Intersection

    Directory of Open Access Journals (Sweden)

    Leng Jun-qiang

    2012-01-01

    Full Text Available The travel time of left-turning vehicles at signalized intersection was discussed. Under the assumption that the opposing through vehicles headway follows M3 distribution, the travel time model was established on the basis of gap theory and queue theory. Comparison was done with the common model based on the assumption that the opposing through vehicles headway follows negative exponential distribution. The results show that the model in this paper has stronger applicability and its most relative error is less than 15%. In addition, the sensitivity analysis was done. The results show that the opposing through flow rate has significant impact on travel time. The impact of left-turning flow rate and following headway is light when the opposing through flow rate is small, the threshold is about 0.18 veh/s. The model established in this paper can well calculate travel time of left-turning vehicles at intersection, and the methodology may provide reference to other occasions.

  17. Travel Time Model for Right-Turning Vehicles of Secondary Street at Unsignalized Intersections

    Directory of Open Access Journals (Sweden)

    Feng Yu-Qin

    2013-01-01

    Full Text Available The travel time of right-turning vehicles on secondary street at unsignalized intersection is discussed in this paper. Under the assumption that the major-street through vehicles’ headway follows Erlang distribution and secondary-street right-turning vehicles’ headway follows Poisson distribution. The right-turning vehicles travel time model is established on the basis of gap theory and M/G/1 queue theory. Comparison is done with the common model based on the assumption that the major-street vehicles’ headway follows Poisson distribution. An intersection is selected to verify each model. The results show that the model established in this paper has stronger applicability, and its most relative error is less than 15%. In addition, the sensitivity analysis has been done. The results show that right-turning flow rate and major-street flow rate have a significant impact on the travel time. Hence, the methodology for travel time of right-turning vehicles at unsignalized intersection proposed in this paper is effective and applicable.

  18. Modeling Travel Time Reliability of Road Network Considering Connected Vehicle Guidance Characteristics Indexes

    Directory of Open Access Journals (Sweden)

    Jiangfeng Wang

    2017-01-01

    Full Text Available Travel time reliability (TTR is one of the important indexes for effectively evaluating the performance of road network, and TTR can effectively be improved using the real-time traffic guidance information. Compared with traditional traffic guidance, connected vehicle (CV guidance can provide travelers with more timely and accurate travel information, which can further improve the travel efficiency of road network. Five CV characteristics indexes are selected as explanatory variables including the Congestion Level (CL, Penetration Rate (PR, Compliance Rate (CR, release Delay Time (DT, and Following Rate (FR. Based on the five explanatory variables, a TTR model is proposed using the multilogistic regression method, and the prediction accuracy and the impact of characteristics indexes on TTR are analyzed using a CV guidance scenario. The simulation results indicate that 80% of the RMSE is concentrated within the interval of 0 to 0.0412. The correlation analysis of characteristics indexes shows that the influence of CL, PR, CR, and DT on the TTR is significant. PR and CR have a positive effect on TTR, and the average improvement rate is about 77.03% and 73.20% with the increase of PR and CR, respectively, while CL and DT have a negative effect on TTR, and TTR decreases by 31.21% with the increase of DT from 0 to 180 s.

  19. Involuntary Mental Time Travel and Its Effect on Prospective Teachers' Situational Intrinsic Motivations

    Science.gov (United States)

    Eren, Altay

    2010-01-01

    Recent cognitive psychological research has argued that involuntary mental time travel is an important individual difference variable that has the potential to affect an individual's motivation. However, this issue has not been empirically investigated in educational settings such as teacher education. Therefore, this study aimed to explore the…

  20. Assessment of Smolt Condition for Travel Time Analysis, 1993-1994 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Schrock, Robin M; Beeman, John W; VanderKooi, Scott P [US Geological Survey, Western Fisheries Research Center, Columbia River Research Laboratory, Cook, WA

    1999-02-01

    The assessment of smolt condition for travel time analysis (ASCTTA) project provided information on the level of smoltification in Columbia River hatchery and wild salmonid stocks to the Fish Passage Center (FPC), for the primary purpose of in-river management of flows.

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

    Science.gov (United States)

    Paunonen, Matti

    1993-01-01

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

  2. Travel cost inference from sparse, spatio-temporally correlated time series using markov models

    DEFF Research Database (Denmark)

    Yang, B.; Guo, C.; Jensen, C.S.

    2013-01-01

    of such time series offers insight into the underlying system and enables prediction of system behavior. While the techniques presented in the paper apply more generally, we consider the case of transportation systems and aim to predict travel cost from GPS tracking data from probe vehicles. Specifically, each......The monitoring of a system can yield a set of measurements that can be modeled as a collection of time series. These time series are often sparse, due to missing measurements, and spatiotemporally correlated, meaning that spatially close time series exhibit temporal correlation. The analysis...... road segment has an associated travel-cost time series, which is derived from GPS data. We use spatio-temporal hidden Markov models (STHMM) to model correlations among different traffic time series. We provide algorithms that are able to learn the parameters of an STHMM while contending...

  3. Travelling wave solutions for some time-delayed equations through factorizations

    Energy Technology Data Exchange (ETDEWEB)

    Fahmy, E.S. [King Saud University, Women Students Medical Studies and Sciences Sections, Mathematics Department, P.O. Box 22452, Riyadh 11495 (Saudi Arabia)], E-mail: esfahmy@operamail.com

    2008-11-15

    In this work, we use factorization method to find explicit particular travelling wave solutions for the following important nonlinear second-order partial differential equations: The generalized time-delayed Burgers-Huxley, time-delayed convective Fishers, and the generalized time-delayed Burgers-Fisher. Using the particular solutions for these equations we find the general solutions, two-parameter solution, as special cases.

  4. Effects of task complexity and time pressure on activity-travel choices: heteroscedastic logit model and activity-travel simulator experiment

    NARCIS (Netherlands)

    Chen, C.; Chorus, C.G.; Molin, E.J.E.; Van Wee, G.P.

    2015-01-01

    This paper derives, estimates and applies a discrete choice model of activity-travel behaviour that accommodates potential effects of task complexity and time pressure on decision-making. To the best of our knowledge, this is the first time that both factors (task complexity and time pressure) are

  5. Effects of task complexity and time pressure on activity-travel choices: heteroscedastic logit model and activity-travel simulator experiment

    NARCIS (Netherlands)

    Chen, C.; Chorus, C.G.; Molin, E.J.E.; Van Wee, G.P.

    2015-01-01

    This paper derives, estimates and applies a discrete choice model of activity-travel behaviour that accommodates potential effects of task complexity and time pressure on decision-making. To the best of our knowledge, this is the first time that both factors (task complexity and time pressure) are j

  6. A crust and upper mantle model of Eurasia and North Africa for Pn travel time calculation

    Energy Technology Data Exchange (ETDEWEB)

    Myers, S; Begnaud, M; Ballard, S; Pasyanos, M; Phillips, W S; Ramirez, A; Antolik, M; Hutchenson, K; Dwyer, J; Rowe, C; Wagner, G

    2009-03-19

    We develop a Regional Seismic Travel Time (RSTT) model and methods to account for the first-order effect of the three-dimensional crust and upper mantle on travel times. The model parameterization is a global tessellation of nodes with a velocity profile at each node. Interpolation of the velocity profiles generates a 3-dimensional crust and laterally variable upper mantle velocity. The upper mantle velocity profile at each node is represented as a linear velocity gradient, which enables travel time computation in approximately 1 millisecond. This computational speed allows the model to be used in routine analyses in operational monitoring systems. We refine the model using a tomographic formulation that adjusts the average crustal velocity, mantle velocity at the Moho, and the mantle velocity gradient at each node. While the RSTT model is inherently global and our ultimate goal is to produce a model that provides accurate travel time predictions over the globe, our first RSTT tomography effort covers Eurasia and North Africa, where we have compiled a data set of approximately 600,000 Pn arrivals that provide path coverage over this vast area. Ten percent of the tomography data are randomly selected and set aside for testing purposes. Travel time residual variance for the validation data is reduced by 32%. Based on a geographically distributed set of validation events with epicenter accuracy of 5 km or better, epicenter error using 16 Pn arrivals is reduced by 46% from 17.3 km (ak135 model) to 9.3 km after tomography. Relative to the ak135 model, the median uncertainty ellipse area is reduced by 68% from 3070 km{sup 2} to 994 km{sup 2}, and the number of ellipses with area less than 1000 km{sup 2}, which is the area allowed for onsite inspection under the Comprehensive Nuclear Test Ban Treaty, is increased from 0% to 51%.

  7. Analytic solutions for seismic travel time and ray path geometry through simple velocity models.

    Energy Technology Data Exchange (ETDEWEB)

    Ballard, Sanford

    2007-12-01

    The geometry of ray paths through realistic Earth models can be extremely complex due to the vertical and lateral heterogeneity of the velocity distribution within the models. Calculation of high fidelity ray paths and travel times through these models generally involves sophisticated algorithms that require significant assumptions and approximations. To test such algorithms it is desirable to have available analytic solutions for the geometry and travel time of rays through simpler velocity distributions against which the more complex algorithms can be compared. Also, in situations where computational performance requirements prohibit implementation of full 3D algorithms, it may be necessary to accept the accuracy limitations of analytic solutions in order to compute solutions that satisfy those requirements. Analytic solutions are described for the geometry and travel time of infinite frequency rays through radially symmetric 1D Earth models characterized by an inner sphere where the velocity distribution is given by the function V (r) = A-Br{sup 2}, optionally surrounded by some number of spherical shells of constant velocity. The mathematical basis of the calculations is described, sample calculations are presented, and results are compared to the Taup Toolkit of Crotwell et al. (1999). These solutions are useful for evaluating the fidelity of sophisticated 3D travel time calculators and in situations where performance requirements preclude the use of more computationally intensive calculators. It should be noted that most of the solutions presented are only quasi-analytic. Exact, closed form equations are derived but computation of solutions to specific problems generally require application of numerical integration or root finding techniques, which, while approximations, can be calculated to very high accuracy. Tolerances are set in the numerical algorithms such that computed travel time accuracies are better than 1 microsecond.

  8. Impulse Travel Time from the Magnetotail to the Aurora Region during substorm: OpenGGCM Simulation

    Science.gov (United States)

    Ferdousi, Banafsheh; Raeder, Jimmy

    2016-07-01

    The onset of substorms is an unsolved problem in Space Physics although there are many models explaining the substorm process. Studying the processes that occur during first 2 minutes of substorm depends critically on the correct timing between different signals in the plasma sheet and the ionosphere. This has been difficult to accomplish with data alone, since signals are sometimes ambiguous, or they have not been observed in the right locations. To investigate signal propagation paths and signal travel times, we use Magnetohydrodynamic global simulations of the Earth magnetosphere: OpenGGCM. The waves are created at different locations in the magnetotail by perturbing plasma pressure in the plasma sheet. Thus, we can study wave path in the magnetotail and determine its travel time to the ionosphere. Contrary to previous studies, we find that wave travel reach the ionosphere from the midtail around 60 seconds. We also find that waves travel faster through the lobes, and the Tamao path is not generally the preferred path for waves originating in the plasma sheet. Furthermore, we find that the impulses that are generated closer to earth lead to dispersed ionosphere signatures, whereas the impulses originated in midtail region lead to more localized signatures.

  9. Optimal paths planning in dynamic transportation networks with random link travel times

    Institute of Scientific and Technical Information of China (English)

    孙世超; 段征宇; 杨东援

    2014-01-01

    A theoretical study was conducted on finding optimal paths in transportation networks where link travel times were stochastic and time-dependent (STD). The methodology of relative robust optimization was applied as measures for comparing time-varying, random path travel times for a priori optimization. In accordance with the situation in real world, a stochastic consistent condition was provided for the STD networks and under this condition, a mathematical proof was given that the STD robust optimal path problem can be simplified into a minimum problem in specific time-dependent networks. A label setting algorithm was designed and tested to find travelers’ robust optimal path in a sampled STD network with computation complexity of O(n2+n·m). The validity of the robust approach and the designed algorithm were confirmed in the computational tests. Compared with conventional probability approach, the proposed approach is simple and efficient, and also has a good application prospect in navigation system.

  10. [Groundwater].

    Science.gov (United States)

    González De Posada, Francisco

    2012-01-01

    From the perspective of Hydrogeology, the concept and an introductory general typology of groundwater are established. From the perspective of Geotechnical Engineering works, the physical and mathematical equations of the hydraulics of permeable materials, which are implemented, by electric analogical simulation, to two unique cases of global importance, are considered: the bailing during the construction of the dry dock of the "new shipyard of the Bahia de Cádiz" and the waterproofing of the "Hatillo dam" in the Dominican Republic. From a physical fundamental perspective, the theories which are the subset of "analogical physical theories of Fourier type transport" are related, among which the one constituted by the laws of Adolf Fick in physiology occupies a historic role of some relevance. And finally, as a philosophical abstraction of so much useful mathematical process, the one which is called "the Galilean principle of the mathematical design of the Nature" is dealt with.

  11. Inferring changes in water cycle dynamics of intensively managed landscapes via the theory of time-variant travel time distributions

    Science.gov (United States)

    Danesh-Yazdi, Mohammad; Foufoula-Georgiou, Efi; Karwan, Diana L.; Botter, Gianluca

    2016-10-01

    Climatic trends and anthropogenic changes in land cover and land use are impacting the hydrology and water quality of streams at the field, watershed, and regional scales in complex ways. In poorly drained agricultural landscapes, subsurface drainage systems have been successful in increasing crop productivity by removing excess soil moisture. However, their hydroecological consequences are still debated in view of the observed increased concentrations of nitrate, phosphorus, and pesticides in many streams, as well as altered runoff volumes and timing. In this study, we employ the recently developed theory of time-variant travel time distributions within the StorAge Selection function framework to quantify changes in water cycle dynamics resulting from the combined climate and land use changes. Our results from analysis of a subbasin in the Minnesota River Basin indicate a significant decrease in the mean travel time of water in the shallow subsurface layer during the growing season under current conditions compared to the pre-1970s conditions. We also find highly damped year-to-year fluctuations in the mean travel time, which we attribute to the "homogenization" of the hydrologic response due to artificial drainage. The dependence of the mean travel time on the spatial heterogeneity of some soil characteristics as well as on the basin scale is further explored via numerical experiments. Simulations indicate that the mean travel time is independent of scale for spatial scales larger than approximately 200 km2, suggesting that hydrologic data from larger basins may be used to infer the average of smaller-scale-driven changes in water cycle dynamics.

  12. A Vehicle Traveling Time Prediction Method Based on Grey Theory and Linear Regression Analysis

    Institute of Scientific and Technical Information of China (English)

    TU Jun; LI Yan-ming; LIU Cheng-liang

    2009-01-01

    Vehicle traveling time prediction is an important part of the research of intelligent transportation system. By now, there have been various kinds of methods for vehicle traveling time prediction. But few consider both aspects of time and space. In this paper, a vehicle traveling time prediction method based on grey theory (GT) and linear regression analysis (LRA) is presented. In aspects of time, we use the history data sequence of bus speed on a certain road to predict the future bus speed on that road by GT. And in aspects of space, we calculate the traffic affecting factors between various roads by LRA. Using these factors we can predict the vehicle's speed at the lower road if the vehicle's speed at the current road is known. Finally we use time factor and space factor as the weighting factors of the two results predicted by GT and LRA respectively to find the fina0l result, thus calculating the vehicle's travehng time. The method also considers such factors as dwell time, thus making the prediction more accurate.

  13. Interactive, open source, travel time scenario modelling: tools to facilitate participation in health service access analysis.

    Science.gov (United States)

    Fisher, Rohan; Lassa, Jonatan

    2017-04-18

    Modelling travel time to services has become a common public health tool for planning service provision but the usefulness of these analyses is constrained by the availability of accurate input data and limitations inherent in the assumptions and parameterisation. This is particularly an issue in the developing world where access to basic data is limited and travel is often complex and multi-modal. Improving the accuracy and relevance in this context requires greater accessibility to, and flexibility in, travel time modelling tools to facilitate the incorporation of local knowledge and the rapid exploration of multiple travel scenarios. The aim of this work was to develop simple open source, adaptable, interactive travel time modelling tools to allow greater access to and participation in service access analysis. Described are three interconnected applications designed to reduce some of the barriers to the more wide-spread use of GIS analysis of service access and allow for complex spatial and temporal variations in service availability. These applications are an open source GIS tool-kit and two geo-simulation models. The development of these tools was guided by health service issues from a developing world context but they present a general approach to enabling greater access to and flexibility in health access modelling. The tools demonstrate a method that substantially simplifies the process for conducting travel time assessments and demonstrate a dynamic, interactive approach in an open source GIS format. In addition this paper provides examples from empirical experience where these tools have informed better policy and planning. Travel and health service access is complex and cannot be reduced to a few static modeled outputs. The approaches described in this paper use a unique set of tools to explore this complexity, promote discussion and build understanding with the goal of producing better planning outcomes. The accessible, flexible, interactive and

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

    Science.gov (United States)

    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.

  15. Geochemical and isotopic investigations on groundwater residence time and flow in the Independence Basin, Mexico

    Science.gov (United States)

    Mahlknecht, J.; Gárfias-Solis, J.; Aravena, R.; Tesch, R.

    2006-06-01

    The Independence Basin in the semi-arid Guanajuato state of central Mexico is facing serious groundwater resources deficiency due to an increasing demand linked to a rapid population growth and agricultural development. This problem is aggravated by an inadequate evaluation of groundwater resources in the region. Geochemistry and isotopic tracers were used in order to investigate the groundwater flow system and estimate the groundwater residence time. The groundwater is characterized by low salinity with some exceptions associated to a contribution of more saline groundwater from deep formations. The predominant reactions are CO 2 gas dissolution, carbonate dissolution, albite weathering, kaolinite and chalcedony precipitation. Six principal hydrochemical zones were recognized, which provided information on plausible recharge sources and groundwater chemical evolution. The 14C concentration varies between 19 and 94 pmc. The high 14C values indicating recent recharge are observed at the basin margins and a trend to lower 14C values is observed along the modern groundwater flow paths. The groundwater residence time according to radiocarbon estimations ranges between recent and ˜11 ka. The residence time distribution matches the regional important discharge zones west in the basin center (from Dolores Hidalgo and southwest from Doctor Mora). Hydrochemical tracers are in general agreement with the predeveloped and current hydraulic-head configuration, however, show some inconsistencies with the predeveloped head in the downgradient areas, which means that the impact by gradually increasing groundwater extraction during the last decades is reflected on radiocarbon age distribution. Geochemical evidences imply that the recharge input from the northern basin area is insignificant.

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

    Science.gov (United States)

    Zhao, Guangyu; Ruan, Shigui

    2011-06-01

    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(*).

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

    Science.gov (United States)

    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*. PMID:21572575

  18. Branch-and-cut-and-price for the traveling salesman problem with time windows

    DEFF Research Database (Denmark)

    Røpke, Stefan; Madsen, Oli B.G.

    In the traveling salesman problem with time windows (TSPTW) one is given a depot and a set of nodes to be visited by a salesman. The salesman starts his trip at the depot and must visit all nodes while respecting time windows at the nodes. The objective of the problem is to minimize the total...... distance traveled by the salesman. The TSPTW is formulated as a set-partitioning problem which is solved by using combined cut and column generation. The pricing sub problem in the column generation procedure is a shortest path problem with time window constraints and 2-cycle elimination. A standard column...... generation process converges slowly for the problem and therefore a stabilization procedure is implemented. Valid inequalities expressed in the original, arc-based variables are added to the LP relaxation to strengthen the lower bound. The proposed algorithm is compared to exact algorithms based on other...

  19. Modeling Effect of Travel Time Uncertainty and Traffic Information on Use of Park-and-Ride Facilities

    NARCIS (Netherlands)

    Bos, D.M.; Ettema, D.; Molin, E.J.E.

    2004-01-01

    An approach is presented to determine the effect of travel time uncertainty and traffic information on mode choice in general and on the potential patronage of park-and-ride (P&R) facilities in particular. An expected-utility approach is applied to model the effect of travel time uncertainty and

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Alkın Yurtkuran

    2014-01-01

    Full Text Available 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.

  2. Travel-time tomography in shallow water: experimental demonstration at an ultrasonic scale.

    Science.gov (United States)

    Roux, Philippe; Iturbe, Ion; Nicolas, Barbara; Virieux, Jean; Mars, Jérôme I

    2011-09-01

    Acoustic tomography in a shallow ultrasonic waveguide is demonstrated at the laboratory scale between two source-receiver arrays. At a 1/1,000 scale, the waveguide represents a 1.1-km-long, 52-m-deep ocean acoustic channel in the kilohertz frequency range. Two coplanar arrays record the transfer matrix in the time domain of the waveguide between each pair of source-receiver transducers. A time-domain, double-beamforming algorithm is simultaneously performed on the source and receiver arrays that projects the multi-reflected acoustic echoes into an equivalent set of eigenrays, which are characterized by their travel times and their launch and arrival angles. Travel-time differences are measured for each eigenray every 0.1 s when a thermal plume is generated at a given location in the waveguide. Travel-time tomography inversion is then performed using two forward models based either on ray theory or on the diffraction-based sensitivity kernel. The spatially resolved range and depth inversion data confirm the feasibility of acoustic tomography in shallow water. Comparisons are made between inversion results at 1 and 3 MHz with the inversion procedure using ray theory or the finite-frequency approach. The influence of surface fluctuations at the air-water interface is shown and discussed in the framework of shallow-water ocean tomography.

  3. Estimating the Value of Life, Injury, and Travel Time Saved Using a Stated Preference Framework.

    Science.gov (United States)

    Niroomand, Naghmeh; Jenkins, Glenn P

    2016-06-01

    The incidence of fatality over the period 2010-2014 from automobile accidents in North Cyprus is 2.75 times greater than the average for the EU. With the prospect of North Cyprus entering the EU, many investments will need to be undertaken to improve road safety in order to reach EU benchmarks. The objective of this study is to provide local estimates of the value of a statistical life and injury along with the value of time savings. These are among the parameter values needed for the evaluation of the change in the expected incidence of automotive accidents and time savings brought about by such projects. In this study we conducted a stated choice experiment to identify the preferences and tradeoffs of automobile drivers in North Cyprus for improved travel times, travel costs, and safety. The choice of route was examined using mixed logit models to obtain the marginal utilities associated with each attribute of the routes that consumers choose. These estimates were used to assess the individuals' willingness to pay (WTP) to avoid fatalities and injuries and to save travel time. We then used the results to obtain community-wide estimates of the value of a statistical life (VSL) saved, the value of injury (VI) prevented, and the value per hour of travel time saved. The estimates for the VSL range from €315,293 to €1,117,856 and the estimates of VI from € 5,603 to € 28,186. These values are consistent, after adjusting for differences in incomes, with the median results of similar studies done for EU countries. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. [Differences between Dutch provinces in perinatal mortality and travel time to hospital].

    Science.gov (United States)

    Ravelli, Anita C J; Rijninks-van Driel, Greta C; Erwich, Jan Jaap H M; Mol, Ben Willem J; Brouwers, Hens A A; Abu Hanna, Ameen; Eskes, Martine

    2011-01-01

    To investigate differences in perinatal mortality between Dutch provinces and to determine the significance of risk factors including travel time from home to the hospital during labour. Cohort study. The study was based on 1,242,725 singleton births in 2000-2006 as recorded in the Netherlands Perinatal Registry. The influence of province on perinatal mortality was estimated, with logistic regression analysis adjusting for risk factors (age, parity, ethnicity, socioeconomic status) and care factors such as start of antenatal care and travel time. The perinatal mortality rate in the Netherlands was 9.9 per 1000 births. The provinces with the highest mortality rates were Friesland (11.3‰), Groningen (11.1‰), Zeeland (10.6‰) and Flevoland (10.4‰). Noord-Brabant (9.2‰) and Limburg (9.2‰) had the lowest mortality rates. These differences were significantly higher for Friesland (odds ratio: 1.16; 95%-CI: 1.05-1.28) and Groningen (odds ratio: 1.13; 95%-CI: 1.02-1.26). Starting late with perinatal care, at 18 weeks of gestation or later was an important risk factor (adjusted odds ratio 1.8; 95%-CI: 1.7-1.8). Low socio-economic status could partly be associated with the higher mortality risk in Groningen. Longer travel time (≥ 20 minutes) was an independent risk factor associated with perinatal mortality. On average 19% of the women travelled ≥ 20 minutes to the hospital. In the provinces Groningen, Friesland, Flevoland and Zeeland these percentages ranged between 32 and 36%. The adjusted odds ratio of travel time was 1.7 (95%-CI 1.6-1.7). The perinatal mortality differs per province. This can be explained by longer travel time to the hospital during labour. Late start of perinatal care and low socio-economic status also affect the mortality rate. These risk factors need to be taken into account during registration, investigation, audit and obstetric policy.

  5. Urban Freight Management with Stochastic Time-Dependent Travel Times and Application to Large-Scale Transportation Networks

    Directory of Open Access Journals (Sweden)

    Shichao Sun

    2015-01-01

    Full Text Available This paper addressed the vehicle routing problem (VRP in large-scale urban transportation networks with stochastic time-dependent (STD travel times. The subproblem which is how to find the optimal path connecting any pair of customer nodes in a STD network was solved through a robust approach without requiring the probability distributions of link travel times. Based on that, the proposed STD-VRP model can be converted into solving a normal time-dependent VRP (TD-VRP, and algorithms for such TD-VRPs can also be introduced to obtain the solution. Numerical experiments were conducted to address STD-VRPTW of practical sizes on a real world urban network, demonstrated here on the road network of Shenzhen, China. The stochastic time-dependent link travel times of the network were calibrated by historical floating car data. A route construction algorithm was applied to solve the STD problem in 4 delivery scenarios efficiently. The computational results showed that the proposed STD-VRPTW model can improve the level of customer service by satisfying the time-window constraint under any circumstances. The improvement can be very significant especially for large-scale network delivery tasks with no more increase in cost and environmental impacts.

  6. 41 CFR 301-71.306 - Are there exceptions to collecting an advance at the time the employee files a travel claim?

    Science.gov (United States)

    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...

  7. Efficient evaluation of shortest travel-time path queries through spatial mashups

    KAUST Repository

    Zhang, Detian

    2017-01-07

    In the real world, the route/path with the shortest travel time in a road network is more meaningful than that with the shortest network distance for location-based services (LBS). However, not every LBS provider has adequate resources to compute/estimate travel time for routes by themselves. A cost-effective way for LBS providers to estimate travel time for routes is to issue external route requests to Web mapping services (e.g., Google Maps, Bing Maps, and MapQuest Maps). Due to the high cost of processing such external route requests and the usage limits of Web mapping services, we take the advantage of direction sharing, parallel requesting and waypoints supported by Web mapping services to reduce the number of external route requests and the query response time for shortest travel-time route queries in this paper. We first give the definition of sharing ability to reflect the possibility of sharing the direction information of a route with others, and find out the queries that their query routes are independent with each other for parallel processing. Then, we model the problem of selecting the optimal waypoints for an external route request as finding the longest simple path in a weighted complete digraph. As it is a MAX SNP-hard problem, we propose a greedy algorithm with performance guarantee to find the best set of waypoints in an external route request. We evaluate the performance of our approach using a real Web mapping service, a real road network, real and synthetic data sets. Experimental results show the efficiency, scalability, and applicability of our approach.

  8. An empirical method for estimating travel times for wet volcanic mass flows

    Science.gov (United States)

    Pierson, Thomas C.

    1998-01-01

    Travel times for wet volcanic mass flows (debris avalanches and lahars) can be forecast as a function of distance from source when the approximate flow rate (peak discharge near the source) can be estimated beforehand. The near-source flow rate is primarily a function of initial flow volume, which should be possible to estimate to an order of magnitude on the basis of geologic, geomorphic, and hydrologic factors at a particular volcano. Least-squares best fits to plots of flow-front travel time as a function of distance from source provide predictive second-degree polynomial equations with high coefficients of determination for four broad size classes of flow based on near-source flow rate: extremely large flows (>1 000 000 m3/s), very large flows (10 000–1 000 000 m3/s), large flows (1000–10 000 m3/s), and moderate flows (100–1000 m3/s). A strong nonlinear correlation that exists between initial total flow volume and flow rate for "instantaneously" generated debris flows can be used to estimate near-source flow rates in advance. Differences in geomorphic controlling factors among different flows in the data sets have relatively little effect on the strong nonlinear correlations between travel time and distance from source. Differences in flow type may be important, especially for extremely large flows, but this could not be evaluated here. At a given distance away from a volcano, travel times can vary by approximately an order of magnitude depending on flow rate. The method can provide emergency-management officials a means for estimating time windows for evacuation of communities located in hazard zones downstream from potentially hazardous volcanoes.

  9. Stability of Intelligent Transportation Network Dynamics: A Daily Path Flow Adjustment considering Travel Time Differentiation

    Directory of Open Access Journals (Sweden)

    Ming-Chorng Hwang

    2015-01-01

    Full Text Available A theoretic formulation on how traffic time information distributed by ITS operations influences the trajectory of network flows is presented in this paper. The interactions between users and ITS operator are decomposed into three parts: (i travel time induced path flow dynamics (PFDTT; (ii demand induced path flow dynamics (PFDD; and (iii predicted travel time dynamics for an origin-destination (OD pair (PTTDOD. PFDTT describes the collective results of user’s daily route selection by pairwise comparison of path travel time provided by ITS services. The other two components, PTTDOD and PFDD, are concentrated on the evolutions of system variables which are predicted and observed, respectively, by ITS operators to act as a benchmark in guiding the target system towards an expected status faster. In addition to the delivered modelings, the stability theorem of the equilibrium solution in the sense of Lyapunov stability is also provided. A Lyapunov function is developed and employed to the proof of stability theorem to show the asymptotic behavior of the aimed system. The information of network flow dynamics plays a key role in traffic control policy-making. The evaluation of ITS-based strategies will not be reasonable without a well-established modeling of network flow evolutions.

  10. Adjoint Tomography of Taiwan Region: From Travel-Time Toward Waveform Inversion

    Science.gov (United States)

    Huang, H. H.; Lee, S. J.; Tromp, J.

    2014-12-01

    The complicated tectonic environment such as Taiwan region can modulate the seismic waveform severely and hamper the discrimination and the utilization of later phases. Restricted to the use of only first arrivals of P- and S-wave, the travel-time tomographic models of Taiwan can simulate the seismic waveform barely to a frequency of 0.2 Hz to date. While it has been sufficient for long-period studies, e.g. source inversion, this frequency band is still far from the applications to the community and high-resolution studies. To achieve a higher-frequency simulation, more data and the considerations of off-path and finite-frequency effects are necessary. Based on the spectral-element and the adjoint method recently developed, we prepared 94 MW 3.5-6.0 earthquakes with well-defined location and focal mechanism solutions from Real-Time Moment Tensor Monitoring System (RMT), and preformed an iterative gradient-based inversion employing waveform modeling and finite-frequency measurements of adjoint method. By which the 3-D sensitivity kernels are taken into account realistically and the full waveform information are naturally sought, without a need of any phase pick. A preliminary model m003 using 10-50 sec data was demonstrated and compared with previous travel-time models. The primary difference appears in the mountainous area, where the previous travel-time model may underestimate the S-wave speed in the upper crust, but overestimates in the lower crust.

  11. Near surface spatially averaged air temperature and wind speed determined by acoustic travel time tomography

    Directory of Open Access Journals (Sweden)

    Armin Raabe

    2001-03-01

    Full Text Available Acoustic travel time tomography is presented as a possibility for remote monitoring of near surface airtemperature and wind fields. This technique provides line-averaged effective sound speeds changing with temporally and spatially variable air temperature and wind vector. The effective sound speed is derived from the travel times of sound signals which propagate at defined paths between different acoustic sources and receivers. Starting with the travel time data a tomographic algorithm (Simultaneous Iterative Reconstruction Technique, SIRT is used to calculate area-averaged air temperature and wind speed. The accuracy of the experimental method and the tomographic inversion algorithm is exemplarily demonstrated for one day without remarkable differences in the horizontal temperature field, determined by independent in situ measurements at different points within the measuring field. The differences between the conventionally determined air temperature (point measurement and the air temperature determined by tomography (area-averaged measurement representative for the area of the measuring field 200m x 260m were below 0.5 K for an average of 10 minutes. The differences obtained between the wind speed measured at a meteorological mast and calculated from acoustic measurements are not higher than 0.5 ms-1 for the same averaging time. The tomographically determined area-averaged distribution of air temperature (resolution 50 m x 50 m can be used to estimate the horizontal gradient of air temperature as a pre-condition to detect horizontal turbulent fluxes of sensible heat.

  12. Assessment of Smolt Condition for Travel Time Analysis, 1990 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Beeman, John W.; Rondorf, Dennis W.; Faler, Joyce C. (Seattle National Fishery Research Center, Columbia River Field Station, Cook, WA)

    1991-12-01

    As a part of the Northwest Power Planning Council`s Fish and Wildlife Program, the Fish Passage Center collects information on the migrational characteristics of juvenile salmon and steelhead (Oncorhynchus sp.) in the Columbia River basin. This information is collected through the Smolt Monitoring Program, and is used as a tool in the management and evaluation of the Water Budget. The Water Budget is a volume of water used to enhance environmental conditions (flows) to aid in the seaward migration of juvenile salmon and steelhead. Implicit in the Water Budget concept is that by augmenting flows, travel time of juvenile salmonids will be decreased, thereby increasing survival via reductions in delayed migration and exposure to predators. This study was initiated to (1) provide physiological information about the juvenile salmonids used for these travel time estimates, (2) to analyze the physiological data, and (3) to determine if an ``index`` of smolt condition could be developed to aid in management of the Water Budget.

  13. Incorporating patient travel times in decisions about size and location of dialysis facilities.

    Science.gov (United States)

    Eben-Chaime, M; Pliskin, J S

    1992-01-01

    This report demonstrates the power and usefulness of mathematical optimization as a decision support tool in the medical services industry by presenting an application to dialysis service planning. Models to predict the number of dialysis beds in a given region are usually population-based. Dialysis planners and providers have found a need to accommodate sparsely populated regions by making some allowance for patient travel times. A formal approach to incorporating travel times into dialysis planning, based on the formulation and solution of a mixed-integer programming model, is presented. The development of a method for dialysis planning serves as a platform to demonstrate the use of integer programming to support decision making. Major modeling principles are presented; output interpretation and sensitivity analysis are illustrated by examples; and computational requirements are discussed.

  14. Model-based Integration of Past & Future in TimeTravel

    DEFF Research Database (Denmark)

    Khalefa, Mohamed E.; Fischer, Ulrike; Pedersen, Torben Bach

    2012-01-01

    usually exhibits seasonal behavior, models in this index incorporate seasonality. To construct a hierarchical model index, the user specifies seasonality period, error guarantees levels, and a statistical forecast method. As time proceeds, the system incrementally updates the index and utilizes......We demonstrate TimeTravel, an efficient DBMS system for seamless integrated querying of past and (forecasted) future values of time series, allowing the user to view past and future values as one joint time series. This functionality is important for advanced application domain like energy...

  15. [Travel time and participation in breast cancer screening in a region with high population dispersion].

    Science.gov (United States)

    Borda, Alfredo; Sanz, Belén; Otero, Laura; Blasco, Teresa; García-Gómez, Francisco J; de Andrés, Fuencisla

    2011-01-01

    To analyze the association between travel time and participation in a breast cancer screening program adjusted for contextual variables in the province of Segovia (Spain). We performed an ecological study using the following data sources: the Breast Cancer Early Detection Program of the Primary Care Management of Segovia, the Population and Housing Census for 2001 and the municipal register for 2006-2007. The study period comprised January 2006 to December 2007. Dependent variables consisted of the municipal participation rate and the desired level of municipal participation (greater than or equal to 70%). The key independent variable was travel time from the municipality to the mammography unit. Covariables consisted of the municipalities' demographic and socioeconomic factors. We performed univariate and multivariate Poisson regression analyses of the participation rate, and logistic regression of the desired participation level. The sample was composed of 178 municipalities. The mean participation rate was 75.2%. The desired level of participation (≥ 70%) was achieved in 119 municipalities (67%). In the multivariate Poisson and logistic regression analyses, longer travel time was associated with a lower participation rate and with lower participation after adjustment was made for geographic density, age, socioeconomic status and dependency ratio, with a relative risk index of 0.88 (95% CI: 0.81-0.96) and an odds ratio of 0.22 (95% CI: 0.1-0.47), respectively. Travel time to the mammography unit may help to explain participation in breast cancer screening programs. Copyright © 2010 SESPAS. Published by Elsevier Espana. All rights reserved.

  16. TWO-PHASE ALGORITHM FOR SOLVING HETEROGENEOUS TRAVELLING REPAIRMEN PROBLEM WITH TIME WINDOWS

    Directory of Open Access Journals (Sweden)

    Nenad Bjelić

    2015-03-01

    Full Text Available Heterogeneous travelling repairmen problem with time windows (hetTRPTW is customer oriented problem with large possibilities for practical applications in logistics area. Models and algorithms developed for solving one problem with a cumulative objective function may be, with a little effort, transformed for solving similar problem with a cumulative function. In that sense, aim of this paper is to present results obtained by implementing an algorithm developed for solving cumulative capacitated vehicle routing problem in solving hetTRPTW.

  17. Travel time to maternity care and its effect on utilization in rural Ghana: a multilevel analysis.

    Science.gov (United States)

    Masters, Samuel H; Burstein, Roy; Amofah, George; Abaogye, Patrick; Kumar, Santosh; Hanlon, Michael

    2013-09-01

    Rates of neonatal and maternal mortality are high in Ghana. In-facility delivery and other maternal services could reduce this burden, yet utilization rates of key maternal services are relatively low, especially in rural areas. We tested a theoretical implication that travel time negatively affects the use of in-facility delivery and other maternal services. Empirically, we used geospatial techniques to estimate travel times between populations and health facilities. To account for uncertainty in Ghana Demographic and Health Survey cluster locations, we adopted a novel approach of treating the location selection as an imputation problem. We estimated a multilevel random-intercept logistic regression model. For rural households, we found that travel time had a significant effect on the likelihood of in-facility delivery and antenatal care visits, holding constant education, wealth, maternal age, facility capacity, female autonomy, and the season of birth. In contrast, a facility's capacity to provide sophisticated maternity care had no detectable effect on utilization. As the Ghanaian health network expands, our results suggest that increasing the availability of basic obstetric services and improving transport infrastructure may be important interventions. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Travel Time Estimation Using Freeway Point Detector Data Based on Evolving Fuzzy Neural Inference System.

    Science.gov (United States)

    Tang, Jinjun; Zou, Yajie; Ash, John; Zhang, Shen; Liu, Fang; Wang, Yinhai

    2016-01-01

    Travel time is an important measurement used to evaluate the extent of congestion within road networks. This paper presents a new method to estimate the travel time based on an evolving fuzzy neural inference system. The input variables in the system are traffic flow data (volume, occupancy, and speed) collected from loop detectors located at points both upstream and downstream of a given link, and the output variable is the link travel time. A first order Takagi-Sugeno fuzzy rule set is used to complete the inference. For training the evolving fuzzy neural network (EFNN), two learning processes are proposed: (1) a K-means method is employed to partition input samples into different clusters, and a Gaussian fuzzy membership function is designed for each cluster to measure the membership degree of samples to the cluster centers. As the number of input samples increases, the cluster centers are modified and membership functions are also updated; (2) a weighted recursive least squares estimator is used to optimize the parameters of the linear functions in the Takagi-Sugeno type fuzzy rules. Testing datasets consisting of actual and simulated data are used to test the proposed method. Three common criteria including mean absolute error (MAE), root mean square error (RMSE), and mean absolute relative error (MARE) are utilized to evaluate the estimation performance. Estimation results demonstrate the accuracy and effectiveness of the EFNN method through comparison with existing methods including: multiple linear regression (MLR), instantaneous model (IM), linear model (LM), neural network (NN), and cumulative plots (CP).

  19. Time of travel of solutes in the Sabine River basin, Texas, August-November 1996

    Science.gov (United States)

    Raines, Timothy H.

    1997-01-01

    The U.S. Geological Survey (USGS), in cooperation with the Sabine River Authority, did a time-of-travel study in the Sabine River Basin during low flow from August to November 1996. The study was done to provide accurate estimates of the time-of-travel and dispersion characteristics for solutes during low flow in a 1.8-mile (mi) reach of Grace Creek, a 23.9-mi reach of the mainstem Sabine River, a 3.4-mi reach of Hawkins Creek, and a 1.9-mi reach of Rocky Creek. This report explains the approach and documents the results of the study. The results of the study will be used by the Texas Natural Resource Conservation Commission in a water-quality model to determine waste-load allocation in Segment 0505 of the Sabine River Basin. The time-of-travel and dispersion characteristics also provide useful information on the probable behavior of soluble contaminants that might be introduced into the streams measured in this study.

  20. Assessment of Smolt Condition for Travel Time Analysis, 1988 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Beeman, John W.; Wagner, Eric J.; Rondorf, Dennis W. (Seattle National Fishery Research Center, Columbia River Field Station, Cook, WA)

    1989-03-01

    Estimates of migration rates and travel times of juvenile salmonids within index reaches of the Columbia River basin are collected through the Smolt Monitoring Program for use by the Fish Passage Center. With increased reliance upon travel time estimates in 1988 by the Fish Passage Center, this study was implemented to monitor the biological attributes of juvenile chinook salmon Oncorhynchus tshawytscha and steelhead trout O. mykiss used for the travel time estimates. The physiological ability of fish to respond to stress was assessed by measuring levels of plasma cortisol, glucose, and chloride before and after a stress-challenge test. The development of smoltification was evaluated by measuring gill Na{sup +}K{sup +}-ATPase, plasma thyroxine, purines, and body morphology. Most groups were similar at the hatcheries but differed as the migration to McNary Dam proceeded. The prevalence of bacterial kidney disease (BKD) in spring chinook salmon was evaluated using the enzyme linked immunosorbent assay (ELISA) and fluorescent antibody technique (FAT). Prevalence of BKD in groups tested using the ELISA method was as high as 99% at some downstream locations. A review of indices is presented as a guide to the development of an index of smolt condition and preliminary data are presented. An index could be used as a tool to synthesize information on fish condition to assist with management and evaluation of the Water Budget.

  1. 41 CFR 302-3.512 - How many times are we required to pay for an employee's return travel?

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 4 2010-07-01 2010-07-01 false How many times are we required to pay for an employee's return travel? 302-3.512 Section 302-3.512 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES RELOCATION ALLOWANCES 3-RELOCATION...

  2. Body wave travel times and amplitudes for present-day seismic model of Mars

    Science.gov (United States)

    Raevskiy, Sergey; Gudkova, Tamara

    At the moment Martian interior structure models are constrained by the satellite observational data (the mass, the moment of inertia factor, the Love number k _{2}) (Konopliv et al., 2011) and high pressure experimental data (Bertka and Fei, 1997). Seismological observations could provide unparalleled capability for studying Martian interiors. Future missions include seismic experiments on Mars (Lognonné et al., 2012). The main instrument for these seismic experiments is a broadband seismometer (Robert et al., 2012). When seismic measurements are not yet available, physically consistent interior models, characterized by properties of relevant minerals, make possible to study of the seismic response of the planet. \\To estimate travel times for direct P, S, core reflected PcP, ScS and core refracted PKP body waves as a function of epicentral distance and hypocentral depth, as well as their amplitudes at the surface for a given marsquake, software product was developed in MatLab, as it encompasses many plotting routines that plot resulting travel times and ray paths. The computational results have been compared with the program TTBox (Knapmeyer, 2004). The code computes seismic ray paths and travel times for a one-dimentional spherical interior model (density and seismic velocities are functions of a radius only). Calculations of travel times tables for direct P, S, core reflected PcP, ScS and core refracted PKP waves and their amplitudes are carried out for a trial seismic model of Mars M14_3 from (Zharkov et al., 2009): the core radius is 1800 km, the thickness of the crust is 50 km. Direct and core reflected P and S waves are recorded to a maximum epicentral distance equal to about 100(°) , and PKP arrivals can be detected for epicental distances larger than 150(°) . The shadow zone is getting wider in comparison with previous results (Knapmeyer, 2010), as the liquid core radius of the seismic model under consideration is larger. Based on the estimates of

  3. An efficient General Variable Neighborhood Search for large Travelling Salesman Problem with Time Windows

    Directory of Open Access Journals (Sweden)

    Mladenović Nenad

    2013-01-01

    Full Text Available General Variable Neighborhood Search (GVNS is shown to be a powerful and robust methodology for solving travelling salesman and vehicle routing problems. However, its efficient implementation may play a significant role in solving large size instances. In this paper we suggest new GVNS heuristic for solving Travelling salesman problem with time windows. It uses different set of neighborhoods, new feasibility checking procedure and a more efficient data structure than the recent GVNS method that can be considered as a state-of-the-art heuristic. As a result, our GVNS is much faster and more effective than the previous GVNS. It is able to improve 14 out of 25 best known solutions for large test instances from the literature.

  4. Travel time and attrition from VHA care among women veterans: how far is too far?

    Science.gov (United States)

    Friedman, Sarah A; Frayne, Susan M; Berg, Eric; Hamilton, Alison B; Washington, Donna L; Saechao, Fay; Maisel, Natalya C; Lin, Julia Y; Hoggatt, Katherine J; Phibbs, Ciaran S

    2015-04-01

    Travel time, an access barrier, may contribute to attrition of women veterans from Veterans Health Administration (VHA) care. We examined whether travel time influences attrition: (a) among women veterans overall, (b) among new versus established patients, and (c) among rural versus urban patients. This retrospective cohort study used logistic regression to estimate the association between drive time and attrition, overall and for new/established and rural/urban patients. In total, 266,301 women veteran VHA outpatients in the Fiscal year 2009. An "attriter" did not return for VHA care during the second through third years after her first 2009 visit (T0). Drive time (log minutes) was between the patient's residence and her regular source of VHA care. "New" patients had no VHA visits within 3 years before T0. Models included age, service-connected disability, health status, and utilization as covariates. Overall, longer drive times were associated with higher odds of attrition: drive time adjusted odds ratio=1.11 (99% confidence interval, 1.09-1.14). The relationship between drive time and attrition was stronger among new patients but was not modified by rurality. Attrition among women veterans is sensitive to longer drive time. Linking new patients to VHA services designed to reduce distance barriers (telemedicine, community-based clinics, mobile clinics) may reduce attrition among women new to VHA.

  5. A multinational investigation of time and traveling costs in attending anticoagulation clinics.

    Science.gov (United States)

    Jowett, Sue; Bryan, Stirling; Mahé, Isabelle; Brieger, David; Carlsson, Jonas; Kartman, Bernt; Nevinson, Mark

    2008-01-01

    Anticoagulation is used in patients with atrial fibrillation to reduce the risk of ischemic stroke. The therapy requires regular monitoring and, frequently, dose adjustment. This study aimed to determine the time and traveling costs that patients incur to themselves and society in attending anticoagulation clinics. A subset of patients from 105 primary and secondary care clinics allocated to the warfarin arm of SPORTIF III (patients from Australia, France, Portugal, Spain, Sweden, and the UK) completed a questionnaire. Patients indicated the type of transport used for clinic visits, and estimated traveling expenses. Patients were also asked to estimate total traveling and clinic attendance time, and to confirm whether they were currently employed and whether they had to give up time from work to attend the clinic. Time cost of companions was also taken into consideration. Cost per visit was calculated (euro, 2003 prices). Questionnaires for a total of 381 patients were analyzed, with the majority of patients from Sweden (n = 130) and the UK (n = 101). Mean cost to patients varied widely between countries, ranging from euro6.9 (France) to euro20.5 (Portugal) per visit. For most countries, time costs (value of lost working and leisure time) were the main driver of costs. Mean time cost to society ranged from euro5.6 (France) to euro31.7 (Portugal) per visit. Patients incur considerable costs when visiting anticoagulation clinics, and these costs vary by country. The results suggest the importance of taking a broad economic perspective when considering the cost-effectiveness of warfarin.

  6. Decreasing patient cost and travel time through pediatric rheumatology telemedicine visits.

    Science.gov (United States)

    Kessler, Elizabeth A; Sherman, Ashley K; Becker, Mara L

    2016-09-20

    There is a critical shortage of pediatric rheumatologists in the US. Substantial travel to clinics can impose time and monetary burdens on families. The aim of this study was to evaluate the cost of in-person pediatric rheumatology visits for families and determine if telemedicine clinics resulted in time and cost savings. Factors associated with interest in telemedicine were also explored. Surveys were offered to parents and guardians of patients in Pediatric Rheumatology follow-up clinics in Kansas City, Missouri, the primary site of in-person care, and at a telemedicine outreach site 160 miles away, in Joplin, Missouri. Survey questions were asked about non-medical, out-of-pocket costs associated with the appointment and interest in a telemedicine clinic. At the primary Kansas City clinic, the median distance traveled one-way was 40 miles [IQR = 18-80]. In the Joplin sample, the median distance traveled to the telemedicine clinic was 60 miles [IQR = 20-85] compared to 175 miles [IQR = 160-200] for the same cohort of patients when seen in Kansas City (p < 0.001). When the Joplin cohort was seen via telemedicine they missed less time from work and school (p = 0.028, p = 0.003, respectively) and a smaller percentage spent money on food compared to when they had traveled to Kansas City (p < 0.001). There was no statistical difference between the Joplin cohort when they had traveled to Kansas City and the Kansas City cohort in terms of miles driven to clinic, time missed from work and school, and percentage of subjects who spent money on food. Traditional in-person visits can result in a financial toll on families, which can be ameliorated by the use of telemedicine. Telemedicine leveled the economic burden of clinic visits so that when the Joplin cohort was seen via telemedicine, they experienced costs similar to the Kansas City cohort.

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

    Science.gov (United States)

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

    2017-08-01

    Time-distance helioseismology is one of the primary tools for studying the solar meridional circulation. 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 P-angle uncertainty of solar images. Here 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 for the two data sets and then compared to examine the consistency of MDI and HMI travel times after correcting the systematic errors.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.

  8. Characterization of mean transit time at large springs in the Upper Colorado River Basin, USA: A tool for assessing groundwater discharge vulnerability

    Science.gov (United States)

    Solder, John; Stolp, Bernard J.; Heilweil, Victor M.; Susong, David D.

    2016-01-01

    Environmental tracers (noble gases, tritium, industrial gases, stable isotopes, and radio-carbon) and hydrogeology were interpreted to determine groundwater transit-time distribution and calculate mean transit time (MTT) with lumped parameter modeling at 19 large springs distributed throughout the Upper Colorado River Basin (UCRB), USA. The predictive value of the MTT to evaluate the pattern and timing of groundwater response to hydraulic stress (i.e., vulnerability) is examined by a statistical analysis of MTT, historical spring discharge records, and the Palmer Hydrological Drought Index. MTTs of the springs range from 10 to 15,000 years and 90 % of the cumulative discharge-weighted travel-time distribution falls within the range of 2−10,000 years. Historical variability in discharge was assessed as the ratio of 10–90 % flow-exceedance (R 10/90%) and ranged from 2.8 to 1.1 for select springs with available discharge data. The lag-time (i.e., delay in discharge response to drought conditions) was determined by cross-correlation analysis and ranged from 0.5 to 6 years for the same select springs. Springs with shorter MTTs (<80 years) statistically correlate with larger discharge variations and faster responses to drought, indicating MTT can be used for estimating the relative magnitude and timing of groundwater response. Results indicate that groundwater discharge to streams in the UCRB will likely respond on the order of years to climate variation and increasing groundwater withdrawals.

  9. Impact of a University-Based Outpatient Telemedicine Program on Time Savings, Travel Costs, and Environmental Pollutants.

    Science.gov (United States)

    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 CO2, 50 metric tons of CO, 3.7 metric tons of NOx, 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.

  10. Reduced Resolution Groundwater Modeling in the Rio Grande for Real Time Scenario Evaluation

    Science.gov (United States)

    Roach, J. D.; Tidwell, V. C.

    2006-12-01

    As the finite, and often over-allocated water resources of the western United States are challenged by growing demands, computer based simulations can provide a powerful tool for evaluating potential water use scenarios in support of hydrologic decision making and water policy analysis. To represent the complexities of water resource management, a model should capture the salient behaviors and interactions between, the groundwater, surface water, and human behavioral systems, while to effectively connect science to the decision process, the model should run quickly enough to allow real time evaluation of a wide range of scenarios by stakeholders and decision makers themselves. As these potentially mutually exclusive objectives are pursued, the tradeoffs between resolution, run time, and the degree of coupling between modeled systems must be considered. In the Upper Rio Grande in New Mexico, three MODFLOW based, distributed groundwater models of the Espanola, Albuquerque, and Socorro groundwater basins have been used to calibrate a spatially simplified representation of the groundwater system in the region. The groundwater model is dynamically coupled to surface water and human behavioral systems as part of an integrated system dynamics based model which runs quickly enough to support rapid basin scale water policy scenario evaluation. This presentation will focus on development of the simplified groundwater model, and the performance tradeoffs and gains associated with spatial aggregation and dynamic coupling to the surface water system.

  11. A Three-Stage Saving-Based Heuristic for Vehicle Routing Problem with Time Windows and Stochastic Travel Times

    Directory of Open Access Journals (Sweden)

    Zheng Wang

    2016-01-01

    Full Text Available This paper presents a saving-based heuristic for the vehicle routing problem with time windows and stochastic travel times (VRPTWSTT. One of the basic ideas of the heuristic is to advance the latest service start time of each customer by a certain period of time. In this way, the reserved time can be used to cope with unexpected travel time delay when necessary. Another important idea is to transform the VRPTWSTT to a set of vehicle routing problems with time windows (VRPTW, each of which is defined by a given percentage used to calculate the reserved time for customers. Based on the above two key ideas, a three-stage heuristic that includes the “problem transformation” stage, the “solution construction” stage, and the “solution improvement” stage is developed. After the problem transformation in the first stage, the work of the next two stages is to first construct an initial solution for each transformed VRPTW by improving the idea of the classical Clarke-Wright heuristic and then further improve the solution. Finally, a number of numerical experiments are conducted to evaluate the efficiency of the described methodology under different uncertainty levels.

  12. Sources and Residence Times of Groundwater in Shasta County, CA Determined by Isotopic Tracers

    Science.gov (United States)

    Peters, E.; Moran, J. E.; Deinhart, A.; Roberts, S. K.; Esser, B.; Visser, A.

    2015-12-01

    Large-volume springs are a significant source of water to communities in Shasta County. Aquifers in this region are developed in young volcanic formations and the age and flow of groundwater is not well characterized, making predicting the impact of drought and climate change on spring flow difficult. To better understand the water resources and the hydrogeology of the region and to better constrain the age of water produced by springs, we have sampled water from wells, springs, and streams for a suite of geochemical and isotopic tracers. We are using isotopic tracers because of the limited number of sampling points over a large area, leaving traditional hydrogeologic methods such as water levels and pump tests inadequate for a regional study. We analyzed samples for sulfur-35 (87.4 day half-life) and found detections in two springs, confirming the presence of a fraction of recently (1-2 years) recharged groundwater. Tritium (12.3 year half-life) activities show that some wells produce water recharged more than 5 decades ago, but most produce more recently recharged water. We will also report results for sodium-22 (2.6 year half-life), krypton-85 (10.8 year half-life), carbon-14 (5,730 year half-life), dissolved noble gases, stable isotopes of water, and helium isotopic composition. These isotopes are applied to determine the age (residence time) of groundwater over a broad age distribution, from less than one year to tens of thousands of years. These tracers should also provide information on aquifer volumes, help delineate groundwater flow, and help to identify recharge areas. A collection of groundwater ages from springs at high elevations to wells in the upper Sacramento Valley will help delineate groundwater flowpaths. Finally, groundwater residence times will help determine groundwater volume and recharge rates, and resolve questions related to drought vulnerability and effective adjustments in water resource management.

  13. Time Is Not Space: Core Computations and Domain-Specific Networks for Mental Travels.

    Science.gov (United States)

    Gauthier, Baptiste; van Wassenhove, Virginie

    2016-11-23

    Humans can consciously project themselves in the future and imagine themselves at different places. Do mental time travel and mental space navigation abilities share common cognitive and neural mechanisms? To test this, we recorded fMRI while participants mentally projected themselves in time or in space (e.g., 9 years ago, in Paris) and ordered historical events from their mental perspective. Behavioral patterns were comparable for mental time and space and shaped by self-projection and by the distance of historical events to the mental position of the self, suggesting the existence of egocentric mapping in both dimensions. Nonetheless, self-projection in space engaged the medial and lateral parietal cortices, whereas self-projection in time engaged a widespread parietofrontal network. Moreover, while a large distributed network was found for spatial distances, temporal distances specifically engaged the right inferior parietal cortex and the anterior insula. Across these networks, a robust overlap was only found in a small region of the inferior parietal lobe, adding evidence for its role in domain-general egocentric mapping. Our findings suggest that mental travel in time or space capitalizes on egocentric remapping and on distance computation, which are implemented in distinct dimension-specific cortical networks converging in inferior parietal lobe.

  14. Non-stationarity of solute travel time distribution observed in a controlled hydrologic transport volume

    Science.gov (United States)

    Queloz, P.; Bertuzzo, E.; Carraro, L.; Botter, G.; Miglietta, F.; Rao, P. S.; Rinaldo, A.

    2014-12-01

    Experimental data were collected over a year-long period in a transport experiment carried out within a controlled transport volume (represented by a 2m-deep, 1m-diameter lysimeter fitted with bottom drainage). The soil surface was shielded from natural rainfall, replaced by an artificial injection (Poisson process) at the daily timescale. Bottom drainage out-flows were continuously monitored with leakage tipping bucket and evapotranspiration (prompted by a willow tree growing within the system) was measured trough precision load cells, which also allow an accurate and continuous reading of the total water storage. Five artificial soluble tracers (species of fluorobenzoic acid, FBAs, mutually passive) were selected based on low-reactivity and low-retardation in our specific soil and used to individually mark five rainfall inputs of different amplitudes and occurring at various initial soil moisture conditions. Tracer discharge concentration and hydrologic fluxes measurements provide a direct method for the assessment of the bulk effects of transport on the (backward and forward) travel time distributions in the hydrological setting. The large discrepancies observed in terms of mass recovery in the discharge (supported by ex post FBAs quantification in the soil and in the vegetation) and tracer out-fluxes dynamics emphasized the dependence of the forward travel time on the various injection times and the stages experienced by the system during the migration of the pulse. Rescaling the measured travel time distribution by using the cumulative drainage volume as an independent variable instead of the time elapsed since the injection also fails to yield to stationary distributions, as it was argued by Niemi (1997). Our experimental results support earlier theoretical speculations centered on the key role of non-stationarity on the characterization of the properties of hydrologic flow and transport phenomena. A travel time based model, with all in- and out- hydrological

  15. Effects of Land Use and Travel Time on the Distribution of Nitrate in the Kirkwood-Cohansey Aquifer System in Southern New Jersey

    Science.gov (United States)

    Kauffman, Leon J.; Baehr, Arthur L.; Ayers, Mark A.; Stackelberg, Paul E.

    2001-01-01

    Residents of the southern New Jersey Coastal Plain are increasingly reliant on the unconfined Kirkwood-Cohansey aquifer system for public water supply as a result of increasing population and restrictions on withdrawals from the deeper, confined aquifers. Elevated nitrate concentrations above background levels have been found in wells in the surficial aquifer system in agricultural and urban parts of this area. A three-dimensional steady-state ground-water-flow model of a 400-square-mile study area near Glassboro, New Jersey, was used in conjunction with particle tracking to examine the effects of land use and travel time on the distribution of nitrate in ground and surface water in southern New Jersey. Contributing areas and ground-water ages, or travel times, of water at ground-water discharge points (streams and wells) in the study area were simulated. Concentrations of nitrate were computed by linking land use and age-dependent nitrate concentrations in recharge to the discharge points. Median concentrations of nitrate in water samples collected during 1996 from shallow monitoring wells in different land-use areas were used to represent the concentration of nitrate in aquifer recharge since 1990. On the basis of upward trends in the use of nitrogen fertilizer, the concentrations of nitrate in aquifer recharge in agricultural and urban areas were assumed to have increased linearly from the background value in 1940 (0.07 mg/L as N) to the 1990 (2.5-14 mg/L as N) concentrations. Model performance was evaluated by comparing the simulation results to measured nitrate concentrations and apparent ground-water ages. Apparent ground-water ages at 32 monitoring wells in the study area determined from tritium/helium-3 ratios and sulfur hexafluoride concentrations favorably matched simulated travel times to these wells. Simulated nitrate concentrations were comparable to concentrations measured in 27 water-supply wells in the study area. A time series (1987-98) of nitrate

  16. What can environmental tracer concentrations tell us about groundwater residence time?

    Science.gov (United States)

    McCallum, J. L.; Engdahl, N. B.; Cook, P. G.; Simmons, C.

    2013-12-01

    Quantification of groundwater age distributions through the use on lumped parameter models and environmental tracer concentrations is an ongoing practice. These models are based on simple geometries and sampling conditions and may not be applicable outside of ideal conditions, limiting the results that can be obtained. We have developed a method that requires no underlying assumptions about the structure of the groundwater age distribution. This method assumes that the convolution relationship describes the relationship between temporal atmospheric concentrations and measured groundwater sample concentrations. We looked at synthetically generated groundwater age distributions and a number of levels of tracer data including a long time series of tritium, the use of CFCs and SF6 sampled at various times and the use of CFCs, SF6, 3H and 14C sampled at a single time. In general, we found that environmental tracers are not very informative of groundwater age distributions resulting in estimates being highly non-unique. The exception was the use of a time series of tritium data. Tritium is more informative due to the temporal variations of atmospheric concentrations and a short half-life reducing the correlation of sequential measurements. The ability of CFC compounds to estimate entire distributions was limited due to the lack of variation in temporal atmospheric concentrations and correlation between sampled concentrations. Despite varying ability of the method to predict whole distributions, some indicators such as the mean age and some arrival time statistics were estimated well by the method. The implications of this show that care should be taken in the choice of lumped parameter model used in conjunction with environmental tracer techniques to constrain entire groundwater age distributions. Interestingly, the ability to correct for mixing bias of mean ages despite poor estimates of entire groundwater age distributions shows some promise.

  17. Inpatient child mortality by travel time to hospital in a rural area of Tanzania.

    Science.gov (United States)

    Manongi, Rachel; Mtei, Frank; Mtove, George; Nadjm, Behzad; Muro, Florida; Alegana, Victor; Noor, Abdisalan M; Todd, Jim; Reyburn, Hugh

    2014-05-01

    To investigate the association, if any, between child mortality and distance to the nearest hospital. The study was based on data from a 1-year study of the cause of illness in febrile paediatric admissions to a district hospital in north-east Tanzania. All villages in the catchment population were geolocated, and travel times were estimated from availability of local transport. Using bands of travel time to hospital, we compared admission rates, inpatient case fatality rates and child mortality rates in the catchment population using inpatient deaths as the numerator. Three thousand hundred and eleven children under the age of 5 years were included of whom 4.6% died; 2307 were admitted from time between admission and death. Assuming uniform mortality in the catchment population, the predicted number of deaths not benefiting from hospital admission prior to death increased by 21.4% per hour of travel time to hospital. If the same admission and death rates that were found at <3 h from the hospital applied to the whole catchment population and if hospital care conferred a 30% survival benefit compared to home care, then 10.3% of childhood deaths due to febrile illness in the catchment population would have been averted. The mortality impact of poor access to hospital care in areas of high paediatric mortality is likely to be substantial although uncertainty over the mortality benefit of inpatient care is the largest constraint in making an accurate estimate. © 2014 The Authors Tropical Medicine & International Health Published by John Wiley & Sons Ltd.

  18. A method for generating an illusion of backwards time travel using immersive virtual reality-an exploratory study.

    Science.gov (United States)

    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.

  19. Assessment of smolt condition for travel time analysis. Annual report 1988

    Science.gov (United States)

    Rondorf, D.W.; Beeman, J.W.; Faler, J.C.; Free, M.E.; Wagner, E.J.

    1989-01-01

    Estimates of migration rates and travel times of juvenile salmonids within index reaches of the Columbia River basin are collected through the Smolt Monitoring Program for use by the Fish Passage Center. With increased reliance upon travel time estimates in 1988 by the Fish Passage Center, this study was implemented to monitor the biological attributes of juvenile chinook salmon Oncorhynchus tshawytscha and steelhead trout 0.- mykiss used for the travel time estimates, The physiological ability of fish to respond to stress was assessed by measuring levels of plasma cortisol, glucose, and chloride before and after a stress-challenge test. Most mid-Columbia and Snake river groups responded normally to the stress challenge exhibiting an increase in plasma glucose and cortisol and a slight decrease in chloride. Fish trucked to release sites were more stressed than those released directly from the hatchery, but most still responded to the stress challenge test normally. An abnormal or extreme stress response occurred when there were deviations from preferred protocol, disease problems at hatcheries, or when fish were trucked over long periods (7h). The development of smoltification was evaluated by measuring gill Na+K+-ATPase, plasma thyroxine, purines, and body morphology. Most groups were similar at the hatcheries but differed as the migration to McNary Dam proceeded. Gill ATPase activity increased 2-3 fold during the first 20 days of migration, after which it changed little. Fish with longer in-river travel times appeared to be more smolted than those which were in the river for a shorter period of time. The prevalence of bacterial kidney disease (BKD) in spring chinook salmon was evaluated using the enzyme linked immunosorbent assay (ELISA) and fluorescent antibody technique (FAT). Prevalence of BKD in groups tested using the ELISA method was as high as 99% at some downstream locations. A review of indices is presented as a guide, to the development of an index of

  20. An assessment of travel time for spills management - using HEC-RAS water quality analysis

    Energy Technology Data Exchange (ETDEWEB)

    Disley, Tom; Gharabaghi, Bahram; Perdikaris, John [University of Guelph, Guelph, (Canada); Singh, Amanjot; Dougherty, Jennifer [Credit Valley Conservation Authority, Mississauga, (Canada)

    2010-07-01

    In order to mitigate the detrimental effects that contaminants such as petrochemical and chemical spills may have on the environment it is critical to understand their transport. This paper presented an assessment of travel time for spills management using HEC-RAS water quality analysis on the Credit River Watershed. It is a 1000 km2 area of urban and rural landscapes drained by 90 km of the main Credit River. The study focused on the mixing characteristics of 5 stream reaches in the Credit River watershed. Dye tracing was done under three different flow conditions to obtain a longitudinal dispersion coefficient, which is a necessary parameter for predicting and modelling time concentration curves downstream of a spill. The longitudinal dispersion coefficient was input into the US Army Corp of Engineers, Hydrologic Engineering Centers River Analysis System (HEC RAS) to predict time concentration curves. The HEC RAS model produced average travel time close to those measured in the field after final calibration was completed.

  1. Time and travel costs incurred by women attending antenatal tests: A costing study.

    Science.gov (United States)

    Verhoef, Talitha I; Daley, Rebecca; Vallejo-Torres, Laura; Chitty, Lyn S; Morris, Stephen

    2016-09-01

    to estimate the costs to women, their friends and family for different antenatal tests in the Down's syndrome (DS) screening pathway. questionnaire-based costing study. eight maternity clinics across the UK. pregnant women (n=574) attending an appointment for DS screening, NIPT or invasive testing between December 2013 and September 2014. using data collected from the questionnaires we calculated the total costs to women by multiplying the time spent at the hospital and travelling to and from it by the opportunity costs of the women and accompanying person and adding travel and childcare costs. Assumptions about the value of opportunity costs were tested in one-way sensitivity analyses. The main outcome measure was the mean cost to the women and friends/family for each test (DS screening, NIPT, and invasive testing). mean costs to women and their family/friend were £33.96 per visit, of which £22.47 were time costs, £9.15 were travel costs and £2.34 were childcare costs. Costs were lowest for NIPT (£22), £32 for DS screening (£44 if combined with NIPT), and highest for invasive testing (£60). Sensitivity analysis revealed that variations around the value of leisure time opportunity costs had the largest influence on the results. there are considerable costs to women, their friends and family when attending different tests in the DS screening pathway. when assessing the cost-effectiveness of changes to this pathway, costs to women should be considered. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Travel Time Estimation Using Freeway Point Detector Data Based on Evolving Fuzzy Neural Inference System.

    Directory of Open Access Journals (Sweden)

    Jinjun Tang

    Full Text Available Travel time is an important measurement used to evaluate the extent of congestion within road networks. This paper presents a new method to estimate the travel time based on an evolving fuzzy neural inference system. The input variables in the system are traffic flow data (volume, occupancy, and speed collected from loop detectors located at points both upstream and downstream of a given link, and the output variable is the link travel time. A first order Takagi-Sugeno fuzzy rule set is used to complete the inference. For training the evolving fuzzy neural network (EFNN, two learning processes are proposed: (1 a K-means method is employed to partition input samples into different clusters, and a Gaussian fuzzy membership function is designed for each cluster to measure the membership degree of samples to the cluster centers. As the number of input samples increases, the cluster centers are modified and membership functions are also updated; (2 a weighted recursive least squares estimator is used to optimize the parameters of the linear functions in the Takagi-Sugeno type fuzzy rules. Testing datasets consisting of actual and simulated data are used to test the proposed method. Three common criteria including mean absolute error (MAE, root mean square error (RMSE, and mean absolute relative error (MARE are utilized to evaluate the estimation performance. Estimation results demonstrate the accuracy and effectiveness of the EFNN method through comparison with existing methods including: multiple linear regression (MLR, instantaneous model (IM, linear model (LM, neural network (NN, and cumulative plots (CP.

  3. Travel Time Estimation Using Freeway Point Detector Data Based on Evolving Fuzzy Neural Inference System

    Science.gov (United States)

    Tang, Jinjun; Zou, Yajie; Ash, John; Zhang, Shen; Liu, Fang; Wang, Yinhai

    2016-01-01

    Travel time is an important measurement used to evaluate the extent of congestion within road networks. This paper presents a new method to estimate the travel time based on an evolving fuzzy neural inference system. The input variables in the system are traffic flow data (volume, occupancy, and speed) collected from loop detectors located at points both upstream and downstream of a given link, and the output variable is the link travel time. A first order Takagi-Sugeno fuzzy rule set is used to complete the inference. For training the evolving fuzzy neural network (EFNN), two learning processes are proposed: (1) a K-means method is employed to partition input samples into different clusters, and a Gaussian fuzzy membership function is designed for each cluster to measure the membership degree of samples to the cluster centers. As the number of input samples increases, the cluster centers are modified and membership functions are also updated; (2) a weighted recursive least squares estimator is used to optimize the parameters of the linear functions in the Takagi-Sugeno type fuzzy rules. Testing datasets consisting of actual and simulated data are used to test the proposed method. Three common criteria including mean absolute error (MAE), root mean square error (RMSE), and mean absolute relative error (MARE) are utilized to evaluate the estimation performance. Estimation results demonstrate the accuracy and effectiveness of the EFNN method through comparison with existing methods including: multiple linear regression (MLR), instantaneous model (IM), linear model (LM), neural network (NN), and cumulative plots (CP). PMID:26829639

  4. Imaging the Mediterranean upper mantle by p- wave travel time tomography

    Directory of Open Access Journals (Sweden)

    A. Morelli

    1997-06-01

    Full Text Available Travel times of P-waves in the Euro-Mediterranean region show strong and consistent lateral variations, which can be associated to structural heterogeneity in the underlying crust and mantle. We analyze regional and tele- seismic data from the International Seismological Centre data base to construct a three-dimensional velocity model of the upper mantle. We parameterize the model by a 3D grid of nodes -with approximately 50 km spacing -with a linear interpolation law, which constitutes a three-dimensional continuous representation of P-wave velocity. We construct summary travel time residuals between pairs of cells of the Earth's surface, both inside our study area and -with a broader spacing -on the whole globe. We account for lower mantle heterogeneity outside the modeled region by using empirical corrections to teleseismic travel times. The tomo- graphic images show generai agreement with other seismological studies of this area, with apparently higher detail attained in some locations. The signature of past and present lithospheric subduction, connected to Euro- African convergence, is a prominent feature. Active subduction under the Tyrrhenian and Hellenic arcs is clearly imaged as high-velocity bodies spanning the whole upper mantle. A clear variation of the lithospheric structure beneath the Northem and Southern Apennines is observed, with the boundary running in correspon- dence of the Ortona-Roccamonfina tectonic lineament. The western section of the Alps appears to have better developed roots than the eastern, possibly reflecting à difference in past subduction of the Tethyan lithosphere and subsequent continental collision.

  5. Tempa voja^go kaj geodezioj en ^generala relativeco / Time travel and geodesics in general relativity

    CERN Document Server

    Paiva, F M

    2011-01-01

    In the homogeneous metric of Som-Raychaudhuri, in general relativity, we study the three types of geodesics: timelike, null, and spacelike; in particular, the little known geodesics of simultaneities. We also study the non-geodetic circular motion with constant velocity, particularly closed timelike curves, and time travel of a voyager. ------------------- ^Ce la ^Generala Relativeco, en homogena metriko de Som-Raychaudhuri, ni studas geodeziojn de la tri tipoj: tempa, nula, kaj spaca, speciale la malmulte konatajn samtempajn geodeziojn. Ni anka^u studas ne-geodezian cirklan movadon kun konstanta rapido, speciale fermitajn kurbojn de tempa tipo, kaj movadon de voja^ganto al estinto.

  6. High-resolution mapping of flows in the solar interior: Fully consistent OLA inversion of helioseismic travel times

    CERN Document Server

    Jackiewicz, J; Birch, A C

    2008-01-01

    To recover the flow information encoded in travel-time data of time-distance helioseismology, accurate forward modeling and a robust inversion of the travel times are required. We accomplish this using three-dimensional finite-frequency travel-time sensitivity kernels for flows along with a 2+1 dimensional (2+1D) optimally localized averaging (OLA) inversion scheme. Travel times are measured by ridge filtering MDI full-disk Doppler data and the corresponding Born sensitivity kernels are computed for these particular travel times. We also utilize the full noise covariance properties of the travel times which allow us to accurately estimate the errors for all inversions. The whole procedure is thus fully consistent. Due to ridge filtering, the kernel functions separate in the horizontal and vertical directions, motivating our choice of a 2+1D inversion implementation. The inversion procedure also minimizes cross-talk effects among the three flow components, and the averaging kernels resulting from the inversion...

  7. Using nonparametrics to specify a model to measure the value of travel time

    DEFF Research Database (Denmark)

    Fosgerau, Mogens

    2007-01-01

    Using a range of nonparametric methods, the paper examines the specification of a model to evaluate the willingness-to-pay (WTP) for travel time changes from binomial choice data from a simple time-cost trading experiment. The analysis favours a model with random WTP as the only source...... of randomness over a model with fixed WTP which is linear in time and cost and has an additive random error term. Results further indicate that the distribution of log WTP can be described as a sum of a linear index fixing the location of the log WTP distribution and an independent random variable representing...... unobserved heterogeneity. This formulation is useful for parametric modelling. The index indicates that the WTP varies systematically with income and other individual characteristics. The WTP varies also with the time difference presented in the experiment which is in contradiction of standard utility theory....

  8. Remote sensing of temperature and wind using acoustic travel-time measurements

    Directory of Open Access Journals (Sweden)

    Manuela Barth

    2013-04-01

    Full Text Available A remote sensing technique to detect area-averaged temperature and flow properties within an area under investigation, utilizing acoustic travel-time measurements, is introduced. This technique uses the dependency of the speed of acoustic signals on the meteorological parameters temperature and wind along the propagation path. The method itself is scalable: It is applicable for investigation areas with an extent of some hundred square metres as well as for small-scale areas in the range of one square metre. Moreover, an arrangement of the acoustic transducers at several height levels makes it possible to determine profiles and gradients of the meteorological quantities. With the help of two examples the potential of this remote sensing technique for simultaneously measuring averaged temperature and flow fields is demonstrated. A comparison of time histories of temperature and wind values derived from acoustic travel-time measurements with point measurements shows a qualitative agreement whereas calculated root-mean-square errors differ for the two example applications. They amount to 1.4 K and 0.3 m/s for transducer distances of 60 m and 0.4 K and 0.2 m/s for transducer distances in the range of one metre.

  9. Travel time source-specific station corrections related to lithospheric structures in the Mediterranean region

    Science.gov (United States)

    Giuntini, A.; Materni, V.; Console, R.; Chiappini, S.; Chiappini, M.

    2017-01-01

    We compare the locations obtained from arrival times collected by the International Seismological Centre from a network of regional and teleseismic stations for a cluster of Italian earthquakes with the locations of the same events obtained by the dense national seismic network operated by the Istituto Nazionale di Geofisica e Vulcanologia. We find mislocations on the order of 15 km for epicentral coordinates and on the order of 25 km for depths calculated from the regional and teleseismic network and using the standard IASP91 travel times. These mislocations are generally larger than the sizes of the respective error ellipse semi-axes. We then show that systematic shifts of hypocentral coordinates can be substantially reduced by applying source-specific station corrections. Moreover, we find that the size of error ellipses characterizing the teleseismic locations is significantly reduced by the application of such corrections. Our travel time corrections are compared and found fairly consistent with information available in the literature on tomographic studies on the crust and upper mantle in the European-Mediterranean region.

  10. 41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?

    Science.gov (United States)

    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...

  11. The TimeGeo modeling framework for urban motility without travel surveys.

    Science.gov (United States)

    Jiang, Shan; Yang, Yingxiang; Gupta, Siddharth; Veneziano, Daniele; Athavale, Shounak; González, Marta C

    2016-09-13

    Well-established fine-scale urban mobility models today depend on detailed but cumbersome and expensive travel surveys for their calibration. Not much is known, however, about the set of mechanisms needed to generate complete mobility profiles if only using passive datasets with mostly sparse traces of individuals. In this study, we present a mechanistic modeling framework (TimeGeo) that effectively generates urban mobility patterns with resolution of 10 min and hundreds of meters. It ties together the inference of home and work activity locations from data, with the modeling of flexible activities (e.g., other) in space and time. The temporal choices are captured by only three features: the weekly home-based tour number, the dwell rate, and the burst rate. These combined generate for each individual: (i) stay duration of activities, (ii) number of visited locations per day, and (iii) daily mobility networks. These parameters capture how an individual deviates from the circadian rhythm of the population, and generate the wide spectrum of empirically observed mobility behaviors. The spatial choices of visited locations are modeled by a rank-based exploration and preferential return (r-EPR) mechanism that incorporates space in the EPR model. Finally, we show that a hierarchical multiplicative cascade method can measure the interaction between land use and generation of trips. In this way, urban structure is directly related to the observed distance of travels. This framework allows us to fully embrace the massive amount of individual data generated by information and communication technologies (ICTs) worldwide to comprehensively model urban mobility without travel surveys.

  12. Accuracy of travel time distribution (TTD) models as affected by TTD complexity, observation errors, and model and tracer selection

    Science.gov (United States)

    Green, Christopher T.; Zhang, Yong; Jurgens, Bryant C.; Starn, J. Jeffrey; Landon, Matthew K.

    2014-01-01

    Analytical models of the travel time distribution (TTD) from a source area to a sample location are often used to estimate groundwater ages and solute concentration trends. The accuracies of these models are not well known for geologically complex aquifers. In this study, synthetic datasets were used to quantify the accuracy of four analytical TTD models as affected by TTD complexity, observation errors, model selection, and tracer selection. Synthetic TTDs and tracer data were generated from existing numerical models with complex hydrofacies distributions for one public-supply well and 14 monitoring wells in the Central Valley, California. Analytical TTD models were calibrated to synthetic tracer data, and prediction errors were determined for estimates of TTDs and conservative tracer (NO3−) concentrations. Analytical models included a new, scale-dependent dispersivity model (SDM) for two-dimensional transport from the watertable to a well, and three other established analytical models. The relative influence of the error sources (TTD complexity, observation error, model selection, and tracer selection) depended on the type of prediction. Geological complexity gave rise to complex TTDs in monitoring wells that strongly affected errors of the estimated TTDs. However, prediction errors for NO3− and median age depended more on tracer concentration errors. The SDM tended to give the most accurate estimates of the vertical velocity and other predictions, although TTD model selection had minor effects overall. Adding tracers improved predictions if the new tracers had different input histories. Studies using TTD models should focus on the factors that most strongly affect the desired predictions.

  13. Mean Transit Time as a Predictor of Groundwater Discharge Response in the Upper Colorado River Basin

    Science.gov (United States)

    Solder, J. E.; Heilweil, V. M.; Stolp, B. J.; Susong, D.

    2015-12-01

    The Colorado River and its tributaries support 40 million municipal water users and 5.5 million acres of agriculture in the south western United States (U.S. Bureau of Reclamation, 2012). Recent estimates by Rumsey et al. (2015) suggest that a significant portion (about 50 percent) of surface water flow in the Upper Colorado River Basin (UCRB) is sustained by groundwater discharge to streams. Predicted climate variation (Cook et al., 2015) and increased water demand (U.S. Bureau of Reclamation, 2012) within the UCRB suggest future decreases in groundwater discharge, however transient groundwater responses are not well understood. In this study we calculate groundwater mean transit time (MTT) and transit time distribution (TTD) as predictors of the pattern and timing of groundwater response to hydraulic stress. Samples from nineteen large springs within the UCRB were analyzed for environmental tracers to determine MTT and TTD. The predictive value of the MTT is examined by a statistical analysis of MTT, historical spring discharge records, and the Palmer Hydrological Drought Index. MTTs of the 19 springs range from 10 to 15,000 years with a flow-weighted average of 1,650 years. The composite TTD of the 19 springs suggest that flowpaths representing 45 percent of their combined discharge have transit times greater than 100 years. However, spring discharge records indicate that flow responds to drought on much shorter (0.5 - 6 year) time scales, indicative of a hydraulic pressure response. Springs with shorter MTTs ( 100) also show a hydraulic pressure response. While not fully representative of the UCRB, results from the 19 springs indicate that groundwater discharge responds to climate variation and water-demand imbalances over a relatively short time period of years.

  14. How accessible are coral reefs to people? A global assessment based on travel time.

    Science.gov (United States)

    Maire, Eva; Cinner, Joshua; Velez, Laure; Huchery, Cindy; Mora, Camilo; Dagata, Stephanie; Vigliola, Laurent; Wantiez, Laurent; Kulbicki, Michel; Mouillot, David

    2016-04-01

    The depletion of natural resources has become a major issue in many parts of the world, with the most accessible resources being most at risk. In the terrestrial realm, resource depletion has classically been related to accessibility through road networks. In contrast, in the marine realm, the impact on living resources is often framed into the Malthusian theory of human density around ecosystems. Here, we develop a new framework to estimate the accessibility of global coral reefs using potential travel time from the nearest human settlement or market. We show that 58% of coral reefs are located travel time from the market is a strong predictor of fish biomass on coral reefs. We also highlight a relative deficit of protection on coral reef areas near people, with disproportional protection on reefs far from people. This suggests that conservation efforts are targeting low-conflict reefs or places that may already be receiving de facto protection due to their isolation. Our global assessment of accessibility in the marine realm is a critical step to better understand the interplay between humans and resources. © 2016 John Wiley & Sons Ltd/CNRS.

  15. Assessment of Smolt Condition for Travel Time Analysis, 1989 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Beeman, John W.; Rondorf, Dennis W.; Faler, Joyce C. (Seattle National Fishery Research Center, Columbia River Field Station, Cook, WA)

    1990-11-01

    The Water Budget is a volume of water used to enhance environmental conditions (flows) in the Columbia and Snake rivers for juvenile salmonids during their seaward migration. To manage the Water Budget, the Fish Passage Center estimates travel times of juvenile salmonids in index reaches of the main-stem rivers, using information on river flows and the migrational characteristics of the juvenile salmonids. This study was initiated to provide physiological information on the juvenile salmonids used for these travel time estimates. The physiological ability to respond to stressors was evaluated by measuring concentrations of plasma cortisol, glucose, and chlorides before and after a 30-s handling-stress challenge test. The development of smoltification was assessed by measuring gill Na{sup +}--K{sup +} ATPase activity and plasma thyroxine concentrations. Prevalence of bacterial kidney disease in spring chinook salmon was generally higher than in 1988, ranging from 81--100{percent} using an enzyme-linked immunosorbent assay (ELISA) method. Fish from Snake River hatcheries had more severe infections than those from mid-Columbia hatcheries. 42 refs., 19 figs., 4 tabs.

  16. Helioseismic Holography of Simulated Sunspots: Magnetic and Thermal Contributions to Travel Times

    Science.gov (United States)

    Felipe, T.; Braun, D. C.; Crouch, A. D.; Birch, A. C.

    2016-10-01

    Wave propagation through sunspots involves conversion between waves of acoustic and magnetic character. In addition, the thermal structure of sunspots is very different than that of the quiet Sun. As a consequence, the interpretation of local helioseismic measurements of sunspots has long been a challenge. With the aim of understanding these measurements, we carry out numerical simulations of wave propagation through sunspots. Helioseismic holography measurements made from the resulting simulated wavefields show qualitative agreement with observations of real sunspots. We use additional numerical experiments to determine, separately, the influence of the thermal structure of the sunspot and the direct effect of the sunspot magnetic field. We use the ray approximation to show that the travel-time shifts in the thermal (non-magnetic) sunspot model are primarily produced by changes in the wave path due to the Wilson depression rather than variations in the wave speed. This shows that inversions for the subsurface structure of sunspots must account for local changes in the density. In some ranges of horizontal phase speed and frequency there is agreement (within the noise level in the simulations) between the travel times measured in the full magnetic sunspot model and the thermal model. If this conclusion proves to be robust for a wide range of models, it would suggest a path toward inversions for sunspot structure.

  17. Magnetic and Thermal Contributions to Helioseismic Travel times in Simulated Sunspots

    Science.gov (United States)

    Braun, Douglas; Felipe, Tobias; Birch, Aaron; Crouch, Ashley D.

    2016-05-01

    The interpretation of local helioseismic measurements of sunspots has long been a challenge, since waves propagating through sunspots are potentially affected by both mode conversion and changes in the thermal structure of the spots. We carry out numerical simulations of wave propagation through a variety of models which alternately isolate either the thermal or magnetic structure of the sunspot or include both of these. We find that helioseismic holography measurements made from the resulting simulated wavefields show qualitative agreement with observations of real sunspots. Using insight from ray theory, we find that travel-time shifts in the thermal (non-magnetic) sunspot model are primarily produced by changes in the wave path due to the Wilson depression rather than variations in the wave speed. This shows that inversions for the subsurface structure of sunspots must account for local changes in the density. In some ranges of horizontal phase speed and frequency there is agreement (within the noise level of the measurements) between the travel times measured in the full magnetic sunspot model and the thermal model. If this conclusion proves to be robust for a wide range of models, it suggests a path towards inversions for sunspot structure. This research has been funded by the Spanish MINECO through grant AYA2014-55078-P, by the NASA Heliophysics Division through NNX14AD42G and NNH12CF23C, and the NSF Solar Terrestrial program through AGS-1127327.

  18. Modelling pedestrian travel time and the design of facilities: a queuing approach.

    Directory of Open Access Journals (Sweden)

    Khalidur Rahman

    Full Text Available Pedestrian movements are the consequence of several complex and stochastic facts. The modelling of pedestrian movements and the ability to predict the travel time are useful for evaluating the performance of a pedestrian facility. However, only a few studies can be found that incorporate the design of the facility, local pedestrian body dimensions, the delay experienced by the pedestrians, and level of service to the pedestrian movements. In this paper, a queuing based analytical model is developed as a function of relevant determinants and functional factors to predict the travel time on pedestrian facilities. The model can be used to assess the overall serving rate or performance of a facility layout and correlate it to the level of service that is possible to provide the pedestrians. It has also the ability to provide a clear suggestion on the designing and sizing of pedestrian facilities. The model is empirically validated and is found to be a robust tool to understand how well a particular walking facility makes possible comfort and convenient pedestrian movements. The sensitivity analysis is also performed to see the impact of some crucial parameters of the developed model on the performance of pedestrian facilities.

  19. Schizophrenia spectrum disorders show reduced specificity and less positive events in mental time travel

    Directory of Open Access Journals (Sweden)

    Xing-jie Chen

    2016-07-01

    Full Text Available Mental time travel refers to the ability to recall past events and to imagine possible future events. Schizophrenia patients have problems in remembering specific personal experiences in the past and imagining what will happen in the future. This study aimed to examine episodic past and future thinking in schizophrenia spectrum disorders including schizophrenia patients and individuals with schizotypal personality disorder (SPD proneness who are at risk for developing schizophrenia. Thirty-two schizophrenia patients, 30 SPD proneness individuals, and 33 healthy controls participated in the study. The Sentence Completion for Events from the Past Test (SCEPT and the Sentence Completion for Events in the Future Test (SCEFT were used to measure past and future thinking abilities. Results showed that schizophrenia patients showed significantly reduced specificity in recalling past and imagining future events, they generated less proportion of specific and extended events compared to healthy controls. SPD proneness individuals only generated less extended events compared to healthy controls. The reduced specificity was mainly manifested in imagining future events. Both schizophrenia patients and SPD proneness individuals generated less positive events than controls. These results suggest that mental time travel impairments in schizophrenia spectrum disorders and have implications for understanding their cognitive and emotional deficits.

  20. Modelling pedestrian travel time and the design of facilities: a queuing approach.

    Science.gov (United States)

    Rahman, Khalidur; Ghani, Noraida Abdul; Kamil, Anton Abdulbasah; Mustafa, Adli; Kabir Chowdhury, Md Ahmed

    2013-01-01

    Pedestrian movements are the consequence of several complex and stochastic facts. The modelling of pedestrian movements and the ability to predict the travel time are useful for evaluating the performance of a pedestrian facility. However, only a few studies can be found that incorporate the design of the facility, local pedestrian body dimensions, the delay experienced by the pedestrians, and level of service to the pedestrian movements. In this paper, a queuing based analytical model is developed as a function of relevant determinants and functional factors to predict the travel time on pedestrian facilities. The model can be used to assess the overall serving rate or performance of a facility layout and correlate it to the level of service that is possible to provide the pedestrians. It has also the ability to provide a clear suggestion on the designing and sizing of pedestrian facilities. The model is empirically validated and is found to be a robust tool to understand how well a particular walking facility makes possible comfort and convenient pedestrian movements. The sensitivity analysis is also performed to see the impact of some crucial parameters of the developed model on the performance of pedestrian facilities.

  1. Schizophrenia Spectrum Disorders Show Reduced Specificity and Less Positive Events in Mental Time Travel

    Science.gov (United States)

    Chen, Xing-jie; Liu, Lu-lu; Cui, Ji-fang; Wang, Ya; Chen, An-tao; Li, Feng-hua; Wang, Wei-hong; Zheng, Han-feng; Gan, Ming-yuan; Li, Chun-qiu; Shum, David H. K.; Chan, Raymond C. K.

    2016-01-01

    Mental time travel refers to the ability to recall past events and to imagine possible future events. Schizophrenia (SCZ) patients have problems in remembering specific personal experiences in the past and imagining what will happen in the future. This study aimed to examine episodic past and future thinking in SCZ spectrum disorders including SCZ patients and individuals with schizotypal personality disorder (SPD) proneness who are at risk for developing SCZ. Thirty-two SCZ patients, 30 SPD proneness individuals, and 33 healthy controls participated in the study. The Sentence Completion for Events from the Past Test (SCEPT) and the Sentence Completion for Events in the Future Test were used to measure past and future thinking abilities. Results showed that SCZ patients showed significantly reduced specificity in recalling past and imagining future events, they generated less proportion of specific and extended events compared to healthy controls. SPD proneness individuals only generated less extended events compared to healthy controls. The reduced specificity was mainly manifested in imagining future events. Both SCZ patients and SPD proneness individuals generated less positive events than controls. These results suggest that mental time travel impairments in SCZ spectrum disorders and have implications for understanding their cognitive and emotional deficits. PMID:27507958

  2. Possible evolutionary and developmental mechanisms of mental time travel (and implications for autism).

    Science.gov (United States)

    Allman, Melissa J; Mareschal, Denis

    2016-04-01

    Through an interdisciplinary perspective integrating behavior, neurobiology and evolution, we present a cognitive framework underpinning the development of 'time in mind' in animals (phylogeny) and humans (ontogeny). We distinguish between conscious processing of events immediately available (in the present) to those that are hypothetical (in the past or future). The former is present in animals and neonates, whereas the latter emerges later in phylogeny and ontogeny (around 4 years of age in humans) and is related to the development of episodic memory (expanded working memory, complex actions, social-cognitive abilities). We suggest that forms of temporal representation that rely upon current bodily sensation across time, space, and action (through embodied interoceptive and motor systems) may be critical causal factors for the evolution of mental time travel.

  3. Modeling the time-varying interaction between surface water and groundwater bodies

    Science.gov (United States)

    Gliege, Steffen; Steidl, Jörg; Lischeid, Gunnar; Merz, Christoph

    2016-04-01

    The countless kettle holes (small lakes) in the Late Pleistocene landscapes of Northern Europe have important ecological and hydrological functions. On the one hand they act as depressions in which water and solutes of mainly agriculturally used catchments accumulate. On the other hand they operate as biochemical reactors with respect to greenhouse gas emissions, carbon sequestration, and as major sinks for nutrients and contaminants. Even small kettle holes often are hydraulically connected to the uppermost groundwater system: Groundwater discharges into the kettle hole on one side, and the aquifer is recharged from the kettle hole water body on the other side. Thus kettle hole biogeochemical processes are both affected by groundwater and vice versa. Groundwater flow direction and velocity into and out of the kettle hole often is not stable over time. Groundwater flow direction might reverse at the downstream part, resulting in repeated recycling of groundwater and corresponding solute turnover within the kettle holes. A sound understanding of this intricate interplay is a necessary prerequisite for better understanding of the biogeochemistry of this terrestrial-aquatic interface. A numerical experiment was used to quantify the lateral solute exchange between a kettle hole and the surrounding groundwater. A vertical cross section through the real existing catchment of a kettle hole was chosen. Glacial till represents the lower boundary. The heterogeneity of the subsurface was reproduced by various parameterizations of the soil hydraulic properties as well as varying the thickness of the unconfined aquifer or the lateral boundary conditions. In total 24 different parameterizations were implemented in the modeling software HydroGeoSphere (HGS). HGS is suitable to calculate the fluid exchange between surface and subsurface simultaneously and in a physically based way. The simulation runs were done for the period from November 1994 to October 2014. All results were

  4. Travelling diabetics.

    Science.gov (United States)

    Chełmińska, Katarzyna; Jaremin, Bogdan

    2002-01-01

    During the past several decades, the number of both business and tourist travels has greatly increased. Among them are persons suffering from chronic diseases, including diabetics for whom travels pose the additional health-hazard. Irrespective of better education, self-control and constantly improving quality of specialistic equipment available, diabetics still are the group of patients requiring particular attention. In the case of travelling diabetics, problems may occur concerning the transport and storage of insulin, as well as control of glycaemia, all caused by irregularity of meals, variable diet, physical activity, stress, kinetosis (sea voyages), and the change of time zones. The travel may as well evoke ailments caused by the change of climate and concomitant diseases such as traveller's diarrhoea, malaria, etc. Apart from avoiding glycaemia fluctuations, important for retaining health of diabetics is the prevention of other diseases and carrying the necessary drugs.

  5. Associations between time spent traveling in motor vehicles and physical activity in Colombian adults from urban areas.

    Science.gov (United States)

    Paez, Diana C; Gomez, Luis F; Mallarino, Christina; Arango, Carlos M; Flórez, Alberto; Nylander, Andrew; Parra, Diana C

    2014-11-01

    Sedentary behaviors are associated with less physical activity. Little evidence exists about this association and its relation with commuting time in Latin America. This study examined the association between time spent traveling in motor vehicles and physical activity levels in the domains of leisure time physical activity and transportation, among Colombian adults in urban areas. A secondary data analysis of the 2010 National Nutrition Survey was conducted. Time spent traveling in motor vehicles and physical activity were assessed using the International Physical Activity Questionnaire. Binary logistic regressions were conducted. Time spent traveling in motor vehicles for 120 minutes or more was reported among 27.6% of the sample. The prevalence of walking and bicycling as a means of transportation for at least 150 minutes per week was 34% and 4.4%, respectively. Achieving at least 150 minutes of leisure time physical activity a week was reported by 18.4% of the sample. This study suggests negative associations between time spent traveling in motor vehicles and active transport, with significant trend associations in stratified analyses. No significant associations were found between time spent traveling in motor vehicles and leisure time physical activity.

  6. 41 CFR 302-3.219 - Is there a limit on how many times I may receive reimbursement for tour renewal travel?

    Science.gov (United States)

    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...

  7. 41 CFR 302-4.204 - If my spouse does not accompany me but travels unaccompanied at a different time, what per diem...

    Science.gov (United States)

    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...

  8. Travel Times of Later Phases for Transmitting Waves through a Fracturing Westerly Granite Sample under a Triaxial Compressive Condition

    Science.gov (United States)

    Imahori, A.; Kawakata, H.; Hirano, S.; Yoshimitsu, N.; Takahashi, N.

    2015-12-01

    In laboratory, it is well-known that the elastic wave speed varies prior to compression fracture of the rock (e.g., Lockner et al., 1977, JGR). Using an enough number of travel times of elastic wave paths in a sample, we can estimate internal structure of the sample. However, the number of the elastic wave transducers is limited, and only the travel times of the first arrival are available in most experiments. Employing broadband transducers (Yoshimitsu et al., 2014, GRL), later phases become available to be analyzed. In the present study, we conduct a triaxial compressive test at room temperature under a dry condition and a confining pressure of 50 MPa, using a cylindrical Westerly granite sample of 100 mm long by 50 mm in diameter. Eight transducers are attached on the sample surface. One of the transducers is used as a wave source and voltage steps are repeatedly applied to it. The elastic waves passing through the sample are sensed by the other broadband transducers, and recorded at a sampling rate of 20 Msps. P-wave speed is estimated from the travel time of the direct P, and Vp/Vs value is assumed to be the √3 to give S-wave speed. We assume that all wave paths never bend except at the top and bottom surface of the sample. We calculate the travel times of later phases reflected at the top and/or bottom surfaces within 3 times. We collate the calculated travel times with observed waveforms. We can identify the travel time of two phases: single reflection from both top and bottom of the sample. On the other hand, some other observed and calculated phase arrivals do not match with each other. Then, we try to identify some remarkable phases using the calculated travel times of PS and SP converted waves and interfacial waves, taking into consideration of wave speed anisotropy.

  9. The Traveling Salesman Problem: Low-Dimensionality Implies a Polynomial Time Approximation Scheme

    CERN Document Server

    Bartal, Yair; Krauthgamer, Robert

    2011-01-01

    The Traveling Salesman Problem (TSP) is among the most famous NP-hard optimization problems. We design for this problem a randomized polynomial-time algorithm that computes a (1+eps)-approximation to the optimal tour, for any fixed eps>0, in TSP instances that form an arbitrary metric space with bounded intrinsic dimension. The celebrated results of Arora (A-98) and Mitchell (M-99) prove that the above result holds in the special case of TSP in a fixed-dimensional Euclidean space. Thus, our algorithm demonstrates that the algorithmic tractability of metric TSP depends on the dimensionality of the space and not on its specific geometry. This result resolves a problem that has been open since the quasi-polynomial time algorithm of Talwar (T-04).

  10. Catching the tail: Empirical identification of the distribution of the value of travel time

    DEFF Research Database (Denmark)

    Börjesson, Maria; Fosgerau, Mogens; Algers, Staffan

    2012-01-01

    Recent methodological advances in discrete choice analysis in combination with certain stated choice experiments have allowed researchers to check empirically the identification of the distribution of latent variables such as the value of travel time (VTT). Lack of identification is likely...... to be common and the consequences are severe. E.g., the Danish value of time study found the 15% right tail of the VTT distribution to be unidentified, making it impossible to estimate the mean VTT without resorting to strong assumptions with equally strong impact on the resulting estimate. This paper analyses...... VTT distribution. In addition to informing the design of future choice experiments, the results are also of interest as a validity test of the stated choice methodology. Failure in identifying the right tail of the VTT would have made it difficult to maintain that respondents’ behaviour is consistent...

  11. Assessment of smolt condition for travel time analysis. Annual report 1989

    Science.gov (United States)

    Beeman, J.W.; Rondorf, D.W.; Faler, J.C.; Free, M.E.; Haner, P.V.

    1990-01-01

    The Water Budget is a volume of water used to enhance environmental conditions (flows) in the Columbia and Snake rivers for juvenile salmonids during their seaward migration. To manage the Water Budget, the Fish Passage Center estimates travel times of juvenile salmonids in index reaches of the main-stem rivers, using information on river flows and the migrational characteristics of the juvenile salmonids. This study was initiated to provide physiological information on the juvenile salmonids used for these travel time estimates. The physiological ability to respond to stressors was evaluated by measuring concentrations of plasma cortisol, glucose, and chlorides before and after a 30-s handling-stress challenge test. As in 1988, most groups responded satisfactorily to the challenge. The scope for response was compromised among two groups of juvenile chinook salmon that were trucked to release sites and in steelhead from one hatchery after unusual marking and transportation protocols were used. The development of smoltification was assessed by measuring gill Na+-K+ ATPase activity and plasma thyroxine concentrations. Mean ATPase activities of marked hatchery groups of juvenile chinook salmon and steelhead changed little during the month before release and rose sharply for about the first 20 d of the migration after release. Mean plasma thyroxine was highest during the first 20 d after release. Mean gill ATPase activity of spring chinook salmon from the migration-at-large peaked at about the 90th percentile of passage at Rock Island and Lower Granite dams, and at about the 50th percentile of passage at McNary Dam. Mean gill ATPase activity of wild steelhead was higher than gill ATPase activity of hatchery steelhead at Rock Island Dam, the Snake River Trap, and Lower Granite Dam, but not at McNary Dam. This was attributed to a time-dependent relationship between increases in ATPase activity and the number of days fish migrated before recapture. Correlations of gill

  12. Rapid Adjustment of Circadian Clocks to Simulated Travel to Time Zones across the Globe.

    Science.gov (United States)

    Harrison, Elizabeth M; Gorman, Michael R

    2015-12-01

    Daily rhythms in mammalian physiology and behavior are generated by a central pacemaker located in the hypothalamic suprachiasmatic nuclei (SCN), the timing of which is set by light from the environment. When the ambient light-dark cycle is shifted, as occurs with travel across time zones, the SCN and its output rhythms must reset or re-entrain their phases to match the new schedule-a sluggish process requiring about 1 day per hour shift. Using a global assay of circadian resetting to 6 equidistant time-zone meridians, we document this characteristically slow and distance-dependent resetting of Syrian hamsters under typical laboratory lighting conditions, which mimic summer day lengths. The circadian pacemaker, however, is additionally entrainable with respect to its waveform (i.e., the shape of the 24-h oscillation) allowing for tracking of seasonally varying day lengths. We here demonstrate an unprecedented, light exposure-based acceleration in phase resetting following 2 manipulations of circadian waveform. Adaptation of circadian waveforms to long winter nights (8 h light, 16 h dark) doubled the shift response in the first 3 days after the shift. Moreover, a bifurcated waveform induced by exposure to a novel 24-h light-dark-light-dark cycle permitted nearly instant resetting to phase shifts from 4 to 12 h in magnitude, representing a 71% reduction in the mismatch between the activity rhythm and the new photocycle. Thus, a marked enhancement of phase shifting can be induced via nonpharmacological, noninvasive manipulation of the circadian pacemaker waveform in a model species for mammalian circadian rhythmicity. Given the evidence of conserved flexibility in the human pacemaker waveform, these findings raise the promise of flexible resetting applicable to circadian disruption in shift workers, frequent time-zone travelers, and any individual forced to adjust to challenging schedules. © 2015 The Author(s).

  13. Nonlinear teleseismic tomography at Long Valley caldera, using three-dimensional minimum travel time ray tracing

    Energy Technology Data Exchange (ETDEWEB)

    Weiland, C.M. [Univ. of California, Santa Barbara, CA (United States); Steck, L.K. [Los Alamos National Lab., NM (United States); Dawson, P.B. [Geological Survey, Menlo Park, CA (United States)] [and others

    1995-10-10

    The authors explore the impact of three-dimensional minimum travel time ray tracing on nonlinear teleseismic inversion. This problem has particular significance when trying to image strongly contrasting low-velocity bodies, such as magma chambers, because strongly refracted/and/or diffracted rays may precede the direct P wave arrival traditionally used in straight-ray seismic tomography. They use a simplex-based ray tracer to compute the three-dimensional, minimum travel time ray paths and employ an interative technique to cope with nonlinearity. Results from synthetic data show that their algorithm results in better model reconstructions compared with traditional straight-ray inversions. The authors reexamine the teleseismic data collected at Long Valley caldera by the U.S. Geological Survey. The most prominent feature of their result is a 25-30% low-velocity zone centered at 11.5 km depth beneath the northwestern quandrant of the caldera. Beneath this at a depth of 24.5 km is a more diffuse 15% low-velocity zone. In general, the low velocities tend to deepen to the south and east. The authors interpret the shallow feature to be the residual Long Valley caldera magma chamber, while the deeper feature may represent basaltic magmas ponded in the midcrust. The deeper position of the prominent low-velocity region in comparison to earlier tomographic images is a result of using three-dimensional rays rather than straight rays in the ray tracing. The magnitude of the low-velocity anomaly is a factor of {approximately}3 times larger than earlier models from linear arrival time inversions and is consistent with models based on observations of ray bending at sites within the caldera. These results imply the presence of anywhere from 7 to 100% partial melt beneath the caldera. 40 refs., 1 fig., 1 tab.

  14. Accessing doctors at times of need-measuring the distance tolerance of rural residents for health-related travel.

    Science.gov (United States)

    McGrail, Matthew Richard; Humphreys, John Stirling; Ward, Bernadette

    2015-05-29

    Poor access to doctors at times of need remains a significant impediment to achieving good health for many rural residents. The two-step floating catchment area (2SFCA) method has emerged as a key tool for measuring healthcare access in rural areas. However, the choice of catchment size, a key component of the 2SFCA method, is problematic because little is known about the distance tolerance of rural residents for health-related travel. Our study sought new evidence to test the hypothesis that residents of sparsely settled rural areas are prepared to travel further than residents of closely settled rural areas when accessing primary health care at times of need. A questionnaire survey of residents in five small rural communities of Victoria and New South Wales in Australia was used. The two outcome measures were current travel time to visit their usual doctor and maximum time prepared to travel to visit a doctor, both for non-emergency care. Kaplan-Meier charts were used to compare the association between increased distance and decreased travel propensity for closely-settled and sparsely-settled areas, and ordinal multivariate regression models tested significance after controlling for health-related travel moderating factors and town clustering. A total of 1079 questionnaires were completed with 363 from residents in closely-settled locations and 716 from residents in sparsely-settled areas. Residents of sparsely-settled communities travel, on average, 10 min further than residents of closely-settled communities (26.3 vs 16.9 min, p time prepared to travel (54.1 vs 31.9 min, p time remained significant after controlling for demographic and other constraints to access, such as transport availability or difficulties getting doctor appointments, as well as after controlling for town clustering and current travel times. Improved geographical access remains a key issue underpinning health policies designed to improve the provision of rural primary health care

  15. Narrative time in video games and films: from loop to travel in time

    OpenAIRE

    Lluís Anyó

    2015-01-01

    Within the broad framework of audiovisual theories, this paper deals with the analysis of narrative time in video games. Starting with the concept of participation time, which is taken from the interactive media, the now classic concepts of the narratology of film studies are applied to clarify the main mutual influences between the two media in relation to narrative time. Unlike the cinema, the narrative character of video games is not always clear. Generally, video games are always games an...

  16. Aggregation effects on tritium-based mean transit times and young water fractions in spatially heterogeneous catchments and groundwater systems

    Directory of Open Access Journals (Sweden)

    M. K. Stewart

    2017-09-01

    Full Text Available Kirchner (2016a demonstrated that aggregation errors due to spatial heterogeneity, represented by two homogeneous subcatchments, could cause severe underestimation of the mean transit times (MTTs of water travelling through catchments when simple lumped parameter models were applied to interpret seasonal tracer cycle data. Here we examine the effects of such errors on the MTTs and young water fractions estimated using tritium concentrations in two-part hydrological systems. We find that MTTs derived from tritium concentrations in streamflow are just as susceptible to aggregation bias as those from seasonal tracer cycles. Likewise, groundwater wells or springs fed by two or more water sources with different MTTs will also have aggregation bias. However, the transit times over which the biases are manifested are different because the two methods are applicable over different time ranges, up to 5 years for seasonal tracer cycles and up to 200 years for tritium concentrations. Our virtual experiments with two water components show that the aggregation errors are larger when the MTT differences between the components are larger and the amounts of the components are each close to 50 % of the mixture. We also find that young water fractions derived from tritium (based on a young water threshold of 18 years are almost immune to aggregation errors as were those derived from seasonal tracer cycles with a threshold of about 2 months.

  17. A Computational Method for 3D Anisotropic Travel-time Tomography of Rocks in the Laboratory

    Science.gov (United States)

    Ghofranitabari, Mehdi; Young, R. Paul

    2013-04-01

    True triaxial loading in the laboratory applies three principal stresses on a cubic rock specimen. Elliptical anisotropy and distributed heterogeneities are introduced in the rock due to closure and opening of the pre-existing cracks and creation and growth of the new aligned cracks. The rock sample is tested in a Geophysical Imaging Cell that is armed with an Acoustic Emission monitoring system which can perform transducer to transducer velocity surveys to image velocity structure of the sample during the experiment. Ultrasonic travel-time tomography as a non-destructive method outfits a map of wave propagation velocity in the sample in order to detect the uniformly distributed or localised heterogeneities and provide the spatial variation and temporal evolution of induced damages in rocks at various stages of loading. The rock sample is partitioned into cubic grid cells as model space. Ray-based tomography method measuring body wave travel time along ray paths between pairs of emitting and receiving transducers is used to calculate isotropic ray-path segment matrix elements (Gij) which contain segment lengths of the ith ray in the jth cell in three dimensions. Synthetic P wave travel times are computed between pairs of transducers in a hypothetical isotropic heterogeneous cubic sample as data space along with an error due to precision of measurement. 3D strain of the squeezed rock and the consequent geometrical deformation is also included in computations for further accuracy. Singular Value Decomposition method is used for the inversion from data space to model space. In the next step, the anisotropic ray-path segment matrix and the corresponded data space are computed for hypothetical anisotropic heterogeneous samples based on the elliptical anisotropic model of velocity which is obtained from the real laboratory experimental data. The method is examined for several different synthetic heterogeneous models. An "Inaccuracy factor" is utilized to inquire the

  18. Calibration of transient groundwater models using time series analysis and moment matching

    NARCIS (Netherlands)

    Bakker, M.; Maas, K.; Von Asmuth, J.R.

    2008-01-01

    A comprehensive and efficient approach is presented for the calibration of transient groundwater models. The approach starts with the time series analysis of the measured heads in observation wells using all active stresses as input series, which may include rainfall, evaporation, surface water leve

  19. Groundwater recharge and time lag measurement through Vertosols using impulse response functions

    Science.gov (United States)

    Hocking, Mark; Kelly, Bryce F. J.

    2016-04-01

    Throughout the world there are many stressed aquifers used to support irrigated agriculture. The Condamine River catchment (southern Queensland, Australia) is one example of a globally significant agricultural region where groundwater use has exceeded recharge over the last 50 years. There is a high dependence on groundwater in this catchment, because yearly rainfall is highly variable, and actual evapotranspiration often exceeds rainfall. To better manage the aquifer there is a need to correctly conceptualise the primary inputs and outputs of the system, and characterise the lags in system response to all forcings. In catchment models it is particularly important to correctly proportion diffuse (areal) rainfall recharge and to account for the lag between rainfall and recharge at the water table. Throughout large portions of the Condamine Catchment, groundwater levels are now 20 or more metres below the ground surface. This study aimed to better quantify the lag between rainfall and recharge at the water table using the predefined impulse response function in continuous time method (PIRFICT; von Asmuth et al., 2002; von Asmuth, 2012). The PIRFICT method was applied to 255 multi-decadal groundwater level data sets throughout the catchment. Inputs into the modelling include rainfall, irrigation deep drainage, stream water level, evapotranspiration, and groundwater extractions. As an independent check the PIRFICT model derived diffuse recharge estimates are compared to point lysimeter and geochemical recharge estimates in the Vertosol soils within this catchment. It is estimated using the PIRFICT method that in the Condamine Catchment between 1990 and 2012, the mean rain-derived groundwater recharge is 4.4 mm/year. Mean groundwater response from rainfall was determined to be 5.3 years: range 188 days to 48 years. The recharge estimates are consistent with both geochemical and lysimeter point measurements of recharge. It is concluded that where extensive groundwater

  20. Geochemical modelling of groundwater evolution and residence time at the Olkiluoto site

    Energy Technology Data Exchange (ETDEWEB)

    Pitkaenen, P.; Luukkonen, A. [VTT Communities and Infrastructure, Espoo (Finland); Ruotsalainen, P. [Fintact Oy (Finland); Leino-Forsman, H.; Vuorinen, U. [VTT Chemical Technology, Espoo (Finland)

    1999-05-01

    external conditions such as glaciation, palaeo Baltic stages, land uplift and ancient hydrothermal events, have had a significant effect on local palaeohydrogeological conditions. They have caused great variability, which is observable in the chemical data notably in salinity (up to 70 g/l), water type and contents of conservative parameters, such as Cl, Br and stable isotopes of water. However, their influence is also significant on the water-rock interaction that principally controls the pH and redox conditions - varying 7.5 to 8 and -200 to -300 mV, respectively - in the groundwater, although the calculated mass transfer in the reactions is minor compared with conservative mixing at the site. Calcite in fractures is interpreted to principally control pH level in groundwater. Sulphidic redox conditions dominate in the upper 500 m in brackish and slightly saline groundwater. Deeper sulphur species are absent and methanic processes are obtained. The water types can be connected to certain palaeo stages. This enables to estimate mean residence time of groundwaters. Current meteoric recharge stage (< 2500 a) mainly dominates in the upper 150 m. Groundwater from Litorina stage (7500-2500 a ago) forms the bulk at 100 - 250 m. Glacial melt water (about 10 000 a old) is an important component of groundwater between 100 - 500 m. However, any remarks of oxygen intrusion cannot be interpreted neither from mineralogy nor from groundwater. Deeper, subglacial and older saline groundwater predominates. Despite the current locations of different groundwater bodies it seems according to hydrogeochemical interpretation that dynamic flow conditions has been limited to upper 150 - 200 m. (orig.) 82 refs.

  1. Application of the Netherlands Groundwater Model, LGM, for calculating concentration of nitrate and pesticides at abstraction wells in sandy soil areas of the Netherlands

    NARCIS (Netherlands)

    Kovar K; Pastoors MJH; Tiktak A; Gaalen FW van; LBG, LWD

    1998-01-01

    In a study aimed at assessing the impact of historical and future solute leaching into saturated groundwater, the quasi-three-dimensional RIVM groundwater model, LGM (version 2), was used for calculating pathlines, travel times and concentration breakthrough curves at 165 groundwater abstraction loc

  2. Travel time analysis for a subsurface drained sub-watershed in Upper Big Walnut Creek Watershed, Ohio

    Science.gov (United States)

    Runoff travel time, which is a function of watershed and storm characteristics, is an important parameter affecting the prediction accuracy of hydrologic models. Although, time of concentration (tc) is a most widely used time parameter, it has multiple conceptual and computational definitions. Most ...

  3. A Link Travel Time Prediction Algorithm Based on Travel-time Field Traversing%基于行程-时间域的路段行程时间预测

    Institute of Scientific and Technical Information of China (English)

    张安泰; 柴干; 丁闪闪

    2013-01-01

    In order to improve the real-time and accuracy of the highway link travel time prediction, a travel time prediction algorithm based on travel-time field traversing was proposed. Based on the real-time traffic data detection and predicting every time unit space mean speed of link units by BP neural network, the algorithm constructed the travel-time field. The predicted travel time was obtained by traversing the travel-time field. Data detected by highway traffic detector was taken full advantage of by the travel-time field traversing. Through simulation research, the fact that travel-time field traversing is superior to traditional neural network prediction algorithm was revealed by comparison. Taking the link of Shanghai-Nanjing Freeway as background and based on Vissim simulation software, the accuracy and feasibility of the proposed algorithm was verified.%为了提高高速公路路段行程时间预测的实时性与准确性,提出了基于行程-时间域的路段行程时间预测算法.该算法依据实时检测的交通数据和BP神经网络预测路段单元在不同时间单元的空间平均车速,构建车辆出行的行程-时间域,通过车辆穿越行程-时间域获得路段的预测行程时间.通过比较行程-时间域算法与传统神经网络预测算法,揭示了行程-时间域算法在预测精度上优于传统神经网络算法.以沪宁高速公路路段作为示例背景,基于Vissim仿真软件,验证了所提算法的准确性与可行性.

  4. A Hard Day’s Knights: Movie Time Travel, the Middle Ages, and a New Millenium

    Directory of Open Access Journals (Sweden)

    John Engle

    2012-10-01

    Full Text Available This article addresses the cinematic treatment of the Middle Ages through an analysis of two recent mass-audience American films, Black Knight and Timeline, both of which feature time travel as a leading plot element. Providing context for this discussion is a brief analysis of other similar films, as well as remarks regarding Twain's Connecticut Yankee, Ruskin's The Stones of Venice, and The Idylls of the King by Tennyson. As in these other works, the films in question use certain popular stereotypes of the Middle Ages—endemic violence, rigid class distinctions, religious fanaticism, spiritual cohesion, etc.—as lens through which to view the contemporary world. In addition to their roles as comic or action entertainment vehicles, Black Knight indirectly addresses American individualism and a cutthroat modern corporate culture, whereas Timeline touches upon millennial anxiety, '90's ethnic cleansing, and the American misadventure in Iraq.

  5. Helioseismic holography of simulated sunspots: magnetic and thermal contributions to travel times

    CERN Document Server

    Felipe, T; Crouch, A D; Birch, A C

    2016-01-01

    Wave propagation through sunspots involves conversion between waves of acoustic and magnetic character. In addition, the thermal structure of sunspots is very different than that of the quiet Sun. As a consequence, the interpretation of local helioseismic measurements of sunspots has long been a challenge. With the aim of understanding these measurements, we carry out numerical simulations of wave propagation through sunspots. Helioseismic holography measurements made from the resulting simulated wavefields show qualitative agreement with observations of real sunspots. We use additional numerical experiments to determine, separately, the influence of the thermal structure of the sunspot and the direct effect of the sunspot magnetic field. We use the ray approximation to show that the travel-time shifts in the thermal (non-magnetic) sunspot model are primarily produced by changes in the wave path due to the Wilson depression rather than variations in the wave speed. This shows that inversions for the subsurfac...

  6. Travel Times, Congestion Levels, and Delays at Intersections Calculated on the Basis of Floating Car Data

    DEFF Research Database (Denmark)

    Lahrmann, Harry; Torp, Kristian

    2010-01-01

    Traditionally, the mapping of flow rate in a road network has been based on spot and intersection counting. Using these counting techniques, detailed information about traffic at a few well-picked spots in the road network is obtained. However, these techniques give no exact information about...... traffic only a few meters away from the measuring spots. The situation is totally the opposite when it comes to log data from GPS receivers in cars. Here detailed information about individual cars in the entire road network is obtained. However, the GPS data is only available from a small subset...... of the cars. This paper presents a method to determine travel time, congestion levels and delays using GPS data from moving vehicles – the so-called floating car data....

  7. The time travelling self: comparing self and other in narratives of past and future events.

    Science.gov (United States)

    Grysman, Azriel; Prabhakar, Janani; Anglin, Stephanie M; Hudson, Judith A

    2013-09-01

    Mental time travel research emphasizes the connection between past and future thinking, whereas autobiographical memory research emphasizes the interrelationship of self and memory. This study explored the relationship between self and memory when thinking about both past and future events. Participants reported events from the near and distant past and future, for themselves, a close friend, or an acquaintance. Past events were rated higher in phenomenological quality than future events, and near self events were rated higher in quality than those about friends. Although future events were more positive than past events, only valence ratings for self and close friend showed a linear increase in positivity from distant past to future. Content analysis showed that this increase in positivity could not be ascribed to choosing events from the cultural life script. These findings provide evidence for the role of personal goals in imagining the future.

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

    Science.gov (United States)

    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.

  9. Integrating stochastic time-dependent travel speed in solution methods for the dynamic dial-a-ride problem.

    Science.gov (United States)

    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.

  10. Helioseismic holography of simulated sunspots: dependence of the travel time on magnetic field strength and Wilson depression

    Science.gov (United States)

    Felipe, T.; Braun, D. C.; Birch, A. C.

    2017-08-01

    Improving methods for determining the subsurface structure of sunspots from their seismic signature requires a better understanding of the interaction of waves with magnetic field concentrations. We aim to quantify the impact of changes in the internal structure of sunspots on local helioseismic signals. We have numerically simulated the propagation of a stochastic wave field through sunspot models with different properties, accounting for changes in the Wilson depression between 250 and 550 km and in the photospheric umbral magnetic field between 1500 and 3500 G. The results show that travel-time shifts at frequencies above approximately 3.50 mHz (depending on the phase-speed filter) are insensitive to the magnetic field strength. The travel time of these waves is determined exclusively by the Wilson depression and sound-speed perturbation. The travel time of waves with lower frequencies is affected by the direct effect of the magnetic field, although photospheric field strengths below 1500 G do not leave a significant trace on the travel-time measurements. These results could potentially be used to develop simplified travel-time inversion methods.

  11. Modeling the light-travel-time effect on the far-infrared size of IRC +10216

    Science.gov (United States)

    Wright, Edward L.; Baganoff, Frederick K.

    1995-01-01

    Models of the far-infrared emission from the large circumstellar dust envelope surrounding the carbon star IRC +10216 are used to assess the importance of the light-travel-time effect (LTTE) on the observed size of the source. The central star is a long-period variable with an average period of 644 +/- 17 days and a peak-to-peak amplitude of two magnituds, so a large light-travel-time effect is seen at 1 min radius. An attempt is made to use the LTTE to reconcile the discrepancy between the observations of Fazio et al. and Lester et al. regarding the far-infrared source size. This discrepancy is reviewed in light of recent, high-spatial-resolution observations at 11 microns by Danchi et al. We conclude that IRC +10216 has been resolved on the arcminute scale by Fazio et al. Convolution of the model intensity profile at 61 microns with the 60 sec x 90 sec Gaussian beam of Fazio et al. yields an observed source size full width at half maximum (FWHM) that ranges from approximately 67 sec to 75 sec depending on the phase of the star and the assumed distance to the source. Using a simple r(exp -2) dust distribution and the 106 deg phase of the Fazio et al. observations, the LTTE model reaches a peak size of 74.3 sec at a distance of 300 pc. This agrees favorably with the 78 sec x 6 sec size measured by Fazio et al. Finally, a method is outlined for using the LTTE as a distance indicator to IRC +10216 and other stars with extended mass outflows.

  12. Spatially Distributed Characterization of Soil Dynamics Using Travel-Time Distributions

    Science.gov (United States)

    Hesse, Falk; Zink, Matthias; Attinger, Sabine

    2016-04-01

    The description of storage and transport of both water and solved contaminants in catchments is very difficult due to the high heterogeneity of the subsurface properties that govern their fate. This heterogeneity, combined with a generally limited knowledge about the subsurface, results in high degrees of uncertainty. As a result, stochastic methods are increasingly applied, where the relevant processes are modeled as being random. Within these methods, quantities like the catchment travel or residence time of a water parcel are described using probability density functions (PDF). The derivation of these PDF's is typically done by using the water fluxes and states of the catchment. A successful application of such frameworks is therefore contingent on a good quantification of these fluxes and states across the different spatial scales. The objective of this study is to use travel times for the characterization of an ca. 1000 square kilometer, humid catchment in Central Germany. To determine the states and fluxes, we apply the mesoscale Hydrological Model mHM, a spatially distributed hydrological model to the catchment. Using detailed data of precipitation, land cover, morphology and soil type as inputs, mHM is able to determine fluxes like recharge and evapotranspiration and states like soil moisture as outputs. Using these data, we apply the above theoretical framework to our catchment. By virtue of the aforementioned properties of mHM, we are able to describe the storage and release of water with a high spatial resolution. This allows for a comprehensive description of the flow and transport dynamics taking place in the catchment. The spatial distribution of such dynamics is then compared with land cover and soil moisture maps as well as driving forces like precipitation and potential evapotranspiration to determine the most predictive factors. In addition, we investigate how non-local data like the age distribution of discharge flows are impacted by, and

  13. Spatially Distributed Characterization of Catchment Dynamics Using Travel-Time Distributions

    Science.gov (United States)

    Heße, F.; Zink, M.; Attinger, S.

    2015-12-01

    The description of storage and transport of both water and solved contaminants in catchments is very difficult due to the high heterogeneity of the subsurface properties that govern their fate. This heterogeneity, combined with a generally limited knowledge about the subsurface, results in high degrees of uncertainty. As a result, stochastic methods are increasingly applied, where the relevant processes are modeled as being random. Within these methods, quantities like the catchment travel or residence time of a water parcel are described using probability density functions (PDF). The derivation of these PDF's is typically done by using the water fluxes and states of the catchment. A successful application of such frameworks is therefore contingent on a good quantification of these fluxes and states across the different spatial scales. The objective of this study is to use travel times for the characterization of an ca. 1000 square kilometer, humid catchment in Central Germany. To determine the states and fluxes, we apply the mesoscale Hydrological Model mHM, a spatially distributed hydrological model to the catchment. Using detailed data of precipitation, land cover, morphology and soil type as inputs, mHM is able to determine fluxes like recharge and evapotranspiration and states like soil moisture as outputs. Using these data, we apply the above theoretical framework to our catchment. By virtue of the aforementioned properties of mHM, we are able to describe the storage and release of water with a high spatial resolution. This allows for a comprehensive description of the flow and transport dynamics taking place in the catchment. The spatial distribution of such dynamics is then compared with land cover and soil moisture maps as well as driving forces like precipitation and temperature to determine the most predictive factors. In addition, we investigate how non-local data like the age distribution of discharge flows are impacted by, and therefore allow to infer

  14. The first study of the light-travel time effect in massive LMC eclipsing binaries

    CERN Document Server

    Zasche, P; Vrastil, J; Pilarcik, L; Jurysek, J

    2016-01-01

    Aims: New CCD observations for semidetached and detached eclipsing binaries from the Large Magellanic Cloud were carried out using the Danish 1.54-m telescope located at the La Silla Observatory in Chile. The selected systems were monitored for their times of minima, which were required to be able to study the period changes taking place in them. In addition, many new times of minima were derived from the photometric surveys OGLE-II, OGLE-III, and MACHO. Methods: The O-C diagrams of minima timings were analysed using the hypothesis of the light-travel time effect, i.e. assuming the orbital motion around a common barycenter with the distant component. Moreover, the light curves of these systems were also analysed using the program PHOEBE, which provided the physical parameters of the stars. Results: For the first time, in this study we derived the relatively short periods of modulation in these systems, which relates to third bodies. The orbital periods resulted from 3.6 to 11.3 yr and the eccentricities were ...

  15. A method to filter out the effect of river stage fluctuation on groundwater level using time series models

    Science.gov (United States)

    Yoon, Heesung; Park, Eungyu; Yoon, Pilsun; Lee, Eunhee; Kim, Gyoo-Bum

    2016-04-01

    A method to filter out the effect of river stage fluctuations on groundwater level was designed using an artificial neural network-based time series model of groundwater level prediction. The designed method was applied to daily groundwater level data near the Gangjeong-Koryeong Barrage in the Nakdong river, South Korea. First, one-step ahead direct prediction time series models were successfully developed for both cases of before and after the barrage construction using past measurement data of rainfall, river stage, and groundwater level as inputs. The correlation coefficient values between observed and predicted data were over 0.97. Based on the direct prediction models, recursive prediction models for the simulation of groundwater level fluctuations were designed. The effect of river stage fluctuation on groundwater level data was filtered out by setting a constant value for river stage inputs of the recursive time series models. The hybrid water table fluctuation method was employed to estimate the groundwater recharge using the filtered data. The calculated ratios of groundwater recharge to precipitation before and after the barrage construction were 11.0% and 4.3%, respectively. It is expected that the proposed method can be a useful tool for groundwater level prediction and recharge estimation in the riverside area.

  16. A Modified Groundwater Flow Model Using the Space Time Riemann-Liouville Fractional Derivatives Approximation

    Directory of Open Access Journals (Sweden)

    Abdon Atangana

    2014-01-01

    Full Text Available The notion of uncertainty in groundwater hydrology is of great importance as it is known to result in misleading output when neglected or not properly accounted for. In this paper we examine this effect in groundwater flow models. To achieve this, we first introduce the uncertainties functions u as function of time and space. The function u accounts for the lack of knowledge or variability of the geological formations in which flow occur (aquifer in time and space. We next make use of Riemann-Liouville fractional derivatives that were introduced by Kobelev and Romano in 2000 and its approximation to modify the standard version of groundwater flow equation. Some properties of the modified Riemann-Liouville fractional derivative approximation are presented. The classical model for groundwater flow, in the case of density-independent flow in a uniform homogeneous aquifer is reformulated by replacing the classical derivative by the Riemann-Liouville fractional derivatives approximations. The modified equation is solved via the technique of green function and the variational iteration method.

  17. Determination Method of Focal Depth of Local Earthquake Using the Travel-time Difference between Pn and sPn

    Institute of Scientific and Technical Information of China (English)

    Wang Dengwei; Xu Qinping; Ma Fuhong; Cheng Xuefen

    2011-01-01

    In this paper, we derived the relationships between the travel time difference of sPn and Pn and the local earthquake focal depth. In these equations, the travel time difference of sPn and Pn is not related to the epicentral distance, but depends only on the regional crustal mode and the focal depth. According to the equations, we provided a simple and accurate method to determine local earthquake focal depth by using the travel time difference between phase sPn and Pn. This method has been used to determine the focal depths of two earthquake of Ms6. 1 and Ms5.6 which occurred at the junction of Panzhihua and Huili, Sichuan on August 30 and 31, 2008. The results were compared to those from other sources such as the China Earthquake Networks Center, and the comparison shows that the results are accurate and reliable.

  18. Implementation and Comparison of Acoustic Travel-Time Measurement Procedures for the Helioseismic and Magnetic Imager Time-Distance Helioseismology Pipeline

    Science.gov (United States)

    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

  19. Coupling groundwater residence time and 234U/238U isotopic ratios in a granitic catchment (Vosges, Eastern France)

    Science.gov (United States)

    Viville, Daniel; Aquilina, Luc; Ackerer, Julien; Chatton, Eliot; Labasque, Thierry; Pierret, Marie-Claire; Granet, Mathieu; Perrone, Thierry; Chabaux, François

    2016-04-01

    Weathering processes are active in surface waters but groundwater also represents no neglectable chemical fluxes. As residence-time in groundwater are high, silicate weathering might take place and control Si, Ca and C fluxes. Weathering processes can be deduced from U isotopic ratios but the kinetics of these processes remain relatively poorly constrained. In order to better characterize these processes, we have coupled residence-times deduced from anthropogenic gases (CFC and SF6) analysis and 234U/238U isotopic ratios determination. Samples were collected in the Strengbach catchment (Hydro-geochemical Observatory OHGE, Vosges, eastern France). Two campaigns were carried out in May and August 2015 during two highly contrasted hydro-climatic periods. Both springs and boreholes down to 80 m depth have been sampled. A very clear geochemical distinction is observed between groundwater from surface springs and deeper groundwater from boreholes. Springs show much lower residence-time (few years) and specific chemical composition. Deeper groundwater have residence-time of several decades and different geochemical composition. A clear SF6 production is observed with increasing SF6 concentrations with residence-time. The campaign of May is characterized by highly groundwater levels and spring fluxes. All groundwater show very low residence time, except in the boreholes at depth greater than 40 m. Conversely, during low groundwater-level period in August, the residence times are much higher and CFC concentrations indicate a large mixing process between surface groundwater and deeper levels. The 234U/238U isotopic ratios confirm this vertical zonation in the boreholes, with much higher activity ratios in the deep ground-waters from borehole than in the surface and spring waters; Such high U activity ratios are indicative of long water-rock interactions, which is consistent with the long residence times deducted from the CFC and SF6 data.

  20. Karst spring real time monitoring to identify the groundwater circulation in the feeding aquifer

    Science.gov (United States)

    Sappa, Giuseppe; Ferranti, Flavia; De Filippi, Francesco M.; Cardilo, Giulia

    2017-04-01

    About one quarter of the world's population is largely or entirely dependent on groundwater from karst systems. However, karst aquifers have specific hydraulic and hydrogeological characteristics that render them highly vulnerable to pollution from human activities. Intrinsic vulnerability of a karst aquifer takes account of the inherent geological, hydrological and hydrogeological characteristics of an area; however, it is independent of the nature of contaminants. Groundwater circulation is usually very rapidly as a function of high rainfall input. As consequence, in case of contamination, these systems are characterized by limited attenuation processes in the unsaturated zone. The analysis of karst spring responses to rainfall events, at the catchment scale, is one promising approach for groundwater flow characterization. Karst springs are, in fact, an important source of information in order to understand the circulation characteristics in such complex systems. The karst Pertuso Spring, located in the Upper Valley of Aniene River, is the main outlet of a large aquifer which is one of the most important water resource in the southeast part of Latium Region, Central Italy, used for drinking, agriculture and hydroelectric supplies. This paper deals with Pertuso Spring data collected from December 2014 to March 2016, using a multiparametric probe which directly interfaces with a data logger for real-time recording of hourly data. This instrument simultaneously measures up to 6 parameters (pH, groundwater level, temperature, electric conductivity, redox and dissolved oxygen). In particular, water temperature, electrical conductivity and rainfall data coming from meteorological stations have been studied to identify the groundwater circulation in the aquifer feeding Pertuso Spring. The study of the lag time between peak rainfall and peak of T and EC allow to highlight the seasonal vulnerability of this aquifer.

  1. Travel Times, Streamflow Velocities, and Dispersion Rates in the Yellowstone River, Montana

    Science.gov (United States)

    McCarthy, Peter M.

    2009-01-01

    The Yellowstone River is a vital natural resource to the residents of southeastern Montana and is a primary source of water for irrigation and recreation and the primary source of municipal water for several cities. The Yellowstone River valley is the primary east-west transportation corridor through southern Montana. This complex of infrastructure makes the Yellowstone River especially vulnerable to accidental spills from various sources such as tanker cars and trucks. In 2008, the U.S. Geological Survey (USGS), in cooperation with the Montana Department of Environmental Quality, initiated a dye-tracer study to determine instream travel times, streamflow velocities, and dispersion rates for the Yellowstone River from Lockwood to Glendive, Montana. The purpose of this report is to describe the results of this study and summarize data collected at each of the measurement sites between Lockwood and Glendive. This report also compares the results of this study to estimated travel times from a transport model developed by the USGS for a previous study. For this study, Rhodamine WT dye was injected at four locations in late September and early October 2008 during reasonably steady streamflow conditions. Streamflows ranged from 3,490 to 3,770 cubic feet per second upstream from the confluence of the Bighorn River and ranged from 6,520 to 7,570 cubic feet per second downstream from the confluence of the Bighorn River. Mean velocities were calculated for each subreach between measurement sites for the leading edge, peak concentration, centroid, and trailing edge at 10 percent of the peak concentration. Calculated velocities for the centroid of the dye plume for subreaches that were completely laterally mixed ranged from 1.83 to 3.18 ft/s within the study reach from Lockwood Bridge to Glendive Bridge. The mean of the completely mixed centroid velocity for the entire study reach, excluding the subreach between Forsyth Bridge and Cartersville Dam, was 2.80 ft/s. Longitudinal

  2. Residence time, mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone

    Science.gov (United States)

    Santoni, S.; Huneau, F.; Garel, E.; Vergnaud-Ayraud, V.; Labasque, T.; Aquilina, L.; Jaunat, J.; Celle-Jeanton, H.

    2016-09-01

    This study aims at establishing groundwater residence times, identifying mineralization processes and determining groundwater origins within a carbonate coastal aquifer with thick unsaturated zone and lying on a granitic depression. A multi-tracer approach (major ions, SiO2, Br-, Ba+, Sr2+, 18O, 2H, 13C, 3H, Ne, Ar) combined with a groundwater residence time determination using CFCs and SF6 allows defining the global setting of the study site. A typical mineralization conditioned by the sea sprays and the carbonate matrix helped to validate the groundwater weighted residence times from using a binary mixing model. Terrigenic SF6 excesses have been detected and quantified, which permits to identify a groundwater flow from the surrounding fractured granites towards the lower aquifer principally. The use of CFCs and SF6 as a first hydrogeological investigation tool is possible and very relevant despite the thick unsaturated zone and the hydraulic connexion with a granitic environment.

  3. Groundwater residence times in Shenandoah National Park, Blue Ridge Mountains, Virginia, USA: A multi-tracer approach

    Science.gov (United States)

    Plummer, L.N.; Busenberg, E.; Böhlke, J.K.; Nelms, D.L.; Michel, R.L.; Schlosser, P.

    2001-01-01

    Chemical and isotopic properties of water discharging from springs and wells in Shenandoah National Park (SNP), near the crest of the Blue Ridge Mountains, VA, USA were monitored to obtain information on groundwater residence times. Investigated time scales included seasonal (wet season, April, 1996; dry season, August-September, 1997), monthly (March through September, 1999) and hourly (30-min interval recording of specific conductance and temperature, March, 1999 through February, 2000). Multiple environmental tracers, including tritium/helium-3 (3H/3He), chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), sulfur-35 (35S), and stable isotopes (??18O and ??2H) of water, were used to estimate the residence times of shallow groundwater discharging from 34 springs and 15 wells. The most reliable ages of water from springs appear to be based on SF6 and 3H/3He, with most ages in the range of 0-3 years. This range is consistent with apparent ages estimated from concentrations of CFCs; however, CFC-based ages have large uncertainties owing to the post-1995 leveling-off of the CFC atmospheric growth curves. Somewhat higher apparent ages are indicated by 35S (> 1.5 years) and seasonal variation of ??18O (mean residence time of 5 years) for spring discharge. The higher ages indicated by the 35S and ??18O data reflect travel times through the unsaturated zone and, in the case of 35S, possible sorption and exchange of S with soils or biomass. In springs sampled in April, 1996, apparent ages derived from the 3H/3He data (median age of 0.2 years) are lower than those obtained from SF6 (median age of 4.3 years), and in contrast to median ages from 3H/3He (0.3 years) and SF6 (0.7 years) obtained during the late summer dry season of 1997. Monthly samples from 1999 at four springs in SNP had SF6 apparent ages of only 1.2 to 2.5 ?? 0.8 years, and were consistent with the 1997 SF6 data. Water from springs has low excess air (0-1 cm3 kg-1) and N2-Ar temperatures that vary

  4. A new approach to calibrate steady groundwater flow models with time series of head observations

    Science.gov (United States)

    Obergfell, C.; Bakker, M.; Maas, C.

    2012-04-01

    We developed a new method to calibrate aquifer parameters of steady-state well field models using measured time series of head fluctuations. Our method is an alternative to standard pumping tests and is based on time series analysis using parametric impulse response functions. First, the pumping influence is isolated from the overall groundwater fluctuation observed at monitoring wells around the well field, and response functions are determined for each individual well. Time series parameters are optimized using a quasi-Newton algorithm. For one monitoring well, time series model parameters are also optimized by means of SCEM-UA, a Markov Chain Monte Carlo algorithm, as a control on the validity of the parameters obtained by the faster quasi-Newton method. Subsequently, the drawdown corresponding to an average yearly pumping rate is calculated from the response functions determined by time series analysis. The drawdown values estimated with acceptable confidence intervals are used as calibration targets of a steady groundwater flow model. A case study is presented of the drinking water supply well field of Waalwijk (Netherlands). In this case study, a uniform aquifer transmissivity is optimized together with the conductance of ditches in the vicinity of the well field. Groundwater recharge or boundary heads do not have to be entered, which eliminates two import sources of uncertainty. The method constitutes a cost-efficient alternative to pumping tests and allows the determination of pumping influences without changes in well field operation.

  5. Substrate size rather than heterogeneity controls downstream travel time distributions in replicate small streams

    Science.gov (United States)

    Aubeneau, A. F.; Hanrahan, B.; Tank, J. L.; Bolster, D.

    2013-12-01

    Dissolved solutes are exported from watersheds with water flow and fluxes are therefore influenced by advection, that carries them further, but also retention processes, that delay their travel. It is especially important to understand the factors controlling network solute retention for biogeoreactive species that can be processed if afforded extended residence. In alluvial systems, substrate characteristics play a crucial role in slowing downstream transport. The roughness size (i.e., grain size relative to water depth) is associated with the distortion of the velocity profile and therefore is related to short term delays from additional dispersion. Surface and subsurface water also continually turn over, creating longer delays in the slow-flowing hyporheic region below the water/sediment interface. Sediment structure could also control transport, as pockets of slower hydraulic conductivity may influence the longest travel times. We present results from multiple solute injection experiments testing the influence of sediment size (pea gravel vs. coarse gravel) and heterogeneity (alternating sections vs. well mixed) on solute transport dynamics in four experimental streams located at the Notre Dame Linked Experimental Ecosystem Facility (ND-LEEF). We show that the stream with homogeneously coarse gravel induced more short-term delays but less long-term retention than the stream with smaller pea gravel. Inverse modeling suggested that the short-term delays were exponentially distributed while the long-term retention followed a truncated power-law behavior. Even though transport in all four streams was anomalous, the scaling truncation time was influenced by sediment size, with the smaller pea gravel exhibiting scaling longer than the coarse gravel. Streams with heterogeneous substrate had an intermediate cut-off. These results uniquely associate transport scaling in fluvial systems and substrate characteristics. The streams revealed truncation timescales that had

  6. Simulation of Runoff Hydrograph on Soil Surfaces with Different Microtopography Using a Travel Time Method at the Plot Scale.

    Science.gov (United States)

    Zhao, Longshan; Wu, Faqi

    2015-01-01

    In this study, a simple travel time-based runoff model was proposed to simulate a runoff hydrograph on soil surfaces with different microtopographies. Three main parameters, i.e., rainfall intensity (I), mean flow velocity (vm) and ponding time of depression (tp), were inputted into this model. The soil surface was divided into numerous grid cells, and the flow length of each grid cell (li) was then calculated from a digital elevation model (DEM). The flow velocity in each grid cell (vi) was derived from the upstream flow accumulation area using vm. The total flow travel time through each grid cell to the surface outlet was the sum of the sum of flow travel times along the flow path (i.e., the sum of li/vi) and tp. The runoff rate at the slope outlet for each respective travel time was estimated by finding the sum of the rain rate from all contributing cells for all time intervals. The results show positive agreement between the measured and predicted runoff hydrographs.

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

    Science.gov (United States)

    Kory, Carol L.; Andro, Monty

    2002-01-01

    For the first time, a time-dependent, physics-based computational model has been used to provide a direct description of the effects of the traveling wave tube amplifier (TWTA) 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 and operating characteristics 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. First, the TWT model using the three dimensional (3D) electromagnetic code MAFIA is presented. Then, this comprehensive model is used to investigate approximations made in conventional TWT black-box models used in communication system level simulations. To quantitatively demonstrate the effects these approximations have on digital signal performance predictions, including intersymbol interference (ISI), the MAFIA results are compared to the system level analysis tool, Signal Processing Workstation (SPW), using high order modulation schemes including 16 and 64-QAM.

  8. Time-Dependent Traveling Wave Tube Model for Intersymbol Interference Investigations

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    Kory, Carol L.; Andro, Monty

    2002-01-01

    For the first time, a time-dependent, physics-based computational model has been used to provide a direct description of the effects of the traveling wave tube amplifier (TWTA) 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 and operating characteristics 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. First, the TWT model using the three dimensional (3D) electromagnetic code MAFIA is presented. Then, this comprehensive model is used to investigate approximations made in conventional TWT black-box models used in communication system level simulations. To quantitatively demonstrate the effects these approximations have on digital signal performance predictions, including intersymbol interference (ISI), the MAFIA results are compared to the system level analysis tool, Signal Processing Workstation (SPW), using high order modulation schemes including 16 and 64-QAM.

  10. "I can see clearly now": the effect of cue imageability on mental time travel.

    Science.gov (United States)

    Rasmussen, Katrine W; Berntsen, Dorthe

    2014-10-01

    Mental time travel (MTT) is the ability to mentally project oneself backward or forward in time, in order to remember an event from one's personal past or to imagine a possible event in one's personal future. Recent work has suggested that, although past and future MTT may rely on shared neurocognitive substrates, the two temporal directions may interact differently with components of this underlying system. Here, we asked 151 participants to recall or imagine past and future autobiographical events in response to high- and low-imageable cue words. The results showed that high- and low-imageable cued events differed markedly on almost all measures, suggesting that imagery acts as a facilitator when constructing both past and possible future events. In line with previous work, future events less often referred to specific events, contained fewer details, and were more positive and idyllic than past events. However, these main effects were qualified by a number of interactions. In particular, we found an increased effect of cue imageability for past as compared to future events, suggesting that the generation of past events is more sensitive to the ability of the cues to invoke the sensory components of the encoding context, whereas the construction of future events is more driven by context-independent schemata.

  11. Nonparametric estimation of groundwater residence time distributions: What can environmental tracer data tell us about groundwater residence time?

    Science.gov (United States)

    McCallum, James L.; Engdahl, Nicholas B.; Ginn, Timothy R.; Cook, Peter. G.

    2014-03-01

    Residence time distributions (RTDs) have been used extensively for quantifying flow and transport in subsurface hydrology. In geochemical approaches, environmental tracer concentrations are used in conjunction with simple lumped parameter models (LPMs). Conversely, numerical simulation techniques require large amounts of parameterization and estimated RTDs are certainly limited by associated uncertainties. In this study, we apply a nonparametric deconvolution approach to estimate RTDs using environmental tracer concentrations. The model is based only on the assumption that flow is steady enough that the observed concentrations are well approximated by linear superposition of the input concentrations with the RTD; that is, the convolution integral holds. Even with large amounts of environmental tracer concentration data, the entire shape of an RTD remains highly nonunique. However, accurate estimates of mean ages and in some cases prediction of young portions of the RTD may be possible. The most useful type of data was found to be the use of a time series of tritium. This was due to the sharp variations in atmospheric concentrations and a short half-life. Conversely, the use of CFC compounds with smoothly varying atmospheric concentrations was more prone to nonuniqueness. This work highlights the benefits and limitations of using environmental tracer data to estimate whole RTDs with either LPMs or through numerical simulation. However, the ability of the nonparametric approach developed here to correct for mixing biases in mean ages appears promising.

  12. Isotopic and geochemical tracers in the evaluation of groundwater residence time and salinization problems at Santiago Island, Cape Verde

    Energy Technology Data Exchange (ETDEWEB)

    Carreira, Paula M.; Nunes, Dina [Quimica Analitica e Ambiental, IST/ITN, Universidade Tecnica de Lisboa, Estrada Nacional no. 10, 2686-953 Sacavem (Portugal); Marques, Jose M. [Centro de Petrologia e Geoquimica. Instituto Superior Tecnico, UTL, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Monteiro Santos, Fernando A. [Universidade de Lisboa-IDL, 1749-016 Lisboa (Portugal); Goncalves, Rui [Inst. Politecnico de Tomar, Quinta do Contador, Estrada da Serra, 2300 Tomar (Portugal); Pina, Antonio; Mota Gomes, Antonio [Instituto Superior de Educacao, Praia, Santiago (Cape Verde)

    2013-07-01

    Stable isotopes (δ{sup 18}O, δ{sup 2}H) and tritium ({sup 3}H), together with geochemistry and geophysical data, were used for evaluating groundwater recharge sources, flow paths, and residence times in a watershed on Santiago Island, Cape Verde, West Africa. Stable isotopes indicate the predominance of high-elevation precipitation that undergoes little evaporation prior to groundwater recharge. Low tritium concentrations at seven sampling sites indicate groundwater residence times greater than 50 years. Higher tritium values at other locations suggest more recent recharge. Young ages indicate local recharge and potential groundwater vulnerability to surface contamination and/or salt-water intrusion. Geochemical results indicate that water-rock interaction mechanisms are the major processes responsible for the groundwater quality (mainly calcium-bicarbonate type), reflecting the lithological composition of subsurface soil. (authors)

  13. KIC 11401845: An Eclipsing Binary with Multiperiodic Pulsations and Light-travel Time

    Science.gov (United States)

    Lee, Jae Woo; Hong, Kyeongsoo; Kim, Seung-Lee; Koo, Jae-Rim

    2017-02-01

    We report the {\\text{}}{Kepler} photometry of KIC 11401845 displaying multiperiodic pulsations, superimposed on binary effects. Light-curve synthesis shows that the binary star is a short-period detached system with a very low mass ratio of q = 0.070 and filling factors of F1 = 45% and F2 = 99%. Multiple-frequency analyses were applied to the light residuals after subtracting the synthetic eclipsing curve from the observed data. We detected 23 frequencies with signal-to-noise ratios larger than 4.0, of which the orbital harmonics (f4, f6, f9, f15) in the low-frequency domain may originate from tidally excited modes. For the high frequencies of 13.7–23.8 day‑1, the period ratios and pulsation constants are in the ranges of {P}{pul}/{P}{orb}=0.020{--}0.034 and Q = 0.018–0.031 days, respectively. These values and the position on the Hertzsprung–Russell diagram demonstrate that the primary component is a δ Sct pulsating star. We examined the eclipse timing variation of KIC 11401845 from the pulsation-subtracted data and found a delay of 56 ± 17 s in the arrival times of the secondary eclipses relative to the primary eclipses. A possible explanation of the time shift may be some combination of a light-travel-time delay of about 34 s and a very small eccentricity of e\\cos ω < 0.0002. This result represents the first measurement of the Rømer delay in noncompact binaries.

  14. Simple estimation of fastest preferential contaminant travel times in the unsaturated zone: application to Rainier Mesa and Shoshone Mountain, Nevada

    Directory of Open Access Journals (Sweden)

    B. A. Ebel

    2010-06-01

    Full Text Available Simulating contaminant transport in unsaturated zones with sparse hydraulic property information is a difficult, yet common, problem. When contaminant transport may occur via preferential flow, simple modeling approaches can provide predictions of interest, such as the first arrival of contaminant, with minimal site characterization. The conceptual model for unsaturated zone flow at two areas within the Nevada Test Site, Rainier Mesa and Shoshone Mountain, establishes the possibility of preferential flow through lithologies between potential radionuclide sources and the saturated zone. Lithology, saturated or near-saturated conditions in portions of the rock matrix, and relatively high recharge rates may act in concert at Rainier Mesa to promote preferential flow, despite the semi-arid climate. After identifying preferential flow as a possible contaminant transport process at Rainier Mesa and Shoshone Mountain, we apply a simple model to estimate fastest unsaturated travel times for conservatively-transported radionuclides to initially reach the saturated zone. Preferential flow travel times at Rainier Mesa are tens to hundreds of years for non-ponded water sources and one to two months for continuously-ponded water sources. If preferential flow occurs at Shoshone Mountain, the fastest travel times are approximately twice the Rainier Mesa estimates. A siliceous rock unit is present at Shoshone Mountain that may provide a barrier to preferential flow; if so, estimated transport times increase to more than a thousand years. Our analysis of unsaturated transport of radionuclides via preferential flow, using a relatively simple model, suggests that contaminated locations associated with continuously-supplied water sources, such as effluent ponds and water-filled tunnels, may have significantly shorter radionuclide travel times than locations not associated with such sources. The simple approach demonstrated here for estimating travel times can be

  15. Improvements of Travel-time Tomography Models from Joint Inversion of Multi-channel and Wide-angle Seismic Data

    Science.gov (United States)

    Begović, Slaven; Ranero, César; Sallarès, Valentí; Meléndez, Adrià; Grevemeyer, Ingo

    2016-04-01

    Commonly multichannel seismic reflection (MCS) and wide-angle seismic (WAS) data are modeled and interpreted with different approaches. Conventional travel-time tomography models using solely WAS data lack the resolution to define the model properties and, particularly, the geometry of geologic boundaries (reflectors) with the required accuracy, specially in the shallow complex upper geological layers. We plan to mitigate this issue by combining these two different data sets, specifically taking advantage of the high redundancy of multichannel seismic (MCS) data, integrated with wide-angle seismic (WAS) data into a common inversion scheme to obtain higher-resolution velocity models (Vp), decrease Vp uncertainty and improve the geometry of reflectors. To do so, we have adapted the tomo2d and tomo3d joint refraction and reflection travel time tomography codes (Korenaga et al, 2000; Meléndez et al, 2015) to deal with streamer data and MCS acquisition geometries. The scheme results in a joint travel-time tomographic inversion based on integrated travel-time information from refracted and reflected phases from WAS data and reflected identified in the MCS common depth point (CDP) or shot gathers. To illustrate the advantages of a common inversion approach we have compared the modeling results for synthetic data sets using two different travel-time inversion strategies: We have produced seismic velocity models and reflector geometries following typical refraction and reflection travel-time tomographic strategy modeling just WAS data with a typical acquisition geometry (one OBS each 10 km). Second, we performed joint inversion of two types of seismic data sets, integrating two coincident data sets consisting of MCS data collected with a 8 km-long streamer and the WAS data into a common inversion scheme. Our synthetic results of the joint inversion indicate a 5-10 times smaller ray travel-time misfit in the deeper parts of the model, compared to models obtained using just

  16. The Comparison of Mode Choice Sensitivity to the Reduction of Travel Time and Cost in Multimodal Trip

    Directory of Open Access Journals (Sweden)

    Mohammad Ganji

    2013-07-01

    Full Text Available Nowadays, with the extension of travel distances and accessibility to the various commuting options, multimodal trip proposes as the most competent travelling strategy. However, with increasing in demand by using these options as well as metro, subway, buses, cycles and sidewalk, some problems arose. The import of this quantitative study is to sympathize with the significance of the multimodal as a novel factor in the transportation. In this study, we discussed about cost and time as two significant factors, which affect everybody's life. While improving these two factors have a meaningful effect on encouraging/discouraging private vehicle commuters to switch to public transport. The methodology of this study is an empirical research in which a survey was conducted among the students at The National University of Malaysia with a numeric sample. Hence, a case study based on areas around UKM campus is used to demonstrate the results. What were investigated in this study were the attributes of a reduction in either travel cost or time to promote people who use their own vehicles to shift toward public transportation. The results show that the two factors: time and cost made a significant contribution in motivating private vehicle users to switch public transport. However, the most important purpose of this study was determining the most effective factor (at least based on our condition since it's not practically possible to have the travel time and cost reduction together.

  17. Analysed potential of big data and supervised machine learning techniques in effectively forecasting travel times from fused data

    Directory of Open Access Journals (Sweden)

    Ivana Šemanjski

    2015-12-01

    Full Text Available Travel time forecasting is an interesting topic for many ITS services. Increased availability of data collection sensors increases the availability of the predictor variables but also highlights the high processing issues related to this big data availability. In this paper we aimed to analyse the potential of big data and supervised machine learning techniques in effectively forecasting travel times. For this purpose we used fused data from three data sources (Global Positioning System vehicles tracks, road network infrastructure data and meteorological data and four machine learning techniques (k-nearest neighbours, support vector machines, boosting trees and random forest. To evaluate the forecasting results we compared them in-between different road classes in the context of absolute values, measured in minutes, and the mean squared percentage error. For the road classes with the high average speed and long road segments, machine learning techniques forecasted travel times with small relative error, while for the road classes with the small average speeds and segment lengths this was a more demanding task. All three data sources were proven itself to have a high impact on the travel time forecast accuracy and the best results (taking into account all road classes were achieved for the k-nearest neighbours and random forest techniques.

  18. Mental Time Travel into the Past and the Future in Healthy Aged Adults: An fMRI Study

    Science.gov (United States)

    Viard, Armelle; Chetelat, Gael; Lebreton, Karine; Desgranges, Beatrice; Landeau, Brigitte; de La Sayette, Vincent; Eustache, Francis; Piolino, Pascale

    2011-01-01

    Remembering the past and envisioning the future rely on episodic memory which enables mental time travel. Studies in young adults indicate that past and future thinking share common cognitive and neural underpinnings. No imaging data is yet available in healthy aged subjects. Using fMRI, we scanned older subjects while they remembered personal…

  19. Causes of intraplate seismicity in central Brazil from travel time seismic tomography

    Science.gov (United States)

    Rocha, Marcelo Peres; Azevedo, Paulo Araújo de; Marotta, Giuliano Sant'Anna; Schimmel, Martin; Fuck, Reinhardt

    2016-06-01

    New results of travel time seismic tomography in central Brazil provide evidence that the relatively high seismicity in this region is related to the thinner lithosphere at the limit between the Amazonian and São Francisco paleocontinents. The transition between these paleocontinents is marked by low velocity anomalies, spatially well correlated with the high seismicity region, which are interpreted as related to the lithospheric thinning and consequent rise of the asthenosphere, which have increased the temperature in this region. The low-velocity anomalies suggest a weakness region, favorable to the build-up of stress. The effective elastic thickness and the strain/stress regime for the study area are in agreement with tomographic results. A high-velocity trend is observed beneath the Parnaíba Basin, where low seismicity is observed, indicating the presence of a cratonic core. Our results support the idea that the intraplate seismicity in central Brazil is related to the thin lithosphere underlying parts of the Tocantins Province between the neighboring large cratonic blocks.

  20. Travel-time correction surface generation for the DOE Knowledge Base

    Energy Technology Data Exchange (ETDEWEB)

    Hipp, J.; Young, C.; Keyser, R.

    1997-08-01

    The DOE Knowledge Base data storage and access model consists of three parts: raw data processing, intermediate surface generation, and final output surface interpolation. The paper concentrates on the second step, surface generation, specifically applied to travel-time correction data. The surface generation for the intermediate step is accomplished using a modified kriging solution that provides robust error estimates for each for each interpolated point and satisfies many important physical requirements including differing quality data points, user-definable range of influence for each point, blend to background values for both interpolated values and error estimates beyond the ranges, and the ability to account for the effects of geologic region boundaries. These requirements are outlined and discussed and are linked to requirements specified for the final output model in the DOE Knowledge Base. Future work will focus on testing the entire Knowledge Base model using the regional calibration data sets which are being gathered by researchers at Los Alamos and Lawrence Livermore National Laboratories.

  1. Pinsker estimators for local helioseismology: inversion of travel times for mass-conserving flows

    Science.gov (United States)

    Fournier, Damien; Gizon, Laurent; Holzke, Martin; Hohage, Thorsten

    2016-10-01

    A major goal of helioseismology is the three-dimensional reconstruction of the three velocity components of convective flows in the solar interior from sets of wave travel-time measurements. For small amplitude flows, the forward problem is described in good approximation by a large system of convolution equations. The input observations are highly noisy random vectors with a known dense covariance matrix. This leads to a large statistical linear inverse problem. Whereas for deterministic linear inverse problems several computationally efficient minimax optimal regularization methods exist, only one minimax-optimal linear estimator exists for statistical linear inverse problems: the Pinsker estimator. However, it is often computationally inefficient because it requires a singular value decomposition of the forward operator or it is not applicable because of an unknown noise covariance matrix, so it is rarely used for real-world problems. These limitations do not apply in helioseismology. We present a simplified proof of the optimality properties of the Pinsker estimator and show that it yields significantly better reconstructions than traditional inversion methods used in helioseismology, i.e. regularized least squares (Tikhonov regularization) and SOLA (approximate inverse) methods. Moreover, we discuss the incorporation of the mass conservation constraint in the Pinsker scheme using staggered grids. With this improvement we can reconstruct not only horizontal, but also vertical velocity components that are much smaller in amplitude.

  2. Is the closest facility the one actually used? An assessment of travel time estimation based on mammography facilities.

    Science.gov (United States)

    Alford-Teaster, Jennifer; Lange, Jane M; Hubbard, Rebecca A; Lee, Christoph I; Haas, Jennifer S; Shi, Xun; Carlos, Heather A; Henderson, Louise; Hill, Deirdre; Tosteson, Anna N A; Onega, Tracy

    2016-02-18

    Characterizing geographic access depends on a broad range of methods available to researchers and the healthcare context to which the method is applied. Globally, travel time is one frequently used measure of geographic access with known limitations associated with data availability. Specifically, due to lack of available utilization data, many travel time studies assume that patients use the closest facility. To examine this assumption, an example using mammography screening data, which is considered a geographically abundant health care service in the United States, is explored. This work makes an important methodological contribution to measuring access--which is a critical component of health care planning and equity almost everywhere. We analyzed one mammogram from each of 646,553 women participating in the US based Breast Cancer Surveillance Consortium for years 2005-2012. We geocoded each record to street level address data in order to calculate travel time to the closest and to the actually used mammography facility. Travel time between the closest and the actual facility used was explored by woman-level and facility characteristics. Only 35% of women in the study population used their closest facility, but nearly three-quarters of women not using their closest facility used a facility within 5 min of the closest facility. Individuals that by-passed the closest facility tended to live in an urban core, within higher income neighborhoods, or in areas where the average travel times to work was longer. Those living in small towns or isolated rural areas had longer closer and actual median drive times. Since the majority of US women accessed a facility within a few minutes of their closest facility this suggests that distance to the closest facility may serve as an adequate proxy for utilization studies of geographically abundant services like mammography in areas where the transportation networks are well established.

  3. Increasing the Road Capacity Not Always Improves the Travel Time: A Before and After Study in Tirana

    Directory of Open Access Journals (Sweden)

    Edison Barhani

    2017-01-01

    Full Text Available The rapid growth of the car ownership last two decades in Albania has increased the need for higher transportation capacity. One of the most affected cities in Albania is Tirana where the capacity has not met the demand. Inevitably, the center of Tirana (Skanderbeg Square plays a crucial part in Tirana Transportation System. After a closure of about 2 years, being under reconstruction planned to be car-free area, Skanderbeg Square opened to traffic in 2011 by motorizing it again. This study analyses performance parameters such as: Travel Time, Waiting Time, and Passenger Movements for bus and passenger cars passing through the Skanderbeg Square before and after it was opened to traffic. Kinostudio-Kombinat bus line has been selected as the only line passing through the center of Tirana. Changing the land use from car-free to motorized one has created a valuable possibility to compare the traditional approach; which focuses only on cost to the sustainable one; which includes the environment and social aspects, too in the evaluation. Wider roads, shorter travel times and higher speed travel at the center (CBD have made vehicle usage more attractive. At the same time, bus travel times have been improved at the center of Tirana. However, the total travel times were not only enhanced, but at some locations (especially near the CBD where deteriorated. This study showed that traffic congestion problems are not solved but are shifted to other parts of Tirana Transportation System. In addition, public transportation revealed to be overcrowded, forcing passengers to use other modes like passenger car. Last but not least, other modes like bike or motorcycle riding should be encouraged as alternative to the passenger car.

  4. Spatial distribution of triazine residues in a shallow alluvial aquifer linked to groundwater residence time.

    Science.gov (United States)

    Sassine, Lara; Le Gal La Salle, Corinne; Khaska, Mahmoud; Verdoux, Patrick; Meffre, Patrick; Benfodda, Zohra; Roig, Benoît

    2017-03-01

    At present, some triazine herbicides occurrence in European groundwater, 13 years after their use ban in the European Union, remains of great concern and raises the question of their persistence in groundwater systems due to several factors such as storage and remobilization from soil and unsaturated zone, limited or absence of degradation, sorption in saturated zones, or to continuing illegal applications. In order to address this problem and to determine triazine distribution in the saturated zone, their occurrence is investigated in the light of the aquifer hydrodynamic on the basis of a geochemical approach using groundwater dating tracers ((3)H/(3)He). In this study, atrazine, simazine, terbuthylazine, deethylatrazine, deisopropylatrazine, and deethylterbuthylazine are measured in 66 samples collected between 2011 and 2013 from 21 sampling points, on the Vistrenque shallow alluvial aquifer (southern France), covered by a major agricultural land use. The frequencies of quantification range from 100 to 56 % for simazine and atrazine, respectively (LQ = 1 ng L(-1)). Total triazine concentrations vary between 15 and 350 ng L(-1) and show three different patterns with depth below the water table: (1) low concentrations independent of depth but related to water origin, (2) an increase in concentrations with depth in the aquifer related to groundwater residence time and triazine use prior to their ban, and (3) relatively high concentrations at low depths in the saturated zone more likely related to a slow desorption of these compounds from the soil and unsaturated zone. The triazine attenuation rate varies between 0.3 for waters influenced by surface water infiltration and 4.8 for water showing longer residence times in the aquifer, suggesting an increase in these rates with water residence time in the saturated zone. Increasing triazine concentrations with depth is consistent with a significant decrease in the use of these pesticides for the last 10

  5. Wilde Rewound: Time-Travelling with Oscar in Recent Author Fictions

    Directory of Open Access Journals (Sweden)

    Kirby Joris

    2012-05-01

    Full Text Available In the early 1980s historical figures in general – and writers from the past in particular – entered a kind of Golden Age thanks to fiction. Through various forms of semi-biographical novels and other narratives, they have, from that time forward, been enjoying a pampered life in a new genre called “the author-as-character” (Franssen and Hoenselaars 1999 or “author fictions” (Savu 2009 that reanimate them or conjure them up in a present that constantly seeks to reassert its link with the past. This is particularly true of Oscar Wilde’s life, for his disparate and colourful personality has been time and again re-appropriated in recent fiction. This article focuses on three of these contemporary fictional depictions: an epistolary novel, an epistolary website and a fictional interview, all three dealing with a fictionalised Oscar Wilde conversing with a contemporary author who is also an interviewer in his or her own way and right. Because they are very close to each other in terms of narration (i.e. impersonation and pastiche and subject, putting words in Wilde’s mouth as though they were his own, The Unauthorized Letters of Oscar Wilde, the website Dialogus, and Coffee with Oscar Wilde, represent three fascinating means of exploring how Oscar’s rebirth as a man and author actually takes place. Among the numerous fictional portraits of Oscar Wilde, I have thus chosen to pay particular attention to the depictions that are well anchored in the twentieth and twenty-first centuries and which do not, therefore, display a narrative that would merely take place during the fin de siècle, with only period-style people in period costume. By contrast, the three portraits are literal time-travelling narratives that endeavour to bridge the gap between past, present and future.

  6. Global teleseismic earthquake relocation with improved travel times and procedures for depth determination

    Science.gov (United States)

    Robert, Engdah E.; Van Hilst, R. D.; Buland, Raymond P.

    1998-01-01

    We relocate nearly 100, 000 events that occurred during the period 1964 to 1995 and are well-constrained teleseismically by arrival-time data reported to the International Seismological Centre (ISC) and to the U. S. Geological Survey's National Earthquake Information Center (NEIC). Hypocenter determination is significantly improved by using, in addition to regional and teleseismic P and S phases, the arrival times of PKiKP, PKPdf, and the teleseismic depth phases pP, pwP, and sP in the relocation procedure. A global probability model developed for later-arriving phases is used to independently identify the depth phases. The relocations are compared to hypocenters reported in the ISC and NEIC catalogs and by other sources. Differences in our epicenters with respect to ISC and NEIC estimates are generally small and regionally systematic due to the combined effects of the observing station network and plate geometry regionally, differences in upper mantle travel times between the reference earth models used, and the use of later-arriving phases. Focal depths are improved substantially over most other independent estimates, demonstrating (for example) how regional structures such as downgoing slabs can severely bias depth estimation when only regional and teleseismic P arrivals are used to determine the hypocenter. The new data base, which is complete to about Mw 5. 2 and includes all events for which moment-tensor solutions are available, has immediate application to high-resolution definition of Wadati-Benioff Zones (WBZs) worldwide, regional and global tomographic imaging, and other studies of earth structure.

  7. Geochemical modelling of groundwater evolution and residence time at the Kivetty site

    Energy Technology Data Exchange (ETDEWEB)

    Pitkaenen, P.; Luukkonen, A. [VTT Communities and Infrastructure, Espoo (Finland); Ruotsalainen, P. [Fintact Oy, Helsinki (Finland); Leino-Forsman, H.; Vuorinen, U. [VTT Chemical Technology, Espoo (Finland)

    1998-12-01

    groundwater are due to carbonate reactions: oxidising of organic carbon, and dissolution and precipitation of calcite. The carbonate reactions and slight hydrolysis of silicates stabilise the pH value at 8-9. In addition to aerobic oxidation of organic matter, oxidative dissolution of biotite seems to be an important oxygen consumer at shallow depth during recharge. The most important process controlling the redox state deeper in the bedrock was interpreted to be the microbially mediated sulphate reduction with simultaneous anaerobic respiration of organic carbon. This process buffers the redox level of about -200 - -300 mV depending on the pH. Even though the salinities of the groundwater samples and mass-transfer along flow paths remain low, the geochemical evolution was fully developed and has reached quite a stable thermodynamic state. The residence times of the groundwater samples cover the time span back to glaciation. Young ages seem to be limited to the upper part of bedrock, and any really dynamic natural flowpath with deep observed recently recharged water cannot be demonstrated. Deglacial or subglacial ages (over 9,700 years old at Kivetty) are typical below the 150-300m level in the bedrock. Subglacial waters are interpreted to derive from mixing of preglacial water and meltwater, the input of which is estimated to be about 20% at the most. Indications of elevated oxygen intrusion cannot be observed in groundwater having glacial signals. (orig.) 122 refs.

  8. The influence of travel time on emergency obstetric care seeking behavior in the urban poor of Bangladesh: a GIS study.

    Science.gov (United States)

    Panciera, Rocco; Khan, Akib; Rizvi, Syed Jafar Raza; Ahmed, Shakil; Ahmed, Tanvir; Islam, Rubana; Adams, Alayne M

    2016-08-22

    Availability of Emergency Obstetric Care (EmOC) is crucial to avert maternal death due to life-threatening complications potentially arising during delivery. Research on the determinants of utilization of EmOC has neglected urban settings, where traffic congestion can pose a significant barrier to the access of EmOC facilities, particularly for the urban poor due to costly and limited transportation options. This study investigates the impact of travel time to EmOC facilities on the utilization of facility-based delivery services among mothers living in urban poor settlements in Sylhet, Bangladesh. A cross-sectional EmOC health-seeking behavior survey from 39 poor urban clusters was geo-spatially linked to a comprehensive geo-referenced dataset of EmOC facility locations. Geo-spatial techniques and logistic regression were then applied to quantify the impact of travel time on place of delivery (EmOC facility or home), while controlling for confounding socio-cultural and economic factors. Increasing travel time to the nearest EmOC facility is found to act as a strong deterrent to seeking care for the urban poor in Sylhet. Logistic regression results indicate that a 5-min increase in travel time to the nearest EmOC facility is associated with a 30 % decrease (0.655 odds ratio, 95 % CI: 0.529-0.811) in the likelihood of delivery at an EmOC facility rather than at home. Moreover, the impact of travel time varies substantially between public, NGO and private facilities. A 5-min increase in travel time from a private EmOC facility is associated with a 32.9 % decrease in the likelihood of delivering at a private facility, while for public and Non-Government Organizations (NGO) EmOC facilities, the impact is lower (28.2 and 28.6 % decrease respectively). Other strong determinants of delivery at an EmOC facility are the use of antenatal care and mother's formal education, while Muslim mothers are found to be more likely to deliver at home. Geospatial evidence points to

  9. Implementation and Comparison of Acoustic Travel-Time Measurement Procedures for the Solar Dynamics Observatory-Helioseismic and Magnetic Imager Time-Distance Helioseismology Pipeline

    Science.gov (United States)

    Couvidat, S.; Zhao, J.; Birch, A. C.; Kosovichev, A. G.; Duvall, Thomas L., Jr.; Parchevsky, K.; Scherrer, P. H.

    2010-01-01

    The Helioseismic and Magnetic Imager (HMI) instrument onboard 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 (Zhao et al., Solar Phys. submitted, 2010) 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, SCORE'96: Solar Convection and Oscillations and Their Relationship, ASSL, Dordrecht, 241, 1997), a minimization relative to a reference cross-covariance function (Gizon and Birch, Astrophys. J. 571, 966, 2002), and a linearized version of the minimization method (Gizon and Birch, Astrophys. J. 614, 472, 2004). Using Doppler-velocity data from the Michelson Doppler Imager (MDI) instrument onboard SOHO, we tested and compared these definitions for the mean and difference traveltime perturbations measured from reciprocal signals. Although all three procedures return similar travel times in a quiet-Sun region, the method of Gizon and Birch (Astrophys. J. 614, 472, 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 (SCORE'96: Solar Convection and Oscillations and Their Relationship, ASSL, Dordrecht, 241, 1997) and Gizon and Birch (Astrophys. J. 571, 966, 2002). We investigated the relationships among

  10. InSAR time-series analysis of land subsidence due to groundwater overexploitation in groundwater basins of central and northeast Iran

    Science.gov (United States)

    Sharifi, M.; Motagh, M.; Aipour, S.; Akbari, V.; Walter, T.; Rajabi, M.; Samadzadegan, F.; Djamour, Y.; Sedighi, M.

    2008-12-01

    We use Interferometric Synthetic Aperture (InSAR) observations acquired by the Envisat satellite during 2002-2008 to study land subsidence caused by groundwater over-exploitation in groundwater basins of central and northeast Iran. Earlier studies in these regions using a few interferograms showed rapid subsidence in the order of several centimetres per year. Here we use additional ENVISAT data and perform a time-series analysis using the small-baseline concept to better determine the temporal and spatial evolution of surface deformation.

  11. A method for generating an illusion of backwards time travel using immersive virtual reality - an exploratory study

    Directory of Open Access Journals (Sweden)

    Doron eFriedman

    2014-09-01

    Full Text Available We introduce a new method, based on immersive virtual reality, to give people the illusion of having travelled 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.

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

    Science.gov (United States)

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

    2014-11-01

    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.

  13. Tracking thoughts: Exploring the neural architecture of mental time travel during mind-wandering.

    Science.gov (United States)

    Karapanagiotidis, Theodoros; Bernhardt, Boris C; Jefferies, Elizabeth; Smallwood, Jonathan

    2017-02-15

    The capacity to imagine situations that have already happened or fictitious events that may take place in the future is known as mental time travel (MTT). Studies have shown that MTT is an important aspect of spontaneous thought, yet we lack a clear understanding of how the neurocognitive architecture of the brain constrains this element of human cognition. Previous functional magnetic resonance imaging (MRI) studies have shown that MTT involves the coordination between multiple regions that include mesiotemporal structures such as the hippocampus, as well as prefrontal and parietal regions commonly associated with the default mode network (DMN). The current study used a multimodal neuroimaging approach to identify the structural and functional brain organisation that underlies individual differences in the capacity to spontaneously engage in MTT. Using regionally unconstrained diffusion tractography analysis, we found increased diffusion anisotropy in right lateralised temporo-limbic, corticospinal, inferior fronto-occipital tracts in participants who reported greater MTT. Probabilistic connectivity mapping revealed a significantly higher connection probability of the right hippocampus with these tracts. Resting-state functional MRI connectivity analysis using the right hippocampus as a seed region revealed greater functional coupling to the anterior regions of the DMN with increasing levels of MTT. These findings demonstrate that the interactions between the hippocampus and regions of the cortex underlie the capacity to engage in MTT, and support contemporary theoretical accounts that suggest that the integration of the hippocampus with the DMN provides the neurocognitive landscape that allows us to imagine distant times and places. Copyright © 2016 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  16. Numerical evaluation of the PERTH (PERiodic Tracer Hierarchy) method for estimating time-variable travel time distribution in variably saturated soils

    Science.gov (United States)

    Kim, M.; Harman, C. J.

    2013-12-01

    The distribution of water travel times is one of the crucial hydrologic characteristics of the catchment. Recently, it has been argued that a rigorous treatment of travel time distributions should allow for their variability in time because of the variable fluxes and partitioning of water in the water balance, and the consequent variable storage of a catchment. We would like to be able to observe the structure of the temporal variations in travel time distributions under controlled conditions, such as in a soil column or under irrigation experiments. However, time-variable travel time distributions are difficult to observe using typical active and passive tracer approaches. Time-variability implies that tracers introduced at different times will have different travel time distributions. The distribution may also vary during injection periods. Moreover, repeat application of a single tracer in a system with significant memory leads to overprinting of break-through curves, which makes it difficult to extract the original break-through curves, and the number of ideal tracers that can be applied is usually limited. Recognizing these difficulties, the PERTH (PERiodic Tracer Hierarchy) method has been developed. The method provides a way to estimate time-variable travel time distributions by tracer experiments under controlled conditions by employing a multi-tracer hierarchy under periodical hydrologic forcing inputs. The key assumption of the PERTH method is that as time gets sufficiently large relative to injection time, the average travel time distribution of two distinct ideal tracers injected during overlapping periods become approximately equal. Thus one can be used as a proxy for the other, and the breakthrough curves of tracers applied at different times in a periodic forcing condition can be separated from one another. In this study, we tested the PERTH method numerically for the case of infiltration at the plot scale using HYDRUS-1D and a particle

  17. DTWT (Dispersive Tsunami Wave Tool): a new tool for computing the complete dispersion of tsunami travel time.

    Science.gov (United States)

    Reymond, Dominique

    2017-04-01

    We present a tool for computing the complete arrival times of the dispersed wave-train of a tsunami. The calculus is made using the exact formulation of the tsunami dispersion (and without approximations), at any desired periods between one hour or more (concerning the gravity waves propagation) until 10s (the highly dispersed mode). The computation of the travel times is based on the a summation of the necessary time for a tsunami to cross all the elementary blocs of a grid of bathymetry following a path between the source and receiver at a given period. In addition the source dimensions and the focal mechanism are taken into account to adjust the minimum travel time to the different possible points of emission of the source. A possible application of this tool is to forecast the arrival time of late arrivals of tsunami waves that could produce the resonnance of some bays and sites at higher frequencies than the gravity mode. The theoretical arrival times are compared to the observed ones and to the results obtained by TTT (P. Wessel, 2009) and the ones obtained by numerical simulations. References: Wessel, P. (2009). Analysis of oberved and predicted tsunami travel times for the Pacic and Indian oceans. Pure Appl. Geophys., 166:301-324.

  18. A computer program for estimating instream travel times and concentrations of a potential contaminant in the Yellowstone River, Montana

    Science.gov (United States)

    McCarthy, Peter M.

    2006-01-01

    The Yellowstone River is very important in a variety of ways to the residents of southeastern Montana; however, it is especially vulnerable to spilled contaminants. In 2004, the U.S. Geological Survey, in cooperation with Montana Department of Environmental Quality, initiated a study to develop a computer program to rapidly estimate instream travel times and concentrations of a potential contaminant in the Yellowstone River using regression equations developed in 1999 by the U.S. Geological Survey. The purpose of this report is to describe these equations and their limitations, describe the development of a computer program to apply the equations to the Yellowstone River, and provide detailed instructions on how to use the program. This program is available online at [http://pubs.water.usgs.gov/sir2006-5057/includes/ytot.xls]. The regression equations provide estimates of instream travel times and concentrations in rivers where little or no contaminant-transport data are available. Equations were developed and presented for the most probable flow velocity and the maximum probable flow velocity. These velocity estimates can then be used to calculate instream travel times and concentrations of a potential contaminant. The computer program was developed so estimation equations for instream travel times and concentrations can be solved quickly for sites along the Yellowstone River between Corwin Springs and Sidney, Montana. The basic types of data needed to run the program are spill data, streamflow data, and data for locations of interest along the Yellowstone River. Data output from the program includes spill location, river mileage at specified locations, instantaneous discharge, mean-annual discharge, drainage area, and channel slope. Travel times and concentrations are provided for estimates of the most probable velocity of the peak concentration and the maximum probable velocity of the peak concentration. Verification of estimates of instream travel times and

  19. Groundwater and security

    NARCIS (Netherlands)

    Conti, K.I.; Kukurić, N.; Gupta, J.; Pahl-Wostl, C.; Bhaduri, A.; Gupta, J.

    2016-01-01

    Humans abstract two hundred times more groundwater than oil, annually. Ironically, the role of groundwater in water management and supply is underappreciated, partially due to its invisibility. By conducting a literature survey and investigating groundwater information databases, this chapter answer

  20. Non Linear Travel Time Tomography With The Use of Sobolev Norms

    Science.gov (United States)

    Tondi, R.; de Franco, R.

    We present a method for the determination of 3-D velocity crustal structure and in- terface geometry, by inversion of seismic refraction and wide-angle reflection trav- eltimes. To minimize the deviation between the synthetic and exact wavefields we consider the minimization of a nonlinear objective function which considers: 1. the Euclidean norm of the misfit between observed and calculated data; 2. the L_2 norm of the misfit between the value of the parameter in the model been sought and the value of the parameter in the "a priori" mean model; 3. the minimization of the inaccuracies and costs of ray tracing in complex models, expressed in terms of the Sobolev norms of the relative parameters. In particular two Sobolev norms are relevant to ray tracing: as the complicated behaviour of rays depends on the second velocity derivatives, it may be restricted by minimizing the Sobolev norm of the velocity function in the H^2 space; as the second order travel-time perturbations depend on the perturbation of the first velocity derivatives, it may be useful to limit the velocity model updates, within individual iterations of the linearized inversion, by means of the minimization of the Sobolev norm in the H^1 space (Klimes, "PAGEOPH", 2002). Through the use of 3-D synthetic tests recovered from real models, we show that including the minimization of Sobolev norm is necessary, when modelling with ray methods. The initial model to be inverted is chosen in order to satisfy mathematical stability and, in analysing final solution reliability, estimate of the misfit or chi squared and "a posteriori" model covariance is given. Calculations were performed with the use of programs developed by the Consortium for Seismic Waves in Complex 3-D Structures (CW3D) at Charles University in Prague. Application of the method to field data collected in the framework of TOMOVES (TOMOgraphy of Mt.VESuvius) experiment is a check on the validity of the inversion scheme.

  1. Testing & Validating: 3D Seismic Travel Time Tomography (Detailed Shallow Subsurface Imaging)

    Science.gov (United States)

    Marti, David; Marzan, Ignacio; Alvarez-Marron, Joaquina; Carbonell, Ramon

    2016-04-01

    A detailed full 3 dimensional P wave seismic velocity model was constrained by a high-resolution seismic tomography experiment. A regular and dense grid of shots and receivers was use to image a 500x500x200 m volume of the shallow subsurface. 10 GEODE's resulting in a 240 channels recording system and a 250 kg weight drop were used for the acquisition. The recording geometry consisted in 10x20m geophone grid spacing, and a 20x20 m stagered source spacing. A total of 1200 receivers and 676 source points. The study area is located within the Iberian Meseta, in Villar de Cañas (Cuenca, Spain). The lithological/geological target consisted in a Neogen sedimentary sequence formed from bottom to top by a transition from gyspum to silstones. The main objectives consisted in resolving the underground structure: contacts/discontinuities; constrain the 3D geometry of the lithology (possible cavities, faults/fractures). These targets were achieved by mapping the 3D distribution of the physical properties (P-wave velocity). The regularly space dense acquisition grid forced to acquire the survey in different stages and with a variety of weather conditions. Therefore, a careful quality control was required. More than a half million first arrivals were inverted to provide a 3D Vp velocity model that reached depths of 120 m in the areas with the highest ray coverage. An extended borehole campaign, that included borehole geophysical measurements in some wells provided unique tight constraints on the lithology an a validation scheme for the tomographic results. The final image reveals a laterally variable structure consisting of four different lithological units. In this methodological validation test travel-time tomography features a high capacity of imaging in detail the lithological contrasts for complex structures located at very shallow depths.

  2. Applying petrophysical models to radar travel time and electrical resistivity tomograms: Resolution-dependent limitations

    Science.gov (United States)

    Day-Lewis, F. D.; Singha, K.; Binley, A.M.

    2005-01-01

    Geophysical imaging has traditionally provided qualitative information about geologic structure; however, there is increasing interest in using petrophysical models to convert tomograms to quantitative estimates of hydrogeologic, mechanical, or geochemical parameters of interest (e.g., permeability, porosity, water content, and salinity). Unfortunately, petrophysical estimation based on tomograms is complicated by limited and variable image resolution, which depends on (1) measurement physics (e.g., electrical conduction or electromagnetic wave propagation), (2) parameterization and regularization, (3) measurement error, and (4) spatial variability. We present a framework to predict how core-scale relations between geophysical properties and hydrologic parameters are altered by the inversion, which produces smoothly varying pixel-scale estimates. We refer to this loss of information as "correlation loss." Our approach upscales the core-scale relation to the pixel scale using the model resolution matrix from the inversion, random field averaging, and spatial statistics of the geophysical property. Synthetic examples evaluate the utility of radar travel time tomography (RTT) and electrical-resistivity tomography (ERT) for estimating water content. This work provides (1) a framework to assess tomograms for geologic parameter estimation and (2) insights into the different patterns of correlation loss for ERT and RTT. Whereas ERT generally performs better near boreholes, RTT performs better in the interwell region. Application of petrophysical models to the tomograms in our examples would yield misleading estimates of water content. Although the examples presented illustrate the problem of correlation loss in the context of near-surface geophysical imaging, our results have clear implications for quantitative analysis of tomograms for diverse geoscience applications. Copyright 2005 by the American Geophysical Union.

  3. 41 CFR 302-3.314 - Is there a time limit when I must begin my travel and transportation upon separation?

    Science.gov (United States)

    2010-07-01

    ...-3.314 Is there a time limit when I must begin my travel and transportation upon separation? Yes, all... 41 Public Contracts and Property Management 4 2010-07-01 2010-07-01 false Is there a time limit when I must begin my travel and transportation upon separation? 302-3.314 Section 302-3.314 Public...

  4. Effect of fare and travel time on the demand for domestic air transportation

    Science.gov (United States)

    Eriksen, S. E.; Liu, E. W.

    1979-01-01

    An econometric travel demand model was presented. The model was used for analyzing long haul domestic passenger markets in the United States. The results showed the sensitivities of demand to changes in fares and speed reflecting technology through more efficient aircraft designs.

  5. The eclipsing system V404 Lyr: Light-travel times and γ Doradus pulsations

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Woo; Kim, Seung-Lee; Hong, Kyeongsoo; Lee, Chung-Uk; Koo, Jae-Rim, E-mail: jwlee@kasi.re.kr, E-mail: slkim@kasi.re.kr, E-mail: kshong@kasi.re.kr, E-mail: leecu@kasi.re.kr, E-mail: koojr@kasi.re.kr [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)

    2014-08-01

    We present the physical properties of V404 Lyr exhibiting eclipse timing variations and multiperiodic pulsations from all historical data including the Kepler and SuperWASP observations. Detailed analyses of 2922 minimum epochs showed that the orbital period has varied through a combination of an upward-opening parabola and two sinusoidal variations, with periods of P {sub 3} = 649 days and P {sub 4} = 2154 days and semi-amplitudes of K {sub 3} = 193 s and K {sub 4} = 49 s, respectively. The secular period increase at a rate of +1.41 × 10{sup –7} days yr{sup –1} could be interpreted as a combination of the secondary to primary mass transfer and angular momentum loss. The most reasonable explanation for both sinusoids is a pair of light-travel-time effects due to two circumbinary objects with projected masses of M {sub 3} = 0.47 M {sub ☉} and M {sub 4} = 0.047 M {sub ☉}. The third-body parameters are consistent with those calculated using the Wilson-Devinney binary code. For the orbital inclinations i {sub 4} ≳ 43°, the fourth component has a mass within the hydrogen-burning limit of ∼0.07 M {sub ☉}, which implies that it is a brown dwarf. A satisfactory model for the Kepler light curves was obtained by applying a cool spot to the secondary component. The results demonstrate that the close eclipsing pair is in a semi-detached, but near-contact, configuration; the primary fills approximately 93% of its limiting lobe and is larger than the lobe-filling secondary. Multiple frequency analyses were applied to the light residuals after subtracting the synthetic eclipsing curve from the Kepler data. This revealed that the primary component of V404 Lyr is a γ Dor type pulsating star, exhibiting seven pulsation frequencies in the range of 1.85-2.11 day{sup –1} with amplitudes of 1.38-5.72 mmag and pulsation constants of 0.24-0.27 days. The seven frequencies were clearly identified as high-order low-degree gravity-mode oscillations which might be excited

  6. The Eclipsing System V404 LYR: Light-travel Times and γ Doradus Pulsations

    Science.gov (United States)

    Lee, Jae Woo; Kim, Seung-Lee; Hong, Kyeongsoo; Lee, Chung-Uk; Koo, Jae-Rim

    2014-08-01

    We present the physical properties of V404 Lyr exhibiting eclipse timing variations and multiperiodic pulsations from all historical data including the Kepler and SuperWASP observations. Detailed analyses of 2922 minimum epochs showed that the orbital period has varied through a combination of an upward-opening parabola and two sinusoidal variations, with periods of P 3 = 649 days and P 4 = 2154 days and semi-amplitudes of K 3 = 193 s and K 4 = 49 s, respectively. The secular period increase at a rate of +1.41 × 10-7 days yr-1 could be interpreted as a combination of the secondary to primary mass transfer and angular momentum loss. The most reasonable explanation for both sinusoids is a pair of light-travel-time effects due to two circumbinary objects with projected masses of M 3 = 0.47 M ⊙ and M 4 = 0.047 M ⊙. The third-body parameters are consistent with those calculated using the Wilson-Devinney binary code. For the orbital inclinations i 4 >~ 43°, the fourth component has a mass within the hydrogen-burning limit of ~0.07 M ⊙, which implies that it is a brown dwarf. A satisfactory model for the Kepler light curves was obtained by applying a cool spot to the secondary component. The results demonstrate that the close eclipsing pair is in a semi-detached, but near-contact, configuration; the primary fills approximately 93% of its limiting lobe and is larger than the lobe-filling secondary. Multiple frequency analyses were applied to the light residuals after subtracting the synthetic eclipsing curve from the Kepler data. This revealed that the primary component of V404 Lyr is a γ Dor type pulsating star, exhibiting seven pulsation frequencies in the range of 1.85-2.11 day-1 with amplitudes of 1.38-5.72 mmag and pulsation constants of 0.24-0.27 days. The seven frequencies were clearly identified as high-order low-degree gravity-mode oscillations which might be excited through tidal interaction. Only eight eclipsing binaries have been known to contain

  7. From time-to space-traveller -tadpole shrimp Triops cancriformis (Crustacea: Notostraca)

    Science.gov (United States)

    Zierold, Thorid

    The Notostraca is a small ancient crustacean order dating back to the Carboniferous and possibly up to the Devonian period. In fact, there are Upper Triassic Triops fossils from Germany which are almost indistinguishable from the present Triops cancriformis and thus Triops is considered to be one of the best examples of evolutionary stasis or `living fossil'. Fossil records have shown that the occurrence of Triops is linked to strata resulting from inland freshwater bodies with alternating phases of flooding and drying out. Still today Notostraca species are known from ephemeral ponds and puddles throughout the world. Several Large Branchiopod species such as the European T. cancriformis present adaptations to desiccation, the main one being the production of thick-walled resting cysts. A high number of resting cysts is laid during the flooded period into the pond sediment or is fixed on plants during the adulthood. The drought resistant portion of cysts undergoes an extreme form of diapause. During this resting time the embryo is protected by different (cement)-layers against desiccation, UV-radiation and pressure. Thus their life cycle is perfectly adapted to extreme environments which resulted in the survival of more than 200 Million years. Among the Notostraca a wide range of reproductive modes are present including bisexual -the putatively ancestral state -, androdioecious and hermaphrodite populations. As hermaphroditism and androdioecy confer a colonisation advantage, Triops are suitable for populating experiments whatsoever. Triops is an ideal model organism due to their easy culture and breeding in the lab. Without any impact on the hatching success the resting cysts can easily be extracted from the soil and prepared for controlled experiments. Furthermore their biology has been studied in depth and optimal breeding conditions are known. The ancient group "travelled" successfully through time and is now ready for experiments in the outer space. At the

  8. Joint 3D seismic travel time and full channel electrical resistivity inversion with cross gradient structure constraint

    Science.gov (United States)

    Gao, J.; Zhang, H.

    2015-12-01

    Near surface geophysical exploration for the purpose of engineering design or construction For this reason, geophysical imaging demands a higher resolution and a better quantitative interpretation. Seismic travel time tomography and direct current resistivity tomography are two main methods for the near surface survey. Because of the limited coverage of observation system and the complex physical relationship between physical parameters and observations, individual geophysical method suffers issues of non-uniqueness and resolution limitation to some degree. We have developed a joint inversion method to combine seismic travel time tomography and full channel resistivity tomography. For the full channel resistivity survey, it uses two electrodes for power supply and all the other electrodes for recording. Compared with the traditional resistivity method, it collects more data and has a better model converge. Our joint inversion strategy relies on the structure constraint enforced through minimizing cross gradients between seismic velocity and resistivity models (Gallardo, 2003). For resistivity tomography, sensitivity kernels are obtained through the adjoint method by solving the electrostatic field equation with the finite-difference method. For seismic travel time tomography, ray paths and travel times are calculated using the fast marching method. We have tested our joint inversion method for a 2D cross-hole problem where two small zones with high and low velocity/resistivity anomalies. Seismic/electrical sources/receivers are installed in two boreholes. For separate seismic inversion, the smearing effect is evident and two anomaly zones are distorted and misplaced. For separate electric resistivity inversion, although two anomaly zones are positioned correctly their values are not accurate. By joint inversion, two velocity anomaly zones are clearly imaged and the smearing effect is greatly reduced. In comparison, for the resistivity model, the two anomaly zones

  9. Refinement and Pattern Formation in Neural Circuits by the Interaction of Traveling Waves with Spike-Timing Dependent Plasticity

    Science.gov (United States)

    Bennett, James E. M.; Bair, Wyeth

    2015-01-01

    Traveling waves in the developing brain are a prominent source of highly correlated spiking activity that may instruct the refinement of neural circuits. A candidate mechanism for mediating such refinement is spike-timing dependent plasticity (STDP), which translates correlated activity patterns into changes in synaptic strength. To assess the potential of these phenomena to build useful structure in developing neural circuits, we examined the interaction of wave activity with STDP rules in simple, biologically plausible models of spiking neurons. We derive an expression for the synaptic strength dynamics showing that, by mapping the time dependence of STDP into spatial interactions, traveling waves can build periodic synaptic connectivity patterns into feedforward circuits with a broad class of experimentally observed STDP rules. The spatial scale of the connectivity patterns increases with wave speed and STDP time constants. We verify these results with simulations and demonstrate their robustness to likely sources of noise. We show how this pattern formation ability, which is analogous to solutions of reaction-diffusion systems that have been widely applied to biological pattern formation, can be harnessed to instruct the refinement of postsynaptic receptive fields. Our results hold for rich, complex wave patterns in two dimensions and over several orders of magnitude in wave speeds and STDP time constants, and they provide predictions that can be tested under existing experimental paradigms. Our model generalizes across brain areas and STDP rules, allowing broad application to the ubiquitous occurrence of traveling waves and to wave-like activity patterns induced by moving stimuli. PMID:26308406

  10. The Effects of the Planned High-Speed Rail System on Travel Times and Spatial Development in the European Alps

    Directory of Open Access Journals (Sweden)

    Elisa Ravazzoli

    2017-02-01

    Full Text Available One of the direct effects of introducing high-speed railway lines is a significant reduction in travel times between major cities. This is particularly relevant in mountain areas. It not only makes cities more easily reachable with more sustainable transport systems but can also encourage different travel behavior and reduce environmental pressures on sensitive areas. A comprehensive analysis of the spatiotemporal effects of the introduction of high-speed railways in the Alpine arc has not yet been developed. To help fill this gap, this study uses multidimensional scaling and the geographical information system to illustrate the time–space compression. This term indicates the erosion of spatial and temporal distances in the areas of the Alps directly affected by the new railway lines. Six trans-Alpine high-speed railway lines are analyzed, comparing current and projected travel times by train. A time-based map is created to show the time–space compression in every transversal direction, particularly on the French and the Austrian side of the Alps. Implications in terms of local accessibility are also analyzed, focusing on the Autonomous Province of Bolzano/Bozen-South Tyrol. Finally, the paper discusses the importance of time-based maps for the understanding of sociospatial dynamics and the possible implications for spatial development.

  11. Response of the hyporheic zone to transient groundwater fluctuations on the annual and storm event time scales

    Science.gov (United States)

    Malzone, Jonathan M.; Lowry, Christopher S.; Ward, Adam S.

    2016-07-01

    The volume of the water stored in and exchanged with the hyporheic zone is an important factor in stream metabolism and biogeochemical cycling. Previous studies have identified groundwater direction and magnitude as one key control on the volume of the hyporheic zone, suggesting that fluctuation in the riparian water table could induce large changes under certain seasonal conditions. In this study, we analyze the transient drivers that control the volume of the hyporheic zone by coupling the Brinkman-Darcy equation to the Navier-Stokes equations to simulate annual and storm induced groundwater fluctuations. The expansion and contraction of the hyporheic zone was quantified based on temporally dynamic scenarios simulating annual groundwater fluctuations in a humid temperate climate. The amplitude of the groundwater signal was varied between scenarios to represent a range of annual hydrologic forcing. Storm scenarios were then superimposed on the annual scenario to simulate the response to short-term storm signals. Simulations used two different groundwater storm responses; one in-phase with the surface water response and one 14 h out-of-phase with the surface water response to represent our observed site conditions. Results show that annual groundwater fluctuation is a dominant control on the volume of the hyporheic zone, where increasing groundwater fluctuation increases the amount of annual variation. Storm responses depended on the antecedent conditions determined by annual scenarios, where the time of year dictated the duration and magnitude of the storm induced response of the hyporheic zone.

  12. Use of acoustic wave travel-time measurements to probe the near-surface layers of the Sun

    Science.gov (United States)

    Jefferies, S. M.; Osaki, Y.; Shibahashi, H.; Duvall, T. L., Jr.; Harvey, J. W.; Pomerantz, M. A.

    1994-01-01

    The variation of solar p-mode travel times with cyclic frequency nu is shown to provide information on both the radial variation of the acoustic potential and the depth of the effective source of the oscillations. Observed travel-time data for waves with frequency lower than the acoustic cutoff frequency for the solar atmosphere (approximately equals 5.5 mHz) are inverted to yield the local acoustic cutoff frequency nu(sub c) as a function of depth in the outer convection zone and lower atmosphere of the Sun. The data for waves with nu greater than 5.5 mHz are used to show that the source of the p-mode oscillations lies approximately 100 km beneath the base of the photosphere. This depth is deeper than that determined using a standard mixing-length calculation.

  13. The influence of travel time on emergency obstetric care seeking behavior in the urban poor of Bangladesh: a GIS study

    OpenAIRE

    Panciera, Rocco; Khan, Akib; Rizvi, Syed Jafar Raza; Ahmed, Shakil; Ahmed, Tanvir; Islam, Rubana; Adam, Alayne M.

    2016-01-01

    Background Availability of Emergency Obstetric Care (EmOC) is crucial to avert maternal death due to life-threatening complications potentially arising during delivery. Research on the determinants of utilization of EmOC has neglected urban settings, where traffic congestion can pose a significant barrier to the access of EmOC facilities, particularly for the urban poor due to costly and limited transportation options. This study investigates the impact of travel time to EmOC facilities on th...

  14. The influence of travel time on emergency obstetric care seeking behavior in the urban poor of Bangladesh: a GIS study

    OpenAIRE

    Panciera, Rocco; Khan, Akib; Rizvi, Syed Jafar Raza; Ahmed, Shakil; Ahmed, Tanvir; Islam, Rubana; Adam, Alayne M.

    2016-01-01

    Background Availability of Emergency Obstetric Care (EmOC) is crucial to avert maternal death due to life-threatening complications potentially arising during delivery. Research on the determinants of utilization of EmOC has neglected urban settings, where traffic congestion can pose a significant barrier to the access of EmOC facilities, particularly for the urban poor due to costly and limited transportation options. This study investigates the impact of travel time to EmOC facilities on th...

  15. Faulting and groundwater in a desert environment: constraining hydrogeology using time-domain electromagnetic data

    Science.gov (United States)

    Bedrosian, Paul A.; Burgess, Matthew K.; Nishikawa, Tracy

    2013-01-01

    Within the south-western Mojave Desert, the Joshua Basin Water District is considering applying imported water into infiltration ponds in the Joshua Tree groundwater sub-basin in an attempt to artificially recharge the underlying aquifer. Scarce subsurface hydrogeological data are available near the proposed recharge site; therefore, time-domain electromagnetic (TDEM) data were collected and analysed to characterize the subsurface. TDEM soundings were acquired to estimate the depth to water on either side of the Pinto Mountain Fault, a major east-west trending strike-slip fault that transects the proposed recharge site. While TDEM is a standard technique for groundwater investigations, special care must be taken when acquiring and interpreting TDEM data in a twodimensional (2D) faulted environment. A subset of the TDEM data consistent with a layered-earth interpretation was identified through a combination of three-dimensional (3D) forward modelling and diffusion time-distance estimates. Inverse modelling indicates an offset in water table elevation of nearly 40 m across the fault. These findings imply that the fault acts as a low-permeability barrier to groundwater flow in the vicinity of the proposed recharge site. Existing production wells on the south side of the fault, together with a thick unsaturated zone and permeable near-surface deposits, suggest the southern half of the study area is suitable for artificial recharge. These results illustrate the effectiveness of targeted TDEM in support of hydrological studies in a heavily faulted desert environment where data are scarce and the cost of obtaining these data by conventional drilling techniques is prohibitive.

  16. Natural Attenuation Software (NAS): A computer program for estimating remediation times of contaminated groundwater

    Science.gov (United States)

    Mendez, E.; Widdowson, M.; Brauner, S.; Chapelle, F.; Casey, C.; ,

    2004-01-01

    This paper describes the development and application of a modeling system called Natural Attenuation Software (NAS). NAS was designed as a screening tool to estimate times of remediation (TORs), associated with monitored natural attenuation (MNA), to lower groundwater contaminant concentrations to regulatory limits. Natural attenuation processes that NAS models include advection, dispersion, sorption, biodegradation, and non-aqueous phase liquid (NAPL) dissolution. This paper discusses the three main interactive components of NAS: 1) estimation of the target source concentration required for a plume extent to contract to regulatory limits, 2) estimation of the time required for NAFL contaminants in the source area to attenuate to a predetermined target source concentration, and 3) estimation of the time required for a plume extent to contract to regulatory limits after source reduction. The model's capability is illustrated by results from a case study at a MNA site, where NAS time of remediation estimates compared well with observed monitoring data over multiple years.

  17. Stochastic analysis of radionuclides travel times at the waste isolation pilot plant (WIPP), in New Mexico (U. S. A. )

    Energy Technology Data Exchange (ETDEWEB)

    Capilla Roma, J. E.; Gomez-Hernandez, J. J.; Sahuquillo Herraiz, A. (Universidad Politecnia de Valencia (Spain))

    1999-12-15

    Multiple equally likely transmissivity fields that honor piezo metric head measurements are generated as input to a Monte-Carlo exercise, for the stochastic analysis of travel times in the Culebra dolomite overlaying the Waste Isolation Pilot Plant (WIPP) in New Mexico, USA. Results of the analysis show the importance of modeling variable-density flow as accurately as possible, and of including as much information as possible in the simulations of alternative scenarios. Results also unveil a channel of high transmissivity when transmissivity fields are conditioned to piezo metric data. This channel leads to important reductions of travel time from the WIPP area to the south boundary. The uncertainty of the boundary conditions is analyzed searching for alternative boundary conditions can be obtained that improve the reproduction of piezo metric data and yield a reduction of the minimum travel times to the south boundary. Results of the Monte-Carlo exercise are compared with those from a deterministic analysis showing the limitations of the latter method when trying to estimate extreme values or characterizing the uncertainty of their predictions. The report ends with a brief study on the impact of the small transmissivity measurements at location P-18, showing that its value is not consistent with the model of spatial variability inferred from the data and that it has an important effect on model predictions. (Author)

  18. A Novel Approach to Extract Significant Patterns of Travel Time Intervals of Vehicles from Freeway Gantry Timestamp Sequences

    Directory of Open Access Journals (Sweden)

    Jing-Doo Wang

    2017-08-01

    Full Text Available It is attractive to extract and determine the key features of traffic patterns for mitigating road congestion and predicting travel time of vehicles in traffic analysis. Based on the previous work that is a scalable approach via a Hadoop MapReduce programming model, this paper aims to extract significant patterns of travel time intervals of vehicles from freeway traffic in Taiwan, and meanwhile to compute the statistics of these patterns from the point of view one may concern. Experimental resources are the records of timestamp gantry sequences of vehicles passed in five months from 2016/11 to 2017/3 that were downloaded from the Traffic Data Collection System, one of Taiwan government open data platforms. To select one specific gantry sequence for demonstration, the longest sequence on the trip within the Taiwan National Freeway No. 5 is selected. Experimental results show that some statistics of vehicle travel time intervals according to 24 h per day are computed for illustration. These statistics can not only provide clues to experts to analyze traffic congestions, but also help drivers how to avoid rush hours. Furthermore, this work is able to handle a larger amount of real data and be promising for further traffic and transportation research in the future.

  19. Probability distributions of bed load particle velocities, accelerations, hop distances, and travel times informed by Jaynes's principle of maximum entropy

    Science.gov (United States)

    Furbish, David J.; Schmeeckle, Mark; Schumer, Rina; Fathel, Siobhan L.

    2016-01-01

    We describe the most likely forms of the probability distributions of bed load particle velocities, accelerations, hop distances, and travel times, in a manner that formally appeals to inferential statistics while honoring mechanical and kinematic constraints imposed by equilibrium transport conditions. The analysis is based on E. Jaynes's elaboration of the implications of the similarity between the Gibbs entropy in statistical mechanics and the Shannon entropy in information theory. By maximizing the information entropy of a distribution subject to known constraints on its moments, our choice of the form of the distribution is unbiased. The analysis suggests that particle velocities and travel times are exponentially distributed and that particle accelerations follow a Laplace distribution with zero mean. Particle hop distances, viewed alone, ought to be distributed exponentially. However, the covariance between hop distances and travel times precludes this result. Instead, the covariance structure suggests that hop distances follow a Weibull distribution. These distributions are consistent with high-resolution measurements obtained from high-speed imaging of bed load particle motions. The analysis brings us closer to choosing distributions based on our mechanical insight.

  20. Connected Traveler

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Alex

    2015-11-01

    The Connected Traveler project is a multi-disciplinary undertaking that seeks to validate potential for transformative transportation system energy savings by incentivizing efficient traveler behavior. This poster outlines various aspects of the Connected Traveler project, including market opportunity, understanding traveler behavior and decision-making, automation and connectivity, and a projected timeline for Connected Traveler's key milestones.

  1. Application limits of the interpretation of near-surface temperature time series to assess groundwater recharge

    Science.gov (United States)

    Gosselin, J. S.; Rivard, C.; Martel, R.; Lefebvre, R.

    2016-07-01

    The main objective of this study was to test the application limits of a groundwater recharge assessment technique based on the inversion of a vertical one-dimensional numerical model of advective-conductive heat transport, using temperature time series at three different depths (1, 3, 5 m) in the unsaturated zone. For this purpose, several synthetic hourly datasets of subsurface temperatures, representing various weather, ground cover, and soil texture conditions, thus covering a wide range of groundwater recharge values, were produced with the vertical one-dimensional coupled heat and moisture transport simulator SHAW (Simultaneous Heat and Water model). Estimates of the vertical flux of water in the soil were then retrieved from these realistic temperature profiles using a simple one-dimensional numerical simulator of advective and conductive heat transport in the unsaturated zone that was developed as part of this study. The water flux was assumed constant on a weekly, monthly, semiannual, and annual basis. From these vertical water flux estimates, annual (potential) groundwater recharge rates were then computed and results were compared to those calculated previously with SHAW to assess the accuracy of the method. Results showed that, under ideal conditions, it would be possible to estimate annual recharge rates that are above 200 mm/y, with an acceptable error of less than 20%. These "ideal" conditions include the resolution of the water flux on a weekly basis, error-free temperature measurements below the soil freezing zone, and model parameter values (thermal conductivity and heat capacity of the soil) known a priori with no uncertainty. However, this work demonstrates that the accuracy of the method is highly sensitive to the uncertainty of the input model parameters of the numerical model used to carry out the inversion and to measurement errors of temperature time series. For the conditions represented in this study, these findings suggest that, despite

  2. Understanding infiltration and groundwater flow at an artificial recharge facility using time-lapse gravity data

    Science.gov (United States)

    Kennedy, Jeffrey

    Groundwater provides a fundamental resource for modern life. Throughout the world, groundwater is managed by storing (recharging) it underground in natural aquifers for future withdrawal and consumptive use. In Arizona, over 4 million people benefit from managed aquifer storage, but little effort is made to track the movement of recharged water through the subsurface. Motivated by current limitations in our ability to monitor percolation and groundwater movement at the scale of a recharge facility, an effort to collect time-lapse gravity data was carried out at the Southern Avra Valley Storage and Recovery Project (SAVSARP) operated by the City of Tucson, Arizona. In addition to collecting water-level data 12 wells, there were three primary gravity experiments: (1) five continuously-recording gravity meters (2 iGrav superconducting gravity meters and 3 gPhone gravity meters) were installed semi-permanently in control buildings adjacent to the recharge basins, (2) absolute gravity measurements were made at nine locations over a 17 month period, and (3) three relative-gravity campaigns were carried out on a network of 70 stations. This large-scale controlled experiment, with known infiltration and pumping rates, resulted in one of the most comprehensive datasets of its kind. Gravity data led to several hydrologic insights, both through direct measurement and modeling. First, the infiltration rate could be estimated accurately based on the initial rate of gravity change during infiltration, regardless of the specific yield. Using two gravity meters, the depth, and therefore speed, of the wetting front beneath a recharge basin was observed, including the time at which the water table was reached. Spatial maps of gravity change from relative gravity surveys show areas where infiltration efficiency is highest, and where groundwater accumulates; storage accumulated preferentially to the west of the recharge basins, away from pumping wells. Such information would be

  3. Tritium activity concentrations and residence times of groundwater collected in Rokkasho, Japan.

    Science.gov (United States)

    Hasegawa, Hidenao; Ueda, Shinji; Akata, Naofumi; Kakiuchi, Hideki; Hisamatsu, Shun'ichi

    2015-11-01

    Tritium ((3)H) concentrations were measured in groundwater samples from four surface wells (4-10 m deep), four shallow wells (24-26.5 m deep) and a 150-m-deep well in the Futamata River catchment area, which is adjacent to the large-scale commercial spent nuclear fuel reprocessing plant in Rokkasho, Japan. The (3)H concentrations in most of the surface- and shallow-well samples (<0.03-0.57 Bq l(-1)) were similar to those in precipitation (annual mean: 0.31-0.79 Bq l(-1)), suggesting that the residence time of the water in those wells was 0-15 y. The (3)H concentrations in the samples from a 26-m-deep well and the 150-m-deep well were lower than those in the other wells, indicating that groundwater with a long residence time exists in deep aquifers and the estuary area of the catchment. It is not clear whether (3)H released during test operation of the plant with actual spent nuclear fuel affected the (3)H concentrations observed in this study. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  4. Space-Time Modelling of Groundwater Level Using Spartan Covariance Function

    Science.gov (United States)

    Varouchakis, Emmanouil; Hristopulos, Dionissios

    2014-05-01

    Geostatistical models often need to handle variables that change in space and in time, such as the groundwater level of aquifers. A major advantage of space-time observations is that a higher number of data supports parameter estimation and prediction. In a statistical context, space-time data can be considered as realizations of random fields that are spatially extended and evolve in time. The combination of spatial and temporal measurements in sparsely monitored watersheds can provide very useful information by incorporating spatiotemporal correlations. Spatiotemporal interpolation is usually performed by applying the standard Kriging algorithms extended in a space-time framework. Spatiotemoral covariance functions for groundwater level modelling, however, have not been widely developed. We present a new non-separable theoretical spatiotemporal variogram function which is based on the Spartan covariance family and evaluate its performance in spatiotemporal Kriging (STRK) interpolation. The original spatial expression (Hristopulos and Elogne 2007) that has been successfully used for the spatial interpolation of groundwater level (Varouchakis and Hristopulos 2013) is modified by defining the following space-time normalized distance h = °h2r-+-α h2τ, hr=r- ξr, hτ=τ- ξτ; where r is the spatial lag vector, τ the temporal lag vector, ξr is the correlation length in position space (r) and ξτ in time (τ), h the normalized space-time lag vector, h = |h| is its Euclidean norm of the normalized space-time lag and α the coefficient that determines the relative weight of the time lag. The space-time experimental semivariogram is determined from the biannual (wet and dry period) time series of groundwater level residuals (obtained from the original series after trend removal) between the years 1981 and 2003 at ten sampling stations located in the Mires hydrological basin in the island of Crete (Greece). After the hydrological year 2002-2003 there is a significant

  5. Estimating groundwater evapotranspiration by a subtropical pine plantation using diurnal water table fluctuations: Implications from night-time water use

    Science.gov (United States)

    Fan, Junliang; Ostergaard, Kasper T.; Guyot, Adrien; Fujiwara, Stephen; Lockington, David A.

    2016-11-01

    Exotic pine plantations have replaced large areas of the native forests for timber production in the subtropical coastal Australia. To evaluate potential impacts of changes in vegetation on local groundwater discharge, we estimated groundwater evapotranspiration (ETg) by the pine plantation using diurnal water table fluctuations for the dry season of 2012 from August 1st to December 31st. The modified White method was used to estimate the ETg, considering the night-time water use by pine trees (Tn). Depth-dependent specific yields were also determined both experimentally and numerically for estimation of ETg. Night-time water use by pine trees was comprehensively investigated using a combination of groundwater level, sap flow, tree growth, specific yield, soil matric potential and climatic variables measurements. Results reveal a constant average transpiration flux of 0.02 mm h-1 at the plot scale from 23:00 to 05:00 during the study period, which verified the presence of night-time water use. The total ETg for the period investigated was 259.0 mm with an accumulated Tn of 64.5 mm, resulting in an error of 25% on accumulated evapotranspiration from the groundwater if night-time water use was neglected. The results indicate that the development of commercial pine plantations may result in groundwater losses in these areas. It is also recommended that any future application of diurnal water table fluctuation based methods investigate the validity of the zero night-time water use assumption prior to use.

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

    Science.gov (United States)

    Obayashi, Masayuki; Ishihara, Yasushi; Suetsugu, Daisuke

    2017-03-01

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

  7. Groundwater age, life expectancy and transit time distributions in advective-dispersive systems: 1. Generalized reservoir theory

    CERN Document Server

    Cornaton, F; 10.1016/j.advwatres.2005.10.009

    2011-01-01

    We present a methodology for determining reservoir groundwater age and transit time probability distributions in a deterministic manner, considering advective-dispersive transport in steady velocity fields. In a first step, we propose to model the statistical distribution of groundwater age at aquifer scale by means of the classical advection-dispersion equation for a conservative and nonreactive tracer, associated to proper boundary conditions. The evaluated function corresponds to the density of probability of the random variable age, age being defined as the time elapsed since the water particles entered the aquifer. An adjoint backward model is introduced to characterize the life expectancy distribution, life expectancy being the time remaining before leaving the aquifer. By convolution of these two distributions, groundwater transit time distributions, from inlet to outlet, are fully defined for the entire aquifer domain. In a second step, an accurate and efficient method is introduced to simulate the tr...

  8. Global paths of time-periodic solutions of the Benjamin-Ono equation connecting arbitrary traveling waves

    Energy Technology Data Exchange (ETDEWEB)

    Ambrose, David M.; Wilkening, Jon

    2008-12-11

    We classify all bifurcations from traveling waves to non-trivial time-periodic solutions of the Benjamin-Ono equation that are predicted by linearization. We use a spectrally accurate numerical continuation method to study several paths of non-trivial solutions beyond the realm of linear theory. These paths are found to either re-connect with a different traveling wave or to blow up. In the latter case, as the bifurcation parameter approaches a critical value, the amplitude of the initial condition grows without bound and the period approaches zero. We propose a conjecture that gives the mapping from one bifurcation to its counterpart on the other side of the path of non-trivial solutions. By experimentation with data fitting, we identify the form of the exact solutions on the path connecting two traveling waves, which represents the Fourier coefficients of the solution as power sums of a finite number of particle positions whose elementary symmetric functions execute simple orbits in the complex plane (circles or epicycles). We then solve a system of algebraic equations to express the unknown constants in the new representation in terms of the mean, a spatial phase, a temporal phase, four integers (enumerating the bifurcation at each end of the path) and one additional bifurcation parameter. We also find examples of interior bifurcations from these paths of already non-trivial solutions, but we do not attempt to analyze their algebraic structure.

  9. Application of isotopes to estimate water ages in variable time scales in surface and groundwaters

    Science.gov (United States)

    Kralik, Martin

    2014-05-01

    Water-Isotopes (2H, 3H, 18O) are ideal tracers not only to determine the origin of waters in precipitation, surface water (river + lakes) as well as in groundwater close to the surface and in deep groundwater but also the mean residence time (MRT) in many applied projects as drinking water supply, hydroelectric power plants, road tunnels etc. . Their application has a long history, but must be always evaluated by a feasible hydrogeological concept and/or other isotope and geochemical tracers. In Alpine areas the retention of precipitation in form of snow and ice in the winter half year is indicated by the lowest 18O-values. The snow melt of the highest part of the recharge area is marked by the lowest 18O-values in the river water, but may not coincide with the maximum flow. Time-series of precipitation station in the mountain and on river station indicate the arrival of the peak snow-melt water in the river and in Low-land areas 4-7 month later. Tritium series indicate that MRTs of several Austrian rivers are in the range of 4 - 6 years. The seasonal input variation of in 18O in precipitation and/or river waters can be used to calculate by lumped parameter models MRT of groundwater at a certain well and compare it with lysimeter measurements and transient model simulations. The MRT of the dispersion model is in good agreement with the estimated time calculated by the numerical transport model and the vertical lysimeter measurements. The MRT of spring water was studied by several methods (3H/3He, SF6 and 85Kr) and a long time series of 3H-measurements. The gas tracers are in good agreement in the range of 6-10 year whereas the 3H-series model (dispersion model) indicate ages in the range of 18-23 years. The hydrogeological concept indicate that the precipitation infiltrates in a mountainous karst area, but the transfer into the porous aquifer in the Vienna Basin occurs either through rivers draining away in the basin or through the lateral transport from the karst

  10. Factors influencing modes of transport and travel time for obstetric care: a mixed methods study in Zambia and Uganda.

    Science.gov (United States)

    Sacks, Emma; Vail, Daniel; Austin-Evelyn, Katherine; Greeson, Dana; Atuyambe, Lynn M; Macwan'gi, Mubiana; Kruk, Margaret E; Grépin, Karen A

    2016-04-01

    Transportation is an important barrier to accessing obstetric care for many pregnant and postpartum women in low-resource settings, particularly in rural areas. However, little is known about how pregnant women travel to health facilities in these settings. We conducted 1633 exit surveys with women who had a recent facility delivery and 48 focus group discussions with women who had either a home or a facility birth in the past year in eight districts in Uganda and Zambia. Quantitative data were analysed using univariate statistics, and qualitative data were analysed using thematic content analysis techniques. On average, women spent 62-68 min travelling to a clinic for delivery. Very different patterns in modes of transport were observed in the two countries: 91% of Ugandan women employed motorized forms of transportation, while only 57% of women in Zambia did. Motorcycle taxis were the most commonly used in Uganda, while cars, trucks and taxis were the most commonly used mode of transportation in Zambia. Lower-income women were less likely to use motorized modes of transportation: in Zambia, women in the poorest quintile took 94 min to travel to a health facility, compared with 34 for the wealthiest quintile; this difference between quintiles was ∼50 min in Uganda. Focus group discussions confirmed that transport is a major challenge due to a number of factors we categorized as the 'three A's:' affordability, accessibility and adequacy of transport options. Women reported that all of these factors had influenced their decision not to deliver in a health facility. The two countries had markedly different patterns of transportation for obstetric care, and modes of transport and travel times varied dramatically by wealth quintile, which policymakers need to take into account when designing obstetric transport interventions.

  11. 41 CFR 302-2.10 - Does the 2-year time period in § 302-2.8 include time that I cannot travel and/or transport my...

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 4 2010-07-01 2010-07-01 false Does the 2-year time period in § 302-2.8 include time that I cannot travel and/or transport my household effects due to... time that I cannot travel and/or transport my household effects due to shipping restrictions to or from...

  12. Travelers' Health: Pregnant Travelers

    Science.gov (United States)

    ... Zika is present and take precautions to avoid sexual transmission of the virus. If travel cannot be avoided, pregnant women should strictly follow steps to prevent mosquito bites. Additional information, including the most current list of countries and territories where Zika virus is a risk, ...

  13. Community variations in population exposure to near-field tsunami hazards as a function of pedestrian travel time to safety

    Science.gov (United States)

    Wood, Nathan J.; Schmidtlein, Mathew C.

    2013-01-01

    Efforts to characterize population exposure to near-field tsunami threats typically focus on quantifying the number and type of people in tsunami-hazard zones. To develop and prioritize effective risk-reduction strategies, emergency managers also need information on the potential for successful evacuations and how this evacuation potential varies among communities. To improve efforts to properly characterize and differentiate near-field tsunami threats among multiple communities, we assess community variations in population exposure to tsunamis as a function of pedestrian travel time to safety. We focus our efforts on the multiple coastal communities in Grays Harbor and Pacific Counties (State of Washington, USA), where a substantial resident and visitor population is threatened by near-field tsunamis related to a potential Cascadia subduction zone earthquake. Anisotropic, path-distance modeling is conducted to estimate travel times to safety and results are merged with various population data, including residents, employees, public venues, and dependent-care facilities. Results suggest that there is substantial variability among communities in the number of people that may have insufficient time to evacuate. Successful evacuations may be possible in some communities assuming slow-walking speeds, are plausible in others if travel speeds are increased, and are unlikely in another set of communities given the large distances and short time horizon. Emergency managers can use these results to prioritize the location and determine the most appropriate type of tsunami risk-reduction strategies, such as education and training in areas where evacuations are plausible and vertical-evacuation structures in areas where they are not.

  14. Characterization of surface and ground water δ18O seasonal variation and its use for estimating groundwater residence times

    Science.gov (United States)

    Reddy, Michael M.; Schuster, Paul; Kendall, Carol; Reddy, Micaela B.

    2006-01-01

    18O is an ideal tracer for characterizing hydrological processes because it can be reliably measured in several watershed hydrological compartments. Here, we present multiyear isotopic data, i.e. 18O variations (δ18O), for precipitation inputs, surface water and groundwater in the Shingobee River Headwaters Area (SRHA), a well-instrumented research catchment in north-central Minnesota. SRHA surface waters exhibit δ18O seasonal variations similar to those of groundwaters, and seasonal δ18O variations plotted versus time fit seasonal sine functions. These seasonal δ18O variations were interpreted to estimate surface water and groundwater mean residence times (MRTs) at sampling locations near topographically closed-basin lakes. MRT variations of about 1 to 16 years have been estimated over an area covering about 9 km2 from the basin boundary to the most downgradient well. Estimated MRT error (±0·3 to ±0·7 years) is small for short MRTs and is much larger (±10 years) for a well with an MRT (16 years) near the limit of the method. Groundwater transit time estimates based on Darcy's law, tritium content, and the seasonal δ18O amplitude approach appear to be consistent within the limits of each method. The results from this study suggest that use of the δ18O seasonal variation method to determine MRTs can help assess groundwater recharge areas in small headwaters catchments.

  15. Constraints on the crustal structure beneath the Sinai subplate, SE Mediterranean, from analysis of local and regional travel times

    Directory of Open Access Journals (Sweden)

    Mohamed K. Salah

    2013-03-01

    Full Text Available The Sinai Peninsula has been recognized as a subplate of the African Plate located at the triple junction of the Gulf of Suez rift, the Dead Sea Transform fault, and the Red Sea rift. The upper and lower crustal structures of this tectonically active, rapidly developing region are yet poorly understood because of many limitations. For this reason, a set of P- and S-wave travel times recorded at 14 seismic stations belonging to the Egyptian National Seismographic Network (ENSN from 111 local and regional events are analyzed to investigate the crustal structures and the locations of the seismogenic zones beneath central and southern Sinai. Because the velocity model used for routine earthquake location by ENSN is one-dimensional, the travel-time residuals will show lateral heterogeneity of the velocity structures and unmodeled vertical structures. Seismic activity is strong along the eastern and southern borders of the study area but low to moderate along the northern boundary and the Gulf of Suez to the west. The crustal Vp/Vs ratio is 1.74 from shallow (depth ≤ 10 km earthquakes and 1.76 from deeper (depth > 10 km crustal events. The majority of the regional and local travel-time residuals are positive relative to the Preliminary Reference Earth Model (PREM, implying that the seismic stations are located above widely distributed, tectonically-induced low-velocity zones. These low-velocity zones are mostly related to the local crustal faults affecting the sedimentary section and the basement complex as well as the rifting processes prevailing in the northern Red Sea region and the ascending of hot mantle materials along crustal fractures. The delineation of these low-velocity zones and the locations of big crustal earthquakes enable the identification of areas prone to intense seismotectonic activities, which should be excluded from major future development projects and large constructions in central and southern Sinai.

  16. First case of detection of Plasmodium knowlesi in Spain by Real Time PCR in a traveller from Southeast Asia

    Directory of Open Access Journals (Sweden)

    Arroyo Eduardo

    2010-07-01

    Full Text Available Abstract Previously, Plasmodium knowlesi was not considered as a species of Plasmodium that could cause malaria in human beings, as it is parasite of long-tailed (Macaca fascicularis and pig-tailed (Macaca nemestrina macaques found in Southeast Asia. A case of infection by P. knowlesi is described in a Spanish traveller, who came back to Spain with daily fever after his last overseas travel, which was a six-month holiday in forested areas of Southeast Asia between 2008 and 2009. His P. knowlesi infection was detected by multiplex Real time quantitative PCR and confirmed by sequencing the amplified fragment. Using nested multiplex malaria PCR (reference method in Spain and a rapid diagnostic test, the P. knowlesi infection was negative. This patient was discharged and asymptomatic when the positive result to P. knowlesi was reported. Prior to this case, there have been two more reports of European travellers with malaria caused by P. knowlesi, a Finnish man who travelled to Peninsular Malaysia during four weeks in March 2007, and a Swedish man who did a short visit to Malaysian Borneo in October 2006. Taken together with this report of P. knowlesi infection in a Spanish traveller returning from Southeast Asia, this is the third case of P. knowlesi infection in Europe, indicating that this simian parasite can infect visitors to endemic areas in Southeast Asia. This last European case is quite surprising, given that it is an untreated-symptomatic P. knowlesi in human, in contrast to what is currently known about P. knowlesi infection. Most previous reports of human P. knowlesi malaria infections were in adults, often with symptoms and relatively high parasite densities, up to the recent report in Ninh Thuan province, located in the southern part of central Vietnam, inhabited mainly by the Ra-glai ethnic minority, in which all P. knowlesi infections were asymptomatic, co-infected with P. malariae, with low parasite densities and two of the three

  17. Combining numerical simulations with time-domain random walk for pathogen risk assessment in groundwater

    Science.gov (United States)

    Cvetkovic, V.; Molin, S.

    2012-02-01

    We present a methodology that combines numerical simulations of groundwater flow and advective transport in heterogeneous porous media with analytical retention models for computing the infection risk probability from pathogens in aquifers. The methodology is based on the analytical results presented in [1,2] for utilising the colloid filtration theory in a time-domain random walk framework. It is shown that in uniform flow, the results from the numerical simulations of advection yield comparable results as the analytical TDRW model for generating advection segments. It is shown that spatial variability of the attachment rate may be significant, however, it appears to affect risk in a different manner depending on if the flow is uniform or radially converging. In spite of the fact that numerous issues remain open regarding pathogen transport in aquifers on the field scale, the methodology presented here may be useful for screening purposes, and may also serve as a basis for future studies that would include greater complexity.

  18. Emergency obstetrical complications in a rural African setting (Kayes, Mali): the link between travel time and in-hospital maternal mortality.

    Science.gov (United States)

    Pirkle, Catherine McLean; Fournier, Pierre; Tourigny, Caroline; Sangaré, Karim; Haddad, Slim

    2011-10-01

    The West African country of Mali implemented referral systems to increase spatial access to emergency obstetrical care and lower maternal mortality. We test the hypothesis that spatial access- proxied by travel time during the rainy and dry seasons- is associated with in-hospital maternal mortality. Effect modification by caesarean section is explored. All women treated for emergency obstetrical complications at the referral hospital in Kayes, Mali were considered eligible for study. First, we conducted descriptive analyses of all emergency obstetrical complications treated at the referral hospital between 2005 and 2007. We calculated case fatality rates by obstetric diagnosis and travel time. Key informant interviews provided travel times. Medical registers provided clinical and demographic data. Second, a matched case-control study assessed the independent effect of travel time on maternal mortality. Stratification was used to explore effect modification by caesarean section. Case fatality rates increased with increasing travel time to the hospital. After controlling for age, diagnosis, and date of arrival, a travel time of four or more hours was significantly associated with in-hospital maternal mortality (OR: 3.83; CI: 1.31-11.27). Travel times between 2 and 4 h were associated with increased odds of maternal mortality (OR 1.88), but the relationship was not significant. The effect of travel time on maternal mortality appears to be modified by caesarean section. Poor spatial access contributes to maternal mortality even in women who reach a health facility. Improving spatial access will help women arrive at the hospital in time to be treated effectively.

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

    National Research Council Canada - National Science Library

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

    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...

  20. [Travelers' vaccines].

    Science.gov (United States)

    Ouchi, Kazunobu

    2011-09-01

    The number of Japanese oversea travelers has gradually increased year by year, however they usually pay less attention to the poor physical condition at the voyage place. Many oversea travelers caught vaccine preventable diseases in developing countries. The Vaccine Guideline for Oversea Travelers 2010 published by Japanese Society of Travel Health will be helpful for spreading the knowledge of travelers' vaccine and vaccine preventable diseases in developing countries. Many travelers' vaccines have not licensed in Japan. I hope these travelers' vaccines, such as typhoid vaccine, meningococcal vaccine, cholera vaccine and so on will be licensed in the near future.