Search results for "Travel"
showing 10 items of 402 documents
Time-dependent asymmetric traveling salesman problem with time windows: Properties and an exact algorithm
2019
Abstract In this paper, we deal with the Time-Dependent Asymmetric Traveling Salesman Problem with Time Windows. First, we prove that under special conditions the problem can be solved as an Asymmetric Traveling Salesman Problem with Time Windows, with suitable-defined time windows and (constant) travel times. Second, we show that, if the special conditions do not hold, the time-independent optimal solution provides both a lower bound and (eventually) an upper bound with a worst-case guarantee for the Time-Dependent Asymmetric Traveling Salesman Problem with Time Windows. Finally, a branch-and-bound algorithm is presented and tested on a set of 4800 instances. The results have been compared…
A qualitative study on the role of the built environment for short walking trips
2015
The present study uses a qualitative approach with the aim to identify built environmental factors influencing short walking distances for transportation among adults (18-65 years), with special attention to micro-scale attributes. Three focus groups were held in Valencia (Spain) and conducted with participants who undertook, at least once a week, one short non-shopping trip in any travel mode (were "short trip" is defined as less than 3045 min walking distance). A thematic analysis of the data was performed and six categories of factors emerged related to the built environment. Factors were also classified as either barriers to walking, or secondary factors related to the attractiveness of…
Quantitative global mapping of terrestrial vegetation photosynthesis
2017
Although traditional remote sensing systems based on spectral reflectance can already provide estimates of the 'potential' photosynthetic activity of terrestrial vegetation through the quantification of total canopy chlorophyll content or absorbed photosynthetic radiation, the determination of the 'actual' photosynthetic activity of terrestrial vegetation requires information about how the absorbed light is used by plants, such as vegetation fluorescence, using very high spectral resolution spectroscopy in the range 650-800 nm. The Fluorescence Explorer (FLEX) mission, selected in November 2015 as the 8th Earth Explorer by the European Space Agency (ESA), carries the FLORIS spectrometer, wi…
Variability and Uncertainty Challenges in Scaling Imaging Spectroscopy Retrievals and Validations from Leaves Up to Vegetation Canopies
2019
Imaging spectroscopy of vegetation requires methods for scaling and generalizing optical signals that are reflected, transmitted and emitted in the solar wavelength domain from single leaves and observed at the level of canopies by proximal sensing, airborne and satellite spectroradiometers. The upscaling embedded in imaging spectroscopy retrievals and validations of plant biochemical and structural traits is challenged by natural variability and measurement uncertainties. Sources of the leaf-to-canopy upscaling variability and uncertainties are reviewed with respect to: (1) implementation of retrieval algorithms and (2) their parameterization and validation of quantitative products through…
The 2013 FLEX—US Airborne Campaign at the Parker Tract Loblolly Pine Plantation in North Carolina, USA
2017
The first European Space Agency (ESA) and NASA collaboration in an airborne campaign to support ESA’s FLuorescence EXplorer (FLEX) mission was conducted in North Carolina, USA during September–October 2013 (FLEX-US 2013) at the Parker Tract Loblolly Pine (LP) Plantation (Plymouth, NC, USA). This campaign combined two unique airborne instrument packages to obtain simultaneous observations of solar-induced fluorescence (SIF), LiDAR-based canopy structural information, visible through shortwave infrared (VSWIR) reflectance spectra, and surface temperature, to advance vegetation studies of carbon cycle dynamics and ecosystem health. We obtained statistically significant results for fluorescence…
Red and far-red sun-induced chlorophyll fluorescence as a measure of plant photosynthesis
2015
Remote estimation of Sun-induced chlorophyll fluorescence emitted by terrestrial vegetation can provide an unparalleled opportunity to track spatiotemporal variations of photosynthetic efficiency. Here we provide the first direct experimental evidence that the two peaks of the chlorophyll fluorescence spectrum can be accurately mapped from high-resolution radiance spectra and that the signal is linked to variations in actual photosynthetic efficiency. Red and far red fluorescence measured using a novel airborne imaging spectrometer over a grass carpet treated with an herbicide known to inhibit photosynthesis was significantly higher than the corresponding signal from an equivalent untreated…
Sun-induced fluorescence - a new probe of photosynthesis: First maps from the imaging spectrometer HyPlant.
2015
Variations in photosynthesis still cause substantial uncertainties in predicting photosynthetic CO2 uptake rates and monitoring plant stress. Changes in actual photosynthesis that are not related to greenness of vegetation are difficult to measure by reflectance based optical remote sensing techniques. Several activities are underway to evaluate the sun-induced fluorescence signal on the ground and on a coarse spatial scale using space-borne imaging spectrometers. Intermediate-scale observations using airborne-based imaging spectroscopy, which are critical to bridge the existing gap between small-scale field studies and global observations, are still insufficient. Here we present the first …
The crevice of the picture: Behind-the-scenes look at the early cinematographic representations of the ainu people (1897-1918)
2014
El presente trabajo plantea un recorrido histórico por la representación del pueblo ainu en el cine de los orígenes. Hemos dividido el corpus en tres bloques: primero, la presencia ainu entre las primeras actualités de los Lumière rodadas en Japón. Segundo, en las actualités de la compañía Pathé y la referencia a un documental perdido de Torii Rūyzō. Tercero, en los travelogues realizados en Japón por los exploradores en los años 10 Frederick Starr y Benjamin Brodsky. Al comparar el análisis cinematográfico con la realidad social del pueblo ainu se pone de relieve cómo los documentales trataron de proyectar una etnicidad correspondiente a un tiempo anterior al momento en que fueron filmados…
What distance do university students walk and bike daily to class in Spain
2016
Abstract Introduction Physical activity levels are low in the general population and these levels decrease from childhood to adolescence, as well as from adolescence to adulthood. Active commuting (AC) is an opportunity to increase the physical activity levels. The distance between home and destinations is a main correlate of AC; however, the distance that university students walk or cycle to university is unknown. Methods Participants self-reported their modes and time of commuting to and from university in a questionnaire, and the main mode of commuting was identified. Moreover, they reported their home address, and the Spanish version of Mapquest software was used to measure street-netwo…
Producing social mobility. Class and Travel in the Romanian Novel 1901-1932
2020
The present article addresses the Romanian novelistic production between 1901 and 1932 in the attempt of identifying a series of patterns regarding the protagonists’ social mobility. Starting with the most mentioned destinations throughout the novels, I analyse how and why the different social classes travel and try to determine the landmarks between which they dispute their physical presence, on the one hand, and their aspirations, on the other. On this basis, the second part of the article conducts a quantitative analysis of the major means of transport in the period – the train, the tramway, the coach/carriage, the automobile, the aeroplane, the ship, and the waggon – and attempts to pin…