Search results for "LINE SOURCE"
showing 7 items of 7 documents
Thermal response test analysis for U-pipe vertical borehole heat exchangers under groundwater flow conditions
2021
[EN] Conventional models used in the analysis of thermal response test data only consider conduction as heat transfer mechanism. In cases where presence of groundwater is detected, convection heat transmission plays an important role, so its influence must be determined in the calculation of the effective thermal conductivity, usually overestimated in these situations, increasing its value the higher the power injected and the time elapsed. In this work, based on the data collected in a borehole located at UPV (Valencia) in which have been carried out three thermal response tests with different characteristics, has been implemented a variation of the finite line source model introducing an …
Student evaluations of the credibility and argumentation of online sources
2021
This study investigated upper secondary school students’ skills in evaluating the credibility and argumentative content of a blog text and a YouTube video. Both sources concerned child vaccination, the blog text opposing and the YouTube video supporting it. Students rated each source as credible, fairly credible or non-credible, justified their ratings, and analyzed the argumentation of both sources. Their justifications were analyzed for trustworthiness and expertise and their argument analyses for identification of the main position of the source and the reasons supporting it. Students’ justification skills proved fairly weak, and they also struggled with recognizing unbalanced argumentat…
An evaluation of the estimation of road traffic emission factors from tracer studies
2010
Road traffic emission factors (EFs) are one of the main sources of uncertainties in emission inventories; it is necessary to develop methods to reduce these uncertainties to manage air quality more efficiently. Recently an alternative method has been proposed to estimate the EFs. In that work the emission factors were estimated from a long term tracer study developed in Ho Chi Minh City (HCMC) Vietnam. A passive tracer was continuously emitted from a finite line source placed in one side of an urban street canyon. Simultaneously, the resulting tracer concentrations were monitored at the other side of the street. The results of this experiment were used to calculate the dispersion factors an…
Laser-Generated Acoustic Signal Interaction with Surface Flaws on Rail Wheels
2005
Long- and short-range acoustic-signal interaction with surface-breaking cracks and geometric boundaries of the rail-wheel tread area are presented in this article. Ultrasonic signals are generated using a laser-line source of varying length and distance from a crack and are detected with a 1-MHz contact transducer to map the sound field behind the crack in the near, intermediate, and far fields of the insonified region. The factors that affect the behavior of a laser-generated surface acoustic wave propagating along the tread area of a rail wheel are discussed. A signal normalization method is proposed to help in sensing the presence of a crack from the transmitted signal unaffected by the …
Geometric efficiency for a circular detector and a linear source of arbitrary orientation and position
2010
A new axisymmetric radiation vector potential which is singular along its entire axis of symmetry is derived for a spherically symmetric point radiation source. This potential and a previously given non-singular point source potential are integrated to give radiation vector potentials for a straight linear source of constant strength. Analytical solutions are given for the geometric efficiency G of a line source and a circular disk detector when the line source is parallel to the detector axis. The analytical solution is also given for the case where the line source is parallel to the disk surface, such that the source axis and the detector axis intersect. All other cases are given as simpl…
A prototype of very high resolution small animal PET scanner using silicon pad detectors
2007
Abstract A very high-resolution small animal positron emission tomograph (PET), which can achieve sub-millimeter spatial resolution, is being developed using silicon pad detectors. The prototype PET for a single slice instrument consists of two 1 mm thick silicon pad detectors, each containing a 32×16 array of 1.4×1.4 mm pads readout with four VATAGP3 chips which have 128 channels low-noise self-triggering ASIC in each chip, coincidence units, a source turntable and tungsten slice collimator. The silicon detectors were located edgewise on opposite sides of a 4 cm field-of-view to maximize efficiency. Energy resolution is dominated by electronic noise, which is 0.98% (1.38 keV) FWHM at 140.5…
Generation of narrowband antisymmetric lamb waves using a formed laser source in the ablative regime
2007
A formed laser source, using a four-element lenticular array, is used in the ablative regime to generate select, narrowband, acoustic plate waves. The arrangement of the array produces acoustical signals that have frequencies compatible with the response of the broadband capacitive air-coupled transducer used in this study. A simplified concept is presented to explain the effect of a line array source on the frequency content of acoustic waves. The analytical model for a point pulse surface displacement is derived from the point load solution to Lamb's problem. The point pulse displacement elements of a line array source are summed mathematically, taking into account all applicable propagat…