https://uvadoc.uva.es/handle/10324/1298 Dpto. Física Aplicada - Artículos de revista 2026-04-17T11:46:57Z https://uvadoc.uva.es/handle/10324/84165 We report results of the Stark broadening calculations for Sr+ and Ba+ resonance lines in ultra- cold plasmas using semiempirical formulas and numerical computer simulation technique. The simulation results show that strong collisions dominate Stark broadening at very low electron temperatures and weak collision approximation used recently by Vrinceanu et al. cannot be applied in this temperature region. Consequently, the temperature trend of Stark widths and shifts changes from 1/ T successfully used at elevated temperatures to an increasing trend with temperature, which is characteristic for strong collisions at low temperature. 2006-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84163 Studies of charge-charge (ion-ion, ion-electron, and electron-electron) coupling properties for ion impurities in an electron gas are carried out on the basis of a regularized electron-ion potential without short-range Coulomb divergence. This work is motivated, in part, by questions arising from recent spectroscopic measurements revealing discrepancies with present-day theoretical descriptions. Many of the current radiative property models for plasmas include only single electron-emitter collisions and neglect some or all charge-charge interactions. A molecular-dynamics simulation of dipole relaxation is proposed here to allow proper account of many electron-emitter interactions and all charge-charge couplings. As illustrations, molecular-dynamics simulations are reported for the cases of a single ion embedded in an electron plasma and for a two-component ion-electron plasma. Charge-charge coupling effects are discussed for hydrogenlike Balmer alpha lines at weak coupling conditions. 2005-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84161 Balmer-alpha, -beta and -gamma lines have been calculated using computer simulations including ion dynamics effects for equilibrium and non-equilibrium conditions. The results obtained allow us to supply diagnostic maps based on the widths of those lines, as well as the Stark broadened full line profiles and the dipolar correlation functions obtained in the simulations. These profiles and correlation functions are a better diagnostic tool than the widths of the profiles in case of non-equilibrium plasmas. Calculations cover the range of electron densities between 1020 and 1025 m3 and of electron temperatures between 1000 and 175 000 K. The emitter and the perturber ions kinetic temperature may vary between the value of the electrons temperature and one tenth of it. 2003-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84160 Electron broadening for ion emitters is investigated with a molecular dynamics based spectral line shape simulation. A regularized Coulomb potential that removes the divergence at short distances is used for the ion–electron interaction. The method presented here allows one to account for all the correlations between charged particles, which is in distinction to the standard electron broadening of the impact approximation. Two cases are considered: 8rst, a single ion impurity embedded into an electron gas is considered; and second,two-component ion–electron plasma is studied. Simulations show non-negligible charge correlation effects on line shapes opening new possibilities to improve line shape models and interpretations of experiments. a 2003-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84035 The ion–electron coupling properties for an ion impurity in an electron gas and for a two-component plasma are carried out on the basis of a regularized electron–ion potential removing the short-range Coulomb divergence. This work is largely motivated by the study of radiator dipole relaxationplasmas which makes a real link between models and experiments. Current radiative property models for plasmas include single electron collisions neglecting charge–charge correlations within the classical quasi-particle approach commonly used in this field. The dipole relaxation simulation based on electron–ion molecular dynamics proposed here will provide a meansbenchmark and improve model developments. Benefiting from a detailed study of a single ion embedded in an electron plasma, the challenging two-component ion–electron molecular dynamics simulations are proved accurate. They open new possibilities of obtaining reference lineshape data. 2003-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84034 A program for the determination of plasma electron number density, 10 20F(Ne )F10 23 m y3 , from the comparison of experimental and theoretical hydrogen Balmer beta (Hb) line profiles is described in detail. Three theoretical data sets (one set is calculated within the framework of this paper) are included with the program and may be selected as a user’s choice. Apart from Ne determination from the comparison of the whole experimental and theoretical profiles, this program offers a fast estimation of Ne from the halfwidth of the experimental line shape. If necessary, certain parts of the experimental profile may be neglected in the procedure of comparison with theory. This possibility enables the use of noisy line shape recordings for N e determination. The H b asymmetry study may be carried out by generating the difference between experimental and best-fitted theoretical line profiles. 2002-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84033 A virtual physics laboratory is being developed in the Escuela Técnica Superior de Ingenierı́a Informática of the Universidad de Valladolid (UVA). This laboratory will be accessible via the internet, and its main aim is to provide support for the real physics laboratory. In this paper we describe the main steps taken to develop such a laboratory. This virtual laboratory is currently accessible from http://cawdor.fa2.etit.uva.es/laboratorio/index.html. 2002-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84032 In this work, the scope of the hypothesis of the physical and statistical independence between ionic (slow variation) and electronic (fast variation) microfields applied to spectral lines calculation in plasmas is analyzed. This hypothesis is used in some spectral profiles calculation methods. This analysis has been done by computer simulation. 2001-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84024 This paper shows the results of calculations, obtained by computer simulation, of the Stark broadening of the dipolar Lyman−α line of hydrogen considering fine structure, of two–photon absorption profiles for the transition 1S→2S of hydrogen and of the profiles that could be obtained using two–photon polarization spectroscopy techniques for the aforementioned transition. Calculations have been carried forward for wide ranges of electron density, between 4 1019 and 1023 m−3 and temperature, between 2 000 and 100 000 K. We have considered ion dynamics effects with perturbers of different masses. In this paper we give the obtained profiles and the autocorrelation functions. These autocorrelation functions could be used in order to add another broadening mechanisms before obtaining the spectral profiles. 2000-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84023 We present calculations, obtained by computer simulation, of the polarization spectrum by two-photon absorption in the transition 1S→2S of hydrogen in plasmas at low electronic density. Fine structure and ion dynamic effects have been included. The obtained results allow one to make a map of linewidths as a function of the electronic density and temperature to be applied for diagnosis in plasmas. S1063-651X~98!08710-8# 1998-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84019 We have obtained a precise spectrum of the Balmer-alpha line, corrected for self-absorption effects, from a constant-electron-density plasma with different optical depths, in order to compare it with theoretical models and simulation techniques. The reconstruction process of the non-self-absorbed profile is highly eproducible and may be applied to both optically-thin and thick plasmas. 1989-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/84018 A design procedure is described to obtain monochromators for specific applications, which are made from optical devices that can be easily acquired or built. This procedure makes use of a constant angular deviation system consisting of a transmission grating, operating in a symmetrical arrangement, and a flat mirror which makes a fixed angle with it. An analysis of the characteristic parameters of the design and of the constraints which have an effect on them, is presented as well as two examples of applications of the procedure. 1988-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/83807 To comparatively assess the Evapoporometry (EP) technique vis-à-vis the Liquid-Liquid Displacement Porosimetry (LLDP) technique, the pore size distributions, mean pore diameters (davg) and porosities of five polymeric (namely, nylon, PES, PTFE, PET and PVDF) and one inorganic (namely, alumina) UF/tight MF membranes were quantified by both techniques. For all the membranes, the pore size ranges were generally narrower and the pore size distributions had distinctive peaks for the LLDP technique. For the nylon, PES and PTFE membranes, the davg values obtained from the two techniques agreed well. However, for the PET and PVDF membranes, the differences were twofold due to the higher pressure needed for the LLDP tests. Specifically, for PET, the davg value obtained via EP was half that via LLDP, because the higher pressure compacted the lower mechanical strength polymer, leading to pore closure. On the other hand, for PVDF, due to the rubber nature, the higher pressure caused the pores to be stretched, leading to larger pores. As for the alumina membrane, because of the more ideal cylindrical pores, the d4-weighting of the LLDP measurement gave a greater davg value than that of the d2-weighting of the EP measurement. Also, porosity measurements were erroneous for LLDP if the active layer cannot be precisely quantified. With respect to MWCO, while EP does not explicitly quantify this, the LLDP generally over-estimated the values, because of the errors associated with the measurement of the first (largest) pores at the lowest pressures. 2019-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/83806 This works aims to propose and demonstrate the accuracy of a novel method of characterization aimed for non-destructive analysis of microfiltration (MF) membrane cartridges. The method adapts conventional liquid–liquid displacement porosimetry (LLDP) for performing an in-line porosimetric analysis of the membrane cartridges, getting their pore size distributions (PSDs) and mean pore diameters (davg). Six commercial filtration cartridges featuring polyethersulfone (PES) pleated membranes were analyzed using a newly designed filtration rig, based on the liquid–liquid displacement porometer, developed at the Institut de la Filtration et des Techniques Séparatives (IFTS) and operated at constant flow. The experimental rig allows the direct and non-destructive characterization of the cartridge in its original presentation. Results have been compared with those obtained by using gas–liquid displacement porosimetry (GLDP) on small membrane coupons detached from such cartridges. The comparison allows us to conclude that the proposed method gives enough accuracy in the determination of porosimetric characteristics of the filters. This method can be used as a precise characterization technique for a non-destructive in-line study of filter performance and can be envisaged as useful to periodic quality or fouling control of the commercial cartridges. 2020-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/83728 Wind direction is a variable that plays a secondary role in wind analyses since air flow is first studied. This paper focuses on its behaviour in ten cities and at two rural sites to investigate urban impact on wind direction. The database covered 18 years with a resolution of 1 km2, and hourly values were used. Two main procedures were followed. The first calculated the wind rose with high angular resolution from the average wind in each region studied as opposed to the usual calculations, where wind direction is measured at only one site. Two smoothing procedures were posited to acquire information about the data structure and specific details in one-degree roses. Bandwidth selection was based on the agreement with observations. Results revealed that westerly directions prevailed, although three patterns were observed. The most frequent was formed by a wide westerly sector, which may be attributed to synoptic flow, followed by wind roses with well-determined directions, such as Munich, where a mixture of relief and synoptic pattern could explain the rose shape. Finally, orographic influence is noticeable in specific roses, such as in Cologne, where the Rhine valley influence prevails. The second procedure is based on the direction turning field followed by the gradient calculation. This analysis was performed following wind direction, and two noticeable patterns of clear turning changes were occasionally found. The first pattern was formed by very close turning centres, which appear to be linked to the city, such as in Frankfurt for the easterly flow with a turning of around 65 degrees. Stuttgart, where the direction rose was barely affected by orographic features, showed a similar value of direction turning for the southerly flow, although following a different pattern formed by turning bands. Robust statistics showed the urban-rural contrast. Finally, three groups may be formed following the response against the turning field, with the weakest being for the largest cities –Berlin and Hamburg– where pollutant dispersion could prevail. An intermediate response was observed for most of the studied sites. However, Stuttgart and Frankfurt stood out due to their accused turnings that might determine complex pollution transport. 2026-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/83721 Studying urban heat islands (UHIs) in Southern Europe is crucial, as they amplify heat risks under climate change. UHIs and their temporal variability at seven urban–rural pair locations in Spain were analysed from 1970 to 2023. The UHI was defined as the air temperature difference between each urban site and its neighbouring rural sites, and trends were analysed using the non-parametric Mann–Kendall test with Sen’s slope estimator. Based on daily minimum air temperature data, results indicated a mean UHI intensity ranging from −0.15 °C in Alicante to 2.28 °C in A Coruña. The UHI annual trend was significant, increasing in Valladolid (0.023 °C/year) and Alicante (0.009 °C/year) and decreasing in Santander (-0.015 °C/year). Seasonal analysis showed statistically significant trends in Valladolid, particularly in spring and summer (0.029 °C/year). In Alicante, an increase of around 0.012 °C/year was observed in spring and summer, while Madrid showed a trend of 0.012 °C/year in winter. However, a warming effect at the rural site was identified in Barcelona (−0.028 ºC/year in autumn) and in Santander −0.025 °C/year in spring and summer), corresponding to negative UHI trends. The influence of synoptic patterns on UHI yielded values between 3 and 4 °C in A Coruña and Madrid for anticyclonic southeasterly, anticyclonic southerly, and southeasterly air flows. Lower intensities were found in Barcelona (2.5 °C) and were associated with hybrid anticyclonic westerly flows. UHI intensities below 2 °C were obtained at the other locations, with the lowest values being linked to hybrid cyclonic westerly and cyclonic north-westerly flows. 2026-01-01T00:00:00Z