Results 1 - 10 of 35
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[en] We analyzed the linear energy transfer (LET; energy deposited onto the target per unit length) effects on the scintillation properties of Bi4Ge3O12 (BGO) with an emphasis on the dynamical aspect. We irradiated BGO with 20 MeV H±, 50 MeV He±, and 220 MeV C5+. We observed that the rise and the decay of the scintillation temporal profiles are faster at higher LET. The faster decay at higher LET is attributed to the competition between the radiative transition of self-trapped excitons (STEs) localized at Bi3+ ions and the quenching caused by the interaction between STEs. The faster rise can be explained in terms of the competition between the quenching caused by the interaction between excited states and the formation of the STEs.
[en] The paper aims at to study the sources associated with growth of L band scintillation over Guwahati, an Appleton anomaly region. Starting with the analysis of diurnal and seasonal characteristic features of scintillation from a minimum sunspot number (Rz) of 10 to a maximum of 140, the paper shows that scintillations are more likely to develop during high solar activity period. It also highlights the explosive increase in occurrence of scintillation from post sunset to pre midnight hours in vernal equinoctial months when the background TEC is 50% more than on a normal day, accompanied by enhanced TEC decay rate. The role of equatorial anomaly effects through EXB drift processes are brought into discussion as possible sources on the growth of small scale irregularities leading to such scintillations. (author)
[en] Results of monitoring projects in the Netherlands with respect to the technical and energetic performance of underground energy storage systems have been evaluated
[nl]Doel van dit onderzoek is de prestatie (zowel energetisch als technisch) van energieopslag in de bodem in algemene zin neer te zetten. Daarnaast zijn vanuit de ervaring van meerdere gemonitorde projecten leerpunten aangegeven die van belang zijn voor de verdere optimalisatie van energieopslag in de bodem
[en] Several important ELM control techniques are in large part motivated by the empirically observed inverse relationship between average ELM energy loss and ELM frequency in a plasma. However, to ensure a reliable effect on the energy released by the ELMs, it is important that this relation is verified for individual ELM events. Therefore, in this work the relation between ELM energy loss and waiting time is investigated for individual ELMs in a set of ITER-like wall plasmas in JET. A comparison is made with the results from a set of carbon-wall and nitrogen-seeded ITER-like wall JET plasmas. It is found that the correlation between W ELM and for individual ELMs varies from strongly positive to zero. Furthermore, the effect of the extended collapse phase often accompanying ELMs from unseeded JET ILW plasmas and referred to as the slow transport event (STE) is studied on the distribution of ELM durations, and on the correlation between W ELM and . A high correlation between W ELM and , comparable to CW plasmas is only found in nitrogen-seeded ILW plasmas. Finally, a regression analysis is performed using plasma engineering parameters as predictors for determining the region of the plasma operational space with a high correlation between W ELM and . (paper)
[en] Spatio-temporal entropy (STE) analysis is used as an alternative mathematical tool to identify possible magnetic cloud (MC) candidates. We analyze Interplanetary Magnetic Field (IMF) data using a time interval of only 10 days. We select a convenient data interval of 2500 records moving forward by 200 record steps until the end of the time series. For every data segment, the STE is calculated at each step. During an MC event, the STE reaches values close to zero. This extremely low value of STE is due to MC structure features. However, not all of the magnetic components in MCs have STE values close to zero at the same time. For this reason, we create a standardization index (the so-called Interplanetary Entropy, IE, index). This index is a worthwhile effort to develop new tools to help diagnose ICME structures. The IE was calculated using a time window of one year (1999), and it has a success rate of 70% over other identifiers of MCs. The unsuccessful cases (30%) are caused by small and weak MCs. The results show that the IE methodology identified 9 of 13 MCs, and emitted nine false alarm cases. In 1999, a total of 788 windows of 2500 values existed, meaning that the percentage of false alarms was 1.14%, which can be considered a good result. In addition, four time windows, each of 10 days, are studied, where the IE method was effective in finding MC candidates. As a novel result, two new MCs are identified in these time windows.
[en] Luminescence of crystalline α-quartz and silica glass was studied under focused laser excitation. It was found that in crystalline α-quartz the luminescence of self-trapped exciton (STE) is excited in two-photon regime with ArF (193 nm) excimer laser. In the case of KrF (248 nm) laser excitation mainly luminescence related to near surface area is seen even without laser beam focusing. The near surface luminescence has an emission band similar to that of STE in bulk. Temperature quenching is also similar, therefore this luminescence is attributed to STE created in the area of surface. Luminescence decay kinetic of surface STE is longer than bulk STE decay (tens of ms compared to 1 ms at 80 K). Electron or/and hole self-trapping near the surface is assumed. Their recombination could provide longer duration of surface STE luminescence. Similar surface luminescence was not excited with ArF (193 nm) excimer laser. The nature of absorption for laser 248 nm photons at surface is not yet clear. Luminescence of silica glass of III type excited with focused beam of KrF (248 nm) laser resembles that of previously studied luminescence of STE in silica.
[en] The results of a study on heat supply systems for residential buildings in the Netherlands, based on seasonal storage of solar heat, are presented. The results are answers to five questions: (1) what technologies are available for seasonal storage and which are the most promising for the Dutch market; (2) what is the energetic, environmental and economical performance of those technologies; (3) which are the positive and negative forces that influence the market introduction; (4) what market interventions are required, both for small and large storage systems; and (5) what is the potential of solar heat storage for residential buildings in the Netherlands? 35 refs
[en] Contaminants in septic tank effluent (STE) are expected to be removed by the soil system before discharging to the environment. However, potential contaminants such as phosphorus (P), caffeine and artificial sweeteners do find their way to watercourses impacting aquatic eco systems. In this study, the attenuation of STE P, caffeine and saccharin were investigated in untreated soil and in soil with reduced microbial activity, in aqueous solutions and in the complex matrix of STE. Time series sorption and desorption experiments using batch equilibrium and a column experiment of STE P attenuation were conducted. The results revealed that the soil distribution coefficients (Kd) were: P 81.57 > caffeine 22.16 > saccharin 5.98 cm3/g, suggesting greater soil affinity to P adsorption. The data revealed that 80% of saccharin and 33% of caffeine attenuation was associated with microbial activities rather than adsorption processes. However, a complete removal of saccharin and caffeine did not occur during the equilibration period, suggesting their leaching potential. The dominant mechanism of P attenuation was adsorption (chemical and physical), yielding P retention of >73% and 35% for P in aqueous solution and in STE matrix, respectively, for batch equilibrium. The soil in the column acted as effluent P sink retaining 125 μg P/g soil of effluent P. The attenuation of P, caffeine and saccharin in the aqueous solution was greater than in STE, suggesting that the complex composition of STE reduced soil adsorption ability, and that other substances present in STE may be competing for soil binding sites. The data revealed that caffeine and P had similarities in the interaction with soils and thus caffeine may be considered as a STE tracer of anthropogenic source of P in receiving waters. - Highlights: • Sorption distribution coefficient Kd: phosphorus (P)> caffeine > saccharin. • Caffeine, saccharin and P's sorption in STE differed from that in aqueous solutions. • The complex composition of STE reduced sorption ability of the tested substances. • Phosphorus and caffeine had similar attenuation behaviour in the test soil. • Phosphorus had the greatest desorption and leaching ability followed by caffeine. - Septic tank effluent behaved differently on contact with soil relative to aqueous solution. Less Phosphorus was removed from septic tank effluent by the soil as the complex composition of STE may have competed for soil adsorption sites.
[en] The spectroscopic properties of undoped and Tb3+-doped Na3Ln (BO3)2 (Ln = Y, Gd) have been investigated in the UV–VUV region. The self-trapped excitons (STEs) emission of undoped-Na3Y (BO3)2 (NYB) was observed upon host excitation at low temperature and the emission intensity decreased with the increase of temperature. When Gd3+ was doped in NYB, the emission intensity of STEs was greatly reduced; instead, strong Gd3+ emission appeared. In Na3Gd (BO3)2: Tb3+, host excitation energy was predominantly transferred to Tb3+ through Gd3+ ions. The energy transfer efficiency from Gd3+ to Tb3+ increased with the increase of Tb3+ content. The results indicate that Gd3+ ions play a crucial intermediate role in host sensitization of Tb3+, which will provide some insights for developing new efficient green-emitting VUV-excited phosphors. - Highlights: • The spectroscopic properties of Tb3+-doped Na3Ln (BO3)2 (Ln = Y, Gd) were investigated in the UV–VUV range. • The energy transfer processes from host to Tb3+ through Gd3+ were evidenced. • The results suggest Tb3+-doped gadolinium host is a promising candidate for development of efficient VUV-excited phosphors.