The effects of pressure, nozzle diameter and meteorological conditions on the performance of agricultural impact sprinklers

19 Pags. The definitive version, with Figs. y Tabls., is available at: http://www.sciencedirect.com/science/journal/03783774This study evaluates agricultural impact sprinklers under different combinations of pressure (p), nozzle diameter (D) and meteorological conditions. The radial curve (Rad) of an isolated sprinkler, i.e., the water distribution along the wetted radius, was evaluated through 25 tests. Christiansen's uniformity coefficient (CUC) and the wind drift and evaporation losses (WDEL) were evaluated for a solid-set system using 52 tests. The Rad constitutes the footprint of a sprinkler. The CUC is intimately connected to the Rad. The Rad must be characterized under calm conditions. Very low winds, especially prevailing winds, significantly distort the water distribution. The vector average of the wind velocity (V’) is recommended as a better explanatory variable than the more popular arithmetic average (V). We recommend characterizing the Rad under indoor conditions or under conditions that meet V’ < 0.6 m s−1 in open-air conditions. The Rad was mostly affected by the sprinkler model. V’ was the main explanatory variable for the CUC; p was significant as well. V was the main variable explaining the WDEL; the air temperature (T) was significant, too. Sprinkler irrigation simulators simplify the selection of a solid-set system for farmers, designers and advisors. However, the quality of the simulations greatly depends on the characterization of the Rad. This work provides useful recommendations in this area.This research was funded by the Government of Spain through grants AGL2004-06675-C03-03/AGR, AGL2007-66716-C03 and AGL2010-21681, by the Government of Aragón through grant PIP090/2005, and by the INIA and CITA through the PhD grants program.Peer reviewe

Optimization of single crystal mirrors for ITER diagnostics

Diagnostic mirrors are planned to be used in all optical diagnostics in ITER. Degradation of mirrors due to e.g. deposition of plasma impurities will hamper the entire performance of affected diagnostics. in situ mirror cleaning by plasma sputtering is presently envisaged for the recovery of contaminated mirrors. There are observations showing a signature of sputtering dependence on crystal orientation. Should such a dependence exist, the sputtering of single crystal mirrors could be minimized, thus prolonging a mirror lifetime. Four single crystal molybdenum mirrors with different orientations were produced to study the effect of crystal orientation on sputtering. Mirrors were exposed to argon plasma under identical plasma conditions relevant to those expected in the mirror cleaning systems of ITER. The energy of impinging ions was about 60 eV. The amount of sputtered material corresponded to about a hundred mirror cleaning cycles in argon. Plasma exposures did not affect the mirror reflectivity. The maximum decrease of specular reflectivity did not exceed 5% at 250 nm. The mirrors with orientations [110]/[101] demonstrated up to 42% less sputtering than the mirrors with other crystal orientations. These findings outline the advantage of a favorable crystal orientation for a cleaning of heavy contaminants from ITER mirrors.Peer reviewe

Smart Tungsten-based Alloys for a First Wall of DEMO

During an accident with loss-of-coolant and air ingress in DEMO, the temperature of tungsten first wall cladding may exceed 1000 °C and remain for months leading to tungsten oxidation. The radioactive tungsten oxide can be mobilized to the environment at rates of 10–150 kg per hour. Smart tungsten-based alloys are under development to address this issue. Alloys are aimed to function as pure tungsten during regular plasma operation of DEMO. During an accident, alloying elements will create a protective layer, suppressing release of W oxide. Bulk smart alloys were developed by using mechanical alloying and field-assisted sintering technology. The mechanical alloying process was optimized leading to an increased powder production by at least 40 %. Smart alloys and tungsten were tested under a variety of DEMO-relevant plasma conditions. Both materials demonstrated similar sputtering resistance to deuterium plasma. Under accident conditions, alloys feature a 40-fold reduction of W release compared to that of pure tungsten.</p

Cone Beam Computertomography (CBCT) in Interventional Chest Medicine – High Feasibility for Endobronchial Real Time Navigation

Introduction: Currently there are several advanced guiding techniques for pathoanatomical diagnosis of incidental solitary pulmonary nodules (iSPN): Electromagnetic navigation (EMN) with or without endobronchial ultrasound (EBUS) with miniprobe, transthoracic ultrasound (TTUS) for needle approach to the pleural wall and adjacent lung and computed tomography (CT)-guidance for (seldom if ever used) endobronchial or (common) transthoracical approach. In several situations one technique is not enough for efficient diagnosis, therefore we investigated a new diagnostic technique of endobronchial guided biopsies by a Cone Beam Computertomography (CBCT) called DynaCT (SIEMENS AG Forchheim, Germany). Method and Material: In our study 33 incidental solitary pulmonary nodules (iSPNs) (28 malignant, 5 benign; mean diameter 25 +/-12mm, shortest distance to pleura 25+/-18mm) were eligible according to in- and exclusion criteria. Realtime and onsite navigation were performed according to our standard protocol.22 All iSPN were controlled with a second technique when necessary and clinical feasible in case of unspecific or unexpected histological result. In all cases common guidelines of treatment of different iSPNs were followed in a routine manner. Results: Overall navigational yield (ny) was 91% and diagnostic yield (dy) 70%, dy for all accomplished malignant cases (n=28) was 82%. In the subgroup analysis of the invisible iSPN (n=12, 11 malignant, 1 benign; mean diameter 15+/-3mm) we found an overall dy of 75%. For the first time we describe a significant difference in specifity of biopsy results in regards to the position of the forceps in the 3-dimensional volume (3DV) of the iSPN in the whole sample group. Comparing the specifity of biopsies of a 3D-uncentered but inside the outer one third of an iSPN-3DV with the specifity of biopsies of centered forceps position (meaning the inner two third of an iSPN-3DV) reveals a significant (p=0,0375 McNemar) difference for the size group (\u3e1cm) of 0,9 for centered biopsies vs. 0,3 for uncentered biopsies. Therefore only 3D-centered biopsies should be relied on especially in case of a benign result. Conclusion: The diagnostic yield of DynaCT navigation guided transbronchial biopsies (TBB) only with forceps is at least up to twofold higher than conventional TBB for iSPNs \u3c2cm. The diagnostic yield of DynaCT navigation guided forceps TBB in invisible SPNs is at least in the range of other navigation studies which were performed partly with multiple navigation tools and multiple instruments. For future diagnostic and therapeutic approaches it is so far the only onsite and realtime extrathoracic navigation approach (except for computed tomography (CT)-fluoroscopy) in the bronchoscopy suite which keeps the working channel open. The system purchase represents an important investment for hospitals but it is a multidisciplinary and multinavigational tool with possible access via bronchial airways, transthoracical or vascular approach at the same time and on the same table without the need for an expensive disposable instrument use

Data on erosion and hydrogen fuel retention in Beryllium plasma-facing materials

ITER will use beryllium as a plasma-facing material in the main chamber, covering a total surface area of about 620 m(2). Given the importance of beryllium erosion and co-deposition for tritium retention in ITER, significant efforts have been made to understand the behaviour of beryllium under fusion-relevant conditions with high particle and heat loads. This paper provides a comprehensive report on the state of knowledge of beryllium behaviour under fusion-relevant conditions: the erosion mechanisms and their consequences, beryllium migration in JET, fuel retention and dust generation. The paper reviews basic laboratory studies, advanced computer simulations and experience from laboratory plasma experiments in linear simulators of plasma-wall interactions and in controlled fusion devices using beryllium plasma-facing components. A critical assessment of analytical methods and simulation codes used in beryllium studies is given. The overall objective is to review the existing set of data with a broad literature survey and to identify gaps and research needs to broaden the database for ITER.Peer reviewe