Tritium clouds environmental impact in air into the Western Mediterranean Basin evaluation

The paper considers short-term releases of tritium (mainly but not only tritium hydride (HT)) to the atmosphere from a potential ITER-like fusion reactor located in the Mediterranean Basin and explores if the short range legal exposure limits are exceeded (both locally and downwind). For this, a coupled Lagrangian ECMWF/FLEXPART model has been used to follow real time releases of tritium. This tool was analyzed for nominal tritium operational conditions under selected incidental conditions to determine resultant local and Western Mediterranean effects, together with hourly observations of wind, to provide a short-range approximation of tritium cloud behavior. Since our results cannot be compared with radiological station measurements of tritium in air, we use the NORMTRI Gaussian model. We demonstrate an overestimation of the sequence of tritium concentrations in the atmosphere, close to the reactor, estimated with this model when compared with ECMWF/FLEXPART results. A Gaussian “mesoscale” qualification tool has been used to validate the ECMWF/FLEXPART for winter 2010/spring 2011 with a database of the HT plumes. It is considered that NORMTRI allows evaluation of tritium-in-air-plume patterns and its contribution to doses

Nano-scratching resistance of highchromium white cast iron and its correlation with wear of cBN tool in machining

In this paper, a nano-scratch testing approach was used to measure and evaluate the abrasion wear resistance of high-chromium white cast irons in order to understand the wear mechanism in the interaction between the high-chromium white cast iron and the cBN cutting tool during the machining process. Scratch testing was performed on a nanoindentation instrument using a diamond indenter as the scratch tool. Linear multi-pass scratches in the same path were made on pre-worn surfaces of test materials. The correlation of the scratching resistance and tool wear measured from the machining is presented by the flank wear and maximum scratch depth. The appearance of the cutting edge on a cBN tool suggests that the abrasion wear is mainly related with a combined effect of the carbides and the matrix during machining the high-chromium white cast iron.Досліджено зносостійкість білих чавунів з високим вмістом хрому при використанні наноподряпання для того, щоб зрозуміти механізм зношування при взаємодії високохромістого білого чавуну і різального інструменту з КБН під час процесу обробки. Випробування наноподряпанням виконано на приладі для наноіндентування з використанням алмазного індентора. Лінійні багатопрохідні подряпини на одній і тій же ділянці було зроблено на попередньо зношених поверхнях матеріалів, що випробували. Кореляцію спротиву подряпанню і зносу інструменту, виміряних при точіння, визначено при порівнянні зносу фальца і максимальної глибини подряпини. Зовнішній вигляд ріжучої кромки на інструменті з cBN дозволяє припустити, що абразивний знос матеріалу в основному пов'язаний з взаємодією карбідів і матриці під час обробки високохромистого білого чавуну.Исследована износостойкость белых чугунов с высоким содержанием хрома при использовании наноцарапание для понимания механизма износа при взаимодействии высокохромистого белого чугуна и режущего инструмента из cBN во время процесса обработки. Испытания царапанием проводили на приборе наноиндентирования с использованием алмазного индентора. Линейные многопроходные царапины на одном и том же участке выполняли на предварительно изношенных поверхностях испытываемых материалов. Корреляция сопротивления царапанию и износа инструмента, измеренного при точении, показана при сравнении износа фланца и максимальной глубиной царапины. Внешний вид режущей кромки на инструменте из cBN свидетельствует о том, что абразивный износ в основном связан с взаимодействием карбидов и матрицы при обработке высокохромистого белого чугуна

Kelvin waves and internal bores in the marine boundary layer inversion and their relationship to coastally trapped wind reversals

Detailed observations of a coastally trapped disturbance, or wind reversal, on 10-11 June 1994 along the California coast provide comprehensive documentation of its structure, based on aircraft, wind profiler, radio acoustic sounding system, and buoy measurements. Unlike the expectations from earlier studies based on limited data, which concluded that the deepening of the marine boundary layer (MBL) was a key factor, the 1994 data show that the perturbation was better characterized as an upward thickening of the inversion capping the MBL. As the event propagated over a site, the reversal in the alongshore wind direction occurred first within the inversion and then 3-4 h later at the surface. A node in the vertical structure (defined here as the altitude of zero vertical displacement) is found just above the inversion base, with up to 200-m upward displacements of isentropic surfaces above the node, and 70-m downward displacements below. Although this is a single event, it is shown that the vertical structure observed is representative of most other coastally trapped wind reversals. This is determined by comparing a composite of the 10-11 June 1994 event, based on measurements at seven buoys, with surface pressure perturbations calculated from aircraft data. These results are compared to the composite of many events. In each case a weak pressure trough occurred between 2.4 and 4.0 h ahead of the surface wind reversal, and the pressure rose by 0.32-0.48 mb between the trough and the wind reversal. The pressure rise results from the cooling caused by the inversion's upward expansion. The propagation and structure of the event are shown to be best characterized as a mixed Kelvin wave-bore propagating within the inversion above the MBL, with the MBL acting as a quasi-rigid lower boundary. If the MBL is instead assumed to respond in unison with the inversion, then the theoretically predicted intrinsic phase speeds significantly exceed the observed intrinsic phase speed. The hybrid nature of the event is indicated by two primary characteristics: 1) the disturbance had a much shallower slope than expected for an internal bore, while at the same time the upward perturbation within the inversion was quasi-permanent rather than sinusoidal, which more closely resembles a bore; and 2) the predicted phase speeds for the "solitary" form of nonlinear Kelvin wave and for an internal bore are both close to the observed intrinsic phase speed

Asymptotic behaviour of the spectrum of a waveguide with distant perturbations

We consider the waveguide modelled by a $n$-dimensional infinite tube. The operator we study is the Dirichlet Laplacian perturbed by two distant perturbations. The perturbations are described by arbitrary abstract operators ''localized'' in a certain sense, and the distance between their ''supports'' tends to infinity. We study the asymptotic behaviour of the discrete spectrum of such system. The main results are a convergence theorem and the asymptotics expansions for the eigenvalues. The asymptotic behaviour of the associated eigenfunctions is described as well. We also provide some particular examples of the distant perturbations. The examples are the potential, second order differential operator, magnetic Schroedinger operator, curved and deformed waveguide, delta interaction, and integral operator

Ising model with periodic pinning of mobile defects

A two-dimensional Ising model with short-range interactions and mobile defects describing the formation and thermal destruction of defect stripes is studied. In particular, the effect of a local pinning of the defects at the sites of straight equidistant lines is analysed using Monte Carlo simulations and the transfer matrix method. The pinning leads to a long-range ordered magnetic phase at low temperatures. The dependence of the phase transition temperature, at which the defect stripes are destabilized, on the pinning strength is determined. The transition seems to be of first order, with and without pinning.Comment: 7 pages, 7 figure

Preliminary results for RR Lyrae stars and Classical Cepheids from the Vista Magellanic Cloud (VMC) Survey

The Vista Magellanic Cloud (VMC, PI M.R. Cioni) survey is collecting $K_S$-band time series photometry of the system formed by the two Magellanic Clouds (MC) and the "bridge" that connects them. These data are used to build $K_S$-band light curves of the MC RR Lyrae stars and Classical Cepheids and determine absolute distances and the 3D geometry of the whole system using the $K$-band period luminosity ($PLK_S$), the period - luminosity - color ($PLC$) and the Wesenhiet relations applicable to these types of variables. As an example of the survey potential we present results from the VMC observations of two fields centered respectively on the South Ecliptic Pole and the 30 Doradus star forming region of the Large Magellanic Cloud. The VMC $K_S$-band light curves of the RR Lyrae stars in these two regions have very good photometric quality with typical errors for the individual data points in the range of $\sim$ 0.02 to 0.05 mag. The Cepheids have excellent light curves (typical errors of $\sim$ 0.01 mag). The average $K_S$ magnitudes derived for both types of variables were used to derive $PLK_S$ relations that are in general good agreement within the errors with the literature data, and show a smaller scatter than previous studies.Comment: 7 pages, 6 figure. Accepted for publication in Astrophysics and Space Science. Following a presentation at the conference "The Fundamental Cosmic Distance Scale: State of the Art and the Gaia Perspective", Naples, May 201

Correlation between edge radius of the cBN cutting tool and surface quality in hard turning

In this study, the attempt has been made to investigate the correlation between the cutting tool edge radius and surface quality in terms of the surface roughness and subsurface deformation through a FE simulation and experiment. Machining tests under different machining conditions were also conducted and the surface roughness and subsurface deformation were measured. Surface roughness and subsurface deformation were produced by the cutting tools with different edge radii under various cutting parameters. Both results from the FE simulation and machining tests confirmed that there was a significant influence on the surface quality in terms of both the surface roughness and subsurface quality from the edge radius. There is a critical edge radius of cBN tools in hard turning in terms of surface quality generated.У даному дослідженні було зроблено спробу дослідити взаємозв’язок між радіусом закруглення крайки різального інструменту і якістю поверхні, які оцінюються шорсткістю поверхні і деформацією підповерхневого шару, методами скінчено-елементного моделювання і експериментально. Було здійснено низку експериментів при різних умовах обробки з одночасним вимірюванням шорсткості поверхні і деформації підповерхневих шарів. Також застосовували різальні інструменти з різними радіусами різальної крайки при різних режимах різання. Результати моделювання і випробувань підтвердили значний вплив радіуса закруглення крайки на якість і шорсткість поверхні, а також якість підповерхневого шару. Виявлено оптимальний радіус округлення крайки інструменту з КНБ, який треба застосовувати при обробці надтвердих матеріалів для отримання найкращої якості поверхні.В данном исследовании была сделана попытка изучить взаимосвязь между радиусом скругления кромки режущего инструмента и качеством поверхности, оцениваемой шероховатостью поверхности и деформацией подповерхностного слоя, методами конечно-элементного моделирования и экспериментально. Были проведены испытания при различных условиях обработки с одновременным измерением шероховатости поверхности и деформации подповерхностного слоя. Применялись режущие инструменты с различными радиусами режущей кромки при различных режимах резания. Результаты моделирования и испытаний подтвердили значительное влияние радиуса скругления кромки на шероховатость поверхности, а также на качество подповерхностного слоя. При точении закаленной стали инструментом из сBN имеется оптимальный радиус режущей кромки инструмента, который следует применять при обработке сверхтвердых материалов для получения наилучшего качества поверхности

Tunable variation of optical properties of polymer capped gold nanoparticles

Optical properties of polymer capped gold nanoparticles of various sizes (diameter 3-6 nm) have been studied. We present a new scheme to extract size dependent variation of total dielectric function of gold nanoparticles from measured UV-Vis absorption data. The new scheme can also be used, in principle, for other related systems as well. We show how quantum effect, surface atomic co - ordination and polymer - nanoparticle interface morphology leads to a systematic variation in inter band part of the dielectric function of gold nanoparticles, obtained from the analysis using our new scheme. Careful analysis enables identification of the possible changes to the electronic band structure in such nanoparticles.Comment: 13 pages,7 figures, 1 tabl

Observations and analysis of the 10-11 June 1994 coastally trapped disturbance

A coastally trapped disturbance (CTD), characterized by southerly flow at the surface on 10-11 June 1994, was observed from the California Bight to Bodega Bay during a field experiment along the California coast. (North-south approximates the coast-parallel direction.) Data from a special observational network of wind profilers, radio acoustic sounding systems, special surface data, balloon ascents, and a research aircraft were used with satellite and synoptic data to explore both the CTD structure and the regional-scale changes before the event. The disruption of the climatological northerly flow along the central California coast, which preconditioned the area for the development of a CTD, began with the eastward movement of a surface high into Washington and Oregon and the amplification of a thermal low in northern California. As with most CTDs in the region, this occurred over the 2-3 days preceding the CTD's initiation. These large-scale changes caused westward advection of warm continental air across much of the California coast, which increased temperatures by 10°-12°C in the layer from 0.4 to 2.0 km above mean sea level (MSL) during the 48 h before southerly flow appeared offshore at the surface. The warming reversed the alongshore sea level pressure gradients near the coast by creating a region of pressure falls extending along 600-1000 km of the coast. This also modified the cross-shore pressure gradient and thus the geostrophic alongshore flow. The warming along the coast also increased the strength of the temperature inversion capping the marine boundary layer (MBL) by a factor of 2-4 over 48 h. The synoptic-scale changes also moved the axis of the climatological near-surface, northerly jet much farther offshore from central California and strengthened this jet near the headlands of Capes Mendocino and Blanco, The development and decay of southerly flow at the surface along the coast coincided roughly with the evolution of a mesoscale low 200 km offshore, and of a coastal ridge roughly 100 km wide. However, the CTD initiation also followed a 500-m thickening of the MBL inversion in the California Bight region where a Catalina eddy was initially present. At surface sites, the CTD was marked by the passage of a pressure trough, followed by a gradual shift to southerly flow and the appearance of clouds. The area of low cloud was not coincident with the region of southerly flow. The transition to southerly flow propagated northward along shore at 1 1.9 ± 0.3 m s-1 on 10 June, stalled for 11-12 h during the part of the diurnal cycle normally characterized by enhanced northerly flow, and then continued propagating northward along shore at 11.6 m s-1. Both the geostrophic wind and the isallobaric component of the ageostrophic wind were consistent with southerly flow at the surface. Southerly flow was observed up to 5 km MSL in this event and in others, which indicates that the synopticscale environment of many CTDs in this region may include a deep tropospheric cyclonic circulation or trough offshore. Both cross-shore and alongshore flights performed by a research aircraft documented the CTD structure and showed that the southerly flow extended at least 100 km offshore and appeared first within the MBL inversion as the inversion thickened upward. While the top of the inversion rose, the height of the inversion's base remained almost unchanged. The thickening of the inversion decreased with distance offshore, and there was no significant change in the MBL depth (i.e., the inversion base height), until 12-14 h after the surface wind shift. Thus, it is suggested that two-layer, shallow water idealizations may be unable to represent this phenomenon adequately. Nonetheless, the gradual wind shift, the thickening inversion, and the correlation between southerly flow and a mesoscale coastal pressure ridge are consistent with a coastally trapped Kelvin wave, albeit one with a higher-order vertical structure that can exist in a two-layer model. However, the semipermanent nature of the changes in the MBL and its inversion is more characteristic of a shallowly sloped internal bore. The temperature increase and lack of southerly flow exceeding the northward phase speed are inconsistent with gravity current behavior

Light scattering from disordered overlayers of metallic nanoparticles

We develop a theory for light scattering from a disordered layer of metal nanoparticles resting on a sample. Averaging over different disorder realizations is done by a coherent potential approximation. The calculational scheme takes into account effects of retardation, multipole excitations, and interactions with the sample. We apply the theory to a system similar to the one studied experimentally by Stuart and Hall [Phys. Rev. Lett. {\bf 80}, 5663 (1998)] who used a layered Si/SiO$_2$/Si sample. The calculated results agree rather well with the experimental ones. In particular we find conspicuous maxima in the scattering intensity at long wavelengths (much longer than those corresponding to plasmon resonances in the particles). We show that these maxima have their origin in interference phenomena in the layered sample.Comment: 19 pages, 12 figure