We have analysed the broad-bandUBV colours and the intermediate banduvby colours of Persei, Pleiades, and the Scorpio-Centaurus association for rotation effects. An attempt was made to see if we can discriminate normal single stars from that of binary and peculiar stars after taking the observed rotation effects into account. It is found that the spread in the observed colours does not allow in general such a discrimination except that the objects with large reddening are double-lined binaries, peculiar stars or emission-lined objects. The few normal stars in these three clusters with such large reddening are listed as they are likely to belong to one of the above classes.On leave of absence from Assumption College, Changanacherry, Kerala. 相似文献
Hydrocyclones are widely used in the mining and chemical industries. An attempt has been made in this study, to develop a CFD (computational fluid dynamics) model, which is capable of predicting the flow patterns inside the hydrocyclone, including accurate prediction of flow split as well as the size of the air-core. The flow velocities and air-core diameters are predicted by DRSM (differential Reynolds stress model) and LES (large eddy simulations) models were compared to experimental results. The predicted water splits and air-core diameter with LES and RSM turbulence models along with VOF (volume of fluid) model for the air phase, through the outlets for various inlet pressures were also analyzed. The LES turbulence model led to an improved turbulence field prediction and thereby to more accurate prediction of pressure and velocity fields. This improvement was distinctive for the axial profile of pressure, indicating that air-core development is principally a transport effect rather than a pressure effect. 相似文献
Summary The rate of oceanic heat storage of the upper 200m of the Arabian Sea is explained in terms of net air-sea heat flux (QF), heat change due to horizontal divergence and vertical motion (QV) and heat change due to lateral advection (QA). The analysis revealed that the heat storage of the Arabian Sea is mainly controlled byQV while the effect ofQA is much larger than expected. Parameterisation of summer cooling revealed that the depletion of energy from the mixed layer is mainly due to upwelling and horizontal advection though large amount of heat is accumulated due to net air-sea heat flux. The annual heat balance of the upper 200m of the Arabian Sea suggested large heat gain by air-sea exchange processes. About two third of this heat gain is compensated by horizontal advection and one third by vertical advection.With 4 Figures 相似文献
Asia is key to a richer understanding of many important lithospheric processes such as crustal growth,continental evolution and orogenesis. But to properly decipher the secrets Asia holds, a first-order tectonic context is needed. This presents a challenge, however, because a great variety of alternative and often contradictory tectonic models of Asia have flourished. This plethora of models has in part arisen from efforts to explain limited observations(in space, time or discipline) without regard for the broader assemblage of established constraints. The way forward, then, is to endeavor to construct paleogeographic models that fully incorporate the diverse constraints available, namely from quantitative paleomagnetic data, the plentiful record of geologic and paleobiologic observations, and the principles of plate tectonics. This paper presents a preliminary attempt at such a synthesis concerning the early Paleozoic tectonic history of Asia. A review of salient geologic observations and paleomagnetic data from the various continental blocks and terranes of Asia is followed by the presentation of a new, full-plate tectonic model of the region from middle Cambrian to end-Silurian time(500-420 Ma). Although this work may serve as a reference point, the model itself can only be considred provisional and ideally it will evolve with time. Accordingly, all the model details are released so that they may be used to test and improve the framework as new discoveries unfold. 相似文献
The Northern Indian Ocean (NIO) is unique due to seasonal reversal of wind patterns, the formation of vortices and eddies which make satellite observations arduous. The veracity of sea surface wind (SSW) and sea surface temperature (SST) products of sun-synchronous AMSR-2 satellite are compared with high-temporal moored buoy observations over the NIO. The two year-long (2013–2014) comparisons reveal that the root-mean-square-error (RMSE) of AMSR-2 SST and SSW is \(<0.4{^{\circ }}\hbox {C}\) and \(<1.5\hbox { ms}^{-1}\), respectively, which are within the error range prescribed for the AMSR-2 satellite (\(\pm 0.8{^{\circ }}\hbox {C}\), \(\pm 1.5\hbox { ms}^{-1})\). The SST–wind relation is analyzed using data both from the buoy and satellite. As a result, the low-SST is associated with low-wind condition (positive slope) in the northern part of the Bay of Bengal (BoB), while low SST values are associated with high wind conditions (negative slope) over the southern BoB. Moreover, the AMSR-2 displayed larger slope for SST–wind relation and could be mainly due to overestimation of SST and underestimation of wind as compared to the buoy. The AMSR-2 SSW exhibited higher error during post-monsoon followed by monsoon season and could be attributed to the high wind conditions associated with intense oceanic vortices. The study suggests that the AMSR-2 products are reliable and can be used in tropical air–sea interactions, meso-scale features, and weather and climate studies. 相似文献
Many have speculated about the presence of a stiff fluid in very early stage of the universe. Such a stiff fluid was first introduced by Zel’dovich. Recently the late acceleration of the universe was studied by taking bulk viscous stiff fluid as the dominant cosmic component, but the age predicted by such a model is less than the observed value. We consider a flat universe with viscous stiff fluid and decaying vacuum energy as the cosmic components and found that the model predicts a reasonable background evolution of the universe with de Sitter epoch as end phase of expansion. More over, the model also predicts a reasonable value for the age of the present universe. We also performed a dynamical system analysis of the model and found that the end de Sitter phase predicted by the model is stable. 相似文献
The Multi-Application Solar Telescope (MAST) is a 50 cm off-axis Gregorian telescope that has recently become operational at the Udaipur Solar Observatory (USO). An imaging spectropolarimeter is being developed as one of the back-end instruments of MAST to gain a better understanding of the evolution and dynamics of solar magnetic and velocity fields. This system consists of a narrow-band filter and a polarimeter. The polarimeter includes a linear polarizer and two sets of liquid crystal variable retarders (LCVRs). The instrument is intended for simultaneous observations in the spectral lines 6173 Å and 8542 Å, which are formed in the photosphere and chromosphere, respectively. In this article, we present results from the characterization of the LCVRs for the spectral lines of interest and the response matrix of the polarimeter. We also present preliminary observations of an active region obtained using the spectropolarimeter. For verification purposes, we compare the Stokes observations of the active region obtained from the Helioseismic Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) with that of MAST observations in the spectral line 6173 Å. We find good agreement between the two observations, considering the fact that MAST observations are limited by seeing. 相似文献
The Indonesian throughflow (ITF) transports a significant amount of warm freshwater from the Pacific to the Indian Ocean, making it critical to the global climate system. This study examines decadal ITF variations using ocean reanalysis data as well as climate model simulations from the Coupled Model Inter-comparison Project Phase 5 (CMIP5). While the observed annual cycle of ITF transport is known to be correlated with the annual cycle of sea surface height (SSH) difference between the Pacific and Indian Oceans, ocean reanalysis data (1959–2015) show that the Pacific Ocean SSH variability controls more than 85% of ITF variation on decadal timescales. In contrast, the Indian Ocean SSH variability contributes less than 15%. While those observed contributions are mostly reproduced in the CMIP5 historical simulations, an analysis of future climate projections shows a 25–30% increase in the Indian Ocean SSH variability to decadal ITF variations and a corresponding decrease in the Pacific contribution. These projected changes in the Indian Ocean SSH variability are associated with a 23% increase in the amplitudes of negative zonal wind stress anomalies over the equatorial Indian Ocean, along with a 12º eastward shift in the center of action in these anomalies. This combined effect of the increased amplitude and eastward shift in the zonal wind stress increases the SSHA variance over the Indian Ocean, increasing its contribution to the ITF variation. The decadal ITF changes discussed in this study will be crucial in understanding the future global climate variability, strongly coupled to Indo-Pacific interactions.