Approximate analytical solutions of the Lane–Emden equation for a self-gravitating isothermal gas sphere

The isothermal Lane–Emden equation arises in many astrophysical problems, in particular in modelling of a self-gravitating, polytropic gas in a spherically symmetric configuration. In this work, the isothermal Lane–Emden equation is investigated using the fractional approximation technique. The method provides an efficient and accurate way of obtaining approximate analytic solution to the Lane–Emden equation thus is useful in the modelling of self-gravitating gaseous spheres in astrophysics.     

Pt/十六烷基三甲基溴化铵纳米聚集体修饰玻碳电极促进析氢(英文)

A novel, cost-effective, and simple electrocatalyst based on a Pt-modified glassy carbon electrode(GCE), using cetyltrimethylammonium bromide(CTAB) as a cationic surfactant, is reported. Amphiphilic CTAB molecules were adsorbed on GCE by immersion in a CTAB solution. The positively charged hydrophilic layer, which consisted of small aggregates of average size less than 100 nm,was used for accumulation and complexation of [PtCl2. anions by immersing the electrode in Ksolution. The modified electrode was characterized using scanning electron microscopy,energy-dispersive X-ray spectroscopy, impedance spectroscopy, and electrochemical methods. The electrocatalytic activity of the Pt particles in the hydrogen evolution reaction(HER) was investigated.The results show that the CTAB surfactant enhances the electrocatalytic activity of the Pt particles in the HER in acidic solution.     

On the development of ship anti-roll tanks

This paper reviews the development of ship anti-roll tanks from the 1880s to the present day including their modelling and control strategies. Mention is also made of other ship roll stabilization systems and the application of the technology to stabilization of other structures. The potential for the use of roll stabilization tanks on modern, high speed multi-hull craft which also have a low speed operational requirement is also discussed.     

Online GPS processing services: an initial study

There are a number of online Global Positioning System (GPS) processing services that provide GPS processing results to the user free of charge and with unlimited access. These services provide solutions for a user-submitted Receiver Independent Exchange Format (RINEX) file based on differential methods using reference stations or precise point positioning using precise GPS orbit and clock data. Different data sets varying in time and location were submitted to the online services and their results compared. Although the quality of results depends on many factors, in most cases the users can expect reliable online processing results for a 10-h data set made by a geodetic dual frequency receiver anywhere in the world.     

Watershed modeling of rainfall excess transformation into runoff

In this paper an attempt is made to present a distributed physiographic conceptual model that uses the principles of flow continuity and momentum. For this purpose, the watershed under study is divided into subwatersheds keeping in view the drainage patterns and characteristics. Then the main tributaries are identified and their drainage areas are delineated to form tributary subwatersheds. The main channel subwatersheds have taken care of the remaining area in the vicinity of the main channel. The kinematic wave theory is applied for the overland runoff computations from these subwatersheds. Further, the overland flows are superimposed onto the main channel. The dynamic wave theory is used to route the flows through the main channel to compute the watershed responses at the outlet. The proposed model is tested onto a natural watershed. The computations were performed for few storm events. Comparison of the significant parameters of the computed and the observed hydrographs shows that the maximum relative error in prediction is 5.8%. Thus, the results are satisfactory. Better results can be obtained when measured rainfall-excess data are available or a more realistic loss index is adopted for rainfall-excess separation.     

Nouvelles données structurales et datations 40K–40Ar sur les roches métamorphiques de la région de Neyriz (zone de Sanandaj–Sirjan,Iran méridional). Leur intérêt dans le cadre du domaine néo-téthysien du Moyen-Orient

The metamorphic rocks of the Neyriz area (Sanandaj–Sirjan zone) represent a Palaeozoic sequence, the upper part of which being palaeontologically dated from the Carboniferous and the Permian. Field structural analysis of the whole sequence, detailed in laboratory by microstructural one and ⁴⁰K–⁴⁰Ar dating carried on separated minerals, lead to establish that the whole sequence, from gneisses to Permian rocks, has suffered a unique synmetamorphic deformation, of variable intensity, marked by a foliation. Isotopic ages measured on extracted amphiboles and micas, clustered in four groups between 300 and 60 Ma, show the successive stages of their slow exhumation, which ended by the end of the Cretaceous. To cite this article: R. Sheikholeslami et al., C. R. Geoscience 335 (2003).     

Three Recent Extreme Floods in Bangladesh: A Hydro-Meteorological Analysis

Bangladesh is highly vulnerableto floods due to its geographical location at the deltas of the Ganges, Brahmaputra and Meghna (GBM) rivers. About 92.5 per cent of the area of three basins lies outside the boundaries of the country. More than 80 per cent of the annual precipitation of Bangladesh occurs in the monsoon period between June and September. The hydro-meteorological characteristics of the three river basins are unique and they often cause large to extremely large floods in Bangladesh. It is possible that these floods could inundate 70 per cent of the country and the physical damage could be very serious for the economy of Bangladesh with its low gross domestic product (GDP). In 1987, 1988 and 1998, Bangladesh experienced three extreme floods, leaving trails of devastation and human misery. In this article it is demonstrated that these floods differed in terms of magnitude, extent, depth and duration. The external and internal hydro-meteorological dynamics were also different.     

Application of Geographic Information Systems to Analyses and Modeling of Hydrocarbons Anomaly in Yakla,North Tarim Basin,Xinjiang,China

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Precision rectification of high resolution satellite imagery without ephemeris data

The huge capability of high resolution satellite imageries (HRSI), that includes spatial, spectral, temporal and radiometric resolutions as well as stereoscopic vision introduces them as a powerful new source for the Photogrammetry, Remote Sensing and GIS communities. High resolution data increases the need for higher accuracy of data modeling. The satellite orbit, position, attitude angles and interior orientation parameters have to be adjusted in the geometrical model to achieve optimal accuracy with the use of a minimum number of Ground Control Points (GCPs). But most high resolution satellite vendors do not intend to publish their sensor models and ephemeris data. There is consequently a need for a range of alternative, practical approaches for extracting accurate 2D and 3D terrain information from HRSI. The flexibility and good accuracy of the alternative models demonstrated with KFA-1000 and the well-known SPOT level 1A images. A block of eight KFA-1000 space photos in two strips with 60% longitudinal overlap and 15% lateral sidelap and SPOT image with rational function, DLT, 2D projective, polynomials, affine, conformal, multiquadric and finite element methods were used in the test. The test areas cover parts of South and West of Iran. Considering the quality of GCPs, the best result was found with the DLT method with a RMSE of 8.44 m for the KFA-1000 space photos.