长输管道局部腐蚀体积型缺陷逐次评价     

陈婷  赵民  乌效鸣  王俊波  李列平 《岩土钻凿工程》2014,(2):145-147

局部腐蚀包括缝隙腐蚀、应力腐蚀、腐蚀磨损、氢腐蚀,H2S应力腐蚀和氢腐蚀是长输管道最容易发生的一种局部腐蚀方式。针对长输管道易发生局部腐蚀的特点,参考其他管道评价方法,根据现场管道的安全状况,提出了适用于现场的含局部腐蚀体积型缺陷管道的三步评价法。该方法不需要考虑管道的腐蚀裕量,简化公式,便于现场计算。  相似文献   

Giant HVC’s and the Rotation Curves of the Milky Way and M31     

E. Casuso  J. E. Beckman 《Astrophysics and Space Science》2006,306(3):139-145

We have modelled, for the cases of Milky Way and M31, the effects on the galactic discs, of the arrival at high velocity (≥150 km s⁻¹) of giant HI clouds, with masses of up to 10⁸M⊙. Predictions are compared with the detailed structure of the observed rotation curves for these two galaxies. The model explains the rises and falls observed at large distances from the centre of each galaxy, distributed with a degree of regularity in radius, in terms of a specific type of perturbations driven by the infall of the high velocity clouds (HVC's) arriving from the intracluster medium of the Local Group. The underlying rotation curve is explained conventionally via the distribution of the baryonic and dark matter components of the galaxy in question. This scenario, though tested here on the two major Local Group objects, is in principle applicable to galaxies undergoing minor mergers with subgalactic mass gas clouds.  相似文献   

Dark matter in dwarf spheroidals – II. Observations and modelling of Draco     

J.Kleyna  M. I.Wilkinson  N. W.Evans  G.Gilmore  C.Frayn 《Monthly notices of the Royal Astronomical Society》2002,330(4):792-806

We present stellar radial velocity data for the Draco dwarf spheroidal (dSph) galaxy obtained using the AF2/WYFFOS instrument combination on the William Herschel Telescope. Our data set consists of 186 member stars, 159 of which have good quality velocities, extending to a magnitude   V ≈19.5  with a mean velocity precision of ≈2 km s⁻¹. As this survey is based on a high-precision photometric target list, it contains many more Draco members at large radii. For the first time, this allows a robust determination of the radial behaviour of the velocity dispersion in a dSph.
We find statistically strong evidence of a rising velocity dispersion consistent with a dark matter halo that has a gently rising rotation curve. There is a <2 σ signature of rotation about the long axis, inconsistent with tidal disruption as the source of the rising dispersion. By comparing our data set with earlier velocities, we find that Draco probably has a binary distribution and fraction comparable to those in the solar neighbourhood.
We apply a novel maximum likelihood algorithm and fit the velocity data to a two parameter spherical model with an adjustable dark matter content and velocity anisotropy. Draco is best fit by a weakly tangentially anisotropic distribution of stellar orbits in a dark matter halo with a very slowly rising rotation law  ( v _circ∝ r ^0.17)  . We are able to rule out both a mass-follows-light distribution and an extended halo with a harmonic core at the 2.5 to 3 σ significance level, depending on the details of our assumptions about Draco's stellar binary population. Our modelling lends support to the idea that the dark matter in dwarf spheroidals is distributed in the form of massive, nearly isothermal haloes.  相似文献   

银河系厚盘的本地空间密度   总被引：1，自引：0，他引：1  

容建湘 《天文学报》1996,37(3):272-277

本文利用北银极天区的现代恒星计数资料，采用标准的银河系模型，通过恒星统计积分方程对参数值组合模型的亮度函数进行计数分析，证明了银河系厚盘恒星成份存在的必要性，并进一步得出太阳附近厚盘成份的空间密度的最佳期望值为薄盘密度的０．０４１．  相似文献   

Nonlinear regional economic dynamics: continuous-time specification,estimation and stability analysis     

Gianfranco Piras  Kieran P. Donaghy  Giuseppe Arbia 《Journal of Geographical Systems》2007,9(4):311-344

This paper presents an innovative approach to the study of regional economic dynamics within a nonlinear continuous-time econometric framework—a generalized specification of the Lotka–Volterra system of equations. This specification, which accounts for interdependent behavior of three industrial sectors and spillover effects of activities in neighboring regions, is employed in an analysis of five Italian regions between 1980 and 2003. For these regions, we report estimation results, characterize the varying systems dynamics, analyze the models’ local and global stability properties, and determine via sensitivity analyses which structural features appear to exert the greatest influence on these properties.

Kieran P. DonaghyEmail:

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“Becoming” an environmentalist in Indonesia     

《Geoforum》2015

This article looks at how five environmental leaders in Jogjakarta became environmentally active, and at the groups and interventions they formed. Interview data are drawn from a broader project that aimed to find out what might turn an Indonesian person into someone who cares for the environment. It examines the journey in leadership as “becoming” in the terms of Deleuze and Guattari (1987); a journey constituted in the desire to make something different. Against a backdrop of day-today practices in Central Java that do not favour environmental conservation and sustainability, the five informants seized upon an idea, a praxis, and explored it in the company of like-minded others, to join or make an organisation or action dedicated to redressing environmental crisis or neglect.  相似文献   

Tele-connecting local consumption to global land use   总被引：1，自引：0，他引：1  

Yang Yu  Kuishuang Feng  Klaus Hubacek 《Global Environmental Change》2013,23(5):1178-1186

Globalization increases the interconnectedness of people and places around the world. In a connected world, goods and services consumed in one country are often produced in other countries and exchanged via international trade. Thus, local consumption is increasingly met by global supply chains oftentimes involving large geographical distances and leading to global environmental change. In this study, we connect local consumption to global land use through tracking global commodity and value chains via international trade flows. Using a global multiregional input–output model with sectoral detail allows for the accounting of land use attributed to “unusual” sectors – from a land use perspective – including services, machinery and equipment, and construction. Our results show how developed countries consume a large amount of goods and services from both domestic and international markets, and thus impose pressure not only on their domestic land resources, but also displace land in other countries, thus displacing other uses. For example, 33% of total U.S. land use for consumption purposes is displaced from other countries. This ratio becomes much larger for the EU (more than 50%) and Japan (92%). Our analysis shows that 47% of Brazilian and 88% of Argentinean cropland is used for consumption purposes outside of their territories, mainly in EU countries and China. In addition, consumers in rich countries tend to displace land by consuming non-agricultural products, such as services, clothing and household appliances, which account for more than 50% of their total land displacement. By contrast, for developing economies, such as African countries, the share of land use for non-agricultural products is much lower, with an average of 7%. The emerging economies and population giants, China and India, are likely to further increase their appetite for land from other countries, such as Africa, Russia and Latin America, to satisfy their own land needs driven by their fast economic growth and the needs and lifestyles of their growing populations.  相似文献   

Masses of the local group and of the M81 group estimated from distortions in the local velocity field     

I. D. Karachentsev  O. G. Kashibadze 《Astrophysics》2006,49(1):3-18

Based on high precision measurements of the distances to nearby galaxies with the Hubble telescope, we have determined the radii of the zero velocity spheres for the local group, R₀ = 0.96±0.03Mpc, and for the group of galaxies around M 81/M 82, 0.89±0.05Mpc. These yield estimates of M_T = (1.29±0.14)· 10¹² M_⊙ and (1.03±0.17)· 10¹² M_⊙, respectively, for the total masses of these groups. The R₀ method allows us to determine the mass ratios for the two brightest members in both groups, as well. By varying the position of the center of mass between the two principal members of a group to obtain minimal scatter in the galaxies on a Hubble diagram, we find mass ratios of 0.8:1.0 for our galaxy and Andromeda and 0.54:1.00 for the M82 and M81 galaxies, in good agreement with the observed ratios of the luminosities of these galaxies. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 5–22 (February 2006).  相似文献   

Chandra observations of the nucleus of M33     

Guillaume Dubus  Robert E. Rutledge 《Monthly notices of the Royal Astronomical Society》2002,336(3):901-906

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A photometrically and kinematically distinct core in the Sextans dwarf spheroidal galaxy     

Jan T. Kleyna  Mark I. Wilkinson  N. Wyn Evans  Gerard Gilmore 《Monthly notices of the Royal Astronomical Society》2004,354(4):L66-L72

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