The influence of heat conduction on evaporation from sunken pans in hot, dry environment     

I. M. Oroud 《Journal of Hydrology》1998,210(1-4):1-10

Lateral heat conduction across a large circular sunken pan located in a hot, dry environment is evaluated using a numerical procedure. Heat flow across the sunken pan–adjacent soil boundary is calculated using a two-dimensional soil plane. Calculations show that a large temperature differential across the pan–substrate boundary develops during the entire diurnal cycle during January and July, leading to consistently positive heat flow from the soil towards the sunken pan. Heat conduction across the pan–substrate boundary represents 10 and 34% of net radiation over the sunken pan during July and January, respectively. This additional heat source, which is not available for shallow lakes, increases annual evaporation from the sunken pan by about 5–8% in July and January, respectively. In hot arid environments, a sunken pan will overestimate evaporation from a nearby shallow lake/dam due to a larger surface roughness and consistently positive conduction heat flow across the pan–substrate boundary.  相似文献   

Record-High Losses for Weather Disasters in the United States During the 1990s: How Excessive and Why?     

Changnon  Stanley A.  Changnon  David 《Natural Hazards》1998,18(3):287-300

During 1990–1996 the United States experienced record-setting insured property losses due to numerous weather catastrophes, each event causing $100 million or more in losses (1991 dollars). The total loss in this 7-year period, after adjustment to inflation and other factors, was $39.65 billion with $15 billion coming from one event, Hurricane Andrew. In the 1990s, 72 catastrophes occurred, half of the total number in the 40 preceding years, 1950–1989. Although the total loss and the number of catastrophes were exceptionally high in the 1990s, the average loss per event was $551 million, only slightly more than the $467 million average for catastrophes during 1950–1989. Furthermore, storm intensities in the 1990s were slightly less than those during the preceding 40 years, revealing the excess losses of the 1990s to be a result of an extremely large number of damaging storms causing losses exceeding $100 million. Examination of historical values of most weather extremes including hurricanes, floods, and tornadoes, did not show an increase during the 1990s, revealing that weather changes were not the principal cause of more catastrophes. Examination of recent demographic shifts in the U.S. reveals two changes, each based on major re-locations to higher-valued property concentrated in areas either with a high frequency of damaging storms (Gulf and East Coast), or to where even a small but intense storm can cause huge losses (urban areas and West Coast). These shifts, plus the continuing growth of population in other storm-prone areas have greatly increased society's vulnerability to storm damage. An in-depth analysis of many conditions was required to establish that the high losses and numerous catastrophes of the 1990s were largely the result of societal changes and not major weather changes. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

明矾石合成4A沸石的试验研究   总被引：3，自引：0，他引：3  

朱继存 《化工矿产地质》1998,20(3):259-264

以明矾石矿为原料,成功地合成了物理化学性能较好的４Ａ沸石。通过对４Ａ沸石合成的基本原理、工艺条件和主要工作参数的研究,提供了合成４Ａ沸石的新途径,丰富了明矾石矿综合利用的新内容。  相似文献   

Infrared spectroscopy of the Be/X-ray transient A0535+26     

J. S. Clark  I. A. Steele  M. J. Coe  & P. Roche 《Monthly notices of the Royal Astronomical Society》1998,297(3):657-666

We present infrared spectroscopy of the Be/X-ray binary HDE 245770/A0535+26 obtained over the period 1992–1995. The spectra show significant variability, reflecting changes in the circumstellar environment during this time. A reduction in the flux observed in the Paschen series lines between 1993 December and 1994 September correlates with a similar reduction in both the strength of Hα and the optical continuum emission, which can be attributed to a reduction in the emission measure of the disc. A turnover between optically thin and thick emission is seen for both Paschen and Brackett series lines, and allows an estimate of the disc density as ∼10¹² cm⁻³. Echelle spectroscopy reveals strong similarities between the He I 1.008, 2.058 μm, Hα and Paschen series line profiles, suggesting their formation in a similar (and asymmetric) region of the disc. In contrast, the line profile of He I 6678 Å indicates that it is formed at smaller radii than the other transitions.  相似文献   

X-ray and radio observations of the poor cluster A3581 which hosts the radio galaxy PKS 1404 − 267     

R. M. Johnstone  A. C. Fabian  & G. B. Taylor 《Monthly notices of the Royal Astronomical Society》1998,298(3):854-860

We present new X-ray and H  I 21-cm data on the poor cluster of galaxies Abell 3581. The ASCA spectrum requires a low temperature, has a strong requirement for excess absorption and shows evidence for multi-temperature components. The ROSAT HRI image shows the strongly peaked emission indicative of a cooling flow. Despite the low temperature (∼ 1.5–2.0 keV) and low luminosity (∼ 2 × 10⁴² erg s⁻¹ in the 2–10 keV band), Abell 3581 has a mass deposition rate ∼ 80 M⊙ yr⁻¹ which is larger than found for other nearby low-luminosity objects. VLA observations in the 21-cm band set velocity width and spin temperature dependent limits on the column density of atomic hydrogen.  相似文献   

Globular cluster calibration of the peak brightness of the Type Ia supernova 1992A and the value of H₀     

M. Della Valle  M. Kissler-Patig  J. Danziger  & J. Storm 《Monthly notices of the Royal Astronomical Society》1998,299(1):267-276

We have determined the absolute magnitude at maximum light of SN 1992A by using the turnover magnitude of the globular cluster luminosity function of its parent galaxy, NGC 1380. A recalibration of the peak of the turnover magnitude of the Milky Way clusters using the latest Hipparcos results has been made with an assessment of the complete random and systematic error budget. The following results emerge: a distance to NGC 1380 of 18.6 ± 1.4 Mpc, corresponding to ( m  −  M )  31.35 ± 0.16, and an absolute magnitude of SN 1992A at maximum of M _B (max)  −18.79 ± 0.16. Taken at face value, SN 1992A seems to be more than half a magnitude fainter than the other SNe Ia for which accurate distances exist. We discuss the implications of this result and present possible explanations. We also discuss the Phillips relationship between rate of decline and the absolute magnitude at maximum, on the basis of nine SNe Ia, the individual distances of which have been obtained with Cepheids and the globular cluster luminosity function. The new calibration of this relationship, applied to the most distant SNe of the Calan–Tololo survey, yields H ₀ = 62 ± 6 km s⁻¹ Mpc⁻¹.  相似文献   

ROSAT PSPC observations of the outer regions of the Perseus cluster of galaxies     

S. Ettori  A. C. Fabian  & D. A. White 《Monthly notices of the Royal Astronomical Society》1998,300(3):837-856

We present an analysis of four off-axis ROSAT Position Sensitive Proportional Counter (PSPC) observations of the Perseus cluster of galaxies (Abell 426). We detect the surface brightness profile to a radius of 80 arcmin (∼2.4 h⁻¹₅₀ Mpc) from the X-ray peak. The profile is measured in various sectors and in three different energy bands. First, a colour analysis highlights a slight variation of N _H over the region, and cool components in the core and in the eastern sector. We apply the β-model to the profiles from different sectors and present a solution to the, so-called, β-problem. The residuals from an azimuthally-averaged profile highlight extended emission both in the east and in the west, with estimated luminosities of about 8 and 1 ×10⁴³ erg s⁻¹, respectively. We fit several models to the surface brightness profile, including the one obtained from the Navarro, Frenk &38; White potential. We obtain the best fit with the gas distribution described by a power law in the inner, cooling region and a β-model for the extended emission. Through the best-fitting results and the constraints from the deprojection of the surface brightness profiles, we define the radius where the overdensity inside the cluster is 200 times the critical value, r ₂₀₀, at 2.7 h⁻¹₅₀ Mpc. Within 2.3  h⁻¹₅₀ Mpc (0.85 r ₂₀₀), the total mass in the Perseus cluster is 1.2 × 10¹⁵ M_⊙ and its gas fraction is about 30 per cent.  相似文献   

Millimetre and submillimetre continuum observations of the core and hotspots of Cygnus A     

E. I. Robson    L. L. Leeuw    J. A. Stevens  & W. S. Holland 《Monthly notices of the Royal Astronomical Society》1998,301(4):935-940

We present millimetre photometry and submillimetre imaging of the central core and two hotspots in the radio lobes of the galaxy Cygnus A. For both hotspots and the central core, the synchrotron spectrum continues smoothly from the radio to a frequency of 677 GHz. The spectral index of the hotspots is constant over our frequency range, with a spectral index of α ≈ −1.0 ( S _ν ∝ ν^α), which is steeper than at lower frequencies and represents the emission from an aged population of electrons. The core is significantly flatter, with α = −0.6 ± 0.1, suggestive of an injected spectrum with no ageing, but some evidence for steepening exists at our highest observing frequency. Although IRAS data suggest the presence of dust in Cygnus A, our 450-μm data show no evidence of cold dust, therefore the dust component must have a temperature lying between 85 and 37 K, corresponding to dust masses of 1.4 × 10⁶ and 1.0 × 10⁸ M_⊙ respectively.  相似文献   

Theorising middle class consumption from the global South: A study of everyday ethics in South Africa’s Western Cape     

《Geoforum》2015

Emerging research on the increasing significance of consumption in the global South is concerned with its links to the globalizing middle classes. Against the backdrop of optimism invested in the new global middle classes to fuel consumption-led growth, this paper contributes to new debate about the articulations and significance of ethical consumption in the global South. Missing from much current mainstream policy, media and academic debate is acknowledgement of the diversity of the global middle classes and an understanding of how ethical interpretations and behaviour differ in various consumer markets around the world. In response, this paper draws on qualitative research in South Africa’s Western Cape to explore the cultural significance of everyday ethical realities in shaping consumption in the global South. In addition to addressing the relative absence of research into ethical consumption in global South contexts, the paper makes two key contributions based our findings. First, it challenges the tendency, particularly in economic discourses, to generalise about the ‘new’ global middle class consumers by highlighting the significance of locality and context in shaping consumption practices in the Western Cape; specifically it finds that, for diverse middle class consumers, thrift is an important ethical choice and practice determining consumption patterns. Second, it highlights the significance of everyday ethical practices in shaping consumption in the Western Cape, focusing specifically on how thrift is imbricated in concerns with not just economic constraint, but also care, habit and aspiration. The paper concludes with reflections on the wider implications of these findings and suggests that they illustrate a need to theorise ethical consumption from contexts in the global South, on their own terms.  相似文献   

从《福楼拜的鹦鹉》看人物传记的真实戏仿     

徐颖颖 《广东海洋大学学报》2009,29(2)

传统的人物传记是基于历史的真实而展开的,但戏仿是带有后现代文学色彩的人物传记一大特点,朱利安·巴恩斯的《福楼拜的鹦鹉》对历史真实进行了独特的艺术处理,其包括悖论式的矛盾、权威的消亡与重建、表现手法的拼凑和真实与虚构的杂糅等四种方面,从而挖掘后现代人物传记的魅力所在。  相似文献