Generalized strain probing of constitutive models     

Youssef M. A. Hashash  Qingwei Fu  Jeremy Butkovich 《国际地质力学数值与分析法杂志》2004,28(15):1503-1519

Advanced material constitutive models are used to describe complex soil behaviour. These models are often used in the solution of boundary value problems under general loading conditions. Users and developers of constitutive models need to methodically investigate the represented soil response under a wide range of loading conditions. This paper presents a systematic procedure for probing constitutive models. A general incremental strain probe, 6D hyperspherical strain probe (HSP), is introduced to examine rate‐independent model response under all possible strain loading conditions. Two special cases of HSP, the true triaxial strain probe (TTSP) and the plane‐strain strain probe (PSSP), are used to generate 3‐D objects that represent model stress response to probing. The TTSP, PSSP and general HSP procedures are demonstrated using elasto‐plastic models. The objects resulting from the probing procedure readily highlight important model characteristics including anisotropy, yielding, hardening, softening and failure. The PSSP procedure is applied to a Neural Network (NN) based constitutive model. It shows that this probing is especially useful in understanding NN constitutive models, which do not contain explicit functions for yield surface, hardening, or anisotropy. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Observations of SN1988e: A mature supernova     

Gillian Pearce  Bruce Patchett  Paul Murdin  Jeremy Allington-Smith 《Astrophysics and Space Science》1990,164(1):59-62

We present the spectrum of the supernova SN1988e over the wavelength range 4750–9000 Å as recorded on 11 February, 1988. The spectrum was taken in one 2000 s exposure using the Faint Object Spectrograph on the 4.2 m William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos.We conclude that SN1988e was a type I supernova, and that at the time of observation it had faded 7.5 mag from its predicted magnitude at maximum light. Spectra taken at such late stages in the light curve are comparatively rare, and are made possible only with the application of modern instrumentation.  相似文献   

Integral field spectroscopy with the GEMINI multiobject spectrographs     

Jeremy Allington-Smith  Graham Murray  Robert Content  George Dodsworth  Bryan W. Miller  James Turner  Inger Jorgensen  Isobel Hook 《Experimental Astronomy》2002,13(1):1-37

We describe the integral field unit (IFU) which converts the Gemini Multiobject Spectrograph (GMOS) installed on the Gemini-North telescope to an integral field spectrograph,which produces spectra over a contiguous field of view of 7 × 5 arcsec with spatial sampling of 0.2 arcsecover the wavelength range 0.4-1.0 μm.GMOS is converted to this mode by the remote insertion of the IFU into thebeam in place of the masks used for the multiobject mode. A separate fieldof half the area of the main field, but otherwise identical, is alsoprovided to improve background subtraction. The IFU contains 1500lenslet-coupled fibres and was the first facility of any type for integralfield spectroscopy employed on an 8/10 m telescope.We describe the design, construction and testing of the GMOS IFU and present measurements of the throughput both in the laboratory and at the telescope. We compare these with a theoretical prediction made before construction started. All are in good agreement with each other, with the on-telescope throughput exceeding 60% (averaged over wavelength). Finallywe show an example of data obtained during commissioning to illustrate the power of the device.  相似文献   

阿尔金断裂昌马大坝—宽滩山段全新世活动特征   总被引：9，自引：2，他引：7  

陈柏林  刘建生  王春宇  张永双  刘建民  董诚  吴乃芬 《地质学报》2008,82(4):433-440

阿尔金断裂是我国西部著名的巨型走滑断裂带之一,也是全新世活动断裂和发震断裂。该断裂昌马大坝—宽滩山段运动方式为以左行走滑占主导,伴有弱的垂直运动;在距今2.7ka以来发生过明显的新构造活动（和地震）。在沙坪—宽滩山段全新世左行走滑位移速率为0.9～2.2mm/a,明显低于阿尔金断裂东段昌马大坝以西地区4～5mm/a和中西段9～11mm/a的位移速率。阿尔金断裂东段在肃北和昌马大坝出现二次位移速率的锐减,锐减的部分分别转化为海原活动断裂西段（党河南山断裂）和祁连山北缘活动断裂西段的左行走滑和逆冲,且在位移速率数值上相互之间具有非常好的对应性。阿尔金断裂在肃北位移速率减少部分（4.6mm/a）与海原活动断裂西段（党河南山断裂）的位移速率（4～5mm/a）非常接近,同样阿尔金断裂在昌马大坝位移速率减少部分（3.2mm/a）与祁连山北缘活动断裂的位移速率（3.0mm/a）也非常接近。  相似文献   

Cambridge deep Ocean geophone     

Jeremy Duschenes  Chris Potts  Martyn Rayner 《Marine Geophysical Researches》1985,7(4):455-466

We describe recent mechanical andeelectronic modifications to the Cambridge Ocean Bottom Hydrophone system, enabling it to record in addition three geophone channels from a deployed, disposable geophone package. Examples of data from seismic refraction experiments show good correspondence between records of ground motion detected by the hydrophone and the vertical geophone. Seismic signals are undistorted by noise from instrument related sources. Clear examples of P to S conversions just below the receiver are observed. Improved recording conditions are achieved by deploying the geophones in a small pressure vessel as far away as possible from the main instrument package.  相似文献   

Long-Term Changes in Water Quality and Productivity in the Patuxent River Estuary: 1985 to 2003     

Jeremy M. Testa  W. Michael Kemp  Walter R. Boynton  James D. Hagy III 《Estuaries and Coasts》2008,31(6):1021-1037

We conducted a quantitative assessment of estuarine ecosystem responses to reduced phosphorus and nitrogen loading from sewage treatment facilities and to variability in freshwater flow and nonpoint nutrient inputs to the Patuxent River estuary. We analyzed a 19-year dataset of water quality conditions, nutrient loading, and climatic forcing for three estuarine regions and also computed monthly rates of net production of dissolved O₂ and physical transport of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) using a salt- and water-balance model. Point-source loading of DIN and DIP to the estuary declined by 40–60% following upgrades to sewage treatment plants and correlated with parallel decreases in DIN and DIP concentrations throughout the Patuxent. Reduced point-source nutrient loading and concentration resulted in declines in phytoplankton chlorophyll-a (chl-a) and light-saturated carbon fixation, as well as in bottom-layer O₂ consumption for upper regions of the estuary. Despite significant reductions in seaward N transport from the middle to lower estuary, chl-a, turbidity, and surface-layer net O₂ production increased in the lower estuary, especially during summer. This degradation of water quality in the lower estuary appears to be linked to a trend of increasing net inputs of DIN into the estuary from Chesapeake Bay and to above-average river flow during the mid-1990s. In addition, increased abundance of Mnemiopsis leidyi significantly reduced copepod abundance during summer from 1990 to 2002, which favored increases in chl-a and allowed a shift in total N partitioning from DIN to particulate organic nitrogen. These analyses illustrate (1) the value of long-term monitoring data, (2) the need for regional scale nutrient management that includes integrated estuarine systems, and (3) the potential water quality impacts of altered coastal food webs.  相似文献   

祁连山北缘—河西走廊西段晚新生代逆冲推覆断裂发育模式   总被引：1，自引：0，他引：1  

陈柏林  王春宇  崔玲玲  刘建民 《地学前缘》2008,15(6)

祁连山北缘—河西走廊西段地处青藏高原东北缘,是我国新构造活动最强烈的地区之一。通过野外对研究区主要活动断裂的调查研究、结合年代学测试和综合分析,认为祁连山北缘—河西走廊西段地区的旱峡—大黄沟断裂、玉门断裂、新民堡断裂和阴洼山断裂都是晚更新世至全新世活动断裂。旱峡—大黄沟断裂形成于中新世晚期,一直活动至今;玉门断裂形成于上新世早期,在距今7.6ka左右和3.2ka左右发生过2次强烈的新构造活动(古地震),也是2002年玉门地震的发震断裂;阴洼山断裂形成于上新世晚期(3.0Ma左右),在距今19.9～21.0ka、8.6～10.0ka、4.1～5.0ka发生过3次强烈的新构造活动,也可能是1785年惠民堡(现新民堡)地震的发震断裂;但是位于近盆地中心的新民堡断裂形成时代明显晚的多,起始于中更新世晚期(0.17Ma左右),在距今28.3ka、4.4ka和1.2ka左右发生过强烈的3次新构造活动。在运动形式上,上述4条断裂均为自南南西向北北东的逆冲推覆。在变形性质上,新民堡断裂以非地震性的蠕滑为主,其他3条断裂主要为地震性的粘滑变形。在祁连山北缘—河西走廊西段的北北东剖面上,逆冲推覆断裂表现为前展-后展复合发育模式,即形成时代最新的是位于酒西盆地中心的新民堡断裂,在酒西盆地中心以南部分的剖面中断裂发育为前展式,由祁连山腹地向河西走廊盆地中心断裂形成时代越来越新,而酒西盆地中心以北部分的剖面中断裂发育为后展式,即从盆地中心到盆地北缘断裂形成时代越来越老。  相似文献   

The stellar populations within theρ Oph cloud cores     

Karen M. Strom  Jeremy Kepner  Stephen E. Strom 《Astrophysics and Space Science》1994,217(1-2):223-224

We have obtained infrared colors and limiting magnitudes from 1.25–4.8µm for a sample of 26 of the cm continuum radio sources located in the core of the Oph molecular cloud. Their colors demonstrate that the majority of the sources appear to be heavily reddened objects surrounded by circumstellar accretion disks. In these cases the radio emission most likely diagnoses accretion driven energetic outflow phenomena: either ionized winds or possibly synchrotron emission from shocked gas associated with stellar jets.  相似文献   

The impact of natural hazards on the health sector in the Caribbean: Implications for health sector planning     

Jeremy McA Collymore 《GeoJournal》1992,26(1):61-64

In the last decade significant initiatives have been taken in the health sector with the view to better manage and respond to natural disaster emergencies. However, the recent hurricane disasters related to Hugo and Gilbert have highlighted many areas of health sector emergency planning still to be adressed. This paper briefly summarises the impact of recent natural disaster on the health sector in the Caribbean and comments on the performance of the sector during the emergencies. An effort is then made to detail what are the policy and programming issues to be tackled, if desired improvements are to be achieved.The reader may like to see GeoJournal vol. 23, no. 4 (April 1991) on Caribbean Hurricanes  相似文献   

Absolute spectrophotomery of comets 1973XII and 1975IX: II. Profiles of the Swan bands     

Lucy L. Danylewych  Ralph W. Nicholls  John S. Neff  Jeremy B. Tatum 《Icarus》1978,35(1):112-120

Absolute spectrophotometric measurements of the Swan bands of two comets have been compared with computed synthetic spectra using modern Franck-Condon and Hönl-London factors, and varying rotational, vibrational, and electronic excitation temperatures. Rotational and vibrational temperatures were obtained for the comets. Although the electronic excitation temperature and the molecular column density cannot be separated, a relationship is found between these two quantities. A review is made of recent determinations of column densities for CN in comets.  相似文献