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Lu Sun 《国际地质力学数值与分析法杂志》2003,27(1):69-84
A closed‐form deflection response of a beam rest is presented in this paper using the integral transform method. The theory of linear partial differential equations is used to represent the deflection of beam subjected to a moving harmonic line load in integration form. The solution is finally carried out using the inverse Fourier transform. To evaluate the integration analytically, poles of the integrand are identified with the help of algebraic equation theory. Residue theorem is then utilized to represent the integration as a contour integral in the complex plane. Closed‐form deflections and numerical results are provided for different combinations of load frequency and velocity. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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1 IntroductionAnicecoreobtainedfrom polarglaciersoricesheetsisoneofthemostimportantarchivestoreconstructpaleoclimaticandpaleoatmosphericcondition .Informationonpale o environmentcanbeextractedfromicecoresaschemicaland/orphysicalsignals.Amongthechemicalsignals,heavymetalsarenotedassignalsofterrestrialenvironmentalchangeandanthropogenicpollution (e.g .Murozumietal.1 969;NgandPatterson 1 981 ;Hongetal.1 994) .SinceconcentrationsofmostofthemetalsinpolarsnowincentralGreen landareatorbelowthepptl… 相似文献
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The Waterman Metamorphic Complex of the central Mojave Desert was exposed as a consequence of early Miocene detachment-dominated extension. However, it has evidence consistent with a more extensive geological history that involves collision of a crustal fragment(s), tectonic thickening by overthrusting and two periods of extension. The metamorphic complex contains granitoid intrusives and felsic mylonitic gneisses as well as polymetamorphic rocks that include marble, calc-silicate, quartzite. mafic granulite, pyribolite, amphibolite, migmatite and biotite schist. The latter group of rocks was affected by an initial series of high-grade metamorphic events (M1 and M2) and a localized lower grade overprint (M3). The initial metamorphism (M1) can be separated into two stages along its high-grade P–T path: M1a, a granulite facies metamorphism at 800–850° C and 7.5–9 kbar and Mlb, an upper amphibolite facies overprint at 750–800° C and 10–12 kbar. M1a developed mineral assemblages and textures consistent with granulite facies conditions at a reduced activity of H2O and is associated with intense ductile deformation (D1) and minor local partial melting. M1b overprinted the granulite assemblages with a series of hydrous phases under conditions of increasing pressure and H2O activity and is accompanied by little or no deformation. M2 developed at lower pressures and temperatures (650–750° C, 4.5–5.5 kbar) and is distinguished by a second local overprint of hydrous phases that reflects an input of aqueous fluids probably associated with the intrusion of a series of granitic dykes and veins. Effects of M3 are confined to the Mitchel detachment zone, an anastomosing early Miocene detachment fault, and are characterized by local ductile/brittle deformation (D2) of the pre-existing high-grade rocks and granitoid intrusives and by the production of mylonites and mylonitic gneisses under greenschist facies conditions (300–350° C, 3–5 kbar). The initial overprint (M1a) represents metamorphism, devolatilization and minor partial melting of supracrustal rocks under granulite facies conditions as a consequence of tectonic and, possibly, magmatic thickening. The increasing pressure transition of M1a to M1b reflects a period of continued compressional tectonism, thrusting and influx of H2O, in part, locally related to crystallization of partial melts. The near isothermal decompression between M1b and M2 probably represents a pre-112-Ma extensional episode that may have been the result of a decompressional readjustment of a thickened crust. Following the initial extensional event, the metamorphic complex remained at depths of 10–17 km for at least 90 Ma until it was uplifted following Miocene extension. M3 develops locally in response to this second extensional period resulting from the early Miocene detachment faulting. 相似文献
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PROPAGATION OF 30—60 DAY LOW FREQUENCY OSCILLATIONS AND THEIR INFLUENCE UPON THE SUBTROPICAL WESTERLIES JET STREAM DURING NORTHERN HEMISPHERE WINTER 下载免费PDF全文
Based on daily ECMWF gridpoint data of two winters during 1981—1983 including an ENSOyear,propagation of low frequency oscillations(LFO)during Northern Hemisphere winters andtheir influences upon 30—60 day oscillations of the subtropical jet stream are studied with the sta-tistical methods as complex empirical orthogonal function(CEOF)and so on.Results show that inthe winter of a normal year(1981—1982),30—60 day oscillations in the subtropical zone aremainly in the northern and southern flanks of exit region of jet stream.In the ENSO year(1982—1983),they are mainly in the vicinity of entrance and exit regions of jet stream.Intraseasonalchanges of subtropical jet stream manifested themselves as latitudinal fluctuation or longitudinalprogression or regression of about 40 day period.There are marked differences between propagat-ing passages of low frequency modes responsible for changes of subtropical jet stream in the normalyear(1981—1982)and in the ENSO year(1982—1983).Changes of oscillation amplitude showobvious phases.In general,the one in late winter is stronger than that in early winter,strongestone occurs in February. 相似文献
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章仲根 《广东海洋大学学报》2004,24(5):13-18
宁波商帮是我国十大商帮之一 ,百年经久不衰 ,究其原因是宁波商帮受到独特的宁波城市文化熏陶。宁波得天独厚的海洋优势 ,造就了有悠久历史凝结和中外文化交融的宁波海洋文化。海洋文化是一种先进的文化 ,具有大海的许多秉性 :大度、创新、包容。宁波城市文化把中国传统的儒家文化和宁波海洋文化很好地结合起来。正是这种独特的宁波城市文化 ,才哺育出顽强开拓、勇于创新 ,克勤克俭、脚踏实地 ,注重团队、和衷共济的“宁波商帮精神”。 相似文献
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宁潭岩体是由马田、亭子、陈冲、老虎头 4个单元组成的遭受了变形变质改造的花岗岩复式岩体。岩石学、岩石化学、地球化学特征反映该岩体属后碰撞强过铝花岗岩。其源区既包含有不成熟的富含长英质物质的特性 ,也有成熟的、富含粘土的特性。岩体的形成温度为 85 0~ 92 5℃ ,同位素年龄为 35 4~ 4 4 0Ma。可能是加里东期扬子板块与华夏板块碰撞后 ,在拉伸构造作用下岩浆底辟侵位而成 相似文献
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本文着重描述了SGR钻孔处冰盖上的积雪在密实化过程中的特征变化,并对该过程进行了分段的和全面的回归分析.结果表明,冰盖密度随深度增大,但增长幅度随深度减小.作者提出密度变化减小度的概念.计算得出的所研究冰芯钻取点的密度变化减小度为-0.15kg/m~3·m~2,粒雪成冰前的密实速率平均值为4.08kg/m~3·a.本文得到的冰盖密度变化“临界点”与以往报道的有所不同.分析这一现象时,作者强调当积雪还在活动层时冰盖温度的影响,并以此解释密度剖面的异常变化以及离差的回升.特别指出,积雪的密度变化具有气候学意义,它在一定程度上能够反映出积雪形成及变化过程中气候变化的某些信息.本文由密度变化确定的钻孔点雪冰转化深度为50米. 相似文献
10.
In the northern limb of the 2.06-Ga Bushveld Complex, the Platreef is a platinum group elements (PGE)-, Cu-, and Ni-mineralized
zone of pyroxenite that developed at the intrusion margin. From north to south, the footwall rocks of the Platreef change
from Archaean granite to dolomite, hornfels, and quartzite. Where the footwall is granite, the Sr-isotope system is more strongly
perturbed than where the footwall is Sr-poor dolomite, in which samples show an approximate isochron relationship. The Nd-isotope
system for samples of pyroxenite and hanging wall norite shows an approximate isochron relationship with an implied age of
2.17 ± 0.2 Ga and initial Nd-isotope ratio of 0.5095. Assuming an age of 2.06 Ga, the ɛNd values range from −6.2 to −9.6 (ave.
−7.8, n = 17) and on average are slightly more negative than the Main Zone of the Bushveld. These data are consistent with local
contamination of an already contaminated magma of Main Zone composition. The similarity in isotope composition between the
Platreef pyroxenites and the hanging wall norites suggests a common origin. Where the country rock is dolomite, the Platreef
has generally higher plagioclase and pyroxene δ
18O values, and this indicates assimilation of the immediate footwall. Throughout the Platreef, there is considerable petrographic
evidence for sub-solidus interaction with fluids, and the Δ
plagioclase–pyroxene values range from −2 to +6, which indicates interaction at both high and low temperatures. Whole-rock and mineral δD values suggest that the Platreef interacted with both magmatic and meteoric water, and the lack of disturbance to the Sr-isotope
system suggests that fluid–rock interaction took place soon after emplacement. Where the footwall is granite, less negative
δD values suggest a greater involvement of meteoric water. Consistently higher values of Δ
plagioclase–pyroxene in the Platreef pyroxenites and hanging wall norites in contact with dolomite suggest prolonged interaction with CO2-rich fluid derived from decarbonation of the footwall rocks. The overprint of post crystallization fluid–rock interaction
is the probable cause of the previously documented lack of correlation between PGE and sulfide content on the small scale.
The Platreef in contact with dolomite is the focus of the highest PGE grades, and this suggests that dolomite contamination
played a role in PGE concentration and deposition, but the exact link remains obscure. It is a possibility that the CO2 produced by decarbonation of assimilated dolomite enhanced the process of PGE scavenging by sulfide precipitation. 相似文献