A thermo-plastic constitutive law for brittle-plastic behavior of rocks at high temperatures     

Tomasz Hueckel  Alberto Peano  Rita Pellegrini 《Pure and Applied Geophysics》1994,143(1-3):483-510

Mechanical properties of rocks change under the influence of, temperature. Stress at the onset of yielding, ultimate strength, dilatancy, strain hardening and softening, and the confining pressure at brittle-ductile transition are all reduced by the increasing temperature. This study presents a framework of constitutive modeling of thermo-brittle-plastic behavior of rocks which encompasses these changes. The constitutive law is based on a thermo-plasticity theory first proposed for metals byPrager (1958). Two phenomenological mechanisms have been identified as central for the modeling: temperature dependence of the yield locus (thermal softening), and temperature dependence of the strain-hardening function (thermally enhanced ductility). Material parameters for two rocks, Carrara marble and Westerly granite, were determined on the basis of additional hypotheses. These parameters are used in numerical simulations of triaxial tests at different temperatures. The obtained stress-strain curves compare well to the experimental results. The changes with temperature in the stress at the onset of yielding are more accurately reproduced that the evolution of hardening or softening. Suggestions for possible improvements and future research directions are indicated.  相似文献   

太阳活动,大气臭氧和平流层温度相关分析研究   总被引：1，自引：4，他引：1  

言穆弘  华贵义 《高原气象》1993,12(3):302-311

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近百余年上海气温变化的若干特征   总被引：7，自引：0，他引：7  

徐家良 《地理学报》1993,48(1):26-32

本文根据1873—1990年上海的年、冬、夏平均气温资料,并利用1956—1990年其郊区气温资料,对城市热岛效应对气温的影响作了处理,重建了近118a的上海气温序列。在此基础上对上海的气温变化特征进行分析,并与同期的北半球气温变化作了比较。结果表明,上海的气温变化有其明显的阶段性、跃变性和周期性。近百余年上海气温变化的总体特征与北半球相似,呈缓慢变暖趋势,但具体的变化过程和幅度有差别,尤其近20多年来的变化与北半球不一致,没有明显的增温现象。  相似文献   

我国夏季气温、降水场的时空特征分析   总被引：16，自引：0，他引：16       下载免费PDF全文

黄嘉佑 《大气科学》1991,15(3):124-132

本文用主分量及转动主分量分析方法对我国夏季气温及降水量场(1951—1985年期间)的时空特征进行了研究。从所提取的空间模式中发现气温的解释方差较降水的大,且具有较好的均匀性;从对应的时间分量分析发现气温与降水均具有2—3年的主要变化周期,与东亚大气环流的关系分析中以气温表现较为密切。 对气温和降水场时空特征的稳定性分析表明,无论在持续性、周期性及与东亚大气环流的关系上,进入70年代后均有较明显的变化。比较表明气温场的稳定性较降水为好。 气温场与降水场相互关系分析发现它们有显著的反相关,表现显著的地区为长江中下游、华南及华北等。  相似文献   

卫星资料在上海浦东新区热力场分析中的应用   总被引：5，自引：1，他引：5       下载免费PDF全文

杨星卫  楼萌 《应用气象学报》1994,5(3):369-373

文章利用１９９２年春、夏、秋、冬四季６个时相的ＮＯＡＡ－１１／ＡＶＨＲＲ资料，在与上海区域行政图（边界以乡为单位）进行几何精度纠正的基础上，通过图象增强处理和多通道信息组合，提取上海市区和浦东新区的热力场分布特征，并用直接对比法，建立亮温。气温的相关关系，取得较好的效果。据上海温度分布图象分析，新区的两个热中心与工业群体区、建筑群体区相对应；市区的３个热中心与商业经济密集区及工业群体区相对应。   相似文献   

吉林省太古宙TTG岩类固结的温度压力条件     

孙德有  周永胜 《吉林地质》1995,14(2):57-63

吉林省太古宙ＴＴＧ岩类型成于变质上壳岩系麻粒岩相变质作用晚期阶段。详细的岩相学研究表明，ＴＴＧ岩类中存在岩浆结晶的绿帘石，角闪石和黑云母等。绿帘石的出现标志了一定的压条件。  相似文献   

平流层下部气温年际异常的旋转主成分分析   总被引：2，自引：0，他引：2       下载免费PDF全文

章基嘉  吴洪宝 《应用气象学报》1995,6(3):265-272

利用旋转主成分方法分析了北半球冬季平流层下部月平均气温距平，得到的4个主要的空间分布型，分别表示中纬、低纬的纬向对称异常、太平洋北部暖中心和极区冷中心的异常。还指出中纬异常的时间演变最单调，整个冬季有持续性，年际变化呈现明显的准两年振荡周期(QBD)。  相似文献   

Crustacean zooplankton distribution patterns and their biomass as related to trophic indicators of 29 shallow subtropical lakes   总被引：3，自引：0，他引：3  

Songbo Wang  Ping Xie  Shikai Wu  Aiping Wu 《Limnologica》2007,37(3):242-249

A comparative limnological study was carried out to present a snapshot of crustacean zooplankton communities and their relations to environmental factors to test whether there is a consistent relationship between crustacean biomass and trophic indicators among lake groups with similar trophic conditions. The study lakes showed a wide range of trophic status, with total phosphorus (TP) ranging from 0.008 to 1.448 mg L⁻¹, and chlorophyll a from 0.7 to 146.1 μg L⁻¹, respectively. About 38 species of Crustacea were found, of which Cladocera were represented by 25 taxa (20 genera), and Copepoda by 13 taxa (11 genera). The most common and dominant species were Bosmina coregoni, Moina micrura, Diaphanosoma brachyurum, Cyclops vicinus, Thermocyclops taihokuensis, Mesocyclops notius and Sinocalanus dorrii. Daphnia was rare in abundance. Canonical correspondence analysis showed that except for four species (D. hyalina, S. dorrii, C. vicinus and M. micrura), almost all the dominant species had the same preference for environmental factors. Temperature, predatory cyclopoids and planktivorous fishes seem to be the key factors determining species distribution. TP was a relatively better trophic indicator than chlorophyll a to predict crustacean biomass. Within the three groups of lakes, however, there was no consistent relationship between crustacean biomass and trophic indicators. The possible reason might be that top-down and bottom-up control on crustaceans vary with lake trophic state. The lack of significant negative correlation between crustacean biomass and chlorophyll a suggests that there was little control of phytoplankton biomass by macrozooplankton in these shallow subtropical lakes.  相似文献   

Stratospheric warming effects on the tropical mesospheric temperature field   总被引：1，自引：0，他引：1  

M.G. Shepherd  D.L. Wu  I.N. Fedulina  S. Gurubaran  J.M. Russell  M.G. Mlynczak  G.G. Shepherd 《Journal of Atmospheric and Solar》2007,69(17-18):2309

Temperature observations at 20–90 km height and 5–15°N during the winter of 1992–1993, 1993–1994 and 2003–2004, from the Wind Imaging Interferometer (WINDII) and Microwave Limb Sounder (MLS) experiments on the Upper Atmosphere Research Satellite (UARS) satellite and the Sounding the Atmosphere using Broadband Emission Radiometry (SABER) experiment on the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite are analyzed together with MF radar winds and UK Meteorological Office (UKMO) assimilated fields. Mesospheric cooling is observed at the time of stratospheric warming at the tropics correlative with stratospheric warming events at middle and high latitudes. Planetary waves m=1 with periods of 4–5, 6–8, 10 and 12–18 days are found to dominate the period. Westward 7- and 16-day waves at the tropics appear enhanced by stationary planetary waves during sudden stratospheric warming events.  相似文献   

Thermal surface characteristics of coal fires 1 results of in-situ measurements     

Jianzhong Zhang  Claudia Kuenzer   《Journal of Applied Geophysics》2007,63(3-4):117-134

Natural underground coal fires are fires in coal seams occurring subsurface. The fires are ignited through a process named spontaneous combustion, which occurs based on a natural reaction but is usually triggered through human interaction. Coal mining activities expose coal to the air. This leads to the exothermal oxidation of the carbon in the coal with the air's oxygen to CO₂ and – under certain circumstances – to spontaneous combustion. Coal fires occur in many countries world wide – however, currently the Chinese coal mining industry faces the biggest problems with coal fires. Coal fires destroy the valuable resource coal and furthermore lead to many environmental degradation phenomena such as the deterioration of surrounding vegetation, land subsidence and the emission of toxic gasses (CO, N₂O). They additionally contribute to the emission of green house relevant gasses such as CO₂ and CH₄ to the atmosphere.In this paper we present thermal characteristics of coal fires as measured in-situ during a field campaign to the Wuda coal fire area in south-central Inner Mongolia, China. Thermal characteristics include temperature anomaly measurements at the surface, spatial surface temperature profiles of fire areas and unaffected background areas, diurnal temperature profiles, and temperature measurements inside of coal fire induced cracks in the overlying bedrock. For all the measurements the effects of uneven solar heating through influences of slope and aspect are considered.Our findings show that coal fires result in strong or subtle thermal surface anomalies. Especially the latter can easily be influenced by heating of the surrounding background material through solar influences. Temperature variation of background rocks with different albedo, slope, aspect or vegetation cover can substantially influence the detectability of thermal anomalies. In the worst case coal fire related thermal anomalies can be completely masked by solar patterns during the daytime. Thus, night-time analysis is the most suitable for thermal anomaly mapping of underground coal fires, although this is not always feasible. The heat of underground coal fires only progresses very slowly through conduction in the rock material. Anomalies of coal fires completely covered by solid unfractured bedrock are very weak and were only measured during the night. The thermal pattern of underground coal fires manifested on the surface during the daytime is thus the pattern of cracks and vents, which occur due to the volume loss underground and which support radiation and convective energy transport of hot gasses. Inside coal fire temperatures can hardly be measured and can only be recorded if the glowing coal is exposed through a wider crack in the overlaying bedrock. Direct coal fire temperatures measured ranged between 233 °C and 854 °C. The results presented can substantially support the planning of thermal mapping campaigns, analyses of coal fire thermal anomalies in remotely sensed data, and can provide initial and boundary conditions for coal fire related numerical modeling.In a second paper named “Thermal Characteristics of Coal Fires 2: results of measurements on simulated coal fires” [Zhang J., Kuenzer C., Tetzlaff A., Oettl D., Zhukov B., Wagner W., 2007. Thermal Characteristics of Coal Fires 2: Result of measurements on simulated coal fires. Accepted for publication at Journal of Applied Geophysics. doi:10.1016/j.jappgeo.2007.08.003] we report about thermal characteristics of simulated coal fires simulated under simplified conditions. The simulated set up allowed us to measure even more parameters under undisturbed conditions — especially inside fire temperatures. Furthermore we could demonstrate the differences between open surface coal fires and covered underground coal fires. Thermal signals of coal fires in near range thermal remotely sensed imagery from an observing tower and from an airplane are presented and discussed.  相似文献