C3植物光合作用日变化的模拟

对前人光合作用-气孔导度耦合模型进行了修正,建立了光合作用-蒸腾作用-气孔导度的耦合模型,它概括了叶片上各主要物理过程和生理过程之间的相互联系和制约关系。 用数值方法研究了不同环境因子（太阳辐射、温度、湿度和风速等）对光合作用、蒸腾作用和气孔导度的日变化及中午降低（midday depression）的影响。 主要结果是:（1）当边界层导度减小时,光合“午睡”加剧,蒸腾作用减弱,但作为反馈调节,气孔导度增加。 （2）气孔导度的最适温度最低,光合作用次之,蒸腾作用最适温度最高。当光合作用中午受到高温的胁迫时,气孔导度下降的幅度最大,光合作用次之,蒸腾作用的降幅最小。一天中,气孔导度降低的持续时间最长,蒸腾作用降低的持续时间最短。（3）空气绝对湿度越低,气孔导度越低,光合午睡越明显。蒸腾作用则决定于饱和水汽压差(Vpd)和气孔导度两个因素的相反的作用。蒸腾作用随Vpd增加而增大,但Vpd超过一定值后,反而使蒸腾作用下降。 （4）当温度在光合最适温度以上时,太阳辐射的增加使叶温增加,引起光合“午睡”的加剧和气孔导度的降低。（5）ci/cs在中午的降低表明气孔的关闭是光合作用“午睡”现象的原因。     

Records of the Moon‐forming impact and the 470 Ma disruption of the L chondrite parent body in the asteroid belt from U‐Pb apatite ages of Novato (L6)

Novato, a newly observed fall in the San Francisco Bay area, is a shocked and brecciated L6 ordinary chondrite containing dark and light lithologies. We have investigated the U‐Pb isotope systematics of coarse Cl‐apatite grains of metamorphic origin in Novato with a large geometry ion microprobe. The U‐Pb systematics of Novato apatite reveals an upper intercept age of 4472 ± 31 Ma and lower intercept age of 473 ± 38 Ma. The upper intercept age is within error identical to the U‐Pb apatite age of 4452 ± 21 Ma measured in the Chelyabinsk LL5 chondrite. This age is interpreted to reflect a massive collisional resetting event due to a large impact associated with the peak arrival time at the primordial asteroid belt of ejecta debris from the Moon‐forming giant impact on Earth. The lower intercept age is consistent with the most precisely dated Ar‐Ar ages of 470 ± 6 Ma of shocked L chondrites, and the fossil meteorites and extraterrestrial chromite relicts found in Ordovician limestones with an age of 467.3 ± 1.6 Ma in Sweden and China. The lower intercept age reflects a major disturbance related to the catastrophic disruption of the L chondrite parent body most likely associated with the Gefion asteroid family, which produced an initially intense meteorite bombardment of the Earth in Ordovician period and reset and degassed at least approximately 35% of the L chondrite falls today. We predict that the 470 Ma impact event is likely to be found on the Moon and Mars, if not Mercury.     

A research on grey numerical imitation and modeling of groundwater seepage system

Based on grey set, grey numbers and their operation properties, the grey numerical model of groundwater seepage system was set up for the first time, the whole grey solving method of the model was given and it was proved that the common solving method of the model was only a special case of the grey solving methods. At the same time, the grey solving method was compared widely with common solving method, classical numerical method. The study shows that the grey solving method is better in depicting the procedure of transporting grey data of groundwater system. On the basis of the theoretical study, two basic kinds of cases about groundwater seepage were selected: the prediction of pit yield and the evaluation of groundwater resources on a groundwater basin. In the cases, systematical analyses were made for generalization and greylization of the hydrogeologic conditions, setting up of the grey model, identification and correction of the model as well as its prediction and evaluation. It was pointed out that when the grey numerical model is used to predict pit yield, the upper limit of the “grey band” of groundwater level cannot be higher than planed safe groundwater level, when evaluating the groundwater resource, the lower limit of the “grey band” of groundwater level cannot be lower than controlled level of groundwater.     

Application of a Discrete-Continuum Model to Karst Aquifers in North China

A generalized discrete-continuum model is developed to simulate ground water flow in the karst aquifers of North China. The model is a hybrid numerical flow model, which takes into account both quick conduit flow and diffusive fissure flow. The conduit flow is represented by a discrete network model, and the fissure flow is modeled by a continuum approach. The developed model strongly emphasizes the function of the conduits in the flow fields. They control the general drainage pattern, as demonstrated in the simulation of a complex karst aquifer in North China. The model reproduces reasonably well the flow field in response to an unanticipated discharge of ground water from the karst aquifer into an underground mine based on the aquifer parameters that are manually calibrated from a multiple-well pumping test. Sensitivity of the model to the aquifer parameters was evaluated in the context of the case study.     

Changes of temperature extremes for 1960–2004 in Far-West China

The spatial and temporal patterns of the temperature extremes defined by 5th and 95th percentiles based on daily maximum/minimum temperature dataset were analyzed using Mann–Kendall test and linear regression method. The research results indicate that: (1) the seasonal minimum temperature is in stronger increasing trend than the seasonal maximum temperature; (2) in comparison with the changes of the maximum temperature, more stations display significantly increasing trends of minimum temperature in frequency and intensity; (3) comparatively, more stations have significantly decreasing trends in the intra-seasonal extreme temperature anomaly in summer and winter than in spring and autumn. The areal mean minimum temperature is in stronger increasing trend than areal mean maximum temperature; (4) the warming process in the Far-West (FW) China is characterized mainly by significantly increasing minimum temperature. The research will be helpful for local human mitigation to alterations in water resource and ecological environment in FW China due to changes of temperature extremes, as the ecologically fragile region of China.     

P wave velocity structure of upper and middle crust beneath the Three Gorges reservoir dam and adjacent regions

The three-dimensional P wave velocity structures of upper and middle crust beneath the Three Gorges reservoir dam and adjacent regions were reconstructed by means of the seismic tomography, using the absolute P-arrivals from the events observed by the Three Gorges seismic network. Our preliminary study of the deep structure shows: (1) the lithology of the Huangling anticline, integral and highly solidified, exhibits a uniformity. Down to a depth of 20 km, the Huangling anticline still shows high-velocity anomalies. Note that the characteristics of the velocity images with the different depths are not the same; (2) the depth of the sedimentary rocks beneath the entire Zigui basin is not constant, which is less than 6 km; (3) the top boundary of the crystalline basement varies from 0 to 7 km, whereas the bottom one between 14 and 16 km; (4) the partially molten substances of the upper mantle are located in the Badong-Zigui and its adjacent regions as well as nearby Peishi area. The development and evolution of the current tectonics are associated with the cooling and solidifying process of the molten substances within the upper mantle; (5) the different velocity structures of the deep crust in both east and west side of the Jiuwanxi fault are to be investigated in order to understand the origin of gravitational gradient zone in the Three Gorge areas; and (6) the velocities within the upper crust would be affected by reservoir water permeability. Supported by National Natural Science Foundation of China (Grant No. 40574039), National Key Technology R& D Program (Grant No. 2008BAC38B02)     

基于纤维模型的高墩连续刚构桥地震行波效应分析

本文基于在MSC.Marc中加入纤维模型编制的THUFIBER程序的基础上,分别采用纤维模型和三维实体单元模型模拟桥墩和上部结构,建立高墩大跨连续刚构桥有限元模型。同时,采用2008年汶川地震波,分析了行波效应对四川某高墩大跨连续刚构桥非线性地震反应的影响。结果表明：行波效应对高墩桥的墩顶位移和墩底剪力影响较大,墩顶位移减小了20%—50%;而墩底剪力增大了20%—30%。     

Evidence of multistage late Quaternary strong earthquakes on typical segments of Longmenshan Active Fault Zone in Sichuan,China

Investigation of offset landforms and trench excavation are important means to acquire the evidence of multistage activities of active faults. Here we present the result of fault trough investigation in Beichuan County and the Pingtong Town of Pingwu County along the Longmenshan Central Fault Belt, as well as the result from trench excavation at the platform foreslope in Hanwang Town of Mianzhu County on the Longmenshan Front Range Fault Belt. These results show that at least three fault activity events, in...     

地下流体水位观测地震前兆机理研究

本文主要研究锦州沈家台汤池子观测站地下流体数字化水位的年、月、日动态特征及数字化资料映震性能分析。检验理论固体潮与实际观测水位的潮汐因子、相对误差,排除气压对水位观测的干扰因素,识别水位观测水动态中较大幅度的脉冲和突变、阶变、潮汐畸变,水位上升打破年变等因素,提高利用地下流体观测地震前兆的监测效能。     

Deformation features of garnet-bearing granites from Huwan,western Dabie Mountains

Foliated garnet-bearing granite, usually associated with high pressure and ultrahigh -pressure (UHP) metamophic rocks, is a particular rock-type extensively exposed in the Mesozoic Dabie-Sulu orogenic belt of China. This study focuses on deformation features and SHRIMP zircon dating of foliated garnet granite in a high-pressure metamorphic unit from Huwan, western Dabie Mountains in order to resolve discrepancies in current versions of its petrogenesis and structural evolution. SHRIMP dating reveals a zircon age of 762 ± 15 Ma (MSWD=1.7) for Huwan granites, representing the Middle to Late Neoproterozoic age of intrusion and crystallization. Field and microstructural studies show that the Huwan granite body underwent multiple-stage deformation. The deformation was manifested by an early stage of rootless folding and imposition of relict foliation (S₁); an Indosinian main stage marked by imposition of north-dipping penetrative gneissosity (S₂) and development of ductile shear zones under NNE-SSW directed compression; and a final Indosinian stage of southward thrusting of the Huwan high-pressure unit. Shallow level extension prevailed after the Late Triassic, giving rise to south-dipping thrust faults and north-dipping normal faults. Supported by the National Natural Science Foundation of China (Grant Nos. 40802046 and 40334037) and the Project of Science & Technology Research and Development from Sinopec (Grant No. P02009)