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81.
软土路基沉降实时建模动态预测 总被引:6,自引:2,他引:4
在路基填筑施工过程中,用多项式与时间序列AR组合模型预测其沉降变形发展。根据沉降观测值,采用统计分析方法识别和建立多项式预测模型,预测在某时期沉降趋势值;用平稳时间序列分析方法建立随机部分模型,并预测沉降随机部分值,二者之和即为某时期沉降预测值。随着新观测数据的不断加入,及时修改预测模型参数值,达到实时预测之目的。工程实例研究表明:组合模型预测值明显优于单一趋势模型预测值。组合模型一步预测误差绝对值大多数情况下小于5 mm。预测步数越多,预测误差则越大。 相似文献
82.
Qichun Yang Xuesong Zhang James E. Almendinger Maoyi Huang Guoyong Leng Yuyu Zhou Kaiguang Zhao Ghassem R. Asrar Xia Li Jiali Qiu 《水文研究》2019,33(5):864-875
Insufficiently calibrated forest parameters of the Soil & Water Assessment Tool (SWAT) may introduce uncertainties to water resource projections in forested watersheds. In this study, we improved SWAT forest parameterization and phosphorus cycling representations to better simulate forest ecosystems in the St. Croix River basin, and we further examined how those improvements affected model projections of streamflow, sediment, and nitrogen export under future climate conditions. Simulations with improved forest parameters substantially reduced model estimates of water, sediment, and nitrogen fluxes relative to those based on default parameters. Differences between improved and default projections can be attributed to the enhanced representation of forest water consumption, nutrient uptake, and protection of soil from erosion. Better representation of forest ecosystems in SWAT contributes to constraining uncertainties in water resource projections. Results of this study highlight the importance of improving SWAT forest ecosystem representations in projecting delivery of water, sediment, and nutrients from land to rivers in response to climate change, particularly for watersheds with large areas of forests. Improved forest parameters and the phosphorus weathering algorithms developed in this study are expected to help enhance future applications of SWAT to investigate hydrological and biogeochemical consequences of climate change. 相似文献
83.
Emma Hodgson Stephen T. Grimes Gregory D. Price Meriel E.J. Fitzpatrick Malcolm B. Hart Melanie J. Leng 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(3):460-471
This study demonstrates that the Bunkers Hill borehole, which is located within the Hampshire Basin, contains a carbon isotope excursion (CIE) in the Upnor Formation followed by a positive recovery from another CIE within the overlying Reading Formation. This study has also shown that the CIE in the Upnor Formation predates the Paleocene/Eocene Thermal Maximum (PETM), while the carbon isotope recovery at the base of the Reading Formation is most likely related to it. The positive carbon isotope trend, before a return to more negative values, seen throughout the majority of the Reading Formation can also be seen in coeval deposits in the Jubilee 404T borehole in the London Basin and in the Tienen Formation in the Doel and Kallo boreholes from the Belgium Basin. This indicates that this post-PETM carbon isotope signal may, therefore, be regional if not global in nature. 相似文献
84.
Catherine N. Jex Andy Baker Jonathan M. Eden Warren J. Eastwood Ian J. Fairchild Melanie J. Leng Louise Thomas Hilary J. Sloane 《Quaternary Research》2011,75(3):399-405
A verified instrumental calibration of annually resolved δ18O for a stalagmite from Gümü?hane in northeast Turkey is presented and cross-validated using a ‘leave-one-out’ technique. The amount of late autumn to winter precipitation is negatively correlated with stalagmite δ18O between AD 1938 and 2004. The observed relationship is extrapolated back to ~ AD 1500 leading to the first long winter precipitation reconstruction for this region. Modern day October to January precipitation is linked to pressure fields in Western Russia. Anomalously lower reconstructed rainfall is recorded in AD 1540–1560 at which time higher pressure over the Caspian Sea region is inferred. 相似文献
85.
Bernhard Chapligin Melanie J. Leng Anne Alexandre Akira Ijiri Aldo Shemesh Ulrike Herzschuh Hanno Meyer Yusuke Okazaki Zachary D. Sharp Corinne Sonzogni Florence Sylvestre Ruth Yam 《Geochimica et cosmochimica acta》2011,75(22):7242-7256
Several techniques have been introduced in the last decades for the dehydration and release of O2 from biogenic silica (opal-A) for oxygen-isotope analysis. However, only one silica standard is universally available: a quartz standard (NBS28) distributed by the IAEA, Vienna. Hence, there is a need for biogenic silica working standards. This paper compares the existing methods of oxygen-isotope analyses of opal-A and aims to characterize additional possible working standards to calibrate the δ18O values of biogenic silica. For this purpose, an inter-laboratory comparison was organized. Six potential working standard materials were analysed repeatedly against NBS28 by eight participating laboratories using their specific analytical methods. The materials cover a wide range of δ18O values (+23 to +43‰) and include diatoms (marine, lacustrine), phytoliths and synthetically-produced hydrous silica. To characterize the proposed standards, chemical analyses and imaging by scanning electron microscopy (SEM) were also performed. Despite procedural differences at each laboratory, all methods are in reasonable agreement with a standard deviation (SD) for δ18O values between 0.3‰ and 0.9‰ (1σ). Based on the results, we propose four additional biogenic silica working standards (PS1772-8: 42.8‰; BFC: 29.0‰; MSG60: 37.0‰; G95-25-CL leaves: 36.6‰) for δ18O analyses, available on request through the relevant laboratories. 相似文献
86.
87.
88.
Michèle L. Clarke Antoni E. Milodowski Jon E. Bouch Melanie J. Leng Kevin J. Northmore 《第四纪科学杂志》2007,22(4):361-371
Windblown dust deposits or loess, locally known in the UK as brickearth, blanket many parts of southern England outside the limits of the British and Irish Ice Sheet. The best‐studied loess exposures occur in Kent, southeast England, where the deposits are believed to be Late Glacial in age. New sedimentological evidence is presented for phases of accretion with two distinct units, a calcareous brickearth exhibiting periglacial cryoturbation and a non‐calcareous, massive brickearth. Optically stimulated luminescence (OSL) dating has been applied to chemically isolated modal quartz silts to derive a chronology for sediment accretion and to better understand the palaeoclimatic significance of these deposits. © British Geological Survey/Natural Environment Research Council copyright 2007. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd. 相似文献
89.
Y.T. Hong B. Hong Q.H. Lin Y. Shibata Y.X. Zhu X.T. Leng Y. Wang 《Quaternary Science Reviews》2009,28(9-10):840-849
A peat cellulose δ18O record spanning around 14,000 years from the Hani peat mire in northeastern China reveals several abrupt temperature anomalies in the period from the last deglaciation through the Holocene. The timing of these anomalies coincides well with the notable cooling events recorded respectively using the GISP2 ice core and ice-rafted sediment of the North Atlantic Ocean, such as the Older Dryas, Inter-Allerød, Younger Dryas, and the nine ice-rafted debris events. The results demonstrate that this repeating pattern of abrupt temperature deterioration is not limited to the North Atlantic area at high latitude but also exists in the western North Pacific region at middle latitude. The synchronous temperature anomalies possibly are resulted from the joint effects of meltwater discharge into the North Atlantic Ocean and reduced solar activity. In the period from around 8600 to 8200 cal. yrs BP the Hani peat record shows a broad δ18O peak that may reflect compound climate signals resulting from the two kinds of forcing factors: the temperature drop related to reduced solar activity at around 8600–8250 cal. yrs BP, and the temperature anomaly attributed to the meltwater effect at around 8220 ± 70 cal. yrs BP. This result may provide palaeo-temperature evidence for existence of the sharp “8.2 k” event in the western North Pacific region. In addition, our results have revealed that in the period from the last deglaciation through the Holocene the synchronous temperature anomalies before and after the “8.2 k” event seem to be related to meltwater outflow and reduced solar activity, respectively. It is important that the all temperature anomalies—whether because of reduced solar activity in the late Holocene or from meltwater discharge in the early Holocene—are accompanied by an abrupt decline in the Indian Ocean summer monsoon and abrupt strengthening of the East Asian summer monsoon. It is likely that reduced solar activity and meltwater outflow appear to modulate Earth system changes in the same direction. The influences could be compounded. Reduced solar activity and meltwater outburst both appear to act as triggers for occurrence of the El Niño phenomenon in the equatorial Pacific Ocean, which may result in broad teleconnections between the temperature anomaly in the Northern Hemisphere and abrupt variation of the Asian monsoon. 相似文献
90.
The results of drift bottle and drift card experiments in the Bohai Sea and Huanghai Sea obtained by researchers of the Institute
of Oceanology, Academia Sinica from 1975–1980 are reported in this article. Of over 50,000 bottles and cards released, around
10,000 were recovered.
The results gave some convincing evidences for the existence of the Huanghai Sea Coastal Current, the Huanghai Sea Warm Current,
the cyclonic movement around the northern Huanghai Sea Cold Water Mass, the anticyclonic eddy in the area near the Shidao-Qingdao
coast and the flow of some of the Huanghai Sea water to the Japan Sea and to the North Pacific off Tokyo. The results show
that the drift bottles and cards are still useful for getting the flow pattern of enclosed and semi-enclosed seas.
Contribution No. 1312, Institute of Oceanology, Academia Sinica, Qingdao. 相似文献