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981.
基于层状导电和可极化大地表面,电偶源电场的时间谱在无随机干扰和有随机干扰时,进行频谱转换的计算结果,证明了时—频转换的误差传递问题严重。但是,采用窗口(圆滑)滤波可以有效压制随机干扰,使时—频转换达到必要的计算精度。 相似文献
982.
针对边界条件取值过于保守导致架空输电线路载流量过小而无法充分发挥输电线路的载流能力的问题,本文提出了一种基于K-Means算法的架空输电线路载流量计算方法.首先对历史气象数据进行统计分析,然后根据每月气象数据的相似性,使用K-Means算法划分时段,并选取各时段最为合适的边界条件,最后基于选定的边界条件使用摩根公式进行仿真计算.通过这种方法,可以在保证线路运行安全的条件下挖掘输电线路的隐性输送能力. 相似文献
983.
Mário E.C. Vieira 《Estuarine, Coastal and Shelf Science》1985,21(3):411-427
Utilizing 20 days of current meter and sea level elevation records taken in two cross-sections in mid-Chesapeake Bay an objective interpolation procedure was devised to allow the computation of vertical profiles of the laterally integrated subtidal volume fluxes at each section, at 3-h intervals over the period of the experiment. The presence of a classical mean estuarine circulation was observed; however, departures from this gravitational circulation were revealed on a shorter time scale, reaching the value of 20 000 m3 s?1 over a day, and featuring behaviors of reverse estuarine, storage and discharge modes.The volume flux computations through each cross-section based on the measured current velocities, the freshwater inflow and the calculated Stokes transport were in agreement with each other. A two-layered box model of the mean subtidal circulation in the segment of the estuary bound by the two cross-sections is offered.A comparison was made between the computations of net volume flux into and out of the Bay above these sections using two independent methods: (1) the accounting of volume continuity based upon direct measurements of volume flux through the sections; and (2) the direct calculation of the time rate of change of volume of the upper Bay obtained from tide gauge records. The agreement between the two results was found to be very good. Further evidence is provided for the upward phase propagation of the oscillations in the residual motion of estuarine waters. 相似文献
984.
Information obtained from various parts of the two books on Montagne Pelée by Lacroix enables an estimate to be made of the size of l’Etang Sec summit crater, the volume of the 1902–1905 lava dome and its growth rate at various stages of development. During the week preceding the 8 May nuée ardente, dome growth was between 28 and 38 m3 s–1, leading to a volume of 17–23×106 m3 on the morning of the catastrophe. Considering that significant parts of the dome (~1/3?) were removed by the 8 and 20 May climactic eruptions, a high magmatic flux could have continued until at least 27 May, when the total remaining volume was estimated to 53×106 m3. After moderate activity in June–July (of order 10 m3 s–1), vigorous dome growth resumed dramatically, leading to the third climactic eruption of 30 August (a true calculation for this period being not feasible because of poor quality of the data). From November 1902 to July 1903 most of the effusive activity was concentrated in the great spine (erupted volume ~15×106 m3, magma flux 1.2 m3 s–1), which was eventually destroyed by collapse and minor nuées ardentes. The end of the eruption was characterized by a very low effusion rate, <1 m3 s–1 in average from August 1903 to October 1905. 相似文献
985.
Complex proximal deposition during the Plinian eruptions of 1912 at Novarupta,Alaska 总被引:2,自引:1,他引:1
Bruce?F.?HoughtonEmail author C.?J.?N.?Wilson J.?Fierstein W.?Hildreth 《Bulletin of Volcanology》2004,66(2):95-133
Proximal (<3 km) deposits from episodes II and III of the 60-h-long Novarupta 1912 eruption exhibit a very complex stratigraphy, the result of at least four transport regimes and diverse depositional mechanisms. They contrast with the relatively simple stratigraphy (and inferred emplacement mechanisms) for the previously documented, better known, medial–distal fall deposits and the Valley of Ten Thousand Smokes ignimbrite. The proximal products include alternations and mixtures of both locally and regionally dispersed fall ejecta, and numerous thin complex deposits of pyroclastic density currents (PDCs) with no regional analogs. The locally dispersed component of the fall deposits forms sector-confined wedges of material whose thicknesses halve radially from and concentrically about the vent over distances of 100–300 m (cf. several kilometers for the medial–distal fall deposits). This locally dispersed fall material (and many of the associated PDC deposits) is rich in andesitic and banded pumices and richer in shallow-derived wall-rock lithics in comparison with the coeval medial fall units of almost entirely dacitic composition. There are no marked contrasts in grain size in the near-vent deposits, however, between locally and widely dispersed beds, and all samples of the proximal fall deposits plot as a simple continuation of grain size trends for medial–distal samples. Associated PDC deposits form a spectrum of facies from fines-poor, avalanched beds through thin-bedded, landscape-mantling beds to channelized lobes of pumice-block-rich ignimbrite. The origins of the Novarupta near-vent deposits are considered within a spectrum of four transport regimes: (1) sustained buoyant plume, (2) fountaining with co-current flow, (3) fountaining with counter-current flow, and (4) direct lateral ejection. The Novarupta deposits suggest a model where buoyant, stable, regime-1 plumes characterized most of episodes II and III, but were accompanied by transient and variable partitioning of clasts into the other three regimes. Only one short period of vent blockage and cessation of the Plinian plume occurred, separating episodes II and III, which was followed by a single PDC interpreted as an overpressured "blast" involving direct lateral ejection. In contrast, regimes 2 and 3 were reflected by spasmodic sedimentation from the margins of the jet and perhaps lower plume, which were being strongly affected by short-lived instabilities. These instabilities in turn are inferred to be associated with heterogeneities in the mixture of gas and pyroclasts emerging from the vent. Of the parameters that control explosive eruptive behavior, only such sudden and asymmetrical changes in the particle concentration could operate on time scales sufficiently short to explain the rapid changes in the proximal 1912 products.Editorial responsibility: R. Cioni 相似文献
986.
987.
988.
《海洋学报(英文版)》1997,16(4):537-551
Reseach on three-dimensional tide current mathemtical model of coast and its applicationTXReseachonthree-dimensionaltidecurren... 相似文献
989.
宽带多卜勒测流仪(BBADCP)信号特性分析 总被引:11,自引:0,他引:11
本文介绍了二进制相应编码测流声纳(BBADCP)信号的相关和频谱特性,讨论了有关参数选择的原则。 相似文献
990.
I~IOWIn winter, on the impacts Of the Chriolis force and the current along the shore of the EastChina ho, the residual current from the Changjiang River flows south along the shore and enters the ~ Bay in the north, then it moves out of the bay in the south and flows southin the East China Sea (Su and Wang, 1989; Zhu and Shen, 1997). In recent years, scholars have made further analyse on obSerVed date, and have obtained more profound viewson the residual current and mass transport (Pn … 相似文献