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61.
We have inferred the temperature sensitivity of Dorne Margolin choke ring antennas by direct estimation from differential
clock estimates for two GPS sites separated by 2400 km. At each site, the cable and receiver systems are very well isolated
from environmental variations. By direct comparison of the observed clock variations between these sites with local temperature
measurements, empirical temperature coefficients for each system have been estimated. These thermal coefficients most likely
apply to the only uncontrolled components of the systems, the Dorne Margolin choke ring antennas. Based on these results,
the short-term (diurnal) stability of the antennas appears to be better than 2 ps/°C. The possibility that longer-term effects
exist due to sensitivity in the daily average of the pseudorange observations has not been tested and cannot be excluded.
? 2001 John Wiley & Sons, Inc. 相似文献
62.
We assess two parametrisations of sea-ice in a coupled atmosphere–mixed layer ocean–sea-ice model. One parametrisation represents
the thermodynamic properties of sea-ice formation alone (THERM), while the other also includes advection of the ice (DYN).
The inclusion of some sea-ice dynamics improves the model's simulation of the present day sea-ice cover when compared to observations.
Two climate change scenarios are used to investigate the effect of these different parametrisations on the model's climate
sensitivity. The scenarios are the equilibrium response to a doubling of atmospheric CO2 and the response to imposed glacial boundary conditions. DYN produces a smaller temperature response to a doubling of CO2 than THERM. The temperature response of THERM is more similar to DYN in the glacial case than in the 2×CO2 case which implies that the climate sensitivity of THERM and DYN varies with the nature of the forcing. The different responses
can largely be explained by the different distribution of Southern Hemisphere sea-ice cover in the control simulations, with
the inclusion of ice dynamics playing an important part in producing the differences. This emphasises the importance of realistically
simulating the reference climatic state when attempting to simulate a climate change to a prescribed forcing. The simulated
glacial sea-ice cover is consistent with the limited palaeodata in both THERM and DYN, but DYN simulates a more realistic
present day sea-ice cover. We conclude that the inclusion of simple ice dynamics in our model increases our confidence in
the simulation of the anomaly climate.
Received: 24 May 2000 / Accepted: 25 October 2000 相似文献
63.
天津及邻区1999~2000年地震震源机制研究 总被引:2,自引:0,他引:2
文中使用的是天津市、河北省地震台的 P,Pn波初动方向资料 ,研究了 1 999~ 2 0 0 0年发生在天津及邻区的 4个地震的震源机制。其中 1 999年 8月 1 1日河北省大城县 ML 3.1地震发生在大城断裂上 ,震源机制解的节面 (走向 2 0 8°,倾角 54°,滑动角 1 2°)与大城断裂的走向一致。2 0 0 0年 1月 2 6日蓟县 ML 3.3地震发生在蓟县 -邦均断裂上 ,震源机制解的节面 (走向 2 85°,倾角 77°,滑动角 1 38°)与蓟县 -邦均断裂的走向一致。表明这两个断层在活动 ,这两个地震发生在多年来 (有感 )地震不多的地区 ,并且是发生在首都圈中部 ,应该引起注意 相似文献
64.
IntroductionWith the most feasible and powerful technical support provided by the high-precision GPS measurement for the study on horizontal crustal deformation, the obtainment of various-scale horizontal movement data and its study over the whole world is now in the ascendant, and its applicable fields is now expanding successively. In China, besides the GPS monitoring networks for different applications arranged by many agencies and departments, the key scientific project Crustal Movement… 相似文献
65.
FAN Jiahua Prof. Senior Engineer Inst. Water Conservancy Hydroelectric Power Research P.O. Box Beijing China 《国际泥沙研究》1993,(3)
I. INTRODUCTIONA discharge of 100--200 m3 / s is needed to be diverted from a tidal reach and utilized as cooling water for a Droposed power plant in the Yangtze Estuary. The diversionchannel is divided into two parts by a levee along the river bank, an open channel stretchinside the levee is connected with a trench dredged on the floodplain, as shown in Pig. 1.Since the flow and sediment regimes in these two stretches are different, analysis is madeseparately for each of them.11. ESTI… 相似文献
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E.T.C. Spooner R.D. Beckinsale P.C. England A. Senior 《Geochimica et cosmochimica acta》1977,41(7):857-871
During ocean-floor hydrothermal metamorphism of a 225 m thick allochthonous Jurassic sequence of ophiolitic pillow lavas and underlying material in E. Liguria, Italy, the rocks were hydrated, enriched in 18O and oxidised. H2O+ contents increased from ~0.3 to 3.8 wt.%, δ18O values increased from ~ +6‰ to values as high as +13.2‰, and (1) increased from 0.18 to ratios as high as 1.0. Both δ18O values and oxidation ratios decrease in the original direction of increasing depth. Pillow margins are consistently more enriched in 18O and are more oxidised than cores.These observations are qualitatively interpreted in terms of a non-isothermal, heterogeneous reaction model of interaction of basalt with oxygen-bearing sea water during flow through the packed bed of pillows. Fluid flow approximated undirectional downward motion, and occurred in the recharge part of a cycle of single pass convection. Mass transfer through the pile was by flow (infiltration metasomatism), whereas intra-pillow mass transfer was diffusional. Oxygen isotope exchange and oxidation did not occur under conditions of perfect incremental equilibrium. An integrated bulk volumetric water/rock ratio of ~2 × 103:1 is estimated from the oxidation profile. 相似文献