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951.
Ji Yang Ying-Xi Zuo Zheng LOU Jing-Quan Cheng Qi-Zhou Zhang Sheng-Cai Shi Jia-Sheng Huang Qi-Jun Yao Zhong Wang 《天体物理学报》2013,(12):1493-1508
As the highest, coldest and driest place in Antarctica, Dome A provides exceptionally good observing conditions for ground-based observations over terahertz wavebands. The 5 m Dome A Terahertz Explorer (DATES) has been proposed to explore new terahertz windows, primarily over wavelengths between 350 and 200 pm. DATE5 will be an open-air, fully-steerable telescope that can function by unmanned operation with remote control. The telescope will be able to endure the harsh polar environment, including high altitude, very low temperature and very low air pressure. The unique specifications, including high accuracies for surface shape and pointing and fully automatic year-around remote operation, along with a stringent limit on the periods of on-site assembly, testing and maintenance, bring a number of challenges to the design, construction, assembly and operation of this telescope. This paper intro- duces general concepts related to the design of the DATE5 antenna. Beginning from an overview of the environmental and operational limitations, the design specifications and requirements of the DATE5 antenna are listed. From these, major aspects on the conceptual design studies, including the antenna optics, the backup structure, the pan- els, the subreflector, the mounting and the antenna base structure, are explained. Some critical issues of performance are justified through analyses that use computational fluid dynamics, thermal analysis and de-icing studies, and the proposed approaches for test operation and on-site assembly. Based on these studies, we conclude that the specifications of the DATE5 antenna can generally be met by using enhanced technological approaches. 相似文献
952.
As a solid reservoir, a glacier can regulate regional water resources. The annual net mass balance directly reflects the
fluctuation of the glacier and climate variability. Based on 51 years of mass balance observation data, the mass balance of
Tianshan Mountains Urumqi Glacier No. 1 experienced a nine times positive balance fluctuation and nine times negative
balance fluctuation. There were 35 and 16 negative and positive balance years, respectively. From 1996/97 to 2008/09, 12
consecutive negative balance years were observed at Tianshan Mountains Urumqi Glacier No. 1. These results demonstrate
that the Urumqi Glacier No. 1 is experiencing a strong negative balance, and the strongest negative balance, -931
mm w.e. (mm water equivalent), during the observation period occurred in 2008. In addition, the cumulative mass balance
reached 13,709 mm w.e. in 2008. However, in 2009, the mass balance was positive at 63 mm w.e. The equilibrium-line altitude
changes with the fluctuation in the mass balance, and the effective mass balance gradient is 7.4 mm/m. In this paper,
the headwaters of the Urumqi River were analyzed using meteorological data from 1958 to 2009, including the average
seasonal temperature and precipitation. The results showed that the main factor associated with the mass balance variation
of Glacier No. 1 is the fluctuation in the summer air temperature, followed by changes in the precipitation. 相似文献
953.
The principle of water balance is well known, but its application often causes controversy. One recent debate is the use of the water balance equation to determine the safe yield and sustainable yield. Two extreme opinions exist on natural groundwater recharge. One misconception is that the development of groundwater is considered to be safe if the pumping rate does not exceed the rate of natural recharge. Another is that the sustainable pumping rate has nothing to do with natural recharge, but depends on the increased recharge and decreased discharge (called capture) induced by pumping. The truth is that both the natural recharge and dynamic development of the capture determine the safe yield or sustainable yield of a groundwater basin. This paper clarifies the water budget controversy and uses the water balance equation to critically analyse the concepts of safe yield and sustainable yield. Numerical simulation of a hypothetical case was used to demonstrate the natural groundwater balance, effects of pumping and the dynamic development of the capture. 相似文献
954.
955.
956.
设定地震及其烈度影响判别 总被引:1,自引:0,他引:1
设定地震常用于震害预测、地震小区划和重大工程选址,烈度衰减模型反映了地震引起的地面震动及其影响的强弱程度分布。设定地震包括确定性和非确定性设定两种方法,确定性方法基于构造或历史地震,非确定性方法是基于概率危险性方法,用于估计区域或城市未来可能遭遇的地震危险。缺失等震线或震害记载不详的历史地震和概率设定地震都不能确切地反映地震破坏影响,借助于烈度衰减关系模型和GIS,可直观地判别其影响分布情况,便于设定地震的取舍。 相似文献
957.
O.?NovotnyEmail author J.?Jansky V.?Plicka H.?Lyon-Caen 《Studia Geophysica et Geodaetica》2008,52(1):123-131
The western part of the Gulf of Corinth attracts attention due to its seismically active fault system and considerable seismic
hazard. Detailed studies of the seismic activity of the region have been carried out especially as part of the so-called Corinth
Rift Laboratory (CRL) Project. For standard earthquake locations, the CRL uses the HYPO algorithm and a special structural
model that is composed of homogeneous layers (Rigo et al., 1996). This model was derived from a passive seismic experiment
in a broader area around the western part of the Gulf. A significant part of the seismic activity is concentrated close to
the town of Aigion, which was damaged by a strong earthquake in 1995. A sequence of smaller earthquakes occurred to the south
of this town in the year 2001. In the present paper, we have used this sequence to derive an improved structural model for
the region in the vicinity of the town of Aigion. This new model is based on the minimization of travel-time residuals. In
particular, we used arrival times from a subset of 88 events recorded by at least 5 stations of the southern part of the CRL
network, had magnitudes of over 2.3, and were recorded at the nearest station (station code AIO). A variant of the method
of conjugate gradients has been used for this purpose. In comparison with the model derived by Rigo et al. (1996), the new
model is characterized by a higher νP/νS velocity ratio and by higher velocities to a depth of about 7 km. The new model was derived with the aim to get more accurate
locations of future events in the vicinity of the town of Aigion. 相似文献
958.
959.
The main purpose of this paper is comparison of two different approaches of solution to the Simple Molodensky’s Problem, the
Molodensky’s Approach and the Analytical Continuation Approach, based on numerical computation. Although these approaches
have been described theoretically by several authors, e.g. Molodensky et al. (1960), Heiskanen and Moritz (1967), Vaníček
(1974), Moritz (1980) and Holota (1991, unpublished results) and theoretical proof of equivalence was given by Heiskanen and
Moritz (1967), Moritz (1971), Ecker (1971) and Pellinen (1972, unpublished results), only very few practical experiences about
the differences between particular solutions and computational efficiency exist. In this paper we compare the above two mentioned
approaches in terms of the G1-effect on quasigeoid. Both quasigeoid solutions are tested by the independent GPS/levelling approach and are also compared
with the previous quasigeoid model of Slovakia where the G1-term has been approximated using the classical terrain correction. The effect of the G2-term is also numerically estimated, revealing that it might be significant for the precise quasigeoid determination. Some
practical comments and recommendations are given at the end of the paper. 相似文献
960.
T. Francke J. A. López‐Tarazón D. Vericat A. Bronstert R. J. Batalla 《地球表面变化过程与地形》2008,33(13):2064-2077
Upland erosion and the resulting reservoir siltation is a serious issue in the Isábena catchment (445 km2 Central Spanish Pyrenees). During a three‐month period, water and sediment fluxes have been monitored at the catchment outlet (Capella), two adjacent subcatchments (Villacarli, 41 km2; Cabecera, 145 km2) and the elementary badland catchment Torrelaribera (8 ha). This paper presents the results of the monitoring, a method for the calculation of a sedigraph from intermittent measurements and the derived sediment yields at the monitored locations. The observed suspended sediment concentrations (SSCs) demonstrate the role of badlands as sediment sources: SSCs of up to 280 g l?1 were encountered for Villacarli, which includes large badland areas. SSCs at the Cabecera catchment, with great areas of woodland, barely exceeded 30 g l?1. SSCs directly at the sediment source (Torrelaribera) were comparable to those at Villacarli, suggesting a close connection within this subcatchment. At Capella, SSCs of up to 99 g l?1 were observed. For all sites, SSC displayed only a loose correlation with discharge, inhibiting the application of a simple sediment rating curve. Instead, ancillary variables acting as driving forces or proxies for the processes (rainfall energy, cumulative discharge, rising/falling limb data) were included in a quantile regression forest model to explain the variability in SSC. The variables with most predictive power vary between the sites, suggesting the predominance of different processes. The subsequent flood‐based calculation of sediment yields attests high specific sediment yields for Torrelaribera and Villacarli (6277 and 1971 t km?2) and medium to high yields for Cabecera and Capella (139 and 410 t km?2) during the observation period. In all catchments, most of the sediment was exported during intense storms of late summer. Later flood events yield successively less sediment. Relating upland sediment production to yield at the outlet suggests considerable effects of sediment storage within the river channel. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献