亚毫米波射电天文用超导SIS接收机的研制(英文)     

史生才 《紫金山天文台台刊》2003,(1)

为了研制亚毫米波射电天文用超导SIS(超导 -绝缘体 -超导 )接收机 ,我们重点开展了如下研究 ,1 )Nb超导SIS结在其能隙频率附近的量子混频特性 ,及其结合高能隙超导薄膜 (NbTiN)和高电导率金属薄膜 (Al)分布结阵在 780 - 950GHz频率区间的量子混频特性 ;2 )亚毫米波超导混频器嵌入阻抗的数值和实验表征 ;3)高电流密度小面积Nb超导SIS结的制备和特性表征 ;4)一个 60 0 - 72 0GHz超导SIS混频器的研制和特性表征。本文详细介绍了相关的数值分析和实验测量结果。  相似文献   

Tidal effects on temperature front in the Yellow Sea   总被引：5，自引：0，他引：5  

Ma Jian  Qiao Fangli  Xia Changshui  Yang Yongzeng 《中国海洋湖沼学报》2004,22(3):314-321

Temperature front (TF) is one of the important features in the Yellow Sea, which forms in spring, thrives in summer, and fades in autumn as thermocline declines. TF intensity ⋎S _T ⋎ is defined to describe the distribution of TF. Based on the MASNUM wave-tide-circulation coupled model, temperature distribution in the Yellow Sea was simulated with and without tidal effects. Along 36°N, distribution of TF from the simulated results are compared with the observations, and a quantitative analysis is introduced to evaluate the tidal effects on the forming and maintaining processes of the TF. Tidal mixing and the circulation structure adapting to it are the main causes of the TF. Supported by the National Basic Research Program of China (No. G1999043809) and the National Science Foundation of China (No. 49736190).  相似文献   

The Latest Research Progress on El Nino     

CHEN Dianyou  WANG Ruiting  WANG Xudong 《世界地质(英文版)》2002,5(1)

Cold water in the deep Pacific can be drawn up to the surface (or west warm water drifts eastwards ) because strong tide increases the mixing of seawater both in vertical and horizontal. In this way greenhouse effect is decreased or increased by means of absorbing (or releasing) CO2. Therefore, La Nina cold event (or El Nino warm event) may occur,which is caused by wanning - up or cooling - down air above the ocean. Volcanic action at sea bottom is also controlled by strong tide.  相似文献   

Studying Hydrodynamic Instability Using Shock-Tube Experiments     

O. Sadot  K. Levy  A. Yosef-Hai  D. Cartoon  Y. Elbaz  Y. Srebro  G. Ben-Dor  D. Shvarts 《Astrophysics and Space Science》2005,298(1-2):305-312

The hydrodynamic instability, which develops on the contact surface between two fluids, has great importance in astrophysical phenomena such as the inhomogeneous density distribution following a supernova event. In this event acceleration waves pass across a material interface and initiate and enhance unstable conditions in which small perturbations grow dramatically. In the present study, an experimental technique aimed at investigating the above-mentioned hydrodynamic instability is presented. The experimental investigation is based on a shock-tube apparatus by which a shock wave is generated and initiates the instability that develops on the contact surface between two gases. The flexibility of the system enables one to vary the initial shape of the contact surface, the shock-wave Mach number, and the density ratio across the contact surface. Three selected sets of shock-tube experiments are presented in order to demonstrate the system capabilities: (1) large-initial amplitudes with low-Mach-number incident shock waves; (2) small-initial amplitudes with moderate-Mach-number incident shock waves; and (3) shock bubble interaction. In the large-amplitude experiments a reduction of the initial velocity with respect to the linear growth prediction was measured. The results were compared to those predicted by a vorticity-deposition model and to previous experiments with moderate- and high-Mach number incident shock waves that were conducted by others. In this case, a reduction of the initial velocity was noted. However, at late times the growth rate had a 1/t behavior as in the small-amplitude low-Mach number case. In the small-amplitude moderate-Mach number shock experiments a reduction from the impulsive theory was noted at the late stages. The passage of a shock wave through a spherical bubble results in the formation of a vortex ring. Simple dimensional analysis shows that the circulation depends linearly on the speed of sound of the surrounding material and on the initial bubble radius.  相似文献   

Experimental study on the deterioration and natural remediation of the Ariake Sea tidal mud caused by the sea laver treatment acid practice and the upward seepage of pore water liquid     

Yan-Jun Du  Song-Yu Liu  Shigenori Hayashi 《Environmental Geology》2008,55(4):889-900

This study presents a laboratory study of the following two aspects: (1) the influence of sea laver treatment acid on the geoenvironmental properties of Ariake Sea tidal mud, and (2) the natural remediation effect on the sea laver treatment acid contaminated Ariake Sea tidal mud caused by the upward seepage of pore water liquid in the mud. Firstly, the mechanisms of the transport of sea laver treatment acid in the Ariake Sea tidal mud and the generation mechanisms of the upward seepage flow in the Ariake Sea tidal mud are discussed. Secondly, a series of one-dimensional laboratory infiltration tests were carried out to investigate the deterioration of the Ariake Sea tidal mud caused by the sea laver acid treatment practice. Test results reveal that the acid treatment practice caused considerable change in the geochemical properties of the mud in terms of increase in sulfide content and decrease in pH value. After the treatment by the sea laver treatment acid, the sulfide content of the mud even exceeded the safe limit value for the benthos, which represents undesirable living condition for benthos. Thirdly, series of laboratory fresh seawater infiltration tests for the deteriorated Iida site mud were conducted to illustrate this natural remediation efficiency. It is found that with the infiltration of the fresh seawater, the sulfide content of the Iida site mud was considerably reduced and pH value increased to an acceptable range for benthos living in the tidal flat mud. With the increase in the infiltration time and the hydraulic gradient, the remediation efficiency could be increased.  相似文献   

Magma Ascent and Crustal Accretion at Ultraslow-Spreading Ridges: Constraints from Plagioclase Ultraphyric Basalts from the Arctic Mid-Ocean Ridge   总被引：2，自引：0，他引：2  

Hellevang  Bjarte; Pedersen  Rolf B. 《Journal of Petrology》2008,49(2):267-294

Plagioclase ultraphyric basalts (PUBs) with up to 54% plagioclasephenocrysts were dredged in the rift valley and adjacent flanksof the ultraslow-spreading Mohns and Knipovich ridges. The PUBsshow large variations in crystal morphologies and zoning. Thelarge variations suggest that single basalt samples containa mixture of plagioclase crystals that aggregated at differentlevels in the magma conduits. Resorbed crystals and repeatedreverse zones suggest that the magma reservoirs were replenishedand heated several times. Thin concentric zones with melt inclusions,and sharp reductions in the anorthite content of 3–7%,are common between the reverse zones. These zones, and skeletalcrystals with distinctly lower anorthite contents than massivecrystals, are interpreted to be the result of rapid crystalliztionduring strong undercooling. The changes between short periodsof cooling and longer periods with reheating are explained bymultiple advances of crystal-rich magma into cool regions followedby longer periods of gradual magma inflow and temperature increase.The porphyritic basalts are characterizd by more depleted andmore fractionated compositions than the aphyric basalts, withlower (La/Sm)_N, K₂O and Mg-numbers. This relationship, and theobservation that PUBs are sampled only close to segment centresalong these ridges, suggests that the PUBs formed by higherdegrees of melting and evolved in more long-lived magma reservoirs.We propose that the zoning patterns of plagioclase crystalsand crystal morphologies of these PUBs reflect the developmentand flow of magma through a stacked sill complex-like conduitsystem, whereas the aphyric equivalents represent later flowof magma through the conduit. The formation of voluminous higher-degreemelts may trigger the development of the magma conduits andexplain the generally depleted compositions of PUB magmas. KEY WORDS: basalt; mineral chemistry; MORB; magma mixing; magma chamber; major element  相似文献   

Tidal inundation mapping under enhanced land subsidence in Semarang,Central Java Indonesia   总被引：3，自引：0，他引：3  

Muh Aris Marfai  Lorenz King 《Natural Hazards》2008,44(1):93-109

Tidal inundation by high tide under enhanced land subsidence is a damaging phenomenon and a major threat to the Semarang urban area in Indonesia. It impacts on economic activities, as well as the cost of an emergency program and causes interruption of pubic services, danger of infectious diseases and injury to human lives. This study examines a spatial analysis tool on the GIS-raster system for the tidal inundation mapping based on the subsidence-benchmark data and modified detail digital elevation model. Neighborhood operation and iteration model as a spatial analysis tool have been applied in order to calculate the encroachment of the tidal inundation on the coastal area. The resulting map shows that the tidal flood spreads to the lowland area and causes the inundation of coastal settlement, infrastructure, as well as productive agricultural land, i.e., the fish-pond area. The monitoring of the vulnerable area due to the tidal inundation under the scenario of extended land subsidence plays an important role in long-term coastal zone management in Semarang.  相似文献   

江西永平铜矿区花岗岩热液蚀变与岩石成因:矿物化学、元素地球化学和Sr-Nd-Hf同位素制约   总被引：15，自引：11，他引：4  

朱碧  蒋少涌  丁昕  姜耀辉  倪培  顾连兴 《岩石学报》2008,24(8)

永平铜矿床是位于华南钱塘江-信江断裂坳陷带中的一个大型铜矿床.矿区内出露的岩浆岩主要有似斑状黑云母花岗岩体和少量石英斑岩脉,黑云母花岗岩岩体内及接触带发育斑岩型和矽卡岩型铜钼钨多金属矿化.对岩体中黑云母的电子探针成分分析表明,似斑状黑云母花岗岩中黑云母具有富镁贫铁高钛的特点,Fe/(Fe Mg)为0.21～0.33,TiO2含量为2.12%～4.28%;而石英斑岩脉中黑云母更加富镁贫铁,Fe/(Fe MS)为0.10～0.15,TiO2含量为2.43%～3.86%.黑云母的化学组成表明花岗质岩浆形成时的氧逸度很高,与长江中下游地区其他含铜花岗质岩体相吻合.永平花岗岩体遭受了较强的热液蚀变作用,部分黑云母蚀变为绿泥石.石英斑岩中绿泥石具有富铁贫镁低钛的特征(Fe/(Fe Mg)=0.72～0.76;TiO2=0.02%～0.06%),其形成温度为139～224℃.而似斑状黑云母花岗岩中绿泥石相对贫铁富镁高钛(Fe/(Fe Mg)=0.36～0.44;TiO2=0.05%～0.36%),形成温度稍高,为229～346℃,与该矿床流体包裹体研究获得的成矿温度(220～400℃)基本吻合.Sr-Nd-Hf同位素综合研究表明,永平似斑状黑云母花岗岩具有变化较大且相对较高的εHf(t)值(-0.1～-10.3)和εNd(t)值(-5.83～-7.95),反映岩石具有明显的壳幔混合成因特征.而石英斑岩的εHf(t)值(-8.4～-12.5)和εNd(t)值(-9.93～-10.2)均稍低于似斑状黑云母花岗岩,反映其形成过程中幔源物质贡献相对较小.永平岩体的地壳端元很可能就是该区中元古代基底地层重熔的产物.  相似文献   

Temporal variability of Pb fluxes and bioturbation in shelf sediments beneath the high primary production area off Concepción, central-southern Chile (36°S)     

Praxedes Muñoz  Javier Sellanes  Carina Lange  Maritza Palma 《Progress in Oceanography》2007,75(3):586-602

We estimated monthly fluxes of ²¹⁰Pb in shelf sediments beneath a high productivity area off central-southern Chile (36°S) during 1 year (September 2002-August 2003). Sediment cores were obtained using a multiple corer and were analyzed mainly for ²¹⁰Pb, total pigments, and macrofauna abundance. The ²¹⁰Pb inventories and fluxes were estimated for surface sediments (0-5 cm) and bioturbation coefficients were inferred using chlorophyll-a (reactive) profiles. In general, ²¹⁰Pb content was inversely correlated with phytodetritus fluxes. High photosynthetic pigment contents in surface sediments were consistently associated with lower ²¹⁰Pb contents. Macrofaunal activity responded to oxygen and organic matter supplies at the sediment surface, generally concentrated in the first centimeters, but particularly so during months of high organic matter fluxes and deficient bottom water oxygen conditions. At this study site, several processes involved in the ²¹⁰Pb surface distribution make it difficult to accurately estimate ages at the surface. We postulate that the organic fluxes promote changes in the faunal activity, which, in combination with sediment resuspension and water circulation over the shelf, produce seasonal variations in the ²¹⁰Pb inventories.  相似文献   

Tidal and Subtidal Flow along a Cross-Shelf Transect on the East China Sea     

Arnoldo Valle-Levinson  Takeshi Matsuno 《Journal of Oceanography》2003,59(5):573-584

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