海洋表层流模式和月尺度海气耦合试验

本文第一部分设计了一个海洋表层流模式，较成功地模拟出冬夏季海表层中的大尺度洋流和海面高度第二部分是月时间尺度的海气耦合试验，将海表层洋流模式和球带范围的大气模式相耦合，用数值试验讨论了洋流和海气耦合方式对模拟结果的影响。     

9406号台风登陆造成华南及长江中游暴雨过程的数值模拟试验

本文应用有限区域数值预报模式，并根据不同的积云参数化方案对１９９４年第６号台风登陆后低压的移动规律及其对应降水分布进行了数值模拟试验，结果表明积云对流参数化对于台风移动及其降水分布影响极大，是作出台风暴雨预报的关键过程。     

Biotite stability in peraluminous granitic melts: Compositional dependence and application to the generation of two-mica granites in the South Bohemian batholith (Bohemian Massif, Czech Republic)

Crystallization experiments have been conducted in the system Na₂O–K₂O–MgO–FeO–Al₂O₃–SiO₂–H₂O (with 4% normative corundum) in order to constrain the stability of biotite as a function of water activity and the Mg# of biotite [Mg/(Mg +Fe_total)] in equilibrium with peraluminous granitic melts. The temperature at which biotite breakdown starts is strongly dependent on the Mg# of biotite. At 500 MPa, the temperature of biotite breakdown to form orthopyroxene increases from 750 °C to 830 °C, as the Mg# of biotite increases from 0.4 to 0.5. Considering that the system investigated is relevant for Ca-poor peraluminous biotite-bearing rocks (metapelites), the biotite dehydration curves obtained are used to discuss the melting reactions and the temperatures that lead to the formation of two distinct types of two-mica granites found in the South Bohemian batholith (specifically the Eisgarn and Deštná granites). The phase relationships were determined experimentally for the composition of these two granites in order to constrain the composition of the biotite in equilibrium with the melt in the protoliths. We demonstrate that Eisgarn granitic melts may have been generated at temperatures in the range 830–850 °C from melting reactions involving biotite with a Mg# up to 0.5 as a reactant. In contrast, Deštná granitic melts cannot have been generated from dehydration melting reactions involving biotite.     

The Influence of the Prandtl Number on the Style of Vigorous Thermal Convection

The effect of the Prandtl number on convection in a planar three-dimensional geometry is investigated in this study. We have employed a numerical scheme to integrate the governing equations. Differently from previous studies we have chosen stress-free boundaries. Experiments have been performed at a Rayleigh number of Ra = 10 6 for Prandtl numbers (Pr) ranging from 0.025 to 100. We have further conducted one experiment in the limiting case of infinite Prandtl number. Despite the differences in the geometry and the boundary conditions, as compared to other studies, we find a similar transition in the dynamics of the flow when the Prandtl number is increased. While the velocity and the temperature structure show diffusive character at low Pr, sharp thermal boundary layers form at high Pr. The heat transport efficiency increases with Pr until a transition value is reached, from there on Nu behaves almost asymptotically. The transition can not be caused by a change in hierarchies between velocity and thermal boundary layers, as suggested in other studies. Due to the stress-free boundaries, a velocity boundary layer does not exist. We observe that the toroidal part of the flow is strong at low Pr and looses its strength with increasing Pr, thus it is likely to be responsible for the transition. In a further chapter we demonstrate that due to the neglect of the toroidal part in two-dimensional calculations at low Pr results are obtained which are misleading, even in a qualitative sense. Infinite Pr results from 2D calculations closely resemble the dynamics of fully 3D flows.     

Dynamics of explosive volcanism at Unzen volcano: an experimental contribution

Knowledge of the dynamics of magma fragmentation is necessary for a better understanding of the explosive behaviour of silicic volcanoes. Here we have measured the fragmentation speed and the fragmentation threshold of five dacitic samples (6.7–53.5 vol% open porosity) from Unzen volcano, Kyushu, Japan. The measurements were carried out using a shock-tube-based fragmentation apparatus modified after Alidibirov and Dingwell (1996a,b). The results of the experimental work confirm the dominant influence of porosity on fragmentation dynamics. The velocity of the fragmentation front increases and the value of the fragmentation threshold decreases with increasing porosity. Further, we observe that the fragmentation speed is strongly influenced by the initial pressure difference and the texture of the dacite. At an initial pressure difference of 30 MPa, the fragmentation speed varies from 34 m/s for the least porous sample to 100 m/s for the most porous sample. These results are evaluated by applying them to the 1990–1995 eruptive activity of Unzen volcano. Emplacements of layered lava dome lobes, Merapi-type pyroclastic flows and minor explosive events dominated this eruption. The influence of the fragmentation dynamics on dome collapse and Vulcanian events is discussed.     

The Deep Impact oblique impact cratering experiment

The Deep Impact probe collided with 9P Tempel 1 at an angle of about 30° from the horizontal. This impact angle produced an evolving ejecta flow field very similar to much smaller scale oblique-impact experiments in porous particulate targets in the laboratory. Similar features and phenomena include a decoupled vapor/dust plume at the earliest times, a pronounced downrange bias of the ejecta, an uprange “zone of avoidance” (ZoA), heart-shaped ejecta ray system (cardioid pattern), and a conical (but asymmetric) ejecta curtain. Departures from nominal cratering evolution, however, provide clues on the nature of the impact target. These departures include: fainter than expected flash at first contact, delayed emergence of the self-luminous vapor/dust plume, uprange-directed plume, narrow early-time uprange ray followed by a late-stage uprange plume, persistence of ejecta asymmetries (and the uprange ZoA) throughout the approach sequence, emergence of a downrange ZoA at late times, detachment of uprange curved rays, very long lasting non-radial ejecta rays, and high-angle ejecta plume lasting over the entire encounter. The first second of crater formation most closely resembles the consequences of a highly porous target, while later evolution indicates that the target may be layered as well. Experiments also reveal that impacts into highly porous targets produce a vapor/dust plume directed back up the incoming trajectory. This uprange plume is attributed to cavitation within a narrow penetration funnel. The observed lateral expansion speed of the initial vapor plume downrange provides an estimate for the total vaporized mass equal to ∼5mp (projectile masses) of water ice or 6mp of CO₂. The downrange plume speed is consistent with the gas expansion added to the downrange horizontal component of the DI probe. Based on high-speed spectroscopy of experimental impacts, the observed delay in brightening of the DI plume may be the result of delayed condensation of carbon, in addition to silicates. Observed molecular species in the initial self-luminous vapor plume likely represent recombination products from completely dissociated target materials. The crater produced by the impact can be estimated from Earth-based observations of total ejected mass to be 130-220 m in diameter. This size range is consistent with a 220 m-diameter circular feature at the point of impact visible in highly processed, deconvolved HRI images. The final crater, however, may resemble an inverted sombrero-hat, with a deep central pit surrounded by a shallow excavation crater. Excavated distal material observed from the Earth was likely from the upper few meters contrasted with ballistic ejecta observed from the DI flyby, which included deep materials (10-30 m) within the diffuse plume above the crater and shallower (5-10 m) materials within the ejecta curtain.     

Optical measurements of tsunami inundation through an urban waterfront modeled in a large-scale laboratory basin

This paper presents optical measurements of tsunami inundation through an urban waterfront in a laboratory wave basin. The physical model was constructed at 1:50 scale and was an idealization of the town of Seaside, Oregon. The fixed-bed model was designed to study the initial inundation zone along an urban waterfront, such that the flow around several large buildings could be observed. This paper presents an analysis of the optical measurements made with two overhead video cameras, focusing on tracking the leading edge of the tsunami inundation through the urban waterfront and quantifies the accuracy of the algorithm used to track the edge. The results show that the methodology provides high-resolution information in both time and space of the leading edge position, and that these data can be used to quantify the influence of large macro-roughness features on the tsunami inundation processes in laboratory settings. The overall effect of the macro-roughness was to decrease the bore propagation speed relative to the control section with no macro-roughness. The bore speed could be reduced by as much as 40% due to the presence of the macro-roughness relative to the control section.     

Design of a model blasting system to measure peak p-wave stress

Literature review information and model scale rock blasting tests have been utilized to study the effects of some blast and fragmentation parameters on peak p-wave stress. A method for modelling scaled blasting in sandstone blocks with dimensions 515×335×215 mm³ has been presented. The dynamic and static properties of the sandstone are given. The results from model blasting experiments instrumented with pressure gauges are discussed. It is also shown there exists a useful correlation between blast, fragmentation parameters and peak p-wave stress.     

EXPERIMENTAL STUDY ON BED SCOUR IN A 90° CHANNEL BEND

1 INTRODUCTION Scouring in the bend ways leads to deep sections at the toe of the outer bank of the bend. The presenceof secondary currents and the greater depths at the outer bank cause high velocity along the outer bank.The high velocity and shear stres…     

浅议CE法在我国盐湖生态系统服务价值评估中的适宜性

随着西部大开发战略的实施,盐湖资源的开发利用程度越来越高,为我国西部经济的快速发展做出了很大的贡献。由于人们对盐湖生态价值缺乏认识,盐湖资源开发过程中存在先开发后治理的趋向,使盐湖生态系统服务功能逐步下降,严重阻碍了盐湖资源的可持续开发利用。盐湖生态系统服务价值评估对其资源的合理开发利用、环境保护及实现可持续利用等方面有着重要的意义。系统回顾各类生态系统服务价值评估方法,结合盐湖生态系统服务的特点,对比分析其适用性及优缺点。结果表明,采用CE法对盐湖生态系统服务价值进行评估具有很大的优势,能较好且全面地体现其生态系统服务价值,对盐湖资源的保护及可持续利用具有重要的意义。