盐湖丰产元素与Zintl化合物(续完)

Zintl化合物是以Edward Zintl命名的化合物,是一类由电正性的碱金属或碱土金属与电负性的13族或14族元素形成的特殊金属间化合物。其价键模式可以是离子键、金属键和共价键共存,其中的准金属可以共价键的形式形成各种形式的离子簇,因而其结构复杂多样。这类化合物的部分阴离子簇不仅具有稳定的笼状、层状和链状结构,并且具有特殊的光、电、磁等性能,使得在半导体、催化、电极材料等方面都有应用的前景和发展潜力。介绍了几个特殊Zintl化合物体系,盐湖丰产元素在Zintl化合物中的作用,指出了含有盐湖丰产元素的Zintl化合物的应用前景和方向。     

山地灾害和人类活动干扰下九寨沟下季节海的沉积变化

九寨沟是我国旅游强度最大的山地旅游地之一,山地灾害是其旅游发展过程中面临的主要挑战.为了探讨山地灾害和人类活动对湖泊生态系统的影响,以下季节海湖泊沉积物为研究对象,利用137Cs和210Pb建立年代标尺,对沉积物粒度进行了分析.137Cs和210Pb定年法确定湖底下38.5 cm处为1952年的沉积物,50 cm处为1848年的;沉积物粒度分析结果显示,剖面内中值粒径平均值偏大,沉积速率和粗颗粒含量在1952年之后呈明显增大趋势.结果表明,沉积物来源主要是泥石流等山地灾害造成的泥砂人湖、旅游开发过程中道路等基础设施建设带来的颗粒物质;湖泊沉积对流域内的山地灾害,如泥石流等有较好的响应;森林采伐和旅游开发在一定程度上促进了湖泊沉积.     

Climatic changes have led to significant expansion of endorheic lakes in Xizang (Tibet) since 1995

Robust climate warming has led to significant expansion of lakes in the central Tibetan Plateau. Using remote sensing data, our quantitative analysis indicates that Siling Co, a saline lake in a characteristic endorheic basin in the central region of the Plateau, has expanded more than 600 km² in area since 1976. Particularly since 1995, the lake has significantly expanded in response to increasing precipitation, decreasing water surface evaporation caused by weaker winds and less solar radiation, and increased glacier meltwater draining to the lake. Glacier–lake interactions are important in governing lake expansion and are also part of a feedback loop that influences the local climate. Worsening climatic conditions (decreased precipitation and increased temperatures) that could have caused the lake to shrink during 1976–1994 were offset by increasing glacier meltwater feeding the lake, which made the lake nearly stable. We demonstrate that this pattern changed during 1995–2009, when glacier meltwater actually decreased but participation runoff increased and evaporation decreased, leading to expansion of the lake. If climatic conditions became suitable for further lake development, which would be indicated by expansion in lake area, glacier meltwater could be saved in a stable reservoir.     

Analysis and prediction of vortex-induced vibrations of variable-tension vertical risers in linearly sheared currents

Many studies have tackled the problem of vortex-induced vibrations (VIV) of a vertical riser with a constant tension and placed in uniform currents. In this study, attention is focused on the cross-flow VIV modelling, time-domain analysis and prediction of variable-tension vertical risers in linearly sheared currents. The partial-differential equation governing the riser transverse motion is based on a flexural tensioned-beam model with typical pinned-pinned supports. The hydrodynamic excitation model describing the modulation of lift force is based on a distributed van der Pol wake oscillator whose nonlinear equation is also partial-differential due to the implementation of a diffusion term. The variation of empirical wake coefficients with system parameters and the water depth-dependent Reynolds number is introduced. Based on the assumed Fourier mode shape functions obtained by accounting for the effect of non-uniform tension, the Galerkin technique is utilized to construct a low-dimensional multi-mode model governing the coupled fluid-riser interaction system due to VIV. Numerical simulations in the case of varying sheared flow profiles are carried out to systematically evaluate riser nonlinear dynamics and highlight the influence of fluid-structure parameters along with associated VIV aspects. In particular, the effects of shear and tensioned-beam (tension versus bending) parameters are underlined. Some comparisons with published experimental results and observations are qualitatively and quantitatively discussed. Overall parametric analysis and prediction results may be worthwhile for being a new benchmark against future experimental testing and/or numerical results predicted by an alternative model and methodology.     

深水高弯度水道-堤岸沉积体系形态及特征

在海底扇研究及油气勘探中,不断发现一种形态类似曲流河的高弯度水道-堤岸沉积体系,其在形态及沉积特征方面与海底扇有较大差异.在国内外研究成果的基础上,结合对重力流的实际研究工作,对该体系的沉积模式及沉积特征等开展了进一步的研究,并从沉积环境、流体类型、形态等方面与曲流河进行比较.深水高弯度水道-堤岸沉积体系主要包括水道、...     

Quantifying the influence of channel sinuosity on the depositional mechanics of channelized turbidity currents: A laboratory study

Here we present results from a suite of laboratory experiments that highlight the influence of channel sinuosity on the depositional mechanics of channelized turbidity currents. We released turbidity currents into three channels in an experimental basin filled with water and monitored current properties and the evolution of topography via sedimentation. The three channels were similar in cross-sectional geometry but varied in sinuosity. Results from these experiments are used to constrain the run-up of channelized turbidity currents on the outer banks of moderate to high curvature channel bends. We find that a current is unlikely to remain contained within a channel when the kinetic energy of a flow exceeds the potential energy associated with an elevation gain equal to the channel relief; setting an effective upper limit for current velocity. Next we show that flow through bends induces a vertical mixing that redistributes suspended sediment back into the interiors of depositional turbidity currents. This mixing counteracts the natural tendency for suspended sediment concentration and grain size to stratify vertically, thereby reducing the rate at which sediment is lost from a current via deposition. Finally, the laboratory experiments suggest that turbidity currents might commonly separate from channel sidewalls along the inner banks of bends. In some cases, sedimentation rates and patterns within the resulting separation zones are sufficient to construct bar forms that are attached to the channel sidewalls and represent an important mechanism of submarine channel filling. These bar forms have inclined strata that might be mistaken for the deposits of point bars and internal levees, even though the formation mechanism and its implications to channel history are different.     

Numerical simulation of wave-induced currents combined with parabolic mild-slope equation in curvilinear coordinates

Researches on breaking-induced currents by waves are summarized firstly in this paper. Then, a combined numerical model in orthogonal curvilinear coordinates is presented to simulate wave-induced current in areas with curved boundary or irregular coastline. The proposed wave-induced current model includes a nearshore current module established through orthogonal curvilinear transformation form of shallow water equations and a wave module based on the curvilinear parabolic approximation wave equation. The wave module actually serves as the driving force to provide the current module with required radiation stresses. The Crank-Nicolson finite difference scheme and the alternating directions implicit method are used to solve the wave and current module, respectively. The established surf zone currents model is validated by two numerical experiments about longshore currents and rip currents in basins with rip channel and breakwater. The numerical results are compared with the measured data and published numerical results.     

Analysis of southeast Australian zooplankton observations of 1938-42 using synoptic oceanographic conditions

The research vessel Warreen obtained 1742 planktonic samples along the continental shelf and slope of southeast Australia from 1938-42, representing the earliest spatially and temporally resolved zooplankton data from Australian marine waters. In this paper, Warreen observations along the southeast Australian seaboard from 28°S to 38°S are interpreted based on synoptic meteorological and oceanographic conditions and ocean climatologies. Meteorological conditions are based on the NOAA-CIRES 20th Century Reanalysis Project; oceanographic conditions use Warreen hydrological observations, and the ocean climatology is the CSIRO Atlas of Regional Seas. The Warreen observations were undertaken in waters on average 0.45 °C cooler than the climatological average, and included the longest duration El Niño of the 20th century. In northern New South Wales (NSW), week time-scale events dominate zooplankton response. In August 1940 an unusual winter upwelling event occurred in northern NSW driven by a stronger than average East Australian Current (EAC) and anomalous northerly winds that resulted in high salp and larvacean abundance. In January 1941 a strong upwelling event between 28° and 33°S resulted in a filament of upwelled water being advected south and alongshore, which was low in zooplankton biovolume. In southern NSW a seasonal cycle in physical and planktonic characteristics is observed. In January 1941 the poleward extension of the EAC was strong, advecting more tropical tunicate species southward. Zooplankton abundance and distribution on the continental shelf and slope are more dependent on weekly to monthly timescales on local oceanographic and meteorological conditions than continental-scale interannual trends. The interpretation of historical zooplankton observations of the waters off southeast Australia for the purpose of quantifying anthropogenic impacts will be improved with the use of regional hindcasts of synoptic ocean and atmospheric weather that can explain some of the physically forced natural variability.     

舟山凉潭岛填海工程对水动力及海床演变影响的模拟预测分析

用一个三维(ECOMSED)模式对舟山凉潭岛填海工程前后的潮流场变化进行模拟,做出预测。潮流场模拟结果与实测基本吻合。经分析可知,工程对潮流的影响主要在围堤的东南角小范围内:工程后流速明显减小,造成淤积现象,但淤积程度不大,1年后的淤积为13cm左右,5年后的淤积为0.8—1.2m左右。工程对较深水层的潮流运动影响很小。通过对施工期间产生的悬浮物在涨落潮时的分布模拟可知,涨潮时,悬浮物从工程区域的一个悬浮物源不断排出,主要对工程附近及其上游地区造成一定的影响;落潮时,悬浮物主要影响工程外围及其下游地区,整个落潮期间悬浮物能影响的范围比涨潮期间要大。总体上工程对该附近海域的潮流场及冲淤影响很小。