Deriving depths of deep chlorophyll maximum and water inherent optical properties: A regional model

The Bohai Sea is a semi-enclosed inland sea with case-2 waters near the coast. A comprehensive set of optical data was collected during three cruises in June, August, and September 2005 in the Bohai Sea. The vertical profile measurements, such as chlorophyll concentration, water turbidity, downwelling irradiance, and diffuse attenuation coefficient, showed that the Bohai Sea was vertically stratified with a relative clear upper layer superimposed on a turbid lower layer. The upper layer was found to correspond to the euphotic zone and the deep chlorophyll maximum (DCM) occurs at the base of this layer. By tuning a semi-analytical model (24 and 25) for the Bohai Sea, we developed a method to derive water inherent optical properties and the depth of DCM from above-surface measurements. Assuming a ‘fake’ bottom in the stratified water, this new method retrieves the ‘fake’ bottom depth, which is highly correlated with the DCM depth. The average relative error between derived and measured values is 33.9% for phytoplankton absorption at 440 nm, 25.6% for colored detrital matter (detritus plus gelbstoff) absorption at 440 nm, and 24.2% for the DCM depth. This modified method can retrieve water inherent optical properties and monitor the depth of DCM in the Bohai Sea, and the method is also applicable to other stratified waters.     

壳体稳定性问题的研究进展

为探索大地震成因的物理机理,根据板壳理论的研究结果,综述多年来柔韧壳体非线性大挠度变形研究中与地震成因相关的壳体结构变形问题的研究进展、壳体结构变形过程中的稳定性问题。同时,介绍壳体曲率变化对其变形过程中稳定性的影响,期望能为探索大地震成因机理的研究提供某些有用的物理依据与理论基础。     

Holocene Deposits in Saga Plain: Leaching Mechanism and Soil Sensitivity

The Saga Plain in Japan contains a 10–30 m thick Holocene clayey soil deposit with a natural water content generally more than 100% and a liquidity index (I _L ) larger than 1.0. Most of this is a marine deposit known as the Ariake clay formation. Using salinity in the pore water of this deposit as an index, the mechanism of post-depositional salinity leaching from the Ariake clay formation has been investigated. This has been achieved using current measurements of the salinity distribution in the deposit and the groundwater flow velocity in an underlying Pleistocene gravelly sand layer, together with advection–diffusion analyses. It is suggested that diffusion together with possible rainfall percolation and/or upward seepage flow from the Pleistocene gravelly sand layer was the main mechanism causing salinity leaching. Detailed analysis of the test results from four boreholes indicates that for the locations where the activity of the clay minerals was less than 1.25, salinity leaching probably accounts for the observed low undrained shear strength (<0.5 kPa) of remoulded soil samples, high values of the sensitivity (S _t ), and the formation of a quick clay.     

Development of dynamic slip model for a shear crack

<正>The objective of this paper is to develop a dynamic slip model for a shear crack under constant stress drop.This crack problem is formulated by a traction boundary integral equation(BIE) in the frequency domain and then solved by the hyper-singular boundary element method as well as the regularization technique proposed in this paper.Based on the spectral integral form of the kernel function,the unbounded term can be isolated and extracted from the hyper-singular kernel function by using the method of subtracted and added back in wave number domain.Finally,based on the inverse transformation from the frequency domain to the time domain,the time histories of crack opening displacement under constant stress drop can be determined.Three rupture models(simultaneous rupture model,symmetric bilaterally-propagating model and unilaterally propagating model) with specified time histories of stress drop are considered in this paper.Even though these three models will cause the same final slip shapes because of the same constant stress drop,the associated slip time functions differ significantly from each other during the rupture process.     

转型期深圳居民日常活动的时空特征及其变化

基于2007年深圳居民活动日志调查的一手资料,结合时间地理学方法与GIS三维可视化技术,对深圳居民日常活动的时空间特征进行描述,将近期数据与历史数据进行对比,以揭示近年来居民行为发生的变化。研究发现:工作在居民的日常活动中仍占有不可替代的地位,男性的工作强度大于女性;工作日出行以单次多目的为主,休息日出行以多次多目的为主,休息日出行比工作日活跃;近年来,居民在时间利用及出行特征方面都发生了显著变化,工作、移动、购物活动时间增加,工作日出行频度下降,休息日出行频度上升,出行的多目的率显著增加。     

云南高海拔湖泊对末次冰消期气候突变的响应

气象观测资料表明,在当前全球暖化背景下高海拔地区的增温速率更快,其气候对全球气候变化的响应更为敏感。但是,高海拔地区如何响应快速气候事件,由于古气候古环境重建资料在高海拔地区较少,这一问题还没有很好的回答。为此选择云南省高山湖泊错恰湖为研究对象（海拔约3960 m）,分析了湖泊沉积岩芯（深度范围90~244 cm）中正构烷烃的分布特征,重建了末次冰消期（19000~9500 a B.P.）沉积物有机质来源的变化,进而推断古气候演变。在17800~17000 a B.P.,错恰湖有机质以陆源输入为主,水生贡献相对减少,气候以暖湿为主;在17000~15100 a B.P.,水生有机质的贡献的比例增加,气候以冷干为主;在15100~12700 a B.P.,湖泊沉积有机质的陆源贡献增加,水生贡献相对减少,气候相对暖湿;在12700~11400 a B.P.时段,湖泊沉积水生有机质来源相对增多,气候相对冷干。与其他区域和全球气候记录对比发现,错恰湖的沉积记录指示的气候变化事件,受高纬冰量以及北大西洋驱动的西南季风突变所影响,在末次冰消期记录的4个明显的千年尺度气候事件,在时间上与First warmth、H1、B-A和YD事件相对应。与云南地区其他湖泊记录对比发现,小型湖泊或高海拔湖泊对这些全球快速气候事件的响应更加敏感。

     

Seasonal and interannual variability of carbon cycle in South China Sea: A three-dimensional physical-biogeochemical modeling study

The South China Sea (SCS) exhibits strong variations on seasonal to interannual time scale, and the changing Southeast Asian Monsoon has direct impacts on the nutrients and phytoplankton dynamics, as well as the carbon cycle. A Pacific basin-wide physical-biogeochemical model has been developed and used to investigate the physical variations, ecosystem responses, and carbon cycle consequences. The Pacific basin-wide circulation model, based on the Regional Ocean Model Systems (ROMS) with a 50-km spatial resolution, is driven with daily air-sea fluxes derived from the National Centers for Environmental Prediction (NCEP) reanalysis between 1990 and 2004. The biogeochemical processes are simulated with the Carbon, Si(OH)₄, Nitrogen Ecosystem (CoSINE) model consisting of multiple nutrients and plankton functional groups and detailed carbon cycle dynamics. The ROMS-CoSINE model is capable of reproducing many observed features and their variability over the same period at the SouthEast Asian Time-series Study (SEATS) station in the SCS. The integrated air-sea CO₂ flux over the entire SCS reveals a strong seasonal cycle, serving as a source of CO₂ to the atmosphere in spring, summer and autumn, but acting as a sink of CO₂ for the atmosphere in winter. The annual mean sea-to-air CO₂ flux averaged over the entire SCS is +0.33 moles CO₂ m⁻²year⁻¹, which indicates that the SCS is a weak source of CO₂ to the atmosphere. Temperature has a stronger influence on the seasonal variation of pCO₂ than biological activity, and is thus the dominant factor controlling the oceanic pCO₂ in the SCS. The water temperature, seasonal upwelling and Kuroshio intrusion determine the pCO₂ differences at coast of Vietnam and the northwestern region of the Luzon Island. The inverse relationship between the interannual variability of Chl-a in summer near the coast of Vietnam and NINO₃ SST (Sea Surface Temperature) index in January implies that the carbon cycle and primary productivity in the SCS is teleconnected to the Pacific-East Asian large-scale climatic variability.     

Cs2NaMF6(M＝Al,Ga):Cr3+ 络合分子体系局域结构和基态分裂的理论研究

采用双自旋轨道耦合系数模型并结合完全能量矩阵的方法对Cs₂NaMF₆(M=Al, Ga):Cr³⁺ 体系中Cr³⁺ 离子的基态分裂和局域结构进行了研究.通过模拟光谱和EPR谱确定了Cr³⁺ 取代 M³⁺ 形成的两种占位结构的畸变角,发现用双自旋轨道耦合系数模型与单自旋轨道耦合系数模型计算出的畸变角Δθ存在较大的差异.这表     

How does the water–rock interaction of marly rocks affect its mechanical properties in the Three Gorges reservoir area,China?

Marly rock is a sensitive rock group of landslides in the Three Gorges reservoir area, China. It is composed predominantly of carbonate and clay minerals, water–rock interaction (WRI) of which could activate landslides in the reservoir area. To study the mechanism by which WRI affects the mechanical properties of marly rock, samples were collected from two boreholes (depth 301.78 and 307.14 m) and slope surface. Then, laboratory tests were designed to study the quantitative relationship between mineral contents and mechanical properties of intact rock, to analyze both change process of mineral composition and microstructure under short-term and long-term WRI. Finally, the change in mechanical properties and its effect on slope stability are suggested. This study indicates that the uniaxial compressive strength and Poisson ratio can be estimated by linear regression equations: (1) σ _c = 8.959 × (C/Q) ? 0.744 × CM + 58.516; (2) μ = 0.014 × (C/Q) ? 0.001 × CM + 0.234. The chemical reactions of WRI mainly included dissolution and ion exchange. On the slope surface, dissolution mainly acts on calcite, illite, dolomite, feldspar and other minerals dissolved in water. Underground, both chemical reactions of dissolution and ion exchange easily approach equilibrium with long-term seepage. Small-size minerals and micropores damage the stable microstructure of marly rock. These changes of minerals and microstructure can trigger shallow slope failure and develop deep creep deformation along some crash zones in the reservoir shoreline.     

天然土石坝稳定性初步研究

滑坡堵塞江河形成的天然土石坝是自然作用的产物，不同于人工土石坝，天然土石坝形成后有些存在几十年，几百年，有些形成后不久就溃决，这与坝体本身的性质和河水入流量有关，依据野外实测资料，证了土石坝的稳定性的主要是同土石坝的物质组成，几何形状和堰塞湖入流量等因素决定的，这一研究为天然土石坝的稳定性预测奠定了基础。