南海反气旋涡旋温度细结构特征分析

基于水下滑翔机观测资料,对南海北部一个反气旋涡旋的温度细结构进行了特征分析.温度细结构强度由温度的脉动值确定,并随着尺度的增加呈指数衰减.在垂直方向上,细结构强度随着深度的加深而减弱,细结构特征在海洋表层(0～100m)和表层以下(＞100 m)存在显著区别.表层内,垂向混合和水平混合对细结构强度均有贡献,细结构强度大...     

Regional Temperature Forecast for the Next Day in Hong Kong

For a century or so, the Hong Kong Observatory (HKO) has been providing temperature forecast for the whole of Hong Kong with the HKO Headquarters as the reference location. In recent decades, due to spreading of population from the main urban center to satellite towns, there is an increasing demand for regional temperature forecasts. To support such provision, the HKO has developed a regression model to provide objective guidance to forecasters in formulating forecasts of maximum and minimum temperatures for the next day at various locations in Hong Kong. In this paper, the regression model is presented, together with the assessment of its performance. Based on the verification of one year of forecasts, it is found that the root mean square errors (RMSEs) of maximum (minimum) temperature forecasts are from about 1.3 to 2.1 (1.1 to 1.4) degrees, respectively. The regression model is shown to have generally out-performed the operational regional spectral model then operated by HKO. Regional temperature forecast methods of other meteorological or research centers are also surveyed. Equipped with the regression model, the HKO has launched an online regional temperature forecast service for the next day in Hong Kong since March 2008.     

2008年汶川地震相关堆积物的细颗粒石英光释光测年研究

现代强震相关堆积物的释光测年研究有助于理解古地震相关沉积物释光测年的地质意义,提高古地震测年的精度和准确度,更好地认识大地震发生的规律.文中选择了若干典型的2008年汶川大地震的相关堰塞湖堆积物、泄洪堆积物和喷砂堆积物,进行了细颗粒石英光释光测年研究.结果表明,这些地震相关沉积物中的细颗粒石英灵敏度较高,但释光信号并未...     

Simulation of spatially correlated earthquake ground motions for engineering purposes

A new model to simulate spatially correlated earthquake ground motions is developed. In the model, the main factors that characterize three distinct effects of spatial variability, namely, the incoherency effect, the wave-passage effect and the site-response effect, are taken into account, and corresponding terms/parameters are incorporated into the well known model of uniform ground motions. Some of these terms/parameters can be determined by the root operation, and others can be calculated directly. The proposed model is fi rst verif ied theoretically, and examples of ground motion simulations are provided as a further illustration. It is proven that the ensemble expected value and the ensemble auto-/cross-spectral density functions of the simulated ground motions are identical to the target spectral density functions. The proposed model can also be used to simulate other correlated stochastic processes, such as wave and wind loads.     

2008年加拿大海盆次表层暖水的精细结构的研究

自2004年以来,在加拿大海盆频繁发生的次表层暖水(near surface temperature maximum,NSTM)现象是北极快速变化响应的事实之一.采用2008年中国第3次北极科学考察的CTD数据和西北冰洋联合研究计划与美国波弗特环流观测系统计划2008年航次的CTD数据以及冰浮标ITP18数据,对加拿大...     

树根桩在厂房扩建工程地基处理中的应用

在苏南某工业厂房扩建工程中,为了妥善解决新旧熔炉区的不均匀沉降,通过多方案的比选,最终采用树根桩托换技术进行地基加固。并且对新旧熔炉区的基础进行了化学植筋连接和防渗漏处理。     

青海东部查明一大型微细浸染型金矿床

加吾金矿位于青海省东部同德县境内,是武警黄金部队近年来发现的又一处具大型规模的金矿床。该矿床在大地构造位置上处于西秦岭与东昆仑的衔接部位。矿体赋存于中下三叠统中,在平面上呈舒缓波状,在剖面上为脉状、似层状。矿石中金属矿物主要为黄铁矿和毒砂,金主要以微细粒分布于石英裂隙和毒砂、黄铁矿等矿物粒间。区内中下三叠统隆务河群板岩中的金丰度值和有机碳含量高,是有利的赋矿层位。矿体产于北西向和近东西向构造蚀变带内,受区内断裂带控制明显。矿体在空间上与印支期中酸性岩浆岩相伴产出。研究表明,该矿床为受构造蚀变带控制的、与沉积作用和岩浆活动有成因联系的微细浸染型金矿床。截止目前,该矿共计探明金矿脉22条,累计提交金资源量超过20t。该矿的发现和评价对指导青海东部微细浸染型金矿找矿具有重要的示范意义。     

Evidence of late oligocene/early miocene backthrusting in the central alpine “root zone”

Abstract

Two groups of stretching lineations can be distinguished in the Central Alpine " root zone " between Ticino and Mera :

1) Steeply plunging lineations formed during retrograde metamor-Phism under amphibolite/greenschist facies conditions indicate an uplift movement of the Central Alps. The lineations can be related to an important back-thrusting event of late Oligocene/early Miocene age.

2) Gently plunging lineations formed under lower greenschist facies conditions display a pattern typical of a dextral strike-slip system. These lineations are of early Miocene age.

This cpmbined movement, achieved by ductile deformation along the lnsubric line was followed by a stage of brittle deformation in a dextral strike-slip system (= Tonale line).

The signification of this interpretation is shown in a new crustal cross section through the Central Alpine/Southern Alpine border zone in the Iicino area.     

Enhanced application of root‐reinforcement algorithms for bank‐stability modeling

Riparian vegetation is known to exert a number of mechanical and hydrologic controls on bank stability. In particular, plant roots provide mechanical reinforcement to a soil matrix due to the different responses of soils and roots to stress. Root reinforcement is largely a function of the strength of the roots crossing potential shear planes, and the number and diameter of such roots. However, previous bank stability models have been constrained by limited field data pertaining to the spatial and temporal variability of root networks within stream banks. In this paper, a method is developed to use root‐architecture data to derive parameters required for modeling temporal and spatial changes in root reinforcement. Changes in root numbers over time were assumed to follow a sigmoidal curve, which commonly represents the growth rates of organisms. Regressions for numbers of roots crossing potential shear planes over time showed small variations between species during the juvenile growth phase, but extrapolation led to large variations in root numbers by the time the senescent phase of the sigmoidal growth curve had been reached. In light of potential variability in the field data, the mean number of roots crossing a potential shear plane at each year of tree growth was also calculated using data from all species and an additional sigmoidal regression was run. After 30 years the mean number of roots predicted to cross a 1 m shear plane was 484, compared with species‐specific curves whose values ranged from 240 roots for black willow trees to 890 roots for western cottonwood trees. In addition, the effect of spatial variations in rooting density with depth on stream‐bank stability was modeled using the bank stability and toe erosion model (BSTEM). Three root distributions, all approximating the same average root reinforcement (5 kPa) over the top 1 m of the bank profile, were modeled, but with differing vertical distributions (concentrated near surface, non‐linear decline with depth, uniform over top meter). It was found that stream‐bank F_S varied the most when the proportion of the failure plane length to the depth of the rooting zone was greatest. Copyright © 2008 John Wiley & Sons, Ltd.     

Influence of seepage undercutting on the stability of root‐reinforced streambanks

Several mechanisms contribute to streambank failure including fluvial toe undercutting, reduced soil shear strength by increased soil pore‐water pressure, and seepage erosion. Recent research has suggested that seepage erosion of noncohesive soil layers undercutting the banks may play an equivalent role in streambank failure to increased soil pore‐water pressure. However, this past research has primarily been limited to laboratory studies of non‐vegetated banks. The objective of this research was to utilize the Bank Stability and Toe Erosion Model (BSTEM) in order to determine the importance of seepage undercutting relative to bank shear strength, bank angle, soil pore‐water pressure, and root reinforcement. The BSTEM simulated two streambanks: Little Topashaw Creek and Goodwin Creek in northern Mississippi. Simulations included three bank angles (70° to 90°), four pore‐water pressure distributions (unsaturated, two partially saturated cases, and fully saturated), six distances of undercutting (0 to 40 cm), and 13 different vegetation conditions (root cohesions from 0·0 to 15·0 kPa). A relative sensitivity analysis suggested that BSTEM was approximately three to four times more sensitive to water table position than root cohesion or depth of seepage undercutting. Seepage undercutting becomes a prominent bank failure mechanism on unsaturated to partially saturated streambanks with root reinforcement, even with undercutting distances as small as 20 cm. Consideration of seepage undercutting is less important under conditions of partially to fully saturated soil pore‐water conditions. The distance at which instability by undercutting became equivalent to instability by increased soil pore‐water pressure decreased as root reinforcement increased, with values typically ranging between 20 and 40 cm at Little Topashaw Creek and between 20 and 55 cm at Goodwin Creek. This research depicts the baseline conditions at which seepage undercutting of vegetated streambanks needs to be considered for bank stability analyses. Copyright © 2008 John Wiley & Sons, Ltd.