Stratified convection with multiple states

A simplified box model of the cooling of a salt-stratified ocean is analyzed analytically and numerically. A large isothermal basin of salt water has a layer of fresh water at the surface. Beside this is a small basin, cooled from above and connected to the large basin by horizontal tubes at the top, middle and bottom. For small cooling rate, fresh water enters the small basin, is cooled and leaves through the middle tube. For greater cooling rate, the fresh water leaves the small basin through the middle and bottom tube. If the top tube is smaller than the deeper tubes and the fresh water layer is sufficiently shallow, flow in the middle tube reverses at a critical cooling rate. In this case, a mixture of salt and fresh water is cooled and leaves the bottom tube. Increased cooling produces much greater flow rate; consequentially temperature increases rather than decreases in the small basin. A relaxation heat flow condition results in multiple equilibria. One of the stable modes has fresh surface water descending in the small basin and flowing out through the middle and bottom tube. The other has a greater rate of flow of both fresh and salty water (through the middle tube) into the basin with the flow of mixed salty water out of the bottom tube. Implications for deep convection in the ocean are discussed.     

建筑边坡岩体分类及其应用合理性研究

当前的建筑边坡岩体分类不含外倾软弱结构面控制的边坡和倾倒崩塌型破坏的边坡,把岩体完整程度、结构面结合程度、结构面产状、岩石坚硬程度和地下水发育程度作为分类因素。对这种分类及其应用存在的问题进行了分析。研究表明,这个分类在分类规律、分类对象、分类因素等方面均不合理,也没有实际意义,已有的关于岩体性状的通用分类和专用于边坡的单因素分类对于边坡工程已经够用。提出了取消专用于边坡的岩体综合分类的建议。     

基于PHC3.0数据集的北冰洋水团分析

基于PHC3.0极地科学中心水文气候数据集(简称PHC3.0数据集)的温度和盐度资料,使用聚类分析和Bayes判别分析的方法,对北纬70°以北海域的水团结构进行了分析,在北冰洋区域划分出4个水团:北冰洋表层水(ASW)、大西洋中层水(AIW)、太平洋水(PW)和北冰洋深层水(ADW)。北冰洋表层水(ASW)遍布于欧亚海盆和加拿大海盆,以低温低盐为特征。大西洋中层水(AIW)位于约200～900m深度,在北冰洋环极边界流的作用下,其影响可达到加拿大海盆。太平洋水(PW)受经白令海峡进入北冰洋的海水影响,相对高温低盐,夏季时影响显著。北冰洋深层水(ADW)在海盆中相当均匀,几乎没有季节变化,盐度约在34.95psu,温度在加拿大海盆约为-0.3℃,欧亚海盆约为-0.7℃。     

Deep water ventilation traced by <Emphasis Type="Italic">Synechococcus</Emphasis> cyanobacteria

The paper describes a finding of photoautotroph cyanobacteria Synechococcus in deep Adriatic waters during the spring of 2006. The maximum abundance in early May was positioned at 800 m, being of order of the values referred for the surface waters in the Adriatic Sea. The deep abundance maximum has been associated to the fast ventilation of deep Adriatic waters, usually occurring during wintertime strong cooling events. Two processes were detected: (1) deep convection in the South Adriatic Pit (SAP) and (2) density current going downslope. The first process was responsible for bringing the cyanobacteria down to 600-m depth in the area of convection, and the second one triggered the downslope transport of the cyanobacteria to the SAP very bottom. The depletion rate of Synechoccocus cyanobacteria in an extremely hostile environment has been computed to equal about 1 month.     

溪洛渡水电站某危岩体稳定性及加固措施研究

在现场调查分析的基础上,提出了溪洛渡水电站某危岩体的两种可能失稳模式（剪切坠落或拉裂倾倒失稳）,进而建立了相应的稳定性计算极限平衡力学模型,而且对危岩体的变形和破坏特征进行了数值模拟分析,分析结果表明,危岩体抗拉裂倾倒稳定性较差,剪切坠落失稳的稳定性系数较高。在稳定性分析的基础上,计算出危岩体倾倒失稳时,安全系数为1.5时的锚固力,进而提出了危岩体加固方案：充填凹岩腔+填充裂隙+预应力锚索＋锚杆联合加固,数值模拟表明此加固方案效果良好。     

浅埋人防隧洞围岩加固处理技术及分析

根据埋深为6～13 m的某浅埋人防隧洞的前期稳定性分析,提出了对该人防隧洞选取灌浆加固处理方法。在工程的具体实施中,进行了两种浆液的配比实验,并分别确定了该人防隧洞在积水段和无积水段的加固材料及其配比。依据工程实际制定了灌浆施工工序,确立了浆液扩散半径以及3套灌浆终止条件。由灌浆扩散半径及岩芯强度测试的工程灌浆效果检验得知,此次加固措施完全达到了预期的效果和目的。     

潮间带低速层中高速埋伏岩体计算模式的建立

在某些沿海潮间带区域的低速层中常存在一定数量的巨大高速滚石埋伏岩体。这些埋伏岩体会给工程地质勘察带来很大的困难 ,甚至无法进行工程地质勘察。根据浅层折射波方法原理利用浅层折射波相遇时距曲线与折射波射线路径关系建立了求取浅层高速埋伏岩体的埋深及其厚度的计算模式 ,利用这些公式可以较准确地确定高速埋伏岩体的位置、埋深及其厚度 ,对工程地质勘察是十分有利的。     

Observations of the gamma-ray flux from the galaxy Mk 501

We present two-year-long observations of the flux of very-high-energy (～10¹² eV) gamma rays from the active galactic nucleus Mk 501 performed with a Cherenkov detector at the Crimean Astrophysical Observatory. A gamma-ray flux from the object was shown to exist at confidence levels of 11 and 7 standard deviations for 1997 and 1998, respectively. The flux varied over a wide range. The mean flux at energies >10¹² eV, as inferred from the 1997 and 1998 data, is (5.0±0.6)×10^?11 and (3.7±0.6)×10^?11 cm^?2 s^?1, respectively. The errors are the sum of statistical observational and modeling errors. The mean power released in the form of gamma rays is ～2×10⁴³ erg s^?1 sr^?1.     

X线选射电噪活动星系核的多波段性质

基于被ROSAT全天区巡天观测和射电4．85GHz巡天观测同时探测到的活动星系核的大样本,研究了X射线选的射电噪活动星系核的多波段性质．通过分析该样本中的活动星系核的宽波段能量分布,确认了来自射电、光学和X射线波段的辐射光度之间的显著相关性．这种相关性对于类星体、赛弗特、蝎虎座天体和射电星系是有区别的．同时,探讨了从光学到X射线波段之间的谱指数与红移以及5000A和4．85GHz处的单色光度的相关性．     

裂隙岩体渗流模型综述

系统综述了裂隙岩体渗流分析的各类模型,从各类模型所反映的渗透机理出发,阐明了它们的优缺点和适用条件及其工程应用情况。集等效连续介质模型和离散裂隙网络模型优点的等效-离散耦合模型是有实用前景的裂隙渗流模型。