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71.
通过对Ⅳ#松散堆积体的稳定性分析计算后认为,该堆积体在水库蓄水后,虽然在各种不利因素影响下其稳定性有所降低,但其整体仍处于稳定状态,不会发生整体滑动,也不会发生局部滑动而堵塞黄河。  相似文献   
72.
Located on the extensive continental shelf of the Bering Sea, the Pribilof Islands, Alaska are the site of one of the largest breeding colonies of seabirds in the northern hemisphere. During summer these islands are surrounded by a front that separates vertically homogeneous waters from well stratified waters farther seaward. We studied the front with hydrographic data and the bird distributions with concurrent counts during summer 1977 and spring, summer and fall 1978. Murres (Uria lomvia and U. aalge) sitting on the water aggregated near the front during summer 1977 and probably during summer 1978. Other species, such as northern fulmars (Fulmarus glacialis) and auklets (Aethia pusilla and A. cristatella) were unaffected by the front. We hypothesize that the aggregation of the murres was related to an enhanced availability of their food near the front.  相似文献   
73.
Recently one of the most challenging problems for civil engineers is how to construct new structures/infrastructures adjacent pre-existing ones and how to evaluate the effect of the new construction on the pre-existing structures (so-called neighbouring construction). The Manifold Method (MM) is one of the discontinuum based numerical approaches to simulate the mechanical behaviour of fractured rock masses including large deformation/displacement along fractures as well as stress/strain conditions of the rock blocks/masses. In this study, the MM was used to investigate the stability of the cut slope in the highly fractured rock masses along one of the national roads in Japan, focusing on the effects of new construction on the pre-existing structures/infrastructures. The effect of reinforcement during the construction such as rock bolts, anchors, etc. was also investigated and evaluated quantitatively by numerical simulations using MM.  相似文献   
74.
The optimum multiparameter (OMP) method was often used to determine the percentages of water masses based on temperature, salinity and other parameters, like nutrient or dissolved oxygen (DO). There are a number of water masses in the East China Sea (ECS), a marginal sea of the western Pacific Ocean. However, it is difficult to clarify the proportion of water masses using traditional parameters, such as temperature, salinity, nutrient or DO because of the occurring of intensive biogeochemical processes in the near shore and shelf areas. Here, we reported the use of 234U/238U activity ratio embedded in the OMP method. The results indicate that seawater in the northern ECS mainly consisted of the estuarine water of Changjiang River (CEW), Kuroshio water (KW), and Yellow Sea Coastal Current (YSCC). In March 2017, the CEW only influenced the offshore waters shallower than 30 m; the KW affected the east edge and the YSCC contributed more than 75% in the northern ECS.  相似文献   
75.
基于岩体不连续面三维分形维岩体质量评价研究   总被引:1,自引:0,他引:1  
周福军  陈剑平  徐黎明  谭春 《岩土力学》2012,33(8):2315-2322
岩体内部不连续面分布具有随机性、不规则性,但又具有统计自相似性。基于三维随机不连续面网络模拟技术,对岩体结构统计均质区内的不连续面进行计算机模拟,并应用分形理论计算岩体不连续面分布的分形维数。岩体不连续面分布分维数具有尺寸效应,随着岩体尺寸增大分维数减小,到一定程度趋于稳定。这一稳定的分维值称之为表征分维数,用此值描述不连续面分布特征。将岩体不连续面分布的表征分维数与按传统岩体分类标准所得岩体质量等级进行对比,提出以岩体不连续面分布表征分维数为指标的岩体质量分类方法。在岩体分类基础上,提出基于表征分维数的岩体等效抗剪强度指标的折减计算。  相似文献   
76.
荣冠  王思敬  王恩志  刘顺桂 《岩土力学》2009,30(10):3013-3019
详细分析了白鹤滩坝址河谷边坡柱状节理玄武岩岩体地质条件和特征,建立了合适河谷边坡演化离散元的计算模型,考虑坝址关键地层P2?3可能的岩体质量范围进行了多种工况河谷演化模拟计算。在此基础上深入研究了各工况河谷现今阶段边坡应力分布、变形情况、屈服区及稳定系数等基本规律,并与目前河谷实际的地质条件及现状进行了全面对比。最后采用拟似度信息量评分法对P2?3岩层工程级别进行了初步评定,认为白鹤滩水电站可行性研究阶段坝址P2?3岩层按III1类质量岩体来评估其工程性状和确定相应岩体力学参数较适合。同时,坝址河谷边坡岩体的工程特性可参考相应工况的模拟结果评价。  相似文献   
77.
目的:探讨肺部肿块的CT血流灌注的特征及临床价值.方法:对35例患者(男21例,女14例;平均年龄,64.7岁,年龄范围,24~83岁)进行CT灌注检查.使用64排螺旋CT,先平扫有问题的结构区域,然后选定肿块扫描层面,使用高压注射器,经肘静脉注入50mL·300mg·100mL-1的优维显,速率为4mL·s-1,延迟5 s后,以电影模式行多层灌注扫描,持续35~40 s.使用Perfusion 3灌注软件测量血容量及表面透过性乘积.3个独立样本(肺癌组、结核组及炎症组)两两进行统计学分析(t检验).结果:恶性肿块20例(4例鳞癌,12例腺癌,1例未分化癌,3例转移癌),炎性肿块8例,结核灶7例.肺癌、结核灶及炎性肿块的灌注均值(BV和PS)分别为:(8.43±2.44)mL·100g-1,(24.30±5.80)mL·min-1·100g-1;(1.90±0.60)mL·min-1·100g-1,(1.19±0.37)mL·min-1·100g-1;(19.73±6.65)mL·100g-1,(30.01±9.06)mL·min-1·100g-1.肺癌组与结核灶组及炎性肿块组与结核灶组之间的灌注均值均有显著差异(p<0.05);肺癌组与炎性肿块组之间的BV均值有显著差异(p=0.014,t=2.639),但二者PS均值无统计学意义(p=0.506,t=0.674).结论:利用灌注值可以区分肺癌与结核灶、炎性肿块与结核灶,虽然单独依靠灌注值很难区分肺癌与炎性肿块,但是血流灌注仍间接反映了肺部肿块的生物学行为.  相似文献   
78.
江苏主要含矿花岗岩体的地球化学特征及找矿方向   总被引:2,自引:2,他引:0  
分析了江苏省主要含矿花岗岩体的主元素、微量元素含量,所含黑云母的成分以及包裹体的类型等地球化学特征.结果表明它们大多属于岩浆花岗岩,且以I型花岗岩为主.成矿元素Cu、Pb、Zn在I型含矿花岗岩中普遍有一定程度的富集,其中以Cu的富集程度最好;Cr、Co、Ni在此类岩体中含量亦较高.广泛发育多种包裹体,尤其是发育含子矿物多相包裹体是含矿花岗岩体的重要特征.指出应加强在宁镇中段某些I型花岗岩体中寻找Cu多金属矿的工作.  相似文献   
79.
Hydrographic data collected during surveys carried out in austral winter 2003 and summer 2004 are used to analyze the distributions of temperature (T) and salinity (S) over the continental shelf and slope of eastern South America between 27°S and 39°S. The water mass structure and the characteristics of the transition between subantarctic and subtropical shelf water (STSW), referred to as the subtropical shelf front (STSF), as revealed by the vertical structure of temperature and salinity are discussed. During both surveys, the front intensifies downward and extends southwestward from the near coastal zone at 33°S to the shelf break at 36°S. In austral winter subantarctic shelf water (SASW), derived from the northern Patagonia shelf, forms a vertically coherent cold wedge of low salinity waters that locally separate the outer shelf STSW from the fresher inner shelf Plata Plume Water (PPW) derived from the Río de la Plata. Winter TS diagrams and cross-shelf T and S distributions indicate that mixtures of PPW and tropical water only occur beyond the northernmost extent of pure SASW, and form STSW and an inverted thermocline characteristic of this region. In summer 2004, dilution of Tropical water (TW) occurs at two distinct levels: a warm near surface layer, associated to PPW–TW mixtures, similar to but significantly warmer than winter STSW, and a colder (T∼16 °C) salinity minimum layer at 40–50 m depth, created by SASW–STSW mixtures across the STSF. In winter, the salinity distribution controls the density structure creating a cross-shore density gradient, which prevents isopycnal mixing across the STSF. Temperature stratification in summer induces a sharp pycnocline providing cross-shelf isopycnal connections across the STSF. Cooling and freshening of the upper layer observed at stations collected along the western edge of the Brazil Current suggest offshore export of shelf waters. Low T and S filaments, evident along the shelf break in the winter data, suggest that submesoscale eddies may enhance the property exchange across the shelf break. These observations suggest that as the subsurface shelf waters converge at the STSF, they flow southward along the front and are expelled offshore, primarily along the front axis.  相似文献   
80.
Mach's relativity of inertia does not necessarily imply an anisotropy of inertial masses in an anisotropic universe and the Mach-Einstein doctrine is compatible with the isotropy of mass in each cosmos.  相似文献   
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