热带东风中经向扰动与纬向扰动的相互作用

本文解释了热带大尺度大气运动速度的分布,从线性化涡度方程和散度方程求出了波速公式,该公式等于罗斯贝波速与含有X和t的谐和函数之和,其周期约3.5天,并证明,此时扰动为正压不稳定,这种现象的产生是经向扰动和纬向扰动相互作用的结果。     

犬齿牙鲆幼鱼呼吸耗氧率的研究

对犬齿牙鲆幼鱼在不同环境条件下的呼吸频率、耗氧率以及窒息浮头现象进行了观测研究。结果表明:犬齿牙鲆在适宜温度范围,呼吸频率随温度的升高而加快,在适宜生长温度范围,其呼吸频率为60～100次/min。耗氧量与鱼体重正相关,二者之间的相关关系符合M=1.8469W0.8317(r=0.9116)模式。其耗氧率随温度和盐度的增加而增加,在水温20℃左右,体重108g的犬齿牙鲆24h平均耗氧率为1.6676μg/(min·g),明显低于褐牙鲆(体重69.3～151.4g)耗氧率2.68μg/(min·g)和大菱鲆(17℃体重70～110g)耗氧率3.4667μg/(min·g)的水平。其耗氧率白天为1.824μg/(min·g),夜间为1.511μg/(min·g),白天耗氧率是夜间的1 21倍,昼夜差异明显。犬齿牙鲆20℃半数死亡窒息点耗氧率为0 747mg/L,全部死亡窒息点耗氧率为0 569mg/L。     

赞比亚卢弗里安弧构造带再活化的证据:锆石和磷灰石裂变径迹年代学

锆石和磷灰石裂变径迹年代学对揭示构造热事件的形成及演化过程具有重要的研究意义.利用锆石和磷灰石裂变径迹测试及热史模拟探讨了卢弗里安弧构造带自泛非构造运动以来的构造热演化过程.谦比希铜矿床和恩昌加铜（钴）矿床位于卢弗里安弧铜-钴成矿带中的赞比亚境内.对采自该两个矿床中的5件新鲜岩石样品进行挑选,获得了5件锆石和4件磷灰石样品.首次获得了卢弗里安弧构造带中的裂变径迹年龄,5件锆石样品的年龄分别为265±22 Ma、230±10 Ma、228±9 Ma、225±9 Ma和221±10 Ma.4件磷灰石样品的年龄分别为145±10 Ma、133±10 Ma、130±10 Ma和92±9 Ma,径迹长度介于（11.4±2.4）~（11.8±2.4）μm.从热历史模拟结果可看出,从300~260 Ma,古地温持续降低至90 ℃左右;随后,缓慢降低至现今的地表温度.对比卢弗里安弧构造带、赞比西构造带和达马拉构造带中的年龄数据,研究表明非洲中南部地区二叠纪-白垩纪的构造活动是一个区域性的构造活动事件.      

Field Observation and Analysis of Wave-Current-Sediment Movement in Caofeidian Sea Area in the Bohai Bay, China

In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer (BBL). Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath (under the lowest tidal level), a tripod system was installed with AWAC (Acoustic Wave And Current), ADCP (Acoustic Doppler Current Profilers), OBS-3A (Optical Backscatter Point Sensor), ADV (Acoustic Doppler Velocimeters), etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt: 1) The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m3 and the average value being 0.03 kg/m3; 2) The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension.     

甘新蒙北山地区构造格局及演化

甘新蒙北山地区地处天山东段、北山及阿拉善地区 ,为古生代哈萨克斯坦板块、塔里木板块和华北板块交汇地带。可分为 7个二级构造单元 (构造区 )、2 6个三级构造单元 (地块、褶皱带 )。该区构造演化史漫长而复杂。太古宙时期 ,是古陆核形成萌芽阶段 ,古元古代初陆壳开始生成 ,出现薄壳结构的宽广的裂陷活动带 ,到了中、新元古代后期显露出板块构造运动 ,新元古代晚期经历重大热事件———晋宁运动 ,发生陆块间汇聚—碰撞并形成了榴辉岩—花岗岩岩浆带。震旦纪在晋宁期的拼合古陆上再一次裂解 ,经历了板块构造演化史。晚古生代 ,本区主体转入板内构造时期 ,以开合构造为主 ,花岗岩浆活动广泛发育。中、新生代进入板内造山和现今的盆山构造格局时期     

波士顿共享单车出行与街区建成环境的关系研究——基于广义可加混合模型

共享单车作为低碳环保的交通出行方式，在全球许多城市得到了快速发展。但已有共享单车与建成环境的关系研究较少关注街区空间尺度及形态因素，且忽略了影响因素的非线性作用。基于波士顿共享单车出行数据，分析共享单车出行的时空特征；运用广义可加混合模型，解析骑行量与街区建成环境的关系。结果表明：(1)波士顿共享单车骑行量由中心区向城市外围呈圈层梯度递减趋势，骑行距离具有3km集中骑行圈与6km极限骑行圈特征；(2)周末、天气、温度等时变因素会显著影响单车使用；(3)骑行量与街区总人口数、路网密度和地铁接入性显著正相关，与街区路网方向熵、平均路段长度分别呈L形、倒U形的非线性关系。最后，从可骑行社区构建、TOD慢行系统建设以及精准化共享单车投放等方面，阐述了研究对我国城市的启示。     

Effects of skeleton void ratio on the strength and deformation characteristics of coarse-grained soilEI北大核心

粗粒土强度变形特性与初始级配和制样干密度密切相关。为研究不同级配和密度组合的粗粒料强度变形特性,提出了一种计算简便、易于推广的粗粒土骨架孔隙比计算方法。开展的室内试验结果表明,该计算方法所得的骨架孔隙比与粗粒土力学特性之间存在较为明显的单调性变化规律。当试样尺寸一致时,随着骨架孔隙比减小,破坏剪应力增大,破坏摩擦角增大,黏聚力减小;平均初始切线弹性模量增大,平均初始切线泊松比减小。整体而言,骨架孔隙比越小,粗粒土强度、刚度越大。基于该结论,笔者提出了一种等骨架孔隙比粗粒土缩尺方法。