粒状碎屑溜砂坡运动方程与砂坡土r压力计算（溜砂坡系列研究之三）

在溜砂坡系列研究之二的基础上,对风干砂的运动特征进行了细致观察。将干砂流视为连续介质的流动,对干砂流的运动动力和阻力进行了深入研究,建立了干砂流垂线流速分布方程和干砂流体底面、表面滑动速度方程。结合挡砂工程,将干砂流体视为沿底面（此种砂坡的天然休止角）滑动的三角体,从而导出粒状碎屑溜砂坡水平土压力（或水平推力）计算模型。     

Road Surface Modeling and Representation from Point Cloud Based on Fuzzy Clustering

A scheme for an automatic road surface modeling from a noisy point cloud is presented. The normal vectors of the point cloud are estimated by distance-weighted fitting of local plane. Then, an automati...     

一种复杂轮廓线的真三维TIN算法

针对多层轮廓线三维重构问题，研究了真三维复杂轮廓线的空间分布特征，通过引入参考基准面概念，提出了一种顾及局部平展特性的真三维TIN生成算法。该方法在递增生成表面过程中，利用了加权最小三角化方法，动态建立参考基准面，将三角面片自身形态和局部邻接轮廓点的相对空间关系有机地结合起来，避免了面片的遮掩重叠和自相交，使得重建表面和原始表面的拓扑差异最小。选取三维地震量测的多层反射波剖面数据进行了实验，并对不同算法得到的实验结果进行了分析比较，得出实验结论：本文算法快速可靠，重建出来的三维表面过渡光滑、自然，更接近实际的表面形态。该方法对于石油、地质勘探三维地质构造形态辅助解译具有现实的应用意义。     

大脑中动脉狭窄程度与脑梗死前期CT灌注参数的相关性

目的:探讨单侧大脑中动脉(MCA)狭窄程度与脑梗死前期CT灌注(CTP)参数的关系,并分析梗死前期血管表面通透性(PS)的变化。方法:回顾性分析我院2018年7月1日至2019年10月1日期间经头颈部CTA诊断单侧MCA狭窄患者108例,观察CTP成像特点,测量各组患侧、镜像侧剩余函数达峰时间(TMax)、平均通过时间(MTT)、脑血流量(CBF)、脑血容量(CBV)以及表面通透性(PS),并计算各灌注参数的相对值(患侧/镜像侧),分析单侧大脑中动脉狭窄程度与脑梗死前期CT灌注参数的相关性。结果:①108例单侧大脑中动脉狭窄患者中39例出现灌注异常,不同程度血管狭窄的灌注分期差异具有统计学意义(P=0.009)。单侧大脑中动脉狭窄程度与灌注异常分期呈中等正相关(r=0.557,P=0.000)。②单侧大脑中动脉不同程度狭窄组间rCBF值、rMTT值差异有统计学意义(P<0.05),而rCBV值、r TMax值差异无统计学意义(P>0.05)。单侧大脑中动脉狭窄程度与rTMax值、rMTT值呈正相关(分别为r=0.458,P=0.003,r=0.765,P=0.000),与rCBF呈负相关相关(r=-0.600,P=0.000),而狭窄程度与rCBV值无明显相关性。③Ⅱa、Ⅱb期患者患侧与镜像侧PS绝对值差异有统计学意义(P<0.05),Ⅱa、Ⅱb期患者组间PS相对值差异没有统计学意义(P>0.05)。结论:单侧MCA狭窄程度与脑梗死前期分期具有一定相关性,单侧MCA狭窄程度越严重,rTMax、rMTT值越大,rCBF越小;在脑梗死前期的II期出现血管表面通透性升高的改变。      

Arc／Info—Grid模块及其水文模型应用

利用地理信息系统可以建立流域的数字高程模型,并与grid模块的水文表面分析工具结合,形成直观的流域环境三维显示,再通过计算、统计与分析,即可获取精确的水文因子数据,为进一步水文定量研究及应用提出了一种高效的方法。     

硬质合金钎头胎体表面渗硼强化实验研究

对钎头胎体表面渗硼方法和工艺进行了实验研究,给出了有关工艺参数与方法。它对提高硬质合金钎头胎体表面和耐磨性,延长钎头的使用寿命具有积极的意义。     

A sub-surface eddy at inertial current layer in the Canada Basin,Arctic Ocean

An Arctic Ocean eddy in sub-surface layer is analyzed in this paper by use of temperature,salinity and current profiles data obtained at an ice camp in the Canada Basin during the second Chinese Arctic Expedition in summer of 2003.In the vertical temperature section,the eddy shows itself as an isolated cold water block at depth of 60 m with a minimum temperature of-1.5℃,about 0.5℃ colder than the ambient water.Isopycnals in the eddy form a pattern of convex,which indicates the eddy is anticyclonic.Although maximum velocity near 0.4 m s-1 occurs in the current records observed synchronously,the current pattern is far away from a typical eddy.By further analysis,inertial frequency oscillations with amplitudes comparable with the eddy velocity are found in the sub-surface layer currents.After filter the inertial current and mean current,an axisymmetric current pattern of an eddy with maximum velocity radius of 5 km is obtained.The analysis of the T-S characteristics of the eddy core water and its ambient waters supports the conclusion that the eddy was formed on the Chukchi Shelf and migrated northeastward into the northern Canada Basin.     

鲨鱼二则之鲸鲨的几何学

<正>鲸鲨是海洋里面最大的鱼类,它们的身体通常可以达到10米。鲸鲨的身体表面有许许多多黄色的斑点,就像是密密麻麻的小星星一样。有意思的是,每头鲸鲨身体表面斑点的分布都是不同的,科学家们可以以此作为鲸鲨的身份识别标志。鲸鲨可以说是一个"慢性子",它们常常缓慢地在     

Fine-resolution simulation of surface current and sea ice in the Arctic Mediterranean Seas

A fine-resolution model is developed for ocean circulation simulation in the National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Chinese Academy of Sciences, and is applied to simulate surface current and sea ice variations in the Arctic Mediterranean Seas. A dynamic sea ice model in elastic-viscous-plastic rheology and a thermodynamic sea ice model are employed. A 200-year simulation is performed and a dimatological average of a 10-year period (141st-150th) is presented with focus on sea ice concentration and surface current variations in the Arctic Mediterranean Seas. The model is able to simulate well the East Greenland Current, Beaufort Gyre and the Transpolar Drift, but the simulated West Spitsbergen Current is small and weak. In the March climatology, the sea ice coverage can be simulated well except for a bit more ice in east of Spitsbergen Island. The result is also good for the September scenario except for less ice concentration east of Greenland and greater ice concentration near the ice margin. The extra ice east of Spitsbergen Island is caused by sea ice current convergence forced by atmospheric wind stress.