Tomographic measurements of pore filling at infiltration fronts     

David A. DiCarlo  L. Don Seale  Kyungmin Ham  Clinton S. Willson 《Advances in water resources》2010

For certain porous media and initial conditions, constant flux infiltrations show a saturation profile which exhibits overshoot. This overshoot is the cause of gravity driven fingering, cannot be described by standard models of unsaturated flow, and is likely controlled by the exact nature of the pore filling at the initial front. Here we report synchrotron X-ray micro-tomography measurements of the porous medium and measure which pores are filled by water and air at the initial wetting front as a function of flux. We find that at high fluxes all the pores are filled with water; for intermediate fluxes, the pores along the edge of the column remain unsaturated; and for low fluxes the pores in the bulk of the experimental column remain unsaturated. This suggests that the unsaturated overshoot conditions observed at higher fluxes are primarily an edge effect of the column. The results can help delineate the correct continuum models that can capture overshoot and gravity driven fingering.  相似文献   

Diffraction of plane P waves around an alluvial valley in poroelastic half-space     

Zhongxian Liu  Jianwen Liang 《地震学报(英文版)》2010,(1):35-43

Diffraction of plane P waves around an alluvial valley of arbitrary shape in poroelastic half-space is investigated by using an indirect boundary integral equation method. Based on the Green’s functions of line source in poroelastic half-space, the scattered waves are constructed using the fictitious wave sources close to the interface of the valley and the density of fictitious wave sources are determined by boundary conditions. The precision of the method is verified by the satisfaction extent of boundary...  相似文献   

磷酸铝结合剂改性绿松石的结构特征     

陈全莉  袁心强  陈敬中  周金花 《地球科学》2010,35(6):1023-1028

疏松绿松石经磷酸铝结合剂浸胶充填处理后,宝石学参数、力学和工艺性质均得到明显改善,与天然绿松石相仿.为查明这类改性绿松石的结构和探讨磷酸铝无机结合剂对绿松石的改善机理,采用环境扫描显微镜(ESEM)、差热分析(TG-DSC)、红外吸收光谱(IR)和X射线粉晶衍射分析方法(XRD),对此类浸胶充填处理后的绿松石结构、物相及热性质等特征进行了研究.结果显示充填入的磷酸铝结合剂呈凝胶状分布在绿松石微孔隙间,处理后绿松石的分子结构和矿物组构与处理前一致,但产生了一定程度的非晶质化,与磷酸铝结合剂的填充作用有关,即磷酸铝结合剂在固化过程中生成氢,结合形成无机网络高分子结构;处理后绿松石的热反应温度较处理前普遍有所降低,主要是由于添加入的磷酸铝结合剂具有较低的吸热反应温度所致.   相似文献   

婴幼儿X线胸片对胸腺增大的分析诊断   总被引：1，自引：0，他引：1  

代燕增  冯建明  张巧权 《CT理论与应用研究》2010,19(2):69-74

目的:探讨婴幼儿胸腺影增大的X线表现。方法:收集我院近年婴幼儿X线胸片观察到增大的胸腺影300例,主要讨论婴幼儿胸腺的影像表现、诊断与鉴别诊断。结果:对X线胸片上显示的300例增大的胸腺影在性别、年龄、形态、位置等方面进行分析总结。其中右上纵隔旁僧帽状90例,双侧纵隔旁杯形90例,右上纵隔旁船帆状75例,右肺尖圆块状30例,左上纵隔旁椭圆形15例。结论:X线胸片对婴幼儿胸腺影增大的诊断与鉴别具有一定作用,定性诊断最后尚需依靠穿刺活检及结合临床综合分析。  相似文献   

基于改进重建滤波器的局部CT重建算法     

李保磊  张耀军 《CT理论与应用研究》2010,19(4):11-17

鉴于实际工程应用需求,基于截断投影数据的CT图像局部重建是X射线CT重建的一个重要课题,本文概述了现有的局部重建算法,分析了其优缺点,提出了一种基于改进重建滤波器的局部CT重建算法。通过对滤波函数的改进,使其能量主要集中在中心位置,使旁瓣迅速下降,进而使滤波函数具有局部重建功能。另外改进的滤波函数压制了低频信息,突出了高频信息,具有提高成像空间分辨率的功能,但对图像噪声有所放大,实际实验数据验证了算法的可行性。  相似文献   

胰腺导管内乳头状黏液性肿瘤的CT诊断     

詹勇  向子云  王静波  朱宇辉  杨雪 《CT理论与应用研究》2010,19(4):85-90

目的:探讨胰腺导管内乳头状黏液性肿瘤(IPMN)的CT表现特征,以提高对该病的诊断能力。方法:回顾性分析经临床手术病理证实的16例IPMN病例CT图像,并作文献复习。结果:16例IPMN病例中,主胰管型3例,表现为主胰管扩张伴管壁结节样突起;分支胰管型7例,表现为分叶状单发囊性病变或葡萄串样多发囊性病变伴腔内分隔或结节样突起;混合型6例,表现为主胰管扩张和囊性病变合并存在。结论:IPMN的CT表现有一定特征性,有助于对该病的正确诊断。  相似文献   

GCL对垃圾渗滤液中阳离子和有机质的吸附能力          下载免费PDF全文

徐超  祁昌伟  李志斌 《水文地质工程地质》2011,38(3):77-81

通过对渗透前后垃圾填埋场渗滤液进行化学成分的测定和分析,研究了GCL的吸附能力及其变化规律,并采用X射线荧光光谱分析对试验结果进行了验证。研究结果表明在渗透过程中GCL对渗滤液中的有机物和阳离子存在吸附作用,水化液对GCL的吸附能力有一定影响;在渗透开始阶段,GCL对垃圾渗滤液中阳离子和有机物的吸附能力比较强,而后逐渐达到吸附饱和状态而丧失吸附能力,因此用GCL作为防渗屏障,主要是依靠其低渗透特性,而非其对溶液中有机质和有害离子的吸附作用。通过对膨润土进行X射线荧光光谱分析也发现:经过渗透后的膨润土中除常见氧化物外,还有来自渗透液中被吸附的物质,但含量不大。  相似文献   

Short-crested waves interaction with a concentric porous cylinder system with partially porous outer cylinder     

刘俊  林皋  李建波 《中国海洋工程》2012,26(2):217-234

In this paper, based on the linear wave theory, the interaction of short-crested waves with a concentric dual cylindrical system with a partially porous outer cylinder is studied by using the scaled boundary finite element method (SBFEM), which is a novel semi-analytical method with the advantages of combining the finite element method (FEM) with the boundary element method (BEM). The whole solution domain is divided into one unbounded sub-domain and one bounded sub-domain by the exterior cylinder. By weakening the governing differential equation in the circumferential direction, the SBFEM equations for both domains can be solved analytically in the radial direction. Only the boundary on the circumference of the exterior porous cylinder is discretized with curved surface finite elements. Meanwhile, by introducing a variable porous-effect parameter G, non-homogeneous materials caused by the complex configuration of the exterior cylinder are modeled without additional efforts. Comparisons clearly demonstrate the excellent accuracy and computational efficiency associated with the present SBFEM. The effects of the wide range wave parameters and the structure configuration are examined. This parametric study will help determine the various hydrodynamic effects of the concentric porous cylindrical structure.  相似文献   

腮腺Warthin瘤的影像学分析     

段芙红  邱士军  姜建威 《CT理论与应用研究》2012,21(3):527-533

目的:分析腮腺Warthin瘤CT、MRI影像学表现,提高对本病的认识。方法:回顾性分析经手术病理证实的37例腮腺Warthin瘤CT、MRI表现。其中男32例,女5例。年龄27～80岁,平均59岁,50岁以上26例(70.2%)。有吸烟史30例(81%)。结果:37例共56个病灶,单侧单发28例(28个病灶),单侧多发4例(12个病灶),双侧多发5例(16个病灶);CT及MRI表现:病灶长径0.5～4.8cm,呈圆形或椭圆形,边界清楚,内部密度或信号均匀或不均;CT增强扫描病灶实质部分呈早期明显强化,MRI增强扫描病灶呈不均匀强化。结论:腮腺Warthin瘤有一定的临床和CT、MRI特点,结合患者年龄、性别及病史,可提高对其诊断准确率,减少误诊。  相似文献   

强直性脊柱炎骶髂关节病变CT与MRI诊断比较     

陈超  徐凯  郑燕  尹燕  张秀莉 《CT理论与应用研究》2012,21(3):557-562

目的：探讨强直性脊柱炎骶髂关节病变的影像学特征,并比较CT和MRI检查在诊断骶髂关节病变方面的作用。方法：回顾性分析51例经临床证实的AS患者骶髂关节CT及MRI表现特点,根据CT及MRI征象进行分级,对其分级结果进行统计学分析。结果：病变主要累及髂骨侧,对于I级病变,MRI较CT发现更多病灶,两者检出率差别有统计学意...  相似文献