Relationship between porosity and chloride diffusivity in cement-based composite materials

For investigating the effect of porosity in cement-based composite materials on diffusion coefficient of chloride ion, a series of mortar specimens with different water-cement ratios, different volume fractions and different diameters and graduation of aggregates are cast, and then chloride diffusivity of mortar specimens are measured by steady-state electric acceleration method and pore structure parameters of corresponding samples are obtained by mercury intrusion porosimetry. At the same time, the pore size distributions are visualized by X-ray micro-focus computer tomography. The results show that porous interfacial transition zones between aggregate and bulk cement paste significantly change the distribution of pore structure in hardened cement paste, and the smaller water-cement ratio is, the more significant the effect of interfacial transition zones on pore structures of hardened cement paste is. A good correlation between the total porosity, capillary porosity and the diffusion coefficient of chloride ion in cement-based composite materials has been determined and the continuous pore diameter is linearly related to the diffusion coefficient of those. Furthermore, the larger the continuous pore diameter is, the larger the value of chloride diffusivity is.     

螺旋CT对大脑中动脉供血区超急性期脑梗死的诊断价值

目的探讨螺旋CT对大脑中动脉供血区超急性期脑梗死的诊断价值.方法对62例大脑中动脉供血区超急性期脑梗死（发病6 h内）的CT征象进行分析.结果大脑中动脉供血区脑梗死超急性期CT表现为MCA高密度征、点状征及豆状核边缘模糊,密度减低;岛叶密度减低,相应侧裂池变窄;颞叶灰质密度减低,脑沟变窄或消失,灰白质界限不清.结论螺旋CT对大脑中动脉供血区超急性期脑梗死有很高的诊断价值.     

A NEW TYPE OF RADIOGRAPHIC BONE REMODELING IN THE DISTAL RADIAL AND ULNAR METAPHYSIS IN 54 NEWFOUNDLAND DOGS

In this longitudinal observational study, 118 growing Newfoundland dogs were followed with sequential radiographic examination of the right front limb, which were scheduled at ages 3, 4, 6, 12, 18, and 24 months to record evidence of skeletal changes. All affected dogs had evidence of changes at 6 months and dogs included in this study had radiographic examination at 6 months and at least two other scheduled examinations that included either 4 or 12 months. The dogs were privately owned and had individualized nutrition and environment with no maintenance protocol required by the project leaders. Irregularities in bone remodeling in the distal radius and ulna were seen in radiographs of 54 of 118 (45.8%) dogs. These irregularities differ from changes previously described in the Newfoundland dog. The reported irregularities were seen as islands of reduced opacity outlined by thickened, radiopaque osseous trabeculae, which were aligned with the axis of stress. All the 54 dogs with irregularities during some phase of development consistently had changes at 6 months of age. Reorganization of the changes in the bone was slow, and residual changes were visible at 18-24 months of age in many cases. The significance of these findings may lie in their potential for misinterpretation if they had been discovered in the presence of clinical signs such as any lameness or growth arrest. Radiographic appearance indicates disturbances in the bone maturation. The etiopathogenesis is unclear. Nutritional, environmental and genetic factors have to be studied.     

X射线衍射法测定圆锯片的适张残余应力

该文应用X射线衍射应力测定仪对不同状态的圆锯片进行了残余应力分布的实验测定，并对实验方法和最终得出的应力分布进行了详细的分析讨论.结果表明，对于未适张锯片，辊压带内外锯片上切向和径向应力均为压应力；对于正常适张的锯片，其切向应力在辊压带外为拉应力，辊压带内侧为压应力，径向应力在辊压带内外均为压应力；对于已使用多年，适张失效锯片，其切向和径向应力均为压应力. 实验中还发现入射的X射线除了沿半径方向外，沿其他方向入射，在其表层都呈φ角分离现象，在经电解研磨去除20～30 μm锯片表层后此现象消失.      

Quantitative analysis of earthworm burrow systems with respect to biological soil-structure regeneration after soil compaction

 On arable land, tilled with conventional tillage (CT) and conservation tillage (CS) respectively, plots were compacted by wheeling them 6 times with a 5 Mg wheel load in spring 1995. Immediately after compaction, undisturbed soil monoliths were excavated from the compacted and uncompacted plots. The monoliths were defaunated and inoculated with either Lumbricus terrestris or Aporrectodea caliginosa. One monolith from each plot remained uninoculated as a control. After 6 months the monoliths were defaunated again and then scanned with X-ray helical computed tomography. The data were transformed, the void systems inside the monoliths were reconstructed and visualised, and the parameters total void length, total void volume, tortuosity and continuity were quantified. The parameters' values were generally lower in the controls than in the inoculated monoliths. Differences in burrow construction could be explained by the different life strategies of the two earthworm species. Changes in burrow morphology due to tillage system and soil compaction were minor. Only the continuity of the burrow systems clearly changed: decreasing for L. terrestris and increasing for A. caliginosa. This can be explained by a change in the earthworms' burrowing activity to minimise energy expenditure in compacted soil. By extrapolating field data, we concluded that earthworms have great potential for biologically regenerating the soil structure after a single compaction event. Due to higher earthworm abundances in soil managed by CS the regeneration of the soil structure is assumed to be better in these plots than those tilled by CT. Received: 17 December 1997     

Quantitative Phase Analysis of Weight Factors of X-ray Intensity

A new method is applied in this article to the quantitative phase analysis for weight factors of X-ray diffraction intensity. This method overcame the defect of traditional sampling and quantitative analysis method which only single out one plane web diffraction peaks for quantitative analysis from the phases of the sample to be tested. The method applied in this article is that the sample processing and taking measurements to the samples only once, then determining the weight factors by the intensity corresponding to n X-ray diffraction peaks from the phases of the sample to be tested. Thus we can get the relative percentage of each phase in the sample.     

X-ray diffraction studies of poly(aryl ether ether ketone) fibers with different degrees of crystallinity and orientation

A selection of commercially available poly(ethylene terephthalate) fibers with different degrees of molecular alignment and crystallinity have been investigated utilizing a wide range of techniques including optical microscopy, infrared spectroscopy together with thermal and wide-angle X-ray diffraction techniques. Annealing experiments showed increased molecular alignment and crystallinity as shown by the increased values of birefringence and melting enthalpies. Crystallinity values determined from thermal analysis, density, unpolarized infrared spectroscopy and X-ray diffraction are compared and discussed in terms of the inherent capabilities and limitations of each measurement technique. The birefringence and refractive index values obtained from optical microscopy are found to decrease with increasing wavelength of light used in the experiments. The wide-angle X-ray diffraction analysis shows that the samples with relatively low orientation possess oriented non-crystalline array of chains whereas those with high molecular orientation possess well defined and oriented crystalline array of chains along the fiber axis direction. X-ray analysis showed increasing crystallite size trend with increasing molecular orientation. SEM images showed micro-cracks on low oriented fiber surfaces becoming smooth on highly oriented fiber surfaces. Excellent bending characteristics were observed with knotted fibers implying relatively easy fabric formation.     

西藏拉屋和扎西康矿区土壤的黏粒矿物组成研究

采集西藏拉屋和扎西康两矿区代表性土壤样品,测定了土壤基本性状、黏土矿物和氧化铁含量。结果表明:拉屋矿区土壤呈酸性,扎西康矿区土壤呈碱性。拉屋矿区土壤有机质含量和CEC明显高于扎西康矿区的;两矿区的主要黏土矿物有水云母、高岭石、绿泥石、蛭石、1.4 nm过渡矿物和少量的混层矿物。拉屋矿区主要矿物是水云母和高岭石,扎西康矿区主要矿物是水云母;两矿区土壤的游离氧化铁均以晶形氧化铁为主,非晶形氧化铁所占比例很少。     

香菇栽培前后基质中纤维素结构的变化

为了探讨食用菌栽培料和菌糠纤维素微观结构的差异,本研究以黑龙江省常见的香菇栽培料和香菇菌糠为实验材料,利用扫描电子显微镜(SEM)观察香菇栽培前后纤维素微观表面的变化,利用光衍射(XRD)和红外光谱(FT-IR)研究了香菇栽培前后纤维素结晶度和微观结构分子基团的改变。扫描电镜观察到栽培食用菌后,纤维素微观结构整体变化不大,但纤维素表面出现了更多的细小洞穴;XRD和FT-IR测定的香菇菌糠纤维素结晶区的结晶度和纤维素特征吸收峰的吸收强度都明显低于香菇栽培料,表明纤维素晶体结构遭到破坏,这正好和SEM观察到的图像吻合。栽培香菇后纤维素结构分子间和分子内氢键发生重排,这也是纤维素降解困难的原因。     

肉中异物X射线检测的肉厚度激光双三角测量方法

针对不规则形状肉X射线系统成像受肉厚度影响产生灰度偏差的问题,提出一种激光三角法测量肉的厚度以补偿X射线图像灰度偏差的方法,建立了激光测量肉厚度模型及一种基于对称式结构的激光双三角法肉厚度测量系统。通过标定将左右CCD相机采集的两幅激光图像统一到同一个坐标下,采用基于灰度的图像拼合法将两幅肉激光图像拼合为一个完整的肉激光图像。三维扫描试验表明,肉图像外部形状基本对应,灰度变化相似,肉图像厚度变化与肉厚度轮廓接近。