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981.
Improved understanding of the development with time of pitting and corrosion of the external surfaces of buried cast iron water pipes is crucial for the management of water supply distribution networks. The present study reports observations of surface topography of cast iron pipes exposed between 34 and 129 years in clay soils. Pit depths, surface areas and widths associated with deeper pits are reported, including as functions of exposure period. Pitting appears to progress in a step-wise manner as also earlier reported for the corrosion of steels. While there is a relation between pit depth and lateral size of pits through the amalgamation of pits to form plateaus into which new pits tend to form, the predominant progression of material loss through corrosion and pitting is into the metal rather than laterally. The practical implications of these observations are discussed. 相似文献
982.
针对深海采矿系统在海底黑暗地带工作无法直观、便捷地监测这一问题,设计和实现了一种基于Visual C++和Vega Prime软件联合开发的深海采矿视景仿真系统。利用Terra Vista软件和Multigen Creator 软件构建了三维虚拟场景,包括采矿系统三维实体模型的创建和海底地形的生成,并在Vega Prime软件中实现了视景仿真。介绍了利用Visual C++二次开发Vega Prime视景仿真系统的方法,根据加载的实时数据驱动集矿机模型,控制其运动路径。阐述了Vega Prime与OpenGL联合开发的关键技术及方法,并绘制了集矿机的行走轨迹图。仿真结果表明:此方案能逼真、准确、实时地模拟集矿机在海底的动态运动,对深海采矿作业的顺利进行具有一定的参考意义。 相似文献
983.
为研究加速度不对称波浪作用下的海床响应特征,基于Biot多孔弹性介质理论建立了波浪作用下海床响应数学模型,采用水槽实验数据对模型进行了验证。通过引入加速度不对称波浪压力边界条件的计算方法,模拟分析了波浪加速度不对称性对海床内部孔隙水压力、有效应力以及土体液化的影响。结果表明,波浪加速度不对称性会引起海床表层正向孔压幅值的显著衰减,使孔压的空间分布变得偏斜,减小了液化深度和宽度,使海床液化区域变得窄而浅。 相似文献
984.
985.
Yu YANG Hui CHENG Biao LIANG Guoyi HOU Di ZHAO Chun LIU Kaifu ZHANG 《Frontiers of Mechanical Engineering》2021,16(4):840
In this paper, an improved fractal interpolation model is proposed to reconstruct the surface topography of composite hole wall. This model adopts the maximum positive deviations and maximum negative deviations between the measured values and trend values to determine the contraction factors. Hole profiles in 24 directions are measured. Fractal parameters are calculated to evaluate the measured surface profiles. The maximum and minimum fractal dimension of the hole wall are 1.36 and 1.07, whereas the maximum and minimum fractal roughness are 4.05 × 10 −5 and 4.36 × 10 −10 m, respectively. Based on the two-dimensional evaluation results, three-dimensional surface topographies in five typical angles (0°, 45°, 90°, 135°, and 165°) are reconstructed using the improved model. Fractal parameter D s and statistical parameters Sa, Sq, and Sz are used to evaluate the reconstructed surfaces. Average error of D s, Sa, Sq, and Sz between the measured surfaces and the reconstructed surfaces are 1.53%, 3.60%, 5.60%, and 9.47%, respectively. Compared with the model in published literature, the proposed model has equal reconstruction effect in relatively smooth surface and is more advanced in relatively rough surface. Comparative results prove that the proposed model for calculating contraction factors is more reasonable. 相似文献
986.
987.
B. Fink P. J. Matts S. Röder R. Johnson M. Burquest 《International journal of cosmetic science》2011,33(2):126-131
Perception of age and health is critical in the judgement of attractiveness. The few studies conducted on the significance of apparent skin condition on human physical appearance have studied faces alone or isolated fields of images facial skin. Little is known about whether perception of the face matches that of other body parts or if body skin affects overall age and attractiveness perception when presented in combination with facial skin. We hypothesized that independent presentation of female faces, chests and arms (including hands) – cropped from a full face and upper body image – would result in significant differences in perception of age and attractiveness compared to the corresponding composite. Furthermore, we sought to investigate whether relatively young and attractive looking skin on selected, individual parts of the body affects overall perception. Digital photographs of 52 women aged 45–65 years were collected and processed to yield four derivative sets of images: One set showed the composite of all features, i.e. the face, the chest and the arms, whereas the other three were cropped carefully to show each part of the upper body described above independently. A total of 240 participants judged these faces for perceived age and attractiveness. Our results showed significant differences in perception with the chest and the arms being judged significantly younger than the face or composite image of the same women. Moreover, arms and chest images were perceived as more attractive than face and composite images. Finally, regression analysis indicated that differences between the perceived and chronological values of overall age perception could be predicted by age perception of the face and arms. These results continue to support the significance of facial age perception in assessment of a woman’s age, but highlight that body skin also plays a role in overall age impression. 相似文献
988.
The existing surface roughness standards comprise only two dimensions. However, the real roughness of the surface is 3D (three-dimensional). Roughness parameters of the 3D surface are also important in analyzing the mechanics of contact surfaces. Problems of mechanics of contact surfaces are related to accuracy of 3D surface roughness characteristic. One of the most important factors for 3D characteristics determination is the number of data points per x and y axes. With number of data points we understand its number in cut-off length. Number of data points have substantial influence on the accuracy of measurement results, measuring time and size of output data file (especially along the y-axis direction, where number of data points are number of parallel profiles). Number of data points must be optimal. Small number of data points lead to incorrect results and increase distribution amplitude, but too large number of data points do not enlarge range of fundamental information, but substantially increase measuring time. Therefore, we must find optimal number of data points per each surface processing method. 相似文献
989.
Moo-Chin Wang Huy-Zu Cheng Huey-Jiuan Lin Chien-Fu Wang Chi-Shiung Hsi 《Materials Chemistry and Physics》2013
The crystallization behavior and magnetic properties of 10Li2O–9MnO2–16Fe2O3–25CaO–5P2O5–35SiO2 (10LFS) glass have been studied using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) to observe the crystallization behavior and a superconducting quantum interference device (SQUID) for measurements of the magnetic properties. The DTA shows that the 10LFS glass has one broad exothermic peak at approximately 674 °C and one sharp (the highest) exothermic peak at 764 °C. When the 10LFS glass crystallized at 850 °C for 4 h, the crystalline phases identified by XRD were lithium silicate (Li2SiO3), β-wollastonite (β-CaSiO3), lithium orthophosphate (Li3PO4), magnetite (FeFe2O4) and triphylite (Li(Mn0.5Fe0.5)PO4). The SEM surface analysis revealed that the β-wollastonite and lithium silicate have a lath morphology. The TEM microstructure examination showed that the largest FeFe2O3 particles have a size of approximately 0.3 μm. When the 10LFS glass was heat treated at 850 °C for 16 h and a magnetic field of 1000 Oe was applied, a very small remnant magnetic induction of 0.01 emu g−1 and a coercive force of 50 Oe were obtained, which revealed an inverse spinel structure. 相似文献
990.
针对提升小波提取非对称表面形貌特征时存在平移变动性和较差的方向选择性,将具有平移不变性和良好的方向选择性的冗余提升形态Haar小波应用到非对称表面的特征提取中。开展了该形态小波对具有显著特征的非对称平顶珩磨的缸套内表面进行特征提取的分析;同时结合仿真的方法,研究了该形态Haar小波对一个模拟的具有一定长度沟槽特征的空间表面进行特征提取的效果。研究结果表明,冗余提升形态Haar小波对非对称表面形貌进行形态特征提取时,在各尺度重构的信号沿特征边缘几乎没有变动且无畸变,可实现准确提取。 相似文献