排序方式: 共有13条查询结果,搜索用时 15 毫秒
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采用磁控溅射技术在聚甲基丙烯酸甲酯(PMMA)树脂基托表面沉积一层纳米银(Ag NPs)涂层.研究了纳米银改性PMMA树脂基托的机械性能,为改性材料的临床应用提供理论基础.根据国际标准ISO2409:2007描述的划格法对涂层与基底的附着力强度进行测试,各组试件的接触角采用静态液滴法测量,三点弯曲法检测试件的弯曲强度.结果显示,各组涂层与PMMA基底材料结合良好,各组试件的表面润湿性变化不大,其中PMMA-Ag NPs80s组疏水性略有提高,各组试件的弯曲强度均符合国家标准. 相似文献
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为了实现对危化品仓储堆垛安全距离的实时监测和预警,采用由激光测距、旋转云台、编码器等组成的激光扫描监控阵列对垛距进行安全监测。针对激光测距扫描点云数据中异常噪声的问题,采用差值去噪算法。该算法是将扫描得到的激光测距数据点按角度值进行从小到大排序后,相邻两点的距离值依次取差值,然后对距离差值与预设阈值进行比较,滤掉噪点数据。针对几种不同尺寸和形状的障碍物进行了实验研究,结果表明差值去噪方差值明显小于加权二乘、Savitzky-Golay等拟合算法,该算法不仅能有效去除扫描点云数据中的异常噪声,同时较另外两个算法,数据完整性和可靠性更高。 相似文献
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为研究混凝土靶侵彻后空腔对爆炸效应的影响,开展了450~700 m/s速度下混凝土靶体侵彻与爆炸模型实验。基于10组实验结果,结合量纲分析等方法,研究了侵彻结果对爆坑深度的影响。结果表明,可采用无量纲冲击系数表征侵彻深度、开坑体积以及侵彻损伤值等侵彻效应,不考虑装药长径比的影响,侵彻后爆炸带来的破坏深度增加量he主要受无量纲冲击系数Ip与爆炸系数Ie的影响。利用实验数据获得了长径比为5时he的影响规律:(1) Ip较小时,侵彻深度较小,Ie的变化对爆炸弹坑深度he变化影响较小;(2) 随着Ip的增加,he不断增加,但增加幅度逐渐变小,Ie对he的影响不断变大;(3)随着Ip增加到一定程度,he趋于常数,Ie对he的影响趋于稳定。 相似文献
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In order to investigate the influence of surface roughness on turbulent flow and examine the wall-similarity hypothesis of Townsend, three-dimensional numerical study of turbulent channel flow over smooth and cube-rough walls with different roughness height has been carried out by using large eddy simulation(LES) coupled with immersed boundary method(IBM). The effects of surface roughness array on mean and fluctuating velocity profiles, Reynolds shear stress, and typical coherent structures such as quasi-streamwise vortices(QSV) in turbulent channel flow are obtained. The significant influences on turbulent fluctuations and structures are observed in roughness sub-layer(five times of roughness height).However, no dramatic modification of the log-law of the mean flow velocity and turbulence fluctuations can be found by surface cube roughness in the outer layer. Therefore, the results support the wall-similarity hypothesis. Moreover, the von Karman constant decreases with the increase of roughness height in the present simulation results. Besides, the larger size of QSV and more intense ejections are induced by the roughness elements, which is crucial for heat and mass transfer enhancement. 相似文献
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The particle motions of dispersion and transport in air channel flow are investigated using a large eddy simulation(LES) and Lagrangian trajectory method. The mean and fluctuating velocities of the fluids and particles are obtained,and the results are in good agreement with the data in the literature. Particle clustering is observed in the near-wall and low-speed regions. To reveal the evolution process and mechanism of particle dispersion and transport in the turbulent boundary layer, a multi-group Lagrangian tracking is applied when the two-phase flow has become fully developed: the fluid fields are classified into four sub-regions based on the flow characteristics, and particles in the turbulent region are divided accordingly into four groups when the gas–particle flow is fully developed. The spatiotemporal transport of the four groups of particles is then tracked and analyzed. The detailed relationship between particle dispersion and turbulent motion is investigated and discussed. 相似文献
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本工作针对含硫脲基咪唑憎水功能离子液体在溶液中Cu2+萃取方面的应用及其机理进行研究. 考察了萃取两相体积比、金属离子浓度、时间、无机盐NaCl、溶液pH及离子液体烷基链长等因素的影响. 结果表明: 室温条件下, 0.1 mL离子液体[CnMPSM][PF6] (n=4、6、8)与5 mL 21.94 mg/L的氯化铜溶液室温条件下超声混合30 min, 溶液中Cu2+的去除率即超过95%; 且此类离子液体对金属离子的萃取效果顺序为: n=4≈n=6>n=8. 以[HMPSM][PF6]为研究对象, 发现溶液中无机盐NaCl的含量以及溶液pH 对金属离子的萃取效果影响不明显. 与传统离子液体[Cnbim][PF6] (n=6、8)相比, 硫脲基的引入使其萃取率由20%左右提高到99%, 且有效避免因阳离子交换而引起水中咪唑阳离子含量增加问题. 通过理论计算发现, 功能离子液体对金属离子的萃取依赖于官能团中的S元素与Cu2+之间较强的静电及路易斯酸碱作用, 与萃取实验中离子液体未和Cu2+发生阳离子交换作用相吻合. 相似文献
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