气淬法制备高炉渣玻璃微珠的性能

通过实验分别检测了高炉渣珠的堆积密度、粒度分布、化学侵蚀性、筒压强度和表观特性.结果表明,堆积密度随粒径的增加先增加后减小,0.3~1mm粒径范围内渣珠堆积密度最大,并且渣珠粒径主要集中在0.30~1.0mm之间,成珠率较高;渣珠不耐酸,在同一侵蚀溶液中,粒径较大的渣珠的抗侵蚀能力强于粒径较小的渣珠;粒径越小,渣珠筒压强度越大,渣珠承受压力的能力越强;高炉渣珠表面光滑平整,呈圆球状,粒径大小均匀;由于渣珠气淬的冷却速率较快,渣珠非晶相含量较高,当渣珠粒径<0.30mm时,XRD曲线变为馒头峰,基本不再有晶相析出,矿相变为非晶相.     

磁性花生壳负载钯催化剂的制备及催化氨硼烷释氢性能

以高锰酸钾改性后的花生壳为原料,通过共沉淀法制备了磁性花生壳(PSK-Fe_3O_4)复合材料,并以其为载体制备了磁性花生壳负载钯催化剂(Pd/PSK-Fe_3O_4).以XRD、FT-IR、TEM、XPS、TG等表征手段对该催化剂进行了表征,并将其应用于催化氨硼烷水解释氢.结果表明:Pd/PSK-Fe_3O_4催化剂在催化氨硼烷水解反应中表现出较好的催化活性,其转换频率(TOF)为6.7 mol_(H2)·mol_(Pd)~(-1)·min~(-1),表观活化能(E_(app))为28.0 kJ mol~(-1).Pd/PSK-Fe_3O_4催化氨硼烷水解释氢反应对于催化剂浓度和氨硼烷浓度的反应级数分别为一级和零级.此外,循环实验表明该催化剂具有较好的循环稳定性.     

冰箱压缩机壳体辐射噪声的数值分析

采用有限元边界元耦合的方法分析在平面声源激励下的压缩机辐射噪声,并改变壳体形状设计后分析压缩机辐射噪声,发现新的壳体设计可以降低2 000 Hz附近的壳体辐射噪声。     

舰载制导炮弹三点法弹道仿真

在分析实战态势的情况下,建立了相关坐标系,给出了仿真所用的主要数学模型.基于基本作战流程,对仿真流程进行了详细的描述.在给定条件下,利用Visual C 和Matlab编程工具对三点法导引弹道进行了仿真,并分析了仿真结果,验证了模型的正确性.最后指出了仿真有待深入的部分和战术应用前景.     

游泳馆钢-木混合结构的体系选型和关键设计问题

崇明游泳馆采用钢-胶合木混合网壳结构.通过对胶合木力学特性和游泳馆结构静力的分析,计算屋面网壳结构钢和胶合木的合理应用范围.讨论了钢夹板木结构连接节点刚度对结构整体刚度的影响,并通过节点试验得到了节点的实际刚度.参考《空间网格结构技术规程》中关于网壳结构的稳定性分析和极限承载力的计算方法,考虑木材的材质缺陷和无塑性发展...     

考虑界面效应的纳米流体的热传导模型

借鉴图论的有关做法。结合威尔逊空间相互作用模型。构建区域中心城市区位选择的模型,从而试图定量分析封闭和开放两种条件下区域中心城市的适宜区位．从模型中可以看出,在封闭条件下区域中心城市适宜区位趋于区域的地理中心。而在开放条件下区域中心城市适宜区位趋于主导联系方向．作者选取浙江省嘉兴市对模型进行实证分析,分别考察了封闭和开放两种条件下嘉兴区域中心城市适宜区位的变化趋势．     

What is the matter with Corbicula fluminea (Mollusca: Bivalvia: Cyrenidiae)? Occurrence of unusual shell erosion in Northern Italy

ABSTRACT

Corbicula fluminea is a bivalve considered to be among the 100 worst invasive species in Europe due to its economic and ecological impacts in freshwater ecosystems. Here, we report for the first time a phenomenon of shell erosion observed in two distinct populations of C. fluminea collected in 2015 from two semi-natural small streams of the River Ticino hydrographic basin (Northern Italy). We measured several biometric variables in order to quantify the shell damage: length and thickness of the right valve and the shell free dry weight of each specimen and compared results with those of ‘normal’ populations from another stream of the same area. Our results confirmed that there was abnormal shell erosion and a reduction in shell thickness in both populations. We hypothesised several potential causes for the observed erosion, but none of them could provide sufficient explanation: neither the pH of the water, nor the level of calcium or total hardness of the water or granulometry of the substrates differed among streams. Similarly, predation pressure cannot be considered a reasonable explanation, since in the study area only a few animals actively prey on these bivalves and the marks they leave on the shells are completely different from the ones observed on our specimens. Lastly, we hypothesised that the bivalves may have been affected by a disease or parasitic infestation that had weakened their shells or prevented them from self-repairing and identified a fungal parasite that could possibly cause a disease to C. fluminea, namely the Ascomycota Geotrichum candidum. However, this species occurred only in one of the two abnormally eroded populations. In conclusion, a valid explanation for the morphological alteration that our study revealed has yet to be found.     

淡水养殖的珍珠贝壳热分解行为研究

采用FTIR实时红外检测方法研究室温～600 ℃范围内贝壳珍珠层的红外光谱特征,结合热重分析考察淡水养殖珍珠贝壳中的有机和无机组分变化情况.采用扫描电子显微镜观察珍珠层的微结构,并利用X-射线衍射方法测量不同温度下贝壳中无机成分的晶相变化.结果表明,贝壳中氨基酸类有机物热分解后部分以胺的形式挥发,另一部分则转化为不可挥...     

饱和结构性黄土不排水柱孔扩张问题弹塑性解

为导出饱和黄土中不排水柱孔扩张问题严格解,采用结构性黄土修正剑桥模型描述黄土力学特性。在弹性区采用小变形假设求解孔周土体应力与变形,同时将塑性区柱孔扩张边值问题转化为3个以应力分量为基本未知量的一阶非线性常微分方程求解问题。以弹塑性界面上应力分量作为初始条件求解控制方程,得到孔周塑性区应力分布,然后对径向平衡方程积分求得孔隙水压力。通过算例分析验证了该方法的正确性。结果表明:退化解与已有数值解完全吻合,并且黄土结构性对孔周应力、超静孔压以及弹塑性半径等影响显著。     

阶梯孔磁壳的冷挤压工艺研究

根据阶梯孔磁壳零件的结构特点,采用锻造分析软件Qform3D对其冷挤压一次反挤成形方案和改进方案进行数值模拟分析。经工艺分析及参数计算,分两次挤压成形减少了模具对变形材料的约束,增大了金属流动速度,降低了挤压力。因此确定分两次挤压的改进方案为阶梯孔磁壳零件的合理工艺方案,对该零件的生产应用具有重要的指导意义。