A dilatometry study of the influence of green density on anisothermal and isothermal shrinkage of plain iron green parts

ABSTRACT

The influence of green density between 6.5 and 7.3?g?cm^?3 on the anisothermal and isothermal shrinkage of atomized plain iron was investigated by dilatometry. The geometrical activity deriving from the extension of the interparticle contact areas and the structural activity provided by the defectiveness of the interparticle contacts promote anisotropic anisothermal shrinkage starting from 500°C up to the bcc to fcc iron transformation. It displays a minimum at 6.9?g?cm^?3, resulting from the combined effects of the thermodynamic driving force and of geometrical and structural activity. Anisothermal shrinkage is caused by an anisotropic increase in the internal radius of the neck. Anisotropic isothermal shrinkage is smaller than the anisothermal one and is almost independent on green density. No anisothermal shrinkage was observed on the tapped powder, demonstrating that anisothermal shrinkage in green specimens is due to geometrical and to structural activity introduced by prior cold compaction.     

Using the aeromagnetic data for mapping the basement depth and contact locations,at southern part of Tihamah region,western Yemen

The present study aims to produce an excellent picture for the basement depth and contact locations, deduced from the available aeromagnetic data. The total intensity aeromagnetic map was first corrected by the application of the reduction to the magnetic pole (for low latitude areas) technique. On the other hand, this map shows different anomalies of varying frequencies and amplitudes that reveal various causative sources, as well as varying compositions and depths. So, the fast Fourier transform is applied on the RTP map to show the regional and residual sources and their depths, using the radial averaged power spectrum which divided into three segments, according to the slope,: the maximum depth is 12,500 m that probably reflect the crustal thickness at this place, depths of deep sources which reflect the maximum depth to the basement complex is found to be 10,388 m and the shallow sources and noise (near-surface geological structures), its depth will be 2410 m. This slope probably represents the minimum depth to the basement, especially at the eastern part of the study area (along the great escarpment). At the western part, the basement will be deeper than the eastern part. Different edge detection processes, for example, tilt angle derivative (TDR) and its total horizontal derivative (HD_TDR) as well as 3D-Euler deconvolution; can determine the edges of these sources. These techniques were carried out on the aeromagnetic data of Tihamah region (the study area). The estimated Euler solutions were plotted on the tilt angle derivative map. An excellent correlation was noticed between these techniques indicating that both of them can be attributed in delineating the general structural framework of the area. These techniques indicated that the southern part of Tihamah region was highly affected by Red Sea–Gulf of Aden rift system, that represent two legs of Afar Triple Junction. Moreover that, two depth methods were applied, analytic signal (AS) and source parameter imaging (SPI). They reflected similar results for estimating the basement depths. From both of them the depth ranges from 2050 to 10,885 m. On the other hand, all the methods used in this study gave a similar results to the depth of the basement rocks, ranging in depth between 2250and 10,400 m.     

湿地沉积模式及其地质意义

湿地是陆地和水域（湖泊、海洋）之间的过渡区域,是一类重要的沉积相。从沉积学的角度对湿地的定义进行了重新厘定和分类,将湿地分为两类,即沼泽湿地（或称沼泽）和湿原湿地（或称湿原）,前者沉积为煤,后者沉积为富含植物化石的泥岩。很多研究者把暗色泥岩都归为水下还原环境（湖泊）沉积,当作潜在的生油岩,这显然是错误的,因为一些暗色泥岩可能是湿原沉积,不能形成生油岩。因此,掌握湿地的沉积模式和识别特征,正确区分湿原与湖泊沉积,对盆地生油潜力评价及湖盆演化历史认识具有重要意义。     

河南龙门店银矿地质特征及成矿规律研究

龙门店银矿位于熊耳山成矿带西段,区内构造发育,岩浆活动强烈。在总结矿区地质特征的基础上,分析龙门店银矿K1银矿体分布规律及矿化富集特点,认为K1 矿体在空间上大致呈等间距分布,主成矿元素Ag 与Au 呈正相关关系,而与Cu、Pb 元素并无明显的相关性,表明Ag、Au 与Cu、Pb 元素形成于不同时期。通过开展槽探工程,矿区共发现20 多条含矿构造蚀变带,找矿前景好,属于进一步工作的重点区域。其中,Ⅰ号蚀变带是该矿区主要的含矿构造蚀变带之一,今后应在其深部加大探矿力度,找寻更多的资源。     

三点弯曲下混凝土断裂性能参数试验研究

采用三点弯曲试验对混凝土断裂性能参数进行研究,测试了一系列尺寸相同、强度不同的预制切口梁.通过采用等效裂缝模型和双参数模型确定混凝土的断裂韧度,结果表明:采用等效裂缝模型和双参数模型计算的混凝土断裂参数基本相同;随着抗压强度的增加,断裂韧度呈上升趋势,通过曲线拟合,提出根据抗压强度确定断裂韧度的经验公式.通过对试验荷载-挠度曲线进行三种不同的处理,包括国际材料和结构实验室联合会(RILEM)建议、对曲线尾部进行延伸以及采用实际的曲线,得到基于虚拟裂缝模型的断裂能.结果表明,RILEM建议得到的断裂能偏大,当曲线下降段的最低荷载与峰值荷载比值Pmin/Pc≤0.04时,采用实际荷载-挠度曲线得到的断裂能与尾部延伸后曲线得到的断裂能误差小于5％,可为实际断裂试验的实施提供参考.     

洞庭湖区水土流失特征及综合防治研究

洞庭湖是重要的水源涵养区,具有丰富的生物资源和土地资源。根据湖南、湖北2省统计资料,结合现场调查,分析了洞庭湖区水土流失面积、水土流失强度、水土流失可能产生的影响,总结了湖南、湖北2省近年来所采取的水土流失综合治理措施,提出了洞庭湖区水土流失防治目标。根据区域特点和地貌特征划分了丘岗区和平原区2个防治分区,针对每个分区提出了相应的治理模式,进一步按照工程措施和植物措施计算了相应工程量。分区规划和分区治理对防治洞庭湖区水土流失非常重要,对促进洞庭湖区生态恢复和可持续发展具有重要意义,同时也强调应做好洞庭湖流域中上游的水土保持工作。     

关节轴承摩擦温度场计算方法

以推力型关节轴承为研究对象,分析了轴向载荷下的接触应力,并根据试验所得摩擦力矩反推出了动态摩擦因数。结合接触应力及摩擦因数求出了摩擦热流率,并将其作为第二类边界条件进行了轴承非定常温度场有限元分析,最后利用红外热像仪拍摄了摩擦过程中轴承侧表面温度分布,检验仿真结果的可靠性。仿真与试验结果表明：该计算方法解决了球面摩擦副摩擦因数的精确计算和热流率的空间分配问题,建模时忽略球面间隙会直接影响接触应力分布并造成温度场分布出现较大误差,考虑球面间隙可以更精确地计算轴承摩擦温度场。     

基于神经网络与遗传算法的关节轴承挤压模具优化

针对实际生产中关节轴承内外圈间隙分布不均问题,以GEW12关节轴承为例,应用ABAQUS软件对关节轴承挤压装配过程进行了数值模拟。采用BP神经网络建立了挤压模具形状与内外圈最大间隙与最小间隙之差的映射关系。以关节轴承内外圈间隙均匀分布为目标,结合遗传算法,提出了一种集数值仿真、人工神经网络和遗传算法为一体的关节轴承挤压模具型腔优化设计方法。实验结果表明,模具型腔经过优化后,轴承内外圈间隙均匀性得到了很大的改善,轴承金属流动速度更加均匀。     

冲积平原水源地资源量计算

水源地资源量计算在水源地勘察中非常重要。本文结合河南省永城市新城水厂小李庄水源地的地下水资源量计算实践,系统地阐述了冲积平原水源地地下水资源量计算的内容及要求。其中,地下水补给量包括大气降水入渗补给量和农业井灌回渗补给量。地下水排泄量包括地下水的蒸发量、开采量、侧向径流排泄量和地表水侧渗排泄量。     

信息化对资源型企业经营绩效影响评价研究:以河南煤业化工集团公司为例

以资源型企业信息化与绩效的关系作为研究对象,从信息化对河南煤化集团绩效的直接影响指标和间接影响指标2个层面确定了河南煤化集团绩效与信息化关系评价指标体系,采用层次分析法和专家打分法构建判断矩阵,确定信息化与绩效关系评价指标的权重,以河南煤化集团2009—2012年的相关数据为样本,应用本文所构建的绩效评价指标体系,对信息化对河南煤化集团经营绩效的影响进行评价,通过对河南煤化集团实证分析,得出信息化建设对资源型企业的绩效影响不仅存在着直接的影响,还通过影响其他促进企业绩效的因素来增加企业绩效。