干式变压器铁芯接地故障分析

本文通过对20kV及以下系统干式变压器铁芯接地故障进行分析,从定期检查、检修维护、设备管理方面提出了相应的防范措施,可为水电站机组安全运行提供借鉴。     

干船坞中的环境保护技术探讨

通过分析我国造、修船工业存在的环境污染问题,参考美国船厂的环境保护措施,结合我国的实际情况,提出了几点合理化建议。     

On the oxidative coupling of methane with carbon dioxide over CeO2/ZnO nanocatalysts

The nano-CeO₂/ZnO catalysts were prepared using a novel combination of homogeneous precipitation with micro-emulsion for oxidative coupling of methane with CO₂ as an oxidant. The prepared catalysts were compared with those prepared using the conventional impregnation. The catalysts prepared in two ways were characterized with FTIR, TEM, XRD and CO₂-TPD. The effects of the reaction temperature, the amount of ZnO doped in the catalysts and the average size were investigated. The experimental investigation demonstrated that methane conversion over the nano-CeO₂/ZnO catalysts prepared by the combined technique was higher than that obtained over catalysts prepared by the conventional impregnation. A better low-temperature activity has also been achieved over the nanocatalysts. There was no clear trend between the average size of nano-CeO₂/ZnO catalysts and their catalytic performance but methane conversion increased with increasing fractal dimension of nanocatalysts.     

Chemical Stability of Ti-Modified MCM-41 Catalysts in the Hydroxylation of Benzene in the Liquid Phase

Ti-substituted MCM-41 and Ti-grafted MCM-41 materials possessing both well-ordered long-range and pore structures have been used as catalysts for the hydroxylation of benzene in the liquid phase. The stability of the catalytic performance and the changes in the structural characteristics of Ti-modified MCM-41 resulting from the hydroxylation reaction have been investigated. It has been found that Ti-grafted MCM-41 exhibits better stability of catalytic performance than Ti-substituted MCM-41. For the Ti-substituted MCM-41, the migration of framework Ti into non-framework sites results in a decrease in the catalytic performance and the partial collapse of the pore structure. For the Ti-grafted MCM-41, the hydroxylation of benzene induces a smaller decrease in the pore volume and specific surface area than that observed for Ti-substituted MCM-41.     

二甲醚催化氧化制下游产品(Ⅱ)V/Mn改性的SnO2/MgO催化氧化制碳氢化合物

考察了SnO2/MgO催化剂和添加助剂V、Mn对二甲醚（DME）催化氧化制取乙二醇二甲醚（DMET）和其他碳氢化合物的催化性能。结果表明，锡镁催化剂对DME在275～325 ℃有良好的催化活性；添加VOx能较大提高DME转化率和产物DMET的选择性，DME转化率可达23％，DMET选择性可达44％，在300℃收率达9％以上。     

CO2泡沫压裂液的流变性及井筒摩阻计算方法研究

进行了CO2泡沫压裂液的室内配制、流变性测定以及摩阻计算方法研究。室内实验中观测了CO2泡沫压裂液的形成、动态变化、泡沫结构,测定了CO2泡沫压裂液的流变性,发现其属于假塑性非牛顿流体。推导了CO2泡沫压裂液在油管内流动的摩阻计算公式,计算了不同管径、不同排量、不同泡沫质量时的摩阻曲线,进行了井筒内CO2泡沫压裂液摩阻压降实测,与计算方法相比误差在工程应用允许范围内。该研究所得到的CO2泡沫压裂液流动特性、摩阻压降计算方法、经验图版等,可供工程应用中参考。     

强震区土石坝筑坝材料动力特性试验研究(投稿研究生论坛)

土石坝筑坝材料的动力特性是进行坝工设计和动力评价的基础。以西部强震区某土石坝工程为研究对象,采用室内动三轴试验,对其坝壳料、心墙料和坝基断层料进行动力特性试验研究,并以Hardin-Drnevich模型为基础,确定筑坝材料的动弹模、阻尼比等特性参数,试验表明：在动应变在10-6 ～ 10-5 范围内,动模量与围压、固结比成正相关;随动模量的增大,相关性降低;动应变和振级的拟合指数模型则表明不同围压、固结比的心墙料的应变-振级曲线趋势一致,坝壳料较为离散;试验中固结围压对粗骨料阻尼比-应变曲线的影响较固结比大,可为强震区土石坝的动力稳定评价提供可靠的理论依据。     

New software developments for quality mesh generation and optimization from biomedical imaging data

In this paper we present a new software toolkit for generating and optimizing surface and volumetric meshes from three-dimensional (3D) biomedical imaging data, targeted at image-based finite element analysis of some biomedical activities in a single material domain. Our toolkit includes a series of geometric processing algorithms including surface re-meshing and quality-guaranteed tetrahedral mesh generation and optimization. All methods described have been encapsulated into a user-friendly graphical interface for easy manipulation and informative visualization of biomedical images and mesh models. Numerous examples are presented to demonstrate the effectiveness and efficiency of the described methods and toolkit.     

相容剂及其在PC/ABS合金中的应用

采用水相悬浮聚合法合成了SAN-g-MAH、SAN-g-MMA、SAN-g-GMA3种相容剂,比较了3种相容剂对PC/ABS合金的增容效果,着重研究了工艺条件对接枝率的影响及相容剂用量对合金力学性能的影响。结果表明,相容剂的最大接枝率可达5.76%,添加相容剂后,PC/ABS合金的力学性能有明显提高,拉伸强度和缺口冲击强度分别可达61.91MPa和10.12kJ/m2。     

不同混凝剂处理高藻水效果对比研究

针对北方某水源有机物和藻类较高这一问题,进行了混凝、气浮,砂滤等常规工艺下FeCl_3和高效聚合铝盐(HPAC)混凝剂对浊度、有机物和藻类去除效果对比试验。结果表明,低投量下的Fe盐混凝剂去除TOC的效果优于低投量的Al盐,但高投量下却相反;从除藻效果分析,两种混凝剂差别不大。考虑混凝剂价格时,相同混凝剂费用下二者投量比(分别以FeCl 3和Al_2O_3计)为FeCl_3:HPAC=13:1,且在满足浊度出水水质情况下,最优Al盐费用少于Fe盐,但在以COD_(Mn)为控制指标时却相反。