12E3加弹机EB系统故障探讨与性能提升

针对12E3加弹机EB系统设计缺陷及故障偏高的问题,从EB结构特点、工作原理、电器控制方面进行分析和探讨,提出了EB系统典型故障的解决办法和系统部件优化改进措施,以达到EB系统稳定运行、加弹机设备整体性能有效提升的目的。     

冷拔螺旋钢筋预应力空心板结构性能试验研究

本文通过对 10块冷拔螺旋钢筋预应力空心板的弯曲破坏试验 ,分析了这种空心板的强度、挠度、裂缝等特点 ,并和现行《钢筋混凝土结构设计规范》中的计算公式作了比较 ,结果发现这种空心板的开裂弯矩和极限弯矩用现行《规范》计算的结果和试验值相差不多 ,而挠度的计算结果和试验值相差较多 ,且偏于不安全。本文根据试验结果的分析给出了冷拔螺旋钢筋预应力空心板的挠度计算公式。     

双代号网络图的绘制方法

从教学及实践的角度出发，就双代号网络图的绘制方法与技巧进行了归纳总结，以便在绘图时能很好地控制整个图形的布局，正确清楚地表达逻辑关系，快速准确地绘出双代号网络图。     

冷拔螺旋肋钢筋粘结锚固性能试验研究

通过对 72根冷拔螺旋肋钢筋拔出试验的研究 ,分析了冷拔螺旋肋钢筋的粘结锚固特点和各主要因素对平均粘结强度的影响 ,回归了平均粘结强度的计算公式 ,推导了在拉拔状态下临界锚固长度的计算公式 ,并给出了在各种情况下的临界锚固长度值。     

文物建筑外墙风化检测与分析

通过北京大学红楼外墙风化检测实例，提出了文物建筑外墙风化检测的重要性，并介绍了砖体动态弹性模量超声检测，粘结拉拔检测和砖体含盐量检测方法。     

聚烯烃/PET共混物的微纤形成及力学性能

研究了聚烯烃/聚对苯二甲酸乙二酯(PET)共混物的微纤形成、制备工艺条件、连续相聚烯烃的选择和力学性能。用单螺杆挤出机挤出嵌段共聚聚丙烯(PP-B)/PET和高密度聚乙烯/PET时,挤出产物中会形成部分短而粗的微纤;采用"熔融挤出—热拉伸—淬火"工艺制备的PP-B/PET共混物中会生成更多长径比较大的PET微纤,且随拉伸比的增加,微纤数量增多,长径比增大,共混物的熔体流动速率降低;在挤出工艺条件下,最适合的连续相是PP-B,最适宜的工艺条件是:从进料口到机头温度分别为220,250,260,220℃,螺杆转速为50 r/min,拉伸比为3;PP-B/PET原位微纤共混物的拉伸屈服应力比纯PP-B提高约33%;增大拉伸比可提高共混物的拉伸屈服应力和抗冲击性能。     

双曲扁壳类汽车覆盖件刚度的试验研究

为进一步掌握汽车覆盖件刚度控制机制,建立了以双曲扁壳件为研究模型的成形试验及刚度测试分析系统.分别完成了成形工艺条件中不同压边力、拉深深度条件下,双曲扁壳件的成形试验,5种约束方式下的双曲扁壳件刚度测试试验.分析了压边力、拉深深度和约束方式对刚度的影响规律.研究表明:刚度测试时的约束方式对刚度有重要影响,约束越大,刚度越大;约束的改变对刚度的影响远大于其他工艺条件(压边力和拉深深度)对刚度的影响,提出刚度测试时为准确获得成形工艺条件等对刚度影响的最佳约束方式;工艺条件中压边力及拉深深度的变化对刚度亦有不同程度的影响,刚度随着压边力的增加而增大;成形时的拉深深度越大,刚度值也越大.上述工艺条件的改变对刚度的影响远大于厚度减薄对刚度的影响,在实际生产中,可以通过调整成形时的工艺参数提高汽车覆盖件的刚度.     

Side draw control design for a high purity multi-component distillation column

Industrial methanol production involves a multi component feed containing methanol, water and trace levels of ethanol being refined to produce AA grade methanol at high product recovery. Due to practical constraints, the bottoms discharge of the column is primarily water with only trace of methanol impurities. As a result of these constraints, ethanol, which is a non-key middle boiling component gets “trapped” near the side draw of the column forming an ethanol bulge, which in turn results in non-linear, inverse, time and state varying behaviour of the side draw ethanol composition. In this work, we established that the existence of the ethanol bulge creates the complex process behaviour of the side draw ethanol composition and that this bulge needs to be explicitly controlled. This type of explicit composition bulge analysis and subsequent control has not been attempted on methanol distillation columns before. For this purpose a novel, robust and practical side draw control scheme to detect and remedy the excess ethanol bulge movement using override control is presented. The side draw controller, together with other regulatory controllers is shown to maintain on-specification operations of the column. Disturbance rejection tests carried out illustrate that the side draw control scheme will keep the column operating within commercial specification. It is also shown that a traditional DV control structure is unable to achieve this objective.     

Acoustic properties of sound-absorbing polyester fabrics woven with thick staple and thin draw textured yarn for use in interior decoration

Environmental pollution in our daily life because of noise is an increasing public health concern. We designed and woven with staple- and draw-textured yarns, for sound absorbance purposes. For wefts and warps, two different thicknesses of the thick staple-yarn and thin draw-textured filament yarn were used. The prepared fabrics were classified in porous, medium, and dense, on the basis of their densities and air permeabilities, and the sound absorption coefficients of the fabrics were found to be linearly related to the air permeability. The sound absorption coefficient determined by the impedance tube method was higher for porous fabrics compared with that for dense fabrics in the high frequency region. By the reverberant field method, the sound absorption coefficients for all fabrics were highest in the low frequency region. Porous fabrics exhibited a shorter reverberation time and a higher sound absorption coefficient than dense fabrics owing to their good sound absorption property.     

正渗透汲取液的研究进展

正渗透是以膜两侧汲取液和原料液之间的渗透压差为驱动力,使水从原料液(较低渗透压)一侧自发传递到汲取液(较高渗透压)一侧的膜分离技术。汲取液是影响正渗透分离性能的重要因素之一,然而目前使用的大多数汲取液面临反向溶质渗透严重和再生能耗高的问题,这导致了正渗透性能的显著下降。简要介绍了近几年国内外主要研究的新型汲取液,分析总结了不同汲取液的优点及其应用范围。