火电厂输煤系统犁煤器分档配煤方案的研究

针对火电厂输煤系统的犁煤器配煤部分提出了犁煤器分档配煤方案,较好地解决了多个原煤斗同时缺煤存在竞争的情况,并给出了低煤位危险指标Dt的定义,用于表征在相同条件下,不同犁煤器配煤方案的优劣。给出了犁煤器配煤方案的具体决策步骤,可以指导设计人员完成自动配煤设计。最后通过仿真获得了不同配煤方案的低煤位危险指标Dt值,通过比较得出了分档控制方案比传统的不分档控制方案优越的结论。     

Particulate flow modelling in a spiral separator by using the Eulerian multi-fluid VOF approach

The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator,and thus a Eulerian multi-fluid volume of fluid(VOF) model was first proposed to describe the particulate flow in spiral separators. In order to improve the applicability of the model in the high solid concentration system, the Bagnold effect was incorporated into the modelling framework. The capability of the proposed model in terms of predicting the flow film shape in a LD9 spiral separat...     

不同螺杆组合和加料工艺对改性ABS力学性能的影响

介绍啮合同向双螺杆挤出机的常用螺杆组合元件并对螺杆组合进行优化,研究了不同螺杆组合和加料工艺对改性(丙烯腈/丁二烯/苯乙烯)共聚物(ABS)力学性能的影响,并设计出适合于改性ABS加工的螺杆组合及加料工艺。结果表明,采用适当的螺杆组合和分开加料方式制得的改性ABS的力学性能得到显著提高。     

螺旋焊管波浪压痕的消除

简要介绍和分析了螺旋焊管生产过程中产生的波浪压痕及其成因,并给出了消除方法。通过生产实践证明,在螺旋焊管生产过程中,经过理论计算,只要能准确地给出成型器1～3号微型辊组的位置参数,就能够消除焊管管体的波浪压痕。     

某机械设备液压系统分析

供弹系统是影响舰炮发射速度的因素,为了提高其供弹速度设计一套快速供弹系统本文从敏捷供弹系统的组成出发、叙述了扬弹机构的工作原理,设计了扬弹机的液压系统,对液压缸和蓄能器进行了具体的分析和计算,从理论上证明了此方案的可行性。     

大伙房水库输水工程隧洞施工竖井投料还原试验分析

大伙房水库地下隧洞式输水工程,隧洞掘进采用TBM为主,钻爆法为辅的施工方案.主洞混凝土衬砌料部分采用竖井方式进行投料,竖井深度多为100～200 m深,还原试验主要研究混凝土拌合物经过竖井段靠重力自由下落,在井底瞬间缓冲停止,拌合物中粗骨料自身参数的变化及其对混凝土物理指标的影响.     

一种红枣去核机上料机构的设计与分析

设计了一种红枣去核机的上料机构,主要包括:振动料斗、送枣管道、拨枣转盘、拨枣齿、推枣杆、曲柄滑块机构.通过料斗的振动实现红枣定向输送,通过拨枣转盘的圆周运动和曲柄滑块机构的往复直线运动带动推枣杆完成红枣的上料.     

Rickettsial Pathogen Perturbs Tick Circadian Gene to Infect the Vertebrate Host

Ixodes scapularis is a medically important tick that transmits several microbes to humans, including rickettsial pathogen Anaplasma phagocytophilum. In nature, these ticks encounter several abiotic factors including changes in temperature, humidity, and light. Many organisms use endogenously generated circadian pathways to encounter abiotic factors. In this study, we provide evidence for the first time to show that A. phagocytophilum modulates the arthropod circadian gene for its transmission to the vertebrate host. We noted a circadian oscillation in the expression of arthropod clock, bmal1, period and timeless genes when ticks or tick cells were exposed to alternate 12 h light: 12 h dark conditions. Moreover, A. phagocytophilum significantly modulates the oscillation pattern of expression of these genes. In addition, increased levels of clock and bmal1 and decreased expression of Toll and JAK/STAT pathway immune genes such as pelle and jak, respectively, were noted during A. phagocytophilum transmission from ticks to the vertebrate host. RNAi-mediated knockdown of clock gene expression in ticks resulted in the reduced expression of jak and pelle that increased bacterial transmission from ticks to the murine host. Furthermore, clock-deficient ticks fed late and had less engorgement weights. These results indicate an important role for circadian modulation of tick gene expression that is critical for arthropod blood feeding and transmission of pathogens from vector to the vertebrate host.     

铝合金激光双光点焊接工艺特性

对铝合金薄板激光单光点和双光点焊接(包括不填丝和填丝)的焊缝成形、对接间隙和准直度容许裕度以及气孔状况进行了比较,并分析了双光点能量分布的激光对铝合金焊接的影响.结果表明,与激光单光点焊接相比,激光双光点焊接铝合金所得焊缝表面质量更好,焊缝熔宽更大,对接间隙和准直度容许裕度明显放宽.激光双光点焊接铝合金可以显著减少焊缝中大气孔的数量,但对焊缝中小气孔数量的影响不明显.此外,填加焊丝可以进一步改善焊缝表面质量并放宽对接间隙和准直度容许裕度,但将增大焊缝产生大气孔的倾向,采用激光双光点焊接仍可使焊缝中大气孔的数量明显减少.     

Plastid Transformation of Micro-Tom Tomato with a Hemipteran Double-Stranded RNA Results in RNA Interference in Multiple Insect Species

Plant-mediated RNA interference (RNAi) holds great promise for insect pest control, as plants can be transformed to produce double-stranded RNA (dsRNA) to selectively down-regulate insect genes essential for survival. For optimum potency, dsRNA can be produced in plant plastids, enabling the accumulation of unprocessed dsRNAs. However, the relative effectiveness of this strategy in inducing an RNAi response in insects using different feeding mechanisms is understudied. To investigate this, we first tested an in vitro-synthesized 189 bp dsRNA matching a highly conserved region of the v-ATPaseA gene from cotton mealybug (Phenacoccus solenopsis) on three insect species from two different orders that use leaf-chewing, lacerate-and-flush, or sap-sucking mechanisms to feed, and showed that the dsRNA significantly down-regulated the target gene. We then developed transplastomic Micro-tom tomato plants to produce the dsRNA in plant plastids and showed that the dsRNA is produced in leaf, flower, green fruit, red fruit, and roots, with the highest dsRNA levels found in the leaf. The plastid-produced dsRNA induced a significant gene down-regulation in insects using leaf-chewing and lacerate-and-flush feeding mechanisms, while sap-sucking insects were unaffected. Our results suggest that plastid-produced dsRNA can be used to control leaf-chewing and lacerate-and-flush feeding insects, but may not be useful for sap-sucking insects.