Experimental study on hysteresis phenomena of shock wave structure in an over-expanded axisymmetric jet

In recent studies on two-dimensional supersonic jets, it is reported that the hysteresis phenomenon for the reflection type of shock waves in the jet flow field is occurred under the quasi-steady flow condition and this phenomenon is affected by the transitional pressure ratio between the regular reflection and Mach reflection. However, so far, there are few researches on the hysteresis phenomenon for the transition of shock waves between regular and Mach reflection in over-expanded supersonic jets and the phenomenon has not been investigated satisfactorily. Therefore, the purpose of this study is to clarify the hysteresis phenomena for the reflection type of shock wave in the over-expanded axi-symmetric supersonic jet experimentally, and to discuss the relationship between hysteresis phenomenon and rate of the change of pressure ratio with time. Furthermore, the effect of Mach number at the nozzle exit on hysteresis loop was investigated for two kinds of nozzle.     

Present or Past Herbivory: A Screening of Volatiles Released from <Emphasis Type="Italic">Brassica rapa</Emphasis> Under Caterpillar Attacks as Attractants for the Solitary Parasitoid, <Emphasis Type="Italic">Cotesia vestalis</Emphasis>

Females of the solitary endoparasitoid Cotesia vestalis respond to a blend of volatile organic compounds (VOCs) released from plants infested with larvae of their host, the diamondback moth (Plutella xylostella), which is an important pest insect of cruciferous plants. We investigated the flight response of female parasitoids to the cruciferous plant Brassica rapa, using two-choice tests under laboratory conditions. The parasitoids were more attracted to plants that had been infested for at least 6 hr by the host larvae compared to intact plants, but they did not distinguish between plants infested for only 3 hr and intact plants. Although parasitoids preferred plants 1 and 2 days after herbivory (formerly infested plants) over intact plants they also preferred plants that had been infested for 24 hr over formerly infested plants. This suggests that parasitoids can distinguish between the VOC profiles of currently and formerly infested plants. We screened for differences in VOC emissions among the treatments and found that levels of benzyl cyanide and dimethyl trisulfide significantly decreased after removal of the host larvae, whereas terpenoids and their related compounds continued to be released at high levels. Benzyl cyanide and dimethyl trisulfide attracted parasitoids in a dose-dependent manner, whereas the other compounds were not attractive. These results suggest that nitrile and sulfide compounds temporarily released from plants under attack by host larvae are potentially more effective attractants for this parasitoid than other VOCs that are continuously released by host-damaged plants.     

Predator Avoidance by Phytophagous Mites is Affected by the Presence of Herbivores in a Neighboring Patch

When predators invade a leaf patch inhabited by herbivores, the herbivores disperse to a neighboring predator-free leaf patch, thus escaping from the predators. However, the neighboring patch might already be used by con- or heterospecific herbivores. We used laboratory bioassays to examine whether perception of odor from con- or heterospecific competitors on a neighbored lima bean leaf patch influences dispersal behavior of the herbivorous mite Tetranychus urticae when attacked by predatory mites Phytoseiulus persimilis. The dispersal rates of T. urticae that perceived odors from leaf patches infested by conspecifics or cowpea aphids (Aphis craccivora) did not differ from the control (the dispersal rate of T. urticae that perceived odor from uninfested leaf patches). By contrast, the dispersal rate of T. urticae was reduced when they perceived odors from leaf patches that were currently or had previously been infested by larvae of the common cutworm (Spodoptera litura). Previous herbivory by S. litura larvae induced resistance in leaf patches to T. urticae as indicated by the reduced number of eggs laid by T. urticae. Our results are discussed with respect to the feeding behavior of the tested competitors of T. urticae and the impact of the plant and arthropod community on the dispersal behavior of these mites.     

不同结构的横向 PNP型晶体管低剂量率辐照增强效应研究

采用相同工艺制作的横向 PNP晶体管进行了低剂量率辐照实验,研究了不同周长面积比、不同基区有效宽度、不同发射极面积及不同氧化层厚度的双极晶体管的低剂量率辐射损伤增强效应。实验结果表明:通过提高横向 PNP管周长面积比、减小基区有效宽度、增加发射极面积和减薄氧化层厚度,在低剂量率下横向 PNP双极晶体管辐照前后增益降低小于 50%,且辐照后增益大于 100,大幅度提升了横向 PNP管的抗辐射能力。     

基于纳米压痕的IP防腐涂层本构模型反演分析

目的 得到IP防腐涂层的本构模型。方法 通过连续刚度法对涂层表面进行纳米压痕试验,得到硬度和弹性模量,输出载荷-位移曲线。利用量纲分析法的 定理,建立各本构参数之间的无量纲函数,确定涂层的本构模型,最后将本构模型代入有限元模型,模拟纳米压痕试验,对比仿真与试验的载荷-位移曲线,验证本构模型的准确性。结果 涂层的硬度为5.49 GPa,弹性模量为69.31 GPa。有限元仿真时,若特征应变偏小,在加载阶段,曲线随硬化指数减小而下移;在卸载阶段,曲线随硬化指数的增大而左移。特征应变偏大时,载荷-位移曲线表现则相反。经对比试验与有限元仿真得到的载荷-位移曲线,二者较为一致。结论 涂层具有较高的表面硬度,表面抗变形能力较好。特征应变偏小时,载荷-位移曲线变化是因为硬化指数变大,加载阶段塑性功增加,总功也增加;特征应变偏大时的相反趋势是因为计算的屈服强度大幅度下降和特征应力点后移导致的塑性功增加。获得的涂层本构模型具有较高的精度且该方法具有可靠性。     

计及碳交易机制的电–气联合系统快速动态鲁棒优化运行

多园区综合能源系统具有能源互济互联、协调合作运行、利益主体多元的重要特征,这对各园区间能量交互与协同管理提出了自主自治、隐私安全等要求。为此就多园区综合能源系统能量交易模式及物理实现架构,提出一种分区自治式能量合作社区及优化调度模式。首先针对能量交易模式,引入能源供需比和讨价还价博弈模型,构建合作社区内部交易及其定价机制,模拟能源供需形势及利益分配对社区内部交易的影响,有效激励园区参与合作;其次针对物理实现架构,构建各园区内综合能源系统模型及园区间输送管网模型,建立多园区系统的联合优化调度模型,应用交替方向乘子法分布式求解架构提出了上、下分层的解算方法,实现合作社区能源交互交易,保证园区交易自主、运行自治、信息隐私;最后算例验证了该合作社区与调度模式能够充分挖掘园区互济效益,实现共享收益公平分配,促进园区可持续合作共赢,提升能源利用效率。