The natural history of the parasitic wasp Trogus pennator (Hymenoptera: Ichneumonidae): Host‐finding behaviour and a possible host countermeasure

The parasitic wasp Trogus pennator (Ichneumonidae) attacks the larvae of swallowtail butterflies (Papilionidae). Female T. pennator were followed in the field as they searched for larvae of the zebra swallowtail butterfly, Eurytides marcellus (Papilionidae), feeding on Asimina (Annonaceae) in central Florida, USA. Predictions of host‐finding theory and interactions with the host were thus investigated in a natural setting. Wasps seldom flew to plants other than Asimina and apparently recognized the plants by visual cues. Plants were attractive regardless of host presence, as the wasps approached plants lacking E. marcellus feeding damage twice as often as they approached damaged plants. However, wasps approached damaged plants at a rate greater than their frequency in the Asimina population, indicating that they can detect host damage before they approach the plants. After approaching within 0.5?m of plants, wasps tended not to land on plants lacking feeding damage. A comparison of the plants they landed on, however, showed no consistent preferences for damaged plants. The weaker trends in the latter data indicate that the presence of feeding damage was not the sole criterion for landing, although it evidently influenced behaviour. After landing, wasps spent more time searching damaged plants than undamaged plants. Butterflies preferred to oviposit on plants shorter than those searched by T. pennator. Possible adaptive consequences of this phenomenon are discussed.     

FPGA在图象处理中的应用

介绍了FPGA的硬件结构和特性 ,以及采用现场可编程器件FPGA设计图象处理板的原理和设计方法 ,给出了实现图象左右翻转的应用实例。实践证明这种方法速度快 ,编程简单 ,设备具有很高的性能价格比。     

建立麦克斯韦方程组的新途径

用普通物理学的方法推导了不同惯性系之间产场量的变换式，在此基础上，给出了一咱简便、快捷并且物理意义清晰的建立麦克斯韦方程组的新途径。     

新产品WK-668在下二门联合站的性能评估及应用

分析了河南下二门油矿含油污水处理现状，论述了新型破乳剂WK-668的应用。     

Speed-Sensorless Control Using Elman Neural Network

1. INTanDUCTIONControlling induction motor without sensor is available nowadays. In order to aclileve two-level closed lOops,i. e., digital current lOop and digital speed loop, it is necessary to sense.and digitize the motor phase currentand motor speed. Howver, the sensors involved have the followillg disadvantages. First, they aJre eXPensiveand make up a significan portion of the total cost. Second, they may result in electrical or mechaulcal fault.Based on speed estimation, it is pos…     

金属表面合金化的研究

Rh(001),(111)和(111)表面被Mo合金化的原子绪构已首次成功地用场离子显微镜直接观察到。表面合金化是采用在超高真空系统中气相沉积及随后淬火,低温扩散来实现。交换机制是可能的扩散机制。观察到的环状结构是Rh-Mo合金中Mo原子优先场蒸发造成的。     

提高抽油机井系统效率技术及应用

以河南油田为例,从地面和井下两方面分析了影响抽油机井系统效率的因素,提出了提高系统效率的技术措施。     

无限扩域的Galois群之拓扑紧性与一致化拓扑的完备性

本文对无限Galois扩城的Galais群,在给定的拓扑下,做了如下工作:1.证明了群G的拓扑紧性。2.论证了拓扑群G在一致化拓扑下的完备性,进而对Krull定理赋予了新的拓扑形式。3.对于可数无限扩域的Galois群,论证了它可度量化的特征。     

我国历代食莼初探

莼菜作为古代常见的野蔬之一，其食用历史长达三千多年。古人食用莼菜始于春秋时期，魏晋南北朝时期莼菜开始名闻遐迩，唐至宋元时期其倍受文人骚客的青睐，明代将其食用价值和药用价值载入史册，其声誉在清代达到了历史最高峰。历史时期人们就十分注重对莼菜的开发和利用：莼菜的烹饪方法不断推陈出新，食用部位也在不断转变；药用价值的不断探究等，莼菜在一定程度上还起了救荒疗饥的作用。     

关于光在界面上反射时位相跃变的讨论

本文运用薄膜光学的理论基础--Fresnel公式,研究光在界面上的位相关系。文中对不同的观点进行了讨论。从而提出了一个判断位相跃变可靠而全面的方法。