Abnormal dielectric characteristics of PMN-32%PT single crystal under dc bias

It has been reported that the single crystal of relaxor ferroelectrics (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) with the compositions near the morphotropic phase boundary (MPB, 0.28相似文献   

浅谈大学生择业与职业生涯规划

阐述了职业生活和大学生职业生涯规划的重要性,论述了择业方式对大学生择业的影响,分析了大学生择业价值取向的特点。     

具有挠性附件的全充液刚体耦合系统的姿态控制动力学与稳定性

建立了一类带有挠性结构附件的全充液刚体耦合系统主动控制动力学模型，给出了系统的控制律，进而研究了控制与镇定问题，得到了受控系统姿态定位和指数渐近稳定的结论。     

浅谈广告的创意

介绍了广告创意的内涵、金字塔原理、过程及其思考方法,途述了广告创意的U SP广告策略、品牌形象策略和广告定位策略。     

Chemical ecology of oviposition in phytophagous insects

Summary Selection of a suitable site for oviposition by phytophagous insects is critical for successful development of the offspring. The behavioral events leading to oviposition are mediated to a large extent by chemical cues associated with potential host plants. Orientation and landing are primarily guided by volatile constituents of a plant, whereas assessment of a leaf surface depends on contact stimuli. Chemical mechanisms that ensure adequate spacing of progeny on limited resources include the production of oviposition-deterring pheromones as well as recognition of plant constituents released as a result of previous damage. Perception of chemical cues that affects oviposition involves receptors on antennae, tarsi, mouthparts or the ovipositor. Complex behavior such as tarsal drumming or stem runs may serve to provide increased receptor contact with chemical stimuli. Abiotic and biotic environmental factors often influence the production or release of behavior-modifying chemicals by a plant, and therefore affect oviposition preferences. Plant chemistry may be involved in associative learning, but may also lead to mistakes. Thus a clear correlation between oviposition preference and offspring success does not always exist.     

同步卫星轨道平面倾斜效应的图示法

轨道偏离赤道平面的同步卫星,其星下点(或视位置)的口漂移轨迹址对称于静止位置的“8”字形。文献[1]给出的数学表达式对“8”字形轨迹的解释不直观,物理图象欠清晰。本文给出新的数学表达式,能用图示法形象直观地描绘出“8”字形轨迹,并简明地给出“8”字形的高度和宽度。     

日凌中断预测分析

本文阐述了太阳噪声干扰使通信广播卫星接收站信号中断的自然现象及规律,导出日凌中断与通信广播卫星定点及卫星接收站,位置关系的数学表示式。文中应用作者研究的“卫星电视接收网的系统分析”的计算机软件,预测卫星接收站信号发生日凌中断日期、时刻、持续天数和时间的部分计算实例。     

卫星遥感资料存档系统的研究

卫星遥感资料存档系统是３Ｓ系统研究领域之一,分析了由作者设计的存档分析试验系统的基本框架,数据结构,索引方式及查询方式,讨论了资料存档及常规处理方法的结合,对于图象,图形及属性数据显示采用了统一的处理过程。     

Dissection of the pheromone-modulated flight of moths using single-pulse response as a template

The upwind flight of male moths to conspecific females is mediated by the chemical and structural characteristics of a pheromone plume. We describe the reaction of maleCadra cautella, the almond moth, to the interception of single pulses of sex pheromone, the smallest structural units of odour plumes. Following loss of a pheromone plume, males cast, that is fly a crosswind course without progressing upwind. The response of casting males to interception of a pulse of 0.25 s duration was, after a delay of 0.21±0.07 s, to turn and briefly fly straighter upwind, resulting in average net upwind displacements of 18 cm in a 50 cm s^–1 wind. Upwind progress in the single-pulse response was the result of steering more upwind and an increase in airspeed, although average ground speed remained unchanged. During the last third of the surge, males turned crosswind, returning to casting flight. These behavioural reactions to pheromone contact and loss support the phasic-tonic model of odour-modulated flight, in which an underlying tonic counterturning rhythm, expressed upon pheromone loss, is briefly overridden by phasic upwind surges, expressed upon interception of the pheromone filament. The surge portion of the cast-surge-cast response was diminished and more crosswind if individual pulses were shorter (0.02 s), probably due to sub-optimal contact with pheromone. The cast-surge-cast response to interception of a single 0.25 s pulse was used as a template to interpret the form of flight tracks in plumes of known structure. The template matched portions of flight tracks of males flying in plumes of low pheromone pulse frequency, thus reflecting the male's pattern of pulse encounter. In plumes ensuring a high frequency of pulse interception, only the upwind surge portion of the template was expressed, resulting in nearly straight upwind flight tracks. Similar nearly straight upwind flight tracks occurred in flights along plumes of low pulse frequency with large volume. Thus flight tracks of maleC. cautella to point sources of pheromone depend on both the frequency and the size of filaments encountered.     

影响木材火焰传播速度特征量的实验研究

木材着火时火焰的传播规律将为木材在火灾场景中的行为提供重要参考,分析了木材燃烧的机理和影响木材燃烧时火焰传播速度的特征量,借助于实验的方法,研究了空间方位角和几何尺寸等特征量对火焰传播速度的影响.结果表明,方位角越小,不同尺寸木条火焰传播速度差别越大;火焰传播速度随方位角的增大而增大;木条宽度越大,火焰传播速度越慢.