适应于滤子的随机环境分枝过程个体数的平衡

给定一个带有一个适应于渐增滤子的随机环境分枝过程,利用条件期望的性质讨论了该随机环境分枝过程的灭绝概率,并给出了其个体数稳定平衡于两个已知数之间的条件。     

带有适应渐增滤子随机环境分枝过程的两个结果

给定一个随机环境适应于渐增滤子的随机环境分枝过程,这里渐增滤子是一个由包含过程本身迄今的历史和其它外界随机影响因素所生成的一个σ域族。利用鞅论和极限定理的方法,给出了P{Zn→∞}=0的两个充分条件。     

随机环境中的泊松过程

引进了随机环境中的泊松过程模型,推导出其转移概率,讨论了该过程与均匀分布和Γ分布之间的特殊关系,证明了当环境过程为坐标过程时随机环境中泊松过程是一类特殊的随机环境中马氏过程,并给出了该过程的随机Kolmogorov方程.     

推进我国企业应用环境管理会计的建议

本文总结了目前我国企业在环境管理会计的应用过程中存在内因、外因、人员和理论等方面的困难,并从构建环境管理会计法规制度体系、构建完善的环境管理会计专业人才培养机制、构建理论联系实际的环境管理会计研究模式三个方面给出了建议.     

基于数据库的多级联动菜单的实现

讨论了一种在ASP环境下,选项基于数据库的多级联动菜单的实现过程,指出了设计多级联动菜单的三个关键部分,给出了设计代码.     

常利率带干扰的两类相关理赔风险模型

考虑了保费收取为Poisson-Geometric过程,常利率环境条件下带干扰的两类相关理赔风险过程,把相关的两类理赔计数过程转换为两个独立的Poisson-Geometric过程和推广的Erlang(n)过程,并给出其折现罚金函数所满足的微积分方程。     

Markov环境中生灭过程的衰减速度

首先给出了 Ｍａｒｋｏｖ环境中的生灭过程可配称的充要条件,然后用分解方法给出了过程指 数 衰 减 速 度 的 上 下界估计      

双语教学的探讨及实践

本文通过对双语教学存在问题的分析,指出加强师资队伍建设,培养学生对双语教学的兴趣以及创造良好的英语学习环境等几个重要环节是影响双语教学成败的关键,结合作者在双语教学过程中的实践和体会,并运用心理学及教育学原理给出具体解决方案。     

电子元器件工业潜在的环境问题与绿色发展前景

电子工业是人类最伟大的技术成就之一,本文简述了电子元器件的集成电路,印刷线路板生产过程以及组装过程中的资源消耗、环境问题,预测电子工业在环境方面的工艺趋势、产品趋势以及法规趋势,最后给出了电子工业的发展前景。     

论OpenGL在卫星在轨飞行仿真中的应用研究

在VC＋＋6.0环境中运用OpenGL开发并实现了具有交互功能的卫星实时在轨运行及轨道参数的三维显示。介绍了实现可视化过程所需的几个关键技术,论述了三维可视化仿真场景的建立和可视化实现方法,给出了卫星在轨飞行过程的仿真场景效果图。     

微重力下热管内融化特性(英文)

探索了微重力环境下航天用热管内启动融化特性的地面实验技术,设计了专门的实验段模拟热管绝热段内的融化特性,并进行了实验观测. 建立了未考虑液体对流影响的二维融化分析模型,与实验测试和观察结果很好地相一致.理论分析和实验都表明,几乎整个融化过程中对流影响都非常小,而且热管的中间部分融化过程具有一维特性.     

VXI总线从模块时序控制器的VHDL语言设计

介绍了VXI总线从模块时序控制器的动作过程及其特点,并基于VHDL硬件描述语言,用异步MEALY状态机的方法进行VXI总线寄存器基接口的时序控制器的设计.     

Flying in a flock comes at a cost in pigeons

Flying birds often form flocks, with social, navigational and anti-predator implications. Further, flying in a flock can result in aerodynamic benefits, thus reducing power requirements, as demonstrated by a reduction in heart rate and wingbeat frequency in pelicans flying in a V-formation. But how general is an aerodynamic power reduction due to group-flight? V-formation flocks are limited to moderately steady flight in relatively large birds, and may represent a special case. What are the aerodynamic consequences of flying in the more usual 'cluster' flock? Here we use data from innovative back-mounted Global Positioning System (GPS) and 6-degrees-of-freedom inertial sensors to show that pigeons (1) maintain powered, banked turns like aircraft, imposing dorsal accelerations of up to 2g, effectively doubling body weight and quadrupling induced power requirements; (2) increase flap frequency with increases in all conventional aerodynamic power requirements; and (3) increase flap frequency when flying near, particularly behind, other birds. Therefore, unlike V-formation pelicans, pigeons do not gain an aerodynamic advantage from flying in a flock. Indeed, the increased flap frequency, whether due to direct aerodynamic interactions or requirements for increased stability or control, suggests a considerable energetic cost to flight in a tight cluster flock.     

Urea excretion as a strategy for survival in a fish living in a very alkaline environment

Ammonia is toxic to all vertebrates. It can be converted to the less toxic urea, but this is a metabolically expensive process found only in terrestrial vertebrates that cannot readily excrete ammonia and marine fish that use urea as an osmotic filler. Freshwater fish mostly excrete ammonia with only a small quantity of urea. It seems the ornithine cycle for urea production has been suppressed in all freshwater teleosts except for some airbreathers which, when exposed to air, increase urea synthesis via the cycle. Here we show that the tilapia fish Oreochromis alcalicus grahami, the only fish living in Lake Magadi, an alkaline soda lake (pH = 9.6-10) in the Kenyan Rift Valley, excretes exclusively urea and has ornithine-urea cycle enzymes in its liver. A closely related species that lives in water at pH 7.1 lacks these enzymes and excretes mainly ammonia with small amounts of urea produced via uricolysis. It dies within 60 min when placed in water from Lake Magadi. We suggest that urea production via the ornithine-urea cycle permits O. a. grahami to survive the very alkaline conditions in Lake Magadi.     

Deleting a marked state in quantum database in a duality computing mode

In this article, we present a deletion algorithm in the duality computer that deletes a marked state from an even superposition of all basis-states with certainty. This duality computer deletion algorithm requires a single query, and this achieves exponential speedup over classical algorithm. Using a duality mode and recycling quantum computing, we provide a realization of this duality computer deletion algorithm in quantum computer.     

Flexible filaments in a flowing soap film as a model for one-dimensional flags in a two-dimensional wind

The dynamics of swimming fish and flapping flags involves a complicated interaction of their deformable shapes with the surrounding fluid flow. Even in the passive case of a flag, the flag exerts forces on the fluid through its own inertia and elastic responses, and is likewise acted on by hydrodynamic pressure and drag. But such couplings are not well understood. Here we study these interactions experimentally, using an analogous system of flexible filaments in flowing soap films. We find that, for a single filament (or 'flag') held at its upstream end and otherwise unconstrained, there are two distinct, stable dynamical states. The first is a stretched-straight state: the filament is immobile and aligned in the flow direction. The existence of this state seems to refute the common belief that a flag is always unstable and will flap. The second is a flapping state: the filament executes a sinuous motion in a manner akin to the flapping of a flag in the wind. We study further the hydrodynamically coupled interaction between two such filaments, and demonstrate the existence of four different dynamical states.     

Speciation in a ring

The evolutionary divergence of a single species into two has never been directly observed in nature, primarily because speciation can take a long time to occur. A ring species, in which a chain of intergrading populations encircles a barrier and the terminal forms coexist without interbreeding, provides a situation in which variation in space can be used to infer variation in time. Here we reconstruct the pathway to speciation between two reproductively isolated forms of greenish warbler (Phylloscopus trochiloides). These two taxa do not interbreed in central Siberia but are connected by a long chain of intergrading populations encircling the Tibetan Plateau to the south. Molecular data and climatic history imply that the reproductively isolated taxa came into contact following expansions northward around the western and eastern sides of the plateau. Parallel selection pressures for increased song complexity during the northward expansions have been accompanied by divergence in song structure. Playback experiments show that the two Siberian forms do not recognize each other's songs. Our results show how gradual divergence in a trait involved in mate choice leads to the formation of new species.