竞争Lotka-Volterra扩散系统的全局稳定性和周期解

本文讨论一类竞争扩散系统,此系统有两种种群ｎ 个斑块,其中一种种群可以在ｎ 个斑块中自由扩散,而另一种种群被限制在一个斑块中不能扩散,当系数满足一定的积分不等式时,得到系统的全局稳定性和周期解．     

带有扩散和时滞的非自治捕食系统的持续生存和全局稳定性

讨论带有扩散和时滞的非自治捕食系统,有两种种群：一个能在两个斑块中自由扩散;而另一个被限定一个斑块中不能扩散,在一定的条件下,得到系统持续生存和全局稳定性。     

含时滞扩散合作系统的一致持久性和全局稳定性

考虑了含连续时滞的两种群扩散合作的系统，其中一个种群能在两个斑块中移动，另一个种群限制在一个斑块中不能移动，给出了该系统一致持久性和全局稳定性的充分性条件。     

一类非线性时滞扩散竞争系统的一致持续生存和全局吸引性

讨论了一类非线性时滞扩散竞争系统,该系统包括两个斑块,两个竞争种群:其中一种群可以在两个斑块中自由扩散,但另一种群限制在第一斑块中.通过利用微分方程比较定理和构造适当的Lyapunov泛函,得到了保证系统一致持续生存和全局吸引的充分条件.     

一类捕食与被捕食系统的持续生存性与周期解

讨论了一类一个捕食者种群和两个食饵种群构成的非自治生态系统．系统中食饵种群有各自的避难所，它们在避难所内外可以迁移．应用常微分方程定性和稳定性的方法，得到了在一定条件下系统是持续生存的；进一步，若系统是一个周期系统，则在合适的条件下，系统存在唯一的、全局渐近稳定的周期解     

一类具有阶段结构的单种群扩散模型

提出并研究了一类具有阶段结构的单种群扩散模型,得到了其在正平衡点处的稳定性和零平衡点处的不稳定性。     

光谱仪的微机化及其应用

50～60年代生产的光谱仪器一般不具备数据处理及贮存功能,且操作麻烦,精确度较差,但其主体光学系统一般仍能满足分析的要求。本文中将电子学性能不够稳定、样品和参比通道电信号平衡能力差的SP700的扫描单色器,单点读数式的QR50的浸反射附件等与AppleⅡ微机联成一体,组成一套波段范围广(54000～2800 cm~(-1))、     

一类具时滞和比率的扩散系统正周期解

研究一类具有时滞和比率的,且有Machaelis-Menten型功能性反应的非自治两种群捕食者-食饵扩散系统,其中所有参数都是周期函数.系统由两种群及两斑块构成,食饵种群能够在两斑块间扩散,而捕食者种群被限制在某一斑块中.文中应用重合度理论中的延拓定理,结合分析技巧构造一个同伦变换,得出系统存在正周期解的充分条件,且这些条件与扩散系数是无关.     

具扩散的捕食与被捕食Lotka—Volterra模型研究

证明了一类具扩散的捕食与被捕食Lotka-Volterra模型的如下性质：当该模型存在正平衡点时，它的一切正解是有界的，并且是强持续生存的；当扩散率较小时，系统的正平衡点是稳定的；当扩散率增大且在某一开区间变化时，系统的正平衡点是不稳定的，而且分支出唯一的小振幅空间周期解；当扩散率继续增大时，系统的正平衡点又变成稳定的。     

一类生态系统的持续生存和全局稳定性

讨论了一类具有连续时滞和功能性反应的两种群两缀块的一类生态系统的动力学行为。两种群之一能在两缀块中迁移,另一种群限制在一个缀块中,应用微分方程定性和稳定性的方法,证明了系统在一定条件下是持续生存的。进一步,得到了系统为全局稳定的充分条件     

温度对氨吹脱工艺中氨扩散传质的影响

研究低气速下的氨吹脱系统,建立了定量的氨扩散传质动力学模型,分析系统温度对氨扩散传质的影响。结果表明,氨吹脱过程中,在废水pH值大于12的条件下,氨分子大部分通过气泡扩散,只有极少量通过液相表面扩散;氨的气液传质阻力主要来自于气膜;随着系统温度的升高,气泡直径略微减小,气泡上升时间基本稳定,液相总传质系数迅速增大,气液传质阻力大幅降低。     

具有避难所的非自治Lotka-Volterra扩散模型的持久性与周期解

研究了一类具有避难所的非自治Lotka-Volterra扩散系统，其中食饵种群在环境相异的两个缀块间有限制地扩散，并且食饵种群有逃避天敌的避难所，得到了系统持久性的条件，进一步给出了系统存在唯一全局渐近稳定周期解的充分条件。     

油藏数值仿真系统若干功能的改进

油藏数值模拟是剩余油宏观分布等研究的重要方法之一,油藏数值仿真系统是在已有数值模拟软件基础上研制的软件系统。该系统是针对常规油藏数值模拟而设计的一套仿真系统,在油田开发过程中,油藏参数不断发生变化,对其功能进行了改进,以满足数值模拟过程中实现储层参数动态变化、发散原因跟踪及图象显示灵活的需要。改进后的油藏数值模拟仿真系统在孤岛中一区与西区精细油藏描述中进行了应用,取得了很好的效果     

Cosmic gamma-ray background from structure formation in the intergalactic medium

The Universe is filled with a diffuse background of gamma-ray radiation, the origin of which remains one of the unsolved puzzles of cosmology. Less than one-quarter of the gamma-ray flux can be attributed to unresolved discrete sources, such as active galactic nuclei; the remainder appears to constitute a truly diffuse background. Here we show that the shock waves induced by gravity in the gas of the intergalactic medium, during the formation of large-scale structures like filaments and sheets of galaxies, produce a population of highly relativistic electrons. These electrons scatter a small fraction of the cosmic microwave background photons in the local Universe up to gamma-ray energies, thereby providing the gamma-ray background. The predicted diffuse flux agrees with the observed background across more than four orders of magnitude in photon energy, and the model predicts that the gamma-ray background, though generated locally, is isotropic to better than five per cent on angular scales larger than a degree. Moreover, the agreement between the predicted and observed background fluxes implies a mean cosmological density of baryons that is consistent with Big Bang nucleosynthesis.     

Scattering by chorus waves as the dominant cause of diffuse auroral precipitation

Earth's diffuse aurora occurs over a broad latitude range and is primarily caused by the precipitation of low-energy (0.1-30-keV) electrons originating in the central plasma sheet, which is the source region for hot electrons in the nightside outer magnetosphere. Although generally not visible, the diffuse auroral precipitation provides the main source of energy for the high-latitude nightside upper atmosphere, leading to enhanced ionization and chemical changes. Previous theoretical studies have indicated that two distinct classes of magnetospheric plasma wave, electrostatic electron cyclotron harmonic waves and whistler-mode chorus waves, could be responsible for the electron scattering that leads to diffuse auroral precipitation, but it has hitherto not been possible to determine which is the more important. Here we report an analysis of satellite wave data and Fokker-Planck diffusion calculations which reveals that scattering by chorus is the dominant cause of the most intense diffuse auroral precipitation. This resolves a long-standing controversy. Furthermore, scattering by chorus can remove most electrons as they drift around Earth's magnetosphere, leading to the development of observed pancake distributions, and can account for the global morphology of the diffuse aurora.     

Cross-presentation by intercellular peptide transfer through gap junctions

Major histocompatibility complex (MHC) class I molecules present peptides that are derived from endogenous proteins. These antigens can also be transferred to professional antigen-presenting cells in a process called cross-presentation, which precedes initiation of a proper T-cell response; but exactly how they do this is unclear. We tested whether peptides can be transferred directly from the cytoplasm of one cell into the cytoplasm of its neighbour through gap junctions. Here we show that peptides with a relative molecular mass of up to approximately 1,800 diffuse intercellularly through gap junctions unless a three-dimensional structure is imposed. This intercellular peptide transfer causes cytotoxic T-cell recognition of adjacent, innocent bystander cells as well as activated monocytes. Gap-junction-mediated peptide transfer is restricted to a few coupling cells owing to the high cytosolic peptidase activity. We present a mechanism of antigen acquisition for cross-presentation that couples the antigen presentation system of two adjacent cells and is lost in most tumours: gap-junction-mediated intercellular peptide coupling for presentation by bystander MHC class I molecules and transfer to professional antigen presenting cells for cross-priming.     

存在镜面反射时的双目立体匹配

传统的立体匹配方法建立在Lambertian的漫反射模型之上,漫反射模型的立体匹配在一个图像的大多部分是有效的,但是在处理图像中包含镜面反射的部分时结果会产生严重的匹配错误。笔者利用漫反射和镜面反射在灰度和最大色度上的不同,分离出镜面反射的像素,然后采用一种针对镜面反射的匹配测度,在图像中漫反射部分和镜面反射部分都能匹配得到正确的视差。结果证明了方法的有效性。     

包膜型控释肥料养分释放、运移的传质分析

根据菲克定律、改性传质双膜论、液膜寿命分布函数,建立了包膜型控释肥料养分释放的偏微分方程组。用拉普拉斯变换法求解该方程组,并将拉普拉斯变换与液膜寿命分布函数结合,得到了养分释放速率的表达式,为进一步研究提供了理论基础。     

空调系统能耗分析用散射分离模型

进行建筑物空调系统全年或季节能耗分析，需要太阳总辐射和散射辐射数据，我国大多数地方只有总辐射观测，没有直接辐射或散射辐射观测，因此需要一种估计散射的方法。文章根据北京和成都两地的实测数据，分析了日散射与日总射的关系，分别建立了两地散射系数Kd与总辐射系数Kt的多项式拟合模型，该模型以日总辐射为唯一输入进行日散射估计。经检验，模型有很好的拟合性能，拟合数据与建模数据具有一致的月均值和自相关结构，在比较两模型后认为北京模型可以作为通用模型。     

模糊信息优化处理技术在决策支持系统中的应用

提出用模糊信息优化处理技术解决决策支持系统中的非参数输入问题，实践证明，把正态扩散估计方法用于模糊输入可不断提高系统的精度，具有较强的实用价值。