COMPONENT ALLEE EFFECTS AND STAGE‐SPECIFIC PREDATION: A BRIEF INSIGHT INTO CONSERVATION AND BIOLOGICAL CONTROL ISSUES

In this paper, we propose a two‐stage structured population model subject to component Allee effects in fecundity and maturation, and with two disturbances (predation only and harvest and predation) acting on both stages. It is shown that this combination leads to a demographic Allee effect—a characteristic that could be exploited in pest biological control, but on the other hand, it represents a bane in conservation biology. The analysis is performed for disturbances with functional responses type 2 and 3, and the models show that they yield qualitatively similar results. This characteristic is discussed from the species conservation and biological control point of view, together with possible extensions of this work.     

Effects of cannibalism on a basic stage structure

In this paper, we discuss the effects of cannibalism on a basic stage-structured population model for a single species. A threshold condition for extinction versus persistence is obtained, and numerical simulations of the population dynamics are presented. These simulations suggest that cannibalism has a stabilizing effect on the population, promoting equilibrium of the adult population level.     

Trajectory statistical solutions for the 3D Navier–Stokes equations: The trajectory attractor approach

In this article, we construct the trajectory statistical solution for the 3D incompressible Navier–Stokes equations via the natural translation semigroup and trajectory attractor. In our construction, the trajectory statistical solution is an invariant space–time probability measure which is carried by the trajectory attractor of the natural translation semigroup defined on the trajectory space, and the trajectory statistical solution possesses the invariant property under the acting of the translation semigroup.     

A BIOECONOMIC SHEEP–VEGETATION TRADE‐OFF MODEL: AN ANALYSIS OF THE NORDIC SHEEP FARMING SYSTEM

Abstract. The paper studies the economy and ecology of sheep farming at the farm level and includes 2 different categories of the animals, ewes (adult females) and lambs. The model is analyzed in a Nordic economic and biological setting. During the outdoor grazing season, animals face limited grazing resources so that the weight gain of lambs is determined by the per‐animal vegetation consumption. On the other hand, the number of grazing animals, lambs as well as ewes, determines the grazing pressure. This problem is studied under the assumption of a rational and well‐informed farmer who aims to maximize profit in ecological equilibrium with zero animal and vegetation growth. We find that lamb‐only slaughtering is optimal and that it is never beneficial for the farmer to keep livestock that overgraze pasture. It is also shown that higher meat prices and more profitable slaughtering make it economically rewarding for the farmer to keep more animals. A numerical illustration indicates that the optimal sheep farming decision may be more sensitive to changes in pasture quality and productivity than changes in economic conditions.     

一类带时滞的阶段结构捕食模型的定性分析

研究了一类具有时滞和阶段结构的捕食模型系统,给出了系统持续生存的充分条件.利用比较定理和构造适当的Lyapunov泛函得到了该系统正平衡态全局渐近稳定的充分条件.     

N(~4S_u) CH(a~4∑~-)体系的分子反应动力学研究

用轨线法对Ｎ（４Ｓｕ）＋ＣＨ（０，０）→ＣＮ（ｖ′，Ｊ′）＋Ｈ（２Ｓｇ）和Ｎ（４Ｓｕ）＋ＣＨ（０，０）→ＮＨ（ｖ′，Ｊ′）＋Ｃ（３Ｐｇ）反应进行计算，研究了两个反应的阈能、反应截面、产物散射分析和微观反应机理     

Approximate solution for two stage open networks with Markov-modulated queues minimizing the state space explosion problem

Analytical solutions for two-dimensional Markov processes suffer from the state space explosion problem. Two stage tandem networks are effectively used for analytical modelling of various communication and computer systems which have tandem system behaviour. Performance evaluation of tandem systems with feedbacks can be handled with these models. However, because of the numerical difficulties caused by large state spaces, considering server failures and repairs at the second stage employing multiple servers has not been possible. The solution proposed in this paper is approximate with a high degree of accuracy. Using this approach, two stage open networks with multiple servers, break downs, and repairs at the second stage as well as feedback can be modelled as three-dimensional Markov processes and solved for performability measures. Results show that, unlike other approaches such as spectral expansion, the steady state solution is possible regardless of the number of servers employed.     

一个组面试问题的最佳顺序安排

采用边界阶段方法讨论最优组面试问题的最佳划分选择策略,在允许调整面试顺序的情况下,得到最优组面试问题中如何重新安排面试顺序能够以最大概率录用到最优应聘者的排序策略.     

The role of thiophosphoryl disulfide on the co‐cure of CR‐EPDM blends: effect of white fillers

Bis(diisopropyl) thiophosphoryl disulfide (DIPDIS) being a rubber accelerator has a definite role as a coupling agent in the silica filled polychloroprene rubber with ethylene propylene diene rubber (CR‐EPDM) blends. Diethylene glycol can further improve the beneficial effect of DIPDIS in silica filled CR‐EPDM blends. Two‐stage vulcanization technique further improves the physical properties of silica filled CR‐EPDM blends. The results have been compared with non‐reinforcing calcium carbonate filled systems. Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the silica filled CR‐EPDM blend vulcanizates obtained from this two‐stage process. Copyright © 2004 John Wiley & Sons, Ltd.     

高聚物结晶后期动力学过程的研究进展

回顾了描述高聚物结晶后期动力学过程的各种模型、方程以及数据处理方法，并就影响高聚物结晶后期动力学过程的某些因素进行了讨论。