Changes in post world war ii distribution and status of monsoon rainforests in the Darwin area

Monsoon rainforests in the Darwin area occur as isolated patches ranging in size from 2 to 112 ha. Aerial photographic records over a 45 year period indicate a 60 per cent reduction in the cover of pre‐1945 rainforest. Urban development, cyclone damage, weed invasion and wildfire were identified as the major causes of this contraction. Urban development contributed 40 per cent of the total rainforest loss during this period. Rainforests occurring on dry substrates have been most affected by urban development. Cyclonic storm damage and indirect human affects such as weed invasion and anthropogenic fires continue to disturb the remaining rainforest patches. Although the largest expanses of rainforest presently occur within parks and reserves, providing adequate protection from further urban encroachment, smaller remnants occurring on vacant crown land are vulnerable to changes in land use. As well as the introduction of appropriate legislation, the control of fire and weeds should be given the highest priority by land managers to ensure the stability and long‐term maintenance of this remnant vegetation.     

湿位涡方程及其应用

本文在湿绝热、无摩擦条件下，推导了湿位涡方程及其近似表达式。然后通过尺度分析得到了大尺度条件下湿位涡守恒的性质，其形式与干位涡一样。由于考虑了水汽的作用，使用它较干位涡更为方便。最后，我们把湿位涡用于江南岭北3 月有无连阴雨的分析，其结果与预报员经验是一致的。     

五强溪水电站左岸船闸边坡开挖监控设计的理论与实践

五强溪水电站船闸左岸边坡，是由前震旦系的Ｐｔ１（主要为千枚状板岩）和Ｐｔ２（主要为砂岩、板岩）组成。因断层穿插，岩体破碎，边坡稳定性很差。为确保边坡在开挖施工期的安全，作者根据工程地质力学和系统科学相结合的方法，对之进行监控设计，取得了成功。     

关于成矿系列的结构

成矿系列是一个自然系统,它由若干矿床成因类型组成。各矿床类型间的时空结构关系表现为各类型间的“共生性”、“过渡性”和“重叠性”;其物质结构关系表现为“互补性”.本文按系统论观点,分析了上述结构,提出长江中下游铁铜成矿系列的新模式,并指出研究成矿系列的结构对预测矿产的重要意义.     

Low frequency waves in plasmas with spatially varying electron temperature

Low frequency electrostatic waves are studied in magnetized plasmas with an electron temperature which varies with position in a direction perpendicular to the magnetic field. For wave frequencies below the ion cyclotron frequency, the waves need not follow any definite dispersion relation. Instead a band of phase velocities is allowed, with a range of variation depending on the maximum and minimum values of the electron temperature. Simple model equations are obtained for the general case which can be solved to give the spatial variation of a harmonically time varying potential. A simple analytical model for the phenomenon is presented and the results are supported by numerical simulations carried out in a 2.5-dimensional particle-in-cell numerical simulation. We find that when the electron temperature is striated along B₀ and low frequency waves (_ci) are excited in this environment, then the intensity of these low frequency waves will be striated in a manner following the electron temperature striations. High frequency ion acoustic waves (_ci) will on the other hand have a spatially more uniform intensity distribution.     

地理科学的信息化与现代化

20世纪我国地理学的成就是空前辉煌的,奠定了现代化的科学基础,21世纪面对全球化、网络化和知识经济的机遇和挑战,需要把全球研究提到日程上来,对地观测技术系统的进步和时、空分辨率的提高,已使全球化同步动态监测成为现实,“地球信息科学”和“数字地球”战略研究提高了对城市化与资源、生态、环境问题的再认识;增强了地理战略决策和参予工程规划、设计的能力。地理学本来就是取法自然、又以人为本的综合性学科,从来就很注重探索时间规律与空间格局及其转换,通过全球化、网络化和智能化,21世纪的地理科学、必将焕然一新。     

我国气象科技期刊发展与作用

在对历史资料研究的基础上，对气象科技期刊的发展历程与作用进行了回顾及评述，并对目前气象科技期刊的现状及存在的问题做了简要分析。