Hydrological management strategies for the control of algal blooms in regulated lowland rivers

Reservoirs of lowland floodplain rivers with eutrophic backgrounds cause variations in the hydrological and hydraulic conditions of estuaries and low-dam reservoir areas, which can promote planktonic algae to proliferate and algal bloom outbreaks. Understanding the ecological effects of variations in hydrological and hydraulic processes in lowland rivers is important for algal bloom control. In this study, the middle and lower reaches of the Han River, China, a typical regulated lowland river with a eutrophic background, are selected. Based on the effect of hydrological and hydraulic variability on algal blooms, a hydrological management strategy for river algal bloom control is proposed. The results showed that (a) differences in river morphology and background nutrient levels cause significant differences in the critical threshold flow velocities for algal bloom outbreaks between natural river and low-dam reservoir sections; there is no uniform threshold flow velocity for algal bloom control. (b) There are significant differences in the river hydrological/hydraulic conditions between years with and without algal blooms. The average river flow, water level and velocity in years with algal blooms are significantly lower than those in years without algal blooms. (c) For different river sections where algal blooms occur and to meet the threshold flow velocities, the joint operation of cascade reservoirs and diversion projects is an effective method to prevent and control algal blooms in regulated lowland rivers. This study is expected to deepen our understanding of the ecological significance of special hydrological processes and guide algal bloom management in regulated lowland rivers.     

Study of the flood control scheduling scheme for the Three Gorges Reservoir in a catastrophic flood

The Three Gorges Project is the world's largest water conservancy project. According to the design standards for the 1,000‐year flood, flood diversion areas in the Jingjiang reach of the Yangtze River must be utilized to ensure the safety of the Jingjiang area and the city of Wuhan. However, once these areas are used, the economic and life loss in these areas may be very great. Therefore, it is vital to reduce this loss by developing a scheme that reduces the use of the flood diversion areas through flood regulation by the Three Gorges Reservoir (TGR), under the premise of ensuring the safety of the Three Gorges Dam. For a 1,000‐year flood on the basis of a highly destructive flood in 1954, this paper evaluates scheduling schemes in which flood diversion areas are or are not used. The schemes are simulated based on 2.5‐m resolution reservoir topography and an optimized model of dynamic capacity flood regulation. The simulation results show the following. (a) In accord with the normal flood‐control regulation discharge, the maximum water level above the dam should be not more than 175 m, which ensures the safety of the dam and reservoir area. However, it is necessary to utilize the flood diversion areas within the Jingjiang area, and flood discharge can reach 2.81 billion m³. (b) In the case of relying on the TGR to impound floodwaters independently rather than using the flood diversion areas, the maximum water level above the dam reaches 177.35 m, which is less than the flood check level of 180.4 m to ensure the safety of the Three Gorges Dam. The average increase of the TGR water level in the Chongqing area is not more than 0.11 m, which indicates no significant effect on the upstream reservoir area. Comparing the various scheduling schemes, when the flood diversion areas are not used, it is believed that the TGR can execute safe flood control for a 1,000‐year flood, thereby greatly reducing flood damage.     

影响鸢乌贼手钓上钩率的因子探讨

根据印度洋西北部鸢乌贼（Sym plectoteuthis oualaniensis）作业渔场的现场调查数据．分析了作业水深、作业时段、摄食等级和月相等因子对手钓上钩率的影响。统计表明．晚上、午夜和凌晨3个不同时段和不同作业水深对手钓上钩率均有显著性影响。3个时段中，其摄食等级呈先低后高再低的现象。午夜和凌展，上钩率的变化趋势与摄食等级的变化趋势呈显著的负相关。在月相的影响下．离朔日三四天之前，手钓产量呈上升趋势；离望日五六天之前。手钓产量呈明显的下降趋势。     

AGGLOMERATION AND RADIATION EFFECT OF THE PULL OF URBANIZATION

In order to explore the train of thought for China‘s urbanizing development and coordinated rural eco-nomic development, and to find good ways of solving rural problems through urbanization, this paper absorbs the push-and-pull forces theory and the systematic dynamic theory in the traditional population migration theories, views urbanization as a dynamic system, makes research on the push-and-pull mechanism of urbanization. The pulling power of urbanization is analyzed according to two aspects, the agglomeration effect and the radiation effect of cities. The agglomeration effect provides continuous propelling force for urbanization, and the radiation effect further accelerates the urbanization process by pushing forward the development of rural economy. Of course, the slow de-velopment of urbanization can result in the hindrance to rural economic development.     

交通流量分析与实时最优控制

通过将车流量的增大或减小转化为路长权重的变化。将交通流量的动态问题转化为静态问题，用解决最短路问题的Dijkstra方法，给出交通流量实时最优控制的可行性模型及其有效算法。     

Opposition polarimetry and photometry of S- and E-type asteroids

The first results of the observational program devoted to simultaneous investigation of asteroid polarimetric and photometric opposition phenomena are presented. UBVRI polarimetric and V-band photometric observations of the S-type Asteroid 20 Massalia and the E-type Asteroids 214 Aschera and 620 Drakonia were carried out in 1996-1999 down to phase angles of 0.08°, 0.7°, and 1.2°, correspondingly. The S-type Asteroid 20 Massalia is characterized by the pronounced brightness opposition surge with an amplitude larger than that observed for the E-type asteroids. A sharp peak of negative polarization at small phase angles was not observed for this asteroid. The value of polarization degree at phase angle α<1° is less than 0.5% for both S and E types. The negative polarization branches of S and especially E-asteroids have an asymmetrical shape. The phase angle at which the polarization minimum occurs is close to the angle at which non-linear increase begins in the asteroid magnitude phase curves. A relation of the observed effects to the mechanism of coherent backscattering is discussed.     

LAMOST总控系统程序设计

国家重大科学工程项目LAMOST总控系统的程序设计是一个庞大的软件工程．其总控系统下共包括8个既相互独立又互有关联的子系统．如何通过良好的软件设计方法来处理好这8个子系统之间的关系使其协调运转，以及如何确保软件开发的可维护性、可持续性是研究重点．     

基于专家系统决策的多模式控制及其应用

将专家系统技术与常规控制、模糊控制、超前控制、仿人智能操作控制以及计算机控制技术相结合,设计了一种新的基于专家系统决策的多模式控制(MCDBES)。经试验和实际运行结果表明,MCDBES系统对未知数学模型的被控对象,具有良好的控制性能。本文提出的MCDBES已成功地应用于燃油陶瓷窑炉计算机控制系统。     

运输系统的区域效应研究

运输系统改进—运距缩短—产业布局调整这一空间过程对不同的区域可能具有完全不同的意义。本文通过对一个两区域—两部门经济模型的研究得出结论:当较落后的资源产区与经济中心之间的距离由于运输系统的改进而缩短时,资源产区的经济结构向单一化转变,初级产品的生产和输出在经济建设中逐渐占主导地位,加工工业逐渐萎缩,地方经济发展受到阻碍,而且这种变化是在距离的某一特定值处突然出现的,带有跃变的性质。这一研究结果表明,对区域运输系统的任何改进措施都应该慎而行之,以免造成与本来目标相悖的区域效应。