A numerical algorithm coupling a bifurcating indicator and a direct method for the computation of Hopf bifurcation points in fluid mechanics

This paper deals with the computation of Hopf bifurcation points in fluid mechanics. This computation is done by coupling a bifurcation indicator proposed recently (Cadou et al., 2006) [1] and a direct method (Jackson, 1987; Jepson, 1981) [2] and [3] which consists in solving an augmented system whose solutions are Hopf bifurcation points. The bifurcation indicator gives initial critical values (Reynolds number, Strouhal frequency) for the direct method iterations. Some classical numerical examples from fluid mechanics, in two dimensions, are studied to demonstrate the efficiency and the reliability of such an algorithm.     

基于MSP430的二线制高精度表头设计

针对传统的二线制表头在高温下测量精度差、温漂大的特点,提出了一种在高温下的高精度数显表头的设计方案。分别介绍了其软硬件的实现方法,即采用超低功耗微处理器MSP430F4250采集回路中的电流值,采用24位ADC转换器ADS1244进行模数转换,最后将经过运算的变送器输出信号值在LED数码管中加以显示。实测结果证明,该表头在高温下测量精度高、工作可靠、抗干扰性强、实用性强,势必会成为无源二线制仪表的发展方向。     

Checking determinism of XML Schema content models in optimal time

We consider the determinism checking of XML Schema content models, as required by the W3C Recommendation. We argue that currently applied solutions have flaws and make processors vulnerable to exponential resource needs by pathological schemas, and we help to eliminate this potential vulnerability of XML Schema based systems. XML Schema content models are essentially regular expressions extended with numeric occurrence indicators. A previously published polynomial-time solution to check the determinism of such expressions is improved to run in linear time, and the improved algorithm is implemented and evaluated experimentally. When compared to the corresponding method of a popular production-quality XML Schema processor, the new implementation runs orders of magnitude faster. Enhancing the solution to take further extensions of XML Schema into account without compromising its linear scalability is also discussed.     

无线传感器网络跳数和通信距离自适应差错控制策略

无线传感器网络(WSNS)的动态信道特性、网络带宽和节点能量受限等特点,使得在无线环境下为数据传输提供可靠性保证面临更大的挑战.本文提出一种适用于WSNS的自适应链路层差错控制策略(AEC-Hops/RSSI),以便改善WSNS的通信性能.首先建立数学模型,分析数据帧被转发所经历的跳数与能效的变化规律,然后分析前向纠错...     

Analysis of black water aggregation in Taihu Lake

Black water aggregation (BWA) in Taihu Lake is a disaster for the lake environment. It is a phenomenon resulting from water environmental deterioration and eutrophication caused by accumulation of pollutants in the lake, according to research on the water quality, pollutants of BWA, and occurrence mechanisms of BWA. Dead algae are the material base of BWA, the polluted sediment is an important factor for the formation of BWA, and hydrological and meteorological conditions such as sun light, air temperature,...     

电子式车速里程表

详细介绍霍尔速度传感器,里程计数脉冲的产生,步进电机的驱动和ＢＬ２１１５集成电路在电子式车速里程表中的应用。     

网管系统的性能模糊综合评价模型

针对网管系统性能评价研究中的度量问题,运用性能指标和模糊数学方法对性能评价进行模糊化处理,以度量的性能数据为基础,采用模糊综合评价方法评价质量因子,通过建立性能综合评价模型,有效地解决了多指标评价问题,可用于指导软件开发人员进行网管系统性能改进。     

水生态文明的内涵及评价体系探讨

阐述了水生态文明的概念和内涵,提出了由两个系统（水生态系统及社会经济系统）、6个对象类型及20个指标共3层构成的水生态文明多层评价指标体系。在评价方法方面,引入了弹性分级评分系统。分级评价标准考虑了我国不同地区的自然和经济社会特点,将水生态文明状况划分为五级,以体现不同地区水生态文明的差异性。     

旱情预警几个主要技术问题的探讨

旱灾是我国主要的自然灾害之一。近年来,我国干旱灾害发生频繁,对经济社会造成的影响不断加剧。加强旱情监测,提高旱情综合评判能力,探索旱情预警方法等,显得十分必要和紧迫。目前,我国旱情监测工作相对薄弱,旱情预测预报起步较晚,旱情预警尚处于研究和探索阶段。本文结合吉林省旱情预警模型研究的有关成果,探讨预警指标、预测模型、预警综合指数等主要技术问题的创建思路,为旱情预警系统研究提供借鉴和参考作用。     

Simulation of thermomechanical behavior during continuous casting process based on MiLE method

A new method called mixed Lagrangian and Eulerian method(MiLE method) was used to simulate the thermomechanical behavior during continuous casting process of steel YF45MnV.The simulation results are basically in agreement with the measured data.The delaying period at the beginning of solidification is about 0.1 in square root of solidification time which is agreement with the data in literatures,and shell thickness increases in linear relation to square root of solidification time.The bloom surface temperature decreases gradually as the casting proceeds.The effective stress in the corner is much larger than that in the mid-face.The corner area is the dangerous zone of cracking.The effects of mold flux break temperature on the air gap and hot tearing indicator were also modeled.The model predicts that the bloom surface temperature increases with the increase of the mold flux break temperature,but the heat flux decreases with the increase of the mold flux break temperature.The hot tearing indicator is much smaller when the mold flux break temperature is higher.