小河口灌区可持续发展对策初析

从小河口灌区的水源工程、渠系工程、田间灌溉管理现状分析入手，提出了适合灌区可持续发展的初步对策。     

随机潜蚤病模型的动力学行为分析

潜蚤病是贫困地区的一种人畜共患病,其发病过程极易受到随机波动环境因素的影响。因此,建立并讨论了一类以正确卫生习惯为控制策略的随机潜蚤病模型。首先,通过构造恰当的Lyapunov函数并利用It$\hat{\rm o}$公式证明了随机系统全局正解的存在唯一性。其次,在一定的条件下证明了随机系统的正解围绕在确定性系统平衡点附近的振荡行为。最后,通过数值模拟验证了理论结果的正确性。数值结果表明,当随机干扰强度足够大时将会导致疾病灭绝。     

Promotion in Heterogeneous Catalysis: A Topic Requiring a New Approach?

Promoters, and their counterparts poisons, are two topics that have been studied extensively since heterogeneous catalysts have been used industrially. Commercial catalysts tend to involve multiple promoters to enhance the activity, selectivity, lifetime and structural integrity, in addition to guard beds or feedstock purification measures that are used to avoid the adsorption of poisons. Yet, at a fundamental level, there is still considerable debate as to how specific promoters function. Promoter effects tend to be specific to a particular catalyst formulation and generic effects are not common, yet this would be desirable. Generally, in acid catalysis and hydrogenation reactions, promoter effects can be dramatic and unexpected. However, in oxidation reactions of alkanes and alkenes, the promotion effects observed to date are somewhat limited. In this paper, the topic of promotion in heterogeneous catalysis is discussed. The complex interplay between structural and electronic effects of promoters is described using examples of both well defined metal surfaces (e.g., the promoted iron catalyst for ammonia synthesis) and multicrystalline metal, metal oxide and metal phosphate catalysts (e.g., Li-doped MgO for methane oxidation). Subsequently, a molecular approach for the promotion of heterogeneous catalysts is prepared and discussed. This is based on observations from well defined molecular catalysts for homogeneously catalysed processes of ligand accelerated reactions. Examples are described where the effects of ligand acceleration, increasing reaction rate by over two orders of magnitude, can be observed for heterogeneous catalysts for hydrogenation and acid catalysed reactions. The remaining challenge is to identify similar effects for partial oxidation reactions, and it is questioned whether a molecular approach can be developed to meet this challenge.     

H∞ position transfer and regulation for floating offshore wind turbines

This paper proposes ${\rm H}_\infty$ controller design for platform position transfer and regulation of floating offshore wind turbines. The platform movability of floating wind turbines can be utilized in mitigating the wake effect in the wind farm, thereby maximizing the wind farm''s total power capture and efficiency. The controller is designed so that aerodynamic force is adjusted to meet the three objectives simultaneously, that is, 1) to generate the desired electrical power level, 2) to achieve the desired platform position, and 3) to suppress the platform oscillation. To acquire sufficient aerodynamic force to move the heavy platform, the pitch-to-stall blade pitching strategy is taken instead of the commonly-used pitch-to-feather strategy. The desired power level is attained by the standard constant-power strategy for the generator torque, while ${\rm H}_\infty$ state-feedback control of blade pitch and nacelle yaw angles is adopted for the position regulation and platform oscillation suppression. Weighting constants for the ${\rm H}_\infty$ controller design are adjusted to take the trade-off between the position regulation accuracy and the platform motion reduction. To demonstrate the efficiency of the proposed controller, a virtual 5-MW semi-submersible wind turbine is considered. Simulation results show that the designed ${\rm H}_\infty$ controller successfully accomplishes the platform position transfer and regulation as well as the platform oscillation reduction against wind and wave disturbances, and that it outperforms a previously-proposed linear quadratic controller with an integrator.     

南水北调工程天津干线下穿京九铁路隧道工程设计

为研究和解决南水北调天津干线工程下穿京九铁路隧道施工安全问题,采用有限元软件对隧洞开挖过程进行分析计算,进行了隧洞防渗设计和铁路加固设计,最大限度地克服施工期间箱涵与铁路运营之间的相互干扰,保障施工安全。设计方案体现了临时支护拆除量少,成洞质量高、速度快,对列车限速时间短等特点,既减少了施工对铁路运营造成的影响,又保证了天津干线箱涵输水运行及检修安全。推荐的设计方案在京广铁路和津霸铁路上进行了推广使用。     

基于改进S变换的手掌静脉身份识别

针对目前基于手掌静脉的身份识别问题,分析了 掌脉图像的纹理特性,提出一种利用改进的S变换 能量特征的识别方法。首先对掌脉图像进行二维离散正交S变换(2D-DOST),将变换后的 频域图像作为 掌脉纹理特征的一种体现,即形成S变换能量曲面(STES);然后将不同掌脉能量曲面进行 减法运算,得 到能量差曲面,进一步计算曲面的标准差,并以此为依据对不同掌脉进行分类识别。在通 用的接触式标 准掌脉图库上测试的结果表明,本文方法正确识别率为99.892,识 别时间为0.017s;同时使用自主 设计的采集仪在非接触环境下测试的结果表明,本文方法正确识别率可达99.480,识别时间为 0.020s。相比其他典型和流行算法,本文算 法提高了手掌静脉识别系统的性能,具有可行性和有效性。     

Effect of temperature on reproductive parameters and the longevity of Acarus farris (Acari: Acaridae)

Reproductive parameters and the longevity of Acarus farris were examined at six constant temperatures, ranging from 7 to 29 °C, and a relative humidity of 90±5%. As temperature increased, the preoviposition period rapidly decreased to a minimum, above 25 °C. Fecundity was adversely affected by extreme temperatures while the oviposition period increased as temperature was reduced. The relationship between reproductive parameters and temperature was fitted using different polynomial and non-linear models. Male and female longevity increased as temperature decreased, except for the males at 7 °C, which showed significantly lower longevity than at 10 °C. Moreover, males showed significantly greater longevity than females. The effect of temperature on the capacity for increase of A. farris populations was also established. The non-linear Lactin model provided a reliable fit of the relationship between intrinsic rate of increase and temperature (R²>0.99). The optimum temperature for development was calculated to be 25 °C. At this temperature, the population doubling time was 2.8 days. The lower and upper thermal thresholds for A. farris populations were established at 6.4 and 29.9 °C, respectively.     

圆形池壁滑模提升系统设计与施工

本文阐述了郑州污水处理厂等直径钢筋混凝土消化池 ,采用滑升模板施工 ,连续浇筑混凝土提高工效 ,符合设计要求 ,保证工程质量 ,取得较好的结果