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101.
On Constrained MMVC of Discrete‐Time First‐Order Linear Stochastic Systems with PSI I: The Critically Stable Case 下载免费PDF全文
This paper is devoted to the study of the modified minimal variance control (MMVC) of discrete‐time first‐order linear critically stable stochastic systems with prospective strong intervention (PSI) and control input constraints. Due to different evolutionary characteristics of systems with PSI, that is, the two modes of tending to infinity and having bounded oscillations, the discrete‐time first‐order linear critically stable systems can be partitioned into two types regarding the signs of a key system parameter a. A necessary and sufficient condition for the state mean convergence of a system with a = 1 is derived and the corresponding design of MMVC is formulated. For the critical stable system with a =? 1, its oscillation amplitudes of state means can be effectively suppressed or the means can converge under control. Finally, the effectiveness and advantages of the proposed control strategies comparing with MVC are confirmed by numerical simulations. 相似文献
102.
Floc architecture of bioflocculation sediment by ESEM and CLSM 总被引:1,自引:0,他引:1
Sediment flocculation is a critical component for the understanding of cohesive sediment dynamics. Traditionally, the referred study has largely been devoted to forming mechanism, influencing factors and physicochemical sediment conditions of all kinds of organic-flocculation and inorganic-flocculation. However, during the last decade, the bioflocculation of sediment by biological activity has been given increasing attention. But most studies have focused on the interrelations between biological and sedimentological variables. With the assistance of a newly developed field kit and correlative microscopy (which includes environmental scanning electron microscopy and confocal laser scanning microscopy), this article begins to bridge the resolution gap between sediment particles and biological activities as well as its metabolic products biofilm, in order to better understand the role of polymeric material biofilm in floc ultrastructure and outward floc behavior of bioflocculation sediment. Results have demonstrated that bioflocculation sediment was observed to be composed of complex networks of biofilm and appeared to be of complicated physical floc structures. The biofilm was found to embed particles and permeate the void space, representing the dominant physical bridging mechanism of the flocs and contributed to the extensive surface area, architecture characteristics, and mechanical properties of bioflocculation sediment. 相似文献
103.
104.
坡耕地小区坡面不同坡段侵蚀泥沙贡献率的7Be示踪研究 总被引:1,自引:0,他引:1
侵蚀泥沙来源的研究对深化侵蚀规律的认识,优化水土保持措施的配置等有重要的意义。本文利用7Be示踪技术结合传统的土壤侵蚀研究方法,通过建立不同坡度的径流小区,分别探讨了坡耕地小区坡面不同坡段片蚀、细沟侵蚀对侵蚀泥沙的贡献率及小区泥沙输移比。研究发现,片蚀主要发生在小区坡面距坡顶0~2m区域,占总片蚀量的60%以上,细沟侵蚀主要发生在小区坡面距坡顶2~5m区域,占总细沟侵蚀总量的75%以上,总体而言,侵蚀泥沙主要来源于小区坡面距坡顶1~4m区域,上部和下部泥沙贡献相对较小。对于降雨强度高的15°小区,片蚀泥沙几乎来自与全坡面,坡面不同坡段对总侵蚀泥沙的贡献率从坡顶向坡脚呈增加趋势。利用7Be示踪计算出各小区泥沙输移比在0.643~0.979之内,除5°小区外,其它小区泥沙输移比都大于0.9。 相似文献
105.
106.
通过引入随机理论及其相关处理方法,详细分析随机概念下的泥沙冲淤模式,建立了基于随机理论的泥沙数学模型。此模型避开了恢复饱和系数意义不明、取值不确定问题,以及含沙量与挟沙力的复杂性问题。通过水库淤积、水槽冲刷及一般河道的冲淤计算应用,结果证明本模式定性合理,可与确定性的传统水沙动力学方法作对比。 相似文献
107.
为掌握三峡水库175 m试验性蓄水过程中库区水位、流量、含沙量变化过程,通过三峡库区寸滩、清溪场、万县、朱沱(三)水文站实测的水位、流量、含沙量、水面比降资料,分析了蓄水过程中三峡库区沿程水面比降、库区水文站的水位流量关系、含沙量变化、库区冲淤变化等。分析结果为认识掌握三峡水库175 m蓄水后库区水文泥沙的变化规律积累了资料,对探索三峡库区水文泥沙的监测方式和分析研究将具有积极作用。 相似文献
108.
针对淤积型水库溃坝洪水计算中是否考虑泥沙因素影响、产生怎样影响的问题,利用MIKE21中的水动力模块(HD)与输沙模块(ST)耦合,模拟淤积水库清水、浑水溃坝洪水演进过程,并通过溃坝峰顶流量值、溃坝最大水位值及溃坝洪水淹没历时的变化,分析泥沙因素对水库溃坝洪水影响。结果表明:库区泥沙可使下游各断面溃坝峰顶流量值变小,淹没历时变长;泥沙的中值粒径对峰顶流量、水位、淹没历时有影响。 相似文献
109.
110.
EXPERIMENTAL STUDY ON SEDIMENT RESUSPENSION IN TAIHU LAKE UNDER DIFFERENT HYDRODYNAMIC DISTURBANCES 总被引:1,自引:0,他引:1
QIAN Jin ZHENG Sha-sha WANG Pei-fang WANG Chao Key Laboratory of Integrated Regulation Resource Department on Shallow Lakes Ministry of Education College of Enviroment Hohai University Nanjing China 《水动力学研究与进展(B辑)》2011,(6):826-833
Contaminants resuspension in sediments induced by wind-wave could influence the water quality in shallow lakes. Resuspension of surface sediments from the Zhushan Bay, Taihu Lake was simulated under different wind forcing by using a pneumatic annular flume in this study. Acoustic Doppler Velocimeter (ADV) was used to measure flow velocity at each wind speed, and the characteristics of sediment resuspension were studied with the layered sampling technology. The experimental results show that the flow velocity increases with wind speed obviously and 6m/s is a critical wind speed which affected hydrodynamic conditions significantly. The distribution of flow velocity and water depth is different from that in ordinary open channel. With the enhanced hydrodynamic factors, the Suspended Solids Concentration (SSC) in water increases accordingly, and the incipient velocity of sediment resuspension is about 0.21 m/s. Based on the analysis of wind speed and average SSC in water column, the quantitative relationship is obtained. The SSC of the bottom layer is higher than the content of surface layer under different hydrodynamic conditions, and there are similar distributions between SSC and flow velocity in different water layers. 相似文献