Wind turbine response to parameter variation of analytic inflow vortices

As larger wind turbines are placed on taller towers, rotors frequently operate in atmospheric conditions that support organized, coherent turbulent structures. It is hypothesized that these structures have a detrimental impact on the blade fatigue life experienced by the wind turbine. These structures are extremely difficult to identify with sophisticated anemometry such as ultrasonic anemometers. This study was performed to identify the vortex characteristics that contribute to high‐amplitude cyclic blade loads, assuming that these vortices exist under certain atmospheric conditions. This study does not attempt to demonstrate the existence of these coherent turbulent structures. In order to ascertain the idealized worst‐case scenario for vortical inflow structures impinging on a wind turbine rotor, we created a simple, analytic vortex model. The Rankine vortex model assumes that the vortex core undergoes solid body rotation to avoid a singularity at the vortex centre and is surrounded by a two‐dimensional potential flow field. Using the wind turbine as a sensor and the FAST wind turbine dynamics code with limited degrees of freedom, we determined the aerodynamic loads imparted to the wind turbine by the vortex structure. We varied the size, strength, rotational direction, plane of rotation, and location of the vortex over a wide range of operating parameters. We identified the vortex conformation with the most significant effect on the blade root bending moment cyclic amplitude. Vortices with radii on the scale of the rotor diameter or smaller caused blade root bending moment cyclic amplitudes that contribute to high damage density. The rotational orientation, clockwise or counter‐clockwise, produces little difference in the bending moment response. Vortices in the XZ plane produce bending moment amplitudes significantly greater than vortices in the YZ plane. Published in 2005 by John Wiley & Sons, Ltd.     

格栅式水泥搅拌桩支护在西涌泵站的应用

简介水泥搅拌桩的支护机理,以西涌泵站为例介绍采用格栅式水泥搅拌桩作支护结构的设计及计算方法,指出该技术能较好地解决软湿粘性土地区枢纽深基础开挖问题.     

考虑渗流力的基坑涌砂分析

本文根据基坑防渗帷幕周围的地下水渗流特征，分析了渗流力对基坑流砂的影响，提出了按涌砂安全系数进行防渗帷幕埋入深度计算的方法。     

皮革加油原理及注意事项

本文从乳液出发，阐述乳液形成，稳定，破乳以及皮革加油过程。要求使用最少的油剂达到最佳的目的。     

Structural and surface properties of thermally prepared Ti/RhxTi(1−x)Oy electrodes: I—influence of preparation parameters

Electrodes of Rh_xTi_(1−x)O_y nominal composition were prepared by thermal decomposition of the chloride or nitrate precursor salts dissolved in strongly acidic medium and applied by brush to both sides of a Ti° support. A systematic study of the influence of calcination temperature and time as well as oxygen flux was conducted. The coatings were characterised by SEM, EDAX, XRD, open circuit potential measurements and cyclic voltammetry (CV). Visible-ultraviolet spectrophotometry was employed to identify the chemical form of the precursor in solution while thermogravimetric analysis (TGA) was used to assess the decomposition temperature ranges. Optimisation of the coating preparation parameters showed coatings obtained from [Rh(H₂O)₆](NO₃)₃ precursor dissolved in HNO₃ 1:2 (v/v) and fired at 430 °C for 2 h in a 5 l min⁻¹ oxygen stream-furnished stable electrodes having the highest electrochemically active surface area.     

SYMMETRIC STABLE SEQUENCES WITH MISSING OBSERVATIONS

Abstract. A procedure for evaluating optimal linear estimates of missing values in the minimum dispersion sense is proposed for stationary symmetric stable processes. Analytical expressions for the estimates are obtained for the autoregressive moving-average process and it is shown that the finite variance setting results are special cases. Cases of one and more than one missing value are considered.     

ON THE CALCULATION OF FLOW OVER AND THROUGH A ROCK-FILL DAM

1.INTRODUCTIONInthedesignofanovertoppedrock--filldam,oneofthemajortasksistodecidethesizeofthedownstreamprotection.Theovertoppedrock--filldamismadeofporousmedia,thereforethewaterwillpenetrateintothedamfromtheupperfaceandemergeoutofitfromthelowerpart,whileitflowsoverthedam.Hence,theprotectionissubjectedtotheactionofboththeoverflowandtheseepageflow,andneitherofthemcanbenegligible.Inthiscase,theflowfieldconsistsoftwoparts:theopenflowandtheseepageflow,whichhavedifferentproperties.Infact,forthe…     

具有时变状态滞后2-D离散系统的稳定与镇定(英文)

针对一类由局部状态空间(LSS)Fornasini-Marchesini(FM)第二模型描述的,具有时变状态滞后的2-D离散系统,其中时变滞后项的上、下界均为正实数,研究了其稳定性和控制综合问题。首先,利用Lyapunov-Krasovski泛函方法,提出了系统的稳定性准则。再根据这一准则,分别设计状态反馈和动态输出反馈控制器保证系统的稳定性。状态反馈控制律和输出反馈矩阵可由线性矩阵不等式(LMI)求得。最后,通过数值算例说明所得结果的有效性。     

Globally asymptotic stabilization for nonlinear time-delay systems with ISS inverse dynamics

The output feedback stabilization is considered for a class of nonlinear time-delay systems with inverse dynamics in this paper.An appropriate state observer is constructed for the unmeasurable system states in order to realize the control objective.By adopting the backstepping and Lyapunov-Krasovskii functional methods,a systematic design procedure for a memoryless output feedback control law is presented.It is shown that the designed controller can make the closed-loop system globally asymptotically stable while keeping all signals bounded.An illustrative example is discussed to show the effectiveness of the proposed control strategy.     

The properties of electroactive ruthenium oxide coatings supported by titanium-based ternary carbides

Electroactive oxide coatings on titanium, known in industrial chlorine production as dimensionally stable anodes (DSA), are of limited service life owing to the dissolution of active oxide, but also due to low corrosion stability of titanium, at high anodic potentials and elevated temperatures. In order to improve the anode stability, ternary carbide, Ti₃SiC₂, could be a promising material for the coating support, since chemical corrosion stability of Ti₃SiC₂ is significantly higher if compared to Ti. In this work, the possibility of the sol-gel preparation of RuO₂-TiO₂ coating on Ti₃SiC₂ is investigated and comparison of the basic characteristics of sol-gel processed oxide coating, Ru_0.5Ti_0.5O₂, applied onto Ti₃SiC₂ and Ti, is reported. Microscopic investigation of the coating surface showed that considerably less cracked coating is formed onto the Ti₃SiC₂ support. Slightly higher voltammetric currents are registered for Ti₃SiC₂-supported coating in H₂SO₄ and NaCl solution. The activity for chlorine evolution is higher, while the currents of oxygen evolution reaction are lower for Ru_0.5Ti_0.5O₂/Ti₃SiC₂ anode in comparison to Ru_0.5Ti_0.5O₂/Ti anode. Even though these preliminary results on the basic electrochemical properties of Ru_0.5Ti_0.5O₂/Ti₃SiC₂ anode and chemical stability of Ti₃SiC₂ are promising, the accelerated stability test in NaCl solution showed that coated Ti₃SiC₂ is not anodically stable and lasts considerably shorter than Ru_0.5Ti_0.5O₂/Ti anode prepared and tested under the same conditions.