Non-probabilistic reliability method and reliability-based optimal LQR design for vibration control of structures with uncertain-but-bounded parameters

Uncertainty is inherent and unavoidable in almost all engineering systems. It is of essential significance to deal with uncertainties by means of reliability approach and to achieve a reasonable balance between reliability against uncertainties and system performance in the control design of uncertain systems. Nevertheless, reliability methods which can be used directly for analysis and synthesis of active control of structures in the presence of uncertainties remain to be developed, especially in non-probabilistic uncertainty situations. In the present paper, the issue of vibration con- trol of uncertain structures using linear quadratic regulator （LQR） approach is studied from the viewpoint of reliabil- ity. An efficient non-probabilistic robust reliability method for LQR-based static output feedback robust control of un- certain structures is presented by treating bounded uncertain parameters as interval variables. The optimal vibration con- troller design for uncertain structures is carried out by solv- ing a robust reliability-based optimization problem with the objective to minimize the quadratic performance index. The controller obtained may possess optimum performance un- der the condition that the controlled structure is robustly re- liable with respect to admissible uncertainties. The proposed method provides an essential basis for achieving a balance between robustness and performance in controller design ot uncertain structures. The presented formulations are in the framework of linear matrix inequality and can be carried out conveniently. Two numerical examples are provided to illustrate the effectiveness and feasibility of the present method.

Shareholder Structure and Discretionary Regulation of Accounting Results in Enterprises: The Case of Cameroon

Debates on shareholder structure and discretionary management of accounting results have carried forward controversial results. This study is intended to analyze within the Cameroonian context the impact of shareholder structure on the management of accounting results in enterprises. More specifically, its objective is to analyze the impact of shareholder structure on the adjustment of regulating discretionary accounting variables. A panel of enterprises is constituted over the periods 2013, 2014, and 2015 in Cameroon. The modeling of regulating discretionary accounting variables has been carried out according to the model of Jones (1991). The different results obtained show that the degree of concentration of the capital seems not to dissuade the management of result per long-term positions. Foreign ownership and state property stimulate management by regulating discretionary accounting variables.

Attitude Control of Multiple Rigid Bodies with Uncertainties and Disturbances

Decentralized attitude synchronization and tracking control for multiple rigid bodies are investigated in this paper. In the presence of inertia uncertainties and environmental disturbances, we propose a class of decentralized adaptive sliding mode control laws. An adaptive control strategy is adopted to reject the uncertainties and disturbances. Using the Lyapunov approach and graph theory, it is shown that the control laws can guarantee a group of rigid bodies to track the desired time-varying attitude and angular velocity while maintaining attitude synchronization with other rigid bodies in the formation. Simulation examples are provided to illustrate the feasibility and advantage of the control algorithm. © 2014 Chinese Association of Automation.

Study of Comparative Saturated Sliding Mode Control and LQR Controller

The saturation problem is the one of the most common handicaps for applying to real applications, especially the actuator saturation. This paper focuses on the robustness of the sliding mode control （SMC） which incorporates a saturation constraint technique compared to classical linear quadratic regulator （LQR） with saturation. In the first step, the authors present a design methodology of SMC of a class of linear saturated systems. The authors present the structure of the saturation, after that the synthesis of the sliding surface is formulate as a problem of root clustering, which leads to the development of a continuous and non-linear control law that ensures the reaching condition of the sliding mode. The second step is devoted to present briefly the LQR controller technique. Finally, to validate results, the authors demonstrate an example of a quarter of vehicle system.

Research progress of Ag_3PO_4-based photocatalyst: Fundamentals and performance enhancement

Ag3PO4 is found to be a highly efficient photocatalyst and receives great attention. The high activity of the photocatalyst is credited to the intrinsic electronic structure. The morphology control and nano-composite fabrication are used to improve the performance and practicability. This paper reviews the structure, properties and some theoretical aspects of Ag3PO4 single crystal. Also, the major strategies, namely the morphology control and hetero-nanostructure construction, as ways to improve the performance of Ag3PO4-based photocatalysts, are summarized with the aid of some typical instances.

Lithostructural controls in Douala-Buea Region landscape (SW Cameroon margin):Insights from morphometric analysis

The Douala-Buea Region(DBR;4°-5°N,9°-10°30’E),a portion of the southern Cameroon passive margin,developed on the Proterozoic granito-gneissic basement and the Cretaceous to Recent volcanosedimentary cover,was explored in order to evaluate the lithology and tectonics controls on its landscape usingthequalitativeandquantitative geomorphological analyses based on 30 m resolution Digital Elevation Models(DEM)and field evidences.This area displays an uneven and complex landscape differentiated into four morphological units:Douala,Nkondjock,Kumba and Buea Units.The Douala Unit corresponds to the Coastal Plain and is extended on the Douala-Kribi/Camposedimentarybasin.The Nkondjock Unit represents a middle plateau developed on a Proterozoic granito-gneissic basement.The Kumba Unit matches with the southernmost volcanic Western Cameroon High Plateau.The Buea Unit corresponds to the Mount Cameroon stratovolcano.The relief analysis through mountain-front sinuosity(Smf,1.19–1.43)and relative relief ratio(Rr,0.10–2.31)vary from one unit to another.The drainage network analysis including drainage patterns,stepped longitudinalriverprofiles,theassociated morphometric indexes,notably the concavity index(IC,0.56–0.88),deviation(D,267–2912 m),basin asymmetry factor(A_(F),6.37–42.12),hypsometric integral(HI,0.10–0.29),valley floor width to valley height ratio(V_(f),0.36–2.75),elongation ratio(R_(e),0.30–0.50),watershed slope(S,6.88–88.88)and stream length gradient index(SL,0–3332)vary from one basin to another too.These results also show the heterogeneous and uneven DBR landscape controlled by its lithology and active tectonics.The drainage system reveals concave to concavo-convex longitudinal river profile shapes with knick points,asymmetric basins,and fault reactivations,and highlights the tectonics activity that used to occur through the time and their control on the morphology.Together,they document the lithostructural controls on the DBR landscape evolution,extendable in the whole SW Cameroon margin.

MOFs衍生物在尿素氧化中的研究进展

尿素氧化反应(UOR)在缓解现代氢能源制备和废水处理等压力中起着关键作用,引入性能优异的电催化剂有助于降低电化学能耗。金属-有机骨架(MOFs)衍生物因能克服MOFs原有导电性及稳定性差的固有缺陷备受关注,被认为是一种很有前途的电催化剂。本文回顾和总结了基于MOFs衍生物的设计和构建的相关研究:(i)基于镍基/非镍基的UOR的机理分析;(ii)概括了利用结构调控、形貌控制、界面工程和缺陷工程的手段提高电子电导率的策略,同时概括了材料物理特性改变与催化活性的相关性;(iii) MOFs衍生物基于UOR的应用研究。最后,对UOR的后期研究挑战和发展提出了合理的建议。

Structural Analysis of Thermally-Annealed Bulk Heterojunction Films Based on Sexithiophene and Fullerene

Recently, power conversion efficiencies of organic photovoltaics based on small molecules have been dramatically improved by means of the bulk heterojunction (BHJ) structure. Moreover, to optimize photovoltaic performance, thermal annealing treatments have often been used because of the simplicity of the process. However, the elucidation of effects of thermal annealing treatment on BHJ film structure based on small molecules is still not enough. Here, we report the results of structural analysis with synchrotron radiation of α-sexithiophene:fullerene BHJ films before and after thermal annealing treatment. In particular, the open-circuit voltage was increased to as high as 0.72 V;moreover, the BHJ films based on α-sexithiophene and fullerene were also clearly crystallized by the thermal annealing treatment. In this study, we found that the optimal crystal size existed in BHJ films for high-performance organic photovoltaics.

Dof转录因子研究进展

Dof(DNA Binding with one finger)转录因子是植物特有的一类转录因子,在植物生长发育过程中扮演重要作用,如种子萌发、光响应、贮藏蛋白积累、生物胁迫、碳氮代谢等。介绍了Dof转录因子的结构,并综述了其对植物的调控作用,以期为Dof转录因子的进一步研究提供理论依据。

Rational design and structural regulation of near-infrared silver chalcogenide quantum dots

Silver chalcogenides(Ag_(2)E;E=S,Se,or Te)quantum dots(QDs)have emerged as promising candidates for near-infrared(NIR)applications.However,their narrow bandgap and small exciton Bohr radius render the optical properties of Ag_(2)E QDs highly sensitive to surface and size variations.Moreover,the propensity for the formation of silver impurities and their low solubility product constants pose challenges in their controllable synthesis.Recent advancements have deepened our understanding of the relationship between the multi-hierarchical structure of Ag_(2)E QDs and their optical properties.Through rational design and precise structural regulation,the performance of Ag_(2)E QDs has been significantly enhanced across various applications.This review provides a comprehensive overview of historical and current progress in the synthesis and structural regulation of Ag_(2)E QDs,encompassing aspects such as size control,crystal structure engineering,and surface/interface engineering.Additionally,it discusses outstanding challenges and potential opportunities in this field.The aim of this review is to promote the custom synthesis of Ag_(2)E QDs for applications in biological imaging,and optoelectronics applications.

Morphology and strain control of hierarchical cobalt oxide nanowire electrocatalysts via solvent effect

Designing highly efficient and low-cost electrocatalysts for oxygen evolution reaction is important for many renewable energy applications.In particular,strain engineering has been demonstrated as a powerful strategy to enhance the electrochemical performance of catalysts;however,the required complex catalyst preparation process restricts the implementation of strain engineering.Herein,we report a simple self-template method to prepare hierarchical porous Co_(3)O_(4)nanowires(PNWs)with tunable compressive strain via thermal-oxidation-transformation of easily prepared oxalic acid-cobalt nitrate(Co(NO_(3))_(2))composite nanowires.Based on the complementary theoretical and experimental studies,the selection of proper solvents in the catalyst preparation is not only vital for the hierarchical structural evolution of Co_(3)O_(4) but also for regulating their compressive surface strain.Because of the rich surface active sites and optimized electronic Co d band centers,the PNWs exhibit the excellent activity and stability for oxygen evolution reaction,delivering a low overpotential of 319 mV at 10 mA·cm^(−2)in 1 M KOH with a mass loading 0.553 mg·cm^(−2),which is even better than the noble metal catalyst of RuO_(2).This work provides a cost-effective example of porous Co_(3)O_(4)nanowire preparation as well as a promising method for modification of surface strain for the enhanced electrochemical performance.

风速可调的地空一体化风力灭火遥控机结构设计与性能分析

风力灭火遥控机作为地面灭火装备的一种创新形式,具备机动性强、远程操作、快速响应等特点,能够在复杂的火情环境中灵活作业,大大提高了灭火效率和安全性。为探讨风力灭火遥控机在应对森林和草原地表火灾地空一体化监测系统中的角色与作用,对风力灭火遥控机进行结构设计,分析旋转开合结构的安装位置和开口大小对出口风速的影响。利用Fluent软件对风力灭火筒进行流体仿真,结合Design Expert软件对仿真数据进行处理,建立了位置S和开口大小d对出口平均风速和出口最大风速的响应曲面和二次模型。结果表明,安装位置和开口大小均为出口风速的重要影响因素,当风筒入口风速设定为70 m/s、旋转开合结构开口大小为30 mm且安装在位置5处时,出口平均风速和出口最大风速达到最大,分别为97.7551 m/s和290.001 m/s。相较于开口大小,安装位置对出口平均风速和出口最大风速的影响更大,且安装位置越靠近风筒出口处风力灭火机的灭火性能越好。

非串级结构下的双三相永磁同步电机调速控制和电流谐波抑制研究

该文针对多源时变干扰影响的双三相永磁同步电机系统,研究其基波平面内的调速控制问题和谐波平面内的谐波电流抑制问题。首先,在基波平面采用非串级控制结构,通过构造广义比例积分观测器(generalized proportional integral observer,GPIO)估计转速环的多源快变干扰;然后,针对q轴电流的过流保护问题,在传统比例微分反馈控制器的基础上利用障碍函数设计思想,结合干扰估计信息,得到基于GPIO的电流约束复合控制器;其次,在谐波平面,通过设计2个GPIO精准估计电流环的多源快变干扰,并与比例反馈控制器结合形成复合控制器来抑制2个电流环中的谐波电流。最后,给出严谨的稳定性分析,并通过对比实验验证所提方法的有效性。

碱性生物炭强化脱氮效能及定向调控机制

生物脱氮是污水处理厂氮污染物去除的主流方法,具有低碳、低成本的优势。面向城市污水为代表的低碳氮比废水,如何强化反硝化功能菌群、稳定生物脱氮效能仍有待研究。该研究以玉米秸秆为原料,通过酸、碱改性制备2种强化脱氮功能生物炭载体,构建强化反硝化脱氮工艺。研究结果表明:与未投加生物炭的系统相比,投加生物炭后系统总氮去除率提高了7.29%~29.51%。经过酸、碱改性生物炭定向强化脱氮效能分析,较未改性生物炭系统总氮去除率分别提高19.37%和29.55%,其中碱改性生物炭系统总氮去除率最高可达59.76%。在电子转移活性和亚硝酸盐还原酶活性方面,碱改性生物炭强化系统较未投加生物炭系统分别提高了91.8%和47.1%。高通量测序结果表明碱改性生物炭中参与反硝化作用相关菌群占比约为67.3%,具有反硝作用的芽孢杆菌属(Bacillus)、陶厄氏菌属(Thauera)为碱改性生物炭系统的优势菌属,碱改性生物炭比酸改性生物炭更能促进脱氮菌群的生长,从而构建反硝化脱氮能力定向调控。

多元醇液相还原法制备银纳米线的研究

银纳米线(AgNWs)因具有高导电性、高透光性及良好的耐弯曲柔性,已成为传统氧化铟锡(ITO)透明导电材料的替代品。采用液相多元醇还原法制备了不同规格的银纳米线,并通过SEM、UV-Vis、XRD等测试手段对制备的银纳米线进行了表征。结果表明,不同的制备参数可以获得颗粒状、短棒状、线状等不同形态的银产物。反应温度160℃,反应体系中聚乙烯吡咯烷(PVP)与AgNO_(3)的摩尔比为2∶1,FeCl_(3)的浓度保持在0.1~0.2mmol/L之间时,可以制备得到长度约30μm、直径约50nm的高纯度银纳米线。

基于结构调控的Pt基氧还原催化剂的研究进展

贵金属Pt基催化剂作为氧还原反应(ORR)中重要的催化剂之一,因储量有限且价格昂贵,限制了其规模化应用。如何提高Pt的利用率是目前开发高性能氧还原催化剂的关键。特别是,对催化剂进行结构调控(形貌、晶相、晶面、电子结构),可以有效提升Pt原子利用率及其本征活性,但由于表面效应和小尺寸效应使Pt纳米粒子具有较高的表面能和化学活性,导致它在化学反应中不稳定,影响催化剂的寿命。因此,开发具有高本征活性、高暴露活性晶面且结构稳定的Pt基催化剂依然是质子交换膜燃料电池领域的一个重大挑战。针对近年来该领域催化剂的研究进展进行综述。重点讨论通过调控Pt基纳米催化剂的形貌、晶相、晶面和电子结构等结构要素,提高Pt基纳米催化剂氧还原性能的设计理念与制备技术。最后简要总结Pt基纳米催化剂面临的挑战和研究重点。

金属波纹管开裂失效分析与防控策略研究

金属波纹管开裂失效是化工流程生产安全重点关注的技术问题。为了提高金属波纹管的安全稳定性,在对金属波纹管开裂失效的主要原因进行综合分析的基础上,以三氯氢硅储罐出料管线金属波纹管开裂失效为例,重点从断口宏观形貌分析、金相组织分析等方面入手,对该金属波纹管开裂失效的行为和原因进行了深入研究,结合现场生产实际运行数据,对金属波纹管开裂失效提出了有意义的防控策略。这有助于及时预防金属波纹管开裂失效事故,对确保设备长周期安全稳定运行具有重要指导意义。

全功率型风电机组调频控制器的实用化辨识方法

建立和实际调频响应特性一致的风电机组模型,是分析高比例新能源电力系统频率安全稳定的前提和基础。目前,针对风电机组涉频仿真建模的研究较少,多在调频控制器结构已知的前提下采用智能算法进行控制参数的辨识,缺乏通用性与工程实用性。首先,文中建立了能够涵盖国内主流型号全功率型风电机组的通用电磁暂态模型,并在此基础上,针对风电机组的可行调频控制策略,构建了包括超速减载控制、桨距角控制、虚拟惯量控制和下垂控制的全要素综合调频控制系统。然后,基于机组调频响应特性与调频控制策略/参数的对应关系,提出了采用机组实测频率响应特性曲线形态辨识调频控制器结构、采用机组实测频率响应特性曲线特征值辨识调频控制器参数的实用化辨识方法。最后,通过所提实用化调频控制器辨识方法建立的机组电磁暂态模型与厂家“黑盒”模型及现场试验的调频响应特性的对比,验证了所提调频控制器辨识方法的有效性。

Morphology design of microporous organic polymers and their potential applications:an overview

Microporous organic polymers(MOPs) have attracted considerable research interest because of their well-defined porosity,high surface area, lightweight nature, and tunable surface chemistry. The morphology of MOPs are demonstrated to play a significant role in various applications although limited examples manifesting the importance of the MOP morphology in numerous applications have been reported. This review summarizes the recent progress in the design of MOPs using different techniques, including hard and soft template and direct synthesis methods. In addition, their applications, which possibly attribute to their shape, are discussed. Furthermore, the advantages and disadvantages of different methods are discussed, as well as their development and future challenges.

海南石碌铁矿矿体分布和形态特征的构造控制规律

石碌复向斜是石碌铁矿的主控构造,既有弯滑弯流褶皱(顺层剪切作用形成)的特征,也有中和面褶皱的特征。本文通过总结石碌矿区铁矿体的分布和形态发现:铁矿体主要分布区位于次级褶皱的翼部,相当于弯滑弯流褶皱的剪切应变区(简单剪切应变);次要分布区为次级褶皱的核部,相当于中和面褶皱的挤压区(纯剪应变);铁矿体,特别是富铁矿体在纵弯褶皱翼部多为扁长透镜体状、似层状,与顺层剪切作用中应变透镜体形态接近;在核部则多为粗短透镜状或不规则团块状,也与中和面褶皱作用中挤压应变透镜体形态接近。石碌复式向斜不仅改造、控制了铁矿体的形态和分布,还与富铁矿体的富集和形成密切相关。石碌矿区铁矿体的分布和形态特征反映了纵弯褶皱的控矿规律,是纵弯褶皱成矿作用的宏观反映,也是纵弯褶皱成矿的一个宏观证据。