Fe–Mn/MCM-41: Preparation,Characterization,and Catalytic Activity for Methyl Orange in the Process of Heterogeneous Fenton Reaction     

Xubin Zhang  Jianxin Dong  Zhencheng Hao  Wangfeng Cai  Fumin Wang 《天津大学学报(英文版)》2018,(4)

Active Fe-and Mn-loaded MCM-41(Fe–Mn/MCM-41),which was synthesized via a hydrothermal reaction followed by impregnation,is used in the heterogeneous Fenton reaction to degrade methyl orange(MO) in aqueous solution. The synthesized samples were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,N_2 adsorption–desorption isotherm analysis,Fourier transform infrared spectroscopy,and X-ray photoelectron spectroscopy. Compared with Fe/MCM-41 and Mn/MCM-41,Fe–Mn/MCM-41 showed higher activity for MO degradation and mineralization. Effects of various operating parameters,such as pH,Mn content,and H_2O_2 dosage,on the degradation process were subsequently investigated. Results of experiments on the effect of radical scavengers revealed that the degradation of MO could be attributed to oxidation by HO_·. The synergy of Fe and Mn species in the Fenton oxidation process was also explained.  相似文献   

Centralized security-guaranteed filtering in multirate-sensor fusion under deception attacks     

Zidong Wang  Dong Wang  Bo Shen  Fuad E. Alsaadi 《Journal of The Franklin Institute》2018,355(1):406-420

In this paper, the centralized security-guaranteed filtering problem is studied for linear time-invariant stochastic systems with multirate-sensor fusion under deception attacks. The underlying system includes a number of sensor nodes with a centralized filter, where each sensor is allowed to be sampled at different rate. A new measurement output model is proposed to characterize both the multiple rates and the deception attacks. By exploiting the lifting technique, the multi-rate sensor system is cast into a single-rate discrete-time system. With a new concept of security level, the aim of this paper is to design a filter such that the filtering error dynamics achieves the prescribed level of the security under deception attacks. By using the stochastic analysis techniques, sufficient conditions are first derived such that the filtering error system is guaranteed to have the desired security level, and then the filter gain is parameterized by using the semi-definite programme method with certain nonlinear constraints. Finally, a numerical simulation example is provided to demonstrate the feasibility of the proposed filtering scheme.  相似文献   

Optimal residual generation for fault detection in linear discrete time-varying systems with uncertain observations     

Yueyang Li  Hamid Reza Karimi  Choon Ki Ahn  Yuan Xu  Dong Zhao 《Journal of The Franklin Institute》2018,355(7):3330-3353

This work deals with the problem of optimal residual generation for fault detection (FD) in linear discrete time-varying (LDTV) systems subject to uncertain observations. By introducing a generalized fault detection filter (FDF) with four parameter matrices as the residual generator, a novel FDF design scheme is formulated as two bi-objective optimization problems such that the sensitivity of residual to fault is enhanced and the robustness of residual to unknown input is simultaneously strengthened. A generalized operator based optimization approach is proposed to deduce solutions to the corresponding optimization problems in operator forms, where the related H_∞/H_∞ or $H_{?}/H_{\infty }$ FD performance index is maximized. With the aid of the addressed methods, the connections among the derived solutions are explicitly announced. The parameter matrices of the FDF are analytically derived via solving simple matrix equations recursively. It is revealed that our proposed results establish an operator-based framework of optimal residual generation for some kinds of linear discrete-time systems. Illustrative examples are given to show the applicability and effectiveness of the proposed methods.  相似文献   

Fractional-order follower observer design for tracking consensus in second-order leader multi-agent systems: Periodic sampled-based event-triggered control     

Aijuan Wang  Xiaofeng Liao  Tao Dong 《Journal of The Franklin Institute》2018,355(11):4618-4628

This paper investigates the tracking consensus problem for the second-order leader systems by designing fractional-order observer, where a periodic sampled-based data event-triggered control is employed. In order to track the position information of leader, observers for followers are designed by fractional-order system, where only the relative position information is available. Furthermore, in the process of observers design, a sampled-based event-triggered strategy is proposed so that observers use the event-triggered sampled-data, to reduce the overall load of the network. In our proposed event-triggered strategy, the event detection only works at every sampling time instant which determines whether the sampled-data should be discarded or used. Under this control strategy, the Zeno-behavior is absolutely excluded since the minimum of inter-event times is inherently lower bounded by one sampling period. It is found that the followers can track state of the leader if fractional-order observers are appropriately designed and relevant parameters are properly selected. By using the generalized Nyquist stability criterion, a necessary and sufficient condition for the observer tracking consensus of the second-order leader systems is derived. The results show that the real and imaginary parts of the eigenvalues of the augmented Laplacian matrix, and fractional-order α of observer play a vital role in reaching consensus.  相似文献   

Error-driven nonlinear feedback-based fuzzy adaptive output dynamic surface control for nonlinear systems with partially constrained tracking errors     

Shigen Gao  Hairong Dong  Bin Ning  Hongwei Wang 《Journal of The Franklin Institute》2018,355(13):5452-5474

In this paper, a novel error-driven nonlinear feedback technique is designed for partially constrained errors fuzzy adaptive observer-based dynamic surface control of a class of multiple-input-multiple-output nonlinear systems in the presence of uncertainties and interconnections. There is no requirements that the states are available for the controller design by constructing fuzzy adaptive observer, which can online identify the unmeasurable states using available output information only. By transforming partial tracking errors into new error variables, partially constrained tracking errors can be guaranteed to be confined in pre-specified performance regions. The feature of the error-driven nonlinear feedback technique is that the feedback gain self-adjusts with varying tracking errors, which prevents high-gain chattering with large errors and guarantees disturbance attenuation with small errors. Based on a new non-quadratic Lyapunov function, it is proved that the signals in the resulted closed-loop system are kept bounded. Simulation and comparative results are given to demonstrate the effectiveness of the proposed method.  相似文献   

Terminal iterative learning control for discrete-time nonlinear systems based on neural networks     

Jian Han  Dong Shen  Chiang-Ju Chien 《Journal of The Franklin Institute》2018,355(8):3641-3658

The terminal iterative learning control is designed for nonlinear systems based on neural networks. A terminal output tracking error model is obtained by using a system input and output algebraic function as well as the differential mean value theorem. The radial basis function neural network is utilized to construct the input for the system. The weights are updated by optimizing an objective function and an auxiliary error is introduced to compensate the approximation error from the neural network. Both time-invariant input case and time-varying input case are discussed in the note. Strict convergence analysis of proposed algorithm is proved by the Lyapunov like method. Simulations based on train station control problem and batch reactor are provided to demonstrate the effectiveness of the proposed algorithms.  相似文献   

A decentralized control method for frequency restoration and accurate reactive power sharing in islanded microgrids     

Zhanqiang Zhang  Chunxia Dou  Dong Yue  Bo Zhang  Wei Luo 《Journal of The Franklin Institute》2018,355(17):8874-8890

To achieve the frequency restoration (FR) and accurate reactive power sharing (RPS) in islanded microgrids (MGs), an improved P-f droop control is proposed. Firstly, the inverter impedance, whose value is set by the virtual impedance method, is used to minimize the impact of line resistance on powers coupling and RPS. Then, in order to restore the frequency of distributed generations (DGs) to the rated value, the reference is changed for compensating the frequency deviation (FD) caused by loads change. And the fast FR rate is achieved under a large constant k. Besides, in order to eliminate the inaccuracy of RPS caused by voltages difference (VD), the line voltage drop (LVD) is used to compensate the voltage droop characteristics. The use of voltage feedback ensures that the obtained voltage is desired after the LVD compensation. Finally, the simulation in RT-LAB indicates the effectiveness of proposed method in an islanded MG model.  相似文献   

Correction to: Do Teachers’ Instructional Practices Moderate Equity in Mathematical and Scientific Literacy?: An Investigation of the PISA 2012 and 2015     

Jihyun Hwang  Kyong Mi Choi  Yejun Bae  Dong Hoon Shin 《International Journal of Science and Mathematics Education》2018,16(8):1629-1631

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高中生职业生涯选择能力培养对策研究     

雷海燕  董文军 《当代教育论坛》2018,(3):101-106

新高考改革抓住了选择性和多样性两个核心概念,赋予了学生更多的自主选择权,给学生提供了一系列选科、选课、选考、选学校、选专业以及选未来职业等选择机会,是实现个人能力和加速自主发展的好契机.新高考改革要求培养高中生自主选择能力,包括对职业生涯选择能力培养也提出了更高的要求,这让很多普通高中学校和家长、学生在短期内都感到不适.在诸多选择面前,如何培养高中生选择能力越来越引发各界关注.只有以新高考制度推行为载体,通过分析新高考政策中的选择元素,培养高中生科学的职业生涯选择能力,才能有效帮助高中生选择最理想的职业.  相似文献   

创新研究群体典型项目的合作网络特征     

廖青云  朱东华  汪雪锋  黄颖  万冬 《科技管理研究》2018,(7):9-15

运用社会网络分析方法,对国家自然科学基金委员会(NSFC)设立的创新研究群体科学基金资助的10个典型创新研究群体,从结构特征、负责人影响力和演化特征三方面进行研究发现:创新研究群体合作网络在结构上具有高连通性,但群体紧密程度差异明显,合作网络的集权程度也存在较大差异,大多数群体负责人在群体中具有较大影响力,但也有少数影响力相对较弱;合作网络中子群的演化路径可以分为汇聚和分离两类。总体来说,在创新研究群体项目的支持下,群体的规模、合作紧密程度都得到了持续稳定的发展。NSFC的创新研究群体项目切实促进了创新研究群体的建设,资助绩效显著。  相似文献