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Optimal control strategies for stochastically excited quasi partially integrable Hamiltonian systems

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Acta Mechanica Sinica 2007年第3期23卷 311-319页

作者： Ronghua Huan Maolin deng Weiqiu Zhu Department of Mechanics State Key Laboratory of Fluid Power Transmission and Control Zhejiang UniversityHangzhou 310027 China

In this paper two different control strategies designed to alleviate the response of quasi partially integrable Hamiltonian systems subjected to stochastic excitation are proposed. First, by using the stochastic averaging method for quasi partially integrable Hamiltonian systems, an n-DOF controlled quasi partially integrable Hamiltonian system with stochastic excitation is converted into a set of partially averaged It^↑o stochastic differential equations. Then, the dynamical programming equation associated with the partially averaged It^↑o equations is formulated by applying the stochastic dynamical programming principle. In the first control strategy, the optimal control law is derived from the dynamical programming equation and the control constraints without solving the dynamical programming equation. In the second control strategy, the optimal control law is obtained by solving the dynamical programming equation. Finally, both the responses of controlled and uncontrolled systems are predicted through solving the Fokker-Plank-Kolmogorov equation associated with fully averaged It^↑o equations. An example is worked out to illustrate the application and effectiveness of the two proposed control strategies.

关键词： Nonlinear system Stochastic excitation Stochastic averaging Optimal control Dynamical programming

Bromate ion formation in dark chlorination and ultraviolet/chlorination processes for bromide-containing water

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Journal of Environmental Sciences 2008年第2期20卷 246-251页

作者： HUANG Xin GAO Naiyun deng Yang State Key Laboratory of Pollution Control and Resource Reuse Tongji University Shanghai 200092 China Department of Construction Management and Civil Engineering Technology Georgia Southern University R O. Box 8047 Statesboro GA 30460-8047 USA

Bormate （BrO3^-） is a carcinogenic chemical produced in ozonation or chlorination of bromide-containing water. Although its formation in seawater with or without sunlight has been previously investigated, the formation of bromate in dilute solutions, particularly raw water for water treatment plant, is unknown. In this article, the results of bench scale tests to measure the formation rates of bromate formation in dilute solutions, including de-ionized water and raw water from Yangtze River, were presented in dark chlorination and ultraviolet （UV）/chlorination processes. And the effects of initial pH, initial concentration of NaOCl, and UV light intensity on bromate formation in UV/chlorination of the diluted solutions were investigated. Detectable bromate was formed in dark chlorination of the two water samples with a relatively slow production rate. Under routine disinfecting conditions, the amount of formed bromate is not likely to exceed the national standards （10 μg/L）. UV irradiation enhanced the decay of free chlorine, and, simultaneously, 6.6%-32% of Br^- was oxidized to BrO3^-. And the formation of bromate exhibited three stages： rapid stage, slow stage and plateau. Under the experimental conditions （pH = 4.41-11.07, CCl2= 1.23-4.50 mg/L）, low pH and high chlorine concentration favored the generation of bromate. High light intensity promoted the production rate of bromate, but decreased its total generation amount due to acceleration of chlorine decomposition.

关键词： bromate chlorination raw water Yangtze River ultraviolet (UV) irradiation

超高性能混凝土断裂全过程声发射分形特征及损伤机理

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长安大学学报（自然科学版） 2024年第3期44卷 93-103页

作者：袁明邓俊杰刘昀颜东煌黄练韩怀志长沙理工大学土木工程学院湖南长沙410114 广西交投科技有限公司广西南宁531400 湖南交通职业技术学院路桥工程学院湖南长沙410132 广西民族大学建筑工程学院广西南宁530006

为研究超高性能混凝土(UHPC)轴拉破坏全过程的声发射(AE)机理和分形特征,首先,开展了不同钢纤维(端钩形、微波纹形和直圆形)增强的UHPC轴拉试件破坏试验,得到UHPC轴拉破坏过程中的声发射信号;其次,利用快速傅里叶变换计算信号的主频,分... 详细信息

为研究超高性能混凝土(UHPC)轴拉破坏全过程的声发射(AE)机理和分形特征,首先,开展了不同钢纤维(端钩形、微波纹形和直圆形)增强的UHPC轴拉试件破坏试验,得到UHPC轴拉破坏过程中的声发射信号;其次,利用快速傅里叶变换计算信号的主频,分析主频在试验过程中的分布特征;然后,基于分形理论利用分形盒维度计算方法对信号进行分形分析,并探究分形盒维度与主频之间的关联性;最后,利用小波包变换方法计算破坏过程中的平均频带能量,分析不同应力状态下各频带能量的演变规律。试验结果表明:变形纤维的端钩和波纹与基体滑移过程产生较高的主频信号,而直圆纤维与基体滑移过程产生较低的主频信号;试件破坏阶段主频段信号分布增多,但依然以基体微裂和钢纤维相对滑移为主;分形盒维度在试件开裂前分布较集中,且在即将破坏时分形盒维度增大,开裂后变分散,新生微裂纹产生的信号分形盒维度与开裂前类似,宏观裂纹扩展产生的信号分形盒维度降低;平均分形盒维度随主频的增大而增大,呈近似二阶多项式变化,主频越高的信号复杂程度越高;AE信号能量集中于1~4频段,不同纤维增强试件的主要能量在频段上的分布不同,但在即将破坏时所有试件能量均由低频向高频转变。说明声发射信号具有良好的分形特征,且能很好地反映UHPC轴拉破坏过程中的损伤特性。

关键词：桥梁工程超高性能混凝土声发射裂缝扩展信号分类波形分形频谱特征

基于BERT-LSTM模型的WebShell文件检测研究

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网络安全与数据治理 2024年第4期43卷 24-27页

作者：邓全才徐怀彬河北建筑工程学院信息工程学院河北张家口075000

针对基于传统规则的WebShell文件检测难度大,采用文本分类的思想,设计了一种基于BERT-LSTM模型的WebShell检测方法。首先,对现有公开的正常PHP文件和恶意PHP文件进行清洗编译,得到指令opcode码;然后,通过变换器的双向编码器表示技术(BE... 详细信息

针对基于传统规则的WebShell文件检测难度大,采用文本分类的思想,设计了一种基于BERT-LSTM模型的WebShell检测方法。首先,对现有公开的正常PHP文件和恶意PHP文件进行清洗编译,得到指令opcode码;然后,通过变换器的双向编码器表示技术(BERT)将操作码转换为特征向量;最后结合长短期记忆网络(LSTM)从文本序列角度检测特征建立分类模型。实验结果表明,该检测模型的准确率为98.95%,召回率为99.45%,F1值为99.09%,相比于其他模型检测效果更好。

关键词： BERT LSTM WebShell PyTorch

Nanocarbons and their hybrids as catalysts for non-aqueous lithium–oxygen batteries

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Journal of Energy Chemistry 2016年第6期25卷 957-966页

作者： Yunchuan Tu Dehui deng Xinhe Bao State Key Laboratory of Catalysis iChEM Dalian Institute of Chemical Physics Chinese Academy of Sciences Collaborative Innovation Center of Chemistry for Energy Materials College of Chemistry and Chemical Engineering Xiamen University University of Chinese Academy of Sciences

Rechargeable lithium-oxygen (Li–O2) batteries have been considered as the most promising candidates for energy storage and conversion devices because of their ultra high energy density. Until now, the critical scientific challenges facing Li–O2batteries are the absence of advanced electrode architectures and highly efficient electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which seriously hinder the commercialization of this technology. In the last few years, a number of strategies have been devoted to exploring new catalysts with novel structures to enhance the battery performance. Among various of oxygen electrode catalysts, carbon-based materials have triggered tremendous attention as suitable cathode catalysts for Li–O2batteries due to the reasonable structures and the balance of catalytic activity, durability and cost. In this review, we summarize the recent advances and basic understandings related to the carbon-based oxygen electrode catalytic materials, including nanostructured carbon materials (one-dimensional (1D) carbon nanotubes and carbon nanofibers, 2D graphene nanosheets, 3D hierarchical architectures and their doped structures), and metal/metal oxide-nanocarbon hybrid materials (nanocarbon supporting metal/metal oxide and nanocarbon encapsulating metal/metal oxide). Finally, several key points and research directions of the future design for highly efficient catalysts for practical Li–O2batteries are proposed based on the fundamental understandings and achievements of this battery field. © 2016 Science Press

关键词： Carbon nanofibers Catalyst activity Catalysts Electric batteries Electrocatalysis Electrocatalysts Electrodes Electrolytic reduction Lithium Lithium batteries Oxygen Secondary batteries Yarn

园林绿化废弃物有机肥养分释放特征及对油松生长的影响

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植物营养与肥料学报 2024年第6期30卷 1173-1184页

作者：杨海婷祁文俊高超前于凌霄彭祚登北京林业大学北京100083 中国计量科学研究院北京100029 北京市大兴区林业工作站北京102600

【目的】研究园林绿化废弃物有机肥(LWOF)养分释放特征和施用后对油松(Pinus tabulaeformis)生长的影响,为合理利用园林废弃物资源提供科学依据。【方法】养分释放特征研究采用尼龙网袋法,将50 g干LWOF装入孔径8.47μm的尼龙袋中,分别... 详细信息

【目的】研究园林绿化废弃物有机肥(LWOF)养分释放特征和施用后对油松(Pinus tabulaeformis)生长的影响,为合理利用园林废弃物资源提供科学依据。【方法】养分释放特征研究采用尼龙网袋法,将50 g干LWOF装入孔径8.47μm的尼龙袋中,分别埋置在0—20和20—40 cm两个土层。之后每隔1.5个月取1次样,共取4次,测定袋内LWOF以及含有的有机质和氮磷钾残留量,计算残留率。施用效果田间试验在北京平原沙地进行,供试材料为2015年营建的油松林。试验设6个LWOF施用水平处理:0、10、15、20、25、30 kg/株,依次记为CK、T1、T2、T3、T4和T5。测定试验开始时和一年后土壤理化性质,以及油松生长指标。【结果】1)LWOF干物质和有机质残留率随时间推移逐渐下降,埋置在20—40 cm土层的LWOF分解速率快于0—20 cm土层,0—20、20—40 cm土层6个月分解后的残留率有机质分别为52.46%和48.72%,氮分别为58.73%和56.93%;埋置1.5个月时0—20、20—40 cm土层的磷素残留率分别为52.23%和52.15%,之后呈现波动,没有明显下降趋势;钾素残留率在埋置1.5个月后0—20、20—40 cm土层仅分别为27.95%和28.54%,6个月后分别为22.73%和20.89%。2)施用LWOF一年后土壤有机质含量显著增加。与CK相比,T4处理0—20 cm土层土壤全氮含量升高41.81%,T4处理0—20 cm土层有效磷含量升高53.13%,T5处理20—40 cm土层速效钾含量是CK的1.63倍。3)T3处理的油松树高增长率,T1处理的油松材积增长率,T4和T5处理的油松叶片养分含量较CK均显著提高。叶绿素a、b及总叶绿素含量随施肥量的增加均呈“先上升后下降”的趋势,均在T4处理达到最大,最大值相比于CK分别增加了81.25%、85.71%和90.00%。综合油松生长和养分含量,不同处理对油松的促生效应表现为:T4>T5>T3>T1>T2>CK。【结论】园林废弃物有机肥在20—40 cm土层内的分解速率快于0—20 cm土层,其所含的氮素释放速率较为均匀,磷素释放在1.5个月内较快,氮、磷在6个月后的总释放率分别约为40%、50%,而钾素释放最为迅速,且6个月的释放率超过2/3。施用园林废弃物有机肥能改善土壤质量,提升土壤肥力。经综合评价,在环状施肥方式下以25 kg/株的施用量对油松生长的促进作用最为显著。

关键词：园林绿化废弃物有机肥土壤油松养分释放灰色关联综合评判值

Codimension 2 reversible heteroclinic bifurcations with inclination flips

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Science China Mathematics 2009年第7期52卷 1801-1814页

作者： XU YanCong ZHU DeMing deng GuiFeng Department of Mathematics Hangzhou Normal UniversityHangzhou(Xiasha)310036China Department of Mathematics East China Normal UniversityShanghai 200241China School of Mathematics and Information Shanghai Lixiu University of CommerceShanghai 201620China

In this paper, the heteroclinic bifurcation problem with real eigenvalues and two incli- nation-flips is investigated in a four-dimensional reversible system. We perform a detailed study of this case by using the method originally established in the papers "Problems in Homoclinic Bifurcation with Higher Dimensions" and "Bifurcation of Heteroclinic Loops," and obtain fruitful results, such as the existence and coexistence of R-symmetric homoclinic orbit and R-symmetric heteroclinic loops, R-symmetric homoclinic orbit and R-symmetric periodic orbit. The double R-symmetric homoclinic bifurcation (i.e., two-fold R-symmetric homoclinic bifurcation) for reversible heteroclinic loops is found, and the existence of infinitely many R-symmetric periodic orbits accumulating onto a homoclinic orbit is demonstrated. The relevant bifurcation surfaces and the existence regions are also located.

关键词： heteroclinic bifurcation inclination flips reversible system 37G40 37C29 34C37

Transient heat transfer analysis in packed beds: Entropy generation model and multi-objective optimization

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Science China(Technological Sciences) 2019年第11期62卷 1999-2008页

作者： MA XiaoTeng deng YuCheng CUI Zheng Institute of Thermal Science and Technology Shandong UniversityJinan 250061China School of Engineering Sciences KTH Royal Institute of TechnologyStockholm SE-10044Sweden

Due to the important role of the unsteady heat transfer process of packed beds in industrial production,the construction of the transient heat transfer model is of great significance for the operation and *** present study performs a transient thermal analysis of packed bed,in which the convective heat transfer and conductive thermal resistance within the particles are considered simultaneously.A mathematical model is established of the total entropy generations(0-t)contributed by viscous dissipation and heat transfer;the influence of particle diameter,air flow rate,and pressure drop,is then *** of the time cost,these results present some different trends from the steady-state ***,for a laboratory heat transfer system,with the aid of the genetic algorithm we adopt a multi-objective genetic algorithm model and modified expressions of the entropy generations are set as objective ***,optimal operational and structural parameters are obtained for different fan power *** the fan power is 300 W,the optimal particle diameter and inlet wind speed are 14 mm and 2.4 m/s,*** results also suggest that the time cost is reduced with increasing fan power consumption.

关键词： packed beds unsteady heat transfer process time cost entropy generation multi-objective genetic algorithm

Insulation Performance of CF3I-N2 Gas Mixtures as Alternative for SF6 in GIS/C-GIS

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高电压技术 2013年第9期39卷 2288-2293页

作者： deng Yunkun XIAO dengming CHEN Jiong Department of Electrical Engineering Shanghai Jiao Tong University Shanghai 200030 China School of Electric Power and Automation Engineering Shanghai University of Electric Power Shanghai 200090 China

CF3I has been widely considered as a potential alternative for SF6,because it has low global warming potential(GWP)but an insulation capability that is 1.2 times greater than that of *** this paper,the electron swarm parameters of CF3I and its gas mixture with N2,including the effective ionization coefficient and electron drift velocity,are examined theoretically through the Boltzmann equation method in the condition of steady-state Townsend(SST)*** on the derived data of the limiting field strength of CF3I-N2gas mixture,taking into consideration of environmental aspects such as GWP,ozone depletion potential(ODP),liquefaction temperature and toxicity,we studied the possibility of applying the gas mixture as the insulation medium in gas-insulated switchgears(GIS)or cubic type gas-insulated switchgears(C-GIS).It is found that CF3I-N2gas mixtures contained 30%～70%CF3I perform comprehensively better than pure SF6and compressed N2,and especially in medium and low voltage environments,the boiling point of CF3I-N2gas mixture meets the domestic and global requirements in mid-low latitude *** we conclude that the gas mixture is acceptable for replacing SF6as the insulation medium in C-GISs.

关键词： SF6气体 C-GIS 混合气体绝缘性能气体绝缘开关装置气体混合物玻尔兹曼方程地理信息系统