检索结果-南通市图书馆

Journal of Advanced Ceramics 2022年第3期11卷 392-402页

作者： Chao feng xu ZHOU Bingjing TAO Haitao WU Shifeng huang Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials University of JinanJinan250022China School of Environmental and Material Engineering Yantai UniversityYantai264005China

Dense microwave dielectric ceramics of Ce_(2)[Zr_(1−x)(Al_(1/2)Ta_(1/2))_(x)]_(3)(MoO_(4))_(9)(CZMAT) (x = 0.02–0.10) were prepared by the conventional solid-state route. The effects of (Al1/2Ta1/2)^(4+) on their microstructures, sintering behaviors, and microwave dielectric properties were systematically investigated. On the basis of the X-ray diffraction (XRD) results, all the samples were matched well with Pr_(2)Zr_(3)(MoO_(4))_(9) structures, which belonged to the space group R3¯c. The lattice parameters were obtained using the Rietveld refinement method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips—Van Vechten—Levine (P—V—L) theory. Excellent dielectric properties of Ce_(2)[Zr_(0.94)(Al_(1/2)Ta_(1/2))_(0.06)]_(3)(MoO_(4))_(9) with a relative permittivity (ε_(r)) of 10.46, quality factor (Q × f) of 83,796 GHz, and temperature coefficient of resonant frequency (τ_(f)) of −11.50 ppm/℃ were achieved at 850 ℃.

关键词： microwave dielectric ceramics Ce_(2)[Zr_(1−x)(Al_(1/2)Ta_(1/2))_(x)]_(3)(MoO_(4))_(9)(CZMAT) Phillips-Van Vechten-Levine(P-V-L)theory low sintering temperature

Optimal design of a novel cylindrical sandwich panel with double arrow auxetic core under air blast loading

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2020年第3期16卷 617-626页

作者： xu-ke Lan Qi huang Tong Zhou Shun-shan feng State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

The increasing threat of explosions on the battle field and the terrorist action requires the development of more effective blast resistance materials and *** structure can support the external loads effectively by virtue of their spatial *** review of the excellent energy absorption property of auxetic structure,employing auxetic structure as core material in curved sandwich shows the potential to improve the protection *** this study,a novel cylindrical sandwich panel with double arrow auxetic(DAA) core was designed and the numerical model was built by *** to the complexity of the structure,systematic parameter study and optimal design are *** cases of optimal design were considered,case1 focuses on reducing the deflection and mass of the structure,while case2 focuses on reducing the deflection and increasing the energy absorption per unit *** study and optimal design were conducted based on Latin Hypercube Sampling(LHD)method,artificial neural networks(ANN) metamodel and the nondominated sorting genetic algorithm(NSGA-Ⅱ).The Pareto front was obtained and the cylindrical DAA structure performed much better than its equal solid panel in both blast resistance and energy absorption *** results can be used as a reference for different applications.

关键词： Auxetic structure Blast response Finite element analysis(FEA) Optimal design

Multivariate Time Series Forecasting with Transfer Entropy Graph

在线全文

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2023年第1期28卷 141-149页

作者： Ziheng Duan Haoyan xu Yida huang Jie feng Yueyang Wang School of Big Data and Software Engineering Chongqing UniversityChongqing 401331China College of Control Science and Engineering Zhejiang UniversityHangzhou 310027China

Multivariate Time Series(MTS)forecasting is an essential problem in many *** forecasting results can effectively help in making *** date,many MTS forecasting methods have been proposed and widely ***,these methods assume that the predicted value of a single variable is affected by all other variables,ignoring the causal relationship among *** address the above issue,we propose a novel end-to-end deep learning model,termed graph neural network with neural Granger causality,namely CauGNN,in this *** characterize the causal information among variables,we introduce the neural Granger causality graph in our *** variable is regarded as a graph node,and each edge represents the casual relationship between *** addition,convolutional neural network filters with different perception scales are used for time series feature extraction,to generate the feature of each ***,the graph neural network is adopted to tackle the forecasting problem of the graph structure generated by the *** benchmark datasets from the real world are used to evaluate the proposed CauGNN,and comprehensive experiments show that the proposed method achieves state-of-the-art results in the MTS forecasting task.

关键词： Multivariate Time Series(MTS)forecasting neural Granger causality graph Transfer Entropy(TE)

A Shakedown Strength Based Parametric Optimization Technique and Its Application on an Airtight Module

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2022年第4期35卷 139-151页

作者： Songhua huang Yugong xu Lele Zhang Geng Chen feng Liu School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China National International Science and Technology Cooperation Base on Railway Vehicle Operation Beijing Jiaotong UniversityBeijing 100044China Beijing Institute of Spacecraft System Engineering Academy of Space TechnologyBeijing 100094China

In aerospace engineering,design and optimization of mechanical structures are usually performed with respect to elastic *** causing insufcient use of the material,such design concept fails to meet the ever growing needs of the light weight *** remedy this problem,in the present study,a shakedown theory based numerical approach for performing parametric optimization is *** this approach,strength of the structure is measured by its shakedown limit calculated from the direct *** numerical method developed for the structural optimization consists of nested loops:the inner loop adopts the interior point method to solve shakedown problems pertained to fxed design parameters,while the outer loop employs the genetic algorithm to fnd optimal design parameters leading to the greatest shakedown *** method established is frst verifed by the classic plate-with-a-circular-hole example,and after that it is applied to an airtight module for determining few key design *** carefully analyzing results generated during the optimization process,it is convinced that the approach can become a viable means for designing similar aerospace structures.

关键词： Parametric optimal design Shakedown analysis Direct method(DM) Genetic algorithm

Neural network-based model predictive control with fuzzy-SQP optimization for direct thrust control of turbofan engine

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2022年第12期35卷 59-71页

作者： Yangjing WANG Jinquan huang Wenxiang ZHOU feng LU Wenhao xu Jiangsu Province Key Laboratory of Aerospace Power System College of Energy and Power EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China

A nonlinear model predictive control method based on fuzzy-Sequential Quadratic Programming(SQP)for direct thrust control is proposed in this paper for the sake of improving the accuracy of thrust *** designed control system includes four parts,namely a predictive model,rolling optimization,online correction,and feedback *** the strong nonlinearity of engine,a predictive model is established by Back Propagation(BP)neural network for the entire flight envelope,whose input and output are determined with random forest algorithm and actual situation *** optimization typically uses SQP as the optimization algorithm,but SQP algorithm is easy to trap into local ***,the fuzzy-SQP algorithm is proposed to prevent this disadvantage using fuzzy algorithm to determine the initial value of *** addition to the traditional three parts of model predictive control,an online correction module is added to improve the predictive accuracy of the predictive model in the predictive time *** results show that the BP predictive model can reach a certain degree of predictive accuracy,and the proposed control system can achieve good tracking performance with the limited parameters within the safe range。

关键词： Direct thrust control Fuzzy-SQP algorithm Limit protection Neural network Nonlinear model predictive control Random forest Turbofan engine

Near ground wind characteristics during typhoon Meari:Turbulence intensities, gust factors, and peak factors

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2017年第10期24卷 2421-2430页

作者： WANG xu huang Peng YU Xian-feng huang Chao State Key Laboratory Breeding Base of Mountain Bridge and Tunnel Engineering Chongqing Jiaotong University State Key Laboratory of Disaster Reduction in Civil Engineering Tongji University State Key Laboratory of Subtropical Building Science South China University of Technology

Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds and directions, turbulence intensities, gust factors, and peaks were analyzed using the time records of wind speed. The results show that turbulence intensity components in longitudinal, lateral, and vertical directions decrease with mean wind speed, regardless of elevations, and the turbulence intensities are in a linear relationship with mean wind speeds. The ratios of three turbulence intensity components(i.e. Iu, Iv, Iw) at heights of 10, 20 and 40 m were calculated and equal to be 1:0.88:0.50, 1:0.84:0.57, and 1:0.9:0.49, respectively. In addition, the gust factors in three directions exhibit a reduction with increasing mean wind speed. The peak factors at different heights show a similar trend and slightly decrease with mean wind speed; average peak factors for all 10-min data from Typhoon Meari are 2.43, 2.48, and 2.47, respectively.

关键词： typhoon Meari wind characteristics turbulence intensity gust factor peak factor

Laser-generated thermoelastic acoustic sources and acoustic waves in anisotropic plate

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2009年第3期52卷 566-574页

作者： xu BaiQiang WANG feng feng jun WANG Jijun SUN HongXiang LUO Ying Faculty of Science Jiangsu UniversityZhenjiang 212013China

The effect of anisotropy on the ultrasound wave generation and propagation in the unidirectional fi- ber-reinforced composite plate has been investigated. A quantitative numerical model for the la- ser-generated ultrasound in the thermoelastic regime was presented by using a finite element method. All factors, such as spatial and time distributions of the incident laser beam, optical penetration, ther- mal diffusivity, and source-receiver distance can be taken into account. Numerical results show that the effect on ultrasound waveform of the size of the laser volume source produces strong bipolar longitu- dinal waves and improves the amplitude and directivity of the longitudinal waves. A fiber-reinforced composite material exhibits isotropic or homogenous behavior for ultrasonic wave propagation per- pendicular to the fiber direction. For ultrasonic propagation along the fiber direction, ultrasonic dis- persion resulting from the inhomogeneous nature of the material affects the laser ultrasonic waveforms. As the dimensions of the laser pulse are increased in space and time, the displacement waveform be- comes broader and its magnitude decreases.

关键词： laser ultrasound numerical simulation anisotropic material

The regulatory mechanism of rapid lignification for timely anther dehiscence

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Plant Biology 2024年第8期66卷 1788-1800页

作者： jing-Shi xue Yi-feng feng Ming-Qi Zhang Qin-Lin xu Ya-Min xu jun-Qin Shi Li-Fang Liu Xiao-feng Wu Shui Wang Zhong-Nan Yang Shanghai Key Laboratory of Plant Molecular Sciences College of Life SciencesShanghai Normal UniversityShanghai 200234China National Key Laboratory of Plant Molecular Genetics CAS Center for Excellence in Molecular Plant SciencesInstitute of Plant Physiology and EcologyChinese Academy of SciencesShanghai 200032China University of the Chinese Academy of Sciences Beijing 100049China Development Center of Plant Germplasm Resources College of Life SciencesShanghai Normal UniversityShanghai 200234China

Anther dehiscence is a crucial event in plant reproduction,tightly regulated and dependent on the lignification of the anther *** this study,we investigated the rapid lignification process that ensures timely anther dehiscence in *** findings reveal that endothecium lignification can be divided into two distinct *** Phase Ⅰ,lignin precursors are synthesized without polymerization,while Phase Ⅱ involves simultaneous synthesis of lignin precursors and *** transcription factors MYB26,NST1/2,and ARF17 specifically regulate the pathway responsible for the synthesis and polymerization of lignin monomers in Phase Ⅱ.MYB26-NST1/2 is the key regulatory pathway responsible for endothecium lignification,while ARF17 facilitates this process by interacting with ***,our results demonstrate that the lignification of the endothecium,which occurs within approximately 26 h,is much faster than that of the vascular *** findings provide valuable insights into the regulation mechanism of rapid lignification in the endothecium,which enables timely anther dehiscence and successful pollen release during plant reproduction.

关键词： anther dehiscence ARF17 endothecium lignin MYB26 NST

Behavior of reinforced concrete beams and columns subjected to blast loading

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2018年第5期14卷 550-559页

作者： Yan Liu jun-bo Yan feng-lei huang State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology

In this study, the blast performance of steel reinforced concrete(RC) beams was experimentally and analytically investigated. The experiment consists of a total of 10 one-half-scale beams subjected to different levels of blast loading using live explosives. The reflected pressure-time histories were recorded and different damage levels and modes were observed. The blast resilience of the damaged beams was quantified by measuring the time-dependent displacements. Experiment results show that the damage in steel reinforced concrete beams with higher explosive mass is enhanced compared with that of the beams with smaller explosive mass at the same scaled distance. Based on the experiment data, an empirical expression is developed via dimensional analysis to correct the relationship between the midspan displacement and scaled distance. Besides, a complex single degree of freedom model(SDOF)incorporating complex features of the material behavior, high strain-rate effect and the column geometry was proposed and validated by test results.

关键词： Blast Steel reinforced concrete beams Dynamic response Scaling SDOF

Identification of Sphaeroma terebrans via morphology and the mitochondrial cytochrome c oxidase subunit I (COI) gene

在线全文

学校读者我要写书评

暂无评论

Zoological Research 2016年第5期37卷 307-312页

作者： Xiu-feng LI Chong HAN Cai-Rong ZHONG jun-Qiu xu Jian-Rong huang School of Life Sciences Sun Yat-Sen University Guangzhou 510275 China Management Bureau of Dongzhaigang Mangrove Natural Reserve Haikou 571129 China

Sphaeroma terebrans, a wood-boring isopoda, is distributed worldwide in tropical and subtropical mangroves. The taxonomy of S. terebrans is usually based on morphological characteristics, with its molecular identification still poorly understood. The number of teeth on the uropodal exopod and the length of the propodus of the seventh pereopod are considered as the major morphological characteristics in S. terebrans, which can cause difficulty in regards to accurate identification. In this study, we identified S. terebrans via molecular and morphological data. Furthermore, the validity of the mitochondrial cytochrome c oxidase subunit I （COl） gene as a DNA barcode for the identification of genus Sphaeroma, including species S. terebrans, S. retrolaeve, and S. serratum, was examined. The mitochondrial COl gene sequences of all specimens were sequenced and analysed. The interspecific Kimura 2-parameter distances were higher than intraspecific distances and no intraspecificinterspecific distance overlaps were observed. In addition, genetic distance and nucleotide diversity （TT） exhibited no differences within S. terebrans. Our results revealed that the mitochondrial COl gene can serve as a valid DNA barcode for the identification of S. terebrans. Furthermore, the number of teeth on the uropodal exopod and the length of the propodus of the seventh pereopod were found to be unreliable taxonomic characteristics for S. terebrans.

关键词： Sphaeroma terebrans DNA barcode COl gene Molecular identification