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Experimental Research on Structural Behaviors of Glulam I-Beam with a Special-Shaped Section

Journal of Renewable Materials 2020年第2期8卷 113-132页

作者： Ruyuan Yang Chaokun Hong Xiaofeng Zhang Quan Yuan Youfu Sun College of Materials Science and Engineering Nanjing Forestry UniversityNanjingChina College of Civil Engineering Nanjing Forestry UniversityNanjingChina College of media and Art Nanjing University of Information Science&TechnologyNanjingChina

In order to enhance the bearing capacity of structural components,save materials,and reduce cost,a glued laminated timber(glulam)I-beam that is theoretically suitable for engineering application was *** this study,18 glulam specimens were fabricated using larch dimension lumber and resorcinol-formaldehyde ***-point bending tests were carried out to compare the ultimate bearing capacity,strain,and deflection of various *** results showed that:(1)The typical failure mode at bending is the web shear failure parallel to *** the failure,cracks and sounds appear at the beam web,which represent the sudden brittle failure.(2)The cross-sectional strain of glulam beam changed linearly with the beam height,indicating that the plane section assumption was basically established.(3)Stiffener could improve the initial flexural stiffness of glulam beam,which experiences an increase of 28.21%.Larger the shear span ratio,smaller the initial flexural *** initial flexural stiffness improves by 10-23.5%with the increase in the thickness of the lower flange.(4)The effects of stiffener and shear-span ratio on shear strength are relatively *** the stiffeners are set at the support and the loading point in pairs,the shear strength of the glulam beam increases by 15.05%*** the increase in the shear-span ratio,the shearing strength of the glulam I-beam gradually *** equation of the shearing strength with the shear span ratio is obtained,which is shown by high fitting precision.(5)The shear strength correlation,as proposed by Soltis and Rammer,is suitable not only for rectangular beams,but also for glulam I-beams.

关键词： Glulam I-beam stiffener shear span ratio flange thickness

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Effect of the Cylindrical Interface Properties on Ultrasonic Transverse Wave Scattering

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Chinese Physics Letters 1994年第4期11卷 211-214页

作者： WANG Yaojun OU Xianhua NING Wei institute of Acoustics Nanjing UniversityNanjing 210008

A simplified model for ultrasonic transverse wave scattering in cylindrically layered composite with thin interface layers is *** ultrasonic transverse wave attenuation due to the scattering in a fiber reinforced composite is found to be greatly affected by the properties of the interface layers which are simulated as viscoelastic media.

关键词： composite interface transverse

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Acoustic Localization in Weakly Compressible Elastic media Permeated with Air Bubbles

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Chinese Physics Letters 2006年第4期23卷 871-874页

作者：梁彬朱哲民程建春 Laboratory of Modern Acoustics and institute of Acoustics Nanjing University Nanjing 210093

The propagation of longitudinal acoustic waves in weakly compressible elastic media permeated with air bubbles is investigated on the basis of the radial pulsation equation of a single bubble. The multiple scattering of waves in such media is rigorously described by using a self-consistent approach. Theoretical results show that there exists strong acoustic localization in a range of frequency slightly above the bubble resonance frequency, even for a very small volume fraction of bubbles. Further study reveals that the localization is in fact attributed to collection behaviour of bubbles, allowing for an efficient cancellation of propagating waves. This is essentially consistent with the known conclusions recently drawn for bubbly liquid by Kou et al. [2003 Appl. Phys. Left. 83 4247]

关键词： PROPAGATION TRANSITION LIQUIDS WAVES WATER

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Optimal Acoustic Attenuation of Weakly Compressible media Permeated with Air Bubbles

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Chinese Physics Letters 2007年第6期24卷 1607-1610页

作者：梁彬程建春 Laboratory of Modern Acoustics and institute of Acoustics Nanjing University Nanjing 210093

Based on fuzzy logic （FL） and genetic algorithm （GA）, we present an optimization method to obtain the optimal acoustic attenuation of a longitudinal acoustic wave propagating in a weakly compressible medium permeated with air bubbles. In the optimization, the parameters of the size distribution of bubbles in the medium are optimized for providing uniformly high acoustic attenuation in the frequency band of interest. Compared with other traditional optimization methods, the unique advantage of the present method is that it can locate the global optimum quickly and effectively in need of knowing the mathematical model precisely. As illustrated by a numerical simulation, the method is effective and essential in enhancing the acoustic attenuation of such a medium in an optimal manner. The bubbly medium with optimized structural parameters can effectively attenuate longitudinal waves at intermediate frequencies with an acoustic attenuation approximating a constant value of lO（dB/cm）. Such bubbly media with optimal acoustic attenuations may be applied to design acoustic absorbent by controlling broader attenuation band and higher efficiency.

关键词： GENETIC ALGORITHM WAVE

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Pd nanoparticles embedded in N-Enriched MOF-Derived architectures for efficient oxygen reduction reaction in alkaline media

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Green Energy & Environment 2023年第4期8卷 1205-1215页

作者： Daqiang Yan Lin Zhang Lei Shen Runyu Hu Weiping Xiao Xiaofei Yang College of Science Institute of Materials Physics and ChemistryNanjing Forestry UniversityNanjing210037China

Developing high efficient Pd-based electrocatalysts for oxygen reduction reaction(ORR) is still challenging for alkaline membrane fuel cell,since the strong oxygen adsorption energy and easy agglomerative intrinsic properties. In order to simultaneously solve these problems, Pd/Co_(3)O_(4)–N–C multidimensional materials with porous structures is designed as the ORR catalysts. In details, the ZIF-67 with polyhedral structure was firstly synthesized and then annealed at high-temperature to prepare the N-doped Co_(3)O_(4)carbon-based material, which was used to homogeneously confine Pd nanoparticles and obtained the Pd/Co_(3)O_(4)–N–C series catalysts. The formation of Co–N and C–N bond could provide efficient active sites for ORR. Simultaneously, the strong electronic interaction in the interface between the Pd and N-doped Co_(3)O_(4)could disperse and avoid the agglomeration of Pd nanoparticles and ensure the exposure of active sites, which is crucial to lower the energy barrier toward ORR and substantially enhance the ORR kinetics. Hence, the Pd/Co_(3)O_(4)–N–C nanocompounds exhibited excellent ORR catalytic performance, ideal Pd mass activity, and durability in 0.1 mol L-1KOH solution compared with Co_(3)O_(4)–N–C and Pd/C. The scalable synthesis method, relatively low cost, and excellent electrochemical ORR performance indicated that the obtained Pd/Co_(3)O_(4)–N–C electrocatalyst had the potential for application on fuel cells.

关键词： Oxygen reduction reaction Electrocatalysis Pd/Co_(3)O_(4)–N–C Carbon-based materials Co–N and C–N bond

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An Analysis and Proof on Self-Similarity Property of Flash P2P Internet Video Traffic

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Chinese Journal of Electronics 2015年第1期24卷 26-32页

作者： JI Yimu YUAN Yongge HAN Zhijie WANG Hao HAN Lei SUN Yanfei WANG Ruchuan Computer of Science Nanjing University of Posts and Telecommunications institute of Advanced Technology Nanjing University of Posts and Telecommunications

In order to study the amount of bandwidth resource loss caused by flash P2 P technique, its influence on network load and its maintenance cost, the characteristic of Internet traffic of flash P2 P is studied. On the basis of analysis of features of Real time media flow protocol(RTMFP), the traffic of flash P2 P can be identified from the Internet traffic. By extraction and analysis of the traffic of the three largest online video content providers in China(Youku, Iqyi and Sohu Video) and the calculation of probability distribution of the traffic, it is found that the transmission time of flash P2 P traffic and the transmission time interval obeys the heavy-tailed distribution. This accounts for the self-similarity of the flash P2 P traffic. To better explain the phenomenon, the long-range dependent model is established based on the current traffic. By the established mathematical model, it is strictly proved that flash P2 P traffic has self-similar characteristic.

关键词： Video traffic Flash P2P Self-similarity Empirical mode decomposition(EMD) Autoregressive integrated moving average(ARAMA) model.

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Adaptive Extended Isogeometric Analysis for Steady-State Heat Transfer in Heterogeneous media

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Computer Modeling in Engineering & Sciences 2021年第3期126卷 1315-1332页

作者： Weihua Fang Tiantang Yu Yin Yang nanjing Automation institute of Water Conservancy and Hydrology Ministry of Water ResourcesNanjing210012China Department of Engineering Mechanics Hohai UniversityNanjing211100China Lake Research institute Hydraulic Research Institute of Jiangsu ProvinceNanjing210017China

Steady-state heat transfer problems in heterogeneous solid are simulated by developing an adaptive extended isogeometric analysis(XIGA)method based on locally refined non-uniforms rational B-splines(LR NURBS).In the XIGA,the LR NURBS,which have a simple local refinement algorithm and good description ability for complex geometries,are employed to represent the geometry and discretize the field variables;and some special enrichment functions are introduced into the approximation of temperature field,thus the computational mesh is independent of the material interfaces,which are described with the level *** to the approximation of temperature field,a temperature gradient recovery technique for heterogeneous media is proposed,and based on the Zienkiewicz–Zhu recovery technique a posteriori error estimator is defined to automatically identify the locally refined *** convergence and performance properties of the developed method are verified by using three numerical *** numerical results show that(1)The convergence speed of the adaptive local refinement is faster than that of the uniform global refinement;(2)The convergence rate of the high-order basis functions is faster than that of the low-order basis functions;and(3)The existing inclusions change the local distributions of the temperature,and the extreme values of the temperature gradients take place around the inclusion interfaces.

关键词： Heterogeneous media steady-state heat transfer adaptive XIGA LR NURBS heat dissipation

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Energy efficient TDMA-based MAC protocol associated with GAF for wireless sensor networks

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The Journal of China Universities of Posts and Telecommunications 2007年第1期14卷 6-11页

作者： XIAO Xiao ZHENG Bao-yu YAN Zhen-ya CHEN Chao institute of Signal and Information Processing Nanjing University of Posts and Telecommunications Nanjing 210003 China

The design of media access control （MAC） protocol for wireless sensor networks （CSNs） with the idea of cross layer attracts more and more attention. People can improve the MAC protocol by obtaining certain information regarding the network layer and physical layer. This article synthesizes and optimizes certain cross-layer protocols which have existed. On the basis of the muting, topology information in the network layer, and transmission power information in the physical layer, the thne slot assignment algorithm has been improved in the MAC layer. By using geographical adaptive fidelity algorithm （GAF） to divide the grids, controlling of transmission power and scheduling the work/sleep duty cycle for sensor nodes, a new MAC protocol has been proposed to decrease energy consumption and enlarge the lifetime of WSNs. Simulation results show that the MAC protocol functions well.

关键词： power controlled time division multiple access(TDMA) WSNs MAC GAF

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Experimental demonstration of influence of underwater turbulence on ghost imaging

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Chinese Physics B 2019年第9期28卷 180-185页

作者： Man-Qian Yin Le Wang Sheng-Mei Zhao institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications

It is difficult to obtain a clear image in underwater turbulence environment with classical imaging methods due to the absorption, scattering, and underwater turbulence on the propagation ***, ghost imaging(GI), a nonlocally imaging technique, has shown the turbulence-free ability in atmospheric turbulence by exploiting the second-order correlation between the signal beam and the reference *** this paper, we experimentally investigate the imaging quality of GI affected by the underwater environment, where the underwater environment is simulated by a 1 m×0.4 m×0.4 m tank with distilled *** water temperature is controlled by a heater inside the tank, and a temperature gradient is obtained by putting the heater at different positions of the *** water vibration is produced by a heavy force, and the turbid medium is obtained by dissolving very small specks of CaCO3 in the water.A set of Hadamard speckle pattern pairs are generated and modulated on the incident beam, and then the beam illuminates on an unknown object after passing through the simulated underwater *** the second-order correlations, the image is reconstructed under different temperature gradients, water vibration, and turbid medium *** results show that GI has the turbulence-free ability under lower temperature gradient, water vibration, and turbid *** structural similarity image measurement(SSIM)values of the reconstructed images only start to decrease when the temperature gradient is greater than 4.0℃.The same temperature gradient produced at the different positions has a little effect on the quality of the underwater GI.

关键词： underwater ghost imaging temperature gradient turbid media water vibration

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Stress corrosion cracking of magnesium alloys:A review

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Journal of Magnesium and Alloys 2023年第6期11卷 1906-1930页

作者： Jiahao Jiang Xue Geng Xiaobo Zhang School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167China Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing 211167China

Magnesium(Mg)alloys have been widely used in automobile,aviation,computer,and other fields due to their lightweight,high specific strength and stiffness,low pollution,and good electromagnetic shielding ***,the chemical stability of Mg alloys is poor,especially in the corrosive medium environment with high stress corrosion sensitivity,which causes sudden damage to structural components and restricts their application *** recent years,owing to the increasing failure rate of engineering structures caused by stress corrosion of Mg alloys,it has become necessary to understand and pay more attention to the stress corrosion cracking(SCC)behavior of Mg *** this paper,the SCC mechanisms and test methods of Mg alloys have been *** recent research progress on SCC of Mg alloys has been reviewed from the aspects of alloying,preparation process,surface modification,corrosive medium,and strain *** importantly,future research trends in the field of SCC of Mg alloys have also been proposed.

关键词： Magnesium alloys Stress corrosion cracking Alloying Preparation process Corrosion media Surface treatment

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