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Effect of catalyst diesel particulate filter aging and catalyst loadings on particulate emission characteristics from a diesel vehicle

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Journal of Environmental Sciences 2024年第2期136卷 35-44页

作者： Yunhua zhang Diming Lou Piqiang Tan Zhiyuan Hu liang Fang School of Automotive Studies Tongji UniversityShanghai 201804China

In this study,the effect of new and used catalyzed diesel particulate filter(CDPF)with different catalyst loadings on the particulate emissions including the particle mass(PM),particle number(PN),particle size distribution(PSD)and geometric mean diameter(GMD)from a diesel vehicle were investigated based on a heavy chassis *** showed that more than 97.9%of the PN and 95.4%of the PM were reduced by the CDPF,and the reduction efficiency was enhanced by the catalyst *** using the CDPF,the PSD transformed from bimodal to trimodal with the peak shifting towards smaller particle size,more nucleation mode particles were reduced compared with accumulation mode ones,but the reduction effect on the accumulation mode particles was more significantly influenced by the catalyst ***,the CDPF increased the accumulation mode particles proportion,producing a larger *** the used CDPF,its reduction effect on the particulate emissions enhanced,especially for the PM in accumulation *** PSD returned to bimodal,but the peak at accumulation mode began to be higher than that at nucleation mode,illustrating that more nucleation mode particles was *** aging of the CDPF resulted in greater effect on the PN-based PSD than that of PM-based PSD,but the effect of catalyst loading on the PN and PM emission factors was *** used CDPF further increased the GMD,and the effect of catalyst loading on the GMD was strengthened,a higher catalyst loading led to a reduction in the GMD.

关键词： Catalyzed diesel particulate filter (CDPF) Catalyst loading Aging Particle Particle size distribution Geometric mean diameter

Elastic buckling analysis and optimization of thin-walled bamboo-like pipe beam subjected to pure bending

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Chinese Journal of Aeronautics 2024年第3期37卷 133-152页

作者： Yayun YU Dongli MA liang zhang Xiaopeng YANG Hao GUAN School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China

In this paper,a stiffening design imitating the bamboo node is proposed for weight reduction of the long composite pipe beam subjected to bending *** distribution of bamboo nodes can efficiently suppress the ovalization of the section,thus significantly improving the bending resistance of the *** on this principle,ring stiffeners are proposed to be fixed to the pipe beam,making the long beam equivalent to the combination of a series of short pipes that suffered less section ovalization.A database of the optimal laminate orientations for different normalized lengths is obtained through optimizations,where the discreteness of the ply count is *** on this database,weight optimizations are conducted,and the optimal designs of beams with and without stiffeners are obtained and *** comparison results show that the proposed bamboo-like stiffened beam not only regains a near-linear load–displacement relationship,but also reduces the weight by up to 16%under the same buckling *** addition,it is found that for the pipe beams with radius-to-thickness ratios of more than 18,increasing the radius leads to a decrease in elastic buckling resistance when the weight remains a constant,which is opposite to the design for strength and *** model and database developed in this paper can provide a reference for weight reduction design and weight estimation for composite pipe beams.

关键词： Composite beam Buckling Thin-walled structure Unmanned aerial vehicles Bamboo

Strategy for suppressing abnormal grain growth of ZK60 Mg alloy during solution by pre-compression:A quasi-in-situ study

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Journal of Materials Science & Technology 2024年第4期171卷 115-128页

作者： Zhenxu Wang liang Chen Jianwei Tang Cunsheng zhang Guoqun Zhao Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinanShandong 250061China Department of Mechanical Engineering Kyushu UniversityFukuoka 819-0395Japan

Abnormal grain growth(AGG)easily takes place in Mg alloys during high-temperature solutions,result-ing in deterioration of mechanical ***,the compression prior to solution(pre-compression)was conducted to suppress AGG,and the microstructure evolution as well as suppressing mechanisms was investigated based on quasi-in-situ *** compression along the transverse direction,//ED grains preferentially nucleated and rapidly grew up,and the initial//ED texture was *** grain growth modes of heat-induced and strain-induced grain boundary migrations were *** former was attributed to the high interfacial energy of grain boundaries with large *** latter consumed the adjacent grains with high storage energy,forming abnormal grains with irregular *** compression with a reduction>6%could obviously suppress *** suppressing effects were mainly attributed to weakening the size advantage of//ED grains,increasing nucleation,reducing grain boundary character distribution,and redistributing storage energy *** 12%compression along the transverse direction,30°misorientation of//ED grains and high energy grain boundaries were ***{10-12}tensile twins and{10-15}high index twins induced by com-pression increased the nucleation of static ***,compression introduces high-density dislocations,which also contributed to suppressing AGG behavior during solution.

关键词： Quasi-in-situ analysis Mg alloy Abnormal grain growth Compression Microstructure

Application of the finite analytic numerical method to a flowdependent variational data assimilation

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Acta Oceanologica Sinica 2024年第3期43卷 30-39页

作者： Yan Hu Wei Li Xuefeng zhang Guimei Liu liang zhang Tianjin Key Laboratory for Marine Environmental Research and Service School of Marine Science and TechnologyTianjin UniversityTianjin 300072China School of Marine Science and Technology Tianjin UniversityTianjin 300072China National Marine Environmental Forecasting Center Ministry of Natural ResourcesBeijing 100081China

An anisotropic diffusion filter can be used to model a flow-dependent background error covariance matrix,which can be achieved by solving the advection-diffusion *** of the directionality of the advection term,the discrete method needs to be chosen very *** finite analytic method is an alternative scheme to solve the advection-diffusion *** a combination of analytical and numerical methods,it not only has high calculation accuracy but also holds the characteristic of the auto *** demonstrate its ability,the one-dimensional steady and unsteady advection-diffusion equation numerical examples are respectively solved by the finite analytic *** more widely used upwind difference method is used as a control *** result indicates that the finite analytic method has higher accuracy than the upwind difference *** the two-dimensional case,the finite analytic method still has a better *** the three-dimensional variational assimilation experiment,the finite analytic method can effectively improve analysis field accuracy,and its effect is significantly better than the upwind difference and the central difference ***,it is still a more effective solution method in the strong flow region where the advective-diffusion filter performs most prominently.

关键词： finite analytic method advection-diffusion equation data assimilation flow-dependent

Shock-induced chemical reaction characteristics of PTFE-Al-Bi_(2)O_(3)reactive materials

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Defence Technology（防务技术） 2024年第6期36卷 1-12页

作者： Chunlan Jiang Rong Hu Jingbo zhang Zaicheng Wang liang Mao State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

A ternary system of PTFE/Al/Bi_(2)O_(3)is constructed by incorporating PTFE-based reactive material and thermite for enhancing the energy release of the PTFE-based reactive *** effects of Bi_(2)O_(3)in the PTFE/Al/Bi_(2)O_(3)on both mechanical properties and the energy release were investigated through various tests such as thermogravimetry-differential scanning calorimetry,adiabatic oxygen bomb test and split Hopkinson pressure bar *** microstructure observed through scanning electron microscope and Xray diffraction results are used to analyze the ignition and reaction mechanism of PTFE/Al/Bi_(2)O_(3).The results indicate that the PTFE/Al/Bi_(2)O_(3)are capable of triggering the exothermic reaction of molten PTFE/Bi_(2)O_(3)and Al/Bi_(2)O_(3)over the PTFE/Al reactive materials,thereby promoting *** excessive aluminum in the ternary system is beneficial for increasing energy *** ignition of shock-induced chemical reactions in PTFE/Al/Bi_(2)O_(3)is closely related to the material *** dominant mechanism for hot-spot generation under Split Hopkinson Pressure Bar test is the frictional temperature rise at the microcrack after failure.

关键词： PTFE/Al/Bi_(2)O_(3) Shock-induced chemical reaction Energy release

Statistical QoS Provisioning Architecture for 6G Satellite-Terrestrial Integrated Networks

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Journal of Communications and Information Networks 2024年第1期9卷 34-42页

作者： Jingqing Wang Wenchi Cheng Wei zhang Hui liang School of Telecommunications Engineering Xidian UniversityXi’an 710071China School of Electrical Engineering and Telecommunications the University of New South WalesSydneyAustralia School of Electrical Engineering and Intelligentization Dongguan University of TechnologyDongguan 523808China Peng Cheng Laboratory Shenzhen 518055China.

The emergence of massive ultra-reliable and low latency communications (mURLLC) as a category of age/time/reliability-sensitive service over 6G wireless networks has received considerable research attention, which has presented unprecedented challenges. As one of the key enablers for 6G,satellite-terrestrial integrated networks (STIN) have been developed to offer more expansive connectivity and comprehensive 3D coverage in space-aerial-terrestrial domains for supporting 6G mission-critical mURLLC applications while fulfilling diverse and rigorous quality of service (QoS) requirements. In the context of these mURLLC-driven satellite services, data freshness assumes paramount importance, as outdated data may engender unpredictable or catastrophic *** effectively measure data freshness in satellite-terrestrial integrated communications,age of information(AoI)has recently surfaced as a new dimension of QoS metric to support time-sensitive applications. It is crucial to design new analytical models that ensure stringent and diverse QoS metrics bounded by different key parameters,including AoI,delay,and reliability,over 6G satellite-terrestrial integrated networks. However,due to the complicated and dynamic nature of satellite-terrestrial integrated network environments, the research on efficiently defining new statistical QoS provisioning schemes while taking into account varying degrees of freedom has still been in their infancy. To remedy these deficiencies, in this paper we develop statistical QoS provisioning schemes over 6G satellite-terrestrial integrated networks in the finite blocklength regime. Particularly, we firstly introduce and review key technologies for supporting ***,we formulate a number of novel fundamental statistical-QoS metrics in the finite blocklength ***,we conduct a set of simulations to validate and evaluate our developed statistical QoS provisioning schemes over satellite-terrestrial integrated networks.

关键词： statistical QoS provisioning mURLLC peak AoI satellite-terrestrial integrated networks QoS exponents hybrid automatic repeat request finite blocklength coding

Resource Allocation for Space-Air-Ground Integrated Networks:A Comprehensive Review

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Journal of Communications and Information Networks 2024年第1期9卷 1-23页

作者： Hui liang Zhiqing Yang Guobin zhang Hanxu Hou School of Electrical Engineering and Intelligentization Dongguan University of TechnologyDongguan 523808China Peng Cheng Laboratory Shenzhen 518055China School of Electronics and Information Engineering Shenzhen UniversityShenzhen 518061China School of Electrical Engineering and Intelligentization Dongguan University of TechonologyDongguan 523808China School of Information and Communication Engineering Guangzhou Maritime UniversityGuangzhou 510725China

The space-air-ground integrated networks (SAGIN) has emerged as a critical paradigm to address the growing demands for global connectivity and enhanced communication services. This paper gives a thorough review of the strategies and methodologies for resource allocation within SAGIN, focusing on the challenges and solutions within its complex structure. With the advent of technologies such as 6G, the dynamics of resource optimization have become increasingly complex, necessitating innovative approaches for efficient management. We examine the application of mathematical optimization, game theory, artificial intelligence (AI), and dynamic optimization techniques in SAGIN,offering insights into their effectiveness in ensuring optimal resource distribution, minimizing delays, and maximizing network throughput and stability. The survey highlights the significant advances in AI-based methods,particularly deep learning and reinforcement learning, in tackling the inherent challenges of SAGIN resource allocation. Through a critical review of existing literature, this paper categorizes various resource allocation strategies, identifies current research gaps, and discusses potential future directions. Our findings highlight the crucial role of integrated and intelligent resource allocation mechanisms in realizing the full potential of SAGIN for next-generation communication networks.

关键词： space-air-ground integrated networks resource allocation 6G optimization theory game theory artificial intelligence

Formation and transformation of metastable LPSO building blocks clusters in Mg-Gd-Y-Zn-Zr alloys by spinodal decomposition and heterogeneous nucleation

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Journal of Magnesium and Alloys 2024年第2期12卷 673-686页

作者： Xin Zhao Zhong Yang Jiachen zhang Minxian liang Liying Wang School of Materials Science and Chemical Engineering Xi’an Technological UniversityXi’an 710021China Xi’an Tianli Metal Composite Material Co.Ltd. Xi’an 710299China

To study the formation and transformation mechanism of long-period stacked ordered(LPSO)structures,a systematic atomic scale analysis was conducted for the structural evolution of long-period stacked ordered(LPSO)structures in the Mg-Gd-Y-Zn-Zr alloy annealed at 300℃~500℃.Various types of metastable LPSO building block clusters were found to exist in alloy structures at different temperatures,which precipitate during the solidification and homogenization *** stability of Zn/Y clusters is explained by the first principles of density functional *** LPSO structure is distinguished by the arrangement of its different Zn/Y enriched LPSO structural units,which comprises local fcc stacking sequences upon a tightly packed *** presence of solute atoms causes local lattice distortion,thereby enabling the rearrangement of Mg atoms in the different configurations in the local lattice,and local HCP-FCC transitions occur between Mg and Zn atoms occupying the nearest neighbor *** finding indicates that LPSO structures can generate necessary Schockley partial dislocations on specific slip surfaces,providing direct evidence of the transition from 18R to *** of the LPSO,devoid of any defects and non-coherent interfaces,was observed separately from other precipitated *** a result,the precipitation sequence of LPSO in the solidification stage was as follows:Zn/Ycluster+Mg layers→various metastable LPSO building block clusters→18R/24R LPSO;whereas the precipitation sequence of LPSO during homogenization treatment was observed to be as follows:18R LPSO→various metastable LPSO building block clusters→14H *** these,14H LPSO was found to be the most thermodynamically stable structure.

关键词： LPSO Spinodal decomposition Homogenization treatment Clusters Phase transformation

High-performance terahertz modulators induced by substrate field in Te-based all-2D heterojunctions

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Light(Science & Applications) 2024年第3期13卷 577-586页

作者： Pujing zhang Qihang liang Qingli Zhou Jinyu Chen Menglei Li Yuwang Deng Wanlin liang liangliang zhang Qinghua zhang Lin Gu Chen Ge Kui-juan Jin Cunlin zhang Guozhen Yang Department of Physics Key Laboratory of Terahertz OptoelectronicsMinistry of Educationand Beijing Advanced Innovation Center for Imaging Theory and TechnologyCapital Normal UniversityBeijing 100048China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China Department of Materials Science and Engineering Beijing National Center for Electron Microscopy and Laboratory of Advanced MaterialsTsinghua UniversityBeijing 100084China

High-performance active terahertz modulators as the indispensable core components are of great importance for the next generation communication ***,they currently suffer from the tradeoff between modulation depth and ***,we introduce two-dimensional(2D)tellurium(Te)nanofilms with the unique structure as a new class of optically controlled terahertz modulators and demonstrate their integrated heterojunctions can successfully improve the device performances to the optimal and applicable levels among the existing all-2D broadband *** photoresponse measurements confirm the significant impact of the stacking *** first clarify the direction of the substrate-induced electric field through first-principles calculations and uncover the unusual interaction mechanism in the photoexcited carrier dynamics associated with the charge transfer and interlayer exciton *** advances the fundamental and applicative research of Te nanomaterials in high-performance terahertz optoelectronics.

关键词： performance field terahertz