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Acta Mechanica Sinica 2024年第8期40卷 45-66页

作者： Zhiwen Cui Lihao Zhao Applied Mechanics laboratory Department of Engineering MechanicsTsinghua UniversityBeijing100084China laboratory of Flexible Electronics Technology Tsinghua UniversityBeijing100084China

The alignment of elongated fibers and thin disks is known to be significantly influenced by the presence of fluid coherent structures in near-wall turbulence(Cui et al.2021).However,this earlier study is confined to the spheroids with infinitely large or small aspect ratio,and the shape effect of finite aspect ratio on the alignment is not *** current study investigates the shape-dependent alignment of inertialess spheroids in structure-dominated regions of channel *** utilizing an ensemble-averaged approach for identifying the structure-dominated regions,we analyze the eigensystem of the linear term matrix in the Jeffery equation,which is governed by both particle shape and local fluid velocity *** contrast to earlier conventional analysis based on local vorticity and strain rate,our findings demonstrate that the eigensystem of the Jeffery equation offers a convenient,effective,and universal framework for predicting the alignment behavior of inertialess spheroids in turbulent *** leveraging the eigensystem of the Jeffery equation,we uncover a diverse effect of fluid coherent structures on spheroid alignment with different particle ***,we provide explanations for both shape-independent alignments observed in vortical-core regions and shape-dependent alignments around near-wall streamwise vortices.

关键词： Non-spherical particle Direct numerical simulation Wall turbulence Particle-laden flow

N-Heterocyclic carbene-catalyzed enantioselective(dynamic) kinetic resolutions and desymmetrizations

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Science China Chemistry 2024年第2期67卷 482-511页

作者： Yi Zhang Hui Cai Xiuhai Gan Zhichao Jin National Key laboratory of Green Pesticide Key Laboratory of Green Pesticide and Agricultural BioengineeringMinistry of EducationGuizhou UniversityHuaxi DistrictGuiyang550025China

N-heterocyclic carbene-catalyzed enantioselective kinetic resolutions,dynamic kinetic resolutions,and desymmetrization reactions are systematically *** content is organized according to the activation modes involved i... 详细信息

关键词： N-heterocyclic carbene kinetic resolution dynamic kinetic resolution desymmetrization organocatalysis

Catalyst design and structure control for photocatalytic refineries of cellulosic biomass to fuels and chemicals

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Journal of Energy Chemistry 2024年第7期94卷 102-127页

作者： Lulu Sun Nengchao Luo State Key laboratory of Catalysis Dalian National Laboratory for Clean EnergyDalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina

Lignocellulosic biomass is the largest renewable hydrocarbon resource on *** cellulose,one of the major components of lignocellulose,powered by solar energy is a promising way of providing lowcarbon-footprint energy chemicals such as H_(2),HCOOH,CO,and transportation ***-of-the-art biorefineries target the full use of biomass feedstocks as they have a maximum collection radius of 75-100 km,requesting efficient and selective photocatalysts that significantly influence the outcome of photocatalytic ***-performed photocatalysts can harvest a broad solar spectrum and are active in breaking the chemical bonds of cellulose,decreasing the capital investments of ***,photocatalysts should control the selectivity of cellulose conversion,originating target products to level down separation *** separation in photocatalysts and interfacial charge transfer between photocatalysts and cellulose affect the activity and selectivity of cellulose refineries to H2 and carbonaceous *** account for the challenges above,this review summarizes photocatalysts for the refineries of cellulose and downstream platform molecules based on the types of products,with the structure features of different types of photocatalysts discussed in relation to the targets of either improving the activity or product *** addition,this review also sheds light on the methods for designing and regulating photocatalyst structures to facilitate photocatalytic refineries of cellulose and platform molecules,meanwhile summarizing proposed future research challenges and opportunities for designing efficient photocatalysts.

关键词： Photocatalysts Biorefineries Cellulose Fuels Hydrogen

Enhanced Flexoelectricity in Barium Titanate-Cellulose Composite Thin Films

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Acta Mechanica Solida Sinica 2024年第4期37卷 521-527页

作者： Wensi Xing Hongyu Cao Xin Zhang Xu Liang Jianwei Song Shengping Shen Chemomechanics and Intelligent Media laboratory State Key Laboratory for Strength and Vibration of Mechanical StructuresSchool of Aerospace EngineeringXi’an Jiaotong UniversityXi’an710049China

Biopolymers,the potential flexoelectric materials,are environment-friendly,degradable,lightweight,cost-effective,and possess remarkable processing properties catering to the requirements of advanced ***,the flexoelectric coefficient of biopolymers is normally much weaker than that of ceramic materials,limiting their potential applications for designing high-performance green electromechanical coupling *** improve the flexoelectric response in biopolymers,we composited barium titanate(BTO)with 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized cellulose nanofibrils(TOCNF)to enhance the flexoelectric response of *** to the high permittivity and flexoelectric effect of BTO,the relative dielectric constant and flexoelectric coefficient of 33.3 wt%BTO-TOCNF films reached 30.94@1 kHz and 50.05±1.88 nC/m@1 Hz,which were almost 172 times and 27 times higher than those of TOCNF,*** composite thin film contains high dielectric constant and flexoelectric coefficient,as well as excellent *** study provided a straightforward and efficient method for improving the flexoelectric effect of biopolymers,and demonstrated its great potential applications in flexoelectric-based devices.

关键词： Flexoelectricity Cellulose BaTiO_(3) Composite Thin films

Revisiting the sodium-ion storage capability of hard carbon in carbonate-based electrolytes via a sodium-metal-free protocol

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Science China Chemistry 2024年第7期67卷 2240-2247页

作者： Gaopan Liu Yanbing Mo Jiawei Chen Yu Peng Xiao Zhu Fei Wang Xiaoli Dong Yongyao Xia Department of Chemistry and Shanghai Key laboratory of Molecular Catalysis and Innovative Materials Institute of New EnergyLaboratory of Advanced MaterialsFudan UniversityShanghai 200438China

Common evaluation methodology of sodium(Na)-containing two-electrode or three-electrode configurations overlooks the interference from highly reactive Na metal,leading to the underestimation or inconsistent performance of low-potential hard carbon(HC)***,the trap of Na metal was systematically investigated with or without applied current,uncovering its inadequacy as the reference or counter electrode in different configurations.A Na-metal-free three-electrode protocol is proposed for evaluating the actual Na^(+)-storage capability of the typical low-potential HC *** avoiding Na crosstalk and precisely controlling the working electrode's potential,the actual electrochemical performance of HC in the carbonate esterbased electrolyte can be recognized with high capacity of 222 mAh g^(-1)at 2 C and 113 mAh g^(-1)at 5 C,correcting the misunderstanding of the inferior performance of HC in coin-type half cells(68%and 50%undervaluation at 2 C and 5 C,respectively).The advanced protocol is expected to reduce misunderstandings or underestimation due to evaluation methods and to guide the development of high-performance battery materials.

关键词： highly reactive sodium potential drift carbonate ester sodium-metal-free protocol sodium storage capability

Toward a rapid and convenient nanoplastic quantification method in laboratory-scale study based on fluorescence intensity

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Frontiers of Environmental Science & Engineering 2024年第5期18卷 117-126页

作者： Ruiqi Yan Sen Lin Qian Ding Lei Zhang Xia Yu Wentao Zhao Qian Sui State Environmental Protection Key laboratory of Environmental Risk Assessment and Control on Chemical Process School of Resources and Environmental EngineeringEast China University of Science and TechnologyShanghai200237China State Key laboratory of Pollution Control and Resource Reuse College of Environmental Science and EngineeringTongji UniversityShanghai200092China Shanghai Institute of Pollution Control and Ecological Security Shanghai200092China

The thorough investigation of nanoplastics(NPs)in aqueous environments requires efficient and expeditious quantitative analytical methods that are sensitive to environmentally relevant NP concentrations and convenient to *** analysis-based quantitative methods have been acknowledged as effective and rapid approaches for quantifying NP concentrations in laboratory-scale ***,we compared three commonly used optical response indicators,namely fluorescence intensity(FI),ultraviolet absorbance,and turbidity,to assess their performance in quantifying ***,orthogonal experiments were conducted to evaluate the influence of various water quality parameters on the preferred indicator-based quantification *** results revealed that FI exhibits the highest correlation coefficient(>0.99)with NP ***,the limit of quantification(LOQ)for various types of NPs is exceptionally low,ranging from 0.0089 to 0.0584 mg/L in ultrapure water,well below environmentally relevant *** variations in water quality parameters such as pH,salinity,suspended solids(SS),and humic acid,a robust relationship between detectable FI and NP concentration was ***,an increased matrix,especially SS in water samples,results in an enhanced LOQ for ***,the quantitative method remains applicable in real water bodies,especially in drinking water,with NP LOQ as low as 0.0157–0.0711 mg/*** exceeds the previously reported detectable concentration for 100 nm NPs at 40µg/mL using surface-enhanced Raman *** study confirms the potential of FI as a reliable indicator for the rapid quantification of NPs in aqueous environments,offering substantial advantages in terms of both convenience and cost-effectiveness.

关键词： Nanoplastic quantification Fluorescence intensity Drinking water Limit of quantification(LOQ) Matrix effects

Impact of Annealing on the Melt Recrystallization of a-PDLA/α-PLLA Double-layered Films

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Chinese Journal of Polymer Science 2024年第2期42卷 230-238,I0009页

作者： Yun-Peng Li Hao-Ran Shen Shao-Juan Wang Hao Zhang Jian Hu Rui Xin Xiao-Li Sun Shou-Ke Yan Key laboratory of Rubber-Plastics Ministry of Education/Shandong Provincial Key Laboratory of Rubber-plasticsQingdao University of Science&TechnologyQingdao266042China State Key laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing100029China

Poly(lactic acid)(PLA) as a bio-based polymer with biodegradability and biocompatibility has attracted much attention. To manipulate its properties for different applications, regulation of crystal structure and crystalline morphology becomes an attractive research topic. In this work, the structure evolution of layered samples containing an amorphous poly(D-lactide)(PDLA) layer and a crystalline poly(L-lactide)(PLLA)layer with highly oriented edge-on α lamellar crystals after annealing at 150 ℃ or/and after melt-recrystallization has been studied by AFM, FTIR,and TEM combined with electron diffraction. The results demonstrate that melt recrystallization of the as-prepared sample leads to the formation of abundant randomly oriented PLA stereo-complex(PLA SC) crystals. Annealing at 150 ℃ results in the formation of a small amount of oriented PLA SC crystals at the interface. These PLA SC crystals show great impact on the recrystallization behavior of sample after melting at 190 ℃ and then crystallizing at 90 ℃. First, they impede the mutual diffusion of the overlying PDLA and underlying PLLA, and thus reduce their stereocomplexation ability as manifested by the decreased amount of PLA SC crystals. Second, they act as substrate to initiate the epitaxial crystallization of the overlying PDLA and underlying PLLA, which ensures the production of a highly oriented structure of PDLA and PLLA after melt recrystallization again.

关键词： Poly(L-lactide) Poly(D-lactide) Double layer Stereocomplex

Cobalt-Catalyzed Switchable[4+1]and[4+1+1]Spirocyclization of Aromatic Amides with 2-Diazo-1H-indene-1,3(2H)-dione:Access to Spiro Indene-2,1'-isoindolinones and Spiro Isochroman-3,1'-isoindolinones

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Chinese Journal of Chemistry 2024年第4期42卷 363-369页

作者： Bin Li Mengmeng Xie Jingyu Li Nana Shen Xinying Zhang Xuesen Fan State Key laboratory of Antiviral Drugs Pingyuan LaboratoryKey Laboratory of Green Chemical Media and ReactionsKey Laboratory for Yellow River and Huai River Water Environmental Pollution ControlMinistry of EducationSchool of EnvironmentSchool of Chemistry and Chemical EngineeringHenan Normal UniversityXinxiangHenan453007 China

Herein,we report a condition-controlled divergent synthesis of spiro indene-2,1'-isoindolinones and spiro isochroman-3,1'-isoindolinones through cobalt-catalyzed formal[4+1]and[4+1+1]spirocyclization of aromatic amides with 2-diazo-1H-indene-1,3(2H)-*** the reaction is carried out under air in ethyl acetate,spiro indene-2,1'-isoindolinones are formed through Co(II)-catalyzed C—H/N—H[4+1]*** the reaction is run under O2 in CH3CN,on the other hand,spiro isochroman-3,1'-isoindolinones are generated through Baeyer-Villiger oxidation of the in situ formed spiro indene-2,1'-isoindolinones with O2 as a cheaper and environmental-friendly oxygen *** general,these protocols have advantages such as using non-precious and earth-abundant metal catalyst,no extra additive,high efficiency and regioselectivity.A gram-scale synthesis and the removal of the directing group further highlight its utility.

关键词： Spiro indene-2,1'-isoindolinones Spiro isochroman-3,1'-isoindolinones 3d Transition metals Cobalt-catalyzed C-H Activation Switchable[4+1]and[4+1+1]spirocyclization Aromatic amides 2-Diazo-1H-indene-1,3(2H)-dione

Design and preparation of a crosslinkable,oil-resistant,and bio-based elastomer from fumarate

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Science China Chemistry 2024年第2期67卷 622-631页

作者： Hui Yang Haijun Ji Xinxin Zhou Shihan Yang Liwei Li Chaoying Sun Weiwei Lei Runguo Wang Liqun Zhang Beijing State Key laboratory of Organic-Inorganic Composites&Beijing laboratory of Biomedical Materials Beijing University of Chemical TechnologyBeijing100029China Hubei Key laboratory of Polymer Materials Faculty of Materials Science and EngineeringHubei UniversityWuhan430062China

Poly(diethyl fumarate-co-methoxyethyl acrylate-co-vinyl chloroacetate)(PDEFMV),a novel bio-based elastomer with a saturated structure,was synthesized via redox emulsion *** glass-transition temperatures of PDEFMV,adjusted through the variation of the diethyl fumarate-to-methoxyethyl acrylate feeding ratio,ranged from-36.1 to-14.8 ℃.The number-average molecular weights of PDEFMV ranged from 384,000 to 46,000 g/*** designing the molecular structure,vinyl chloroacetate was used to provide active sites for subsequent vulcanization and *** active chlorine groups within the PDEFMV chain reacted with the crosslinking agent trithiocyanuric acid under high temperature and pressure to form a nonsulfur crosslinked three-dimensional network *** achieve the desired properties,carbon black(CB,N330) was incorporated to reinforce PDEFMV,leading to the formation of PDEFMV/CB composites.A comprehensive study was conducted on the high-temperature oil resistance of PDEFMV/CB *** immersion in IRM903 oil at temperatures of 150 and 200 ℃ for 72 h,the mass and volume changes in PDEFMV/CB were lower than those observed in commercially available acrylate rubber(AR)/CB,indicating that PDEFMV exhibited superior oil ***,the aging characteristics and mechanisms of oil resistance in the PDEFMV/CB and AR/CB composites were investigated at different temperatures(150,200,and 250 ℃).The results provide insights into the operational temperature ranges suitable for PDEFMV/CB and offer valuable guidance for potential industrial applications.

关键词： diethyl fumarate molecular design bio-based elastomer solvent-free synthetic route high-temperature oil resistance

A credible traffic prediction method based on self-supervised causal discovery

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Science China(Information Sciences) 2024年第5期67卷 244-258页

作者： Dan WANG Yingjie LIU Bin SONG State Key laboratory of Integrated Services Networks Xidian University

Next-generation wireless network aims to support low-latency, high-speed data transmission services by incorporating artificial intelligence(AI) technologies. To fulfill this promise, AI-based network traffic prediction is essential for pre-allocating resources, such as bandwidth and computing power. This can help reduce network congestion and improve the quality of service(QoS) for users. Most studies achieve future traffic prediction by exploiting deep learning and reinforcement learning, to mine spatio-temporal correlated variables. Nevertheless, the prediction results obtained only by the spatio-temporal correlated variables cannot reflect real traffic changes. This phenomenon prevents the true prediction variables from being inferred, making the prediction algorithm perform poorly. Inspired by causal science, we propose a novel network traffic prediction method based on self-supervised spatio-temporal causal discovery(SSTCD). We first introduce the Granger causal discovery algorithm to build a causal graph among prediction variables and obtain spatio-temporal causality in the observed data, which reflects the real reasons affecting traffic ***, a graph neural network(GNN) is adopted to incorporate causality for traffic prediction. Furthermore,we propose a self-supervised method to implement causal discovery to to address the challenge of lacking ground-truth causal graphs in the observed data. Experimental results demonstrate the effectiveness of the SSTCD method.

关键词： wireless network traffic prediction causal discovery self-supervised