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Recyclable High-performance Carbon Fiber Reinforced Epoxy Composites Based on Dithioacetal Covalent Adaptive Network

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Chinese Journal of Polymer Science 2024年第10期42卷 1514-1524,I0011页

作者： Gui-Lian Shi Ting-Cheng Li Dao-Hong zhang jun-heng zhang Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education&Hubei Key Laboratory of Catalysis and Materials Science Hubei R&D Center of Hyperbranched Polymers Synthesis and ApplicationsSouth-Central Minzu UniversityWuhan430074China State Key Laboratory of New Textile Materials and Advanced Processing Technologies Wuhan Textile UniversityWuhan430200China Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials Hubei UniversityWuhan430062Chin

Recycling of carbon fiber reinforced composites is important for sustainable development and the circular *** the use of dynamic chemistry,developing high-strength recyclable CFRPs remains a major challenge due to the mutual exclusivity between the dynamic and mechanical properties of ***,we developed a high-strength recyclable epoxy resin(HREP)based on dynamic dithioacetal covalent adaptive network using diglycidyl ether bisphenol A(DGEBA),pentaerythritol tetra(3-mercapto-propionate)(PETMP),and vanillin epoxy resin(VEPR).At high temperatures,the exchange reaction of thermally activated dithioacetals accelerated the rearrangement of the network,giving it significant reprocessing ***,HREP exhibited excellent solvent resistance due to the increased cross-linking *** this high-strength recyclable epoxy resin as the matrix and carbon fiber modified with hyperbranched ionic liquids(HBP-AMIM+PF6-)as the reinforcing agent,high performance CFRPs were successfully *** tensile strength,interfacial shear strength(IFSS)and interlaminar shear strength(ILSS)of the optimized formulation(HREP20/CF-HBPPF6)were 1016.1,70.8 and 76.0 MPa,*** addition,the CFRPs demonstrated excellent solvent and acid/*** CFRPs could completely degrade within 24 h in DMSO at 140℃,and the recycled CF still maintained the same tensile strength and ILSS as the original after multiple degradation cycles.

关键词： Epoxy resin Hyperbranched ionic liquid Recycling Carbon fiber Composites

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Large low-field reversible magnetocaloric effect in K_(3)Gd(PO_(4))_(2) at sub-Kelvin temperature

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Journal of Rare Earths 2024年第6期42卷 1087-1092,I0003页

作者： Haojie Wang Zhaojun Mo Jianjian Gong heng Tu Guochun zhang jun Shen School of Rare Earths University of Science and Technology of ChinaHefei230026China Ganjiang Innovation Academy Chinese Academy of SciencesGanzhou341119China Center for Crystal Research and Development Key Laboratory of Functional Crystals and Laser TechnologyKey Laboratory of CryogenicsTechnical Institute of Physics and ChemistryChinese Academy of SciencesBeijing100190China Department of Energy and PowerEngineering School of Mechanical EngineeringBeijing Institute of TechnologyBeijing100081China

We synthesized a potassium gadolinium phosphate K3Gd(PO_(4))_(2)with monoclinic structure(P2_(1/m))by the high-temperature solid-state reaction *** lattice constants obtained by Rietveld refinements of XRD curve are a=0.7411 nm,b=0.5624 nm,and c=0.9433 *** and magnetocaloric properties of K_(3)Gd(PO_(4))_(2)were investigated in *** magnetic phase transition temperature of K3Gd(PO_(4))2 was determined by ultra-low temperature testing to be 0.58 K.K_(3)Gd(PO_(4))2 exhibits large magnetic entropy changes(-ΔSM).The maximum-ΔSM are 20.2 and 29.4 J/(kg·K)in the magnetic field variation(ΔH)of 1 and 2 T,respectively,which are larger than that of the commercial Gd_(3)Ga_(5)O_(12)(GGG).The maximum adiabatic temperature change(ΔT_(ad))reaches 5.91 K under a magnetic field change(ΔH)of 1 T.K_(3)Gd(PO_(4))_(2)is a potential magnetic refrigeration material for obtaining sub-Kelvin temperatures.

关键词： Ultra-low temperature Magnetocaloric effect Magnetic entropy change Magnetic refrigeration Rare earths

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Preparation and Rheological Characterization of Long Chain Branching Polyglycolide

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Chinese Journal of Polymer Science 2024年第8期42卷 1177-1184页

作者： Wei-Lin Liu Ming-Fu Lyu heng-Yuan zhang Jian-Ye Liu Shi-jun zhang Beijing University of Chemical Technology Beijing 100029China SINOPEC(Beijing)Research Institute of Chemical Industry Co. Ltd.Beijing 100013China

The long chain branching(LCB)polyglycolide(PGA)was successfully prepared by the successive reactions of the terminal hydroxyl groups of PGA with triglycidyl isocyanurate(TGIC)and pyromellitic dianhydride(PMDA).The influence of LCB produced by functional group reaction on rheological and crystallization behavior was studied and discussed through linear rheology,uniaxial elongation and DSC(differential scanning calorimetry).The much higher viscosity and the more notable strain hardening behavior of modified PGA indicates the LCB with high degree of entanglements are *** melt strength of PGA is finally improved greatly and can make su re that the supercritical CO_(2)foaming can be carried out successfully.

关键词： Polyglycolide(PGA) Long chain branching(LCB) Rheology

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Value iteration algorithm for continuous-time linear quadratic stochastic optimal control problems

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Science China(Information Sciences) 2024年第2期67卷 170-180页

作者： Guangchen WANG heng zhang School of Control Science and Engineering Shandong University

In this study, we investigate a continuous-time infinite-horizon linear quadratic stochastic optimal control problem with multiplicative noise in control and state variables. Using the techniques of stochastic stability, exact observability, and stochastic approximation, a value iteration algorithm is developed to solve the corresponding generalized algebraic Riccati equation. Unlike the existing policy iteration algorithm, this algorithm does not rely on an initial stabilizing control. Further, this algorithm can also be used to compute policy evaluation steps that arise in the policy iteration algorithm. Herein, a simulation example is provided to validate the obtained results.

关键词： stochastic systems optimal control linear quadratic stochastic problem generalized algebraic Riccati equation value iteration algorithm

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Multi-junction cascaded vertical-cavity surface-emitting laser with a high power conversion efficiency of 74%

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Light(Science & Applications) 2024年第3期13卷 555-565页

作者： Yao Xiao jun Wang heng Liu Pei Miao Yudan Gou Zhicheng zhang Guoliang Deng Shouhuan Zhou College of Electronics and Information Engineering Sichuan UniversityChengdu 610064China Suzhou Everbright Photonics Co. LtdSuzhou 215163China

High electro-optical conversion efficiency is one of the most distinctive features of semiconductor lasers as compared to other types of *** further increase remains a significant *** enhancing the efficiency of edgeemitting lasers(EEL),which represent the highest efficiency among semiconductor lasers at present,is *** efficiency of vertical cavity surface emitting lasers(VCSELs)has always been relatively low compared to *** paper,combining modeling with experiments,demonstrates the potential of multi-junction cascaded VCSELs to achieve high efficiency beyond that of EELs,our simulations show,that a 20-junction VCSEL can achieve an efficiency of more than 88%at room *** fabricated VCSEL devices with different numbers of junctions and compared their energy efficiency.15-junction VCSELs achieved a maximum efficiency of 74%at room temperature under nanosecond driving current,the corresponding differential quantum efficiency exceeds 1100%,being the largest electro-optical conversion efficiency and differential quantum efficiency reported until now for VCSELs.

关键词： cascaded power cavity

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An attention graph stacked autoencoder for anomaly detection of electro-mechanical actuator using spatio-temporal multivariate signals

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Chinese Journal of Aeronautics 2024年第9期37卷 506-520页

作者： Jianyu WANG heng zhang Qiang MIAO College of Electrical Engineering Sichuan UniversityChengdu 610065China

Health monitoring of electro-mechanical actuator(EMA)is critical to ensure the security of *** is difficult or even impossible to collect enough labeled failure or degradation data from actual *** autoencoder based on reconstruction loss is a popular model that can carry out anomaly detection with only consideration of normal training data,while it fails to capture spatio-temporal information from multivariate time series signals of multiple monitoring *** mine the spatio-temporal information from multivariate time series signals,this paper proposes an attention graph stacked autoencoder for EMA anomaly ***,attention graph con-volution is introduced into autoencoder to convolve temporal information from neighbor features to current features based on different weight ***,stacked autoencoder is applied to mine spatial information from those new aggregated temporal ***,based on the bench-mark reconstruction loss of normal training data,different health thresholds calculated by several statistic indicators can carry out anomaly detection for new testing *** comparison with tra-ditional stacked autoencoder,the proposed model could obtain higher fault detection rate and lower false alarm rate in EMA anomaly detection experiment.

关键词： Anomaly detection Spatio-temporal informa-tion Multivariate time series signals Attention graph convolution Stacked autoencoder

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Numerical manifold method for steady-state nonlinear heat conduction using Kirchhoff transformation

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Science China(Technological Sciences) 2024年第4期67卷 992-1006页

作者： zhang LiMei KONG heng Zheng Hong Key Laboratory of Urban Security and Disaster Engineering Ministry of EducationBeijing University of TechnologyBeijing 100124China Beijing Municipal Construction Co. Ltd.Beijing 100048China

The numerical manifold method(NMM)introduces the mathematical and physical cover to solve both continuum and discontinuum problems in a unified *** this study,the NMM for solving steady-state nonlinear heat conduction problems is presented,and heat conduction problems consider both convection and radiation boundary ***,the nonlinear governing equation of thermal conductivity,which is dependent on temperature,is transformed into the Laplace equation by introducing the Kirchhoff *** transformation reserves linearity of both the Dirichlet and the Neumann boundary conditions,but the Robin and radiation boundary conditions remain ***,the NMM is employed to solve the Laplace equation using a simple iteration procedure because the nonlinearity focuses on parts of the problem domain ***,the temperature field is retrieved through the inverse Kirchhoff *** examples are analyzed,demonstrating the advantages of the Kirchhoff transformation over the direct solution of nonlinear equations using the NewtonRaphson *** study provides a new method for calculating nonlinear heat conduction.

关键词： numerical manifold method nonlinear heat conduction temperature-dependent thermal conductivity Kirchhoff transformation convection and radiation boundary conditions

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Simulation of roof snow loads based on a multi-layer snowmelt model:Impact of building heat transfer

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Building Simulation 2024年第6期17卷 907-932页

作者： Xuanyi Zhou heng Chen Yue Wu Tiange zhang State Key Laboratory of Disaster Reduction in Civil Engineering Tongji UniversityShanghai200092China

To investigate the impact of building heat transfer on roof snow loads,roof snow loads and snow load thermal coefficients from 61 Chinese sites over a period of 50 years are simulated based on basic meteorological data such as temperature,humidity,wind speed,and precipitation,and a multi-layer snowmelt model considering the building heat ***,the accuracy of the multi-layer snowmelt model is validated using the data of observed ground snow load and roof snow melting *** relationship between meteorological conditions,snow cover characteristics,and thermal coefficients of snow loads in three representative sites is then ***,the characteristics of thermal coefficients in each zone are analyzed by combining them with the statistical results of meteorological data from 1960 to 2010,and the equations of thermal coefficients in different zones on indoor temperatures and roof heat transfer coefficients are fitted ***,the equations in this paper are compared with the thermal coefficients in the main snow load *** results indicate that the snowmelt model using basic meteorological data can effectively provide samples of roof snow *** the cold zone where the snow cover lasts for a long time and does not melt easily,the thermal coefficients of the snow loads on the heating buildings are lower than those in the warm zone due to the long-term influence of the heat from inside the *** coefficients are negatively correlated with indoor temperatures and roof heat transfer *** the indoor temperature is too low or the roof insulation is good,the roof snow load may exceed the ground snow *** thermal coefficients for heated buildings in the main snow load codes are more conservative than those calculated in this paper,and the thermal coefficients for buildings with lower indoor temperatures tend to be smaller.

关键词： snowmelt model roof snow load building heat transfer thermal coefficient load code

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Fluid identification and tight oil layer classification for the southwestern Mahu Sag,junggar Basin using NMR logging-based spectrum decomposition

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Energy Geoscience 2024年第2期5卷 62-69页

作者： Wenbiao Huang Yibing Guo jun Qin Zhongchen Ba Zongbin zhang Luning Bai heng Li School of Geosciences China University of Petroleum(East China)QingdaoShandong266580China PetroChina Xinjiang Oilfield Company KaramayXinjiang834000China

The intricate distribution of oil and water in tight rocks makes pinpointing oil layers *** conventional identification methods offer potential solutions,their limited accuracy precludes them from being effective in their applications to unconventional *** study employed nuclear magnetic resonance(NMR)spectrum decomposition to dissect the NMR T_(2)spectrum into multiple ***,it employed laboratory NMR experiments to ascertain the fluid properties of these sub-spectra,aiming to enhance identification *** findings indicate that fluids of distinct properties overlap in the T_(2)spectra,with bound water,movable water,bound oil,and movable oil appearing sequentially from the low-value zone to the high-value ***,an oil layer classification scheme was proposed,which considers the physical properties of reservoirs,oil-bearing capacity,and the characteristics of both mobility and the oil-water two-phase *** applied to tight oil layer identification,the scheme's outcomes align closely with actual test results.A horizontal well,deployed based on these findings,has produced high-yield industrial oil flow,underscoring the precision and dependability of this new approach.

关键词： Nuclear magnetic resonance Fluid identification Oil layer identification NMR T_(2)spectrum decomposition Normal distribution simulation

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Preparation,optical properties and energy transfer of SrLaAlO4:Dy3+,Eu3+

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Journal of Rare Earths 2024年第11期42卷 2058-2067页

作者： Wei Chen heng zhang Desheng Zhu School of Physic and Optoelectronic Engineering Yangtze University

A series of Dy3+/Eu3+single doped and co-doped SrLaAlO4phosphors was synthesized by the traditional high-temperature solid-state method,and their structure,morphology and optical properties were *** X-ray diffraction（XRD） shows a small amount of doping with Dy3+and Eu3+does not change the crystal structure of the matrix SrLaAlO4and the best synthesis temperature is 1450℃.The scanning electron microscopy（SEM） indicates the particle size directly ranges from 1 to 5μm roughly and the energy dispersive spectroscopy（EDS） patterns show that SrLaAlO4:Dy3+phosphor and SrLaAlO4:Dy3+,Eu3+phosphor were successfully ***4:Dy3+phosphor can be effectively excited by near-ultraviolet light,producing two strong emission lights at 483 nm（blue light） and 579 nm（yellow light）,presenting a cold white light;SrLaAlO4:Eu3+phosphor can be effectively excited by nearultraviolet light,producing red lights at 622 nm;the characteristic emission peaks of Dy3+and Eu3+can be shown simultaneously under the same excitation wavelength in SrLaAlO4:Dy3+, Eu3+*** changing the relative doping concentration ratio of Dy3+and Eu3+,the modulation of SrLaAlO4:Dy3+,Eu3+phosphor from cold white to warm white light can be *** addition,the study of the luminescent mechanism and lifetime shows that there is energy transfer between Dy3+and Eu3+in SrLaAlO4:Dy3+,Eu3+phosphor.

关键词： Energy transfer High-temperature solid-phase method Luminescence properties Rare earths SrLaAlO4: Dy3+, Eu3+ White phosphor

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