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Numerical Simulation Study on Influence of Equation of State on Internal Flow Field and Performance of S-CO_(2)Compressor

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Journal of Thermal Science 2024年第3期33卷 888-898页

作者： ZHANG Lei YANG Zhenyu SUN Enhui ZHANG Qian AN Guangyao YUAN Wei Hebei Key Laboratory of Low Carbon and high Efficiency Power Generation Technology North China Electric Power UniversityBaoding071003China school of Energy Power&Mechanical EngineeringNorth China Electric Power UniversityBaoding071028China

The low power consumption of the near-critical compressor is the key factor for the high efficiency of supercritical CO_(2)Brayton *** the numerical simulation of the compressor,the rapid changes in the thermophysical properties of the CO_(2)near the critical point make it difficult to capture the condensation *** paper investigates the influence of fluid physical properties on the condensation ***,the differences in the physical properties of CO_(2)in the SRK EOS(equation of state),PR EOS,and SW EOS are ***,the simulation of nozzles and compressors were carried out and *** show that the condensation positions predicted by the three EOSs are basically the *** with SW EOS,the disparities between the maximum condensation mass fraction predicted by the PR and SRK EOSs is5.7%and 11.5%,and that of total pressure ratio is 0.3%and 3.8%,*** results show that PR EOS can be considered for numerical simulation in engineering *** its physical property calculation results are closer to the actual physical properties while the physical properties change more gently,it has considerable accuracy and numerical stability.

关键词： supercritical carbon dioxide equation of state centrifugal compressor numerical simulation condensation

Perpendicularly assembled oriented electrospinning nanofibers based piezoresistive pressure sensor with wide measurement range

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Nano Research 2024年第7期17卷 6493-6501页

作者： Xiaoxue Bi Zhigang Duan Xiaojuan Hou Shuo Qian Mengjiao Yuan Jiajun Hu Jie Zhang Yuchen Lu Yanli Liu Jian He Zhiling Peng Xiujian Chou school of Mechanical and Electrical Engineering North University of ChinaTaiyuan 030051China Science and Technology on Electronic Test and Measurement Laboratory North University of ChinaTaiyuan 030051China school of Software North University of ChinaTaiyuan 030051China school of Information and Communication Engineering North University of ChinaTaiyuan 030051China

With the rapid development of wearable electronics,flexible pressure sensors have attracted wide attention in human–computer interaction and intelligent ***,it is a challenge to achieve a sensor with high sensitivity,wide measurement range,and wearing ***,we develop an oriented electrospinning thermoplastic polyurethane/polyacrylonitrile(TPU/PAN)nanofibers(OETPN)based piezoresistive pressure sensor(PONPS)in which the active layer and the electrode are assembled *** interdigital electrode is fabricated by spraying silver nanowires(AgNWs)on the OETPN through a mask *** active layer is composed of OETPN coated with MXene,encapsulated on the electrode by polyurethane(PU)*** porous structure of nanofibers membrane broadens the measurement range of the *** oriented nanofibers as active layer can improve the sensitivity in low pressure,because oriented nanofibers without interweaving nanofibers are more compressible than disordered *** prepared using the spraying method creates nanoscale microstructure and increases *** perpendicular assembly has greater response between the active layer and the electrode than the parallel assembly to improve the *** sensor exhibits high sensitivity(6.71 kPa^(−1),0.02–2 kPa)and wide measurement range(0.02–700 kPa).The sensor can detect weak signals such as radial artery.A pressure array constructed precisely represents the distribution of *** intelligent throat is created by combining machine learning algorithms with the *** can detect and recognize subtle throat vibrations while speaking,achieving recognition accuracy up to 100%using support vector machine(SVM)for five words with different *** fabricated sensor shows promising prospects in personal healthcare and intelligent robots.

关键词： oriented nanofibers perpendicular assembly parallel assembly intelligent throat machine learning algorithms

Temperature-sensing array using the metal-to-insulator transition of Nd_(x)Sm_(1-x)NiO_(3)

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1694-1700页

作者： Fengbo Yan Ziang Li Hao Zhang Yuchen Cui Kaiqi Nie Nuofu Chen Jikun Chen school of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China school of Renewable Energy North China Electric Power UniversityBeijing 102206China Beijing Synchrotron Radiation Facility Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China

Rare-earth nickelates(RENiO_(3))show widely tunable metal-to-insulator transition(MIT)properties with ignorable variations in lattice constants and small latent heat across the critical temperature(TMIT).Particularly,it is worth noting that compared with the more commonly investigated vanadium oxides,the MIT of RENiO_(3)is less abrupt but usually across a wider range of *** sheds light on their alternative applications as negative temperature coefficient resistance(NTCR)thermistors with high sensitivity compared with the current NTCR thermistors,other than their expected use as critical temperature resistance *** this work,we demonstrate the NTCR thermistor functionality for using the adjustable MIT of Nd_(x)Sm_(1-x)NiO_(3)within 200–400 K,which displays larger magnitudes of NTCR(e.g.,more than 7%/K)that is unattainable in traditional NTCR thermistor *** temperature dependence of resistance(R–T)shows sharp variation during the MIT of Nd_(x)Sm_(1-x)NiO_(3)with no hysteresis via decreasing the Nd content(e.g.,x≤0.8),and such a R–T tendency can be linearized by introducing an optimum parallel *** sensitive range of temperature can be further extended to 210–360 K by combining a series of Nd_(x)Sm_(1-x)NiO_(3)with eight rare-earth co-occupation ratios as an array,with a high magnitude of NTCR(e.g.,7%–14%/K)covering the entire range of temperatures.

关键词： rare-earth nickelates metal-to-insulator transition correlated oxides perovskites

ZIF-8-functionalized polymer electrolyte with enhanced performance for high-temperature solid-state lithium metal batteries

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Rare Metals 2024年第3期43卷 984-994页

作者： Jin-Fang Zhang Yuan-Yuan Wang Xiao-Feng Li Gen-Yan Zhang Ying Li Rong Liu Sheng-Liang Hu Tuo-Ping Hu Ruth Knibbe Qing-Bing Xia school of Materials Science and Engineering North University of ChinaTaiyuan030051China school of Energy and Power Engineering North University of ChinaTaiyuan030051China school of Chemistry and Chemical Engineering North University of ChinaTaiyuan030051China school of Mechanical and Mining Engineering The University of QueenslandBrisbaneQLD4072Australia

Solid polymer electrolytes(SPEs)with high ionic conductivity are desirable for solid-state lithium metal batteries(SSLMBs)to achieve enhanced safety and energy *** nanofillers into a polymeric matrix to develop nanocomposite solid electrolytes(NCSEs)has become a promising method for improving the ionic conductivity of the ***,a novel ZIF-8-functionalized NCSE was prepared for high-temperature S SLMB s using an in situ radical polymerization *** is found that the ZIF-8 nanoparticles could reduce the crystallinity of polymer segments and offer a Lewis acid surface that promotes the dissociation of lithium bis(trifluoromethanesulfonyl)imide(LiTFSI)and stabilizes the TFSI^(-) anion ***,the as-prepared NCSE exhibits an outstanding ionic conductivity of 1.63×10^(-3)S·cm^(-1),an electrochem ical stability window of 5.0 V at 80℃,and excellent interface compatibility with lithium metal anode with a stable polarization over 2000 ***,the assembled SSLMBs with LiFePO_(4)cathode show dendrite-free Li-metal surface,good rate capability,and stable cycling stability with a capacity retention of 70%over 1000 cycles at a high temperature of 80℃.This work provides valuable insights into promoting the ionic conductivity of SPEs.

关键词： Lithium metal batteries Metal-organic frameworks Solid polymer electrolytes Lithium metal anode Interfacial compatibility

Pre-Training Physics-Informed Neural Network with Mixed Sampling and Its Application in high-Dimensional Systems

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Journal of Systems Science & Complexity 2024年第2期37卷 494-510页

作者： LIU Haiyi ZHANG Yabin WANG Lei school of Mathematics and Physics North China Electric Power UniversityBeijing 102206China school of Control and Computer Engineering North China Electric Power UniversityBeijing 102206China

Recently,the physics-informed neural network shows remarkable ability in the context of solving the low-dimensional nonlinear partial differential ***,for some cases of high-dimensional systems,such technique may be time-consuming and *** this paper,the authors put forward a pre-training physics-informed neural network with mixed sampling(pPINN)to address these *** based on the initial and boundary conditions,the authors design the pre-training stage to filter out the set of the misfitting points,which is regarded as part of the training points in the next *** authors further take the parameters of the neural network in Stage 1 as the initialization in Stage *** advantage of the proposed approach is that it takes less time to transfer the valuable information from the first stage to the second one to improve the calculation accuracy,especially for the high-dimensional *** verify the performance of the pPINN algorithm,the authors first focus on the growing-and-decaying mode of line rogue wave in the Davey-Stewartson I *** case is the accelerated motion of lump in the inhomogeneous Kadomtsev-Petviashvili equation,which admits a more complex evolution than the uniform *** exact solution provides a perfect sample for data experiments,and can also be used as a reference frame to identify the performance of the *** experiments confirm that the pPINN algorithm can improve the prediction accuracy and training efficiency well,and reduce the training time to a large extent for simulating nonlinear waves of high-dimensional equations.

关键词： high-dimensional systems mixed sampling nonlinear wave pre-training physics-informed neural network

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Diophantine equations and Fermat's last theorem for multivariate(skew-)polynomials

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Applied Mathematics(A Journal of Chinese Universities) 2024年第1期39卷 159-173页

作者： PAN Jie JIA Yu-ming LI Fang school of Mathematical Sciences Zhejiang UniversityHangzhou 310058China Henan Experimental high school Zhengzhou 450003China

Fermat’s Last Theorem is a famous theorem in number theory which is diﬃcult to ***,it is known that the version of polynomials with one variable of Fermat’s Last Theorem over C can be proved very *** aim of this paper is to study the similar problems about Fermat’s Last Theorem for multivariate(skew)-polynomials with any characteristic.

关键词： Fermat's last theorem polynomial ring skew polynomial ring

Recent advances in nickel-based catalysts in eCO_(2)RR for carbon neutrality

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Carbon Energy 2024年第2期6卷 61-91页

作者： Weikang Peng Fengfeng Li Shuyi Kong Chenxi Guo Haotian Wu Jiacheng Wang Yi Shen Xianguang Meng Mingxi Zhang Hebei Key Laboratory of Inorganic Nonmetallic Materials School of Materials Science and EngineeringNorth China University of Science and TechnologyTangshanHebeiChina Hebei Iron and Steel Laboratory North China University of Science and TechnologyTangshanChina State Key Laboratory of high Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghaiChina school of Materials Science and Engineering Taizhou UniversityZhejiangChina

The excessive use of nonrenewable energy has brought about serious greenhouse *** CO_(2) into high-value-added chemicals is undoubtedly the best choice to solve energy *** to the excellent cost-effectiveness and dramatic catalytic performance,nickel-based catalysts have been considered as the most promising candidates for the electrocatalytic CO_(2) reduction reaction(eCO_(2)RR).In this work,the electrocatalytic reduction mechanism of CO_(2) over Ni-based materials is *** strategies to improve the eCO_(2)RR performance are ***,the research on Ni-based materials for syngas generation is briefly ***,the prospects of nickel-based materials in the eCO_(2)RR are provided with the hope of improving transition-metal-based electrocatalysts for eCO_(2)RR in the future.

关键词： carbon energy carbon neutrality CO_(2)reduction electrocatalysis nickel-based materials

Strengthening effect of prefabrication(10-12) tensile twinning on AZ80+0.4%Ce magnesium alloy and inhibition mechanism of discontinuous precipitation

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Journal of Magnesium and Alloys 2024年第5期12卷 1918-1930页

作者： Zhen Wang Xi Zhao Zhimin Zhang Yaojin Wu Kai Chen Xianwei Ren Dengkui Wang Wei Wang school of Mechanical and Electrical Engineering North University of China Engineering Technology Research Center for Integrated Precision Forming of Shanxi Province North University of China

This paper provided an effective method to further improve the mechanical properties of the AZ80+0.4%Ce magnesium alloy wheel spoke. The effect of high strength and ductility was obtained with a yield strength of 295.36 MPa, an elongation of 10%, by the combination of pre-deformation(7% deformation) and two-stage aging treatment(120 ℃/9 h + 175 ℃/24 h). The evolution of the microstructure and properties of the alloy was explored under the coupling conditions of different pre-deformation degrees and multi-stage aging. The results show that, pre-deformation introduced a large number of(■) tensile twinning and dislocations, which greatly promoted the probability of continuous precipitates(CPs) appearing. On the contrary, the discontinuous precipitates(DPs) were limited by the vertical and horizontal twin structure. As a result, the pre-nucleation method of two-stage aging increased the proportion of CPs by 34%-38%. Owing to the DPs was effectively suppressed, the alloy's yield strength has been greatly improved. Besides, under multi-stage aging, the twin boundaries induce protruding nucleation to form static recrystallization by hindering the migration of dislocations, and the matrix swallows the twins, then the texture gradually tilts from the two poles to the basal plane. As an important supplement, the grain refinement and oblique texture promoted the improvement of the yield strength of the component.

关键词： Magnesium alloy Pre-deformed Two-stage aging Tensile twinning Continuous precipitates Texture

Perception field based imitation learning for unlabeled multi-agent pathfinding

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Science China(Information Sciences) 2024年第5期67卷 115-135页

作者： Wenjie CHU Ailun YU Wei ZHANG Haiyan ZHAO Zhi JIN school of Computer Science Peking University Key Laboratory of high-Confidence Software Technologies (Peking University) Ministry of Education

This paper proposes an imitation learning method to learn a universal agent policy for unlabeled multi-agent pathfinding(unlabeled MAPF) in grid environments. The method transforms the unlabeled MAPF problem into a series of temporal-independent homogeneous classification problems for each *** on this transformation, a neural network is designed to imitate a distance-optimal expert *** neural network consists of two successive modules: perception field learner and field integrating *** former refines and encodes the current system state into a perception field for each agent by combining a set of learnable field-generating functions. The latter takes an agent's perception field as input and decides the agent's next action based on a triplet cross-attention mechanism. We evaluate our method on a diverse set of unlabeled MAPF tasks. Compared with state-of-the-art counterparts, the experimental results manifest the superiority of the proposed method in both generalization ability and scalability.

关键词： unlabeled multi-agent pathfinding perception field triplet cross-attention multi-agent imitation learning learning-based planning