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Challenges and opportunities in Quaternary palynology

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Science china Earth Sciences 2024年第7期67卷 2148-2161页

作者： qinghai XU Houyuan LU Zhuo ZHENG College of Geographical Sciences Hebei Key Laboratory of Environmental Change and Ecological ConstructionHebei Normal UniversityShijiazhuang 050024China Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China School of Earth Sciences and Engineering Sun Yat-sen UniversityZhuhai 519082China

Quaternary palynology plays a pivotal role in investigating global climate change and various other research fields,serving as an essential tool for the quantitative analysis of paleoenvironment ***,due to the vast diversity of terrestrial ecosystems and intricate interactions between vegetation,climate,and human activities,further advancements are required in the following aspects within this discipline.(1)The accuracy of classification in pollen morphology and fossil pollen identification needs improvement,particularly at the species *** represents a significant challenge in present Quaternary ***-aided intelligent recognition holds promise as a solution for species identification based on more detail pollen morphology.(2)Most pollen-based vegetation and climate reconstructions overlook the significance of bare *** bare ground can lead to substantial inaccuracies when quantitatively reconstructing past vegetation and climate.(3)While pollen records provide reliable information on paleoclimate changes,current quantitative climate reconstruction models heavily rely on modern pollen datasets derived from present-day vegetation disturbed more or less by human *** introduces bias and uncertainties into paleoclimate reconstruction.(4)Although pollen can serve as an indicator of human activities,accurately quantifying the intensity of human influence remains *** accurate identification of crop pollen,reconstructing reliable land cover/use data,and integrating multidisciplinary data may enhance the identification and quantification of signals related to human activity in pollen records.

关键词： Quaternary palynology Paleoclimate Paleovegetation Human activity

Probabilistic-Ellipsoid Hybrid Reliability Multi-Material Topology Optimization Method Based on Stress Constraint

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computer Modeling in Engineering & Sciences 2024年第7期140卷 757-792页

作者： Zibin Mao qinghai Zhao Liang Zhang College of Mechanical and Electrical Engineering Qingdao UniversityQingdao266071China National Engineering Research Center for Intelligent Electrical Vehicle Power System Qingdao UniversityQingdao266071China

This paper proposes a multi-material topology optimization method based on the hybrid reliability of the probability-ellipsoid model with stress constraint for the stochastic uncertainty and epistemic uncertainty of mechanical loads in optimization *** probabilistic model is combined with the ellipsoidal model to describe the uncertainty of mechanical *** topology optimization formula is combined with the ordered solid isotropic material with penalization(ordered-SIMP)multi-material interpolation *** stresses of all elements are integrated into a global stress measurement that approximates the maximum stress using the normalized p-norm ***,the sequential optimization and reliability assessment(SORA)is applied to transform the original uncertainty optimization problem into an equivalent deterministic topology optimization(DTO)*** response surface and sparse grid technique are combined with SORA to get accurate information on the most probable failure point(MPP).In each cycle,the equivalent topology optimization formula is updated according to the MPP information obtained in the previous *** adjoint variable method is used for deriving the sensitivity of the stress constraint and the moving asymptote method(MMA)is used to update design ***,the validity and feasibility of the method are verified by the numerical example of L-shape beam design,T-shape structure design,steering knuckle,and 3D T-shaped beam.

关键词： Stress constraint probabilistic-ellipsoid hybrid topology optimization reliability analysis multi-material design

Selective hydrodeoxygenation of guaiacol to cyclohexanol using activated hydrochar-supported Ru catalysts

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Frontiers of Chemical Science and Engineering 2024年第5期18卷 13-22页

作者： Kaile Li Shijie Yu qinghai Li Yanguo Zhang Hui Zhou Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Beijing Key Laboratory of CO_(2) Utilization and Reduction TechnologyDepartment of Energy and Power EngineeringTsinghua UniversityBeijing 100084China department of Chemical and Biomolecular Engineering National University of SingaporeSingapore117585Singapore

Lignin,an abundant aromatic polymer in nature,has received significant attention for its potential in the production of bio-oils and chemicals owing to increased resource availability and environmental *** hydrodeoxygenation of guaiacol,a lignin-derived monomer,can produce cyclohexanol,a nylon precursor,in a carbon-negative and environmentally friendly *** study explored the porous properties and the effects of activation methods on the Ru-based catalyst supported by environmentally friendly and cost-effective *** selective cleavage of C_(ary)-O bonds was achieved under mild conditions(160°C,0.2 MPa H_(2),and 4 h),and alkali activation further improved the catalytic *** characterization methods revealedthat hydrothermal treatment and alkali activation relatively contributed to the excellent performance of the catalysts and influenced their porous structure and Ru dispersion.X-ray photoelectron spectroscopy results revealed an increased formation of metallic ruthenium,indicating the effective regulation of interaction between active sites and *** synergistic approach used in this study,involving the valorization of cellulose-derived hydrochar and the selective production of nylon precursors from lignin-derived guaiacol,indicated the comprehensive and sustainable utilization of biomass resources.

关键词： hydrochar guaiacol cyclohexanol activation full-component utilization

Cooperation between single atom catalyst and support to promote nitrogen electroreduction to ammonia:A theoretical insight

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Journal of Energy Chemistry 2024年第9期96卷 336-344页

作者： Wanying Guo Siyao Wang Hongxia Wang qinghai Cai Jingxiang Zhao College of Chemistry and Chemical Engineering Harbin Normal UniversityHarbin 150025HeilongjiangChina

The co-catalysis between single atom catalyst(SAC)and its support has recently emerged as a promising strategy to synergistically boost the catalytic activity of some complex electrochemical reactions,encompassing multiple intermediates and ***,we utilized defective BC_(3)monolayer-supported SACs as a prototype to investigate the cooperative effects of SACs and their support on the catalytic performance of the nitrogen reduction reaction(NRR)for ammonia(NH_(3))*** results showed that these SACs can be firmly stabilized on these defective BC_(3)supports with high stability against ***,co-activation of the inert N_(2)reactant was observed in certain embedded SACs and their neighboring B atoms on certain BC3 sheets due to the noticeable charge transfer and significant N–N bond *** high-throughput screening revealed that the Mo/DV_(CC)and W/DV_(CC)exhibit superior NRR catalytic performance,characterized by a low limiting potential of−0.33 and−0.43 V,respectively,which can be further increased under acid conditions based on the constant potential ***,varying NRR catalytic activities can be attributed to the differences in the valence state of active ***,further microkinetic modeling analysis displayed that the turnover frequency of N_(2)–to–NH_(3)conversion on Mo/DV_(CC)is as large as 1.20×10^(−3)s^(−1)site^(−1) at 700 K and 100 bar,thus guaranteeing its ultra-fast reaction *** results not only suggest promising advanced electrocatalysts for NRR but also offer an effective avenue to regulate the electrocatalytic performance via the co-catalytic metal–support interactions.

关键词： Co-catalysis Single atom catalyst Nitrogen reduction DFT computations

New possibility for PET plastic recycling by a tailored hydrolytic enzyme

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Green Energy & Environment 2024年第2期9卷 163-165页

作者： Shijie Yu qinghai Li Yanguo Zhang Hui Zhou Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Beijing Key Laboratory of CO_(2)Utilization and Reduction TechnologyDepartment of Energy and Power EngineeringTsinghua UniversityBeijing 100084China

Plastic waste puts a huge burden on the ecosystem due to the current lack of mature recycling ***(ethylene terephthalate)(PET)is one of the most produced plastics in the *** decomposition holds the promise of recovering monomers from PET plastic,and the monomers can be used to regenerate new PET ***,there are still limitations in the activity and thermal stability of the existing PET *** recent study by Lu et *** a novel PET hydrolase via machine learning-aided *** obtained PET hydrolase showed excellent activity and thermal stability in the hydrolysis of PET and is capable of directly degrading large amounts of postconsumer PET *** approach provides an effective method for recycling PET waste and is expected to improve the current state of plastic pollution worldwide.

关键词： Plastic waste Poly(ethylene terephthalate) Hydrolysis Machine learning Enzymatic depolymerization Hydrolases

Electrolysis of Magnesia from Bischofite in qinghai Salt Lakes

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Rare Metals 2001年第4期20卷 209-212页

作者： Huimin Lu1, Lanlan Yu1, Pei Liang2, Yitian Liang2 1)department of Nonferrous Metallurgy, university of Science and Technology Beijing, Beijing 100083, china 2) Laboratory of Nonferrous Metallurgy, qinghai university. xining 810016, china 北京科技大学北京 100083 青海大学青海西宁 810016

A new technique of magnesia electrolysis from bischofite in qinghai salt lakes was investigated experimentally. Magnesia was prepared by ammonia processing. On an electrolysis cell of about 100 A capacity at 700degreesC, magnesium metal was obtained with a current efficiency of 90.23% and a specific energy consumption of 11.5 kW(.)h. The new technique has the advantages of energy saving, high current efficiency and environmental amity.

关键词： bischofite ammonia processing magnesia molten salt electrolysis

All-optical nanoscale thermometry with silicon carbide color centers

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Photonics Research 2024年第8期12卷 1696-1702页

作者： CHENGYING LIU HAIBO HU ZHENGTONG LIU SHUMIN XIAO JUNFENG WANG YU ZHOU qinghai SONG Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System Guangdong Provincial Key Laboratory of Semiconductor Optoelectronic Materials and Intelligent Photonic SystemsHarbin Institute of TechnologyShenzhen 518055China Pengcheng Laboratory Shenzhen 518055China Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area Shenzhen-Hong Kong International Science and Technology ParkShenzhen 518045China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China College of Physics Sichuan UniversityChengdu 610065China

All-optical thermometry plays a crucial role in precision temperature measurement across diverse *** defects in solids are one of the most promising sensors due to their excellent sensitivity,stability,and ***,it faces limitations,such as the microwave heating effect and the complexity of spectral *** these challenges,we introduce a novel approach to nanoscale optical thermometry using quantum defects in silicon carbide(SiC),a material compatible with complementary metal-oxide-semiconductor(CMOS)*** method leverages the intensity ratio between anti-Stokes and Stokes emissions from SiC color centers,overcoming the drawbacks of traditional techniques such as optically detected magnetic resonance(ODMR)and zero-phonon line(ZPL)*** technique provides a real-time,highly sensitive(1.06%K^(-1)),and diffraction-limited temperature sensing protocol,which potentially helps enhance thermal management in the future miniaturization of electronic components.

关键词： carbide optical centers

SpikingMiniLM: energy-efficient spiking transformer for natural language understanding

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Science china(Information Sciences) 2024年第10期67卷 115-128页

作者： Jiayu ZHANG Jiangrong SHEN Zeke WANG qinghai GUO Rui YAN Gang PAN Huajin TANG College of computer Science and Technology Zhejiang University The State Key Lab of Brain-Machine Intelligence Zhejiang University Collaborative Innovation Center of Artificial Intelligence Zhejiang University Advanced Computing and Storage Laboratory Huawei Technologies Co. Ltd. College of computer Science and Technology Zhejiang University of Technology MOE Frontier Science Center for Brain Science and Brain-Machine Integration Zhejiang University

In the era of large-scale pretrained models, artificial neural networks（ANNs） have excelled in natural language understanding（NLU） tasks. However, their success often necessitates substantial computational resources and energy consumption. To address this, we explore the potential of spiking neural networks（SNNs） in NLU——a promising avenue with demonstrated advantages, including reduced power consumption and improved efficiency due to their event-driven characteristics. We propose the SpikingMiniLM,a novel spiking Transformer model tailored for natural language understanding. We first introduce a multi-step encoding method to convert text embeddings into spike trains. Subsequently, we redesign the attention mechanism and residual connections to make our model operate on the pure spike-based paradigm without any normalization technique. To facilitate stable and fast convergence, we propose a general parameter initialization method grounded in the stable firing rate principle. Furthermore, we apply an ANN-to-SNN knowledge distillation to overcome the challenges of pretraining SNNs. Our approach achieves a macro-average score of 75.5 on the dev sets of the GLUE benchmark, retaining 98% of the performance exhibited by the teacher model MiniLMv2. Our smaller model also achieves similar performance to BERTMINIwith fewer parameters and much lower energy consumption, underscoring its competitiveness and resource efficiency in NLU tasks.

关键词： spiking neural networks natural language understanding spiking Transformer spike-based attention multi-step encoding ANN-to-SNN distillation

Composite Braking Control Strategy for Electromechanical-Hydraulic Vehicles

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CSEE Journal of Power and Energy Systems 2024年第4期10卷 1722-1732页

作者： Zewen Meng Jichao Hong Hongxin Zhang Tiezhu Zhang Xiaoming Xu qinghai Zhao Jian Yang College of Mechanical and Electrical Engineering Qingdao UniversityQingdao 260071China Power Integration and Energy Storage Systems Engineering Technology Center(Qingdao) Qingdao 260071China School of Mechanical Engineering University of Science and Technology BeijingBeijing 100083China Shunde Graduate School of university of Science and Technology Beijing Foshan 528000China

Short driving ranges and low braking energy recovery efficiencies are two recognized technical bottlenecks to be overcome in electric vehicles. In this paper, a novel electromechanical-hydraulic coupling system is proposed and integrated as a powertrain for electric vehicles, which can assist the electric vehicle to fully utilize its braking energy. The hydraulic regenerative braking force and electric regenerative braking force can provide all the braking needs using the medium and small braking intensities. Furthermore, an improved compound brake control strategy based on the braking force distribution is proposed and simulated. The results show that under the premise of ensuring braking stability, the electromechanical-hydraulic coupling driving electric vehicle can adapt to various working conditions with excellent energy-saving results. The hydraulic accumulator recovery efficiency is above 99%, and the state of charge consumption rate of the battery pack can be reduced by more than 9%. More importantly, the proposed hybrid power system can significantly improve the driving range and energy efficiency, as well as reduce the consumers' mileage anxiety in electric vehicles.

关键词： Braking control strategy electric vehicle electromechanical-hydraulic coupling energy recovery state of charge