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Performance Analysis of a Coupled System based on Organic Rankine Cycle and Double Effect Absorption Refrigeration for Waste Heat Recovery in Data Center

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Journal of Thermal Science 2025年第1期34卷 188-205页

作者： LI Peng XU Jiaqi WANG Binbin LIU Jianyang zhao wensheng HAN Zhonghe School of Energy Power and Mechanical Engineering North China Electric Power University Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology North China Electric Power University

During data center operation,it generates a significant volume of low-grade waste *** recover waste heat,a coupled system including solar collector,double effect absorption refrigeration and organic Rankine cycle is *** system performance is analyzed in *** the organic Rankine cycle,five organic working fluids(R245fa,R245ca,R123,R11,and R113) are selected.R245fa,R113 and R245ca obtain the maximum net power output,thermal efficiency and exergy efficiency,*** the double effect absorption refrigeration system,the evaporation temperature,condensation temperature,and generation pressure affect the COP and exergy *** the generator pressure is unchanged,the COP increases with increasing evaporation temperature and decreasing condensation *** the COP reaches 1.3,the COP slightly decreases as the evaporation temperature or condensation temperature ***,the exergy efficiency of refrigeration systems exhibits the same trend as the COP,and the exergy efficiency maximum value appears at approximately 0.32.A new performance indicator,rPUE,was defined to evaluate the data center power utilization *** flow distribution ratio and heat source temperature were optimized with multi-objective *** the mass flow distribution rate is 0.6 and the heat source temperature is 441.5 K,rPUE and the total unit production costs of the system obtain the optimal solution.

关键词： Exergy

Numerical simulations of propeller cavitation flows based on OpenFOAM

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Journal of Hydrodynamics 2020年第6期32卷 1071-1079页

作者： Min-sheng zhao Wei-wen zhao de-cheng Wan Computational Marine Hydrodynamics Lab(CMHL) State Key Laboratory of Ocean EngineeringSchool of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

In order to study the cavitation and hydrodynamic characteristics of propeller under uniform and non-uniform flows,numerical investigations are performed using interPhaseChangeDyMFoam in the open source computational fluid dynamics(CFD)software platform OpenFOAM with Schnerr-Sauer cavitation *** simulation results can be used as a reference to evaluate the working ability of a propeller in case of actual navigation.A new grid encryption method is adopted in the research to better capture the existence of vortex cavitation at the propeller *** method of function input is carried out in the study to simulate the condition of non-uniform flow and reduce the calculation *** unsteady dynamics are predicted by the Reynolds-averaged Navier-Stokes(RANS)method with a modified shear stress transport(SST)k−ωturbulence *** numerical results of the propeller such as cavitation shape and pressure distribution under uniform and non-uniform flow are analyzed and compared with each other.

关键词： OpenFOAM E779A propeller cavitation non uniform flow

Experimental study of dual nano-network, high-temperature resistant aerogel material as an integration of thermal management functions

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Journal of Energy Chemistry 2025年第1期100卷 157-170页

作者： Yueyue Xiao Tianke Mao Zun zhao Yuelei Pan Heping Zhang Xudong Cheng State Key Laboratory of Fire Science University of Science and Technology of China

Thermal management system is highly desirable to guarantee the performance and thermal safety of lithium-ion batteries,but it reduces the energy density of battery modules and even is unable to provide highly effective ***,a thermal management function integrated material is presented based on high-temperature resistant aerogel and phase change material and is applied at both charge–discharge process and thermal runaway *** this sandwich structure Paraffin@SiC nanowire/Aerogel sheet （denoted as PA@SAS） system,SiC nanowires endow the middle aerogel sheet （SAS） a dual nano-network *** enhanced mechanical properties of SAS were studied by compressive tests and dynamic mechanical ***,the thermal conductivity of SAS at 600°C is only 0.042 W/（m K）.The surface phase change material layers facilitate temperature uniformity of batteries （surface temperature difference less than 1.82°C） through latent ***,a large-format battery module with four 58 Ah LiNi0.5Co0.2Mn0.3O2LIBs was ***@SAS successfully prevents thermal runaway propagation,yielding a temperature gap of 602°C through the 2 mm-thick cross ***@SAS also exhibits excellent performance in other safety issues such as temperature rise rate,flame heat flux,*** lightweight property and effective insulation performance achieves significant safety enhancement with mass and volume energy density reduction of only 0.79%and 5.4%,*** originality of the present research stems from the micro and macro structure design of the proposed thermal management material and the combination of intrinsic advantages of every *** work provides a reliable design of achieving the integration of thermal management functions into an aerogel composite and improves the thermal safety of lithium-ion batteries.

关键词： Thermal insulation

Channel pruning on frequency response

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Science China(Information Sciences) 2025年第1期68卷 159-170页

作者： Hang LIN Yifan PENG Lin BIE Chenggang YAN Xibin zhao Yue GAO School of Software Tsinghua University School of Automation Hangzhou Dianzi University

Network pruning has a significant role in reducing network parameters and accelerating the inference time of the network. Some existing methods prune the network based on the frequency of the data, and finally obtain a sub-network with high accuracy. However, according to our experimental analysis, different frequencies of information in the data contribute differently to the accuracy of the model, and using this information directly for pruning without making a selection will lead to incorrect results. We believe that pruning should retain the convolutional kernels in the network that process important information, while those kernels that process unimportant information should be removed. In this paper, we first investigate the meaning of each frequency band information in the spectrum and their contribution to the prediction accuracy of the network,and according to these results, we propose a new pruning method based on frequency response(PFR). Our PFR finds and removes the convolutional kernels in the network that specialize in processing unimportant information, resulting in a compact neural network model. PFR obtains significant experimental results on different datasets, for example, a 56.0% raduction of float points operations(FLOPs) on Res Net-50 and only 0.37% of Top-1 accuracy degradation on the Image Net dataset.

关键词： deep learning model compression filter pruning channel pruning frequency response

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Engineering nanoparticle structure at synergistic Ru-Na interface for integrated CO2 capture and hydrogenation

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Journal of Energy Chemistry 2025年第1期100卷 779-791页

作者： Hanzi Liu Ling Cen Xinlin Xie Lei Liu zhao Sun Zhiqiang Sun Hunan Engineering Research Center of Clean and Low-Carbon Energy Technology School of Energy Science and Engineering Central South University

The development of dual functional material for cyclic CO2capture and hydrogenation is of great significance for converting diluted CO2into valuable fuels,but suffers from kinetic limitation and deactivation of adsorbent and ***,we engineered a series of RuNa/γ-Al2O3materials,varying the size of ruthenium from single atoms to clusters/*** coordination environment and structure sensitivity of ruthenium were quantitatively investigated at atomic *** findings reveal that the reduced Ru nanoparticles,approximately 7.1 nm in diameter with a Ru-Ru coordination number of 5.9,exhibit high methane formation activity and selectivity at 340°*** Ru-Na interfacial sites facilitate CO2migration through a deoxygenation pathway,involving carbonate dissociation,carbonyl formation,and ***-situ experiments and theoretical calculations show that stable carbonyl intermediates on metallic Ru nanoparticles facilitate heterolytic C–O scission and C–H bonding,significantly lowering the energy barrier for activating stored CO2.

关键词： Carbon capture and utilization

Flow characteristics and bubble statistics during the fragmentation process of the ingested main cavity in plunging breaking waves

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Journal of Hydrodynamics 2024年第3期36卷 546-555页

作者： wen-bin Zhang Wei-wen zhao de-cheng Wan Computational Marine Hydrodynamics Lab(CMHL) School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

Plunging breaking waves play an important role in the exchange of heat,momentum,and mass between the atmosphere and *** this paper,a series of direct numerical simulations is conducted to investigate the fragmentation process of the ingested main cavity in plunging breaking *** two-phase Navier-Stokes equations are solved using the finite-volume method based on adaptive refinement *** free surface is captured using a geometrical volume of fluid *** 2-D,3-D simulations are *** flow fields at different stages of wave breaking are presented and quantitative analysis for bubbles is *** 2-D instantaneous vorticity field and local velocity field are visualized to discuss the general flow characteristics during the fragmentation *** a 2-D parametric study is conducted to investigate the differences in the flow characteristics during the fragmentation process under different wave parameters including initial wave steepness(ε),Bond number(Bo),and Reynolds number(Re).3-D vortex structures are shown to further investigate the mechanisms behind the differences in the flow *** bubble size distributions under two different initial wave steepness are also discussed with their relationship to the fragmentation process of the ingested main *** research offers a significant understanding of the distinct procedures and fundamental dynamics involved in wave breaking,enhancing our comprehension of this intricate event.

关键词： Plunging breaking waves multiphase flow bubble statistics

Rise of β-furanosyl ribonucleosides as the extant RNA component facilitated by simple divalent transition-metal minerals

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Science China Chemistry 2025年

作者： Qianqian Chen Haoxing Xu Bingyue zhao Yeersen Patehebieke Zerun zhao Xiao Wang School of Chemistry and Chemical Engineering Nanjing University Frontiers Science Center for Critical Earth Material Cycling Nanjing University

The selective nucleoside synthesis through direct condensation between nucleobase and unactivated sugar in aqueous media has long been a formidable obstacle for the early chemical transformations hypothesized to construct the RNAWorld, due to product complexity and the low selectivity of the desired isomer. The preference of β-furanoside, the extant RNA component, has never been documented. Here we report an aqueous ribosylation mediated by divalent transition-metal ions, which unprecedentedly enhances the selectivity of furanosyl ribonucleosides as opposed to the traditionally predominating pyranosyl ones, with the furanoside/pyranoside ratio reaching up to 9/1. Furthermore, β-furanoside stands out for the first time as the most prevalent isomer in the presence of zinc and ammonium salts. The mechanism of this selectivity is elucidated with density functional theory calculations. The selectivity for β-furanoside can be further elevated via the adsorption on a zinc mineral. These findings exhibit as the first example that the selection of nucleosides with the desired, canonical configuration might be completed in the early stage of the RNA-forming process as opposed to later evolution, promoted by simple and widespread transition-metal minerals. The study may also find its value in synthetic chemistry as a guideline for developing a sustainable and selective glycosylation process.

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Oxygen vacancies enriched Ir/WOx catalysts for the directly chem-catalytic conversion of cellulose to ethanol

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Tungsten 2025年第1期7卷 88-99页

作者： Yu-Jing weng zhao-Ying Ding Ying-Chao Li Yuan-Feng Wu Yuan-Yang Xu Rui Chen Xiao-Lei zhao Hai-Yong Wang Da-Lei Zhang Yu-Long Zhang Henan Key Laboratory of Coal Green Conversion and International Joint Laboratory of Coal Clean Utilization College of Chemistry and Chemical Engineering Henan Polytechnic University Key Laboratory of Renewable Energy Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Liaoning Institute of Energy Technology

Tungsten and its oxides are highly versatile catalysts with unique properties that hold great promise for a wide array of applications,including biological pathways and chemical *** chemo-catalysis of cellulose to ethanol presents a promising avenue for ethanol synthesis with the potential for enhanced efficiency compared to conventional methods,offering a sustainable and carbon-neutral alternative to existing petrochemical and biological ***,Ir/WOxcatalysts enriched with oxygen vacancies were meticulously prepared and demonstrated remarkable catalytic performance in converting cellulose to ethanol directly in the presence of tungstic *** catalyst achieved a high ethanol yield of 66.5%under optimal reaction conditions,approaching the theoretical yield limit of traditional ethanol *** results revealed the presence of oxygen defects,Bronsted/Lewis acidity,and Ir nanoclusters on the catalyst surface,working synergistically to facilitate the cascade catalysis of cellulose hydrolysis,sugar retro-aldol condensation reaction,and C2 intermediate hydrodeoxygenation to *** situ Fourier transform infrared spectrometer analysis confirmed the catalyst's ability to enhance the adsorption and activation of ethylene glycol for ethanol *** manipulating subtle structural features,this study offers a fresh perspective on tungsten group catalyst design and underscores the importance of synergistic effects among catalytic sites for the efficient production of ethanol from cellulose.

关键词： Cellulosic ethanol Chem-catalysis Hydrogenolysis Retro-aldol condensation Tungsten

Unraveling the significance of cobalt on transformation kinetics,crystallography and impact toughness in high-strength steels

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International Journal of Minerals,Metallurgy and Materials 2025年第2期32卷 380-390页

作者： Yishuang Yu Jingxiao zhao Xuelin Wang Hui Guo Zhenjia Xie Chengjia Shang Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic *** results show that the Co-bearing steel exhibits finer blocks and a lower ductile-brittle transition temperature than the steel without ***,the Co-bearing steel reveals higher transformation rates at the intermediate stage with bainite volume fraction ranging from around 0.1 to *** improved impact toughness of the Co-bearing steel results from the higher dense block boundaries dominated by the V1/V2 variant ***,the addition of Co induces a larger transformation driving force and a lower bainite start temperature(BS),thereby contributing to the refinement of blocks and the increase of the V1/V2 variant *** findings would be instructive for the composition,microstructure design,and property optimization of high-strength steels.

关键词： high-strength steel cobalt transformation kinetics crystallography impact toughness

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