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Characteristics and mechanism investigation on drag reduction of oblique riblets

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Journal of Central South University 2017年第6期24卷 1379-1386页

作者： GU Yun-qing FAN Tian-xing MOU Jie-gang wu deng-hao ZHENG Shui-hua College of Mechanical and Engineering Zhejiang University of TechnologyHangzhou 310014China Zhijiang College Zhejiang University of TechnologyHangzhou 310024China Institute National Polytechnique of Grenoble Joseph Fourier UniversityGrenoble 38031France

This work primarily focuses on the drag reduction characteristics and mechanism investigation of oblique riblets. First, a calculation model of the oblique riblets surface is established, and Reynolds stress model(RSM) turbulence model is used for numerical simulation of the oblique riblets flow field. Subsequently, the influence of inclination angle between flow direction and arrangement direction of riblets on friction resistance and drag reduction rate is further analyzed. Through the investigation of the distribution of shear stress, pressure stress and velocity in oblique riblets boundary layer, the oblique riblets drag reduction mechanism is finally revealed. Results show that, with increase of velocity and inclination angle, the pressure resistance increases obviously, along with the decreasing of the viscous resistance distinctly. The maximum drag reduction rate of the oblique riblets is 7.33%. Moreover, when the inclination angle increases, the wall shear stress reduces on oblique riblets surface; while differential pressure increases at both sides of oblique riblets tips. In addition, when inclination angle is small, the secondary vortex at oblique riblets tips will disappear soon. New vortices will be formed inside the oblique riblets and cause the decrease of viscosity resistance. Thus, oblique riblets show a better drag reduction effect and have an effective control on boundary layer.

关键词： oblique riblets drag reduction Reynolds stress model (RSM) secondary vortex numerical simulation

Synergistic effects of multiscale TiC and dual-phase structure on tensile properties of particle-reinforced steel

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Journal of Iron and Steel Research International 2024年第5期31卷 1232-1245页

作者： Ye Jia Xiang-tao deng Qi Wang Cheng-ru Li hao wu Zhao-dong Wang State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang110819LiaoningChina

The conventional melting methods were used to obtain in situ TiC particle-reinforced dual-phase steel,followed by hot rolling and heat treatment *** aim was to investigate the effect of TiC particles on the fracture behavior of dual-phase steel at different annealing temperatures,by analyzing the microstructure and tensile behavior of the multiscale TiC particle-reinforced dual-phase *** results showed that TiC particles precipitated in the as-cast microstructure of dual-phase steel were distributed along the grain *** hot rolling,the grain boundary-like morphology of the micron-sized TiC particles was disrupted,and the particles became more refined and evenly distributed in the *** tensile tests revealed that the strength of the TiC particle-reinforced dual-phase steel increased with increasing martensite content,while the elongation *** results were similar to those of conventional *** addition of 1 vol.%multiscale TiC particles improved the strength of the dual-phase steel but did not affect elongation of the *** and holes were primarily concentrated around the TiC particles rather than at the interface of martensite and *** main causes of crack sprouting were TiC particle interface cracking and TiC particle internal ***,the study demonstrated the potential of multiscale TiC particle-reinforced dual-phase steel as a strong and tough *** refined distribution of TiC particles in the matrix improved the strength of the material without compromising its *** results also highlighted the importance of careful selection of reinforcement particles to avoid detrimental effects on the fracture behavior of the material.

关键词： TiC particle Dual-phase structure TiC-reinforced dual-phase steel Tension Fracture behavior

Enhancing Offensive Language Detection with Data Augmentation and Knowledge Distillation

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Research 2024年第2期6卷 29-40页

作者： Jiawen deng Zhuang Chen hao Sun Zhexin Zhang Jincenzi wu Satoshi Nakagawa Fuji Ren Minlie Huang The CoAl group DCSTInstitute for Artificial InteligenceState Key Lab of Intelligent Technology and SystemsBeijing National Research Center for Information Science and TechnologyTsinghua UniversityBeijing 100084China Graduate School of Information Science&Technology The University of Tokyo.Tokyo 1138654Japan School of Computer Science and Engineering University of Electronic Science and Technology of ChinaChengduSichuan611731China

Offensive language detection has received important attention and plays a crucial role in promoting healthy communication on social platforms,as well as promoting the safe deployment of large language *** data is the basis for developing detectors;however,the available offense-related dataset in Chinese is severely limited in terms of data scale and coverage when compared to English *** significantly affects the accuracy of Chinese offensive language detectors in practical applications,especially when dealing with hard cases or out-of-domain *** alleviate the limitations posed by available datasets,we introduce AugCOLD(Augmented Chinese Offensive Language Dataset),a large-scale unsupervised dataset containing 1 million samples gathered by data crawling and model ***,we employ a multiteacher distillation framework to enhance detection performance with unsupervised *** is,we build multiple teachers with publicly accessible datasets and use them to assign soft labels to *** soft labels serve as a bridge for knowledge to be distilled from both AugCOLD and multiteacher to the student network,i.e.,the final offensive *** conduct experiments on multiple public test sets and our well-designed hard tests,demonstrating that our proposal can effectively improve the generalization and robustness of the offensive language detector.

关键词： COLD dealing limitations

Application of in-situ characterization techniques in modern aqueous batteries

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Rare Metals 2024年第8期43卷 3553-3575页

作者： Jia-hao wu Hong-Wei Cai Zhao-Hui deng Jean-Jacques Gaumet Yu Bao Wen Luo Department of Physics State Key Laboratory of Advanced Technology for Materials Synthesis and ProcessingSchool of Materials Science and EngineeringWuhan University of TechnologyWuhan430070China Laboratoire de Chimie Et Physique:Approche Multi-Echelles Des Milieux Complexes(LCP-A2MC)Institut Jean BarriolUniversitéde Lorraine57070MetzFrance Department of Medicinal Chemistry Hubei College of Chinese MedicineJingzhou 434020China

The development of high-performance aqueous batteries calls for an in-depth knowledge of their chargedischarge redox and failure mechanism,as well as a systematic understanding of the dynamic evolution of microstructure,phase composition,chemical composition,and local chemical environment of the materials for ***-situ characterization technology is expected to understand and reveal the problems faced by aqueous rechargeable batteries,such as the dissolution of electrode materials,the growth of metal negative electrode dendrites,passivation,corrosion,side reactions and a series of *** on this,typical in-situ characterization techniques and their basic mechanisms are summarized,including in-situ optical visualization,in-situ microscopy techniques(in-situ scanning electron microscopy(SEM),in-situ transmission electron microscopy(TEM)),in-situ X-ray techniques(in-situ X-ray diffraction(XRD),in-situ X-ray photoelectron spectroscopy(XPS),in-situ near-edge structural X-ray absorption spectroscopy(XANES)),and in-situ spectroscopy techniques(in-situ Raman spectroscopy,in-situ Fourier transform infrared(FTIR)).Moreover,some emerging techniques concerning aqueous battery research,especially gas evolution and materials dissolution issues,such as in-situ electrochemical quartz crystal microbalance(EQCM).in-situ fiber-optic sensing,in-situ gas chromatography(GC) are *** last,the applications of advanced in-situ characterizations in future research of aqueous batteries are emphasized and discussed,along with some of the remaining challenges and possible solutions.

关键词： Aqueous battery In-situ characterization Phase transformation Solid electrolyte interphase Zinc dendrite growth

Coordination structure regulation in non-flammable electrolyte enabling high voltage lithium electrochemistry

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Journal of Energy Chemistry 2024年第9期96卷 282-290页

作者： Zhiwen deng Ye Jia Yan deng Changhaoyue Xu Xuemei Zhang Qiujie He Jianan Peng hao wu Wenlong Cai College of Materials Science and Engineering Sichuan UniversityChengdu 610064SichuanChina Engineering Research Center of Alternative Energy Materials and Devices Sichuan UniversityChengdu 610064SichuanChina

High-voltage battery systems bring significant increases in energy density but are also accompanied by fast degradation of electrochemical performance and serious safety ***,Li^(+)coordination structure regulation was conducted to formulate a non-flammable electrolyte,which consists of 1.5 M lithium bis(fluor sulfonyl)imide(LiFSI)in triethyl phosphate and methyl 2,2,2-trifluoromethyl carbonate(FEMC).The renamed TEP-FEMC-FEC(TFF)electrolyte exhibits an FSI^(−)-dominated solvation structure contributed by the weakly-solvating ability of *** generated inorganic-rich interfacial layers are conducive to stabilizing the phase transition of high-voltage cathodes while suppressing the dendritic growth on lithium metal or co-intercalation behavior in graphite *** TFF electrolyte enables LiCoO_(2)||Li batteries to achieve capacity maintenance over 79%after 400 cycles with high-rate of 5 C at an ultra-high voltage of 4.6 V,and an outstanding capacity exceeding 100 mA h g^(−1)even at a super-high current density of 20 ***,the Ah-level LiCoO_(2)||graphite pouch cells also exhibit high capacity retention and satisfactory safety performance even under fast *** work provides a novel research direction for the pursuit of high energy density non-flammable electrolytes.

关键词： Non-flammable Solvation structure High-voltage Lithium batteries

A new interacting capillary bundle model on the multiphase flow in micropores of tight rocks

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Petroleum Science 2024年第2期21卷 1099-1112页

作者： Wen-Quan deng Tian-Bo Liang Wen-Zhong Wang hao Liu Jun-Lin wu Fu-Jian Zhou National Key Laboratory of Petroleum Resources and Engineering China University of Petroleum(Beijing)Beijing102249China

Surfactants are widely used in the fracturing fluid to enhance the imbibition and thus the oil recovery rate. However, current numerical models cannot capture the physics behind capillary imbibition during the wettability alteration by surfactants. Although the interacting capillary bundle(ICB) model shows potential in characterizing imbibition rates in different pores during wettability alteration, the existing ICB models neglect the influence of wettability and viscosity ratio on the imbibition behavior, making it difficult to accurately describe the oil-water imbibition behavior within the porous media. In this work,a new ICB mathematical model is established by introducing pressure balance without assuming the position of the leading front to comprehensively describe the imbibition behavior in a porous medium under different conditions, including gas-liquid spontaneous imbibition and oil-water *** the pore size distribution of a tight rock is known, this new model can predict the changes of water saturation during the displacement process in the tight rock, and also determine the imbibition rate in pores of different sizes. The water saturation profiles obtained from the new model are validated against the waterflooding simulation results from the CMG, while the imbibition rates calculated by the model are validated against the experimental observations of gas-liquid spontaneous imbibition. The good match above indicates the newly proposed model can show the water saturation profile at a macroscopic scale while capture the underlying physics of the multiphase flow in a porous medium at a microscopic scale. Simulation results obtained from this model indicate that both wettability and viscosity ratio can affect the sequence of fluid imbibition into pores of different sizes during the multiphase flow, where less-viscous wetting fluid is preferentially imbibed into larger pores while more-viscous wetting fluid tends to be imbibed into smaller pores. Fur

关键词： Imbibition Multiphase flow Tight rock Interacting capillary bundle model Wettability

Enhanced nitrite electroreduction to ammonia via interfacial dual-site adsorption

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Journal of Energy Chemistry 2024年第9期96卷 328-335页

作者： Xiaokang Chen Shengliang Zhai Yi Tan Le Su Dong Zhai Wei-Qiao deng hao wu Institute of Frontier Chemistry School of Chemistry and Chemical EngineeringShandong UniversityQingdao 266071ShandongChina College of Physics and Information Engineering Shanxi Normal UniversityTaiyuan 030031ShanxiChina Suzhou Research Institute of Shandong University Suzhou 215123JiangsuChina

The nitrite(NO_(2)^(−))to ammonia(NH3)electroreduction reaction(NO_(2)^(−)RR)would be impeded by sluggish proton-coupled electron transfer kinetics and competitive hydrogen evolution reaction(HER).A key to improving the NH_(3) selectivity is to facilitate adsorption and activation of NO_(2)^(−),which is generally undesirable in unitary *** this work,an efficient NO_(2)^(−)RR catalyst is constructed by cooperating Pd with In2O3,in which NO_(2)^(−)could adsorb on interfacial dual-site through“Pd–N–O–In”linkage,leading to strengthened NO_(2)^(−)adsorption and easier N=O bond cleavage than that on unitary Pd or ***,the Pd/In_(2)O_(3)composite exhibits moderate H^(*)adsorption,which may facilitate protonation kinetics while inhibiting competitive *** a result,it exhibits a fairly high NH_(3)yield rate of 622.76 mmol h^(−1)g^(−1)cat with a Faradaic efficiency(FE)of 95.72%,good selectivity of 91.96%,and cycling stability towards the NO_(2)^(−)RR,surpassing unitary In_(2)O_(3)and Pd/C ***,computed results indicate that NH_(3)production on Pd/In_(2)O_(3)follows the deoxidation to hydrogenation *** work highlights the significance of H^(*)and NO_(2)^(−)adsorption modulation and N=O activation in NO_(2)^(−)RR electrochemistry by creating synergy between a mediocre catalyst with an appropriate cooperator.

关键词： Dual-site adsorption Nitrite electroreduction Ammonia Pd Hydrogenation

Numerical study on local failures of reinforced concrete slabs against underwater close-in explosions

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第8期25卷 650-669页

作者： Fei ZHOU Hedong LI hao wu College of Civil Engineering Tongji UniversityShanghai 200092China School of Civil Engineering and Architecture Zhejiang Sci-Tech UniversityHangzhou 310018China

Reinforced concrete(RC)slabs are the primary load-carrying member of underwater *** can suffer severe local failures such as cratering,spalling,or breaching as a result of underwater close-in(UWCI)*** this study,we established a fully validated high-fidelity finite element analysis approach to precisely reproduce the local failures of RC slabs after a UWCI explosion.A recently proposed dynamic constitutive model is used to describe wet *** effects of free water content on the material properties,including the tensile/compressive strength,elastic modulus,strain rate effect,failure strength surface,and equation of state,are comprehensively calibrated based on existing test *** calibrated material parameters are then verified by a single-element test.A high-fidelity finite element analysis(FEA)approach of an RC slab subjected to a UWCI explosion is established using an arbitrary Lagrangian-Eulerian(ALE)*** previous UWCI explosion tests on RC orifice targets and underwater contact explosion tests on saturated concrete slabs showed that the established FEA approach could accurately reproduce the pressure-time history in water and damage patterns,including the cracking,cratering,and spalling,of the RC orifice target and saturated concrete ***,parametric studies conducted by simulating an RC slab subjected to a UWCI explosion showed that:(i)the local failure of an RC slab enlarges with increased charge weight,reduced standoff distance,and reduced structural thickness;(ii)compared to a water-backed RC slab,an air-backed RC slab exhibits much more obvious local and structural ***,to aid the anti-explosion design of relevant underwater facilities,based on over 90 simulation cases empirical formulae are summarized to predict local failure modes,i.e.,no spall,spall,and breach,of water-and air-backed RC slabs subjected to a UWCI explosion.

关键词： Reinforced concrete slab(RC) Underwater close-in(UWCI)explosion Saturated concrete Failure modes Numerical simulation

A level line of the Gaussian free field with measure-valued boundary conditions

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Science China Mathematics 2024年第2期67卷 367-404页

作者： Titus Lupu hao wu Laboratoire de Probabilités Statistique et ModélisationSorbonne Universitéand UniversitéParis CitéCNRSParis F-75005France Yau Mathematical Sciences Center Tsinghua UniversityBeijing 100084China

In this article, we construct samples of Schramm-Loewner-evolution-like curves out of samples ofthe conformal loop ensemble and Poisson point processes of Brownian excursions. We show that the laws of thesecurves depend continuously on the intensity measure of the Brownian excursions. Using such a construction ofcurves, we extend the notion of level lines of the Gaussian free field to the case where the boundary conditionis measure-valued.

关键词： Schramm-Loewner evolution conformal loop ensemble Brownian excursion Gaussian free field