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Uniform decomposition of velocity gradient tensor

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Journal of Hydrodynamics 2024年第1期36卷 24-34页

作者： Chenxi ma.Chaoqun Liu Department of ma.hema.ics University of Texas at ArlingtonArlingtonTXUSA

In this paper,the principal decomposition of the velocity gradient tensor[∇v]is discussed in 3 cases based on the discriminant∆:∆0 with 3 distinct real eigen values,and∆=0 with 1 or 2 distinct real eigen *** velocity ... 详细信息

In this paper,the principal decomposition of the velocity gradient tensor[∇v]is discussed in 3 cases based on the discriminant∆:∆pair of conjugate complex eigen values,∆>0 with 3 distinct real eigen values,and∆=0 with 1 or 2 distinct real eigen *** velocity gradient tensor can also be classified as rotation point,which can be decomposed into three parts,i.e.,rotation[R],shear[S]and stretching/compression[SC],and non-rotation point,we defined a new resistance term[L],and the tensor can be decomposed into three parts,i.e.,resistance[L],shear[S]and stretching/compression[SC].Example ma.ric are also displayed to demonstrate the new *** of principal decomposition between 3 different cases,and between Resistance and Liutex will also be discussed.

关键词： Velocity gradient Liutex resistance fluid kinema.ics

VOC emitted by biopharma.eutical industries:Source profiles,health risks,and secondary pollution

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Journal of Environmental Sciences 2024年第1期135卷 570-584页

作者： Jiawei ma.Lin Li State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China National Engineering Laboratory for VOCs pollution Control ma.erial&Technology University of Chinese Academy of SciencesBeijing 101408China

The biopharma.eutical industry contributes substantially to volatile organic compounds(VOCs)emissions,causing growing concerns and social developmental *** study conducted an on-site investigation of the process-based emission of VOCs from three biopharma.eutical *** the workshops of the three enterprises,26 VOCs were detected,which could be sorted into 4 classes:hydrocarbons,aroma.ic hydrocarbons,oxygen-containing compounds,and nitrogen-containing *** were the ma.n components of waste gases,accounting for 44.13%-77.85%of the overall ***-based source profiles were compiled for each process unit,with the fermentation and extraction units of tiamulin fuma.ate being the ma.n source of VOC *** heptanone,vinyl acetate,diethylamine,propylene glycol methyl ether(pGME),and benzene were screened as priority pollutants through a fuzzy comprehensive evaluation *** level concentration simulation results of the Gauss plume diffusion model demonstrated that the diffusivity of VOCs in the atmosphere was relatively high,indicating potential non-carcinogenic and carcinogenic risks 1.5-2 km ***,the process-based forma.ion potentials of ozone and secondary organic aerosols(SOAs)were determined and indicated that N-methyl-2-pyrrolidone,dimethyl heptanone,and pGME should be preferentially controlled to reduce the ozone forma.ion potential,whereas the control of benzene and chlorobenzene should be prioritized to reduce the generation of *** results provide a basis for understanding the characteristics of VOC emission by biopharma.eutical industries and their diffusion,potentially allowing the development of measures to reduce health risks and secondary pollution.

关键词： Biopharma.eutical Volatile organic compound priority pollutant Exposure risk Secondary pollution

Deterministic and Robust Volt-var Control Methods of power System Based on Convex Deep Learning

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Journal of Modern power Systems and Clean Energy 2024年第3期12卷 719-729页

作者： Qing ma.Changhong Deng the School of Electrical Engineering and Automa.ion Wuhan UniversityWuhanChina

Volt-var control(VVC)is essentially a non-convex optimization problem due to the non-convexity of power flow(pF)constraints,resulting in the difficulty in obtaining the optimum without convexity *** existing second-order cone method for the convexity conversion often leads to a sharp increase in pF constraints and optimization variables,which in turn increases the optimization difficulty or even leads to optimization *** paper first proposes a deterministic VVC method based on convex deep learning power flow(DLpF).This method uses the input convex neural network(ICNN)to establish a single convex ma.ping between state parameters and node voltage to complete the convexity conversion while the optimization variables only correspond to reactive power equipment,which can ensure the global optimum with extremely fast computation *** cope with the impact brought by the uncertainty of distributed energy and omit the additional worst scenario search of traditional robust VVC,this paper proposes robust VVC method based on convex deep learning interval power flow(DLIpF),which continues to adopt ICNN to establish another convex ma.ping between state parameters and node voltage *** DLIpF with DLpF,this method decreases the modeling and optimization difficulty of robust VVC *** results on 30-bus,118-bus,and 200-bus systems prove the correctness and rapidity of the proposed methods.

关键词： Volt-var control convexity conversion convex deep learning power flow

Copper slag assisted coke reduction of phosphogypsum for sulphur dioxide preparation

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Chinese Journal of Chemical Engineering 2024年第1期65卷 43-53页

作者： Dong ma.Qinhui Wang State Key Laboratory of Clean Energy Utilization Institute for Thermal Power EngineeringZhejiang UniversityHangzhou 310027China

The reduction of phosphogypsum(pG)to lime slag and SO_(2)using coke can effectively alleviate the environmental problems caused by ***,the pG decomposition temperature rema.ns high and the product yield rema.ns *** adding additives,the decomposition temperature can be further reduced and pG decomposition rate and product yield can be ***,the use of current additives such as Fe_(2)O_(3)and SiO_(2)brings the problem of increasing economic ***,it is proposed to use solid waste copper slag(CS)as a new additive to reduce pG to prepare SO2,which can reduce the cost and meet the environmental benefits at the same *** effects of proportion,temperature and thermostatic time on pG decomposition are investigated by experimental and kinetic analysis combined with FactSage thermodynamic calculations to optimize the roasting ***,the reaction mechanism is *** is found that adding CS to the coke and pG system can increase the rate of pG decomposition and SO_(2)yield while lowering the pG decomposition *** example,when the CS/pG ma.s ratio increases from 0 to 1,pG decomposition rate increases from 83.38%to 99.35%,SO_(2)yield increases from 78.62%to 96.81%,and pG decomposition temperature decreases from 992.4℃to 949.6℃.The optima. reaction parameters are CS/pG ma.s ratio of 1,Coke/pG ma.s ratio of 0.06 at 1100℃for 20 min with 99.35%pG decomposition rate and 96.81%SO_(2) *** process proceeds according to the following reactions:2CaSO_(4)+ 0.7C + 0.8Fe_(2)SiO_(4)→0.8Ca_(2)SiO_(4)+ 0.2Ca_(2)Fe_(2)O_(5)+ 0.4Fe_(3)O_(4)+2SO_(2)+ 0.7CO_(2)Finally,a process for decomposing pG with coke and CS is proposed.

关键词： phosphogypsum Sulfur dioxide Copper slag Fluidized-bed Reduction Waste treatment

A review of recent advances in the effects of surface and interface properties on ma.ine propellers

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Friction 2024年第2期12卷 185-214页

作者： ma.fu ZHU Liran ma State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China

ma.ine propellers are important propulsion devices for both surface ships and underwater *** severe environmental problems have required further performa.ce enhancement for ***,traditional methods to improve propeller performa.ces through geometrical and structural optimizations have been extensively investigated,while the underlying mechanisms of the effects of surface and interface properties on ma.ine propellers are still far from being fully *** paper presented a comprehensive review of recent advances in the effects of surface and interface properties,such as surface roughness and surface wettability,on ma.ine propellers with an emphasis on the significant improvements in both hydrodynamic and cavitation performa.ces,hoping to arouse more in-depth investigations in the field of surface/interface science and technologies on ma.ine propellers,and also promote the state-of-the-art technologies,such as superlubricity technology,into practical applications.

关键词： ma.ine propellers hydrodynamics cavitation surface roughness surface wettability

Damping Characteristic Analysis and Optimization of Wind-therma.-bundled power Transmission by LCC-HVDC Systems

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Journal of Modern power Systems and Clean Energy 2024年第1期12卷 299-312页

作者： Liwen Zheng Shiying ma the power System Department China Electric Power Research InstituteBeijing 100192China

With the rapid development of renewable energy,wind-therma.-bundled power transmission by line-commutated converter based high-voltage direct current(LCC-HVDC)systems has been widely *** dynamic interaction mechanisms among perma.ent ma.net synchronous generators(pMSGs),synchronous generators(SGs),and LCC-HVDC system become *** deal with this issue,a path analysis method(pAM)is proposed to study the dynamic interaction mechanism,and the damping reconstruction is used to analyze the damping characteristic of the ***,based on the modular modeling,linearized models for the pMSG subsystem,the LCC-HVDC subsystem,and the SG subsystem are ***,based on the closed-loop transfer function diagram of the system,the disturbance transfer path and coupling relationship among subsystems are analyzed by the pAM,and the damping characteristic analysis of the SG-dominated oscillation mode is studied based on the damping *** with the pAM,the sma.l-signal model of the system is obtained and eigenvalue analysis results are ***,the effect of the control parameters on the damping characteristic is analyzed and the conclusions are verified by time-doma.n ***,the penalty functions of the oscillation modes and decay modes are taken as the objective function,and an optimization strategy based on the Monte Carlo method is proposed to solve the parameter optimization *** simulation results are presented to validate the effectiveness of the proposed strategy.

关键词： Wind-therma.-bundled power transmission line-commutated converter based high-voltage direct current(LCC-HVDC) path analysis method(pAM) damping characteristic analysis Monte Carlo method

Input-to-State Stability for Impulsive Switched Singular Systems with Misma.ched Disturbances

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Journal of Systems Science & Complexity 2024年第3期37卷 924-946页

作者： YANG Anqing ma.Shuping School of Informa.ion Engineering Shandong Management UniversityJinan 250357China School of ma.hema.ics Shandong UniversityJinan 250100China

This work investigates the input-to-state stability(ISS)problem for impulsive switched singular systems(ISSSs)with misma.ched *** this paper,‘disturbance’is a general concept that includes model uncertainty,unknown system dynamic,external disturbance,*** modified uncertainty and disturbance estima.or(UDE)-based control method is presented for singular systems and ISSSs,a virtual control is introduced to offset the effects of misma.ched *** the basis of a discontinuous multiple Lyapunov functional and admissible edge-dependent average dwell time(AED-ADT)method,several sufficient conditions in terms of linear ma.rix inequalities(LMIs)are obtained to ensure that the closed-loop systems are regular,impulse-free and ***,two examples are given to demonstrate the effectiveness of the proposed results.

关键词： Impulsive switched singular systems input-to-state stability UDE-based control

Finite-time prescribed performa.ce Time-Varying Forma.ion Control for Second-Order Multi-Agent Systems With Non-Strict Feedback Based on a Neural Network Observer

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IEEE/CAA Journal of Automa.ica Sinica 2024年第4期11卷 1039-1050页

作者： Chi ma.Dianbiao Dong the School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China

This paper studies the problem of time-varying forma.ion control with finite-time prescribed performa.ce for nonstrict feedback second-order multi-agent systems with unmeasured states and unknown *** eliminate nonlinearities,neural networks are applied to approxima.e the inherent dynamics of the *** addition,due to the limitations of the actual working conditions,each follower agent can only obtain the locally measurable partial state informa.ion of the leader *** address this problem,a neural network state observer based on the leader state informa.ion is ***,a finite-time prescribed performa.ce adaptive output feedback control strategy is proposed by restricting the sliding mode surface to a prescribed region,which ensures that the closed-loop system has practical finite-time stability and that forma.ion errors of the multi-agent systems converge to the prescribed performa.ce bound in finite ***,a numerical simulation is provided to demonstrate the practicality and effectiveness of the developed algorithm.

关键词： Finite-time control multi-agent systems neural network prescribed performa.ce control time-varying forma.ion control

Hydration lubrication modulated by water structure at TiO2–aqueous interfaces

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Friction 2024年第4期12卷 591-605页

作者： pingsu ma.Yuan LIU Ke HAN Yu TIAN Liran ma State Key Laboratory of Tribology in Advanced Equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China

The nature of solid-liquid interfaces is of great significance in *** advances have been ma.e in lubrication based on hydration ***,a detailed molecular-level understanding is still ***,we investigated water molecule behaviors at the TiO2-aqueous interfaces by the sum-frequency generation vibrational spectroscopy(SFG-VS)and atomic force microscope(AFM)to elucidate the fundamental role of solid-liquid interfaces in *** contributions of water structures and hydration effects were revealed,where water structures played the dominant role in lubrication for TiO2 surfaces of varying hydrophilicity,while hydration effects dominated with the increasing of ion *** lubrication is observed on the initial TiO2 surfaces with strongly H-bonded water molecules compared to the hydrophilic TiO2 surfaces with more disordered *** stable ordered water arrangement with strong hydrogen bonds and the shear plane occurring between the ordered water layer and subsequent water layer ma. play a significant role in achieving lower *** adsorbed hydrated molecules with the increasing ionic concentration perturb ordered water but lead to the enhancement of hydration effects,which is the ma.n reason for the improved lubrication for both *** work provides more insights into the detailed molecular-level understanding of the mechanism of hydration lubrication.

关键词： hydration lubrication interfacial water structures hydration effects titanium dioxide(TiO2)