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A robust algorithm for moving interface of multi-material fluids based on Riemann solutions

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Acta Mechanica Sinica 2006年第6期22卷 509-519页

作者： Xueying Zhang ning Zhao College of Science Hohai University Nanjing 210098 China College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

In the paper, the numerical simulation of interface problems for multiple material fluids is studied. The level set function is designed to capture the location of the material interface. For multi-dimensional and multi-material fluids, the modified ghost fluid method needs a Riemann solution to renew the variable states near the interface. Here we present a new convenient and effective algorithm for solving the Riemann problem in the normal direction. The extrapolated variables are populated by Taylor series expansions in the direction. The anti-diffusive high order WENO difference scheme with the limiter is adopted for the numerical simulation. Finally we implement a series of numerical experiments of multi-material flows. The obtained results are satisfying, compared to those by other methods.

关键词： Multi-material fluids Ghost fluidmethod Riemann problem Level set method WENO scheme

Property analysis of logic Petri nets by marking reachability graphs

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Frontiers of Computer Science 2014年第4期8卷 684-692页

作者： Yuyue DU Yuhui ning College of Information Science and Engineering Shandong University of Science and Technology Qingdao 266590 China

Logic Petri nets （LPNs） are suitable to describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. To investigate the dynamic properties of LPNs directly, a new method for analyzing LPNs is proposed based on marking reachability graphs in this paper. Enabled conditions of transitions are obtained and a marking reachability graph is constructed. All reach- able markings can be obtained based on the graph; the fairness and reversibility of LPNs are analyzed. Moreover, the computing complexity of the enabled conditions and reachable markings can be reduced by this method. The advantages of the proposed method are illustrated by examples and analysis.

关键词： logic Petri nets enabled condition reachable marking graph fairness reversibility

Research Progress on Artemisinin and Its Derivatives against Hematological Malignancies

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Chinese Journal of Integrative Medicine 2020年第12期26卷 947-955页

作者： LI Ying SHAN ning-ning SUI Xiao-hui Department of Hematology Shandong Provincial Hospital Affiliated to Shandong UniversityJinan(250021)China

Although current therapeutic methods against hematological malignancies are effective in the early stage,they usually lose their effectiveness because of the development of drug *** new drugs with significant therapeutic effects is one of the current research ***,an extract from the plant Artemisia annua Linne,and its derivatives have excellent antimalarial effects in clinical applications as well as excellent *** studies have documented that artemisinin and its derivatives(ARTs)also have significant effects against multiple types of tumours,including hematological *** review focuses on the latest research achievements of ARTs in the treatment of hematological malignancies as well as its mechanisms and future *** mechanisms of ARTs against different types of hematological malignancies mainly include cell cycle arrest,induction autophagy and apoptosis,inhibition of angiogenesis,production of reactive oxygen species,and induction of ***,the review also summarizes the anticancer effects of ARTs in many drug-resistant hematological malignancies and its synergistic effects with other drugs.

关键词： artemisinin artesunate dihydroartemisinin hematological malignancies review

Impact of non-ideal UE hardware on cell-free massive MIMO network with centralized operation

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Science China(Information Sciences) 2024年第4期67卷 255-271页

作者： ning LI Pingzhi FAN Institute of Mobile Communications Southwest Jiaotong University

This paper investigates the impact of non-ideal user equipment(UE) hardware on a cell-free(CF) massive MIMO(mMIMO) network with centralized operation under spatially correlated channels. The minimum mean-squared error(MMSE) estimator can be derived with the help of the generic non-ideal UE hardware model. It is demonstrated that even if the effective signal-to-noise ratio approaches infinity, pilot contamination and imperfect hardware can cause a non-zero estimation error floor. After that, a lower bound is determined for the ergodic uplink capacity of the centralized CF mMIMO network under non-ideal UE hardware. Moreover, the optimal receive combining vector is obtained to maximize the uplink spectral efficiency(SE). The maximum ratio(MR) and regularized zero-forcing(RZF) combining schemes are offered as alternatives in light of the computational complexity of the MMSE receiver. Comparing the RZF to the MMSE scheme under different levels of hardware impairments, our findings indicate that the RZF receiver suffers a negligible loss in total SE. For MR combining, a novel closed-form uplink achievable SE expression is obtained based on the MMSE estimator and the use-and-then-forget bounding technique. This expression gives vital insights into the achievable uplink performance with UE hardware impairments. Besides, for various hardware impairment factors, the impact of pilot sequence length on average sum SE is disclosed for different receive combining schemes. To increase the overall SE of the max-min fairness scheme, a heuristic fractional power control scheme with UE hardware impairments is developed, which can essentially avoid sacrificing the SE of other UEs while maximizing the SE of the unluckiest UE in the whole network. Finally,our theoretical performance analysis and power control algorithm are validated by simulation results, and fundamental design guidelines are provided for selecting hardware satisfying the practical UE requirements.

关键词： cell-free massive MIMO centralized operation spatially correlated channels hardware impairments channel estimation uplink spectral efficiency optimal receive combining pilot length design fractional power control

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ROTATIONAL RESISTANCE AND SHEAR-INDUCED ANISOTROPY IN GRANULAR MEDIA

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Acta Mechanica Solida Sinica 2014年第1期27卷 1-14页

作者： Jidong Zhao ning Guo Department of Civil and Environmental Engineering The Hong Kong University of Science and Technology

This paper presents a micromechanical study on the behavior of granular materials under confined shear using a three-dimensional Discrete Element Method （DEM）. We consider rotational resistance among spherical particles in the DEM code as an approximate way to account for the effect of particle shape. Under undrained shear, it is found rotational resistance may help to increase the shear strength of a granular system and to enhance its resistance to liquefaction. The evolution of internal structure and anisotropy in granular systems with different initial conditions depict a clear bimodal character which distinguishes two contact subnetworks. In the presence of rotational resistance, a good correlation is found between an analytical stress-force-fabric relation and the DEM results, in which the normal force anisotropy plays a dominant role. The unique properties of critical state and liquefaction state in relation to granular anisotropy are also explored and discussed.

关键词： granular media anisotropy discrete element method (DEM) rotational resistance liquefaction critical state

Biological object recognition approach using space variant resolution and pigeon-inspired optimization for UAV

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Science China(Technological Sciences) 2017年第10期60卷 1577-1584页

作者： XIN Long XIAN ning State Key Laboratory of 14rtual Reality Technology and Systems Beihang University Beijing 100191 China

Recognizing the target from a rotated and scaled image is an important and difficult task for computer vision. Visual system of humans has a unique space variant resolution mechanism(SVR) and log-polar transformations(LPT) is a mapping method that is invariant to rotation and scale. Motivated by biological vision, we propose a novel global LPT based template-matching algorithm(GLPT-TM) which is invariant to rotational and scale changes; and with pigeon-inspired optimization(PIO) used to optimize search strategy, a hybrid model of SVR and pigeon-inspired optimization(SVRPIO) is proposed to accomplish object recognition for unmanned aerial vehicles(UAV) with rotational and scale changes of the target. To demonstrate the efficiency, effectiveness and reliability of the proposed method, a series of experiments are carried out. By rotating and scaling the sample image randomly and recognizing the target with the method, the experimental results demonstrate that our proposed method is not only efficient due to the optimization, but effective and accurate in recognizing the target for UAV.

关键词： biological vision space variant resolution mechanism (SVR) log-polar transformations (LPT) pigeon-inspiredoptimization (PIO) object recognition

Influence of baffle position on liquid sloshing during braking and turning of a tank truck

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第5期11卷 317-324页

作者： ning KANG Kui LIU School of Transportation Science and Engineering University of A eronautics and Asttvnautics Beijing 100191 China

The influence of baffle position on liquid sloshing during the braking and turning of a tank truck was studied using a volume of fluid (VOF) model. The forces,their positions and weight distribution during braking and the forces and rolling moment during turning were calculated. The reliability of the calculation method was validated by comparisons with experimental results. The results showed that during braking,liquid splashes in the tank and the maximum forces and G (the ratio of weight acting on the front axle to the rear axle) are large when A (the ratio of the arch area above the baffle to the area of cross section)≤0.1. When A≥0.2,as the position of the baffle is lowered,the maximum of Fx (the force in direction x) first decreases then increases,and the maximum of Fy (the force in direction y) and G increase. During turning,liquid splashes in the tank and the maximum forces and M (the rolling moment) are large when D (the ratio of the arch area above the baffle to the area of cross section)≤0.2. When D≥0.3,as the position of the baffle is lowered,the maximums of Fy,Fz (the force in direction z) and M increase.

关键词： Tank truck Volume of fluid (VOF) method Liquid sloshing Two phase flow Baffle

Numerical investigation of the dynamics of flexible vegetations in turbulent open-channel flows

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Journal of Hydrodynamics 2022年第4期34卷 681-699页

作者： Dong Xu Jia-ning Liu Yun-feng Wu Chun-ning Ji State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

Aquatic vegetations widely exist in natural rivers and play an essential role in the evolution of the water environment and ecosystem by changing the river’s hydrodynamic characteristics and transporting sediments and *** reality,most aquatic vegetations are highly flexible,which invalidates the“rigid-cylinder”assumption widely adopted in many *** explore the dynamics of submerged flexible vegetation in open-channel flows and its feedback to turbulent flow structures,numerical simulations are carried out using an in-house fluid-structure interaction(FSI)*** the simulations,the geometry of vegetation plants is grid-resolved,the turbulent flow is simulated using the large eddy simulation(LES),the dynamics of the flexible plants are solved using the vector form intrinsic finite element(VFIFE)method,and the turbulent flow and the plants are two-way coupled using the immersed boundary(IB)*** dynamic responses of the flexible vegetation with different plant flexibility,spacing,and submergence are *** results show that flexible plants are subjected to complex flow-induced vibrations(FIVs)rather than static *** FIV involves both streamwise and cross-flow motions driven by the small-scale vortex shedding around the plants and the large-scale Kelvin-Helmholtz(K-H)vortices developed in the vegetation canopy *** vegetations exhibit pulsive wave motion of different patterns in relatively long and narrow open *** with the open-channel flows with static plants with equivalent bending deformation,the dynamic responses of flexible plants may increase the turbulent Reynolds stress of the open-channel flow by 70%–100%and increase the invasion depth of the K-H vortices by 30%–50%.

关键词： Flexible vegetation dynamic responses flow-induced vibration(FIV) fluid-structure interaction(FSI)

Validation of a novel mixing-plane method for multistage turbomachinery steady flow analysis

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Chinese Journal of Aeronautics 2016年第6期29卷 1563-1574页

作者： Du Pengcheng ning Fangfei School of Aeronautic Science and Engineering Beihang University School of Energy and Power Engineering Beihang University

The steady calculation based on the mixing-plane method is still the most widely-used three-dimensional flow analysis tool for multistage turbomachines. For modern turbomachines,the trend of design is to reach higher aerodynamic loading but with still further compact size. In such a case, the traditional mixing-plane method has to be revised to give a more physically meaningful prediction. In this paper, a novel mixing-plane method was proposed, and three representative test cases including a transonic compressor, a highly-loaded centrifugal compressor and a highpressure axial turbine were performed for validation purpose. This novel mixing-plane method can satisfy the flux conservation perfectly. Reverse flow across the mixing-plane interface can be resolved naturally, thus making this method numerically robust. Artificial reflection at the mixing-plane interface is almost eliminated, and then its detrimental impact on the flow field is minimized. Generally, this mixing-plane method is suitable to simulate steady flows in highly-loaded multistage turbomachines.

关键词： Centrifugal compressor Flux conservation Mixing-plane method Reverse flow Turbomachinery