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Research on data assimilation strategy of turbulent separated flow over airfoil

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Applied Mathematics and Mechanics(English Edition) 2022年第4期43卷 571-586页

作者： Ying zhang Lin DU Weiwei Zhang Zichen DENG National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of AeronauticsNorthwestern Polytechnical UniversityXi'an 710072China Complex System Dynamics and Control Academic Exchange Center School of Mathematics and StatisticsNorthwestern Polytechnical UniversityXi'an 710119China Rotor Aerodynamics Key Laboratory China Aerodynamics Research and Development CenterMianyang 621000Sichuan ProvinceChina

In order to increase the accuracy of turbulence field reconstruction,this paper combines experimental observation and numerical simulation to develop and establish a data assimilation framework,and apply it to the study of S809 low-speed and high-angle airfoil flow.The method is based on the ensemble transform Kalman filter(ETKF)algorithm,which improves the disturbance strategy of the ensemble members and enhances the richness of the initial members by screening high flow field sensitivity constants,increasing the constant disturbance dimensions and designing a fine disturbance interval.The results show that the pressure distribution on the airfoil surface after assimilation is closer to the experimental value than that of the standard Spalart-Allmaras(S-A)model.The separated vortex estimated by filtering is fuller,and the eddy viscosity field information is more abundant,which is physically consistent with the observation information.Therefore,the data assimilation method based on the improved ensemble strategy can more accurately and effectively describe complex turbulence phenomena.

关键词： turbulence data assimilation ensemble disturbance strategy large angle of attack separation ensemble transform Kalman filter(ETKF)

Unleashing the power of pseudo-code for binary code similarity analysis

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Cybersecurity 2023年第2期6卷 44-61页

作者： Weiwei Zhang Zhengzi Xu Yang Xiao Yinxing Xue School of Computer Science and Engineering University of Science and Technology of ChinaHefeiChina School of Computer Science and Engineering Nanyang Technological UniversitySingaporeSingapore Institute of Information Engineering Chinese Academy of SciencesBeijingChina School of Cyber Security University of Chinese Academy of SciencesBeijingChina

Code similarity analysis has become more popular due to its significant applicantions,including vulnerability detection,malware detection,and patch analysis.Since the source code of the software is difficult to obtain under most circumstances,binary-level code similarity analysis(BCSA)has been paid much attention to.In recent years,many BCSA studies incorporating Al techniques focus on deriving semantic information from binary functions with code representations such as assembly code,intermediate representations,and control flow graphs to measure the similarity.However,due to the impacts of different compilers,architectures,and obfuscations,binaries compiled from the same source code may vary considerably,which becomes the major obstacle for these works to obtain robust features.In this paper,we propose a solution,named UPPC(Unleashing the Power of Pseudo-code),which leverages the pseudo-code of binary function as input,to address the binary code similarity analysis challenge,since pseudocode has higher abstraction and is platform-independent compared to binary instructions.UPPC selectively inlines the functions to capture the full function semantics across different compiler optimization levels and uses a deep pyramidal convolutional neural network to obtain the semantic embedding of the function.We evaluated UPPC on a data set containing vulnerabilities and a data set including different architectures(X86,ARM),different optimization options(O0-O3),different compilers(GCC,Clang),and four obfuscation strategies.The experimental results show that the accuracy of UPPC in function search is 33.2%higher than that of existing methods.

关键词： Binary code similarity Machine learning Software security Pseudo-code

Paired box 5 increases the chemosensitivity of esophageal squamous cell cancer cells by promoting p53 signaling activity

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Chinese Medical Journal 2022年第5期135卷 606-618页

作者： Weiwei Zhang Wenji Yan Niansong Qian Quanli Han Weitao zhang Guanghai Dai Chinese People’s Liberation Army Medical School Beijing 100853China Department of the Third Health Care The Second Medical CenterChinese People’s Liberation Army General HospitalBeijing 100853China Department of Oncology The First Medical CenterChinese People’s Liberation Army General HospitalBeijing 100853China Department of Oncology The Hainan Medical CenterChinese People’s Liberation Army General HospitalSanya 572022China Cancer Center Beijing Tongren Hospital Affiliated to Capital Medical UniversityEconomic and Technological Development ZoneBeijing 100176China

Background:Gene promoter methylation is a major epigenetic change in cancers,which plays critical roles in carcinogenesis.As a crucial regulator in the early stages of B-cell differentiation and embryonic neurodevelopment,the paired box 5(PAX5)gene is downregulated by methylation in several kinds of tumors and the role of this downregulation in esophageal squamous cell carcinoma(ESCC)pathogenesis remains unclear.Methods:To elucidate the role of PAX5 in ESCC,eight ESCC cell lines,51 primary ESCC tissue samples,and eight normal esophageal mucosa samples were studied and The Cancer Genome Atlas(TCGA)was queried.PAX5 expression was examined by reverse transcription-polymerase chain reaction and western blotting.Cell apoptosis,proliferation,and chemosensitivity were detected by flow cytometry,colony formation assays,and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assays in ESCC cell lines with PAX5 overexpression or silencing.Tumor xenograft models were established for in vivo verification.Results:PAX5 methylation was found in 37.3%(19/51)of primary ESCC samples,which was significantly associated with age(P=0.007)and tumor-node-metastasis stage(P=0.014).TCGA data analysis indicated that PAX5 expression was inversely correlated with promoter region methylation(r=-0.189,P=0.011 for cg00464519 and r=-0.228,P=0.002 for cg02538199).Restoration of PAX5 expression suppressed cell proliferation,promoted apoptosis,and inhibited tumor growth of ESCC cell lines,which was verified in xenografted mice.Ectopic PAX5 expression significantly increased p53 reporter luciferase activity and increased p53 messenger RNA and protein levels.A direct interaction of PAX5 with the p53 promoter region was confirmed by chromatin immunoprecipitation assays.Re-expression of PAX5 sensitized ESCC cell lines KYSE150 and KYSE30 to fluorouracil and docetaxel.Silencing of PAX5 induced resistance of KYSE450 cells to these drugs.Conclusions:As a tumor suppressor gene regulated by promoter region methylation in human ESCC,PAX5 inhibit

关键词： PAX5 DNA methylation Esophageal cancer p53 signaling Chemosensitivity

Machine learning of partial differential equations from noise data

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Theoretical & Applied Mechanics Letters 2023年第6期13卷 441-446页

作者： Wenbo Cao Weiwei Zhang School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

Machine learning of partial differential equations(PDEs)from data is a potential breakthrough for addressing the lack of physical equations in complex dynamic systems.Recently,sparse regression has emerged as an attractive approach.However,noise presents the biggest challenge in sparse regression for identifying equations,as it relies on local derivative evaluations of noisy data.This study proposes a simple and general approach that significantly improves noise robustness by projecting the evaluated time derivative and partial differential term into a subspace with less noise.This method enables accurate reconstruction of PDEs involving high-order derivatives,even from data with considerable noise.Additionally,we discuss and compare the effects of the proposed method based on Fourier subspace and POD(proper orthogonal decomposition)subspace.Generally,the latter yields better results since it preserves the maximum amount of information.

关键词： Partial differential equation Machine learning Sparse regression Noise data

Traffic Accident Detection Based on Deformable Frustum Proposal and Adaptive Space Segmentation

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Computer Modeling in Engineering & Sciences 2022年第1期130卷 97-109页

作者： Peng Chen Weiwei Zhang Ziyao Xiao Yongxiang Tian School of Mechanical and Automotive Engineering Shanghai University of Engineering ScienceShanghai201620China Shanghai Fire Research Institute of MEM Shanghai200032China

Road accident detection plays an important role in abnormal scene reconstruction for Intelligent Transportation Systems and abnormal events warning for autonomous driving.This paper presents a novel 3D object detector and adaptive space partitioning algorithm to infer traffic accidents quantitatively.Using 2D region proposals in an RGB image,this method generates deformable frustums based on point cloud for each 2D region proposal and then frustum-wisely extracts features based on the farthest point sampling network(FPS-Net)and feature extraction network(FE-Net).Subsequently,the encoder-decoder network(ED-Net)implements 3D-oriented bounding box(OBB)regression.Meanwhile,the adaptive least square regression(ALSR)method is proposed to split 3D OBB.Finally,the reduced OBB intersection test is carried out to detect traffic accidents via separating surface theorem(SST).In the experiments of KITTI benchmark,our proposed 3D object detector outperforms other state-of-theartmethods.Meanwhile,collision detection algorithm achieves the satisfactory performance of 91.8%accuracy on our SHTA dataset.

关键词： Traffic accident detection 3D object detection deformable frustum proposal adaptive space segmentation

Electromagnetic-thermal-mechanical characteristics with active feedback control in a high-temperature superconducting noinsulation magnet

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Science China(Physics,Mechanics & Astronomy) 2022年第9期65卷 92-103页

作者： Donghui Liu Dongke Li Weiwei Zhang Huadong Yong Youhe Zhou Key Laboratory of Mechanics on Disaster and Environment in Western China Ministry of Education of ChinaLanzhou UniversityLanzhou 730000China Department of Mechanics and Engineering Sciences College of Civil Engineering and MechanicsLanzhou UniversityLanzhou 730000China

High-temperature superconducting(HTS) magnets consisting of no-insulation(NI) double-pancake coils(DPCs) with high thermal stability have been proposed for use in the preparation of high-field magnets. However, increased ramp time is a known disadvantage of the NI approach. To solve this problem, a proportional and integral(PI) active feedback control has been proposed in the charging experiments of the NI magnet. In this study, the electromagnetic-thermal-mechanical characteristics of an NI magnet with and without PI are analyzed to ensure the safety and reliability of PI control. Due to the increase in the radial current of the magnet, the turn-to-turn loss energy of the magnet with PI is more than twice that without PI. However, the magnetization loss energy of the magnet has a small difference with and without PI. It can be also found that the NI magnet with PI has a large temperature rise, and thus it has a low thermal stability margin. Moreover, in the high field, the hoop stress and hoop strain peaks of a magnet with PI are larger than those without PI. Thus, PI control can induce a relatively high risk of mechanical damage in the applications of NI magnets.

关键词： no-insulation magnet active feedback control loss energy temperature rise strain and stress

The Innovation and Development of Internet of Vehicles

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中国通信：英文版 2016年第5期13卷 122-127页

作者： Weiwei Zhang Xiaoqiang Xi China Academy of Telecommunication Research of the Ministry of Industry and Information Technology Xi'an University of Posts and Telecommunications

With the advancements in wireless sensor networks, Internet of Vehicles(IOV) has shown great potential in aiding to ease traffic congestion. In IOV, vehicles can easily exchange information with other vehicles and infrastructures, thus, the development of IOV will greatly improve vehicles safety, promote green information consumption and have a profound impact on many industries. The purpose of this paper is to promote the innovation and development of IOV. Firstly, this paper presents general requirements of IOV such as guidelines, basic principles, and the goal of development. Secondly, we analyze critical applications, crucial support, and business model to promote the industrial development of IOV. Finally, this paper proposes some safeguard measures to further promote the development of IOV.

关键词：互联网车辆创新无线传感器网络消费信息交通拥堵基础设施商业模式

Abnormal changes of dynamic derivatives at low reduced frequencies

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Chinese Journal of Aeronautics 2018年第7期31卷 1428-1436页

作者： Weiwei Zhang Yiming GONG Yilang LIU School of Aeronautics Northwestern Polytechnical University

A number of studies have found that abnormal changes of dynamic derivatives occurred at very low reduced frequencies, but its inducement mechanism is not very clear. This paper has researched the abnormal changes and analyzed the influence on some parameters by solving the unsteady flow around forced oscillation airfoils based on Navier-Stokes equations. Results indicate that when the reduced frequency approaches to zero, the dynamic derivatives obtained by the numerical method will diverge. We have also proven it in theory that this phenomenon is not physical but completely caused by numerical singularity. Furthermore, the abnormal phenomenon can be effectively mitigated by using the time spectral method to solve the aerodynamic forces and the integral method to obtain the dynamic derivatives. When the reduced frequency is in the range of 0.001–0.01, the dynamic derivative maintains nearly unchanged for the whole speed region. This study can provide a reference for the reasonable choice of the reduced frequency in calculations and experiments of dynamic derivatives.

关键词： Dynamic derivatives Numerical diverge Reduced frequency Time spectral method Unsteady flow

Porphyrin-based metal-organic framework nanocrystals for combination of immune and sonodynamic therapy

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Nano Research 2023年第7期16卷 9633-9641页

作者： Sen Jiang Congcong Liu Qijia He Kun Dang Weiwei Zhang Yang Tian Department of Chemistry Analytical Instrumentation CenterCapital Normal UniversityBeijing 10048China School of Life Science Capital Normal UniversityBeijing 10048China

Immune therapy based on programmed death-ligand 1(PD-L1)is widely used to treat human tumors.The current strategies to improve immune checkpoint blockade therapy fail in rescuing increased expression of PD-L1 in tumor issues.Here,we for the first time synthesized the metal-organic framework(MOF)nanocrystals of rare-earth element dysprosium(Dy)coordinated with tetrakis(4-carboxyphenyl)porphyrin(TCPP),which show well-defined two-dimensional morphologies.The MOF nanocrystals of Dy-TCPP could apparently reduce PD-L1 expression in tumor cells both in vitro and in vivo,and therefore display effective tumor treatment through immune therapy without any immune checkpoint inhibitor drugs.Considering the sensitivity of TCPP ligand toward ultrasound,the prepared Dy-TCPP can also realize sonodynamic therapy(SDT)besides immune therapy.In addition,the Dy-TCPP nanocrystals can efficiently obtain T_(2)-weight magnetic resonance imaging(MRI)of tumor sites.Our study provides the Dy-TCPP nanocrystals as promising diagnostic MRI-guided platforms for the combined treatment on tumors with SDT and immune therapy.Moreover,this strategy succeeds in reducing the elevated expression of PD-L1 in tumor cells,which might serve as a novel avenue for tumor immunotherapy in future.

关键词： metal-organic frameworks(MOFs) nanosheet porphyrin immune therapy sonodynamic therapy(SDT)