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Developing modified k–εturbulence models for neutral atmospheric boundary layer flow simulation using OpenFOAM

Building Simulation 2024年第12期17卷 2281-2295页

作者： Yuanbo Wang Jiqin Li Wei Liu Jiankai Dong Jing Liu School of Architecture Harbin Institute of TechnologyKey Laboratory of Cold Region Urban and Rural Human Settlement Environment Science and TechnologyMinistry of Industry and Information TechnologyHarbin 150090China Tianjin Key Laboratory of Indoor Air Environmental Quality Control School of Environmental Science and EngineeringTianjin University92 Weijin RoadTianjin 300072China Division of Sustainable Buildings Department of Civil and Architectural EngineeringKTH Royal Institute of TechnologyBrinellvägen 2310044 StockholmSweden

Accurate turbulence modeling is essential for simulation studies of urban *** this study,the comprehensive atmospheric boundary layer(ABL)model involving a variable model coefficient and an additional turbulent dissipation source term was implemented using the open-source software *** with consistent inlet wind profiles and rough wall functions of different turbulence variables based on the aerodynamic roughness,the model maintained the horizontal homogeneity ***,a hybrid approach was introduced to consider buildings immersed in ABL flows,enabling automatic transformation of the turbulence model between the region around the buildings and the free flow region away from any ***,the effects of applying different model forms to the airflow field around buildings were evaluated in detail through three-dimensional building cases representing six urban prototypes based on three wind tunnel *** findings indicated that all modified k–εmodels perform well in reproducing the flow data of the CEDVAL and Architectural Institute of Japan(AIJ)experiments consisting of a single building,an array of buildings,and an isolated high-rise ***,the modified k–εmodel with an additional correction term performed poorly in the database of Niigata Institute of technology and the case of complex terrain and urban building configurations,because the correction term inhibited the generation of turbulent kinetic *** addition,from the comparison between the experimental data of all cases,the model with the original formulation of the coefficient performed the best in terms of prediction *** root mean square errors of the normalized velocity were 0.1250,0.0879,0.1145,0.1350,and 0.1492 in different cases,which proved the reliability of this turbulence model.

关键词： urban airflow computational fluid dynamics(CFD) atmospheric boundary layer OpenFOAM turbulence model

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Joint self-supervised and reference-guided learning for depth inpainting

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Computational Visual Media 2022年第4期8卷 597-612页

作者： Heng Wu Kui Fu Yifan Zhao Haokun Song Jia Li State Key Laboratory of Virtual Reality Technology and Systems School of Computer Science and EngineeringBeihang UniversityBeijing 100191China

Depth information can benefit various computer vision tasks on both images and ***,depth maps may suffer from invalid values in many pixels,and also large *** improve such data,we propose a joint self-supervised and reference-guided learning approach for depth *** the self-supervised learning strategy,we introduce an improved spatial convolutional sparse coding module in which total variation regularization is employed to enhance the structural information while preserving edge *** module alternately learns a convolutional dictionary and sparse coding from a corrupted depth ***,both the learned convolutional dictionary and sparse coding are convolved to yield an initial depth map,which is effectively smoothed using local contextual *** reference-guided learning part is inspired by the fact that adjacent pixels with close colors in the RGB image tend to have similar depth *** thus construct a hierarchical joint bilateral filter module using the corresponding color image to fill in large *** summary,our approach integrates a convolutional sparse coding module to preserve local contextual information and a hierarchical joint bilateral filter module for filling using specific adjacent *** results show that the proposed approach works well for both invalid value restoration and large hole inpainting.

关键词： depth inpainting self-supervised learning reference-guided learning

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Potentially Practical Catalytic systems for Olefin-Polar Monomer Coordination Copolymerization

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CCS Chemistry 2024年第4期6卷 882-897页

作者： Chen Tan Min Chen Chen Zou Changle Chen Institutes of Physical Science and Information Technology Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of EducationKey Laboratory of Environment-Friendly Polymeric Materials of Anhui ProvinceAnhui UniversityHefeiAnhui 230601 CAS Key Laboratory of Soft Matter Chemistry Department of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefei 230026

Studies on transition-metal catalyzed olefin-polar monomer coordination copolymerization and their resulting polar-functionalized polyolefin materials have attracted attention from both academia and *** decades of research,recent developments in a variety of high-performance catalytic systems have shown that this field is on the brink of *** review summarizes representative olefin-polar monomer coordination copolymerization catalyst systems that may be suitable for industrial polyolefin production via homogeneous solution-phase processes or heterogeneous gas-phase/slurry-phase processes.

关键词： olefin copolymerization polar monomer catalyst solution polymerization heterogeneous

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Cas-FNE:Cascaded Face Normal Estimation

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IEEE/CAA Journal of Automatica Sinica 2024年第12期11卷 2423-2434页

作者： Meng Wang Jiawan Zhang Jiayi Ma Xiaojie Guo the Tianjin Key Laboratory of Autonomous Intelligence Technology and Systems Tianjin 300350 the School of Computer Science and Technology Tiangong UniversityTianjin 300387China IEEE the College of Intelligence and Computing Tianjin UniversityTianjin 300365China the Electronic Information School Wuhan UniversityWuhan 430072China

Capturing high-fidelity normals from single face images plays a core role in numerous computer vision and graphics *** significant progress has been made in recent years,how to effectively and efficiently explore normal priors remains *** existing approaches depend on the development of intricate network architectures and complex calculations for in-the-wild face *** overcome the above issue,we propose a simple yet effective cascaded neural network,called Cas-FNE,which progressively boosts the quality of predicted normals with marginal model parameters and computational ***,it can mitigate the imbalance issue between training data and real-world face images due to the progressive refinement mechanism,and thus boost the generalization ability of the ***,in the training phase,our model relies solely on a small amount of labeled *** earlier prediction serves as guidance for following *** addition,our shared-parameter cascaded block employs a recurrent mechanism,allowing it to be applied multiple times for optimization without increasing network *** and qualitative evaluations on benchmark datasets are conducted to show that our Cas-FNE can faithfully maintain facial details and reveal its superiority over *** code is available at https://***/AutoHDR/***.

关键词： Cascaded learning face normal progressive refinement shared-parameter

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DIG: Improved DINO for Graffiti Detection

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IEEE Transactions on systems, Man, and Cybernetics: systems 2025年第5期55卷 3557-3569页

作者： Wang, Bingshu Mao, Qianchen Liu, Aifei Chen, Long Chen, C. L. Philip Northwestern Polytechnical University School of Software Xi’an710129 China Shenzhen University Guangdong Key Laboratory of Intelligent Information Processing Shenzhen Key Laboratory of Media Security Shenzhen518060 China University of Macao Department of Computer and Information Science China South China University of Technology School of Computer Science and Engineering Guangzhou510641 China

Graffiti detection is essential in historic building protection and urban neighborhood management. Graffiti detection has made significant progress in recent years based on the development of deep learning. However, small-scale graffiti, interference from the background, and the false detection of word parts in graffiti make it a challenging problem. This article proposes a Transformer-based high-precision graffiti detection method, namely DIG. Precisely, it consists of three modules: 1) Spatial query selection (SQS), scale-aware IoU loss (SIL);2) Denoising Task with binary contrastive denoising (BCDN);and 3) IoU-guided box denoising (IBD) modules. To detect small-scale graffiti, this paper proposes SIL to help the loss function to perceive small-scale graffiti and large-scale graffiti fairly. To reduce the false detection of word parts, this article presents the SQS module, which integrates spatial information into the query selection process of the Encoder to filter out falsely detected bounding boxes within the graffiti. To reduce the interference from the background, this article introduces a denoising task with BCDN and IBD modules, improving the model’s ability to distinguish graffiti from the background and accurately select appropriate bounding boxes. A large number of experimental results on the STORM dataset show that our method achieves state-of-the-art results with an AP50 of 87.9%. Moreover, DIG achieved competitive results on the FineFM dataset for mask detection. This indicates that DIG can also be conveniently transferred to detect other scenarios. © 2013 IEEE.

关键词： Historic preservation

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Strain concentration factor of heterogeneous materials and analytical influence functions based on Eshelby tensor

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Theoretical & Applied Mechanics Letters 2024年第4期14卷 306-313页

作者： Shanqiao Huang Zifeng Yuan HEDPS Center for Applied Physics and TechnologyDepartment of Mechanics and Engineering SciencePeking UniversityBeijing 100871China State Key Laboratory for Turbulence and Complex Systems Peking UniversityBeijing 100871China

In this manuscript,Eshelby tensor is employed to assess the strain concentration that arises in the matrix phase at the interface,offering precise values and locations of maximum strain under specific loading conditions for both spherical and cylindrical *** compared to numerical simulation results,the analytical predictions grounded in the Eshelby tensor exhibit satisfactory *** an analytical calculation method based on Eshelby tensor for the elastic strain influence functions of reduced-order homogenization(ROH)method is developed and adopted on particle-reinforced and fibrous composites,presenting its feasibility and advantage on off-line stage calculation of ROH *** error analyses between analytical and numerical results are *** numerical results also exhibit the necessity of finer interface partitioning to obtain the response on micro-scale with higher resolution.

关键词： Eshelby tensor Strain concentration Composite structures Reduced-order-homogenization Influence functions

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High-Precision DOA Estimation Method Based on Synthetic Aperture Technique

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Journal of Beijing Institute of technology 2024年第2期33卷 111-118页

作者： Yongjia Dou Guangcai Sun Yuqi Wang Mengdao Xing National Key Laboratory of Radar Signal Processing Xidian UniversityXi’an 710071China School of Communication and Information Engineering Xi’an University of Science and TechnologyXi’an 710054China

The existing direction-of-arrival(DOA)estimation methods only utilize the current received signals,which are susceptible to *** this paper,a method for DOA estimation based on a motion platform is proposed to achieve high-precision DOA estimation by utilizing past and present *** concept of synthetic aperture is introduced to construct a linear DOA estima-tion model.A DOA fine-tuning method based on the linear model is proposed to eliminate the lin-ear DOA variation,achieving a non-coherent accumulation of DOA ***,the baseband modulation and the phase modulation caused by the range history are compensated to achieve the coherent accumulation of all the DOA *** results show that the proposed method can significantly improve the DOA estimated accuracy at low signal-to-noise ratios(SNR).

关键词： synthetic aperture direction-of-arrival(DOA)estimation coherent accumulation

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Modular access toπ-conjugated planar chiral diradicaloids using redox-active pillararenes

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science China Chemistry 2025年

作者： Yuting Xue Yi Zeng Yafei Shi Yu Tian Cuiping Sun Niu Zhang Xiaoyan Zheng Pangkuan Chen Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials Key Laboratory of Cluster Science of the Ministry of Education Key Laboratory of Medical Molecule Science and Pharmaceutics Engineering of the Ministry of Industry and Information Technology School of Chemistry and Chemical Engineering Beijing Institute of Technology Analysis & Testing Centre Beijing Institute of Technology

Open-shell chiral diradicals that feature both the unique chiroptical properties and tunable spin states have kindled numerous interests in organic synthesis and material *** present a new class of such model systems based on theπ-extended planar chiral pillar[5]arene derivatives P5Flu and P5Cz,where the pillar[5]arene-based chiral scaffolds are coupled with sterically encumbered fluorenyl and carbazolyl moieties as highly luminescent redox-active emitters,*** molecules in neutral states can readily undergo chemical oxidations leading toπ-conjugated chiral diradicals of the dehydrogenated P5Flu2·and a positively charged dication P5Cz2+2·.Characterization of the resulting Müller’s open-shell species by variable-temperature electron spin resonance （VT-ESR）,UV-vis-NIR absorption,VT-NMR and by computational studies revealed a singlet (ΔES-T=?1.63 kcal mol-1) and a nearly degenerate singlet-triplet ground state (ΔES-T=0.05 kcal mol-1,with a diradical character index y0=0.89) for P5Cz2+2·and P5Flu2·,*** particularly show in this work a new journey for pillar[5]arenes from the conventionally available closed-shell structures to different open-shell spin states with potential applications in chirospintronics and NIR-active chiroptoelectronic materials.

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Anomalous enhancing effects of electric pulse treatment on strength and ductility of TC17 linear friction welding joints

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Journal of Materials science & technology 2024年第36期203卷 155-166页

作者： Xin Zhang Junjie Zhang Yunkui Yao Qingsong Qiao Lixing Zhao Leichang Liu Feng Jin Mei Zhan Hongwei Li Key Laboratory of High-Performance Manufacturing for Aero Engine Ministry of Industry and Information TechnologyNorthwestern Polytechnical UniversityXi’an 710072China Engineering Research Center of Advanced Manufacturing Technology for Aero Engine Ministry of EducationNorthwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment Northwestern Polytechnical UniversityXi’an 710072China School of Materials Science and Engineering Jiangsu UniversityZhenjiang 212013China State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China

Mechanical properties of TC17 titanium alloy undergo a significant reduction after linear friction welding(LFW),of which the strength and ductility are hard to be improved simultaneously by traditional aging heat treatment(AHT),seriously limiting the application of LFW in the manufacturing of TC17 titanium alloy *** this end,the present work proposes to use electric pulse treatment(EPT)to enhance the strength and ductility of TC17 LFW joints simultaneously by improving its *** results show that,in comparison to the uneven distribution ofαphases in the welding zone(WZ),heat-affected zone(HAZ),and base metal(BM)zone after AHT,EPT can selectively homogenize theαphase distribution of WZ and HAZ without impacting the *** selective effect of EPT is reflected as the synergistic influence of the local Joule heating effect and the electron wind effect,which promotes the diffusion ofβphase stabilizing element Mo and leads to a competitive precipitation ofβphase andαphase in theαphase transition temperature *** ratio ofαphase toβphase in the WZ and HAZ finally approaches an equilibrium point which is similar to that of BM,leading to a uniform distribution ofαphase and realizing the synergy of strength-ductility of LFW joint:the maximum strength increase observed is 12.9%,accompanied by a corresponding elongation increase of 122%(by AHT&EPT),and the maximum plasticity improvement is 185%,accompanied by a corresponding strength increase of 4.3%(by EPT for 1 h).This study provides essential insights for improving the strength and ductility of LFW TC17 titanium alloy blisks and enhancing the applications of LFW in aeroengine components.

关键词： Linear friction welding TC17 titanium alloy Electric pulse treatment Phase transformation Local joule heating effect

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Brightness and Lifetime Improved Light-Emitting Diodes from Sr-Doped Quasi-Two-Dimensional Perovskite Layers

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Tsinghua science and technology 2023年第1期28卷 131-140页

作者： Dan Chen Taoran Liu Yuhua Zuo Chuanbo Li Jun Zheng Zhi Liu Baoyu Liu Buwen Cheng State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorChinese Academy of SciencesBeijing 100083China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China School of Science Minzu University of ChinaBeijing 100081China Beijing Advanced Innovation Center for Materials Genome Engineering Beijing Key Laboratory for SensorMOE Key Laboratory for Modern Measurement and Control Technologyand Beijing Information Science and Technology UniversityBeijing 100101China

Green Perovskite Light-Emitting Diodes(PeLEDs)have attracted wide attention for full spectrum ***,the inferior film morphology and luminescence property of quasi-two-dimensional(quasi-2D)perovskite layers limit the photoelectric property of the *** this paper,the effect of strontium(Sr)doped in quasi-2D perovskite layers is investigated to obtain a high-quality active *** morphologies and optical properties of Sr-doped quasi-2D perovskite films with different concentrations are *** the addition of strontium,more low-dimensional-layer perovskite phases(n D 2 and n D 3)appear in quasi-2D perovskite films,providing efficient intraband carrier funneling pathway and facilitating radiative *** photoluminescence(PL)peak intensity of optimized Sr-doped quasi-2D perovskite layers increases 50%compared with the non-strontium ***,green PeLEDs based on a Sr-doped quasi-2D perovskite layer reach a maximum luminance(Lmax)of 2943.77 cd/m^(2),which is three times of the control *** electroluminescence(EL)peaks of Maximum External Quantum Efficiency(MEQE)and Lmax of Sr-doped PeLEDs exhibite a slight shift,indicating the excellent stability and performance of Sr-doped *** optimized device can continuously operate for 360 s at MEQE driving voltage,resulting in a half-lifetime of60 s,which is 3-fold greater than that of the control PeLEDs.

关键词： Perovskite Light-Emitting Diodes(PeLED) Sr-doped brightness improved lifetime increased

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