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Automatic character detection and segmentation in natural scene images

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第1期8卷 63-71页

作者： Zhu kai-hua qi Fei-hu JIANG Ren-jie XU Li Department of Computer Science and Technology Shanghai Jiao Tong University Shanghai 200030 China

We present a robust connected-component (CC) based method for automatic detection and segmentation of text in real-scene images. This technique can be applied in robot vision, sign recognition, meeting processing and video indexing. First, a Non-Linear Niblack method (NLNiblack) is proposed to decompose the image into candidate CCs. Then, all these CCs are fed into a cascade of classifiers trained by Adaboost algorithm. Each classifier in the cascade responds to one feature of the CC. Proposed here are 12 novel features which are insensitive to noise, scale, text orientation and text language. The classifier cascade allows non-text CCs of the image to be rapidly discarded while more computation is spent on promising text-like CCs. The CCs passing through the cascade are considered as text components and are used to form the segmentation result. A prototype system was built, with experimental results proving the effectiveness and efficiency of the proposed method.

关键词： Text detection and segmentation Adaboost NLNiblack decomposition method Attentional cascade

Structure optimization of gas-liquid combined loop reactor using a CFD-PBE coupled model

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Petroleum Science 2012年第3期9卷 379-388页

作者： qi Nana Zhang kai Xu Gang Yang Yongping Zhang hu School of Energy Power and Mechanical Engineering North China Electric Power UniversityBeijing 102206China School of Chemical Engineering University of AdelaideSouth AustraliaSA 5005Australia

Flow characteristics, such as flow pattern, gas holdup, and bubble size distribution, in an internal loop reactor with external liquid circulation, are simulated to investigate the influence of reactor internals by using the computational fluid dynamics （CFD）-population balance equations （PBE） coupled model. Numerical results reveal that introducing a downcomer tube and a draft tube can help to improve the mass and heat transfer of the reactor through enhanced liquid circulation, increased gas holdup and reduced bubble diameter. The hydrodynamic behavior in the internal loop reactor with external liquid circulation can be managed effectively by adjusting the diameter and axial position of the draft tube.

关键词： Loop reactor Structure optimization Hydrodynamics CFD-PBE coupled model

CFD-PBE simulation of gas-phase hydrodynamics in a gas-liquid-solid combined loop reactor

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Petroleum Science 2013年第2期10卷 251-261页

作者： qi Nana Zhang kai Xu Gang Yang Yongping Zhang hu School of Energy Power and Mechanical Engineering North China Electric Power University School of Chemical Engineering University of AdelaideSouth AustraliaSA 5005Australia

The computational fluid dynamics （CFD）-population balance equations （PBE） coupled model is employed to investigate the hydrodynamics in a gas-slurry internal loop reactor with external slurry circulation. The predicted radial profiles of local gas holdup and bubble diameter are in good agreement with the corresponding experimental data. The spatio-temporal velocity profile of the gas phase reveals that the upward movement of gas is slowed down and the residence time of gas is prolonged by the downward momentum of the slurry, introduction of the external slurry can greatly improve the uniformity of gas holdup distribution in the reactor, especially in the downcomer-tube action region. Moreover, the interaction between the downward slurry and upward gas can lead to small bubble size and high interfacial area as well as good mass and heat transfer. The above results suggest the function of external slurry circulation for the internal loop reactor and would be helpful for optimizing the design and scale up of reactors.

关键词： CFD-PBE simulation external slurry circulation gas-liquid-solid hydrodynamics,population balance model

Controls on the regional distribution of landslide dams and implications for fluvial landform evolution in Bhutan and its surrounding area

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Journal of Mountain Science 2023年第8期20卷 2107-2132页

作者： ZHANG qi-yuan hu kai-heng LIU Shuang LIU Wei-ming Institute of Mountain Hazards and Environment Chinese Academy of Sciences(CAS)Chengdu 610041China University of Chinese Academy of Sciences Beijing 100149China China-Pakistan Joint Research Center on Earth Sciences Islamabad 30001Pakist

The regional distribution of landslide dams can provide valuable insights into the interactions among various factors,including lithology,topography,climate,and fluvial landforms in tectonically active *** rivers are frequently impacted by large-scale landslide damming,which profoundly influence fluvial *** this study,we identified 1652 landslide dams in four major rivers of Bhutan and its surrounding area by remote sensing ***,approximately 71%of these landslide dams are found in regions composed of quartzite or ***-related tectonic activity plays a significant role in governing the distribution of these landslide dams,as approximately 83%of the mapped landslide dams are found within a 10 km radius of the nearest *** majority of the identified landslide dams are situated in areas with relatively modest local relief,ranging from 227 m to 327 *** dams tend to cluster in the tributaries,and the stream power of almost 95%of them is typically below 1×10^(6) kg m^(2) s^(-3).Our data,combining the erosion rate and kernel density map of the landslide dams,reveals that regions with high erosion rates do not consistently align with the major high-density distribution of landslide *** is shown that the distribution of landslide dams is strongly influenced by the valley *** comparison to U-shaped valleys,V-shaped valleys exhibit a higher density of landslide ***,we also find a positive correlation between the landslide-dam distribution density and the erosion rate only in relatively arid regions with mean annual rainfall less than 500 ***,the length of the upstream reach protected by the knickpoint associated with both lithology and landslide damming is about three times longer than that protected by the knickpoint associated only with landslide damming.

关键词： Bhutan Himalayas Landslide dams Erosion rate Geomorphological impacts Landscape evolution

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天然和饱水红砂岩三轴压缩蠕变变形试验研究

三峡大学学报（自然科学版） 2025年第1期47卷 9-15页

作者：刘桃根胡凯李玲王伟湖南工学院土木与建筑工程学院湖南衡阳421002 河海大学岩土工程科学研究所南京210098 江西职业技术大学建筑工程学院江西九江332007

蠕变特性和长期强度是红砂岩地区岩体工程安全评价的关键要素,饱水软化效应对红砂岩蠕变特性和长期强度具有重要影响.采用全自动岩石三轴压缩伺服流变仪,开展天然与饱水红砂岩的三轴压缩试验和三轴压缩蠕变试验.试验结果表明:峰值强度... 详细信息

蠕变特性和长期强度是红砂岩地区岩体工程安全评价的关键要素,饱水软化效应对红砂岩蠕变特性和长期强度具有重要影响.采用全自动岩石三轴压缩伺服流变仪,开展天然与饱水红砂岩的三轴压缩试验和三轴压缩蠕变试验.试验结果表明:峰值强度、弹性模量和蠕变破坏应力因饱水软化效应而降低,围压对其降幅有削弱作用,蠕变破坏应力与峰值强度的比值在0.75~0.98之间;饱水软化效应能增强蠕变瞬时变形,减弱蠕变变形及蠕变应变速率;环向应变比轴向应变更早进入稳态蠕变阶段和加速蠕变阶段;稳态蠕变速率与偏压的变化关系符合指数函数关系;长期强度因饱水软化作用而降低,却因围压增加而增大,长期强度与峰值强度的比值在0.62~0.92之间;裂纹损伤应力与长期强度相差较大,裂纹损伤应力视为长期强度有待进一步考究.

关键词：红砂岩蠕变特性长期强度饱水软化效应裂纹损伤应力

Electrochemical Corrosion Behavior and Mechanical Response of Selective Laser Melted Porous Metallic Biomaterials

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Acta Metallurgica Sinica(English Letters) 2023年第8期36卷 1235-1246页

作者： kai hu Lei Zhang Yuanjie Zhang Bo Song Shifeng Wen qi Liu Yusheng Shi State Key Laboratory of Materials Processing and Die and Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan430074China Department of Mechanical Engineering City University of Hong KongTat Chee AvenueKowloonHong KongChina AVIC Manufacturing Technology Institute Science and Technology on Power Beam Processes LaboratoryBeijing Key Laboratory of High Power Beam Additive Manufacturing Technology and EquipmentAeronautical Key Laboratory for Additive Manufacturing TechnologiesBeijing100024China

The porous metallic biomaterials have attracted significant attention for implants because their lower young's modulus matches the human bones, which can eliminate the stress shielding effect and facilitate the growth of bone tissue cells. The porous metallic biomaterials fabricated by selective laser melting (SLM) have broad prospects, but the surface of the SLM-built porous structure has been severely adhered with unmelted powders, which affects the forming accuracy and surface quality. The porous metallic biomaterials face the corrosion problem of complex body fluid environments during service, so their corrosion resistance in the human body is extremely important. The surface quality will affect the corrosion resistance of the porous metallic biomaterials. Therefore, it is necessary to study the effect of post-treatment on the corrosion resistance of SLMed samples. In this work, the mechanical response and the electrochemical corrosion behavior in simulated body fluid of diamond and pentamode metamaterials Ti-6Al-4V alloy fabricated by SLM before and after sandblasting were studied. After sandblasting, the mechanical properties of the two porous metallic biomaterials were slightly improved, and the self-corrosion potential and pitting potential were more negative;meanwhile, the self-corrosion current density and passive current density increased, indicating that its corrosion performance decreased, and the passive film stability of sandblasted samples got worse.

关键词： Selective laser melting Porous metallic biomaterials Mechanical behavior Electrochemical corrosion behavior Ti-6A1-4V

A learning-based method to detect and segment text from scene images

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第4期8卷 568-574页

作者： JIANG Ren-jie qi Fei-hu XU Li WU Guo-rong Zhu kai-hua Department of Computer Science and Technology Shanghai Jiao Tong University Shanghai 200240 China

This paper proposes a learning-based method for text detection and text segmentation in natural scene images. First, the input image is decomposed into multiple connected-components (CCs) by Niblack clustering algorithm. Then all the CCs including text CCs and non-text CCs are verified on their text features by a 2-stage classification module, where most non-text CCs are discarded by an attentional cascade classifier and remaining CCs are further verified by an SVM. All the accepted CCs are output to result in text only binary image. Experiments with many images in different scenes showed satisfactory performance of our proposed method.

关键词： Text detection Text segmentation Text feature Attentional cascade

Numerical simulation of fluid dynamics in the stirred tank by the SSG Reynolds Stress Model

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Frontiers of Chemical Science and Engineering 2010年第4期4卷 506-514页

作者： Nana qi hui WANG kai ZHANG hu ZHANG State Key Lab of Heavy Oil Processing China University of PetroleumBeijing 102249China School of Chemical Engineering University of AdelaideAdelaide SA 5005Australia Beijing Aerospace WanYuan Coal Chemical Engineering Technology CO. LtdBeijing 100176China National Engineering Lab for Biomass Power Generation Equipment North China Electric Power UniversityBeijing 102206China

The Speziale,Sarkar and Gatski Reynolds Stress Model(SSG RSM)is utilized to simulate the fluid dynamics in a full baffled stirred tank with a Rushton turbine *** levels of grid resolutions are chosen to determine an optimised number of grids for further *** model data in terms of the flow field,trailing vortex,and the power number are compared with published experimental *** comparison shows that the global fluid dynamics throughout the stirred tank and the local characteristics of trailing vortices near the blade tips can be captured by the SSG *** predicted mean velocity components in axial,radial and tangential direction are also in good agreement with experiment *** power number predicted is quite close to the designed value,which demonstrates that this model can accurately calculate the power number in the stirred ***,the simulation by using a combination of SSG RSM and MRF impeller rotational model can accurately model turbulent fluid flow in the stirred tank,and it offers an alternative method for design and optimisation of stirred tanks.

关键词： stirred tank fluid dynamics numerical simulation SSG Reynolds Stress Model MRF

Hybridization-mediated quasiparticle and phonon dynamics in single crystal cerium films

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Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 146-153页

作者： Yunhe Pei Yi Wu kai hu Zhengxing Wei YiFeng Yang Yang Liu Jingbo qi State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu 611731China Center for Correlated Matter and Department of Physics Zhejiang UniversityHangzhou 310058China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Songshan Lake Materials Laboratory Dongguan 523808China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

We report the ultrafast optical pump-probe spectroscopy measurements on the single-crystal cerium *** experimental results of temperature-dependent quasiparticle dynamics reveal development of the hybridization between localized f moments and conduction electrons,i.e.,evolving from fluctuating hybridization to collective *** phonon renormalization is discovered to appear at the emerging temperature(T^(+))of fluctuating hybridization apart from its known presence at the coherent temperature(T^(*)),and can hardly be explained by the mean-field *** quasiparticle relaxation at high temperatures indicates coexistence of nonthermal electron-electron scattering and inelastic Kondo scattering,while its behavior at low temperatures suggests onset ofαphase in theγ-phase dominated *** also extract the indirect gap below T^(*),representing the appearance of collective *** findings provide novel information about the hybridization and phase evolution in the heavy fermion systems.

关键词： cerium quasiparticle dynamics hybridization phonon renormalization