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IMAGE SUPER-RESOLUTION RECONSTRUCTION BY HUBER REGULARIZATION AND TAILORED FINITE POINT METHOD

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Journal of Computational Mathematics 2024年第2期42卷 313-336页

作者： Wenli Yang Zhongyi Huang Wei Zhu School of Mathematics China University of Mining and TechnologyXuzhou 221116China Department of Mathematics Tsinghua UniversityBeijing 100084China Department of Mathematics University of AlabamaTuscaloosaAL 35487USA

In this paper,we propose using the tailored finite point method(TFPM)to solve the resulting parabolic or elliptic equations when minimizing the Huber regularization based image super-resolution model using the augmented Lagrangian method(ALM).The Hu-ber regularization based image super-resolution model can ameliorate the staircase for restored images.TFPM employs the method of weighted residuals with collocation tech-nique,which helps get more accurate approximate solutions to the equations and reserve more details in restored images.We compare the new schemes with the Marquina-Osher model,the image super-resolution convolutional neural network(SRCNN)and the classical interpolation methods:bilinear interpolation,nearest-neighbor interpolation and bicubic interpolation.Numerical experiments are presented to demonstrate that with the new schemes the quality of the super-resolution images has been improved.Besides these,the existence of the minimizer of the Huber regularization based image super-resolution model and the convergence of the proposed algorithm are also established in this paper.

关键词： Image super-resolution Variational model Augmented Lagrangian methods Tailored finite point method

Multi-Phase Segmentation Using Modified Complex Cahn-Hilliard Equations

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Numerical Mathematics(Theory,Methods and Applications) 2022年第2期15卷 442-463页

作者： Xiakai Wang Zhongyi Huang Wei Zhu Department of Mathematical Sciences Tsinghua UniversityBeijing 100084China Department ofMathematics University of AlabamaBox 870350TuscaloosaAL 35487USA

In this paper,we propose a novel PDE-based model for the multi-phase segmentation problem by using a complex version of Cahn-Hilliard equations.Specifically,we modify the original complex system of Cahn-Hilliard equations by adding the mean curvature term and the fitting term to the evolution of its real part,which helps to render a piecewisely constant function at the steady state.By applying the K-means method to this function,one could achieve the desired multiphase segmentation.To solve the proposed system of equations,a semi-implicit finite difference scheme is employed.Numerical experiments are presented to demonstrate the feasibility of the proposed model and compare our model with other related ones.

关键词： Image segmentation Cahn-Hilliard equation semi-implicit finite difference scheme

Novel robust simultaneous localization and mapping for long-term autonomous robots

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Frontiers of Information Technology & Electronic Engineering 2022年第2期23卷 234-245页

作者： wei wei Xiaorui zhu Yi WANG School of Mechanical Engineering and Automation Harbin Institute of TechnologyShenzhen 518055China zhuhai Big Data Research Institute Zhuhai 519000China

A fundamental task for mobile robots is simultaneous localization and mapping(SLAM).Moreover,long-term robustness is an important property for SLAM.When vehicles or robots steer fast or steer in certain scenarios,such as low-texture environments,long corridors,tunnels,or other duplicated structural environments,most SLAM systems might fail.In this paper,we propose a novel robust visual inertial light detection and ranging(Li Da R)navigation(VILN)SLAM system,including stereo visual-inertial Li Da R odometry and visual-Li Da R loop closure.The proposed VILN SLAM system can perform well with low drift after long-term experiments,even when the Li Da R or visual measurements are degraded occasionally in complex scenes.Extensive experimental results show that the robustness has been greatly improved in various scenarios compared to state-of-the-art SLAM systems.

关键词： Simultaneous localization and mapping(SLAM) Long-term Robustness Light detection and ranging(LiDaR) Visual inertial LiDaR navigation(VILN)

Relationship between time in range and corneal nerve fiber loss in asymptomatic patients with type 2 diabetes

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Chinese Medical Journal 2022年第16期135卷 1978-1985页

作者： Wejing Zhao Jingyi Lu Lei Zhang wei Lu Wei Zhu Yuqian Bao Jjian Zhou 'Department of Endocrinology and Metabolism Shanghai Jiao Tong Universty Ailatede Sith People's HospitalShanghai Cinical Center for DiabetesShanghai Key Clinical Center for Metabolic DiseaseShanghai Diabetes IstuteShanghai Key Laboratory of Diabetes MellitusShanghai 200233China Shanghai Clinical Center for Metabolic Diseases Shanghai Key Laboratory of Diabetes MeliusShanghai Diabetes IstituteShanghai Jiao Tong University Alilatedae Sith People's HospitalShanghai 200233China Department of Endocrinology and Metabolism Jinshan Branch of Shanghai Jiao Tong University Aflatedae Sixth People's HospitalShanghai 201500China

Background: Corneal confocal microscopy (CCM) is a noninvasive technique to detect early nerve damage of diabetic sensorimotor polyneuropathy (DSPN). Time in range (TIR) is an emerging metric of glycemic control which was reported to be associated with diabetic complications. We sought to explore the relationship between TIR and corneal nerve parameters in asymptomatic patients with type 2 diabetes (T2DM).Methods: In this cross-sectional study, 206 asymptomatic inpatients with T2DM were recruited. After 7 days of continuous glucose monitoring, the TIR was calculated as the percentage of time in the glucose range of 3.9 to 10.0 mmol/L. CCM was performed to determine corneal nerve fiber density, corneal nerve branch density, and corneal nerve fiber length (CNFL). Abnormal CNFL was defined as ≤15.30 mm/mm2.Results: Abnormal CNFL was found in 30.6% (63/206) of asymptomatic subjects. Linear regression analyses revealed that TIR was positively correlated with CCM parameters both in the crude and adjusted models (all P< 0.05). Each 10% increase in TIR was associated with a 28.2% (95% CI: 0.595–0.866,P = 0.001) decreased risk of abnormal CNFL after adjusting for covariates. With the increase of TIR quartiles, corneal nerve fiber parameters increased significantly (allP for trend <0.01). The receiver operating characteristic curve indicated that the optimal cutoff point of TIR was 77.5% for predicting abnormal CNFL in asymptomatic patients.Conclusions: There is a significant independent correlation between TIR and corneal nerve fiber loss in asymptomatic T2DM patients. TIR may be a useful surrogate marker for early diagnosis of DSPN.

关键词： Continuous glucose monitoring Corneal confocal microscopy Time in range Type 2 diabetes

Risk assessment of erosive aggressiveness due to the condensation shock by numerical simulation

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Journal of Hydrodynamics 2022年第2期34卷 200-206页

作者： wei Zhang Bing zhu Science and Technology on Water Jet Propulsion Laboratory Marine Design and Research Institute of ChinaShanghai200011China School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai200093China

Cavitation is,for the engineering areas such as fluid machinery and ship propulsion,a known source of erosion.The erosion damage due to cavitation bubble collapse can lead to extreme failure events,implying the replacement of a ship propeller or a turbine in a hydropower plant,all of which are very costly operations.The dynamics of cavitation hydraulic structure is of great importance for cavitation erosion.As a result,the blade surface endures some extremely high stresses,which lead to the cause of wear.Two major mechanisms,re-entrant jet as well as condensation shock,are known to such transient cavitating flow.In the present work we study the latter since less has been reported for the erosion caused by such an unsteady cavitating flow.We adopted an energy transportation equation based method,combined with a collapse event detection strategy,to carry out numerical erosion risk assessment for erosive aggressiveness due to the condensation shock.Comparing with the paint test,our result shows good agreement in the erosive pattern.We further discussed the hydrodynamics of the related flow structures.

关键词： Condensation shock numerical simulation cavitation erosion

Improving the water electrolysis performance by manipulating the generated nano/micro-bubbles using surfactants

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Nano Research 2023年第1期16卷 420-426页

作者： Houpeng Wang Zhaoxiang Xu wei Lin Xue Yang Xianrui Gu Wei Zhu Zhongbin zhuang SINOPEC Research Institute of Petroleum Processing Beijing 100083China State Key Lab of Organic-Inorganic Composites and Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical TechnologyBeijing 100029China Beijing Key Laboratory of Energy Environmental Catalysis Beijing University of Chemical TechnologyBeijing 100029China

The impeded mass transfer rate by on-site-generated gas bubbles at both cathode and anode dramatically reduces the energy conversion efficiency of the proton exchange membrane water electrolyzer(PEMWE).Herein,we report a surfactant-assistant method to accelerate the nano/micro-bubble detachment and the mass transfer rate by reducing the surface tension,resulting in an increase in overall efficiency.Four kinds of surfactants are studied in this work.Only potassium perfluorobutyl sulfonate(PPFBS),which has the structural similarity to Nafion,shows a significant promotion of activity and stability for both hygrogen evolution reaction(HER)and oxygen evolution reaction(OER)in the acidic medium at the high current density region.The HER overpotential at 0.1 A·cm−2 decreased 22%,and the current density at−0.4 V increased 31%by adding PPFBS.The promotion of overall efficiency by PPFBS on a homemade PEMWE was also proven.The reduced surface tension and electrostatic repulsion were the probable origins of the accelerated bubble detachment.

关键词： proton exchange membrane water electrolysis bubble overpotential surfactant electrostatic repulsion

High-sensitivity self-powered temperature/pressure sensor based on flexible Bi-Te thermoelectric film and porous microconed elastomer

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Journal of Materials Science & Technology 2022年第8期103卷 1-7页

作者： Yaling Wang Wei Zhu Yuan Deng Pengcheng zhu Yuedong Yu Shaoxiong Hu Ruifeng Zhang School of Materials Science and Engineering Beihang UniversityBeijing 100191China Hangzhou Innovation Institute Beihang UniversityHangzhou 310052China Research Institute for Frontier Science Beihang UniversityBeijing 100083China Beijing Advanced Innovation Center for Biomedical Engineering Beihang UniversityBeijing 100191China College of Science Henan Agricultural UniversityZhengzhou450002China

Electronic skins are artificial skin-type multifunctional sensors,which hold great potentials in intelligent robotics,limb prostheses and human health monitoring.However,it is a great challenge to independently and accurately read various physical signals without power supplies.Here,a self-powered flexible temperature-pressure bimodal sensor based on high-performance thermoelectric films and porous microconed conductive elastic materials is presented.Through introducing flexible heat-sink design and harvesting body heat energy,the thin-film thermoelectric device could not only precisely sense temperature signal but also drive the pressure sensor for detecting external tactile stimulus.The integration of Bi-Te based thermoelectric film with high stability in wide temperature range enables the sensor to sense the ambient temperature with high resolution(<0.1 K)as well as excellent sensitivity(3.77 mV K^(-1)).Meanwhile,the porous microconed elastomer responds to pressure variation with low-pressure detection(16 Pa)and a high sensitivity of 37 kPa^(-1).Furthermore,the bimodal sensor could accurately and simultaneously monitor human wrist pulse and body temperature in real time,which demonstrates promising applications in self-powered electronic skins for human health monitoring systems.

关键词： Bimodal sensor Body heat energy Porous microconed architecture Bi-Te based thermoelectric film Self-powered E-skins

Dynamic coupled thermo-hydro-mechanical problem for heterogeneous deep-sea sediments under vibration of mining vehicle

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Applied Mathematics and Mechanics(English Edition) 2023年第4期44卷 603-622页

作者： Wei Zhu Xingkai MA Xinyu SHI Wenbo MA Hunan Key Laboratory for Computation and Simulation in Science and Engineering Xiangtan UniversityXiangtan 411105Hunan ProvinceChina School of Mathematics and Computational Science Xiangtan UniversityXiangtan 411105Hunan ProvinceChina School of Mechanical Engineering and Mechanics Xiangtan UniversityXiangtan 411105Hunan ProvinceChina

Due to the influence of deep-sea environment,deep-sea sediments are usually heterogeneous,and their moduli of elasticity and density change as depth changes.Combined with the characteristics of deep-sea sediments,the thermo-hydro-mechanical coupling dynamic response model of heterogeneous saturated porous sediments can be established to study the influence of elastic modulus,density,frequency,and load amplitude changes on the model.Based on the Green-Lindsay generalized thermoelasticity theory and Darcy’s law,the thermo-hydro-mechanical coupled dynamic response model and governing equations of heterogeneous deep-sea sediments with nonlinear elastic modulus and density are established.The analytical solutions of dimensionless vertical displacement,vertical stress,excess pore water pressure,and temperature are obtained by means of normal modal analysis,which are depicted graphically.The results show that the changes of elastic modulus and density have few effects on vertical displacement,vertical stress,and temperature,but have great effects on excess pore water pressure.When the mining machine vibrates,the heterogeneity of deep-sea sediments has great influence on vertical displacement,vertical stress,and excess pore water pressure,but has few effects on temperature.In addition,the vertical displacement,vertical stress,and excess pore water pressure of heterogeneous deep-sea sediments change more gently.The variation trends of physical quantities for heterogeneous and homogeneous deep-sea sediments with frequency and load amplitude are basically the same.The results can provide theoretical guidance for deep-sea mining engineering construction.

关键词： heterogeneous deep-sea sediment coupled thermo-hydro-mechanical Green-Lindsay generalized thermoelastic theory normal modal anlalysis dynamic re-sponse

Hierarchical Cluster Coordination Control Strategy for Large-scale Wind Power Based on Model Predictive Control and Improved Multi-time-scale Active Power Dispatching

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Journal of Modern Power Systems and Clean Energy 2023年第3期11卷 827-839页

作者： Ying zhu Yanan Zhang Zhinong wei College of Energy and Electrical Engineering Hohai UniversityNanjing 210098China

The grid-connection of large-scale and high-penetration wind power poses challenges to the friendly dispatching control of the power system.To coordinate the complicated optimal dispatching and rapid real-time control,this paper proposes a hierarchical cluster coordination control(HCCC)strategy based on model predictive control(MPC)technique.Considering the time-varying characteristics of wind power generation,the proposed HCCC strategy constructs an improved multitime-scale active power dispatching model,which consists of five parts:formulation of cluster dispatching plan,rolling modification of intra-cluster plan,optimization allocation of wind farm(WF),grouping coordinated control of wind turbine group(WTG),and real-time adjustment of single-machine power.The time resolutions are sequentially given as 1 hour,30 min,15 min,5 min,and 1 min.In addition,a combined predictive model based on complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN),wavelet thresholding(WT),and least squares support vector machine(LSSVM)is established.The fast predictive feature of this model cooperates with the HCCC strategy that effectively improves the predictive control precision.Simulation results show that the proposed HCCC strategy enables rapid response to active power control(APC),and significantly improves dispatching control accuracy and wind power accommodation capabilities.

关键词： Wind power active power dispatching model predictive control(MPC) hierarchical control wind power prediction