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Multi-temporal InSAR for Urban Deformation Monitoring:Progress and Challenges

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雷达学报（中英文） 2020年第2期9卷 277-294页

作者： WU Songbo LE Yongyao ZHANG Lei ding xiaoli Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic UniversityHung HomKLNHong Kong 999077China Xi’an Engineering Investigation and Design Research Institute of China National Nonferrous Metals Industry Co.Ltd. Xi’an 710000China

Multi-temporal Interferometric Synthetic Aperture Radar(MT-InSAR) is one of the most powerful Earth observation techniques, especially useful for measuring highly detailed ground deformation over large ground areas. Much research has been carried out to apply MT-InSAR to monitor ground and infrastructure deformation in urban areas related to land reclamation, underground construction and groundwater *** paper reviews the progress in the research and identifies challenges in applying the technology, including the inconsistency in coherent point identification when different approaches are used, the reliability issue in parameter estimation, difficulty in accurate geolocation of measured points, the one-dimensional line-of-sight nature of InSAR measurements, the inability of making complete measurements over an area due to geometric distortions, especially the shadowing effects, the challenges in processing large SAR datasets, the decrease of the number of coherent points with the increase of the length of SAR time series, and the difficulty in quality control of MT-InSAR results.

关键词： Urban deformation Monitoring Multi-temporal InSAR

SAR image despeckling with a multilayer perceptron neural network

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International Journal of Digital Earth 2019年第3期12卷 354-374页

作者： Xiao Tang Lei Zhang xiaoli ding Department of Land Surveying and Geo-informatics The Hong Kong Polytechnic UniversityKowloonHong Kong

Speckle noise in synthetic-aperture radar (SAR) images severely hindersremote sensing applications;therefore, the appropriate removal ofspeckle noise is crucial. This paper elaborates on the multilayerperceptron (MLP) neural-network model for SAR image despeckling byusing a time series of SAR images. Unlike other filtering methods thatuse only a single radar intensity image to derive their parameters andfilter that single image, this method can be trained using archivedimages over an area of interest to self-learn the intensitycharacteristics of image patches and then adaptively determine theweights and thresholds by using a neural network for imagedespeckling. Several hidden layers are designed for feedforwardnetwork training, and back-propagation stochastic gradient descent isadopted to reduce the error between the target output and neuralnetwork output. The parameters in the network are automaticallyupdated in the training process. The greatest advantage of MLP is thatonce the despeckling parameters are determined, they can be used toprocess not only new images in the same area but also images incompletely different locations. Tests with images from TerraSAR-X inselected areas indicated that MLP shows satisfactory performance withrespect to noise reduction and edge preservation. The overall imagequality obtained using MLP was markedly higher than that obtainedusing numerous other filters. In comparison with other recentlydeveloped filters, this method yields a slightly higher image quality,and it demonstrates the powerful capabilities of computer learningusing SAR images, which indicate the promising prospect of applyingMLP to SAR image despeckling.

关键词： Multilayer perceptron synthetic aperture radar despeckling neural network

Ultrapermeable membranes based on connected cluster of hollow polydimethylsiloxane nanoparticles for gas separation

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Particuology 2023年第8期79卷 45-53页

作者： xiaoli ding Fangfang Tan Hongyong Zhao Qingping Xin Yuzhong Zhang State Key Laboratory of Separation Membranes and Membrane Processes National Center for International Joint Research on Separation MembranesTiangong UniversityTianjin300387China Tianjin Key Laboratory of Hollow Fiber Membrane Materials and Processes(Tiangong University) Tianjin300387China

Mixed matrix membranes(MMMs)with the performance between the matrix and the filler is a promising strategy for membranes with excellent gas *** this study,the hollow polydimethylsiloxane nanoparticles were synthesized and then incorporated with the poly(oxide ethylene)monomer and tri-functional cross-linker to form mixed matrix membranes by in situ *** hollow nanoparticles formed the independent closed nanocavities in membranes,which enhanced the gas permeability contributed by both the improved diffusivity and *** high loading,the hollow polydimethylsiloxane nanoparticle was converted into the continuous phase with the cross-linked poly(oxide ethylene)as the dispersed *** preferred to permeate through the connected cluster of hollow polydimethylsiloxane nanoparticles,finally leading to ultrahigh gas per-meabilities far going beyond the instinct values of polydimethylsiloxane and the cross-linked poly(oxide ethylene).The optimized membrane with 34 wt%hollow nanoparticles loadings exhibited ultrahigh permeabilities with the values of 44186 Barrer for CO_(2) and 11506 Barrer for O_(2),accompanied with a CO_(2)/N_(2) selectivity of 9.9 and an O_(2)/N_(2) selectivity of 2.6,which exceeded the 2008 Robeson upper bound for O_(2)/N_(2) and located at the 2008 Robeson upper bound for CO_(2)/N_(2).

关键词： Hollow nanoparticles Polydimethylsiloxane nanoparticles Mixed matrix membranes Nanocavity Gas separation

Gas permeation properties of a metallic ion-cross-linked PIM-1 thin-film composite membrane supported on a UV-cross-linked porous substrate

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Chinese Journal of Chemical Engineering 2018年第12期26卷 2477-2486页

作者： Hongyong Zhao Lizhong Feng xiaoli ding Xiaoyao Tan Yuzhong Zhang State Key Laboratory of Separation Membranes and Membrane Processes/National Center for International Joint Research on Separation Membranes Tianjin Polytechnic UniversityTianjin 300387China School of Environmental and Chemical Engineering Tianjin Polytechnic UniversityTianjin 300387China Institute of Separation Matenal and Process Control School of Material Science and Engmeering Tianjin Polytechnic UniversityTianjin 300387China

Metallic ion-cross-linked polymer of intrinsic microporosity(PIM-1) thin-film composite(TFC) membranes supported on an ultraviolet(UV)-cross-linked porous substrate were fabricated. The UV-cross-linked porous substrate was prepared via polymerization-induced phase separation. The PIM-1 TFC membranes were fabricated via a dip-coating procedure. Metallic ion-cross-linked PIM-1 TFC membranes were fabricated by hydrolyzing the PIM-1 TFC membrane in an alkali solution and then cross-linking it in a multivalent metallic ion solution. The pore size and porous structures were evaluated by low-temperature N_2 adsorption–desorption analysis. The membrane structure was investigated by field-emission scanning electron microscopy. The effects of heat treatment and pore-forming additives on the gas permeance of the UV-cross-linked porous substrate are reported. The effects of different pre-coating treatments on the gas permeance of the metallic ion-cross-linked PIM-1 TFC membrane are also discussed. The metallic ion-crosslinked PIM-1 TFC membrane displayed high CO_2/N_2 selectivity(23) and good CO_2 permeance(1058 GPU).

关键词： Gas separation Polymerization-induced phase separation UV-cross-linked porous substrate Metallic ion-cross-linked PIM-1TFC membrane

On stress-forecasting strategy of earthquakes from stress buildup,stress shadow and stress transfer(SSS) based on numerical approach

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Earthquake Science 2009年第1期22卷 53-62页

作者： Chunan Tang Tianhui Ma xiaoli ding Center for Rock Instability and Seismicity Research Northeastern University Shenyang China Department of Land Surveying and Geo-Informatics Hong Kong Polytechnic University Kowloon Hong Kong China

Global Positioning System （GPS） and Interferometric Synthetic Aperture Radar （InSAR）, used for monitoring crust deformation, are found to be very promising in earthquake prediction subject to stress-forecasting. However, it is recognized that unless we can give reasonable explanations of these curious precursory phenomena that continue to be serendipitously observed from time to time, such high technology of GPS or InSAR is difficult to be efficiently used. Therefore, a proper model revealing the relation between earthquake evolution and stress variation, such as the phenomena of stress buildup, stress shadow and stress transfer （SSS）, is crucial to the GPS or InSAR based earthquake prediction. Here we address this question through a numerical approach of earthquake development using an intuitive physical model with a map-like configuration of discontinuous fault system. The simulation provides a physical basis for the principle of stress-forecasting of earthquakes based on SSS and for the application of GPS or InSAR in earthquake prediction. The observed SSS associated phenomena with images of stress distribution during the failure process can be continuously simulated. It is shown that the SSS are better indicators of earthquake precursors than that of seismic foreshocks, suggesting a predictability of earthquakes based on stress-forecasting strategy.

关键词： stress-forecasting earthquake stress buildup stress shadow stress transfer

Inferring three-dimensional surface displacement field by combining SAR interferometric phase and amplitude information of ascending and descending orbits

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Science China Earth Sciences 2010年第4期53卷 550-560页

作者： HU Jun LI ZhiWei ZHU JianJun REN XiaoChong ding xiaoli Department of Survey Engineering and Geomatics Central South UniversityChangsha 410083China Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic UniversityHong KongChina

Conventional Interferometric Synthetic Aperture Radar(InSAR) technology can only measure one-dimensional surface displacement(along the radar line-of-sight(LOS) direction).Here we presents a method to infer three-dimensional surface displacement field by combining SAR interferometric phase and amplitude information of ascending and descending *** method is realized in three steps:(1) measuring surface displacements along the LOS directions of both ascending and descending orbits based on interferometric phases;(2) measuring surface displacements along the azimuth directions of both the ascending and descending orbits based on the SAR amplitude data;and(3) estimating the three-dimensional(3D) surface displacement field by combining the above four independent one-dimensional displacements using the method of least squares and Helmert variance component *** apply the method to infer the 3D surface displacement field caused by the 2003 Bam,Iran,*** results reveal that in the northern part of Bam the ground surface experienced both subsidence and southwestward horizontal movement,while in the southern part uplift and southeastward horizontal movement *** displacement field thus determined matches the location of the fault very well with the maximal displacements reaching 22,40,and 30 cm,respectively in the up,northing and easting ***,we compare the 3D displacement field with that simulated from the Okada *** results demonstrate that the method presented here can be used to generate reliable and highly accurate 3D surface displacement fields.

关键词： InSAR amplitude matching azimuth offset three-dimensional surface displacement Bam earthquake

H_2/CO_2 Gas Transport Performance in Poly(Ethylene Oxide) Reverse-selective Membrane with Star-like Structures

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Journal of Wuhan University of Technology(Materials Science) 2019年第1期34卷 195-200页

作者： ZHAO Hongyong ding xiaoli State Key Laboratory of Separation Membranes and Membrane Processes/National Center for International Joint Research on Separation Membrane Tianjin Polytechnic University Tianjin Key Laboratory of Hollow Fiber Membrane Materials and Processes Tianjin Polytechnic University School of Environmental and Chemical Engineering Tianjin Polytechnic University Institute of Separation Material and Process Control School of Material Science and EngineeringTianjin Polytechnic University

A series of poly(ethylene oxide)(PEO) membranes with star-like structures for CO_2/H_2 separation were prepared by the photo-polymerization method. The structure of PEO membrane was characterized by Fourier transform infrared spectroscopy(FTIR). The thermal property and inter-segmental distance of polymer chain were investigated by differential scanning calorimetry and wide-angle X-ray diffraction, respectively. The density was determined by hydrostatic weighing method. The gas permeability, solubility and diffusivity of CO_2 and H_2 were investigated in the star-like PEO membranes. The relationship between gas permeation performances and physical properties was also discussed. The membrane exhibits outstanding CO_2 permeability(about 9.7×10^(-11) cm^3(STP) cm/cm^2/s/Pa) and CO_2/H_2 selectivity(about 11) compared with other membranes.

关键词： hydrogen purification reverse-selective membrane poly(ethylene oxide) star-like structure

A review of methods for mitigating ionospheric artifacts in differential SAR interferometry

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Geodesy and Geodynamics 2022年第2期13卷 160-169页

作者： Bochen Zhang Wu Zhu xiaoli ding Chisheng Wang Songbo Wu Qin Zhang MNR Key Laboratory for Geo-Environmental Monitoring of Great Bay Area&Guangdong Key Laboratory of Urban Informatics&Shenzhen Key Laboratory of Spatial Smart Sensing and Services Shenzhen University518060 ShenzhenChina College of Civil and Transportation Engineering Shenzhen University518060 ShenzhenChina School of Geology Engineering and Geomatics Chang'an UniversityXi'anShaanxiChina Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic UniversityKowloonHong KongChina School of Architecture&Urban Planning Shenzhen University518060 ShenzhenChina

Interferometric synthetic aperture radar(InSAR)has been widely used to measure ground displacements related to geophysical and anthropic activities over the past three *** SAR systems use microwave signals that interact with the ionosphere when they travel through it during the imaging *** this context,ionospheric variations can significantly contaminate SAR imagery,which in turn affects spaceborne InSAR *** bias also leads to a decrease in the coherence and accuracy of InSAR measurements,especially for the low-frequency SAR *** this paper,we give an overview of the latest methods for mitigating the ionospheric contributions in InSAR,including Faraday rotation method,azimuth shift method,and range split-spectrum method,and only focus on the single pair of InSAR *** current challenges and future perspectives are outlined at the end of this paper.

关键词： InSAR Ionospheric artifacts Azimuth pixel shift Faraday rotation Range split-spectrum

Partial pore blockage and polymer chain rigidification phenomena in PEO/ZIF-8 mixed matrix membranes synthesized by in situ polymerization

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Chinese Journal of Chemical Engineering 2018年第3期26卷 501-508页

作者： xiaoli ding Xu Li Hongyong Zhao Ran Wang Runqing Zhao Hong Li Yuzhong Zhang State Key Laboratory of Separation Membranes and Membrane Processes/National Center for International Joint Research on Separation Membranes Tianjin Polytechnic University Tianjin Key Laboratory of Hollow Fiber Membrane Materials and Processes Tianjin Polytechnic University Institute of Separation Material and Process Control School of Material Science and Engineering Tianjin Polytechnic University School of Environmental and Chemical Engineering Tianjin Polytechnic University

Nanostructured zeolitic imidazolate frameworks(ZIF-8) was incorporated into the mixture of poly(ethylene glycol) methyl ether acrylate(PEGMEA) and pentaerythritol triacrylate(PETA) to synthesize mixed matrix membranes(MMMs) by in situ polymerization for CO_2/CH_4 separation. The solvent-free polymerization between PEGMEA and PETA was induced by UV light with 1-hydroxylcyclohexyl phenyl ketone as initiator. The chemical structural characterization was performed by Fourier transform infrared spectroscopy. The morphology was characterized by scanning electron microscope. The average chain-to-chain distance of the polymer chains in MMMs was investigated by X-ray diffraction. The thermal property was evaluated by differential scanning calorimetry. The CH_4 and CO_2 gas transport properties of MMMs are reported. The relationship between gas permeation–separation performances or physical properties and ZIF-8 loading is also discussed. However, the permeation–separation performance was not improved in Robeson upper bound plot compared with original polymer membrane as predicted. The significant partial pore blockage and polymer rigidification effect around the ZIFs confirmed by the increase in glass temperature and the decrease in the d-spacing, were mainly responsible for the failure in performance improvement, which offset the high diffusion induced by porous ZIF-8.

关键词： Mixed matrix membrane Partial pore blockage Polymer chain rigidification CO2 separation