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  • MDPI AG  (11)
  • Sun, Weiwei  (11)
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  • MDPI AG  (11)
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  • 1
    Online Resource
    Online Resource
    R-CNN-Based Ship Detection from High Resolution Remote Sensing Imagery
    MDPI AG ; 2019
    In:  Remote Sensing Vol. 11, No. 6 ( 2019-03-15), p. 631-
    Details
    In: Remote Sensing, MDPI AG, Vol. 11, No. 6 ( 2019-03-15), p. 631-
    Abstract: Offshore and inland river ship detection has been studied on both synthetic aperture radar (SAR) and optical remote sensing imagery. However, the classic ship detection methods based on SAR images can cause a high false alarm ratio and be influenced by the sea surface model, especially on inland rivers and in offshore areas. The classic detection methods based on optical images do not perform well on small and gathering ships. This paper adopts the idea of deep networks and presents a fast regional-based convolutional neural network (R-CNN) method to detect ships from high-resolution remote sensing imagery. First, we choose GaoFen-2 optical remote sensing images with a resolution of 1 m and preprocess the images with a support vector machine (SVM) to divide the large detection area into small regions of interest (ROI) that may contain ships. Then, we apply ship detection algorithms based on a region-based convolutional neural network (R-CNN) on ROI images. To improve the detection result of small and gathering ships, we adopt an effective target detection framework, Faster-RCNN, and improve the structure of its original convolutional neural network (CNN), VGG16, by using multiresolution convolutional features and performing ROI pooling on a larger feature map in a region proposal network (RPN). Finally, we compare the most effective classic ship detection method, the deformable part model (DPM), another two widely used target detection frameworks, the single shot multibox detector (SSD) and YOLOv2, the original VGG16-based Faster-RCNN, and our improved Faster-RCNN. Experimental results show that our improved Faster-RCNN method achieves a higher recall and accuracy for small ships and gathering ships. Therefore, it provides a very effective method for offshore and inland river ship detection based on high-resolution remote sensing imagery.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs11060631
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
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  • 2
    Online Resource
    Online Resource
    Accuracy Evaluation of Two High-Resolution Satellite-Based Rainfall Products: TRMM 3B42V7 and CMORPH in Shanghai
    MDPI AG ; 2018
    In:  Water Vol. 10, No. 1 ( 2018-01-05), p. 40-
    Details
    In: Water, MDPI AG, Vol. 10, No. 1 ( 2018-01-05), p. 40-
    Abstract: Satellite-based rainfall products have extensive applications in global change studies, but they are known to contain deviations that require comprehensive verification at different scales. In this paper, we evaluated the accuracies of two high-resolution satellite-based rainfall products: the Tropical Rainfall Measurement Mission (TRMM) rainfall product 3B42V7 and the Climate Prediction Center morphing (CMORPH) technique from January 2010 to December 2011 in Shanghai, by using categorical metrics (Probability of Detection, False Alarm Ratio, and Critical Success Index) and statistical indicators (Mean Absolute Error, Root Mean Square Error, Relative Bias, and Correlation Coefficient). Our findings show that, firstly, CMORPH data has a higher accuracy than 3B42V7 at the daily scale, but it underestimates the occurrence frequency of daily rainfall for some intensity ranges. Most errors of the two products are distributed between −10 and 10 mm/day. Second, at the monthly scale, the total accuracy of 3B42V7 is higher than CMORPH in terms of the value of the Correlation Coefficient (CC) and Relative Bias (RB). Finally, CMORPH brings about daily rainfall detection results from categorical metrics computation better than 3B42V7. Generally, the two satellite-based rainfall products show a high correlation with rain gauge data in Shanghai, particularly in spring and winter. Unfortunately, in summer, both of them do not perform well in detecting the short-duration heavy rainfall events. Overall, the relatively poor data accuracy has limited their further applications in Shanghai and similar urban areas.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w10010040
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
    detail.hit.zdb_id: 2521238-2
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  • 3
    Online Resource
    Online Resource
    Spatial Distribution and Ecological Risk Assessment of Potentially Harmful Trace Elements in Surface Sediments from Lake Dali, North China
    MDPI AG ; 2019
    In:  Water Vol. 11, No. 12 ( 2019-12-01), p. 2544-
    Details
    In: Water, MDPI AG, Vol. 11, No. 12 ( 2019-12-01), p. 2544-
    Abstract: Potentially harmful trace element (PHTE) pollution in lakes has important implications for regional management in North China, yet is seldom investigated. Surface sediments from 13 sites in Lake Dali were collected for PHTE analysis. Combined with the enrichment factor, potential ecological risk index, and multivariate statistical analysis, the spatial distribution and ecological risk of the pollutants were studied. The results showed that the contamination levels of As, Cd, Cr, Cu, Ni, Pb, and Zn were minor to moderate. Cd, Cr, Cu, Ni, Zn, and part of Pb pollution were mainly attributed to atmospheric deposition with the development of industry in North China, and As pollution resulted from the agricultural use of chemical fertilizers and As-containing pesticides. For the overall lake, the southwest part requires the most management, and targeted measures should be tailored to mitigate the ecological risk of PHTE pollution.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w11122544
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
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  • 4
    Online Resource
    Online Resource
    Source Identification and Ecological Risk of Potentially Harmful Trace Elements in Lacustrine Sediments from the Middle and Lower Reaches of Huaihe River
    MDPI AG ; 2023
    In:  Water Vol. 15, No. 3 ( 2023-01-30), p. 544-
    Details
    In: Water, MDPI AG, Vol. 15, No. 3 ( 2023-01-30), p. 544-
    Abstract: Sediment pollution caused by potentially harmful trace elements (PHTEs) has attracted a great deal of attention, due to the persistent risks it poses to human beings and ecosystems. However, the pollution status and source identification of PHTEs from the middle and lower reaches of Huaihe River remains unclear. In this study, arsenic, cadmium, chromium, copper, nickel, zinc, lead and isotopic ratios in the lacustrine sediments of this river are investigated to determine the source of, and ecological risk posed by, these PHTEs. The results show that the concentrations of chromium, copper, nickel and zinc are generally close to the background values in the lacustrine sediments, and are assessed as representing a low degree of contamination. By contrast, significantly higher concentrations of arsenic and cadmium are commonly measured in the upper sediments, which are mainly derived from the agricultural application of fertilizers, pesticides and wastewater. Meanwhile, possible atmospheric lead deposition is identified by the isotopic analysis. Among these PHTEs, adverse biological effects of arsenic, chromium, and nickel may occur in lakes according to consensus-based sediment quality guidelines, but cadmium is selected as a PHTE for priority control according to potential ecological risk index. Our study highlights that developing regional sediment quality guidelines and soil restoration in the catchment are crucial for the freshwater ecosystem in the middle and lower reaches of Huaihe River.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w15030544
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
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  • 5
    Online Resource
    Online Resource
    Mechanism of Roof Deformation and Support Optimization of Deeply Buried Roadway under Mining Conditions
    MDPI AG ; 2022
    In:  Applied Sciences Vol. 12, No. 23 ( 2022-11-25), p. 12090-
    Details
    In: Applied Sciences, MDPI AG, Vol. 12, No. 23 ( 2022-11-25), p. 12090-
    Abstract: Large deformations in local areas during service in a mine roadway are prone to roofing hazards, seriously threatening people’s lives and urgently needing to be addressed by means of support optimization. Traditional methods of studying the stability of the roadway roof are mainly based on the theory of the surrounding rock loosening circle, but few studies analyze the stability of roadway roofs around the failure distribution and expansion of weak interlayers. Therefore, the relationship between the deformation characteristics of the tunnel envelope and the thickness of the soft and weak interlayer and the underlying hard rock layer was investigated using a comprehensive research method such as theoretical analysis, numerical simulation, and field monitoring. The results show that the form of roadway roof failure is determined by weak interlayer thickness. For a mining-disturbed roadway, if the weak interlayer thickness remains unchanged, as the underlying hard strata thickness increases, the existence of a more integral hard stratum cannot prevent plastic zones from forming in the weak interlayer but can prevent them from developing in the key layer 1. If the underlying hard strata thickness remains unchanged, the smaller the weak interlayer thickness, the smaller the area of plastic zone failure in the roadway roof. After the deformation characteristics of the roadway containing the weak interlayer were clarified, according to its characteristics, the support optimization method of increasing the length of anchor bolt and anchor cable is proposed. The displacement of the roadway roof was reduced by 35% after verification by numerical simulation. After applying the support optimization method on site, the roadway displacement basically stabilized after 40 days, with the roof slab sinkage, two gang convergence and bottom bulge reaching 53 mm, 42 mm and 39 mm, respectively. The overall deformation of the roadway was small, effectively controlling the surrounding rock deformation and reducing economic losses for the mine.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app122312090
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2704225-X
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  • 6
    Online Resource
    Online Resource
    Preparation and Performance Analysis of Ceramsite Asphalt Mixture with Phase-Change Material
    MDPI AG ; 2022
    In:  Materials Vol. 15, No. 17 ( 2022-08-31), p. 6021-
    Details
    In: Materials, MDPI AG, Vol. 15, No. 17 ( 2022-08-31), p. 6021-
    Abstract: In this paper, phase-change material (PCM) and ceramsite were used to increase the heat resistance of the asphalt mixture. The ceramsite asphalt mixture with PCM can bring a specific cooling effect to the road surface and alleviate the rapid deterioration at high temperature. Two phase-change materials, PCM-43 and PCM-48, were compared and selected as the heat absorption material of the asphalt mixture. It is found that PCM-43 has better thermal stability, temperature regulation performance, higher enthalpy value, and a less adverse effect on the rheological properties of asphalt. According to the road performance of the asphalt mixture, it suggests that the maximum content of ceramsite is 40%. The specific heat capacity of asphalt mixtures was studied by the method of the insulation bucket test, and the thermal conductivity coefficient of asphalt mixtures was tested by a thermal conductivity instrument. The results show that the specific heat capacity and thermal conductivity of the asphalt mixture can be reduced by adding PCM and ceramsite. The effect of ceramsite asphalt concrete with PCM on the temperature field of road structure was further analyzed by finite element method. Due to the thermal resistance of ceramsite in the upper layer, the cooling range and depth in the middle and lower surface layers can be improved. Meanwhile, the heat absorption of phase-change material can alleviate the heating phenomenon of the upper layer. Therefore, ceramsite asphalt concrete with PCM is effective for decreasing the high temperatures in the asphalt pavements.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma15176021
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2487261-1
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  • 7
    Online Resource
    Online Resource
    A New Adaptive Remote Sensing Extraction Algorithm for Complex Muddy Coast Waterline
    MDPI AG ; 2022
    In:  Remote Sensing Vol. 14, No. 4 ( 2022-02-11), p. 861-
    Details
    In: Remote Sensing, MDPI AG, Vol. 14, No. 4 ( 2022-02-11), p. 861-
    Abstract: Coastline is an important geographical element of the boundary between ocean and land. Due to the impact of the ocean-land interactions at multiple temporal-spatial scales and the intensified human activities, the waterline of muddy coast is undergoing long-term and continuous dynamic changes. Using traditional remote sensing-based waterline extraction methods, it is difficult to achieve ideal results for muddy coast waterlines, which are faced with problems such as limited algorithm stability, weak algorithm migration, and discontinuous coastlines extraction results. In response to the above challenges, three different types of muddy coasts, Yancheng, Jiuduansha and Xiangshan were selected as the study areas. Based on the Sentinel-2 MSI images, we proposed an adaptive remote sensing extraction algorithm framework for the complex muddy coast waterline, named AEMCW (Adaptive Extraction for Muddy Coast Waterline), including main procedures of high-pass filtering, histogram statistics and adaptive threshold determination, which has the capability to obtain continuous and high-precision muddy coastal waterline. NDWI (Normalized Difference Water Index), MNDWI (Modified Normalized Difference Water Index) and ED (Edge Detection) methods were selected to compare the extraction effect of AEMCW method. The length and spatial accuracy of these four methods were evaluated with the same criteria. The accuracy evaluation presented that the length errors of ED method in all three study areas were minimum, but the waterline results were offset more to the land side, due to spectral similarity, turbid water and tidal flats having similar values of NDWI and MNDWI. Therefore, the length and spatial accuracies of NDWI and MNDWI methods were lower than AEMCW method. The length errors of the AEMCW algorithm in Yancheng, Jiuduansha, and Xiangshan were 14.4%, 18.0%, and 7.7%, respectively. The producer accuracies were 94.3%, 109.6%, and 94.2%, respectively. The user accuracies were 82.4%, 92.9%, and 87.5%, respectively. These results indicated that the proposed AEMCW algorithm can effectively restrain the influence of spectral noise from various land cover types and ensure the continuity of waterline extraction results. The adaptive threshold determination equation reduced the influence of human factors on threshold selection. The further application on ZY-1 02D hyperspectral images in the Yancheng area verified the proposed algorithm is transferable and has good stability.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs14040861
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
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  • 8
    Online Resource
    Online Resource
    A Probabilistic Weighted Archetypal Analysis Method with Earth Mover’s Distance for Endmember Extraction from Hyperspectral Imagery
    MDPI AG ; 2017
    In:  Remote Sensing Vol. 9, No. 8 ( 2017-08-14), p. 841-
    Details
    In: Remote Sensing, MDPI AG, Vol. 9, No. 8 ( 2017-08-14), p. 841-
    Abstract: A Probabilistic Weighted Archetypal Analysis method with Earth Mover’s Distance (PWAA-EMD) is proposed to extract endmembers from hyperspectral imagery (HSI). The PWAA-EMD first utilizes the EMD dissimilarity matrix to weight the coefficient matrix in the regular Archetypal Analysis (AA). The EMD metric considers manifold structures of spectral signatures in the HSI data and could better quantify the dissimilarity features among pairwise pixels. Second, the PWAA-EMD adopts the Bayesian framework and formulates the improved AA into a probabilistic inference problem by maximizing a joint posterior density. Third, the optimization problem is solved by the iterative multiplicative update scheme, with a careful initialization from the two-stage algorithm and the proper endmembers are finally obtained. The synthetic and real Cuprite Hyperspectral datasets are utilized to verify the performance of PWAA-EMD and five popular methods are implemented to make comparisons. The results show that PWAA-EMD surpasses all the five methods in the average results of spectral angle distance (SAD) and root-mean-square-error (RMSE). Especially, the PWAA-EMD obtains more accurate estimation than AA in almost all the classes of endmembers including two similar ones. Therefore, the PWAA-EMD could be an alternative choice for endmember extraction on the hyperspectral data.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs9080841
    Language: English
    Publisher: MDPI AG
    Publication Date: 2017
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  • 9
    Online Resource
    Online Resource
    A Randomized Subspace Learning Based Anomaly Detector for Hyperspectral Imagery
    MDPI AG ; 2018
    In:  Remote Sensing Vol. 10, No. 3 ( 2018-03-08), p. 417-
    Details
    In: Remote Sensing, MDPI AG, Vol. 10, No. 3 ( 2018-03-08), p. 417-
    Abstract: This paper proposes a randomized subspace learning based anomaly detector (RSLAD) for hyperspectral imagery (HSI). Improved from robust principal component analysis, the RSLAD assumes that the background matrix is low-rank, and the anomaly matrix is sparse with a small portion of nonzero columns (i.e., column-wise). It also assumes the anomalies do not lie in the column subspace of the background and aims to find a randomized subspace of the background to detect the anomalies. First, random techniques including random sampling and random Hadamard projections are implemented to construct a coarse randomized columns subspace of the background with reduced computational cost. Second, anomaly columns are searched and removed from the coarse randomized column subspace by solving a series of least squares problems, resulting in a purified randomized column subspace. Third, the nonzero columns in the anomaly matrix are located by projecting all the pixels on the orthogonal subspace of the purified subspace, and the anomalies are finally detected based on the L2 norm of the columns in the anomaly matrix. The detection performance of RSLAD is compared with four state-of-the-art methods, including global Reed-Xiaoli (GRX), local RX (LRX), collaborative-representation based detector (CRD), and low-rank and sparse matrix decomposition base anomaly detector (LRaSMD). Experimental results show good detection performance of RSLAD with lower computational cost. Therefore, the proposed RSLAD offers an alternative option for hyperspectral anomaly detection.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs10030417
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
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  • 10
    Online Resource
    Online Resource
    A Comparative Study on Blast-Resistant Performance of Steel and PVA Fiber-Reinforced Concrete: Experimental and Numerical Analyses
    MDPI AG ; 2020
    In:  Crystals Vol. 10, No. 8 ( 2020-08-16), p. 707-
    Details
    In: Crystals, MDPI AG, Vol. 10, No. 8 ( 2020-08-16), p. 707-
    Abstract: This paper deals with the blast-resistant performance of steel fiber-reinforced concrete (SFRC) and polyvinyl alcohol (PVA) fiber-reinforced concrete (PVA-FRC) panels with a contact detonation test both experimentally and numerically. With 2% fiber volumetric content, SFRC and PVA-FRC specimens were prepared and comparatively tested in comparison with plain concrete (PC). SFRC was found to exhibit better blast-resistant performance than PVA-FRC. The dynamic mechanical responses of FRC panels were numerically studied with Lattice Discrete Particle Model-Fiber (LDPM-F) which was recently developed to simulate the meso-structure of quasi-brittle materials. The effect of dispersed fibers was also introduced in this discrete model as a natural extension. Calibration of LDPM-F model parameters was achieved by fitting the compression and bending responses. A numerical model of FRC contact detonation was then validated against the blast test results in terms of damage modes and crater dimensions. Finally, FRC panels with different fiber volumetric fractions (e.g., 0.5%, 1.0% and 1.5%) under blast loadings were further investigated with the validated LDPM-F blast model. The numerical predictions shed some light on the fiber content effect on the FRC blast resistance performance.
    Type of Medium: Online Resource
    ISSN: 2073-4352
    URL: Article
    DOI: 10.3390/cryst10080707
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2661516-2
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