Effective feature representations play a decisive role in content-based remote sensing image retrieval (CBRSIR). Recently, learning-based features have been widely used in CBRSIR and they show ...powerful ability of feature representations. In addition, a significant effort has been made to improve learning-based features from the perspective of the network structure. However, these learning-based features are not sufficiently discriminative for CBRSIR. In this paper, we propose two effective schemes for generating discriminative features for CBRSIR. In the first scheme, the attention mechanism and a new attention module are introduced to the Convolutional Neural Networks (CNNs) structure, causing more attention towards salient features, and the suppression of other features. In the second scheme, a multi-task learning network structure is proposed, to force learning-based features to be more discriminative, with inter-class dispersion and intra-class compaction, through penalizing the distances between the feature representations and their corresponding class centers. Then, a new method for constructing more challenging datasets is first used for remote sensing image retrieval, to better validate our schemes. Extensive experiments on challenging datasets are conducted to evaluate the effectiveness of our two schemes, and the comparison of the results demonstrate that our proposed schemes, especially the fusion of the two schemes, can improve the baseline methods by a significant margin.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Nowadays, several remote sensing image capturing technologies are used ranging from unmanned aerial vehicles to satellites. Powerful learning-based discriminative features play an essential role in ...content-based remote sensing image retrieval (CBRSIR). Cross-source CBRSIR (CS-CBRSIR) is used to find relevant remote sensing images across different remote sensing sources (i.e., multispectral images and panchromatic images). But it is limited by large cross-source and intrasource variations caused by different semantic objects, spatial resolution, and spectral resolution. The main limitation of CS-CBRSIR is that it cannot address the inconsistency between different sources and exploit the intrinsic relation between them. This study proposes a discriminative distillation network for CS-CBRSIR to address this limitation. To enlarge the interclass variations and reduce the intraclass differences, the discriminative features from the first source are first extracted with a well-designed joint optimization configuration (JOC) on the basis of deep neural networks. Thereafter, the features extracted from the first source are used as a supervision signal for the second source; feature distribution in common feature space between the first and second sources are made significantly similar. The method proposed in this study simultaneously handles the cross-source and intersource variations, unlike the existing methods. Extensive experiments on the DSRSID dataset with Euclidean distance verify the effectiveness of our proposed method.
Maritime activities are essential aspects of human society. Accurate classification of ships is vital for maritime surveillance and meaningful to numerous civil and military applications. However, ...most studies conducted are limited to the coarse-grained ship classification. Few studies on fine-grained ship classification have been undertaken despite its accuracy and practicability. In this study, we construct a new benchmark for fine-grained ship classification which consists of 23 fine-grained categories of ships. Besides the category label, the benchmark contains several other attribute information. To solve the problem of interclass similarity, an attribute-guided multilevel enhanced feature representation network (AMEFRN) is proposed. Concretely, a multilevel enhanced visual feature representation is designed to fuse the reweighted regional features in order to focus more on the silent region and suppress the other regions. Further to this, considering the complementary role of attribute information in ship identification, an attribute-guided feature extraction branch is proposed, which extracts the auxiliary attribute features by utilizing the attribute information as supervision. Finally, the attribute features and the enhanced visual features jointly function as a feature representation for classification. Compared to other existing classification models, AMEFRN has better performance with an overall accuracy rate of 93.58% on the established fine-grained ship classification dataset. Moreover, it can be easily embedded into most CNN models as well as trained end-to-end.
The imidazolium cation degrades in accordance with a three-step degradation mechanism under alkaline conditions. This mechanism usually includes a nucleophilic reaction, a ring-opening reaction, and ...a rearrangement reaction. In this study, we have further ascertained the degradation mechanism of a α-C methyl substituted imidazolium cation (trimethylimidazolium, TMIM), and of three α-C unsubstituted imidazolium cations (dimethylimidazolium, DMIM, 1 – benzyl-3 – methyl imidazole, BeMIM, and 1-butyl-3 – methylimidazolium, BMIM) using density functional theory (DFT). For these four Imidazolium cations, the activation energies of the nucleophilic reaction and the ring-opening reaction were calculated, along with the lowest unoccupied molecular orbital (LUMO) energy. The results obtained revealed that under alkaline conditions, the α-C methyl substituted imidazolium cation (TMIM) was more stable than the α-C unsubstituted imidazolium cations (DMIM, BeMIM, and BMIM) due to the hyper-conjugation between the methyl group at the α-C and the imidazole ring, and due to the stearic effect of the methyl group. The activation energies for the nucleophilic reaction and the ring-opening reaction for TMIM were 57.1 and 107.6 kJ/mol respectively, and its LUMO energy was −1.013 eV.
•Energy changes along the alkaline pathway for imidazolium cations were studied.•C–N bond energy is 2.5 times of the activate energy for the ring-opening reaction.•α-carbon substituted imidazolium cations are more stable than un-substituted.•This is the reason that the space steric hindrance of the methyl group on α-carbon.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Deep learning-based methods have achieved great success in target detection tasks of computer vision, but when it comes to Synthetic Aperture Radar (SAR) image ship detection, some new challenges ...appear because of the wide swath of images, diverse appearances of ships and lack of detail information, which make the detection inefficient and less effective. Aiming to these issues, in this paper, a lightweight feature optimizing network (LFO-Net) based on popular single shot detector (SSD) model is proposed for single polarization SAR image ship detection. Firstly, a simpler structure called lightweight single shot detector (LSSD) is designed, which can be trained from scratch and can reduce the training and testing time without accuracy cost. Secondly, a new bi-directional feature fusion module including one semantic aggregation block and one feature reuse block is proposed to improve the performance of multi-scale targets detection by enhancing the features of both low feature layers and high feature layers. Then the features are further optimized by leveraging attention mechanism, which is beneficial to catch the silent information more efficiently. A set of experiments are implemented to verify the effectiveness of the proposed method using the public SAR ship detection dataset (SSDD). The results show that the proposed method has significant advantages in both speed and accuracy, and outperforms other state-of-art methods. Additionally, a test on GF-3 satellite SAR data with multiple modes verifies the generalization performance of this model.
A fluorinated poly(aryl ether oxadiazole)s (FPAEO) was prepared from 2,5-bis(2,3,4,5,6-pentafluorophenyl)-1,3,4-oxadiazole (FPOx), 4,4′-isopropylidenebis(2,6-dimethylphenol) (TM-BPA) and ...4,4′-(hexafluoroisopropylidene)diphenol (6F-BPA). The fluorinated cross-linked anion exchange membrane (FCAEM) was synthesized by bromination of FPAEO, quaternization with 1–methyl imidazole and cross-linking with N,N,N′,N′-tetramethyl-1,6-hexanediamine (TMHDA). Electrochemical characteristics, physical characteristics and mechanical properties of FCAEM were studied. It exhibited higher conductivity, better mechanical property, and dimensional stability. It showed the hydroxide ion conductivity about 1.7 × 10−2 S/cm, tensile strength about 28.02 MPa, water uptake about 51% and swelling ratio about 6% at 20 °C. The cross-linked anion exchange membrane could meet the requirement for alkaline electrolyte membrane fuel cells (AEMFCs).
•A fluorinated cross-linked anion exchange membrane was designed and synthesized.•The membrane structures well controlled by the amount of the cross-linker.•The membrane exhibited higher conductivity and better mechanical property.•The hydroxide ion conductivity was up to 1.7 × 10−2 S/cm.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
China is severely affected by storm surge disasters, which result in substantial economic losses and casualties in coastal regions. Assessing the risk of storm surge disasters can provide valuable ...insights into the expected losses and severity of future impacts, offering critical foresight for disaster prevention and mitigation strategies. This study assesses the quantitative risk of storm surge disasters, focusing on coastal buildings since they are particularly susceptible to storm surges and frequently bear the brunt such disasters. Xiamen city, China, was used as case study. A high-precision numerical model, using Finite Volume Community Ocean Model (FVCOM), was developed to simulate inundation during storm surges. By referencing historical storm surge records, we defined key parameters for probable maximum typhoon-induced storm surge (PMTSS) in Xiamen. These parameters were used to calculate the corresponding inundation range and water depth distribution within the region. Subsequently, the results were integrated with vulnerability curves that represent the susceptibility of buildings in Xiamen to storm surge-induced damage, enabling the quantitative risk assessment for associated loss risks. The study findings offer valuable guidance for urban planning and functional layout design in coastal areas. Furthermore, the findings contribute to understanding storm surge disaster risks and facilitating informed decision-making processes, ultimately enhancing disaster preparedness and resilience in vulnerable coastal regions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The alkaline stability of imidazolium-based anion exchange membranes was studied by FT-IR and 13C solid state NMR. Imidazolium groups are susceptible to attack by hydroxide ions and undergo ...degradation in alkaline conditions through a ring-opening mechanism. Density functional theory (DFT) studies were performed to better understand the degradation pathway and the relative stability of imidazolium cations on exposure to hydroxide. The ring-opening degradation pathway follows the following three steps: (a) a nucleophilic reaction, (b) a ring-opening reaction, and (c) a rearrangement reaction. The structural changes induced in the imidazole ring were studied using a model of the dimethylimidazolium cation (DMIM+). The energy changes along the degradation pathway were obtained from reaction path calculations. The effect of hydroxide ion concentration and dielectric constant of surrounding medium on reaction energy barriers were studied. The hydroxide-ion induced degradation of the dimethylimidazolium cation was found to be more facile in high-pH environments. Good solvation of the dimethylimidazolium cation and the hydroxide ion was helpful in minimizing the degradation and enhancing the chemical stability of anion exchange membranes based on these cations.
•OH− induced degradation pathway of dimethylimidazolium was studied by DFT.•Effect of OH− concentration and dielectric constant on degradation was discussed.•High OH− concentration was identified as an accelerator of degradation.•Good solvation was helpful in minimizing the degradation of dimethylimidazolium.•There was good agreement between results obtained by DFT and experimental data.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Traditional Track Segment Association (TSA) methods used track position vectors or other track information to get association results. However, simply extracting the track position information to ...form track vectors will lead to the loss of irregular structure information. To solve this problem, a Track Graph Representation Association (TGRA) method is proposed. Through node‐level local track point embedding and graph‐level track graph embedding, representations of track segments can be obtained and irregular structure information can be retained simultaneously. Then, by the constraint of loss function, track segments belonging to the same target become closer, track segments belonging to different targets become farther in representation space. Finally, the nearest neighbour embedding in representation space is picked as associated tracks. Simulation results demonstrate that TGRA has good adaptability and anti‐noise ability, and it can outperform other TSA methods in both quality and efficiency. Compared with the best performance, the average true association rate of TGRA can be increased by 2.8% in short interrupt intervals and 1.3% in long interrupt intervals, respectively.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A novel cross-linked fluorinated poly (aryl ether oxadiazole) s having diallyl methylimidazole groups (FPAEO-DA-x) membranes were prepared via copolymerization, bromination, solution casting and ...hydroxide exchanging using a thermal cross-linking method. The membrane materials synthesized via copolymerization of 2,5-bis(2,3,4,5,6-pentafluorophenyl)-1,3,4-oxadiazole (FPOx) and diallyl bisphenol A (DABPA), bromination of the allyl and imidazolidation with N-methylimidazole (NMI). The anion exchange membranes (FPAEO-DA-x) were obtained by solution casting method, followed by hydroxide exchanging in sodium hydroxide solution and cross-linked by using the thermal cross-linking method. The chemical structures and properties of the cross-linked FPAEO-DA-x membranes (CFPAEO-DA-x) were studied. The highest ionic conductivity of the CFPAEO-DA-x membrane was achieved at 1.94 × 10−2 S cm−1 at 20 °C. Its swelling ratio and TGA properties revealed their good mechanical and thermal stability.
•A high performance anion exchange membrane which monomer contains two double-bonds was synthesized.•The double bond plays an active role in the effective synthesis of high purity cross-linked polymer.•The highest ionic conductivity of the membrane was achieved at 1.94 × 10−2 S cm−1 at 20 °C.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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