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  • 1
    In: Atmosphere, MDPI AG, Vol. 14, No. 1 ( 2023-01-10), p. 155-
    Abstract: The longitudinal distribution of upper atmospheric density has been broadly studied. However, the studies mostly focused on 24 h averaged distribution. This study presents the longitudinal distribution of thermospheric density at dawn and dusk, using observations collected by the atmospheric density detector onboard the Chinese satellite APOD (Atmospheric Density Detection and Precise Orbit Determination) during low solar activity. The APOD observations show a significant relative longitudinal variation of thermospheric density with global maxima (Δρrmax) near the geomagnetic pole, especially in the winter hemisphere. The annual maximum of Δρrmax appears in the Southern Hemisphere around the June solstices and reaches 26.3% and 39.6% at dawn and dusk, respectively. The auroral heating and meridional wind might play a significant role in the longitudinal variation of thermospheric density. We further compare the APOD observations with the semi-empirical atmospheric model MSIS (Mass Spectrometer Incoherent Scatter Radar) 2.0 predictions under low solar activity conditions. The MSIS 2.0 model reproduces similar longitudinal variations to the observations, with hemispheric asymmetry. The longitudinal variation of thermospheric density from APOD should be related to the distribution of the atmospheric average molecular weight from the model. More observational data are needed to verify the results of this study further.
    Type of Medium: Online Resource
    ISSN: 2073-4433
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2605928-9
    SSG: 23
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  • 2
    In: Sensors, MDPI AG, Vol. 21, No. 22 ( 2021-11-09), p. 7448-
    Abstract: Continuous sensing of water parameters is of great importance to fluid dynamic progress study in oceans, coastal areas and inland waters. The acoustic tomography technique can perform water temperature field measurements horizontally and vertically using sound wave travel information. The layer-averaged water temperature can also be measured with the acoustic tomography method. However, investigations focusing on the stratified mechanism, which consists of stratification form and its influence on inversion error, are seldom performed. In this study, an acoustic tomography experiment was carried out in a reservoir along two vertical slices to observe the layer-averaged water temperature. Specifically, multi-path sound travel information is identified through ray tracing using high-precision topography data obtained via a ship-mounted ADCP during the experiment. Vertical slices between sound stations are divided into different layers to study layer division inversion methods in different preset types. The inversion method is used to calculate the average water temperature and inversion temperature error of every layer. Different layer methods are studied with a comparison of results. The layer division principle studied in this paper can be used for layer-averaged water temperature sensing with multi-path sound transmission information.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2052857-7
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  • 3
    Online Resource
    Online Resource
    MDPI AG ; 2017
    In:  Sensors Vol. 17, No. 11 ( 2017-11-06), p. 2558-
    In: Sensors, MDPI AG, Vol. 17, No. 11 ( 2017-11-06), p. 2558-
    Type of Medium: Online Resource
    ISSN: 1424-8220
    Language: English
    Publisher: MDPI AG
    Publication Date: 2017
    detail.hit.zdb_id: 2052857-7
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  • 4
    Online Resource
    Online Resource
    MDPI AG ; 2019
    In:  Sensors Vol. 19, No. 11 ( 2019-06-04), p. 2549-
    In: Sensors, MDPI AG, Vol. 19, No. 11 ( 2019-06-04), p. 2549-
    Abstract: The existing compressive sensing (CS) reconstruction algorithms require enormous computation and reconstruction quality that is not satisfying. In this paper, we propose a novel Dual-Channel Reconstruction Network (DC-Net) module to build two CS reconstruction networks: the first one recovers an image from its traditional random under-sampling measurements (RDC-Net); the second one recovers an image from its CS measurements acquired by a fully connected measurement matrix (FDC-Net). Especially, the fully connected under-sampling method makes CS measurements represent original images more effectively. For the two proposed networks, we use a fully connected layer to recover a preliminary reconstructed image, which is a linear mapping from CS measurements to the preliminary reconstructed image. The DC-Net module is used to further improve the preliminary reconstructed image quality. In the DC-Net module, a residual block channel can improve reconstruction quality and dense block channel can expedite calculation, whose fusion can improve the reconstruction performance and reduce runtime simultaneously. Extensive experiments manifest that the two proposed networks outperform state-of-the-art CS reconstruction methods in PSNR and have excellent visual reconstruction effects.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2052857-7
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  • 5
    In: Crystals, MDPI AG, Vol. 13, No. 8 ( 2023-08-20), p. 1287-
    Abstract: Generally, the addition of Chromium (Cr) into the dual-phase (DP) steels can suppress bainitic transformation. In this work, the continuous hot-dip galvanization of DP980 steel is thermally simulated with various Cr contents of 0/0.3/0.6 wt.%, and the effect of Cr on bainitic transformation and properties of steels is studied. The results indicate that the bainitic transformation is obviously inhibited. The fraction of bainite decreases with the increasing Cr content. The incubation time is prolonged in the 0.6Cr steel with a slower bainitic transformation rate. Compared to that of 0 and 0.3Cr steels, the 0.6Cr steel exhibits a high tensile strength of 1033 MPa and uniform elongation of 9.1% due to the rapid strain-hardening rate. As a result, the mechanical properties of 0.6Cr steel satisfy the requirements of hot-dip galvanized DP980 steel.
    Type of Medium: Online Resource
    ISSN: 2073-4352
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2661516-2
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  • 6
    In: Nanomaterials, MDPI AG, Vol. 6, No. 1 ( 2016-01-04), p. 7-
    Type of Medium: Online Resource
    ISSN: 2079-4991
    Language: English
    Publisher: MDPI AG
    Publication Date: 2016
    detail.hit.zdb_id: 2662255-5
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  • 7
    In: Remote Sensing, MDPI AG, Vol. 13, No. 13 ( 2021-07-05), p. 2633-
    Abstract: The continuous sensing of water parameters is of great importance to the study of dynamic processes in the ocean, coastal areas, and inland waters. Conventional fixed-point and ship-based observing systems cannot provide sufficient sampling of rapidly varying processes, especially for small-scale phenomena. Acoustic tomography can achieve the sensing of water parameter variations over time by continuously using sound wave propagation information. A multi-station acoustic tomography experiment was carried out in a reservoir with three sound stations for water temperature observation. Specifically, multi-path propagation sound waves were identified with ray tracing using high-precision topography data obtained with ship-mounted ADCP. A new grid inverse method is proposed in this paper for water temperature profiling along a vertical slice. The progression of water temperature variation in three vertical slices between acoustic stations was mapped by solving an inverse problem. The reliability and adaptability of the grid method developed in this research are verified by comparison with layer-averaged water temperature results. The grid method can be further developed for the 3D mapping of water parameters over time, especially in small-scale water areas, where sufficient multi-path propagation sound waves can be obtained.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2513863-7
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  • 8
    In: Marine Drugs, MDPI AG, Vol. 19, No. 4 ( 2021-04-16), p. 224-
    Abstract: Ten new (1–10) and 26 known (11–36) compounds were isolated from Penicillium griseofulvum MCCC 3A00225, a deep sea-derived fungus. The structures of the new compounds were determined by detailed analysis of the NMR and HRESIMS spectroscopic data. The absolute configurations were established by X-ray crystallography, Marfey’s method, and the ICD method. All isolates were tested for in vitro anti-food allergic bioactivities in immunoglobulin (Ig) E-mediated rat basophilic leukemia (RBL)-2H3 cells. Compound 13 significantly decreased the degranulation release with an IC50 value of 60.3 μM, compared to that of 91.6 μM of the positive control, loratadine.
    Type of Medium: Online Resource
    ISSN: 1660-3397
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2175190-0
    SSG: 15,3
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  • 9
    Online Resource
    Online Resource
    MDPI AG ; 2023
    In:  Electronics Vol. 12, No. 7 ( 2023-03-23), p. 1515-
    In: Electronics, MDPI AG, Vol. 12, No. 7 ( 2023-03-23), p. 1515-
    Abstract: As one of the more difficult problems in the field of computer vision, utilizing object image detection technology in a complex environment includes other key technologies, such as pattern recognition, artificial intelligence, and digital image processing. However, because an environment can be complex, changeable, highly different, and easily confused with the target, the target is easily affected by other factors, such as insufficient light, partial occlusion, background interference, etc., making the detection of multiple targets extremely difficult and the robustness of the algorithm low. How to make full use of the rich spatial information and deep texture information in an image to accurately identify the target type and location is an urgent problem to be solved. The emergence of deep neural networks provides an effective way for image feature extraction and full utilization. By aiming at the above problems, this paper proposes an object detection model based on the mixed attention mechanism optimization of YOLOv5 (MAO-YOLOv5). The proposed method fuses the local features and global features in an image so as to better enrich the expression ability of the feature map and more effectively detect objects with large differences in size within the image. Then, the attention mechanism is added to the feature map to weigh each channel, enhance the key features, remove the redundant features, and improve the recognition ability of the feature network towards the target object and background. The results show that the proposed network model has higher precision and a faster running speed and can perform better in object-detection tasks.
    Type of Medium: Online Resource
    ISSN: 2079-9292
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662127-7
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  • 10
    In: Applied Sciences, MDPI AG, Vol. 13, No. 2 ( 2023-01-10), p. 957-
    Abstract: On 12 June 2021, an earthquake with MS 5.0 occurred in Yingjiang, adjacent to eastern Myanmar, where seismic activity is frequent due to plate collision. To explore the mechanism of this earthquake, the regional stress field of the Yingjiang zone was inverted using the focal mechanisms of 187 historical earthquakes in this area. Furthermore, based on the obtained orientation of the principal stress axes and the stress shape ratio, the fault slip tendency (Ts) was also estimated to evaluate fault instability in the study area. The stress variation results show that the diffusion and migration of the aftershocks suggested strike–slip-type stress accumulation in Yingjiang with a principal compressive stress axis direction-oriented NNE–SSW. Fault slip tendency results show that the seismogenic faults feature strikes within the ranges of 40~80° and 110~150° and dips of 60~90° and exhibit enhanced stress coupling. The distribution of the aftershock sequence is conjectured to have a high correlation with local fluid migration and was likely controlled by the hydrated rock-induced ruptures of the stressed fault systems near the source region. This study provides insights into potential earthquake risks in this region.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704225-X
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