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  • MDPI AG  (28)
  • 1
    Online Resource
    Online Resource
    Recrystallization Behavior of a Pure Cu Connection Interface with Ultrasonic Welding
    MDPI AG ; 2020
    In:  Metals Vol. 11, No. 1 ( 2020-12-30), p. 61-
    Details
    In: Metals, MDPI AG, Vol. 11, No. 1 ( 2020-12-30), p. 61-
    Abstract: Three-dimensional metal waveguide components are key components in the next generation of radio telescopes. Ultrasonic additive manufacturing technology combining ultrasonic welding and micro electrical discharge machining (micro-EDM) provides a new method for the overall manufacturing of waveguide elements, and the effective welding of Electrolytic Tough Pitch copper (Cu-ETP) sheets is the key process of this method. This study demonstrates that the orthogonal test optimization method is used to conduct ultrasonic welding tests on Cu-ETP. Specifically, electron backscattered diffraction (EBSD) technology is used to analyze the crystal grains, grain boundary types and texture changes during interface recrystallization. In addition, the finite element software ABAQUS 6.13 is employed to calculate the temperature field in order to determine the possibility of recrystallization of the welding interface. The results showed that the average grain size of the welding interface decreased from 20 to 1~2 μm. The Cu-ETP matrix is mainly composed of coarse grains with high-angle grain boundaries (HAGBs), while a large number of low-angle grain boundaries (LAGBs), subcrystals and fine equiaxed grains appear in the welded joint. At the same time, discontinuous dynamic recrystallization (DDRX) occurs in the less strained area, and continuous dynamic recrystallization (CDRX) is predominant in the greater strain area. The temperature field calculation shows that the peak temperature of the welding interface exceeds the recrystallization temperature of Cu-ETP from 379.05 to 433.2 °C.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met11010061
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2662252-X
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  • 2
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    Development and Vibration Control of Frequency Adjustable Tuned Mass Damper Based on Magnetorheological Elastomer
    MDPI AG ; 2022
    In:  Materials Vol. 15, No. 5 ( 2022-02-28), p. 1829-
    Details
    In: Materials, MDPI AG, Vol. 15, No. 5 ( 2022-02-28), p. 1829-
    Abstract: Tuned mass dampers (TMD) have been widely used in passive vibration control, but their main disadvantage is that the vibration reduction effect may be greatly affected by the natural frequency of the main structure. In order to solve this limitation, we designed a frequency adjustable tuned mass damper (FATMD) based on a magneto rheological elastomer (MRE), which is a new type of magneto rheological smart material, with adjustable stiffness, obtained by changing the magnetic induction. We used MRE to change the stiffness of FATMD to track the natural frequency of the main structure. However, adding TMD will change the natural frequency of the system. Therefore, we combined Hilbert–Huang transform (HHT) and a natural excitation technique (NExT), with Simulink/dSPACE, to identify the natural frequency of the system in real time, and then calculated the natural frequency of the main structure through the TMD optimal design theory. This can help adjust FATMD to its optimum tuning state. To verify the applicability and effectiveness of FATMD, this paper compares the FATMD and traditional TMD experimental results. The natural frequency of steel beams can be changed by adding mass blocks. The experimental results indicate that FATMD, using the frequency tracking method, can effectively track the natural frequency of the main structure to ensure that the system is always in the optimum tuning state. In addition, FATMD can still achieve a good vibration reduction effect when the natural frequency of the main structure changes.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma15051829
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2487261-1
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  • 3
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    An Upscaling–Downscaling Optimal Seamline Detection Algorithm for Very Large Remote Sensing Image Mosaicking
    MDPI AG ; 2022
    In:  Remote Sensing Vol. 15, No. 1 ( 2022-12-24), p. 89-
    Details
    In: Remote Sensing, MDPI AG, Vol. 15, No. 1 ( 2022-12-24), p. 89-
    Abstract: For the mosaicking of multiple remote sensing images, obtaining the optimal stitching line in the overlapping region is a key step in creating a seamless mosaic image. However, for very large remote sensing images, the computation of finding seamlines involves a huge amount of image pixels. To handle this issue, we propose a stepwise strategy to obtain pixel-level optimal stitching lines for large remote sensing images via an upscaling–downscaling image sampling procedure. First, the resolution of the image is reduced and the graph cut algorithm is applied to find an energy-optimal seamline in the reduced image. Then, a stripe along the preliminary seamline is identified from the overlap area to remove the other inefficient nodes. Finally, the graph cut algorithm is applied nested within the identified stripe to seek the pixel-level optimal seamline of the original image. Compared to the existing algorithms, the proposed method produces fewer spectral differences between stitching lines and less-crossed features in the experiments. For a wide range of remote sensing images involving large data, the new method uses less than 10 percent of the time needed by the SLIC+ graph cut method.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs15010089
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2513863-7
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  • 4
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    Remote Sensing of Sea Surface pCO2 in the Bering Sea in Summer Based on a Mechanistic Semi-Analytical Algorithm (MeSAA)
    MDPI AG ; 2016
    In:  Remote Sensing Vol. 8, No. 7 ( 2016-06-30), p. 558-
    Details
    In: Remote Sensing, MDPI AG, Vol. 8, No. 7 ( 2016-06-30), p. 558-
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs8070558
    Language: English
    Publisher: MDPI AG
    Publication Date: 2016
    detail.hit.zdb_id: 2513863-7
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  • 5
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    SQNet: Simple and Fast Model for Ocean Front Identification
    MDPI AG ; 2023
    In:  Remote Sensing Vol. 15, No. 9 ( 2023-04-28), p. 2339-
    Details
    In: Remote Sensing, MDPI AG, Vol. 15, No. 9 ( 2023-04-28), p. 2339-
    Abstract: The ocean front has a non-negligible role in global ocean–atmosphere interactions, marine fishery production, and the marine military. Hence, obtaining the positions of the ocean front is crucial in oceanic research. At present, the positioning method of recognizing an ocean front has achieved a breakthrough in the mean dice similarity coefficient (mDSC) of above 90%, but it is difficult to use to achieve rapid extraction in emergency scenarios, including marine fisheries and search and rescue. To reduce the its dependence on machines and apply it to more requirements, according to the characteristics of an ocean front, a multi-scale model SQNet (Simple and Quick Net) dedicated to ocean front position recognition is designed, and its perception domain is expanded while obtaining current scale data. In experiments along the coast of China and the waters of the Gulf of Mexico, it was not difficult to find that SQNet exceedingly reduced running time while ensuring high-precision results (mDSC of higher than 90%). Then, after conducting intra-model self-comparison, it was determined that expanding the perceptual domain and changing the weight ratio of the loss function could improve the accuracy and operational efficiency of the model, which could be better applied in ocean front recognition.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs15092339
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2513863-7
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  • 6
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    Streptococcus suis Uptakes Carbohydrate Source from Host Glycoproteins by N-glycans Degradation System for Optimal Survival and Full Virulence during Infection
    MDPI AG ; 2020
    In:  Pathogens Vol. 9, No. 5 ( 2020-05-18), p. 387-
    Details
    In: Pathogens, MDPI AG, Vol. 9, No. 5 ( 2020-05-18), p. 387-
    Abstract: Infection with the epidemic virulent strain of Streptococcus suis serotype 2 (SS2) can cause septicemia in swine and humans, leading to pneumonia, meningitis and even cytokine storm of Streptococcal toxic shock-like syndrome. Despite some progress concerning the contribution of bacterial adhesion, biofilm, toxicity and stress response to the SS2 systemic infection, the precise mechanism underlying bacterial survival and growth within the host bloodstream remains elusive. Here, we reported the SS2 virulent strains with a more than 20 kb endoSS-related insertion region that showed significantly higher proliferative ability in swine serum than low-virulent strains. Further study identified a complete N-glycans degradation system encoded within this insertion region, and found that both GH92 and EndoSS contribute to bacterial virulence, but that only DndoSS was required for optimal growth of SS2 in host serum. The supplement of hydrolyzed high-mannose-containing glycoprotein by GH92 and EndoSS could completely restore the growth deficiency of endoSS deletion mutant in swine serum. EndoSS only hydrolyzed a part of the model glycoprotein RNase B with high-mannose N-linked glycoforms into a low molecular weight form, and the solo activity of GH92 could not show any changes comparing with the blank control in SDS-PAGE gel. However, complete hydrolyzation was observed under the co-incubation of EndoSS and GH92, suggesting GH92 may degrade the high-mannose arms of N-glycans to generate a substrate for EndoSS. In summary, these findings provide compelling evidences that EndoSS-related N-glycans degradation system may enable SS2 to adapt to host serum-specific availability of carbon sources from glycoforms, and be required for optimal colonization and full virulence during systemic infection.
    Type of Medium: Online Resource
    ISSN: 2076-0817
    URL: Article
    DOI: 10.3390/pathogens9050387
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2695572-6
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  • 7
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    A Unified Algorithm for the Atmospheric Correction of Satellite Remote Sensing Data over Land and Ocean
    MDPI AG ; 2016
    In:  Remote Sensing Vol. 8, No. 7 ( 2016-06-24), p. 536-
    Details
    In: Remote Sensing, MDPI AG, Vol. 8, No. 7 ( 2016-06-24), p. 536-
    Abstract: The atmospheric correction of satellite observations is crucial for both land and ocean remote sensing. However, the optimal approach for each area is different due to the large spectra difference in the ground reflectance between land and ocean. A unified atmospheric correction (UAC) approach based on a look-up table (LUT) of in situ measurements is developed to remove this difference. The LUT is used to select one spectrum as the in situ ground reflectance needed to obtain the initial aerosol reflectance, which in turn is used for determining the two closest aerosol models. The aerosol reflectance, obtained from these aerosol models, is then used to deduce the estimated ground reflectance. This UAC model is then used to process the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data, and its performance is validated with a large number of in situ measurements. The mean bias of the land reflectance for this model is 6.59% with a root mean square error (RMSE) of 19.61%. The mean bias and RMSE of the water-leaving reflectance are 7.59% and 17.10% validated by the in situ measurements using the above-water method, while they are 13.60% and 22.53% using the in-water method. The UAC model provides a useful tool for correcting the satellite-received reflectance without separately having to deal with land and ocean pixels. Further, it can seamlessly expand the satellite ocean color data for terrestrial use and improve quantitative remote sensing over land.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs8070536
    Language: English
    Publisher: MDPI AG
    Publication Date: 2016
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  • 8
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    Evaluation of Remote-Sensing Reflectance Products from Multiple Ocean Color Missions in Highly Turbid Water (Hangzhou Bay)
    MDPI AG ; 2021
    In:  Remote Sensing Vol. 13, No. 21 ( 2021-10-23), p. 4267-
    Details
    In: Remote Sensing, MDPI AG, Vol. 13, No. 21 ( 2021-10-23), p. 4267-
    Abstract: Validation of remote-sensing reflectance (Rrs) products is necessary for the quantitative application of ocean color satellite data. While validation of Rrs products has been performed in low to moderate turbidity waters, their performance in highly turbid water remains poorly known. Here, we used in situ Rrs data from Hangzhou Bay (HZB), one of the world’s most turbid estuaries, to evaluate agency-distributed Rrs products for multiple ocean color sensors, including the Geostationary Ocean Color Imager (GOCI), Chinese Ocean Color and Temperature Scanner aboard HaiYang-1C (COCTS/HY1C), Ocean and Land Color Instrument aboard Sentinel-3A and Sentinel-3B, respectively (OLCI/S3A and OLCI/S3B), Second-Generation Global Imager aboard Global Change Observation Mission-Climate (SGLI/GCOM-C), and Visible Infrared Imaging Radiometer Suite aboard the Suomi National Polar-orbiting Partnership satellite (VIIRS/SNPP). Results showed that GOCI and SGLI/GCOM-C had almost no effective Rrs products in the HZB. Among the others four sensors (COCTS/HY1C, OLCI/S3A, OLCI/S3B, and VIIRS/SNPP), VIIRS/SNPP obtained the largest correlation coefficient (R) with a value of 0.7, while OLCI/S3A obtained the best mean percentage differences (PD) with a value of −13.30%. The average absolute percentage difference (APD) values of the four remote sensors are close, all around 45%. In situ Rrs data from the AERONET-OC ARIAKE site were also used to evaluate the satellite-derived Rrs products in moderately turbid coastal water for comparison. Compared with the validation results at HZB, the performances of Rrs from GOCI, OLCI/S3A, OLCI/S3B, and VIIRS/SNPP were much better at the ARIAKE site with the smallest R (0.77) and largest APD (35.38%) for GOCI, and the worst PD for these four sensors was only −13.15%, indicating that the satellite-retrieved Rrs exhibited better performance. In contrast, Rrs from COCTS/HY1C and SGLI/GCOM-C at ARIAKE site was still significantly underestimated, and the R values of the two satellites were not greater than 0.7, and the APD values were greater than 50%. Therefore, the performance of satellite Rrs products degrades significantly in highly turbid waters and needs to be improved for further retrieval of ocean color components.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs13214267
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
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  • 9
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    Global Vibration Comfort Evaluation of Footbridges Based on Computer Vision
    MDPI AG ; 2022
    In:  Sensors Vol. 22, No. 18 ( 2022-09-19), p. 7077-
    Details
    In: Sensors, MDPI AG, Vol. 22, No. 18 ( 2022-09-19), p. 7077-
    Abstract: The vibration comfort evaluation is a control standard other than strength and deflection, but the general comfort evaluation method only considers the response of the mid-span position and does not consider the difference in the vibration response of different positions at the same time. It is crucial to study how pedestrians actually feel when they walk on footbridges. The computer vision-based vibration comfort evaluation method is a novel method with advantages, such as noncontact and long-distance. In this study, a computer vision-based method was used to evaluate the global vibration comfort of footbridges under human-induced excitation. The improved Lucas–Kanade optical flow method is used for multitarget displacement identification of footbridges. Additionally, the YOLOv5 algorithm for pedestrian detection is used to obtain the position information of pedestrians on the footbridges. Then, according to the pedestrian position information, the structural responses of different pedestrian positions corresponding to time periods are extracted from the displacement responses of each point, and they are combined to obtain the structural global displacement. The global acceleration can be obtained by calculating the global displacement. The rms value can be calculated based on the global acceleration and compared with the standard for comfort evaluation. The global comfort evaluation method is validated by pedestrian walking experiments with different frequencies on a laboratory footbridge. The experimental results show that the computer vision-based global comfort evaluation method for footbridges is feasible and is a more specific and real-time comfort evaluation method.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    URL: Article
    DOI: 10.3390/s22187077
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2052857-7
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  • 10
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    Endogenous Driving Forces in Ecology-Production-Living Space Changes at Micro-Scale: A Mountain Town Example in Inland China
    MDPI AG ; 2022
    In:  Land Vol. 11, No. 12 ( 2022-12-13), p. 2289-
    Details
    In: Land, MDPI AG, Vol. 11, No. 12 ( 2022-12-13), p. 2289-
    Abstract: Studying land use transition and restructuring has value for promoting sustainable regional development, especially in China’s vast rural areas, which are undergoing rapid changes. Current research tends to focus on the macro level, and analyses of driving forces are mostly based on the correlation analysis of influencing factors. However, in the case of villages and towns, which are at the micro level, it is important to know who promotes land use transition and how to promote it under the influence of the macro environment. This study, therefore, focused on the endogenous driving force behind land use transition and its characteristics at the micro level of villages and towns. On the basis of our theoretical framework, an empirical study was carried out on the transformation and restructuring of ecology–production–living (EPL) spaces in the town of Zhulin in Central China over the past 30 years. We found the following: (1) The overall distribution of EPL spaces in Zhulin shifted from mixed distribution to relatively concentrated distribution, and the spatial transfer of EPL spaces showed fluctuations in the expansion and contraction of different types of spaces. (2) Land use transition was more active in spatial interface areas than in noninterface areas, where the interconversion of ecological space and agricultural production space was concentrated at the terrain interface. In addition, transformation processes related to living space and non-agricultural production space were concentrated at the urban–rural interface. (3) Macro-level social and economic changes were the root cause of land use transformation, and the autonomous spatial governance capability of villagers’ self-organization institutions was key to regulating land use transformation. The spatial interface was a sensitive area for land use transformation in a natural state. An endogenous driving mode of active response to land use transformation based on rural autonomous spatial governance capability and spatial interface sensitivity is proposed. How to improve the rural governance capacity of key local actors in different regions and at different levels is an aspect worthy of further consideration.
    Type of Medium: Online Resource
    ISSN: 2073-445X
    URL: Article
    DOI: 10.3390/land11122289
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2682955-1
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