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  • MDPI AG  (7)
  • 1
    Online Resource
    Online Resource
    Two-Dimensional Mechanical Behavior Analysis of Multilayered Solids Subjected to Surface Contact Loading Based on a Semi-Analytical Method
    MDPI AG ; 2020
    In:  Coatings Vol. 10, No. 5 ( 2020-04-26), p. 429-
    Details
    In: Coatings, MDPI AG, Vol. 10, No. 5 ( 2020-04-26), p. 429-
    Abstract: In this paper, a two-dimensional semi-analytical method is developed for the mechanical behavior analysis of multilayered solids subjected to surface contact loading, which is indispensable for realizing an optimized tribological performance from the mechanical behavior point of view. Firstly, the explicit analytical frequency response functions of the multilayered solid are derived in a recursive form by analytically solving a system of linear equations established according to the boundary conditions and the interface continuous conditions. Then, the two-dimensional elastic field solution in the subsurface of multilayered solids in the space domain is converted from its corresponding frequency response functions by employing a numerical conversion method based on the inverse fast Fourier transformation. The present method is validated by comparing with the solution given by other methods. Lastly, the stress analysis of multilayered coatings with various structure layouts and various layer number of the multilayers were performed with the present method.
    Type of Medium: Online Resource
    ISSN: 2079-6412
    URL: Article
    DOI: 10.3390/coatings10050429
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2662314-6
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  • 2
    Online Resource
    Online Resource
    Effects of Global Warming on the Growth and Proliferation of Attached Sargassum horneri in the Aquaculture Area near Gouqi Island, China
    MDPI AG ; 2022
    In:  Journal of Marine Science and Engineering Vol. 11, No. 1 ( 2022-12-21), p. 9-
    Details
    In: Journal of Marine Science and Engineering, MDPI AG, Vol. 11, No. 1 ( 2022-12-21), p. 9-
    Abstract: With global warming, in recent years, golden tides have frequently occurred off the coasts of China. Sargassum horneri, which attach to aquaculture rafts, can float and form small-scale golden tides after falling off. Temperature will affect the growth and reproduction of algae. In order to explore whether the temperature is the potential influence factor of the golden tide outbreak, in this study, the effects of global warming on the growth and proliferation of S. horneri in the mussel aquaculture area of Gouqi Island will be discussed. Samples of the macroalgae were collected monthly from August 2021 to July 2022 at various stages of its life cycle, and the relationship between algal growth and temperature was analyzed based on the concept of effective accumulated temperature, combined with the parameters of sea surface temperature, photosynthetic rate, growth rate, and growth cycle. Based on the continuous temperature variation observed, the growth cycle could be divided into five stages: the decreasing temperature period (October to November), the low-temperature adaptation period (December), the second suitable low-temperature period (January to February), and the high-temperature decay period (February to May). The effective accumulated temperature stored by S. horneri from 2021 to 2022 was 2772.4 °C·d; compared with previous studies, it decreased by about 800 °C·d. The winter temperature in 2022 was higher than the average temperature in the previous 5 years, allowing the macroalgae to enter the reproductive period in advance. This had a significant impact on the blooming time of golden tides and led to an earlier outbreak and extinction. Therefore, in the future, we can set up a monitoring system for the early warning of golden tides according to the change of SST in winter.
    Type of Medium: Online Resource
    ISSN: 2077-1312
    URL: Article
    DOI: 10.3390/jmse11010009
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2738390-8
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  • 3
    Online Resource
    Online Resource
    Fault Feature Extraction and Diagnosis of Rolling Bearings Based on Enhanced Complementary Empirical Mode Decomposition with Adaptive Noise and Statistical Time-Domain Features
    MDPI AG ; 2019
    In:  Sensors Vol. 19, No. 18 ( 2019-09-19), p. 4047-
    Details
    In: Sensors, MDPI AG, Vol. 19, No. 18 ( 2019-09-19), p. 4047-
    Abstract: In this paper, a novel method is proposed to enhance the accuracy of fault diagnosis for rolling bearings. First, an enhanced complementary empirical mode decomposition with adaptive noise (ECEEMDAN) method is proposed by determining two critical parameters, namely the amplitude of added white noise (AAWN) and the ensemble trails (ET). By introducing the concept of decomposition level, the optimal AAWN can be determined by judging the mutation of mutual information (MI) between adjacent intrinsic mode functions (IMFs). Furthermore, the ET is fixed at two to reduce the computational cost. This method can avoid disturbance of the spurious mode in the signal decomposition and increase computational speed. Enhanced CEEMDAN demonstrates a more significant improvement than that of the traditional CEEMDAN. Vibration signals can be decomposed into a set of IMFs using enhanced CEEMDAN. Some IMFs, which are named intrinsic information modes (IIMs), effectively reflect the vibration characteristic. The evaluated comprehensive factor (CF), which combines the shape, crest and impulse factors, as well as the kurtosis, skewness, and latitude factor, is developed to identify the IIM. CF can retain the advantage of a single factor and make up corresponding drawbacks. Experiment results, especially for the extraction of bearing fault under variable speed, illustrate the superiority of the proposed method for the fault diagnosis of rolling bearings over other methods.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    URL: Article
    DOI: 10.3390/s19184047
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2052857-7
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  • 4
    Online Resource
    Online Resource
    Three-Dimensional Thermoelastic Contact Model of Coated Solids with Frictional Heat Partition Considered
    MDPI AG ; 2018
    In:  Coatings Vol. 8, No. 12 ( 2018-12-19), p. 470-
    Details
    In: Coatings, MDPI AG, Vol. 8, No. 12 ( 2018-12-19), p. 470-
    Abstract: In this paper, a three-dimensional thermoelastic contact model of coated solids with the frictional heat partition considered is developed by introducing a frictional heat partition model. The influence coefficients of the temperature rise, normal displacement and stress components in the three-dimensional thermoelastic contact model are converted from their corresponding frequency response functions (FRFs) with a conversion method based on the fast Fourier transform (FFT), and the FRFs of solids coated with a homogeneous coating subjected to a coupled action of the mechanical loading and the frictional heat flux on its surface are deduced in the frequency domain by introducing a two-dimensional Fourier integral transform. The contact pressure and the frictional heat partition between the two bodies are solved by employing a fast numerical algorithm based on the conjugate gradient method (CGM) and a discrete convolution fast Fourier transformation (DC-FFT). Comparison between the solutions of the present model and those of a thermoelastic contact model in literature is conducted in order to validate the present model. Several specific conclusions on the effect of the sliding speed, thermoelastic properties and thickness of the coating are drawn based on the result of numerical investigation by utilizing the present model.
    Type of Medium: Online Resource
    ISSN: 2079-6412
    URL: Article
    DOI: 10.3390/coatings8120470
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
    detail.hit.zdb_id: 2662314-6
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  • 5
    Online Resource
    Online Resource
    Stress Analysis of Multilayered Coatings Subjected to Surface Point Contact Loading Based on Its Three-Dimensional Elastic Field Solution
    MDPI AG ; 2020
    In:  Coatings Vol. 10, No. 9 ( 2020-08-28), p. 838-
    Details
    In: Coatings, MDPI AG, Vol. 10, No. 9 ( 2020-08-28), p. 838-
    Abstract: In order to investigate the effect of the structural layout of multilayered coatings on its mechanical behavior, a three-dimensional elastic field solution is developed for multilayered solids subjected to surface point contact loading, which is converted from the elastic field solution in frequency domain by using a numerical conversion algorithm. The elastic field solution in frequency domain is obtained by numerically solving a group of linear equations involving the unknown constants in the general elastic field solution of layered material that is obtained by using Fourier integral transform technique. The present solution is validated by comparing with the exact analytical solution for uncoated solids and finite element solution for solids coated with 30 layers. Lastly, the effect of structural layout of multilayered coatings is further investigated with present solution. The result shows that the gradient structural layout with elasticity modulus decreasing gradually from the top layer to the substrate, which is preferable to a larger friction coefficient for multilayered solids subjected to surface line contact loading, is preferable for a smaller friction coefficient 〈 0.1 for multilayered solids subjected to surface point contact loading, and the gradient structural layout with elasticity modulus increasing first in the top layers and then decreasing in the bottom layers, which is preferable to a smaller friction coefficient for multilayered solids subjected to surface line contact loading, is preferable for a friction coefficient 〉 0.2.
    Type of Medium: Online Resource
    ISSN: 2079-6412
    URL: Article
    DOI: 10.3390/coatings10090838
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2662314-6
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  • 6
    Online Resource
    Online Resource
    Distribution and Identification of Ulva aragoensis (Ulvaceae, Chlorophyta), a Constituent Species of Green Tides in the Southern Yellow Sea, Based on Molecular Data
    MDPI AG ; 2022
    In:  Journal of Marine Science and Engineering Vol. 10, No. 11 ( 2022-11-17), p. 1767-
    Details
    In: Journal of Marine Science and Engineering, MDPI AG, Vol. 10, No. 11 ( 2022-11-17), p. 1767-
    Abstract: Green tides are a serious global ecological disaster; the largest occur in the Southern Yellow Sea (SYS). Early-stage green tides in the SYS are composed of four species (Ulva prolifera, Ulva flexuosa, Ulva linza, and Ulva compressa). We found that U. aragoensis is a constituent species of green tides in the SYS based on molecular data. Furthermore, this study re-evaluated the proportion of U. aragoensis in green tides and found that it was more prevalent in micro-propagules cultured from surface seawater during an early-stage green tide in 2021. The internal transcribed spacers, tufA, 18S, rbcL, large subunit, psbA, and rps2-trnL gene sequences were compared; the tufA and rbcL gene sequences were the most suitable DNA barcodes for distinguishing U. aragoensis. A haplotype analysis of the sequences of floating U. aragoensis and its micro-propagules was performed to study the correlation between green tide macroalgae and micro-propagules; close haplotype similarities occurred between them. This study further clarified the species composition of SYS green tides and provided a reference for assessing the relationship between micro-propagules and green tide macroalgae.
    Type of Medium: Online Resource
    ISSN: 2077-1312
    URL: Article
    DOI: 10.3390/jmse10111767
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2738390-8
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  • 7
    Online Resource
    Online Resource
    Epizoans on Floating Golden Tide Macroalgae in the Southern Yellow Sea
    MDPI AG ; 2023
    In:  Journal of Marine Science and Engineering Vol. 11, No. 3 ( 2023-02-23), p. 479-
    Details
    In: Journal of Marine Science and Engineering, MDPI AG, Vol. 11, No. 3 ( 2023-02-23), p. 479-
    Abstract: Golden tide macroalgae have been accumulating in the Southern Yellow Sea (SYS) for several years, causing serious damage to local coastal economy and ecosystems. However, little is known about the environmental and ecological significance of the epizoans drifting on the floating macroalgae. In this study, floating macroalgae collected from four stations were identified as Sargassum horneri. Furthermore, morphological and molecular (based on the Cytochrome C Oxidase Subunit I, COI) identification revealed that the 28 epizoans on the macroalgae consisted of four crustacean (Ampithoe lacertosa, Idotea metallica, Apohyale sp., and Peramphithoe tea). Apohyale sp. and P. tea were found at all stations, while A. lacertosa is found at only one station. The weight range of Apohyale sp., P. tea, I. metallica, and A. lacertosa is 0.0037~0.0420 g, 0.0057~0.0304 g, 0.0222~0.6592 g, and 0.0047 g, respectively. The specific roles of these epizoans in the golden tide in SYS deserve further study. Our results provide a reference for future studies of invasive macroalgae and epizoans.
    Type of Medium: Online Resource
    ISSN: 2077-1312
    URL: Article
    DOI: 10.3390/jmse11030479
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2738390-8
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