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  • IOP Publishing  (4)
  • 2020-2024  (4)
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  • IOP Publishing  (4)
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  • 2020-2024  (4)
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  • 1
    Online Resource
    Online Resource
    IOP Publishing ; 2023
    In:  Measurement Science and Technology Vol. 34, No. 2 ( 2023-02-01), p. 025025-
    In: Measurement Science and Technology, IOP Publishing, Vol. 34, No. 2 ( 2023-02-01), p. 025025-
    Abstract: Elastic moduli, including Young’s modulus, shear modulus, bulk modulus, etc, are key parameters that are used to characterize the ability of a solid material to resist various types of deformation. The moduli can be extracted from the natural frequencies of a cantilever beam. In this paper, the relationships between moduli and natural frequencies, for the first time, are quantified by the finite element method. The optimized three-dimensional proportion of the cantilever beam is selected to be implemented simple error compensation. Experimentally, to precisely obtain the natural frequencies of the cantilever beam, an efficient time-averaged electronic speckle pattern interferometry(ESPI) system has been developed. The efficiency and precision are reflected in the following aspects: firstly, according to the slender character of the cantilever beam, a large shear optical path arrangement is designed to facilitate isolation from environmental interference; secondly, a resonance search method, based on the moiré effect is employed to recognize the natural frequencies accurately and efficiently; thirdly, a novel dynamic phase-shifting method is proposed based on the arrangement of the large shear optical path for clearer visualization of the mode shape of the cantilever beam. The proposed methods are verified by three kinds of common materials. The results suggest that Young’s modulus and shear modulus derived from natural frequencies are higher than the known value, and the error compensation can significantly reduce the calculation error. Furthermore, the experiments carried out on the woven carbon fiber reinforced plastic laminates illustrate the potential of the proposed methods in the evaluation of elastic moduli of composites. Given that the exciter attached to the specimen surfaces can be replaced with some special counterparts, the proposed ESPI system has considerable potential to test the objects loaded in some extreme environments, e.g. at high temperatures or underwater, where contact detection methods are difficult to be implemented.
    Type of Medium: Online Resource
    ISSN: 0957-0233 , 1361-6501
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 1362523-8
    detail.hit.zdb_id: 1011901-2
    SSG: 11
    Location Call Number Limitation Availability
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  • 2
    Online Resource
    Online Resource
    IOP Publishing ; 2020
    In:  Journal of Physics: Conference Series Vol. 1574, No. 1 ( 2020-06-01), p. 012174-
    In: Journal of Physics: Conference Series, IOP Publishing, Vol. 1574, No. 1 ( 2020-06-01), p. 012174-
    Abstract: In this study, by using descriptive statistical analysis and the method of setting up multiple study areas for comparison, with the help of high spatial resolution remote sensing interpretation data, the spatial distribution characteristics of land use in the study areas of World Heritage occurrence environment are studied. The results show that: (1) the mean value of each occurrence environment of Hailongdun World Heritage site is small, the degree of patch fragmentation is large, and the corresponding standard deviation is large, which is caused by the large difference of patch size. (2) The area of residential land, industrial and mining storage land, special land, cultivated land and forest land in Hailongdun World Heritage site is increasing from the core area, buffer area, Hailongdun village to the village boundary, which is in direct proportion to the area change of each environment.
    Type of Medium: Online Resource
    ISSN: 1742-6588 , 1742-6596
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2166409-2
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  • 3
    In: Applied Physics Express, IOP Publishing, Vol. 15, No. 3 ( 2022-03-01), p. 031003-
    Abstract: The conductive channel induced by aluminum (Al) diffusion into high-resistivity Si substrates is one of the main contributors to RF loss of GaN-on-Si RF devices. However, it has been unclear how and when the Al diffuses into the substrates. Here, we study the origins of the Al impurity in the substrates. It’s revealed that trimethylaluminum (TMAl) flow rate during the pretreatment is a considerable contributor to the Al diffusion. By restricting the TMAl preflow rate, high-quality GaN layers with RF loss of 0.3 dB mm −1 at 10 GHz and dislocation density of 1.6 × 10 9 cm −2 have been achieved on Si substrates.
    Type of Medium: Online Resource
    ISSN: 1882-0778 , 1882-0786
    RVK:
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2417569-9
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  • 4
    In: Applied Physics Express, IOP Publishing, Vol. 15, No. 8 ( 2022-08-01), p. 081001-
    Abstract: We demonstrate 1.5 μ m thick buffer-free GaN layers directly on physical vapor deposited (PVD) AlN/Si templates via delayed coalescence growth. The full width of half maximum of the X-ray diffraction rocking curves for GaN (002)/(102) planes are 525/527 arcsec. The PVD-AlN with low density and large size AlN nuclei, combined with 3D growth mode of the GaN, contribute to the delayed coalescence growth and thus crack-free GaN layers. The PVD-AlN can also effectively suppress the Ga/Al diffusion and lead to a low radio frequency loss of 0.20 dB mm −1 at 10 GHz for the GaN layers.
    Type of Medium: Online Resource
    ISSN: 1882-0778 , 1882-0786
    RVK:
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2417569-9
    Location Call Number Limitation Availability
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