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Abstract

In order to improve the efficiency and ensure the security of power supply used in a mine, this paper mainly studies the quasi-resonant flyback secondary power supply and analyzes its operational principles based on the requirements of soft-switching technology. In accordance with the maximum energy of a short-circuit and the request of maximum output voltage ripple, this paper calculates the spectrum value of the output filter capacitor and provides its design and procedures to determine the parameters of the main circuit of power supply. The correctness and availability of this theory are eventually validated by experiments.
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Abstract

The shipping noise near channels and ports is an important contribution to the ambient noise level, and the depth of these sites is often less than 100 m. However less attention has been paid to the measurement in shallow water environments (Brooker, Humphrey, 2016). This paper presents extensive measurements made on the URN (underwater radiated noise) of a small fishing boat in the South China Sea with 87 m depth. The URN data showed that the noise below 30 Hz was dominated by the background noise. The transmission loss (TL) was modelled with FEM (finite element method) and ray tracing according to the realistic environmental parameters in situ. The discrepancy between the modelled results and the results using simple law demonstrates both sea surface and bottom have significant effect on TL for the shallow water, especially at low frequencies. Inspired by the modelling methodology in AQUO (Achieve QUieter Oceans) project (Audoly et al., 2015), a predicted model applied to a typical fishing boat was built, which showed that the URN at frequencies below and above 100 Hz was dominated by non-cavitation propeller noise and mechanical noise, respectively. The agreement between predicted results and measured results also demonstrates that this modelling methodology is effective to some extent.
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Abstract

In this paper, the different mechanical behaviors of layered rocks with different bedding angles during uniaxial compression tests are studied. Numerical simulation models of layered rock are validated based on laboratory tests, and uniaxial compression tests are conducted by using Particle Flow Code (PFC). Using these simulations, the uniaxial compressive strength, failure patterns, development of micro-cracks, and displacement of meso particles are analyzed. When the bedding angle is similar to the failure angle, the macro failure planes develop directly along the beddings, the bedding behavior dictates the behavior of the layered rock, reducing the compressive strength.
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Abstract

An efficient system of micropropagation via somatic embryogenesis from root-derived callus was established in Arabica coffee (Coffea arabica L.). Twenty-six callus lines were induced on MS (Murashige and Skoog, 1962) medium supplemented with combinations of NAA (0, 0.1, 0.5, 1 and 2 mg/L) plus BA (0, 1 and 2 mg/L), or 2,4-D (0, 0.1, 0.5, 1 and 2 mg/L) plus TDZ (0, 1 and 2 mg/L). Subsequently, two types of somatic embryos were obtained from callus cultures and named S-type and I-type embryos. The S-type embryos were obtained from an 18-monthold callus line which was induced and maintained at 2 mg/L TDZ and 0.1 mg/L 2,4-D near the end of each period of the subculture. These embryos have a developmental barrier, which did not pass through the torpedo stage and could be overcome by a supplement of 2 or 5 mg/L BA. The I-type embryos were induced from 3-month-old callus when transferred onto induction media, i.e., MS supplemented with TDZ (2 and 5 mg/L) plus 2,4-D (0 and 0.1 mg/L). The significantly highest response, i.e., 13.3 embryos per callus clump was obtained at 2 mg/L TDZ. In this study, the results reveal that TDZ has a crucial effect on embryogenic callus induction, proliferation and subsequent somatic embryogenesis.
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