Wyniki wyszukiwania - Biblioteka Nauki

1

Robust dictionary learning for erratic noise corrupted seismic data reconstruction

100%

Zhao Q. , Du Q. , Li Q. , Fu L.

Acta Geophysica

|

2020

|

tom Vol. 68, no. 3

687--700

EN

Dictionary learning methods adaptively train their bases from the given data in an iterative manner; hence, they can capture more detailed features and achieve sparser representation than a method that uses a fxed basis. However, there also exists a good chance of erratic noise corrupting the dictionary because of the insufciency of the L1-norm regularization in distinguishing the signal and erratic noise, causing the inaccuracy of both dictionary learning and its application. A robust dictionary learning method is proposed to reconstruct the missing data even in the presence of strong erratic noise. Specifcally, a projected operator, which is constructed with the robust Huber misft, is used to damp erratic noise to a low-amplitude level. In the dictionary learning step, erratic noise is gradually reduced to an acceptable level with the help of this projected operator, from which the signal prototypes (or atoms) can be safely extracted in each iteration. Then, the learned dictionary is used to iteratively estimate the signal from the noisy and under-sampled data, performing noise attenuation as well as data interpolation at non-recording locations. We test the proposed dictionary learning method using 2D and 3D noisy seismic examples and compare it with other state-of-the-art methods. Numerical results demonstrate its superior efectiveness at recovering missing data and increasing signal-to-noise ratio in the presence of erratic noise.

2

Finite Element Analysis and Experimental Study on the Thermal Resistance Characteristics of Motor Coolers

88%

Xu K. , Yang J. , Tang C. , Zhao Q. , Li T.

Journal of Power Technologies

|

2020

|

tom Vol. 100, nr 3

279--289

EN

Motor coolers are operated with the coupling of temperature and pressure fields, in which the change rule is affected by multiple factors. In this study, the thermal resistance of the motorcooler was examined using the velocity coefficient method to reveal the influence of heat transfer and wind resistance. The temperature and pressure fields were analyzed using the finite element method based on the hydrodynamics and momentum theorem. By varying the heat transfer and wind resistance coefficients to reflect temperature and pressure characteristics, wind and water velocities were determined. Results demonstrate that the total convective heat transfer and wind resistance coefficients of the cooler model are sensitive to variations in face-to-face wind velocity, but not to those of the cooling water flow rate. When wind velocity increases from 0.8 to 5.19m/s, the total convective heat transfer increases by 1.85 times and wind resistance increases by 18.74 times. Variations in cooling water velocity has little effect on the Nusselt numberon the air side and the Euler number of the single row tube, which are multiplied with the increase of the Reynolds number. When the Reynolds number increases from 1020 to 6345, the Nusselt number increases by 2.05 times and the Euler numer decreases by 2.29 times. The results provide references for the design and performance testing of high-power motor coolers.

3

Research on magnetic regulation characteristics of axial-radial flux type permanent magnet synchronous machine

88%

Yang C. , Wang K. , Liu Z. , Xiong B. , Zhao Q.

Archives of Electrical Engineering

|

2022

|

tom Vol. 71, nr 1

75--90

EN

Due to the fixed rotor magnetic field, the main magnetic flux of conventional permanent magnet synchronous motors (PMSMs) cannot be flexibly adjusted. Recently, the axial-radial flux type permanent magnet synchronous machine (ARFTPMSM) based on the hybrid excitation concept is proposed, which provides a new method for the speed and magnetic field regulations for PMSMs. To analyze the mechanism of magnetic field variation inside the ARFTPMSM, in this paper, three – dimensional finite element models for electromagnetic field calculation of the ARFTPMSM are established. On this basis, the influence of the axial device on the motor is discussed, and the mechanism of flux regulation is explained. By the quantitative calculation of air-gap flux density and the noload back-electromotive force (EMF), the flux regulation capability of the ARFTPMSM is verified. In addition, the effect of the excitation magnetomotive force on the magnetic field harmonics is analyzed combined with the winding theory, and the influence of the axial magneto-motive force (MMF) on the torque fluctuation is obtained. The flux regulation performance of the motor and the validity of the numerical calculation analysis are verified by the experiments.

4

Study of N, N-bis (2-hydroxyethyl) -N-methyl dodecyl ammonium chloride as the novel collector in selective flotation separation of quartz and hematite

75%

Liu W. , Liu W. , Zhao Q. , Wang X. , Duan H. , Peng X. , Wang B.

Physicochemical Problems of Mineral Processing

|

2020

|

tom Vol. 56, iss. 2

286--299

EN

A quaternary ammonium salt, N, N-bis (2-hydroxyethyl)-N-methyl dodecyl ammonium chloride (BHMDC), with high surface activity, was screened and firstly introduced in the reverse flotation of hematite ores based on Density Functional Theory (DFT) calculation and surface tension measurement. The interaction mechanism of BHMDC on the surfaces of quartz and hematite was studied by zeta potential measurement, X-ray photoelectron spectroscopy (XPS) and Fourier transforms infrared spectroscopy (FTIR), respectively. The results of DFT calculation and surface tension measurement indicated that BHMDC had higher selectivity and hydrophobicity than dodecylamine (DDA). The analyses of zeta potential measurement, FTIR, and XPS demonstrated that the adsorption of BHMDC on hematite and quartz surfaces were mainly dependent on hydrogen bonding and electrostatic interaction. Due to the more active sites (O atoms), the weaker charge and larger size of polar groups, BHMDC had better simulation results in performance than DDA, especially in selectivity. The flotation tests showed that BHMDC exhibited better flotation performance, which was consistent with the results of DFT calculation. And the efficient separation of hematite and quartz within the wide pH value range (4.0-10.0) was determined, which was also confirmed by zeta potential measurement. It also indicated that BHMDC was an excellent collector in the reverse flotation of hematite ores with great industrial potential, which could obtain the concentrate with the Fe grade of 65.37% and recovery of 88.92%