Wyniki wyszukiwania - Biblioteka Nauki

1

Assessing system impedance based on data regrouping

100%

Xu S. , Xiao X. , Wang Y. , Wu J.

Metrology and Measurement Systems

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2021

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tom Vol. 28, nr 1

191--208

EN

In recent years, assessing supply system impedance has become crucial due to the concerns on power quality and the proliferation of distributed generators. In this paper, a novel method is shown for passive measurement of system impedances using the gapless waveform data collected by a portable power quality monitoring device. This method improves the overall measurement accuracy through data regrouping. Compared with the traditional methods that use the consecutive measurement data directly, the proposed method regroups the data to find better candidates with less flotation on the system side. Simulation studies and extensive field tests have been conducted to verify the effectiveness of the proposed method. The results indicate that the proposed method can serve as a useful tool for impedance measurement tasks performed by utility companies.

2

Carrollite Leaching in H2SO4-NaClO3 Media at Atmospheric Pressure

88%

Dong B. , Wu J.-H. , Wu J. , Zhang X.-P. , Zhai J.-J.

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2020

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tom Vol. 65, iss. 1

313--319

EN

A new extraction process suitable for treating refractory CuCo2S4 under atmospheric pressure acidic leaching conditions was investigated. The effect of variables such as oxidant species, liquid-to-solid ratio, leaching time, oxidizing agent and mineral quality ratio, H2SO4 concentration, temperature and sodium chloride concentration on the extraction efficiency of Co, Cu and Fe from CuCo2S4 were investigated. Under optimal conditions including P80-P90 of the sample was d < 0.0074 mm, stirring speed of 400 rpm, leaching time of 8 h with sodium chlorate (NaClO3) and mineral quality ratio of 0.5, 2 mol/L H2SO4, liquid-to-solid ratio of 7, leaching temperature of 90°C and 4 mol/L sodium chloride. The leaching efficiency of Co, Cu, and Fe were nearly 97.08%, 100%, and 92.45%, respectively. Furthermore, the contents of cobalt and copper in leaching residue were all less than 0.4 wt.%, which satisfies the requirements of industrial production.

3

Study on strength characteristics and permeability of chlorite schist during triaxial compression permeability

88%

Wang F. , Xue W. , Qiao Z. , Wu J. , Jing L.

Archives of Civil Engineering

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2023

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tom Vol. 69, nr 2

353--365

EN

In order to grasp the strength characteristics and permeability of chlorite schist, the triaxial compression permeability test of chlorite schist was carried out by using a rock triaxial servo testing machine equipped with seepage device. Based on the test results, the failure strength, initial permeability and permeability development of rock samples under different confining pressure and different pore water pressure are compared, and the failure types of rock samples under triaxial compression permeability and their influence on permeability are analyzed. The results show that the increase of confining pressure is conducive to the improvement of failure strength of chlorite schist, and the increase of pore water pressure reduces the failure strength, which is related to the inhibition of crack development in rock samples by confining pressure and the promotion of crack expansion by pore water pressure. The mechanical deformation of chlorite schist in triaxial compression permeability process has experienced initial compaction stage, linear elastic stage and crack stable propagation to failure stage. As a consequence, permeability shows three trends of decline, stable development and rise, which is closely related to the development of the internal structure of rock samples at each stage. During the failure of triaxial compression permeability, there is a local compression zone in chlorite schist, and the rising rate slows down due to the influence of the compression zone.

4

An Improved Generative Design Approach based on Graph Grammar for Pattern Drawing

88%

Liu Y. , Zhou Y. , Yang F. , Li S. , Wu J.

Machine Graphics and Vision

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2024

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tom Vol. 33, No. 1

3--20

EN

Generative design is used to efficiently generate design solutions with powerful computational methods. Generative design based on shape grammar is currently the most commonly used approach, but it is difficult for shape grammar to formally analyze the generated pattern. Graph grammar derived from one-dimensional character grammar is mainly used for generating and analyzing abstract models of visual languages. However, there is a significant gap between the generated node-edge graphs and the representation of shape appearance. To address these problems, we propose an improved generative design approach based on virtual-node based continuous Coordinate Graph Grammar (vcCGG). This approach defines a new type of grammatical rule named node transformation rules to convert nodes into shapes with node transformation applications. By combining node transformation applications and L-applications in vcCGG, we can generate a node-edge graph as the structure of the pattern through L-applications, and then draw the shape outline, next adjust the positions of these shapes, thus relating abstract structures and the physical layouts of visual languages. At the end of the paper, we provide an example application of this approach: generating an illustration from Emma Talbot using a combination of node transformation applications and L-applications.

5

Parameter Measurement of Biaxial Braided Composite Preform Based on Phase Congruency

75%

Xiao Z. , Pei L. , Zhang F. , Sun Y. , Geng L. , Wu J. , Tong J.

Autex Research Journal

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2019

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tom Vol. 19, no. 1

8--16

EN

In this paper, a new method based on phase congruency is proposed to measure pitch lengths and surface braiding angles of two-dimensional biaxial braided composite preforms. Lab space transform and BM3D (block-matching and 3D filter) are used first to preprocess the original acquired images. A corner detection algorithm based on phase congruency is then proposed to detect the corners of the preprocessed images. Pitch lengths and surface braiding angles are finally measured based on the detected corner maps. Experimental results show that our method achieves the automatic measurement of pitch lengths and the surface braiding angles of biaxial braided composite preforms with high accuracy.

6

Failure study of weathered granite based on critical slowing down theory and acoustic emission b-value

63%

Huang Q. , Zhao K. , Yan Y. , Wu J. , Nie Q. , Chen J. , Xiao W. , Wang H.

Archives of Civil and Mechanical Engineering

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2023

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tom Vol. 23, no. 3

art. no. e196, 2023

EN

To investigate the precursor characteristics of failure of weathered granite (WG), we conducted uniaxial compression tests on WG specimens using the RMT-150C rock mechanics testing system and the PCI-II acoustic emission (AE) device. We analyzed the AE parameters based on the critical slowing down (CSD) and AE b-value theoretical methods. The study shows that the peak strain value of WG under uniaxial compression is < 1% and the stress falls off rapidly after the peak, and the specimen mainly undergoes brittle failure. The failure process can be divided into four stages: compression stage, elastic deformation stage, plastic development stage, and post-peak failure stage, in which the compression stage lasts longer. The ringing count rate and its cumulative amount can effectively indicate the process of WG failure during loading. As the failure nears, microcracks within the WG accumulate and expand, leading to the appearance of macroscopic cracks. At the same time, the cumulative ringing count rate increases rapidly while the ringing count rate converges to the peak. Furthermore, the rapid increase of autocorrelation coefficient and variance obtained from the CSD theory analysis of ringing counts can be used as a precursor signal of WG failure. The “inflection point” before the sharp rise of the variance curve can be regarded as an early warning point of failure. Based on the characteristic that the b-value shows a large rate fluctuation decrease before the failure of WG, the autocorrelation coefficient and variance variation law obtained by CSD theory and the early warning point are analyzed simultaneously with the b-value variation law, which can accurately grasp the failure characteristics of WG in mines.