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Volumes 72-83 (2023)
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Volume 83
Pages 1-258 (December 2023)
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Volume 82
Pages 1-204 (November 2023)
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Volume 81
Pages 1-188 (October 2023)
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Volume 80
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Volume 79
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Volume 78
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Volume 77
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Volume 76
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Volume 75
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Volume 74
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Volume 73
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Volume 72
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Volume 83
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Volumes 60-71 (2022)
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Volume 71
Pages 1-108 (December 2022)
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Volume 70
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Volume 69
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Volume 68
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Volume 67
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Volume 66
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Volume 65
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Volume 64
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Volume 63
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Volume 62
Pages 1-104 (March 2022)
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Volume 61
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Volume 60
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Volume 71
- Volumes 54-59 (2021)
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• Equilibrium charge and triboelectric coefficient were proposed to characterize the tribo-charging process.
• Effects of material type, rotation speed and relative humidity on contact electrification were studied.
• Charge relaxation constant and charge generation constant were compared.
Contact electrification occurs in many granular material systems due to particle-particle and particle-wall contacts. In this paper, we used a simple device to characterize the electrification of different spheres in a rotating spherical container. The charge of the spheres was quantified by a Faraday cup after rotating for various time and the disperse behaviors of charged spheres were recorded by a camera. The effects of the rotational time, sphere size, rotational speed, sphere material, and relative humidity on the equilibrium charge and triboelectric coefficient were analyzed. The results show that the equilibrium surface charge density is independent of the sphere size and the rotating speed, whereas the larger rotating speed enhances the triboelectric coefficient. It is also shown that charge relaxation constants are two orders of magnitude lower than the charge generation constants for all spheres at a low relative humidity. The increase of water molecules in the air was found to result in the decline of charge generation constant and the rise of charge relaxation constant, which together cause the decrease of the equilibrium surface charge density.