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Impinging air jets can be used to dewater, heat, and dry the web of tissue paper. High velocities of the air jets degrade the paper, and appropriate adjustments to the jet velocity and the distance of the nozzle from the surface of the wet web are crucial to obtain the highest quality product. This work investigated the correlation between the velocity of the air jet and the strength of paper subjected to the impingement method. Papers with an initial moisture content of 20% and various pulp mixes were tested, and the physical properties of papers were explored. After impinging an air jet, different tensile strength limits were obtained in the machine and cross directions. The paper had lower apparent density and higher roughness compared to classical pressing. The dependence of tensile strength and roughness on the fibers composition also was determined. Increasing the amount of eucalyptus fibers in impingement dewatered paper resulted in a decrease in its tensile strength and roughness. The value of elongation before breaking was the highest for softwood papers after the impingement method. The maximum velocity of an air jet that can be used to dewater or dry paper without the risk of damage to the papers was determined. [ABSTRACT FROM AUTHOR]

• Novel method of measuring the uniformity of liquid penetration through fibrous porous materials was proposed. • Texture entropy and contrast were taken into account in the proposed method. • Correlations between the dynamics of liquid penetration and the examined texture parameters were found. • New parameters were introduced for better evaluation of the nature of the liquid flow through the porous material structure. The interaction of liquids with materials is an important factor influencing many technological processes and describing the quality of the material itself. However, characterization of the wetting and penetration of liquids phenomena through the materials of heterogeneous structure is a very difficult task. Paper is an example of such material. Paper sizing is one of the most important operations in paper technology. Its purpose is to reduce the wettability of the paper. The aim of the present study was to evaluate the suitability of the texture analysis to assess the uniformity of liquid penetration through the paper structure in terms of the degree of the paper sizing. As a result of the research, a new method of measuring was proposed based on dynamic changes in their texture parameters. For this purpose, such texture parameters as entropy and contrast were used. Characteristic points were determined on the curves of the dynamic changes of both parameters. It was proved that there is a correlation between the dynamics of liquid penetration through the paper structure and the examined texture parameters. It was found that the maximum value of entropy and contrast, the time of reaching both values, the points of inflection of the curves during their decrease, and the times by which these points were reached can be useful parameters that provide information about the nature of the liquid flow through the porous material structure. [ABSTRACT FROM AUTHOR]