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1

Rheological performance of Portland cement pastes containing different fineness of circulating fluidized bed combustion ashes

Zhang Lei

Archives of Civil Engineering

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2025

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Vol. 71, nr 1

203--223

EN

Circulating fluidized bed combustion (CFBC) ash, a by-product of fluidized bed coal-fired sulfur fixation technology, presents an opportunity for recycling and reuse when employed as a supplementary cementitious material in cement composite systems, thereby alleviating environmental pressure. Meanwhile, the rheological characteristics of cement pastes are crucial for optimizing its workability, facilitating diverse engineering applications such as pumping, formwork pressure calculation, and 3D printing. Against this backdrop, this study systematically explores the impact of CFBC ash, varying in particle size and content, on the rheological properties of Portland cement (PC) paste. Findings reveal that elevated CFBC content correlates with heightened yield stress and viscosity of the paste, with the paste incorporating 40% CFBC ash having the highest yield stress of 71.6 Pa. Furthermore, incorporating CFBC with finer particle size distribution amplifies these rheological parameters. Thixotropy mirrors the alterations in dynamic yield stress and viscosity, indicating that CFBC ash addition enhances paste thixotropy. In PC-CFBC ash composites, G' values consistently surpass G'', suggesting early-stage elasticity during oscillation testing. Thixotropy in PC-CFBC ash composites is intricately linked to superplasticizer adsorption capacity, while viscoelastic evolution of the paste is governed by hydration kinetics.

2

Research on the shrinkage performance and pore characteristics of flexible solidified silt based on solid waste

Xu Xianjin, Zhang Lei, Liu Shuai, Meng Shutao, Li Chao, Sun Zhaoyun, Wei Jincheng, Zhang Hongbo

Archives of Civil Engineering

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2025

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Vol. 71, nr 3

145--163

EN

This study aimed to verify the effect of solidification materials based on solid waste on the shrink-age performance of silt, the main raw materials of solid waste were red mud, zeolite powder, and matrix asphalt. Temperature shrinkage and drying shrinkage tests were conducted to compare and analyze the shrinkage characteristics using three kinds of solidification materials (2%, 4%, and 6%), with 6% cement-solidified soil and plain soil used as control. The results showed that the solidification material based on solid waste effectively reduced the temperature shrinkage strain and temperature shrinkage coefficient of soil; moreover, the material had good resistance to temperature shrinkage deformation. A drying shrinkage test showed that the addition of solidification materials based on solid waste considerably improved the early water retention capacity of the test soil. The water loss process mainly occurred in the first 7 days of the test. Meanwhile, the addition of the solidification material considerably reduced the drying shrinkage strain and drying shrinkage coefficient of the test soil, and the effect was more obvious as the content amount increased. Through NMR and CT scanning tests, the pore size and pore volume of the solidified material mixed with solid waste were found to be significantly reduced. The dominant pore size ranged from 0.01 μm to 1 μm. The solidification material based on solid waste improved the crack resistance of the soil, providing a new reference measure for subgrade and roadbed fillers, as well as a new means for the recycling of solid waste.

3

The Influential Factors and Prediction of Kuroshio Extension Front on Acoustic Propagation-Tracked

Xu Weishuai, Zhang Lei, Wang Hua

Archives of Acoustics

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2024

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Vol. 49, nr 1

95--106

EN

The Kuroshio Extension front (KEF) considerably influences the underwater acoustic environment; however, a knowledge gap persists regarding the acoustic predictions under the ocean front environment. This study utilized the high-resolution ocean reanalysis data (JCOPE2M, 1993–2022) to assess the impact of the KEF on the underwater acoustic environment. Oceanographic factors were extracted from the database using the Douglas-Peucker algorithm, and acoustic propagation characteristics were obtained using the Bellhop raytracing model. This study employed a backpropagation neural network to predict the acoustic propagation affected by the KEF. The depth of the acoustic channel axis and the vertical gradient of the transition layer of sound speed were identified as the fundamental factors influencing the first area of convergence, with correlations between the former and the distance of the first convergence zone ranging from 0.52 to 0.82, and that for the latter ranging from −0.42 to −0.7. The proposed method demonstrated efficacy in forecasting first convergence zone distances, predicting distances with less than 3 km error in >90% of cases and less than 1 km error in 68.61% of cases. Thus, this study provides a valuable predictive tool for studying underwater acoustic propagation in ocean front environments and informs further research.

4

Material flow law and mechanical property of 5052 aluminum alloy sheets under dynamic and quasi-static hole-flanging

Zhang Lei, Cui Xiaohui, Yan Ziqin, Yang Guang

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e203, 2023

EN

The formability of aluminum alloys at room temperature is low, which can lead to the fracture of the sheets under traditional stamping. In this work, electromagnetic forming (EMF) and stamping flanging of 5052 aluminum alloy sheets were performed by experimentally and 3D numerical simulation. Under stamping flanging, when the prefabricated hole diameter decreases, the flanging height increases, but the gap between the flanged part and die and maximum thinning rate becomes larger. With the increase of discharge voltage, the fittability of the flanged parts is improved. There is a critical discharge voltage, under which the fittability and maximum thinning rate are optimal. Compared with stamping, the sheet flanging height is larger under EMF. This is due to the inner and outer layers of sheet fillet are subjected to greater radial tensile strain, and the thickness of sheet fillet are reduced after EMF. In addition, the sheet mouth collides with die at high speed, which causes the mouth material extend radially. The results revealed that the hardness of outer and middle layers at the sheet fillet was larger after EMF than that after stamping, while that of the inner layer was relatively small. This distribution of hardness corresponds to material strain.

5

Dynamic failure mechanism of copper foil in laser dynamic flexible forming

Shen Zongbao, Zhang Lei, Li Pin, Liu Kai, Lin Youyu, Zhou Guoyang, Wang Yang, Zhang Jindian, Liu Huixia, Wang Xiao

Materials Science Poland

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2020

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Vol. 38, No. 4

684--692

EN

Laser dynamic flexible forming (LDFF) is a novel high velocity forming (HVF) technology, in which the foil metal is loaded by laser shock wave. Strain localization is readily to occur around the bulge edge, which will result in the ultimate dynamic failure. In this work, the microstructures before and after dynamic fracture are characterized by transmission electron microscopy (TEM) to investigate the dynamic failure mechanism. The plastic deformation regions of copper foil are composed of shock compression, strain localization and bulge. Microstructure refinement was observed in three different plastic deformation regions, particularly, dynamic recrystallization (DRX) occurs in the strain localization and bulge regions. In bulge region, extremely thin secondary twins in the twin/matrix (T/M) lamellae are formed. The microstructure features in the strain localization region show that superplastic flow of material exists until fracture, which may be due to DRX and subsequent grain boundary sliding (GBS) of the recrystallized grains. The grain coarsening in strain localization region may degrade the material flowing ability which results in the dynamic fracture.

6

Experimental study on the joint application of innovative techniques for the improved drivage of roadways at depths over 1 km: a case study

Zhang Wei, Tang Jia-Jia, Zhang Dong-Sheng, Zhang Lei, Sun Yuyan, Zhang Wei-Sheng

Archives of Mining Sciences

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2020

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Vol. 65, no. 1

159--178

EN

Finding effective ways to efficiently drive roadways at depths over 1 km has become a hotspot research issue in the field of mining engineering. In this study, based on the local geological conditions in the Xinwen Mining Area (XMA) of China, in-situ stress measurements were conducted in 15 representative deep roadways, which revealed the overall tectonic stress field pattern, with the domination of the horizontal principal stresses. The latter values reached as high as 42.19 MPa, posing a significant challenge to the drivage work. Given this, a comprehensive set of innovative techniques for efficiently driving roadways at depths over 1 km was developed, including (i) controlled blasting with bidirectional energy focusing for directional fracturing, (ii) controlled blasting with multidirectional energy distribution for efficient rock fragmentation, (iii) wedge-cylinder duplex cuts centered on double empty holes, and (iv) high-strength supports for deep roadways. The proposed set of techniques was successfully implemented in the –1010 west rock roadway (WRR) drivage at the Huafeng Coal Mine (HCM). The improved drivage efficiency was characterized by the average and maximum monthly advances of 125 and 151 m, respectively. The roadway cross-sectional shape accuracy was also significantly improved, with the overbreak and underbreak zones being less than 50 mm. The deformation in the surrounding rock of roadway (SRR) was adequately controlled, thus avoiding repeated maintenance and repair. The relevant research results can provide technical guidance for efficient drivage of roadways at depths over 1 km in other mining areas in China and worldwide.

7

Motion control and collision avoidance algorithms for unmanned surface vehicle swarm in practical maritime environment

Zhuang Jiayuan, Zhang Lei, Qin Zihe, Sun Hanbing, Wang Bo, Cao Jian

Polish Maritime Research

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2019

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nr 1

107--116

EN

The issue of controlling a swarm of autonomous unmanned surface vehicles (USVs) in a practical maritime environment is studied in this paper. A hierarchical control framework associated with control algorithms for the USV swarm is proposed. In order to implement the distributed control of the autonomous swarm, the control framework is divided into three task layers. The first layer is the tele-operated task layer, which delivers the human operator’s command to the remote USV swarm. The second layer deals with autonomous tasks (i.e. swarm dispersion, or avoidance of obstacles and/or inner-USV collisions), which are defined by specific mathematical functions. The third layer is the control allocation layer, in which the control inputs are designed by applying the sliding mode control method. The motion controller is proved asymptotically stable by using the Lyapunov method. Numerical simulation of USV swarm motion is used to verify the effectiveness of the control framework.

8

A practical approach to the assessment of waterjet propulsion performance: the case of a waterjet-propelled trimaran

Zhang Lei, Zhang Jia-ning, Shang Yu-chen, Dong Guo-xiang, Chen Wei-min

Polish Maritime Research

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2019

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nr 4

27--38

EN

To obtain a reasonable evaluation of the performance of waterjet propulsion at the design stage, a semi-theoretical and semi-empirical method is used to calculate the fundamental parameters of waterjet propulsion performance using an iterative approach. To calculate the ship’s resistance, a boundary element method based on three-dimensional potential flow theory is used to solve the wave-making resistance, and an empirical approach is used to evaluate the viscous resistance. Finally, the velocity and pressure of the capture area of the waterjet propulsion control volume are solved based on turbulent boundary layer theory. The iteration equation is established based on the waterjet-hull force-balance equation, and the change in the ship’s attitude and the local loss of the intake duct are considered. The performance parameters of waterjet propulsion, such as resistance, waterjet thrust, thrust deduction, and the physical quantity of the control volume, are solved by iteration. In addition, a PID-controlled free-running ship model is simulated using the RANS CFD method as a comparison. We apply the proposed approach and the RANS CFD method to a waterjetpropelled trimaran model, and the simulation process and the results are presented and discussed. Although there are some differences between the two methods in terms of the local pressure distribution and thrust deduction, the relative error in the evaluation results for the waterjet propulsion performance is generally reasonable and acceptable. This indicates that the present method can be used at the early stages of ship design without partial information about the waterjet propulsion system, and especially in the absence of a physical model of the pump.