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625 results on '"Li, Guichen"'

179. Seismic Performance of Axially Restrained Reinforced Concrete Frame Beams

Author

Wei Zhang, Chunyu Zhang, Ying Tian, Li Guichen, Luo Wenwen, Liu Siwei, and Wang Liping

Subjects
021110 strategic, defence & security studies, Materials science, Concrete beams, business.industry, Mechanical Engineering, Frame (networking), 0211 other engineering and technologies, 02 engineering and technology, Building and Construction, Structural engineering, Reinforced concrete, Moment (mathematics), Cracking, Flexural strength, Mechanics of Materials, General Materials Science, Axial symmetry, business, Civil and Structural Engineering
Abstract

Reinforced concrete beams tend to elongate after flexural cracking and yielding; however, the elongation is restrained by the surrounding structural components in a RC moment frame. Experim...

Published
2019

181. Experimental investigation on solid waste-based high performance soilcrete.

Author

Sun, Yuantian, Li, Guichen, Shu, Jianjian, Qin, Yanting, and Tao, Wenjin

Subjects
*GYPSUM, *SOLID waste, *WASTE products, *MINE waste, *SCANNING electron microscopes, *SOIL structure
Abstract

Soilcrete is produced by adding a curing agent, such as cement, to the soil and mixing it thoroughly to form a solid, stable substance, but usually with poor early strength. To improve the early strength and stability of soilcrete, in this paper, solid waste materials such as mineral powder, and natural gypsum powder were added proportionately to replace parts of cement (called composite curing agent). The unconfined compressive strength (UCS), and dry-wet cycle strength of soilcrete were tested to evaluate the optimum mix design. The scanning electron microscope (SEM) and XRD test were applied for investigating the mechanism of early strength of solid waste-based soilcrete. The results show that the optimal mix ratio of cement and mineral powder is 4:6, the 7-day UCS is 1.61 MPa, and the 28-day UCS is 3.37 MPa. The composite curing agent mixed with gypsum powder and water glass has a good curing effect on silt and clay respectively, and the 28-day strength of the clay specimen can reach 3.97. During the dry-wet cycle test, the strength of the soilcrete increases first and then decreases with the number of cycles. The SEM results show that the soilcrete particles were denser, had more hydration products, and the soil particle morphology changed from loose to aggregated, accompanied by a decrease in pores. The study provides a cheaper and high-performance composite curing agent based on solid waste materials for soilcerte than conventional cement, which can promote the application in such field. • An early-strength, low-cost solicrete was proposed using solid waste materials, namely mineral powder and natural gypsum. • The UCS (Unconfined Compressive Strength), dry-wet cycle strength, and soil types of soilcrete were tested systematically. • The mechanism of the new solid waste material on soilcrete was revealed through SEM, XRD, and hydration analysis. [ABSTRACT FROM AUTHOR]

Published
2024
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182. Rock bolts under cyclic loading: Mechanical performance and damage assessment by acoustic emissions.

Author

He, Fengzhen, Li, Guichen, Carvelli, Valter, Xu, Xingliang, Feng, Xiaowei, and Kan, Jiaguang

Subjects
*ROCK bolts, *CYCLIC loads, *FATIGUE limit, *ACOUSTIC emission, *UNDERGROUND construction, *ROCK fatigue
Abstract

• Effect of the rock strength on the fatigue performance of rock bolt systems. • Effect of the cyclic load frequency and amplitude on the damage of rock bolt systems. • Acoustic Emission for the damage evolution in rock bolt systems under cyclic loading. • Cumulative AE energy slope method for macro crack initiation assessment. Rock bolt support is one of the key methods to maintain the stability of underground space. The durability of the rock bolt can be weakened by cyclic loading, resulting in premature failure of the underground structures. A comprehensive understanding of the performance of the bolting system under cyclic loading is essential to assess the safety of the bolting system and underground structures. In this context, this study investigated the mechanical performance of rock bolts installed in simulated soft and medium hard rock and subjected to cyclic loading. The Acoustic Emission (AE) technique was used to monitor internal damage to the bolt system under different loading conditions. A cumulative AE energy slope method has been proposed to determine the onset of the macro crack formation stage. The rock bolt demonstrated an extended fatigue life in soft rock, but its condition worsened when implanted in medium hard rock. The cyclic loading resulted in a slight improvement in the load bearing capacity of the soft rock bolt system and a significant deterioration in the medium hard rock bolt counterpart. The main fatigue failure modes of the rock bolt systems were splitting and shear failure of the surrounding rock, and debonding of the interface. Increasing the amplitude of the cyclic loading reduced the macro crack initiation cycle for both rock bolt systems, whereas increasing the frequency had different effects. The damage variable increased with frequency and amplitude for both rock bolt systems. The toughness of the soft rock bolt degraded during cyclic loading, while the high frequency cyclic loading did not modify the toughness of the medium hard rock bolt. [ABSTRACT FROM AUTHOR]

Published
2024
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183. Recognition of the toxicity of aristolochic acid

Author

Zhihui Sun, Wei Zhou, Xiao-Hu Zhao, Hong-Mei Zhang, Ji-Qiu Hou, Guang-Chen Liu, Lirui Sun, and Li Guichen

Subjects
Male, Carcinoma, Hepatocellular, Aristolochic acid, Pharmacology, 030226 pharmacology & pharmacy, Aristolochia, Nephrotoxicity, Age and gender, 03 medical and health sciences, chemistry.chemical_compound, 0302 clinical medicine, Sex Factors, Risk Factors, Medicine, Humans, Pharmacology (medical), 030212 general & internal medicine, Carcinogen, biology, business.industry, Liver Neoplasms, Age Factors, Aristolochic acid nephropathy, Aristolochia fangchi, biology.organism_classification, chemistry, Toxicity, Aristolochic Acids, Female, Kidney Diseases, business
Abstract

What is known and objective Aristolochic acid (AA) is an abundant compound in Aristolochia plants and various natural herbs. In the 1990s, a slimming formula used in Belgium that contains Aristolochia fangchi was reported to cause kidney damage and bladder cancer, and aristolochic acid nephropathy (AAN) is now well recognized worldwide. In October 2017, researchers reported an AA signature that is closely associated with hepatocellular carcinoma (HCC) worldwide. Comment There are differing opinions on the toxicity of AA, and different countries have taken different measures to address the issue. There is a lack of clarity on the causal role of AA in hepatocarcinogenesis and on the potential underlying mechanisms for the reported nephrotoxicity and carcinogenicity. The toxicity of AA differs depending on gender and age, and other risk factors that could explain the variability in the toxicity of AA remain to be identified. What is new and conclusion Whether preparations containing AA, such as many Chinese medicines, should be used remains controversial, and this issue warrants further investigation before definite conclusions can be drawn.

Published
2018

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