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Influence of nanosized magnesia on the hydration of borehole-sealing cements prepared using different methods

International Journal of Coal Science & Technology 2023年第4期10卷 343-360页

作者： Quanle Zou Jinfei Zhan Xin Wang Zhen Huang State Key Laboratory of Coal Mine Disaster Dynamics and Control School of Resources and Safety EngineeringChongqing UniversityChongqing 400044China

Gas drainage is an efective technology for gas control in coal mines.A high borehole-sealing quality is the fundamental precondition for efcient gas *** expansibilities of cement pastes used in borehole-sealing processes are critical for the borehole-sealing *** magnesia expansive agents are used to improve the expansibilities of cement pastes and improve the borehole-sealing *** magnetic resonance spectrometry and scanning electron microscopy were adopted to study the efects of nanosized magnesia on the hydration of borehole-sealing cements used with diferent preparation *** results showed that an increase in the mass fraction of the nanosized magnesia promoted cement hydration,and the mass fraction was positively correlated with the promotion *** use of diferent preparation methods did not change the water-phase distribution in the *** using the wet-mixing preparation method,nanosized magnesia promoted the induction,acceleration,and deceleration periods of hydration;when using the dry-mixing preparation method,the nanosized magnesia promoted the induction period of cement hydration,and the promotion efect was less obvious than that seen when using the wet-mixing *** using the wet-mixing preparation method,the nanosized magnesia was uniformly dispersed,thus enlarging the surface area of the reaction,which provided more nucleation sites for the hydration products of the cement and therefore accelerated the hydration *** using the dry-mixing preparation method,the nanosized magnesia powders were dispersed nonuniformly and *** these conditions,only a few nanosized magnesia particles on the surfaces of the aggregated clusters took part in hydration,so only a small number of nucleation sites were provided for the hydration products of *** led to inconsistent hydration of cement pastes prepared using the dry-mixing *** surface porosity of the cement prepared with the wet-mi

关键词： Borehole-sealing cement Nanosized magnesia Preparation method Hydration Morphological analysis Nuclear magnetic resonance relaxation analysis

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A theoretical model for impact protection of flexible polymer material

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Theoretical & Applied Mechanics Letters 2024年第3期14卷 217-226页

作者： Huifeng Xi Hui Pan Song Chen Heng Xiao MOE Key Lab of Disaster Forecast and Control in Engineering School of Machanics and Construction EngineeringJinan UniversityGuangzhou 510632China Doctor Workstation of Xuwen County Guangdong Hydropower Energy Co. Ltd.Xuwen 524100China

The relationship between the protective performance of flexible polymer material and material parameters(elasticmodulus,viscosity coefficient)is explored,an impact collision motion equation between two bodies is establishedfrom the viscoelastic material constitutive,and the relationship between the kinematic response and the materialparameters is *** on the Kelvin constitutive model,a theoretical model for impact between the pro-tective body and the protected body is established,then the dynamic response is *** feasibility of themodel was verified by drop hammer experiment,and the material parameters(elastic modulus,viscosity coeffi-cient)were obtained by *** model is discretized and the relationship between local impact response andmaterial parameters is *** discussion results on the relationship between the impact response and theprotective material performance indicate that adjusting the elastic modulus,viscosity coefficient,and thicknessof the protective material can effectively improve protective effect.

关键词： Flexible polymer material Viscoelastic material Kelvin modelDynamic response Elastic modulus and viscosity coefficient

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High Resolution Mode Shapes Identification of Bridge Using Limited Sensors 6th

High Resolution Mode Shapes Identification of Bridge Using L...

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6th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures, SMAR 2022

作者： Nie, Zhenhua Xia, Guanghao Ma, Hongwei College of Science and Engineering Jinan University Guangdong Guangzhou China The Key Laboratory of Disaster Forecast and Control in Engineering Guangzhou Guangdong China Dongguan University of Technology Dongguan China

ISBN: (纸本)9789819933617

In this paper, a new method is proposed for high resolution mode shapes identification of bridge using a limited number of sensors based on proper orthogonal decomposition (POD). Through the physical interpretation of the POD for a simple bridge under moving load, the components of generalize coordinate of POD are verified as the instantaneous status of the modals of the bridge. Based on the physical interpretation, the results proved that each component of the POD consists of a mode shape and the dynamic information of this mode, so that the mode shape can be identified by filtering the dynamic information. This mode shape with a high resolution is completely different from the traditional method which can only provide a spare mode shape because of the limitation of sensors. The simulation results proved that the proposed method can accurately identify the mode shapes with a high resolution. © Tongji University Press 2024.

关键词： Information filtering

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Physical and numerical investigations of target stratum selection for ground hydraulic fracturing of multiple hard roofs

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International Journal of Mining Science and Technology 2024年第5期34卷 699-712页

作者： Binwei Xia Yanmin Zhou Xingguo Zhang Lei Zhou Zikun Ma State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China School of Resources and Safety Engineering Chongqing UniversityChongqing 400044China

Ground hydraulic fracturing plays a crucial role in controlling the far-field hard roof,making it imperative to identify the most suitable target stratum for effective *** experiments are conducted based on engineering properties to simulate the gradual collapse of the roof during longwall top coal caving(LTCC).A numerical model is established using the material point method(MPM)and the strain-softening damage constitutive model according to the structure of the physical *** simulations are conducted to analyze the LTCC process under different hard roofs for ground hydraulic *** results show that ground hydraulic fracturing releases the energy and stress of the target stratum,resulting in a substantial lag in the fracturing of the overburden before collapse occurs in the hydraulic fracturing *** hydraulic fracturing of a low hard roof reduces the lag effect of hydraulic fractures,dissipates the energy consumed by the fracture of the hard roof,and reduces the abutment ***,it is advisable to prioritize the selection of the lower hard roof as the target stratum.

关键词： Target stratum selection Ground hydraulic fracturing Hard roof control Fracture network Material point method

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In-situ forming ultra-mechanically sensitive materials for high-sensitivity stretchable fiber strain sensors

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National Science Review 2024年第6期11卷 254-263页

作者： Rouhui Yu Changxian Wang Xiangheng Du Xiaowen Bai Yongzhong Tong Huifang Chen Xuemei Sun Jing Yang Naoji Matsuhisa Huisheng Peng Meifang Zhu Shaowu Pan State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and Engineering Donghua University MOE Key Lab of Disaster Forecast and Control in Engineering School of Mechanics and Construction Engineering Jinan University State Key Laboratory of Molecular Engineering of Polymers Department of Macromolecular Science and Institute of Fiber Materials and Devices Fudan University Department of Cardiology Shanghai Xuhui Central HospitalZhongshan-Xuhui Hospital Fudan University Research Center for Advanced Science and Technology and Institute of Industrial Science The University of Tokyo

Fiber electronics with flexible and weavable features can be easily integrated into textiles for wearable applications. However, due to small sizes and curved surfaces of fiber materials, it remains challenging to load robust active layers, thus hindering production of high-sensitivity fiber strain sensors. Herein, functional sensing materials are firmly anchored on the fiber surface in-situ through a hydrolytic condensation *** anchoring sensing layer with robust interfacial adhesion is ultra-mechanically sensitive, which significantly improves the sensitivity of strain sensors due to the easy generation of microcracks during stretching. The resulting stretchable fiber sensors simultaneously possess an ultra-low strain detection limit of 0.05%, a high stretchability of 100%, and a high gauge factor of 433.6, giving 254-folds enhancement in sensitivity. Additionally, these fiber sensors are soft and lightweight, enabling them to be attached onto skin or woven into clothes for recording physiological signals, e.g. pulse wave velocity has been effectively obtained by them. As a demonstration, a fiber sensor-based wearable smart healthcare system is designed to monitor and transmit health status for timely intervention. This work presents an effective strategy for developing high-performance fiber strain sensors as well as other stretchable electronic devices.

关键词： fiber strain sensor stretchable wearable healthcare

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A merged machine learning model for seasonal climate prediction in China

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Science China Earth Sciences 2025年第5期68卷 1469-1484页

作者： Danwei QIAN Yanyan HUANG Huijun WANG State Key Laboratory of Climate System Prediction and Risk Management/Key Laboratory of Meteorological Disaster Ministry of Education/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and Technology Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) Nansen-Zhu International Research Centre Institute of Atmospheric Physics Chinese Academy of Sciences

Improving the current level of skill in seasonal climate prediction is urgent for achieving sustainable socioeconomic development, and this is especially true in China where meteorological disasters are experienced frequently. In this study, based upon big climate data and traditional statistical prediction experiences, a merged machine learning model(Y-model) was developed to address this, as well as to further explore unknown potential predictors. In Y-model, empirical orthogonal function analysis was firstly applied to reduce the data dimensionality of the target predictand(temperature and precipitation in the four seasons over China). Image recognition techniques were used to automatically identify possible predictors from the big climate data. These predictors, associated with significant circulation anomalies, were recombined into a large ensemble according to different threshold settings for five factors determining the statistical forecast skill. Facebook Prophet was chosen to conduct the independent hindcasts for each season's climate at a lead time of two months. During 2011–2022, the seasonal climate in China was skillfully predicted by Y-model, with an averaged pattern correlation coefficient skill of 0.60 for temperature and 0.24 for precipitation, outperforming CFSv2. Potential predictor analysis for recent extreme events suggested that prior signals from the Indian Ocean and the stratosphere were important for determining the super Mei-yu in 2020, while the prior sea surface temperature over the western Pacific and the soil temperature over West Asia may have contributed to the extreme high temperatures in 2022. Our study provides new insights for seasonal climate prediction in China.

关键词： Machine learning Seasonal climate prediction China’s climate Image recognition techniques Large ensemble

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The application of improved SURF optical flow algorithm in seismic support safety monitoring system

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International Journal of Cognitive Computing in engineering 2025年第1期6卷 109-119页

作者： Wang, Jiahui School of Electronics and Control Engineering Institute of Disaster Prevention Sanhe065201 China Hebei Key Laboratory of Seismic Disaster Instrument and Monitoring Technology Sanhe065201 China Langfang Key Laboratory of Accurately-Controlled Active Seismic Source Sanhe065201 China

Frequent earthquakes pose a major threat to the safety of building structures. As a critical component of earthquake-resistant systems, dynamic health monitoring of seismic isolation bearings is essential. However, existing monitoring methods are limited by high cost and poor environmental adaptability, and it is difficult to meet real-time requirements under complex conditions. Therefore, this study combines the stable acceleration feature point matching with the optical flow algorithm, and uses the proportional purification method and the bidirectional purification method to effectively match and purify the feature points. By optimizing the feature point matching and dynamic tracking accuracy, a seismic bearing safety monitoring system based on the improved feature optical flow algorithm is designed. The experimental results show that the improved model achieves a feature recognition rate of >90 %, and the number of feature tracking losses is © 2024

关键词： Structural health monitoring

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Experimental study on permeability evolution of deep high-stressed coal under major horizontal stress unloading paths

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International Journal of Mining Science and Technology 2024年第11期34卷 1495-1508页

作者： Chao Liu Jiahao Zhang Songwei Wu Jinghua Qi Beichen Yu Liang Wang School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhou 221116China State Key Laboratory of Mining Disaster Prevention and Control Ministry of EducationShandong University of Science and TechnologyQingdao 266590China School of Safety Engineering China University of Mining and TechnologyXuzhou 221116China State Key Laboratory of Coal Mine Disaster Prevention and Control China University of Mining and TechnologyXuzhou 221116China Key Laboratory of Theory and Technology on Coal and Rock Dynamic Disaster Prevention and Control National Mine Safety AdministrationChina University of Mining and TechnologyXuzhou 221116China

Both bulk stress(σ_(i i))and stress path(SP)significantly affect the transportation characteristics of deep gas during reservoir pressure ***,the experimental study of horizontal stress unloading on seepage behavior of gas-bearing coal under constantσi i-constraints is *** results show that coal permeability is affected by horizontal stress anisotropy(σ_(H)≠σh),and the contribution of minor horizontal stress to permeability is related to the differential response of horizontal *** slippage phenomenon is prominent in deep high-stress regime,especially in low reservoir pressure.σ_(i i)and SP jointly determine the manifestation of slippage effect and the strength of stress sensitivity(γ)of *** reservoir implies an incremental percentage of slip-based permeability,and SP weakens the slippage effect by changing the elastic–plastic state of ***,γis negatively correlated with slippage *** the Walsh model,narrow(low aspect-ratio)fractures within the coal under unloading SP became the main channel for gas seepage,and bring the effective stress coefficient of permeability(χ)less than 1 for both low-stress elastic and high-stress damaged *** the raise of the effective stress,the effect of pore-lined clay particles on permeability was enhanced,inducing an increase inχfor highstress elastic coal.

关键词： True triaxial stress path Constant bulk stress Horizontal stress Effective stress coefficient of permeability Slippage effect

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Energy Absorption Characteristics of a Novel Asymmetric and Rotatable Re-entrant Honeycomb Structure

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Acta Mechanica Solida Sinica 2021年第4期34卷 550-560页

作者： Huifeng Xi Jiachu Xu Shende Cen Shiqing Huang MOE Key Laboratory of Disaster Forecast and Control in Engineering and School of Mechanics and Construction Engineering Jinan UniversityGuangzhou510632China

Based on the symmetric re-entrant honeycomb(S-RH)structure with negative Poisson’s ratios,a novel asymmetric and rotatable re-entrant honeycomb(AR-RH)structure was *** the S-RH structure and AR-RH structure were produced by the 3D printing *** experimental test and finite element simulation,the deformation mechanism and energy absorption characteristics of the AR-RH structure and the S-RH structure with negative Poisson’s ratios at different impact velocities were *** experimental test and finite element simulation results show that the novel AR-RH structure with negative Poisson’s ratios has stronger energy absorption capacity than the S-RH structure,and it has been verified that the rotatability of AR-RH can indeed absorb ***,the degree of asymmetry of the AR-RH structure was discussed.

关键词： Asymmetric and rotatable re-entrant honeycomb structure Dynamic compression Energy absorption characteristics Metal 3D printing technology

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Micro-characteristics of granite impinged by abrasive water jet from a mineralogical perspective

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Journal of Rock Mechanics and Geotechnical engineering 2025年第2期17卷 1008-1017页

作者： Zhongtan Li Zhaolong Ge Qinglin Deng Zhe Zhou Lei Liu Jianming Shangguan Chuanfu Shao State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing400044China School of Resources and Safety Engineering Chongqing UniversityChongqing400044China

An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on the formation of perforation by AWJ is unclear *** this study,we investigate AWJ impacts on three types of granite samples with different mineral fractions using a polarizing microscope and scanning electron microscope(SEM).The results show that when the grain size is doubled,the perforation depth increases by 16.22%under the same type of structure and *** general,fractures are more likely to be created at the position of rough surfaces caused by abrasive impact,and the form of fractures is determined by the mineral *** addition,microstructure analysis shows that transgranular fractures typically pass through large feldspar particles and quartz removal occurs along mineral *** longitudinal extension of perforation depends mainly on the strong kinetic energy of the jet,while the lateral extension is controlled by the *** results contribute to a better understanding of the process involved in the breaking of hard rock by abrasive jets during deep geothermal drilling.

关键词： Abrasive water jet(AWJ) Drilling Hot dry rock(HDR) Perforation Fracture generation Removal mechanism

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