Engineering geological and hydro-geological characteristics of foundation rock and surrounding rock mass are the main factors that affect the stability of underground engineering. This paper presents the concept of mu...Engineering geological and hydro-geological characteristics of foundation rock and surrounding rock mass are the main factors that affect the stability of underground engineering. This paper presents the concept of multiscale hierarchical digital rock mass models to describe the rock mass, including its structures in different scales and corresponding scale dependence. Four scales including regional scale,engineering scale, laboratory scale and microscale are determined, and the corresponding scaledependent geological structures and their characterization methods are provided. Image analysis and processing method, geostatistics and Monte Carlo simulation technique are used to establish the multiscale hierarchical digital rock mass models, in which the main micro-and macro-structures of rock mass in different geological units and scales are reflected and connected. A computer code is developed for numerically analyzing the strength, fracture behavior and hydraulic conductivity of rock mass using the multiscale hierarchical digital models. Using the models and methods provided in this paper, the geological information of rock mass in different geological units and scales can be considered sufficiently,and the influence of downscale characteristics(such as meso-scale) on the upscale characteristics(such as engineering scale) can be calculated by considering the discrete geological structures in the downscale model as equivalent continuous media in the upscale model. Thus the mechanical and hydraulic properties of rock mass may be evaluated rationally and precisely. The multiscale hierarchical digital rock mass models and the corresponding methods proposed in this paper provide a unified and simple solution for determining the mechanical and hydraulic properties of rock mass in different scales.展开更多
Bananas are highly perishable after harvest,and processing them into dried products is a crucial approach to reducing losses and adding their economic values.To address the inefficiency and prolonged duration of tradi...Bananas are highly perishable after harvest,and processing them into dried products is a crucial approach to reducing losses and adding their economic values.To address the inefficiency and prolonged duration of traditional hot air drying(HAD)and the quality inconsistency associated with single infrared drying(IRD),this study proposed a novel hot air-infrared combined drying(HAD-IRD)strategy.The effects of HAD,IRD,and HAD-IRD on the drying kinetics,color,rehydration capacity,moisture diffusion mechanism,and sensory quality of banana slices were systematically investigated.The parameters of the combined drying process were optimized using an L_(9)(3^(3))orthogonal experimental design.Results indicated that both IRD and HAD-IRD significantly reduced drying time compared to single HAD.While single IRD achieved a rapid drying rate,the lack of effective convective airflow led to potential case-hardening and unstable product quality.In contrast,the HAD-IRD strategy demonstrated a synergistic effect.The optimal parameters were determined as follows:hot air temperature of 70℃,infrared temperature of 60℃,and radiation distance of 16 cm.Under these optimized conditions,HAD-IRD reduced the total drying time by over 70%while simultaneously yielding products with superior color,higher sensory scores,and improved rehydration ratio.This study confirms that HAD-IRD is an efficient and high-quality drying method for banana slices,providing a reliable theoretical foundation and technical solution for the drying of thermosensitive fruits.展开更多
The corrosion behavior of Ni-Co-CeO_(2) composite coating was investigated under a simulated high-temperature marine atmosphere alongside Ni-Co coating. The corrosion kinetics, phase composition and microstructure evo...The corrosion behavior of Ni-Co-CeO_(2) composite coating was investigated under a simulated high-temperature marine atmosphere alongside Ni-Co coating. The corrosion kinetics, phase composition and microstructure evolution of the coatings were analyzed. A multi-layered oxide scale formed due to the synergistic corrosion by H_(2)O and NaCl. The growth mechanism of the Co_(3)O_(4), Fe_(3)O_(4), Fe_(2)O3, CoFe_(2)O_(4), NiFe_(2)O_(4) and NiO in the scale was proposed according to the distribution of the CeO_(2) particles. Compared to Ni-Co cating, the Ni-Co-CeO_(2) coating exhibited superior corrosion resistance in the H_(2)O/NaCl steam, which is beacause the CeO_(2) exerted a blocking effect on retarding the diffusion of Fe atoms and corrosive medium, contributing to a reduced corrosion rate and an improved oxide adhesion compared to Ni-Co coating.展开更多
Based on the characteristics of fractures in naturally fractured reservoir and a discrete-fracture model, a fracture network numerical well test model is developed. Bottom hole pressure response curves and the pressur...Based on the characteristics of fractures in naturally fractured reservoir and a discrete-fracture model, a fracture network numerical well test model is developed. Bottom hole pressure response curves and the pressure field are obtained by solving the model equations with the finite-element method. By analyzing bottom hole pressure curves and the fluid flow in the pressure field, seven flow stages can be recognized on the curves. An upscaling method is developed to compare with the dual-porosity model （DPM）. The comparisons results show that the DPM overestimates the inter-porosity coefficient ）, and the storage factor w. The analysis results show that fracture conductivity plays a leading role in the fluid flow. Matrix permeability influences the beginning time of flow from the matrix to fractures. Fractures density is another important parameter controlling the flow. The fracture linear flow is hidden under the large fracture density. The pressure propagation is slower in the direction of larger fracture density.展开更多
A new well test model for a vertical fractured well is developed based on a discrete-fracture model in which the fractures are discretized as one dimensional（1-D） entities.The model overcomes the weakness of complex...A new well test model for a vertical fractured well is developed based on a discrete-fracture model in which the fractures are discretized as one dimensional（1-D） entities.The model overcomes the weakness of complex meshing,a large number of grids, and instability in conventional stripe-fracture models. Then, the discrete-fracture model is implemented using a hybrid element finite-element method.Triangular elements are used for matrix and line elements for the fractures. The finite element formulation is validated by comparing with the semi-analytical solution of a single vertical fractured well. The accuracy of the approach is shown through several examples with different fracture apertures,fracture conductivity, and fracture amount. Results from the discrete-fracture model agree reasonably well with the stripefracture model and the analytic solutions. The advantages of the discrete-fracture model are presented in mesh generation, computational improvement, and abilities to handle complex fractures like wedge-shaped fractures and fractures with branches. Analytical results show that the number of grids in the discrete-fracture model is 10 % less than stripefracture model, and computational efficiency increases by about 50 %. The more fractures there are, the more the computational efficiency increases.展开更多
Although refractory high-entropy alloys(RHEAs)possess excellent softening resistance and thermal sta-bility at high temperatures,their practical application is often limited due to room temperature(RT)brit-tleness.In ...Although refractory high-entropy alloys(RHEAs)possess excellent softening resistance and thermal sta-bility at high temperatures,their practical application is often limited due to room temperature(RT)brit-tleness.In this work,we successfully achieved RT plasticization in a brittle(TaMoTi)_(92)Al_(8)RHEA via in situ forming heterogeneous structure(HS)with the doping of Zr.Different from the mainstream design con-cept of“soft solid solution matrices with hard intermetallic phases”proposed in the literature,the newly developed TaMoZrTiAl RHEA is featured by a hard disordered BCC phase embedded into a soft intermetal-lic B2 matrix.Such an HS leads to the remarkable strength-plasticity synergy in this alloy at RT,showing a large plasticity of>20%,associated with a high strength of>2380 MPa.It was found that solid solu-tion strengthening and heterodeformation-induced strengthening caused by dislocation pile-ups at phase boundaries are responsible for the enhancement in the yield strength,while deformation-induced strain partition and the frequent operation of dislocation cross-slip substantially improve the work hardening capacity of alloy,thus enabling the high strength and good RT plasticity.In short,the current work not only reveals the micromechanisms of the influence of heterogeneous dual-phase structure on the RT me-chanical behaviour in RHEAs but also provides a useful strategy for plasticizing brittle RHEAs.展开更多
In order to find an effective way to improve the quality of school management,finding valuable information from students' original data and providing feedback for student management are necessary. Firstly,some new...In order to find an effective way to improve the quality of school management,finding valuable information from students' original data and providing feedback for student management are necessary. Firstly,some new and successful educational data mining models were analyzed and compared. These models have better performance than traditional models( such as Knowledge Tracing Model) in efficiency,comprehensiveness,ease of use,stability and so on. Then,the neural network algorithm was conducted to explore the feasibility of the application of educational data mining in student management,and the results show that it has enough predictive accuracy and reliability to be put into practice. In the end,the possibility and prospect of the application of educational data mining in teaching management system for university students was assessed.展开更多
Additive remanufacturing technology,as one of the key technologies of remanufacturing engineering,can realize the integrated repair of the structure and function of high value-added key metal parts of large and comple...Additive remanufacturing technology,as one of the key technologies of remanufacturing engineering,can realize the integrated repair of the structure and function of high value-added key metal parts of large and complex equipment,which can significantly reduce the use and maintenance costs,save labor and time costs.It applies to the on-site repair and remanufacturing of key parts in the aerospace,energy and chemical industry,heavy haul machinery,and other fields,as well as the on-site rapid repair of parts in special environments such as tunnels,open seas,and space.Additive remanufacturing technology can promote the reform of the maintenance and support mode of weapons and equipment and become the research hotspot of major military-developed countries.This paper expounds on the connotation and characteristics of additive remanufacturing technology and introduces its evolution process.The research achievements of the author in the development of additive remanufacturing platforms,material design,and process optimization were summarized.Given the problems(such as control shape,control performance,and control position)in the additive remanufacturing process,the author puts forward solutions and looks forward to the future development direction of additive remanufacturing technology.展开更多
基金the Outstanding Youth Science Foundation of National Natural Science Foundation (Grant No. 51522903)the National Key Research and Development Plan (Grant No. 2016YFC0501104)+1 种基金the National Natural Science Foundation of China (Grant Nos. U1361103, 51479094 and 51379104)the Open Research Fund Program of the State Key Laboratory of Hydroscience and Engineering,Tsinghua University (Grant Nos. 2015-KY-04, 2016-KY-02 and 2016KY-05)
文摘Engineering geological and hydro-geological characteristics of foundation rock and surrounding rock mass are the main factors that affect the stability of underground engineering. This paper presents the concept of multiscale hierarchical digital rock mass models to describe the rock mass, including its structures in different scales and corresponding scale dependence. Four scales including regional scale,engineering scale, laboratory scale and microscale are determined, and the corresponding scaledependent geological structures and their characterization methods are provided. Image analysis and processing method, geostatistics and Monte Carlo simulation technique are used to establish the multiscale hierarchical digital rock mass models, in which the main micro-and macro-structures of rock mass in different geological units and scales are reflected and connected. A computer code is developed for numerically analyzing the strength, fracture behavior and hydraulic conductivity of rock mass using the multiscale hierarchical digital models. Using the models and methods provided in this paper, the geological information of rock mass in different geological units and scales can be considered sufficiently,and the influence of downscale characteristics(such as meso-scale) on the upscale characteristics(such as engineering scale) can be calculated by considering the discrete geological structures in the downscale model as equivalent continuous media in the upscale model. Thus the mechanical and hydraulic properties of rock mass may be evaluated rationally and precisely. The multiscale hierarchical digital rock mass models and the corresponding methods proposed in this paper provide a unified and simple solution for determining the mechanical and hydraulic properties of rock mass in different scales.
基金funded by the National Natural Science Foundation of China,grant number 52306124(received by Dan Huang),URL:https://mp.weixin.qq.com/s/HHNYjgYKAynqYR7ySxYwzQ(accessed on 01 January 2025)the Changsha Municipal Natural Science Foundation,grant number kq2402259(received by Shuai Huang),URL:http://kjj.changsha.gov.cn/zfxxgk/tzgg_27202/202501/t20250122_11726939.html(accessed on 01 January 2025)the Regional Joint Funds of the Natural Science Foundation of Hunan Province,grant num-ber 2025JJ70463(received by Shuai Huang),URL:https://kjt.hunan.gov.cn/kjt/xxgk/tzgg/tzgg_1/202502/t20250212_33585991.html(accessed on 01 January 2025).
文摘Bananas are highly perishable after harvest,and processing them into dried products is a crucial approach to reducing losses and adding their economic values.To address the inefficiency and prolonged duration of traditional hot air drying(HAD)and the quality inconsistency associated with single infrared drying(IRD),this study proposed a novel hot air-infrared combined drying(HAD-IRD)strategy.The effects of HAD,IRD,and HAD-IRD on the drying kinetics,color,rehydration capacity,moisture diffusion mechanism,and sensory quality of banana slices were systematically investigated.The parameters of the combined drying process were optimized using an L_(9)(3^(3))orthogonal experimental design.Results indicated that both IRD and HAD-IRD significantly reduced drying time compared to single HAD.While single IRD achieved a rapid drying rate,the lack of effective convective airflow led to potential case-hardening and unstable product quality.In contrast,the HAD-IRD strategy demonstrated a synergistic effect.The optimal parameters were determined as follows:hot air temperature of 70℃,infrared temperature of 60℃,and radiation distance of 16 cm.Under these optimized conditions,HAD-IRD reduced the total drying time by over 70%while simultaneously yielding products with superior color,higher sensory scores,and improved rehydration ratio.This study confirms that HAD-IRD is an efficient and high-quality drying method for banana slices,providing a reliable theoretical foundation and technical solution for the drying of thermosensitive fruits.
基金supported by the National Key Research and Development Programme(2023YFB3408200)the National Nature Science Foundation of China(52201076 and 52471077)+2 种基金the Guangdong Provincial Key R&D Programme(2023B0909020002)the Guangdong Basic and Applied Basic Research Foundation(2021A1515111065,2021B1515120014 and 2022A1515010934)the Fundamental Research Funds for the Central Universities(21623216 and 11623216).
文摘The corrosion behavior of Ni-Co-CeO_(2) composite coating was investigated under a simulated high-temperature marine atmosphere alongside Ni-Co coating. The corrosion kinetics, phase composition and microstructure evolution of the coatings were analyzed. A multi-layered oxide scale formed due to the synergistic corrosion by H_(2)O and NaCl. The growth mechanism of the Co_(3)O_(4), Fe_(3)O_(4), Fe_(2)O3, CoFe_(2)O_(4), NiFe_(2)O_(4) and NiO in the scale was proposed according to the distribution of the CeO_(2) particles. Compared to Ni-Co cating, the Ni-Co-CeO_(2) coating exhibited superior corrosion resistance in the H_(2)O/NaCl steam, which is beacause the CeO_(2) exerted a blocking effect on retarding the diffusion of Fe atoms and corrosive medium, contributing to a reduced corrosion rate and an improved oxide adhesion compared to Ni-Co coating.
基金Project supported by the National Natural Science Foundation of China(No.5140232)the National Science and Technology Major Project(No.2011ZX05038003)the China Postdoctoral Science Foundation(No.2014M561074)
文摘Based on the characteristics of fractures in naturally fractured reservoir and a discrete-fracture model, a fracture network numerical well test model is developed. Bottom hole pressure response curves and the pressure field are obtained by solving the model equations with the finite-element method. By analyzing bottom hole pressure curves and the fluid flow in the pressure field, seven flow stages can be recognized on the curves. An upscaling method is developed to compare with the dual-porosity model （DPM）. The comparisons results show that the DPM overestimates the inter-porosity coefficient ）, and the storage factor w. The analysis results show that fracture conductivity plays a leading role in the fluid flow. Matrix permeability influences the beginning time of flow from the matrix to fractures. Fractures density is another important parameter controlling the flow. The fracture linear flow is hidden under the large fracture density. The pressure propagation is slower in the direction of larger fracture density.
基金supported by the National Natural Science Foundation of China(Grant 51404232)the National Science and Technology Major Project(Grant 2011ZX05038003)the China Postdoctoral Science Foundation(Grant 2014M561074)
文摘A new well test model for a vertical fractured well is developed based on a discrete-fracture model in which the fractures are discretized as one dimensional（1-D） entities.The model overcomes the weakness of complex meshing,a large number of grids, and instability in conventional stripe-fracture models. Then, the discrete-fracture model is implemented using a hybrid element finite-element method.Triangular elements are used for matrix and line elements for the fractures. The finite element formulation is validated by comparing with the semi-analytical solution of a single vertical fractured well. The accuracy of the approach is shown through several examples with different fracture apertures,fracture conductivity, and fracture amount. Results from the discrete-fracture model agree reasonably well with the stripefracture model and the analytic solutions. The advantages of the discrete-fracture model are presented in mesh generation, computational improvement, and abilities to handle complex fractures like wedge-shaped fractures and fractures with branches. Analytical results show that the number of grids in the discrete-fracture model is 10 % less than stripefracture model, and computational efficiency increases by about 50 %. The more fractures there are, the more the computational efficiency increases.
基金supported by the National Key Research&De-velopment Program of China(No.2022YFF0609002)the National Natural Science Foundation of China(Nos.U1908219,52171163,and 52271157)+4 种基金the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-CN-2021-2-2)the key Research&Devel-opment Plan of Jiangxi Province(No.20192ACB80001)the Natu-ral Science Foundation of Liaoning Province(No.2022-BS-001)the China Postdoctoral Science Foundation(No.2022M713210)the Shenyang National Laboratory for Materials Science.
文摘Although refractory high-entropy alloys(RHEAs)possess excellent softening resistance and thermal sta-bility at high temperatures,their practical application is often limited due to room temperature(RT)brit-tleness.In this work,we successfully achieved RT plasticization in a brittle(TaMoTi)_(92)Al_(8)RHEA via in situ forming heterogeneous structure(HS)with the doping of Zr.Different from the mainstream design con-cept of“soft solid solution matrices with hard intermetallic phases”proposed in the literature,the newly developed TaMoZrTiAl RHEA is featured by a hard disordered BCC phase embedded into a soft intermetal-lic B2 matrix.Such an HS leads to the remarkable strength-plasticity synergy in this alloy at RT,showing a large plasticity of>20%,associated with a high strength of>2380 MPa.It was found that solid solu-tion strengthening and heterodeformation-induced strengthening caused by dislocation pile-ups at phase boundaries are responsible for the enhancement in the yield strength,while deformation-induced strain partition and the frequent operation of dislocation cross-slip substantially improve the work hardening capacity of alloy,thus enabling the high strength and good RT plasticity.In short,the current work not only reveals the micromechanisms of the influence of heterogeneous dual-phase structure on the RT me-chanical behaviour in RHEAs but also provides a useful strategy for plasticizing brittle RHEAs.
基金Sponsored by the Ability Enhancement Project of Teaching Staff in Harbin Institute of Technology(Grant No.06)
文摘In order to find an effective way to improve the quality of school management,finding valuable information from students' original data and providing feedback for student management are necessary. Firstly,some new and successful educational data mining models were analyzed and compared. These models have better performance than traditional models( such as Knowledge Tracing Model) in efficiency,comprehensiveness,ease of use,stability and so on. Then,the neural network algorithm was conducted to explore the feasibility of the application of educational data mining in student management,and the results show that it has enough predictive accuracy and reliability to be put into practice. In the end,the possibility and prospect of the application of educational data mining in teaching management system for university students was assessed.
基金supported by National Key R&D Program of China(Grant No.YS2018YFB110130).
文摘Additive remanufacturing technology,as one of the key technologies of remanufacturing engineering,can realize the integrated repair of the structure and function of high value-added key metal parts of large and complex equipment,which can significantly reduce the use and maintenance costs,save labor and time costs.It applies to the on-site repair and remanufacturing of key parts in the aerospace,energy and chemical industry,heavy haul machinery,and other fields,as well as the on-site rapid repair of parts in special environments such as tunnels,open seas,and space.Additive remanufacturing technology can promote the reform of the maintenance and support mode of weapons and equipment and become the research hotspot of major military-developed countries.This paper expounds on the connotation and characteristics of additive remanufacturing technology and introduces its evolution process.The research achievements of the author in the development of additive remanufacturing platforms,material design,and process optimization were summarized.Given the problems(such as control shape,control performance,and control position)in the additive remanufacturing process,the author puts forward solutions and looks forward to the future development direction of additive remanufacturing technology.
