Considering the uncertainty of material performance, geometric characteristic and analysis method, the analysis of statistical parameters of the resistance of cast ball-and-socket support joints and the reliability an...Considering the uncertainty of material performance, geometric characteristic and analysis method, the analysis of statistical parameters of the resistance of cast ball-and-socket support joints and the reliability analysis are carried out by JC method (improved first-order second-moment method) based on the relevant experimental data. Results show that the resistance partial factor of the joint increases with the increase of the reliability index. The resistance partial factors are suggested corresponding to the reliability index under different load combinations. Moreover, the suggested resistance partial factor is adopted in reliability design, and it is found that the reliability index of the joint is larger than the target reliability index. The optimal load combination is the one in which live load plays an important control role. Finally, based on the suggested resistance partial factors, the reliability analysis of cast ball-and-socket support joints of a project is conducted.展开更多
Adopting the load and resistance factor design format, the design method for steel jaeket platform structures is developed. Firstly, the limit state equations and design format for steel jacket platform structures are...Adopting the load and resistance factor design format, the design method for steel jaeket platform structures is developed. Firstly, the limit state equations and design format for steel jacket platform structures are introduced. Then, the ratio of live load effect to dead load effect is estimated. The target reliabilities for design of offshore structures in China offshore area are calibrated by past practice in API RP2A-WSD code. The load and resistance factors are optimized by minimizing the difference within the target reliability and the resulting reliability over the range of load effect ratios. Considering the concurrence of different loads, load combination factors are obtained through an optimization process, and the relation between the load combination factor and load correlation coefficient is established. Finally, the design formulae for steel jacket structures in China offshore area are recommended.展开更多
In order to study the influence of highland barley straw ash (HBSA) prepared under certain conditions on the durability of magnesium oxychloride cement mortar (MOCM) under freeze-thaw damage,rapid freeze-thaw cycle te...In order to study the influence of highland barley straw ash (HBSA) prepared under certain conditions on the durability of magnesium oxychloride cement mortar (MOCM) under freeze-thaw damage,rapid freeze-thaw cycle tests were carried out firstly.The relative mass evaluation parameters and the relative compressive strength evaluation parameters,which represent the degradation of freeze-thaw resistance,were used as the indices to study the degradation rule of MOCM.Secondly,nuclear magnetic resonance (NMR) tests were carried out on MOCM under different freeze-thaw cycles to analyze the pore diameter changes in the freeze-thaw process.The microstructure of MOCM was tested by Fourier transform infrared spectroscopy (FTIR),X-ray diffraction (XRD) and scanning electron microscopy (SEM),and then the effect mechanism of HBSA on the anti-freezing performance of MOCM was revealed.Finally,the two-parameter Weibull distribution function was used to analyze the reliability of durability degradation of MOCM added with HBSA under freeze-thaw cycles.The specific conclusions are as follows:With the increase of HBSA's addition,the freeze-thaw resistance of MOCM increase firstly and then decrease.When the addition of HBSA is 10%,the decay rate of relative mass evaluation parameters and relative compressive strength evaluation parameters is the slowest,and the frost resistance is the best.The proportion of harmful pores and more harmful pores in MOCM added with 10% HBSA decreases by 25.11% and 21.34%,compared with that without HBSA before and after freeze-thaw cycles.A lot of magnesium silicate hydrate (M-S-H) gels are generated in MOCM with HBSA content of 10%,which fills part of the pores,so that the proportion of harmful pores and more harmful pores is the lowest.The Weibull function can be effectively applied to the reliability analysis of the freeze-thaw cycle of MOCM added with HBSA,and the theoretical results are in good agreement with the experimental results.展开更多
The actively heated fiber-optic(AHFO)technology has become emerged as a research focus due to its advantages of distributed,real-time measurement and good durability.These attributes have led to the gradual applicatio...The actively heated fiber-optic(AHFO)technology has become emerged as a research focus due to its advantages of distributed,real-time measurement and good durability.These attributes have led to the gradual application of AHFO technology to the water content measurement of in situ soil.However,all existing in situ applications of AHFO technology fail to consider the effect of soilesensor contact quality on water content measurements,limiting potential for the wider application of AHFO technology.To address this issue,the authors propose a method for determining the soilesensor thermal contact resistance based on the principle of an infinite cylindrical heat source.This is then used to establish an AHFO water content measurement technology that considers the thermal contact resistance.The reliability and validity of the new measurement technology are explored through a laboratory test and a field case study,and the spatial-temporal evolution of the soil water content in the case is revealed.The results demonstrate that method for determining the soilesensor thermal contact resistance is highly effective and applicable to all types of soils.This method requires only the moisture content,dry density,and thermal response of the in situ soil to be obtained.In the field case,the measurement error of soil water content between the AHFO method,which takes into account the thermal contact resistance,and the neutron scattering method is only 0.011.The water content of in situ soil exhibits a seasonal variation,with an increase in spring and autumn and a decrease in summer and winter.Furthermore,the response of shallow soils to precipitation and evaporation is significant.These findings contribute to the enhancement of the accuracy of the AHFO technology in the measurement of the water content of in situ soils,thereby facilitating the dissemination and utilization of this technology.展开更多
The dynamic contact resistances of HH52P electromagnetic relays are measured under different ambient air tem- perature. Their diagnostic parameters are extracted and determined. It is found that the ambient air temper...The dynamic contact resistances of HH52P electromagnetic relays are measured under different ambient air tem- perature. Their diagnostic parameters are extracted and determined. It is found that the ambient air temperature obviously influ- ences some parameters. In order to research its influence on the electrical contact reliability of electromagnetic relay, the statistic analysis is applied to study the static contact resistance, the max of the dynamic contact resistance and the bounce time. It is found that the ambient air temperature regularly influences the three parameters. Thoroughly, the phenomenon is studied and analyzed in the point of material science so as to probe into the essential matter of it.展开更多
The resistive random access memory(RRAM)has stimulated a variety of promising applications including programmable analog circuit,massive data storage,neuromorphic computing,etc.These new emerging applications have hug...The resistive random access memory(RRAM)has stimulated a variety of promising applications including programmable analog circuit,massive data storage,neuromorphic computing,etc.These new emerging applications have huge demands on high integration density and low power consumption.The cross-point configuration or passive array,which offers the smallest footprint of cell size and feasible capability of multi-layer stacking,has received broad attention from the research community.In such array,correct operation of reading and writing on a cell relies on effective elimination of the sneaking current coming from the neighboring cells.This target requires nonlinear I-V characteristics of the memory cell,which can be realized by either adding separate selector or developing implicit build-in nonlinear cells.The performance of a passive array largely depends on the cell nonlinearity,reliability,on/off ratio,line resistance,thermal coupling,etc.This article provides a comprehensive review on the progress achieved concerning 3D RRAM integration.First,the authors start with a brief overview of the associative problems in passive array and the category of 3D architectures.Next,the state of the arts on the development of various selector devices and self-selective cells are presented.Key parameters that influence the device nonlinearity and current density are outlined according to the corresponding working principles.Then,the reliability issues in 3D array are summarized in terms of uniformity,endurance,retention,and disturbance.Subsequently,scaling issue and thermal crosstalk in 3D memory array are thoroughly discussed,and applications of 3D RRAM beyond storage,such as neuromorphic computing and CMOL circuit are discussed later.Summary and outlooks are given in the final.展开更多
基金Supported by National Natural Science Foundation of China (No.51078259)Seed Foundation of Tianjin University (No.2010XG-0013)Program for New Century Excellent Talents in University (No.1102010)
文摘Considering the uncertainty of material performance, geometric characteristic and analysis method, the analysis of statistical parameters of the resistance of cast ball-and-socket support joints and the reliability analysis are carried out by JC method (improved first-order second-moment method) based on the relevant experimental data. Results show that the resistance partial factor of the joint increases with the increase of the reliability index. The resistance partial factors are suggested corresponding to the reliability index under different load combinations. Moreover, the suggested resistance partial factor is adopted in reliability design, and it is found that the reliability index of the joint is larger than the target reliability index. The optimal load combination is the one in which live load plays an important control role. Finally, based on the suggested resistance partial factors, the reliability analysis of cast ball-and-socket support joints of a project is conducted.
文摘Adopting the load and resistance factor design format, the design method for steel jaeket platform structures is developed. Firstly, the limit state equations and design format for steel jacket platform structures are introduced. Then, the ratio of live load effect to dead load effect is estimated. The target reliabilities for design of offshore structures in China offshore area are calibrated by past practice in API RP2A-WSD code. The load and resistance factors are optimized by minimizing the difference within the target reliability and the resulting reliability over the range of load effect ratios. Considering the concurrence of different loads, load combination factors are obtained through an optimization process, and the relation between the load combination factor and load correlation coefficient is established. Finally, the design formulae for steel jacket structures in China offshore area are recommended.
基金Funded by the National Natural Science Foundation of China (No.51868044)Basic Research Program of Qinghai Province (No.2022-ZJ-921)。
文摘In order to study the influence of highland barley straw ash (HBSA) prepared under certain conditions on the durability of magnesium oxychloride cement mortar (MOCM) under freeze-thaw damage,rapid freeze-thaw cycle tests were carried out firstly.The relative mass evaluation parameters and the relative compressive strength evaluation parameters,which represent the degradation of freeze-thaw resistance,were used as the indices to study the degradation rule of MOCM.Secondly,nuclear magnetic resonance (NMR) tests were carried out on MOCM under different freeze-thaw cycles to analyze the pore diameter changes in the freeze-thaw process.The microstructure of MOCM was tested by Fourier transform infrared spectroscopy (FTIR),X-ray diffraction (XRD) and scanning electron microscopy (SEM),and then the effect mechanism of HBSA on the anti-freezing performance of MOCM was revealed.Finally,the two-parameter Weibull distribution function was used to analyze the reliability of durability degradation of MOCM added with HBSA under freeze-thaw cycles.The specific conclusions are as follows:With the increase of HBSA's addition,the freeze-thaw resistance of MOCM increase firstly and then decrease.When the addition of HBSA is 10%,the decay rate of relative mass evaluation parameters and relative compressive strength evaluation parameters is the slowest,and the frost resistance is the best.The proportion of harmful pores and more harmful pores in MOCM added with 10% HBSA decreases by 25.11% and 21.34%,compared with that without HBSA before and after freeze-thaw cycles.A lot of magnesium silicate hydrate (M-S-H) gels are generated in MOCM with HBSA content of 10%,which fills part of the pores,so that the proportion of harmful pores and more harmful pores is the lowest.The Weibull function can be effectively applied to the reliability analysis of the freeze-thaw cycle of MOCM added with HBSA,and the theoretical results are in good agreement with the experimental results.
基金supported by the National Natural Science Foundation of China(Grant Nos.42307189 and 42030701)the China Postdoctoral Science Foundation(Grant No.2023M740974).
文摘The actively heated fiber-optic(AHFO)technology has become emerged as a research focus due to its advantages of distributed,real-time measurement and good durability.These attributes have led to the gradual application of AHFO technology to the water content measurement of in situ soil.However,all existing in situ applications of AHFO technology fail to consider the effect of soilesensor contact quality on water content measurements,limiting potential for the wider application of AHFO technology.To address this issue,the authors propose a method for determining the soilesensor thermal contact resistance based on the principle of an infinite cylindrical heat source.This is then used to establish an AHFO water content measurement technology that considers the thermal contact resistance.The reliability and validity of the new measurement technology are explored through a laboratory test and a field case study,and the spatial-temporal evolution of the soil water content in the case is revealed.The results demonstrate that method for determining the soilesensor thermal contact resistance is highly effective and applicable to all types of soils.This method requires only the moisture content,dry density,and thermal response of the in situ soil to be obtained.In the field case,the measurement error of soil water content between the AHFO method,which takes into account the thermal contact resistance,and the neutron scattering method is only 0.011.The water content of in situ soil exhibits a seasonal variation,with an increase in spring and autumn and a decrease in summer and winter.Furthermore,the response of shallow soils to precipitation and evaporation is significant.These findings contribute to the enhancement of the accuracy of the AHFO technology in the measurement of the water content of in situ soils,thereby facilitating the dissemination and utilization of this technology.
文摘The dynamic contact resistances of HH52P electromagnetic relays are measured under different ambient air tem- perature. Their diagnostic parameters are extracted and determined. It is found that the ambient air temperature obviously influ- ences some parameters. In order to research its influence on the electrical contact reliability of electromagnetic relay, the statistic analysis is applied to study the static contact resistance, the max of the dynamic contact resistance and the bounce time. It is found that the ambient air temperature regularly influences the three parameters. Thoroughly, the phenomenon is studied and analyzed in the point of material science so as to probe into the essential matter of it.
基金the National Key R&D Program of China(Grant Nos.2018YFB0407501 and 2016YFA0201800)the National Natural Science Foundation of China(Grant Nos.61804173,61922083,61804167,61904200,and 61821091)the fourth China Association for Science and Technology Youth Talent Support Project(Grant No.2019QNRC001).
文摘The resistive random access memory(RRAM)has stimulated a variety of promising applications including programmable analog circuit,massive data storage,neuromorphic computing,etc.These new emerging applications have huge demands on high integration density and low power consumption.The cross-point configuration or passive array,which offers the smallest footprint of cell size and feasible capability of multi-layer stacking,has received broad attention from the research community.In such array,correct operation of reading and writing on a cell relies on effective elimination of the sneaking current coming from the neighboring cells.This target requires nonlinear I-V characteristics of the memory cell,which can be realized by either adding separate selector or developing implicit build-in nonlinear cells.The performance of a passive array largely depends on the cell nonlinearity,reliability,on/off ratio,line resistance,thermal coupling,etc.This article provides a comprehensive review on the progress achieved concerning 3D RRAM integration.First,the authors start with a brief overview of the associative problems in passive array and the category of 3D architectures.Next,the state of the arts on the development of various selector devices and self-selective cells are presented.Key parameters that influence the device nonlinearity and current density are outlined according to the corresponding working principles.Then,the reliability issues in 3D array are summarized in terms of uniformity,endurance,retention,and disturbance.Subsequently,scaling issue and thermal crosstalk in 3D memory array are thoroughly discussed,and applications of 3D RRAM beyond storage,such as neuromorphic computing and CMOL circuit are discussed later.Summary and outlooks are given in the final.
