High-temperature thin-film strain sensors are advanced technological devices for monitoring stress and strain in extreme environments,but the coupling of temperature and strain at high temperature is a challenge for t...High-temperature thin-film strain sensors are advanced technological devices for monitoring stress and strain in extreme environments,but the coupling of temperature and strain at high temperature is a challenge for their use.Here,this issue is addressed by creating a composite ink that combines Pb_(2)Ru_(2)O_(6) and TiB_(2) using polysilazane(PSZ)as a binder.After direct writing and annealing the PSZ/Pb_(2)Ru_(2)O_(6)/TiB_(2) film at 800℃ in air,the resulting thin film exhibits a low temperature coefficient of resistance(TCR)of only 281 ppm/℃ over a wide temperature range from 100℃ to 700℃,while also demonstrating high sensitivity with a gauge factor approaching 19.8.This exceptional performance is attributed to the intrinsic properties of Pb_(2)Ru_(2)O_(6),which has positive TCR at high temperature,and TiB2,which has negative TCR at high temperature.Combining these materials reduces the overall TCR of the film.Tests showed that the PSZ/Pb_(2)Ru_(2)O_(6)/TiB_(2) film maintains stable strain responses and significant signal output even under varying temperature.These findings provide valuable insights for developing high-temperature strain sensors with low TCR and high sensitivity,highlighting their potential for applications in high-temperature strain measurements.展开更多
The hysteretic behavior and nonlinearity of the equivalent material coefficient of macro fiber composites（MFC） under staircase input conditions are investigated using the Preisach model.Based on a database of first ...The hysteretic behavior and nonlinearity of the equivalent material coefficient of macro fiber composites（MFC） under staircase input conditions are investigated using the Preisach model.Based on a database of first order reversal curves, formulas are derived to predict the hysteresis of strain output and nonlinearity of the equivalent piezoelectric coefficient of MFCs. Formulae are verified by comparing the predicted strains with the measured strains of three MFC specimens,which are driven by a random sequence of staircase voltage inputs. The coefficients obtained by the formulae and experimentation coincide. Further results indicate that the equivalent piezoelectric strain coefficient depends greatly on the value of drive voltage across the entire input range, and the coefficient is asymmetric across the negative and positive input ranges. Deflection testing of an MFC composite cantilever demonstrates the importance of taking the nonlinearity of the equivalent piezoelectric coefficient into consideration in the application of actuation.展开更多
针对现有光功率预测模型在极端天气下预测精度低、天气场景特征解析方式粗糙以及动态补偿机制缺失等问题,提出了一种考虑多场景和差异化补偿策略的光功率预测方法。该方法提出混合天气类型概念,并通过构建具有优化评价功能的聚类(cluste...针对现有光功率预测模型在极端天气下预测精度低、天气场景特征解析方式粗糙以及动态补偿机制缺失等问题,提出了一种考虑多场景和差异化补偿策略的光功率预测方法。该方法提出混合天气类型概念,并通过构建具有优化评价功能的聚类(clustering with optimal evaluation function,COEF)算法,实现天气状态场景的自适应分类;基于极限学习机构建基础值预测模型,并阐明多场景的补偿机理,通过对不同天气场景设计针对性的误差补偿模型,实现对基础预测值的多尺度校正,提高算法的预测精度。最后,选择不同地域和气候特点的多场站实际数据进行仿真测试。仿真结果表明:与物理模型及传统机器学习算法相比,所提出的光功率预测方法在多时间尺度、多场景工况下均有更好的预测效果。展开更多
To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concret...To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concrete T-beams,destructive tests were conducted on full-scale pre-stressed concrete beams.Based on the measurement and ana-lysis of beam deflection,strain,and crack development under various loading levels during the research tests,combined with the verification coefficient indicators specified in the codes,the verification coefficients of bridges at different stages of damage can be examined.The results indicate that the T-beams experience complete,incom-plete linear,and non-linear stages during the destructive test process.In the complete linear elastic stage,both the deflection and bottom strain verification coefficients comply with the specifications,indicating a good structural load-bearing capacity no longer adheres to the code’s requirements.In the non-linear stage,both coefficients exhi-bit a sharp increase,resulting in a further decrease in the structure’s load-bearing capacity.According to the pro-visions of the current code,the beam can be in the incomplete linear stage when both values fall within the code’s specified range.The strain verification coefficient sourced from the compression zone at the bottom of theflange is not recommended for assessing the bridge’s load-bearing capacity.展开更多
Monocrystalline Cu exhibits excellent electrical and signal-transmission properties due to its absence of grain boundaries,making it a critical material for the production of micro-machinery and micro-components;howev...Monocrystalline Cu exhibits excellent electrical and signal-transmission properties due to its absence of grain boundaries,making it a critical material for the production of micro-machinery and micro-components;however,achieving ultrahigh precision and ultralow damage machining of functional devices using traditional techniques such as grinding and polishing is extremely challenging.Consequently,nanocutting has emerged as an efficient means to fabricate monocrystalline materials with complex surface characteristics and high surface integrity.Nevertheless,the macroscopic cutting theory of metal materials cannot be applied to nanocutting.Accordingly,in this paper,both simulations and experiments were conducted to examine the chip deformation mechanisms of monocrystalline Cu.First,large-scale molecular dynamics(MD)simulations were conducted to gain a comprehensive understanding of the deformation behavior during nanocutting.This included examining the influencing factors and the variation patterns of the chip deformation coefficient,cutting force,and minimum cutting thickness.Subsequently,nanocutting experiments were performed using a specially designed nanocutting platform with high-resolution online observation by scanning electron microscopy.The experimental results served to verify the accuracy and reliability of theMDmodeling,as they exhibited excellent consistency with the simulated results.Although this work considered monocrystalline Cu,it is believed that the elucidated chip deformation mechanisms could also be applied to other face-centered-cubic metals.These results are of great value for advancing the understanding of the mechanisms of ultraprecision cutting.展开更多
The training effectiveness of the lower Yellow River(LYR)depends on the understanding of the regularity offlow-sediment transport and riverbed sedimentation.The measured data of dailyflow discharge and sediment transpor...The training effectiveness of the lower Yellow River(LYR)depends on the understanding of the regularity offlow-sediment transport and riverbed sedimentation.The measured data of dailyflow discharge and sediment transport rate at thefive hydrological stations(Xiaolangdi[Xld],Huayuankou[Hyk],Gaocun[Gc],Aishan[As],and Lijin[Lj])in the LYR during the period from 1960 to 2017 are used to investigate the regularity offlow-sediment transport and sedimentation in the LYR.The Xld station is used as the inlet control station,and the LYR is divided into four segments using four other stations,and the whole year is divided into three periods,namely,the dry season,theflood period,and the nonflood period of the wet season.On this basis,the relationships between the sediment transport rates at the four stations(Hyk,Gc,As,and Lj)and the rates at their respective closest upstream stations are analyzed in each of the three periods.According to the incoming sediment coefficient of the Xld station,theflow and sediment processes in the three periods are classified,and the refined equations for the relationship between the sediment transport rates at the downstream station and its upstream station are established.The results show that the calculated amount and process of erosion and deposition in each period and each segment of the LYR using the equations are in good agreement with the measured values.The relationship equations established in this study can conveniently predict the amount of erosion and deposition in different periods and different segments of the LYR in the future,which is of great significance to the rapid decision of the impact of the construction and operation of hydraulic projects in the upper and middle reaches of the Yellow River on the sedimentation in the LYR.展开更多
基金the National Key Research and Development Program of China(Grant No.2021YFB2012100)the Major Science and Technology Projects in Fujian Province(Grant No.2023HZ021005)+1 种基金the Open Project Program of Fujian Key Laboratory of Special Intelligent Equipment Measurement and Control(Grant No.FJIES2023KF06)the Industry-University-Research Co-operation Fund of the Eighth Research Institute of China Aerospace Science and Technology Corporation(Grant No.SAST2023-061).
文摘High-temperature thin-film strain sensors are advanced technological devices for monitoring stress and strain in extreme environments,but the coupling of temperature and strain at high temperature is a challenge for their use.Here,this issue is addressed by creating a composite ink that combines Pb_(2)Ru_(2)O_(6) and TiB_(2) using polysilazane(PSZ)as a binder.After direct writing and annealing the PSZ/Pb_(2)Ru_(2)O_(6)/TiB_(2) film at 800℃ in air,the resulting thin film exhibits a low temperature coefficient of resistance(TCR)of only 281 ppm/℃ over a wide temperature range from 100℃ to 700℃,while also demonstrating high sensitivity with a gauge factor approaching 19.8.This exceptional performance is attributed to the intrinsic properties of Pb_(2)Ru_(2)O_(6),which has positive TCR at high temperature,and TiB2,which has negative TCR at high temperature.Combining these materials reduces the overall TCR of the film.Tests showed that the PSZ/Pb_(2)Ru_(2)O_(6)/TiB_(2) film maintains stable strain responses and significant signal output even under varying temperature.These findings provide valuable insights for developing high-temperature strain sensors with low TCR and high sensitivity,highlighting their potential for applications in high-temperature strain measurements.
文摘The hysteretic behavior and nonlinearity of the equivalent material coefficient of macro fiber composites（MFC） under staircase input conditions are investigated using the Preisach model.Based on a database of first order reversal curves, formulas are derived to predict the hysteresis of strain output and nonlinearity of the equivalent piezoelectric coefficient of MFCs. Formulae are verified by comparing the predicted strains with the measured strains of three MFC specimens,which are driven by a random sequence of staircase voltage inputs. The coefficients obtained by the formulae and experimentation coincide. Further results indicate that the equivalent piezoelectric strain coefficient depends greatly on the value of drive voltage across the entire input range, and the coefficient is asymmetric across the negative and positive input ranges. Deflection testing of an MFC composite cantilever demonstrates the importance of taking the nonlinearity of the equivalent piezoelectric coefficient into consideration in the application of actuation.
文摘针对现有光功率预测模型在极端天气下预测精度低、天气场景特征解析方式粗糙以及动态补偿机制缺失等问题,提出了一种考虑多场景和差异化补偿策略的光功率预测方法。该方法提出混合天气类型概念,并通过构建具有优化评价功能的聚类(clustering with optimal evaluation function,COEF)算法,实现天气状态场景的自适应分类;基于极限学习机构建基础值预测模型,并阐明多场景的补偿机理,通过对不同天气场景设计针对性的误差补偿模型,实现对基础预测值的多尺度校正,提高算法的预测精度。最后,选择不同地域和气候特点的多场站实际数据进行仿真测试。仿真结果表明:与物理模型及传统机器学习算法相比,所提出的光功率预测方法在多时间尺度、多场景工况下均有更好的预测效果。
文摘To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concrete T-beams,destructive tests were conducted on full-scale pre-stressed concrete beams.Based on the measurement and ana-lysis of beam deflection,strain,and crack development under various loading levels during the research tests,combined with the verification coefficient indicators specified in the codes,the verification coefficients of bridges at different stages of damage can be examined.The results indicate that the T-beams experience complete,incom-plete linear,and non-linear stages during the destructive test process.In the complete linear elastic stage,both the deflection and bottom strain verification coefficients comply with the specifications,indicating a good structural load-bearing capacity no longer adheres to the code’s requirements.In the non-linear stage,both coefficients exhi-bit a sharp increase,resulting in a further decrease in the structure’s load-bearing capacity.According to the pro-visions of the current code,the beam can be in the incomplete linear stage when both values fall within the code’s specified range.The strain verification coefficient sourced from the compression zone at the bottom of theflange is not recommended for assessing the bridge’s load-bearing capacity.
基金support of the National Natural Science Foundation of China(Grant No.51805371)the Innovation and Entrepreneurship Training Program of Tianjin University of Commerce(Grant No.202310069067).
文摘Monocrystalline Cu exhibits excellent electrical and signal-transmission properties due to its absence of grain boundaries,making it a critical material for the production of micro-machinery and micro-components;however,achieving ultrahigh precision and ultralow damage machining of functional devices using traditional techniques such as grinding and polishing is extremely challenging.Consequently,nanocutting has emerged as an efficient means to fabricate monocrystalline materials with complex surface characteristics and high surface integrity.Nevertheless,the macroscopic cutting theory of metal materials cannot be applied to nanocutting.Accordingly,in this paper,both simulations and experiments were conducted to examine the chip deformation mechanisms of monocrystalline Cu.First,large-scale molecular dynamics(MD)simulations were conducted to gain a comprehensive understanding of the deformation behavior during nanocutting.This included examining the influencing factors and the variation patterns of the chip deformation coefficient,cutting force,and minimum cutting thickness.Subsequently,nanocutting experiments were performed using a specially designed nanocutting platform with high-resolution online observation by scanning electron microscopy.The experimental results served to verify the accuracy and reliability of theMDmodeling,as they exhibited excellent consistency with the simulated results.Although this work considered monocrystalline Cu,it is believed that the elucidated chip deformation mechanisms could also be applied to other face-centered-cubic metals.These results are of great value for advancing the understanding of the mechanisms of ultraprecision cutting.
基金Open Research Fund of state key Laboratory of simulation and Regulation of Water Cycle in River Basin(China lnstitute of Water Resources and Hydropower Research),Grant/Award Number:IWHR-SKL-202104National Natural Science Foundation of China,Grant/Award Number:U2243237Outstanding Youth scientific research project of Yellow River Conservancy Commission of the Ministry of Water Resources,Grant/Award Number:HQK-202302。
文摘The training effectiveness of the lower Yellow River(LYR)depends on the understanding of the regularity offlow-sediment transport and riverbed sedimentation.The measured data of dailyflow discharge and sediment transport rate at thefive hydrological stations(Xiaolangdi[Xld],Huayuankou[Hyk],Gaocun[Gc],Aishan[As],and Lijin[Lj])in the LYR during the period from 1960 to 2017 are used to investigate the regularity offlow-sediment transport and sedimentation in the LYR.The Xld station is used as the inlet control station,and the LYR is divided into four segments using four other stations,and the whole year is divided into three periods,namely,the dry season,theflood period,and the nonflood period of the wet season.On this basis,the relationships between the sediment transport rates at the four stations(Hyk,Gc,As,and Lj)and the rates at their respective closest upstream stations are analyzed in each of the three periods.According to the incoming sediment coefficient of the Xld station,theflow and sediment processes in the three periods are classified,and the refined equations for the relationship between the sediment transport rates at the downstream station and its upstream station are established.The results show that the calculated amount and process of erosion and deposition in each period and each segment of the LYR using the equations are in good agreement with the measured values.The relationship equations established in this study can conveniently predict the amount of erosion and deposition in different periods and different segments of the LYR in the future,which is of great significance to the rapid decision of the impact of the construction and operation of hydraulic projects in the upper and middle reaches of the Yellow River on the sedimentation in the LYR.
