This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion energy.The model parameters were determi...This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion energy.The model parameters were determined through the extremum features of stress−strain curve.Subsequently,the model predictions were compared with experimental results of marble samples.It is found that when the treatment temperature rises,the coupling damage evolution curve shows an S-shape and the slope of ascending branch gradually decreases during the coupling damage evolution process.At a constant temperature,confining pressure can suppress the expansion of micro-fractures.As the confining pressure increases the rock exhibits ductility characteristics,and the shape of coupling damage curve changes from an S-shape into a quasi-parabolic shape.This model can well characterize the influence of high temperature on the mechanical properties of deep rock and its brittleness-ductility transition characteristics under confining pressure.Also,it is suitable for sandstone and granite,especially in predicting the pre-peak stage and peak stress of stress−strain curve under the coupling action of confining pressure and high temperature.The relevant results can provide a reference for further research on the constitutive relationship of rock-like materials and their engineering applications.展开更多
Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock ma...Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock mass with developed joints was treated as a discrete medium in the calculation. Using the UDEC code, the numerical simulations for thermo-mechanical coupling processes in the surrounding rock mass-supporting system were carried out aiming at the conditions of mean temperature, extreme highest temperature and extreme lowest temperature in one year. The distributions and changes of stresses, displacements, plastic zones, temperatures in the rock mass of near field, as well as the loading states in the model-building concrete and bolting were investigated and compared for these three computation cases. The results show that compared with the case of mean temperature, the ranges, where the temperatures of surrounding rock mass change obviously, are 6.0 m and 6.5 m, respectively, for the cases of extreme highest temperature and extreme lowest temperature; the displacements of tunnel are raised by 3.2 9.3 and 5.7 12.7 times, and the thicknesses of plastic zones reach 1.5 2.5 m and 2.0 4.5 m for case 2 and 3, respectively; the extreme temperatures of air have strong effects on the stress, deformation and failure states of supporting structure of tunnel in cold region, and the influence degree of extreme lowest temperature is the highest.展开更多
互质阵列因具有较低的互耦效应而备受关注,但交替部署的子阵却在一定程度上限制了连续自由度的提升。针对上述问题,该文在分析子阵互差集中冗余虚拟阵元产生条件的基础上,提出了两种子阵移位互质阵列(Coprime Array with Translated Sub...互质阵列因具有较低的互耦效应而备受关注,但交替部署的子阵却在一定程度上限制了连续自由度的提升。针对上述问题,该文在分析子阵互差集中冗余虚拟阵元产生条件的基础上,提出了两种子阵移位互质阵列(Coprime Array with Translated Subarray,CATrS),以改善自由度性能。首先,将子阵平移至适当位置以优化布阵结构,并分析了子阵的平移距离。随后,推导了CATrS结构的自由度、连续自由度、孔洞位置和虚拟阵元权重的闭合表达式。理论分析表明,CATrS结构能够在保持物理阵元数量不变的条件下,有效增加自由度和连续自由度,并抑制阵元互耦。最后,利用仿真实验验证了CATrS结构在波达方向估计中的优越性。展开更多
直接空气碳捕集(direct air capture,DAC)技术作为典型的负碳排放技术,是实现碳中和目标的关键技术之一,但是其依然面临高成本、高能耗问题。DAC技术与碳利用技术的深度耦合,将捕集的CO_(2)转化为高附加值产品,可提升碳减排效率并降低...直接空气碳捕集(direct air capture,DAC)技术作为典型的负碳排放技术,是实现碳中和目标的关键技术之一,但是其依然面临高成本、高能耗问题。DAC技术与碳利用技术的深度耦合,将捕集的CO_(2)转化为高附加值产品,可提升碳减排效率并降低全过程成本,在碳中和路径中具有重要价值。介绍了DAC技术的分类和原理,综述了DAC技术与CO_(2)光、电、热转化技术耦合的研究进展和主要挑战,最后展望了DAC技术与碳利用技术深度耦合的应用前景和发展方向。展开更多
研究质谱的离子传输气体动力学特征对理解和提升质谱仪器灵敏度具有重要意义。基于纳维-斯托克斯(NavierStokes)方程和直接蒙特卡洛(Direct Simulation Monte Carlo)方法联用,可以计算获得气体从大气压连续流到真空稀薄流的流场特征,进...研究质谱的离子传输气体动力学特征对理解和提升质谱仪器灵敏度具有重要意义。基于纳维-斯托克斯(NavierStokes)方程和直接蒙特卡洛(Direct Simulation Monte Carlo)方法联用,可以计算获得气体从大气压连续流到真空稀薄流的流场特征,进一步与电场仿真耦合,可以获得离子的传输与空间分布信息,评价离子光学器件性能。工作基于光电离质谱,构建了毛细管进样、光电离源和取样锥的组合结构模型,建立了离子传输跨流态多物理场仿真方法,得到了两种结构光电离源电极对离子传输效率的影响,并利用自制光电离飞行时间质谱装置验证了仿真方法的可靠性。工作为复杂流场和电场环境下质谱光电离源及离子传输装置设计提供了理论指导依据。展开更多
针对互耦效应和脉冲噪声并存环境下的波达方向(direction of arrival,DOA)估计问题,提出一种结合M估计与稀疏重构的算法。首先,为了消除互耦效应的影响,依据互耦矩阵的托普利兹结构进行恒等变形,得到了不含未知互耦系数的字典。随后,为...针对互耦效应和脉冲噪声并存环境下的波达方向(direction of arrival,DOA)估计问题,提出一种结合M估计与稀疏重构的算法。首先,为了消除互耦效应的影响,依据互耦矩阵的托普利兹结构进行恒等变形,得到了不含未知互耦系数的字典。随后,为了使算法能适应高斯噪声和不同强度的脉冲噪声,将位置得分函数表示为高斯位置得分函数和一系列非线性函数的线性组合,利用噪声样本估计线性组合系数从而建立损失函数。最后,采用迭代硬阈值算法进行稀疏重构,并通过改进信号更新策略提高正确收敛的概率。仿真结果表明,所提算法能有效抑制互耦效应和脉冲(高斯)噪声的干扰,同时相较已有算法在低信噪比、强脉冲特性下的性能有显著提升。展开更多
基金Project(11272119)supported by the National Natural Science Foundation of China。
文摘This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion energy.The model parameters were determined through the extremum features of stress−strain curve.Subsequently,the model predictions were compared with experimental results of marble samples.It is found that when the treatment temperature rises,the coupling damage evolution curve shows an S-shape and the slope of ascending branch gradually decreases during the coupling damage evolution process.At a constant temperature,confining pressure can suppress the expansion of micro-fractures.As the confining pressure increases the rock exhibits ductility characteristics,and the shape of coupling damage curve changes from an S-shape into a quasi-parabolic shape.This model can well characterize the influence of high temperature on the mechanical properties of deep rock and its brittleness-ductility transition characteristics under confining pressure.Also,it is suitable for sandstone and granite,especially in predicting the pre-peak stage and peak stress of stress−strain curve under the coupling action of confining pressure and high temperature.The relevant results can provide a reference for further research on the constitutive relationship of rock-like materials and their engineering applications.
基金Project(2010CB732101) supported by the National Basic Research Program of ChinaProjects(51079145,51379201) supported by the National Natural Science Foundation of China
文摘Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock mass with developed joints was treated as a discrete medium in the calculation. Using the UDEC code, the numerical simulations for thermo-mechanical coupling processes in the surrounding rock mass-supporting system were carried out aiming at the conditions of mean temperature, extreme highest temperature and extreme lowest temperature in one year. The distributions and changes of stresses, displacements, plastic zones, temperatures in the rock mass of near field, as well as the loading states in the model-building concrete and bolting were investigated and compared for these three computation cases. The results show that compared with the case of mean temperature, the ranges, where the temperatures of surrounding rock mass change obviously, are 6.0 m and 6.5 m, respectively, for the cases of extreme highest temperature and extreme lowest temperature; the displacements of tunnel are raised by 3.2 9.3 and 5.7 12.7 times, and the thicknesses of plastic zones reach 1.5 2.5 m and 2.0 4.5 m for case 2 and 3, respectively; the extreme temperatures of air have strong effects on the stress, deformation and failure states of supporting structure of tunnel in cold region, and the influence degree of extreme lowest temperature is the highest.
文摘互质阵列因具有较低的互耦效应而备受关注,但交替部署的子阵却在一定程度上限制了连续自由度的提升。针对上述问题,该文在分析子阵互差集中冗余虚拟阵元产生条件的基础上,提出了两种子阵移位互质阵列(Coprime Array with Translated Subarray,CATrS),以改善自由度性能。首先,将子阵平移至适当位置以优化布阵结构,并分析了子阵的平移距离。随后,推导了CATrS结构的自由度、连续自由度、孔洞位置和虚拟阵元权重的闭合表达式。理论分析表明,CATrS结构能够在保持物理阵元数量不变的条件下,有效增加自由度和连续自由度,并抑制阵元互耦。最后,利用仿真实验验证了CATrS结构在波达方向估计中的优越性。
文摘直接空气碳捕集(direct air capture,DAC)技术作为典型的负碳排放技术,是实现碳中和目标的关键技术之一,但是其依然面临高成本、高能耗问题。DAC技术与碳利用技术的深度耦合,将捕集的CO_(2)转化为高附加值产品,可提升碳减排效率并降低全过程成本,在碳中和路径中具有重要价值。介绍了DAC技术的分类和原理,综述了DAC技术与CO_(2)光、电、热转化技术耦合的研究进展和主要挑战,最后展望了DAC技术与碳利用技术深度耦合的应用前景和发展方向。
文摘研究质谱的离子传输气体动力学特征对理解和提升质谱仪器灵敏度具有重要意义。基于纳维-斯托克斯(NavierStokes)方程和直接蒙特卡洛(Direct Simulation Monte Carlo)方法联用,可以计算获得气体从大气压连续流到真空稀薄流的流场特征,进一步与电场仿真耦合,可以获得离子的传输与空间分布信息,评价离子光学器件性能。工作基于光电离质谱,构建了毛细管进样、光电离源和取样锥的组合结构模型,建立了离子传输跨流态多物理场仿真方法,得到了两种结构光电离源电极对离子传输效率的影响,并利用自制光电离飞行时间质谱装置验证了仿真方法的可靠性。工作为复杂流场和电场环境下质谱光电离源及离子传输装置设计提供了理论指导依据。
文摘针对互耦效应和脉冲噪声并存环境下的波达方向(direction of arrival,DOA)估计问题,提出一种结合M估计与稀疏重构的算法。首先,为了消除互耦效应的影响,依据互耦矩阵的托普利兹结构进行恒等变形,得到了不含未知互耦系数的字典。随后,为了使算法能适应高斯噪声和不同强度的脉冲噪声,将位置得分函数表示为高斯位置得分函数和一系列非线性函数的线性组合,利用噪声样本估计线性组合系数从而建立损失函数。最后,采用迭代硬阈值算法进行稀疏重构,并通过改进信号更新策略提高正确收敛的概率。仿真结果表明,所提算法能有效抑制互耦效应和脉冲(高斯)噪声的干扰,同时相较已有算法在低信噪比、强脉冲特性下的性能有显著提升。
