Based on mesoscopic damage mechanics, numerical code RFPA2D （dynamic edition） was developed to analyze the influence of tunnel reinforcing on failure process of surrounding rock under explosive stress waves. The res...Based on mesoscopic damage mechanics, numerical code RFPA2D （dynamic edition） was developed to analyze the influence of tunnel reinforcing on failure process of surrounding rock under explosive stress waves. The results show that the propagation phenomenon of stress wave in the surrounding rock of tunnel and the failure process of surrounding rock under explosive stress waves are reproduced realistically by using numerical code RFPA2O; from the failure process of surrounding rock, the place at which surrounding rock fractures is transferred because of tunnel reinforcing, and the rockfall and collapse caused by failure of surrounding rock are restrained by tunnel reinforcing; furthermore, the absolute values of peak values of major principal stress, and the minimal principal stress and shear stress at center point of tunnel roof are reduced because of tunnel reinforcing, and the displacement at center point of runnel roof is reduced as well, consequently the stability of tunnel increases.展开更多
多端直流电网架空线路故障概率高、设备耐受过电流能力有限,无选择性的重合将严重危害一次设备的安全性和电网的稳定性,因此提出了一种基于动态时间规整(dynamic time warping, DTW)的重构序列重合方法,实现重合前故障性质的预判。首先...多端直流电网架空线路故障概率高、设备耐受过电流能力有限,无选择性的重合将严重危害一次设备的安全性和电网的稳定性,因此提出了一种基于动态时间规整(dynamic time warping, DTW)的重构序列重合方法,实现重合前故障性质的预判。首先介绍了直流线路的贝杰龙时域等值建模方法,在此基础上,建立了各关键一次设备的贝杰龙等值模型,分析了瞬时性、永久性故障工况下模型等效时域波过程的差异性。然后以瞬时性故障为基准,对直流断路器注入信号所引发的电气分量暂态成分进行理论计算,并借助DTW重构序列量化整定门槛、进一步消除色散误差,最终以此为指标构造判据实现故障性质的识别。基于PSCAD/EMTDC平台的四端直流电网仿真算例显示,所提出的自适应重合方法仅需要单端量,不依赖通信,能够消除死区,且拥有600Ω的灵敏性。展开更多
In this study, kerosene fuel-rich gas produced by the combustion in the gas generator was used as the fuel and oxygen-rich air was used as the oxidant to investigate the propagation characteristics of the rotating det...In this study, kerosene fuel-rich gas produced by the combustion in the gas generator was used as the fuel and oxygen-rich air was used as the oxidant to investigate the propagation characteristics of the rotating detonation wave (RDW). The initiation of the kerosene fuel-rich gas and propagation process of the RDW were analyzed. The influences of the oxygen content in the oxidizer, kerosene mass flow rate of the gas generator, and temperature of the kerosene fuel-rich gas on the propagation process of the RDW were studied. The experimental results revealed that the propagation velocity of the RDW could be improved by increasing the three parameters mentioned above with the kerosene mass flow rate as the strongest factor. The minimum oxygen content that could successfully initiate and maintain the stable propagation of the RDW was 32%, achieving the RDW velocity of 1141.9 m/s. The RDW mainly propagated as two-counter rotating waves and a single wave when the equivalent ratios were 0.62–0.79 and 0.85–0.87, respectively. The highest RDW velocity of 1637.2 m/s was obtained when the kerosene mass flow rate, oxygen content, and equivalent ratio were 74.6 g/s, 44%, and 0.87, respectively.展开更多
The basic objective of time-scale transformation is to compress or expand the signal in time field while keeping the same spectral properties. This paper presents two methods to derive time-scale transformation formul...The basic objective of time-scale transformation is to compress or expand the signal in time field while keeping the same spectral properties. This paper presents two methods to derive time-scale transformation formula based on continuous wavelet transform. For an arbitrary given square-integrable function f(t),g(t) = f(t/λ) is derived by continuous wavelet transform and its inverse transform. The result shows that time-scale transformation may be obtained through the modification of the time-scale of wavelet function filter using equivalent substitution. The paper demonstrates the result by theoretic derivations and experimental simulation.展开更多
基金Projects(50874020, 50504005 and 50490274) supported by the National Natural Science Foundation of ChinaPorject(2007CB209407) supported by Major State Basic Research Development Program of ChinaProject(2005038250) supported by Postdoctoral Science Foundation of China
文摘Based on mesoscopic damage mechanics, numerical code RFPA2D （dynamic edition） was developed to analyze the influence of tunnel reinforcing on failure process of surrounding rock under explosive stress waves. The results show that the propagation phenomenon of stress wave in the surrounding rock of tunnel and the failure process of surrounding rock under explosive stress waves are reproduced realistically by using numerical code RFPA2O; from the failure process of surrounding rock, the place at which surrounding rock fractures is transferred because of tunnel reinforcing, and the rockfall and collapse caused by failure of surrounding rock are restrained by tunnel reinforcing; furthermore, the absolute values of peak values of major principal stress, and the minimal principal stress and shear stress at center point of tunnel roof are reduced because of tunnel reinforcing, and the displacement at center point of runnel roof is reduced as well, consequently the stability of tunnel increases.
文摘多端直流电网架空线路故障概率高、设备耐受过电流能力有限,无选择性的重合将严重危害一次设备的安全性和电网的稳定性,因此提出了一种基于动态时间规整(dynamic time warping, DTW)的重构序列重合方法,实现重合前故障性质的预判。首先介绍了直流线路的贝杰龙时域等值建模方法,在此基础上,建立了各关键一次设备的贝杰龙等值模型,分析了瞬时性、永久性故障工况下模型等效时域波过程的差异性。然后以瞬时性故障为基准,对直流断路器注入信号所引发的电气分量暂态成分进行理论计算,并借助DTW重构序列量化整定门槛、进一步消除色散误差,最终以此为指标构造判据实现故障性质的识别。基于PSCAD/EMTDC平台的四端直流电网仿真算例显示,所提出的自适应重合方法仅需要单端量,不依赖通信,能够消除死区,且拥有600Ω的灵敏性。
文摘In this study, kerosene fuel-rich gas produced by the combustion in the gas generator was used as the fuel and oxygen-rich air was used as the oxidant to investigate the propagation characteristics of the rotating detonation wave (RDW). The initiation of the kerosene fuel-rich gas and propagation process of the RDW were analyzed. The influences of the oxygen content in the oxidizer, kerosene mass flow rate of the gas generator, and temperature of the kerosene fuel-rich gas on the propagation process of the RDW were studied. The experimental results revealed that the propagation velocity of the RDW could be improved by increasing the three parameters mentioned above with the kerosene mass flow rate as the strongest factor. The minimum oxygen content that could successfully initiate and maintain the stable propagation of the RDW was 32%, achieving the RDW velocity of 1141.9 m/s. The RDW mainly propagated as two-counter rotating waves and a single wave when the equivalent ratios were 0.62–0.79 and 0.85–0.87, respectively. The highest RDW velocity of 1637.2 m/s was obtained when the kerosene mass flow rate, oxygen content, and equivalent ratio were 74.6 g/s, 44%, and 0.87, respectively.
文摘The basic objective of time-scale transformation is to compress or expand the signal in time field while keeping the same spectral properties. This paper presents two methods to derive time-scale transformation formula based on continuous wavelet transform. For an arbitrary given square-integrable function f(t),g(t) = f(t/λ) is derived by continuous wavelet transform and its inverse transform. The result shows that time-scale transformation may be obtained through the modification of the time-scale of wavelet function filter using equivalent substitution. The paper demonstrates the result by theoretic derivations and experimental simulation.
