Turbine noise would be one of the dominant noise sources especially in future UHBR (Ultra High Bypass-Ratio) aeroengine, but its currently far from being studied enough. Acoustic mode is crucial for duct propagation b...Turbine noise would be one of the dominant noise sources especially in future UHBR (Ultra High Bypass-Ratio) aeroengine, but its currently far from being studied enough. Acoustic mode is crucial for duct propagation but little study about the relation between serration and mode. Thus, taking axial single-turbine test bench NPU-Turb as object, the effect of Stator with Serrated Trailing-edge (Bionic S) and Rotor with Serrated Leading-edge (Bionic R) on duct acoustic modes of turbine turbulence interac-tion noise were studied in detail using DDES/AA hybrid model validated by acoustic experiment of NPU-Turb. Serval conclusions can be made here. First, for broadband noise, the effect of serrations on duct modes (increased or reduced of PWL<sub>mn</sub>) with the increasing frequency is more prominent. Second, the changing trend of ?PWL<sub>mn</sub> is something like Chinese character “人” with circumferential mode m and alternating with radial mode. Such distribution is more obvious at higher frequency. More theoretical and mechanistic research work needs to be carried out in depth in the future. .展开更多
In this paper a class of risk processes in which claims occur as a renewal process is studied. A clear expression for Laplace transform of the survival probability is well given when the claim amount distribution is E...In this paper a class of risk processes in which claims occur as a renewal process is studied. A clear expression for Laplace transform of the survival probability is well given when the claim amount distribution is Erlang distribution or mixed Erlang distribution. The expressions for moments of the time to ruin with the model above are given.展开更多
机场场面多点定位利用S模式信号到达时间差实现目标定位。针对S模式信号易受接收系统内部非线性影响和机场场面复杂电磁干扰的问题,研究S模式信号失真恢复方法。根据S模式信号频谱特征和接收基站弱非线性记忆系统特征简化Volterra级数,...机场场面多点定位利用S模式信号到达时间差实现目标定位。针对S模式信号易受接收系统内部非线性影响和机场场面复杂电磁干扰的问题,研究S模式信号失真恢复方法。根据S模式信号频谱特征和接收基站弱非线性记忆系统特征简化Volterra级数,降低计算量的同时满足Volterra级数关键核函数对S模式信号非线性失真表示能力,得到S模式信号失真恢复模型。仿真结果表明:3阶简化Volterra级数模型恢复15 dB和0 dB S模式信号前导脉冲的失真前波形,误差仅有2.23%和12.59%,且模型在典型运用环境下满足一定的适用性、抗干扰性和稳定性,为S模式信号到达时间戳的准确提取提供基础。展开更多
With the rapid development of modern technology and all-round reform in national college English teaching,Internet-Based teaching mode has become a new trend of college English teaching.Therefore,in the new teaching m...With the rapid development of modern technology and all-round reform in national college English teaching,Internet-Based teaching mode has become a new trend of college English teaching.Therefore,in the new teaching mode,the teacher should turn an inculcator into an instructor,facilitator and participant in teaching;a passive user of textbook into a dominant and modeler of courses;a planner of teaching specific tasks into an organizer of teaching process,a helper and shepherd of learning knowledge.展开更多
In order to apply the performance-based seismic design, an engineer must first find out whether the column is expected to fail in shear before or after flexural yielding. According to column failure characteristics an...In order to apply the performance-based seismic design, an engineer must first find out whether the column is expected to fail in shear before or after flexural yielding. According to column failure characteristics and failure mode of reinforced concrete column, the UW-PEER structure performance database was discussed and analyzed. In order to investigate the relevance of failure mode and factors such as longitudinal reinforcement ratio, transverse reinforcement ratio, hoop spacing to depth ratio, aspect ratio, shearing resistance demand to shear capacity ratio and axial load ratio, Fisher's discriminant analysis(FDA) of the above factors was carried out. A discriminant function was developed to identify column failure mode. Results show that three factors, i.e., Vp /Vn, hoop spacing to depth ratio and aspect ratio have important influence on the failure mode. The failure mode has less to do with longitudinal reinforcement ratio, transverse reinforcement ratio and axial load ratio. Through using these three factors and the model proposed, over 85.6% of the original grouped cases were correctly classified. The value of coefficient of Vp /Vn is the largest, which means that discriminant equation is most sensitive to the shearing resistance demand to shear capacity ratio.展开更多
文摘Turbine noise would be one of the dominant noise sources especially in future UHBR (Ultra High Bypass-Ratio) aeroengine, but its currently far from being studied enough. Acoustic mode is crucial for duct propagation but little study about the relation between serration and mode. Thus, taking axial single-turbine test bench NPU-Turb as object, the effect of Stator with Serrated Trailing-edge (Bionic S) and Rotor with Serrated Leading-edge (Bionic R) on duct acoustic modes of turbine turbulence interac-tion noise were studied in detail using DDES/AA hybrid model validated by acoustic experiment of NPU-Turb. Serval conclusions can be made here. First, for broadband noise, the effect of serrations on duct modes (increased or reduced of PWL<sub>mn</sub>) with the increasing frequency is more prominent. Second, the changing trend of ?PWL<sub>mn</sub> is something like Chinese character “人” with circumferential mode m and alternating with radial mode. Such distribution is more obvious at higher frequency. More theoretical and mechanistic research work needs to be carried out in depth in the future. .
基金Supported by the NNSF of China(10471076)the NSF of Shandong Province(Y2004A06)the Key Project of the Ministry of Education of China(206091).
文摘In this paper a class of risk processes in which claims occur as a renewal process is studied. A clear expression for Laplace transform of the survival probability is well given when the claim amount distribution is Erlang distribution or mixed Erlang distribution. The expressions for moments of the time to ruin with the model above are given.
文摘机场场面多点定位利用S模式信号到达时间差实现目标定位。针对S模式信号易受接收系统内部非线性影响和机场场面复杂电磁干扰的问题,研究S模式信号失真恢复方法。根据S模式信号频谱特征和接收基站弱非线性记忆系统特征简化Volterra级数,降低计算量的同时满足Volterra级数关键核函数对S模式信号非线性失真表示能力,得到S模式信号失真恢复模型。仿真结果表明:3阶简化Volterra级数模型恢复15 dB和0 dB S模式信号前导脉冲的失真前波形,误差仅有2.23%和12.59%,且模型在典型运用环境下满足一定的适用性、抗干扰性和稳定性,为S模式信号到达时间戳的准确提取提供基础。
文摘With the rapid development of modern technology and all-round reform in national college English teaching,Internet-Based teaching mode has become a new trend of college English teaching.Therefore,in the new teaching mode,the teacher should turn an inculcator into an instructor,facilitator and participant in teaching;a passive user of textbook into a dominant and modeler of courses;a planner of teaching specific tasks into an organizer of teaching process,a helper and shepherd of learning knowledge.
基金Project(2011ZA05) supported by the State Key Laboratory’s Autonomous Project of Subtropical Building Science in South China University of Technology
文摘In order to apply the performance-based seismic design, an engineer must first find out whether the column is expected to fail in shear before or after flexural yielding. According to column failure characteristics and failure mode of reinforced concrete column, the UW-PEER structure performance database was discussed and analyzed. In order to investigate the relevance of failure mode and factors such as longitudinal reinforcement ratio, transverse reinforcement ratio, hoop spacing to depth ratio, aspect ratio, shearing resistance demand to shear capacity ratio and axial load ratio, Fisher's discriminant analysis(FDA) of the above factors was carried out. A discriminant function was developed to identify column failure mode. Results show that three factors, i.e., Vp /Vn, hoop spacing to depth ratio and aspect ratio have important influence on the failure mode. The failure mode has less to do with longitudinal reinforcement ratio, transverse reinforcement ratio and axial load ratio. Through using these three factors and the model proposed, over 85.6% of the original grouped cases were correctly classified. The value of coefficient of Vp /Vn is the largest, which means that discriminant equation is most sensitive to the shearing resistance demand to shear capacity ratio.
