Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fo...Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fourier transform related to the electromagnetic response in the frequency and time domains becomes a sine or cosine transform under the excitation of downward-step current.We established a transformation matrix based on the digital fi ltering calculation for the sine transform,and then the frequency domain projection of the TEM data was determined from the linear transformation system using the smoothing constrained least squares inversion method,in which only the imaginary part was used to maintain the TEM data transformation equivalence in the bidirectional projection.Thus,the time-domain TEM inversion problem was indirectly and effectively solved in the frequency domain.In the 3D inversion of the transformed frequency-domain data,the limited-memory Broyden–Fletcher–Goldfarb–Shannoquasi–Newton(L-BFGS)method was used and modifi ed with a restart strategy to adjust the regularization parameter when the algorithm tended to a local minimum.Synthetic data tests showed that our domain transformation method can stably project the TEM data into the frequency domain with very high accuracy;furthe rmore,the 3D inversion of the transformed frequency-domain data is stable,can be used to recover the real resistivity model with an acceptable effi ciency.展开更多
In the design of 3-D spherically symmetric FIR filters via the McClellan transformation, two methods are proposed to determine the transformation parameters. The first is to improve the original 3-D algorithm by explo...In the design of 3-D spherically symmetric FIR filters via the McClellan transformation, two methods are proposed to determine the transformation parameters. The first is to improve the original 3-D algorithm by exploiting the 2-D effective methods in 3-D. This method can change the constrained optimization algorithm into the unconstrained one and makes the design easier to realize. The second method is to solve the coupled equations under constrained conditions and a set of ideal parameters can be gotten. The design example shows that the two methods are all efficient and easier than the original algorithm.展开更多
现行方法改造广播电视信号模拟传输网络后网络性能仍旧较差,在实践中网络误码率较高,而且广播电视信号模拟传输差错秒较长,无法达到预期改造效果。为此,文章提出基于同步数字体系(Synchronous Digital Hierachy,SDH)数字微波技术的广播...现行方法改造广播电视信号模拟传输网络后网络性能仍旧较差,在实践中网络误码率较高,而且广播电视信号模拟传输差错秒较长,无法达到预期改造效果。为此,文章提出基于同步数字体系(Synchronous Digital Hierachy,SDH)数字微波技术的广播电视信号模拟传输网络改造方法。利用智能无线Mesh自组网技术对广播电视信号模拟传输网络结构进行改造,将网络结构改造为由固定节点、分布节点以及终端用户节点组成,对网络配置进行优化,利用SDH数字微波技术对广播电视信号模拟传输信道均衡处理,实现基于SDH数字微波技术的广播电视信号模拟传输网络改造。实验证明,改造后广播电视信号模拟传输误码率显著降低,信号传输差错秒有效缩短,网络传输性能得到优化,网络改造效果良好。展开更多
基金the National Key Research and Development Program of China(No.2016YFC060110403).
文摘Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fourier transform related to the electromagnetic response in the frequency and time domains becomes a sine or cosine transform under the excitation of downward-step current.We established a transformation matrix based on the digital fi ltering calculation for the sine transform,and then the frequency domain projection of the TEM data was determined from the linear transformation system using the smoothing constrained least squares inversion method,in which only the imaginary part was used to maintain the TEM data transformation equivalence in the bidirectional projection.Thus,the time-domain TEM inversion problem was indirectly and effectively solved in the frequency domain.In the 3D inversion of the transformed frequency-domain data,the limited-memory Broyden–Fletcher–Goldfarb–Shannoquasi–Newton(L-BFGS)method was used and modifi ed with a restart strategy to adjust the regularization parameter when the algorithm tended to a local minimum.Synthetic data tests showed that our domain transformation method can stably project the TEM data into the frequency domain with very high accuracy;furthe rmore,the 3D inversion of the transformed frequency-domain data is stable,can be used to recover the real resistivity model with an acceptable effi ciency.
文摘In the design of 3-D spherically symmetric FIR filters via the McClellan transformation, two methods are proposed to determine the transformation parameters. The first is to improve the original 3-D algorithm by exploiting the 2-D effective methods in 3-D. This method can change the constrained optimization algorithm into the unconstrained one and makes the design easier to realize. The second method is to solve the coupled equations under constrained conditions and a set of ideal parameters can be gotten. The design example shows that the two methods are all efficient and easier than the original algorithm.
文摘现行方法改造广播电视信号模拟传输网络后网络性能仍旧较差,在实践中网络误码率较高,而且广播电视信号模拟传输差错秒较长,无法达到预期改造效果。为此,文章提出基于同步数字体系(Synchronous Digital Hierachy,SDH)数字微波技术的广播电视信号模拟传输网络改造方法。利用智能无线Mesh自组网技术对广播电视信号模拟传输网络结构进行改造,将网络结构改造为由固定节点、分布节点以及终端用户节点组成,对网络配置进行优化,利用SDH数字微波技术对广播电视信号模拟传输信道均衡处理,实现基于SDH数字微波技术的广播电视信号模拟传输网络改造。实验证明,改造后广播电视信号模拟传输误码率显著降低,信号传输差错秒有效缩短,网络传输性能得到优化,网络改造效果良好。
