The W transform and its improved methods for time-frequency analysis of seismic data

The conventional linear time-frequency analysis method cannot achieve high resolution and energy focusing in the time and frequency dimensions at the same time,especially in the low frequency region.In order to improve the resolution of the linear time-frequency analysis method in the low-frequency region,we have proposed a W transform method,in which the instantaneous frequency is introduced as a parameter into the linear transformation,and the analysis time window is constructed which matches the instantaneous frequency of the seismic data.In this paper,the W transform method is compared with the Wigner-Ville distribution(WVD),a typical nonlinear time-frequency analysis method.The WVD method that shows the energy distribution in the time-frequency domain clearly indicates the gravitational center of time and the gravitational center of frequency of a wavelet,while the time-frequency spectrum of the W transform also has a clear gravitational center of energy focusing,because the instantaneous frequency corresponding to any time position is introduced as the transformation parameter.Therefore,the W transform can be benchmarked directly by the WVD method.We summarize the development of the W transform and three improved methods in recent years,and elaborate on the evolution of the standard W transform,the chirp-modulated W transform,the fractional-order W transform,and the linear canonical W transform.Through three application examples of W transform in fluvial sand body identification and reservoir prediction,it is verified that W transform can improve the resolution and energy focusing of time-frequency spectra.

A joint optimization algorithm for focused energy delivery in precision electronic warfare

Focused energy delivery(FED) is a technique that can precisely bring energy to the specific region,which arouses wide attention in precision electronic warfare(PREW).This paper first proposes a joint optimization model with respect to the locations of the array and the transmitted signals to improve the performance of FED.As the problem is nonconvex and NP-hard,particle swarm optimization(PSO) is adopted to solve the locations of the array,while designing the transmitted signals under a feasible array is considered as a unimodular quadratic program(UQP) subproblem to calculate the fitness criterion of PSO.In the PSO-UQP framework established,two methods are presented for the UQP subproblem,which are more efficient and more accurate respectively than previous works.Furthermore,a threshold value is set in the framework to determine which method to adopt to take full advantages of the methods above.Meanwhile,we obtain the maximum localization error that FED can tolerate,which is significant for implementing FED in practice.Simulation results are provided to demonstrate the effectiveness of the joint optimization algorithm,and the correctness of the maximum localization error derived.

Shandong focuses on a clean energy future

According to Shandong Development and Reform Commission, the province’s new energy industry is expected to grow at an annual average rate of 20% to reach

Preliminary study on the dynamic mechanism of the deep equatorial jets

Observations show that the deep equatorial circulation is surprisingly energetic, with alternating eastward adn westward zonal currents(these fkows are commonly referred to as the deep equatorial jets) between 1 000 and 3 000 m. This paper shows that the waves generated by an off-equatorial deep buoyancy oscillation, and their energy radiatin as well as the equatorial focus of waves energy are the viable dynamic mechanisms of forming the deep equatorial jets.The results of testinh the effects of vertical mixing coefficients on the jets show that as the coefficients increase, the jets become weaker and their zonal coherent scales become longer.The solutions for different periods of forcing indicate that lengthening the period of forcing results in the position of the core of the deep jets moving westward and also enhances the zonal coherent scales of the jets.

Redistributing the energy flow of tightly focused ellipticity-variant vector optical fields

The redistribution of the energy flow of tightly focused ellipticity-variant vector optical fields is presented.We theoretically design and experimentally generate this kind of ellipticity-variant vector optical field, and further explore the redistribution of the energy flow in the focal plane by designing different phase masks including fanlike phase masks and vortex phase masks on them. The flexibly controlled transverse energy flow rings of the tightly focused ellipticity-variant vector optical fields with and without phase masks can be used to transport multiple absorptive particles along certain paths, which may be widely applied in optical trapping and manipulation.

A New Energy Focus

New forms of energy will become a key area of China-Europe cooperation The significance of developing new energy resources has been proven far beyond finding energy alternatives. It has become a strategic choice for all nations with which to ensure their energy security, while combating climate change.