Inversion of focal mechanism and events identification using an improved relative amplitude method

The relative amplitude method （RAM） is more suitable for source inversion of low magnitude earthquakes because it avoids the modeling of short-period waveforms. We introduced an improved relative amplitude method （IRAM） which is more robust in practical cases. The IRAM uses a certain function to quantify the fitness between the observed and the predicted relative amplitudes among direct P wave, surface reflected pP and sP waves for a given focal mechanism. Using the IRAM, we got the fault-plane solutions of two earthquakes of mb4.9 and mb3.8, occurred in Issyk-Kul lake, Kyrgyzstan. For the larger event, its fault-plane solutions are consistent with the Harvard＇s CMT solutions. As to the smaller one, the strikes of the solution are consistent with those of the main faults near the epicenter. The synthetic long period waveforms and the predicted P wave first motions of the solutions are consistent with observations at some of regional stations. Finally, we demonstrated that fault-solutions cannot interpret the characteristics of teleseismic P waveforms of the underground nuclear explosion detonated in Democratic People＇s Republic of Korea （DPRK） on October 9, 2006.

Application of the extended Fourier amplitude sensitivity testing(FAST)method to inflated,axial stretched,and residually stressed cylinders

This paper is dedicated to applying the Fourier amplitude sensitivity test(FAST)method to the problem of mixed extension and inflation of a circular cylindrical tube in the presence of residual stresses.The metafunctions and the Ishigami function are considered in the sensitivity analysis(SA).The effects of the input variables on the output variables are investigated,and the most important parameters of the system under the applied pressure and axial force such as the axial stretch and the azimuthal stretch are determined.

A New Method for Detecting Internal Defects in Composite Materials Based on Time of Flight

Carbon-fiber reinforced polymer composites have been widely used to achieve the light-weighted design and high performance due to superior performance. Internal defects in the composite materials are the main factors that determine their performance,which makes reliable and effective detection methods of internal defects essential. Nondestructive testing(NDT)methods are the most widely-used way due to their tremendous advantages. Though the theoretical background is found,experimental results could be quite complicated and confusing,especially for composite materials with complex defects characteristics. In this paper,experimental study on internal defects in composite materials based on the time of flight(ToF)are investigated. The Gaussian echo model and the parameter estimation methods are established to build a theoretical model for measurements. Then,the distance amplitude correction(DAC)method is proposed to effectively improve the signal-to-noise ratio(SNR)and to reduce distortion of the signal during measurements. Finally,the ToF is adopted to determine depth of internal defects. Experiment study is conducted to investigate the porosity defects and the anti-impact performance of composite materials,as well as defects in objects with various thicknesses. Experimental results show that the proposed method is quite helpful for obtaining the intuition and deep understanding of internal defects,thus contributing to the determination of product performance and its improvement.

Calculation of maximum surface settlement induced by EPB shield tunnelling and introducing most effective parameter

This study aims to predict ground surface settlement due to shallow tunneling and introduce the most affecting parameters on this phenomenon.Based on data collected from Shanghai LRT Line 2 project undertaken by TBM-EPB method,this research has considered the tunnel's geometric,strength,and operational factors as the dependent variables.At first,multiple regression(MR) method was used to propose equations based on various parameters.The results indicated the dependency of surface settlement on many parameters so that the interactions among different parameters make it impossible to use MR method as it leads to equations of poor accuracy.As such,adaptive neuro-fuzzy inference system(ANFIS),was used to evaluate its capabilities in terms of predicting surface settlement.Among generated ANFIS models,the model with all input parameters considered produced the best prediction,so as its associated R^2 in the test phase was obtained to be 0.957.The equations and models in which operational factors were taken into consideration gave better prediction results indicating larger relative effect of such factors.For sensitivity analysis of ANFIS model,cosine amplitude method(CAM) was employed; among other dependent variables,fill factor of grouting(n) and grouting pressure(P) were identified as the most affecting parameters.

Spatial diversity and combination technology using amplitude and phase weighting method for phase-coherent underwater acoustic communications

The UWA channel is characterized as a time-dispersive rapidly fading channel, which in addition exhibits Doppler instabilities and limited bandwidth. To eliminate inter- symbol interference caused by multipath propagation, spatial diversity equalization is the main technical means. The paper combines the passive phase conjugation and spatial processing to maximize the output array gain. It uses signal-to-noise-plus-interference to evaluate the quality of signals received at different channels. The amplitude of signal is weighted using Sigmoid function. Second order PLL can trace the phase variation caused by channel, so the signal can be accumulated in the same phase. The signals received at different channels need to be normal- ized. It adopts fractional-decision feedback diversity equalizer （FDFDE） and achieves diversity equalization by using different channel weighted coefficients. The simulation and lake trial data processing results show that, the optimized diversity receiving equalization algorithm can im- prove communication system＇s ability in tracking the change of underwater acoustic channel, offset the impact of multipath and noise and improve the performance of communication system. The performance of the communication receiving system is better than that of the equal gain combination. At the same time, the bit error rate （BER） reduces 1.8%.

Spinless particles in the field of unequal scalar vector Yukawa potentials

We present analytical bound state solutions of the spin-zero Klein–Gordon （KG） particles in the field of unequal mix-ture of scalar and vector Yukawa potentials within the framework of the approximation scheme to the centrifugal potential term for any arbitrary l-state. The approximate energy eigenvalues and unnormalized wave functions are obtained in closed forms using a simple shortcut of the Nikiforov–Uvarov （NU） method. Further, we solve the KG–Yukawa problem for its exact numerical energy eigenvalues via the amplitude phase （AP） method to test the accuracy of the present solutions found by using the NU method. Our numerical tests using energy calculations demonstrate the existence of inter-dimensional degeneracy amongst the energy states of the KG–Yukawa problem. The dependence of the energy on the dimension D is numerically discussed for spatial dimensions D = 2–6.

The Q value variations in the preparing pro－cess of rock rupture

In this paper, the 'spectral amplitude ratio method'(SAR) , 'energy method'(EN) and 'coda wave method'(CW) are used to calculate the Q value variations of gneiss in the preparing rupture process. The obtained results show that the variation state of Q values by SAR features the shape of relative stability gradual increment to the maximum then decrement and final rupture.The variation state of Q values by EN is just contrary to that by SAR,i.e.with the shape of stability decrement increment and final rupture . The varation state of Q values by CW is similar to that by EN, its main frequency features the shape of relatively high value decrement to the minimum increment and final rupture.But to the high frequency (higher than the main frequency),the variation state of Q values features the shape of the stable value increment to the maximum decrement and final rupture.At the same time, the results by coda wave amplitude spectrum show that, when stress reaches 70% of rupture stress, the high frequency component of S wave rapidly reduces( Q c increasing); at the time of impending the main rupture, the main frequency component reduces with a large scale( Q c increasing again), this may be the reason which causes the different variation states of two coda Q values.The result of amplitude spectra of P, S(initial wave) waves also show that with the appearance of microcracks the frequency band of S wave turn to be narrow, the high frequency component is reduced quickly, i.e. the S wave spectra have different variation states with different frequeny components. That is why the Q s obtained by different methods have different variation characteristics.

Amplitude Factorization Method in the Atmospheric Gravity-Wave Equation

A novel amplitude factorization method is applied to solve a discrete buoyancy wave equation with arbitrary wind and temperature height distribution.The solution is given in the form of a cumulative product of complex factors,which are computed by a nonlinear,inhomogeneous,two-member recurrence formula,initiated from a radiative condition on top.Singularities of the wave equation due to evanescent winds are eliminated by turbulent friction.The method provides an estimation of the minimal vertical resolution,required to attain a stable accurate solution.The areas of application of the developed numerical scheme are high resolution modelling of orographic waves for arbitrary orography in general atmospheric stratification conditions,and testing of adiabatic kernels of numerical weather prediction models.

Sidelobe rejection of sectoral multi-element cylinder arrays with amplitude weighting methods

This paper gives the directivity Function of a sectoral multi-element cylinder array, analyze its phase factor, explain in detail the sidelobe rejection by selecting the number of elements , baffling and amplitude weighting. They are particularly useful for directional tracking of acoustical signal and target locating .

Direction Finding with Cyclostationarity Analysis Against Frequency Interference

In this paper, a novel anti-interference direction finding(DF)method for amplitude comparison method based on cyclostationarity is proposed. With the periodic properties of the communication signals, the desired signal’s amplitude value can be effectively obtained even though there is an interference signal whose frequency spectrum overlaps with the desired signal in the environment,and the corresponding incident angle can be estimated accurately with the amplitude comparison method. The influence of interference signal on the amplitude comparison method is discussed and the proposed method’s theoretical feasibility is also analyzed. Compared with the conventional method,simulations are provided to demonstrate the anti-interference capability of the proposed method. The amplitude comparison DF system working at 2.44 GHz and 5.8 GHz is also constructed to verify its feasibility.

TRAVELING WAVE SOLUTIONS AND THEIR STABILITY OF NONLINEAR SCHRDINGER EQUATION WITH WEAK DISSIPATION

In this paper,several new constant-amplitude and variable-amplitude wave solutions（namely,traveling wave solutions） of a generalized nonlinear Schrdinger equation are investigated by using the extended homogeneous balance method,where the balance method is applied to solve the Riccati equation and the reduced nonlinear ordinary differential equation,respectively.In addition,stability analysis of those solutions are also conducted by regular phase plane technique.