A unified Minorization-Maximization approach for estimation of general mixture models

The mixed distribution model is often used to extract information from heteroge-neous data and perform modeling analysis.When the density function of mixed distribution is complicated or the variable dimension is high,it usually brings challenges to the parameter es-timation of the mixed distribution model.The application of MM algorithm can avoid complex expectation calculations,and can also solve the problem of high-dimensional optimization by decomposing the objective function.In this paper,MM algorithm is applied to the parameter estimation problem of mixed distribution model.The method of assembly and decomposition is used to construct the substitute function with separable parameters,which avoids the problems of complex expectation calculations and the inversion of high-dimensional matrices.

A new approach for separating mixed model parameters:application to simultaneous inversion of earthquake source parameters

A method for simultaneous determination of mixed model parameters,which have different physical dimensions or different responses to data,is presented.Mixed parameter estimation from observed data within a single model space shows instabilities and trade-offs of the solutions. We separate the model space into N-subspaces based on their physical properties or computational convenience and solve the N-subspaces systems by damped least-squares and singular-value decomposition. Since the condition number of each subsystem is smaller than that of the single global system,the approach can greatly increase the stability of the inversion. We also introduce different damping factors into the subsystems to reduce the tradeoffs between the different parameters. The damping factors depend on the conditioning of the subsystems and may be adequately chosen in a range from 0.1 % to 10 % of the largest singular value. We illustrate the method with an example of simultaneous determination of source history,source geometry,and hypocentral location from regional seismograms,although it is applicable to any geophysical inversion.

Payload Symbol-Based Nonlinear RF Fingerprint for Wireless QPSK-OFDM Devices

Radio Frequency(RF) fingerprinting is one physical-layer authentication method for wireless communication, which uses the unique hardware characteristic of the transmitter to identify its true identity.To improve the performance of RF Fingerprint(RFF)based on preamble with fixed duration, a nonlinear RF fingerprinting method based on payload symbols is proposed for the wireless OFDM communication with the bit mapping scheme of QPSK. The wireless communication system is modeled as a Hammerstein system containing the nonlinear transmitter and multipath fading channel. A parameter separation technique based on orthogonal polynomial is presented for the estimation of the parameters of the Hammerstein system. The Hammerstein system parameter separation technique is firstly used to estimate the linear parameter with the training signal, which is used to compensate the adverse effect of the linear channel for the demodulation of the successive payload symbols. The demodulated payload symbols are further used to estimate the nonlinear coefficients of the transmitter with the Hammerstein system parameter separation technique again, which is used as the novel RFF for the authentication of the QPSK-OFDM device. Numerical simulations have verified the proposed method, which can also be extended to the OFDM signals with other bit mapping schemes.

Three dimensional velocity structure beneath the Kunming Telemetered Seismic Network

Based on the P wave first arrival time data of 275 local earthquakes recorded by Kunming Telemetered Seismic Network from 1982 to 1989, a 3-D velocity structure beneath the network was obtained by the separationmethod of focal parameter and medium structure parameter and 3-D approximate ray tracing. In view of 'thesituation that the intervals between stations in the network is relatively long, and the local first arrival phasemay be Pn instead of P, so we simulated Pn as the diving wave from the layer beneath Moho and using approximate ray tracing method on the grid model. The final 3-D velocity structure is basically consistent withthe result from the deep seismic sounding and the anomaly inversion of Bouguer gravity. The Dianzhong area(in the vicinity of Dukou and Chuxiong) shows an obvious high velocity zone at depth of 45 km, which canbe interpreted as the uplift of Moho discontinuity. The upper crust in this area displays lower velocity zone,so the uplift of Moho discontinuity is considered as the result of isostatic compensation. The configuration ofvelocity contours indicates that the upper crust and lower crust are complicated, while the middle crust is relatively simple. This feature reveals that Yunnan area belongs to modern tectonically active region. As themain boundary of the major tectonic units in the study area, although there is no obvious evidence about lowvelocity anomaly zone along the Red River Fault, the fault shows up th feature of sturctural divide on themid-lower crustal velocity contours, and it is inferred that the fault passes through the Moho-discontinuity atleast.

Classification of wood surface texture based on Gauss-MRF Model

The basal theory of Gauss-MRF is expounded and 2-5 order Gauss MRF models are established. Parameters of the 2-5 order Gauss-MRF models for 300 wood samples＇ surface texture are also estimated by using LMS. The data analysis shows that： 1） different rexture parameters have a clear scattered distribution, 2） the main direction of texture is the direction represented by the maximum parameter of Gauss-MRF parameters, and 3） for those samples having the same main direction, the finer the texture is, the greater the corresponding parameter is, and the smaller the other parameters are; and the higher the order of Gauss-MRF is, the more clearly the texture is described. On the condition of the second order Gauss MRF model, parameter B1, B2 of tangential texture are smaller than that of radial texture, while B3 and B4 of tangential texture are greater than that of radial texture. According to the value of separated criterion, the parameter of the fifth order Gauss-MRF is used as feature vector for Hamming neural network classification. As a result, the ratio of correctness reaches 88%.

Estimation of the J-resistance curve for Cr2Ni2MoV steel using the modified load separation parameter S_(pb) method

Based on load separation theory, the load separation parameter Spb method is an effective approach for estimating the J-resistance curve from records of load versus displacement directly, using one sharp cracked specimen and an additional reference blunt cracked specimen. However, the effect of the reference blunt cracked specimen on J-resistance determination was not explicitly considered in past work. In this paper, a modified load separation parameter Spb method was developed to eliminate this effect, and then a unique estimation of instantaneous crack length for one sharp cracked specimen could be obtained. Furthermore, a forced blunting calibration method was also adopted to determine the instantaneous crack length in the load inseparable region, referring to a normalization method. Experiments on steam turbine rotator steel Cr2Ni2MoV were carried out to estimate J-resistance curves using an unloading compliance method. By removing unload and reload data from load-displacement records, the J-resistance curve for the same sharp cracked specimen was estimated using the modified separation parameter Spb method. The results indicate that the modified Spb method completely eliminates the effect of the reference blunt cracked specimen on the instantaneous crack length determination of the sharp cracked specimen. However, different J-resistance curves in a small range of crack extension are present when different blunting coefficients are used in the blunting line equation. The J-resistance curve obtained from the modified Spb method agrees well with that obtained from the compliance method.

Numerical analysis of hydroabrasion in a hydrocyclone

The velocity profiles and separation efficiency curves of a hydrocyclone were predicted by an Euler-Euler approach using a computational fluid dynamics tool ANSYS-CFX 14.5. The Euler-Euler approach is capable of considering the particle-particle interactions and is appropriate for highly laden liquid-solid mixtures. Pre- dicted results were compared and validated with experi- mental results and showed a considerably good agreement. An increase in the particle cut size with increasing solid concentration of the inlet mixture flow was observed and discussed. In addition to this, the erosion on hydrocyclone walls constructed from stainless steel 410, eroded by sand particles （mainly SiOz）, was predicted with the Euler-La- grange approach. In this approach, the abrasive solid particles were traced in a Lagrangian reference frame as discrete particles. The increases in the input flow velocity, solid concentration, and the particle size have increased the erosion at the upper part of the cylindrical body of the hydrocyclone, where the tangential inlet flow enters the hydrocyclone. The erosion density in the area between the cylindrical to conical body area, in comparison to other parts of the hydrocyclone, also increased considerably. Moreover, it was observed that an increase in the particle shape factor from 0.1 to 1.0 leads to a decrease of almost 70 % in the average erosion density of the hydrocyclone wall surfaces.

A composite optimization method for separation parameters of large-eccentricity pico-satellites

A spacecraft＇s separation parameters directly affect its flying trace. If the parameters exceed their limits, it will be difficult to adjust the flying attitude of the spacecraft, and the spacescraft may go off-track or crash. In this paper, we present a composite optimization method, which combines angular velocities with external moments for separation parameters of large-eccentricity pico-satellites. By changing the positions of elastic launch devices, the method effectively controls the popping process under the condition of less change in the separation mechanism. Finally, the reasons for deviation of angular velocities and unreliable optimization results are presented and analyzed. This optimization method is proved through a ground test which offsets the gravity. Simulation and test results show that the optimization method can effectively optimize the separation parameters of large-eccentricity pico-satellites. The proposed method adapts particularly to the fixed and non-stable status elastic parameters, the distribution of all kinds of elastic devices, and large-eccentricity spacecrafts for which attitude corrections are difficult. It is gen- erally applicable and easy to operate in practical applications.

A Stochastic Extension of Macroscopic Stability Criterion of Nonequilibrium Steady State in Chemical Reaction Systems Governed by Master Equation

By means of both the separation of the perturbation in accordance with characteristic parnmeters and the Kramers Moyal-expansion of the master equation, it is shown that the time derivative of the partial excess quantity of stochastic entropy due to the deviation from the most probable path is related to the responsibility of a system to the external macroscopic perturbations. This evolution rate of the partial excess stochastic entropy is equivalent to the partlal excess stochastic entropy production, as well as the stochastic excess entropy production rate based on the stochastic potential npproach. It appears also as an eqivalent quantity of the Gibbs excess entropy production for the Polsson distribution. The macroscopic stability of chemical reaction systems is dominnted by this new stochastic quantity when the local equilibrium thermodynamics is broken down .

Surface matching method for profile inspection with touch probe

This paper presents an efficient method for rigid registration of 3-D point sets,which intends to match the feature points inspected using touch probe with the points on designed CAD surface.The alignment error is defined as the least square problem,and the sphere radius of the inspection probe is considered.In this framework,the matching problem is converted into acquiring six Euler variables problem by solving nonlinear equations.Thus,a matrix transformation of parameter separation is presented to get the approximate resolution.Finally,iterative cycles are provided to calculate the nearest points on designed surface corresponding to the inspection points.Experiment verification is realized for the presented surface matching method of robot inspection system.