Papers by Keyword: Optimization Approach

Abstract: This paper presents a local optimal processing approach that can use in the periodic signal input/ output noise enhancement phenomenon. A novel kind of locally optimization approach is established by background noise that generated from Gauss noise and bifurcation noise. It is demonstrated that the approach has its optimal output-input SNR gain at nonzero noise intensity. The papers conclusions bring the bright application future for the nonlinear signal processing theory.

Abstract: China has to confront the groundwater resources crisis and the deterioration of groundwater environment. Reinforcing the studies on groundwater pollution source identification (GPSI) could be an important support to contamination removing, groundwater protecting, drinking water security, and development of society and economy. Exploring the new theory and method on GPSI could push the studies on ill-posed problems, and improve the techniques of contamination remediation. GPSI has been studied for thirty years, and a brief review is given to conclude the characteristics of GPSI problems. The mathematical simulation method can be classified into four types: optimization method, analytical and regression method, direct method, and stochastic method. A specific review of optimization approaches is given in this paper. The configuration, simulation procedures, common optimization algorithms used by the optimization methods are discussed in detail. Both non-heuristic and heuristic algorithm can be used to solve the PSI problem. The heuristic algorithm is more suitable for complex numerical and field cases, but it is time-consuming. The non-heuristic algorithm, especially the algorithm combined with analytical method, is time-economical, but is not suitable for complicated numerical and field tests. Further researches may focus on more complex GPSI problems, expressing physical chemistry and biological process, improving efficiency and model uncertainty of GPSI modeling.

Abstract: The compressive stress distribution below the specimen surface of a nanocrystalline medium carbon steel was investigated nondestructively by using high-energy X-rays from a synchrotron radiation source, SPring-8 (Super Photon ring-8 GeV) in the Japan Synchrotron Radiation Research Institute. A medium carbon steel plate was shot-peened with fine cast iron particles of the size of 50 μm. By using the monochromatic X-ray beam with three energy levels of 10, 30 and 72 keV, the stress values at the arbitrary depth were measured by the constant penetration depth method. The stress was calculated from the slope of the sin2ψ diagram. Measured stress corresponds to the weighted average associated with the attenuation of the X-rays in the material. The real stress distribution was estimated by using the optimization technique. The stress distribution was assumed by the third order polynomial in the near surface layer and the second order polynomial. The coefficients of the polynomials were determined by the conjugate gradient iteration. The predicted stress distribution agreed well with that measured by the conventional surface removal method.