Exploring Regional Profile of Drought History- a New Procedure to Characterize and Evaluate Multi-Scaler Drought Indices Under Spatial Poisson Log-Normal Model

Water Resources Management - Drought is recurrently occurring in many parts of the globe. In contrast to other natural hazards, drought has complex climatic characteristics. Several environmental...     

Image restoration method based on fractional variable order differential

In this paper, we study image restoration problem by using fractional variable order differential technique. Our idea is to make use of fractional order differential diffusion equation of evolution procedure into the image restoration problem. An image often exists different low-frequency and high-frequency components, such as flat, texture and edge, etc. Because fractional order differential can enhance the high-frequency components of a signal, meanwhile, nonlinearly preserve the low-frequency components of the signal, we can adapt suitable fractional differential orders to restore their components. In particular, different differential orders can be used in an image at the same time. In order to obtain the restored image automatically, we choose the fractional differential orders by the value of gradient modulus of the image and use the discrete Fourier transform to implement the numerical algorithm. We also provide an iterative scheme in the frequency domain. Experimental results are reported to demonstrate that the visual effects, the combined image similarity index and the peak signal to noise ratio of restored images by using the proposed method are very good, and are competitive with the other testing methods.     

汽车控制的研究现状与展望

汽车控制技术是推动汽车工业可持续发展的重要保障. 在全球汽车行业竞争日益激烈 的背景下, 如何通过理论与方法的创新, 提高我国汽车控制系统的自主研发能力, 完成从消费大国 向制造强国的过渡是我们目前面临的重大挑战. 本文主要围绕汽车动力总成系统、主动安全系统及新能源汽车中的关键控制问题展开论述, 总结国内外的研究状况, 提炼共性问题, 对汽车控制的发展趋势给出了一些观点.     

Logarithmic Uncertainty Relations for Odd or Even Signals Associate with Wigner–Ville Distribution

Heisenberg’s uncertainty relation is a basic principle in the applied mathematics and signal processing community. The logarithmic uncertainty relation, which is a more general form of Heisenberg’s uncertainty relation, describes the relationship between a function and its Fourier transform. In this paper, we consider several logarithmic uncertainty relations for a odd or even signal f(t) related to the Wigner–Ville distribution and the linear canonical transform. First, the logarithmic uncertainty relations associated with the Wigner–Ville distribution of a signal f(t) based on the Fourier transform are obtained. We then generalize the logarithmic uncertainty relation to the linear canonical transform domain and derive a number of theorems relating to the Wigner–Ville distribution and the ambiguity function; finally, the logarithmic uncertainty relations are obtained for the Wigner–Ville distribution associated with the linear canonical transform. We present an example in which the theorems derived in this paper can be used to provide an estimation for a practical signal.     

A New Weighting Scheme for Diminishing the Effect of Extreme Values in Regional Drought Analysis

Water Resources Management - Climate warming has increased the risk of recurrent drought hazards. Previous research has indicated potential associations between climate warming and extreme climate...