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The theoretical limit of link prediction is a fundamental problem in this field. Taking the network structure as object to research this problem is the mainstream method. This paper proposes a new viewpoint that link prediction methods can be divided into single or combination methods, based on the way they derive the similarity matrix, and investigates whether there a theoretical limit exists for combination methods. We propose and prove necessary and sufficient conditions for the combination method to reach the theoretical limit. The limit theorem reveals the essence of combination method that is to estimate probability density functions of existing links and nonexistent links. Based on limit theorem, a new combination method, theoretical limit fusion (TLF) method, is proposed. Simulations and experiments on real networks demonstrated that TLF method can achieve higher prediction accuracy.

The size distribution and canting angle distribution for non-spherical rain drops are taken into account. Utilizing the Muller matrix, the backscattering power densities are computed at different rain rate and different polarization in millimeter waves band, according the rainfall condition in Xi'an, China. Finally the results obtained are discussed.

A atmosphere structure constant Cn2 model, which varies with height, is presented based on Karasawa's amplitude scintillation model, existing ITU-R Cn2 model for optical and Xi'an area meteorologic measured relative humidity data in cloud cover, at 30∼50GHz. In this Cn2 model it is considered that relative humidity u varies with height. The log-amplitude scintillation deviation σχcalculated in terms of the Cn2 model compare with values predicted by means of STNV2 model applied to Italsat channels. It is emerged that the calculation results based on the Cn2 model are distinctly smaller then the values predicted by STNV2 model. Their differences increase with decrease of u, because the water vapor content in the atmosphere at continental climate Xi'an area is smaller then the one at Italy, which is oceanic cilmate. When the water vapor in atmosphere approach saturation, the calculation results agree almost with prediction results. Therefore, it is shown that the Cn2 model is usable and is applied at the continental climate area as Xi'an area.

A method of determining the rationality for raindrop size distribution is first presented. The relative volume occupied by raindrops is derived. The attenuation and cross-polar discrimination induced by rainfall at millimeter waves are investigated with the incoming expression and a brief analysis is presented.

Dust storms and turbulence consist of a random medium system, its effects on milimeter waves propagation are studied. Attenuation of millimeter waves, its phase shift and cross- polar discrimination are presented. Results show that dust storms mainly effects XPD and phase shift of millimeter waves, turbulence chiefly produces attenuation, in mediocre fluctuation.

Attenuation of millimeter waves induced by sand and dust storms along horizontal paths is analyzed and its expressions applied to earth-space paths is presented. Graphs of the specific attenuation and attenuation versus height and visibility are gotten for two kinds of particle size distribution, namely exponential, lognormal. Results obtained are briefly discussed.