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Increasing gap in wealth distribution is among the key issues that have been discussed worldwide in recent years. In this paper, we use the money transfer model to explain the formation of wealth distribution, by imposing two types of debt constraints, and the analytic function of wealth distribution is derived by adopting Boltzmann statistics. With a limit of individual debt, it is shown that the stationary distribution of wealth follows the exponential law, which is verified by many empirical studies. While the limit is imposed on the total amount of bank loan, the stationary distribution becomes an asymmetric Laplace one. Furthermore, an excellent agreement is found between these analytical probability density functions and numerical results by simulation at the steady state.

We analyse the data from the recently published lists of the richest Chinese from the year 2003 to 2005. The results confirm that in these years the wealth is distributed according to a power law with exponents between 1.758 and 2.285 in the high end. The power distribution is found to be quite robust although the persons in the list change drastically and the wealth increases rapidly. The relation between the wealth and the absolute change of wealth rejects the notion that the wealth evolution is a multiplicative stochastic process.

Photo-induced enhancement processes of the third-order optical nonlinearity were observed in azobenzene solution under a 30ps pulse pumping at 532 nm. Weinvestigated the time evolution of the enhancement and found that it was mainly due to the population of the first excited state. By theoretical simulation of the enhancement processes, the values of the hyperpolarizabilities of the sample-molecules at ground state and at excited state, γg and γs1, were determined to be 1.11 × 10-33 esu and 7.40 × 10-33 esu, respectively.

A theoretical model for formation of light-induced gratings in organic photoisomers is presented. Using this model, dynamic behaviors of the light-induced gratings are studied theoretically for two different cases: in the first case, in addition to a CW laser generating the writing beams and the reading beam, a pulsed laser is used as an optical pump, in the second case, the writing beams are provided by a pulsed laser, and the reading beam comes from a CW laser. Agreement between experiment and theory is also demonstrated.

With income data from Chinese household income projects in 1998–2002, we study the functional form of Chinese income distribution. The fitting results suggest a log-normal distribution plus a power-law tail. This distributional form has changed a lot from its appearance in the early stage of China's reform and turns out to be consistent with that of some complete market economies. The uncertainty and diversity of income growth rate aroused by marketing reform are the main causes of current Chinese income distribution.