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Cuttings transport problem has long been recognized as one of the key difficulties in drilling horizontal wells, and the models in cuttings transport research are usually formulated with highly nonlinear equations set. When using Newton methods to solve real engineering problems with nonlinear equations set, the problems of result dependence on initial values, Jacobian matrix singularity, and variable outflow of its definition domain in iterations are three of the often-encountered difficulties. In this paper, the ant colony algorithm is applied to solve the two-layer cuttings transport model with highly nonlinear equations set. The solution-searching process of solving nonlinear equations set is transformed into an optimization process of searching the minimum value of an objective function by applying ant colony algorithm. Analyzing the results of the example, it can be concluded that ant colony algorithm can be used to solve the highly nonlinear cuttings transport model with good solution accuracy; transforming the solution-searching process of solving nonlinear equations set into an optimization process of searching the minimum value of the objective function is necessary; the real engineering problem should be simplified as much as possible to decrease the number of unknown variables and facilitate the use of ant colony algorithm.

Factors influencing the quality of lensless ghost imaging are investigated. According to the experimental results, we find that the imaging quality is determined by the number of independent sub light sources on the imaging plane of the reference arm. A qualitative picture based on advanced wave optics is presented to explain the physics behind the experimental phenomena. The present results will be helpful to provide a basis for improving the quality of ghost imaging systems in future works.

For a V-type three-level atomic system with two closely spaced upper levels, we investigate the light pulse propagation properties with only one laser field. Due to spontaneously generated coherence, the group velocity of the light pulse can be changed from subluminal to superluminal. The effects of the field intensity and the two-upper level splitting on the group velocity are also shown. At last, an analytical expression for the group velocity is given in the case of a weak field.

We study the spatial behavior of a deflected beam in a coherent Λ-type three-level atomic medium with an inhomogeneous control laser. When the Rabi coupling by the control laser is in a Gaussian profile, the spatial-dependent refraction index of the atomic medium will result in a beam splitting as well as the deflection of the slow probe light under electromagnetically induced transparency. In terms of the phase difference between the two splitting beams and the position of the splitting, the possible interpretation of the splitting is given in theory.

In this paper, the frequency modulation effect of the probe field in a three-level Λ system is discussed. According to the classical equation of motion for the electron, the dielectric susceptibility of the medium is not affected by frequency modulation. Based on the quantum theory and the frequency modulation term expanded in terms of Bessel functions, the effects of the frequency modulation of the probe field on the system are studied, in which, when the modulation frequency of the probe field is large enough, the periodical population evolutions exist in three levels. Meanwhile, the stationary susceptibility of the probe field is given.