Turbulence-induced changes in degree of polarization,degree of coherence and spectrum of partially coherent electromagnetic beams

Based on a recently formulated unified theory of coherence and polarization, a method is described to study turbulence-induced changes in the polarization, the coherence and the spectrum of partially coherent electromagnetic beams on propagation. The electromagnetic Gaussian Schell-model beam is taken as a typical example of partially coherent electromagnetic beams, and the closed-form expressions for the degree of polarization, the degree of coherence and the spectrum of electromagnetic Gaussian Schell-model beams propagating through atmospheric turbulence are derived in the quadratic approximation of Rytov＇s phase structure function. Some interesting results are obtained, which are illustrated by numerical examples and are explained in physics.

Impact of the spatial coherence on self-interference digital holography

Owing to the unique feature that the signal and reference waves of self-interference digital holography(SIDH)contain the same spatial information from the same point of object,compared with conventional digital holography,the SIDH has the special spatial coherence properties.We present a statistical optics approach to analyzing the formation of cross-correlation image in SIDH.Our study reveals that the spatial coherence of illumination light can greatly influence the imaging characteristics of SIDH,and the impact extent of the spatial coherence depends substantially on the recording distance of hologram.The theoretical conclusions are supported well by numerical simulation and optical experiments.

The Application of Cohesion and Coherence Theory in Advanced College English Teaching

In 1976,Halliday and Hassan put forward the concept of cohesion and coherence theory for the first time in their book English Cohesion and discussed five types of cohesion:reference,substitution,omission,conjunction and lexical cohesion.Some scholars enriched and expanded cohesion and coherence from the perspective of cohesion conditions,phonology,structural relations at the level of meaning and discourse.Predecessors pay much attention to the theoretical discussion,while from the perspective of the theoretical application,the cohesion and coherence theory is used for analyzing the advanced college English textbook to provide the guidance for teachers and students in teaching and learning-teachers can judge and adopt appropriate teaching methods according to the cohesion and coherence theory;Students can understand cohesion and coherence in the text as well as the influencing factors,and adequately use the cohesion and coherence mechanism in listening,speaking,reading and writing.

Coherent and incoherent theories for photosynthetic energy transfer

自然界的光合作用有一个显著的特点,即能量传递效率近乎100%.近年来,由于光合作用实验技术的飞速发展,譬如二维光谱实验和单分子泵浦探测实验,其能量传输过程中的量子相干效应已经在实验上得到了证实.传统的非相干理论能够有效计算能量转移效率,如广义的F?rster理论和修正的Redfield理论.然而,为了描述光合作用中的量子相干效应,人们必须利用量子相干理论.例如,除了传统的Redfield理论之外,还有级联运动方程、量子路径积分、相干修正的Redfield理论、小极化子量子主方程、广义Bloch-Redfield理论等.本文综述了上述方法的主要内容,不仅有助于对自然界光合作用中激子能量转移的量子动力学进行有效的量子模拟,并对人工太阳能收集装置的设计提供了一定的指导作用.