A Survey of Structure of Atmospheric Turbulence in Atmosphere and Related Turbulent Effects

The Earth’s atmosphere is the living environment in which we live and cannot escape. Atmospheric turbulence is a typical random inhomogeneous medium, which causes random fluctuations of both the amplitude and phase of optical wave propagating through it. Currently, it is widely accepted that there exists two kinds of turbulence in the aerosphere: one is Kolmogorov turbulence, and the other is non-Kolmogorov turbulence, which have been confirmed by both increasing experimental evidence and theoretical investigations. The results of atmospheric measurements have shown that the structure of atmospheric turbulence in the Earth’s atmosphere is composed of Kolmogorov turbulence at lower levels and non-Kolmogorov turbulence at higher levels. Since the time of Newton, people began to study optical wave propagation in atmospheric turbulence. In the early stage, optical wave propagation in Kolmogorov atmospheric turbulence was mainly studied and then optical wave propagation in non-Kolmogorov atmospheric turbulence was also studied. After more than half a century of efforts, the study of optical wave propagation in atmospheric turbulence has made great progress, and the theoretical results are also used to guide practical applications. On this basis, we summarize the development status and latest progress of propagation theory in atmospheric turbulence, mainly including propagation theory in conventional Kolmogorov turbulence and one in non-Kolmogorov atmospheric turbulence. In addition, the combined influence of Kolmogorov and non-Kolmogorov turbulence in Earth’s atmosphere on optical wave propagation is also summarized. This timely summary is very necessary and is of great significance for various applications and development in the aerospace field, where the Earth’s atmosphere is one part of many links.

Study on Optical Properties of Milk based on Light Propagation Theory

The light propagation in milk based on experimental and theoretical analysis is reviewed. The review is done on light propagation theory which consists of light absorbance, reflection, and scattering. The study covers on types of milk, milk quality and modelling methods based on Mie scattering and Monte Carlo algorithm. The experiments consist of spectrometry methods where visible (VIS) and near infra-red (NIR) are used. Many spectrometry experiments and theoretical modelling are discussed to observe and analyse optical properties of milk.

Breast Acoustic Parameter Reconstruction Method Based on Capacitive Micromachined Ultrasonic Transducer Array

Ultrasound computed tomography (USCT) systems based on capacitive micromachined ultrasonic transducer (CMUT) arrays have a wide range of application prospects. For this paper, a high-precision image reconstruction method based on the propagation path of ultrasound in breast tissue are designed for the CMUT ring array; that is, time-reversal algorithms and FBP algorithms are respectively used to reconstruct sound speed distribution and acoustic attenuation distribution. The feasibility of this reconstruction method is verified by numerical simulation and breast model experiments. According to reconstruction results, sound speed distribution reconstruction deviation can be reduced by 53.15% through a time-reversal algorithm based on wave propagation theory. The attenuation coefficient distribution reconstruction deviation can be reduced by 61.53% through FBP based on ray propagation theory. The research results in this paper will provide key technological support for a new generation of ultrasound computed tomography systems.

Shear Response of Members without Shear Reinforcement—Experiments and Analysis Using Shear Crack Propagation Theory (SCPT)

The determination of the ultimate shear capacity and the identification of the corresponding load-carrying mechanisms of concrete members without shear reinforcement has been an ongoing research topic for over 100 years. Based on a full mechanical model, the Shear Crack Propagation Theory (SCPT) enables to analyze and understand the ever-changing interplay of crack propagation, evolution of stresses at the crack tip and in uncracked concrete parts, as well as the activation of shear transfer actions within the growing shear crack during the entire loading process. In this paper, selected experimental investigations for further validation of the SCPT are presented. These beam shear test results are then compared to the theoretical results emerging from the SCPT algorithm. Finally, the evolution of different shear transfer actions (e.g., aggregate interlock and dowel action) during the entire loading process is evaluated and discussed.