Green's Function of 3-D Helmholtz Equation for Turbulent Medium: Application to Optics

The fundamental problem of optical wave propagation is the determination of the field at an observation point, given a disturbance specified over some finite aperture. In both vacuum and inhomogeneous media, the solution of this problem is given approximately by the superposition integral, which is a mathematical expression of the extended Huygens-Fresnel principle. In doing so, it is important to find the atmospheric impulse response (Green's function). Within a limited but useful region of validity, a satisfactory optical propagation theory for the earth's clear turbulent atmosphere could be developed by using Rytov's method to approximate the Helmholtz equation. In particular, we deal with two optical problems which are the time reversal and apodization problems. The background and consequences of these results for optical communication through the atmosphere are briefly discussed

Characterization of Asphalt Treated Base Course Material

INE/AUTC 11.0

The social protection of rural workers in the construction industry in urban China

The construction industry is important for Chinese rural to urban migrants. Over 90% of urban construction workers are rural migrants, and over a third of all rural migrants work in construction. The construction industry is not only particularly important, but is also different from other industries in its pay and labour recruitment practices. In common with other rural workers, construction workers have long suffered from various problems, including delayed payment of salaries and exclusion from urban social security schemes. State policies designed to deal with these problems have in general had mixed success. Partly as a result of the peculiarities of the construction industry, state policy has been particularly unsuccessful in dealing with the problems faced by construction workers. This paper considers both the risks rural workers in the construction industry face because of the work they do and the risks they face and because of their being rural workers. It shows that social protection needs to take into account both the work related risks and status related risks. The authors first review the literature concerning work related risks, and then build up a framework to analyse the risks embedded in their work and status, and the relationship between these risks and the existing formal social protection. Thirty one in depth interviews with construction workers, carried out in Tianjin, PRC, are used to demonstrate both the risks and the inability of the state-led social policy to tackle these risks. The results suggest that rural construction workers in cities were exposed to all sorts of problems from not being paid for their work in time to miserable living conditions, from having to pay for their own healthcare to no savings for old age. This paper highlights the problems of policy prescriptions that failed to recognise the complexity of the problems faced by these workers and criticises the tendency to seek quick fixes rather than long-term and careful institutional design

Coupling a single NV center with a superconducting qubit via the electro-optic effect

We propose an efficient scheme for transferring quantum states and generating entangled states between two qubits of different nature. The hybrid system consists a single nitrogen vacancy (NV) center and a superconducting (SC) qubit, which couple to an optical cavity and a microwave resonator, respectively. Meanwhile, the optical cavity and the microwave resonator are coupled via the electro-optic effect. By adjusting the relative parameters, we can achieve high fidelity quantum state transfer as well as highly entangled states between the NV center and the SC qubit. This protocol is within the reach of currently available techniques, and may provide interesting applications in quantum communication and computation with single NV centers and SC qubits.Comment: 7 pages, 5 figure