Papers by Keyword: Total Reflection

Abstract: To solve the problem of nonuniform indoor illumination by sunlight and to meet the need of energy conservation, we design a kind of cuneiform light guide plate to transmit sunlight from outside to rooms relying on the law of total reflection. Theoretical deductions and numerical simulations are used to obtain a preliminary plan, and some issues on applications and feasibility are discussed.

Abstract: In order to measure the water drainage volume in soil mechanical tests accurately, it develop a new method which is based on principles of optics. And from both physical and mathematic aspects, it deduces the mathematic relationship between micro change in displacement and the increment projected on screen. The result shows that total reflection condition is better than refraction condition. What’s more, the screen could show the water volume micro variation clearly, so it can improve the accuracy of measurement.

Abstract: Water-jet guided laser micromachining (WJGLM) is the new development of laser machining. It couples the focal laser beam of particular wavelength (low absorptivity of water) with the high speed water-jet which works as the multimode fiber. This paper investigated the necessary condition of coupling of laser and water-jet, and gave the fundamental research on the coupling error of laser coupling into the water-jet. On base of the analysis, the coupling unit is design for the WJGLM, the experimental results show that good cutting quality of Si wafer can be acquired by WJGLM with the coupling unit.

Abstract: The processing effect using water-jet guided laser micromachining technology is determined by the accurate coupling of focused laser and high speed water-jet. In order to realize the effective coupling, based on the analysis and calculation, a coupling unit with special structures was designed. The maximum angle of incidence was researched, which determined whether the total reflection occurred when laser transported in the water-jet. By the aid of fluid dynamical simulation, the coupling unit with uniform distribution of inner-cavity fluid field was designed. The attenuation of laser energy in water-jet fiber was investigated. Using appropriate laser wavelength, pulse energy and filtered and de-ionized water, energy attenuation in fiber was reduced. Experimental results showed that applying this coupling technology, perfect water-jet guided laser micromachining can be achieved.

Abstract: In this work, we studied a few surfaces, of which the structures have not yet been revealed, using reflection high-energy positron diffraction (RHEPD). We studied the Ge(111)/Pb and Ge(111)/Sn surfaces that exhibit the phase transition from 3×3 to √3×√3 periodicities at around 200K. We found that in both phases the equilibrium positions of Pb and Sn adatoms are conserved. That is, in the unit-cell, one of three adatoms is located upper position and two of them are located lower positions (one-up-two-down). The phase transition is interpreted in terms of an order-disorder type. We furthermore studied the quasi-one dimensional Si(111)/In surface which exhibits the metal-insulator transition at around 120K. The high temperature phase is well explained as the zigzag chain structure. We found that a dynamic atomic displacement which leads to the formation of hexagon structure occur below 120 K. We confirmed the appearance of the band gap using the surface structure determined from the RHEPD rocking curves.