Recycling Al-Si Alloy by Semisolid Material Dragged during Continuous-Casting Strip Processing

Recycled Al–Si (9.2%) alloy contaminated with Fe (0.3%), Pb (3.1%) and Sn (11.4 %) was cast and poured at 650 oC, approximately 50 oC above the liquidus line. A cooling slope was used to obtain a semisolid material that feeds a ceramic nozzle designed to function as a good contact area for solidification and improve the quality of strip casting. The internally cooled material rolls in soluble oil (1 oil / 9 water) at a rate of 0.2 l/s and works as a heat exchanger which drags the metallic slurry puddle generated at the roll surface at a speed of 0.12 m/s. This forms a metallic strip with a thickness of 2 mm and a width varying from approximately 45 mm to 60 mm. The cooling system of the rolls, combined with four springs placed at the housing screw, prevented adhering of the metallic strip during production at a pressure of approximately 450 N. Cracks were observed on the strip surfaces; however, these defects did not interrupt the continuous flow of the solidified strip during manufacturing. The strip’s poor surface quality could be related to the Pb and Sn contamination as well as cold cracks due to the low pouring temperature. Al-Si eutectics positioned at a grain boundary of α-Al globular structures, as well as the presence of a Sn phase, resulted in a metallic strip with a yield stress, maximum stress and elongation of 94.5 MPa, 100.2 MPa and 1.6%, respectively.

Bi-funtional resonance effects of plasmon-induced transparency and Fano-like response using an asymmetry metamaterial resonator consisting of three metallic strips at terahertz frequency

Bi-functional metamaterial resonance device operated at terahertz frequency is designed in this paper. It is composed of three metallic strips, in which two parallel metallic strips having the identical dimensions are arranged in the longitudinal direction, and a single metallic strip deviated from the center position is arranged in the horizontal direction. Bi-functional resonance effects of plasmon-induced transparency (PIT) and Fano-like response are simultaneously obtained in this simple metamaterial structure. The formation mechanisms of the two resonance effects are analyzed with the aid of the near-field distributions and the dependence of structure parameters on the whole resonance performance. Results further show that the metallic strip placed horizontally plays an important role in adjusting the resonance response of the metamaterial resonator. More importantly, when the deviation value of the metallic strip in the horizontal direction exceeds a certain amount, for example 10 μm, the metamaterial resonator can realize the effective regulation from bi-functional resonance to single-functional PIT effect. Our proposed structure can be used as valuable platform for ideas to inspire the design of novel electro-optic devices.

Eliminate obstacles of use the solar systems as buildings facades using multilayers optical interference filters

The Building design in a correct way and totalitarian requires integration of using solar energy technologies in the architectural design stage of the roofs and facades as the most appropriate places to obtain solar energy because it greatly affects the architectural aesthetic. This integration has to be taken into account at the design stage, which leads to effective and attractive solutions. Architecture needs the energy to complete its functions to increases human effectiveness and ability to do its tasks better, solar energy is the main factor of providing the necessary energy due to its abundance as well as being clean energy and does not cause polluting emissions to the environment. To provide a comfortable indoor environment for the occupants, Solar Thermal Collectors (STC) and Photovoltaics Cells (PV) used, which convert solar energy into thermal energy and electrical energy, respectively. The main problem of this study is concerning with the problems of the black color, visible tubes, metallic strip gradients (absorption strip), and welding points of the solar systems which gives the facades of the buildings an undesirable view and weakens the aesthetic aspect of the buildings and limits the abilities of architects to use because of their black color and undesirable aspect. The aim of this study is a design of optical interference filter (multilayer coatings) prepared by RF magnetron sputtering as a solution to the problem of black color, visible tubes, metallic strip gradients (absorption strip), and welding points in solar thermal collectors and photovoltaic cells, which are the main reasons for not using solar systems as building facades, this technique works to increase the efficiency of the solar systems and increase the amount of clean energy generated, also enhancing the expressive and aesthetic aspect of facades of buildings. In the NIR region this filter works as an anti-reflective coating. Also the coating includes a high color reflection at a certain wavelength in the VIS region to give the solar system an aesthetic feature, which is used as building facades by using appropriate dielectric substances with high and low reflective indexes likes SiO2 and MgF2 respectively. The results of the study showed that the increase in the number of layers will lead to an increase in the visible reflectivity peak, while near of infrared region remains an anti-reflective with a high Transmission of solar rays, thus increasing solar systems efficiency.

An X-band gain-enhanced bidirectional antenna array using strip-loaded dielectric resonator operating in TE3δ1 mode

A bidirectional dielectric resonator (DR) antenna array using back-to-back quasi-Yagi antenna configuration is proposed and implemented for the first time. The DR operating at higher-order TE3δ1 mode is used as a magnetic dipole, applying for the driver of quasi-Yagi antenna. Due to the high-order mode employment, the antenna gain can be enhanced. By partially loading the metallic strip on the side wall of the DR, the gain can be further enhanced. In addition, a simple dual Marchand balun is constructed for feeding the two quasi-Yagi antennas directly for bidirectional radiation. To verify the design concept, a prototype operating at the X-band is fabricated and measured. Good agreement between the simulated and measured results can be observed.