气固两相流作用下工程玻璃的冲蚀性能及损伤机理研究

根据内蒙古中西部地区风沙环境特征,采用气流挟沙喷射法,通过模拟风沙环境侵蚀实验系统,对比分析冲蚀力学参数对不同特性工程玻璃冲蚀率的影响规律,并结合扫描电镜(SEM)分析其损伤机理。结果表明:钢化玻璃的冲蚀率随冲蚀角度的增加而增大,在90°时达到最大值,表现出脆性材料的特征;有机玻璃的冲蚀率随冲蚀角度增加先增大后减小,在45°处达到最大值,90°时为最小值,表现出半塑性材料的特征。两种玻璃的冲蚀率随沙流量的增加,先迅速减小后趋于平缓;随速度的增加而增加。在高角度冲蚀时,钢化玻璃和有机玻璃冲蚀率和冲蚀速度回归曲线的速度指数较接近,分别为3.94和3.66,均偏离了理论预测的范围。钢化玻璃高角度冲蚀损伤严重,其表面冲蚀损伤机理是与塑性区相关的残余应力,在冲击部位产生横向裂纹,裂纹不断扩展在材料表面交叉引起材料流失;有机玻璃低角度冲蚀磨损严重,其损伤机制主要是微切削作用,损伤程度由材料的硬度控制。

Design and Construction of Axial Mode Mono-Filar Helical Antenna for Hydrogen Line Emission Studies with 4NEC2 Tool

Antennas have come to play a significant role in the reception and transmission of electromagnetic radiation or signals which in turn have improved scientific research in the various areas where they have been used. Astronomy is not left out;as a study of everything beyond earth’s atmosphere, useful signals have to travel great distances to reach us. Hence the need for equipment to detect such signals. The Helical Antenna is known to possess high gain (directivity) and can process signals with any type of orientation/polarization which implies high sensitivity hence the desire to use it. Simulation was done using the legacy 4NEC2 software. The purpose of this paper is to design a circularly polarized helical antenna operating in axial mode that is suitable for detection of neutral hydrogen line emission at the frequency of 1420 MHz and to show how it can be used as a feed for an off-set parabolic dish.