GPS接收机用于两点间精密测距方法的研究

本文叙述了采用两台ＧＰＳ接收机实现两点间精密测距的方法，其测距误差绝对值小于１ｍ。当给定一个基准点后该方法也可推广应用于精密一。文中不仅给出了测距系统的构成方案及实现精密测距挨处理算法，而且给出了激光测距仪和该ＧＰＳ测距系统的测距结果比较。     

SA516—70钢的焊接裂纹

分析了ＳＡ５１６－７０钢ＳＡＷ时横向裂纹和纵向裂纹产生的机理，提出了防止裂纹的工艺措施。     

Joint channel estimation and data detection for high rate orthogonal time frequency space systems

This paper proposes a new pilot pattern in the delay-Doppler (DD) domain for the orthogonal time frequency space (OTFS) system. In contrast to the embedded-pilot schemes, guard intervals are not used so as increase the spectral efficiency. Also, compared to the superimposed design where data symbols and pilots are arranged on the entire DD grid, in the proposed rearrangement, the number of pilots used is only spread over a subgrid of the DD grid. Hence, the interference of pilots with data symbols is reduced. Afterwards, an algorithm for channel estimation (CE) and symbol detection in the DD domain benefiting from the sparsity of the DD channel is designed. The sparse CE step is formulated as a specific marginalization of the maximum a posteriori (MAP) criterion by providing a Bayesian approach via the mean-field approximation that involves the variational Bayesian expectation maximization (VB-EM) algorithm. Detection of data symbols is done using a low complexity MP algorithm. We also propose an interference cancellation (IC) scheme to mitigate contamination of data by pilots that is run after each CE step. To achieve a high CE accuracy, based on the mean mutual incoherence property (MIP), a pilot optimization problem for OTFS is formulated and develop a simulated annealing-based algorithm to solve it. Finally, simulation results show that the proposed scheme achieves a good compromise between spectral efficiency, complexity, and performance in terms of bit error rate (BER) and normalized mean square error (NMSE) when compared to literature benchmarks.     

SA508-3钢回火焊道技术焊道搭接量的分析

针对核电设备常用钢种SA508-3钢,采用钨极氩弧自动焊接方法,对该钢种在使用回火焊道焊接技术修复时的焊道搭接量进行了分析。试验结果表明,焊道搭接量在0%~30%时,相邻的焊道间有明显的凹坑的存在,在后续焊道的焊接过程中容易出现未熔合问题;焊道搭接量达到70%时,焊道表面向瘤状发展,不利于后续焊道的排布,焊道几何尺寸的排布使得回火焊道焊接技术无法实施;焊道搭接量在40%~60%时,焊道分布相对平直,显微硬度及淬硬组织分布均匀,利于回火焊道技术的实施。     

基于SA9604的多功能电能表

介绍了一种以SA9604为计量芯片的多功能电表，并给出功能框图和工作原理，同时给出计算机自动校表的原理和修正公式。     

SA508Gr.4N钢奥氏体晶粒长大行为研究

为研究保温温度和保温时间对SA508Gr.4N钢奥氏体晶粒长大行为的影响,利用光学显微镜和高温激光共聚焦显微镜研究了该钢在保温温度为900 ～1200℃,保温时间0～ 600 min条件下的晶粒长大行为.研究表明,随着保温温度的升高和保温时间的增加,奥氏体晶粒尺寸逐渐增加;在900 ～1000℃,由于部分AlN逐渐回溶...     

SA517 Gr.B焊接工艺

采用E11018-G和E12018-G两种不同强度的焊材,对SA517Gr.B高强钢进行焊接工艺试验研究,进行拉伸试验、侧弯试验和冲击弯试验。结果表明,E11018-G和E12018-G焊接材料均能够满足SA517Gr.B钢材的焊接技术要求,采用E11018-G可有效降低接头焊接应力,降低焊缝裂纹敏感性,提高焊缝质量稳定性。