Cr-Nb系机械合金化及其热压过程中的X射线衍射分析

讨论了X射线衍射测试技术在Cr-Nb系元素机械合金化及随后的热压工艺的物相衍变过程中的应用,包括晶粒细化引起的峰形宽化、不同热压温度对Cr2Nb相形成量的对比.通过X射线衍射测试技术及应用EVA、TOPAS P软件包可以直观地进行分析,在合金相中发现了一种新的Cr2Nb相态.     

一种软件科斯塔斯环的模型建立与实现

文章通过双线性变换法建立了科斯塔斯环的Z域模型,分析了Z域模型下环路各项性能指标和环路参数之间的关系,系统总结了设计步骤和参数的选择方法。试验仿真结果证明捕获与跟踪性能符合理论分析。最后给出了科斯塔斯环在FPGA中的硬件实现结构。     

Real-time ray-based channel generation and emulation for UAV communications

A real-time ray-based hardware emulator for Unmanned Aerial Vehicle (UAV) communication channels which suits for the Three-Dimensional (3D) dynamic scenarios and considers the movements of both terminals is developed in this paper. The time-variant channel parameters, i.e., ray delay, ray gain, and ray Doppler frequency are precalculated in the host by using the Ray Tracing (RT) method. Meanwhile, RT simulation dramatically increases the number of valid rays. To address the problem of resource limitation and huge computational burden in the implementation, an efficient ray coefficients generation method based on iteration is proposed and implemented. With the advantages of low cost and high flexibility, a Software Defined Radio (SDR) hardware platform is used to emulate the ray-based UAV channels by utilizing the compact architecture including the Time-Division (TD) scheme and Tapped-Delay Line (TDL) for channel convolution. Finally, hardware measurement results demonstrate that the properties of emulated channel, i.e., Power Delay Profile (PDP) and Doppler Power Spectrum Density (DPSD) consist with the simulated ones, which verifies the correctness of hardware implementation. The proposed channel emulator provides an efficient way for optimization, verification, and evaluation of UAV communication systems.     

基于卫星轨道软件平台的自主导航计算方法

为增强卫星的自主生存能力，研究了基于卫星轨道软件平台的自主导航计算方法。由星载导航部件获取导航参数，应用数值或解析法进行自主导航计算，以实时获得精确的轨道参数。理论分析和仿真结果表明，读方法正确可行，具有较高的工程应用价值。     

6G service-oriented space-air-ground integrated network: A survey

As an indispensable component of the emerging 6G networks, Space-Air-Ground Integrated Networks (SAGINs) are envisioned to provide ubiquitous network connectivity and services by integrating satellite networks, aerial networks, and terrestrial networks. In 6G SAGINs, a wide variety of network services with the features of diverse requirements, complex mobility, and multi-dimensional resources will pose great challenges to service provisioning, which urges the development of service-oriented SAGINs. In this paper, we conduct a comprehensive review of 6G SAGINs from a new perspective of service-oriented network. First, we present the requirements of service-oriented networks, and then propose a service-oriented SAGINs management architecture. Two categories of critical technologies are presented and discussed, i.e., heterogeneous resource orchestration technologies and the cloud-edge synergy technologies, which facilitate the interoperability of different network segments and cooperatively orchestrate heterogeneous resources across different domains, according to the service features and requirements. In addition, the potential future research directions are also presented and discussed.