基于相控阵天线的“动中通”卫星通信终端研究

提出了一种新的“动中通”卫星终端的设计思路。主要从研究当前国内主流的“动中通”卫星通信终端着手,分析了在“动中通”卫星通信终端中采用相控阵技术的可行性,给出了一个典型的相控阵“动中通”卫星通信终端的实现框架,并进行了可工程实现的收发分离相控阵“动中通”卫星通信终端具体设计,提出设计关键点。     

VSAT卫星信号中的邮件数据分析与提取

随着VSAT网络的不断发展,卫星信道越来越多地被用来传送基于IP协议的多种数据.为获取这类信息,本文对承载IP数据的卫星DVB信号传送数据的MPEG-2协议及多协议封装格式进行了深入研究,并结合实际数据对这些协议在实际数据中的应用进行了深入分析.对数据的分析采用了软件编程的方法,在协议逐层提取的基础上,对数据进行了逐层剥离,在剥离同时对数据按特定关键字段进行分类,得到了所需的邮件数据.最后给出了在VSAT网络卫星DVB信号中提取邮件的流程.     

基于局部形相似的超短期负荷预测方法

在对电力负荷局部特性分析的基础上,定义了一个描述负荷序列形状相似程度的指标--负荷曲线形系数,提出了一种基于局部形相似的超短期负荷预测方法.该方法将预测时刻前一段负荷序列与各相似日同一时段负荷序列的形系数引入到超短期负荷预测中,强调基于形相似基础进行值预测,克服了现有预测方法中对各相似日采用相同权重所导致的平滑效应对拐点负荷预测的影响.研究结果表明,该方法在保证运算速度的同时,提高了总体预测准确性和拐点处的预测准确性.该改进方法可用于对现有多种超短期负荷预测方法的改进.     

VESDA在高大空间火灾报警系统中的应用

对火灾的形成过程进行了分析.针对高大空间,给出了几种火灾探测的方案,并进行了比较.结合某会展中心火灾报警系统的工程设计,介绍了一种新型的极早期烟雾探测预警系统在高大空间火灾报警系统设计中的应用.     

基于虚拟仪器的微速差双转子系统动平衡测试装置的研制

介绍了基于虚拟仪器的微速差双转子系统动平衡测试装置的构成、基本原理以及软硬件的设计方法。     

基于生成式对抗网络的遥感图像半监督语义分割

高分辨率遥感图像的语义分割问题是目前遥感图像处理领域中的研究热点之一。传统的有监督分割方法需要大量的标记数据,而标记过程又较为困难和耗时。针对这一问题,提出一种基于生成式对抗网络的半监督高分辨率遥感图像语义分割方法,只需要少量样本标签即可得到较好的分割结果。该方法为分割网络添加全卷积形式的辅助对抗网络,以助于保持高分辨率遥感图像分割结果中的标签连续性;更进一步,提出一种新颖的能够进行注意力选择的对抗损失,以解决分割结果较好时判别器约束的分割网络更新过程中存在的难易样本不均衡问题。在ISPRS Vaihingen 2D语义标记挑战数据集上的实验结果表明,与现有其它语义分割方法相比,所提出方法能够较大幅度地提高遥感图像的语义分割精度。     

Directivity enhancement of wire monopole antenna using magnetic metamaterials

This article proposes the use of a magnetic metamaterial (MTM) slab over the ground plane of a wire monopole antenna to improve its directivity. In this regard, mu very large (MVL) behavior of the metamaterial is utilized for enhancing the directivity of the monopole. Despite the directivity enhancement of about 5 dB, an improved bandwidth of 35% is obtained for the proposed configuration. Initially, a 2 × 3 array of a single MTM slab has been placed over the ground plane of the monopole. It is shown that, over the whole working band, a significant directivity improvement is maintained compared to the unloaded monopole. Further, the directivity performance has been investigated with different combination of MTM slab.     

Structure characterization within the vicinity of the fine granular area by synchrotron radiation nano‐CT

The three‐dimensional (3D) microstructures within the vicinity of the fine granular area (FGA) were investigated with synchrotron radiation nano‐computed tomography (CT). In this investigation, the very high cycle fatigue test of a high‐strength steel was carried out with an ultrasonic fatigue testing machine. Then, focused ion beam cutting was used to cut a part near the surface of the FGA. Finally, the 3D structure of the sample was obtained with the nano‐CT imaging. The results indicated that the base material was composed of various subgrains that are tens to hundreds nanometres in size. Through analysis of the slices, small granular areas consist of several subgrains. The statistical analysis of the subgrain size indicated that the subgrain size near the surface of the FGA is similar to that far from the surface of the FGA and near the fracture surface except the FGA. It indicated that the refinement has not been found by nano‐CT.     

High‐cycle and very‐high‐cycle fatigue behaviour of a titanium alloy with equiaxed microstructure under different mean stresses

The fatigue behaviour of a titanium alloy Ti‐6Al‐4V with equiaxed microstructure (EM) under different values of tensile mean stress or stress ratio (R) was investigated from high‐cycle fatigue (HCF) to very‐high‐cycle fatigue (VHCF) regimes via ultrasonic axial cycling. The effect of mean stress or R on the fatigue strength of HCF and VHCF was addressed by Goodman, Gerber, and Authors' formula. Three types of crack initiation, namely, surface‐with‐RA (rough area), surface‐without‐RA, and interior‐with‐RA, were classified. The maximum value of stress intensity factor (SIF) at RA boundary for R < 0 keeps constant regardless of R in HCF and VHCF regimes. The SIF range at RA boundary for R > 0 also keeps constant regardless of R in VHCF regime, but this value decreases linearly with the increase of R for surface RA cases. The microstructure observation at RA regions gives a new result of nanograin formation only in the cases of negative stress ratios for the titanium alloy with EM, which is explained by the mechanism of numerous cyclic pressing.     

A GPU‐Adapted Structure for Unstructured Grids

A key advantage of working with structured grids (e.g., images) is the ability to directly tap into the powerful machinery of linear algebra. This is not much so for unstructured grids where intermediate bookkeeping data structures stand in the way. On modern high performance computing hardware, the conventional wisdom behind these intermediate structures is further challenged by costly memory access, and more importantly by prohibitive memory resources on environments such as graphics hardware. In this paper, we bypass this problem by introducing a sparse matrix representation for unstructured grids which not only reduces the memory storage requirements but also cuts down on the bulk of data movement from global storage to the compute units. In order to take full advantage of the proposed representation, we augment ordinary matrix multiplication by means of action maps, local maps which encode the desired interaction between grid vertices. In this way, geometric computations and topological modifications translate into concise linear algebra operations. In our algorithmic formulation, we capitalize on the nature of sparse matrix‐vector multiplication which allows avoiding explicit transpose computation and storage. Furthermore, we develop an efficient vectorization to the demanding assembly process of standard graph and finite element matrices.