双星时差频差无源定位系统定位算法工程指标分析

通过计算时差、频差测量精度,以及卫星运动引起的时差、频差变化率,提出双星时差频 差无源定位系统的信号最佳采样时间为10～100 ms。进一步推导了工程可实现的定位精 度,仿真结果表明双星系统工程可实现的定位精度约为1～3 km。研究和结论对双 星定位系统定位精度指标的论证与分解具有借鉴意义。     

PCMA自适应自干扰对消算法与仿真

讨论了成对载波多址（PCMA）自适应自干扰对消原理,分析了参数估计误差对自干扰 对消的影响。在频偏误差的影响下对消误差为非平稳过程,传统自适应对消滤波器无法收敛 。为了克服频偏误差的影响,提出了一种自适应可变遗忘因子（VFF） RLS算法,同时,给 出了具有高精度低运算量的模糊函数参数估计算法。仿真证明了VFF-RLS对消算法具有良好 的对消性能和稳健性,且需要的额外功率较低,能满足PCMA系统要求。     

微纳卫星组网星间链路设计及关键技术分析

微纳卫星组网应用可大幅度提高航天装备的能力,较单颗大卫星具有明显的优势。首先,介绍了国内外微纳卫星组网的研究情况,以组网侦察应用为例分析了星间测量与通信链路的技术需求,并进行了系统架构和体制设计;其次,在星座设计基础上开展系统仿真,并提出了一体化设备实现方案;最后,分析了微纳卫星组网系统中几项重要的关键技术及其解决方案,对系统的设计和工程实现具有参考价值。     

多核式中卫型产业集群的网络结构分析--以沈阳装备制造业集群为例

“单核式”与“多核式”是中卫型产业集群的两种基本网络结构。以多核式中卫型产业集群作为研究对象,对其进行概念界定,指出其网络结构具有多个中心结点、内部合作关系密切、结点凝聚成小团体、中心结点相互关联等特征,并据此选取了社会网络分析方法中的中心性、黏性、凝聚子群、核心边缘结构作为网络结构指标。运用这些指标,对沈阳装备制造业集群的网络结构进行了实例分析。研究发现：该集群网络中,各产业部门的核心企业充当了中心结点,同一产业部门的企业密切合作组成凝聚子群,核心企业之间关联紧密形成核心区。这些网络结构特征是其获取生产协作、资源配置和知识创新等竞争优势的重要保证。针对该集群网络黏性较低的现状,最后提出相应的网络结构优化建议。     

Effects of personification and anthropomorphic tendency on destination attitude and travel intentions

This research examined how individual differences in anthropomorphic tendency (the tendency to humanize non-human agents/objects) influence how people respond to destination marketing communications. Specifically, this study examined whether individual-level anthropomorphic tendency and text-personification of destination marketing communications interact to influence destination attitude and travel intentions. Results from a study involving 210 Australian participants revealed that destination attitude and travel intentions were most favorable for people with high levels of anthropomorphic tendency and who were exposed to personified tourism messages. These findings indicate that text-personification represents a new communication tactic for tourism – particularly for target consumers who are high in anthropomorphic tendency – and one that can humanize the destination leading to more favorable attitudes and higher intentions to travel. This effect is mediated by positive emotions. People with high anthropomorphic tendency who are exposed to a personified advertisement feel more positive emotions, which lead to positive tourism outcomes.     

基于L频段数字航空通信系统1的F-OFDM波形设计

随着航空飞行器种类和数量的激增以及第五代（5G）移动通信系统和物联网（IoT）时代的到来,下一代航空无线通信系统面临着高安全性、大传输容量、低延时、强鲁棒性、高灵活性和综合业务提供等新的挑战。为此,提出了一种基于L频段数字航空通信系统1（L-DACS1）的滤波正交频分复用（F-OFDM）波形设计方法并探讨了可能的技术演进路径。首先引入了认知无线电、非连续载波干涉码OFDM和滤波器的思想,然后针对不同航空飞行器用户动态自适应配置波形参数。仿真结果表明,该方法得到的系统波形具有较低的带外辐射功率、优良的块误码率性能和较高的吞吐量增益。     

Tradespace exploration of in-space communications network architectures

Making architectural decisions in long lifecycle systems is challenging because the time between system definition and end of operations can span multiple decades, resulting in shifts in stakeholder needs and major advances in technologies. Space-based communications using relay satellite constellations is one such example, requiring substantial up-front planning to define capabilities and size capacity due to the large investment of time and resources. Additionally, there are numerous viable system architectures. In this paper, we build on existing methods to develop a graph-based decision method to assess and explore architectural flexibility in the future evolution of long lifecycle systems. The tradespace graph defines edges between similar architectures, quantifies the switching cost between architectures, using graphs to analyse the potential system evolution pathways. In a test case on NASA communication satellites, we find that hosting government communications payloads, in particular optical payloads, on commercial satellites could reduce cost and increase flexibility of the NASA network.     

长江干流地区跨世纪交通运输网络建设的总体构想

长江干流地区自宜宾至上海长约２８００ｋｍ，横跨中国东、中、西三大经济地带，面积占全国４．３％，有十分重要的战略意义。今后这一区域路网建设的目标是建成以长江干线为主轴，以宜宾、重庆、万县、枝城、武汉、丸江、芜湖、南京、江阴为结点的＂九纵一横＂的路网格局。长江干线包括加深长江航道，建设沿江铁路和沿江高等级公路。同时加强纵向铁路、公路和水运干线建设，形成若干水陆交通枢纽，并加强干线和支线机场建设，在上海、南京、武汉、重庆建成国际航空港。     

基于深度学习模型的种植结构复杂区农作物精细分类研究

目的 卫星遥感技术具有覆盖范围广、探测周期短、调查成本低等优势而广泛应用于大区域农作物分类。然而在种植结构复杂区（如城乡结合部）,因其地块破碎、同期生长的作物种类多且分布分散,利用传统的统计分类或机器学习方法进行农作物分类时仍存在精度不高的问题。为提高种植结构复杂区农作物分类精度。方法 文章选取河北省廊坊市广阳区为研究区,以GF-1 PMS全色多光谱融合影像为数据源,采用U-Net、PSPNet及DeepLabv3+,3种深度学习模型进行农作物分类研究。分析模型参数对农作物分类精度的影响,评价3种深度学习模型的农作物分类精度,优选农作物精细分类方法。结果 （1）学习率与3种深度学习模型的分类精度呈正相关关系,较大的学习率（0.01,0.001）下,3种模型收敛速度快,分类精度高。批样本量与模型分类稳定性相关,批样本量设为100时,3种模型的分类稳定性最好。（2）相比PSPNet、DeepLabv3+模型,U-Net模型分类效果最好,总体分类精度为89.32%。（3）GF-1 PMS影像结合U-Net模型可有效提升种植结构复杂区农作物分类精度,大宗作物春玉米、夏玉米的分类精度在80%以上,花生、红薯、蔬菜小宗作物分类精度在60%以上。结论 该研究可为准确获取种植结构复杂区的农作物类型、面积及空间分布信息提供参考依据。     

Electronic Marketing Communications: An Evolving Environment,but Similar Story Regarding the Perception of Unsolicited Commercial E-Mail and Postal Direct Mail

The internet is still a relatively new mass communication tool for advertisers and marketers. When weighing the potential benefits of electronic techniques against the financial investment, spam seems particularly attractive to marketers for either for-profit or non-profit objectives. Since it is unlikely that marketers will decrease their efforts related to spam and postal direct mail as a form of communicating to mass consumers, it is important to track consumer attitudes so that audiences are not subjected to the backlash predicted by psychological reactance. The results of this study found that spam is more irritating than postal direct mail at both T₁ (2004) and T₂ (2006), and participants in T₂ found both direct marketing communication methods more intrusive than those in T₁.