压控晶体振荡器的设计

本文提出了晶体和频率控制元件的模型,介绍了基本电路的设计,并详细讨论了压控晶体振荡器调制器产生最小音频失真的必要条件。     

变革前消极非正式信息对员工的影响机制研究

组织变革前会有相关的非正式信息,这些信息影响员工对变革的认识。文章探索变革前消极非正式信息量对员工变革抵制意愿的影响,以及员工变革抵制意愿随时间推移的变化,信息频率与尽责性对员工变革抵制意愿变化的调节作用。基于159位员工调查数据的多层次线性增长模型分析表明：消极非正式信息量显著增加员工的变革抵制意愿,但这种抵制意愿随时间推移而显著衰减;消极非正式信息频率与尽责性对员工变革抵制意愿随时间衰减有三维调节作用：在低信息频率下,低尽责性员工的变革抵制意愿随时间衰减更快。研究结果对组织变革有一定理论和实践意义。     

How the sound frequency of background music influences consumers’ perceptions and decision making

This study examined how music frequency affected consumers’ perception and decision making. The results of three experimental studies show that music frequency affects perceived distance between the sound source and the perceiver. Consequently, the representation of marketing message that matched (vs. mismatched) the background music's frequency enhanced consumers’ evaluative judgments. Specifically, Study 1A demonstrates that low‐frequency (vs. high‐frequency) music increased perceived distance. Studies 2, 3A, and 3B indicate that low‐frequency (high‐frequency) music matched products with abstract (concrete) representations and marketing messages signifying far (near) psychological distance. The congruency between psychological distance induced by music frequency and mental representations of products and message orientation offers a novel perspective on the notion of congruency. Moreover, Study 2 provides evidence that supports the congruency–fluency–evaluation chain (i.e., the mediating role of fluency), and Studies 3A and 3B show that the congruency has downstream effects. This study provides a theoretical contribution to the literature on the effects of music in marketing contexts by presenting convergent evidence that individuals exposed to low‐frequency (high‐frequency) music are inclined to construe a marketing message at a high (low) level.     

单频网多播系统中的开环半动态功率分配算法

在单频网多播传输中,传统的全反馈动态功率分配数算法需要根据每个时隙反馈的用户瞬时信道信息进行实时的调整,所以造成了资源分配频率快、上行反馈开销大的缺点。为了克服这个缺点,提出了一个低复杂度、没有用户反馈的单频网多播开环半动态功率分配算法。首先在各小区等功率分配的假设下,根据单频网的形状信息算出各小区等价信道增益,然后再根据这个增益值,实现满足速率需求情况下的各小区功率分配。仿真结果显示,与全反馈的动态功率分配算法相比,该算法以一小部分性能损失为代价,大大减少了单频网的上行反馈和资源分配的开销,因此更适用于实际的单频网多播系统。     

天地一体化超视距雷达的激励源设计

针对单通道天地一体化超视距雷达不能多站组网的问题,设计了一种新型的激励源系统。系统利用现场可编程门阵列（FPGA）和通用串行总线（USB）实现多路发射通道控制,并通过直接数字式频率合成器（DDS）产生初始相位周期变化的线性调频波。理论分析表明,回波信号经过两次频谱变换能产生特定的多普勒频移,从而在多普勒频谱上被展开,实现信号多发一收。实验结果验证了激励源设计的可行性,可用于多站同步观测。     

战场环境中的电波传播模型优化选择方法

针对战场级的复杂电磁环境仿真过程中涉及到全频段覆盖、环境影响、仿真速度要求高等问题,提出了一种综合考虑用频装备、环境信息和模型自身特点的电波传播模型选择方法。该方法首先通过频段对用频装备及电波传播模型进行划分,再结合环境信息中降雨量、海拔、植被覆盖率、气候类型、导电特性等参数进行综合分析,最终得到传播模型的优化选择方案。在典型作战场景仿真应用中,该方法为传播模型的合理选择提供了思路,保证了仿真的精度,同时也为电磁环境仿真中传播模型本地化提供了依据。     

Understanding the drivers of organic foods purchasing of millennials: Evidence from Brazil and Spain

This paper examines the antecedents of millennials' organic food purchasing. A conceptual framework, based on product characteristics, and consumers' concerns and consciousness, is proposed. Data collection was conducted through a survey in two culturally and socioeconomically distinct countries (Brazil vs. Spain) to increase the robustness and generalizability of the results. The results show that product characteristics and consumer concerns improve millennials’ health consciousness and increase their social consciousness, which, in turn, increase their willingness to pay a price premium and their purchase frequency of organic foods. The findings show that the proposed model has high validity, with only one significant difference between the two countries. Theoretical contributions and managerial implications are discussed.     

基于深度学习的跳频信号识别

针对跳频信号分选存在人工提取参数特征具有复杂性的问题,提出了一种基于深度学习的识别方法。首先对跳频信号进行短时傅里叶变换,得到二维的时频矩阵;接着提取信号的轮廓特征,构造三维矩阵作等高线图,并对等高线图进行预处理;最后把预处理后的等高线图输入到卷积神经网络中进行训练、测试,进而实现分类识别。仿真结果表明,在不需要复杂的人工提取参数特征的基础上,在分选率为100〖WT《Times New Roman》〗%〖WTBZ〗时,所提方法经裁剪处理下的信噪比为-15 dB,比支持向量机和传统K-Means聚类算法都低10 dB。实测数据的算法验证表明,所提方法能够将大疆精灵4Pro、hm无人机、司马航模X8HW以及大疆悟2这四类无人机正确分类。     

一种嵌入式软件无线电频谱监测系统

为了降低研发成本,提高频谱系统的灵活性和缩短研制周期,提出了一种基于软件无线电的嵌入式频谱监测系统。首先研究了系统硬件平台组成和特点,在此基础上设计了一种灵活的软件定义系统架构;然后考虑到硬件平台自身性能的限制,重点研究了频率偏移校正、频谱扫描策略等关键技术,分别提出了基于GSM信号和温度传感器的频偏校正方法和基于相关性的扫频策略;最后通过具体实验,对系统性能进行验证与评估,结果表明所提出的频偏校正方法能够将绝对平均频偏控制在1.749×10-6以内,所设计的基于相关性的扫频策略对时变信号的频谱监测效果最好。