港口群、产业群与城市群复合系统的共生关系研究——以厦漳泉同城化为例

港口群、产业群、城市群三群是具有耗散结构特征的开放复合系统。运用共生理论,分析了港口群、产业群、城市群复合系统中的共生单元、共生模式和共生环境等要素,探讨了寄生共生、偏利共生、互惠共生三种共生关系的特点,选择了"三群"复合系统演化的共生模式,并且揭示了内在的共生演进机制。在此基础上,以厦漳泉同城化为例,提出促进"三群"复合系统共生演化的对策,以期提升我国沿海地区新型城镇化水平和促进区域经济可持续发展。     

宽带网络SOQPSK突发波形

空基网络通信应用中,采用恒包络波形体制可以降低设备特别是功放的复杂度,因此高效的成形偏移四相相移键控(SOQPSK)信号非常适合于空基网络。但是机载通信中多普勒频移较大,在低信噪比和短突发条件下,SOQPSK相干接收机必须有精确的载波频率和相位同步才能获得较好的性能。针对低信噪比和短突发场景,提出了基于Turbo乘积码（TPC）编码的扩频SOQPSK宽带网络波形,并设计了导频与数据帧结构,利用译码器输出的软信息来改善载波同步的性能,通过迭代操作和联合解调、解扩,增强了系统的同步性能。仿真结果表明,在误码率为10-6时所需Eb/N0为3.65 dB,达到了波形设计指标要求。     

Making the most of what you have: managerial ability as a source of resource value creation

The current study investigates a central premise of the resource‐based view of the firm—that managers are a potential source of value creation for the firm. Using data from professional sports teams, we test theory regarding the effects of managerial ability, human resource stocks, and managers' actions on resource value creation. While results indicate managerial ability affects resource productivity, this effect is less pronounced with increases in the quality of firm resources. Further, we investigate the extent to which managerial actions that synchronize resource bundles account for the influence of managerial ability and resource context on a firm's performance advantage. These results contribute to our understanding of resource management and provide empirical evidence for the importance of managerial ability in the resource‐based view. Copyright © 2008 John Wiley & Sons, Ltd.     

大动态PCM/FM信号的载波频率同步

针对大动态脉冲编码-频率调制（PCM/FM）遥测信号的载波频率同步，提出了基于快速傅里叶变换（FFT）及频谱重心的载波频率估计方法，并采用了频谱叠加及频谱截取的优化方法提高算法估计精度。相对于其他基于FFT的频率估计算法，频谱重心法有着更高的估计精度及更好的抗噪声性能，而且复杂度代价很小。仿真的均方误差结果表明，基于FFT长度为2 048和2块叠加以及保留信号99.9%能量的频谱截取方案有最好的估计性能。在最大多普勒频率、多普勒一阶变化率及二阶变化率分别为0.5倍、0.3倍及0.2倍符号率的大动态条件下，基于频谱重心法的二阶锁频环能够较好地完成载波频率跟踪。误码率曲线表明，经过频偏校正后的多符号非相干解调（MSD)性能与无频偏情况相比，无性能损失。     

基于前向结构的高动态突发信号载波同步算法

为实现高动态突发通信系统载波快速同步，提出了一种新的基于前向结构的突发信号载波同步算法，采用多级处理方案分级实现多普勒变化率、多普勒频偏及载波相位的估计及恢复。理论分析及数值仿真表明，在高动态低信噪比条件下，新算法的载波同步信噪比损失小于1 dB，且对多普勒变化率及信号电平参数不敏感，实现复杂度低，能够满足高实时性应用需求。     

基于ADS-B的高精度站间同步方法

自动相关监视（ADS-B）可用于多站定位系统中实现时间同步，但直接同步的精度不足以满足工程应用的需要。为了提高同步精度，首先推导了利用ADS-B实现站间同步的机理模型，在实测数据的基础上仿真了直接同步方法的精度水平；其次分析了ADS-B位置误差的类型和来源，得到了不同误差类型的分布特征；最后根据不同误差类型的特点，提出了一种降低ADS-B误差影响的高精度多站同步的方法。该方法可有效降低ADS-B系统延时误差和定位误差对同步精度的影响，以实测数据为基础的仿真结果表明该方法可实现纳秒级的站间同步精度，具有良好的工程应用价值。     

三维穿梭车多轴同步控制策略

为了提高三维穿梭车的控制精度,减小控制误差,获得更好的伺服性能,通过对多轴同步控制策略进行研究,利用Matlab搭建伺服电机基于PI调节的双闭环矢量控制模型和基于虚拟主轴结构的同步控制模型,并利用CoDeSys平台搭建基于虚拟主轴控制模型的实验环境,对比仿真与实验的结果,研究验证基于虚拟主轴同步控制模型在三维穿梭车控制系统中的适用性。研究表明,采用基于PI调节的虚拟主轴同步控制模型后,穿梭车各轴到达稳态的时间在0.05s,超调量不超过2%,同步误差调节时间不超过0.5s,具有实时性好同步性高抗干扰性强的控制效果,可以应用于三维穿梭车非线性多耦合的控制系统。     

基于AS5643总线的机载时间同步

为了使机载电子系统中的各个分系统协同完成既定任务，通常需要一个统一的时间标准。针对采用专用硬件的时间同步方法会造成系统开销较大的问题，提出了一种基于AS5643总线的时间同步方案，利用同步帧分发时间信息，并采用软件方法完成时间偏移测量及补偿，可达到优于50 ns的同步精度。详细介绍了基于AS5643总线的时间同步方法、同步原理及具体实施方案，最后通过实物验证表明该方法正确可行。该方法开销低、精度高，可应用于综合化航空电子系统中。     

网络沟通对股票市场的影响--基于投资者有限关注视角的研究

本文通过雪球网数据构建投资者网络沟通质量指标,并结合分析师预测特色数据,实证检验投资者网络沟通行为对股价同步性及特质性波动的影响。研究发现:网络沟通与股价同步性之间呈U形非线性关系,而与股价的特质性波动呈正相关;分析师预测特色数据通过投资者网络沟通行为进入股票市场,其中网络沟通质量与分析师乐观度的交互项同股价同步性呈负相关,而与股票特质性波动呈正相关。进一步细分市场发现,投资者网络沟通在牛市和熊市中对于股价同步性及特质性波动的影响是非对称的。     

Stock index adjustments and analysts’ forecast optimism: A quasi-natural experiment on the CSI 300 Index

As stock index adjustments comprise a basic system of capital market, their potential influence on analysts’ earnings forecasts is worthy of research. Based on a research sample of 23 adjustments to the CSI 300 Index from June 2007 to June 2018 and the backup stocks announced during the same period, this study examines the impact of additions to stock index on analysts’ forecast optimism using a staggered difference-in-differences model. The research results show that after stocks are added to the stock index, analysts’ earnings forecast optimism about these stocks increases significantly. Cross-sectional analysis indicates that this increase is more significant when the market is bullish, institutional ownership is low, the ratio of listed brokerage firms is low, star analyst coverage is low, firms show seasoned equity offering activity, the ratio of analysts from the top five brokerage firms ranked by commission income is high, and the analysts’ brokerage firms are shareholders. However, analyst-level tests find that analysts’ ability helps to reduce the impact of additions to stock index on earnings forecast optimism. Furthermore, additions to stock index significantly increase analyst coverage and forecast divergence. Economic consequences tests find additions to stock index significantly increases stock price synchronization, which is partly mediated by analysts’ earnings forecast optimism. This study enriches the literature on the impact of basic capital market systems and analyst behavior. The findings suggest that investors should rationally evaluate analysts’ earnings forecasts for stocks added to the stock index and obtain further information from various channels to improve asset allocation efficiency.