Surprise and dispersion: informational impact of USDA announcements

We examine the role of information asymmetry on changes in bid‐ask spreads during major United States Department of Agriculture (USDA) announcements. Our analyses, using corn, wheat, and soybean futures, indicate that information asymmetry is significantly higher on USDA announcement days compared to nonannouncement days. We further observe that the increased information asymmetry prior to news announcements is mainly driven by the divergence in private information possessed by market participants. However, once the USDA news is released, not only the dispersion in investors’ private information but also the surprises in news announcements contribute to increased information asymmetry and widening of bid‐ask spreads.     

Twitter activity,investor attention,and the diffusion of information

We examine the impact of Twitter attention on stock prices by examining over 21 million company‐specific tweets over a 5‐year period. Through a quasi‐natural experiment identifying official Twitter outages, we find that Twitter influences stock trading, especially among small, less visible securities primarily traded by retail investors. In addition, we determine that Twitter activity is associated with positive abnormal returns and when tweets occur in conjunction with traditional news events, more information is spread to investors. Finally, we show that retail investor activity drives the Twitter effect as institutional investors less actively trade the affected stocks.     

Spread determinants and the day-of-the-week effect

In this paper, we examine the determinants of the dollar bid–ask spread for each day of the week over the period 1998–2008. Using a panel cointegration approach, we estimate the determinants of the spread in both the short-run and long-run. Our main findings suggest that: (1) there are day-of-the-week effects for certain groups of firms; (2) the panel error correction model also reveals day-of-the-week effects, and the speed of adjustment to equilibrium following a shock is faster on Fridays; and (3) the effects of volume and volatility on the spread are mixed, with only some sectors experiencing the day-of-the-week effect.     

The impact of individual investor trading on information asymmetry in the Korean stock market

This paper examines the impact of individual investor trading on information asymmetry in the market. In particular, we examine the relationship between the trading volume by individual investors and the corresponding bid-ask spread in the Korean stock market, where the majority of the trading activity is driven by individual investors and therefore information asymmetry can be evident. We find that high trading activity by individual investors increases the bid-ask spread in a short investment horizon, suggesting that individual investors, as uninformed and unsophisticated traders, amplify the degree of information asymmetry in the market through trading.     

Asymmetric structure of bid-ask spreads across the business cycle

This study argues that the structure of bid-ask spreads is asymmetric across the business cycle. During expansion, investors tend to be overconfident, leading to a higher spread component due to information asymmetry. On the other hand, during recession, the markets are more volatile, leading to a higher spread component due to order processing costs. With TAIEX futures contracts as a sample, it is found that the spread component due to information asymmetry is significantly higher in times of expansion than in times of recession, while the spread component due to order processing cost is significantly higher in times of recession than in times of expansion.     

A pairs trading strategy based on linear state space models and the Kalman filter

Among many strategies for financial trading, pairs trading has played an important role in practical and academic frameworks. Loosely speaking, it involves a statistical arbitrage tool for identifying and exploiting the inefficiencies of two long-term, related financial assets. When a significant deviation from this equilibrium is observed, a profit might result. In this paper, we propose a pairs trading strategy entirely based on linear state space models designed for modelling the spread formed with a pair of assets. Once an adequate state space model for the spread is estimated, we use the Kalman filter to calculate conditional probabilities that the spread will return to its long-term mean. The strategy is activated upon large values of these conditional probabilities: the spread is bought or sold accordingly. Two applications with real data from the US and Brazilian markets are offered, and even though they probably rely on limited evidence, they already indicate that a very basic portfolio consisting of a sole spread outperforms some of the main market benchmarks.     

SAW多路正交码扩频调制解调器研究

提出了一种直接序列多路正交码扩频调制解调器的声表面波(SAW)实现方案，并给出了相应的实验结果。     

直接序列扩频系统的多次驻留顺序捕获

本文利用矩阵变换方法对多次驻留顺序捕获的平均捕获时间表示式进行了推导,其过程较信号流图法简单。同时还给出了一次、二次及三次驻留顺序捕获系统的平均捕获时间的计算实例。     

扩频通信系统的中频数字化处理技术

介绍了一种应用于抗干扰综合信息系统的数字扩频通信系统 ,具体讨论了利用匹配滤波器完成PN码的快速捕获和利用谱估计完成载频的频移补偿的数字化处理技术 ,系统可以实现远距离的无线数据通信 ,文中给出了中频数字部分的实现原理以及软硬件框图。