长尾理论为档案信息传播带来的机遇和挑战

本文从长尾理论出发分析档案信息传播中存在的长尾现象,并探讨网络给档案信息传播带来的新挑战。     

LTE系统中利用信道估计的天线端口数检测算法

长期演进(LTE）系统中使用多输入多输出(MIMO)技术来改善通信质量并提升信道容量。天线端口数通过循环冗余校验（CRC）掩码的方式隐含于物理广播信道（PBCH）中,遍历1、2、4三种天线端口数情况,分别作为PBCH解码配置,以CRC校验通过并且PBCH解码成功作为确定天线端口数的标志,从而造成冗余计算和时延的产生。为此,提出了一种基于信道估计的天线端口数检测算法,利用正交频分复用（OFDM）调制的LTE信号在空口环境中受频偏和时延影响,造成信道估计结果相位的线性累加,再通过线性回归方程的门限匹配,解决天线端口数检测中频偏影响大、计算量过多和盲检等问题。理论分析和仿真结果表明,该算法复杂度低、时延小,且在残余频偏较大时具有较高的正确率。     

Modelling international monthly arrivals using seasonal univariate long-memory processes

Seasonal long memory has become an alternative credible way when modelling the seasonal component in many time series. In this paper, a procedure is employed that permits consideration of unit and fractional orders of integration at seasonal frequencies in a raw time series. This method is applied to the international monthly arrivals in the US, using both aggregated and disaggregated data. The results show that the total number of arrivals in the US can be specified in terms of a seasonal I(d) model with d higher than zero but smaller than one, implying long memory and mean reverting behaviour. Attempting to summarize the conclusions for the individual locations, leaves the impression that Asia, Central and South America, Eastern Europe and Oceania present the smallest degrees of integration. On the other hand, Africa and the Caribbean provide the highest values, implying for these two locations a strong degree of persistence to the US as a destination. Finally, another application, based on a longer dataset, is also employed to examine the forecasting properties of this type of model.     

扎龙自然保护区生态旅游发展模式探究

扎龙自然保护区是我国北方同纬度地区中保留最完整、最原始、最开阔的湿地生态系统。根据扎龙生态旅游的资源优势和基础条件，要积极探索其生态旅游可持续发展模式。     

Long memory or structural breaks: can either explain nonstationary real exchange rates under the current float?

This paper considers two potential rationales for the apparent absence of mean reversion in real exchange rates in the post-Bretton Woods era. We allow for (i) fractional integration and (ii) a double mean shift in the real exchange rate process. These methods, applied to CPI-based rates for 17 countries and WPI-based rates for 12 countries, demonstrate that the unit-root hypothesis is robust against both fractional alternatives and structural breaks. This evidence suggests rejection of the doctrine of absolute long-run purchasing power parity during the post-Bretton Woods era.     

Pricing volatility of stock returns with volatile and persistent components

This paper introduces a two-component volatility model based on first moments of both components to describe the dynamics of speculative return volatility. The two components capture the volatile and the persistent part of volatility, respectively. The model is applied to 10 Asia-Pacific stock markets. Their in-mean effects on returns are tested. The empirical results show that the persistent component is much more important for the volatility dynamic process than is the volatile component. However, the volatile component is found to be a significant pricing factor of asset returns for most markets. A positive or risk-premium effect exists between the return and the volatile component, yet the persistent component is not significantly priced for the return dynamic process.

Analysts’ stock recommendations,earnings growth and risk

A key output of sell‐side analysts is their recommendations to investors as to whether they should, buy, hold or sell a company's shares. However, relatively little is known regarding the determinants of those recommendations. This study considers this question, presenting results that suggest that recommendations are dependent on analysts’ short‐term and long‐term earnings growth forecasts, as well as on proxies for the analysts’ unobservable views on earnings growth in the more distant future and risk. Furthermore, analysts who appear to incorporate earnings growth beyond the long‐term growth forecast horizons and risk into their recommendation decisions make more profitable stock recommendations.     

Long‐Term post‐merger announcement performance. A case study of Australian listed real estate

This study examines the long‐term postmerger performance of Australian Real Estate Investment Trusts (A‐REITs). The A‐REIT sector is used as a case study being less vulnerable to agency issues due to its regulatory structure (Eichholtz and Kok, 2008; Ratcliffe et al., 2009). Research on conventional firms has shown, on average, shareholders are worse off in the long run (Alexandridis et al., 2012). In contrast, we find that shareholders experience significantly positive abnormal returns, after accounting for the financial crisis. This outcome suggests that when managers are restricted with the use of retained earnings and the type of investment, they may be less susceptible to hubris and/or agency issues.     

Dependence and mean reversion in stock prices: The case of the MENA region

This paper provides empirical evidence on the long memory behavior of the stock markets of Egypt, Jordan, Morocco, and Turkey. To test for long memory in the returns and volatility, we employ the modified rescaled range statistic R/S proposed by Lo [Lo, A.W., 1991. Long-term memory in stock market prices. Econometrica 59, 1279–1313] and the recently proposed rescaled variance V/S statistic developed by Giraitis et al. [Giraitis, L., Kokoszka, P.S. Leipus, R., Teyssiere, G., 2003. Rescaled variance and related tests for long memory in volatility and levels. J. Econ. 112, 265–294]. Further analysis is conducted by employing the ARFIMA (p, d, q) model to estimate the long memory parameters. Egypt and Morocco show evidence of long memory in the return series, while Jordan and Turkey display negative persistence. For the volatility series, long memory is conclusively demonstrated for all markets. Then, we compare the forecasting performance of ARMA and ARFIMA models and find that the ARFIMA model outperforms in out-of-sample forecasting of the markets. Our results should be useful to regulators, practitioners and derivative market participants, whose success depends on the ability to forecast stock price movements in these markets.