Purchasing power parity in transition countries: Old wine with new bottle

This study questions whether the long-run purchasing power parity (PPP) holds in the transition economies (Bulgaria, the Czech Republic, Hungary, Latvia, Lithuania, Poland, Romanian, and Russia) for the period from January 1995 to October 2011. We employ the Sequential Panel Selection Method (SPSM) procedure using the Panel KSS unit root test with a Fourier function, a novel approach to panel unit root testing. The SPSM approach classifies the whole panel into a group of stationary and non-stationary series and is able to account for structural breaks, nonlinearity, and cross-section dependence. The results indicate that the PPP holds true for more than half of these transition countries studied, with the exception of Hungarian, the Czech Republic and the Russia. The findings have important policy implications for the transition countries.     

基于K空间的核磁共振快速成像技术

磁共振成像技术已经成为现代临床医学影像检查的重要手段之一,而传统的成像手段的主要缺点是其成像速度太慢。文章主要阐述了半傅里叶成像、平行成像以及压缩传感成像的基本原理,从而展现MR快速成像技术巨大的应用价值和研究价值。     

Additional Empirical Evidence on Real Convergence: A Fractionally Integrated Approach

We examine the real convergence hypothesis for 14 OECD countries looking at the fractional order of integration of the differences of real GDP per capita in these countries with respect to the United States. Using parametric procedures, the results vary depending on how we specify the I(0) disturbances. If they are white noise, convergence is achieved for Canada and Australia, and with autocorrelated disturbances, this hypothesis is satisfied for France and the Netherlands. However, allowing for a break at World War II, evidence of convergence is obtained for all countries. JEL no. C32, O41     

Forecasting the business cycle using survey data

Regular business survey data are published as percentages of firms predicting higher, equal or lower values of some reference variable. Time series of such percentages do not fit production data too well. Univariate models often produce forecasts which are just as accurarate. Still, surveys contain anticipative judgement which, when combined with univariate modeling and proper filtering, may produce a good indicator for business cycle turning points. The way survey data are transformed so as to fit statistics on production seems not to be of much importance. A case study of the Finnish forest industry is offered as an example.     

阿贝尔（Abel）方程的一个特殊解法

给出奇异积分方程阿贝尔方程的一种技巧解法，作累次积分及变量替换推出此方程的解式，提出一个注记，拓展了求解积分方程的思路。变量替换、积分变换是求解微分方程和积分方程的一种重要方法。     

Cointegration, Efficiency and Forecasting in the Currency Market

Existing literature on using the cointegration approach to examine the efficiency of the foreign exchange market gives mixed results. Arguments typically focus on econometric testing techniques, with fractional cointegration being the most current one. This paper tries to look at the issue from an economic perspective. It shows that the cointegrating relationship, whether cointegrated or fractionally cointegrated, is found mainly among the currencies of the European Monetary System which are set to fluctuate within a given range. Hence, there is no inconsistency with the notion of market efficiency. Yet, exploiting such a cointegrating relationship is helpful in currency forecasting. There is some evidence that restricting the forecasting model to consist of only cointegrated currencies improves forecasting efficiency.     

双指数跳跃扩散模型下的二元数字期权定价

双指数跳跃扩散模型下的二元数字期权(digital option)定价问题,应考虑上向二元数字期权和下向二元数字期权,给出了这些期权的价格的拉普拉斯变换(laplace transform)。这些期权价格的拉普拉斯变换表达式的获得得益于使用有关双指数跳跃扩散过程的首达时问题的研究结果。     

中国银行业的利润效率研究——基于傅里叶柔性函数的视角

商业银行的经营效率已成为近年来国内外学者研究的热点问题。本文尝试引入傅里叶柔性函数模型测算我国银行业的效率水平,为更加准确地判断商业银行的经营效率提供依据。研究表明：傅里叶函数模型拟合效果要优于超越对数函数模型;1999—2009年,我国商业银行的利润效率估计均值为0.9466,总体效率水平较高。     

EKC-type transitions and environmental policy under pollutant uncertainty and cost irreversibility

Previous studies have suggested that some pollutant levels first increases due to the economic growth and then start decreasing, the pattern being called the “environmental Kuznets curve” (EKC). We examine EKC-type transitions of pollutant levels not with respect to economic growth but more generally in time. Assuming that each policy maker optimally executes the two switching options of regulation and unregulation for pollution, the switching dynamics of environmental policy can be described by an alternating renewal process. It is shown that the double Laplace transform of transition density of a pollutant level can be obtained by a novel application of renewal theory. The expected level of overall pollutants is then calculated numerically and found to exhibit either a Λ‐shaped or an N-shaped pattern in time. Our results present a simple explanation for the EKC-type transitions of pollutant levels within a real options framework.     

基于小波的窄带通信干扰抑制研究的探讨

窄带干扰(NBI)对直接序列扩频通信系统(DSSS)的破坏性很强,当有强窄带干扰存在时仅靠系统自身的抗干扰能力很难保证系统高质量的通信,甚至可能造成系统通信中断。因此,研究有效的窄带干扰抑制技术具有重大的实际意义。