A methodology for the choice of the best fitting continuous-time stochastic models of crude oil price

The crude oil price is generally considered as the fundamental factor in the valuation of undeveloped reserves but it is not the unique one. Undeveloped field value also depends on the uncertainty relating to the convenience yield and the risk-free interest rate. The purpose of this paper is to decide on the best continuous-time stochastic models for these risk factors. The Generalized Method of Moments and the Maximum Likelihood Estimation are implemented to fit the parameters of continuous-time stochastic processes. The results of unit root tests without breaks reveal a mean reversion in convenience yield series. Multiple structural change tests show that the risk-free interest rate can be considered constant. The simulation of continuous-time stochastic processes and the mean error between the simulated prices and the market ones show that the Geometric Brownian Motion with jumps is the best model for the oil price compared to the other commonly used processes.     

Unemployment persistence in OECD countries after the Great Recession

The 2008 economic downturn in the United States resulted in a wave of contractionary effects across many OECD countries. This paper investigates the pattern of the unemployment persistence in the United States and other 28 OECD countries before and after the Great Recession. To detect possible changes in the pattern of unemployment persistence, we employ a mean bias-corrected estimation of the persistence parameter with a rolling window of five years. In addition, we estimate the most likely date of change in the trend function of unemployment to test whether there was any significant change in the pattern of unemployment persistence after the Great Recession. We find significant evidence of a structural break and hysteresis in unemployment rates, with a persistence parameter close to unity, across the United States and other 28 OECD countries. Besides, bootstrap permutation tests show that all half-lives and impulse response functions have significantly changed after the Great Recession. Therefore, our findings call for structural reforms aimed at improving labor market performance, to prevent upward shifts in unemployment across OECD countries from becoming permanent.     

厦门经济特区扩容背景下的城市交通战略规划探讨

在国务院批准厦门经济特区扩大到全市的背景下,结合分析厦门城市近年来交通现状的基础上,紧紧围绕“全城厦门的理念统筹城乡交通战略规划,积极推进岛内岛外交通一体化建设,构筑以公共交通为主体的可持续城市交通发展模式.     

声光双控节能灯电路设计

为解决工厂长明灯现象,设计了一种声光双控节能电路供楼道照明灯用,其功能:夜间有人上下楼时,照明灯自动点亮,灯亮后延时2～3分钟,会自动熄灭;白天照明灯受人走动的控制,灯不会点亮。整个电路由电源电路,放大电路,处理电路(声控电路、光控电路)及延时电路等部分组成。     

Assessing economic convergence in the EU: is there a perspective for the ‘cohesion countries’?

This article analyses the stochastic income convergence within the EU-15. The empirical analysis uses per capita GDP, in PPP and in constant prices of 2005 for the period 1950 to 2010. Apart from the traditional DF type tests we also account for possible structural changes. In this direction, we employ the Zivot-Andrews (1992) and the Lee-Strazicich (1999, 2003) testing procedures, for one and two breaks, endogenously determined. Furthermore, we apply the Carlino and Mills (1993) methodology proposed for the detection of β-convergence. The overall evidence supports the existence of two discrete clubs, the first by the ‘cohesion countries’ (Portugal, Ireland, Greece and Spain) and the second by the remaining members. In particular, there is a clear evidence of convergence within each club, whereas between clubs there is a luck of catching-up effects. Furthermore, investigation of correlation between relative per capita GDP of each country and several factors that are often identified as growth stimulants, namely Total Factor Productivity, FDI, investment and openness confirm, with the exception of Greece, a strong association between these factors and the convergence process. However, progress in the convergence has not been uniform across countries and over time, reflecting the specific interactions between domestic and international factors and their impact on the convergence process of individual countries.     

THE CHOICE OF CELLS IN CHI–SQUARE TESTS

The choice of cells in chi–square goodness of fit tests is a classical problem. Some recent results in this area are discussed. It is shown that the likelihood ratio of alternatives w.r.t. null distributions plays a key role when judging different procedures. The discussion centers on the case of a simple hypothesis, but location–scale models and tests of independence in contingency tables are also considered.     

Detecting nonlinearity in time series by model selection criteria

This article analyzes the use of model selection criteria for detecting nonlinearity in the residuals of a linear model. Model selection criteria are applied for finding the order of the best autoregressive model fitted to the squared residuals of the linear model. If the order selected is not zero, this is considered as an indication of nonlinear behavior. The BIC and AIC criteria are compared to some popular nonlinearity tests in three Monte Carlo experiments. We conclude that the BIC model selection criterion seems to offer a promising tool for detecting nonlinearity in time series. An example is shown to illustrate the performance of the tests considered and the relationship between nonlinearity and structural changes in time series.     

Evaluating effects of excess kurtosis on VaR estimates: Evidence for international stock indices

The calculus of VaR involves dealing with the confidence level, the time horizon and the true underlying conditional distribution function of asset returns. In this paper, we shall examine the effects of using a specific distribution function that fits well the low-tail data of the observed distribution of asset returns on the accuracy of VaR estimates. In our analysis, we consider some distributional forms characterized by capturing the excess kurtosis characteristic of stock return distributions and we compare their performance using some international stock indices. JEL Classification C15 · G10     

Cross‐sectional Restrictions on the Spot and Forward Term Structures of Interest Rates and Panel Unit Root Tests

In this paper we examine the stationarity of all the rates comprising the USD, GBP, DM and JPY spot and forward term structures. Instead of focussing on short maturity interest rates, as most other papers do, we perform a detailed analysis of the whole range of spot and forward interest rates of the 4 main currencies. We investigate the issue of stationarity within the framework of an equilibrium interest rate model such as Vasicek (1977), that defines the cross-sectional and time series properties that interest rates of various maturities must satisfy. We show that within a one-factor interest rate model, such as Vasicek, all interest rates are restricted to exhibit the same mean reverting behaviour. This restriction allows us to apply more powerful panel unit root tests. This methodology increases considerably the number of observations available and as a result the power of the unit root tests. The higher power of these tests allows us to demonstrate that there does exist mean reversion on the spot and forward US interest rates and the forward DM and GBP interest rates.     

二能级原子与光场相互作用模型的流方程解法

利用Wegner流方程方法在平均场近似下研究了二能级原子与光场相互作用系统的本征值与本征函数。由于在幺正变换下产生了新的高阶相互作用项,利用平均场近似手段得到了系统参数随流参数变化的流方程。当具有哈密顿量H(l)的流参数l→∞时,系统中的耦合项参数趋于0,非耦合项参数趋于稳定值。最后,利用流方程方法求出了原子自旋的关联函数。