PLC和软启动器在水电厂油压装置控制系统设计中的应用

针对由普通继电器和接触器构成的油压装置系统在运行中存在的主要问题,结合白石窑水电厂实际情况,提出了以可编程逻辑控制器(PLC)和软启动器为核心的油压装置系统改造方案.介绍了系统的基本配置和软、硬件设计.实践表明,该系统可靠性高、成本低、易于安装和维护.     

二滩水电厂发电机变压器组吸收线路无功最大容量计算

根据二滩水电厂发电机低励限制曲线,计算出发电机通过主变吸收线路无功的最大值,并对计算结果与实际值的偏差进行了处理,得到了理想的效果,可以用于估算电厂的无功平衡.在水库枯水期,对优化机组运行方式、节能增发有一定的指导意义.     

A sequential purchasing power parity test for panels of large cross-sections and implications for investors

In this paper we use monthly time series data for not less than 64 countries and a new sequential approach to test for purchasing power parity (PPP). The results are strong in that the evidence in favor of PPP is very weak. In fact, for the US-dollar-based exchange rates the evidence is basically non-existent. In order to eliminate the effect of the base currency, we also apply the sequential PPP test to all pairs of exchange rates, and find similarly weak evidence of PPP. However, for those rates where evidence is found, using a technical trading rule, we find evidence of significant profits. The predictability of the stationary pairs is therefore important for investors.     

以找矿突破战略行动推动地勘单位的转型发展──以中国冶金地质总局中南局为例

国家实施的找矿突破战略行动为国有地勘单位的转型发展提供了战略机遇,中国冶金地质总局中南局通过厘清发展思路、明确发展目标,努力在参与找矿突破战略行动中实现转型发展。发展理念上做到重视地质成果价值最大化、重视调整产业结构和转变发展方式;实施行动中注重管理创新、技术创新和人才培养模式创新。实现跨越式发展过程中,以资源整合为契机,以整装勘查、老矿山深部找矿等项目为切入点,以重要成矿区为工作重点;以新疆西天山、广西大瑶山勘查开发基地建设为核心,实现矿业权价值最大化,努力实现矿产勘查开发战略目标;加大矿业权获取力度,做好矿业权维护工作,盘活现有矿业权资产,实现矿业权价值最大化。     

Forecasting with preliminary data: a comparison of two methods

This study examines two alternate methods, a vector autoregression error correction model and a state space model, to forecast revised United States trade balance figures. Both these methods incorporate preliminary and revised trade data. The results obtained from these methods were compared to the benchmark forecasts generated by revised-data-only models. This Study finds that the state space model performs worse than the benchmark. The vector autoregression model performs better than the benchmark only in the one-step forecast. These results indicate that incorporating preliminary data may not be useful in forecasting the revised data.     

Museum and monument attendance and tourism flow: a time series analysis approach

This article takes a time-series analysis approach to evaluate the directions of causality between tourism flows, on the one side, and museum and monument attendance, on the other. We consider Italy as a case study, and analyse monthly data over the period January 1996 to December 2010. All the considered series are seasonally integrated, and co-integration links emerge. We focus on the error-correction mechanism among co-integrated time series to detect the directional link(s) of causality. Clear-cut results emerge: bi-directional causality exists in the long-run dynamics, but it is the long-run dynamics of visits to museums and monuments that mainly adjust to tourism variables (arrivals, overnights, average stays). In the short run, there are some causal effects going from the cultural sites’ attendance to tourism dynamics. The nonstationary nature of time series, their co-integration relationships and the direction of causal links suggest specific implications for tourism and cultural policies.     

Comparisons of robust tests for shifts in trend with an application to trend deviations of real exchange rates in the long run

We study the finite sample properties of tests for structural changes in the trend function of a time series that do not require knowledge of the degree of persistence in the noise component. The tests of interest are the quasi-Feasible Generalized Least Squares (FGLS) procedure by Perron and Yabu (2009b Perron, P and Yabu, T. 2009b. Testing for shifts in trend with an integrated or stationary noise component. Journal of Business and Economic Statistics, 27: 369–96. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) and the weighted average of the regression t-statistics by Harvey et al. (2009 Harvey, DI, Leybourne, SJ and Taylor, AMR. 2009. Simple, robust, and powerful tests of the breaking trend hypothesis. Econometric Theory, 25: 995–1029. [Crossref], [Web of Science ®] , [Google Scholar]), both of which have the same limit distribution whether the noise component is stationary or has a unit-root. We analyse the finite sample size and power properties of these tests under a variety of Data-Generating Processes (DGPs). The results show that the Perron–Yabu test has greater power overall. With respect to the size, the Harvey–Leybourne–Taylor test exhibits larger size distortions unless a moving-average component is present. Using the Perron and Yabu procedure to test for structural changes in the trend function of long-run real exchange rates with respect to the US dollar indicates that for 17 out of 19 countries, the series have experienced a shift in trend since the late nineteenth century.     

Coordination versus flexibility in wage formation: a focus on the nominal wage impact of productivity in Germany,Greece, Ireland,Portugal, Spain and the United States

Wage coordination between countries of the European Monetary Union (EMU) aims at aligning nominal wage growth with labour productivity growth at the national level. We analyse the developments in Germany, the EMU’s periphery countries Greece, Ireland, Portugal and Spain along with the United States over the period 1980 to 2010. Apart from the contribution of productivity to nominal wages, we take into account the contributions of prices, unemployment, replacement rates and taxes by means of an econometrically estimated nonlinear equation resulting from a wage bargaining model. We further study the downward rigidities of nominal wages. The findings show that in past times of low productivity, price inflation and reductions in unemployment still put significant upward pressure on nominal wage growth. The periphery countries are far from aligning nominal wage growth with productivity growth. German productivity is a major wage determinant, but surely not the only one. Within the context of a free bargaining process between employers and labour unions, policy-makers can effectively use the replacement rate to steer the nominal wages outcome.     

Testing uncovered interest rate parity using LIBOR

We test uncovered interest rate parity (UIP) using London InterBank Offered Rate (LIBOR) interest rates for a wide range of maturities. In contrast to other markets, LIBOR markets have minimal frictions. Whereas most previous studies reject UIP, we find that UIP holds for several short-term LIBOR maturities using block bootstrap panel unit root tests suggested by Palm et al. (2011) and cointegration techniques by Westerlund (2007). Furthermore, the estimation results suggest that the speed of adjustment to the long-run equilibrium marginally differs across the maturity of the underlying instrument, thus supporting the efficient market hypothesis.     

Do the Spanish regions converge? A unit root analysis for the HDI of the Spanish regions

This article studies the possible stochastic convergence between the Spanish regions in 1980–2010. The application of unit root techniques to the new Human Development Index recently calculated in Herrero et al. (2013) allows us to show that the evolution of the Spanish economy can be better understood as the sum of divergent forces rather than as a group of convergent regions. Similar conclusions can be drawn when the per capita GDP is used, although these two variables exhibit different patterns of behaviour at the end of the sample. Finally, we also observe that the distance between northern and southern regions has increased since 2000.