C8051F020单片机及其在双频激电仪中的应用

文章通过分析双频激电仪中存在的缺陷,引入了美国Cygnal公司推出的C8051F020单片机,并对该单片机的功能和特点进行了应用性探讨,给出了在双频激电仪中采用C8051F020单片机的系统设计构成。     

The economic role of Russia's subsistence agriculture in the transition process

In this article, we analyze the role of subsistence‐oriented agriculture in Russia in the 1990s. We start out by discussing the diverging economic effects of the growth of subsistence agriculture in Russia since the transition process started. The quantitative analysis of this sector's role is carried out by means of an applied computable general equilibrium (CGE) model applying a 1994 social accounting matrix (SAM) as base year data. The novelty of the article is to disaggregate primary agricultural production not by products but by farm types, which enables us to distinguish their institutional and economic characteristics. The model also explicitly differentiates between marketed and subsistence consumption or formal and informal marketing activities of agricultural producers. We simulate two ex post and two ex ante experiments. The results of the first backward‐looking experiment highlight that Russia's subsistence agriculture was an important buffer against further agricultural output declines during transition and, hence, against food insecurity. A simulation, which looks into the effects of a devaluation of the Russian ruble, shows that the financial crisis should have increased the relative competitiveness particularly of large‐scale crop farms versus small‐scale farms. Two forward‐looking experiments indicate that efficiency enhancing institutional change would benefit both large‐scale and small‐scale farms. However, within small‐scale agriculture, a shift from subsistence to commercial agriculture would take place.     

C程序设计中缓冲区溢出问题

C语言对数组边界不进行检查，这容易导致缓冲区溢出，可能使程序运行失败、死机，甚至被利用或攻击。本文分析了在C程序设计中存在的缓冲区溢出问题和潜在的危险性，提出了自己的看法。     

Teacher sorting, teacher quality, and student composition

Using panel data for Norwegian schools, we establish a two-equation supply and demand model for teachers with approved education. Taking into account nationally determined teacher pay and a strict teacher appointment rule, the data enable us to separately estimate supply and demand functions for certified teachers. The results clearly indicate that the student body composition, and in particular students belonging to ethnic minorities, influences both teacher supply and teacher demand. The implied negative relationship between excess demand for certified teachers and the share of minority students is likely to be important for teacher quality.     

The Incremental Predictive Information Associated with Using Theoretical New Keynesian DSGE Models vs. Simple Linear Econometric Models*

In this paper we construct output gap and inflation predictions using a variety of dynamic stochastic general equilibrium (DSGE) sticky price models. Predictive density accuracy tests related to the test discussed in Corradi and Swanson [Journal of Econometrics (2005a), forthcoming] as well as predictive accuracy tests due to Diebold and Mariano [Journal of Business and Economic Statistics (1995) , Vol. 13, pp. 253–263]; and West [Econometrica (1996) , Vol. 64, pp. 1067–1084] are used to compare the alternative models. A number of simple time‐series prediction models (such as autoregressive and vector autoregressive (VAR) models) are additionally used as strawman models. Given that DSGE model restrictions are routinely nested within VAR models, the addition of our strawman models allows us to indirectly assess the usefulness of imposing theoretical restrictions implied by DSGE models on unrestricted econometric models. With respect to predictive density evaluation, our results suggest that the standard sticky price model discussed in Calvo [Journal of Monetary Economics (1983), Vol. XII, pp. 383–398] is not outperformed by the same model augmented either with information or indexation, when used to predict the output gap. On the other hand, there are clear gains to using the more recent models when predicting inflation. Results based on mean square forecast error analysis are less clear‐cut, although the standard sticky price model fares best at our longest forecast horizon of 3 years, it performs relatively poorly at shorter horizons. When the strawman time‐series models are added to the picture, we find that the DSGE models still fare very well, often outperforming our forecast competitions, suggesting that theoretical macroeconomic restrictions yield useful additional information for forming macroeconomic forecasts.     

The Analysis of Welfare Effects of an Environmental Product Tax: An Application to the Taxation of Car Tyres in Hungary

A sophisticated welfare analysis developed by Morris and Kis (1996) is presented here for the study of the effect of a product charge tax on the car tyre market in Hungary. The analysis is extended and complemented in this paper by, first, using the AIDS model and an algorithm developed by Galarraga and Markandya (2000) to estimate demand elasticities from limited data and, second, including the income effects into the analysis. The latter does not have much impact on the results but the generalisation of the model might be useful for the analysis of different goods where the proportion of income spent on them is more important.     

Inverse of the Berge maximum theorem

Summary We consider an inverse of the Berge maximum theorem. We also give an application of our result to fixed point theory.     

Product and country substitution in imports: An empirical comparison of theoretical concepts

Product and Country Substitution in Imports: An Empirical Comparison of Theoretical Concepts. — The paper focuses on the shortcomings of current unit-values based measures for estimating product and country substitution in imports. The results of the bilateral index number technique in measuring changes in the country composition or product mix of imports were found to be inadequate, which was shown in an analysis of data on the French import market for chairs. An improved technique is briefly summarized, and its applicability compared with the bilateral index number technique. The new method performed accurately and provided a reliable basis for a refined analysis of changes within import markets.     

220KV线路微机保护器的运行与维护

随着220KV微机线路保护的广泛应用,微机线路保护的一些缺陷也开始逐渐显现出来。本文针对微机线路经常出现的一些故障和缺陷,提出了在220kv微机保护运行管理中要注意的一些问题。     

An extremely simple proof of the K-K-M-S Theorem

Summary.  An extremely simple proof of the K-K-M-S Theorem is given involving only Brouwer’s fixed point theorem and some elementary calculus. A function is explicitly given such that a fixed point of it yields an intersection point of a balanced collection of sets together with balancing weights. Moreover, any intersection point of a balanced collection of sets together with balancing weights corresponds to a fixed point of the function. Furthermore, the proof can be used to show -balanced versions of the K-K-M-S Theorem, with -balancedness as introduced in Billera (1970). The proof makes clear that the conditions made with respect to by Billera can be even weakened. Received: January 22, 1996; revised version June 9, 1996