模糊自动控制理论在高速公路机电设备中的应用

文章介绍了在直流并励电动机控制中引进模糊自动控制,可以实现电动机恒流起动、恒速运行,降低电机的故障率,保障它的运行。     

Less Government—More Wealth? On the Macroeconomics of a Smaller Public Sector in Europe

In this paper, we analyze the reactions of European economies to a fiscal policy strategy aiming at diminishing the public sector. Within the framework of the MSG3 model, a macroeconomic model of the world economy, we perform several simulation experiments to explore the effects of reducing government expenditures permanently in different phases of the business cycle. For this purpose, we combine the fiscal contraction with negative and positive, Euro Area-wide and global, supply and demand shocks. It turns out that adverse Keynesian effects on output and employment tend to be mostly weak and short-lived, whereas long-run effects on output and employment are favorable. Due to these long-run effects, the fiscal contraction policy raises welfare as measured by an asymmetric quadratic objective function. The size of these welfare effects depends on the initial situation in a non-trivial manner.     

Over-savings and hyperbolic discounting

Hyperbolic discounting models are widely seen as implying that consumers do not save enough, in accordance with the observed low rates of savings of some households. This paper qualifies this view by showing that hyperbolic consumers may ‘oversave’ in the short run. The result extends to uncertainty on future income and does not depend on whether preferences are present-biased or future-biased. A generalized comparative statics analysis of self-control is introduced, and its relationship to the analysis of uncertainty on discount factors is emphasized.     

Flexible exchange rates as shock absorbers

In this paper we analyze empirically the effect of terms of trade shocks on economic performance under alternative exchange rate regimes. We are particularly interested in investigating whether terms of trade disturbances have a smaller effect on growth in countries with a flexible exchange rate arrangement. We also analyze whether negative and positive terms of trade shocks have asymmetric effects on growth, and whether the magnitude of these asymmetries depends on the exchange rate regime. We find evidence suggesting that terms of trade shocks get amplified in countries that have more rigid exchange rate regimes. We also find evidence of an asymmetric response to terms of trade shocks: the output response is larger for negative than for positive shocks. Finally, we find evidence supporting the view that, after controlling for other factors, countries with more flexible exchange rate regimes grow faster than countries with fixed exchange rates.     

Default and aggregate income

This paper studies how default varies with aggregate income. We analyze a model in which optimal contracts enable risk sharing of privately observed, idiosyncratic income by allowing for default. Default provisions allow agents with low idiosyncratic income realizations to repay less and thus provide insurance. Default penalties ensure that only these agents default. We show that default can occur under the optimal contract and that default provisions vary with aggregate income. We provide conditions such that both the amount of default and default penalties vary countercyclically with aggregate income and show that the default rate can be discontinuous.     

Short-memory equilibrium in stochastic overlapping generations economies

In stochastic OLG exchange economies, we show that short-memory equilibria—the natural extension from deterministic economies of steady states, low-order cycles, or finite state-space stationary sunspots equilibria—fail to exist generically in utilities. As a result, even with independent and identically distributed exogenous shocks there is serial correlation in endogenous economic variables in equilibrium. This arises even if utilities are time-separable, some goods inferior, and there are no technological lags. Hence, the origins of economic fluctuations can be traced only to the demographic structure of a heterogeneous agent, multiple-good economy.     

Monetary regimes and the co-ordination of wage setting

A recent literature argues that a strict monetary regime may reduce equilibrium unemployment by disciplining wage setters, as wage setters abstain from raising wages to avoid a monetary contraction. However, in this literature the wage setters are assumed not to co-ordinate their wage setting. The present paper argues that precisely because a strict monetary regime may discipline the unco-ordinated wage setting, thus lowering unemployment in the unco-ordinated outcome, it also reduces wage setters’ incentives to co-ordinate. It is shown that an accommodating monetary regime may reduce equilibrium unemployment, via the strengthening of the wage setters’ incentives to co-ordinate.     

Competitive-search equilibrium in monetary economies

Competitive search was recently introduced in monetary economics by Rocheteau and Wright [Money in search equilibrium, in competitive equilibrium, and in competitive search equilibrium, Econometrica 73 (2005) 175-203]. We extend their work by eliminating the restriction that the fees market makers charge to enter a submarket must be either non-negative or identical for buyers and sellers. Without this restriction, buyers pay a positive fee to enter the submarket they visit and nothing else when they meet a seller. Sellers are remunerated by the market makers from the entry fees collected from the buyers. This trading arrangement allows buyers to perfectly predict their expenses, so the opportunity cost of holding idle money balances is eliminated.