科研成果

The mode identification principles, mode structures, and propagation characteristics of electromagnetic modes in a metal cylindrical waveguide coated with an inside layer of lossy dielectric have been investigated for gyro-traveling-wave-tube applications. For the first time, the loss-induced modal transition is revealed, in which the dispersion curves of a pair of nearby modes cross each other, and their mode structures interchange. The relations among the dispersion curves, mode structures, and propagation attenuations are also presented. The distinctive discriminations of propagation properties between different modes enable us to explore many promising applications using lossy dielectric-coated waveguides.

This paper considers foreign asset holdings and macroeconomic policies in a finite-horizon model with real balances and foreign asset holdings in a small open economy. Both the long- and short-run effects of these macroeconomic policies on the economy are reexamined. The main results stand in striking contrast to those of Obstfeld (1981), who used an endogenous time preference. (1) Foreign exchange intervention leads to more foreign asset holdings and more consumption in the long run. However, it affects foreign asset accumulation ambiguously. (2) Inflation results in more foreign asset accumulation and consumption, but the effect of inflation on real balance holdings is ambiguous. (3) Government spending affects foreign asset accumulation ambiguously, and it always reduces real balances and crowds out private consumption.

With the introduction of Marshallian recursive preferences to the Sidrauski model, this paper re-examines the effects of monetary growth on the economy. It is found that an increase in the monetary growth rate decreases the steady-state value of capital stock, consumption, and real balance holding. Short-run analysis presents the mechanism that inflation affects the economy: An increase in the monetary growth rate leads to an increase of initial consumption and reduction of initial savings, which increases the instantaneous time preference rate and makes people less patient initially. Finally, Friedman's optimal monetary growth rule is also investigated in this paper.