Discrete Physics and the Dirac Equation

We rewrite the 1+1 Dirac equation in light cone coordinates in two significant forms, and solve them exactly using the classical calculus of finite differences. The complex form yields ``Feynman's Checkerboard''---a weighted sum over lattice paths. The rational, real form can also be interpreted in terms of bit-strings.Comment: LaTex 16 pages, 10 figures. To obtain a copy, send e-mail to [email protected]

Continuous detonation reaction engine

Reaction engine operates on the principles of a controlled condensed detonation rather than on the principles of gas expansion. The detonation results in reaction products that are expelled at a much higher velocity

Development of detonation reaction engine

Reaction engine operates on the principle of a controlled condensed detonation. In this engine the gas products that are expelled from the engine to produce thrust are generated by the condensed detonation reaction. The engine is constructed of two basic sections consisting of a detonation wave generator section and a condensed detonation reaction section

The Political Economy of Exchange Rate Policy in Latin America: An Analytical Overview

Exchange rates have been central to the course of economic development in Latin America for decades. From the heyday of import substitution in the 1960s to the rapid expansion of foreign debt in the 1970s, from the debt crisis and its troubled aftermath in the 1980s to the rekindling of growth and borrowing in the 1990s, the exchange rate has been crucial to the mix of government policies that has shaped the region. Indeed, many analysts regard exchange rate policy as a major determinant of other economic outcomes, such as adjustment to the oil shocks of the 1970s and the debt crisis of the 1980s (Sachs, 1985). And currency policies have themselves been at the center of some of the regions most prominent economic processes and events, such as liberalizing reforms in the Southern Cone between 1976 and 1982, the Mexican crises of 1982 and 1994, Argentinas adoption of a currency board in 1991, Brazils 1999 currency crisis, and ongoing discussions of dollarization.

A design procedure and handling quality criteria for lateral directional flight control systems

A practical design procedure for aircraft augmentation systems is described based on quadratic optimal control technology and handling-quality-oriented cost functionals. The procedure is applied to the design of a lateral-directional control system for the F4C aircraft. The design criteria, design procedure, and final control system are validated with a program of formal pilot evaluation experiments

Evolución de la concentración urbana en todo el mundo: un enfoque de panel

(Disponible en idioma inglés únicamente) En este trabajo empleamos un enfoque de panel para estudiar el crecimiento de la población en las principales ciudades del mundo. Hallamos que las principales ciudades crecen con mayor rapidez en economías relativamente atrasadas y en economías más inestables y de crecimiento más rápido. También hallamos que los efectos de las políticas del comercio sobre el crecimiento de ciudades importantes depende considerablemente de la geografía. Mientras que el crecimiento demográfico en importantes ciudades ubicadas en puertos o cerca de ellos no cambia tras un repunte de los flujos de comercio, el crecimiento demográfico en ciudades importantes tierra adentro sí tiende a desacelerarse luego del mismo hecho. Por otro lado, no hallamos efecto alguno del régimen político sobre el crecimiento demográfico de ciudades importantes. Por último, hallamos algunos elementos de prueba de que, si todo lo demás se mantiene igual, las ciudades de mayor tamaño tienden a crecer a un menor ritmo.

Elections and the Timing of Devaluations

This paper presents a rational political budget cycle model for the open economy, in which devaluations are delayed in the run-up to elections, in order to increase the electoral chances of the party in office. By concentrating on the closed economy, previous political cycle models had overlooked the influence of elections on the behavior of exchange rates. We introduce voter uncertainty in two different dimensions. Not only are voters uncertain regarding the competency of the incumbent. They also ignore the degree to which the incumbent is opportunistic, i.e. willing to distort the economy for electoral gain. When there is only uncertainty about competence, we obtain a separating equilibrium, like in the previous political budget cycle literature. However, when uncertainty about opportunism is introduced, a partially pooling equilibrium emerges: an incompetent, opportunistic incumbent delays a devaluation until after elections, mimicking a competent incumbent, while the competent does not distort the optimal pattern of the exchange rate, regardless of the degree of opportunism. The model's prediction that there is a tendency to delay devaluations until after elections is used to look at the empirical evidence on devaluations around elections.devaluations, elections, political budget cycles, incomplete information.

Radon gas, useful for medical purposes, safely fixed in quartz

Radon gas is enclosed in quartz or glass ampules by subjecting the gas sealed at a low pressure in the ampules to an ionization process. This process is useful for preparing fixed radon sources for radiological treatment of malignancies, without the danger of releasing radioactive gases