Landfill Construction and Capacity Expansion

We study the optimal capacity and lifetime of landfills taking into account their sequential nature.Such an optimal capacity is characterized by the so-called Optimal Capacity Condition.Particular versions of this condition are obtained for two alternative settings: first, if all the landfills are to have the same capacity, and second, if each of them is allowed to have a different capacity.In the second case we obtain an Optimal Control problem, with mixed elements of both continuous and discrete time.The resulting optimization problems involve dividing a time horizon of planning into several subintervals of endogenously decided length.The results obtained may be useful to address other economic problems such as private and public investments, consumption decisions on durable goods, etc.investements;resources;capacity;costs

On Recycling and Technological Externalities

recycling;natural resources;production set;externalities

The October 1979 Change in the Monetary Regime: Its Impact on the "Forecastability" of Interest Rates

Subsequent to the October 1979 shift in monetary policy in the United States, interest rates in North America not only reached unprecedented levels,but also exhibited unprecedented volatility. This paper shows that the anticipated quarterly changes in long-term rates associated with the rational expectations model have remained small during this post-shift period. Recorded forecasts of long-term interest rates in Canada continue to prove inferior to the no-change prediction of the martingale model. The "perverse" relationship between the slope of the yield curve and the subsequent movementin long-term rates exists in the Canadian data, but is of only modest value in a forecasting context. The excess return on long-term bonds implicit in the recorded forecasts of the level of interest rates varies sharply, yet there is no evidence that forecasters have identified a predictable component of a time-varying term premium.

Ada in AI or AI in Ada. On developing a rationale for integration

The use of Ada as an Artificial Intelligence (AI) language is gaining interest in the NASA Community, i.e., by parties who have a need to deploy Knowledge Based-Systems (KBS) compatible with the use of Ada as the software standard for the Space Station. A fair number of KBS and pseudo-KBS implementations in Ada exist today. Currently, no widely used guidelines exist to compare and evaluate these with one another. The lack of guidelines illustrates a fundamental problem inherent in trying to compare and evaluate implementations of any sort in languages that are procedural or imperative in style, such as Ada, with those in languages that are functional in style, such as Lisp. Discussed are the strengths and weakness of using Ada as an AI language and a preliminary analysis provided of factors needed for the development of criteria for the integration of these two families of languages and the environments in which they are implemented. The intent for developing such criteria is to have a logical rationale that may be used to guide the development of Ada tools and methodology to support KBS requirements, and to identify those AI technology components that may most readily and effectively be deployed in Ada

School effects on student achievement in Nigeria and Swaziland

This paper provides evidence regarding the effects of schools, teachers and teaching processes on enhancing eighth grade mathematics achievement in Nigeria and Swaziland. A principal conclusion is that the achievement of students in both countries was significantly affected by the school/classroom in which they were enrolled, once effects of family characteristics were controlled. However, the specific school and classroom level variables accounting for these differences were not the same in both countries. Explanations for these between country differences could be both methodological or substantive. The study does, however, show that differences in achievement not attributable to student family background are largely due to differences in teaching quality (the teacher's use of time for lecturing, testing etc.). Teacher effectiveness depends upon finding the appropriate mix of alternative uses of instructional time. Since this seems to differ according to locale, more local research on teaching quality is needed.Teaching and Learning,Gender and Education,Primary Education,Educational Sciences,Health Monitoring&Evaluation

Approximating the radiatively corrected Higgs mass in the Minimal Supersymmetric Model

To obtain the most accurate predictions for the Higgs masses in the minimal supersymmetric model (MSSM), one should compute the full set of one-loop radiative corrections, resum the large logarithms to all orders, and add the dominant two-loop effects. A complete computation following this procedure yields a complex set of formulae which must be analyzed numerically. We discuss a very simple approximation scheme which includes the most important terms from each of the three components mentioned above. We estimate that the Higgs masses computed using our scheme lie within 2 GeV of their theoretically predicted values over a very large fraction of MSSM parameter space.Comment: 31 pages, 10 embedded figures, latex with psfig.sty the complete postscript file of this preprint, including figures, is available via anonymous ftp at ftp://www-ttp.physik.uni-karlsruhe.de/ttp95-09/ttp95-09.ps or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints

Performing an Environmental Tax Reform in a regional Economy. A Computable General Equilibrium

We use a Computable General Equilibrium model to simulate the effects of an Environmental Tax Reform in a regional economy (Andalusia, Spain).The reform involves imposing a tax on CO2 or SO2 emissions and reducing either the Income Tax or the payroll tax of employers to Social Security, and eventually keeping public deficit unchanged.This approach enables us to test the so-called double dividend hypothesis, which states that this kind of reform is likely to improve both environmental and non-environmental welfare.In the economy under analysis, an employment double dividend arises when the payroll tax is reduced and, if CO2 emissions are selected as environmental target, a (limited) strong double could also be obtained.No double dividend appears when Income Tax is reduced to compensate the environmental tax.environmental tax;general equilibrium;regional economics;tax reform;dividends