Foundations in the Washington, DC Region: The Puzzle of a Modest-size Foundation Sector in a Wealthy Area

This paper offers a portrait of the Washington, D.C. foundation sector, addressing its relatively modest size and activity. Looks at factors that shape activity, and includes recommendations for the future. Includes data on giving, assets, and the region's nonprofit sector as a whole. With bibliographical references

Compelled to do the right thing

We use a model of opinion formation to study the consequences of some mechanisms attempting to enforce the right behaviour in a society. We start from a model where the possible choices are not equivalent (such is the case when the agents decide to comply or not with a law) and where an imitation mechanism allow the agents to change their behaviour based on the influence of a group of partners. In addition, we consider the existence of two social constraints: a) an external authority, called monitor, that imposes the correct behaviour with infinite persuasion and b) an educated group of agents that act upon their fellows but never change their own opinion, i.e., they exhibit infinite adamancy. We determine the minimum number of monitors to induce an effective change in the behaviour of the social group, and the size of the educated group that produces the same effect. Also, we compare the results for the cases of random social interactions and agents placed on a network. We have verified that a small number of monitors are enough to change the behaviour of the society. This also happens with a relatively small educated group in the case of random interactions.Comment: 8 pages, 9 figures, submitted to EPJ

A simplex-like search method for bi-objective optimization

We describe a new algorithm for bi-objective optimization, similar to the Nelder Mead simplex algorithm, widely used for single objective optimization. For diferentiable bi-objective functions on a continuous search space, internal Pareto optima occur where the two gradient vectors point in opposite directions. So such optima may be located by minimizing the cosine of the angle between these vectors. This requires a complex rather than a simplex, so we term the technique the \cosine seeking complex". An extra beneft of this approach is that a successful search identifes the direction of the effcient curve of Pareto points, expediting further searches. Results are presented for some standard test functions. The method presented is quite complicated and space considerations here preclude complete details. We hope to publish a fuller description in another place

General Aviation Landing Flare Instructions

The present paper discusses the ability to determine low altitudes and challenges the effectiveness of current general aviation landing flare instructions. Conclusions are based on literary review from a variety of sources such as general aviation flight instruction manuals, aviation literature, and scientific publications. Key findings suggest that current flare instructions are inconsistent, ambiguous, and of limited helpfulness to pilots wishing to learn how to determine altitude before initiating the landing flare