ℒ2-Gain of double integrators with saturation nonlinearity

This note uses quadratic surface Lyapunov functions (SuLFs) to efficiently check if a double integrator in feedback with a saturation nonlinearity has ℒ2-gain less than γ > 0. We show that for many such systems, the ℒ2-gain is nonconservative in the sense that this is approximately equal to the lower bound obtained by replacing the saturation with a constant gain of 1. These results allow the use of classical analysis tools like µ-analysis or integral quadratic constraints to analyze systems with double integrators and saturations, including servo systems like some mechanical systems, satellites, hard disks, compact disk players, etc

Population persistence under advection-diffusion in river networks

An integro-differential equation on a tree graph is used to model the evolution and spatial distribution of a population of organisms in a river network. Individual organisms become mobile at a constant rate, and disperse according to an advection-diffusion process with coefficients that are constant on the edges of the graph. Appropriate boundary conditions are imposed at the outlet and upstream nodes of the river network. The local rates of population growth/decay and that by which the organisms become mobile, are assumed constant in time and space. Imminent extinction of the population is understood as the situation whereby the zero solution to the integro-differential equation is stable. Lower and upper bounds for the eigenvalues of the dispersion operator, and related Sturm-Liouville problems are found, and therefore sufficient conditions for imminent extinction are given in terms of the physical variables of the problem

Essentials for sustainable urban transport in Brazil's large metropolitan areas

Before financing major urban transport projects, decisionmakers should attempt to put in place the basic elements for long-term sustainability of the sector. Specifically, the author contends that each large metropolitan area in Brazil should incorporate into its urban transport strategy, and pursue vigorously, the following four-point agenda: 1) create a regional transport coordination commission in charge of coordinating policies among federal, state, and municipal governments, giving highest priority to major urban transport investments in the metropolitan region and promoting modal integration - all to the end of improving the sector's economic efficiency and long-term sustainability; 2) adopt an integrated land use, urban transport, and air quality strategy that provides a framework in which the community and decisionmakers can evaluate future urban transport investments and policies; 3) enact into law formal financing mechanisms that would ensure that long-run variable costs of urban transport systems are covered by operating and non-operating revenues from the systems and by appropriate user charges; and 4) promote private sector participation in the operation, maintenance, and construction of urban transport systems - through concessions or management contracts - as a way to lessen the financial burden on the government.Roads&Highways,Public Sector Economics&Finance,Banks&Banking Reform,Municipal Financial Management,Environmental Economics&Policies,Urban Transport,Banks&Banking Reform,Roads&Highways,Municipal Financial Management,Environmental Economics&Policies

Breakdown and asymptotic properties of resampled estimates

In this paper we study the breakdown and asymptotic properties of resampled t-estimates. We find that they retain the finite breakdown point of the exact estimator. We also study their consistency and their order of convergence under nonstandard assumptions on the loss functions

Negative Stereotypes and Willingness to Change Them: Testing Theories of Discrimination in South Africa

This paper proposes a new test to distinguish between the two leading theories of discrimination: preference versus information. Discrimination based on preferences occurs when people behave as if they refuse to change their stereotypes about the capabilities of discriminated individuals. Those who discriminate based on information are willing to alter their stereotypes. Using data from a quasi-experiment in South Africa, I test for discrimination against women and non-whites. The preliminary results show no discrimination against the former. In the case of racial discrimination, players' stereotypes benefit non-whites instead of white opponents, but they are reluctant to change their impression for the former. However, they are willing to change their initial impression about white opponents. This has severe implications about the permanency of affirmative action policies.

Job market signals and signs

What happens to job market signaling under two-dimensional asymmetric information? With 2 types of productivity and noise, the equilibrium remains separating if an extended single-crossing condition is satisfied. If not, there are partially pooling equilibria where only extreme types can be distinguished, and supplementary information is needed. On-the-job interaction gives employers private information on productivity, which employment relationships may reveal to the market. While sticky wages lead to public revelation of this private information through dismissals, flexible wages do not, allowing employers to do cream skimming. Beyond the 2x2 case, employment relationships are always a noisy sign, so education is valuable as a life-time job market signal for high-ability workers.two-dimensional asymmetric information, private information, informational rents, single-crossing, signals, signs

Reforming the urban transport sector in the Rio de Janeiro metropolitan region - a case study in concessions

The author describes a bold effort by the state government to increase private sector participation in Rio de Janeiro's urban transport sector, reduce heavy operating subsidies, and establish a foundation for making the sector sustainable. This effort was undertaken with the help of three World Bank-financed loans: * The Rio de Janeiro Metropolitan Transport Loan, which provided assistance for the transfer of federally owned suburban railways to the state government. * The Rio de Janeiro State Reform and Privatization Loan, which helped the state privatize and grant concessions for a number of its enterprises. * The Rio de Janeiro Mass Transit Loan, which supported the reorganization of the sector and the concession of the Rio suburban railways (Flumitrens). Most of the reforms in the urban transport sector have been implemented. The lessons learned from implementation and the results obtained so far suggest that political decisiveness, transparency, and ingenuity in developing incentives are crucial to privatizing urban rail transport systems. But the state also learned that not having a credible staff redundancy program might seriously reduce the benefits expected from concessions.Banks&Banking Reform,Municipal Financial Management,Economic Adjustment and Lending,Roads&Highways,Decentralization,National Governance,Banks&Banking Reform,Municipal Financial Management,Urban Transport,Roads&Highways