On-line costate integration for nonlinear control

The optimal feedback control of nonlinear chemical processes, specially for regulation and set-point changing, is attacked in this paper. A novel procedure based on the Hamiltonian equations associated to a bilinear approximation of the dynamics and a quadratic cost is presented. The usual boundary-value situation for the coupled state-costate system is transformed into an initial-value problem through the solution of a generalized algebraic Riccati equation. This allows to integrate the Hamiltonian equations on-line, and to construct the feedback law by using the costate solution trajectory. Results are shown applied to a classical nonlinear chemical reactor model, and compared against standard MPC and previous versions of bilinear-quadratic strategies based on power series expansions.Fil: Costanza, Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Neuman, C.. Universidad Nacional del Litoral; Argentin

Partial Differential Equations for Missing Boundary Conditions in the Linear-Quadratic Optimal Control Problem

New equations involving the unknown final states and initial costates corresponding to families of LQR problems are found, and their solutions are computed and validated. Having the initial values of the costates, the optimal control can then be constructed, for each particular problem, from the solution to the Hamiltonian equations, now achievable through on-line integration. The missing boundary conditions are obtained by solving (offline) two uncoupled, first-order, quasi-linear, partial differential equations for two auxiliary n × n matrices, whose independent variables are the timehorizon duration T and the final-penalty matrix S. The solutions to these PDEs give information on the behavior of the whole two-parameter family of control problems, which can be used for design purposes. The mathematical treatment takes advantage of the symplectic structure of the Hamiltonian formalism, which allows to reformulate one of Bellman's conjectures related to the “invariantimbedding” methodology. Results are tested against solutions of the differential Riccati equations associated with these problems, and the attributes of the two approaches are illustrated and discussed.Fil: Costanza, Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Neuman, C. E.. Universidad Nacional del Litoral; Argentin

Come on, Come on, Do the Loco-Motion

This themed issue of Preventive Medicine comprises articles following our call for papers on Self-Transportation, Public Transportation, and Health. Prevention-wise, the logic is that using self- or public transportation is likely to increase physical activity and counter the overall trend toward obesity that most populations of the world are now experiencing. The problem is that in countries for which data are available, both the cycling fraction of road traffic and the number of miles walked are declining (Dora, 1999; Haines et al., 2000). The harvest of papers has been rewarding. They show how far we currently are in the process of assembling evidence in support of the self/public transportation and health connection, but they also reflect the deficits in the experimental evidence needed to demonstrate that improving access to public transportation and modifying the built environment to stimulate walking and biking are going to make a meaningful difference in terms of public health

International Variability in Ages at Menarche, First Livebirth, and Menopause

The occurrences and timing of reproduction-related events, such as menarche, first birth, and menopause, play major roles in a woman's life. There is a lack of comparative information on the overall patterns of the ages at and the timing between these events among different populations of the world. This study describes the variability in reproductive factors across populations in Europe, the Americas, Asia, Australia, and Africa. The study sample consisted of 18,997 women from 13 centers in 11 countries interviewed between 1979 and 1988 who comprised the control group in a World Health Organization international, multicenter case-control study of female cancers. All were surveyed with the same questionnaire and methodology. Overall, a typical woman in this study reached menarche at age 14 years and delivered her first live child 8 years later, at age 22. She was 50 years old at natural menopause and had had 36 years of reproductive life. The median ages at menarche varied across centers from 13 to 16 years. For all centers, the median age at first livebirth was 20 or more years, with the largest observed median (25 years) occurring in China. The median delay from menarche to first livebirth ranged from 5 to 11 years. Among the centers, the median age at natural menopause ranged between 49 and 52 years. In most populations, younger women had a first birth at a later age than did older women. This tendency was more accentuated in some populations. These results reveal, perhaps for the first time, the variability of reproductive histories across different populations in a large variety of geographic and cultural settings. Except for menopause, international variability is substantial for both biologically related variables (age at menarche) and culturally related variables (age at first birth). There is a generational effect, characterized by more variability of age at first birth and delay to first birth in the younger than in the older generations. Am J Epidemiol 1998;148:1195-120

What should be done with the revenues from a carbon cap and auction system?

In this article the author discusses the use of the revenues which can be generated from a carbon cap and auction system in the U.S. They believe that auction system will be politically feasible if all individuals share generated revenues equally. A significant fraction from the revenue should pay for related projects like researching and developing renewable energy in developing countries. The shareholders in this atmospheric commons should be both the current and future generations

Experimental approach to measuring functional food consumption for risk factor surveillance

Abstract Objective To develop and integrate the assessment of functional foods (FuF; manufactured foods with altered composition carrying a health claim) consumption into an existing risk factor surveillance system. Design FuF market research followed by an experimental FuF intake study incorporated into an ongoing community-based survey. Concurrent completion of a self-administered semi-quantitative FFQ and a self-administered, qualitative FuF frequency questionnaire (FuFFQ) followed by a face-to-face control step using FuF photographs and combined food group-based data analyses. Setting ‘Bus Santé' risk factor surveillance programme, Geneva/Switzerland. Subjects Population-based random sample of 639 residents (52 % women, aged 35-74 years) surveyed from September 2003 to April 2004. Results Local Geneva/French neighbourhood market research identified 148 FuF in five major FuF food groups which were compiled into a functional ingredient database. Prior to the face-to-face verification, 210 (33 %) individuals categorized themselves as FuF consumers, 429 (67 %) as non-consumers. The control step revealed that 70 % of the 639 participants were already familiar with the FuF concept, and thus were correctly self-categorized as FuF consumers or non-consumers. For the remaining 30 % of participants the true FuF consumption status was established, resulting in a final number of 285 FuF consumers (45 %; 12 % net increase) and 354 (55 %) non-consumers. Conclusions The developed self-administered, brief, qualitative food group-based FuF frequency check list in combination with an FFQ and a photo-assisted control step provides a flexible assessment tool for measuring FuF consumption in the context of a specific fluctuating FuF market and may be applicable to other population settings and time