Mortalidad evitable y políticas en salud: Colombia, 1985-2002

Introducción: La confianza en la capacidad de evitar algunas muertes o diferir su aparición es el fundamento de toda política de salud, uno de cuyos principales resultados debe ser reducir las muertes evitables, y controlar las condiciones que aumentan el riesgo de morir. Objetivos: Establecer variaciones en la tendencia de la mortalidad evitable (ME) registrada en Colombia entre 1985 y 2002, como indicadoras del impacto efectivo que las reformas en la política sanitaria pudieran haber tenido sobre sus determinantes. Métodos: Estudio de la ME con base en los registros oficiales de defunción y en las proyecciones censales de Colombia entre 1985-2002. Para determinar la evitabilidad, se aplicó un inventario de causas de ME (ICME) ajustado a las condiciones epidemiológicas del país durante el período que se analiza. Resultados: De las muertes registradas, 75.3% se clasificaron como evitables. Se identificaron siete patrones de tendencia que reflejan, de manera particular, los efectos de las políticas públicas sobre los determinantes de la mortalidad. Conclusiones: En general, la ME viene disminuyendo en Colombia desde 1985 en la población general y entre los hombres, sin variaciones significativas durante el período. Las variaciones en la tendencia de las tasas ajustadas de varios grupos de causas hacen pensar en un deterioro en el control de sus determinantes, especialmente desde 1990. Los cambios aplicados en las políticas públicas durante los últimos años no se reflejaron en un mejor control de las muertes evitables, aunque el gasto en salud aumentó de modo muy notable en el país.

Simultaneous synthesis of heat exchanger networks with pressure recovery: optimal integration between heat and work

The optimal integration between heat and work may significantly reduce the energy demand and consequently the process cost. This paper introduces a new mathematical model for the simultaneous synthesis of heat exchanger networks (HENs) in which the pressure levels of the process streams can be adjusted to enhance the heat integration. A superstructure is proposed for the HEN design with pressure recovery, developed via generalized disjunctive programming (GDP) and mixed-integer nonlinear programming (MINLP) formulation. The process conditions (stream temperature and pressure) must be optimized. Furthermore, the approach allows for coupling of the turbines and compressors and selection of the turbines and valves to minimize the total annualized cost, which consists of the operational and capital expenses. The model is tested for its applicability in three case studies, including a cryogenic application. The results indicate that the energy integration reduces the quantity of utilities required, thus decreasing the overall cost.

MINLP Optimization Algorithm for the Synthesis of Heat and Work Exchange Networks

This paper introduces a new optimization model for the simultaneous synthesis of heat and work exchange networks. The work integration is performed in the work exchange network (WEN), while the heat integration is carried out in the heat exchanger network (HEN). In the WEN synthesis, streams at high-pressure (HP) and low-pressure (LP) are subjected to pressure manipulation stages, via turbines and compressors running on common shafts and stand-alone equipment. The model allows the use of several units of single-shaft-turbine-compressor (SSTC), as well as helper motors and generators to respond to any shortage and/or excess of energy, respectively, in the SSTC axes. The heat integration of the streams occurs in the HEN between each WEN stage. Thus, as the inlet and outlet streams temperatures in the HEN are dependent of the WEN design, they must be considered as optimization variables. The proposed multi-stage superstructure is formulated in mixed-integer nonlinear programming (MINLP), in order to minimize the total annualized cost composed by capital and operational expenses. A case study is conducted to verify the accuracy of the proposed approach. The results indicate that the heat integration between the WEN stages is essential to enhance the work integration, and to reduce the total cost of process due the need of a smaller amount of hot and cold utilities.

MINLP Model for the Synthesis of Heat Exchanger Networks with Handling Pressure of Process Streams

This paper introduces a new mathematical model for the simultaneous synthesis of heat exchanger networks (HENs), wherein the handling pressure of process streams is used to enhance the heat integration. The proposed approach combines generalized disjunctive programming (GDP) and mixed-integer nonlinear programming (MINLP) formulation, in order to minimize the total annualized cost composed by operational and capital expenses. A multi-stage superstructure is developed for the HEN synthesis, assuming constant heat capacity flow rates and isothermal mixing, and allowing for streams splits. In this model, the pressure and temperature of streams must be treated as optimization variables, increasing further the complexity and difficulty to solve the problem. In addition, the model allows for coupling of compressors and turbines to save energy. A case study is performed to verify the accuracy of the proposed model. In this example, the optimal integration between the heat and work decreases the need for thermal utilities in the HEN design. As a result, the total annualized cost is also reduced due to the decrease in the operational expenses related to the heating and cooling of the streams.