“Exergy based analysis of economic sustainability”

Exergy is presented here as the physical prime-mover of economic systems, and an exergy based concept of value is proposed in this paper. The main exergy fluxes are identified as those carried by raw exergy (primary sources), raw materials, usable exergy and exergy embodied in manufactured commodities. It is shown how efficiency of exergy use is the physical basis for competitiveness and how exergy content (value)can be assigned to skillfulness and expertise. Sustainability of economic systems is analyzed in the light of competitiveness and ability to take extra exergy taken from markets. It is also shown that in competitive economies the ratio (raw exergy)/(total value) tends to decrease, therefore indicating extra exergy from the markets, and this trend is illustrated with the case of the US economy. Finally, the average electricity price in the markets was proposed as a provisional correspondence between exergy content and price of commodities

Constructal view of scaling laws of river basins

River basins are examples of naturally organized flow architectures whose scaling properties have been noticed long ago. Based on data of geometric characteristics, Horton [Horton, R.E., 1932. Drainage basin characteristics. EOS Trans. AGU 13, 350–361.], Hack [Hack, J.T., 1957. Studies of longitudinal profiles in Virginia and Maryland. USGS Professional Papers 294-B, Washington DC, pp. 46–97.], and Melton [Melton, M.A, 1958. Correlation structure of morphometric properties of drainage systems and their controlling agents. J. of Geology 66, 35–56.] proposed scaling laws that are considered to describe rather accurately the actual river basins. What we show here is that these scaling laws can be anticipated based on Constructal Theory, which views the pathways by which drainage networks develop in a basin not as the result of chance but as flow architectures that originate naturally as the result of minimization of the overall resistance to flow (Constructal Law)

“Constructal Theory: From Engineering to Physics, and How Flow Systems Develop Shape and Structure”

Constructal theory and its applications to various fields ranging from engineering to natural living and inanimate systems, and to social organization and economics, are reviewed in this paper. The constructal law states that if a system has freedom to morph it develops in time the flow architecture that provides easier access to the currents that flow through it. It is shown how constructal theory provides a unifying picture for the development of flow architectures in systems with internal flows (e.g., mass, heat, electricity, goods, and people). Early and recent works on constructal theory by various authors covering the fields of heat and mass transfer in engineered systems, inanimate flow structures (river basins, global circulations) living structures, social organization, and economics are reviewed. The relation between the constructal law and the thermodynamic optimization method of entropy generation minimization is outlined. The constructal law is a self-standing principle, which is distinct from the Second Law of Thermodynamics. The place of the constructal law among other fundamental principles, such as the Second Law, the principle of least action and the principles of symmetry and invariance is also presented. The review ends with the epistemological and philosophical implications of the constructal law

and Development, from the Individual Researcher to research Empires

This paper is dated: it was written at the time of the celebration of the 20 years of activity of the Évora Geophysics Centre (CGE). It comprises a brief appraisal of the evolution of scientific research in Europe and in the United States of America, together with a special reference to the development of the Portuguese scientific system. The size distribution of scientific teams in the whole system is addressed, and it is shown that at a state of optimal performance there is room for all team sizes ranging from the individual investigator to research empires. Similarly, we note that research dynamics evolve in time with periods of strong creation intensity that alternate with periods of extension and quiescence. We also note that the new perspectives for the European Research Area, with policies that push strongly to the development side, may be risky in the long term as they might lessen creation, which is the base for sustainability and development. Finally, we briefly address the challenges ahead both for the Portuguese scientific system and the CGE

Constructal view of the scaling laws of street networks — the dynamics behind geometry

The distributions of street lengths and nodes follow inverse-power distribution laws. That means that the smaller the network components, the more numerous they have to be. In addition, street networks show geometrical self-similarities over a range of scales. Based on these features many authors claim that street networks are fractal in nature. What we show here is that both the scaling laws and self-similarity emerge from the underlying dynamics, together with the purpose of optimizing flows of people and goods in time, as predicted by the Constructal Law. The results seem to corroborate the prediction that cities’ fractal dimension approaches 2 as they develop and become more complex

Natural flow patterns and structured people dynamics: a constructal view

Constructal theory that has been successfully applied to planetary circulations and climate and to river basin morphology is shown to provide a useful framework for describing flows of people. We showed here, with simple examples, that intuitive rules of traffic organization can be anticipated based on principle, i.e., based on the Constructal Law. In addition, and similarly to the case of flows of inanimate matter, in the case of flows of people, flow patterns emerge as a necessary consequence of reduction of global flow resistances. These flow patterns point to decreasing resistivity to flows of people and commodities. Pathway length varies inversely with resistivity while pathway number increases with resistivity

Pioneering multilateralism: the sugar agreements 1864 – 1914

This paper examines the negotiations which led to the Brussels Convention of 1902 for the abolition of subsidies on sugar exports, showing how the practice of multilateral commodity trade negotiations was an outcome of this experience. Encompassing diverse fiscal systems, these negotiations began a process of pluri-national harmonization of taxation criteria and regulations, which forced changes to national statutes. They also initiated new forms of economic negotiations and coexistence. When war broke out in 1914, undoing agreements and inaugurating a new era of strict government control of economic activities, multilateralism had been established as a conceptual alternative and a practical possibility.SUGAR TRADE; MULTILATERAL AGREEMENTS; TARIFFS; EXPORT BOUNTIES

Role of Sorption Isotherms in the Analysis of Coupled Heat and Mass Fluxes in Porous Media

The aim of this work is to show the importance of the sorption isotherms in the study of the heat and mass fluxes in unsaturated porous media. General forms of the heat and mass fluxes are presented in terms of experimentally accessible quantities. The role of the isotherm slope in the coupling of heat and mass fluxes and its influence on the effective permeability are shown. Separate relations for vapor and liquid fluxes through the porous medium are presented as functions of the temperature and the isotherm slopes. Nonstationary isothermal mass flux is also analyzed, a relaxation time for this process is identifled, and its relation to the isotherm slope is also discussed

Coal and fuel burning effects on the atmosphere as mediated by the atmospheric electric field and galactic cosmic rays flux

Abstract: Emissions into the atmosphere of Greenhouse Gases (GHGs) and particulate matter resulting from fossil fuel burning are considered to be the main anthropogenic forcing on the global climate. We show here that the external cyclic influences of cosmic origin that modulate the earth’s climate may either reinforce or mitigate the ‘local’ terrestrial forcings. Among the external influences is cosmic radiation, whose intensity shows a cyclic variation of 11 years, accompanying the 11-year cycle of solar activity. We put forward a mechanism to explain how the emission of particulate matter into the atmosphere might influence global lightning activity. With respect to global lightning activity, we show why, during the 11-year cycle, the influence of an increase in particulate matter concentration in the atmosphere may be negligible in some years, while it will be reinforced in other years, depending on the place of the years in the cycle. We also remark that the effect on global warming of fossil fuel burning is also modulated by the cosmic ray flux, whose influence is mediated by the variation that it promotes on the cloud cover

Constructal theory of global circulation and climate

The constructal law states that every flow system evolves in time so that it develops the flow architecture that maximizes flow access under the constraints posed to the flow. Earlier applications of the constructal law recommended it as a self-standing law that is distinct from the second law of thermodynamics. In this paper, we develop a model of heat transport on the earth surface that accounts for the solar and terrestrial radiation as the heat source and heat sink and with natural convection loops as the transport mechanism. In the first part of the paper, the constructal law is invoked to optimize the latitude of the boundary between the Hadley and the Ferrel cells, and the boundary between the Ferrel and the Polar cells. The average temperature of the earth surface, the convective conductance in the horizontal direction as well as other parameters defining the latitudinal circulation also match the observed values. In the second part of the paper, the constructal law is invoked in the analysis of atmospheric circulation at the diurnal scale. Here the heat transport is optimized against the Ekman number. Even though this second optimization is based on very different variables than in the first part of the paper, it produces practically the same results for the earth surface temperature and the other variables. The earth averaged temperature difference between day and night was found to be approximately 7 K, which matches the observed value. The accumulation of coincidences between theoretical predictions and natural flow configuration adds weight to the claim that the constructal law is a law of nature