A multivariate generalization of Costa's entropy power inequality

A simple multivariate version of Costa's entropy power inequality is proved. In particular, it is shown that if independent white Gaussian noise is added to an arbitrary multivariate signal, the entropy power of the resulting random variable is a multidimensional concave function of the individual variances of the components of the signal. As a side result, we also give an expression for the Hessian matrix of the entropy and entropy power functions with respect to the variances of the signal components, which is an interesting result in its own right.Comment: Proceedings of the 2008 IEEE International Symposium on Information Theory, Toronto, ON, Canada, July 6 - 11, 200

Optimal Linear Precoding Strategies for Wideband Non-Cooperative Systems based on Game Theory-Part I: Nash Equilibria

In this two-parts paper we propose a decentralized strategy, based on a game-theoretic formulation, to find out the optimal precoding/multiplexing matrices for a multipoint-to-multipoint communication system composed of a set of wideband links sharing the same physical resources, i.e., time and bandwidth. We assume, as optimality criterion, the achievement of a Nash equilibrium and consider two alternative optimization problems: 1) the competitive maximization of mutual information on each link, given constraints on the transmit power and on the spectral mask imposed by the radio spectrum regulatory bodies; and 2) the competitive maximization of the transmission rate, using finite order constellations, under the same constraints as above, plus a constraint on the average error probability. In Part I of the paper, we start by showing that the solution set of both noncooperative games is always nonempty and contains only pure strategies. Then, we prove that the optimal precoding/multiplexing scheme for both games leads to a channel diagonalizing structure, so that both matrix-valued problems can be recast in a simpler unified vector power control game, with no performance penalty. Thus, we study this simpler game and derive sufficient conditions ensuring the uniqueness of the Nash equilibrium. Interestingly, although derived under stronger constraints, incorporating for example spectral mask constraints, our uniqueness conditions have broader validity than previously known conditions. Finally, we assess the goodness of the proposed decentralized strategy by comparing its performance with the performance of a Pareto-optimal centralized scheme. To reach the Nash equilibria of the game, in Part II, we propose alternative distributed algorithms, along with their convergence conditions.Comment: Paper submitted to IEEE Transactions on Signal Processing, September 22, 2005. Revised March 14, 2007. Accepted June 5, 2007. To be published on IEEE Transactions on Signal Processing, 2007. To appear on IEEE Transactions on Signal Processing, 200

Chiral symmetry and meson exchange approach to hypernuclear decay

We take an approach to the $\Lambda$ nonmesonic weak decay in nuclei based on the exchange of mesons under the guidelines of chiral Lagrangians. The one pion and one kaon exchange are considered, together with the exchange of two pions, either correlated, leading to an important scalar-isoscalar exchange ($\sigma$-like exchange), or uncorrelated (box diagrams). A drastic reduction of the OPE results for the $\Gamma_n/\Gamma_p$ ratio is obtained and the new results are compatible with all present experiments within errors. The absolute rates obtained for different nuclei are also in fair agreement with experiment.Comment: 10 pages, 3 figs. Talk given at the Hypernuclear Conference 2000, Torin

Technical performance and environmental assessment of an ionic liquid-based CCS process for hydrogen production

Hydrogen (H2) production combined with carbon capture and storage (CCS) is anticipated to be an important technology contributing to reduce the carbon footprint of current fossil-based H2 production systems. This work addresses for the first time the techno-environmental assessment of a CCS process based on the ionic liquid [Bmim][Acetate] for H2 production by steam methane reforming (SMR) and the comparison to conventional amine-based systems. Two different SMR plants using MDEA or [Bmim][Acetate] for CO2 capture were rigorously modelled using Aspen Plus to compute material and energy needs and emissions. Literature and simulation results were then used to perform a life cycle impact assessment (LCIA) of these processes based on the ReCiPe model. Solvent synthesis, CCS process and hydrogen production stages were considered for the cradle-to-gate analysis. Results showed that although [Bmim][Acetate] is a priori more harmful to the environment than amines (in a kg-to-kg comparison), LCIAs carried out for both CCS processes showed from 5 to 17 % lower environmental impacts values for all estimated categories when using [Bmim][Acetate] due to a 9.4 % more energy-efficient performance than MDEA, which also reduced a 17.4 % the total utility cost. Indeed, if a typical amine loss rate of 1.6 kg/tCO2 is assumed, the values of the environmental impacts increase up to 14 % for the IL-based CCS plant, but still maintaining its favorable results over MDEA. As consequence, the SMR plant with the IL-based CCS system exhibited 3–20 % lower values for most of the studied impact categories. These results contribute to shed some light on evaluating the sustainability of ILs with respect to conventional solvents for CO2 capture and to guide the synthesis of new more sustainable ILs but also, they would be used to compare the environmental burdens from the synthesis and process performance of other promising ILs for CO2 capture that are not environmentally assed yetThe authors are grateful to Ministerio de Ciencia e Innovacion ´ of Spain (project PID2020-118259RB-I00) and Comunidad de Madrid (project P2018/EMT4348) for financial suppor

Direct air capture based on ionic liquids: From molecular design to process assessment

Direct air capture is a key carbon dioxide removal technology to mitigate climate change and keep the global average temperature rise below 1.5–2 °C. This work addresses for the first time the use of ionic liquids for direct air capture connecting their material design by molecular simulation to process modelling. First, 26 different ionic liquids were designed through quantum chemical calculations and their isotherms were computed to identify those with a positive cyclic working capacity at conditions relevant for direct air capture. Then, the most promising ionic liquids were assessed via process simulations in Aspen Plus. A wide range of operating configurations were screened by modifying the key process variables: air velocity (1 – 3 m/s), solvent mass flow (5 – 50 t/h) and temperature (293 – 323 K), and regeneration pressure (0.1 – 1 bar) and temperature (373 – 393 K). Exergy, energy and productivity were computed to detect optimal operating conditions; moreover, a simplified economic analysis was carried out to highlight the major cost components. The direct air capture system based on [P66614][Im] exhibited the most exergy (5.44 – 16.73 MJ/kg) and energy (15.15 – 35.42 MJ/kg) efficiency for similar productivity (0.5 – 1.3 kg/(m3·h)) thanks to its enhanced cyclic capacity (0.6 – 0.3 mol/kg). The minimum exergy required by [P66614][Im]-based DAC process is slightly better than alkali scrubbing (6.21 MJ/kg) and in line with amine (5.59 MJ/kg) scrubbing. In addition, the assessed DAC process has a theoretical potential to operate in the range of 200 $/tCO2 under reasonable energy and plant expenses. We conclude this work providing guidelines to address future development of direct air capture technologies based on ionic liquidsThe authors are grateful to Ministerio de Ciencia e Innovacion ´ of Spain (project PID2020-118259RB-I00) and Comunidad de Madrid (project P2018/EMT4348) for financial suppor

El área de lengua y literatura en educación primaria: una propuesta didáctica.

Sin resume

Selective CO2/CH4 Separation by Fixed-Bed Technology Using Encapsulated Ionic Liquids

The performance of encapsulated ionic liquid (ENIL) sorbents has been experimentally evaluated in CO2/CH4 separation by means of gravimetric and fixed-bed measurements. Six ionic liquids (ILs) with CO2 chemical absorption ([Emim][Acetate], [Bmim][Acetate], [P66614][CNPyr], [Bmim][GLY], [Bmim][MET], and [Bmim]- [PRO]) were selected for the selective separation of CO2 from CH4. ENIL materials were prepared by encapsulation of these ILs in synthesized carbon submicrocapsules, achieving a ∼70% in mass of IL. Fixed-bed experiments of CO2 capture were carried out to evaluate the CO2/CH4 separation performance of prepared ENIL materials at different CO2 partial pressures and 303 K. Both thermodynamics and kinetics of CO2 sorption were analyzed. The experimental CO2 and CH4 isotherms in ENIL materials obtained from fixed-bed experiments were successfully compared to those obtained by reliable gravimetric tests and fitted to the Langmuir− Freundlich equilibrium model. In addition, experimental CO2 breakthrough curves were well-described by the linear driving force and Yoon and Nelson kinetic models, providing sorption rate constants. ENIL sorbents show high CO2 uptake capacity, comparable to conventional adsorbents, but with drastically higher selectivity, in concordance with the negligible CH4 solubility in ILs at the used operating conditions, with acetate-based ENIL materials being the best sorbents in thermodynamic terms. The obtained kinetic parameters revealed that the CO2 chemical sorption with ENIL materials overcomes the IL mass transfer limitations. The sorption rates are faster than those obtained with ENIL using IL physical absorbents and seem to be controlled by the reaction kinetics. The [P66614][CNPyrr]-based ENIL is found to be the most promising material, combining favorable kinetic and thermodynamic considerations for future development of CO2/CH4 separation using fixed-bed technologyThe authors are grateful to Ministerio de Ciencia e Innovación of Spain (projects PID2020-118259RB-I00 and PDC2021- 120881-I00) and Comunidad de Madrid (project P2018/ EMT4348) for financial support and Centro de Computación Científica de la Universidad Autónoma de Madrid for computational facilitie

End-of-pipe Waste Analysis and Integrated Solid Waste Management Plan

A ten-year integrated solid waste management plan was established for the University of the Philippines Los Baños which complies with the provisions of RA 9003. An end-of-pipe Waste Analysis and Characterization Study (WACS) was performed to identify the classification of wastes in UPLB. Waste generation was found to be 593.67 kg/day on the average and is expected to increase by 2% per year which is 709.49 kg/day on the year 2027. The waste composition by weight of the non-biodegradable wastes are as follows: plastic (55.68%); paper (35.77%); glass bottles (5.22%); metal (2.77%); and residuals (0.55%). A large portion of the wastes, which is 99.45% by weight, are recyclables.  The loose density of wastes is 131.93 kg/ m3. Feasible collection points were assigned to improve efficiency of the collection of wastes in the university. Building units inside the campus were clustered and was assigned to dispose wastes to a single temporary storage facility per cluster. There are 181 units of 240-L garbage bin needed for the 39 clusters in UPLB. Two sets of dimensions of a proposed temporary storage facility were provided for the temporary storage facility; 5 2 2.2 m and 3.5 2 2.2 m. Conceptual design and structural plans of the materials recovery facility were provided. Mass balance was performed, and the theoretical diversion efficiency of the materials recovery facility is 99.445%