Application of the Optimized Baxter Model to the hard-core attractive Yukawa system

We perform Monte Carlo simulations on the hard-core attractive Yukawa system to test the Optimized Baxter Model that was introduced in [P.Prinsen and T. Odijk, J. Chem. Phys. 121, p.6525 (2004)] to study a fluid phase of spherical particles interacting through a short-range pair potential. We compare the chemical potentials and pressures from the simulations with analytical predictions from the Optimized Baxter Model. We show that the model is accurate to within 10 percent over a range of volume fractions from 0.1 to 0.4, interaction strengths up to three times the thermal energy and interaction ranges from 6 to 20 % of the particle diameter, and performs even better in most cases. We furthermore establish the consistency of the model by showing that the thermodynamic properties of the Yukawa fluid computed via simulations may be understood on the basis of one similarity variable, the stickiness parameter defined within the Optimized Baxter Model. Finally we show that the Optimized Baxter Model works significantly better than an often used, naive method determining the stickiness parameter by equating the respective second virial coefficients based on the attractive Yukawa and Baxter potentials.Comment: 11 pages, 8 figure

Mixed-integer-linear-programming-based energy management system for hybrid PV-wind-battery microgrids: Modeling, design, and experimental verification

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksMicrogrids are energy systems that aggregate distributed energy resources, loads, and power electronics devices in a stable and balanced way. They rely on energy management systems to schedule optimally the distributed energy resources. Conventionally, many scheduling problems have been solved by using complex algorithms that, even so, do not consider the operation of the distributed energy resources. This paper presents the modeling and design of a modular energy management system and its integration to a grid-connected battery-based microgrid. The scheduling model is a power generation-side strategy, defined as a general mixed-integer linear programming by taking into account two stages for proper charging of the storage units. This model is considered as a deterministic problem that aims to minimize operating costs and promote self-consumption based on 24-hour ahead forecast data. The operation of the microgrid is complemented with a supervisory control stage that compensates any mismatch between the offline scheduling process and the real time microgrid operation. The proposal has been tested experimentally in a hybrid microgrid at the Microgrid Research Laboratory, Aalborg University.Peer ReviewedPostprint (author's final draft

Orbital X-Ray Variability of the Microquasar LS 5039

The properties of the orbit and the donor star in the high mass X-ray binary microquasar LS 5039 indicate that accretion processes should mainly occur via a radiatively driven wind. In such a scenario, significant X-ray variability would be expected due to the eccentricity of the orbit. The source has been observed at X-rays by several missions, although with a poor coverage that prevents to reach any conclusion about orbital variability. Therefore, we conducted RossiXTE observations of the microquasar system LS 5039 covering a full orbital period of 4 days. Individual observations are well fitted with an absorbed power-law plus a Gaussian at 6.7 keV, to account for iron line emission that is probably a diffuse background feature. In addition, we have taken into account that the continuum is also affected by significant diffuse background contamination. Our results show moderate power-law flux variations on timescales of days, as well as the presence of miniflares on shorter timescales. The new orbital ephemeris of the system recently obtained by Casares et al. have allowed us to show, for the first time, that an increase of emission is seen close to the periastron passage, as expected in an accretion scenario. Moreover, the detected orbital variability is a factor of ~4 smaller than the one expected by using a simple wind accretion model, and we suggest that an accretion disk around the compact object could be responsible for this discrepancy. On the other hand, significant changes in the photon index are also observed clearly anti-correlated with the flux variations. We interpret the overall X-ray spectral characteristics of LS 5039 in the context of X-ray radiation produced by inverse Compton and/or synchrotron processes in the jet of this microquasar.Comment: published in Astrophysical Journal, submission format (real number of pages: 7, 4 figures

La protecció del medi ambient a Catalunya i la criminalització de l'aire

En aquesta conferència Josep C. Vergés posa de manifest, a través d'un cas pràctic d'una empresa tarragonina, com les gestions empresarials que comporten desastres ecològics difícilment poden ser sempre excusades pel medi, menys encara si parlem d'un medi tan obert i dispers com és l'aire.Based on a case history, this paper by Josep C. Vergés analyses the management of a business at ecological accountability level. Environmental damage cannot always be attributed to the environment itself and much less if such an open and disperse element as the air is concerned

La Gestació del pacte

The general elections of 1996 did not provide a clear majority for the winning centre right Popular Party. Two months later all agreement to govern was reached with the Catalan nationalists. The agreement was then extended to the Basque Nationalist Party and the Canarian Coalition. The surprising U-turn for the Popular party included its position on financing the Autonomies or states. The Government of Catalonia has been the poor financial relation of the new democratic Spain. The initial pact of democracy wanted to assimilate Catalonia and the Basque Country by extending autonomy to all Spanish regions. This had been lost with the demands on Catalan solidarity that no other Administration provided. The initial democratic pact seemed to have become merely a only better social distribution to the backward regions. The new agreement, whose financial proposals were written by this author and are published here for the first time, returns to the initial ideas that established democracy in Spain

La Gestació del pacte

The general elections of 1996 did not provide a clear majority for the winning centre right Popular Party. Two months later all agreement to govern was reached with the Catalan nationalists. The agreement was then extended to the Basque Nationalist Party and the Canarian Coalition. The surprising U-turn for the Popular party included its position on financing the Autonomies or states. The Government of Catalonia has been the poor financial relation of the new democratic Spain. The initial pact of democracy wanted to assimilate Catalonia and the Basque Country by extending autonomy to all Spanish regions. This had been lost with the demands on Catalan solidarity that no other Administration provided. The initial democratic pact seemed to have become merely a only better social distribution to the backward regions. The new agreement, whose financial proposals were written by this author and are published here for the first time, returns to the initial ideas that established democracy in Spain