The NOW dilemma

Energy efficiency has found its place at the very core of the discussion in Architecture and Urban Planning. Research & Development, Political Agendas and Education Curriculums are increasingly driven by the need to reach a fair balance between the way we inhabit the world and the energy we require for it. After many decades neglecting this discussion a growing awareness about the carrying capacity of our environment is being brought to actual policies on the built environment. The dominant tendency today privileges economic growth, thus being the maximization of performed labor per energy unit its ultimate goal. Renewal energy sources and energy efficiency are means for, on the one hand, an alternative to finite fossil fuel sources and, on the other hand, the optimization in the use of energy. Very little attention has been paid, however, to a more profound paradigm shift in economy. Some authors, however, have also claimed replacing the myth of economic growth by a more steady-state development as a solution for the current sustainability conundrum. The question is whether withholding the use of energy might be an alternative to its hi-tech optimization. Some of the contemporary authors who have discussed the issue in recent energy crisis are recounted here for a wider and holistic understanding of the problem.Peer ReviewedPostprint (published version

Stone on paper : architects manifesting on their cities

The role of architect in city-making has been the theme of unsolved debates in urbanism. Committed as performers and recipients of a holistic knowledge, architects-urbanists keep acting, still today, in--between idealism and pragmatism. The city, being frequently defined as a text, becomes the molten object where projects brought to materiality are able to build an intangible narrative. The paper presents the ongoing research 6by6, a compared analysis of cities where the apparent contradiction between idealism and practice is solved. Acknowledged American and European cities are analysed as a mean to illustrate the connections between the most extreme city-narrative – architectural manifestos ¿ with the most tangible material commitment – actual and implemented urban projects. This article announces them and reports on the manifestoes they are the cores of.Peer ReviewedPostprint (published version

On the efficiency of revocation in RSA-based anonymous systems

© 2016 IEEEThe problem of revocation in anonymous authentication systems is subtle and has motivated a lot of work. One of the preferable solutions consists in maintaining either a whitelist L-W of non-revoked users or a blacklist L-B of revoked users, and then requiring users to additionally prove, when authenticating themselves, that they are in L-W (membership proof) or that they are not in L-B (non-membership proof). Of course, these additional proofs must not break the anonymity properties of the system, so they must be zero-knowledge proofs, revealing nothing about the identity of the users. In this paper, we focus on the RSA-based setting, and we consider the case of non-membership proofs to blacklists L = L-B. The existing solutions for this setting rely on the use of universal dynamic accumulators; the underlying zero-knowledge proofs are bit complicated, and thus their efficiency; although being independent from the size of the blacklist L, seems to be improvable. Peng and Bao already tried to propose simpler and more efficient zero-knowledge proofs for this setting, but we prove in this paper that their protocol is not secure. We fix the problem by designing a new protocol, and formally proving its security properties. We then compare the efficiency of the new zero-knowledge non-membership protocol with that of the protocol, when they are integrated with anonymous authentication systems based on RSA (notably, the IBM product Idemix for anonymous credentials). We discuss for which values of the size k of the blacklist L, one protocol is preferable to the other one, and we propose different ways to combine and implement the two protocols.Postprint (author's final draft

A lower bound for the area of Plateau foams

Real foams can be viewed as geometrically well-organized dispersions of more or less spherical bubbles in a liquid. When the foam is so drained that the liquid content significantly decreases, the bubbles become polyhedral-like and the foam can be viewed now as a network of thin liquid films intersecting each other at the Plateau borders according to the celebrated Plateau’s laws. In this paper we estimate from below the surface area of a spherically bounded piece of a foam. Our main tool is a new version of the divergence theorem which is adapted to the specific geometry of a foam with special attention to its classical Plateau singularities. As a benchmark application of our results, we obtain lower bounds for the fundamental cell of a Kelvin foam, lower bounds for the so-called cost function, and for the difference of the pressures appearing in minimal periodic foams. Moreover, we provide an algorithm whose input is a set of isolated points in space and whose output is the best lower bound estimate for the area of a foam that contains the given set as its vertex set

Signcryption schemes with threshold unsigncryption, and applications

The final publication is available at link.springer.comThe goal of a signcryption scheme is to achieve the same functionalities as encryption and signature together, but in a more efficient way than encrypting and signing separately. To increase security and reliability in some applications, the unsigncryption phase can be distributed among a group of users, through a (t, n)-threshold process. In this work we consider this task of threshold unsigncryption, which has received very few attention from the cryptographic literature up to now (maybe surprisingly, due to its potential applications). First we describe in detail the security requirements that a scheme for such a task should satisfy: existential unforgeability and indistinguishability, under insider chosen message/ciphertext attacks, in a multi-user setting. Then we show that generic constructions of signcryption schemes (by combining encryption and signature schemes) do not offer this level of security in the scenario of threshold unsigncryption. For this reason, we propose two new protocols for threshold unsigncryption, which we prove to be secure, one in the random oracle model and one in the standard model. The two proposed schemes enjoy an additional property that can be very useful. Namely, the unsigncryption protocol can be divided in two phases: a first one where the authenticity of the ciphertext is verified, maybe by a single party; and a second one where the ciphertext is decrypted by a subset of t receivers, without using the identity of the sender. As a consequence, the schemes can be used in applications requiring some level of anonymity, such as electronic auctions.Peer ReviewedPostprint (author's final draft

Piedra sobre papel : realidad y utopias urbanas a través de manifiestos de arquitectura

Peer ReviewedPostprint (author's final draft

Decomposition of state-space Model with inputs: The theory and an application to estimate the ROI of advertising

This paper shows how to compute the in-sample effect of exogenous inputs on the endogenous variables in any linear model written in state-space form. Estimating this component may be, either interesting by itself, or a previous step before decomposing a time series into trend, cycle, seasonal and error components. The practical application and usefulness of this method is illustrated by estimating the effect of advertising on monthly sales of the Lydia Pinkham vegetable compound.State-space, Signal extraction, Time series decomposition, Seasonal adjustment, Advertising, Lydia Pinkham

From master-plan to punctual interventions : alternative urban approaches for the renewal of former slums in Barcelona

The sloppy process of urbanization that took place in the outskirts of Barcelona from mid XIXth to mid XXth century resulted on large informal slums with evident urban deficiencies. The Metropolitan Masterplan of 1976 and its subsequent amendments could only partially improve the conditions of these areas of the city. Since 2005 some initiatives, in which local community or academic research played an important role, were undertaken following a tactical approach. The paper summarizes six proposed strategies that are a reaction to the traditional planning and zoning approach for the area. Some of them are currently been discussed or have already been included in the planning framework of the city.Postprint (published version

Lessons from the world: Urban growth in the USA : from tracing boundaries to complex management : the Metro Portland case study

Article extending on the presentation made on the IIIrd USEACT Thematic Seminar held in Istanbul, February 2014Preprin

La repercusión del bilingüismo en el rendimiento académico en alumnos de colegios públicos de la Comunidad de Madrid

The purpose of this study is to analyze if there are differences in academic achievement for students in the second and third cycles of Primary Education depending on their attendance in bilingual or non-bilingual public schools in Madrid. A quasi-experimental design has been used with nonequivalent control group. The sample was composed of 2.153 students from 3rd to 6th grade of Primary Education enrolled in 12 public schools in the eastern area of Madrid. The academic achievement is measured by GPA and external examinations (Diagnosis Test of 4th grade of Primary Education and CDI Test of 6th grade of Primary Education). In connection with the CDI test, there are significant differences in favour of bilingual schools in Language and Mathematics. In the external test of 4th grade there were not significant differences. Regarding the GPA, there are significant differences in favour of non-bilingual schools in Science and English.El objetivo del presente estudio es analizar si existen diferencias en el rendimiento académico de alumnos de segundo y tercer ciclo de Educación Primaria en función de su asistencia a colegios públicos bilingües o no de la Comunidad de Madrid. Para lograr el objetivo se ha trabajado con un diseño cuasiexperimental con grupo de control no-equivalente. La muestra estuvo formada por 2.153 alumnos de 3º a 6º de Educación Primaria de 12 colegios públicos de la Comunidad de Madrid pertenecientes a la Dirección de Área Territorial Madrid-Este. El rendimiento académico se ha medido mediante calificaciones escolares y pruebas externas (Evaluación de Diagnóstico de 4º de E.P. y Prueba CDI de 6º de E.P). En relación con la prueba CDI, se han hallado diferencias significativas a favor de los colegios bilingües en Lengua y en Matemáticas. En la prueba externa de 4º de E.P. no hay diferencias significativas. Respecto a las calificaciones escolares, se han hallado diferencias significativas a favor de los colegios no bilingües en Conocimiento del Medio e Inglés