Constructing and verifying a robust Mix Net using CSP

A Mix Net is a cryptographic protocol that unlinks the correspondence between its inputs and its outputs. In this paper, we formally analyse a Mix Net using the process algebra CSP and its associated model checker FDR. The protocol that we verify removes the reliance on a Web Bulletin Board: rather than communicating via a Web Bulletin Board, the protocol allows the mix servers to communicate directly, exchanging signed messages and maintaining their own records of the messages they have received. Mix Net analyses in the literature are invariably focused on safety properties; important liveness properties, such as deadlock freedom, are wholly neglected. This is an unhappy omission, however, since a Mix Net that produces no results is of little use. In contrast, we verify here that the Mix Net is guaranteed to terminate, with each honest mix server outputting the decrypted vector of plaintexts alongside a chain proving that each re-encryption/permutation and partial decryption operation was performed correctly, under the assumption that there is an honest majority of them acting according to the protocol.     

Decentralized spatial partitioning for multi-vehicle systems in spatiotemporal flow-field

We consider the problem of characterizing a generalized Voronoi diagram/partition of a convex polygon in a two-dimensional Euclidean space that encodes information about the proximity relations between a team of aerial/marine vehicles and arbitrary points in the partition space. These proximity relations are determined by the time required for each vehicle to reach an arbitrary point (time-to-go) in the partition space when driven by a locally optimal feedback control law in the presence of a spatiotemporal drift field. The main contribution of this work is the presentation of a partitioning algorithm, which is decentralized, in the sense that each vehicle can independently compute its corresponding cell from the generalized Voronoi partition without computing or receiving information about the cells of the other vehicles. Finally, we present numerical simulations using data from real drift fields to illustrate the key features of the decentralized solution to the proposed class of spatial partitioning problems.     

A framework for rapid evaluation of heterogeneous 3-D NoC architectures

The scalability of communication infrastructure in modern Integrated Circuits (ICs) becomes a challenging issue, which might be a significant bottleneck if not carefully addressed. Towards this direction, the usage of Networks-on-Chip (NoC) is a preferred solution. In this work, we propose a software-supported framework for quantifying the efficiency of heterogeneous 3-D NoC architectures. In contrast to existing approaches for NoC design, the introduced heterogeneous architecture consists of a mixture of 2-D and 3-D routers, which reduces the delay and power consumption with a slight impact on packet hops. More specifically, the experimental results with a number of DSP applications show the effectiveness of the introduced methodology, as we achieve on average 25% higher maximum operation frequency and 39% lower power consumption compared to the uniform 3-D NoCs.     

Back to Von Thunen: a Southern European perspective on mono-centric urban growth,economic structure and non-urban land decline*

This study assesses trends (1960–2010) in forest cover over a Mediterranean metropolitan region (Attica, Greece) with the aim to investigate the role of local contexts promoting changes in the use of land. Forest cover decreased in a spatially heterogeneous manner over the study period determining a land-use structure coherent with the Von Thunen mono-centric model. We used a multivariate exploratory analysis of 26 contextual variables to identify changes in the urban spatial structure at the local scale. The shift from a land-use structure based on urban–rural and cropland-forest polarizations in the early 1960s to a pattern based on the polarization in medium-density, mixed urban/agricultural areas and low-density, sparse forest land has been observed in the last 50 years. Urban expansion into rural land and the establishment of protected areas in economically marginal and remote districts has been identified as relevant drivers of landscape transformation in the area. Our study demonstrates that land-use changes driven by expansion of dispersed settlements may consolidate mono-centric urban structures. A concentric land-use distribution around the central city is compatible with urban sprawl and may be indirectly supported by ‘green belt’ regional planning and environmental policies protecting high-quality natural land.     

On the reduction of 2-D polynomial systems into first order equivalent models

Multidimensional Systems and Signal Processing - In this paper we propose a novel approach for the reduction of a 2-D rectangular polynomial matrix of arbitrary degree, to first-order matrix...     

The influence of ripening and crop year on quality indices,polyphenols, terpenic acids,squalene, fatty acid profile,and sterols in virgin olive oil (Koroneiki cv.) produced by organic versus non‐organic cultivation method

The chemical composition of virgin olive oil is determined by numerous factors. The aim of this study was to evaluate the influence of the olive ripening stage, and crop year on the quality indices of Koroneiki cv. virgin olive oil of organic vs non‐organic cultivation. Drupes of organic and of non‐organic cultivation were sampled at four successive ripening periods in crop years 2000 and 2004. Quality indices, total and simple polyphenols, terpenic acids, squalene, fatty acid profile, and sterols were measured. Statistical analysis demonstrated that peroxide value differed according to cultivation method and according to crop year. Organic Koroneiki cv. olive oils exhibited higher total phenols content. Total phenols differed mainly according to crop year and maturation phase, but also according to cultivation method. Total unsaturated and saturated fatty acids differed according to cultivation method, crop year and maturation. Oleic and palmitoleic acids varied according to cultivation method and according to maturation process. Cholesterol, campesterol and stigmasterol differed according to maturity, while β‐sitosterol differed according to crop year. Overall, olive oil from organic cultivation was of superior quality compared to non‐organic, while composition of olive oils was greatly variable during maturation, whereas it was also affected by the crop year.     

A reinterpretation of the Odar and Hamilton data on the unsteady equation of motion of particles

The experimental data and correlations derived by Odar and Hamilton have been the basis of studies that included the history term in the expression of the unsteady drag. Recent studies have shown that the value of the added mass coefficient is constant and equal to ½ over a very large range of Reynolds numbers. Recent studies on the history term have proven that its form is not correct at high Re. However, the experimental data are accurate at low Re and, most probably, they represent the most reliable set of experimental data on the unsteady force on solid spheres. We conducted a study to re‐calculate the functional form of the history term in the unsteady equation of motion at low Re and to derive a new correlation for the so‐called “history force coefficient,” Δ_H. The new correlation is expressed in terms of the Reynolds and Strouhal numbers of the particle. © 2010 American Institute of Chemical Engineers AIChE J, 2011