Metamaterials and the mathematical Science of invisibility

In this chapter, we review some recent developments in the field of photonics: cloaking, whereby an object becomes invisible to an observer, and mirages, whereby an object looks like another one (say, of a different shape). Such optical illusions are made possible thanks to the advent of metamaterials, which are new kinds of composites designed using the concept of transformational optics. Theoretical concepts introduced here are illustrated by finite element computations.Comment: This is a book chapter. 22 pages, 7 figure

Transformation Optics, Generalized Cloaking and Superlenses

In this paper, transformation optics is presented together with a generalization of invisibility cloaking: instead of an empty region of space, an inhomogeneous structure is transformed via Pendry's map in order to give, to any object hidden in the central hole of the cloak, a completely arbitrary appearance. Other illusion devices based on superlenses considered from the point of view of transformation optics are also discussed.Comment: 7 pages (two columns), 9 figures, to appear in IEEE Trans. Mag., invited paper in Compumag 2009 (Florianopolis, Brasil), corresponding slides available on http://www.fresnel.fr/perso/nicolet

Fast computation of the leastcore and prenucleolus of cooperative games

The computation of leastcore and prenucleolus is an efficient way of allocating a common resource among $N$ players. It has, however, the drawback being a linear programming problem with $2^N-2$ constraints. In this paper we show how, in the case of convex production games, generate constraints by solving small size linear programming problems, with both continuous and integer variables. The approach is extended to games with symmetries (identical players), and to games with partially continuous coalitions. We also study the computation of prenucleolus, and display encouraging numerical results

Using geophysical techniques to characterize tillage effect on soil properties

Tillage practices influence physical, chemical, and biological soil properties, which also affect soil quality and consequently plant growth. In this study, the main objective was to evaluate the effect of different tillage systems on soil physical properties by using geophysical methods, namely, ground-penetrating radar (far-field and near-field GPR), capacitance probes (ThetaProbe and 5TE), electromagnetic induction (EMI) (Profiler and EM38), soil sampling, and by soil penetrometer. Since 2005, three contrasting tillage systems were applied on different plots of an agricultural field: i) conventional tillage (CT) with mouldboard ploughing to 27 cm depth, ii) deep loosening tillage (DL) with a heavy tine cultivator to 30 cm depth, and iii) reduced tillage (RT) with a spring tine cultivator to 10 cm depth. The geophysical and soil strength measurements were performed in April 2010. We observed that tillage influences the soil resistance (deeper tillage decreases soil resistance), which could be partly seen in the radar data. Soil water content reference measurements (capacitance probes and soil sampling) were in a relatively good agreement with the water content estimates from far-field GPR. We also observed that the tillage influences surface water content. Mean surface water content was significantly lower for CT than for DL and RT, which was partly explained by lower macropore connectivity between the topsoil and the deeper layers after conventional tillage. This study confirms the potential of GPR and EMI sensors for soil physical properties determination at the field scale and for the characterization of agricultural management practices

Enhancing the possibilities of comprehensive two-dimensional liquid chromatography through hyphenation of purely aqueous temperature-responsive and reversed-phase liquid chromatography

Comprehensive two-dimensional liquid chromatography (LC X LC) allows for substantial gains in theoretical peak capacity in the field of liquid chromatography. However, in practice, theoretical performance is rarely achieved due to a combination of undersampling, orthogonality, and refocusing issues prevalent in many LC X LC applications. This is intricately linked to the column dimensions, flow rates, and mobile-phase compositions used, where, in many cases, incompatible or strong solvents are introduced in the second-dimension (D-2) column, leading to peak broadening and the need for more complex interfacing approaches. In this contribution, the combination of temperature-responsive (TR) and reversed-phase (RP) LC is demonstrated, which, due to the purely aqueous mobile phase used in TRLC, allows for complete and more generic refocusing of organic solutes prior to the second-dimension RP separation using a conventional 10-port valve interface. Thus far, this was only possible when combining other purely aqueous modes such as ion exchange or gel filtration chromatography with RPLC, techniques which are limited to the analysis of charged or high MW solutes, respectively. This novel TRLC x RPLC combination relaxes undersampling constraints and complete refocusing and therefore offers novel possibilities in the field of LC x LC including temperature modulation. The concept is illustrated through the TRLC x RPLC analysis of mixtures of neutral organic solutes

Simurgh: a fully decentralized and secure NVMM user space file system

The availability of non-volatile main memory (NVMM) has started a new era for storage systems and NVMM specific file systems can support extremely high data and metadata rates, which are required by many HPC and data-intensive applications. Scaling metadata performance within NVMM file systems is nevertheless often restricted by the Linux kernel storage stack, while simply moving metadata management to the user space can compromise security or flexibility. This paper introduces Simurgh, a hardware-assisted user space file system with decentralized metadata management that allows secure metadata updates from within user space. Simurgh guarantees consistency, durability, and ordering of updates without sacrificing scalability. Security is enforced by only allowing NVMM access from protected user space functions, which can be implemented through two proposed instructions. Comparisons with other NVMM file systems show that Simurgh improves metadata performance up to 18x and application performance up to 89% compared to the second-fastest file system.This work has been supported by the European Comission’s BigStorage project H2020-MSCA-ITN2014-642963. It is also supported by the Big Data in Atmospheric Physics (BINARY) project, funded by the Carl Zeiss Foundation under Grant No.: P2018-02-003.Peer ReviewedPostprint (author's final draft

OrthoMap: Homeomorphism-guaranteeing normal-projection map between surfaces

Consider two (n—1)-dimensional manifolds, S and Sʹ in Rn. We say that they are projection-homeomorphic when the closest projection of each one onto the other is a homeomorphism. We give tight conditions under which S and Sʹ are projection-homeomorphic. These conditions involve the local feature size for S and for Sʹ and the Hausdorff distance between them. Our results hold for arbitrary n

Fabrication of W-band TWT for 5G small cells backhaul

The W-band (92 - 95 GHz) Traveling Wave Tube enabling the first Point to multipoint millimeter wave backhaul wireless network is in final phase of fabrication. The challenge is to build a TWT suitable for large volume fabrication to satisfy the cost constraints of network operators. Performances are targeted to provide coverage on sectors up to 90° with 1 km range. Simulations demonstrate a bandwidth of operation in excess of 5 GHz with a saturated output power of 40 W. The TWT is directly connected to a sector horn antenna

Fabrication of W-band TWT for 5G small cells backhaul

The W-band (92 - 95 GHz) Traveling Wave Tube enabling the first Point to multipoint millimeter wave backhaul wireless network is in final phase of fabrication. The challenge is to build a TWT suitable for large volume fabrication to satisfy the cost constraints of network operators. Performances are targeted to provide coverage on sectors up to 90° with 1 km range. Simulations demonstrate a bandwidth of operation in excess of 5 GHz with a saturated output power of 40 W. The TWT is directly connected to a sector horn antenna