Soft beams: when capillarity induces axial compression

We study the interaction of an elastic beam with a liquid drop in the case where bending and extensional effects are both present. We use a variational approach to derive equilibrium equations and constitutive relation for the beam. This relation is shown to include a term due to surface energy in addition of the classical Young's modulus term, leading to a modification of Hooke's law. At the triple point where solid, liquid, and vapor phases meet we find that the external force applied on the beam is parallel to the liquid-vapor interface. Moreover, in the case where solid-vapor and solid-liquid interface energies do not depend on the extension state of the beam, we show that the extension in the beam is continuous at the triple point and that the wetting angle satisfy the classical Young-Dupr\'e relation

The Importance of Interconnection Technologies’ Reliability of Power Electronic Packages

This chapter deals with the reliability of die interconnections used in plastic discrete power packages, dedicated to on‐board electronic systems used in a wide range of applications such as automotive industry. A complete reliability analysis of two bonding technologies—aluminum wire and ribbon bonding—is proposed. This study is particularly focused on interconnection technologies’ aging, when the package is subjected to thermal cycling or power cycling with high‐temperature swings. For thermal cycling, the experimental reliability test results highlight that wire bond package aging is about 2.5 faster than the ribbon bond package. For power cycling, this acceleration factor is about 1.5. In both cases and whatever the bonding technique, the failure mechanism of the package is of a fatigue‐stress nature. Many failure analysis results show wire bond lift‐off. The degradation of the ribbon bond is more difficult to observe. Thermo‐mechanical simulations using finite elements show a high stress concentration in the heel area. For the wire‐bonding technique, the wire is subjected to repeated flexing and pulling that lead to its lift off. The ribbon‐bonding process shows a higher robustness, thanks to a higher contact surface on the die, the low‐loop profile and the stiffness of the ribbon

Experimental demonstration of long-distance continuous-variable quantum key distribution

Distributing secret keys with information-theoretic security is arguably one of the most important achievements of the field of quantum information processing and communications. The rapid progress in this field has enabled quantum key distribution (QKD) in real-world conditions and commercial devices are now readily available. QKD systems based on continuous variables present the major advantage that they only require standard telecommunication technology, and in particular, that they do not use photon counters. However, these systems were considered up till now unsuitable for long-distance communication. Here, we overcome all previous limitations and demonstrate for the first time continuous-variable quantum key distribution over 80 km of optical fibre. The demonstration includes all aspects of a practical scenario, with real-time generation of secret keys, stable operation in a regular environment, and use of finite-size data blocks for secret information computation and key distillation. Our results correspond to an implementation guaranteeing the strongest level of security for QKD reported to date for such long distances and pave the way to practical applications of secure quantum communications

Modeling tree and grass dynamics: from demographic to spatially explicit models

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Sustainability and change in the institutionalized commute in Belgium: exploring regional differences

This paper examines regional differences in commute-energy performance in Belgium, and explores their relationships with spatial characteristics such as the distribution of population and housing, the metropolitan influence of the Brussels agglomeration, and the compactness of cities and towns. We also investigate contradictions between Belgian state-wide commute policy and regional differences in average commuting distance and mode choice. Against a background of long-term federal measures that traditionally encourage long-distance commuting in Belgium, we find striking discrepancies between the structure and the development of commuting patterns in the three administrative regions of Flanders, Wallonia and Brussels. Residents of Brussels show the most sustainable commuting patterns, due to the metropolitan spatial structure. Residents of Wallonia represent the least sustainable commute. Given the rather weak regional economy of Wallonia compared with Flanders, commuters must frequently seek employment far from their residence. Population changes and consequent developments in the housing market seem to exacerbate this competitive disadvantage, since most growth occurs in relatively remote rural areas that are nevertheless within reach of the main employment centres