A sub-nanosecond Synchronized MAC – PHY cross-layer design for Wireless Sensor Networks

In this paper, we present a Wireless Sensor node implementation which aims at solving two major issues in Wireless Sensor Networks. This solution provides nanosecond-scale synchronization between nodes and high data-rate transmission thanks to cross-layer design and the time-domain properties of UltraWide Band (UWB) modulation schemes. The high data rate is achieved through a specific implementation of a IR-UWB physical layer. Specific algorithms are also implanted into the MAC and physical layers and form a cross-layered synchronization protocol for deterministic Wireless Sensor Networks named WiDeCS (Wireless Deterministic Clock Synchronization). This protocol propagates master time reference to nodes of a cluster tree network. WiDeCS Cross layered scheme is possible thanks to flag signals rising in the physical layer. These signals, owing to the UWB time domain properties, capture precise timestamps of transmission and reception. Hardware level simulations show a clock synchronization precision of 2 ns with a 2 GHz bandwidth signal, and an ASIC demonstrator shows 374 ps synchronization precision and 677 ps of standard deviation with the same bandwidth. In this paper, the physical layer implementation is detailed, and the cross-layered WiDeCS scheme is demonstrated.     

When and how authoritarian leadership and leader renqing orientation influence tacit knowledge sharing intentions

In this study of tacit knowledge-sharing intentions in China, we examine the roles of authoritarian leadership and fairness with respect to the way managers make decisions and treat their subordinates. In particular, we examine the role of leader renqing orientation, i.e., the way leaders distribute favors and emotional concern to their subordinates, as a moderating factor. We draw on the research literature in the domains of knowledge management and cross-cultural Psychology to identify constructs that we then test with a survey of 309 Chinese employees. Our findings are counter-intuitive and are discussed in detail before we conclude with implications for research and practice.     

In situ kinetics study of the formation of organic nanoparticles by fluorescence lifetime imaging microscopy (FLIM) along a microfluidic device

In this study, a three-dimensional hydrodynamic focusing microfluidic method is presented that allows full control of the nano-precipitation process of adamantyl mesityl BODIPY (4,4-difluoro-3,5-di-(adamantyl)-8-mesityl-4-bora-3a,4a-diaza-s-indacene) (Adambodipy). The precipitation is achieved by combining a central Adambodipy organic flow with a mixture of water and a cationic surfactant, creating a non-solvent precipitation method. The flow and mixing were simulated using COMSOL Multiphysics^® 3.4. A good agreement between theory and experiment was obtained for the flow velocity, concentration fields and the subsequent precipitation kinetics. Fluorescence lifetime imaging was used to visualize the precipitation domains following the changes in fluorescence lifetime. The lifetime decreases from 6.1 ns for the molecules down to 0.9 ns for nanoparticles. A principal components analysis of the successive fluorescence decay curves showed that the process could be adequately modeled using three components, which can be attributed to monomers (single molecule), clusters (nuclei) and nanoparticles.     

Chemical composition evolution of YAG co-precipitate determined by pH during aging period and its effect on precursor properties

The properties of YAG precursors aged at various pH levels for different aging times were examined to explore the influence of pH on the evolution of the chemical composition and the morphology of the precipitate, on the variation of phase composition during the calcination process. Precursors obtained at pH lower than 8.0 can be transformed into mono-phase YAG by calcination at low temperature, while those obtained at higher pH exhibit a variety of crystalline structures. Aging at high pH increased the impurity content of the calcined powder. Based on monitoring the pH during the precursor aging process, and the measurement of the Y/Al ratio in the precipitates, the mechanism of the chemical variation is discussed and the influence of pH and aging time on the synthesis of YAG precursor is discussed.     

A preliminary design and structural analysis of the lifting tools for 40° sector sub-assembly and handling ITER components

The purpose-built, ITER tokamak assembly tools, which are to be provided by Korea, should be designed to meet: the assembly plan, space reservations, safety standards, simple operations, efficient maintenance, and so on. It is very important that the ITER assembly tools are able to lift and transfer ITER components or their sub-assemblies to their assembled position safely. Furthermore, the lifting tools will lift and handle very heavy loads that can be more than 1200 tonnes sometimes. Therefore, the ITER lifting tools must be designed to endure these heavy load conditions with regard to their structural integrity. Also, these designs should be verified through an appropriate method. The preliminary design of the sector lifting tool and associated lifting attachments are introduced in this paper. The sector lifting tool was designed especially to lift and handle various ITER components by adjusting the lifting centre. The structural analysis results using ANSYS are described considering the heaviest load condition. The results of the analysis show that; all stresses applied on the lifting tool are lower than the allowable stress of the applied material.     

Influence of deposited metal structures on the failure mechanisms of silicon-based components

Miniaturised silicon-based multilayer chips are nowadays widespread as semiconductor components for the mobile device technology. The use of special processing and integration procedures requires such materials to possess a definite mechanical strength to ensure the functionality of the entire device. The strength and mechanical reliability of such components can be described by the Weibull theory, and is highly influenced by the geometry of the metallisation and other near-surface functional layers. In this work, we attempt to clarify the mechanisms leading to the failure of the metallised side of Si-chip components. The combined use of Finite Elements (FE) and Focused Ion Beam (FIB) analyses allowed recognising that cracks are induced in the metal-oxide-silicon interfacial area well before complete failure of the component. Such cracks have a crucial role in the lower strength and higher Weibull modulus observed on the metallised side.     

Compressive and Tensile Behaviours of PLLA Matrix Composites Reinforced with Randomly Dispersed Flax Fibres

Nowadays, the ecological footprint of a material is becoming tremendously important. The Poly l-Lactide Acid (PLLA) matrix composites reinforced by randomly scattered flax fibres have mechanical properties similar to polyester/glass composites [1], lower environmental impacts and can be compost at the end of their lives. In this study, the mechanical characterization of biocomposites has been pushed further with the determination of the compressive and tensile properties. Furthermore, the mechanical properties of single flax fibres have been measured and implemented in a micro-mechanical estimation of the composite elastic modulus. Tensile and compressive stiffness determined by the mechanical analyses show very good correlations with the mathematical estimation.