Thermoelectric properties and stability of glasses in the Cu‐As‐Te system

Chalcogenide glasses and more importantly their glass‐ceramics counterparts have been an interesting but very peculiar class of thermoelectric materials, with inherently low thermal conductivity (<0.3 W/m·K). In this study, we report on the fabrication of glasses in the ternary system Cu‐As‐Te (Cu_xAs_55?xTe₄₅ [5≤x≤20], Cu₁₅As_85?yTe_y [45≤y≤70], and Cu₂₀As_80?yTe_y [45≤y≤65]) by melt‐quenching and subsequent spark plasma sintering treatment. Their thermal and structural properties have been studied by differential scanning calorimetry and Raman spectroscopy, leading to give insights into the structural evolution of the glassy matrix. Coupling this information with the analysis of their electrical transport properties allowed us to deepen further our understanding of the compositional effect on their thermoelectric properties, and indirectly how the evolution of their electronic band structure is at play. Despite exhibiting low ZT values by themselves, Cu‐As‐Te glasses may still be interesting candidates for thermoelectricity through partial crystallization for which knowing the relationship between composition and properties remains essential.     

An experimental investigation on push force and its perception during a flexible hose insertion task encountered in a truck assembly line

The push force and its perception when inserting a flexible hose laterally into a connector were investigated. Effects of hose diameter, glove, target position and obstacle condition were studied. Maximum voluntary insertion forces (MVFs) under similar working conditions were also measured. The larger the diameter, the higher the force required. The peak axial forces for the hoses of 6, 12 and 16 mm in diameter were on average respectively 94, 122 and 184 N, representing 45%, 61% and 93% of MVF. Glove condition, target position and obstacle did not significantly affect the axial insertion force and moment, but they did affect effort perception. Lower effort was perceived with gloves and high and near position. High intra- and inter-individual variability in insertion force for a given hose may suggest that feedback of successful insertion was insufficient. The recognition of a successful insertion must be ensured to avoid unnecessary extra force exertion.

Practitioner summary: The effects of glove, hose diameter, target location and obstacle on push force and its perception were studied when inserting a flexible hose. Solutions for improving the recognition of a successful insertion and the hose/connector system design must be found to reduce force exertion to safe levels.     

Partial state observability recovering for linear systems by additional sensor implementation

This paper deals with the problem of additional sensor location in order to recover the observability of any given part of the state for structured linear systems. The proposed method is based on a graph-theoretic approach and assumes only the knowledge of the system’s structure. We first provide new graphical necessary and sufficient conditions for the generic partial observability. Then, we study the location of additional sensors in order to satisfy the latter conditions. We provide necessary and sufficient requirements to be satisfied by these additional sensors and all their possible locations. The proposed solution is simple to implement because it is based on well-known algorithms, usually used for finding successors and predecessors of vertex subsets or on computation of maximal linkings in a digraph. All the used algorithms have polynomial complexity orders.     

Synthesis and investigation of (1 − x)K0.5Na0.5NbO3–(x)CaSnO3 lead free perovskite ceramics of high dielectric and piezoelectric properties for transducer applications

Journal of Materials Science: Materials in Electronics - The conventional solid state reaction technique was used to synthesize a piezoelectric material of (K0.5Na0.5)NbO3 (KNN) and CS doped KNN...     

Stable Light‐Emitting Diodes Using Phase‐Pure Ruddlesden–Popper Layered Perovskites

State‐of‐the‐art light‐emitting diodes (LEDs) are made from high‐purity alloys of III–V semiconductors, but high fabrication cost has limited their widespread use for large area solid‐state lighting. Here, efficient and stable LEDs processed from solution with tunable color enabled by using phase‐pure 2D Ruddlesden–Popper (RP) halide perovskites with a formula (CH₃(CH₂)₃NH₃)₂(CH₃NH₃)_n?1Pb_nI_3n+1 are reported. By using vertically oriented thin films that facilitate efficient charge injection and transport, efficient electroluminescence with a radiance of 35 W Sr^?1 cm^?2 at 744 nm with an ultralow turn‐on voltage of 1 V is obtained. Finally, operational stability tests suggest that phase purity is strongly correlated to stability. Phase‐pure 2D perovskites exhibit >14 h of stable operation at peak operating conditions with no droop at current densities of several Amperes cm^?2 in comparison to mixtures of 2D/3D or 3D perovskites, which degrade within minutes.     

Microneedles for the Noninvasive Structural and Functional Assessment of Dermal Lymphatic Vessels

The medical and scientific communities' interest in the lymphatic system has been growing rapidly in recent years. It has become evident that the lymphatic system is much more than simply a homeostasis controller and that it plays key roles in several pathological conditions. This work describes the identification of the optimal combination of poly(N‐vinylpyrrolidone) and a near‐infrared dye (indocyanine green) for the manufacturing of soluble microneedles and their application to the imaging of the lymphatic system. Upon application to the skin, the microneedle‐bearing indocyanine green is delivered in the dermal layer, where the lymphatic vessels are abundant. The draining lymphatics can then be visualized and the clearance kinetics from the administration site simply determined using a near‐infrared camera. This painless functional “tattooing” procedure can be used for quantitative assessment of the dermal lymphatic function in several dermal conditions and treatment‐response evaluations. The two components of these microneedles are extensively used in routine medical care, potentially leading to rapid clinical translation. Moreover, this procedure may have a significant impact on preclinical lymphatic studies.     

Contribution à la modélisation de lignes hyperfréquences supraconductrices à haute température critique par la méthode FDTD

The purpose of this study is to determine the electrical behaviour of high-Tc superconductor microstrip lines. TheFdtd method is used to put into discrete terms Maxwell’s equations. The two-fluid model has been chosen to describe the behaviour of the superconductor. The variation of electrical parameters such as surface resistance as a function of frequency up to 60 GHz is presented.     

Gallium nitride MEMS resonators: how residual stress impacts design and performances

Microsystem Technologies - Starting from Gallium Nitride epitaxially grown on silicon, pre-stressed micro-resonators with integrated piezoelectric transducers have been designed, fabricated, and...