ParisTech

About: ParisTech is a education organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Residual stress. The organization has 1888 authors who have published 1965 publications receiving 55532 citations. The organization is also known as: Paris Institute of Technology & ParisTech Développement.

Direct observation of nanoparticle multiple-ring pattern formation during droplet evaporation with dark-field microscopy

Abstract: Controllable protocols towards nanoparticle self-assembly are important for applications of functional nanomaterials. Evaporation is a simple yet effective method to realize a gold nanoparticle ordered self-assembly, but until now, little attention has been paid to viewing the corresponding assembly process. Herein, with the help of dark-field microscopy, we in situ monitored the whole dynamic process of gold nanorod (GNR) assembly as the solvent evaporated. Differently from the previous coffee-ring effect, rod-shaped hydrophilic GNRs, within certain concentrations, spontaneously assembled into a multiple-ring pattern on a hydrophobic substrate via droplet drying. The self-assembly mechanism is consistent with a diffusion-driven kinetics, and the influencing factors, including the GNR surface modification, the colloid concentration, the surface property of the substrate, and the shape of the nanoparticles, were systematically investigated.

Impact of Perturbations on Nonlinear Frequency-Division Multiplexing

Abstract: Nonlinear frequency-division multiplexing (NFDM) is a communication scheme in which users’ signals are multiplexed in the nonlinear Fourier domain. The contributions of this paper are twofold. First, the achievable information rates (AIRs) of NFDM based on an integrable model of the optical fiber are summarized. For this ideal model, it is shown that the AIR of the NFDM is greater than the AIR of the wavelength-division multiplexing (WDM) for a given bandwidth and signal power, in a representative system with five users and one symbol per user. The improvement results from nonlinear signal multiplexing. Second, the impact of some of the main perturbations on NFDM are investigated, including the fiber loss, polarization effects, and the third-order dispersion. For a realistic nonideal model, it is shown that the WDM AIR with joint dual-polarization back-propagation and third-order dispersion compensation is approximately equal to the NFDM AIR with two independent single-polarization demodulations and without third-order dispersion compensation. Using a joint dual-polarization receiver and perturbations compensation is expected to increase the NFDM AIR.

Durability modelling of a BGA component under random vibration

Abstract: This study introduces a computation method to assess damage in electronic solder joints under random vibration. It addresses full 3D dynamic behaviour of electronic board. Finite element modelling (FEM) of electronic BGA (ball grid array) and CGA (column grid array) packages assemblies are developed and adjusted with experimental modal identification of the test board. Vibration FEM simulations are performed to calculate stress transfer functions of critical solder joints. Then, solder joint time-stress responses due to an input random excitation of the board are generated. Stress range distributions are established from rainflow counting. Finally, linear damage computation is done and compared with experimental results by using an empirical damage law. The potential and the limitation of this method are discussed.