Reference model parameter identification of space–time dependent reactivity in a CANDU-PHWR

The problem of estimating reactivity transients from an observed neutron flux transient is considered. This is relevant, for example, to analyzing a power rundown test or to estimating reactivity variations associated with some computer codes that do not specifically compute individual reactivity components. A method is presented which utilizes inverse space–time kinetics and optimal state estimators to extract the components of the reactivity transient from observed neutron flux measurements. The approach takes into account geometric characteristics and composition of the reactor core, as well as reactor operating conditions. Measurements from a limited number of in-core neutron flux detectors are the inputs used to extract reactivity components that fit a modal model of the reactor, referred to as the “reference model”. An improved solution for the reactivity components is then generated using the modal approximation solution for the neutron transport equation in conjunction with optimal estimation techniques. The method has been applied to a reactivity initiated accident in which a transient is initiated by a non-uniform loss-of-coolant. This results in a spatially varying neutron overpower transient that is terminated by the asymmetric insertion of shutoff rods. In this paper the Joint Extended Kalman Filter and Rauch–Tung–Striebel smoother is employed to estimate the neutron flux distribution in the core and identify the reactivity components of the reference model. The reference model in the state space and the Kalman filter algorithm are shown. Results of numerical simulations of the reactor transient and the optimal estimation of the reactivity components are presented to demonstrate the capabilities of the method.     

Eco-friendly reactive dyeing of modified silk fabrics using corona discharge and chitosan pre-treatment

The aim of the current research is to study the improvement of dyeability of silk fabrics using surface modification performed by corona discharge and chitosan pre-treatment. Effects of some operational variables such as corona treatment time, concentration of chitosan, time, and temperature on grafting process were examined through dyeability of silk fabrics using two commercial reactive dyes. Fourier transform infra-red and scanning electron microscopy spectroscopy data revealed the surface modification of the silk by corona discharge and grafting of chitosan onto the silk fabric. Optimal grafting values obtained were corona treatment time 30 min, concentration of chitosan 18% owf, time 2 h and temperature 60 °C. It was found that silk pretreatment with corona discharge and chitosan improved dyeability from 1.84 to 4.58 for RY and from 3.05 to 6.40 for RB. The results indicated that the color fastness and tensile strength of silk fabrics were not significantly affected irrespective of the grafting with corona and chitosan pre-treatment. The results of this study provide the potential making of eco-friendly modification and reactive dyeing of textile fibers using corona discharge and chitosan pre-treatment.     

Massively Multiplexed Submicron Particle Patterning in Acoustically Driven Oscillating Nanocavities

Nanoacoustic fields are a promising method for particle actuation at the nanoscale, though THz frequencies are typically required to create nanoscale wavelengths. In this work, the generation of robust nanoscale force gradients is demonstrated using MHz driving frequencies via acoustic‐structure interactions. A structured elastic layer at the interface between a microfluidic channel and a traveling surface acoustic wave (SAW) device results in submicron acoustic traps, each of which can trap individual submicron particles. The acoustically driven deformation of nanocavities gives rise to time‐averaged acoustic fields which direct suspended particles toward, and trap them within, the nanocavities. The use of SAWs permits massively multiplexed particle manipulation with deterministic patterning at the single‐particle level. In this work, 300 nm diameter particles are acoustically trapped in 500 nm diameter cavities using traveling SAWs with wavelengths in the range of 20–80 µm with one particle per cavity. On‐demand generation of nanoscale acoustic force gradients has wide applications in nanoparticle manipulation, including bioparticle enrichment and enhanced catalytic reactions for industrial applications.