Dynamics of moving interface in porous media for power law fluids with yield stress

In this paper the dynamic of moving interface in a porous medium for non-Newtonian fluids of power law with yield stress is investigated. The frontal advance theory, which describes the flow of two immiscible fluids separated by a moving interface, in which the displacing fluid is of power law with yield stress and the displaced one is Newtonian, has been used to illustrate the deviation from Newtonian behaviour in oil displacement mechanism. The limitations of this theory for non-Newtonian fluids have been shown and discussed. A criterion for determining the conditions under which the viscous fingering effect is eliminated and the interface movement may be in a regular manner has also been obtained. An approximate analytical solution for determining the interface position and its velocity at any time is presented.     

Experimental investigation in the TOSQAN facility of heat and mass transfers in a spray for containment application

TOSQAN is an experimental program undertaken by the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) in order to perform thermal hydraulic containment studies. The TOSQAN facility is a large enclosure devoted to simulate typical accidental thermal hydraulic flow conditions in nuclear-pressurized water reactor (PWR) containment. The TOSQAN facility which is highly instrumented with non-intrusive optical diagnostics is particularly adapted to nuclear safety CFD code validation. The present work is devoted to studying the interaction of a water spray injection used as a mitigation means in order to reduce the gas pressure and temperature in the containment, to produce gases mixing and washout of fission products. In order to have a better understanding of heat and mass transfers between spray droplets and the gas mixture, and to analyze mixing effects due to spray activation, we perform detailed characterization of the two-phase flow.     

Nebulized Gadolinium‐Based Nanoparticles: A Theranostic Approach for Lung Tumor Imaging and Radiosensitization

Lung cancer is the most common and most fatal cancer worldwide. Thus, improving early diagnosis and therapy is necessary. Previously, gadolinium‐based ultra‐small rigid platforms (USRPs) were developed to serve as multimodal imaging probes and as radiosensitizing agents. In addition, it was demonstrated that USRPs can be detected in the lungs using ultrashort echo‐time magnetic resonance imaging (UTE‐MRI) and fluorescence imaging after intrapulmonary administration in healthy animals. The goal of the present study is to evaluate their theranostic properties in mice with bioluminescent orthotopic lung cancer, after intrapulmonary nebulization or conventional intravenous administration. It is found that lung tumors can be detected non‐invasively using fluorescence tomography or UTE‐MRI after nebulization of USRPs, and this is confirmed by histological analysis of the lung sections. The deposition of USRPs around the tumor nodules is sufficient to generate a radiosensitizing effect when the mice are subjected to a single dose of 10 Gy conventional radiation one day after inhalation (mean survival time of 112 days versus 77 days for irradiated mice without USRPs treatment). No apparent systemic toxicity or induction of inflammation is observed. These results demonstrate the theranostic properties of USRPs for the multimodal detection of lung tumors and improved radiotherapy after nebulization.     

Thermal stability analysis of Cu-11.8 wt%Al milled samples by TEM and HT-XRD

In this work, the thermal stability of two samples of Cu-11.8 wt%Al obtained by different milling processes is analyzed. Several TEM techniques were used and HT-XRD experiments performed to determine the crystal structure and the morphological microstructure of the samples obtained during different heat treatments. The heat treatments were: quenching from 850 °C to room temperature and two consecutive calorimetric runs at 5 °C/min. After the quenching,α₂ is the major phase observed, reaching 95 mass%. The remaining 5 mass% consisted of martensitic phases: one sample had γ′, a hexagonal structure, and the other β₁′, a rhombohedral structure. During the first calorimetric run, the sample containing the γ′ phase exhibited a calorimetric event and the sample containing the β₁′ phase did not. The calorimetric event is attributed to the austenitic transformation γ′ → β₁. The lack of calorimetric event in the sample containing the β₁′ is associated with the inhibition of the transformation β₁′ → β₁ because of the precipitation of the γ₂ phase. Finally, the absence of a calorimetric event in the second run with the first sample is associated with the retransformation to β₁′ instead to γ′ phase during cooling of the first calorimetric run. These studies determined that the first sample is a better candidate than the second sample to produce a shape memory alloy after thermo-mechanical treatments of the milled powders.     

Covariance Structure Maximum-Likelihood Estimates in Compound Gaussian Noise: Existence and Algorithm Analysis

Recently, a new adaptive scheme [Conte (1995), Gini (1997)] has been introduced for covariance structure matrix estimation in the context of adaptive radar detection under non-Gaussian noise. This latter has been modeled by compound-Gaussian noise, which is the product c of the square root of a positive unknown variable tau (deterministic or random) and an independent Gaussian vector x, c=radictaux. Because of the implicit algebraic structure of the equation to solve, we called the corresponding solution, the fixed point (FP) estimate. When tau is assumed deterministic and unknown, the FP is the exact maximum-likelihood (ML) estimate of the noise covariance structure, while when tau is a positive random variable, the FP is an approximate maximum likelihood (AML). This estimate has been already used for its excellent statistical properties without proofs of its existence and uniqueness. The major contribution of this paper is to fill these gaps. Our derivation is based on some likelihood functions general properties like homogeneity and can be easily adapted to other recursive contexts. Moreover, the corresponding iterative algorithm used for the FP estimate practical determination is also analyzed and we show the convergence of this recursive scheme, ensured whatever the initialization.     

A Multicriteria Decision Support Methodology for Annual Rehabilitation Programs of Water Networks

Abstract:   This article provides an overview of a multicriteria decision support methodology for annual rehabilitation programs of water networks. A first set of criteria is formulated for the purpose of comparing and ranking rehabilitation projects. Each proposed criterion is a measure of a particular impact of the condition of a pipe. The ELECTRE TRI method is implemented for defining rehabilitation priorities . Two reference profiles are used to define the limits of three categories associated with three increasing priority levels. With these two reference profiles, applying the ELECTRE TRI method to an asset stock ( a set of pipes that are candidates for rehabilitation ) means assigning each pipe to one of six possible priority groups. A second set of criteria, based on the concept of efficiency, is proposed for comparing alternative rehabilitation programs ( subsets of the asset stock ).     

Evaluation of performance improvement by model predictive control in a renewable energy system with hydrogen storage

Nowadays islanded microgrids mostly rely on diesel generator. In order to reduce greenhouse emissions, two islanded microgrids with hydrogen storage have been installed and are currently working autonomously in Reunion Island and France. Energy management implemented on these stations fall in the myopic control category. This study aims to determine the performance improvement that could be achieve on such stations using model predictive control. Ability to supply to the loads and energy losses minimisation are our main objectives. Lifetime degradation is also taken in consideration. Simulations shows that significant improvement can be brought, with a 76% decrease of the station's defaults time and better fill rate of hydrogen tank and batteries. In the meantime, chemical and electrical losses are reduced by 38 and 11%, and the batteries degradations are decreased by around 1%. The relevance of taking into account the electrolyser and fuel cell degradations depends on the time-step of the control. These results give a performance target in order to implement a real-time model predictive control in the microgrids, and eventually can be used to better sizing of future microgrids with similar architecture.     

Nano-Design für Makroschichten

Nano design for macroscopic coatings – new application potentials by PVD coatings up to 100 μm thickness Non-homogeneous coatings still limit the application of thicker layers due to defect growth and irregular layer thickness distribution along the surface of complex shaped components. Therefore, the layer thickness is usually limited to about 10 μm. In order to limit the surface roughness by the growing layer, multilayer coating systems are deposited by highly ionized plasmas. This allows significantly smoother layers to be produced, which until now could only be produced by mechanical finishing. Furthermore, by combining selected material systems and targeted parameter selection, structures can be deposited during coating, especially on edges, which result in a reduction of the cutting edge radius. In future, edge geometries should therefore be able to be specifically adjusted through the coating process.