Viscosity and Electrical Conductivity of Aqueous NaCl Solutions with Dissolved CO2

AbstractWith the perspective of long term CO2 storage, thermodynamic data are necessary for the simulations of CO2 injection in aquifers of depleted oil reservoirs. We focus here on the determination of the resistivity and viscosi ty of aqueous NaCl solutions with dissolved CO2. It is well known that dissolved CO2 increases slightly the water density. Recently, Bando et al. (2004) measured the viscosity of CO2 saturated brines and found an increase of viscosity with increasing amoun t of dissolved CO2. For resistivity, no data is available to our knowledge.We evaluated the effect of dissolved CO2 simultaneously on the resistivity and viscosity of three NaCl solutions covering the range of salinity usually encountered in potential CO2 storage geological formations. At a constant temperature of 35 ∘C, we show that the variation of resistivity and viscosity are proportional to the amount of dissolved CO2. For viscosity, our data are in agreement with previous observations. The observed variations are small, at maximum of the order of 10%. The increase of viscosity is well correlated with the variation of conductivity because ions are moving in a more viscous solvent and th erefore conductivity decreases. For the temperature dependence, w e used the Arps model to describe the measured variation of conductivity as a function of temperature. We propose a simple model to take into account the small modifications of conductivity and viscosity as a function of the dissolved CO2 fraction and temperature. Finally, we examine two potential impact s of these findings

State space geometry of the chaotic pilot-wave hydrodynamics

We consider the motion of a droplet bouncing on a vibrating bath of the same fluid in the presence of a central potential. We formulate a rotation symmetry-reduced description of this system, which allows for the straightforward application of dynamical systems theory tools. As an illustration of the utility of the symmetry reduction, we apply it to a model of the pilot-wave system with a central harmonic force. We begin our analysis by identifying local bifurcations and the onset of chaos. We then describe the emergence of chaotic regions and their merging bifurcations, which lead to the formation of a global attractor. In this final regime, the droplet's angular momentum spontaneously changes its sign as observed in the experiments of Perrard et al. (Phys. Rev. Lett., 113(10):104101, 2014).Comment: Accepted for publication in Chaos: An Interdisciplinary Journal of Nonlinear Scienc

A bi-objective stochastic approach for stochastic CARP

The Capacitated Arc Routing Problem (CARP) occurs in applications like urban waste collection or winter gritting. It is usually defined in literature on an undirected graph G = (V, E) , with a set V of n nodes and a set E of m edges. A fleet of identical vehicles of capacity Q is based at a depot node. Each edge i has a cost (length) ci and a demand qi (e.g. an amount of waste), and it may be traversed any number of times. The edges with non-zero demands or tasks require service by a vehicle. The goal is to determine a set of vehicle trips (routes) of minimum total cost, such that each trip starts and ends at the depot, each task is serviced by one single trip, and the total demand handled by any vehicle does not exceed Q . To the best of our knowledge the best published method is a memetic algorithm first introduced in 2001. This article provides a new extension of the NSGA II (Non-dominated Sorting Genetic Algorithm) template to comply with the stochastic sight of the CARP. The main contribution is: - to introduce mathematical expression to evaluate both cost and duration of the longest trip and also standard deviation of these two criteria. - to use a NGA-II template to optimize simultaneously the cost and the duration of the longest trip including standard deviation. The numerical experiments managed on the thee well-known benchmark sets of DeArmon, Belenguer and Benavent and Eglese, prove it is possible to obtain robust solutions in four simultaneous criteria in rather short computation times

Farming and livestock production in the Sahel : merging the two solutions

French version available in IDRC Digital Library: Fin des deux solitudes de l'élevage et de l'agriculture au SahelArabic version available in IDRC Digital LibraryThe women of Toukounous, a small town 20 km from Niamey, are participating in a new departure from the agricultural history of Niger and the Sahel. Only now is integrated farming and livestock production coming to their region, and it represents an essential step toward raising and sustaining agricultural yields