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Kircheva N.,French National Center for Scientific Research | Kircheva N.,LEM Group | Outin J.,French National Center for Scientific Research | Perrier G.,French National Center for Scientific Research | And 3 more authors.

The aim of this work was to study the behavior over time of a separator made of a low-cost and non-selective microporous polyethylene membrane (RhinoHide®) in an air-cathode microbial fuel cell with a reticulated vitreous carbon foam bioanode. Performances of the microporous polyethylene membrane (RhinoHide®) were compared with Nafion®-117 as a cationic exchange membrane. A non-parametric test (Mann-Whitney) done on the different sets of coulombic or energy efficiency data showed no significant difference between the two types of tested membrane (p<0.05). Volumetric power densities were ranging from 30 to 90W·m-3 of RVC foam for both membranes. Similar amounts of biomass were observed on both sides of the polyethylene membrane illustrating bacterial permeability of this type of separator. A monospecific denitrifying population on cathodic side of RhinoHide® membrane has been identified. Electrochemical impedance spectroscopy (EIS) was used at OCV conditions to characterize electrochemical behavior of MFCs by equivalent electrical circuit fitted on both Nyquist and Bode plots. Resistances and pseudo-capacitances from EIS analyses do not differ in such a way that the nature of the membrane could be considered as responsible. © 2015 Elsevier B.V. Source

Madsen S.B.,University of Aalborg | Ibsen C.H.,LEM Group | Gervang B.,University of Aalborg | Kristensen A.S.,University of Aalborg
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP

The focus of this paper is the validation and comparison of simplified numerical models of the mechanical rolling process used in tube to tubesheet joints. The investigated models is an axisymmetric model and planar models with plane strain and stress. There are different pros and cons for the different simplified models and therefore they are compared to an experiment where all geometries are measured before and after expansion. This comparison gives an insight into when the different models are valid. The models investigated is an axisymmetric model, a simple 2D expansion model with both plane strain and stress assumptions. Therefore, it is desirable to investigate how close these simplified models can predict the geometry changes after expansion measured in the experiment. The conclusion of the paper is that a planer model with plane strain is the best model at predicting the actual deformation after expansion. Copyright © 2015 by ASME. Source

Zorlu O.,Middle East Technical University | Zorlu O.,Ecole Polytechnique Federale de Lausanne | Kejik P.,Ecole Polytechnique Federale de Lausanne | Teppan W.,LEM Group
Sensors and Actuators, A: Physical

In this paper, we present a new microfabricated fluxgate sensor structure using cascaded planar rings as the ferromagnetic core. The planar ring structures provide closed magnetic excitation loops enabling uniform core saturation with relatively small excitation magnetic field. The magnetic excitation is provided with a rod passing through the ring cores. Planar coils placed under the edges of the core are used as sensing elements. By using this structure, fluxgate sensors having a closed core configuration are realized with a developed microfabrication process in a very small area (<0.1 mm 2) with reduced number of via connections. The ferromagnetic rings are realized with a standard FeNi (iron-nickel) electroplating process. The main advantage of this structure is the possibility to arrange the linear operation range of the sensor by only changing the number of ring cores, without affecting the excitation mechanism. This is demonstrated by simulations and microfabricated prototypes having 18 and 12 ring cores with ±300 μT and ±550 μT linear operation ranges, respectively. A maximum linear operation range of ±2 mT is achieved with a larger size, 4-ring core. This is the widest linear operation range achieved with the microfabricated fluxgate type sensors, without using a feedback loop, to the best of our knowledge. © 2010 Elsevier B.V. All rights reserved. Source

Amaral P.,University of Evora | Correia A.,University of Evora | Lopes L.,University of Evora | Rebola P.,LEM Group | And 3 more authors.
Key Engineering Materials

The use of dimension stones in architecture and civil engineering implies the knowledge of several mechanical, physical, and chemical properties. Even though it has been usual practice to measure physical and mechanical properties of dimension stones the same is not true for thermal properties such as thermal conductivity, thermal diffusivity, specific heat capacity, and heat production. These properties are particularly important when processes related with heating and cooling of buildings must be considered. Thermal conductivity, thermal diffusivity, and specific heat capacity are related with the way thermal energy is transmitted and accumulated in stones; heat production has to do with the amount of radioactive elements in the rocks and so with the environmental impact of radioactivity and public health problems. It is important to start to measure on a routine basis those four thermal properties in rocks and, in particular, in dimension rocks so that their application can be improved and optimized. With this is mind three sets of different rock types (granites, limestones, and marbles) were collected to measure the thermal conductivity, the thermal diffusivity, and the specific heat capacity with the objective of characterizing them in terms of those properties. Since the same set of rocks has also been studied for other physical properties, a correlation amongst all the measured properties is attempted. For each rock type several samples were used to measure the thermal conductivity, the thermal diffusivity, and the specific heat capacity, and average values were obtained and are presented. As an example, for granites the thermal conductivity varies between 2.87 and 3.75 W/mK; for limestones varies between 2.82 and 3.17 W/mK; and for marbles varies between 2.86 and 3.02 W/mK. It is hoped that measuring thermal properties on dimension stones will help to better adequate them to their use in civil engineering as well as to adequate their use in terms of a CE product. © (2013) Trans Tech Publications. Source

Lupker M.,French National Center for Scientific Research | France-Lanord C.,French National Center for Scientific Research | Lave J.,French National Center for Scientific Research | Bouchez J.,IPG Inc | And 6 more authors.
Journal of Geophysical Research: Earth Surface

The Ganga River is one of the main conveyors of sediments produced by Himalayan erosion. Determining the flux of elements transported through the system is essential to understand the dynamics of the basin. This is hampered by the chemical heterogeneity of sediments observed both in the water column and under variable hydrodynamic conditions. Using Acoustic Doppler Current Profiler (ADCP) acquisitions with sediment depth profile sampling of the Ganga in Bangladesh we build a simple model to derive the annual flux and grain size distributions of the sediments. The model shows that ca. 390 (30) Mt of sediments are transported on average each year through the Ganga at Haring Bridge (Bangladesh). Modeled average sediment grain size parameters D 50 and D84 are 27 (±4) and 123 (±9) μm, respectively. Grain size parameters are used to infer average chemical compositions of the sediments owing to a strong grain size chemical composition relation. The integrated sediment flux is characterized by low Al/Si and Fe/Si ratios that are close to those inferred for the Himalayan crust. This implies that only limited sequestration occurs in the Gangetic floodplain. The stored sediment flux is estimated to c.a. 10% of the initial Himalayan sediment flux by geochemical mass balance. The associated, globally averaged sedimentation rates in the floodplain are found to be ca. 0.08 mm/yr and yield average Himalayan erosion rate of ca. 0.9 mm/yr. This study stresses the need to carefully address the average composition of river sediments before solving large-scale geochemical budgets. Copyright 2011 by the American Geophysical Union. Source

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