Effect of the aggressive environment on the damage of a glass polyester composite developed by hand layup process

This work treats the behavior of a glass fibre/unsaturated polyester (UP) composite with structural deffects subjected to the attack of two corrosive solutions: H2SO4 and NaOH. The gravimetric analysis, the uptake mass of the resin, and the interfaces in the composite are established according to the proportion of the matrix/composite. The obtained results showed that, in the acidic solution, the glass fibre and the fibre/matrix interface absorption share is more significant than the alkaline solution. While the Fourier transform infrared analysis (FT-IR) of the UP resin revealed the presence of chemical degradation phenomenon (hydrolysis), the fibre corrosion was characterized by the atomic absorption analysis (AAS). The fibres/matrix interfaces degradation was confrmed by microscopic observations (SEM). The difusion kinetics of the both acid and alkaline solutions and chemical and mechanical degradation are afected by the presence of the pores in elaborated materia

COMPARATIVE STUDY ON THE USE OF ZEOLITE AND PRECIPITATION AGENTS TO RETARD SCALE FORMATION IN THE SEAWATER PRETREATMENT PROCESS

The scale formation in heat transfer surfaces in seawater desalination plants by multi stage flash processes (MSF). This scale is formed during the precipitation of salts containing in seawater such as calcium and magnesium carbonates. The pretreatment is based on the removal of the calcium and magnesium cations from seawater, using zeolite as cation exchanger and precipitator agents as: lime, soda ash, and mixture of soda ash with soda. DRX, SEM, and EDX analyses were employed to characterize the zeolite before and after pretreatment so as to demonstrate the change composition on the zeolite surface. The results revealed that the pretreatment by a mixture of soda ash (13g/L) and soda (4g/L) favor the precipitation of calcium and magnesium ions. The calcium and magnesium ion concentrations in seawater were reduced, respectively, from 620 mg/L and 644 mg/L to 5 mg/L and 9.11 mg/L

Do TETRA (Airwave) base station signals have a short-term impact on health and well-being? A randomized double-blind provocation study

Background: "Airwave" is the new communication system currently being rolled out across the United Kingdom for the police and emergency services, based on the Terrestrial Trunked Radio Telecommunications System (TETRA). Some police officers have complained about skin rashes, nausea, headaches, and depression as a consequence of using their Airwave handsets. In addition, a small subgroup in the population self-report being sensitive to electromagnetic fields (EMFs) in general. Objectives: We conducted a randomized double-blind provocation study to establish whether short-term exposure to a TETRA base station signal has an impact on the health and well-being of individuals with self-reported "electrosensitivity" and of participants who served as controls.Methods: Fifty-one individuals with self-reported electrosensitivity and 132 age and sex-matched controls participated in an open provocation test; 48 sensitive and 132 control participants went on to complete double-blind tests in a fully screened semianechoic chamber. Heart rate, skin conductance, and blood pressure readings provided objective indices of short-term physiological response. Visual analog scales and symptom scales provided subjective indices of well-being.Results: We found no differences on any measure between TETRA and sham (no signal) under double-blind conditions for either controls or electrosensitive participants, and neither group could detect the presence of a TETRA signal at rates greater than chance (50%). When conditions were not double blind, however, the self-reported electrosensitive individuals did report feeling worse and experienced more severe symptoms during TETRA compared with sham.Conclusions: Our findings suggest that the adverse symptoms experienced by electrosensitive individuals are due to the belief of harm from TETRA base stations rather than to the low-level EMF exposure itself

Drop Traffic in Microfluidic Ladder Networks with Fore-Aft Structural Asymmetry

We investigate the dynamics of pairs of drops in microfluidic ladder networks with slanted bypasses, which break the fore-aft structural symmetry. Our analytical results indicate that unlike symmetric ladder networks, structural asymmetry introduced by a single slanted bypass can be used to modulate the relative drop spacing, enabling them to contract, synchronize, expand, or even flip at the ladder exit. Our experiments confirm all these behaviors predicted by theory. Numerical analysis further shows that while ladder networks containing several identical bypasses are limited to nearly linear transformation of input delay between drops, mixed combination of bypasses can cause significant non-linear transformation enabling coding and decoding of input delays.Comment: 4 pages, 5 figure

Does Short-Term Exposure to Mobile Phone Base Station Signals Increase Symptoms in Individuals Who Report Sensitivity to Electromagnetic Fields? A Double-Blind Randomized Provocation Study

BACKGROUND: Individuals with idiopathic environmental illness with attribution to electromagnetic fields (IEI-EMF) believe they suffer negative health effects when exposed to electromagnetic fields from everyday objects such as mobile phone base stations. OBJECTIVES: This study used both open provocation and double-blind tests to determine if sensitive and control individuals experience more negative health effects when exposed to base station-like signals compared with sham. METHODS: Fifty-six self-reported sensitive and 120 control participants were tested in an open provocation test. Of these, 12 sensitive and 6 controls withdrew after the first session. The remainder completed a series of double-blind tests. Subjective measures of well-being and symptoms as well as physiological measures of blood volume pulse, heart rate, and skin conductance were obtained. RESULTS: During the open provocation, sensitive individuals reported lower levels of well-being in both the global system for mobile communication (GSM) and universal mobile telecommunications system (UMTS) compared with sham exposure, whereas controls reported more symptoms during the UMTS exposure. During double-blind tests the GSM signal did not have any effect on either group. Sensitive participants did report elevated levels of arousal during the UMTS condition, whereas the number or severity of symptoms experienced did not increase. Physiological measures did not differ across the three exposure conditions for either group. CONCLUSIONS: Short-term exposure to a typical GSM base station-like signal did not affect well-being or physiological functions in sensitive or control individuals. Sensitive individuals reported elevated levels of arousal when exposed to a UMTS signal. Further analysis, however, indicated that this difference was likely to be due to the effect of order of exposure rather than the exposure itself

Droplet group production in an AC electro-flow-focusing microdevice

We report the production of droplet groups with a controlled number of drops in a microfluidic electro-flow focusing device under the action of an AC electric field. This regime appears for moderate voltages (500-700 V peak-to-peak) and signal frequencies between 25 and 100 Hz, much smaller than the droplet production rate ( ≈500 Hz). For this experimental conditions the production frequency of a droplet package is twice the signal frequency. Since the continuous phase flow in the microchannel is a Hagen-Poiseuille flow, the smaller droplets of a group move faster than the bigger ones leading to droplet clustering downstream.Ministerio de Economía y Competitividad DPI2013-46485-C3-1-RMinisterio de Economía y Competitividad FIS2014-54539- PJunta de Andalucía P11-FQM-791

Procédé de fabrication de structure en composite verre/polyester

92 p. : ill. ; 30 cmCe travail consiste en une caractérisation analytique et expérimentale d’un matériau composite stratifié en verre/ polyester préparé par le procédé moulage au contact et utilisé dans la fabrication des bateaux (pèche et plaisance). Cette caractérisation a pris en compte l’influence de la séquence de stratification et du mode d’élaboration (taux de catalyseur et température d’élaboration). L’analyse spectrale FT-IR de la résine avant et après durcissement a confirmé que la réticulation s’est produite avec des conversions assez élevées. Les tests de réactivité ont montré que l’augmentation de la concentration en catalyseur et l’augmentation de la température augmentent la vitesse de la réaction et réduisent le temps de gélification et de maximum d’exothermie. Les propriétés mécaniques sont optimales pour les échantillons élaborés à 40°C avec 1% de catalyseur et pour ceux élaborés à 20°C avec 2% de catalyseur. L’emplacement du roving dans la séquence de stratification joue un rôle prépondérant dans le mode de comportement du stratifié surtout pour la sollicitation de flexio

Effect of periodic horizontal gradients on the retrieval of atmospheric profiles from occultation measurements

International audienceSpherical symmetry is generally assumed during the retrieval process of atmospheric profiles from occultation measurements. The existence of periodic horizontal gradients, occurring on scales comparable to the distances traveled by the rays around their tangent point, is produced by gravity waves. These waves can introduce density perturbations of up to 1 or 2% in amplitude and affect the retrieved parameters accordingly. We show the consequences of ignoring these gradients in the retrieved refractivity profiles when spherical symmetry is assumed. We find that only the waves, with horizontal wavelengths close to the horizontal distance mat rays travel in their final 6 or 8 km in the vertical before they are tangent in the atmosphere, will have an influence on the retrieved profiles by introducing a phase delay in the local profile of the retrieved refractivity. The horizontal wavelength of these waves corresponds to the minimum horizontal resolution associated with the retrieved profiles. We also find that smaller scale waves do not have any significant impact on the retrieved profiles, as their contribution cancels out by averaging through the periodic perturbation, while waves with very long horizontal wavelengths are in good agreement with a local spherical symmetry assumption