Self‐similarity analysis of vehicle driver's electrodermal activity

This paper characterizes stress levels via a self‐similarity analysis of the electrodermal activity (EDA) collected in a real‐world driving context. To characterize the EDA richness over scales, the fractional Brownian motion (FBM) process and its corresponding exponent H, estimated via a wavelet‐based approach, are used. Specifically, an automatic scale range selection is proposed in order to detect the linearity in a log scale diagram. The procedure is applied to the EDA signals, from the open database drivedb, originally captured on the foot and the hand of the drivers during a real‐world driving experiment, designed to evoke different levels of arousal and stress. The estimated Hurst exponent H offers a distinction in stress levels when driving in highway versus city, with a reference to restful state of minimal stress level. Specifically, the estimated H values tend to decrease when the driving environmental complexity increases. In addition, the estimated H values on the foot EDA signals allow a better characterization of the driving task than that of hand EDA. The self‐similarity analysis was applied to various physiological signals in literature but not to the EDA so far, a signal which was found to correlate most with human affect. The proposed analysis could be useful in real‐time monitoring of stress levels in urban driving spaces, among other applications.     

Influence of pressurised cryogenic nitrogen technology on Arthrospira platensis (spirulina) preservation during storage

In this study, preservation of spirulina using the new pressurised cryogenic nitrogen technology (PCN) was compared to classical methods used in laboratories and industry. Spirulina morphology was better preserved by PCN compared to unpressurised cryogeny and classical freezing at −20 °C that led to cells fragmentation. A 25% loss of Phycocyanin-C content against 60% were measured after 98 days storage for 6-Bar PCN process and frozen samples, respectively. The Total AntiOxidant Power (PAOT Liquid Technology^®) was used for determination of total antioxidant and oxidant power of spirulina extracts. PAOT value of PCN samples was 50% higher than the frozen sample. From ABTS measurements on PCN spirulina fractions sonicated or not, it was suggested that pressurisation at 6 bars allowed a better preservation of free antioxidants (outside the cells) due to replacement of oxygen by nitrogen in the frozen beads. After dehydration, phycocyanin-C content variation during storage at 20 °C and 33% RH showed higher loss for freeze-dried spirulina treated at 0 compared to 6 Bars.     

Temperature stability of a pure metakaolin based K-geopolymer: Part 2. Variations in the mesoporous network and its rehydration stability

The thermal behavior of a model MK-based K-geopolymer was investigated between room temperature and 1400°C in order to evaluate its potentiality for high-temperature applications. The purpose of our study was to monitor the behavior of a geopolymer during a temperature rise in order to better understand its variations with respect to temperature. The works from the present paper focus only changes in the porous network; it follows a first part devoted to variations in the mineral matrix. The results obtained here show that the geopolymer material preserves its porous integrity up to 800°C, while maintaining the reversibility of water exchanges corresponding to about 25 weight percent. Together with the results of part 1, the findings of this study allow us to affirm that geopolymer materials are only very little affected by temperatures up to 800°C, or even 900°C (keeping its mesoporous amorphous structure).     

Kinetic and mechanistic investigations of progesterone reaction with ozone

The removal of progesterone by ozone in aqueous solution was studied in this work. The absolute rate constant was evaluated and first by-products were identified. The reaction was studied in the 2.0-8.0 pH range and was found to be a second-order reaction, first-order relative to each compound concentration. The rate constant, determined by kinetic experiments in presence of an OH radical scavenger (tert-butanol), was independent of pH. The value was evaluated to be equal to 480+/-30 M(-1)s(-1) by two kinetic methods. Mass spectrometry analyses were performed to investigate primary degradation products generated by the reaction of ozone with progesterone. Two by-products were evidenced. According to these results, a degradation pathway of progesterone reacting with ozone was proposed.     

Screening of plant species for the phytotreatment of wastewater containing sulphonated anthraquinones

Sulphonated anthraquinones are known to be recalcitrant to biodegradation and are not eliminated by traditional wastewater treatment plants, leading to their accumulation in fresh water. Due to the high cost and limited efficiency of existing physical-chemical treatments, alternative cheaper processes are required to remove these compounds from industrial effluents. Four plant species were tested under hydroponic conditions for their ability to treat model effluents contaminated with mono- and disulphonated anthraquinones. Among them, Rheum rabarbarum (rhubarb) showed the most promising results and was chosen for further investigation. The apparent transpiration stream concentration factor obtained with this plant species reached up to 2.5, indicating a strong phytotreatment potential that should be further explored then exploited.     

巴黎:城墙内外的城市发展

在古代,城墙是城市普遍采用的一种军事防御工事,同时也是城市的边界,至今世界上仍有许多城市还保留着古代城墙的遗迹.从古至今,城墙的存在对城市形态、城市发展和城市居民生活方式发挥着非常深刻的影响;在某些城市,甚至在城墙消失之后,它的影响还依然存在.本文以巴黎为例,对巴黎城墙的演变及其对巴黎城市发展和巴黎地区城市空间结构的影响进行了分析.     

Influence of plastic deformation in flexible pad laser shock forming – experimental and numerical analysis

Flexible Pad Laser Shock Forming (FPLSF) is a new microforming process using laser-induced shock pressure and a hyperelastic flexible pad to induce high strain-rate (~10⁵ s^?1) plastic deformation on metallic foils to produce 3D microcraters. This paper studies the effect of two significant process parameters of FPLSF, flexible pad material and its thickness, on the deformation characteristics of the metal foils using experiments and finite element analysis. A finite element model is developed to simulate the FPLSF process. The stress-strain distribution across the foil and the flexible pad at different process stages of FPLSF are studied using FE analysis. Flexible pad materials including silicone rubber, polyurethane rubber, and natural rubber with thicknesses ranging between 300 μm and 3000 μm have been investigated in detail. Experimental results highlight that both the hardness and thickness of the flexible pad significantly influence the deformed crater geometry, thickness distribution across the formed crater and surface hardness at the crater surfaces. The experimental results are correlated with the stress-strain distributions from finite element analysis to study the underlying behaviors.     

Improving the performances of earth air heat exchangers through Constructal design

Earth to air heat exchanger (EAHE) is a well‐known technique used to preheat or precool outdoor air before blowing it into a building. However, its geometry is often very simple as it consists in one or multiple straight pipes, while more complex arrangements can be found in heat exchangers design. In this paper, we explore the advantage of designing an EAHE as a network through the Constructal law point of view. A methodology is first proposed to design a single pipe EAHE when the need is defined in terms of cooling power, overall efficiency and enthalpy difference between the inlet air and the ground. Next, the single pipe EAHE is used as a reference for designing a tree‐shaped network under the constraint of identical fluid volume and cooling power. The geometrical features are allowed to change for the different branches of the network. The network coefficient of performance is found to increase significantly with the bifurcation level, illustrating the superior performances of the network. This approach was found to be robust as the improvements were not depending on the cooling demand or the environmental conditions. However, further work is needed to move from this theoretical result to practical considerations.