Acidic pretreatment of wheat straw in decanol for the production of surfactant, lignin and glucose

Wheat straw is an abundant residue of agriculture which is increasingly being considered as feedstock for the production of fuels, energy and chemicals. The acidic decanol-based pre-treatment of wheat straw has been investigated in this work. Wheat straw hemicellulose has been efficiently converted during a single step operation into decyl pentoside surfactants and the remaining material has been preserved keeping all its promises as potential feedstock for fuels or value added platform chemicals such as hydroxymethylfurfural (HMF). The enzymatic digestibility of the cellulose contained in the straw residue has been evaluated and the lignin prepared from the material characterized. Wheat-based surfactants thus obtained have exhibited superior surface properties compared to fossil-based polyethoxylates decyl alcohol or alkyl oligoglucosides, some of which are largely used surfactants. In view of the growing importance of renewable resource-based molecules in the chemical industry, this approach may open a new avenue for the conversion of wheat straw into various chemicals.     

Giant coupling effect between metal nanoparticle chain and optical waveguide

We demonstrate that the optical energy carried by a TE dielectric waveguide mode can be totally transferred into a transverse plasmon mode of a coupled metal nanoparticle chain. Experiments are performed at 1.5 μm. Mode coupling occurs through the evanescent field of the dielectric waveguide mode. Giant coupling effects are evidenced from record coupling lengths as short as ~560 nm. This result opens the way to nanometer scale devices based on localized plasmons in photonic integrated circuits.     

Revisiting aqueous alkaline silicates as precursors for sol-gel optical coatings

Alkaline silicates are well-known soluble silica derivatives already widely used for industrial purposes. Nevertheless, their applications for the elaboration of functional optical coatings have largely been discarded by the sol-gel community who mainly focused on alkoxide precursors. The objective of this work is to reconsider the alkaline silicates sol-gel chemistry, targeting optical coatings of a few hundreds of nanometers. The structures of Li⁺, Na⁺, and K⁺ silicate coatings are discussed on the basis of spectroscopic characterizations. We show that a simple washing process allows a postdeposition removal of most alkaline ions, thus preventing the efflorescence effect and improving the aqueous stability of the films. Finally, several examples are shown for the application of alkaline silicates in the elaboration of functional optical coatings following conventional sol-gel chemistry.     

Modeling nuisance variabilities with factor analysis for GMM-based audio pattern classification

Audio pattern classification represents a particular statistical classification task and includes, for example, speaker recognition, language recognition, emotion recognition, speech recognition and, recently, video genre classification. The feature being used in all these tasks is generally based on a short-term cepstral representation. The cepstral vectors contain at the same time useful information and nuisance variability, which are difficult to separate in this domain. Recently, in the context of GMM-based recognizers, a novel approach using a Factor Analysis (FA) paradigm has been proposed for decomposing the target model into a useful information component and a session variability component. This approach is called Joint Factor Analysis (JFA), since it models jointly the nuisance variability and the useful information, using the FA statistical method. The JFA approach has even been combined with Support Vector Machines, known for their discriminative power. In this article, we successfully apply this paradigm to three automatic audio processing applications: speaker verification, language recognition and video genre classification. This is done by applying the same process and using the same free software toolkit. We will show that this approach allows for a relative error reduction of over 50% in all the aforementioned audio processing tasks.     

Switching loss reduction in nonlinear piezoelectric conversion under pulsed loading

Energy conversion enhancement of piezoelectric materials has been subject to intensive research over the last decade. Among the proposed solutions (for instance, single crystal), it has been shown that applying a simple and low-cost nonlinear treatment to the voltage output can significantly increase the conversion abilities of such materials. However, such an approach also adds significant electrical losses, dramatically reducing the available electric energy generated from the mechanical excitation. Such an observation is even more important when the energy in the system is limited, for example when the structure is submitted to a pulsed excitation. The purpose of this paper is to describe an efficient approach for reducing such losses, based on the transfer of the electrostatic energy when it starts to decrease. It is shown that such an approach allows increasing the converted energy by a gain up to a factor of 3, especially for weakly coupled electromechanical systems.     

Sex differences in upper limb 3D joint contributions during a lifting task

Sex-related differences in work technique may contribute to increasing the risk of musculoskeletal joint disorders among women. In lifting tasks, sex differences have been reported for the trunk and lower limb, although women present a higher prevalence of shoulder disorders. We investigated sex differences in the upper limb technique during a lifting task. Trunk and upper limb kinematics were recorded in 27 women and 27 men lifting a box (6 or 12?kg) from hip to eye level. Work technique was quantified through the three-dimensional contribution of each joint to overall box height. The glenohumeral joint showed a higher contribution in women with a 6?kg box and wrist and elbow joints did with a 12?kg box, compared to men at either 6 or 12?kg. Sex differences occurred systematically above shoulder level. Our results argue for careful consideration of sex during ergonomic intervention, particularly during the overhead task.

Practitioner Summary: We investigated the sex-related differences in upper limb technique during lifting tasks. Results highlight a sex-specific kinematic strategy above the shoulder level on the glenohumeral joint and on the wrist and elbow joints. To help reduce women’s shoulder disorders in overhead task, ergonomic interventions should account for those differences.

Abbreviations: DoF: degree-of-freedom; WR/EL: wrist and elbow; GH: glenohumeral; SC/AC: sternoclavicular and acromioclavicular; TR/PE: pelvo-thoracic     

Advanced laboratory electrolyser for production of pure hydrogen

A laboratory scale diaphragmless water electrolyser has been developed for the production of pure hydrogen at a pressure of up to 140 kPa by electrolysis of a KOH solution. Porous electrodes with a nickel catalyst and a copper cover layer serve as cathodes, and nickel sheets as anodes. Modular construction of the electrolyser permits simple combination of its cells into larger units. Thus, up to 20 cells with disc-shaped electrodes of 7 cm in diameter were connected in series and provided with electrolyte manifolds and automatic pressure and electrolyte level control devices. The dimensions of the electrolyte manifolds were optimized on the basis of calculations of parasitic currents. A good agreement between the calculated and measured current efficiencies was found at various cell numbers and total currents.     

Theory of porous electrodes—XVIII. The iron electrode

A model of the negative plate of the NiFe accumulator is proposed, similar to that of the negative plate of the NiCd accumulator. Besides volume changes of the solid phase and other obvious effects, the dependence of the tortuosity factor of the pores on porosity was also taken into account. The best agreement with the theory is obtained with electrodes prepared from pure sintered iron powder, eventual deviations being attributed to partial passivation. The influence of various factors is discussed in detail.     

Theory of porous electrodes—XVI. The nickel hydroxide electrode

A model of the positive plate of a nickel—cadmium accumulator is proposed, based on the known electrochemical behaviour of hydrated nickel oxides and on transport equations similar to those used previously for the cadmium electrode. The mathematical treatment of this model allows to predict the theoretical discharge characteristics, which are compared with those measured on a real electrode. A comparison of the calculated and measured discharge time suggests that the composition of the oxidised form is intermediate between NiO_1.5 and NiO_1.8.