Countercurrent reactor design and flowsheet for iodine-sulfur thermochemical water splitting process

A conceptual design is presented for the I/S process for the production of hydrogen using a high-temperature nuclear heat source to split water. The process includes a countercurrent reactor being developed by CEA within the framework of an international collaboration (I-NERI project) with DOE at General Atomics (San Diego, CA). A ProsimPlus? model of the flowsheet indicates 600 kJ high-temperature heat and 69 kJ electric power are consumed per mole of H₂ product (with an assumed pressure of 120 bars). The net thermal efficiency would be 38% (HHV basis) if electric power is available at a conversion efficiency of 45%.     

Bunsen section thermodynamic model for hydrogen production by the sulfur–iodine cycle

A model for the Bunsen section of the Sulfur–Iodine thermo-chemical cycle is proposed, where sulfur dioxide reacts with excess water and iodine to produce two demixing liquid aqueous phases (H₂SO₄ rich and HI rich) in equilibrium. Considering the mild temperature and pressure conditions, the UNIQUAC activity coefficient model combined with Engels' solvation model is used. The complete model is discussed, with HI solvation by water and by iodine as well as H₂SO₄ solvation by water, leading to a very high complexity with almost hundred parameters to be estimated from experimental data. Taking into account the water excess, a successful reduced model with only 15 parameters is proposed after defining new apparent species. Acids total dissociation and total H⁺ solvation by water are the main assumptions. Results show a good agreement with published experimental data between 25 °C and 120 °C.     

Impedance study of membrane dehydration and compression in proton exchange membrane fuel cells

Electrochemical impedance spectroscopy (EIS) is used to measure drying and rehydration in proton exchange membrane fuel cells running under load. The hysteresis between forward and backward acquisition of polarization curves is shown to be largely due to changes in the membrane resistance. Drying tests are carried out with hydrogen and simulated reformate (hydrogen and carbon dioxide), and quasi-periodic drying and rehydration conditions are studied. The membrane hydration state is clearly linked to the high-frequency arc in the impedance spectrum, which increases in size for dry conditions indicating an increase in membrane resistance. Changes in impedance spectra as external compression is applied to the cell assembly show that EIS can separate membrane and interfacial effects, and that changes in membrane resistance dominate. Reasons for the presence of a capacitance in parallel with the membrane resistance are discussed.     

"Cognitive-neuropsychological function in chronic physical aggression and hyperactivity": Correction to Séguin et al. (2004).

Reports an error in Cognitive-Neuropsychological Function in Chronic Physical Aggression and Hyperactivity by Jean R. Séguin, Daniel Nagin, Jean-Marc Assaad and Richard E. Tremblay (Journal of Abnormal Psychology, 2004[Nov], Vol 113[4], 603-613). The use of a weighted procedure within SAS PROC GLM inflated F statistics and underestimated standard errors that affected only conclusions from secondary analyses that were drawn about the specificity of working memory effects to physical aggression and hyperactivity. The corrected conclusions are presented in the erratum. The last two sentences of the abstract also needed to be corrected in order to reflect the new conclusions. The corrected sentences appear in the erratum as well. (The following abstract of the original article appeared in record 2004-20178-011.) Histories of violence and of hyperactivity are both characterized by poor cognitive-neuropsychological function. However, researchers do not know whether these histories combine in additive or interactive ways. The authors tested 303 male young adults from a community sample whose trajectories of teacher-rated physical aggression and motoric hyperactivity from kindergarten to age 15 were well defined. No significant interaction was found. In a 1st model, both histories of problem behavior were independently associated with cognitive-neuropsychological function in most domains. In a 2nd model controlling for IQ, general memory, and test motivation, the 3 working-memory tests (relevant to executive function) remained associated with physical aggression, and 1 remained associated with hyperactivity. These results support an additive model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of fiber surface modification on the mechanical and water absorption characteristics of sisal/polyester composites fabricated by resin transfer molding

Sisal fibers were subjected to various chemical and physical modifications such as mercerization, heating at 100 °C, permanganate treatment, benzoylation and silanization to improve the interfacial bonding with matrix. Composites were prepared by these fibers as reinforcement, using resin transfer molding (RTM). The mechanical properties such as tensile, flexural and impact strength were examined. Mercerized fiber-reinforced composites showed 36% of increase in tensile strength and 53% in Young’s modulus while the permanganate treated fiber-reinforced composites performed 25% increase in flexural strength. However, in the case of impact strength, the treatment has been found to cause a reduction. The water absorption study of these composites at different temperature revealed that it is less for the treated fiber-reinforced composites at all temperatures compared to the untreated one. SEM studies have been used to complement the results emanated from the evaluation of mechanical properties.     

Eco-friendly TiO2–AC Photocatalyst for the Selective Photooxidation of 4-Chlorophenol

The influence of surface pH of activated carbon on selectivity of TiO₂ during the photooxidation of 4-chlorophenol on UV-irradiation was studied. Chlorine substitution by p-hydroxylation yielding hydroquinone in equilibrium with benzoquinone and o-hydroxylation to 4-chlorocathecol were detected as the main intermediates in the photooxidation of 4CP. Changes in surface pH of carbons from basic to closely neutral induce a remarkably increase in the production of 4-chlorocatechol by a factor of 22 on TiO₂–AC in comparison of TiO₂ alone. A mechanism of interaction between both solids is proposed to explain changes both in photoactivity and photoselectivity of TiO₂. In conclusion, results showed that TiO₂–AC can be used as an alternative green photocatalyst in organic synthesis.     

Estimates of fracture density and uncertainties from well data

This paper aims at building a method to estimate the probability law governing the 3D fracture density of a fractured rock conditioned to the number of traces observed on a borehole image when the spatial distribution of fracture centers is assumed to follow a Poisson process. A closed-form expression of this law, allowing to calculate its mean value as well as a confidence interval, is derived in both cases of a lineic well (scanline) and a cylindrical well. The latter is better adapted to the situation of fracture size of the same order of magnitude as the well radius, which enables the presence of partial traces. In particular, the method takes into account the bias in the density estimate due to the fact that a fracture may cut the well along two distinct traces according to the considered fracture size. Monte Carlo simulations finally show a good agreement with the theoretical results of mean density and confidence interval.     

Numerical method coupling finite elements and boundary elements to model forming process tools

Nowadays, the simulation of forming process is rather well integrated in the industrial numerical codes. However, in order to take into account the possible modifications of the tool during rates of working, a dedicated numerical software is currently developed within the laboratory Roberval, this software allows to simulate forming process. The tool is discretized by boundary elements and the product, which is subjected to non-linearities, is discretized by finite elements. For the product, an isotrope law of behaviour is integrated, and the damage is taken into account by the uncoupled Rice and Tracey model. This paper deals with a contact algorithm, coupling boundary elements and finite elements, programmed in the software KSP. For that, friction is described by the Coulomb law and the resolution of contact problems is done by the penalty method. An adaptive step has been developed in order to increase the robustness of the contact algorithm.     

Optimal control law for classical and multiconjugate adaptive optics

Classical adaptive optics (AO) is now a widespread technique for high-resolution imaging with astronomical ground-based telescopes. It generally uses simple and efficient control algorithms. Multiconjugate adaptive optics (MCAO) is a more recent and very promising technique that should extend the corrected field of view. This technique has not yet been experimentally validated, but simulations already show its high potential. The importance for MCAO of an optimal reconstruction using turbulence spatial statistics has already been demonstrated through open-loop simulations. We propose an optimal closed-loop control law that accounts for both spatial and temporal statistics. The prior information on the turbulence, as well as on the wave-front sensing noise, is expressed in a state-space model. The optimal phase estimation is then given by a Kalman filter. The equations describing the system are given and the underlying assumptions explained. The control law is then derived. The gain brought by this approach is demonstrated through MCAO numerical simulations representative of astronomical observation on a 8-m-class telescope in the near infrared. We also discuss the application of this control approach to classical AO. Even in classical AO, the technique could be relevant especially for future extreme AO systems.