Production of hydrogen over bimetallic Pt–Ni/δ-Al2O3: I. Indirect partial oxidation of propane

Indirect partial oxidation (IPOX) of propane was studied over bimetallic 0.2 wt.% Pt–15 wt.% Ni/δ-Al₂O₃ catalyst in the 623–743 K temperature range. The unreduced and reduced forms of the catalyst were characterized by ESEM–EDAX and X-ray diffraction (XRD). In the IPOX tests, the effects of steam to carbon ratio (S/C), carbon to oxygen ratio (C/O₂) and residence time (W/F (g_cat h/mol HC)) on the hydrogen production activity, selectivity and product distribution were studied in detail. The effect of temperature program applied (increasing from 623 to 743 K, ITP; decreasing from 743 to 623 K, DTP) during reaction was also tested. The results showed that the Pt–Ni bimetallic system has superior performance characteristics compared to the monometallic catalysts reported in literature. The reason is thought to be the utilization of the catalyst particles as micro heat exchangers during IPOX; the heat generated by Pt sites during exothermic total oxidation (TOX) being readily transferred through the catalyst particles acting as micro heat exchangers to the Ni sites, which promote endothermic steam reforming (SR). The optimal conditions were found as S/C = 3, C/O₂ = 2.70 and W/F = 0.51 g_cat h/mol HC for IPOX of propane on the basis of high hydrogen productivity and selectivity between 623 and 748 K for the experimental conditions tested. The thermo-neutral points obtained showed the sustainability of reaction in terms of energy.     

THE ELECTROIMPACT COMPACTION OIF POWDERS: MECHANICS, STRUCTURE AND PROPERTIES

An electroimpact compaction method recently developed for powder consolidation is described In terms of the basic principles of electric discharge and dynamic compaction processes. The influence of processing parameters, microstructural characteristics and mechanical properties of preforms obtained are discussed. Mathematical models for the mechanics of compaction, electrical resistance, discharge current variations and comparisons with experimental results are presented. The best set of properties are obtained when electrical discharge is applied to cause interparticle fusion at the instant when dynamic compaction pressure attains its peak level.     

Alumina scale growth at zirconia-MCrAlY interface: a microstructural study

High-temperature oxide scale growth at the ceramic-metal interface is a major contributor to the thermomechanical resistance of thermal barrier coatings for hot stages of gas turbines. In order to better understand this phenomenon, microstructural observations of the alumina scales formed at 1100 and 1200 °C under air, between low-pressure plasma-sprayed NiCrAlY and air plasma-sprayed ZrO₂-8.5 wt % Y₂O₃, have been performed by classical and analytical transmission electron microscopy on transverse thin foil specimens. The evolution of the oxide grain morphology from the metal-oxide to the oxide-oxide interface suggests that the scale growth principally takes place at the metal-oxide interface. Segregation of yttrium at oxide grain boundaries has been detected as well as significant quantities of zirconium inside the alumina grains. The oxide growth seems to be dominated by a classical grain-boundary oxygen diffusion mechanism. The presence of zirconium inside the alumina grains also suggests that Al₂O₃ partially forms by chemical reduction of ZrO₂ by AI. The comparison between the microstructures observed and that of alumina scales grown under similar conditions on bare MCrAlY alloys gives some insight into how the ceramic top-coat modifies NiCrAlY high-temperature oxidation mechanisms.     

Poly-functional Catalyst Development for Benzene Production from Alkyl-aromatic Mixture via Hydrodealkylation

Development of a poly-functional catalyst that has higher hydrodealkylation activity based on 15% Cr/γ- Al₂ O₃ was researched for benzene production from an alkyl-aromatic mixture via hydrodealkylation. For this goal, the effects of the promoters like Fe, Co, or Ni and their concentrations on the activity of a Cr/Al₂ O₃ catalyst were investigated. Toluene + n-heptane + tetrahydrotiophene (89:10:1 w%) model mixture, which has the same content as industrial aromatics, was used as feedstock. The activities of catalysis in reactions of hydrodealkylation, hydrocracking, and hydrogenolize with respect to conversions of toluene, heptane, and tetrahydrotiophene were tested, respectively. As to the obtained results, the catalyst including 5% Fe has a higher hydrodealkylation activity, compared to the catalyst including Co, and especially to the alumocrom catalyst not including a promoter, while it has a lower coke formation and reduced activity to the catalyst including Ni.     

Automatic recognition fingerspelling gestures in multiple languages for a communication interface for the disabled

This paper presents the design and evaluation of a multi-lingual fingerspelling recognition module that is designed for an information terminal. Through the use of multimodal input and output methods, the information terminal acts as a communication medium between deaf and blind people. The system converts fingerspelled words to speech and vice versa using fingerspelling recognition, fingerspelling synthesis, speech recognition and speech synthesis in Czech, Russian, and Turkish languages. We describe an adaptive skin color based fingersign recognition system with a close to real-time performance and present recognition results on 88 different letters signed by five different signers, using above four hours of training and test videos.     

Hydrogen Sulfide Metabolite,Sodium Thiosulfate: Clinical Applications and Underlying Molecular Mechanisms

Thiosulfate in the form of sodium thiosulfate (STS) is a major oxidation product of hydrogen sulfide (H₂S), an endogenous signaling molecule and the third member of the gasotransmitter family. STS is currently used in the clinical treatment of acute cyanide poisoning, cisplatin toxicities in cancer therapy, and calciphylaxis in dialysis patients. Burgeoning evidence show that STS has antioxidant and anti-inflammatory properties, making it a potential therapeutic candidate molecule that can target multiple molecular pathways in various diseases and drug-induced toxicities. This review discusses the biochemical and molecular pathways in the generation of STS from H₂S, its clinical usefulness, and potential clinical applications, as well as the molecular mechanisms underlying these clinical applications and a future perspective in kidney transplantation.     

Unveiling the presence of mixed oxidation states of Europium in Li7+δEuxLa3−δZr2−δO12−δ garnet and its impact on the Li-ion conductivity

Recently, lanthanides have been employed by researchers to examine their impact on the structure and properties of Li₇La₃Zr₂O₁₂ (LLZO) garnets. In this regard, we developed Europium oxide (Eu₂O₃) doped LLZO (Li_7+δEu_xLa_3−δZr_2−δO_12−δ) solid electrolyte which demonstrates a cubic phase with the symmetry of Iad (No.230) at room temperature. In this investigation, different concentrations of Eu ranging from 0.1 to 0.6 atoms per formula unit (pfu) were doped into Li₇La₃Zr₂O₁₂ to evaluate the impact of Eu on the stability of the cubic phase and thereby the ionic conductivity. The results unveiled that upon doping Eu³⁺ ions, the Eu²⁺ state is also formed and is then self-doped into the structure in which Rietveld refinement coupled with XPS, EPR, and solid-state NMR suggests that Eu³⁺ ions most probably partially occupy Zr⁴⁺ (16a) site, the Eu²⁺ ions occupy La³⁺ (24d) site, and the Li⁺ ions occupy two different sites (24d and 96h). It was further found that such a site preference induces distortion at LaO₈ polyhedrons opening up the neck for Li-ions diffusion, thereby enhancing the ionic conductivity. Moreover, it was revealed that Li-ions probably hop from 96h to 24d and then to 96h site to generate the Li-ion movement. Overall, by introducing Eu ions into the LLZO structure, an enhanced bulk ionic conductivity of 0.30 × 10⁻³ S/cm at 298 K with a minimum electronic conductivity of 2.547 × 10⁻⁹ S/cm at 298 K was achieved.     

Mechanical and viscoelastic properties of polyethylene-based microfibrillated composites from 100% recycled resources

In this study, recycled polyethylene (rPE) based microfibrillated composites (MFCs) were developed while incorporating recycled poly(ethylene terephthalate) (rPET) and recycled polyamide 6 (rPA) as the reinforcing fibrillar phases at a given weight ratio of 80 wt% (rPE)/20 wt% (rPET or rPA). The blends were first melt processed using a twin-screw extruder. The extrudates were then cold stretched at a drawing ratio of 2.5 to form rPET and rPA fibrillar structures. Next, the pelletized drawn samples were injection molded at the barrel temperatures below the melting temperatures of rPET and rPA. The tensile, three-point bending, impact strength, dynamic thermomechanical, and rheological properties of the fabricated MFCs were analyzed. The effects of injection molding barrel temperature (i.e., 150°C and 190°C) and extrusion melt processing temperature (i.e., 250°C and 275°C) on the generated fibrillar structure and the resultant properties were explored. A strong correlation between the fibrillar morphology and the mechanical properties with the extrusion and injection molding temperatures was observed. Moreover, the ethylene/n-butyl acrylate/glycidyl methacrylate (EnBAGMA) terpolymer and maleic anhydride grafted PE (MAH-g-PE) were, respectively, melt processed with rPE/rPET and rPE/rPA6 blends as compatibilizers. The compatibilizers refined the fibrillar structure and remarkably influenced mechanical properties, specifically the impact strength.     

Yttria-stabilized hafnia-zirconia thermal barrier coatings: The influence of hafnia addition on TBC structure and high-temperature behaviour

The search for more reliable and durable thermal barrier systems is a key factor for future aircraft turbine engines success. Hafnia is therefore an attractive ceramic component due to its similarity to zirconia and its elevated structural transformation temperatures. We report here structural and thermomechanical investigations of various plasma-sprayed coatings composed of ZrO₂+x mol% HfO₂ (x=0, 25, 50 and 100), partially stabilized by 4.53 mol% yttria. X-ray diffraction studies show that, a metastable, non-transformable, high yttrium content, tetragonal solid solution is the only phase observed on the as-sprayed samples. This phase is crystallographically equivalent to the t phase described for classical yttrium-partially stabilized zirconia (Y-PSZ) thermal barrier coatings (TBCs). Upon high-temperature annealing in air (T=1200C), however, the return of this t phase to equilibrium differs from the classical tt+c reaction. According to literature data, reactions of the type tt+c+m should prevail at the highest hafnia contents (x50). Indeed, important quantities of monoclinic phase are accordingly being observed upon cooling. Thermal cycling of TBC samples in air has been performed at 1100C. The Young's modulus of the ceramic coating, which progressively increases when hafnia is substituted for zirconia, has a strong influence on TBC thermomechanical resistance.     

Joint forecasts of Dow Jones stocks under general multivariate loss function

When forecasts are assessed by a general loss (cost-of-error) function, the optimal point forecast is, in general, not the conditional mean, and depends on the conditional volatility—which, for stock returns, is time-varying. In order to provide forecasts of daily returns of 30 DJIA stocks under a general multivariate loss function, the following issues are addressed. We discuss what conditions define a multivariate loss function, and a simple class of such functions is proposed. Based on suitable combinations of univariate losses, the suggested multivariate functions are convenient for practical applications with many variables. To keep the computational aspect tractable, a flexible multivariate GARCH model is employed in estimating the conditional forecast distributions. The model easily copes with large number of series while allowing for skewness, fat tails, non-ellipticity, and tail dependence. Based on Engle’s DCC GARCH, it uses multivariate affine generalized hyperbolic distributions as conditional probability law, and the number of parameters to be estimated simultaneously does not depend on the number of series. The model is fitted using daily data from 2002 to 2007 (keeping data from 2008 for out-of-sample forecasts), and a bootstrap procedure is used to derive point forecasts under several multivariate loss functions of the proposed type.