One-pot sonication-assisted polyol synthesis of trimetallic core–shell (Pd,Co)@Pt nanoparticles for enhanced electrocatalysis

In this report, the synthesis and characterization of trimetallic (Pd,Co)@Pt nanoparticles (NPs) with Pt-enriched surfaces are detailed. (Pd,Co)@Pt NPs supported on carbon with different elemental compositions (Pd₅₀Co₂₀Pt₃₀, Pd₃₄Co₂₇Pt_39, and Pd₂₁Co₃₄Pt₄₅) are synthesized by sonochemical reactions of Pt(acac)₂, Pd(acac)₂, and Co(acac)₂ in ethylene glycol. The NPs are subsequently characterized by X-ray diffractometry, transmission electron microscopy, and inductively coupled plasma − atomic emission spectroscopy to determine their particle size, morphology, and elemental composition. The existence of a Pt-enriched surface on the (Pd,Co)@Pt NPs is demonstrated by line profiles obtained via scanning transmission microscopy − energy dispersive spectroscopy. The NPs are applied to electrocatalysis for oxygen reduction reactions. When compared to a commercial Pt catalyst, the onset potential of the NPs increased by 22 mV, while the specific and mass activities were enhanced by factors of ∼ 2.7–4.9 and 4.3–6.3, respectively. The (Pd,Co)@Pt NPs also showed superior stability, as the onset potential was reduced by 11–19 mV after 5000 potential cycles when compared to the 45 mV reduction observed for a commercial Pt catalyst.     

Solar radiation assisted mixed convection MHD flow of nanofluids over an inclined transparent plate embedded in a porous medium

The present paper investigates analytically and numerically the magneto-hydrodynamic (MHD) mixed convection flow of nanofluid over a nonlinear stretching inclined transparent plate embedded in a porous medium under the solar radiation. The two-dimensional governing equations are obtained considering the dominant effect of boundary layer and also in presence of the effects of viscous dissipation and variable magnetic field. These equations are transformed by the similarity transformation to two coupled nonlinear transformed equations and then solved using a numerical implicit method called Keller-Box. The effect of various parameters such as nanofluid volume fraction, magnetic parameter, porosity, effective extinction coefficient of porous medium, solar radiation flux, plate inclination angle, diameter of porous medium solid particles and dimensionless Eckert, Richardson and Prandtl numbers have been studied on the dimensionless temperature and velocity profiles. Also the results are presented based on Nusselt number and Skin friction coefficient.     

Mono and co-substitution of Sr2+ and Ca2+ on the structural,electrical and optical properties of barium titanate ceramics

In this work, Ba_0.9Sr_0.1TiO₃, Ba_0.7Sr_0.3TiO₃, Ba_0.5Sr_0.5TiO₃, Ba_0.5Ca_0.25Sr_0.25TiO₃ and Ba_0.5Ca_0.5TiO₃ have been synthesized to evaluate the influence of mono and co-substitution of A-site dopants (Sr²⁺ and Ca²⁺) on the structural, electrical and optical properties of BaTiO₃ ceramics. Sr²⁺ added samples showed a tetragonal structure which became slightly distorted with increasing Sr²⁺ concentration and finally achieved a cubic structure for x?=?0.50. Ba_0.5Ca_0.5TiO₃ also retained their tetragonality with limited solubility. Presence of second phase, CaTiO₃ demonstrated the fact of restricted solubility. The concurrent effect of Sr²⁺ and Ca²⁺ didn't alter the tetragonal structure. Sr²⁺ substitution enhanced the apparent density as well as grain size which stimulated the domain wall motion and improved dielectric properties. However, the ferroelectric nature of Ba_1-xSr_xTiO₃ was poor due to the redistribution of point defect at grain boundary. The optical band gap was found to be reduced from 3.48?eV to 3.28?eV with increasing Sr²⁺ content. Co-substitution of cations improved the electrical property significantly. The highest value of dielectric constant was found to be ～547 for Ba_0.5Ca_0.25Sr_0.25TiO₃ ceramics. Both Ba_0.5Ca_0.25Sr_0.25TiO₃ and Ba_0.5Ca_0.5TiO₃ had developed P-E loop having lower coercive field and moderate optical band gap energy. Co-doping with Sr²⁺ and Ca²⁺ was a good approach enhancing materials electrical as well as optical property.     

Effect of Si and Ge Surface Doping on the Be<Subscript>2</Subscript>C Monolayer: Case Study on Electrical and Optical Properties

The electronic and optical properties of X (Si, Ge) doped Be₂C monolayer has been investigated using the all-electron full potential linear augmented plane wave (FP-LAPW + lo) method in a scalar relativistic version as embodied in the Wien2k code based on the density functional theory. Using cohesive energy calculation, it has been shown that the Si and Ge doped to Be₂C monolayer have stable structures and the doping processes modified the direct band gaps. The calculated electronic band structure confirm the direct band gap nature since the conduction band minimum and the valence band maximum are located at the center of the Brillouin zone. The total and partial density of states help to gain further information regarding the hybridizations and the orbitals which control the energy band gap. The calculated optical properties help to gain deep insight into the electronic structure. Our calculated results indicate that the X (Si, Ge) doped Be₂C monolayer can be have potential application in optoelectronics devices.     

Modeling of threshold voltage of a quadruple gate transistor

In this paper, a three dimensional analytical solution of electrostatic potential is presented for undoped (or lightly doped) quadruple gate MOSFET by solving 3-D Poisson's equation. It is shown that the threshold voltage predicted by the analytical solution is in close agreement with TCAD 3-D numerical simulation results. For numerical simulation, self-consistent Schrodinger-Poisson equations, calibrated by 2D non equilibrium green function simulation, are used. This analytical model not only provides useful physics insight of effects of gate length and body width on the threshold voltage, but also serves as a basis for compact modeling of quadruple gate MOSFETs.     

An integer‐valued data envelopment analysis model with bounded outputs

Integer‐valued data envelopment analysis (DEA) with alternative returns to scale technology has been introduced and developed recently by Kuosmanen and Kazemi Matin. The proportionality assumption of their introduced “natural augmentability” axiom in constant and nondecreasing returns to scale technologies makes it possible to achieve feasible decision‐making units (DMUs) of arbitrary large size. In many real world applications it is not possible to achieve such production plans since some of the input and output variables are bounded above. In this paper, we extend the axiomatic foundation of integer‐valued DEA models for including bounded output variables. Some model variants are achieved by introducing a new axiom of “boundedness” over the selected output variables. A mixed integer linear programming (MILP) formulation is also introduced for computing efficiency scores in the associated production set.     

Experimental evaluation of mechanically stabilized earth walls with recycled crumb rubbers

Traditional techniques for treatment of waste rubber, such as burning, generate some highly non-degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic, chromium, lead, manganese and nickel. For this, scrap tires are used as lightweight alternative materials in many engineering applications, such as retaining wall backfilling. In the present study, 90 laboratory models were prepared to evaluate the stability of mechanically stabilized earth (MSE) walls with plate anchors. Then, the bearing capacity and horizontal displacements of the retaining walls were monitored by exerting a static loading to investigate the effects of adding different contents (5 wt%, 10 wt%, 15 wt% and 20 wt%) of recycled crumb rubber (RCR) to the fill of a mechanically stabilized retaining wall with plate anchors. To visualize the critical slip surface of the wall, the particle image velocimetry (PIV) technique was employed. Results showed that the circular anchor plates almost continually provided a higher bearing capacity and wall stability than the square plates. Moreover, the backfill with 15 wt% RCR provided the maximum bearing capacity of the wall. Increasing the weight percentage of RCR to 20 wt% resulted in a significant reduction in horizontal displacement of the wall, which occurred due to the decrease in lateral earth pressure against the whole walls. An increase in RCR content resulted in the decrease in the formation of failure wedge and the expansion of the wall slip surface, and the failure wedge did not form in the sand mixtures with 15 wt% and 20 wt% RCRs.     

The comparison of postoperative multiple organ failure with arterial disease to that with gastrointestinal cancer]

The clinical features of 22 postoperative multiple organ failure (MOF) patients, comprised of 8 with arterial disease (A-MOF) and 14 with gastrointestinal cancer (G-MOF), were investigated. Differences in the operative time, blood loss, and mortality were not significant. The initial organ impaired was the lungs in 78.6% of G-MOF patients and the heart or kidneys in all A-MOF patients. Infection developed in over 80% of both groups. In many A-MOF patients, the pneumonia or septicemia developed secondary to organ failure, while intraabdominal infection triggered respiratory failure in many G-MOF patients. Our organisms in infected specimens and their antibiotic sensitivities was valuable for the early administration of effective antibiotics. Upper gastrointestinal tract bleeding was important in the prognosis of both groups and occurred more frequently in A-MOF than in G-MOF patients. Consumption coagulopathy in A-MOF patients and DIC induced by infection in G-MOF patients mainly caused such bleeding. Preoperative administration of heparin was effective in improving coagulopathy. Furthermore, measurement of intramural pH with tonometer in the stomach and gastric irrigation with oxygenated perfluorochemicals were effective in the prediction and prevention of gastrointestinal bleeding.