Metal-free graphitic carbon nitride as mechano-catalyst for hydrogen evolution reaction

Graphitic carbon nitride (g-C3N4), as a promising metal-free catalyst for photo-catalytic and electrochemical water splitting, has recently attracted tremendous research interest. However, the underlying catalytic mechanism for the hydrogen evolution reaction (HER) is not fully understood. By using density functional theory calculations, here we have established that the binding free energy of hydrogen atom (ΔGH∗0) on g-C3N4 is very sensitive to mechanical strain, leading to substantial tuning of the HER performance of g-C3N4 at different coverages. The experimentally-observed high HER activity in N-doped graphene supported g-C3N4 (Zheng et al., 2014) is actually attributed to electron-transfer induced strain. A more practical strategy to induce mechanical strain in g-C3N4 is also proposed by doping a bridge carbon atom in g-C3N4 with an isoelectronic silicon atom. The calculated ΔGH∗0 on the Si-doped g-C3N4 is ideal for HER. Our results indicate that g-C3N4 would be an excellent metal-free mechano-catalyst for HER and this finding is expected to guide future experiments to efficiently split water into hydrogen based on the g-C3N4 materials.

Response And Stability Of A Stochastic Beam-Column Using Stochastic Fem

A beam-column resting on continuous Winkler foundation and discrete elastic supports is considered. The beam-column is of variable cross-section and the variation of sectional properties along the axis of the beam-column is deterministic. Young's modulus, mass per unit length and distributed axial loadings of the beam-column have a stochastic distribution. The foundation stiffness coefficient of the Winkler model, the stiffnesses of discrete elastic supports, stiffnesses of end springs and the end thrust, are all considered as random parameters. The material property fluctuations and distributed axial loadings are considered to constitute independent, one-dimension uni-variate homogeneous real stochastic fields in space. The foundation stiffness coefficient, stiffnesses of the discrete elastic supports, stiffnesses of end springs and the end thrust are considered to constitute independent random variables. Static response, free vibration and stability behaviour of the beam-column are studied. Hamilton's principle is used to formulate the problem using stochastic FEM. Sensitivity vectors of the response and stability parameters are evaluated. Using these statistics of free vibration frequencies, mode shapes, buckling parameters, etc., are evaluated. A numerical example is given.

Synthesis of nanoparticles of the giant dielectric material, CaCu3Ti4O12 from a precursor route

A complex oxalate precursor, CaCu3(TiO)(4)(C2O4)(8)center dot 9H(2)O, (CCT-OX), was synthesized and the precipitate that obtained was confirmed to be monophasic by the wet chemical analyses, X-ray diffraction, FTIR absorption and TG/DTA analyses. The thermal decomposition of this oxalate precursor led to the formation of phase-pure calcium copper titanate, CaCu3Ti4O12, (CCTO) at a parts per thousand yen680A degrees C. The bright-field TEM micrographs revealed that the size of the as synthesized crystallites to be in the 30-80 nm range. The powders so obtained had excellent sinterability resulting in high density ceramics which exhibited giant dielectric constants upto 40000 (1 kHz) at 25A degrees C, accompanied by low dielectric losses.

Index properties of illite-bentonite mixtures in electrolyte solutions

Bentonite, commonly used for liner constructions in waste containment systems, possesses many limitations. Illite or illite containing bentonite has been proposed as an alternative material for liner construction. Their properties in different types of pore fluids are important to assess the long-term performance of the liner. Further, the illite-bentonite interaction occurs and changes their properties. The effect of these interactions is known when the pore fluid is only water. How their properties are modified in electrolyte solutions has been brought out in this paper. The index properties have been studied since they give an indication of their engineering properties. Due to reduction in the thickness of the diffused double layer and consequent particle aggregation in bentonite, the effect of clay-clay interaction reduces in electrolyte solutions. In electrolyte solutions, the liquid limit, the plasticity index, and free swell index of bentonite are lower than illite. The plasticity index of bentonite is further reduced in KCI solution. Clays with a higher plasticity index perform better to retain pollutants and reduce permeability. Hence, the presence of both illite and bentonite ensures better performance of the liner in different fluids.

Controversy on the Free Energy of Formation of CaO Additional Evidence in Support of Thermochemical Data

The standard free energies of formation of CaO derived from a variety of high-temperature equilibrium measurements made by seven groups of experimentalists are significantly different from those given in the standard compilations of thermodynamic data. Indirect support for the validity of the compiled data comes from new solid-state electrochemical measurements using single-crystal CaF2 and SrF2 as electrolytes. The change in free energy for the following reactions are obtained: CaO + MgF2 --> MgO + CaF2 Delta G degrees = -68,050 -2.47 T(+/-100) J mol(-1) SrO + CaF2 --> SrF2 + CaO Delta G degrees = -35,010 + 6.39 T (+/-80) J mol(-1) The standard free energy changes associated with cell reactions agree with data in standard compilations within +/- 4 kJ mol(-1). The results of this study do not support recent suggestions for a major revision in thermodynamic data for CaO.

Remarkable Capacity Retention of Nanostructured Manganese Oxide upon Cycling as an Electrode Material for Supercapacitor

Electrochemical capacity retention of nearly X-ray amorphous nanostructured manganese oxide (nanoMnO2) synthesized by mixing directly KMnO4 with ethylene glycol under ambient conditions for supercapacitor studies is enhanced significantly. Although X-ray diffraction (XRD) pattern of nanoMnO2 shows poor crystallinity, it is found that by Mn K-edge X-ray absorption near edge structure (XANES) measurement that the nanoMnO2 obtained is locally arranged in a δ-MnO2-type layered structure composed of edge-shared network of MnO6 octahedra. Field emission scanning electron microscopy and XANES measurements show that nanoMnO2 contains nearly spherical shaped morphology with δ-MnO2 structure, and 1D nanorods of α-MnO2 type structure (powder XRD) in the annealed (600 °C) sample. Volumetric nitrogen adsorption−desorption isotherms, inductively coupled plasma analysis, and thermal analysis are carried out to obtain physicochemical properties such as surface area (230 m2 g−1), porosity of nanoMnO2 (secondary mesopores of diameter 14.5 nm), water content, composition, etc., which lead to the promising electrochemical properties as an electrode for supercapacitor. The nanoMnO2 shows a very high stability even after 1200 cycles with capacity retention of about 250 F g−1.

Image-based midsole insert design and the material effects on heel plantar pressure distribution during simulated walking loads

The primary objective of this paper is to study the use of medical image-based finite element (FE) modelling in subjectspecific midsole design and optimisation for heel pressure reduction using a midsole plug under the calcaneus area (UCA). Plugs with different relative dimensions to the size of the calcaneus of the subject have been incorporated in the heel region of the midsole. The FE foot model was validated by comparing the numerically predicted plantar pressure with biomechanical tests conducted on the same subject. For each UCA midsole plug design, the effect of material properties and plug thicknesses on the plantar pressure distribution and peak pressure level during the heel strike phase of normal walking was systematically studied. The results showed that the UCA midsole insert could effectively modify the pressure distribution, and its effect is directly associated with the ratio of the plug dimension to the size of the calcaneus bone of the subject. A medium hardness plug with a size of 95% of the calcaneus has achieved the best performance for relieving the peak pressure in comparison with the pressure level for a solid midsole without a plug, whereas a smaller plug with a size of 65% of the calcaneus insert with a very soft material showed minimum beneficial effect for the pressure relief.

Unsteady Free-Convection Flow on a Rotating flat-Plate Under Nonuniform Gravity

The free convection problem with nonuniform gravity finds applications in several fields. For example, centrifugal gravity fieldsarisein many rotating machinery applications. A gravity field is also created artificially in an orbital space station by rotation. The effect of nonuniform gravity due to the rotation of isothermal or nonisothermal plates has been studied by several authors [l-5] using various mathematical techniques.

#auspol: The hashtag as community, event, and material object for engaging with Australian politics

Critical, loud, highly discursive and polarised; the #auspol hashtag represents a space, an event and a network for politically involved individuals to engage in and with Australian politics and speak to, at and about a variety of involved stakeholders. Contributors declare, debate and often berate each other’s opinions about current Australian politics. The hashtag itself is an important material object and engagement event involved within this performance of political participation. As a long-standing institution in the Twittersphere, and one studied by the authors and their colleagues since its early beginnings (Bruns and Burgess, 2011; Bruns and Stieglitz, 2012; 2013), the #auspol hashtag provides a potent case study through which to explore the discursive and affective dimensions of a hashtag public. This chapter that engages both empirically and theoretically with the use of this particular hashtag on Twitter to provide a qualitatively illustrated case in point for thinking about the long-term use of political hashtags as engagement events.

"Do Not Celebrate Your Feast without Your Neighbours" : A Study of References to Feasts and Festivals in Non-Literary Documents from Ramesside Period Deir el-Medina

This dissertation is a study of the forms and functions of feasts and feasting in the ancient Egyptian village of Deir el-Medina in Thebes (modern Luxor). This particular village, during the New Kingdom (c. 1550 1069 BC), was inhabited by the men (and their families) who constructed the Royal Tombs in the Valley of the Kings and the Valley of the Queens. The royal artisans were probably more literate than the average Egyptians and the numerous Ramesside Period (c. 1295 1069 BC) non-literary texts found in the excavations of the village and its surroundings form the source material for this study. In this study, the methods used are mainly Egyptological and the references to feasts and feasting are considered in view of what is known of New Kingdom Egypt, Thebes, and Deir el-Medina. Nevertheless, it is the use of the methodological concept local vernacular religion that has resulted in the division of the research findings into two sections, i.e., references to feasts celebrated both in and outside the community and other references to feasts and feasting in the village. When considering the function of the feasts celebrated at Deir el-Medina, a functional approach to feasts introduced by anthropologists and archaeologists is utilized. The Deir el-Medina feasts which were associated with the official religion form a festival calendar of feasts celebrated annually on the same civil calendar day. The reconstructed festival calendar of Deir el-Medina reflects the feasts celebrated around Thebes or, at least, in Western Thebes. The function of the nationally and regionally observed feasts (which, at least at Deir el-Medina, resulted in a work-free day) may have been to keep people content so that they would continue to work which was to the advantage of the king and the elite surrounding him. Local feasts appear to have been observed more irregularly at Deir el-Medina or perhaps according to the lunar calendar. Feasts celebrated by the community as a whole served to maintain the unity of the group. In addition to feasts celebrated by the entire community, the inhabitants of Deir el-Medina could mark their own personal feasts and organize small gatherings during public feasts. Through such feasts, an individual man might form alliances and advance his chances of a favourable marriage or of acquiring a position on the work crew.

Algebraic and geometric intersection numbers for free groups

We show that the algebraic intersection number of Scott and Swarup for splittings of free groups Coincides With the geometric intersection number for the sphere complex of the connected sum of copies of S-2 x S-1. (C) 2009 Elsevier B.V. All rights reserved.

Mesh-free approximations via the error reproducing kernel method and applications to nonlinear systems developing shocks

Error estimates for the error reproducing kernel method (ERKM) are provided. The ERKM is a mesh-free functional approximation scheme [A. Shaw, D. Roy, A NURBS-based error reproducing kernel method with applications in solid mechanics, Computational Mechanics (2006), to appear (available online)], wherein a targeted function and its derivatives are first approximated via non-uniform rational B-splines (NURBS) basis function. Errors in the NURBS approximation are then reproduced via a family of non-NURBS basis functions, constructed using a polynomial reproduction condition, and added to the NURBS approximation of the function obtained in the first step. In addition to the derivation of error estimates, convergence studies are undertaken for a couple of test boundary value problems with known exact solutions. The ERKM is next applied to a one-dimensional Burgers equation where, time evolution leads to a breakdown of the continuous solution and the appearance of a shock. Many available mesh-free schemes appear to be unable to capture this shock without numerical instability. However, given that any desired order of continuity is achievable through NURBS approximations, the ERKM can even accurately approximate functions with discontinuous derivatives. Moreover, due to the variation diminishing property of NURBS, it has advantages in representing sharp changes in gradients. This paper is focused on demonstrating this ability of ERKM via some numerical examples. Comparisons of some of the results with those via the standard form of the reproducing kernel particle method (RKPM) demonstrate the relative numerical advantages and accuracy of the ERKM.