Growing Self-Reconstruction Maps

In this paper, we propose a new method for surface reconstruction based on growing self-organizing maps (SOMs), called growing self-reconstruction maps (GSRMs). GSRM is an extension of growing neural gas (GNG) that includes the concept of triangular faces in the learning algorithm and additional conditions in order to include and remove connections, so that it can produce a triangular two-manifold mesh representation of a target object given an unstructured point cloud of its surface. The main modifications concern competitive Hebbian learning (CHL), the vertex insertion operation, and the edge removal mechanism. The method proposed is able to learn the geometry and topology of the surface represented in the point cloud and to generate meshes with different resolutions. Experimental results show that the proposed method can produce models that approximate the shape of an object, including its concave regions, boundaries, and holes, if any.      

Simultaneous removal of 3d transition metals from multi-component solutions by activated carbons from co-mingled wastes

The main purpose of the present work was to study the simultaneous removal of 3d transition metals from multi-component solutions by novel porous material obtained from carbon-containing liquid and solid waste. The activated carbon was prepared from co-mingled natural organic waste: 25% sunflower husks, 50% petroleum waste and 25% low-grade bituminous coal. The porous carbon material was obtained via stages of pre-oxidation with binary eutectic Na/K carbonates (in order to avoid melting and coke formation), followed by “step by step” carbonization at 100–400 °C in an inert atmosphere and activation with steam at 850 °C.

The adsorption of the 3d transition metals: copper (II), cobalt (III), nickel (II), iron (III), and chromium (III), on novel activated carbons has been investigated using multi-component model solutions. Experiments have been carried out on the thermodynamics of the simultaneous adsorption of the 3d transition metals in a static mode. The total metal removal combines the process of metal hydroxide precipitation in the solution with the metal cation adsorption on negatively charged carbon surface in a single operation unit. The carbon/metals interaction at the surface of spent adsorbents is discussed.     

MCM-41 anchored manganese salen complexes as catalysts for limonene oxidation

This work reports the covalent attachment of three different salen-based complexes on MCM-41, using two different methods. In both methods, a diisocyanate is used as a binder. All the prepared catalysts were tested on the liquid phase limonene oxidation reaction, using diluted t-butyl hydroperoxide as oxidant. Limonene oxide, carveol, carvone and a polymer were the main products obtained. The preservation of the MCM-41 channel system was checked by X-ray diffraction, nitrogen adsorption analysis and transmission electron microscopy (TEM). Catalytic activity seems to increase in the following order: Mn(4-OHsalen) < Mn(4-OHsalhd) < Mn(4-OHsalophen).The most active catalysts were used in four consecutive experiments without any activity loss, confirming the success of the anchoring process and the catalysts stability.     

Transparent p-type CuxS thin films

The effect of different mild post-annealing treatments in air, at 270 °C, for 4-6 min, on the optical, electrical, structural and chemical properties of copper sulphide (Cu_xS) thin films deposited at room temperature are investigated. Cu_xS films, 70 nm thick, are deposited on glass substrates by vacuum thermal evaporation from a Cu₂S:S (50:50 wt.%) sulphur rich powder mixture. The as-deposited highly conductive crystalline CuS (covellite) films show high carrier concentration (∼10²² cm⁻³), low electrical resistivity (∼10⁻⁴ Ω cm) and inconclusive p-type conduction. After the mild post-annealing, these films display increasing values of resistivity (∼10⁻³ to ∼10⁻² Ω cm) with annealing time and exhibit conclusive p-type conduction. An increase of copper content in Cu_xS phases towards the semiconductive Cu₂S (chalcocite) compound with annealing time is reported, due to re-evaporation of sulphur from the films. However, the latter stoichiometry was not obtained, which indicates the presence of vacancies in the Cu lattice. In the most resistive films a Cu₂O phase is also observed, diminishing the amount of available copper to combine with sulphur, and therefore the highest values of optical transmittance are reached (65%). The appearance on the surface of amorphous sulphates with annealing time increase is also detected as a consequence of sulphur oxidation and replacement of sulphur with oxygen. All annealed films are copper deficient in regards to the stoichiometric Cu₂S and exhibit stable p-type conductivity.     

A comparison between techniques for global surface interpolation inshaped reflector analysis

Usual geometrical optics based syntheses of shaped reflectors provide numerically defined surfaces which must be interpolated for subsequent evaluation of the antenna secondary field to check against design specifications. The implementation of three techniques capable of performing global interpolations of numerically defined (3D) surfaces, namely, the quintic pseudosplines, polynomial Fourier series, and Jacobi polynomial-sinusoidal expansions, is explored. The relative superior stability of the first is demonstrated for the synthesis of shaped reflectors presenting critical behavior of their principal curvatures     

Sampled fibre Bragg grating sensors for simultaneous strain andtemperature measurement

A new scheme is presented for simultaneous measurement of strain and temperature using a sampled fibre Bragg grating based on a long period structure written using the electric arc technique. The temperature and strain measurement resolutions are estimated to be ±0.50°C/√Hz and ±3.38 μϵ/√Hz, respectively     

Some explicit formulas for mixed exponential service systems

We present some explicit formulas for queue length and waiting time distributions of customers in the M/HE_m/1 queue. The formulas are obtained with the aid of roots of quadratic, cubic, and quartic polynomials constructed from a recurrence equation. With an example, we demonstrate that the formulas for queueing distributions are extremely accurate, while the corresponding infinite history M/GI/1 recurrence equation is not. Applications include computation of queueing distributions, accurate tail probabilities, and in systems where exponentiality can be replaced by hyperexponentiality. The explicit solutions are easier to use than the problem-specific partial fraction expansions of the Pollachek-Khinchin transform.     

Influence of substrate temperature on N-doped ZnO films deposited by RF magnetron sputtering

Nitrogen-doped ZnO films were deposited by RF magnetron sputtering in 75% of N₂ / (Ar + N₂) gas atmosphere. The influence of substrate temperature ranging from room temperature (RT) to 300 °C was analyzed by X-ray diffractometry (XRD), spectrophotometry, X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS) and Hall measurements setup. The XRD studies confirmed the hexagonal ZnO structure and showed that the crystallinity of these films increased with increasing substrate temperature (T_s). The optical studies indicate the average visible transmittance in the wavelength ranging 500-800 nm increases with increasing T_s. A minimum transmittance (9.84%) obtained for the films deposited at RT increased with increasing T_s to a maximum of 88.59% at 300 °C (500-800 nm). Furthermore, it was understood that the band gap widens with increasing T_s from 1.99 eV (RT) to 3.30 eV (250 °C). Compositional analyses (XPS and SIMS) confirmed the nitrogen (N) incorporation into the ZnO films and its decreasing concentration with increasing T_s. The negative sign of Hall coefficients confirmed the n-type conducting.     

A new and easy method for anchoring manganese salen on MCM-41

This work reports a new method to covalently attach manganese salophen complex onto MCM-41, using a diisocyanate as a binder. The prepared catalyst was tested on the liquid phase limonene oxidation reaction. Diluted t-Butyl hydroperoxide was used as oxygen supplier. Limonene oxide, carveol and carvone are formed, but the main product obtained was a polymer. The preservation of the MCM-41 channel system was checked by X-ray diffraction and nitrogen adsorption analysis. The use of the same catalyst sample in four consecutive experiments, without loss of activity, is a confirmation of the success of the anchoring process.     

Organizational Improvisation: From the Constraint of Strict Tempo to the Power of the Avant‐Garde

Improvisation is too simple a name for a complex class of processes. The improvisational label, in fact, covers very different processes, from impromptu, ad‐libbed responses to carefully designed organizational choreographies. We discuss different forms of organizational improvisation (ad‐hoc, covert, provocative and managed), and trace their roots in the discipline of organization theory, in order to promote a granular and power‐sensitive understanding of improvisation in organizations.