The dual role of silver during silicon etching in HF solution

ABSTRACT: It was reported that during silicon etching, silver was subjected to have a controversial role. Some researchers debate that silver protects silicon, and, at the same time, other ones confirm that silver catalyzes silicon underneath. In this paper, we give experimental results arguing the dual role that silver has during the formation of silicon nanostructures. We give a proof that the role of silver depends on the experimental details and the intrinsic properties of silver during its deposition on the silicon wafer. Through our investigations, we tracked the silver particles that indicated which mechanism is involved. Characterizations of the prepared samples were made using a Scanning Electron Microscope (SEM).     

Re-evaluation of Adhesive Fracture Energy

A model to evaluate the Energy Release Rate (ERR) of adhesives using the Double Cantilever Beam (DCB) specimen is described. The model accounts for the adhesive bond thickness and its material properties. The analysis, considered as an improvement to the built-in cantilever beam model, treats the adherend as a finite beam which is partly free and partly supported by an elastic foundation and the adhesive bond as a thin strip under prescribed displacement. The results show significant effect of the adhesive parameters on the total ERR and that the built-in cantilever model underestimates the ERR. In general, the contribution of the adhesive bond to the ERR increases for softer adhesives, shorter cracks and thicker bonds.     

On the simplex algorithm ‘revised form’

The purpose of this paper is an amelioration of the ‘product form of the inverse’ related to the revised simplex method. We give an algorithm to compute the inverse of the current basic matrix. This calculation requires approximately m² operations by using a tensor product and matrix addition. We apply this idea to the Gauss and Gauss–Jordan algorithms.     

Multiscale Fusion of Visible and Thermal IR Images for Illumination-Invariant Face Recognition

This paper describes a new software-based registration and fusion of visible and thermal infrared (IR) image data for face recognition in challenging operating environments that involve illumination variations. The combined use of visible and thermal IR imaging sensors offers a viable means for improving the performance of face recognition techniques based on a single imaging modality. Despite successes in indoor access control applications, imaging in the visible spectrum demonstrates difficulties in recognizing the faces in varying illumination conditions. Thermal IR sensors measure energy radiations from the object, which is less sensitive to illumination changes, and are even operable in darkness. However, thermal images do not provide high-resolution data. Data fusion of visible and thermal images can produce face images robust to illumination variations. However, thermal face images with eyeglasses may fail to provide useful information around the eyes since glass blocks a large portion of thermal energy. In this paper, eyeglass regions are detected using an ellipse fitting method, and replaced with eye template patterns to preserve the details useful for face recognition in the fused image. Software registration of images replaces a special-purpose imaging sensor assembly and produces co-registered image pairs at a reasonable cost for large-scale deployment. Face recognition techniques using visible, thermal IR, and data-fused visible-thermal images are compared using a commercial face recognition software (FaceIt^®) and two visible-thermal face image databases (the NIST/Equinox and the UTK-IRIS databases). The proposed multiscale data-fusion technique improved the recognition accuracy under a wide range of illumination changes. Experimental results showed that the eyeglass replacement increased the number of correct first match subjects by 85% (NIST/Equinox) and 67% (UTK-IRIS).     

Kinetic and equilibrium studies of methylene blue biosorption by Posidonia oceanica (L.) fibres

Batch biosorption experiments were carried out for the removal of methylene blue, a basic dye, from aqueous solution using raw Posidonia oceanica (L.) fibres, a marine lignocellulosic biomass. A series of assays were undertaken to assess the effect of the system variables, i.e. contact time, solution pH, biosorbent dosage and initial dye concentration. The results had showed that biosorption capacity was optimal using 6-9 solution pH range and by increasing the biosorbent concentration up to 1 g/L. The biosorption kinetics were analyzed using irreversible-first-order, reversible-first-order and pseudo-second-order and the sorption data were very well described by the pseudo-second-order model for the entire adsorption time with squared correlation coefficients equal to unity for all experimented initial dye concentrations. Besides, equilibrium data were very well represented by both Langmuir and Redlich-Peterson isotherm models followed by Freundlich, which confirm the monolayer coverage of methylene blue molecules onto P. oceanica fibres.     

Radial Supershapes for Solid Modeling

In the previous work, an efficient method has been proposed to represent solid objects as multiple combinations of globally deformed supershapes. In this paper, this framework is applied with a new supershape implicit function that is based on the notion of radial distance and results are presented on realistic models composed of hundreds of hierarchically globally deformed supershapes. An implicit equation with guaranteed differential properties is obtained by simple combinations of the primitives' implicit representations using R-function theory. The surface corresponding to the zero-set of the implicit equation is efficiently and directly polygonized using the primitives' parametric forms. Moreover, hierarchical global deformations are considered to increase the range of shapes that can be modeled. The potential of the approach is illustrated by representing complex models composed of several hundreds of primitives inspired from CAD models of mechanical parts.     

Flying Capacitor Multilevel Inverter Control Considering Lower Order Harmonics Elimination Based on Newton-Raphson Algorithm

Newton-Raphson-based flying capacitor multilevel inverter modeling is investigated for capacitor voltage balancing. Without using voltage feedback, Newton-Raphson method determines the best switching pattern for maintaining nil mean current in all capacitors, hence minimizing the capacitor voltage fluctuation and eliminating certain harmonic orders. Flying capacitor multilevel inverter (FCMI) modeling is developed to work with the selective harmonic elimination (SHE) technique to obtain a programmable pulse generator for multilevel inverter commutation cell control. Theoretical results are verified by experiments and simulations for a flying capacitor four-level inverter. Results show that the proposed method does effectively eliminate a number of specific low order harmonics, and the output voltage is resulted in low total harmonic distortion and with balanced flying capacitors.     

Correlation between structure and photoluminescence of the europium doped glaserite-type phosphate Na2SrMg(PO4)2

A new phosphate Na₂SrMg(PO₄)₂ has been synthesized and investigated by X-ray diffraction, DTA, ³¹P NMR spectroscopy and photoluminescence measurements. This compound crystallizes in the space group P2₁/a of the monoclinic system with the cell parameters: a = 9.158(1) Å, b = 5.267(1) Å, c = 13.498 (1) Å, β = 90.01(1)° and four formula units per cell. Its structure is closely related to that of the mineral glaserite K₃Na(SO₄)₂ and thus it can be described by the general formula XY₂M(TO₄)₂. The X, Y, M and T sites are fully occupied by Sr²⁺, Na⁺, Mg²⁺ and P⁵⁺ cations, respectively. The anionic framework is consisted by the stacking along the [001] direction of two kinds of alternating [MgP₂O₈⁴⁻]_∞ mixed layers parallel to the (a, b) plane and resulting from a corner-sharing between MgO₆ octahedra and PO₄ tetrahedra. The Sr²⁺ cations are located within the interlayer space, while those Na⁺ are found in large cavities bounded to the layers. The DTA analysis showed a congruent melting of this compound at 1374 K. The ³¹P NMR spectroscopy confirmed the presence of two distinct phosphors sites in the structure. Optical studies were performed on the Na₂SrMg(PO₄)₂ compound doped with Eu³⁺ and Eu²⁺. The trivalent europium was used as a local probe, replacing strontium and sodium, what gives complementary and consistent results to the crystallographic analyses. The divalent europium was used to analyze preliminary the potentiality for this compound to be integrated as phosphor in Light Emitting Diode (LED).     

Effect of Mg Substitution on Room Temperature Dielectric and Magnetic Properties of Sr-Doped Bismuth Ferrite

Mg-co-substituted BiFeO₃ was synthesized. We investigated the structure and multiferroic properties of Sr- and Mg-co-substituted bismuth ferrite. The purity and structural changes induced by Mg doping are confirmed by X-ray powder diffraction and Raman spectra. It was found that a small amount of Mg doping leads to dramatic enhancement in dielectric permittivity, along with an apparent improvement in ferromagnetism .Meanwhile, the co-substitution can effectively reduce the leakage current and increase the dielectric constant. The release of latent magnetization after Sr and Mg co-doping is stronger than the sum of two single dopings, indicating a nonlinear enhancement in Sr and Mg codoping. The ferromagnetism can be ascribed to the creation of unbalanced Fe³⁺ spins and relative long-range coupling mediated by the oxygen vacancies trapped localized electrons. Compared to the pristine bismuth ferrite, Bi_0.95Sr_0.05Fe_0.9Mg_0.1O₃ exhibits more than fivefold improved magnetization with simultaneously improved electrical properties demonstrating the possibility of co-doped BiFeO₃ for practical applications.     

Use of limestone sands and fillers in concrete without superplasticizer

This paper deals with the effects of the amount of limestone fillers with respect to the rheological, mechanical, and dimensional properties of concretes without superplasticizer. These concretes were made with two limestone coarse aggregates and one limestone sand from the same quarry, in order to avoid any artifact. Five sand containing fillers rate between 1.8% and 24% – representative rates of the categories defined in the EN 12260 norm for aggregates for concretes – were produced by mixture of original sand with its fine fraction or its grained fraction extracted beforehand by washing. The concretes were mix designed with the BetonlabPro2 software, whose algorithms take into account the presence of the limestone fillers. The experimental results show that the concretes containing from 100 to 150 kg/m³ limestone fillers often present optimal properties, with equal consistency. But, higher quantities of fillers do not deteriorate significantly the properties of the concretes, even if their packing density decreases. This behavior is explained not only by the binding effect allotted to the limestone fillers, but also by an improvement of the paste-aggregates bond.