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).     

Evaluation of Ethylcellulose as A Matrix for Prolonged Release Formulations. I. Water Soluble Drugs: Acetaminophen and Theophylline

In this study ethylcellulose was evaluated as a carrier for the preparation of prolonged release solid dispersions of relatively water soluble drugs, acetaminophen and theophylline. The solid dispersions containing various concentrations (7.5, 15.0 and 30.0 % by weight of drug) of ethylcellulose of different viscosity grades (21, 95, 209 and 350 cps) were prepared by the solvent method. The concentration of polymer in the formulation was the determining factor in controlling release rate of the drug, as the results indicate prolongation in release of the drug with increase in amount of ethylcellulose. The higher the viscosity grade of ethylcellulose, slower the release of drug from the solid dispersions. The release of drug from the tablets was more prolonged compared to the granular solid dispersions. In vitro release of acetaminophen and theophylline was more or less similar in both dissolution media. The viscosity grade of ethylcellulose showed slight influence on the release rate of drug from the tablet formulations, while it was quite noticeable in granular solid dispersions.     

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.     

CMOS wireless transceivers: the new wave

A new generation of wireless transceivers is being intergrated into CMOS IC technology, which so far has been used mainly to realize digital and mixed analog-digital baseband circuits. This article reviews some of the RF CMOS circuit design techniques, and shows how an understanding of the strengths and weaknesses of these circuits influences choice of radio architecture. The CMOS approach to radio design calls for the elimination of discrete components in favor of high levels of on-chip integration which freely use translators and mix analog and digital functionality; in these respects, it departs from traditional RF circuit practices. Successful wireless devices of the future will require that radio system design evolve around these new trends in RF integration     

Cellulose-based monoliths with enhanced surface area and porosity

This study reports on a strategy of using sol–gel and supercritical drying techniques to prepare aerocellulose monoliths with enhanced specific surface area and porosity by adding NaCl particles into the cellulose solution. The addition of 5 wt% of NaCl particles led to increased specific surface area of aerocellulose monoliths (from 114 m²/g to 205 m²/g), as well as their porosity (by ~5%). The aerocellulose monoliths prepared by adding NaCl particles achieved improved porous characteristics, lightweight, lower crystallinity, and better thermal stability, as compared to the control. This study demonstrates the effectiveness of NaCl particles to tune the surface area and the pore characteristics, which provides a facile route to achieve enhanced surface area and improved pore characteristics of aerocellulose monoliths.     

Power-conscious design of wireless circuits and systems

The great importance of power consciousness is well understood in mobile wireless communications. However, with growing experience the fundamental principles underlying power conscious design of RF circuits, systems, and networks are only now becoming known. Using as example ultralow-power wireless devices for messaging such as paging receivers and wireless sensor networks, the first part of this paper presents the relationship between current consumption and dynamic range of low-noise amplifiers, mixers, oscillators, and active filters. The second part of the paper covers issues of modulation, protocols, and networking that would be required in dense networks of wireless sensors, which communicate using very little energy. These ideas are expected to find use in most forms of digital wireless communications