Characteristics of hemocompatible TiO<Subscript>2</Subscript> nano-films produced by the sol-gel and anodic oxidation techniques

Hemocompatible films can be obtained by different techniques which must produce a smooth surface and a desired combination of crystal structure including rutile and anatase structures. Two of the simplest techniques include sol-gel and anodic oxidation. The characteristics of the films associated with the process variables are presented. The most important characteristics of the films are thickness, structure, roughness, and mechanical properties such as adhesion and wear resistance.     

Evaluating requirements modeling methods based on user perceptions: A family of experiments

Numerous methods and techniques have been proposed for requirements modeling, although very few have had widespread use in practice. One drawback of requirements modeling methods is that they lack proper empirical evaluations. This means that there is a need for evaluation methods that consider both the theoretical and practical aspects of this type of methods and techniques. In this paper, we present a method for evaluating the quality of requirements modeling methods based on user perceptions. The evaluation method consists of a theoretical model that explains the relevant dimensions of quality for requirements modeling methods, along with a practical instrument with which to measure these quality dimensions. Basically, it allows us to predict the acceptance of a particular requirements modeling method in practice, based on the effort of applying the method, the quality of the requirements artifacts produced, and the user perceptions with regard to the quality of the method. The paper also presents an empirical test of the proposed method for evaluating a Rational Unified Process (RUP) extension for requirements modeling. That test was carried out through a family of experiments conducted with students and practitioners and provides evidence of the usefulness of the evaluation method proposed.     

Comparative analysis of power variables in high performance embedded and x86 architectures using GNU/Linux

In this work a comparative analysis of typical power variables is made using several hardware architectures and GNU/Linux software. Voltage and current data are simulated for an industrial device, comparing the performance of x86 and ARM in order to demonstrate the technical feasibility of using embedded hardware to manage high volumes of interesting data in the study of power quality systems.Voltage, current, active power, reactive power and harmonic distortion (both voltage and current) were obtained with simulated data provided by MATLAB and using Discrete Fourier Transform (DFT) implementations like Fast Fourier Transform (FFT) and libraries like FFTW and KISS FFT.All the software used in our work was open source, running Linux behind them. Results show the feasibility of using high performance embedded systems to develop advanced tasks in analyzing power signals.     

Dealing with limited data in ballistic impact scenarios: an empirical comparison of different neural network approaches

In the domain of high-speed impact between solids, the simulation of one trial entails the use of large resources and an elevated computational cost. The objective of this research is to find the best neural network associated with a new problem of ballistic impact, maximizing the quantity of trials available and simplifying their architecture. To achieve this goal, this paper proposes a tuning performance process based on four stages. These stages include existing statistical techniques, a combination of proposals to improve the performance and analyze the influence of each variable. To measure the quality of the different networks, two criteria based on information theory have been incorporated to reflect the fit of the data with respect to their complexity. The results obtained show that the application of an integrated tuning process in this domain permits improvement in the performance and efficiency of a neural network in comparison with different machine learning alternatives     

Analysis and implementation of a step–up power converter with input current ripple cancelation

This paper proposes a power electronics converter capable of canceling the input current ripple at preselected duty cycle. The proposed converter is an extended topology of a buck–boost converter aided by a boost‐type converter that improves the quality of the current drawn from the direct current source. The voltage gain of the proposed converter is increased as well, with a minimum of extra component added to the original buck–boost power converter. These features make the proposed converter ideal for low voltage generation sources, such as photovoltaic panel and fuel cell applications. Along this paper, the state space mathematical model is developed to provide the key design guidelines. The theoretical analysis is validated through computer simulation and hardware prototyping.     

ZnO-based varistor thick films with high non-linear electrical behavior

Thick films of ZnO-based ceramic varistors prepared by tape casting technique typically show a poor electrical response that still limits their application as protective devices. The excessive volatilization of Bi₂O₃ during sintering at high temperatures, especially dramatic in the film geometry due to its high area–volume ratio, is found to be the origin of this poor electrical behavior. The problem is overcome by sintering the films in a controlled Bi-rich sealed atmosphere, leading to a high reliability and reproducibility in their non-linear response.     

2D Phononic Crystals: Progress and Prospects in Hypersound and Thermal Transport Engineering

The central concept in phononics is the tuning of the phonon dispersion relation, or phonon engineering, which provides a means of controlling related properties such as group velocity or phonon interactions and, therefore, phonon propagation, in a wide range of frequencies depending on the geometries and sizes of the materials. Phononics exploits the present state of the art in nanofabrication to tailor dispersion relations in the range of GHz for the control of elastic waves/phonons propagation with applications toward new information technology concepts with phonons as state variable. Moreover, phonons provide an adaptable approach for supporting a coherent coupling between different state variables, and the development of nanoscale optomechanical systems during the last decade attests this prospect. The most extended approach to manipulate the phonon dispersion relation is introducing an artificial periodic modulation of the elastic properties, which is referred to as phononic crystal (PnC). Herein, the focus is on the recent experimental achievements in the fabrication and application of 2D PnCs enabling the modification of the dispersion relation of surface and membrane modes, and presenting phononic bandgaps, waveguiding, and confinement in the hypersonic regime. Furthermore, these artificial materials offer the potential of modifying and controlling the heat flow to enable new schemes in thermal management.     

A Critical Discourse Analysis of three US municipal wireless network initiatives for enhancing social inclusion

The US has a long history of telecommunications policy aimed at providing equitable access to information and communication services. In this paper we examine the most recent of these efforts, municipal wireless broadband Internet networks. Using three cases (Philadelphia, PA; San Francisco, CA; and Chicago, IL) we examine how social inclusion is expressed in the digital inclusion policy articulated in each municipality’s broadband network public rhetoric. Using Critical Discourse Analysis, our findings confirms that the growing use of digital inclusion rhetoric around broadband deployments has brought the social inclusion issue to the forefront, and effectively links discourse and technology with discursive practices and types.     

Structural, morphological, optical and electrical properties of CdTe films deposited by CSS under an argon-oxygen mixture and vacuum

CdTe thin films were deposited by CSS at a pressure of 1 mbar, under different mixtures of argon and oxygen and in vacuum, on glass substrates. The samples were prepared under three source-substrate temperature conditions. The films were characterized by X-ray diffraction, UV-vis spectroscopy, SEM and two-probe resistivity. XRD patterns indicated that the films grown at low oxygen content and source temperature of 550 °C with substrate temperature of 400 °C showed a high preferential orientation in the (1 1 1) plane. The crystalline grain size was between 31 and 40 nm. The films had a direct band gap in the range 1.44-1.49 eV. SEM images showed higher aggregate sizes for the films deposited at higher temperatures and grain size decreases as oxygen content increases. The resistivity of the films was around 1×10⁶ Ω cm.