Metrics and Criteria for Quality Assessment of Testable Hw/Sw Systems Architectures

The purpose of this paper is to present a novel methodology for assessing the quality of architecture solutions of hw/sw systems, with particular emphasis on testability. Criteria and metrics for quality assessment are proposed and used to assist the design team in selecting a best-fitted architecture that satisfies not only functional requirements, but also test requirements. The methodology makes use of object-oriented modeling techniques. Near-optimum clustering of methods and attributes into objects is carried out, in such a way that objects with moderate complexity, low coupling and high functional autonomy, result. The main features of the methodology are ascertained through a case study.     

A New Hand-Held Microsystem Architecture for Biological Analysis

This paper presents a hand-held microsystem based on new fully integrated magnetoresistive biochips for biomolecular recognition (DNA hybridization, antibody antigen interaction, etc.). Magnetoresistive chip surfaces are chemically treated, enabling the immobilization of probe biomolecules such as DNA or antibodies. Fluid handling is also integrated in the biochip. The proposed microsystem not only integrates the biochip, which is an array of 16times16 magnetoresistive sensors, but it also provides all the electronic circuitry for addressing and reading out each transducer. The proposed architecture and circuits were specifically designed for achieving a compact, programmable and portable microsystem. The microsystem also integrates a hand-held analyzer connected through a wireless channel. A prototype of the system was already developed and detection of magnetic nanoparticles was obtained. This indicates that the system may be used for magnetic label based bioassays     

1.2 nm capacitance equivalent thickness gate stacks on Si-passivated GaAs

Experiments to increase the specific capacitance of MOS capacitors consisting of HfO₂ on a passivating interfacial layer (IL) of amorphous Si (a-Si) on GaAs are described. XPS analysis of the layers and electrical measurements on the capacitors are combined to study the evolution of the gate stack during deposition and subsequent heat treatments. It is shown that oxidation of the a-Si IL is a major factor in preventing the attainment of a scaled capacitance equivalent thickness (CET). By controlling the deposition of the layers, the gate metal and the heat treatments, a highly scaled gate stack with a CET of 1.2 nm and a leakage reduction of more than 4 orders of magnitude with respect to SiO₂/Si was realized.     

An energy efficient middleware for an ad-hoc AAL wireless sensor network

DIA (Dispositivo Inteligente de Alarma, in Spanish) is an AAL (Ambient Assisted Living) system that allows to infer a potential dangerous action of an elderly person living alone at home. This inference is obtained by a specific sensorisation with sensor nodes (portables and fixes) and a reasoning layer embedded in a PC that learns of the users behaviour patterns and advices when actual one differs significantly of the normal patterns. In AAL systems, energy is a limited resource therefore sensor devices need to be properly managed to conserve energy. In this paper, we introduce the design and implementation of innovative and specific mechanisms at the sensory layer middleware which is capable of, first to discriminate spurious motion detections assuming that these signals do not resemble the patterns of real motion detections and, second to reduce the dynamics of messages by a sensor signal processing in order to compress the whole information in one single event. The middleware achieves power saving by modifying the raw information from sensors and adapting it to the predefined semantic of the reasoning layer. It manages the important task of data processing from sensors (raw information), and transfers the pre-processed information into the top layer of reasoning in a more energy efficient way. We also address the trade-off between reducing power consumption and reducing delay for incoming data. We present results from experiments using our implementation of these mechanisms at the middleware that comprises from node firmware to the PC driver. The number of messages of the proposed method with respect to the raw data is reduced by approximately 98.5%. The resources used in the PIR signal processing is reduced by approximately 85%. The resulting delay introduced is small (10–19 s) but system dynamics is slow enough to avoid contextualisation errors or reduction of system performance. We consider these results as very satisfactory.     

Hydroxyapatite Modified with Carbon‐Nanotube‐Reinforced Poly(methyl methacrylate): A Nanocomposite Material for Biomedical Applications

The paper reports on a freeze‐granulation technique to prepare a novel nanocomposite of poly(methyl methacrylate) (PMMA)‐modified hydroxyapatite (HA) with multiwalled carbon nanotubes (MWCNTs) as reinforcement for a new generation biomedical bone cement and implant coatings. By using this technique it is possible to increase material homogeneity and also enhance the dispersion of MWCNTs in the composite matrix. The phase composition and the surface morphology of the nanocomposite material were studied using X‐ray diffraction, field‐emission scanning electron microscopy, and micro‐Raman spectroscopy. Additionally, nanomechanical properties of different concentrations of MWCNT‐reinforced nanocomposite were performed by a nanoindentation technique, which indicates that a concentration of 0.1 wt % MWCNTs in the PMMA/HA nanocomposite material gives the best mechanical properties.     

Routing and mobility approaches in IPv6 over LoWPAN mesh networks

It is foreseeable that any object in the near future will have an Internet connection—this is the Internet of Things vision. All these objects will be able to exchange and process information, most of them characterized by small size, power constrained, small computing and storage resources. In fact, connecting embedded low‐power devices to the Internet is considered the biggest challenge and opportunity for the Internet. There is a strong trend of convergence towards an Internet‐based solution and the 6LoWPAN may be the convergence solution to achieve the Internet of Things vision. Wireless mesh networks have attracted the interest of the scientific community in recent years. One of the key characteristics of wireless mesh networks is the ability to self‐organize and self‐configure. Mesh networking and mobility support are considered crucial to the Internet of Things success. This paper surveys the available solutions proposed to support routing and mobility over 6LoWPAN mesh networks. Copyright © 2011 John Wiley & Sons, Ltd.     

Recyclable,Flexible, Low‐Power Oxide Electronics

The ability to process and dimensionally scale field‐effect transistors with and on paper and to integrate them as a core component for low‐power‐consumption analog and digital circuits is demonstrated. Low‐temperature‐processed p‐ and n‐channel integrated oxide thin‐film transistors in the complementary metal oxide semiconductor (CMOS) inverter architecture are seamlessly layered on mechanically flexible, low‐cost, recyclable paper substrates. The possibility of building these circuits using low‐temperature processes opens the door to new applications ranging from smart labels and sensors on clothing and packaging to electronic displays printed on paper pages for use in newspapers, magazines, books, signs, and advertising billboards. Because the CMOS circuits reported constitute fundamental building blocks for analog and digital electronics, this development creates the potential to have flexible form factor computers seamlessly layered onto paper. The holistic approach of merging low‐power circuitry with a recyclable substrate is an important step towards greener electronics.     

Spectrum sensing in cognitive radio networks: requirements, challenges and design trade-offs [cognitive radio communications]

Opportunistic unlicensed access to the (temporarily) unused frequency bands across the licensed radio spectrum is currently being investigated as a means to increase the efficiency of spectrum usage. Such opportunistic access calls for implementation of safeguards so that ongoing licensed operations are not compromised. Among different candidates, sensing-based access, where the unlicensed users transmit if they sense the licensed band to be free, is particularly appealing due to its low deployment cost and its compatibility with the legacy licensed systems. The ability to reliably and autonomously identify unused frequency bands is envisaged as one of the main functionalities of cognitive radios. In this article we provide an overview of the regulatory requirements and major challenges associated with the practical implementation of spectrum sensing functionality in cognitive radio systems. Furthermore, we outline different design trade-offs that have to be made in order to enhance various aspects of the system's performance.     

Micrometer‐Scale Porous Buckling Shell Actuators Based on Liquid Crystal Networks

Micrometer‐scale liquid crystal network (LCN) actuators have potential for application areas like biomedical systems, soft robotics, and microfluidics. To fully harness their power, a diversification in production methods is called for, targeting unconventional shapes and complex actuation modes. Crucial for controlling LCN actuation is the combination of macroscopic shape and molecular‐scale alignment in the ground state, the latter becoming particularly challenging when the desired shape is more complex than a flat sheet. Here, one‐step processing of an LCN precursor material in a glass capillary microfluidic set‐up to mold it into thin shells is used, which are stretched by osmosis to reach a diameter of a few hundred micrometers and thickness on the order of a micrometer, before they are UV crosslinked into an LCN. The shells exhibit radial alignment of the director field and the surface is porous, with pore size that is tunable via the osmosis time. The LCN shells actuate reversibly upon heating and cooling. The decrease in order parameter upon heating induces a reduction in thickness and expansion of surface area of the shells that triggers continuous buckling in multiple locations. Such buckling porous shells are interesting as soft cargo carriers with capacity for autonomous cargo release.     

Antenna gain against interference in CDMA macrodiversity systems

In a multiantenna system, there is a potential antenna gain against interference, in addition to the diversity gain achieved against fading. It is well known that in order to attain most of the diversity gain (against fading), the antenna elements should be placed apart with a distance (many times) greater than the wavelength=[speed of light]/[frequency] of the carrier. The results presented in this paper indicate that in order to attain most of the antenna gain (against interference) in the reverse-link of finite-bandwidth interference-limited CDMA systems, the interantenna distance should be (many times) greater than a new parameter which is defined as the chiplength=[speed of light]/[chip rate] of the spreading code.