Making a mesh router/gateway from a smartphone: Is that a practical solution?

This paper aims at answering the question whether it is practical to build a mesh-phone or not. A mesh-phone is a smartphone acting as a mesh router, i.e. either actively participating in the process of packet forwarding towards a mesh gateway, or acting itself as a gateway toward the Internet. Technical aspects of the mesh-phone implementation, such as design constraints and implementation details, are addressed. The technical feasibility is validated by describing the implementation of a prototype of the mesh-enabled phone over the Openmoko^TM open platform. Besides technical feasibility also convenience of the addressed solution is analyzed in terms of the consumed power, and some “energy-saving” related enhancements are suggested to be applied to future user’s devices.     

Resonances and Complexity: From Stripes to Superstripes

The present issue of Journal of Superconductivity and Novel Magnetism collects the papers presented at the International Conference on “Quantum Phenomena in Complex Matter.” Superstripes 2010 held in Erice, Italy, from July 19 to 25, 2010, at the Ettore Majorana Foundation and Centre for Scientific Culture. In this preface, I discuss the scientific scenario of the search for the mechanism of the macroscopic quantum coherent phase at high temperature “superconductivity in complexity.”     

Constrained scheduling of the inspection activities on semiconductor wafers grouped in families with sequence-dependent set-up times

The scheduling of families of semiconductor wafers within the inspection department of a company producing electronic devices is considered in this paper. Changing the family of wafers to be inspected by an inspection machine requires a sequence-dependent set-up time; furthermore, due to the limited space availability of the inspection area, the available interoperational buffer capacity between the inspection machines is finite. The objective of the scheduling is the maximization of inspection department productivity, measured through the sequence makespan. A permutational flowshop group-scheduling problem (GSP) with sequence-dependent set-up times and limited interoperational buffer capacity has been taken into account. A benchmark of process scenarios considering different numbers of inspection machines wafers codes and families to be inspected has been generated. A Genetic Algorithm is here proposed as an efficient tool to solve the investigated problem. A comparison with a tabu search and a Nawaz, Enscore, and Ham procedure improving the currently available scheduler tool within the inspection department has been performed on the benchmark of problems. Finally, the influence on line productivity due to the finite interoperational buffer capacity is investigated.     

Vacuum-based preservation of surgical specimens: An environmentally-safe step towards a formalin-free hospital

Formalin as a fixative has no practical substitutes, but is toxic and potentially carcinogenic, so caution of its use in hospitals and elsewhere is mandatory. In our hospital, preservation of surgical specimens into formalin to be transferred to pathology labs was replaced by under-vacuum sealing (UVS) tissues into plastic bags and preservation at 4 °C until transfer. Data analysis showed UVS processing to be superior in terms of staff satisfaction and of gross anatomic preservation; no problems in terms of technical feasibility or histopathologic preservation were encountered. Formalin was confined to pathology labs while its use on hospital premises was vastly reduced.     

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

A low-cost patterning of electrodes was investigated looking forward to replacing conventional photolithography for the processing of low-operating voltage polymeric thin-film transistors. Hard silicon, etched by sulfur hexafluoride and oxygen gas mixture, and flexible polydimethylsiloxane imprinting molds were studied through atomic force microscopy (AFM) and field emission gun scanning electron microscopy. The higher the concentration of oxygen in reactive ion etching, the lower the etch rate, sidewall angle, and surface roughness. A concentration around 30 % at 100 mTorr, 65 W and 70 sccm was demonstrated as adequate for submicrometric channels, presenting a reduced etch rate of 176 nm/min. Imprinting with positive photoresist AZ1518 was compared to negative SU-8 2002 by optical microscopy and AFM. Conformal results were obtained only with the last resist by hot embossing at 120 °C and 1 kgf/cm² for 2 min, followed by a 10 min post-baking at 100 °C. The patterning procedure was applied to define gold source and drain electrodes on oxide-covered substrates to produce bottom-gate bottom-contact transistors. Poly(3-hexylthiophene) (P3HT) devices were processed on high-κ titanium oxynitride (TiO _x N _y ) deposited by radiofrequency magnetron sputtering over indium tin oxide-covered glass to achieve low-voltage operation. Hole mobility on micrometric imprinted channels may approach amorphous silicon (～0.01 cm²/V s) and, since these devices operated at less than 5 V, they are not only suitable for electronic applications but also as sensors in aqueous media.     

利用KPI调试和优化UMTS网络

从语音到视频到网上游戏,UMTS网络提供了各种客户服务,对移动网络运营商来说,调试或优化网络正变得越来越复杂.网络运营商一直把传统网络的主要性能指标(KPI)看作理解和调试网络性能的工具.     

Analysis of Frequency Selective Surfaces at Millimeter Wave Band Using the Hertz Vector Potential Method

In this work, the Hertz vector potential method was used to obtain the dyadic Green’s function components for frequency selective surfaces (FSS) on an anisotropic layer. The considered structures are composed by periodic arrays of conducting crossed dipole and rectangular patch elements. Results of reflected power were obtained by using the moment method. Curves for the reflected power versus frequency are presented as function of the structural parameters, assuming x, y, and z orientation for the optical axis in the anisotropic substrate.     

Energy harvesting with pairs of variable capacitors without control circuits

This work describes several electronic electrostatic generators that can be built using two pairs of complementary variable capacitors, in a way that dispenses control circuits for their operation. In all cases, a basic unstable generator based on an electrostatic charge multiplier is used to bias variable capacitors, and the current generated by these capacitors is then rectified and sent to the load. Experimental versions of the proposed generators were built using variable capacitors made with 3D-printing techniques, moved in a back-and-forth way by a small motor. As these generators operate at high impedance level, always with small currents, they are insensitive to the resistivity of the conductive plastic used to make the variable capacitors. Several new structures are presented, and their properties are evaluated theoretically and experimentally.     

Technological development of Brazilian telecommunications in past decades

Brazilian telecommunications sector has undergone important modifications in the last 40 years. From a badly structured system of municipal level operators in 1960, with barely one million fixed lines to a large, nation-wide system with about 50 million fixed plus another 75 million mobile lines in 2005. This work paper reviews the institutional framework of telecommunications industrial and technological policy in Brazil in the last four decades, its results and present situation. Infrastructure and services modernisation and expansion process that happened in early 1970s were carried out at the expense of massive import of products and technology. A government strategy was, then, devised to stimulate local industrial and technological development in telecommunications, under the general guidelines of import substitution policy. Essential to this strategy was the creation of an innovation system around TELEBRÁS Research and Development Centre. This technological development model was successful while a protectionist economic policy existed. When economic and political circumstances could not anymore sustain an import substitution approach, in the 1990-decade, the model fell apart and has not been replaced by any other sectorial policy. A critical assessment is carried out, analysing the adopted actions in face of the digital technology maturing process that occurred in meantime.     

Very Low Degree of Energetic Disorder as the Origin of High Mobility in an n‐channel Polymer Semiconductor

Charge transport is investigated in high‐mobility n‐channel organic field‐effect transistors (OFETs) based on poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2), Polyera ActivInk? N2200) with variable‐temperature electrical measurements and charge‐modulation spectroscopy. Results indicate an unusually uniform energetic landscape of sites for charge‐carrier transport along the channel of the transistor as the main reason for the observed high‐electron mobility. Consistent with a lateral field‐independent transport at temperatures down to 10 K, the reorganization energy is proposed to play an important role in determining the activation energy for the mobility. Quantum chemical calculations, which show an efficient electronic coupling between adjacent units and a reorganization energy of a few hundred meV, are consistent with these findings.