Design of different planar geometries of antenna arrays for isoflux radiation in GEO satellites

The synthesis of different planar geometries of antenna arrays for isoflux radiation is presented in this paper. This synthesis considers the reduction of the side lobe level and the isoflux radiation requirements for Geostationary Earth Orbit satellites. The behavior of the radiation is studied in three geometries of two-dimensional antenna arrays such as uniform planar arrays, aperiodic planar arrays (APA) and concentric ring arrays (CRA). The well-known methods of genetic algorithm and particle swarm optimization are utilized for the optimization problem. In this way, the designs of APA and CRA presented in this paper could provide an acceptable solution for reducing the antenna hardware and simplifying the power feeding even more than results presented previously in the literature.     

Shallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology

Buried‐channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high mobility (5 × 10⁵ cm² V^?1 s^?1) is demonstrated in a very shallow strained germanium (Ge) channel, which is located only 22 nm below the surface. The top‐gate of a dopant‐less field effect transistor controls the channel carrier density confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The high mobility leads to mean free paths ≈ 6 µm, setting new benchmarks for holes in shallow field effect transistors. The high mobility, along with a percolation density of 1.2 × 10¹¹cm^?2, light effective mass (0.09m_e), and high effective g‐factor (up to 9.2) highlight the potential of undoped Ge/SiGe as a low‐disorder material platform for hybrid quantum technologies.     

Impact of Ge-Sb-Te compound engineering on the set operation performance in phase-change memories

The phase-change memory (PCM) technology is considered as one of the most attractive non-volatile memory concepts for next generation data storage. It relies on the ability of a chalcogenide material belonging to the Ge-Sb-Te compound system to reversibly change its phase between two stable states, namely the poly-crystalline low-resistive state and the amorphous high-resistive state, allowing the storage of the logical bit. A careful study of the phase-change material properties in terms of the set operation performance, the program window and the electrical switching parameters as a function of composition is very attractive in order to enlarge the possible PCM application spectrum. Concerning the set performance, a crystallization kinetics based interpretation of the observed behavior measured on different Ge-Sb-Te compounds is provided, allowing a physics-based comprehension of the reset-to-set transition.     

Mobility analysis of the typical gait of a radial symmetrical six-legged robot

Radial symmetrical hexapod robots have attracted the attention of the research community because of their flexibility. There is nonetheless still much to study on their kinematics, dynamics and locomotion. In this paper, initially, full body kinematics of a radial symmetrical six-legged robot with statically stable movements are reviewed. The kinematics analysis is made on cooperated swing legs over supporting legs. Using the robot screw theory and exponential product equations, the velocities and accelerations referring to the object reference frame of each robot part are presented in a compact form. This makes it easy to calculate kinetic energy and so to build the dynamics model using the Lagrangian method. Many ways of walking of six-legged robots have been introduced in specialized literature. However, mobility comparison is still open to research. Two main aspects of mobility are analyzed in detail in this paper. The first one concerns the mobility of three statically stable ways of walking (the insect-wave gait, mammal-kick gait and mixed gait) with the same duty factor on the same radial symmetrical hexapod robot. The stability, energy efficiency, turning flexibility, and terrain or environment adaptability among those gaits have been compared. The mixed gait presents important advantages over the other two, while those two are useful for some special terrain conditions where the mixed gait is limited. The second aspect that has been analyzed focuses on the mobility of the body. The body height, measured from the body bottom to the supporting surface, and the stride optimization factors are proposed according to the obstacles’ configuration and the energy optimization. The results of our study can be used for the intelligent locomotion control of some articulated multi-legged robots for walking statically-stably on a complicated surface.Most of our analyses have been successfully verified on the prototype which has been designed by Politecnico di Milano (POLIMI) and Beijing University of Astronautics and Aeronautics (BUAA) and developed by POLIMI in 2007.     

Applications and design issues for mobile agents in wireless sensor networks

Recently, research interest has increased in the design, development, and deployment of mobile agent systems for high-level inference and surveillance in a wireless sensor network (WSN). Mobile agent systems employ migrating codes to facilitate flexible application re-tasking, local processing, and collaborative signal and information processing. This provides extra flexibility, as well as new capabilities to WSNs in contrast to the conventional WSN operations based on the client-server computing model. In this article we survey the potential applications of mobile agents in WSNs and discuss the key design issues for such applications. We decompose the agent design functionality into four components, that is, architecture, itinerary planning, middleware system design, and agent cooperation. This taxonomy covers low-level to high-level design issues and facilitates the creation of a component-based and efficient mobile agent system for a wide range of applications. With a different realization for each design component, it is expected that flexible trade-offs (e.g., between energy and delay) can be achieved according to specific application requirements.     

Highly Stretchable Conducting SIBS‐P3HT Fibers

Poly(styrene‐β‐isobutylene‐β‐styrene)‐poly(3‐hexylthiophene) (SIBS‐P3HT) conducting composite fibers are successfully produced using a continuous flow approach. Composite fibers are stiffer than SIBS fibers and able to withstand strains of up 975% before breaking. These composite fibers exhibit interesting reversible mechanical and electrical characteristics, which are applied to demonstrate their strain gauging capabilities. This will facilitate their potential applications in strain sensing or elastic electrodes. Here, the fabrication and characterization of highly stretchable electrically conducting SIBS‐P3HT fibers using a solvent/non‐solvent wet‐spinning technique is reported. This fabrication method combines the processability of conducting SIBS‐P3HT blends with wet‐spinning, resulting in fibers that could be easily spun up to several meters long. The resulting composite fiber materials exhibit an increased stiffness (higher Young’s modulus) but lower ductility compared to SIBS fibers. The fibers’ reversible mechanical and electrical characteristics are applied to demonstrate their strain gauging capabilities.     

FASANT: past computer tool for the analysis of on-board antennas

FASANT is a computer tool for the analysis of antennas on-board satellites, ships, aircraft, and other complex bodies. The structure under analysis, which can be metallic or dielectric (with and/or without losses), must be modeled by plane and/or curved surfaces. The geometrical input files are in DXF format, and can be generated by the most commonly used computer-aided geometrical-design (CAGD) tools. The code can also be applied to the analysis of arrays and arbitrarily shaped reflectors. The kernel of the code is based on the uniform theory of diffraction (UTD). Special algorithms have been developed to speed up the ray-tracing computation for both flat and curved surfaces. FASANT can obtain far-field patterns, field levels at points near the structure, can calculate the mutual coupling between antennas or between array elements, and can show each ray-tracing mechanism     

Epoxy-based aqueous-processable photodielectric dry film andconductive ViaPlug for PCB build-up and IC packaging

DuPont formulated a new generation of photoimageable permanent resists and conductive ViaPlug polymer to be used as building blocks for sequential build-up of printed circuit boards (PCB's), multichip module-laminates (MCM-Ls), and plastic integrated circuit (IC) packages. The buzzwords for these structures are high density interconnection structures (HDIS) and microvias. The conventional method of making PCB's and MCM-Ls is a sequential lamination of innerlayer cores or interplanes, followed by at least one mechanical drilling. In this paper we will discuss a new approach of using semi-additive plating which means starting with a multilayer core, mechanically drilling for through hole connection, filling the through-hole with conductive ViaPlug, then adding layers of dielectric to make blind or buried vias for interconnection and routing of circuits, and heat dissipation. The paper will discuss the challenges in each application, relevant industry specifications for each application, and the dielectric and conductor materials properties to meet the challenges. From the viewpoint of technology choices, we will compare photoimaging versus laser ablation and plasma etching. Lastly, we will discuss our reliability data developed internally and in conjunction with several consortia     

Electrical and Optical Characterization of Melt-Grown Bulk InAs<Subscript>1−<Emphasis Type="Italic">y</Emphasis></Subscript>P<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> Crystals

Bulk ternary InAs_1−y P _y polycrystals with diameters up to 50 mm were grown from a pseudobinary InP-InAs melt using the vertical Bridgman technique. Electrical and optical properties were investigated as functions of alloy composition and sample temperature. As-grown undoped crystals have been found to exhibit n-type conductivity irrespective of alloy composition. Though the bulk InAs_1−y P _y substrates show high optical transmission out to long wavelengths as well as high carrier mobility, they exhibit random compositional fluctuations across the substrate area.     

Metabolic P Systems： A Discrete Model for Biological Dynamics

A recent methodology to model biochem- ical systems is here presented. It is based on a concep- tual framework rooted in membrane computing and de- veloped with concepts typical of discrete dynamical sys- tems. According to our approach, from data observed at suitable macroscopic temporal scales, one can deduce, by means of algebraic and algorithmic procedures, a dis- crete model （called Metabolic P system） which accounts for the experimental data, and opens the possibility to under- stand the systemic logic of the investigated phenomenon. The procedures of such a method have been implemented within a computational platform, a Java software called MetaPlab, processing data and simulating behaviors of metabolic models. In the paper, we briefly describe the theory underlying the modeling of biochemical systems by Metabolic P systems, along with its development stages and the related extensive literature.