Depletion isolation effect in Vertical MOSFETS during transition from partial to fully depleted operation

A simulation study is made of floating-body effects (FBEs) in vertical MOSFETs due to depletion isolation as the pillar thickness is reduced from 200 to 10 nm. For pillar thicknesses between 200–60 nm, the output characteristics with and without impact ionization are identical at a low drain bias and then diverge at a high drain bias. The critical drain bias Vdc for which the increased drain–current is observed is found to decrease with a reduction in pillar thickness. This is explained by the onset of FBEs at progressively lower values of the drain bias due to the merging of the drain depletion regions at the bottom of the pillar (depletion isolation). For pillar thicknesses between 60–10 nm, the output characteristics show the opposite behavior, namely, the critical drain bias increases with a reduction in pillar thickness. This is explained by a reduction in the severity of the FBEs due to the drain debiasing effect caused by the elevated body potential. Both depletion isolation and gate–gate coupling contribute to the drain–current for pillar thicknesses between 100–40 nm

Classificació paleoecològica de les formes dels rudistes -una eina per a l'anàlisi paleoambiental

Els rudistes com a suspensívors epibentònics sèssils sols podien adaptar-se a les pressions ambientals per mitjà del creixement de la closca. Per això, les closques dels rudistes mostren una sèrie de formes, les característiques bàsiques de les quals estan en estreta relació amb el caràcter de l'hàbitat que ocupaven. Skelton & Gili (en premsa) classifiquen les closques dels rudistes en tres morfotipus ecològics generals, basats en els paradigmes definits per Skelton (1979a). En aquest treball exposem els trets principals d'aquesta classificació, fent ressaltar les seves implicacions paleoecològiques. Elevadors (elevators): tot el marge de creixement de la valva fixa estava involucrat en el creixement cap amunt. L'índex d'elevació, E, que comprèn la mitjana entre la màxima (α) i la mínima (β) inclinació de la paret externa del marge de creixement de la valva fixa, s'aproximava a 90°. E podia variar, pero el límit inferior per al creixement normal és per definició E=45°. Aconseguien l'estabilització per la implantació passiva de la valva fixa en el sediment, eventualment reforçada per la fixació lateral en els veïns. Ocupaven substrats tous, generalment fangosos, amb acumulació neta positiva. Els rudistes elevadors estaven, doncs, restringits a ambients d'energia baixa a moderada, rarament subjectes a torrents tractius. Adherents (clingers): una part del marge de creixement de la valva fixa creixia directament sobre el substrat, cimentant-se, si era dur, (adherents fixos) o adaptant-se a la seva superfície (adherents friccionals). Com que (β tendia aixi a 0°, E havia de ser per definició 0.75. Ocupaven substrats des de relativament estables a durs amb sedimentació neta de negligible a positiva, però amb fluxos de sediment solament ocasionals. La majoria dels rudistes adherents podien afrontar entrades de sediment intermitents fent crèixer cap amunt, escalonadament, la superfície de creixement basal. Les condicions de corrent associades podien implicar la inhibició freqüent o regular de deposició, però els torrents tractius eren rars. Ajaçats (recumbents): la clau d'aquest morfotipus era també l'estabilització, generant amb els marges Mures de les valves sobre el substrat una base ampla per a la closca. E era així, una altra vegada < 45°. Però a diferència de l'adherent, l'àrea de contacte amb el substrat (inestable), A, tenia poca importància per a 1'estabilització. Els rudistes ajaçats extremaven els diàmetres efectius del contorn de la base de la closca (és a dir A') de manera que aquesta adquiria una forma arquejada o estrellada que resistia la boleiada i soscavació dels corrents. En consequència, A/A' era menor que 1, i per definició havia de ser < 0.75. Ocupaven sorres calcàries mòbils, amb removiments de sediment freqüents i sedimentació positiva neta negigible

Structural and Aerodynamics Analysis on Different Architectures for the Elettra Twin Flyer Prototype

In this paper, the authors analyze and compare two airship configurations for the Elettra Twin Flyer prototype, an innovative airship concept which is remotely-controlled and intended for monitoring, surveillance, exploration and reconnaissance missions. The aim of the comparison is to determine the most appropriate solution in terms of performance, cost and maneuvering capabilities. In particular two potential solutions are analyzed: the first consists of a double-hull configuration, characterized by the presence of a primary support structure connected to a couple of twin inflatable hulls. The second architecture is a soap-shaped exoskeleton configuration which features a single inflated section, incorporating two separate elements, which are held internally by a system of ribs

Asymmetric gate induced drain leakage and body leakage in vertical MOSFETs with reduced parasitic capacitance

Vertical MOSFETs, unlike conventional planar MOSFETs, do not have identical structures at the source and drain, but have very different gate overlaps and geometric configurations. This paper investigates the effect of the asymmetric source and drain geometries of surround-gate vertical MOSFETs on the drain leakage currents in the OFF-state region of operation. Measurements of gate-induced drain leakage (GIDL) and body leakage are carried out as a function of temperature for transistors connected in the drain-on-top and drain-on-bottom configurations. Asymmetric leakage currents are seen when the source and drain terminals are interchanged, with the GIDL being higher in the drain-on-bottom configuration and the body leakage being higher in the drain-on-top configuration. Band-to-band tunneling is identified as the dominant leakage mechanism for both the GIDL and body leakage from electrical measurements at temperatures ranging from ?50 to 200?C. The asymmetric body leakage is explained by a difference in body doping concentration at the top and bottom drain–body junctions due to the use of a p-well ion implantation. The asymmetric GIDL is explained by the difference in gate oxide thickness on the vertical (110) pillar sidewalls and the horizontal (100) wafer surface

Verification in Relevant Environment of a Physics-Based Synthetic Sensor for Flow Angle Estimation

In the area of synthetic sensors for flow angle estimation, the present work aims to describe the verification in a relevant environment of a physics-based approach using a dedicated technological demonstrator. The flow angle synthetic solution is based on a model-free, or physics-based, scheme and, therefore, it is applicable to any flying body. The demonstrator also encompasses physical sensors that provide all the necessary inputs to the synthetic sensors to estimate the angle-of-attack and the angle-of-sideslip. The uncertainty budgets of the physical sensors are evaluated to corrupt the flight simulator data with the aim of reproducing a realistic scenario to verify the synthetic sensors. The proposed approach for the flow angle estimation is suitable for modern and future aircraft, such as drones and urban mobility air vehicles. The results presented in this work show that the proposed approach can be effective in relevant scenarios even though some limitations can arise

Flight control system rapid prototyping for the remotely-controlled elettra-twin-flyer airship

Nautilus S.p. A. is a small company investing in the design and development of a low-cost multipurpose multi-mission platform, known as Elettra-Twin-Flyer, which is a very innovative radio-controled airship, equipped with high precision sensors and telecommunication devices. In the prototype phase, Nautilus policy is oriented towards a massive employment of external collaborators to reduce the development costs. The crucial problem of this kind of management is the harmonious integration of all the teams involved on the project. This paper describes the integration process of the PC-104 on-board computer with the avionic devices, which are electronic systems characterized by complex communication protocols. Attention is focused on the testing, verification, validation and final translation of the embedded control software into the on-board computer, through techniques derived from the automatic code generation, such as Rapid Prototyping and Hardware-In-the-Loop. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved

Occlusion points identification algorithm

In this paper a very simple and efficient algorithm is proposed, to calculate the invisible regions of a scene, or shadowed side of a body, when it is observed from a pre-set point. This is done by applying a deterministic numerical procedure to the portion of scene in the field of view, after having been projected in the observer reference frame. The great advantage of this approach is its generality and suitability for a wide number of applications. They span from real time renderings, to the simulation of different types of light sources, such as diffused or collimated, or simply to calculate the effective visible surface for a camera mounted on board of an aircraft, in order to optimize its trajectory if remote sensing or aerial mapping task should be carried out. Optimizing the trajectory, by minimizing at any time the occluded surface, is also a powerful solution for a search and rescue mission, because a wider area in a shorter time can be observed, particularly in situations where the time is a critical parameter, such as, during a forest fire or in case of avalanches. For its simplicity of implementation, the algorithm is suitable for real time applications, providing an extremely accurate solution in a fraction of a millisecond. In this paper, the algorithm has been tested by calculating the occluded regions of a very complex mountainous scenario, seen from a gimbal-camera mounted on board of a flying platform