Plug & Test at System Level via Testable TLM Primitives

With the evolution of Electronic System Level (ESL) design methodologies, we are experiencing an extensive use of Transaction-Level Modeling (TLM). TLM is a high-level approach to modeling digital systems where details of the communication among modules are separated from the those of the implementation of functional units. This paper represents a first step toward the automatic insertion of testing capabilities at the transaction level by definition of testable TLM primitives. The use of testable TLM primitives should help designers to easily get testable transaction level descriptions implementing what we call a "Plug & Test" design methodology. The proposed approach is intended to work both with hardware and software implementations. In particular, in this paper we will focus on the design of a testable FIFO communication channel to show how designers are given the freedom of trading-off complexity, testability levels, and cos

Machine safety issues with respect to the extension of ECRH systems at ASDEX Upgrade

The beam intensity of electron cyclotron resonance heating at ASDEX Upgrade has the potential to seriously damage in-vessel components, whenever not fully absorbed by the plasma. Operation is, therefore, interlocked with both plasma current and density above a given threshold. Microwave protection detectors installed in several ports on the low field side switch the heating system off, in case the stray radiation exceeds a given threshold. During regular inspections, however, damages were reported in the vicinity of the launchers and in particular around the tiles of the heat shield. On one hand, it was found that insulating material, which may not face the plasma, degraded due to millimetre wave absorption. The waves entered the free space behind the heat shield through gaps. On the other hand, local damage even of metallic components was observed on surfaces, which were directly exposed to the microwave beam. Polarisation errors, which led to a local shine through of significant beam power, were responsible. We note that this happened mainly on the high field side in a certain distance to the microwave protection detectors, which were not triggered by the events. In order to increase the level of protection, we identify three necessary measures: Firstly, polarisation control is to be automated such, that mode content and shine through can be monitored. Secondly, by installing additional detectors, the spatial coverage of stray radiation monitoring is enlarged. Thirdly, the heat shield tiles will be redesigned in order to increase the shielding against millimetre waves

Discovery of a Shell of Neutral Atomic Hydrogen Surrounding the Carbon Star IRC+10216

We have used the Robert C. Byrd Green Bank Telescope to perform the most sensitive search to date for neutral atomic hydrogen (HI) in the circumstellar envelope (CSE) of the carbon star IRC+10216. Our observations have uncovered a low surface brightness HI shell of diameter ~1300" (~0.8 pc), centered on IRC+10216. The HI shell has an angular extent comparable to the far ultraviolet-emitting astrosphere of IRC+10216 previously detected with the GALEX satellite, and its kinematics are consistent with circumstellar matter that has been decelerated by the local interstellar medium. The shell appears to completely surround the star, but the highest HI column densities are measured along the leading edge of the shell, near the location of a previously identified bow shock. We estimate a total mass of atomic hydrogen associated with IRC+10216 CSE of M_HI~3x10e-3 M_sun. This is only a small fraction of the expected total mass of the CSE (<1%) and is consistent with the bulk of the stellar wind originating in molecular rather than atomic form, as expected for a cool star with an effective temperature T_eff<~2200 K. HI mapping of a 2 deg x 2 deg region surrounding IRC+10216 has also allowed us to characterize the line-of-sight interstellar emission in the region and has uncovered a link between diffuse FUV emission southwest of IRC+10216 and the Local Leo Cold Cloud.Comment: Accepted to MNRAS. 16 pages. A version with full resolution figures may be found at http://www.haystack.mit.edu/hay/staff/lmatthew/Matthews_etal_IRC+10216.pd

Extended Gauge Invariance in Geometrical Particle Models and the Geometry of W-Symmetry

We prove that particle models whose action is given by the integrated $n$-th curvature function over the world line possess $n+1$ gauge invariances. A geometrical characterization of these symmetries is obtained via Frenet equations by rephrasing the $n$-th curvature model in $\reals^d$ in terms of a standard relativistic particle in $S^{d-n}$. We ``prove by example'' that the algebra of these infinitesimal gauge invariances is nothing but \W_{n+2}, thus providing a geometrical picture of the \W-symmetry for these models. As a spin-off of our approach we give a new global invariant for four-dimensional curves subject to a curvature constraint.Comment: plain TeX (macros included). Slightly modified version published in Nuc. Phys.

Preliminary evaluation of joining Al-PEEK via through hole extrusion welding

The guideline for future automotive and structural application is to reduce the weight with high performance in terms of mechanical resistance. In automotive field this has an additional benefit that is related to the environmental issues that are becoming increasingly stricter. The competitiveness in this industrial field will be guaranteed through hybrid solutions which involve lightweight metals and engineering polymers. Different joining techniques between dissimilar materials were already proposed and established, but sometimes these methods are not very effective. The purpose of this work is to introduce a preliminary evaluation of a new approach to join dissimilar materials. THEW (Through Hole Extrusion Welding) is the new tested joining technique for dissimilar materials. The process consists to extrude the viscoplasticised aluminum alloy through an extrusion die to soften, penetrate, and pressurise the polymer component. The aluminum alloy is brought to the condition of viscoplastic through the stirring effect due to the probe used for this technology. At the same time the shoulder guarantees a total closure of the welding surface and a forging action on the welding region. The penetration of the aluminum will cause a pressurisation and a consequent upward flow of the polymer ensuring the formation of the so called “Crab Claw” joint. The most important involved joining mechanisms are mechanical interlocking and adhesive bonding. The material involved for the final version of the THEW joint are AA5754-H111, PEEK and Ti Gr 1 with a respective thickness of 5 mm, 5 mm, and 0.6 mm. To implement this new kind of dissimilar materials joining technique an experimental plan is made involving the design of new tools, process parameters and clamping system. Different set of tools and process parameters are tested on different base materials. After the experimental phase, a best set of preliminary process parameters, tools and base materials are selected. The process is also implemented for non-linear paths and in a double side version. Mechanical, microstructural, and macrostructural tests are used to analyse the joint from different point of views (mechanical, geometric, and microstructural point of view). The results are analysed and commented to do appropriate analyses on the possible impact of this new joining technique