Single Chord Polarimetry results on RFX

A single-chord FIR polarimeter (λ=118.8μm) has been mounted on RFXand is now under test. The purpose of the diagnostic is to ascertain the feasibility of measuring a Faraday rotation effect n the RFX plasma and to discover what requirements are necessary for a future six-chord diagnostic. The diagnostic should measure small Faraday rotation angles (of the order of a few degrees) and the required resolution is of ±0.2 . The tests carried out reveal various sources of disturbance: electrical disturbances in the signals vibration effects on the optical components, detector noise and perturbations on the laser syste

Range-only SLAM with a mobile robot and a Wireless Sensor Networks

This paper presents the localization of a mobile robot while simultaneously mapping the position of the nodes of a Wireless Sensor Network using only range measurements. The robot can estimate the distance to nearby nodes of the Wireless Sensor Network by measuring the Received Signal Strength Indicator (RSSI) of the received radio messages. The RSSI measure is very noisy, especially in an indoor environment due to interference and reflections of the radio signals. We adopted an Extended Kalman Filter SLAM algorithm to integrate RSSI measurements from the different nodes over time, while the robot moves in the environment. A simple pre-processing filter helps in reducing the RSSI variations due to interference and reflections. Successful experiments are reported in which an average localization error less than 1 m is obtained when the SLAM algorithm has no a priori knowledge on the wireless node positions, while a localization error less than 0.5 m can be achieved when the position of the node is initialized close to the their actual position. These results are obtained using a generic path loss model for the transmission channel. Moreover, no internode communication is necessary in the WSN. This can save energy and enables to apply the proposed system also to fully disconnected networks

Single Cord far-infrared polarimetry experiment on RFX

This paper summarises the work of the authors in the realisation and testing of a pilot single chord polarimetry experiment on the RFX (reversed field experiment) machine, at the far-infrared wavelength of 118.8 µm. The fundamental purpose of this experiment is to demonstrate the feasibility of a Faraday rotation angle measurement on RFX, with the required resolution, and to clarify all the aspects which may be useful for the final six-chord version of the diagnostic. The apparatus which has been developed is described, with emphasis on some of the modifications which proved essential in order to obtain a satisfactory measurement, in spite of the hostile environment of the machine. Typical results of Faraday angle measurements are presented and discussed, and the reliability of the measurement is demonstrated. In particular, the required +0.2o accuracy is achieved and the results are consistent with magnetic field profiles similar to the ones predicted by the Bessel function model. Suitable design considerations are formulated in order to guarantee the required performance in the six-chord version, even when the machine moves into full regime

Exploiting Transition Locality in the disk based Murphi Verifier

Exploiting Transition Locality in the disk based Murphi Verifie

Synchronized Regular Expressions

Synchronized Regular Expression

A Probabilistic Approach to Space-Time Trading in Automatic Verification of Concurrent Systems

A Probabilistic Approach to Space-Time Trading in Automatic Verification of Concurrent System

Synchronized Regular Expressions

Synchronized Regular Expression

Synchronized Regular Expressions1 1An extended version of this paper is considered for publication in Acta Informatica

AbstractText manipulation is one of the most common tasks for everyone using a computer. The increasing number of textual information in electronic format that every computer user collects everyday stresses the need of more powerful tools to interact with texts. Indeed, much work has been done to provide nonprogramming tools that can be useful for the most common text manipulation issues. Regular Expressions (RE), introduced by Kleene, are well–known in the formal language theory. RE received several extensions, depending on the application of interest. In almost all the implementations of RE search algorithms (e.g. the egrep [A] UNIX command, or the Perl [17] language pattern matching constructs) we find backreferences (as defind in [1]), i.e. expressions that make reference to the string matched by a previous subexpression. Generally speaking, it seems that all the kinds of synchronizations between subexpressions in a RE can be very useful when interacting with texts. Therefore, we introduce the Synchronized Regular Expressions (SRE) as a derivation of the Regular Expressions. We use SRE to present a formal study of the already known backreferences extension, and of a new extension proposed by us, which we call the synchronized exponents. Moreover, since we are talking about formalisms that should have a practical utility and can be used in the real world, we have the problem of how to present SRE to the final users. Therefore, in this paper we also propose a user–friendly syntax for SRE to be used in implementations of SRE–powered search algorithms

Investigation on an Anomalous Behavior of the Polarimetric Measurements at JET

The far-infrared polarimeter at JET is affected by an anomaly that makes difficult the interpretation of both Faraday and Cotton\u2013Mouton effect measurements. The anomaly is clearly displayed during calibration operations in the absence of plasma: As the polarization of the probing beam is rotated, the phase shift of the polarimetric signal with respect to the interferometric signal is not constant, as expected, and changes significantly. It affects all the polarimetric measurement channels and has so far been removed by an empirical preprocessing of the raw data. It can be ascribed to a nonideal behavior of some optical components. Looking for a possible explanation of the anomaly, in this paper, we analyze the optical setup of the JET polari\u2013interferometer according to the laws of classical polarization optics. At first, the optical characteristics of the recombination plates are analyzed in detail. Although they produce ellipticity in the transmitted and reflected beams, the results show that the recombination plates should not be responsible of the anomaly of the polarimeter. Then, the dielectric waveguides used to transfer the recombined beams from the torus hall to the detectors are, for the first time, considered as a possible origin of the anomaly. The anomalous behavior is expected to be mainly originated by reflections on metal mirrors, which may produce rotations of the polarization of the beams. A calculation has been performed in order to analyze the effects of a rotation of the polarization of the recombined beam on the detector signals. As a result, a rotation of the polarization along the line could explain the anomaly. We also suggest some simple and feasible tests, which are useful to give an experimental support to this conclusion, and discuss possible modifications of the optical setup to remove or greatly reduce the anomaly in future measurements

Exploiting Transition Locality in Automatic Verification

In this paper we present an algorithm to contrast state explosion when using Explicit State Space Exploration to verify protocols. We show experimentally that protocols exhibit transition locality. We present a verification algorithm that exploits transition locality as well as an implementation of it within the Murphi verifier. Our algorithm is compatible with all Breadth First (BF) optimization techniques present in the Murphi verifier and it is by no means a substitute for any of them. In fact, since our algorithm trades space with time, it is typically most useful when one runs out of memory and has already used all other state reduction techniques present in the Murphi verifier. Our experimental results show that using our approach we can typically save more than 40% of RAM with an average time penalty of about 50% when using (Murphi) bit compression and 100% when using bit compression and hash compaction