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In recent years it has been made more and more clear that the critical issue in gradient methods is the choice of the step length, whereas using the gradient as search direction may lead to very effective algorithms , whose surprising behaviour has been only partially explained, mostly in terms of the spectrum of the Hessian matrix. On the other hand, the(More)
— Preserving connectivity of a network topology is a crucial aspect for multi-robot systems in order to perform almost any collaborative task. This problem turns out to be significantly challenging in the case of a heterogeneous multi-robot system equipped with different sensors with limited field of view. Such an interaction scheme, in fact, is described(More)
We propose a new gradient method for quadratic programming, named SDC, which alternates some SD iterates with some gradient iterates that use a constant steplength computed through the Yuan formula. The SDC method exploits the asymptotic spectral behaviour of the Yuan steplength to foster a selective elimination of the components of the gradient along the(More)
We analyze the regularization properties of two recently proposed gradient methods applied to discrete linear inverse problems. By studying their filter factors, we show that the tendency of these methods to eliminate first the eigencomponents of the gradient corresponding to large singular values allows to reconstruct the most significant part of the(More)
An ageing test of three ATLAS production RPC stations is in course at X5-GIF, the CERN irradiation facility. The chamber efficiencies are monitored using cosmic rays triggered by a scintillator hodoscope. Higher statistics measurements are made when the X5 muon beam is available. We report here the measurements of the efficiency versus operating voltage at(More)
Started in 1994 the L3 experiment has been equipped with a forward}backward muon spectrometer triggered by an RPC system. Made of 192 double-gap RPCs, it has been working for six years in streamer mode and it will continue to run at least one year more. We monitored the behaviour of the system during the L3 run periods and in this paper we report on its(More)
Discrimination of different cell types is very important in many medical and biological applications. Existing methodologies are based on cost inefficient technologies or tedious one-by-one empirical examination of the cells. Recently, Raman spectroscopy, a inexpensive and efficient method, has been employed for cell discrimination. Nevertheless, the(More)
The absolute muon flux between 20 and 3000 GeV is measured with the L3 magnetic muon spectrometer for zenith angles ranging from 0 • to 58 •. Due to the large exposure of about 150 m 2 sr d, and the excellent momentum resolution of the L3 muon chambers, a precision of 2.3% at 150 GeV in the vertical direction is achieved. The ratio of positive to negative(More)
The RPC chambers in the L3 forward–backward muon spectrometer have been operational from 1994 to the end of LEP running. After dismantling of the L3 detector some of the RPCs modules have been transported to Napoli where their performance has been re-measured with cosmic rays. Results of long-term performance in the LEP environment and of laboratory tests(More)
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