Study of the beam-cavity interaction in the PS 10 MHz RF system

The eleven main accelerating cavities of the Proton Synchrotron (PS) at CERN consist of two ferrite-loaded coaxial lambda/4 resonators each. Both resonators oscillate in phase, as their gaps are electrically connected by short bars. They are in addition magnetically coupled via the bias loop used for cavity tuning. The cavities are equipped with a wide-band feedback system, limiting the beam loading, and a further reduction of the beam induced voltage is achieved by relays which short-circuit each half-resonator gap when the cavity is not in use. Asymmetries of the beam induced voltage observed in the two half-cavities indicate that the coupling between the two resonators is not as tight as expected. The total cavity impedance coupling to the beam may be affected differently by the contributions of both resonators. A dedicated measurement campaign with high-intensity proton beam and numerical simulation have been performed to investigate the beam-cavity interaction. This paper reports the result of the study and the work aiming at the development of a model of the system, including the wide-band feedback, which reproduces this interaction

Video Coding with Motion Estimation at the Decoder

Predictive video coding is based on motion estimation. In such systems, the temporal correlation is exploited at the encoder, whereas at the decoder, the correlation between the previously decoded frames and the current frame is never exploited. In this chapter, we propose a method for motion estimation at the decoder. Based on the prediction residue and on the already decoded frames, the decoder is able to partially reconstruct the motion field, which therefore can be skipped in the encoded stream. The proposed approach is based on Least Square Estimation (LSE) prediction, and is suitable for low bit-rate video coding, in which the transmission of the motion field has a significant impact on the overall bit-rate. The same technique could also be useful in case of high definition video coding, where a detailed and accurate motion field is required. Preliminary results seem to be very promising

Error Resilience Performance Evaluation of a Distributed Video Codec

Distributed Video Coding (DVC), one of the most active research field in the video coding community, is based on the combination of Slepian-Wolf coding techniques with the idea of performing the prediction at the decoder side rather than at the encoder side. Besides its main property, which is flexible allocation of computational complexity between encoder and decoder, the distributed approach has other interesting properties. One of the most promising DVC characteristics is its intrinsic robustness to transmission errors. In this work we have evaluated the error resilience performance of a video codec based on the DVC scheme proposed by Stanford, and we have carried out a preliminary comparison with traditional H.264 encoding, showing that at high error probabilities and high bitrates the distributed approach can also outperform the traditional one

Performance of a Distributed Video Codec Behaviours in Presence of Transmission Errors

Distributed Video Coding (DVC) is one of the most important and active research fields in video coding. The basic idea underlying DVC is to exploit the temporal correlation among frames directly in the decoding phase. The main properties of a distributed video coding system is that the computational load could in principle be shifted towards the decoder, with respect to a traditional video coding system. Anyway, the distributed coding approach has other interesting properties. In particular, one of the most promising benefits derived by the use of DVC is its natural error resilience to channel errors. Nevertheless, very few results on the actual error resilience properties of distributed video coding systems have been presented in literature. In this contribution we present a detailed analysis of the error resilience properties of a video coding system based on Stanford architecture. We analyze the behavior of such codec in presence of channel error, first focusing on the effect of such errors on the different parts of the encoded stream, and then making a preliminary comparison with H264

A wireless method to obtain the impedance from scattering parameters

The coaxial wire method is a common and appreciated choice to assess the beam coupling impedance (BCI) of an accelerator element. Nevertheless, the results obtained from wire measurements could be inaccurate due to the presence of the stretched conductive. The aim of this work is to establish a solid technique to obtain the BCI from electromagnetic simulations, without modifications of the device under test. In this framework, we identified a new relation to get the resistive wall beam coupling impedance of a circular chamber directly from the scattering parameters. Furthermore, a possible generalization of the method to arbitrary cross section geometries has been studied and validated with numerical simulations

AUDIO CLASSIFICATION IN SPEECH AND MUSIC: A COMPARISON OF DIFFERENT APPROACHES

This paper presents a comparison between different techniques for audio classification into homogeneous segments of speech and music. The first method is based on Zero Crossing Rate and Bayesian Classification (ZB), and it is very simple from a computational point of view. The second approach uses a Multi Layer Perceptron network (MLP) and requires therefore more computations. The performance of the proposed algorithms has been evaluated in terms of misclassification errors and precision in music-speech change detection. Both the proposed algorithms give good results, even if the MLP shows the best performance