Analysis of Vibration Isolators for Hermetic Compressors

Nowadays, the customers of refrigerators and freezers have become more exigent in respect to the acoustic comfort of these home appliances. Among the noise sources, there are the refrigerant flow, the fans and the compressors. The compressors might be responsible for a part of the cabinet low frequency noise which could be generated either by the gas pulsation that excites the tubing or the compressor low frequency vibration that transfers energy to the cabinet base plate and tubing. The compressor low frequency vibration is a function of the mechanism loads and the gas pressure that acts on the piston and it is modulated by its running frequency and harmonics. Besides, at low frequencies, the compressor behaves as a rigid body assembled on isolators or grommets which link the compressor to the cabinet base plate. If one knows these rigid body natural frequencies, it’s possible to optimize the refrigerator project, providing a better acoustic performance for manufacturers and final customers. Based on this context, this paper aims to present a study of the compressor grommets, usually made in rubber. First of all, an investigation about the materials is carried out using a technique with a single degree-of-freedom system. In a second time, an analysis of the static behavior of an isolator using the rubber properties is done. Finally, a numerical model to predict the modal behavior of a compressor assembled on a rigid base is created and validated experimentally

Experimental Demonstration of Vibration Sensing and Positioning on Multiple Metropolitan Fibers

We investigate on simultaneous polarization sensing on multiple fibers to detect and time-position anomalous vibration events. We experimentally demonstrate that our “threshold and cross-correlate” algorithm obtains timing with 40 ms rms accuracy when tested on deployed fibers (35km and 10km) in Turin urban area

Generation of sub-picosecond electron bunches from RF photoinjectors

Abstract In this paper we discuss the possibility to generate sub-picosecond electron bunches directly from a photoinjector by illuminating a photo-cathode in an RF cavity with a phase-locked sub-picosecond laser pulse. In particular, we address all de-bunching effects taking place during acceleration and transport through a photoinjector. We provide analysis of the beam dynamics, as well as the comparison with numerical simulations. The possible performances of the present SATURNUS linac setup are presented, as well as the anticipated capabilities of a multi-cell RF gun structure based on the PWT linac presently in operation at UCLA

Collective bargaining in the construction industry Wages, hours and vocational training in Belgium, the Federal Republic of Germany, France, Italy, Spain and the United Kingdom.

OOPEC 90031

Lumbricus webis: a parallel and distributed crawling architecture for the Italian web

Web crawlers have become popular tools for gattering large portions of the web that can be used for many tasks from statistics to structural analysis of the web. Due to the amount of data and the heterogeneity of tasks to manage, it is essential for crawlers to have a modular and distributed architecture. In this paper we describe Lumbricus webis (short L.webis) a modular crawling infrastructure built to mine data from the web domain ccTLD .it and portions of the web reachable from this domain. Its purpose is to support gathering of advanced statics and advanced analytic tools on the content of the Italian Web. This paper describes the architectural features of L.webis and its performance. L.webis can currently download a mid-sized ccTLD such as ".it" in about one week

Higher harmonic inverse free-electron laser interaction

We expand the theory of the inverse free electron laser (IFEL) interaction to include the possibility of energy exchange that takes place when relativistic particles traversing an undulator interact with an electromagnetic wave of a frequency that is a harmonic of the fundamental wiggler resonant frequency. We derive the coupling coefficients as a function of the IFEL parameters for all harmonics, both odd and even. The theory is supported by simulation results obtained with a three-dimensional Lorentz equation solver code. Comparisons are made between the results of theory and simulations, and the recent UCLA IFEL experimental results where higher harmonic IFEL interaction was observed