Search results for "NOISE"
showing 10 items of 1375 documents
Residual Phase Noise Measurement of Optical Second Harmonic Generation in PPLN Waveguides
2017
We report on the characterization, including residual phase noise and fractional frequency instability, of fiber-coupled PPLN non-linear crystals. These components are devoted to frequency doubling 871 nm light from an extended-cavity diode laser to produce a 435.5 nm beam, corresponding to the ytterbium ion electric quadrupole clock transition. We measure doubling efficiencies of up to 117.5 %/W. Using a Mach-Zehnder interferometer and an original noise rejection technique, the residual phase noise of the doublers is estimated to be lower than ${\rm -35\, dBrad^2/Hz}$ at 1 Hz, making these modules compatible with up-to-date optical clocks and ultra-stable cavities. The influence of externa…
Phase-Noise and Amplitude-Noise Measurement of DACs and DDSs
2019
This article proposes a method for the measurement of Phase Noise (PN, or PM noise) and Amplitude Noise (AN, or AM noise) of Digital-to-Analog Converters (DAC) and Direct Digital Synthesizers (DDS) based on modulation-index amplification. The carrier is first reduced by a controlled amount (30-40 dB) by adding a reference signal of nearly equal amplitude and opposite in phase. Then, residual carrier and noise sidebands are amplified and sent to a conventional PN analyzer. The main virtues of our method are: (i) the noise specs of the PN analyzer are relaxed by a factor equal to the carrier suppression ratio; and, (ii) the capability to measure the AN using a PN analyzer, with no need for th…
Frequency Stability Measurement of Cryogenic Sapphire Oscillators with a Multichannel Tracking DDS and the Two-Sample Covariance
2018
This article shows the first measurement of three 100 MHz signals exhibiting fluctuations from 2E-16 to parts in 1E-15 for integration time tau between 1 s and 1 day. Such stable signals are provided by three Cryogenic Sapphire Oscillators (CSOs) operating at about 10 GHz, also delivering the 100 MHz output via a dedicated synthesizer. The measurement is made possible by a 6-channel Tracking DDS (TDDS) and the two-sample covariance tool, used to estimate the Allan variance. The use of two TDDS channels per CSO enables high rejection of the instrument background noise. The covariance outperforms the Three-Cornered Hat (TCH) method in that the background converges to zero "out of the box," wi…
Prediction of hydraulic and acoustic properties of open-graded mixes
2014
The use of open-graded mixes increases significantly the hydraulic permeability of pavement and contributes to reduce the noise impact in comparison to traditional pavement. Such characteristics are very appealing and would greatly increase driver's safety. However, during service life, the pores tend to be clogged by many factors among them secondary traffic compaction and filling of voids by fine materials are relevant, especially on heavy routes. In this case the noise reduction and drainage capabilities will gradually disappear, causing serious problems for road safety and maintenance. In this paper we propose a simulation approach in order to predict the drainage and acoustic behavior …
An intensimetric method to localize secondary sources
2003
Research is presented to find out the amount and direction of the early reflections of a primary sound source in a room. Two rooms, very different in dimensions, were taken into account: the smallest one is about 100 m3 and the largest one 1100 m3. The measurement system consists of a PC equipped with a sound-board connected to the signals coming from the two microphones of an intensity probe at the input and to a loudspeaker at the output. A sweep signal was used for the excitation of the environment. Signal processing software was developed using LabVIEW by National Instruments. The results of the two measurement sessions are presented as amplitude-direction diagrams and amplitude-directi…
A Robust Multi Stage Technique for Image Binarization of Degraded Historical Documents
2017
International audience; Document image binarization is a central problem in many document analysis systems. Indeed, it represents one of the basic challenges, especially in case of historical documents analysis. In this paper, we propose a novel robust multi stage framework that combines different existing document image thresholding methods for the purpose of getting a better binarization result. CLAHE technique is introduced to significantly enhance contrast in some poor images. The proposed method then uses a hybrid algorithm to partition image into foreground and background. A special procedure is finally applied in order to remove small noise and correct characters morphology. Experime…
Analysis of ecological shifts in the two‐age structured population model with Allee effect and environmental noise
2020
We study noise-induced transformations in the two-age structured population model with the Allee effect and environmental fluctuations. In this bistable model, ecological shifts are associated mathematically with random transitions between basins of coexisting attractors. The following phenomena are revealed and studied: (i) noise-induced extinction, (ii) stochastic regeneration, and (iii) excitement of random mixed-mode oscillations. Constructive abilities of the analytical method of confidence domains are demonstrated in the parametric study of these phenomena.
STUDY ON NOISE LEVEL GENERATED BY HUMAN ACTIVITIES IN SIBIU CITY, ROMANIA
2014
In this paper I have proposed an analysis and monitoring of the noise sources in the open spaces of air traffic, rail and car in Sibiu. From centralizing data obtained from the analysis of the measurements performed with equipment noise levels, we concluded that the noise and vibration produced by means of Transportation (air, road, rail) can affect human health if they exceed limits. Noise is present and part of our lives and always a source of pollution as any of modern man is not conscious.
The Effect of Using Noise Cancellation Earplugs in Open-plan Offices of the Work Well-being and Work Performance of Software Professionals
2017
The popularity of open-plan offices has been on the rise recently and expanded to all sectors of working life. While moving to open-plan offices brings savings to companies, open-plan offices have been connected with various different negative consequences, such as noise. Noise has been found to be a central cause of dissatisfaction towards working in an open-plan office and lead to subsequent negative outcomes, such as decreased self-perceived health and weakened cognitive performance. Therefore, it is important to study the ways and technologies that could possibly mitigate the negative effects of noise on work well-being and work performance. This explorative study investigates both the …
Stochastic model for a biological complex system: analysis of the bacterial growth in food products
2012
The Physics of Complex Systems has recently taken a more and more important role in the description of natural systems because of the interactions, both deterministic and noisy, between such systems and the environment. In particular the noise plays a relevant role in biological systems, whose dynamics is strongly influenced by environmental variables subject to random fluctuations. In this work a stochastic model is exploited to reproduce the growth of bacteria in food of animal origin. Specifically the dynamics of a bacterial species, Listeria monocytogenes, is analyzed in the presence of lactic acid bacteria (LAB) during the period of the fermentation of meat products. The model, based o…