On-Line Detection And Measurement Of Partial Discharge Signals In A Noisy Environment

In extracting partial discharge (PD) signals embedded in excessive noise, the need for an online and automated tool becomes a crucial necessity. One of the recent approaches that have gained some acceptance within the research arena is the Wavelet multi-resolution analysis (WMRA). However selecting an accurate mother wavelet, defining dynamic threshold values and identifying the resolution levels to be considered in the PD extraction from the noise are still challenging tasks. This paper proposes a novel wavelet-based technique for extracting PD signals embedded in high noise levels. The proposed technique enhances the WMRA by decomposing the noisy data into different resolution levels while sliding it into Kaiser's window. Only the maximum expansion coefficients at each resolution level are used in de-noising and measuring the extracted PD signal. A small set of coefficients is used in the monitoring process without assigning threshold values or performing signal reconstruction. The proposed monitoring technique has been applied to a laboratory data as well as to a simulated PD pulses embedded in a collected laboratory noise

Streamers Optical and Electrical Characteristics Correlations in Liquid Dielectrics Under Alternating Current Stress

International audienceThis paper is devoted to the analysis of optical and electrical characteristics of positive streamers (namely the emitted light and current signals, electric field, velocity and electrical charge) propagating in mineral oil, tetra-ester and toluene, in a point-plane electrode arrangement, under alternating current voltage. Correlations are established between the different characteristics of streamers especially between the velocity and the current derivative indicating that the streamers present also a certain inductive nature, contrarily to the generally used assumptions where streamers propagating are considered of only resistive and capacitive nature. The frequency spectra of the current pulses are also investigated and enlighten all similarities and differences between the studied oils. Each type of discharge can be well identified in relation with the nature of the liquid by the analysis of the frequency behaviour of the corresponding currents or emitted lights. The behaviour of each current streamer is found to be highly influenced by the liquid temperature of evaporation and its electronic affinity

Obesity surgery: evidence-based guidelines of the European Association for Endoscopic Surgery (EAES)

BACKGROUND: The increasing prevalence of morbid obesity together with the development of laparoscopic approaches has led to a steep rise in the number of bariatric operations. These guidelines intend to define the comparative effectiveness and surrounding circumstances of the various types of obesity surgery. METHODS: A consensus panel representing the fields of general/endoscopic surgery, nutrition and epidemiology convened to agree on specific questions in obesity surgery. Databases were systematically searched for clinical trial results in order to produce evidence-based recommendations. Following two days of discussion by the experts and a plenary discussion, the final statements were issued. RECOMMENDATIONS: After the patient's multidisciplinary evaluation, obesity surgery should be considered in adults with a documented BMI greater than or equal to 35 and related comorbidity, or a BMI of at least 40. In addition to standard laboratory testing, chest radiography, electrocardiography, spirometry, and abdominal ultrasonography, the preoperative evaluation of obesity surgery patients also includes upper gastrointestinal endoscopy or radiologic evaluation with a barium meal. Psychiatric consultation and polysomnography can safely be restricted to patients with clinical symptoms on preoperative screening. Adjustable gastric banding (GB), vertical banded gastroplasty (VBG), Roux-en-Y gastric bypass (RYGB) and biliopancreatic diversion (BPD) are all effective in the treatment of morbid obesity, but differ in degree of weight loss and range of complications. The choice of procedure therefore should be tailored to the individual situation. There is evidence that a laparoscopic approach is advantageous for LAGB, VBG, and GB (and probably also for BPD). Antibiotic and antithromboembolic prophylaxis should be used routinely. Patients should be seen 3 to 8 times during the first postoperative year, 1 to 4 times during the second year and once or twice a year thereafter. Outcome assessment after surgery should include weight loss and maintainance, nutritional status, comorbidities and quality-of-life