Wave Energy Converter through Piezoelectric Polymers

This note addresses the concept of wave energy conversion by means of piezoelectric material. The ocean surface waves represent an important source of energy power.A multiphysics simulation is used to focus ondifferent aspects, namely the free surface wave,the fluid-structure-interaction, the mechanical energy input to the piezoelectric material and finally the electric power output using anequivalent open circuit model. The authors designed several feasible devices which are all similar, as long as they are forced by the wave action at a characteristic wave frequency. For the sake of simplicity, a basic system is analyzed here. The amount of energy generated bythe piezoelectric materials appears very small, nevertheless some application of interest will be presented

Analysis of Empirical Core Loss Evaluation Methods For Non-Sinusoidally Fed Medium Frequency Power Transformers

Nowadays medium voltage conversion systems, like traction and energy distribution systems, aim to increase power density. Volume, weight and material reduction are gaining the market today. Due to the development of new high power semiconductor devices a new working frequency range is conceived, where magnetic component reduction is feasible. The core element of these new conversion systems is the medium frequency transformer. For an optimized design of the conversion system, the correct determination of transformer core losses is essential. Sinusoidal approaches, accurate enough for line frequency transformers, do not cope with the non-sinusoidal waveforms of future medium voltage conversion systems. In the past few years several empirical methods derived from the original Steinmetz equation have been introduced to determine magnetic core losses for non-sinusoidal waveforms. This paper proposes extended expressions for core loss determination in case of rectangular three level voltage waveforms, typical of high power converters. These expressions are compared in simulation and with experimental results obtained in the same conditions using a reduced scale dc-ac conversion system prototype that includes a 61.6 kVA/2 kHz transformer. It is shown that some of these techniques allow a considerable loss estimation accuracy (error below 12% for any ratio)

Rendements Energétiques de Convertisseurs DC-AC 25kVA Isolés à Deux ou Trois Etages

Dans le cadre du projet européen UNIFLEX-PM, deux topologies de convertisseur AC/AC ont été étudiées et implémentés. Les deux convertisseurs réalisés sont isolés par un étage transformateur moyenne fréquence pour une puissance nominale de 25kW. La première topologie, symétrique, est constituée de quatre étages onduleurs de tensions. De part et d’autre du transformateur moyenne fréquence, se trouvent deux étages DC intermédiaires de 1.1kV. La deuxième topologie considérée possède la même structure du côté primaire du transformateur et un étage cycloconvertisseur au secondaire. L’étude des rendements s’est focalisée sur une partie de ces convertisseurs, à savoir, la chaine de transformation entre un étage DC intermédiaire vers une charge alternative de 25kW. Les rendements expérimentaux ont été comparés aux rendements théoriques. Les résultats montrent que le cycloconvertisseur possède un rendement inférieur à la solution symétrique

Description and Efficiency Comparison of Two 25 kVA DC/AC Isolation Modules

In the frame of the European project UNIFLEX-PM, two AC/AC converter topologies hove been studied and implemented. Both converters, rated for 25 kVA, are isolated by a medium-frequency power transformer. The first topology is based on a dual active bridge containing two additional voltage source inverters for the connection of both DC links to the interfaced grids. The second topology is based on a cycloconverter for the connection of the secondary side of the transformer to the grid without a DC link capacitor Both topologies hove an identical primary side so the efficiency study is focussed on the chain link from one DC link to a 25 kW output load. Experimental efficiencies are compared to theoretical expectations. Due to soft-switching operation hi the dual active-bridge, the cycloconverter based solution shows a lower efficiency than in the symmetrical topology

Centre de la prostate: une approche multidisciplinaire pour une prise en charge globale du patient [Prostate cancer center: a multidisciplinary approach to accurately manage patients with prostate cancer]

The prostate cancer is a complex pathology involving oncological, functional and psychosocial items. The prostate's center of CHUV harmonize the know-how of urologists, oncologist, radiotherapists and clinical nurses to offer a global management to patients attempts by prostate cancer, from diagnosis to therapy and follow-up

Randomized controlled trial of peripherally inserted central catheters vs. peripheral catheters for middle duration in-hospital intravenous therapy.

INTRODUCTION: Intravenous (i.v.) therapy may be associated with important catheter-related morbidity and discomfort. The safety, efficacy, comfort, and cost-effectiveness of peripherally inserted central catheters (PICCs) were compared to peripheral catheters (PCs) in a randomized controlled trial. METHODS: Hospitalized patients requiring i.v. therapy >or= five days were randomized 1:1 to PICC or PC. Outcomes were incidence of major complications, minor complications, efficacy of catheters, patient satisfaction, and cost-effectiveness. RESULTS: 60 patients were included. Major complications were observed in 22.6% of patients in the PICC group [six deep venous thrombosis (DVT), one insertion-site infection] and 3.4% of patients in the PC group [one DVT; risk ratio (RR) 6.6; P = 0.03]. Superficial venous thrombosis (SVT) occurred in 29.0% of patients in the PICC group and 37.9% of patients in the PC group (RR 0.60; P = 0.20). Patients in the PICC group required 1.16 catheters on average during the study period, compared with 1.97 in the PC group (P < 0.04). The mean number of venipunctures (catheter insertion and blood sampling) was 1.36 in the PICC group vs. 8.25 in the PC group (P < 0.001). Intravenous drug administration was considered very or quite satisfying by 96.8% of the patients in the PICC group, and 79.3% in the PC group. Insertion and maintenance mean cost was 690 US$for PICC and 237 US$ for PC. DISCUSSION: PICC is efficient and satisfying for hospitalized patients requiring i.v. therapy >or= five days. However, the risk of DVT, mostly asymptomatic, appears higher than previously reported, and should be considered before using a PICC