Design and control of parallel three phase voltage source Inverters in low voltage AC microgrid

Design and hierarchical control of three phase parallel Voltage Source Inverters are developed in this paper. The control scheme is based on synchronous reference frame and consists of primary and secondary control levels. The primary control consists of the droop control and the virtual output impedance loops. This control level is designed to share the active and reactive power correctly between the connected VSIs in order to avoid the undesired circulating current and overload of the connected VSIs. The secondary control is designed to clear the magnitude and the frequency deviations caused by the primary control. The control structure is validated through dynamics simulations.The obtained results demonstrate the effectiveness of the control structure

Activity of highly dispersed Co/SBA-15 catalysts (low content) in carbon black oxidation

Peer reviewedPublisher PD

Global Retinoblastoma Presentation and Analysis by National Income Level.

Importance: Early diagnosis of retinoblastoma, the most common intraocular cancer, can save both a child's life and vision. However, anecdotal evidence suggests that many children across the world are diagnosed late. To our knowledge, the clinical presentation of retinoblastoma has never been assessed on a global scale. Objectives: To report the retinoblastoma stage at diagnosis in patients across the world during a single year, to investigate associations between clinical variables and national income level, and to investigate risk factors for advanced disease at diagnosis. Design, Setting, and Participants: A total of 278 retinoblastoma treatment centers were recruited from June 2017 through December 2018 to participate in a cross-sectional analysis of treatment-naive patients with retinoblastoma who were diagnosed in 2017. Main Outcomes and Measures: Age at presentation, proportion of familial history of retinoblastoma, and tumor stage and metastasis. Results: The cohort included 4351 new patients from 153 countries; the median age at diagnosis was 30.5 (interquartile range, 18.3-45.9) months, and 1976 patients (45.4%) were female. Most patients (n = 3685 [84.7%]) were from low- and middle-income countries (LMICs). Globally, the most common indication for referral was leukocoria (n = 2638 [62.8%]), followed by strabismus (n = 429 [10.2%]) and proptosis (n = 309 [7.4%]). Patients from high-income countries (HICs) were diagnosed at a median age of 14.1 months, with 656 of 666 (98.5%) patients having intraocular retinoblastoma and 2 (0.3%) having metastasis. Patients from low-income countries were diagnosed at a median age of 30.5 months, with 256 of 521 (49.1%) having extraocular retinoblastoma and 94 of 498 (18.9%) having metastasis. Lower national income level was associated with older presentation age, higher proportion of locally advanced disease and distant metastasis, and smaller proportion of familial history of retinoblastoma. Advanced disease at diagnosis was more common in LMICs even after adjusting for age (odds ratio for low-income countries vs upper-middle-income countries and HICs, 17.92 [95% CI, 12.94-24.80], and for lower-middle-income countries vs upper-middle-income countries and HICs, 5.74 [95% CI, 4.30-7.68]). Conclusions and Relevance: This study is estimated to have included more than half of all new retinoblastoma cases worldwide in 2017. Children from LMICs, where the main global retinoblastoma burden lies, presented at an older age with more advanced disease and demonstrated a smaller proportion of familial history of retinoblastoma, likely because many do not reach a childbearing age. Given that retinoblastoma is curable, these data are concerning and mandate intervention at national and international levels. Further studies are needed to investigate factors, other than age at presentation, that may be associated with advanced disease in LMICs

Travel burden and clinical presentation of retinoblastoma: analysis of 1024 patients from 43 African countries and 518 patients from 40 European countries

BACKGROUND: The travel distance from home to a treatment centre, which may impact the stage at diagnosis, has not been investigated for retinoblastoma, the most common childhood eye cancer. We aimed to investigate the travel burden and its impact on clinical presentation in a large sample of patients with retinoblastoma from Africa and Europe. METHODS: A cross-sectional analysis including 518 treatment-naïve patients with retinoblastoma residing in 40 European countries and 1024 treatment-naïve patients with retinoblastoma residing in 43 African countries. RESULTS: Capture rate was 42.2% of expected patients from Africa and 108.8% from Europe. African patients were older (95% CI -12.4 to -5.4, p<0.001), had fewer cases of familial retinoblastoma (95% CI 2.0 to 5.3, p<0.001) and presented with more advanced disease (95% CI 6.0 to 9.8, p<0.001); 43.4% and 15.4% of Africans had extraocular retinoblastoma and distant metastasis at the time of diagnosis, respectively, compared to 2.9% and 1.0% of the Europeans. To reach a retinoblastoma centre, European patients travelled 421.8 km compared to Africans who travelled 185.7 km (p<0.001). On regression analysis, lower-national income level, African residence and older age (p<0.001), but not travel distance (p=0.19), were risk factors for advanced disease. CONCLUSIONS: Fewer than half the expected number of patients with retinoblastoma presented to African referral centres in 2017, suggesting poor awareness or other barriers to access. Despite the relatively shorter distance travelled by African patients, they presented with later-stage disease. Health education about retinoblastoma is needed for carers and health workers in Africa in order to increase capture rate and promote early referral

Oxydation ménagée du méthane par le dioxyde d azote sur des catalyseurs à base de cobalt dispersé sur des silices mésoporeuses de type SBA-15

Les catalyseurs à base de cobalt et de silices mésoporeuses SBA-15 ont été préparés par trois méthodes : imprégnation (à l eau ou à deux solvants) et synthèse directe. Un échantillon de référence a été préparé par dépôt-précipitation à l urée. Des informations ont été obtenues par des techniques texturales, structurales, spectroscopiques et par réduction en température programmée sous H2. L architecture 2D hexagonale de la silice ne s effondre pas lors des étapes de préparation. Différentes espèces contenant du cobalt ont pu être mises en évidence : des nanoparticules de Co3O4, des ions dispersés et des particules d un oxyde de type CoO. Au-delà de l identification, une quantification issue des RTP est proposée et l incidence des traitements thermiques (oxydants et/ou réducteurs) utilisés lors de la préparation des catalyseurs est étudiée. L activité des catalyseurs dans l activation du méthane par NO2 a été mesurée sur les catalyseurs.L espèce la plus active est un intermédiaire de type CoO formé par réduction partielle des nanoparticules de Co3O4 localisées à l intérieur des mésopores. La longueur et le diamètre des mésopores jouent un rôle déterminant sur l activité catalytique.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Characterizations and performances of Ni/diatomite catalysts for dry reforming of methane

International audienceMonometallic 5 wt% Ni containing catalysts were prepared by a two-solvent (cyclohexane/water) deposition method using cheap and widely available natural diatomites (Ni/AW2 and Ni/MN3) as supports. The fresh samples were characterized by SEM, EDX microanalysis, N2 adsorption–desorption isotherms, XRD and tested after reduction (in hydrogen) in dry reforming of methane. Spent catalysts were further characterized by TPH coupled with mass spectrometry. Although slightly less active than a reference Ni/Aerosil (Ni/SiO2) catalyst prepared in similar conditions, the Ni/diatomites catalysts showed good activity with 90% methane conversion reached on Ni/MN3 at 800 °C and a high selectivity towards dry reforming reaction (H2:CO molar ratio around unity over the entire temperature range). The catalysts were also relatively stable during catalytic measurements conducted at 650 °C for 12 h. In addition, depending on the nature of the diatomite and on the conditions of thermal activation, carbon deposits with lower toxicity (easier to remove by reactivation) than those formed on the Ni/Aerosil were obtained

Effect of pore geometry of mesoporous supports on catalytic performances in methane reforming

Catalysts prepared using three dimensional SBA-16 silica support (composed of micropores and cage-like mesopores) were tested in the reaction of methane dry reforming, in comparison with 2D hexagonal mesoporous SBA-15 support. The samples were evaluated by N2 sorption and X-Ray diffraction (XRD) for the assessment of their textural and structural properties. The reducibility was characterized by temperature programmed reduction (TPR). The catalytic performances were evaluated in methane dry reforming and spent catalysts (after reaction) were characterized for the evaluation of sintering and coke formation by TPH/MS, XRD and HR-TEM

Porous Nickel‐Alumina Derived from Metal‐Organic Framework (MIL‐53): A New Approach to Achieve Active and Stable Catalysts in Methane Dry Reforming

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