SCR-Based Wind Energy Conversion Circuitry and Controls for DC Distributed Wind Farms

The current state of art for electrical power generated by wind generators are in alternating current (AC). Wind farms distribute this power as 3-phase AC. There are inherent stability issues with AC power distribution. The grid power transfer capacity is limited by the distance and characteristic impedance of the lines. Furthermore, wind generators have to implement complicated, costly, and inefficient back-to-back converters to generate AC. AC distribution does not offer an easy integration of energy storage. To mitigate drawbacks with AC generation and distribution, direct current (DC) generation and high voltage direct current (HVDC) distribution for the wind farms is proposed. DC power distribution is inherently stable. The generators convert AC power to DC without the use of a back-to-back converter. DC grid offers an easy integration of energy storage. The proposed configuration for the generator is connected to a HVDC bus using a 12 pulse thyristor network, which can apply Maximum Power Point Tracking (MPPT). To properly control the system, several estimators are designed and applied. This includes a firing angle, generator output voltage, and DC current estimators to reduce noise effects. A DSP-based controller is designed and implemented to control the system and provide gate pulses. Performance of the proposed system under faults and drive train torque pulsation are analyzed as well. Additionally, converter paralleling when turbines operate at different electrical power levels are also studied. The proposed new Wind Energy Conversion System (WECS) is described in detail and verified using MATLAB®/ Simulink® simulation and experimental test setup. The proposed solution offers higher reliability, lower conversion power loss, and lower cost. The following is proposed as future work: 1) Study different control methods for controlling the SCR\u27s. 2) Investigate reducing torque pulsations of the PMSG and using the proposed power conversion method for DFIG turbines. 3) Explore options for communication/control between PMSG, circuit protection and grid-tied inverters. 4) Investigate the best possible configuration for DC storage/connection to the HVDC/MVDC bus. 5) Study the filtering needed to improve the DC bus voltage at the generator

Molecular Weight Tuning of Organic Semiconductors for Curved Organic-Inorganic Hybrid X-Ray Detectors

Curved X-ray detectors have the potential to revolutionize diverse sectors due to benefits such as reduced image distortion and vignetting compared to their planar counterparts. While the use of inorganic semiconductors for curved detectors are restricted by their brittle nature, organic-inorganic hybrid semiconductors which incorporated bismuth oxide nanoparticles in an organic bulk heterojunction consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) are considered to be more promising in this regard. However, the influence of the P3HT molecular weight on the mechanical stability of curved, thick X-ray detectors remains less well understood. Herein, high P3HT molecular weights (>40 kDa) are identified to allow increased intermolecular bonding and chain entanglements, resulting in X-ray detectors that can be curved to a radius as low as 1.3 mm with low deviation in X-ray response under 100 repeated bending cycles while maintaining an industry-standard dark current of mu C Gy(-1) cm(-2). This study identifies a crucial missing link in the development of curved detectors, namely the importance of the molecular weight of the polymer semiconductors used

Tissue Equivalent Curved Organic X-ray Detectors Utilizing High Atomic Number Polythiophene Analogues

Organic semiconductors are a promising material candidate for X-ray detection. However, the low atomic number (Z) of organic semiconductors leads to poor X-ray absorption thus restricting their performance. Herein, the authors propose a new strategy for achieving high-sensitivity performance for X-ray detectors based on organic semiconductors modified with high –Z heteroatoms. X-ray detectors are fabricated with p-type organic semiconductors containing selenium heteroatoms (poly(3-hexyl)selenophene (P3HSe)) in blends with an n-type fullerene derivative ([6,6]-Phenyl C71 butyric acid methyl ester (PC70BM). When characterized under 70, 100, 150, and 220 kVp X-ray radiation, these heteroatom-containing detectors displayed a superior performance in terms of sensitivity up to 600 ± 11 nC Gy−1 cm−2 with respect to the bismuth oxide (Bi2O3) nanoparticle (NP) sensitized organic detectors. Despite the lower Z of selenium compared to the NPs typically used, the authors identify a more efficient generation of electron-hole pairs, better charge transfer, and charge transport characteristics in heteroatom-incorporated detectors that result in this breakthrough detector performance. The authors also demonstrate flexible X-ray detectors that can be curved to a radius as low as 2 mm with low deviation in X-ray response under 100 repeated bending cycles while maintaining an industry-standard ultra-low dark current of 0.03 ± 0.01 pA mm−2

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Additional file 2: of Cytotoxic effects of ergone, a compound isolated from Fulviformes fastuosus

1D, 2D and mass spectra. (DOCX 12600 kb

Additional file 1: of Cytotoxic effects of ergone, a compound isolated from Fulviformes fastuosus

A summary of the data obtained from MTT assay. (XLSX 10 kb

MOSEL Survey: JWST Reveals Major Mergers/strong Interactions Drive the Extreme Emission Lines in the Early Universe

Extreme emission line galaxies (EELGs), where nebular emissions contribute 30%–40% of the flux in certain photometric bands, are ubiquitous in the early Universe ( z > 6). We utilize deep NIRCam imaging from the JWST Advanced Deep Extragalactic Survey ( JADES ) to investigate the properties of companion galaxies (projected distance 6

Molecular weight tuning of organic semiconductors for curved organic-inorganic hybrid X-ray detectors

Curved X-ray detectors have the potential to revolutionise diverse sectors due to benefits such as reduced image distortion and vignetting compared to their planar counterparts. While the use of inorganic semiconductors for curved detectors are restricted by their brittle nature, organic-inorganic hybrid semiconductors which incorporated bismuth oxide nanoparticles in an organic bulk heterojunction consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) are considered to be more promising in this regard. However, the influence of the P3HT molecular weight on the mechanical stability of curved, thick X-ray detectors remains less well understood. Herein, high P3HT molecular weights (>40 kDa) are identified to allow increased intermolecular bonding and chain entanglements, resulting in X-ray detectors that can be curved to a radius as low as 1.3 mm with low deviation in X-ray response under 100 repeated bending cycles while maintaining an industry-standard dark current of <1 pA mm-2 and a sensitivity of ~0.17 μC Gy-1 cm-2. This study identifies a crucial missing link in the development of curved detectors, namely the importance of the molecular weight of the polymer semiconductors used