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This paper presents a time-efficient modeling and simulation strategy for aggregated microinverters in large-scale photovoltaic systems. As photovoltaic microinverter systems are typically comprised of multiple power electronic converters, a suitable modeling and simulation strategy that can be used for rapid prototyping is required. Dynamic models incorporating switching action may induce significant computational burdens and long simulation durations. This paper introduces a single-matrix-form approach using the average model of a basic microinverter with two power stages consisting of a dc-dc and dc-ac converter. The proposed methodology using a common or intermediate source between two average models of cascaded converters to find the overall average model is introduced and is applicable to many other converter topologies and combinations. It provides better flexibility and simplicity when investigating various power topologies in system-level studies of microinverter and other power electronic systems. A 200 W prototype microinverter is tested to verify the proposed average and dynamic models. Furthermore, MATLAB/Simulink (2010a, Mathworks, Natick, MA, USA) is used to show the improved simulation speed and maintained accuracy of the multiple microinverter configurations when the derived average model is compared to a dynamic switching simulation model. [ABSTRACT FROM AUTHOR]

In this paper, power loss and cost models of power electronic converters based on converter ratings and datasheet information are presented. These models aid in creating rapid prototypes which facilitate the component selection process. Through rapid prototyping, users can estimate power loss and cost which are essential in design decisions. The proposed approach treats main power electronic components of a converter as building blocks that can be arranged to obtain multiple topologies to facilitate rapid prototyping. In order to get system-level power loss and cost models, two processes are implemented. The first process automatically provides minimum power loss or cost estimates and identifies components for specific applications and ratings; the second process estimates power losses and costs of each component of interest as well as the whole system. Two examples are used to illustrate the proposed approaches—boost and buck converters in continuous conduction mode. Achieved cost and loss estimates are over 93% accurate when compared to measured losses and real cost data. This research presents derivations of the proposed models, experimental validation of the models and demonstration of a user friendly interface that integrates all the models. Tools presented in this paper are expected to be very useful for practicing engineers, designers, and researchers, and are flexible and adaptable with changing or new technologies and varying component prices. [ABSTRACT FROM AUTHOR]

This paper presents a combinational-logic-based approach for identifying faults that could occur in the drivetrain of an electric vehicle (EV). A real-time simulation model of an EV is used to study the behavior of available sensor signals and control commands, with specific measured quantities, during vehicle operation. Those quantities could be, but are not limited to, mean values of the phase currents, DC bus current, traction motor speed (if available), in addition to control command quantities. Focus is given to these quantities which are abundant in vehicle inverters and controllers for no added sensing costs. Those quantities carry information of offsets and disturbances that could occur under faulty operating conditions compared to nominal operation, and are thus observed and studied under these conditions. Using such information, a method is developed using simple combinational logic and thresholds to diagnose a fault occurring at any time during a vehicle drive cycle. By combining features of measured quantities that behave similarly irrespective of when the fault occurs during a driving cycle, the proposed method is fault-time-insensitive. The proposed method is presented and validated by real-time simulations to capture over 20 different faults injected at different drive cycle times and in different drivetrain components—electric machine, inverter, transmission, and sensors. Results show that the proposed method is able to robustly and successfully diagnose different faults irrespective of when would they occur. [ABSTRACT FROM AUTHOR]

The aim of this study was to gauge the reasons for accepting or declining influenza vaccine in healthcare staff in Saudi Arabia. A questionnaire was administered to healthcare workers in Saudi Arabia. In all, 633 respondents who provided gender, nationality and profession were included. Reasons for vaccine uptake or refusal were assessed according to profession and educational level. Uptake of vaccine was lower in the period from 2010 to 2014 (3-13.3%) compared to pre-2010 figures (20.7%), rising to 44.1% in 2015. Comparing data for 'never having been vaccinated' to 'being vaccinated in 2015', there was no significant difference in distribution between nurses (9.27% v 38.8%), physicians (13.9% v 56.0%) and laboratory technicians (15.9% v 33.5%) (p= 0.08). The top reason for vaccination was protection of self and family, while the top reason for refusal was not considering the vaccine to be necessary. Education level had no significant effect on the likelihood of being vaccinated. Improvement of healthcare worker vaccination levels in Saudi Arabia might be achieved by addressing staff concerns on vaccine safety and efficacy, emphasizing the potential dangers of influenza and capitalizing on the staff's focus on protecting themselves and their families.

An increasing number of infections due to Elisabethkingia spp. have been observed and reported in recent years. Here we report the microbiological aspects of 13 cases with positive cultures for Elizabethkingia spp. from 1998 to 2017. Elizabethkingia isolates were identified using the Vitek 2 Compact 60 (AES software) Gram-Negative Identification test (GNI) card (bioMerieux. Marcy-l'Etoile, France). The MICs were determined using Vitek 2 and interpreted according to CLSI guidelines based on the interpretive MIC breakpoints for Acinetobacter spp. Vitek 2 susceptibility results were confirmed using the manual E-test and the colistin result was confirmed using the broth dilution method. Twelve cases were observed between 2010 and 2017 with four cases in 2017. Of the 2017 samples, three out of four isolates were obtained outside the intensive care units compared to one out of eight samples between 2010 and 2016. There was variable susceptibility to trimethoprim/sulfamethoxazole (58.3%), ciprofloxacin (41.7%), piperacillin/tazobactam and gentamicin (16.6% each), and all were resistant to colistin. There is a high rate of drug resistance and further studies to identify the source of the infection are needed to build up a profile of Elizabethkingia spp. to inform public health policy in this context.

Studies have shown a correlation between a cleaner patient environment and lower infection rates and reduced risk of transmission. Privacy curtains are potentially important sites of bacterial contamination in hospitals. Privacy curtains integrated with antimicrobial properties have been shown to increase the time to first contamination compared with standard privacy curtains. In this study, we examined the difference in bacterial colonization of different curtains. We experimentally contaminated antibacterial Fantex protective curtains and compared the bacterial counts to natural contamination of privacy curtains. There was a significant reduction in the CFU/cm2 on antibacterial Fantex protective privacy curtains after 24 hours of experimental contamination with Pseudomonas aeruginosa, Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus (MRSA) or extended-spectrum-producing organisms (Escherichia coli or Klebsiella pneumoniae), compared to standard privacy curtains. Levels of environmental contamination with S. epidermis, Streptococcus viridians, E. coli, S. haemolyticus, S. aureus, S. capitis, non-fermenting Gram-negative bacteria, and Bacillus species were also significantly less on the Fantex curtains after two months hanging in the emergency department. Healthcare facilities may find that addressing surfaces, including use of antibacterial privacy curtains, is an effective horizontal strategy for addressing healthcare-associated infections across the board.