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Background Cefazolin (CZ) is a 1st-line therapy for methicillin-susceptible Staphylococcus aureus (MSSA) infections due to its tolerability, lower toxicity, and convenient dosing. However, some strains exhibit reduced susceptibility to CZ when present in high inoculum. Treatment failure and worsened outcomes are documented in BSI cohorts treated with CZ when infections are caused by strains demonstrating this inoculum effect (IE) (Miller, 2018). The objective of our study was to investigate the incidence of MSSA strains demonstrating IE over time across a general population, free of referral bias. Methods All initial isolates of first episodes of MSSA BSI from persons in Calgary, Canada were analyzed during 2012-14 and 2019. CZ minimum inhibitory concentration (MIC) was determined at standard (SI: 5x105 CFU/mL) and high inocula (HI: 5x107 CFU/mL) using the broth microdilution method at 24 hours as per 2009 CLSI criteria. Isolates were defined as having the CZ IE if they had a ≥ 4-fold difference between MIC at SI and HI. Isolates were defined as having a pronounced IE (pIE), if they were susceptible at SI but resistant at HI with an MIC ≥ 32µg/mL. Population density of Calgary was obtained from census data. Annual incidence rates (IR) were calculated by dividing the number of IE and pIE by the mid-year population data, and IR ratios (IRR) were calculated for IE and pIE by comparing 2019 to 2012 rates. Results During the years of study, 1040 individuals experienced at least one episode of MSSA BSI. The mean incidence rates of IE and pIE were 6.50 and 0.98 per 100,000 person-years, respectively. Comparing 2019 to 2012, rates of IE decreased significantly with an IRR of 0.67 (95% CI 0.47 – 0.95) but rates of pIE were not significantly different (IRR 1.24; 95% CI 0.43 – 3.86). Incidence rates of IE and pIE in Calgary, Canada in 2012-14 and 2019. MSSA BSIs in Calgary, Canada over the years are shown alongside corresponding rates of IE and pIE. The population density was used to find rates for IE/pIE per 100,000 person-years. Conclusion Population-based studies on MSSA BSI with the IE and pIE phenotype are lacking. Herein, we observed that while the incidence of MSSA with pIE has not changed, those occurring with the IE have decreased. Further studies on the clinical implications of pIE are needed. Disclosures All Authors: No reported disclosures.

In this article, a hybrid high voltage gain converter module for medium voltage dc conversion in wind energy systems is proposed. The converter consists of step-up resonant circuit with coupled voltage-quadruplers to achieve the step-up voltage conversion function. The coupled voltage-quadrupler modules are connected to the resonant circuit via a 1:1:1 high frequency transformer. As a result, high turns ratio transformers are not required in the proposed design while at the same time, the output voltage of each voltage-quadrupler is well balanced due to the shared coupled-inductor. All the primary side silicon carbide (SiC) MOSFETs and secondary side SiC diodes exhibit zero switching losses. The output voltage of the converter module is controlled with variable frequency control. Simulation results on a 4 MW modular design of SiC-based converter system with 3.3 kV/18 kV, 670 kW per module, and experimental results on a laboratory-scale prototype with per-module rating: 500 V/2.7 kV, 3.7 kW are provided to validate the theoretical analysis and to highlight the merits of the proposed work. Results confirmed that a peak efficiency of close to 99% is achieved in both simulation and experimental works.

In this article, a novel power factor correction, soft-switched, bridgeless ac–dc converter is presented for step-up voltage conversion in medium voltage dc grid applications. To reduce the number of conversion stages, the proposed bridgeless boost rectifier is integrated with isolated high-frequency step-up resonant converter with voltage multiplier modules to form a single-stage ac–dc step-up converter. Almost sinusoidal input currents with near unity power factor are achieved at the three-phase ac input side, while at the same time, the converter achieves a very high voltage gain at the output. The proposed converter is able to reduce the number of lossy diodes required for the front-end rectifier, and to achieve soft switching for all the Silicon Carbide (SiC) mosfet s and SiC diodes, thus enhancing the converter efficiency. Simulation results on a 100-kW, 1-kVac/15-kVdc design, and experimental results on a laboratory scale proof-of-concept 2-kW, 250-Vac/4-kVdc medium voltage prototype are presented to verify with the proposed converter's performance.

In conventional photovoltaic (PV)-battery systems, a centralized battery storage system (BSS) is typically connected through a separate bidirectional converter at the common dc link to support the PV system. It is known that a bidirectional converter typically requires more switches than a unidirectional converter, and hence, a complete PV-battery power interface will result in a high-cost system and will suffer high power losses. This paper proposed an integrated battery storage interface with soft-switching capability for module-integrated PV systems. In the proposed system, a multi-input converter (MIC) structure that consists of an integrated soft-switched quasi-resonant (QR) Cuk- and flyback-based circuit is presented. In this approach, the battery charging circuit is integrated with the input side of the PV power optimizer while the battery discharging circuit of the proposed system shares the output filter of the PV power optimizer, resulting in a compact and efficient system. The proposed converter is capable of tracking the maximum power point (MPP) and following the charging profile (constant voltage and constant current) of the battery. Moreover, all the switches in the proposed converter are able to achieve soft-switched turn on and turn off for different operating conditions. The operating principles and the theoretical analysis of the proposed system are presented. Experimental results on a 175-W proof-of-concept prototype are presented to demonstrate the features of the proposed converter.

A new soft-switched, single-switch electrolytic capacitor-less step-up dc/dc microconverter for photovoltaic applications is presented in this article. The proposed circuit is an improved coupled-magnetics based single-switch topology that has low-voltage stress across the switch compared to the high voltage dc bus level (380–400 V). The proposed circuit is able to achieve zero voltage switching turn- on and zero current switching turn- off for the switch. Since the input inductor in the proposed circuit operates in continuous conduction mode, the required input filter capacitance is reduced and hence, allows for the small-size nonelectrolytic capacitor to be used. The main advantage of the proposed circuit is that it is able to achieve high voltage gain while the ratio between the peak switch voltage and the output dc-bus voltage is reduced compared to other coupled-inductor based topologies. In addition, the proposed converter is able to achieve maximum power point tracking through variable switching frequency control. Results are provided on a 40-V/380-V, 200-W system to highlight the merits of the proposed circuit.

In this article, a new bidirectional dc/dc converter topology based on a hybrid string-inverter/rectifier structure with an isolated CLLC resonant circuit is presented for energy storage applications. In this topology, a novel inverter/rectifier leg is presented that enables this circuit to operate in rectifying mode with much lower voltage ripple compared to the standard four-switch string rectifier circuit with the same capacitive filter. Compared to the dual-active-bridge circuit structure, the proposed inverter/rectifier leg is able to reduce the number of high-voltage switches required. A CLLC resonant circuit is employed to step-up/down the dc voltage levels. The operating principles of the proposed converter are discussed in this article. Silicon Carbide switches are used in both legs of the proposed converter, with zero-voltage switching turn- on and zero-current switching (ZCS) turn- off realized for all switches, whereas ZCS turn- on and off are achieved for all diodes. Simulation and experimental results are provided on a 1-kW, 100-kHz, 400-V/700-V converter system to highlight the merits of the proposed converter. Experimental results demonstrated that an efficiency of close to 97% is achieved in the proposed converter in both boost mode and buck mode at the full-load condition.

Im Gegensatz zu in der Strawinsky-Literatur gelaufigen Ansichten zur Bedeutung von Oktatonik fur Strawinskys Werk kann dessen ›Leitharmonie‹ als ein verschlungenes pentatonisches Netzwerk verstanden werden: Das diesem zugrundeliegende melodische Pattern – kleine Terz, Ganzton – ist aus der anhemitonischen pentatonischen Skala ableitbar, welche Strawinsky in einem Brief von 1913 als ›pseudo-chinesische Skala‹ bezeichnet hatte. Im Unterschied zu gangigen oktatonischen Interpretationen hebt mein Zugang die ›Pentatonisierung‹ des chromatischen Tonraums hervor und beleuchtet zwei Beispiele dieses verschleierten ›Pentatonizismus‹, die der zweiten Kompositionsphase der Oper Le Rossignol (1913–14) vorangehen: erstens eine Leitharmonie-Skizze zur Einleitung des ersten Akts (1908–09), wo orthographische und modale Eigenheiten die Gegenwart der ›pseudo-chinesischen Skala‹ maskieren; zweitens einige Stellen in L’Oiseau de feu (1909), wo dieselbe Skala wiederum durch eine vertikale Uberlagerung pentatonischer Ketten mit Kleinterz-Ganzton-Zellen verschleiert ist. Eine Charakterisierung dieser bislang kaum untersuchten Techniken verlangt es, der Schlusselrolle der pentatonischen Skala in den zwei besprochenen (wie auch moglicherweise in anderen zwischen 1908 und 1914 entstandenen) Werken Aufmerksamkeit zuzuwenden. ›Pentatonizismus‹ – eine oft vernachlassigte Facette von Strawinskys Kompositionspraxis um 1910 – kann sowohl auf den Einfluss einer modernen Pariser als auch der traditionellen chinesischen Klanglichkeit zuruckgefuhrt werden; er manifestiert sich in der ›Leitharmonie‹ und durchdringt Strawinskys Musik auch jenseits von Chinoiserien in der Oper. The present study offers an alternative understanding of Stravinsky’s ›Leitharmonie‹ that reads it as an intricate pentatonic network instead of octatonicism. The underlying melodic pattern – minor third with whole tone – is derivable from the anhemitonic pentatonic scale, which Stravinsky referred to in a letter from 1913 as the ›pseudo-Chinese scale‹. Contrary to existing octatonic interpretations, my approach highlights the ›pentatonicisation‹ of the chromatic pitch space and illuminates two instances of this disguised pentatonicism that precedes the second composition phase of the opera, Le Rossignol (1913–14): firstly, a ›Leitharmonie‹ sketch for the Introduction to Act I (1908–1909), where orthographical and modal idiosyncrasies mask the presence of the ›pseudo-Chinese scale‹; secondly, several passages in L’Oiseau de feu (1909), where the same scale is again veiled through vertical superimposition of pentatonic chains with minor-third-major-second cells. A characterisation of these little-examined techniques calls for critical attention to the key roles of the pentatonic scale in the two discussed works (and potentially others created between 1908 and 1914). Pentatonicism – an oft-neglected facet of Stravinsky’s compositional practice around 1910 – can be traced back to the influence of modern Parisian as well as traditional Chinese sonorities; it manifests in ›Leitharmonie‹ and penetrates Stravinsky’s music beyond the chinoiseries in the opera.

This paper presents a converter that takes an AC input and provides both of the voltages required to power a magnetron. By utilizing a bridgeless PFC stage at the input that utilizes a DCM operated inductor, the converter is able to achieve high PF of 0.99 and reduced input rectifier conduction losses as well as sharing the switches of the PFC stage with those of a resonant converter. The converter utilizes a step-up parallel CL resonant circuit with voltage doubler output to achieve a high voltage for the anode-cathode connection, and an LLC resonant circuit to provide the step-down for the low voltage filament connection. The circuit is then verified through PSIM with a 1.55 kW typical power magnetron with a peak of 1.8 kW power.

Failures in bidirectional power converters can be critical and challenging especially in the energy storage applications due to their nature and high replacement costs. This paper presents a modified topology based on the 6-switch hybrid string converter. In the modified structure, the diodes have been replaced by the active switches to add switching redundancy and to provide open circuit fault-tolerant control while improving the efficiency by means of synchronous rectification. As a result, post fault operation at full power can be performed preventing the power to be interrupted in case of any OCF incidents. The processor-in-the-loop (PIL) test results have been provided on a 1 kW 400VDC/700VDC converter to demonstrate the performance of the proposed converter along with the fault-tolerant control. A 1kW 400VDC/700VDC prototype has been designed to verify the feasibility of the proposed concept.

a new single-stage fully soft-switched bidirectional resonant AC/DC converter is proposed for hybrid micro-grid application. The proposed AC/DC converter is capable of achieving ZVS turn-on for all of the switches with simple modulation scheme. Galvanic isolation is provided by connecting a front-end half-bridge LLC resonant converter to AC link. Two switch pairs are controlled with sinusoidal PWM and they are connected to an output LC-type filter on the secondary side of the high frequency AC link, to provide the required sinusoidal AC side current. An active ripple energy storage is used on the DC side in order to eliminate bulky DC link capacitor. Power factor correction and low voltage ripple are achieved with implanted closed loop control algorithms. Results are provided on 1.5kW system, with a switching frequency of 103 kHz to validate the performance of the proposed AC/DC converter.

This paper presents a novel single-stage single-phase onboard charger that consists of interleaved bridgeless boost converter modules integrated with isolated LLC resonant converters with semi-active voltage doubler rectifiers. The proposed bridgeless boost modules operate in discontinuous conduction mode (DCM); hence, the input current waveform follows the sinusoidal voltage waveform that eliminates the need for a current control loop. In addition, the interleaved approach results in low input current ripple that minimize the size of input filter. The proposed converter integrates the front-end rectifier with the isolated LLC converter by employing stacked SiC switches. This reduces the number of semiconductor devices, while soft-switching commutation can be achieved for all semiconductor devices. Experimental results are given on a 85~240Vac/800Vdc charging system to highlight the merits of the proposed converter.

Although compact fluorescent lamps (CFLs) have been in the market for a long time, many of them do not achieve the same power factor as the incandescent lamps do, which appears to be a significant problem for the utility with the current widespread use of CFLs for household lightings. A single-stage single-switch electronic ballast with active power factor correction is presented in this study for CFL applications. Unlike other single-switch ballast circuits, the presented integrated dual-boost converter circuit can produce a symmetric bipolar square-wave voltage, thus generating a near-pure high-frequency sinusoidal voltage on the lamp, which is beneficial to the CFL lifetime. Moreover, its soft-switching variant can achieve the ZVZC turn-on and ZV turn-off for the MOSFET to improve the conversion efficiency. Detailed operating principles and circuit analysis of the proposed circuit have been provided in this study. Simulation and experimental results on a prototype of a 15 W CFL validate the theoretical analysis and highlight the merits of the presented work.

In this paper, a new step-up dc–dc converter module that consists of three resonant submodules interconnecting with 1:1 turns ratio three-phase transformer and coupled current-fed voltage doubler modules is presented for medium voltage dc converter design in wind energy application. By utilizing step-up resonant circuits with three-phase transformer and combining it with a “multistring” inverter, the proposed circuit structure completely utilizes all the switching circuits to transfer power to the output. In addition, the proposed topology is able to achieve high voltage gain without using large turns ratio high frequency step-up transformers. Zero voltage switching turn- on and near zero current switching (ZCS) turn- off are maintained for all the switches. A modular 1.5 MW, 1 kV (dc-link), 20 kV (output) converter system is presented to validate the performance of the proposed circuit. Experimental results on a laboratory-scale 2.8 kW, 0.3 kV (dc-link), 6 kV (output), prototype are provided to highlight the merits of this work. Silicon Carbide (SiC) MOSFETs and SiC Schottky diodes are utilized in both designs. Results confirm that a peak efficiency of 97.6% is achieved in the prototype.

In this paper, a fully soft-switched silicon carbide (SiC)-based modular step-up resonant converter with magnetically integrated zero current switching voltage doublers is proposed for medium-voltage (MV) dc conversion in wind energy systems. Conventional step-up resonant dc/dc converters employ either high turns-ratio step-up transformer or step-up resonant circuits to achieve step-up voltage conversion. As a result, they require either complicated expensive transformer structure due to high-voltage electrical isolation requirement or highly voltage-gain sensitive step-up resonant circuits, which are not ideal for designing MV converters for wind energy application. In order to solve the aforementioned drawbacks, the proposed converter configuration utilizes both modular step-up resonant circuits and magnetically integrated voltage doublers to achieve the step-up voltage conversion function. The output voltage of each module of the dc/dc step-up converter is regulated through variable frequency control, whereas asymmetrical pulsewidth modulation (APWM) control is utilized to balance all the resonant currents in all the resonant circuit modules in each converter module. Since APWM control is used, a simple passive auxiliary circuit is included in each converter module to extend soft-switching operation over a wide range of operating conditions. Simulation results on a 1-kV/28-kV, 5-MW converter system with commercial 1.2-kV SiC MOSFET modules and experimental results on a laboratory-scale 300-V/4.8-kV, 5.6-kW proof-of-concept prototype with commercial SiC MOSFET and SiC Schottky diodes are provided to validate the theoretical analysis and to highlight the merits of the proposed work.

A new single-stage fully soft-switched resonant grid-connected inverter is proposed in this paper. The proposed inverter is able to provide ZVS turn-on for all the switches without requiring complex switching modulation or using additional passive auxiliary circuits. A front-end half-bridge LLC resonant inverter is connected to a high frequency AC link, where galvanic isolation is provided. On the secondary side of the high frequency AC link, two switch pairs are controlled with sinusoidal PWM and they are connected to an output LC-type filter to provide the required sinusoidal grid side current. The operating stages of the proposed circuit and the circuit’s characteristics are discussed. A closed loop control algorithm based on a proportional resonant and a harmonic compensator controller is implemented so that the output grid current is synchronized with the grid voltage and can achieve very low THD. Results are provided on 1.5kW system, an input voltage range of 200–300V and an AC output voltage of 120Vac,rms with a switching frequency of 103 kHz to validate the performance of the proposed inverter.

A MHz DC/DC micro converter with extended zero voltage switching turn-on and step-up voltage capability for PV energy applications is presented. The proposed converter consists of a boost converter integrated with a CL parallel resonant converter. An auxiliary circuit is employed to achieve soft-switching operation at all conditions, and its inductor is coupled with the boost inductor to reduce the size and weight of the overall system. This in turn, allows for duty cycle based maximum power extraction control to be applied to the boost switch. The operating frequency of the converter’s switches are on the order of mega-hertz to further decrease the size and cost of passive components. Theoretical analysis and the operating principles of the proposed converter is provided. Simulation results on a 1.06MHz, 200W and 380V-output converter are presented to highlight the merits of the proposed topology. Experimental results are provided on a proof of concept prototype to highlight the features of the circuit.

This paper presents a new step up LLC resonant converter with re-structural feature that employs a novel pulse-width modulated (PWM) voltage multiplier. The proposed converter consists of a reconfigurable full-bridge to half-bridge inverter with fixed switching frequency at the input-side and a new PWM-controlled voltage multiplier rectifier at the output side. Wide voltage gain for different loading condition can be realized by adaptively changing the configuration at the input and controlling the duty ratio of the voltage multiplier in the output, with constant switching frequency. As a result, the circulating energy, and hence, the conduction losses of the LLC resonant tank are reduced. Zero voltage switching for all silicon carbide (SiC) switches and zero current switching for all the diodes are achieved for a wide range of voltage gain and loading conditions. Simulation and experimental results are provided on a laboratory scale 5kV, 4kW proof of concept prototype.

Prior studies have highlighted the importance of General Education (GE) in reinvigorating higher education. In spite of the significant contribution of GE, students’ engagement in the course is also frequently negative. Formative e-assessment (FEA) is supposed to enhance undergraduates’ learning engagement due to the nature of formative assessment and the relative affordability of technology. An FEA intervention was included in GE foundation course tutorials which used Kahoot!, Mentimeter, and Google+. This study adopted a quasi-experimental design to demonstrate the effectiveness of FEA intervention on student tutorial engagement. At the end of one-term tutorial, two experimental groups and one control group completed a survey on course engagement, and eight students from experimental groups attended two focus group interviews. The findings reveal that students in experimental groups were more engaged than those in the control group although the difference was not significant. Kahoot! was perceived the most useful to engage students, and Google+ was believed the least effective to engage students due to their unfamiliarity with it, examination-oriented learning attitudes, low course learning motivation, and time constraints.

Two asymmetrical embedded switched-inductor Z-source inverters (AESL-ZSI) are introduced in this paper. It divides proposed Inverters into two types; ripple input current asymmetrical embedded switched-inductor Z-source inverter (rAESL-ZSI) and continuous input current asymmetrical embedded switched-inductor Z-source inverter (cAESL-ZSI). In both topologies, insert two DC voltage sources into impedance network to attain smooth current across the sources using no further passive filter, which reduces complications of resonant considerations in the proposed system. Proposed topologies provide higher voltage gain with a lower number of components compared to similar previous works that reduce the cost and size of the inverters. In comparison with conventional switched-inductor ZSI, presented AESL-ZSI can suppress start-up inrush current that prevents damage to the devices. As a result, high voltage boost ability, continuous input current with no inrush current and embedded DC sources make the proposed inverters appropriate for renewable energy resources such as PV and fuel cells. Also, embedded DC-sources give flexible control features to the proposed inverters to attain the required output voltage. Simulation results validate the working principle and theoretical analysis of the proposed inverters.

The voltage output at the terminals of a DC generating source such as Photovoltaic and Fuel cells is not enough to be integrated with the DC bus of a microgrid. Therefore, an efficient DC-DC converter is demanded for boosting the voltage. The available conventional converter needs to be operated at an extremely large duty ratio resulting in various detrimental effects on the converter circuit. Impaired transient response, increased EMI and voltage spikes are observed as a consequence of large duty ratio. High gain DC/DC converters are thus sought which must be attaining sufficiently high voltage on moderate duty ratio. This paper presents a novel converter utilizing two switches and switch inductors to come across the voltage suitable for integration of a renewable energy source into a DC microgrid. This particular converter does not uses transformers, coupled inductors, or some cascaded configurations. Moreover, the switches being controlled simultaneously do not need a complex control circuitry. The analysis of the introduced converter is done in CCM and DCM along with the boundary conditions. The performance is verified through simulation and experimental results.

This paper proposes a new structure of high gain DC-DC converter named as "Double Duty Converter (DDC)" with voltage boosting module and showing the wide voltage gain control. The proposed converter is operated with three switches which are controlled by two different duty pulses. Therefore, the voltage gain of the proposed converter depends on the two pulses which allow the converter to operate with high voltage gain at a low duty ratio. The key features of the proposed configurations are: i) three switches are controlled by two different duty cycles for wide voltage control, ii) continuous input current, iii) lower voltage stress on the switch, and iv) high voltage gain. Mathematical analysis, operational modes of the proposed converters and effect of the Effective Series Resistance (ESR) of inductors and diodes on voltage gain are presented in detail. Finally, the proposed converter configuration is validated using detailed simulation studies.

A new dc-dc LLC resonant converter with four configurable modes of operation is proposed in this paper. The proposed converter employs a reconfigurable full-bridge to asymmetrical half-bridge at the input-side and reconfigurable voltage doubler to voltage quadrupler rectifier at the output side, using only one low profile switch. The input voltage range is widely extended within a limited frequency range by changing the configurations and using a hybrid control technique. Reduced circulating current, and conduction losses of the LLC resonant tank as well as zero voltage switching for all silicon carbide (SiC) switches and zero current switching for all the diodes results in a high efficiency for a wide range of voltage gain and loading conditions in the proposed converter. The operation principles are analyzed and a proof of concept prototype with 300-700V input voltage and 6.6kV output voltage is built and tested to evaluate the feasibility of the proposed method.