Design and Implementation a Single-Switch Step-Up DC-DC Converter Based on Cascaded Boost and Luo Converters

We designed and implemented a single-switch step-up DC-DC converter based on cascaded boost and Luo converters. The proposed converter demonstrated a quadratic voltage gain and a high efficiency, which makes it suitable for renewable energy applications, where a high voltage gain ratio is desired without imposing a high number of bulky items or employing a high duty cycle of the active switches. This converter benefits from the continuity of the input current waveform, which equips the maximum utilisation of renewable energy sources. While a transformer-less high voltage-gain was achieved, the voltage and current stresses of the power switch and diodes were kept low in comparison with the existing quadratic DC-DC converters. We analysed the converter in both continuous and discontinuous conduction modes. A non-ideal model of components was considered for power loss and efficiency calculations and comparisons. Finally, the simulation results were extracted with PLECS and validated with experiments on a 120 W prototype.

Extreme duty cycles in the acoustic signals of tiger moths: Sexual and natural selection operating in parallel

Sound production in tiger moths (Erebidae: Arctiinae) plays a role in natural selection. Some species use tymbal sounds as jamming signals avoiding bat predation. High duty cycle signals have the greatest efficacy in this regard. Tiger moth sounds can also be used for intraspecific communication. Little is known about the role of sound in the mating behavior of jamming species or the signal preferences underlying mate choice. We recorded sound production during the courtship of two high duty cycle arctiines, Bertholdia trigona and Carales arizonensis. We characterized variation in their acoustic signals, measured female preference for male signals that vary in duty cycle, and performed female choice experiments to determine the effect of male duty cycle on the acceptance of male mates. Although both species produced sound during courtship, the role of acoustic communication appears different between the species. Bertholdia trigona was acoustically active in all intraspecific interactions. Females preferred and ultimately mated with males that produced higher duty cycles. Muted males were never chosen. In C. arizonensis however, sound emissions were limited during courtship and in some successful matings no sound was detected. Muted and clicking males were equally successful in female mate-choice experiments, indicating that acoustic communication is not essential for mating in C. arizonensis. Our results suggest that in B. trigona natural and sexual selection may work in parallel, to favor higher duty cycle clicking.

BURNING MODES OF A BIPOLAR PULSED DISCHARGE IN CO2

We have studied the burning modes of the bipolar pulsed discharge in CO2 within the frequency range between 20 and 300 kHz and the duty cycle of 11...97 %. The current and voltage waveforms within the pressure range between 0.1 to 1 Torr were registered. We have established that the duty cycle values may affect the axial structure of the discharge considerably causing the voltage drop redistribution across the electrodes. The bipolar pulsed discharge may burn in a high-current mode (with cathode sheaths near every electrode) as well as in a low-current one (with a low discharge current and weak glow). The transition between these modes may be observed at high duty cycle values. We have found that one may make a shift of the complete oscilloscope voltage pattern higher or lower along the voltage axis and produce a self-bias constant voltage the value and sign of which depend on the duty cycle, amplitude and frequency of the applied voltage.

The Pump-Leak/Donnan ion homeostasis strategies of skeletal muscle fibers and neurons

ABSTRACTSkeletal muscle fibers (SMFs) and neurons are low and high duty-cycle excitable cells constituting exceptionally large and extraordinarily small fractions of vertebrate bodies. The immense ClC-1-based chloride-permeability (PCl) of SMFs has thwarted understanding of their Pump-Leak/Donnan (P-L/D) ion homeostasis. After formally defining P-L/D set-points and feedbacks, we therefore devise a simple yet demonstrably realistic model for SMFs. Hyper-stimulated, it approximates rodent fibers’ ouabain-sensitive ATP-consumption. Size-matched neuron-model/SMF-model comparisons reveal steady-states occupying two ends of an energetics/resilience P-L/D continuum. Excitable neurons’ costly vulnerable process is Pump-Leak dominated. Electrically-reluctant SMFs’ robust low-cost process is Donnan dominated: collaboratively, Donnan effectors and [big PCl] stabilize Vrest, while SMFs’ exquisitely small PNa minimizes ATP-consumption, thus maximizing resilience. “Classic” excitable cell homeostasis ([small PCl][big INaleak]), de rigueur for electrically-agile neurons, is untenable for vertebrates’ (including humans’) major tissue. Vertebrate bodies evolved thanks to syncytially-efficient SMFs using a Donnan dominated ([big PCl][small INaleak]) ion homeostatic strategy.

Robust asteroseismic properties of the bright planet host HD 38529

ABSTRACT The Transiting Exoplanet Survey Satellite (TESS) is recording short-cadence, high duty-cycle timeseries across most of the sky, which presents the opportunity to detect and study oscillations in interesting stars, in particular planet hosts. We have detected and analysed solar-like oscillations in the bright G4 subgiant HD 38529, which hosts an inner, roughly Jupiter-mass planet on a $14.3\, \mathrm{d}$ orbit and an outer, low-mass brown dwarf on a $2136\, \mathrm{d}$ orbit. We combine results from multiple stellar modelling teams to produce robust asteroseismic estimates of the star’s properties, including its mass $M=1.48\pm 0.04\, \mathrm{M}_\odot {}$, radius $R=2.68\pm 0.03\, \mathrm{R}_\odot {}$, and age $t=3.07\pm 0.39\, \mathrm{Gyr}{}$. Our results confirm that HD 38529 has a mass near the higher end of the range that can be found in the literature and also demonstrate that precise stellar properties can be measured given shorter timeseries than produced by CoRoT, Kepler, or K2.

Special features of radio pulse spectral density analysis

The spectrum analysis of the periodic sequence radio pulses is often described in textbooks. However, if this method is applied to short radio pulses with a large period between them, then large errors occur. In this article, we described a new method of pulse gating. This method allows us to measure the spectral density of radio signals with high duty cycle. The main advantages of our method are a high signal-to-noise ratio, a large dynamic range of measurements, and a higher accuracy of spectral density measurements.