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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16

High-Power Polyphase PCB-Type Inductive Coupler for Wireless Electric Vehicle Charging

The cost and manufacturing difficulty of traditionally wound coils for wireless charging of electric vehicles has led to the exploration of alternative manufacturing for scalable deployment at a range of rated powers. A rotating-field polyphase wireless coupler is developed with balanced fully pitched coils which are not possible with conventional Litz wire. The usage of printed circuit board (PCB) technology is proposed for the innovative construction at large dimensions due to reduced cost, increased ease of manufacturability, and potential geometric customization compared to would coils. Design considerations specific to PCBs are detailed for wireless power transfer coils including advantages such as the potential for many turns and transposition with planar interconnections. A design procedure is developed which may be used to investigate the frequency to power to dimension correlation and limits associated with PCB coils. Designs are simulated in 3D electromagnetic finite element analysis (FEA) for the polyphase coil to evaluate the coupling between coils with varying geometric parameters at 100mm and 500mm outer diameters. A discussion is included on methods to increase PCB power ratings through a mixture of layer stacking, connections, and material selection.

Lewis, Donovin D.↗

Phase Shift Control of a Three-Phase Inverter for Balanced Secondary Currents in Misaligned Three-Phase Inductive Power Transfer Systems

This paper presents a strategy for generating fundamental reference voltage commands for a double-sided LCC tuned three-phase wireless power transfer (WPT) system to achieve balanced output currents when the receiver and transmitter are not perfectly aligned. Formulas for translating the normalized fundamental current commands into phase-shift commands for two of the phase legs in a two-level three-phase inverter are derived. The methodology is validated through circuit simulations performed using coupler models derived from finite-element simulations. Simulation results for a 1.5 k W system design are included, which indicate near perfect correction of imbalance in the secondary currents for a typical misalignment case.

Pries, Jason↗

Local carbon reserves are insufficient for phloem terpene induction during drought in Pinus edulis in response to bark beetle–associated fungi

Stomatal closure during drought inhibits carbon uptake and may reduce a tree's defensive capacity. Limited carbon availability during drought may increase a tree's mortality risk, particularly if drought constrains trees' capacity to rapidly produce defenses during biotic attack. We parameterized a new model of conifer defense using physiological data on carbon reserves and chemical defenses before and after a simulated bark beetle attack in mature Pinus edulis under experimental drought. Attack was simulated using inoculations with a consistent bluestain fungus (Ophiostoma sp.) of Ips confusus, the main bark beetle colonizing this tree, to induce a defensive response. Trees with more carbon reserves produced more defenses but measured phloem carbon reserves only accounted for c. 23% of the induced defensive response. Our model predicted universal mortality if local reserves alone supported defense production, suggesting substantial remobilization and transport of stored resin or carbon reserves to the inoculation site. Our results show that de novo terpene synthesis represents only a fraction of the total measured phloem terpenes in P. edulis following fungal inoculation. Without direct attribution of phloem terpene concentrations to available carbon, many studies may be overestimating the scale and importance of de novo terpene synthesis in a tree's induced defense response.

59 BASIC BIOLOGICAL SCIENCES↗

In situ amplification of spin echoes within a kinetic inductance parametric amplifier

The use of superconducting microresonators together with quantum-limited Josephson parametric amplifiers has enhanced the sensitivity of pulsed electron spin resonance (ESR) measurements by more than four orders of magnitude. So far, the microwave resonators and amplifiers have been designed as separate components due to the incompatibility of Josephson junction–based devices with magnetic fields. This has produced complex spectrometers and raised technical barriers toward adoption of the technique. Here, we circumvent this issue by coupling an ensemble of spins directly to a weakly nonlinear and magnetic field–resilient superconducting microwave resonator. We perform pulsed ESR measurements with a 1-pL mode volume containing 6 × 10 7 spins and amplify the resulting signals within the device. When considering only those spins that contribute to the detected signals, we find a sensitivity of 2.8 x 10 3 spins / $\sqrt{Hz}$ for a Hahn echo sequence at a temperature of 400 mK. In situ amplification is demonstrated at fields up to 254 mT, highlighting the technique’s potential for application under conventional ESR operating conditions.

42 ENGINEERING↗