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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Photo-Switching of Protein Dynamical Collectivity

We examine changes in the picosecond structural dynamics with irreversible photobleaching of red fluorescent proteins (RFP) mCherry, mOrange2 and TagRFP-T. Measurements of the protein dynamical transition using terahertz time-domain spectroscopy show in all cases an increase in the turn-on temperature in the bleached state. The result is surprising given that there is little change in the protein surface, and thus, the solvent dynamics held responsible for the transition should not change. A spectral analysis of the measurements guided by quasiharmonic calculations of the protein absorbance reveals that indeed the solvent dynamical turn-on temperature is independent of the thermal stability/photostate however the protein dynamical turn-on temperature shifts to higher temperatures. This is the first demonstration of switching the protein dynamical turn-on temperature with protein functional state. The observed shift in protein dynamical turn-on temperature relative to the solvent indicates an increase in the required mobile waters necessary for the protein picosecond motions, that is, these motions are more collective. Melting-point measurements reveal that the photobleached state is more thermally stable, and structural analysis of related RFP’s shows that there is an increase in internal water channels as well as a more uniform atomic root mean squared displacement. These observations are consistent with previous suggestions that water channels form with extended light excitation providing O2 access to the chromophore and subsequent fluorescence loss. We report that these same channels increase internal coupling enhancing thermal stability and collectivity of the picosecond protein motions. The terahertz spectroscopic characterization of the protein and solvent dynamical onsets can be applied generally to measure changes in collectivity of protein motions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Smart and Efficient Building Envelopes: Thermal Switches and Thermal Storage for Energy Savings and Load Flexibility

The building envelope has traditionally been seen as a static component. Much of the past thermal advancements in building envelopes has consisted of developing higher R/inch insulation. While a suitable approach for static situations, it does not consider the dynamic nature of the ambient environment or the varying needs of the electrical grid. This paper will examine three possible ways that building envelopes can be actively managed: 1. thermal switches, 2. thermal storage, and 3. the coupling of the two. Spurring innovation to make building envelopes smarter will help reduce building energy consumption and peak energy usage and contribute to flexibility in energy demand in the future.

Mumme, Sven↗
DOE OSTI2020

Monolithically-integrated AC switch having JBSFETs therein with commonly-connected drain and cathode electrodes

A monolithically-integrated AC switch includes a semiconductor substrate having first and second insulated-gate field effect transistors therein, which contain first and second spaced-apart and independently-controllable source terminals extending adjacent a first surface of the semiconductor substrate, yet share a common drain electrode extending adjacent a second surface of the semiconductor substrate. According to some of these embodiments of the invention, the first and second insulated-gate field effect transistors include respective first and second independently-controllable gate electrodes, which extend adjacent the first surface. The first and second insulated-gate field effect transistors may be configured as first and second vertical power MOSFETs, respectively. The semiconductor substrate may also include at least one edge termination region therein, which extends between the first and second vertical power MOSFETs.

42 ENGINEERING↗
DOE OSTI2021

GaN-based threshold switching device and memory diode

A switching device including a GaN substrate; an unintentionally doped GaN layer on a first surface of the GaN substrate; a regrown unintentionally doped GaN layer on the unintentionally doped GaN layer; a regrowth interface between the unintentionally doped GaN layer and the regrown unintentionally doped GaN layer; a p-GaN layer on the regrown unintentionally doped GaN layer; a first electrode on the p-GaN layer; and a second electrode on a second surface of the GaN substrate.

Fu, Kai↗
DOE OSTI2021

Efficient IGBT switching

Embodiments of the invention provide IGBT circuit modules with increased efficiencies. These efficiencies can be realized in a number of ways. In some embodiments, the gate resistance and/or voltage can be minimized. In some embodiments, the IGBT circuit module can be switched using an isolated receiver such as a fiber optic receiver. In some embodiments, a single driver can drive a single IGBT. And in some embodiments, a current bypass circuit can be included. Various other embodiments of the invention are disclosed.

Ziemba, Timothy↗
DOE OSTI2022

Ultrafast optical switches using quantum wells

Colloidal quantum wells have discrete energy states and electrons in the quantum wells undergo interband and intersubband state transitions. The transmissivity of a colloidal quantum well may be tuned by actively controlling the states of the colloidal quantum wells enabling ultrafast optical switching. A primary excitation source is configured to provide a primary excitation to promote a colloidal quantum well from a ground state to a first excitation state. A secondary excitation source is configured to provide a secondary excitation to the colloidal quantum well to promote the colloidal quantum well from the first excitation state to the second excitation state with the first and second excitation states being subbands in the conduction band of the colloidal quantum well.

Diroll, Benjamin↗
DOE OSTI2022

Wide bandgap optical switch circuit breaker

A high-voltage switch is adapted for use as a medium-voltage direct current circuit breaker, which provides a low-cost, small-footprint device to mitigate system faults. In one example, a method for operating a wideband optical device includes illuminating the wide bandgap optical device with a light within a first range of wavelengths and a first average intensity, allowing a current to propagate therethrough without substantial absorption of the current, illuminating the wide bandgap optical device with light within the first range of wavelengths and a second average intensity that is lower than the first average intensity to allow a sustained current flow though the wide bandgap optical device, and illuminating the wide bandgap optical device with light within a second range of wavelengths to stop or substantially restrict propagation of the current through the wide gap material.

Voss, Lars F.↗
DOE OSTI2022

GaN-based threshold switching device and memory diode

A switching device including a GaN substrate; an unintentionally doped GaN layer on a first surface of the GaN substrate; a regrown unintentionally doped GaN layer on the unintentionally doped GaN layer; a regrowth interface between the unintentionally doped GaN layer and the regrown unintentionally doped GaN layer; a p-GaN layer on the regrown unintentionally doped GaN layer; a first electrode on the p-GaN layer; and a second electrode on a second surface of the GaN substrate.

Fu, Kai↗
DOE OSTI2023

High voltage switch with cascaded transistor topology

A switching apparatus includes three or more series-connected transistors, and it further includes a balancing network. The balancing network includes a resistor network configured to divide a voltage from a voltage source across the series-connected transistors. The resistor network includes at least two resistive legs connected in parallel. In each resistive leg, two or more resistors are connected in series. The balancing network may further comprise at least one capacitive leg of series-connected capacitors connected across the series-connected transistors, and it may further comprise at least one leg of series-connected avalanche diodes connected across the series-connected transistors for overvoltage protection. In example embodiments, the series-connected transistors are JFETs. In other example embodiments, the series-connected transistors may be HEMTs or GaN transistors.

Gill, Lee↗
DOE OSTI2023

Seismic detection switch

A seismic switch (SS) that is able to detect and signal when internal faults have occurred within the SS is described. The SS provides safety class functionality to the detection of seismic activity. For example, the SS may detect earthquakes above a specified level, resulting in the disconnection of electrical power to a radioactive waste storage facility, which could result in the ignition of waste materials should the storage facility and/or storage container fail during a seismic event. By reducing the risk of fire under these circumstances, the possibility of offsite releases is significantly reduced.

Hayward, Allen D.↗
DOE OSTI2024

Solid-state information pattern discriminating switch

A maze-based switch generally having three functional blocks is disclosed. The first functional block handles communications by accepting an entered maze pattern from an external system controller and outputting the entered maze pattern (and optionally its directional complement) to the second functional block. The second functional block stores the maze pattern (and optionally its directional complement) to a permanent storage element and outputs the stored, entered maze pattern and its directional complement to a series of transistors in the third functional block. The third functional block is an electronic maze in which a correct maze pattern and its directional complement must be received by the transistors for the transistors to pass electrical power through the electronic maze to a connected element. The third functional block may alternatively be implemented with optical elements, optoelectronic elements, microelectromechanical elements, or elements formed by other microsystem technologies.

Galambos, Paul C.↗
DOE OSTI2024

Efficient IGBT switching

Embodiments of the invention provide IGBT circuit modules with increased efficiencies. These efficiencies can be realized in a number of ways. In some embodiments, the gate resistance and/or voltage can be minimized. In some embodiments, the IGBT circuit module can be switched using an isolated receiver such as a fiber optic receiver. In some embodiments, a single driver can drive a single IGBT. And in some embodiments, a current bypass circuit can be included. Various other embodiments of the invention are disclosed.

Ziemba, Timothy↗
DOE OSTI2024

Wide bandgap optical switch circuit breaker for controlling propagation of current therethrough a wide bandgap optical device

A high-voltage switch is adapted for use as a medium-voltage direct current circuit breaker, which provides a low-cost, small-footprint device to mitigate system faults. In one example, a method for operating a wideband optical device includes illuminating the wide bandgap optical device with a light within a first range of wavelengths and a first average intensity, allowing a current to propagate therethrough without substantial absorption of the current, illuminating the wide bandgap optical device with light within the first range of wavelengths and a second average intensity that is lower than the first average intensity to allow a sustained current flow though the wide bandgap optical device, and illuminating the wide bandgap optical device with light within a second range of wavelengths to stop or substantially restrict propagation of the current through the wide gap material.

Voss, Lars F.↗