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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Using the transverse digital damper as a real-time tune monitor for the Booster synchrotron at Fermilab

The Fermilab Booster is a fast ramping (15Hz) synchrotron which accelerates protons from 400MeV to 8GeV. During commissioning of a transverse digital damper system, it was shown that the damper could provide a measurement of the machine tune throughout the cycle by exciting just 1 of the 84 bunches with minimal impact on the machine operation. The algorithms used to make the measurement have been incorporated into the damper FPGA firmware allowing for real-time tune monitoring of all Booster cycles. A new Booster tune monitor was implemented in the digital damper which has minimal impact on the Booster operation. The tune measures the tunes in two planes over the energy ramping cycle with an accuracy of 0.01 in real time.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

6 Batch Injection and Slipped Beam Tune Measurements in Fermilab?s Main Injector

During NOVA operations it is planned to run the Fermilab Recycler in a 12 batch slip stacking mode. In preparation for this, measurements of the tune during a six batch injection and then as the beam is decelerated by changing the RF frequency have been carried out in the Main Injector. The coherent tune shifts due to the changing beam intensity were measured and compared well with the theoretically expected tune shift. The tune shifts due to changing RF frequency, required for slip stacking, also compare well with the linear theory, although some nonlinear affects are apparent at large frequency changes. These results give us confidence that the expected tunes shifts during 12 batch slip stacking Recycler operations can be accommodated.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Implementation and Investigation of a Weather- and Jam Density-tuned Network Perimeter Controller

This paper implements and evaluates the performance of a network fundamental diagram (NFD) proportional-integral perimeter controller (PC) using base tuned parameters (clear weather conditions and a base jam density of 160 veh/km/lane). The parameters were then re-tuned separately for different weather conditions and jam density values (reflecting different percentage of trucks), resulting in two new control methods: a weather-tuned perimeter controller (WTPC) and a jam density-tuned perimeter controller (JTPC). The WTPC was shown to outperform the no control strategy and the PC for different weather conditions. Specifically, the WTPC decreased the congestion inside the protected network (PN) and improved the overall performance of the full network (FN) by decreasing the average vehicle travel time, decreasing the vehicle total delay, increasing the average vehicle speed and decreasing the average vehicle fuel consumption. Alternatively, the JTPC was shown to perform similar to the PC for jam densities higher than the base-case jam density used in the PC (in our case 160 veh/km/lane). However, the JTPC outperformed the PC for smaller jam densities given that these smaller jam densities result in queues spilling back faster to upstream traffic signals. The results demonstrate the need to tune the controller to the actual jam density especially when the jam density decreases (e.g. trucks are introduced to the network). http://pubsindex.trb.org/

42 ENGINEERING↗
DOE OSTI2019

RF performance sensitivity to tuning of Nb3Sn coated CEBAF cavities

Nb3Sn has the potential to surpass niobium as the material of choice for SRF applications. The potential of this material stems from a larger superconducting energy gap, which leads to expectations of a higher RF critical field and a lower RF surface resistance. The appeal of better superconducting properties is offset by the relative complexity of producing practical Nb3Sn structures, and Nb3Sn sensitivity to lattice disorder challenges the use of the material for practical applications. Such sensitivity is indirectly probed during SRF cavity development, when the cavity is tuned to match the desired accelerator frequency. In the course of recent experiments we have coated and tuned several multi-cell cavities. Cold RF measurements before and after tuning showed degradation in cavity performance after tuning. The results of RF measurement were compared against strain evolution on Nb3Sn surface during tuning based on CST and ANSYS models.

Eremeev, G. V.↗
DOE OSTI2026

Broad frequency tuning of a Nb$_{3}$Sn superconducting microwave cavity for dark matter searches

We demonstrate a novel broad-frequency tuning mechanism for superconducting microwave cavities designed for dark matter searches. Using a Nb$_3$Sn-coated cigar-shaped cavity operating at approximately 9 GHz, we achieve continuous frequency tuning exceeding 1 GHz by mechanically separating the two cavity halves: a "tuning-by-opening" technique. Finite-element method simulations predict that radiative losses do not degrade the quality factor even for large openings, as a closed cavity with an intrinsic quality factor of $10^7$ maintains this value for apertures up to 9 mm, corresponding to a tuning range from 9.0 to 7.5 GHz. Experimental validation using both copper ring spacers and a continuous sliding mechanism confirms $Q_0$ values exceeding the dark matter quality factor across the entire explored frequency range, despite mechanical imperfections and film non-uniformities. This tuning approach avoids inserting elements into the resonant volume, making it particularly suitable for high-Q superconducting cavities in axion haloscope experiments and readily applicable to REBCO-based implementations capable of operating in multi-tesla magnetic fields.

Maiello, D. [Padua U.; INFN, Padua] (ORCID:0009000↗
DOE OSTI2022

Chemical Tuning Meets 2D Molecular Magnets

Two-dimensional (2D) magnets provoke a surge of interest in large anisotropy in reduced dimensions and are promising for next-generation information technology where dynamic magnetic tuning is essential. Until recently, the crucial metal-organic magnet Cr(pyz) 2 ∙xLiCl∙yTHF with considerable high coercivity and high-temperature magnetic order opens up a new platform to control magnetism in metal-organic materials at room temperature. Here we report an in-situ chemical tuning route to realize the controllable transformation of low-temperature magnetic order into room-temperature hard magnetism in Cr(pyz) 2 ∙xLiCl∙yTHF. The chemical tuning via electrochemical lithiation and solvation/desolvation exhibits continuously variable magnetic features from cryogenic magnetism to the room-temperature optimum performance of coercivity (H c ) of 8500 Oe and energy product of 0.6 MGOe. Such chemically flexible tunability of room-temperature magnetism is ascribed to the different degrees of lithiation and solvation that modify the stoichiometry and Cr-pyrazine coordination framework. Furthermore, the additively manufactured hybrid magnets show air stability and electromagnetic induction, providing potential applications. Our findings here suggest chemical tuning as a universal approach to control the anisotropy and magnetism of 2D hybrid magnets at room temperature, promising for data storage, magnetic refrigeration, and spintronics.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Optimum phase noise reduction and repetition rate tuning in quantum-dot mode-locked lasers

Competing approaches exist, which allow control of phase noise and frequency tuning in mode-locked lasers, but no judgement of pros and cons based on a comparative analysis was presented yet. Here, we compare results of hybrid mode-locking, hybrid mode-locking with optical injection seeding, and sideband optical injection seeding performed on the same quantum dot laser under identical bias conditions. We achieved the lowest integrated jitter of 121 fs and a record large radio-frequency (RF) tuning range of 342 MHz with sideband injection seeding of the passively mode-locked laser. The combination of hybrid mode-locking together with optical injection-locking resulted in 240 fs integrated jitter and a RF tuning range of 167 MHz. Using conventional hybrid mode-locking, the integrated jitter and the RF tuning range were 620 fs and 10 MHz, respectively.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Gain and frequency tuning within the mouse cochlear apex

Normal mammalian hearing requires cochlear outer hair cell active processes that amplify the traveling wave with high gain and sharp tuning, termed cochlear amplification. We have used optical coherence tomography to study cochlear amplification within the apical turn of the mouse cochlea. We measured not only classical basilar membrane vibratory tuning curves but also vibratory responses from the rest of the tissues that compose the organ of Corti. Basilar membrane tuning was sharp in live mice and broad in dead mice, whereas other regions of the organ of Corti demonstrated phase shifts consistent with additional filtering beyond that provided by basilar membrane mechanics. We use these experimental data to support a conceptual framework of how cochlear amplification is tuned within the mouse cochlear apex. We will also study transgenic mice with targeted mutations that affect different biomechanical aspects of the organ of Corti in an effort to localize the underlying processes that produce this additional filtering.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

A novel technique for tuning of co-axial cavity of multi-beam klystron

Multi-beam Klystrons (MBKs) have gained wide acceptances in the research sector for its inherent advantages. But developing a robust tuning technique for an MBK cavity of coaxial type has still remained a challenge as these designs are very prone to suffer from asymmetric field distribution with inductive tuning of the cavity. Such asymmetry leads to inhomogeneous beam-wave interaction, an undesirable phenomenon. Described herein is a new type of coaxial cavity that has the ability to suppress the asymmetry, thereby allowing tuning of the cavity with a single tuning post.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Bayesian optimization of PYTHIA 8 tunes

A new tune (set of model parameters) is found for the six most important parameters of the PYTHIA 8 final state parton shower and hadronization model using Bayesian optimization. The tune fits the Large Electron-Positron collider (LEPI) data from ALEPH better than the default tune in PYTHIA 8. To the best of our knowledge, we present the most comprehensive application of Bayesian optimization to the tuning of a parton shower and hadronization model using the LEPI data.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Etching sharp tips from thin metallic wires for tuning-fork-based scanning probe microscopy

Sharp tips are critical for obtaining high resolution images in scanning probe microscopy (SPM), particularly in samples with large variations in topography. For tuning-fork-based SPM, such tips are commonly obtained by electrochemical etching of metallic wires (e.g., tungsten). Electrochemical etching of metallic wires is the preferred means of preparing tips for scanning tunneling microscopy (STM), and techniques for obtaining sharp tips have been investigated extensively. However, the requirements for STM and tuning-fork-based SPM are different. In particular, the wires used in STM are typically 250-500 μ m in diameter, while the wires used for tuning-fork-based SPM are usually an order of magnitude narrower in order to minimize loading of the tuning fork: 25-50 μ m and sometimes down to a few micrometers in diameter. Consequently, many of the recipes developed for etching thicker metallic wires for STM tips do not give optimal results for smaller diameter wires. The authors describe here a modification of the etching circuit of Ibe et al . that significantly improves the reproducibility and reliability of the etching process for thin wires, and discuss the parameters that affect the aspect ratio of produced tips.

42 ENGINEERING↗
DOE OSTI2013

Taming parallel I/O complexity with auto-tuning

We present an auto-tuning system for optimizing I/O performance of HDF5 applications and demonstrate its value across platforms, applications, and at scale. The system uses a genetic algorithm to search a large space of tunable parameters and to identify effective settings at all layers of the parallel I/O stack. The parameter settings are applied transparently by the auto-tuning system via dynamically intercepted HDF5 calls. To validate our auto-tuning system, we applied it to three I/O benchmarks (VPIC, VORPAL, and GCRM) that replicate the I/O activity of their respective applications. We tested the system with different weak-scaling configurations (128, 2048, and 4096 CPU cores) that generate 30 GB to 1 TB of data, and executed these configurations on diverse HPC platforms (Cray XE6, IBM BG/P, and Dell Cluster). In all cases, the auto-tuning framework identified tunable parameters that substantially improved write performance over default system settings. In conclusion, we consistently demonstrate I/O write speedups between 2x and 100x for test configurations.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Dynamic Modeling of a Kaplan Hydroturbine Using Optimal Parametric Tuning and Real Plant Operational Data

To address grid variability caused by renewable energy integration and to maintain grid reliability and resilience, hydropower must quickly adjust its power generation over short time periods. This changing energy generation landscape requires advance technology integration and adaptive parameter optimization for hydropower systems via digital twin effort. However, this is difficult owing to the lack of characterization and modeling for the nonlinear nature of hydroturbines. To solve this issue, this paper first formulates a six-coefficient Kaplan hydroturbine model and then proposes a parametric optimization tuning framework based on the Nelder–Mead algorithm for adaptive dynamic learning of the six-coefficients so as to build models that describe the turbine. To assess the performance of the proposed optimal parametric tuning technique, operational data from a real-world Kaplan hydroturbine unit are collected and used to model the relationship between the gate opening and the generated power production. The findings show that the proposed technique can effectively and adaptively learn the unknown dynamics of the Kaplan hydroturbine while optimally tune the unknown coefficients to match the generated power output from the real hydroturbine unit with an inaccuracy of less than 5%. The method can be used to provides optimal tuning of parameters critical for controller design, operational optimization and daily maintenance for hydroturbines in general.

13 HYDRO ENERGY↗
NASA NTRS2015

Design and Testing of a Dynamically-Tuned Magnetostrictive Spring with Electrically-Controlled Stiffness

This paper details the development of an electrically-controlled, variable-stiffness spring based on magnetostrictive materials. The device, termed a magnetostrictive Varispring, can be applied as a semi-active vibration isolator or switched stiffness vibration controller for reducing transmitted vibrations. The Varispring is designed using 1D linear models that consider the coupled electrical response, mechanically-induced magnetic diffusion, and the effect of internal mass on dynamic stiffness. Modeling results illustrate that a Terfenol-D-based Varispring has a rise time almost an order of magnitude smaller and a magnetic diffusion cut-off frequency over two orders of magnitude greater than a Galfenol-based Varispring. The results motivate the use of laminated Terfenol-D rods for a greater stiffness tuning range and increased bandwidth. The behavior of a prototype Varispring is examined under vibratory excitation up to 6 MPa and 25 Hz using a dynamic load frame. For this prototype, stiffness is indirectly varied by controlling the excitation current. Preliminary measurements of continuous stiffness tuning via sinusoidal currents up to 1 kHz are presented. The measurements demonstrate that the Young's modulus of the Terfenol-D rod inside the Varispring can be continuously varied by up to 21.9 GPa. The observed stiffness tuning range is relatively constant up to 500 Hz, but significantly decreases thereafter. The stiffness tuning range can be greatly increased by improving the current and force control such that a more consistent current can be applied and the Varispring can be accurately tested at a more optimal bias stress.

Vibration control↗
DOE OSTI2020

Building Tune-Up Accelerator Program (Final Technical Report)

In 2016, the City of Seattle passed a mandatory Building Tune-Up requirement for all commercial buildings 50,000 square feet (SF) and larger as part of its Climate Action strategy. The requirement is phased in by size with large buildings (greater than 200,000 SF) required first. This allowed Seattle’s Office of Sustainability & Environment (OSE) to offer the Building Tune-Up Accelerator (TUA) Program to the “mid-size” building market (less than 100,000 SF) to meet the requirements early. With funding from the US DOE, a package of technical and financial support was developed for building owners and energy service providers to encourage this hard-to-reach market to participate in the tune-up—and even go beyond requirements for greater energy savings. Seattle City Light, the municipal electric utility, offered participants a simple per square foot financial incentive. Partners at the University of Washington Integrated Design Lab, Smart Buildings Center and Pacific Northwest National Lab (PNNL) offered service provider trainings, analytical tools and technical support. This final technical report summarizes the program, projected energy and emissions savings and lessons learned from program development to implementation to final evaluation for the 102 buildings that participated.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2021

Active Tuning of Optical Constants in the Visible–UV: Praseodymium-Doped Ceria—a Model Mixed Ionic–Electronic Conductor

Mixed ionic-electronic conductors offer chemical and electrical means for active tuning of their optical constants, e.g. with variations in oxygen non-stoichiometry in Pr 0.1 Ce 0.9 O 2-δ , enabling implementation of adaptive thin film optical devices. Here, we demonstrate in-situ chemo-tuning of the extinction coefficient in Pr 0.1 Ce 0.9 O 2-δ at elevated temperatures and provide a tuning model that treats the interdependence of mobile oxygen vacancies and small polarons coupled to variations in optically active praseodymium ions. Further, a new means for electro-tuning of the optical constants of mixed ionic-electronic conductors was demonstrated experimentally and modeled for Pr 0.1 Ce 0.9 O 2-δ thin films deposited on grid-like electrode structures. Modeling of non-steady state optical transmittance modulations in the latter allows for estimation of oxygen vacancy mobility that determines the switching speed of the device. Quenched-in values of nr and k to room temperature become nonvolatile, providing a modulation range in the extinction coefficient of Δk ~0.1 (change of ~800%) and in the refractive index of Δn r ~0.1 (relative to initial n r of ~2.35). Key figures of merit including, transmission optical modulation of ~0.04 per 1 mV nm -1 , switching energy per area of 670 pJ μm -2 and switching times of seconds, were demonstrated, with further improvements possible.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Automated workflow for non-empirical Wannier-localized optimal tuning of range-separated hybrid functionals

Here, we introduce an automated workflow for generating non-empirical Wannier-localized optimally-tuned screened range-separated hybrid (WOT-SRSH) functionals. WOT-SRSH functionals have been shown to yield highly accurate fundamental band gaps, band structures, and optical spectra for bulk and 2D semiconductors and insulators. Our workflow automatically and efficiently determines the WOT-SRSH functional parameters for a given crystal structure and composition, approximately enforcing the correct screened long-range Coulomb interaction and an ionization potential ansatz. In contrast to previous manual tuning approaches, our tuning procedure relies on a new search algorithm that only requires a few hybrid functional calculations with minimal user input. We demonstrate our workflow on 23 previously studied semiconductors and insulators, reporting the same high level of accuracy. By automating the tuning process and improving its computational efficiency, the approach outlined here enables applications of the WOT-SRSH functional to compute spectroscopic and optoelectronic properties for a wide range of materials.

Gant, Stephen E. [University of California, Berkel↗
DOE OSTI2011

Tuning of magnetic parameters in cobalt-polystyrene nanocomposites by reduction cycling

Graphical abstract: Cobalt nanoparticles were prepared by a reduction process inside polymer pores. A porous polymer network (polystyrene) was chosen as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The concentration of cobalt can be tuned in this technique by repeating the cycling process. Highlights: {yields} Elementary cobalt nanoparticles were synthesized inside polystyrene by a novel process. {yields} The self protection is achieved by the auto-shelling with the metal oxide. {yields} The magnetisation and coercivity could be tuned by repeating the cycles. {yields} Tuning of magnetic properties (both coercivity and magnetisation) could be achieved by the repetition of reduction cycles. {yields} Synthesized nanocomposite can act as a catalyst for carbon nanotube synthesis. -- Abstract: Cobalt nanoparticles were prepared by a reduction process inside polymer pores using CoSO{sub 4}.7H{sub 2}O and NaBH{sub 4}. A porous polymer network (sulphonated polystyrene) was chosen, as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The concentration of cobalt can be tuned in this technique by repeating the cycling process.

36 MATERIALS SCIENCE↗