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At least 127 records · Page 7

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Comparison of Active and Passive Head Impulse Testing of the Horizontal Vestibulo-Ocular Reflex: Exploring the Feasibility of Different Approaches for Spaceflight

INTRODUCTION: Astronauts experience a wide variety of sensorimotor disturbances primarily due to microgravity-induced vestibular adaptations during spaceflight. Head Impulse Testing (HIT) will be conducted during the Complement of Integrated Protocols for Human Exploration Research program(CIPHER) Vestibular Health study to examine changes in the horizontal vestibulo-ocular reflex in response to high-velocity head movements to detect changes in peripheral vestibular function [1,2]. However, correct interpretation will require consideration of potential artifacts and the constraints of conducting this test across different phases of the mission. Therefore, the aims of our study were to (1) examine reliability across different test operators, and (2) compare results of active (aHIT) versus passive (pHIT) approaches to evaluate the feasibility of self-administered versus operator-assisted approaches. A comparison of responses with visual viewing of a wall target (default condition) versus vision occluded evaluated the influence of other oculomotor control influence across conditions, and comparison with computer-generated rotator head impulse tests (rHIT) examined the variability associated with the ocular responses independent of the variability in executing the head movements themselves. METHODS: Seventeen non-astronaut volunteers (male n=12, age=22.9 ± 3.0; female n=5, age=27.0 ± 6.0, mean ± std) completed HIT testing using video-oculography (VOG) goggles and a high-torque rotator system. The test order was counterbalanced across conditions: (1) passive head-on-torso (pHIT, default condition for flight study) using two operators (Op1 and Op2), (2) active head-on-torso (aHIT, subject initiated), and (3) passive head and torso using rotary chair (rHIT). Eye and head movement data were processed to obtain gain in each direction. The main outcome measures were average gain and asymmetry [1], as well as the percentage of acceptable trials not excluded due to insufficient head amplitude or recording artifacts. RESULTS: While the pHIT gains were similar with vision (1.032 ± 0.043) and vision occluded (1.029 ± 0.038) conditions, the percentage of acceptable trials was greater with vision (Op1 = 93.0%, Op2 = 93.2%) versus occluded (Op1 = 70.7%, Op2 = 67.6%). The reliability between operators was greater for pHIT gain (Intraclass Correlation, ICC = 0.66, p = 0.001) than for pHIT asymmetry (ICC = 0.57, p = 0.01). The percentage of acceptable trials reduced by ~20% during the self-administered aHITs for both visual conditions and tended to be lower than computer-generated rHITs (76% versus 83%). While the aHIT gains were not significantly different than pHIT gains for vision or vision occluded conditions, these measures were poorly correlated. Both aHIT and pHIT gains were significantly greater than the rHIT gains, presumably due to the reduced velocities from the rotator. The asymmetry measures were poorly correlated across pHIT, aHIT, and rHIT conditions, although none of the subjects had asymmetries greater than 16%. DISCUSSION: Our findings support the feasibility of using the standard pHIT methodology for spaceflight. Similarities between visual conditions reflect that these responses are mediated by the peripheral lateral canals rather than other oculomotor mechanisms. The inter-tester reliability was acceptable despite differences in the tester training. In addition to concerns of non-vestibular mechanisms introduced during self-administered aHITs [2], operator-assisted pHITs resulted in higher percentage of acceptable trials and should result in more efficient and reliable measures during spaceflight.

M R Ehrenburg↗

DOE OSTI2025

Dominant balance-based adaptive mesh refinement for incompressible fluid flows

This work introduces a novel adaptive mesh refinement (AMR) method that utilizes dominant balance analysis (DBA) for efficient and accurate grid adaptation in computational fluid dynamics (CFD) simulations. The proposed method leverages a Gaussian mixture model (GMM) to classify grid cells into active and passive regions based on the dominant physical interactions within the equation space. By modeling truncation error probabilistically from discretized terms, the method identifies regions of high interaction where numerical accuracy is most sensitive to resolution. Unlike traditional AMR strategies, this approach does not rely on heuristic-based sensors or user-defined thresholds, providing a fully automated and problem-independent framework for AMR. Applied to the incompressible Navier-Stokes equations for steady and unsteady flow past a cylinder, the DBA-based AMR method achieves comparable accuracy to high-resolution grids while reducing computational costs by up to 70 %. The validation highlights the method’s effectiveness in capturing complex flow features while minimizing grid cells, directing computational resources toward regions with the most critical dynamics. This modular and scalable strategy is adaptable to a wide range of applications, presenting a promising tool for efficient high-fidelity simulations in CFD and other multiphysics domains.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS2001

Psychophysiological Control of Acognitive Task Using Adaptive Automation

The major focus of the present proposal was to examine psychophysiological variables related to hazardous states of awareness induced by monitoring automated systems. With the increased use of automation in today's work environment, people's roles in the work place are being redefined from that of active participant to one of passive monitor. Although the introduction of automated systems has a number of benefits, there are also a number of disadvantages regarding worker performance. Byrne and Parasuraman have argued for the use of psychophysiological measures in the development and the implementation of adaptive automation. While both performance based and model based adaptive automation have been studied, the use of psychophysiological measures, especially EEG, offers the advantage of real time evaluation of the state of the subject. The current study used the closed-loop system, developed at NASA-Langley Research Center, to control the state of awareness of subjects while they performed a cognitive vigilance task. Previous research in our laboratory, supported by NASA, has demonstrated that, in an adaptive automation, closed-loop environment, subjects perform a tracking task better under a negative than a positive, feedback condition. In addition, this condition produces less subjective workload and larger P300 event related potentials to auditory stimuli presented in a concurrent oddball task. We have also recently shown that the closed-loop system used to control the level of automation in a tracking task can also be used to control the event rate of stimuli in a vigilance monitoring task. By changing the event rate based on the subject's index of arousal, we have been able to produce improved monitoring, relative to various control groups. We have demonstrated in our initial closed-loop experiments with the the vigilance paradigm that using a negative feedback contingency (i.e. increasing event rates when the EEG index is low and decreasing event rates when the EEG index is high) results in a marked decrease of the vigilance decrement over a 40 minute session. This effect is in direct contrast to performance of a positive feedback group, as well as a number of other control groups which demonstrated the typical vigilance decrement. Interestingly, however, the negative feedback group performed at virtually the same level as a yoked control group. The yoked control group received the same order of changes in event rate that were generated by the negative feedback subjects using the closed-loop system. Thus it would appear to be possible to optimize vigilance performance by controlling the stimuli which subjects are asked to process.

Freeman, Frederick↗

DOE OSTI2025

Digital twin framework for PIP-II linac: AI-driven multi-scale modeling from ion source to 800 MeV

The PIP-II superconducting linac at Fermilab is designed to deliver multi-megawatt proton beams for neutrino physics and other high-intensity applications. To expedite commissioning and enhance operational reliability, we have developed an EPICS-based data flow framework that seamlessly integrates digital twins (DT) with physical twins (PT). These digital twins comprise high-fidelity beam dynamics models or data-driven surrogate models connected to their physical counterparts through real-time diagnostics and advanced machine-learning algorithms.Central to this framework is Linac_Gen, an accelerated simulation tool that incorporates convolutional neural networks, random forests, and genetic algorithms to provide up to a tenfold speedup in optimizing the accelerator geometry model. An EPICS translator layer ensures interoperability by efficiently mapping lattice parameters across diverse simulation platforms.Our EPICS-based framework supports multiple operational modes—monitoring, passive learning, closed-loop control, and online learning—covering the entire machine lifecycle. By leveraging HPC resources and multi-objective optimization techniques, the digital twin enables adaptive trajectory correction, real-time fault detection, and predictive modeling of beam stability. This comprehensive approach paves the way for robust, high-intensity operation and data-driven accelerator R&D at Fermilab.

Pathak, Abhishek [Fermilab]↗

DOE OSTI2025

Contextual subspace variational quantum eigensolver calculation of the dissociation curve of molecular nitrogen on a superconducting quantum computer

Abstract We present an experimental demonstration of the Contextual Subspace Variational Quantum Eigensolver on superconducting hardware. Calculating the potential energy curve of molecular nitrogen proves challenging for many conventional quantum chemistry techniques, since static correlation dominates in the dissociation limit. Our quantum simulations retain good agreement with the Full Configuration Interaction energy, outperforming all benchmarked single-reference wavefunction techniques in capturing the bond-breaking appropriately. Moreover, our methodology is competitive with multiconfigurational approaches but at a saving of quantum resource, meaning larger active spaces can be treated for a fixed qubit allowance. To achieve this result, we deploy an error mitigation/suppression strategy comprised of Dynamical Decoupling, Measurement-Error Mitigation and Zero-Noise Extrapolation. Circuit parallelization also provides passive noise-averaging and improves the effective shot yield to reduce the measurement overhead. Furthermore, we introduce a modified adaptive ansatz construction algorithm that incorporates hardware awareness into our variational circuits, minimizing the transpilation cost for the target qubit topology.

Physics↗

NASA NTRS1988

Experimental studies of active members in control of large space structures

Intelligent structures for precision spacecraft applications are structural systems incorporating sensors, actuators, and built-in electronic logic that facilitate self-monitoring of structure responses to disturbances. Attention is presently given to adaptive structures, in which the electronic logic need not be integral to the structure. Active members are used to replace selected passive members of truss-type structures; the sensors employed allow measurement of the elastic strain and deformation experienced by the structure. Two struss-type testbed structures are described.

Fanson, J. L.↗

NASA NTRS1999

Exercise Training During +Gz Acceleration

The overall purpose is to study the effect of passive (without exercise) and active (with exercise) +Gz (head-to-foot) acceleration training, using a short-arm (1.9m radius) centrifuge, on post- training maximal oxygen uptake (VO2 max, work capacity) and 70 deg head-up tilt (orthostatic) tolerance in ambulatory subjects to test the hypothesis that (a) both passive and active acceleration training will improve post-training tilt-tolerance, and (b) there will be no difference in tilt-tolerance between passive and active exercise acceleration training because increased hydrostatic and blood pressures, rather than increased muscular metabolism, will provide the major adaptive stimulus. The purpose of the pilot study was to test the hypothesis that there would be no significant difference in the metabolic responses (oxygen uptake, heart rate, pulmonary ventilation, or respiratory exchange ratio) during supine exercise with moderate +Gz acceleration.

Greenleaf, J. E.↗

NASA NTRS1987

Simple robust control laws for robot manipulators. Part 1: Non-adaptive case

A new class of exponentially stabilizing control laws for joint level control of robot arms is introduced. It has been recently recognized that the nonlinear dynamics associated with robotic manipulators have certain inherent passivity properties. More specifically, the derivation of the robotic dynamic equations from the Hamilton's principle gives rise to natural Lyapunov functions for control design based on total energy considerations. Through a slight modification of the energy Lyapunov function and the use of a convenient lemma to handle third order terms in the Lyapunov function derivatives, closed loop exponential stability for both the set point and tracking control problem is demonstrated. The exponential convergence property also leads to robustness with respect to frictions, bounded modeling errors and instrument noise. In one new design, the nonlinear terms are decoupled from real-time measurements which completely removes the requirement for on-line computation of nonlinear terms in the controller implementation. In general, the new class of control laws offers alternatives to the more conventional computed torque method, providing tradeoffs between robustness, computation and convergence properties. Furthermore, these control laws have the unique feature that they can be adapted in a very simple fashion to achieve asymptotically stable adaptive control.

Wen, J. T.↗

DOE OSTI2022

Aerosol Inlets for a Mid-Sized Uncrewed Aerial System (UAS)

The purpose of this technical report is to document the efforts to design and test two inlet systems for aerosol sampling suitable for deployment on a medium-sized fixed-wing Uncrewed Aerial System (UAS). This work, which was supported by the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) user facility, was conducted at the Pacific Northwest National Laboratory (PNNL) for the ARM Aircraft Facility (AAF) starting in November 2017. The current work is a part of AAF efforts to instrument the ArcticShark (a mid-sized UAS owned and operated by the AAF) for atmospheric research and develop a scientific payload for deployment on a similar-sized UAS with minimal adaptation and integration. An aerosol inlet system is necessary to sample and transport ambient air sample to the scientific instrumentation with minimal distortions to the aerosols. Two isokinetic aerosol inlets were designed: the first is a simple passive system for a single instrument suitable to be installed in a wing pylon; the second is a system with active control designed to sample and distribute air among several heterogeneous instruments and to provide basic humidity control of the air sample so that the measured aerosol parameters should correspond to “dry” conditions (a common requirement). Both systems could be easily adapted for deployment on another platform and/or with a different set of instrumentation. Several conducted flight tests showed that the inlets’ performance met our design goals.

42 ENGINEERING↗

DOE OSTI2024

A New Method for Creating Structured High-Performance Current Collectors for Electrochemical Applications

A significant challenge in many electrochemical systems is finding a stable, high-performing current collector material that is mechanically robust, adaptable in form factor, and free of precious metals. Titanium electrodes are robust in many of these regards but exhibit poor charge transfer performance due to self-passivation. Herein, a new materials processing paradigm based on the titanium/titanium nitride (Ti/TiN) system which allows for robust, stable, and low-resistance current collectors of arbitrary form factor is presented. Specifically, a gas-nitriding process for 3D-printed titanium electrodes that results in a 20-fold improvement of charge transfer characteristics relative to the untreated material is outlined. The ability to utilize 3D-structured current collectors with a net 40-fold improvement in performance over nonstructured electrodes is further demonstrated. This novel approach to creating electrochemical current collectors requires minimal laboratory resources and can be widely adapted for a variety of applications, including desalination, electrolysis, energy storage, and basic research. In conclusion, the work described herein provides both a means for accelerating research and opens the door to hierarchical tuneability for enhanced performance.

36 MATERIALS SCIENCE↗

NASA NTRS2010

Active Vibration Reduction of Titanium Alloy Fan Blades (FAN1) Using Piezoelectric Materials

The NASA Glenn Research Center is developing smart adaptive structures to improve fan blade damping at resonances using piezoelectric (PE) transducers. In this paper, a digital resonant control technique emulating passive shunt circuits is used to demonstrate vibration reduction of FAN1 Ti real fan blade at the several target modes. Single-mode control and multi-mode control using one piezoelectric material are demonstrated. Also a conceptual study of how to implement this digital control system into the rotating fan blade is discussed.

Choi, Benjamin↗

NASA NTRS1978

Preliminary design trade-offs for a multi-mission stored cryogen cooler

Preliminary design studies were performed for a multi-mission solid cryogen cooler having a wide range of application for both the shuttle sortie and free flyer missions. This multi-mission cooler (MMC) is designed to be utilized with various solid cryogens to meet a wide range of instrument cooling from 10 K (with solid hydrogen) to 90 K. The baseline cooler utilizes two stages of solid cryogen and incorporates an optional, higher temperature third stage which is cooled by either a passive radiator or a thermoelectric cooler. The MMC has an interface which can accommodate a wide variety of instrument configurations. A shrink fit adapter is incorporated which allows a drop-in instrument integration. The baseline design provides cooling of approximately 1 watt over a 60 to 100 K temperature range and about 0.5 watts from 15 to 60 K for a one year lifetime. For low cooling loads and with use of the optional radiator shield, cooling lifetimes as great as 8 years are predicted.

Sherman, A.↗

NASA NTRS1991

Mechanically induced alterations in cultured skeletal muscle growth

Model systems are available for mechanically stimulating cultured skeletal muscle cells by passive tensile forces which simulate those found in vivo. When applied to embryonic muscle cells in vitro these forces induce tissue organogenesis, metabolic adaptations, and muscle cell growth. The mechanical stimulation of muscle cell growth correlates with stretch-induced increases in the efflux of prostaglandins PGE2 and PGF2(alpha) in a time and frequency dependent manner. These prostaglandins act as mechanical 'second messengers' regulating skeletal muscle protein turnover rates. Since they also effect bone remodelling in response to tissue loading and unloading, secreted prostaglandins may serve as paracrine growth factors, coordinating the growth rates of muscle and bone in response to external mechanical forces. Cell culture model systems will supplement other models in understanding mechanical transduction processes at the molecular level.

Vandenburgh, H. H.↗

NASA NTRS2013

Acoustic Characterization of Compact Jet Engine Simulator Units

Two dual-stream, heated jet, Compact Jet Engine Simulator (CJES) units are designed for wind tunnel acoustic experiments involving a Hybrid Wing Body (HWB) vehicle. The newly fabricated CJES units are characterized with a series of acoustic and flowfield investigations to ensure successful operation with minimal rig noise. To limit simulator size, consistent with a 5.8% HWB model, the CJES units adapt Ultra Compact Combustor (UCC) technology developed at the Air Force Research Laboratory. Stable and controllable operation of the combustor is demonstrated using passive swirl air injection and backpressuring of the combustion chamber. Combustion instability tones are eliminated using nonuniform flow conditioners in conjunction with upstream screens. Through proper flow conditioning, rig noise is reduced by more than 20 dB over a broad spectral range, but it is not completely eliminated at high frequencies. The low-noise chevron nozzle concept designed for the HWB test shows expected acoustic benefits when installed on the CJES unit, and consistency between CJES units is shown to be within 0.5 dB OASPL.

Doty, Michael J.↗

DOE OSTI2022

Aerosol Inlets for a Mid-Sized Uncrewed Aerial System (UAS)

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1996

Spatial Transformation of the Vestibulo-Ocular Reflex during Spaceflight

It was hypothesized that the absence of the gravitational reference cues may be responsible for adaptive changes in the vestibulo-ocular reflex (VOR). These changes result in the alteration of the direction of the compensatory slow phase (SP) eye movements in microgravity. In order to test this hypothesis, the direction of the VOR SP relative to head motion was investigated in three astronauts during and after an eight-day orbital flight by passive sinusoidal pitch or yaw angular motion at two frequencies. The results of the inflight and postflight testing are considered. The observed deviation between VOR SP and head motion suggests that spatial transformation in the VOR occurred during adaptation to microgravity. It is considered that, although this spatial transformation might be due to a sensory bias, it may reflect central changes in the reference system used for spatial orientation in microgravity.

Clement, Gilles↗

NASA NTRS1984

Assessment of lift- and blockage-induced wall interference in a three-dimensional adaptive-wall tunnel

A three-dimensional adaptive-wall wind tunnel experiment was conducted at Ames Research Center. This experiment demonstrated the effects of wall interference on the upwash distribution on an imaginary surface surrounding a lifting wing. This presentation demonstrates how the interference assessment procedure used in the adaptive-wall experiments to determine the wall adjustments can be used to separately assess lift- and blockage-induced wall interference in a passive-wall wind tunnel. The effects of lift interference on the upwash distribution and on the model lift coefficient are interpreted by a simple horseshoe vortex analysis.

Schairer, E. T.↗

DOE OSTI2021

A comprehensive review of nonlinear oscillators in hydrokinetic energy harnessing using flow-induced vibrations

A comprehensive review of hydrokinetic energy converters based on alternating lift technology (ALT) is provided. Emphasis is on nonlinear oscillators based on Flow Induced Vibration (FIV) or Oscillation (FIO). Due to strong coupling in Fluid-Structure Interaction (FSI), and in order to maximize the hydrokinetic harnessed energy, design of nonlinear oscillators and analysis by model tests or computational fluid dynamics dominates this area. Research confirmed that the nonlinear oscillator can harvest energy from a stochastic excitation modeled by a generic wide spectrum, and overcome the most severe oscillator limitations: specifically, the need for continuous frequency tuning due to the narrow bandwidth response, and low efficiency outside the narrow bandwidth oscillator response. This review covers the following aspects of nonlinear oscillators in ALT converters: (1) Geometric changes in oscillator cross-section; e.g., circular, square, rectangular, or trilateral shapes. (2) Passive turbulence control of FIV/FIO. (3) Position based nonlinear stiffness. (4) Multi-cylinder synergistic FIV/FIO. (5) Mechanically linked oscillators. (6) Velocity-based, nonlinear, adaptive harnessing damping.

42 ENGINEERING↗