Herglotz-Noether theorem in conformal space- time.
Dyadic formalism to prove Herglotz-Noether theorem for flat manifolds
THEOREM PROVING↗
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Exploring the Use of Alfven Waves in Magnetometer Calibration at Geosynchronous Orbit
An Alfven wave is a type magnetohydrodynamicwave that travels through a conducting fluid under the influence of a magnetic field. Researchers have successfully calculated offset vectors of magnetometers in interplanetary space by optimizing the offset to maximize certain Alfvenic properties of observed waves (Leinweber, Belcher). If suitable Alfven waves can be found in the magnetosphere at geosynchronous altitude then these techniques could be used to augment the overall calibration plan for magnetometers in this region such as on the GOES spacecraft, possibly increasing the time between regular maneuvers. Calibration maneuvers may be undesirable because they disrupt the activities of other instruments. Various algorithms to calculate an offset using Alfven waves were considered. A new variation of the Davis-Smith method was derived because it can be mathematically shown that the Davis-Smith method tolerates filtered data, which expands potential applications. The variant developed was designed to find only the offset in the plane normal to the main field because the overall direction of Earth's magnetic field rarely changes, and theory suggests the Alfvenic disturbances occur transverse to the main field. Other variations of the Davis-Smith method encounter problems with data containing waves that propagate in mostly the same direction. A searching algorithm was then designed to look for periods of time with potential Alfven waves in GOES 15 data based on parameters requiring that disturbances be normal to the main field and not change field magnitude. Final waves for calculation were hand-selected. These waves produced credible two-dimensional offset vectors when input to the Davis-Smith method. Multiple two-dimensional solutions in different planes can be combined to get a measurement of the complete offset. The resulting three dimensional offset did not show sufficient precision over several years to be used as a primary calibration method, but reflected changes in the offset fairly well, suggesting that the method could be helpful in monitoring trends of the offset vector when maneuvers cannot be used.
calibration↗
Space magnetics - The Mariner V magnetometer experiment.
Vector helium magnetometer for Mariner 4 /Mars 1964/ and Mariner 5 /Venus 1967/, discussing efforts to reduce spacecraft stray fields
Connor, B. V.↗
End-to-End Automated Segmentation Framework for Four-Dimensional Scanning Transmission Electron Microscopy Data
Four-dimensional scanning transmission electron microscopy (4D-STEM) is powerful for rapidly characterizing arrays of nanoparticles produced via high-throughput synthesis. However, such 4D-STEM datasets typically contain thousands of nanoparticles, each characterized by thousands of diffraction patterns spatially distributed across the nanoparticle, necessitating efficient and comprehensive analysis. We propose an end-to-end segmentation framework to automatically segment each nanoparticle into regions with distinct composition/orientation of crystal grains, using only the 4D-STEM data. Bragg disk information is extracted in a physics-informed manner from the diffraction patterns at each spatial location and combined with the real space coordinates to form feature vectors. These feature vectors are then used as inputs to a Gaussian mixture model (GMM) to segment the nanoparticle into distinct regions. We also develop two visualization tools based on the GMM outputs to infer the interface transition and the degree of superposition. Our framework comprehensively integrates machine learning tools and physics knowledge, and provides a basis for substantially compressing enormous 4D-STEM datasets, e.g., by replacing the full 4D-STEM dataset for each nanoparticle with only a single set of Bragg disk features for each distinct crystal grain identified in the nanoparticle. In this article, we demonstrate the power of our framework by presenting results for real, complex datasets.
47 OTHER INSTRUMENTATION↗
Loop-string-hadron approach to SU(3) lattice Yang-Mills theory: Hilbert space of a trivalent vertex
The construction of gauge-invariant states of SU(3) lattice gauge theories has garnered new interest in recent years, but implementing them is complicated by the need for SU(3) Clebsch-Gordon coefficients. In the loop-string-hadron (LSH) approach to lattice gauge theories, the elementary excitations are strictly gauge invariant, and constructing the basis requires no knowledge of Clebsch-Gordon coefficients. Originally developed for SU(2), the LSH formulation was recently generalized to SU(3), but limited to one spatial dimension. In this work, we generalize the LSH approach to constructing the basis of SU(3) gauge-invariant states at a trivalent vertex—the essential building block to multidimensional space. A direct generalization from the SU(2) vertex yields a legitimate basis; however, in certain sectors of the Hilbert space, the naive LSH basis vectors so defined suffer from being nonorthogonal. The issues with orthogonality are directly related to the “missing label” or “outer multiplicity” problem associated with SU(3) tensor products and may also be phrased in terms of Littlewood-Richardson coefficients or the need for a “seventh Casimir” operator. The states that are unaffected by the problem are orthonormalized in closed form. For the sectors that are afflicted, we discuss the nonorthogonal bases and their orthogonalization. A few candidates for seventh Casimir operators are readily constructed from the suite of LSH gauge-singlet operators. The diagonalization of a seventh Casimir represents one prescriptive solution toward obtaining a complete orthonormal basis, but a closed-form general solution remains to be found. Published by the American Physical Society 2025
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Predictive Complexity of Quantum Subsystems
We define predictive states and predictive complexity for quantum systems composed of distinct subsystems. This complexity is a generalization of entanglement entropy. It is inspired by the statistical or forecasting complexity of predictive state analysis of stochastic and complex systems theory but is intrinsically quantum. Predictive states of a subsystem are formed by equivalence classes of state vectors in the exterior Hilbert space that effectively predict the same future behavior of that subsystem for some time. As an illustrative example, we present calculations in the dynamics of an isotropic Heisenberg model spin chain and show that, in comparison to the entanglement entropy, the predictive complexity better signifies dynamically important events, such as magnon collisions. It can also serve as a local order parameter that can distinguish long and short range entanglement.
Asplund, Curtis T. (ORCID:0000000305575850)↗
Solar aspect determination system
Sensor containing commercially available solid-state position-sensitive light detector provides complete space-vehicle sun or moon vector information.
Farthing, W. H.↗
Suggested architecture for a specialized fluid dynamics computer
Future flow simulations in 3-D will require computers with extremely large main memories and an advantageous ratio between computer cost and arithmetic speed. Since random access memories are very expensive, a pipeline design is proposed which allows the use of much cheaper sequential devices without any sacrifice in speed for vector references (even with arbitrary spacing between successive elements). Also scalar arithmetic can be performed efficiently. The comparatively low speed of the proposed machine (about 10 to the 7th power operations per second) would be offset by a very low price per unit, making mass production possible.
Fornberg, B.↗
On-board Attitude Determination System (OADS)
The requirements, capabilities and system design for an on-board attitude determination system (OADS) to be flown on advanced spacecraft missions were determined. Based upon the OADS requirements and system performance evaluation, a preliminary on-board attitude determination system is proposed. The proposed OADS system consists of one NASA Standard IRU (DRIRU-2) as the primary attitude determination sensor, two improved NASA Standard star tracker (SST) for periodic update of attitude information, a GPS receiver to provide on-board space vehicle position and velocity vector information, and a multiple microcomputer system for data processing and attitude determination functions. The functional block diagram of the proposed OADS system is shown. The computational requirements are evaluated based upon this proposed OADS system.
Carney, P.↗
Analysis of multispectral data using an unsupervised classification technique: Application to VAS
A statistical classification method based on clustering of multidimensional histograms was applied to several channels of the VAS multispectral imagery. The method automatically discriminates and classifies atmospheric ground features such as cloud types, atmospheric moisture patterns, ocean, or ground. Such a clustering method has the advantage of forming natural data groupings, without a priori classification. Clusters are not limited by straight lines or plane surfaces as is the case in threshold methods. The method was applied to simultaneous full resolution images from channels 8 (11.2 micron), 10 (6.7 micron), and 12 (3.9 micron). Twenty image segments of 64 by 64, 12 image segments of 128 by 128, and 4 image segments of 254 by 254 picture elements were analyzed. In addition, normal VISSR mode images at 1800, 1830, and 2000 GMT were used to identify the classes. The gray levels measured along a scan line and the result of the classification scheme (dashed curves) for the three channels investigated are shown. Each point of the image is affected to a class. Each class is identified by a center of gravity that is represented by a vector in the three dimensional space of gray levels.
Szejwach, G.↗
Simplified Convolution Codes
Simple recursive algorithm efficiently calculates minimum-weight error vectors using Diophantine equations. Recursive algorithm uses general solution of polynomial linear Diophantine equation to determine minimum-weight error polynomial vector in equation in polynomial space.
Truong, T. K.↗
The dissociation of subjective measures of mental workload and performance
Dissociation between performance and subjective workload measures was investigated in the theoretical framework of the multiple resources model. Subjective measures do not preserve the vector characteristics in the multidimensional space described by the model. A theory of dissociation was proposed to locate the sources that may produce dissociation between the two workload measures. According to the theory, performance is affected by every aspect of processing whereas subjective workload is sensitive to the amount of aggregate resource investment and is dominated by the demands on the perceptual/central resources. The proposed theory was tested in three experiments. Results showed that performance improved but subjective workload was elevated with an increasing amount of resource investment. Furthermore, subjective workload was not as sensitive as was performance to differences in the amount of resource competition between two tasks. The demand on perceptual/central resources was found to be the most salient component of subjective workload. Dissociation occurred when the demand on this component was increased by the number of concurrent tasks or by the number of display elements. However, demands on response resources were weighted in subjective introspection as much as demands on perceptual/central resources. The implications of these results for workload practitioners are described.
Yeh, Y. H.↗
NASA Marshall Space Flight Center solar observatory
A description is provided of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility and a summary is given of its observations and data reduction during Jan. to Mar. 1988. The systems that make up the facility are a magnetograph telescope, an H-alpha telescope, a Questar telescope, and a computer center. The data are represented by longitudinal contours with azimuth plots.
Smith, James E.↗
NASA Marshall Space Flight Center solar observatory report, January - December 1987
This report provides a description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility and gives a summary of its observations and data reduction during January to December 1987. The systems that make up the facility are a magnetograph telescope, an H-alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.
Smith, James E.↗
NASA Marshall Space Flight Center Solar Observatory report, January - June 1990
A description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility is presented and a summary of its observations and data reduction is given. The systems that make up the facility are a magnetograph telescope, an H alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.
Smith, James E.↗
Factors influencing manual ability to recover from an anomalous thruster input during a simulated docking maneuver
An experiment was performed in the Space Station Proximity Operations Simulator. Five test subjects were instructed to perform twenty remote docking maneuvers of an orbital maneuvering vehicle (OMV) to the Space Station in which they were located. The OMV started from an initial range of 304.8 m on the Space Station's negative velocity vector. Time and fuel to return to a nominal trajectory, total mission duration, total fuel consumption, failure rate, and time histories of commanded burns were recorded for each trial. Analyses of the results added support to the hypothesis that slow approach velocities are not inherently safer than their more rapid counterparts. Naive subjects were capable of docking successfully at velocities faster than those prescribed by the '0.1 pct Rule' even when a simulated faulty thruster disturbed the nominal trajectory.
Brody, Adam R.↗
Recovery from an anomalous thruster input during a simulated docking maneuver
An experiment was performed in the Space Station Proximity Operations Simulator at the NASA Ames Research Center. Five test subjects were instructed to perform twenty simulated remote docking maneuvers of an orbital maneuvering vehicle (OMV) to the space station in which they were located. The OMV started from an initial range of 304.8 m (1000 ft) on the space station's negative velocity vector. Anomalous out-of-plane thruster firings of various magnitudes (simulating a faulty thruster) occurred at one of five ranges from the target. Initial velocity, range of anomalous burn, and magnitude of anomalous burn were the factors varied. In addition to whether the trial was successful, time and fuel to return to a nominal trajectory, total mission duration, total fuel consumption, and time histories of commanded burns were recorded. Analysis of the results added support to the hypothesis that slow approach velocities are not inherently safer than their more rapid counterparts. Naive subjects were capable of docking successfully at velocities faster than those prescribed by the 0.1 percent rule even when a simulated faulty thruster disturbed the nominal trajectory. Little to no justification for slow approach velocities remains from a human factors standpoint.
Brody, Adam R.↗
NASA Marshall Space Flight Center Solar Observatory report, October - December 1990
A description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility is provided, and a summary of its observations and data reduction during Oct. - Dec. 1990 is presented. The systems that make up the facility are a magnetograph telescope, and H-alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.
Smith, James E.↗