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NASA NTRS2003

Preparation of Regular Specimens for Atom Probes

A method of preparation of specimens of non-electropolishable materials for analysis by atom probes is being developed as a superior alternative to a prior method. In comparison with the prior method, the present method involves less processing time. Also, whereas the prior method yields irregularly shaped and sized specimens, the present developmental method offers the potential to prepare specimens of regular shape and size. The prior method is called the method of sharp shards because it involves crushing the material of interest and selecting microscopic sharp shards of the material for use as specimens. Each selected shard is oriented with its sharp tip facing away from the tip of a stainless-steel pin and is glued to the tip of the pin by use of silver epoxy. Then the shard is milled by use of a focused ion beam (FIB) to make the shard very thin (relative to its length) and to make its tip sharp enough for atom-probe analysis. The method of sharp shards is extremely time-consuming because the selection of shards must be performed with the help of a microscope, the shards must be positioned on the pins by use of micromanipulators, and the irregularity of size and shape necessitates many hours of FIB milling to sharpen each shard. In the present method, a flat slab of the material of interest (e.g., a polished sample of rock or a coated semiconductor wafer) is mounted in the sample holder of a dicing saw of the type conventionally used to cut individual integrated circuits out of the wafers on which they are fabricated in batches. A saw blade appropriate to the material of interest is selected. The depth of cut and the distance between successive parallel cuts is made such that what is left after the cuts is a series of thin, parallel ridges on a solid base. Then the workpiece is rotated 90 and the pattern of cuts is repeated, leaving behind a square array of square posts on the solid base. The posts can be made regular, long, and thin, as required for samples for atom-probe analysis. Because of their small volume and regularity, the amount of FIB-milling time can be much less than that of the method of sharp shards. Individual posts can be broken off for mounting in a manner similar to that of the method of sharp shards. Alternatively, the posts can be left intact on the base and the base can be cut to a small square (e.g., 3 by 3 mm) suitable for mounting in an atom probe of a type capable of accepting multiple-tip specimens. The advantage of multiple-tip specimens is the possibility of analyzing many tips without the time-consuming interchange of specimens.

Kuhlman, Kim↗

NASA NTRS2011

Pre-Finishing of SiC for Optical Applications

13 Manufacturing & Prototyping A method is based on two unique processing steps that are both based on deterministic machining processes using a single-point diamond turning (SPDT) machine. In the first step, a high-MRR (material removal rate) process is used to machine the part within several microns of the final geometry. In the second step, a low-MRR process is used to machine the part to near optical quality using a novel ductile regime machining (DRM) process. DRM is a deterministic machining process associated with conditions under high hydrostatic pressures and very small depths of cut. Under such conditions, using high negative-rake angle cutting tools, the high-pressure region near the tool corresponds to a plastic zone, where even a brittle material will behave in a ductile manner. In the high-MRR processing step, the objective is to remove material with a sufficiently high rate such that the process is economical, without inducing large-scale subsurface damage. A laser-assisted machining approach was evaluated whereby a CO2 laser was focused in advance of the cutting tool. While CVD (chemical vapor deposition) SiC was successfully machined with this approach, the cutting forces were substantially higher than cuts at room temperature under the same machining conditions. During the experiments, the expansion of the part and the tool due to the heating was carefully accounted for. The higher cutting forces are most likely due to a small reduction in the shear strength of the material compared with a larger increase in friction forces due to the thermal softening effect. The key advantage is that the hybrid machine approach has the potential to achieve optical quality without the need for a separate optical finishing step. Also, this method is scalable, so one can easily progress from machining 50-mm-diameter samples to the 250-mm-diameter mirror that NASA desires.

Rozzi, Jay↗

NASA NTRS2019

A Fundamental Plane for Gamma-Ray Pulsars

We show that the γ-ray pulsar observables, i.e., their total γ-ray luminosity, L(sub γ), spectral cutoff energy, ϵ (sub cut), stellar surface magnetic field, B(sub ⋆), and spin-down power ε, obey a relation of the form L(sub γ) = f (ϵ (sub cut), B(sub ⋆), ε ), which represents a 3D plane in their 4D logspace. Fitting the data of 88 pulsars of the second Fermi pulsar catalog, we show this relation to be L(sub γ) ∝ ϵ (sub cut)(sup 1.18±0.24 B(sub ⋆)(sup 0.17± 0.05) ε(sup 0.41±0.08), a pulsar fundamental plane (FP). We show that the observed FP is remarkably close to the theoretical relation L(sub γ) ∝ ϵ (sub cut)(sup 4/3) B(sub ⋆)(sup 1/6) ε(sup 5/12) obtained assuming that the pulsar γ-ray emission is due to curvature radiation by particles accelerated at the pulsar equatorial current sheet just outside the light cylinder. Interestingly, the FP seems incompatible with emission by synchrotron radiation. The corresponding scatter about the FP is ∼0.35 dex and can only partly be explained by the observational errors while the rest is probably due to the variation of the inclination and observer angles. We predict also that ϵ (sub cut) ∝ ε (sup 7/16) toward low ε for both young and millisecond pulsars implying that the observed death line of γ-ray pulsars is due to ϵ (sub cut) dropping below the Fermi band. Our results provide a comprehensive interpretation of the observations of γ-ray pulsars, setting requirements for successful theoretical modeling.

Kalapotharakos, Constantinos↗

DOE OSTI2017

Convolution Correction Factor Adjustments on Static PRA Models for Event Assessment

Current probabilistic risk assessment (PRA) models will contain cut sets that have time-constrained basic events such as switched components, recovery of failed components, and failures in time. For these cut sets that have multiple time-constrained events that interact (e.g., offsite power recover at the same time as multiple diesel generators fail to run), there is the possibility that the minimal cut set quantified result is too large. Since current PRA models typically assume that the accident scenario starts at “time zero,” the fails-to-run basic events use this starting time as the basis for their respective reliability models. Over time, the standard practice was to recognize this issue and accept it as part of the conservatism built into the event tree/fault tree PRA models. However, now that these same PRA models are being used in a regulatory forum, this conservatism needs to be addressed. Further, this issue exists not only for the baseline PRA results, but for deficiencies that have been observed or those that have the potential of occurrence, whether the deficiency is complete failure or just a degraded condition. We have found that this conservatism becomes very important when evaluating scenarios such as station blackout sequences and other loss of offsite power sequences. This paper will address the theory and implemented process used by the Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) PRA software. Starting with SAPHIRE version 8, the process that was developed is to calculate a “convolution correction factor” based on three distinct calculations. The first calculation is the cut set based frequency calculated via the standard event tree/fault tree PRA model (assuming all run failures start at time equal to zero). The second calculation is to perform the exact time-constrained calculation by integrating the component failure models over the time period of interest (e.g., time to recover, a mission time). For example, this exact calculation for the case of the diesel generators is to convolve their failure models with the offsite power recovery model to obtain the exact frequency. The third calculation is to produce the convolution correction factor by dividing the exact frequency calculation by the standard cut set frequency. This convolution correction factor is then applied to the PRA cut sets in order to remove the time-constrained conservatism. The process used to obtain the convolution correction factor for the baseline PRA is important; however, in this paper we also describe what happens when there is degradation of a component or a potential deficiency. These issues become very important in order to ensure that the convolution correction factor is re-calculated correctly. If the correction factor does not get re-calculated and the same baseline convolution correction factor is used, the final analysis result could be over conservative or under conservative. This paper will discuss how these issues are addressed and provide examples on how SAPHIRE automatically makes the necessary adjustments. MathCad verification results can be computed using the provided equations and input data.

99 GENERAL AND MISCELLANEOUS↗

DOE OSTI2015

Advanced dismantling techniques applied in an industrial project for the dismantling of highly activated equipment - 15446

Commissioned in 1958 on the CEA nuclear site of Marcoule (France) and shut down in 1997, the former UP1 plant was dedicated to reprocess the spent fuel from G1, G2 and G3 GCR reactors. Since 1998, a wide program for cleaning-up and dismantling the plant has been developed in order to dismantle the process equipment, eliminate any radiological risk in all buildings concerned and remove all the resulting waste. Major technical challenges are related to the wide range of complex components and equipment in the facilities such as chemical dissolvers, extractor batteries, evaporators, tanks; and to a high risk of exposure, due to the presence of fission products. To address these challenges, CEA led R and D programs to develop advanced tools for complex dismantling projects: immersive virtual reality, laser cutting techniques, special remote-controlled arms combining dexterity and high resistance to irradiation The purpose of this paper is to provide an overview of a practical implementation and to show first results of these advanced techniques on a real case: the dismantling of dissolver's equipment from the dissolution workshop of UP1 plant. ONET Technologies has been chosen by CEA to design, build and operate the overall dismantling and waste treatment system for this project. ONET Technologies designed two main subsystems to meet all the requirements for this project: first, the 'Remotely-Operated Handling and Cutting Unit' and second the 'Waste Extraction and Conditioning Unit' and the combining innovative technologies. During the design phase, the 'Immersive Virtual Reality' has been used to qualify the kinematics in the final environment and the preliminary dismantling scenario. Following a first R and D program of CEA regarding the laser cutting technique applied to nuclear decommissioning, ONET Technologies and CEA realized elementary inactive tests based on a 6 kW Nd-Yag laser source to qualify the cutting performance according to material and thickness. Main objective was to meet the safety criteria and to check the physical characteristics of waste resulting from the laser cutting operation. The Remotely-Operated Handling and Cutting Unit was equipped with a MAESTRO manipulator, resulting from ten years of research and development cooperation between CEA and Cybernetix. This manipulator, a 6 axis hydraulic manipulator-arm specifically designed to work in harsh environment, entered in its industrial phase. ONET Technologies was responsible for the overall system integration, confinement and performance. A comprehensive qualification program in real conditions has been driven during 2014. The dismantling scenario was tested with a mockup at a full scale of dissolver equipment and confirmed at this stage the expected level of performance and safety. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

Contribution of lianas to plant area index and canopy structure in a Panamanian forest

Abstract Lianas are an important component of tropical forests, where they reduce tree growth, fecundity, and survival. Competition for light from lianas may be intense; however, the amount of light that lianas intercept is poorly understood. We used a large‐scale liana‐removal experiment to quantify light interception by lianas in a Panamanian secondary forest. We measured the change in plant area index ( PAI ) and forest structure before and after cutting lianas (for 4 yr) in eight 80 m × 80 m plots and eight control plots (16 plots total). We used ground‐based Li DAR to measure the 3‐dimensional canopy structure before cutting lianas, and then annually for 2 yr afterwards. Six weeks after cutting lianas, mean plot PAI was 20% higher in control vs. liana removal plots. One yr after cutting lianas, mean plot PAI was ~17% higher in control plots. The differences between treatments diminished significantly 2 yr after liana cutting and, after 4 yr, trees had fully compensated for liana removal. Ground‐based Li DAR revealed that lianas attenuated light in the upper‐ and middle‐forest canopy layers, and not only in the upper canopy as was previously suspected. Thus, lianas compete with trees by intercepting light in the upper‐ and mid‐canopy of this forest.

Rodríguez‐Ronderos, M. Elizabeth↗

DOE OSTI2023

Random Tensor Networks with Non-trivial Links

Abstract Random tensor networks are a powerful toy model for understanding the entanglement structure of holographic quantum gravity. However, unlike holographic quantum gravity, their entanglement spectra are flat. It has therefore been argued that a better model consists of random tensor networks with link states that are not maximally entangled, i.e., have non-trivial spectra. In this work, we initiate a systematic study of the entanglement properties of these networks. We employ tools from free probability, random matrix theory, and one-shot quantum information theory to study random tensor networks with bounded and unbounded variation in link spectra, and in cases where a subsystem has one or multiple minimal cuts. If the link states have bounded spectral variation, the limiting entanglement spectrum of a subsystem with two minimal cuts can be expressed as a free product of the entanglement spectra of each cut, along with a Marchenko–Pastur distribution. For a class of states with unbounded spectral variation, analogous to semiclassical states in quantum gravity, we relate the limiting entanglement spectrum of a subsystem with two minimal cuts to the distribution of the minimal entanglement across the two cuts. In doing so, we draw connections to previous work on split transfer protocols, entanglement negativity in random tensor networks, and Euclidean path integrals in quantum gravity.

Physics↗

DOE OSTI2022

Preliminary Study on Machining of Additively Manufactured Ti-6Al-4V

We report additively manufactured metals differ from their conventionally produced counterparts due to the inherent material inhomogeneity, porosity, and thermal stress induced by the process. These differences make the machining of additively manufactured metals more difficult and cause premature tool failure or unexpected surface finish at certain conditions. This study takes the first step to investigate and identify the causes of these issues, particularly for Ti-6Al-4V. Printed and wrought samples, as well as heat treatment effect, are compared in a dry cutting condition at a cutting speed of 90 m/min in terms of cutting power, vibration, temperature, and produced surface finish. The results show a lower cutting power and more vibration for as-printed Ti samples, indicating a less ductile microstructure and inclusion of pores. Heat treatment can eliminate these phenomena. There is no significant difference found in the produced surface finish at the current cutting condition.

36 MATERIALS SCIENCE↗

DOE OSTI2018

A mathematical model of tree harvesting in age-structured forests subject to beetle infestations

In this paper, we investigate a mathematical model for age-structured forest–beetle interactions that includes harvesting of trees. The aim is to broaden the understanding of the synergistic effects of harvesting and insect infestation on the age structure of the forests and the harvesting benefit. In the first part of this study, we consider different scenarios of the forest infestation by beetles and observe that the quantitative age profile of the forest depends significantly on whether the beetle population is in its endemic or epidemic states. In the second part, we also include harvesting of the forest trees and analyze two different harvesting strategies: cutting all trees older than a certain age, and cutting a fixed proportion of trees older than a certain age. Numerical simulations are implemented to determine the optimal cutting age for both harvesting strategies. The numerical simulations reveal that, independent of the steady state of the beetle population (that is, no beetles, endemic or epidemic state) clear cutting all trees older than a given age provides a higher harvesting benefit. Our numerical simulations further indicate that to obtain a fixed harvesting yield, a forest under a beetle epidemic state has to be cut at a younger age than if the forest were at an endemic beetle state or a no-beetle state.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2023

Listeria monocytogenes loss of cultivability on carrot is associated with the formation of mesosome-like structures

Raw carrot is known to have antimicrobial activity against Listeria monocytogenes, but the mechanism of action has not been fully elucidated. In this study, we examined carrot antilisterial activity against several strains of Listeria species (including L. grayi, L. innocua, L. seeligeri, and L. welshimeri) and L. monocytogenes. A representative strain of L. monocytogenes was subsequently used for further characterizing carrot antilisterial activity. Exposure to fresh-cut carrot for 15 min resulted in a similar loss of cultivability, ranging from 2.5 to 4.7 log units, across all Listeria strains evaluated. L. monocytogenes recovered from the fresh-cut surface of different raw carrots was 1.6 to 4.1 log lower than levels obtained from paired boiled carrot samples with abolished antilisterial activity. L. monocytogenes levels recovered from fresh-cut carrot were 2.8 to 3.1 log lower when enumerated by culture-dependent methods than by the culture-independent method of PMAxx-qPCR, a qPCR assay that is performed using DNA pre-treated to selectively sequester DNA from cells with injured membranes. These results suggested that L. monocytogenes loss of cultivability on fresh-cut carrot was not associated with a loss of L. monocytogenes cell membrane integrity and putative cell viability. Transmission electron microscopy imaging revealed that L. monocytogenes rapidly formed mesosome-like structures upon exposure to carrot fresh-cut surface but not upon exposure to boiled carrot surface, suggesting there may be an association between the formation of these mesosome-like structures and a loss of cultivability in L. monocytogenes. As a result, further research is necessary to conclude the causality of this association.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2015

Prospective, Multicenter Validation Study of Magnetic Resonance Volumetry for Response Assessment After Preoperative Chemoradiation in Rectal Cancer: Can the Results in the Literature be Reproduced?

Purpose: To review the available literature on tumor size/volume measurements on magnetic resonance imaging for response assessment after chemoradiotherapy, and validate these cut-offs in an independent multicenter patient cohort. Methods and Materials: The study included 2 parts. (1) Review of the literature: articles were included that assessed the accuracy of tumor size/volume measurements on magnetic resonance imaging for tumor response assessment. Size/volume cut-offs were extracted; (2) Multicenter validation: extracted cut-offs from the literature were tested in a multicenter cohort (n=146). Accuracies were calculated and compared with reported results from the literature. Results: The review included 14 articles, in which 3 different measurement methods were assessed: (1) tumor length; (2) 3-dimensonial tumor size; and (3) whole volume. Study outcomes consisted of (1) complete response (ypT0) versus residual tumor; (2) tumor regression grade 1 to 2 versus 3 to 5; and (3) T-downstaging (ypT<cT). In the multicenter cohort, best results were obtained for the validation of the whole-volume measurements, in particular for the outcome ypT0 (accuracy 44%-80%), with the optimal cut-offs being 1.6 cm{sup 3} (after chemoradiation therapy) and a volume reduction of Δ80% to 86.6%. Accuracies for whole-volume measurements to assess tumor regression grade 1 to 2 were 52% to 61%, and for T-downstaging 51% to 57%. Overall accuracies for tumor length ranged between 48% and 53% and for 3D size measurement between 52% and 56%. Conclusions: Magnetic resonance volumetry using whole-tumor volume measurements can be helpful in rectal cancer response assessment with selected cut-off values. Measurements of tumor length or 3-dimensional tumor size are not helpful. Magnetic resonance volumetry is mainly accurate to assess a complete tumor response (ypT0) after chemoradiation therapy (accuracies up to 80%).

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2020

High accuracy in-situ direct gas analysis of Li-ion batteries

Cycling of lithium-ion batteries containing Ni-rich NMC cathodes at high voltage involves intense gas generation. From the safety standpoint, it is critical to understand how different gas species respond to changes of upper cut-off voltages. In this manuscript, we introduce a novel experimental set up for real-time analysis of gas generation in prismatic pouch cells. In a typical experiment, a lithium-ion pouch cell is directly connected to a quadruple mass spectrometer by glass capillary. Pressure difference helps move the generated gases to the mass spectrometer column for full analysis. The gaseous species are probed during both formation cycle and aging cycles in Li-ion pouch cells comprising NMC811 cathode and graphite anode. The gases are generated upon the creation of the solid electrolyte interphase on graphite during the first formation charge. Besides ethylene gas, C 2 H 4 , whose occurrence is related to the decomposition of ethylene carbonate, a minor solvent decomposition happened at a lower voltage is demonstrated to be associated with residue water on the electrode. For aging cycles, three upper cut-off voltages have been selected to investigate the gas evolution behavior upon charging to 4.2, 4.4 and 4.6 V. Higher upper cut-off voltages do not affect the amount of O 2 measured as a part of the generated oxygen could have reacted with electrolytes. Quite similar and low amounts of O 2 remain in the cells upon charging to the selected cut-off voltages. On the other hand, the generation of CO 2 has been found to be very sensitive to upper cut-off voltage. During similar aging cycles, 6167 nmol $g_{NMC}^{-1}$ of CO 2 is generated at 4.6 V, versus 1650 nmol $g_{NMC}^{-1}$ of CO 2 at 4.4 V, versus 91 nmol $g_{NMC}^{-1}$ of CO 2 at 4.2 V.

25 ENERGY STORAGE↗

DOE OSTI2022

Evaluation of automated stability testing in machining through closed-loop control and Bayesian machine learning

Here, this paper describes a system for automated identification of the optimal stable cutting parameters in milling through Bayesian machine learning and closed-loop control. The closed-loop control system consists of a process monitoring architecture, an analysis framework, and a feedback mechanism. The analysis framework consists of a Bayesian machine learning algorithm that learns a stability map given test results. The learned stability map is used to select parameters for stability testing using an expected improvement in the material removal rate criterion. The test parameters are communicated to the machine controller to complete the test cut through a feedback mechanism. The test cuts were monitored using an audio signal; the stability of the test cut was determined by analyzing the frequency content of the audio signal. The test result was fed back to the Bayesian learning algorithm to complete the loop. Experimental results demonstrate that the system can identify the optimal stable parameters without information about the cutting force model or the structural dynamics. The system provides a low-cost method for optimal stable parameter identification in an industrial environment.

Chatter↗

DOE OSTI2021

Autonomous reinforcement learning agent for stretchable kirigami design of 2D materials

Abstract Mechanical behavior of 2D materials such as MoS 2 can be tuned by the ancient art of kirigami. Experiments and atomistic simulations show that 2D materials can be stretched more than 50% by strategic insertion of cuts. However, designing kirigami structures with desired mechanical properties is highly sensitive to the pattern and location of kirigami cuts. We use reinforcement learning (RL) to generate a wide range of highly stretchable MoS 2 kirigami structures. The RL agent is trained by a small fraction (1.45%) of molecular dynamics simulation data, randomly sampled from a search space of over 4 million candidates for MoS 2 kirigami structures with 6 cuts. After training, the RL agent not only proposes 6-cut kirigami structures that have stretchability above 45%, but also gains mechanistic insight to propose highly stretchable (above 40%) kirigami structures consisting of 8 and 10 cuts from a search space of billion candidates as zero-shot predictions.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Quantum Max-flow/Min-cut

The classical max-flow min-cut theorem describes transport through certain idealized classical networks. We consider the quantum analog for tensor networks. By associating an integral capacity to each edge and a tensor to each vertex in a flow network, we can also interpret it as a tensor network and, more specifically, as a linear map from the input space to the output space. The quantum max-flow is defined to be the maximal rank of this linear map over all choices of tensors. The quantum min-cut is defined to be the minimum product of the capacities of edges over all cuts of the tensor network. We show that unlike the classical case, the quantum max-flow=min-cut conjecture is not true in general. Under certain conditions, e.g., when the capacity on each edge is some power of a fixed integer, the quantum max-flow is proved to equal the quantum min-cut. However, concrete examples are also provided where the equality does not hold. We also found connections of quantum max-flow/min-cut with entropy of entanglement and the quantum satisfiability problem. We speculate that the phenomena revealed may be of interest both in spin systems in condensed matter and in quantum gravity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2014

An optimized method to identify RR Lyrae stars in the SDSS×Pan-STARRS1 overlapping area using a bayesian generative technique

We present a method for selecting RR Lyrae (RRL) stars (or other types of variable stars) in the absence of a large number of multi-epoch data and light curve analyses. Our method uses color and variability selection cuts that are defined by applying a Gaussian Mixture Bayesian Generative Method (GMM) on 636 pre-identified RRL stars instead of applying the commonly used rectangular cuts. Specifically, our method selects 8115 RRL candidates (heliocentric distances < 70 kpc) using GMM color cuts from the Sloan Digital Sky Survey (SDSS) and GMM variability cuts from the Panoramic Survey Telescope and Rapid Response System 1 3π survey (PS1). Comparing our method with the Stripe 82 catalog of RRL stars shows that the efficiency and completeness levels of our method are ∼77% and ∼52%, respectively. Most contaminants are either non-variable main-sequence stars or stars in eclipsing systems. The method described here efficiently recovers known stellar halo substructures. It is expected that the current completeness and efficiency levels will further improve with the additional PS1 epochs (∼3 epochs per filter) that will be observed before the conclusion of the survey. A comparison between our efficiency and completeness levels using the GMM method to the efficiency and completeness levels using rectangular cuts that are commonly used yielded a significant increase in the efficiency level from ∼13% to ∼77% and an insignificant change in the completeness levels. Hence, we favor using the GMM technique in future studies. Although we develop it over the SDSS×PS1 footprint, the technique presented here would work well on any multi-band, multi-epoch survey for which the number of epochs is limited.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

DeepSZ: identification of Sunyaev–Zel’dovich galaxy clusters using deep learning

Galaxy clusters identified via the Sunyaev–Zel’dovich (SZ) effect are a key ingredient in multiwavelength cluster cosmology. In this paper, we present and compare three methods of cluster identification: the standard matched filter (MF) method in SZ cluster finding, a convolutional neural networks (CNN), and a ‘combined’ identifier. We apply the methods to simulated millimeter maps for several observing frequencies for a survey similar to SPT-3G, the third-generation camera for the South Pole Telescope. The MF requires image pre-processing to remove point sources and a model for the noise, while the CNN requires very little pre-processing of images. Additionally, the CNN requires tuning of hyperparameters in the model and takes cut-out images of the sky as input, identifying the cut-out as cluster-containing or not. We compare differences in purity and completeness. The MF signal-to-noise ratio depends on both mass and redshift. Our CNN, trained for a given mass threshold, captures a different set of clusters than the MF, some with signal-to-noise-ratio below the MF detection threshold. However, the CNN tends to mis-classify cut-out whose clusters are located near the edge of the cut-out, which can be mitigated with staggered cut-out. We leverage the complementarity of the two methods, combining the scores from each method for identification. The purity and completeness are both 0.61 for MF, and 0.59 and 0.61 for CNN. The combined method yields 0.60 and 0.77, a significant increase for completeness with a modest decrease in purity. We advocate for combined methods that increase the confidence of many low signal-to-noise clusters.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2024

Process damping identification using Bayesian learning and time domain simulation

Process damping can provide improved machining productivity by increasing the stability limit at low spindle speeds. However, existing methods for identifying process damping models experimentally require specialized setups and/or multiple cutting tests. While the phenomenon is well known, the modeling challenges limit pre-process parameter selection that leverages the potential increases in material removal rates. This paper proposes a physics-informed Bayesian method that can identify the cutting force and process damping models from a limited set of test cuts without requiring direct measurements of cutting force or vibration. The method uses time domain simulation to incorporate process damping and provide a basis for test selection. Here, new strategies for efficient sampling and dimensionality reduction are applied to lower computation time and minimize the effect of model error. The proposed method is demonstrated and the identified cutting and damping force coefficients are compared to values obtained using machining tests and least-squares fitting.

42 ENGINEERING↗