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IEEE International Conference on Plasma Science (ICOPS)

作者： L. P. Beving S. Baalrud M. Hopkins University of Michigan Applied Physics Program Ann Arbor Michigan United States of America Department of Nuclear Engineering and Radiological Sciences University of Michigan Ann Arbor Michigan United States of America Sandia National Laboratories Applied Optical and Plasma Sciences Albuquerque New Mexico United States of America

Electric fields are commonplace in plasmas and affect transport by driving currents and in some cases instabilities. Here, we use particle-in-cell simulations to demonstrate that an instability, named the electron-field instability, can be driven by a sufficiently weak $(\$ \vert\backslash \text{textrm} \{\mathrm{E}_{-}0\vert \backslash \text{lesssim} \mathrm{T}_\mathrm{e}/(\text{ellambda}_{-}\{\text{De}\})\$) \text{and large-scale} (\$\vert\backslash \text{textrm}\{\mathrm{E}\}_0/\text{nabla}\vert \text{textrm} \{\mathrm{E}\}_{-}0\vert\backslash\text{gtrsim}100\backslash\text{lambda}_{-}\{\text{De}\}\$)$ electric field. The instability has a wavelength of around 30 electron Debye lengths and has a growth-rate that is proportional to the electric field strength. The instability occurs from electrons accelerating above the Langmuir wave phase velocity at about 5 times the electron thermal velocity. Unlike other instabilities, the electron-field instability only requires that the electrons interact with the field and does not result from the relative drift between electron populations (a beam instability) or electrons and ions (the Buneman instability). In fact, the instability occurs near the electron plasma frequency which is much higher than both the beam or Buneman instabilities. The ubiquity of macroscopic electric fields in plasmas means the electron-field instability is possible in a host of systems ranging across low-temperature, space, and fusion plasmas. When comparing our simulations to linear theory we find that both agree until a non-linear state is reached in the simulations.

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Ortho-positronium Lifetime For Soft-tissue Classification

arXiv

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arXiv 2024年

作者： Avachat, Ashish V. Mahmoud, Kholod H. Leja, Anthony G. Xu, Jiajie J. Anastasio, Mark A. Sivaguru, Mayandi Di Fulvio, Angela Department of Mechanical Engineering and Materials Science University of Pittsburgh United States Department of Bioengineering University of Illinois Urbana-Champaign United States Department of Nuclear Plasma and Radiological Engineering University of Illinois Urbana-Champaign United States Department of Clinical Medicine University of Illinois Urbana-Champaign United States Animal Care Program University of Illinois Urbana-Champaign United States Cytometry and Microscopy to Omics Facility Roy J Carver Biotechnology Center University of Illinois Urbana-Champaign United States

The objective of this work is to showcase the ortho-positronium lifetime as a probe for soft-tissue characterization. We employed positron annihilation lifetime spectroscopy to experimentally measure the three components of the positron annihilation lifetime-para-positronium (p-Ps), positron, and ortho-positronium (o-Ps)-for three types of porcine, non-fixated soft tissues ex vivo: adipose, hepatic, and muscle. Then, we benchmarked our measurements with X-ray phase-contrast imaging, which is the current state-of-the-art for soft-tissue analysis. We found that the o-Ps lifetime in adipose tissues (2.54 }0.12 ns) was approximately 20% longer than in hepatic (2.04 }0.09 ns) and muscle (2.03 }0.12 ns) tissues. In addition, the separation between the measurements for adipose tissue and the other tissues was better from o-Ps lifetime measurement than from X-ray phase-contrast imaging. This experimental study proved that the o-Ps lifetime is a viable non-invasive probe for characterizing and classifying the different soft tissues. Specifically, o-Ps lifetime as a soft-tissue characterization probe had a strong sensitivity to the lipid content that can be potentially implemented in commercial positron emission tomography scanners that feature list-mode data acquisition. © 2024, CC BY-NC-ND.

关键词： Probes

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Autonomous Electron Tomography Reconstruction with Machine Learning

arXiv

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arXiv 2023年

作者： Millsaps, William Schwartz, Jonathan Di, Zichao Wendy Jiang, Yi Hovden, Robert Department of Nuclear Engineering & Radiological Sciences University of Michigan Ann ArborMI United States Department of Materials Science and Engineering University of Michigan Ann ArborMI United States Mathematics and Computer Science Division Argonne National Laboratory LemontIL United States Advanced Photon Source Facility Argonne National Laboratory LemontIL United States Applied Physics Program University of Michigan Ann ArborMI United States

This manuscript is published in Microscopy and Microanalysis (DOI: 10.1093/micmic/ozad083). Modern electron tomography has progressed to higher resolution at lower doses by leveraging compressed sensing methods that minimize total variation (TV). However, these sparsity-emphasized reconstruction algorithms introduce tunable parameters that greatly influence the reconstruction quality. Here, Pareto front analysis shows that high-quality tomograms are reproducibly achieved when TV minimization is heavily weighted. However, in excess, compressed sensing tomography creates overly smoothed 3D reconstructions. Adding momentum to the gradient descent during reconstruction reduces the risk of over-smoothing and better ensures that compressed sensing is well behaved. For simulated data, the tedious process of tomography parameter selection is efficiently solved using Bayesian optimization with Gaussian processes. In combination, Bayesian optimization with momentum-based compressed sensing greatly reduces the required compute time-an 80% reduction was observed for the 3D reconstruction of SrTiO3 nanocubes. Automated parameter selection is necessary for large scale tomographic simulations that enable the 3D characterization of a wider range of inorganic and biological materials. © 2023, CC BY.

关键词： Compressed sensing

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Investigation of air-water two-phase flow characteristics in a 25.4 mm diameter circular pipe

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Progress in nuclear Energy 2021年 138卷 103813-103813页

作者： Wang, Dewei Shi, Shanbin Fu, Yucheng Song, Kyle Sun, Xiaodong Tentner, Adrian Liu, Yang Nuclear Engineering Program Department of Mechanical Engineering Virginia Tech 635 Price Fork Road BlacksburgVA24061 United States Department of Nuclear Engineering and Radiological Sciences University of Michigan 2355 Bonisteel Blvd Ann ArborMI48109 United States Department of Mechanical Aerospace and Nuclear Engineering Rensselaer Polytechnic Institute 110 8th Street TroyNY12180 United States Argonne National Laboratory 9700 Cass Ave LemontIL60439 United States

High-quality two-phase flow data are essential for further developing various two-phase flow models and validating two-phase flow codes. The work presented in this paper aims to perform detailed measurements of air-water two-phase flow in a 25.4 mm inner diameter pipe using several techniques developed recently. The gas-phase information is obtained by an integrated method synergizing conductivity probe, high-speed imaging system, and X-ray densitometry system while the Particle Image Velocimetry and Planar Laser-Induced Fluorescence (PIV-PLIF) technique are utilized to measure liquid-phase velocity and turbulence characteristics. Selected conditions in the bubbly, slug, and churn-turbulent flow regimes with the gas and liquid superficial velocities ranging from 0.05 to 4.99 m/s and from 0.10 to 3.88 m/s, respectively, are investigated in this work. The two-phase flow interfacial structures are visualized by both high-speed optical and X-ray images. In fully developed bubbly flows, "wall-peak" void profiles are observed, which is due to the transverse lift force effect. The gas-phase velocities share similar profiles as the liquid-phase velocity but have slightly higher magnitudes due to the buoyancy force effect. In this work, flow development in different flow regimes is investigated as well. As bubbly flows develop along the axial direction, the void profiles may change, and the discrepancy between gas-phase and liquid phase velocities will diminish in the process. © 2021 Elsevier Ltd

关键词： Two phase flow

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Simulations of the Collisional Bohm Criterion and Edge-to-Center Density Ratio Over a Range of Gas Pressure

Simulations of the Collisional Bohm Criterion and Edge-to-Ce...

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IEEE International Conference on Plasma Science (ICOPS)

作者： L. P. Beving M. Hopkins S. D. Baalrud University of Michigan Applied Physics Program Ann Arbor Michigan United States of America Applied Optical and Plasma Sciences Sandia National Laboratories Albuquerque New Mexico United States of America Department of Nuclear Engineering and Radiological Sciences University of Michigan Ann Arbor Michigan United States of America

ISBN: (纸本)9781665479264

The flux of plasma into the sheath is the product of the ion velocity and density at the sheath edge Γ=n se V se . When ionneutral collisions are rare Bohm's criterion relates the sheath edge flux to bulk parameters Γ=h l n 0 c s , where h l is the edge-tocenter density ratio and c s is the sound speed. However, when the gas pressure increases and the ion-neutral mean free path approaches the electron Debye length the ions are not expected to reach c s , but instead a collisional Bohm criterion a l c s where 0

关键词： Conferences Predictive models Ions Plasmas

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Extension and verification of multi-group JFNK-generated uniform discontinuity factors for nodal diffusion applications

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Annals of nuclear Energy 2025年 223卷

作者： Jacob D. Smith Bailey Painter Emil Fridman Dan Kotlyar Nuclear and Radiological Engineering and Medical Physics Program George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta GA 30332-0405 USA Helmholtz-Zentrum Dresden-Rossendorf Bautzner Landstraße 400 01328 Dresden Germany

Monte Carlo (MC) neutron transport codes (e.g., MCNP, Serpent) yield high-fidelity spatial flux distributions, but are relatively resource intensive – to the point of being prohibitive – for advanced neutronics analyses (e.g., multiphysics coupling, transient simulations). MC codes can also generate few-group homogenized constants for use in reduced-order homogenous flux solvers, such as nodal diffusion codes. Discontinuity factors (DFs) are commonly applied to ensure that these codes reproduce the eigenvalue, node-average fluxes, and net surface currents obtained by a MC solver. A closely related approach is to use the Jacobian-free Newton Krylov (JFNK) method to generate a set of uniform discontinuity factors (JFNK-UDFs). The primary objective of this work is to compare the Flux Discontinuity Ratios (FDRs) associated with JFNK-UDFs against FDRs associated with reference DFs (RDFs), calculated via the nodal expansion method (NEM). Multiple verification cases, ranging from a 1D multi-nodal problem to a 2D small modular reactor (SMR) core, are used to compare the FDRs and the corresponding flux solutions. The homogenous solutions obtained by the nodal diffusion code, DYN3D, yield near perfect agreement with the reference power profiles only when complemented by the generated RDFs or the JFNK-UDFs.

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Multimaterial 3D Nanoprinting of a 2 Fr Soft Robotic Microcatheter for Transarterial Chemoembolization of Liver Cancer

Multimaterial 3D Nanoprinting of a 2 Fr Soft Robotic Microca...

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IEEE International Conference on Soft Robotics (RoboSoft)

作者： Bailey M. Felix Jordi T. Andreou Sarah McHugh Jack E. McCann Olivia M. Young Molly A. Carton Dheeraj Gandhi Miroslaw Janowski Mark Fuge Axel Kreiger Clifford R. Weiss Christopher R. Bailey Ryan D. Sochol Fischell Department of Bioengineering University of Maryland College Park MD USA Department of Mechanical Engineering University of Maryland College Park MD USA Department of Diagnostic Radiology and Nuclear Medicine Program in Image Guided Neurointerventions University of Maryland School of Medicine Baltimore MD USA Department of Mechanical Engineering ETH Zurich Zurich Switzerland Department of Mechanical Engineering Johns Hopkins University Baltimore MD USA The Russell H. Morgan Department of Radiology and Radiological Science Division of Vascular and Interventional Radiology Johns Hopkins University School of Medicine Baltimore MD USA Maryland Robotics Center University of Maryland College Park MD USA Robert E. Fischell Institute for Biomedical Devices University of Maryland College Park MD USA

ISBN: (数字)9798331520205

ISBN: (纸本)9798331520212

Transarterial chemoembolization (TACE)—i.e., the delivery of chemotherapeutics directly into the vasculature of liver tumors—necessitates the use of guidewire-microcatheter systems to navigate tortuous vascular networks. These guide-wires and microcatheters typically lack effective steering controls, making successful navigation through geometrically complex anatomy challenging. Recent advancements in the area of soft microrobotics could offer a pathway to remotely steerable microcatheters at size scales relevant to TACE procedures; however, the difficulties associated with fabricating such systems have represented a critical hurdle. To overcome this barrier, here we present a multimaterial additive nanomanufacturing— or "three-dimensional (3D) nanoprinting"—strategy to achieve steerable soft robotic microcatheters that not only facilitate on-demand regulation of catheter tip deflection, but also comprise 2 French (Fr) outer dimensions (i.e., ⌀ = 666 μm) that are suitable for clinical chemoembolization of liver cancers. Specifically, we use "Two-Photon Direct Laser Writing (DLW)" to 3D nanoprint 1.5 mm-tall microcatheters capable of unidirectional tip bending of approximately 140° as well as mediating delivery of a fluidic payload. Experimental results for navigating the soft robotic microcatheter through a vascular phantom to deliver fluid payloads to target sites suggest the presented strategy holds promise for TACE as well as additional endovascular interventions and minimally invasive surgeries.

关键词： Liver cancer Actuators Navigation Deformation Phantoms Liver Soft robotics Bending Three-dimensional printing Payloads

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Collective excitations in the tetravalent lanthanide honeycomb antiferromagnet Na2PrO3

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Physical Review B 2021年第12期103卷 L121109-L121109页

作者： M. J. Daum A. Ramanathan A. I. Kolesnikov S. Calder M. Mourigal H. S. La Pierre School of Physics Georgia Institute of Technology Atlanta Georgia 30332 USA School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta Georgia 30332 USA Neutron Scattering Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Nuclear and Radiological Engineering and Medical Physics Program School of Mechanical Engineering Georgia Institute of Technology Atlanta Georgia 30332 USA

Thermomagnetic and inelastic neutron-scattering measurements on Na2PrO3 are reported. This material is an antiferromagnetic honeycomb magnet based on the tetravalent lanthanide Pr4+ and has been proposed to host dominant antiferromagnetic Kitaev interactions. These measurements reveal magnetic fluctuations in Na2PrO3 below an energy of 2 meV as well as crystal-field excitations around 230 meV. The latter energy is comparable to the scale of the spin-orbit interaction and explains both the very small effective moment of around 1.0μB per Pr4+ and the difficulty to uncover any static magnetic scattering below the ordering transition at TN= 4.6 K. By comparing the low-energy magnetic excitations in Na2PrO3 to those of the isostructural spin-only compound, Na2TbO3, a microscopic model of exchange interactions is developed that implicates dominant and surprisingly large Heisenberg exchange interactions J≈1.1(1) meV. Although antiferromagnetic Kitaev interactions with K≤0.2J cannot be excluded, the inelastic neutron-scattering data of Na2PrO3 is best explained with a Δ=1.22 easy-axis XXZ exchange anisotropy.

关键词： Spin dynamics Lanthanides Crystal-field theory Kitaev-Heisenberg model

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An Approach for 3D Microprinting Soft Robotic Surgical Tools at 1.5 French Length Scales for Endovascular Interventions

An Approach for 3D Microprinting Soft Robotic Surgical Tools...

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IEEE International Conference on Soft Robotics (RoboSoft)

作者： Bailey M. Felix Olivia M. Young Jordi T. Andreou Nicholas Portwood Kieran J. Barvenik Noah Barnes Clifford R. Weiss Christopher R. Bailey Dheeraj Gandhi Miroslaw Janowski Jeremy D. Brown Eleonora Tubaldi Mark Fuge Axel Krieger Ryan D. Sochol Department of Bioengineering University of Maryland College Park MD USA Department of Mechanical Engineering University of Maryland College Park MD USA Department of Mechanical Engineering Johns Hopkins University Baltimore MD USA The Russell H. Morgan Department of Radiology and Radiological Science Division of Vascular and Interventional Radiology Johns Hopkins University School of Medicine Baltimore MD USA Department of Diagnostic Radiology and Nuclear Medicine Program in Image Guided Neurointerventions University of Maryland School of Medicine Baltimore MD USA Maryland Robotics Center University of Maryland College Park MD USA Robert E. Fischell Institute for Biomedical Devices University of Maryland College Park MD USA

A wide range of endovascular interventions rely on surgical tools such as guidewire-catheter systems for navigating through blood vessels to, for example, deliver embolic materials, stents, and/or therapeutic agents to target sites as well as biopsy tools (e.g., forceps and punch needles) for medical diagnostics. In response to the difficulties in maneuvering such endovascular instruments safely and effectively to access intended sites in the body, researchers have developed an array of soft robotic surgical tools that harness fluidic (e.g., pneumatic or hydraulic) actuation schemes to support on-demand steering and control. Despite considerable progress, scaling these tools down to the sizes required for medical procedures such as cerebral aneurysm treatment and liver chemoembolization have been hindered by manufacturing-induced constraints. To provide a pathway to overcome these miniaturization challenges, this work presents a novel additive manufacturing strategy for 3D microprinting integrated soft actuators directly atop multilumen microfluidic tubing via “Two-Photon Direct Laser Writing (DLW)”. As an exemplar, a two-actuator tip was 3D printed onto custom dual-lumen tubing-resulting in a system akin to a 1.5 French (Fr) guidewire with a steerable tip. Experimental results revealed independent actuator control via the discretized lumens, with tip bending of approximately 60° under input pressures of 130 kPa via hydraulic actuation. These results suggest that the presented strategy could be extended to achieve new classes of fluidically actuated soft robotic surgical tools at unprecedented length scales for emerging applications in minimally invasive surgery.

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Efficient sampling of polycyclic aromatic compounds for free energy predictions through active learning

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Energy and AI 2025年

作者： Mohammed I. Radaideh Matt Raymond Paolo Elvati Jacob C. Saldinger Majdi I. Radaideh Angela Violi Department of Mechanical Engineering University of Michigan Ann Arbor MI 48109-2125 United States Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2125 United States Department of Chemical Engineering University of Michigan Ann Arbor MI 48109-2125 United States Department of Nuclear Engineering and Radiological Sciences University of Michigan Ann Arbor MI 48109-1500 United States Biophysics Program University of Michigan Ann Arbor MI 48109-1500 United States

The physical growth of Polycyclic Aromatic Compounds (PACs) to soot particles plays a significant role in understanding the chemistry of soot formation. Insights into the process can be gained from PACs’ free energy of dimerization landscape. However, because the infeasibly large space of possible PAC dimers cannot be exhaustively simulated, researchers must train machine learning models on a subset of data to impute the rest. To this end, we propose and assess an active learning approach to discovering the optimal PACs for training a machine learning model to predict PACs’ association and dissociation free energies. The comparison between active learning and random sampling showed that active learning has faster loss convergence, requiring fewer training samples to reach the same level of accuracy. The trained model accurately modeled unseen PACs and exhibited robustness against changes in the sampling space used to train the model. More broadly, this work shows how active learning can optimize the design and improve the understanding of more expensive models in specific domains.

关键词： Free energy Polycyclic aromatic compounds (PACs) Active learning Gaussian process regression Representer theorem SHAP

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