217 research outputs found
A Physics-informed Machine Learning-based Control Method for Nonlinear Dynamic Systems with Highly Noisy Measurements
This study presents a physics-informed machine learning-based control method
for nonlinear dynamic systems with highly noisy measurements. Existing
data-driven control methods that use machine learning for system identification
cannot effectively cope with highly noisy measurements, resulting in unstable
control performance. To address this challenge, the present study extends
current physics-informed machine learning capabilities for modeling nonlinear
dynamics with control and integrates them into a model predictive control
framework. To demonstrate the capability of the proposed method we test and
validate with two noisy nonlinear dynamic systems: the chaotic Lorenz 3 system,
and turning machine tool. Analysis of the results illustrate that the proposed
method outperforms state-of-the-art benchmarks as measured by both modeling
accuracy and control performance for nonlinear dynamic systems under high-noise
conditions
A neural network approach for chatter prediction in turning
[EN] Machining processes, including turning, are a critical capability for discrete part production. One limitation to high material removal rates and reduced cost in these processes is chatter, or unstable spindle speed-chip width combinations that exhibit self-excited vibration. In this paper, an artificial neural network (ANN) is applied to model turning stability. The analytical stability limit is used to generate a data set that trains the ANN. It is observed that the number and distribution of training points influences the ability of the ANN model to capture the smaller, more closely spaced lobes that occur at lower spindle speeds. Overall, the ANN is successful (>90% accuracy) at predicting the stability behavior after appropriate training.The authors gratefully acknowledge financial support from the UNC ROI program. Elena Perez-Bernabeu and Miguel Selles also acknowledge support from Universitat Politenica de Valencia (PAID-00-17). Additionally, some of the neural net figures and the 10-fold cross validation figures are based on the TikZ codes provided on StackExchange-TeX by various users. Harish Cherukuri would like to thank them for their valuable advice.Cherukuri, H.; Pérez Bernabeu, E.; Sellés, M.; Schmitz, TL. (2019). A neural network approach for chatter prediction in turning. Procedia Manufacturing. 34:885-892. https://doi.org/10.1016/j.promfg.2019.06.1598858923
Immune Reactivity and Pseudoprogression or Tumor Flare in a Serially Biopsied Neuroendocrine Patient Treated with the Epigenetic Agent RRx-001.
Neuroendocrine tumors (NETs) are grouped together as a single class on the basis of histologic appearance, immunoreactivity for the neuroendocrine markers chromogranin A and synaptophysin, and potential secretion of hormones, neurotransmitters, neuromodulators and neuropeptides. Nevertheless, despite these common characteristics, NETs differ widely in terms of their natural histories: high-grade NETs are clinically aggressive and, like small cell lung cancer, which they most closely resemble, tend to respond to cisplatin and etoposide. In contrast, low-grade NETs, which as a rule progress and behave indolently, do not. In either case, the treatment strategy, apart from potentially curative surgical resection, is very poorly defined. This report describes the case of a 28-year-old white male with a diagnosis of high-grade NET of undetermined primary site metastatic to the lymph nodes, skin and paraspinal soft tissues, treated with the experimental anticancer agent RRx-001, in the context of a phase II clinical trial called TRIPLE THREAT (NCT02489903); serial sampling of tumor material through repeat biopsies demonstrated an intratumoral inflammatory response, including the amplification of infiltrating T cells, which correlated with clinical and symptomatic benefit. This case suggests that pseudoprogression or RRx-001-induced enlargement of tumor lesions, which has been previously described for several RRx-001-treated patients, is the result of tumoral lymphocyte infiltration
Contemporary particle-in-cell approach to laser-plasma modelling
Particle-in-cell (PIC) methods have a long history in the study of laser-plasma interactions. Early electromagnetic codes used the Yee staggered grid for field variables combined with a leapfrog EM-field update and the Boris algorithm for particle pushing. The general properties of such schemes are well documented. Modern PIC codes tend to add to these high-order shape functions for particles, Poisson preserving field updates, collisions, ionisation, a hybrid scheme for solid density and high-field QED effects. In addition to these physics packages, the increase in computing power now allows simulations with real mass ratios, full 3D dynamics and multi-speckle interaction. This paper presents a review of the core algorithms used in current laser-plasma specific PIC codes. Also reported are estimates of self-heating rates, convergence of collisional routines and test of ionisation models which are not readily available elsewhere. Having reviewed the status of PIC algorithms we present a summary of recent applications of such codes in laser-plasma physics, concentrating on SRS, short-pulse laser-solid interactions, fast-electron transport, and QED effects
Effects of radial immersion and cutting direction on chatter instability
ABSTRACT Low radial immersion end-milling involves intermittent cutting. If the tool is flexible, its motion in both the x-and ydirections affects the chip load and cutting forces, leading to chatter instability under certain conditions. Interrupted cutting complicates stability analysis by imposing sharp periodic variations in the dynamic model. Stability predictions for the 2-DOF model differ significantly from prior 1-DOF models of interrupted cutting. In this paper stability boundaries of the 2-DOF milling process are determined by three techniques and compared: (1) a frequency-domain technique developed b
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
Clinical, laboratory and pathological findings in dogs experimentally infected with Angiostrongylus vasorum
The aim of this comparative study was to investigate the development of clinical signs and accompanying haematological, coproscopic and pathological findings as a basis for the monitoring of health condition of Angiostrongylus vasorum infected dogs. Six beagles were orally inoculated with 50 (n = 3) or 500 (n = 3) A. vasorum third stage larvae (L3) obtained from experimentally infected Biomphalaria glabrata snails. Two dogs were treated with moxidectin/imidacloprid spot-on solution and two further dogs with an oral experimental compound 92 days post infection (dpi), and were necropsied 166 dpi. Two untreated control dogs were necropsied 97 dpi. Prepatency was 47-49 days. Dogs inoculated with 500 L3 exhibited earlier (from 42 dpi) and more severe respiratory signs. Clinical signs resolved 12 days after treatment and larval excretion stopped within 20 days in all four treated dogs. Upon necropsy, 10 and 170 adult worms were recovered from the untreated dogs inoculated with 50 and 500 L3, respectively. Adult worms were also found in two treated dogs, in the absence of L1 or eggs. Despite heavy A. vasorum infection load and severe pulmonary changes including vascular thrombosis, only mild haematological changes were observed. Eosinophilia was absent but the presence of plasma cells was observed. Neutrophilic leucocytes showed a transient increase but only after treatment. Signs for coagulopathies were slight; nevertheless coagulation parameters were inoculation dose dependent. Ten weeks after treatment pulmonary fibrosis was still present. Infections starting from 50 L3 of A. vasorum had a massive impact on lung tissues and therefore on the health of affected dogs, particularly after prepatency, although only mild haematological abnormalities were evident
Country Concepts and the Rational Actor Trap: Limitations to Strategic Management of International NGOs
Growing criticism of inefficient development aid demanded new planning instruments of donors, including international NGOs (INGOs). A reorientation from isolated project-planning towards holistic country concepts and the increasing rationality of a result-orientated planning process were seen as answer. However, whether these country concepts - newly introduced by major INGOs too - have increased the efficiency of development cooperation is open to question. Firstly, there have been counteracting external factors, like the globalization of the aid business, that demanded structural changes in the composition of INGO portfolios towards growing short-term humanitarian aid; this was hardly compatible with the requirements of medium-term country planning. Secondly, the underlying vision of rationality as a remedy for the major ills of development aid was in itself a fallacy. A major change in the methodology of planning, closely connected with a shift of emphasis in the approach to development cooperation, away from project planning and service delivery, towards supporting the socio-cultural and political environment of the recipient communities, demands a reorientation of aid management: The most urgent change needed is by donors, away from the blinkers of result-orientated planning towards participative organizational cultures of learning.Des critiques croissantes de l'aide au dĂ©veloppement inefficace exigent de nouveaux instruments de planification des bailleurs de fonds, y compris les ONG internationales (ONGI). Une rĂ©orientation de la planification des projets isolĂ©s vers des concepts holistiques de la planification de lâaide par pays ainsi que la rationalitĂ© croissante d'un processus de planification orientĂ©e vers les rĂ©sultats ont Ă©tĂ© considĂ©rĂ©s comme rĂ©ponse. Toutefois, si ces concepts de pays - nouvellement introduites par les grandes OING eux aussi - ont augmentĂ© l'efficacitĂ© de la coopĂ©ration au dĂ©veloppement est ouvert Ă la question. Tout d'abord, il y a eu lâimpact des facteurs externes, comme la mondialisation de l'entreprise de l'aide, qui a exigĂ© des changements structurels dans la composition des portefeuilles des OING vers la croissance de l'aide humanitaire Ă court terme. Cela Ă©tait difficilement compatible avec les exigences de l'amĂ©nagement du territoire Ă moyen terme. DeuxiĂšmement, la vision sous-jacente de la rationalitĂ© accrue de la planification, concentrĂ© sur les resultats, comme un remĂšde pour les grands maux de l'aide au dĂ©veloppement Ă©tait en soi une erreur. Un changement majeur dans la mĂ©thodologie de la planification, Ă©troitement liĂ©e Ă un changement d'orientation dans l'approche de la coopĂ©ration au dĂ©veloppement, qui nâest pas concentrer sur planification du projet et la prestation de services, mais qui soutienne l'environnement socio-culturel et politique des communautĂ©s bĂ©nĂ©ficiaires, exige une rĂ©orientation de la gestion de lâaide: Le changement le plus urgent est un changement par les donateurs eux-mĂȘmes, qui devrait implanter des cultures de collaboration Ă©troit avec les partenaires et la population locale
Search for dark matter produced in association with bottom or top quarks in âs = 13 TeV pp collisions with the ATLAS detector
A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fbâ1 of protonâproton collision data recorded by the ATLAS experiment at âs = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements
The Science Performance of JWST as Characterized in Commissioning
This paper characterizes the actual science performance of the James Webb
Space Telescope (JWST), as determined from the six month commissioning period.
We summarize the performance of the spacecraft, telescope, science instruments,
and ground system, with an emphasis on differences from pre-launch
expectations. Commissioning has made clear that JWST is fully capable of
achieving the discoveries for which it was built. Moreover, almost across the
board, the science performance of JWST is better than expected; in most cases,
JWST will go deeper faster than expected. The telescope and instrument suite
have demonstrated the sensitivity, stability, image quality, and spectral range
that are necessary to transform our understanding of the cosmos through
observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures;
https://iopscience.iop.org/article/10.1088/1538-3873/acb29
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