431 research outputs found

    Synthesis and characterization of tin sulfide nanomaterials and thin films by pulsed laser ablation in liquid.

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    Tin monosulfide (SnS) and tin disulfide (SnS2) nanoparticles were synthesized by employing pulsed laser ablation in liquid (PLAL) technique in various organic solvents where the influence of different laser parameters and solvents were investigated. Spray deposition technique has been implemented as a method to fabricate thin films of these materials where the spray parameters were optimized depending on the solvent and material. Combination of pulsed laser ablation in liquid with spray technique was used for the first time in the work. In the case of SnS nanoparticles, they were first prepared by laser ablation in isopropanol and N,N-dimethyl formamide and thin films of the same were deposited by spraying the laser generated nanocolloids onto heated substrates where the films fabricated were characterized for their structure, morphology and opto-electronic and electrochemical properties. Moreover, colloidal graphene oxide was mixed with SnS nanocolloids at different volume concentrations (0.1%, 0.5% and 1%) to obtain SnS: GO or SnS: rGO thin films where the nanocomposite films showed enhanced opto-electronic and electrochemical properties compared to the pristine SnS thin films. A solar cell configuration of glass/ CdS/ Sb2S3/ SnS:rGO was also fabricated using the SnS: rGO layer as the absorber and photoconversion efficiency of 2.3% was achieved. In the case of SnS2 nanoparticles, effect of four different solvents (acetone, isopropanol, ethanol and DMF) and two different laser wavelengths (1064 nm and 532 nm) on the morphologies and properties of SnS2 particles were studied in detail. Furthermore, influence of ablation fluence, liquid medium temperature and post irradiation on the SnS2 nanoparticles were investigated in detail and the hydrogen evolution activity of these nanoparticles were tested in acidic medium. Electrochemical properties of the SnS2 thin films deposited from SnS2 nanoparticles in ethanol and isopropanol and after different post annealing treatments (200, 250 and 300 ℃) were analyzed and the results were compared. For majority of the cases, the prepared nanoparticles and thin films were analyzed for their structure, crystalline nature, composition and morphology by XRD, Raman, XPS, TEM and SEM whereas the optical, opto-electronic and electrochemical properties were elucidated using the UVVisible spectroscopy, I-V measurements under dark and illumination and electrochemical measurements respectively

    Synthesis of surfactant free stable nanofluids based on barium hexaferrite by pulsed laser ablation in liquid

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    Barium hexaferrite nanofluids based on five different solvents have been prepared by employing Pulsed Laser Ablation in Liquid (PLAL) at two different wavelengths of 532 nm and 1064 nm. They were then characterized using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), UV-Vis spectroscopy, and Vibrating Sample Magnetometry (VSM). The chemical states of the ablated nanoparticles were identified from XPS analysis and found to be matching with that of the target. The crystallinity of the nanoparticles were confirmed from high resolution TEM (HRTEM) images and SAED patterns. It is found that different liquid environments lead to the formation of barium ferrite nanoparticles with different particle diameters. The plausible mechanism involved in this process is discussed. This study can pave way for the synthesis of stable magnetic nanofluids of permanent magnets. Further, this technique could be utilized for tailoring the morphology of nanoparticles with a judicious choice of the solvents and other ablation parameter

    Automating Spacecraft Analysis: The Era of Ontological Modeling & Simulation

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    Verification by analysis is a predicted compliance of a design to imposed requirements. The levels of performance specified by performance requirements can be related to Technical Performance Measures (TPM) in a Model-Based Systems Engineering (MBSE) environment, but engineers performing verification by analysis are not commonly versed in professional Systems Engineering (SE) techniques or modeling languages such as SysML. As the formal application of Systems Engineering (SE) results in a diminution of time, effort, and money for large-scale projects, enabling technical engineers performing verification by analysis to contribute to MBSE improvements in the course of their daily work is financially incentivized. Ontologies applied to technical analysis methodologies are shown to improve the quality of verification by analysis activities while adhering to professional organization standards such as the International Council on Systems Engineering (INCOSE) SE Handbook and the National Aeronautics and Space Administration (NASA) standard 7009A: Standard for Models and Simulations

    MUSiC : a model-unspecific search for new physics in proton-proton collisions at root s=13TeV

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    Results of the Model Unspecific Search in CMS (MUSiC), using proton-proton collision data recorded at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1), are presented. The MUSiC analysis searches for anomalies that could be signatures of physics beyond the standard model. The analysis is based on the comparison of observed data with the standard model prediction, as determined from simulation, in several hundred final states and multiple kinematic distributions. Events containing at least one electron or muon are classified based on their final state topology, and an automated search algorithm surveys the observed data for deviations from the prediction. The sensitivity of the search is validated using multiple methods. No significant deviations from the predictions have been observed. For a wide range of final state topologies, agreement is found between the data and the standard model simulation. This analysis complements dedicated search analyses by significantly expanding the range of final states covered using a model independent approach with the largest data set to date to probe phase space regions beyond the reach of previous general searches.Peer reviewe

    Measurement of prompt open-charm production cross sections in proton-proton collisions at root s=13 TeV

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    The production cross sections for prompt open-charm mesons in proton-proton collisions at a center-of-mass energy of 13TeV are reported. The measurement is performed using a data sample collected by the CMS experiment corresponding to an integrated luminosity of 29 nb(-1). The differential production cross sections of the D*(+/-), D-+/-, and D-0 ((D) over bar (0)) mesons are presented in ranges of transverse momentum and pseudorapidity 4 < p(T) < 100 GeV and vertical bar eta vertical bar < 2.1, respectively. The results are compared to several theoretical calculations and to previous measurements.Peer reviewe

    Development and validation of HERWIG 7 tunes from CMS underlying-event measurements

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    This paper presents new sets of parameters (“tunes”) for the underlying-event model of the HERWIG7 event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in HERWIG7, and are obtained from a fit to minimum-bias data collected by the CMS experiment at s=0.9, 7, and 13Te. The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the dat

    Measurement of the W gamma Production Cross Section in Proton-Proton Collisions at root s=13 TeV and Constraints on Effective Field Theory Coefficients

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    A fiducial cross section for W gamma production in proton-proton collisions is measured at a center-of-mass energy of 13 TeV in 137 fb(-1) of data collected using the CMS detector at the LHC. The W -> e nu and mu nu decay modes are used in a maximum-likelihood fit to the lepton-photon invariant mass distribution to extract the combined cross section. The measured cross section is compared with theoretical expectations at next-to-leading order in quantum chromodynamics. In addition, 95% confidence level intervals are reported for anomalous triple-gauge couplings within the framework of effective field theory.Peer reviewe

    Observation of the Production of Three Massive Gauge Bosons at root s=13 TeV

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    The first observation is reported of the combined production of three massive gauge bosons (VVV with V = W, Z) in proton-proton collisions at a center-of-mass energy of 13 TeV. The analysis is based on a data sample recorded by the CMS experiment at the CERN LHC corresponding to an integrated luminosity of 137 fb(-1). The searches for individualWWW, WWZ, WZZ, and ZZZ production are performed in final states with three, four, five, and six leptons (electrons or muons), or with two same-sign leptons plus one or two jets. The observed (expected) significance of the combinedVVV production signal is 5.7 (5.9) standard deviations and the corresponding measured cross section relative to the standard model prediction is 1.02(-0.23)(+0.26). The significances of the individual WWW and WWZ production are 3.3 and 3.4 standard deviations, respectively. Measured production cross sections for the individual triboson processes are also reported

    Reconstruction of signal amplitudes in the CMS electromagnetic calorimeter in the presence of overlapping proton-proton interactions

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    A template fitting technique for reconstructing the amplitude of signals produced by the lead tungstate crystals of the CMS electromagnetic calorimeter is described. This novel approach is designed to suppress the contribution to the signal of the increased number of out-of-time interactions per beam crossing following the reduction of the accelerator bunch spacing from 50 to 25 ns at the start of Run 2 of the LHC. Execution of the algorithm is sufficiently fast for it to be employed in the CMS high-level trigger. It is also used in the offline event reconstruction. Results obtained from simulations and from Run 2 collision data (2015-2018) demonstrate a substantial improvement in the energy resolution of the calorimeter over a range of energies extending from a few GeV to several tens of GeV.Peer reviewe

    Performance of the CMS muon trigger system in proton-proton collisions at √s = 13 TeV

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    The muon trigger system of the CMS experiment uses a combination of hardware and software to identify events containing a muon. During Run 2 (covering 2015-2018) the LHC achieved instantaneous luminosities as high as 2 × 10 cm s while delivering proton-proton collisions at √s = 13 TeV. The challenge for the trigger system of the CMS experiment is to reduce the registered event rate from about 40 MHz to about 1 kHz. Significant improvements important for the success of the CMS physics program have been made to the muon trigger system via improved muon reconstruction and identification algorithms since the end of Run 1 and throughout the Run 2 data-taking period. The new algorithms maintain the acceptance of the muon triggers at the same or even lower rate throughout the data-taking period despite the increasing number of additional proton-proton interactions in each LHC bunch crossing. In this paper, the algorithms used in 2015 and 2016 and their improvements throughout 2017 and 2018 are described. Measurements of the CMS muon trigger performance for this data-taking period are presented, including efficiencies, transverse momentum resolution, trigger rates, and the purity of the selected muon sample. This paper focuses on the single- and double-muon triggers with the lowest sustainable transverse momentum thresholds used by CMS. The efficiency is measured in a transverse momentum range from 8 to several hundred GeV
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