Journal articles: 'Shape parametrisation'

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BARTEL, JOHANN, and KRZYSZTOF POMORSKI. "JACOBI SHAPE TRANSITIONS WITHIN THE LSD MODEL AND THE SKYRME-ETF APPROACH." International Journal of Modern Physics E 17, no. 01 (January 2008): 100–109. http://dx.doi.org/10.1142/s0218301308009598.

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The "Modified Funny-Hills parametrisation" is used together with the Lublin-Strasbourg Drop Model to evaluate the stability of rotating nuclei. The Jacobi transition into triaxial shapes is studied. By a comparison with selfconsistent semiclassical calculations in the framework of the Extended Thomas-Fermi method, the validity of the present approach is demonstrated and possible improvements are indicated.

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Martinelli, Massimiliano, and François Beux. "Multi-level gradient-based methods and parametrisation in aerodynamic shape design." European Journal of Computational Mechanics 17, no. 1-2 (January 2008): 169–97. http://dx.doi.org/10.3166/remn.17.169-197.

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Mesnil, Romain, Cyril Douthe, Christiane Richter, and Olivier Baverel. "Fabrication-aware shape parametrisation for the structural optimisation of shell structures." Engineering Structures 176 (December 2018): 569–84. http://dx.doi.org/10.1016/j.engstruct.2018.09.026.

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Tomášik, Boris, Jakub Cimerman, and Christopher Plumberg. "Averaging and the Shape of the Correlation Function." Universe 5, no. 6 (June 13, 2019): 148. http://dx.doi.org/10.3390/universe5060148.

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A brief pedagogical introduction to correlation femtoscopy is given. We then focus on the shape of the correlation function and discuss the possible reasons for its departure from the Gaussian form and better reproduction with a Lévy stable distribution. With the help of Monte Carlo simulations based on asymmetric extension of the Blast-Wave model with resonances we demonstrate possible influence of averaging over many events and integrating over wide momentum bins on the shape of the correlation function. We also show that the shape is strongly influenced by the use of the one-dimensional parametrisation in the q i n v variable.

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Nerlo-Pomorska, B., K. Pomorski, J. Bartel, and H. Molique. "On Shape Isomers of Pt–Pb Isotopes in the 4D Fourier Parametrisation." Acta Physica Polonica B Proceedings Supplement 13, no. 3 (2020): 449. http://dx.doi.org/10.5506/aphyspolbsupp.13.449.

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Kijanski, Wojciech, and Franz-Joseph Barthold. "Two-scale shape optimisation based on numerical homogenisation techniques and variational sensitivity analysis." Computational Mechanics 67, no. 4 (March 6, 2021): 1021–40. http://dx.doi.org/10.1007/s00466-020-01955-6.

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AbstractThis contribution presents a theoretical and computational framework for two-scale shape optimisation of nonlinear elastic structures. Particularly, minimum compliance optimisation problems with composite (matrix-inclusion) microstructures subjected to static loads and volume-type design constraints are focused. A homogenisation-based FE$$^2$$ 2 scheme is extended by an enhanced formulation of variational (shape) sensitivity analysis based on Noll’s intrinsic, frame-free formulation of continuum mechanics. The obtained overall two-scale sensitivity information couples shape variations across micro- and macroscopic scales. A numerical example demonstrates the capabilities of the proposed variational sensitivity analysis and the (shape) optimisation framework. The investigations involve a mesh morphing scheme for the design parametrisation at both macro- and microscopic scales.

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Ugail, H., and M. J. Wilson. "Efficient shape parametrisation for automatic design optimisation using a partial differential equation formulation." Computers & Structures 81, no. 28-29 (November 2003): 2601–9. http://dx.doi.org/10.1016/s0045-7949(03)00321-3.

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Capitán-Agudo, Carlos, Beatriz Pontes, Pedro Gómez-Gálvez, and Pablo Vicente-Munuera. "Evolutionary 3D Image Segmentation of Curve Epithelial Tissues of Drosophila melanogaster." Applied Sciences 11, no. 14 (July 12, 2021): 6410. http://dx.doi.org/10.3390/app11146410.

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Analysing biological images coming from the microscope is challenging; not only is it complex to acquire the images, but also the three-dimensional shapes found on them. Thus, using automatic approaches that could learn and embrace that variance would be highly interesting for the field. Here, we use an evolutionary algorithm to obtain the 3D cell shape of curve epithelial tissues. Our approach is based on the application of a 3D segmentation algorithm called LimeSeg, which is a segmentation software that uses a particle-based active contour method. This program needs the fine-tuning of some hyperparameters that could present a long number of combinations, with the selection of the best parametrisation being highly time-consuming. Our evolutionary algorithm automatically selects the best possible parametrisation with which it can perform an accurate and non-supervised segmentation of 3D curved epithelial tissues. This way, we combine the segmentation potential of LimeSeg and optimise the parameters selection by adding automatisation. This methodology has been applied to three datasets of confocal images from Drosophila melanogaster, where a good convergence has been observed in the evaluation of the solutions. Our experimental results confirm the proper performing of the algorithm, whose segmented images have been compared to those manually obtained for the same tissues.

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Corrales, Marta Lucia, and Edilberto Cepeda-Cuervo. "A Bayesian Approach to Mixed Gamma Regression Models." Revista Colombiana de Estadística 42, no. 1 (January 1, 2019): 81–99. http://dx.doi.org/10.15446/rce.v42n1.69334.

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Gamma regression models are a suitable choice to model continuous variables that take positive real values. This paper presents a gamma regression model with mixed effects from a Bayesian approach. We use the parametrisation of the gamma distribution in terms of the mean and the shape parameter, both of which are modelled through regression structures that may involve fixed and random effects. A computational implementation via Gibbs sampling is provided and illustrative examples (simulated and real data) are presented.

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Nerlo-Pomorska, B., K. Pomorski, J. Bartel, and C. Schmitt. "Potential Energy Surfaces of Mercury up to Uranium Isotopes in the 4D Fourier Shape Parametrisation." Acta Physica Polonica B Proceedings Supplement 10, no. 1 (2017): 173. http://dx.doi.org/10.5506/aphyspolbsupp.10.173.

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BARTEL, JOHANN, ARTUR DOBROWOLSKI, and KRZYSZTOF POMORSKI. "SADDLE-POINT MASSES OF EVEN-EVEN ACTINIDE NUCLEI." International Journal of Modern Physics E 16, no. 02 (February 2007): 459–73. http://dx.doi.org/10.1142/s0218301307005892.

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In the framework of the macroscopic-microscopic approach the Yukawa folding procedure is used together with the Lublin-Strasbourg Drop liquid-drop type energy to describe atomic nuclei in the actinide region. The nuclear deformation is described by a 4-dimensional shape parametrisation similar to the well-known Funny-Hills expression. It is demonstrated that left-right asymmetry and non-axiality are present at the first and second saddle and should be included in the theoretical description. The importance of a different deformation of the proton and the neutron distribution also appears in the present analysis.

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Jimenez-Garcia, A., M. Biava, G. N. Barakos, K. D. Baverstock, S. Gates, and P. Mullen. "Tiltrotor CFD Part II - aerodynamic optimisation of tiltrotor blades." Aeronautical Journal 121, no. 1239 (May 2017): 611–36. http://dx.doi.org/10.1017/aer.2017.21.

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ABSTRACTThis paper presents aerodynamic optimisation of tiltrotor blades with high-fidelity computational fluid dynamics. The employed optimisation framework is based on a quasi-Newton method, and the required high-fidelity flow gradients were computed using a discrete adjoint solver. Single-point optimisations were first performed to highlight the contrasting requirements of the helicopter and aeroplane flight regimes. It is then shown how a trade-off blade design can be obtained using a multi-point optimisation strategy. The parametrisation of the blade shape allowed the twist and chord distributions to be modified and a swept tip to be introduced. The work shows how these main blade shape parameters influence the optimal performance of the tiltrotor in helicopter and aeroplane modes, and how an optimised blade shape can increase the overall tiltrotor performance. Moreover, in all the presented cases, the accuracy of the adjoint gradients resulted in a small number of flow evaluations for finding the optimal solution, thus indicating gradient-based optimisation as a viable tool for modern tiltrotor design.

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Linek, T., T. Tański, and W. Borek. "Numerical analysis of the cavitation effect occurring on the surface of steel constructional elements." Archives of Materials Science and Engineering 85, no. 1 (May 1, 2017): 24–34. http://dx.doi.org/10.5604/01.3001.0010.1555.

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Purpose: The aim of the work is to present the results of own investigations concerning the geometric optimisation of constructional elements working in the environment of cavitation wear together with a computer numerical analysis. The engineering material used for constructional elements working in the environment of cavitation wear is steel, commonly used for pressure devices working at elevated temperatures, P265GH, acc. to PN-EN 10028:2010. Design/methodology/approach: SOLID EDGE ST 7 software, for synchronous designing, was used for the parametrisation of the shape, distribution, configuration and size of openings in constructional elements. Five models, with a different spacing and number of openings, were proposed for the optimisation of internal geometry of the cavitation generator and for the investigations; the models were then subjected to a numerical analysis using specialised software, ANSYS FLUENT v.16, employed for modelling the effects associated with fluid mechanics (Computational Fluid Dynamics - CFD). The data was implemented for this purpose in the software used, such as: density, yield point, tensile strength, heat conductivity coefficient for steel P265GH, material surface roughness, medium (water) flow rate, constant pressure loss of medium, pressure of steam saturation in a medium; and such data was called boundary conditions. Findings: The authors’ principal accomplishment is the optimisation of the shape, the selection of the most appropriate geometry of a constructional element generating the maximum number of cavity implosions in the environment of a flowing medium (water), with the use of computer tools dedicated to engineering design: a 3D and numerical computer analysis of fluid mechanics, CFD. Moreover, an attempt was made in this work to develop a methodology for characterisation of the phenomena accompanying the environment of cavitation wear. Practical implications: A possibility of examining the phenomena and a process of wear of a constructional element made of P265GH grade steel for pressure devices working at elevated temperatures. The demonstration and presentation of potential places, areas and sizes of erosion existing on constructional elements working in the environment of cavitation wear.

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Hanhart, C., Yu S. Kalashnikova, P. Matuschek, R. V. Mizuk, A. V. Nefediev, and Q. Wang. "A practical parametrisation of line shapes of near-threshold resonances." Journal of Physics: Conference Series 675, no. 2 (February 5, 2016): 022016. http://dx.doi.org/10.1088/1742-6596/675/2/022016.

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Müller, Jens-Dominik, Xingchen Zhang, Siamak Akbarzadeh, and Yang Wang. "Geometric continuity constraints of automatically derived parametrisations in CAD-based shape optimisation." International Journal of Computational Fluid Dynamics 33, no. 6-7 (August 9, 2019): 272–88. http://dx.doi.org/10.1080/10618562.2019.1683166.

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Guo, F. K., C. Hanhart, Yu S. Kalashnikova, P. Matuschek, R. V. Mizuk, A. V. Nefediev, Q. Wang, and J. L. Wynen. "Phenomenology of near-threshold states: a practical parametrisation for the line shapes." EPJ Web of Conferences 137 (2017): 06020. http://dx.doi.org/10.1051/epjconf/201713706020.

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BARTEL, JOHANN, BOZENA NERLO-POMORSKA, and KRZYSZTOF POMORSKI. "JACOBI BIFURCATION IN HOT ROTATING NUCLEI WITH A LSD + YUKAWA FOLDED APPROACH." International Journal of Modern Physics E 18, no. 04 (April 2009): 986–95. http://dx.doi.org/10.1142/s0218301309013130.

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The "Modified Funny-Hills parametrisation" is used together with the Lublin-Strasbourg Drop Model and Strutinsky type shell corrections to determine the stability of hot rotating nuclei. Both the macroscopic and the microscopic part of the nuclear energy are evaluated by taking into account their dependence on the nuclear temperature and the rotational angular momentum. The Jacobi transition into triaxial shapes and the centrifugal-fission instability are studied.

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Yang, Rui-zhi, Ervin Kafexhiu, and Felix Aharonian. "Exploring the shape of the γ-ray spectrum around the “π0-bump”." Astronomy & Astrophysics 615 (July 2018): A108. http://dx.doi.org/10.1051/0004-6361/201730908.

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The “pion-decay” bump is a distinct signature of the differential energy spectrum of γ-rays between 100 MeV and 1 GeV produced in hadronic interactions of accelerated particles (cosmic rays) with the ambient gas. We use recent parametrisations of relevant cross-sections to study the formation of the “pion-decay” bump. The γ-ray spectrum below the maximum of this spectral feature can be distorted because of contributions of additional radiation components, in particular, due to the bremsstrahlung of secondary electrons and positrons, the products of decays of π±-mesons, accompanying the π0-production. At energies below 100 MeV, a non-negligible fraction of γ-ray flux could originate from interactions of sub-relativistic heavy ions. We study the impact of these radiation channels on the formation of the overall γ-ray spectrum based on a time-dependent treatment of evolution of energy distributions of the primary and secondary particles in the γ-ray production region.

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Djondjorov, P. A., V. M. Vassilev, and I. M. Mladenov. "Analytic description and explicit parametrisation of the equilibrium shapes of elastic rings and tubes under uniform hydrostatic pressure." International Journal of Mechanical Sciences 53, no. 5 (May 2011): 355–64. http://dx.doi.org/10.1016/j.ijmecsci.2011.02.005.

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Geoghegan, Jack A., Nicholas F. Giannelis, and Gareth A. Vio. "A Numerical Investigation of the Geometric Parametrisation of Shock Control Bumps for Transonic Shock Oscillation Control." Fluids 5, no. 2 (April 10, 2020): 46. http://dx.doi.org/10.3390/fluids5020046.

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At transonic flight conditions, shock oscillations on wing surfaces are known to occur and result in degraded aerodynamic performance and handling qualities. This is a purely flow-driven phenomenon, known as transonic buffet, that causes limit cycle oscillations and may present itself within the operational flight envelope. Hence, there is significant research interest in the development of shock control techniques to either stabilise the unsteady flow or raise the boundary onset. This paper explores the efficacy of dynamically activated contour-based shock control bumps within the buffet envelope of the OAT15A aerofoil on transonic flow control numerically through unsteady Reynolds-averaged Navier–Stokes modelling. A parametric evaluation of the geometric variables that define the Hicks–Henne-derived shock control bump will show that bumps of this type lead to a large design space of applicable shapes for buffet suppression. Assessment of the flow field, local to the deployed shock control bump geometries, reveals that control is achieved through a weakening of the rear shock leg, combined with the formation of dual re-circulatory cells within the separated shear-layer. Within this design space, favourable aerodynamic performance can also be achieved. The off-design performance of two optimal shock control bump configurations is explored over the buffet region for M = 0.73, where the designs demonstrate the ability to suppress shock oscillations deep into the buffet envelope.

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Barthold, F. J. "A structural optimisation viewpoint on growth phenomena." Bulletin of the Polish Academy of Sciences: Technical Sciences 60, no. 2 (October 1, 2012): 247–52. http://dx.doi.org/10.2478/v10175-012-0033-6.

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Abstract. Evolutionary solid bodies undergoing changes of mass, of properties, and of shapes are considered in models of growth and adaptation and similarily in structural optimisation. A fundamental separation of different growth phenomena and a subsequent parametrisation using independent design variables for the amount of substance as well as for molar mass and molar volume facilitates an efficient formulation of the design space. Thus, the effects of design variations, i.e. change of amount of substance, on the variations of the structural response, i.e. the deformation in physical space, can be clearly described. Overall, a novel treatment of growth processes based on an evolution of the amount of substance is outlined. The parallelism of variations in physical and design space are highlighted and compared with the multiplicative decomposition of the deformation gradient into a growth and an elastic part incorporating an incompatible intermediate configuration. This drawback is overcome by a compatible manifold based on material points modelling the amount of substance outside of any geometrical space.

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Longobardi, Giuseppe. "Theory and experiment in Parametric Minimalism: the case of Romance Negation." Revista Linguíʃtica 13, no. 2 (September 1, 2017): 108. http://dx.doi.org/10.31513/linguistica.2017.v13n2a13506.

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This paper has a double goal: frst, it lays down and refnes the basic hypotheses on the parametric structure of Romance negative systems that were originally introduced in my presentation at the Venice GLOW Workshop on Dialect Variation in 1987 (especially sections 3-9 and 11-13)3; then it further elaborates on them (sections 10 and 14-15), and revisits the conclusions (sections 16-22) in light of a more recent minimalist approach to the possible formats of parametric variation (the Principles & Schemata model, sketched in Longobardi 2005a). More generally, the theoretical focus of the article is on exploring how minimalist research on syntactic diversity could be conducted.In the spirit of Borer (1984), the parameters of negation can be argued to be essentially encoded in the lexical entries of the sentential negation morpheme and of the negative determiners of each language. No space is left in this framework for such generic notions as (strict or non-strict) ‘negative concord’ vs. ‘double negation’ languages. In fact, these notions looked at best epiphenomenal and obsolete already in 1987: in spite of their continued use even in recent literature, they turn out to be both insuffcient and unnecessary, and are potentially misleading.Now, a good deal of the negation parametrisation can be shown to have to do with the feature composition of lexical entries and to be actually nearly ‘perfect’, in three minimalist senses: frst, given Boolean conditions on feature association, the parametric choices exhaust the set of logical possibilities, determining whether the values of such features may, must, or may not co-occur on one and the same (class of) item(s); second, all the parameters needed for crosslinguistic descriptive adequacy ft into independently attested and restrictive schemata; third, they are shaped by, or interact with, natural third-factor conditions (Chomsky 2005); fnally the parametrisation hypothesised is ‘complete’ in the technical sense that all the typologically possible combinations of values turn out to be attested.With respect to UG principles, I show how objections against the possible universality of conditions on covert long-distance dependencies, as established by Italian negative operators (Rizzi 1982, Longobardi 1991), can be successfully addressed and eventually dismissed. Furthermore, such conditions are argued to be fully structural principles rather than functional preferences.

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Soldateschi, J., N. Bucciantini, and L. Del Zanna. "Magnetic deformation of neutron stars in scalar-tensor theories." Astronomy & Astrophysics 645 (January 2021): A39. http://dx.doi.org/10.1051/0004-6361/202038826.

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Scalar-tensor theories are among the most promising alternatives to general relativity that have been developed to account for some long-standing issues in our understanding of gravity. Some of these theories predict the existence of a non-linear phenomenon that is spontaneous scalarisation, which can lead to the appearance of sizable modifications to general relativity in the presence of compact matter distributions, namely neutron stars. On the one hand, one of the effects of the scalar field is to modify the emission of gravitational waves that are due to both variations in the quadrupolar deformation of the star and the presence of additional modes of emission. On the other hand, neutron stars are known to harbour extremely powerful magnetic fields which can affect their structure and shape, leading, in turn, to the emission of gravitational waves – in this case due to a magnetic quadrupolar deformation. In this work, we investigate how the presence of spontaneous scalarisation can affect the magnetic deformation of neutron stars and their emission of quadrupolar gravitational waves, both of tensor and scalar nature. We show that it is possible to provide simple parametrisations of the magnetic deformation and gravitational wave power of neutron stars in terms of their baryonic mass, circumferential radius, and scalar charge, while also demonstrating that a universal scaling exists independently of the magnetic field geometry and of the parameters of the scalar-tensor theory. Finally, we comment on the observability of the deviations in the strain of gravitational waves from general relativity by current and future observatories.

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Martinelli, Massimiliano, and François Beux. "Multi-level gradient-based methods and parametrisation in aerodynamic shape design." European Journal of Computational Mechanics, September 19, 2008, 169–97. http://dx.doi.org/10.13052/remn.17.169-197.

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The present study focuses on multi-level approaches in the context of discrete gradient-based methods for aerodynamic shape design. More precisely, the minimisation is done alternatively on different control subspaces according to multigrid-like cycles, providing at each sub-level a particular gradient preconditioning. Starting from an existing multi-level gradient-based formulation associated to shape grid-points coordinates, a possible generalisation to more compact shape representations is proposed through the construction of adequate sets of embedded shape sub-parametrisations. The behaviour of the new formulation is illustrated on different 2D inverse problems for inviscid flows.

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Ananthanarayan, B., I. Caprini, Diganta Das, and I. Sentitemsu Imsong. "Parametrisation-free determination of the shape parameters for the pion electromagnetic form factor." European Physical Journal C 73, no. 8 (August 2013). http://dx.doi.org/10.1140/epjc/s10052-013-2520-9.

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Wainwright, Caroline M., John H. Marsham, David P. Rowell, Declan L. Finney, and Emily Black. "Future changes in seasonality in Eastern Africa from regional simulations with explicit and parametrised convection." Journal of Climate, December 1, 2020, 1–54. http://dx.doi.org/10.1175/jcli-d-20-0450.1.

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AbstractThe Eastern Africa precipitation seasonal cycle is of significant societal importance, and yet the current generation of coupled global climate models fails to correctly capture this seasonality. The use of convective parametrisation schemes is a known source of precipitation bias in such models. Recently, a high-resolution regional model was used to produce the first pan-African climate change simulation that explicitly models convection. Here, this is compared with a corresponding parametrised-convection simulation, to explore the effect of the parametrisation on representation of Eastern Africa precipitation seasonality. Both models capture current seasonality, although an overestimate in September-October in the parametrised simulation leads to an early bias in the onset of the boreal autumn short rains, associated with higher convective instability and near-surface moist static energy. This bias is removed in the explicit model. Under future climate change both models show the short rains getting later and wetter. For the boreal spring long rains, the explicit convection simulation shows the onset advancing but the parametrised simulation shows little change. Over Uganda and western Kenya both simulations show rainfall increases in the January-February dry season, and large increases in boreal summer and autumn rainfall, particularly in the explicit convection model, changing the shape of the seasonal cycle, with potential for pronounced socio-economic impacts. Interannual variability is similar in both models. Results imply that parameterisation of convection may be a source of uncertainty for projections of changes in seasonal timing from global models, and that potentially impactful changes in seasonality should be highlighted to users.

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Lucchini, M., F. Krauß, and S. Markoff. "The unique case of the AGN core of M87: a misaligned low power blazar?" Monthly Notices of the Royal Astronomical Society, August 5, 2019. http://dx.doi.org/10.1093/mnras/stz2125.

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Abstract M87 hosts one of the closest jetted active galactic nucleus (AGN) to Earth. Thanks to its vicinity and to the large mass of is central black hole, M87 is the only source in which the jet can be directly imaged down to near-event horizon scales with radio very large baseline interferometry (VLBI). This property makes M87 a unique source to isolate and study jet launching, acceleration and collimation. In this paper we employ a multi-zone model designed as a parametrisation of general relativistic magneto-hydrodynamics (GRMHD); for the first time we reproduce the jet’s observed shape and multi-wavelength spectral energy distribution (SED) simultaneously. We find strong constraints on key physical parameters of the jet, such as the location of particle acceleration and the kinetic power. However, we under-predict the (unresolved) γ-ray flux of the source, implying that the high-energy emission does not originate in the magnetically-dominated inner jet regions. Our results have important implications both for comparisons of GRMHD simulations with observations, and for unified models of AGN classes.

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Shitrit, S. "Adjoint-based aerodynamic drag minimisation with trim penalty." Aeronautical Journal, September 7, 2021, 1–25. http://dx.doi.org/10.1017/aer.2021.78.

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Abstract The aerodynamic performance of conventional aircraft configurations are mainly affected by the wing and horizontal tail. Drag reduction by shape optimisation of the wing, while taking into account the aircraft trimmed constraint, has more benefit than focusing solely on the wing. So in order to evaluate this approach, the following study presents results of a single and multipoint aerodynamic shape optimisation of the wing-body-tail configuration, defined by the Aerodynamic Design Discussion Group (ADODG). Most of the aerodynamic shape optimisation problems published in the last years are focused mainly on the wing as the main driver for performance improvement, with no trim constraint and/or excess drag obtained from the fuselage, fins or other parts. This work partially fills this gap by an investigation of RANS-based aerodynamic optimisation for transonic trimmed flight. Mesh warping and geometry parametrisation is accomplished by fitting the multi-block structured grid to a B-spline volumes and performing the mesh movement by using surface control points embedded within the free-form deformation (FFD) volumes. A gradient-based optimisation algorithm is used with an adjoint method in order to compute the derivatives of the objective and constraint functions with respect to the design variables. In this work the aerodynamic shape optimisation of the CRM wing-body-tail configuration is investigated, including a trim constraint that is satisfied by rotating the horizontal tail. The shape optimisation is driven by 432 design variables that envelope the wing surface, and 120 shape variables for the tail, as well as the angle of attack and tail rotation angles. The constraints are the lift coefficient, wing’s thickness controlled by 1,000 control points, and the wing’s volume. For the untrimmed configuration the drag coefficient is reduced by 5.76%. Optimising the wing with a trim condition by tail rotation results in shock-free design with a considerably improved drag, even better than the untrimmed-optimised case. The second optimisation problem studied is a single and multi-point lift constraint drag minimisation of a gliding configuration wing in transonic viscous flow. The shock is eliminated, reducing the drag of the untrimmed configuration by more than 60%, using 192 design variables. Further robustness is achieved through a multi-point optimisation with more than 45% drag reduction.

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Shaw, Avirup. "The impact of nonminimal universal extra dimensional model on $$\Delta B=2$$ transitions." European Physical Journal C 81, no. 2 (February 2021). http://dx.doi.org/10.1140/epjc/s10052-021-08937-9.

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AbstractWe measure the impact of nonvanishing boundary localised terms on $$\Delta B=2$$ Δ B = 2 transitions in five-dimensional Universal Extra Dimensional scenario where masses and coupling strengths of several interactions of Kaluza–Klein modes are significantly modified with respect to the minimal counterpart. In such scenario we estimate the Kaluza–Klein contributions of quarks, gauge bosons and charged Higgs by evaluating the one-loop box diagrams that are responsible for the $$\Delta B=2$$ Δ B = 2 transitions. Using the loop function (obtained from one-loop box diagrams) we determine several important elements that are involved in Wolfenstein parametrisation. Moreover, with these elements we also study the geometrical shape of unitarity triangle. Besides, we compute the quantity $$\Delta M_s$$ Δ M s scaled by the corresponding Standard Model value. Outcomes of our theoretical predictions have been compared to the allowed ranges of the corresponding observables simultaneously. Our current analysis shows that, depending on the parameters in this scenario the lower limit on the inverse of the radius of compactification can reach to an appreciable large value ($$\approx 1.48$$ ≈ 1.48 TeV or even higher).

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Aavaste, Age, Liis Sipelgas, Rivo Uiboupin, and Kristi Uudeberg. "Impact of Thermohaline Conditions on Vertical Variability of Optical Properties in the Gulf of Finland (Baltic Sea): Implications for Water Quality Remote Sensing." Frontiers in Marine Science 8 (May 26, 2021). http://dx.doi.org/10.3389/fmars.2021.674065.

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Vertical variability of inherent optical properties (IOPs) affect the water quality retrievals from remote sensing data. Here, we studied the vertical variability of IOPs and simulated apparent optical properties (AOPs) in the Gulf of Finland (Baltic Sea) under three characteristic (non)stratification conditions. In the case of mixed water column, the vertical variability of optically significant constituents (OSC) and IOPs was relatively small. While in case of stratified water column the IOPs of surface layer were three times higher compared to the IOPs below the thermocline and the IOPs were strongly correlated with the physical parameters (temperature, salinity). Measurements of IOPs in stratified water column showed that the ratio of scattering (b(440)) to absorption (a(440)) changed under the thermocline (b(440)/a(440) < 1) i.e., absorption became the dominant component of attenuation under thermocline while the opposite is true for the upper layer. Simulated (from IOPs) spectral irradiance reflectance (R(λ)) and spectral diffuse attenuation coefficient (Kd(λ)) from deeper layers (below thermocline) have significantly smaller magnitude and smoother shape. This becomes relevant during upwelling events—a common process in the coastal Baltic Sea. We quantified the effect of upwelling on surface water properties using simulated AOPs. The simulated AOPs (from IOPs measurements) showed a decrease of the signal up to 68.8% and an increase of optical depth (z90(λ)) from 2.3 to 4.3 m in the green part of the spectrum in case upwelled water mass reaches the surface. In the coastal waters a vertical decrease of Kd(λ) in the PAR region (400–700 nm) by 6.8% (surface to 20 m depth) was observed, while vertical decrease of chlorophyll-a (Chl-a) and total suspended matter (TSM) was 31.7 and 42.1%, respectively. The ratio R(490)/R(560)≥0.77 indicates also the upwelled water mass. The study showed that upwelling is a process that, in addition to biological activity, horizontal transport of OSC, and temperature changes, alters the optical signal of surface water measured by a remote sensor. Knowledge about the vertical variability of IOPs and AOPs relation to upwelling can help the parametrisation of remote sensing algorithms for retrieving water quality estimates in the coastal regions.

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31

B¨ohm, Thomas. "Remaining Useful Life Prediction for Railway Switch Engines Using Classification Techniques." International Journal of Prognostics and Health Management 8, no. 3 (November 17, 2020). http://dx.doi.org/10.36001/ijphm.2017.v8i3.2666.

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A highly available infrastructure is a premise for capable railway operation of high quality. Therefore, maintenance is necessary to keep railway infrastructure elements available. Railway switches, especially, are critical because they connect different tracks and allow a train to change its moving direction without stopping. Their inspection, maintenance and repair have long been identified as a cost driver. Switch failures, particularly, are responsible for a comparable high number of failures and delay minutes. The reduction of failures would not only save maintenance costs, but also let more trains arrive on time and hence increase the attractiveness of the railway transport. Therefore, upcoming failures need to be revealed early enough to allow an effective planning and execution of failure preventing maintenance activities. Research is exploring ways to predict the remaining useful life of switches.This paper presents an approach to predict the remaining useful life (RUL) of railway switch engine failures. The development is based on measurement data of the electrical power consumption of switch engines. The two year time series of 29 switches of Deutsche Bahn was recorded by a commercial switch diagnostic system leading to roughly 250 000measurement tuples. Since earlier researched showed that the electrical data alone is not sufficient enough, additional data is integrated. It takes into account the dependency of the switch condition data from climatic conditions and certain properties of the switch construction type.Predicting a RUL is quite challenging in many PHM applications. To avoid common problems with uncertainty in measurement data, a long prediction horizon (month) of small time units (hours) and to stabilise end user acceptance the approach transforms the RUL prediction problem into a classification problem of multiple classes. It, then, uses two different supervised classification techniques, Artificial Neural Networks (aNN) and Support Vector Machines (SVM), to predict the RUL in the form of classes. However, as known from the no free lunch-theorem of classification, there is no ultimately best performing technique. The success depends on the problem and data structure as well as on the parametrisation of the technique or the selected algorithm respectively. Especially aNN and SVM have a high number of possible parametrisations. They can fail the task or result in a very good performance under the heavy influence of their parametrisation. Hence, it is an important aspect of this paper to share how the different parameters effect the RUL prediction and which parameters result in maximum performance. In order to compare the performance, two metrics are chosen, the Matthews Correlation Coefficient (MCC) as single value metric and a visualisation of the confusion matrix as more comprehensible metric. Finally, deriving those parameters maximising the RUL prediction results enables one of the two classification techniques to reveal upcoming failures of the switch engine early enough to prevent them.

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Aaij, R., C. Abellán Beteta, T. Ackernley, B. Adeva, M. Adinolfi, H. Afsharnia, C. A. Aidala, et al. "Measurement of the shape of the $$ {B}_s^0\to {D}_s^{\ast -}{\mu}^{+}{\nu}_{\mu } $$ differential decay rate." Journal of High Energy Physics 2020, no. 12 (December 2020). http://dx.doi.org/10.1007/jhep12(2020)144.

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Abstract The shape of the $$ {B}_s^0\to {D}_s^{\ast -}{\mu}^{+}{\nu}_{\mu } $$ B s 0 → D s ∗ − μ + ν μ differential decay rate is obtained as a function of the hadron recoil parameter using proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.7 fb−1 collected by the LHCb detector. The $$ {B}_s^0\to {D}_s^{\ast -}{\mu}^{+}{\nu}_{\mu } $$ B s 0 → D s ∗ − μ + ν μ decay is reconstructed through the decays $$ {D}_s^{\ast -}\to {D}_s^{-}\gamma $$ D s ∗ − → D s − γ and $$ {D}_s^{-}\to {K}^{-}{K}^{+}{\pi}^{-} $$ D s − → K − K + π − . The differential decay rate is fitted with the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) parametrisations of the form factors, and the relevant quantities for both are extracted.

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Lopez, Diego, Tiziano Ghisu, and Shahrokh Shahpar. "Global Optimisation of a Transonic Fan Blade Through AI-Enabled Active Subspaces." Journal of Turbomachinery, August 12, 2021, 1–33. http://dx.doi.org/10.1115/1.4052136.

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Abstract The increased need to design higher performing aerodynamic shapes has led to design optimisation cycles requiring high-fidelity CFD models and high-dimensional parametrisation schemes. The computational cost of employing global search algorithms on such scenarios has typically been prohibitive for most academic and industrial environments. In this paper, a novel strategy is presented that leverages the capabilities of Artificial Neural Networks for regressing complex unstructured data, while coupling them with dimensionality reduction algorithms. This approach enables employing global-based optimisation methods on high-dimensional applications through a reduced computational cost. This methodology is demonstrated on the efficiency optimisation of a modern jet engine fan blade with constrained pressure ratio. The outcome is compared against a state-of-the-art adjoint-based approach. Results indicate the strategy proposed achieves comparable improvements to its adjoint counterpart with a reduced computational cost, and can scale better to multi-objective optimisation applications.

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Journal articles on the topic 'Shape parametrisation'

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