Miracle-dz/UniFAR-FTUs huggingface dataset:
A THREE-DIMENSIONAL MODELLING OF LOW VELOCITY IMPACT DAMAGE IN COMPOSITE LAMINATES

The modelling of the behaviour of laminates during low velocity impact requires, first, an analysis of the efficiency of the numerical tool used. A logical development in relation to the numerical structure of the code and the experimental observations is proposed. Four aspects of the code implementation are discussed. The first one is the representation of the impact loading by a macro-contact model using the Lagrange multiplier technique. The second is the development of this technique on the meso-scale to represent the assembly of plies of the laminate. The third step is the modelling of the evolution of the non homogeneous cracked state in the composite with an averaging technique, based on the Laws–Dvorak–Hejazi model, developed on the finite element scale. The fourth step is the modelling of the delamination between plies as a lack of contact set off by a mixed criterion matrix-cracking/interfacial forces. Numerical results on a glass-epoxy [02/906/02] laminate impacted at 27 J are in a good agreement with experimental observations.
Parametric Investigation of Viscous Dissipation Effects on Optimized Air Cooling Microchanneled Heat Sinks

The effects of viscous dissipation of working fluid on the optimum heat sink parameters are investigated for the case of air cooling with a micro-/narrow-channeled compact heat sink. For this purpose, an optimization method is introduced first on the basis of dimensionless groups while employing several assumptions. This method yields minimum pumping work or pressure drop with a set of optimized geometric/hydrodynamic parameters when outer dimension of a heat sink and imposed thermal load are specified. Especially for the case of laminar flow, the procedure presents an explicit existence of cooling limit by the viscous heat generation, giving an analytical expression of the maximum removable heat Q max . The relationships between thermal load and each parameter are calculated for both laminar and turbulent regimes under the conditions of compact heat sink dimension (20 mm 2 20 mm 2 2 mm) and circular cross-sectional shape of channels. The results show that the cooling capability under such conditions is largely limited by the salient manifestation of viscous dissipation, when compared with our previous investigation on water cooling presented in [1]. From the discussion, it was concluded that when a micro-/narrow-channeled heat sink is to be designed with air, the effect of viscous dissipation should be taken into account in order to avoid falling on wrong optimum solutions.
Nonlinear dynamics of thin current sheets

Observations indicate that the current sheet in the Earth’s geomagnetic tail may compress to a thickness comparable to an ion gyro-radius prior to substorm onset. In recent years, there has been considerable controversy regarding the kinetic stability of these thin structures. In particular, the growth rate of the kink instability and its relevance to magnetotail dynamics is still being debated. In this work, a series of fully kinetic particle-in-cell simulations are performed for a thin Harris sheet. The ion to electron mass ratio is varied between mi/me=4→400 and careful comparisons are made with a formally exact approach to the linear Vlasov theory. At low mass ratio mi/me<64, the simulations are in excellent agreement with the linear theory, but at high mass ratio the kink instability is observed to grow more rapidly in the kinetic simulations than predicted by theory. The resolution to this apparent discrepancy involves the lower hybrid instability which is active on the edge of the sheet and rapidly.
Exact-exchange-based quasiparticle calculations

One-particle wave functions and energies from Kohn-Sham calculations with the exact local Kohn-Sham exchange and the local density approximation (LDA) correlation potential [EXX(c)] are used as input for quasiparticle calculations in the GW approximation (GWA) for eight semiconductors. Quasiparticle corrections to EXX(c) band gaps are small when EXX(c) band gaps are close to experiment. In the case of diamond, quasiparticle calculations are essential to remedy a 0.7 eV underestimate of the experimental band gap within EXX(c). The accuracy of EXX(c)-based GWA calculations for the determination of band gaps is as good as the accuracy of LDA-based GWA calculations. For the lowest valence band width a qualitatively different behavior is observed for medium- and wide-gap materials. The valence band width of medium- (wide-) gap materials is reduced (increased) in EXX(c) compared to the LDA. Quasiparticle corrections lead to a further reduction (increase). As a consequence, EXX(c)-based quasiparticle calculations give valence band widths that are generally 1-2 eV smaller (larger) than experiment for medium- (wide-) gap materials. (c) 2000 The American Physical Society.
Atlantic Tropical Cyclogenesis: A Three-Way Interaction between an African Easterly Wave, Diurnally Varying Convection, and a Convectively Coupled Atmospheric Kelvin Wave

AbstractThis paper explores a three-way interaction between an African easterly wave (AEW), the diurnal cycle of convection over the Guinea Highlands (GHs), and a convectively coupled atmospheric equatorial Kelvin wave (CCKW). These interactions resulted in the genesis of Tropical Storm Debby over the eastern tropical Atlantic during late August 2006. The diurnal cycle of convection downstream of the GHs during the month of August is explored. Convection associated with the coherent diurnal cycle is observed off the coast of West Africa during the morning. Later, convection initiates over and downstream of the GHs during the afternoon. These convective features were pronounced during the passage of the pre-Debby AEW. The superposition between the convectively active phase of a strong CCKW and the pre-Debby AEW occurred shortly after merging with the diurnally varying convection downstream of the GHs. The CCKW–AEW interaction preceded tropical cyclogenesis by 18 h. The CCKW provided a favorable environment.
Phenomenological Model Combining Dipole-Interaction Signal and Background Effects for Analyzing Modulated Detection in Apertureless Scanning Near-Field Optical Microscopy

Modulation methods such as homodyne and heterodyne detections are employed in A-SNOM in order to eliminate serious background efiects from scattering flelds. Usually, the frequency- modulated detection signal in apertureless scanning near-fleld optical microscopy (A-SNOM) is generally analyzed using a simple dipole- interaction model based only on the near-fleld interaction. However, the simulated A-SNOM spectra obtained using such models are in poor agreement with the experimental results since the efiects of background signals are ignored. Accordingly, this study proposes a new phenomenological model for analyzing the A-SNOM detection signal in which the efiects of both the dipole-interaction and the background flelds are taken into account. It is shown that the simulated A-SNOM spectra for 6H-SiC crystal and polymethylmethacrylate (PMMA) samples are in good agreement with the experimental results. The validated phenomenological model is used to identify the experimental A-SNOM parameter settings which minimize the efiects of background signals and ensure that the detection signal approaches the pure near- fleld interaction signal. Finally, the phenomenological model is used to evaluate the efiects of the residual stress and strain in a SiC substrate on the corresponding A-SNOM spectrum.
Dissipationless galaxy formation revisited

A large set of numerical simulations has been performed by using two different N-body codes to derive detailed properties of the end-product of dissipationless collapse. Three classes of initial mass distribution have been adopted, characterized by different inhomogeneity scales, with velocity dispersion corresponding to a virial ratio in a range 5 × 10 −4 -0.2. The results show that the phase space properties of the final equilibrium state depend strongly on the initial mass distribution.
Fuzzy approximation-based indirect adaptive controller for multi-input multi-output non-affine systems with unknown control direction

A fuzzy approximation-based indirect adaptive control is investigated for a class of unknown non-affine non-linear systems with unknown control direction. An equivalent model in affine-like form is first derived for the original non-affine system by using a Taylor series expansion. Next, a fuzzy indirect adaptive control is designed based on this affine-like equivalent model. In this control scheme, the adaptive fuzzy systems are used to appropriately approximate the equivalent affine model’s unknown non-linearities, whereas the Nussbaum gain function is used to deal with the unknown control directions (being closely related to the sign of control gain matrix). A decomposition property of the control gain matrix is fully exploited in the controller design and the stability analysis. It is proven that, under some appropriate assumptions, the proposed control scheme can achieve that all the signals in the closed-loop control system are bounded and the tracking errors converge to a small neighbourhood around zero. Effectiveness of the developed scheme is illustrated by two simulation examples.
Creating the UK National Statistics 2001 output area classification

Summary. The paper describes the creation of the Office for National Statistics 2001 output area classification, which was created in collaboration with the authors. The classification places each 2001 census output area into one of seven clusters based on the socio‐economic attributes of the residents of each area. The classification uses cluster analysis to reduce 41 census variables to a single socio‐economic indicator. The classification was made available with a host of supporting and descriptive information as a National Statistic via National Statistics on line. The classification forms part of a suite of area classifications that were produced by the Office for National Statistics from 2001 census data. Classifications of local authorities, statistical wards and health areas are also available.
Measurement of Head Scatter Factor for Linear Accelerators using Indigenously Designed Columnar Mini Phantom

Measurement of Head Scatter Factor for Linear Accelerators using Indigenously Designed Columnar Mini Phantom A columnar mini phantom is designed as recommended by ESTRO to measure the Head Scatter Factor (Sc) for 6 MV beam of two linear accelerators. The measurement of Sc at different orientations of the chamber, parallel and perpendicular at 1.5 cm depth predicts the deviation of 2.05% and 1.9% for Elekta and Siemens linear accelerators respectively. The measurement of Sc at 1.5 cm is higher compared to 10 cm depth for both the linear accelerators suggesting the electron contamination at 1.5 cm depth. The effect of wedges on Sc yields a significant contribution of 3.5% and 5% for Siemens and Elekta linear accelerators respectively. The collimator exchange effect reveals the opening of upper jaw increases the Sc irrespective of the linear accelerator. The result emphasizes the need of Sc measurement at 10 cm. The presence of wedge influences the Sc value and the SSD has no influence on Sc. The measured Sc values are in good agreement with the published data.
Circumprotostellar environments. I: Molecular outflows from protostar candidates in Taurus

We report on the search for molecular outflows from a complete, flux-limited, IRAS-selected sample of cold, low-mass protostar candidates located in the Taurus cloud complex. We find that 18 of the 24 sources have outflows associated with them, only four of which have been previously reported, implying that these sources are predominantly protostars in an early stage of evolution. We argue that at least a few of the outflows are very small in extent, indicating that their dynamical ages are less than a few thousand years.
Theoretical Analysis of the Aerodynamics of Low-Speed Fans in Free and Load-Controlled Windmilling Operation

The present work is a contribution to understanding the windmilling operation of low-speed fans. Such an operating situation is described in the literature, but the context (mainly windmilling of aero-engines) often involves system dependence in the analysis. Most of the time, only regimes very close to the free-windmilling are considered. A wider range is analyzed in the present study, since the context is the examination of the energy recovery potential of fans. It aims at detailing the isolated contribution of the rotor, which is the only element exchanging energy with the flow. Other elements of the system (including the stator) can be considered as loss generators and be treated as such in an integrated approach. The evolution of the flow is described by the use of theoretical and experimental data. A theoretical model is derived to predict the operating trajectories of the rotor in two characteristic diagrams. A scenario is proposed, detailing the local evolution of the flow when a gradual progression toward free and load-controlled windmilling operation is imposed. An experimental campaign exerted on two low-speed fans aims at the analysis of both the local and global aspects of the performance, for validation. From a global point of view, the continuity of the operating trajectory is predicted and observed across the boundary between the quadrants of the diagrams. The flow coefficient value for the free-windmilling operation is fairly well predicted. From a local point of view, the local co-existence of compressor and turbine operating modes along the blade span is observed as previously reported. It is further demonstrated here that this configuration is not exclusive to free-windmilling operation and occurs inside a range that can be theoretically predicted. It is shown that for a given geometry, this local topology strongly depends on the value of the flow coefficient and is very sensitive to the inlet spanwise velocity distribution.
Quasi-three dimensional analysis of global instabilities: onset of vortex shedding behind a wavy cylinder

In this paper the global-stability theory is extended to account for weak spanwise-flow variations using a quasi-three-dimensional framework. The analysis considers the onset of vortex shedding behind a circular cylinder with a spanwise-varying diameter. The quasi-three-dimensional approach models the fully three-dimensional flow structure as a series of two-dimensional eigenvalue problems representing the sectional-flow behaviour. The sectional results are coupled together using the Ginzburg–Landau equation, which models the diffusive coupling and provides the global response. The onset of global instability (and thus vortex shedding) is linked to both the sectional growth rates (characterized by the maximum-diameter location) and the spanwise extent of the zone of instability. Unsteady numerical simulations are used to guide the global-stability analysis and to assess the fidelity of the predictions. Results from the stability analysis are shown to be in good agreement with the numerical simulations, which are in close agreement with experiments.
Natural convection in a square cavity: A comparison exercise

A number of contributed solutions to the problem of laminar natural convection in a square cavity have been compared with what is regarded as a solution of high accuracy. The purposes of this exercise have been to confirm the accuracy of the bench mark solution and to provide a basis for the assessment of the various methods and computer codes used to obtain the contributed solutions.
Electron spin resonance and Raman studies of Mn-doped ZnO ceramics

In the present work, the influence of annealing on structure, electron spin resonance (ESR), and Raman scattering (RS) spectra of x at. % Mn-doped ZnO (x=4 and 8) ceramic compounds has been systematically investigated. The samples were annealed at temperatures (Tan) between 400 and 1000°C for 12h. The obtained results revealed the strong dependence of x-ray diffraction, ESR, and RS spectra on the annealing temperature Tan. Mn2+ ions did not substitute into Zn2+ sites in samples annealed in the range of 400–600°C but started to substitute into Zn2+ sites for annealing temperatures Tan>600°C. The results of this investigation provide further insights into the physical processes occurring in Mn-doped ZnO materials due to annealing.
Results of an attempt to generate a homogeneous turbulent shear flow

An approximately homogeneous turbulent shear flow is generated in an open-return wind tunnel test-section by a plane parallel-rod grid of uniform rod diameter and non-uniform rod spacing. The grid design is based upon an analysis by Owen & Zienkiewicz (1957). Hot-wire measurements taken in this flow include mean velocities, component turbulence intensities, shear and two-point space correlations, and energy spectra. In addition, microscales, obtained both from instantaneous time derivatives of the hot-wire signal and from two-point space correlations, and integral scales, calculated both from correlations and energy spectra, are reported. Based upon these results, it is concluded that, far enough away from the grid and the test-section wall boundary layers: The turbulence intensities are maintained at uniform values by the nearly constant mean shear. The turbulent shear stress approaches an asymptotic value. Measured two-point space correlation coefficients and one-dimensional energy spectra attain self-preserving forms. When distance downstream of the grid is measured in terms of the number of ‘local’ grid rod spacings, (see discussion of microscales obtained from time derivatives), the Taylor microscale defined by the correlation coefficient Ruu(rX, 0, 0) grows linearly with this ‘effective’ distance over most of the region measured. The limited number of integral scale determinations and experimental uncertainty allow only the statements that the magnitude of the longitudinal scale is roughly one-eighth the lateral dimension of the square test-section and tends to increase slightly with ‘effective’ distance from the grid. The lateral integral scales are approximately one-half the longitudinal scales and also increases with distance from the grid. The integral scale which characterizes the size of the eddy primarily responsible for momentum transfer is roughly one-tenth the test-section lateral dimension (measured at one point only).
Automatic Mesh Adaptivity for Hybrid Monte Carlo/Deterministic Neutronics Modeling of Difficult Shielding Problems

Abstract The well-established Consistent Adjoint Driven Importance Sampling (CADIS) and the Forward Weighted Consistent Adjoint Driven Importance Sampling (FW-CADIS) hybrid Monte Carlo/deterministic techniques have dramatically increased the efficiency of neutronics simulations, yielding accurate solutions for increasingly complex problems through full-scale, high-fidelity simulations. However, for full-scale simulations of very large and geometrically complex nuclear energy systems, even the CADIS and FW-CADIS techniques can reach the CPU and memory limits of all but the very powerful supercomputers. In this work, three mesh adaptivity algorithms were developed to reduce the computational resource requirements of CADIS and FW-CADIS without sacrificing their efficiency improvements. First, a macromaterial approach was developed to enhance the fidelity of the deterministic models without changing the mesh. Second, a deterministic mesh refinement algorithm was developed to generate meshes that capture as much geometric detail as possible without exceeding a specified maximum number of mesh elements. Finally, a weight window (WW) coarsening (WWC) algorithm was developed to decouple the WW mesh and energy bins from the mesh and energy group structure of the deterministic calculations. By removing the memory constraint of the WW map from the resolution of the mesh and the energy group structure of the deterministic calculations, the WWC algorithm allows higher-fidelity deterministic calculations that, consequently, increase the efficiency and reliability of the CADIS and the FW-CADIS simulations. The three algorithms were used to enhance an FW-CADIS calculation of the prompt dose rate throughout the ITER experimental facility. Using these algorithms increased both the number of mesh tally elements in which nonzero results were obtained (+23.3%) and the overall efficiency of the calculation (a factor of >3.4). The three algorithms enabled this difficult calculation to be accurately solved using an FW-CADIS simulation on a 94-CPU computer cluster, eliminating the need for a world-class supercomputer.
An ILC scheme for a class of nonlinear continuous‐time systems with time‐iteration‐varying parameters subject to second‐order internal model

In this paper, a new iterative learning control (ILC) scheme is proposed to deal with unknown time‐iteration‐varying parameters for a class of nonlinear continuous‐time systems. The parametric non‐repetitiveness in the iteration domain is described by a second‐order internal model, which includes systems with iteration‐invariant parameters as a subset. By incorporating the internal model into the parametric learning law, the proposed ILC scheme can handle more generic systems with parametric uncertainties, and includes existing ILC schemes as a special case with the first‐order internal model. The conditions under which the new ILC scheme can guarantee learning convergence are delicately explored. Utilizing the information of the previous two iterations and the method of composite energy function (CEF), it is able to derive pointwise convergence along the time axis and asymptotic convergence along the iteration axis. The controller design is further extended to the case for systems with mixed parameters and unknown time‐varying input gain. Copyright © 2010 John Wiley & Sons, Ltd.
Spatial and temporal distributed acceleration of cosmic rays by supernova remnants three-dimensional simulations

The results of a three-dimensional code designed to simulate distributed cosmic-ray acceleration by supernova remnant (SNR) shock waves in the Galaxy are presented. The model is intended to attack the problem in a realistic form that includes the decoupling of the main acceleration region and secondary particle production region. This decoupling is introduced by considering the dependence of the interstellar medium density on the height above the galactic plane and the different scale height of the SNR distribution. The latter's dependence on galactocentric distance is also considered. Two mechanisms of transport are taken into account: diffusion (dependent on particle's momentum, charge, mass, and position) and random wandering of convective cells (momentum independent)
Man-machine interaction in human-face identification

How well can a computer identify a human face which is described by a person who is inspecting a photograph? We give an account of an interactive system that takes advantage both of the human's superiority in detecting and describing noteworthy features and of the machine's superiority in making decisions based on accurate knowledge of population statistics of stored face-features. Experiments using a population of 255 faces and 10 or fewer feature-descriptions showed that the population containing the described individual could be narrowed down to less than 4 percent in 99 percent of all trials.
Linear Elasticity and Potential Theory: a Comment on Gurtin (1972)

In an exhaustive presentation of the linear theory of elasticity by Gurtin [The Linear Theory of Elasticity (Springer-Verlag, 1972)], the author included a chapter on the relation of the theory of elasticity to the theory of potentials. Potential theory distinguishes two fundamental physical categories: divergence-free and divergence-involving problems. From the criteria given in the source quoted by the author, it is evident that elastic deformation of solids falls into the latter category. It is documented in this short note that the author presented volume-constant elastic deformation as a divergence-free physical process, systematically ignoring all the information that was available to him that this is not so.