We report the detection of a point-like source of very high energy (VHE) γ-rays coincident within $1'$ of Sgr A*, obtained with the HESS array of Cherenkov telescopes. The γ-rays exhibit a power-law ...energy spectrum with a spectral index of $-2.2 \pm 0.09 \pm 0.15$ and a flux above the 165 GeV threshold of $(1.82 \pm 0.22) \times 10^{-7}$ m-2 s-1. The measured flux and spectrum differ substantially from recent results reported in particular by the CANGAROO collaboration.
Decision Enhancement (DE) is a field of practice aimed at extending lessons, principles and tools built up over a thirty year period, largely under the term 'Decision Support'. Enhancement goes ...beyond support which has mostly focused on helping managers make use of interactive computer models and methods. DE substantially adds to the opportunities, especially in the use of the Internet as both an information resource and communications base for collaboration between groups but it also goes well beyond it in two important regards: a focus on enhancement of the processes that influence the quality of decisions that really matter in an organization; the ones that are most consequential, complex, and uncertain, and a shift from the design of computer- and telecommunications-based tools to a far more comprehensive 'studio' approach to the integration of change management, collaborative development and use, and a new generation of visual technology. DE is a lens that focuses on stakeholders in decision arenas and their decisions that matter. It continues with its invitation to bring stakeholders, domain experts and suite designers into its studios. The invitation extends to experts in domains relevant to making DE studios effective, as well as to the suite designers and providers of technology capabilities needed to provide the tools within the studio. DE provides services to guide a journey where executives, their advisors, change management specialists, experts in multi-disciplinary fields and technology developers can come together to make a substantive new impact on effective decision making in any organization. This book will add to the old - the proven lessons and expertise of these fields - and to their innovation. It is in this sense that it is an invitation and written to encourage reflection and discussion within and across them.
The aim of this article is to study the accuracy of finite element simulations in predicting the tool force occurring during the single point incremental forming (SPIF) process. The forming of two ...cones in soft aluminum was studied with two finite element (FE) codes and several constitutive laws (an elastic–plastic law coupled with various hardening models). The parameters of these laws were identified using several combinations of a tensile test, shear tests, and an inverse modeling approach taking into account a test similar to the incremental forming process. Comparisons between measured and predicted force values are performed. This article shows that three factors have an influence on force prediction: the type of finite element, the constitutive law and the identification procedure for the material parameters. In addition, it confirms that a detailed description of the behavior occurring across the thickness of the metal sheet is crucial for an accurate force prediction by FE simulations, even though a simple analytical formula could provide an otherwise acceptable answer.
We derive the theoretical and numerical framework for investigating nonequilibrium properties of spin-orbit coupled wires with Zeeman splitting proximized by a superconductor in the nonlinear ...diffusive regime. We demonstrate that the anisotropic behavior of triplet Cooper pairs in this system leads to novel spin accumulation profiles tunable by the magnetic field and strength of applied voltage bias. This paves the way for enhanced manipulation of superconducting spintronic devices, and it enables further investigation of nonequilibrium effects in proximity-coupled superconducting structures more generally.
Direct Ink Writing of 4D Structural Colors Sol, Jeroen A. H. P.; Smits, Luc G.; Schenning, Albert P. H. J. ...
Advanced functional materials,
07/2022, Letnik:
32, Številka:
30
Journal Article
Recenzirano
Odprti dostop
Additive manufacturing with stimuli‐responsive materials—4D printing—is a rapidly growing field, with direct ink writing allowing deposition of a wide variety of materials. The synthesis of a ...humidity‐sensitive cholesteric liquid crystal oligomer ink is reported. With the responsive cholesteric ink, demonstrator devices exhibiting the ink's “four dimensionality” are printed in disparate fashions: as a structural color change or as a preprogrammed deformation mode. After printing, the photonic ink changes color in response to atmospheric humidity, demonstrated as a hydrochromic coating precisely deposited atop a 3D‐printed beetle. After activation in aqueous acid, the beetle exhibits vibrant color shifts across the visible spectrum. Alternatively, a scallop‐inspired actuator with a 3D‐programmed structural color is selectively treated with acid, to allow reversible “opening” and “closing” when exposed to humid and dry air, respectively. The ink enables additive manufacturing of both monolithic and multimaterial stimuli‐responsive, shape‐changing, structurally colored objects, toward broad application of cholesterics in future “smart,” 4D structurally colored devices.
Inspired by natural examples of hydrochromicity, an ink is developed to “4D print” objects with environmentally responsive structural colors. The devices designed using this ink exploit their reversible response to water in two distinct manners: as color or shape changes.
The permeability of textile reinforcements is a crucial input for the simulation of the impregnation stage of a composite material fabrication process. In this paper, we present a fast and accurate ...simulation method for the permeability of a textile reinforcement, based on a finite difference discretisation of the Stokes equations. Results for single layer, multi-layer and sheared models are discussed. The influence of intra-yarn flow and periodic or wall boundary conditions are considered. We compare the numerically computed permeability values with experimental data.
We present a new analysis of the first mid-infrared N-band long-baseline interferometric observations of an extragalactic source: the nucleus of the Seyfert 2 galaxy NGC 1068, obtained with MIDI ...(Mid-InfrareD Interferometer), the mid-infrared beamcombiner at the European Southern Observatory (ESO) Very Large Telescope Interferometer (VLTI). The resolution of $\lambda/B \sim 10$ mas allows us to study the compact central core of the galaxy between 8 and 13 μm. Both visibility measurements and MIDI spectrum are well reproduced by a simple radiative transfer model with two concentric spherical components. The derived angular sizes and temperatures are ~35 and 83 mas, and ~361 K and 226 K for these two components respectively. Other evidence strongly supports such low temperatures. This modeling also provides the variation of optical depth as a function of wavelength for the extended component across the N-band suggesting the presence of amorphous silicate grains. This shows that MIDI has carried out the first direct observations of the distribution of dust around the central engine.
Measurements of the dynamic railpad properties Maes, J.; Sol, H.; Guillaume, P.
Journal of sound and vibration,
01/2006, Letnik:
293, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
Numerical models of a railway track rarely take the nonlinear dynamic component behaviour of the railpad into account due to three important problems: first, the considerable amount of calculation ...time consumed by nonlinear numerical models; second, the lack of validation tools for nonlinear numerical models; third, the lack of data on the nonlinear properties of those components. The ever-increasing power of computers will solve the first problem. Scale models can be a solution for the validation problem. This paper discusses a practical solution for the third problem.
The paper will present an alternative set-up for railpad testing allowing for the measurement of stiffness and damping values between 20 and 2500
Hz with variable preload. It shows the important variation of the dynamic stiffness and the loss factor throughout the chosen frequency range. It is also found that the nonlinear dynamic behaviour of this railway track component certainly affects the dynamic behaviour of the complete track.
The Vela supernova remnant (SNR) is a complex region containing a number of sources of non-thermal radiation. The inner section of this SNR, within 2 degrees of the pulsar PSR B0833-45, has been ...observed by the HESS γ-ray atmospheric Cherenkov detector in 2004 and 2005. A strong signal is seen from an extended region to the south of the pulsar, within an integration region of radius $0.8\ensuremath{^{\circ}}$ around the position ($\rm \alpha = 08^{h} 35^{m} 00^{s}$, $\delta = -45\ensuremath{^{\circ}}36\arcmin$ J2000.0). The excess coincides with a region of hard X-ray emission seen by the ROSAT and ASCA satellites. The observed energy spectrum of the source between 550 GeV and 65 TeV is well fit by a power law function with photon index $\Gamma = 1.45 \pm 0.09\ensuremath{_{{\rm stat}}}\ \pm 0.2\ensuremath{_{{\rm sys}}}$ and an exponential cutoff at an energy of $13.8 \pm 2.3\ensuremath{_{{\rm stat}}}\ \pm 4.1\ensuremath{_{{\rm sys}}}$ TeV. The integral flux above 1 TeV is $(1.28 \pm 0.17\ensuremath{_{{\rm stat}}}\ \pm 0.38\ensuremath{_{{\rm sys}}}) \times 10^{-11}\ \ensuremath{{\rm cm}^{-2}\,{\rm s}^{-1}}$. This result is the first clear measurement of a peak in the spectral energy distribution from a VHE γ-ray source, likely related to inverse Compton emission. A fit of an Inverse Compton model to the HESS spectral energy distribution gives a total energy in non-thermal electrons of ~$2 \times 10^{45}$ erg between 5 TeV and 100 TeV, assuming a distance of 290 parsec to the pulsar. The best fit electron power law index is 2.0, with a spectral break at 67 TeV.
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