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Electroluminescence of intrashell transitions in Eu doped single ZnO nanowires
摘要： Tunable nanoscale light emitters are essential to accomplish future multifunctional optoelectronic nano-devices. Here, we present an approach for achieving red electroluminescence from single ZnO nanowires implanted with Europium ions. The electroluminescence is emitted mainly from the end facets of ZnO nanowires at room temperature under the application of an AC voltage. The corresponding electroluminescence spectrum is attributed to the radiative intrashell transitions of the Eu ions, while contributions from near band edge or deep level emission of the ZnO remain absent. The total intensity of the electroluminescence is linearly proportional to the length of the nanowires, whereas there is no clear correlation with other morphology factors of the nanowire based device such as the diameter. Furthermore, the underlying excitation mechanism of the electroluminescence is proposed as direct-impact excitation of Eu ions by hot electrons in the ZnO nanowires.
关键词： electroluminescence,Zinc oxide (ZnO),Europium (Eu),nanowires,rare earth elements,ion beam doping
更新于2025-09-09 09:28:46
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Recovering the “new twin”: Analysis of secondary neodymium sources and recycling potentials in Europe
摘要： Sustainable management strategies for securing long–term supply of rare earth elements is priority for Europe due to a complex and interlinked production chain and its dependence on Chinese export. Among rare earth elements, neodymium captured most attention due to its essential role in a wide spectrum of applications including green–energy technologies such as wind turbines and electric vehicles. Being complementary to primary production, end–of–life recycling would diversify neodymium supply, relieve the Chinese dominance on primary production and contrast the balance problem. However, neodymium recycling at end–of–life is not yet in place. In this work, we developed a dynamic material ?ow model to investigate neodymium stocks and ?ows in the EU–28 to 2016. The analysis enabled a detailed investigation of secondary sources of neodymium, which set essential boundary conditions for material recovery and recycling. We found that roughly up to 50% of the annual neodymium demand in the EU–28 could be met by domestic secondary supply, if latent recycling potentials were turned into actual capacity. Signi?cant energy savings and GHG emissions cut could be also attained. However, product design, end–of–life collection, and scrap price issues are primary obstacles to neodymium recovery. Thus, unless going beyong those limits, establishing and maintaining a sustainable recycling chain for neodymium in the EU–28 will remain problematic.
关键词： Rare earth elements,Voice coil motors,Permanent magnets,Balance problem,Electric vehicles,Wind turbines
更新于2025-09-04 15:30:14
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Inverse photonic design of functional elements that focus Bloch surface waves
摘要： Bloch surface waves (BSWs) are sustained at the interface of a suitably designed one-dimensional (1D) dielectric photonic crystal and an ambient material. The elements that control the propagation of BSWs are defined by a spatially structured device layer on top of the 1D photonic crystal that locally changes the effective index of the BSW. An example of such an element is a focusing device that squeezes an incident BSW into a tiny space. However, the ability to focus BSWs is limited since the index contrast achievable with the device layer is usually only on the order of Δn≈0.1 for practical reasons. Conventional elements, e.g., discs or triangles, which rely on a photonic nanojet to focus BSWs, operate insufficiently at such a low index contrast. To solve this problem, we utilize an inverse photonic design strategy to attain functional elements that focus BSWs efficiently into spatial domains slightly smaller than half the wavelength. Selected examples of such functional elements are fabricated. Their ability to focus BSWs is experimentally verified by measuring the field distributions with a scanning near-field optical microscope. Our focusing elements are promising ingredients for a future generation of integrated photonic devices that rely on BSWs, e.g., to carry information, or lab-on-chip devices for specific sensing applications.
关键词： focusing elements,scanning near-field optical microscope,integrated photonic devices,Bloch surface waves,photonic design
更新于2025-09-04 15:30:14
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A Non-conformal Surface Integral Equation for Electromagnetic Scattering by Multiscale Conducting Objects
摘要： We present a non-conformal surface integral equation (SIE) method for the analysis of time-harmonic electromagnetic (EM) scattering by multiscale perfect electrically conducting (PEC) objects. To alleviate the burden of geometrical processing, a mixed triangle/quadrilateral mesh with arbitrary non-conformity is adopted in this method. A vectorial piecewise constant basis function is defined over the unstructured mesh as the trial and test function. The recently developed reverse operation self-consistent evaluation (ROSE) approach is employed to evaluate the hyper-singular integrals. Due to the utilization of this locally defined basis function, the function space is enlarged from the commonly used div-conforming space to the square-integrable counterpart. Therefore, it will be possible to apply different polygonal elements or basis functions with different orders according to the local characteristics of the geometry. Several numerical results are presented to validate the accuracy and demonstrate the versatility of the proposed method for modeling multiscale and electrically-large PEC objects.
关键词： Non-conformal,mixed elements,surface integral equation,multiscale,discontinuous Galerkin
更新于2025-09-04 15:30:14
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Standardization of Proton Induced X-Ray Emission for Analysis of Trace Elements in Thick Targets
摘要： This paper presents the standardization of Proton Induced X-rays Emission (PIXE) technique for the trace element analysis of thick standard samples. Three standard reference materials (SRMs) viz-à-vis titanium, copper and iron base alloys were used for the study due to their availability. The protons beam was accelerated up to 2.57 MeV energy by 5UDH-II tandem Pelletron accelerator and samples were irradiated at different geometry and durations. Spectrum was acquired using a multi-channel spectrum analyzer while spectrum analysis was done using a GUPIXWIN model for determination of elemental concentrations of trace elements. The obtained experimental data was compared with theoretical data and results were found in close agreement.
关键词： GUPIXWIN Software,PIXE Standardization,Trace Elements
更新于2025-09-04 15:30:14