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Influences of sol-gel progress on luminescent properties of Li <sub/>1.0</sub> Nb <sub/>0.6</sub> Ti <sub/>0.5</sub> O <sub/>3</sub> :Eu <sup>3+</sup> red phosphor
摘要： Li1.0Nb0.6Ti0.5O3:3wt.%Eu3+ red phosphor was synthesized by sol-gel method. The influences of the pH value and the citric acid(CA)/ metal cations(M) ratio on the luminescent properties of the samples were discussed. The properties of the samples were characterized by X-ray diffraction(XRD) and photoluminescence spectroscopy, respectively. The results showed that the samples were consist of “M- phase”. Under the 466nm excitation, the orange emission at 592nm and the red emission at 612nm could be observed. The emission intensity increased with the increasing of pH value firstly and then decreased. The optimum pH value was 5.5. Moreover, the emission intensity decreased with the increasing of CA/M ratio. The relatively high emission intensity of the sample could be obtained when the CA/M was 3:1. Emission spectra and CIE coordinate of Li1.0Nb0.6Ti0.5O3:3wt.% Eu3+ were superior to commercial red phosphor Y2O3:Eu3+,which showed the red phosphor could have potential application in the White-LED field.
关键词： the red phosphor,Eu3+-doped,emission spectrum,Sol-gel method
更新于2025-09-23 15:23:52
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Classification of pre-dyed textile fibers exposed to weathering and photodegradation by non-destructive excitation-emission fluorescence spectroscopy paired with discriminant unfolded-partial least squares
摘要： Undyed textile fabrics such as Acrylic 864, Nylon 361 and Cotton 400 were pre-dyed with Basic Green 4 (BG4), Acid Yellow 17 (AY17) and Direct Blue 1 (DB1) dyes, respectively; and then exposed to two extremely diverse weather conditions in the United States: desert and humid environmental settings in Arizona (AZ) and Florida (FL) respectively, for different time intervals of exposure, which included 0, 3, 6, 9 and 12 months. After every interval of a 3 months period, ten fibers were uniformly sampled from each cloth piece, and fluorescence microscopy was employed to collect two-dimensional excitation and fluorescence spectra (2-D spectra) and three-dimensional (3D) excitation-emission matrices (EEMs). A significant loss of fluorescence intensity was observed upon fiber exposure to outdoor weathering conditions. For a comprehensive statistical data analysis and to be able to discriminate between any two single fibers weathered under different conditions, a multiway calibration algorithm known as discriminant unfolded partial least-squares (DU-PLS) method was applied to the exposed fibers. Results indicate that fluorescence spectroscopy combined with DU-PLS has the ability to appropriately classify and differentiate between any two pairs of dyed cotton or nylon fibers (acrylic in some cases) exposed to dry versus humid weather environments under different time intervals of exposure. These results provide the foundation for future studies towards a non-destructive approach capable to provide information on the weathering history of the fiber.
关键词： Discriminant unfolded partial least squares,Fiber analysis,Photodegradation,Excitation emission matrices,Weathering,Fluorescence spectroscopy
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Hangzhou, China (2018.8.13-2018.8.17)] 2018 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Nanofabrication Techniques Used for Suppressing Multipactor in Space Applications
摘要： A significant trouble in high power microwave (HPM) systems is multipactor discharge – an avalanche of electrons resulting from the secondary electron emission (SEE). It would cause serious problems and limits the attainable power. Nano fabrication techniques, such as sputtering, photolithography, etching and Graphene, are adopted to reduce the secondary electron yield (SEY) of a material to improve multipactor discharge threshold. It is clearly demonstrated that these fabrications can suppress the SEY efficiently. The influence of surface characteristic on SEY is discussed to find that increase porosity and aspect ratio will reduce SEY. These results provided a criterion to determine nanofabrication techniques for multipactor suppression.
关键词： nanofabrication techniques,secondary electron emission,suppression,multipactor
更新于2025-09-23 15:23:52
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[IEEE 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - Amsterdam (2018.8.27-2018.8.30)] 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - Emission Measurement of a Solar Park in the Frequency Range of 2 to 150 kHz
摘要： Although a few years have passed since the first electromagnetic compatibility problems occurred in the frequency range of 2 to 150 kHz, but we still lack fundamental standards, especially related to emission, that would ensure electromagnetic compatibility. Our aim was to get a better picture about the emission of a solar inverter and also about how disturbances generated by more inverters spread and aggregate on the grid. Thus, based on on-site measurements, this paper investigates the non-intentional supraharmonic emission (both current and voltage) of a solar park that consists of a total of 50 individual PV (photovoltaic) modules and inverters. Supraharmonic voltages and currents were measured at three locations: at one individual PV unit, at a busbar collecting the production of ten PV units and at the transformer, which connects the park with the grid. It was shown that the aggregation of these disturbances is a very complex process, but supraharmonic currents are more likely to flow between the inverters than into the grid. Another important result is that an alteration in production does not significantly change emission levels.
关键词： 2 kHz – 150 kHz,electromagnetic compatibility,supraharmonic emission,inverter,solar park
更新于2025-09-23 15:23:52
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[IEEE 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - Amsterdam (2018.8.27-2018.8.30)] 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE) - Retrofitting a Shielded Camera Enclosure with an Internet Protocol Camera and Testing for Radiated Immunity and Emission in a Reverberation Chamber
摘要： Shielded cameras are required to observe the device under test during an immunity test in a reverberation chamber. The camera in the reverberation chamber needs to withstand the electromagnetic field and should give a good quality of the picture in real time. In this paper, the retrofitting of an existing shielded camera enclosure with a new low-cost commercial-off-the-shelf network camera is described. The camera's communication is transduced into optical fibers using media converters. The shielded camera is tested in the large reverberation chamber of the Otto von Guericke University in Magdeburg according to the IEC 61000-4-21 for radiated immunity and emission.
关键词： shielded camera,mode-stirred chamber,reverberation chamber,radiated immunity,radiated emission
更新于2025-09-23 15:23:52
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Exact Evaluation of K. Jensen's General Thermal-Field-Photoemission Integral
摘要： Jensen has developed a general expression for the current density JGT F emitted from a surface by thermal or field emission, or by a combination of these processes; he has also shown how the same expression may be analytically extended to compute the current density due to photoemission. JGT F is expressed as a single integral, which Jensen evaluates analytically in certain limits and numerically outside those limits. In this paper, we show how the integral may be expressed generally as convergent series that are easily evaluated numerically for all values of the physical parameters. No real or apparent singularities, like those that appear in the function Z defined by Jensen occur in the series obtained here.
关键词： photoemission,field emission,thermal emission,Electron emission
更新于2025-09-23 15:22:29
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Engineering Tunable Broadband Near-Infrared Emission in Transparent Rare-Earth Doped Nanocrystals-in-Glass Composites via a Bottom-Up Strategy
摘要： Applications of trivalent rare earth (RE3+)-doped light sources in solid-state laser technology, optical communications, biolabeling, and solar energy management have stimulated a growing demand for broadband emission with flexible tunability and high efficiency. Codoping is a conventional strategy for manipulating the photoluminescence of active RE3+ ions. However, energy transfer between sensitizers and activators usually induces nonradiative migration depletion that brings detrimental luminescent quenching. Here, a transparent framework is employed to assemble ordered RE3+-doped emitters to extend the emission spectral range by extracting photons from a variety of RE3+ ions with sequential energy gradient. To block migration-mediated depletion between different RE3+ ions, a nanoscopic heterogeneous architecture is constructed to spatially confine the RE3+ clusters via a 'nanocrystals-in-glass composite' (NGC) structure. This bottom-up strategy endows the obtained RE3+-doped NGC with high emission intensity (nearly one order of magnitude enhancement) and broadband near-infrared emission from 1300 to 1600 nm, which covers nearly the whole low-loss optical communication window. Most crucially, NGC is a versatile approach to design tunable broadband emission for the potential applications in high-performance photonic devices, which also provides new opportunities for engineering multifunctional materials by integration and manipulation of diverse functional building units in a nanoscopic region.
关键词： luminescence,rare earth doping,broadband emission,nanocrystals-in-glass composite,near-infrared emission
更新于2025-09-23 15:22:29
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Novel SPECT Technologies and Approaches in Cardiac Imaging
摘要： Recent novel approaches in myocardial perfusion single photon emission CT (SPECT) have been facilitated by new dedicated high-efficiency hardware with solid-state detectors and optimized collimators. New protocols include very low-dose (1 mSv) stress-only, two-position imaging to mitigate attenuation artifacts, and simultaneous dual-isotope imaging. Attenuation correction can be performed by specialized low-dose systems or by previously obtained CT coronary calcium scans. Hybrid protocols using CT angiography have been proposed. Image quality improvements have been demonstrated by novel reconstructions and motion correction. Fast SPECT acquisition facilitates dynamic flow and early function measurements. Image processing algorithms have become automated with virtually unsupervised extraction of quantitative imaging variables. This automation facilitates integration with clinical variables derived by machine learning to predict patient outcome or diagnosis. In this review, we describe new imaging protocols made possible by the new hardware developments. We also discuss several novel software approaches for the quantification and interpretation of myocardial perfusion SPECT scans.
关键词： fast myocardial perfusion single photon emission computed tomography,quantification,single photon emission computed tomography,low dose,myocardial perfusion imaging,stress only
更新于2025-09-23 15:22:29
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Recent Trends Concerning Upconversion Nanoparticles and Near-IR Emissive Lanthanide Materials in the Context of Forensic Applications
摘要： Upconversion nanoparticles (UCNPs) are materials that, upon absorbing multiple photons of low energy (e.g. infrared radiation), subsequently emit a single photon of higher energy, typically within the visible spectrum. The physics of these materials have been the subject of detailed investigations driven by the potential application of these materials as medical imaging devices. One largely overlooked application of UCNPs is forensic science, wherein the ability to produce visible light from infrared light sources would result in a new generation of fingerprint powders that circumvent background interference which can be encountered with visible and ultraviolet light sources. Using lower energy, infrared radiation would simultaneously improve the safety of forensic practitioners who often employ light sources in less than ideal locations. This review article covers the development of UCNPs, the use of infrared radiation to visualise fingerprints by the forensic sciences, and the potential benefits of applying UCNP materials over current approaches.
关键词： Upconversion nanoparticles,Fingerprint visualisation,Near-IR emissive lanthanide materials,Forensic applications,NIR emission
更新于2025-09-23 15:22:29
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Cathodoluminescent lamp for general lighting using carbon fiber field emission cathode
摘要： The prototype of cathodoluminescent bulb for general lighting with field emission cathode on the basis of carbon fiber is manufactured. The bulb comprises a high-voltage built-in AC-DC converter of the electric line voltage and a standard E27 cap. A high frequency converter is used to obtain high voltage. The anode voltage relative to the modulator is up to +20 kV; the cathode voltage is up to –4 kV; the current value is of the order of 1 mA. The voltage converter is located in the bulb cap and around the neck of the glass envelope.
关键词： cathode-ray-tube phosphor,carbon fiber,light sources,field emission cathodes,cathodoluminescence
更新于2025-09-23 15:22:29