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European Microscopy Congress 2016: Proceedings || An in-situ Low Energy Argon Ion Source for Local Surface Modification
摘要： A new in-situ low energy ion source for surface modification of a sample surface has been designed. The source is based on the principle of low energy ion bombardment from a beam of ions such as Ar+, N+, or He+ can be used for a local modification of the sample surface. Typical energies are in the range 10 - 100 eV, covering the interaction types from chemical reaction to ion etching and to ion implantation. The source is based on the following principle: electrons from a filament are accelerated towards a grid by a potential difference between the filament and the grid. The electrons enter a gas-filled region between the grid and the sample, where they ionize the gas. The ions are then accelerated towards the sample by a potential difference between the grid and the sample. The source produces a static beam of ions with a selectable energy of 10-100 eV and a full width half maximum (FWHM) of 7.1 um. This corresponds to a central ion current density of 0.019 nA/um2 at 100 eV, which is very similar to the current density at 100 eV of a regular ICP source. In this way, the sample area that is affected by the low energy ions can be more or less defined by the applied bias voltage. The first application can be polishing the top surface of a TMD laminate produced by CVD, or improvement of and LPE surface prepared by ICP. An example of the interaction with the beam is shown in Figure 1, where a native oxide on Si has been removed in 25 seconds, using 100 eV Ar+ ions.
关键词： Ar+,surface modification,low energy ion source,chemical reaction,FWHM,native oxide removal,ion etching,ICP,current density,static beam,N+,ion bombardment,TMD,He+,LPE,ion implantation,in-situ,gas ionization,filament,grid,CVD
更新于2025-09-19 17:15:36
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AlGaN deep-ultraviolet light-emitting diodes grown on SiC substrates
摘要： The disinfection industry would greatly benefit from efficient, robust, high-power deep-ultraviolet light-emitting diodes (UV-C LEDs). However, the performance of UV-C AlGaN LEDs is limited by poor light-extraction efficiency (LEE) and the presence of a large density of threading dislocations. We demonstrate high power AlGaN LEDs grown on SiC with high LEE and low threading dislocation density. We employ a crack-free AlN buffer layer with low threading dislocation density and a technique to fabricate thin-film UV LEDs by removing the SiC substrate, with a highly selective SF6 etch. The LEDs (278 nm) have a turn-on voltage of 4.3 V and a CW power of 8 mW (82 mW/mm2) and external quantum efficiency (EQE) of 1.8% at 95 mA. KOH submicron roughening of AlN surface (nitrogen-polar) and improved p-contact reflectivity are found to be effective in improving the LEE of UV light. We estimate the improved LEE by semi-empirical calculations to be 33% (without encapsulation). This work establishes UV LEDs grown on SiC substrates as a viable architecture to large-area, high-brightness, and high power UV LEDs.
关键词： AlGaN LEDs,UV-C LEDs,light extraction efficiency,disinfection technology,AlN,external quantum efficiency,SiC,substrate removal
更新于2025-09-19 17:13:59
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Laser hair removal following forehead flap for nasal reconstruction
摘要： The forehead flap is a dependable option for nasal reconstruction owing to its reliability and anatomic likeness to nasal skin. For patients with low hairlines, the vertical design of the paramedian forehead flap can intrude into the scalp, thus incorporating hair into the nasal reconstruction. The inadequate length of the forehead flap or shift to an oblique design may result in eyebrow elevation and asymmetry. Therefore, laser hair removal (epilation) on the forehead flap has been proposed to improve esthetic results. An alexandrite laser (755 nm, 10 to 20 ms, 18-mm spot size) with a Dynamic Cooling Device? (DCD?) cooling system was used for hair removal in 22 patients (16 male and 6 female patients) after nasal reconstructions using forehead flaps from December 2011 to September 2016. All patients received cryogen spray cooling laser treatment (CSC-LT). The mean follow-up period was 24 months, with a range between 18 and 50 months. The average duration of treatment was 1.8 months (range, 1–5 months). The energy density ranged from 14 to 18 J/cm2 with an average of 17.2 J/cm2. The number of treatments ranged from 2 to 4 (mean 2.8). Patients had satisfactory esthetic results over 11.1 months (range, 8–18 months). Residual white hairs were observed in 3 patients, and 4 patients had tiny black residual hairs without deteriorating cosmesis. Using an alexandrite laser to remove hair on the forehead is safe and reliable in nasal reconstruction with superior recipient site cosmesis.
关键词： Hair removal,Epilation,Nasal reconstruction,Forehead flap,Laser
更新于2025-09-19 17:13:59
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Improvement of ablation capacity of sapphire by gold film-assisted femtosecond laser processing
摘要： Sapphire is widely used in civilian and military equipment owing to its superior optical and mechanical properties. Femtosecond laser has been demonstrated to be an effective tool to process sapphire material. However, the direct processing of sapphire by femtosecond laser still meets some challenges, such as poor ablation morphology and low laser energy absorption. In this work, femtosecond laser processing of sapphire coated with a 12-nm-thick gold film (Au-coated sapphire) has been investigated. The experimental results have revealed that the ablation morphology of Au-coated sapphire has been improved, featuring fewer molten materials and thermal cracks, as well as regular crater shape and uniform periodic surface structures. It has also been found that, under 100 shots condition, the threshold fluence of Au-coated sapphire is reduced by about 56% compared to that of uncoated one. Meanwhile, the incubation effect of Au-coated sapphire is stronger than that of uncoated one. We also illustrate that the material removal rate of Au-coated sapphire is increased up to about two times higher than that of uncoated one. In order to reveal the effective mechanism of the gold film in the laser processing of sapphire, the energy transfer process among incident photons, free electrons and sapphire lattice phonons was studied. Our study provides a guidance for improving the laser ablation capacity of sapphire.
关键词： Gold film,Sapphire,Material removal rate,Ablation morphology,Femtosecond laser processing
更新于2025-09-19 17:13:59
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A 3D net-like structured fluorescent aerogel based on carboxy-methylated cellulose nanofibrils and carbon dots for a highly effective adsorbent and sensitive optical sensor of Cr(VI)
摘要： To effectively detect and remove Cr(VI) from aqueous solution, a 3D net-like structured fluorescent aerogel was designed and synthesized using highly photoluminescent carbon dots (CDs) and renewable natural carboxy-methylated cellulose nanofibrils (CM-CNF). The surface morphology, microstructure, chemical elements and fluorescence properties of this novel aerogel were studied. Sorption experiments were designed to investigate the sorption properties of Cr(VI) onto this fluorescent aerogel. The adsorption process was described by pseudo-second-order kinetic model and Freundlich model, and the maximum adsorption capacity for Cr(VI) reached 433.5 mg g–1. Furthermore, this novel aerogel emitted bright blue fluorescence with a quantum yield of 11.8 % when applied to Cr(VI) sensing, and a good linear relationship between the quantum yield and Cr(VI) concentration was demonstrated. Accordingly, this novel 3D net-like structured fluorescent aerogel should be a promising smart sorbent for the removal of Cr(VI) with advantages of the 3D net-like structure and rich functional groups that accelerate Cr(VI) sorption and the wrapped fluorescent probe that improves Cr(VI) sensing.
关键词： optical sensor,Cr(VI) removal,3D net-like structured fluorescent aerogel,carboxy-methylated cellulose nanofibrils,carbon dots
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - An Assessment of Perovskite Solar Cells for Low-Intensity-Low-Temperature (LILT) Space Missions
摘要： We propose a sampling scheme that can perfectly reconstruct a collection of spikes on the sphere from samples of their lowpass-filtered observations. Central to our algorithm is a generalization of the annihilating filter method, a tool widely used in array signal processing and finite-rate-of-innovation (FRI) sampling. The proposed algorithm can reconstruct spatial samples. For large , this sampling requirement improves over previously known FRI sampling schemes on the sphere by a factor of four. We showcase the versatility of the proposed algorithm by applying it to three problems: 1) sampling diffusion processes induced by localized sources on the sphere, 2) shot noise removal, and 3) sound source localization (SSL) by a spherical microphone array. In particular, we show how SSL can be reformulated as a spherical sparse sampling problem.
关键词： sparse sampling,spherical harmonics,finite rate of innovation,sphere,Annihilation filter,diffusion sampling,shot noise removal,sound source localization
更新于2025-09-19 17:13:59
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Influence of surface treatment with infrared nanosecond laser on adhesion performance of adhesion-bonded carbon fiber/epoxy composite
摘要： The surface treatment of carbon fiber/epoxy composites with a pulsed infrared (1064 nm wavelength) nanosecond (7 ns pulse duration) laser has been investigated. It is found that single 1064 nm laser pulse can remove the polymer matrix from composite surface to expose the carbon fibers by expansion of the pyrolysis gas resulting from laser-induced polymer degradation. The influences of laser power density and scan strategy on matrix removal process have been studied. The bonding strength of laser processed, adhesion-bonded CFRP (carbon fiber reinforced plastic) increase with lower matrix residues on the fibers and a linear relation is found. The adhesion-bonding strength of CFRP surfaces, tested by lap-joint shear test, exceeds the strength measured for untreated and abrasion treated (SiC paper) samples. The main origin of fiber damage of the laser-treated surface is mechanical fracture rather than thermal damage as found by laser scanning confocal microscope and scanning electron microscope. The characteristic morphologies and failure modes of shear-tested surfaces are analyzed. The obvious improvement of adhesive strength is achieved by the laser-treated surfaces attributed to matrix removal and carbon fibers protruding. A 1 D model is established to describe temperature and internal gas pressure of the irradiated surface. The new laser treatment method needs less laser energy and low pulse numbers and prove the way to an efficient, low-cost surface treatment for preparation of high quality adhesion bonded CFRP components.
关键词： matrix removal,adhesion strength,1064 nm laser,Carbon fiber/epoxy composite
更新于2025-09-19 17:13:59
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Solution‐Processed Laminated Perovskite Layers for High‐Performance Solar Cells
摘要： In this study, the combined effect of dissolved oxygen (DO) and COD/N on nitrogen (N) removal as well as the corresponding mechanisms were investigated in aerated constructed wetlands (CWs). At each investigated COD/N level, the ammonium removal efficiency increased as DO concentration increased. However, the highest total N removal efficiency occurred at different DO concentration at each COD/N level. The results of functional gene analysis and cyclic N profile studies indicated that DO supply and COD/N influence the N removal performance, which is not only exert a direct effect on nitrification-denitrification process, but also change N removal pathway in intermittent aerated CWs. At a relatively high influent COD/N of 20, the simultaneous nitrification and denitrification (SND) via nitrite was almost the exclusive N removal pathway at all investigated DO concentration. With the decrease of COD/N from 20 to 2 at DO of ～1.8, ～3.5 and ～6.0 mg/L, SND efficiency all decreased, however, its decreasing rate was much higher at relatively high DO level of ～6.0 mg/L than that at DO levels of ～1.8 and ～3.5 mg/L. In comparison, a simultaneously partial nitrification, anammox and denitrification was established at DO of ～0.8 mg/L along with reducing influent COD/N.
关键词： Oxygen,Removal,Intermittent,Aeration,Dissolved,COD/N,Constructed wetlands,Nitrogen
更新于2025-09-19 17:13:59
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[IEEE 2019 International Conference on ENERGY and ENVIRONMENT (CIEM) - Timisoara, Romania (2019.10.17-2019.10.18)] 2019 International Conference on ENERGY and ENVIRONMENT (CIEM) - Interharmonic and Harmonic Steady-State Computation of a Grid-Tied Photovoltaic System
摘要： We propose a sampling scheme that can perfectly reconstruct a collection of spikes on the sphere from samples of their lowpass-filtered observations. Central to our algorithm is a generalization of the annihilating filter method, a tool widely used in array signal processing and finite-rate-of-innovation (FRI) sampling. The proposed algorithm can reconstruct spatial samples. For large, this sampling requirement improves over previously known FRI sampling schemes on the sphere by a factor of four. We showcase the versatility of the proposed algorithm by applying it to three problems: 1) sampling diffusion processes induced by localized sources on the sphere, 2) shot noise removal, and 3) sound source localization (SSL) by a spherical microphone array. In particular, we show how SSL can be reformulated as a spherical sparse sampling problem.
关键词： sparse sampling,spherical harmonics,finite rate of innovation,sphere,Annihilation filter,diffusion sampling,shot noise removal,sound source localization
更新于2025-09-19 17:13:59
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Paint Removal with Pulsed Laser: Theory Simulation and Mechanism Analysis
摘要： This paper studies paint removal using laser technology. A finite element model was created using COMSOL Multiphysics software, and the temperature field generated during the cleaning process was analyzed and verified. Laser paint removal behavior was investigated using a fiber laser, and its mechanism studied by combining Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. In-depth analysis of this relatively new technology could provide the theoretical basis for industrial application. The results of this study show that, when compared to the original paint layer, the infrared absorption spectrum of the cleaned surface had two additional two peaks—1333.36 cm?1 and 678.82 cm?1. In addition, there was a decrease in C element content on the treated surface and an increase in O content. In addition, new organic and complex compounds were formed on the cleaned surface as a result of bond cleavage and rearrangement. Furthermore, paint particles of varying sizes and shapes were produced by the impact of plasma shock. Under high-energy laser irradiation, the paint layer underwent combustion, resulting in spherical nanoparticles of uniform shape.
关键词： plasma,mechanism,combustion,paint removal,chemical bond,pulsed laser
更新于2025-09-19 17:13:59