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EMD- PNN based welding defects detection using laser-induced plasma electrical signals
摘要： The plasma electrical signal has gained extensive attention for characterizing the behavior of the laser-induced plasma due to the advantages of easy acquisition and feedback control. In this paper, the electrical signals were measured by a passive probe based on the principle of plasma sheath effect. To explore the mutation characteristics of plasma electrical signals during defect generation in laser deep penetration welding, wavelet packet transform (WPT) and empirical mode decomposition (EMD) were used to compress data and extract features, respectively. Based on the analysis of the time-frequency spectrum of a typical plasma electrical signal, the approximate coefficients of 0?390 Hz frequency range were reconstructed. The residual term which characterizes the change trend of electrical signal was obtained by the further adaptive decomposition. For better identifying weld defects, another two statistical features, mean value and standard deviation, were extracted by carrying out statistical analysis in the time domain. The feature database is built with above features and used as inputs of the predictive model based on the probabilistic neural network (PNN). The result showed the average prediction accuracy was as high as 90.16% when recognizing five statuses of weld seam, including sound weld and four kinds of weld defects.
关键词： Wavelet packet transformation,Empirical mode decomposition,Laser welding,Plasma electrical signal,Probabilistic neural network
更新于2025-09-12 10:27:22
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Stress-controlled decomposition routes in cubic AlCrN films assessed by in-situ high-temperature high-energy grazing incidence transmission X-ray diffraction
摘要： The dependence of decomposition routes on intrinsic microstructure and stress in nanocrystalline transition metal nitrides is not yet fully understood. In this contribution, three Al0.7Cr0.3N thin films with residual stress magnitudes of ?3510, ?4660 and ?5930 MPa in the as-deposited state were in-situ characterized in the range of 25–1100 °C using in-situ synchrotron high-temperature high-energy grazing-incidence-transmission X-ray diffraction and temperature evolutions of phases, coefficients of thermal expansion, structural defects, texture as well as residual, thermal and intrinsic stresses were evaluated. The multi-parameter experimental data indicate a complex intrinsic stress and phase changes governed by a microstructure recovery and phase transformations taking place above the deposition temperature. Though the decomposition temperatures of metastable cubic Al0.7Cr0.3N phase in the range of 698–914 °C are inversely proportional to the magnitudes of deposition temperatures, the decomposition process itself starts at the same stress level of ~?4300 MPa in all three films. This phenomenon indicates that the particular compressive stress level functions as an energy threshold at which the diffusion driven formation of hexagonal Al(Cr)N phase is initiated, provided sufficient temperature is applied. In summary, the unique synchrotron experimental setup indicated that residual stresses play a decisive role in the decomposition routes of nanocrystalline transition metal nitrides.
关键词： thin films,AlCrN,phase decomposition,thermal expansion,microstructure,in-situ XRD,residual stress
更新于2025-09-12 10:27:22
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Photovoltaic active power control based on BESS smoothing
摘要： The power fluctuation of photovoltaic (PV) is harmful to power systems, so the battery energy storage system (BESS) was applied to smooth power fluctuation in PV. At present, the main ways to get configuration of BESS are low-pass filter and spectrum compensation, which have some drawbacks. In this paper, a method that combines empirical mode decomposition (EMD) with wavelet analysis (WA) is proposed to get grid-connected active power expectation of PV properly. Based on simulation of PV output, the minimum sizing of BESS is determined by different batteries’ state-of-charging (SOC) and efficiency. Comparing traditional low-pass filter and spectrum compensation, this method not only acquires the capacity of BESS accurately, but also improves the effect to smoothing power fluctuation of PV effectively. Finally, a case is proposed to verify correctness of the theory.
关键词： Sizing energy storage capacity,Empirical mode decomposition (EMD),Wavelet analysis,Photovoltaic output
更新于2025-09-12 10:27:22
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Using Terahertz Spectrometry to Study the Thermal Decomposition of Energy Materials
摘要： This paper describes experimental results on using nonstationary spectrometry in a terahertz frequency range to determine the composition of gaseous products of decomposition of energy materials. Dependences of analytical signals on lines of the main products of ammonium nitrate and PETN decomposition on time are obtained.
关键词： terahertz spectrometry,energy materials,ammonium nitrate,PETN,thermal decomposition,decomposition kinetics,decomposition products
更新于2025-09-11 14:15:04
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[IEEE 2019 2nd International Conference on Electrical Materials and Power Equipment (ICEMPE) - Guangzhou, China (2019.4.7-2019.4.10)] 2019 2nd International Conference on Electrical Materials and Power Equipment (ICEMPE) - Elemental Analysis of Aged Composite Insulators Based on Laser Induced Breakdown Spectroscopy
摘要： This paper aims at proposing a novel 2D non-linear phase decomposition of images, which performs the image processing tasks better than the traditional Fourier transformation (linear phase decomposition), but further, it has additional mathematical properties allowing more effective image analysis, including adaptive decomposition components and positive instantaneous phase derivatives. 1D unwinding Blaschke decomposition has recently been proposed and studied. Through factorization it expresses arbitrary 1D signal into an infinite linear combination of Blaschke products. It offers fast converging positive frequency decomposition in the form of rational approximation. However, in the multi-dimensional cases, the usual factorization mechanism does not work. As a consequence, there is no genuine unwinding decomposition for multi-dimensions. In this paper, a 2D partial unwinding decomposition based on algebraic transforms reducing multi-dimensions to the 1D case is proposed and analyzed. The result shows that the fast convergence offers efficient image reconstruction. The tensor type decomposing terms are mutually orthogonal, giving rise to 2D positive frequency decomposition. The comparison results show that the proposed method outperforms the standard greedy algorithm and the most commonly used methods in the Fourier category. An application in watermarking is presented to demonstrate its potential in applications.
关键词： hardy space,Fourier transform,adaptive Fourier decomposition,greedy algorithm,Nevanlinna factorization,unwinding Blaschke decomposition
更新于2025-09-11 14:15:04
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Topological and electrical properties of capped and annealed (0001) hydride vapor phase epitaxy GaN films on sapphire
摘要： In light of the necessity to anneal GaN to activate implanted dopants, the effects of the annealing temperature and time, the quality of the hydride vapor phase epitaxy grown GaN film, the quality of the annealing cap, and the effects of the stresses generated by the difference in the coefficients of thermal expansion of the film and the substrate are examined topographically using atomic force microscopy, and electrical measurements are made on Schottky diodes fabricated on the annealed samples. The results show that thermal decomposition begins at threading edge dislocations that form polygonized small angle grain boundaries during the annealing process; donor defects, probably nitrogen vacancies, are formed near the surface; and the donors are created more quickly when the annealing temperature is higher, the annealing time is longer, and the thermal stresses on the annealing cap are greater. The results suggest that the maximum annealing temperature is ～1300 °C, and at that annealing temperature, the annealing time should not exceed 4 min.
关键词： thermal decomposition,nitrogen vacancies,Schottky diodes,atomic force microscopy,GaN,annealing
更新于2025-09-11 14:15:04
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High-Precision Modal Decomposition of Laser Beams Based on Globally Optimized SPGD Algorithm
摘要： We propose a globally optimized stochastic parallel gradient descent (SPGD) algorithm to analyze the modal content of laser beams with high precision. Modal decomposition (MD) based on conventional SPGD algorithms often falls to a local minimum when a laser beam consists of six or more ?ber eigenmodes, which results in a false combination of modes. While keeping the simplicity and speed advantages of the SPGD algorithm, we adopted several optimization techniques to discern the global minimum from local minima and achieve better accuracy. The enhanced SPGD algorithm includes the annealing of the learning rates, identifying and escaping of local minima with large perturbations, and comparing of the transient error function with a reference value. We were able to exactly analyze the modal content of beams from six-mode optical ?bers with high precision in seconds. Calculation of the modal weight and phase percentage errors, as well as simulations of far-?eld evolution images, con?rmed the importance of ?nding the global minimum in improving the accuracy and real-time analysis of MD. The simple structure of the enhanced algorithm and its global optimization ability in multimode ?bers will accelerate numerical MD in diverse laser applications.
关键词： SPGD algorithm,Modal decomposition,?ber laser,global minimum
更新于2025-09-11 14:15:04
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Well‐Controlled Decomposition of Copper Complex Inks Enabled by Metal Nanowire Networks for Highly Compact, Conductive, and Flexible Copper Films
摘要： Highly compact and conductive Cu films are successfully fabricated by introducing mechanically robust and highly conductive metal nanowires (NWs) as fillers and optimizing amine-based ligands in Cu complex inks. The metal NWs (AgNWs and CuNWs) dispersed in the complex inks provide networks of nucleation sites for the in situ formed Cu particles and thereby control the decomposition of Cu complex inks at low temperatures to realize Cu films with high uniformity and integrality. The high affinity between metal NWs and the in situ formed Cu element enables the growth of Cu particles along the metal NWs to create a compact structure. Besides, the amine-based ligands such as 2-amino-2-methyl-1-propanol (AMP), 2-ethylhexylamine (Ethy), and hexylamine (Hexy) are varied to adjust the size of Cu particles and further improve the microstructure and conductivity of the sintered Cu films. The Cu-Ethy complex/metal NW inks sintered at 140 °C exhibit the lowest resistivity of 14.9 μ? cm, which is about one-third that fabricated from the pure Cu-AMP complex inks. The flexible light-emitting diode circuits and V-shaped dipole antennas prepared from the Cu complex/metal NW inks have excellent performance due to their outstanding conductivity and flexibility, showing great potential in the fabrication of cost-effective, flexible printed electronic devices.
关键词： antennas,controllable decomposition,metal nanowires,Cu complex inks,amine-based ligands
更新于2025-09-11 14:15:04
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Coherent Ray Tracing Simulation Of Non-Imaging Laser Beam Shaping With Multi-Aperture Elements
摘要： The application of laser light sources for illumination tasks like in mask aligner lithography relies on non-imaging optical systems with multi-aperture elements for beam shaping. When simulating such systems, the traditional approach is to separate the beam-shaping part (incoherent simulation) from dealing with coherence properties of the illuminating laser light source (diffraction theory with statistical treatment). We present an approach using Gaussian beam decomposition to include coherence simulation into ray tracing, combining these two parts, to get a complete picture in one simulation. We discuss source definition for such simulations, and verify our assumptions on a well-known system. We then apply our approach to an imaging beam shaping setup with microoptical multi-aperture elements. We compare the simulation to measurements of a similar beam-shaping setup with a 193 nm continuous-wave laser in a mask-aligner configuration.
关键词： Gaussian beam decomposition,laser beam shaping,mask aligner lithography,coherent ray tracing,multi-aperture elements
更新于2025-09-11 14:15:04
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Chemical inhibition of reversible decomposition for efficient and super-stable perovskite solar cells
摘要： Despite the remarkable photovoltaic characteristics and printability of perovskite solar cells, their intrinsic instability has been the most serious drawback toward future commercialization. In this work, we have investigated the stability of perovskite films in terms of morphology, electronic properties and chemical compositions. Specifically, the chemical decomposition inhibition strategy was introduced in perovskite films through iodine bromide to modify the crystal defects, leading to PSCs with suppressed hysteresis effects, superior durability and attractive PCE of 21.5%. Femto-second transient absorption spectra and GIWAXS measurements provide deep insight into the reduced carrier recombination and indicate the improved crystallinity of the modified perovskite films. Furthermore, an efficient hole-transporting material, PDPP4T, without using any doping process is applied to achieve PSCs with enhanced open-circuit voltage and better repeatability. As a consequence, the modified PSCs could maintain 82% of their initial efficiency after 5000 h of storage in ambient conditions and 90% of their initial efficiency after 1000 h of light soaking process. An excellent water resistance up to 100 h of the PSCs is also obtained by encapsulation technology. Besides, after coating Ce3+-CsPbI3 nanocrystals as luminescent down-shifting layers on the front side of the PSCs, the PCE of the device was further improved to 22.16 %.
关键词： iodine bromide,stability,perovskite solar cells,chemical inhibition,decomposition
更新于2025-09-11 14:15:04