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[IEEE 2019 XXIX International Scientific Symposium "Metrology and Metrology Assurance" (MMA) - Sozopol, Bulgaria (2019.9.6-2019.9.9)] 2019 XXIX International Scientific Symposium "Metrology and Metrology Assurance" (MMA) - The metod of reducing measurement error of the propagation delays in optical elements and optical fibers
摘要： The paper presents a method of reducing the measurement error propagation delays of signals in optical elements and optical fibers, based on the approximation of the recorded form of optical pulses and determining the time intervals between pulses, using the values of the parameters of the approximating functions. The scheme of the installation implementing the proposed method is presented, as well as the results of experimental approbation of the method.
关键词： optical element,optical fiber,signal propagation delay,approximation
更新于2025-09-23 15:21:01
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<i>(Invited)</i> Electrochemical Formation of Nanoporous Indium Phosphide in KOH Electrolytes
摘要： Anodization of highly doped n-InP in KOH can result in a nanoporous sub-surface layer. Pores originate from surface pits and an isolated porous domain is initially formed beneath each pit. Domains are separated from the surface by a thin non-porous layer and each is connected to the electrolyte by its pit. Pores emanate along the <111>A directions to form truncated tetrahedral domains. We propose a three-step model of electrochemical pore formation: (1) hole generation at pore tips, (2) hole diffusion and (3) electrochemical oxidation of the semiconductor to form etch products. Step 1 determines the overall etch rate. However, if the kinetics of Step 3 are slow relative to Step 2, then etching can occur at preferred crystallographic sites leading to pore propagation in preferential directions. Pore width decreases with increasing anodization temperature and with increasing KOH concentration up to 9 mol dm-3, above which it decreases. At low current densities pores have sharp tips and triangular cross-sections; at higher current densities, the pore tips and cross-sections become more rounded while the pore width decreases. These observations are explained by the three-step model.
关键词： electrochemical formation,nanoporous,pore propagation,indium phosphide,KOH electrolytes
更新于2025-09-23 15:21:01
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Study on high-efficiency separation of laminated glass by skillfully combining laser-induced thermal-crack propagation and laser thermal melting
摘要： Laminated glass has a wide range of applications, but the cutting process is too cumbersome. In this paper, a novel laser composite separation method was proposed to separate the laminated glass by one time and simplify the cutting process from five steps to two steps for the first time by skillfully combining laser-induced thermal-crack propagation and laser thermal melting. This method generated three laser foci, and each laser focus is acting on one layer of laminated glass. Then, the composite mechanism combining laser-induced thermal-crack propagation for glass layers and laser thermal melting separation for PVB layer was realized to separate entire laminated glass. The experiments of separating laminated glass with thickness of 5 + 0.38 + 5 mm were carried out by laser composite separation successfully, and the separation side wall was very smooth (roughness of glass layer reached 10.24 nm) without any separation defects such as chipping, micro-cracks or subsurface damage. A mathematical model was also established to analyze the separation mechanism.
关键词： Laser melting,Numerical simulation,Laser-induced thermal-crack propagation,Laser separation,Laminated glass
更新于2025-09-23 15:21:01
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Spatial Retrieval of Broadband Dielectric Spectra
摘要： A broadband soil dielectric spectra retrieval approach (1 MHz–2 GHz) has been implemented for a layered half space. The inversion kernel consists of a two-port transmission line forward model in the frequency domain and a constitutive material equation based on a power law soil mixture rule (Complex Refractive Index Model—CRIM). The spatially-distributed retrieval of broadband dielectric spectra was achieved with a global optimization approach based on a Shuffled Complex Evolution (SCE) algorithm using the full set of the scattering parameters. For each layer, the broadband dielectric spectra were retrieved with the corresponding parameters thickness, porosity, water saturation and electrical conductivity of the aqueous pore solution. For the validation of the approach, a coaxial transmission line cell measured with a network analyzer was used. The possibilities and limitations of the inverse parameter estimation were numerically analyzed in four scenarios. Expected and retrieved layer thicknesses, soil properties and broadband dielectric spectra in each scenario were in reasonable agreement. Hence, the model is suitable for an estimation of in-homogeneous material parameter distributions. Moreover, the proposed frequency domain approach allows an automatic adaptation of layer number and thickness or regular grids in time and/or space.
关键词： soil measurements,electromagnetic scattering inverse problems,dielectric measurements,modeling,microwave propagation,dielectric materials
更新于2025-09-23 15:21:01
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Influence of laser weld shape on mechanical and fatigue behaviour of single lap laser welded joints
摘要： Traditional manufacturing processes, like arc welding and resistance spot welding, are still the main welding processes to join structural components used across the on/o?-road vehicle industry. Due to the abundance of data, experiences and insights over the decades of usage, lot of fatigue design data has been generated for different joint geometries produced using these methods. The laser welding process has excellent capabilities to join thin sheet metal structures with minimum heat input resulting into lower deformation and improved productivity that offers significant benefit as compared to the arc and resistance welding processes. However, due to the agility of designing joint configurations and limited availability of understanding regarding the fatigue behaviour of laser welded joints, the need arises for the fatigue design data. Most of the research presents the use of straight linear shape laser welds and limited knowledge exist regarding the influence of shape of laser welds on mechanical and fatigue performance of the laser welded joints. The laser welded joints produce small notch like radius at the root of laser weld which could act as a stress raiser causing early crack initiation. For this work, C-shape laser weld has been selected as the geometric shape in comparison to the straight linear shape of laser weld produced on a series of single lap joints. Detailed fatigue experimental investigation has been carried out for linear and C-shape laser welded joints tested in 3 different orientations with respect to the applied cyclic load and several different R-ratio’s and the results are compared. The metallurgical studies have been carried out to understand the failure mode and micro-hardness variations across the weld and heat affected zone. Further, the residual stress profiles have been compared for the C-shape laser weld with the linear welds using detailed X - Ray Diffraction based residual stress measurement.
关键词： Laser Weld,Ultra-high strength steel,C Shape,Crack propagation,High strength low alloy steel,Crack initiation
更新于2025-09-23 15:21:01
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Patterns of propagation of high-order nonlinear dispersion wave modelled by the generalised KP equation
摘要： A wide range of two-dimensional nonlinear wave is described by Kadomtsev–Petviashvili (KP) equation. We obtained the classi?cation of travelling wave patterns to the generalised KP equation with high-order nonlinear dispersive and dissipative terms. Among these patterns, some new phenomena can be acquired for the ?rst time. Representations of wave propagation patterns were achieved by taking speci?c values of parameters. This means that all these patterns can be realised under appropriate physical conditions.
关键词： patterns of propagation,solitons.,Complete discrimination system for the polynomial,generalised Kadomtsev–Petviashvili equation
更新于2025-09-23 15:21:01
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Photonic transmission spectra in graphene-based Gaussian random multilayers
摘要： The light-matter interaction is a very active and attractive research field and it is the basis of the photonic devices based on the generation, processing and storage of photons. In this work, we theoretically study the propagation of electromagnetic waves in one-dimensional photonic crystals consisting of two different dielectric slabs (silicon dioxide and titanium dioxide) separated by graphene. The spatial arrangement of the slabs is periodic, but we introduce randomness by using a Gaussian distribution of thickness with a specific standard deviation σ. The well-known transfer-matrix method is used as the mathematical approach. Our main goals are to investigate how the presence of such randomness can change the light transmission spectra and the emergence of robust photonic band gaps. For a given angle of incidence, our numerical results show that the two lowest frequency bandgaps are insensitive to the influence of the Gaussian distribution. Those band gaps emerge from two different mechanisms: one is due to the presence of graphene, while the other is due to the Bragg’s scattering. A strong transmission dependence on the standard deviation σ is also observed in our numerical results. More interesting, for the transversal magnetic case (angle of incidence θ ? 60°) the system can be adjusted to present transmission coefficient near to 1 and work like a perfect transparent media, what is useful for technological applications.
关键词： Electromagnetic waves propagation,Light waves transmission,Graphene,Photonic crystals,Random multilayers
更新于2025-09-23 15:21:01
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Flame Propagation Enhancement by Dielectric Barrier Discharge-Generated Intermediate Species
摘要： The interaction between nonthermal plasma (NTP) and fuel-air mixtures was studied both experimentally and by means of simulations, to elucidate their promotional effect on flame propagation. A promotional effect on flame propagation velocity was experimentally observed by generating a dielectric barrier discharge (DBD), prior to spark plug ignition of an n-heptane mixture in a high-pressure and -temperature environment, using a rapid compression and expansion machine (RCEM). A novel method of concentration calibration for mass-spectral analysis was conducted, to determine the intermediate species in the fuel-air mixtures passing through the DBD plasma. The effect of the intermediate chemical species on flame propagation was examined numerically using the PREMIX code, with the observed species being considered as initial additives in the calculations. The promotional effect was reproduced numerically with the addition of alkyl hydroperoxide to an n-heptane/air mixture; and the higher the temperature and leaner the mixture in the parameter region, the more pronounced was the effect. The promotional behavior was examined using reaction path analysis, on the basis of which enhanced low-temperature oxidation reactions, due to the dissociation of the alkyl hydroperoxide, were determined in pre-flame region.
关键词： dielectric barrier discharge,flame propagation velocity,Plasma-assisted combustion,low-temperature oxidation,isomerization
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE 5G World Forum (5GWF) - Silicon Valley, CA, USA (2018.7.9-2018.7.11)] 2018 IEEE 5G World Forum (5GWF) - Multipath Propagation Analysis of 5G Systems at Higher Frequencies in Courtyard (Small Cell) Environment
摘要： The main target of this paper is to study the propagation characteristics of an outdoor and indoor user utilizing 5G system at higher frequency in a courtyard surrounded by building walls i.e. small cell environment. This research work is carried out by doing 3D ray tracing simulations utilizing “sAGA” – a 3D ray tracing tool. Unlike the conventional cellular network frequencies, the considered frequencies in the scope of this work are 15 GHz, 28 GHz and 60 GHz. For simulation routes, the results are provided in the form of received signal strength. For static points, the results are presented in the form of power angular spectrum and power delay profile. The achieved simulation results show that an adequate outdoor and indoor service can be provisioned at the considered frequencies. However, it is challenging to provide services to indoor user at 60 GHz using an outdoor base station even in such a small cell environment.
关键词： 3D ray tracing,multipath propagation,small cell,system performance,millimeter wave frequencies,5G
更新于2025-09-23 15:21:01
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Spatial characteristics of the truncated circular Airyprime beam
摘要： The circular Airyprime (CiAiP) beam is introduced in this paper. The spatial proprieties are well discussed and compared to the first order radial Laguerre–Gaussian beam LG10. The width, the divergence and the beam propagation factor are calculated based on the second order moments method, the latter is equal to M2 = 3.08. The free propagating CiAiP beam exhibits an unexpected non-diffracting character, it doesn’t spread through propa- gation. The on-axis intensity of the focused circular Airyprime beam is also explored, it exhibits a dual focus corresponding to two on-axis intensity maxima, it could be modified under diffraction using a hard circular aperture. The latter presents a cheap beam shaper, it is shown that a hard aperture could transform an input circular Airyprime beam into per- fect ringed beam, a perfect Gaussian beam and a top hat beam. By combining the axial and the transversal behavior of a truncated circular Airyprime beam for a particular aperture diameter a perfect cylindrical optical bottle beam is obtained. The present work could be of big interest in the field of structured light.
关键词： Beam shaping,Propagation and focusing,Circular Airyprime beam
更新于2025-09-23 15:21:01