- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Atomic Diffusion Behavior and Interface Waveform on the Laser Shock Welding of Aluminum to Nickel
摘要： Atomic diffusion behavior and interface waveform characteristics and formation mechanism during laser shock welding were investigated by using a molecular dynamics (MD) model and smooth particle hydrodynamics (SPH) modeling. The MD simulation showed that the diffusion coef?cient of Al atom was larger than that of the Ni atom. Ni atom is easily diffused deeply into the Al lattice during impact welding. The SPH simulation showed that the wavelength and amplitude of the welding interface increased with loading speed, and SPH simulations at different loading speeds demonstrated that the movement direction of the Ni wave peak is the same as the welding direction, whereas the movement direction of the Al wave peak is opposite to the welding direction. The effective plastic strain and temperature were mainly distributed at the interface waveform. The shear stress of the composite and substrate foil is in opposite direction near the collision point, and the pressure near the collision point was as high as about 10 GPa. Energy-dispersive spectroscopy line scanning analysis showed the presence of a 2.5-lm-thick element diffusion layer at the wavy interface between Al and Ni, verifying the element diffusion between Al and Ni in the MD simulation.
关键词： laser shock welding,molecular dynamics,smoothed particle hydrodynamics,welding characteristics
更新于2025-09-23 15:19:57
-
Comparison of size-dependent characteristics of blue and green InGaN microLEDs down to 1a?? <b> <i>??</i> </b> m in diameter
摘要： There is growing interest in microLED devices with lateral dimensions between 1 and 10 lm. However, reductions in external quantum ef?ciency (EQE) due to increased nonradiative recombination at the surface become an issue at these sizes. Previous attempts to study size-dependent EQE trends have been limited to dimensions above 5 lm, partly due to fabrication challenges. Here, we present size-dependent EQE data for InGaN microLEDs down to 1 lm in diameter fabricated using a process that only utilizes standard semiconductor processing techniques (i.e., lithography and etching). Furthermore, differences in EQE trends for blue and green InGaN microLEDs are compared. Green wavelength devices prove to be less susceptible to reductions in ef?ciency with the decreasing size; consequently, green devices attain higher EQEs than blue devices below 10 lm despite lower internal quantum ef?ciencies in the bulk material. This is explained by smaller sur- face recombination velocities with the increasing indium content due to enhanced carrier localization.
关键词： InGaN,microLEDs,size-dependent characteristics,external quantum efficiency,blue and green wavelengths
更新于2025-09-23 15:19:57
-
Modeling the Functioning of the Half-Cells Photovoltaic Module under Partial Shading in the Matlab Package
摘要： In this paper, the usefulness of photovoltaic modules built of half cells for partially obstructed photovoltaic (PV) installations was analyzed based on veri?ed simulation studies. The parameters of these modules are similar to the classic, but the internal structure is di?erent. Instead of 60 cells in a typical classic PV module, there are twice as many cells in modules with half cells. A simulation model was built in the Matlab/Simulink engineering calculations package, using the “Solar Cell” component, which is a double-diode PV cell replacement model. The simulation model re?ects the internal structure of the PV module from half cells so that the output current is divided into two equal parts inside, and the structure of the module is divided into six sections. Simulation tests were performed for the same parameters that were measured during actual measurements of the current–voltage characteristics of the partially shaded PV module. Veri?cation tests were carried out for the photovoltaic module—JAM60S03-320/PR—using the I–V 400 meter. Four di?erent cases of partial shading of the module were veri?ed and one for the case of no shading, but in conditions di?erent from the standard, given by the manufacturer.
关键词： current–voltage characteristics,partial shading,photovoltaics,photovoltaic module
更新于2025-09-23 15:19:57
-
Complex Bianisotropy Effect on the Propagation Constant of a Shielded Multilayered Coplanar Waveguide Using Improved Full Generalized Exponential Matrix Technique
摘要： A theoretical study of the electromagnetic propagation in a complex medium suspended multilayer coplanar waveguide (CPW) is presented. The study is based on the generalized exponential matrix technique (GEMT) combined with Galerkin’s spectral method of moments applied to a CPW printed on a bianisotropic medium. The analytical formulation is based on a Full-GEMT, a method that avoids usual procedures of heavy and tedious mathematical expressions in the development of calculations and uses matrix-based mathematical expressions instead. These particularities are exploited to develop a mathematical model for the characterization of wave propagation in a three-layer shielded suspended CPW structure. This study is based on the development of mathematical formulations in full compact matrix-based expressions resulting in Green’s functions in a matrix form. The implemented method incorporates a new accelerating procedure developed in the GEMT which provides an initial value used to speed up searching for the exact solution in the principal computation code. This helped us to obtain accurate solutions with tolerable computing time. Good agreements have been achieved with the literature in terms of accuracy and rapid convergence. The results for di?erent cases of bianisotropy have been investigated, and particularly, the e?ect on the dispersion characteristics is presented and compared with the isotropic case.
关键词： Muller’s method,dispersion characteristics,chiral,acceleration procedure,complex propagation constant,full-GEMT,multilayer CPW structure,Tellegen
更新于2025-09-23 15:19:57
-
A Fast Analysis Method for Blue-Green Laser Transmission through the Sea Surface
摘要： The fast estimation of blue-green laser transmission characteristics through the fluctuating sea surface, such as refraction angles and transmittance, is very important to correct operating parameters, detection depth and anti-detection warning in airborne Light Detection and Ranging (LiDAR) applications. However, the geometry of the sea surface is changed by complex environment factors, such as wind and wave, which significantly affect the rapid acquisition of the blue-green laser transmission characteristics. To address this problem, a fast analysis method is provided to rapidly compute the blue-green laser transmittance and refraction angles through the fluctuating sea surface driven by different wind directions and speeds. In the method, a three-dimensional wave model driven by the wind was built to describe the wave spatial distribution varying with time. Using the wave model, the propagation path of the scanning laser footprint was analyzed using the proposed meshing method, thus the transmittance and refraction angles of the optical path can be fast obtained by using parallel computing. The simulation results imply that the proposed method can reduce the time consumption by 70% compared with the traditional analytical method with sequential computing. This paper provides some statistical laws of refraction angles and transmittance through the fluctuating sea surface under different wind conditions, which may serve as a basic for fast computation of airborne LiDAR transmission characteristics in complex environments.
关键词： blue-green laser,sea surface,refraction angles,wave model,transmission characteristics,transmittance,airborne LiDAR
更新于2025-09-23 15:19:57
-
Coupling characteristics of the spun optical fiber with multiple stress elements
摘要： Possible coupling between fundamental modes and higher order modes in a spun optical ?ber with multiple stress elements is analyzed. It shows that only the higher order HEmn mode with the opposite circular polarization state can be coupled with the fundamental HE11 mode. The coupling between the fundamental HE11 mode and the TE, TM or EH modes can never be occurred. In the possible coupling between HEmn mode and HE11 mode, m should be equal to N-1, where N is the number of the stress elements. As a comparison, the coupling property in a spun optical ?ber with single stress element is also demonstrated. In this case, the fundamental HE11 mode can not only be coupled with the higher orderHE2n mode but also can be coupled with the higher order TE mode.
关键词： Coupling characteristics,Polarization,Stress elements,Spun optical fiber,Optical fiber
更新于2025-09-23 15:19:57
-
Gain characteristics of the hybrid slot waveguide amplifiers integrated with NaYF <sub/>4</sub> :Er <sup>3+</sup> NPs-PMMA covalently linked nanocomposites
摘要： Waveguide amplifiers based on slot waveguide have enormous capacity due to their ability to confine light strongly to a narrow slot waveguide. NaYF4:Er3+ nanoparticles-polymeric methyl methacrylate covalently linked nanocomposites were synthesized and filled into the slot. The stability and the Er3+ concentration doped in this novel material were improved. The slot waveguide was designed accurately. The rigorous numerical method, full-vector finite difference method, was used to analyze the modal characteristics and optimize the slot combined with the maximum power confinement in the slot and the minimum effective mode area of the slot. A four-level spectroscopic model pumped at 1480 nm was presented. The rate equations and propagation equations were solved and the gain characteristics of the slot waveguide amplifier were numerically simulated. The primary parameters were optimized. A net gain of 5.78 dB was achieved when the signal power was 0.001 mW at 1530 nm, pump power was 20 mW, Er3+ concentration was 1.3 (cid:1) 1027 m(cid:3)3, and the waveguide length was 1.5 cm.
关键词： NaYF4:Er3+ NPs-PMMA,slot waveguide,erbium-doped polymer waveguide amplifier,full-vector finite difference method,gain characteristics
更新于2025-09-23 15:19:57
-
Experimental Demonstration of Directly Modulated DFB Lasers with Negative Chirp over Wide Temperature Operation
摘要： Massive expansion of wireless body area networks (WBANs) in the field of health monitoring applications has given rise to the generation of huge amount of biomedical data. Ensuring privacy and security of this very personal data serves as a major hurdle in the development of these systems. An effective and energy friendly authentication algorithm is, therefore, a necessary requirement for current WBANs. Conventional authentication algorithms are often implemented on higher levels of the Open System Interconnection model and require advanced software or major hardware upgradation. This paper investigates the implementation of a physical layer security algorithm as an alternative. The algorithm is based on the behavior fingerprint developed using the wireless channel characteristics. The usability of the algorithm is established through experimental results, which show that this authentication method is not only effective, but also very suitable for the energy-, resource-, and interface-limited WBAN medical applications.
关键词： Wireless body area networks,physical layer security,wireless channel characteristics,authentication
更新于2025-09-23 15:19:57
-
Laser-Assisted Machining of Ti-6Al-4V Fabricated by DED Additive Manufacturing
摘要： Recently, the commercialization of hybrid machine tools that combine directed energy deposition (DED) additive manufacturing (AM) technology and subtractive manufacturing (SM) has rapidly progressed. This technology trend has been developed to meet the market demand for processing quality (precision) and productivity, and to produce products such as lightweight parts, and complex and special functional parts, as well as to facilitate mold production and part repair. Compared to SM technology, metal AM technology has limitations in terms of surface quality and shape accuracy. Therefore, post-processing is necessary for the AM output. Laser-assisted machining (LAM) is an innovative hybrid technique in which surface quality and productivity can be improved by enhancing the machinability of difficult-to-cut materials. LAM studies have mainly been performed on titanium alloys, nickel based alloys and ceramic materials. However, except for ceramics, no high-strength material studies have been conducted to analyze the LAM process machining characteristics of workpieces fabricated by AM process. Therefore, in this study, LAM is applied to post-processing of output fabricated by AM of Ti-6Al-4V. DED device was developed using metal powder feeder and a laser. The Ti-6Al-4V workpieces were successfully fabricated through many tests. The cutting depth for LAM was selected through thermal analysis for LAM of the fabricated workpiece. Compared to the case of traditional machining without preheating, machining characteristics in LAM experiments were analyzed and property testing was performed.
关键词： Machining characteristics,Additive manufacturing,Directed energy deposition,Ti-6Al-4V,Laser-assisted machining
更新于2025-09-23 15:19:57
-
The environment coefficients effect on I-V and P-V characteristics curves of photovoltaic cell using Matlab/Simulink
摘要： Many parameters and environments conditions will affect the behavior of the photovoltaic cell. This paper investigates, theoretically the variation of each temperature and irradiation effects on the output of the photovoltaic cell characteristics. Modeling of the photovoltaic cell scheme essentially requires taking weather data (temperature and irradiance) as input variables. The photovoltaic outputs are the current, voltage and power. Though, conclude the characteristics I-V or P-V desires of these important variables. Any variation in the entries directly shows variations in outputs. The characteristic curves are obtained with the use practical readings and measurements are illustrated directly from the solar power plant in the Technical Engineering College of Mosul. The complete modeling is then computer-generated using MATLAB/Simulink software owing to its common use and its helpfulness.
关键词： Solar Cell,PV Cell,Single Diode,PV Temperature,PV Irradiation,I-V and P-V Characteristics
更新于2025-09-23 15:19:57