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oe1(光电查) - 科学论文

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出版时间
  • 2019
  • 2018
  • 2014
研究主题
  • MPPT
  • photovoltaic (PV) power systems
  • Induction motor
  • three-phase four switch inverter
  • two-inductor boost converter
  • SrTiO3
  • Encapsulation
  • Epoxy
  • Permittivity
  • Composites
应用领域
  • Electrical Engineering and Automation
  • Optoelectronic Information Science and Engineering
  • Composite Materials and Engineering
  • Electronic Science and Technology
  • New Energy Science and Engineering
机构单位
  • Université de Toulouse
  • International Islamic University Malaysia
  • State Grid Shanxi Electric Power Research Institute
  • Shenzhen University
  • Beijing University of Technology
  • CEPRI
  • Xi’an Jiaotong University
  • Hassan II University of Casablanca
  • Zhengzhou University
  • Northern (Arctic) Federal University named after M.V. Lomonosov
1898 条数据
?? 中文（中国） ▾

  • Mechanism study on the effects of power modulation on energy coupling efficiency in infrared laser welding of highly-reflective materials

    摘要： High-reflectivity of materials, such as magnesium, copper and aluminum, results in low thermal efficiency of their infrared laser welding processes. AZ31 magnesium alloy was selected to study the effects of power modulation on energy coupling efficiency in laser welding of highly-reflective materials. A model for the relationship between energy coupling efficiency and modulation parameters was obtained. The energy coupling efficiency in optimized modulated-power laser welding was about 1.58 times that in constant-power welding. The mechanism was explored by analyzing keyhole evolution and the resulted pressure distribution along keyhole wall during welding. The keyhole evolutions in laser continuous welding of common material (Q345 steel, reflectivity of 65%) and highly-reflective material (AZ31, reflectivity of 85%) were observed through high-speed imaging by utilizing a half sandwich method. The results indicated that the secret of improving energy coupling efficiency of laser welding process of highly-reflective materials through power modulation was the formation of a deep keyhole and its long life. When instantaneous power decreased from the peak, there was still enough recoil pressure at the bottom of keyhole to resist surface tension and hydrostatic pressure of liquid metal, which was the fundamental reason for the long time existence of keyhole with a large depth.

    关键词： laser welding,magnesium alloy,recoil pressure,keyhole,highly-reflective materials,power modulation

    更新于2025-11-28 14:24:20

  • Effects of tilt angle between laser nozzle and substrate on bead morphology in multi-axis laser cladding

    摘要： Laser cladding has been increasingly used for repairing and remanufacturing critical and high-value components due to its unique benefits such as high solidification rates and a small heat-affected zone. In laser cladding, tilt angle between a laser nozzle and a substrate has a significant impact on deposited bead morphology. To ensure the quality of laser cladding, the effects of tilt angle on bead morphology are investigated in this study. An analytical model is introduced to predict bead shapes for three tilting postures. In the first case, a substrate remains horizontal while the nozzle is tilted. All three parameters, including width, height, and peak point offset, will be influenced by the laser beam power distribution. In the second case, a substrate is tilted while the laser nozzle is kept axial to the substrate’s normal, the peak point offset will ascend along with the increasing of the tilt angle (gravity effect). In the third case, the laser nozzle remains vertical while the substrate is tilted, which leads to variations of cladding width, cladding height, and especially peak point shifting value. These parameters will be dependent on the integrated effect of gravity and the laser beam power distribution. A set of experiments is conducted to demonstrate the effectiveness of the proposed model. This study illustrates that the variation of cladding width and height with the tilt angle can be accurately calculated by the predictive model, and that the peak point shifting value is roughly smaller than 5% of cladding width when the tilt angle is less than 30°. These findings show that trajectory planning of multi-axis laser cladding can be optimized using an acceptable range of tilt angle between the laser nozzle and substrate.

    关键词： Bead morphology,Laser beam power distribution,Laser cladding,Tilting posture,Gravity effect

    更新于2025-11-28 14:24:20

  • Effects of Power Modulation, Multipass Remelting and Zr Addition Upon Porosity Defects in Laser Seal Welding of End Plug to Thin-Walled Molybdenum Alloy

    摘要： Aiming to solve the serious porosity defects in laser welded girth joints of thin-walled tube and end plug made of nano-sized Ce2O3 doped Mo alloy (NC-Mo), the influences of laser power modulation, multipass remelting and zirconium (Zr) addition on the number, size and distribution of porosity defects were experimentally studied. By utilizing X-ray computed tomography (XCT), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, transmission electron microscope (TEM) and Raman spectrum (RS), the porosity feature of welded joints achieved under various conditions was analyzed. The results showed that welding cycles had a significant influence on the porosity ratio of fusion zone (FZ) while the amplitude and frequency of laser power waveform slightly influenced the porosity. When the welding cycles increased from 2 to 8, the porosity ratio of FZ decreased from about 1.00% to about 0.48% and the maximum and average pore diameters reduced by about 53% and 27%, respectively. Adding minor Zr in molten pool can further reduce the RP of FZ to about 0.35%. Through analysis, it can be seen that the pores in FZ can be divided into irregularly-shaped keyhole-induced pores and spherical metallurgy-induced pores. The latter was generated possibly because some impurity elements (including O and H) pre-existing in base metal (BM). Increasing welding cycles can promote the gas in molten pool to float and outflow, thus significantly decreasing the porosity. Moreover, Zr added in molten pool can be preferentially reacted with O to generate ZrO2, which can inhibit the precipitation of volatile MoO2 to thus suppress the generation of metallurgy-induced pores.

    关键词： Molybdenum alloy,Multipass remelting,Power-Modulated laser welding,Zirconium addition,Porosity

    更新于2025-11-28 14:24:20

  • Evaluation of fluences and surface characteristics in laser polishing SKD 11 tool steel

    摘要： In this paper, a continuous-wave laser beam from a multimode fiber laser was applied to study the polishing effect. Three kinds of surface morphologies were acquired by fast-speed (FS) & lower-speed (LS) wire electrical discharge machining (EDM), milling processing methods on SKD11 tool steel. Then influence of laser fluence on the polished surface characteristics was analyzed. The results showed that surface roughness parameters (Ra, Rz, Rt, and Sa) can be significantly affected by this effect. With laser fluence increasing, the polished surface underwent a comprehensive topographical evolution from superficial surface melting to surface over-melting. The improvements by FS-EDM, LS-EDM, and milling in roughness were 86.83%, 90.70% and 86.07%, respectively. The corresponding laser fluences were 14.26 J/mm2, 12.73 J/mm2 and 13.55 J/mm2, indicating that LS-EDM tool steel surface has the best polishing effect. The comparative statistical results of the bearing area curve, bidirectional reflectance distribution function, and power spectral density from the LS-EDM surfaces showed the best polishing results. In addition, all the pre-prepared surfaces could be polished to Ra < 0.5 μm using high polishing velocities. These findings also signified that laser beam with top-hat distribution has a great potential for high-efficiency polishing of tool steel surfaces.

    关键词： Power spectral density,Surface morphology,Bearing area curve,Fluence,Laser polishing,Tool steel

    更新于2025-11-28 14:24:20

  • High Power 1.5 μm Broad Area Laser Diodes Wavelength Stabilized by Surface Gratings

    摘要： Wavelength stabilization against temperature variation of high-power broad area 1.5-μm InGaAsP/InP laser diodes is demonstrated by employing surface gratings. The development targets application in eye-safe automotive LIDAR systems, which would bene?t from deploying narrowband receiver ?lters to block ambient solar radiation for improved signal-to-noise ratio. The surface grating is monolithically integrated on the laser chip using nanoimprint lithography. The peak power of the lasers exceeded 6 W in pulsed mode, for an FWHM spectral width of 0.3 nm and a peak wavelength drift of only 0.1 nm/°C. The wavelength shift with temperature is reduced by ?ve times compared to broad area high-power Fabry–Perot laser diodes typically employed in LIDAR systems.

    关键词： high power,distributed Bragg re?ector,LIDAR,Diode lasers

    更新于2025-11-28 14:24:03

  • High-power, high-spectral-purity GaSb-based laterally coupled distributed feedback lasers with metal gratings emitting at 2? <i> <b>μ</b> </i> m

    摘要： We report on the fabrication of high-power, high-spectral-purity GaSb-based laterally coupled distributed feedback (LC-DFB) lasers emitting at 2 μm. Second-order Chromium-Bragg-gratings are fabricated alongside the ridge waveguide by lift off. Due to the introduction of gain coupling, the lasers exhibit a stable single mode operation [side-mode suppression ratio (SMSR) >40 dB] from 10 °C to 50 °C and the maximum SMSR is as high as 53 dB. At a heat-sink temperature of 10 °C, the lasers emit more than 40 mW continuous-wave in a single longitudinal mode. A high external quantum efficiency of 48% is obtained, resulting in a notable increase in power conversion efficiency peaking at 13%. The lasers achieve a comparable output power with that of the index-coupled LC-DFB lasers, while maintaining a better single mode performance. Thus, we prove the feasibility of the metal-grating LC-DFB structure to achieve high-power, frequency-stable semiconductor lasers through a simpler and much more convenient way.

    关键词： metal gratings,high-spectral-purity,high-power,distributed feedback lasers,GaSb-based lasers

    更新于2025-11-28 14:24:03

  • High-Power Continuous-Wave and Acousto-Optical Q-Switched Ho:(Sc <sub/>0.5</sub> Y <sub/>0.5</sub> ) <sub/>2</sub> SiO <sub/>5</sub> Laser Pumped by Laser Diode

    摘要： We experimentally investigate the continuous-wave (cw) and acousto-optical (AO) Q-switched performance of a diode-pumped Ho:(Sc0.5Y0.5)2SiO5 (Ho:SYSO) laser. A fiber-coupled laser diode at 1.91 ??m is employed as the pump source. The cw Ho:SYSO laser produces 13.0 W output power at 2097.9 nm and 56.0% slope efficiency with respect to the absorbed pump power. In the AO Q-switched regime, at a pulse repetition frequency of 5 kHz, the Ho:SYSO laser yields 2.1 mJ pulse energy and 21 ns pulse width, resulting in a calculated peak power of 100 kW. In addition, at the maximum output level, the beam quality factor of the Q-switched Ho:SYSO laser is measured to be about 1.6.

    关键词： Laser Diode Pumped,Continuous-Wave,Acousto-Optical Q-Switched,High-Power,Ho:(Sc0.5Y0.5)2SiO5 Laser

    更新于2025-11-28 14:23:57

  • Surface plasmon resonance of naked gold nanoparticles for photodynamic inactivation of Escherichia coli

    摘要： Although antimicrobial photothermal inactivation of naked gold nanostructures using powerful pulsed lasers has been previously studied, there are little reports about their photodynamic antimicrobial properties under the irradiation of low-power density continuous wave lasers. Therefore, this paper attempts to fill this gap. In this paper, we studied the effects of a 40-mW/cm2 continuous Nd:Yag laser at 532 nm and naked gold nanoparticles on inactivation of Escherichia coli ATCC25922. According to our results, 60 min illumination using the Nd:Yag laser caused a 0.15log reduction of the bacterial viability. Also, the employed gold nanoparticles with an average size of 15 nm were toxic to E. coli ATCC 25922 in the concentrations above 0.5 μg/ml. In addition, synergistic effects of 0.5 μg/ml gold nanoparticles and the light illumination led to a 2.43log reduction of the viability after a 60-min exposure and did not show any considerable temperature change on the media. The obtained results were justified based on the possible interaction mechanisms of low-power density laser lights and naked gold nanoparticles. The paper is proposed as a prelude for future research about localized inactivation of resistant pathogens with minimum side effects on neighbor tissues.

    关键词： Photodynamic inactivation,Gold nanoparticles,Low-power density laser,Surface plasmon resonance

    更新于2025-11-25 10:30:42

  • Stable Sn/Pb-Based Perovskite Solar Cells with a Coherent 2D/3D Interface

    摘要： Low-band-gap metal halide perovskite semiconductor based on mixed Sn/Pb is a key component to realize high-ef?ciency tandem perovskite solar cells. However, the mixed perovskites are unstable in air due to the oxidation of Sn2+. To overcome the stability problem, we introduced N-(3-aminopropyl)-2-pyrrolidinone into the CH3NH3Sn0.5Pb0.5IxCl3-x thin ?lm. The carbonyl group on the molecule interacts with Sn2+/Pb2+ by Lewis acid coordination, forming vertically oriented 2D layered perovskite. The 2D phase is seamlessly connected to the bulk perovskite crystal, with a lattice coherently extending across the two phases. Based on this 2D/3D hybrid structure, we assembled low-band-gap Sn-based perovskite solar cells with power conversion ef?ciency greater than 12%. The best device was among the most stable Sn-based organic-inorganic hybrid perovskite solar cells to date, keeping 90% of its initial performance at ambient condition without encapsulation, and more than 70% under continuous illumination in an N2-?lled glovebox for over 1 month.

    关键词： power conversion efficiency,2D/3D interface,stability,Sn/Pb-based,perovskite solar cells

    更新于2025-11-21 11:18:25

  • Low Power Consumption Red Light-Emitting Diodes Based on Inorganic Perovskite Quantum Dots under an Alternating Current Driving Mode

    摘要： Inorganic perovskites have emerged as a promising candidate for light-emitting devices due to their high stability and tunable band gap. However, the power consumption and brightness have always been an issue for perovskite light-emitting diodes (PeLEDs). Here, we improved the luminescence intensity and decreased the current density of the PeLEDs based on CsPbI3 quantum dots (QDs) and p-type Si substrate through an alternating current (AC) driving mode. For the different driving voltage modes (under a sine pulsed bias or square pulsed bias), a frequency-dependent electroluminescent (EL) behavior was observed. The devices under a square pulsed bias present a stronger EL intensity under the same voltage due to less thermal degradation at the interface. The red PeLEDs under a square pulsed bias driving demonstrate that the EL intensity drop-off phenomenon was further improved, and the integrated EL intensity shows the almost linear increase with the increasing driving voltage above 8.5 V. Additionally, compared to the direct current (DC) driving mode, the red PeLEDs under the AC condition exhibit higher operating stability, which is mainly due to the reducing accumulated charges in the devices. Our work provides an effective approach for obtaining strong brightness, low power consumption, and high stability light-emitting devices, which will exert a profound in?uence on coupling LEDs with household power supplies directly.

    关键词： low power consumption,perovskite quantum dots,silicon,light emitting diodes,alternating current driving

    更新于2025-11-21 11:01:37