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- 2020
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- high step-up gain
- high efficiency
- ?uk-based converter
- low voltage stress
- non-isolated inductor
- resilience diamond
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- Electrical Engineering and Automation
- Universidad Industrial de Santander
- Fraunhofer Institute for Solar Energy Systems ISE
- Iran University of Science and Technology
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Butt welding-brazing of steel to aluminum by hybrid laser-CMT
摘要： A laser penetration welding-brazing combined with Cold Metal Transfer (CMT) arc, was proposed to improve weld shape and interfacial reaction inhomogeneity of 5052 aluminum alloy and Q235 low carbon steel with ER5356 welding wire in butt joint. The effects of wire feed speed, beam offset and welding speed on weld shape, interfacial microstructures and tensile strength of joints was studied. This method improved the undercut defect existed in butt laser welding-brazing, obtained well-formed joints and promoted the uniform distribution of the interface reaction. The interfacial intermetallic compounds (IMCs) layer consisted of Fe2Al5 and Fe4Al13 and the thicknesses were controlled to 3-5 μm. Microstructures of weld seam was composed of α-Al and Al3Mg2. The brittle IMCs layer thickened and then the tensile strength decreased with increasing the wire feed speed. The thickness of the IMCs layer decreased but weld shape became worse when the welding speed or the offset increased. The tensile strength increased first and then decreased. The highest tensile strength reached higher than 80 MPa and the joint fractured in IMCs layer along the interface.
关键词： intermetallic compound,Laser–CMT arc hybrid welding-brazing,dissimilar metals welding,low carbon steel,aluminum alloy
更新于2025-11-28 14:24:20
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25 nJ, 634 ps and 1 MHz all-fiber passively mode-locked fiber laser based on a GaAs saturable absorber
摘要： We demonstrate an all-fiber passively mode-locked Tm-Ho co-doped fiber laser based on a GaAs saturable absorber (SA) fiber laser at 1875.2 nm. With a 10% output coupler, the fiber laser outputs 1.13 MHz, 634 ps and 25 nJ pulses at 1875.2 nm with a 3 dB-bandwidth of 18.4 nm. The Q-switched mode-locking (QML), the mode-locking at fundamental repetition rate (FRR) and the mode-locking at second harmonic of repetition rate (SHRR) are also observed with the increase of the pump power. The main reason of the SHRR is soliton pulse energy quantization effect.
关键词： Low repetition rate,Mode-locked fiber laser,Soliton pulse,Nanosecond pulse,Soliton pulse energy quantization effect
更新于2025-11-28 14:24:03
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All-polarization-maintaining, semiconductor saturable absorbing mirror mode-locked femtosecond Er-doped fiber laser with a gigahertz fundamental repetition rate
摘要： A passively mode-locked fiber laser with a 1.03 GHz fundamental repetition rate and a low noise performance is demonstrated. The compact and robust laser operates at a central wavelength of 1553.9 nm with a 3 dB spectral bandwidth of 7.9 nm and a temporal width of 550 fs. All the fibers and components used in the laser are polarization-maintaining (PM), so the output pulses are linearly polarized. The degree of polarization of the optical pulses is measured to be 0.9994. The phase noise of the seventh harmonic (7.21 GHz) is measured and a low timing jitter of 11.7 fs is obtained by integrating the phase noise from 30 MHz down to 100 Hz. The noise performance is analyzed in detail, and the methods for further optimizing the timing jitter are also proposed. So far, we know this to be the first-reported low-noise all-PM erbium-doped fiber laser with a gigahertz level pulse repetition rate.
关键词： low-timing jitter,polarisation-maintaining (PM),high-pulse repetition rate
更新于2025-11-28 14:23:57
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Low-level laser therapy affects dentinogenesis and angiogenesis of in vitro 3D cultures of dentin-pulp complex
摘要： To investigate the effects of gallium-aluminum-arsenide (GaAlAs) diode laser low-level laser therapy (LLLT) on angiogenesis and dentinogenesis of the dentin-pulp complex in a human tooth slice-based in vitro model. Forty tooth slices were prepared from 31 human third molars. Slices were cultured at 37 °C, 5% CO2, and 95% humidity and randomly assigned to one of the following groups: group I: no laser treatment, group II: 660-nm diode laser; energy density = 1 J/cm2, group III: 660-nm diode laser; energy density = 3 J/cm2, group IV: 810-nm diode laser; energy density = 1 J/cm2 and group V: 810-nm diode laser; energy density = 3 J/cm2. LLLT was applied on the third and fifth days of culture. After 7 days, tissues were retrieved for real-time RT-PCR analysis to investigate the expression of VEGF, VEGFR2, DSPP, DMP-1, and BSP in respect to controls. Lower energy density (1 J/cm2) with the 660 nm wavelength showed a statistically significant up-regulation of both angiogenic (VEGF: 15.3-folds and VEGFR2: 3.8-folds) and odontogenic genes (DSPP: 6.1-folds, DMP-1: 3-fold, and BSP: 6.7-folds). While the higher energy density (3 J/cm2) with the 810 nm wavelength resulted in statistically significant up-regulation of odontogenic genes (DSPP: 2.5-folds, DMP-1: 17.7-folds, and BSP: 7.1-folds), however, the angiogenic genes had variable results where VEGF was up-regulated while VEGFR2 was down-regulated. Low-level laser therapy could be a useful tool to promote angiogenesis and dentinogenesis of the dentin-pulp complex when parameters are optimized.
关键词： Low-level laser therapy,Dentinogenesis,Dentin-pulp complex,Angiogenesis,Tooth slice model
更新于2025-11-25 10:30:42
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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
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Combined treatment of low‐level laser therapy and phloroglucinol for inhibition of fibrosis
摘要： Background and Objectives: Fibrosis is a highly prevalent disease, which is responsible for 45% of deaths through pathological effects in developed countries. Previous studies have reported that low‐level laser therapy (LLLT) can modulate fibrotic activity, but significant enhancement of therapeutic efficacy is still required for clinical translation. The aim of this study is to evaluate the feasible effect of LLLT combined with phloroglucinol (PHL) on the inhibition of fibrosis in vitro. Study Design/Materials and Methods: NIH/3T3 murine embryonic fibroblasts cells were cultured and transforming growth factor‐β1 (TGF‐β1) was treated for transition of fibroblasts. After TGF‐β1 treatment, LLLT and PHL were used, respectively, and in combination to suppress fibrosis. 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide and BrdU assays were performed to estimate the cell viability and proliferation. To evaluate the expression of fibrotic markers, we used confocal immunofluorescence and western blot. Results: When compared with respectively treated groups, the group with the combined treatment of LLLT and PHL significantly reduced cell viability and proliferation. Immunofluorescence staining showed that the combined group minimized more α‐smooth muscle actin (α‐SMA) and type I collagen than the other groups. Western blot analysis showed that the combined treatment had significant decreases in α‐SMA, TGF‐β1, and type I collagen. Conclusions: PHL‐assisted LLLT may be an effective treatment to inhibit fibrosis due to its additive effects. The combined treatment has a potential to be an alternative treatment for fibrosis.
关键词： low‐level laser therapy,phloroglucinol,combined therapy,fibrosis
更新于2025-11-21 11:08:12
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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
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Improvement of Ga distribution with Sb incorporation for two-step low-temperature processing of CIGSe thin film solar cells
摘要： In this study, the application of Sb incorporation for low-temperature (≤ 450 °C) processing of Cu(In,Ga)Se2 (CIGSe) solar cells is explored. At low reaction temperature, most Ga remains at the back of the ?lm adjacent to the Mo back contact. We observed that the incorporated Sb enhanced grain size and improved device performance compared with similarly processed CIGSe ?lms made without Sb. From the energy-dispersive spectroscopy analysis and secondary ion mass spectrometry results, it was determined that elemental Ga accumulation at the back of the reacted ?lm after the two-step selenization process was signi?cantly alleviated owing to Sb incorporation. Signi?cant Sb-induced grain size enhancement was con?rmed using cross-sectional scanning electron microscopy. The electronic and optical properties of the Sb incorporated CIGSe ?lms were examined with admittance spectroscopy and ?uorescence lifetime imaging techniques.
关键词： Ga distribution,Thin ?lm solar cell,Sb incorporation,Low temperature process
更新于2025-11-14 17:28:48
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Highly Stretchable, High‐Mobility, Free‐Standing All‐Organic Transistors Modulated by Solid‐State Elastomer Electrolytes
摘要： Highly stretchable, high-mobility, and free-standing coplanar-type all-organic transistors based on deformable solid-state elastomer electrolytes are demonstrated using ionic thermoplastic polyurethane (i-TPU), thereby showing high reliability under mechanical stimuli as well as low-voltage operation. Unlike conventional ionic dielectrics, the i-TPU electrolyte prepared herein has remarkable characteristics, i.e., a large specific capacitance of 5.5 μF cm?2, despite the low weight ratio (20 wt%) of the ionic liquid, high transparency, and even stretchability. These i-TPU-based organic transistors exhibit a mobility as high as 7.9 cm2 V?1 s?1, high bendability (Rc, radius of curvature: 7.2 mm), and good stretchability (60% tensile strain). Moreover, they are suitable for low-voltage operation (VDS = ?1.0 V, VGS = ?2.5 V). In addition, the electrical characteristics such as mobility, on-current, and threshold voltage are maintained even in the concave and convex bending state (bending tensile strain of ≈3.4%), respectively. Finally, free-standing, fully stretchable, and semi-transparent coplanar-type all-organic transistors can be fabricated by introducing a poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid layer as source/drain and gate electrodes, thus achieving low-voltage operation (VDS = ?1.5 V, VGS = ?2.5 V) and an even higher mobility of up to 17.8 cm2 V?1 s?1. Moreover, these devices withstand stretching up to 80% tensile strain.
关键词： free-standing all-organic transistors,stretchable and conformal electronics,high-mobility,elastomer electrolyte,low-voltage operation
更新于2025-11-14 17:28:48
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The Preparation and Characterization of Fluorinated Graphene Oxide with Different Degrees of Oxidation
摘要： For many excellent graphene derivatives, tailoring the material properties is crucial to get a broader application. In the present work, a series of fluorinated graphene oxide (FGO) with various oxidation degree were synthesized using a modified Hummers method at different reaction temperatures. The structure and property of FGO were analyzed by X-ray diffraction (XRD), Fourier transform infra-red spectra (FT-IR), X-ray photoelectron spectra (XPS) and Zeta potential analysis. The results indicate that the oxygen contents range from 5.61 % to 21.96 % in FGO can be tuned by altering the reaction temperatures. The oxygen in FGO is presented mainly in the form of epoxide and carboxyl groups. With increasing reaction temperature from 50 °C to 90 °C, the oxygen content in FGO decreases and thicker multilayered FGO is formed with lower dispersibility.
关键词： Controllable oxidation,Fluorinated Graphene Oxide,Low temperature reaction
更新于2025-11-14 17:04:02