Search Results (565)

Objective: This study aimed to systematically evaluate the therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) on gait, motor function, and balance in patients with Parkinson’s disease (PD) and identify optimal stimulation parameters for clinical application. Methods: This systematic review and meta-analysis of randomized controlled trials (CTs) was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, EMBASE, Cochrane Central, Scopus, and Ovid-LWW were searched until December 2024 for RCTs evaluating the effects of rTMS on PD-related gait, balance, or motor outcomes. Nineteen studies (n = 547) met the inclusion criteria. Data on study characteristics, rTMS protocols (frequency, target area, pulses, session duration, number of sessions, and treatment duration), and outcome measures (freezing of gait questionnaire [FOG-Q], gait speed, Unified Parkinson’s Disease Rating Scale Part III [UPDRS-III], UPDRS total, and timed up and go [TUG] test) were extracted. Effect sizes (Hedges’ g) were pooled using inverse variance meta-analysis, heterogeneity was assessed using I², and publication bias was assessed using funnel plots and Egger’s regression. Results: rTMS produced significant improvements in gait freezing (FOG-Q: g = −0.74; 95% confidence interval [CI] [−1.05, −0.43]; p < 0.001), gait speed (g = 0.62; 95% CI [0.29, 0.95]; p < 0.001), and motor symptoms (UPDRS-III: g = −0.42; 95% CI [−0.70, −0.15]; p = 0.003). No significant effects were observed for UPDRS total (g = 0.18; p = 0.58) or balance (TUG, g = −0.29; p = 0.06). Egger’s test indicated publication bias for gait speed (p = 0.016); however, trim-and-fill imputed zero studies. Subgroup analyses indicated that high-frequency stimulation of the supplementary motor area (SMA) for ≥20 min over 10 sessions (total duration <2 weeks or ≥2 weeks) optimally improved gait speed, whereas low-frequency stimulation targeting M1 and SMA with >1000 pulses per session for 20 min over 10 sessions within <2 weeks most effectively improved the UPDRS-III scores. Conclusions: rTMS exerts moderate and significant benefits on gait and motor performance in PD, particularly when tailored protocols involving SMA or M1 stimulation are employed. High-frequency SMA protocols improve gait speed, whereas low-frequency M1/SMA protocols optimize motor symptom relief. These findings provide evidence-based guidance for rTMS implementation in PD rehabilitation. Full article

We experimentally demonstrate an 80 Gbit/s Nyquist-dense wavelength division multiplexed (Nyquist-DWDM) transmission system operating in a simulated atmospheric turbulence channel. The system utilizes eight wavelength-tunable lasers with 100 GHz spacing, modulated by cascaded Mach–Zehnder modulators, to generate phase-locked Nyquist pulse sequences with a 10 GHz repetition rate and a temporal width of 66.7 ps. Each channel is synchronously modulated with a 10 Gbit/s pseudo-random bit sequence (PRBS) and transmitted through controlled weak turbulence conditions generated by a temperature-gradient convection chamber. Experimental measurements reveal that, as the turbulence intensity increases from $C_n^2=1.01\times {10}^{-16}$ to $5.71\times {10}^{-16} {\mathrm{m}}^{-2/3}$, the signal-to-noise ratio (SNR) of the edge channel (C29) and central channel (C33) decreases by approximately 6.5 dB while maintaining stable Nyquist waveform profiles and inter-channel orthogonality. At a forward-error-correction (FEC) threshold of $3.8\times {10}^{-3}$, the minimum receiver sensitivity is −17.66 dBm, corresponding to power penalties below 5 dB relative to the back-to-back condition. The consistent SNR difference (<2 dB) between adjacent channels confirms uniform power distribution and low inter-channel crosstalk under turbulence. These findings verify that Nyquist pulse shaping substantially mitigates phase distortion and scintillation effects, demonstrating the feasibility of high-capacity DWDM free-space optical (FSO) systems with enhanced spectral efficiency and turbulence resilience. The proposed configuration provides a scalable foundation for future multi-wavelength FSO links and hybrid fiber-wireless optical networks. Full article

A 50.9-W all-fiber mid-infrared (MIR) supercontinuum (SC) laser with a conversion efficiency of over 76.7% is demonstrated in a ZBLAN (ZrF₄–BaF₂–LaF₃–AlF₃–NaF) fiber. The entire system consists of a broadband thulium-doped fiber amplifier (TDFA) operating at 1.9–2.6 μm and a piece of ZBLAN fiber. The system features an all-fiber architecture, which is achieved by directly splicing the pigtail fiber of the TDFA to the ZBLAN fiber. The system’s stability and reliability were ensured by the utilization of the water-cooled fusion splicing joint between the silica fiber and ZBLAN fiber, and an AlF₃ fiber endcap. When the seed pulse repetition rate (PRR) was 3 MHz and the pulse duration was 6 ns, a MIR SC laser with an average power of 50.9 W and a spectral range of 1.9–3.6 μm was obtained, with a corresponding power conversion efficiency (from the TDFA output to the SC laser output) of 76.7%. By adjusting the pulse duration to 4 ns, the generated SC laser exhibited a spectral range of 1.9–3.7 μm and an average power of 50.1 W, corresponding to a power conversion efficiency of 75.1%. Such a supercontinuum (SC) laser paves the way for the application of high-power SC lasers in a wide range of fields. Full article

A high-power, long-pulse-width acousto-optical Q-switched 1064 nm laser based on a multi-pass cavity (MPC) is reported in this paper. First, a plano-concave MPC structure satisfying the Q-preserving configuration was designed and introduced into an acousto-optical Q-switched plano-plano cavity Nd:YAG laser, extending the original laser cavity length by 1200 mm. The laser achieved a maximum average output power of 123.6 W with a repetition rate of 10 kHz. At this power level, the laser pulse width was broadened to 157.5 ns, which can be compared to 82.5 ns without the MPC structure, achieving a broadening ratio of 90.9%. The beam quality factors were $M_x^2$ = 10.75 in the horizontal direction and $M_y^2$ = 11.37 in the vertical direction. The experimental results demonstrate that inserting an MPC into the cavity is an effective method for broadening the pulse width of nanosecond lasers. Full article

The paper investigates the feasibility of laser-induced synthesis of crystalline silicon compounds from a powder system consisting of metallic aluminum, amorphous silica, and carbon atoms. Using pulsed laser radiation (wavelength 1064 nm), it is experimentally demonstrated that varying the processing parameters—pulse energy, repetition rate, scanning speed, and pulse duration—allows for targeted control of the phase composition of the products. Modes for the selective formation of crystalline silicon, mullite, and intermediate acid-soluble aluminosilicates are established. Using a simplified thermal model, a correlation is demonstrated between the achieved temperature in the irradiation zone and the formation of specific phases, with not only the peak temperature at the laser point but also the exposure time playing a key role. It is shown that crystalline acid-soluble silicate phases preceded the formation of mullite. The results of low-temperature laser synthesis of crystalline silicon-containing materials hold great promise for various applications. Full article

Ytterbium-doped femtosecond fiber lasers are widely used in scientific research, industrial processing, and other fields due to their high quantum efficiency, wide gain bandwidth, and compact structure. This article addresses the problems of low processing efficiency and difficulty in increasing the average power of femtosecond lasers. A high repetition rate fiber chirped pulse amplification system is built, which uses a high repetition rate Figure-9 fiber laser as the seed source and an acousto-optic modulator (AOM) to shape the dense pulse train in the time domain. The main amplification stage uses a large mode field ytterbium-doped fiber to achieve full fiberization of the amplification system, and a volume grating (VBG) is selected as the pulse compressor to make the laser system highly integrated. When the repetition rate is 67.5 MHz, the compressed output laser has an average power of 20.5 W, a pulse width of 447 fs, a pulse train energy of 750 μJ, a spot ellipticity of 0.96, and a beam quality M² better than 1.4 ($M_x^2=1.33$, $M_y^2=1.16$). Full article

The dual-pulse heterodyne demodulation distributed acoustic sensing (HD-DAS) system has superior performance but is fundamentally limited by the short sensing range, which poses a significant obstacle to its application in long-distance monitoring. This paper proposes and experimentally demonstrates a novel binary-tree structure DAS (BTS-DAS) aimed at overcoming this critical limitation. By physically decoupling the long-distance transmission fiber from the final sensing part, this structure effectively expands the system’s remote sensing capability without compromising the high pulse repetition rate for high-performance measurement. We identified modulation instability (MI), rather than stimulated Brillouin scattering (SBS), as the dominant nonlinear noise source in the extended fiber chain. Through careful power management, we established an optimal launch power window. The practical feasibility of the system was verified during on-site testing, where vibrations were successfully detected over a 10 km transmission link with sensing occurring in the 250 m sensing fiber segment, achieving a low background noise of −59.79 dB ref rad/$\sqrt{\mathrm{Hz}}$. This work presents a robust and scalable solution for long-range, high-performance acoustic sensing. Full article

This study investigates the physicochemical processes in aqueous solutions treated with a high-current (up to 300 A) pulsed multispark discharge. Pulse length was 2 μs at a 50 Hz repetition rate. The discharge occurred within bubbles of argon injected between the stainless-steel electrodes at the constant flow rate. The erosion of electrode material during the discharge led to iron and other alloy components entering the liquid. Optical emission spectra confirmed the erosion of electrode material (Fe, Cr, Ni atoms and ions). EDTA and its disodium salt were used in order to study their effect on the metal particle formation process. Treatment with deionized water led to an increase in conductivity and the generation of hydrogen peroxide (up to 1200 µM). In contrast, the presence of EDTA and its disodium salt drastically altered the reaction pathways: the H₂O₂ yield decreased, and the solution conductivity dropped substantially for the acidic form of EDTA, while the decrease was minor for EDTA-Na₂. This effect is attributed to the buffered chelation of eroded metal ions, forming stable Fe-EDTA complexes, as confirmed by a characteristic absorption band at 260 nm. The results demonstrate the critical role of complex-forming agents in modulating plasma–liquid interactions, shifting the process from direct erosion products to the formation of stable coordination compounds. Full article

This paper introduces a versatile approach to achieve specific surface functionality with-out the need for detailed knowledge of surface topography. This is accomplished for applications targeting wettability properties by integrating contact angle measurement into a micromachining setup with a nanosecond pulsed UV laser, allowing for fully automated programs to find optimal functionalization without requiring knowledge on the topography or on possible laser-induced chemical changes itself. This study investigates the impact of various processing parameters, including laser pulse energy, scanning speed, hatching distance, jump speed, and laser repetition rate, on the wetting properties of two widely used polymers: polyethylene (PE) and ethylene propylene diene monomer (EPDM). A design of experiment (DOE) approach is used for experimental design and subsequent modeling. Finally, the effectiveness of this new approach is evaluated and compared with conventional methods. Full article

Laser processing of heterogeneous composites requires a clear understanding of coupled thermal and mechanical responses to ensure structural integrity and patterning precision. In this study, a thermal–mechanical coupling model based on the finite element method was developed to investigate laser–material interactions in Al–Tedlar–Kevlar composite films. The effects of key parameters—including pulse energy, spot size, pulse duration, and repetition frequency—on the evolution of temperature and stress fields were systematically examined. The simulations reveal that pulse energy leads to a linear rise in peak temperature, while pulse duration exerts a nonlinear influence on energy density and thermal uniformity. Increasing repetition frequency promotes thermal accumulation, enlarging the heat-affected zone. Coupled analyses further indicate significant stress concentrations at material interfaces, which may trigger delamination and compromise film reliability. Through comprehensive parameter evaluation, the optimal processing conditions were identified as 0.5 mJ pulse energy, 20 kHz repetition rate, 45 μm spot diameter, and 120 ns pulse duration. These findings clarify the governing mechanisms of thermal–mechanical interactions in multilayer composites and provide theoretical guidance for optimizing laser micropatterning processes while enhancing interfacial stability and manufacturing quality. Full article

This study focuses on the high-precision microhole machining of 304 stainless steel and explores a backwater-assisted picosecond laser trepanning technique. The laser used is a 30 W green picosecond laser with a wavelength of 532 nm, a repetition rate of 1000 kHz, and a pulse width of less than 15 ps. Experiments were conducted under both water-based and non-water-based laser processing environments to systematically investigate the effects of laser power and scanning cycles on hole roundness, taper, and overall hole quality. The experimental results further confirm the advantages of the backwater-assisted technique in reducing slag accumulation, minimizing roundness variation, and improving hole uniformity. In addition, thermal effects during the machining process were analyzed, showing that the water-based environment effectively suppresses the expansion of the heat-affected zone and mitigates recast layer formation, thereby enhancing hole wall quality. Compared with conventional non-water-based methods, the backwater-assisted approach demonstrates superior processing stability, better hole morphology, and more efficient thermal management. This work provides a reliable technical route and theoretical foundation for precision microhole machining of stainless steel and exhibits strong potential for engineering applications. Full article

High-average-power extreme ultraviolet (EUV) sources are essential for large-scale nanoscale chip manufacturing, yet commercially available laser-produced plasma sources face challenges in scaling to the kilowatt level. We propose a novel scheme that combines the high repetition rate of a diffraction-limited storage ring with a regenerative amplifier free-electron laser (RAFEL) employing a transverse gradient undulator (TGU). By introducing dispersion in the storage ring, electrons of different energies are directed into corresponding magnetic field strengths of the TGU, thereby satisfying the resonance condition under a large energy spread and increasing the FEL gain. Simulations show that at equilibrium, the average EUV power exceeds 1 kW, with an output pulse energy reaching ∼2.86 μJ, while the energy spread stabilizes at ∼0.45%. These results demonstrate the feasibility of ring-based RAFEL with TGU as a promising route toward kilowatt-level EUV sources. Full article

We report the simultaneous generation of conventional solitons (CSs) and dissipative solitons (DSs) in an erbium-doped mode-locked fiber laser with a dual-branch cavity configuration based on the nonlinear polarization rotation (NPR) technique. By incorporating fibers with different dispersion properties in two propagation branches, the laser can establish simultaneous operation in the normal and anomalous dispersion regimes within the respective loops, enabling the generation of two distinct soliton types. The CSs exhibit a 3 dB spectral bandwidth of 9.7750 nm and a pulse duration of 273 fs, while the DSs have a quasi-rectangular spectrum spanning 18.7074 nm and a pulse duration of 2.2 ps, which can be externally compressed to 384 fs. The fundamental repetition rate is approximately 21 MHz, with a repetition rate difference of 216 Hz for the two pulse trains. Stable second-order, third-order, and fourth-order harmonic mode-locking (HML) can be achieved through optimization of pump power and intracavity polarization states. The laser we build in this work has significant potential for applications in high-precision spectroscopy and asynchronous optical sampling. Full article

This work details the development of a 10-stage solid-stage linear transformer driver (SSLTD) capable of producing 24 kV, 1 kA pulses with a rise-time of ∼10 ns utilizing SiC MOSFET switches. Throughout the development process, various design parameters were investigated for their influence on the LTD’s performance. Among these considerations was an evaluation of the behavior of several nanocrystalline magnetic core materials subject to high-voltage pulsed conditions, with an emphasis on minimizing energy losses. Another design parameter of interest lies in the physical layout of the LTD structure, particularly the diameter of the central stalk and the dielectric material, which together define the characteristics of the coaxial transmission line, as well as the overall height of each stage. The influence of each of these parameters was weighed to optimize the final design for fastest output pulse rise-time, highest efficiency, and cleanest output pulse waveform profile across varying load resistance. This work also introduces a pulsed reset technique, where repetition-rated burst testing was used to find the maximum operational frequency of the LTD without driving the magnetic cores into saturation. Full article

Indirect detection phase control algorithms, such as the dithering algorithm and the stochastic parallel gradient descent algorithm (SPGD), have simple system structures and are applicable to filled-aperture coherent combinations with high efficiency. The performances of these algorithms are limited when applied to a coherent combination of pulsed fiber lasers with a low repetition rate (≤5 kHz). Firstly, due to the overlap of the phase noise frequency and repetition rate, conventional algorithms cannot effectively distinguish the phase noise from the pulse fluctuation, and directly applying filtering will result in the phase information being filtered out. Secondly, if the pulse fluctuation is ignored and only the continuous part of the phase information is utilized, it relies on the presetting of conditions to separate the pulse from the continuous part and loses the phase information of the pulse part. In this article, we propose a waveform self-referencing algorithm (WSRA) based on a two-channel near-infrared laser coherent combination system to overcome the above challenges. Firstly, by modelling a self-referencing waveform, a nonlinear scaling operation is performed on the combined signal to generate a pseudo-continuous signal, which removes the intrinsic pulse fluctuation while preserving the phase noise information. Secondly, the phase control signal is calculated based on the pseudo-continuous signals after parallel perturbation. Finally, the phase noise is corrected by optimization. The results show that our method effectively suppresses the waveform fluctuation at a 5 kHz repetition rate, the light intensity reaches an ideal value (0.9939 $I_{\max }$), and the root-mean-square (RMS) phase error is only 0.0130 $\lambda$. This method does not require the presetting of pulse detection thresholds or conditions, and solves the challenge of coherent combination at a low repetition rate, with adaptability to different pulse waveforms. Full article