Search Results (715)

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

Background/Objectives: Adenomyosis is increasingly being identified in women of childbearing age as a cause of infertility and adverse pregnancy outcomes. As hysterectomies are not suitable for fertile women, conservative surgical management has become a promising solution. We aimed to synthesize current evidence on conservative uterus-sparing surgical techniques for adenomyosis, focusing on implications for infertility treatment and pregnancy outcomes. Methods: A search of PubMed, Google Scholar, and Europe PMC from 2022 to July 2025 was conducted using combinations of the words “adenomyosis,” “fertility,” “infertility,” “pregnancy outcomes,” “adenomyomectomy,” and “uterine-sparing surgery.” Sixteen high-relevance studies were chosen that included reproductive-aged women who had conservative surgery for adenomyosis. Results: Excisional techniques such as adenomyomectomy yield pregnancy rates of >50% and live birth rates of up to 70% in focal disease, with less success in diffuse disease. Non-excisional approaches—high-intensity focused ultrasound (HIFU), radiofrequency ablation (RFA), and uterine artery embolization (UAE)—yield equivalent pregnancy (40–53%) and live birth (35–74%) rates in selected patients, with fewer surgical complications. Adjunctive hormonal therapy, particularly GnRH agonists, appears to improve outcomes. Risks include placenta accreta spectrum disorders and uterine rupture (≤6%), especially in diffuse adenomyosis. The type of lesion, location, and junctional zone thickness are strong predictors of fertility outcomes. Conclusions: Conservative surgery can augment fertility in appropriately chosen women with adenomyosis, with removal being the preferred treatment for focal disease and non-removal techniques offering encouraging alternatives in mild or intracorporeal disease. The addition of adjunct hormonal therapy and standardized patient selection criteria will optimize results. The lack of European professional society guidelines underscores the need for harmonized protocols in order to standardize the diagnosis, surgery, and reporting of results. Full article

In this study, we present the development of a high-average-power, exceptionally stable extreme-ultraviolet (EUV) laser source based on a high-order harmonic generation (HHG) technique. The spectrum of an ytterbium-doped laser is broadened through self-phase modulation (SPM) in a gas-filled hollow fiber and compressed down to 25.3 fs for efficient harmonic generation. The high harmonics are generated in a krypton (Kr) gas cell, delivering a total power of 241 μW within the 30–60 nm spectral range, corresponding to a single harmonic output of 166 μW at a central wavelength of 46.8 nm. Notably, the system demonstrates good power stability with a root-mean-square (RMS) deviation of only 1.95% over 12 h of continuous operation. This advanced light source holds great potential for applications in nano- and quantum-material development and in semiconductor wafer defect detection. Future work aims to further enhance the output power in the 30–60 nm band to the milliwatt level, which would significantly bolster scientific research and technological development in related fields. Full article

During operation, the voltage and current waveforms output by pulse width modelation (PWM) inverters often contain high-frequency ripples. Compared to the average model, the generalized average model (GAM) can take into account the effects of high-frequency components and harmonics, further improving the accuracy of the model calculations. However, as the order of GAM increases, the construction of its mathematical model becomes increasingly complex and may lose the original harmonic characteristics of the system. To facilitate the analysis of the influence of the order of the generalized average model on the harmonic characteristics of its original system, a GAM of the PWM inverter was constructed using the Modelica language based on the mapping rules from the time-domain state-space model to the multi-frequency-domain GAM. Subsequently, based on the spectral distribution of the external control signal, a configuration strategy for the characteristic harmonic frequencies of the GAM was proposed. Simulation experiments were conducted separately for one-phase and three-phase inverters. The results indicate that the proposed configuration strategy for the characteristic harmonic frequencies of GAM not only preserves the harmonic characteristics of the original system but also improves the computational efficiency of the system model. Full article

In this study, the nonlinearity characteristics of bilayer graphene field-effect transistors (Bi-GFETs) are analyzed by using a small-signal equivalent circuit. The static nonlinearity is determined by applying mathematical operation on the drain current equation of Bi-GFETs. Furthermore, the closed expressions for the second- and third-order harmonic distortion (HD) and the intermodulation (IM) distortion of the second- and third-order for Bi-GFETs are analyzed graphically. Dynamic nonlinearity is studied and illustrated in the results by examining the input and output characteristics; i.e., the drain current versus the negative drain to the source voltage and the transfer characteristic curve at various gate voltages controlled by both the top gate as well as the back gate. The characteristic behavior of the gate voltage in Bi-GFETs at short channel lengths is observed and compared; that is, the characteristic curves exhibits strong nonlinearity, with a low power point with some kinks at high gate biasing and a constant linear region at low gate biasing. The quantitative values of the second-order harmonic distortion (HD) and intermodulation distortion (IM) of the proposed analytical model are −40 dB and −45 dB. Quantitative and qualitative outcomes of the characteristics of Bi-GFETs are compared with existing experimental data, which is available in the literature. Full article

High-order harmonic generation with mid-infrared laser fields has been considered the most promising method to produce soft X-rays attosecond pulses, which provides an important tool for probing the ultrafast electronic dynamics in atoms, molecules, and solids in real time. However, quantum diffusion of the electron wavepacket can lead to a dramatic drop of the harmonic yield when a mid-infrared laser field is used. Here we theoretically demonstrate that a spatially structured (SS) laser field can suppress quantum diffusion of the electron wavepacket and lead to a significant enhancement of high-order harmonic generation, compared with those generated by the spatially homogeneous (SH) laser field. The SS laser field is inhomogeneous in transverse direction perpendicular to the laser polarization and homogeneous in the polarization direction of the laser field. The electric field presents a valley structure. It is found that this valley structure can confine the electron wavepacket around the parent ion, prevent the electron wavepacket spreading, and finally lead to the significant enhancement of the high-order harmonics. Our results provide a novel method for controlling the ultrafast electron wavepacket dynamics of HHG. Full article

In this study, a high-efficiency permanent magnet synchronous motor (PMSM) was designed for a geared electric vehicle. The motor was developed for use in an L-category electric vehicle with four wheels and a two-passenger capacity. During the design process, application-specific dimensional constraints, electromagnetic requirements, and material limitations were taken into consideration. A spoke-type rotor structure was adopted to achieve both mechanical robustness and high efficiency with minimized leakage flux. In addition, the combination of a 12-stator slot and a 10-rotor pole was selected to suppress low-order harmonic components and improve torque smoothness. The motor model was analyzed using Siemens Simcenter SPEED software (Product Version 2020.3.1), and an efficiency above 94% was achieved, meeting the IE6 efficiency class. Magnetic flux analysis results showed that the selected core material operated within the magnetic saturation limits. The findings demonstrate that a compact and high-efficiency PMSM design is feasible for electric vehicle applications. Full article

Fractional-order models provide a powerful framework for capturing memory-dependent and viscoelastic dynamics in mechanical systems, which are often inadequately represented by classical integer-order characterizations. This study addresses the identification of dynamic parameters in both single-degree-of-freedom (1-DOF) and three-degree-of-freedom (3-DOF) Duffing oscillators with fractional damping, modeled using the Grünwald–Letnikov characterization. The 1-DOF system includes a cubic nonlinear restoring force and is excited by a harmonic input to induce steady-state oscillations. For both systems, time domain simulations are conducted to capture long-term responses, followed by Fourier decomposition to extract steady-state displacement, velocity, and acceleration signals. These components are combined with a GL-based fractional derivative approximation to construct structured regressor matrices. System parameters—including mass, stiffness, damping, and fractional-order effects—are then estimated using pseudoinverse techniques. The identified models are validated through a comparison of reconstructed and original trajectories in the phase space, demonstrating high accuracy in capturing the underlying dynamics. The proposed framework provides a consistent and interpretable approach for frequency domain system identification in fractional-order nonlinear systems, with relevance to applications such as mechanical vibration analysis, structural health monitoring, and smart material modeling. Full article

We theoretically investigate high-order harmonic generation from ethylbenzene (C₈H₁₀), toluene (C₇H₈), and benzene (C₆H₆) molecules driven by a circularly polarized laser field using time-dependent density functional theory. By comparing the harmonic spectra of these structurally related molecules, we find that ethylbenzene, which features a larger molecular size due to the ethyl group, exhibits a higher harmonic cutoff and stronger harmonic intensity than toluene and benzene. Time-resolved electron density distributions, together with the probability current density analysis, indicate that under long-wavelength conditions (e.g., 1200 nm), the ethyl group in ethylbenzene and the methyl group in toluene significantly enhance the probability of ionized electrons from neighboring nuclei colliding with nearby nuclei, thereby leading to stronger harmonic emission, with ethylbenzene > toluene > benzene. In contrast, under short-wavelength conditions (e.g., 200 nm), the harmonic intensities of the three molecules show little difference, and the effects of the ethyl and methyl groups on the harmonic yield can be neglected. The influence of laser intensity and wavelength on high-order harmonic generation is further analyzed, confirming the robustness of the structural enhancement effect. Additionally, we study the harmonic ellipticity of ethylbenzene under different carrier-envelope phases, and find that while circularly polarized harmonics can be obtained, their spectral continuity is insufficient for synthesizing isolated circularly polarized attosecond pulses. This limitation is attributed to the broken ring symmetry caused by the ethyl substitution. Our findings offer insight into the relationship between molecular structure and harmonic response in strong-field physics, and provide a pathway for designing efficient circularly polarized attosecond pulse sources. Full article

The extraordinary mechanical flexibility, high electrical conductivity, and nanoscale instability of freestanding graphene make it an excellent candidate for vibration energy harvesting. When freestanding graphene is stretched taut and subject to external forces, it will vibrate like a drum head. Its vibrations occur at a fundamental frequency along with higher-order harmonics. Alternatively, when freestanding graphene is compressed, it will arch slightly out of the plane or buckle under the load. Remaining flat under compression would be energetically too costly compared to simple bond rotations. Buckling up or down, also known as ripple formation, naturally creates a bistable situation. When the compressed system vibrates between its two low-energy states, it must pass through the high-energy middle. The greater the compression, the higher the energy barrier. The system can still oscillate but the frequency will drop far below the fundamental drum-head frequency. The low frequencies combined with the large-scale movement and the large number of atoms coherently moving are key factors addressed in this study. Ten ripples with increasing compressive strain were built, and each was studied at five different temperatures. Increasing the temperature has a similar effect as increasing the compressive strain. Analysis of the average time between curvature inversion events allowed us to quantify the energy barrier height. When the low-frequency bistable data were time-averaged, the authors found that the velocity distribution shifts from the expected Gaussian to a heavy-tailed Cauchy (Lorentzian) distribution, which is important for energy harvesting applications. Full article

As a continuation of Schneider et al., Atoms 2022 10, 26, we report recent progress in the development and deployment of the interface between the computational codes B-Spline R-matrix (BSR) and R-Matrix with Time dependence (RMT). These advances have been achieved within the context of the $LS$-coupling scheme. In its current state, the interface handles atomic target states described by single configurations and supports the Fano–Racah phase convention, as required by RMT. As first example of an application, we use the interface to investigate multiphoton single ionization of helium exposed to a linearly polarized laser field with wavelengths between 280 and 316 nm and a peak intensity of $3\times {10}^{14}$ W/cm². As a second example, we consider high-order harmonic generation (HHG) in carbon, driven by an intense 30-cycle laser field at 800 nm and a peak intensity of $1\times {10}^{12}$ W/cm². Full article

This paper presents a wideband D-band frequency sextupler chain implemented in a 100 nm GaAs pHEMT process. The proposed circuit comprises an input-stage frequency tripler, an inter-stage harmonic-rejection power amplifier, and an output-stage frequency doubler. The tripler adopts a balanced topology, which effectively suppresses the fundamental frequency component. The inter-stage power amplifier not only delivers sufficient drive power to the doubler but also enhances suppression of undesired harmonics. The output doubler employs a single-balanced configuration to suppress odd-order harmonics while extracting the second harmonic. The measured peak output power of the sextupler chain is 2.33 dBm, corresponding to an input power of 2 dBm, resulting in a conversion gain of 0.33 dB. The 3 dB output bandwidth spans from 126.3 to 152.7 GHz, corresponding to a relative bandwidth of 18.9%. Owing to the balanced multiplier topology and harmonic-rejection PA, the 5th and 7th harmonics are suppressed by more than 20 dBc. The combination of high output power, wide operating bandwidth, and excellent harmonic suppression makes the design well suited for wideband D-band signal generation in diverse applications. Full article

In this paper, a lightweight permanent magnet in-wheel (LW-PMIW) motor is proposed. This research focuses on using a multi-modulation design to enhance the amplitude of the fundamental wave while suppressing high-order harmonics, thereby enabling the motor to achieve high output torque, a light weight, and a high efficiency. Firstly, a combined trade-off factor related to motor mass, losses, and torque is defined specifically to provide guidance for the design. Secondly, a dual-rotor structure is adopted, and a harmonic injection (HI) design is applied to the permanent magnets (PMs). By designing a targeted harmonic injection ratio coefficient, the non-working harmonics of the PM magnetomotive force (MMF) can be weakened. Then, two iron modulating blocks are introduced to asynchronously modulate the PM MMF, which can further enhance the fundamental amplitude and improve the distribution of the airgap magnetic field. Finally, to verify the effectiveness of the multi-modulation design, the electromagnetic performance of the motor is evaluated and analyzed. The analytical and simulation results show that the torque of the proposed motor can reach 35.4 Nm, which is an increase of 19.6% while the torque ripple remains unchanged compared with the initial motor. Meanwhile, the output power increased by 0.37 kW. Hence, the rationality and effectiveness of the motor design are verified. Full article

Large synchronous motors are typically used to drive various load equipment, such as reciprocating compressors. Due to the continuous oscillation of the load, the pulsating torque acting on the main shaft of the synchronous motor will continuously vary with the load changes. This leads to forced oscillations during the dynamic stable operation of the unit, subsequently causing severe problems such as overheating, noise, and failures. Moreover, the rotor length of large synchronous motors is generally greater than the rotor diameter, giving the rotor certain flexible characteristics. During a motor’s operation, it is necessary to cross the first-order critical speed, making resonance highly likely to occur. Therefore, the analysis of dynamic characteristics of large synchronous motors is particularly important. This study investigates the dynamic characteristics of a 7800 kW-18P large synchronous motor rotor system through comprehensive theoretical and experimental analyses. The research encompasses three key aspects: (1) modal analysis comparing fan-equipped and fan-free configurations, (2) harmonic response evaluation, and (3) critical speed determination under concentrated mass conditions. Experimental validation was performed via impact hammer testing, with measured natural frequencies showing a strong correlation with simulated results for the magnetic pole core assembly. The findings not only confirm the operational speed validity but also establish a reliable foundation for the subsequent structural optimization of high-power synchronous machines. Full article

We report the crystal structure and nonlinear optical (NLO) characterization of the monohydrate form of N′-[(E)-(2-fluorophenyl)methylidene]-4-hydroxybenzohydrazide (o-FHH), an organic compound showing strong potential for second-order nonlinear optical applications. The compound crystallizes in a non-centrosymmetric tetragonal space group. The supramolecular features of the novel crystal structure are strongly related to the role of the water molecule that stabilized columns of o-FHH through strong hydrogen bonding interactions. This structural feature is reflected in the high thermal stability of the compound, which is evidenced by its ability to withstand temperatures in excess of 100 °C without losing the water molecule. Second-harmonic generation (SHG) imaging confirms bulk nonlinearity throughout the entire volume of the crystal, consistent with the acentric class of the novel compound. The combination of a dense hydrogen-bonding network, structural robustness, and the ability to grow millimeter-sized single crystals makes o-FHH a good candidate for further development as an organic NLO material. Full article