Search Results (162)

In recent years, graph neural networks (GNNs) have shown powerful performance in processing non-Euclidean data. However, similar to other machine-learning algorithms, GNNs can amplify data bias in high-risk decision-making systems, which can easily lead to unfairness in the final decision-making results. At present, a large number of studies focus on solving the fairness problem of GNNs, but the existing methods mostly rely on building complex model architectures or rely on technical means in the field of non-GNNs. To this end, this paper proposes FairCNCB (Fair Graph Neural Network based on Counterfactual and Category Balance) to address the problem of class imbalancing in minority sensitive attribute groups. First, we conduct a causal analysis of fair representation and employ the adversarial network to generate counterfactual node samples, effectively mitigating bias induced by sensitive attributes. Secondly, we calculate the weights for minority sensitive attribute groups, and reconstruct the loss function to achieve the fairness of sensitive attribute classes among different groups. The synergy between the two modules optimizes GNNs from multiple dimensions and significantly improves the performance of GNNs in terms of fairness. The experimental results on the three datasets show the effectiveness and fairness of FairCNCB. The performance metrics (such as AUC, F1, and ACC) have been improved by approximately 2%, and the fairness metrics (△sp, △eo) have been enhanced by approximately 5%. Full article

Somatic hybridization represents a powerful tool for generating novel chemotypes with enhanced biosynthetic capabilities. This study provides the first comprehensive phytochemical characterization of interspecific somatic hybrids between Gentiana cruciata L. and Gentiana tibetica King ex Hook.f., two medicinally important yet regionally rare gentians. A total of 107 compounds were detected using UHPLC-DAD-ESI-MS³, of which 31 were identified as metabolites across eight phytochemical classes. Comparative profiling revealed that all hybrids retained a conserved core of iridoids and secoiridoids while integrating lineage-specific compounds and producing hybrid-specific metabolites not detected in either parent. Despite inheriting plastids from G. tibetica, hierarchical clustering showed that the phytochemical profiles of hybrid lines were more similar to G. cruciata, the donor of the nuclear genome. Quantitative analysis of the major secoiridoids, such as gentiopicroside, swertiamarin, and sweroside, demonstrated that several hybrid lines, particularly F30A-5 and F30A-6, matched or surpassed the biosynthetic output of G. tibetica, the more productive parent. These lines also exhibited elevated antioxidant capacity, underscoring their phytochemical and functional potential. Altogether, our findings show that somatic hybridization not only preserves but may amplify the secondary metabolite capacity of the parental genotypes, offering a viable platform for sustainable in vitro production of pharmacologically relevant secoiridoids. Full article

This paper presents the first hybrid supply modulator (HSM) designed for envelope tracking power amplifiers (ET-PAs) in base station applications. The focus is on a rail-to-rail Class-AB linear amplifier (LA) optimized for high-voltage and wide-bandwidth operation. The LA is designed using 130 nm BCD technology, utilizing Laterally Diffused Metal-Oxide Semiconductor (LDMOS) transistors for high-voltage operation and incorporating shielding MOSFETs to protect the low-voltage devices. The circuit utilizes dual power supply domains (5 V and 30 V) to improve power efficiency. The proposed LA achieves a bandwidth of 100 MHz and a slew rate of +1003/−852 V/$\mathsf{\mu }\mathrm{s}$, with a quiescent power consumption of 0.89 W. Transient simulations using a 50 MHz bandwidth 5G NR envelope input demonstrate that the proposed HSM achieves a power efficiency of 83%. Consequently, the proposed HSM supports high-output (100 W) wideband 5G NR transmission with enhanced efficiency. Full article

Fine-grained recognition tasks face significant challenges in differentiating subtle, class-specific details against cluttered backgrounds. This paper presents an efficient architecture built upon the Res2Net backbone, significantly enhanced by a dynamic Sparse Attention mechanism. The core approach leverages the inherent multi-scale representation power of Res2Net to capture discriminative patterns across different granularities. Crucially, the integrated Sparse Attention module operates dynamically, selectively amplifying the most informative features while attenuating irrelevant background noise and redundant details. This combined strategy substantially improves the model’s ability to focus on pivotal regions critical for accurate classification. Furthermore, strategic architectural optimizations are applied throughout to minimize computational complexity, resulting in a model that demands significantly fewer parameters and exhibits faster inference times. Extensive evaluations on benchmark datasets demonstrate the effectiveness of the proposed method. It achieves a modest but consistent accuracy gain over strong baselines (approximately 2%) while simultaneously reducing model size by around 30% and inference latency by about 20%, proving highly effective for practical fine-grained recognition applications requiring both high accuracy and operational efficiency. Full article

This paper presents a class-D outphasing power amplifier (PA) that incorporates a non-isolating balun combiner employing a 180° phase shift. Both isolating and non-isolating outphasing combiners are analyzed for signal restoration and combining efficiency. The proposed non-isolating balun combiner employing the 180° phase shift was experimentally evaluated and compared with a commercial isolating Wilkinson combiner. When two constant-envelope signals derived from a 10 MHz long-term evolution (LTE) signal are applied to the inputs of the outphasing combiners, both combiners demonstrate successful signal reconstruction. The measured adjacent channel leakage ratios (ACLRs) are −47 dBc for the Wilkinson combiner and −46 dBc for the proposed balun combiner. At 6 dB power back-off (PBO), the proposed balun combiner achieves a combining efficiency of 85.1%, representing an improvement of nearly 60% over the Wilkinson combiner. With a center frequency of 650 MHz, targeting 5G FR1 applications, a class-D outphasing PA was designed in a 28 nm CMOS process using the measured S-parameter data from both outphasing combiners. Simulation results show that the class-D outphasing PA incorporating the proposed balun combiner achieves a peak drain efficiency (DE) of 82.9% with an output power of 17.7 dBm. At 6 dB PBO, the DE reaches 61%, which is approximately 37% higher than that of the outphasing PA using the Wilkinson combiner. Moreover, the designed outphasing PA supports broadband operation over the 360–860 MHz range. Full article

The global allocation of over 5 GHz of spectral bandwidth around the 60 GHz frequency band offers significant potential for ultra-high data rate wireless communication over short distances and enables the implementation of high-resolution frequency-modulated continuous-wave (FMCW) radar applications. In this study, a Front-End Receiver covering frequencies from 57 to 64 GHz was designed and characterized in a 40 nm CMOS process. The proposed architecture includes a Low-Noise Amplifier (LNA), a novel double-balanced mixer offering variable conversion gain, and a low-power class-C Voltage-Controlled Oscillator (VCO). From post-layout simulation results, the LNA presents a noise figure (NF) less than 4.8 dB and a gain more than 19 dB, while the input compression point (P1dB) reaches −15.6 dBm. The double-balanced mixer delivers a noise figure of less than 11 dB, a conversion gain of 14 dB, and an input-referred compression point of −13 dBm. The VCO achieves a phase noise of approximately −93 dBc/Hz at 1 MHz offset from 60 GHz and a tuning range of about 8 GHz, dissipating only 6.6 mW. Overall, the receiver demonstrates a maximum conversion gain of more than 39 dB, a noise figure of less than 9.2 dB, an input- referred compression point of −37 dBm, and a power dissipation of 56 mW. Full article

Energy-efficient integrated circuits require scaled-down supply voltages, posing challenges for analog design, particularly for operational transconductance amplifiers (OTAs) essential in high-accuracy CMOS feedback systems. Below 1 V, gate-driven OTAs are limited in common-mode input range and minimum supply voltage. This work investigates CMOS Bulk-Driven (BD) sub-threshold techniques as an efficient alternative for ultra-low voltage (ULV) and ultra-low power (ULP) designs. Although BD overcomes MOS threshold voltage limitations, historical challenges like lower transconductance, latch-up, and layout complexity hindered its use. Recent advancements in CMOS processes and the need for ULP solutions have revived industrial interest in BD. Through theoretical analysis and computer simulations, we explore BD topologies for ULP OTA input stages, classifying them as tailed/tail-less and class A/AB, evaluating their effectiveness for robust analog design, while offering valuable insights for circuit designers. Full article

This paper extends the quasi-load insensitive (QLI) Class-E Doherty power amplifier (PA) design methodology to address Doherty PA combiners with complex load impedance trajectories. Additionally, the QLI operation is analyzed for generalized class-E output matching networks with input series inductors and finite DC-feed inductors. We demonstrate that the QLI class-E Doherty operation can be achieved for various Doherty combiners by selecting the appropriate combination of class-E outputs matching network resonance factors and input series inductances. Moreover, a modified class-E output network is proposed to overcome the frequency limitation that might be caused by the class-E network resonance factor choice. To validate the proposed methodology, two 40 W Doherty PAs are designed and simulated using commercial GaN HEMT transistors achieving more than 70% efficiency over a 6 dB output power back-off at 3.8 GHz. Full article

High-test peroxide (HTP) monopropellant thrusters are being considered for spacecraft lander missions due to their simplicity and reduced toxicity compared to traditional propellants. Pulse-Width Modulation (PWM) throttling is a key technique for precise thrust control in such systems. However, PWM throttling can lead to pressure surges and oscillations in the propellant feed system, potentially compromising system reliability. This study investigates the influence of PWM parameters, specifically duty cycle and frequency, on pressure surges and oscillations in a 50-newton-class HTP monopropellant thruster. The objective is to identify stable operating conditions that mitigate these effects, thereby enhancing the reliability of PWM throttling for lander applications. An experimental setup was developed, including a 50-newton-class thruster with a ${\mathrm{MnO}}_2{\mathrm{/La/Al}}_2{\mathrm{O}}_3$ catalyst and a solenoid valve for PWM control. Cold flow tests using water characterized the valve response and water hammer effects, while hot fire tests with 90 wt.% HTP were used to evaluate thruster performance under steady-state and PWM conditions. Analytical methods, including Joukowsky’s equation and power spectral density analysis, were used to interpret the data and understand the underlying mechanisms. The results showed that while surge pressures generally aligned with steady-state values, specific PWM conditions led to amplified surges, particularly at low duty cycles. Additionally, high duty cycles induced chugging instability. The natural frequencies of the feed system were found to play a crucial role in these phenomena. Stable operating conditions were identified by avoiding duty cycles that cause constructive interference of pressure waves. This research demonstrates that by carefully selecting PWM parameters based on the feed system’s dynamic characteristics, pressure surges and oscillations can be minimized, ensuring reliable operation of HTP monopropellant thrusters in PWM throttling mode. These findings contribute to the development of more efficient and safer propulsion systems for spacecraft landers. Full article

Class-D power amplifiers driving variable loads, such as inductively coupled plasma (ICP), typically require an impedance matching network, which has a relatively slow matching speed, generally in the millisecond range. To address this issue, this paper proposes a solution that uses a fully digital control method for Class-D power amplifiers to directly drive ICP loads. This solution eliminates the need for an impedance matching network, reducing the overall output power regulation time to just tens of microseconds. Compared to traditional methods that use a VI probe to detect output power, the proposed method in this paper only requires measuring the resonant current in the loop to control the output power, thereby reducing costs and ensuring that the Class-D power amplifier achieves zero-voltage switching (ZVS) throughout the adjustment process. This paper provides a detailed introduction to the design method of the Class-D power amplifier and the overall digital control scheme and validates them via simulation and experimentation. The Class-D power amplifier prototype was designed using SiC MOSFETs, with a Xilinx ZYNQ-XC7Z100 FPGA as the control board. The output frequency varies around 4 MHz, successfully generating plasma. Full article

This study employs Monte Carlo (MC) models and thermal-statistical analysis to investigate the production mechanisms of strange ($K_S^0$, $\mathrm{\Lambda }$) and multi-strange ($\mathrm{\Xi }$, $\mathrm{\Omega }$) hadrons in high-multiplicity proton–proton collisions. Through systematic comparisons with experimental data, we evaluate the predictive power of EPOS, PYTHIA8, QGSJETII04, and Sibyll2.3d. EPOS, with its hydrodynamic evolution, successfully reproduces low-$p_T$$K_S^0$ and $\mathrm{\Lambda }$ yields in high-multiplicity classes (MC1–MC3), mirroring quark-gluon plasma (QGP) thermalization effects. PYTHIA8’s rope hadronization partially mitigates mid-$p_T$ multi-strange baryon suppression but underestimates $\mathrm{\Xi }$ and $\mathrm{\Omega }$ yields due to the absence of explicit medium dynamics. QGSJETII04, tailored for cosmic-ray showers, overpredicts soft $K_S^0$ yields from excessive soft Pomeron contributions and lacks multi-strange hadron predictions due to enforced decays. Sibyll2.3d’s forward-phase bias limits its accuracy at midrapidity. No model fully captures $\mathrm{\Xi }$ and $\mathrm{\Omega }$ production, though EPOS remains the closest. Complementary Tsallis distribution analysis reveals a distinct mass-dependent hierarchy in the extracted effective temperature ($T_{\mathrm{eff}}$) and non-extensivity parameter (q). As multiplicity decreases, $T_{\mathrm{eff}}$ rises while q declines—a trend amplified for heavier particles. This suggests faster equilibration of heavier particles compared to lighter species. The interplay of these findings underscores the necessity of incorporating QGP-like medium effects and refined strangeness enhancement mechanisms in MC models to describe small-system collectivity. Full article

A high-power and high-repetition KTiOAsO₄ (KTA) optical parametric oscillator (OPO) was established in this study, with the adoption of plane-parallel and ring cavities. The pump was a high-power Nd:YAG master oscillator power amplifier (MOPA) system with a pulse repetition frequency (PRF) of 300 Hz, and the corresponding beam quality factors were M_x² = 3.4 and M_y² = 3.2. In the plane-parallel cavity experiment, powers of 51.1 W (170 mJ) and 15.9 W (53 mJ) in the signal and idler were obtained, respectively. In terms of the average power of 1 μm of a pumped KTA OPO, to our knowledge, this is the highest average power for KTA OPO. The ring cavity was constructed to achieve lasers with both high power and beam quality. The output powers of the ring cavities for the signal and idler were 33.9 W (113 mJ) and 8.7 W (29 mJ), respectively, and the corresponding beam quality factors of the signal were M_x² = 5.3 and M_y² = 7.9. The 300 Hz 100 mJ class 1.54 μm laser with a beam quality factor of less than 10 is an ideal eye-safe light detection and ranging (LiDAR) source. Full article

The advent of CMOS power amplifiers has enabled compact and cost-effective solutions for RF applications. Among the available options, switching amplifiers are the most competitive due to their superior efficiency. In this paper, we present the design of a fully integrated 130 nm CMOS class-E RF power amplifier optimized for 2.4 GHz ISM band operations that is compliant with the Bluetooth Low Energy (BLE) standard. The amplifier is based on a cascode configuration with charging acceleration capacitance and a combination of standard and high-voltage (HV) MOSFETs, ensuring optimal performance while maintaining device reliability. To identify the best configuration for the proposed circuit, we first provide an overview of basic class-E amplifier operations and critically review optimization techniques proposed in the scientific literature. This review is complemented by a numerical analysis of the potential advantages of using a combined standard-HV MOSFET structure. Post-layout simulations with parasitic parameter extraction demonstrated that the amplifier achieves 40.85% Power Added Efficiency and 20.52 dBm output power. Full article

This paper critiques the Western-centric lens in gender studies, emphasising the need for decolonial, intersectional, and inclusive methodologies in community-based tourism (CBT) research. It argues that universalist narratives often overlook local power structures, gendered labour divisions, and socio-economic inequalities, disregarding localised knowledge and the structural barriers that shape women’s realities in tourism. In the case of rural women, these dominant perspectives fail to address key issues such as the unequal distribution of benefits, the complexities of tourism participation, and the tensions between market demands, social change, and cultural preservation. This paper calls for context-sensitive approaches that amplify women’s voices and lived experiences in CBT. It highlights the urgency of decolonising knowledge, challenging hegemonic epistemologies that homogenise women’s experiences and reinforce Eurocentric gender norms. The study also underscores intersectionality as a crucial tool to expose the overlapping systems of oppression—including ethnicity, class, race, and access to global tourism markets—that deepen gender inequalities in CBT. Without a decolonial and intersectional lens, tourism studies risk reproducing extractivist logics that marginalise local voices and perpetuate inequitable structures. Future research must move beyond Western frameworks, fostering more ethical, sustainable, and socially just approaches to gender studies in tourism. Full article

This review explores two main topics: the state-of-the-art and emerging capabilities of high-peak-power, ultrafast (picosecond and femtosecond) long-wave infrared (LWIR) laser technology based on CO₂ gas laser amplifiers, and the current and advanced scientific applications of this laser class. The discussion is grounded in expertise gained at the Accelerator Test Facility (ATF) of Brookhaven National Laboratory (BNL), a leading center for ultrafast, high-power CO₂ laser development and a National User Facility with a strong track record in high-intensity physics experiments. We begin by reviewing the status of 9–10 μm CO₂ laser technology and its applications, before exploring potential breakthroughs, including the realization of 100 terawatt femtosecond pulses. These advancements will drive ongoing research in electron and ion acceleration in plasma, along with applications in secondary radiation sources and atmospheric energy transport. Throughout the review, we highlight how wavelength scaling of physical effects enhances the capabilities of ultra-intense lasers in the LWIR spectrum, expanding the frontiers of both fundamental and applied science. Full article