Black phosphorus (BP) has been extensively investigated in ultrafast photonics due to its unique direct bandgap energy, which can be tuned by altering the number of layers. However, the reduction of BP layers induces optical limiting effects, such as two-photon absorption and reverse saturable absorption, which hinder stable mode-locked operation at high pump powers. Herein, we demonstrate stable soliton pulse generation by encapsulating bulk BP within polydimethylsiloxane (PDMS). The fabricated BP/PDMS-saturable absorber with a 6% modulation depth was integrated into “eye-safe” thulium-doped fiber laser (TDFL) and thulium-holmium-doped fiber laser (THDFL) systems. We achieved picosecond pulses with high output powers, pulse energies, and peak powers of 63.13 mW (21.90 mW), 5.28 nJ (3.33 nJ), and 4.06 kW (1.35 kW) for the TDFL (THDFL), respectively. Owing to the absence of optical limiting effects from the BP/PDMS-saturable absorber, fundamental soliton regimes were maintained over a wide range of pump powers with no sign of pulse breakup. Finally, 4-hour stability assessments of the TDFL and THDFL under 75% relative humidity validated the reliability of the BP/PDMS-saturable absorber, opening new possibilities for robust ultrafast photonic applications in the near future.
In recent years, the adoption of civilian drones has accelerated, creating new challenges for the regulation of low-altitude airspace. Countries also exhibit considerable variation in the timing of UAV regulatory adoption. This paper examines the timing of adoption of two foundational UAV regulations, namely UAV registration and remote pilot licensing, across 76 countries from 2013 to 2024. Using discrete-time event history analysis, the paper evaluates the associations between economic development, institutional capacity, aviation system pressure, and regional policy diffusion with the timing of UAV regulatory adoption. The findings indicate that countries within the same region tend to adopt UAV regulations during similar periods, suggesting regional clustering in regulatory adoption. Although baseline models show a positive association between prior regional adoption and the timing of regulatory adoption, this relationship is no longer statistically significant after controlling for regional heterogeneity. Economic development shows a positive association with the adoption of UAV registration in the baseline models, but this relationship is not robust to the inclusion of regional controls. Aviation system pressure and institutional capacity do not display consistent or statistically significant associations with adoption timing. Overall, the findings suggest that similarities in adoption timing are more consistent with structured regional interdependence than with an independent peer diffusion effect. The results further indicate that regional context appears to play a more important role than domestic structural characteristics in explaining cross-country variation in the timing of UAV regulatory adoption, highlighting the potential importance of regional coordination in the governance of emerging aviation technologies.
Renewable energy transitions change rather than remove the geopolitical dimensions of energy systems. In recent years, geopolitical fragmentation, strategic rivalry, and geoeconomic insecurity have increased the importance of security, resilience, and strategic dependence within Europe's energy transition. Against this background, this study examines how geopolitical risk exposure is associated with four observable transition adjustment outcomes across 25 EU member states from 2001 to 2023: external energy dependence, domestic renewable energy capacity, economic globalization, and climate-significant public investment. Geopolitical risk exposure was measured by interacting the annual Global Geopolitical Risk Index with countries' geographical proximity to Russia, allowing the empirical models to incorporate both country and year fixed effects. The empirical analysis combined conventional two-way fixed-effects estimation with double machine learning (DML), alternative exposure specifications, robustness analyses, moderation analyses, and heterogeneity analyses. The results showed that greater geopolitical risk exposure is associated with lower external energy dependence, greater domestic renewable energy capacity, and lower economic globalization, while its relationship with climate-significant public investment is statistically insignificant. The moderating and heterogeneity analyses further indicated that these relationships vary with countries' energy-consumption levels, innovation capability, industrial structure, Russian energy dependence, and institutional capacity. Overall, the findings indicate selective rather than uniform adjustment across Europe's energy transition.
Radio-frequency (RF) and microwave dielectric ceramics are key materials for high-frequency electronic devices. Among them, perovskites outperform conventional dielectrics due to their high quality factor ( Q = 1/dielectric loss) and exceptional reliability. However, their practical application is limited by the trade-off between Q & times; f and the temperature coefficient of resonant frequency ( rf ), as well as by their high densification temperature ( >= 1500 degrees C). Here, a synergistic strategy combining B-site complex-ion modification with composite sintering-aid engineering is proposed. The optimized 95CZT05CMN composition exhibits excellent microwave dielectric properties of dielectric constant sr = 32.4, Q & times; f = 34,240 GHz, and rf = + 16.8 ppm/ degrees C at 1540 degrees C. More importantly, the 5G1L0.5C-modified ceramics can be densified at 950-1050 degrees C while retaining favorable dielectric properties ( sr = 27.3-31.9, Q & times; f = 12,920-13,400 GHz, rf = -6.1 to -11.6 ppm/ degrees C), together with a high flexural strength of 212 MPa. Furthermore, a C-band dielectric resonator antenna delivers radiation efficiency above 85%, while multilayer ceramic capacitors (MLCCs) fabricated show excellent C0G-type stability ( AC / C25 degrees C within +/- 0.3%) and a dielectric loss of similar to 0.06% at 1 MHz. These results establish a viable route toward low sintering temperature, low-loss and thermally stable CaZrO3 -based perovskites for advanced RF and integrated electronic applications. (c) 2026 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
Aging is associated with changes in the structure of road safety risks, but the relationship between road network composition and elderly road safety remains poorly understood. We empirically examine the association between the ratio of mobility-oriented to accessibility-oriented roads and the elderly road death (ERD) rate. Using an unbalanced panel of 82 countries covering 1990–2023, we examine this association, including its direct component and its growth-mediated component through economic development. We find a U-shaped association between the mobility-to-accessibility (MTA) ratio and the ERD rate. Both relatively low and relatively high MTA values are associated with higher ERD rates, with the fitted relationship reaching its minimum at an intermediate MTA level. The association between road network composition and economic development varies across structural settings. While mobility-oriented infrastructure is positively associated with economic growth in highly urbanized and export-dependent economies, the association is weaker or negative in less urbanized and less export-oriented settings. These findings indicate that road network composition provides information beyond the aggregate size of road infrastructure when examining elderly road safety. The findings further suggest that the safety implications of road network composition vary with economic development, urbanization, and export orientation, highlighting the limitations of a uniform policy approach.
