Nanoantennas Inversely Designed to Couple Free Space and a Metal–Insulator–Metal Waveguide

The metal–insulator–metal (MIM) waveguide, which can directly couple free space photons, acts as an important interface between conventional optics and subwavelength photoelectrons. The reason for the difficulty of this optical coupling is the mismatch between the large wave vector of the MIM plasmon mode and photons. With the increase in the wave vector, there is an increase in the field and Ohmic losses of the metal layer, and the strength of the MIM mode decreases accordingly. To solve those problems, this paper reports on inversely designed nanoantennas that can couple the free space and MIM waveguide and efficiently excite the MIM plasmon modes at multiple wavelengths and under oblique angles. This was achieved by implementing an inverse design procedure using a topology optimization approach. Simulation analysis shows that the coupling efficiency is enhanced 9.47-fold by the nanoantenna at the incident wavelength of 1338 nm. The topology optimization problem of the nanoantennas was analyzed by using a continuous adjoint method. The nanoantennas can be inversely designed with decreased dependence on the wavelength and oblique angle of the incident waves. A nanostructured interface on the subwavelength scale can be configured in order to control the refraction of a photonic wave, where the periodic unit of the interface is composed of two inversely designed nanoantennas that are decoupled and connected by an MIM waveguide

Study on the Effect of Regional Water Pollution—Take Huaxi River in Chongqing as an Example

Water pollution management plays a crucial role in China’s ecological environment development. It has evolved from being solely the responsibility of the government to a collaborative effort involving multiple entities. This paper presents findings from a field survey conducted around the collaborative capacity and effectiveness of wastewater treatment in Huaxi River, Chongqing. The study collected 427 valid questionnaires and employed SPSS26.0 software and AMOS24.0 software, utilizing structural equation modelling and regression analysis to verify the relationship between the variables. The results highlight that synergy mechanism acts as a mediating variable between synergy capability and synergy governance effect, underscoring the role of mechanism in the relationship between capability and governance effect. The conclusion emphasizes the importance of enhancing synergistic capacity and synergistic mechanism to effectively promote synergistic governance effect in the water pollution management of Huaxi River in Chongqing. This can be achieved by improving the abilities of multiple stakeholders in managing water pollution, enhancing cooperation among parties, and encouraging participation of social organizations, the public, and enterprises in the management process to achieve sustainable development of ecological civilization

The effects of litter input and increased precipitation on soil microbial communities in a temperate grassland

Global warming has contributed to shifts in precipitation patterns and increased plant productivity, resulting in a significant increase in litter input into the soils. The enhanced litter input, combined with higher levels of precipitation, may potentially affect soil microbial communities. This study aims to investigate the effects of litter input and increased precipitation on soil microbial biomass, community structure, and diversity in a temperate meadow steppe in northeastern China. Different levels of litter input (0%, +30%, +60%) and increased precipitation (0%, +15%, +30%) were applied over a three-year period (2015–2017). The results showed that litter input significantly increased the biomass of bacteria and fungi without altering their diversity, as well as the ratio of bacterial to fungal biomass. Increased precipitation did not have a notable effect on the biomass and diversity of bacteria and fungi, but it did increase the fungal-to-bacterial biomass ratio. However, when litter input and increased precipitation interacted, bacterial diversity significantly increased while the fungal-to-bacterial biomass ratio remained unchanged. These findings indicate that the projected increases in litter and precipitation would have a substantial impact on soil microbial communities. In energy-and water-limited temperate grasslands, the additional litter inputs and increased precipitation contribute to enhanced nutrient and water availability, which in turn promotes microbial growth and leads to shifts in community structure and diversity

Tower Air-gaps discharge characteristics and insulation coordination for UHV AC double-circuit line

In order to give out inverse V-type insulator tower air-gaps configuration of double-circuit UHV AC power transmission line, different distance air-gaps from high-voltage electrode to tower frame discharge tests of inverse V-string are carried out. Discharge characteristics curves of power frequency voltage, 1000 μs long wave-front switching impulse voltage, and lightning impulse of UHV AC double-circuit tower are obtained. Results show that the 50% discharge voltage gradient of bottom phase air-gaps is higher than middle phase. 1000 μs wave-front switching impulse 50% discharge voltage gradient of bottom phase air-gaps is 4.6% higher than the middle phase. Based on the test results and the characters of operating voltage and overvoltage of UHV AC power transmission system, the UHV AC double-circuit tower inverse V-type insulator air-gaps configuration is proposed. The air-gap configurations of power frequency voltage and switching overvoltage are 2.9 and 6.5 m, and the lightning protection air-gaps are 6.7 and 7.2 m, in mountains and plains

Experimental Study of Aged and Seriously Damaged RC Beams Strengthened Using CFRP Composites

This paper presents results from experiments on aged and seriously damaged reinforced concrete (RC) beams strengthened with different arrangements of external carbon fiber-reinforced polymer (CFRP) laminates and end anchorages. Seven RC beams from an old bridge, measuring 250 × 200 × 2300 mm, were tested. All specimens were loaded to yield load to evaluate initial mechanical properties. Then, these seriously damaged specimens were repaired using different CFRP-reinforcing schemes and reloaded to failure. The yield load growth due to CFRP reinforcement ranged from 5% to 36%. Different parameters including CFRP dimension and position, bonding length, and end anchorage were investigated and facilitated conclusions on beam ductility, load-midspan deflection response, and failure mode. This research contributes to knowledge about the CFRP repair of aged and seriously damaged beams to ensure better performance in overloaded conditions

Corrosion Activity on CFRP-Strengthened RC Piles of High-Pile Wharf in a Simulated Marine Environment

We report test results from an experimental study to investigate the effectiveness of carbon fiber-reinforced polymer (CFRP) against reinforcing steel bar corrosion. Twelve reinforced-concrete pile specimens of 180 mm square by 1,600 mm long were cast. Three pile specimens were corroded to 5% steel mass loss and then strengthened with CFRP sheets; four specimens were strengthened by using CFRP sheets, whereas the remaining five specimens were not strengthened. The specimens were placed in a simulated marine environment, and corrosion was induced by an impressed current technique. At different theoretical corrosion degrees, nondestructive tests were performed to investigate the corrosion activity of the pile specimens, and destructive tests were performed to determine reinforcing steel bar mass loss. Based on the findings, the effectiveness of the CFRP-strengthened RC piles under aggressive marine environmental conditions was established

Multi-component yttrium aluminosilicate (YAS) fiber prepared by melt-in-tube method for stable single-frequency laser

The multi-component glass fibers have demonstrated their unique advantages in the application of single-frequency lasers due to their higher solubility of rare-earth ions and thus a higher gain per unit length in a compact fiber laser cavity. In this study, multi-component yttrium aluminosilicate (YAS) fiber with high doping concentration of Yb3+ was prepared by the "melt-in-tube" (MIT) method. A unit-length gain of 3 dB/cm was obtained in a 4.4 cm-long YAS fiber, the laser output slope efficiency reached 23.8% in a 10 cm-long Yb:YAS fiber. Single-frequency laser operation was achieved in a 1.7-cm-long Yb:YAS active fiber. To the best of our knowledge, this is the first demonstration of single-frequency laser with this YAS glass fiber as gain medium. The novel multi-component YAS fiber can be applied as a new gain material to realize single-frequency fiber laser