Explore the vast range of titles available.

Among the many novel photocatalytic systems developed in very recent years, plasmonic photocatalytic composites possess great potential for use in applications and are one of the most intensively investigated photocatalytic systems owing to their high solar energy utilization efficiency. In these composites, the plasmonic nanoparticles (PNPs) efficiently absorb solar light through localized surface plasmon resonance and convert it into energetic electrons and holes in the nearby semiconductor. This energy transfer from PNPs to semiconductors plays a decisive role in the overall photocatalytic performance. Thus, the underlying physical mechanism is of great scientific and technological importance and is one of the hottest topics in the area of plasmonic photocatalysts. In this review, we examine the very recent advances in understanding the energy transfer process in plasmonic photocatalytic composites, describing both the theoretical basis of this process and experimental demonstrations. The factors that affect the energy transfer efficiencies and how to improve the efficiencies to yield better photocatalytic performance are also discussed. Furthermore, comparisons are made between the various energy transfer processes, emphasizing their limitations/benefits for efficient operation of plasmonic photocatalysts. Photocatalysis: plasmonic enhancement Recent developments in plasmonic enhancement of photocatalysis are reviewed with a focus on the energy transfer mechanisms involved. The use of plasmonic nanoparticles to enhance photocatalysis—the process whereby light is used to split water into its constituent parts of hydrogen and oxygen—is a topic of great interest. Xiangchao Ma and co-workers from Shandong University in China describe the theoretical basis and experimental demonstrations of localized surface plasmon resonances in plasmonic metal nanoparticles. They then compare the various energy transfer processes that can occur between such nanoparticles and a nearby semiconductor photocatalyst, namely plasmon-induced hot electron injection, plasmon-induced radiative energy transfer, plasmon-induced resonance, and plasmon-induced direct electron injection. Finally, the scientists give guidance for optimizing plasmonic photocatalytic activity and provide an outlook for the future of the field.

Recent advances in nonlinear optics have revolutionized integrated photonics, providing on-chip solutions to a wide range of new applications. Currently, state of the art integrated nonlinear photonic devices are mainly based on dielectric material platforms, such as Si 3 N 4 and SiO 2 . While semiconductor materials feature much higher nonlinear coefficients and convenience in active integration, they have suffered from high waveguide losses that prevent the realization of efficient nonlinear processes on-chip. Here, we challenge this status quo and demonstrate a low loss AlGaAs-on-insulator platform with anomalous dispersion and quality ( Q ) factors beyond 1.5 × 10 6 . Such a high quality factor, combined with high nonlinear coefficient and small mode volume, enabled us to demonstrate a Kerr frequency comb threshold of only ∼36 µW in a resonator with a 1 THz free spectral range, ∼100 times lower compared to that in previous semiconductor platforms. Moreover, combs with broad spans (>250 nm) have been generated with a pump power of ∼300 µW, which is lower than the threshold power of state-of the-art dielectric micro combs. A soliton-step transition has also been observed for the first time in an AlGaAs resonator. Despite larger nonlinear coefficients, waveguide losses have prevented using semiconductors instead of dielectric materials for on-chip frequency-comb sources. By significantly reducing waveguide loss, ultra-low-threshold Kerr comb generation is demonstrated in a high- Q AlGaAs-on-insulator microresonator system.

Silicon nitride (SiN) waveguides with ultra-low optical loss enable integrated photonic applications including low noise, narrow linewidth lasers, chip-scale nonlinear photonics, and microwave photonics. Lasers are key components to SiN photonic integrated circuits (PICs), but are difficult to fully integrate with low-index SiN waveguides due to their large mismatch with the high-index III-V gain materials. The recent demonstration of multilayer heterogeneous integration provides a practical solution and enabled the first-generation of lasers fully integrated with SiN waveguides. However, a laser with high device yield and high output power at telecommunication wavelengths, where photonics applications are clustered, is still missing, hindered by large mode transition loss, non-optimized cavity design, and a complicated fabrication process. Here, we report high-performance lasers on SiN with tens of milliwatts output power through the SiN waveguide and sub-kHz fundamental linewidth, addressing all the aforementioned issues. We also show Hertz-level fundamental linewidth lasers are achievable with the developed integration techniques. These lasers, together with high- Q SiN resonators, mark a milestone towards a fully integrated low-noise silicon nitride photonics platform. This laser should find potential applications in LIDAR, microwave photonics and coherent optical communications. Achieving high output power and low noise integrated lasers is a major challenge. Here the authors experimentally demonstrate integrated lasers from a Si/SiN heterogeneous platform that shows Hertz-level linewidth, paving the way toward fully integrating low-noise silicon nitride photonics in volume using real devices for lasing.

Great earthquakes are one of the major threats to modern society due to their great destructive power and unpredictability. The maximum credible earthquake (MCE) for a specific fault, i.e., the largest magnitude earthquake that may occur there, has numerous potential scenarios with different source processes, making the future seismic hazard highly uncertain. We propose a full-scenario analysis method to evaluate the MCE hazards with deterministic broadband simulations of numerous scenarios. The full-scenario analysis is achieved by considering all uncertainties of potential future earthquakes with sufficient scenarios. Here we show an application of this method in the seismic hazard analysis for the Xiluodu dam in China by simulating 22,000,000 MCE scenarios in 0–10 Hz. The proposed method can provide arbitrary intensity measures, ground-motion time series, and spatial ground-motion fields for all hazard levels, which enables more realistic and accurate MCE hazard evaluations, and thus has great application potential in earthquake engineering. Deterministic numerical simulations are employed to study the maximum credible earthquake hazard for a specific fault. The method is then applied for seismic hazard analysis at the Xiluodu dam in China, and its potential for earthquake engineering is evaluated.

Ceramic coating can effectively isolate the dissimilar metal contact between the pipes of the seawater system, block the circuit of the chemical battery, and improve the anti-corrosion performance of the pipes. However, after welding, the ceramic coating at the joint of the pipeline cracks, rendering its anti-corrosion function ineffective and seriously affecting the safety and reliability of the seawater system. Based on the penetration method, the cracked ceramic coating was repaired with ethanol as solvent and polydimethylsiloxane as the active component. The repair effect was verified by dye penetrant inspection, insulation test, and pressure sealing test. The results show that the repair method can fill the cracks effectively. The installation resistance after repair is greater than 1kΩ, which meets the requirements of insulation performance. After repair, the water seepage of the pipeline is zero, which meets the requirement of pressure sealing. This method has practical significance for the further application of ceramic coating in Marine water system corrosion prevention.

Photonic integrated circuits are widely used in applications such as telecommunications and data-centre interconnects 1 – 5 . However, in optical systems such as microwave synthesizers 6 , optical gyroscopes 7 and atomic clocks 8 , photonic integrated circuits are still considered inferior solutions despite their advantages in size, weight, power consumption and cost. Such high-precision and highly coherent applications favour ultralow-noise laser sources to be integrated with other photonic components in a compact and robustly aligned format—that is, on a single chip—for photonic integrated circuits to replace bulk optics and fibres. There are two major issues preventing the realization of such envisioned photonic integrated circuits: the high phase noise of semiconductor lasers and the difficulty of integrating optical isolators directly on-chip. Here we challenge this convention by leveraging three-dimensional integration that results in ultralow-noise lasers with isolator-free operation for silicon photonics. Through multiple monolithic and heterogeneous processing sequences, direct on-chip integration of III–V gain medium and ultralow-loss silicon nitride waveguides with optical loss around 0.5 decibels per metre are demonstrated. Consequently, the demonstrated photonic integrated circuit enters a regime that gives rise to ultralow-noise lasers and microwave synthesizers without the need for optical isolators, owing to the ultrahigh-quality-factor cavity. Such photonic integrated circuits also offer superior scalability for complex functionalities and volume production, as well as improved stability and reliability over time. The three-dimensional integration on ultralow-loss photonic integrated circuits thus marks a critical step towards complex systems and networks on silicon. Three-dimensional integration of distributed-feedback lasers and ultralow-loss silicon nitride waveguides results in ultralow-noise lasers without the need for optical isolators.

A Gemini cationic surfactant was synthesized through an aldehyde-amine condensation reaction to address challenges related to bacterial corrosion and foaming during shale gas extraction. This treatment agent exhibits sterilization, corrosion mitigation, and foaming properties. The mechanism of action was characterized through tests measuring surface tension, particle size, sterilization efficacy, corrosion mitigation efficiency, and foaming behavior. Results from the surface tension test indicate that at 60 °C, surfactants with a low carbon chain structure achieve the lowest surface tension of 32.61 mN/m at the critical micelle concentration. Particle size distribution (PSD) tests reveal that within the 1–10 critical micelle concentration range, three types of surfactants can form aggregates through self-assembly, with a PSD range of 100–400 nm. Antibacterial performance tests demonstrate that a concentration of 0.12 mmol/L at 20–60 °C achieves a bactericidal rate exceeding 99%, maintained even after 24 h of contact. The bactericidal effect is enhanced under acidic and alkaline conditions. Corrosion mitigation tests show that at 50 °C, the corrosion mitigation rate reaches an optimal value of over 70%. Bubble performance evaluation results suggest that the optimal surfactant concentration is 1 mmol/L at 60 °C, exhibiting resistance to mineralization up to 200 g/L. The development of this surfactant establishes a foundation for effectively addressing issues related to bacterial corrosion and wellbore fluid encountered in shale gas wells.

Numerous modern technologies are reliant on the low-phase noise and exquisite timing stability of microwave signals. Substantial progress has been made in the field of microwave photonics, whereby low-noise microwave signals are generated by the down-conversion of ultrastable optical references using a frequency comb 1 – 3 . Such systems, however, are constructed with bulk or fibre optics and are difficult to further reduce in size and power consumption. In this work we address this challenge by leveraging advances in integrated photonics to demonstrate low-noise microwave generation via two-point optical frequency division 4 , 5 . Narrow-linewidth self-injection-locked integrated lasers 6 , 7 are stabilized to a miniature Fabry–Pérot cavity 8 , and the frequency gap between the lasers is divided with an efficient dark soliton frequency comb 9 . The stabilized output of the microcomb is photodetected to produce a microwave signal at 20 GHz with phase noise of −96 dBc Hz −1 at 100 Hz offset frequency that decreases to −135 dBc Hz −1 at 10 kHz offset—values that are unprecedented for an integrated photonic system. All photonic components can be heterogeneously integrated on a single chip, providing a significant advance for the application of photonics to high-precision navigation, communication and timing systems. We leverage advances in integrated photonics to generate low-noise microwaves with an optical frequency division architecture that can be low power and chip integrated.

Acoustic stealth performance is an important performance index of Underwater Unmanned Aerial Vehicles. Due to equipment installation and other reasons, there will be a sea port on the bulkhead of the aircraft. Because the sea port destroys the flow field on the surface of the aircraft and produces noise, which affects the underwater communication of the aircraft. In this paper, the numerical simulation method is used to analyze the flow induced noise characteristics of the bulkhead of an underwater unmanned vehicle, and the main noise frequency characteristics at the bulkhead of the estuary are obtained, which provides data reference for the structural design of the estuary and the layout of the underwater communication system.

The paper analyzes several key technologies of data monitoring and quality control system based on the Internet of Things technology from the perspective of system integration, including Web database access, real-time display of dynamic data, dynamic drawing of curves, etc., and gives technical difficulties. Routes and improvements have solved the problems of the system in terms of real time and security. The Zigbee wireless sensor network is used as the data acquisition end, and the server receives the data collected by the wireless sensor network through the serial communication to connect the CC2530 wireless communication module. At the same time, the paper combines the actual needs of users, and designs the server system according to the software engineering development process. While realizing the normal PC browser access to the server, the Android application of the mobile terminal is developed and the mobile is realized. In terminal access to the server, users can access the server by accessing computers on the network and mobile phones with Android systems. Viewing the running status of the device, authorized users can also make judgments based on real-time data and can send control commands and adjust the environment.