Science China Technological Sciences最新文献

Superhydrophobic surfaces have demonstrated exceptional efficacy in combatting biofouling contaminations of optical devices and equipment in marine applications. However, the fabrication of highly transparent superhydrophobic materials remains a formidable challenge due to the inherent trade-off between surface roughness for superhydrophobicity and optical transparency. Herein, we design a robust and transparent superhydrophobic coating (Si-POSS) embedded silica nanoparticles (200 nm) with fluorinated polyhedral oligomeric silsesquioxanes (F-POSS) and zinc pyrithione (ZPT). The Si-POSS coating exhibits excellent water repellence toward diverse liquids and optical transmittance exceeding 90% in the visible spectrum. Moreover, the Si-POSS coating sustains long-term anti-bacterial (> 99.11%) and anti-algal effects for over 30 days, accompanied by mechanical, chemical, and thermal stability. This research asserts that the Si-POSS coating with outstanding combined characteristics holds significant potential for marine applications, particularly in self-cleaning and antifouling endeavors.

Structural superlubricity (SSL) refers to a state of ultralow friction and zero wear when two solid surfaces slide against each other. Recent investigations have identified amorphous carbon at the edge of the graphite mesa as the primary source of friction in such SSL systems. Here, the tensile stress of metal thin film is exploited to engineer vertically conductive edge-warping graphite mesas (EWGM). Through this approach, robust SSL performance is realized, demonstrated by sliding an 8 µm side length square EWGM on an atomically smooth Au substrate for 10000 cycles at a constant voltage of 1 mV. In this SSL system, differential friction coefficients lower than 1.5 × 10⁻⁴ are achieved, with static contact resistance between EWGM and Au substrate as low as 28 Ω and sliding contact resistance as low as 32 Ω. Moreover, the EWGM exhibits SSL behavior on polished Si wafer substrates. Furthermore, because of the no-edge contact with the substrate during sliding, friction is independent of the sliding speed of the EWGM. This study presents the first successful fabrication of conductive EWGM. Remarkably, in both EWGM-Au and EWGM-Si SSL systems, the measured frictions are more than one order of magnitude lower than those of ordinary self-retracting graphite mesas with no-edge warping, and no wear is observed during extended current-carrying sliding. Overall, these findings establish a solid groundwork for the future realization of macroscale conductive SSL systems.

As a natural biaxial hyperbolic material, α-phase molybdenum trioxide (α-MoO₃) exhibits dielectric and metallic properties in the plane, rendering it an exceptional candidate for polarization-dependent devices. In this work, we design a lithography-free polarization-dependent absorber consisting of an α-MoO₃ film, a germanium layer, and a silver substrate. The results show that a narrowband absorption of up to 0.99 is achieved at a wavelength of 12.2 µm for transverse magnetic polarization. In contrast, the absorption is only 0.06 at this wavelength for transverse electric polarization. This remarkable polarization-dependent absorption performance is attributed to the coupling of epsilon-near-zero modes and Fabry-Perot resonances, which is confirmed by the electric field and power dissipation density distributions. Furthermore, strong polarization-dependent performance could also be achieved when the crystal axis of α-MoO₃ is rotated in the out-of-plane. This work demonstrates that in-plane anisotropic α-MoO₃ has the potential for designing high polarization-dependent devices.

Superlubricity is an ideal lubrication state where friction nearly vanishes between contact interfaces. It has become one of the most important research topics and approaches owing to its significance in reducing energy consumption and preventing device failures. As an efficient and universal lubricating principle capable of achieving superlubricity, rolling lubrication has attracted widespread attention in recent years. In this review, the theoretical concept of rolling lubrication and the experimental research progress of spherical/scroll structures are summarized. The review focuses on the possibility of achieving rolling lubrication using spherical/scroll structures (such as spherical fullerenes, carbon nanotubes, and formed and constructed spherical/scroll structures). The challenges in achieving rolling lubrication are summarized, and the possibility of molecular rolling lubrication, as well as its potential applications in superlubrication, are discussed.

Point clouds and RGB images are both critical data for 3D object detection. While recent multi-modal methods combine them directly and show remarkable performances, they ignore the distinct forms of these two types of data. For mitigating the influence of this intrinsic difference on performance, we propose a novel but effective fusion model named LI-Attention model, which takes both RGB features and point cloud features into consideration and assigns a weight to each RGB feature by attention mechanism. Furthermore, based on the LI-Attention model, we propose a 3D object detection method called image attention transformer network (IAT-Net) specialized for indoor RGB-D scene. Compared with previous work on multi-modal detection, IAT-Net fuses elaborate RGB features from 2D detection results with point cloud features in attention mechanism, meanwhile generates and refines 3D detection results with transformer model. Extensive experiments demonstrate that our approach outperforms state-of-the-art performance on two widely used benchmarks of indoor 3D object detection, SUN RGB-D and NYU Depth V2, while ablation studies have been provided to analyze the effect of each module. And the source code for the proposed IAT-Net is publicly available at https://github.com/wisper181/IAT-Net.

The development of regional integrated electric-thermal energy systems (RIETES) is considered a promising direction for modern energy supply systems. These systems provide a significant potential to enhance the comprehensive utilization and efficient management of energy resources. Therein, the real-time power balance between supply and demand has emerged as one pressing concern for system stability operation. However, current methods focus more on minute-level and hour-level power optimal scheduling methods applied in RIETES. To achieve real-time power balance, this paper proposes one virtual asynchronous machine (VAM) control using heat with large inertia and electricity with fast response speed. First, the coupling time-scale model is developed that considers the dynamic response time scales of both electric and thermal energy systems. Second, a real-time power balance strategy based on VAM control can be adopted to the load power variation and enhance the dynamic frequency response. Then, an adaptive inertia control method based on temperature variation is proposed, and the unified expression is further established. In addition, the small-signal stability of the proposed control strategy is validated. Finally, the effectiveness of this control strategy is confirmed through MATLAB/Simulink and HIL (Hardware-in-the-Loop) experiments.

The self-cascade (SC) method is an effective technique for chaos enhancement and complexity increasing in chaos maps. Additionally, the controllable self-cascade (CSC) method allows for more accurate control of Lyapunov exponents of the discrete map. In this work, the SC and CSC systems of the original map are derived, which enhance the chaotic performance while preserving the fundamental dynamical characteristics of the original map. Higher Lyapunov exponent of chaotic sequences corresponding to higher frequency are obtained in SC and CSC systems. Meanwhile, the Lyapunov exponent could be linearly controlled with greater flexibility in the CSC system. The verification of the numerical simulation and theoretical analysis is carried out based on the platform of CH32.

Against the backdrop of increasingly serious climate change, researchers are attempting to extend macroscale carbon reduction research to smaller scales. With the rapid development and widespread application of electric vehicles (EVs), an effective approach for carbon reduction based on EVs has the potential to be developed. To coordinate and manage the EV platform in diverse application scenarios, the concept of an on-board nanogrid (OBNG), in which a nanogrid is combined with the EV, is proposed and defined, and the characteristics summarized. A configuration that includes a physical layer with the on-board hardware system; an information layer for logical control, energy management, and communication coordination; and an application layer that can cope with different working environments is proposed. A detailed introduction to the basic architecture and management mode of each layer is provided along with information concerning the relevant technologies for coordinated operation. New ideas and approaches to improve the existing performance are proposed, and finally, combined with a background of smart and low-carbon cities, major application scenarios are envisioned.

Swarming behaviors play an eminent role in both biological and engineering research, and show great potential applications in many emerging fields. Traditional swarming models still lack integrity, uniformity, and stability in swarm forming processes, resulting in fragmentation and void phenomena. Inspired by the shepherding behaviors observed in nature, we propose an integrated negotiation-control scheme for distributed swarm control of massive robots. The core idea of this scheme is that the robots at the boundary of the group herd the internal robots to form an equilibrium swarm. For this purpose, we introduce a concept of virtual group center towards which boundary robots herd internal robots. Then, a distributed negotiation mechanism is designed to allow each robot to negotiate the virtual group center only through local interactions with its neighbors. After that, we propose a shepherding-inspired swarm control law to drive a group of robots to form an integrated, uniform, and stable configuration from any initial states. Both numerical and flight simulations are presented to verify the effectiveness of our proposed swarm control scheme.

Light frame walls (LFWs) serve as common partition walls in prefabricated buildings due to their lightweight nature, cost-effectiveness, energy efficiency, and adaptability for rapid on-site assembly. However, their acoustic insulation capability is hindered by issues such as sound bridges, resonance, and coincidence dips, resulting in inadequate sound insulation. This study aims to propose LFW designs with superior acoustic insulation suitable for practical engineering while meeting prevailing national standards. Nine full-scale LFW configurations were subjected to laboratory testing to evaluate the impact of staggered stud arrangements, stud types, and incorporation of compounded materials. The tests were performed between 100 and 5000 Hz, and the sound pressure level and reverberation time at 1/3 octave band were measured and used to calculate the weighted sound insulation index (R_w). Results demonstrated that the outlined design modifications significantly enhanced the sound insulation of the LFW. These modifications effectively mitigate the influence of sound bridges while addressing resonance and coincidence dips inherent in the wall system. Particularly noteworthy was the superior sound insulation achieved by staggered-stud LFWs with compounded materials, surpassing that of autoclaved lightweight concrete walls commonly used in prefabricated constructions despite having lesser thickness and surface density. R_w values increased from 43 to 54 dB compared to conventional LFWs, translating to a notable elevation in airborne sound insulation level from 4 to 7 as an internal separation component, meeting the requisite standards for most applications.