Science China Technological Sciences最新文献

High-stability thermal management is critical for the measurements of high sensitivity for temperature, but also challenging because any small thermal disturbances could lead to unacceptable temperature fluctuations. The present work delivers a design for passive temperature control, customized for a component in the satellites for gravitational wave detection. A novel sandwichlike structure is proposed with the configurations of proper materials, consisting of a layer of insulation material and two layers of nanocomposite phase change materials, bringing an integration of heat insulation and absorption/storage. Its performance is examined using an improved thermal network model and the revised transfer function method (TFM). The basic results of the two methods are validated by present COMSOL simulations and available numerical and experimental data in the literature. An effective reduction of temperature fluctuation is achieved to the scale of 0.1 K, even under two thermal disturbances from different directions: a radiative heat flux of 20 W m⁻² (inside) and a temperature fluctuation of about 20 K (outside). Moreover, the TFM is employed to analyze the effects of the frequency of thermal disturbance: excellent damping performance is obtained for over 3.2 mHz and the underlying mechanism is discussed. Overall, the present design is expected to be combined with active temperature control to explore more possible ways for temperature control with higher stability.

Wearable pressure sensors made from conductive hydrogels hold significant potential in health monitoring. However, limited pressure range (Pa to hundreds of kPa) and inadequate antibacterial properties restrict their practical applications in diagnostic and health evaluation. Herein, a wearable high-performance pressure sensor was assembled using a facilely prepared porous chitosan-based hydrogel, which was constructed from commercial phenolphthalein particles as a sacrificial template. The relationship between the porosity of hydrogels and sensing performance of sensors was systematically explored. Herein, the wearable pressure sensor, featuring an optimized porosity of hydrogels, exhibits an ultrawide sensing capacity from 4.83 Pa to 250 kPa (range-to-limit ratio of 51,760) and high sensitivity throughout high pressure ranges (0.7 kPa⁻¹, 120–250 kPa). The presence of chitosan endows these hydrogels with outstanding antibacterial performance against E. coli and S. aureus, making them ideal candidates for use in wearable electronics. These features allow for a practical approach to monitor full-range human motion using a single device with a simple structure.

Femtosecond laser direct writing provides an efficient approach to fabricating single nitrogen vacancy (NV) color centers with a relatively high yield. Different from previously reported NV color centers with a random distribution in a bulk diamond or nanocrystals, this gives an opportunity to study the photophysical properties of single NV color centers with precise numbers and positions. However, ultrafast studies on single NV color centers prepared by localization femtosecond laser direct writing are still rare, especially for the graphitization inside a diamond and its relationship with single NV color centers. Here, we report the broadband transient absorption (TA) spectroscopic features of the graphitization and NV color centers in a diamond fabricated by localization femtosecond laser direct writing at room temperature under 400 nm excitation. In comparison with the graphene oxide film, the bleaching features of the graphitization point array in a diamond are similar to reduced graphene oxide, accompanied by excited state absorption signals from local carbon atom vacancy defects in graphene-like structures induced by laser writing. On the other hand, transient features of laser processing array containing single NV color centers with a yield of ∼50% are different from those of the graphitization point array. Our findings suggest that for ultrashort pulse processing of diamonds, broadband TA spectral signals are sensitive to the surrounding atomic environment of processing sites, which could be applied to laser writing point defects in other materials used as solid-state single photon sources.

Cancer immunotherapies, which train the natural immune system to specifically kill tumor cells while sparing the healthy cells, have helped revolutionize cancer treatments and demonstrated promising clinical therapeutic benefits for decades. However, the therapeutic outcome of immunotherapies, even for the most successful immune checkpoint blockade (ICB) therapy, remains unsatisfactory in the clinical practice, mainly due to the low immunogenicity of solid tumors and its immunosuppressive tumor microenvironment (TME). Notably, several cancer treatment modalities, including chemotherapy, radiotherapy, and phototherapy, have been revealed to evoke tumor immunogenicity and reverse immunosuppressive TME via inducing immunogenic cell death (ICD) of tumor cells, which synergistically sensitized tumors to ICB therapy. Nanomedicines have been extensively applied to augment ICD-inducing treatment modalities and potentiate ICB therapeutic efficacy therapy due to the opportune convergence of immunotherapy and nanotechnology. Here, we discuss the recent advances in nanomedicine-mediated ICD and its combination with ICB therapy.

As a critical component of a tunnel boring machine (TBM), the precise condition monitoring and fault analysis of the main bearing is essential to guarantee the safety and efficiency of the TBM cutter drive. Currently, under conditions of strong noise and complex working environments, traditional signal decomposition and machine learning methods struggle to extract weak fault features and achieve high fault classification accuracy. To address these issues, we propose a novel residual denoising and multiscale attention-based weighted domain adaptation network (RDMA-WDAN) for TBM main bearing fault diagnosis. Our approach skillfully designs a deep feature extractor incorporating residual denoising and multiscale attention modules, achieving better domain adaptation despite significant domain interference. The residual denoising component utilizes a convolutional block to extract noise features, removing them via residual connections. Meanwhile, the multiscale attention module uses a 4-branch convolution and 3 pooling strategy-based channel-spatial attention mechanism to extract multiscale features, concentrating on deep fault features. During training, a weighting mechanism is introduced to prioritize domain samples with clear fault features. This optimizes the deep feature extractor to obtain common features, enhancing domain adaptation. A low-speed and heavy-loaded bearing testbed was built, and fault data sets were established to validate the proposed method. Comparative experiments show that in noise domain adaptation tasks, proposed the RDMA–WDAN significantly improves target domain classification accuracy by 42.544%, 23.088%, 43.133%, 16.344%, 5.022%, and 9.233% over dense connection network (DenseNet), squeeze-excitation residual network (SE-ResNet), antinoise multiscale convolutional neural network (ANMSCNN), multiscale attention module-based convolutional neural network (MSAMCNN), domain adaptation network, and hybrid weighted domain adaptation (HWDA). In combined noise and working condition domain adaptation tasks, the RDMA–WDAN improves the accuracy by 45.672%, 23.188%, 43.266%, 16.077%, 5.716%, and 9.678% compared with baseline models.

Non-targeted analysis (NTA) was conducted to identify semi-volatile organic compounds (SVOCs) in a museum in China using the gas chromatography (GC)-Orbitrap-mass spectrometer (MS). Approximately 160 SVOCs were detected, of which 93 had not been reported in previous studies of museum environments. Many of the detected SVOCs were found to be associated with the chemical agents applied in conservation treatment and the materials used in furnishings. The results of hierarchical cluster analysis (HCA) indicated a spatial variation of SVOCs in the indoor air in the museum, but there were no obvious temporal differences of SVOCs observed in indoor dust. Spearman’s correlation analysis showed that several classes of SVOCs were well correlated, suggesting their common sources. Fragrances and plasticizers were found to be the primary sources of SVOC pollution detected in the museum. Compared with compounds in outdoor air, indoor SVOCs had a lower level of unsaturation and more portions of chemically reduced compounds. This study is the first of its kind to comprehensively characterize SVOCs in a museum using an automated NTA approach with GC-Orbitrap-MS. The SVOCs identified in the current study are likely to be present in other similar museums; therefore, further examination of their potential impacts on cultural heritage artifacts, museum personnel, and visitors may be warranted.

Experimental determination of heat generation rates is crucial in the thermal safety design of automotive batteries. A thermal protection method (TPM) is proposed to determine the heat generation rates of 18650 cylindrical lithium-ion batteries under different discharge rates. The physical model based on the thermal protection method is established, and its feasibility is demonstrated through theoretical analysis. In the experimental setup, by introducing lateral thermal protection batteries (TPB) to minimize the heat loss of the center test battery (CTB), heat generation rates of the battery can be obtained based on the temperature change of the CTB. The average heat generation rates of the battery at 1, 2, and 3 C discharge rates are found to be 0.255, 0.844, and 1.811 W, respectively, which can be quadratically correlated with the discharge rate. In addition, a benchmark test of the present measurement against the commonly used accelerating rate calorimeter (ARC) was conducted. Relatively small deviations of 3.77%, 4.20%, and 1.09% were identified in the heat generation rates for the discharge rates at 1, 2, and 3 C. In comparison with the ARC equipment, the present TPM can be more representative of the transient battery heat generation characteristics with a much shorter time for thermal equalization. Finally, to further verify the accuracy of the present method, standard samples of the same size as the actual battery were made, which were capable of controlling heat generation through a direct current power supply. A comparison of the heat inputs of the standard sample with the heat generation rates measured by the thermal protection method shows a relative deviation of 1.01% maximum. With high measurement accuracy and an easy-to-build experimental setup, the proposed method has promising prospects in automotive applications.

According to Kirchhoff’s radiation law, the spectral-directional absorptivity (α) and spectral-directional emissivity (e) of an object are widely believed to be identical, which places a fundamental limit on photonic energy conversion and management. The introduction of Weyl semimetals and magneto-optical (MO) materials into photonic crystals makes it possible to violate Kirchhoff’s law, but most existing work only report the unequal absorptivity and emissivity spectra in a single band, which cannot meet the requirements of most practical applications. Here, we introduce a defect layer into the structure composed of one-dimensional (1D) magnetophotonic crystal and a metal layer, which realizes dual-band nonreciprocal thermal radiation under a 3-T magnetic field with an incident angle of 60°. The realization of dual-band nonreciprocal radiation is mainly due to the Fabry-Perot (FP) resonance occurring in the defect layer and the excitation of Tamm plasmon, which is proved by calculating the magnetic field distribution. In addition, the effects of incident angle and structural parameters on nonreciprocity are also studied. What is more, the number of nonreciprocal bands could be further increased by tuning the defect layer thickness. When the defect layer thickness increases to 18.2 µm, tri-band nonreciprocal thermal radiation is realized due to the enhanced number of defect modes in the photonic band gap and the FP resonance occurring in the defect layer. Finally, the effect of defect location on nonreciprocity is also discussed. The present work provides a new way for the design of multi-band or even broad-band nonreciprocal thermal emitters.

The traditional telecommunications band performs poorly in harsh weather conditions due to atmospheric absorption. In recent years, researchers have begun to study optical communication through atmospheric windows, and optical switches are an essential component of optical communication. A broadband atmospheric window optical switch was proposed based on Vanadium dioxide and magnetic polaritons (MP). It is formed by the stacking of two metal-dielectric-metal structures. The simulation results show that the modulation depth can reach 98.38%, and the extinction ratio is 17.93 dB. By calculating the magnetic field, we confirmed that the reason for the “off” mode is the coupling between the different MP modes, while the “on” mode is the excitation of MP. The optical switch we proposed may be applied to radiation cooling and optical satellite communication.

Walking on the water surface is an effective method for miniature robots to transport payloads with dramatically decreased interfacial drag. Current aquatic robots reported are generally actuated by a beam of focused light that can trigger asymmetrical deformation, enabling the directional movement through horizontal momentum transfer of photoinduced actuation force to the water. However, the operations are heavily dependent on manual manipulation of the focused light, making the long-term actuation and application of the aquatic robots in vast scenarios challenging. Herein, we developed a kind of water strider-inspired robot that can autonomously manage the motion on the water surface under solar irradiation, with their direction steerable by a magnetic field. The motion of this bioinspired robot on the water surface was achieved by the use of a solar cell panel as a driving module to enable propulsive motion based on the conversion of light-electric-mechanical energies. The superhydrophobic design of its leg surfaces enables the aquatic robots with weight-bearing and drag-reducing abilities. With the assistance of magnetic navigation, the bioinspired robot can continuously and controllably locomote to the oily spill floating on the water body and collect them with high efficiency. For further demonstration, the treatment of oil spills in a campus pool with high efficiency has also been achieved. This on-site oil-spill treating strategy, taking advantage of a home-made bioinspired robot actuated by natural sunlight under magnetic steering, shows great potential applications in water-body remediation.