摘要 : Pumped two-phase loop integrated with thermal storage is an emerging solution for the short-term high-heat-flux cooling. The transient microchannel boiling heat transfer of pumped two-phase loop (PTL) integrated with latent heat storage (LHS) under step heat load are experimentally investigated, with special focuses on dynamic thermal response of two-phase loop and latent heat storage unit. The transient thermal behaviors of PTL-LHS are determined based on the wide variations of heat load and flow rate. A thermal behavior regime diagram is proposed to quantitatively recognize the transient thermal response of PTL-LHS, depending on the heat load and flow rate. The results indicate that the fast tracking mode and the delay response mode are observed and sequentially experienced for PTL-LHS as the step heat load increases. With respect to delay response mode, thermal storage efficiency is high with short thermal storage duration but cooling performance is insufficient, while the transient thermal performances are contrary under the fast tracking mode. The increase of heat load accelerates the transformation of the heat transfer mechanism in LHS from sensitive-heat-dominated to latent-heat-dominated, while increasing flow rate is conducive for the enhancements of thermal capacity and thermal stability of PTL-LHS. Increasing heat load brings about a larger critical flow rate of the transient thermal behavior regime transition, and hence the range of flow rate tends to be larger for the delay response mode. Particularly, the proposed variable flow rate optimization strategy is validated by comparative experiments, showing better cooling performance (the average evaporator wall temperature decreases by 10 °C) and more remaining load of phase change material.

摘要 : The prevention of material leakage and improvement of thermal conductivity are very important for thermal energy storage application. In this work, nano-TiO 2 @ n -docosane microcapsules were synthesized by the fine emulsion interface polymerization method using tetra- n -butyl titanate (TBT). This approach enhances the encapsulation rate and efficiency of phase change microcapsules. The microcapsules formation process was observed using a biological microscope. The diameter of the microcapsules decreased significantly with the increase of stirring rate. The phase transition temperature of the optimal microcapsules is 42.4 °C. The encapsulation rate and efficiency reach up to 90.7% and 91.0%, respectively. The average thermal conductivity of nano-TiO 2 @ n -docosane microcapsules is 215% higher than that of n -docosane. SEM and infrared spectroscopy testing results confirm the successful coating of n -docosane by TiO 2 . Thermogravimetric analysis presents that TiO 2 forms a shell, which reduces the leakage of n -docosane. The melting and solidification processes of n -docosane and nano-TiO 2 @ n -docosane microcapsules were simulated numerically. In comparison to n -docosane, nano-TiO 2 @ n -docosane microcapsules exhibit a 14.89% increase in peak storage power and a 12.47% increase in heat transfer coefficient during charging. Additionally, during discharging, these values rise by 3.23% and 6.46%, respectively. Nano-TiO 2 @ n -docosane microcapsules enhance heat transfer and the charging/discharging process of phase change materials.

摘要 : In this study, a pilot-scale anaerobic membrane bioreactor (AnMBR) was developed to continuously produce volatile fatty acids (VFAs) from kitchen waste slurry under an alkaline condition. The alkaline fermentation effectively suppressed methanogenesis, thus achieving high VFAs production of 60.3 g/L. Acetic acid, propionic acid, and butyric acid accounted for over 95.0 % of the total VFAs. The VFAs yield, productivity, and chemical oxygen demand (COD) recovery efficiency reached 0.5 g/g-COD influent, 6.0 kg/m 3 /d, and 62.8 %, respectively. Moreover, the COD VFAs /COD effluent ratio exceeded 96.0 %, and the COD VFAs /NH 3 -N ratio through ammonia distillation reached up to 192.5. The microbial community was reshaped during the alkaline fermentation with increasing salinity. The membrane fouling of the AnMBR was alleviated by chemical cleaning and sludge discharge, and membrane modules displayed a sustained filtration performance. In conclusion, this study demonstrated that high-quality VFAs could be efficiently produced from kitchen waste slurry using an AnMBR process via alkaline fermentation.

摘要 : In this paper, we report an unprecedented copper-catalyzed disulfides or sulfides coupling reaction involving unactivated alkyl halides and N-dithiophthalimides. This reaction can be conducted under mild conditions using low-cost metal catalysts and exhibits high chemical selectivity and functional group compatibility, enabling the efficient assembly of various sulfides and disulfides.

摘要 : Developing highly reliable infrared radiation materials with broadband high emissivity at high temperatures, low thermal conductivity, and excellent thermal stability is highly desirable for aerospace thermal protection applications. However, it remains a huge challenge to take into account infrared radiation heat dissipation and blocking heat transfer through low thermal conduction simultaneously. In this work, we reported a broadband high emissivity Ca 2+ -doped YbCrO 3 ceramic with emissivity above 0.89 at room temperature across the entire range of wavelength (1–14 μm). This doping strategy leads to the introduction of impurity energy levels into the band gap of YbCrO 3, which increases the possibility of light absorption to promote electron transition, improving the emissivity of the near-infrared band (1–3 μm). Simultaneously, un-equivalent doping induces electron exchange between chromate ceramic ions, which complicates the electronic structure (producing lattice distortion and extra multi-mode vibrations) and reduces the band gap width, thus boosting the emissivity in the mid-infrared band (3–14 μm). More importantly, (Yb 0.8 Ca 0.2 )CrO 3 presents a high emissivity (0.76) at an elevated temperature of 1200 °C, together with low thermal conductivity (2.5 W m −1 K −1 at 1000 °C) due to strong phonon scattering. Moreover, the doping-dominating phase stabilization effect contributes to impressive thermal stability (stable at 1300 °C for 50 h) and a high coefficient of thermal expansion (9.0–9.5 × 10 −6 K −1 ), which makes it suitable for long-term high-temperature thermal protection application. All these merits render the development of thermally stable high-temperature infrared radiation ceramic materials core competitive.

摘要 : In order to investigate the effect of positional isomerization on the photoelectric properties of thermally activated delayed fluorescence (TADF) emitters, thereby fully stimulating the potential of the molecular backbone, herein, two red TADF isomers, oTPA-PPP and mTPA-PPP, were developed and synthesized by linking triphenylamine (TPA) donor into different positions of the pyrido [2′, 3′:5, 6] pyrazino [2, 3-f] [1, 10] phenanthroline (PPP). Their photoluminescent quantum yields (PLQYs) and external quantum efficiencies (EQEs) were significantly different by manipulating the substitution position of the donor. Compared with mTPA-PPP, oTPA-PPP exhibited higher PLQY benefiting from intramolecular hydrogen bonding and larger fluorescence radiative decay rate, as confirmed by both theoretical and experimental analyses. As a result, oTPA-PPP-based organic light-emitting diode (OLED) realized high EQE max of 19.2 % with red emission at 603 nm, whereas mTPA-PPP achieves an EQE max of 7.9 % at 596 nm. This work provides a simple and feasible molecular design strategy to design and select red TADF emitters with excellent properties.

摘要 : Microwave heating for the production of activated carbons has garnered significant research interest in the realms of gas adsorption. Nonetheless, the effect of tunable-energy-density microwave irradiation on the production of activated carbons is unclear. Herein, we report a tunable-energy-density microwave heating strategy to rapidly prepare highly microporous activated carbons. With the raising microwave energy density, the pore volume increases from 0.68 cm 3 g −1 to 0.89 cm 3 g −1, with a 70% decrease in the preparation time. Moreover, due to the high ratio of micropore (84.4%–86.6%) and great hydrophobicity, the optimal toluene adsorption capacity reaches 0.56 g g −1 and 0.47 g g −1 in the dry and wet (97% RH) environment, respectively. Due to the high ratio of ultramicropore (62.6%–69.0%), at 1 bar, the optimal CO 2 uptake for 25 °C and 0 °C reaches 4.27 mmol g −1 and 6.41 mmol g −1, respectively. This study introduces a straightforward and effective method for the swift production of activated carbons, applicable across a spectrum of uses.

摘要 : The Herglotz-type vakonomic dynamics of nonholonomic constrained systems with delayed arguments and its Noether theory are studied in this paper. First of all, the Herglotz-type equations of time-delayed vakonomic dynamics for nonholonomic systems are established, and the Herglotz-type local extremal equations are given. Secondly, on the basis of derivation of the variational formulas of Hamilton–Herglotz action with time delay, the Herglotz-type Noether symmetry criteria for time-delayed vakonomic dynamics are investigated. Thirdly, the Herglotz-type Noether's theorems and inverse theorems for time-delayed vakonomic dynamics of nonholonomic systems are deduced. Finally, an example is presented to demonstrate the application of the results.

摘要 : Facing the significant challenge of 3D object detection in complex weather conditions and road environments, existing algorithms based on single-frame point cloud data struggle to achieve desirable results. These methods typically focus on spatial relationships within a single frame, overlooking the semantic correlations and spatiotemporal continuity between consecutive frames. This leads to discontinuities and abrupt changes in the detection outcomes. To address this issue, this paper proposes a multi-frame 3D object detection algorithm based on a deformable spatiotemporal Transformer. Specifically, a deformable cross-scale Transformer module is devised, incorporating a multi-scale offset mechanism that non-uniformly samples features at different scales, enhancing the spatial information aggregation capability of the output features. Simultaneously, to address the issue of feature misalignment during multi-frame feature fusion, a deformable cross-frame Transformer module is proposed. This module incorporates independently learnable offset parameters for different frame features, enabling the model to adaptively correlate dynamic features across multiple frames and improve the temporal information utilization of the model. A proposal-aware sampling algorithm is introduced to significantly increase the foreground point recall, further optimizing the efficiency of feature extraction. The obtained multi-scale and multi-frame voxel features are subjected to an adaptive fusion weight extraction module, referred to as the proposed mixed voxel set extraction module. This module allows the model to adaptively obtain mixed features containing both spatial and temporal information. The effectiveness of the proposed algorithm is validated on the KITTI, nuScenes, and self-collected urban datasets. The proposed algorithm achieves an average precision improvement of 2.1% over the latest multi-frame-based algorithms.

摘要 : As removal performance of tetracyclines in traditional wastewater treatment plants cannot satisfy the increasingly strict discharge requirements, developing an efficient approach to overcome this problem is quite urgent. Herein, a novel functionalized magnetic chitosan-based adsorbent (Fe 3 O 4 @CAA) with core-shell structure and unique magnetic responsiveness was facilely prepared by ultrasound-initiated radical grafting copolymerization and cross-link reaction. The as-prepared Fe 3 O 4 @CAA was fully characterized with TEM, SEM, BET, FTIR, TGA, XRD, VSM, and served as an efficient adsorbent for tetracycline hydrochloride (TCH) removal. Adsorption behaviors of TCH by Fe 3 O 4 @CAA were deeply evaluated at different adsorption time, initial TCH concentration, reaction temperature, solution pH, and background pollutant concentration. Results showed that Fe 3 O 4 @CAA presented a more competitive adsorption capacity of 325.04 mg g −1 compared with Fe 3 O 4 @CS and other reported adsorbent, due to the introduction of more active adsorption sites by abundant functional groups, including amino groups, hydroxyl groups, and sulfonic acid groups. After saturated adsorption, TCH loaded Fe 3 O 4 @CAA was easily collected by magnetic separation, and recycled after acid pickling. Fe 3 O 4 @CAA was successfully reused in five adsorption-desorption cycles, without obvious adsorption capacity loss. In binary pollutant systems, inorganic cations and Pb(II) restrained TCH adsorption by competitive effect, while proper amount of Cu(II) promoted TCH adsorption by bridge effect. FTIR and XPS analyses revealed that the adsorption mechanism of TCH by Fe 3 O 4 @CAA mainly included electrostatic interaction and hydrogen bonding, and Cu(II) could play a "mediator" role to form a strong Cu(II)-TCH complex to enhance TCH removal performance. This study provides an effective strategy for the design of magnetic chitosan-based adsorbents and valuable guidance for the removal of tetracyclines from wastewater.