Search

Abstract Exploration of efficient and stable photocatalysts to mimic natural leaves for the conversion of atmospheric CO2 into hydrocarbons utilizing solar light is very important but remains a major challenge. Herein, we report the design of four novel metal–salen‐incorporated conjugated microporous polymers as robust artificial leaves for photoreduction of atmospheric CO2 with gaseous water. Owing to the rich nitrogen and oxygen moieties in the polymeric frameworks, they show a maximum CO2 adsorption capacity of 46.1 cm3 g−1 and adsorption selectivity for CO2/N2 of up to 82 at 273 K. Under air atmosphere and simulated solar light (100 mW cm−2), TEPT‐Zn shows an excellent CO yield of 304.96 μmol h−1 g−1 with a selectivity of approximately 100%, which represents one of the best results in terms of organic photocatalysts for gas‐phase CO2 photoreduction so far. Furthermore, only small degradation in the CO yield is observed even after 120‐h continuous illumination. More importantly, a good CO yield of 152.52 μmol g−1 was achieved by directly exposing the photocatalytic reaction of TEPT‐Zn in an outdoor environment for 3 h (25–28°C, 52.3 ± 7.9 mW cm−2). This work provides an avenue for the continued development of advanced polymers toward gas‐phase photoconversion of CO2 from air.

The electromagnet module, as a fundamental component providing levitation force for maglev trains, plays a crucial role in ensuring the stability of train operation. However, vibrations can easily occur due to the mechanical coupling between the two suspension points of the electromagnet module. To reveal the inherent instability of the system and the coupling relationship between the state variables, a state-space equation that considers the mechanical coupling between the two suspension points is established. Furthermore, a differential control algorithm based on geometric feature transformation is proposed to mitigate the structural coupling vibration. Simulation experiments are conducted to compare the dynamic characteristics of the system before and after implementing the improvement algorithm under complex conditions. At the same time, the influence of control parameters on electromagnetic vibration was analyzed, focusing particularly on vibrations resulting from parameter mismatch, offering crucial insights for enhancing system stability. Additionally, suspension tests are carried out on the high-speed double bogie test platform in the Key Laboratory of Hunan Province to further validate the effectiveness of the proposed algorithm. The proposed control framework is both effective and concise, making it easy to implement in engineering applications. This research holds significant practical value in improving the stability of maglev trains.

Abstract The engineering of atomically-precise nanopores in two-dimensional materials presents exciting opportunities for both fundamental science studies as well as applications in energy, DNA sequencing, and quantum information technologies. The exceptional chemical and thermal stability of hexagonal boron nitride (h-BN) suggest that exposed h-BN nanopores will retain their atomic structure even when subjected to extended periods of time in gas or liquid environments. Here we employ transmission electron microscopy to examine the time evolution of h-BN nanopores in vacuum and in air and find, even at room temperature, dramatic geometry changes due to atom motion and edge contamination adsorption, for timescales ranging from one hour to one week. The discovery of nanopore evolution contrasts with general expectations and has profound implications for nanopore applications of two-dimensional materials.

Hydrogen represents an ideal fuel with environmental‐friendly properties and high energy density. It is attractive to directly produce clean hydrogen from inexhaustible solar energy and the most abundant seawater on the earth. Nevertheless, the search for highly efficient and stable photocatalysts remains a big challenge so far because of the dissolved salts in natural seawater, which may result in the decomposition of photocatalysts and undesirable side reactions. Herein, three polyfluorene‐based conjugated polyelectrolytes (CPEs) with different grafted groups in the polymer backbone for hydrogen production in natural seawater under solar light illumination are reported. The change in the grafted groups on the main chain of CPEs provides them very similar UV light absorption, but PFNH‐Br grafted with H group exhibits significantly improved charge transport and lower emission intensity compared with PFN‐Br (grafted with C8H17) and PFPABr (grafted with CH2CH2N(CH3)3Br). As a result, PFNH‐Br yield the highest hydrogen evolution rate (HER) of 1806 μmol h−1 g−1 without external cocatalysts under simulated solar light, while lower HERs of 356 and 225 μmol h−1 g−1 are found for PFN‐Br and PFPABr, respectively. This study shows that grafted group optimization is a powerful strategy to maximize the activity of polyfluorene‐based CPEs for direct photocatalytic seawater splitting.

In order to improve the performance of the active vibration isolation system (AVIS) with electromagnetic actuator, several problems of vibration control are studied. Position control is a critical component in suspension systems, and the position sensor noise can extremely affect the stability of the system, so a tracking differentiator (TD) is proposed to obtain effective differential signal from relative position sensor. In vibration control, the feedback of acceleration combined with PD position feedback is presented to suppress transmission of periodic vibrations. Then, taking the acceleration transmission as the evaluation index, the acceleration transmission under the presented control method is derived, and the influence of control parameters on vibration isolation performance is discussed in detail. The vibration isolation performance is improved from 24.47 dB to 2.4 dB at resonance frequency, and −34 dB attenuation is achieved at 100 Hz with respect to vibration isolation mount system tested on the ground. The experimental results demonstrate that the performance of active vibration isolation system are improved by the proposed acceleration feedback control.

The relative position sensor of a high-speed maglev train is an important part of train location and speed detection for motor traction, but its output signal is not only related to position but also related to the suspension gap of the maglev train. The fluctuation of the suspension gap will affect the amplitude of the output signal of the sensor (i.e., the suspension wave signal is coupled with the output signal). The prediction normalization method currently used can eliminate the effect of the suspension fluctuation to a certain extent, but there is a limitation. Aiming at this problem, this paper analyzes the frequency characteristics of the suspension gap fluctuation caused by track irregularities and proposes a gap estimation algorithm based on the adaptive filter. The Kalman filter is used to estimate the gap and then the output signal is compensated according to the numerical relationship between the gap and the output signal of the sensor, so as to achieve the decoupling between the gap and the position measurement. Finally, the effectiveness of the method is proved by the comparison experiments.

A mild and practical synthesis of spirooxindole [1,3]oxazino derivatives from N-substituted isatins and 1,3-dicarbonyl compounds with pyridine derivatives is reported. The reactions provided good to excellent yields. Further exploration of the molecular diversity of these compounds is demonstrated through Diels–Alder reactions.

This paper mainly researches one method of speed and location detection for maglev vehicles. As the maglev train doesn’t have any physical contact with the rails, it has to use non-contact measuring methods. The technology based on the inductive loop-cable could fulfill the requirement by using an on-board antenna which could detect the alternating magnetic field produced by the loop-cable on rails. This paper introduces the structure of a speed and position system, and analyses the electromagnetic field produced by the loop-cable. The equivalent model of the loop-cable is given and the most suitable component of the magnetic flux density is selected. Then the paper also compares the alternating current (AC) resistance and the quality factor between two kinds of coils which the antenna is composed of. The effect of the rails to the signal receiving is also researched and then the structure of the coils is improved. Finally, considering the common-mode interference, 8-word coils are designed and analyzed.

This paper introduces in brief the traction system of a permanent magnet electrodynamic suspension (EDS) train. The synchronous traction mode based on long stators and track cable is described. A speed and position detection system is recommended. It is installed on board and is used as the feedback end. Restricted by the maglev train’s structure, the permanent magnet electrodynamic suspension (EDS) train uses the non-contact method to detect its position. Because of the shake and the track joints, the position signal sent by the position sensor is always aberrant and noisy. To solve this problem, a linear discrete track-differentiator filtering algorithm is proposed. The filtering characters of the track-differentiator (TD) and track-differentiator group are analyzed. The four series of TD are used in the signal processing unit. The result shows that the track-differentiator could have a good effect and make the traction system run normally.

Objective To establish a model that can predict the occurrence of acute kidney injury (AKI) in elderly patients with HBV-related acute-on-chronic liver failure (HBV-ACLF), and to conduct a preliminary evaluation of the performance of the model. Methods A total of 276 patients with HBV-ACLF hospitalised in The First Affiliated Hospital of Harbin Medical University from January 2020 to January 2023 were retrospectively included and divided into 72 (26.09%) in the AKI group and 204 (73.91%) in the non AKI group, according to whether AKI occurred during hospitalisation. The clinical data of all patients were extracted and screened for independent risk factors for AKI during hospitalisation using multivariate logistic regression. A prediction model was constructed accordingly, and then the efficacy of the prediction model was evaluated using ROC curves. Results Multivariate logistic regression analysis showed that age ＞70 years (OR=1.404, 95%CI: 1.134～1.737), procalcitonin＞1 ng/L (OR=1.473, 95%CI: 1.074～2.019), model for end stage liver disease (MELD) score ＞34 (OR=1.702, 95%CI: 1.254～2.311), and combined upper gastrointestinal bleeding (OR=1.516, 95%CI: 1.123～2.047) were independent risk factors for the occurrence of AKI in HBV-ACLF patients during hospitalisation (P＜0.05). A prediction model for the occurrence of AKI in HBV-ACLF patients during hospitalisation was established based on the above four parameters, and the ROC curve showed that the AUC predicted by the model was 0.882 (95%CI: 0.838～0.917), with a sensitivity of 66.67%, a specificity of 93.14% and an accuracy of 86.23%. Conclusion Elderly, high MELD score and procalcitonin level, and concomitant upper gastrointestinal bleeding are independent risk factors for AKI in patients with HBV-ACLF during hospitalisation, and the model constructed accordingly can predict the risk of AKI, thus assisting clinical disease management.