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Josephson junction is an active electric component and its channel current can be adjusted by external magnetic field, which can trigger additive phase error along the junction. From physical viewpoint, the Josephson junction can capture and release field energy when it is exposed to a magnetic field, and this time-varying current can be used to excite neural circuit for generating target firing patterns. In this paper, a Josephson junction is connected to a simple neural circuit, which is made of a capacitor, induction coil, a nonlinear resistor, two linear resistors and one constant voltage source in the branch, and the improved neural circuit is adjusted to percept external magnetic field and estimate the potential application of Josephson junction in nonlinear circuits. Bifurcation analysis is applied to explore the mode selection and dynamics dependence on parameters setting in the biophysical neural circuits. Furthermore, the neural circuit is exposed to external magnetic field and its physical effect is estimated by applying scale transformation on the variables and parameters in the neural circuit. It is confirmed that the neural circuit can be controlled and the neural activity shows distinct mode transition by taming the intensity (or angular frequency in periodic field) of external magnetic field. This kind of neural circuit can be further used as smart sensor for detecting weak magnetic field.  相似文献   
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Borate is considered one of the most important additives for improving the fire-resistance of combustible polymers because of its smoke suppression, low toxicity, and good thermal stability. However, the size of prepared borate is usually in the micrometer range, which makes it difficult to disperse in a polymer matrix, thus hindering its use as fire-retardant material. The preparation and application of borate nanomaterial as flame retardant is considered an effective method. However, the preparation of barium borate nanomaterials as flame retardant has not been reported. In this paper, nanosheets and nanoribbons with different sizes for a new barium borate BaO·4B2O3·5H2O are prepared by hydrothermal method, and characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), thermogravimetric analysis-differential scanning calorimetry (TG-DSC), and scanning electron microscope (SEM). The flame-retardant properties of polypropylene (PP)/BaO·4B2O3·5H2O composites are investigated by thermogravimetric analysis (TG), differential scanning calorimetry (DSC) thermal analysis methods and limited oxygen index (LOI) method. Considering the near TG mass losses and the near LOI values for PP with 10% prepared BaO·4B2O3·5H2O nanosheet and nanoribbon, their flame-retardant properties need to be further evaluated by non-isothermal decomposition kinetic method. The apparent activation energy for this decomposition reaction was obtained from the slope by plotting ln(β/Tp2) against 1/Tp according to Kissinger's model. With the reduction of TG mass loss, increased heat absorption in DSC under N2 atmosphere, increased apparent activation energy Ea for the thermal decomposition of PP/BaO·4B2O3·5H2O composite as well as increased LOI value, the flame-retardant performance of prepared BaO·4B2O3·5H2O samples with PP gradually improved from bulk to nanoribbon to nanosheet. This can be attributed to the decrease in the size of BaO·4B2O3·5H2O samples because the smaller sample size leads to improved dispersion and increased contact area with the polymer. The flame-retardant mechanism is discussed by analyzing the after-flame chars of the PP/BaO·4B2O3·5H2O composite in SEM images, which show that the char layer is more compact and continuous for the PP/BaO·4B2O3·5H2O nanosheet composite. The influence of loading BaO·4B2O3·5H2O nanomaterials on the mechanical properties of PP is also tested using a universal material testing machine, in which the PP/BaO·4B2O3·5H2O nanosheet composite has higher tensile strength. The PP/BaO·4B2O3·5H2O nanosheet composite has the best flame-retardant and mechanical properties, which is promising to be developed for the application as flame-retardant material.  相似文献   
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《中国化学快报》2022,33(9):4380-4384
Carbon dioxide electrochemical reduction (CO2RR) has been recognized as an efficient way to mitigate CO2 emissions and alleviate the pressure on global warming and associated environmental consequences. Gold (Au) is reported as stable and active electrocatalysts to convert CO2 to CO at low overpotential due to its moderate adsorption strength of *COOH and *CO. The request for improved catalytic performance, however, is motivated by current unsatisfied catalytic selectivity because of the side hydrogen evolution reaction. In this context, the design of Au based binary catalysts that can boost CO selectivity is of great interest. In the present work, we report that Au nanoparticles can be feasibly dispersed and anchored on silicon nanowires to form Au-Si binary nanomaterials. The Au-Si may stably drive CO2RR with a CO Faraday efficiency of 95.6% at ?0.6 V vs. RHE in 0.5 mol/L KHCO3 solution. Such selectivity outperforms Au particles by up to 61%. Controlled experiments illustrate that such catalytic enhancement can chiefly be ascribed to electronic effects of binary catalysts. Theoretical calculations reveal that spontaneously produced silicon oxide may not only inhibit hydrogen evolution reaction, but also stabilize the key intermediate *COOH in CO formation.  相似文献   
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Hong Fan 《中国物理 B》2021,30(7):78703-078703
To solve the problem that the magnetic resonance (MR) image has weak boundaries, large amount of information, and low signal-to-noise ratio, we propose an image segmentation method based on the multi-resolution Markov random field (MRMRF) model. The algorithm uses undecimated dual-tree complex wavelet transformation to transform the image into multiple scales. The transformed low-frequency scale histogram is used to improve the initial clustering center of the K-means algorithm, and then other cluster centers are selected according to the maximum distance rule to obtain the coarse-scale segmentation. The results are then segmented by the improved MRMRF model. In order to solve the problem of fuzzy edge segmentation caused by the gray level inhomogeneity of MR image segmentation under the MRMRF model, it is proposed to introduce variable weight parameters in the segmentation process of each scale. Furthermore, the final segmentation results are optimized. We name this algorithm the variable-weight multi-resolution Markov random field (VWMRMRF). The simulation and clinical MR image segmentation verification show that the VWMRMRF algorithm has high segmentation accuracy and robustness, and can accurately and stably achieve low signal-to-noise ratio, weak boundary MR image segmentation.  相似文献   
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本文以水作为理想流体,考虑到水头损失和孔口缩流效应,对小孔流速实验涉及的容器排水问题进行了系统的理论和实验研究.从理论上推导得出了圆柱形容器排水时间的解析解,分析了排水时间和自由液面速度、流量系数之间的规律,提出了排水时间的等效性.实验上,加工了底部开有不同小孔的大型圆柱形容器,测量了容器排水时间随液面高度的变化关系,借助实验结果计算了流量系数值,验证了容器排水时间的等效性关系,实验结果与理论计算符合较好.  相似文献   
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A highly selective and sensitive electrogenerated chemiluminescence (ECL) biosensor for the detection of prostate PC-3 cancer cells was designed using a prostate specific antibody as a capture probe and ruthenium complex-labelled wheat germ agglutinin as a signal probe. The ECL biosensor was fabricated by covalently immobilising the capture probe on a graphene oxide-coated glassy carbon electrode. Target PC-3 cells were selectively captured on the surface of the biosensor, and then, the signal probe was bound with the captured PC-3 cells to form a sandwich. In the presence of tripropylamine, the ECL intensity of the sandwich biosensor was logarithmically directly proportion to the concentration of PC-3 cells over a range from 7.0 × 102 to 3.0 × 104 cells mL−1, with a detection limit of 2.6 × 102 cells mL−1. The ECL biosensor was also applied to detect prostate specific antigen with a detection limit of 0.1 ng mL−1. The high selectivity of the biosensor was demonstrated in comparison with that of a lectin-based biosensor. The strategy developed in this study may be a promising approach and could be extended to the design of ECL biosensors for highly sensitive and selective detection of other cancer-related cells or cancer biomarkers using different probes.  相似文献   
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