ISSN 0253-2778

CN 34-1054/N

2019 Vol. 49, No. 12

Display Method:
Experimental study on pedestrian and evacuation dynamics
ZHANG Jun, LI Hongliu, SONG Weiguo
2019, 49(12): 947-956. doi: 10.3969/j.issn.0253-2778.2019.12.001
Harmful events occur from time to time as a result of large-scale crowd gatherings
Progresses on multipass-cavity-assisted atomic devices
CAI Bo, HAO Chuanpeng, SHENG Dong
2019, 49(12): 957-964. doi: 10.3969/j.issn.0253-2778.2019.12.002
Atomic instrumentation is an interdisciplinary research area. It combines the high stability property of atomic spectroscopy and the miniaturization technique from precision engineering. There have been considerable research efforts and application promise in such fields as atomic clocks, atomic magnetometers and atomic interferometers. The introduction of multipass cavities could effectively increase the interaction length between atoms and light, without changing other experimental parameters. This could improve the device sensitivity while keeping the instrument size small. In this paper, recent progress on atomic devices using multipass cavities was reviewed, and Herriott-cells-assisted atomic magnetometers were discussed at length. Using anodic bonding and 3D printing techniques, optical adjustments were removed, and the multipass cells were applied in the electron spin and nuclear spin magnetometers.
A non-iterative approach to kernel logistic regression for imbalanced data
CUI Wenquan, YU Demei, CHENG Haoyang
2019, 49(12): 965-973. doi: 10.3969/j.issn.0253-2778.2019.12.003
A non-iterative kernel logistic regression learning method for severely imbalanced data was proposed. The method is an improvement on the iterative weighted least squares method for classical kernel logistic regression. It not only reduces the computational burden caused by iteration, but also utilizes the knowledge of the ratio of the benchmark category, and can avoid problems normally encountered when processing imbalanced data such as undersampling, oversampling and cost-sensitive learning. Thus, this method enables the efficient and fast modelling of kernel based logistic regression in the case of large-scale imbalanced data, through the construction of a robust modified least square logistic classifier. Theoretical research indicates that the proposed method has some excellent properties, and simulation research and empirical studies show that its classification effect is good.
A new random projection-based ensemble classifier for high-dimensional data
CUI Wenquan, HUANG Yuqiao
2019, 49(12): 974-984. doi: 10.3969/j.issn.0253-2778.2019.12.004
A decision tree ensemble method based on random projection(projection forest, PJForest) was proposed to solve the classification problem of high-dimensional data. This method used the decision tree as the base classifier and reduced the dimensionality of the data by using a series of random projections. Then based on dimensionally reduced data, a series of decision trees were constructed, and then the ensemble classifier was constructed through ensemble learning. Using appropriate random projection to reduce the dimensionality of the data can preserve the information contained in the geometric structure of the data. Moreover, perturbation of raw data through random projection can enrich the diversity of decision trees. After proper ensemble learning, it can effectively overcome the influence of noise and improve the generalization ability of PJForest. The limiting property of PJForest generalization error was proved and the convergence rate of generalization error under certain conditions was obtained. Many simulation studies were conducted and empirical studies on real life data were empirically analyzed. The simulation results showed that the method of PJForest can effectively classify high dimensional data with a large amount of noises, and has better properties than current classification methods such as random forest, Xgboost.
Effects of radial temperature and pressure distribution on energy distribution and wave field in helicon plasma
HE Chao, WU Dongsheng, PING Lanlan
2019, 49(12): 985-994. doi: 10.3969/j.issn.0253-2778.2019.12.005
The steady-state process of RF-heated plasma was studied. Under the conditions of parabolic distribution and Gaussian distribution of plasma density, the radial pressure and temperature gradient were analyzed for the influence of power deposition and electric field and the distribution of current density in the two-density distribution of helicon plasma. Three gradient models were considered: positive gradient, negative gradient and zero gradient. Studies have shown that positive temperature gradients are more conducive to the absorption of power at the center of the plasma. The positive pressure gradient increases the induced electric field at the edge of the plasma, reduces the current density at the center, and weakens the power deposition at the edge. The wave energy coupling depth is deepened, which is more conducive to the coupling absorption of power at the center. Under the Gaussian density distribution, the electric field intensity is higher at the edge of the plasma, and the current density is smaller. The deposition energy of the radio frequency wave at the edge position is less and the change is not large, and the coupling depth of the wave energy is greatly increased. Under the parabolic density distribution, the power deposition at the center and the edge of the plasma is large, and the power deposition near the edge is particularly prominent and significantly higher than that under the Gaussian density distribution.It was found that the three temperature and pressure distributions have similar effects on the electric field strength and current density distribution and the change trend in the plasma of the two density structures, thus demonstrating the stability of the m=1 mode.
Carbon nanofibers by electrospun for high-performance supercapacitors
PAN Shiquan, JIN Hongchang, QI Zhikai, JI Hengxing
2019, 49(12): 995-1001. doi: 10.3969/j.issn.0253-2778.2019.12.006
Recently, metal-organic frameworks (MOFs) have been regarded as an ideal precursor for preparing nanoporous carbon materials for the electrodes of supercapacitors due to their ability to tune the material’s structure from the molecular scale. However, the MOF-derived carbons usually exhibit a low graphitization level and large interface resistance between the particles which yield a poor electrical conductivity of the electrode disc that greatly limits their electrochemical performance. Herein, we demonstrate that pyrolysis of ZIF-67 that is embedded
Oral halloysite nanotubes-induced subacute toxicity in the large intestine of mice and recovery
HU Tingting, RUI Rong, WANG Xiaoqin, TAN Weihang, WANG Ziyi, XU Xiaolong
2019, 49(12): 1002-1009. doi: 10.3969/j.issn.0253-2778.2019.12.007
Natural halloysite nanotubes (HNTs) with a hollow lumen have been widely applied in many fields, such as traditional Chinese medicines, drug carriers, cosmetics, feed additives, antibacterials and water purification. However their toxicity in the gastrointestinal tract is still unclear. The aim of this study is to evaluate subacute oral toxicity of HNTs in the large intestines of mice and their recovery from it. Oral HNTs at low dose (5 mg/kg) for 30 days had no obvious adverse effect on the large intestine. Oral HNTs at high dose (50 mg/kg) for 30 days induced Al and Si accumulation and oxidative stress in the large intestine as indicated by the significant decreases in GSH-Px and SOD activities and the significant increase in MDA level in the large intestine, which caused significant increases in COX-2 and iNOS levels and inflammatory response and iNOS-mediated damages in the large intestine. Oral HNTs-induced changes at high dose described above were not observed after a 30 days recovery period, suggesting that oral HNTs-induced subacute toxicity in the large intestine was reversible.
Chemically responsive charge transfer plasmon for glucose detection
HUANG Shan, ZHU Yujun
2019, 49(12): 1010-1017. doi: 10.3969/j.issn.0253-2778.2019.12.008
Au-Ag bimetallic plasmonic nanostructures were successfully prepared by introducing silver into the nano gap of the gold nanoparticles(AuNPs) dimer based on the silver ion soldering method and the seed-mediated growth method. Due to the etching effect of H2O2 on the silver conductive junction which was formed by enzymatic oxidation of glucose, the charge transfer plasmon (CTP) would have a good response to glucose. Based on this, it could be applied to the detection of glucose. The relationship between glucose concentration and the intensity, wavelength of CTP peak,and surface enhanced Raman spectroscopy (SERS) intensity, as well as the selectivity of the sensor were investigated. The experimental results show that the method has high sensitivity and good selectivity towards glucose. Two linear relationships were identified between the CTP peak intensity change value and the glucose concentration in the range of 0.5~4 μmol/L and 4~10 μmol/L, respectively, with a limit of detection (3σ rule) reaching 0.2 μmol/L. The naked-eye detection of glucose can reach the micromolar level. The SERS also exhibited a linear response toward glucose, within the concentration range of 1~10 μmol/L.
Tellurium-assisted synthesis of two-dimensional transition metal dichalcogenide heterostructure and alloy
GUO Peng, DUAN Hengli, YAN Wensheng
2019, 49(12): 1018-1024. doi: 10.3969/j.issn.0253-2778.2019.12.009
Two-dimensional (2D) transition metal dichalcogenide (TMDC) alloys and heterostructures have a great potential in next generation optoelectronic devices due to their unique optoelectronic properties. However, controllable synthesis of 2D TMDC remains a major challenge. Taking the heterostructure and alloy of WS2and MoS2as examples, we introduce various contents of low melting point Tellurium powder to effectively reduce the growth temperature of WS2, and then regulate the nucleation and growth rate of WS2. Then the WS2/MoS2vertical heterostructure and the Mo1-xWxS2alloy could be controllably synthesized by a one-step chemical vapor deposition method. Raman and photoluminescence spectra and mapping show that the prepared WS2/MoS2vertical heterostructure is formed by superimposing monolayer WS2and monolayer MoS2. The content of W (x) is 0.83 in the as-synthesized Mo1-xWxS2alloy. This work provides a simple and effective method for two-dimensional TMDC heterostructures and alloys.