Table of Content

  

20 May 2021
Volume 56 Issue 5

Firing and synchronization of a neocortical neuron under electromagnetic induction

QI Hui-min, ZHANG Li, AN Xin-lei, QIAO Shuai, XIAO Ran

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  1-11.  doi:10.6040/j.issn.1671-9352.0.2020.712

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A four-dimensional neuron model of a class of neocortical neurons is established by introducing the flux variable to modulate the membrane potential of the electromagnetic induced current. Based on single parameter bifurcation diagram, the double parameter bifurcation diagram and the corresponding maximum Lyapunov exponent diagram analysis of the discharge characteristics of the model in detail and bifurcation model, the numerical results show that the model in the appropriate external stimuli and under the action of electromagnetic induction intensity will produce complex bifurcation behaviors, namely periodic bifurcation and period-doubling and inverse period-doubling bifurcation, etc. Interestingly, the model has a “comb-shaped” chaotic structure in a two-parameter plane, which means that the model has a period-added bifurcation model with chaos. Meanwhile, based on Lyapunov stability theory, it is proved that the model can achieve complete synchronization under appropriate flux coupling strength, but will destroy the synchronization behavior under strong coupling condition.

Stability and Hopf bifurcation of a flux neuron model with time delay

WEI Li-xiang, ZHANG Jian-gang, NAN Meng-ran, ZHANG Mei-jiao

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  12-22.  doi:10.6040/j.issn.1671-9352.0.2020.586

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A time-delayed flux neuron model with magnetically controlled memristor to study the effects of time delay and external stimulation current on the dynamic behavior of the model is put forward. The stability of the model at the equilibrium point is discussed by using the Routh-Hurwitz criterion and the stability of the Hopf bifurcation at the critical point is further studied by using the central manifold theorem. By numerical stimulation, the time series and single-double bifurcation diagrams of the model with different time delays. When the time lag and external forcing current are changed, it is found that there are many discharge patterns in the model. By selecting appropriate time lag or external forcing current, the resting state, spiking state and periodic bursting state are obtained, which is conducive to explain the abnormal discharge behavior of brain or nerve center caused by electromagnetic radiation.

Vertex-distinguishing Ⅰ-total coloring and Ⅵ-total coloring of almost complete graphs

ZHANG Sheng-gui, CHEN Xiang-en

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  23-25.  doi:10.6040/j.issn.1671-9352.0.2019.389

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Let G be a simple graph. Suppose f is a general total coloring of graph G(i.e., an assignment of several colors to all vertices and edges of G), if any two adjacent vertices and any two adjacent edges of graph G are assigned different colors, then f is called an Ⅰ-total coloring of a graph G; if any two adjacent edges of G are assigned different colors, then f is called a Ⅵ-total coloring of a graph G. For an Ⅰ-total coloring(or Ⅵ-totalcoloring)f of a graph G, if C(u)≠C(v) for any two distinct vertices u and v of V(G), where C(x) denotes the set of colors of vertex x and the edges incident with x under f, then f is called a vertex distinguishing Ⅰ-total coloring(or vertex distinguishing Ⅵ-total coloring)of G. Let χⁱ_vt(G)=min{k|G has a k-VDIT coloring}, then χⁱ_vt(G) is called the VDIT chromatic number of G. Let χ^vi_vt(G)=min{k|G has a k-VDVIT coloring}, then χ^vi_vt(G) is called the VDVIT chromatic number of G. The VDIT coloring(or VDVIT coloring)of almost complete graphs and the VDIT chromatic number(VDVIT chromatic number)of them has been obtained by using analytical method and proof by contradiction.

Vertex weighted neighbor tenacity of graphs

SHI Ming, WEI Zong-tian, LIU Yong, WENG Ting-ting

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  26-32.  doi:10.6040/j.issn.1671-9352.0.2020.676

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The neighbor invulnerability parameter is generalized to weighted graphs, and a new concept, vertex weighted neighbor tenacity, is proposed. By constructing two types of composite star graphs, several extreme graphs under vertex weighted neighbor tenacity are studied by using mathematical modeling methods.

Simulation of alpine wetlands CO₂ flux and its influencing factors based on BP neural network optimized by genetic algorithm in Qinghai-Tibet Plateau

CAO Jia-xi, WANG Xin, LEI Guang-chun

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  33-41.  doi:10.6040/j.issn.1671-9352.0.2021.141

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A three-layer BP neural network was constructed to simulate CO₂ emission flux of wetlands ecosystem by using latent heat flux, sensible heat flux, air temperature, total radiation, effective radiation, soil temperature and soil volume water content. After determining the topological structure of BP neural network, the optimal initial threshold and weight of BP neural network training are obtained by genetic algorithm. The established BP neural network is trained and verified by normalizing 2 190 sets of measured CO₂ fluxes and corresponding training data in wetlands ecosystem in Haibei alpine wetlands of Qinghai-Tibet Plateau. The validation results show that the regression coefficients of training group, validation group and test group are 0.942, 0.935 and 0.938, respectively. The overall regression coefficient is 0.941, the root mean square error between simulated and measured values is 0.92%, and the simulated CO₂ flux in wetlands ecosystem is 1.207-13.767 g/(m²·d), with an average value of 6.008 g/(m²·d). Correlation analysis shows that the correlation coefficient r between CO₂ flux and input neurons in alpine wetlands ecosystem is: soil temperature(0.77)> air temperature(0.72)> soil volume water content(0.39)> latent heat flux(0.30)> sensible heat flux(0.29)> total radiation(0.09)> effective radiation(0.02)(P<0.01). The dominant factors of CO₂ flux in alpine wetlands ecosystem are soil temperature and air temperature, and the weights of these two factors should be increased in the subsequent modeling work.

Distribution and its influencing factors of rare and endangered plants in Shandong Province

ZHANG Xiu-hua, QI Hai-ying, LIU Jian, WANG Ren-qing, ZHAO Jing

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  42-50.  doi:10.6040/j.issn.1671-9352.0.2020.537

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Statistics and analysis of rare and endangered plants in Shandong Province found that there are 65 families, 123 genera, and 159 species of rare and endangered species in Shandong Province. Among them, 5 families, 5 genera, and 6 pecies belong to pteridophytes; 8 families 17 genera 26 species belong to gymnosperms; 52 families, 101 genera, and 127 species belong to angiosperms. The distribution of rare and endangered plant is extremely uneven. Rare and endangered plants are also abundant in areas with more mountains and hills, such as Qingdao, Yantai and Taian, where more than 100 species of rare and endangered plants are protected. The study also found that 95.59% of rare and endangered plants are protected in 25 nature reserves above the provincial level. Temperature and altitude were the main determinant factors of species richness of rare and endangered plant in the two scales(nature reserve and region). Altitude has stronger effects on rare and endangered plant under the regions scale than the nature reserve scale. The results indicate that habitat heterogeneity should be taken seriously in biodiversity conservation.

Synthesis of N-doped carbon/polyimide aerogel with enhanced photocatalytic performance for oxytetracycline degradation

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  51-56.  doi:10.6040/j.issn.1671-9352.0.2020.538

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Polyimide(PI)aerogel was prepared by sol-gel method and ethanol super-critical technology. Then PI aerogel was calcined to be N-doped carbon aerogel(C(N))at 800 ℃. Furthermore, the obtained C(N)was coupled with PI aerogel. C(N)/PI aerogel photocatalyst was used to degrade OTC. The photocatalytic performance demonstrated that OTC had been degraded 82% in 360 min over C(N)/PI aerogel photocatalyst. Because the high surface area and pore property of C(N)/PI aerogel can provide more active sites and enhance the absorption of visible light. Thus, the photocatalytic activity was improved.

Short text classification based on semi-supervised graph neural network

ZHANG Bin-yan, ZHU Xiao-fei, XIAO Zhao-hui, HUANG Xian-ying, WU Jie

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  57-65.  doi:10.6040/j.issn.1671-9352.1.2020.060

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This paper proposes to introduce the global structural relationship between terms and terms and between terms and documents in the process of short text modeling to enhance the representation of short text. Due to the lack of labeled training data, existing global structural relationship modeling methods, such as TextGCN, cannot learn high-quality terms and document global structure representations. Therefore, we further propose to adopt the idea of semi-supervised learning to solve the problem of insufficient training data. On the benchmark dataset MEDUI, we compare with the existing related models. The experimental results show that the method proposed in this paper improves the F₁ index by 1.91% compared with the best benchmark model.

An extractive topic brief representation generation method to event

WANG Wei-yu, SHI Cun-hui, YU Xiao-ming, LIU Yue, CHENG Xue-qi

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  66-75.  doi:10.6040/j.issn.1671-9352.1.2020.029

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This paper takes advantage of the fact that event description contents are highly similar, and proposes an extractive topic brief representation generation method, which takes the titles in the event document set as the processing object, and extracts the common information retaining the original word order from different titles, further integrates these common information to generate a topic brief representation of the event. The experimental results on the event data from search engines show that this method can well generate the topic brief representation with concise and accurate form, clear and complete semantics and good readability.

Pseudo-relevance feedback method based on locational relationship in document

WANG Xue-yan, HE Ting-ting, HUANG Xiang, WANG Jun-mei, PAN Min

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  76-84.  doi:10.6040/j.issn.1671-9352.1.2020.019

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This paper proposes a location-based Rocchio framework(LRoc), with three variants. The method uses different kernel functions to model the term location in the feedback documents, obtains the importance information from the locations of candidate expansion terms, and integrates it into the classic Rocchio model. When selecting and evaluating the candidate expansion terms, this method not only considers term frequency, but also considers the influence of term location, which helps to obtain the expansion terms that are more likely to be relevant to the query. Finally, a series of experiments are performed on five standard text REtrieval conference(TREC)datasets. The proposed three models(LRoc1, LRoc2 and LRoc3)based on the LRoc framework all have got significant improvements over the baseline model in terms of the mean average precision(MAP)and precision at position 20(P@20)indicators.

Chinese word representation learning based on Gaussian distribution and Chinese character component characteristics

YI Jie, ZHONG Mao-sheng, LIU Gen, WANG Ming-wen

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  85-91.  doi:10.6040/j.issn.1671-9352.1.2020.032

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We use a distributed embedded representation based on density, and give a method to learn the space representation of the Gaussian distribution, so as to better capture the uncertainty about the representation and its relationship, to express the asymmetry of the words more naturally than the dot product cosine similarity. At the same time, according to the characteristics of Chinese characters, the semantic information of the Chinese characters components is added to the word embedding training. Compared with existing methods, our model has better performance in terms of word similarity or downstream tasks, and can express the uncertainty of words.

Survey on blockchain data privacy protection

KANG Hai-yan, DENG Jie

JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE). 2021, 56(5):  92-110.  doi:10.6040/j.issn.1671-9352.0.2020.595

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The research progress of blockchain, high-quality data in China and abroad are summarized, such as blockchain, blockchain and other related technologies. First of all, according to the latest blockchain technology architecture, this paper extracts and classifies the content of blockchain data privacy threats in the literature. Then, on the basis of classification, the core technologies and methods to solve these data privacy threats are classified and summarized. Finally, the paper introduces the new blockchain technology DAG technology, compares the characteristics of existing blockchain technology and DAG technology, and points out the technical problems to be solved and the future research direction.