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    A novel drug delivery system—red blood cell membranes biomimetic nanoparticles
    HUANG Jiwei, JIANG Caiyun, LUO Yuyan, GUO Zhefei, ZHANG Yongming
       2019, 58 (5): 114-118.   doi:10.13471/j.cnki.acta.snus.2019.05.014
    Abstract251)      PDF (1585KB)(131)      

    The study reported a novel drug delivery system, red blood cell membranes biomimetic nanoparticles (RBCM-NP) drug delivery system. The system was constructed by combining the excellent drug-carrying properties of nanoparticles and cell membranes as shells to encapsulate the synthesized nanoparticle which makes it disguise as an endogenous substance to reduce uptake of reticuloendothelial system and immune recognition. Nanoparticles (NP) were prepared by reverse solvent method, while red blood cell membranes (RBCM) were extracted by centrifugal extraction. Different ratios of RBCM and NP were co-extruded for different times to prepare RBCM-NP. RBCM-NP were characterized by transmission electron microscopy and Malvern particle size meter. The aggregation reaction of biotinylated nanoparticle (BTNP) and streptavidin (ST) were used to study the coverage of red blood cell membranes. The particle sizes of NP and RBCM-NP were uniformed. In optimized formulation, RBCM could completely encapsulate NP with good reproducibility.

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    Geochemistry characteristics and their geological significances of cherts in the tectonic belt from Mianlue,southern Qinling orogenic belt
    CHEN Shuo,ZHOU Yongzhang,ZHANG Yanlong,ZHOU Weili
       2019, 58 (5): 59-72.   doi:10.13471/j.cnki.acta.snus.2019.05.009
    Abstract221)      PDF (4516KB)(74)      

    Paleozoic cherts outcrops were widely developed in the Mianlue tectonic belt, which could reveal the sedimentary environment and tectonic background of southern Qinling orogenic belt. In Sanchazi area, the cherts were found in the Sanhekou Group of the Middle Devonian. Geochemical analyses showed that Sanchazi cherts were high in SiO2 (94.04%-98.08%, with a mean value of 96.92%) and low in Al2O3 and TiO2; and were relatively high in Ba and U, but was relatively low in Zr for trace elements. The U/Th and Ba/Sr ratios were relatively high too. ΣREE content was significantly low (7.61-51.04 μg/g, with an average valve of 2251 μg/g). PAASnormalized REE distribution pattern inclined to the left, rich in HREE and with positive Eu anomaly and negative Ce anomaly. The Al/(A1+Fe+Mn), Fe/Ti and (Fe+Mn)/Ti values indicated the origin of hydrothermal sedimentation of the cherts. Al/(Al+Fe), Al2O3/(Al2O3+Fe2O3+MnO), Al2O3/(Al2O3+Fe2O3), δCe and (La/Ce)N values indicated that the cherts were mainly formed in the continental margin. The values of (La/Lu)N, (La/Yb)N and δEu could be related to the hydrothermal activities controlled by the deep fractures. Th/U, U/Th, δU values indicated the cherts were formed in the anoxic depositional environment. The above-mentioned geochemical evidences inferred that Sanchazi cherts were formed in a sedimentary environment of rifted basin at continental margin in the north of South China Block during the Paleozoic. During the rifting period, while a series of extensional structures, such as rift or fault basin and syngenetic faults, were formed, accompanied magma activities could provide heat source for the thermal water, and the regional syngenetic faults provided the channel for upwelling of the thermal water. Hence, the convective hot water became rich in SiO2 through the leaching and dissolving of chemical composition from surrounding strata, and contributed to the forming of hydrothermal sediment cherts of different geologic ages in the Mianlue tectonic belt.

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     A concise survey on graph convolutional networks
    Acta Scientiarum Naturalium Universitatis Sunyatseni    2020, 59 (2): 1-14.   doi:10.13471/j.cnki.acta.snus.2020.02.001
    Abstract123)      PDF (2215KB)(118)      
    In recent years, many new technologies are constantly emerging in every aspect of our lives. More and more data have been generated and stored in graph format. Graphs are irregular data, which possess the characteristic of being distributive and disordered. Besides its capability that nodes can endow with data features, edge information can further depict the similarities among nodes. Despite the fact that classic convolutional neural networks are capable of handling regular format data such as images, videos and speech, directly applying these networks to graph data seems to be problematic. Recently, quite a few of researches were proposed to consider how to generalize classic convolutional neural networks for graph data and many high efficient learning algorithms were developed. This work aims to summarize and discuss the promising development of graph convolutional neural networks that were specifically designed for graph data. Nonetheless, due to the limited space, we cannot provide all the details of graph convolutional neural networks. Instead, we tend to introduce the motivations of those models, the analyses of the pros and cons of each model, and a brief summary of the major applications of graph convolutional neural networks.
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    Overview of person re-identification in unconstrained environments
    FENG Zhanxiang, ZHU Rong, WANG Yujuan, LAI Jianhuang
    Acta Scientiarum Naturalium Universitatis Sunyatseni    2020, 59 (3): 1-11.   doi:10.13471/j.cnki.acta.snus.2020.03.001
    Abstract104)      PDF (2212KB)(145)      
    In the last few years, with the development of deep learning theory and person re-identification (re-id) methods, re-id techniques has achieved great breakthrough and gained high recognition accuracy in constrained environments. However, the existing re-id approaches perform poor in unconstrained environments and are still far from practical applications. There are many significant challenges in unconstrained environments, including lack of training samples, dramatic illumination variations, person occlusion and open-set tests, which significantly decreases the performance of re-id models. In this paper, we will introduce the latest improvements, the involved datasets, the existing problems and the future trends of the unconstrained person re-identification techniques, especially for unsupervised re-id, visible-infrared re-id, occlusion re-id, and open-set re-id.
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    Spatial distribution and accessibility analysis of airports in mainland China
    ZHANG Yihan, LIU Wanhua, XU Xiaocong, CHEN Xiaowei, QIAO Jigang
       2019, 58 (6): 56-63.   doi:10.13471/j.cnki.acta.snus.2019.06.007
    Abstract101)      PDF (2863KB)(49)      

    The spatial distribution and network characteristics of airports in mainland China were analyzed, then improved average travel time was used to analyze airport accessibility and correlation analysis method is adopted to study transport, service, operations and environment. The results showed that airports density in the east is larger than that in the west region. There are 27 airports with more than 1 000 flights in a week, among them 22 airports are located in provincial capital cities, and only 5 airports are in non-provincial capital cities, i.e. Shenzhen, Xiamen, Dalian, Qingdao and Sanya, respectively. The top three of the busiest routes are those between Shenzhen-Beijing, Shenzhen-Shanghai and ShanghaiBeijing, and main departure & destination cities for the top 20 of the busiest routes are Shanghai, Beijing, Shenzhen, Chengdu, Chongqing, Guangzhou and Xiamen. From the perspective of accessibility, eastern regions show higher accessibility than western regions in China. High accessibility areas include Beijing-Tianjin-Hebei, the Yangtze River Delta and the Pearl River Delta. Furthermore, the airport accessibility is often affected by transport, service, operations and environment, among which the most important factors are related to number of connected airports, outbound flights in peak hours, outbound domestic direct-flights and actual outbound flights. The correlation values are 0.706, 0.822, 0.777 and 0.808, respectively. The accessibility also has a strong correlation with number of parking, number of runways, GDP and population, with correlation values of 0.776,0.701,0.679 and 0.695, respectively.

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    Optimizing the rate and capacity of the on-street parking lot
    GUAN Songheng, LI Jun
       2019, 58 (5): 39-43.   doi:10.13471/j.cnki.acta.snus.2019.05.006
    Abstract93)      PDF (835KB)(210)      

    The indicator of “Parking service level” is defined for curb parking to describe the probability that the drivers can find the available parking space. An integer optimization model is proposed to maximize the parking service level considering the rate of utilization of parking lot, so that a combination of the rate and the capacity of parking lot can be used to optimize the price scheme. A case study of an curb parking in Guangzhou CBD was presented, it verified the validity and rationality of the indicator parameters and models, and the study was found that the current combination of the rate and the capacity of parking lot led to a lose-lose for both the users and operator.

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    Simulation analysis of seabed gas hydrate cutter suction mining single tooth crushing process
    WANG Guangshen, WANG Guorong, ZHONG Lin, ZHANG Yichi, QIU Shunzuo
       2019, 58 (5): 1-7.   doi:10.13471/j.cnki.acta.snus.2019.05.001
    Abstract93)      PDF (1856KB)(275)      

    Cutter suction gas hydrate solid state fluidized mechanical mining is one of technical solutions proposed for seabed hydrate mining. Based on the discrete element method (DEM), a quasi-3D numerical simulation model for single-tooth cutting hydrate is established to study the hydrate breaking process and the force of the cutter teeth in the cutting process. The results show that:1) Hydrate fracture still follows the failure mechanism of rock, pure hydrate is plastically destroyed, and marine hydrate deposition is brittle fracture; 2) the deeper of cutting thickness, the larger volume of the collapsed marine hydrate deposits; 3) when the cutting thickness is less than 8 mm, the cutting force increases linearly with the cutting thickness. The feasibility of study to crush hydrate by threedimensional discrete element method. The research results can provide basis for the design and mining parameters of the cutter suction mechanical mining and the cutter head.

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    Suggestions for the quality standard in Chinese pharmacopoeia of Citri Grandis Exocarpium and the establishment of its grade standard
    LI Panlin, PENG Wei, WU Hao, WANG Yonggang, LI Peibo, ZHANG Mimi, SU Weiwei
    Acta Scientiarum Naturalium Universitatis Sunyatseni    2019, 58 (6): 1-13.   doi:10.13471/j.cnki.acta.snus.2019.06.001
    Abstract92)      PDF (1911KB)(164)      

    This study is aimed to address the main deficiencies in the quality standard of Citri Grandis Exocarpium (CGE) in current Chinese Pharmacopoeia, including the confusion of the plant origins and the inconsistency between the actual and the specified medicinal parts. Based on large amounts of historical evolution studies, market researches and testing results, several suggestions were proposed as follows: Citrus grandis‘Tomentosa’ (CGT) was the original plant source of CGE while  (L.) Osbeck (CGO) was used as a substitute when shortage of CGT resources. However, there were great differences between the chemical compositions and contents of CGT and CGO, and thus it is necessary to make them distinguished. We suggested that CGT should be used as the only plant origin of CGE. Meanwhile, the medicinal parts of CGE gradually transformed from the epicarp to immature fruit during the practical process, the immature fruit had the same chemical compositions with epicarp and higher contents of the active components. So we suggested supplementing the medicinal parts of CGE with immature fruit. Furthermore, we established the grade standard of CGE, which could be applied to distinguish the plant origins and evaluate the quality grades. In conclusion, this study provides suggestions for the improvement of the quality standard of CGE, which is of great significance for standardizing its marketing activities, promoting the rational use of plant resources and accelerating CGE into the international market.

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    Progress of the study on Landau-Ginzburg A model
    FAN Huijun, JIANG Wenfeng, YANG Dingyu
    Acta Scientiarum Naturalium Universitatis Sunyatseni    2020, 59 (1): 1-8.   doi:10.13471/j.cnki.acta.snus.2020.01.001
    Abstract92)      PDF (1121KB)(56)      
    A brief introduction of Landau-Ginzburg A model (LG Amodel) in homological mirror symmetry is given. Firstly, a short review of the general picture of the homological mirror symmetry is given. Then the background of Landau-Ginzburg model and its role in homological mirror symmetry are discussed. Finally,  a brief introduction of our recent work on the Fukaya category of LG model is included. Both mathematical and physical backgrounds are tried to include in this introduction as much as posible.

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    Application of radar and satellite data assimilation in a rainstorm forecast in Southern China
    ZHANG Shaoting; WANG Donghai; YU Xing;CHEN Quanliang;DING Weiyu
       2019, 58 (5): 80-93.   doi:10.13471/j.cnki.acta.snus.2019.05.011
    Abstract86)      PDF (4833KB)(106)      

    ARW-WRF and GSI 3D-Var methods were used to build a set of operational prediction systems and assimilate Doppler Weather Radar (DWR) reflectivity and velocity, Himawari-8 meteorological satellite AHI data. Regarding problems of data application and forecasting effect of unconventional data, multiple sets of comparative experiments were designed to perform simulation analysis and assessment of data assimilation (DA) results based on a case of severe precipitation process in southern China. The results show that during the heavy precipitation period in the coastal areas of Guangdong on 17-18 July 2017, the system can grasp the scope and intensity of precipitation and the simulation of radar reflectivity. Particularly, the assimilation of satellite data has ability to analyze cloud-water materials and weather process on the sea. Assimilating conventional data, radial velocity, reflectivity, and satellite data can improve simulation tactics such as temperature, wind vector, humidity, and precipitation. However, their prediction results are not absolutely superior to the test of certain types of data.

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    Trajectory accompanying patterns mining method based on spatialtime segmentation and word vector similarity
    LI Xin
       2019, 58 (5): 17-25.   doi:10.13471/j.cnki.acta.snus.2019.05.003
    Abstract83)      PDF (2052KB)(133)      

    A trajectory big data mining method based on spatial-time Hausdorff distance segmentation and word vector similarity is designed in this paper. It can analyze the accompanying rules accurately and efficiently, and truly reflect the flow behavior of people and vehicles. The one-to-three Hausdorff distance algorithm based on time series characteristics can exclude the reverse trajectory and mine the accompanying relations. The set of trajectory segments separated by the time sliding window can establish the basis for the similarity measurement. The method of trajectory similarity measurement based on word vector establishes the analogical relationship between trajectory and sentences, reflects the spatial, temporal and directional heterogeneity of the trajectory, and accurately measures the structural similarity of the accompanying trajectories. It provides a reference for exploring similar objectives, detecting frequent paths as well as other related applications.

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    Properties of sublinear g-expectations and their applications
    JI Ronglin;ZHOU Jinming
       2019, 58 (5): 153-158.   doi:10.13471/j.cnki.acta.snus.2019.05.019
    Abstract76)      PDF (851KB)(87)      

    Under the basic assumptions on generators of backward stochastic differential equations, the one-to-one correspondence between subadditivity (resp. homogeneity) of g-expectations and generators of backward stochastic differential equations is obtained. Thus it is proved that the definitions of dynamic coherent risk measures in Detlefsen-Scandolo (2005) and Jiang (2008) are completely same under the framework of g-expectations. Furthermore, the relationship between time-consistent dynamic coherent risk measures via g-expectations and sublinearity of g-expectations is established.

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    Exploring the properties of Levi-Civita and Kronecker symbols through antisymmetrization  
    PENG Junjin, LEI Liangjian
       2019, 58 (5): 26-32.   doi:10.13471/j.cnki.acta.snus.2019.05.004
    Abstract74)      PDF (888KB)(106)      

    In this paper, on basis of the determinant for the metric tensor, together with the identities got via anti-symmetrizing the Kronecker delta symbol and Levi-Civita tensor, we prove one of the properties of the Levi-Civita symbol (tensor), which shows that two Levi-Civita symbols (tensors) with the contraction for some or total indices can be expressed by a series of Kronecker delta symbols or the generalized Kronecker delta symbol. We further present two important deductions from the property of the Levi-Civita tensor, which are proved in other ways. Besides, we analyze several important properties for the generalized Kronecker delta symbol.

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    The geological risk assessment model based on extension method in subway construction and operation period
    CHEN Qing, GAO Yan, ZHU Yuxun, YUAN Quan
       2019, 58 (5): 49-58.   doi:10.13471/j.cnki.acta.snus.2019.05.008
    Abstract67)      PDF (2518KB)(103)      

    The construction of underground project can be seriously affected due to the uncertainty and ambiguity of geological conditions. However, the geological risk factors are not given a thorough consideration in the risk assessment methods, while the weight is determined subjectively. In this paper, six first-level geological risk assessment indicators: soil mechanical properties, rock mass properties, inrush conditions, groundwater, karst, and regional stability are selected. Each of first-level indicators is characterized by several secondary-level evaluation indicators. Then a more comprehensive and reasonable geological risk evaluation index system is established by integrating and applying existing evaluation methods of single geological risk evaluation indicators to determine the risk level of the first-level evaluation indicators. In view of the diversity of the indicators and the incompatibility of the assessment result given by a single indicator, a geological risk assessment model is established based on the extension method. The simple correlation function in extension theory is used to calculate the weight of each indicator, which is more objective and reasonable than traditional methods. The model was adopted to evaluate the risk of a station in Guangzhou. It is found that the geological risk level division is reasonable, and can reflect the local geological risk situation objectively; the geological risk level of the station in untreated condition is “moderate risk”, and the eigenvalues of risk grade is 1.94, which indicates that “moderate risk” is biased toward the “low risk” level. The assessment result agrees with the site investigation, so the evaluation result is precise.

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    Quasiperiodic motion of a buckled beam with 1∶3 internal resonance
    XIAO Longjiang, HUANG Jianliang
    Acta Scientiarum Naturalium Universitatis Sunyatseni    2020, 59 (1): 24-34.   doi:10.13471/j.cnki.acta.snus.2020.01.004
    Abstract67)      PDF (1355KB)(32)      
    This study investigates nonlinear dynamics of a fixedfixed buckled beam with 1∶3 internal resonance in the first two symmetric modes subject to uniform base harmonic excitation. The Galerkin method is employed to discretize the governing equation, the traditional incremental harmonic balance (IHB) method with single time scale is used to track periodic responses of the buckled beam,and the Floquet theory is used to analyze stability and bifurcation of the solution. It is found that the antisymmetric modes can be excited with increasing the excitation amplitude due to 1∶3 internal resonance, continuously increasing the excitation amplitude, Hopf bifurcation occurs which leads to quasi-periodic motion whose spectrum contains uniformly spaced sidebands around integer multiples of excitation frequency with increasing the excitation amplitude. The IHB method with two timescales is used to investigate quasi-periodic motion, whose solutions are in good agreement with those from numerical integration using the fourth-order Runge-Kutta method.

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    Spatial differentiation and aggregation characteristics of ecological security of urban agglomeration in the Pearl River Delta 
    LI Miao, HU Mengmeng, XIA Beicheng
    Acta Scientiarum Naturalium Universitatis Sunyatseni    2020, 59 (1): 96-104.   doi:10.13471/j.cnki.acta.snus.2020.01.012
    Abstract65)      PDF (1580KB)(23)      
    The Pearl River Delta (PRD) urban agglomeration is an important part of the Guangdong-Hong Kong-Macao Greater Bay. It is of great significance to study the ecological security and spatial pattern of the PRD urban agglomeration under the background of the national policy of implementing the construction of the Guangdong-Hong Kong-Macao Greater Bay. The ecological security evaluation system of urban agglomeration was constructed in the PRD based on the PSR conceptual model, and the set pair analysis and spatial autocorrelation analysis methods were applied to analyze the spatial heterogeneity and aggregation characteristics of urban agglomeration ecological security. The results show that the PRD is affected by urbanization, and the ecological security level shows an obvious spatial differentiation. The ecological security level of the central area, where it highly urbanized, is significantly lower than that of the peripheral area. The peripheral area forms an ecological barrier to the central area. The level of ecological security has a significant relationship with regional economic development, and the level of ecological security and economic development are negatively correlated in space. The clustering of ecological security in cities shows a “low-high” or “high-low” agglomeration situation. Cities with higher ecological security tend to be adjacent to cities with lower ecological security, showing a complementary spatial pattern. This spatial differentiation and aggregation characteristics have important guiding significance for the future ecological planning, urban ecological construction and ecological management of the urban agglomerations of the PRD and Guangdong-Hong Kong-Macao Greater Bay. 

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    The seasonal variation of tidal currents in the Haikou Bay
    CHEN Yizhan, CAO Yonggang, XIAO Zhijian, LIU Changjian, LI Ruixiang, DONG Chao
       2019, 58 (5): 73-79.   doi:10.13471/j.cnki.acta.snus.2019.05.010
    Abstract63)      PDF (2091KB)(105)      

    The seasonal variations of tidal currents in the Haikou Bay are analyzed based on the obtained data in 2016. The results demonstrate that: (1) the irregular diurnal tides were observed during spring, summer and autumn, while the irregular semi-diurnal tides were obtained in winter. (2) Because of the eddy influence, it is easier to obtain the irregular semidiurnal tidal currents near the cape area. (3) The tidal currents are mainly M2, K1 and O1, and their constituents are similar. (4) The strongest water transportation is from east to west in winter. (5) In this area, there are compensation currents during spring, summer and winter, while no obvious compensation currents could be obtained in autumn.

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    Acta Scientiarum Naturalium Universitatis Sunyatseni    2020, 59 (2): 152-.   doi:10.13471/j.cnki.acta.snus.2020.02.018
    Abstract62)      PDF (698KB)(71)      
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    Characteristics analysis of PM2.5 and NO2 pollution at Beijing traffic stations during the Spring Festival from 2014 to 2018#br#
    LUO Yinping, CHEN Tong, DING Hui, CHEN Jincai, LIU Yonghong, QU Xinming
    Acta Scientiarum Naturalium Universitatis Sunyatseni    2020, 59 (1): 50-63.   doi:10.13471/j.cnki.acta.snus.2020.01.007
    Abstract60)      PDF (2693KB)(33)      
    Based on hourly observation data of PM2.5 and NO2 concentrations at Beijing traffic stations during the Spring Festival from 2014 to 2018, the effects of vehicle emission reduction and fireworks forbidden and the impacts of emissions from fireworks and meteorological conditions on air quality were analyzed by comparing concentration characteristics and ratio of PM2.5 to CO The results showed that characteristics of PM2.5 and NO2 concentrations were different during the Spring Festival. The average PM2.5 concentrations from 2014-2018 were 103.6 μg/m3 and 25.3% higher than those before and after the Spring Festival. Significantly affected by vehicle emission reduction at traffic stations, the NO2 concentration was 53.8 μg/m3 and 19.5% lower than those before and after the Spring Festival. The concentrations of PM2.5 during the Spring Festival was lowest in 2014, and decreased year by year from 2015-2018. The burning of fireworks had relatively greater impacts on PM2.5 than NO2 During the New Years Eve, the maximum contribution of hourly PM2.5 concentration from burning fireworks was 283.4-704.1 μg/m3 Compared with the average of the previous four years, the concentrations of PM2.5 decreased by 25.2% and NO2 reduced by only 2.4%, which implied PM2.5 pollution was improved significantly by the measures of banning fireworks within the Fifth Ring Road in 2018. Under the meteorological conditions unfavorable to atmospheric diffusion, the maximum contribution of PM2.5 concentration during the New Year’s Eve was still 45.0% lower than that of the previous four years, indicating great reduction effect of fireworks prohibition measures. The effect of meteorological conditions on the PM2.5  during the Spring Festival was more significant than those of NO2. The meteorological condition favorable for atmospheric diffusion was the main reason for the great improvement of PM2.5 pollution in 2014.

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    The solitary wave solution in quantum plasma model
    FENG Yihu, WANG Weigang, MO Jiaqi
       2019, 58 (5): 145-152.   doi:10.13471/j.cnki.acta.snus.2019.05.018
    Abstract60)      PDF (1223KB)(164)      

    The quantum plasma system is discussed. A nonlinear dynamic disturbed model is studied. Using the undetermined coefficients method for the hyperbolic functions, perturbation theory and method, the solitary wave solution of corresponding model is solved. And the characteristics of corresponding physical quantity are expounded.

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