Table of Content

    25 May 2020, Volume 59 Issue 3
    Overview of person re-identification in unconstrained environments
    FENG Zhanxiang, ZHU Rong, WANG Yujuan, LAI Jianhuang
    2020, 59(3):  1-11.  doi:10.13471/j.cnki.acta.snus.2020.03.001
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    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.
    The relationship among iron ion, secondary mineral assemblage and heavy metals distribution in the acid mine drainage(AMD) at Dabaoshan mine, Guangdong province
    GOU Xiying, CHEN Binghui, CAO Lina, LI Wen, ZHANG Yao
    2020, 59(3):  12-22.  doi:10.13471/j.cnki.acta.snus.2020.03.002
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    Taking the water and its sediments in the acid mine drainage (AMD) at Dabaoshan mine, Guangdong province as the study object, 11 sampling points at Caoduikeng and Tielong tailing ponds were sampled. The concentrations of iron and heavy metal ions in the collected water samples were determined, and the phase analysis and morphological observation of the sediments were carried out to study the effects of iron ion on the formation of secondary minerals and the migration and transformation of heavy metal ions in the AMD. Our study  suggests that the total iron (TFe) concentrations in the AMD water were ranged in between 0.135 3~5.6154 mg/L, the ratio of Fe(Ⅲ)/TFe was mostly above 90% and the oxidation reduction potential (Eh) was mostly in between 400~600 mV, indicating a high oxidation condition. There are negative correlations between Fe() concentrations and pH values, and positive correlations between Fe() concentrations and Eh values in waters There are positive correlations between Fe() and heavy metal elements such as Mn,Pb,Zn,Cu in waters,and apparent negative relations betweent Fe() in waters and Mn,Pb,Zn,Cu in the sediments at the AMD in Caoduikeng tailing pond. The common iron-bearing secondary minerals are ferric oxyhydroxide and iron hydroxyl sulfate minerals such as jarosite, schwertmannite, goethite and other alum minerals. The jarosite and coquimbite occurred in low pH values (<3.00) and high Fe()contents (>3.955 mg/L). Schwertmannite occurred in relatively high pH values (3.00~4.00) and low Fe(Ⅲ)contents (<1.610 mg/L). Goethite and other alum minerals occurred in relatively wide pH values (2.58~3.72)and Fe(contents(0.158 0~4.564 3 mg/L)in the studied water samples. The various distribution of heavy metal elements in water and its sediment resulted from the absorption and co-precipitation of heavy metals by various iron-bearing secondary minerals formed at different pH values and Fe()concentrations.
    Numerically simulating the runout volume of debris flow at urgent steep gully in the earthquake areas based on FLO-2D—Illustrated with a case of Wayao gully
    FANG Qunsheng, CHEN Zhihe, TANG Chuan, XU Huiliang
    2020, 59(3):  23-31.  doi:10.13471/j.cnki.acta.snus.2020.03.003
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    The mountain was seriously broken in the earthquake area after the Wenchuan earthquake. The critical threshold for inducing geological disasters such as debris flow and landslide was low. A type of urgent-steep gully debris flow was triggered, which led to extreme destruction. This type of debris flow has a shorter outbreak duration, a large volume concentration and a large average density, showing a strong “snowball effect” and strong “fire hose effect”. The engineering measures have an important influence on FLO-2D numerical simulation of urgent-steep gully debris flows. Therefore, FLO-2D is used to simulate the runout volumes of typical urgent-steep gully debris flows under engineering measures and nonengineering measures scenarios respectively, taking Wayao gully in Wenchuan earthquake area as an example. The accuracy of numerical simulation results is 86.4%. The block dam in the circulation area can divide block debris flow into sections under the engineering measures, which makes the debris flow run out volume reduced. When the rainfall frequency is P =2%, under the engineering treatment measures scenario, the runout volume is 83.16%, the accumulation fan area is 75.81%, and the average accumulation depth is 30.25% less than those in the natural scenario. The research results can provide reference for disaster prevention and mitigation engineering and early warning of debris flow of urgent-steep gullies in earthquake areas.

    Holocene diatom records in the Rongjiang Plain and implications for palaeoenvironmental changes
    ZHANG Kai, LING Ken, LIU Chunlian, YIN Jian, WU Yueqin
    2020, 59(3):  32-42.  doi:10.13471/j.cnki.acta.snus.2020.03.004
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    Holocene palaeoenvironmental reconstruction was carried out based on diatom records, together with sedimentology analysis and dating results of boreholes ZK01 and ZK02 from the Rongjiang Plain. A flood plain-freshwater swampy environment developed between 10.4 and 8.5 ka B.P..During this time the seawater has not intruded into the study area yet. At around 8.5ka B.P., diatoms showed up for the impact of seawaters and the environment was characterized by an intertidal marsh. Between5.5 and 3.9 ka B.P., an estuary environment dominated in the study area with the rapid transgression. The maximum transgression occurred around 5.5 ka B.P., evidenced by the highest abundance and diversity of diatoms. A short-time regression occurred between 3.9 and 3.7 ka B.P. while a brackish marsh environment existed. From 3.7 to 2.4 ka B.P., the sea level gradually rose to a stable level and an estuary environment developed. Three short-term fluctuations were recorded by diatoms in this period, indicating changes in water depth and salinity. Since 2.4 ka B.P., the seawater retreated and an alluvial plain developed in the study area.

    The ecological flow of the middle and lower reaches of the Lancang River based on priority protection fishes identification
    PENG Wei, LIU Bingjun, QIU Jiangchao, ZENG Hui, ZHANG Mingzhu, LI Dan
    2020, 59(3):  43-50.  doi:10.13471/j.cnki.acta.snus.2020.03.005
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    Maintaining reasonable ecological flow in the river to meet the needs of aquatic habitats is an important guarantee for the health of its ecosystem. In this paper, the middle and lower reaches of the Lancang River is selected as the study area, and the river priority conservation species fishes assessment method is constructed based on three dimensions of risk coefficient, disturbance coefficient and value coefficient, then the priority protected fishes in this area are identified. Based on Instream Flow Incremental Methodology, hydraulic habitat suitability index and high/medium/low suitable proportion were selected as habitat suitability assessment indicators, and the relationship curve between them and the flow was established to study the suitable ecological flow of priority protected fishes in spawning and adulthood. The results show that: 1) the fish with the highest priority protection level in the middle and lower reaches of the Lancang River is Tor sinensis; 2) the optimum ecological flows of Tor sinensis in the spawning and adult stages are 2 100 m3/s and 1 200  m3/s respectively, and the suitable ecological flow ranges are 1 700~3 300 m3/s and 800~1 500 m3/s respectively, the results are between good and maximum levels of the Tennant method.

    Protective effects of communic acid against the TBHP-induced oxidative stress injury in SH-SY5Y nerve cells
    YAN Li, HE Xiang, MA Zekang, LI Peibo, SU Weiwei
    2020, 59(3):  51-58.  doi:10.13471/j.cnki.acta.snus.2020.03.006
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    The aim of this study was to investigate the neuroprotective effects of communic acid against cell oxidative stress injury induced by t-butylhydroperoxide (TBHP) in human neuroblastoma cells and its mechanisms. Meanwhile, MTS method, SA-glycosyl lactate dehydrogenase (LDH) staining method, Annexin v-fitc /PI double dyeing method, 2′,7′- dichlorofluorescein diacetate (dcfh-da) method and Enzyme-linked immunosorbent assay (ELISA) was used to detect the activity and senescence of cells.The results showed that communic acid has a protective effect on TBHP=induced oxidative damage in SH-SY5Y cells, and can reduce the cell senescence ratio and the apoptosis level. The mechanism may be that TBHP reduced oxidative damage in cell membrane and DNA, and decreased the level of ROS content by improving enzyme activities such as antioxidant enzymes SOD.

    Seasonal variation of physical and chemical factors and distribution characteristics  of phytoplankton in a subtropical reservoir: a case study from Lianhe Reservoir, South China
    CAI Yangyang, TANG Changyuan, CAO Yingjie
    2020, 59(3):  59-72.  doi:10.13471/j.cnki.acta.snus.2020.03.007
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    The hydrological characteristics influence the distribution of phytoplanktons in subtropical reservoirs. However, phytoplanktons also provide feedback to the ambient environment. Taking Lianhe Reservoir as a representative subtropical eutrophication reservoir, the hydrological, chemical, and biological conditions were studied from 2014 to 2015. The results showed that the vertical profiles of pH, dissolved oxygen, and chlorophyll a in the water column changed greatly during the thermal stratification period. It was found that the dominant species were from the reservoir itself, not from the shore or receiving rivers, and they were suspected to overcome poor living conditions by entering dormancy in the bottom. The phytoplankton community also had a seasonal variation, with Cyclotella meneghiniana as the dominant species during the isothermal mixing period and Microcystis densa during the thermal stratification period. The alternative appearance of these species was considered to be influenced mainly by temperature and available light. However, the distribution of phytoplankton could affect the oxygen content in the water column. Furthermore, both phytoplankton and dissolved oxygen determined the vertical profile of total phosphorus. For the one-year budget, it was found that there was a net retention of both nitrogen and phosphorus in the reservoir, and nitrogen input mainly from rainfall and rivers and phosphorus from rivers and sediments.

    Community structure of rotifera and black-odor level analysis in Gu River of Guangzhou city
    LI Ling, LIU Yu, YU Fei, HE Shuwen, LIANG Rensi, YANG Xiangfei
    2020, 59(3):  73-81.  doi:10.13471/j.cnki.acta.snus.2020.03.008
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    Gu River, a tributary of the Pearl River can be defined as urban black-odor water bodies. As important indicator organisms, rotifers have been widely used in the evaluation of water body nutrition and pollution status, but the research on the relationship between rotifers community structure and black-odor water body is limited. Three surveys of rotifers and black-odor water bodies were investigated in the part of Gu River along the campus of Sun Yat-sen University in Guangzhou from November 2017 to March 2018. The eutrophication of water quality was evaluated by composition of pollution indicative species of rotifer, E/O index, QB/T index and Shannon-ack odorous water in Gu River. The black-odor indexes with parameters of multifactor (IB) were used to evaluate the situation of black odorous water in the Gu River. The results showed that there were a total of 35 species of rotifera in the part of Gu River along the campus of Sun Yat-sen University, belonging to 10 families and 16 genera, among which 23 species are pollution indicator. Both E/O index and QB/T index showed that Gu river segment reached eutrophication level. Gu river was determined as α medium pollution type and β-medium pollution type by the H′. Pearson correlation analysis showed that there was significantly correlations between the abundance and species of rotifera with water temperature (t), CODMn, dissolved oxygen (DO), Chlorophyll a (Chl a)(P﹤0.05). CCA analysis showed that algae abundance, Chl a, temperature, CODMn and DO were the major environmental factors affecting the rotifer community in Gu river, and the relation of Proales,Asplanchna priodonta to black-odor degree (IB) was extremely significant. These species can used as an indicator of increased water pollution. However, there was no significantly correlations between rotifer abundance, Brachionus abundance, Brachionus abundance percentage and IB. This study showed that rotifera could be used as an effective indicator of water pollution to evaluate the nutritional status of Gu river, but further studies are needed for the use of rotifers for black-odor evaluation.

    Nitrogen-contained compounds of mangrove endophytic Fusarium sp. from Dongzhai Harbor
    CHEN Xiaoqing, LIANG Cuifang, LIN Huimei, ZHAO Jiayu, HUANG Chuyu, TAO Yiwen
    2020, 59(3):  82-86.  doi:10.13471/j.cnki.acta.snus.2020.03.009
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    Mangrove endophytic fungus Fusarium sp. KL11 from Dongzhai Harbor of Hainan Province was fermented in rice media, and six compounds were isolated and purified by modern separation and purification technologies. By mass spectrum (MS) and nuclear magnetic resonance spectroscopy (NMR), these compound were identified as bassiatin (1), beauvericin (2), bostrycoidin (3), 5-methoylbostrycoidin (4), 8-methoylbostrycoidin (5) and 5,8-dimethoylbostrycoidin (6), respectively, and all of them are nitrogen-contained compounds.

    Recognition of traffic mode of mobile phone data based on the combination of point of interest data and navigation data
    ZHONG Shuqi, DENG Rufeng, DENG Hongping, CAI Ming
    2020, 59(3):  87-96.  doi:10.13471/j.cnki.acta.snus.2020.03.010
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    Mobile phone data has many advantages, including large sample volume, low collection cost and strong following performance. Thus, analysis of citizens'trip characteristic based on mobile phone data is of significance. A framework of user trip characteristic analysis based on mobile phone data is designed, including data cleaning, trajectory recognition, trip chain extraction, point of interest (POI) analysis and traffic mode recognition. The user's traffic mode is divided into driving, transit, walking and riding based on POI data, road network data and navigation data. The result shows that, with the combination of POI data and navigation data, the precision of traffic mode recognition has a significantly better than only use navigation data, and the promotion is more than 10%. In general, the traffic mode recognition algorithm is high accuracy and suitable for citizens'trip characteristic analysis.

    Research on the effect of ammonium on the engineering properties of undisturbed soft soil of Nansha,Guangzhou
    QUE Jiaping, ZHANG Chengbo, LI Jiaxi, HENG Song
    2020, 59(3):  97-106.  doi:10.13471/j.cnki.acta.snus.2020.03.011
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    The Groundwater of Nansha,Guangzhou is highly rich in ammonium that is very rare in the world, and the highest concentration of ammonium is up to 390 mg/L. This region is in a central position of Guangdong-Hong Kong-marco Greater Bay Area, where a large number of projects have been built or are about to be built. The influence of ammonium has not been specially concerned, taking Nansha Section of Guangzhou Metro line 18 as an example, the effect of ammonium on the engineering properties of soil has been researched. Unlike previous methods that remolded soil is applied as experimental material, after processed by pickling with pH=1 hydrochloric acid, washing with deionized water and permeation with ammonium solution, undisturbed soft soil of Nansha was used to do consolidation and direct shear test in this research. The result shows that an increased ammonium concentration leads to compressibility enhancement and higher shear strength of soil.

    Deformation characteristics of foundation pit excavation of row-pile supporting in deep water-rich sandy stratum
    QIU Mingming, YANG Guolin, SHEN Quan, DUAN Junyi, ZHANG Peiran
    2020, 59(3):  107-117.  doi:10.13471/j.cnki.acta.snus.2020.03.012
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    Deep foundation pit construction has the characteristics of high risky, great difficulty and complex structure stress in deep water-rich sandy stratum. Based on the foundation pit of a subway station, the deformation characteristics of a row-pile supporting foundation pit induced by deep excavation in deep water-rich sandy stratum are studied by field monitoring and numerical simulation method. The research results show that the horizontal displacement distribution curve of retaining wall develops from a “oblique line” shape to that of a “bow” and “inverted-V” with excavation depth. The maximum horizontal displacement of retaining wall and its location with excavation depth could be described by linear function. The maximum horizontal displacement Ux,max is about (0.03%~0.15%he (he is excavation depth), and the location of maximum horizontal displacement Hx,max is about (0.4~1.0he. The distribution curve of ground vertical displacement behaves as a inverted-S with time, and the ground vertical displacement behaves as a groove shaped curve with an increase of transverse horizontal distance during the construction. The width of settlement trough is about (1.0~2.0)he, and the location of maximum ground vertical displacement is about (0.30~0.50)he away from the edge of foundation pit. The control measures such as ensuring construction quality and anti-seepage effect of waterproof curtain, attention to the prediction and feedback function of construction monitoring are proposed to ensure the construction safety of foundation pit in water-rich sandy stratum. The conclusion could be referenced for the supporting structure design and construction deformation control of deep foundation pit in water-rich sandy region.

    Development and application on online VOCs adsorption/thermal desorption system
    LAN Jie, CHEN Yanrui, TAN Guobin, CHE Xinxin, SU Haibo, HUANG Fugui , WANG Tong, LIU Shulin, GAO Wei, HUANG Zhengxu
    2020, 59(3):  118-126.  doi:10.13471/j.cnki.acta.snus.2020.03.013
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    An online VOCs adsorption/thermal desorption system was developed for enhancing the sensitivity of online VOCs mass spectrometry. By integrating a fast and precise temperature control module, a large flow rate sampling strategy and a switch mode pre-concentration module, the new system can be coupled to both online VOC detection instruments and offline ones. The performance of the system, such as operating conditions, enrichment capacity, stability, was tested by using a benzene series standard gas. Meanwhile the system was used to analyze the VOCs components in indoor air. The result show that the sensitivity of the online VOCs mass spectrometry was increased by two orders of magnitude. Secondly, compared to single online VOCs mass spectrometry, the system coupled to online VOCs mass spectrometry can greatly enhance the detectability of trace amount VOCs components in indoor air. This system will provide a new technology for trace VOCs gas detection.

    Study of the structures and hydrogen storage properties of Na atoms decorated tetrahedron Si4 cluster
    RUAN Wen, SONG Honglian, WU Donglan, LUO Wenlang, XIE Andong, ZHAO Fangjie, GAN Yaling
    2020, 59(3):  128-133.  doi:10.13471/j.cnki.acta.snus.2020.03.014
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    Based on the alkali metal sodium atoms decorated tetrahedron Sismall cluster, the geometric structures, electronic properties and hydrogen storage properties of tetrahedral Na4Si4 cluster were studied by using the Minnesota density functional theory (DFT, M06) method. The results show that the tetrahedron Sican be decorated by alkali metal Na atoms on the four surfaces stably and Na atoms do not occur clustering. Hydrogen molecules can be adsorbed around the Na atoms, in which every Na atom can adsorb six hydrogen molecules efficiently,corresponding to a maximum mass fraction of 19.15% with an average adsorption energies of 3.926~9.927 kJ·mol-1 per H2 molecule.The results demonstrate that the tetrahedral Na4Si4 cluster has the potential to become an effective hydrogen storage medium under the room temperature and atmospheric pressure conditions.

    Reliability on crack resistance of CRTS Ⅱ track slab based on highorder moment method
    ZHANG Longwen, ZHOU Jin
    2020, 59(3):  134-142.  doi:10.13471/j.cnki.acta.snus.2020.03.015
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     Based on the high-order moment method, the reliability analysis method on crack resistance of CRTS Ⅱ track slab is proposed. Firstly, the mechanical model of CRTS Ⅱ slab ballastless track under vertical train load is established by using ANSYS finite element software, and the performance function of crack resistance of track slab is established by considering the effect of lateral train load and gradient temperature . Then, the first four moments of the implicit function considering the effect of vertical load are solved by combining the two-dimensional point estimation method with the structural finite element analysis. Finally, the first four moments of the performance function of anti-cracking are calculated according to the Monte-Carlo simulation method, and the reliability index of the performance function is estimated based on the high-order moment method. A numerical example shows that relative error between the result of proposed method and Monte-Carlo simulation results is less than 5%. The reliability index estimated by the proposed method is 4.63, which satisfies the requirement of the code. The proposed method has the advantages of simplicity, effectiveness and fewer simulation times, and it provides an efficient and reasonable tool for reliability analysis of crack resistance of CRTS Ⅱ track slab under implicit function condition.

    Multiple periodic solutions for impulsive differential systems with variable exponent
    ZHANG Shengui
    2020, 59(3):  143-149.  doi:10.13471/j.cnki.acta.snus.2020.03.016
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    The existence for periodic solution of impulsive differential systems with variable exponent is studied. When the nonlinearity has a suplinear growth, some results for existence of infinitely many periodic solutions are obtained by using the fountain theorem in critical point theory.

    Virtual machine placement algorithms based on complementary mechanism
    SUN Suyun
    2020, 59(3):  150-158.  doi:10.13471/j.cnki.acta.snus.2020.03.017
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    By using an effective virtual machine placement algorithm, computing resources can be allocated optimally, therefore the utilization efficiency of cloud computing resources can be also improved. Based on analyzing the problems in resource allocation, a virtual machine placement algorithm is proposed by using complementary mechanisms. Firstly, based on the resource complementarity relationship among virtual machines, the virtual machines with smaller resource granularity are combined into a new virtual machine. Then, based on the resource complementarity relationship between the virtual machine and the server, the virtual machine is placed in the complementary server in turn, so that each resource type in the server is distributed evenly. Simulation results show that the number of servers and the energy consumption in the data center are decreased effectively, and the usage efficiency of cloud computing resources has been improved by using the CBVMP algorithm. 

    Lower bound for the blow-up time of a nonlinear non-local porous medium equation under nonlinear boundary condition
    OUYANG Baiping, LIU Yan
    2020, 59(3):  159-164.  doi:10.13471/j.cnki.acta.snus.2020.03.018
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    The blow up phenomenon for the nonlinear non-local porous medium equation is studied. Using the technique of differential inequality, the lower bound for the blow up time under the nonlinear boundary condition is determined if blow-up does really occur.