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Table of Content

    20 September 2018, Volume 54 Issue 5
    Dynamic Model of Pivoting Friction and Experimental Evidence
    WANG Chen, ZHANG Hongjian, WANG Xiaojun, SHI Yuhong, ZHANG Xi, LIU Caishan, WANG Haiying
    2018, 54(5):  915-920.  DOI: 10.13209/j.0479-8023.2018.020
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    An experimental apparatus was designed to test the pivoting friction moment of annular friction disc under either constant normal force and variable normal force. The experimental results demonstrated the applicability of the classical pivoting friction model under the continuous variable normal contact force, and showed that the rotary velocity affects the properties of the pivoting friction. By considering the Stribeck effect of the local friction at a contact point, a theoretical model was proposed for the pivoting friction. Good agreement between proposed theoretical and experimental results sheds light on the physical mechanism underlying the pivoting friction.

    Signal Processing Method for Mattress-Type Physiological Monitoring
    SHEN Jinpeng, WANG Xin’an
    2018, 54(5):  921-926.  DOI: 10.13209/j.0479-8023.2018.012
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    An empirical mode decomposition (EMD) based algorithm is proposed for mattress-type physiological monitoring. Fast Fourier Transform (FFT) is executed for the mixed physiological signal to estimate the frequency range of the respiration signal and heartbeat signal. Then the physiological signal is decomposed into several IMF components by EMD method, some of which are used to reconstruct the respiration signal and the heartbeat signal, according to the respiration or heartbeat spectrum energy in proportion of the total spectrum energy. The experiment result shows that the accuracy of measured respiration rate and heartbeat rate are both over 90%, compared with the polysomnography.

    A Design of 10B SAR ADC with Novel Mixed-Monotonic Capacitor Switching Scheme
    GE Binjie, LI Yan, YU Hang, FENG Xiaoxing
    2018, 54(5):  927-934.  DOI: 10.13209/j.0479-8023.2018.048
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    A mixed-monotonic capacitor switching scheme which can provide stable common-mode voltage (Vcm) without any additional voltage regulator and compensation capacitor array is proposed for the successive approximation register (SAR) analog-to-digital (ADC). The proposed scheme contains two equal amplitude but opposite monotonicity switched capacitor arrays, the stabilization of the common mode voltage is achieved with self-complementation of the differential voltage. Based on this technique, a 10-bit 50 MS/s prototype is designed in CMOS 0.18 μm technology. A window opening SAR logic is used to reduce the transmission time from the comparator out to DAC control signal. An adaptive delay chain is used in the comparator loop to reduce the conversion time of lower bit in the SAR ADC. Measurement result shows that the SAR ADC can achieve a SNDR equal to 57.31 dB, and INL and DNL are equal to 1.81 LSB and 0.98 LSB respectively.

    The HLBP and CHLBP Features for Pedestrian Detection
    CHENG Ruzhong, ZHANG Yongjun, LI Jingjing, WANG Guopin, LEI Kai, ZHAO Yong
    2018, 54(5):  935-945.  DOI: 10.13209/j.0479-8023.2018.017
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    Two improved texture features (hybrid local binary pattern, HLBP) and (color based hybrid local binary pattern, CHLBP) which are based on gray image texture and color space are proposed for pedestrian detection. The experimental results show that, when FPPW is 10–4, the detection rate of HLBP is 93.96% which is about 3.46% and 9.68% higher than Uniform LBP and CSLBP respectively. At the same time, when combined with the HIKSVM classifier, CHLBP feature based on L′C′C′ space makes the detection rate up to 98.58%, and its detection performance has been greatly improved, by this method an good result could be obtained in pedestrian detection.

    Improvements on Transient Power Law Model under HBM Stress
    CAO Xin, CAO Jian, WANG Yize, WANG Yuan, ZHANG Xing
    2018, 54(5):  946-950.  DOI: 10.13209/j.0479-8023.2018.044
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    An improved model is proposed based on the transient power law model under Human Body Model (HBM) stress. This model can predict the gate oxide breakdown statistically under HBM stress. Through HSPICE simulation tool, the corresponding DC effective voltage on the MOS can be calculated. The scatter chart of the precharge voltage of the HBM circuit with the effective DC voltages of the MOS shows a linear relationship. Using the Laplace transform, the linear relationship is proved. Compared with the existing transient power law model, the improved model reduces the computational complexity under the HBM stress and is easier to predict the MOS gate oxide breakdown statistically. The proposed model provides an important reference for the evaluation of the reliability of the MOS gate oxide under the impact of HBM.

    Microlens-Based Continuous Depth Map Estimation with the Plenoptic Camera
    YANG Peng, YAN Lei, ZHAO Shoujiang, YAN Yizhen, ZHAO Hongying
    2018, 54(5):  951-960.  DOI: 10.13209/j.0479-8023.2018.053
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    Because the micro lenses segment the plenoptic image physically, the global optimization method is hard to be applied on the depth estimation progress and the WTA (winner-take-all) method based on the multibaseline system will generate very coarse but continuous depth map. The global optimizations method always generate robust but concrete depth map when using multi-label technique. So cost projection strategy by directly processing the lenslet plenoptic image is proposed to build the cost volume based on the projection image for global optimization. A method based on Markov Random Fields Propagation (MRFsP) is adopted by merging the modified WTA depth result to refine the concrete depth map. For validation, the depth map built with the proposed method is compared with the microlens-based optimization result, and the result shows obvious improvement.

    Identification of Supercooled Water Clouds by Using Micro Pulse Lidar
    SONG Jiye, TAN Wangshu, LI Chengcai, YU Yingli, LI Jian, CHU Yiqi
    2018, 54(5):  961-969.  DOI: 10.13209/j.0479-8023.2018.022
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    On the basis of a previous algorithm of cloud detection, clouds and aerosols are distinguished by analyzing the backscatter signals of a micro pulse lidar. In this way, the content of clouds are classified into ice, water, mixed-phase clouds and horizontal oriented ice flakes. Finally, the supercooled water clouds are distinguished from water clouds by the information of temperature profiles. The monthly changes of the appearance heights and proportions of the various clouds are also calculated with one-year observations over the lidar site. The supercooled clouds are found to appear at 9.84% of all the cloudy time, and 11.99% of all the time for clouds at from 0℃ to − 40℃.

    Application of SOM Method in Summer Precipitation Patterns in Eastern China
    LUO Weimeng, QIAN Weihong, JIANG Ning, LEUNG Cheuk-Hin
    2018, 54(5):  970-982.  DOI: 10.13209/j.0479-8023.2018.047
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    Based on SOM (self-organizing maps) and EOF (empirical orthogonal function) methods, the dailymean and seasonal-mean summer precipitation patterns in Eastern China are analyzed and compared. Results show that the SOM method, compared with EOF, describes precipitation distributions more realistically. The spatial structures of summer precipitation patterns can be well explained by 850 hPa wind anomaly and 700 hPa specific humidity anomaly. As a posterior problem, 850 hPa height anomaly can well explain the corresponding precipitation area. However, as a prediction problem, due to other conditions such as moisture and temperature anomaly, the negative height anomaly in the numerical weather forecasting does not always indicate strong precipitation.

    Passive Source Reverse Time Migration Method to Image Discontinuity Beneath Irregular Free-Surface
    LIANG Zuokui, GE Zengxi
    2018, 54(5):  983-993.  DOI: 10.13209/j.0479-8023.2017.110
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    Because the most used finite difference method to calculate wave propagation cannot handle irregular boundaries easily, a hybrid boundary element and finite difference method is proposed. Firstly, the boundary element method is used to obtain the wavefileds along a horizontal boundary which is going to be the boundary condition of the finite difference method in the next stop. Then the finite difference method is applied to obtain the wavefields under the interface. The wavefields are separated to vector P-wave and S-wave constituents, and considering the coherence of P-wave and S-wave in a conversion point, the image condition of cross-correlation between P- and S-waves is applied to obtain discontinuity image underground. Synthetic tests show the effectiveness of the proposed method.

    A High Precision Automatic 3D Geological Modeling Method Based on ANSYS Workbench: A Case Study of Gas Hydraterelated Slipstream Submarine Slide
    LONG Songbo, HE Tao, LIANG Qianyong, LAN Kun, LIN Jinqing, DONG Yifei, HE Jian
    2018, 54(5):  994-1002.  DOI: 10.13209/j.0479-8023.2018.051
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    In the study of gas hydrate-related Slipstream submarine slide, the finite element analysis software ANSYS is used to construct the 3D model with complicated submarine slump topography acquired by multibeam sounding system. The lower part of sliding surface buried by slump accumulation is estimated from the main scarp geometry, and the original ground surface before slump is reconstructed according to the morphological similarity of surrounding ridges. Then, the high precision 3D geological model is automatically completed by running Jscript file in ANSYS Workbench, which greatly improves the efficiency of complex geometric modeling and thus provides a key guarantee for the accuracy of subsequent finite element numerical analysis. The stability simulation of Slipstream Ridge under its self-weight condition showes that the maximum shear stress in sediments above a shallow gas hydrate concentration layer at about 100 meters below seafloor is distributed as a series of high value bands in wedge shape, which matches well with the stepped topography observed on the current slump surface and verifies the accuracy of the 3D geological model and the validity of the proposed modeling method.

    Shallow Sea Deghosting with Pseudo Velocity Method
    CAO Luqing, HU Tianyue
    2018, 54(5):  1003-1009.  DOI: 10.13209/j.0479-8023.2018.028
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    Based on marine single-component seismic data acquired by conventional acquisition method, the vertical component of velocity (pseudo-Vz) at the same position is estimated. The pseudo-Vz is then combined with the single component of pressure data to get the aim of deghosting. By applying the sparsity constraint deconvolution method as an intermediate procedure, improvements of shallow sea single-component seismic data in resolution as well as in filling the frequency notches, which are caused by the interference of the up- and downgoing waves at the receivers are achieved. In addition, the energy of low-frequency signal is enhanced. The proposed method can be used for re-processing the existing single-component data through which can broaden the frequency bandwidth.

    Origin of Cherts during the Ediacaran-Cambrian Transition in Hunan and Guizhou Provinces, China: Evidences from REE and Ge/Si
    WEI Shuaichao, CHEN Qifei, FU Yong, CUI Tao, LIANG Houpeng, GE Zhihua, ZHANG Peng, ZHANG Yong
    2018, 54(5):  1010-1020.  DOI: 10.13209/j.0479-8023.2018.035
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    Two types of Liuchapo Formation cherts, bedded cherts and mounded cherts, were deposited in Bahuang section of Tongren in Guizhou Province and Ganziping section of Zhangjiajie in Hunan Province. The origin of the cherts was discussed by analyzing the characteristics of major, trace elements and REE compositions and Ge/Si ratios. It was revealed that the content of SiO2 in bedded cherts was range from 96.06% to 99.61%, and the content of SiO2 in mounded cherts was range from 98.62% to 99.56%, averaging 99.13%, and the contents of other chemical components were very low. Thus, two types of cherts are pure cherts. Moreover, the ΣREE of the bedded cherts in Bahuang section is ranged from 20.14 to 248.56 μg/g (averaging 100.62 μg/g), and no obvious abnormality in Eu/Eu* which is ranged from 0.90 to 1.10 (averaging 1.06), and the ratio of Ge/Si is 0.13−0.98 μmol/mol (averaging is 0.50 μmol/mol), indicating that the origin of bedded cherts affected terrigenous input. Whereas, the ΣREE of the mounded cherts in Ganziping district is ranged from 3.75 to 7.24 μg/g (averaging 5.73 μg/g), the ratio of Ce/Ce* is 0.46−0.66 (averaging 0.57) which shows a negative abnormal, Eu/Eu* is ranged from 2.28 to 11.07 (averaging 4.60) which shows a positive abnormal, and Ge/Si ratio is 1.09−1.43 μmol/mol, (averaging 1.25 μmol/mol) all of which reflect a hydrothermal origin of the mounded cherts. Otherwise, the relationship between Al2O3 and ΣREE in the bedded cherts has an excellent correlation, while in the mounded cherts has a poor correlation. It also illustrates that continental substance plays an important role in controlling the formation of bedded cherts, and the mounded cherts is originated from submarine volcanic or hydrothermal activity. The relationship between Al2O3 and Ge/Si also reflect the origin of cherts. Combined with the paleogeographic environment, it can conclude that the mounded cherts were deposited in syngenetic fault at the margin of the basin, originated from submarine hydrothermal activity, while the bedded cherts were deposit in the deep basin, mainly influenced by terrigenous input. What’s more, using 1 μmol/mol as the critical value of Ge/Si may provide a new way to trace the material sources of cherts.

    The Aeolian Bedforms and the Reconstruction of Late Holocene Wind Direction in Qaidam Basin
    WU Tongwen, LI Jianghai, YANG Menglian
    2018, 54(5):  1021-1027.  DOI: 10.13209/j.0479-8023.2018.042
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    Using remote sensing image for the aeolian morphology and high resolution ancient monsoon indicators, the authors restore how the wind blows in Qaidam Basin since late Holocene. The results show that the prevailing winds of the basin were northwest winds, at the same time there were a small amount of westerly and north wind, with the summer monsoon and westerly circulation having little effect on the wind models. The eastern dune and Yardang landforms of the basin recorded the westerly winds of the last glacial, but the landforms in the midwest indicated that the Asian winter monsoon developed from the northwest during late Holocene. The changes in the atmospheric circulation model took place around 4000 aBP years ago, which was an important node, basin climate shifting from warm and humid to cold and dry.

    Comprehensive Depositional System and Reservoir Characterization Study of Chang 4+5 Reservoir of Yanchang Group, Infill Well Region in Baiyushan Area, Ordos Basin
    LIU Yuyang, PAN Mao, LIU Shiqi, SHI Yongmin, DONG Yue, ZHANG Zhiqiang, WANG Ziyuan
    2018, 54(5):  1028-1038.  DOI: 10.13209/j.0479-8023.2018.045
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    The authors focus on the ultra-low permeability reservoirs of Chang 4+5 reservoir period of Yanchang Group, Jing’an oil field, Ordos Basin. Cores, thin sections, wireline logs, and imaging logs were used to understand depositional systems, reservoirs and to furtherly characterize vertical and horizontal distribution patterns of sandstones. The results show that main reservoirs of Chang 4+5 of Yanchang Group are composed of medium-tofine grained arkose. Parallel beddings and cross beddings are common. Interpartical pores and a few fractures are main reservoir spaces and reservoir quality is poor. Sand bodies are uniformly distributed in the horizontal direction with brand shape and thickness between 2 to 5 meters. Front delta is the main sedimentary subfacies. Distributary main channel, distributary shallow channel, distributary shoal, and inner distributary bay are four main sedimentary microfacies. In the vertical direction, distributary main channels and distributary shallow channels are distributed reciprocally related to the variation of hydrodynamic power. The research result is a guidance on the hydrocarbon exploration in this region.

    Influence of Two Quinolone Antibiotics on Mercury Methylation Bacteria of Geobacter sulphurreducens PCA
    TAO Huchun, MA Biao, DING Lingyun, WU Qingqing, GAO Yue
    2018, 54(5):  1039-1045.  DOI: 10.13209/j.0479-8023.2018.016
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    Using one kind of main mercury methylation iron reducing bacteria of Geobacter sulphurreducens PCA strains as targeting bacteria, two kinds of quinolones ciprofloxacin and ofloxacin were chosen to study the influence of antibiotics on PCA strains and its ability to methylate mercury in combined pollution. The experiment results showed that a promoting effect of antibiotics on growth PCA was found under the low concentration. Through the detection of the concentration of antibiotic and the figure of ESI scan, it was found that Geobacter sulphurreducens PCA could metabolize ofloxacin, but ciprofloxacin could not be degraded by Geobacter sulphurreducens PCA. Methylation of mercury was promoted by the presence of two kinds of antibiotics, the methyl-mercury conversion rate of ofloxacin to Geobacter sulphurreducens PCA was 4.21 times higher than that of the control group, ciprofloxacin was 2.27 times, and the addition of two mixed kinds of antibiotics was nearly 2 times respectively. In the mixed solution, there is no superimposed effect of methyl-mercury.

    Research on Adsorption of Nitrate and Phosphate from Aqueous Solution by Covalently Bounded Quaternary Ammonium Activated Carbon
    YANG Yaxin, WANG Hong, ZHAO Huazhang
    2018, 54(5):  1046-1052.  DOI: 10.13209/j.0479-8023.2018.039
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    A novel adsorbent of covalently bounded quaternary ammonium activated carbon (CQA) was prepared by silylation reaction with both organosilicon quaternary ammonium salt (QA) and activated carbon (AC) as raw materials. The CQA was characterized by FTIR, SEM and BET. The results showed that QA was successfully loaded on the surface of AC by covalent binding, and had an important influence on the morphology and structure of AC. The nitrate and phosphate adsorption capacities for CQA were greatly improved. The adsorption behaviors of nitrate and phosphate from aqueous solutions on CQA were investigated using batch experiments. The kinetics study revealed that adsorption of nitrate and phosphate onto CQA followed the pseudo-second-order kinetic model, indicating that the adsorption process was mainly controlled by the chemisorptions. The adsorption data fitted Langmuir and Freundlich isotherm models well, and the maximum nitrate and phosphate adsorption capacities for CQA were 14.829 and 8.442 mg/g, respectively. The effects of pH on the adsorption of nitrate and phosphate were also investigated. The results showed that when pH was from 4 to 9, it was suitable for simultaneous removal of nitrate and phosphate from aqueous solution by CQA.

    Hydrology Effect Evaluation of Green Infrastructure Based on HSPF: A Case Study on Dalang River Basin
    XING Yinghua, CHENG Xiang, QIN Huapeng, ZHAO Zhijie
    2018, 54(5):  1053-1059.  DOI: 10.13209/j.0479-8023.2018.019
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    Taking Dalang River Basin, Shenzhen city of Guangdong Province as an example, HSPF model was used to simulate hydrological effects of rainfall runoff under different scenarios. The results showed that runoff rate of the efficacy maximization, economical and moderate scenario were decreased by 34.9%, 14.2% and 28.5% than that in background scenario. The peak value of these three scenarios were lower 40.5%, 19.8% and 33.0% than that in background scenario. Base flow of these three scenarios were higher 88.9%, 11.1% and 44.4% than that in background scenario. The economical scenario didn’t reach good effect. The effect of moderate scenario was better than economical scenario and inferior to efficacy maximization scenario.

    Fast Determination of Multiple Antibiotics in Mussels Based on Extraction and UPLC-MS/MS
    XU Yaru, LI Jie, WANG Zhifen, GAO Yue, XU Nan
    2018, 54(5):  1060-1066.  DOI: 10.13209/j.0479-8023.2018.009
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    A fast and simple method for simultaneous determination of fifteen antibiotics (sulfadiazine, ciprofloxacin, penicillin, spechromycin and roxithromycin) in mussels using ultrasound extraction, solid phase extraction purification and ultra performance liquid chromatography-tandem mass spectrometric was established. The mussel samples were extracted by ultrasonic extraction, followed by solid-phase extraction (SPE) as the cleanup procedure. Ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS) was used for identification and quantification of antibiotics. The performance of two kinds of SPE cartridges, Oasis HLB and Oasis PRiME HLB, was compared, with the latter showing better results. Recoveries ranged from 64% to 121% at spiking levels of 50 ng/g, with RSD being 0.5%–19%, and from 67% to 117% at spiking levels of 100 ng/g, with RSD being 1%–9%. Limits of detection (LODs) ranged from 0.004 to 0.5 ng/g (dry weight) and limits of quantification (LOQs) ranged from 0.013 to 1.67 ng/g (dry weight). The recoveries were reasonable and the detection limit was low. Finally, the method was successfully applied to the determination of the target antibiotics in mussel samples (Hyriopsis cumingii) collected from Poyang Lake. 9 out of 15 selected antibiotics were detected in the collected mussel tissues. The concentration and detection frequency of trimethoprim in mussels were the highest. The concentration of trimethoprim was 78.8 ng/g, followed by spectinmycin (41.2 ng/g) and ciprofloxacin (39.8 ng/g).

    Comparative Study on Macroinvertebrate Communities in Confluence Areas from Typical Tributaries to Mainstream of the Yellow River
    XIE Yuan, JIANG Xiaohui, WANG Ting, XU Xuming, NI Jinren
    2018, 54(5):  1067-1076.  DOI: 10.13209/j.0479-8023.2018.014
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    The benthic macroinvertebrate communities in the confluence areas from tributaries to mainstream could play an important role in understanding interactions between materials flows from rivers and their ecological consequences. Based on monitoring on conducted in the four typical tributaries (Huangshui River, Fenhe River, Weihe River and Luohe River) to the Yellow River during spring and autumn in 2015, the characteristics of macroinvertebrate communities are systematically compared. As results, sorted by the number of macroinvertebrate species in both seasons for all confluences, Luohe River (28)>Huangshui River (26)>Fenhe River (23)>Weihe River (17). Moreover, the collecter-gather becomes dominant functional feeding group in both seasons for all confluences except scraper dominated in autumn in Luohe River. Detrended Correspondence Analysis (DCA) reveals that substrate is of significance in structuring benthic macroinvertebrate communities. The survival of aquatic plants seems more favorable to survival of benthic macroinvertebrate. Furthermore, Redundancy Analysis (RDA) suggests that benthic macroinvertebrate communities are mainly influenced by pH and conductivity. The present study provides new information on species composition, density, biomass, functional feeding group of benthic macroinvertebrate communities, and the relationship between macroinvertebrate communities and habitat factors, which would be of particular use to deeper understand the aquatic organism in the Yellow River receiving tributaries, which are interfered to various degree by human activities.

    Occurrence of Antibiotics in Water, Sediments and Seafood in Aquaculture Area of the Pearl River Estuary
    HAO Hongshan, XU Yaru, GAO Yue, WANG Zhifen, LI Jie, XU Nan
    2018, 54(5):  1077-1084.  DOI: 10.13209/j.0479-8023.2018.018
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    The occurrence of 22 antibiotics in water samples, sediments, fish and shellfish in aquaculture area of the Pearl River Estuary (Zhuhai and Daya Bay) was studied, using ultrasonic extraction combined with ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The main pollutants detected in aquaculture area of the Pearl River Estuary are quinolones such as norfloxacin, ofloxacin, ciprofloxacin and flumequine. Higher Σantibiotics were observed in Zhuhai Bay in water and sediments compared with Daya Bay. The concentrations of antibiotics in water samples, ranging from 0.13 (sulfamethoxazole) to 4.68 (spectinomycin) ng/L on average, were strongly affected by precipitation. The concentrations of antibiotics in sediments, ranging from 0.02 (isochlortetracycline) to 8.77 (spectinomycin) ng/g (dry weight) on average, accumulated over time. The concentrations of antibiotics in seafood ranged from 0.06 (sulfamerazine) to 46.75 (norfloxacin) ng/g (dry weight). The concentration levels of antibiotics in shellfish and fish were similar and did not show any significant difference. The correlation analysis showed that the concentration levels of antibiotics among sediments were the same; for most seafood, it was same; and for water samples, the difference was great.

    Spatial Analysis of Reverse Logistics for Waste Mobile Phone Based on Extended Producer Responsibility
    HUANG Huiting, WANG Tao, TONG Xin
    2018, 54(5):  1085-1094.  DOI: 10.13209/j.0479-8023.2018.040
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    This paper takes mobile phone as an example to analyze the innovation of WEEE takeback system in Guangdong. With interviews on various enterprises at different stage along the recycling chain, three models of waste mobile phone collection were identified. Spatial analysis was conducted on the cost of reverse logistics under each model for waste mobile phone collection in Guangdong. The results show that Guangdong will have 16.62 million wasted mobile phones in 2020. The cost of collection for environmental recycling by the municipal waste transportation system is much cheaper than the cost of collection directly by producers. While considering the net profit of internet collection for second-hand sales, the internet collection is more profitable. In conclusion, it is suggested that the producer could integrate the different collection system into their reverse logistic system under the principle of EPR, using the profits from second market sales through internet to cover the cost of environmental recycling.

    Exploring Recovery Time of Eutrophic Lakes with a Minimal Phosphorus Recycling Model
    WU Sifeng, LIANG Zhongyao, LIU Yong
    2018, 54(5):  1095-1102.  DOI: 10.13209/j.0479-8023.2018.043
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    To investigate the nonlinearity between recovery time of eutrophic lakes and the intensity of external load reduction, as well as the factors that could modify this time span, a quantitative analysis was conducted by model simulation. The authors employed a widely-applied phosphorous recycling model, and calculated the recovery time of a eutrophic lake to revert to clear state under different reduction rate. The parameters were set to different values to uncover how different attributes of the lake ecosystem could influence the recovery time. The model results showed that, there was a significant nonlinear relationship between load reduction and recovery time. When the external load reduced to slightly below the threshold, the recovery time would be longer than 40 years. Increasing reduction rate would result in significant decrease in recovery time, while its marginal effect became less significant. Lake type and morphology has significant influence on recovery time. Under the same reduction rate, recovery time of deeper lakes in colder regions is shorter; high sediment release rate requires longer recovery time; and longer hydraulic retention time leads to longer recovery time. Therefore, ecological remediation to reduce sediment release, or improve the hydro-dynamic conditions, may be effective. Moreover, this would both lower the threshold for clear phase, which lead to lower load reduction, and also shorten the recovery time, which made the remediation much easier.

    Risk Assessment of Exposure to PM2.5 in Beijing Using Multi-Source Data
    ZHANG Xiya, HU Haibo
    2018, 54(5):  1103-1113.  DOI: 10.13209/j.0479-8023.2018.031
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    Through GIS spatial analysis, this study firstly conducts spatial distribution of PM2.5 concentrations using PM2.5 data from 35 automatic air quality monitoring stations in Beijing during the period of 2014–2016. Then population spatial processing is carried out based on DMSP/OLS nighttime light data. On this basis, the authors assess the exposure risk to PM2.5 pollution in Beijing from four aspects: PM2.5 concentration, the characteristic of population exposure, the population exposure intensity, and the population weighted concentration. The results show that 1) high PM2.5 concentrations were mainly distributed in the south, while low concentrations were distributed in the north. There was a good spatial coincidence between the distribution of population exposure to PM2.5 and population distribution, i.e. the densely populated area had high risk of population exposure to PM2.5. 2) During 2014–2016, 100% of population exposed to high PM2.5 yearly mean concentrations (>35 μg/m3) which exceeded the secondary level of Ambient Air Quality Standards (GB 3095–2012), and the ratio of population exposed to 24 hourly mean concentrations (>75 μg/m3) declined over a 3-year period. The share of population exposure to exceeding standard PM2.5 concentration was much higher than those in global average level. 3) The population weighted PM2.5 yearly average concentrations and PM2.5 yearly average concentrations had difference, which is related with exposed population and the distribution of PM2.5 pollution. 4) The distributions of PM2.5 concentration and population are different, so the real impact level on health of human of PM2.5 pollution is different from PM2.5 concentration. Thus, taking the factor of population into account, the risk assessment of exposure to PM2.5 pollution is more accurate.

    Spatial Characteristics of Retail Stores in Multiple-Size of Cities in the Central Region of China
    CAI Ailing, WANG Jun, LI Jingxian, DU Yihang
    2018, 54(5):  1114-1122.  DOI: 10.13209/j.0479-8023.2018.024
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    Three cities (Wuhan, Xiangyang, and Yidu) were selected as samples of three typical sizes of cities (large, medium, and small) in China to study the spatial layout of retail stores. The authors analyzed the spatial characteristics of different types of retail stores and the influential factors of their spatial distributions using tools of spatial statistics, based on big data of retail stores from the Baidu map. The results show that the spatial distribution of retail stores in the large city of Wuhan shows the characteristics of multi-center and multi-layer, while Xiangyang, the medium-sized city, shows a single center layout, and Yidu, the small city, shows dispersed layout. The agglomeration levels of different types of retail stores show a sequence: integrated retail store > professional retail store > supermarket > special retail store. Population size, transportation accessibility, types of retailing, and green-space accessibility are the main factors which affect the spatial distributions of retail stores. The results can provide the scientific basis for spatial planning and optimization of retail stores in multiple sizes of cities.

    Harmonious Personality, Social Support, Self-Control and Work-Family Conflict: Comparison of Three Models Based on Occupational Groups
    CHEN Yidi, GAN Yiqun
    2018, 54(5):  1123-1132.  DOI: 10.13209/j.0479-8023.2018.049
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    In order to examine the relationship among harmony, social support, self-control, and work-family conflict, three models were proposed on the basis of relevant theories: simple mediation model, complex mediation model with self-control as the mediating variable, and complex mediation model with social support and selfcontrol as mediation variables. The simple mediation model refers to the harmonious personality, social support indirectly predict the work-family conflict in parallel through self-control; complex mediation model with selfcontrol as mediation variable refers to harmony personality and social support predict work-family conflict through self-control; complex mediation model with social support and self-control as mediation variables refers to harmony personality predict work-family conflict through social support and self-control. The social support scale, self-control scale (SCS), impulsive scale (BIS), work-family conflict were administered to 200 employees from medical industry, financial industry and sales industry in Beijing. Model comparison of the three models using Structural Equation Modeling indicated that complex mediation model with self-control as mediation variable fit best to the data. Harmony personality acted as the predictive variable, self-control as the mediator, and work-family conflict as the outcome variable. In the complex mediation model, self-control was estimated as -0.043, with 95% confidence interval of mediation [-0.071, -0.022]. Self-control mediated the relationship of harmony personality, social support and work-family conflict, the compound mediation model that takes self-control as the mediating variable fits best.

    Transmission Mediums Based Ecosystem Services Classification System
    WU Shuyao, LI Shuangcheng
    2018, 54(5):  1133-1136.  DOI: 10.13209/j.0479-8023.2018.041
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    After reviewing some current common ecosystem service classification systems, it is found that current classification systems were not able to reflect the fact of different ecosystem types often produce different services due to their unique components, structures and environments. The authors used ecosystem components to create a new ecosystem service classification system based on transmission medium. Ecosystem services are classified into water-transmitted, rock and soil-transmitted, air-transmitted, organism-transmitted and whole ecosystemtransmitted services. Some water-transmitted services include water yield, water purifying, water regulation etc.; rock and soil-transmitted services include soil retention, soil formation, geologic hazard prevention etc.; airtransmitted services include carbon sequestration, air purifying, climate regulation etc.; organism-transmitted services include food production, pollination, pest bio-control etc.; last but not least, whole ecosystem-transmitted services include aesthetic information, recreation, education etc. The proposed classification system may help differentiating services provided by different ecosystem types and identifying some common services provided by the same ecosystem type.