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Environmental Factors Influencing Women’s Safety Perception in Non-commercial Alleys in Urban Villages: A Case Study of Pingshan Village, Shenzhen
WANG Junjing, HAN Xili
Acta Scientiarum Naturalium Universitatis Pekinensis    2022, 58 (4): 655-663.   DOI: 10.13209/j.0479-8023.2022.038
Abstract476)   HTML    PDF(pc) (11076KB)(193)       Save
Taking non-commercial alleys in Pingshan Village, Nanshan District, Shenzhen as an example, this study identified and extracted 5 categories of 32 environmental factors that have negative effects on women’s safety perception, then ranked and discussed the environmental factors that have significant negative effects, and explored whether women’s socio-demographic variables would lead to differences in safety perception. The results showed that the social environment factors in the alley were more likely to make women feel uneasy than the physical environment factors. Negative special groups and animal activities were the most important factors causing women’s uneasiness, followed by the lack of maintenance of the vertical features of the alleys, such as falling objects and chaotic electrical facilities. In addition, there are significant differences in women’s safety perception among different social backgrounds, that is, educated women, knowing about negative reports in urban villages, and young women are more likely to feel insecure.
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Estimation of Area of Completed Houses Based on Statistical Yearbooks and Online Big Data
YUAN Wen, WANG Jun, SHEN Hongyi, WANG Xinmin
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (5): 804-814.   DOI: 10.13209/j.0479-8023.2021.020
Abstract773)   HTML    PDF       Save
The authors select several indicators in the Beijing Yearbook to construct an economic and social factor system, and uses partial least squares regression, LASSO regression and RBF neural network models to predict the area of completed buildings in Beijing in 2017 and 2018. However, considering the difference of statistical channels and granularity of the yearbook indicators, and the delay in the release of some indicator data for the construction industry in 2019, it is hard to estimate the area of the year by model fitting. Therefore, crawler technology is used to obtain high-quality data and dig deep to obtain information of online big data to estimate the completed area. Firstly, a web-based building data acquisition framework is established, to crawl the attribute data of eight types of buildings in Beijing by calling service interface, keyword search and other technologies. Secondly, regular expressions and conditional filtering are used to extract and clean the HTML data returned by web pages. Finally, the area of completed houses in Beijing and the area of each functional partition in 2019 are estimated.
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Study on Characteristics of Virtual Water Flow Spatial Change and Influencing Factors in China
DU Yihang, WANG Jun, LU Shunzi, LI Jingxian, CAI Ailing
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (6): 1141-1151.   DOI: 10.13209/j.0479-8023.2019.117
Abstract1447)   HTML    PDF(pc) (2675KB)(351)       Save
Population migration and aggregation of industrial factories in the process of urbanization in China has further increased water demand in the relatively developed areas of China. The existing water transfer projects couldn’t meet the increasing demand for water resources in water-scarce areas. The calculation of virtual water based on the input-output analysis and the implementation of reasonable virtual water transfer have become new approaches to relax the demanding pressure on regional water resources. This analysis used the regional inputoutput tables of the years 1997 and 2010 and the water resources bulletins of China to build a multi-regional inputoutput calculation model of virtual water and calculate the exchange relationships and transfer volumes among virtual waters of different industries in detail. This study also analyzed the association of regional virtual water flows with inter-regional population migration and geographic transfers of industries. The results showed that there were highly correlated relationships between the characteristics of regional population migration and virtual water spatial transfer in the context of urbanization in China. The geographic transfers of industries continue to affect the volume and direction of virtual water flows. In the future, researchers should consider the relationship between physical water transfers, virtual water flows, population migration and geographic transfers of industries in the context of urbanization to ensure the supply of water resources in China.
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Spatial Characteristics of Retail Stores in Multiple-Size of Cities in the Central Region of China
CAI Ailing, WANG Jun, LI Jingxian, DU Yihang
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (5): 1114-1122.   DOI: 10.13209/j.0479-8023.2018.024
Abstract739)   HTML    PDF(pc) (4141KB)(285)       Save

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.

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Object-Oriented Precise Decision-Making (OOPD) for Water Quality Improvementin Lake Yilong
ZOU Rui, SU Han, YU Yanhong, WANG Junsong, YE Rui, LIU Yong
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (2): 426-434.   DOI: 10.13209/j.0479-8023.2017.164
Abstract997)   HTML2)    PDF(pc) (2337KB)(451)       Save

A framework called Object-Oriented Precise Decision-making (OOPD) was proposed which oriented to the lake itself. The framework was based on Numerical Source Apportionment powered by 3-dimensional water quality model, which then quantified the causality of water quality improvement and load reduction. The proposed framework was applied to support short-term decision making of Lake Yilong, a eutrophic lake. Results showed that Chenghe sub-watershed and Chengbeihe sub-watershed were important pollution source no matter considering which monitoring station and under which water diversion scenario. In addition, comprehensive pollution control should be considered to ensure that Huzhong monitoring station or Hudong monitoring station meet water quality standards. However, considerable load reduction cannot guarantee water quality if there was no water diversion. Water quality of three monitoring stations would be improved a lot under 20 and 30 million m³ annual water diversion scenario. Finally, based on the analyses above, suggestion of focused pollution control project was given for each sub-watershed and an evaluation of one bean product wastewater treatment extension project was given to illustrate how to combine micro and macro aspects in OOPD.

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On-road Transportation Carbon Emission Characteristics of Main Roads and Low-Carbon Transportation Development Scenarios in Shenzhen, China
XU Ye, WANG Jun, LIU Shuangshuang, ZENG Hui, HUANG Lian
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (1): 146-156.   DOI: 10.13209/j.0479-8023.2017.136
Abstract1502)   HTML12)    PDF(pc) (3588KB)(357)       Save

Using the international vehicle emission (IVE) model and on-road vehicle monitoring data, the carbon emission factors of three main types of vehicles in Shenzhen were calculated. Then, the authors estimated carbon emission intensities of several main roads and analyzed the spatial-temporal characteristics of transportation carbon emissions in Shenzhen. Finally, scenario analysis was used to quantitatively compare three kinds of low-carbon transport development strategies. The results showed that the transportation carbon emissions of the investigated roads were highly spatially heterogeneous, and the intensities of transportation carbon emissions in urban centers and the roads linking urban centers were higher than other roads. The transportation carbon emissions of the investigated roads had apparent daily cycle, and they had four main types: single-peak curve, double-peak curve, fluctuation curve, and stable curve. The transportation carbon emissions were high in morning and evening commuting hours during workdays. The comparative analyses of three low-carbon transportation development scenarios indicated that the mild-constraint carbon mitigation scenario could better meet the targets of socioeconomic development and transportation development of Shenzhen.

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Approaches of Buildings Carbon Mitigation Based on Spatial-Temporal Characteristics of Civil Building Energy Consumption: A Case Study on Shenzhen, China
LIU Shuangshuang, WANG Jun, XU Ye, ZENG Hui
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (1): 125-136.   DOI: 10.13209/j.0479-8023.2017.129
Abstract957)   HTML11)    PDF(pc) (3070KB)(535)       Save

The DeST model is used to simulate the energy consumption of typical civil buildings in Shenzhen, and the temporal and spatial characteristics of energy consumption of various types of buildings are summarized. The results show that different civil buildings in Shenzhen have different energy consumption characteristics in space and time. Residential buildings with low energy consumption per unit area are most widely distributed, and commercial buildings with limited numbers have the largest volume and high energy intensity, so the total consumption can not be ignored. Meanwhile, office buildings, most sensitive to the parameters change, have great energy saving potential. Combined with the development plan of Shenzhen 13th Five-Year Plan, suggestions on the strategy of building carbon reduction in Shenzhen can be summarized as follows: 1) building a comprehensive smart city, creating an exhaustive monitoring network for measuring energy consumption of various types of buildings, managing energy consumption behavior more scientifically; 2) constructing green buildings in an allround way, implementing green building standards when constructing new buildings, and valuing the reconstruction of old buildings as well, taking appropriate measures (for instants, taking part of the transformation, demolishing and reconstructing, optimizing the room combination and improving energy efficiency) when reconstructing according to the different energy consumption characteristics of the different types of buildings.

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An Analytical Model of Gate-All-Around Nanowire Tunnel FET
HE Yuan,WANG Juncheng,WEI Kangliang,LIU Xiaoyan
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract806)      PDF(pc) (562KB)(839)       Save
An analytical model for gate-all-around (GAA) nanowire tunnel FETs (TFET) is proposed. It proves that the TFETs have good performance in sub-threshold region. Research shows that the sub-threshold slop of GAA nanowire TFET is proportional to several model parameters, such as the diameter, the thickness of oxide layer, and the voltage of drain. The model and simulation would lay a good foundation for its future application in low-power circuits.
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Investigation of Heavy Metals Pollution in Predominant Plants around a Municipal Solid Waste Incineration Plant: A Case Study in Shenzhen Qingshuihe MSWI Plant
ZHONG Xiuping,WANG Junjian,ZHAO Hongwei,LIU Yangsheng,ZENG Hui
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract850)            Save
To investigate heavy metals (HMs) pollution in the different kinds of plants including trees, shrubs and herbs resulting from municipal solid waste incineration (MSWI), leaf samples in 34 species of 22 families around the Shenzhen Qingshuihe MSWI plant were collected. The levels and bioaccumulation factors of mercury (Hg), chromium (Cr), cadmium (Cd) and lead (Pb) in the leaves were determined. Results show that, these plants were polluted by HMs and the characteristics of pollution were different among trees, shrubs and herbs. Trees were mainly polluted by Cr, while shrubs and herbs by Hg. Significant differences ( Pt ≤ 0. 028) were observed in concentrations and bioaccumulation factors between trees and shrubs, and also between trees and herbs. The potential species for different HM pollution remediation are recommended as follows: 1) for Hg, the tree plants of Acacia auriculif ormis and Eucalyptus citriodora; 2) for Cr, the herb of Miscanthus floridulus and the shrub of Bougainvillea spectabilis; 3) for Cd, the shrub of Ilex asprella and tree of Acronychiapedunculata; and 4) for Pb, the herbs of Oxalis corniculata and Dicranopteris dichotoma. Consequently, building a multi-level botanical structure consisting of trees, shrubs and herbs is helpful to phytoremediate the pollution of heavy metals.
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Fabrication of Hydrophobic PVDF Hollow Fiber Membranes for Desalination of Brackish Water through Membrane Distillation
HOU Deyin,WANG Jun,WANG Baoqiang,SUN Xiangcheng,LUAN Zhaokun,REN Xiaojing
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract687)            Save
The mixture of inorganic salt LiCl and soluble polymer polyethylene glycol (PEG) as non-solvent additive was introduced to fabricate hydrophobic polyvinylidene fluoride ( PVDF) hollow fiber membrane by phase inversion process. The membrane exhibited high rejection of inorganic salt solutes and a maximum permeate flux 40. 5kg/ (m2?h) was obtained. During direct contact membrane distillation (DCMD) process, the precipitation of CaCO3 would be formed and clog the hollow fiber inlets with gradual concentration of the feed when natural brackish water was used directly as feed solution, which resulted in a rapid decline of membrane module efficiency. The negative influence of scale deposits could be eliminated by acidification of the feed. The DCMD desalination experiment of acidified brackish water showes that the PVDF membrane had stable permeate flux and the conductivity of the obtained distillate remained below 10 μS/ cm during the whole process.
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Analysis and Simulation of Cultivated Land Conversion and Distribution in Beijing Mountainous Areas Based on GIS and Logistic Regression Model
ZENG Lingyun,WANG Jun,WANG Hongya
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract655)            Save
Taking Beijing mountainous areas as a study case, this paper analyzes and simulates the cultivated land change between 1996 and 2004 using ARCGIS and Logistic regression model with the data of land use map, DEM, population, GDP, and so on. The results show that: 1) during the year of 1996-2004, one third of cultivated land lost and mainly transited to built-up land and forest land; 2) by spatial Logistic regression, sople, elevation, GDP density, population density, and distance to the nearest road were the most influential factors in controling cultivated land distribution in the Beijing mountainous areas; 3) the total correction percentage of the results simulated by the spatial Logistic regression model was 78%, the correction percentage of cultivated land was 70%, and the non-cultivated land was 79%.
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Study on Net Primary Production Variations in the Central Part of Inner-Mongolia during 1981-2000
WANG Jun,MENG Jijun
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract692)            Save
Based on AVHRR GLOPEM NPP dataset and climate data in the corresponding period, the authors analyzed the situation of the net primary production degradation in the central part of Inner-Mongolia and its correlation relationship with climate change during 1981-2000. The results show that: 1) from the eastern to the western part, the spatial distribution of net primary production had a descending tendency, and the inter-annual variation of net primary production in the whole area was apparent, especially during 1990-2000, and the variation rate could be due to 10.32gC/m2?a; 2) the inter-annual variation of net primary production had apparent spatial differentiation; 3) correlation coefficients between inter-annual variation of net primary production and inter-annual variations of climate factors had apparent spatial differentiations; 4) various vegetation types had various responses to climate change, and the inter-annual variation of precipitation had more significant impact on vegetation dynamics than the inter-annual variation of temperature in the study area. This study displays the situation of the net primary production degradation in the central part of Inner-Mongolia and the correlation ralationship between climate change and the net primary production degradation. Moreover, it will provide scientific references for the restoration and reconstruction of the degraded vegetation.
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Enhanced Tunneling Magnetoresistance in Fe3O4 Nanopowder Compact Coated with SiO2
SONG Pengyun,WANG JunfengYAN Huijuan
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract580)            Save
Fe3O4 is considered to be half metal nature and has a comparatively high Curie temperature of 858 K compared with other metal oxides, which makes it more attractive in spin, electronic application. The extrinsic magnetoresistance of Fe3O4 has been studied extensively, however, so far few progress is acheieved. Here, a new way is given to obtain higher MR. Fe3O4 nanospheres with the average diameter of about 200 nm is prepared and coated by SiO2, which forms a shell of several nms. The nanopowder with SiO2 shells, which serves as grain boundaries, is pressed and then sintered into compacts, which show enhanced MR. At different temperatures MR curves of compacts with SiO2 and without SiO2 differ much, and the former display a linear respond at high field range, which is interpreted as the existance of insulating SiO2 grain boundaries.
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Characteristics and Tendencies of Climate Change in the Southwestern Karst Region of China in the Recent 45 Years
WANG Jun,MENG Jijun
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract885)            Save
Climate change has seasonal and regional characteristics. Many researchers have paid more attention to regional climate change in China. This paper analyzes characteristics and tendencies of climate change in the southwestern karst region of China in the recent 45 years (1960—2004) using wavelet analysis, artificial neural network and GIS spatial interpolation analysis, and so on. The results show that this regional climate change demonstrates significant periodic variations. The principal period of temperature variations is about 7 years, and the principal period of rainfall variations is about 25 years. It also has obvious seasonal characteristics and regional variations. By calculating seasonal temperature and rainfall variation rates with spatial interpolation, regional distributions of seasonal temperature and rainfall variations are obtained. Temperature and rainfall variations during the past 45 years are classified by means of SOFM network. Spatial distributions of the temperature and rainfall variations are obtained using spatial interpolation analysis. Finally, climate tendency is predicted with the RBFN model. Results show that variations of temperature and rainfall are both in a relatively low value period during 2005—2010.
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Research Progress of Horizontal Gene Transfer Applied in Pollution Treatment
LIU Jiangjiang,CHEN Lüjun,WEN Donghui,WANG Jun
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract758)            Save
As the rapid development of economy, the environmental problem of the toxic refractory pollutants has been increasingly serious. By now, biological treatment is the most frequently used method, in which bioaugmentation is the best technology to cope with the refractory pollutants. However, its efficiency is not reliable. Some foreign researchers found that certain genetic elements could automatically transfer or exchange between different microbe individuals, which they called as horizontal gene transfer. In this way, the transfer of degradative gene from the donor to the indigenous microbes could increase the number of adaptable microbes greatly in the polluted site, therefore the degradation of the pollutants were strengthened. Those findings inspired a new thought for alternating the traditional bioaugmentation to solve the serious pollution caused by refractory pollutants. This paper describes the concept of horizontal gene transfer, introduces the research progress applied in the pollution treatment, and also discusses its prospect in the treatment of the toxic refractory pollutants.
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