Temporal Variability of the Bioaerosol Background at a Subway Station: Concentration Level, Size Distribution, and Diversity of Airborne Bacteria

ABSTRACTNaturally occurring bioaerosol environments may present a challenge to biological detection-identification-monitoring (BIODIM) systems aiming at rapid and reliable warning of bioterrorism incidents. One way to improve the operational performance of BIODIM systems is to increase our understanding of relevant bioaerosol backgrounds. Subway stations are enclosed public environments which may be regarded as potential bioterrorism targets. This study provides novel information concerning the temporal variability of the concentration level, size distribution, and diversity of airborne bacteria in a Norwegian subway station. Three different air samplers were used during a 72-h sampling campaign in February 2011. The results suggested that the airborne bacterial environment was stable between days and seasons, while the intraday variability was found to be substantial, although often following a consistent diurnal pattern. The bacterial levels ranged from not detected to 103CFU m−3and generally showed increased levels during the daytime compared to the nighttime levels, as well as during rush hours compared to non-rush hours. The airborne bacterial levels showed rapid temporal variation (up to 270-fold) on some occasions, both consistent and inconsistent with the diurnal profile. Airborne bacterium-containing particles were distributed between different sizes for particles of >1.1 μm, although ∼50% were between 1.1 and 3.3 μm. Anthropogenic activities (mainly passengers) were demonstrated as major sources of airborne bacteria and predominantly contributed 1.1- to 3.3-μm bacterium-containing particles. Our findings contribute to the development of realistic testing and evaluation schemes for BIODIM equipment by providing information that may be used to simulate operational bioaerosol backgrounds during controlled aerosol chamber-based challenge tests with biological threat agents.

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Characterization of Airborne Bacteria at an Underground Subway Station

Applied and Environmental Microbiology ◽

10.1128/aem.07212-11 ◽

2012 ◽

Vol 78 (6) ◽

pp. 1917-1929 ◽

Cited By ~ 48

Author(s):

Marius Dybwad ◽

Per Einar Granum ◽

Per Bruheim ◽

Janet Martha Blatny

Keyword(s):

Real Life ◽

Performance Criteria ◽

Anthropogenic Sources ◽

Subway Station ◽

Airborne Bacteria ◽

Surveillance Systems ◽

Operational Environment ◽

Biological Detection ◽

Content Type ◽

Subway Stations

ABSTRACTThe reliable detection of airborne biological threat agents depends on several factors, including the performance criteria of the detector and its operational environment. One step in improving the detector's performance is to increase our knowledge of the biological aerosol background in potential operational environments. Subway stations are enclosed public environments, which may be regarded as potential targets for incidents involving biological threat agents. In this study, the airborne bacterial community at a subway station in Norway was characterized (concentration level, diversity, and virulence- and survival-associated properties). In addition, a SASS 3100 high-volume air sampler and a matrix-assisted laser desorption ionization–time of flight mass spectrometry-based isolate screening procedure was used for these studies. The daytime level of airborne bacteria at the station was higher than the nighttime and outdoor levels, and the relative bacterial spore number was higher in outdoor air than at the station. The bacterial content, particle concentration, and size distribution were stable within each environment throughout the study (May to September 2010). The majority of the airborne bacteria belonged to the generaBacillus,Micrococcus, andStaphylococcus, but a total of 37 different genera were identified in the air. These results suggest that anthropogenic sources are major contributors to airborne bacteria at subway stations and that such airborne communities could harbor virulence- and survival-associated properties of potential relevance for biological detection and surveillance, as well as for public health. Our findings also contribute to the development of realistic testing and evaluation schemes for biological detection/surveillance systems by providing information that can be used to mimic real-life operational airborne environments in controlled aerosol test chambers.

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Influence of Ground Structure on the Seismic Response of Underground Subway Station in Soft Site

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.368-373.2769 ◽

2011 ◽

Vol 368-373 ◽

pp. 2769-2775 ◽

Cited By ~ 1

Author(s):

Hui Long ◽

Guo Xing Chen ◽

Hai Yang Zhuang

Keyword(s):

Seismic Response ◽

Underground Structure ◽

Outer Part ◽

Subway Station ◽

Analysis Model ◽

Ground Structure ◽

Element Analysis ◽

High Rise ◽

Underground Subway Station ◽

Subway Stations

This paper selected representative soft site along the subway lines and created two-dimensional overall finite element analysis model about nonlinear dynamic interaction among soil, underground subway station, and ground structure based on Nanjing underground subway station. It explored the seismic response influence of neighboring high-rise structure on the two-layer and three-span island-type underground subway stations. The results showed that the structure near the subway station had a significant constraint effect on the deformation of subway station which is oriented to the structure, and the influence of deformation of subway station which is backward to the structure is related to vibration characteristics of the soil-underground structure interaction system. The influence of neighboring ground structure on the strain stress response of subway station is useful in most part of important nodes. However, this influence is disadvantageous in the outer part of connections of side walls and plates and middle plate-interior column connections.

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Adaptability Analysis of Service Facilities in Transfer Subway Stations

Mathematical Problems in Engineering ◽

10.1155/2012/701852 ◽

2012 ◽

Vol 2012 ◽

pp. 1-12 ◽

Cited By ~ 3

Author(s):

Liya Yao ◽

Lishan Sun ◽

Wuhong Wang ◽

Hui Xiong

Keyword(s):

Flow Characteristics ◽

Transportation Systems ◽

Subway Station ◽

Security Level ◽

Service Capability ◽

Subway Stations ◽

Pedestrian Transportation ◽

Planning And Construction ◽

Facility Size ◽

Operation Status

Service capability and matching degree of transfer facilities are directly related to the operational efficiency and safety of a subway station. Owing to differences in planning and construction, the transfer subway stations in developing countries have some defects in facility size and serviceability, which cause a decline in service performance, operation efficiency, and security level. In order to solve the problems, traffic investigations were conducted on the form, size, and operation status of several typical transfer subway facilities. The service facilities were classified within a subway station in this research by considering service objects, service forms, service functions, and several other features. In addition, pedestrian behavior and pedestrian flow characteristics in different service facilities were analyzed in detail. The research results are deemed meaningful for the optimization of service facilities in subway stations and for the development of urban pedestrian transportation systems.

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Risk Analysis and Control Factors Based on Excavation of a Large Underground Subway Station under Construction

Symmetry ◽

10.3390/sym12101629 ◽

2020 ◽

Vol 12 (10) ◽

pp. 1629

Author(s):

Zhien Zhang ◽

Mingli Huang ◽

Baohua Wu

Keyword(s):

Large Scale ◽

Complex Structure ◽

Subway Station ◽

Multidimensional Space ◽

Large Space ◽

Control Factors ◽

Underground Subway Station ◽

Subway Stations ◽

Under Construction ◽

And Control

Considering the convenience of pedestrian transfer, reasonable structural stress and beautiful shape design, most subway stations adopt symmetrical design. At present, the new subway station is developing in the direction of a multidimensional space, as well as a large scale, and complex structure. Tunnel construction also presents unpredictability, coupling amplification and high risks. For example, a subway extension project involves construction, which would affect the normal use of the subway or damage its structure. Based on excavation of the largest underground subway station under construction in China, the Erligou station extension project (line 16 of Beijing Metro), and using theoretical analysis, numerical simulation, monitoring data, and other research methods, this paper quantitatively analyzes the risk of a large space station’s construction process on the adjacent existing station structure and track, as well as highlights key, high-risk sub-projects, or construction steps, combined with specific engineering measures to ensure safety during construction of a new station. The general rules concerning large space subway station construction are further summarized to provide reference for similar projects.

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Use of the Swebrec Function to Model Particle Size Distribution in an Industrial-Scale Ni-Co Ore Grinding Circuit

Metals ◽

10.3390/met9080882 ◽

2019 ◽

Vol 9 (8) ◽

pp. 882

Author(s):

Alfredo L. Coello-Velázquez ◽

Víctor Quijano Arteaga ◽

Juan M. Menéndez-Aguado ◽

Francisco M. Pole ◽

Luis Llorente

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Estimation Error ◽

Simulated Data ◽

Operating Parameters ◽

Distribution Models ◽

Sampling Campaign ◽

Swebrec Function ◽

Statistical Criteria

Mathematical models of particle size distribution (PSD) are necessary in the modelling and simulation of comminution circuits. In order to evaluate the application of the Swebrec PSD model (SWEF) in the grinding circuit at the Punta Gorda Ni-Co plant, a sampling campaign was carried out with variations in the operating parameters. Subsequently, the fitting of the data to the Gates-Gaudin-Schumann (GGS), Rosin-Rammler (RRS) and SWEF PSD functions was evaluated under statistical criteria. The fitting of the evaluated distribution models showed that these functions are characterized as being sufficiently accurate, as the estimation error does not exceed 3.0% in any of the cases. In the particular case of the Swebrec function, reproducibility for all the products is high. Furthermore, its estimation error does not exceed 2.7% in any of the cases, with a correlation coefficient of the ratio between experimental and simulated data greater than 0.99.

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Soft Sensor with Deep Learning for Functional Region Detection in Urban Environments

Sensors ◽

10.3390/s20123348 ◽

2020 ◽

Vol 20 (12) ◽

pp. 3348

Author(s):

Yicao Ma ◽

Shifeng Liu ◽

Gang Xue ◽

Daqing Gong

Keyword(s):

Smart Cities ◽

Experimental Testing ◽

Rapid Development ◽

Reference Value ◽

Urban Environments ◽

Subway Station ◽

Functional Region ◽

Feature Map ◽

Passenger Flow ◽

Subway Stations

The rapid development of urbanization has increased traffic pressure and made the identification of urban functional regions a popular research topic. Some studies have used point of interest (POI) data and smart card data (SCD) to conduct subway station classifications; however, the unity of both the model and the dataset limits the prediction results. This paper not only uses SCD and POI data, but also adds Online to Offline (OTO) e-commerce platform data, an application that provides customers with information about different businesses, like the location, the score, the comments, and so on. In this paper, these data are combined to and used to analyze each subway station, considering the diversity of data, and obtain a passenger flow feature map of different stations, the number of different types of POIs within 800 m, and the situation of surrounding OTO stores. This paper proposes a two-stage framework, to identify the functional region of subway stations. In the passenger flow stage, the SCD feature is extracted and converted to a feature map, and a ResNet model is used to get the output of stage 1. In the built environment stage, the POI and OTO features are extracted, and a deep neural network with stacked autoencoders (SAE–DNN) model is used to get the output of stage 2. Finally, the outputs of the two stages are connected and a SoftMax function is used to make the final identification of functional region. We performed experimental testing, and our experimental results show that the framework exhibits good performance and has a certain reference value in the planning of subway stations and their surroundings, contributing to the construction of smart cities.

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Research on the Effects of Heterogeneity on Pedestrian Dynamics in Walkway of Subway Station

Discrete Dynamics in Nature and Society ◽

10.1155/2016/4961681 ◽

2016 ◽

Vol 2016 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Haoling Wu ◽

Zhenzhou Yuan ◽

Huixuan Li ◽

Junfang Tian

Keyword(s):

Walking Speed ◽

Field Model ◽

Subway Station ◽

Major Objective ◽

Pedestrian Dynamics ◽

Proposed Model ◽

Negative Effect ◽

Floor Field ◽

Subway Stations ◽

Positive Effect

The major objective of this paper is to study the effects of heterogeneity on pedestrian dynamics in walkway of subway station. We analyze the observed data of the selected facility and find that walking speed and occupied space were varied in the population. In reality, pedestrians are heterogeneous individuals with different attributes. However, the research on how the heterogeneity affects the pedestrian dynamics in facilities of subway stations is insufficient. The improved floor field model is therefore presented to explore the effects of heterogeneity. Pedestrians are classified into pedestrians walking in pairs, fast pedestrians, and ordinary pedestrians. For convenience, they are denoted asP-pedestrians,F-pedestrians, andO-pedestrians, respectively. The proposed model is validated under homogeneous and heterogeneous conditions. Three pedestrian compositions are simulated to analyze the effects of heterogeneity on pedestrian dynamics. The results show thatP-pedestrians have negative effect andF-pedestrians have positive effect. All of the results in this paper indicate that the capacity of walkway is not a constant value. It changes with different component proportions of heterogeneous pedestrians. The heterogeneity of pedestrian has an important influence on the pedestrian dynamics in the walkway of the subway station.

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Solutions for Extracting Air and Smoke in Underground Subway Station

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.700.239 ◽

2014 ◽

Vol 700 ◽

pp. 239-244

Author(s):

Wen Jie Chen ◽

Lei Chong ◽

Jian Ru Liang ◽

Ming Lai Yang

Keyword(s):

Ventilation System ◽

Subway Station ◽

Three Solutions ◽

Underground Subway Station ◽

Subway System ◽

Subway Stations ◽

Underground Station ◽

Enclosed Space ◽

Air Circulation ◽

Valve Control

Everyday there are about 7 million passengers commuting by subway in Shanghai, China. Although Shanghai has one of the largest subway networks in the world, yet this subway system is still full of passengers during the rush hours. Extracting air and smoke is important part of the station ventilation system which supplies enough fresh air in the crowded station. As we know, the underground subway stations are built in an enclosed space where needs air circulation far more than other type of station. This paper focuses on the designs of duct layout and valve control in an underground subway station. The authors give three solutions to return air and exhaust smoke in the underground station platform area and entrance area. The goal of this paper is to compare these three ventilation solutions in the normal time and in the fire accident. The result of analyzing and applying these solutions are concluded in the paper.

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Damage Assessment of Subway Station Columns Subjected to Blast Loadings

International Journal of Structural Stability and Dynamics ◽

10.1142/s0219455418500347 ◽

2018 ◽

Vol 18 (03) ◽

pp. 1850034 ◽

Cited By ~ 8

Author(s):

Q. S. Yan

Keyword(s):

Reinforced Concrete ◽

Bearing Capacity ◽

Damage Assessment ◽

Terrorist Attack ◽

Near Field ◽

Subway Station ◽

Reinforced Concrete Column ◽

Key Factor ◽

Subway Stations ◽

Blast Loadings

With the increasing threat of terrorism attack, the probability of explosion inside the subway is very large. Reinforced concrete columns are the main supporting members of subway stations. If the columns of a subway station were subjected to near-field explosions, their damages can affect the safety of the subway after explosion. By using the finite element method, this paper established a coupling “explosive-air-concrete” model and verified the feasibility of the model through experiments. This model can be used in the damage assessment of subway station columns in terms of the bearing capacity, by which the damage of a reinforced concrete column can be divided into different levels. Furthermore, the effect of different parameters on the damage and bearing capacity of the subway station is discussed. The results demonstrate that the stirrup reinforcement ratio of a reinforced concrete is the key factor in determining the column damage under blast loadings. The present study therefore provides a key reference for assessing the damage of subway structures after terrorist attack.

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