Subway Environment Research Articles

Learning to detect subway arrivals for passengers on a train

The use of traditional positioning technologies, such as GPS and wireless local positioning, rely on underlying infrastructure. However, in a subway environment, such positioning systems are not available for the positioning tasks, such as the detection of the train arrivals for the passengers in the train. An alternative approach is to exploit the contextual information available in the mobile devices of subway riders to detect train arrivals. To this end, we propose to exploit multiple contextual features extracted from the mobile devices of subway riders to precisely detecting train arrivals. Following this line, we first investigate potential contextual features which may be effective to detect train arrivals according to the observations from 3D accelerometers and GSM radio. Furthermore, we propose to explore the maximum entropy (MaxEnt) model for training a train arrival detector by learning the correlation between contextual features and train arrivals. Finally, we perform extensive experiments on several real-world data sets collected from two major subway lines in the Beijing subway system. Experimental results validate both the effectiveness and efficiency of the proposed approach.

Frequency-Cepstral Features for Bag of Words Based Acoustic Context Awareness

음향 상황 인지(acoustic context awareness)는 다양하게 발생되는 음원들로부터 어떠한 장소인지 또는 어떠한 사건이 발생하는지를 판단하는 기술로 음향 이벤트 검출 또는 인식 보다 한 단계 더 복잡한 문제이다. 기존의 상황인지 기술은 음향 이벤트 검출 또는 인식 기술에 기반하여 현재 상황을 인지하는 방법을 사용하고 있다. 하지만 이와 같은 접근 방법은 여러 음원이 동시에 발생하거나 유사한 음원이 발생하는 실제 환경에서 정확한 상황 판단이 어렵다. 특히 버스와 지하철은 승객들에 의한 잡음으로 상황을 인지하기 힘들다. 이러한 문제를 극복하기 위해 본 논문에서는 유사한 음향 이벤트가 발생하는 버스와 지하철 상황을 인식할 수 있는 Bag of Words 기반의 상황 인지 알고리즘을 연구하고 코드북 생성을 위한 특징벡터를 제안한다. 제안하는 특징벡터의 효용성은 Support Vector Machine을 이용한 실험을 통해 검증했다. Among acoustic signal analysis tasks, acoustic context awareness is one of the most formidable tasks in terms of complexity since it requires sophisticated understanding of individual acoustic events. In conventional context awareness methods, individual acoustic event detection or recognition is employed to generate a relevant decision on the impending context. However this approach may produce poorly performing decision results in practical situations due to the possibility of events occurring simultaneously or the acoustically similar events that are difficult to distinguish with each other. Particularly, the babble noise acoustic event occurring at a bus or subway environment may create confusion to context awareness task since babbling is similar in any environment. Therefore in this paper, a frequency-cepstral feature vector is proposed to mitigate the confusion problem during the situation awareness task of binary decisions: bus or metro. By employing the Support Vector Machine (SVM) as the classifier, the proposed feature vector scheme is shown to produce better performance than the conventional scheme.

The Design of Wireless Sensor Network System for the Subway Environment Monitoring

This paper has designed a wireless sensor network (WSN) system which is suitable for the subway security environment. The system uses ZigBee wireless communication technology to form a network, uses the chip CC2530 as the core processor to design the hardware circuit for the network node, and the design of the embedded software is based on Z-Stack protocol stack. Through analyzing the factors having affection on the security environment, the system collects a variety of environmental information with some sensors, and completes the design of the sensor modules. The test results show that this system has the characteristics of low-power, low-cost and high reliability.

Prediction of the maximum air velocities created by metro trains using an artificial neural network approach

The maximum air velocity created by a moving train inside a tunnel is obtained using an artificial neural network approach. A neural network model is developed to represent a single train travelling in a single tunnel. A set of non-dimensional groups, which are known to influence the induced flow characteristics, is used for the training of the neural network. Various test runs are compared with the results of the authoritative software, Subway Environmental Simulation. The presence of ventilation shafts within a tunnel is included in the model by defining an aerodynamically equivalent single tunnel using major head loss characteristics of different parts of the system. This approach eliminated the requirement to train the neural network for a large number of possible tunnel/shaft configurations.

Culture-Independent Analysis of Aerosol Microbiology in a Metropolitan Subway System

The goal of this study was to determine the composition and diversity of microorganisms associated with bioaerosols in a heavily trafficked metropolitan subway environment. We collected bioaerosols by fluid impingement on several New York City subway platforms and associated sites in three sampling sessions over a 1.5-year period. The types and quantities of aerosolized microorganisms were determined by culture-independent phylogenetic analysis of small-subunit rRNA gene sequences by using both Sanger (universal) and pyrosequencing (bacterial) technologies. Overall, the subway bacterial composition was relatively simple; only 26 taxonomic families made up ~75% of the sequences determined. The microbiology was more or less similar throughout the system and with time and was most similar to outdoor air, consistent with highly efficient air mixing in the system. Identifiable bacterial sequences indicated that the subway aerosol assemblage was composed of a mixture of genera and species characteristic of soil, environmental water, and human skin commensal bacteria. Eukaryotic diversity was mainly fungal, dominated by organisms of types associated with wood rot. Human skin bacterial species (at 99% rRNA sequence identity) included the Staphylococcus spp. Staphylococcus epidermidis (the most abundant and prevalent commensal of the human integument), S. hominis, S. cohnii, S. caprae, and S. haemolyticus, all well-documented human commensal bacteria. We encountered no organisms of public health concern. This study is the most extensive culture-independent survey of subway microbiota so far and puts in place pre-event information required for any bioterrorism surveillance activities or monitoring of the microbiological impact of recent subway flooding events.

The Effective Use of the Piston Effect, Natural Cold Sources, and Energy Saving in Beijing Subways

With the development of the subway, the energy consumption of subway ventilation and air-conditioning systems is increasing rapidly. To solve this problem, this paper describes the environment of a subway station in Beijing subway line no. 2 from July to September, 2011, and uses numerical methods to quantitatively analyze and evaluate the contributions of the subway piston effect and natural outdoor cold sources to energy saving in the air-conditioning system and improvement of the subway environment. The results show that the piston effect can be used for ventilation in each area of the subway station. During summer, part of the subway air-conditioning season, a natural cold source can introduce a cold capacity of 5,100 GJ to the subway station.

Sustainable Monitoring of Indoor Air Pollutants in an Underground Subway Environment Using Self-Validating Soft Sensors

The purpose of this study is to develop a self-validating soft sensor to improve the prediction performance of indoor air quality soft sensors in an underground subway station. The reconstruction-based self-validation method was proposed and implemented in order to: (1) determine the optimal number of principal components when building a principal component analysis training model, (2) enhance the diagnosis accuracy when identifying faulty sensors and (3) reconstruct faulty measurements in a straightforward manner. Two soft sensors based on partial least squares and recursive partial least squares models were developed and their prediction performance was compared in the cases of using faulty sensor measurements and using reconstructed sensor values. Two types of sensor faults including a bias fault and a drifting fault were evaluated using the proposed method. The monitoring results show that the developed sensor self-validation strategy has a powerful ability to correctly detect, identify and reconstruct the sensor faults in the subway system. In addition, the proposed self-validation soft sensing technique could achieve sustainable monitoring of indoor air pollutants in the underground subway environment, because the reconstructed values can be used to replace the measured data when sensor faults have been detected by the detection indices.

Simulation and Comparative Analysis on Environmental Control in Subway

To ensure passengers can have a comfortable thermal environment in the subway waiting room is one of the main targets in subway environment control. By using the CFD software, this paper takes an island platform with double-layer of Shenyang as the object to simulate the thermal environment of platform screen door and ventilation in the open system, then detailed analysis on the variation of the temperature field, airflow velocity field in the typical position. The results indicated that average temperature of no-PSD system platform is 2.5 ~3 °C higher than that of PSD system, standing room is 1.5 °C higher than that of PSD system , but these also meet the requirement of the standards of the environmental control and passengers’ thermal comfort. Meanwhile, through the comparative analysis to the energy consumption of the two systems, we find ventilating condition has superior to PSD system in energy saving, and it is more suitable for the local climate in the northeast.

The Importance-Performance Analysis of Subway Environment Use from a Gender-Sensitive Perspective

The Importance-Performance Analysis of Subway Environment Use from a Gender-Sensitive Perspective

The Analysis of Tianjin Subway Environmental Control System

The paper takes Tianjin subway as an example, and use the Subway Environment Simulation (SES) program to establish subway system with platform screen doors or different characteristics of two systems to carry out the simulate computation in summer, transition season and winter of the two systems; by analyzing the difference between two environment control modes, get the chart of the temperature distribution characteristic. The table result showed that it has more advantages using closed system than PSD system in Tianjin by using the primary invests and saving energy consumption.

Design of Subway Intelligent Environment Monitoring System Based on ZigBee

We designed a subway intelligent environment monitoring system based on ZigBee. The system makes use of the wireless sensor networks to achieve real-time monitoring to the subway environment.

Ventilation Efficiency in the Subway Environment for the Indoor Air Quality

Ventilation Efficiency in the Subway Environment for the Indoor Air Quality

Measurement of Distributed Antenna Systems at 2.4 GHz in a Realistic Subway Tunnel Environment

Accurate characterization of the radio channel in tunnels is of great importance for new signaling and train control communications systems. To model this environment, measurements have been taken at 2.4 GHz in a real environment in Madrid subway. The measurements were carried out with four base station transmitters installed in a 2-km tunnel and using a mobile receiver installed on a standard train. First, with an optimum antenna configuration, all the propagation characteristics of a complex subway environment, including near shadowing, path loss, shadow fading, fast fading, level crossing rate (LCR), and average fade duration (AFD), have been measured and computed. Thereafter, comparisons of propagation characteristics in a double-track tunnel (9.8-m width) and a single-track tunnel (4.8-m width) have been made. Finally, all the measurement results have been shown in a complete table for accurate statistical modeling.

Health effects of a subway environment in mild asthmatic volunteers

Particle exposure is known to have negative health effects. In Stockholm the environment in the subway has been reported to have higher particle exposure levels, measured as PM(2.5) and PM(10), than roads with intense traffic in the inner city area. We have recently shown that healthy volunteers exposed to subway environment had statistically significant increase of fibrinogen and CD4 cells expressing regulatory T-cell marker CD25(bright)/FOXP3 in blood. The aim of the present study was to find out whether a more vulnerable population, asthmatics, would demonstrate similar or other changes in the lungs or in the peripheral blood. Sixteen mild asthmatics were exposed to a subway and a control environment for 2h while being monitored by measurements of lung function, and inflammatory response in the lower airways evaluated by bronchoscopy and in peripheral blood. An attempt to standardize the exposures was done, by letting the volunteers alternate 15min intervals of moderate exercise on a bicycle ergometer with 15min of rest. We found a statistically significant increased frequency of CD4 cells expressing T-cell activation marker CD25 in bronchoalveolar lavage fluid, but no significant increase of regulatory T-cells in blood as was found in healthy volunteers. Our study shows that airway inflammatory responses after exposure in subway environment differ between asthmatic and healthy humans.

지하철 환경에서 CDMA 이동통신시스템의 기지국 용량 분석

본 논문에서는 지하철의 전파환경과 트래픽 특성이 지상과 상이함을 밝히고 CDMA 이동통신시스템의 지하철 기지국 용량을 분석하고자 한다. 이를 위해 다중경로 페이딩에 의한 신호대 잡음비, 셀 구조에 따른 섹터화 이득, 전파환경에 의한 경로손실 지수 및 주파수재사용 계수 등을 분석하여 지하철 구간의 무선 파라미터를 도출하고 링크용량을 산정한다. 또한, 지하철 기지국에서 peakedness 지수를 측정하여 지하철 기지국에 peaked 트래픽이 발생함을 밝힌다. 마지막으로 포아송 트래픽을 가정하는 열랑-B 모형 대신 peaked 트래픽을 고려하는 Neal-Wilkinson 모형을 이용하여 지하철 기지국의 얼랑 용량을 산정한다. We analyze the capacity of CDMA base stations in the subway environment. We investigate the characteristics of multipath fading, cell structures, and propagation environment in the subway, analyze signal to noise ratio, sectorization gain, path-loss exponent, frequency reuse factor, and obtain the link capacity of a base station in the subway. We measure the peakedness factor and reveal that base stations in the subway have peaked traffic. We use Neal-Wilkinson model to obtain the Erlang capacity instead of Erlang-B model based on Poisson traffic.

Efficiency Evaluation of Adsorbents for the Removal of VOC and NO2 in an Underground Subway Station

Adsorbent combination studies have been carried out to remove nitrogen dioxide (<TEX>$NO_2$</TEX>) and volatile organic compounds (VOCs: BTEX) out of a subway environment characterized by high flow and low concentration. Optimal conditions for the high removal efficiency of the concerned target compounds were obtained through testing a series of control factors such as adsorbent sorts, thicknesses, and superficial velocity. It was found that the efficiencies increased as the specific surface area of activated carbon and its thickness increased, and external void fraction decreased. Furthermore, mixed activated carbon with granular and constructed contents was extensively tested to reduce pressure drop through the carbon bed. It was found that the performance of higher contents of granular activated carbon was better than that of higher contents of the constructed carbon. When the mixed carbon was applied to the subway ventilation system in order to eliminate <TEX>$NO_2$</TEX> and VOC simultaneously, the removal efficiencies were found to be 75% and 85%, respectively.

지하철 환경조형물에 대한 지역별 이용 승객 인식도 분석

지하철역사의 환경조형물은 단순히 승객운송을 위한 기능주의적 정거장에서 벗어나 획일적인 지하공간을 다양한 문화공간으로 창조하며 지역의 문화를 알리는 중요한 시각적 지표내지는 지역의 고유한 이정표의 기능을 갖는다. 따라서 지하철 환경조형물은 단순히 개인의 취향이나 사적인 입장보다는 공공설치물이나 공공예술이란 범주에서 지하철 이용자의 기대에 대한 다수의 유의한 감정의 공감대 형성에 필요한 디자인 접근이 요구되고 있다. 본 연구는 지하철 환경조형물 설치에 있어 지하철을 이용하는 이용자들의 관점에서 어떻게 평가되고 선호하는지를 규명하기 위해 지역별 이용자에 대한 환경조형물의 인지도와 선호도 및 작품의 시각적 이미지를 평가할 수 있는 요인에 대하여 조사, 분석을 시행하였다. 환경조형물에 대해서는 대체적으로 긍정적인 요소가 많이 나타나는 것으로 조사되었으나 역사 환경의 특성과 조화가 이루어지지 않는다면 오히려 지하철 환경의 시각적 질을 저해시킬 수 있는 것으로 판단된다. Environmental sculptures not only play a part as various cultural facilities but also symbolize local unique culture beyond the limit of functional role. Therefore subway environmental sculptures not only should be approached in terms of public installations and beauty but also should be designed to meet the needs of subway users appropriately. In order to find out what subway users think about environment sculptures installed in subway stations, the factors that can evaluate awareness and preference for environment sculptures and visual image of environment sculptures were examined and analyzed. Positive elements have been shown with regard to environment sculptures but it was judged that visual quality of subway environment can be improved more if environment sculptures keep in harmony with the characteristics of stations.

Health effects of a subway environment in healthy volunteers

Environmental particle exposure, often estimated as the particulate mass of particles with a diameter <10 microm, <2.5 microm or <1 microm (PM(10), PM(2.5) or PM(1)), is known to have a negative impact on the health of the population. Little is known about how the size and origin of particles influence the effects. We have previously shown that exposure to a road tunnel environment causes a cellular inflammatory response in the airways of healthy individuals. In the present study, our aim was to investigate potential airway health effects from exposure to a subway environment. 20 healthy volunteers were exposed to a subway and a control environment for 2 h, followed by measurements of lung function and the inflammatory response in the lower airways (bronchoscopy) and in the peripheral blood. No cellular response was found in the airways after exposure to the subway environment. In the blood, we found a statistically significant increase in fibrinogen and regulatory T-cells expressing CD4/CD25/FOXP3. Subway and road tunnel environments have similar levels of PM(10) and PM(2.5), whilst the concentrations of ultrafine particles, nitrogen monoxide and dioxide are lower in the subway. Although no cellular response was detected, the findings indicate a biological response to the subway environment. Our studies show that using gravimetric estimates of ambient particulate air pollution alone may have clear limitations in health-risk assessment.

Wave motion of smoke in subway fire environment

Wave motion in subway or tunnel fire is an intrinsic property of smoke. As the pressure of smoke changes with mass of certain power, a kind of linear wave equation for smoke can be derived from the conservation equations of its mass and momentum, under nearly homogeneous zone assumption. The smoke movement of 4 subway fires was simulated with Airpak. By fitting the pressure-mass functions to the simulated data, wave equations of the smoke were derived, and wave motions of smoke were thus validated. It can be seen that smoke wave is a kind of mass wave, whose velocity is inversely proportional to smoke mass, and wave of a bigger fire propagates slower.

An Approach to the Study of Transport and Dispersion of Threat Agents in a Subway Station

The objective of the proposed research is to assess the exposure of subway riders and workers to threat agents introduced in the subway environment. This article presents the study plan, considerations, and expected outcomes of a novel approach to study this issue. A modular scale model of a subway station has been erected from Metropolitan Transportation Authority of New York design specifications. This model will be used in a series of experiments to analyze airflow and dispersion patterns in the wake of a moving train and in an empty tunnel. Particle image velocimetry will be used to measure transient velocity profiles and concentration profiles.