Delineating Intra-Urban Spatial Connectivity Patterns by Travel-Activities: A Case Study of Beijing, China

Travel activities have been widely applied to quantify spatial interactions between places, regions and nations. In this paper, we model the spatial connectivities between 652 Traffic Analysis Zones (TAZs) in Beijing by a taxi OD dataset. First, we unveil the gravitational structure of intra-urban spatial connectivities of Beijing. On overall, the inter-TAZ interactions are well governed by the Gravity Model $G_{ij} = {\lambda}p_{i}p_{j}/d_{ij}$, where $p_{i}$, $p_{j}$ are degrees of TAZ $i$, $j$ and $d_{ij}$ the distance between them, with a goodness-of-fit around 0.8. Second, the network based analysis well reveals the polycentric form of Beijing. Last, we detect the semantics of inter-TAZ connectivities based on their spatiotemporal patterns. We further find that inter-TAZ connections deviating from the Gravity Model can be well explained by link semantics.Comment: 6 pages, 4 figure

Shaking table model tests of reinforced concrete tunnels under multiple earthquake shakings

The cumulative effect of multiple relatively low or moderate seismic events on tunnels is not well-understood within an earthquake prone region. To investigate the effect of multiple earthquakes on the integrity of tunnel structures, 1 g shaking table tests were performed. This research also explored the impact of tunnel presence on the soil response, namely analyzing soil-structure interaction effects. Within the tests, a free-field model and a soil-tunnel model were employed synchronously. The shaking table study was designed and conducted following a new set of scaling laws able to faithfully simulate cracking of tunnel lining, and white noise tests were applied after each seismic shaking for dynamic identification. Except for the measurement of acceleration and bending strain, a new cracking monitoring system equipped with wireless mini-cameras was proposed to detect the evolution of tunnel damages during the tests, while Light Detection and Ranging (LiDAR) technology was utilized to examine the ground deformations in the two model configurations. Based on the point cloud data, it was observed that sand densification effects were obvious in the two models and the influence of tunnel presence on the soil response was restricted in a limited region. The trend in the evolution of an image-based damage index kept similar to that in the progression of surface settlements, implying that the seismically-induced ground failure might play an important role in the seismic response of shallow tunnels. Also, the frequency shifting behaviour of lining did not follow the intuitive pattern, where a reduction in natural frequencies is expected when structural damage occurs. Moreover, the variation of acceleration amplification factors of the tunnel was almost consistent with that of the soil, and the trend of strain agreed with that of surface settlements. The findings from this study provide an insight to better understand the resilience and life-long performance of earthquakes exposed underground structures

Numerical Investigation of Closed-Form Solutions for Seismic Design of a Circular Tunnel Lining (by Quasi-Static Method)

In this paper, four known analytical methods including Wang (1993), Penzien (2000), Park et al. (2009), and Bobet (2010) were Evaluated based on seismic design of circular tunnel in Tehran Metro Line 6. For this purpose, a quasi-static numerical method was applied in the framework of finite difference method (FDM) under the same assumptions. In both numerical and analytical methods, to consider the nonlinear behavior of soil, linear equivalent properties of soil derived from ground analysis were incorporated in EERA software. obtained results shown that the Park’s analytical solution under various conditions of interaction between the tunnel lining and soil provides very close results to the of numerical modeling. Afterward, a comprehensive validation was performed to assess the impact of the rigidity of the surrounding ground and the maximum shear strain value. In this regard, several earthquake scenarios with different shear wave rates were used to achieve a wide range of flexibility ratio (F) and maximum shear strain. The results showed a significant difference between the results of Penzine’s and Bobet’s methods under the no-slip conditions and those of numerical analyses for a certain range of flexibility and shear strain ratios. In the final part of the paper, a quasi-static seismic numerical study was performed under realistic soil-structure interaction conditions to illustrate the importance of the actual interaction between the tunnel lining and surrounding soil. The results showed that the actual interaction conditions governing estimation of the axial force play a very important role. Also, it was found that Park’s solution, because of the ability to consider the slip at the interface provides results very close to those of the numerical modeling. In contrast, one of the serious limitations of the other analytical methods is their inability to simulate the slip interface between the tunnel lining and soil

Intelligent Transportation Related Complex Systems and Sensors

Building around innovative services related to different modes of transport and traffic management, intelligent transport systems (ITS) are being widely adopted worldwide to improve the efficiency and safety of the transportation system. They enable users to be better informed and make safer, more coordinated, and smarter decisions on the use of transport networks. Current ITSs are complex systems, made up of several components/sub-systems characterized by time-dependent interactions among themselves. Some examples of these transportation-related complex systems include: road traffic sensors, autonomous/automated cars, smart cities, smart sensors, virtual sensors, traffic control systems, smart roads, logistics systems, smart mobility systems, and many others that are emerging from niche areas. The efficient operation of these complex systems requires: i) efficient solutions to the issues of sensors/actuators used to capture and control the physical parameters of these systems, as well as the quality of data collected from these systems; ii) tackling complexities using simulations and analytical modelling techniques; and iii) applying optimization techniques to improve the performance of these systems. It includes twenty-four papers, which cover scientific concepts, frameworks, architectures and various other ideas on analytics, trends and applications of transportation-related data

Underutilised Resources in Urban Environments

This book is the result of a Special Issue of the journal Resources. The Special Issue was initiated to identify promising solutions and specific challenges in the context of underused resources in urban environments. Authors focus on two main areas: the establishment of circular economy schemes based on valorizing wastes that occur in urban areas and the exploitation of renewable energies. The circular economy and renewable resources hold key potential for increasing the sustainability of cities, and the presented studies enhance our understanding of how to unlock this potential. Effective regulatory frameworks and policymaking processes that balance the power between stakeholders are required to successfully manage energy transition and the transition to more circular economies. The positive role of community engagement merits high attention. To recover valuable resources from household waste, a focus on technology and infrastructure is required but is insufficient; motivational factors and knowledge of citizens are the most essential elements. The need to more reliably quantify and better characterize recyclable material streams also evidently remains, especially where population numbers are further growing. This book provides a rich source to explore promising solutions, challenges, and research needed for the sound management of resources in urban settings

Investigation of a super performance dew point air cooler and its application in buildings

Based on extensive literature reviews, technical opportunities were identified to improve the energy efficiency of a dew point air cooler. This applied research aimed to develop a super-performance dew point air cooler to replace or partly replace the conventional energy-intensive air conditioners applicable to buildings.This research followed the methodology of combined theoretical and experimental investigation and a procedure of concept formation, validating and updating. A simulation software was developed and validated to investigate the impacts of the geometric configuration and operational conditions on the unit’s cooling performance and assist the prototype design. As a result, a novel dew point air cooler prototype, featuring innovative structure of the heat and mass exchanger, application of new materials and new processes, unique water distribution and control scheme and exclusive self-developed simulation software, was constructed and tested under controlled laboratory environment. Two patents were generated, one of which has been authorized by the China State Intellectual Property Office and the other has been filed in the Intellectual Property Office of the United Kingdom.Under standard testing conditions, i.e. dry-bulb temperature of 37.8oC and the coincident wet-bulb temperature of 21.1oC, the prototype cooler achieved a wet-bulb cooling effectiveness of 114% and dew-point cooling effectiveness of 75%, yielding a significantly high Coefficient of Performance (COP) of 52.5 at the optimal working air ratio of 0.364. The performance testing was also carried out under various simulated conditions representing the climates of hot & dry, warm & dry, moderate, warm & humid and the wet-bulb effectiveness of the prototype kept in the range 112% to 128% and dew-point effectiveness of 67%-76%, giving a COP of 37.4-52.5. Compared to the conventional vapour compression air conditioners which have a COP of around 3, the prototype cooler had 11-17 times higher COP, leading to a reduction in electrical power consumption by around 92% to 94%.A dedicated case study of the proposed dew point cooler based on conditions in Beijing, a representative city in warm and humid climate, was carried out to predict the annual operational performance, economic rewards, and associated environmental benefits. Compared to the conventional packaged air conditioners, 91.4% of annual power demand could be saved. The annual water consumption is less than 0.3 tonnes to provide the cooling of 2428.1 kWh. And the payback period of static investments would be less than 4 years to replace an equivalent packaged air conditioner.A significant leap forward has been achieved with this study and this is expected to open enormous global business in the very near future, thus bringing about great economic, environmental and sustainability benefits worldwide

The (re)positioning of the Spanish metropolitan system within the European urban system (1986-2006)

The thesis seeks to demonstrate that during the period between 1986 and 2006, some of the principal cities of the Spanish metropolitan system1, have undergone significant change in terms of their European competitiveness. It is suggested that in the case of Madrid and Barcelona in particular this change has been of such a magnitude to proportion them a much more important place within the European spatial configuration than that which they occupied in the mid-1980s. Empirical evidence is offered to support this conjecture. The thesis lies wholly within the framework of spatial planning at the European territorial scale.It charts the comparative ascent of the Spanish cities from the moment of Spain's entry into the European Union (EU) in 1986 against the background of the development of European spatial policy, increased economic integration across Europe, the increased importance of the 'territorial' dimension of EU cohesion policy and an eventual waning of the applicability of the terminology of 'core' and 'periphery' to describe European geographical location.Part One (Chapter 1) addresses the processes of urbanisation in general from a global perspective and then focuses on metropolitan growth in a number of different historical contexts from the start of the 19th Century. Parts Two (Chapters 2-5) and Three (Chapters 6-9) of the thesis carry out analyses at two contrasting but complementary spatial scales. Part Two examines the metropolitan growth processes in Spain, in the period since 1857, detecting the historical moments in which there were surges in the metropolitan populations of the seven cities of the metropolitan system. The dimensions of the spatial units of analysis corresponding to the seven Spanish metropolitan urban regions are described, based upon a methodology first developed by the Universitat Politècnica de Catalunya (UPC) in the context of a transnational spatial planning project of the INTERREG community initiative2. These seven spatial units form the basis for a socio-economic analysis of the structure of the metropolitan system, drawing upon data principally from the 2001 Census. If by 1930 one of the key characteristics of Spain's urban system was having not just one but two cities (Madrid and Barcelona) belonging to the group of 27 cities across the world with populations in excess of 1 million inhabitants3, this same differentiation between the country's two largest cities and the remainder of the urban system is equally valid today. Spain's urban system remains clearly bicephalous in being dominated by these same two cities in terms of demographic and economic strength.Part Three begins by examining the evolution of European spatial policy against the background of an ever-enlarging European Union and changes with regard to the notion of cohesion - from a concept understood in terms of economic and social factors, to one in which the territorial dimension has become increasingly important. The European urban system is then critically examined through a number of key and influential studies, with particular regard to the rankings and hierarchies of metropolitan urban regions deriving there from and the changes in the placing of the Spanish metropolitan urban regions therein.Taking inspiration from the seminal contribution of Manuel Castells4 in the context of the structural changes resulting from the informational and technological revolution, the thesis seeks to replicate the concept of a 'space of flows'. This is carried out through a 'network analysis' approach drawing upon air passenger flows between some 28 European metropolitan urban regions of the EU15+2 group of countries, enabling the analysis of the interaction between these 28 cities. This methodology enables arriving at a number of descriptive indicators which in turn, through the application of a multi-dimensional scaling mathematical technique, permits comparing the functional and physical distances of each of the metropolitan urban regions from the centre of the 'conceptual space of air passenger flows' and the centre of gravity. The resulting map of the functional positioning of the cities offers a spatial vision of metropolitan Europe quite different to that based upon Cartesian coordinates. Such an approach enables demonstrating that cities such as Barcelona, Madrid, Helsinki, Lisbon and Athens, traditionally considered as physically peripheral to the European core area, appear to be more favourably positioned in functional terms. Furthermore in the case of Spain the results indicate that Barcelona lies closer to the centre of the conceptual 'space of air passenger flows' than Madrid.In light of this empirical evidence, together with the signs of increased economic integration across some parts of Spain, the prospects of Spain forming part of a wider European territorial concentration of flows and activities, and the recognition of the territorial capital of Madrid and Barcelona within recent EU spatial policy declarations, the thesis concludes in Part Four that these two metropolitan regions have undergone a clear consolidation and (re)positioning within the European metropolitan hierarchy.La tesis trata de demostrar que durante el período entre 1986 y 2006, unas de las principales ciudades del sistema metropolitano español, han experimentado un cambio significativo en términos de su competitividad europea. Es sugerido que en el caso de Madrid y Barcelona en particular este cambio ha sido de tal magnitud para proporcionarlas un lugar mucho más importante dentro de la configuración territorial espacial europea que dichas ciudades ocuparon en el mediado de los años 80. Se ofrece evidencia empírica para sostener esta conjetura. La tesis se sitúa dentro demarco de la ordenación territorial a la escala europea. Traza la subida relativa de las ciudades españolas desde el momento de la entrada de España en la Unión Europea(UE) en 1986, contra el fondo del desarrollo de la política territorial europea, la integración económica aumentada a través de Europa, la importancia aumentada de la dimensión "territorial" de la política de la cohesión de UE y una eventual disminución de la aplicabilidad de la terminología del "centro" y la "periferia" para describir la ubicación geográfica europea. La Primera Parte (Capítulo 1) está dirigida a evaluar los procesos de la urbanización en general, desde una perspectiva global, y después se centra en examinar el crecimiento metropolitano en varios contextos históricos, a partir del comienzo del siglo XIX. La Segunda (Capítulos 2-5) y Tercera Partes (Capítulos 6-9) de la tesis llevan a cabo unos análisis en dos escalas territoriales contrastantes pero complementarias. La Segunda Parte examina los procesos del crecimiento metropolitano en España, a partir de 1857, discerniendo los momentos históricos en los que había oleadas en las poblaciones ‘metropolitanas’ de las siete ciudades del sistema metropolitano. Se describe las dimensiones de las unidades espaciales de análisis que corresponden a las siete regiones urbanas metropolitanas españolas, basadas en una metodología desarrollado por el Universidad Politécnica de Cataluña (UPC) en el contexto de un proyecto trasnacional de ordenación territorial de la iniciativa comunitaria INTERREG. Estas siete unidades espaciales forman la base para un análisis socioeconómico de la estructura del sistema metropolitano, utilizando datos principalmente del 2001 Censo. Si en el año 1930 una de las características claves del sistema urbano de España era de tener no sólo una, pero dos ciudades (Madrid y Barcelona) perteneciendo al grupo de 27 ciudades a través del mundo con poblaciones por encima de 1 millón de habitantes, esta misma diferenciación entre las dos ciudades más grandes del país y el resto del sistema urbano es hoy igualmente válida. El sistema urbano de España se queda claramente bicéfalo en ser dominado por estas mismas dos ciudades en términos de fuerza demográfica y económica. La Tercera Parte comienza examinando la evolución de la política territorial europea contra el fondo de una Unión Europea cada vez más grande y los cambios con respecto a la noción de la cohesión – de un concepto entendido en términos de factores económicos y sociales, a uno en que la dimensión territorial ha llegado a ser cada vez más importante. A continuación, se examina de manera crítica el sistema urbano europeo mediante algunos estudios influyentes, con la consideración particular a las clasificaciones y las jerarquías de las regiones urbanas metropolitanas que derivan de estos estudios, y a los cambios en la colocación de las regiones urbanas metropolitanas españolas en dichos estudios. Tomando inspiración de la contribución seminal de Manuel Castells en el contexto de los cambios estructurales que resultan de la revolución de información y tecnológica, la tesis trata de replicar el concepto de un 'espacio de flujos'. Esto es llevado a cabo por un enfoque de "network analysis" que utiliza los flujos de pasajeros aéreos entre unas 28 regiones urbanas metropolitanas europeas del grupo de EU15+2 países, permitiendo el análisis de la interacción entre estas 28 ciudades. Esta metodología permite desarrollar varios indicadores descriptivos que permiten, a su vez, por la aplicación de una técnica matemática de escalamiento multi-dimensional, comparar las distancias funcionales y físicas de cada una de las regiones urbanas metropolitanas del centro del 'espacio conceptual de flujos de pasajeros aéreos’ y el centro de la gravedad. El mapa resultante del posicionamiento funcional de las ciudades ofrece una visión espacial de Europa metropolitana bastante diferente a la que se base en los coordinados cartesianos. Tal enfoque permite demostrar que ciudades como Barcelona, Madrid, Helsinki, Lisboa y Atenas, consideradas tradicionalmente como físicamente periféricas al área central de europea, parecen ser posicionadas más favorablemente en términos funcionales. Además, en el caso de España, los resultados indican que Barcelona queda más cerca al centro del conceptual 'espacio de flujos de pasajero aéreos’ que Madrid. A la luz de esta evidencia empírica, junto con los signos de la integración económica aumentada a través de algunas partes de España, las perspectivas de que España formará parte una más amplia concentración territorial europea de flujos y actividades y del reconocimiento de la capital territorial de Madrid y Barcelona dentro de las recientes las declaraciones de política territorial de la UE, la tesis concluye, en la Cuarta Parte que estas dos regiones metropolitanas han experimentado una clara consolidación y (re)posicionamiento dentro de la jerarquía metropolitana europea.Postprint (published version