Exploring the Element Integration of Urban and Rural“Space of Flows”in the Context of Consumption Upgrading:A Case Study of Changsi Village in Anhui Province

The mobility and interaction between urban and rural areas are becoming more and more intensive,and their links and exchanges are increasingly closer due to constant flow of factors such as information,capital,personnel and technology.In this context,the element integration of urban and rural“space of flows”can promote the integrated development of urban and rural areas,improve the consumption environment and experience,and promote the industrial upgrading and technological progress.To realize the element integration of urban and rural“space of flows”,it is necessary to explore and innovate in infrastructure construction,information technology application,industrial cooperation and cultural exchanges.Government departments,enterprises and social organizations also need to work together to give play to their respective advantages and jointly promote the process of element integration of urban and rural“space of flows”.

Numerical Simulation of Dam-Break Flows Using Radial Basis Functions: Application to Urban Flood Inundation

Dam-break flows pose significant threats to urban areas due to their potential for causing rapid and extensive flooding. Traditional numerical methods for simulating these events struggle with complex urban landscapes. This paper presents an alternative approach using Radial Basis Functions to simulate dam-break flows and their impact on urban flood inundation. The proposed method adapts a new strategy based on Particle Swarm Optimization for variable shape parameter selection on meshfree formulation to enhance the numerical stability and convergence of the simulation. The method’s accuracy and efficiency are demonstrated through numerical experiments, including well-known partial and circular dam-break problems and an idealized city with a single building, highlighting its potential as a valuable tool for urban flood risk management.

A Laboratory Model for the Flow in Urban Street Canyons Induced by Bottom Heating

Water tank experiments are carried out to investigate the convection flow induced by bottom heating and the effects of the ambient wind on the flow in non-symmetrical urban street canyons based on the PIV (Particle Image Visualization) technique. Fluid experiments show that with calm ambient wind, the flows in the street canyon are completely driven by thermal force, and the convection can reach the upper atmosphere of the street canyon. Horizontal and vertical motions also appear above the roofs of the buildings. These are the conditions which favor the exchange of momentum and air mass between the street canyon and its environment. More than two vortices are induced by the convection, and the complex circulation pattern will vary with time in a wider street canyon. However, in a narrow street canyon, just one vortex appears. With a light ambient wind, the bottom heating and the associated convection result in just one main vortex. As the ambient wind speed increases, the vortex becomes more organized and its center shifts closer to the leeward building.

Physical Experiments to Investigate the Effects of Street Bottom Heating and Inflow Turbulence on Urban Street-Canyon Flow

The effects of street bottom heating and inflow turbulence on urbanstreet-canyon flow are experimentally investigated using a circulating water channel. Threeexperiments are carried out for a street canyon with a street aspect ratio of 1. Results from eachexperiment with bottom heating or inflow turbulence are compared with those without bottom heatingand appreciable inflow turbulence. It is demonstrated that street bottom heating or inflowturbulence increases the intensity of the canyon vortex. A possible explanation on how street bottomheating or inflow turbulence intensifies the canyon vortex is given from a fluid dynamicalviewpoint.

Effects of a Building’s Density on Flow in Urban Areas

The effects of a building＇s density on urban flows are investigated using a CFD model with the RNG k - ε turbulence closure scheme. Twenty-seven cases with different building＇s density parameters （e.g., building and street-canyon aspect ratios） are numerically simulated. As the building＇s density parameters vary, different flow regimes appear. When the street canyon is relatively narrow and high, two counterrotating vortices in the vertical direction are generated. The wind speed along streets is mainly affected by the building＇s length. However, it is very difficult to find or generalize the characteristics of the street-canyon flows in terms of a single building＇s density parameter. This is because the complicated flow patterns appear due to the variation of the vortex structure and vortex number. Volume-averaged vorticity magnitude is a very good indicator to reflect the flow characteristics despite the strong dependency of flows on the variation of the building＇s density parameters. Multi-linear regression shows that the volume-averaged vorticity magnitude is a strong function of the building＇s length and the street-canyon width. The increase in the building＇s length decreases the vorticity of the street-canyon flow, while, the increase in the street- canyon width increases the vorticity.

Suitable Weir Heights to Improve the Provision of Environmental Flows in Urban Rivers

Many studies have been conducted on environmental flow(e-flow)assessment and supply,but e-flow shortages remain common in many urban rivers.In addition to known reasons such as ever-increasing competition among water users and inadequate execution of designed e-flow supply plans,we propose that designing weir heights without explicitly considering e-flows is another major cause of this problem.In this paper,we suggest that the measures for satisfying e-flows be extended from the water supply stage to the river channel design stage.We establish a new weir height determination framework that would more effectively satisfy the required e-flows.The new framework differs from previous frameworks,in which flood control and water retention are the major concerns and the flow during floods is set as the inflow.In the new framework,e-flow provision and flow velocity maintenance are added concerns and the actual flows for e-flow supply are set as the inflow.As a case study of the new framework’s effectiveness,we applied it to the Shiwuli River,a typical channelized urban river in Hefei,China.The old framework specified too-high weir height to meet the e-flow requirements,whereas the new framework offered more reasonable heights that improved e-flow provision.

Combination forecast for urban rail transit passenger flow based on fuzzy information granulation and CPSO-LS-SVM

In order to obtain the trend of urban rail transit traffic flow and grasp the fluctuation range of passenger flow better,this paper proposes a combined forecasting model of passenger flow fluctuation range based on fuzzy information granulation and least squares support vector machine(LS-SVM)optimized by chaos particle swarm optimization(CPSO).Due to the nonlinearity and fluctuation of the passenger flow,firstly,fuzzy information granulation is used to extract the valid data from the window according to the requirement.Secondly,CPSO that has strong global search ability is applied to optimize the parameters of the LS-SVM forecasting model.Finally,the combined model is used to forecast the fluctuation range of early peak passenger flow at Tiyu Xilu Station of Guangzhou Metro Line 3 in 2014,and the results are compared and analyzed with other models.Simulation results demonstrate that the combined forecasting model can effectively track the fluctuation of passenger flow,which provides an effective method for predicting the fluctuation range of short-term passenger flow in the future.

The Research of Urban Rail Transit Sectional Passenger Flow Prediction Method

This paper studies the short-term prediction methods of sectional passenger flow, and selects BP neural network combined with the characteristics of sectional passenger flow itself. With a case study, we design three different schemes. We use Matlab to realize the prediction of the sectional passenger flow of the Beijing subway Line 2 and make comparative analysis. The empirical research shows that combining data characteristics of sectional passenger flow with the BP neural network have good prediction accuracy.

A New Method of Assessing Environmental Flows in Channelized Urban Rivers

Assessing environmental flows （e-flows） for urban rivers is important for water resources planning and river protection, Many e-flow assessment methods have been established based on species＇ habitat pro- vision requirements and pollutant dilution requirements, To avoid flood risk, however, many urban rivers have been transformed into straight, trapezoidal-profiled concrete channels, leading to the disappearance of valuable species, With the construction of water pollution-control projects, pollutant inputs into rivers have been effectively controlled in some urban rivers, For these rivers, the e-flows determined by tradi- tional methods will be very small, and will consequently lead to a low priority being given to river pro- tection in future water resources allocation and management, To more effectively assess the e-flows of channelized urban rivers, we propose three e-flow degrees, according to longitudinal hydrological con- nectivity （high, medium, and low）, in addition to the pollutant dilution water requirement determined by the mass-balance equation, In the high connectivity scenario, the intent is for the e-flows to maintain flow velocity, which can ensure the self-purification of rivers and reduce algal blooms; in the medium connectivity scenario, the intent is for the e-flows to permanently maintain the longitudinal hydrological connectivity of rivers that are isolated into several ponds by means of weirs, in order to ensure the exchange of material, energy, and information in rivers; and in the low connectivity scenario, the intent is for the e-flows to intermittently connect isolated ponds every few days （which is designed to further reduce e-flows）, The proposed methods have been used in Shiwuli River, China, to demonstrate their effectiveness, The new methods can offer more precise and realistic e-flow results and can effectively direct the construction and management of e-flow supply projects,

Application of unsteady flow simulation technology to lightening urban storm waterlogged disaster

The application of unsteady simulation to lightening urban storm waterlogged disaster involves six blocks: the main program, the database of drainage networks, the abstractions and losses block, the calculating inflow of sewer block, the drainage networks routing block and the waterlogged areas calculating block. This model can be used for simulating sewer surcharge and calculating area and water depth of waterlogged areas under storm conditions. The best design of rebuilding storm sewer system or combined sewer system can be provided by simulating existing state of built drainage pipeline. The model was used for rebuilding Shenyang drainage works last year, and the good results were obtained.

Spatial Distribution and Influencing Factors of Urban Shrinkage from the Perspective of Factor Flow - A Case Study of National Urban Agglomerations

This paper examines national urban agglomerations by taking factor flows as the focal point as the research subject.By dividing the stages of urban agglomeration development,a comprehensive framework of urban shrinkage is constructed,encompassing economic,population,and social shrinkage.The study explores the spatial distribution characteristics of urban shrinkage during different stages of urban agglomeration and investigates the influencing factors using a geographic detector model.The findings reveal that urban shrinkage within urban agglomerations is widely spread,predominantly in peripheral areas.During the diffusion stage,urban shrinkage is scattered,with population shrinkage concentrated in peripheral regions,economic shrinkage concentrated on old industrial cities,and social shrinkage concentrated on the northeast.The outcomes of the geographic detector model indicate that traffic flow,capital flow,information flow,node importance,network connectivity,government investment,openness,and environmental regulations all play significant roles in shaping the spatial distribution of urban shrinkage.

Multi-Level Approach of the Ecotoxicological Impact of a Combined Sewer Overflow on a Peri-Urban Stream

In periurban zones, urban wet weather discharges have been recognized as the most significant vector of pollution in aquatic environments. The discharge of this water without treatment into the aquatic environment could present an ecotoxicological risk for biocenosis. The aim of the INVASION project is to assess the potential ecotoxicological impact of a combined sewer overflow (CSO) on a peri-urban stream. A comparative study between upstream and downstream areas of the CSO allowed observing significant effects of this overflow on the river. We studied three layers of stream: surface water, benthic layer and hyporheic layer. To characterize the potential ecotoxicological risk of water and sediments, we used a battery of 4 bioassays: Daphnia magna, Vibrio fischeri, Brachionus calyciflorus and Heterocypris incongruens. In parallel, we measured the physico-chemical parameters: ammonium (NH4+), chromium (Cr), copper (Cu) and lead (Pb). An ecological risk is greatest for the hyporheic zone in downstream river, particularly for the solid phase. These results corroborated with the physico-chemical data obtained.

Towards Urban Resource Flow Estimates in Data Scarce Environments: The Case of African Cities

Data sourcing challenges in African nations have led many African urban infrastructure developments to be implemented with minimal scientific backing to support their success. In some cases this may directly impact a city’s ability to reach service delivery, economic growth and human development goals, let alone the city’s ability to protect ecosystem services upon which it relies. As an attempt to fill this gap, this paper describes an exploratory process used to determine city-level demographic, economic and resource flow data for African nations. The approach makes use of scaling and clustering techniques to form acceptable and utilizable representations of selected African cities. Variables that may serve as the strongest predictors for resource consumption intensity in African nations and cities were explored, in particular, the aspects of the Koppen Climate Zones, estimates of average urban income and GDP, and the influence of urban primacy. It is expected that the approach examined will provide a step towards estimating and understanding African cities and their resource profiles.

Urban Forest and Tree Valuation Using Discounted Cash Flow Analysis: Impact of Economic Components

Discounted cash flow analysis is one of the standard methods used to value urban forests and trees. It involves calculating today’s value for all benefits and costs attributed to an investment;that is discounting all cash flows to today’s value using an appropriate interest rate. This requires each benefit and cost be stated in terms of its cash flow. Urban tree benefits are complex. Little notice is given to the components of these benefits. Total urban tree benefits are a summation of partial benefits, including property value increase, storm water reduction, air quality improvement, carbon sequestration, natural gas savings, and electricity savings. We discuss the nature of these partial benefits, especially the geographical, temporal, diameter size, and rate of growth differences. These differences are even reflected in nursery stock valuation. Net present value analysis is used to illustrate the impact of these differences on financial return. An understanding of these components will prove valuable to those attempting to estimate urban forest and tree benefits.

Study on the Mechanism of the Integration of Urban and Rural Development from the View of Elements Flow

Fromthe enterprise,individual and government,which are the three main economic behavior subject,this paper analysis factors impact of flow behavior main body and the change of the objective function,constraint function and the impact of the change of behavior equation,and then summarizes their effects on the integration of urban and rural development,to build fromexogenous shocks to the endogenous to adapt to the economic decision-making framework,clarify elements flow affect the running mechanismof the urban-rural integration.

Debris flow runout behaviors considering the influences of densely populated buildings

Debris flows pose serious risks to communities in mountainous areas,often resulting in large losses of human life and property.The impeding presence of urban buildings often affects the runout behavior and deposition of debris flows.But the impact of different building densities and sizes on debris flow dynamics has yet to be quantified to guide urban planning in debris flow risk zones.This study focused on a debris flow that occurred in Zhouqu County,Gansu Province,China on August 7th,2010,which was catastrophic and destroyed many buildings.The FLO-2D software was used to simulate this debris flow in two scenarios,i.e.the presence and the absence of buildings,to obtain debris-flow intensity parameters.The developed model was then used to further analyze the influence of large buildings and narrow channels within the urban environment.The simulation results show that considering the presence of buildings in the simulation is essential for accurate assessment of debris flow intensity and deposition distribution.The layout of buildings in the upstream urban area,such as large buildings or parallel buildings which form narrow channels,can affect the flow velocity and depth of debris flow heading towards downstream buildings.To mitigate damage to downstream buildings,the relative spacing(d/a)between upstream and downstream buildings should not exceed a value of two and should ideally be even lower.These findings provide valuable insights for improving the resistance of mountainous cities to urban debris flows.

Urban Dynamics and Emergence of New Centers in the Dakar Region (Senegal)

Due to the status of the Dakar region as the former capital of AOF (French West Africa) and current capital of the Republic of Senegal, it is home to a very large part of the population and most of the socio-economic, administrative and cultural activities on a very small area of the country (0.28%). This situation makes it a very attractive region and subject to strong land pressure. The objective of this article is to study past and current urban dynamics as well as changes in natural spaces, in order to identify new urban centers. The methodological approach consists in analyzing satellite images to understand the evolution of different forms of spatial occupation in the Dakar region, and to study population movement flows and urban forms in order to reveal new urban centers. The results of the study show that the Dakar urban space is characterized by diverse forms which express a heterogeneous set of spaces. They also revealed the emergence of new clusters between 1986 and 2016, notably Ngor, Grand Yoff, Parcelles Assainies in the North-West, and Keur Massar and the North of the communes of Rufisque in the eastern part of the Dakar region.

RESOURCE RECOVERY AND MATERIALS FLOW IN THE CITY Zero Waste and Sustainable Consumption as Paradigm in Urban Development

Beyond energy efficiency,there are now urgent challenges around the supply of resources,materials,food and water.After debating energy-efficiency for the last decade,the focus has shifted to include resource and material-efficiency.In this context,urban farming has emerged as a valid urban design strategy in Europe,where food is produced and consumed locally within city boundaries,turning disused sites into productive urban landscapes and community gardens.Agricultural activities allow for effective composting of organic waste,returning nutrients to the soil and improving biodiversity in the urban environment.Urban farming will help to feed the 9 billion by 2050(predicted population growth,UN-Habitat forecast 2009).This paper reports on best practice of urban design principles in regard to materials flow,material recovery,adaptive re-use of building elements and components(‘design for disassembly’;prefabrication of modular building components),and other relevant strategies to implement zero waste by avoiding waste creation,reducing harmful consumption and changing behaviour.The paper touches on two important issues in regard to the rapid depletion of the world’s natural resources:the construction sector and the education of architects and designers.The construction sector:Prefabricated multi-story timber buildings for inner-city living can set new benchmarks for minimizing construction wastage and for sustainable on-site assembly.Today,the construction and demolition(C&D)sector is one of the main producers of waste;it does not engage enough with waste minimization,waste avoidance and recycling.Education and research:It’s still unclear how best to introduce a holistic understanding of these challenges and to better teach practical and affordable solutions to architects,urban designers,industrial designers,and so on.One of the findings of this paper is that embedding‘zero-waste’requires strong industry leadership,new policies and effective education curricula,as well as raising awareness(education)and refocusing research agendas to bring about attitudinal change and the reduction of wasteful consumption.

Spatial Interaction and Network Structure Evolvement of Cities in Terms of China's Rail Passenger Flows

Cities separated in space are connected together by spatial interaction (SI) between them. But the studies focusing on the SI are relatively few in China mainly because of the scarcity of data. This paper deals with the SI in terms of rail passenger flows, which is an important aspect of the network structure of urban agglomeration. By using a data set consisting of rail O-D (origin-destination) passenger flows among nearly 200 cities, intercity rail distance O-D matrixes, and some other indices, it is found that the attenuating tendency of rail passenger is obvious. And by the analysis on dominant flows and spatial structure of flows, we find that passenger flows have a trend of polarizing to hubs while the linkages between hubs upgrade. However, the gravity model reveals an overall picture of convergence process over time which is not in our expectation of integration process in the framework of globalization and economic integration. Some driven factors for the re-organization process of the structure of urban agglomeration, such as technique advance, globalization, etc. are discussed further based on the results we obtained.

Vehicle actuation based short-term traffic flow prediction model for signalized intersections

Traffic flow prediction is an important component for real-time traffic-adaptive signal control in urban arterial networks.By exploring available detector and signal controller information from neighboring intersections,a dynamic data-driven flow prediction model was developed.The model consists of two prediction components based on the signal states(red or green) for each movement at an upstream intersection.The characteristics of each signal state were carefully examined and the corresponding travel time from the upstream intersection to the approach in question at the downstream intersection was predicted.With an online turning proportion estimation method,along with the predicted travel times,the anticipated vehicle arrivals can be forecasted at the downstream intersection.The model performance was tested at a set of two signalized intersections located in the city of Gainesville,Florida,USA,using the CORSIM microscopic simulation package.Analysis results show that the model agrees well with empirical arrival data measured at 10 s intervals within an acceptable range of 10%-20%,and show a normal distribution.It is reasonably believed that the model has potential applicability for use in truly proactive real-time traffic adaptive signal control systems.