Dense City Research Articles

A novel acceleration approach to shadow calculation based on sunlight channel for urban building energy modeling

Shadow effect among buildings has great impacts on the building energy consumption and the performance of building photovoltaic, and calculating shadows on building surfaces in urban building energy modeling (UBEM) faces challenges of inefficiency, especially for dense urban areas. In this study, a novel shadow calculation approach based on sunlight channel is proposed that can streamline the surrounding environment and accelerate the shadow calculation process. The sunlight-channel algorithm can further accelerate the shadow calculation process by dynamically predetermining the shading surfaces according to the actual solar position. In a real urban context, the proposed approach can accelerate the computation process by over 10 times over the baseline and over 34 times over the non-accelerated method, with a mean absolute percentage error (MAPE) of 1.13% for the total solar radiation. The proposed approach copes well with both large-scale urban models and the complexity of building structures, particularly for urban models with complex changes in building heights. This approach can significantly enhance the computational efficiency in complex urban environments, facilitating an accurate and rapid analysis of the energy consumption and solar potential of buildings in dense cities.

Unravelling the last-mile conundrum: A comparative study of autonomous delivery robots, delivery bicycles, and light commercial vehicles in 14 varied European landscapes

In this study, the growing need for efficient delivery services in the expanding e-commerce sector is addressed, with a focus on real-life consumption data. A comprehensive modelling framework is proposed to evaluate the efficiency of various transportation modes, including Light Commercial Vehicles (LCVs), cargo bicycles, and Autonomous Delivery Robots (ADRs). Utilizing the Google API, delivery destinations are identified, origin-destination matrices are created, and routes are optimized using Google OR-Tools and a capacitated vehicle routing problem solver. The study's robustness is further enhanced by incorporating real-life consumption data, considering diverse European contexts, varying urban scales, traffic patterns, and topographical factors, thus assessing their impact on transportation efficiency. The findings reveal that ADRs are efficient in pedestrian-focused, traffic-limited areas, while bicycles are more effective in dense city centres. This research highlights the necessity of tailoring transportation mode choice to specific urban characteristics for optimal efficiency and consumer satisfaction.Overall, the present study offers valuable insights into optimizing delivery services in different urban settings, providing a significant model for improving last-mile delivery systems. It contributes to understanding how different transportation modes can be effectively integrated into urban logistics, addressing environmental sustainability, operational efficiency, and real-life consumer demands.

The production of Asian public space: the role of the transnational developer

ABSTRACT Accounts of projects generally credit design vision to the landscape architect or architect, relegating the role of the developer to the client. This essay offers an alternative perspective, arguing for the recognition of the Asian developer as an agent of transnational design innovation. While there has been ample discussion of the wealth to be made in the Asian property market, little attention has been paid to the developer’s motives and ambitions beyond economic gain. Through the discussion of two transnational development companies, CapitaLand and Swire Properties, we demonstrate the role these Asian-based developers have played in establishing an emerging urban public domain in some dense Asian cities.

Design and eco-technoeconomic analysis of a natural gas cogeneration energy management center (EMC) with short-term thermal storage

This work proposes a non-islanded cogeneration energy management center (EMC) that can be used to displace grid-level natural gas turbine systems and natural gas combustion systems for heat. The design of the proposed EMC included a weighted multi-objective optimization aimed at minimizing: i) natural gas consumption; ii) capital costs; iii) utility costs; and iv) unmet thermal demand. The decision variables consisted of the existence and capacity of the equipment comprising the EMC, including: i) a natural gas boiler; ii) an internal combustion engine that generates heat and electricity; and iii) a hot water thermal storage system. Four resulting candidates EMC designs were then compared with the status-quo (SQ) in an eco-technoeconomic analysis; The SQ draws electricity from the grid and heating for dwellings come from natural gas boilers. Emissions at grid level change which alternative is favored. The findings showed that, for a system that serves 4–5 dense urban city blocks over a 20-year lifetime, the SQ system had cumulative levelized costs of 9.6 million USD for the final consumer, while the levelized costs of the EMC designs ranged from 12.9 to 15.1 million USD. In terms of emissions, the SQ emitted 959 tonnes of CO2eq per year, while the EMC system produced around 500 tonnes of CO2eq per year depending on the year, yielding a CCA varying between 364 and 653 USD/tonneCO2eq

EVOLVING RESEARCH METHOD IN THREE-DIMENSIONAL AND VOLUMETRIC URBAN MORPHOLOGY OF A HIGHLY DENSE CITY: ASSESSING PUBLIC AND QUASI-PUBLIC SPACE TYPOLOGIES

An appropriate urban density is a vital part of a sustainable urban fabric. However, when it comes to measuring the built urban fabric and how people walk through it and use, a difficulty has been observed in defining applicable measurement tools. With the intention of identifying the variables that will allow the best characterization of this fabric and movement, a multi-variable analysis methodology from the field of artificial intelligence (AI) is proposed. The main objective of this paper is to prove the capacity of AI as an evolving research method in urban morphology and specifically to evaluate the capacity of such a methodology to measure the way in which people travel through defined multi-levels of typologies of public urban space. The research uses the case of Hong Kong as a dense city that is three-dimensionally activated in terms of its public realm, not just at street level, but also via below ground subways and upper-level walkways, public and quasi-public spaces. This includes the three-dimensional volumetric assessment of public and quasi-public space typologies within a highly dense city. For the purpose of the study, a characterization and term definition of these spaces has been further developed: “Junctions”, “Landmarks”, “Intersections”, “Districts”, “Passages” and “Lobbies” (both outdoor and indoor) based on Lynch’s 5 main key elements (District, landmark, path, edges, node). The results obtained using AI prove to be more robust and rational than those based on a more limited range of tools, evidencing that using AI can offer operational opportunities for better understanding of morphological and typological evolution within the vertical and volumetric built urban fabric.

Spatial inequity index for essential facility access at building-level in highly dense urban areas

Equity and inclusion continue to pose significant challenges for many cities. Disparities in access to resources and facilities among the residents of these areas are often influenced by factors such as geographical location and income level, among others. Therefore, creating a quantitative basis to detect spatial and socio-economic inequities in residents' access to vital infrastructures is crucial for advancing smart cities. This paper introduces a novel measure of Spatial Inequity that is based on 1) computing building-level scores for each building in terms of access to facilities, and 2) comparing the distribution of the scores of these facilities using the Gini coefficient. The proposed building-level scores will enable the identification of GIS hotspots at a high resolution. Then, the Gini-based measure will facilitate a comparison of the distribution of the scores, and determine if they are evenly distributed and equitably accessible. The Gini coefficient was highest (0.89) for waste management and elderly care, and lowest (0.56) for hospitals, reflecting varying levels of inequality. This study applies this Spatial Ineqity methodological framework to Hong Kong, a representative of Highly Dense Cities. The framework benchmarks urban infrastructure, identifies hotspots, and selects interventions for equitable urban development.

Comparative Study of Aerosol Optical Properties along a Megacity

Interest in the study and characterization of aerosols has been growing given its multiple connections with air quality and climate. However, the limited ground-based stations for measurements in many countries are not enough to completely study a big city or a region. Low-cost technology arises as a viable alternative to improve the spatial resolution of measurements. This study aims to demonstrate that the properties of aerosols may change within a megacity and that is advisable to segment measurements according to their characteristics. We measured the optical properties of aerosols in the outskirts of Buenos Aires and compared the data obtained with AERONET data from the city center. This is the first study of its kind in the region. The comparison of concentration, sizes, and types of aerosols shows differences between the sites regardless of the background levels that they share regionally. While the city center has a strong influence from traffic and sea particles and levels of pollution typical of a dense city, the outskirts present several aerosol sources and characteristics of a semi-rural site with a moderate influence of anthropogenic sources.

Impact of Settlement Size and Regional Density on the Frequency of Different Holiday Types

Despite its contribution to climate change, holiday travel has received less attention in research than daily travel. Research has revealed that individuals residing in dense and large settlements tend to travel more frequently and over longer distances. Whether this is attributable to compensation for shortcomings of dense cities or a reflection of lifestyle is still inconclusive, yet important to uncover for formulating mitigation strategies for the environmental impact. To advance this discussion, we analyze the 2019 Norwegian holiday travel survey to determine to what extent settlement size and regional density in Norway are associated with different holiday types that reflect different lifestyles and motivations. Using negative binomial and logistic regression while controlling for socioeconomic factors, we find that (1) it is not settlement size that influences the number of holiday trips, but whether a settlement lies in a dense county; (2) making nature getaways in Scandinavia and intercontinental trips are both positively associated with county density; (3) making city trips does not show a consistent link with spatial characteristics; (4) Mediterranean seaside holidays are typical for all Norwegians, no matter the place of residence. Our results indicate compensatory motivation behind nature getaways. However, dense everyday surroundings are not detrimental to visiting other densely populated areas on city vacations. The increased likelihood of intercontinental trips among people in dense areas may be explained by lifestyle and cosmopolitan attitudes rather than being a result of compensation.

Novel approach to roof rainwater harvesting and aquifer recharge in an urban environment: Dry and wet infiltration wells comparison

In urban environments there is a severe reduction of infiltration and groundwater recharge due to the existence of large impervious areas. During rain events, large volumes of water that could have recharged groundwater and surface water bodies are diverted into the municipal drainage system and lost from the freshwater storage. Moreover, extreme rain events impose high peak flows and large runoff volumes, which increase the risk of urban floods. Recent studies have suggested the use of rainwater harvesting for groundwater recharge, as a plausible solution for these challenges in dense urban environments. While the benefits of this approach are well understood, research on its practical, engineering, and hydrological aspects is relatively limited. The objective of the present study was to examine the use of infiltration wells for groundwater recharge with harvested rainwater collected from building rooftops under Mediterranean climate conditions. Two types of wells with similar hydraulic and technical properties were examined: a well that reaches the groundwater (wet well); and a well that discharges the harvested water into the unsaturated zone (dry well). Infiltration capacities of the wells were compared in controlled experiments conducted during summer months, and in operational recharge of harvested rainwater, during winter. Both dry and wet wells were found to be suitable for purposes of groundwater recharge with rooftop-harvested rainwater. Infiltration capacity of the wet well was about seven times greater than the infiltration capacity of the dry well. While the infiltration capacity of the wet well was constant throughout the entire length of the study (∼10 m3/h/m), the dry well infiltration capacity improved during winter (from 0.5 m3/h/m to 1.5 m3/h/m), a result of development of the dry well with time. Considering Tel-Aviv, Israel, as a case study for a dense modern city in a Mediterranean climate, it is demonstrated herein that the use of infiltration wells may reduce urban drainage by ∼40 %.

Dense city centers support less evolutionary unique bird communities than sparser urban areas

Urbanization alters avian communities, generally lowering the number of species and contemporaneously increasing their functional relatedness, leading to biotic homogenization. Urbanization can also negatively affect the phylogenetic diversity of species assemblages, potentially decreasing their evolutionary distinctiveness. We compare species assemblages in a gradient of building density in seventeen European cities to test whether the evolutionary distinctiveness of communities is shaped by the degree of urbanization. We found a significant decline in the evolutionary uniqueness of avian communities in highly dense urban areas, compared to low and medium-dense areas. Overall, communities from dense city centers supported one million years of evolutionary history less than communities from low-dense urban areas. Such evolutionary homogenization was due to a filtering process of the most evolutionarily unique birds. Metrics related to evolutionary uniqueness have to play a role when assessing the effects of urbanization and can be used to identify local conservation priorities.

Disentangling agglomeration economies from selection under policy distortions in China

ABSTRACT This paper explores the competing sources of productivity gains observed in China’s urban agglomerations focusing on three pillar industries: agro-food processing, textiles and electronics. The main results reveal that the higher aggregate productivity observed in denser Chinese cities is driven by both agglomeration and selection forces. Subsequent analysis shows that industrial support policies help to mitigate the selection penalty, but come at the expense of reducing agglomeration benefits. Complementing the city-level analysis, we estimate dynamic and distributive firm-level panel data models to explore the policy rationale of propping up inefficient firms, despite creating a less competitive environment. The micro-based results reveal that inefficient firms targeted by industrial support policies benefit from productivity spillovers in denser cities, mainly in the electronics industry, providing some policy rationale for keeping them in the market.

Building the city under financial frictions

Weak financial institutions may affect developing countries due to slowing the much-needed construction process of residential housing. Using novel data collected from Nairobi, I document considerable heterogeneity in the construction duration of new residential buildings, with about 40% of buildings started in 2009 still unfinished in 2018. To understand the role of financial development in constructing residential housing, I develop a heterogeneous agent model with financial frictions in which households construct individual housing units. Counterfactual simulations show that improvements in credit provision can substantially speed up the expansion of the aggregate housing stock and increase the city's density by enabling the construction of taller buildings. The model also predicts that investments in incomplete structures emerge as an alternative savings vehicle in the absence of reliable savings accounts.

Reform, redevelopment and rent: Dilemmas of the social function of property in the private domain of the Brazilian metropolis

This paper discusses the disappointing outreach of Brazilian urban reform by analyzing the underlying tensions and contradictions of its key principle, that is, the social, function of property (SFP), from a perspective of contemporary theoretical debates on the double nature of rent (i.e., related to monopoly positions and emerging from market, circulation). The SFP principle is grounded in anti-rentier, agrarian reform thinking, which stressed that individual monopoly landowners should not be allowed to retain their property for speculative purposes and use it productively to increase food supplies. In contemporary dense cities, however, using property “productively” implies redevelopment, that is, transformation of existing structures of the built environment, into alternative ones. This has two implications, one related to the essence of the SFP, (its being), the other regarding what it means having a SFP in an urban setting. In relation to the former, despite its anti-rentier stance, in cities the SFP triggers a redevelopment-rent nexus due to the circulation of rents in non-competitive markets. Regarding the latter implication, having a SFP in cities requires complex, open-ended and utilitarian negotiations between state and non-state actors aimed at the appropriation of rents to articulate the conflicting interests of individual property owners with the collective good. The theoretical argument of the paper is illustrated with a short, heuristic case on redevelopment in the city of São Paulo, while its conclusion provides elements for a research agenda on the limits of market-based, reformist versus right- based planning beyond this specific context.

Acoustic environment and its restorative potential in small urban green spaces

Small urban green spaces (SUGS) in dense city areas have been widely demonstrated to have restorative benefits to surrounding residents. However, residents' usage and experience of SUGS were indicated to be adversely influenced by adjacent traffic noise, whilst natural sounds inside could provide restorative soundscape resources. Thus, this study investigated the acoustic quality and its restorative potential in 12 SUGS in Qingdao via field measurements and questionnaire surveys. The results show that: (1) The noise level of SUGS largely ranged in 50-60 dBA, with dominant road traffic noise. Three perceptual soundscape dimensions were identified: appreciation, diversity and dynamics. (2) Scenic SUGS featured more natural sounds, lower noise levels, and more appreciation; residential SUGS featured more human sounds and worse soundscape evaluation; and business SUGS featured higher noise levels. (3) The acoustic environments in scenic SUGS showed much more restorative potential than residential and business ones, and the restorative potential of SUGS was highly influenced by sound levels (LAeq, L10, and L90), sound sources (traffic noise and natural sounds), and soundscape qualities (appreciation and diversity). The findings were expected to provide references for the sustainable planning and design of small urban green spaces in dense cities.

Awareness and risk perception of a multi-hazard megacity: The case of adolescent students

Gaining a better understanding of adolescents’ multi-hazards awareness and risk perception may help to devise measures to aid them to respond to multi-hazards in a highly dense and complex city. To date, there has not been published research on multi-hazards in Mexico City. This study aims to fill that gap by assessing adolescents’ awareness and risk perception to a sample of n = 1,246 from seven preparatory schools. An ordinal logistic regression approach was employed to find the relationship between the explanatory factors and the likelihood of the multi-hazard occurrence. The research results show that in general, adolescents are aware of the negative effects of fire & explosion, crime, earthquake, air pollution and floods; however, they were unaware of the negative effects of severe climate, landslides, and volcanic eruption. Students attending evening-shift schooling contributed negatively to earthquakes, severe weather, and air pollution risk perception, even though these hazards are the most prevalent in the city. The projected probability of the likelihood of floods, earthquakes, air pollution and crime increase with age. Overall, the findings revealed that adolescents’ awareness and risk perception vary among the hazards. Also, the characteristics of the hazards and the adolescents shape risk perception, which is consistent with similar studies being conducted on adults. It is hoped that by conducting studies such as the presented herein may help to gain a better understanding of multi-hazards and build resilience and increase vulnerability of residents living under a permanent threat of these.

Reasons to Pedestrianise Urban Centres: Impact Analysis on Mobility Habits, Liveability and Economic Activities

Pedestrianisation entails the full removal of motorised vehicles. It promotes walking and active means of transport and has a wide range of benefits in terms of health, the environment, mobility and the economy. However, it often faces widespread opposition. This results in a lack of political will and, to a lesser degree, in temporary pedestrianisations, which can be reverted. We consider that infrastructural change and long-term pedestrianisation are key for long-lasting benefits and more resilient and sustainable cities. To explore and assess this, a survey of pedestrians and semi-structured interviews with businesses were conducted in recently pedestrianised areas of Madrid, a large capital city. Data on satisfaction and changes in mobility, liveability and business were gathered. Over 755 citizens and 38 local businesses answered. The results show high levels of satisfaction (2/3) among citizens, while 1/2 businesses consider it positive for their commercial activity. Car use has fallen, active means of transport have been fostered and perceived attractiveness has increased, although some congestion has been noticed in nearby streets. This and the rest of the evidence presented in this paper can be used to back long-term restrictive policies in other dense and busy cities.

Estimating costs and CO2 emissions for last mile delivery of groceries in Paris using alternative modes and routing strategies

ABSTRACT Last mile delivery is a significant component in the growth of e-commerce, especially in urban areas. The deliveries in dense cities cause several serious issues such as air/noise pollution and congestion. In this study, we compare the financial costs and CO2 emissions from different last mile delivery strategies of grocery bins in a scenario in Paris with four types of delivery vehicles (diesel/electric vans, cargo bikes, and autonomous delivery vehicles). We use costs associated with each vehicle type, location data with constraints for establishments in Paris, and delivery scenarios obtained by solving the vehicle routing problem for an overall cost comparison. We consider an economic analysis of the daily delivery to optimise the costs and estimate the CO2 emissions. The results highlight the competitiveness among last mile delivery and reflect the transition knowing the transport expenses since 2018: electric van costs become competitive with diesel ones, it concluded by some perspectives with cargo bikes and autonomous vehicles with their current limits. The strategies show a great impact on overall cost and emissions, which are vital in the development of sustainable urban last-mile delivery.

Winds and eddy dynamics in the urban canopy layer over a city: A parameterization based on the mixing-layer analogy

Urban atmospheric flows are vital to the global ecology. This study characterizes urban canopy layer (UCL) dynamics and parameterizes the flows in the atmospheric surface layer (ASL) over heterogeneous urban surfaces. Large-eddy simulations (LESs) are used to transiently calculate the winds over a real, dense city. A linear function of eddy diffusivity of momentum KM is applied to the lower UCL. Analogous to its mixing-layer counterpart, the strong UCL top shear manifests an inflected mean wind speed profile which aligns well with the exponential law. The solutions to the mixing length lm and the turbulent momentum flux are analytically derived by consolidating the mixing-layer type shear and the form drag from the explicitly resolved roughness elements. The behavior of lm in the lower UCL, especially its peaked level, is captured well. Based on the balance between shear and form drag, an aerodynamic effective roof level Hae is designated where the ground effect is alleviated under shear dominance. Results reveal that a rougher urban surface generates eddies with a larger shear length scale, thus enhancing momentum transport. In-canopy turbulence mixing, which slows down wind decay, is also enhanced, resulting in stronger street-level breezes. The newly developed ASL flow model will be beneficial to urban planning by offering reliable predictions, effectuating the management of urban sustainability.

Quality Assessment of Online Resources for Gender-affirming Surgery.

As visibility of the transgender patient population and utilization of online resources increases, it is imperative that web-based gender-affirming surgery (GAS) materials for patients are readable, accessible, and of high quality. A search trends analysis was performed to determine frequency of GAS-related searches over time. The top 100 most common results for GAS-related terms were analyzed using six readability formulas. Accessibility of patient-facing GAS sources was determined by categorizing types of search results. Frequency of article types was compared in low- and high-population dense areas. Quality was assigned to GAS web-based sources using the DISCERN score. Search engine trend data demonstrates increasing occurrence of searches related to GAS. Readability scores of the top 100 online sources for GAS were discovered to exceed recommended levels for patient proficiency. Availability of patient-facing online information related to GAS was found to be 60%, followed by information provided by insurance companies (17%). Differences in availability of online resources in varying dense cities were found to be minimal. The average quality of sources determined by the DISCERN score was found to be 3, indicating "potential important shortcomings." Despite increasing demand for web-based GAS information, the readability of online resources related to GAS was found to be significantly greater than the grade level of proficiency recommended for patients. A high number of nonpatient-facing search results appear in response to GAS search terms. Quality sources are still difficult for patients to find, as search results have a high incidence of low-quality resources.

COVID and Cities, Thus Far

Key reasons for the existence of cities are the externalities created when people cluster together in close proximity. During the COVID-19 pandemic, such interactions came with health risks and people found other ways to interact. This article documents how cities changed during COVID-19 and considers how the persistence of new ways of interacting, particularly remote work, will shape the development of cities in the future. It first summarizes evidence showing how residential and commercial prices and activity adjusted at different distances from dense city centers during and since the pandemic. The analysis employs a textbook monocentric city model to demonstrate that two adjustments associated with remote work—reduced commuting times and increased housing demand—generate the patterns observed in the data. The authors then consider how these effects might be magnified by changes in urban amenities and agglomeration forces, and what such forces might mean for the future of cities.