Explore the vast range of titles available.

The deployment of fifth-generation (5G) wireless networks has already laid the ground-work for futuristic smart cities but along with this, it has also triggered the rapid growth of a wide range of applications, for example, the Internet of Everything (IoE), online gaming, extended/virtual reality (XR/VR), telemedicine, cloud computing, and others, which require ultra-low latency, ubiquitous coverage, higher data rates, extreme device density, ultra-high capacity, energy efficiency, and better reliability. Moreover, the predicted explosive surge in mobile traffic until 2030 along with envisioned potential use-cases/scenarios in a smart city context will far exceed the capabilities for which 5G was designed. Therefore, there is a need to harness the 6th Generation (6G) capabilities, which will not only meet the stringent requirements of smart megacities but can also open up a new range of potential applications. Other crucial concerns that need to be addressed are related to network security, data privacy, interoperability, the digital divide, and other integration issues. In this article, we examine current and emerging trends for the implementation of 6G in the smart city arena. Firstly, we give an inclusive and comprehensive review of potential 6th Generation (6G) mobile communication technologies that can find potential use in smart cities. The discussion of each technology also covers its potential benefits, challenges and future research direction. Secondly, we also explore promising smart city applications that will use these 6G technologies, such as, smart grids, smart healthcare, smart waste management, etc. In the conclusion part, we have also highlighted challenges and suggestions for possible future research directions. So, in a single paper, we have attempted to provide a wider perspective on 6G-enabled smart cities by including both the potential 6G technologies and their smart city applications. This paper will help readers gain a holistic view to ascertain the benefits, opportunities and applications that 6G technology can bring to meet the diverse, massive and futuristic requirements of smart cities.

Urban population now exceeds rural population globally, and 60-80% of global energy consumption by households, businesses, transportation, and industry occurs in urban areas. There is growing evidence that built-up infrastructure contributes to carbon emissions inertia, and that investments in infrastructure today have delayed climate cost in the future. Although the United Nations statistics include data on urban population by country and select urban agglomerations, there are no empirical data on built-up infrastructure for a large sample of cities. Here we present the first study to examine changes in the structure of the world's largest cities from 1999 to 2009. Combining data from two space-borne sensors-backscatter power (PR) from NASA's SeaWinds microwave scatterometer, and nighttime lights (NL) from NOAA's defense meteorological satellite program/operational linescan system (DMSP/OLS)-we report large increases in built-up infrastructure stock worldwide and show that cities are expanding both outward and upward. Our results reveal previously undocumented recent and rapid changes in urban areas worldwide that reflect pronounced shifts in the form and structure of cities. Increases in built-up infrastructure are highest in East Asian cities, with Chinese cities rapidly expanding their material infrastructure stock in both height and extent. In contrast, Indian cities are primarily building out and not increasing in verticality. This new dataset will help characterize the structure and form of cities, and ultimately improve our understanding of how cities affect regional-to-global energy use and greenhouse gas emissions.

For children living in one of the 30 megacities around the world, green spaces may be far away or tokenistic, with growing accounts of youth exhibiting a variety of nature deficit disorders. Amidst increasing pressure for more high-density metropolitan areas (HDMAs), international advocacy agencies are calling for policy makers and service providers to ensure good quality urban green spaces (UGSs) for all children. Furthermore, these green spaces need to be purposefully designed to cater to children’s needs, which continue to evolve amidst extreme weather such as heat waves. Recently, pandemics have placed additional constraints on how far children can travel and their time spent outdoors, making the quality of this experience for children even more important. This systematic literature review explored the roles of HDMA-UGSs for children during pandemics. From 551 studies retrieved and curated using the PRISMA methodology, 40 papers were subsequently thematically analysed. Four roles were synthesised for HDMA-UGSs in supporting children’s experiences during pandemics, which also benefit children during ‘normal’ day-to-day life’: (1) sustaining growth and development, (2) bridging social stratifications, (3) encouraging self-agency, and (4) facilitating independent mobility. Thirteen principles were distilled to support decision making in enabling these outcomes in new-build and refurbishment projects. The results are of immediate use for decision makers who are responsible for HDMA-UGS planning, procurement, installation, and maintenance. The UGS role descriptions enable targeted design interventions for supporting children’s health and well-being, including during times of constrained outdoor time.

This article analyzes impact that initiatives for improving freight system performance can generate in fuel distribution in urban areas, especially in mega-cities. We propose a comprehensive methodology to identify initiatives with the most potential in terms of cost and efficiency for the fuel distribution process in urban areas, and then to assess impacts of such initiatives in terms of environmental and economic sustainability. Results indicated off-hours deliveries as having a higher potential to increase sustainability in fuel distribution within city borders. Therefore, an application of the proposed methodology is presented to assess results of a live experiment of off-hours deliveries held in a fuel-distribution process in a mega-city in comparison to daytime deliveries, which is companies’ standard practice. Several positive results were observed during off-hour deliveries, such as reduction in fuel consumption, reduction in the emission of air pollutants and greenhouse gases, reduction in travel time, increase in average operational speed as well as the possibility of carrying out two trips with the same vehicle per day leading to a reduction in expenses with drivers when there is an increase in daily truck deliveries. Although the case assessed was conducted during the Olympic Games of Rio de Janeiro, the method can be applied in any other mega-city.

This study examines the mediating effect of subjective housing quality between housing conditions and mental health, using survey data from ten Chinese mega-cities. The results from multi-level linear regression models show that housing areas are highly associated with subjective housing quality and that renters have lower levels of subjective housing quality than homeowners. At the community level, the age of housing tends to diminish its subjective quality, while a lower plot ratio is associated with more favorable evaluations of housing conditions. Surprisingly, educational resources in proximity to housing are negatively associated with subjective housing quality. Subjective housing quality is closely linked to mental health. Additionally, the results show that home ownership significantly strengthens the association between subjective housing quality and mental health. Namely, the mediating effect of subjective housing quality on the relationship between housing conditions and mental health is stronger for homeowners than for renters.

After four decades of reform and development, China is confronting a domestic waste crisis. As the world's largest waste-generating nation, the World Economic Forum projects that by 2030, the volume of household waste in China will be double that of the United States. Starting in the early 2000s, Chinese policymakers came to see waste management as an object of environmental governance central to the creation of \"modern\" cities, and experimented with the circular economy, in which technology and policy could convert all forms of waste back into resources. Based on long-term research in Guangzhou, Circular Ecologies critically analyzes the implementation of technologies and infrastructures to modernize a mega-city's waste management system, and the grassroots ecological politics that emerged in response. In Guangzhou, waste's transformation revealed uncomfortable truths about China's environmental governance: a preference for technology over labor, the aestheticization of order, and the expropriation of value in service of an ecological vision. Amy Zhang argues that in post-reform China, waste—the material vestige of decades of growth and increasing consumption—is a systemic irritant that troubles China's technocratic governance. Waste provoked an unlikely coalition of urban communities, from the middle class to precarious migrant workers, that came to constitute a nascent, bottom-up environmental politics, and offers a model for conceptualizing ecological action under authoritarian conditions.

Over the past decades, urbanization and industrialization have led to a change in air quality, bringing researchers to a full realization of the damaging effects of human activities on the environment. This study focused on describing air quality during the initial phase of the Novel Coronavirus disease (COVID-19) pandemic (since there were fewer anthropogenic activities) in 10 Chinese mega-cities. Using the independent t-test, the means of air quality index (AQI) scores and individual air pollutants concentration during the outbreak were compared with the means before the outbreak. Cohen’s d was estimated to quantify how much difference was observed. Based on the AQI score, the air quality in these 10 cities ranged from excellent (Shenzhen) to light pollution (Xi’an) with 44.8 μg m−3 and 119.7 μg m−3, respectively. In comparison to the 2019 air quality, Guangzhou and Wuhan noted major differences in air quality during the outbreak. Indicators of traffic pollution, particularly NO2, were significantly lower during the outbreak in all cities. Particulate matter pollution varied, with some cities observing lower concentrations and other higher concentrations during the outbreak. There was a significant decrease in air pollution levels during the outbreak. More researchers should observe changes in air quality during peculiar or major events. Implementation of stringent regulation on vehicle use should be considered in mega-cities. Relevant findings should be employed in emphasizing the detrimental effects of anthropogenic activities and support the need for stringent emission control regulations.

The COVID-19, the most deadly challenge human being could have imagined, has become a reality now and the whole world is passing through the worst pandemic situation. From the challenges of invention of life saving vaccine or medicine to keeping economy at right track are the most talked about hurdles in front of all of us. But if we look at the other side of the coin, the blessings that came in form of disguise could be realised. The paper emphasizes on those aspects during lockdown that was imposed in India for three weeks initially that is 24th March to 14th April 2020 and later on till 3 rd of May 2020. As a result of this forced restrictions, pollution level in whole India, specially in metro or mega cities where large population and pollution is a deadly combination, drastically changed. For analysing air quality, the metro-cities like Delhi, Kolkata, Chennai and Mumbai has been investigated here. The pollutant parameters PM 2.5 , SO 2 , NO 2 , along with CO, O 3 and overall AQI (Air Quality index) has been collected and comparative study was done before and after lockdown and even for the year 2018 and 2019 too. Reduction of level of pollutants in significant amount of percentage is observed for all the metro cities where variation of reduction level from city to city is also significant. The effectiveness of lockdown over different metro cities are also very significant, pointing towards alertness of local people and population concentration. Finally, the study can be used in future as case study for controlling pollution with controlled lockdown and this can be practiced in future once or twice yearly to save our motherland.

Greater Cairo is one of the largest metropolitan areas in the world, yet the tempo-spatial trends of PM 2.5 and loaded metal(loid)s) in its atmosphere, and their potential health risks, are poorly understood. We investigated the air concentrations of PM 2.5 , and associated Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn, in one urban and one industrial locations within Greater Cairo for one year in each location. Statistical analysis suggested that PM 2.5 and its chemical composition in Greater Cairo are more influenced by land-use and local activities rather than meteorological conditions. Both annual and daily levels of PM 2.5 were well above the WHO air quality guidelines, with annual averages of c. 37 and 56 µg m −3 , and daily maximums of 165 and 176 µg m −3 , in the urban and industrial areas, respectively. This indicates high probability of PM 2.5 inflicted short- and long-term health risks to the population of Greater Cairo. Health risk modelling indicated that the residents of Greater Cairo are facing high non-carcinogenic and carcinogenic risks (up to 47 and 28 times the recommended hazard indices, respectively) from the studied 12 metal(loid)s combined. Lead (Pb) was the highest single threat to the health of Greater Cairo residents amounting up to 56% and 83% of the total non-carcinogenic and carcinogenic risks, respectively. Nevertheless, most of the exposure to Pb originated from ingestion rather than inhalation which was marginal. For all elements combined, and for some other individual elements, inhalation was a significant route of exposure but only for non-carcinogenic risks. For carcinogenic risks, the contribution of inhalation to the total risk was negligible.

Climate change leading to Climate extremes in the twenty-first century is more evident in megacities across the world, especially in West Africa. The Greater Accra region is one of the most populated regions in West Africa. As a result, the region has become more susceptible to climate extremes such as floods, heatwaves, and droughts. The study employed the Coupled Model Intercomparison Project 6 models in simulating climate extreme indices under the Shared Socioeconomic Pathway scenarios (SSPs) over West Africa between 1979 and 2059 as exemplified by the Greater Accra region. The study observed a generally weak drought in the historical period and expected to intensify especially under SSP585 in Greater Accra. For instance, continuous dry days (CDD) reveal an increasing trend under the SSPs. Similarly, the overall projected trend of CDD over West Africa reveals an increase signifying a more frequent and longer drought in the future. The flood indices revealed a surge in the intensity and duration of extreme precipitation events under the SSPs in the region. For instance, R99pTOT and Rx5days are expected to significantly increase under the SSPs with intensification under the SSP245, SSP370, and SSP585. A similar trend has been projected across West Africa, especially along the Guinean coast. The study foresees a gradual and intensifying rise in heatwave indices over the Greater Accra region. The warming and cooling indices reveal an increasing and decreasing trend respectively in the historical period as well as under the SSPs particularly within urban centers like Accra and Tema. Most West African countries are projected to observe more frequent warm days and nights with cold nights and days becoming less frequent. Expected effects of future climate extreme indices pose potential threats to the water, food, and energy systems as well as trigger recurrent floods and droughts over Greater Accra. The findings of the study are expected to inform climate policies and the nationally determined contribution of the Paris Agreement as well as address the sustainable development goal 11 (Sustainable cities) and 13 (Climate action) in West Africa.