Integrity is one criteria to evaluate GNSS performance, which was first introduced in the aviation field. It is a measure of trust which can be placed in the correctness of the information supplied ...by the total system. In recent years, many GNSS-based applications emerge in the urban environment including liability critical ones, so the concept of integrity attracts more and more attention from urban GNSS users. However, the algorithms developed for the aerospace domain cannot be introduced directly to the GNSS land applications. This is because a high data redundancy exists in the aviation domain and the hypothesis that only one failure occurs at a time is made, which is not the case for the urban users. The main objective of this paper is to provide an overview of the past and current literature discussing the GNSS integrity for urban transport applications so as to point out possible challenges faced by GNSS receivers in such scenario. Key differences between integrity monitoring scheme in aviation domain and urban transport field are addressed. And this paper also points out several open research issues in this field.
The urban environment has changed vastly over past decades, which also has had an impact on our sleep and dietary patterns and possibly health outcomes. Some studies have shown that sleep duration ...and sleep quality has declined over past decades, especially in children. In parallel, our lifestyle and dietary patterns have also changed including more shift work, more meals outside the home or family setting and more irregular eating patterns, including breakfast skipping and late-night eating. This new area of research in nutritional sciences studying the impact of the timing of eating on health outcomes is called chrono-nutrition, and combines elements from nutritional research with chrono-biology. The objectives of this paper were to discuss secular trends in sleep patterns and related dietary patterns, introduce basic concepts and mechanisms of chrono-nutrition and discuss the evidence for the importance of sleep and chrono-nutrition in relation to health outcomes. Overall, chrono-nutrition could mediate the effects between sleep, diet and urbanisation, and more research is needed to elucidate the importance of chrono-nutrition for metabolic health and its impact on public health.
Existing literature has widely explored the individual roles of housing and neighborhood quality, and there is limited research examining their interactive effects on mental health. This 3-year ...cohort study utilized a longitudinal design to investigate the individual and interactive effects of housing and neighborhood quality on mental health among 962 community-dwelling adults in Hong Kong. Participants were asked to rate their residential qualities over the 3-year period. Mental health outcomes, including levels of psychological distress and common mental disorders (CMD), were assessed using the Revised Clinical Interview Schedule (CIS-R). Logistic regression and generalized linear models were used to examine the association between housing and neighborhood quality and CMD/psychological distress, adjusting for sociodemographic and residential characteristics and baseline mental disorders. Housing quality was associated with the 3-year CMD (adjusted OR 0.95; 95% CI 0.91 to 0.98). Likewise, neighborhood quality was associated with CMD over 3 years (adjusted OR 0.92; 95% CI 0.87 to 0.96). In a separate model including both quality measures, the effect of housing quality on CMD was attenuated, whereas the neighborhood impact remained significant (adjusted OR 0.92; 95% CI 0.87 to 0.98). Generalized linear models indicated that for participants residing in substandard housing, those with high neighborhood quality had lower CIS-R scores at follow-up compared to those with low neighborhood quality (p = 0.041). Better neighborhood quality alleviated the detrimental effects of poor housing quality on mental health. Planning for an enhanced neighborhood would improve population mental health in an urban environment.
In an urban environment, dual vertical axis wind turbines (VAWTs) are expected to demonstrate more advantage than horizontal axis wind turbine. For VAWT, solidity is one of the most important ...characteristics, while it has not been well studied. In this study, to investigate the effect of rotor solidity and other characteristics on the power output of counter-rotating dual VAWTs at different rotor centre spacings in a low turbulence intensity condition, twelve wind tunnel experiments for dual VAWTs and six wind tunnel experiments for an isolated VAWT were conducted. The results show that the effect of the dual VAWTs configuration on the VAWT power output is small compared with isolated VAWT under low wind speeds in an urban environment, but the effect exhibits a slight improvement with an increase in rotor solidity. As rotor solidity decreases, the sensitivity of the effect on rotor centre spacing increases. The effect of skewed flow on the power output of dual VAWTs are also well discussed. Furthermore, dual-VAWT systems are studied under real urban environment of a number of major cities such as Guangzhou, London, and Copenhagen. Potentials in different heights are compared with different configurations based on the city planning of those major cities.
•An experimental test on various dual-rotor system was conducted in a wind tunnel.•The relationship between solidity and the dual rotor system is analyzed.•The performance of the dual rotor system under skewed flow is discussed.•The potential of dual rotor system on building are studied in various major cities.
Urban subsurface monitoring requires high temporal‐spatial resolution, low maintenance cost, and minimal intrusion to nearby life. Distributed acoustic sensing (DAS), in contrast to conventional ...station‐based sensing technology, has the potential to provide a passive seismic solution to urban monitoring requirements. Based on data recorded by the Stanford Fiber Optic Seismic Observatory, we demonstrate that near‐surface velocity changes induced by the excavation of a basement construction can be monitored using existing fiber optic infrastructure in a noisy urban environment. To achieve satisfactory results, careful signal processing comprising of noise removal and source signature normalization are applied to raw DAS recordings. Repeated blast signals from quarry sites provide free, unidirectional, and near‐impulsive sources for periodic urban seismic monitoring, which are essential for increasing the temporal resolution of passive seismic methods. Our study suggests that DAS will likely play an important role in urban subsurface monitoring.
Plain Language Summary
Seismic monitoring can provide crucial information about near‐surface changes due to natural or manmade activities. However, the high cost and the “after‐effect” nature of conventional station‐based monitoring methods limit their application in urban environments where near real‐time and meter‐scale resolution are required. Distributed acoustic sensing has the potential to achieve all requirements utilizing existing communication infrastructure. Using Stanford Fiber Optic Seismic Observatory, we demonstrate that its recordings of quarry blasts 13.3 km away carry important subsurface velocity information within the footprint of the array. These short bursts of quarry blast signals provide us free, unidirectional, and repetitive sources that sample the urban subsurface at an interval frequent enough for monitoring. We observe large velocity decrease from the recordings close to the excavation site. Our study suggests that telecommunications fiber repurposed for distributed acoustic sensing will potentially play an important role in many urban subsurface monitoring applications.
Key Points
Using the Stanford DAS array, we demonstrate the reliability of urban DAS recordings when deployed in existing infrastructures
Short DAS recordings of far‐field quarry blasts show sensitivity to the changes in near‐surface velocity within the boundaries of the array
DAS can play an important role in real‐time, high‐resolution, and long‐term urban monitoring applications
The dynamic development of modern cities requires new solutions to urban planning and management by local regional authorities. The paper focuses on ecological indicators based on Earth Remote ...Sensing Data (ERSD) of the snow cover with the purpose to evaluate the city and to plan ecological environment protection strategy. The paper deals with the method of using space images to assess the snow cover pollution of Chelyabinsk, a large Russian industrial city. The assessment of the snow cover of Chelyabinsk was carried out by comparing the heavy metals concentrations with the Landsat 8 data. The spectral indices were calculated for fourteen sites evenly distributed over the urban area of four types: courtyards, car parks, industrial zones and roads. We found a statistically significant difference between the Swirl/Green index and the site type and a correlation with the concentrations of dissolved and suspended forms of heavy metals in snow cover. Snow cover indices can be used as ecological indicators of urban environment.
The concentrations, sources, and risk of twenty organochlorine pesticides (OCPs) in soils and dusts from a typical urban setting in the Niger Delta of Nigeria were examined. The Σ20 OCP ...concentrations (ng g−1) varied from 4.49 to 150 with an average value of 32.6 for soil, 4.67 to 21.5 with an average of 11.7 for indoor dust, and 1.6 to 96.7 with an average value of 23.5 for outdoor dust. The Σ20 OCP concentrations in these media were in the order: soil > outdoor dust > indoor dust, which was in contrast with the order of the detection frequency, i.e., indoor dust (95 to 100 %) > soil (60 to 90 %) > outdoor dust (30 to 80 %). The concentrations of the different OCP classes in these media followed the order: aldrin + dieldrin + endrin and its isomers (Drins) > chlordanes > dichlorodiphenyltrichloroethane (DDTs) > hexachlorocyclohexane (HCHs) > endosulfans for outdoor dust and soil, while that of the indoor dust followed the order: Drins > chlordanes > endosulfans > DDTs > HCHs. The cancer risk values for human exposure to OCPs in these sites exceeded 10−6 which indicates possible carcinogenic risks. The sources of OCPs in these media reflected both past use and recent inputs.
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•OCPs in dust and soils from Port Harcourt city were investigated.•OCP concentrations in soils were higher than those of outdoor and indoor dusts.•Drins and chlordanes were the dominant OCPs in these media.•Exposure to OCPs in these media pose a risk to humans.•OCPs in these media originated from predominantly aged used sources.
Gas-phase oxygenated organic molecules (OOMs) can contribute substantially to the growth of newly formed particles. However, the characteristics of OOMs and their contributions to particle growth ...rate are not well understood in urban areas, which have complex anthropogenic emissions and atmospheric conditions. We performed long-term measurement of gas-phase OOMs in urban Beijing during 2018–2019 using nitrate-based chemical ionization mass spectrometry. OOM concentrations showed clear seasonal variations, with the highest in the summer and the lowest in the winter. Correspondingly, calculated particle growth rates due to OOM condensation were highest in summer, followed by spring, autumn, and winter. One prominent feature of OOMs in this urban environment was a high fraction (∼75%) of nitrogen-containing OOMs. These nitrogen-containing OOMs contributed only 50–60% of the total growth rate led by OOM condensation, owing to their slightly higher volatility than non-nitrate OOMs. By comparing the calculated condensation growth rates and the observed particle growth rates, we showed that sulfuric acid and its clusters are the main contributors to the growth of sub-3 nm particles, with OOMs significantly promoting the growth of 3–25 nm particles. In wintertime Beijing, however, there are missing contributors to the growth of particles above 3 nm, which remain to be further investigated.
Thermal comfort in outdoor space is essential for human health and human wellbeing. The comfortable outdoor space enhances urban livability and sustainability. Currently, the influence of ...environmental quality on human thermal comfort is not conclusive. Research on the interrelation between perceived environmental quality and subjective human thermal comfort is needed to have a concrete argument. This paper examines the relationship between perceived aesthetics, perceived acoustics, and the outdoor thermal comfort in Hong Kong during the hot summer, by conducting questionnaires and on-site meteorological measurement. Thermal sensation vote (TSV) showed a strong, negative association with the perceived aesthetics vote and acoustics vote as calculated for 1 °C UTCI bin. It was also revealed that the groups with satisfactory of perceived acoustic and aesthetics have a significantly higher comfort vote than that of unsatisfactory groups. Findings suggest that humans in a perceptually quiet and beautiful outdoor environment have a significantly higher thermal tolerance, and lower thermal sensitivity. This work provides valuable data on the effects of perceived environmental quality on outdoor thermal comfort in subtropical hot summers in high density urban settings. These findings help the urban development in the outdoor urban environment in our changing climate. Urban planner and designer can create a more satisfactory aesthetic and acoustic environment to improve the thermal tolerance and adaptation of individuals in the outdoor urban environment.
•Perceived environmental quality has considerable influence on thermal perception.•Thermal sensation is negatively associated with aesthetic and acoustic votes.•People feel more comfortable if feeling satisfied with aesthetics and acoustics.•Humans in a quiet, beautiful environment show higher tolerance and lower sensitivity.
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