Can changing the timing of outdoor air intake reduce indoor concentrations of traffic‐related pollutants in schools?

Traffic emissions have been associated with a wide range of adverse health effects. Many schools are situated close to major roads, and as children spend much of their day in school, methods to reduce traffic‐related air pollutant concentrations in the school environment are warranted. One promising method to reduce pollutant concentrations in schools is to alter the timing of the ventilation so that high ventilation time periods do not correspond to rush hour traffic. Health Canada, in collaboration with the Ottawa‐Carleton District School Board, tested the effect of this action by collecting traffic‐related air pollution data from four schools in Ottawa, Canada, during October and November 2013. A baseline and intervention period was assessed in each school. There were statistically significant (P < 0.05) reductions in concentrations of most of the pollutants measured at the two late‐start (9 AM start) schools, after adjusting for outdoor concentrations and the absolute indoor–outdoor temperature difference. The intervention at the early‐start (8 AM start) schools did not have significant reductions in pollutant concentrations. Based on these findings, changing the timing of the ventilation may be a cost‐effective mechanism of reducing traffic‐related pollutants in late‐start schools located near major roads.     

Evaluation of indoor environmental quality conditions in elementary schools׳ classrooms in the United Arab Emirates

This study presents findings of indoor environmental quality (IEQ) investigations conducted in elementary schools׳ classrooms in the United Arab Emirates (UAE). Average TVOC, CO₂, O₃, CO, and particle concentrations measured in the classrooms were 815 µg/m³, 1605 ppm, 0.05 ppm, 1.16 ppm, and 1730 µg/m³, respectively. Whereas, local authority known as Dubai Municipality recommended 300 µg/m³, 800 ppm, 0.06 ppm, 9 ppm, and 150–300 µg/m³ for TVOC, CO₂, O₃, CO, and particle, respectively. Dubai Municipality recommended temperature and relative humidity (RH) levels of 22.5 °C to 25.5 °C and 30%–60%, respectively. Average temperature and RH levels measured in the classrooms were 24.5 °C and 40.4%, respectively. Average sound level in the classrooms was 24 dB greater than recommended sound level limit of 35 dB. Six (6) classrooms had average lux levels in the range of 400–800 lux. Two (2) classrooms had average lux levels in the range of 100–200 lux. The remaining classrooms had lux levels around the recommended 300 lux. High occupancy density was observed in majority of the studied classrooms. Observations during walkthrough investigations could be used to explain measured IEQ data. Poor IEQ conditions in the studied classrooms highlight the need for further research investigation to understand how poor classrooms׳ IEQ condition could influence students׳ health, comfort, attendance rate, and academic performance.     

Analysing the influence of operating conditions on the performance of algal–bacterial granular sludge processes for wastewater treatment: A review

This article discussed the effect of the main operating parameter involved in the operation of algal–bacterial granular sludge (ABGS) systems as promising biological processes for wastewater treatment. The focus was on the operational ranges reported in the literature capable of achieving better granule properties, good stability and high removal capacities. This review identified that hydraulic retention time (HRT), light intensity (LI) and light/dark periods were the most influential operating factors on the formation, stability, settleability and organic pollutant removal efficiency of ABGS. The discussion argued that ABGS systems enhance industrial and domestic wastewater treatment due to additional advantages that provide the symbiotic interactions to process performance, maintaining lesser operating costs concerning aerobic granular sludges (AGS) and microalgae consortia. This review will improve the understanding of the operation of ABGS systems and thus further expand possible operating combinations that help to enhance microbial interactions, microalgae growth and external aeration self-sufficiency in further research with a focus on its scaling up.     

What should housing vouchers do? A review of the recent literature

This paper challenges the assumption that housing vouchers help recipients move from crime-ridden inner-city areas to ‘good’ lower-poverty neighborhoods and, in turn, to achieve self-sufficiency. A review of the American and European literature on housing mobility programs and on mixed-income communities fails to support this belief. Efforts to maintain, and expand, the voucher program should be based on the program’s proven ability to provide decent and affordable housing rather than on unproven claims that it promotes poverty deconcentration and family self-sufficiency. I find considerable evidence that voucher recipients cluster spatially and that this promotes social decline in neighborhoods already vulnerable to change. Policymakers need to monitor voucher settlement patterns and to address programmatic weaknesses that cause negative neighborhood effects and voucher controversies.     

A parametric study on the effects of displacer-cylinder-circumferential-wall thermal conditions on the performance of a γ-type LTD Stirling engine

ABSTRACT

Regarding a Stirling engine’s heat source and heat sink, most of the studies in the literature focus only on the magnitude of temperature difference between them. However, different Stirling engines adopt very different heat-source and heat-sink configurations. This study is aimed at understanding the effects of different displacer-cylinder-wall thermal conditions on engine performance using computational fluid dynamics (CFD). Results include p–V diagrams, heat flux distributions, temperature variations, and effects of three displacer-cylinder-wall parameters on indicated power and efficiency. It is found that the thermal conditions on the displacer-cylinder-circumferential wall (DCCW) impose significant effects on engine performance. Within the ranges of parameters investigated in this study, extending the coverage of heat source and heat sink on this wall improves up to 28% in indicated power at the cost of losing about 10% in efficiency, proving the significance of DCCW conditions on engine performance.     

What is the relationship between indoor air quality parameters and airborne microorganisms in hospital environments? A systematic review and meta-analysis

Airborne microorganisms in hospitals have been associated with several hospital-acquired infections (HAIs), and various measures of indoor air quality (IAQ) parameters such as temperature, relative humidity, carbon dioxide (CO₂), particle mass concentration, and particle size have been linked to pathogen survival or mitigation of pathogen spread. To investigate whether there are quantitative relationships between the concentration of airborne microorganisms and the IAQ in the hospital environment. Web of Science, Scopus and PubMed databases were searched for studies reporting airborne microbial levels and any IAQ parameter(s) in hospital environments, from database inception to October 2020. Pooled effect estimates were determined via random-effects models. Seventeen of 654 studies were eligible for the meta-analysis. The concentration of airborne microbial measured as aerobic colony count (ACC) was significantly correlated with temperature (r = 0.25 [95% CI = 0.06–0.42], p = 0.01), CO₂ concentration (r = 0.53 [95% CI = 0.40–0.64], p ˂ 0.001), particle mass concentration (≤5 µg/m³; r = 0.40 [95% CI = 0.04–0.66], p = 0.03), and particle size (≤5 and ˃5 µm), (r = 0.51 [95% CI = 0.12–0.77], p = 0.01 and r = 0.55 [95% CI = 0.20–0.78], p = 0.003), respectively, while not being significantly correlated with relative humidity or particulate matter of size >5 µm. Conversely, airborne total fungi (TF) were not significantly correlated with temperature, relative humidity, or CO₂ level. However, there was a significant weak correlation between ACC and TF (r = 0.31 [95% CI = 0.07–0.52], p = 0.013). Although significant correlations exist between ACC and IAQ parameters, the relationship is not definitive; the IAQ parameters may affect the microorganisms but are not responsible for the presence of airborne microorganisms. Environmental parameters could be related to the generating source, survival, dispersion, and deposition rate of microorganisms. Future studies should record IAQ parameters and factors such as healthcare worker presence and the activities carried out such as cleaning, sanitizing, and disinfection protocols. Foot traffic would influence both the generation of microorganisms and their deposition rate onto surfaces in the hospital environment. These data would inform models to improve the understanding of the likely concentration of airborne microorganisms and provide an alternative approach for real-time monitoring of the healthcare environment.     

How do the indoor size distributions of airborne submicron and ultrafine particles in the absence of significant indoor sources depend on outdoor distributions?

Although almost all epidemiological studies of smaller airborne particles only consider outdoor concentrations, people in Central Europe actually spend most of their time indoors. Yet indoor pollutants such as organic gases, allergens and dust are known to play a prominent role, often affecting human health more than outdoor ones. The aim of this study was to ascertain how the indoor particle size distributions of submicron and ultrafine particles correlate with the outdoor concentrations in the absence of significant indoor sources. A typical indoor particle size distribution pattern has one or two modes. In the absence of significant indoor activities such as smoking, cooking etc., outdoor particles were found to be a very important source of indoor particles. The study shows that in the absence of significant indoor sources, the number of indoor concentrations of particles in this size range are clearly lower than the outdoor concentrations. This difference is greater, the higher the number of outdoor concentrations. However, the drop in concentration is not uniform, with the decrease in concentration of smaller particles exceeding that of larger ones. By contrast, the findings with larger particle sizes (diameter > 1 microm) exhibit rather linear concentration decreases. The non-uniform drop in the number of concentrations from outdoors to indoors in our measurements considering smaller particles ( >0.01 microm) is accompanied by a shift of the concentration maxima to larger particle diameters.     

Evaluation of natural illumination and thermal comfort conditions in the Ribeirao Preto’s Technological Village

The results of post-occupancy surveys of the 11 different construction systems used in the dwellings of the Technological Village of Ribeirao Preto are analyzed. The analyses focus on evaluating the natural illumination and thermal comfort conditions in selected habitation units after 2 years of use. All systems were devised to provide living conditions to low-income families with low purchasing power and, most importantly, to disseminate construction technologies adapted to, and appropriate for, this specific region of the country. The results indicate that the methodology employed is not appropriate using only classical factors to assess the illumination conditions, i.e. illuminance level and daylight factor, for a direct quantification of the illumination. The isolated use of these factors can result in distortions. The evaluation of the environmental conditions is relevant to observe that there can be differences between theoretical thermo-physical properties and actual features of the materials and construction systems analyzed.     

Experiences and lessons from the use of TBM in the Himalaya – A review

Tunnel boring machine (TBM), with its many advanced features, is being regularly planned now for the excavation of long tunnels in the difficult geology of the Himalayan region. The experience, so far, with the TBMs in three tunnels of Himalayas in India has not been encouraging. However, efforts are being made to overcome the problems and make the TBM a successful venture in the difficult grounds of Himalaya in India. The recent successful completion of 14.75 km long TBM portion of head race tunnel in Kishanganga hydroelectric project in J&K state has shown that the TBM can be used in the Himalayan tunnels as well.In the paper the experiences of TBM in four Himalayan tunnels are briefly highlighted. In case of Tapovan-Vishnugad head race tunnel, the variation of ground in terms of difficulty in managing the TBM thrust and penetration rate has also been highlighted. At the end, some issues have been presented which seems to be important for the success of TBM in the difficult grounds.     

What are the strategies to manage megaproject supply chains? A systematic literature review and research agenda

This systematic literature review explores strategies to manage complex supply chains in megaprojects, connecting project management and operations management literatures. A total of 2,106 titles and abstracts were analyzed and 94 papers were fully reviewed, identifying six categories of strategies: inter-firm collaboration and coordination, governance, procurement, projects as networks, production and logistics, and risk management. We present the multi-level Megaproject Supply Chain (MSC) framework, unpacking the complex inter-organizational structure of megaprojects in five levels and units of analysis to guide future research. The MSC framework identifies the micro, meso and macro levels of megaprojects and introduces two additional hybrid levels to identify inter-organizational relationships: the meso‑micro and meso‑macro. We suggest four avenues to advance supply chain management in megaprojects through multi-level explorations: (i) Supply Chain Structure: Permanent vs Temporary, (ii) Strategic Procurement and Commercial, (iii) Supply Chain Design: Standardization vs Customization, (iv) Supply Chain Governance: Collaboration and Coordination.     

A lone light? A critical assessment of the outcomes of the Rundle Convergence Project in Adelaide,South Australia

Flagship urban design projects are increasingly employed by governments to achieve global recognition. Despite the political value placed upon and significant economic investment in flagship urban design projects, measuring their success and failure is extremely subjective. This research engages with this challenge though a critical analysis of the Rundle Convergence Project. Initiated by the City of Adelaide in 2006, this project sought to reinvigorate a drab intersection in the heart of Adelaide, South Australia. Touted alternatively as Adelaide’s Piccadilly Circus or Times Square, the Rundle Convergence Project promised much. However, arguably little has been realized in the intervening decade. Drawing on textual analysis of policy documents, landscape analysis and semi-structured interviews with key professionals and local government elected members involved with the Rundle Convergence Project, this research explores the successful and unsuccessful elements of flagship urban design projects in determining project outcomes. Tracing the Rundle Convergence Project’s conceptualization and development highlights the importance of appropriate contextualization and reveals the influence that individual vision, personal/political agendas and political cycles hold for the success or otherwise of flagship urban design projects. The paper concludes with a series of proposals in order to avoid the pitfalls and issues that bedevilled the Rundle Convergence Project.     

Analysis and prediction of TBM performance in blocky rock conditions at the Lötschberg Base Tunnel

This paper focuses on the analysis of the TBM performance recorded during the excavation of the Lötschberg Base Tunnel. The southern part of the tunnel was excavated by two gripper TBMs, partly through blocky rock masses at great depth. The jointed nature of the blocky rock mass posed serious problems concerning the stability of the excavation face. A detailed analysis has been carried out to obtain a relationship between the rock mass conditions and the TBM performance, using the Field Penetration Index (FPI). In blocky rock conditions, the FPI is defined as the ratio between the applied thrust force and the actual penetration rate. A database of the TBM parameters and the geological/geotechnical conditions for 160 sections along the tunnel has been established. The analysis reveals a relationship between the FPI and two rock mass parameters: the volumetric joint count (J_v) and the intact rock uniaxial compressive strength (UCS). Through a multivariate regression analysis, a prediction model for FPI in blocky rock conditions (FPI_blocky) is then introduced. Finally, other TBM performance parameters such as the penetration rate, the net advance rate and the total advance rate are evaluated using FPI_blocky.     

Cleaning practices and cleaning products in nurseries and schools: to what extent can they impact indoor air quality?

In the framework of a nationwide survey on indoor air quality conducted from September 2009 to June 2011 in 310 nurseries, kindergartens, and elementary schools in all regions of France, cleaning practices and products were described through an extensive questionnaire completed on‐site by expert building inspectors. The questionnaire included the cleaning frequencies and periods, cleaning techniques, whether windows were open during cleaning, and the commercial names of the products used. Analysis of the questionnaire responses showed that cleaning was generally performed daily for furniture and floors. It was performed mostly in the evening with wet mopping and with one or more windows open. Five hundred eighty‐four different cleaning products were listed, among which 218 safety data sheets (SDSs) were available and analyzed. One hundred fifty‐two chemical substances were identified in the SDSs. The typical substances in cleaning products included alcohols, chlorides, terpenes, aldehydes, and ethers; more than half of them are irritants. Two endocrine disruptors, 2‐phenylphenol and Galaxolide, were identified in two cleaning products used every day to clean the floors, in seven kindergartens and in a nursery respectively. Eleven reactive substances containing C=C double bonds, mostly terpenes, were identified in a wide variety of cleaning products.     

Do classroom ventilation rates in California elementary schools influence standardized test scores? Results from a prospective study

Limited evidence has associated lower ventilation rates (VRs) in schools with reduced student learning or achievement. We analyzed longitudinal data collected over two school years from 150 classrooms in 28 schools within three California school districts. We estimated daily classroom VRs from real‐time indoor carbon dioxide measured by web‐connected sensors. School districts provided individual‐level scores on standard tests in Math and English, and classroom‐level demographic data. Analyses assessing learning effects used two VR metrics: average VRs for 30 days prior to tests, and proportion of prior daily VRs above specified thresholds during the year. We estimated relationships between scores and VR metrics in multivariate models with generalized estimating equations. All school districts had median school‐year VRs below the California VR standard. Most models showed some positive associations of VRs with test scores; however, estimates varied in magnitude and few 95% confidence intervals excluded the null. Combined‐district models estimated statistically significant increases of 0.6 points (P = 0.01) on English tests for each 10% increase in prior 30‐day VRs. Estimated increases in Math were of similar magnitude but not statistically significant. Findings suggest potential small positive associations between classroom VRs and learning.     

Do political links influence water prices? Determinants of water prices in Germany

We explain water prices in Germany by analyzing demand and cost drivers, governance structures and political links to local politicians. First, we find evidence for economies of scope between supply and wastewater treatment. Soil rigidity significantly influences water prices, and prices tend to be higher in municipalities with declining populations. Second, we analyze governance structures and political links between local mayors and water utilities. We find weak indication that these factors influence prices. The existence of multiple political interests in the governance bodies overseeing water utilities tends to coincide with higher prices. As most of our governance and many of our political factors lack statistical significance, we conclude that it is mainly cost and demand factors that determine prices, and political links play a minor role.     

Fire resistance performance of unprotected wood–wood–wood and wood–steel–wood connections: A literature review and new data correlations

This paper reviews fire resistance tests of double shear timber connections, including wood–wood–wood connections with nails, bolts and dowels and wood–steel–wood connections with bolts and dowels. Test data are used to assess the effects of the load ratio and the member geometry on the fire resistance of timber connections. New relationships are proposed and analysis results show good agreement with the test results. Design rules presented in Eurocode 5 are also discussed and compared with the proposed calculation method.