A Conductometric Indium Oxide Semiconducting Nanoparticle Enzymatic Biosensor Array

We report a conductometric nanoparticle biosensor array to address the significant variation of electrical property in nanomaterial biosensors due to the random network nature of nanoparticle thin-film. Indium oxide and silica nanoparticles (SNP) are assembled selectively on the multi-site channel area of the resistors using layer-by-layer self-assembly. To demonstrate enzymatic biosensing capability, glucose oxidase is immobilized on the SNP layer for glucose detection. The packaged sensor chip onto a ceramic pin grid array is tested using syringe pump driven feed and multi-channel I–V measurement system. It is successfully demonstrated that glucose is detected in many different sensing sites within a chip, leading to concentration dependent currents. The sensitivity has been found to be dependent on the channel length of the resistor, 4–12 nA/mM for channel lengths of 5–20 μm, while the apparent Michaelis-Menten constant is 20 mM. By using sensor array, analytical data could be obtained with a single step of sample solution feeding. This work sheds light on the applicability of the developed nanoparticle microsensor array to multi-analyte sensors, novel bioassay platforms, and sensing components in a lab-on-a-chip

A study on the effect of vertical greening on the thermal environment of street canyons based on ENVI-met simulation

Vertical greening is one of the effective measures to improve the microclimate and air quality of high-density urban street canyons, and its impact on the thermal environment is closely related to the street canyon morphology. In this paper, based on the characteristics of high-density urban street canyons in the context of Shenzhen City, 12 sets of cases (two orientations, two aspect ratios, and three height-to-width ratios) were simulated and designed using ENVI-met software to study the effects of vertical greening on the thermal environment of buildings under different street canyon morphologies, and to summarize the impact of vertical greening on the microclimate of different street canyons. The results of the study show that the orientation of the street canyon is the most influential factor in the thermal efficiency of vertical greening under the street canyon geometry with the same amount of greening and that the vertical greening effect of east-west oriented street canyons is generally better than that of north-south oriented street canyons in terms of cooling, humidification, and improvement of thermal comfort at the walking level

A Grey Box Modeling Method for Fast Predicting Buoyancy-Driven Natural Ventilation Rates through Multi-Opening Atriums

The utilization of buoyancy-driven natural ventilation in atrium buildings during transitional seasons helps create a healthy and comfortable indoor environment by bringing fresh air indoors. Among other factors, the air flow rate is a key parameter determining the ventilation performance of an atrium. In this study, a grey box modeling method is proposed and a prediction model is built for calculating the buoyancy-driven ventilation rate using three openings. This model developed from Bruce’s neutral height-based formulation and conservation laws is supported with a theoretical structure and determined with 7 independent variables and 4 integrated parameters. The integrated parameters could be estimated from a set of simulated data and in the results, the error of the semi-empirical predictive equation derived from CFD (computational fluid dynamics) simulated data is controlled within 10%, which indicates that a reliable predictive equation could be established with a rather small dataset. This modeling method has been validated with CFD simulated data, and it can be applied extensively to similar buildings for designing an expected ventilation rate. The simplicity of this grey box modeling should save the evaluation time for new cases and help designers to estimate the ventilation performance and choose building optimal opening designs

The influence of envelope features on interunit dispersion around a naturally ventilated multi-story building

This study examines the influence of building envelope features on interunit dispersion around multi-story buildings, when the presence of an upstream interfering building is also considered. Validated CFD methods in the steady-state RANS framework are employed. In general, the reentry ratios of pollutant from a source unit to adjacent units are mostly in the order of 0.1%, but there are still many cases being in the order of 1%. The influence of envelope features is dependent strongly on the interaction between local wind direction and envelope feature. In a downward dominated near-facade flow field, the presence of vertical envelope features forms dispersion channels to intensify the unidirectional spread. Horizontal envelope features help induce the dilution of pollutant to the main stream and weakens largely the vertical interunit dispersion. The large influences caused by the presence of envelope features extend the existing understanding of interunit dispersion based on flat-facade buildings. © 2018, Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature

Effects of envelope features on wind flow and pollutant exposure in street canyons

Traffic pollution has posed a serious threat to the health of near-road city residents and pedestrians, especially in high-density cities. However, the influences of envelope features, including balconies, overhangs and wing walls, on pollutant exposure to near road residents and pedestrians have not been fully understood. This paper investigates the effects of three commonly-used envelope features on wind flow and pollutant exposure to residents in street canyon with three different aspect ratios. The evaluation metrics of personal intake fraction and daily pollutant exposure are used to quantitatively assess the influences caused by different envelope features on healthy risk of near-road residents and pedestrians, alongside with wind flow pattern and pollutant distribution. The results show that these envelope features have increased the risk of pollutant exposure for the leeward side residents, while the risk of pollutant exposure for the windward side residents is reduced for most cases, in particular for the first floor. This observation is especially prominent when the canyon has the highest aspect ratio among the tested ratios, with the increased ratio of personal intake fraction reaching up to 540%. Moreover, the pollutant concentration is overall higher on leeward side of upstream building than that of windward side of downstream building. These findings can help urban planners and architects to build healthy and sustainable urban environment. © 202

On-site evaluation of pedestrian-level air quality at a U-type street canyon in an ancient city

Urban building disposition plays an important role in determining local microclimate including air quality. Ancient cities normally have some special building dispositions to reduce the penetration of cold wind in winter, which, however, may impact adversely on air pollutant dilution today. This paper investigated the pedestrian-level air quality at a common building disposition in Chinese ancient cities, namely a U-type street canyon. On-site measurements were conducted comparatively at a U-type street canyon and a nearby open space in Xi'an China during January 2015. Three primary air pollutants (PM10, PM2.5 and NO2) as well as wind speed and direction, air temperature and relative humidity were measured continuously from 8:00 a.m. to 8:00 p.m. for a six-day period that covered both clean and hazy days. Pedestrian-level wind condition at the U-type street canyon is mostly independent of that above the canyon, where adverse dilution condition is clearly evident for pollutants. PM2.5/PM10 ratio at the street canyon reached up to 0.9, which is nearly twice that at the nearby observatory. Overall, air quality index (AQI) in the street canyon is, on average, higher by 20% than that at the open space. These findings suggest that this ancient design should be discouraged

Effects of building layouts and envelope features on wind flow and pollutant exposure in height-asymmetric street canyons

The influences of building layouts on pollutant dispersion within urban street canyons have been widely studied, although they have been rarely considered with envelope features. Different envelope features, such as wing walls, balconies and overhangs, have not yet been quantitatively assessed for their effects on the wind flow patterns around street canyons to a certain degree. Adopting the evaluation indicators of personal intake fraction and daily pollutant exposure, this study aims to investigate the potential influences of building layouts and envelope features that affect pollutant exposure risks for pedestrians and near-road residents via computational fluid dynamics (CFD). The turbulence modelling approach and numerical methods are validated by reported experiments in the literature. Asymmetric street canyons with an aspect ratio of 2 and two typical building layouts, namely, step-up and step-down notch configurations, are further investigated to test their effects. The results indicate that the step-down configuration provides worse situations for wind environments and pollutant dispersion than symmetric and step-up configurations. More specifically, the presence of overhangs has the greatest impact on the personal intake fraction (P_IF) change ratio, followed by balconies. The largest P_IF change ratio occurs on the fifth floor of an upstream building when overhangs are applied to the step-down street canyon. The aforementioned findings are helpful to understand the influences of building layouts together with envelope features on the wind environment as well as pollutant exposure risks experienced by pedestrians and near-road residents