Chao YUAN

• PhD in architecture
• CEO at National University of Singapore

In the context of urbanization and compact urban living, conventional experience-based planning and design often cannot adequately address the serious environmental issues, such as thermal comfort and air quality. The ultimate goal of this book is to facilitate a paradigm shift from the conventional experience-based ways to a more scientific, evide...

This study develops an approach to model the pedestrian-level wind speed at high spatial resolution within urban areas. The aerodynamic properties of urban areas are a necessary component in the current urban planning and design. However current numerical modelling methods, such as Computational Fluid Dynamics (CFD), cannot balance modelling cost w...

Shape-edged buildings impose large frictional drag on the flow in the urban boundary layer. In the sub-tropics, especially during hot and humid summers, compact building blocks create stagnant air that worsens outdoor urban thermal comfort. The current study adapts the κ–ω SST turbulence model to simulate air flow in urban areas. The accuracy of th...

Convective heat transfer coefficient (h) between a building surface and adjacent air determines the heat loss (or heat gain) from thermal masses. Quantifying h is challenging, as h depends on many factors such as building geometry, surface orientation and flow velocity near the surface. This paper aims to quantify h for the indoor surfaces in the Y...

Hypochlorite (ClO-) exposure has been confirmed to be associated with many serious diseases. Although abundant organic molecule-based probes have demonstrated high sensitivity and selectivity for ClO- response, they often suffer from limitations including tedious preparation steps, poor water solubility, and the use of toxic solvent. In this work,...

Urban areas are known for their complex atmospheric environments, with the building morphology having a significant impact on local climate patterns, air quality, and overall urban microclimate. Understanding the heat and fluid flow in complex urban environments is crucial for improving urban climate resilience. In order to gain a better understand...

In this study, high-temperature nitriding was used to improve the surface hardness and wear resistance of Co–27Cr–22Fe alloy in a thermogravimetric analyzer. The high-temperature nitriding treatments were performed at 1200 °C for 3 and 10 h. Subsequently, at room temperature, the dry sliding wear test was carried out, and the possible effects of lo...

Development of accurate and efficient TCs residue analysis methods is of great significance for the protection of environment, food safety and public health. Herein, a dual-responsive ratiometric fluorescence sensor being capable of simple and sensitive detection of tetracycline (TC) was presented, which was constructed by immobilizing europium ion...

2,4,6-trinitrophenyl phenol (TNP) and dichromate (Cr2O72-) have serious toxicological effects on environment. Therefore, it is very important to detect and remove TNP and Cr2O72- in environmental matrix. In this work, a dual-functional UiO type metal-organic framework (Zr-Sti) was synthesized for simultaneous detection and removal of those pollutan...

Smart city initiatives have been a driving force for city-level dataset collection and the development of data-driven applications that benefit effective city management. There is a need to demonstrate use cases for effective city management using the available dataset. Urban Digital Twin (UDT) is a 3D city model that can integrate multi-discipline...

Hydrazine (N2H4) can cause serious damage to human health, while intracellular viscosity is highly associated with many diseases and cellular dysfunctions. Herein, we report the synthesis of a dual-responsive organic molecule-based fluorescent probe with excellent water solubility being capable of detection of N2H4 and viscosity through dual-fluore...

Heat released from the energy consumption in buildings (QB) is an important component of anthropogenic heat, which is a major contribution to the urban heat island (UHI) phenomenon. However, it is still a challenge to integrate all the available data to improve the estimation of QB due to inconsistences among multiple data sources. This paper prese...

In the process of sustainable transformation, resource-based cities (RBCs) in Heilongjiang are in a dilemma. Resilience is a key capability to help RBCs deepen sustainable development, adapt to shocks, and exit the transformation dilemma. This study aims to clarify the resilience measurements and dynamics of RBCs and propose targeted resilience enh...

Elderly people are more vulnerable than other age groups to the increasing urban heat risk caused by both climate change and urbanization. This study developed a systematic method to assess the urban heat health risk to the aging population in high-density tropical cities. Based on the assessment, the study identifies high heat health risk district...

Urban areas are experiencing excessive heating. Addressing the heat is a challenging but essential task where not only engineering and climatic knowledge matters but also a deep understanding of social and economic dimensions. We synthesize the state of the art in heat mitigation technologies and develop an 'ITE index' framework that evaluates the...

Beating excessive urban heat calls for a whole-system approach, where several individual mitigation measures have to be implemented together. We assess the use of green walls, green roofs, reflective roofs, thermally efficient buildings, high-efficiency indoor cooling, urban forestry, evaporative pavement, and constructed shade for directly reducin...

Although development of sensors being capable of a specific tetracycline antibiotics detection has been extensively documented recently, total quantification of this harmful antibiotics seems to be more imperative from the perspective of environmental monitoring. In this work, 5-aminoisophthalic acid-based metal-organic framework (Zn/H2aip) probe w...

Owing to their unique plasmonic properties, noble metals have been the materials of choice for photovoltaics, photocatalysis and sensors. Here, we demonstrate novel gold(Au) monolayers with tailorable particle diameters and optical property on transparent indium tin oxide (ITO) using a simple electrochemical deposition. The nanoparticles on ITO are...

Heat removal from street canyons to the urban boundary layer above buildings is one of physical processes that may largely determine the (local) urban heat island (UHI) effects. Only few studies show the impact of a buoyant approaching boundary layer flow on heat removal. In this study, we show that heat removal from street canyons is enhanced when...

Since a vast majority of mercury ion (Hg²⁺)-responsive fluorescence probes suffer from significant false positive interference in practical applications originating from their fluorescence quenching mechanism, it is still a challenge to develop a fluorescence enhancement sensor for its assay. In this work, single hexagonal boron nitride quantum dot...

This study explores the buoyancy effect on traffic pollutant dispersion at neighborhood scale, in which a wide range of wind-buoyancy ratios is examined. Pollutant dispersion is solved using a Large Eddy Simulation (LES) turbulence model, where realistic urban morphology and historical traffic pollutant emission data are adopted. For no incoming wi...

Tetracycline antibiotic residues have attracted worldwide attention due to the serious damage to human health and the environment. However, most of the reported fluorescent probes were based on a single fluorescence channel-based response, which often suffered from signal fluctuation-induced poor reproducibility. Herein, by taking advantage of the...

The coexistence of developed areas and historic buildings is an important topic in urban planning. Our study focuses on this topic from the perspective of urban microclimate. A multi-physics CFD simulation is applied to model urban microclimate with anthropogenic heat and buoyancy effects. First, we clarified the impact of new development, i.e., hi...

The vertical wind speed profile is crucial to urban ventilation assessment and urban planning/design. This study uses Light Detection and Ranging (LiDAR) observation as benchmark to evaluate accuracy of wind profiles estimated by conventional methods. The conventional methods include Boundary Layer Wind Tunnel (BLWT), Regional Atmospheric Modeling...

Heat released from the energy consumption in buildings (QB) is an important component of anthropogenic heat, which is a major contribution to the urban heat island (UHI) phenomenon. However, it is still a challenge to integrate all the available data to improve the estimation of QB due to inconsistencies among multiple data sources. This paper pres...

Development of selective and sensitive methods for the detection of 2, 6-dipicolinic acid (DPA), a biomarker produced by bacterial spores, is of great significance for maintaining public health and food safety. Herein, a ratiometric fluorescence strategy using graphene carbon nitride (g-C3N4) coupled with Eu³⁺ is designed for the assay of DPA. As t...

Natural ventilation is an important resource to cool down indoor areas at sub/tropical areas. However, within the high density urban context, anthropogenic heat from mechanical cooling system could have significant impact on the thermal environment at naturally ventilated indoor areas. This study focuses on residential neighbourhood and aims to dev...

There is mounting evidence suggesting that workplace design directly connects with workers’ health and wellbeing. Additionally, the personal status of the mind can affect subjective attitudes and feelings towards the environment. In this study, the impacts of biophilic design attributes in offices on workers’ health and wellbeing are examined. A ne...

There is mounting evidence suggesting that workplace design directly connects with workers’ health and wellbeing. Additionally, the personal status of the mind can affect subjective attitudes and feelings towards the environment. In this study, the impacts of biophilic design attributes in offices on workers’ health and wellbeing are examined. A ne...

Urban air temperature projection is essential to prepare cities for future heat risks. This study aims to anticipate future air temperature increment contributed by climate change and urbanization. First, we identified the rural area in Singapore by historical data, and downscaled global/regional modelling results to investigate climate change at t...

Climate change and heatwaves challenge urban dwellers’ thermal comfort and health. In Hong Kong, more frequent and intensive extreme heat has been observed recently. This study uses Light Detection and Ranging (LiDAR) to observe vertical wind profiles and calibrate numerical simulation methods for urban ventilation assessment in nighttime extreme h...

Plain Language Summary Heat waves (HWs) are a series of days of extremely high temperatures. They can pose serious impacts on public health, for example, morbidity and mortality. Climate change makes HW events globally longer, more frequent, and more intensive. Southeast Asia is very vulnerable to HWs, but suffers from serious lack of HW research d...

Building Energy Modelling (BEM) plays a significant role in projecting future building energy demands and predicting urban climate resilience in the context of climate change and urbanization. Accurate weather data are important components in BEM. In this study, we investigate how the BEM performance is affected by weather datasets, including 1) th...

The evaluation of buoyancy effect on urban ventilation, especially on low wind conditions, is important for the extreme urban heat islands to improve urban climate resilience. To provide suggestions for reliable climate simulation study in the future and support the development of city-scale outdoor ventilation models, this study conducted a critic...

In a highly populated country like Singapore, a significant percentage of our gross annual electricity consumption stems from our domestic electricity usage in our residential houses. Analyzing and understanding factors that could influence such patterns is thus essential in order to derive effective measures to reduce usage. In this research, 16 i...

The work tells of the design and construction of an on-site test facility conceived for the tropical weather characterized by precipitation, humidity, and solar conditions. The unmanned laboratory is a test-bed for clean and sustainable technologies application covering different types of solar photovoltaic modules in the vertical application; the...

It is well known that greenery biophilic design can improve health and productivity, but studies are still needed to quantify greenery dose and corresponding well-being benefits to support design practice. In this study, we investigated impacts of various greenery dose on workplace well-being from the perspectives of physiological, psychological, a...

The stress-controlled low cycle fatigue and ratcheting fatigue behaviors of a nickel-based superalloy were proposed under a series of symmetric and asymmetric cyclic loadings at 650 ℃ to explore the effects of stress amplitude and mean stress on fatigue life. The results show that ratcheting strain increases with cycle numbers increasing. Ratchetin...

In this study, the ratcheting fatigue behaviours of GH742 superalloy at 923 K were investigated through a series of symmetric and asymmetric stress-controlled tests. The effects of stress amplitude and mean stress on the fatigue behaviours were analysed through scanning electron microscopy, transmission electron microscopy and electron backscatter...

The microstructural evolution of a wrought Ni-based superalloy GH742 during long-term thermal exposure at 1023 K for durations up to 10,000 h was investigated. The influence of the microstructure degradation on the stress rupture properties at 923 K/823 MPa and 1023 K/510 MPa was systematically analysed. Scanning electron microscopy and electron pr...

Urban trees ameliorate heat stress for urban dwellers. However, it is difficult to quantitatively assess the integrated impacts of tree planting and street layouts on visual and thermal comfort in simulations and urban field experiments. We conducted scaled outdoor experiments in Guangzhou to investigate the influence of tree plantings on pedestria...

In this study, the effects of annealing on microstructures and the properties of GH3536 superalloy sheets were studied in detail by means of Electron Backscatter Diffraction (EBSD), Scanning Election Microscopy (SEM) and Transmission Electron Microscopy (TEM). The results show that a series of phenomena happened after annealing at 950 °C. The recry...

Coronavirus disease 2019 (COVID-19) is a challenging global problem. COVID-19 has caused shocks to various urban systems, and the tourism industry is no exception. We analyzed the impact on vacation rentals by conducting diachronic data mining on nearly 10 GB of rental data (calendar, listings, and reviews) in twelve highly internationalized megaci...

A 3D numerical modelling is conducted to investigate the thermal plumes merging and buoyancy-driven airflow in urban areas, in which poor natural ventilation causes both thermal comfort and air quality issue. The performances of five different turbulence models, i.e., three URANS (Unsteady Reynolds-averaged Navier–Stokes equations) models and two L...

Anthropogenic heat emission is an important factor for street air warming. In this study, the transient street air warming process caused by anthropogenic heat is investigated by both the analytical model and Large-Eddy Simulation (LES). A new analytical model is developed based on the empirical exchange velocity modelling and heat exchange rate es...

High cycle fatigue properties with different stress levels were performed on GH4742 alloy at room temperature (RT) and 750 °C by staircase method. Comparative analyses of failure mode were made at the two different temperatures. The results show that failure mode changes gradually from surface defects failure to interior crystallographic facets fai...

Anthropogenic heat is one of the key factors that causes intensive Urban Heat Island (UHI) due to its direct impact on ambient temperature in urban areas. Stagnated airflow due to closely packed tall buildings causes weak dilution and removal of anthropogenic heat. Consequently, research is critically needed to investigate the effect of urban morph...

Being able to understand pedestrians behavior is essential for urban planning. Despite a burgeoning research effort directed at the design and modelling of effective urban spaces for pedestrians, remarkably little is known about how pedestrians actually negotiate urban spaces in severely cold areas. By adopting computer vision technology, this pape...

Urban compact buildings impose large frictional drag on boundary-layer air flow and create stagnant air within the building environment. It results in exacerbating the street-level outdoor thermal comfort (OTC). It is common to perform in-situ measurements of the OTC in different urban forms and to study their relationship. However, it is impossibl...

This study numerically investigates the thermal behaviour and airflow characteristics of the Building Integrated Photovoltaic (BIPV) façade. A three-dimensional model is developed based on the typical BIPV façade. Computational Fluid Dynamics (CFD) with the shear stress transport (SST) κ-omega turbulent model is used in the study. The effects of ge...

Tropical countries, like Singapore, are hot and humid throughout the year. Coupled with the Urban Heat Island effect from rapid urbanisation, Singapore has seen a long-term increase in annual average temperatures over the years. One solution is the use of misting systems that tap on the principle of latent heat of vaporisation to provide cooling. T...

Heavy traffic flows commonly result in large vehicular pollutant exposure in near-road buildings. Street layouts and pollutant source settings are key factors. Advertisement boards are sometimes adopted for business purpose, but their impacts on pollutant dispersion and exposure are still unclear. Thus, this paper numerically investigates the influ...

While vertical farming can promote sustainable living and mitigate urban heat island, vegetation could worsen the cross natural ventilation due to additional drag force on air flow. This study aims to investigate the impact of vertical farming on ventilation performance that is important to the thermal comfort especially at tropical/subtropical cit...

Low-cycle fatigue (LCF) behavior of wrought superalloy GH4742 was studied at room-temperature (RT) and 700 °C. Scanning electron microscope (SEM) and Transmission electron microscope (TEM) were used to study the development of cracks and deformation mechanism. An obvious decrease in fatigue life occurred as the temperature was increased from RT to...

Singapore’s high dependence on imported energy and food resources, and the lack of available land requires an efficient use of the built environment in order to increase energy and food autonomy. This paper proposes the concept of a productive façade (PF) system that integrates photovoltaic (PV) modules as shading devices as well as farming planter...

To improve the photovoltaic (PV) power generation, the temperature control measures and optimization of BIPV systems are critical, particularly in tropical weather. There are two categories of cooling mechanisms, i.e. passive and active cooling. In the present study, a simplified numerical model is set up to evaluate the effect of passive cooling o...

A semi-empirical multilayer urban canopy model is developed to estimate the vertical dispersion of traffic emissions in high density urban areas. It is motivated by the heterogeneity of urban morphology in real urban cities and the need of quick urban design and planning. The urban canopy is divided into multiple layers, to include the impact of bu...

High-density urban areas are often associated with limited outdoor natural ventilation. Given the growing call for more vegetation in the cities, it is important to study the wind resistant of urban trees in order to address outdoor natural ventilation problem in the landscape planning. Currently, Computational Fluid Dynamics (CFD) simulation and w...

A semi-empirical multilayer urban canopy model is developed to estimate the vertical dispersion of traffic emissions in high density urban areas. It is motivated by the heterogeneity of urban morphology in real urban cities and the need of quick urban design and planning. The urban canopy is divided into multiple layers, to include the impact of bu...

The study focuses on the creation of an algorithm in Grasshopper using Ladybug and Honeybee plugins to simulate a large number of façade design variants with the integration of photovoltaic (PV) panels as shading devices and farming systems. The algorithm aims to facilitate such simulations in a semi-automated way complying with standard practise i...

The regenerative design framework aims to ‘engage a broader range of possibilities by moving beyond the immediate building and site boundaries’. It implies that the environmental performance of buildings requires a revised definition so that it considers not only the building itself, but also its contribution beyond its own boundary, i.e. neighbour...

Singapore has committed to reduce greenhouse gases emissions as part of the Paris Agreement. Increasing energy and food self-sufficiency through integration of solar and vertical farming systems into buildings’ envelope could play a significant role in achieving Singapore’s targeted reductions. This paper focuses on the design optimization of the f...

Given the high rate of urbanization, compact urban planning enables more efficient utilization of resources in the cities by decreasing traffic cost and land use. However, high-density urban living has been associated with serious environmental issues, such as Urban Heat Island (UHI). In Singapore, commercial and residential building energy consump...

There is evidence that access to green spaces have positive effects on health, possibly through beneficial effects on exercise, air quality, urban heat islands, and stress. Few previous studies have examined the associations between green space and mortality, and they have given inconsistent results. This ecological study relates green space to mor...

Building facades in tropical low-latitude regions usually receive ample sunlight; hence, the integration of solar and farming systems may greatly contribute to the productive role of buildings. This paper discusses the development and optimisation of modular productive solar facade (PSF) prototypes suitable for residential buildings involving the i...

Oxidation behaviors of a spray-forming disk superalloy LSHR were investigated in the temperature range of 750-900°C. The composition and morphology of oxidation scales were investigated by X-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), and electron probe microanalysis (EPMA). Oxidation...

This study investigates ventilation performance in parametric urban scenarios using a large-eddy simulation (LES) model called the Parallelized LES Model (PALM). With various combinations of planning parameters, air flows and pedestrian-level velocity ratios in a total of 48 scenarios are investigated. Major findings and recommendations are: First,...

As the operating temperature of disk service was elevated from 650 °C to 700 °C, the creep properties urged to be paid attention. To investigate the creep properties of spray-formed low solvus, high refractory (LSHR) superalloy at about 700 °C, creep tests were conducted under seven different stress ranging from 690 MPa to 897 MPa. By means of cree...

The purpose of this study is to evaluate the effects of hot isostatic pressing (HIP) on the porosity healing and the microstructure evolution of a cast superalloy K452, which is generally applied for fabrication the vanes with the bigger size. The annihilation degree of the porosity, related to the location and shape of the porosity as well as HIP...

This study investigates ventilation performance in parametric urban scenarios using a large-eddy simulation (LES) model. The LES codes are first validated using computational fluid dynamics (CFD) guidelines for building simulations, and then utilized in the simulations of parametric-designed urban configurations. With various combinations of planni...