Turbulent flow modification in the atmospheric surface layer over a dense city.

Winds in the atmospheric surface layer (ASL) over distinctive urban morphology are investigated by building-resolved large-eddy simulation (LES). The exponential law is applied to urban canopy layers (UCLs) unprecedentedly to parameterize vertical profiles of mean-wind-speed u¯ and examine the influence of morphological factors. The skewness of streamwise velocity S is peaked at the zero-plane displacement d (drag center) where flows decelerate mostly.

The effect of microchannel height on the acoustophoretic motion of sub-micron particles.

Acoustophoresis is an effective technique for particle manipulation. Acoustic radiation force scales with particle volume, enabling size separation. Yet, isolating sub-micron particles remains a challenge due to the acoustic streaming effect (ASE).

Empirical mode decomposition of the atmospheric flows and pollutant transport over real urban morphology.

The momentum transport and pollutant dispersion in the atmospheric surface layer (ASL) are governed by a broad spectrum of turbulence structures. Whereas, their contributions have not been explicitly investigated in the context of real urban morphology. This paper aims to elucidate the contributions from different types of eddies in the ASL over a dense city to provide the reference of urban planning, realizing more favorable ventilation and pollutant dispersion.

Wavelet analysis of the atmospheric flows over real urban morphology.

Winds are the basic forces for atmospheric transport such as pollutant removal and pedestrian thermal comfort. The transport capability is commonly measured in terms of length and velocity scales. In this connection, the flows in the atmospheric surface layer (ASL) over the Kowloon Peninsula, Hong Kong (HK) are scrutinized by the large-eddy simulation (LES) to characterize the motion scales over real urban morphology.

Localized Characteristics of the First Three Typical Condensation Frosting Stages in the Edge Region of a Horizontal Cold Plate.

Condensation frosting usually causes a negative influence on heat exchangers employed in engineering fields. As the relationships among the first three typical condensation frosting stages in the edge regions of cold plates are still unclear, an experimental study on the localized condensation frosting characteristics in the edge region of a cold plate was conducted. The edge effects on the water droplet condensation (WDC), water droplet frozen (WDF) and frost layer growth characteristics were quantitatively investigated.

All-weather thermochromic windows for synchronous solar and thermal radiation regulation.

Adaptive control of solar and thermal radiation through windows is of pivotal importance for building energy saving. However, such synchronous passive regulations are challenging to be integrated into one thermochromic window. Here, we develop a solar and thermal regulatory (STR) window by integrating poly(-isopropylacrylamide) (pNIPAm) and silver nanowires (AgNWs) into pNIPAm/AgNW composites.

Infection control measures for public transportation derived from the flow dynamics of obstructed cough jet.

During the COVID-19 pandemic, WHO and CDC suggest people stay 1 m and 1.8 m away from others, respectively. Keeping social distance can avoid close contact and mitigate infection spread.

Airborne infection risk of nearby passengers in a cabin environment and implications for infection control.

Background: Expiratory droplets cause high infection risk to nearby passengers via airborne route.

Methods: We built a two-row four-seat setup to simulate a public transport cabin. A cough generator and a nebulizer were used to simulate the cough and talk processes respectively.

A Solution-Processed Inorganic Emitter with High Spectral Selectivity for Efficient Subambient Radiative Cooling in Hot Humid Climates.

Daytime radiative cooling provides an eco-friendly solution to space cooling with zero energy consumption. Despite significant advances, most state-of-the-art radiative coolers show broadband infrared emission with low spectral selectivity, which limits their cooling temperatures, especially in hot humid regions. Here, an all-inorganic narrowband emitter comprising a solution-derived SiO N layer sandwiched between a reflective substrate and a self-assembly monolayer of SiO microspheres is reported.

The effect of head orientation and personalized ventilation on bioaerosol deposition from a cough.

Head orientations directly determine movement directions of exhaled pathogen-laden droplets, while there is a lack of research about the effect of the infected person's head orientations on respiratory disease transmission during close contact. This work experimentally investigated the effect of different head orientations of an infected person (IP) on the bioaerosol deposition on a healthy person (HP) during close contact. Also, the effectiveness of PV flow in reducing bioaerosol deposition on the HP under the IP's different head orientations was investigated.

Biotechnology of Plastic Waste Degradation, Recycling, and Valorization: Current Advances and Future Perspectives.

Invited for this month's cover is the collaborative group of Dr. Carol Sze Ki Lin and Dr. Xiang Wang.

Respiratory bioaerosol deposition from a cough and recovery of viable viruses on nearby seats in a cabin environment.

Respiratory bioaerosol deposition in public transport cabins is critical for risk analysis and control of contact transmission. In this work, we built a two-row four-seat setup and an air duct system to simulate a cabin environment. A thermal manikin on the rear left-hand seat was taken as the infected passenger (IP) and "coughed" three times through a cough generator.

Biotechnology of Plastic Waste Degradation, Recycling, and Valorization: Current Advances and Future Perspectives.

Although fossil-based plastic products have many attractive characteristics, their production has led to severe environmental burdens that require immediate solutions. Despite these plastics being non-natural chemical compounds, they can be degraded and metabolized by some microorganisms, which suggests the potential application of biotechnologies based on the mechanism of plastic biodegradation. In this context, microbe-based strategies for the degradation, recycling, and valorization of plastic waste offer a feasible approach for alleviating environmental challenges created by the accumulation of plastic waste.

Solution-Processed All-Ceramic Plasmonic Metamaterials for Efficient Solar-Thermal Conversion over 100-727 °C.

Low-cost and large-area solar-thermal absorbers with superior spectral selectivity and excellent thermal stability are vital for efficient and large-scale solar-thermal conversion applications, such as space heating, desalination, ice mitigation, photothermal catalysis, and concentrating solar power. Few state-of-the-art selective absorbers are qualified for both low- (<200 °C) and high-temperature (>600 °C) applications due to insufficient spectral selectivity or thermal stability over a wide temperature range. Here, a high-performance plasmonic metamaterial selective absorber is developed by facile solution-based processes via assembling an ultrathin (≈120 nm) titanium nitride (TiN) nanoparticle film on a TiN mirror.

Bio-inspired TiO nano-cone antireflection layer for the optical performance improvement of VO thermochromic smart windows.

Vanadium dioxide (VO) is a promising material for thermochromic glazing. However, VO thermochromic smart windows suffer from several problems that prevent commercialization: low luminous transmittance (T) and low solar modulation ability (ΔT). The solution to these problems can be sought from nature where the evolution of various species has enabled them to survive.

Study of particle resuspension from dusty surfaces using a centrifugal method.

Particle resuspension has been recognized as a secondary source of indoor air pollution by many field studies. However, some laboratory studies showed that the air velocities or force fields required to resuspend aerosol particles are very high that rarely occurred in indoor environments. In fact, the surfaces used in these studies were treated to ensure cleanliness, but in reality, dusty surfaces are ubiquitous in our daily life.

Dataset on critical parameters of dispersion stability of Cu/AlO nanofluid and hybrid nanofluid for various ultra-sonication times.

The data presented in this data article comprises the critical parameters of dispersion stability such as the particle effective diameter, zeta potential, sedimentation velocity and stability factor for Cu/AlO single particle nanofluid and hybrid nanofluid samples at various ultra-sonication times, that is, 0.5 h, 1.0 h, 2.

Differential gene expression in Escherichia coli during aerosolization from liquid suspension.

Comparative transcriptome analysis was used to determine the differentially expressed genes in Escherichia coli during aerosolization from liquid suspension. Isogenic mutant studies were then used to examine the potential part played by some of these genes in bacterial survival in the air. Bioaerosols were sampled after 3 min of nebulization, which aerosolized the bacteria from the liquid suspension to an aerosol chamber (A0), and after further 30 min of airborne suspension in the chamber (A30).

Effects of surface material, ventilation, and human behavior on indirect contact transmission risk of respiratory infection.

Infectious particles can be deposited on surfaces. Susceptible persons who contacted these contaminated surfaces may transfer the pathogens to their mucous membranes via hands, leading to a risk of respiratory infection. The exposure and infection risk contributed by this transmission route depend on indoor surface material, ventilation, and human behavior.

Evaluation of the drag force on single-walled carbon nanotubes in rarefied gases.

The drag force on carbon nanotubes (CNTs) in dilute gases has been previously derived. However, the drag force formulae involve collision integrals, which are complex functions of the gas-CNT interaction potential. The unavailability of the collision integrals and interaction potential makes the application of the theoretical drag force laws impossible.

Use of risk assessment and likelihood estimation to analyze spatial distribution pattern of respiratory infection cases.

Obvious spatial infection patterns are often observed in cases associated with airborne transmissible diseases. Existing quantitative infection risk assessment models analyze the observed cases by assuming a homogeneous infectious particle concentration and ignore the spatial infection pattern, which may cause errors. This study aims at developing an approach to analyze spatial infection patterns associated with infectious respiratory diseases or other airborne transmissible diseases using infection risk assessment and likelihood estimation.

Removal and leakage of environmental tobacco smoke from a model smoking room.

Experimental studies on the removal of accumulated environmental tobacco smoke (ETS) and the effectiveness of ETS leakage control were carried out in a model smoking room using carbon monoxide, nicotine, 3-ethenylpyridine, respirable suspended particulates, and ultrafine particles (UFP) as the ETS tracers. The study investigated the effectiveness of the designated smoking room, equipped with a displacement ventilation system under different ventilation rates (10-58 L/sec per person,) in removing the ETS tracers. The extent of ETS leakage through different door operating scenarios under various ventilation rates was intensively studied.

Personalized ventilation as a control measure for airborne transmissible disease spread.

The protective role of personalized ventilation (PV) against plausible airborne transmissible disease was investigated using cough droplets released from a 'coughing machine' simulating the human cough at different distances (1, 1.75 and 3 m) from the PV user. Particle image velocimetry was used to characterize and visualize the interaction between the cough-generated multiphase flow and PV-induced flow in the inhalation zone of the thermal breathing manikin.

Co-firing coal with rice husk and bamboo and the impact on particulate matters and associated polycyclic aromatic hydrocarbon emissions.

The potential of co-firing rice husk and bamboo with coal was studied in a bench-scale pulverized fuel combustion reactor. Experimental parameters including biomass blending ratio in the fuel mixture, biomass grinding size, excess air ratio and relative moisture content in the biomass were investigated. Particulate Matters in the forms of PM(10), PM(2.