Assessing respiratory airflow unsteadiness under different tidal respiratory frequencies using large eddy simulation method.

Unsteady respiratory airflow characteristics play a crucial role in understanding the deposition of toxic particles and inhaled aerosol drugs in the human respiratory tract. Considering the variations in respiratory flow rate and glottis motion under different respiratory frequencies, these respiratory airflow characteristics are studied by large-eddy simulations, including pressure field, power loss, modal spatial patterns, and vortex structures. Firstly, the results reveal that varying respiratory frequencies significantly affect airflow unsteadiness, turbulent evolution, and vortex structure dissipation, as they increase the complexity and butterfly effect introduced by the turbulent disturbance.

Modelling physical contacts to evaluate the individual risk in a dense crowd.

Tumble and stampede in a dense crowd may be caused by irrational behaviours of individuals and always troubles the safety management of crowd activities. Risk evaluation based on pedestrian dynamical models can be regarded as an effective method of preventing crowd disasters. Here, a method depending on a combination of collision impulses and pushing forces was used to model the physical contacts between individuals in a dense crowd, by which the acceleration error during physical contacts caused by a traditional dynamical equation can be avoided.

Public opinion changing patterns under the double-hazard scenario of natural disaster and public health event.

In the context of the COVID-19 epidemic, a "double-hazard scenario" consisting of a natural disaster and a public health event occurring simultaneously is likely to arise. Focusing on this double-hazard scenario, this study developed a new opinion dynamics model that verifies the effect of opinion dynamic in practical applications and extends the realistic meaning of the logic matrix. The new model can be used to quickly identify changing trends in public opinion about two co-occurring public safety events in China, helping the government to better anticipate and respond to these real double-hazard scenarios.

Numerical study of transient indoor airflow and virus-laden droplet dispersion: Impact of interactive human movement.

Human movement affects indoor airflow and the airborne transmission of respiratory infectious diseases, which has attracted scholars. However, the interactive airflow between moving and stationary people has yet to be studied in detail. This study used the numerical method validated by experimental data to explore the transient indoor airflow and virus-laden droplet dispersion in scenes with interactive human movement.

A numerical tool for assessing human thermal safety and thermal comfort in cold-weather activities.

This paper describes a newly developed software tool to evaluate human thermal safety and thermal comfort in cold-weather activities aimed at guiding users to arrange activity plans and select appropriate clothing ensembles. The software inputs include conditions of activity, environment, human body, and clothing ensemble. It outputs physiological temperatures, cold injury risks, thermal sensations, and thermal comforts in intuitive ways like cloud maps and curves.

A Multi-Segmented Human Bioheat Model for Asymmetric High Temperature Environments.

In workplaces such as steel, power grids, and construction, firefighters and other workers often encounter non-uniform high-temperature environments, which significantly increase the risk of local heat stress and local heat discomfort for the workers. In this paper, a multi-segment human bioheat model is developed to predict the human thermal response in asymmetric high-temperature environments by considering the sensitivity of the modeling to angular changes in skin temperature and the effects of high temperatures on human thermoregulatory and physiological responses simultaneously. The extended model for asymmetric high-temperature environments is validated with the current model results and experimental data.

Multi-person movement-induced airflow and the effects on virus-laden expiratory droplet dispersion in indoor environments.

The multi-person movement might cause complex induced airflow and affect the virus-laden expiratory droplet transmission in indoor environments. Using the dynamic mesh model in computational fluid dynamics, the multi-person movement with different personnel location distributions was realized. The induced airflow patterns, virus-laden droplet dispersion, and concentration distribution were investigated in detail.

Transient and continuous effects of indoor human movement on nanoparticle concentrations in a sitting person's breathing zone.

Particle concentration in a sitting person's breathing zone can be influenced by human movement around the person, and the transient and continuous effects may differ. In this study, a set of full-scale experiments was conducted to sample the nanoparticle concentration in the breathing zone of a sitting thermal breathing manikin (STBM). The transient fluctuation of the nanoparticle concentration was recorded continuously and analyzed.

COVID-19 virus released from larynx might cause a higher exposure dose in indoor environment.

COVID-19 virus can replicate in the infected individual's larynx independently, which is different from other viruses that replicate in lungs only, e.g. SARS.

A Risk Assessment Method for Multi-Hazard Coupling Disasters.

Multi-hazard coupling disasters, in which multiple hazards occur simultaneously and interact to compound the consequences, are a common phenomenon. The assessment of the individual risk in multi-hazard coupling disasters faces several difficulties due to the nonlinear additivity of risks from multiple hazards. This article presents the Choquet integral multiple linear regression model as a method of overcoming the problems of nonlinear additivity.

Experimental study on individual risk in crowds based on exerted force and human perceptions.

Frequent and intense interactions between individuals inevitably occur in crowd disasters. Previous studies indicate that the primary risk evaluation parameters for individuals in crowds during these interactions are exerted force and its duration. In this study, a series of controlled laboratory experiments simulating static and fluctuant loads were conducted to obtain real-time exerted force data and the associated individual subjective feelings.

Investigation of inhalation and exhalation flow pattern in a realistic human upper airway model by PIV experiments and CFD simulations.

In this study, flow field characteristics in the trachea region in a realistic human upper airway model were firstly measured by particle image velocimetry (PIV) in the air under three constant inhalation and exhalation conditions: 36 L/min, 64 L/min and 90 L/min, representing flow rates of 18 L/min, 32 L/min and 45 L/min in real human airway (the model was twice the size of a human airway). Computational fluid dynamics (CFD) analyses were performed on four turbulence models, with boundary conditions corresponding to the PIV experiments. The effects of flow rates and breathing modes on the airflow patterns were investigated.

Synergic effects in the assessment of multi-hazard coupling disasters: Fires, explosions, and toxicant leaks.

The study of multi-hazard coupling disasters involves various challenges. One of the toughest challenges is analyzing the interactions between incidents, known as "synergic effects." As its research object, this paper takes multi-hazard coupling disasters involving fire, explosions, and toxicant leaks in hazardous chemicals scenarios.

Assessment of occupant-behavior-based indoor air quality and its impacts on human exposure risk: A case study based on the wildfires in Northern California.

The recent wildfires in California, U.S., have caused not only significant losses to human life and property, but also serious environmental and health issues.

Fate of the inhaled smoke particles from fire scenes in the nasal airway of a realistic firefighter: A simulation study.

Understanding the inhalation, transport and deposition of smoke particles during fire missions are important to evaluating the health risks for firefighters. In this study, measurements from Underwriters Laboratories' large-scale fire experiments on smoke particle size distribution and concentration in three residential fire scenes were incorporated into models to investigate the fate of inhaled toxic ultrafine particulates in a realistic firefighter nasal cavity model. Deposition equations were developed, and the actual particle dosimetry (in mass, number and surface area) was evaluated.

Association of Ozone Exposure With Cardiorespiratory Pathophysiologic Mechanisms in Healthy Adults.

Importance: Exposure to ozone has been associated with cardiovascular mortality, but the underlying biological mechanisms are not yet understood.

Objective: To examine the association between ozone exposure and cardiopulmonary pathophysiologic mechanisms.

Design, Setting, And Participants: A longitudinal study involving 89 healthy adult participants living on a work campus in Changsha City, China, was conducted from December 1, 2014, to January 31, 2015.

Integrating a human thermoregulatory model with a clothing model to predict core and skin temperatures.

This paper aims to integrate a human thermoregulatory model with a clothing model to predict core and skin temperatures. The human thermoregulatory model, consisting of an active system and a passive system, was used to determine the thermoregulation and heat exchanges within the body. The clothing model simulated heat and moisture transfer from the human skin to the environment through the microenvironment and fabric.

Review on modeling heat transfer and thermoregulatory responses in human body.

Several mathematical models of human thermoregulation have been developed, contributing to a deep understanding of thermal responses in different thermal conditions and applications. In these models, the human body is represented by two interacting systems of thermoregulation: the controlling active system and the controlled passive system. This paper reviews the recent research of human thermoregulation models.

A coupling system to predict the core and skin temperatures of human wearing protective clothing in hot environments.

The aim of this study is to predict the core and skin temperatures of human wearing protective clothing in hot environments using the coupling system. The coupling system consisted of a sweating manikin Newton controlled by a multi-node human thermal model, and responded dynamically to the thermal environment as human body. Validation of the coupling system results was conducted by comparison with the subject tests.

Experimental and numerical study of physiological responses in hot environments.

This paper proposed a multi-node human thermal model to predict human thermal responses in hot environments. The model was extended based on the Tanabe's work by considering the effects of high temperature on heat production, blood flow rate, and heat exchange coefficients. Five healthy men dressed in shorts were exposed in thermal neutral (29 °C) and high temperature (45 °C) environments.

Effect of human movement on airborne disease transmission in an airplane cabin: study using numerical modeling and quantitative risk analysis.

Background: Airborne transmission of respiratory infectious disease in indoor environment (e.g. airplane cabin, conference room, hospital, isolated room and inpatient ward) may cause outbreaks of infectious diseases, which may lead to many infection cases and significantly influences on the public health.

Impact of travel patterns on epidemic dynamics in heterogeneous spatial metapopulation networks.

We report the results of a series of simulations of a susceptible-infected-recovered epidemic model in heterogeneous spatial metapopulation networks with quantitative knowledge of human traveling statistics that human travel behavior obeys scaling laws in the sense of geographical distance and period of waiting time. By tuning the edge length distribution of the spatial metapopulation network, we can conveniently control the distribution of human travel distance. The simulation results show that the occurrence probability of global outbreaks is significantly dependent on the characteristic travel distance, the characteristic waiting time, and the memory effects of human travel.

Cellular automata-based systematic risk analysis approach for emergency response.

Emergency response is directly related to the allocation of emergency rescue resources. Efficient emergency response can reduce loss of life and property, limit damage from the primary impact, and minimize damage from derivative impacts. An appropriate risk analysis approach in the event of accidents is one rational way to assist emergency response.