Dynamic Analysis of Closed Die Electromagnetic Sheet Metal Forming to Predict Deformation and Failure of AA6061-T6 Alloy Using a Fully Coupled Finite Element Model.

This research presents a fully coupled 3D numerical model to analyse the dynamics of high-speed electromagnetic forming process for aluminium alloy AA6061-T6. The effect of Lorentz force distribution, velocity and kinetic energy on deformation, the bounce back effect and failure of the sheet has been investigated. Experiments were performed for AA6061-T6 alloy using an 18.

Natural Ventilation and Air Purification for Effective Removal of Airborne Virus in Classrooms with Heater Operation.

Mass COVID-19 infection cases in indoor spaces have been continuously reported since its global outbreak, generating increasing public interest in reducing the spread of the virus. This study considered a situation in which an infected individual continuously releases the virus into the air in a classroom, simulated by continuous injection of NaCl particles ≤ 5 μm, with heater operation during winter. The effects of applying natural ventilation and operating one or two air purifiers on the removal of virus-containing aerosols were experimentally compared and analyzed based on the spatiotemporal changes in NaCl concentration within the classroom.

Study on the Ventilation Method to Maintain the PM Concentration in a Subway Cabin below 35 μg/m.

The city of Seoul will limit the maximum particulate matter (PM) concentration to ≤35 μg/m (from 2024). Herein, a numerical parametric study was conducted on the PM removal efficiency of the heating, ventilation, and air conditioning (HVAC) filters installed in the ceiling of subway cabins. The PM concentration distribution was explored according to the flow rate and flow rate ratio of the air introduced into the cabin.

Enhancement and Homogenization of Indoor Air Quality in a Classroom Using a Vertical Airflow Ventilation Scheme.

Since air quality has a great influence on students' health and learning ability, enhancing air quality in classrooms is important. Currently, widely distributed ventilation systems operate by moving airflow horizontally from ventilation inlets and outlets on the ceiling. This method can reduce the average pollution in a space by diluting it through air exchange; however, it is limited regarding homogeneous cleanliness due to air stagnation at some locations.

Reducing PM and PM Concentrations in a Subway Station by Changing the Diffuser Arrangement.

According to the stringent regulations on particulate matter (PM) concentrations in Seoul, Korea, the PM and PM concentrations in subway stations must be maintained below 50 and 30 μg/m, respectively, by 2024. Therefore, the PM concentrations in a subway station were analyzed considering air-conditioning diffuser arrangement and filtration efficiency, with the total ventilation flow rate of the station maintained constant. Dynamic analysis was performed under a worst-case scenario, wherein outdoor air was introduced through ground entrances and high-concentration dust (PM, PM) was introduced from stationary train cabins into the platforms through open platform screen doors (PSDs).

Comparison of Indoor Air Quality in Summer and Winter According to Four-Way Cassette Fan Coil Unit Operation in a Four-Bed Ward.

This study targeted a four-bed ward with a ventilation system and a four-way cassette fan coil unit (4-way FCU) installed on the ceiling. The indoor air quality under summer and winter conditions was comparatively analyzed. The age of air was calculated by conducting tests and simulations under diverse conditions, assuming that the ventilation system and 4-way FCU were continuously operating.

Rheology of electromagnetohydrodynamic tangent hyperbolic nanofluid over a stretching riga surface featuring dufour effect and activation energy.

The present model deals with the consequence of Dufour, activation energy, and generation of heat on electromagnetohydrodynamic flow of hyperbolic tangent nanofluid via a stretching sheet. This offers a broad significance in several engineering fields. With adequate similarity variables, the regulating governing equations of PDEs are renovated into nonlinear ODEs.

Investigation of the Optimal Operating Position of an Air Cleaner in Terms of Indoor Air Quality in a Four-Bed Hospital Ward.

The use of air cleaners indoors has increased with the increase in indoor activities driven by the COVID-19 outbreak. In this study, the indoor air quality was determined at the location of each patient's respirator in a four-bed hospital ward equipped with a ventilation system and curtains, by varying the position of one air cleaner. By operating the air cleaner alone without the ventilation system, it was confirmed that it is better to place the air cleaner close to the center of the ward, regardless of whether curtains are used.

Analytic simulation of thermophoretic second grade fluid flow past a vertical surface with variable fluid characteristics and convective heating.

The study considers the effect of thermophoresis particle deposition on the flow properties of second grade fluid with variable viscosity, variable thermal conductivity and variable concentration diffusivity subjected to a convective boundary condition. To further describe the transport phenomenon, the special case of assisting and opposing flows is explored. Using similarity transformations, the governing equations of the fluid model are transformed and parameterized into a system of nonlinear ordinary differential equations.

Development of Three-Stage Bioaerosol Sampler for Size-Selective Sampling.

In this study, a three-stage bio-aerosol sampler with a sampling flow rate of 170 L/min was designed and fabricated for sampling the bio-aerosols released during human breathing and coughing, and its performance was evaluated. The sampler was constructed using a cyclone separator with a cutoff size of 2.5 μm as a preseparator, a multinozzle virtual impactor with a cutoff size of 0.

Induced magnetic field and viscous dissipation on flows of two immiscible fluids in a rectangular channel.

The unsteady, magneto-hydrodynamic generalized Couette flows of two immiscible fluids in a rectangular channel with isothermal walls under the influence of an inclined magnetic field and an axial electric field have been investigated. Both fluids are considered electrically conducting and the solid boundaries are electrically insulated. Approximate analytical solutions for the velocity, induced magnetic, and temperature fields have been determined using the Laplace transform method along with the numerical Stehfest's algorithm for the inversion of the Laplace transforms.

Development of a high-volume ambient aerosol sampling inlet with an adjustable cutoff size and its performance evaluation using road dust.

Aerosol samplers are generally classified into particulate matter (PM or PM) and total suspended particle (TSP) samplers. As changing the cutoff size is cumbersome, it necessitates either replacing the particle size separator or adjusting the sampling flow rate. In this study, a novel high-volume aerosol-sampling inlet with an adjustable cutoff size was developed.

High-volume sampler for size-selective sampling of bioaerosols including viruses.

Owing to the recent global spread of the new coronavirus SARS-CoV-2, the development of technology to effectively detect viruses in crowded public places is urgently needed. In this study, a three-stage high-volume bioaerosol sampler was developed for the size-selective sampling of bioaerosols through the suction of air at a high flow rate of 1000 L/min. In stage 1, an omnidirectional inlet cyclone separator that can draw air from all directions was applied to collect bioaerosols larger than 10 μm in the collection fluid.

Size-dependent characteristics of diurnal particle concentration variation in an underground subway tunnel.

Understanding characteristics of diurnal particle concentration variation in an underground subway tunnel is important to reduce subway passengers' exposure to high levels of toxic particle pollution. In this study, real-time particle monitoring for eight consecutive days was done at a shelter located in the middle of a one-way underground subway tunnel in Seoul, Republic of Korea, during the summer of 2015. Particle mass concentration was measured using a dust monitor and particle number concentration using an optical particle counter.

Overestimation of on-road air quality surveying data measured with a mobile laboratory caused by exhaust plumes of a vehicle ahead in dense traffic areas.

The unintended influence of exhaust plumes emitted from a vehicle ahead to on-road air quality surveying data measured with a mobile laboratory (ML) at 20-40 km h in dense traffic areas was investigated by experiment and life-sized computational fluidic dynamics (CFD) simulation. The ML equipped with variable sampling inlets of five columns by four rows was used to measure the spatial distribution of CO and NO concentrations when following 5-20 m behind a sport utility vehicle (SUV) as an emitter vehicle equipped with a portable emission monitoring system (PEMS). The PEMS measured exhaust gases at the tailpipe for input data of the CFD simulations.