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1.
Micromachines ; 14(1):169, 2023.
Article in English | ProQuest Central | ID: covidwho-2216616

ABSTRACT

In this study, a tunable terahertz (THz) metamaterial using the micro-electro-mechanical system (MEMS) technique is proposed to demonstrate pressure sensing application. This MEMS-based tunable metamaterial (MTM) structure is composed of gold (Au) split-ring resonators (SRRs) on patterned silicon (Si) substrate with through Si via (TSV). SRR is designed as a cantilever on the TSV structure. When the airflow passes through the TSV from bottom to up and then bends the SRR cantilever, the SRR cantilever will bend upward. The electromagnetic responses of MTM show the tunability and polarization-dependent characteristics by bending the SRR cantilever. The resonances can both be blue-shifted from 0.721 THz to 0.796 THz with a tuning range of 0.075 THz in transverse magnetic (TM) mode and from 0.805 THz to 0.945 THz with a tuning range of 0.140 THz in transverse electric (TE) mode by changing the angle of SRR cantilever from 10° to 45°. These results provide the potential applications and possibilities of MTM design for use in pressure and flow rate sensors.

2.
Mathematics ; 11(2):426, 2023.
Article in English | ProQuest Central | ID: covidwho-2208629

ABSTRACT

Airborne pandemics have caused millions of deaths worldwide, large-scale economic losses, and catastrophic sociological shifts in human history. Researchers have developed multiple mathematical models and computational frameworks to investigate and predict pandemic spread on various levels and scales such as countries, cities, large social events, and even buildings. However, attempts of modeling airborne pandemic dynamics on the smallest scale, a single room, have been mostly neglected. As time indoors increases due to global urbanization processes, more infections occur in shared rooms. In this study, a high-resolution spatio-temporal epidemiological model with airflow dynamics to evaluate airborne pandemic spread is proposed. The model is implemented, using Python, with high-resolution 3D data obtained from a light detection and ranging (LiDAR) device and computing model based on the Computational Fluid Dynamics (CFD) model for the airflow and the Susceptible–Exposed–Infected (SEI) model for the epidemiological dynamics. The pandemic spread is evaluated in four types of rooms, showing significant differences even for a short exposure duration. We show that the room's topology and individual distribution in the room define the ability of air ventilation to reduce pandemic spread throughout breathing zone infection.

3.
Journal of Physics: Conference Series ; 2385(1):012094, 2022.
Article in English | ProQuest Central | ID: covidwho-2187977

ABSTRACT

The airborne transmission of the COVID-19 virus was considered the main cause of infection. The increasing concern about the virus spread in confined spaces, characterized by high crowding indexes and an often-inadequate air exchange system, pushes the scientific community to the design of many studies aimed at improving indoor air quality. The risk of transmission depends on several factors such as droplet properties, virus characteristics, and indoor airflow patterns. The main transmission route of the SARS-CoV-2 virus to humans is the respiratory route through small (<100 μm) and large droplets. In an indoor environment, the air exchange plays a fundamental role on the dispersion of the droplets. In this study, an integrated approach was developed to evaluate the influence of the ventilation strategy on the dispersion of respiratory droplets emitted inside a coach bus. There are no specific guidelines and standards on the air exchange rate (AER) values to be respected in indoor environments such as coach buses. The aim of this work is to analyse the influence of ventilation strategy on the respiratory droplet concentration and distribution emitted in a coach bus. Ansys FLUENT was used to numerically solve the well-known transient Navier-Stokes equations (URANS equations), the energy equation and using the Lagrangian Discrete Phase Model (DPM) approach to construct the droplet trajectories. The geometry is representative of an intercity bus, a vehicle constructed exclusively for the carriage of seated passengers. The 3D CAD model represented a coach bus with an HVAC system, within which an infected subject was present. The positions of exhaust vents and air-conditioning vents were chosen to ensure complete air circulation throughout the bus. The infected subject emitted droplets with a well-defined size distribution and mass through the mouth. The air exchange is provided in two different ways: general ventilation (from air intakes positioned along the bus windows and top side of central corridor) and personal ventilation (with air intakes for each passenger). For the general ventilation a single AER value was set (0.3 m3 s−1). The first results obtained showed a slight particle dispersion in the computational domain due to the airflow rate entered through the HVAC system, but a still elevated level of particle concentration tended to accumulate on the area near to infected subject. Additional analysis was executed to evaluate the beneficial effects linked to further addition of airflow through personal air-conditioning vents placed above every passenger's head. The results show the importance of the use of the ventilation system inside a coach bus, highlighting how the contribution linked to of the personal air exchange rate can lead to a significant reduction of droplet concentration exposure and consequently a reduction of the risk of infection from airborne diseases.

4.
ASHRAE Journal ; 64(7):10-12,14,16-18,20-21, 2022.
Article in English | ProQuest Central | ID: covidwho-2126121

ABSTRACT

Computational fluid dynamics (CFD) models of an aircraft cabin and an indoor commercial space (ICS) were used to characterize the spread of aerosols generated by a coughing or breathing person suffering from a respiratory illness. Occupant exposure to these aerosols was then compared between the ICS and the aircraftcabin. The lifetime of the aerosols, system designs and airflow patterns that reduce their concentration over time were also examined. Differences between steady state and well-mixed conditions were identified and comparisons made between the model environments. The CFD analysis results were also compared to empirical data from a U.S. Transportation Command study that tracked particles introduced by simulated infectious individuals in an airplane cabin environment.

5.
Journal of Medical Devices-Transactions of the Asme ; 16(4), 2022.
Article in English | Web of Science | ID: covidwho-2121314

ABSTRACT

Aerosols generated during endoscopic sinus procedures present a concern to the health and safety of healthcare personnel, especially with the presence of coronavirus disease (COVID-19). The purpose of this study is to describe the design and testing of a nasal cover to restrict aerosolized pathogens. The nasal cover was designed to sit overtop the nose with conformal slits for insertion of endoscopic instrumentation. Polydimethylsiloxane (PDMS) was chosen as the nasal mask material and its composition, thickness, and slit geometry were selected using a Taguchi experimental design and survey with clinical collaborators at Penn State Milton S. Hershey Medical Center. The nasal cover was designed using principles of origami engineering to be manufactured flat and then folded into its operating state. Form and functionality were evaluated by surgeons, fellows, and residents in the aforementioned survey. Aerosol containment was evaluated by measuring smoke, representative of surgical aerosols, with an optical particle counter. A 25:1 composition PDMS with 3 mm thickness and vertical slit geometry was chosen for the nasal cover design. Survey results demonstrated that the origami cover sat well on the nose and did not significantly impact the surgical conditions with single instrumentation. On average, this nasal cover was found to restrict more than 93% of 0.3 mu m aerosols, and more than 99% of all aerosols larger than 0.5 mu m in size. The use of a patient worn nasal cover has the potential to drastically reduce the risk to hospital personnel during endonasal surgeries by reducing aerosol generation and potential pathogen spread.

6.
ASHRAE Journal ; 64(11):48-50,52-55, 2022.
Article in English | ProQuest Central | ID: covidwho-2112122

ABSTRACT

The COVID-19 pandemic has driven public interest in building ventilation rates. The ASHRAE Epidemic Task Force's recommendation that buildings "provide and maintain at least the minimum outdoor airflow rates for ventilation as specified by applicable codes and standards" put quantitative ventilation system assessments in high demand. Throughout the pandemic, many building owners conducted assessments of building systems, including ventilation, to reduce risk of COVID-19 transmission. A recent study of assessments at 95 commercial office buildings found that 77% provided minimum ventilation rates or could make minor adjustments to do so. However, 23% of buildings were underventilated and would require significant capital investment to meet current standards. All but one of these buildings were designed between 1981 and 1992, with ventilation rates as low as 9 cfm/person (4 L/s person) (assuming default occupant density).

7.
3rd International Conference on Artificial Intelligence in Electronics Engineering, AIEE 2022 ; : 80-84, 2022.
Article in English | Scopus | ID: covidwho-2053338

ABSTRACT

This article presents the design and prototyping of an electronic mask as personal protective equipment for the virus pandemic known as COVID - 19. Needs were identified such as: tightness and comfort. Requirements for use for long periods of time;this was considered for the design, also it has an adjustable ventilation system. The mask was simulated and validated with Solidworks Flow Simulation software, in addition a PID control model was implemented, thereby, it was shown that enough flow is generated to vary the temperature in a range of 20 to 37.2 ° C inside the mask. The design considers an outlet duct and an inlet duct with filters that prevent the entry of polluting particles, providing adequate protection. The prototype was made by 3D printing, And the thermal stability was achieved with the implementation of the temperature regulation system. The results obtained were validated, and they allow to future research to provide greater efficiency to masks. © 2022 ACM.

8.
Arab J Chem ; 15(11): 104302, 2022 Nov.
Article in English | MEDLINE | ID: covidwho-2041577

ABSTRACT

Traditional Chinese medicine (TCM) is the key to unlock treasures of Chinese civilization. TCM and its compound play a beneficial role in medical activities to cure diseases, especially in major public health events such as novel coronavirus epidemics across the globe. The chemical composition in Chinese medicine formula is complex and diverse, but their effective substances resemble "mystery boxes". Revealing their active ingredients and their mechanisms of action has become focal point and difficulty of research for herbalists. Although the existing research methods are numerous and constantly updated iteratively, there is remain a lack of prospective reviews. Hence, this paper provides a comprehensive account of existing new approaches and technologies based on previous studies with an in vitro to in vivo perspective. In addition, the bottlenecks of studies on Chinese medicine formula effective substances are also revealed. Especially, we look ahead to new perspectives, technologies and applications for its future development. This work reviews based on new perspectives to open horizons for the future research. Consequently, herbal compounding pharmaceutical substances study should carry on the essence of TCM while pursuing innovations in the field.

9.
Journal of Physics: Conference Series ; 2335(1):012061, 2022.
Article in English | ProQuest Central | ID: covidwho-2037308

ABSTRACT

The demand of ventilators has been increasing dramatically from the past few years due to the spike in the COVID-19 cases globally. Around the World, the abscence of availability of ventilators have taken a lot of lives in just the past couple of years. The use of ventilators has been proven to be helpful from preventing the danger of lung harm through low- quantity airflow and helps us to get the adequate amount of influx of pure air. The ventilators available are expensive and scarce in supply. They are heavy and would normally weigh around 7 to 8 kgs, which makes it inconvenient to carry from place to place due to its enormous size. Our project aims at developing a smart ventilator system using a microcontroller board and sensors based on Internet of Things (IOT). The smart ventilator will be portable and very light in weight, which makes it handy to use and requires no additional expertise to handle it. The usage of the high torque motor enables us to change the pressure as per the requirement. The sensors used collects the temperature and the Pulse oximetry levels and the same is updated on the LCD display.

10.
Physical Review Applied ; 18(2), 2022.
Article in English | Scopus | ID: covidwho-2018422

ABSTRACT

Clusters of contaminations have been identified within rehearsing choirs during the COVID-19 pandemic. In particular, singing and playing wind instruments are known to generate enhanced release of respiratory droplets, which are then transported by the expiratory flows. By tracking the air exhaled by professional opera singers and musicians from the MET Orchestra in New York City, we measure the spatial extent of the various air flows in opera. While loud singing is often associated with fast flows, professional opera singers and musicians are usually exhaling air flows slower than the air jets exhaled by a person breathing at rest. However, we identify a few situations leading to the release of rapid air jets that are able to enhance the transport of pathogenic droplets within an orchestra. Finally, we show how singing with a facemask and covering the bell of a wind instrument provide a strong reduction of the transport of respiratory droplets, in addition to the filtration features of a mask. © 2022 American Physical Society.

11.
Journal of Thermal Engineering ; 8(5):93-103, 2022.
Article in English | Academic Search Complete | ID: covidwho-2010834

ABSTRACT

COVID-19 virus, which is a member of the coronavirus family, is a virulent virus that is transmitted by physical contact or air and results in death in infected people. People infected by the COVID-19 virus must be kept in quarantine in a closed area. Therefore, it is very important for the health of the individuals (patient, doctor, nurse, etc.) in the isolation room that, where the area kept closed is completely free of virus. This study was conducted to examine the flow dynamics of the air in the isolation chamber. With the simultaneous operation of the sanitized air machine and the ventilation in the room, it is aimed to investigate the virus killing effect of the air mixed with each other. The flow dynamics, velocity, temperature and turbulence kinetic energy of the air in the isolation chamber were examined. Investigations were carried out to ensure that the mixture of the two air in the room was better and distributed throughout the room. [ FROM AUTHOR] Copyright of Journal of Thermal Engineering is the property of Journal of Thermal Engineering, Yildiz Technical University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)

12.
Energies ; 15(15):5443, 2022.
Article in English | ProQuest Central | ID: covidwho-1993960

ABSTRACT

Interest in the development of electro-fluid-dynamic devices (EFDs) based on corona discharge is growing due to their advantages and applicability across different industrial sectors. On the one hand, their performance as forced convection motors, in terms of weight, volume, and absence of noise and moving parts, make them competitive against traditional systems such as fans. On the other hand, the actions of the corona discharge, in terms of elimination of viruses and bacteria, are already known. This paper studies the characteristics of corona discharge in terms of air flow for a new proposed configuration and geometry of electrodes. A systematic study is performed through a parametric study of the distances, power consumption, and size of the corona electrode. The characteristic voltage–current (CVCCs) and flow–pressure curves obtained provide design rules to use the generated corona discharge and the device itself, as a silent air propeller, which may also sterilize the surrounding environment and surfaces.

13.
Journal of Physics: Conference Series ; 2312(1):012012, 2022.
Article in English | ProQuest Central | ID: covidwho-1991987

ABSTRACT

Air sterilizer is one of the essential components in combating the Covid-19. A wind tunnel model of the air sterilizer using a dielectric barrier discharge plasma is proposed to destroy the virus by direct contact with the plasma. Dangerous ozone production in the plasma reactor should be controlled to a safe level. Two parameters affecting the ozone concentration, i.e., electrical power and airflow, were investigated. The DBD reactor was a cell constructed from an array of alternate electrodes. The plasma was generated by an AC high voltage generator with a range of 2kV -3kV. The power and the high voltage were varied by controlling the DC input voltage of the generator. The airflow was varied by controlling the speed of an exhaust fan from 0.5 m/s to 3.0 m/s. The state was characterized using optical emission spectroscopy in the range of 200 nm – 1000 nm. The results showed that both parameters played a significant role in ozone concentration. The trend of the ozone is strongly correlated with the OH species, which reacts with oxygen. The highest ozone concentration of 4.51 ppm was observed at the DC voltage around 19 volts or the power of 34.2 watts. However, a decrease of the ozone concentration at a voltage higher than 19 volts related to 2.9 kV was observed. In general, the data showed that faster airflow decreases ozone concentration. A drastic decrease of the nitrogen species sustaining the plasma occurred at the airflow higher than 2 m/s.

14.
Geoscientific Instrumentation, Methods and Data Systems ; 11(2):263-277, 2022.
Article in English | ProQuest Central | ID: covidwho-1988295

ABSTRACT

Climate science depends upon accurate measurements of air temperature and humidity, the majority of which are still derived from sensors exposed within passively ventilated louvred Stevenson-type thermometer screens. It is well-documented that, under certain circumstances, air temperatures measured within such screens can differ significantly from “true” air temperatures measured by other methods, such as aspirated sensors. Passively ventilated screens depend upon wind motion to provide ventilation within the screen and thus airflow over the sensors contained therein. Consequently, instances of anomalous temperatures occur most often during light winds when airflow through the screen is weakest, particularly when in combination with strong or low-angle incident solar radiation. Adequate ventilation is essential for reliable and consistent measurements of both air temperature and humidity, yet very few systematic comparisons to quantify relationships between external wind speed and airflow within a thermometer screen have been made. This paper addresses that gap by summarizing the results of a 3-month field experiment in which airflow within a UK-standard Stevenson screen was measured using a sensitive sonic anemometer and comparisons made with simultaneous wind speed and direction records from the same site. The mean in-screen ventilation rate was found to be 0.2 m s-1 (median 0.18 m s-1), well below the 1 m s-1 minimum assumed in meteorological and design standard references, and only about 7 % of the scalar mean wind speed at 10 m. The implications of low in-screen ventilation on the uncertainty of air temperature and humidity measurements from Stevenson-type thermometer screens are discussed, particularly those due to the differing response times of dry- and wet-bulb temperature sensors and ambiguity in the value of the psychrometric coefficient.

15.
ASHRAE Transactions ; 127:246-253, 2021.
Article in English | ProQuest Central | ID: covidwho-1980710

ABSTRACT

The purpose of a ventilation system for indoor spaces is to create a safe environment for the occupants by diluting the concentration levels of hazardous contaminants and to minimize the risk of infection due to spread of airborne pathogens. The effectiveness of ventilation system depends on several inter related factors including the supply airflow rate, number and locations of supply diffusers, and number and locations of return grilles. With the help of Computational Fluid Dynamics (CFD) analyses, this study systematically evaluates the impact of three different HVAC configurations on the airflow patterns, distribution of contaminant, and the risk of infection in a small office space with two cubicles. The HVAC configuration with a single supply and a single return can create adverse airflow patterns which can promote spread of contaminants and increase the risk of infection farther from the source. When an additional supply diffuser is introduced with the same single return, the zone of high risk of infection remained in the vicinity of the source. However, the overall risk of infection in the space remained the same. Addition of another return created aerodynamic containment zones in the space which provided easy path for the contaminated air to leave the space and reduced the overall risk of infection. Since the location of an infected individual is not known a priori, the aerodynamic containment with distributed supply and distributed return can be the best strategy for reducing the probability of infection in indoor spaces. These studies demonstrate that CFD analyses can help in identifying the potential risk of high infection due to poor airflow distribution into a space and can provide valuable insights for developing appropriate mitigation strategies to create safe indoor environment.

16.
ASHRAE Transactions ; 127:174-184, 2021.
Article in English | ProQuest Central | ID: covidwho-1980303

ABSTRACT

Thirty years of evidence supports the efficacy of ultra-clean air in preventing surgical site infection (SSI). Ultraclean is defined as fewer than 10 Colony Forming Units (CFUs) per cubic meter or <10CFU/m3 (35ft3) However, achieving and maintaining ultraclean conditions in the contemporary operating room has proven challenging. For decades, Laminar Air Flow (LAF) systems were recommended for use in rooms where infection sensitive joint arthroplasty procedures are performed. But, a growing body of evidence has called the efficacy of LAF in prevention of these infections into question. As a result, CD C no longer recommends use of LAF for joint arthroplasty. The WHO has gone a step further issuing a conditional recommendation against its use in these procedures. At the same time, demand for total hip and knee arthroplasties are expected to grow exponentially over the next decade and for reasons that are unclear rates of prosthetic joint infection (PJI) are on the rise. Taken together, these factors suggest that the time has come to rethink management of airborne contamination and ventilation technology in the operating room. Temperature-controlled Air Flow (TcAF) is a novel ventilation technology that has been proven to maintain ultra-clean conditions throughout the entire operating room. TcAF uses continuous HEPA filtration and combines a robust central unidirectional down-flow driven by gravity from a temperature gradient together with mixing ventilation in the periphery of the room. While TcAF has been scientifically validated to maintain ultra-clean conditions of <10CFU/m3(35ft3) throughout the entire operating room, the impact of TcAF on prevention of surgical site infection was unknown. The aim of this study was to evaluate the efficacy of TcAF on prosthetic joint infection (PJI). A retrospective case control study was performed with 1,000 consecutive cases of primary total joint arthroplasty before and 1,000 consecutive cases after the installation of an ultra-clean TcAF system. TcAF was associated with a statistically significant reduction in surgical site infection. With reduction in surgical site infection proving to be ever more challenging and demand for infection sensitive procedures rising, more rigorous attention to airborne contamination may represent a new pathway to improvement. While not the focus of this paper, the advent of Covid-19 should bring into greater focus the risk of airborne transmission andfurther incentiviņe mitigation.

17.
ASHRAE Transactions ; 128:340-347, 2022.
Article in English | ProQuest Central | ID: covidwho-1970581

ABSTRACT

The wavelength band of200-280 nm of UV-C radiation generated by the Ultraviolet Germicidal Irradiation (UVGI) system can destroy the reproduction ability of microorganisms. Severalfactors related to UVfixtures, HVAC layout, and the resulting airflow flow patterns can affect the performance of upper-room UVGI applications. With the help of Computational Fluid Dynamics (CFD) analyses, this study systematically evaluates the impact of UV-C intensities on the effectiveness of an upper room UVGI system. It shows that the addition of even a small amount of UV-C energy in the upper region of space can significantly reduce the probability of infection as predicted by the Wells-Riley model. Increasing the UV-C output shows a further reduction in the infection probability, although with a diminishing impact. A further investigation is necessary to evaluate the effect of airflow patterns on the performance of UVGI systems. These studies demonstrate that CFD analyses can help optimize the performance of UVGI systems to minimize the probability of infection in indoor spaces.

18.
20th ACM International Conference on Mobile Systems, Applications and Services, MobiSys 2022 ; : 634-635, 2022.
Article in English | Scopus | ID: covidwho-1950289

ABSTRACT

With the global spread of the COVID-19 pandemic, ventilation indoors is becoming increasingly important in preventing the spread of airborne viruses. However, while sensors exist to measure wind speed and airflow gradients, they must be manually held by a human or an autonomous vehicle, robot, or drone that moves around the space to build an airflow map of the environment. In this demonstration, we present DAE, a novel drone-based system that can automatically navigate and estimate air flow in a space without the need of additional sensors attached onto the drone. DAE directly utilizes the flight controller data that all drones use to self-stabilize in the air to estimate airflow. DAE estimates airflow gradients in a room based on how the flight controller adjusts the motors on the drone to compensate external perturbations and air currents, without the need for attaching additional wind or airflow sensors. © 2022 Owner/Author.

19.
International Journal of Numerical Methods for Heat & Fluid Flow ; 32(9):2964-2981, 2022.
Article in English | ProQuest Central | ID: covidwho-1948670

ABSTRACT

Purpose>The purpose of this paper is to devise a tool based on computational fluid dynamics (CFD) and machine learning (ML), for the assessment of potential airborne microbial transmission in enclosed spaces. A gated recurrent units neural network (GRU-NN) is presented to learn and predict the behaviour of droplets expelled through breaths via particle tracking data sets.Design/methodology/approach>A computational methodology is used for investigating how infectious particles that originated in one location are transported by air and spread throughout a room. High-fidelity prediction of indoor airflow is obtained by means of an in-house parallel CFD solver, which uses a one equation Spalart–Allmaras turbulence model. Several flow scenarios are considered by varying different ventilation conditions and source locations. The CFD model is used for computing the trajectories of the particles emitted by human breath. The numerical results are used for the ML training.Findings>In this work, it is shown that the developed ML model, based on the GRU-NN, can accurately predict the airborne particle movement across an indoor environment for different vent operation conditions and source locations. The numerical results in this paper prove that the presented methodology is able to provide accurate predictions of the time evolution of particle distribution at different locations of the enclosed space.Originality/value>This study paves the way for the development of efficient and reliable tools for predicting virus airborne movement under different ventilation conditions and different human positions within an indoor environment, potentially leading to the new design. A parametric study is carried out to evaluate the impact of system settings on time variation particles emitted by human breath within the space considered.

20.
TANAFFOS Journal of Respiratory Disease, Thoracic Surgery, Intensive Care and Tuberculosis ; 20(3):240-245, 2021.
Article in English | GIM | ID: covidwho-1898036

ABSTRACT

Background: Ventilation system besides other prevention strategies such as surface disinfecting and personal protective equipment (PPE) decrease the risk of coronavirus disease 2019 (COVID-19) infection. This study aimed to examine the ventilation system of an intensive care unit (ICU) in a hospital in Tehran, Iran to evaluate the potency of heating, ventilation, and air conditioning system (HVAC) for COVID-19 spread. Materials and Methods: Contamination of air turnover caves was evaluated in supplier diffuser and extractor grills of negative pressure HVAC by ten samples. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the samples was evaluated by the real time reverse transcription-polymerase chain reaction (PCR). Moreover, air conditioning and sick building syndrome (SBS) was assessed according to MM040EA questioning from health care workers.

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