Changes In Airflow Research Articles

A Study on Establishing a Dynamic Color Schlieren System to Observe Airflow and Predict Temperature Changes

A Study on Establishing a Dynamic Color Schlieren System to Observe Airflow and Predict Temperature Changes

Flutter and divergence zones of perovskite solar cell-based panels of aircraft wings in subsonic airflow

Solar-powered aircraft have advantages such as quite long flight time and resource conservation. In recent years, with the improvements in solar cell efficiency, lightweight structural design, microelectronics, and automation control technology, more and more countries and organizations have conducted research on solar-powered aircraft. Solar cells are an important component of solar-powered aircraft systems. Perovskite solar cells have the advantages of high flexibility, lightweight, and high specific power, making them the ideal material for solar-powered aircraft wings. To receive as much sunlight radiation as possible and improve the lift-to-drag ratio of the entire aircraft, solar-powered aircraft have a high aspect ratio, making them more sensitive to changes in airflow. Therefore, the stability zones and vibration of perovskite solar cell (PSC) panels in subsonic airflow were studied for the first time. Additionally, to enhance the novelty of the paper and present more comprehensive results, the effect of the nanomaterial properties of one-layered perovskite solar cell substrates reinforced by carbon nanotubes and graphene platelets on the flutter and divergence phenomenon was investigated. To accurately simulate the displacement field after the composite perovskite panel is bent, Reddy's high-order shear deformation theory was adopted. The PSC panel's aerodynamic-elastic coupling motion equations were established by combining Hamilton's principle with the linear potential flow theory and the Bernoulli equation. The dynamic equations were discretized using a meshless numerical method to obtain the generalized multi-parameter characteristic equations. The obtained natural frequencies and critical divergence speeds were compared with published literature to validate the correctness of the aerodynamic model and laminated board model. The divergence instability and flutter instability of the PSC nanocomposite panel were investigated for changing the thickness, nano-fillers, porosity, laying angle, and aspect ratio of the substrate. We showed, that the PSC panel has a divergence instability state first, and then flutter instability appears. Additionally, the substrate nanomaterial parameters of the PSC panel significantly affect shifting divergence and flutter zones. Interestingly, the corresponding natural frequency increases when flutter occurs with an increase in the porosity volume.

Selected routine laboratory tests in the clinical assessment of patients with obstructive sleep apnea.

Obstructive sleep apnea (OSA) is a chronic disease characterized by repetitive complete or partial occlusion of the upper airways during sleep with respiratory muscle effort, which leads to consecutive apneas and hypopneas. Obstruction of the upper airways during sleep leads to repetitive episodes of disrupted airflow and consequent changes in blood oxygenation, resulting in hypoxaemia and hypercapnia. Intermittent hypoxaemia induces the production of pro-inflammatory factors and promotes metabolic dysregulation and platelet aggregation. The main aim of this study was to determine differences, if any, in selected standard parameters in routine laboratory tests often used in GP practice between patients with obstructive sleep apnea, without comorbidities, and a well-defined control group with the absence of this syndrome proven in polygraphic examination. Of the 192 clinically assessed persons with suspected OSA and admitted to the Internal Medicine Department in Lublin, 85 were qualified for the study after application of exclusion criteria. Demographic and health behaviour-related data, medical history regarding sleep habits and cardiovascular disease, were collected from each patient. Apart from significantly higher MCV and MCH among the cpontrol group, no significant differences were found between patients with obstructive sleep apnea and the control group. The results can be useful for the holistic assessment of the health status of patients with newly-diagnosed OSA.

Comparing Synoptic Conditions and Environmental Characteristics for Fronts with and without Prefrontal Convection Initiation and Heavy Rain over Coastal South China

Abstract To understand why convection initiation and heavy rain sometimes occur ahead of fronts over South China in the presummer rainy season but sometimes do not, a climatology of 137 fronts is constructed, in which 34% of the fronts exhibit no prefrontal convection initiation (NoPCI), 31% of the fronts exhibit prefrontal convection initiation (PCI), and 35% of the fronts exhibit prefrontal convection initiation and heavy rain (PCI+HR). An anticyclonically curved upper-level jet streak and midtropospheric QG forcing produce synoptic-scale descent for the prefrontal region in NoPCI events, whereas the right-entrance region of a straight upper-level jet streak and forcing for ascent dominate the prefrontal region in PCI and PCI+HR events. Whether prefrontal convection and heavy rain occur is also related to the character of low-level flows. NoPCI features anticyclonic southerly winds, with an environment having low dewpoint throughout the troposphere, unfavorable for convection initiation. However, synoptic circulation of PCI and PCI+HR events favors a broad prefrontal surface low, which determines the greater cyclonic character of airflows in PCI+HR events, in contrast with that of the PCI events. Convective available potential energy is useful in distinguishing NoPCI and PCI events, and the three events have statistically significant differences in precipitable water. Moreover, larger magnitudes of precipitable water and bulk wind shear in PCI+HR events are conducive for prefrontal convection to produce heavy rain compared to those of PCI events. These results indicate the importance of the upper-level forcing on the prefrontal convection initiation, and heavy rain is sensitive to the changes in prefrontal airflow and moisture. Significance Statement Convection and heavy rain sometimes occur a few hundred kilometers ahead of fronts in the warm air over South China in early summer. To understand atmospheric conditions favoring or inhibiting convection and heavy rain ahead of fronts, we examine 46 fronts without prefrontal convection, 43 fronts with prefrontal convection, and 48 fronts with prefrontal convection and heavy rain. These scenarios have similarities in environmental behaviors but different large-scale conditions that favor or inhibit ascent in the prefrontal area. Specifically, prefrontal heavy rain tends to occur in a very moist environment with a prefrontal surface low. These findings help researchers and operational forecasters better discriminate the subtle conditions that favor or inhibit prefrontal convection and heavy rain over South China.

Insights from 3D modeling and fluid dynamics in COVID-19 pneumonia.

We address the lack of research regarding aerodynamic events behind respiratory distress at COVID-19. The use of chest CT enables quantification of pneumonia extent; however, there is a paucity of data regarding the impact of airflow changes. We reviewed 31 COVID-19 patients who were admitted in March 2020 with varying severity of pulmonary disease. Lung volumes were segmented and measured on CT images and patient-specific models of the lungs were created. Incompressible, laminar, and three-dimensional Navier-Stokes equations were used for the fluid dynamics (CFD) analyses of ten patients (five mild, five pneumonia). Of 31 patients, 17 were female, 18 had pneumonia, and 2 were deceased. Effective lung volume decreased in the general group, but the involvement of the right lung was prominent in dyspnea patients. CFD analyses revealed that the mass flow distribution was significantly distorted in pneumonia cases with diminished flow rate towards the right lung. In addition, the distribution of flow parameters showed mild group had less airway resistance with higher velocity (1.228 m/s vs 1.572 m/s) and higher static pressure values at airway branches (1.5112 Pa vs 1.3024 Pa). Therefore, we conclude that airway resistance and mass flow rate distribution are as important as the radiological involvement degree in defining the disease severity.

Effect of Temperature and Water Droplets on Production of Prodigious Hydrogen Oxides by Electrical Discharges

AbstractRecently, electrical discharges have been identified as a potentially significant source of the atmosphere's most important oxidant, the hydroxyl radical. Measurements of hydroxyl, the closely related hydroperoxyl radical, and the nitrogen oxides from sparks and subvisible discharges were made in the laboratory under different environmental and electrical conditions representing those found in the troposphere. However, there were still several conditions not yet investigated that could impact hydroxyl and hydroperoxyl production in electrical discharges. In this study, the production of electrically generated hydroxyl and hydroperoxyl (LHOx) and nitrogen oxides (LNOx) was measured under three new conditions not tested previously, including lower pressure, different temperatures, and the presence of cloud droplet‐sized water droplets. In spark discharges, LHOx was mostly independent of pressure, increased with increasing temperature, and was unaffected by the water droplets. LNOx generation was independent of temperature from −10 to 40°C and the presence of water droplets, but increased 1.5‐fold with decreasing pressure. LNOx generation was also found to be sensitive to changes in spark intensity and air flow in the laboratory setup. Increasing temperature also made it more likely that a discharge was visible instead of subvisible, but did not impact LHOx production in subvisible discharges. Even under these new conditions, the laboratory results agree with results of LHOx from a field campaign, demonstrating the relevance of the laboratory experiments to the atmosphere.

The Online Identification of the Behaviour of Pollutants inside the Tunnel Tube

A tunnel tube is a relatively small space that allows for the accumulation of gaseous and liquid substances containing harmful substances. Given this fact, a ventilation system is the most critical component of a tunnel’s technological equipment, greatly influencing its reliability and safe operation. The dynamic behaviour of pollutants in the tunnel tube is characterized by a significant stochastic component and changing parameters over time due to pressure, airflow, and atmospheric condition changes. This work addresses the issue of modelling individual parts of the tunnel tube for optimal tunnel ventilation control. It is necessary to create a model of a controlled system that is used for predicting process variables to calculate optimal control action. By using recursive identification methods in conjunction with a predictive controller, the proposed concept can be applied to numerous similar applications.

Effect of Thyroidectomy on Tracheal Remodeling and Airway Physiology in Apparently Asymptomatic Patients with Goiter: A Prospective Study.

Tracheal airflow limitation is frequently reported in patients with goiter but is severely underestimated, and studies on how goiter and its treatment affect trachea are scarce. Moreover, the choice of the optimal treatment for individual patient with asymptomatic goiter is not straightforward. Therefore, in this study we aim to investigate the effect of goiter and subsequent thyroidectomy on tracheal anatomy and change in airflow in asymptomatic patient with goiter. Seventy patients undergoing total/hemithyroidectomy (TT/HT) from Feb 2020 to Feb 2021 satisfying inclusion criteria were enrolled in the study. Neck radiograph (NR) and forced spirometry (FS) were performed preoperatively and on postoperative day 10 and 6weeks and 3months. Out of 70 patients, 84.3% patients were female, and mean duration and weight of goiter were 54.7months and 72.21gm, respectively. Of 70 patients, 57 were of benign pathology. Significant improvement in tracheal compression with moderate improvement in deviation was observed after surgery. Preoperative spirometry showed significant reduction in almost all parameters. After surgery, a weak improvement was observed at postoperative day 10 and 6weeks; however, significant improvement in FEV1, PEFR, FEV1/FEV0.5, and FEF50%/FIF50% was observed at postoperative 3months. Patient with right sided and those with ≥ 8mm deviation were associated with poorer pulmonary function. Weak correlation was observed between neck NR and spirometry parameters. Weight of the thyroid gland significantly correlated with ratio of MVV/FEV1. Patients with asymptomatic goiter can have significant abnormal changes in airflow as evidenced by FS and NR. Thyroidectomy is followed by gradual restoration of tracheal deviation and compression with significant improvement in pulmonary airflow.

전산유체역학 기반 좌상엽 절제술 후 기도 형상에 따른 기류 변화 분석

전산유체역학 기반 좌상엽 절제술 후 기도 형상에 따른 기류 변화 분석

Development of a Deep Learning-Based Epiglottis Obstruction Ratio Calculation System.

Surgeons determine the treatment method for patients with epiglottis obstruction based on its severity, often by estimating the obstruction severity (using three obstruction degrees) from the examination of drug-induced sleep endoscopy images. However, the use of obstruction degrees is inadequate and fails to correspond to changes in respiratory airflow. Current artificial intelligence image technologies can effectively address this issue. To enhance the accuracy of epiglottis obstruction assessment and replace obstruction degrees with obstruction ratios, this study developed a computer vision system with a deep learning-based method for calculating epiglottis obstruction ratios. The system employs a convolutional neural network, the YOLOv4 model, for epiglottis cartilage localization, a color quantization method to transform pixels into regions, and a region puzzle algorithm to calculate the range of a patient's epiglottis airway. This information is then utilized to compute the obstruction ratio of the patient's epiglottis site. Additionally, this system integrates web-based and PC-based programming technologies to realize its functionalities. Through experimental validation, this system was found to autonomously calculate obstruction ratios with a precision of 0.1% (ranging from 0% to 100%). It presents epiglottis obstruction levels as continuous data, providing crucial diagnostic insight for surgeons to assess the severity of epiglottis obstruction in patients.

Nasal cavity perforation by implant fixtures: case series with emphasis on panoramic imaging of nasal cavity extending posteriorly

The nasal cavity is an important landmark when considering implant insertion into the anterior region of the maxillary arch. The perforation of implants into the nasal cavity may cause complications, such as implant migration, inflammation, or changes in nasal airflow; thus, precise assessment of the nasal cavity is mandatory.Three cases of nasal cavity perforation by dental implants are presented, including one case of implant fixture migration into the nasal cavity. On panoramic radiographs of the patients, the following common features were observed: the horizontal radiopaque line of the hard palate was observed to be inferior to or similar to that of the antral floor and the bone between the lateral wall of the nasal cavity and the medial wall of the maxillary sinus was emphasized in a triangular shape.When the maxillary sinus is small and alveolar bone resorption is severe, panoramic evaluation may cause overestimation of the available residual bone, particularly in the maxillary canine/premolar region. Therefore, the residual bone should be reevaluated three-dimensionally to measure the exact bony shape and volume.

Erratum to “Airflow change and exergy analysis due to the installation of various types of partitions in the collector of a solar chimney power plant”

Erratum to “Airflow change and exergy analysis due to the installation of various types of partitions in the collector of a solar chimney power plant”

Expiratory airflow at 7–8 years of age in children born extremely low birthweight from 14 years before to 14 years after the introduction of exogenous surfactant

It is unclear if expiratory airflow in survivors born extremely low birth weight (ELBW; 500-999g) has improved after the introduction of exogenous surfactant into clinical practice in 1991. The primary aim of this study was to describe the changes in airflow at 7-8 years of age of survivors born ELBW in five discrete cohorts from 14 years before to 14 years after the introduction of exogenous surfactant into clinical practice. The cohorts comprised consecutive survivors born ELBW in 1977-82 and 1985-87at the Royal Women's Hospital, Melbourne, and in 1991-92, 1997 and 2005 in the state of Victoria, Australia. Survival rates to 2-years of age for infants born ELBW in the state of Victoria rose from approximately 1-in-4 to 3-in-4 over the time of this study. Expiratory airflow measurements at 7-8 years included the forced expired volume in 1s (FEV1), converted to z-scores for age, height, sex, and race. There were 596 ELBW participants with expiratory flow data, 280 (47%) of whom had bronchopulmonary dysplasia (BPD). Overall, there was little change in zFEV1 over the 28-year period (mean change per year; 0.003, 95% CI-0.010, 0.015, P=0.67). There was, however, evidence of an interaction between BPD and year; zFEV1 in those who had BPD fell over time (mean change per year-0.019, 95% CI-0.037,-0.009, P=0.035), whereas zFEV1 improved in those who did not have BPD (mean change per year 0.021, 95% CI 0.006, 0.037, P=0.007). Contrary to recent evidence, expiratory airflow of children born ELBW has not improved with the introduction of surfactant, and may be deteriorating in those who had BPD. National Health and Medical Research Council (Australia); Victorian Government's Operational Infrastructure Support Program.

Ventilation Mechanics.

A fundamental task of the respiratory system is to operate as a mechanical gas pump ensuring that fresh air gets in close contact with the blood circulating through the lung capillaries to achieve O2 and CO2 exchange. To ventilate the lungs, the respiratory muscles provide the pressure required to overcome the viscoelastic mechanical load of the respiratory system. From a mechanical viewpoint, the most relevant respiratory system properties are the resistance of the airways (R aw), and the compliance of the lung tissue (C L) and chest wall (C CW). Both airflow and lung volume changes in spontaneous breathing and mechanical ventilation are determined by applying the fundamental mechanical laws to the relationships between the pressures inside the respiratory system (at the airway opening, alveolar, pleural, and muscular) and R aw, C L, and C CW. These relationships also are the basis of the different methods available to measure respiratory mechanics during spontaneous and artificial ventilation. Whereas a simple mechanical model (R aw, C L, and C CW) describes the basic understanding of ventilation mechanics, more complex concepts (nonlinearity, inhomogeneous ventilation, or viscoelasticity) should be employed to better describe and measure ventilation mechanics in patients.

Respiratory System Dynamics.

While static mechanical forces govern resting lung volumes, dynamic forces determine tidal breathing, airflow, and changes in airflow and lung volume during normal and abnormal breathing. This section will examine the mechanisms, measurement methodology, and interpretation of the dynamic changes in airflow and lung volume that occur in health and disease. We will first examine how the total work of breathing can be described by the parameters of the equation of motion, which determine the pressure required to move air into and out of the lung. This will include a detailed description of airflow characteristics and airway resistance. Next, we will review the changes in pressure and flow that determine maximal forced inspiration and expiration, which result in the maximal flow-volume loop and the clinically important forced expired volume in 1 second. We will also assess the mechanisms and interpretation of bronchodilator responsiveness, dynamic hyperinflation, and airways hyperresponsiveness.

Influence of airflow rates on air source heat pump operating parameters

Air source heat pumps (ASHPs) are energy-efficient and environmentally friendly heating systems widely used to meet the heating needs of buildings. Therefore, researches that ensure the effective use of ASHP systems are crucial for improving the energy efficiency of buildings. Faults, design flaws, or user-controlled settings can cause changes in the airflow rates of the evaporator and condenser in ASHPs. This study examines the effect of changes in the airflow rates of the evaporator and condenser on the operating parameters of ASHPs in heating mode using a developed physics-based model. Although the results of experimental studies in the literature provide useful information in this regard, a model-based study would allow for the examination of different systems with their specific parameters. The model is an advanced version of the author's previous model, which now includes the effects of airflow rates in addition to outdoor air conditions, and it has been validated by comparison with experimental data correlations published in the literature. The logarithmic mean temperature difference-based solution method employed by the model allows for its potential for further development and improvement. Four different sizes of air conditioners with heating capacities ranging from 2.5 kW to 8.2 kW were investigated. Corresponding to EN-14511 test standards, 7 °C outdoor temperature and 90% relative humidity condition and 20 °C indoor temperature condition were taken account. The effects on the ASHP parameters were determined by varying the airflow rates in ratios between 0.2 and 1.4 with 0.2 intervals. The airflow ratio term is defined as the ratio of the flow rate to the maximum airflow rate provided by the fans. It is assumed that the condenser heat load is kept constant at its nominal rate to maintain a consistent indoor temperature using inverter-driven variable speed compressor technology. The results show that changes in the condenser airflow rate have a greater impact on system parameters than changes in the evaporator airflow. Reducing the condenser airflow ratio to 0.4 with the silent mode option reduces the COP value by 21% and increases energy consumption by 44%, indicating that manufacturers should inform customers about the potential decrease in performance when using lower condenser airflow rates. A devastating performance drop is observed when airflow ratios in either the condenser or evaporator drop below 0.4. The performance curve of the ASHP produced by the model can help determine the optimum airflow rates for optimal performance. Systems which can be designed close to optimum airflow rates are less affected by airflow changes. In frost-free conditions, the impact of changes in evaporator airflow on performance is less significant than that of the condenser. However, decreasing the evaporator airflow rate increases the susceptibility of the ASHP to frosting. For example, reducing the evaporator airflow to 0.6 extends the frosting condition limits from 6 °C and %65 relative humidity to 9.7 °C and %50 relative humidity. The results of this study will be valuable for researchers, manufacturers and users in terms of performance evaluation and improvement based on airflow rates. The presented model can be further improved and has the potential to facilitate the investigation of various conditions, including frosting, in future studies.

Comparison of electrical impedance tomography and spirometry-based measures of airflow in healthy adult horses.

Electrical impedance tomography (EIT) is a non-invasive diagnostic tool for evaluating lung function. The objective of this study was to compare respiratory flow variables calculated from thoracic EIT measurements with corresponding spirometry variables. Ten healthy research horses were sedated and instrumented with spirometry via facemask and a single-plane EIT electrode belt around the thorax. Horses were exposed to sequentially increasing volumes of apparatus dead space between 1,000 and 8,500mL, in 5-7 steps, to induce carbon dioxide rebreathing, until clinical hyperpnea or a tidal volume of 150% baseline was reached. A 2-min stabilization period followed by 2minutes of data collection occurred at each timepoint. Peak inspiratory and expiratory flow, inspiratory and expiratory time, and expiratory nadir flow, defined as the lowest expiratory flow between the deceleration of flow of the first passive phase of expiration and the acceleration of flow of the second active phase of expiration were evaluated with EIT and spirometry. Breathing pattern was assessed based on the total impedance curve. Bland-Altman analysis was used to evaluate the agreement where perfect agreement was indicated by a ratio of EIT:spirometry of 1.0. The mean ratio (bias; expressed as a percentage difference from perfect agreement) and the 95% confidence interval of the bias are reported. There was good agreement between EIT-derived and spirometry-derived peak inspiratory [-15% (-46-32)] and expiratory [10% (-32-20)] flows and inspiratory [-6% (-25-18)] and expiratory [5% (-9-20)] times. Agreement for nadir flows was poor [-22% (-87-369)]. Sedated horses intermittently exhibited Cheyne-Stokes variant respiration, and a breath pattern with incomplete expiration in between breaths (crown-like breaths). Electrical impedance tomography can quantify airflow changes over increasing tidal volumes and changing breathing pattern when compared with spirometry in standing sedated horses.

Thermal perception of non-uniform and dynamic air-conditioned environment in the elderly

Due to the decline of the elderly's thermophysiology, the elderly is more sensitive to changes in airflow. Traditional thermal sensation equation was a steady-state model only based on the average of surrounding thermal environment parameters, which cannot describe the thermal perception to the spatial uniformity and temporal fluctuation of the parameters. To characterize the thermal perception of non-uniform and dynamic air-conditioned environments in the elderly, this study determined the characteristics of thermal environment at twenty-four monitoring points (three heights and eight directions) around the elderly through laboratory test. Seven elderly participated in the experiment and were asked to fill in the questionnaire to obtain thermal perception. Different typical airflow with 26 °C set temperature of air-conditioner were set as the measuring conditions. Uniformity and fluctuation indexes were proposed to qualify the spatial and temporal distribution. The results showed that the average of the parameters was basically in the acceptable comfort zone. Through establishing the thermal sensation model based on the average, uniformity, and fluctuation indexes, thermal sensations were only significantly affected by fluctuation of temperature, velocity uniformity, turbulence, and average relative humidity. Compared to traditional model, established model can not only depict the elderly's strong perception of temperature change by temperature fluctuation index, but also refine the elderly's relatively weak perception of static average velocity into a strong perception of the velocity uniformity and turbulence. The R square of this model was 0.153 greater than that of traditional model.

Variations of olfactory function with circadian timing and chronotype.

Cumulative animal studies have suggested that olfaction can be regulated by circadian clock. However, human studies on the topic are relatively limited. The present study thus aimed to investigate diurnal variation in olfaction in healthy adults while examining potential modulating factors. We conducted four rounds of testing on 56 healthy adults (32 women) aged 31 ± 12 years, throughout a single day, during morning (8:00-10:00 h), noon (12:00-14:00 h), afternoon (16:00-18:00 h), and evening (20:00-22:00 h). At the first appointment, participants completed full olfactory function testing using the Sniffin’ Sticks, questionnaires on medical history, nasal symptoms, sleep quality, and chronotype, and were assessed for blood pressure, heart rate, peak nasal inspiratory flow (PNIF), attention level, and rated their smell ability, nasal patency, wakefulness, and concentration level using visual analog scale (VAS) ratings. Subsequent appointments measured olfactory threshold, attentional level, PNIF, blood pressure, heart rate and VAS ratings repeatedly. Olfactory threshold (OT) scores varied significantly between different times of the day, with the highest score in the evening and the lowest in the morning. Similar differences were also observed in PNIF, with the highest value in the evening and the lowest in the morning. However, there were no significant correlations between OT score and PNIF across all four-time testing, as well as between differences in [OT evening â€" OT morning] and [PNIF evening â€" PNIF morning]. Furthermore, a generalized linear mixed model indicated that the testing time of the morning, evening chronotype, self-reported body mass index (BMI), rated smell ability, and rated nasal patency significantly predicted the Sniffin' Sticks OT score. Olfactory function fluctuates throughout the waking hours of the day, with the highest olfactory sensitivity observed in the evening and the lowest in the morning. This pattern is also seen in nasal patency. However, it appears that the circadian changes of nasal airflow may not significantly depend on the circadian changes of the olfactory sensitivity. In addition, chronotype and BMI may regulate such olfactory-circadian variation. These findings provide important insights for future research on the accurate diagnosis and treatment of olfactory dysfunction.

Airflow change and exergy analysis due to the installation of various types of partitions in the collector of a solar chimney power plant

Airflow change and exergy analysis due to the installation of various types of partitions in the collector of a solar chimney power plant