Level Of Airflow Research Articles

A novel method for positive airway pressure delivery: pulsating airflow.

The primary objective is to determine if pulsating airflow can achieve therapeutic pharyngeal pressure levels without requiring a tight-sealing mask. A pilot study included 12 nasal-breathing adults who are currently using positive airway pressure (PAP) for therapy. Patients were awake, and pharyngeal pressures were measured using a miniature pressure probe inserted through their nares. Pulsating airflow was applied via a nasal cannula with a customized valve. The inspiratory flow rate was increased until the pharyngeal pressure matched or exceeded the participant's prescribed PAP level. The expiratory flow rate was maintained at a constant low level of continuous airflow. The study demonstrated that pulsating airflow could generate pharyngeal pressures equivalent to or higher than those achieved with PAP therapy in all participants. The peak inspiratory pressures with pulsating airflow followed an oscillatory pattern matching the pulsation frequency. The mean peak pressure increased linearly with the pulsating flow rate. Compared to a high-flow nasal cannula, pulsating airflow produced significantly higher inspiratory pharyngeal pressures, reaching nearly 20 cmH2O. Pulsating airflow could be a viable method for delivering PAP therapy to patients with respiratory or sleep disorders without needing a tight-sealing mask. Further research is required to establish whether this method can improve patient compliance with PAP therapy, assess long-term safety and efficacy, and explore the impact of varying pulsation parameters on treatment outcomes.

On compression level of hypersonic airflow in high-mach scramjet

High-Mach scramjet is one of the most promising air-breathing propulsion devices to realize integration of air and space transportation. The current paper investigates a key step in design of high-Mach scramjet, namely, the compression level to be executed. The influence of compression level on hydrogen-fuel scramjet performance was analyzed using the modified thermodynamic cycle analysis method for high-Mach conditions. The theoretical results indicate that different from classical thermodynamic cycle analysis, the scramjet thrust reaches the maximum when Mach number at the entrance of combustor approaches 3. The flow loss and heat release in scramjet reach a balance near the maximum thrust state. Excessive compression can cause severe flow loss, while insufficient compression will lead to poor combustion. The numerical simulation further supports the theoretical analysis. When compression level of airflow is inadequate, the heat release rate of fuel will significantly drop. To extended the ideal operating range of high-Mach scramjet, it is suggested that the flow loss in inlet and isolator should be minimized, and the combustion efficiency of fuel in supersonic environment should be improved.

Bronchodilator Responsiveness Defined by the 2005 and 2021 ERS/ATS Criteria in Patients with Asthma as Well as Chronic Obstructive Pulmonary Disease.

BackgroundIn the 2021 ERS/ATS interpretive strategies for routine lung function tests, a positive bronchodilator response (BDR) was updated as a change of >10% relative to the predicted value in forced expiratory volume in 1 second (FEV1) or forced vital capacity (FVC). We aimed to explore the differences between the 2005 and 2021 ERS/ATS criteria applied to patients with asthma as well as chronic obstructive pulmonary disease (COPD).MethodsBDR test data about asthma patients aged 6–80 years and COPD patients aged 18–80 years were derived from the National Respiratory Medicine Center, First Affiliated Hospital of Guangzhou Medical University, from January 2017 to March 2022. BDR results defined by the 2005 and 2021 ERS/ATS criteria were named 2005-BDR and 2021-BDR, respectively. We compared differences between 2005-BDR and 2021-BDR and analyzed the trend in the proportion of positive BDR (BDR+) with the level of airflow obstruction.ResultsA total of 4457 patients with asthma and 7764 patients with COPD were included in the analysis. The percentages of 2005-BDR+ and 2021-BDR+ were 63.32% and 52.84% for asthma, 30.92% and 22.94% for COPD, respectively. Of patients with 2005-BDR+, 81.86% for asthma and 70.18% for COPD showed 2021-BDR+ results, and these patients had higher FEV1%pred, FVC%pred (all P<0.05). Whichever BDR criterion was adopted, the proportion of BDR+ had an upward linear trend with the increased degree of airflow obstruction in COPD, but exhibited an approximate inverted U-shaped curve in asthma. In COPD, the proportion of BDRFEV1 was negatively associated with the degree of airflow obstruction, while BDRFVC was positively associated (all P<0.05).ConclusionCompared with 2005-BDR+, the proportion of 2021-BDR+ reduced markedly in patients with asthma and COPD, but their trends with the degree of airflow obstruction did not change. Patients with consistent BDR+ had higher initial FEV1%pred and FVC%pred.

Atmospheric circulation regimes for prescribed burns along the U.S. Gulf of Mexico coast

The regional-to-synoptic-scale steering atmospheric circulation is important for advecting energy, mass, and momentum across space, with the near-surface wind being the local manifestation of this circulation. The local winds can affect phenomena of economic, ecological, and/or aesthetic values, such as bird migrations and prescribed burns to restore bird habitats. The purpose of this research is to classify the days from 1979 to 2018 based on circulation patterns near the surface (i.e., 1000-hPa) and at the highest level of airflow affecting bird migration (i.e., 700-hPa), across the Gulf Coast region of the United States. The resulting patterns, derived from Ward's clustering method on rotated principal component scores, are used as input in a fire management plan to restore niches for bird species such as black and yellow rails and mottled ducks. Results suggest that for the (near-surface) 1000-hPa level, a classification system consisting of eight circulation types maximizes the between-group variability while minimizing the within-group variability, with a total of 95.8 percent of the dataset variance explained, and reasonable correspondence with existing manual, subjective and semi-automated techniques. At the 700-hPa level, a system of eight circulation types was derived, explaining 95.05 percent of the dataset variance. In general, the western U.S. Gulf of Mexico arc is more likely than the eastern to respond to synoptic control in the form of weather types, while the eastern region may have more influence from local-to-meso-scale land and sea breezes. These results will assist in optimizing the success of controlled burn conditions while enhancing efforts to minimize advection to populated areas.

Efecto de parámetros de mínima cantidad de lubricación en reducción de desgaste de herramienta

The objective of this work is to determine the influence of Minimum Quantity Lubrication (MQL) parameters on flank wear during face milling. Furthermore, the values of each factor in which the MQL resulted to be effective were determined. A designed experiment with two level, three factor and two replicas was used to test tool wear on P45 grade inserts at relatively high cutting speed (~900 m/min) on steel AISI 1045. A commercial MQL system was used with vegetable base lubricant non soluble in water. Results show that amount of lubricant and vertical angle are key factors that affects the effectiveness of the process. A response surface equation was obtained in order to determine the zones in which the factors resulted in the lowest tool wear. A flank wear decrease of 7 times, respect to the maximum observed, was found by using low level of air flow, low level of vertical angle and high level of lubricant.

Investigation of energy-efficient solid desiccant system for wheat drying

The study investigates the applicability of solid desiccant system for drying of freshly harvested wheat grains in order to reduce the moisture content to an optimum level. Fast and low-temperature drying systems are required by today’s drying industries in order to provide economical and safe drying. Therefore, comparison of desiccant drying has been made with the conventional method in terms of drying kinetics, allowable time for safe storage, the total time for drying cycle, and overall energy consumption. It has been found that the air conditions of proposed desiccant drying system provides a high drying rate and longer allowable storage time for safe drying. As the desiccants possess water adsorbing ability by means of vapor pressure deficit, therefore, the desiccant system successfully provides low-temperature drying which ensures the quality of wheat grains. Overall energy consumption is estimated for both conventional hot air drying and desiccant drying system. It has been found that the desiccant system requires less energy as drying is accomplished at minimum level of air flow and within allowable storage time. In addition, the overall performance index of the desiccant system is higher at all temperatures. The study is useful for developing a low-cost and sustainable drying technology for various agricultural products. Keywords: desiccant, solid desiccant system, drying, grain, wheat, performance evaluation DOI: 10.25165/j.ijabe.20191201.3854 Citation: Hanif S, Sultan M, Miyazaki T, Koyama S. Investigation of energy-efficient solid desiccant system for wheat drying. Int J Agric & Biol Eng, 2019; 12(1): 221–228.

System identification analysis for an air compressor system and enhancement proposal by sensors based in nanostructures

An Air Compressor System is an equipment (mechanical system) which can transmit energy due to increase air pressure level of air flow that through it. This energy can be used in many applications, such as in drills for mining, adding air to tires on vehicles, spraying crops, etc. Therefore, it is necessary to know the mathematical model of an Air Compressor System to study all the thermodynamical variables: “Temperature, Pressure, Air Flow” which let to get a formalized explanation of the energy transfer through this equipment. Furthermore it is described that Air Compressor System can be enhanced while it uses sensors/actuators based in nanostructures.

Correlation analysis among quality of life, knowledge, beliefs, behavioral and pulmonary function outcomes in stable-stage patients with chronic obsturctive pulmonary disease

Objective To explore the relationship between quality of life and knowledge, beliefs, behavioral, pulmonary function outcomes in stable-stage patients with chronic obsturctive pulmonary disease (COPD). Methods Using the general data questionnaire, COPD assessment test (CAT), knowledge, attitude and behavior questionnaire to investigate 93 stable-stage COPD patients in urban and rural areas, and measure the level of forced expiratory volume in one second (FEV1%). Results CAT total score was (22.56 ± 6.40) points which was in severe level; knowledge, beliefs, behavior total score was (41.94 ± 8.20) points, and FEV1% was (59.81 ± 7.64) %.The CAT was negatively correlated with knowledge, beliefs, behavior total score and two dimensions of beliefs, behavior and FEV1%, r values were -0.262, -0.288, -0.217,-0.256 respectively, P < 0.05. Conclusions The COPD patients in stable-stage have a high level of CAT. Targeted invention should be combined with the status of the knowledge, beliefs and behavior to improve the level of air flow, and quality of life of patients. Key words: Quality of life; Health knowledge, attitudes, practice; Pulmonary diseases, chronic obstructive

A semi-centralized, valveless and demand controlled ventilation system in comparison to other concepts in field tests

The idea of adapting the air supply rate to the actual demand in a building is not a new one. In commercial buildings it is already state-of-the-art to establish a demand controlled ventilation, where the level of air flow is based on sensors or time control. In residential buildings however, mechanical ventilation systems, whether centralized or decentralized, are in most cases operated in a constant modus, providing fresh air regardless if the fresh air is needed or not, even though the technology and the components needed for demand controlled ventilation exist and can be purchased at reasonable prices. In this article, results of field tests with a semi-centralized demand feedback-controlled ventilation system are shown and compared to outcomes with other demand controlled systems. The semi-centralized prototype includes decentralized fans per ventilation zone, making a room-wise ventilation possible and valves to balance the system hydraulically unnecessary. It is shown that each presented concept of demand controlled ventilation can save energy by decreasing the operational time or the mean air flow rate without compromising air quality. Concepts which make a zone- or even a room-wise control of air flow possible, showed the highest energy saving potential of up to two-thirds compared to a system operating at constant flow rates. In addition to the energy savings due to decreased operational time, the maintenance and filter costs are decreased while the user comfort is increased, as natural ventilation in spring, summer and autumn may easily be added when ΔT between inside and outside is small.

Experimental investigation of personal air supply nozzle use in aircraft cabins

To study air passengers' use of individual air supply nozzles in aircraft cabins, we constructed an experimental chamber which replicated the interior of a modern passenger aircraft. A series of experiments were conducted at different levels of cabin occupancy. Survey data were collected focused on the reasons for opening the nozzle, adjusting the level of air flow, and changing the direction of the air flow. The results showed that human thermal and draft sensations change over time in an aircraft cabin. The thermal sensation response was highest when the volunteers first entered the cabin and decreased over time until it stablized. Fifty-one percent of volunteers opened the nozzle to alleviate a feeling of stuffiness, and more than 50% adjusted the nozzle to improve upper body comfort. Over the period of the experiment the majority of volunteers chose to adjust their the air flow of their personal system. This confirms airline companies' decisions to install the individual aircraft ventilation systems in their aircraft indicates that personal air systems based on nozzle adjustment are essential for cabin comfort. These results will assist in the design of more efficient air distribution systems within passenger aircraft cabins where there is a need to optimize the air flow in order to efficiently improve aircraft passengers' thermal comfort and reduce energy use.

Snoring sounds variability as a signature of obstructive sleep apnea

Snoring sounds vary significantly within and between snorers. In this study, the variation of snoring sounds and its association with obstructive sleep apnea (OSA) are quantified. Snoring sounds of 42 snorers with different degrees of obstructive sleep apnea and 15 non-OSA snorers were analyzed. The sounds were recorded by a microphone placed over the suprasternal notch of trachea, simultaneously with polysomnography (PSG) data over the entire night. We hypothesize that snoring sounds vary significantly within a subject depending on the level of obstruction, and thus the level of airflow. We also hypothesize that this variability is associated with the severity of OSA. For each individual, we extracted snoring sound segments from the respiratory recordings, and divided them into three classes: non-apneic, hypopneic, and post-apneic using their PSG information. Several features were extracted from the snoring sound segments, and compared using a nonparametric statistical test. The results show significant shift in the median of features among the snoring sound classes (p<0.00001) of an individual. In contrast to hypopneic and post-apneic classes, the characteristics of snoring sounds did not vary significantly over time in non-apneic class. Therefore, we used the total variation norm of each subject to classify the participants as OSA and non-OSA snorers. The results showed 92.9% sensitivity, 100% specificity and 96.4% accuracy.

Dynamic Hyperinflation During Daily Activities: Does COPD Global Initiative for Chronic Obstructive Lung Disease Stage Matter?

One of the contributors to exercise limitation in COPD is dynamic hyperinflation. Although dynamic hyperinflation appears to occur during several exercise protocols in COPD and seems to increase with increasing disease severity, it is unknown whether dynamic hyperinflation occurs at different severity stages according to the Global initiative for chronic Obstructive Lung Disease (GOLD) in daily life. The present study, therefore, aimed to compare dynamic hyperinflation between COPD GOLD stages II-IV during daily activities.Thirty-two clinically stable patients with COPD GOLD II (n = 10), III (n = 12), and IV (n = 10) participated in this study. Respiratory physiology during a daily activity was measured at patients' homes with Oxycon Mobile. Inspiratory capacity maneuvers were performed at rest, at 2-min intervals during the activity, and at the end of the activity. Change in inspiratory capacity is commonly used to reflect change in end-expiratory lung volume (DeltaEELV) and, therefore, dynamic hyperinflation. The combination of static and dynamic hyperinflation was reflected by inspiratory reserve volume (IRV) during the activity.Overall, increase in EELV occurred in GOLD II-IV without significant difference between the groups. There was a tendency for a smaller DeltaEELV in GOLD IV. DeltaEELV was inversely related to static hyperinflation. IRV during the daily activity was related to the level of airflow obstruction.Dynamic hyperinflation occurs independent of GOLD stage during real-life daily activities. The combination of static and dynamic hyperinflation, however, increases with increasing airflow obstruction.

Modelling the heat dynamics of building integrated and ventilated photovoltaic modules

This paper deals with mathematical modelling of the heat transfer of building integrated photovoltaic (BIPV) modules. The efficiency of the photovoltaic (PV) module and its temperature are negatively correlated. It is therefore of interest to lower the temperature of the PV module by increasing the heat transfer from the PV module. The experiment and data originate from a test reference module the EC-JRC Ispra. The set-up provides the opportunity of changing physical parameters, the ventilation speed and the type of air flow, and this makes it possible to determine the preferable set-up. To identify best set-up, grey-box models consisting of stochastic differential equations are applied. The models are first order stochastic state space models. Maximum likelihood estimation and the extended Kalman filter are applied in the parameter estimation phase. To validate the estimated models, plots of the residuals and autocorrelation functions of the residuals are analyzed. The analysis has revealed that it is necessary to use non-linear state space models in order to obtain a satisfactory description of the PV module temperature, and in order to be able to distinguish the variations in the set-up. The heat transfer is increased when the forced ventilation velocity is increased, while the change in type of air flow does not have as striking influence. The residual analysis show that the best description of the PV module temperature is obtained when fins, disturbing the laminar flow and making it turbulent, are applied in the set-up combined with high level of air flow. The improved description by the model is mainly seen in periods with high solar radiation.

Secagem e armazenamento de sementes de maracujá amarelo (Passiflora edulis Sims f. flavicarpa Degener)

Este trabalho foi desenvolvido com os objetivos de avaliar os efeitos imediato e latente da temperatura de secagem e de dois tipos de embalagem sobre a qualidade fisiológica de sementes de maracujá-amarelo após três e seis meses de armazenamento. Empregaram-se quatro níveis de temperatura do ar de secagem (ambiente à sombra, 30, 35 e 40 ºC), um nível de fluxo de ar, 48 m³ min-1 m-2, e teores de água inicial e final de cerca de 35 e 10 % b.u., respectivamente. Os tratamentos de secagem foram realizados em protótipo de secador de leito fixo, em camada delgada, com fluxo de ar ascendente. Avaliou-se a qualidade fisiológica por meio de testes de germinação e vigor. Depois da secagem, as sementes foram embaladas e armazenadas em câmara do tipo B.O.D. a 15±1 ºC. As temperaturas utilizadas na secagem das sementes não influenciam a germinação. O armazenamento por três e seis meses não afetou a qualidade fisiológica das sementes. A secagem das sementes de mamão pode ser realizada à sombra ou em temperaturas de 30 a 40 ºC sem afetar a qualidade fisiológica das mesmas.

持続音声における呼気流量の経時変化について

To explore the voice regulating system during sustained phonation kept at a comfortable level, air flow, intensity and frequency level were examined under a variety of conditions. Experiments consisted of four conditions : 1) normal condition 2) keeping constant flow 3) keeping constant intensity 4) exposure to 125Hz band noise. In the second and the third experiments, test subjects wereinstructed to keep their constant level of air flow or intensity for five seconds, while watching loci on a CRT and in the fourth experiment, 70dB band noise was given one second after test subjects produced voice.Results : Air flow decrease over the time course was observed in all of the tests. Intensity showed a slightly decreasing level over the time course, and frequency was maintained at a constant level during the tests in each subjects.Decrease of air flow implies the improvement of air flow consumption efficiency in sustained phonation, resulting from increasing resistance of the glottis. Decrease of intensity remains in a small range imperceptible to test subjects, which suggests that regulating system works on maintaining the voice intensity level during sustained phonation.

Effect of tension, stiffness, and airflow on laryngeal resistance in the in vivo canine model.

This study used an in vivo canine model of phonation to determine the effects of airflow on glottal resistance at low, medium, and high levels of recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN) stimulation. Static and dynamic trials of changing airflow were used to study the effects of airflow on glottal resistance during phonation. As reported previously, glottal resistance varies inversely as a function of airflow. Increasing levels of RLN stimulation resulted in a statistically significant increase in glottal resistance for each level of airflow evaluated. Variation in SLN stimulation had no statistically effects on the relationship between flow and resistance. At airflow rates greater than 590 milliliters per second (mL/s), glottal resistance approached 0.1 mm Hg per mL/s for all levels of RLN and SLN stimulation tested. These data support the collapsible tube model of phonation.

A Generalized Control-strategy for Near-ambient Drying of Wheat Under Canadian-prairie Climate

Computer simulation was used to explore options for varying airflow in the control of near-ambient drying of wheat in the Canadian prairies. Earlier work had identified that the best way to use ambient air for drying in the prairie climate was not to adjust air humidity by the addition of heat, but to take advantage of diurnal swings in humidity by making appropriate variations in airflow. Year-to-year variation in the general level of the climate affected the required base level of airflow.

Effect of positive nasal pressure on upper airway pressure-flow relationships.

To determine the influence of changes in nasal pressure (Pn) on airflow mechanics in the upper airway, we examined the effect of elevations in Pn on upper airway resistance and critical pressure (Pcrit) during stage I/II sleep in six patients with obstructive sleep apnea. When Pn was elevated above a Pcrit, periodic occlusions of the upper airway were eliminated and inspiratory airflow limitation was demonstrated by the finding that inspiratory airflow (VI) became maximal (VImax) and independent of fluctuations in hypopharyngeal pressure (Php) when Php fell below a specific Php (Php'). As Pn was elevated, VI vs. Php demonstrated 1) marked decreases in early and late inspiratory resistances from 75.9 +/- 34.7 and 54.6 +/- 19.0 to 8.0 +/- 1.7 and 7.6 +/- 1.6 cmH2O.l-1.s (P less than 0.05), respectively, and 2) increases in early and late inspiratory Php' to levels that exceeded Pcrit by 3.0 +/- 0.6 and 3.1 +/- 0.7 cmH2O, respectively, at the highest level of Pn applied (P less than 0.01). This latter finding suggests that elevations in Pn result in increases in Pcrit. We suggest that elevations in Pn produce distinct alterations in upper airway resistance and collapsibility, which may influence oppositely the level of airflow through the upper airway during sleep.

Comparison of The Performance of Two Mini Peak Flow Meters

Two mini peak flow meters commonly used to monitorize the peak expiratory flow rate (PEFR) are compared to assess their agreement, precision and, with respect to a standard pneumotachygraph, accuracy. Precision of the mini-Wright peak flow meter is greater, possibly as result of a systematic overestimation of PEFR values. The Assess peak-flow meter is more accurate, but its ability to reproduce the actual well-known PEFR variability is dependent from the absolute level of air flow. The agreement between two instruments is very poor, both in asthmatics and in normals, so that it is mandatory to use always the same mini peak flow meter in population studies and during the follow-up of asthmatic patients.

Augmentation of phrenic neural activity by increased rates of lung inflation.

Studies were conducted in anesthetized paralyzed dogs using a cycle-triggered constant-flow ventilator, which ventilated the animal in phase with the recorded phrenic neural activity. Intermittently tests were performed in which the animal was ventilated with a different airflow for a single breath. Increased airflows, within the range generated during spontaneous breathing, caused an increased rate of rise of the moving average phrenic neurogram and a shortening of the duration of the nerve burst. The magnitude of the increase in the rate of rise of the neurogram was related to the level of inspiratory airflow. Tests with brief pulses of airflow showed that an increase in the rate of rise of the phrenic neurogram could be produced without inflating the lung above the resting tidal volume of the animal. Similar results were obtained with negative-pressure ventilation and the effects were abolished by vagotomy. This vagally mediated augmentation of phrenic neural output may accelerate the inspiratory volume change in the lung during spontaneous breathing at hyperpneic levels.