Airflow Impedance Research Articles

Features and Associated Comorbidities of Laryngomalacia in Saudi Arabia.

Laryngomalacia (LM) is defined as the collapse of supraglottic structures during inspiration, resulting in intermittent airflow impedance and associated stridor. LM is the most prevalent cause of congenital stridor in newborns. The aim of this study is to determine the features and associated comorbidities of LM in Saudi Arabia and to delineate the diagnostic and therapeutic measures used, based on the severity of the case and related comorbidities. This is a three-year retrospective study of children diagnosed with LM and treated in the pediatric otorhinolaryngology outpatient clinic at Maternity and Children Hospital, Dammam, Saudi Arabia, between January 2018 and January 2022. The inclusion criteria were patients with signs and symptoms of LM who are younger than 14 years old. The diagnosis of LM was based on clinical evaluation and confirmed by nasopharyngolaryngoscopy in awake patients and/or direct laryngoscopy and scoping under general anesthesia with spontaneous ventilation for dynamic evaluation. The Olney classification was used for the morphological classification of LM. The exclusion criteria were patients lost to follow-ups. Follow-up duration was two years minimum. A total of 52 patients were included in the study. Among the participants, females accounted for 71% and males accounted for 29% of cases. Our results were in accordance with the relevant literature, except for the higher prevalence of LM in full-term neonates who were found to account for 69.2% of the cases. Understanding the patterns and characteristics of breathing may help clinicians distinguish the noisy breathing of LM from other illnesses because infants are frequently misdiagnosed with these conditions.

Improvement of a High-Current-Density Power Backplane Design With a PID Fan Control Cooling System on an Enterprise Server

Power consumption saving and direct airflow to enhance a system’s cooling efficiency are important for the per watt index performance both of a server system and a data center’s application. In this research project, we design the high-current-density power distribution printed circuit board (PCB) as an enterprise server power backplane board. This project also includes a design of both the vent hole size and the location to distribute the direct current path not only to attain a satisfactory loading balance but also to obtain the necessary direct airflow to improve cooling efficiency. In addition, we design the proportional–integral–derivative (PID) control module as a universal management control module for an enterprise server as a rack system assembly, in order to control the fan speed duty cycle more efficiently, all of which depends on a temperature that is different from the present error, the accumulation of past errors, and the prediction of future errors. We also consider the server system airflow impedance and fan speed duty and their dependence on other items, to ensure that the airflow is controllable and to prevent not only interference but also noise between enterprise server systems.

On the aerodynamic fog collection efficiency of fog water collectors via three-dimensional numerical simulations

Fog water collection gained interest in recent years as an emerging solution for water scarcity in arid and semi-arid areas. During a fog event, a porous mesh screen of plastic polymer retains the water through droplet impaction, where the droplets coalesce and trickle into a gutter for collection. This type of collecting system has existed since the 1960s; however, a substantial lack of understanding remains as to the aerodynamics that dominates the collection phenomena. The Aerodynamic Collection Efficiency (ηa) is the determining factor in the overall performance of such systems. This paper aims to further the fundamental knowledge on the aerodynamic behavior during fog collection. For this, a three-dimensional computational fluid dynamics model was developed, where the collector's mesh was modeled as a porous medium, which simulates a conventional two-dimensional double layer mesh. A parametric study was carried out varying the mesh's geometric characteristics (flat and concave), mesh-to-ground distance, and wind speed. The effect of wind speed on aerodynamic collection efficiency is mainly determined by the relative relationship between the viscous and inertial pressure drop in the porous medium. A greater curvature reduces the mesh's airflow impedance, leading to a significant improvement of the aerodynamic collection efficiency. Within the parameter range of our study, we found a maximum aerodynamic collection efficiency of 35% for the largest curvature (1.1 m), the highest mesh-to-ground distance (2 m), and the maximum wind speed (5 to 7 m s−1).

Breast epithelial cell infiltration in enhanced electrospun silk scaffolds

In the present study, the effects of air-flow impedance electrospinning and air-flow rates on silk-based scaffolds for biological tissues were investigated. First, the properties of scaffolds obtained from 7% and 12% silk concentrations were defined. In addition, cell infiltration and viability of MCF-10A breast epithelial cells cultured onto these scaffolds were used to determine the biological suitability of these nanostructures. Air-flow impedance electrospun scaffolds resulted in an overall larger pore size than scaffolds electrospun on a solid mandrel, with the largest pores in 7% silk electrospun with an air pressure of 100 kPa and in 12% silk electrospun with an air pressure of 400 kPa (13.4 ± 0.67 and 26.03 ± 1.19 µm, respectively). After 14 days in culture, the deepest MCF-10A cell infiltration (36.58 ± 2.28 µm) was observed into 7% silk air-flow impedance electrospun scaffolds subjected to an air pressure of 100 kPa. In those scaffolds MCF-10A cell viability was also highest after 14 days in culture. Together, these results strongly support the use of 7% silk-based scaffolds electrospun with a 100 kPa air-flow as the most suitable microenvironment for MCF-10A infiltration and viability.

The use of air-flow impedance to control fiber deposition patterns during electrospinning

Electrospun non-woven structures have the potential to form bioresorbable vascular grafts that promote tissue regeneration in situ as they degrade and are replaced by autologous tissue. Current bioresorbable grafts lack appropriate regeneration potential since they do not have optimal architecture, and their fabrication must be altered by the manipulation of process parameters, especially enhancing porosity. We describe here an air-impedance process where the solid mandrel is replaced with a porous mandrel that has pressurized air exiting the pores to impede fiber deposition. The mandrel design, in terms of air-flow rate, pore size, and pore distribution, allows for control over fiber deposition and scaffold porosity, giving greater cell penetration without a detrimental loss of mechanical properties or structural integrity.

Three Important Considerations in Posttraumatic Rhinoplasty

Introduction: Many factors must be considered when performing a posttraumatic rhinoplasty. Since nasal fractures are the most common fractures in the adult facial skeleton, many patients who suffer midface trauma also suffer from nasal deformity/deviation and nasal airflow impedance. There are three specific regions within the nose which may impede airflow: nasal septum, internal nasal valves, and inferior turbinates. Each component of functional and posttraumatic rhinoplasty has been studied independently. However, a review of posttraumatic rhinoplasty procedures in which multiple regions of the nasal anatomy were addressed, when indicated, has not been elucidated much in the literature. Materials and Methods: A retrospective review of the medical charts and operative reports of 42 consecutive patients who underwent a post-traumatic rhinoplasty from July 2002 to December 2006 by the same surgeon was undertaken to determine which specific regions of the nose required secondary repair. Postoperative results were then reviewed to determine objective complications and subjective complaints. The specific techniques employed in the each operative procedure were then analyzed and objective complications and subjective complaints were recorded. Results: The most common preoperative patient complaint included difficulty breathing and nasal complex deformity followed by difficulty breathing alone and isolated deviation/deformity. The most common preoperative objective findings included airflow obstruction and nasal deformity, followed by isolated airflow obstruction, and isolated deviation/deformity with no air flow disturbance. All patients underwent a secondary posttraumatic septorhinoplasty. Septoplasty was performed in 78.6% of the patients; spreader grafts were used in 74% of the patients, and inferior turbinate surgery was done in 62% of the patients. Postoperatively, subjective findings revealed no complaints in 38 patients (90.5%). Two patients had complaints of persistent nasal deformity and air flow obstruction; 1 patient had persistent nasal deformity, and another patient had persistent air flow obstruction. Objectively, 5 patients had persistent nasal deformity, 2 patients had persistent air flow obstruction, and two patients had persistent airflow obstruction and nasal deformity. Conclusion: When indicated, by appropriately addressing the key regions of the nasal complex, including the septum, internal nasal valves, and inferior turbinates, the majority of patients (90.5%) will have no subjective complaints of difficulty breathing or a nasal complex deformity.

Effects of body position on the ventilatory response to hypercapnia

Effect of posture on the hypercapnic ventilatory response was studied on the anaesthetized rats by using rebreathing techniques in the supine and head-down positions. There were no statistically significant alterations in tidal volume, frequency, minute ventilation, and PETCO2 between the head-down and supine positions during breathing at rest. However, the esophageal pressure inspiratory swings were significantly greater in the head-down compared with supine position. Moreover, we found that body position did not affect the hypercapnic ventilatory response, but did affect the relationship between inspiratory driving pressure and the increase of end tidal PCO2. Greater inspiratory pressure is required to maintain the same level of the ventilatory response to hypercapnia in the horizontal position with the head-down. We believe that the discrepancy between postural alterations in the hypercapnic ventilatory and pressure responses is presumably a result of decreased lung compliance and increased airflow impedance of respiratory system in the head-down position.

Development of a low profile acoustical door for use on racks and cabinets for the information technology industry

This paper presents the design of 19 inch rack acoustical doors balancing acoustical attenuation, airflow impedance and distribution in a short depth by combining air foil technology with acoustic baffle design. Design optimization was done utilizing fluid flow analytical modeling and verified with a air flow bench and an acoustical rack door test fixture. Higher heat loads in rack mounted computer equipment drive higher cooling requirements. In order to provide air cooling solutions, higher volumetric air flow is required resulting in higher acoustical noise levels. These noise levels can result in noise levels that are unacceptable to the customer. Acoustical doors lower noise levels but are prone to high flow impedance, uneven flow distribution and large physical depth. High impedances require higher air moving device speeds to offset the lost volumetric air flow. This decreases the effective acoustical attenuation. Various rack modules have different inlet and outlet air flow locations making the distribution of the air from the door (front) or into the door(rear) important. Solutions to these problems usually require large depths in order to provide blockage of line of site and gradual air flow lines to keep impedance low and provide even distribution of the air.

Radiated noise from structural vibrations of a PC

Computer systems typically contain several noise sources like fans, hard drives, and optical drives. The noise emission of these devices can be characterized on the component level, for example with sound power measurements. For fans, the backpressure effect due to chassis airflow impedance can be characterized to capture an installation effect. However, the induced vibration levels and resulting radiated structural noise when sources are placed in a system are less well understood. This paper focuses on a quantification of the radiated noise from enclosure vibrations due to vibration of a source. The surface acceleration distribution on the enclosure panels was measured. This measured vibration pattern was then used to calculate the radiated noise with several models: the Rayleigh integral model, the radiation mode model, and finally a boundary element model. The panel radiation noise was compared to the measured total noise level. This allowed a quantification of the enclosure vibration noise contribution. The results indicated significant contributions at the rotational frequency and its harmonics. The chassis enclosure resonances were apparent.

Mechanical properties and microstructure of sintered PVC powder. II. Permeability and porous structure

Static and dynamic air-flow impedance measurements were conducted with thin specimens of a variously sintered PVC powder. The results were interpreted by a statistical theory that expresses the parameters of a quasihomogeneous acoustic absorber in terms of porosity averages of channel radius and orientation. The low-frequency behavior of the air-flow impedance is determined by the porosity, a structure factor, and three different average channel radii that are related by inequalities. The latter could be established from general statistical considerations and were confirmed in most cases by experiment. Photomicrographs of sections through sintered powder layers were analyzed by stereological techniques in terms of specific surfaces. The channel radii derived from such measurements compared favorably with the average acoustic channel radii.

Effect of hypothermia on responses to imposed trachea obstruction.

Respiratory and circulatory responses to three levels of imposed tracheal obstruction were measured in normothermic dogs; the same measurements were repeated after the blood temperature of the animals had been reduced to 28 C by immersion in ice water. Respiratory rate increased, tidal volume decreased, and arterial oxygen saturation progressively declined as a result of tracheal impedance at 37 C. The induction of the hypothermic condition caused a fall in respiratory rate, an increase in tidal volume, and no change in arterial oxygen saturation in response to the same obstruction to air flow. Cardiac output and systemic pressure increased as the magnitude of obstruction was increased in the normothermic animals but were not altered by the same degree of obstruction in the hypothermic animals. The differences in responses observed at the two temperatures studied seem to be related to the degree to which hypoxia develops in the normothermic animals as a result of tracheal air flow impedance. Submitted on May 16, 1961

Effects of graded resistance to tracheal air flow in man.

Experiments were made on 11 human subjects to determine the effects of four levels of air flow resistance when added independently or simultaneously to inspiration and expiration. Resistance ranged from 0.10 to 0.43 mm H2O/cc/sec. a) The primary effect of resistance to air flow is a reduction in air flow velocity and an increase in duration of the impeded phase; b) resistance on one phase may alter the pattern of air flow of the other phase as well. This alteration is generally an elevated maximal flow velocity; c) reduction in respiratory frequency, increase in tidal volume and increase in expiratory reserve, usually exhibited by individuals breathing in and out through resistance, are mainly associated with the impedance of expiratory flow; d) the extra work associated with breathing through the spectrum of resistances studied increases in a linear fashion; e) as a result of air flow impedance, pulmonary ventilation is reduced and alveolar carbon dioxide rises and oxygen tension falls. Levels of resistance used have only a slight respiratory effect when subjects are at rest but bring about dramatic changes in alveolar gas composition when ventilatory demands are increased by moderate exercise. Submitted on October 18, 1956