Efficient Airflow Research Articles

.MU.-Opioid and N-Methyl-D-aspartate Receptors Are Localized at Laryngeal Motoneurons of Guinea Pigs

The glottic movement is important for generating efficient airflow in respiration and related reflexes such as coughing. The superior laryngeal nerve (SLN) innervates the cricothyroid muscle and regulates the glottic aperture. A total of 620 laryngeal motoneurons (LMNs) providing efferent fibers to the SLN were retrogradely identified with fluorescent wheat germ agglutinin (WGA) in 8 guinea pigs. The WGA-labeled cells were distributed in the ventrolateral part of nucleus ambiguus, extending 1.8-2.2 mm lateral to the midline, 0.8-1.2 mm from the ventral surface and 1.7-2.6 mm rostral to the obex. Double staining revealed that 28.4% of LMNs (44 out of 155 cells examined) were immunopositive to N-methyl-D-aspartate (NMDA) receptors and 29.2% of LMNs (55 out of 185 cells) to mu-opioid receptors. The present study demonstrates phenotypic variation in the synaptic transmission to the LMNs in guinea pigs. These results suggest modulation of the glottic movement by mu-opioid and NMDA mechanisms.

Soil vapor extraction in sandy soils: Influence of airflow rate

Airflow rate is one of the most important parameters for the soil vapor extraction of contaminated sites, due to its direct influence on the mass transfer occurring during the remediation process. This work reports the study of airflow rate influence on soil vapor extractions, performed in sandy soils contaminated with benzene, toluene, ethylbenzene, xylene, trichloroethylene and perchloroethylene. The objectives were: (i) to analyze the influence of airflow rate on the process; (ii) to develop a methodology to predict the remediation time and the remediation efficiency; and (iii) to select the most efficient airflow rate. For dry sandy soils with negligible contents of clay and natural organic matter, containing the contaminants previously cited, it was concluded that: (i) if equilibrium between the pollutants and the different phases present in the soil matrix was reached and if slow diffusion effects did not occur, higher airflow rates exhibited the fastest remediations, (ii) it was possible to predict the remediation time and the efficiency of remediation with errors below 14%; and (iii) the most efficient remediation were reached with airflow rates below 1.2 cm 3 s −1 standard temperature and pressure conditions.

Considerations for Efficient Airflow Design in Cleanrooms

A high-performance cleanroom should provide efficient energy performance in addition to effective contamination control. Energy-efficient designs can yield capital and operational cost savings, and can be part of a strategy to improve productivity in the cleanroom industry. Based upon in-situ measurement data from ISO Class 5 clean rooms, this article discusses key factors affecting cleanroom air system performance and benefits of efficient airflow design in clean rooms. Cleanroom HVAC systems used in the semiconductor, pharmaceutical, and healthcare industries are very energy intensive, requiring large volumes of cleaned air to remove or dilute contaminants for satisfactory operations. There is a tendency, however, to design excessive airflow rates into cleanroom HVAC systems, due to factors such as design conservatism, lack of thorough understanding of airflow requirements, concerns about cleanliness reliability, and potential design and operational liabilities. Energy use of cleanroom environmental systems varies with system type and design, cleanroom functions, and the control of critical parameters such as temperature and humidity. In particular, cleanroom cleanliness requirements specified by cleanliness class have an impact on overall energy use. A previous study covering Europe and the US reveals annual cleanroom electricity usage for cooling and fan energy varies significantly depending on cleanliness class, and may account for up to three-quarters of total annual operating costs. A study on a semiconductor cleanroom in Japan found air delivery systems account for more than 30% of total power consumption. It is evident that the main factors dictating cleanroom operation energy include airflow rates and HVAC system efficiency. Improving energy efficiency in clean rooms may potentially contribute to significant savings in the initial costs of the facilities as well as operation and maintenance costs. For example, energy consumption by a typical chip manufacturer can be cut 40% or more, and the associated greenhouse emissions even more. Cleanroom HVAC systems provide huge opportunities for energy savings in the semiconductor industry. In addition to direct cost reductions in cleanroom investment and operation, energy-efficient designs can reduce maintenance costs, increase power reliability, improve time-to-market in cleanroom production, and improve environmental quality. Companies that use energy efficiency to lower costs and increase productivity can gain a competitive advantage and achieve a higher return on investment. In addition, energy-efficient cleanroom systems conserve energy and natural resources, heightening the company's reputation as an environmentally conscious leader in the community and the industry. A significant portion of energy use in cleanroom environmental systems is associated with recirculating air systems. We will review and analyze design factors and operational performance of airflow systems in ISO Class 5 clean rooms. We will also discuss benefits of efficient cleanroom airflow designs in conjunction with effective cleanroom contamination control. We will consider the following common recirculating air system designs: fan-tower (FT) with pressurized-plenum; distributed air handler unit (AHU); and fan-filter unit (FFU).

The role of maxillofacial osteotomies in the treatment of obstructive sleep apnea.

Selective osteotomies of the maxillofacial skeleton can improve airway dynamics and allow for more efficient airflow in patients with obstructive sleep apnea (OSA). The success of these procedures for patients with OSA is well documented. This article reviews the indications and treatment considerations for maxillofacial osteotomies to improve airway dynamics in patients with OSA.

Anechoic Duct Termination Development Using Scale Model Theory

A 10 000 cfm aerodynamic and acoustic fan test facility required development of an anechoic section to facilitate in-duct sound testing. The resulting design incorporates sound absorbing material to reduce the plane-wave resonance effects within the test duct while permitting efficient air flow passage in either axial direction. This anechoic section is located between the end of the test duct and a 180° full radius elbow. The aerodynamic measuring section and auxiliary exhaust supply are connected to the elbow and physically located above the test duct. Using a one-to-four scale ratio, the 18-in. diam test duct was simulated by a 4.5-in. diam pipe. Conical, exponential, and catenoidal horn flaring geometries were reviewed as possible candidates for the termination's external configuration. The design value for the ratio of the maximum to minimum sound pressure occurring in the model test section as a result of the standing wave formed by incident and reflected plane waves was specified as 1.5 bB for the model frequency range of 240–1600 Hz. Results of the model test study indicate that an anechoic section having a catenoidal horn profile will provide satisfactory performance. The optimum acoustical performance (minimum SWR) was obtained with a sound absorbing material filling the termination cavity except for an aerodynamic passage through the center of the horn. Performance of a full scale design is compared with the model.