BACKGROUND A limitation of bronchoscopic balloon dilatation (BBD) is that airflow must be completely blocked for as long as possible during the operation. However, the patient often cannot hold his or her breath for a long period affecting the efficacy of the procedure. In this study, we used an extra-small-diameter tube to provide assisted ventilation to patients undergoing BBD and assessed th...

The influences of diameter and length of the Fe-N₄-patched carbon nanotubes (Fe-N₄/CNTs) on oxygen reduction reaction (ORR) activity were investigated by density functional theory method using the BLYP/DZP basis set. The results indicate that the stability of the Fe-N₄ catalytic site in Fe-N₄/CNTs will be enhanced with a larger tube diameter, but reduced with shorter tube length. A tube with to...

The paper studies optimization of shell-and-tube heat exchangers using the particle swarm optimization technique. A total cost function is formulated based on initial and annual operating costs of the heat exchangers. Six variables – shell inside diameter, tube diameter, baffle spacing, baffle cut, number of tube passes and tube layouts (triangular or square) – are considered as the design para...

The use of a modified paediatric tube and capsule for suction biopsy of the mucosa of the small intestine is discussed. The tube is small in diameter and can be introduced through the nose without local trauma and with minimal discomfort. The intubation technique was followed in 72 instances to obtain suction biopsies from the proximal mucosa of the small intestine in protein-calorie malnourish...

The objective of this paper was to fabricate a biodegradable tubular scaffold for small diameter (d<6 mm) blood vessel tissue engineering. The tube scaffold needed a porous wall for cell attachment, proliferation and tissue regeneration with its degradation. A novel method given in this paper was to coat a porous layer of poly (epsilon-caprolactone) (PCL) on the outside of a poly (glycolic-co-l...

A strategy by multi-objective genetic algorithm (MOGA) combined with Kriging response surface is proposed for optimum design of wavy fin tube in an air cooler, while minimum pressure loss factor, maximum heat transfer factor and overall performance as three objective functions. The results show that the effects height density on are positive wave number angle negative; parallel higher than stag...

The effect of roughness on pressure drop and heat transfer in circular tubes has been extensively studied in literature. The pioneering work of Nikuradse (1933) established the sand grain roughness as a major parameter in defining the friction factor during laminar and turbulent flows. Recent studies have indicated a transition to turbulent flows at Reynolds number values much below 2300 during...

The distance over which the upstream flow conditions in a tube are disturbed by a stenosis downstream, i.e. the outlet length, was investigated for Reynolds numbers in the range 210-2900. Two methods were used, the Navier-Stokes equations were solved with a computer and a physical model was constructed and maximal velocities were measured with an ultrasound Doppler system. The computer model sh...