There is renewed interest in the hospital environment as a potentially important factor for cross-infection with methicillin-resistant Staphylococcus aureus (MRSA) and other nosocomial pathogens. The aim of this study was to evaluate the effectiveness of a portable high-efficiency particulate air (HEPA)-filtration unit (IQAir Cleanroom H13, Incen AG, Goldach, Switzerland) at reducing MRSA envir...

The effects of air loading on the acoustical properties of tabla, an Indian musical drum, are investigated by idealizing it as a composite membrane backed by a rigid cylindrical cavity. The coupled boundary value problem for membrane vibration and acoustic pressure, assuming acoustic radiations to be the only source of dissipation, is solved using a Green's function method. It is shown that air...

The entrainment of air by advancing contact lines is studied by plunging a solid plate into a very viscous liquid. Above a threshold velocity, we observe the formation of an extended air film, typically 10 microns thick, which subsequently decays into air bubbles. Exploring a large range of viscous liquids, we find an unexpectedly weak dependence of entrainment speed on liquid viscosity, pointi...

Evaporation of micro-liter drops from solid surfaces at room condition is mainly governed by diffusion. Therefore, there should be no difference between evaporation rate of sessile and pendant drops. However, some studies indicate a difference and explain the difference using buoyancy. The objective here is to reconcile the inconsistency in the literature. For that, first, by comparing two iden...

Abstract. Natural convection heat transfer in a square cavity induced by heated plate is studied numerically. Top and bottom of the cavity are adiabatic, the two vertical walls of the cavity have constant temperature lower than the plate’s temperature. The flow is assumed to be two-dimensional. The discretized equations were solved by finite difference method using Alternating Direction Implici...

Microperforated panel (MPP) absorbers are promising as a basis for the next-generation of sound absorbing materials. A microperforated panel absorber is backed by an air-cavity with a rigid-back wall and its typical use is for a sound-absorbing ceiling. However, MPPs have some limitations and disadvantages: its sound absorbing mechanism is limited to a Helmholtz resonator caused by perforations...

This letter presents a 4 × single-layer dual-band array antenna operating in the K- and Ka-band using gap waveguide (GW) technology. Radiating elements consist of I-shaped slots located on top plate backed by novel coaxial cavity with dual-frequency operation. The two ports, one for each band, radiates directive far field pattern linear polarization. A wideband corporate-feed network is used to...

Defects and cracks in dried natural timber (relative permittivity 2–5) may cause structural weakness enhanced warping beams. For a pine wood beam (1200 mm × 70 mm), microwave reflection (S11) transmission (S21) measurements using cavity-backed slot antenna on the surface showed variations caused by imperfections defects wood. Reflection at 4.4 GHz increased (>5 dB) above major knot evident w...