purpose : to determine the prevalence of the uncorrected refractive errors in bojnourd students methods : in a cross-sectional study, the samples were selected proportionate to the population of the schools using stratified randomized cluster sampling. the target population was the primary and junior high school students of the city of bojnourd. visual acuity (va) (snellen chart) and cycloplegi...

This paper reports the outcome of applying two di erent low-Reynolds-number eddy-viscosity models to resolve the complex three-dimensional motion that arises in turbulent ows in ducts with 90◦ bends. For the modelling of turbulence, the Launder and Sharma low-Re k– model and a recently produced variant of the cubic non-linear low-Re k– model have been employed. In this paper, developing turbule...

Ducts are widely used in an industry field. For example, air conditioning ducts, exhaust smoke elimination ducts and silencers have been various ducts. In general, the a flow vortices generated duct sometimes cause resonance phenomenon self-sustained tone. Once occurs, high level sound is suppression of this strongly quickly required. It necessary to know natural acoustic frequency for examinat...

OBJECTIVE To determine the prevalence of smoking among dentists in the Federal District of Brasília, Brazil. METHODS A descriptive, cross-sectional survey, involving 446 dentists residing in the Federal District, was conducted in the second semester of 2004. Data regarding the smoking habit were obtained using a World Health Organization questionnaire that was translated and validated for use...

the present paper deals with the prediction of three-dimensional fluid flow and heat transfer in rib-roughened ducts of square cross-section. such flows are of direct relevance to the internal cooling system of modern gas turbine blades. the main objective is to assess how a recently developed variant of a cubic non-linear model (proposed by craft et al. (1999)), that has been shown to produce ...

We discuss the self-assembly system of triangular tiles instead of square tiles, in particular right triangular tiles and equilateral triangular tiles. We show that the triangular tile assembly system, either deterministic or non-deterministic, has the same power to the square tile assembly system in computation, which is Turing universal. By providing counter-examples, we show that the triangu...