Percentage Difference In Values Research Articles

The value of orthodontics: Do parents' willingness to pay values reflect the IOTN?

Given the limited evidence about the benefits of orthodontic treatment, many health care systems have rationed access to orthodontic care with the Index of Orthodontic Treatment Need (IOTN) being one tool used to attempt to allocate resources based on need. However, it is not clear whether patient and public valuations of different levels of need (as described by the IOTN) reflect the resource allocation decisions. The aim of this project was therefore to determine the values parents placed on correction of malocclusions at different IOTN levels using the willingness to pay (WTP) technique. 401 parents of children attending hospital-based orthodontic clinics in the North of England were recruited to complete a questionnaire eliciting WTP for the correction of seven malocclusions with different IOTN scores. In addition demographic and orthodontic history characteristics were collected. Results were analysed with appropriate pairwise significance tests and regression. A significant difference in WTP was noted between all the possible pairs of malocclusions with the exception of overjets with moderate versus great need of treatments. At moderate levels, correction of crowding was valued less than overjet but this was reversed at great need levels. Very little of the variance in WTP was explained by the variables collected. When looking at factors affecting percentage difference between values for different pairs of malocclusions, in general, no factors predicted the magnitude of difference. Median valuations for correction of malocclusions vary significantly for different levels of need (as judged by IOTN), with increasing levels of need generating higher values. However, there was a limited effect of demographic or orthodontic characteristics on the magnitude of percentage difference in values for correcting malocclusions different levels of need.

Stress intensity factors for semi-elliptical surface cracks in plate-to-plate butt welds with parallel misalignment of same thickness

A set of fatigue and fracture assessment equations had been incorporated into British Standard 7910:2013 (BS 7910:2013) to estimate the effect of misalignment for various geometric configurations containing a surface crack. In this study, extensive 3-D finite element (FE) analyses are carried out to determine the dimensionless stress intensity factors (Y) at the crack deepest point and crack ends of plate-to-plate butt welds with parallel misalignment of same thickness. In comparison to BS 7910:2013, it is observed that the assessment equations underestimate the Y values for shallow cracks and overestimate the corresponding values for deeper cracks with percentage differences in values being as high as 82% and 12%, respectively. New Y equations for misaligned butt welds are proposed using multiple regression analyses.

Determination of dimensionless stress intensity factor of plate-to-plate butt welds between axially aligned members of different thickness

British Standard 7910:2013 (BS 7910:2013) includes a set of equations for estimating the effect of misalignment on different types of welded joints with a semi-elliptical surface crack. In this study, extensive finite element (FE) analyses are carried out to determine the dimensionless stress intensity factor (Y) of plate-to-plate butt-welded joints between axially aligned members of different thickness. The Y values at the crack deepest points and the crack ends are determined. It is observed that BS 7910:2013 underestimates the Y results of misaligned butt welds for shallow cracks with percentage difference in values being as high as 56%. An overestimation percentage difference of 26% for deep cracks is given by BS 7910:2013. The new Y equations for misaligned butt welds are proposed using multiple regression analyses.

New weld toe magnification factors for semi‐elliptical cracks in plate‐to‐plate butt‐welded joints

AbstractBritish Standard 7910:2013 includes a single set of equations for estimating the weld toe magnification factor (Mk) of different types of welded joints with a semi‐elliptical surface crack. In this study, extensive finite element analyses are performed to determine the Mk of plate‐to‐plate butt‐welded joints subjected to axial and bending loading. The Mk values at the crack deepest points and the crack ends are determined. It is found that the Mk results of butt welds are different with those of single T‐butt joints with percentage difference in values being as high as 63.8% and 97.4% for axial and bending loading cases, respectively. Percentage differences of 60.4% and 358.2% for axial and bending loading cases are observed between butt welds and X‐joints. New Mk equations for butt welds are proposed using multiple regression analyses.

Buoyancy-induced flow and heat transfer in a porous annulus between concentric horizontal circular and square cylinders

ABSTRACTThis paper reports on natural convection heat transfer in a porous annulus between concentric horizontal circular and square cylinders. The heated inner circular cylinder is maintained at the uniform hot temperature Th, whereas the cooled outer square duct is held at the uniform cold temperature Tc. A pressure-based collocated finite-volume method is used to numerically investigate the effects on the total heat transfer of Rayleigh number (Ra), Prandtl number (Pr), Darcy number (Da), porosity (ϵ), and annulus aspect ratio (R/L). Results demonstrate that at low Ra values, conduction is the dominant heat transfer mode. Convection contribution to total heat transfer becomes more important beyond a critical Ra value, which decreases with an increase in Da and/or ϵ. Furthermore, an increase in the enclosure aspect ratio (R/L) leads to an increase in total heat transfer. A similar behavior is obtained with Prandtl number, where predictions indicate higher heat transfer rates at higher Pr values with its effect increasing as Ra increases. Streamlines and isotherms reveal flow separation for some of the reported cases. Limited computations are also performed for natural convection in a porous annulus between two horizontal concentric circular cylinders having the same inner and outer perimeters as the investigated enclosure. Comparison of the predicted average Nusselt number estimates with similar ones obtained in the original enclosure reveals a large percentage difference in values, demonstrating the strong influence of geometry on natural convection in enclosures.

New weld toe magnification factors for semi-elliptical cracks in double-sided T-butt joints and cruciform X-joints

British Standard BS7910:2005 has a single set of equations for estimating the weld toe magnification factor (Mk) of different types of welded joints containing a surface crack. The equations are based on the finite element (FE) results of single sided T-butt joint. In this study, extensive FE analyses are carried out to determine the Mk of double-sided T-butt joint and cruciform X-joint. Both the joints are subjected to axial and bending loading, and Mk at crack ends and deepest points of the surface crack are determined. It is found that Mk results for cruciform X-joint differ with those of double-sided T-butt joint with percentage difference in values being as high as 136% and 76% for axial and bending loading cases, respectively. Finally, a new set of Mk equations for cracked double-sided T-butt joint and X-joint are proposed based on multiple regression analyses.

On Two Formulae for Calculating the Effective Rate of Protection (Notes & Comments)

In the literature on effective tariff protection, two formulae have been used, more or less equivalently. One defines effective protection as the percentage difference , between value added at domestic prices and value added at world prices. The other defines it as the percentage difference in value added per unit of output at the two sets of prices. The first definition has been used by Balassa (1965) Bhagwati and Desai (1970) and Lewis and Guisinger (1968), whereas the second definition seems to have been used by Basevi (1966), Corden (1966) and Leith (1967 and 1968). There is some ambiguity in the works of the last three authors as to the meaning of value added per unit of output at domestic prices. Part of the confusion arises because none of these authors explicitly defines this concept. Leith (1967) implicitly defines this as value added at domestic prices divided by the value of output at domestic prices [5, foot-note 14, p, 60, equation (A-5 and A-6) p.70]. Basevi (1966) implicitly used this definition at one place [2, p. 140] but at another he implicitly defines value added per unit of output at domestic prices as value added at domestic prices divided by the value of output at world prices. [2,p. 148]. The last definition also seems to have been used by Corden (1966).