Design of a wind turbine rotor for maximum aerodynamic efficiency

The design of a three‐bladed wind turbine rotor is described, where the main focus has been highest possible mechanical power coefficient, CP, at a single operational condition. Structural, as well as off‐design, issues are not considered, leading to a purely theoretical design for investigating maximum aerodynamic efficiency. The rotor is designed assuming constant induction for most of the blade span, but near the tip region, a constant load is assumed instead. The rotor design is obtained using an actuator disc model, and is subsequently verified using both a free‐wake lifting line method and a full three‐dimensional Navier–Stokes solver. Excellent agreement is obtained using the three models. Global CP reaches a value of slightly above 0.51, while global thrust coefficient CT is 0.87. The local power coefficient C_p increases to slightly above the Betz limit on the inner part of the rotor; the local thrust coefficient C_t increases to a value above 1.1. This agrees well with the theory of de Vries, which states that including the effect of the low pressure behind the centre of the rotor stemming from the increased rotation, both C_p and C_t will increase towards the root. Towards the tip, both C_p and C_t decrease due to tip corrections as well as drag. Copyright © 2008 John Wiley & Sons, Ltd.     

Protection value and functional service life of heritage timber buildings

ABSTRACT

The development of objective methodologies for the preventive conservation of historic buildings is extremely relevant to mitigate the deterioration of buildings and sites with exceptional cultural value. In this sense, there is a growing need to develop comprehensive, coherent plans to manage, preserve and protect heritage buildings in areas that are extremely susceptible to natural disasters, such as the case of the Pacific coast of South America. Two methodologies are presented in this study to assess the functional service life and protection level of cultural heritage in Chile. This research intends to establish a correlation between the functional performance of heritage buildings and the Chilean code related to the definition of the preservation of historic heritage buildings. This study applies both methodologies to 25 heritage buildings (timber housing) located in the city of Valdivia, Chile. A multiple linear regression analysis is applied in order to rank the influence of the variables used to define the protection level, according to the Chilean standard, in the functionality index of timber heritage constructions. The information obtained in this study is exceptionally relevant for the researchers and stakeholders responsible for the definition and implementation of maintenance programmes in building stocks.     

Patterns of scientific communication among Latin American countries,in the field of medical education

This work reports on the medical subject headings that build-up the medical education field in Latin America, through the content and citation analysis ofEducation Medica y Salud (EMS). An attempt was made to establish the articulations between the citing and cited countries in the region. It was generally found that EMS was built-up by subjects of Medical Education, Health Manpower, Water Supply, and Health Policy. Although strongly citing/cited/indexed countries, Brazil, Mexico, and Colombia have not established significant information flows among them. Further research lines are proposed.Paper presented at the International Conference on Science Indicators for Developing Countries, Paris, 15–19 October, 1990.     

Response of large and small vessels to alpha and beta adrenoceptor stimulation in heart failure: effect of angiotensin converting enzyme inhibition

Understanding sexual fantasies is important to the scientific study of human sexuality. A sexual fantasy refers to a private or covert experience in which the imagination of desirable sexual activity with a partner is sexually arousing to the individual. Prior sexual experiences of an individual appear to increase the incidence of sexual fantasies, as well as the variety of sexual themes in a fantasy, which permit a greater elaboration of the fantasy theme when compared to less sexually experienced individuals. The present study was an investigation of the factors or sexual themes that emerge in a college male population, as well as a comparison of college men with human samples obtained in other studies: a sample of men and women and a sample of sexually variant men. In this study, 116 male students, all of whom identified themselves as heterosexual, completed the Wilson Sex Fantasy Questionnaire (WSFQ). Results indicated that the present sample had significantly more exploratory, intimate, impersonal, and total sexual fantasies than sexual fantasies reported by female respondents in another study using the WSFQ and significantly more intimate, impersonal, and total sexual fantasizing when compared with a male sample in another study. The men in this study also evidenced less deviant areas of sexual fantasizing when compared with a group of sexually variant men in another study. A principal components analysis extracted four factors, which accounted for 45% of the total variance. The four sexual fantasy topic areas for the most part replicated prior findings by Wilson (1988) but are also more heterogeneous, indicating that male college students engage in a variety of sexual fantasies but seem to favor more intimate, less deviant or exploratory sexual themes that are in line with nonclinical samples and different from several clinical samples of sexually variant men.     

Design and evaluation of ECO: an augmentative and alternative communication tool

Universal Access in the Information Society - Current technology provides new challenges to improve skills on people with special necessities. In fact, persons with communications needs can take...     

The Effect of Aniline Hydrochloride Hydrotrope on the Phase Behavior of SDS/Water System

The aim of this work was to determine the detailed phase behavior of the sodium dodecyl sulfate/aniline hydrochloride/water system as a function of concentration of sodium dodecyl sulfate (SDS), aniline hydrochloride (AHC) to sodium dodecyl sulfate molar ratio (R = [AHC]/[SDS]) and temperature. Phase behavior information was obtained via polarizing microscopy, differential scanning calorimetry (DSC), cryo-scanning electron microscopy (Cryo-SEM) and oscillatory linear rheological measurements with good agreement among these techniques. It is well known that SDS in water forms spherical micelles at concentrations lower than 40 wt% and temperatures above its Krafft temperature (T _k = 16–21 °C). In this region, the SDS/water system exhibits Newtonian rheological behavior, which is characteristic of spherical micellar solutions. The addition of the hydrotrope, aniline hydrochloride, to SDS aqueous solutions produces a viscosity increase in this system as R augments, and a maximum of about five orders of magnitude was found at R = 0.47 for 5 wt% SDS at 20 °C. Moreover, the system shows a transition from viscous to strong viscoelastic behavior. These changes in the rheological behavior are produced by the transitions from sphere to rodlike micelles, which are induced by the hydrophobicity of AHC causing it to be absorbed into the core and the hydrophilic interface of the micelles, which screens the repulsions between the charged head groups.     

Effect of dentin pretreatment with potassium oxalate: A 6‐year follow‐up

Oxalate‐based products are effective against dentine sensitivity and have been studied as an option to improve long‐term adhesive bonding strength. Our aim was to evaluate the effect of potassium oxalate on the microtensile bond strength (µTBS) of the dentin/resin interface after 24 h, 1, and 6 years. Dentin on the occlusal surface of 16 human premolars was exposed and etched with 35% phosphoric acid. The teeth were divided into four groups. Two groups received 3% monohydrated potassium oxalate and the following adhesive systems and composites: Adper Scotchbond Multipurpose + FiltekZ350 (3M/ESPE) and Prime & Bond NT + Esthet‐X (Dentsply). Two control groups did not receive potassium oxalate. Teeth were cut into sticks and kept in distilled water at 37°C for 24 h, 1, and 6 years. The sticks underwent µTBS testing after storage. ANOVA, Tukey's post hoc test, and paired t test were used to compare storage times (α = 0.05). The fracture mode of the specimens was classified under a stereomicroscope (40×). Morphology of the hybrid layer and the fracture pattern were observed with scanning electronic microscopy (SEM). Mean µTBS was high at 24 h and decreased after 1 and 6 years. After 6 years, the mean µTBS values were similar with no statistically significant difference between the groups (p = .121). SEM images showed proper dentin hybridization. Dentin pretreatment with potassium oxalate did not affect hybrid layer formation, but bond strength decreased over time after 24 h. Therefore, the clinical use of potassium oxalate to increase dentin bond durability is not indicated.