Effect of non-uniform flexibility on hydrodynamic performance of pitching propulsors

International audienceMany aquatic animals propel themselves efficiently through water by oscillating flexible fins. ese fins are, however, not homogeneously flexible, but instead their flexural stiffness varies along their chord and span. Here, we developed a low order model of these functionally-graded materials where the chordwise flexibility of the foil is modeled by one or two torsional springs along the chordline. The torsional spring structural model is then strongly coupled to a boundary element fluid model to simulate the fluid-structure interactions. We show that the effective flexibility of the combined fluid-structure system scales with the ratio of the added mass forces acting on the passive portion of the foil and the elastic forces defined by the torsional spring hinge. We further detail the dependency of the propulsive performance on the flexibility and location of the single torsional spring for a foil that is actively pitching about its leading edge. Our results show that increasing the flexion ratio by moving the spring away from the leading edge leads to enhanced propulsive efficiency, but compromises the thrust production. Proper combination of two flexible hinges, however, can result in a gain in both the thrust production and propulsive efficiency

En tudelad värld – Hugo Chávez och demokratiidealet

Sedan Hugo Chávez tillträdde makten i februari 1999 har kritiken mot de medborgerliga och politiska rättigheterna i Venezuela ökat. Denna uppsats ämnar undersöka utvecklingen av denna kritik mellan åren 1999 och 2007. Underlaget baseras på årsrapporter från fyra icke-statliga organisationer; Amnesty International, Freedom House, Human Rights Watch samt Transparency International och deras kritik gentemot den människorättspolitik som förs i Venezuela. Genom att analysera kritiken utifrån ett demokratiideal i form av Förenta Nationernas konvention angående medborgerliga och politiska rättigheter har vi utgått ifrån en nästintill allmängiltig måttstock i syfte att kunna operationalisera dessa rättigheter. Undersökningen baseras på Norman Faircloughs kritiska diskursanalys utifrån konstruktivistisk teori. Med denna teori strävar vi efter att påvisa att den polemik som råder mellan Venezuela och omvärlden i själva verket är resultatet av en tudelad värld där skilda sociala verkligheter existerar

Sexual function in Iranian women using different methods of contraception

Aims and objectives. To determine the sexual function in Iranian women using different methods of contraception. Background. Failure in family planning programmes can lead to reduced quality of life and threaten the health of the families in developing countries. One of the major causes of failure in family planning methods could be due to complications of them. One of the major unpleasant side effects of these methods, as an important cause of the rejection, is sexual dysfunction. Design. A case–control study. Methods. In this study, samples included 608 married women aged 15–49 years from Shahin Shahr health centres in Isfahan. Stratified sampling method was used to determine entitlement to select health centres, and convenience sampling method was used for women selection. The selected samples, based on using contraceptive methods, were divided into case group (n = 306) and control group (n = 302). Data were collected using sexual function questionnaire in women using different methods of contraception. Data were analysed by descriptive statistic and ANOVA. Results. Results of independent t-test showed significant difference in all domains of sexual function in two groups (p < 0�05). Most contraceptive methods in control group were natural methods (28�4%), and the least used was vasectomy (1�8%). Findings showed that the least sexual dysfunction in Iranian women was in condom use method, and the most was in vasectomy method. There was asignificant difference between all domains of sexual function (except pain) in types of contraceptive methods (p < 0�05). Conclusions. This study revealed that in family planning programmes, contraceptive methods in women that are more effective and have less sexual function impairments should be recommended. Relevance to clinical practice. Knowledge and awareness of the healthcare professionals regarding the sexual problems should be increased. Management of sexual dysfunction in a holistic approach in the primary care services might improve the wellness and quality of life of the women

Environmental design solutions for existing concrete flat roofs in low-cost housing to improve passive cooling in western Mexico

The development of real estate in Mexico has largely ruled out the comfort of users that focused on economic matters and made it difficult to make substantial progress in adopting measures to improve indoor environmental quality. Current research projects in Mexico found that roof construction in low-cost housing struggles to meet the requirements of the indoor climate. Passive cooling strategies are techniques to control heat gain and heat dissipation in buildings to maximise the comfort and health of building users while minimising energy use. Passive cooling systems recognize climate conditions and utilise renewable sources of energy such as the sun and wind to provide cooling and ventilation. Therefore, this study aims to develop a green and sustainable solution for existing concrete flat roofs with no major interventions and investments to save energy. The design of a passive device was tested to assess its effectiveness to protect flat roofs from shortwave radiation and to allow for heat dissipation in Mexican buildings. The study used a quantitative approach based on experiments and simulation tests to evaluate design efficiency. The results showed that a perforated device with an opening percentage of 88% and a cavity of 0.05m between the roof and the device provided effective protection. Also, the device with blinds of 45° showed lower operative temperatures within a range of mean values between 0.8°C and 0.9°C compared to a roof with a full shade cover in the hot and humid season. However, the perforated device with blinds of 90° in black colour delivered the best performance compared to other models and recorded a mean value of 1.13°C in the hot sub-humid season. The results revealed the efficiency of the proposed device that can be observed within different geometric configurations, surface properties as well as the use of the nocturnal radiative cooling potential in blocking solar radiation in Mexican buildings

När samvetet möter realiteten - En jämförande idéanalys av Thoreaus, Gandhis och Kings relation till civil olydnad

Few political ideas have become as rooted in widely different societies and cultures during such long time and extent as civil disobedience. It has been used as a conscientious form of protest by people from all layers of society, and has also been applied to innumerable political situations. However, three individuals have distinguished themselves as both developers and practitioners of civil disobedience: namely Henry Thoreau, Mahatma Gandhi and Martin Luther King. By using idea analysis as a method, this thesis aims to elucidate and compare how these actors interpreted and used civil disobedience as a political instrument. Subsequently, the same ideational value has been attached to thought as well as action, which is explained by the fact that actions are brought forth by cognition. Based upon this notion, and through the usage of theories regarding civil disobedience, an analytical framework using dimensions was created with the intention of putting these actors in a classification scheme. The results of the analysis show that although some similarities can be found between Thoreau, Gandhi, and King, their understanding and utilization of civil disobedience differ in several critical aspects