Clustering of vertically constrained passive particles in homogeneous, isotropic turbulence

We analyze the dynamics of small particles vertically confined, by means of a linear restoring force, to move within a horizontal fluid slab in a three-dimensional (3D) homogeneous isotropic turbulent velocity field. The model that we introduce and study is possibly the simplest description for the dynamics of small aquatic organisms that, due to swimming, active regulation of their buoyancy, or any other mechanism, maintain themselves in a shallow horizontal layer below the free surface of oceans or lakes. By varying the strength of the restoring force, we are able to control the thickness of the fluid slab in which the particles can move. This allows us to analyze the statistical features of the system over a wide range of conditions going from a fully 3D incompressible flow (corresponding to the case of no confinement) to the extremely confined case corresponding to a two-dimensional slice. The background 3D turbulent velocity field is evolved by means of fully resolved direct numerical simulations. Whenever some level of vertical confinement is present, the particle trajectories deviate from that of fluid tracers and the particles experience an effectively compressible velocity field. Here, we have quantified the compressibility, the preferential concentration of the particles, and the correlation dimension by changing the strength of the restoring force. The main result is that there exists a particular value of the force constant, corresponding to a mean slab depth approximately equal to a few times the Kolmogorov length scale, that maximizes the clustering of the particles

Kampaania “Kumm on seks!” vastuvõtt sihtrühmas

Reception of campaign "Kumm on seks!" in the target group. Keywords: social marketing, risk communication, HIV and STI prevention, social and group norms, reception analysis. The present thesis sets an aim to analyse the reception in the target group of an HIV prevention campaign “Kumm on seks!” held in Estonia in late 2011. The campaign was directed to young sexually active women (16-24 years old). The target group was reached by different mass mediums, including mainstream TV and radio commercials, large scale outdoor banners and a smaller social media approach (homepage and viral videos). HIV is a significant problem in different demographics of Estonian youth. In 2001 the Ministry of Social Affairs claimed the outbreak of HIV positive patients to be concidered as an epidemic. Since then the number of HIV positive patients has grown significantly and there might be a large group of nondiagnosed carriers (Praxis 2004). There have been many HIV prevention campaigns in Estonia over the last decade, but this campaign differs enormously, since it is targeted to a smaller segment of the target group. The main aim of the campaign is to motivate young women to neglect any negative feeling towards talking about using a condom and to encourage women to take their and their partner’s health into their own hands via carrying a condom with them (as apposed to assuming the male partner will do it for them). The message was conveyed to the target group by currently popular mainstream spokeswomen. The aim of this research was to analyse the reception of the campaign, how the target group interpreted the messages that th National Institute of Health Development (TAI) coded in their commercials. For the analysis, eight semi-structured in-depth interviews were conveyed with representatives of the target group. At the final stage of the research an interview with a repserentative of TAI was held, to compare the results with their own views on the campaign, its purpose and its success. The analysis was conducted by the example of Dr. Carolyn Michelle’s consolidated framework of reception analysis (Michelle 2007). The results were viewed in three larger sections. Firstly, the target groups’ alleged sexual behaviour and attitude towards sexual pracitces. In addition to their own practices, it was analysed how the target group viewed the social group norms (and risk perception) linked to sexual behaviour in their social networks. Secondly, the target group was introduced to four different campaign materials - the TV commerical and three articles that were either writted by TAI or the official spokeswomen. The analysis mapped the messages that the target group discovered and asked them to comment on the issues the materials talked about. The results showed that the target groups’ alleged behaviour was mostly coherent with the campaigns suggested behaviours. One representative even claimed, that she had carried condoms with her at all times, when she was single. The attitude towards condom use and STD-testing (a subject emphasised in one of the articles) was mostly positive and well accepted in the target group. The biggest incoherency appeared when talking about the suggested role for women of empowerment via having your own condon at all times. It was apparent, that the target group is accustomed to the current social norm, where the responsibility and the obligation to have a condom, lies on men. It is linked to women’s self-image and how it is not acceptable for a woman to “behave as a man”, meaning plan a casual sexual relationship, since it is mostly ascribed to men and their behaviour. The second important object of analysis was risk perception. It was apparent, that different risks were ascribed to singles and committed women. For a single person, the main risk is a STI infection, but for a person in a committed relatsionship, the risk is mainly unwanted pregnancy. In perceveing risks and the messages conveyed of risks in this campaign, HIV was mostly seen as a risk on the social level, but not on a personal level. Many of the representatives stuggeled to include themselves in the riskgroup of any STI. Although the representatives discovered the messages included by TAI, it was unsure, wether the messages and the knowledge of the messages had any influence on the target groups behaviour or future intentions in using a condom. Influencing the target group is by social marketing standards the main objective of a social campaign, so it is unclear, if the campaign had any bigger role to support, besides bringing the topic into the public sphere. For further reseacrh, it is advised to look into changing group norms and influencing collective behaviours, rather than concentrating on chaing the individuals perception of things. In this research, the non-acceptance of new social norms implies strongly, that for a change of this porportion, the change has to start from the collective and not from the invidudual.http://tartu.ester.ee/record=b2610662~S1*es

A community of fans, friends and power-users

Estonia is recognised as a beacon of E-Government achievement and is making strides in using technology to include citizens in democratic processes. The key to sustainable E-Participation is to ensure that all E-Participation initiatives contribute to establishing an overall community of Wikipedia-like users who believe that their commitment and investment of time really makes a difference. Over time, citizens’ roles and contributions may vary a lot, but this essential public infrastructure and policy has to be provided systematically for E-Participation to become a reality - whatever new technology comes along, and however successful individual projects are. This is the real meaning of sustainable E-Participation

Evaluatie van de verzuringsdoelstellingen: kwantificering van de effecten van emissievarianten op half-natuurlijke terrestrische ecosystemen

In het kader van de evaluatie verzuringsdoelstellingen zijn depositiescenario's geëvalueerd met de dynamische modellen SMART2/MOVE. Het blijkt dat door naijleffecten overschrijdingen van normen kunnen optreden, terwijl kritische depositieniveaus niet meer overschreden worden. De vertraging is ongeveer tien jaar. Voor adequate bescherming van bossen en natuurgebieden is het van belang dat naast Nederlandse ook buitenlandse emissies gereduceerd worden

Scenario-ontwikkeling voor het natuurbeleid

De Natuurverkenning 2010-2040 is als scenariostudie uitgevoerd om te verkennen welke richtingen het natuurbeleid op termijn zou kunnen inslaan. Via de scenario-onderdelen worden beleidsmakers stap voor stap in het langetermijndenken meegenomen. Dit wordt versterkt doordat de onderdelen het karakter van kwalitatieve verhalen hebben gekregen, die bovendien toegankelijk zijn verbeeld en op onderdelen kwantitatief zijn uitgewerkt. Doordat beleidsmakers zelf in de verkenning hebben geparticipeerd is hun ontvankelijkheid ervoor vergroot. Over: natuurverkenning, scenariomethode, normatieve scenario's en stakeholderparticipati

Two identical tandem square prisms with rounded edges and hard marine fouling at incidence in cross-flow: effect of spacing and Reynolds number on unsteady fluid dynamics

Because of their long submerged columns, deep-draft semi-submersible floating structures are particularly susceptible to vortex-induced motions. This paper focuses on the steady and unsteady forces that act on such a column pair, as well as on the frequency and strength of the shed vortices behind the downstream column. Wind tunnel experiments were performed on two rounded and lightly rough square-section prisms in cross-flow for Reynolds numbers from 100,000 up to 7 million. They are arranged inline at centre-to-centre distances of S/D = 2.8, 4, and 5.6 and at 0° or 45° incidence angle. The trend of the drag curve for the upstream prism deviates at S/D = 2.8 and 4 sharply from that for a single prism. The drag force on the downstream prism strongly depends on both S/D and α. At S/D = 2.8, a thrust force occurs either in certain (α = 0°) or in all (α = 45°) flow states. Larger spacing values lead to an overall higher drag and a flattening of the Cd2 (ReD) curve. The highest fluctuating lift forces on the downstream prism are obtained at α = 45°. Regarding the vortex shedding frequency, differences between both incidence angles occur at S/D = 5.6 only