Application of FDS and firefoam in large eddy simulations of a turbulent buoyant helium plume

Large eddy simulations are conducted in the near-field region of a large turbulent buoyant helium plume. Such plumes are of relevance for fire safety research due to the similar flow features as in the buoyant (smoke) plumes above the fire source. The transient and mean flow dynamics are discussed with and without the use of a Smagorinsky-type subgrid scale (SGS) model. For this purpose, two different computational fluid dynamics (CFD) packages are used. Small-scale structures, formed at the edge of the plume inlet due to a baroclinic and gravitational mechanism and subject to flow instabilities, interact with large-scale features of the flow, resulting in a puffing cycle. This puffing cycle is recovered in the simulations. In general, the LES calculations reproduce the main features of the turbulent plume. Mean velocity results compare well with the experimental data. The mass fractions are overpredicted on the centerline though, and higher on the domain

Verification of the accuracy of CFD simulations in small-scale tunnel and atrium fire configurations

A

Non-Beiter ternary cyclotomic polynomials with an optimally large set of coefficients

Let l>=1 be an arbitrary odd integer and p,q and r primes. We show that there exist infinitely many ternary cyclotomic polynomials \Phi_{pqr}(x) with l^2+3l+5<= p<q<r such that the set of coefficients of each of them consists of the p integers in the interval [-(p-l-2)/2,(p+l+2)/2]. It is known that no larger coefficient range is possible. The Beiter conjecture states that the cyclotomic coefficients a_{pqr}(k) of \Phi_{pqr} satisfy |a_{pqr}(k)|<= (p+1)/2 and thus the above family contradicts the Beiter conjecture. The two already known families of ternary cyclotomic polynomials with an optimally large set of coefficients (found by G. Bachman) satisfy the Beiter conjecture.Comment: 20 pages, 7 Table

Investigating the socio-constructivist dimension of online interactions: the case of synchronous audio-graphic conferencing systems

This study explores the quality of interactive patterns in audio-graphic conferencing environments and learners' involvement in interaction. Supporters of this technology claim that online interactions support socio-constructivist language learning. However, the existing literature does not indicate whether the quality of interaction required for realising constructivist principles of learning can affectively be ensured in such environments. The study is based on the Open University's online audio-graphic tuition environment, Lyceum. It investigates the verbal and written interactions of adult Open University students learning French. The data is analysed by different models of analysis pertaining to different socio-constructivist and cognitive models of analysis. The results show that students use high forms of thinking to engage in a cyclical rather than a linear process of knowledge construction. However, there is no evidence that this process is supported by the audio-graphic system itself. The tutor's style and task design play a more important role in supporting the learning process

Gender differences in the use of cardiovascular interventions in HIV-positive persons; the D:A:D Study

Peer reviewe

Numerical case studies of vertical wall fire protection using water spray

AbstractStudies of vertical wall fire protection are evaluated with numerical method. Typical fire cases such as heated dry wall and upward flame spread have been validated. Results predicted by simulations are found to agree with experiment results. The combustion behavior and flame development of vertical polymethylmethacrylate slabs with different water flow rates are explored and discussed. Water spray is found to be capable of strengthening the fire resistance of combustible even under high heat flux radiation. Provided result and data are expected to provide reference for fire protection methods design and development of modern buildings

Tra Logudoro e Campidani: i volgari sardi e le espressioni della cultura

Sommario: 1. La comparsa del volgare nell'isola e i principali documenti in sardo antico. - 2. Lingua, cultura e società