Techniques for improving the performance of frequency-hopped multiple-access communication systems

Imperial Users onl

Quantitative and Qualitative Analysis of Reported Dreams and the Problem of Double Hermeneutics in Clinical Research

The aim of this article is to show that statistical analysis and hermeneutics are not mutually exclusive. Although statistical analysis may capture some patterns and regularities, statistical methods may themselves generate different types of interpretation and, in turn, give rise to even more interpretations. The discussion is lodged within the context of a quantitative analysis of dream content. I attempted to examine the dialogical texts of reported dreams monologically, but soon found myself returning to dialogic contexts to make sense of statistical patterns. One could cogently argue that the reported statistical relationships in this study, rather than pointing to any interaction among the "signifieds," speak only to the relationships among the "signifiers" that were being played out through various actors on the analytic or scientific stage, since all of the constructs used in theorizing about, interpreting, and telling dreams come from the same discursive system

An Investigation of Premixed Flame Propagation in a Straight Rectangular Duct

This work reports on the premixed propane-air flame propagation in a long length (1.8 m) straight rectangular (51\times25 mm) duct. The mixture is assumed to be homogenous inside of the duct. Different equivalence ratios are examined. Two cases of fully opened and fully closed end outlet conditions are considered here. The flame behavior along with its propagation in the duct including initial stage of flame growing after the ignition, flame finger shape, flame-wall touch, flame flatten profile, tulip flame formation, tulip flame lips collapsing, and possible subsequent inversion/inversions are discussed. At each step, the flame-feeding flow interchangeable effect is explored using numerical simulations. Furthermore, the physical mechanisms behind the tulip flame and the subsequent inversion/inversions (especially the first flame inversion in opened end outlet case) are illustrated. Also, similarities and differences between these two phenomena are studied. In terms of the numerical method, two CFD software packages, Star CCM+ and OpenFOAM have been utilized. The available EBU (Eddy Break-Up) combustion model in Star CCM+ code, while its reaction rate is limited to Arrhenius reaction rate, is employed (semi-laminar model). The XiFoam model which is the embedded turbulent combustion model in OpenFOAM is also used. Other famous numerical combustion models such as TFC (turbulent model), FSC (it can capture both laminar and turbulent conditions simultaneously), and TFM (laminar and turbulent combustion model) are made based on the XiFoam model. Also, these models (XiFoam, TFCFoam, FSCFoam, and TFMFoam) are coupled with adaptive mesh library in order to make the finer mesh at the flame location (3D geometries). The new models are named: XiDymFoam, TFCDymFoam, FSCDymFoam, and TFMDymFoam. Moreover, further modifications are made to make these new models ready for 2D cases. The capability of these models for simulation of premixed propane-air flame propagation in the duct has been examined. The analytical works published by other research groups were also modified for the rectangular channel, and the results employed as another datum for validation of experimental and numerical results

Comparative transcriptomics in plants

Comparative genomics is the study of the structural and functional rela- tionships between the genomes of different species or strains. Recently microarray experiments have yielded massive amounts of expression infor- mation for many genes under various conditions or in different tissues for different model species. Expression compendia grouping multiple microar- ray experiments performed in similar (or different) experimental condition make it possible to define correlated expression patterns between genes. Genes within such a coexpression cluster are expected to have more similar functionality compared to genes lacking expression similarity. In this thesis the different steps required to systematically compare expres- sion data across species are described and some future applications of plant comparative transcriptomics are highlighted. Then we analyzed if function- ally related genes show coexpression in Arabidopsis and rice and developed a general framework to measure expression context conservation (ECC) for orthologous genes. Additionally, we studied the evolutionary parameters influencing ECC conservation and compared expression with sequence evo- lution. At the end, a new method is presented to define high quality tis- sue specific genes in seven different plant species; A.thaliana (Arabidopsis), Z.mays (Maize), M.truncatula (Medicago), P.trichocarpa (Poplar), O.sativa (Rice), G.max (Soybean) and V.vinifera (Grape) using Affymetrix microar- ray expression profiles. We also performed an in-depth study on the rela- tionship between leaf tissue specific genes coexpression clusters, within a species and in comparison with other species for a set of strictly selected genes