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DECOMPOSITION METHODS FOR A PIV DATA ANALYSIS WITH APPLICATION TO A BOUNDARY LAYER SEPARATION DYNAMICS
Uruba, Václav
Separation of the turbulent boundary layer (BL) on a flat plate under adverse pressure gradient was studied experimentally using Time-Resolved PIV technique. The results of spatio-temporal analysis of flow-field in the separation zone are presented. For this purpose, the POD (Proper Orthogonal Decomposition) and its extension BOD (Bi-Orthogonal Decomposition) techniques are applied as well as dynamical approach based on POPs (Principal Oscillation Patterns) method. The study contributes to understanding mechanisms of a boundary layer separation process. The acquired information could be used to improve strategies of a boundary layer separation control.
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Sphagnum mosses – Ecosystem engineers of bogs
Hájek, Tomáš
I evaluated production and decomposition characteristics of six dominant Sphagnum species in their natural microhabitats distributed along the gradient of water table in an open ombrotrophic bog. The growth in length was much higher in pools and hollows than in hummocks but the resulting annual production was roughly similar between the microhabitats due to a greater shoot and bulk density in hummocks. Although hummocks provided much higher potential for decomposition than hollows, the Sphagnum litter decomposed more slowly in hummocks due to much lower litter quality of the hummock sphagna. Thus the hummock Sphagnum species possess both principal mechanisms participating in maintaining hummocks above hollows – a sufficient production rate and limited decomposition rate. These mechanisms emphasize the role of Sphagnum mosses as autogenic ecosystem engineers controlling also the microhabitat diversification in patterned mires.
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Microarthropods and microbial participation in oak and beech litter decomposition
Farská, Jitka ; Jínová, Kristýna ; Jirout, Jiří ; Petrásek, Jiří ; Čápová, Lenka ; Rusek, Josef ; Krištůfek, Václav ; Elhottová, Dana ; Starý, Josef
The aim of our work was to describe the impact of a simulated vegetation zone shift to higher altitudes (i) on the quantity and quality of microarthropods and microbial communities, and (ii) on the decomposition rate of allochthonous leaf litter. In November 2002, 480 litterbags filled with oak or beech leaf litter were placed into spruce and beech forests (950 m a. s. l.) on Kleť Mt. (1083 m; Blanský les Protected Landscape Area, South Bohemia). Three different mesh sizes were used for certain soil biota exclusion: > 2 mm, 0.5 mm and 42 μm. Litterbags were sampled after 2, 4, 6, 12, 24 and 36 months of exposure in the field. Litter pH and moisture were determined in the laboratory immediately after retrieval. Soil microarthropods (Oribatida, Gamasida and Collembola) were extracted using Tullgren funnels. Soil bacteria and micromycetes were isolated using the dilution plate method and specific growth media.
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Klasifikátor založený na inverzních hodnotách indexů II. teorie a příloha
Jiřina, Marcel ; Jiřina jr., M.
A theory of a new method for the classification of data into classes is presented. The method is based on the sum of reciprocals of neighbors' indexes. We show that neighbors' indexes are in close relation to the approximate polynomial transform of the neighbors' distances. The sum of the reciprocals of indexes for all neighbors forms truncated harmonic series due to a finite number of its elements. For the neighbors of one class there is a sum of the selected elements of this truncated series. It is proved that the ratio of these sums gives just the probability that the point to be classified - the query point - is of that class.
Fulltext: content.csg -  PDF
Plný tet: v1041-08 - PDF
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Klasifikátor založený na inverzních hodnotách indexů
Jiřina, Marcel ; Jiřina jr., M.
A new method for the classification of data into classes is presented. The method is based on the sum of reciprocals of neighbors' indexes. We show that neighbors' indexes are in close relation to the polynomial transform of the neighbors' distances. The sum of the reciprocals of indexes for all neighbors forms truncated harmonic series due to a finite number of its elements. For the neighbors of one class there is a sum of the selected elements of this truncated series. It is proved that the ratio of these sums gives just the probability that the point to be classified -- the query point -- is of that class. The classification ability is demonstrated on real-life data from the Machine Learning Repository and the results are compared with published results obtained through other methods.
Fulltext: content.csg - PDF
Plný tet: v1034-08 - PDF
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Aplikace ortogonálních dekompozičních metod
Uruba, Václav ; Knob, Martin
Orthogonal decomposition techniques are introduced with respect to application to time-resolved PIV data. Several modifications of the techniques are taken into account, particularly the Proper Orthogonal Decomposition in continuous and snapshot variants for space analysis only as well as the Bi-Orthogonal Decomposition to be used for joint space-time analysis.
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