Simple 3D distributions of the interplanetary dust cloud deríved from observations in the visible and distributions suggested by IR investigators are compared. Predictions of visual brightness based on IR models are falrly compatible with observations for large (ε<70°) elongations but not close to the Sun. Some reasons for this behaviour and first steps towards more realistic models are díscussed.
If the Shields number of a flow above an erodible bed is higher than one, then the current exerts so high shear stress at the top of a granular bed that the upper part of the bed is eroded and the top of the non-eroded rest of the bed is flat (no bed forms occur). This flow regime is typical for flows over a stationary bed in pipes but it can occur also in open-channel flows, particularly under flood conditions when both the depth and velocity of the flow are high. The current picks up particles from the eroded part of the bed and transports them within the flow. The total load of transported particles is composed of particles transported either as the contact load or as the suspended load, depending on the dispersive mechanism that keeps the particles inside the flow. Solids distribution (i.e. the shape of the concentration profile) of the transported particles across the flow helps to identify an acting dispersive mechanism and hence a mechanism through which the transported particles contribute to flow friction. The paper analyzes the concentration-profile measurements in a medium-sand-slurry current above an erodible stationary bed in a 150-mm pipe. The experiments revealed interesting effects of high shear stress on the shapes of concentration profiles across the flow above the bed. The analysis suggests that carrier turbulence is a prevailing dispersion mechanism within the upper part of the discharge area above the bed for flow conditions characterized by values of the ratio u*b/vt higher than say 4.5. It seems that the shearing action as an exclusive particle dispersion mechanism is confined to the region not far above the top of the bed. Apparently, the high shear stress at the top of the stationary bed is capable of producing turbulent suspension that transports a considerable amount of medium-sand particles (average delivered volumetric concentrations of transported particles up to 0.26) through the 150-mm pipe. and Při proudění vody nad pohyblivým dnem za podmínek vysokého smykového napětí na povrchu dna (Shieldsovo číslo větší než 1) je horní vrstva dna erodována proudem vody a na povrchu neerodované části dna nevznikají dnové útvary. Takové proudění se vyskytuje například v potrubí dopravujícím směs nad sedlinou na dně potrubí, ale může se vyskytnout i v otevřeném korytě, zvláště za povodňové situace, kdy jsou pro proudění typické velká rychlost a velká hloubka vody. Proud unáší částice z erodované vrstvy dna. Mechanismy, které mohou udržovat částice v proudu, jsou v principu dva: turbulentní suspenze a mezičásticový kontakt. Každý z těchto mechanismů způsobuje jiné rozdělení částic, tj. jiný koncentrační profil, po svislici proudu. Měřením koncentračních profilů by tedy mělo být možné odhadnout, jaký mechanismus převažuje v proudění za určitých sledovaných podmínek. Příspěvek analyzuje koncentrační profily měřené v potrubí průměru 150 mm při proudění vodní směsi střednězrnného písku nad pískovou sedlinou. Analýza výsledků měření ukázala, že turbulence v proudu vody je převažujícím mechanismem podpory částic přinejmenším v horní polovině výšky průtočné části potrubí při podmínkách charakterizovaných hodnotou poměru třecí rychlosti ve dně a usazovací rychlosti unášené částice (u*b/vt) větší než přibližně 4,5. Na rozdíl od dřívějších závěrů v literatuře se zdá, že mezičásticové kolize se jako výhradní mechanismus disperze částic uplatňují jen v poměrně omezené oblasti proudu nad povrchem dna. Vysoké smykové napětí ve dně tak přispívá nejen ke vzniku mezičásticových kolizí, ale i k turbulentní podpoře částic. Turbulentní podpora umožňuje dosažení vysokých hodnot (až do 0,26) dopravní koncentrace částic střednězrnného písku ve směsi proudící potrubím průměru 150 mm.
Observations of photometric and spectroscopic data for open clusters and associations have been intensive during the last few years. Incentives are many:
- each cluster is an object for which the state of evolution and other
characteristics can be studied much better than for individual stars
- the systems of open clusters and associations in our own and other galaxies give information about the recent evolution of the galaxies themselves
- the clusters and associations are sensors of the conditions in interstellar space
Collections of observed data have been made by Alter, Ruprecht, Balazs, Vanysek and White in the comprehehsive Prague-Budapest card catalogues. My own efforts in this direction have resulted in computer readable catalogue of open cluster data, of which the 5th edition appeared recently. In collaboration with K. Janes and C.
Tilley of Boston University, I have now entered weight classes. The purpose of these is to monitor the reliability of conclusions based on cluster data. It seems that physical systems of 10-1000 stars can be divided into three categories;
- associations and unbound open clusters
- bound open clusters in the disk
- old open clusters
Properties such as age, linear diameter and abundances are discussed for these categories on the basis of the data contained in the Lund catalogue. The galactic distribution of young clusters and associations shows the existence of complexes inside the thin disk. The system of old open clusters seems to back up the concept of a thick disk.
The results of measurement of polychlorinated biphenyls (PCBs) in surface bottom sediments contaminated by technical PCB mixtures Delor collected from the Červený potok (stream in the Litavka River catchment), Czech Republic in 2008 are presented. The sediment samples of two different grain size fractions (< 2 mm and < 200 μm) were analyzed for 8 congeners of PCBs using Soxhlet extraction and gas chromatography (GC-ECD). Total concentrations of PCBs ranged from 15.3 to 997 ng g-1 (dry weight) in < 2 mm fraction and from 29.9 to 952 ng g-1 in < 200 μm fraction, where PCBs 28, 52, 101, 138, 153, 180 and 194 were found in all the samples. The highest levels of PCBs were found in sediment collected from the area below the discharge of municipal wastewater treatment plant and local engineering industry in the Komárov village. High percentage of PCBs 28, 153 and 138 (22-74%, 5-22% and 5-20% respectively) indicates the contamination by PCBs commercial mixtures Delor 103 and Delor 105 (an equivalent of AROCLOR 1242 and 1254). The result of PCA analysis indicates that the more highly chlorinated PCB congeners tend to be more associated with finer organic carbon particles of the < 200 μm sediment fraction. and Práce se zabývá distribucí polychlorovaných bifenylů (PCB) v povrchových sedimentech Červeného potoka (povodí Litavky), kontaminovaných technickými směsmi Delor. Ve dvou zrnitostních frakcích sedimentů (< 2 mm a < 200 μm) odebraných v roce 2008 byly prostřednictvím Soxhletovy extrakce a plynové chromatografie (GC-ECD) stanoveny koncentrace 8 indikačních kongenerů PCB. Celkové koncentrace PCB se v zrnitostní frakci < 2 mm pohybovaly od 15,3 do 997 ng g-1 sušiny, ve frakci < 200 μm bylo rozpětí koncentrací 29,9 až 952 ng g-1 sušiny. PCB kongenery 28, 52, 101, 138, 153, 180 a 194 byly naměřeny ve všech vzorcích sedimentů. Z výsledků vyplývá, že nejvyšší koncentrace PCB byly zjištěny v sedimentech odebraných z lokality pod zaústěním odtoku z čistírny odpadních vod v obci Komárov, do které ústí i kanalizační větev z místního strojírenského podniku. Vysoké procentuální zastoupení kongenerů PCB 28, 153 a 138 (22-74%, 5-22% a 5-20%) v sumě všech osmi kongenerů značí kontaminaci technickými směsmi Delor 103 a Delor 105 (srovnatelných se směsmi AROCLOR 1242 a 1254). Z výsledků PCA analýzy vyplývá, že vícechlorované kongenery PCB jsou intenzivněji asociovány s organickou hmotou v jemnější frakci sedimentu < 200 μm.
In this article we study, using elementary and combinatorial methods, the distribution of quadratic non-residues which are not primitive roots modulo ph or 2ph for an odd prime p and h ≥ 1 an integer.
Combustion of lignite with limestone, co-combustion of lignite with limestone and wood, and combustion of wood were performed in a circulating fluidised bed in 7 different combustion regimes. The in organic matter composition and properties of all input and output materials were characterized. For each com bustion regime the material streams and the boiler outputs were calculated. The total inorganic mass and the mass of selected trace elements in fuels (Cl, Zn, As, Se, Hg, and Pb) were based on the output of a 1 GW circulating fluidised-bed boiler; additionally, the concen trations of volatile elements (As, Se, Hg) in fly ash (FA) were evaluated in relation to the mass of FA. Element (Cl, Zn, As, Se, Hg, and Pb) enrichment in FA compared with BA was related to the ratio R between the co mbusted mass of organic wood wastes and total combusted fuel. Additionally, the unburned carbon in bottom ash (BA) and fly ash (FA) was determined, and sel ected elements were studied in unburned materials separated from BA. The results show that combustion of wood and/or co-combustion of lignite with wood waste brings about significant environmental benefits., Zdeněk Klika, Lucie Bartoňová and Jana Serenčíšová., and Obsahuje bibliografické odkazy
Schweizer and Smítal introduced the distributional chaos for continuous maps of the interval in B. Schweizer, J. Smítal, Measures of chaos and a spectral decomposition of dynamical systems on the interval. Trans. Amer. Math. Soc. 344 (1994), 737–854. In this paper, we discuss the distributional chaos DC1–DC3 for flows on compact metric spaces. We prove that both the distributional chaos DC1 and DC2 of a flow are equivalent to the time-1 maps and so some properties of DC1 and DC2 for discrete systems also hold for flows. However, we prove that DC2 and DC3 are not invariants of equivalent flows although DC2 is a topological conjugacy invariant in discrete case.
We give characterizations of the distributional derivatives $D^{1,1}$, $D^{1,0}$, $D^{0,1}$ of functions of two variables of locally finite variation. Then we use these results to prove the existence theorem for the hyperbolic equation with a nonhomogeneous term containing the distributional derivative determined by an additive function of an interval of finite variation. An application of the above theorem to a hyperbolic equation with an impulse effect is also given.
We apply the larger sieve to bound the number of $2\times 2$ matrices not having large order when reduced modulo the primes in an interval. Our motivation is the relation with linear recursive congruential generators. Basically our results establish that the probability of finding a matrix with large order modulo many primes drops drastically when a certain threshold involving the number of primes and the order is exceeded. We also study, for a given prime and a matrix, the existence of nearby non-similar matrices having large order. In this direction we find matrices of large order when the trace is restricted to take values in a short interval.