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Start Over Language Slovak Rights http://creativecommons.org/licenses/by-nc-sa/4.0/

82. Basset force in numerical models of saltation

Creator:
Lukerchenko, Nikolay, Dolanský, Jindřich, and Vlasák, Pavel
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Basset force, bed load transport, numerical model, particle-bed collision, Bassetova historická síla, pohyb splavenin, numerický model, and kolise částice se dnem
Language:
Slovak
Description:
In numerical models of fluid flow with particles moving close to solid boundaries, the Basset force is usually calculated for the particle motion between particle-boundary collisions. The present study shows that the history force must also be taken into account regarding particle collisions with boundaries or with other particles. For saltation - the main mode of bed load transport - it is shown using calculations that two parts of the history force due to both particle motion in the fluid and to particle-bed collisions are comparable and substantially compensate one another. The calculations and comparison of the Basset force with other forces acting on a sand particle saltating in water flow are carried out for the different values of the transport stage. The conditions under which the Basset force can be neglected in numerical models of saltation are studied. and V numerických modelech proudění tekutin s pevnými částicemi v blízkosti pevné stěny je Bassetova historická síla obvykle počítána pro pohyb částice mezi jejími jednotlivými kolisemi se dnem. Předložená studie ukazuje, že při výpočtu Bassetovy historické síly je nutné brát v úvahu kolisi částice s pevným dnem nebo s jinými částicemi. Pro saltaci, hlavní typ pohybu splavenin u dna koryta, je na základě použitých výpočtů ukázáno, že dvě části Bassetovy historické síly, tj. síly způsobené pohybem částice v tekutině a kolisí částice se dnem, jsou srovnatelné a mohou se vzájemně významně kompensovat. Výpočet Bassetovy historické síly a její srovnání s ostatními silami působícími na písčitou částici při jejím saltačním pohybu ve vodě je uskutečněn pro různé hodnoty tzv. transport stage (poměr aktuálního a kritického smykového napětí na dně). Zároveň byly studovány podmínky, za nichž může být Bassetova historická síla v numerických modelech zanedbána.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

83. Bayesian estimation of the hydraulic and solute transport properties of a small-scale unsaturated soil column

Creator:
Moreira, Paulo H. S., van Genuchte, Martinus Th., Orlande, Helcio R. B., and Cotta, Renato M.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Markov Chain Monte Carlo method, Metropolis-Hastings algorithm, hydraulic parameters, transport parameters, and soil column experiment
Language:
Slovak
Description:
In this study the hydraulic and solute transport properties of an unsaturated soil were estimated simultaneously from a relatively simple small-scale laboratory column infiltration/outflow experiment. As governing equations we used the Richards equation for variably saturated flow and a physical non-equilibrium dual-porosity type formulation for solute transport. A Bayesian parameter estimation approach was used in which the unknown parameters were estimated with the Markov Chain Monte Carlo (MCMC) method through implementation of the Metropolis-Hastings algorithm. Sensitivity coefficients were examined in order to determine the most meaningful measurements for identifying the unknown hydraulic and transport parameters. Results obtained using the measured pressure head and solute concentration data collected during the unsaturated soil column experiment revealed the robustness of the proposed approach.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

84. Bedform characteristics in a gravel-bed river

Creator:
Afzalimehr, Hossein, Maddahi, Mohammad Reza, and Sui, Jueyi
Type:
article, model:article, and TEXT
Subject:
bedform characteristics, gravel-bed river, field measurements, and form friction factor
Language:
Slovak
Description:
Estimation of hydraulic and geometric parameters of a gravel-bed river such as dimensions of bedforms is very difficult task, although they play a fundamental role in river engineering projects. One of the methods to get essential information regarding the bedform characteristics is to find the relations between the flow parameters and bedform dimensions. We conducted this field study in the Babolroud River in northern Iran to investigate the application of double averaged method in unspecific gravel bedforms to evaluate friction factor. Using data collected from several river reaches with total length of 356 m of a gravel-bed river, the relationship between bedform geometry (height and the length of bedforms) and flow parameters including shear velocity, transport stage parameter with friction factor is investigated. Different methods for estimating bedforms dimensions are examined to assess the ability of predicting bedform parameters (length and height) in a gravel-bed river. Using bedform parameters, the contribution of particle and form friction is estimated. Results confirm the application of the double averaged method and existing bedform parameters for unspecific bedforms. There exists a similar trend between aspect ratio and friction factor in gravel bedforms.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

85. Bedload equation analysis using bed load-material grain size

Creator:
Haddadchi, Arman, Omid, Mohammad H., and Dehghani, Amir A.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
sediment transport, grain size, gravel-bed river, and evaluation
Language:
Slovak
Description:
Twelve predictive bedload sediment transport equations are rated against 14 sets of gravel-bed river field data collected by handheld bedload sampler in Narmab River, northeastern Iran. To evaluate these formulas two types of grain size namely bedload and bed material were used. The results show that the equations of Engelund and Hansen, Van Rijn and Einstein perform well with bed material grain size, while Shocklitsch, Meyer-Peter and Mueller, and Frijlink yield the best results using the bedload grain size.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

86. Bedload transport and morphological effects of high-magnitude floods in small headwater streams - Moravskoslezské Beskydy Mts. (Czech Republic)

Creator:
Galia, Tomáš and Hradecký, Jan
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
incipient motion, bedload transport, headwater stream, Moravskoslezské Beskydy Mts., počátek pohybu, dnový transport, pramenný tok, and Moravskoslezské Beskydy
Language:
Slovak
Description:
Bedload transport observed during a flood in May 2010 gave rise to several forms of accumulations in small headwater basins located in the Western Flysch Carpathian Mountains, Czech Republic. We have investigated critical conditions of incipient motion of the largest boulders deposited during a c. Q100 flood event (flood competence method). We have tested several formulas designed for high gradient streams in two small basins in the conditions of local mid-mountain relief. The results show that a flood of such a magnitude is able to transport almost all surface bed material and that bedload transport in steep headwater streams (A ≤ 1 km2 ) is probably less selective as for the grain size than that in lower gradient gravel-bed streams. The authors discuss the importance of local basin predispostion factors in order to determine critical conditions for the onset of bedload transport. and Dnový transport sedimentů zapříčinil během květnových povodní v roce 2010 vznik různých typů akumulací v malých pramenných tocích nacházejících se ve flyšových pohořích Západních Karpat. Studie se zaměřuje na určení kritických podmínek nutných pro uvedení největších klastů do pohybu, jež byly následně uloženy do akumulací během této cca Q100 povodně (metoda účinnosti povodně). V rámci výzkumu byly ověřeny některé rovnice vytvořené pro vysokogradientové toky na dvou malých povodích v podmínkách reliéfu hornatin. Výsledky ukazují, že povodeň takové intenzity je schopna transportovat téměř celou povrchovou vrstvu sedimentů a dnový transport je na malých povodích pravděpodobně méně velikostně selektivní než v tocích s nižším gradientem dna. Důraz byl kladen také na lokální predizpoziční faktory ovlivňující kritické podmínky pro uvedení určité velikostní frakce sedimentů do pohybu.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

87. Beyond the conversation: the pervasive danger of slurs

Creator:
Moreno, Alba and Pérez-Navarro, Eduardo
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
context, derogation, nonderogatory occurrences of slurs, normalization, and slurs
Language:
Slovak
Description:
Although slurs are conventionally defined as derogatory words, it has been widely noted that not all of their occurrences are derogatory. This may lead us to think that there are “innocent” occurrences of slurs, i.e., occurrences of slurs that are not harmful in any sense. The aim of this paper is to challenge this assumption. Our thesis is that slurs are always potentially harmful, even if some of their occurrences are nonderogatory. Our argument is the following. Derogatory occurrences of slurs are not characterized by their sharing any specific linguistic form; instead, they are those that take place in what we call uncontrolled contexts, that is, contexts in which we do not have enough knowledge of our audience to predict what the uptake of the utterance will be. Slurs uttered in controlled contexts, by contrast, may lack derogatory character. However, although the kind of context at which the utterance of a slur takes place can make it nonderogatory, it cannot completely deprive it of its harmful potential. Utterances of slurs in controlled contexts still contribute to normalizing their utterances in uncontrolled contexts, which makes nonderogatory occurrences of slurs potentially harmful too.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

88. Biocrust effects on soil infiltrability in the Mu Us Desert: soil hydraulic properties analysis and modeling

Creator:
Guan, Hongjie and Liu, Xinyu
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
cyanobacteria, lichen, moss, infiltration, inverse approach, and hydraulic parameter
Language:
Slovak
Description:
The presence of biocrusts changes water infiltration in the Mu Us Desert. Knowledge of the hydraulic properties of biocrusts and parameterization of soil hydraulic properties are important to improve simulation of infiltration and soil water dynamics in vegetation-soil-water models. In this study, four treatments, including bare land with sporadic cyanobacterial biocrusts (BL), lichen-dominated biocrusts (LB), early-successional moss biocrusts (EMB), and latesuccessional moss biocrusts (LMB), were established to evaluate the effects of biocrust development on soil water infiltration in the Mu Us Desert, northwest of China. Moreover, a combined Wooding inverse approach was used for the estimation of soil hydraulic parameters. The results showed that infiltration rate followed the pattern BL > LB > EMB > LMB. Moreover, the LB, EMB, and LMB treatments had significantly lower infiltration rates than the BL treatment. The saturated soil moisture (θs) and shape parameter (αVG) for the EMB and LMB treatments were higher than that for the BL and LB treatments, although the difference among four treatments was insignificant. Water retention increased with biocrust development at high-pressure heads, whereas the opposite was observed at low-pressure heads. The development of biocrusts influences van Genuchten parameters, subsequently affects the water retention curve, and thereby alters available water in the biocrust layer. The findings regarding the parameterization of soil hydraulic properties have important implications for the simulation of eco-hydrological processes in dryland ecosystems.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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