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1472. Linear stability analysis reveals exclusion zone for sliding bed transport
- Creator:
- Talmon, Arnold M.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- stratification, hydrotransport, transients, and bed layer
- Language:
- Slovak
- Description:
- A bend or any another pipe component disturbs solids transport in pipes. Longitudinal pressure profiles downstream of such a component may show a stationary transient harmonic wave, as revealed by a recent settling slurry laboratory experiment. Therefore the fundamental transient response of the two-layer model for fully stratified flow is investigated as a first approach. A linear stability analysis of the sliding bed configuration is conducted. No stationary transient harmonic waves are found in this analysis, but adaptation lengths for exponential recovery are quantified. An example calculation is given for a 0.1 m diameter pipeline. Also consequences for long stretches of pipe line emerged. A so far undiscovered exclusion zone is found in the I-V diagram. This exclusion zone is situated adjacent to the deposit limit velocity locus curve. This simplified physical system reveals that flow velocities should be taken about 10% greater than the calculated maximum deposit limit velocity for stable converging flow.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1473. Linkage between in-stream total phosphorus and land cover in Chugoku district, Japan: an ann approach
- Creator:
- Amiri, Bahman Jabbarian, Sudheer, K. P., and Fohrer, Nicola
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- water quality modeling, land use, total phosphorus, ANN, uncertainty analysis, modelovanie kvality vody, využívanie krajiny, celkový obsah fosforu, and analýza neurčitosti
- Language:
- Slovak
- Description:
- Development of any area often leads to more intensive land use and increase in the generation of pollutants. Modeling these changes is critical to evaluate emerging changes in land use and their effect on stream water quality. The objective of this study was to assess the impact of spatial patterns in land use and population density on the water quality of streams, in case of data scarcity, in the Chugoku district of Japan. The study employed artificial neural network (ANN) technique to assess the relationship between the total phosphorous (TP) in river water and the land use in 21 river basins in the district, and the model was able to reasonably estimate the TP in the stream water. Uncertainty analysis of ANN estimates was performed using the Monte Carlo framework, and the results indicated that the ANN model predictions are statistically similar to the characteristics of the measured TP values. It was observed that any reduction in forested area or increase in agricultural land in the watersheds may cause the increase of TP concentration in the stream. Therefore, appropriate watershed management practices should be followed before making any land use change in the Chugoku district. and Rozvoj územia často súvisí so zintenzívnením využívania krajiny a produkciou znečistenia. Dôležité je modelovanie týchto zmien a ich vplyvu na kvalitu vody v tokoch. Cieľom štúdie je určiť vplyv priestorových zmien pri využívaní krajiny a zmeny hustoty osídlenia na kvalitu vody v tokoch v čase nedostatku vody v oblasti Chugoku, Japonsko. Pri riešení sa využívajú umelé neurónové siete (artificial neural network -ANN), prostredníctvom ktorých sa určuje vzťah medzi celkovým obsahom fosforu (TP) v toku a využívaním kajiny v 21 povodiach oblasti; tento model je schopný vypočítať TP v tokoch. Analýza neurčitosti výsledkov dosiahnutých pomocou ANN bola vykonaná metódou Monte Carlo; výsledky analýzy naznačujú, že predpovede pomocou metódy ANN sú štatisticky podobné meraným hodnotám TP. Bolo zistené, že redukcia lesnatosti a zvýšenie plochy poľnohospodársky využívanej pôdy v povodí môže viesť k zvýšeniu koncentrrácie TP v toku. Je preto potrebné pred zmenou vo využívaní krajiny prijať zodpovedajúce opatrenia v manažmente krajiny, ktoré budú minimalizovať negatívne dôsledky zmien využívania krajiny.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1474. Linking soils and streams during events: response of stream water K+ concentration to soil exchangeable K+ concentration in small catchments with fragipan soils (Carpathian Foothills, Poland)
- Creator:
- Siwek, Joanna P., Szymański, Wojciech, Siwek, Janusz, Żelazny, Mirosław, and Klimek, Mariusz
- Format:
- počítač and online zdroj
- Type:
- model:article and TEXT
- Subject:
- hystereses of K+, rainfall and snowmelt events, soil exchangeable K+ concentration, fragipan, agricultural and woodland catchments, and Carpathian foothills
- Language:
- Slovak
- Description:
- The study aimed to determine the linkage between soil exchangeable potassium (K+) concentration and stream water K+ concentration during rainfall and snowmelt events in small catchments with different land use (Carpathian Foothills, Poland). The complementary geochemical and hydrochemical approach used in the study produced new information on the role of particular soil horizons and contributing areas such as hillslope or riparian areas in K+ delivery to stream channels during events. Horizons lying above the nearly impermeable fragipan (Btx) play the most important role in the process of K+ influx to streams during most event types except snowmelts with frozen soils, in all the studied catchments. In the woodland catchment, rapid flushing of K+ from the topsoil Ah horizon with higher hydraulic conductivity (Ksat) and higher exchangeable K+ concentrations than in the lying lower E horizon resulted in a clockwise hysteresis of K+ in stream water during most events. In agricultural catchments, changes in stream water K+ concentration during events were determined by distinct differences between soil exchangeable K+ concentrations on hillslopes and in riparian areas.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
1475. Linking surface and subsurface properties of biocrusted and non-biocrusted habitats of fine-grained fluvial sediments (playas) from the Negev Desert
- Creator:
- Kidron, Giora J.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- available water content, loess, and soil moisture
- Language:
- Slovak
- Description:
- With biocrusts playing a cardinal role in C and N fixation in arid zones, information regarding the factors that determine their limits of growth is of uttermost importance for the study of ecosystem structure and function. This is also the case in the western Negev dunefields, where although abundant on the sandy surfaces, biocrusts are scarce on finegrained (mainly loessial) sediments, termed playas. In the Nizzana research site (NRS), visibly distinct surfaces, with and without biocrusts were noted within a single playa. In an attempt to characterize these distinct surfaces, a set of random measurements were carried out, which included measurements of crack density, microrelief and chlorophyll content of the upper 0-1 cm. Following a cluster analysis, four distinct types of surfaces (hereafter habitats) were defined, one with substantial amount of chlorophyll content which can be regarded as biocrust (P4), and three non-crusted surfaces (P1- P3). Within each type, two 50 cm-deep pits were dug and the pH, electrical conductivity (EC) and fine (silt and clay) content (FC) of samples collected at 1-5, 5-10, 10-20, 20-30, 30-40 and 40-50 cm-depth were analyzed. In addition, periodical moisture measurements were carried out (in pairs) to a depth of 0-20 cm at each surface type during 2013/14. All non-crusted habitats (P1-P3) were characterized by loessial subsurface sediments. Conversely, P4 was either characterized by loessial subsurface sediments (and in this case it was characterized by a slightly concave surface) or having a sandy subsurface (at ~5-10 cm depth). While the non-crusted surfaces exhibited low moisture content, P4 exhibited deeper and higher moisture content explained either by the more sandy sediments or by lower water loss through runoff. The findings point to the close link between surface and subsurface properties and indicate that water availability may explain biocrust establishment and growth also at the loessial playa surfaces. Biocrusts may thus serve as bioindicators for habitats with high moisture content.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1476. Lithobiont-dependent ionic composition in runoff water
- Creator:
- Kidron, Giora J. and Starinsky, Abraham
- Format:
- počítač and online zdroj
- Type:
- model:article and TEXT
- Subject:
- cyanobacteria, dew, lichens, magnesium, potassium, and Negev desert
- Language:
- Slovak
- Description:
- Rock dwelling organisms (lithobionts) such as cyanobacteria (prokaryotes) and chlorolichens (eukaryotes) abound in the Negev Desert, where they cover almost all calcareous bedrocks and rock particles (cobbles, boulders). In a small limestone watershed in the Negev Highlands, cyanobacteria inhabit the south-facing (SF) bedrocks, epilithic lichens (accompanied by endolithic lichens) inhabit the north-facing (NF) bedrocks, while endolithic lichens cover most of the cobbles and boulders in both aspects. In order to study their contribution to runoff water, a pair of runoff plots was established on habitats with cyanobacteria, endolithic lichens, and epilithic lichens. Rain and runoff were collected during the hydrological year 2006/07, and the chemical composition (Ca, Mg, Na, K, Cl, SO4, HCO3, Si) of the rain and runoff water was analyzed. Several patterns were observed: (a) as indicated by Si, more dust accumulated on the bedrocks; (b) all substrates exhibited high amounts of Ca, and HCO3; (c) while SF-bedrocks showed enrichment in K, both bedrocks (and especially the NF bedrocks), as well as the NF boulders showed an enrichment in Mg. While the enrichment in Ca and HCO3 can be explained by the contribution of the limestone parent material, the enrichment in K and Mg can be explained by the contribution of the living lithobionts, with K being mainly contributed by the cyanobacteria and Mg mainly by the epilithic lichens. Ion enrichment may therefore be aspect-dependent, reflecting the lithobiont distribution within the drainage basin, partially explaining the enrichment in K and Mg previously recorded in runoff water from the Negev.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
1477. Local head loss in plastic pipeline joint welded by butt fusion
- Creator:
- Melichar, Jan, Háková, Jaroslava, Veselský, Jaroslav, and Michlík, Luboš
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- local loss, frictional loss, plastic pipelines, místní ztráta, ztráta třením, and plastové potrub
- Language:
- Slovak
- Description:
- The article deals with experimental determination of local head loss in straight polypropylene pipeline (PP) joint connected by butt-welding. A local loss coefficient is introduced for turbulent flow of water in plastic pipeline of circular cross-section. The value of local loss coefficient has not been experimentally quantified so far and hence its determination is significant for designers of plastic pipeline systems. and Článek pojednává o experimentálním stanovení místní ztráty ve spoji přímého potrubí z polypropylenu (PP), zhotoveného svařováním na tupo. Je uvedena velikost součinitele místní ztráty spoje plastového potrubí kruhového průřezu při turbulentním proudění čisté vody. Místní ztráta doposud nebyla experimentálně kvantifikována, a proto je její stanovení pro projektanty potrubních systémů z plastů významné.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1478. Local scour around complex pier groups and combined piles at semi-integral bridge
- Creator:
- Akib, Shatirah, Jahangirzadeh, Afshin, and Basser, Hossein
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- semi-integral bridge, complex pier groups, combined piles, scour, pier, and scour depth
- Language:
- Slovak
- Description:
- This research presents an experimental study on the scouring mechanism at semi-integral bridge piers. Based on laboratory experiments, this study focuses on the relationship between scour depth in complex pier groups and combined piles bridge and various parameters including the variation of inflow velocity, distance, and time. 1 200 data were collected for flow velocity and scour. The flow pattern and scour were analyzed for different flow discharges and flow depths. The results showed that the scour development with respect to time was greater for higher flow depth and bigger flow discharge at semi-integral bridges. In addition, the equilibrium scour depth increased with the approach flow depth around piers at semi-integral bridges. Velocity distribution also affected the scour development. It decreased when approaching the bridge but increased from upstream to downstream of the flume.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
1479. Logic and rational requirements
- Creator:
- Tajer, Diego
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- ogic and rationality, normativity of logic, and rational requirements
- Language:
- Slovak
- Description:
- In this paper, I discuss the relation between logic and rationality. I develop (formally and conceptually) a rational requirement which can respond to the classic objections by Harman (1986). On the one hand, the requirement pays attention to the relevance of the premises and the conclusion, which is formally expressed by the notion of weak relative closure. The requirement also takes care of the complexity of the inferences. This notion of complexity is formally represented by a partially ordered scale of the difficulty of inferences, which is weaker than the notion of complexity as number of steps., V tomto příspěvku se zabývám vztahem logiky a racionality. Formálně a koncepčně rozvíjím racionální požadavek, který může reagovat na klasické námitky Harmana (1986). Požadavek na jedné straně věnuje pozornost významu prostor a závěru, který je formálně vyjádřen konceptem slabého relativního uzavření. Požadavek se také stará o složitost závěrů. Tento pojem složitosti je formálně reprezentován částečně uspořádaným měřítkem obtížnosti závěrů, což je slabší než pojem složitosti jako počet kroků., and Diego Tajer
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
1480. Logic programming and interactive applications
- Creator:
- Šimko, Alexander and Šiška, Jozef
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- answer set programming, declarative problem solving, interactive applications, logic programming, programování sady odpovědí, deklarativní řešení problémů, interaktivní aplikace, and logické programování
- Language:
- Slovak
- Description:
- Answer Set Programming (ASP) is a logic programming based, truly declarative formalism for general purpose problem solving. Its declarative nature allows users to solve problems by defining what the solutions are instead of how to find them. Complete lack of an imperative component in ASP makes creation of end user applications or integration with other systems demanding. External tools that can process and interpret the output of ASP solvers are needed. To address this issue in the case of simple applications with an input – output interaction loop we introduce a framework for iterative logic applications. Such applications consist of a core logic program that is used to evaluate user actions w.r.t. their current state and to derive a new state of the application. We take care to define the framework in a way that allows it to be used also with other formalism, especially SAT solvers. We also present a web based implementation of such framework for ASP., Programování odpovědí Set (ASP) je logické programování založené na skutečně deklarativním formalismu pro řešení obecných problémů. Jeho deklarativní charakter umožňuje uživatelům řešit problémy definováním toho, jaká řešení jsou namísto toho, jak je najít. Úplný nedostatek imperativní komponenty v ASP umožňuje vytváření aplikací pro koncové uživatele nebo integraci s jinými systémy náročnými. Jsou zapotřebí externí nástroje, které mohou zpracovávat a interpretovat výstupy řešitelů ASP. Pro řešení tohoto problému v případě jednoduchých aplikací se vstupní a výstupní interakční smyčkou představujeme rámec pro iterativní logické aplikace. Tyto aplikace se skládají z jádrového logického programu, který se používá k vyhodnocení akcí uživatele s jejich aktuálním stavem a odvození nového stavu aplikace. Dbáme na to, abychom tento rámec definovali způsobem, který umožní jeho použití i s jiným formalismem, zejména SAT řešiteli. Představujeme také webovou implementaci takového rámce pro ASP., and Alexander Šimko ; Jozef Šiška
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public