In recent years, due to the occurrence of water shortage and drought problems, particularly in arid and semiarid regions of the world, new methods to reduce evaporation from the surface of dam reservoirs, lakes, and other waterfree surfaces are investigated. This study aimed to use hydrophobic bentonite to reduce water evaporation from water surfaces, on a laboratory scale, and field conditions for the first time. Bentonite initially became hydrophobic by stearic acid (SA). Under such conditions, hydrophobic bentonite floats on the surface of water and forms a thin coating layer. The produced hydrophobic bentonite had a contact angle of 150°, indicating its superhydrophobicity. Evaporation reduction was measured under laboratory and field conditions and it was compared to hexadecanol as the reference material. The results demonstrated that the hydrophobic bentonite efficiency under laboratory conditions was similar to that of hexadecanol and prevented water evaporation by 36%. However, under field conditions, hydrophobic bentonite and hexadecanol efficiencies were 40% and 23% to reduce evaporation for 30 days, respectively. In terms of stability, hexadecanol needed to be re-injected after three days, while hydrophobic bentonite was stable and remained on the surface for more than 100 days under laboratory conditions and for more than 15 days under field conditions without needing reinjection. This coverage with method can be used to reduce evaporation from lakes, tanks, and reservoirs of small dams.
Gravity-driven open-channel flows carrying coarse sediment over an erodible granular deposit are studied. Results of laboratory experiments with artificial sediments in a rectangular tilting flume are described and analyzed. Besides integral quantities such as flow rate of mixture, transport concentration of sediment and hydraulic gradient, the experiments include measurements of the one-dimensional velocity distribution across the flow. A vertical profile of the longitudinal component of local velocity is measured across the vertical axis of symmetry of a flume cross section using three independent measuring methods. Due to strong flow stratification, the velocity profile covers regions of very different local concentrations of sediment from virtually zero concentration to the maximum concentration of bed packing. The layered character of the flow results in a velocity distribution which tends to be different in the transport layer above the bed and in the sediment-free region between the top of the transport layer and the water surface. Velocity profiles and integral flow quantities are analyzed with the aim of evaluating the layered structure of the flow and identifying interfaces in the flow with a developed transport layer above the upper plane bed.
Snow accumulation and melt are highly variable. Therefore, correct modeling of spatial variability of the snowmelt, timing and magnitude of catchment runoff still represents a challenge in mountain catchments for flood forecasting. The article presents the setup and results of detailed field measurements of snow related characteristics in a mountain microcatchment (area 59 000 m2 , mean altitude 1509 m a. s. l.) in the Western Tatra Mountains, Slovakia obtained in winter 2015. Snow water equivalent (SWE) measurements at 27 points documented a very large spatial variability through the entire winter. For instance, range of the SWE values exceeded 500 mm at the end of the accumulation period (March 2015). Simple snow lysimeters indicated that variability of snowmelt and discharge measured at the catchment outlet corresponded well with the rise of air temperature above 0°C. Temperature measurements at soil surface were used to identify the snow cover duration at particular points. Snow melt duration was related to spatial distribution of snow cover and spatial patterns of snow radiation. Obtained data together with standard climatic data (precipitation and air temperature) were used to calibrate and validate the spatially distributed hydrological model MIKE-SHE. The spatial redistribution of input precipitation seems to be important for modeling even on such a small scale. Acceptable simulation of snow water equivalents and snow duration does not guarantee correct simulation of peakflow at shorttime (hourly) scale required for example in flood forecasting. Temporal variability of the stream discharge during the snowmelt period was simulated correctly, but the simulated discharge was overestimated.
Extensive experimental investigations were carried out to evaluate the rheological behaviour of fly ash (FA) slurry without and with the addition of bottom ash (BA) and BA slurry without and with the addition of FA. The FA slurries exhibited Bingham behaviour at solid mass concentrations ranging from 60-65% and mixing proportions from 10- 40%. A substantial reduction in yield stress was observed except for mixing proportion of 40% on which the yield stress and viscosity were increased drastically for all solid concentrations. Hence, it can be concluded that the yield stress and viscosity of FA slurry were very much influenced by adding BA up to the mixing proportion of 30%. The rheological behaviour of BA slurries with and without the addition of FA in proportions of 10-50% was investigated and exhibited Newtonian behaviours for solid mass concentrations ranging from 30-50% without and with the addition of FA. The viscosity increases with increasing the solid concentrations and proportion of FA. Based on these experimental data, a correlation was developed to predict the relative viscosity of BA slurries as a function of solid volume fraction and FA mass proportion of 0-50% and the RMSE and R2 values showed good agreement between the experimental and the predicted data.
The experimental basins in the Jizera Mountains were established at the beginning of the 1980th as a result of the forest devastation due to acid rain and repercussions of following human activities during its disposal with the aim to gain data for the quantification of runoff conditions changes in a changing environment. Seven small catchments with an area from 1.87 km2 to 10.6 km2 are situated in the spring regions in an elevation from 700 m a.s.l. to 1100 m a.s.l. in the catchments of the Černá Nisa, Kamenice, Jizerka and Směda streams. The long-term average annual temperature in the elevation of 780 m a.s.l. is +4.4°C, the long-term annual precipitation sum fluctuates between 1300 mm and 1800 mm. The Jizera Mountains are known for numerous intensive rainfalls in the summer period. The administrator of the experimental basins is the Czech Hydrometeorological Institute (CHMI), Department of Hydrological Research, Experimental Base Jablonec nad Nisou, which performs all operative activities and basic processing of data. In the basins, the monitored elements are water stages and discharges in rivers, surface water quality, rainfall, snow depth and snow water equivalent and climatological parameters. The following contribution gives an overview of information obtained from the hydrological research in the period 1981 - 2004. and Příspěvek se zabývá přehledem poznatků z hydrologického výzkumu v období let 1982-2005 v experimentálních povodích Českého hydrometeorologického ústavu (ČHMÚ) v imisně poškozené oblasti Jizerských hor. Základnu tvoří 7 malých povodí s rozlohou od 1,87 km2 do 10,6 km2 celkové plochy 37 km2 . Všechna povodí leží ve vrcholové části Jizerských hor v Chráněné krajinné oblasti Jizerské hory, na rozvodí řek Labe a Odry. Nadmořská výška povodí se pohybuje mezi 700 až 1100 m. Správcem povodí je Oddělení hydrologického výzkumu, pracoviště Jablonec nad Nisou. Zpočátku byly práce zaměřeny převážně na získání co největšího počtu informací o srážkách, sněhu, množství a jakosti povrchové vody. Po roce 1995 byl monitoring rozšířen na více parametrů hydrologické bilance, sledování klimatických prvků a složek hydrologického procesu. Následně byl upřesňován jejich režim i jejich prostorové rozložení. Byla studována problematika rozdílnosti akumulace a odtávání sněhu na mýtině a v lese a odtoková a kvalitativní odezva na srážkovou činnost a tání sněhu. Za pomoci hydrologických a chemických modelů byly hledány odhady změn jejich závislosti na změně vegetačního pokryvu.
An experimental study on initial water flow through an empty pipe under conditions of free level and steady inflow into the pipe. The study presents results of the analysis of experimental values of wave front velocity and outflow from a pipe and their experimental eqautions. and Experimentální studie pojednává o napouštění prázdného potrubí vodou s volnou hladinou a s konstantním přítokem do potrubí. Studie předkládá výsledky rozboru experimentálních hodnot rychlostí čela vlny a odtoku vlny z potrubí i jejich experimentální rovnice.
Inspired by the work of Sellars, Cumpa (2014, 2018) and Buonomo (2021) have argued that we can evaluate our metaphysical proposals on fundamental categories in terms of their capacity for reconciling the scientific and the manifest image of the world. This criterion of fundamentality would allow us to settle the question of which categories among those proposed in the debate—e.g., substance, structure or facts—have a better explanatory value. The aim of this essay is to argue against a central assumption of the criterion: semantic descriptivism. Specifically, I aim at showing that the criterion rests on the idea that the manifest picture is mostly a description of the world, and thus, it commits us with certain realism. Instead, I argue that at least some of the vocabulary we use to construct our manifest picture of the world, mental vocabulary, is evaluative rather than descriptive and thus creates problems in reconciling the manifest picture with scientific psychology and neurosciences. I conclude with some remarks on alternatives that could provide a way out of the fundamentality criterion.
Suspended sediment dynamics during hydrological events influenced by rainstorms and factors controlling changes in sediment dynamics were investigated in a small basin scale, since small basins can be considered as one of the most important sediment sources. The study focuses on the agricultural microbasin Rybárik, near Považská Bystrica (Western Slovakia). Suspended sediment concentrations were measured during discharge waves in the years 1987-1990, 1992, 2000 and 2001. The behaviour of suspended sediments in watercourses is not only a function of energy conditions, but also a function of sediment availability. The variations in sediment supply and sediment depletion result in so-called hysteresis effects. Thus, suspended sediment concentrations at rising and falling limbs are different for equal discharges. Positive and anti-clockwise hysteresis was observed at Rybárik basin. The procedure of separation of factors controlling sediment dynamics has given more realistic view on production and transport of suspended sediments. It is confirmed that spatial and temporal variability of sediment availability and suspended sediment dilution by the baseflow, mainly in the case of two or more waves following one after another control significantly suspended sediment dynamics. and Keďže malé povodia možno považovať za jeden z hlavných zdrojov sedimentov, na malom povodí bol skúmaný režim plavenín počas hydrologických udalostí spôsobených prívalovými zrážkami, a faktory ovplyvňujúce zmeny v dynamike plavenín. Štúdia bola vykonaná na poľnohospodárskom mikropovodí Rybárik pri Považskej Bystrici. Koncentrácie plavenín boli merané počas prietokových vĺn v rokoch 1987- 1990, 1992, 2000 a 2001. Režim plavenín vo vodných tokoch nie je funkciou len transportnej kapacity toku, ale aj dostupnosti sedimentov. Zmeny v zásobovaní a vyčerpávaní sedimentov spôsobujú tzv. hysterézny efekt. To znamená, že koncentrácie plavenín na stúpajúcej a klesajúcej vetve vlny sú rozdielne pri tých istých prietokoch. V povodí Rybárik bola pozorovaná pozitívna aj opačná hysteréza. Postup izolovania faktorov, ktoré ovplyvňujú dynamiku plavenín, prináša reálnejší obraz o tvorbe a transporte plavenín. Ukazuje sa, že zrieďovanie koncentrácií plavenín základným odtokom a časová a priestorová heterogenita územia z hľadiska dostupnosti sedimentov, predovšetkým v situácii tesne za sebou nasledujúcich prívalových vĺn, sa významne podieľajú na celkovej dynamike plavenín.
I explain how Karl Popper resolved the problem of induction but not the pragmatic problem of induction. I show that Popper's proposed solution to the pragmatic problem of induction is inconsistent with his solution to the problem of induction. I explain how Popper’s falsificationist epistemology can solve the pragmatic problem of induction in the same negative way that it solves the problem of induction.
It is widely assumed that the possibility of faultless disagreement is to be explained by the peculiar semantics and/or pragmatics of special kinds of linguistic construction. For instance, if A asserts “o is F” and B asserts this sentence’s denial, A and B can disagree faultlessly only if they employ the right kind of predicate as their “F”. In this paper, I present an argument against this assumption. Focusing on the special case when the expression of interest is a predicate, I present a series of examples in which the same pairs of sentences are employed, but in different contexts. In some cases, we get an impression of faultless disagreement and in some cases we don’t. I identify a pattern across these contexts and conclude that faultless disagreement is made possible, not by a special kind of predicate, but instead by a special kind of context.