The complexity of flow conditions at junctions amplifies significantly with supercritical flow. It is a pronounced three-dimensional two-phased flow phenomenon, where standing waves with non-stationary water surface are formed. To analyse the hydrodynamic conditions at an asymmetric right-angled junction with incoming supercritical flows at Froude numbers between 2 and 12, an experimental approach was used. For a phenomenological determination of the relations between the integral parameters of incoming flows and the characteristics of standing waves at the junction area, water surface topographies for 168 scenarios at the junction were measured using non-intrusive measurement
techniques. The new, phenomenologically derived equations allow for determination of location, height and extent of the
main standing waves at the junction. Research results give important information on the processes and their magnitude
for engineering applications.
Weighing lysimeters can be used for studying the soil water balance and to analyse evapotranspiration (ET). However, not clear was the impact of the bottom boundary condition on lysimeter results and soil water movement. The objective was to analyse bottom boundary effects on the soil water balance. This analysis was carried out for lysimeters filled with fine- and coarse-textured soil monoliths by comparing simulated and measured data for lysimeters with a higher and a lower water table. The eight weighable lysimeters had a 1 m2 grass-covered surface and a depth of 1.5 m. The lysimeters contained four intact monoliths extracted from a sandy soil and four from a soil with a silty-clay texture. For two lysimeters of each soil, constant water tables were imposed at 135 cm and 210 cm depths. Evapotranspiration, change in soil water storage, and groundwater recharge were simulated for a 3-year period (1996 to 1998) using the Hydrus-1D software. Input data consisted of measured weather data and crop model-based simulated evaporation and transpiration. Snow cover and heat transport were simulated based on measured soil temperatures. Soil hydraulic parameter sets were estimated (i) from soil core data and (ii) based on texture data using ROSETTA pedotransfer approach. Simulated and measured outflow rates from the sandy soil matched for both parameter sets. For the sand lysimeters with the higher water table, only fast peak flow events observed on May 4, 1996 were not simulated adequately mainly because of differences between simulated and measured soil water storage caused by ET-induced soil water storage depletion. For the silty-clay soil, the simulations using the soil hydraulic parameters from retention data (i) were matching the lysimeter data except for the observed peak flows on May, 4, 1996, which here probably resulted from preferential flow. The higher water table at the lysimeter bottom resulted in higher drainage in comparison with the lysimeters with the lower water table. This increase was smaller for the finer-textured soil as compared to the coarser soil.
Soil sorptivity is considered a key parameter describing early stages of water (rain) infiltration into a relatively dry soil and it is related to build-up complexity of the capillary system and soil wettability (contact angles of soil pore walls). During the last decade an increasing water repellency of sandy soils under pine forest and grassland vegetation has been frequently observed at Mlaky II location in SW Slovakia. The dry seasons result in uneven wetting of soil and up to hundredfold decrease in soil sorptivity in these vegetated soil as compared to reference sandy material, which was out of the reach of ambient vegetation and therefore readily wettable. As far as water binding to low moisture soils is governed by adsorption processes, we hypothesized that soil water repellency detected by water drop penetration test and by index of water repellency should also influence the water vapour adsorption parameters (monolayer water content, Wm, specific surface area, A, maximum adsorption water, Wa, maximum hygroscopic water MH, fractal dimension, DS and adsorption energies, Ea) derived from BET model of adsorption isotherms. We found however, that the connection of these parameters to water repellency level is difficult to interpret; nevertheless the centres with higher adsorption energy prevailed evidently in wettable materials. The water repellent forest and grassland soils reached less than 80% of the adsorption energy measured on wettable reference material. To get more conclusive results, which would not be influenced by small but still present variability of field materials, commercially available homogeneous siliceous sand was artificially hydrophobized and studied in the same way, as were the field materials. This extremely water repellent material had two-times lower surface area, very low fractal dimension (close to 2) and substantially lower adsorption energy as compared to the same siliceous sand when not hydrophobized.
Mosses are often overlooked; however, they are important for soil-atmosphere interfaces with regard to water exchange. This study investigated the influence of moss structural traits on maximum water storage capacities (WSCmax) and evaporation rates, and species-specific effects on water absorption and evaporation patterns in moss layers, mosssoil- interfaces and soil substrates using biocrust wetness probes. Five moss species typical for Central European temperate forests were selected: field-collected Brachythecium rutabulum, Eurhynchium striatum, Oxyrrhynchium hians and Plagiomnium undulatum; and laboratory-cultivated Amblystegium serpens and Oxyrrhynchium hians. WSCmax ranged from 14.10 g g–1 for Amblystegium serpens (Lab) to 7.31 g g–1 for Plagiomnium undulatum when immersed in water, and 11.04 g g–1 for Oxyrrhynchium hians (Lab) to 7.90 g g–1 for Oxyrrhynchium hians when sprayed, due to different morphologies depending on the growing location. Structural traits such as high leaf frequencies and small leaf areas increased WSCmax. In terms of evaporation, leaf frequency displayed a positive correlation with evaporation, while leaf area index showed a negative correlation. Moisture alterations during watering and desiccation were largely controlled by species/substrate-specific patterns. Generally, moss cover prevented desiccation of soil surfaces and was not a barrier to infiltration. To understand water’s path from moss to soil, this study made a first contribution.
Short term streamflow forecasting is important for operational control and risk management in hydrology. Despite a wide range of models available, the impact of long range dependence is often neglected when considering short term forecasting. In this paper, the forecasting performance of a new model combining a long range dependent autoregressive fractionally integrated moving average (ARFIMA) model with a wavelet transform used as a method of deseasonalization is examined. It is analysed, whether applying wavelets in order to model the seasonal component in a hydrological time series, is an alternative to moving average deseasonalization in combination with an ARFIMA model. The one-to-ten-steps-ahead forecasting performance of this model is compared with two other models, an ARFIMA model with moving average deseasonalization, and a multiresolution wavelet based model. All models are applied to a time series of mean daily discharge exhibiting long range dependence. For one and two day forecasting horizons, the combined wavelet - ARFIMA approach shows a similar performance as the other models tested. However, for longer forecasting horizons, the wavelet deseasonalization - ARFIMA combination outperforms the other two models. The results show that the wavelets provide an attractive alternative to the moving average deseasonalization.
The aim of this article is to analyze the main contributions of Wesley C. Salmon to the philosophy of science, that is, his concepts of causation, common cause, and theoretical explanation, and to provide a critique of them. This critique will be based on a comparison of Salmon’s concepts with categories developed by Hegel in his Science of Logic and which can be applied to issues treated by Salmon by means of the above given three concepts. It is the author’s contention that by means of Hegelian categories it becomes possible to provide a critique of Salmon’s philosophy of science and at the same time to enlarge the concept framework of philosophy of science., Cílem tohoto článku je analyzovat hlavní přínosy Wesleyho C. Lososa k filosofii vědy, tj. K jeho příčinám, společné příčině a teoretickému vysvětlení, a poskytnout jim kritiku. Tato kritika bude založena na srovnání konceptů Salmon s kategoriemi vyvinutými Hegelem v jeho Science of Logic a které lze aplikovat na otázky ošetřené lososem pomocí výše uvedených tří pojmů. Je to autorovo tvrzení, že prostřednictvím hegelovských kategorií je možné poskytnout kritiku Salmonovy filosofie vědy a zároveň rozšířit koncepční rámec filozofie vědy., and Igor Hanzel
Since Antiquity, logic has always enjoyed a status of something crucially important, because it shows us how to reason, if we are to reason correctly. Yet the twentieth century fostered an unprecedented boost in logical studies and delivered a wealth of results, most of which are not only not understandable by non-specialists, but their very connection with the original agenda of logic is far from clear. In this paper, I survey how the achievements of modern logic are construed by non-specialists and subject their construals to critical scrutiny. I argue that logic cannot be taken as a theory of the limits of our world and that its prima facie most plausible construal as a theory of reasoning is too unclear to be taken at face value. I argue that the viable construal of logic takes it to be explicative of the constitutive (rather than strategic) rules of reasoning, not of the rules that tell us how to reason, but rather of rules that make up the tools with which (or in terms of which) we reason., Od starověku se logika vždy těšila stavu něčeho zásadně důležitého, protože nám ukazuje, jak rozumět, pokud máme správně rozumět. Dvacáté století však podpořilo bezprecedentní oživení v logických studiích a přineslo mnoho výsledků, z nichž většina není nejen srozumitelná pro nešpecializované odborníky, ale jejich samotné spojení s původní logikou logiky není zdaleka jasné. V tomto příspěvku zkoumám, jak jsou úspěchy moderní logiky konstruovány nešpecializovanými odborníky a podřizují jejich konstrukty kritické kontrole. Domnívám se, že logiku nelze považovat za teorii hranic našeho světa a její prima facienejspolehlivější konstrukční jako teorie uvažování je příliš nejasná, aby mohla být přijata v nominální hodnotě. Domnívám se, že životaschopná konstrukce logiky má za to, že je vysvětlující konstitutivní (spíše než strategická) pravidla uvažování, nikoli pravidla, která nám říkají, jak rozumět, ale spíše pravidla, která tvoří nástroje, s nimiž (nebo v podmínky) rozumíme., and Jaroslav Peregrin
The article considers the nature of descriptive statements and the ontological status of descriptive constructs in linguistics, taking the example of a phoneme of English. It is argued that descriptive statements should be seen as expressions of the content of descriptive models or as hypotheses. Furthermore, it is argued that descriptive models and constructs in linguistics have a purely explanatory function in relation to speech events and without ontological commitment to corresponding entities in the real world., Článek pojednává o povaze popisných výroků a ontologickém stavu deskriptivních konstrukcí v lingvistice, přičemž vychází z příkladu fonému angličtiny. Argumentuje se tím, že popisná prohlášení by měla být chápána jako vyjádření obsahu popisných modelů nebo jako hypotézy. Dále, to je argumentoval, že popisné modely a konstrukce v lingvistice mají čistě vysvětlující funkci ve vztahu k událostem řeči a bez ontologického závazku k odpovídajícím entitám v reálném světě., and Paul Rastall
The paper sketches and defends two instances of the strategy Let N’s be whatever they have to be to explain our knowledge of them—one in which N’s are natural numbers and one in which N’s are propositions. The former, which makes heavy use of Hume’s principle and plural quantification, grounds our initial knowledge of number in (a) our identification of objects as falling under various types, (b) our ability to count (i.e. to pair memorized numerals with individuated objects of one’s attention), (c) our (initially perceptual) recognition of plural properties (e.g. being three in number), and (d) our predication of those properties of pluralities that possess them (even though no individuals in the pluralities do). Given this foundation, one can use Fregean techniques to non-paradoxically generate more extensive arithmetical knowledge. The second instance of my metaphysics-in-the-service-of-epistemology identifies propositions (i.e. semantic contents of some sentences, objects of the attitudes, and bearers of truth, falsity, necessity, contingency, and apriority) with certain kinds of purely representational cognitive acts, operations, or states. In addition to providing natural solutions to traditionally un-addressed epistemic problems involving linguistic cognition and language use, I argue that this metaphysical conception of propositions expands the solution spaces of many of the most recalcitrant and long-standing problems in natural-language semantics and the philosophy of language.