A Moderate Anti-realist (MAR) approach to truth and meaning, built around the concept of knowability, will be introduced and argued for in this essay. Our starting point will be the two fundamental anti-realists principles that claim that neither truth nor meaning can outstrip knowability and our focus will be on the challenge of adequately formalizing these principles and incorporating them into a formal theory. Accordingly, I will introduce a MAR truth operator that is built on a distinction between being true and being factual. I will show then that this approach partitions propositions into eight classes, on the basis of their knowability. We will then ask the following question: Given the anti-realist principles, what kind of theory of propositional meaning can properly explain the meaninglessness of fully unknowable propositions? This question will lead us to the claim that the meaning/content of propositions should be identified not with the set of possible worlds in which the propositions are true/factual, but rather in which they are known. This modified approach will then be used to analyze both the Liar Paradox and the Strengthened Liar. To anticipate the conclusion of this essay, it will be shown that a MAR framework can render definite truth and factuality values to the Liar sentence and it will also confirm our intuition that such paradoxical sentences are devoid of proper meaning. and Moderní antirealistní (MAR) přístup k pravdě a významu, postavený na konceptu znalosti , bude představen a projednáván v této eseji. Naším výchozím bodem budou dvě základní principy antirealistů, které tvrdí, že ani pravda, ani význam nemohou překonat znalost a naše zaměření bude na výzvu adekvátně formalizovat tyto zásady a začlenit je do formální teorie. Proto zavedu operátor MAR pravdy, který je postavený na rozdílu mezi skutečností a skutečností. Ukážeme tedy, že tento přístup rozděluje návrhy do osmi tříd na základě jejich znalosti. Potom budeme klást následující otázku: Vzhledem k antirealistickým principům, jaká teorie proposativálního významu může správně vysvětlitnesmyslnost z plně nepoznatelných výroků? Tato otázka nás vede k tvrzení, že smysl / obsah tvrzení by neměl být identifikován se souborem možných světů, ve kterých jsou tvrzení pravdivá / věcná , ale spíše ve kterých jsou známé . Tento modifikovaný přístup pak bude použit pro analýzu jak Liar Paradoxu, tak Posíleného Lháře . Předvídat závěr této eseje, bude ukázáno, že rámec MAR může poskytnout definitivní pravdivost a faktografické hodnoty věrnosti Liar a také potvrdí naši intuici, že takové paradoxní věty nemají správný význam.
Field observations showed that in many gravel-bed rivers, rice stems and gravel interact with each other and affect the flow structure. This calls to conduct research in more details in laboratory to better understand impacts of interaction between rice stems and gravel bed rivers on the flow structure. The outcome of such investigations can improve the estimation of drag coefficient in hydrodynamic models. Experiments were carried out in a flume with gravel bed and the vegetated vertical flume walls to investigate turbulence characteristics under favorable pressure gradient flows. Results showed that the stress fraction involves both the sweep and ejection dominance near the vegetated flume walls, showing no negative Reynolds shear stress near water surface. The values of exuberance ratio play a significant role on the magnitude of the Reynolds shear stress which varies with the distance from the vegetation. Quadrant analysis reveals that a major part of the momentum flux is transported during a short period of strong turbulence activity near the bed at the central axis. Augmentation of the hole size makes difference between contributions of sweep and ejection with those of the outward and inward interactions near the bed, however, the hole size doesn’t play any role near the water surface.
Turbulence of flow over mobile bedforms in natural open channels is not yet clearly understood. An attempt is made in this paper to determine the effect of naturally formed mobile bedforms on velocities, turbulent intensities and turbulent stresses. Instantaneous velocities are measured using a two-dimensional particle image velocimetry (PIV) to evaluate the turbulence structure of free surface flow over a fixed (immobile) bed, a weakly mobile bed and a temporally varying mobile bed with different stages of bedform development. This paper documents the vertical distribution of velocity, turbulence intensities, Reynolds shear stress and higher-order moments including skewness and turbulent diffusion factors. Analysis of the velocity distributions shows a substantial decrease of velocity near the bed with increasing bedform mobility due to increased friction. A modified logarithmic law with a reduced von Kármán constant and increased velocity shift is proposed for the case of the mobile bedforms. A significant increase in the Reynolds shear stress is observed in the mobile bedforms experiments accompanied by changes over the entire flow depth compared to an immobile bed. The skewness factor distribution was found to be different in the case of the flow over the mobile bedforms. All higher-order turbulence descriptors are found to be significantly affected by the formation of temporally varying and non-equilibrium mobile bedforms. Quadrant analysis indicates that sweep and outward events are found to be dominant in strongly mobile bedforms and govern the bedform mobility.
The study presents experimental investigations of spatial turbulence intensity and scales of turbulent eddies (macroeddies) in a rectangular channel and the impact of the hydraulic jump on their vertical and streamwise distributions over a flat and scoured bed. The results of four tests and two different discharge rates are presented. Intensive mixing caused by the hydraulic jump has an impact on the instantaneous velocity, turbulence intensity and sizes of macroeddies, as well as their vertical and longitudinal distributions along the channel. The largest differences in turbulence characteristics were reported directly after the hydraulic jump, above the eroded bed. The interaction between the stream of the increased turbulence and the bed is a direct cause of formation of scour downstream water structures, which has a great effect on overall flow characteristics. The scour hole that arose downstream the jump moderated, in a small degree, the turbulence intensity at its end. Just next to the hydraulic jump only the small longitudinal relative sizes of macroeddies were present, while at the end of the analyzed reach, downstream of the scour, the relative scale reached around 1.5 depth of the stream.