This paper presents the results of a laboratory study on the flow characteristics of sharp-crested weirs, broad-crested weirs, and labyrinth weirs. The variation of the maximum bubble penetration depth for different weir types is investigated depending on overfall jet expansion, discharge, and drop height. Moreover, most efficient depth, length and width of the downstream receiving pool in an open channel system are studied by considering the penetration depth, overfall jet expansion, jet trajectory and the bubble zone. The results show that overfall jet expansion at the labyrinth weirs is significantly wider than the rectangular sharp-crested weirs and the trapezoidal sharp-crested weir. It is demonstrated that the labyrinth weirs have the lowest values of bubble penetration depth among the weirs tested. Furthermore, it is found that the rectangular and the trapezoidal weirs are observed to have the highest bubble penetration depth among all weirs. Consequently, empirical equations are obtained for predicting the maximum penetration depth of bubbles, trajectory of free overfall nappe, jet expansion of free overfall nappe, and the length of the bubble zone. and Príspevok prezentuje výsledky laboratórneho výskumu charakteristík prúdenia cez ostrohranné priepady, cez priepady so širokou hranou a cez labyrintové priepady. Bola študovaná variácia maximálnej hĺbky prieniku vzduchových bublín pre rozdielne typy priepadov v závislosti od rozšírenia prúdu, prietoku a výšky priepadu. Okrem toho bola analyzovaná efektívna hĺbka, šírka a dĺžka vývaru v systéme otvorených kanálov s uvážením rozšírenia prúdu, prietoku a výšky priepadu a oblasti so vzduchovými bublinami. Z výsledkov vyplýva, že rozšírenie prúdu pri labyrintových priepadoch je výrazne väčšie, ako pri pravouhlých a lichobežníkových ostrohranných priepadoch. Bolo ukázané, že labyrintové priepady majú najmenšiu hĺbku prieniku vzduchových bublín spomedzi všetkých testovaných priepadov. Zistilo sa však, že pravouhlé a lichobežníkové priepady majú najväčšie hĺbky prieniku vzduchových bublín spomedzi všetkých testovaných priepadov. Tieto výsledky výskumu viedli k empirickým rovniciam, umožňujúcim výpočet maximálnej hĺbky prieniku vzduchových bublín, trajektórií prepadového lúča, rozšírenia prúdu a dĺžky prevzdušnenej oblasti.
The heat tolerance of 8 temperate- and 1 subtropical-origin C3 species as well as 17 tropical-origin ones, including C3, C4, and CAM species, was estimated using both F0-T curve and the ratio of chlorophyll fluorescence parameters, prior to and after high temperature treatment. When leaves were heated at the rate of ca. 1 °C min-1 in darkness, the critical temperature (Tc) varied extensively among species. The Tc's of all 8 temperate-origin species ranged between 40-46 °C in winter (mean temperature 16-19 °C), and between 32-48 °C in summer (mean temperature ca. 30 °C). Those for 1 subtropical- and 12 tropical-origin C3 species ranged between 25-44 °C and 35-48 °C, and for 1 CAM and 4 C4 species were 41-47 and 45-46 °C, respectively. Acclimating three C3 herbaceous plants at high temperature (33/28 °C, day/night) for 10 d in winter caused their Tc's rising to nearly the values measured in summer. When leaves were exposed to 45 °C for 20 min and then kept at room temperature in darkness for 1 h, a significant correlation between RFv/m (the ratio of Fv/Fm before and after 45 °C treatment) and Tc was observed for all tested temperate-origin C3 species as well as tropical-origin CAM and C4 species. However, F0 and Fv/Fm of the tropical-origin C3 species were less sensitive to 45 °C treatment, regardless of a large variation of Tc; thus no significant correlation was found between their RFv/m and Tc. Thus Tc might not be a suitable index of heat tolerance for plants with wide range of environmental adaptation. Nevertheless, Tc's of tropical origin C3 species, varying and showing high plasticity to seasonal changes and temperature treatment, appeared suitable for the estimation of the degree of temperature acclimation in the same species. and J.-H. Weng, M.-F. Lai.
The paper by Jarušková and Hanek (2006) advocated application of the peaks over threshold method (POT method) for estimating the probability that a precipitation or discharges series exceeds a chosen high level. If daily precipitation amounts or average discharges are obtained at several stations one might be interested in estimating the probability that in the same time all variables of interest, e.g. precipitation amounts measured at several stations, exceed some chosen high levels. The paper explains how the method based on the point process approach may be used to get good estimates of such probabilities. Moreover, it presents some useful parametric models that were successfully applied by the author to some precipitation and discharges series of northern Moravia. and Článek navazuje na práci Jarušková, Hanek (2006), kde autoři doporučovali používání metody špiček nad prahem k odhadu pravděpodobností, s jakou srážková nebo průtoková řada překročí danou vysokou úroveň. V případě, že se denní srážková či průtoková řada měří ve více stanicích, může nás zajímat, s jakou pravděpodobností současně (to znamená ve stejný den) všechny studované řady, to je například srážkové řady měřené v několika stanicích, překročí nějaké předem stanovené vysoké úrovně. Článek vysvětluje, jak lze k odhadu takových pravděpodobností použít metodu založenou na bodovém procesu. Zároveň uvádí některé parametrické modely, které byly úspěšně použity autorkou článku pro odhady pravděpodobností překročení pro srážkové a průtokové řady na severní Moravě.
An empirical mode decomposition (EMD) model for BeiDou Navigation Satellite System (BDS) code bias has been established upon the observation model of multiple global navigation satellite systems (multi-GNSS). To validate the correctness and effectiveness of the model, seven days from day of year (DOY) 213-219, 2015 from eight Multi-GNSS Experiment (MGEX) stations were processed. Results show that after code bias correction, the standard deviation of the multipath combination (MP) series on B1 and B2 frequencies decreased by 38.63 % and 17.4 %, respectively. The timespan needed for convergence in BDS precise point positioning (PPP) was improved by 7.9 % after inclined geosynchronous orbit (IGSO) and medium earth orbit (MEO) code bias correction, and another improvement of 11.4 % was generated by applying geostationary orbit (GEO) code bias correction. Despite the improvement of convergence time, the accuracy of the single-day solution barely increased for PPP in multi-GNSS as compared to the single GNSS. A continuous decrease in percentage along with prolonged timespan for PPP convergence was observed with increasing cut-off elevation angle. However, the performance of multi-GNSS PPP, which was superior to that of the single GNSS, shows that it is extremely valuable for practical applications in mountainous or sheltered areas.
One of the basic estimation problems for continuous time stationary processes Xt, is that of estimating E{Xt+β|Xs:s∈[0,t]} based on the observation of the single block {Xs:s∈[0,t]} when the actual distribution of the process is not known. We will give fairly optimal universal estimates of this type that correspond to the optimal results in the case of discrete time processes.
The need for continuous recording rain gauges makes it difficult to determine the rainfall erosivity factor (Rfactor) of the Universal Soil Loss Equation in regions without good spatial and temporal data coverage. In particular, the R-factor is only known at 16 rain gauge stations in the Madrid Region (Spain). The objectives of this study were to identify a readily available estimate of the R-factor for the Madrid Region and to evaluate the effect of rainfall record length on estimate precision and accuracy. Five estimators based on monthly precipitation were considered: total annual rainfall (P), Fournier index (F), modified Fournier index (MFI), precipitation concentration index (PCI) and a regression equation provided by the Spanish Nature Conservation Institute (RICONA). Regression results from 8 calibration stations showed that MFI was the best estimator in terms of coefficient of determination and root mean squared error, closely followed by P. Analysis of the effect of record length indicated that little improvement was obtained for MFI and P over 5- year intervals. Finally, validation in 8 additional stations supported that the equation R = 1.05·MFI computed for a record length of 5 years provided a simple, precise and accurate estimate of the R-factor in the Madrid Region.
The probability density function of the stochastic cusp model belongs to the class of generalized exponential distributions. It accommodates variable skewness, kurtosis, and bimodality. A statistical test for bimodality of the stochastic cusp model using the maximum likelihood estimation and delta method for Cardan's discriminant is introduced in this paper, as is a necessary condition for bimodality, which can be used for simplified testing to reject bimodality. Numerical maximum likelihood estimation of the cusp model is simplified by analytical reduction of the parameter space dimension, and connection to the method of moment estimates is shown. A simulation study is used to determine the size and power of the proposed tests and to compare pertinence among different tests for various parameter settings.
The molten reactor core-concrete interaction, which describes the effect of molten reactor spread on the concrete oor of the reactor cavity, is a very complex process to simulate and predict, but the knowledge of this process is of major importance for planning the emergency counteractions for severe accidents with respect to the Stress Tests requirements after the Fukushima-Daiichi accident. The key issue is to predict the rate and most probable focusation of the melt-through process which is affected by the concrete composition, especially by the aggregate type. A limited number of small-scale experiments have been conducted over the past years along with accompanying numerical models which focused mainly on the siliceous type of aggregate. It is common for the concrete structures that the limestone type or the mixture of these two types of aggregate are used as well. Then, the objective of this paper is to extend the knowledge gained from the experiments with the siliceous aggregate to the concrete structures which are made of limestone aggregate or their combination, such as limestone sand and siliceous gravel. The proposed one-dimensional model of the melt-through process is based on the fuzzy-logic interpretation of the thermodynamic trends which reflect the aggregate type. This approach allows estimating the asymptotic cases in terms of the melt-through depth in the concrete oor over time with respect to the aggregate type, which may help to decide the rather expensive further experimental efforts.
There is an overlap of carrier-mediated L-amino acid transport and apparent simple diffusion when measured in intestinal brush border membrane vesicles. Using L-threonine and L-glutamine as representative amino acids, this study was undertaken to estimate apparent simple diffusion of L-amino acids and to establish the effective dosage of HgCl2 for completely blocking carrier-mediated L-amino acid transport in porcine jejunal enterocyte brush border membrane vesicles. Jejunal mucosa was scraped from three pigs weighing 26 kg. Enterocyte brush border membrane vesicles, with an average enrichment of 24-fold in sucrase specific activity, were prepared by Mg2+-precipitation and differential centrifugation. In vitro uptake was measured by the fast filtration manual procedure. HgCl2 blocked the carrier-mediated initial transport of L-threonine and L-glutamine under Na+-gradient condition in a dose-dependent manner. At the minimal concentration of 0.165 mmol HgCl2 mg-1 protein, carrier-mediated L-threonine and L-glutamine transport was completely inhibited. The apparent L-threonine and L-glutamine diffusion was estimated to be 8.6±0.7 and 12.4±1.0 % of the total uptake at the substrate concentrations of 5 mM (L-threonine) and 50 mM (L-glutamine). Therefore, the treatment of porcine brush border membrane vesicles with a minimum of 0.165 mmol HgCl2 mg-1 protein completely blocks carrier-mediated L-amino acid transport and enables the direct estimation of apparent L-amino acid diffusion in enterocyte brush border membrane vesicles., M. Z. Fan, O. Adeola, E. K. Asem., and Obsahuje bibliografii
The Sacramento soil moisture-accounting model has been used to simulate the discharges of a major catchment (Pra river basin) in southern Ghana. Through the simulation it was possible to assess the temporal variability of evapotranspiratio, base flow proportions and groundwater in storage, as well as the average groundwater recharge to the weathered aquifers. Groundwater recharge was estimated by considering the measured discharge of groundwater across the boundary of the basin over periods of equivalent storage, to be equal to the net recharge inside the catchment. The direct groundwater recharge rate over the basin of area 22,836 km2 amounted to an annual average of 50 mm. This represented 4 % of mean annual rainfall of 1300 mm, giving natural groundwater resources potential of 1.6 l s-1 km-2. For regional groundwater resources assessment, the results obtained could be applied to other river basins in southwest Ghana. and Použitím SAC-SMA modelu byly simulovány odtoky z povodí řeky Pra v jižní části Ghany. Tímto bylo možno odhadnout časové tměny evapotranspirace, podzemního odtoku a zásoby podzemní vody, i průměrné doplňování podzemní vody do zvětralé zóny hydrogeologických kolektorů. Doplňování podzemní vody bylo stanoveno s uvážením měřených odtoků podzemní vody přes hranice povodí tak, aby se v obdobích stejné zásoby rovnaly výslednému doplňování uvnitř infiltrační oblasti. Roční průměr přirozeného doplňování podzemní vody v povodí s plochou 22 836 km2 činilo 50 mm. To odpovídá 4 % ročního průměru srážky (1300 mm) a 1,61 s-1 km-2 specifického odtoku podzemní vody. Dosažené výsledky mohou být aplikovány na další povodí v jihozápadní Ghaně pro regionální odhad zásoby podzemní vody.