Management of reservoirs for drinking water supply should be based on a thorough knowledge of water quality changes within variable conditions of hydrology, climate, nutrient loading and water storage. The two-dimensional longitudinal water quality model CE-QUAL-W2 was tested for its ability to predict concentrations of organic matter and trophic conditions in Rimov Reservoir, a small dimictic reservoir (volume 33,000,000 m3, maximum depth 43 m, hydraulic retention time 40 to 160 d) suffering from seasonally increased concentrations of humic substances and symptoms of eutrophication. The model was calibrated on two seasonal courses differing in hydrology and validated on a 1074 day period. The averages of absolute mean errors between simulated and measured vertical profiles of temperature, and concentrations of dissolved organic matter, dissolved oxygen and chlorophyll a in the validation run were 0.9 °C, 0.8 mg l-1, 1.2 mg l-1 and 0.008 mg l-1, respectively. Analysis of results and sensitivity analysis of modelling phytoplankton and phosphorus showed suitability of the mathematical description of their dynamics in the photic zone but not in the deeper layers. In spite of this partial problem, the model was found appropriate for the reliable predictions of water quality dynamics in Rimov Reservoir. and Hospodaření s vodou ve vodárenských nádržích by mělo být založeno na podrobné znalosti vlivu hydrologických, klimatických a limnologických veličin na kvalitu vody. Možnosti matematického modelování změn kvality vody byly testovány pro nádrž Římov na Malši za pomoci dvourozměrného modelu kvality vody CE-QUAL-W2. Model byl zkalibrován na dvou sezónních řadách dat pro hydrologicky různá období a poté byl uplatněn na 1074-denní řadě dat. Byly vyhodnoceny rozdíly mezi měřenými a simulovanými vertikálními profily teploty, koncentrací rozpuštěných organických látek, rozpuštěného kyslíku a chlorofylu. Tyto rozdíly vyjádřené jako velikost absolutní střední chyby byly 0,9 °C, 0,8 mg l-1 , 1,2 mg l-1 a 0.008 mg l-1 . Analýza získaných výsledků a citlivostní analýza modelu ukazují dobrou shodu mezi naměřenou a simulovanou dynamikou zmíněných veličin v eufotické zóně, v nižších a tmavších vrstvách nádrže dochází k nárůstu odchylek modelu od reality. Přes tyto dílčí problémy byl model shledán jako užitečný a nenahraditelný pomocník při úlohách řešících dopad vnějších vlivů na kvalitu vody v nádrži.
Presented work concerns with a sensitivity analysis of a harmonically excited bending vibration of a rotating couple of blades with a friction element with regard to the parameters of the friction characteristic. Either of the blades is discretized by FEM using beam elements and continuously distributed weight is concentrated in nodal points. The friction in central contact points between blade shrouds and the friction element is approximated by a continuous function depending on slip velocities of the shrouds relative to the friction element. Considered friction characteristic respects the micro-slip phase at the very low slip velocities and the macro-slip (full-slip) phase at the higher slip velocities. The values of the friction characteristic parameters are identified by comparison of the numerical simulations of a transient vibration with experiments used in IT AS CR. and Obsahuje seznam literatury
Operation of railway vehicles at higher speeds is conditioned by assurance of a stable run of the vehicle in straight track with a high level of geometric parameters. This property is usually reached by retrofitting of a joint between the vehicle body and the bogies with an efficient damping with suitable characteristics. As the relative motion between the vehicle body and the bogies in the straight track shows low amplitudes and high velocities, special longitudinal dampers - so-called yaw dampers - are used for these purposes. The aim of this paper is a theoretical analysis of influence of yaw dampers characteristics on the stability limit of a locomotive performed by means of sensitivity analysis. and Obsahuje seznam literatury
Basic methods of the sensitivity analysis applicable in combination with numerical Monte Carlo type simulation methods are presented in the paper. An example of the influence of a plane steel fame initial imperfections on its load-carrying capacity variability is given there. It is shown in this paper that basic sensitivity analysis methods can be inaccurate in some cases. The updated modification of the procedures mentioned is proposed so that it were possible to apply them to the most various structure types solved by means of simulation methods. The influence of initial imperfections on the load-carrying capacity of steel plane frame is analysed by auxiliary sensitivity analysis. The realisations of input random quantities were simulated by the Latin Hypercube Sampling method. The load-carrying capacity was solved by geometrically and materially nonlinear solution. and Obsahuje seznam literatury
Mathematical modelling is shown as an efficient tool for studying the behaviour of reservoir ecosystems. Two mathematical models, namely ASTER and DYRESM-WQ and their characteristic features are described. The parameters of both models and their values used for simulation of reservoir Rimov are presented. Sensitivity analysis for both models was performed in the scope to demonstrate the sensitivity of simulation results to the parameter changes. The simulation results were compared to the measurements in situ with satisfying accuracy. The suitability of application of both models on the food web simulation of valley reservoirs is discussed. and Článek ukazuje matematické modelování jako účinný prostředek pro studium chování ekosystémů údolních nádrží. Popisuje dva matematické modely, a to ASTER a DYRESM-WQ, a jejich charakteristické rysy. Podrobně jsou ukázány parametry obou modelů a rovněž jejich hodnoty, jichž bylo použito k simulaci údolní nádrže Římov. Pomocí citlivostní analýzy byla zjištěna u obou modelů velikost odezvy systému na změny některých parametrů. Porovnání výsledků simulací s hodnotami naměřenými v nádrži ukazuje dostatečnou přesnost matematického modelování. V závěru je diskutována vhodnost použití matematického modelování pro simulaci potravního řetězce v údolních nádržích.
This paper introduces a new sensitivity analysis method using nonsupervised neural nets, based on the Adaptive Resonance Theory (ART).This new method introduces the possibility of a sensitivity analysis being adaptive and being conducted at the saine tirne as net learning is taking place, taking advantage of the property of continuous (as opposed to phase-wise) learning of ART models. A sensitivity analysis can be conducted likewise, i.e. continuous by and capably adapting to any new relationships appearing among the input data. The method has been validated in the field of feature detection for iniage classification and, more specifically, for face recognition.
Summary: By means of analytical relations the influences of orbital errors (along-track, accross-track and radial component) on the range, range-difference, and range-rate measurements were studied and compared. In a similar manner the design matrices for the determination of pole coordinates and variation of earth rotation by means of these measurements were discussed.
The aim of the paper is to show the influence of design parameters on the suppression of rotating blade vibration. The derivation of nonlinear mathematical model of a blade couple mutually connected by a friction element is summarized. After that, the linearization of the mathematical model is performed by harmonic balance method. The linearized model is used for sensitivity analysis of real and imaginary parts of eigenvalues in the course of rotation and sensitivity analysis of stead-state response with respect to the design parameters of internal friction coupling. and Obsahuje seznam literatury
With the gradual increase of coal mining intensity, many coal pillars need to be left near the stope. The stability of the composite structure of coal pillars and their overlying strata determines the safety of the whole stope and the surface. This paper conducts uniaxial compression tests on coal-rock composite structures with the same lithology and the same coal-rock height ratio and finds the coal-rock composite structure’s mechanical properties and failure characteristics have greater discreteness. Combining the CT images of rock and coal, it is concluded that the main reason for the discreteness of the composite structure test results is the different crack characteristics in the rock specimen and the coal specimen. Therefore, this paper uses the PFC numerical simulation software to analyzes the influence of the crack characteristics on the mechanical properties, failure characteristics, and impact energy index of the coal-rock composite structure. The sensitivity factors are used to analyze the influence of crack angle, crack length, crack number and crack position on the peak stress, total crack number, and impact energy index of the coal-rock composite structure. The research results can provide a theoretical basis and guidance for preventing the instability and failure of the coal pillar-roof composite structure.
A one-dimensional dual-continuum model (also known as dual-permeability model) was used to simulate the lateral component of subsurface runoff and variations in the natural 18O content in hillslope discharge. Model predictions were analyzed using the GLUE generalized likelihood uncertainty estimation procedure. Model sensitivity was evaluated by varying two separate triplets of parameters. The first triplet consisted of key parameters determining the preferential flow regime, i.e., the volumetric proportion of the preferential flow domain, a first-order transfer coefficient characterizing soil water exchange between the two flow domains of the dual-continuum system, and the saturated hydraulic conductivity of the preferential flow domain. The second triplet involved parameters controlling exclusively the soil hydraulic properties of the preferential flow domain, i.e., its retention curve and hydraulic conductivity function. Results of the analysis suggest high sensitivity to all parameters of the first triplet, and large differences in sensitivity to the parameters of the second triplet. The sensitivity analysis also confirmed a significant improvement in the identifiability of preferential flow parameters when 18O content was added to the objective function. and K simulacím laterální složky podpovrchového proudění a změn koncentrace izotopu kyslíku 18O ve vodě vytékající ze svahu byl použit jednorozměrný model využívající přístupu duálního kontinua. Nejistota modelových předpovědí byla odhadnuta s využitím metody zobecněné věrohodnosti (GLUE). Citlivost modelu byla zjišťována pomocí variací dvou samostatných trojic parametrů. První trojice sestávala z klíčových parametrů pro určení režimu preferenčního proudění, tj. objemového podílu preferenční domény proudění, přenosového koeficientu charakterizujícího výměnu vody mezi oběma doménami duálního systému a nasycené hydraulické vodivosti preferenční domény. Druhá trojice zahrnovala výhradně parametry určující hydraulické charakteristiky preferenční domény proudění, tj. retenční křivku a funkci hydraulické vodivosti. Z výsledků analýzy vyplývá vysoká citlivost modelu na všechny parametry z první trojice a velké rozdíly v citlivostech parametrů druhé trojice. Analýza dále potvrdila významné zlepšení zjistitelnosti parametrů preferenční domény v případě, kdy je do cílové funkce přidána koncentrace izotopu kyslíku 18O.