This study addresses a particular phenomenon in open channel flows for which the basic assumption of hydrostatic pressure distribution is essentially invalid, and expands previous suggestions to flows where streamline curvature is significant. The proposed model incorporates the effects of the vertical curvature of the streamline and steep slope, in making the pressure distribution non-hydrostatic, and overcomes the accuracy problem of the Saint-Venant equations when simulating curvilinear free surface flow problems. Furthermore, the model is demonstrated to be a higher-order one-dimensional model that includes terms accounting for wave-like variations of the free surface on a constant slope channel. Test results of predicted flow surface and pressure profiles for flow in a channel transition from mild to steep slopes, transcritical flow over a short-crested weir and flow with dual free surfaces are compared with experimental data and previous numerical results. A good agreement is attained between the experimental and computed results. The overall simulation results reveal the satisfactory performance of the proposed model in simulating rapidly varied gravity-driven flows with predominant non-hydrostatic pressure distribution effects. This study suggests that a higher-order pressure equation should be used for modelling the pressure distribution of a curvilinear flow in a steeply sloping channel.
Understanding mitochondrial role in normal physiology and pathological conditions has proven to be of high importance as mitochondrial dysfunction is connected with a number of disorders as well as some of the most common diseases (e.g. diabetes or Parkinson’s disease). Modeling mitochondrial dysfunction has been difficult mainly due to unique features of mitochondrial genetics. Here we discuss some of the most important mouse models generated so far and lessons learned from them., S. A. Dogan, A. Trifunovic., and Obsahuje bibliografii a bibliografické odkazy
Winter wheat plants were grown in open top chambers either at 365 µmol mol-1 (AC) or at 700 µmol mol-1 (EC) air CO2 concentrations. The photosynthetic response of flag leaves at the beginning of flowering and on four vertical leaf levels at the beginning of grain filling were measured. Net photosynthetic rates (PN) were higher at both developmental phases in plants grown at EC coupled with larger leaf area and photosynthetic pigment contents. The widely accepted Farquhar net photosynthesis model was parameterised and tested using several observed data. After parameterisation the test results corresponded satisfactorily with observed values under several environmental conditions. and N. Harnos, Z. Tuba, K. Szente.
One of the key indicators of the quality of service for urban transportation control systems is the queue length. Even in unsaturated conditions, longer queues indicate longer travel delays and higher fuel consumption. With the exception of some expensive surveillance equipment, the queue length itself cannot be measured automatically, and manual measurement is both impractical and costly in a long term scenario. Hence, many mathematical models that express the queue length as a function of detector measurements are used in engineering practice, ranging from simple to elaborate ones. The method proposed in this paper makes use of detector time-occupancy, a complementary quantity to vehicle count, provided by most of the traffic detectors at no cost and disregarded by majority of existing approaches for various reasons. Our model is designed as a complement to existing methods. It is based on Gaussian-process model of the occupancy-queue relationship, it can handle data uncertainties, and it provides more information about the quality of the queue length prediction.
A fully preserved 14th-century AD bloomery furnace was excavated in 2014 on the settlement of Kolesovka-4 (Russia, Tula district). This extraordinary find has been taken as a model for experimental work. The iron ore used came from the Loknya River, a metallurgical conglomerate used came from the archaeological site of Staraya Ryazan. The most successful result was achieved by using the conglomerate from Staraya Ryazan – three pieces of blooms were made, weighing about 1 kg, and consisting of soft iron and a large number of very coarse slag inclusions. These show a similar trace-element composition as the medieval bloom coming from the same site. Experiments conducted have shown that the bloomery furnace uncovered at the Kolesovka-4 settlement is a rational pyrotechnological construction, allowing for a large number of smelting cycles. and V roce 2014 byla na sídlišti Kolesovka-4 (Rusko, okres Tula) odkryta plně zachovaná železářská pec ze 14. stol. n. l. Tento mimořádný nález posloužil jako model pro experimentální práce. Použitá železná ruda pochází z řeky Loknja, použitý metalurgický konglomerát pak z archeologické lokality Stará Rjazaň. Nejlepšího výsledku bylo dosaženo použitím konglomerátu ze Staré Rjazani – získány byly tři kusy železné houby vážící asi 1 kg a sestávající z měkkého železa a velkého množství velmi hrubých struskových vměstků. Ty vykazují podobné složení stopových prvků jako železná houba pocházející z té samé lokality. Provedené pokusy ukázaly, že redukční pec odkrytá na sídlišti Kolesovka-4 je racionální pyrotechnologické zařízení umožňující řadu výrobních cyklů.
The paper presents a simple box model simulating the temporal variation of atmospheric 13CO2 concentration, atmospheric CO2 mixing ratio and 13C content of plant material. The model is driven by observed meteorological and measured biosphere-atmosphere CO2 exchange data. The model was calibrated and validated using measurements from a Hungarian atmospheric monitoring station. The simulated atmospheric stable carbon isotope ratio data agreed well with the measured ratios considering both the magnitude and the seasonal dynamics. Observed deviations between the measured and simulated δ13Cair values were systematically negative in winters, while deviations were random in sign and smaller by an order of magnitude during periods when the vegetation was photosynthetically active. This difference, supported by a significant correlation between the deviation and modeled fossil fuel contributions to CO2 concentration, suggests the increased contribution of 13C-depleted fossil fuel CO2 from heating and the lower boundary layer heights during winter. and D. Hidy ... [et al.].
The paper presents cellular automata as a promising modeling approach to simulate the diffusion process as a 2D task. The proposed methodology is applied to the degradation assessment of civil engineering structures describing more realistically the spatial and temporal variability of harmful substance ingress (e.g. chloride ions in concrete). Some illustrative examples are presented together with an example of application to a particular bridge. and Obsahuje seznam literatury
Computer support of design activities within precision devices speeds up achieving proper technical solutions, makes documentation to be developed more easily and reduces risk of making errors. Computer simulation of operation of devices being designed plays a significant role in this process. Besides performance characteristics of the device determined this way it also seems to be important to predict analytically other kinds of product characteristics i.e. reliability and availability. A concept of modelling of electrical drive systems for precision devices, verified along the years there is presented in the paper. It seems to be convenient from the point of view of designer. A proposal to utilise simulation results for better prediction of the device reliability is added. and Obsahuje seznam literatury
The paper presents the basic assumptions and relations for underlying the solution of ground water flow using an integral equations method. The basic laws of physics used for this solution are briefly introduced. The mathematical model describes the flow in a saturated domain both for the spatial and the plane problems. The principal parts of the numeric solution of the problem are treated in more detail. To provide an example of an application, a simple model of a dike is presented. For a homogeneous, isotropic dike the solution describes the development of the flow with time and the corresponding changes to the free surface of ground water. The resulting steady-state flow through the dike is compared with the published results (Polubarina-Kočina, 1952). Another example describes the flow through an nonhomogeneous, isotropic dike if a variable hydraulic conductivity depends on the geometric height. Singularities distributed within the domain are used for an iterative solution of the nonlinear partial differential equation describing the ground water flow. and Příspěvek uvádí základní předpoklady a vztahy pro řešení proudění podzemní vody metodou integrálních rovnic. Stručně jsou uvedeny základní fyzikální zákony potřebné pro řešení. Matematický model popisuje proudění v nasycené oblasti jak pro prostorovou, tak i pro rovinnou úlohu. Podrobněji jsou probrány hlavní části numerického řešení problému. Příkladem aplikace je jednoduchý model hráze. Řešení sleduje vývoj proudění v čase a odpovídající změny volné hladiny podzemní vody pro homogenní isotropní hráz. Výsledný ustálený stav proudění hrází je porovnán s výsledky publikovanými v literatuře (Polubarina-Kočina, 1952). Další příklad popisuje proudění nehomogenní isotropní hrází se součinitelem filtrace proměnným v závislosti na geometrické výšce. Pro iterační řešení nelineární parciální diferenciální rovnice proudění podzemní vody jsou využity singularity rozložené uvnitř oblasti.
The paper deals with determination of the effect of newly built driven road tunnels within the capital city of Prague on the groundwater flow pattern and groundwater table position. In order to assess the changes in groundwater flow in the vicinity of these underground structures, a numerical model was used. Despite the three-dimensional nature of groundwater flow in the vicinity of tunnel structures, under certain conditions the flow may be simulated as two-dimensional flow in a vertical plane. This plane’s direction corresponds to the prevailing direction of groundwater flow, and runs perpendicular to the tunnel tubes’ axis. The used numerical model is based on the equation of two-dimensional steady groundwater flow with free surface in a non-homogeneous anisotropic porous domain. The effect of tunnels on groundwater flow was subject of research in several versions considering different conditions before, during and after the construction of the tunnel structures. The results of numerical modelling have been assessed by means of piezometric head isolines, trajectories, hydraulic head values and seepage values. and Příspěvek se zabývá stanovením vlivu nově budovaných ražených silničních tunelů v oblasti hlavního města Prahy na režim proudění podzemních vod a na polohu hladiny podzemní vody. Pro ohodnocení změn proudění podzemní vody v okolí těchto podzemních staveb byl použit numerický model. Ačkoliv je proudění podzemní vody v okolí tunelových děl třírozměrné, je možné za určitých předpokladů simulovat proudění jako dvourozměrné ve svislé rovině. Tato rovina má směr odpovídající převládajícímu směru proudění podzemní vody a je vedena kolmo na osu tunelových trub. Použitý numerický model vychází z rovnice dvourozměrného ustáleného proudění podzemní vody s volnou hladinou v nehomogenním anizotropním porézním prostředí. Vliv tunelů na proudění podzemní vody byl zkoumán v několika variantách zohledňujících rozdílné podmínky před výstavbou, v průběhu výstavby a po výstavbě tunelových děl. Výsledky numerického modelování jsou vyhodnoceny pomocí izočar piezometrické výšky, trajektorií, hodnot hydraulických gradientů a velikostí průsaků.