Experimental measurement is performed on a simple fibre-mass system: a moving mass coupled with the frame by a fibre. Dynamic response of the mass is measured. The same system is numerically investigated by means of a simple multibody model. The influence of the model parameters on the coincidence of results of experimental measurements and of simulations are evaluated. The simulations aim is to create a phenomenological model of a fibre, which will be utilizable in fibre modelling in the case of more complicated mechanical or mechatronic systems. and Obsahuje seznam literatury
Water deficit is one of the major limiting factors in vegetation recovery and restoration in loess, hilly-gully regions of China. The light responses of photosynthesis in leaves of two-year old Prunus sibirica L., Hippophae rhamnoides L., and Pinus tabulaeformis Carr. under various soil water contents were studied using the CIRAS-2 portable photosynthesis system. Light-response curves and photosynthetic parameters were analyzed and fitted using the rectangular hyperbola model, the exponential model, the nonrectangular hyperbola model, and the modified rectangular hyperbola model. Under high light, photosynthetic rate (PN) and stomatal conductance (gs) were steady and photoinhibition was not significant, when the relative soil water content (RWC) varied from 56.3-80.9%, 47.9-82.9%, and 33.4-92.6% for P. sibirica, H. rhamnoides, and P. tabulaeformis, respectively. The light-response curves of PN, the light compensation point (LCP), and the dark respiration rate (RD) were well fitted using the above four models. The nonrectangular hyperbola was the best model in fitting the data; the modified rectangular hyperbola model was the second, and the rectangular hyperbola model was the poorest one. When RWC was higher or lower than the optimal range, the obvious photoinhibition and significant decrease in PN with increasing photosynthetic photon flux density (PPFD) were observed in all three species under high light. The light saturation point (LSP) and apparent quantum yield also decreased significantly, when the upper limit of PPFD was 200 μmol m-2 s-1. Under these circumstances, only the modified rectangular hyperbola model was able to fit well the curves of the light response, LCP, LSP, RD, and light-saturated PN. and Y. Lang ... [et al.].
Oscillations in many of photosynthetic quantities with a period of about 1 min can be routinely measured with higher plant leaves after perturbation of the steady state by sudden change in gas phase. Among all hypotheses suggested so far to explain the oscillations, an effect of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activation status to control the oscillations is highly probable, at least upon high temperature (HT) treatment when in vivo RuBPCO activity controlled by RuBPCO activase (RuBPCO-A) decreases. Therefore, we measured the oscillations in fluorescence signal coming from barley leaves (Hordeum vulgare L. cv. Akcent) after their exposure for various time intervals to different HTs in darkness. We also evaluated steady state fluorescence and CO2 exchange parameters to have an insight to functions of electron transport chain within thylakoid membrane and Calvin cycle before initiation of the oscillations. The changes in period of the oscillations induced by moderate HT (up to 43 °C) best correlated with changes in non-photochemical fluorescence quenching (qN) that in turn correlated with changes in gross photosynthetic rate (PG) and rate of RuBPCO activation (kact). Therefore, we suggest that changes in period of the oscillations caused by moderate HT are mainly controlled by RuBPCO activation status. For more severe HT (45 °C), the oscillations disappeared which was probably caused by an insufficient formation of NADPH by electron transport chain within thylakoid membrane as judged from a decrease in photochemical fluorescence quenching (qP). Suggestions made on the basis of experimental data were verified by theoretical simulations of the oscillations based on a model of Calvin cycle and by means of a control analysis of the model. and D. Lazár ... [et al.].
This article deals with determining the size of linear wear of acetabulum of total hip endoprosthesis by experimental modelling. The creation of an experimental sample and the equipment to simulate human walking are described in detail. The greatest attention is paid to the method form determining the topography of polyethylene cup and measuring of the loss of polyethylene during the simulation of walking. Holographic interferometry was selected to determine the loss of polyethylene cup on the basis of extensive analysis. Further parts of the article focus on first experience with the application of this method results and other possibilities. and Obsahuje seznam literatury
The paper describes results of experiments with rotating spherical particles moving in water. Rubber spherical balls with the density close to that of water were speeded up in a special inclined chute that ensured the required particle rotational and translational velocity in the given plane. A standard video system was used to capture particle trajectory and the evaluation was focused on the effects of two dimensionless parameters of the particle motion, Reynolds number and rotational Reynolds number. The values of the drag force and drag torque coefficients were determined from the experimental data and compared with the results of the numerical simulation of the particle motion. Relationships describing the above mentioned quantities, taking into account the mutual influence of the translational and the rotational particle movements and convenient for numerical models were found. and V příspěvku jsou prezentovány výsledky experimentálního výzkumu pohybu rotující kulovité částice ve vodě. Kulovitá částice vyrobená z gumy o hustotě blízké hustotě vody byla uvedena do pohybu v šikmé štěrbině, kde získala rotační i translační rychlost v osové rovině štěrbiny. Trajektorie částic ve vodě byly snímány standardní video kamerou a byl vyhodnocen vliv dvou bezrozměrných parametrů (Reynoldsova čísla a rotačního Reynoldsova čísla) na pohyb částice. Z experimentálních údajů byly určeny hodnoty odporového koeficientu a odporového momentu částice a tyto hodnoty byly porovnány s výsledky numerické simulace pohybu částice. Byly vyhodnoceny vztahy vhodné pro využití při numerickém modelování a popisující vzájemné závislosti výše uvedených veličin a vzájemný vliv translačního a rotačního pohybu částice.
The life cycle of marine Eubothrium sp. (Cestoda: Pseudophyllidea), from Atlantic salmon (Salmo salar L.) was experimentally completed in one year and included only one intermediate host (Acartia tonsa Dana) (Copepoda: Calanoida). Adult cestodes were collected from farmed salmon, and ripe eggs released by the cestodes were fed to Acartia tonsa. Ingested eggs hatched in the gut and the larvae developed in the haemocoel of the copepod for 15 days at 16°C. A total of 170 seawater-reared salmon were exposed to infected copepods and the total prevalence of Eubothrium sp. in the salmon after infection was 95.3%, with a mean intensity of 15.0 (range 1-87). The infected salmon were kept in the laboratory where the growth of the cestodes was studied for eleven months. Mean length of the cestodes increased with time, but a large variation among the cestodes was observed. Growth and maturation of the cestodes were dependent on host size and the number of worms present in the intestine. No evidence of mortality of Eubothrium sp. was observed during the experimental period.
An experimental infection with the microsporidian Encephalitozoon cuniculi Levaditi, Nicolau et Schoen, 1923 was studied using a model of immunocompetent BALB/c mice and immunodeficient SCID mice. The course of infection after intraperitoneal inoculation of E. cuniculi spores was evaluated using the presence of spores in peritoneal macrophages as a criterion. First significant decrease in the proportion of infected cells was recorded on day 9 post infection (p.i.) in BALB/c mice. From day 14 p.i. no spores were observed in macrophages from BALB/c mice, while the number of infected macrophages from SCID mice increased until the death of the mice. The natural killer (NK) cell activity of mouse splenocytes was compared with the production of interferon gamma (IFN-γ) by these cells. While in BALB/c mice NK activity peaked on days 9 and 14 p.i., in SCID mice the marked increase of NK activity was recorded close before death of mice, on day 21 p.i. in correlation with the production of IFN-γ. Production of specific antibodies was demonstrated from day 9 p.i. in sera from BALB/c mice. It is concluded that intraperitoneal infection of SCID mice with spores of E. cuniculi results in the marked increase in the number of peritoneal exudate cells and in the percentage of infected cells close before death of mice. Neither high activity of NK cells nor increased production of IFN-γ are sufficient for the recovery of SCID mice from an E. cuniculi infection.
In the paper, the authors refer to measurement of a car cabin heat load and indoor environment during driving in real traffic conditions. The primary aim was to obtain data for boundary conditions, model testing and results comparison of the 1D car cabin heat load model. The secondary aim was better understanding of cabin environment inside a car cabin under different operational conditions. As test vehicle Škoda Felicia Combi with dark blue painting was used and GPS data, parameters of ventilation, cabin environnment and ambient environment were measured. Measurements were preformed for summer, autumn and winter conditions including parking and driving test circuits around Brno. Driving circuit included driving in the city, out of the city and on the highway D1. and Obsahuje seznam literatury
The effect of solid concentration and mixture velocity on the flow behaviour, pressure drops, and concentration distribution of coarse particle-water mixtures in horizontal, vertical, and inclined smooth stainless steel pipes of inner diameter D = 100 mm was experimentally investigated. Graded basalt pebbles were used as solid particles. The study revealed that the coarse-grained particle-water mixtures in the horizontal and inclined pipes were significantly stratified. The solid particles moved principally in a layer close to the pipe invert; however for higher and moderate flow velocities, particle saltation became the dominant mode of particle conveyance. Frictional pressure drops in the horizontal pipe were found to be markedly higher than in the vertical pipe, while the frictional pressure drops in the ascending pipe increased with inclination angle up to about 30°.
For the safe and economical design and operation of freight pipelines it is necessary to know slurry flow behaviour in inclined pipe sections, which often form significant part of pipelines transporting solids. Fine-grained settling slurry was investigated on an experimental pipe loop of inner diameter D = 100 mm with the horizontal and inclined pipe sections for pipe slopes ranging from –45° to +45°. The slurry consisted of water and glass beads with a narrow particle size distribution and mean diameter d50 = 180 μm. The effect of pipe inclination, mean transport volumetric concentration, and slurry velocity on flow behaviour, pressure drops, deposition limit velocity, and concentration distribution was studied. The study revealed a stratified flow pattern of the studied slurry in inclined pipe sections. Frictional pressure drops in the ascending pipe were higher than that in the descending pipe, the difference decreased with increasing velocity and inclination. For inclination less than about 25° the effect of pipe inclinations on deposition limit velocity and local concentration distribution was not significant. For descending pipe section with inclinations over –25° no bed deposit
was observed.