The paper deals with selected procedures used to calculate the shape of compact nappe during free overfall from a smooth horizontal channel with rectangular cross section. Calculated and measured water surface and velocity conditions in the end section, the level of water surface upstream in front of the end section and the shape of the compact part of an overfall nappe are described for a particular compared case.
In this study shape optimization of fibers in composite fiber reinforced structure is presented. The problem targets the optimal shape with respect to the maximum bearing capacity and the minimum deformation of the whole composite set up. The shape is constrained by a constant volume (area) ratio. The optimization includes a process of seeking the overall properties of composites, i.e. localization and homogenization. Since no a priori estimate of the shape of fibers is known, numerical tool, finite element method, is employed. Such a problem is important in a wide range of applications, prevailingly in fiber reinforced concrete assessment, biomechanics, biophysics, and in the mechanics of classical composites with epoxy matrix. Since many types of fibers are used in various fiber reinforced concretes (fibers from polypropylene, steel, glass, clay, basalt, hemp, etc.), a deeper study is of importance to engineers and researchers. Application on FRC is preferred, i.e. fiber volume ratio is small, while classical composites require relatively very high volume ratio. The theory involves an original procedure leading to the optimal shape of fibers; it is then applied in the form of a numerical study. Also two examples from experiments verify the theoretical results. The problems are solved as two-dimensional, i.e. a unidirectional distribution of fibers is supposed., Petr P. Procházka and Martin Válek., and Obsahuje bibliografii
Rayleigh waves in the period range 0.2 - 3.0 s from eight quarry blasts are analyzed to obtain S-wave velocity model beneath the Příbram seven-station array in the Czech Republic. Locations and origin times of blasts are estimated using P- and S-wave onsets and then verified at the quarry in the vicinity of the location. This blind test confirms a sufficient precision of the location procedure for identification of quarries. Epicentral distances are in the range from 16 to 52 km. Group velocity dispersion curves of Rayleigh waves are determined by the frequency-time analysis. An average group velocity beneath the array for each period is computed with the help of mean travel-time curve for all blasts and stations. The resultant group velocity dispersion curve is inverted to obtain a 1-D S-wave velocity model using the Isometric method. The results are compared with known geological structure in the area of interest., Renata Gaždová, Petr Kolínský, Jiří Málek and Jan Vilhelm., and Obsahuje bibliografii
We examined 126 wild tortoises to evaluate the shell changes due to sexual dimorphism and ontogenesis by the geometric morphometrics. Adult body shape varies substantially in males and females; adults showed different ontogenetic patterns between sexes: in females the posterior portion of the carapace narrows in the dorsal view, the carapace tends to assume a pyriform shape in the lateral view, and the plastron tends to lengthen of the midline and shows a slight lateral enlargement. Male shape changes towards the posterior portion of the carapace, a bending of the seam between marginal and pleural scutes, allowing the body to assume a hemispherical shape, and ventrally, the plastron narrows strongly, posteriorly. The latter feature was mainly due to the shortening of the anal scutes, probably facilitating copulation by allowing more space to move the long tail. A wider posterior in male angulate tortoises may convey greater stability in male-to-male combat. All the ontogenetic changes suggest a modification of the plastron formula, an important feature for chelonian systematics and taxonomy.
The steady-state photosynthetic irradiance and temperature responses of Viola hondoensis and V. keiskei (Violaceae) growing in proximity in their nati ve environment and under three levels of artificial shade of relative irradiance (RI) of 7, 20 and 50 % were investigated. The maximum photosynthetic rates and temperature optima under natural conditions were much higher in V. keiskei than in V. hondoensis, except when in leaves of V. keiskei chlorophyll was degraded due to autumn frosts. When grown under artificial shade, both species had higher temperature optima as RI decreased. Since leaves under the three RI conditions experienced a similar leaf temperature, it was concluded that the shifts in the temperature responses with RI resulted from acclimation to the varying irradiance. The higher temperature optima observed in V. keiskei under natural conditions were probably due to the fact that V. keiskei grew in more shady microhabitats than V. hondoensis.