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HAVLÍČEK, M., NEDOMOVÁ, Š., SIMEONOVOVÁ, J., SEVERA, L., KŘIVÁNEK, I.: On the evaluation of chicken egg shape variability. Acta univ. agric. et silvic. Mendel. Brun., 2008, LVI, No. 5, pp. 69-74 Although recently reported models for determining egg shape are highly accurate, certain com pli cated measurements or computations are to be performed. Thus relatively simple and attainable analysis methods of chicken egg shape variability were chosen and used for the purpose of presented research. Sample of 250 eggs of ISA BROWN strain was examined. Geometrical parameters were measured and calculated with following expression of their coeffi cient of variation -namely egg length 3.56 %, egg maximum width 2.84 %, shape index 3.80 %, surface area 5.08 %, and egg volume 7.23 %. The second method consisted in shape quantitative measuring by the score of the principal components of elliptic Fourier descriptors (EFDs). The fi rst four principles components which could explain over 99 % of the egg shape variations were found to be very good measures of the monitored phenomenon. It was found that 87.41 % of the total shape variation can be accounted to length to width ratio. Usefulness and relevance of the shape index usage was confi rmed. chicken egg, shape variability, elliptic Fourier analysis

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Precise quantification of the profile of a hen egg can provide a powerful tool for analysis of egg shape and following solving of various technological problems. The article presents a new approach of the eggshell geometry determination using and analyzing the egg digital image and edge detection techniques. The detected points on the eggshell contour were fitted by the Fourier series. The obtained equations describing an egg profile were used to calculate the egg volume, surface area, and radius of curvature with a much higher degree of precision in comparison with previously published approaches. It was shown that radii of curvature at the critical points of the egg profile are independent on the egg shape index. The article shows and quantifies the limitations of the common and frequent procedures.

The objective of this study is to measure how the viscosity of engine oil changes with temperature. Six different commercially distributed engine oils (primarily intended for motorcycle engines) of 10W–40 viscosity grade have been evaluated. Four of the oils were of synthetic type, two of semi–synthetic type. All oils have been assumed to be Newtonian fluids, thus flow curves have not been determined. Oils have been cooled to below zero temperatures and under controlled temperature regulation, kinematic viscosity (mm2 / s) have been measured in the range of −5 °C and +115 °C. Anton Paar digital viscometer with concentric cylinders geometry has been used. In accordance with expected behavior, kinematic viscosity of all oils was decreasing with increasing temperature. Viscosity was found to be independent on oil’s density. Temperature dependence has been modeled using se­ve­ral mathematical models – Vogel equation, Arrhenius equation, polynomial, and Gaussian equation. The best match between experimental and computed data has been achieved for Gaussian equation (R2 = 0.9993). Knowledge of viscosity behavior of an engine oil as a function of its temperature is of great importance, especially when considering running efficiency and performance of combustion engines. Proposed models can be used for description and prediction of rheological behavior of engine oils.

The study is focused on analysis of mechanical behavior of hen's eggshell expressed in terms of average rupture force and corresponding deformation. Some other physical properties such as mass, length, diameter, geometric mean diameter, surface area, sphericity, and volume were also evaluated. The egg samples were compressed along their X and Z-axes. Two different experimental methods were used: compression between two plates (loading rates 0.0167, 0.167, and 1.67 mm/s) and impact of a free-falling cylindrical bar (loading rates up to 17 mm/s). Surface displacement and surface velocity were measured using the laser-vibrometer. The increase in rupture force with loading rate was observed for loading in all direction (along main axes). Dependence of the rupture force on loading rate was quantified and described. The highest rupture force was obtained when the eggs were loaded along the X-axis. Compression along the Z-axis required the least compressive force to break the eggshells.