A b s t r a c t. The aim of this study was to acquire data on the physical properties and compression loading behaviour of seed of six corn hybrid varieties. The mean values of length, width, thickness, geometric diameter, surface area, porosity, single kernel mass, sphericity, bulk and true density, 1 000 kernel mass and coefficient of friction were studied at single level of corn seed moisture content. The calculated secant modulus of elasticity during compressive loading for dent corn was 0.995 times that of the semi-flint type; there were no significant differences in the value of this mechanical property between semi-flint and dent corn varieties. The linear model showed a decreasing tendency of secant modulus of elasticity for all hybrids as the moisture content of seeds increased.K e y w o r d s: corn, physical properties, secant modulus of elasticity INTRODUCTIONThe importance of corn processing industries is increasing. Recent concepts in corn marketing emphasise the identification of the specific, rigorous quality needs of individual users, and there is considerable interest in grain quality as an end-use value. Parameters useful in the evaluation and recognition of such specific values include, among others, the physical properties of corn kernels. These properties include the three perpendicular dimensions, which affect cleaning and grading processing, the kernel surface, which affects drying, sphericity and thousand kernels mass, which affect packaging of seed, bulk density (affecting storage capacity), true density (affecting vehicle load), porosity (aeration possibility, drying), coefficient of static friction (moving on inclined plane) and compression loading behaviour, which affects milling, extruding and flake preparation. Previous studies have described the physical properties of corn kernels. Coskun et al. (2006) determined sweet corn seed properties as a function of moisture content, while Karababa (2006) reported similar results on popcorn kernels; sweet corn kernel properties were reported by Karababa and Coskuner (2007) and those of dent corn by Esref and Nazmi (2007). The quality of corn kernels is not evaluated solely by the physical traits mentioned above. The behaviour of the corn kernel during compressive loading is one of its textual properties. The processing of corn for food and feed requires various types of mechanical treatment that depend on external forces. The main component of corn kernels is starch granules; these have a complex hierarchical structure consisting of polysaccharide macromolecules that are partially arranged in ordered conformations as single and double helices and entangled to form supra-and sub-molecular structures Gaytan-Martinez et al. (2006). Proteins form a matrix surrounding and embedding the starch granules. The endosperm of corn, which is horny and floury, is a complex mixture of starch granules and protein. The proportion of horny and floury endosperm in the kernel differs in different types of corn, the general classes of which are flint corn, dent ...

The width and thickness of the analyzed kernels were small compared with the length, and bulk densities were also moderate. The yield point force values of the two hard varieties were 2.2 times higher than the values of the soft variety, at a moisture content of 0.136 kg kg(-1) for Simonida, 0.133 kg kg(-1) for Dragana and 0.141 kg kg(-1) for NS 40S.

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This paper identifies and analyses some drawbacks of the logistic map which is still one of the most used chaotic maps in image encryption algorithms. As some of the disadvantages are caused by inappropriate implementations of the logistic map, this paper proposes a set of rules which should lead to enhancement of the desired chaotic behavior. Probably the most important rule introduces alternating value of parameter utilized by the logistic map. With careful choice of values and an adapted quantization technique, some of the issues should be fixed and theoretically also the values of numerical parameters should be improved. These assumptions are verified by applying the proposed set of rules on an algorithm from our prior work. Effects of the proposed rules on the used algorithm are investigated and all necessary modifications are thoroughly discussed. The paper also compares obtained values of commonly used numerical parameters and computational complexity with some other image encryption algorithms based on more complex chaotic systems.