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.

The goal of this work was to evaluate the potential of reduced application rates in apple trees as well as the potential of selective spray applications by using sensor-based tree detection techniques in Serbian fruit production. Their economical and biological effect was evaluated based on the quality and efficiency of the crop protection and technoeconomic analysis. Results showed that during suitable weather conditions and with properly adjusted sprayer settings, a reduced application rate of 381 L ha -1 gave same quality of crop protection as a medium application rate of 759 L ha -1 . A two-year efficiency trial on Venturia inaequalis and Podosphaera leucitricha infecting apple also showed that there was no significant difference in crop protection results for different types of orchard application techniques and application rates. The techno-economic analysis showed that selective application should be introduced in practice in areas > 3 ha given that the cost of their introduction pays off after 2-3 seasons. Every subsequent season would give a clear economic profit. Besides the economic benefits, selective application technique also has a significant positive ecological effect due to reduction of spray losses and the amount of plant protection products used.

The object of this research is the new concept of the original universal system for air quality and energy control in laboratory conditions (wet scrubbing system) based on the ?clean air in/out?principle. Namely, the process involves a partial or complete exchange of recirculated treated air. From the aspect of water, as a pure medium, the system is characterized by broad application in the open, semi-open, and closed air treatment systems: primarily in the breeding and accompanying agricultural facilities, industrial, cultural, sports, tourist, medical and other controlled spaces. The analysis showed that the system at its inlet unit and with the block structure and logical phase development, proved energy, environmental and qualitative efficiency in the removal of PM10 and PM2.5 particles from the controlled dust doses in laboratory air. The measurements of PM10 and PM2.5 concentrations were performed with two Alphasense OPC-N3 optical counters at the inlet and outlet of the system. Five operating regimes with frequency regulated number of revolutions of the turbo elements that was taken as an independent variable, achieved different degrees of removal of PM10 and PM2.5 from the treated laboratory air: 97.70 to 98.53% and 62.19 to 75.75%, respectively. The assessment of system energy use was done by parallel measuring of electric power and comparative deviations of its absolute values in the first decimal. Energy consumption for the treatment of 1m3 of air ranged from 0.00011 to 0.00016 kWm-3. Statistical analysis of qualitative indicators revealed significant differences between the operating regimes and the obtained values.

SAŽETAK U radu je naveden postupak određivanja udaljenosti tačaka noža od trajektorije njegovog vrha i kritična vrednost ugla postavljanja noža pri suprotnosmernom obrtanju rotora rotacione sitniolice. U zavisnosti od promene radne brzine u granicama od 0,43 do 1,08 m/s kritična vrednost ugla postavljanja krila noža  kreće se u grnanicama 75,11° do 69,24°. Niže vrednosti ugla postavljanja krila noža izračunate su za veće vrednosti radne brzine. Poznavanjem vrednosti ugla postavljanja krila noža  može se odrediti oblast primene već postojećih rotacionih sitnilica, a nove konstrukcije rotacionih sitnilica sa noževima montiranim pod optimalnim uglom postavljanja mogu da ostvare rezanje pri minimalnim vrednostima ugla rezanja što bi dovelo do sniženja vrednosti energije angažovane za obradu rotacionom sitnilicom. Računanjem rastojanja pojedinih tačaka na zadnjem delu noža od tačke izlaska noža na površini zemljišta preduslov je za izračunavanje optimalnog oblika krila noža, sa stanovišta eliminacije nepotrebnog trenja sa zadnjim delom noža o neobrađeno zemljište. Ključne reči:obrada zemljišta, rotaciona sitnilica, ugao postavljanja krila noža, ugao rezanja 1. UVOD Na nožu "L" tipa rotacione sitnilice razlikuju se tri dela: vertikalni deo (nosač), zakrivljeni deo i horizontalni podrezujući deo (krilo), (Marković, 1994). Ugao između poluprečnika rotora i gornjeg dela krila noža naziva se ugao postavljanja noža γ i on ima konstantnu vrednost. Ukoliko se od ugla između poluprečnika rotora i tangente na trohoidu oduzme ugao postavljanja noža γ dobije se ugao rezanja  (Matjašin et al, 1988). Povećanjem vrednosti ugla postavljanja noža γ smanjuje se ugao rezanja . Kod rotacionih radnih alata ugao rezanja  se stalno menja. Ugao rezanja raonika kod plugova, kultivatorskih motičica i drugih radnih organa sa pravolinijskim kretanjem, za minimalnu angažovanu energiju kreće su granicama 20-30° (Matjašin et al, 1988). Kod rotacionih radnih alata ugao rezanja  ima znatno veću vrednost pa je to jedan od razloga povećanja angažovane energije pri njihovom radu. Obimna radna brzina, radna dubina, broj obrtaja rotora, prečnik i smer obrtanja rotora rotacione sitnilice, predstavljaju parametre na osnovu kojih treba definisati vrednost ugla postavljanja krila noža γ (Ponjičan i dr, 2013).