Research in Agricultural Engineering, 2008 (vol. 54), issue 2
80 years of Professor Radoš Řezníček
J. Blahovec
Res. Agr. Eng., 2008, 54(2):i | DOI: 10.17221/999-RAE 
Influence of soil and tire parameters on traction
M. Schreiber, H.D. Kutzbach
Res. Agr. Eng., 2008, 54(2):43-49 | DOI: 10.17221/3105-RAE
The drawbar pull, travel reduction (slip), and rolling resistance are the main criteria to describe the traction behaviour of off road vehicles. Besides the engine performance, the drawbar pull is influenced by the traction conditions such as soil and the tire parameters. These traction conditions have to be described by a limited number of parameters which can be easily determined. Empirical equations were used to analyse roughly 850 traction curves measured and published by Steinkampf. As a result, the important parameters to describe the traction conditions are three tire parameters (radius, width, inflation pressure) and five soil parameters (soil...
Airflow resistance of wheat bedding as influenced by the filling method
J. Łukaszuk, M. Molenda, J. Horabik, B. Szot, M.D. Montross
Res. Agr. Eng., 2008, 54(2):50-57 | DOI: 10.17221/8/2008-RAE
A study was conducted to estimate the degree of variability of the airflow resistance in wheat caused by the filling method, compaction of the sample, and airflow direction. Two types of grain chambers were used: a cylindrical column 0.95 m high and 0.196 m in diameter, and a cubical box of 0.35 m side. All factors examined were found to influence considerably the airflow resistance. Gravitational axial filling of the grain column from three heights (0.0, 0.95 and 1.8 m) resulted in the pressure drops of 1.0, 1.3, and 1.5 kPa at the airflow velocity of 0.3 m/s. Consolidation of axially filled samples by vibration resulted in a maximum 2.2 times increase...
Nitrogen conversion and nitrous oxide hot spots in energy crop cultivation
H.J. Hellebrand, V. Scholz, J. Kern
Res. Agr. Eng., 2008, 54(2):58-67 | DOI: 10.17221/1001-RAE
Since 1999, nitrous oxide (N2O) soil emissions from sites cultivated with energy plants have been measured by gas chromatography and gas flux chambers in experimental fields. The main aim of this study was the nitrogen conversion factor and its variability for sandy soils under climatic conditions of Central Europe. Annual plants (hemp, rape, rye, sorghum, triticale) and perennial plants (grass, perennial rye, poplar, willow) were fertilised with three different levels of nitrogen (150 kg N/ha/year, 75 kg N/ha/year, and none). The annual nitrogen conversion factors were derived from the annual mean differences between the fertilised sites...
A study on applications of intersecting flows in water reservoir for improvement of water environment problems
S. Umeda, W.-J. Yang
Res. Agr. Eng., 2008, 54(2):68-79 | DOI: 10.17221/3106-RAE
This paper deals with the applications of intersecting flows for the improvement of water environments in water reservoirs. First, the present authors' research results are summarised for flow characteristics in intersecting channels placed in horizontal or vertical positions. All physical phenomena involved are identified and their mechanisms are explained. Subsequently, appropriate methods are obtained for solving the problems of stratified water and eutrophication in water reservoirs. A novel drainage system is developed and a particle ejection experiment for sediment flushing is investigated utilising a reservoir model with glass beads replacing...
Physical properties of cereal grain and rape stem
S. Grundas, G. Skubisz
Res. Agr. Eng., 2008, 54(2):80-90 | DOI: 10.17221/3/2008-RAE
The paper presents the results of a study on the mechanical properties of cereal grain and of rape stems, conducted within the framework of the continuing long-term cooperation between the Bohdan Dobrzański Institute of Agrophysics, The Polish Academy of Sciences (IA PAS) in Lublin, and the Czech University of Life Sciences (CULS) in Prague, Czech Republic. Within the scope of the mechanical properties of cereal grain, the study showed a significant relation between the physical conditions of kernels of common wheat as determined through X-ray detection, and their mechanical properties determined by means of standard tests used in the mechanics of...
Mechanical properties of cereal stem
J. Dunca
Res. Agr. Eng., 2008, 54(2):91-96 | DOI: 10.17221/5/2008-RAE
The paper deals with the measurement of the resonance frequencies of wheat stems with special respect to different wheat varieties. For the measurement, the dynamical method of the transverse frequency was used. Formulas were derived for the calculation of the bending toughness of stems. The t-test was used for the evaluation of the strength coefficient in bending for the samples of stems of different wheat varieties. The results can be used for the evaluation of the wheat resistance to lodging.
Influence of packing method on colour perception improving the appearance of fruits and vegetables
B. Dobrzański, Jr., R. Rybczyński
Res. Agr. Eng., 2008, 54(2):97-103 | DOI: 10.17221/4/2008-RAE
The appearance of fruits and vegetables has a major influence on the perceived quality. Therefore, colour is one of the most important quality parameters in consumers' preferences. Fruits differently exposed to the sun differ in colour, frequently looking unripe and reach full maturity just on handling or transport, some still green and appearing unripe. Oranges, carrot, red beet, and parsley were used for the study of the quality estimation. Different nets used for the packing of fruits were tested. The measurements of lightness and chromaticity parameters were performed according to L*a*b* system. The red net used for the packing of oranges caused...
Dielectric properties of agricultural products and some applications
S.O. Nelson
Res. Agr. Eng., 2008, 54(2):104-112 | DOI: 10.17221/1000-RAE
The use of dielectric properties of agricultural products for sensing moisture in grain and seed and their application in radio-frequency and microwave dielectric heating is discussed briefly. Values for the dielectric properties of a number of products, including grain and seed, fruits and vegetables, and poultry products, are presented graphically to show the dependence of these properties on frequency, moisture content, and temperature. The potential for using the dielectric properties to sense quality factors other than moisture content is also considered.
Dielectric properties of deformed early potatoes
J. Blahovec
Res. Agr. Eng., 2008, 54(2):113-122 | DOI: 10.17221/3104-RAE
The permittivity of potato tissue was studied during uniaxial compression of cylindrical specimens prepared from two early varieties. Both the real and the imaginary permitivity components were determined repeatedly during the loading and unloading tests. The analysis of the results obtained shows that small differences exist between the permittivity of the late and early potato varieties. The differences are concentrated mainly at frequencies higher than 1 kHz with a maximum between 10 and 100 kHz. The effect of deformation is concentrated into frequencies between 1 and 100 kHz. The effect of deformation on the permittivity values can be divided into...