Tag Archives: porosity

1769–1778 M. Stehlík, A. Czako, M. Mayerová and M. Madaras
Influence of organic and inorganic fertilization on soil properties and water infiltration
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Influence of organic and inorganic fertilization on soil properties and water infiltration

M. Stehlík¹²*, A. Czako¹, M. Mayerová¹ and M. Madaras¹

¹Division of Crop Management Systems, Crop Research Institute, Drnovská 507, CZ 16106 Prague, Czech Republic
²Department of Agricultural Machines, Czech University of Life Sciences, Kamýcká 129, CZ 16521 Prague, Czech Republic
*Correspondence: martin.stehlik@vurv.cz

Abstract:

Soil aggregate stability (SAS) belongs to the most important parameters determining the quality of soil and fertilizer influence on soil aggregation. We evaluated the relationship between SAS, hydro–physical soil properties and infiltration rates in three long–term field experiments founded in 1956 on different soils. Soil properties under three fertilization regimes–no fertilization, farmyard manure, farmyard manure and mineral fertilization–were evaluated at silty loam Chernozem, silty loam Phaeozem and sandy loam–loam Cambisol. A significant impact of fertilization on SAS was found, even though the differences in SAS were rather low. The lowest SAS was recorded at plots with manure and mineral fertilization (25.1%) compared with plots without fertilization (28.7%) and plots with manure–only fertilization (28.2%). The highest SAS (36.5%) and the highest semi–capillary porosity (SP; 11%) were observed at sandy loam–loam soil. Hydro–physical soil properties were more favourable at fertilized plots (SP 9.6% and bulk density ρb 1.31 g cm-3) compared with unfertilized ones (SP 8.8% and ρb 1.35 g cm-3). The lowest SP (8.32%) and the highest ρb (1.37 g cm-3) were recorded at Phaeozem, which corresponded with the lowest SAS (19.4%). Chernozem had similar soil texture to Phaeozem, but SAS (24.7%), SP (9%) and ρb (1.27 g cm-3) were more favourable. Despite the low level of statistical significance due to the large variation of infiltration measurements, a higher infiltration rate was recorded at fertilized plots (45 mm hour-1) compared to unfertilized ones (35 mm hour-1).

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1485–1494 A. Vagová, L Chládek and P. Vaculík
The determination of impact of malt grist moisture on porosity and permeability using measurement of differential air pressure
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The determination of impact of malt grist moisture on porosity and permeability using measurement of differential air pressure

A. Vagová*, L Chládek and P. Vaculík

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21 Prague 6 – Suchdol, Czech Republic
*Correspondence: vagova@tf.czu.cz

Abstract:

This article is focused on determination of malt grist and spent grains porosity and permeability using measurement of differential pressure of the air passing through the layer of malt grist and spent grains. For preparation of malt grist were used different disintegration equipment (two roller mill and disc mill). The method of differential pressure measuring is used for the determination of porosity of malt grist layer, defined as fraction of the volume of voids over the total volume. Measurement confirmed the logical assumption; the higher-pressure difference is above and below the spent grain layer, the lower value of porosity.

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1050–1056 V. Křepčík, J. Lev and F. Kumhála
Development and testing of apparatus for wooden chips voids measurement
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Development and testing of apparatus for wooden chips voids measurement

V. Křepčík¹*, J. Lev² and F. Kumhála¹

¹ Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Agricultural Machines, Kamýcká 129, CZ165 00 Praha 6 – Suchdol, Czech Republic
² Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Physics, Kamýcká 129, CZ165 00 Praha 6 - Suchdol, Czech Republic
*Correspondence: krepcik@tf.czu.cz

Abstract:

The interparticle porosity of wooden chips (commonly called voids) is a very important factor which significantly affects properties of wooden chips, i.e. bulk density, combustion speed or dielectric properties. Dielectric properties can be used for the measurement of its moisture content and it is the moisture content which is one of the most important factors that affect wooden chips calorific value. This paper is focusing on the development of measuring apparatus for wooden chips voids measurement. The principle of measuring apparatus is based on a gas displacement method. Measuring apparatus is composed from two chambers; both with the same volume. One from chambers is comparative one and second is experimental one. The pressure operating range was from 1,000 to 1,500 Pa. Results showed nontrivial behaviour of wooden material with the change of moisture content which was probably caused by different structures of tested materials.

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1116–1122 P. Valášek
Study on impact strength of sisal fibers reinforced epoxy composites using experimental methods
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Study on impact strength of sisal fibers reinforced epoxy composites using experimental methods

P. Valášek

Department of Material Science and Manufacturing Technology, Faculty of Engineering, Czech University of Life Sciences Prague, Kamýcká 129, CZ 165 21 Prague; e-mail: valasekp@tf.czu.cz

Abstract:

 Among the advantages of composite materials is their ability to exploit the properties of partial phases that creates the composite. Common materials used as matrix materials include polymeric composites. The properties of these matrices can be optimized by using synthetic or also natural fibers. Natural fibers are inexpensive, ranks among renewable resources and when respecting their biological nature, they can replace synthetic fibers in many applications. This paper describes the impact strength of epoxy resins filled with unordered short sisal fibers with a length of 2–6 mm. From the experimental results it is evident that the presence of fibers of sisal examined as epoxy resins, increases the impact strength, up to 143%. SEM (scanning electron microscopy) was used to assess the failure of mechanism of these composites.

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