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Open access

W. Janke, A. Hapka and M. Oleksy

DC characteristics of the SiC Schottky diodes

The isothermal and non-isothermal characteristics of silicon carbide Schottky diodes in the wide range of currents and ambient temperatures are investigated in this paper. The measurements of the diodes characteristics have been performed with the use of a pulse method, with fast registration of measurement points after the diode current turning on, or with the use of a fully static method, in which the self-heating phenomenon is taken into account. Apart from the measurements, the series of numerical experiments, giving the isothermal and non-isothermal characteristics as a result, were executed. The complex, accurate numerical procedures as well as simplified analytical calculations were implemented. A good conformity of all calculation and measurement results have been obtained.

In the presented investigations, for relatively high currents and ambient temperatures, the influence of self-heating on the SiC Schottky diodes static characteristics is significant. The large (even 4 V for the ambient temperature 300°C) values of voltages corresponding to the nominal diode currents have been observed.

Open access

T. Zając, A. Oleksy, A. Stokłosa, A. Klimek-Kopyra and J. Macuda

Abstract

The study aimed at evaluating the distribution of mass in the straw of cereal species and also at assessing the straw yield and its losses resulting from the amount of the stubble left in the field. It was found empirically that the wheat culms are composed of five internodes, and in barley, triticale and oats of six. The highest straw mass per 1 cm was found in the second internode in both forms of wheat and winter triticale, whereas barley and oats gathered the highest weight in the first internode. In the southern part of Silesia species and forms of cereals differed in the straw yield, which can be arranged as follows, from the highest: winter wheat > spring wheat, winter triticale, winter barley, and oats > spring barley. Due to the specific distribution of dry matter in each of internodes of both wheat forms - winter and spring, they loose less stubble mass (22 and 24%, respectively), comparing to other cereals, especially spring barley, which loose 31% yield of straw in the stubble of 15 cm height.

Open access

Tomasz Zając, Agnieszka Synowiec, Andrzej Oleksy, Jan Macuda, Agnieszka Klimek-Kopyra and Franciszek Borowiec

Open access

Tomasz Zając, Agnieszka Synowiec, Andrzej Oleksy, Jan Macuda, Agnieszka Klimek-Kopyra and Franciszek Borowiec

Abstract

Cereal straw is an important biomass source in Europe. This work assessed: 1) the morphological and energetic characteristics of culms of spring and winter cereals, 2) the energy deposited in the different aboveground parts of cereals, 3) losses of energy due to different cutting heights. The straw of winter and spring cereals was collected from arable fields during the seasons 2009/10 and 2010/11 in southern Poland. Detailed biometric measurements of culms and internodes were performed. The losses of straw biomass and energy were assessed during simulation of cutting the culm at different heights, up to 50 cm. Longer and heavier culms were developed by winter wheat and triticale and oat. Cutting of straw up to 10 cm did not lead to significant losses in straw yield. The total amount of energy in the culms was as follows: triticale > winter wheat > oat > spring wheat > winter barley > spring barley. Cutting the culms above 20 cm led to significant differences in terms of biomass energy between cereal species. The smallest losses of energy were recorded for spring and winter barley. Oat and barley accumulated the highest energy in grains.

Open access

M. Iwańska, A. Oleksy, M. Dacko, B. Skowera, T. Oleksiak and E. Wójcik-Gront

Summary

Wheat is one of the modern world’s staple food sources. Its production requires good environmental conditions, which are not always available. However, agricultural practices may mitigate the effects of unfavorable weather or poor-quality soils. The influence of environmental and crop management variables on yield can be evaluated only based on representative long-term data collected on farms through well-prepared surveys.The authors of this work analyzed variation in winter wheat yield among 3868 fields in western and eastern Poland for 12 years, as dependent on both soil/weather and crop management factors, using the classification and regression tree (CART) method. The most important crop management deficiencies which may cause low wheat yields are insufficient use of fungicides, phosphorus deficiency, non-optimal date of sowing, poor quality of seeds, failure to apply herbicides, lack of crop rotation, and use of cultivars of unknown origin not suitable for the region. Environmental variables of great importance for the obtaining of high yields include large farm size (10 ha or larger) and good-quality soils with stable pH. This study makes it possible to propose strategies supporting more effective winter wheat production based on the identification of characteristics that are crucial for wheat cultivation in a given region.