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2 2018

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Regional carbon uptake of croplands in Poland between 1960 and 2009

Nyćkowiak J., Leśny J., Olejnik J., Merbold L., Niu S.

Meteorology Hydrology and Water Management. Research and Operational Applications

2018

Vol. 6, Iss. 1

67--76

Croplands have been identified as binding large amounts of carbon. About one third of the total area in Poland is covered by croplands. In this paper, we analyze data describing the yields and structure of crops available for 13 selected subareas of Poland between 1960 and 2009 to evaluate the greenhouse gas mitigation potential due to carbon (C) uptake of this land cover type. Seven selected subareas located in Western Poland (area A), and six subareas in the southeast of Poland (area B) were chosen for detailed analysis. Cereals were identified as the most dominant crop planted in both areas during 1960-2009. Still, differences in yield could be found, with larger production in area A than in area B. By the year 2009, arable land (cereals, beetroot, potato, rapeseed and maize) covered nearly 10 Mio ha of Poland. The average uptake of C by crops between 1960 and 2009 was 3,24 ± 0,17 Mg C ha-1 a-1 for area A, 2,84 ± 0,12 Mg C ha-1 a-1 for area B and 2,88 ± 0,11 Mg C ha-1 a-1 for the whole country. Given the fact that about 3% of the total assimilated carbon remains in the soil, we calculated that 0,98 Tg C were stored in Polish croplands in 2009. Due to this fact, croplands are short time storage of carbon and thus contribute to greenhouse gas mitigation.

A prediction method for load distribution in threaded connections

Zhang D., Gao S., Niu S., Liu H.

Journal of Theoretical and Applied Mechanics

2018

Vol. 56 nr 1

157--168

A new method has been developed for predicting the load distribution along the thread portion of a bolt and nut connection. The calculated results were validated by comparison with three-dimensional finite element analysis and Yamamoto’s method. It was shown that the load distribution predicted by the model in this paper was in good agreement with the results from finite element model, and the load ratio on the first thread by the prediction model and finite element model was slightly larger than the results from Yamamoto’s method. In addition, the results of calculation and finite element analysis indicated that the decreasing of the lead angle could improve the load distribution, the increasing of the length of thread engaged could significantly improve the load bearing capacity of the first thread, and the adopting of a material with low stiffness for the nut with respect to the bolt could improve the load distribution slightly.