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Analytical study on the cutting force and residual stress in whirlwind milling of a large screw

Guo Qin, Wang Yulin, Zhou Bin

Journal of Theoretical and Applied Mechanics

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2023

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Vol. 61 nr 1

65--76

EN

The finite element method (FEM) is developed to simulate a discontinuous cutting in the whirlwind milling. Firstly, a simplified arc-cutting model for simulating the actual circular cutting, and a plane-cutting model for simplification were both developed and verified by experiments. Then, the effects of cutting parameters on the cutting force and residual stress were effectively investigated based on the plane-cutting model. Moreover, a plane-second- -cutting model was further developed. It showed that a minor decrease of cutting force and a higher maximum compressive stress were generated in the second cutting. Those results were conducive to predict and improve the whirlwind milling.

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Economic and Ecological Assessment of Transport of Various Types of Waste

Guzdek Sylwia, Malinowski Mateusz, Religa Arkadiusz, Liszka Daniel, Petryk Agnieszka

Journal of Ecological Engineering

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2020

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Vol. 21, nr 5

19--26

EN

The amount of generated waste has been increasing for several years in Poland. There is a lot of research in the field of the environmental and economic evaluation of waste treatment processes. Waste transport is considered to be one of the most important elements of waste management (WM), because it integrates the whole WM system. The environmental impact of waste transport is rising (emissions to air). The European Union introduced provisions on the principle of proximity in the Waste Framework Directive. This principle suggests that waste should generally be transported, treated or disposed of as near to its place of origin as possible. The main aim of the study was to perform an ecological and technical-economic analysis of transportation of selected types of waste (mixed municipal solid waste, construction and demolition waste, separately collected waste called: segregation). The research applied data obtained from a municipal enterprise operating in the South Poland. SimaPro 8.1 software with Ecoinvent 3.3 database was employed to calculate the environmental impact. As a result of the analysis, it was found that the transportation of 1 Mg construction waste had twice as much negative impact on the environment as transportation of 1 Mg mixed municipal waste and segregated waste. This is connected with higher fuel consumption per 1 Mg of transported construction waste and twice the distance that an average hooklift truck must cover in order to collect 1 Mg of construction waste.

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Two types of Markov property

Kasprzyk A., Szczotka W.

Probability and Mathematical Statistics

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2008

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Vol. 28, Fasc. 1

75--90

EN

The paper gives some insight into the relations between two types of Markov processes – in the strict sense and in the wide sense – as well as into two aspects of periodicity. It concerns Markov processes with finite state space, the elements of which are complex numbers. Firstly it is shown that under some assumptions this space can be transformed in such a way that the resulting Markov process is also Markov in the wide sense. Next, sufficient conditions are given under which periodic homogeneous Markov chain is a periodically correlated process.