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Issue 9 (1970)
The present generation of foresters continues the planting of trees by traditional methods to obtain the yield for the third and fourth generation of people to come, thus limiting themselves to the knowledge of the actual site conditions and respecting the monopolistic role of the laws of nature. Under conditions of planned economy still a third condition comes into play, viz. the effect of economic laws that react objectively. Therefore, the elaboration and improvement of the long-time forecasts of the wood balance is necessary for at least one cycle of the forest production, viz. 80-100 years, both on national and regional scale.
The attempts of patterning such forecasts, performed lately in Czechoslovakia, German Democratic Republic and Federal Republic of Germany, have proved them to be appropriate in theory and useful in practice both in economics and planning. The author presents a variant of the wood balance for Poland for the period of 1965-2050, elaborated by himself, and recommends the forecasts to be introduced by gradual bringing them nearer as the development of science and progress in technology in the field of wood substitution goes by.
Paper presents results of studies concerning the use of a magnetic field for vibration damping in the whirling circular saw. The decrease of vibration amplitude while whirling under the influence of magnetic field on idle run was between 0.0 to 55.8% for different cases. Maximum achieved decrease of vibration amplitude for working conditions was approximately 12.5%.
This paper deals with the results of the modification of The properties of changed colophony when heated in carbon dioxyde atmosphere are given. The softening point of investigated colophony does not change when heated in temperatures between 260-300°C. The softening point of esters obtained form colophony and pentaerythritol is higher by about 21°C then the same of colophony. Time period of heating is rather long (16 hours).
It was found the linear increment of softening point when the amount of added maleic anhydride grows. The reaction with maleic anhydride is rather speedy in 270°C (15 minutes).
Quite good results were obtained when the modification was conducted at the same time with both reagents: pentaerythritol and maleic anhydride. Product reaction obtained from twenty parts (by weight) of colophony, six parts of pentaerythritol and three arts of maleic anhydride has the following properties: softening point 112°C (increment by over 47°C) and acid number 13.