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The ultrasound propagation speed can provide information on several wood properties. In traditional measurement methods the distance between the transmitter and the receiver of ultrasound signal needs to be equal to the total length of the tested element. In special cases an alternative, local measurement method is recommended. The aim of this paper is to determine and analyse the effect of measuring length on results of local measurement of ultrasound propagation speed in wood.
Resistance of lime wood (Tilia sp) impregnated with Paraloid B-72 resin against cellar fungus Coniophora puteana (Schum., Fr.) Karst. Work deals with resistance of Paraloid B-72 synthetic resin impregnated lime wood against cellar fungus Coniophora puteana. Resin solutions of 5, 10 and 20% concentrations were used. In laboratory conditions, impregnated samples were exposed to fungus for 16 weeks. It was determined that lime wood impregnated with Paraloid B-72 resin is not resistant against fungi. Keywords: Paraloid B-72, Coniophora puteana, weight loss.
Comparison of stereometric and radiometric (based on Compton effect), methods of measuring wood density. The stereometric measurements of wood density involve accurate preparing of special, regular specimens. On the contrary to stereometric method the radiometric densitometry is non-destructive, quick and enables to determine local value of wood density. The relation between results obtained by means of both (compared) methods can be characterised by quite high correlation coefficient (r-0,88).
The distribution of density in the stem of spruce wood. The aim of the study was to determine the distribution of local density in the stem of spruce wood. The settings of radiometric densimeter allow to measure the density of wood contained in the quite small cylinder (diameter of the cylinder: 50 mm). The weak decrease in the density of wood was observed for an increase in distance from the butt end (for an increase in height of measuring point). The instantaneous (the distance between nearest measuring points was 50 mm) change in density of wood can reach 50 kg/m3.
Traditional measurement of ultrasound propagation speed provide averaged results for the whole volume of the tested element. Therefore in special cases an alternative, local measurement method is recommended. Local measurements (involving application of the testing equipment heads to the same surface of the element being tested) provide particularly good method for identifying properties of materials located not deeper than 15 mm from the sample surface.
Chemical studies of ozone impact on pinewood (Pinus sylvestris L.) degradation. The purpose of these studies was verification the impact of ozone on wood degradation. Study the degree of wood degradation was carried out using classical chemical methods – content determination of substances soluble in 1% NaOH, extractives and cellulose isolated by Seifert method. Also, in this work modern analytical SEC method was used to determine the polymerization degree of the main wood structural component – cellulose. On the basis of these results, it was observed, that ozone increases of the content of substances soluble in 1% NaOH and extractives. This indicates, that the wood structural substances are decomposed: the part of lignin and polysaccharides (hemicelluloses, cellulose) - especially with a low degree of polymerization. On the basis of chromatographic analysis (SEC), it appears that the cellulose of the highest molar mass is also prone to depolymerization. Although the percentage content of the cellulose does not change, but under the influence of ozone comes to qualitative change of cellulose - decrease of polymerization degree.
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