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Hodnocení vybraného elektrického vlhkoměru při měření vlhkosti dřeva smrku v průběhu procesu navlhání
Konečný, Filip
The content of this bachelor's thesis deals with the measurement of the moisture content of spruce wood (Picea abies (L.) Karst.) in the wetting process. Spruce wood was added to zero moisture (w = 0%) and then stored in an air-conditioned room. Wood moisture was measured using an Orion 950 dielectric hygrometer. The moisture values measured on this hygrometer were subsequently compared with the actual moisture found, which was determined using the gravimetric method. The interface of the selected hygrometer enables the setting of the wood density value as well, thus allowing the comparison of the wood moisture with the actual density and with the table density given in the tables from the wood hygrometer manufacturer. The measured spruce wood samples were divided into two groups of 15 pieces each, namely samples without defects or with only minimal defects, and samples with larger defects, especially with resin streaks or knots. Most accurately, the hygrometer measured with the actual density of the samples for both groups. There was always a very significant difference of values when the table density was set.
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TEMPERATURE MOISTURE PROCESS STUDY IN MODERN WOOD STRUCTURES
Dohnal, Jakub ; Hradil, Petr (referee) ; Straka,, Bohumil (referee) ; Pěnčík, Jan (advisor)
In building structures wood is very often used as construction material and can also be used for supplemental non-supporting structures, e.g. as wood panelling, screening elements, etc. The most common woody plant species that can found in the biotope of the Czech Republic are Norway spruce (Picea abies L.) and Scots pine (Pinus sylvestris L.). Wood as construction material is popular in architect comunity as well as this material like also investors, who prefer living in healthy and natural environments. Wooden structures are also popular with structural engineers for their good mechanical properties and low weight, which, however, depends on moisture. Wood properties vary in every natural way and need to be taken into account at the beginning of the designing process. This dissertation aims to contribute to the description of mechanical characteristics of wood during changes of moisture content in the wood structure. Various experimental tests and numerical modelling were used in the thesis in order to reach the aims. The experimental tests examined mechanical properties at different sample moisture of selected woody plant species. Subsequently, the obtained values were compared with values available in specialist and scientific literature, so that these values could subsequently be used as input values for numeric calculations. The conclusions of the dissertation will contribute to more accurate calculations and further analysis.
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Monitoring dynamiky půdní vlhkosti v agroekosystému
Bednařík, Martin
The aim of my thesis was to monitor and analyse the dynamics of soil moisture (Θ) through the gravimetric method using Kopecky's physical rollers (KFV) and the capacitance method using Theta Probe ML2x (FDR) and CS616 (TDR) sensors. The measurement took place in the cadastral areas of the village Vícemelice and Polkovice. I conducted 10 parallel measurement campaigns of KFV and Theta Probe in Vícemilice and 4 in Polkovice. CS616 sensors were located stationary in both locations throughout the whole period and provided continual time series Θ. In Vícemilice, Theta Probe undervalued by 11.4 % compared to the KFV. The CS616 undervalued by 6.5 % compared to KFV and overvalued by 3.9 % Theta Probe. In Polkovice, Theta Probe undervalued by 1 % compared to KFV. The CS616 sensors systematically overvalued compared to the other two methods. It overvalued by 40.9 % compared to KFV and by 42.1 % compared to Theta Probe. Furthermore, the overvaluation was higher with a greater depth, while it was only 11 % at the top layer. Lastly, a survey of the suction pressure of soil water in relation to Θ was conducted near Vícemilice and the results of Θ measured by CS616 sensors were compared to the values simulated by SoilClim model which is one of the tools used to monitor water supplies in soil, in particular the occurrence of drought at the national level. Based on the results obtained in the framework of the submitted thesis, it can be stated that the indirect methods, in particular the Theta Probe, have proven to be useful tools for monitoring soil moisture. Compared to the destructive method, they represent significant time savings and, due to their accuracy, they can be recommended for drought monitoring, calibration of mathematical models, satellite imaging, or testing of a variety of hypotheses related to the water balance in scientific experiments.
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