The Influence of Roughness on the Discharge Coefficient of a Broad-Crested Weir The use of environmentally-friendly materials in hydraulic engineering (e.g. the stone lining of weirs at levees) calls for the more accurate estimation of the discharge coefficient for broad-crested weirs with a rough crest surface. However, in the available literature sources the discharge coefficient of broad-crested weirs is usually expressed for a smooth crest. The authors of this paper have summarized the theoretical knowledge related to the effect of weir crest surface roughness on the discharge coefficient. The method of determination of the head-discharge relation for broad-crested weirs with a rough crest surface is proposed based on known discharge coefficient values for smooth surfaces and on the roughness parameters of the weir. For selected scenarios the theoretical results were compared with experimental research carried out at the Laboratory of Water Management Research, Faculty of Civil Engineering (FCE), Brno University of Technology (BUT).

Forest stands in the semi-arid environment of northern Mongolia have an essential role in controlling ongoing desertification in the surrounding landscape. Over the last decade, the total forest area has decreased dramatically. The aim of this study was to evaluate the potential of natural regeneration as an essential element for ensuring sustainability of these forests. Based on field measurements from 120 plots in six sites, our assessment tool revealed five qualitative categories of forest regeneration, allowing us to assess impacts of both grazing and environmental conditions on the regeneration process. Grazing is a crucial factor and adversely affects regeneration. For sites with relatively low grazing intensity, low soil moisture levels represent the main reason for reduced regeneration. The approach to classification proposed in this study allows for the identification and interpretation of stand conditions where natural regeneration has failed. This study provides an important foundation to inform decision- making related to land protection and restoration actions. Our findings could be used in comparative studies and, importantly, may aid further mapping of Mongolian forests.

The paper deals with selected procedures used to calculate the shape of compact nappe during free overfall from a smooth horizontal channel with rectangular cross section. Calculated and measured water surface and velocity conditions in the end section, the level of water surface upstream in front of the end section and the shape of the compact part of an overfall nappe are described for a particular compared case.

Electrical impedance tomography as a nondestructive, non-invasive diagnostic method finds wide application within multiple fields and disciplines. Measuring the electrical voltage on the surface of an investigated object then constitutes a procedure that facilitates the reconstruction of the inner specific electrical conductivity. The accuracy of such measurement, together with elimination of the noise and uncertainties, embodies a central factor for any precise specific conductivity reconstruction. This paper discusses a novel multiplexer to switch between the supply source, measuring electrodes, and devices that automatize the tomographic procedure. In general terms, the design of the measuring card has to respect not only the accuracy and speed requirements but also the fabrication costs. The concept proposed herein exploits the MOSFET technology, utilizing galvanic separation of the current source and the electrodes that potential-measuring electrodes; significantly, the design is compared with commercially available solutions.