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Within the framework of the project for design and optimization of the Remotely Operated Vehicle (ROV), research on its propulsion has been carried out. Te entire project was supported by CFD and FEM calculations taking into account the characteristics of the underwater vehicle. One of the tasks was to optimize the semi-open duct for horizontal propellers, which provided propulsion and controllability in horizontal plane. In order to create a measurable model of this task it was necessary to analyze numerical methodology of propeller design, along with the structure of a propellers with nozzles and contra-rotating propellers. It was confronted with theoretical solutions which included running of the analyzed propeller near an underwater vehicle. Also preliminary qualitative analyses of a simplified system with contra-rotating propellers and a semi-open duct were carried out. Te obtained results enabled to make a decision about the ROVs duct form. Te rapid prototyping SLS (Selective Laser Sintering) method was used to fabricate a physical model of the propeller. As a consequence of this, it was necessary to verify the FEM model of the propeller, which based on the load obtained from the CFD model. Te article contains characteristics of the examined ROV, a theoretical basis of propeller design for the analyzed cases, and the results of CFD and FEM simulations.
I Einführung Zur Untersuchung, ob ggf. auch im Rahmen eines ROV eine FFH-VP durchgeführt werden muss, soll zunächst ein kurzer Überblick über die Grundlagen des ROV gegeben werden. Im Anschluss daran ist der Frage nachzugehen, welche rechtlichen und praktischen Probleme bei einer Integration der FFH-VP in das ROV möglicherweise auftreten und welche Auswirkungen sich für nachfolgende Verfahren ergeben können. Um eine bundesweite Gültigkeit dieser Untersuchung zu ermöglichen und um den Rahmen dieses Beitrags nicht zu sprengen, werden grundsätzlich die
The article presents a proposal, based on an analysis of the software used for displaying parameters of two underwater vehicles, for extending display applications by using the Lab View environment. The purpose of the solution presented is to uniform data displays transmitted from underwater vehicles, used by operators to operate these vehicles as well as consider the possibility for extending the software offered by producers of vehicles by new elements facilitating evaluation of the vehicle’s condition and the effect of the environment on this condition when the vehicle is being operated.
The Net Present Value (NPV) approach is widely applied to assess forest investments, but this method has serious shortcomings, which we propose to overcome by switching to the assessment through the Real Options Approach (ROA). The model in this paper starts with the simulation of the forest’s growth, combined with the projection of the products’ prices and valuing the assets using a binomial model. We include an option of postponement, determining the optimal period of felling. We find that ROA is more robust than the NPV approach because it relaxes the assumption of constancy of both the prices and the discount rate, allowing the determination of the optimal time of felling based on the growth rate of either the forest or the prices of its products. Contrary to the traditional NPV approach, the results obtained with ROA exhibit longer harvest turns and consequently higher profits. The key variable in the ROA, the Real Option Value (ROV) can be shown to be less (albeit moderately) sensitive to decreases of the discount rate than NPV. Moreover, ROV is moderately sensitive to decreases in the price of logs and is negligibly affected by rises in the costs of harvesting, loading and transporting rolls.
Communications applications in the underwater environment have recently developed a considerable development due to the demand for underwater research with Robot Underwater Vehicle (ROV). The most important aspects addressed by researchers are related to the speed and distance of data transmissions. In most cases, this data signal may be electromagnetic, optical or acoustic. The first two cases have limitations on the distance of the communication channel due to signal attenuation. That is why the acoustic field can be considered the favorite in this choice. In this case, the limitations of use are given by the acoustic field propagation, which depends on the temperature, salinity and pressure of the underwater environment and the result is the variation of the propagation speed. The influence of frequency on attenuation and reverberation are important factors limiting the use of the acoustic field. Based on these considerations, the paper presents an experimental transceiver model of data transmission using Frequency Shift Keying (FSK), modulation with phase discontinuity for transmitting and receiving commands at the speed of 2kbits / s
Comparison of the monitored and modeled soil water storage of the upper soil layer: the influence of soil properties and groundwater table level
In the study of Tomlain (1997) a soil water balance model was applied to evaluate the climate change impacts on the soil water storage in the Hurbanovo locality (Southwestern Slovakia), using the climate change scenarios of Slovakia for the years 2010, 2030, and 2075 by the global circulation models CCCM, GISS and GFD3. These calculations did not take into consideration neither the various soil properties, nor the groundwater table influence on soil water content. In this study, their calculated data were compared with those monitored at the same sites. There were found significant differences between resulting soil water storage of the upper 100 cm soil layer, most probably due to cappilary rise from groundwater at sites 2 and 3. It was shown, that the soil properties and groundwater table depth are importat features strongly influencing soil water content of the upper soil layer; thus the application of the soil water balance equation (Eq. (1)), neglecting the above mentioned factors, could lead to the results far from reality.