The properties of wave fields induced by high-speed ferries and recently introduced conventional ferries with increased cruise speeds are analysed for a site in Tallinn Bay, the Gulf of Finland, the Baltic Sea, located about 3 km from the sailing line and up to 8 km from the wave production area. The analysis is based on high-resolution profiling of the water surface for about 650 wakes from fast ferries, measured during 4 weeks in June-July 2008. The new large conventional ferries with cruise speeds of 25-30 knots (~45-55 km/h) sail at near-critical speeds along extensive sections of eastern Tallinn Bay, and excite wakes equivalent to those of high-speed ferries. The peak periods of these wakes are between 10 and 13 s. The typical daily highest ship wave is approximately 1.2 m, measured prior to wake breaking. The largest recorded ship wave in calm conditions had a height of 1.5 m and in the presence of some wind wave background 1.7 m. The cumulative impact of ship wakes results in a gradual increase in the suspended matter concentration in near-bottom water over the course of a day. The largest and longest ship waves produce considerable wave runup at the coast and prevent several coastal sections from achieving an equilibrium state. The largest ship waves have an asymmetric shape both in terms of the water surface elevation above and below the mean level and in terms of the shape of the wave front and back. The overall intensity of anthropogenic waves has remained at the same level as it was in the year 2002, although the ships that produced the highest waves in the past are no longer in service
Visual wave observations from the north-eastern coast of the Baltic Proper and from the southern coast of the Gulf of Finland and numerically hindcast wave properties for the entire Baltic Sea were used for the identification of combinations of wave heights and periods in extreme storms and long-term changes in extreme wave heights and wave propagation directions. The extreme wave heights and periods are about 7 m and 10-12 s in the northern Baltic Proper, about 6 m and 8-11 s at the entrance to the Gulf of Finland, and about 4 m and 6-8 s in the eastern part of this gulf. Wave hindcasts show no statistically significant trends in the 95%-iles and 99%-iles of the wave heights. Significant observed changes in the directional distribution of waves at Narva-Jõesuu from the 1980s are not represented in hindcasts.
The major factor shaping the coast of the micro-tidal Baltic Sea is wave activity, the impact of which is limited by the presence or absence of sea ice. Existing studies have revealed almost no correlation between the annual mean wave height and the duration of the ice season. We attempt to evaluate the correlation between ice season duration and bulk wave energy flux (wave power), mean energy and average wave height over the ice-free season for three segments of the Estonian coast (Vilsandi, Pakri and Narva-Jõ esuu). Statistically significant correlation at the 95% confidence level exists between the duration of the ice season at Vilsandi (a site fully open to the predominant winds) and bulk wave energy flux derived from both observed and modelled wave properties. Similarly strong correlation exists between the mean wave energy and the duration of the ice season at the largely sheltered Narva-Jõ esuu site.
This study presents the analyses of students’ preferences, satisfaction and perception of learning mathematical subjects at higher education maritime institutions in Croatia, Latvia, Estonia and Poland. All these institutions participate as project partners in the MareMathics project. In order to evaluate the effectiveness of teaching and learning mathematics, a preliminary student survey was conducted in all project partner institutions. Two indicators were analyzed: exam success rate and learning outcomes achieved. The developed online questionnaire contained a number of questions about the teaching methods and tools used by lecturers. Students assessed the impact of different teaching methods, expressed their satisfaction with learning materials, their impact on the results achieved by them, and the overall course. The analysis of the obtained data revealed that students faced difficulties in completing their tasks within subjects on mathematics and statistics. These research results lead to the conclusion that the used methods and tools of teaching mathematics and statistics, which are the essential influential factors on the overall satisfaction of students, are not effective and need to be modernized in the institutions under consideration. And this fact is crucial in the process of study and teaching of mathematical subjects as those subjects make up the base and necessary tools in learning other courses contained in the study program, especially in technical and engineering studies.
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