Extracurricular activities as a variety of organizational forms of students gathering in free extracurricular time at elementary school have predominantly cultural, artistic, sporting, technical, recreational or scientific character (Cindrić, 1992). Through them, students meet their needs and develop the culture of using their leisure time. Thanks to its pedagogic potential, chess is increasingly used as an educational tool and taught in elementary schools around the world. This trend begins to follow Croatia, where chess in many schools is carried out as an extracurricular and/or extracurricular activity. In this paper we will present and analyze the advantages that chess has for the elementary school students and empirically determine the occurrence of chess as an extracurricular activity in the schools in the City of Zagreb. Also, based on the results of the qualitative research, the views of the chess teachers regarding advantages of chess implementation, ways of determining the interests of students, and teaching methods used in chess teaching will be presented.

Izvannastavne aktivnosti kao različiti organizacijski oblici okupljanja učenika u slobodno izvannastavno vrijeme u školi imaju pretežito kulturnoumjetničko, športsko, tehničko, rekreacijsko ili znanstveno obilježje (Cindrić, 1992). Kroz njih učenici zadovoljavaju svoje potrebe i razvijaju kulturu korištenja slobodnog vremena. Zahvaljujući svom pedagoškom potencijalu, šah se sve više implementira u kurikulume škola i poučava na svim razinama obrazovanja. Ovaj trend počinje pratiti i Hrvatska, u kojoj se šah u mnogo škola provodi kao izvannastavna i/ili izvanškolska aktivnost. U ovome radu prikazat će se i analizirati prednosti koje bavljenje šahom ima za učenike osnovnih škola te će se empirijskim istraživanjam utvrditi pojavnost izvannastavne aktivnosti šaha u školama Grada Zagreba. Temeljem rezultata kvalitativnog istraživanja prikazat će se stavovi voditelja šaha kao izvannastavne aktivnosti o prednostima njegove implementacije, načinima utvrđivanja interesa te o načinima rada voditelja i polaznika/učenika.

In the article we determine the suitability of the phytocenose as a basic unit for determining soil susceptibility to mechanized logging. A total of 90 measurements of skid trail profiles were taken on a 13.9 km long sample transect. The forest infrastructure studied was categorized into primary and secondary skid trails, trails intended for CTL harvesting and undocumented trails. The following indicators were determined on the profiles: tyre track depth, trail width, trail slope, amount of rock present, presence of roots and road category. The deepest ruts were found in Blechno-Fagetum (6.9 cm), followed by Galio rotundifolii-Abietetum (6.4 cm) and Hacquetio-Fagetum (5.6 cm), while the shallowest ruts were found in Omphalodo-Fagetum (5.3 cm). The deepest ruts were found on primary skid trails (7.0 cm), followed by secondary skid trails (5.8 cm), while the shallowest ruts were found on skid trails used by CTL technology and on undocumented trails (1.9 cm). No significant difference in track depth was found between the four individual phytosociological units, but more extensive research should be conducted in the future.

Experimental Investigation and Modelling of FDM Process Parameters for Tensile Strength Improvement Using RSM Abstract Fused Deposition Modeling (FDM) is one of the most popular additive manufacturing technologies for various engineering applications. The FDM built part is especially anisotropic in nature due to layer-by-layer building mechanism. Therefore, the mechanical properties, especially the tensile strength severaly depend on the process parameters. Hence, the present work focuses on extensive study to understand the effect of four important parameters such as layer thickness, infill density, printing temperature and wall thickness on the tensile strength of test specimens. A total of 30 test specimens were printed using varying processing parameters according Central Composite Design of experiments (CCD) in order to reduce the experimental runs. The RSM method was used to generate a mathematical model, ie an equation (second order polynomial) which describes the process. Experimental results indicate that the wall thickness and infill density have the significant influence on tensile strength, and tensile strength increases with increasing wall thickeness and infill density. Printing temperature and layer thickness have less of an effect on tensile strength. Tensile strength increases with increasing printing temperature and decreases with increasing in layer thickness, especially at lower printing temperature. This paper examines the influence of selected FDM process parameters (layer thickness, infill density, printing temperature and wall thickness) on the tensile strength of the built parts. Design of experiment for doing the experiments makes use of Circumscribed Central Composite Design (CCCD). Empirical relationship between response and different process parameters is established using RSM, and its validity is checked using ANOVA. The developed relationship between tensile strength (output) and process parameters (input) is able to explain the 91.84% of variability in the response. Effect of various factors and their interactions are explained using response surface plots. It shown that the tensile strength is influenced significantly infill density and wall thickness; and less significantly printing temperature and layer thickness. In order to improve the tensile strength of FDM parts made of PLA materials, it is necessary to increase the infill density and wall thickness, decrease the layer thickness, and set the printing temperature in range 200 – 230 °C. The future research is to investigate the effect of all analyzed parameters on tensile strength for different building directions.