Analysis of the Internal Mounting Forces and Strength of Newly Designed Fastener to Joints Wood and Wood-Based Panels

This study aimed to numerically and experimentally analyze the effects of internal mounting forces and selected materials on the stiffness and bending moment capacity of L-type corner joints connected with novelty-designed 3D printed fasteners. The experiments were carried out using medium-density fiberboard, high-density fiberboard, beech plywood, particleboard, and beech (Fagus silvatica L.) wood. The results showed that the joints made of beech wood were characterized by the largest bending moment capacity (12.34 Nm), while the worst properties were shown by particleboard (2.18 Nm). The highest stiffness was demonstrated by plywood joints (6.56 kNm/rad), and the lowest by particleboard (0.42 kNm/rad). Experimental studies have reasonably verified the results of numerical calculations. The test results confirmed that the geometry of new fasteners promotes the mounting forces under the assembly of the joints. It was shown that the higher the density of the materials, the greater the value of the mounting forces (164 N–189 N).

Influence of Citric Acid on the Bond Strength of Beech Wood

In this study, beech wood (Fagus silvatica L.) has been chemically modified with citric acid (Acidum citricum) and sodium hypophosphate (SHP) as the catalyst and gradually thermo-condensed in the dryer. Afterwards, wetting angle, surface energy, and shear strength of glued joints of modified and unmodified wood were determined. Testing of the bond strength according to standard EN 204 and comparison between modified and unmodified samples were executed. The adhesive used for bonding samples was polyvinyl acetate (PVAC), commonly used for gluing solid wood panels. Testing material was divided into three groups (dry, wet, and wet conditioned samples), within which statistical analysis was performed, and the significance of the differences between the modified and unmodified samples was determined. Surface energy is correlated with the bond strength, indicating that modification with citric acid negatively affects the adhesive properties of beech wood. A reduction in the bond strength of modified wood glued with PVAC glue compared to unmodified wood was determined. All the results indicate that the modified samples do not meet the minimum requirements for EN 204 bonded with PVAC glue. Therefore, it will be necessary to conduct further studies using other types of adhesives to investigate whether modified wood might be suitable for gluing.

Impact of Irregular Tooth Pitch of Circular Saw Blades on Power for Wood Cross-Cutting

The article deals with the influence of irregular tooth pitch on energy consumption of cross-cutting wood. In this article, the effect was assessed of feeding velocity and parameters of saw blade on the cutting power Pc of spruce (Picea Abies), pine (Pinus Sylvestris) and beech (Fagus Silvatica) wood during sawing with a guided circular saw. For the research, two types of circular saw blades were used, one of them having irregular tooth pitch. The circular saw blades had sintered carbide inserts with a diameter of D = 350 mm and the same number of teeth. The feed velocities were vf = 4, 8,12 m∙min-1 and revolutions n = 3000 min-1. The results showed that the circular saw blades with irregular tooth pitch have higher energy consumption than the circular saw blades with regular tooth pitch. The highest cutting power Pc was shown in the case of beech. It was also shown that energy consumption is increasing linearly with increasing feed velocity.

Фотосинтетичні індикатори стану забруднення атмосферного повітря Покутсько-Буковинських Карпат

Досліджено взаємозв'язок стану атмосферного повітря та показників фотосинтетичного апарату представників дендрофлори Покутсько-Буковинських Карпат бука звичайного (Fagus silvatica L.) та тополі пірамідальної (Topulus pyramidalis Moenoh.), що вегетують в умовах різного антропогенного навантаження. Зразки листків відбирали із чотирьох екотопів, що відрізняються рівнем функціонального призначення та забруднення атмосферного повітря. Вивчено вміст хлорофілів та їх співвідношення, а також інтенсивність процесів світлової фази фотосинтезу. Встановлено, що зменшення відносного вмісту хлорофілу "b" в умовах забруднення атмосферного повітря тісно корелює із швидкістю переносу електронів по електрон-транспортному ланцюгу (реакція Хілла). У порівняно чистих, за показниками атмосферного повітря, територіях (заповідній зоні та зоні стаціонарної рекреації національного природного парку) існує тісна позитивна кореляція між вмістом легких негативних аероіонів, нагромадженням зелених пігментів та активністю фотофізичних процесів. Побудовано кореляційну матрицю взаємозалежності показників активності фотосинтетичного апарату рослин та стану атмосферного повітря досліджених територій. Обґрунтовано доцільність використання фотосинтетичних показників дендрофлори заповідної зони об'єктів природоохоронних територій як індикаторів стану екологічної безпеки атмосферного повітря. Результати досліджень опрацьовано статистично.

Differences in humic acids structure of various soil types studied by DRIFT spectroscopy

The method of diffuse reflectance infrared spectroscopy (DRIFT) proved to be useful for studying the soil organic matter structure. The aim of this study was to compare DRIFT spectra of humic acids (HAs) separated from various soils and to identify their specific nature. Samples of agricultural soils (Dystric Cambisol, Haplic Chernozem, Greyic Phaeozem, and Haplic Luvisol) were collected from humic (A) horizons. Soil samples of reclaimed dumpsites (Haplic Technosol (molic) and (calcic)) were taken from the upper part of the soil profile. Samples of forest soils were collected from surface organic (H) horizons of Cambisols in spruce (Picea abies L. Karst.) and beech (Fagus silvatica L.) forests. The selected soil types differ in pH, carbon content, texture, and humus quality. An extraction of HAs was performed using a mixture of 0.5 M NaOH and 0.1 M Na₄P₂O₇. The separated HAs were freeze-dried and analyzed using a DRIFT spectrometer (Thermo Nicolet Nexus) without KBr dilution. There were found differences in relative aromaticity among the agricultural soils HAs. The most aromatic character was observed in HAs from Chernozems and the least in Cambisols. Preservation of the natural structure of Chernozem HAs during the reclamation process was documented on the HAs spectra from Haplic Technosols (molic). By using the DRIFT spectra of HAs of forest H horizons, it is possible to identify the fragments of decomposed material (gymnosperms or angiosperms). HAs isolated from these horizons represent a certain interstage between lignin and the matured soil humic acids.

Analysis of variations in and correlations between selected physical parameters of common beech (Fagus silvatica L.) nuts

The basic dimensions and the mass of common beech nuts and seeds from five nut batches, harvested from tree stands in northern Poland, were determined. Environmental conditions had a greater influence on seed plumpness than the age of tree stands. The results of measurements were analyzed statistically by analysis of variance, correlation analysis and linear regression analysis. Despite differences in their plumpness, nuts were characterized by nearly identical cross-sections which resembled an equilateral triangle. The thickness of nuts and seeds was highly correlated with their mass, and this information can facilitate seed husking and separation into mass categories. Before and after husking, seeds should be separated with the use of a mesh screen with longitudinal openings. Medium-sized (most numerous) seeds were separated into the following plumpness categories using a screen separator with ≠6 mm and ≠7 mm openings: 84% of moderately plump seeds, 3% of seeds with reduced plumpness, and 13% of plump seeds.

Species of honeydew producing insects useful to apicu1ture in Greece

In many countries of Europe as well as in Greece a high percentage (40-70%) of the honey production derives from honeydew producing insects which belong to Hemiptem-Homoptera and mainly to the superfamilies Aphidoidea, Coccoidea, Psyloidea and Aleuroidea. To identify these useful to apiculture insects in Greece, a survey work has been carried out since 1977. From this research thirty eight species were observed and listed in the period of 1977-1983. Fifty eight species producing honeydew exploited by bees have been also observed in Central Europe. At least 120 species of honeydew pro­ducing insects (Rhynchota), on various host plants, have been recorded in Greece, therefore the number of insects useful to apiculture might be higher. This work aimed at finding more sources of honey production in our country and for this reason a survey was carried out in many areas to collect and identify the honeydew producing insects on which bees were observed to forage. The work was based on the method used previously. For that, sampling was carried out everywhere bees were observed to forage on insects honeydew. Bees were captured and examined according to the method described by Gary and Lorenzen to find out if and when the bees forage on this honeydew. The data collected during this period, 1984 to 1989, are recorded in this note. List of Species: I) Aphidoidea: A) Aphididae: 1) Acyrthosiphon caraganae (Cholodkovsky) (Aphidinae). It was found on the shrub Colutea arborescens L. at Portaria, Pelion, in May 1986. The bees forage from late April to June. This host plant exists almost all over Greece, but in high numbers in Peloponnesus, Sterea Hellas and Thessaly. A. caraganae was found in all these areas, while the bees were observed to forage on this aphid. 2) Corylobium avellanae (Schrank) (Aphidinae). It was observed on filbert trees (Corylus avellana L.) in the Grevena area in 1984 and later in Aghia, Larissa co. and Katerini, Pieria co. It is found on the under side of the leaf and pro­duces honeydew from May to mid July. 3) Hyalopterus ainvgdafi (Blanchard) (Aphidinae). This aphid appears at high population levels on almond trees (Prunus dulcis (Miller) D.A. Webb.) in Locrida and Attiki (Central Greece) and on the island of Kea. It produces large quantities of honeydew in May, June, July. B) Lachnidae: 1) Cinara juniperi (De Geer) (Cinarinae). It was observed on Juniperus spp. in Giona mountain, in May 1986, at an altitude where the fir trees grow. The bees forage from May to early June. This honeydew is produced earlier than that excreted by the coccid Physokerines hemicryphus Dalman which lives on fir trees, and is very useful to apiculture in Greece. There are indications that the existence of this aphid close to fir forests, is a prediction that the coccid P. hemicryphus is going to attain high populations at the same year, but this has to be verified. 2) Cinara tujufilina (del Guercio) (Cinarmae). This aphid was observed on ornamental Thuja spp. in Votanikos Athens and Kiphissia, Attiki in April 1984. The bees forage late in April to May. This insect is new to the Greek fauna. C) Drepanosiphidae: 1) Phyllaphis phagi (L.) (Phyllaphidinae). Common aphid on Fagus silvatica L. It was found almost everywhere this host exists as in the mountains of Iti, Tymphristos, Pelion, Vermion and others. This insect produces honeydew in May, June and July. 2) Pterocallis maculata (Von Heyden) (Drepanosiphinae). It was found at low population levels on Alnus q1tifinosa Garth. in the mountains Pelion and Olympus in Central Greece in May 1987. This aphid produces honeydew in May, June and July. 3) Tuberculoides eggleri Burnes (Drepanosiphinae). This aphid was found on various species of Quercus spp. on the mountains, Zeria, Kalidromon, Iti, Pelion and Olympus, at relatively small population levels. The hon­eydew appears in May. II) Coccoidea: A) Aclerdidae: 1) Aclerda berlesei Buffa. This scale insect was found in Korinthia in July 1988 on Arundo donor L.. later it was observed everywhere this host-plant was sampled as in Lamia, Tricalla, Larissa, Platamonas (Central Greece). The population of this insect is always in high levels and it produces large quantities of honeydew. The honeydew appears early in June and continues in July, August and early September. The bees forage on it, mainly in August. The honey from this honeydew has good appearance, good taste but has not so good smell. B) Coccidae 1) Physokertnes piceae Schrank. This scale was recently found at low population levels on fir trees in Parnassus and Giona mountains in Central Greece and this is the first record in Greek fauna. All, but Aclerda berlesei, abovementioned species are recorded also in Central Europe as honeydew producing insects. It seems that amongst these ten honeydew producing insects, the most important for the apiculture of Greece are the aphid C. juniperi and the scale A. berlesei.

A novel device to measure gaseous permeability over a wide range of pressures: characterisation of slip flow for Norway spruce, European beech, and wood-based materials

A novel device was conceived and built to measure the apparent gaseous permeability of porous media over a large range of permeability values (10−10–10−18 m2) and mean pressures (from 1 bar down to ca. 40 mbar). An extensive series of experimental data are presented and analysed for various porous media: (1) Norway spruce (Picea abies) and European beech (Fagus silvatica) in the three anatomical directions, and, for comparison, (2) three simpler porous media, i.e. an autoclaved aerated concrete (AAC, light concrete) and two wood-based panels. For all porous media, the intrinsic permeability, the gas slippage factor, and the effective pore size were determined from the variations of the apparent permeability as a function of mean pressure. These results are in good agreement with those of previous studies for spruce and bring new insights for beech and wood-based materials, in general. For all products, the effective pore sizes identified with the new instrument are closely linked to the medium morphology. In particular, it was found that in spite of the huge anisotropic ratios between wood’s longitudinal and tangential directions, the identified pore size is similar and corresponds to anatomical features: openings in margo for spruce and scalariform perforation plates for beech. Besides, the pore size identified for beech in the radial direction suggests that radial permeability is most probably controlled by the openings in ray cells (either pits or intercellular voids).