WOOD RESEARCH Volume 65, Number 1, 2020
Jian Wen, Zhaoxi Li, and Jiang Xiao

Noise removal in tree radar b-scan images based on shearlet

There are often many scars and hollows in ancient and famous trees. As a convenient and effective non-destructive testing tool, ground-penetrating (GPR) has a technical advantage in detecting abnormality in trees. But the tree radar images always inherit some extent of noise in them. Thus, denoising is very important to extract useful information from a tree radar image. Shearlet is a directional multi-scale framework, which has been shown effective to identify sparse anisotropic edges even in the presence of a large quantity of noise. This article presents an efficient denoising method based on shearlet applied on the tree radar images. Experimental results on forward modeling and standing trees radar data substantiate that the proposed method has the best denoising performance, especially in preserving the edge information as compared with the other methods which are based on wavelet, curvelet and contourlet.

WOOD RESEARCH Volume 65, Number 1, 2020
DUŠAN JOKANOVIĆ, Dragica Vilotić, VESNA NIKOLIĆ JOKANOVIĆ, Sara Lukić, and Tatjana Ćirković-Mitrović

Site influence on anatomical structure of bald cypress

The paper deals with length of tracheids of bald cypress at two alluvial sites in Serbia. Scope of the paper was to establish site inf luence (climate, soil, etc.) on mentioned anatomical feature and to quantify it, as well. Axial tracheid changes have been observed depending on three factors: cambial age, zone inside growth ring and stem height where sampling was performed. The paper established gradually increasing of axial tracheid length with cambial age and that did not depend on zone inside growth ring and stem height. There was also significant inf luence of the zone inside growth ring to axial tracheid length, while stem height where sampling was performed does not have significant inf luence. There was found relation between factors that determine site such as physical and chemical soil properties and climate from one and axial tracheid length from another side.

WOOD RESEARCH Volume 65, Number 1, 2020
Juraj Gigac, Mária Fišerová, Maroš Kováč, and Monika Stankovská

Paper substrates for inkjet printing of uhf rfid antennas

Conventional papers are not suitable for printed electronics because they have a rougher surface than the plastic film commonly used for electronics printing. The paper surfaces were modified by coating and calendering processes to reduce surface roughness and electrical resistance of inkjet-printed UHF RFID antennas. The composition of coatings, the main component which included aluminum oxide pigment, had an influence on the surface roughness, the surface pore content and the electrical resistance of the inkjet-printed UHF RFID antennas on coated papers. Papers coated with a mixture containing 25% polyvinyl alcohol binder in combination with the cationic polymer PDADMAC without glyoxal crosslinker had the lowest surface roughnesses and the lowest electrical resistances of the inkjet-printed antennas. As the coating basis weight increased, the electrical resistance of the antennas increased. Reduction of the electrical resistance of the antennas was achieved after calendering coated paper. The design of the antennas had a significant effect on their electrical resistance, which increased with the length of the antenna.

WOOD RESEARCH Volume 65, Number 1, 2020
Wei Yan, Wansi Fu, Bin Zhang, and Jianbo Zhou

Hygrothermal effect on axial compressive properties of bionic bamboo element

Bionic bamboo element is innovative form inspired by honeycomb, and its axial compressive strength and node’s contribution to strength under different environment were studied to explore the mechanical properties. Crack morphology and stress distribution were analyzed. The results indicated that, the strength of bionic bamboo element was 50.72 MPa, while the strength declined by 39.74%, 43.85% and 36.05% after being immersed in water for 30 days and hygrothermal pretreatment for 30 days and 15 days. Node had negative influence on strength due to fiber hydroscopic swelling and loose compared with the control samples, and lower humidity condition was beneficial to enhance the compressive strength, e.g. the strength of samples in humidity 20% condition for 30 days improved by 56.70% compared with the control group. Crack showed hierarchical damage with fibers’ tear in length and fracture in lateral, stress distribution exhibited symmetry, and the maximum stress focused on the end of bionic bamboo element, and its thin wall was susceptible damaged. Bionic bamboo element retained the mechanical superiority of bamboo culm and promoted its recombination utilization.

WOOD RESEARCH Volume 65, Number 1, 2020
Petar Antov, Viktor Savov, and Nikolay Neykov

Sustainable bio-based adhesives for eco-friendly wood composites. A review

The aim of the present review is to summarize the current state of research in the field of sustainable bio-based adhesives used for production of eco-friendly wood composite materials. The article is focused mainly on the use of lignin, starch and tannins as raw materials and alternatives to the existing conventional adhesives. It is expected that increased amounts of bio-based adhesives will be used in the production of wood composites in order to meet the current needs for development of sustainable and innovative materials which will make the wood-based panel industry more sustainable and lower its dependence on fossil fuels. However, there are still substantial challenges for the complete replacement of petroleum-based wood adhesives with bio-based adhesives, mainly because of their relatively poor water resistance, low bonding strength and large natural variations due to different growing conditions. In this respect, fundamental research is still need in order to determine the factors for formulating bio-based adhesives with optimal properties and broaden their application in wood-based panel industry.

WOOD RESEARCH Volume 65, Number 1, 2020
Zehui Ju, Qian He, Tianyi Zhan, Haiyang Zhang, Lu Hong, and Xiaoning Lu

Calculation of sound insulation of softwood samples at normal incidence and comparison with experimental data

The acoustic simulations were carried out for softwood and composites in order to evaluate their sound properties. Theoretical value of sound insulation was predicted by regarding the substances in the wood cell wall as equivalence to specific medium based on Biot model, and the wood microscopic characteristics, such as the length and diameter of tracheid, diameter of pit, and porosity, were taken into account for determining the equivalent density and bulk modulus of wood. By comparing the tested and predicted values of sound insulation, the conclusions were drawn as follows: the predicted values of sound insulation were significantly correlated with the tested values for wood and wood composites. As for Masson pine, the adjacent of earlywood and latewood was considered as sandwich structure for the calculation of sound insulation. The transfer function involved in sound insulation simulation provided an effective method to characterize the sound insulation volume of wood and wood composite in construction and decoration areas.

WOOD RESEARCH Volume 65, Number 1, 2020
Marcin Jakubowski, Arkadiusz Tomczak, Tomasz Jelonek, and Witold Grzywiński

Variations of wood properties of birch (Betula pendula Roth) from a 23-year old seed orchard

This work presents the results of selected wood properties in birch trees grown on a provenance experiment plot established as a seed orchard. The study concerned: basic density, oven-dry density and compression strength along the grain at a moisture content of 0% and at moisture content above fiber saturation point. Analyses were performed on 971 wood samples collected from 28 trees at the level of breast height. It was found high variability for diameter of breast height (22%) and relatively low for basic density (9%) and oven-dry density (11%). Average basic density was 446.5 kg.m-3 and average oven-dry density was 537.9 kg.m-3. The compression strength at 0% moisture content was four times higher (65 MPa) than the strength at moisture content above the fiber saturation point (16.6 MPa). Most of clones had similar properties within the limits of statistical errors, but a few clones exhibited statistically significant low value.

WOOD RESEARCH Volume 65, Number 1, 2020
Caglar Altay, Ergun Baysal, Hilmi Toker, Turkay Turkoglu, Mustafa Kucuktuvek, Ahmet Gunduz, and Huseyin Peker

Effects of natural weathering on surface characteristics of scots pine impregnated with wolmanit CX-8 and varnished

In this study, it was aimed to investigate the effects of weathering on some surface characteristics such as color and surface roughness changes of Scots pine impregnated with copper-containing chemical such as Wolmanit CX-8 (WCX-8) and varnished with synthetic varnish (SV), cellulosic varnish (CV), and polyurethane varnish (PV) were investigated. Results showed that while the WCX-8 impregnated and PV coated Scots pine specimens showed better color stability than other treatment groups after weathering, only CV coated Scots pine gave the most negative effect on color stability. While, the untreated (control) wood surface turned from red to green and yellow to blue respectively, after weathering, other all treatment groups gave reddish and yellowish tone after weathering. Weathering conditions increased the surface roughness of control (untreated) and other all treatment groups. The control group gave a rougher surface than other treatment groups after weathering. Surface roughness increases were the lower for CV coated Scots pine wood than other treatment groups. The results showed that while WCX-8 impregnation before varnishing gave better color characteristics, generally it caused to increase the surface roughness of Scots pine after weathering.

WOOD RESEARCH Volume 65, Number 1, 2020
Krisztián Andor and Bertalan Bellovics

Analysis of modulus of elasticity of spruce beams under bending with and without fibre reinforcement

The modulus of elasticity has been assumed constant during the finite element (FE) analysis of CFRP reinforced real sized timbers analyzed in load test in laboratory. The latest investigations have shown that it varies significantly during the loading process. Analysis of the modulus of elasticity during the loading provides answers to several questions, by which the FE analysis can be profoundly optimized and yield more accurate estimates. Analysis has been extended to load-modulus functions of previous investigations. Specimens without reinforcement were also included in the investigations, in order to eliminate anomalies of previous measurements and to get easier comparison.

WOOD RESEARCH Volume 65, Number 1, 2020
Tomasz Biadała, Rafał Czarnecki, and Dorota Dukarska

Water resistant plywood of increased elasticity produced from European wood species

The paper investigates the possibility of producing the water-resistant plywood of increased elasticity with use of veneers attained from European wood species, such as alder, birch, beech, pine as well as linden, poplar, willow and spruce. Plywood was produced in two variants. Variant I of plywood was made from various wood species, yet the veneers were of the same thickness. In variant II the centre layer in each case was made from 1 mm thick pine veneer and the face layers were made from 1.4 mm thick veneers of various wood species. The produced plywood was subjected to tests on modulus of rupture, modulus of elasticity and tensile strength, bond quality and compression ratio. Specific values of modulus of rupture and modulus of elasticity were also determined taking into consideration the differences in the thickness of applied veneers. Based on these investigations, the authors concluded that, regardless of the manufacturing method, the highest values of modulus of rupture as well as modulus of elasticity and bond quality are achieved for plywood made from linden, poplar, willow and spruce. The change in the plywood structure (variant II) resulted in a considerable decrease in the values of modulus of rupture and modulus of elasticity (and their specific values) both parallel and across the grain. The lowest values of these parameters were obtained for poplar, linden and willow plywood. What is more, as a result of the applied procedure the bond quality of the produced plywood increased and the compression ratio was reduced. Taking the above into account, we can assume that linden, poplar and willow wood is an optimum choice for the face veneers of plywood with increased elasticity. The centre layer of this kind of plywood can be made from pine veneer of lesser thickness.

WOOD RESEARCH Volume 65, Number 1, 2020
Shupin Luo, Li Gao, and Wenjing Guo

Effect of face layer manipulation on the density profile and properties of low density particleboard

Density reduction has gradually become a trend for the particleboard and furniture industries due to increased price and insufficient supply of wood. However, reduced density of the panels by the simple reduction of the wood material comes along with deterioration of the properties. In this study, to achieve sufficient properties (bending properties in particular), the particle moisture content (MC) and geometry in face layers were manipulated to manufacture low density particleboards (500 kg.m-3), with the core layer composed of a mixture of wood particles (92.5 wt %) and expanded polystyrene (7.5 wt %). This strategy was assumed to increase face layer density and generate a more pronounced vertical density profile, which is expected to improve panel properties. The density profile, mechanical properties and dimensional stability of the particleboards were investigated. Results showed that increasing the moisture content of face layer particles from 8% to 16% or using small-sized particle in face layer resulted in a more pronounced density profile, as well as using fiber in face layer. However, the higher density in the face layer was not necessarily related with better mechanical performance. The optimum physic-mechanical properties were obtained with the board of face layer made of 16% MC fiber, which met the requirements for P2 boards used in dry conditions (EN 312).

WOOD RESEARCH Volume 65, Number 1, 2020
Miroslav Hájek and Pavla Vrabcová

Consideration of forest ecosystem services in environmental management accounting

The environmental management accounting aims at capturing economic and environmental benefits and it should include externalities too. The aim of the paper is to propose a methodological approach for how to include non-market forest ecosystem services in the environmental management accounting so that the information could be used in economic analyzes. For this purpose, it is necessary to identify information relevant to related costs, sales revenues and the value of non-production ecosystem services. It is possible to perform the financial analysis needed for decision making in forest management. In the University Forest Establishment, the rated value of non-market ecosystem services was 3.2 million EUR, and this value was estimated to be twice as much as the value of market ecosystem services. In the Forest Plant Židlochovice, the value of non-market ecosystem services was 0.4 million EUR. Profitability increased from 1.346 to 4.093 and from 1.181 to 3.492.

WOOD RESEARCH Volume 65, Number 1, 2020
Candan Kus Sahin and Busra Onay

Alternative wood species for playgrounds wood from fruit trees

A number of orchard woods have been investigated for suitability in the playgrounds, in the view of responders. In this sense, photos were taken of the specially prepared samples as stimuli, and there were three different groups of respondents. It was observed that the participants were effective in terms of age grouping and material preferences. For group A and C, majority of the participants preferred wooden elements for playground material. However, the majority of participants in group B (50.5%) preferred plastic elements, followed by wooden (31.5%), and then metal (18.0%). Moreover, it was seen that the most significant factors for selection of material for a playground should be safety for both Group A (79%), and C (76.5%), whereas it was aesthetic appearance, for group B (71%). Similar results were found for color properties of wood — the majority of participants of all three groups preferred light colored wooden elements in playgrounds. The results for the aesthetic preferences of wood species judged one-by-one and judged together received similar results. The preference scores for fig wood (Figus canica) is significantly higher than for other wood species, while “wood color” and “aesthetic appearance” are reliable positive predictors to aesthetic preferences.

WOOD RESEARCH Volume 65, Number 1, 2020
Zhonghua Zhagn and Boming Xu

Tang dynasty chair feature design based on Kansei evaluation and eye tracking system

Tang dynasty (AD 618–907) chairs were manufactured during an important period of Chinese furniture development. This paper aims to identify design elements that impact on people’s subjective impressions, so as to guide the design of Tang dynasty style chairs. The study combined eye tracking and Kansei evaluation methods to assess the semantic reception of Tang dynasty chairs. The results showed that the influential factors can be grouped into two main categories: decoration and shape. The decorative features of Tang dynasty chairs that have the most significant impact on visual attention were identified. The study determined that the backrests, armrests, and legs of Tang dynasty chairs design were the most important morphological features. Through these morphological features, we can define the Tang dynasty chair style, guide the design of modern Tang dynasty style chairs, and carry out targeted design of Tang dynasty chair style features.

WOOD RESEARCH Volume 65, Number 1, 2020
Anderson Renato Vobornik Wolenski, Rodrigo Guerra Peixoto, Veronika Fedotova, André Luis Christoforo, and Francisco Antonio Rocco Lahr

Short note: Shear strength estimation model for tropical wood species

For safety reasons, wood strength values are calculated based on their characteristic values. Brazilian national standard (NBR, in Portuguese “Norma Brasileira Regulamentadora”) 7190 (1997) establishes ratios for characteristic strength estimation and three forms of wood characterization, with an emphasis on the simplified procedure for common species, which allows obtaining the strength characteristic values through equations correlating different mechanical properties. The present work evaluates the accuracy of the relation proposed by NBR 7190 (1997) of shear strength along the grain (fv0,k) to compression strength along the grain (fc0,k) (fv0,k=0.12 fc0,k). 960 experimental measurements of shear and compression strength values were performed for 40 hardwood species, and the precision of the relation proposed by the Brazilian standard was evaluated using the analysis of variance (ANOVA) method. Linear, exponential, logarithmic, and geometric regression models were used as an alternative to the NBR relation for shear strength estimation. The statistical analysis revealed that the geometric regression is the model of best fit.