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We report for the first time on the existence of a localized reduction in elasticity caused by repeated compression impaction applied along the tangential wood direction. Previous research indicates that localized strain profiles are generated by such cyclic impacting on wood along its radial direction. This finding is significant for the paper/board-making industry where wood is exposed to cyclic unipolar compression during grinding. However, the effect of the impacting direction, with respect to the orientation of the annual rings, on the localization phenomenon is unknown. In addition, the shape of the developing fatigue layer is unclear. We revisit the localization phenomenon with a focus on tangential impacting. We employed ultrasonics and x-ray tomography to quantify the induced fatigue. An interlacing technique increased the precision of the ultrasonic stiffness depth profiling technique. We studied both radial and tangential wood annual ring geometries. We used ultrasound to quantify the drop in shear modulus resulting from impacting. Both radial and tangential geometries featured strain localization, but the shape of the fatigued layer was different in the radial and tangential wood geometries (steeper profile in the radial geometry). The fatiguing reduced the shear modulus. These results tell us about the ratio of the number of hits that need to be delivered along the radial and tangential direction of the ground wood, respectively. This insight may translate into a design pattern for an energy saving grind stone surface. [ABSTRACT FROM AUTHOR]

The accurate measurement of wood dielectric properties and their relationship with many influencing factors are not only necessary for the study of other relevant wood properties, but also improve the wood dielectric moisture content detection method. In this study, the relationships between dielectric properties and frequency, as well as between moisture content and texture direction were analyzed. The results showed that the effect of the moisture content on the dielectric constant is significant. With increasing moisture content, the dielectric constant increased exponentially below the fiber saturation point. The effect of texture direction slightly exceeded that of the radial direction, and the change rate of the tangential direction above the fiber saturation point was higher than that of the radial direction. The relationship between the dielectric constant and frequency was related to the wood moisture content. The dielectric loss was approximately linear with the frequency below the fiber saturation point. [ABSTRACT FROM AUTHOR]

The comparison of accuracy and ease of operation was made between voltammetry and digital bridge method for electrical resistance measurement in Populus davidiana wood specimens and the factors influencing voltammetry were examined. The results showed that current types, waveforms, voltages and frequency had different effects on the resistance values of voltammetry. The measured DC resistance decreased with the increasing voltage. DC resistance presented a turning point at the voltage of 8 V, while AC impedance remained constant over the entire voltage range. The effects of waveform on resistance was minor. No remarkable difference in resistances was found between the two methods above fiber saturated point (FSP) and voltammetry was relatively stable below FSP. The relationship between MC and resistances confirmed the previous findings from other scholars. Compared to the digital bridge, the voltammetry of AC with 1000 Hz sine waves was found to be the superior method for wood resistance measurement. [ABSTRACT FROM AUTHOR]

One challenge of monitoring and inspecting timber bridges is the difficulty of measuring the moisture content anywhere other than close to the surface. Damage or design mistakes leading to water penetration might not be detected in time, leading to costly repairs. By placing electrodes between the glulam beams, the moisture content through the bridge deck can be measured. Due to the logarithmic decrease of the resistance in wood as a function of electrode length, the model must be calibrated for measurement depth. Two models were created: one for electrode lengths of 50 mm and one for electrode lengths up to 1355 mm. The model for short electrodes differed by no more than 1 percentage points compared with the oven dry specimens. The model for long electrodes differed up to 2 percentage points for lengths up to 905 mm, and over that it could differ up to 4 percentage points. [ABSTRACT FROM AUTHOR]

This paper examines how wood decay fungi affect the electrical resistance (resistivity) of wood to determine whether an electrical resistance probe could be deployed as a remote sensor in a wall to detect wood decay. Electrical resistance measurements were taken on wood blocks exposed to Gloeophyllum trabeum in a standard soil bottle tests (AWPA E10) as a function of time. To understand how and why resistance changed with time, results were compared against resistance measurements taken in sterilized, un-inoculated wood at high moisture contents; concentrations of certain mineral ions in the wood were also measured. Results indicate that most of the changes in electrical resistance in the soil bottle test could be described by changes in moisture content alone. When the moisture effects were removed, decay fungi decreased the resistance at small amounts of weight loss but increased the resistance at high weight loss. The results presented herein help to explain the mechanism by which empirical, electrical resistance nondestructive testing devices work and also the limitations on using resistance measurements to detect wood decay. [ABSTRACT FROM AUTHOR]

Pyrolysis of earth ‐ abundant wood yields to ultra ‐ thick, low ‐ tortuosity, and mesoporous carbon anodes for sodium ‐ ion batteries. Such a low ‐ tortuosity and porous structure promotes electrolyte diffusion and provides fast transport channels for Na ions, which ENables a high areal capacity. [ABSTRACT FROM AUTHOR]

The electrical properties of thermally modified wood (TMW) of southern pine (Pinus spp.) have been investigated, while the samples were modified at 150°C, 175°C, 200°C, and 225°C for 4 h. After conditioning the samples at five relative humidities, the constants for electrical resistance (kR) and dielectricity (kP) were measured and calculated according to the model "electrical properties vs. moisture content". The correlations between kR and kP and mass loss (ML), CIEL*a*b* color and bending properties in terms of modulus of rupture and modulus of elasticity were established. The coefficients of determination (R2) between these parameters were found to be between 0.926 and 0.999. TM influenced both kR and kP via changing the concentration and mobility of ions inside the wood and decreasing amount of polar groups of wood polymers. The conclusion is that the severity of TM such as the mechanical properties of TMW is in a close relation to the electrical properties. [ABSTRACT FROM AUTHOR]

This paper addresses the thawing of frozen wood by microwave. The effect of thermal and dielectric anisotropy on thawing wood is considered. The nonlinear heat conduction problem involving phase changes such as wood freezing is solved using three-dimensional volumetric specific enthalpy based on finite-element analysis. The dielectric and thermophysical properties are a function of temperature, moisture content and structural orientation. The specific volumetric enthalpy approach is validated by analytical, numerical and experimental testing. Finally, we studied the thermal effect and dielectric anisotropy on thawing frozen sugar maple wood ( Acer saccharum) at 2466 MHz. [ABSTRACT FROM AUTHOR]

A model has been developed aiming at the description of the effect of thermal modification on the electrical conductivity of wood. The intention was to calculate the moisture content (MC) of thermally modified timber (TMT) through the parameters electrical resistance R, wood temperature T, and CIE L*a*b* color data, which are known to correlate well with the intensity of a heat treatment. Samples of Norway spruce (Picea abies Karst.) and beech (Fagus sylvatica L.) samples were thermally modified in laboratory scale at 11 different heat treatment intensities and the resistance characteristics of the samples were determined. Within the hygroscopic range, a linear relationship between the resistance characteristics and the mass loss (ML) through the heat treatment was established. Based on this, a model was developed to calculate MC from R, T, and ML. To validate this model, color values of 15 different TMTs from industrial production were determined for estimation of their ML and fed into the model. MC of the 15 arbitrarily heat-treated TMTs was calculated with an accuracy of ± 3.5% within the hygroscopic range. The material-specific resistance characteristics based on experimental data led to an accuracy of ± 2.5%. [ABSTRACT FROM AUTHOR]

The thermal and dielectric properties of medium density fiberboard (MDF) with different moisture contents were measured by light flash and the parallel-plane capacitor method, respectively. The results show that increasing moisture content has a positive effect on both thermal properties and dielectric properties. The higher the moisture content, the higher the thermal conductivity and dielectric properties were. The thermal conductivity of MDF with different moisture contents varies in the temperature range of 25 to 150 ºC in a double-hump pattern rather than a proportional pattern. The dielectric constant decreases with increasing frequency up to 1000 MHz. The dielectric loss factor undulates within the frequency range of 1 to 100 MHz, and the peak value occurs at around 10 MHz. The results presented in this study can be used for radio frequency heating, wood building energy, material design, and radio frequency evaluation. [ABSTRACT FROM AUTHOR]

Abstract: Triboelectrification for a rolling contact between hardwood and softwood spheres and a polytetrafluoroethylene (PTFE) plane is studied. For a variety of experimental parameters, the saturation charge developed on the spheres was measured. The results are compared with those reported previously where PTFE spheres were rolled on wood planes. The observations suggest that different principles are involved in the two experimental situations; however, in both cases the saturation charge developed depends on the apparent area of contact. [Copyright &y& Elsevier]

This research had the objective of studing the variation of the calorific power along the shaft of the species forest Acacia mearnsii de Wild, Eucalyptus grandis W. Hill, Mimosa scabrella Benth. and Ateleia glazioveana Baill and also to evaluate the number and the positions of the samples along the shaft for the estimate of calorific power of these species. For so much, they were solitary disks of approximately two centimeters of thickness, along 0%, 25%, 50% and 75% of the total height of trees, with a year of age, for determination of the power calorific superior in calorimeter (C5000, IKA WORKS). For the Eucalyptus grandis and the Ateleia glazioveana it is possible to esteem the power calorific superior starting from a disk, respectively in the positions 50% and 0%, and for the Mimosa scabrella with two disks, in the positions 0+75% and for the Acacia mearnsii, three disks, in the positions 0+25+75%. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this paper is to determine the dielectric characteristics of tropical wood species at microwaves frequency in order to use them as planar antenna substrate. The measurements have been done on dried wood in the frequency range 8.2–12.4GHz. The suitability of wood as a microwave printed antenna substrate will be determined by the values taken by the complex parameters “permittivity” and “permeability” and the loss tangent . The measurement methods were based on the waveguide method and the open resonator technique. The first method gave us the reference values while the second one confirmed the previous measurements. Values obtained in the three principal axis of each species confirm the anisotropic nature of wood. These measurements will also confirm that the losses which are the main criteria of selecting wood as substrate grow with the density of the wood. [Copyright &y& Elsevier]

In this paper, the thermal conductivity and dielectric parameters for pine [Pinus sylvesttfs (L.)] woods were d~ermined in transverse directions for moisture conditions from oven-dry to 22 percent at a room temperature of 22 to 24 °C. Results indicate that the behaviors of thermal conductivity and dielectric parameters with moisture content and structural directions were similar. In general, the properties increased within the range studied with increasing moisture content. The radial values were similar to tangential values for both thermal conductivity and dielectric properties. The data presented here should be useful in most design problems where pine wood is subjected to microwave electric fields and heat changes. [ABSTRACT FROM AUTHOR]

In this paper, a new woodceramics impregnated with liquefied wood is developed and the effect of carbonization temperature on the dimension shrinkage, weight loss, density, compressive strength, and volume electrical resistivity is investigated. The results show that, the higher the carbonization temperature is, the higher the dimension shrinkage is, the higher the compressive strength is, and the lower the electrical resistivity is. [ABSTRACT FROM AUTHOR]