Experimental verification of an orthotropic finite element model for numerical simulations of ultrasonic testing of wood poles

Ultrasonic testing is a non-destructive and non-invasive method which has been used for internal condition assessment of wood poles in electric transmission and distribution lines. The reliability of this method of evaluation relies on a good understanding of propagation of ultrasonic waves in wood. However, a full-waveform analysis in ultrasonic testing is rarely performed in practice because of difficulties in establishing realistic values for the elastic parameters, modeling the material damping and characterizing the dynamic response of an ultrasonic transmitter. In this paper, a calibrated orthotropic finite element model for numerical simulations of ultrasonic testing of a sound red pine pole is presented. In the calibrated model, the dynamic modulus of elasticity in the radial and tangential directions, Poisson’s ratio and damping ratios are estimated from ultrasonic testing; whereas the dynamic modulus of elasticity in the longitudinal direction is estimated from transverse-vibration testing. The measured response of an ultrasonic transmitter to a one-cycle sinusoidal pulse of 50 kHz is used as dynamic excitation and introduced in the numerical model as displacement-time history. Results of the first arrival of compression waves and the frequency response magnitude computed at three receiver locations are in good agreement with the obtained ones from ultrasonic testing. The calibrated orthotropic finite element model will be used for a better understanding of propagation of surface and compression waves in ultrasonic testing for the detection of early stages of decay in wood poles.     

Investigation of the volatile organic substances that cause the characteristic odor of pentachlorophenol treated wood utility poles

The nature of the volatile organic compounds that could be at the origin of the characteristic odor of treated wood utility poles was investigated by the study of compositional changes in the chromatographic profiles of fresh-pentachlorophenol (PCP) solvent samples and weathered samples collected from an in-service red pine pole. Over 99 peaks were identified in the chromatogram of the fresh solvent from which a large portion of the C3-, C4-, C5-, C6-alkylbenzene isomers and early eluting n-alkanes was missing from the analysis of weathered samples. Three domains in the chromatographic profile (volatile, semivolatile, and nonvolatile components) were confirmed by assessing the headspace of fresh-PCP solvent samples using direct syringe sampling and solid-phase microextraction. A first level of field validation was achieved using an emission cell for measuring substances emanating from sapwood specimens at different temperatures. The average latent heat of vaporization (deltaHvap) of the PCP-solvent components was estimated at 99.9 kJ/mol from these results. Finally, the analysis of airborne substances at a treating plant and a utility pole storage site confirmed that the C4-, C5-, and C6-alkylbenzene isomers could contribute to the characteristic odor perceived by humans.     

Comparative environmental impact analysis of techniques for cleaning wood wine barrels

We compare four techniques that are commonly used for cleaning and disinfection of oak wine barrels with 225 l of capacity used in the red wine aging process through a life cycle analysis (LCA). The analysed techniques were pressurised water (at 90 °C) plus sulphur dioxide (SO₂) wick (7.5 g per barrel), water vapour (at 105 °C) plus sulphur dioxide (SO₂), ozone (O₃) (4 ppm), and carbon dioxide (CO₂) (50 kg/h for 180 s). The results showed that the barrel cleaning technique with the lowest impact on all water scarcity indexes and is the carbon dioxide, due mainly to low water usage. However, in the global warming category, carbon dioxide technology is the technique that has the greatest environmental impact with a value of 4.080 kg CO₂ per cleaned barrel, due mainly to CO₂ and air consumption.     

浸渍纸层压木质地板现状问题及其发展

综述我国浸渍纸层压木质地板的现状、特点，存在问题及其发展方向。     

Differential pressure characteristics of wood impregnated with compressed gases, liquids and supercritical fluids

Pressure difference characteristics at high pressure impregnation of two hardwood and three softwood species with CO₂, ethanol, hexane and supercritical mixtures were analysed in a high pressure autoclave. The investigation shows that typical penetration characteristics of wood depending on species measured in terms of pressure difference between the surrounding and the centre are true for gases, liquids and supercritical fluids. The known fact that pressures higher than 16 bar may cause wood destruction is confirmed once more. In contrast to known investigations we can show that pressures up to 175 bar can be applied to wood samples without wood destruction if the pressure difference between surrounding and centre does not exceed 16 bar. The supercritical phase of ethanol/CO₂-mixture is a potential media for technical application. It allows fast penetration at high pressures increasing at 16 bar/5 min combined with low pressure differences even at high pressure levels of 175 bar without wood destruction.     

Fate of Cu, Cr, and As during combustion of impregnated wood with and without peat additive

The E.U. Directive on incineration of waste regulates the harmful emissions of particles and twelve toxic elements, including copper, chromium, and arsenic. More information is critically needed on the speciation and behavior of these trace elements during combustion, including the effects of different process variables, as well as of different fuels and fuel mixtures. Using a 15 kW pellets-fueled grate burner, experiments were performed to determine the fate of copper, chromium, and arsenic during combustion of chromate copper arsenate (CCA) preservative wood. The effects of co-combustion of CCA-wood with peat were also studied since peat fuels previously have proved to generally reduce ash related problems. The fate and speciation of copper, chromium, and arsenic were determined from analysis of the flue gas particles and the bottom ash using SEM-EDS, XRD, XPS, and ICP-AES. In addition, chemical equilibrium model calculations were performed to interpret the experimental findings. The results revealed that about 5% copper, 15% chromium, and 60% arsenic were volatilized during combustion of pure CCA-wood, which is lower than predicted volatilization from the individual arsenic, chromium, and copper oxides. This is explained by the formation of more stable refractory complex oxide phases for which the stability trends and patterns are presented. When co-combusted with peat, an additional stabilization of these phases was obtained and thus a small but noteworthy decrease in volatilization of all three elements was observed. The major identified phases for all fuels were CuCrO2(s), (Fe, Mg, Cu)(Cr, Fe, Al)04(s), Cr2O3(s), and Ca3(AsO4)2(s). Arsenic was also identified in the fine particles as KH2AsO4(s) and As2O3(s). A strong indication of hexavalent chromium in the form of K2CrO4 or as a solid solution between K3Na(CrO4)2 and K3Na(SO4)2 was found in the fine particles. Good qualitative agreement was observed between experimental data and chemical equilibrium model calculations.     

Adhesives and techniques open new possibilities for the wood processing industry

The 10 years' industrial and research experience in South Africa in the manufacture, formulation and application of tannin-based adhesives for particleboard, plywood, glulam and fingerjoints is reviewed and discussed. The results obtainable for wood products manufactured with tannin-based adhesives are presented. New techniques for industrial application and some important characteristics of the adhesive correlated to their chemical structure are reviewed.     

Comparative utility of hermetic and conventional grain storage bags for smallholder farmers: a meta-analysis

Postharvest management is critical to attaining household food, nutrition, and income security. Hermetic grain storage bags offer an effective pesticide-free way to protect stored grain against fungal and insect infestation. We evaluated articles indexed in the Web of Science that included experiments comparing the storage efficacy of conventional and hermetic storage bags based on grain germination rate, insect infestation, physical damage, mycotoxin contamination, and changes in weight and moisture content. Compared with grain stored in hermetic bags, grain stored in conventional bags lost 3.6-fold more seed viability, contained 42-fold more insects, had 11-fold more physical damage, and lost 23-fold more grain weight, while grain moisture levels were similar for both hermetic and conventional storage bags. Mycotoxin contamination levels were not as frequently assessed. Levels could be low in grain stored in both types of bags, or levels could be low in hermetic bags and significantly higher in conventional bags. The improved properties of grain stored in hermetic bags can increase food security and household income by providing safe storage options for maintaining seed germinability, and for consumption and/or sale when food supplies are high, or when prices are low. Hermetic bags are economically feasible for use by subsistence farmers in Sub-Saharan Africa for grain for household consumption and for carrying-over seed for planting in the next season. Additional studies are needed to verify the mycotoxin contamination results and to determine if there are differences in functional food characteristics, e.g. flavor and cooking properties, that have not been as comprehensively studied. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Preliminary evaluation of acetic acid-based processes for wood utilization

The fractionation ofEucalyptus globulus wood in acetic acid media was assessed by means of both technical and economic calculations. From a process diagram, material and energy balances were formulated on the basis of reported kinetic models in order to obtain the information necessary for preliminary economic estimates. The economic study included the evaluation of a base-case, optimization and analyses of sensitivity to the major economic variables.

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Vorl?ufige Bewertung von Acetosolv-Prozessen für die Holznutzung

Zusammenfassung Die Fraktionierung von Eukalyptus-Holz in essigsauren Medien wurde sowohl in technischer als auch ?konomischer Hinsicht rechnerisch verfolgt. Aufgrund eines Proze?-Schemas wurden Material- und Energieeinsatz entsprechend früher ver?ffentlichter Modelle formuliert, um daraus die Information für eine wirtschaftliche Bewertung abzuleiten. In die Betrachtungen wurden neben dem grundlegenden Proze? auch m?gliche Optimierungen und die Auswirkungen der haups?chlichen ?konomischen Variablen einbezogen.

     

Preliminary evaluation of acetic acid-based processes for wood utilization

Eucalyptus globulus wood in acetic acid media was assessed by means of both technical and economic calculations. From a process diagram, material and energy balances were formulated on the basis of reported kinetic models in order to obtain the information necessary for preliminary economic estimates. The economic study included the evaluation of a base-case, optimization and analyses of sensitivity to the major economic variables.

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Thermal characterization of pine wood by photoacoustic and photothermal techniques

Photoacoustic and photothermal techniques are used to investigate the thermophysical properties at room temperature for each of the three main planes of nine species of pine wood. The open-photoacoustic-cell approach is used to measure thermal diffusivity, α, and the photothermal technique of continuous illumination of the sample in vacuum is used to measure the product of density and specific heat capacity, ρc. Thermal conductivity and effusivity are derived from the measurements for α and ρc. We conclude that these techniques are well suited to study thermal properties of wood.     

CT-scanning and modelling of the capillary water uptake in aspen, oak and pine

This study utilises Computer Tomography (CT-scanning) to characterize the capillary water uptake in wood specimens. CT-scanning makes it possible to study the capillary rise of water as a function of height in wood specimens after a specific exposure time. The study has also included the development of a theoretical model, which determines the capillary characteristics of wood in relation to its structure. The model developed was tested using experimental results, considering the capillary suction height and the water content change after a specific time as boundary values. A comparison between the theoretical model and the experimental results shows that not all the cells in the wood samples take part in the capillary water transport. It also appears that there is a structural resistance to capillary flow.     

Comparison of pulsed NMR and ultrasonic velocity techniques for determining solid fat contents

An ultrasonic velocity technique has been compared with pulsed NMR'weight' and 'direct' methods of determining solid fat contents (SFC). Measurements were made at 18°C using samples 0–20% of rapidly cooled tristearin in paraffin oil, tristearin in sunflower oil and tripalmitin in paraffin oil. Correlations between the amount of triglyceride added and the SFC predicted by each of the techniques were always better than 0.995 ( n ± 13). The precisions of the ultrasonic technique (0.2%) and the weight method (0.3%) were significantly better than that of the direct method (0.7%). The ultrasonic technique may therefore offer a suitable alternative or adjunct to the established pulsed NMR technique for SFC determinations; it has considerably lower capital cost and a faster sampling rate.     

超声检测接木及在食品安全检测中的研究进展

低能超声检测技术由于其非破坏性、快速、精确、易于实现自动化,同时与其他新型电子技术相比较价格低廉,而且能对高浓度食品和光不透明性材料进行检测,在食品检测中有其独特的优势,目前在食品安全检测中的应用也越来越广泛.本文对超声检测技术在食品外源异物检测、成分检测、包装食品的无损检测和微生物检测方面的应用和进展进行了综述.