Volume 11 Issue 1

Air-coupled ultrasound has shown excellent sensitivity and specificity for the nondestructive imaging of wood-based material. However, it is time-consuming, due to the high scanning density limited by the Nyquist law. This study investigated the feasibility of applying compressed sensing techniques to air-coupled ultrasound imaging, aiming to reduce the number of scanning lines and then accelerate the imaging. Firstly, an undersampled scanning strategy specified by a random binary matrix was proposed to address the limitation of the compressed sensing framework. The undersampled scanning can be easily implemented, while only minor modification was required for the existing imaging system. Then, discrete cosine transform was selected experimentally as the representation basis. Finally, orthogonal matching pursuit algorithm was utilized to reconstruct the wood images. Experiments on three real air-coupled ultrasound images indicated the potential of the present method to accelerate air-coupled ultrasound imaging of wood. The same quality of ACU images can be obtained with scanning time cut in half.

The influences of heat treatment under vacuum on the mechanical properties and corrosion resistance of untreated poplar wood were investigated in this study. Wood samples were heated in a vacuum atmosphere in laboratory conditions at 140 to 200 °C for 1 to 3 h. The color of the poplar’s surface after heat treatment was deeper than that of the untreated wood, and the dimensional stability of poplar was improved by increasing the temperature and time. However, the compressive strength parallel to the grain of heat-treated samples was slightly lower than that of the control samples. The modulus of rupture of samples heat-treated at 200 °C for 3 h decreased 41.25% compared with the untreated samples. The corrosion resistance of heat-treated poplar increased with increasing temperature and time. The white-rot fungus resistance of the treated poplar was better than its resistance to brown-rot fungus.

The conformational preferences of the lignin guaiacyl structural unit were studied by several quantitative chemistry calculation methods using vanillin as a model compound. The potential energy surfaces of the vanillin molecule were scanned by the methods of HF and DFT to find the most stable conformation, as well as three local minimum conformations and six transient conformations. Bonds strength of all kinds of bonds in vanillin molecules at five temperature were calculated by methods of DFT, MP2, and CBS. The calculation results indicated that temperature had little impact on bond strength; the large bond strength was Ar-OH, Ar-H, followed by Ar-CHO, Ar-OCH3, and the C-H in the aldehyde group, and O-CH3 bond strength in methoxyl was lowest (only 61 Kcal/mol), which may be cracked in pyrolysis. The calculation about the model dimer O-α-β-O-4 also showed that the stable order was O-4 > 1-α> α-β> β-O, which agreed well with the fact that there are a lot of phenolic compounds in pyrolysis products of biomass or lignin.

The article examines deformation of wood veneer and internal forces resulting from bending. Wood is modelled as an orthotropic material. A thin circular wooden plate hemispherically supported at its free edge is bent by axial hubbing of the punch with a hemispherical end. The analysis of the models is carried out by the ANSYS software. Geometric boundary conditions are calculated and set by a macro formed by the APDL (ANSYS Parametric Design Language) scenario language. For the reason of comparison the models were solved for a given plate with simplified boundary conditions.

A pilot-scale aerated lagoon was used for the aerobic treatment of pulp and paper mill effluent from September 1 to December 1, 2014. The aerated lagoon was installed at the chemistry laboratory in the Chemical Engineering Department at the Durango Institute of Technology and was fed with real pulp and paper mill effluent. The experimental work was run under various operating conditions. The operating parameters (total and volatile suspended solids (VSS) and dissolved oxygen concentration (DO)) and environmental variables (temperature, pH, COD, and BOD5 of influent water) were monitored daily. In all the experiments conducted, the aerated lagoon generated an effluent of optimal quality complying with the requirements of SEMARNAT (2003) and CONAGUA (2003). A model that explains the behavior of the system under realistic operating conditions was obtained. The model indicated an optimal DO of approximately 4 mg/L for concentrations up to 1000 mg/L, showing variations in concentrations above this value. This data indicate that the flexibility of the bacterial formulation and its ability to adapt to environmental changes play an important role in the stability of an aerated lagoon.

Kenaf powder was incorporated with natural rubber latex (NRL) compound and foamed to make natural rubber latex foam (NRLF) by using a well known technique called the Dunlop method. Different loadings of kenaf powder were added to NRL compound and was foamed to make NRLF. The mechanical properties, density, compression, thermal, and micro-structural characterization of control NRLF and kenaf incorporated NRLF were studied. Increasing content of kenaf reduced the tensile strength, elongation at break, and compressive strength of a NRLF. Modulus at 100% elongation and density of the NRLF increased with an increase in filler loading. Higher kenaf loading indicated higher elasticity of kenaf-filled NRLF, but the recovery percentage of kenaf-filled NRLF decreased with increasing kenaf loading. From thermogravimetric analysis (TGA) result, an increase in the amount of kenaf loading from 1 to 7 phr increased the thermal stability of kenaf-filled NRLF. Morphological and micro-structural characterization performed by using scanning electron microscopy (SEM) showed that kenaf powder filled up the micro-sized pores in the open cell structure of kenaf-filled NRLF.

Conocarpus pruning waste, an agricultural byproduct, was converted into low-cost activated and non-activated carbons and used for the remediation of Cd2+, Cu2+, and Pb2+ from aqueous solutions. The carbonization was carried out at 400 °C, while the activation was carried out in the presence of KOH and ZnCl2. Batch single-solute and multi-solute equilibrium and kinetic experiments were carried out to determine the adsorption capacities of the prepared activated and non-activated carbons, and these were further compared with commercially available activated carbon. The results showed that KOH-activated carbon (CK) outperformed the other activated and non-activated carbons in terms of adsorption efficiency. CK removed >50% of the applied Cd2+ and Cu2+ and 100% of Pb2+ at the initial concentration of 40 mg L-1. Interestingly, the performance of Conocarpus-derived non-activated carbon was better than that of the commercial activated carbon, as observed from the Langmuir maximum adsorption capacities of 65.61, 66.12, and 223.05 µmol g-1 for Cd2+, Cu2+, and Pb2+, respectively. The Pb2+ was the metal most easily removed from aqueous solution because of its large ionic radius. The kinetic dynamics were well described by the pseudo-second order and Elovich models.

High-temperature thermomechanical pulps (HT-TMP, defibrated at 150 to 170 °C) were compared to a reference TMP (defibrated at 130 °C) as a reinforcement for polylactic acid (PLA). Composites were prepared by melt compounding, followed by injection molding, gradually increasing the used fiber content from 0 to 20 wt.%. The injection-molded specimens were characterized by tensile and impact strength tests, scanning electron microscopy, water absorption tests, and differential scanning calorimetry. The TMP fiber damage was also characterized before and after melt compounding by optical analysis. At 20% fiber content, the Young’s modulus increased significantly, while the tensile strength remained unchanged and the impact strength decreased slightly. All fibers suffered damage during melt compounding, but the tensile strength remained about the same as in pure PLA. All types of TMP were able to increase the PLA rate of crystallization. The HT-TMP fibers were dispersed more evenly in PLA than the 130 °C TMP. The 170 °C TMP produced composites of lower water absorption than the other two TMP types, probably because of its lower hemicellulose content and its higher surface coverage by lignin.

The mechanisms regarding the influence of dissolved organics in papermaking whitewater together with metal ions on the fouling of an ultrafiltration (UF) membrane were studied in this paper. A series of experiments were carried out to characterize the organic matters’ size and membrane flux. The associated fouling mechanism was investigated using the modified Hermia empirical model, resistance distribution, and specific resistance of the cake layer. The results indicated that the addition of metal ions aggravated membrane fouling. Increasing concentrations of metal ions resulted in the higher specific resistance of the cake layer and greater membrane fouling due to their chelation with dissolved organics. Increased pH values influenced the interaction between the metal ions and dissolved organics, resulting in a relatively slow membrane flux decline. Increasing concentrations of Na+ resulted in greater membrane fouling. Cake layer formation played a major role in treating the water samples with high-concentration metal ions, whereas intermediate blocking formation may be the dominant fouling mechanism when treating the solution without metal ions.

In recent years, there has been a rapid rise in the development of engineered bamboo materials, which have the potential to play an important role as alternatives to conventional building materials. Despite the growing diversity of bamboo products available on the market, the international standardization of both bamboo products and their constituent elements is limited, and a lack of universal nomenclature is recognized as one of the main constraints on developing standards. Similar or identical terminology is used interchangeably to describe different bamboo elements, processes, or products across sectors and continents. In some cases, translated colloquial names are misleading and scientifically inaccurate, which forms a barrier to global collaboration and research, creates ambiguity, and potentially limits trade. The present work aims to address this gap by proposing a set of appropriate terms in English that accurately describe and differentiate between currently produced engineered bamboo products and their constituent elements, accompanied by parallel terms in Chinese and Spanish. From these, new categories of engineered bamboo building materials are proposed for the Harmonized System of product codes. This paper highlights current ambiguities and provides terminology together with clear definitions of the main primary elements, processing steps, and products.