Research Articles

In Sarawak, a state of Malaysia on Borneo Island, clean water supply coverage is estimated to be 81.4% in 2020, whereby those without access to clean water are rural residents. Although the state aims to achieve full clean water supply coverage by 2025, budget limitations make this impossible. This research proposes a decentralized water supply system that harvests rainwater and river water to supply rural households with clean water. The selected study area is Pelaman Monggak, a rural village in Bau District, Sarawak. The rainwater storage tank was modelled using the Tangki NAHRIM (NAHRIM Tank). The results showed that for a rural household of five people, the reliability for a tank size of 2 m3 is 84.5%. From 2010 to 2019, the rainwater storage tank can supply rainwater for 3044 days, with the remaining 608 days supplied by river water. As river water is not safe for potable use, treatment is needed. The proposed water treatment process for river water includes bamboo activated carbon adsorption, membrane microfiltration, and UV disinfection to improve the river water quality from Class II to Class I. For rainwater, two treatment processes, namely membrane microfiltration and UV disinfection, are sufficient to produce safe drinking water quality.

A closed-loop wooden pallet rental system was considered in this study, which involved a wooden pallet manufacturer, a wooden pallet leasing company, and several customers. To solve the joint optimization problem of pallet lease pricing and purchase volume under recycling and reusing mode, a mathematical model was constructed with the objective of maximizing the profit of pallet renters under deterministic and stochastic market demand. Meanwhile, comparative analyses were conducted on the optimal pricing, optimal order quantity, and expected profit under the two leasing modes of considering and not considering maintenance. On this basis, sensitivity analyses were performed on some parameters of the two modes. Results showed that pallet renters can adopt the maintenance strategy to increase profits by lowering the rental price appropriately regardless of the market demand. The wood pallet rental supply chain can be more efficient when the pallet residual value, recovery integrity rate, and utilization rate are higher and the out of stock cost and inventory holding cost are lower. Under the maintenance mode, a lower repairing price and higher reparability rate resulted in a more favorable maintenance mode.

The transportation application of the bamboo–wood composite container flooring (BWCCF) has increased considerably. However, materials would be destroyed in the process of common mechanical evaluation, resulting in a waste of resources. Therefore, this paper aims to design artificial neural network (ANN) models to predict mechanical strength of BWCCF. The modulus of rupture (MOR) and the modulus of elasticity (MOE) of BWCCF were predicted by ANN models based on layups configuration, including directions, densities, and thicknesses of 21-layer BWCCF in each layer. According to results, the mean absolute percentage errors (MAPE) and the correlation coefficient (R) were determined as 16.93% and 0.619 in prediction of MOR, and 10.10% and 0.709 in prediction of MOE, respectively. The results indicated that ANN can be applied to predict mechanical properties of BWCCF.

Shallow notch-screw connections, which showed potential superior slip moduli and load-carrying capacity compared with the traditional screwed connections and can be employed in the timber-concrete composite (TCC) floors were examined in this study. Eight groups of shallow notch-screw connections were designed to perform the push-out tests, in which the arrangement of screws, the heavy timber types, and the width of the shallow notch were considered. The depth of the notch was uniformly 15 mm. The vertical screws and the cross inclined screws were separately selected as the reinforcement for the shallow notch connections. The common heavy timber panels, including nail laminated timber (NLT), glulam, and cross laminated timber (CLT), were adopted. The width of the shallow notch tested included 100 and 200 mm. The experimental results showed that the shallow notch connections underwent ductile failure. The effects of testing factors on the shear strength, slip moduli, and ductility were discussed. The design proposals about the slip moduli of the shallow notches using each timber panel types were proposed, aiming to provide guidance for the application of the TCC floors with shallow notches.

Mechanical properties of materials obtained by compression-molding were compared with three-dimensional (3D) printed materials. Firstly, wood flour was added at different levels (0, 5, 10, and 20%) to polylactic acid (PLA) polymer to produce filaments. Then, mechanical test samples were printed from the produced filaments with a 3D printer. The produced filaments were made into pellets, and sheets were obtained by compression molding. According to the mechanical test results, it was observed that the tensile strength of the 3D-printed and compression-molded materials were close to each other, and the elasticity modulus of the compression-molded samples was higher than the 3D-printed samples. In the hardness comparison, the compression-molded specimens exhibited higher hardness values than the 3D-printed specimens. When the morphological properties of the materials were examined, it was seen that the cross-sections of the compression-molded materials were smooth and had less void than the 3D printed ones. The glass transition, crystallization, and melting temperatures of the materials did not change much with the processing methods. Only the 3D-printing process increased the crystallinity percentages.

Low temperature is a major factor limiting the bio-sustainable and efficient conversion of cellulose-based resources in cold regions. In this study, a low-temperature resistant cellulose-degrading fungus with high cellulase production was screened from samples found in a primitive forest in Daqing by straw using the enrichment-restricted culture technique. The fungus was identified as genus Trichoderma harzianum, strain L-8 by morphological and molecular biological analysis. The enzyme production conditions were optimized via response surface methodology, and the optimal conditions for the enzyme production of Trichoderma harzianum L-8 were as follows: a CMC-Na addition of 10.63 g·L-1, an ammonium sulfate addition of 2.22 g·L-1, an initial pH of 5.29, and a lecithin addition of 5.18 g·L-1 when the CMCase reached 53.40 IU·mL-1. The leading enzyme families of Trichoderma harzianum L-8 were identified via proteomic analysis. Proteases including glycosyl hydrolase family 3-4 and cellobiohydrolase play important roles in cellulose degradation. The strain Trichoderma harzianum L-8 showed a strong cellulose degradation ability under low temperatures, providing strain resources for cellulose resource biotransformation technology in cold regions.

The effects of carpenter bee nests were determined for components of timber buildings. An eaves purlin structure was taken as the experimental object, and medical computed tomography (CT) was used to reconstruct the sectional image of the eaves purlin. The digital image reconstruction technology was used to obtain three-dimensional (3D) images of the two eaves purlins. One eaves purlin was not damaged, and the other was seriously eroded by carpenter bees. The carpenter bee nests were displayed, and the two eaves purlins were simulated by the directional force and the uniform directional force. When the eaves purlin was under the downward pressure of the roof, the shear force at both ends of the eaves purlin and the pressure at the middle were relatively large. The results show that CT is an accurate and efficient technology for detecting the mechanical properties of timber building components. Nests are usually distributed in the eaves purlin eroded by carpenter bees, which destroy the stability of the eaves purlin structure and have a great impact on the stability of timber buildings. Therefore, this method to evaluate the damage degree of timber building components is very important for the protection of timber buildings.

The relationship between the dynamic water penetration behavior of top coating color and double-coated paper properties, including pore structure, surface roughness, gloss, and surface latex content, was investigated. Top coating was applied onto the precoated paper prepared using different pigment types, thereby having different pore structures. To investigate the effect of dwell time on pore structure and surface latex content, coating speed and the distance between two coating heads of a laboratory coater were adjusted. As the number of pores of the precoated layer increased, the amount of water that penetrated the precoated paper increased, regardless of low shear viscosity of the top coating color. The relative pore ratio and surface properties of the top coated layer were proportional to those of the precoated layer. A UV absorbance analysis was conducted to examine latex binder migration. The latex content on the surface of the coating layer was mainly affected by the dwell time to the dryer after coating.

Polyamide-epichlorohydrin (PAE) is used in papermaking to increase the paper’s wet strength. High levels of PAE can make repulping of paper more difficult. PAE deposits can also impair paper machine performance by plugging the paper machine felts. The results of a preceding study indicated that the wet strength of paper containing a moderate amount of PAE (added amount 0.3 wt%) can be increased by utilizing internal alkylketene dimer (AKD) sizing. In the present study, the effects of an added amount of PAE and AKD on the wet strength of handsheets made from Nordic bleached softwood pulp (NBSK) were examined. The wet strength was measured after soaking the sheets in ion-exchanged water for up to 1 month. The improving effect of AKD sizing on the wet strength was long-lasting and it was apparent especially with a low and moderate added amount of PAE (0.15 and 0.45 wt%) resulting in higher wet strength than the highest added amount of PAE (1.35 wt%) alone. No clear sign of worsened repulpability was observed at low to moderate treatment levels. The results suggest that use of small or moderate amounts of PAE with AKD can be a viable option for paper mills facing problems related to the high usage of PAE.

Changes of physical and chemical characteristics of sludge were investigated with respect to the pH, process time, and applied voltage by means of the electric field treatments. A model reactor with the desired speed was used to generate an electric field to separate water from the sludge without applying pressure. All electrodes mounted on the reactor were produced from graphite. Two different distances between anode and cathode (2.3 cm and 4.3 cm) were used to examine the effects on dewatering capacity of sludge. Differentiations of dependent variables inferred from the experimental processes were also surveyed by Box-Behnken experimental design. The water in the sludge was separated effectively when the samples were exposed to an electric field. The total solid increased from 1.07% to 6.60% at pH 6.5 when sludge was exposed to 25 V for 60 min. Furthermore, the optimum distance between electrodes was 2.3 cm for dewatering of sludge samples, where the capillary suction time of influent sludge was observed to decrease by approximately 85.5% at raw sludge pH. Similarly, the viscosity parameters decreased by approximately 99%. There was an increase in the soluble chemical oxygen demand, PO4-P, and NH4-N concentrations of water discharged from the model reactor.