The effect of silane coupling agents on radiata pine fibre for use in thermoplastic matrix composites

Gamma-aminopropyltriethoxysilane (GS) and dichlorodiethylsilane (DCS) were employed for surface modification of radiata pine (Pinus radiata) wood fibre. Levels of fibre moisture were carefully controlled to optimise chemical and hydrogen bonding with these silane coupling agents. The effect of pre-treatment using 2% sodium hydroxide, shown to be effective in assisting silane coupling for other natural fibres [Composites, Part B: Engng 30 (1999) 321], was also investigated. X-ray photoelectron spectroscopy and nuclear magnetic resonance (NMR) were used to characterise modification of the wood fibre. Concentrations of up to 3.2 wt% Si were obtained on the fibre surface due to silane coupling, however, pre-treatment was found to dramatically reduce this value. NMR provided evidence that coupling had occurred between the fibre and DCS by reaction producing ether linkages between the hydroxyl groups on the wood fibre and silane. Pre-treatment and treatment were found to have an insignificant effect on fibre strength. Composite sheets were produced by blending fibre (5, 10 and 20 wt%) with polyethylene followed by extrusion. An increase in strength was obtained at fibre contents of 5 wt% for all treatments compared to composites with untreated fibre. This is believed to be mainly due to increased compatibility of the fibre surface to polyethylene. However, there was no such improvement obtained at higher fibre contents. Evidence suggests that the production of voids is limiting composite strength.     

Characterisation and properties of geopolymer composites. Part 2: Role of cordierite-mullite reinforcement

Our previous research paper on geopolymer-mullite composites showed promising results on compressive strength and fire resistance. However, no improvement in thermal shock resistance was observed in the afore mentioned study. In this study, further attempts to improve thermal shock resistance of the geopolymer were explored. The research was performed by compositing a fly ash-based geopolymer with cordierite-mullite at 20, 40 and 60 wt% replacement. X-ray diffraction (XRD) of the cured geopolymer composite specimens showed the existence of cordierite, mullite, quartz, cancrinite and lazurite. It was found that compressive strength and strength retention after thermal exposure at 400 °C were improved in the geopolymer composite specimens, especially those with 20–40 wt% replacement. Upon further heating to 600 °C, all geopolymer specimens showed insignificant differences in compressive strength. Fire resistance was found to improve with increasing proportion of replacement contents.     

Thermal effects in H2O and CO2 assisted direct carbon solid oxide fuel cells

Thermal effects in a H₂O and CO₂ assisted tubular direct carbon solid oxide fuel cell (DC-SOFC) are numerically investigated. Parametric simulations are further conducted to study the effects of operating potential, the distance between carbon and anode, inlet gas temperature, and anode inlet gas flow rate on the thermal behaviors of the fuel cell. It is found that the fuel cell with H₂O as gasification agent performs considerably better than the cell with CO₂ as gasification agent in all cases. It is also found that the temperature field of the fuel cell is highly uneven. The breakdown of the heat sources in the fuel cell shows that the H₂O assisted DC-SOFC has much higher heat generation and consumption than the CO₂ assisted cell. Interestingly, a thermal neutral voltage is observed, at which no heating or cooling of the cell is needed. In addition, the distance between the anode and the carbon layer is required to be as small as possible, which improves the temperature uniformity of the fuel cell. The results of this study demonstrates the importance of thermal effects in DC-SOFCs and form a solid foundation for DC-SOFC thermal management.     

Review-driven configuration scheme evaluation methodology with configuration interaction effects

This study focuses on configuration scheme evaluation (CSE) based on customer perceptions deduced from online reviews. It is noteworthy that customers in different market segments often hold significant differences in their perceptions of the same configuration. Meanwhile, there may exist a potential dependency relationship between configurations referred to as configuration interaction increasing the complexity of CSE. This paper proposes a review-driven interacting CSE methodology fusing with review texts and configuration documents to address these challenges. First, three indexes, namely configuration differentiation, price consistency, and usage scenario similarity, are defined to identify targeted segments. Second, a differentiated calculation strategy is designed to measure configuration performances based on the configuration data and review data in the identified segments. Third, a configuration performance aggregation function that considers configuration interaction is developed based on the Choquet integral. Finally, two CSE problem about car and laptop products is analyzed using the proposed methodology to verify its applicability. Three comparative studies are also conducted to show the effectiveness and stability of the proposals.     

Risk appraisal of passing zones on two-lane rural highways and policy applications

Passing on two-lane rural highways is associated with risks of head-on collision resulting from unsafe completion of passing maneuvers in the opposite traffic lane. In this paper, we explore the use of time-to-collision (TTC) as a surrogate safety measure of the risk associated with passing maneuvers. Logistic regression models to predict the probability to end the passing maneuver with TTC less than 2 or 3 s-threshold were developed with the time-gap from initiation of the maneuver to arrival of the opposite vehicle (effective accepted gap), and the passing duration as explanatory variables. The data used for model estimation was collected using stationary tripod-mounted camcorders at 19 passing zones in Uganda. Results showed that passing maneuvers completed with TTC less than 3 s are unsafe and often involved sudden speed reduction, flashing headlights, and lateral shift to shoulders. Model sensitivity analysis was conducted for observed passing durations involving passenger cars or short trucks (2–3 axles), and long trucks (4–7 axles) as the passed vehicles for 3 s TTC-threshold. Three risk levels were proposed based on the probability to complete passing maneuvers with TTC less than 3 s for a range of opposite direction traffic volumes. Applications of the results for safety improvements of two-lane rural highways are also discussed.     

Discrepancy analysis of driving performance of taxi drivers and non-professional drivers for red-light running violation and crash avoidance at intersections

Due to comfort, convenience, and flexibility, taxis have become increasingly more prevalent in China, especially in large cities. However, many violations and road crashes that occurred frequently were related to taxi drivers. This study aimed to investigate differences in driving performance between taxi drivers and non-professional drivers from the perspectives of red-light running violation and potential crash involvement based on a driving simulation experiment. Two typical scenarios were established in a driving simulator, which includes the red-light running violation scenario and the crash avoidance scenario. There were 49 participants, including 23 taxi drivers (14 males and 9 females) and 26 non-professional drivers (13 males and 13 females) recruited for this experiment. The driving simulation experiment results indicated that non-professional drivers paid more attention to red-light running violations in comparison to taxi drivers who had a higher probability of red-light running violation. Furthermore, it was found that taxi drivers were more inclined to turn the steering wheel in an attempt to avoid a potential collision and non-professional drivers had more abrupt deceleration behaviors when facing a potential crash. Moreover, the experiment results showed that taxi drivers had a smaller crash rate compared to non-professional drivers and had a better performance in terms of crash avoidance at the intersection.