No abstract

In this work, crude glycerol liquefaction of lignins produced in the pulp and paper industry, as well as an organosolv lignin (sugarcane bagasse), was studied with the ultimate aim of preparing bio-based polyols for polyurethane (PU) preparation. This is a proposed strategy to valorise the by-products of biodiesel and lignocellulose biorefineries. Size-exclusion chromatography revealed that the lignins behave differently during liquefaction based on a ranging product molecular weight (MW). The MW of the liquefaction products was concluded to be related to the phenolic and aliphatic hydroxyl group content of the respective lignins, as well as the removal of glycerol and monoacylglycerol during liquefaction. Lignin was modified to yield mostly a solid-phase product. Fourier transform infrared spectroscopy suggests that crude glycerol constituents like glycerol and fatty acid esters are bound to lignin during liquefaction through formation of ether and ester bonds. Liquefaction yield further also varied with lignin type. The liquefaction products were effectively employed as bio-based polyols to prepare PU.

The need for green materials has driven interest in the preparation of rigid polyurethane foam (PUF) from various biomass types. The present study aims at increasing bio-based content by utilizing by-products from both the pulp and paper and biodiesel industries. Bio-based polyols from respective liquefaction of kraft lignin, organosolv lignin and lignosulphonate in crude glycerol were employed to prepare rigid PUFs. The highest foam compressive strength was 345 kPa with density 79 kg m À3 ; thermal conductivity was 0.039 W m À1 K À1 and the corresponding material had 44 wt% renewable content. Thermal characteristics and biodegradability were also evaluated. Technical lignin type was found to determine product properties to a large extent. Based on the use of existing industrial scale by-products in this study, the findings can be beneficial for present and future biorefineries in the valorization of lower value by-product streams.

The various design limitations imposed on RSFQ circuits through synchronous clocking schemes, make the use of asynchronous clocking attractive. We critically review and compare a wide range of asynchronous methodologies that have thus far been proposed in the published literature. Circuits are optimized using a Genetic Algorithm optimizer and are then compared in terms of yield, critical margins and latency. A full-adder is also designed and simulated for each methodology to obtain information regarding implementation above the primitive cell level.

Ultra-high speed microprocessors, clocked at hundreds of Gigahertz, remain the dreams of processor designers and consumers alike. However, such processors would require designs and clocking schemes that differ radically from that of current processors. This paper discusses superconductive asynchronous processors as one alternative to mainstream processors. This asynchronous design approach requires no global clocking, which reduces the complexity of global clock distribution, clock skew and considerations for clock jitter. The design of a 4-bit asynchronous microprocessor with a simple pipeline is covered. RSFQ-AT logic and its design methodology is used, and it is shown to be well suited to large scale asynchronous circuits. We show how the RSFQ-AT design methodology simplifies and speeds up the design process. Methods for performance evaluation of this asynchronous RSFQ microprocessor is also proposed.