The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.

Intrinsic ripples in graphene

Next to cellulose, lignin is the second most abundant biopolymer, and the main source of aromatic structures on earth. It is a phenolic macromolecule, with a complex structure which considerably varies depending on the plant species and the isolation process. Lignin has long been obtained as a by-product of cellulose in the paper pulp production, but had rather low added-value applications. Changes in the paper market have however stimulated the need to focus on other applications for lignins. In addition, the emergence of biorefinery projects to develop biofuels, bio-based materials and chemicals from carbohydrate polymers should also generate large amounts of lignin with the potential for value addition. These developments have brought about renewed interest in the last decade for lignin and its potential use in polymer materials. This review covers both the topics of the direct use of lignin in polymer applications, and of the chemical modifications of lignin, in a polymer chemistry perspective. The future trend toward micro- and nanostructured lignin-based materials is then addressed.

A review on lignin-based polymeric, micro- and nano-structured materials

Preparation of carbon fibers from a lignin copolymer with polyacrylonitrile

The palm oil industry generates significant amounts of solid wastes. The solid wastes, also known as oil palm biomass, includes the trunk (OPT) and fronds (OPT) from the plantation, and empty fruit bunch (EFB), mesocarp fibre (MF) and palm kernel shell (PKS) from the processing mills. Oil palm biomass is not effectively recycled for other applications, and existing disposal practices can cause adverse impacts on the environment. As oil palm biomass is a readily available lignocellulosic biomass, it has the potential to be a low-cost feedstock for conversion into higher value products. The first part of this study provides a comprehensive review of utilisation of oil palm biomass for the production of biofuels, chemicals and biomaterials through direct utilisation and physical conversion, biochemical conversion, thermochemical conversion and synthesis of lignin-based materials. The second part of this study discusses the opportunity for biorefinery development based on existing bioproducts from oil palm biomass, for the production of advanced fuels and platform chemicals that have not been explored in oil palm biomass research. This study proposes integrated biorefinery concepts via the integration of existing oil palm biomass biorefinery products with thermochemical process for upgrading the bioproducts into higher values products. The high-value products integrated biorefinery products include advanced biofuels, fuel additives and platform chemicals. The integrated biorefinery development for oil palm biomass processing is expected to improve the economics of the production of biomass-derived renewable energy and enhance the sustainability of palm oil industry.

/pdf/the-outlook-of-the-production-of-advanced-fuels-and-2qvqrxbhph.pdf

The outlook of the production of advanced fuels and chemicals from integrated oil palm biomass biorefinery

Preparation of cationic softwood kraft lignin and its application in dye removal

Preparation and characterization of a newly water soluble lignin graft copolymer from oil palm lignocellulosic waste

Pedestrians are vulnerable road users, and they are always at risk when making their daily trips. Hence, roadway design and traffic control devices need to consider pedestrians’ safety. Pedestrian walking speed is fundamental to any roadway and traffic control design. Unfortunately, no specific guidelines exist for pedestrian crossing speed in Malaysia. The ultimate goals of this research are to establish the local pedestrian crossing speed and to identify the contributing factors. A total of 1579 samples on pedestrian crossing speed were collected at signalized and non-signalized crosswalks. The Bi-variate analysis (chi-square test) was carried out to study statistically the association of the contributing factors. The Bi-variate analysis shows that crosswalk type, age and gender significantly contribute to pedestrian speed in Malaysia. However, lighting (daytime and night-time) and race are not contributing to the pedestrians’ speed. Besides, pedestrians at non-signalized crosswalk have significantly faster crossing speed than at signalized crosswalk. Chi-square test also showed that children pedestrians are the fastest group, and elderly pedestrians are the slowest group in terms of pedestrian crossing speed. Moreover, male pedestrians have significantly faster crossing speed than female pedestrians do.

http://www.ijtte.com/uploads/2012-12-05/5ebd8343-3a29-afaeIJTTE_Vol%202%284%29_3.pdf

Pedestrian Crossing Speed: The Case of Malaysia

Geopolymers may be the best alternative to ordinary Portland cement because they are manufactured using waste materials enriched in aluminosilicate. Research on geopolymer composites is accelerating. However, considerable work, expense, and time are needed to cast, cure, and test specimens. The application of computational methods to the stated objective is critical for speedy and cost-effective research. In this study, supervised machine learning approaches were employed to predict the compressive strength of geopolymer composites. One individual machine learning approach, decision tree, and two ensembled machine learning approaches, AdaBoost and random forest, were used. The coefficient correlation (R2), statistical tests, and k-fold analysis were used to determine the validity and comparison of all models. It was discovered that ensembled machine learning techniques outperformed individual machine learning techniques in forecasting the compressive strength of geopolymer composites. However, the outcomes of the individual machine learning model were also within the acceptable limit. R2 values of 0.90, 0.90, and 0.83 were obtained for AdaBoost, random forest, and decision models, respectively. The models’ decreased error values, such as mean absolute error, mean absolute percentage error, and root-mean-square errors, further confirmed the ensembled machine learning techniques’ increased precision. Machine learning approaches will aid the building industry by providing quick and cost-effective methods for evaluating material properties.

/pdf/application-of-soft-computing-techniques-to-predict-the-2dvj795u.pdf

Application of Soft Computing Techniques to Predict the Strength of Geopolymer Composites

The mechanics of carbon-based nanomaterials as cement reinforcement — A critical review

Aging process of bitumen is one of the main obstacles, which limit the implementation of porous pavement. An aging process would cause a shorter service life of porous asphalt compared to the conventional hot mix asphalt mixture. The tendency rate of aging processes in porous asphalt is high due to the exposure of bitumen and aggregates binding in an open-graded structure that maximizes oxidation process to occur thus producing aged binder. In this respect to restore the original characteristics of pavement from aged bitumen, rejuvenation of bitumen binder offers an effective option. From the previous research, the performance of waste cooking oil (WCO) is investigated and indicated as one of rejuvenator agents for bitumen regeneration. Thus, this paper reviewed the novelty of the WCO, as an alternative natural rejuvenating agent for aged bitumen to a condition that resembles the original bitumen in the asphalt mixture.

/pdf/a-review-on-application-of-waste-cooking-oil-as-rejuvenator-2oiaffb0wq.pdf

Abdullahi Ali Mohamed

Papers

Preparation and characterization of a newly water soluble lignin graft copolymer from oil palm lignocellulosic waste

Pedestrian Crossing Speed: The Case of Malaysia

Application of Soft Computing Techniques to Predict the Strength of Geopolymer Composites

The mechanics of carbon-based nanomaterials as cement reinforcement — A critical review

A review on application of waste cooking oil as rejuvenator in porous asphalt mixture