Development of mix design method based on statistical analysis of different factors for geopolymer concrete

The present study proposes the mix design method of Fly Ash (FA) based geopolymer concrete using Response Surface Methodology (RSM). In this method, different factors, including binder content, alkali/binder ratio, NS/NH ratio (sodium silicate/sodium hydroxide), NH molarity, and water/solids ratio were considered for the mix design of geopolymer concrete. The 2D contour plots were used to setup the mix design method to achieve the target compressive strength. The proposed mix design method of geopolymer concrete is divided into three categories based on curing regime, specifically one ambient curing (25 °C) and two heat curing (60 and 90 °C). The proposed mix design method of geopolymer concrete was validated through experimentation of M30, M50, and M70 concrete mixes at all curing regimes. The observed experimental compressive strength results validate the mix design method by more than 90% of their target strength. Furthermore, the current study concluded that the required compressive strength can be achieved by varying any factor in the mix design. In addition, the factor analysis revealed that the NS/NH ratio significantly affects the compressive strength of geopolymer concrete.     

A SHAPE AND SIZE OPTIMIZATION ALGORITHM FOR MACHINE TOOL ELEMENT DESIGN

A shape and size optimization algorithm is developed to incorporate the shape and size variables in a recently developed machine tool simulation and design methodology known as Integrated Machining Process Design Simulator (IMPDS). This shape optimization algorithm, using coordinates of master nodes, parameters of geometric equations, coordinate linking and symmetry option approaches presents a general and flexible way of controlling and optimizing the structural shape of machine tool elements. An application of the proposed shape and size optimization algorithm indicates that the shape and size parameters have significant effects on the structural characteristics and the dynamic behavior of machine tool elements.     

KINETIC MODELING OF THE CATALYTIC OXIDATION OF BENZO(A)PYRENE

A catalytic microreaclor has been used to elucidate rates of benzo(a)pyrene oxidation over a wide range of temperature and composition conditions. Catalysts with widely differing properties were utilized in an effort to obtain a single best catalyst. Statistical correlation of the data showed strong preference for the classical Langmuir-Hinshelwood model in all cases.     

Image analysis to reveal crack development using a computer simulation of wear and rolling contact fatigue

Plastic flow of near‐surface rail material under contact loading is a feature of rail–wheel contact, and severe flow typically leads to both wear, and the initiation and development of small surface‐breaking cracks. This paper presents results from a ratcheting based computer simulation, which has been developed to allow the simultaneous investigation of wear, crack initiation and early crack propagation. To identify repeatably small crack‐like flaws, image analysis is applied to the visual representation of the wearing surface generated by the model. This representation shows a good similarity to traditional micrographs taken from sections of worn surfaces. The model clearly reveals the interaction of wear with crack development, processes which are linked because wear truncates surface‐breaking cracks, and can completely remove small surface‐breaking cracks.     

Prevention of RCF damage in curved track through development of the INFRA‐STAR two‐material rail

Results from the European 5th frame research project ‘INFRA‐STAR’ are presented. The goal of the project is to prevent rolling contact fatigue (RCF) and to reduce squeal noise in curves by applying an additional surface layer material on the top of the railhead, resulting in a two‐material rail. In INFRA‐STAR, a dynamic train–track interaction model is used to provide the contact forces. Wheel‐rail profiles, wheel‐rail friction, vehicle data, track data and operating conditions are included to calculate the wheel‐rail contact forces and spin moments, contact positions and load distributions in the contact patch. The contact pressure, friction coefficient, coating thickness, material properties of the coating and the rail material are used in finite element calculations and shakedown theory to calculate shakedown limits, which are then used to predict the RCF performance of the system. The paper details the work on theoretical modelling, twin disc testing, metallurgical research and field testing completed to date (August 2002, the project just passed midterm). The development of the surface layer application methods that are used, and the further objectives of the INFRA‐STAR project, are discussed.     

ANTIOXIDANT ACTIVITY AND QUALITY OF MINIMALLY PROCESSED INDIAN CABBAGE (BRASSICA OLERACEA var CAPITATA)

The effect of different dip treatments and storage period on the antioxidant activity and biochemical quality of Indian cabbage for minimal processing was studied. A gradual decrease in total antioxidant activity was observed during storage at 6C with no detectable activity at the end of 9 days in all the dip treatments, except in treatments containing combination of ascorbic acid and citric acid, and ascorbic acid alone (10 g/L each). Possibility of considering antioxidant activity as a marker of shelf-life has also been proposed. Incorporation of ascorbic acid and citric acid in the dip water improved the overall appearance and retained the maximum antioxidant activity, ascorbic acid and total carotenoids. Based on the overall quality and appearance score, Golden Acre was found suitable for minimal processing with a shelf-life of 9 days.     

Chemical Composition and Protein Quality of Wheat-Triticale Chapatis

Flours of wheat (WH-157) and triticales (TL-183, THS-9, JNK6T-229 and URT-217), and chapatis prepared after substituting different proportions of wheat flour with triticale flours were evaluated for nutritional quality. Flours of triticale varieties contained higher amounts of protein, crude fibre, total and available lysine, and lower contents of gluten than wheat. Losses of amino acids due to chapati making were negligible. As the proportion of triticale flours in chapatis increased the protein quality of chapatis improved.