A cleaner enzymatic approach for producing non-phthalate plasticiser to replace toxic-based phthalates

Clean Technologies and Environmental Policy - Dioctyl phthalate (DOP) is industrially commonly used as a polyvinyl chloride (PVC) plasticiser. As DOP does not form a chemical link with PVC, it...     

Liquefaction and Undrained Response Evaluation of Sands from Drained Formulation

A general approach has been established to assess the undrained stress-strain curve and effective stress path under monotonic loading from drained triaxial tests. An appropriate formulation of a drained and drained rebounded (i.e., overconsolidated) triaxial test response is developed that, in turn, allows the assessment of developing liquefaction and the undrained behavior of saturated sands. The formulation presented is based upon reported experimental drained test results that were obtained from different investigators using different testing techniques. This formulation is a function of the confining pressure and basic properties of the sand, such as relative density, uniformity coefficient, and particle shape (roundness), which can be obtained from visual inspection. The approach is verified by comparing predicted and reported (observed) undrained behavior. The developed formulas allow one to predict the potential of sand to liquefy, the type of liquefaction, the peak and residual strength values, as well as the whole undrained stress-strain curve and effective stress path. The simplicity of this approach makes it an attractive general method to characterize the undrained behavior of sands in a preliminary analysis with no need to run sophisticated experimental tests.     

The influence of natural reinforcement fibres on insulation values of earth plaster for straw bale buildings

This work aimed to measure the thermal conductivity of some natural plaster materials that could be used for straw bale buildings. Thermal conductivity is very important to determine the insulation value and other thermal parameters for natural plaster materials. Plaster materials consisted of soil, sand and straw. Straw is used as a reinforcement fibre for plaster. Three types of fibres were used such as wheat straw, barley straw and wood shavings. The results indicated that the thermal conductivity of all materials decreased with increasing straw fibre content and decreased with increasing sand content. The straw fibres have greater effect on the change of thermal conductivity than the effect of sand. The results also revealed that plaster reinforced by barley straw fibres has the highest values of thermal insulation.     

Flexural Behavior of Continuous GFRP Reinforced Concrete Beams

The results of testing two simply and three continuously supported concrete beams reinforced with glass fiber-reinforced polymer (GFRP) bars are presented. The amount of GFRP reinforcement was the main parameter investigated. Over and under GFRP reinforcements were applied for the simply supported concrete beams. Three different GFRP reinforcement combinations of over and under reinforcement ratios were used for the top and bottom layers of the continuous concrete beams tested. A concrete continuous beam reinforced with steel bars was also tested for comparison purposes. The experimental results revealed that over-reinforcing the bottom layer of either the simply or continuously supported GFRP beams is a key factor in controlling the width and propagation of cracks, enhancing the load capacity, and reducing the deflection of such beams. Comparisons between experimental results and those obtained from simplified methods proposed by the ACI 440 Committee show that ACI 440.1R-06 equations can reasonably predict the load capacity and deflection of the simply and continuously supported GFRP reinforced concrete beams tested.     

Flexural performance of FRP reinforced concrete beams

A numerical method for estimating the curvature, deflection and moment capacity of FRP reinforced concrete beams is developed. Force equilibrium and strain compatibility equations for a beam section divided into a number of segments are numerically solved due to the non-linear behaviour of concrete. The deflection is then obtained from the flexural rigidity at mid-span section using the deflection formula for various load cases. A proposed modification to the mid-span flexural rigidity is also introduced to account for the experimentally observed wide cracks over the intermediate support of continuous FRP reinforced concrete beams.     

Robust and secure fractional wavelet image watermarking

This paper presents an efficient fractional wavelet transform (FWT) image watermarking technique based on combining the discrete wavelet transform (DWT) and the fractional Fourier transform (FRFT). In the proposed technique, the host image is wavelet transformed with two resolution levels, and then, the middle frequency sub-bands are FRFT transformed. The watermark is hidden by altering the selected FRFT coefficients of the middle frequency sub-bands of the 2-level DWT-transformed host image. Two pseudo-random noise (PN) sequences are used to modulate the selected FRFT coefficients with the watermark pixels, and inverse transforms are finally applied to get the watermarked image. In watermark extraction, we just need the same two PN sequences used in the embedding process and the watermark size. The correlation factor is used to determine whether the extracted pixel is one or zero. The proposed fractional wavelet transform (FWT) image watermarking method is tested with different image processing attacks and under composite attacks to verify its robustness. Experimental results demonstrated improved robustness and security.     

Poly[4-Amino-2,6-pyrimidinodithiocarbamate] and Its Cobalt, Nickel, and Copper Complexes

The pyrimidinodithiocarbamate polymer was prepared from the reaction of 2-mercapto-4,6-diaminopyrimidine with carbon disulfide, followed by condensation through the removal of H₂S gas. Three polymer–metal complexes of cobalt, nickel, and copper were then prepared. The polymer and its complexes were investigated by elemental analyses, UV, IR, and magnetic susceptibility. The DC electrical conductivity variation, with the temperature in the region 298–498 K, of the polymer in its undoped and doped (5% iodine and 5% NiCl₂) states and, also, of the three polymer complexes was determined. All the complexes showed an increase in conductivity with an increase in temperature in a semiconductor behavior. The thermal stability of the complexes was studied using the TGA technique. The structures of the polymer and its complexes were assigned. The proposed structure of the complexes is (MLX ₂.mH₂O)_n. All the polymer complexes are thermally stable, are insoluble in common organic solvents, and have high melting points.