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Alloys 617 and 276 are nickel-based super alloys with excellent mechanical properties, oxidation, creepresistance, and phase stability at high temperatures. These alloys are used in complex and stochastic applications. Thus, it is difficult to predict their output characteristics mathematically. Therefore, the non-conventional methods for modeling become more effective. These two alloys have been subjected to time-dependent deformation at high temperatures under sustained loading of different values. The creep results have been used to develop the new models. Artificial neural network (ANN) was applied to predict the creep rate and the anelastic elongation for the two alloys. The neural network contains twenty hidden layer with feed forward back propagation hierarchical. The neural network has been designed with MATLAB Neural Network Toolbox. The results show a high correlation between the predicted and the observed results which indicates the validity of the models. 

ABSTRACT: In this paper life-cycle cost analysis of three biogas digesters is presented. Results show that the cost of biogas depends on the construction of digesters, sizes of methane tank and possibility of heating of the slurry. Biogas and natural gas costs calaculated are observed and found to be comparable. It is recommended that the biogas digesters can be constructed and installed, in principle, for every family and there is no need to built long gas pipe lines. ABSTRAK: Kertaskerja ini membentangkan analisis kos kitar hayat tiga pencerna biogas. Keputusan menunjukkan kos biogas bergantung kepada pembinaan pencerna, saiz tangki metana dan kemungkinan pemanasan buburan. Pengiraan kos biogas dan gas asli diambil kira dan ianya didapati setanding. Adalah disarankan pencerna biogas boleh dibina dan dipasang secara teorinya, bagi setiap keluarga tanpa memerlukan pembinaan paip gas yang panjang.

In the present work, a novel design is presented for producing auxetic laminated faceplates for structures that contain auxetic cores in order to produce fully auxetic sandwich structures. The design is based on the use of periodic cellular networks that are embedded in a fibre-reinforced polymer matrix. These networks have a high in-plane negative Poisson's ratio and a high in-plane stiffness. Two auxetic networks were chosen for this purpose: a classical re-entrant hexagonal network and an anti-tetra chiral auxetic network. The finite elements method was used to model the auxetic network and the faceplate. For the auxetic network, the relative modulus (E s /E m ) was investigated to determine its effect on the behaviour of the faceplate. The auxetic behaviour of the faceplate occurs when the auxetic network has a high relative modulus. For example, for a classical re-entrant hexagonal network faceplate, the auxetic behaviour starts to appear when E s /E m > 33, while for an anti-tetra chiral auxetic network faceplate, the auxetic behaviour starts to appear when E s /E m > 24. Analytical expressions for the elastic constants of the faceplates were developed using the representative volume element model (RVE) and a semi-empirical formula of the rule of mixtures (ROMs). The results of the analytical expressions were compared with the finite elements results for various values of the relative density parameter ρ * . The relative density had a significant effect on the elastic constants of the faceplate. The model produced with the representative volume element method had higher values for the elastic constants than did that created with the finite elements model, but the semi-empirical rule of mixtures gave more accurate results for both types of faceplates. A modified design for the classical re-entrant hexagonal network that increases the in-plane stiffness of the auxetic network is presented since it has been found that it plays a major role in producing a high negative Poisson's ratio. The modified networks are an oval re-entered and a stiffened re-entered network. Experiments were carried out on the oval re-entered faceplates to obtain the in-plane moduli and the Poisson's ratios. The tested faceplate samples clearly showed auxetic behaviour. A good agreement between the finite elements results and the experimental data was obtained.