1. Introduction: Cement treatment produces bonding strength between soils particles that makes their behavior different from the behavior of reconstructed soils without structure. Soft cemented soils show a great change in their void ratio after virgin yielding as the result of destruction of their cemented structure. In this paper the COMPRESSIBILITY of soft cemented soils was investigated in the laboratory. In order to obtain highly compressible cemented soil specimens, an artificially soil was produced mixing clay, silt and sand with cement and polystyrene granules with water content more than liquid limit. …

Accurate determination of the natural gas COMPRESSIBILITY factor is crucial for reservoir simulation and material balance computations in petroleum engineering. The data-driven AI techniques, like artificial neural networks, fuzzy systems, and neuro-fuzzy systems, are gaining momentum in estimating fluid properties. An adaptive neuro-fuzzy inference system (ANFIS) is applied here to develop a model to estimate the COMPRESSIBILITY factor of two natural gas types. The Takagi-Sugeno fuzzy inference system serves as the foundation for constructing the ANFIS model, where the triangular membership functions are applied. The training data consists of 80% of the available data selected randomly, and the remaining 20% is applied in testing. This developed model is of high accuracy in estimating the COMPRESSIBILITY factors of natural gas types, with an average absolute relative deviation of 0.05% and a maximum absolute relative deviation of 0.55% difference between the estimated and experimental value data. Comparing the findings here with the correlations indicates that the ANFIS model in terms of accuracy outperforms its counterparts in this realm.

The impact of COMPRESSIBILITY modified RANS turbulence closures is investigated for high subsonic round and chevron jet flows with Mach = 0. 9 and Re = 1. 03×106, including the predicted acoustic noise generation. The well-documented chevron jet flow and noise cases, namely NASA SMC000 and SMC006 are selected as the simulation configurations. Two COMPRESSIBILITY RANS closures are considered, which are based on the k-ε turbulence model. The first type only considers the COMPRESSIBILITY dissipation rate, and the second type accounts for three modifications of COMPRESSIBILITY dissipation rate, pressure dilation and production limiter. The acoustic noise is calculated employing the SNGR (Stochastic Noise Generation and Radiation) method using the flow prediction of the three-dimensional RANS simulations. The results show that both of the two types of COMPRESSIBILITY modified RANS models improve the accuracy of the mean flow and turbulence quantities. This results in more accurate jet noise predictions than with the standard RANS model. The first type modification is found to be moderate and the second type is remarkable. The noise results by the second type model, i. e. Sarkar2 model, agree with the experimental data quite well. For the mean flow field, the COMPRESSIBILITY modified model (Sarkar2 model) estimates a shorter potential jet core, and improved predictions of the velocity in the downstream region are observed. The study demonstrates the importance of considering the COMPRESSIBILITY modified RANS closure for the noise prediction of high-speed jets via the comparison to experimental data. Hence, the SNGR method is found to be cost effective for jet noise prediction, when compared to other approaches.

In this research, the effects of the powder particle size on the compaction and sintering of Hydride– Dehydride titanium powders are investigated. Commercially pure titanium powders with three different size ranges were utilized. Compaction was accomplished under applied pressures of 200 to 650 MPa. Sintering was carried out at 1100 to 1400 º C temperatures. The COMPRESSIBILITY behavior of the differently-sized powders was studied by measuring the density of the green compacts. The microstructure of the produced compacts was studied using scanning electron microscopy. Results showed that the small powders have the least COMPRESSIBILITY. The COMPRESSIBILITY data was analyzed and studied by common compaction equations. The modified Heckel equation showed the best correspondence. In addition, measuring the density of the sintered compacts showed that the small powders had the highest sinterability. The highest amount of sintered density (98% theoretical) was attained for the small powders compacted under 650 MPa and sintered at 1400 º C. However, the sintering temperature of 1200 º C was recognized as the most appropriate temperature for the middle and large-sized titanium powders. The results of the hardness tests showed that the appropriate mechanical properties could be attained for commercially pure titanium powder compacts by vacuum sintering accomplished at the optimum sintering circumstances.