The design and implementation of a robust single-layer QCA ALU using a novel fault-tolerant three-input majority gate

The Journal of Supercomputing - Inverter and majority gates are considered as two important primitive gates for designing logical circuits in the quantum-dot cellular automata (QCA) technology. Up...     

A review on the natural gas potential of Pakistan for the transition to a low-carbon future

Natural gas is the world’s fastest growing and widely used fossil fuel which can be targeted for transitioning to a low-carbon future. Pakistan was ranked at seventh position among the utmost harmfully affected countries by climate change. It is, therefore, important to develop an effective energy policy toward the reduction of greenhouse gases in the country. This study evaluates the Pakistan’s natural gas industry development by reviewing reserves, production, consumption, infrastructures, and natural gas agreements in place. The total proven natural gas reserve of Pakistan is estimated to be 0.5 Tcm by the end of 2016. There are many active fields in Pakistan among which Sui gas reservoir is the largest. Currently, Pakistan’s natural gas industry is well matured with average size reserves, production capacity, and advanced and organized infrastructure for transmission and distribution network. Therefore, natural gas can be used to feed different sectors of the country, to decrease the financial burden of importing oil, and to reduce CO₂ emissions. However, increasing the gap of demand–supply for natural gas in the future, declining the average gas reserves, and postponing the gas import may challenge the natural gas industry, climate, and performance of Pakistan’s economy. Thus, these concerns must be addressed to help the natural gas industry for an easy transition to a low-carbon future.     

Geosynthetics reinforced interposed layer to protect structures on deep foundations against strike-slip fault rupture

In the present study, the interaction mechanism of a 10-story moment-resisting building frame sitting on the conventional piled raft foundation with a strike-slip fault rupture with a dip angle of 90? is studied via three-dimensional finite element numerical simulation using ABAQUS. In addition, an alternative composite foundation system with geosynthetics reinforced interposed layer between piles and raft is proposed to improve the safety and performance of foundation under strike-slip fault ruptures. The interposed layer is reinforced with two high tensile strength of the geotextile layer. The inelastic behaviour of piles under large ground deformations is simulated using moment-curvature relationships of the real reinforced concrete section of piles and ductility concepts. The performance of both composite and conventional piled raft foundations are evaluated in terms of the geotechnical and structural responses of foundations including rotational and translational displacements and shear forces of the raft, as well as shear forces and ductility capacity of piles. The obtained results show the superior performance of composite foundation with geotextile reinforced interposed layer in terms of a significant reduction in shear forces in the raft and piles, as well as ductility demand in the piles.     

Design and implementation of multiplication algorithm in quantum-dot cellular automata with energy dissipation analysis

The Journal of Supercomputing - QCA is an emerging nanotechnology for the design of digital system circuits based on electron interactions. QCA is used to design nanoscale circuits. Multiplier...     

Assessment of rock fracture surface roughness using Riemannian statistics of linear profiles

The mechanical behaviour of rock masses is complex, due partly to the presence of discontinuities within them. Of the geometrical parameters of discontinuities, surface roughness, which encapsulates the topographical features of a rock surface, is known to play a significant role. Here, a new parameter for quantitative roughness determination based on the distribution of unit normal vectors to a rock profile is presented.The analysis of unit normal vectors in terms of directional statistics is customarily performed in Euclidean space using a Cartesian co-ordinate system. Here, the analysis is developed using Riemannian geometry, with Mahalanobis distances being proposed for discrimination between different rock profiles. Statistical parameters on the unit circle are extracted using Riemannian geometry, and from that a roughness parameter, D_R1, is obtained. This parameter corresponds to 1D Riemannian dispersion, and as such D_R1 increases as profile roughness increases.D_R1 is applied to the analysis of synthetic profiles and some real rock profiles. Conclusions are drawn that demonstrate the advantages of the new method in terms of investigating the scale effect in roughness determination as well as in comparing different profiles.A preliminary study into the correlation between D_R1 and the shear strength of a fracture, using analytical and numerical investigation of the strength of profiles comprising symmetric triangular asperities sheared at different normal stress levels, shows a clear relation between Riemannian roughness parameter and profile shear strength.     

A combined Bayesian–wavelet–data fusion approach for borehole enlargement identification in carbonates

Petrophysical logs are usually acquired in most of the drilled wells and some of them have good correlations with mechanical properties of the rock. In this paper, a new multi-variable workflow is proposed in order to identify the location of borehole enlargements along the wellbore in correlation with some of the petrophysical logs acquired using wireline or logging while drilling tools in addition to mud weight and in-situ vertical stress data. This approach employs number of data processing techniques including Bayesian classification, wavelet de-noising, and data fusion to determine borehole intervals with maximum likelihood of enlargement. The application of the proposed method is to identify enlargement zones and does not provide information about stresses orientations and magnitudes. This paper explains the methodology and presents its results in five study wells in a carbonate field. The study confirms the applicability and the generalization capability of the method in carbonate formations with a significant accuracy.     

Thermal nonlinear optical response of meso-tetraphenylporphyrin under aggregation conditions versus that in the absence of aggregation

In this work, measurement of thermally induced nonlinear refractive index of meso-tetraphenylporphyrin (H₂TPP) at different concentrations in 1,2-dicoloroethane using a double-grating interferometer set-up in a pump–probe configuration is reported. The formation of aggregates of H₂TPP at concentrations greater than ca. 5 × 10^?5 M was evident by deviation from Beer’s law. An almost focused pump beam passes through the solution. A part of the pump beam energy is absorbed by the sample and therefore a thermal lens is generated in the sample. An expanded probe beam propagates through the sample and indicates the sample refractive index changes. Just after the sample a band-pass filter cuts off the pump beam from the path but the distorted probe beam passes through a double-grating interferometer consisting of two similar diffraction gratings with a few centimetres distance. A CCD camera is installed after the interferometer in which on its sensitive area two diffraction orders of the gratings are overlying and producing interference pattern. The refractive index changes of the sample are obtained from the phase distribution of the successive interference patterns recorded at different times after turning on of the pump beam using Fourier transform method. In this study, for different concentrations of H₂TPP in 1,2-dichloroethane solution the thermal nonlinear refractive index is determined. Also, we present the measurement of the temperature changes induced by the pump beam in the solution. We found that value of nonlinear refractive index increased by increasing the concentration up to a concentration of 5 × 10^?4 M and then decreased at higher concentrations. In addition, we have investigated the stability of the observed thermal nonlinearity after a period of two weeks from the sample preparation.     

PIV measurements for a complex topographic terrain

Particle image velocimetry (PIV) measurements are performed on a 1:3000 scale model of complex topographic area. Three distinct topographic features are investigated: a valley, a ridge and a 3D hill.PIV performs well in capturing two-dimensional mean and turbulent velocity fields both horizontally and vertically over extended areas with an approx. 5 m full-scale resolution. The results show that while for the valley and hill cases the flow is relatively well correlated over large spatial extends, the ridge flow is strongly influenced by both local and major topographies.The PIV measurements compare well with hot-wire-based mean velocity profiles for the three cases. Moreover, the turbulence intensity profiles match well for flow regions without recirculation. The ridge wake region shows discrepancies between the two techniques, which are attributed to the complexity of the flow in this region and limitations of both techniques.     

Novel empirical correlations for estimation of bubble point pressure, saturated viscosity and gas solubility of crude oils

Knowledge of petroleum fluid properties is crucial for the study of reservoirs and their development. Estimation of reserves in an oil reservoir or determination of its performance and economics requires a good knowledge of the fluid physical properties. Bubble point pressure, gas solubility and viscosity of oils are the most important parameters in use for petroleum and chemical engineers. In this study a simple-to-use, straight-forward mathematical model was correlated on a set of 94 crude oil data. Three correlations were achieved based on an exponential regression, which were different from conventional empirical correlations, and were evaluated against 12 laboratory data other than those used for the regression. It is concluded that the new exponential equation is of higher precision and accuracy than the conventional correlations and is a more convenient mathematical formulation.