Effects of low-salinity water coupled with silica nanoparticles on wettability alteration of dolomite at reservoir temperature

Wettability alteration in porous media is one of the mechanisms for enhancing oil recovery through injecting low-salinity water into carbonate reservoirs, in which active ions can remove the carboxylic oil component from the rock surface, altering the rock's wettability toward a water-wet condition. This study investigated the concomitant effects of low-salinity water and hydrophilic SiO₂ nanoparticles on oil-wet dolomite rock. Results revealed that low-salinity water coupled with hydrophilic nano-SiO₂ in oil-wet dolomite rock remarkably affected the wettability alteration of the rock, showing that the simultaneous presence of ions in water and hydrophilic nano-SiO₂ led to considerable wettability alteration compared with using just low-salinity water.     

Laboratory evaluation of the effect of bentonite on performance of bitumen and hot mix asphalt mixtures

In this research study, bentonite additive was used to modify original binder (60–70 penetration grade). The experimental program included use of five percentages of bentonite (10%, 15%, 20%, 25%, and 30%) by weight of bitumen. Physical properties of modified and unmodified bitumen were evaluated through penetration grade, softening point, ductility, and temperature susceptibility tests. The performance characteristics of mixtures were determined through indirect tensile strength, resilient modulus, and moisture susceptibility tests. The results demonstrate that addition of bentonite improves Marshall stability, tensile strength, and resilient modulus of mixtures, but led to decrease the resistance to moisture damage.     

Linear quadratic optimal controller for cable-driven parallel robots

In recent years, various cable-driven parallel robots have been investigated for their advantages, such as low structural weight, high acceleration, and large workspace, over serial and conventional parallel systems. However, the use of cables lowers the stiffness of these robots, which in turn may decrease motion accuracy. A linear quadratic (LQ) optimal controller can provide all the states of a system for the feedback, such as position and velocity. Thus, the application of such an optimal controller in cable-driven parallel robots can result in more efficient and accurate motion compared to the performance of classical controllers such as the proportional-integral-derivative controller. This paper presents an approach to apply the LQ optimal controller on cable-driven parallel robots. To employ the optimal control theory, the static and dynamic modeling of a 3-DOF planar cable-driven parallel robot (Feriba-3) is developed. The synthesis of the LQ optimal control is described, and the significant experimental results are presented and discussed.     

Analysis of two‐dimensional porous fins with variable thermal conductivity

Analysis of porous fins for their higher heat transfer in comparison with solid fins with identical volumes has attracted significant attention. In this paper, a two‐dimensional thermal analysis of a porous fin having variable thermal conductivity coefficient is performed using finite difference method. Heat transfer through porous media is simulated using passage velocity from Darcy's model. The thermal conductivity of the solid phase is considered as a linear function of temperature. It is found that the temperature profile of the fin is completely two‐dimensional even for high Rayleigh and Darcy numbers (Ra = 10³～10⁴, Da = 0.01), because the temperature changes significantly along the transverse axis especially for lower Rayleigh and Darcy numbers. Also, the effects of important nondimensional parameters such as Rayleigh and Darcy numbers, porosity, Nusselt, thermal conductivity, and aspect ratio on the temperature profile are investigated. The results demonstrate that the temperature distribution is strongly dependent on the Rayleigh and Darcy numbers.     

评价油井堵水工艺效果的含水特征曲线法

常规堵水效果评价方法,受方法本身局限,不能客观地评价油井堵水工艺效果,更无法对堵水效果进行定量分析评价。含水特征曲线法消除了含水率的偶然性波动对评价效果的影响,考虑了措施前后含水动态变化趋势,可对措施效果进行定性及定量分析评价。     

Homogeneous Penalizers and Constraints in Convex Image Restoration

Recently convex optimization models were successfully applied for solving various problems in image analysis and restoration. In this paper, we are interested in relations between convex constrained optimization problems of the form $\operatorname{argmin}\{ \varPhi(x) \mbox{ subject to } \varPsi(x) \le\tau\}$ and their penalized counterparts $\operatorname{argmin}\{\varPhi(x) + \lambda\varPsi(x)\}$ . We recall general results on the topic by the help of an epigraphical projection. Then we deal with the special setting Ψ:=∥L?∥ with L∈? ^m,n and Φ:=φ(H?), where H∈? ^n,n and φ:? ⁿ →?∪{+∞} meet certain requirements which are often fulfilled in image processing models. In this case we prove by incorporating the dual problems that there exists a bijective function such that the solutions of the constrained problem coincide with those of the penalized problem if and only if τ and λ are in the graph of this function. We illustrate the relation between τ and λ for various problems arising in image processing. In particular, we point out the relation to the Pareto frontier for joint sparsity problems. We demonstrate the performance of the constrained model in restoration tasks of images corrupted by Poisson noise with the I-divergence as data fitting term φ and in inpainting models with the constrained nuclear norm. Such models can be useful if we have a priori knowledge on the image rather than on the noise level.     

Fatigue limit prediction and analysis of nano-structured AISI 304 steel by severe shot peening via ANN

AISI 304 stainless steel is very widely used for industrial applications due to its good integrated performance and corrosion resistance. However, shot peening (SP) is known as one of the effectual surface treatments processes to provide superior properties in metallic materials. In the present study, a comprehensive study on SP of AISI 304 steel including 42 different SP treatments with a wide range of Almen intensities of 14–36 A and various coverage of 100–2000% was carried out. Varieties of experiments were accomplished for the investigation of the microstructure, grain size, surface topography, hardness and residual stresses as well as axial fatigue behavior. After experimental investigations, artificial neural networks modeling was carried out for parametric analysis and optimization. The results indicated that, treated specimens with higher severity had more desirable properties and performances.

     

Calcium carbonate nanoparticles effects on cement plast properties

Microsystem Technologies - Cement plast or polymerized cement is a synthetic stone prepared using polymeric and nanomaterials which change the molecular structure of cement and minerals and create...