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BPNN structure to predict the Apparent Viscosity of Waxy Crude Oil The Back Propagation Neural Network (BPNN) is optimized with Genetic Algorithm (GA). All the chromosomes are decoded to calculate their respective fitness. The high fitness chromosomes will be selected and a better population will be obtained through genetic algorithms. After meeting the requirement (maximum number of generations or goal error), the training will stop and the optimal chromosome can be obtained. The six parameters (K 0 , n 0 , K j , n j , s g and c spw) are input variables of GA-BPNN model. The consistency coefficient (K T) and the flow behavior index (n T) are the output of the model, by which the apparent viscosity of PPD-treated crude oil with shear effect of viscous flow can be determined. • The GA-BPNN model suits different kinds of crude oil, avoids the longtime of experiments and maintains high accuracy. • The entropy generation caused by viscous flow rates is the most important variable in apparent viscosity prediction. • The apparent viscosity should be used with the effect of shear history to design and operate the waxy crude oil pipeline. This study investigated the apparent viscosity of waxy crude oil treated with pour point depressant (PPD). It considered the shear history and thermal history as the main factors to affect the apparent viscosity of the crude oil when transported by a long-distance pipeline. According to previous practice and present laboratory works, the apparent viscosity that can be determined according to the conventional test specifications without taking into account the effect of shear history cannot be used to successfully design and operate a waxy crude oil pipeline. Thus, with the help of entropy generation (s g) combination, which is caused by the viscous flow of crude in the pipeline and the back propagation artificial neural networks (ANN) optimized by a genetic algorithm, a prediction model was developed to determine the viscosity of PPD treated waxy crude oil, which was affected by shear. The performance of the model was evaluated through four statistical indices, such as the Mean Absolute Percentage Error (MAPE). The MAPE of all data of the apparent viscosity was 12.20%. The influence of each variable on the apparent viscosity was investigated through a sensitivity analysis, which revealed that s g caused by viscous flow rates was the most important variable in viscosity prediction. [ABSTRACT FROM AUTHOR]

In this study, a salt-resistant hydrophobic association polymer (PZDY) was synthesized from acrylamide, octadecyl dimethylallyl ammonium chloride, and decane polyoxyethylene ether acrylate by aqueous polymerization. Infrared spectroscopy, fluorescence spectroscopy, scanning electron microscopy, and other characterization methods were used to study its properties and the rheological properties of the PZDY solution were analyzed. The results showed that when concentration of NaCl is less than 5 wt% and that of CaCl2 is less than 1 wt%, the viscosity of 0.4 wt% PZDY increased with an increase of the salt concentration. When the salt concentration continued to increase, the PZDY viscosity gradually decreased. Investigation of the rheological behaviors showed that the 0.6 wt% PZDY in the 5 wt% NaCl and 1 wt% CaCl2 solution could withstand temperatures up to 180 °C after being sheared for 2500 s at 170 s−1 and its viscosity exceeded 50 mPa·s. Moreover, the viscosity of the 0.6 wt% PZDY in 5 wt% NaCl increased from 104 to 205 mPa·s and that in 1 wt% CaCl2 increased from 110 to 157 mPa·s at a shear rate of 170 s–1, at 180 °C, and a shear time of less than 500 s. Meanwhile, scanning electron microscope (SEM) results showed that the salt addition enhanced the quasi-spatial network structure, with closer clustering of PZDY molecules in the NaCl solution than in the CaCl2 solution. The storage modulus (G′) and loss modulus (G″) increased with the increase of the PZDY concentration. Therefore, PZDY can be used to improve the heat and shear resistance of fracturing fluids and enhance oil recovery. [ABSTRACT FROM AUTHOR]

Hydrogels are polymeric materials that can absorb and retain large amounts of water. They have various applications in agriculture, horticulture, oil recovery, and water management. However, conventional hydrogels have limited swelling (Q), equilibrium swelling (Q ∞), and water retention capacities (DQ) under different environmental conditions. In this study, we synthesized a series of hydrophobically associated hydrogels by the aqueous polymerization of acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and a novel amphiphilic hydrophobic monomer (RCS-10). Further, we investigated the effects of the RCS-10 content on Q , the mechanical properties, and water retention capacity (DQ) of the hydrogels. We also examined the influence of temperature, pH, salt type and concentration, and urea concentration on Q , finding that an increase in the RCS-10 content decreased Q and increased the DQ of the hydrogels. The hydrogels exhibited high Q in distilled water, low-salt solutions, and low-urea (1 wt%) solutions. In the latter, the Q ∞ was as high as 768.99 g/g. The hydrogels also showed excellent cyclic swelling performance and maintained high Q ∞ (759.99 g/g) after six cycles. Crucially, the hydrophobic association hydrogels demonstrated superior swelling and water retention properties compared to conventional hydrogels. Thus, the hydrogels have applications in water management in various fields including agriculture and horticulture. [Display omitted] • Novel hydrogels with amphiphilic hydrophobic monomer. • Hydrophobic association hydrogels synthesized without toxic agents. • Swelling effects of pH, temperature, and salt type/concentration studied. • Hydrogels suitable for agriculture, horticulture, and oil/water engineering. [ABSTRACT FROM AUTHOR]

Background: This study was undertaken to test the veracity of the hypothesis that primary incision closure after intestinal stoma reversal in adult patients is associated with a greater risk of surgical site infection (SSI) than are open incisions. Methods: A retrospective cohort study was conducted at the Surgical Department of the Aga Khan University Hospital, Karachi, Pakistan. The study included adult patients who underwent elective loop and double-barreled intestinal stoma (ileostomy or colostomy) reversal through peristomal incisions between January 2005 and May 2011. Files were reviewed independently by two surgeons to establish main exposure (closed or open surgical sites) and outcome; i.e., SSI based on U.S. Centers for Disease Control and Prevention criteria. Results: Sample size calculation prior to the study required 71 patients to be included in each exposure arm. Patients with closed surgical sites were relatively younger (mean 36±15 [standard deviation] years) than those with open surgical sites (41±15 years), with a male preponderance in both groups. Fifteen patients were found to have SSI: 3/71 (4.2%) in open and 12/71 (16.9%) in closed incisions. The risk of SSI in closed surgical sites was 5.8 times greater than in open sites (95% confidence interval for relative risk 1.5-22.5) after adjusting for gender, body mass index (BMI), site of stoma, malignant disease, and preoperative chemo-radiotherapy. Conclusion: The risk of SSI in closed incisions is greater than that in open incisions. It is suggested that incisions not be closed primarily in patients undergoing stoma reversal. [ABSTRACT FROM AUTHOR]