Assessment of Clustering Methods for Predicting Permeability in a Heterogeneous Carbonate Reservoir

Permeability, the ability of rocks to flow hydrocarbons, is directly determined from core. Due to high cost associated with coring, many techniques have been suggested to predict permeability from the easy-to-obtain and frequent properties of reservoirs such as log derived porosity. This study was carried out to put clustering methods (dynamic clustering (DC), ascending hierarchical clustering (AHC) self organizing map (SOM) and multi-resolution graph-based clustering (MRGC)) into practice in order to predict the permeability of a heterogeneous carbonate reservoir in southwest of Iran. In addition, the results are compared with three conventional approaches, empirical models, regression analysis, and ANN. The performance of all the examined methods was compared in order to choose the best approach for predicting permeability in un-cored wells of the studied field. For all clustering methods, selecting the optimal number of clusters is the most important task. The optimal values for the number of clusters are selected by iteration. The optimal number of clusters for MRGC, SOM, DC, and AHC are 7, 9, 9, and 8 respectively. Empirical equations and regression analysis weakly predict permeability and the value of R2 parameters of both approaches are around 0.6. Generally the performance of clustering techniques is acceptable in Fahliyan formation. These techniques predict permeability between 1 and 1000 mD very well and just overestimate permeability values less than 1 mD. SOM performed the best among all examined techniques (R2=0.7911). The constructed and validated SOM model with 9 clusters was selected to predict permeability in one of un-cored wells of the studied field. In this well, the predicted permeability was in good agreement with MDT derived permeability

Collective oscillations of excitable elements: order parameters, bistability and the role of stochasticity

We study the effects of a probabilistic refractory period in the collective behavior of coupled discrete-time excitable cells (SIRS-like cellular automata). Using mean-field analysis and simulations, we show that a synchronized phase with stable collective oscillations exists even with non-deterministic refractory periods. Moreover, further increasing the coupling strength leads to a reentrant transition, where the synchronized phase loses stability. In an intermediate regime, we also observe bistability (and consequently hysteresis) between a synchronized phase and an active but incoherent phase without oscillations. The onset of the oscillations appears in the mean-field equations as a Neimark-Sacker bifurcation, the nature of which (i.e. super- or subcritical) is determined by the first Lyapunov coefficient. This allows us to determine the borders of the oscillating and of the bistable regions. The mean-field prediction thus obtained agrees quantitatively with simulations of complete graphs and, for random graphs, qualitatively predicts the overall structure of the phase diagram. The latter can be obtained from simulations by defining an order parameter q suited for detecting collective oscillations of excitable elements. We briefly review other commonly used order parameters and show (via data collapse) that q satisfies the expected finite size scaling relations.Comment: 19 pages, 7 figure

The Relationship between the Rate of the Use of Computer Games and Academic Procrastination: The Mediatory Role of Goal Orientation in Elementary School Students

This study intended to investigate the relationship between the rate of the use of computer games and elementary school students’ academic procrastination considering the mediatory role of goal orientation. To this end, using a multi-stage cluster sampling procedure, 213 male and female elementary school students (112 female and 101 male students) were selected from the two educational districts of Shiraz. The instruments used in the study included a questionnaire on Academic Procrastination (Savari, 2011), one on Goal Orientation (Elliott, 1999 and McGregor, 2001) and a researcher-made questionnaire on the time spent using computer games daily. Regarding the first two questionnaires, Cronbach's alpha method was used to estimate the reliability and validity of the correlations of the items with the dimensions and the correlation of the dimensions with the total score was also used. The obtained results confirmed the acceptable validity and reliability of the questionnaires. To evaluate the model, path analysis was utilized using SPSS 21 software. Results indicated that there was a negative and significant relationship between academic procrastination, mastery-oriented goal orientation and the rate of the use of computer games. Furthermore, the mastery-avoidance goal orientation was a positive and significant predictor of academic procrastination. However, there was not any statistically significant difference between male and female students in terms of the relationship between goal orientation (performance-oriented, performance-avoidance, mastery-oriented, and mastery-avoidance) and the rate of the use of computer games. Findings of the research indicated that there was a negative and significant relationship between academic proclivity and goal orientation-dominant and tenderness-performance. Also, the use of computer games predicted a positive and significant predictive of academic achievement and predicted a negative and significant predictive the mastery-avoidance goal orientation. Also, there was no significant difference between male and female students in terms of academic procrastination and goal orientation

The variability of thymol and carvacrol contents reveals the level of antibacterial activity of the essential oils from different accessions of Oliveria decumbens

Oliveria decumbens (Apiaceae) is an aromatic herb traditionally employed in the Persian medicine for the treatment of infectious and gastrointestinal disorders. In the present study, we analyzed the chemical composition of essential oils obtained from different Iranian populations and evaluated their efficacy on a panel of human pathogens (Staphylococcus aureus and Escherichia coli), probiotic (Bacillus subtilis), and phytopathogens (Clavibacter michiganensis, Curtobacterium flaccumfaciens, Xanthomonas citri, and Agrobacterium tumefaciens). The gas chromatographic-mass spectrometry analysis put in evidence four main volatile constituents such as thymol (20.3–36.4%), carvacrol (18.8–33.1%), γ-terpinene (10.6–25.9%), and p-cymene (9.5–17.3%), though with significant variability from an essential oil to another. Notably, the oils from the populations sited in Nourabad Mamasani and Dehdasht showed the highest amount of the phenolic monoterpenes thymol (36.4 and 35.2%, respectively) and carvacrol (33.1 and 30.6%, respectively). The antibacterial activity of O. decumbens essential oils was assessed by the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods, showing high activity for the samples from Nourabad Mamasani and Dehdasht populations exhibiting high level of the above phenolics. The obtained MIC and MBC values (mg/ml) were in the ranges 0.0625–2 mg/ml and 1–16 mg/ml, respectively. Noteworthy, in some cases, the antibacterial activity of O. decumbens essential oils was higher than that of chloramphenicol used as positive control. The average MBCs displayed by the O. decumbens samples showed that C. flaccumfaciens had the highest sensitivity to the essential oils. Based on these results, our work shed light on selected O. decumbens populations deserving proper breeding and cultivation strategies in order to warrantee production of bioactive essential oils to be used at pharmaceutical and agricultural level to combat several pathogens

Effect of Putrescine and 1-MCP on Quality Attributes and Storage Life of Strawberry Fruits (Fragaria ananassa Cv. Selva)

Ethylene is an important contributor to the acceleration of fruit ripening and postharvest losses of fruit. Thus, anti ethylene substances could increase storage life of fruits. Thus the effects of 0 (control), 0.5, 0.75 and 1 µL L-1 of 1-MCP and putrescine with 0 (control), 0.5, 1 and 1.5 mM on the storage life (1°C) during 21 day in strawberry fruit Cv. Selva were studied and appearance and the physicochemical characteristics of fruits were measured. A factorial experiment through complete randomized design (CRD) was used. The highest marketability, firmness, citric acid (TA), total soluble solids (TSS), vitamin C and the lowest amount of appearance decay, pH and the ratio of TSS/TA were observed in the treatment of 0.75 and 1 µL L-1 of 1-MCP and 1 and 1.5 mM of putrescine. The results obtained from the experiment showed a positive effect of 1-MCP and putrescine on the storage life of strawberry. The results further showed that the use of 1-MCP and putrescine can act as an effective strategy in postharvest technology of strawberry fruit

Global prevalence of urinary tract infection in pregnant mothers: a systematic review and meta-analysis

Urinary tract infection (UTI) is a prevalent infection during pregnancy that can lead to complications for both the mother and the foetus. The objective of this systematic review and meta-analysis is to determine the global prevalence of UTIs (both symptomatic and asymptomatic) during pregnancy, based on previous studies in this area. Furthermore, this study aims to identify any factors that contribute to heterogeneity in the prevalence of UTIs during pregnancy