Fast automatic medical image segmentation based on spatial kernel fuzzy c-means on level set method

Fast two-cycle (FTC) model is an efficient and the fastest Level set image segmentation. But, its performance is highly dependent on appropriate manual initialization. This paper proposes a new algorithm by combining a spatially constrained kernel-based fuzzy c-means (SKFCM) algorithm and an FTC model to overcome the mentioned problem. The approach consists of two successive stages. First, the SKFCM makes a rough segmentation to select the initial contour automatically. Then, a fuzzy membership matrix of the region of interest, which is generated by the SKFCM, is used in the next stage to produce an initial contour. Eventually, the FTC scheme segments the image by a curve evolution based on the level set. Moreover, the fuzzy membership degree from the SKFCM is incorporated into the fidelity term of the Chan–Vese model to improve the robustness and accuracy, and it is utilized for the data-dependent speed term of the FTC. A performance evaluation of the proposed algorithm is carried out on the synthetic and real images. The experimental results show that the proposed algorithm has advantages in accuracy, computational time and robustness against noise in comparison with the KFCM, the SKFCM, the hybrid model of the KFCM and the FTC, and five different level set methods on medical image segmentation.     

Thermal stability of processed PVC/bamboo blends: effect of compounding procedures

Polyvinyl chloride (PVC) was mixed with bamboo (Bambusa vulgaris) particle and additives by using PVC composite manufacturing system including initial dry blending with hot-cool mixing, followed by granulation via counter-rotating extrusion, and then consolidation by compression moulding to produce compression moulded board (CMB). The effects of different bamboo particle size (75 µm and 1 mm), bamboo particle loading (25 and 50% loading ratio), and differing processing lubricants content level (compositions 1 and 2) on the thermal stability of the composites were determined. Results show no significant trends in glass transition temperature (T_g) between dry blends, granules, and CMB, and between B. vulgaris particle loading at the respective processing steps. For samples with higher lubricant contents, the PVC T_g was observed to decrease up to 5?°C, possibly due to the reduced melt viscosity. The thermal decomposition temperature at 5% mass loss (T_?5%) appeared to decrease from dry blend to CMB due to sample degradation on further processing at higher temperatures. The use of 50% B. vulgaris particle loading also reduced the T_?5% values, assignable to bamboo particle degradation caused by the high processing temperatures. For oxidative induction time (OIT) testing, only granules and CMB from pure PVC composites system showed measurable oxidative times compared with OIT profiles of PVC/B. vulgaris composites system, suggestive of comparatively stabilized thermoplastic composites. This revealed that processing with bamboo particles does not contribute to degradation of PVC composites.     

Effect of engineered water and scale inhibitor concentration on the adsorption performance of gypsum inhibitors on multi-walled carbon nanotubes and crushed sandstone

Engineered waterflooding is an effective process for enhanced oil recovery, but it can lead to mineral scale deposition due to the incompatibility of brines. Previous studies on scale mitigation have mainly focused on high-temperature baryte and anhydrite scales, neglecting gypsum precipitation and inhibitors adsorption at low temperatures. Additionally, earlier research has used simple brines that do not reflect the actual injection and formation water in reservoirs. In this study, the impact of temperature, various brine mixtures, and thermodynamic databases on saturation ratio and scale precipitation is explored using PHREEQC (pH-REdox-EQuilibrium-C program). The study reveals that the copresence of calcium and magnesium ions improves the gypsum inhibition efficiency of scale inhibitors (SIs) at low concentrations to a maximum of 79%. However, this effect is reversed or neutral at higher SI concentrations. The study also shows that the presence of monovalent ions reduces the adsorption of SIs by multi-walled carbon nanotubes (MWCNTs). Removing sodium ions from seawater while leaving calcium and magnesium ions intact increases MWCNTs' adsorption capability to 93%. This is because monovalent cations attach to the adsorbent surface and block the active sites, whereas divalent cations act as a bridge between MWCNT and SIs. The study establishes that the behaviour of SIs regarding adsorption on MWCNT and crushed sandstone depends on various factors, including molecule size, calcium toleration of the SIs, point of zero charge, and solution pH. Understanding these factors can improve the effectiveness of SIs, reduce chemical costs, and prolong the life of oil wells.     

A Numerical Evaluation of the Performance of Film Cooling from a Circular Exit Shaped Hole with Sister Holes Influence

The film cooling effectiveness and the jet exit conditions and the associated vortex structure downstream of the injection hole for both a circular exit shaped hole and an elliptical exit shaped holes were numerically investigated for the blowing ratios of 0.25, 0.5, 1, and 1.5. Four turbulence models, including the standard, RNG, realizable k ? ?, and Reynolds-stress model, in combination with three near-wall approaches, were used for the present simulations. It was found that the predicted results using the realizable k ? ? model combined with the standard wall function were in better agreement with the available experimental data from the literature. Further, the results indicate that the circular exit shaped hole improved the centerline and laterally averaged adiabatic effectiveness, particularly at high blowing ratios. Finally, adding the sister holes provided a notable decrease in the strength of the counterrotating vortex pairs, where the highest effectiveness was achieved for the circular exit shaped hole case with sister holes.     

Fouling of microfiltration membranes by biopolymers

Suppression of fouling due to biopolymers of relevance to the brewing industry has been investigated. The effects of three model biopolymers: casein (protein), catechin (polyphenol), and dextran (polysaccharide) on fouling of asymmetric 0.65 μm polyethersulfone membranes during direct-flow filtration have been studied. While dextran is successful in disrupting interactions between casein and catechin, the associated reduction in aggregate size does not always result in reduced fouling. Solution conditions such as pH and ionic strength modulate the tendency of the aggregates to adsorb onto the membrane surface. Thus, optimizing solution conditions to suppress adsorption of aggregates is essential for increasing the membrane filtration capacity.     

Micromechanical modeling of compressive behavior in freeze-casted ceramic

In this study, a novel computational micromechanical framework is proposed to predict the effective mechanical properties of the ice-templated ceramics under off-axis compressive loading. The mechanical behavior is simulated by a computational micromechanical model and validated against experimental results. Smeared cracking approach was used to describe failure in ice-templated alumina. The representative volume element (RVE) was developed based on the honeycomb analogy of lamellar walls considering the morphology of the material. The periodic boundary conditions were applied in RVE to simulate bulk behavior of the material. The compression testing was conducted on the ice-templated alumina samples to obtain the effective compressive moduli and strength with different loading angles. Digital image correlation method was used to measure strain field during the experiment and quantify the effective misalignment angle corresponding to porous material. The effective stiffness and strength obtained from RVE analysis compared well with experimental results. The proposed micro-mechanical RVE model allows for determining the properties of the ice-templated porous ceramic for various off-axis angles.