A novel active contour model for medical images via the Hessian matrix and eigenvalues

This paper presents a new level set formulation for active contour models (ACM). We propose the idea of integrating the eigenvalue information of Hessian matrix into the level set function. By this new level set function, the principal curvature information of images is used to enhance the ability of segmenting boundary regions. The advantages of our model are as follows: firstly, the interior and exterior object boundaries can be segmented with the initial contour being anywhere in the input image. Secondly, this method can work with heterogeneous images. Thirdly, the proposed model can produce smooth and right boundaries of objects having vital importance in medical operations. Extensive experiments demonstrate that the proposed model can obtain better segmentation results.     

Learning IF–THEN priority rules for dynamic job shops using genetic algorithms

Performing complex, informed priority rules might pose a challenge for traditional operator-driven systems. However, computer-integrated manufacturing systems may significantly benefit from the complex, informed rules such as state-dependent priority rules. A state-dependent priority rule can be defined as a list of IF–THEN priority rules that will be performed if certain system conditions are satisfied. Here, we propose a genetic algorithm based learning system for constructing interval-based, state-dependent priority rules for each interval of queue lengths in dynamic job shops. Our approach builds interval based state-dependent priority rules pairing the priority rules with the intervals of queue lengths, and determines priority rules and their corresponding length of intervals for a given objective. A genetic algorithm is developed for matching queue length intervals with appropriate priority rules during simulation. A system simulation evaluates the efficiencies of interval based state dependent priority rules. The experiments show that interval-based state dependent priority rules obtained by the proposed approach considerably outperform the priority rules including shortest processing time (SPT), minimum slack time (MST), earlier due date (EDD), modified due date (MDD), cost over time (COVERT), and critical ratio (CR) for total tardiness for most of the problems.     

Effects of cyclization and electrostatic interactions on the termination rate of macroradicals in free-radical crosslinking copolymerization

Summary Effects of cyclization and ionic group contents on the termination rate of macroradicals formed at zero monomer conversion were investigated. For this purpose, the pregel regime of free-radical methyl methacrylate / ethylene glycol dimethacrylate (MMA/EGDM) and acrylamide / N,N'-methylenebisacrylamide (AAm/BAAm) copolymerization systems was studied by means of the dilatometric technique. To eliminate the chain-length dependent variation of the termination rates, different sets of experiments were carried out each at a fixed monomer and initiator concentration. At low crosslinker contents, the termination rate of zero-conversion macroradicals was enhanced in crosslinking copolymerizations compared to linear polymerization. This is due to the cyclization reactions which reduce the size of the macroradical coils and thus, enhance the termination rates due to the lowering of the thermodynamic excluded volume effect. As the amount of the crosslinker increases, an enhancement in the initial rate of polymerization is observed in all series of experiments, indicating that steric effects on segmental diffusion dominate at high crosslinker contents. The results also indicate a slower rate of termination of ionic macroradicals compared to the non-ionic radicals of the same molecular weight and points the significance of the thermodynamic excluded volume effect on rising the ionic group content. Received: 15 December 1997/Accepted: 13 February 1998     

Investigation of corrosion behaviors in chloride solutions of G-X 10CrNiMoNb 18-10 austenitic stainless steel produced by different casting techniques

In this study, corrosion resistance of G-X 10CrNiMoNb 18–10 austenitic stainless steel parts, which had been produced through sand molded casting and centrifugal casting methods, and exposed to two-step heat treatments and cooled in different mediums (water, oil, air and oven), in 3.5% NaCl solution were examined according to weight loss, potentiodynamic polarization and impedance spectroscopy. According to the obtained results, it was found that corrosion rate of G-X 10CrNiMoNb 18–10 austenitic stainless steel, which had been cast through the sand molded casting method, heated up to the 1^st stage (1065–1120°C), and then cooled in the air, the lowest.     

Effects of L‐carnitine supplementation to diets with different fat sources and energy levels on fatty acid composition of egg yolk of laying hens

BACKGROUND: The present study was carried out to determine the effects of feeding diets with two different levels of metabolisable energy (ME) (11.51 or 10.88 MJ ME kg^?1 diet) and three different sources of fat (palm oil, sunflower oil or fish oil) with or without supplemental L ‐carnitine (0 or 500 mg kg^?1 diet) on the fatty acid (FA) composition of egg yolk and the passage of n3 polyunsaturated FAs to egg yolk in laying hens. RESULTS: The ∑n3, particularly C22:6n‐3, FA contents of egg yolk were significantly reduced by adding of L ‐carnitine (C2) to different fat sources (P < 0.01). The ratio of n6/n3 was reduced from 53.77 to 17.72 in eggs yolks when ME was lowered in the diet with C2‐sunflower oil (SFO) whereas it was enhanced from 2.19 to 9.31 in C2‐E2 (low energy) diet with fish oil (FO) (P < 0.001). The diet with E2 or C2 containing FO resulted in a decrease of the C22:5n‐3, C22:6n‐3 and ∑n3 FA contents of egg yolk (P < 0.001). On the other hand, supplementation of C2 to diets with SFO or palm oil (PO) caused to a decrease in the C22:6n‐3 and ∑n3 FA contents of egg yolk (P < 0.01). A significant increase of the ratio of n6/n3 in egg yolk can be seen by feeding with E2 diet by adding of C2 to all fat sources like in E1 (normal energy) diet (P < 0.001). CONCLUSION: Dietary treatments resulted in major changes in FA composition of egg yolk. The supplemental C2 in diet decreased the C22:5n‐3, C22:6n‐3 and ∑n3FA contents in egg yolk. The use of FO in diets with E2 significantly reduced the passage rate of C22:6n‐3 FA to egg yolk. Copyright © 2008 Society of Chemical Industry     

Fatigue and fracture analysis of aluminum plate with composite patches under the hygrothermal effect

In this paper, fatigue life of the repaired cracks in 2024-T 3 aluminum with bonded patches made of unidirectional composite plates has been investigated experimentally and numerically for hygrothermal effect. The problem is handled in plane stress and Mode I condition. In the experimental study the mechanical properties of the aluminum plate and patch materials are determined and fatigue experiments are conducted. The results obtained from these experiments and numerical solutions are compared. Thus the reliability of the numerical solution has been proven. For all conditions, numerical solutions have been made and stress intensity factor (K_I) and fatigue life are calculated. Different plate and patch thicknesses are also considered in the experiments.     

ASPHALTENE AND RESID PYROLYSIS: EFFECT OF REACTION ENVIRONMENT

Hondo and Maya vacuum resids and their isolated asphaltenes were pyrolyzed at 400, 425, and 450^°C (752, 797, 842^°F) for batch holding limes ranging from 20 to 180 minutes. Maltene, asphaltene, and coke product fractions were isolated by a solvent extraction sequence; gas yield was determined gravimetrically. Results were summarized in terms of a lumped reaction network. The variation of product yields, kinetics, and apparent activation energies with feedstock and asphaltene environment provided insight into asphaltene structure and thermal reaction pathways.     

A vision-based measurement installation for programmable logic controllers

A vision-based measurement system is presented to obtain an economic installation for control and observe more than one process variables in industrial applications by using a Programmable Logic Controller (PLC) powered via Object Linking and Embedding for Process Control (OPC) technology.     

Semi‐interpenetrating polymer network hydrogels based on aspen hemicellulose and chitosan: Effect of crosslinking sequence on hydrogel properties

Semi‐interpenetrating network hydrogel films were prepared using hemicellulose and chemically crosslinked chitosan. Hemicellulose was extracted from aspen by using a novel alkaline treatment and characterized by HPSEC, and consisted of a mixture of high and low molecular weight polymeric fractions. HPLC analysis of the acid hydrolysate of the hemicellulose showed that its major constituent sugar was xylose. X‐ray analysis showed that the relative crystallinity of hydrogels increased with increasing hemicellulose content up to 31.3%. Strong intermolecular interactions between chitosan and hemicellulose were evidenced by FT‐IR analysis. Quantitative analysis of free amino groups showed that hemicellulose could interrupt the chemical crosslinking of chitosan macromolecules. Mechanical testing and swelling experiments were used to define the effective network crosslink density and average molecular weight between crosslinks. Swelling ratios increased with increasing hemicellulose content and mainly consisted of H‐bonded bound water. Results revealed that by altering the hydrogel preparation steps and hemicellulose content, crosslink density and swelling behavior of semi‐IPN hydrogels could be controlled without deteriorating their mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012