Convex hull ranking algorithm for multi-objective evolutionary algorithms

AbstractDue to many applications of multi-objective evolutionary algorithms in real world optimization problems, several studies have been done to improve these algorithms in recent years. Since most multi-objective evolutionary algorithms are based on the non-dominated principle, and their complexity depends on finding non-dominated fronts, this paper introduces a new method for ranking the solutions of an evolutionary algorithm’s population. First, we investigate the relation between the convex hull and non-dominated solutions, and discuss the complexity time of the convex hull and non-dominated sorting problems. Then, we use convex hull concepts to present a new ranking procedure for multi-objective evolutionary algorithms. The proposed algorithm is very suitable for convex multi-objective optimization problems. Finally, we apply this method as an alternative ranking procedure to NSGA-II for non-dominated comparisons, and test it using some benchmark problems

Insights into galvanic corrosion behavior of Ti-Cu dissimilar joint: Effect of microstructure and volta potential

The effect of microstructure on corrosion behavior of a solid-state explosion welded Ti-Cu bimetal is investigated by means of alternating current-direct current (AC-DC) electrochemical measurements, optical microscopy, scanning electron microscopy, and scanning Kelvin probe force microscopy (SKPFM). The results indicate that the titanium regions in the welding interface, local melted zone (LMZ), and LMZ-Cu interface are potential sites for initiation of corrosion attacks. SKPFM mapping clearly shows that before exposure of the sample to a 3.5% NaCl corrosive solution and at the beginning of the exposure, the Cu side of the bimetal has a higher Volta potential in comparison to that of the Ti region, and thus acts as a cathode. Electrochemical measurements also confirm that titanium acts as an anode and copper as a cathode, in the first moments of immersion, in accordance with macroscopic observations and SKPFM results. However, by growing a passive layer of titanium oxide and titanium hydroxide on the Ti side after about 1 h exposure to the corrosive medium, the titanium side becomes nobler and the polarity arrangement in the galvanic couple reverses

Occurrence and molecular characterization of a 16SrI-R subgroup phytoplasma associated with Aquilegia vulgaris phyllody disease

During 2016–2017 surveys, carried out for phytoplasma diseases in ornamental plants in Chaharmahal and Bakhtiari provinces, Iran, found symptoms of virescence, phyllody, reduced size of leaves and flowers in columbine (Aquilegia vulgaris). Total DNAs extracted from symptomatic and symptomless plants were tested for the presence of phytoplasma using P1/P7 and R16F2n/R16R2 primers in direct and nested PCR producing amplicons of about 1.8 and 1.2 kb, respectively, from all symptomatic A. vulgaris plants, but not from symptomless ones. The consensus sequence of the detected phytoplasma named Aquilegia phyllody (APh) was 100% identical with strains clustering to phytoplasmas enclosed in the 16SrI group as also confirmed by phylogenetic analyses. Both real and virtual restriction fragment length polymorphism analysis of R16F2n/R16R2 amplicons showed profiles that were identical to each other and indicated the affiliation of the APh phytoplasma to the 16SrI-R subgroup. This is the first report of a 16SrI-R phytoplasma associated with this A. vulgaris phyllody disease

Effect of substrate grain size on structural and corrosion properties of electrodeposited nickel layer protected with self-assembled film of stearic acid

In the present study, the impact of copper substrate grain size on the structure of the succeeding electrodeposited nickel film and its consequent corrosion resistance in 3.5% NaCl medium were evaluated before and after functionalization with stearic acid. Nickel layers were electrodeposited on two different copper sheets with average grain size of 12 and 25 \u3bcm, followed by deposition of stearic acid film through self-assembly. X-ray diffraction analysis of the electrodeposited nickel films revealed that the deposition of nickel film on the Cu substrate with small (12 \u3bcm) and large (25 \u3bcm) grains is predominantly governed by growth in the (220) and (111) planes, respectively. Both electrodeposited films initially exhibited a hydrophilic nature, with water-contact angles of 56\ub0 and <10\ub0, respectively. After functionalization with stearic acid, superhydrophobic films with contact angles of ~150\ub0 were obtained on both samples. In a 3.5% NaCl medium, the corrosion resistance of the nickel layer electrodeposited on the copper substrate with 25 \u3bcm grains was three times greater than that deposited on the copper substrate with 12 \u3bcm grains. After functionalization, the corrosion resistance of both films was greatly improved in both short and long immersion times in 3.5% NaCl medium