Hiroyuki Sato

Controlling dominance area of solutions and its impact on the performance of MOEAs

This work proposes a method to control the dominance area of solutions in order to induce appropriate ranking of solutions for the problem at hand, enhance selection, and improve the performance of MOEAs on combinatorial optimization problems. The proposed method can control the degree of expansion or contraction of the dominance area of solutions using a user-defined parameter S. Modifying the dominance area of solutions changes their dominance relation inducing a ranking of solutions that is different to conventional dominance. In this work we use 0/1 multiobjective knapsack problems to analyze the effects on solutions ranking caused by contracting and expanding the dominance area of solutions and its impact on the search performance of a multi-objective optimizer when the number of objectives, the size of the search space, and the complexity of the problems vary. We show that either convergence or diversity can be emphasized by contracting or expanding the dominance area. Also, we show that the optimal value of the area of dominance depends strongly on all factors analyzed here: number of objectives, size of the search space, and complexity of the problems.

Local dominance using polar coordinates to enhance multiobjective evolutionary algorithms

In this paper, we propose a calculation method of local dominance and enhance multiobjective evolutionary algorithms by performing a distributed search based on local dominance. In this method, we first transform all fitness vectors of individuals to polar coordinate vectors in the objective function space. Then we divide the population into several sub-populations by using declination angles. We calculate local dominance for individuals belonging to each sub-population based on the local search direction, and apply selection, recombination, and mutation to individual within each sub-population. We pick up NSGA-II and SPEA2 as two representatives of the latest generation of multiobjective evolutionary algorithms and enhance them with our model. We verify the effectiveness of the proposed method obtaining Pareto optimal solutions satisfying diversity conditions by comparing the search performance between the conventional algorithms and their enhanced versions.

Local dominance and local recombination in MOEAs on 0/1 multiobjective knapsack problems

This work studies and compares the effects on performance of local dominance and local recombination applied with different locality in multiobjective evolutionary algorithms on combinatorial 0/1 multiobjective knapsack problems. For this purpose, we introduce a method that creates a neighborhood around each individual and assigns a local dominance rank after alignment of the principle search direction of the neighborhood by using polar coordinates in objective space. For recombination a different neighborhood determined around a random principle search direction is created. The neighborhood sizes for dominance and recombination are separately controlled by two different parameters. Experimental results show that the optimum locality of dominance is different from the optimum locality of recombination. Additionally, it is shown that the performance of the algorithm that applies local dominance and local recombination with different locality is significantly better than the performance of algorithms applying local dominance alone, local recombination alone, or dominance and recombination globally as conventional approaches do.

Discotic liquid crystals of transition metal complexes 45: parity effect of the number of d-electrons on stacking distances in the columnar mesophases of octakis-(m-alkoxyphenoxy)phthalocyaninato metal(II) complexes

We have synthesized 34 novel homologous discotic liquid crystals, octakis(m-alkoxyphenoxy)phthalocyaninato metal(II) {abbreviated as (m-CnOPhO)8PcM (M = Co(1), Ni(2), Cu(3), Zn(4) and H2(5); n = 8(a), 10(b), 12(c), 14(d), 16(e), 18(f) and 20(g))}, and investigated parity effect of the number of d-electrons on the stacking distances in their columnar mesophases. It was revealed from temperature-dependent wide angle X-ray diffraction studies that each of the cobalt(II) (d7) complexes (1a–1g) and the copper(II) (d9) complexes (3b–3g) showed a single hexagonal ordered columnar (Colho) mesophase with a very short stacking distance at 3.3 A, and that the nickel(II) (d8) complexes (2a–2g) and the metal-free (d0) derivatives (5a–5g) showed a single pseudo-hexagonal ordered columnar (Colrho) mesophase with a little bit longer stacking distances at 3.4 A. Very interestingly, the nickel complex (2a) and metal-free derivatives (5a–5c) gave an extremely big (001) reflection peak with the second (002) reflection peak. Furthermore, the zinc(II) (d10) complexes (4a–4g) showed two different rectangular ordered columnar mesophases, Colro(P2/m) and Colro(P21/a), with a little bit longer stacking distance at 3.4 A. Thus, the shorter stacking distance, 3.3 A, appeared for the odd number of d-electrons, whereas the longer stacking distance, 3.4 A, appeared for the even number of d-electrons. Hence, the stacking distances depend on parity of the number of d-electrons in the central metal(II). To our best knowledge, it is the first example of parity effect on the stacking distances in columnar mesophases.

“Molecular Rope Curtain” Type of Liquid Crystals Based on a Sliding Graft Copolymer Having Mobile PEG Side Chains

A sliding graft copolymer having a polyrotaxane main chain and side chains of polyethylene glycol with a molecular weight of 2000 (PEG2000) was found to be a novel “molecular rope curtain” type of liquid crystalline material, which displayed a smectic A mesophase between 51 °C and 250 °C without any rigid mesogenic moieties.

Local Dominance Including Control of Dominance Area of Solutions in MOEAs

Local dominance has been shown to improve significantly the overall performance of multiobjective evolutionary algorithms (MOEAs) on combinatorial optimization problems. This work proposes the control of dominance area of solutions in local dominance MOEAs to enhance Pareto selection aiming to find solutions with high convergence and diversity properties. We control the expansion or contraction of the dominance area of solutions and analyze its effects on the search performance of a local dominance MOEA using 0/1 multiobjective knapsack problems. We show that convergence of the algorithm can be significantly improved while keeping a good distribution of solutions along the whole true Pareto front by using local dominance with expansion of dominance area of solutions. We also show that by controlling the dominance area of solutions dominance can be applied within very small neighborhoods, which reduces significantly the computational cost of the local dominance MOEA

On the locality of dominance and recombination in multiobjective evolutionary algorithms

This work studies and compares the effects on performance of local dominance and local recombination applied with different locality in multiobjective evolutionary algorithms on combinatorial multiobjective problems. For this purpose, we introduce a method that creates a neighborhood around each individual and assigns a local dominance rank after rotating the principal search direction of the neighborhood by using polar coordinates in objective space. For recombination a different neighborhood determined around a random principle search direction is created. The neighborhood sizes for dominance and recombination are separately controlled by two different parameters. Experimental results show that the optimum locality of dominance is different from the optimum locality of recombination. Additionally, it is shown that the performance of the algorithm that applies local dominance and local recombination with different locality is significantly better than the performance of algorithms applying local dominance alone, local recombination alone, or dominance and recombination globally as conventional approaches do

Discotic liquid crystals of transition metal complexes 46: mesomorphism and antagonist solubility of octaphenoxy-phthalocyaninato copper(II) complex substituted by oligoether chains

We synthesized a novel discotic liquid crystalline compound, octakis[3-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)phenoxy]phthalocyaninato copper(II) (abbreviated as [m-MeO(EtO)3PhO]8PcCu), and established the mesomorphism by using a differential scanning calorimeter, a polarizing optical microscope, and temperature-dependent wide angle X-ray diffraction diffractometer. Very interestingly, this [m-MeO(EtO)3PhO]8PcCu complex showed a hexagonal ordered columnar (Colho) mesophase in the virgin sample, whereas it showed a rectangular ordered columnar (Colro(P21/a)) mesophase in the non-virgin sample. The Colho mesophase gave a dimer stacking distance at 9.26 A, whereas the Colro mesophase gave a short monomer stacking distance at 3.45 A. Furthermore, this novel Pc derivative is readily soluble in polar solvents such as acetone, ethanol and methanol. Using antagonist solubilities of the present hydrophilic [m-MeO(EtO)3PhO]8PcCu derivative in a polar solvent and the previous hydrophobic (C10O)16TzCu derivative in the non-polar solvent, a p-n junction layered thin films could be successfully prepared.

Local dominance and controlling dominance area of solutions in multi and many objectives EAs

This work presents local dominance with alignment of principle search direction and control of dominance area of solutions to enhance selection of MOEAs, aiming to improve their performance on multi and many objectives combinatorial problems. We show that the methods used independently can substantially improve either diversity or convergence. Also, by including control of dominance area of solutions within the local dominance algorithm, we show that diversity and convergence can improve simultaneously while reducing the computational cost of the algorithm.