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As a typical, discrete, and NP-hard problem, assembly sequence planning (ASP) has direct impact on assembly quality and costs. So far, lots of graph-based and meta-heuristic approaches cannot solve this problem effectively. This paper proposes an effective ASP algorithm based on the harmony search (HS) algorithm, which has an outstanding global search ability to obtain the global optimum more efficiently. To solve the ASP problem, an improved harmony search (IHS) algorithm is proposed mainly in four aspects: (1) an encoding of harmony is designed based on ASP problems; (2) an initial harmony memory (HM) is established using the opposition-based learning (OBL) strategy; (3) a particular way to improvise a new harmony is developed; and (4) a local search strategy is introduced to accelerate the convergence speed. Finally, the advantage of the proposed ASP algorithm over the competing algorithms in solving ASP problems is verified by two experiments. Moreover, the proposed ASP algorithm is applied to a practical problem, a propeller of azimuth thruster to verify its practicability.

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With the development of advanced manufacturing technology, more and more enterprises utilize automated guided vehicles to transfer materials for computer numerical control machines in the workshop. Because automated guided vehicle scheduling problem is non-deterministic polynomial-hard, highly efficient automated guided vehicle scheduling algorithms are necessary to improve productivity of the workshop. In order to solve this problem, a mathematical model with a new objective function is established firstly, which incorporates two indicators, that is, the standard deviation of the waiting time of computer numerical control material buffers and the total travel distance of automated guided vehicle, reflecting the overall capacity of computer numerical control machines and the energy efficiency of automated guided vehicles during the actual production, respectively. Then, an improved harmony search algorithm is proposed, which includes an effective discrete encoding scheme of harmony, a new initialization method for harmony memory based on opposition-based learning strategy, a dynamic harmony memory considering rate parameter and a local search strategy. The property of the proposed algorithm is evaluated through three cases from the real-world manufacturing system for producing back cover of smart phone. Compared with the competing algorithms, the results demonstrate the superiority of proposed algorithm for solving automated guided vehicle scheduling problem obviously.

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. 2008. Evaluation of genetic diversity and relationships in orchardgrass (Dactylis glomerata L.) germplasm based on SRAP markers. Can. J. Plant Sci. 88: 53Á60. The present study is the first report of characterizing the levels and patterns of genetic diversity in 60 orchardgrass accessions from four continents by sequence-related amplified polymorphism (SRAP) markers. Twenty-one primer pairs were used to produce 480 bands, of which 405 (84.38%) were polymorphic. The genetic similarity coefficients (GS) varied from 0.5863 to 0.9686 among the 60 collections, with an average of 0.7891. The genetic diversity of orchardgrass from China and the United States of America were found to be higher than that found in other countries. The dendrogram and principal component analysis realized from these markers clustered the materials into four main groups. The cluster analysis showed that orchardgrass from Australia was different from other collections in genetic diversity. Accessions from the same continent were classified into the same group, indicating that the genetic diversity of orchardgrass and the entire genetic basis of cultivars used in a continent is narrow. Furthermore, cluster analyses suggested that there is correlation between karyotype and morphological characterizations according to the analysis of the five subclusters that clustered from the first group. The information given by SRAP markers was concordant with the morphological variability and karyotype. This showed SRAP marker system could be used efficiently in the study of genetic variability and the evolutionary history of orchardgrasses. Based on the analysis of genetic diversity and relationships, the appropriate strategies for collection and conservation of germplasm resources can be developed and this in turn would help breeding of orchardgrass. For personal use only.

. 2010. Diversity comparison and phylogenetic relationships of cocksfoot (Dactylis glomerata L.) germplasm as revealed by SSR markers. Can. J. Plant Sci. 90: 13Á21. Phylogenetic relationships among and within 16 accessions collected from China, Russia, Kazakhstan, India and Japan were investigated using SSR markers. The 21 SSR primer pairs generated a total of 143 polymorphic alleles, with an average of 6.8 alleles per locus, and a range of 3Á13 alleles. The average genetic diversity, as measured by the polymorphic information content (PIC), was 0.33. The average polymorphic rate (P) for this species was 90.7%, suggesting a high degree of genetic diversity. Analysis of molecular variation (AMOVA) revealed larger genetic variation within accessions (65.75%) and geographical regions (75.58%) rather than between them, while among ploidy level variance contributed only 2.62%. A high degree of genetic diversity within tetraploid group was detected based on the polymorphic rate (P 094.23%) and shannon's information index of diversity (I00.4300) when compared with diploid group (P 091.25%, I 00.3922). The values of the genetic identity (GI) among accessions ranged from 0.7320 to 0.9691 and were used to produce a dendrogram using the UPGMA approach. The 16 accessions were grouped into two major clusters (GI00.876); specifically, all tetraploid (2n 04x028) accessions originating from different regions were grouped into the same cluster, whereas the diploid (2n 02x014) accessions were grouped into the two major clusters. The dendrogram was concordant with the morphological variability, agronomic traits and karyotype. Generally, the results of this study indicate that cocksfoot germplasm contains high molecular variation within accession and geographical region. The implications of these results for conservation of the species were discussed. Les 21 paires d'amorces SSR ont donne´143 alle`les polymorphes, avec une moyenne de 6,8 alle`les par locus et une fourchette de 3 a`13 alle`les. La diversite´ge´ne´tique moyenne e´tablie d'apre`s l'importance de l'information polymorphe est de 0,33. Le taux moyen de polymorphisme pour l'espe`ce est de 90,7%, ce qui laisse croire a`une grande diversite´ge´ne´tique. L'analyse de la variation mole´culaire (AMOVA) re´ve`le que la variation ge´ne´tique est plus grande au sein des obtentions (65,75%) et a`l'inte´rieur des re´gions (75,58%) qu'entre elles, mais la variance des ploı¨dies n'explique que 2,62% de cette variation. Le taux de polymorphisme (P 094,23%) et l'indice Shannon de diversite´(I 00,4300) re´ve`lent une grande diversite´ge´ne´tique pour les groupes te´traploı¨des, comparativement aux groupes diploı¨des (P 091,25%, I 00,3922). L'identite´ge´ne´tique (GI) des obtentions varie de 0,7320 a`0,9691; on s'en est servi pour produire un dendrogramme par la me´thode UPGMA. Les 16 obtentions ont e´te´re´unies en deux grandes grappes (GI00,876), plus pre´cise´ment, les obtentions te´traploı¨des (2n04 x028) venant des diverses re´gions se sont toutes retrouve´es dans une grappe, alors ...

Inter-simple Sequence Repeat (ISSR) molecular markers were used to detect the genetic diversity among 50 materials of Dactylis glomerata collected from China and other countries. Twelve primers produced 101 polymorphic bands, averaged 8.41 bands each primer pair. The average percentage of polymorpgic bands was 86.3.8%, and the range of GS (define) was 0.6116-0.9290, indicating a rich genetic diversity of D. glomerata. Based on the cluster and principal component analyses on the genetic characteristics, D. glomerata could be divided into 5 groups according to the nearest phylogenetic relationship. In most cases, accessions from the same continent were classified into the same group, the accessions from China and the United States belong to the different groups, respectively, indicating the geographical distribution of genetic diversity of D. glomerata. The present paper also discussed collection and conservation of germplasm resources in D. glomerata.