On Selecting and Scheduling Assembly Plans Using Constraint Programming

This work presents the application of Constraint Programming to the problem of selecting and sequencing assembly operations. The set of all feasible assembly plans for a single product is represented using an And/Or graph. This representation embodies some of the constraints involved in the planning problem, such as precedence of tasks, and the constraints due to the completion of a correct assembly plan. The work is focused on the selection of tasks and their optimal ordering, taking into account their execution in a generic multi-robot system. In order to include all different constraints of the problem, the And/Or graph representation is extended, so that links between nodes corresponding to assembly tasks are added, taking into account the resource constraints. The resultant problem is mapped to a Constraint Satisfaction Problem (CSP), and is solved using Constraint Programming, a powerful programming paradigm that is increasingly used to model and solve many hard real-life problems

Even and odd pairs in comparability and in P4-comparability graphs

AbstractWe characterize even and odd pairs in comparability and in P4-comparability graphs. The characterizations lead to simple algorithms for deciding whether a given pair of vertices forms an even or odd pair in these classes of graphs. The complexities of the proposed algorithms are O(n + m) for comparability graphs and O(n2m) for P4-comparability graphs. The former represents an improvement over a recent algorithm of complexity O(nm)

A Genetic Algorithm for Assembly Sequence Planning

This work presents a genetic algorithm for assembly sequence planning. This problem is more difficult than other sequencing problems that have already been tackled with success using these techniques, such as the classic Traveling Salesperson Problem (TSP) or the Job Shop Scheduling Problem (JSSP). It not only involves the arranging of tasks, as in those problems, but also the selection of them from a set of alternative operations. Two families of genetic operators have been used for searching the whole solution space. The first includes operators that search for new sequences locally in a predetermined assembly plan, that of parent chromosomes. The other family of operators introduces new tasks in the solution, replacing others to maintain the validity of chromosomes, and it is intended to search for sequences in other assembly plans. Furthermore, some problem-based heuristics have been used for generating the individuals in the population

On the dynamics of Extrasolar Planetary Systems under dissipation. Migration of planets

We study the dynamics of planetary systems with two planets moving in the same plane, when frictional forces act on the two planets, in addition to the gravitational forces. The model of the general three-body problem is used. Different laws of friction are considered. The topology of the phase space is essential in understanding the evolution of the system. The topology is determined by the families of stable and unstable periodic orbits, both symmetric and non symmetric. It is along the stable families, or close to them, that the planets migrate when dissipative forces act. At the critical points where the stability along the family changes, there is a bifurcation of a new family of stable periodic orbits and the migration process changes route and follows the new stable family up to large eccentricities or to a chaotic region. We consider both resonant and non resonant planetary systems. The 2/1, 3/1 and 3/2 resonances are studied. The migration to larger or smaller eccentricities depends on the particular law of friction. Also, in some cases the semimajor axes increase and in other cases they are stabilized. For particular laws of friction and for special values of the parameters of the frictional forces, it is possible to have partially stationary solutions, where the eccentricities and the semimajor axes are fixed.Comment: Accepted in Celestial Mechanics and Dynamical Astronom

Orbital structure of the GJ876 extrasolar planetary system, based on the latest Keck and HARPS radial velocity data

We use full available array of radial velocity data, including recently published HARPS and Keck observatory sets, to characterize the orbital configuration of the planetary system orbiting GJ876. First, we propose and describe in detail a fast method to fit perturbed orbital configuration, based on the integration of the sensitivity equations inferred by the equations of the original $N$-body problem. Further, we find that it is unsatisfactory to treat the available radial velocity data for GJ876 in the traditional white noise model, because the actual noise appears autocorrelated (and demonstrates non-white frequency spectrum). The time scale of this correlation is about a few days, and the contribution of the correlated noise is about 2 m/s (i.e., similar to the level of internal errors in the Keck data). We propose a variation of the maximum-likelihood algorithm to estimate the orbital configuration of the system, taking into account the red noise effects. We show, in particular, that the non-zero orbital eccentricity of the innermost planet \emph{d}, obtained in previous studies, is likely a result of misinterpreted red noise in the data. In addition to offsets in some orbital parameters, the red noise also makes the fit uncertainties systematically underestimated (while they are treated in the traditional white noise model). Also, we show that the orbital eccentricity of the outermost planet is actually ill-determined, although bounded by $\sim 0.2$. Finally, we investigate possible orbital non-coplanarity of the system, and limit the mutual inclination between the planets \emph{b} and \emph{c} orbits by $5^\circ-15^\circ$, depending on the angular position of the mutual orbital nodes.Comment: 36 pages, 11 figures, 3 tables; Accepted to Celestial Mechanics and Dynamical Astronom

Changes In Sexual Behavior Following A Sex Education Program In Brazilian Public Schoolsm [mudanças No Comportamento Sexual De Adolescentes De Escolas Públicas No Brasil Após Um Programa De Educação Sexual]

This paper describes an evaluation of possible changes in sexual behavior in adolescents who participated in a school-based sex education program in selected public schools in four municipalities in the state of Minas Gerais, Brazil. The program is inserted within the context of reproductive rights, deals with risks involved in unsafe sexual practices and focuses on the positive aspects of sexuality. A quasi-experimental design with pre and post-tests and a non-equivalent control group was used to evaluate the intervention. A total of 4,795 questionnaires were included in this analysis. The program succeeded in more than doubling consistent condom use with casual partners and in increasing the use of modern contraceptives during last intercourse by 68%. The intervention had no effect on age at first intercourse or on adolescents' engagement in sexual activities. The sex education program was effective in generating positive changes in the sexual behavior of adolescents, while not stimulating participation in sexual activities.25511681176(2006) Promoting and Safeguarding the Sexual and Reproductive Health of Adolescents, , World Health Organization, Geneva: World Health Organization, (Policy Brief, 4. Implementing the Global Reproductive Health Strategy)Ross, J., Godeau, E., Dias, S., Sexual health (2004) Young People's Health In Context: Health Behaviour In School-aged Children (hbsc) Study. International Report From the 2001/2002 Survey, pp. 153-60. , In: Currie C, Roberts C, Morgan A, Smith R, Settertobulte W, Samdal O, et al., editors, Copenhagen: WHO Regional Office for Europe, (Health Policy for Children and Adolescents, 4)Kirby, D.B., Laris, B.A., Rolleri, L.A., Sex and HIV education programs: Their impact on sexual behaviors of young people throughout the world (2007) J Adolesc Health, 40, pp. 206-17Figueiró, N.M.D., A produção teórica no Brasil sobre educação sexual (1996) Cad Pesqui, (98), pp. 50-63Figueiró, N.M.D., Revendo a história da educação sexual no Brasil: Ponto de partida para construção de um novo rumo (1998) Nuances, 4, pp. 123-33(1998) Temas Transversais: Orientação Sexual, , Secretaria de Educação Fundamental, Ministério da Educação. Parâmetros curriculares nacionais, Brasília: Secretaria de Educação Fundamental, Ministério da EducaçãoPaiva, V., Pupo, L.R., Barboza, R., O direito à prevenção e os desafios da redução da vulnerabilidade ao HIV no Brasil (2006) Rev Saúde Pública, 40 (SUPPL.), pp. 109-19Hughes, J., McCauley, A.P., Improving the fit: Adolescents' needs and future programs for sexual and reproductive health in developing countries (1998) Stud Fam Plann, 29, pp. 233-45Díaz, M., Mello, M.B., Sousa, M.H., Cabral, F., Silva, R.C., Campos, M., Et al., Outcomes of three different models for sex education and citizenship programs concerning knowledge, attitudes, and behavior of Brazilian adolescents (2005) Cad Saúde Pública, 21, pp. 589-97(1999) Projeto Educação Afetivo-sexual: Sucessos E Desafios Na Educação Sexual De Adolescentes Da Rede Pública Estadual De Ensino De Belo Horizonte - Relatório Da Avaliação Externa, , Centro de Pesquisas em Saúde Reprodutiva de Campinas/Fundação Odebrecht, Campinas: Centro de Pesquisas em Saúde Reprodutiva de Campinas/Salvador: Fundação OdebrechtCosta, A.C.G., (2000) Protagonismo Juvenil: Adolescência, Educação E Participação Democrática, , Salvador: Fundação OdebrechtAndrade, H.H.S.M., Marques, C.M., Gouveia, M.C., Gregório, Y.M., Atendimento ambulatorial de adolescentes: A experiência do PAIA/ABEB (1996) J Pediatr (rio J), 72, pp. 319-23Cronbach, L.J., Coefficient alpha and the internal structure of tests (1951) Psychometrika, 16, pp. 297-334Mello, M.B., Fruet, M.S.B., Diaz, M., Silva, R.C., Paiva, V., Avaliação preliminar de impactos de um programa de orientação sexual de longa duração (1999) Anais Do Vii Congresso Brasileiro De Sexualidade Humana, p. 74. , Rio de Janeiro: Sociedade Brasileira de Estudos em Sexualidade HumanaFleiss, J.L., (1981) Statistical Methods For Rates and Proportions, , 2nd Ed. New York: John Wiley and SonsBertrand, J.T., Magnani, R.J., Rutenberg, N., (1996) Evaluating Family Planning Programs: With Adaptations For Reproductive Health, , Chapel Hill: Carolina Population Center, University of North Carolina at Chapel HillHosmer, D.W., Lemeshow, S., (1989) Applied Logistic Regression, , New York: John Wiley and SonsGrunseit, A., Kippax, S., (1997) Impact of Hiv and Sexual Health Education On the Sexual Behaviour of Young People: A Review Update, , Geneva: United Nations Joint Programme on HIV/AIDSKirby, D., (1995) A Review of Educational Programs to Designed to Reduce Sexual Risk-taking Behaviors Among School-aged Youth In the United States, , Santa Cruz: ETR AssociatesKirby, D., (2001) Emerging Answers: Research Findings On Programs to Reduce Teen Pregnancy, , Washington DC: National Campaign to Prevent Teen PregnancyAntunes, M.C., Peres, C.A., Paiva, V., Stall, R., Hearst, N., Diferenças na prevenção da AIDS entre homens e mulheres jovens de escolas públicas em São Paulo, SP (2002) Rev Saúde Pública, 36 (4 SUPPL.), pp. 88-95Magnani, R.J., Gaffikin, L., Aquino, E.M.L., Seiber, E.E., Almeida, M.C.C., Lipovsek, V., Impact of an integrated adolescent reproductive health program in Brazil (2001) Stud Fam Plann, 32, pp. 230-43Taquette, S.R., Vilhena, M.M., Paula, M.C., Doenças sexualmente transmissíveis e gênero: Um estudo transversal com adolescentes no Rio de Janeiro (2004) Cad Saúde Pública, 20, pp. 282-90Oliveira, F.A., Pfleger, V., Lang, K., Heukelbach, J., Miralles, I., Fraga, F., Sexually transmitted infections, bacterial vaginosis, and candidiasis in women of reproductive age in rural Northeast Brazil: A population-based study (2007) Mem Inst Oswaldo Cruz, 102, pp. 751-6(1999) Adolescentes, Jovens E a Pesquisa Nacional Sobre Demografia E Saúde: Um Estudo Sobre Fecundidade, Comportamento Sexual E Saúde Reprodutiva, , Bem-Estar Familiar no Brasil, Rio de Janeiro: Bem-Estar Familiar no BrasilAlmeida, M.C., Aquino, E.M., Barros, A.P., School trajectory and teenage pregnancy in three Brazilian state capitals (2006) Cad Saúde Pública, 22, pp. 1397-409Chalem, E., Mitsuhiro, S.S., Ferri, C.P., Barros, M.C.M., Guinsburg, R., Laranjeira, R., Gravidez na adolescência: Perfil sócio-demográfico e comportamental de uma população da periferia de São Paulo (2007) Brasil. Cad Saúde Pública, 23, pp. 177-86Baraldi, A.C.P., Daud, Z.P., Almeida, A.M., Gomes, F.A., Nakano, A.M.S., Adolescent pregnancy: A comparative study between mothers who use public and private health systems (2007) Rev Latinoam Enferm, 15, pp. 799-805. , (Spe

What are the advantages of living in a community? A microbial biofilm perspective!

Biofilm formation is the preferred mode of growth lifestyle for many microorganisms, including bacterial and fungal human pathogens. Biofilm is a strong and dynamic structure that confers a broad range of advantages to its members, such as adhesion/cohesion capabilities, mechanical properties, nutritional sources, metabolite exchange platform, cellular communication, protection and resistance to drugs (e.g., antimicrobials, antiseptics, and disinfectants), environmental stresses (e.g., dehydration and ultraviolet light), host immune attacks (e.g., antibodies, complement system, antimicrobial peptides, and phagocytes), and shear forces. Microbial biofilms cause problems in the hospital environment, generating high healthcare costs and prolonged patient stay, which can result in further secondary microbial infections and various health complications. Consequently, both public and private investments must be made to ensure better patient management, as well as to find novel therapeutic strategies to circumvent the resistance and resilience profiles arising from biofilm-associated microbial infections. In this work, we present a general overview of microbial biofilm formation and its relevance within the biomedical context

Resonances of low orders in the planetary system of HD37124

The full set of published radial velocity data (52 measurements from Keck + 58 ones from ELODIE + 17 ones from CORALIE) for the star HD37124 is analysed. Two families of dynamically stable high-eccentricity orbital solutions for the planetary system are found. In the first one, the outer planets c and d are trapped in the 2/1 mean-motion resonance. The second family of solutions corresponds to the 5/2 mean-motion resonance between these planets. In both families, the planets are locked in (or close to) an apsidal corotation resonance. In the case of the 2/1 MMR, it is an asymmetric apsidal corotation (with the difference between the longitudes of periastra $\Delta\omega\sim 60^\circ$), whereas in the case of the 5/2 MMR it is a symmetric antialigned one ($\Delta\omega = 180^\circ$). It remains also possible that the two outer planets are not trapped in an orbital resonance. Then their orbital eccentricities should be relatively small (less than, say, 0.15) and the ratio of their orbital periods is unlikely to exceed $2.3-2.5$.Comment: 28 pages, 10 figures, 3 tables; Accepted to Celestial Mechanics and Dynamical Astronom

A resonant-term-based model including a nascent disk, precession, and oblateness: application to GJ 876

Investigations of two resonant planets orbiting a star or two resonant satellites orbiting a planet often rely on a few resonant and secular terms in order to obtain a representative quantitative description of the system's dynamical evolution. We present a semianalytic model which traces the orbital evolution of any two resonant bodies in a first- through fourth-order eccentricity or inclination-based resonance dominated by the resonant and secular arguments of the user's choosing. By considering the variation of libration width with different orbital parameters, we identify regions of phase space which give rise to different resonant ''depths,'' and propose methods to model libration profiles. We apply the model to the GJ 876 extrasolar planetary system, quantify the relative importance of the relevant resonant and secular contributions, and thereby assess the goodness of the common approximation of representing the system by just the presumably dominant terms. We highlight the danger in using ''order'' as the metric for accuracy in the orbital solution by revealing the unnatural libration centers produced by the second-order, but not first-order, solution, and by demonstrating that the true orbital solution lies somewhere ''in-between'' the third- and fourth-order solutions. We also present formulas used to incorporate perturbations from central-body oblateness and precession, and a protoplanetary or protosatellite thin disk with gaps, into a resonant system. We quantify these contributions to the GJ 876 system, and thereby highlight the conditions which must exist for multi-planet exosystems to be significantly influenced by such factors. We find that massive enough disks may convert resonant libration into circulation; such disk-induced signatures may provide constraints for future studies of exoplanet systems.Comment: 39 pages of body text, 21 figures, 5 tables, 1 appendix, accepted for publication in Celestial Mechanics and Dynamical Astronom