Rotational Mobility Analysis of the 3-RFR Class of Spherical Parallel Robots

none4noSpherical parallel manipulators (SPMs) are used to orient a tool in the space with three degrees of freedom exploiting the strengths of a multi-limb architecture. On the other hand, the performance of parallel kinematics machines (PKMs) is often affected by the occurrence of different kinds of singular configurations. The paper aims at characterizing a class of SPMs for which all singularities come to coincide and a single expression is able to describe all the singular configurations of the machines. The study is focused on a class of SPMs with 3-RFR topology (Revolute-Planar-Revolute pairs for each of the three limbs) addressing the mobility and singularity analysis by means of polynomial decomposition and screw theory. The neatness of the equations that are worked out, expressed in a robust formulation based on rotation invariants, allows a straightforward planning of singularity free tasks and simplifies the synthesis of dexterous machines.openCorinaldi, David; Carbonari, Luca; Palpacelli, Matteo-Claudio; Callegari, MassimoCorinaldi, David; Carbonari, Luca; Palpacelli, Matteo-Claudio; Callegari, Massim

Understanding how space travel affects the female reproductive system to the Moon and beyond

As the space industry grows exponentially and aspirations for space travel expand, we are entering a new era where we will very likely become an interplanetary species. Although reproduction is an essential human function and necessary for species survival, we have remarkably little knowledge regarding the impact of space travel on the female reproductive system. The effects of spaceflight on human reproductive potential, fertility, implantation and subsequent pregnancy resulting in a healthy live birth must be considered before planning prolonged spaceflight missions and the colonization of planets. In this review, we explore what is known and what remains to be learned about the effects of space travel on female reproductive endocrinology. We also delve deeper into reproductive endocrinology and discuss normal physiologic mechanisms at the molecular level to have a better understanding of how it may change during spaceflight. The rigors of spaceflight including radiation, gravitational stressors, and circadian rhythm changes could potentially affect ovulation, fertilization, endometrial receptivity, preimplantation embryo development, embryo implantation, placentation, and pregnancy. Thus, we will examine what is known about spaceflight effects on the hypothalamic–pituitary–gonadal (HPG) axis, ovarian folliculogenesis and steroidogenesis, early embryogenesis, endometrial receptivity, and pregnancy. We further discuss the recent advances in reproductive endocrinology and future research platforms. Establishing a better understanding of the effect of space travel on female reproductive health, as well as developing countermeasures to mitigate adverse effects, are decisive components of our species’ successful transition to an interplanetary one

Performance comparison of two constructive algorithms for multilayer perceptrons

International audienc

Non-overconstrained 3-dof spherical parallel manipulators of type: 3-RCC, 3-CCR, 3-CRC

Non-overconstrained 3-dof spherical parallel manipulators of a structural type 3-RCC, 3-CCR, 3-CRC are introduced. The mechanism has three limbs that connect in parallel the moving platform to the fixed base. Each limb is all opened kinematic chain made of a sequence of one revolute pair R and two cylindrical pairs C. The orientation of the end-effector is obtained by actuating simultaneously the three limbs. A structural type analysis and synthesis, which is based oil the algebraic properties of a Lie group Of the displacement set, is employed to find tile geometrical conditions for the assembly of these spherical parallel mechanisms and also the structurally singular configurations. Then all enumeration of the structural types Is given and remarkable special cases of orientational mechanisms are also described, namely 3-HGR, 3-RGH and 3-HGH

Asymmetrical 3-dof spherical parallel mechanisms

The paper deals with the structural synthesis of asymmetrical non-overconstrained 3-dof spherical parallel mechanisms (SPM). Most of SPM described in the literature are composed of three identical limbs, and they can be called symmetrical SPM. New SPM composed of three structurally distinct limbs, which we name asymmetrical SPM, are disclosed. This paper addresses the type synthesis of asymmetrical non-overconstrained SPM. Firstly, a mobility analysis is presented in order to find the degree of freedom of the limbs. In a second step the geometrical conditions of the limb assembly that achieves the spherical motion are established. Finally, limb architectures of asymmetrical non-overconstrained SPM are enumerated. The resulting kind of scientific catalogue is comprehensive under the hypothesis of non-paradoxical mobility. Moreover SPM 4-dof limbs without idle pairs were never revealed before

Weight initialization in BP networks using discriminant analysis techniques

International audienc

Editorial

Este número da revista Texto Livre: Linguagem e Tecnologia dedica-se à área de Humanas, em especial a grande área Linguística Letras e Artes. No entanto, a seção Educação e Tecnologia vem com mais força que as demais, desta vez com três artigos dedicados ao uso de tecnologias digitais no ensino. Jaiza Helena Moisés Fernandes, com o artigo"SOFTWARE LIVRE NA EDUCAÇÃO PARA ALÉM DA INCLUSÃO DIGITAL E SOCIAL: LETRAMENTOS MÚLTIPLOS DE PROFESSORES E ALUNOS" apresenta um bem sucedido caso de utilização do Linux educacional 3.0 numa escola do Ceará. Leila de Almeida Castillo Iabel discute a resistência de professores e educadores no uso de Tecnologias da Informação em suas atividades docentes, no artigo "RELAÇÕES DE ENSINÂNCIA E APRENDÊNCIA ATRAVÉS DO USO DAS TIC'S". Gonzalo Abio, na mesma seção, apresenta uma visão panorâmica e comentada das diretrizes do livro didático no Brasil, no artigo "UN ANÁLISIS PRELIMINAR DE LAS ACTIVIDADES TIC PRESENTES EN LOS LIBROS DIDÁCTICOS ESCOGIDOS POR LOS PNLD 2011 Y 2012 PARA LA ENSEÑANZA DE E/LE A BRASILEÑOS". O artigo foi vertido para o português por Vanderlei Machado e publicado na seção Vindo de Outras Trilhas (Traduções)". A ferramenta Wiki e o trabalho de produção colaborativa de textos é o foco da seção produção Textual e Tecnologia, no artigo "A FERRAMENTA WIKI: DESAFIOS E CONTRIBUIÇÕES NA FORMAÇÃO UNIVERSITÁRIA PRESENCIAL", assinado por Andriza Machado Becker. Finalmente, Isabel Cristina Vieira Coimbra Diniz, na seção Semiótica e Tecnologia, discute a relação entre espaço e corpo no que diz respeito às novas formas de divulgação de espetáculos de dança pela internet, no artigo "A DANÇA EM CENA: DO PALCO À TELA DO COMPUTADOR: UMA ANÁLISE SEMIÓTICA". Convidamos a todos a refletir conosco essas importantes questões. Ana Cristina Fricke Matt

Influence of weight initialization on generalization performance

International audienc