The impact of liberalizing cost-saharing on basic models of network formation

This paper studies the impact of "liberalizing " the cost-sharing of links on some basic models of network formation. This is done in a setting where both doubly supported and singly supported links are possible, and which includes the two seminal models of network formation by Jackson and Wolinsky and Bala and Goyal as extreme cases. In this setting, the notion of pairwise stability is extended and it is proved that liberalizing cost-sharing for doubly supported links widens the range of values of the parameters where the efficient networks formed by such type of links are pairwise stable, while the range of values of the parameters where the efficient networks formed by singly supported links are pairwise stable shrinks, but the region where the latter are e¢ cient and pairwise stable remains the same.

Synthesis and formation mechanism of silver nanowires by a templateless and seedless method

Silver nanowires in large quantities can be obtained through a simple method in the absence of a surfactant or polymer and without addition of external seeding nanocrystallites. A plausible mechanism was proposed to elucidate the formation mechanism of silver nanowires based on TEM studies.

Formation and characterization of tin oxide aerogel derived from sol-gel process based on tetra(n-butoxy)tin(IV)

Transparent and translucent SnO2 aerogels with high specific surface area (>300m(2)/g) have been prepared by sol-gel process using tetra(n-butoxy)tin(IV) as a starting compound, and supercritical drying technique for solvent extraction. Light scattering measurements reveal that the polymeric cluster size distribution in sol system is gradually broadened during sol-gel transition. SEM images show that the aerogels are made up of the cottonlike oxide agglomerates with a large number of Pores. TEM images show that these aerogels seem to be self-similar at different magnifications. Their pore size distribution is pretty wide ranging, from mesopore to macropore especially for that of translucent aerogel. (C) 2004 Elsevier B.V. All rights reserved.

Transverse mode formation in longitudinally pumped miniature slab lasers

The formation of transverse modes in longitudinally pumped miniature slab lasers is investigated theoretically and experimentally. The longitudinally non-uniform gain-guiding is studied by expanding the electric field into the Hermite-Gaussian functions that satisfy boundary conditions of the resonator. Non-Gaussian transversal beam profiles in the near field are found and the beam diameter is reduced when the pump spot becomes smaller. The experimental observation agrees with the theoretical calculation.

Self-formation of quasiperiodic void structure in CaF2 induced by femtosecond laser irradiation

We report the self-formation of quasiperiodic void structure with the length of several hundred micrometers inside the CaF2 crystal. The quasiperiodical voids along the propagation direction of the laser beam were formed spontaneously after the irradiation of a single femtosecond laser beam which was focused at a fixed point inside the crystal sample. The length of the void array varied with the focal depth beneath the sample surface. The possible mechanism of the self-formed void structure was discussed. (c) 2007 American Institute of Physics.

Formation, thermal, optical and physical properties of GeS2-Ga2S3-AgCl novel chalcohalide glasses

Novel GeS2-Ga2S3-AgCl chalcohalide glasses had been prepared by melt-quenching technique, and the glass-forming region was determined by XRD, which indicated that the maximum of dissolvable AgCl was up to 65 mol%. Thermal and optical properties of the glasses were studied by differential scanning calorimetry (DSC) and Visible-IR transmission, which showed that most of GeS2-Ga2S3-AgCl glasses had strong glass-forming ability and broad region of transmission (about 0.45-12.5 mu m). With the addition of AgCl, the glass transition temperature, Tg decreases distinctly, and the short-wavelength cut-off edge (lambda(vis)) of the glasses also shifts to the long wavelength gradually. However, the glass-forming ability of the glass has a complicated evolutional trend depended on the compositional change. In addition, the values of the Vickers microhardness, H (v) , which decrease with the addition of AgCl, are high enough for the practical applications. These excellent properties of GeS2-Ga2S3-AgCl glasses make them potentially applied in the optoelectronic field, such as all-optical switch, etc.

Formation of array microstructures on silicon by multibeam interfered ferntosecond laser pulses

We report on an optical interference method to fabricate array microstructures on the surface of silicon wafers by means of five-beam interference of femtosecond laser pulses. Optical microscope and scanning electron microscope observations revealed microstructures with micrometer-order were fabricated. The diffraction characteristics of the fabricated structures were evaluated. The present technique allows one-step realization of functional optoelectronic devices on silicon surface. (C) 2004 Elsevier B.V. All rights reserved.

Formation of arrayed holes on metal foil and metal film by multibeam interfering femtosecond laser beams

We report on an optical interference method to fabricate arrayed holes on metal nickel foil and aluminum film deposited on glass substrate by means of five-beam interference of femtosecond laser pulses. Optical microscope and scanning electron microscope observations revealed that arrayed holes of micrometre-order were fabricated on both metal foil and metal film. The present technique allows one-step, large-area, micrometric processing of metal materials for potential industrial applications.

Study of crystal formation in titanate glass irradiated by 800 nm femtosecond laser pulse

The structure of the titanate glass is destroyed during irradiation by the femtosecond laser pulses, and (TiO6)(8-) and (TiO4)(4-) anion units are exsolved from the network of the titanate glass. These anion units are rearranged to form some crystals such as anatase and Ba2TiO4 crystals. By Raman spectroscopy, it is found that these crystals have a strong dependence on the intensity of the femtosecond laser pulses. The relation between the generation of these crystals and space distribution of the femtosecond laser power intensity is qualitatively explained. (c) 2005 Elsevier B.V. All rights reserved.

Inclusão escolar de alunos com autismo: quem ensina e quem aprende?

Apesar do recente incremento nas matrículas de alunos com autismo nas escolas comuns, sua participação nas atividades escolares e aprendizagem ainda constitui-se como um grande desafio para os educadores. Considerando as características dos alunos que apresentam o quadro diagnóstico de autismo, a principal demanda para os professores é saber como desenvolver, no cotidiano das escolas, estratégias de ensino que favoreçam o processo de inclusão e aprendizagem deste alunado. O objetivo principal desta pesquisa foi analisar o papel da Educação Especial como suporte ao processo de inclusão escolar através da investigação das práticas pedagógicas de duas professoras do ensino comum que tinham alunos com autismo em suas classes. O objeto de estudo foi o Projeto de Acompanhamento à Inclusão de Alunos com Autismo desenvolvido no município de Angra dos Reis, RJ. O referido projeto tem como propósito subsidiar as escolas comuns da rede pública municipal no processo de inclusão de alunos com autismo, mais especificamente no que se refere à ação docente. Trata-se de uma pesquisa qualitativa, em que a metodologia da pesquisa-ação foi utilizada em dois estudos de caso correspondentes a duas experiências de inclusão de alunos com autismo em classes comuns. Os dados foram coletados por meio de diferentes procedimentos como a observação participante, entrevistas abertas e semi-estruturadas e filmagem. Como resultados consideramos que o acompanhamento direto da Educação Especial ao professor regente, em sala de aula, é favorável à inclusão de alunos com autismo. A utilização de adaptações curriculares com a flexibilização das estratégias de ensino, e a criação de atividades individualizadas para o aluno relacionadas ao proposto para a classe como um todo também foram fatores cuja importância foi evidenciada. Outro dado relevante da pesquisa foi o envolvimento da gestão da escola como facilitador na promoção de inclusão de alunos com autismo. Ainda que obstáculos precisem ser superados, a pesquisa revelou que a inclusão de alunos com autismo na escola comum, com o suporte da Educação Especial, impulsiona a aprendizagem de todos os envolvidos. Destaca-se o progresso dos alunos com autismo, como resultado direto da formação continuada do professor da escola comum. A pesquisa aponta, ainda, a demanda de novos estudos no campo da Educação Especial que permitam desenvolvimento melhores práticas de suporte à inclusão escolar e o processo de escolarização, de modo geral, deste público.