3D measurement simulation and relative pointing error verification of the telescope mount assembly subsystem for the large synoptic survey telescope

An engineering validation of a large optical telescope consists of executing major performing tests at the subsystem level to verify the overall engineering performance of the observatory. Thus, the relative pointing error verification of the telescope mount assembly subsystem is of special interest to guarantee the absolute pointing performance of the large synoptic survey telescope. This paper presents a new verification method for the relative pointing error assessment of the telescope mount assembly, based on laser tracker technology and several fiducial points fixed to the floor. Monte-Carlo-based simulation results show that the presented methodology is fit for purpose, even if floor movement occurs due to temperature variation during the measurement acquisition process. A further research about laser tracker technology integration into the telescope structure may suggest that such laser tracker technology could be permanently installed in the telescope in order to provide an active alignment system that aims to detect and correct possible misalignment between mirrors or to provide the required mirror positioning verification accuracy after maintenance activities. The obtained results show that two on-board laser tracker systems combined with eight measurement targets could result in measurement uncertainties that are better than 1 arcsec, which would provide a reliable built-in metrology tool for large telescopes

Dipolar glass polymers containing polarizable groups as dielectric materials for energy storage applications. A minireview

Materials that have high dielectric constants, high energy densities and minimum dielectric losses are highly desirable for use in capacitor devices. In this sense, polymers and polymer blends have several advantages over inorganic and composite materials, such as their flexibilities, high breakdown strengths, and low dielectric losses. Moreover, the dielectric performance of a polymer depends strongly on its electronic, atomic, dipolar, ionic, and interfacial polarizations. For these reasons, chemical modification and the introduction of specific functional groups (e.g., F, CN and R−S(=O)2−R´) would improve the dielectric properties, e.g., by varying the dipolar polarization. These functional groups have been demonstrated to have large dipole moments. In this way, a high orientational polarization in the polymer can be achieved. However, the decrease in the polarization due to dielectric dissipation and the frequency dependency of the polarization are challenging tasks to date. Polymers with high glass transition temperatures (Tg) that contain permanent dipoles can help to reduce dielectric losses due to conduction phenomena related to ionic mechanisms. Additionally, sub-Tg transitions (e.g., γ and β relaxations) attributed to the free rotational motions of the dipolar entities would increase the polarization of the material, resulting in polymers with high dielectric constants and, hopefully, dielectric losses that are as low as possible. Thus, polymer materials with high glass transition temperatures and considerable contributions from the dipolar polarization mechanisms of sub-Tg transitions are known as “dipolar glass polymers”. Considering this, the main aspects of this combined strategy and the future prospects of these types of material were discussed

Optical, morphological and photocatalytic properties of biobased tractable films of chitosan/donor-acceptor polymer blends

Biobased tractable films consisting of blends of chitosan (CS) with polymer bearing carbazole derivatives as pendant groups and fluorene-thiophene as donor-acceptor units (referred to as DA) were prepared, and their optical, morphological and photocatalytic properties were studied. DA was dissolved in tetrahydrofuran (THF) and mixed with an acidified aqueous solution containing chitosan to obtain chitosan/DA (CS/DA) films by solution casting. The fabricated biobased films were characterized using spectroscopic techniques (FT-IR and UV–vis), thermogravimetry, mechanical assays, contact angle analysis, and atomic force microscopy (AFM). The effects of varying DA compositions and the results of exposure to visible-light irradiation of the films were also analyzed. The results indicated the existence of interactions between chitosan and DA and a potentially profitable light-driven response of these biobased films. This behavior was reflected in the optical, topographical, and contact angle properties of the films, which exhibited different characteristics before and after visible-light exposure. Finally, the photocatalytic performance of the biobased films was tested via the decomposition of methyl orange (MO), as a reaction model system. Our results revealed a significant photocatalytic activity (according to biobased film composition, approximately 64 % and 87 % of methyl orange were degraded under continuous visible-light irradiation for 120 min) of the films which is attributed to the combined presence and synergetic effects of the film-forming ability of chitosan and the photoproperties of DA

Dispersion of carbon nanotubes in nanostructured epoxy systems forcoating application

This study about the dispersion of carbon nanotubes into an epoxy matrix can be considered as a firstapproach to investigate a potential industrial coating. In order to well disperse carboxylic acid-modifiedmultiwalled carbon nanotubes (a-MWCNT) in a commercial epoxy-based resin, its nanostructuring withan amphiphilic epoxidized styrene-b-butadiene-b-styrene triblock copolymer that also acts as surfactantwas carried out. In order to determine if coating performance is suitable for industrial applications, mor-phologies generated for copolymer-modified coating and the dispersion of a-MWCNT was characterizedby atomic force microscopy. Contact angle measurements, Taber abrasion testing and thermogravimetricanalysis were also performed. A tailor-made coating was developed with improved a-MWCNT dispersionand hydrophobicity due to the effect of block copolymer. System modified with 5 wt% of block copoly-mer and filled with 1 wt% a-MWCNT present the lowest value in weight loss in the wear test, whilesystems filled with 0.2 wt% of a-MWCNT showed increased thermal stability. Coating properties ana-lyzed depend largely on the amount of components and a-MWCNT dispersion level, thus adding newapplication possibilities to the coatings, while most of the conventional epoxy-coating advantages areretained.Fil: Espósito, Leandro Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Ramos, J.A. . Vrije Unviversiteit Brussel; BélgicaFil: Kortaberria, G.. Universidad del Pais Vasco; Españ

Combined Mesoscale/Experimental Study of Selective Placement of Magnetic Nanoparticles in Diblock Copolymer Films via Solvent Vapor Annealing

We present a combined theoretical/experimental study to investigate the effect of selective solvent vapor annealing treatment on the obtainment of highly ordered morphologies of symmetric poly(styrene-b-methyl methacrylate) diblock copolymer (PS-b-PMMA DBC) films loaded with compatibilized magnetic (Fe3O4) nanoparticles (NPs). Different amounts of NPs were considered (1, 2, and 5 wt %) to study the effect of the inorganic content on the final properties of Fe3O4/PS-b-PMMA films. A precise control of the DBC nanostructure could be obtained by very simple and cost-effective fabrication steps, compatible with current industrial processes. Moreover, the modified NPs could be selectively placed into the PMMA domains of the DBC up to NP concentration of 5 wt % while preserving the corresponding DBC lamellar morphology

Effects of amine molecular structure on carbon nanotubes functionalization

Three amines with different molecular structure, triethylenetetramine (TETA) and two polyetheramines (Jeffamine D-230 and Jeffamine T-403) were employed to functionalize multi-walled carbon nanotubes (MWCNT) previously oxidized by acid treatment. The functionalized MWCNT were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV-vis spectroscopy and the surface modification was investigated by field emission scanning electron microscopy (FE-SEM). Thermogravimetric analysis (TGA) was employed to quantify the amount of amine groups anchored to MWCNTs. The results have shown that the efficiency of amine functionalization is in the order TETA > D-230 > T-403, thus showing that amine chemical structure and molecular weight are important parameters on functionalization of carbon nanotubes. Copyright © 2009 American Scientific Publishers.Fil: Jimeno, A. Universidad del País Vasco; EspañaFil: Goyanes, Silvia Nair. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Ezeiza, A. Universidad del País Vasco; EspañaFil: Kortaberria, G. Universidad del País Vasco; EspañaFil: Mondragon Iñaki,. Universidad del País Vasco; EspañaFil: Corcuera, M A,. Universidad del País Vasco; Españ