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  • 1
    Electronic Resource
    Electronic Resource
    Highly bright blue organic light-emitting devices using spirobifluorene-cored conjugated compounds (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 577-579 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An efficient and morphologically stable pyrimidine-containing spirobifluorene-cored oligoaryl, 2,7-bis[2-(4-tert-butylphenyl)pyrimidine-5-yl]-9,9′-spirobifluorene (TBPSF), as an emitter or a host for blue organic light-emitting devices (OLEDs), is reported. The steric hindrance inherent with the molecular structure renders the material a record-high neat-film photoluminescence (PL) quantum yield of 80% as a pure blue emitter (PL peak at 430 nm) of low molecular weight, and a very high glass-transition temperature (Tg) of 195 °C. Blue OLEDs employing this compound as the emitter or the emitting host exhibit unusual endurance for high currents over 5000 mA/cm2. When TBPSF is used as a host for perylene in a blue OLED, maximal brightness of ∼80 000 cd/m2 had been achieved, representing the highest values reported for blue OLEDs under dc driving. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1493669
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of proline accumulation in Arabidopsis thaliana (L.) Heynh during development and in response to desiccation (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Significant differences were observed in the amount and proportion of free amino acids in different organs of Arabidopsis thaliana (L.) Heynh, ecotype Columbia. The most notable were found for proline, which formed 17–26% of the total free amino acid concentration in reproductive tissues (floret and seed), but only 1–3% of the total free amino acid concentration in vegetative tissues (rosette leaf and root). Proline accumulation was associated with tissues that had relatively low water contents. Tissues which displayed high water contents, such as rosette leaves, contained low levels of proline. A significant increase in the levels of proline accumulation occurred in plants subjected to experimentally induced low water potentials as compared to unstressed plants. For instance, an 8–10-fold increase in proline was observed in the presence of 120 mmol kg−1 NaCl or KCl, and a 20-fold increase was stimulated by 60 mmol kg−1 PEG. However, in addition to the accumulation of proline, massive accumulation of Na+, K+ and Cl− ions occurred in tissues of plants stressed with salt. No significant differences were observed in mineral ions in plants stressed with PEG. Isotope tracer experiments with 14C compounds established that glutamate, ornithine and arginine are precursors of the proline biosynthesis induced by PEG in response to low water potentials in Arabidopsis thaliana. We conclude that the accumulation of proline in response to PEG occurs through increased biosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00187.x
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  • 3
    Electronic Resource
    Electronic Resource
    Some correlations involving the shear viscosity of polystyrene melts (1989)
    Springer
    Rheologica acta 28 (1989), S. 321-332 
    Details
    ISSN: 1435-1528
    Keywords: Polystyrene melt ; shear viscosity ; second-Newtonian viscosity ; Cross model ; Carreau model ; Cox-Merz relation ; recoverable compliance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Based upon a compilation of steady-shear and dynamic-shear viscosity data from the literature for polystyrene melts, an assessment has been made concerning the relative merits of the Cross and Carreau models in describing the shear-rate dependence of such viscosities. It is shown that the Cross model is decidedly more appropriate for PS of BMWD. Based upon master plots, it is demonstrated that the Cox-Merz relation applies to PS of both BMWD and NMWD. It is also shown that the Cox-Merz relation applies even into the second-Newtonian regime, withη ∞ being independent ofM w and MWD. In addition, the applicability of the Prest-Porter-O'Reilly relationship between shear viscosity and recoverable shear compliance is corroborated in the case of PS of NMWD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01329342
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  • 4
    Electronic Resource
    Electronic Resource
    Surface modification and functionalization of electroactive polymer films via grafting of polyelectrolyte, polyampholyte and polymeric acids (1996)
    Springer
    Journal of materials science 31 (1996), S. 1295-1301 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Films of electroactive polymers, such as polyaniline (PAN) in its emeraldine base form, and poly(3-alkylthiophene), poly(3-hexylthiophene) (P6TH), poly(3-octylthiophene) (P8TH), and poly(3-dodecylthiophene) (P12TH) can be readily functionalized via thermal or near ultraviolet-light-induced surface graft copolymerization with monomers of polyelectrolyte, polyampholyte and polymeric acids. The monomers used in the present work include dimethyl sulphate quaternized dimethylamino-ethylmethacrylate (DMAEM·C2H6SO4), 3-dimethyl(methacryloyloxyethyl)ammonium propane sulphonate (DMAPS), acrylic acid (AAc) and a sodium salt of styrene sulphonic acid (NaSS). The surface structures and compositions of the electroactive polymer films after functionalization via graft copolymerization were characterized by angle-resolved X-ray photoelectron spectroscopy. Graft copolymerization of poly(3-alkylthiophene) films, but not PAN films, with the hydrophilic monomers readily results in a stratified surface microstructure arising from the migration of the hydrophilic graft chains beneath a thin surface layer which is much richer in the substrate chains. On the other hand, graft copolymerization of PAN films with AAc and NaSS readily gives rise to a self-protonated (and thus conductive) surface structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353109
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  • 5
    Electronic Resource
    Electronic Resource
    A unified simulation of the filling and postfilling stages in injection molding. Part II: Experimental verification (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 125-139 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The unified numerical simulation of the filling/postfilling stages of the injection-molding process described in Part I is compared in the present paper with experimental results obtained with instrumented test molds. Flush-mounted pressure traces in the delivery system as well as in the cavity are favorably compared with corresponding predictions for both an amorphous and a semicrystalline polymer. It is demonstrated that the present unified formulation is well suited to handle complicated molds where compressibility effects can become important even during the filling stage, as portions of the cavity fill and undergo a packing behavior even when other regions of the cavity are still only partially filled.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310211
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  • 6
    Electronic Resource
    Electronic Resource
    Shear-rate-dependence modeling of polymer melt viscosity (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 931-938 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Steady-shear-viscosity data sets for commercial-grade acrylonitrile-butadiene-styrene terpolymer, nylon, polycarbonate, poly(methylmethacrylate), and polystyrence are fitted in terms of a generalized Cross/Carreau modeling for the shear-rate dependence. Based upon extensive data sets from the open literature as well as in-house measurements, it is shown that the shear-rate dependence can be more accurately described in terms of the Cross rather than Carreau model. Although the resulting viscosity fits based upon these two models might differ by 20% or more for the same well-characterized data set, the resulting effect upon simulating the injection-molding process is found to be much smaller since such predictions reflect a range of shear stresses (varying linearly from centerline to wall of cavity) over which the two models alternate in relative magnitude. This is demonstrated by detailed representative numerical predictions which are presented for both the filling and post-filling stages.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321404
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  • 7
    Electronic Resource
    Electronic Resource
    A unified simulation of the filling and postfilling stages in injection molding. Part I: Formulation (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 116-124 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This study employs a unified theoretical model to simulate the filling and postfilling stages of the injection-molding process. Implementation of such a model is based on a hybrid finite-element/finite-difference numerical solution of the generalized Hele-Shaw flow of a compressible viscous fluid under nonisothermal conditions. The shear viscosity of the polymeric material is represented by a Cross model for the shear-rate dependence and a WLF-type functional form for the temperature and pressure dependence, whereas the specific volume is modeled in terms of a double-domain Tait equation. The analysis also handles variable specific heat and thermal conductivity of the polymer as a function of temperature. Complex thin parts of variable thickness can be modeled and discretized by flat, triangular finite elements which may have arbitrary orientation in three-dimensional space, whereas runners and possible round pins or bosses in the part are represented as one-dimensional circular-tube elements. A control-volume scheme is employed that leads to automatic melt-front advancement during the cavity-filling stage.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310210
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  • 8
    Electronic Resource
    Electronic Resource
    Postmolding and load-induced deformation analysis of plastic parts in the injection molding process (1991)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 11 (1991), S. 77-89 
    Details
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: To assess warpage and shrinkage of an injection-molded plastic part, an integrated computer-aided engineering (CAE) system has been developed. This integrated system employs a simultaneous analysis of the compressible fluid flow, heat transfer, and residual stresses in the polymer during the filling and postfilling stages of the injection molding process and of mold cooling/heating that occurs throughout the entire process. Using the polymer temperature and pressure distributions as a function of time, an analysis has been performed to predict the residual stresses, treating the polymer as a viscoelastic material. The resultant loading is interfaced with the structural analysis program ABAQUSTM to predict the postmolding shape of the plastic part. Analysis has also been performed to evaluate the load-deflection behavior of a molded part and the effects of different degrees of material anisotropy.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adv.1991.060110201
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  • 9
    Electronic Resource
    Electronic Resource
    Current trends in cae: Simulations of latest innovations in injection molding (1993)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 12 (1993), S. 233-241 
    Details
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The advent of CAE (computer-aided engineering) technology for injection molding and related processes is having a rapidly growing impact on the molding industry. Proper use of this technology has enhanced engineers' capability in handling all aspects of the molding process and has been proven to benefit both productivity and product quality. However, while CAE can serve as a powerful tool to help engineers make rational engineering decisions, it is by no means a panacea for solving all molding problems. The viability of CAE packages depends heavily not only on the scientific principles and numerical methods used for developing the software, but also on the reliability of the input data such as material properties and process conditions. This article discusses the state-of-the-art of the technology with an emphasis on simulations of latest innovations in injection molding. A three-layer approach that systematically integrates and efficiently utilizes various CAE tools to solve design problems at different levels of sophistication is also presented. © 1993 by John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adv.1993.060120302
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