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1

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Geodetic observations of very rapid convergence and back-arc extension at the Tonga arc (1995)

Bevis, Michael ; Taylor, F. W. ; Schutz, B. E. ; [et al.]

[s.l.] : Nature Publishing Group

Nature 374 (1995), S. 249-251

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] It is widely believed that the Lau basin opened as the Tonga ridge rifted and drifted away from the Lau ridge (Fig. 1), but no consensus exists as to how the crust of the Lau basin was formed. For more than twenty years, geologists and geophysic-ists have debated the relative importance of ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/374249a0

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2

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Transformation between SLR/VLBI and WGS-84 reference frames (1995)

Abusali, P. A. M. ; Schutz, B. E. ; Tapley, B. D. ; [et al.]

Springer

Journal of geodesy 69 (1995), S. 61-72

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ISSN: 1432-1394

Source: Springer Online Journal Archives 1860-2000

Topics: Architecture, Civil Engineering, Surveying

Notes: Abstract In geodetic and geophysical applications of GPS, it is important to realize the ephemerides of the GPS satellites and the coordinates of station positions in a consistent reference system. At present, more than one reference system is being used by various GPS users depending on their specific applications. The WGS-84 and various reference frames based on satellite laser ranging (SLR), very long baseline interferometry (VLBI), or a combination of SLR and VLBI are the most commonly used in high precision geophysical applications. The WGS-84 is widely used in applications which rely on the GPS broadcast ephemeris. Station coordinates estimated in one system may have to be transformed to another for further use or for evaluation/comparison purposes. This paper presents a seven-parameter transformation between the WGS-84 and SLR/VLBI reference frames. The GPS double-differenced phase measurements for two consecutive weeks from a set of five Defense Mapping Agency (DMA) sites (defined in the WGS-84 frame) and from an augmented set of fifteen CIGNET sites (defined in the SLR/VLBI frame) were processed in a least squares estimation scheme to determine station coordinates, from which the transformation parameters were determined. A scale difference of about 0.2 ppm and an orientation difference in longitude of about 31 milliarcseconds were found to be the only parameters of significance between the adopted SLR/VLBI and the WGS-84 frames. Transformation between WGS-84 and the ITRF90 is also included, in which the scale difference is the same as before but the longitude rotation is about 16 mas.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00819552

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3

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Processing and physical property relationships in injection-molded isotactic polypropylene. 1. Mechanical properties (1997)

Kalay, Gürhan ; Bevis, Michael J.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 241-263

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ISSN: 0887-6266

Keywords: isotactic polypropylene ; propylene/ethylene copolymers ; injection molding ; SCORIM ; mechanical properties ; impact testing ; Physics ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: The aim of the research reported in these two articles was to explore the relationship between processing conditions and the physical properties of different grades of isotactic polypropylene injection moldings and propylene/ethylene copolymers. This first article describes the methods and processing conditions used for molding, together with mechanical test results. Both conventional and shear-controlled orientation injection molding (SCORIM) have been employed for the production of moldings. SCORIM is based on the application of specific macroscopic shears to a solidifying melt, which in turn, facilitates enhanced molecular alignment. SCORIM results in more pronounced molecular orientation than conventional injection molding, which is consistent with the substantial increase in Young's modulus of moldings produced by SCORIM. By controlling the processing parameters it is possible to control and enhance the stiffness without loss of tensile strength. An increase of up to four times in impact strength has been achieved with SCORIM as well as a substantial increase in Young's modulus. The conventional injection moldings containing pronounced molecular orientation exhibited impact resistance well below that for the SCORIM moldings. The mechanical tests carried out at 80°C showed that the high-temperature mechanical properties of all the materials, converted into moldings using SCORIM, exhibited substantial enhancement when compared with moldings of the same material converted by conventional injection molding. © 1997 John Wiley & Sons, Inc.

Additional Material: 19 Ill.

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Processing and physical property relationships in injection-molded isotactic polypropylene. 2. Morphology and crystallinity (1997)

Kalay, Gürhan ; Bevis, Michael J.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 265-291

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ISSN: 0887-6266

Keywords: isotactic polypropylene ; injection molding ; SCORIM ; γ-phase ; shish-kebab morphology ; molecular alignment ; crystallinity ; Physics ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: A preceding article referred to the processing of various grades of isotactic polypropylene (iPP) and propylene/ethylene copolymers by conventional and shear-controlled orientation injection molding (SCORIM), and considered the mechanical properties of the molded polymers in relation to the processing conditions applied. This article is principally concerned with the morphology and phase relationships that apply in injection-molded iPP. The γ-phase of isotactic polypropylene is reported to occur in moldings with pronounced molecular orientation. The presence of γ-phase in injection moldings is indicative of enhanced Young's modulus, and tensile strength provided that the melt has not been subjected to excessive deformation during processing. The common view that isotactic polypropylene exhibits only α- and β-phases in commercially produced moldings is challenged. SCORIM moldings contain less β-phase than conventional moldings, and exhibit greater overall crystallinity than moldings produced by conventional methods. The difference in the relative proportions of α-, β-, and γ-phases is marked and depends on processing conditions and the molding method. Shear-controlled orientation injection molding (SCORIM) results in more pronounced molecular orientation than conventional injection molding, which is consistent with the substantial increase in Young's modulus of moldings produced by SCORIM. The improved mechanical properties of iPP moldings is attributed to shish-kebab morphology developed by the action of shear to the solidifying melt. A new model is proposed for the oriented region morphology in iPP injection moldings based on the results presented in this article. © 1997 John Wiley & Sons, Inc.

Additional Material: 39 Ill.

Type of Medium: Electronic Resource

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5

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The effect of shear controlled orientation in injection moulding on the mechanical properties of an aliphatic polyketone (1997)

Kalay, Gürhan ; Bevis, Michael J.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 415-430

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ISSN: 0887-6266

Keywords: aliphatic polyketone ; ethylene-carbon monoxide copolymer ; PK ; isotactic polypropylene ; injection moulding ; molecular alignment ; morphology ; SCORIM ; Physics ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: This article relates to an investigation of injection moulding a new commercial polymer, an aliphatic polyketone (PK). A terpolymer and a 30% glass-filled grade were used as study materials together with an isotactic polypropylene that was used as a basis for comparison. Both conventional injection moulding and shear-controlled orientation injection moulding (SCORIM) were employed in processing. Tensile testing was carried out at 80°C as well as at room temperature. Polarized light microscopy and wide-angle x-ray diffraction were used in the characterization of the mouldings. An increase of up to 30% in Young's modulus and 35% in ultimate tensile strength, and a 70-90% increase in strain at peak were gained for the terpolymer (PK) at room temperature, as a result of SCORIM processing. A substantial improvement at 80°C was also recorded for unfilled SCORIM PK mouldings, and is attributed to the pronounced molecular alignment that was induced in SCORIM mouldings, as shown by Debye patterns. It is notable that the SCORIM mouldings of PK exhibit a greater tensile strength at 80°C than the SCORIM mouldings of isotactic polypropylene at 23°C. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 415-430, 1997

Additional Material: 17 Ill.

Type of Medium: Electronic Resource

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6

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Mechanical behavior of injection-molded starch-based polymers (1996)

Reis, Rui L. ; Cunha, António M. ; Allan, Peter S. ; [et al.]

New York, NY : Wiley-Blackwell

Polymers for Advanced Technologies 7 (1996), S. 784-790

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ISSN: 1042-7147

Keywords: starch-based polymers ; biomaterials ; injection molding ; Scorim ; impact performance ; 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: This work evaluates the mechanical performance of injection-molded starch-based copolymers, 60/40 (mol/mol) starch/poly(ethylene vinyl alcohol), and the possibility of improving material properties through deliberately induced anisotropy during processing. Different types of samples were produced by conventional and shear-controlled injection molding (Scorim) and tested under tensile and impact loading. The behavior of three distinct grades is discussed in terms of the respective fracture morphology (evaluated by scanning electron microscopy). A comparison is made between the behavior of conventional and Scorim samples. The results show that the mechanical properties of the materials used were significantly improved by the employment of the Scorim process. The stiffness values of the conventional moldings were doubled, without reducing the ductility of the polymer. The impact data showed a material sensitivity, and consequent loss of properties, to the localized shear imposed to the melt during processing. This situation is attributed to very narrow mold gates (in the case of pingated systems) and leads to much reduced impact performance.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

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