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  • 1
    Electronic Resource
    Electronic Resource
    Flavonol Glycosides from Epimedium pubescens (1990)
    s.l. : American Chemical Society
    Journal of natural products 53 (1990), S. 1337-1339 
    Details
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/np50071a030
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  • 2
    Electronic Resource
    Electronic Resource
    The kinetics, thermal and mechanical properties of epoxy-polycarbonate blends cured with aromatic amine (1998)
    Springer
    Journal of polymer research 5 (1998), S. 115-124 
    Details
    ISSN: 1572-8935
    Keywords: Epoxy ; Blend ; Polycarbonate ; Transesterification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract PC-DER331 blends are transparent and homogeneous due to the transesterification taking place during hot melting process. This transesterification reaction does not occur or occurs insignificantly during the preparation of PC-DER332 blends. PC is separated from the PC-DER332 melt mixture by slow cooling to room temperature but the mixture remains a single phase by quenching with an ice bath. Two systems of PC-epoxy blends, PC-DER331 blends and PC-DER332 blends are cured by the m-phenylene diamine (MPDA) in a stoichiometric ratio. Curing kinetics have been carried out by differential scanning calorimeter (DSC). The presence of PC accelerates the curing reaction. Infrared spectroscopy (IR) indicates the occurrence of transesterification in the PC-DER331/MPDA blends during curing. The flexural modulus increases with the increase of the PC content while the notched Izod impact strength decreases with the increase of the PC content for all the blending systems. The fracture surfaces of the PC-DER331/MPDA blends are smooth, an indication of a homogeneous morphology. The fracture surfaces of the PC-DER332/MPDA blends are rough, an indication of a heterogeneous morphology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10965-006-0047-6
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  • 3
    Electronic Resource
    Electronic Resource
    Optimizing Analysis in the Bending Rigidity of CFRP Circular Plate with Multiple Holes (2005)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 475-479 (Jan. 2005), p. 1055-1058 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Being subjected to the bending load, the structure of plate often has the high demand of bending rigidity. Fiber reinforced composites are used in an increasing number of structural applications, this due to their higher specific strength and specific stiffness compared to homogenous structural materials. For the orthotropic carbon fiber reinforced plastics (CFRP) plate with multiple holes, the application of the classical stress-strain analysis is very difficult because of the anisotropism and the effect of the holes. Therefore, the finite element method (FEM) is used toinvestigate the effect of a plate with multiple holes on the bending rigidity. The bending rigidity in the situation that stiffeners are fixed firmly to the plate is much higher than they are separated. The computation results are consistent to the experiment results. Based on the computation, a FEM model to optimize the bending rigidity of this kind of laminate circular plate with multiple holes is established. The placement of holes, the form and number of stiffeners are optimized in this paper.The computation results show if the number of stiffeners change to 6 and are matched with holes the bending rigidity will be increased remarkably and the weight of plate is reduced simultaneously. The computation results are consistent to the experiment results. The resolution of this study provides a reference for the design of this kind of laminate circular plate with multiple holes
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/09/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.475-479.1055.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental and Analytical Study on the Mechanical Behavior of Stitched Sandwich Composite Panel with a Foam Core (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 477-482 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: To quantify the effect of structural through-thickness reinforcement in foam core sandwichcomposite panels, an experimental study was carried out which included three-point bending tests,core shear tests, flatwise tensile and compression tests, as well as edgewise compression tests.Standard test procedures based on ASTM guidelines are followed to test the behavior of the stitchedpanels with reinforcement at 90 degree orientation with respect to the sandwich faces. The testspecimens were manufactured by using polyurethane foam Rohacell 71 IG and carbon fiberreinforced composite facesheets. The dry perform facesheets and foam core were then assembled in adry lay-up already stitched. Kevlar 29 yarn was used to stitch both sets of panels. The results showeda significant effect of the stitching on the in-plane Young’s modulus which was attributed to localdisplacements of the in-plane fibers and changes in the fiber volume fraction. Stitching of sandwichpanels significantly increases the maximum failure loads under flexure, core shear, flatwise tensile,flatwise compression, and edgewise compression loading.A finite element based unit-cell model was developed to estimate the elastic constants ofstructurally stitched foam core sandwich composite panels taking into consideration the yarndiameter, the stitching pattern and direction as well as the load direction. Depending on theseparameters, local changes of the fiber volume fraction as well as regions with undisturbed anddisturbed fiber orientations within the laminate plies are taken into account. A good match betweenthe finite element modeling and the experimental data was obtained. The present work should beconsidered as a step towards developing a more sophisticated numerical model capable ofdescribing mechanical behavior of sandwich structures
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.477.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    An Experimental Investigation on Composites Through-The-Thickness Stitched Foam Core Sandwich Panels (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 1443-1446 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This study explored the feasibility and potential benefits provided by the addition ofthrough-the-thickness reinforcement to foam core sandwich structures. Through-the-thicknessstitching is proposed to increase the interlaminar strength and damage tolerance of compositesandwich structures. A low-cost, out-of-autoclave processing method was developed to producecomposite sandwich panels with carbon fiber face sheets, a closed-cell foam core, andthrough-the-thickness Kevlar stitching. The sandwich panels were stitched in a dry preform state,vacuum bagged, and infiltrated using Vacuum Assisted Resin Transfer Molding (VARTM)processing. For comparison purposes, unstitched sandwich panels were produced using the samematerials and manufacturing methodology. Five types of mechanical tests were performed: flexuraltesting, flatwise tensile and compression testing, core shear testing, and edgewise compressiontesting. Drop-weight impact testing followed by specimen sectioning was performed to characterizethe damage resistance of stitched sandwich panels. Compression after impact (CAI) testing wasperformed to evaluate the damage tolerance of the sandwich panels. Results show significantincreases in the flexural stiffness and strength, out-of-plane tensile strength, core shear strength,edgewise compression strength, and compression-after-impact strength of stitched sandwichstructures
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.353-358.1443.pdf
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  • 6
    Electronic Resource
    Electronic Resource
    Preparation and Characterization of the Modified Carbon Nanotubes Enhanced Epoxy Resin Composites (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 505-507 (Jan. 2006), p. 1075-1080 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this study, the surfaces of the multi-walled carbon nanotubes (MWNTs) were treated by acrylic acid. The acid-treated MWNTs were functionalized and were characterized by Infrared spectroscopy. The MWNTs were opened at their ends by ultrasonic treating and UV irradiating. Different adding amounts of the opened MWNTs were filled to the epoxy resin, and their mechanical properties and thermal properties were measured by Instron, impact and differential scanningcalorimeter (DSC), etc. The optimum adding amount of MWNTs to the epoxy resin is 2.0%, which is according to the parameters obtained from mechanical testing and Tg. The activation energy of the epoxy resin during curing can be calculated from infrared spectra according to the change of the epoxide band. The electrical conductivity of the MWNTs-filled composites was increased with proper (12.87%) amount of MWNTs adding, this is due to the networks constructed betweenMWNTs completely
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/12/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.505-507.1075.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    A study of the process and kinetics of electrochemical deposition and the hydrothermal synthesis of hydroxyapatite coatings (2000)
    Springer
    Journal of materials science 11 (2000), S. 667-673 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Hydroxyapatite (HAp) coatings were prepared using electrochemical deposition and post-hydrothermal synthesis. The composition and morphology of coatings at each processing step was studied through the application of scanning electron microscopy (SEM), X-ray diffraction (XRD) and infra-red spectroscopy (IR). The mechanism and kinetics of hydrothermal synthesis were considered in particular, and the influnce of the temperature and time on the HAp formation rate was also investigated. The results show that the electrochemical deposition coatings are composed of CaHPO42H2O crystals which are converted into needle-like HAp crystals after post-hydrothermal treatment. The HAp content of the coatings increases with the treatment temperature and time. The synthesis rate also increases with the pH value of the water. The formation of HAp coatings is considered to be a combination of several reactions. An Arrhenius relationship was found between the HAp formation rate and the temperature, and an apparent activation energy of 94.4 KJ/mol was obtained by calculation. © 2000 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008934522363
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  • 8
    Electronic Resource
    Electronic Resource
    Minimization and estimation of geoid undulation errors (1994)
    Springer
    Journal of geodesy 68 (1994), S. 201-219 
    Details
    ISSN: 1432-1394
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract The objective of this paper is to minimize the geoid undulation errors by focusing on the contribution of the global geopotential model and regional gravity anomalies, and to estimate the accuracy of the predicted gravimetric geoid. The geopotential model's contribution is improved by (a) tailoring it using the regional gravity anomalies and (b) introducing a weighting function to the geopotential coefficients. The tailoring and the weighting function reduced the difference (1σ) between the geopotential model and the GPS/levelling-derived geoid undulations in British Columbia by about 55% and more than 10%, respectively. Geoid undulations computed in an area of 40° by 120° by Stokes' integral with different kernel functions are analyzed. The use of the approximated kernels results in about 25 cm (σ) and 190 cm (maximum) geoid errors. As compared with the geoid derived by GPS/levelling, the gravimetric geoid gives relative differences of about 0.3 to 1.4 ppm in flat areas, and 1 to 2.5 ppm in mountainous areas for distances of 30 to 200 km, while the absolute difference (1σ) is about 5 cm and 20 cm, respectively. A optimal Wiener filter is introduced for filtering of the gravity anomaly noise, and the performance is investigated by numerical examples. The internal accuracy of the gravimetric geoid is studied by propagating the errors of the gravity anomalies and the geopotential coefficients into the geoid undulations. Numerical computations indicate that the propagated geoid errors can reasonably reflect the differences between the gravimetric and GPS/levelling-derived geoid undulations in flat areas, such as Alberta, and is over optimistic in the Rocky Mountains of British Columbia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808101
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  • 9
    Electronic Resource
    Electronic Resource
    Gravity field convolutions without windowing and edge effects (1993)
    Springer
    Journal of geodesy 67 (1993), S. 107-118 
    Details
    ISSN: 1432-1394
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract A new set of formulas has been developed for the computation of geoid undulations and terrain corrections by FFT when the input gravity anomalies and heights are mean gridded values. The effects of the analytical and the discrete spectra of kernel functions and that of zero-padding on the computation of geoid undulations and terrain corrections are studied in detail. Numerical examples show that the discrete spectrum is superior to the analytically-defined one. By using the discrete spectrum and 100% zero-padding, the RMS differences are 0.000 m for the FFT geoid undulations and 0.200 to 0.000 mGal for the FFT terrain corrections compared with results obtained by numerical integration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01371374
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  • 10
    Electronic Resource
    Electronic Resource
    A numerical investigation on height anomaly prediction in mountainous areas (1995)
    Springer
    Journal of geodesy 69 (1995), S. 143-156 
    Details
    ISSN: 1432-1394
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract This paper provides numerical examples for the prediction of height anomalies by the solution of Molodensky's boundary value problem. Computations are done within two areas in the Canadian Rockies. The data used are on a grid with various grid spacings from 100 m to 5 arc-minutes. Numerical results indicate that the Bouguer or the topographicisostatic gravity anomalies should be used in gravity interpolation. It is feasible to predict height anomalies in mountainous areas with an accuracy of 10 cm (1σ) if sufficiently dense data grids are used. After removing the systematic bias, the differences between the geoid undulations converted from height anomalies and those derived from GPS/levelling on 50 benchmarks is 12 cm (1σ) when the grid spacing is 1km, and 50 cm (1σ) when the grid spacing is 5′. It is not necessary, in most cases, to require a grid spacing finer than 1 km, because the height anomaly changes only by 3 cm (1σ) when the grid spacing is increased from 100 m to 1000 m. Numerical results also indicate that, only the first two terms of the Molodensky series have to be evaluated in all but the extreme cases, since the contributions of the higher order terms are negligible compared to the objective accuracy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00815483
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