Pavel Kagan  Anath Fischer  Pinhas Z. Bar‐Yoseph 《International journal for numerical methods in engineering》2003,57(8):1145-1175

This article presents two new methods for adaptive refinement of a B‐spline finite element solution within an integrated mechanically based computer aided engineering system. The proposed techniques for adaptively refining a B‐spline finite element solution are a local variant of np‐refinement and a local variant of h‐refinement. The key component in the np‐refinement is the linear co‐ordinate transformation introduced into the refined element. The transformation is constructed in such a way that the transformed nodal configuration of the refined element is identical to the nodal configuration of the neighbour elements. Therefore, the assembly proceeds as with classic finite elements, while the solution approximation conforms exactly along the inter‐element boundaries. For the h‐refinement, this transformation is introduced into a construction that merges the super element from the finite element world with the hierarchical B‐spline representation from the computational geometry. In the scope of developing sculptured surfaces, the proposed approach supports C⁰ as well as the Hermite B‐spline C¹ continuous shapes. For sculptured solids, C⁰ continuity only is considered in this article. The feasibility of the proposed methods in the scope of the geometric design is demonstrated by several examples of creating sculptured surfaces and volumetric solids. Numerical performance of the methods is demonstrated for a test case of the two‐dimensional Poisson equation. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

    

S. C. Chen  C.‐A. Lin  A.‐H. Fu  Y. W. Chuo 《Packaging Technology and Science》2003,16(6):239-247

This study was undertaken to develop a modified atmosphere package to control microbial growth in ready‐to‐eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO₂ : O₂ : N₂ = 30% : 5% : 65%) was used to inhibit the growth of total air‐borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of air‐borne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off‐flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

    

T. Jung  J. Liu  G. Maescher  H. Mauch  F.‐J. Stolze 《Materialwissenschaft und Werkstofftechnik》2003,34(9):859-865

Durability Evaluation in the automotive engineering – from theory to product The procedures for durability evaluation in the automotive engineering are represented, especially the methods, load assumption, fatigue testing and the regulations for the release and quality control. By practical examples of the vehicle development from chassis, aggregate and body the procedure is described, in particular the used experimental and virtual simulation methods  相似文献   

    

L. Gimeno‐Fabra  H. Nizard  H. Benien  J. Vlcek  A. Redjaimia 《Materialwissenschaft und Werkstofftechnik》2003,34(4):410-414

In most high temperature applications, efficiency increases with service temperature of the component. Especially in combustion chambers, higher efficiency is translated into less propellant consumption and therefore a lower weight and a reduction of operational cost. In these components, the use of high performance coatings may simultaneously increase the service temperature and decrease its price. From the many available coating processes, Metal organic Chemical Vapour Deposition (MO‐CVD) is one of the few capable of producing coatings of most precious metals in internal surfaces with intricate geometry. Nevertheless the microstructure control of the films is extremely complicated and characterised by the formation of dendrite structures. This morphology eliminates the coating efficiency, as it is not compact. EADS has had the chance to use the research infrastructure of the AMTT in Seibersdorf to characterise the coatings and determine how the transformation from the compact to the non‐compact microstructure takes place. The understanding of this phenomenon should allow us to develop a process able to produce 100 % dense coatings independently of the coating thickness in an industrial scale.  相似文献   

    

H.‐J. Spies  S. Friedrich  A. Buchwalder 《Materialwissenschaft und Werkstofftechnik》2003,34(1):128-135

Electron beam treatment of PVD – hard coatings Coatings of the type CrN_x, (Ti, Cr)N, (Ti, Al)N, Ti(C, N) and Ti(B,N) were deposited on the quenched and tempered steel C45 to investigate the effect of electron beam treatment on the structure and the properties of hard coated steels. A controlled energy input by electron beams was used to investigate the thermal behaviour of hard coatings with fixing the transformation levels by self‐quenching. Simultaneously a different case hardening of the substrate was caused providing a different effect of supporting the hard layer. There are big differences in the thermal stability of the investigated coatings. The surface hardness, adhesion and wear resistance of the composit hard coating/steel was improved in dependence on the energy input. The use of electron beam technologies enables the generation of support layers which locally increase the working behaviour of hard coated steel.  相似文献   

    

Gye‐Hee Lee  Heung‐Jin Chung  Chang‐Koon Choi 《International journal for numerical methods in engineering》2003,56(3):331-350

In this paper, an adaptive analysis of crack propagation based on the error estimation by the element‐free Galerkin (EFG) method is presented. The adaptivity analysis in quasi‐static crack propagation is achieved by adding and/or removing the nodes along the background integration cells, those are refined or recovered according to the estimated errors. These errors are obtained basically by calculating the difference between the values of the projected stresses and original EFG stresses. To evaluate the performance of the proposed adaptive procedure, the crack propagation behaviour is investigated for several examples. The results of these examples show the efficiency and accuracy of the proposed scheme in crack propagation analysis. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

    

Wai‐Bun Lui  Jinchyau Peng 《Packaging Technology and Science》2003,16(1):1-8

In this study, efforts were focused on the effects of the operating parameters, i.e. die shapes (DS), PVA ratio (PR), additives (AT) on the physical and biodegradable properties of the corn/PVA extrudates. We also evaluated the extrudates as cushioning materials. The process variables were the operating, conditions, die shapes (○, ∞, ? and O ), PVA ratio (40%, 50%, 60%) and additives [sodium bicarbonate (NaHCO₃), calcium carbonate (CaCO₃) and calcium hydroxide (Ca(OH)₂)]. The experiment is a 4 × 3 × 3 factorial design. Samples of each treatment were collected and the physical, mechanical and chemical properties were measured and analysed using the PROC ANOVA and PROC CORR of the SAS 6.0 software package. 35 The experimental results indicated that: (a) The change of die shapes (DS) had a significant effect on the longitudinal expansion, bulk density, compressibility and biodegradability properties of the extrudates; (b) the change of PVA ratio (PR) had a significant effect on the longitudinal expansion, bulk density and compressibility, but no effect on the biodegradability properties of the extrudates; and (c) the change of additives (AT) had a significant effect on the longitudinal expansion, bulk density and compressibility, but no effect on the spring index of the extrudates. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

    

Q.‐H. Yang  S. Bai  J.‐L. Sauvajol  J.‐B. Bai 《Advanced materials (Deerfield Beach, Fla.)》2003,15(10):792-795

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E. Mena‐Osteritz 《Advanced materials (Deerfield Beach, Fla.)》2002,14(8):609-616

The self‐assembling properties of π‐conjugated oligo‐, poly‐, and cyclothiophenes (see Figure) have been studied with different techniques. Scanning tunneling microscopy on perfectly ordered two‐dimensional monolayers at the solution–HOPG (highly oriented pyrolytic graphite) interface has successfully been applied. The submolecular resolution achieved in the STM images provides valuable lattice and molecular information. Supported by X‐ray structure analyses of the 3D bulk material and by theoretical calculations, molecular conformations, molecule–molecule, and molecule–substrate interactions of the oligo‐, poly‐, and cyclomers have been analyzed and discussed.  相似文献   

    

J.H. Chang  L.‐Q. Wang  Y. Shin  B. Jeong  J.C. Birnbaum  G.J. Exarhos 《Advanced materials (Deerfield Beach, Fla.)》2002,14(5):378-382

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