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[en] ICASPA - an Improved Critical and Safe Parameters Algorithm - calculates the size of a fissile body for a given value of k-effective in a system with fixed material properties. ICASPA can be used to calculate criticality handbook curves; in addition ICASPA can calculate safe and critical parameters for more complex arrangements, including arrays of geometrically similar fissile bodies. The ICASPA calculation scheme uses buckling theory in conjunction with the MONK Monte Carlo code. An important feature of this scheme is that it is does not rely on the numerical differentiation of Monte Carlo results. The method provides fast and reliable convergence, even in cases where a relatively large Monte Carlo uncertainty is present. This paper shows how the ICASPA method was derived from buckling theory and describes how the method has been coded using MONK9A on Windows, Linux and Solaris platforms. A series of test results are also given, to illustrate the accuracy and speed of convergence. (authors)

[en] In this paper, geometrically non-linear post-buckling analyses were performed to study the effect of sheet thickness, deployment angle, and load ratio on the crease-wrinkle interaction. A square sheet configuration with a single transverse crease was modeled using thin shell elements. The analysis proceeded by initially providing a realistic deployed state of a creased membrane sheet. Then an uneven corner loading was applied to introduce wrinkling. The effects of the induced anisotropy from the crease on the fine-scale detail of the wrinkle evolution, as a function of sheet thickness, loading, and crease deployment angle were systematically investigated. Significant differences were found in sheet compliance and crease-wrinkle interaction as these parameters were varied

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[en] The paper deals with the problem of optimal design of annular plates against creep buckling. The design variable, i.e. the plate thickness function, is determined so as to minimize the total volume of a plate under given external load (radial pressure) and the critical time. A circularly symmetric thickness function is analysed but unsymmetric buckling modes are also admitted. The problem is solved by the use of Pontryagin's maximum principle. (orig.)

[en] Highlights: • Proposed variable wall thickness distribution methods for thin shells of revolution. • The influence of ellipticity on the buckling of the ellipsoidal head is explored. • Wall thickness of ellipsoidal heads was designed according to the isostrength principles under 4 km deep sea conditions. • The results revealed that the buckling load of the ellipsoidal head with variable wall thickness was higher than that of the ellipsoidal head with constant wall thickness. This study focused on the buckling and strength of ellipsoidal heads with variable wall thicknesses under uniform external pressure. The wall thickness of ellipsoidal heads was designed according to the isostrength principles. The wall thickness distribution of revolution for thin shells were proposed, and the effect of the thickness distribution on the strength of the ellipsoidal head is explored. The buckling of the ellipsoidal heads with variable thicknesses and constant thicknesses were evaluated numerically using the modified Riks method, and the effect of the ellipticity on the buckling performance of the ellipsoidal head was explored and the optimal ellipticity was presented. The results revealed that the buckling load of the ellipsoidal head with variable wall thickness was approximately 17% higher than that of the ellipsoidal head with constant wall thickness, while the volume decreased by 5%. This study can guide the structural design of ellipsoidal heads with variable wall thicknesses.

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[en] The surface structure of a lamellar polystyrene-block-polybutadiene-block-polymethylmethacrylate (SBM) triblock copolymer forms a complex reconstruction, which breaks the two-dimensional continuous translational symmetry of an ideal (homogeneous) SBM surface. Despite the very different types of matter and order, our findings reveal a remarkable analogy with the well-known phenomenon of surface reconstruction of single crystals, in particular, with the (2 x 1) ''buckling row'' reconstruction of the Si(100) surface. Similarities and differences between both classes of materials are discussed on the basis of symmetry considerations