Manipulating Managed Execution Runtimes to Support Self-Healing Systems

Self-healing systems require that repair mechanisms are available to resolve problems that arise while the system executes. Managed execution environments such as the Common Language Runtime (CLR) and Java Virtual Machine (JVM) provide a number of application services (application isolation, security sandboxing, garbage collection and structured exception handling) which are geared primarily at making managed applications more robust. However, none of these services directly enables applications to perform repairs or consistency checks of their components. From a design and implementation standpoint, the preferred way to enable repair in a self-healing system is to use an externalized repair/adaptation architecture rather than hardwiring adaptation logic inside the system where it is harder to analyze, reuse and extend. We present a framework that allows a repair engine to dynamically attach and detach to/from a managed application while it executes essentially adding repair mechanisms as another application service provided in the execution environment

Resolving rotational stacking disorder and electronic level alignment in a 2d oligothiophene-based lead iodide perovskite

Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) represent diverse quantum well heterostructures composed of alternating inorganic and organic layers. While 2D HOIPs are nominally periodic in three dimensions for X-ray scattering, the inorganic layers can orient quasi-randomly, leading to rotational stacking disorder (RSD). RSD manifests as poorly resolved, diffuse X-ray scattering along the stacking direction, limiting the structural description to an apparently disordered subcell. However, local ordering preferences can still exist between adjacent unit cells and can considerably impact the properties, particularly the electronic structure. Here, we elucidate RSD and determine the preferred local ordering in the 2D [AE2T]PbI4 HOIP (AE2T: 5,5′-bis(ethylammonium)-[2,2′-bithiophene]). We use first-principles calculations to determine energy differences between a set of systematically generated supercells with different order patterns. We show that interlayer ordering tendencies are weak, explaining the observed RSD in terms of differing in-plane rotation of PbI6 octahedra in neighboring inorganic planes. In contrast, the ordering preference within a given organic layer is strong, favoring a herringbone-type arrangement of adjacent AE2T cations. The calculated electronic level alignments of proximal organic and inorganic frontier orbitals in the valence band vary significantly with the local arrangement of AE2T cations; only the most stable AE2T configuration leads to an interfacial type-Ib band alignment consistent with observed optical properties. The present study underscores the importance of resolving local structure arrangements in 2D HOIPs for reliable structure-property prediction

SOME RESULTS OF THE BONNET TRANSFORMATION

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A construction algorithm for minimal surfaces

Infinite periodic minimal surfaces are constructed from complex functions, which are simply related to the orientation of flat points on the surface. Two tetragonal families of surfaces are generated, which are shown to reduce in special cases to classical minimal surfaces : the cubic diamond surface (D surface) and the Scherk surface. In all cases the construction algorithm for the complex functions yields the expected results, supporting the validity of the procedure. The algorithm can be used to determine new periodic minimal surfaces.Nous construisons des surfaces minimales périodiques infinies à partir de fonctions complexes qui sont simplement reliées à l'orientation des points plats sur la surface. Nous engendrons deux familles tétragonales de surface, dont nous montrons qu'elles se réduisent dans des cas particuliers à des surfaces minimales classiques : la surface du diamant cubique (surface D) et la surface de Scherk

Exact construction of periodic minimal surfaces : the I-WP surface and its isometries

We have analysed in detail the geometry of the I-WP infinite periodic minimal surface, discovered by Alan Schoen in the 1960's. An exact parametrisation has been found, using the local Weierstrass equations for the surface, involving modified hyperelliptic integrals. We have used rapidly converging integration techniques to calculate the surface to volume ratio of this surface, and found that it differs from the value conjectured by Anderson. Further, the family of isometric minimal surfaces related to the I-WP surface has been found to exhibit a novel sequence of structures ; viz. repeated formation of the I-WP surface itself.On analyse en détail la géométrie de la surface minimale infinie et périodique I-WP, découverte par Alan Schoen dans les années 60. En utilisant les équations de Weierstrass locales pour la surface, on obtient une paramétrisation exacte à l'aide d'intégrales hyperelliptiques modifiées. A l'aide de méthodes d'intégrations numériques rapides, le rapport surface/volume de cette surface est calculé ; il diffère de la valeur conjecturée par Anderson. De plus, on trouve que la famille de surfaces minimales isométriques reliées à la surface I-WP possède une nouvelle suite de structures qui reproduisent la surface I-WP elle-même

Generalizations of the gyroid surface

The deformation of Schoen's gyroid — one of the three examples of triply-periodic minimal surfaces possessing cubic symmetry and genus 3 — is discussed. Lower-symmetry variants (similarly of genus 3) are shown to exist, and the one-variable family of rhombohedrally-distorted gyroids is constructed and parametrised exactly via the Weierstrass representation

Electrical resistivity of one-dimensional quasiperiodic η8-Cu5Sn4

The electrical resistivity, ρ, of one-dimensional quasiperiodic η8-Cu5Sn4 has been studied, and compared with crystalline Cu6Sn5 of identical basic structure (B8) and closely related atomic structure. ρ was measured between 1.5 and 300 K on needle-shaped crystals with their axes along the base lattice c direction, corresponding to the quasiperiodic direction in η8-Cu5Sn4. ρ (4 K) was found to be nine times larger in η8-Cu5Sn4 compared to Cu6Sn5, and the residual ratio R [=ρ(4K)/ρ(300K)<1] was larger by a factor of 3. The similar structures and these large differences in transport properties indicate that the effect of quasiperiodic ordering has been observed in the resistivity of a one-dimensional metal