Escherization with Large Deformations Based on As-Rigid-As-Possible Shape Modeling

Escher tiling is well known as a tiling that consists of one or a few recognizable figures, such as animals. The Escherization problem involves finding the most similar shape to a given goal figure that can tile the plane. However, it is easy to imagine that there is no similar tile shape for complex goal shapes. This article devises a method for finding a satisfactory tile shape in such a situation. To obtain a satisfactory tile shape, the tile shape is generated by deforming the goal shape to a considerable extent while retaining the characteristics of the original shape. To achieve this, both goal and tile shapes are represented as triangular meshes to consider not only the contours but also the internal similarity of the shapes. To measure the naturalness of the deformation, energy functions based on traditional as-rigid-as-possible shape modeling are incorporated into a recently developed framework of the exhaustive search of the templates for the Escherization problem. The developed algorithms find satisfactory tile shapes with natural deformations for fairly complex goal shapes.

Exploiting the Transformation Temperature to Reform an Infolded Nitinol Self-Expanding Peripheral Stent

Purpose: Nickel-titanium (nitinol) alloys possess a special set of properties that allow for a wide range of applications. Specifically, the transformation temperature for self-expanding nitinol peripheral stents allows for easy crimping at or below room temperature and reformation at body temperature becoming superelastic. Case Report: We report the case of an elderly man with iliac stenting 1 month prior, who presented several weeks after recovering from coronavirus disease 2019 with recurrent anterior-wall ST-elevation myocardial infarction. This was complicated by deformation and infolding of the previously implanted nitinol self-expanding stent in his right common iliac artery (CIA). Understanding nitinol’s specific properties, we proceeded with rapid injections of iced saline to cool the nitinol stent to its transformation temperature while nudging the distal end of the stent with a partially inflated balloon. This maneuver softened the nitinol stent, allowing us to “unfold” and reappose it against the wall of the right CIA, resulting in successful restoration of the original shape of the nitinol self-expanding stent. Conclusion: This represents the first reported case describing treatment of an infolded nitinol self-expanding peripheral stent by exploiting the transformation temperature of nitinol using iced cold saline to successfully restore the stent’s original shape and structure.

Microstructure and phase composition of bronze Montefortino helmets discovered Mediterranean seabed to explain an unusual corrosion

Two Monterfortino helmets, recovered in the Mediterranean seabed, show unusual features with respect to the more common helmets of the same period and found in underwater environments. Hence, they were investigated by a multi-analytical approach, which allowed us to identify the compounds constituting the helmets and to make some considerations about their metallurgy, although all the metal was converted to degradation products. The helmets, originally made in bronze, have maintained their original shape because of copper sulphides formation. The observed differences in composition between the two helmets were attributed to the position modification, of one of them, into the seabed along centuries. For the first time, a microstructural investigation permits to reconstruct the history of the aging processes involved in the total oxidation of roman bronze helmet metal.

Design and Analysis of Release Mechanism using Shape Memory Alloy for Spacecraft

Shape memory alloy (SMA) is used as a smart material. It is also called as Nitinol and intelligent material because it regains their original shape after deformation. It works on the principle of shape memory effect which regain their original shape after passing through different temperature phases. SMA get some more attention in incoming years due to their superior and unique properties. This paper presents design and maximum stress analysis of release mechanism using SMA. It also covers the capability and efficiency of notch bolt of Frangibolt mechanism. Its design, calculation and analysis has done in CAD software and simulation software.

Retrodeformation of the Steinheim Cranium: Insights into the Evolution of Neanderthals

A number of different approaches are currently available to digitally restore the symmetry of a specimen deformed by taphonomic processes. These tools include mirroring and retrodeformation to approximate the original shape of an object by symmetrisation. Retrodeformation has the potential to return a rather faithful representation of the original shape, but its power is limited by the availability of bilateral landmarks. A recent protocol proposed by Schlager and colleagues (2018) overcomes this issue by using bilateral landmarks and curves as well as semilandmarks. Here we applied this protocol to the Middle Pleistocene human cranium from Steinheim (Germany), the holotype of an abandoned species named Homo steinheimensis. The peculiar morphology of this fossil, associated with the taphonomic deformation of the entire cranium and the lack of a large portion of the right side of the face, has given rise to different hypotheses over its phylogenetic position. The reconstruction presented here sheds new light on the taphonomic origin of some features observed on this crucial specimen and results in a morphology consistent with its attribution to the Neanderthal lineage.

Place the Vertices Anywhere on the Curve and Simplify

A polygonal curve is simplified to reduce its number of vertices, while maintaining similarity to its original shape. Numerous results have been published for vertex-restricted simplification, in which the vertices of the simplified curve are a subset of the vertices of the input curve. In curve-restricted simplification, i.e. when the vertices of the simplified curve are allowed to be placed on the edges of the input curve, the number of vertices may be much more reduced. In this paper, we present algorithms for computing curve-restricted simplifications of polygonal curves under the local Hausdorff distance measure.

Effect ofOrientation on Spring back for Component with Hole and without Hole

Many components are needed to be formed into different shapes depending upon their applications. Whenever the component is formed, it is associated with little or more amount of spring back. It is because of the elastic stresses that remain in the bent-up part. When the bending force is removed, the elastic stresses remaining in the bent up part try to relieve and due to relieving of these elastic stresses the formed up component tries to regain its original shape. This movement of metal due to relieving of stresses is called spring back. In this paper, the effect of orientation on the spring back is studied for components with holes and without holes. The components are formed in U shape along the rolling direction, 450 to the rolling direction, and 900 to the rolling direction, with hole and without a hole in the component. Springback is measured and compared for all the formed-up components. It is seen that the spring back is minimum both for components with holes and without holes formed along the rolling direction. It is also seen that for the components with holes the spring back is reduced as compared with the component without the hole.

Fabrication of strong macrofibers from plant fiber bundles

The production of long cellulose macrofibers starting from nanofibers is still complex and expensive. This study proposes a method of manufacturing long macrofibers from plant fiber bundles by chemically extracting non-cellulosic substances but preserving the original shape of the fibers. Once the cellulosic fiber bundles are dried, the original cellulose nanofibers are bridged to neighboring nanofibers by the formation of hydrogen bonds, giving shape stability and enhanced mechanical properties. By the process, the tensile strength was increased by about 50% and the modulus doubled from the original plant fiber bundles.