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.

The first fossilized comb-clawed beetle of the genus Asiomira Dubrovina, 1973 (Coleoptera: Tenebrionidae: Alleculinae) from Baltic Amber and notes on the distribution of extant species of the genus

A new species of comb-clawed beetles of the genus Asiomira Dubrovina, 1973 (A. dubrovinae sp. n.) is described from the Eocene Baltic amber. This newly descovered fossil species displays typical generic characters and is the most similar to the extant Asiomira ophtalmica (Seidlitz, 1896). Both species share a similar shape of the pronotum and the flattened posterior angles of the pronotal disc. Asiomira dubrovinae sp. n. can be distinguished from A. ophtalmica by the smaller body size (4.8 mm in contrast to 6–8.12 mm), more serrate antennomeres, and finer and sparser pronotal punctation. Extant species of the genus are distributed in the arid landscapes of Central Asia with the highest diversity occurring in Tajikistan. Therefore the discovery of a new fossil species from Eocene Baltic amber suggests that Asiomira could have a wider range, and the modern distribution of this group is the result of a later secondary expansion of the ancestral representatives that survived in mid-mountain areas with arboreal and shrub vegetation. Relevant corrections to the distribution of extant species, Asiomira ophtalmica (Seidlitz, 1896) and Asiomira firjusana (Dubrovina, 1973), are given.

Different Physiology in the Jellyfish Cassiopea xamachana and C. frondosa in Florida Bay

The jellyfish Cassiopea xamachana and C. frondosa co-occur within some habitats in the Florida Keys, but the frequency with which this occurs is low. It is hypothesized that the symbiosis with different dinoflagellates in the Symbiodiniaceae is the reason: the medusae of C. xamachana contain heat-resistant Symbiodinium microadriaticum (ITS-type A1), whereas C. frondosa has heat-sensitive Breviolum sp. (ITS-type B19). Cohabitation occurs at depths of about 3–4 m in Florida Bay, where the water is on average 0.36 °C cooler, or up to 1.1 °C cooler per day. C. frondosa tends not to be found in the warmer and shallower (<2 m) depths of Florida Bay. While the density of symbionts is about equal in the small jellyfish of the two species, large C. frondosa medusae have a greater density of symbionts and appear darker in color compared to large C. xamachana. However, the number of symbionts per amebocyte are about the same, which implies that the large C. frondosa has more amebocytes than the large C. xamachana. The photosynthetic rate is similar in small medusae, but a greater reduction in photosynthesis is observed in the larger medusae of C. xamachana compared to those of C. frondosa. Medusae of C. xamachana have greater pulse rates than medusae of C. frondosa, suggestive of a greater metabolic demand. The differences in life history traits of the two species were also investigated to understand the factors that contribute to observed differences in habitat selection. The larvae of C. xamachana require lower concentrations of inducer to settle/metamorphose, and they readily settle on mangrove leaves, submerged rock, and sand compared to the larvae of C. frondosa. The asexual buds of C. xamachana are of a uniform and similar shape as compared to the variably sized and shaped buds of C. frondosa. The larger polyps of C. frondosa can have more than one attachment site compared to the single holdfast of C. xamachana. This appears to be an example of niche diversification that is likely influenced by the symbiont, with the ecological generalist and heat-resistant S. microadriaticum thriving in C. xamachana in a wider range of habitats as compared to the heat-sensitive symbiont Breviolum sp., which is only found in C. frondosa in the cooler and deeper waters.

A Rare Belt Plaque in Zoomorphic Style from the Inner Tien Shan

The article publishes a very rare for Saka culture of the Tien Shan region belt plaque, made with the Scythian-Siberian animal motif. It was accidentally found at an altitude of 2300 m. in the northern part of the Inner Tien Shan, and, most likely, it was lost there in antique time. The plaque has a butterfly-shaped shape, and a relief paired heads of a snow leopard was depicted on its outer surface in a realistic manner. On its reverse side there are two small loops indicating the construction of the combat belt on which it was fixed. Apart from the main belt there were additional leather straps which also were used as laces in the front. Belts of a similar construction with plaques of similar shape were previously found only in an elite burial of the Issyk kurgan in Tien Shan region. Nevertheless, outside this region, this belt plaque has close analogies in the synchronous cultures of the Scythian type in the Forest-steppe Altay, Tuva, Ordos and Northern China, as well as in the forest-steppe part of the Urals region. Based on stylistics and analogies, this belt plaque can be dated back to the turn of the 5th and 4th centuries BC. But in these regions, with the exception of the Urals, all similar plaques have one central loop on the back side. This indicates an independent line of development of these belt garment items on the territory of Saka culture of the Tien Shan region, although the origins of this line, undoubtedly, were initially outside its distribution area.

Electrical characteristics of silicon differential photoreceivers

The volt-ampere curve of silicon differential photodiodes were measured. It was found that the current-voltage curve of the photodiodes of the main and additional channels had a similar shape, without revealing a significant dependence on the implantation dose of the additional channel. The main parameters of the equivalent circuits of photodiodes are determined. In the reverse branch, the dominant impact was exerted by the surface leakage conductivity with a differential resistance of about 10 GΩ. Measurements from minus 60 °C to 60 °C showed that when using amplifiers with an input impedance of about 103 Ω, differential photoreceivers can be successfully used as selective short-wavelength and two-color ones.

Aerodynamic Characteristics of Re-Entry Capsules with Hyperbolic Contours

For most re-entry capsules, the shape of the forebody of the capsule is designed based on the blunted nose cone. A similar shape can be created using a hyperboloid of revolution that can control the nose bluntness and the half angle of the cone easily. In this study, the hypersonic aerodynamic characteristics of re-entry capsules designed with hyperbolic contours were investigated using the CFD code, FaSTAR, developed by Japan Aerospace Exploration Agency (JAXA). The CFD results showed that, using the hyperbolic contours, the drag and lift coefficients can be increased compared to those for the Hayabusa re-entry capsule without changing the shape of the capsule drastically. This suggests that shape design based on the hyperbolic contours can improve the aerodynamic characteristics of re-entry capsules.

Method for Generating Mechanical Linkages of Polygons That Fold Into a Similar Shape

Origami techniques, as folding and unfolding, can be utilized in shrinkable structures. Especially when the crease pattern is rigid foldable, it can be treated as a mechanical linkage of rigid panels connected by hinges. Since rigid foldable crease patterns have the strong geometrical constraint of the facets not being able to stretch or bend, it is difficult to design new crease patterns, and variations of existing patterns are limited. However, it is known that there are cases where crease patterns can be made rigid foldable by adding some slits. This paper proposes a mechanical linkage that folds into a similar flat shape by adding slits. A method is presented of generating rigid foldable crease patterns in arbitrary polygons that fold smaller, and it is confirmed that structures that have a mechanism for shrinking can be generated from these crease patterns by using rigid thick panels and hinges.

An Investigation of Pull-Out Force of Semi-Buried Lotus Roots after Hydraulic Scouring

Hydraulic scouring is the most effective approach to harvest lotus roots, but its application is largely restricted by the low harvesting rate. After hydraulic scouring, some mature lotus roots are still partially buried in the soil. Therefore, it is highly necessary to develop an appropriate approach to harvest semi-buried lotus roots. In this work, we for the first time studied the interaction between semi-buried lotus roots and soil, as well as analyzing the pull-out process and the factors affecting the pull-out force of semi-buried lotus roots. Firstly, a simple testing platform was designed based on the virtual prototype technology and the tests on pull-out force were conducted on five lotus roots with similar shape but different weights, with the burial depth and pull-out speed as the experimental factors. The results revealed that the maximum pull-out force is not significantly affected by the pull-out speed, whereas it is significantly influenced by the burial depth and the surface area of lotus roots. The maximum pull-out force increased with increasing lotus root surface area and burial depth. In addition, the discrete element method was employed to simulate the pull-out process of lotus root at different pull-out speeds. The simulation results indicated that a higher pull-out speed would result in a greater pull-out force at the same displacement of the lotus root from the soil. Both experimental and simulation results revealed that soil adhesion contributes the most to the pull-out resistance. It was also observed that a slight loosening of semi-buried lotus roots could drastically reduce the pull-out force. These results suggest that some kind of mechanical structure or improvement of water flow can be applied to the existing lotus root harvester to reduce the adhesion between lotus roots and soil. Overall, our findings provide a novel direction for optimizing hydraulic harvesting machines of lotus roots.

Perceptual Dissimilarity and Cognitive Performance Predict Novel Word Retention, but Not Extension Skills in Down Syndrome

While the influence of cognitive and linguistic capacities and the perceptual features of objects on word-learning skills in people with typical development (TD) are well understood, there is little evidence concerning these mechanisms in people with Down syndrome (DS). Using an eye-tracking task, this study examined the ability of 29 children with DS (mean mental age: 3.44 years) to identify familiar words, fast-map pseudowords to novel objects, retain word-object mappings, and extend these mappings to new objects of similar shape. It also contrasted their word-learning abilities to those of 26 two-to-five-year-olds with TD and examined how cognitive and linguistic skills and perceptual information influenced those abilities. Children with DS were found to have similar identification, fast-mapping, and extension skills as their peers with TD, but retained fewer word-object mappings. Greater retention skills are related to mental age, oral vocabulary, and greater perceptual differences between the target and surrounding objects.