Shell Shape Research Articles

On the possibility of replacing forged blanks from 12X18H10T steel by casting into thin-walled metal shell molds with forced cooling

The possibility of replacing of forged blanks made of 12X18H10T steel with shaped castings obtained by casting into thin-walled metal shell molds with forced cooling is considered. Comparative tests of forged blanks made of 12Х18Н10Т steel and cast ones for strength, plastic properties and impact strength are carried out. Macrostructures, sulfur imprints, and distributions of non-metallic inclusions are studied. It is been established that cast billets are not inferior to forged ones in terms of a set of mechanical properties indicators. With a slight decrease in strength, cast workpieces are characterized by greater plastic properties and toughness. Keywords 12X18H10T and AISI 321 steels, alloy, structure, crystallization, casting, non-metallic inclusions, mechanical properties, metal shell shape

Serbest Sistemde Yetiştirilen Lohmann Sandy Tavuklarında Yumurta Kalite Özelliklerinin Belirlenmesi

Objective: In this study, it was aimed to determine the egg quality traits of hens belonging to Lohmann Sandy genotype raised in the free-range system.
 Materials and methods: In the research, eggs obtained from hens belonging to Lohmann Sandy genotype raised in a private enterprise in Ordu province were used. In each period for egg quality determination, 30 daily eggs were used. After keeping the eggs at room temperature for 24 hours, the internal and external quality traits of eggs were determined.
 Results: The albumen index and the Haugh unit values showed a significant change depending on time and were determined as 11.31 and 92.90 on average, respectively. On the other hand, the yolk index value did not show a significant change depending on the time and the average value was found to be 51.21. Egg weight showed a significant change depending on the time and was determined as 58.84 g on average. Shell surface area and egg volume also showed a significant change depending on time and were calculated as 74.58 cm2 and 54.41 cm3 on average, respectively. Shell thickness, shape index and specific gravity values did not show a significant change depending on time.
 Conclusion: It is of great importance that eggs produced with alternative systems are introduced to the market. In order to increase the consumption level of eggs, the place and importance of eggs in adequate and balanced nutrition should be explained, especially targeting children in developmental age and the elderly.

Impact of aquatic habitat environment on the elemental composition and shell shape variability of the Beringian freshwater mussel Beringiana beringiana (Bivalvia, Unionidae)

Concentrations of the chemical elements were analyzed in the shells of a bivalve mollusk species (Beringiana beringiana), water, and bottom sediments from seven lakes located on the Kamchatka Peninsula, the Kurile Islands, Sakhalin Island, and Primorsky Krai (Northeast Asia). A principal component analysis allowed to determine three factors those were related to environments in the waterbodies. We revealed two groups of samples corresponding to large geographical regions using the determined factors. Statistically significant differences were found between geographical groups of samples, and higher values of element distribution coefficients were determined for samples from lakes on the Kamchatka Peninsula. The highest concentrations of lithophilic elements were measured in the shells from Lake Kurazhechnoye (Kamchatka Peninsula). The highest concentrations of Al and Mg were detected in shells from Lake Peschanoye (Kunashir Island). In Lake Chernoye (Sakhalin Island), the highest concentrations of Sr and Sb in the shells were detected. Zn, Fe, Pb, and rare earth elements were present in large concentrations in the shells from Lake Vaskovskoye, Primorsky Krai. The shells of the Beringian freshwater mussel show large phenotypic plasticity, and their shape demonstrates significant relationships with various environmental parameters, that were assessed based on the geochemical indicators.

A systematic review of the Iberian springsnail subgenus Alzoniella (Navarriella) (Caenogastropoda: Hydrobiidae), with the description of a new potentially relict subfamily

Abstract The threatened springsnail subgenus Alzoniella (Navarriella) in the Iberian Peninsula has been suggested to be an old and relict lineage of the family Hydrobiidae. The subgenus is represented by two morphological species, both endemic to the Pyrenees and their southern foothills. We conducted phylogenetic analyses based on mitochondrial and nuclear gene fragments of topotypes and other populations, four molecular species delimitation methods, and morphological examinations to clarify the uncertain systematic position of the subgenus within the family, assess its species diversity, and understand the population genetic structure of the two geographically restricted species. Our phylogenetic results revealed that Alzoniella (Navarriella) is distantly related to all other species of Alzoniella, even belonging to an independent subfamily-level clade, for which we introduce the new genus Navarriella and the new subfamily Navarriellinae subfam. nov. Molecular methods and geometric morphometric analysis of shell shape identified a single species in the new genus. The significant phylogenetic distance from other hydrobiid taxa, narrow distribution, and limited gene flow among its populations (estimated from mitochondrial cytochrome c oxidase subunit I sequences) highlight Navarriella as an isolated lineage within the family that requires urgent conservation attention. Furthermore, our results cast a new light on the northern Iberian Mountains as a dispersal barrier for ancient spring lineages.

Conical shells made by 4D printing of composites

This paper presents a new, novel method for the manufacturing of composite cones. The method utilizes the principle of 4D printing of composites. The method does not require the use of a mold of conical shape, which is essential using conventional manufacturing methods such as filament winding or hand lay up. Instead, only a flat mold is required. In this technique, layers with different fiber orientations are laid on a flat mandrel. Upon curing and cooling to room temperature, the flat stack of composite layers will curl into the shape of a conical shell. When the edges of the shell are joined together by adhesive bonding, one has a structure that has the shape of a cone. Cones made using this new technique show axial buckling strengths that are comparable to those of cones made from similar materials with the same weight, using filament winding method. The buckling load and buckling mode shape are determined using finite element method. The results agree well with experimental results.

On the Optimality Conditions in the Weight Minimization Problem for a Shell of Revolution at a Given Vibration Frequency

We consider shallow elastic shells with a given circular boundary and seek an axisymmetric shell shape minimizing the weight at a given fundamental frequency of shell vibrations. Using the resulting formula for the linear part of the increment of the frequency functional, the multiplicity of the minimum natural frequency of vibrations of the shell is estimated. The Fréchet differentiability of the frequency functional is also established, and optimal conditions for minimizing the weight of the shell at a given fundamental vibration frequency are obtained.

A bio-inspired, monolithic catalyst support structure for optimized conductive heat removal in catalytic reactors

The performance of catalytic reactors in heterogeneous catalysis is especially dependent on the support structures the catalysts are dispersed on. They determine important properties like the pressure drop as well as the temperature distribution within catalytic reactors. The latter is especially important for reactions like the CO2 methanation, which is highly exothermic, but thermodynamically favored at low temperatures. Here we present a novel monolithic catalyst support structure inspired by the shape of diatom shells. By coupling a genetic algorithm with an FEM solver, a parametric model is optimized towards good radial heat transport. By comparing the optimized structures with honeycombs already used in industry, the beneficial thermal properties are demonstrated both for a pure conductive case as well as for superimposed fluid convection using Computational Fluid Dynamics. The optimized designs give a good basis for honeycomb-like catalyst support structures with good heat removal while preserving very low pressure drops.

Comparative Study of the Vibromechanical Characteristics of Compact Hydroacoustic Longitudinal-Bending Type Transducers with a Complex Radiating Shell Shape

Comparative Study of the Vibromechanical Characteristics of Compact Hydroacoustic Longitudinal-Bending Type Transducers with a Complex Radiating Shell Shape

Shell Shape Influence on Latent Heat Thermal Energy Storage Performance during Melting and Solidification

Phase-change materials have various applications across industries from thermal energy storage through automotive battery temperature management systems to thermal stabilisation. Many of these applications are shell and tube structures with different shell shapes. However, it is not yet known how the shape of the shell affects the melting, solidification times, and heat transport processes in such structures. To fill this research gap, seventeen shell shapes/orientations were compared using a simulation study. The well-known and validated enthalpy porosity algorithm implemented in the Fluent 2021R2 software was used. The numerical calculations were preceded by the measurement of thermal conductivity, phase change enthalpy, and specific heat during melting and solidification of the phase-change material. The shortest melting time was achieved for a semi-circular shell shape in the downward position, which was 44% shorter than the reference circular case. The shortest solidification times were recorded for an isosceles trapezium in an upward orientation relative to the reference circular case. Therefore, it is possible to significantly reduce the melting time in shell-and-tube systems as a result of the appropriate selection of the shell shape.

Upwelling as a stressor event during embryonic development: Consequences for encapsulated and early juvenile stages of the marine gastropod Acanthina monodon

Upwelling phenomena alter the physical and chemical parameters of the sea's subsurface waters, producing low levels of temperature, pH and dissolved oxygen, which can seriously impact the early developmental stages of marine organisms. To understand how upwelling can affect the encapsulated development of the gastropod Acanthina monodon, capsules containing embryos at different stages of development (initial, intermediate and advanced) were exposed to upwelling conditions (pH = 7.6; O2 = 3 mg L−1; T° = 9 °C) for a period of 7 days. Effects of treatment were determined by estimating parameters such as time to hatching, number of hatchlings per capsule, percentage of individuals with incomplete development, and shell parameters such as shell shape and size, shell strength, and the percentage of the organic/inorganic content.We found no significant impacts on hatching time, number of hatchlings per capsule, or percentage of incomplete development in either the presence or absence of upwelling, regardless of developmental stage. On the other hand, latent effects on encapsulated stages of A. monodon were detected in embryos that had been exposed to upwelling stress in the initial embryonic stage. The juveniles from this treatment hatched at smaller sizes and with higher organic content in their shells, resulting in a higher resistance to cracking 30 days after hatching, due to greater elasticity.Geometric morphometric analysis showed that exposure to upwelling condition induced a change in the morphology of shell growth in all post-hatching juveniles (0–30 days), regardless of embryonic developmental stage at the time of exposure. Thus, more elongated shells (siphonal canal and posterior region) and more globular shells were observed in newly hatched juveniles that had been exposed to the upwelling condition. The neutral or even positive upwelling exposure results suggests that exposure to upwelling events during the encapsulated embryonic phase of A. monodon development might not have major impacts on the future juvenile stages. However, this should be taken with caution in consideration of the increased frequency and intensity of upwelling events predicted for the coming decades.

Exploring the three-dimensional space with modular concrete shells: Form-finding, design and structural analysis

Thin concrete shells can span large distances thanks to their structural efficiency, following the optimum force flow. Despite the efficient use of material of well-designed shells, their construction suffers from labor-intensive and time-consuming fabrication techniques. This research therefore proposes a design method for the facilitated manufacturing of freeform shell structures. The manufacturing process has been considered from the design phase on, by generating an extensive range of different shell configurations based on a limited set of form-found modules and thus formworks. The challenge was to define which curved module geometries, after assembly, lead to the largest variety of freeform surfaces. More than sixty configurations resulted from a set of four modules only. This paper will discuss the form-finding process as well as the geometrical arrangement using tessellation patterns for the achievement of those modular configurations, going from domed to undulating shell shapes. In order to evaluate the structural efficiency of the shapes, twenty modular configurations were selected and analyzed under self-weight, using finite element simulations. To conclude, a prototype of one modular base element has been built, using a reusable casting wax in combination with a grid shell box, as the main parts of the formwork. The results demonstrate the structural feasibility and limitations of the modular shell design strategy. The modular approach contributes to circularity by encouraging reuse and allowing various combinations with a repeating set of modules, striving as such towards resource-effective innovative shell structures.

Optimized Design of the Carrier Structure of an Autonomous Glide Marine Seismometer

Mobile Earthquake Recording in Marine Areas by Independent Divers (MERMAID) provides a possibility for long-term and large-scale observation of natural seismic P waves, but it does not have mobility and can only drift with ocean currents, resulting in observation equipment locations that are too sparse or too dense, both of which are not suitable for network observation. Therefore, this paper developed a new type of Autonomous Glide Marine Seismometer (AGMS) with mobility and the ability to adjust the observation position. The AGMS adopts a flying saucer shape, which has better hydrodynamic characteristics and better motion stability. This paper focused on the material, shape, and structure of the pressure-resistant shell for the selection of design and strength checking research. Using the finite element analysis method and introducing the initial defect, the results showed that the yield strength of the pressure-resistant shell decreases with the initial defect value. The calculation results were compared and analyzed with the relevant theoretical formulas and specification calculation results, and all the results met the design requirements. The results of this design could also provide reference for the design of related deep-sea pressure chambers.

Influence of shell shape on flow and acoustic parameters of a steam silencer

Influence of shell shape on flow and acoustic parameters of a steam silencer

Systematization of spatial functional layouts and pedestrian wind comfort assessment for an ultra-thin triangular free form shell structure

This paper aims to study various spatial functional layouts and test how these different design approaches affect pedestrian comfort under shell structures. The considered shell shape was developed aiming an efficient distribution of loads allowing prefabrication with ultra-thin concrete elements. As shell structures can define semi-exterior spaces and assume open locations within some urban contexts, the study of how different design strategies for the underlying space affect user's comfort is of upmost importance.Several wind tunnel tests were performed on a triangular thin shell scale model with a few different spatial user's area layouts allowing to understand to which extent some design decisions compromise pedestrian wind comfort. The experimental campaign follows an iterative process leading to conclusions that can guide future projects and contribute to a multidisciplinary and transversal understanding of these innovative structures.

Evaluating the influence of cage motion on the growth and shell characteristics of oysters (Crassostrea virginica) among several gear types

An influx of new oyster culture gear provides growers with an expanded ability to grow oysters throughout the water column. Each gear type is exposed to a different regime of physical forces, which is thought to affect oyster production differently; however, there is a poor understanding of the physical conditions inside cages and how they influence the production rate and quality of oysters. A greater understanding of the fundamental relationships between cage motion, oyster growth, and shell shape could help to improve the efficiency of off-bottom oyster production. Such understanding is critical for tailoring gear selection and tuning gear performance to suit grower needs. To address this void, cage motion, internal oyster movement, and oyster growth among three common cultivation methods (Virginia-style bottom cages, Seapa® long-line baskets, and floating cages) were monitored over a single growing season to clarify the role of the physical environment on oyster performance (shell and tissue growth). The averages and variance in motion among each cultivation method were noticeably different, which resulted in significant differences in the growth rate and quality of oysters they produced. Movement of the floating cages and long-line baskets could largely be explained by wind waves generated from a single direction in the field (r2 = 0.49, r2 = 0.36, respectively), while bottom cage movement was far less affected by wind waves. The changes in physical conditions inside each cultivation method demonstrated a trade-off between shell growth rate (a metric of time to market) and shell and meat quality (representative of crop value). These results can help inform growers wishing to strategically adopt cultivation methods that are most aligned with their production goals.

STUDY OF THE EFFECT OF COCONUT SHELL MIXTURE AS A SUBSTITUTIONAL MATERIAL FOR COARSE AGGREGATE ON THE COMPRESSIVE STRENGTH OF CONCRETE f'c 20 MPa (COCONUT SHELL EX.PASAR KEMAKMURAN)

Coconut shell is a hard layer made up of lignin and cellulose which has a low water content, the hard structure of coconut shell is caused by silicate (SiO2) which is quite high, silicate itself is known to increase the compressive strength of concrete, the shape of coconut shell has a hard layer and a rough surface texture so that the bond with cement paste will be stronger. Therefore, if coconut shell can be technically proven as a material or aggregate for concrete mixes, it is expected to reduce the impact of environmental pollution. In this research, coconut shells were crushed into pieces with a maximum size of 20 mm x 20 mm and used as a substitute for coarse aggregate mixed with fine aggregate, water and type 1 cement. The percentages of coconut shell used in this study were 0%, 2.5% and 5%. Moulded in the form of a cylinder measuring 15x30 cm. The aim of this study is to analyze the characteristics of f'c 20 MPa concrete with the addition of coconut husk and to obtain effective mix variation through compressive strength tests at 14 and 28 days. From the research results, it can be shown that the compressive strength of normal concrete at the age of 14 and 28 days is 22.081 Mpa, 18.684 Mpa, 20.948 Mpa, 20.099 Mpa, 19.816 Mpa, 24.912 Mpa, 23.213 Mpa, 21.515 Mpa, 20.099 Mpa and 21.231 Mpa respectively. The compressive strength of concrete with 2.5% of coconut shell at 14 and 28 days is 20.948 Mpa, 19.816 Mpa, 16.985 Mpa, 20.948 Mpa, 19.816 Mpa and 16.985 Mpa, respectively. The compressive strength of concrete with 5% of coconut shell at 14 and 28 days is 18.117 Mpa, 16.419 Mpa, 14.154 Mpa, 18.684 Mpa, 18.117 Mpa, 17.551 Mpa, respectively. Thus, the compressive strength of concrete with 2.5% and 5% coconut shell substitution can reduce the compressive strength of concrete from the targeted compressive strength.

Quality recognition method of oyster based on U-net and random forest

Oysters are one of the most important cultivated marine resources globally. The shape of oysters is an essential reference criterion for consumers to judge the quality of oysters. In order to recognize oyster’s shape, the U-Net model and random forest are combined to compose a creative strategy. To be more specific, the U-Net neural network model is firstly developed to segment the image and obtain the contours of oysters, and the shape features of oysters are extracted. Then, a random forest model with shape feature parameters depending on customer preference is created to identify oyster quality. The results indicate that the intersection-over-union of segmentation outcomes achieved by U-Net reaches 99.06%, surpassing the 93.50% obtained by traditional methods. The accuracy of the classification strategy based on the shape features parameters of consumer preference is 94.18%, which further proves the effectiveness of the proposed strategy. This study might provide valuable data and guidelines to oyster product classification based on shell shape within market contexts.

Shell shape-habitat correlations in extant turtles: A global-scale analysis

Animal morphological structure can influence behaviour and interaction with the environment. Owing to their wide range of habitats, from aquatic to terrestrial, and their variation in shell shapes, turtles are highly suitable for ecomorphological studies. However, previous studied have encountered several limitations, including small sample sizes, simplified habitat classification, and no consideration of sexual dimorphism, that may prevent the identification of the ecological mechanisms responsible for divergent morphologies of turtles on a global scale. In this study, we collected the carapace length (CL), carapace width (CW), and carapace height (CH), as an indicators of body size, from 6664 adult individuals of 115 species, 61 genera, and 11 families and calculated the ratio between the CH and CW to delineate shell shape. These turtle species were divided into four habitat types (marine, freshwater, mainland, and island) and eight subtypes (freshwater: large lentic, large lotic, small lentic, small lotic, all water bodies; mainland: desert, flatland, highland) to better understand the ecomorphological alteration of their shell shape. The results of the linear regression showed that shell shape became flat with increasing body size in aquatic turtles, whereas the opposite trend was observed for male mainland tortoises. According to the results of the general linear model, there was a gradual increase in the domed shape of turtle shells from sea to freshwater habitats, from freshwater to mainland terrestrial habitats, and from mainland to island terrestrial habitats. There were no significant differences between the shell shape and habitat subtype for freshwater turtles and mainland tortoises. To the best of our knowledge, this study represents the first investigation into the variation pattern of shell shape in turtles living in habitats ranging from marine to island and its relationship to body size. The study results suggest that conservation strategies for turtles should consider both their shell shape and habitat characteristics.

Water Turbidity and Plant Density Influence Shell Shape in Painted Turtles (Chrysemys picta)

Water Turbidity and Plant Density Influence Shell Shape in Painted Turtles (Chrysemys picta)

Integrative taxonomy reveals the conspecific status of Xerotricha madritensis (Rambur, 1868) and Helicella candoni Thach, 2018 (Gastropoda, Geomitridae)

The Mediterranean region is a biodiversity hotspot. Mollusks represent the second most diverse phylum, with high species richness, endemism, and significant numbers of threatened species. The non-marine species are an especially vulnerable group. New taxa are frequently described although the descriptions often lack biological support. This is true for Helicella candoni Thach, 2018, originally described from Puerto de Santa María, Cádiz, Spain. Thatch (2018) considered H. candoni to be similar to Xerotricha madritensis (Rambur, 1868) but the comparison was made on the basis of basic conchological characters. The present study analyzed topotypes of X. madritensis and H. candoni using integrative taxonomy to evaluate the relationship of the two taxa and their status within Helicella A. Férussac, 1821 and Xerotricha Monterosato, 1892 respectively. A matrix of the mitochondrial cytochrome c oxidase subunit I (COI) yielded a total of 618 bp. Bayesian and Maximum Likelihood analyses showed that H. candoni and X. madritensis clustered closely together along with Helicella itala. Mean sequence divergence for COI between H. candoni and X. madritensis was 1.42 %. Both taxa are similar in shell shape and colour. Genitalia dimensions of H. condoni were very similar to those of X. madritensis. These data indicate that H. candoni is a junior synonym of X. madritensis. The phylogenetic analyses showed that, despite its morphological similarities, X. madritensis is a species of Helicella instead of Xerotricha.