External Shape Research Articles

Artificial mitochondrion for fast latent heat storage: Experimental study and lattice Boltzmann simulation

The packed-bed latent heat storage technique has been widely applied in thermal energy management and harvesting, but its extensive deployment remains limited due to its slow charging rate. Here, inspired by mitochondrion, a bionic design of a PCM capsule is proposed for fast latent heat storage, whose performances are evaluated by both experiment and lattice Boltzmann simulation. The melting time is found to mainly depend on the harmonic mean distance between the centroid and every wall rather than the surface/volume ratio. The mitochondrion-shaped capsule has the fastest thermal storage rate with melting time prominently reduced by 48% compared with the spherical capsule due to its shortest harmonic mean distance. Meanwhile, this capsule has the lowest drag force among six different PCM capsules. In addition, artificial mitochondrion, obtained by mimicking both external shapes and internal membrane conformation of the mitochondrion, can further decrease the melting time by 53% compared with the spherical counterpart. The present study provides a new way to design high-performance PCM capsules and promotes the application of bionics in latent heat storage fields.

Aerodynamic shape optimization of large-span coal sheds for wind-induced effect mitigation using surrogate models

Large-span coal sheds commonly used in thermal power plants are particularly vulnerable to wind loads, and the aerodynamic performances are largely affected by their external shapes. The search for the best performing shape through an aerodynamic optimization is still of importance for the mitigation of the design wind loads and responses. This study investigated the possibility of using surrogate models combined with genetic algorithm to carry out the aerodynamic shape optimization of large-span roof structures. The approach is applied to tri-centered coal sheds with closed and open gables, respectively. The shape optimization is numerically performed to minimize the vertical displacement of the shed model while subjecting to one normal and two oblique wind directions, 0°, 30° and 45°. The aerodynamic forces acting on coal sheds immersed in turbulent flow are obtained by the CFD simulation with RSM turbulence model, and the results are validated with wind tunnel tests. Kriging model is used to establish a global mapping between design variables and objective function by conducting a set of CFD and structural static response analyses. Results show that the aerodynamic loads and the optimal geometry are sensitive to the selection of gable types and wind directions. The optimal design presents a reasonable performance improvement compared with the near-optimal and original designs. Several compromised designs are finally provided in order to seek a balance between the effects of wind directionality and construction cost.

ИССЛЕДОВАНИЕ ХАРАКТЕРИСТИК ПРОЧНОСТИ СИНТЕЗИРОВАННОГО СПЛАВА СИСТЕМЫ Co–Cr–Ni–W–Ta

Additive manufacturing is increasingly used in the aviation industry. Its main feature is the manufacture of parts of complex external and internal geometric shapes without increasing the cost of their production. To calculate the resource of nodes and reliable operation of new equipment, it is necessary to have a set of calculated values of characteristics of structural strength, including the characteristics of tensile, creep rupture and high-cycle fatigue (HCF). The study of characteristics of tensile, creep rupture and HCF of the Co–Cr–Ni–W–Ta alloy obtained by the method of selective laser melting (SLM) is presented in this paper.

The relationship between head shape, head musculature and bite force in caecilians (Amphibia: Gymnophiona).

Caecilians are enigmatic limbless amphibians that, with a few exceptions, all have an at least partly burrowing lifestyle. Although it has been suggested that caecilian evolution resulted in sturdy and compact skulls as an adaptation to their head-first burrowing habits, no relationship between skull shape and burrowing performance has been demonstrated to date. However, the unique dual jaw-closing mechanism and the osteological variability of their temporal region suggest a potential relationship between skull shape and feeding mechanics. Here, we explored the relationships between skull shape, head musculature and in vivo bite forces. Although there is a correlation between bite force and external head shape, no relationship between bite force and skull shape could be detected. Whereas our data suggest that muscles are the principal drivers of variation in bite force, the shape of the skull is constrained by factors other than demands for bite force generation. However, a strong covariation between the cranium and mandible exists. Moreover, both cranium and mandible shape covary with jaw muscle architecture. Caecilians show a gradient between species with a long retroarticular process associated with a large and pennate-fibered m. interhyoideus posterior and species with a short process but long and parallel-fibered jaw adductors. Our results demonstrate the complexity of the relationship between form and function of this jaw system. Further studies that focus on factors such as gape distance or jaw velocity will be needed in order to fully understand the evolution of feeding mechanics in caecilians.

Fundamental Study on Optimal Design Method of Tread Patterns Simultaneously Realizing Functional Properties and Aesthetics

Tread patterns are grooves or notches carved into shoe soles and tire surfaces. They significantly affect physical performance, such as ease of running and stopping. In addition, the complexity of their design and the fact that they form the external shape of a product also demands their visual beauty. This study proposes a multi-objective optimal design method that simultaneously considers functional properties and aesthetics. First, the dataset of aesthetics evaluation is prepared based on the semantic differential method, and it is transformed into a convolutional neural network model using a machine learning technique. It enables the quantitative evaluation of the aesthetics of respective patterns. The physical performance indices are evaluated by the finite elements methods as well. Then we solve multi-objective optimization problems using a data-driven topology design method with physical and sensory indices as objective functions. Finally, we apply the proposed method to an example problem about tire tread patterns to verify its fundamental validity and effectiveness.

Probabilistic Method to Estimate the Scatter of the Fatigue Strength of Shafts in the HCF Region

The fatigue strength of shafts is always subjected to scatter. Knowledge of this scatter is essential—especially in the high-cycle-fatigue (HCF) region—for producing safe shaft designs. Experimental determination is extremely time consuming and cost intensive. Therefore, this paper investigates the possibility of quantifying the scatter of (nominal) fatigue strength in the HCF region by means of a probabilistic model. The basis for establishing such a model is the identification of the parameters influencing the damage mechanism. In this context, the scatter-influencing parameters of external shape, surface and material condition were statistically modelled in a suitable manner. These influencing parameters act as input parameters in a local strength approach in addition to non-scattering parameters. Using a probabilistic model developed on the basis of Monte Carlo simulations, models of shafts and their surfaces can be randomly generated. The shafts so generated are submitted to local strength verifications by means of finite-element analyses of the entire failure-critical shaft surface. The stochastically generated shafts and the application of nominal stresses simulate the experimental testing at different nominal stress levels. By statistical evaluation of these fictitious nominal stress levels with respect to calculated failures and run-outs of the shafts, the probability distribution of the fatigue strength of the shaft population—and thus its scatter—can be determined. The probabilistic model is validated using a shaft population under non-scattering rotating bending load and compared with the experimentally determined scatter of the fatigue strength.

Numerical material testing based on homogenization method for non-periodic media (Formulation using microscopic fluctuation displacement and macroscopic strain)

We propose a method for numerical material testing that does not explicitly assume boundary conditions in homogenization analyses for microstructures with random or localized inhomogeneities. Specifically, instead of the periodic constraint condition on the fluctuation displacement in the RVE, a condition is imposed such that the domain integral of the gradient is zero, which preserves the definition of macroscopic strain in the homogenization theory while also suppressing rigid body rotation. Then, a scale-separated variational problem is defined with this condition introduced as a constraint. Next, the governing equations of the two-variable boundary value problem (BVP) are derived by applying Lagrange multiplier method to this variational problem. The macroscopic BVP is degenerated to a material point, and the microscopic BVP is transformed into a form specialized for numerical material testing and then discretized by the finite element method (FEM). The discretized equations are extended by adding the degrees of freedom corresponding to macroscopic stress and strain. Since the proposed method does not require any restrictions on the external shape of the microstructure and the extraction of external boundaries, it is relatively easy to implement into the FEM. Several numerical examples are presented to demonstrate the validity of the proposed by comparing the results with those of the conventional approach.

A Growth Control by External Shape Input and Optimization of Initial Parameters for Animation of Ice and Frost

本論文では，映像制作に欠かせないビジュアルエフェクツの表現の中でも，氷や霜がオブジェクトに張り付いて広がる様子を表現する一手法を提案する．本手法の主要な要素技術は外形入力と初期値最適化である．本手法では平面のオブジェクト上においてユーザが入力した「広がりの範囲」と「始点」に沿ってシミュレーションを実行する．ここで最急降下法を導入してシミュレーションの初期値を最適化することで，ユーザの所望の速度での広がりを実現する．これにより，始点から指定した範囲内にユーザの所望の速度で氷・霜が樹枝状に広がるアニメーションを制作できる．

Trifluoromethylpyridine thiourea derivatives: design, synthesis and inhibition of the self-assembly of tobacco mosaic virus particles.

Devastating plant virus diseases leading to bad harvests and lower quality of crops have made feeding the beyond seven billion population a huge challenge. Nevertheless, growing resistance and cross resistance of crop protection agents have made this challenge harder. Therefore, an efficient crop protection agent with novel structure and mode of action showing higher efficiency and eco-friendly is urgently needed. The coat protein (CP) of a virus is a potential target for the discovery of new antiviral agents. Antiviral molecules can inhibit infection by obstructing the assembly of virus particles. A series of novel phthalamide-like thiourea derivatives containing trifluoromethylpyridine was designed and synthesized. Most of the compounds exhibited good antiviral activity against tobacco mosaic virus (TMV). Compound 7b showed notable curative, protective and inactivation activities against TMV. Its inactivation half-maximal effective concentration (EC50 ) value (20.5μg mL-1 ) was better even than commercial ningnanmycin (23.2μg mL-1 ). Compound 7b also had stronger TMV-CP binding ability than ningnanmycin and destroyed the external shape of TMV particles and hindered the self-assembly of TMV-CP and TMV-RNA. These phthalamide-like thiourea derivatives especially compound 7b containing trifluoromethylpyridine are potential lead compounds and inhibitors of TMV particle self-assembly. © 2021 Society of Chemical Industry.

Constructing lattices with graded features in spatial distribution for tissue engineering

Here we propose a simple but effective method to build graded lattices for application in tissue engineering. This method can construct a graded lattice mathematically with the targeted gradients represented by a grey image. The lattice architecture can adapt both internal structure and external shape of a complex tissue for biomimetic purpose. The resulting lattice can be fabricated using various materials and suitable additive manufacturing (AM) technologies.

Effect Of Nd:YAG Laser On Ants (Camponotus consobrinus)

The subject of biophysics is interdisciplinary and covers various fields of biology and physics. In this research the effect of some parameters of Nd:YAG laser on ants (Camponotus consobrinus) has been studied . This includes the effect on its external shape, as well as the percentage of the killing rate obtained. A laser radiation of a wavelength (1.064 µm) with different energies: (300, 320, 340, 360, 380 and 480 mJ) was used to irradiate ants placed at a distance of (10 cm) distance from the laser source . The irradiation times were (15 and 20 sec) for each energy. The obtained results showed an increase in the rate of ant mortality, as well as an increase in deformations, as the laser energy and the irradiation time increased. These results were recorded after different time periods (12, 24, 48 and 72 hours) after laser treatment.. The thermal diffusion within the tissues resulting from laser radiation causes increased death rates due to damage of internal structures.

Integrative Approach Uncovers New Patterns of Ecomorphological Convergence in Slow Arboreal Xenarthrans

Identifying ecomorphological convergence examples is a central focus in evolutionary biology. In xenarthrans, slow arboreality independently arose at least three times, in the two genera of ‘tree sloths’, Bradypus and Choloepus, and the silky anteater, Cyclopes. This specialized locomotor ecology is expectedly reflected by distinctive morpho-functional convergences. Cyclopes, although sharing several ecological features with ‘tree sloths’, do not fully mirror the latter in their outstandingly similar suspensory slow arboreal locomotion. We hypothesized that the morphology of Cyclopes is closer to ‘tree sloths’ than to anteaters, but yet distinct, entailing that slow arboreal xenarthrans evolved through ‘incomplete’ convergence. In a multivariate trait space, slow arboreal xenarthrans are hence expected to depart from their sister taxa evolving toward the same area, but not showing extensive phenotypical overlap, due to the distinct position of Cyclopes. Conversely, a pattern of ‘complete’ convergence (i.e., widely overlapping morphologies) is hypothesized for ‘tree sloths’. Through phylogenetic comparative methods, we quantified humeral and femoral convergence in slow arboreal xenarthrans, including a sample of extant and extinct non-slow arboreal xenarthrans. Through 3D geometric morphometrics, cross-sectional properties (CSP) and trabecular architecture, we integratively quantified external shape, diaphyseal anatomy and internal epiphyseal structure. Several traits converged in slow arboreal xenarthrans, especially those pertaining to CSP. Phylomorphospaces and quantitative convergence analyses substantiated the expected patterns of ‘incomplete’ and ‘complete’ convergence for slow arboreal xenarthrans and ‘tree sloths’, respectively. This work, highlighting previously unidentified convergence patterns, emphasizes the value of an integrative multi-pronged quantitative approach to cope with complex mechanisms underlying ecomorphological convergence.

A geometrical formulation for the workspace of parallel manipulators

AbstractIn study this paper, a geometric formulation is proposed to describe the workspace of parallel manipulators by using a recursive approach as an extension of volume generation for solids of revolution. In this approach, the workspace volume and boundary for each limb of the parallel manipulator is obtained with an algebraic formulation derived from the kinematic chain of the limb and the motion constraints on its joints. Then, the overall workspace of the mechanism can be determined as the intersection of the limb workspaces. The workspace of different kinematic chains is discussed and classified according to its external shape. An algebraic formulation for the inclusion of obstacles in the computation is also proposed. Both analytical models and numerical simulations are reported with their advantages and limitations. An example on a 3-SPR parallel mechanism illustrates the feasibility of the formulation and its efficiency.

Eco-friendly application of nano-chitosan for controlling potato and tomato bacterial wilt

Bacterial wilt is one of the main diseases of Solanum spp., which caused by Ralstonia solanacearum (RS), formerly known as Pseudomonas solanacearum. Different concentrations of chitosan nanoparticles have been evaluated as one of the alternative methods of disease management in vitro and in vivo to reduce the risks of pesticide residues. Results in vitro experiment indicated that RS5 isolate was the most virulence one compared to RS1 and RS3. Increasing concentration of nano-chitosan, lead to increase inhibition zone, and this was observed at higher concentrations (100 and 200 µg/ml). In vivo results showed the highest concentration of spraying chitosan nanoparticles increase percentage reduction of disease incidence and severity, in effected potato and tomato plants. Recorded data of disease incidence and severity in treated potato plants were 78.93% and 71.85%, while on tomato plants were 81.64% and 77.63%, respectively compared to untreated infected potato plants were recorded 15.38%, 20.87%, and tomato plants were 20.98% and 28.64%. Results also revealed that 100 µg/ml of chitosan nanoparticles the lowest treatments used as soil amended curative treatments led to incease percentage reduction of disease incidence and severity, respectively on potato and tomato plants, but less than preventive treatment. The results registered that on potato plant were 54.93% and 52.65%, whilst recorded on tomato plants were 59.93% and 56.74%. Transmission electron microscopy (TEM) micrpgraphs illustrated that morphological of healthy R. solanacearum cells were undesirably stained with uranyl. The electron-dense uranyl acetate dye was limited to the cell surface slightly than the cytoplasm, which designated the integrity of the cell film of healthy cells. While bacterial cells treated with nano-chitosan, showed modification in the external shape, such as lysis of the cell wall and loss of cell flagella. Also, the result of using Random amplified polymorphic DNA (RAPD)-PCR observed that differences in treated Ralstonia solanancearum genotype by nano-chitosan compared to the genotype of the same untreated isolate.

Sub-areas in steep rock salt formations – what do we know about the geological composition of North German salt structures?

Abstract. Suitable host rocks for a repository for high-level radioactive waste (HLW) in Germany include not only clay and crystalline rocks but also rock salt formations in so-called flat and steep bedding (StandAG, 2017). Favourable repository relevant properties of rock salt are, e.g. the high heat conductivity, low porosity and permeability, and its viscoplastic deformation behaviour. Thicker salt deposits can be attributed to the formation of approx. 700 salt structures that have formed under various geological conditions in the North German Basin (NGB) over the last 250 million years. According to their shape and genesis, salt structures are classified as salt pillows (considered as flat bedding) or salt diapirs (steep bedding). Out of a total of 74 sub-areas in rock salt, 60 sub-areas in salt diapirs consisting of Permian evaporates were identified within the first phase of the German site selection procedure (BGE, 2020). At the current stage of the site selection process, a conservative approach has been adopted and the internal structure of the salt structures have not yet been taken into account for further classification of the identified sub-areas. However, the interior of the salt structures not only consists of rock salt but also of varying proportions of clay, carbonate and anhydrite rocks, as well as potassium salts formed by progressive evaporation of marine brines. Multi-phase salt tectonics has led to the folding of these differently composed layers and to complex internal structures. Therefore, detailed knowledge of the salt structure compositions is necessary to identify suitable rock salt areas for the designation of the containment providing rock zone. As a result of decades of research through extensive salt and potash mining, cavern storage and exploration for final waste disposal, Permian salt rocks represent a well-studied host rock in Germany. The use of different exploration methods and multidisciplinary data evaluation have led to a comprehensive understanding of the internal composition of some well-studied salt structures. Systematic studies have shown that several factors have influenced the formation of salt structures as well as their external shapes, sizes, and spatial distribution (e.g., Pollok et al., 2020). Furthermore, the amount and distribution of suitable host rocks varies greatly in different salt structures and is closely related to their internal structure. Since the interior of salt structures has not been considered in the site selection process so far, a classification of salt structures (or sub-areas) into certain types with varying internal composition and complexity is presented. By examining their lithofacial composition, genesis, and structural geological position within the basin, it is possible to narrow down these types to specific areas in the NGB. Without the acquisition of additional exploration data in this phase of the site selection process, this salt structure classification provides important data for the legally demanded assessment of the overall favourable geological situation.

CFD Simulations and External Shape Optimization of Missile with Wing and Tailfin Configuration to Improve Aerodynamic Performance

The wing of missile can be considered as an effective factor for determination of lift to drag ratio. However, there are few studies that investigate wing effect on missile aerodynamics. Therefore, the purpose of this study is to indicate wing effect on the missile aerodynamics and optimize wing geometry for enhancement of aerodynamic efficiency. The missile designed tail-fin configuration is selected from a previous study which contains experimental data. In the beginning of study, Computational Fluid Dynamics (CFD) simulations of selected missile are performed and compared with experimental data. Wing is then mounted to the selected missile and CFD solution is repeated for modified missile at 6º angle of attach (AoA) and subsonic and supersonic speeds. The modified missile shows good performance in point of aerodynamics when compared with baseline missile model. In addition, wing geometry is optimized to improve aerodynamic performance using Multi-Objective Genetic Algorithm (MOGA). Objective functions are determined as lift and drag coefficients. Wing geometry parameters are determined as design variables for optimization. After the optimization process, the results are showed that the aerodynamic coefficients are improved when compared with baseline geometry. In addition, response surface analysis is presented to show which design parameters are more effective on drag and lift forces. The findings of study show that optimum results are more efficient in terms of performance. CFD solution method and the optimization procedure can be applied to design or optimize for different geometry.

Highly substituted calcium silicates 3D printed with complex architectures to produce stiff, strong and bioactive scaffolds for bone regeneration

Bone's outstanding biomechanical performance is derived from cooperative interactions between its composition and microarchitecture. Towards developing bioceramic scaffolds with similar biomechanical performance for repairing large bone defects under load, we have developed 13 new bioceramic compositions by doping various concentrations of iron and magnesium into Baghdadite (a Zr-Ca-Silicate: Ca3ZrSi2O9). The resulting bioceramics were printed into scaffolds with precisely controlled internal and external shapes using a versatile photopolymerization-based stereolithography technique. The biomechanical performance of new compositions and scaffolds were determined using mechanical tests with in situ imaging, in vitro cell study, an in vivo animal study, histological analysis, and microcomputed tomography. Mg-doped Baghdadite with composition Ca3Mg0.1Zr0.9Si2O8.9 demonstrated superior bioactivity and mechanical properties, compared to Baghdadite. 3D printed Mg-doped Baghdadite scaffolds with 35% porosity and designed architecture matched the stiffness and strength of cortical bone. These scaffolds were 2–5 times stronger than other bioceramic and bioglass scaffolds with the same porosity made with photopolymerization techniques. In vivo bone ingrowth was 2.2 times higher in Mg-doped Baghdadite than Baghdadite, effectively transforming these mechanically brittle scaffolds into deformable and tough ceramic-bone composites. Mg-doped Baghdadite scaffolds demonstrate a combination of favorable mechanical properties and bone regeneration capacity that show their potential for clinical success.

CEO pay and family firm heterogeneity: A behavioral agency model perspective

We study the effects of family control on CEO pay from the perspective of behavioral agency model (BAM), with particular focus on family firm’s generational stage and CEO family ties. Using a panel of Australian listed firms, we find that family firms present lower total and variable CEO pay, showing also less pay disparity between the CEO and other top executives. We also find that multi-generational family firms and those run by non-family CEOs offer higher total and variable CEO pay and present high pay disparity. The BAM and family’s aversion to socioemotional wealth loss can explain the effects of family control based on the pursuing of non-financial family goals. The decline of these goals derived from the aging of the firm and the hiring of external CEOs shape family control and should be considered in the design of executive compensation policies and by external parties when assessing their suitability. JEL CLASSIFICATION: G30; G32; G34; G38

The Hanging Drape: a Vertex Analogy

Abstract We present a novel, rigidly folding vertex inspired by the shape of the simplest hanging drape. Fold lines in the vertex correspond to pleats and ridges in the drape, and are symmetrically arranged to enable synchronised at folding of facet pairs. We calculate the folded rotation angles exactly using a spherical image specialised for inextensible vertex folding. We show that the vertex shape is bounded by a pair of conical surfaces whose apex semi-angles directly correspond with fold-line rotations, which expresses a geometrical equivalence between the external shape and internal folding motion of the vertex. We discuss how the vertex viz. drape perform as a novel type of conical defect based on its spherical image topography; and we highlight the meaning of bistable behaviour for the vertex, in analytical- and practical terms.

Facilitating creativity: Shaping team processes

Facilitation is important to supporting teams in the creative process during innovation, yet our understanding of the underlying mechanisms of facilitation and its effects on team processes is still limited. This paper addresses this gap by investigating how group facilitation (both internal and external) shapes team processes with respect to teamwork, taskwork and affect. We use a case study approach coupled with protocol analysis to examine the effects of facilitator's actions on team processes as well as interactions between those processes. Our results reveal a distinct distribution of teamwork and taskwork between the facilitator and the team, such that the facilitator guides the teamwork while the team focuses on the taskwork, yet with dynamic shifting in responsibilities between facilitator and team across the duration of the process. Further, we show how a facilitator uses positive affect to mediate interactions between taskwork and teamwork during creative workshops. We contribute to theory on facilitation and team processes in innovation management by offering a novel description of how team processes are structured in a facilitated creativity setting and provide important practical implications for facilitators and managers.