Triangular Plate Research Articles

Tooth Plates ofCeratodus(Dipnoi, Ceratodontidae) from the Upper Jurassic Shaximiao Formation of Guang'an, Sichuan Province, China

AbstractCeratodusis a form genus of ceratodontid lungfishes. Until now, only 14 specimens have been reported from the Mesozoic of China. Detailed measurements and characteristic comparisons based on 15 well‐preserved lungfish tooth plates ofCeratodustype, uncovered from the upper member of the Upper Jurassic Shaximiao Formation at Luojiashan, Qianfeng District, Guang'an, Sichuan Province in 2019, allow us to establish a new species,Ceratodus guanganensissp. nov., on the basis of its small swollen irregular triangular tooth plate with four low and swollen radial crests on the occlusal surface without denticles. Other specimens from the same locality can be referred toC. szechuanensisandC. youngi. This is the first discovery ofCeratodusin the Guang'an region and represents the fifthCeratodusfossil site in the Sichuan Basin. The discovery indicates that the climate was hot and arid in the Sichuan Basin during the Late Jurassic, and reveals a tectonic paleogeographic relationship between the Yangtze block in southwestern China and the Kola Basin in northern Thailand.

THE APPLICATION OF AN ADAPTIVE SOFT STRUCTURE FOR LIGHTWEIGHT FACADES

Building façades play an important role in the performance of buildings. They define the architectural aesthetics of buildings and separate the occupied indoor space from the outdoor environment. Historically, façades were considered to be a load-bearing structural element and limited in their functionality and adaptability to environmental changes. The application of bio-inspired strategies to building façades that are derived from principles found in nature offers more flexibility and adaptability to the external environment. This research presents a bio-inspired adaptive façade system that is derived through the biological analysis of a deformability mechanism, namely, turgor-based actuation, found in plant movements. The adaptive prototype module inspired by a nastic movement is composed of two lightweight triangular plates connected to pneumatic artificial muscles that control folding and unfolding of the device by pressurization. Finally, the application of adaptive modules in a building façade is simulated via computational 3D modelling. The simulation analysis shows the possibility of creating a system from numerous modules that can create a rich palette of typologies resulting in a gradient of openings. This could be an appropriate solution for an external shading device or as regulator for air ventilation and light transmission.

Numerical Simulation of Orbit Controlled Hot-gas Lateral Jet of the triangular plate with rudder

Hypersonic interception weapons have high requirements for the efficiency and accuracy of the control system. As an effective control approach, the thermochemical non-equilibrium effect of jet flow must be considered in order to accurately predict the aerodynamic characteristic. At present, relevant researches are mostly focused on the low-flow rate hot jet, while numerical simulation and wind tunnel test studies on high-flow rate hot jet are rare. In this paper, the interaction flow field of the rail-controlled jet at the altitude of 60Km and 70Km has been simulated by solving the three-dimensional viscous fluid governing equations. The influence of the thermalchemical non-equilibrium effect of the jet interaction on the flow field characteristics and aerodynamic characteristics of the aircraft was analyzed. The primary results show that: (1) The flow fields of the cold-gas jet, frozen-gas jet and hot-gas jet have significant differences under the high-flow rate jet condition, which is mainly reflected the size and the pressure value of the separation region before the nozzle. The separation region length of the cold-gas jet is approximately twice that of the hot-gas jet and the length of the frozen-gas jet is between them; (2)Jet interaction will increase the surface pressure of the aircraft and reduce the skin-friction. When Ma=25, the aerodynamic interaction of hot jet is only about 30% of that of cold jet; (3) Jet interaction on aerodynamic characteristics increases with altitudes. With the increase of Mach number, the difference between the predicted results of hot jet and cold jet is enlarged because of the enhancement of the thermochemical non-equilibrium effect.

Dynamic response of thin triangular plates under gaseous detonation loading

During a high-velocity plate forming process accompanied by dynamic loading, a large deformation is generated in a very short time. Gaseous detonation in an obstructed channel is a good way of producing interior shock waves. Pressure waves with high strength have interacted with a plate as a fundamental mechanism of the whole forming process. This study investigates the response of thin steel plates with three different thicknesses clamped on two different triangular frames under various pre-detonation pressures of acetylene-oxygen mixture experimentally and analytically to determine the permanent deformation profiles of plates. Deflection profiles showed large plastic deformations with the maximum deformation happening at the center of mass of the triangular plate. By adopting an energy method approach developed earlier for circular plates, and incorporating a newly developed condition, upper bounds are obtained for the center of mass deformation of the triangular plate. Besides, the influences of some important parameters including plate thickness, steel yield strength, and triangular clamp sizes on the displacement of the plate were evaluated. The results from analytical studies demonstrated a good agreement compared with experiments and showed that the center of mass displacement decreases greatly involving thicker plates and strain rate. It is indicated that the uniform deflection of the plate induced by the interaction of shock waves and the structure can be promoted by gaseous detonation in a confined truncated conical space. Energy method as a useful tool in the evaluation of the hindrance caused by the limited geometry of the triangular clamp on deformation illustrated that midpoint deflection was suppressed by the smaller size of the exposed area of the plate.

A non-classical couple stress based Mindlin plate finite element framework for tuning band gaps of periodic composite micro plates

Composite micro plates with periodic microstructure at very small length scale have been a focus of intensive research. When length scale of the microstructure descends below millimetre level, size effects may emerge. To account for microstructure effect on the elastic wave band gap of microscopic composite plates, we propose a numerical framework based on the modified couple stress theory of elasto-dynamics associated with a non-classical 3-node triangular (T3) Mindlin plate finite element. Since couple stress elasto-dynamics incorporates dependence on the material scale length, the proposed approach is sensitive to size effects with microscopic problems while remaining compatible with macroscopic problems. In terms of the finite element implementation, we implemented a T3 plate finite element with 9 nodal degrees of freedom under the Mindlin kinematics assumptions. The approach presents enhanced flexibility to discretize complex microstructures owing to the triangular element topology, and offers sensitivity to account for size effects of microscopic problems. Therefore, it represents a good option for the design of band gap periodic composite micro plates. Validation of the framework is performed through comparison with both analytical and numerical models.

Nusaviichthys nerivelai gen. et sp. nov., an Albian crossognathiform fish from the Tlayúa lagerstätte, Mexico

The fish Nusaviichthys nerivelai gen. et sp. nov. is described here based on well-preserved fossils from the Albian deposits of the Tlayúa quarry, near Tepexi de Rodríguez, Puebla, central Mexico. The occurrence of this new fish from Tlayúa expands the taxonomical and morphological diversity of the crossognathiformes of the Caribbean region of America during the Early Cretaceous. The inclusion of the osteological features of this species into comparative and phylogenetic analyses reveal its belonging to the order Crossognathiformes, suborder Pachyrhizodontoidei, and family Notelopidae; some of the most significant of these features include the presence of a large extrascapula bone; circumorbital bones forming a completely closed ring; medioparietal condition of the skull; posterior infraorbitals hypertrophied, covering the entire cheek, and extended up to the anterior part of the opercular bones; the relative short uroneural 1 anteriorly restricted to the preural 1; and the cycloid scales with a crenulated posterior edge. This new species differs from its relatives in the presence of numerous and small conic teeth in both jaws and vomer; the large triangular gular plate, and the numerous radiating grooves ridges present in the supraorbital, dermosphenotic, skull roof bones, opercular bones, and jaws; and the almost horizontal position of the neural and hemal spines of the last caudal centra. Despite the weak support, the naturalness of this extinct teleost order is recovered in the phylogenetic analysis performed here, which includes this new Mexican fossil fish as well as other crossognathiform genera not included in previous studies.

ADBSat: Methodology of a novel panel method tool for aerodynamic analysis of satellites

ADBSat is a novel software that determines the aerodynamic properties of any body in free-molecular flow. Its main advantage is the fast approximation of the aerodynamics of spacecraft in the lower end of the low-Earth orbit altitude range. It is a novel implementation of a panel method, where the body is represented as a set of fundamental elements and the sum of their individual aerodynamic properties makes up the properties of the whole. ADBSat's approach treats the shape as a set of flat triangular plates. These are read from a CAD geometry file in the Wavefront format, which can be created with most common CAD programs. A choice of gas-surface interaction models is available to represent the physics of free-molecular flow under different conditions. Its modular design means that other models can be easily and quickly implemented. It also benefits from a new shading algorithm for fast determination of elemental flow exposure. An example case is presented to show the capability and functionality of the program. Program summaryProgram Title: ADBSatCPC Library link to program files:https://doi.org/10.17632/622n2yjg4w.1Licensing provisions: GPLv3Programming language: MATLABDeveloper's repository link:https://github.com/nhcrisp/ADBSatNature of problem: Quickly and accurately determining the aerodynamics of satellites in free-molecular flow.Solution method: A new implementation of the panel method has been devised. The satellite shape is passed to the program as a CAD model, comprised of a set of flat triangular plates. ADBSat then calculates the aerodynamic characteristics of each element using an appropriate mathematical model, and sums the contributions for the overall properties of the body. A novel shading algorithm identifies and removes the panels which do not contribute to the calculations due to being protected from the flow by other body features. ADBSat also has the capability to account for different materials within the shape.Additional comments including restrictions and unusual features: MATLAB's Aero-space Toolbox is required for the determination of environmental parameters, unless otherwise provided by the user. As the program takes as an input a completed model of the spacecraft, the user is responsible for all mesh quality checks. The methods employed therein are only valid for strict free-molecular flow, which the user must ensure. The accuracy of the method decreases for surfaces with high concavity or multiple particle impingement.

Chunxiania fania: a new genus and species of mole cricket (Orthoptera: Ensifera: Gryllotalpidae) from mid-Cretaceous Kachin amber

As an ancient lineage among ensiferans, the family Gryllotalpidae has been underreported with limited fossil record. Herein, a new mole cricket, Chunxiania fania gen. et sp. nov., is described on the basis of an exquisitely-preserved specimen from mid-Cretaceous Kachin amber. It can be attributed to the family Gryllotalpidae (Orthoptera: Ensifera) based on distinct fossorial forelegs with sturdy femur and inflated tibia, protibia with tympana, and dactyls processes. However, it cannot be incorporated into any existing subfamily or genus of Gryllotalpidae mainly due to protibia with three movable dactyls and a very small, non-articulated denticular process, mesotibia with five apical spurs, and nearly triangular subgenital plate which is slightly curved upwards. This new finding shows novel morphological diversity in fossil Gryllotalpidae, providing insight to the early evolution of the fossorial adaption and palaeoecology of mole crickets.

A Decomposition Solution of Variable Thickness Absorber Plate Solar Collectors With Power Law Dependent Thermal Conductivity

Abstract We present a mathematical model of flat-plate solar collector whose thermal conductivity is a power law function of temperature, and nondimensional length is governed by a profile index. The rectangular, convex, and triangular shape absorber plates are obtained by changing the value of an index of nondimensional length 0, ½, and 1, respectively. The energy equation governing the temperature of rectangular absorber plate is a nonsingular-type equation, and convex and triangular cross-sectional absorber plates are two different singular-type equations. One nonsingular and two different singular value equations are solved separately by different operators, as explained separately in classical and modified Adomian decomposition method (ADM), respectively. The results obtained for the case of the rectangular, convex, and triangular cross-sectional plates are validated by comparison with the exact analytical solution for special case as available in literature. The effects of various thermophysical parameters such as power law thermal conductivity parameter, Biot number, aspect ratio, absorbed solar heat flux, and overall heat transfer coefficient on the temperature distribution are analyzed.

Radar Cross Section Modelling and Analysis of Static and Dynamic Targets using MATLAB

Radar Cross Section (RCS) is an important characteristic of the electromagnetic system for target detection. This study presents detailed modelling of Radar Cross Section (RCS) of static simple objects like sphere, cylinder, triangular plate, circular flat plate, truncated cone and complex objects using MATLAB Radar toolbox. The RCS modelling of simple objects is also done with MATLAB POFACET GUI 4.3 and the results are compared with MATLAB Radar tool box. The RCS of complex objects are vectorially added in MATLAB and modelled in this work. Modelling includes 1. A cylinder with a circular flat plate on both ends 2. A circular cylinder with ellipsoid at front end 3. A truncated cone (frustum) with circular plates at both ends 4. The half ellipsoid with a frustum and the flat plate. The simulation and comparison of the RCS variations in dBsm with respect to aspect angle for parameters such as size and frequency of the simple and complex objects have been carried out in this work. RCS of a complex object with dynamic characteristics is also analysed using the Chi-square probability density function. ’The scope of this paper is limited to the objects with deterministic shapes and the combined objects using those shapes. The detailed experimental study on the sphere shows that RCS remains the constant in all directions for sphere. The study also highlights the RCS return is maximum at 180 degrees when the cylinder is aligned horizontally with the RADAR and minimum RCS is obtained at 90 degrees and 270 degrees. In the case of ellipsoid, the RCS is maximum at 90 degrees and 270 degree and minimum at 180 degrees. For the triangular flat plate, the RCS is maximum at 0 degree and 180 degrees and minimum at 90 degrees. For the truncated cone the RCS has maximum and minimum values at aspect angles of zero degrees and 80 degrees. The model of the frustrum with flat plate at both ends provides maximum RCS due to the frustrum and minimum due to flat plate and the normal incidence occurs at 73.3008 degrees. The Swerling models for the fluctuating RCS are also analysed in detail which will be used to measure RCS of high-speed debris revolving around the earth's surface by the radar in Low Earth Orbit (LEO).

About the representation on the middle frieze of the triangular plate from the kurgan Karagodeuashkh in the Kuban River region

About the representation on the middle frieze of the triangular plate from the kurgan Karagodeuashkh in the Kuban River region

Numerical evaluation of seismic performance of corrugated-plate shaped steel tubes

The current work presents a unique study on the seismic performance of innovative corrugated-plate steel bridge piers. While several previous research was conducted on steel tubes with cross sections such as rounded or semi triangular plates, the seismic performance of such structural members with straight ribbed corrugation geometry under uniaxial cyclic loading remained a research gap. Thus, this research aims to present a new concept that could add a promising design to steel tubes under seismic effect. The seismic performance of such piers was numerically investigated in terms of the load-bearing capacity and local buckling. ABAQUS was employed to accomplish a series of finite element analyses on corrugated-plate steel bridge piers under constant axial dead load and lateral cyclic displacement. Three different geometries of corrugated-shaped steel tubes (i.e., C60, C80, and C146 mm deep) along with four different thicknesses (i.e., 6, 8, 10, and 12 mm) were investigated and compared to the traditional circular-shaped steel tubes (i.e., Cir) having same thicknesses and outer diameter. The results revealed that the innovative corrugated-plate steel bridge piers offered 20% greater load-bearing capacity and 66% more ductility compared to their companions of circular-shaped steel tubes. It was interesting to notice that the peak value of the load-bearing capacity of the C146 column was greater than those of the C80 and C60 columns by 7% and 10%, respectively. Furthermore, the local buckling was generally seen less severe amongst corrugated-plate steel bridge piers. This research raises the importance of corrugated-plate sections used in bridge piers over circular shapes owing to their advantages in strength and aestheticism.

Impulse deformation of triangular plates based on the classical theory

This article discusses the impulse effects of various loads on triangular, isosceles, elastic, isotropic plates. Analytical solutions of the direct problem of determining the internal moments and deflections of the plate, as well as the numerical results of calculations of specific loading case are presented. Goal. The goal is to develop a method for solving direct problems of determining internal moments and deflections in rectangular triangular, isosceles, elastic, thin, isotropic plates. Methodology. To solve the direct problem, the Navier method, the classical theory of modeling vibrations of thin plates and the Laplace transform are used. Results. A technique has been obtained that allows one to obtain numerical and analytical dependences for calculating the internal moments and deflections in a triangular plate. Originality. For the first time, a technique was developed for solving direct non-stationary problems to determine the internal moments and deflections in rectangular triangular, isosceles, elastic, thin, isotropic plates based on the classical theory. Practical value. The obtained analytical dependences can be used to simulate impulse vibrations of square and isosceles rectangular triangular thin isotropic elastic plates, which can be critical structural elements.

3D numerical investigation of the detonation wave propagation influence on the triangular plate deformation using finite rate chemistry model of LS-DYNA CESE method

In this article, an immersed boundary method which couples a Lagrangian structure solver with an Eulerian fluid solver with a chemistry model capable of detonation computation for H2O2 is developed to achieve the fluid-structure interaction, the deformation, and the damage of a thin plate subjected to a gaseous detonation loading. The Johnson-Cook material model was used for the plate which incorporates strain hardening, temperature softening, and strain rate effects. The detonation wave is modeled using LS-DYNA finite rate chemistry model incorporated in conservative element solution element solver. Other objectives of this numerical simulation such as estimation of deflection and stress state failure mechanism of material at high strain rate were derived based on a strain-rate dependent failure criterion. The simulated deformation pattern and the effect of pre-detonation pressure are compared with experimental results and a good agreement was acquired. Further additional simulations revealed that the pre-detonation pressure, ignition point location, and longitudinal capacity of the cylinder have great influences on the deformation and sensed pressure of the plate.

Fracture characteristics of basic roof and mechanism of strata behavior in a pillarless working face

Abstract As a research hotspot, pillarless coal mining technology has a high resource recovery rate and low roadway surrounding rock stress. To grasp the three-dimensional fracture characteristics of the basic roof is the basic to reveal the strata behavior mechanism in the pillarless working face. Thus, aiming at pillarless coal mining, the analytical solution of three-dimensional fracture mechanics models of a basic roof was analyzed by elastic thin plate theory; the principal stress distribution of a basic roof being cut by continuous artificial fractures and discontinuous artificial fractures was analyzed; the fracture characteristics of the basic roof was revealed and the strata behavior mechanism was obtained. The following conclusions can be drawn: (i) an ‘O + X’ fracture occurred in the basic roof of a traditional working face, while an opposite-trapezoid-shaped or ≡-shaped fracture was generated in the pillarless working face. (ii) When the basic roof broke, the trapezoidal or rectangular hinged plate traversed the entire pillarless working face, causing the end supports to be pressured, while the trapezoidal hinged plate did not traverse the entire traditional working face and the end supports were not pressured. (iii) The break of a basic roof induced by artificial fractures in pillarless mining reduced or even eliminated the triangular hinged plate area along the goaf edges, making a roadway in the stress relief zone. (iv) Compared with the fractures in traditional roadways and in a discontinuous roof-cutting roadway, continuous fractures could minimize surrounding rock stress and make it easy to maintain a roof-cutting roadway.

Fabrication and characterization of HPMC-AuNPs nanocomposite films

This paper presents the in-situ generation of gold nanoparticles (AuNPs) by reducing chloroauric acid (HAuCl4·H2O) with low molecular weight hydroxypropyl methylcellulose (HPMC), and HPMC-AuNPs nanocomposites are developed via solution casting method. The generation of AuNPs was initially established by a swap in color from pale yellow to purple, and then by UV–Visible (UV–Vis) spectrophotometry with the surface plasmon resonance (SPR) band observed at λ = 550 nm. The functional groups accountable for the reduction of gold ions to neutral gold atoms were identified using Fourier transform infrared spectroscopy (FT-IR). The crystalline form of the AuNPs with FCC structure was shown by X-ray diffraction (XRD) studies. The size and shape evolution of the different shaped AuNPs are confirmed by the transmission electron microscopy (TEM) study which divulged the presence of triangular plate, hexagonal, quasi spherical, isosceles trapezoid and truncated triangular morphologies of the AuNPs with an average size of 12.5 nm.

The performance of surface enhanced Raman scattering and spatial resolution with triangular plate dimer from ultra-ultraviolet to near-infrared range

The theoretical research on surface enhanced Raman spectroscopy (SERS) of triangular plate dimer (TPD) is of great significance for the design of experimental substrates. In this paper, the SERS properties of the TPD with Au, Ag, Al and Cu have been theoretical investigated in the ultra-ultraviolet, visible and near-infrared region. The influence of the TPD configuration, including the tip radian, the dimer distance and the aspect ratio on the electric field, Raman enhancement and spatial resolution are studied by the finite element method. The results show that there are dipole resonance band and quadruple dipole resonance band in the surface plasmon resonance band of TPD. The tip radian and dimer distance play the dominant role in the electric field enhancement, and the aspect ratio can be mainly used to tune the peak position of the electric field. The smaller tip radian and dimer distance will produce a stronger localized electric field and a small red shift of the peak position. Adjusting the aspect ratio can tune the position of electric field peak from ultraviolet (UV) to near-infrared without changing the peak value of the electric field significantly, especially for Al TPD. The maximum Raman enhancement factor of Au, Ag and Cu all reach 11 orders of magnitude, and 9 orders of magnitude for Al. The spatial resolution changes linearly with the gap distance, and the maximum spatial distributions of Au, Ag, Al and Cu achieve 0.65 nm, 0.67 nm, 0.69 nm and 0.70 nm with the dimer distance of 1 nm. Our results not only provide a better theoretical guidance for the optimization of TPD substrates in the SERS experiment, but also extend its application scope from ultra-UV to near-infrared range.

Design of isotropic porous plates for use in hierarchical plate-lattices

This work deals with the elastic and plastic properties of two-dimensional periodic metamaterials. Design maps are developed to ensure their isotropic elastic response while attaining the theoretical stiffness limits. Numerical simulations of two different topologies - triangular and round hole staggered patterns - are performed to analyze their large deformation response for relative densities ranging from 0.1 to 0.9. The investigations show that the strength of triangular perforated plates is profoundly dependent on the unit cells’ direction concerning the axial loading; 0 and 30 degrees have the lowest and highest yield strength over the entire range of volume fractions. In contrast, the round hole staggered patterns exhibit an almost uniform yield strength in all directions. The yield strength of the circular patterns is significantly lower at low- and intermediate-density ranges; whereas they outperform the triangular ones at relative densities higher than 0.6. Additionally, validation experiments are performed on specimens of 0.3 relative density that have been extracted from DP980 steel sheets using micro waterjet cutting, showing good agreement in terms of force-displacement response and surface strain fields. A foam-like structure is built from periodic sheets and the scaling of the elastic properties of the resulting hierarchical 3D metamaterial are discussed.

Free vibration and dynamic response of sandwich composite plates with auxetic honeycomb core

This paper deals with the free vibration and dynamic responses of composite sandwich plates. The sandwich plate has three layers in which two face sheets are made of isotropic material, and the core layer is made of auxetic honeycomb structures with a negative Poisson's ratio. A smoothed finite element model based on the first-order shear deformation theory is established for the analysis purpose. In the model, only the linear approximation is necessary, and the discrete shear gap method for triangular plate elements is used to avoid the shear locking. The Newmark direct integration technique is used to capture the dynamic responses of the sandwich plates. The convergence study is made, and the accuracy of present results is validated by comparison with available data in the literature. The influence of geometrical parameters, material properties, and boundary conditions are explored and discussed. Numerical results show that auxetic materials have several different responses compared to conventional materials, and these behaviors are strongly influenced by the internal structure of the auxetic material.

Application of Variational Method to Stability Analysis of Cantilever Vertical Plates with Bimodular Effect.

In the design of cantilevered balconies of buildings, many stability problems exist concerning vertical plates, in which reaching a critical load plays an important role during the stability analysis of the plate. At the same time, the concrete forming vertical plate, as a typical brittle material, has larger compressive strength but lower tensile strength, which means the tensile and compression properties of concrete are different. However, due to the complexities of such analyses, this difference has not been considered. In this study, the variational method is used to analyze stability problems of cantilever vertical plates with bimodular effect, in which different loading conditions and plate shapes are also taken into account. For the effective implementation of a variational method, the bending strain energy based on bimodular theory is established first, and critical loads of four stability problems are obtained. The results indicate that the bimodular effect, as well as different loading types and plate shapes, have influences on the final critical loads, resulting in varying degrees of buckling. In particular, if the average value of the tensile modulus and compressive modulus remain unchanged, the introduction of the bimodular effect will weaken, to some extent, the bending stiffness of the plate. Among the four stability problems, a rectangular plate with its top and bottom loaded is most likely to buckle; next is a rectangular plate with its top loaded, followed by a triangular plate with its bottom loaded. A rectangular plate with its bottom loaded is least likely to buckle. This work may serve as a theoretical reference for the refined analysis of vertical plates. Plates are made of concrete or similar material whose bimodular effect is relatively obvious and cannot be ignored arbitrarily; otherwise the greater inaccuracies will be encountered in building designs.