Equilateral Triangular Prism Research Articles

Experimental investigation on the connection between flow fluctuations and vorticity dynamics in the near wake of a triangular prism placed vertically on a plane

Experiments are carried out to investigate on the connection between flow fluctuations and dynamics of different vorticity structures in the wake of an equilateral triangular prism placed vertically on a plane with its apex edge against the incoming flow. Fluctuations at three frequencies are found to dominate in different wake regions; the highest frequency is caused by the alternate vortex shedding from the lateral vertical edges of the prism, while the lowest frequency is connected with an oscillation of the streamwise vorticity structures detaching from the free-end. The fluctuations at the intermediate frequency are shown to originate from an oscillation of the transversal vorticity sheet bounding the recirculation region behind the body. Geometrical modifications are then introduced to successively interfere with the dynamics of the different vorticity structures and thus to identify possible interactions between the various fluctuations. Indentations along the prism vertical edges produce an increase of the mean wake width and a consequent decrease of both the vortex shedding and intermediate frequencies, whereas the low-frequency fluctuations are not affected. The latter remain unaltered even when irregularities are added to the free-end edges and the streamwise vortices are seen to roll-up with a different formation process.

Finishing Characteristics in Barrel Finishing of Centrifugal Disc Type on Flow-Through System

For the improvement of the performance in centrifugal disc finishing, the flow-through system for supplying the compound solution is tried and its influences on finishing characteristics are experimentally investigated. Workpieces (22 mm in diameter and 15 mm in thickness) of plain carbon steel (S45C in JIS), aluminum alloy (A2017) and copper alloy (C3604) are finished with ceramic media (Equilateral triangular prism 6 mm in side and 5 mm in thickness). The conclusions are summarized as follows; The compound solution has more influences on finishing characteristics than plain water. It makes the relative stock removal larger and the surface roughness smaller than the water. The relative stock removal and the media weight loss on the flow-through system are larger than those on the batch system.

Improvement of Mode Distribution in a Triangular Prism Reverberation Chamber by QRS Diffuser

This paper presents the field uniformity characteristics in a triangular prism reverberation chamber that can be substituted for an open area test site or an anechoic chamber to measure electromagnetic interference. To improve size problems of a stirrer that is an official unit to generate a uniform field in the reverberation chamber, we suggest a diffuser of Quadratic Residue Sequence method. To validate the substitution of a diffuser for a stirrer, a diffuser is designed for 1-3GHz, and three types of equilateral triangular prism reverberation chambers are modeled. Afterwards, the field distributions in these three reverberation chambers are both simulated and tested. Using XFDTD 6. 2 of finite difference time domain method, field deviations of each structure are simulated and compared to each other. An evaluation of field uniformity is done by cumulative probability distribution which is specified in the IEC 61000-4-21. The result shows that the field uniformity in the chamber is within ±6dB tolerance and also within ±3dB standard deviation, which means a diffuser can satisfy the requirement of international standards.

On convex surfaces with minimal moment of inertia

We investigate the problem of minimizing the moment of inertia among convex surfaces in R3 having a specified surface area. First, we prove that a minimizing surface exists, and derive a necessary condition holding at points of positive curvature. Then we show that an equilateral triangular prism is the optimal triangular prism, that the cube is the optimal rectangular prism, and that the sphere is (locally) optimal among ellipsoids. Many examples of convex surfaces are examined, among which the lowest moment of inertia is achieved by a truncated tetrahedron. The problem of finding the global minimizing surface remains open. The analogous problem in two dimensions has been solved by Sachs and later by Hall, who showed that the equilateral triangle minimizes the moment of inertia, among all convex curves with given length.

Image inversion and magnification by negative index prisms

A Dove prism and an anamorphic prism pair are investigated in negative index imaging systems. An equilateral triangular prism with refractive index of -1 operates as a negative index Dove prism that inverts as well as images the incident field. A negative index anamorphic prism pair acts as a negative index imaging system with magnification. The relationship between achievable magnification and aberrations is discussed. Both prism systems can be implemented by using negative index photonic crystals, and their performance is demonstrated numerically by the finite-difference time-domain method. These negative index prism structures enhance the functionalities of negative index flat lenses and broaden the applications of negative index materials.

Crystal Structure of Helicobacter pylori Formamidase AmiF Reveals a Cysteine-Glutamate-Lysine Catalytic Triad

Helicobacter pylori AmiF formamidase that hydrolyzes formamide to produce formic acid and ammonia belongs to a member of the nitrilase superfamily. The crystal structure of AmiF was solved to 1.75A resolution using single-wavelength anomalous dispersion methods. The structure consists of a homohexamer related by 3-fold symmetry in which each subunit has an alpha-beta-beta-alpha four-layer architecture characteristic of the nitrilase superfamily. One exterior alpha layer faces the solvent, whereas the other one associates with that of the neighbor subunit, forming a tight alpha-beta-beta-alpha-alpha-beta-beta-alpha dimer. The apo and liganded crystal structures of an inactive mutant C166S were also determined to 2.50 and 2.30 A, respectively. These structures reveal a small formamide-binding pocket that includes Cys(166), Glu(60), and Lys(133) catalytic residues, in which Cys(166) acts as a nucleophile. Analysis of the liganded AmiF and N-carbamoyl d-amino acid amidohydrolase binding pockets reveals a common Cys-Glu-Lys triad, another conserved glutamate, and different subsets of ligand-binding residues. Molecular dynamic simulations show that the conserved triad has minimal fluctuations, catalyzing the hydrolysis of a specific nitrile or amide in the nitrilase superfamily efficiently.

A Try for Improvement of Performance in Dry Barrel Finishing by Centrifugal Disc Type

The speed-up of the disc rotation in dry centrifugal barrel finishing is done and its influence on finishing characteristics is experimentally examined. The workpiece is a sliced cold rolled bar of plain carbon steel (S45C in JIS, HB221). It is 32mm in diameter and finished to10mm in thickness by belt grinding. The equilateral triangular prism nylon media (1010mm, A#320) is used at 20vol% in media charging ratio. The disc rotation speed is increased up to 500min-1. By speeding up the disc rotation, the finishing speed improves, but the total efficiency decreases.

Micromagnetic Simulation of Magnetic Triangularly Shaped Nanoelement Formed by Nanosphere Lithography

The ground states and magnetization process of the triangularly-shaped nanoelements formed by monolayer nanosphere lithography were simulated by micromagnetic formalism. Micromagnetic ground states were presented in the form of a micromagnetic phase diagram with four regions corresponding to in-plane single domain, out-of-plane ferromagnetic, Y-state, and vortex configurations. Micromagnetic simulations showed that it was harder to switch the magnetization of triangularly-shaped nanoelements than that of equilateral triangular prisms for the same lateral size larger than 50 nm

Demagnetization field of ferromagnetic equilateral triangular prisms

An analytic expression is obtained for the point-function demagnetization tensor of the uniformly magnetized equilateral triangular prism element. This result can be used to improve the precision in 3D finite element micromagnetic models, especially for complex boundary geometric shapes. The corresponding magnetometric demagnetization tensors and demagnetization factors are calculated with the expression. The demagnetization field is discussed at various aspect ratios with magnetization perpendicular to the triangle plane.

Structure of the cell-puncturing device of bacteriophage T4

Bacteriophage T4 has a very efficient mechanism for infecting cells. The key component of this process is the baseplate, located at the end of the phage tail, which regulates the interaction of the tail fibres and the DNA ejection machine. A complex of gene product (gp) 5 (63K) and gp27 (44K), the central part of the baseplate, is required to penetrate the outer cell membrane of Escherichia coli and to disrupt the intermembrane peptidoglycan layer, promoting subsequent entry of phage DNA into the host. We present here a crystal structure of the (gp5-gp27)3 321K complex, determined to 2.9 A resolution and fitted into a cryo-electron microscopy map at 17 A resolution of the baseplate-tail tube assembly. The carboxy-terminal domain of gp5 is a triple-stranded beta-helix that forms an equilateral triangular prism, which acts as a membrane-puncturing needle. The middle lysozyme domain of gp5, situated on the periphery of the prism, serves to digest the peptidoglycan layer. The amino-terminal, antiparallel beta-barrel domain of gp5 is inserted into a cylinder formed by three gp27 monomers, which may serve as a channel for DNA ejection.

Micromagnetics of ferromagnetic equilateral triangular prisms

A systematic study of micromagnetic configurations in thin equilateral triangular prisms as a function of lateral size and thickness is reported. The resulting map of a micromagnetic ground state is presented in the form of a micromagnetic phase diagram with two regions corresponding to buckle and Y-state configurations. These configurations led to the formation of a configurational anisotropy field, an ab initio calculation of which is presented and the results are compared with experiment. The calculated six-fold symmetric anisotropy field agreed well with experiment but was found to depend on the applied field in phase and magnitude. The anisotropy field dependence on the triangular nanostructure edge roughness was also investigated and related to the stability of the micromagnetic phases.

Influence of temperature on the liquid–liquid equilibria containing two pairs of partially miscible liquids. Water+nitromethane+1-butanol ternary system

In order to show the influence of the temperature on the liquid–liquid equilibria and obtain an equilateral triangular prism with temperature as the vertical dimension for water+nitromethane+1-butanol ternary system, its solubilities and equilibrium data starting at 303.15 K are reported. One region of immiscibility (band type curve) is shown between 303.15 K and 340.5±0.5 K, but when the temperature increases beyond this value 2 separate binodal curves appear. Solubility data of the 2 partially miscible binary systems: water+nitromethane and water+1-butanol were also obtained. From these experimental results, both binary upper critical solution temperatures (UCST) were reported. When the temperature is decreased below the lower CST, the ternary system presents 2 binodal curves expanding toward each other until they meet with a common plait point at the lowest point on the ridge. This point (`col' or saddle point) is situated at 340.5 K±0.5 K with a ternary composition: w 1=0.61; w 2=0.22 and w 3=0.17. Tie line data were satisfactorily correlated by the method of Othmer and Tobias [D.F. Othmer, P.E. Tobias, Ind. Eng. Chem., 34 (1942) 693–696] on a mass-fraction basis, and their plait point coordinates estimated when 2 separate binodal curves were present. From experimental distribution coefficients and selectivities 1-butanol appears to be a good solvent for extraction purposes particularly when the process is carried out at room temperature.

The characteristics of wind forces acting on an equilateral triangular prism

A triangular prism has a particular cross-sectional shape in the point of view of the aerodynamic lift force which acts on it in winds; in case that one face of a triangular prism is normal to the approaching flow direction, if the face is facing leeward, the lift force on the prism is not affected by Kerman vortices, but on the contrary, if the face is facing windward, the lift force on the prism is strongly affected by Karmen vortices.These phenomena are related to the “after-body” in the wake region: in the former case, the prism has no after-body, and in the latter case, the prism has a volume of after-body in the wake region. The aerodynamic fortes acting on the after-body contribute to the galloping phenomenon, too.In this paper, effects of the after-body on the characteristics of lift force fluctuation and aerodynamic transverse oscillation are described, based on a series of wind tunnel experiments on a three- dimensional triangular prism.

On hearing the shape of rectilinear regions

From complete knowledge of the eigenvalues of the negative Laplacian on a bounded domain, one may extract information on the geometry and the boundary conditions by analyzing the asymptotic expansion of a spectral function. Explicit calculations are performed for an equilateral triangular domain with Dirichlet or Neumann boundary conditions, yielding in particular the corner angle terms. In three dimensions, some applications to eigenvalue problems for an equilateral triangular prism are dealt with, including the solid vertex terms.

Note on ‘low‐frequency scattering of acoustic plane waves by an arbitrary penetrable cylindrical obstacle’

We solve here the two‐dimensional problem of scattering of low‐frequency acoustic plane waves by a penetrable cylindrical obstacle embedded in an infinite medium of different properties and having symmetry with respect to xaxis only. By an integral equation technique, approximate expressions for inner and outer solutions, the far‐field amplitude and the scattering cross‐section of the cylindrical obstacle are derived in terms of its shape factors. These results are further illustrated for the configuration of an equilateral triangular prism.

Interior and exterior solutions for boundary value problems in composite elastic media. I. Two-dimensional problems

We study two-dimensional problems of elasticity when a homogeneous and isotropic solid of an arbitrary shape is embedded in an infinite homogeneous isotropic medium of different properties. Solutions are obtained both inside the guest and host media. These solutions are derived by first transforming the boundary value problems to the equivalent integral equations. The interior displacement field is obtained by a simple method of truncation. By this method the integral equations are recast into an infinite number of algebraic equations and a systematic scheme of solutions is constructed by an appropriate truncation. The exterior solutions are obtained by substituting the interior solutions in the integral equations valid for the entire medium. The boundaries considered are rectangular cylinder, equilateral triangular prism, and elliptic cylinder and its limiting configurations. It emerges that the solutions for the elliptic cylinder and its limiting configurations are exact.

Heat Transfer in Separated Flows : 3rd Report, The Case of Equilateral Triangular Prisms

Heat Transfer in Separated Flows : 3rd Report, The Case of Equilateral Triangular Prisms

Torsion of an equilateral triangular prism with longitudinal holes

The paper presents two torsion solutions, based on method of images, for an equilateral triangular prism: (i) when the prism contains a central longitudinal hole, and (ii) when the prism contains three equal longitudinal holes situated symmetrically in two different ways. The two solutions differ from each other in their formulation. Numerical examples are given in each solution.

Steady-state thermoelastic problem for a triangular prism with a circular hole under non-uniform heat generation

This paper is concerned with a treatment of thermal stresses in an equilateral triangular prism with a central circular hole under steady state of temperature distribution with a non-uniform heat generation which is represented by a linear function of the radius. This problem is an applicable problem in the structure of a moderator as a triangular cell. Moreover, in this paper, a new treatment of solving is presented for the thermoelastic problems of the multiply connected region under non-uniform heat generation.

Temperature distribution in a triangular laser rod

Variational methods are applied to give approximate solutions for the temperature distribution in a right equilateral triangular prism.