Symmetrical Prism Research Articles

Symmetric prism characterisation test to infer heat generation and heat conduction properties of concrete

Performance-based concrete design can accelerate the acceptance of emerging lower carbon concretes to reduce the environmental impact. A semi-adiabatic symmetric concrete prism experimental and analytical approach is proposed as a pathway for concrete thermal characterisation. The prism design promotes 1-D heat flow conditions using a single insulated specimen. The prism dimensions (700 mm ×100 mm ×100 mm) are rationalised to suit usage as a characterisation specimen and mix compositions that replicate those of in-situ concretes can be assessed. The experimental spatial and temporal thermal profiles of a CEM I mix and a high GGBS replacement mix were measured during hydration and through a step change in temperature in the hardened state. Thermocouples and a distributed fibre optic sensor along the central axis of the symmetric prism were used for this purpose. Multi-physics modelling provided a platform to address thermal measurement data uncertainty, extract fundamental concrete thermal parameters and gain insight into the heat generation and heat flow physics in the concrete prism specimens. The complete heat generation and maturity time histories were accurately modelled and ‘concrete thermal footprints’ derived.

Single-prism polarizer for laser emission with higher power

Subject of study. The properties of a new prismatic polarizer-analyzer of laser (optical) emission with higher power were investigated. The polarizer was designed based on a birefringent crystal in the form of a single total internal reflection prism with a triangular cross-section. Spectral dependences of the geometry of the cross-section in the refraction plane were investigated for two selected polarizer materials. Aim. The study was aimed at designing a polarizer in the form of an individual single-element device capable of functioning in the laser beams with higher power that maintains the original direction of radiation propagation with minimum optical losses and without anamorphosis of the beam cross-section. Method. The transmission of radiation through an optically anisotropic crystalline prism with an arbitrary triangular cross-section was investigated using mathematical modeling. Snell’s equations, which were developed for refraction and total internal reflection of radiation on the faces of an anisotropic prism, were used. Based on the obtained solutions, the spectral dependences of angular structural parameters of prismatic polarizers were calculated under conditions of maintaining the collinearity of the input and output rays and their refractions on the input and output faces fixed at Brewster’s angles. The energy losses and spectral ranges of operation of prismatic polarizers composed of two selected crystalline materials with a priori defined geometry were analyzed. Main results. A new prismatic polarizer was designed and investigated. Its main feature corresponds to anisotropic total internal reflection of optical radiation from one of the faces of a birefringent single prism under Brewster’s refractions on the input and output faces. We established that the device exhibits minimum optical losses, collinearity (or coaxiality) of unpolarized and polarized beams, and no anamorphotic distortion of the cross-section of the output p-polarized beam. Furthermore, we demonstrated that in the case of virtually symmetric prisms for which the difference between the structural angles and Brewster’s angles is 3°–7°, the effect of anamorphism of the beam cross-section is negligibly small. The spectral ranges of the device operation were determined for several specific designs. A weak dependence of spectral bands on the selected orientations of the polarizer crystal was observed. It manifests in the symmetry of the obtained dependences. We demonstrated that the prisms composed of YVO4 crystals are the most advantageous for obtaining the widest spectral bands in the near- and mid-infrared spectral ranges. Angular tolerances for the divergence of the incident beams were determined based on analysis of the angular deviations of the incidence angles from the Brewster’s angles. The device can also be used in observational optics as an anisotropic equivalent of the isotropic Dove prism. The difference between the proposed device and the Dove prism is the fact that the proposed device provides the potential of observing an image in ideally linearly polarized light. Practical significance. The proposed single-element design of a prismatic polarizer with Brewster’s input and output faces enables the use of the device for polarization (or polarization analysis) of laser beams with power higher than the values for which the standard multicomponent polarizers are applicable.

Effect of Natural Wind on the Transiting Test for Measuring the Aerodynamic Coefficients of Structures

The aerodynamic coefficients transiting test is a new method for measuring the structural aerodynamic coefficients using the wind generated by a moving vehicle. However, the effect and correction of natural wind on the transiting test has not been studied. Hence, in this study, the investigation of the aerodynamic force and pressure measurements on a special triangular prism model is simulated through the transiting test under different natural wind conditions for 30° and 90° angles of wind incidence. Force and pressure measurement results in the transiting test are used to describe and explain the effect of natural wind in the range of 0–3.0 m/s on the aerodynamic coefficients of the symmetric triangular prism qualitatively and quantitatively. The results show that the driving wind field of the vehicle, aerodynamic force coefficient, and aerodynamic pressure coefficient are significantly influenced by strong natural wind greater than 1.71 m/s, which must be considered and so it is recommended that the structure aerodynamic coefficients transiting test should be conducted under the condition that the natural wind is less than 1.71 m/s. In addition, the method of two-direction round-trip measurement is proposed to modify the effect of natural wind on transiting tests.

Energy savings potential from prismatic glass structure

The simulation analysis of the potential energy savings from the prismatic glass structure has been provided. The two conventional triple glazings and two proposed triple glazings with prismatic glass have been experimentally tested to obtain the realistic angular selective optical properties. The experimental results have been compared with conventional triple glazing with clear glass panes and triple glazing with solar control pane applied. The comparison indicated high potential advantages of triple glazing with prismatic glass structures (especially for reverse symmetrical prism): low transmittance for high solar altitude–summer condition, high transmittance for low solar altitude–winter condition. The obtained transmittance characteristics were used as input data for the annual simulation of a typical office in the Czech Republic. The simulation has been performed in TRNSYS and TRNBuild software. The gathered results confirmed, that prismatic glass structure can bring energy savings for both cooling and heating energy demands.

Comparison of symmetrical prism adaptation to asymmetrical prism adaptation in those with normal binocular vision

This study sought to determine whether symmetrical compared to asymmetrical horizontal prisms (base-out or base-in) evoked different rates of phoria adaptation. Sixteen young adults with normal binocular vision participated in a symmetrical phoria adaptation experiment using a 3Δ base-out or 3Δ base-in binocular prism flipper and an asymmetrical phoria adaptation experiment using a 6Δ base-out or 6Δ base-in monocular wedge prism. The experiments were randomized and counterbalanced to reduce the influence of the prism stimulation order. Asymmetrical base-out prism adaptation was significantly faster than symmetrical prism adaptation for subjects with normal binocular vision. Asymmetrical phoria adaptation with base-in prism was not significantly different from symmetrical phoria adaptation implying that there are directional asymmetries (convergent versus divergent eye movements) in the slow fusional component of vergence. Data suggest that a potential interaction between the version system and the slow fusional vergence system may exist. Results have clinical relevance because patients with convergence or divergence insufficiency/excess may potentially show more pronounced differences between symmetrical and asymmetrical phoria adaptation compared to binocularly normal controls. These differences might also be relevant to clinical measurements such as vergence fusional range, which can be measured symmetrically (with Risley prisms in a phoroptor) or asymmetrically (with prism bar).

Eightfold optical encoder with high-density grating.

A novel grating interferometer configuration with eightfold optical subdivision to achieve ultrahigh resolution using a special symmetrical prism is proposed. The optical subdivision is enhanced by four times compared to traditional linear optical encoders. In this work, we take advantage of a high linear density grating of 1780 lines/mm, which is combined with an eightfold optical subdivision configuration. As a result, a high resolution of 68.6 pm is achieved. The apparatus adopts a symmetrical measurement configuration to reduce the error arising from environmental fluctuations. The verification experiments involve high optical subdivision, long- and short-range displacement measurement, and stability, with all results compared to those obtained with a commercial interferometer. The excellent agreement of the results demonstrates the effectiveness of our proposed system.

Experimental characterization of glazing with glass prisms

The principles of design for two types of prismatic elements have been studied. The theoretical approach has been used for design of the glass prisms to optimize their function for given application and geographic location. The two manufactured prismatic glass elements have been applied in triple glazed window samples with a low emissivity coating and experimentally tested to determine the realistic angular selective optical properties. A specific test stand for glass prism transmittance measurement has been developed and applied. The results have been compared with conventional triple glazing with clear glass panes and triple glazing with solar control pane applied, both alternatives with the identical low emissivity coating. Significant advantages of transmittance selectivity (low transmittance for high solar altitude – summer condition, high transmittance for low solar altitude – winter condition) have been proved especially for triple glazing with reverse symmetrical prism. The results open the possible application of the prismatic structures in modern façade envelopes, e.g. curtain walling facades or greenhouse walls as low-cost alternative to other types of shading devices.

ChemInform Abstract: Efficient Complexation Between Pillar[5]arenes and Neutral Guests: From Host—Guest Chemistry to Functional Materials

AbstractReview: [49 refs.

Assessment of internal forces for intermediate anchorage zone of post-tensioned concrete structure

The purpose of this study is to present a simple way to predict the internal forces in the intermediate anchorage zone of post-tensioned concrete structures. Guyon presented the concept of a symmetrical prism and gave a simple equation to denote the relationship between internal forces and an eccentric load at the end anchorage zone. A series of finite element analyses were conducted to obtain the internal stresses for the intermediate anchorage under different eccentric prestressing loads. By use of Guyon’s concept and by integrating stresses, a series of simple equations to assess the internal forces within the intermediate anchorage zone is obtained. The equations were validated through comparing the predicted internal forces using the proposed equations with the values of the internal forces within the ties of the model presented by the International Federation for Prestressing (FIP).

Numerical Evaluation of Symmetric Prism Method to Analyze the Splitting Forces Due to TBM Jack Loads

Final lining in mechanized excavation includes the precast concrete segments. These segments are designed for applied loads during construction, moving, depot, assembling in the tunnel and service loads that are affected by earth conditions. One of these loads that are applied to the segments after assembling in the ring, are TBM jack loads especially when the TBM should excavate squeeze zones with single mode. As the jack pad section is smaller than the segment section, it causes splitting loads in the segment. Symmetric prism method is an approximate solution to evaluate these forces. In this paper, calculated results by this method are compared to that of numerical solution by ANSYS software. It shows 10 - 20 percent difference between numerical and analytical results.

Volume completion in 4.5-month-old infants

In this study, we examined 4.5-month-old infants' visual completion of self-occluding three-dimensional objects. A previous study on this topic reported that 6-month-old, but not 4-month-old infants extrapolate a convex, symmetric prism from a limited view of its surfaces (Soska & Johnson, 2008). As of yet, studies on the development of amodal completion of three-dimensional, self-occluding objects are scarce. Given 4-month-old infants' abilities to derive three-dimensional shape from a variety of visual cues, three-dimensional amodal completion may well depend on the perceptual strength of three-dimensionality in the stimulus displays. The first experiments (1A and 1B) tested this hypothesis by means of a habituation paradigm and showed that 4.5-month-old infants are indeed able to amodally complete the back of a self-occluding object when sufficient three-dimensional cues are available. Further support for volume completion in 4.5-month-old infants was found in a second experiment, again using a habituation paradigm, that measured perceived connectedness between two visually separated, self-occluding, three-dimensional objects.

Parallelepipeds and centrally symmetric hexagonal prisms circumscribed about a three-dimensional centrally symmetric convex body

Let K be a three-dimensional centrally symmetric compact convex set of unit volume. It is proved that K is contained in a centrally symmetric hexagonal prism (or a parallelepiped) of volume $ {{4} \left/ {{\sqrt[3]{3} < 2.7734451}} \right.} $ . This fact implies that space contains a lattice packing of translates of K with density $ {{{\sqrt[3]{3}}} \left/ {{4 > 0.36056}} \right.} $ . Furthermore, K is contained in a parallelepiped of volume $ \frac{4}{3}{\left( {2 + \sqrt {3} } \right)^{{{2} \left/ {3} \right.}}} < 3.2080203 $ . Bibliography: 6 titles.

The initial stage of collapse of symmetric gaseous prisms

An algorithm is developed for calculating the parameters of a shock-free compressible gas of symmetric tetrahedral gas prisms according to a given law of motion of a section of a piston using characteristic series. It is shown that by taking account of symmetry one can determine uniquely the parameters of the gas flow and the piston shape in a compressible prism. Three subdomains are distinguished in the domain of the perturbed gas flow, in each of which a velocity potential is constructed in the form of a characteristic series. In one subdomain, the solution is defined by the specified law of motion of the piston and, in the other two subdomains the solutions are defined by the conditions that no gas flows across the plane of symmetry and the continuity of its parameters at the boundaries along which the subdomains are joined, which are characteristics. An example of the calculation of a solution is given which, in a part of the domain, is identical to a known, self-similar exact solution when the adiabatic exponent and the magnitude of the dihedral angle of the prism are matched. An exact expression is obtained for the velocity potential and the shape of the wall of the gas prism being compressed.

In-line quarter-wave retarders for the infrared using total refraction and total internal reflection in a prism

IR reflection quarter-wave retarders (QWR5) are described that maintain the collinearity of the transmitted and incident beams. One QWR uses a symmetric prism of Ge (refractive index n = 4) with an apex angle of 119 deg. Light incident parallel to the base of the prism is totally refracted, without change of polarization, at the side faces of the prism that are coated with an appropriate transparent bilayer. Total internal reflection at the prism base produces the desired 90-deg retardance. The second QWR uses a right-angle Ge prism with its base coated with a PbTe layer ( n = 5.1) to introduce the required phase shift at a 55.18-deg angle of incidence. The entrance and exit faces are antireflection coated with a polarization-preserving bilayer. Both QWRs are reasonably insensitive to small (±8 deg) angle-of-incidence errors.

Flat-Top Polygonal Temperature Profiles by Laser Beams

AbstractA method was proposed to generate flat-top polygonal temperature distributions in substrates from a Gaussian-shaped laser source. The original Gaussian beam is equally and diametrically separated into several portions and is then rearranged so that the each portion has its peak intensity allocated toward outside. This can be realized by a symmetrical multi-facet prism. A mathematical model was derived to calculate the temperature rise induced the rearranged portions of the laser beam. Flat-top polygonal temperature profiles with two, three, four and six corners have been investigated by numerical calculations. It is shown that flat-top polygonal temperature distributions can be obtained by this method if the distance between the peaks of the beam portions is arranged to be certain proportions to the original Gaussian beam. It is also found the shape of the temperature profile is almost with the same size as the original Gaussian beam size and does not depend on the incident laser power and the substrate material.

Group theoretic reduction of the electromagnetic impedance matrix for large-contrast symmetric prisms in a layered earth

Calculation using integral equations of the electromagnetic response of a geologic body which is much more conductive than the surrounding media requires the use of both current pulse and current tube basis functions. The impedance matrices for such cases can be large and expensive to form, factor, and solve. However, if the surrounding media is layered and the scatterer is symmetric under symmetry operations which preserve the depth of transformed points, then we can apply group representation theory to drastically reduce storage and computation requirements. I discuss this application of group representation theory in detail, using the symmetry groupC 2 ν for purposes of illustration. In a sample calculation for a body which is invariant under the symmetry operations of the groupC 2 ν , storage was reduced by a factor of 4, matrix formation time was reduced by a factor of 2, and the sum of matrix factorization and solution times was reduced by a factor of 10.

Examination of pressing of powders and norplastics using a modeling material

Metallic powders and polymer granules are used on an increasing scale for producing strong and dense materials. The initial material for producing components from these materials consists of solid particles surrounded with voids filled with gas or a solid binder. In compacting, each particle changes its configuration. The dense specimen may be produced from elements of the same form, with a high density, without voids filling the entire space. 24 types of polyhedrons/parallelohedrons [i] may be used for this filling; of these polyhedrons, the suitable ones are the cube, the hexagonal centrally symmetric prism, the dodecahedron, cubo-octahedron. The models of the porous body may be produced in accordance with these polyhedrons [2].

Symmetrical prism as input coupler for integrated optics

Symmetrical prism as input coupler for integrated optics

The bearing strength of plain concrete

An experimental study is described in which a range of rectangular and square blocks was tested to establish their bearing capacity. The blocks were loaded through small embedded steel plates with an axial duct to simulate the configuration of a prestressing anchorage. The bearing capacity is shown to be directly related to the minimum side dimension of the loaded face of the block and to the tensile strength of the concrete. A second phase of the study examines the validity of Guyon's “symmetrical prism” concept by testing blocks loaded through pairs of anchorages. The “symmetrical prisms” associated with each anchorage were chosen to correspond to a single anchor block from the first test series. The investigation forms the first part of a study of the behavior of reinforced anchorage zones in concrete.

The Influence of Scattering Phenomena on the Performances of a 1/r axially symmetric Field Prism electromagnetic Separator

The elastic scattering in an electromagnetic separator with, 1/r axially symmetric magnetic field prism is treated by consideration of three sections on the ion path. Also some observations on the charge – exchange scattering in a device of this kind are given. Two numerical examples show that 1/r prisms compare favourably with the usual homogeneous and nonhomogeneous field separators also from the point of view of scattering phenomena.