Flat Prism Research Articles

Iterative line laser scanning for full profile of polyhedral freeform prism

Polyhedral freeform surface prism is an important optical part, and the measurement of its full profile plays a crucial role in evaluating and improving its manufacturing process. One of the most suitable methods is to combine line laser scanning with multi-degree-of-freedom motion mechanisms to perform scanning measurements on polyhedral freeform surface prisms. Currently, when using line laser for measuring polyhedral freeform surface prisms, there are issues such as insufficient system degrees of freedom, unstable S/N (signal-to-noise ratio) of the light stripe, and high accuracy requirements for the measurement path, resulting in incomplete measurement results. To address the issue of insufficient system degrees of freedom, this paper establishes a five-axis-based line laser scanning system, ensuring measurement accuracy through system calibration. For the problem of unstable S/N of the light stripe in line laser measurement of freeform prisms, this paper proposes a method to evaluate the S/N of the light stripe and confirms the curve of S/N change with view angle through experiments on the measured surface. The optimal view angles for each surface are selected from this curve to obtain light stripe curves with higher S/N. Regarding the issue of increased accuracy requirements for the measurement path due to the view angle selection, this paper proposes an iterative measurement method. By pre-cognizing the part posture, the initial measurement path and results are obtained, and the part posture is iterated continuously based on the measurement results and model information to converge to the actual posture, thus obtaining a high-precision measurement path and achieving full-profile measurement of the part. Full-profile measurements and comparative experiments on standard spheres, flat prisms, and freeform prisms were conducted. Experimental results show that the measurement accuracy of the system can reach the level of 10 µm, and the measurement repeatability can reach the sub-micrometer level. The measurement area can be expanded by about 30% after several iterations, verifying the feasibility of the proposed view angle selection method and iterative measurement method.

Pengaruh Model Problem Based Learning dengan Pendekatan STEM Terhadap Kemampuan Berpikir Kritis Matematika Siswa SMP

This research is based on the lack of students critical mathematical thinking skills in solving surface area and side volume problems flat prisms and pyramids. This research aims to test whether there are differences significant application of the Problem Based Learning (PBL) model with a STEM approach (Science, Technology, Engineering, Mathematics) on critical thinking skills mathematics for junior high school students. This type of research is quantitative research with an experimental method of pretest-posttest control group design. The research population was class VIII students SMP Negeri 4 Tuban with a research sample of class VIII-B students (experimental class) and class VIII-F (control class) which was selected using a random sampling technique. Technique data collection is a test of critical thinking. From the results of data analysis using the t-test it can be concluded that there is a significant difference in the application of the PBL model with STEM approach to critical thinking skills in mathematics in class VIII junior high school students Negeri 4 Tuban.

Ultra-high-frequency radio-transparent ceramics of cordierite composition doped with MgO–Al2O3–B2O3–SiO2 glass: Synthesis, microstructure, thermal and physical properties

The paper presents the results of a study of radio-transparent cordierite ceramics, in which a part of the components was introduced using the eutectic glass of the MgO–Al2O3–SiO2 pseudoternary system. The formation of α-cordierite occurs during the sintering of ceramics due to the intensive interaction of components of the eutectic glass with crystalline fillers, as well as due to the crystallization of glass. At the same time, densely sintered material was obtained at relatively low temperatures (1300–1350°С). The crystalline phase of α-cordierite fully forms the structural matrix of the ceramic material. Crystals of the cordierite phase are formed in the form of regular-shaped flat prisms, mostly 1–3 μm in size. The pores between cordierite crystals are completely filled with glassy phase, which ensures their strong connection, uniform and dense microstructure of the material, as well as high strength, dielectric and thermal characteristics.

Prism Couplers with Convex Output Surfaces for Nonlinear Cherenkov Terahertz Generation

Sideways THz generation in Mg:LiNbO3 crystal is studied considering Si-prism-lens couplers with different output surface curvatures. A theoretical approach is developed for modeling the angular distributions of THz radiation power inside the crystal, inside the Si coupler and outside in free space. Our calculations show how the imposition of a plano-convex lens on the standard flat prism can substantially improve the THz generation efficiency. The ratio between the lens curvature radius and the distance from the curvature center to the point of generation on the lens axis is found to be one of the most important parameters. The developed general approach can be used for the further design of the optimal THz extraction elements of a different configuration.

A Low-Profile, Risley-Prism-Based, Beam-Steerable Antenna Employing a Single Flat Prism

We present a low-profile, mechanically beam-steerable antenna that implements the Risley prism beam-steering concept using only a single flat prism. The proposed antenna achieves 2-D beam steering and consists of two parts: a holographic leaky-wave antenna and a phase-shifting surface (PSS) that acts as a flat prism. The lower holographic leaky-wave antenna acts as the feed for the prism and provides a phase-shifting gradient over its output aperture. When paired with the flat prism, the system can provide 2-D beam steering by mechanically rotating the two layers against each other. Unlike conventional Risley-prism-based beam-steerable antennas, the proposed approach results in a very low-profile antenna and does not need spatial illumination of a two-prism system with a separate feed antenna. The flat prism is implemented using a PSS consisting of low-pass, hexagonal-shaped, spatial phase shifters. A prototype antenna with an overall thickness of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.1\lambda _{0}$ </tex-math></inline-formula> at 10 GHz was designed, fabricated, and experimentally characterized. Measurement results agree well with theoretical predictions and both show wide-angle beam scanning ranging from 0° to 57° in the elevation plane and 0° to 360° in the azimuth plane. The proposed antenna system has an equivalent aperture diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.1\lambda _{0}$ </tex-math></inline-formula> and a measured peak gain of 22.3 dBc at 10 GHz corresponding to an aperture efficiency of 34.5%. The proposed concept is expected to be useful in designing low-profile, beam-steerable antennas in which the scanning speed can be traded off to reduce system complexity.

A new performance test to evaluate the sulfate resistance of concrete by tensile strength measurements

Concrete structures without sufficient durability can be damaged by sulfates in groundwater and from surrounding rock layers. To evaluate the performance of a concrete mixture, precise and performance-oriented test methods are a must. Therefore, a new a performance oriented concrete test procedure based on tensile strength measurements was developed considering experiences reported in international literature and recommendations of state-of-the-art reports. A vast parameter study with approx. 3850 tensile tests on ASTM briquets, 1900 flexural tensile tests on standard prisms and 2100 expansion tests on mortar flat prisms of different ages and with different storage conditions was statistically assessed. Based on the results a performance-oriented test method could be defined which considers not only the chemical, but also the physical resistance of a concrete against sulfate attack. The method was verified by 23 concretes with different cements or cement fly ash combinations and additional field tests. It could clearly be demonstrated that the results represent the performance of a practical concrete in case of sulfate attack. Furthermore, it leads much faster to an evaluation of the sulfate resistance compared to the most other practical oriented methods.

Removal of Congo Red From Aqueous Solutions at Hardened Cement Paste Surfaces

The removal of azo dyes is a critical issue in current textile industry wastewater treatment. In contemporary wastewater management, many structures that are in direct contact with wastewater are constructed with concrete. In this contribution, the removal of Congo red from aqueous solutions by the material in the surface of hardened binder paste was studied in multiple exposure experiments. Flat prisms made with ordinary Portland cement (OPC) and ground granulated blast-furnace slag (GGBS) were stored in different aqueous solutions. The powdered surface material of these flat prisms was used as a substrate for the removal of Congo red from aqueous solutions. Storage in sodium sulfate solution lead to the formation of hydrotalcite nanosheets on the surfaces of hardened binder pastes rich in magnesium provided by the GGBS. These nanosheets resulted in a large specific surface area and increased the discoloration capacity with respect to binder mass. The results also suggest that the carbonation of ettringite and C-S-H can provide fresh calcite that can act as a secondary adsorbent. The results of this study suggest that cementitious binders with high magnesium contents could contribute to the removal of azo dyes from industrial wastewater by providing economically attractive treatment materials.

No Useful Field Expansion with Full-field Prisms.

Full-field prisms that fill the entire spectacle eye wire have been considered as field expansion devices for homonymous hemianopia (HH) and acquired monocular vision (AMV). Although the full-field prism is used for addressing binocular dysfunction and for prism adaptation training after brain injury as treatment for spatial hemineglect, we show that the full-field prism for field expansion does not effectively expand the visual field in either HH or AMV. Full-field prisms may shift a portion of the blind side to the residual seeing side. However, foveal fixation on an object of interest through a full-field prism requires head and/or eye rotation away from the blind side, thus negating the shift of the field toward the blind side. We fit meniscus and flat full-field 7Δ and 12Δ yoked prisms and conducted Goldmann perimetry in HH and AMV. We compared the perimetry results with ray tracing calculations. The rated prism power was in effect at the primary position of gaze for all prisms, and the meniscus prisms maintained almost constant power at all eccentricities. To fixate on the perimetry target, the subjects needed to turn their head and/or eyes away from the blind side, which negated the field shift into the blind side. In HH, there was no difference in the perimetry results on the blind side with any of the prisms. In AMV, the lower nasal field of view was slightly shifted into the blind side with the flat prisms, but not with the meniscus prisms. Full-field prisms are not an effective field expansion device owing to the inevitable fixation shift. There is potential for a small field shift with the flat full-field prism in AMV, but such lenses cannot incorporate refractive correction. Furthermore, in considering the apical scotoma, the shift provides a mere field substitution at best.

Simple Prediction Method for Rubber Adhesive Friction by the Combining Friction Test and FE Analysis

In the design and development of rubber products, it is important to evaluate the contact load dependency of the friction coefficient. In particular, since the pressure distribution varies depending on the dimensions of sliding bodies and the pattern of the contact surface, a simplified and accurate evaluation method that can take these influences into account is desired. In this study, we proposed a prediction method for the adhesive friction between rubber specimens of arbitrary shapes with arbitrary roughness and a smooth hard surface, by combining the: (1) friction theory considering the influence of roughness; (2) basic friction test; and (3) finite element analysis. Further, we verified the effectiveness of the proposed method by comparing the predicted results with the measurement results of friction between a hemispherical PDMS specimen and a PMMA flat plate and between a PDMS block specimen with a grooved surface and a flat prism. Results show that the prediction accuracy of the contact load dependency of the friction coefficient is reasonably good.

Seeds mediated synthesis of giant gold particles on the glass surface

Herein, we present the protocols of synthesis of two types of gold particles which are in the great interest for the purpose of molecular electronics. The first type is the flat prisms with a triangular/hexagonal shape and a lateral size up to ~ 80 µm. They were synthesized directly on a glass surface pretreated with (3-aminopropyl)-triethoxysilane molecules. The second type of particles was synthesized with using gold seeds with diameter of 18 nm. These seeds were deposited on a glass surface coated with APTES. The resulted three-dimensional structures with a form close to spherical increase in size up to 0.5–0.08 µm. Moreover, these particles grew up separately and did not merge during 48 h of synthesis.

Constraints on interpreting magnetic spectral depths

It is now possible to automate the extraction of magnetic depths over large areas as depth profiles. A depth profile is a graph of the probability of a layer at each depth. Presented in the form of a transect, depth profiles allow layers to be traced across significant distances. The appearance of discontinuous layers, and multiple layers, raises questions for interpretation, here addressed with modelling.Modelling of layers requires simulating the heterogeneity of the material. Accordingly, a method of modelling is demonstrated where flat prisms are populated with very large numbers of dipoles and their fields accumulated for spectral analysis.Thick layers give a depth signal in the transects about 20 m below their top surface. The distinction is minor given that the layer is assumed to extend across a 20 km square.In general, only one depth signal credibly represents the depth of its source. Multiple layers can be picked out on traverses when the deeper layer is sufficiently more magnetised than the layer above it. A weaker depth signal appears closer to a stronger signal. Signals within 100 m of each other tend to merge.The sensitivity of the method is significantly better when the survey has been flown north-south rather than east-west.Near-surface layers are not picked up by the method. The sampling frequency of the original survey dictates how close to the surface estimates can be provided. A rough rule of thumb is that no reliable depth estimates can be expected for sources shallower than half the flight line spacing.

Characterization of the multilayered shell of a limpet, Lottia kogamogai (Mollusca: Patellogastropoda), using SEM–EBSD and FIB–TEM techniques

The microstructure and its crystallographic aspect of the shell of a limpet, Lottiakogamogai, have been investigated, as the first step to clarify the mechanism of shell formation in limpet. The shell consists of five distinct layers stacked along the shell thickness direction. Transmission electron microscopy (TEM) with the focused ion beam (FIB) sample preparation technique was primarily adopted, as well as scanning electron microscopy (SEM) with electron back-scattered diffraction (EBSD). The five layers were termed as M+3, M+2, M+1, M, M-1 from the outside to the inside in previous works, where M means myostracum. The outmost M+3 layer consists of calcite with a "mosaic" structure; granular submicron sub-grains with small-angle grain boundaries often accompanying dislocation arrays. M+2 layer consists of flat prismatic aragonite crystals with a leaf-like cross section, stacked obliquely to the shell surface. It looks that the prismatic crystals are surrounded by organic sheets, forming a compartment structure. M+1 and M-1 layers adopt a crossed lamellar structure consisting of aragonite flat prisms with rectangular cross section. M layer has a prismatic structure of aragonite perpendicular to the shell surface and with irregular shaped cross sections. Distinct organic sheets were not observed between the crystals in M+1, M and M-1 layers. The {110} twins are common in all aragonite M+2, M+1, M and M-1 layers, with the twin boundaries parallel to the prisms. These results for the microstructure of each layer should be considered in the discussion of the formation mechanism of the limpet shell structure.

Polymorphism and phase transformations in cobaltacarborane molecular crystals

The full study of polymorphism in the cobaltacarborane closo-[3-Co(η5-C5H5)-1,2-C2B9H11] (1) compound by a combination of X-ray diffraction, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), IR and hot-stage microscopy (HSM) is reported for the first time. The previously reported Form I (orthorhombic Form, noncentrosymmetric space group P21212) crystallizes as dark yellow to orange flat prisms from polar dichloromethane. A new centrosymmetric modification (Form II) that crystallizes from a mixture of polar and non-polar solvents has been found. Form II crystallizes as pleochroic orange blocks in the monoclinic crystal system and space group P21/c. Phase transformation between both polymorphs has been observed by DSC, IR and HSM, showing that the centrosymmetric Form II (kinetic) converts irreversibly to the noncentrosymmetric Form I (thermodynamic).

Synthesis and Optical Properties of Gold Nanodecahedra with Size Control

The synthesis of nanoparticles with a tight control on their size and shape is a requirement for the achievement of many nanotechnology goals, since these are the main parameters determining the material properties at the nanoscale. Among the many different materials currently under investigation, semiconductor and metal nanoparticles are extremely attractive because of the possibility of controlling their electronic and optical properties through tailoring size and shape during synthesis. For instance, the presence of sharp edges or tips has been shown to increase electric-field enhancement, [1] which is important for applications involving metal nanoparticles as sensors. Additionally, nanoparticle morphology will ultimately determine the way in which nanoparticles can be assembled. While spheres, rods, cubes, and flat prisms are the most thoroughly studied shapes, there have been several reports on the synthesis and detailed characterization of other geometries, and it is believed that metal nanoparticles tend to grow with the structure of one of the Platonic solids, that is, with all faces made of the same regular polygon and the same number of polygons meeting at each corner. [2–4] Non-Platonic structures that have been reported for metal nanocrystals include nanorods, either with the geometry of single-crystal or pentatwinned prisms, [5–9] as well as flat platelets, usually with triangular or hexagonal shape, [10–13] in which faces are made of more than one polygon. Recently, other elaborate geometries have also been reported, such as nanocages [14] or nanostars. [15] In this paper we report the synthesis with tight size control and high monodispersity of nanometer-sized, uniform gold nanoparticles with decahedral morphology, in which all ten faces are equilateral triangles, but not the same number of triangles meet at every corner (four or five are possible), and for this reason they do not qualify as Platonic nanocrystals, but can rather be classified as Johnson structures. These decahedral particles have a lower symmetry (D5h) than Platonic solids, but still display a striking beauty and attractive optical properties that are strongly influenced by particle size. Although the geometry (and thus the aspect ratio) is precisely the same for particles with different sizes, clear changes in the optical responses have been observed and modeled through a boundary element method (BEM) for bicones. The synthesis is based on our previous work where N,N-dimethylformamide (DMF) was used as both solvent and reducing agent [16] to generate silver nanoparticles of various shapes, including spheres, [17] nanoprisms [18] and nanowires. [19] The

プリズム方式採光システムの光搬送ダクトに関する実験的研究

プリズム方式採光システムの光搬送ダクトに関する実験的研究

A super-precision linear slideway with angular correction in three axes

This paper describes a single-axis ultra-high-precision translation stage designed and built using almost exclusively the very-low-thermal-expansion ceramic Zerodur. The device is a test-bed for design principles which may be widely applied for various purposes of different precision. It has compensation for pitch, roll and yaw built into the mechanism through the incorporation of three angular sub-stages. The sliding carriage stands on five PTFE pads to form a single-degree-of-freedom kinematic constraint giving rectilinear traverse along an optically flat prism. The translation resolution is at the ångstrom level and the angular adjustments are at the sub-arc-second level, with some at the milli-arc-second level, while possessing coarse adjustments with large range. Performance tests using an optical interferometer are reported and the stage's behaviour in the elastic and sliding region is studied to understand where the limits of the technology lie.

Light enhancement using E-W aligned long prismatic arrays at high latitude

A computer model to evaluate and optimize the light gain produced by downwardly transmitting or reflecting low elevation winter sunlight is described. Verification of the model is by comparison with the experimental enhancement of winter sunlight provided by two different prismatic arrays. One, of perspex, redirects light both southerly and northerly, the other, of glass, is mounted to transmit light only. Manufacturing irregularities, such as curvature induced in nominally flat prism surfaces, are successfully encompassed within the model and can be used as additional design parameters.

4‐[Tri(n‐butyl)phosphonio]‐2,5‐diselenoxo‐1,3‐diselenacyclopentanide

A new type of phosphorus ylide is represented by the title compound 1, which is obtained as dark red, flat prisms in high yields from CSe2 and nBu3P. Derivatives of 1 might exhibit the properties of “organic metals.”