Multi-Angular Colorimetric Responses of Uni- and Omni-Directional Femtosecond Laser-Induced Periodic Surface Structures on Metals

We investigated the colorimetric behaviors of metal surfaces with unidirectional low-spatial-frequency laser-induced periodic surface structures (UD-LSFLs) and omnidirectional LSFLs (OD-LSFLs) fabricated using femtosecond laser pulse irradiation. With the CIE standard illuminant D65, incident at −45°, we show that UD-LSFLs on metals transform polished metals to gonio-apparent materials with a unique behavior of colorimetric responses, depending on both the detection and rotation angles, whereas OD-LSFLs have nearly uniform gonio-apparent colors at each detection angle, regardless of their rotation. These colorimetric behaviors can be observed not only at the angles of diffraction but also near the angle of reflection, and we find that the power redistribution due to Rayleigh anomalies also plays an important role in the colorimetric responses of UD- and OD-LSFLs, in addition to diffraction.

EXPRESS: Acoustic Steering Using Thermally Induced Optical Reflection of Sound (THORS)

Using the recently discovered THORS phenomenon, it is possible to generate optically induced, local density barriers in air by the absorption of intense, modulated laser light (the THORS phenomenon), which results in abrupt differences in compressibility of the air at these barriers that can efficiently reflect incident acoustic waves. In this note, we demonstrate the ability to optically manipulate and reflect acoustic waves in air as well as optimize the functional parameters (optical modulation and acoustic frequency) and characterize the effects of common physical parameters, including localized thermal gradients and incident angle of reflection on the efficiency of the resulting acoustic reflection. Finally, the ability to efficiently steer acoustic waves around a physical obstruction using THORS is also demonstrated.

Stochastic analysis of impact mixing of bulk materials in a rotary apparatus

The purpose of this work is to analyze the distribution of bulk materials according to the characteristic parameters of the mixing process at the second stage of processing in a rotary apparatus. The design of the rotary device has a wide range, including for the needs of agriculture, for example, when forming mixtures of mineral fertilizers and multifunctional pyrethroid drugs. At this mixing stage, impact interaction with the bump surface of rarefied flows of bulk components occurs, obtained by scattering the rotating drum by elastic blades at the previous stage of the technological chain. The obtained dependencies between the characteristic angle of dispersion of bulk materials by the specified mixing drum (at the first stage) and the angle of reflection of the corresponding flows from the baffle surface (at the second stage) are used in the stochastic analysis of impact mixing. Modeling of the differential functions of the distribution of the number of particles of mixed bulk components by the angle of reflection from the baffle surface is carried out taking into account the physical and mechanical characteristics of the working materials, design parameters, and operating parameters of the rotary apparatus. The calculation results made it possible to reveal the effective ranges of variation of the characteristic parameters for the shock mixing of bulk materials in a rotary apparatus.

La théâtralité académique. L’usage de la métaphore dans la recherche sociologique

We propose to grasp conferences as an institutional ritual, which deploys a whole institutional theatricality. To do this, we use the metaphor of the orchestra; indeed each participant in the conference plays their part by adjusting to each other. The metaphor of the art of composition allows us to detect the process of shaping the knowledge of an academic text. The wide angle of reflection finds its inspiration in symbolic approaches to communication. The use of the metaphor in the understanding of academic practices, drives us to an imaginary approach framing an image, making analogies between the image and the object under study, to then take advantage of this operation of transposing the meaning of the image to the object of study. We thus have access to a fresh and imaginary angle on the rituals which mark the academic life, and which are not only duty bound. ##plugins.themes.academic_pro.article.details##

Focus-Adjustable Head Mounted Display with Off-Axis System

An off-axis system refers to an optical system in which the optical axis and the normal vector at the vertex of each surface do not match. An off-axis optical system can be applied in order to construct a thin and light optical system. In particular, the optical system used for a see-through head-mounted display (HMD) must be designed asymmetrically, with respect to the optical axis. Because the vision of a human is different for each individual, HMD requires focus adjustment. The effective focal length (EFL) of the optical system must be calculated to obtain the focus adjustment. However, the off-axis optical system cannot be calculated by conventional methods. In this study, the EFL was calculated by rotating the coordinates of the rays near the optical axis by the angle of reflection or refraction at the intersection of each surface, with the rays coinciding with the optical axis. The magnitude of movement of the micro-display for focus adjustment was obtained from the calculated EFL, for a see-through type HMD.

Simultaneous Measurement of BRDF and Surface Curvature by using Pattern Illumination

In this study, we propose the simultaneous measurement method of the bidirectional reflection distribution function (BRDF) and the radius of curvature by using pattern illumination. For nonplanar objects, the angle of reflection light changes according to the surface normal angle of curved object. Therefore, it is necessary to consider the effects of curved surfaces when measuring the BRDF on non-planar surfaces. We suppose a convex surface that can be represented by a constant radius of curvature. The pattern of illumination was generated by placing the illumination mask with pattern apertures in the incident light path of the BRDF measurement apparatus in which the incident light is collimated light. We developed the measurement apparatus. We measured four types of sample with different BRDFs on three different radiuses of curvature. The results showed that the BRDF and the radius of curvature can be measured simultaneously by using the pattern illumination.

Bi-reflection of spin waves

When a light wave is refracted at a boundary between two different media, it may split into two rays due to optical anisotropy, a phenomenon called birefringence. On the other hand, for a reflected light wave in an ordinary medium, the angle of reflection is always the same as the incident angle as expected from the law of reflection. Here, we report the observation of a split of reflected spin-waves, or bi-reflection of spin-waves, where a spin-wave refers to a wavy motion of electron spins in a magnetic material. We measured the spin-wave propagation in a magnetic garnet Lu2Bi1Fe3.4Ga1.6O12 by using time-resolved magneto-optical microscopy and found that the spin-wave splits in two as a result of reflection at the sample edge of an out-of-plane magnetized film. Systematic measurements combined with calculations unveiled that the bi-reflection is due to the hybridization with elastic waves.

Analysis and Optimization of Surface Acoustic Wave Floating Electrode Unidirectional Transducers Using Coupling-of-Mode Theory and Finite-Element Method

The performance of a floating-electrode unidirectional transducer (FEUDT) with acoustic wavelength of 30 μm is analyzed by coupling-of-mode (COM) theory. In order to extract the COM parameters, a finite element model is developed. The obtained dispersion curve shows frequencies of four stopband edges different from one another which meets the necessary condition for FEUDT. The phase shift of reflection and transduction centers is derived from the standing wave distributions of electric potential in the whole substrate. When a/p= 0.92 (electrode width/period) and h/p = 0.015 (electrode height/period), the value of ϕ–ψ = 44.8° (ϕ and ψ are phase angle of reflection and transduction centers, respectively) can be obtained fairly close to the 45°. By analyzing SAW energy transportation characteristics, FEUDT is found that the more periods it has, the better directivity it exhibits.

INVESTIGATION OF THE PROCESS OF INTERACTION BETWEEN ROOT AND AUGER SCREW

Increasing the technological efficiency of root harvesting machines by developing and substantiating new technological processes for the operation of root crop heap cleaning systems is an urgent task. The purpose of the study is to develop theoretical mathematical models of the functioning of the working bodies of treatment systems. Mathematical models of the resulting velocity and the angle of reflection of the root crop from the surface of the auger screw, which is mounted above the working branch of the feed conveyor, were obtained.