Refractive beam steering

Capillary pressure force and direct surface tension force are known to be sufficient though probably not necessary to drive the compaction stage of latex film formation. There is abundant evidence that van der Waals force can draw particles together progressively more around the perimeters of interparticle contacts, but their role in compaction remains unanswered. With the powerful technique of high-resolution cryogenic scanning electron microscopy (cryo-SEM), together with fast-freezing and freeze-drying followed by controlled annealing at temperatures below and around the nominal glass transition temperature, we have documented the role of van der Waals force in film formation in the water-free condition, i.e., with capillary pressure and surface tension forces absent. Results of imaging the freeze-dried and annealed coatings are fully consistent with the hypothesis that van der Waals force alone can compact a latex coating. The rate at which particles flatten and thus the coating compacts by annealing increases, as expected, with temperature and time. The results of rewetting tests of coatings annealed at various temperatures demonstrate that compacted coating is not necessarily coalesced, and that even full compaction of solid particles can be elastic, hence reversible, rather than viscoelastic or viscoplastic. Some of the results suggest that soluble ionic surfactant and oligomeric and grafted polymeric stabilizers at particle surfaces, collapse to undetectable dimensions during freeze-drying, yet reswell to detectable size during rewetting, if they have not dissolved into polymer particles during annealing.

We introduce a method of adaptively modifying the screen display to eliminate the ghost fringes observed in deflectometry optical testing. First, the reflection areas on the screen for both front and rear surfaces are labeled by multi-scale Fourier parallel single-pixel imaging (MS-PSI). Then, high-quality front surface information will be obtained by casting the fringe patterns only on the labeled region rather than the whole screen with the traditional phase shift method. Finally, the remaining mixed signals, which are located in the center part, will be filtered out by classic spatial filtering. A plano-convex lens and a plano-concave lens are used to verify the experimental results of the method, and the final reconstruction accuracy reaches sub-microns.

The precise effect of wavelength on the judgment of critical flicker frequency (CFF) has been a controversial issue for a number of years. Some studies report no effect of wavelength; other studies indicate that wavelength is a basic determiner of the CFF threshold. The purpose of this study was to attempt a resolution of the controversy by means of a systematic and thorough investigation of the problem. The apparatus used was the Fordham calorimeter. By means of monochromators it was possible to deliver various spectral colors with a constant passband of 10 mμ to the subject. The intensity of the light source was controlled by means of neutral tint filters and an optical wedge. Flicker was produced by intercepting the beam of light with a sector disk driven by a Graham variable-speed motor. Eight wavelengths covering most of the range of the visible spectrum were used, and CFF thresholds were obtained at seven different luminance levels in eight experimental sessions for each wavelength. Three subjects with normal color vision were employed.The results showed that the wavelength of the stimulating light changes the slope of the curve relating CFF to log I. The curves at the blue end of the visible spectrum are steeper than those at the red end. Furthermore, the greater the separation between wavelengths, the greater is the probability of a significant difference between slope values. The fact that the slopes of the curves differed with wavelength does not mean that the Ferry–Porter law is invalid, but rather that one should adjust the "constants" of the equation for the particular wavelength being used. Consequently, it can be stated that CFF is a function of the wavelength of the stimulating light. The most explicit interpretation that could be made was that this change reflected some sort of change in the receptor system of the eye.

Focus on nanotechnology, lasers, and imaging

This paper demonstrates the design of high efficiency OLEDs by incorporating micro/nano-metric structures on the surface of and inside the substrate layer of the OLEDs. The OLEDs have been designed and simulated using Lumerical FDTD simulator. We also analyze the performance of the OLEDs from various perspectives such as quantum efficiency, normalized transmitted power, intensity, and angular distribution of light. To increase light extraction from the substrate layer, various micro/nano-metric structures, made of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , have been incorporated as light scattering structures. Single layer structures of various size, shape (plano-convex & plano-concave lenses and pillars), and period have been investigated during our simulation. Simulation results confirm higher light extraction, angular distribution, and efficiency in micro/nano-metric structures induced OLEDs, compared to traditional OLEDs. Plano-concave MLA engraved OLEDs show high out-coupling efficiency, whereas, nano-pillars engraved OLED shows consistent light distribution in a wide angular region. We strongly believe that, the proposed OLEDs will have wide range of commercial applications.

A novel type of liquid microlens, bounded by a microfabricated, distensible membrane and activated by a microfluidic liquid-handling system, is presented. By use of an elastomer membrane fabricated by spin coating onto a dry-etched silicon substrate, the liquid-filled cavity acts as a lens whereby applied pressure changes the membrane distension and thus the focal length. Both plano-convex and plano-concave lenses, individual elements as well as arrays, were fabricated and tested. The lens surface roughness was seen to be approximately 9 nm rms, and the focal length could be tuned from 1 to 18 mm. This lens represents a robust, self-contained tunable optical structure suitable for use in, for example, a medical environment.

Utilization of lauric acid-myristic acid/expanded graphite phase change materials to improve thermal properties of cement mortar

Carbon foam was prepared from carboxymethyl cellulose (CMC) and Ag, Al and carbon nanotubes (CNTs), and graphene was added to the foam individually, to investigate the enhancement effects on the thermal conductivity. In addition, we used the vacuum method to impregnate erythritol of the phase change material (PCM) into the carbon foam samples to maximize the latent heat and minimize the latent heat loss during thermal cycling. Carbon foams containing Ag (CF-Ag), Al (CF-Al), CNT (CF-CNT) and graphene (CF-G) showed higher thermal conductivity than the carbon foam without any nano thermal conducting materials (CF). From the variations in temperature with time, erythritol added to CF, CF-Ag, CF-Al, CF-CNT, and CF-G was observed to decrease the time required to reach the phase change temperature when compared with pure erythritol. Among them, erythritol added to CF-G had the fastest phase change temperature, and this was related to the fact that this material had the highest thermal conductivity of the carbon foams used in this study. According to differential scanning calorimetry (DSC) analyses, the materials in which erythritol was added (CF, CF-Ag, CF-Al, CF-CNT, and CF-G) showed lower latent heat values than pure erythritol, as a result of their supplementation with carbon foam. However, the latent heat loss of these supplemented materials was less than that of pure erythritol during thermal cycling tests because of capillary and surface tension forces.

Among the boundary value problems of hydrodynamics of viscous fluid, an important from a practical point of view the class of tasks in the region with a free (previously unknown) boundary, which is determined in the process of direct solving, is distinguished. One of the possible approaches to solving such problems in such an area is a method of hydrodynamic potentials, which translates the basic complexity of research and numerical calculations into certain boundary integral equations, which relate only to the boundary of a given region and take into account the boundary conditions directly. This approach allows you to immediately identify unknown values at the boundary without calculating them in the entire area. This advantage distinguishes the method of boundary integral equations from other methods. The aim of the research was to develop a method for numerical solution of the problems of the viscous fluid movement with a previously unknown boundary. The problem of deformation of a viscous elliptical cylinder under the action of forces of surface tension is formulated and solved in the article. The boundary integral equations are used, which are considered together with the kinematic contour condition. An algorithm for the steps of the numerical solution of the system of boundary integral equations for the problem of viscous fluid with a previously unknown boundary was implemented and computational features were analyzed. On the basis of the conducted research the regularities of the deformation process of the viscous elliptical cylinder under the influence of the forces of surface tension, depending on the viscosity of the liquid and the coefficient of surface tension , were established. A convex contour with continuous curvature deforms into a circle, carrying out fading oscillations around the equilibrium position. Zones of stable synchronous oscillations of points of the contour around the equilibrium position are observed, if , and when , ; in both cases, the density of the liquid was taken equal to one. The liquid body reaches the equilibrium position without oscillation, if . Key words: nucleus, contour discretization interval, curvature, value of the Cauchy integral, surface tension forces, elliptic cylinder

Numerical investigation of interfacial dynamics for the melt pool of Ti-6Al-4V powders under a selective laser

A real-time distance sensing system based on single vision is necessary to obtain distance information and the image at the same time for Advanced Driver Assistance System (ADAS). The sensor system developed in my laboratory uses barrel with three lenses. By simulation of CodeV software for the lens barrel, combination of two plano-convex lenses and one concave-convex lens was optimized for converging to CIS with 90.6% at 17lp/mm and 37.6% at 51lp/mm for f/14 in Modulation Transfer Function (MTF). This paper reports the fabrication of plano-convex lens using only one mask by microfabrication. Diameter and plane surface of lens was determined by using cavity on silicon substrate. The height of glass cylinder depends on Chemical-Mechanical Polishing (CMP) and the glass cylinder transforms to lens with spherical surface in thermal reflow process at 850°C. Whole system including lens barrel has a few cubic centimeter size favorably compared with Lidar and stereo vision.

Capillary constant and surface tension of propane (R-290) with small additives of hydrogen

In this paper we describe the work on application of hot embossing process to fabrication of micro-optical elements transmitting in the visible, near infrared and mid-infrared part of spectrum, using multi-component soft glasses as starting materials. Description of used hot embossing (HE) process is provided, followed by discussion of rheological and viscosity properties of several glass types considered for demonstrator fabrication experiment. Demonstrator microlenses were fabricated from lead-bismuth-gallium oxide (PBG08) and tellurite glasses (TWPN/I/6), with transmission windows extending from the visible up to the mid-infrared (up to around \(6.5\,\upmu {m}\)). Fabricated elements, which included diffractive and refractive lenses and lens arrays, were examined in context of homogeneity (quality of pattern replication) and obtained optical properties (\( {M}^{2}\), focal length, resolution). A demonstrator microscope objective was constructed using refractive plano-concave, plano-convex and biconvex lenses fabricated with the HE setup and its optical characteristics were provided.

Fluidic adaptive lenses with a transformable lens type were demonstrated. By adjusting the fluidic pressure, not only can the lens properties, such as the focal distance and numerical aperture, be tuned dynamically but also different lens types, such as planoconvex, planoconcave, biconvex, biconcave, positive meniscus, and negative meniscus lenses, can be formed. The shortest focal length for a 20 mm aperture adaptive lens is 14.3 mm when the device is transformed into a positive lens, and −6.3 mm when transformed into a negative lens. The maximum resolution of the fluidic lens is better than 40 line pairs/mm.

Biomimetic synthesis of craspedia globosa-shaped Na3V2(PO4)3 with high performance for sodium ion batteries