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Antireflective surfaces, with their great potential applications, have attracted tremendous attention and have been the subject of extensive research in recent years. However, due to the significant optical impedance mismatch between a metal surface and free space, it is still a challenging issue to realize ultralow reflectance on a metal surface. To address this issue, we propose a two-step strategy for constructing antireflective structures on a Ti-6Al-4V (TC4) surface using nanosecond and femtosecond pulsed lasers in combination. By controlling the parameters of the nanosecond laser, microgrooves are first scratched on the TC4 surface to reduce the interface reflection. Then, the femtosecond laser is focused onto the sample surface with orthogonal scanning to induce deep air holes and nanoscale structures, which effectively enhances the broadband absorption. The antireflection mechanism of the dual-scale structures is discussed regarding morphological characterization and hemispherical reflectance measurements. Finally, the modified sample surface covered with micro-nano hybrid structures is characterized by an average reflectance of 3.1% over the wavelengths ranging from 250 nm to 2250 nm. [ABSTRACT FROM AUTHOR]

As carbon fiber reinforced polymer (CFRP) have been widely used as the main material of aeronautic load-carrying parts, there are more and more demands of relevant machining work. Due to the significant anisotropy of CFRPs, defects may easily occur in the machining process. This paper investigated the stress state of carbon fiber and resin microelements and the formation mechanism of machined surface defects at the micro level, and analyzed the fracture mechanism of carbon fibers and its effects on machined surface morphology at various fiber orientation angles θ in the process of CFRP cutting. The results revealed that the cutting mechanism under parallel fiber cutting conditions is the interface layering separation dominated by in-plane shear stress and the machined surface is relatively flat and smooth; the cutting mechanism under perpendicular fiber cutting conditions is shear-fracture separation dominated by shear stress and the machined surface is mainly characterized by regular fiber cross fractures; the cutting mechanism includes the interface layering separation and shear-fracture separation, and the machined surface is characterized by a regular fluctuating surface composed of fiber cross fractures with fiber orientation angle 0° < θ < 90°; the cutting mechanism is the bending fracture separation dominated by in-plane bending stress and the machined surface is mainly characterized by pits with fiber orientation angle 90° < θ < 180°. [ABSTRACT FROM AUTHOR]

We study the principal configurations around an isolated η -umbilical point on a generic spacelike surface S immersed in a null hypersurface M of Minkowski space R 1 4 relative to a well-defined null vector field η orthogonal to the surface S. In the particular case of M being a null rotation hypersurface of R 1 4 we also recover the local Darbouxian principal configurations around that kind of η -umbilical points. [ABSTRACT FROM AUTHOR]

Retinal axons project to their central targets along two orthogonal topographic axes, anterior-posterior (A-P) and dorsal-ventral (D-V). While ephrin-A/EphA signaling determines A-P topography, little has been known about the molecular mechanisms guiding axons along the D-V axis. Two papers by Mann et al. and Hindges et al. in this issue of Neuron provide evidence for both forward and reverse ephrin-B/EphB signaling in regulating D-V topography. [Copyright &y& Elsevier]

One challenge for current surface acoustic wave (SAW) biosensors is reducing nonspecific adsorption. A device propagating Rayleigh and shear horizontal surface acoustic waves in orthogonal directions fabricated in ST quartz has the capability of achieving simultaneous detection and nonspecific binding (NSB) protein removal. Current measurement methods for a SAW sensor system based on this device require large-size and expensive equipment such as a vector network analyzer (VNA), signal generator, and frequency counter, which are not suitable for portable, especially point-of-care, applications. In this work, a portable platform based on a direct digital synthesizer (DDS) is investigated for the orthogonal SAW sensor, integrating signal synthesis, gain control, phase/amplitude measurement, and data processing in a small, portable electronic system. This prototype was verified for both stability and repeatability, and the results matched very well with VNA measurements. Finally, system performance in real-time sensing and NSB removal was evaluated. [ABSTRACT FROM AUTHOR]

In AHWR rod bundle assembly, LOCA could cause failure of the system due to overheating. To overcome this problem, it is proposed to introduce holes in the axial and circumferential direction of central water tube so that water discharges through these holes in the form of a jet and strikes the high-temperature fuel rods resulting in their cooling by gravity-driven flow mechanism. This cooling involves a different mechanism of heat transfer such as two-phase flow, single phase jet impingement, droplet impingement, evaporation, natural convection, and radiation due to the high temperature of the fuel rods. Among all these heat transfer mechanisms, the present study focuses on the horizontal water jet impingement on a vertically oriented surface. The scarcity of research in such cases is the motivation to study the hydrodynamics of the water jet impingement on a vertically oriented surface. A proper understanding of hydrodynamics of the water film on a vertical surface is important in the understanding of heat removal processes. Present study discusses the hydrodynamics of falling water films on a flat surface and a curved surface exposed to horizontal water jet impingement. Effect of the jet exit to surface distance (Z/d), Reynolds number, nozzle diameter (d), and the ratio of curvature of the surface to the diameter of the pipe (D/d) were examined on lateral and vertical spread of the water film at vertically oriented flat and curved surface. [ABSTRACT FROM AUTHOR]

Due to the characteristic of transmitting multiplexed signals in superposed mode over the same spectrum, non-orthogonal multiple access (NOMA) technology is deemed as a promising way to improve spectral efficiency in fifth generation (5G) networks. In this paper, we develop a NOMA cooperative system based on the two-path successive relaying concept, in which the data at the source node is divided into two parallel parts and is transmitted to the destination in superposed mode via the assistance of two amplify-and-forward (AF) relays. On the condition that the transmit power of the individual nodes and the entire system are all constrained, the maximization of achievable rate is formulated as an optimization problem. Following the guidelines of Karush-Kuhn-Tucher (KKT) conditions, the dual decomposition method is adopted to obtain the closed-form expressions of the optimal power allocation. Moreover, to balance the achievable rate between two superposed signals, which is equivalent to minimizing the required spectrum bandwidth, a power allocation scheme between the superposed signals is proposed. In order to verify the effectiveness and efficiency of the proposed power allocation scheme, we conduct extensive numerical simulation on some realistic system setup. The results demonstrate that our analytical insights about the optimal power allocation are aligned with the simulation outcome. [ABSTRACT FROM AUTHOR]

A novel method is proposed to detect the horizontal shift of a specific nanoblock relative to a reference nanoblock using surface plasmon modes at nanometer resolution. To accomplish this task, two orthogonal localized surface plasmon resonances were excited within the air gap region between the silver nanoblocks at the respective wavelengths, 890 nm, and 1100 nm. This technique utilized the scattering far-field intensities of the two block nanostructures at the two specific wavelengths at two specific directional spots. The ratio of the scattering intensities at the two spots changed according to the horizontal shift of the block that moved. Correspondingly, this ratio can be used to provide the precise location of the block. This method can be applied to many fields, including label-free bio-sensing, bio-analysis and alignment during nano-fabrication, owing to the high resolution and simplicity of the process. [ABSTRACT FROM AUTHOR]

In this paper, a scheme of phase gradient metasurface (PGM) coupler was proposed to realize a high-efficiency spoof surface plasmon polariton (SSPP) excitation, and the excitation can be independently designed for two orthogonal linear polarized incident waves. Based on an anisotropic Jerusalem cross metasurface unit cell, the responses for orthogonal linear polarized incidence are affected by different structural parameters. The phase gradient can be designed independently for two orthogonal linear polarized incidences, and then the excitation of SSPPs can be designed independently for two orthogonal polarizations. As proof of the concept, two PGM couplers at 10 GHz were designed to couple the orthogonal linear polarized incidences into orthogonal directions and opposite directions, respectively. Both simulations and measurements demonstrate that the excitation of SSPPs under orthogonal polarizations can be designed independently. [ABSTRACT FROM AUTHOR]

The goal of this study is to present a framework that allows cine images in orthogonal planes to be reconstructed simultaneously using slice-interleaved acquisitions and k-t GRAPPA. Slice-interleaved acquisitions can be interpreted as an undersampled k-t space in which data are desired at skipped frames. Local spatiotemporal correlations can be exploited to interpolate the skipped data to reconstruct images in orthogonal slice groups simultaneously. An in vivo experiment was performed in which interleaved sagittal and coronal balanced steady-state free-precession data were acquired in the abdomens of volunteers breathing normally. k-t GRAPPA weights were calculated from separate calibration scans and applied to the slice-interleaved data. The images from the interpolated frames have a similar contrast to the acquired frames, and the use of k-t GRAPPA improved the anatomical alignment between the orthogonal images in the presence of motion. The k-t GRAPPA reconstruction of slice-interleaved data is a promising method for obtaining cine images of orthogonal slices simultaneously with arbitrary contrast. [ABSTRACT FROM AUTHOR]

In this paper, we present an efficient scheme for remote state preparation of arbitrary n-qubit states with real coefficients. Quantum channel is composed of n maximally two-qubit entangled states, and several appropriate mutually orthogonal bases including the real parameters of prepared states are delicately constructed without the introduction of auxiliary particles. It is noted that the successful probability is 100% by using our proposal under the condition that the parameters of prepared states are all real. Compared to general states, the probability of our protocol is improved at the cost of the information reduction in the transmitted state. [ABSTRACT FROM AUTHOR]

Representations of atomic orbitals based on Monte-Carlo (MC) approaches are not always correct when using various sets of orthogonal coordinates other than Cartesian coordinates. The analysis proposed here gives elements for a proper use of MC methodology. It can be very useful for students and for teachers. [ABSTRACT FROM AUTHOR]

What happens to a liquid in a swing or a loop? Accelerated motions lead to effects that may seem surprising. Consider a liquid in a glass placed on a wooden triangle, in turn attached to a string and moving fast in circle a vertical plane. The surface of the water remains parallel to the bottom of the glass—and orthogonal to the string—as long as gravity and the tension in the string are the only forces acting on the triangle. A key to the understanding is that the tangential acceleration of the liquid, the glass and the triangle, are all identical to the tangential component of the acceleration of gravity. [ABSTRACT FROM AUTHOR]

We consider perturbations of the hydrogen atom by sufficiently small homogeneous static electric and magnetic fields in near-orthogonal configurations. Normalization of the Keplerian symmetry reveals that in the parameter space such systems belong in a 'zone' of systems close to the 1:1 resonance, the latter corresponding to the exactly orthogonal configuration. Integrable approximations obtained from second normalization of systems in the 1:1 zone are classified into several different qualitative types, many of which possess nontrivial monodromy. We compute monodromy of the complete three-dimensional energy-momentum map, compare the joint quantum spectrum to classical bifurcation diagrams, and show the effect of second normalization to the joint spectrum. [ABSTRACT FROM AUTHOR]

Abstract. It has recently been suggested that internal reflection geometry using uncoated optical fiber tips does not deliver subwavelength resolution. Recent experimental results, however, suggest the opposite. Here we model the internal reflection geometry by numerical solution of the full vector Maxwell equations for the electric field. A linearly polarized helium-neon laser is sent down the fiber and reflected from the tip and/or the sample in the near-field back into the fiber. We find that detection in the orthogonal linear polarization mode (OP mode) does deliver subwavelength resolution, whereas detection in the incident linear polarization mode does not. We interpret this effect as depolarization in the near field of the tip-sample region. Best lateral resolutions of about 110 nm, i.e. less than a fifth of the wavelength have been obtained so far in the OP mode. We assume that this value can be improved; work is in progress to show this. The simulations also show that other operation modes, such as far-field excitation and local collection, do not deliver subwavelength resolution, which is consistent with established experiments. [ABSTRACT FROM AUTHOR]