Ultra-large Area Research Articles

New insights into coarse particle lifting performance of a hydraulic ejector with an ultra-large area ratio

Hydraulic ejectors with ultra-large area ratios (HE-ULAR) have potential applications as particle lifting equipment in fluidized coal mining. This study analyzed the effects of area and pressure ratios on the coarse particle lifting performance of HE-ULAR. The cavitation, valid, and failure zones for coarse particle lifting were mapped out. The results show that the pressure gradient force acting on each particle is approximately 2.02–3.70 times greater than the drag force, indicating that the pressure gradient force is the more significant interaction force for particle migration under the influence of HE-ULAR compared to the drag force. Additionally, insufficient energy transfer between the energetic fluid and particles in the valid zone of HE-ULAR reduces the fluid energy density and particle lifting concentration at low pressure ratio conditions. The HE-ULAR exhibits optimal particle performance at the operating conditions with an area ratio of 12.51 and a pressure ratio of 0.0735. Finally, a series of prediction formulas for fluidized coal mining parameters were established based on the optimal operating condition of the HE-ULAR. These results will guide the application of the HE-ULAR in a fluidized mining system.

Customizable Scintillator of Cs3 Cu2 I5 :2% In+ @Paper for Large-Area X-Ray Imaging.

High-resolution X-ray imaging is increasingly required for medical diagnosis and large-area detection. However, the issues of scattering and optical crosstalk are limiting the spatial resolution of the indirect X-ray imaging. In this study, a feasible and efficient strategy is proposed to in situ synthesize flexible Cs3 Cu2 I5 :2%In+ @paper as a superior scintillator film, which can be scaled up to an ultra-large area of 4800 cm2 . The as-obtained Cs3 Cu2 I5 :2%In+ @paper performs a fascinating photoluminescence quantum efficiency up to 88.14%, a steady state light yield of 70169 photons/MeV, and spatial resolution of 15 lpmm-1 . Moreover, the suppressed physical scattering and optical crosstalk of the corresponding film are demonstrated. Accordingly, this work explores a feasible fabrication of customizable scintillation films with large area for high-resolution X-ray detection.

GAWBS Noise in Digital Coherent Transmission

This paper presents recent progress on guided acoustic wave Brillouin scattering (GAWBS) noise in single-core fiber (SCF), multi-core fiber (MCF), and few-mode fiber (FMF). First, we describe theoretical analyses of GAWBS phase noise generated in these various types of fiber. By using three types of SCF, namely ultra-large area fiber (ULAF), standard single-mode fiber (SSMF), and dispersion-shifted fiber (DSF), we show that the GAWBS phase noise depends strongly on the effective core area A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> . We also describe the GAWBS phase noise in four-core fiber (4CF), where it is shown that GAWBS noise in the off-center core is quite different from that in SCF. Furthermore, we describe the GAWBS phase noise in FMF supporting two LP modes. Then, we compare the GAWBS noise powers induced in SCF, MCF, and FMF. Next, we describe experiments on GAWBS phase noise in various fibers, which agree well with the theory. We also measured and analyzed the GAWBS phase noise correlation between the cores in a 4CF, where it is shown that the correlation between cores strongly depends on the core position. Finally, we describe the influence of GAWBS phase noise on digital coherent transmission. We formulate the GAWBS phase noise based on the Gaussian distribution and evaluate its influence on the BER characteristics in a coherent QAM transmission. We found that it is difficult to realize a transoceanic-class QAM transmission with a QAM multiplicity of higher than 64 even without other impairments. Furthermore, we evaluate the SNR penalty induced by the GAWBS noise in a long-haul transmission by taking account of the amplified spontaneous emission (ASE) and nonlinear interference noise, which are unavoidable in actual systems. The calculated results show that the influence of the GAWBS noise is smaller than the other impairments, but it cannot be neglected in system evaluations.

Design and fabrication of single photon detector with ultra-large area superconducting nanowire array

&lt;sec&gt;Superconducting nanowire single-photon detector (SNSPD) is one of the most mainstream single-photon detectors at present, which possesses excellent comprehensive performance, including low time jitter, high efficiency, low dark count, and wide spectrum. However, the traditional single-pixel SNSPD suffers a lack of spatial resolution and a small photosensitive surface, which becomes a bottleneck associated with optical coupling efficiency. In addition, a single-pixel detector has no ability to resolving the photon number, whose working speed cannot be further improved due to the existence of dead time. While array devices can make up for the above deficiencies. Therefore, the development of a large-area SNSPD array is the key to free-space photon detection and other applications. In recent years, the relevant researches have been conducted and great progress has been achieved. However, the large-area SNSPD array is facing some intractable problems, including complex process, low yield, and difficult fabrication, owing to the photosensitive surface consisting of a large number of superconducting nanowires. Photons imaging is verified with this device. At present, in the existing studies mainly used is the three-dimensional technology with complicated process steps to fabricate large array SNSPDs. How to simplify the process has become a research focus.&lt;/sec&gt;&lt;sec&gt;In this work, we design an ultra-large area nanowire array structure and propose an innovative plane process. Taking advantage of the property that the electron beam resists HSQ (hydrogen silsesquioxane polymer) forming a silicon oxide electrical isolation layer after exposure, we fabricate a large array SNSPD with a simplified two-dimensional process and realize dimensionality reduction for the traditional three-dimensional process of a multilayer structure. By measurement in parallel, the devices enjoy high yield with no bad points found. In addition, a full-superconducting electrode is adopted in our design to reduce the thermal effect of resistors. We add series and parallel resistors in the pixels to divide the bias current evenly and expand the array scale optionally. At the same time, we also offer the design details of array SNSPDs, the related simulation of hot spots to verify the rationality of the design, the optimization of the preparation conditions of array devices, measurement scheme formulation, and other related work.&lt;/sec&gt;&lt;sec&gt;This work provides an idea for designing and fabricating ultra-large array SNSPD, which is expected to be applied to the fabrication of megapixel array SNSPDs. Combined with an efficient readout circuit, a focal plane photon detection and imaging system with both a large field of view and high sensitivity can be realized.&lt;/sec&gt;

Crack Suppression in Conductive Film by Amyloid-Like Protein Aggregation toward Flexible Device.

A fatal weakness in flexible electronics is the mechanical fracture that occurs during repetitive fatigue deformation; thus, controlling the crack development of the conductive layer is of prime importance and has remained a great challenge until now. Herein, this issue is tackled by utilizing an amyloid/polysaccharide molecular composite as an interfacial binder. Sodium alginate (SA) can take part in amyloid-like aggregation of the lysozyme, leading to the facile synthesis of a 2D protein/saccharide hybrid nanofilm over an ultralarge area (e.g., >400cm2 ). The introduction of SA into amyloid-like aggregates significantly enhances the mechanical strength of the hybrid nanofilm, which, with the help of amyloid-mediated interfacial adhesion, effectively diminishes the microcracks in the hybrid nanofilm coating after repetitive bending or stretching. The microcrack-free hybrid nanofilm then shows high interfacial activity to induce electroless deposition of metal in a Kelvin model on a substrate, which noticeably suppresses the formation of microcracks and consequent conductivity loss during the bending and stretching of the metal-coated flexible substrates. This work underlines the significance of amyloid/polysaccharide nanocomposites in the design of interfacial binders for reliable flexible electronic devices and represents an important contribution to mimicking amyloid and polysaccharide-based adhesive cements created by organisms.

Superconducting microstrip single-photon detector with system detection efficiency over 90% at 1550 nm

Generally, a superconducting nanowire single-photon detector (SNSPD) is composed of wires with a typical width of ∼ 100 nm . Recent studies have found that superconducting strips with a micrometer-scale width can also detect single photons. Compared with the SNSPD covering the same area, the superconducting microstrip single-photon detector (SMSPD) has smaller kinetic inductance, higher working current, and lower requirements in fabrication accuracy, providing potential applications in the development of ultralarge active area detectors. However, the study of SMSPD is still in its infancy, and the realization of its high-performance and practical use remains an open question. This study demonstrates a NbN SMSPD with a nearly saturated system detection efficiency (SDE) of ∼ 92.2 % at a dark count rate of ∼ 200 cps , a polarization sensitivity of ∼ 1.03 , and a minimum timing jitter of ∼ 48 ps at the telecom wavelength of 1550 nm when coupled with a single-mode fiber and operated at 0.84 K. Furthermore, the detector’s SDE is over 70% when operated at a 2.1 K closed-cycle cryocooler.

Design and evaluation of 2.3 Tb/s (23 ch. × 100 Gb/s) multi-carrier WDM optical transmission systems

Multilevel phase modulation formats with coherent detection enable a new generation of high speed optical transport platform. We demonstrate 23 × 100 Gbps (2.3 Tb/s) WDM Optical systems employing multicarrier generation concept. Three lasers are used to generate 23 sub-carriers using multicarrier generator at transmitter section. Each sub-carrier transmits at a transmission rate of 100 Gbps using polarization division multiplexed quadrature phase shift keying (PDM-QPSK) modulation format with spacing of 25 GHz between sub carriers. The analysis is carried out for 23 × 100 Gb/s (2.3 Tb/s) PDM-QPSK WDM optical systems with ultra large area fiber (ULAF), standard single mode fiber (SSMF) and large effective area fiber (LEAF) at transmission reach from 600 to 5000 km. Coherent detection with DSP is used for all the systems at receiving end. Systems are verified with parameters like symbol error rate, error vector magnitude (EVM) and Q-factor using analytical and simulation results. Improvement of 1.66 dB to 3.21 dB and 2.08 dB to 4.63 dB is noted in Q-factor for system with ULAF in comparison with system using SSMF and LEAF respectively over 600 km to 5000 km transmission reach. EVM values are found 2.24% to 2.68% and 2.68% to 12.43% lower in system with ULAF than system with SSMF and LEAF respectively. Log of estimated symbol error is observed less for system with ULAF than systems with SSMF and LEAF fibers, respectively, at transmission distance of 5000 km. The results clearly show that WDM optical system with ULAF fiber gives better performance.

Ultralarge-area shock imprinting using underwater shock wave and natural leaf mold

Large-area nano-/microarray production in a single shot is a significant challenge in laser shock imprinting (LSI). Materials that can be used to fabricate molds easily will advance LSI techniques. Thus, here, an Al foil was compression-molded in a natural leaf mold using an explosive-derived underwater shock wave. The phytoliths’ inertia triggered Al foil deformation, and microimprinting on an ultralarge area measuring 10−2 m2 was performed. The difference in the Al foil deformation rate caused by the phytoliths influenced the Al foil imprinting depth. Further, even a low-strength base to hold particles could be applied to the mold for LSI.

Fabrication of high porosity Nanocellular polymer foams based on PMMA/PVDF blends

Due to special micro-nano scale heat transfer effect and the ultra-large specific area, nanocellular polymer foams (NPFs), especially NPFs with high porosity, have great application potential in the fields of heat insulation, filtration, and catalysis. However, since the thermodynamic instability of nanoscale bubbles causes lower nucleation density and cells rupture, developing a green and cost-effective method for fabricating high porosity NPFs remains a challenge. Hence, we proposed a novel method for fabricating high porosity NPFs based the design of materials system and foaming process, and the NPFs with a porosity of over 70%, an average cell size of 287 nm, and a nucleation density of over 1014/cm3 were obtained. Firstly, based on the excellent compatibility between poly (methyl methacrylate) (PMMA) and poly (vinylidene fluoride) (PVDF), homogeneous PMMA/PVDF blends were prepared by melt compounding. Then, the PMMA/(PVDF-microcrystals) system was formed by self-assembly through CO2 induced crystallization. Thanks to numerous homo-dispersed PVDF crystallites' facilitating heterogeneous nucleation and enhancing polymer strength, high porosity NPFs with tailored cellular structures were fabricated by heating foaming. This method provides a simple, flexible, and environmentally friendly way for the preparation of high porosity NPFs.

3D hierarchical CuS microflowers constructed on copper powders-filled nickel foam as advanced binder-free electrodes

A novel strategy, consisting of sonication-assisted filling step followed by a chemical-bath surface sulfidization process, was designed to fabricate 3D hierarchical CuS microflowers constructed on copper powders-filled nickel foam (Cu@CuS–NF) as advanced binder-free electrodes for high-performance supercapacitors. Scanning electron microscope, powder X-ray diffraction and X-ray photoelectron spectroscopy techniques were employed to confirm the microstructure and composition. Electrochemical measurements demonstrated that the Cu@CuS–NF electrode has highly improved capacitance with an ultra-high area capacitance of 11.4 F cm−2 at a high current density of 90 mA cm−2. Also, the Cu@CuS–NF electrode has superior cycling stability with more than 100% retention of the initial area capacitance after 3000 cycles at 180 mA cm−2. The excellent electrochemical performance can be mostly attributed to a combination of the ultra-large loading area and very good electroconductive network formed from copper powders filling inside nickel foam. Our work opens a new door to engineering ultra-high-performance nickel-foam-based electrodes for electrochemical devices including water splitting and energy storage/conversion.

Ultra-large area graphene hybrid hydrogel for customized performance supercapacitors: High volumetric, areal energy density and potential wearability

Volumetric and areal energy densities are the key performance metrics for electrochemical supercapacitors (EC) used in portable storage devices, whereas mechanical flexibility and potential for direct integration with conventional cloths are the primary requirements for wearable usage. Herein, highly scalable, versatile EC electrodes are presented based on the spontaneously assembled hydrogel-hybrids of graphene and polyaniline (PANI). Our hydrogel-hybrids exhibit areal capacitance of 853 mF cm−2 (at 1 mA cm−2) with superb cycling stability (95.2% retention after 5000 cycles), which can be readily increased up to 2.2 F cm−2 by the multistacking of electrodes without sacrificing charging-discharging rate capability. Control of hydration level (water < 35 wt%) by means of simple mechanical compression leads to remarkably high volumetric capacitance of 560 F cm−3, while retaining high areal value and rate capability. Moreover, requirement for wearable EC can easily be realized via direct integration of hydrogel-hybrids with carbon cloths. Such a noticeable performance of our hybrid devices is largely owing to the nanoporous graphene framework that offers continuous electronic conduction pathways as well as hydrated ion channels for the effective access to PANI-nanowire surfaces.

Impact of turbulence intensity on the unsteady flow characteristics of the integrated aggressive inter-turbine duct

Aggressive inter-turbine duct (AITD) which has ultra-short axial length and ultra-large area ratio is widely applied in the modern turbofan engine to meet the demand of higher efficiency and better low pressure rotor dynamic characteristics. However, the adverse stream-wise pressure gradient in this duct is enhanced, and there are complicate upstream and downstream flow conditions. The flow field of the AITD and its downstream low pressure turbine is seriously deteriorated and prone to separate, especially in high-altitude cruise state. The integrated AITD which integrates the AITD with strut had been proved to can restrain the traditional AITD's three-dimensional flow separation. Besides, periodic wake can suppress the downstream blade suction surface's flow separation by “calmed region” effect according to former studies. The AITD of this research taken from a real engine utilizes integrated design and inherent upstream wake to suppress the flow separation of the AITD's end wall and low pressure turbine nozzle's suction surface correspondingly. In this article, the computational simulation method is used to quantify the impact of turbulence intensity ( T u) on the integrated AITD's unsteady flow characteristics, especially the separation and transition mechanism of low pressure turbine nozzle's suction surface boundary layer. Research shows that the impact of T u on the integrated AITD's flow property depends on the balance of T u's dual effect.

Sn-Triggered Two-Dimensional Fast Protein Assembly with Emergent Functions.

The discovery of a general strategy for organizing functional proteins into stable nanostructures with the desired dimension, shape, and function is an important focus in developing protein-based self-assembled materials, but the scalable synthesis of such materials and transfer to other substrates remain great challenges. We herein tackle this issue by creating a two-dimensional metal-protein hybrid nanofilm that is flexible and cost-effective with reliable self-recovery, stability, and multifunctionality. As it differs from traditional metal ions, we discover the capability of Sn2+ to initiate fast amyloid-like protein assembly (occurring in seconds) by effectively reducing the disulfide bonds of native globular proteins. The Sn2+-initiated lysozyme aggregation at the air/water interface leads to droplet flattening, a result never before reported in a protein system, which finally affords a multifunctional 2D Sn-doped hybrid lysozyme nanofilm with an ultralarge area (e.g., 0.2 m2) within a few minutes. The hybrid film is distinctive in its ease of coating on versatile material surfaces with endurable chemical and mechanical stability, optical transparency, and diverse end uses in antimicrobial and photo-/electrocatalytic scaffolds. Our approach provides not only insights into the effect of tin ions on macroscopic self-assembly of proteins but also a controllable and scalable synthesis of a potential biomimic framework for biomedical and biocatalytic applications.

Window screen inspired fibrous materials with anisotropic thickness gradients for improving light transmittance.

Fibrous materials with high light transmittance exhibit great potential in a wide range of applications; unfortunately, fabrication of such materials still remains a challenge due to the strong light scattering caused by the rough fibrous structure and the voids between fibers. Window screens are commonly used in our daily life, and their unique woven structure ensures excellent mechanical properties, while the voids between wires allow light to pass through. By learning from the architecture of window screens, we proposed a novel patterned electrospinning approach with window screen like wire meshes as collectors to deposit fibers with anisotropic thickness gradients and further to improve the optical properties. The results indicated that the obtained fibrous mats closely copied the structure of the wire meshes, and exhibited unique thickness anisotropy with most of the fibers densely packed on the wires in a small area, while very few fibers sparsely suspended in the voids over a large area. Owing to the large area of the thin region within fibrous mats, the overall light transmittance of such a well-organized mat was greatly improved as compared with that of an isotropous mat. Furthermore, by carefully investigating the microstructure of the fibrous mats and simulating the electric field distribution with the software Comsol Multiphysics, a novel needle array collector with an ultra large area of voids was designed to achieve optimal light transparency. Finally, as proof of concepts, we investigated the potential use of transparent fibrous mats as a visual wound dressing and a window dust filter, respectively.

Ultralarge Area Sub-10 nm Plasmonic Nanogap Array by Block Copolymer Self-Assembly for Reliable High-Sensitivity SERS.

Effective surface enhancement of Raman scattering (SERS) requires strong near-field enhancement as well as effective light collection of plasmonic structures. To this end, plasmonic nanoparticle (NP) arrays with narrow gaps or sharp tips have been suggested as desirable structures. We present a highly dense and uniform Au nanoscale gap array enabled by the customized design of NP shape and arrangement employing block copolymer self-assembly. Block copolymer self-assembly in thin films offers uniform hexagonally packed nanopost template arrays over the entire surface of a 2 in. wafer. Conventional evaporative metal deposition over the nanotemplate surface allows precise geometric control and positional arrangement of metal NPs, constituting tunable, strong plasmonic near-field enhancement particularly at the "hot spots" near interparticular nanoscale gaps. Underlying field distribution has been investigated by a finite-difference time-domain simulation. In the detection of thiophenol, our Au nanogap array shows a remarkable enhancement of Raman intensity greater than ∼104, a standard deviation as small as 12.3% compared to that of the planar Au thin film. In addition, adenine biomolecules can be detected with a detection limit as low as 100 nM. Our approach proposes highly sensitive and reliable SERS on the basis of a scalable, low-cost bottom-up strategy.

Edge enhancement improves disruptive camouflage by emphasising false edges and creating pictorial relief.

Disruptive colouration is a visual camouflage composed of false edges and boundaries. Many disruptively camouflaged animals feature enhanced edges; light patches are surrounded by a lighter outline and/or a dark patches are surrounded by a darker outline. This camouflage is particularly common in amphibians, reptiles and lepidopterans. We explored the role that this pattern has in creating effective camouflage. In a visual search task utilising an ultra-large display area mimicking search tasks that might be found in nature, edge enhanced disruptive camouflage increases crypsis, even on substrates that do not provide an obvious visual match. Specifically, edge enhanced camouflage is effective on backgrounds both with and without shadows; i.e. this is not solely due to background matching of the dark edge enhancement element with the shadows. Furthermore, when the dark component of the edge enhancement is omitted the camouflage still provided better crypsis than control patterns without edge enhancement. This kind of edge enhancement improved camouflage on all background types. Lastly, we show that edge enhancement can create a perception of multiple surfaces. We conclude that edge enhancement increases the effectiveness of disruptive camouflage through mechanisms that may include the improved disruption of the object outline by implying pictorial relief.

Correlation-steered scanning for scanning probe microscopes to overcome thermal drift for ultra-long time scanning

The thermal effect is one of the most important factors that influence the accuracy of nanoscale measurement and the surface topography of samples in scanning probe microscopes (SPMs). We propose a method called correlation-steered scanning, which is capable of overcoming three-dimensional thermal drifts in real time for ultra-long time scanned images. The image is scanned band by band with overlapping parts between adjacent bands. The vertical drift can be considered as linear and can thus be eliminated together with the tilt of the sample by applying the flattening method. Each band is artificially divided into several blocks for conveniently calculating lateral drifts on the basis of the overlapping area of adjacent bands through digital image correlation. The calculated lateral drifts are compensated to steer the scanning of the subsequent blocks, thus ensuring that all bands are parallel to one another. Experimental results proved that images scanned by the proposed method exhibited less distortions than those obtained from the traditional raster scanning method. The nanoscale measurement results based on the image obtained by the proposed method also showed high accuracy, with an error of less than 1.5%. By scanning as many bands as needed, the correlation-steered scanning method can obtain a highly precise SPM image of an ultra-large area.

Design of a broadband ultra-large area acoustic cloak based on a fluid medium

A broadband ultra-large area acoustic cloak based on fluid medium was designed and numerically implemented with homogeneous metamaterials according to the transformation acoustics. In the present work, fluid medium as the body of the inclusion could be tuned by changing the fluid to satisfy the variant acoustic parameters instead of redesign the whole cloak. The effective density and bulk modulus of the composite materials were designed to agree with the parameters calculated from the coordinate transformation methodology by using the effective medium theory. Numerical simulation results showed that the sound propagation and scattering signature could be controlled in the broadband ultra-large area acoustic invisibility cloak, and good cloaking performance has been achieved and physically realized with homogeneous materials. The broadband ultra-large area acoustic cloaking properties have demonstrated great potentials in the promotion of the practical applications of acoustic cloak.

Rapid fabrication of a large-area close-packed quasi-periodic microlens array on BK7 glass

Large-area close-packed microlens arrays (MLAs) are highly desirable for structured light and integrated optical applications. However, efficient realization of ultralarge area MLAs with a high fill factor is still technically challenging, especially on glass material. In this Letter we propose a high-efficiency MLA fabrication method using single-pulsed femtosecond laser wet etch and close-packed quasi-periodic concave MLAs consisting of three million units fabricated on silica glass within an hour. The fabricated MLAs are demonstrated to have extreme optical smoothness (∼8.5 nm) by an atomic force microscope. It has also been demonstrated that the profile of the quasi-periodic concave structures could be easily tuned by changing the laser scanning speed or the pulse energy. Additionally, the optical performances of the MLA diffusers were investigated by using sharp focusing, high-resolution imaging, and flat-top illumination.

High Spectral Efficiency 400 Gb/s Transmission Using PDM Time-Domain Hybrid 32–64 QAM and Training-Assisted Carrier Recovery

We report the successful transmission of ten 494.85 Gbit/s DWDM signals on the standard 50 GHz ITU-T grid over 32 × 100 km of ultra-large-area (ULA) fiber. A net spectral efficiency (SE) of 8.25 b/s/Hz was achieved, after excluding the 20% soft-decision forward-error-correction (FEC) overhead. Such a result was accomplished by the use of a recently proposed polarization-division-multiplexed (PDM) time-domain hybrid 32-64 quadrature-amplitude-modulation (QAM) format, along with improved carrier frequency and phase recovery algorithms. It is shown that time-domain hybrid QAM provides a new degree of design freedom to optimize the transmission performance by fine tuning the SE of the modulation format for a specific channel bandwidth and FEC redundancy requirement. In terms of carrier recovery, we demonstrate that 1) hardware efficient estimation and tracking of the frequency offset between the signal and local-oscillator (LO) can be achieved by using a new feedback-based method, and 2) a training-assisted two-stage phase estimation algorithm effectively mitigates cyclic phase slipping problems. This new phase recovery algorithm not only improves the receiver sensitivity by eliminating the need for differential coding and decoding, but also enables an additional equalization stage following the phase recovery. We have shown that the introduction of this additional equalization stage (with larger number of taps) helps reduce the implementation penalty. This paper also presents the first experimental study of the impact of inphase (I) and quadrature (Q) correlation for a high-order QAM. It is shown that an adaptive equalizer could exploit the correlation between I and Q signal components to artificially boost the performance by up to 0.7 dB for a PDM time-domain hybrid 32-64 QAM signal when the equalizer length is significantly longer than I/Q de-correlation delay.