Disk Array Research Articles

Self-optimised cost-sensitive classifiers for early field failure prediction in storage systems

Data storage systems such as disk arrays go through rigorous testing in the production phase, however, a few of these DAs fail in the field and are returned back to the manufacturer. Although the failure appears in relatively a small percentage of the manufactured DAs, it results in a significant loss of data, time and money. This paper is motivated by the hypothesis that many of these failures could be predicted at the testing stage through data mining and machine learning. Field failure is modelled as a classification problem, however, as in many real-world problems, the problem suffers from significant class imbalance. Several approaches have been proposed that attempt to improve the performance of imbalanced classification by either modifying the dataset (resampling), or assigning classification costs to the classes’ cost matrix. These methods have been shown to improve performance, but they come with many parameters that need to be set, something that usually requires a lengthy exhaustive search, especially on problems with several classes. This paper presents a new scalable genetic algorithm approach for automating the design of the cost matrix CM along with the algorithm parameters. The proposed algorithms are tested on a real-world manufacturing dataset from Seagate disk arrays; the target is to predict from the devices’ testing data those that are likely to fail in the field. To demonstrate its performance, the proposed approach evaluated on a number of standard datasets and compared with other state-of-the-art methods.

Size effect on single pulse all-optical helicity-independent switching in GdFeCo disk arrays

We experimentally demonstrate single pulse toggle switching of the magnetization of GdFeCo disks with perpendicular to film plane anisotropy, which diameter ranges from 3 μm to 400 nm using 35 fs linearly polarized laser pulses. Two different magnetic states can be observed depending on the laser fluence: either a deterministic switching of the disk magnetization or a randomly oriented disk. We report that the fluence required to observe both magnetic states show a non-monotonic behavior with disk diameter and that the smallest disks require the lowest minimum fluence for achieving single pulse all-optical helicity-independent switching. Different evolution of the fluence thresholds for both phenomenon as a function of the disk size is observed and discussed.

Plasmonic gold disk nanoarrays-based surface lattice resonance sensor with high figure of merit and its near-field and far-field coupling characteristics

In the field of localized surface plasmon resonance sensing, narrow linewidth, high-quality factor, and high absorptivity have always been the goals that researchers are committed to achieving. The primary methods for achieving this goal are near-field coupling and far-field coupling. Due to the limitations of nanomanufacturing processes, current research often only focuses on single coupling methods such as far-field coupling or near-field coupling, with few relevant reports combining the two coupling methods. Based on this, this paper proposes a single-layer gold nano-disk array structure, which is simple and easy to manufacture. Through modal field analysis and structural parameter adjustment, some significant results have been achieved. On the one hand, the suggested gold nano-disk array structure yields a resonant peak based on far-field coupling with a full width at half maximum (FWHM) of less than 0.05 nm and a figure of merit of more than 15 000 (the quality factor is more than 20 000). On the other hand, it has been successfully accomplished to combine near-field coupling and far-field coupling, leading to a composite coupling peak that incorporates the benefits of both types of coupling. Moreover, this coupling peak has excellent characteristics such as narrow FWHM (less than 3 nm) and high absorptivity (up to 80.5%), which is superior to most reported sensing structures and more in line with practical sensing application requirements. In this paper, the potential of the gold disk array structure as a high-performance sensing structure is further explored, providing reference and new ideas for the design of easy-to-prepare and high-performance electromagnetic resonance devices.

Design and verification of a high bandwidth metamaterial based on daily ceramics and its thermal conductivity

Abstract High temperature resistant metamaterial absorbers with broadband and high performance is a promising research field. At present, many reported absorbing materials have the defects of single absorption mechanism, temperature sensitivity, and low temperature resistance. To expand the high-temperature performancs, a daily ceramics-based metamaterial absorber was proposed and verified. The absorption band was excited by the local surface plasma polarization (LSP) mode and the surface plasma polarization (SPP) mode resonance between disk arrays, and the dielectric loss mode resonance of the ceramic substrate. The effects of structural parameters, temperature, preparation process, and type of ceramic substrate on the absorption properties of the metamaterial were measured. The measurement results show that the metamaterial absorber is obvious temperature stability. The absorption band was strengthened by increasing the thickness of the ceramic substrate and the diameter of the disk array. The average value of absorption band was less affected by the preparation technology of daily ceramic substrate. The average absorption based on four preparation technologies (Chemical vapor deposition, Microwave induced synthesis, Sol-gel method, Carbothermal reduction method) are: 0.861, 0.882, 0.857, and 0.842, respectively. The average absorption based on four daily ceramics (SiC, ZrSiO 4 , TmFeO 3 , and ZrSnTiO) were: 0.861, 0.776, 0.908, and 0.857, respectively. In addition, the thermal conductivity and thermal resistance of daily ceramics were important parameters to measure the thermal resonance performance of the ceramic-based metamaterial absorber. The results confirmed the effect of ceramic on the thermal conductivities (thermal response current, thermal resistance and thermal conductivity). Therefore, the proposed daily ceramic-based metamaterial absorber has the following advantages: absorption is temperature-independent, and the high temperature metamaterial is capable of excellent heat conductivity.

Magnetic‐Electric Metamirror and Polarizing Beam Splitter Composed of Anisotropic Nanoparticles

AbstractThe emergence of new materials and fabrication techniques provides progress in the development of advanced photonic and communication devices. Transition metal dichalcogenides (e.g., molybdenum disulfide, MoS2) are novel materials possessing unique physical and chemical properties promising for optical applications. In this paper, a metasurface composed of particles made of bulk MoS2 is proposed and numerically studied considering its operation in the near‐infrared range. In the bulk configuration, MoS2 has a layered structure being a uniaxial anisotropic crystal demonstrating an optical birefringence property. It is supposed that the large‐scale and uniform MoS2 layers are synthesized in a vertical‐standing morphology, and then they are patterned into a regular 2D array of disks to form a metasurface. The natural anisotropy of MoS2 is utilized to realize the splitting of electric and magnetic dipole modes of the disks while optimizing their geometric parameters to bring the desired modes into overlap. At the corresponding resonant frequencies, the metasurface behaves as either an electric or a magnetic mirror, depending on the polarization of incident light. Based on the extraordinary reflection characteristics of the proposed metasurface, it can be considered an alternative to traditional mirrors and optical splitters when designing compact and highly efficient metadevices, which provide polarization and phase manipulation of electromagnetic waves on a subwavelength scale.

Controlling Valley-Specific Light Emission from Monolayer MoS2 with Achiral Dielectric Metasurfaces.

Excitons in two-dimensional transition metal dichalcogenides have a valley degree of freedom that can be optically manipulated for quantum information processing. Here, we integrate MoS2 monolayers with achiral silicon disk array metasurfaces to enhance and control valley-specific absorption and emission. Through the coupling to the metasurface electric and magnetic Mie modes, the intensity and lifetime of the emission of neutral excitons, trions, and defect bound excitons can be enhanced and shortened, respectively, while the spectral shape can be modified. Additionally, the degree of polarization (DOP) of exciton and trion emission from the valley can be symmetrically enhanced at 100 K. The DOP increase is attributed to both the metasurface-enhanced chiral absorption of light and the metasurface-enhanced exciton emission from the Purcell effect. Combining Si-compatible photonic design with large-scale 2D materials integration, our work makes an important step toward on-chip valleytronic applications approaching room-temperature operation.

Narrowband mid-infrared thermal emitters based on the Fabry-Perot type of bound states in the continuum.

The development of narrow-band thermal emitters operating at mid-infrared (MIR) wavelengths is vital in numerous research fields. However, the previously reported results obtained with metallic metamaterials were not successful in achieving narrow bandwidths in the MIR region, which suggests low temporal coherence of the obtained thermal emissions. In this work, we demonstrate a new design strategy to realize this target by employing the bound state in the continuum (BIC) modes of the Fabry-Perot (FP) type. When a disk array of high-index dielectric supporting Mie resonances is separated from a highly reflective substrate by a low refractive index spacer layer with appropriate thickness, the destructive interference between the disk array and its mirror with respect to the substrate leads to the formation of FP-type BIC. Quasi-BIC resonances with ultra-high Q-factor (>103) are achievable by engineering the thickness of the buffer layer. This strategy is exemplified by an efficient thermal emitter operating at a wavelength of 4.587 µm with the on-resonance emissivity of near-unity and the full-width at half-maximum (FWHM) less than 5 nm even along with consideration of metal substrate dissipation. The new thermal radiation source proposed in this work offers ultra-narrow bandwidth and high temporal coherence along with the economic advantages required for practical applications, compared to those infrared sources made from III-V semiconductors.

The association between body mass index and distribution intensity of tumor treating fields (TTFields) in the lungs.

e20559 Background: Tumor Treating Fields (TTFields) therapy is a first-in-class locoregional and noninvasive cancer treatment modality. TTFields are electric fields that disrupt processes necessary for cancer cell viability and tumor progression. A portable medical device generates TTFields, which are delivered noninvasively to the tumor area via 2 pairs of transducer arrays placed on the skin. TTFields therapy is currently approved for recurrent and newly diagnosed glioblastoma and pleural mesothelioma, with studies underway in other solid tumor types, including non-small cell lung cancer (NSCLC). Preclinical studies have shown that the effectiveness of TTFields depends on several factors, including field intensity. Given that 1 in 3 adults is overweight or obese, it is relevant to determine the effect of body mass index (BMI) on TTFields intensity to the lungs. Simulation-based methods were utilized, with the hypothesis that TTFields could be delivered to regions of interest (ROI) at therapeutic field intensities of > 1 V/cm, irrespective of BMI. Methods: Female computer phantom models with BMIs of 22 (healthy), 26 (overweight), and 30 (obese) were used to simulate TTFields intensity using small (13 disk) and large (20 disk) arrays placed on the thoracic region. The distribution of TTFields in each model was then determined using a computer-generated electric field intensity map. Field intensity values across the entire lungs were analyzed and compared. Results: When TTFields were delivered with large arrays, field intensities were clinically meaningful ( > 1 V/cm) in all lobes of the lungs for all BMI models. When TTFields were delivered with small arrays, meaningful levels of field intensity were achieved in all lung lobes, except for the BMI 30 model, where field intensities were slightly lower than 1 V/cm in the right middle lobe. Conclusions: These results show that TTFields can be delivered at therapeutic field intensities in patients with a BMI up to 30, providing the appropriate TTFields array size is used. Results from this simulation-based study support current clinical studies of TTFields therapy in lung cancer, (LUNAR, NCT02973789) and underscore the importance of appropriate array size selection. Additionally, these results may provide guidance for using TTFields therapy to treat a broad population of patients with lung tumors.

14‐2: Angle‐insensitive meta‐surface color filters designed by integrating genetic algorithm with artificial neural network

Next‐generation displays require tiny pixel sizes and are applied to AR/VR and holograms. Conventional color filters have limitations in miniaturization and shows poor reliability from heat, light and other environment. Meta‐surface color filters (MCFs) are one of the solutions to replace conventional color filters, suitable for high‐resolution displays. Structural design parameters are adjusted to determine the filtering properties of the MCFs. In addition, the metal based meta‐surface shows better durability cause of the intrinsic characteristics of the material. However, if the structure is complicated, there require many case‐ studies for verification, which increases trial and error. In addition, resonance by phase matching between structures changes according to the angle of incident light. In this study, we suggest a method to reduce the trial and error required in designing structure. Also, the design parameters of the MCFs of the desired color was extracted through an AI model capable of reverse design. Furthermore, we propose a novel MCFs that shows characteristics independent to the angle of incident light through a coaxial hole and disk array structure.

Phase-resolved optical characterization of nanoscale spin waves

We study theoretically and experimentally the process of Brillouin light scattering on an array of silicon disks on a thin Permalloy layer. We show that phase-resolved Brillouin light scattering microscopy performed on an array of weakly interacting dielectric nanoresonators can detect nanoscale waves and measure their dispersion. In our experiment, we were able to map the evolution of the phase of the spin wave with a wavelength of 204 nm and a precision of 6 nm. These results demonstrate the feasibility of all-optical phase-resolved characterization of nanoscale spin waves.

Efficient Reed–Solomon Redundant Arrays of Independent Disks 6 Exclusive OR Accelerator with Scaling Scheme

Efficient Reed–Solomon Redundant Arrays of Independent Disks 6 Exclusive OR Accelerator with Scaling Scheme

On the Optimal Conductivity of Packed Two-Dimensional Dispersed Composites

Optimal packing is applied in physics for investigation of macroscopic properties of composites and porous media. The present paper demonstrates that the optimal packing of perfectly conducting disks on the plane corresponds to the minimal effective conductivity for macroscopically isotropic composites. Such an optimal location is studied and compared to the pure geometric problem for disks packing on the flat torus. The hexagonal (triangular) array of disks solves the problem for the triangle lattice numbers . The rest of the cases are investigated separately by minimization of structural sums constructed by means of the Eisenstein functions.

Emergent tricriticality in magnetic metamaterials

Metallic discs engineered on the 100 nm scale have an internal magnetic texture which varies from a fully magnetized state to a vortex state with zero moment. The interplay between this internal structure and the inter-disc interactions is studied in magnetic metamaterials made of square arrays of the magnetic discs. The texture is modeled by a mesospin of varying length with O(2) symmetry and the inter-disc interaction by a nearest neighbour coupling between mesospins. The thermodynamic properties of the model are studied numerically and an ordering transition is found which varies from Kosterlitz-Thouless to first order via an apparent tri-critical point. The effective critical exponent characterising the finite size magnetization evolves from the value for the 2D-XY model to less than half this value at the tri-critical point. The consequences for future experiments both in and out of equilibrium are discussed.

Ultra-Broadband Solar Absorber and High-Efficiency Thermal Emitter from UV to Mid-Infrared Spectrum.

Solar energy is currently a very popular energy source because it is both clean and renewable. As a result, one of the main areas of research now is the investigation of solar absorbers with broad spectrum and high absorption efficiency. In this study, we create an absorber by superimposing three periodic Ti-Al2O3-Ti discs on a W-Ti-Al2O3 composite film structure. We evaluated the incident angle, structural components, and electromagnetic field distribution using the finite difference in time domain (FDTD) method in order to investigate the physical process by which the model achieves broadband absorption. We find that distinct wavelengths of tuned or resonant absorption may be produced by the Ti disk array and Al2O3 through near-field coupling, cavity-mode coupling, and plasmon resonance, all of which can effectively widen the absorption bandwidth. The findings indicate that the solar absorber's average absorption efficiency can range from 95.8% to 96% over the entire band range of 200 to 3100 nm, with the absorption bandwidth of 2811 nm (244-3055 nm) having the highest absorption rate. Additionally, the absorber only contains tungsten (W), titanium (Ti), and alumina (Al2O3), three materials with high melting points, which offers a strong assurance for the absorber's thermal stability. It also has a very high thermal radiation intensity, reaching a high radiation efficiency of 94.4% at 1000 K, and a weighted average absorption efficiency of 98.3% at AM1.5. Additionally, the incidence angle insensitivity of our suggested solar absorber is good (0-60°) and polarization independence is good (0-90°). These benefits enable a wide range of solar thermal photovoltaic applications for our absorber and offer numerous design options for the ideal absorber.

Robust and non-robust bound states in the continuum in rotationally symmetric periodic waveguides.

A fiber grating and a one-dimensional (1D) periodic array of spheres are examples of rotationally symmetric periodic (RSP) waveguides. It is well known that bound states in the continuum (BICs) may exist in lossless dielectric RSP waveguides. Any guided mode in an RSP waveguide is characterized by an azimuthal index m, the frequency ω, and Bloch wavenumber β. A BIC is a guided mode, but for the same m, ω and β, cylindrical waves can propagate to or from infinity in the surrounding homogeneous medium. In this paper, we investigate the robustness of nondegenerate BICs in lossless dielectric RSP waveguides. The question is whether a BIC in an RSP waveguide with a reflection symmetry along its axis z, can continue its existence when the waveguide is perturbed by small but arbitrary structural perturbations that preserve the periodicity and the reflection symmetry in z. It is shown that for m = 0 and m ≠ 0, generic BICs with only a single propagating diffraction order are robust and non-robust, respectively, and a non-robust BIC with m ≠ 0 can continue to exist if the perturbation contains one tunable parameter. The theory is established by proving the existence of a BIC in the perturbed structure mathematically, where the perturbation is small but arbitrary, and contains an extra tunable parameter for the case of m ≠ 0. The theory is validated by numerical examples for propagating BICs with m ≠ 0 and β ≠ 0 in fiber gratings and 1D arrays of circular disks.

Achieving Complete Band Gaps of Water Waves with Shallow-Draft Cylinder Arrays

Conventionally, band gaps of water waves can be obtained with periodic arrays of bottom-mounted obstacles or vertical cylinders. However, such structures need to possess a large ratio of volume in water, and may not be easy to build and move in practical ocean engineering. Here, we theoretically propose and experimentally demonstrate that when the water surface is pierced by a fixed, rigid cylinder array, a complete band gap of water waves can be achieved, in which the propagation of water waves is forbidden in all the directions. Such a band gap can exist even when the cylinders have a draft much smaller than the water depth ($d\ensuremath{\ll}h$). Based on the complete band gap, a semicircular shape of the fixed-surface disk array is further constructed, which can block omnidirectional water waves generated by a point source.

Numerical study of convective heat transfer in static arrangements of particles with arbitrary shapes: A monolithic hybrid lattice Boltzmann-finite difference-phase field solver

A compressible lattice Boltzmann-finite difference method is extended by the phase-field approach into a monolithic scheme to study fluid flow and heat transfer through regular arrangements of solid bodies of circular, elliptical and irregular shapes. The advantage of using the phase-field method is demonstrated both in its simplicity of accounting for flow and thermal boundary conditions at solid surfaces with irregular shapes and in the capability of generating such complex-shaped objects. For an array of discs, numerical results for the overall solid-to-gas heat transfer rate are validated via experiments on flow through arrays of hot cylinders. The thus validated compressible LB-FD-PF hybrid scheme is used to study the dependence of heat transfer on flow and thermal boundary conditions (Reynolds number, temperature difference between the hot solid bodies and the inlet gas), porosity as well as on the shape of solid objects. Results are rationalized in terms of the residence time of the gas close to the solid body and downstream variations of gas velocity and temperature. Perspective for further applications of the proposed methodology are also discussed.

Design and analysis of high-sensitivity tunable graphene sensors for cancer detection.

A new metamaterial refractive index sensor based on the impedance matching idea is suggested to provide an ultra-narrowband absorption response at terahertz frequencies. In order to accomplish this, the graphene layer has been modeled as circuit components using the recently developed transmission line method and the recently proposed circuit model of Periodic Arrays of Graphene Disks. The given research gives a flowchart and equations for designing a sensor, greatly simplifying the sensor design approach. This study only explores Periodic Arrays of Graphene Disks but we think the offered technique is extensible to any available graphene forms that past designers supplied with a circuit model. We compare and contrast the full-wave simulation results with the suggested circuit model. The metallic ground prohibited the transmission of the episode wave, and all occurrence electromagnetic waves are restricted in the basic design between the graphene disk. As a consequence, a perfect narrowband absorption peak is obtained. Disk absorption spectra have been discovered for a variety of refractive lists. The findings of the circuit model and full-wave simulations appear to be balanced. This RI sensor is suitable for biomedical sensing because of the combination of its features. The proposed sensor's performance as a cancer early detection sensor was evaluated among biomedical sensors, and the findings indicated that the proposed sensor is an excellent candidate for this application.

Ultra-narrow bandwidth mid-infrared thermal emitters achieved with all-dielectric metasurfaces

Narrow bandwidth and highly efficient mid-infrared (MIR) thermal emitters with low manufacturing cost and simple geometries have been continuously pursued by scientists. Unfortunately, conventional MIR thermal emitters based on metallic metamaterials suffer from large bandwidths mainly due to dissipations losses. In this work, we present our experimental demonstration of MIR thermal emitters with ultra-narrow bandwidth by exploiting the quasi bound-state-in-the-continuum mode supported by an all-dielectric metasurface structure. The whole structure is composed of a zigzag array of germanium elliptical disks, separated from the gold conductive substrate by a dielectric spacer layer made from the refractory material of Al2O3. Our experimental results demonstrate that even with an amorphous form of evaporated materials for both dielectrics, an emission bandwidth around 80 nm in the MIR can be obtained, one order of magnitude narrower than those achieved with metallic metamaterials. The bandwidth can in principle be further narrowed by a large extent when dielectrics of better quality are used. We further demonstrate with numerical results that this thermal emitter features additional advantages including high directionality, linear polarization, and large spectral tunability. Our results represent a significant step towards the realization of high-performance and low-cost MIR thermal emitters.

Reconfigurable optoelectronic absorber based on nested nano disk-ribbon graphene Pattern in THz range

A two-layers, multi-band super absorber with the capability of being tuned is proposed in this paper. The idea behind the design is to realize periodic arrays of graphene disks via graphene ribbons with different lengths. Then circuit modeling is developed to be used alongside the impedance matching concept to achieve more than ten absorption peaks. The exploited spacer is a lossless polymer in the THz frequency range while the bottom of the device is occupied by a relatively thick golden plate. The developed circuit model description is verified by full-wave simulation. According to the simulation results, the proposed absorber shows more than ten peaks with absorption over 90%. The peak frequencies are interestingly able to be shifted via exploited single chemical potential variations. Additionally, deviations of absorber response against graphene electron relaxation time and device geometry are shown to be marginal which makes the presented meta-absorber, a reliable optical device.