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3. Near-field thermal emission from metasurfaces constructed of SiC ellipsoidal particles

Author

Walter, Lindsay P., McKay, Joseph C., Raeymaekers, Bart, and Francoeur, Mathieu

Subjects
Physics - Applied Physics, Physics - Optics
Abstract

We model near-field thermal emission from metasurfaces structured as two-dimensional arrays of ellipsoidal SiC particles. The modeling approach is developed from fluctuational electrodynamics and is applicable to systems of ellipsoidal particles within the dipole limit. In all simulations, the radial lengths of particles are restricted to the range of 10 to 100 nm, and interparticle spacing is constrained to at least three times the particle characteristic length. The orientation and dimensions of constituent ellipsoidal particles are varied to tune localized surface phonon resonances and control the near-field energy density above metasurfaces. Results show that particle orientation can be used to regulate the relative magnitude of resonances in the energy density and particle dimensions may be changed to adjust the frequency of these resonances within the Reststrahlen band. Metasurfaces constructed from particles with randomized dimensions display comparatively broadband thermal emission rather than the three distinct resonances seen in metasurfaces made with ellipsoidal particles of equivalent dimensions. When the interparticle spacing in a metasurface exceeds about three times the particle characteristic length, the spectral energy density above the metasurface is dominated by individual particle self-interaction and can be approximated as a linear combination of single-particle spectra. When interparticle spacing is at the lower limit of three times the characteristic length, however, multiparticle interaction effects increase, and the spectral energy density above a metasurface deviates from that of single particles. This work provides guidance for designing all-dielectric, particle-based metasurfaces with desired near-field thermal emission spectra, such as thermal switches., Comment: 50 pages, 5 figures, 9 supporting figures, 2 supporting tables

Published
2023
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5. Wave-driven assembly of quasi periodic patterns of particles

Author

Cherkaev, Elena, Vasquez, Fernando Guevara, Mauck, China, Prisbrey, Milo, and Raeymaekers, Bart

Subjects
Mathematical Physics, 35B15, 35L05, 74F10
Abstract

We theoretically show that a superposition of plane waves causes small (compared to the wavelength) particles dispersed in a fluid to assemble in quasiperiodic two or three dimensional patterns. We experimentally demonstrate this theory by using ultrasound waves to assemble quasiperiodic patterns of carbon nanoparticles in water using an octagonal arrangement of ultrasound transducers, and we document good agreement between theory and experiments. The theory also applies to obtaining quasiperiodic patterns in other situations where particles move with linear waves, such as optical lattices., Comment: 4 pages, 5 figures

Published
2020
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12. Measuring and Simulating the Transient Packing Density During Ultrasound Directed Self‐Assembly and Vat Polymerization Manufacturing of Engineered Materials.

Author

Noparast, Soheyl, Guevara Vasquez, Fernando, Francoeur, Mathieu, and Raeymaekers, Bart

Subjects
ULTRASONIC imaging, POLYMERIZATION, DENSITY, COMPOSITE materials, MANUFACTURING processes, CAROTID intima-media thickness
Abstract

Ultrasound‐directed self‐assembly (DSA) uses ultrasound waves to organize and orient particles dispersed in a fluid medium into specific patterns. Combining ultrasound DSA with vat photopolymerization (VP) enables manufacturing materials layer‐by‐layer, wherein each layer the organization and orientation of particles in the photopolymer is controlled, which enables tailoring the properties of the resulting composite materials. However, the particle packing density changes with time and location as particles organize into specific patterns. Hence, relating the ultrasound DSA process parameters to the transient local particle packing density is important to tailor the properties of the composite material, and to determine the maximum speed of the layer‐by‐layer VP process. This paper theoretically derives and experimentally validates a 3D ultrasound DSA model and evaluates the local particle packing density at locations where particles assemble as a function of time and ultrasound DSA process parameters. The particle packing density increases with increasing particle volume fraction, decreasing particle size, and decreasing fluid medium viscosity is determined. Increasing the particle size and decreasing the fluid medium viscosity decreases the time to reach steady‐state. This work contributes to using ultrasound DSA and VP as a materials manufacturing process. [ABSTRACT FROM AUTHOR]

Published
2024
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19. The accuracy of the compressible Reynolds equation for predicting the local pressure in gas-lubricated textured parallel slider bearings

Author

Qiu, Mingfeng, Bailey, Brian N, Stoll, Rob, and Raeymaekers, Bart

Subjects
Control Engineering, Mechatronics and Robotics, Engineering, Hydrodynamic lubrication, Surface texture, Reynolds equation, Manufacturing Engineering, Mechanical Engineering, Mechanical Engineering & Transports, Manufacturing engineering, Mechanical engineering
Abstract

The validity of the compressible Reynolds equation to predict the local pressure in a gas-lubricated, textured parallel slider bearing is investigated. The local bearing pressure is numerically simulated using the Reynolds equation and the Navier-Stokes equations for different texture geometries and operating conditions. The respective results are compared and the simplifying assumptions inherent in the application of the Reynolds equation are quantitatively evaluated. The deviation between the local bearing pressure obtained with the Reynolds equation and the Navier-Stokes equations increases with increasing texture aspect ratio, because a significant cross-film pressure gradient and a large velocity gradient in the sliding direction develop in the lubricant film. Inertia is found to be negligible throughout this study.

Published
2014

23. Design of a dual stage actuator tape head with high-bandwidth track following capability

Author

Raeymaekers, Bart, Graham, Matthew R., Callafon, Raymond A., and Talke, Frank E.

Subjects
Engineering, Electronics and Microelectronics, Instrumentation, Mechanical Engineering, Nanotechnology
Abstract

As tape recording density increases, high-frequency track following capability of the tape head actuator becomes more important. This paper details the mechanical design and experimental analysis of a dual state actuator tape head. The dual stage actuator design combines a traditional voice coil motor for low frequency track following with a piezoelectric actuator for high-frequency track following. Non-parametric and parametric modeling techniques are used in the analysis of the dual stage actuator. The performance of the dual stage actuator head shows good correlation with the model and will enable improved track following capability for future high-performance tape drives.

Published
2009

25. Generating synthetic as-built additive manufacturing surface topography using progressive growing generative adversarial networks

Author

Seo, Junhyeon, Rao, Prahalada, Raeymaekers, Bart, Seo, Junhyeon, Rao, Prahalada, and Raeymaekers, Bart

Abstract

Numerically generating synthetic surface topography that closely resembles the features and characteristics of experimental surface topography measurements reduces the need to perform these intricate and costly measurements. However, existing algorithms to numerically generated surface topography are not well-suited to create the specific characteristics and geometric features of as-built surfaces that result from laser powder bed fusion (LPBF), such as partially melted metal particles, porosity, laser scan lines, and balling. Thus, we present a method to generate synthetic as-built LPBF surface topography maps using a progressively growing generative adversarial network. We qualitatively and quantitatively demonstrate good agreement between synthetic and experimental as-built LPBF surface topography maps using areal and deterministic surface topography parameters, radially averaged power spectral density, and material ratio curves. The ability to accurately generate synthetic as-built LPBF surface topography maps reduces the experimental burden of performing a large number of surface topography measurements. Furthermore, it facilitates combining experimental measurements with synthetic surface topography maps to create large data-sets that facilitate, e.g. relating as-built surface topography to LPBF process parameters, or implementing digital surface twins to monitor complex end-use LPBF parts, amongst other applications.

Published
2023

26. Convergence of (Soft) Elastohydrodynamic Lubrication Simulations of Textured Slider Bearings

Author

Allen, Quentin, Raeymaekers, Bart, Allen, Quentin, and Raeymaekers, Bart

Abstract

We study the convergence of elastohydrodynamic lubrication (EHL) simulations of textured slider bearings. EHL simulations are computationally expensive because the equations that describe the lubricant film pressure and the deformation of the bearing surfaces are coupled and, thus, must be solved simultaneously. Additional simulation requirements, such as maintaining a specific bearing load-carrying capacity or lubricant film thickness, further increase the computational cost because they impose additional constraints or add equations that must converge simultaneously with those that describe the lubricant film pressure and bearing surface deformation. We methodically quantify the convergence of EHL simulations of textured slider bearings as a function of simulation parameters, including different convergence metrics and criteria, but also cavitation models, texture design parameters, and bearing operating parameters. We conclude that the interplay between discretization, the convergence metric, and the convergence criterion must be carefully considered to implement numerical simulations that converge to the correct physical solution. Our analysis also illustrates that a well-designed convergence study can minimize the computational cost.

Published
2023

45. Dynamic modeling and control of a piezo-electric dual-stage tape servo actuator

Author

Boettcher, Uwe, Raeymaekers, Bart, de Callafon, Raymond A., and Talke, Frank E.

Subjects
Algorithms -- Usage, Actuators -- Models, Magnetic devices -- Models, Magnetic recorders and recording -- Models, Servomechanisms -- Models, Algorithm, Business, Electronics, Electronics and electrical industries
Abstract

We present a data-based approach for modeling and controller design of a dual-stage tape servo actuator. Our method uses step response measurements and a generalized realization algorithm to identify a multivariable discrete-time model of the actuator. The data acquisition and modeling can be implemented in the servo firmware of a tape drive. We have designed a dual-stage controller, based on the model, using loop shaping techniques adopted for multivariable control problems. We applied the procedure to the prototype of a dual-stage actuator tape head to reduce the effect of lateral tape motion. The prototype consists of a conventional voice coil motor for coarse positioning and a micro-actuator for fine positioning. The micro-actuator, which is mounted on the voice coil motor, uses a piezo crystal to follow high-frequency lateral tape motion (up to the kilohertz regime), while the voice coil motor follows only low-frequency lateral tape motion. Compared to a single-stage design, the dual-stage servo design provides a 25% bandwidth improvement and a voice cot motor control signal that is much smaller in magnitude. Index Terms--Magnetic tape recording, modeling, servosystems.

Published
2009

46. Measurement and sources of lateral tape motion: a review

Author

Raeymaekers, Bart and Talke, Frank E.

Subjects
Magnetic tapes -- Mechanical properties, Reel-to-reel tape -- Mechanical properties, Motion -- Models, Science and technology
Abstract

The sources of lateral tape motion in a tape drive are reviewed. Currently used measurement methods and models for lateral tape motion are analyzed and compared. The effect of roller run-out, tape edge contact, and tape tension transients on lateral tape motion is discussed. A dual stage actuator tape head is investigated to improve track-following capability and increase the track density on a magnetic tape. Keywords: magnetic tape recording, lateral tape motion, magnetic storage

Published
2009

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