Papers by Wonseok Hush Heo
International Journal of Engineering Science, 2023
Magnetophoresis is used in various applications requiring selective collection of magnetic partic... more Magnetophoresis is used in various applications requiring selective collection of magnetic particles. This study is aimed at quantitatively describing magnetophoretic systems via dimensional analysis to assess the relative contribution of hydrodynamics, electromagnetism, and particle dynamics. We introduce dimensionless numbers characterizing the transport of magnetic particles in a fluid. Analytical and numerical studies were conducted for magnetophoretic systems where magnetic particles were suspended in a fluid exposed to magnetic fields generated by permanent magnets. The magnetically induced mobility of the magnetic particles was simulated for a range of parameters relevant in biomedical applications, including the particle and fluid properties, flow velocity, and geometries of the particle, flow channel, and magnet. The numerical results obtained in multiphysics modeling of magnetophoretic systems were analyzed based on the proposed dimensionless numbers, resulting in a functional relationship for the particle capture efficiency (CE), defined as the ratio of captured particles to all particles injected in the flow. The performance of magnetophoretic systems predicted with the dimensional analysis was verified in comparison with published experimental data. Using dimensional analysis, 12 input parameters determining the particle CE were reduced to 3 dimensionless numbers characterizing the ratios of magnetophoretic and hydrodynamic forces, cross-sectional areas of the magnet and the flow channel, and length and diameter of the magnet. A set of curves predicting particle CE was obtained using these dimensionless numbers. A close agreement was found between the CEs predicted by the curves and those obtained in both numerical simulations and experiments where cylindrical magnets were placed in a flow through a cylindrical pipe. This study provides a promising framework for analyzing and predicting performance of various magnetophoretic systems for a range of applications.
Nature Communications, Jan 9, 2024
Magnetic resonance imaging is a widespread clinical tool for the detection of soft tissue morphol... more Magnetic resonance imaging is a widespread clinical tool for the detection of soft tissue morphology and pathology. However, the clinical deployment of magnetic resonance imaging scanners is ultimately limited by size, cost, and space constraints. Here, we discuss the design and performance of a low-field single-sided magnetic resonance sensor intended for point-of-care evaluation of skeletal muscle in vivo. The 11 kg sensor has a penetration depth of >8 mm, which allows for an accurate analysis of muscle tissue and can avoid signal from more proximal layers, including subcutaneous adipose tissue. Low operational power and shielding requirements are achieved through the design of a permanent magnet array and surface transceiver coil. The sensor can acquire high signal-to-noise measurements in minutes, making it practical as a point-of-care tool for many quantitative diagnostic measurements, including T2 relaxometry. In this work, we present the in vitro and human in vivo performance of the device for muscle tissue evaluation. Point-of-care (POC) medical diagnostics are increasingly utilized in both inpatient and outpatient settings 1,2 . The ability to rapidly detect aneurysms, fluid pockets, and other clinical findings that can be managed using an interventional procedure can decrease the time to diagnosis and treatment, leading to improved patient outcomes . The bedside operation of these POC instruments enables measurement of diagnostic information without the need to transport the patient to a centralized-care facilityreducing cost, time to treat, and in some cases, length of stay 5 . Magnetic resonance imaging (MRI) is the primary clinical tool for detecting soft tissue pathology due to high soft tissue contrast. It is non-invasive, does not involve patient exposure to ionizing radiation, and allows for quantification of tissue morphology. Traditionally, MRI is not practical as a POC tool since the high magnetic fields (typically 1.5-3 Tesla) needed for operation present a projectile hazard for ferrous objects if operated outside of an access-controlled scanner suite. Additionally, the need for magnetic and radio frequency (RF) shielding, as well as power requirements that can exceed 25 kW, increase the footprint precluding use at the POC. It is also not compatible with patients that have certain types of metal implants; the high cost of scanner purchase and site infrastructure limitations prevent many facilities from having multiple scanners, limiting capacity despite high demand for instrument use. Recent technical innovations in MRI physics and instrumentation have led to scanners operating at far lower magnetic fields than previously thought possible and have enabled 64 mT MRI scanners to be deployed at the patient bedside for POC use. These low-cost low-field MRI scanners can operate without the shielding and safety requirements of traditional high-field scanners, but their use to date has focused on neuroimaging in critical-care settings . Single-sided magnetic resonance (SSMR) sensors may provide a portable POC diagnostic option that leverages the power of MR-based contrast with purpose-built low-cost hand-held instruments 10 . These devices use magnetic resonance techniques to acquire spectroscopic (i.e., non-imaging) data over a limited tissue depth but have the ability to distinguish between tissue types, intra-and extra-cellular
Research Square (Research Square), Sep 18, 2023
Magnetic resonance (MR) imaging is a powerful clinical tool for the detection of soft tissue morp... more Magnetic resonance (MR) imaging is a powerful clinical tool for the detection of soft tissue morphology and pathology, which often provides actionable diagnostic information to clinicians. Its clinical use is largely limited due to size, cost, time, and space constraints. Here, we discuss the design and performance of a low-eld single-sided MR sensor intended for point-of-care (POC) evaluation of skeletal muscle in vivo. The 11kg sensor has a penetration depth of > 8 mm, which allows for an accurate analysis of muscle tissue and can avoid signal from more proximal layers, including subcutaneous adipose tissue. Low operational power and minimal shielding requirements are achieved through the design of a permanent magnet array and surface transceiver coil. We present the in vitro and human in vivo performance of the device for muscle tissue evaluation. The sensor can acquire high signal-to-noise (SNR > 150) measurements in minutes, making it practical as a POC tool for many quantitative diagnostic measurements, including T2 relaxometry.
International Journal of Engineering Science, 2023
Magnetophoresis is used in various applications requiring selective collection of magnetic partic... more Magnetophoresis is used in various applications requiring selective collection of magnetic particles. This study is aimed at quantitatively describing magnetophoretic systems via dimensional analysis to assess the relative contribution of hydrodynamics, electromagnetism, and particle dynamics. We introduce dimensionless numbers characterizing the transport of magnetic particles in a fluid. Analytical and numerical studies were conducted for magnetophoretic systems where magnetic particles were suspended in a fluid exposed to magnetic fields generated by permanent magnets. The magnetically induced mobility of the magnetic particles was simulated for a range of parameters relevant in biomedical applications, including the particle and fluid properties, flow velocity, and geometries of the particle, flow channel, and magnet. The numerical results obtained in multiphysics modeling of magnetophoretic systems were analyzed based on the proposed dimensionless numbers, resulting in a functional relationship for the particle capture efficiency (CE), defined as the ratio of captured particles to all particles injected in the flow. The performance of magnetophoretic systems predicted with the dimensional analysis was verified in comparison with published experimental data. Using dimensional analysis, 12 input parameters determining the particle CE were reduced to 3 dimensionless numbers characterizing the ratios of magnetophoretic and hydrodynamic forces, cross-sectional areas of the magnet and the flow channel, and length and diameter of the magnet. A set of curves predicting particle CE was obtained using these dimensionless numbers. A close agreement was found between the CEs predicted by the curves and those obtained in both numerical simulations and experiments where cylindrical magnets were placed in a flow through a cylindrical pipe. This study provides a promising framework for analyzing and predicting performance of various magnetophoretic systems for a range of applications.
Bulletin of the American Physical Society, Nov 20, 2017
bursting in oceanic whitecaps is a well-known mechanism of marine aerosol generation. When crude ... more bursting in oceanic whitecaps is a well-known mechanism of marine aerosol generation. When crude oil spills occur, these aerosols may be oil-laden, leading to public health concerns. The introduction of dispersants aimed at accelerating the breakup of slicks, which greatly reduce the oil-water interfacial tension, potentially alters the aerosol number and size distributions. To characterize these effects, controlled bubble plumes are injected into a vertical seawater column (ϕ0.6m, 1.8m high) with an oil-contaminated surface. The aerosol concentrations are measured in the micron (0.5-20m) and nano (10-370nm) size ranges. Tests are performed at the same air injection rate for varying bubble diameters (614, 263 and 89µm), slick thicknesses (50 and 500µm), and oil-water interfacial tensions. The latter are achieved by using crude oil, crude oil premixed with the dispersant Corexit 9500A at a ratio of 1:25, and pure dispersant. The results confirm that bubble bursting causes aerosolization of oil in the micron range, which increases with the introduction of dispersant. An order of magnitude increase in the concentration of nano-aerosols occurs for the largest bubbles, but not the smaller ones, and only for slicks containing pure dispersant or 500 µm thick crude oil-dispersant mixtures.
유체기계 연구개발 발표회 논문집, Dec 1, 2015
The prediction and design of the aerodynamic performance of a compressor are crucial requirements... more The prediction and design of the aerodynamic performance of a compressor are crucial requirements to properly evaluate the aerodynamic performance and characteristics during preliminary design of a centrifugal compressor because it is not clear to figure out the internal flow property of a compressor including complicated three dimensional turbulent flow. In this study the industrial centrifugal compressor was calculated for variations of mass flow and blade Mach number with 2 cases of different number of diffuser vanes. One of the major cause of the impeller loss is the pressure drop when the operating mass flow rate closes to choking flow coefficient. Momentum transfer and loss characteristics of the impeller are important to understand impeller characteristics. The method was suggested to estimate the impeller performance characteristics.
Journal of Geophysical Research: Atmospheres, 2019
Bursting of bubbles in slicks containing crude oil and dispersant mixtures aerosolizes the oil, g... more Bursting of bubbles in slicks containing crude oil and dispersant mixtures aerosolizes the oil, generating micro-and nano-droplets. In ambient air, a tenfold increase in sub-micron particle concentration occurs when large bubbles burst on slicks containing dispersants. Micro-droplets are generated for all bubble plumes and slick types, but their concentration decreases with increasing slick thickness.
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Papers by Wonseok Hush Heo